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Oxidative Coupling of Methane followed by Oligomerization to Liquids

Final Report Summary - OCMOL (Oxidative Coupling of Methane followed by Oligomerization to Liquids)

Executive Summary:
OCMOL, a large-scale collaborative 5 year EU project started on September 1, 2009, was funded by the Seventh European Framework Programme for Research and Technological Development. OCMOL provided a green and flexible process technology, adapted to the exploitation of small natural gas reservoirs from both a technical and an economic point of view. It addressed major problems currently facing the European chemical process industries, within the context of fuels and chemicals production. Seventeen industrial and academic partners from 8 European and 1 non-European country were uniting their efforts within the OCMOL consortium from 2009 to 2014.

The OCMOL project addressed several key challenges in catalysis and chemical engineering, such as oxidative coupling of methane, ethylene oligomerization to liquids, membrane/PSA separation, methane dry reforming, oxygenate synthesis and oxygenate to liquids conversion. For this purpose, OCMOL has developed and implemented high throughput methodologies to accelerate the discovery of new materials, such as catalysts, adsorbents and membranes, and to propose a green integrated chemical process with near zero CO2 emissions.

A considerable number of breakthrough materials have been discovered, demonstrating reduced lab-to-pilot-to-process cycle times, with reduced environmental impact and cost. These achievements have been obtained by developing an advanced process simulation toolkit and high-tech micro-engineering technology as well. This toolkit was systematically applied by the OCMOL partners to the aforementioned chemical objectives.

The main process steps have been implemented in separate test units and were virtually integrated. An economic evaluation of the integrated process resulted into several recommendations for improving the competiveness of the OCMOL process, e.g. increasing the yield towards liquids via ethylene oligomerization. Life cycle analysis indicated that the carbon footprint ‘from cradle to gate’ is smaller compared to other natural gas-to-synthetic diesel processes. Additionally, some key remaining challenges have been identified, in particular the limited ethylene yield of the oxidative coupling of methane and capital expenditures for the separation section.

More information can be found on: www.ocmol.eu

Project Context and Objectives:
Increasing global energy demand and rising crude oil prices urge striving for alternative production routes of liquid hydrocarbons in a more and more favourable economic context. Established processes for natural gas transformation into synthetic fuels require large investments, which are prohibitive for the exploitation of approximately one third of the world’s natural gas reserves, which are considered as stranded due to their limited size and remote location. OCMOL provides a flexible process technology, adapted to the exploitation of small gas reservoirs from both a technical and an economic point of view. It is, among others, based on oxidative coupling of methane (OCM) followed by its subsequent oligomerization to liquids (OL). Major technological challenges, in the fields of OCM, ethylene OL, membrane/PSA separation, methane dry reforming, oxygenate synthesis and oxygenate to liquids conversion are addressed. Microstructured reactors have been manufactured to use the exothermic OCM to supply the heat required for the endothermic methane reforming with CO2 and steam extracted from the OCM effluent, resulting in a lower energy demand. A fully integrated and environmentally friendly industrial process is proposed, being self-sufficient through the re-use and recycling of by-products, in particular CO2, at every process stage. Process intensification via cutting-edge micro reactor technologies enables to skip the expensive scale-up stage to provide a proof of concept of the OCMOL liquefaction route. The OCMOL route aims at a CO2 neutral operation, thus facing global warming constraints, and economic viability at capacities as low as 100 kT/year, which is currently not possible by using state of the art technologies. It offers a product stream flexibility adapted to the market demand, i.e. sulphur free fuels such as gasoline, kerosene, diesel and/or premium quality (petro)chemicals such as ethylene and linear alpha-olefins.

To achieve these goals, OCMOL rely on a partnership gathering 17 entities coming from 8 European countries and 1 non-European country. 7 OCMOL partners are companies, i.e. Bayer Technology Services GmbH, Johnson Matthey plc, LINDE AG, Compañía Española de Petróleos S.A. Haldor Topsoe A/S, INEOS N.V. and ENI S.p.A. with recognized expertise in the field of material development and process engineering. This pool of industrials is supported by 4 academic partners (Ghent University, Ruhr-Universität Bochum, Universitetet i Oslo and University of Cambridge) and 5 experienced research organizations (CNRS - Institut de Recherches sur la Catalyse et l’Environnement, STIFTELSEN SINTEF, CSIC - Instituto de Tecnologia Quimica, Institut für Mikrotechnik Mainz GmbH and Boreskov Institute of Catalysis), which grought their extensive knowledge on the various topics encompassed within the S&T scope of the project.

4.1.2.2. Objectives
In order to ensure that this project is economically and strategically realistic, the overall strategy of the OCMOL project was based on an industrial approach. The work programme was structured in seven S&T sub-projects (SP). As a result of the industrial approach, the SPs were led by industrial partners in order to give an industrial framework to the expertise of the scientific partners. In the next paragraphs, a short introduction to each SP and its goals is given.
Methane conversion (Oxidative coupling and reforming)
The first step in the OCMOL process is the exothermic oxidative coupling of methane (OCM) followed by the endothermic reforming of methane (RM). The heat integration of these two steps could augment the process competiveness by reduced CO2 emissions and energy requirements.

The development of new OCM formulations for a C2 yield of 30% was envisaged. An existing RM catalyst would be coated on microstructured reactors with the aim of a CH4/CO2 conversion close to the thermodynamic equilibrium. A high stability for both catalysts of at least 60 h time-on-stream was also a goal of this SP.

Additionally, the development and use of microkinetic models was planned to elucidate the underlying chemistry and allow for rational catalyst design. Moreover, industrial operating conditions for OCM and RM would be defined. The construction of lab scale reactors operating in an autothermal manner was envisaged.

Separation processes
In the OCMOL process, several streams should be separated and/or purified before they can be sent to other units. For example, impurities from the OCM reactor can highly decrease the performance of the ethylene oligomerization reactor downstream. The preparation and screening of new adsorbent and membrane materials was planned.

Syngas to liquids
In the RM unit, syngas is produced which is fed to the syngas-to-liquids (STL) unit. In fact, this unit consisted out of two different subunits, i.e. syngas-to-oxygenates (STO) and oxygenates-to-liquids (OTL).

Catalysts with improved selectivities for the production of oxygenates from syngas were planned to be developed. Additionally, novel tailor-made zeolitic materials have been developed for the selective (>75%) conversion of methanol/oxygenates to a hydrocarbon stream with a low aromatic content. An integrated two-step process covering both steps will be developed.

Oligomerization
The ethylene produced in the OCM unit is sent to an oligomerization unit. Current technologies for ethylene oligomerization rely on the use of homogeneous organometallic catalysts. Environmental issues, among other reasons, prompts to the replacement of the homogeneous system by more friendly heterogeneous catalysts.

The objective was to construct and test a catalyst library. From this library, an ethene oligomerization catalyst would be selected and optimized to produce liquid fuels with a narrow carbon range distribution, with a productivity to liquids of 5 mmol/(kgcat•s) and a lifetime of at least 60 h time-on-stream. A micro-kinetic model was planned to be constructed and used for the determination of optimal reaction conditions for an industrial ethylene oligomerization unit, as well as a dedicated unit to validate the performance of the selected catalyst(s).

Process integration
Each subunit in the OCMOL process, i.e. OCM/RM, separation, syngas-to-liquids and ethylene oligomerization, was then due to be tested separately using the selected catalysts and determined reaction conditions in dedicated units. The results from these tests would be used as design basis for the virtual integration of the OCMOL process for the economic evaluation and lifecycle analysis.

Toolkit for material and reactor design
A supporting platform was planned to be constructed in order to provide all partners the necessary hard- and software. New catalysts would be developed for OCM/RM, separation, syngas-to-liquids and ethylene oligomerization, and prepared at a larger scale (kg instead of g). New experimental set-ups would be built in order to perform the tests necessary for catalyst evaluation, kinetic data acquisition and industrial condition testing. A methodology for micro-kinetic modelling would be developed.

Process engineering and economic evaluation
The OCMOL process was final planned to be integrated virtually, based upon the different tests performed in process integration SP. This would lead to a list of core equipment, guidelines for development and an optimized flow diagram for the integrated process. An economic evaluation and a lifecycle analysis was planned to be used to determine the viability and the environmental impact of the integrated process.
Project Results:
The technical objectives of this project relate to:
•Methane conversion
•Separation processes
•Syngas to liquids
•Oligomerization
•Process integration
•Toolkit for material and reactor design
•Process engineering and economic evaluation

Before elaborating the S/T results achieved during the project, a summary is given.

Methane conversion (Oxidative coupling and reforming)
Methane conversion via integrated exothermic oxidative coupling and endothermic (dry) reforming is at the heart of the OCMOL process. Novel, innovative catalyst synthesis routes have been validated and catalysts have been optimized to exhibit desired activity and stability. Fundamental kinetic modelling technologies provided an unprecedented understanding of the reaction mechanism and proved to be essential in reaching the performance targets. The integration of both reactions has been established both using ‘conventional fixed bed reactor system’, the so-called multi-bed micro-structured reactor (MMR) as well as the catalytic wall micro-structured reactor (CWMR) technology. Autothermal operation could be achieved and maintained at a time scale of 24h.

No new breakthrough catalyst formulations have been discovered, confirming the well-established intrinsic limitation in C2 yields for OCM. However, various formulas have been found adequate for being coated on micro-structured reactors as planned in OCMOL, and, hence fulfilling the stability performance required for demonstrating the autothermal concept proposed as key objective.
Separation processes
An important criteria for the realisation of the OCMOL process concept has been to address the need for efficient and selective separation processes at the interface of the core process steps. Two specific challenges have been under focus: 1) remove specific by-products that can impact or even "poison" the activity of the catalyst, 2) separate out key components for recycling in order to achieve the overall targets of the OCMOL process. Technologies based on sorbent and membrane separation have been investigated, with the core of the research involving the developing and modifying materials with potential functionality and modelling the process to gauge simulate the potential for the process of the materials.

Syngas to liquids
The conversion of syngas to liquid hydrocarbons via oxygenates, i.e. methanol and dimethyl ether (DME) has been investigated experimentally and via modelling efforts. Due to the ambitious goal of the second step, i.e. the selective conversion of oxygenates to aliphatic C5+ hydrocarbons, main emphasis has been allocated to this activity, while relatively smaller efforts have been devoted to the first step and the combined process.

Fundamental understanding of the oxygenate-to-hydrocarbon synthesis over zeolites has been gained during the project. Improved catalysts for the production of alcohols and ether intermediates and novel tailor-made zeolite materials for the conversion of methanol/oxygenates to hydrocarbons with low aromatics selectivity have been tested. An integrated, two-step, syngas to low-aromatic fuel process scheme has been established.

Oligomerization
A large catalyst library (±100 samples) has been tested from which the promising catalysts have been selected and optimized. From this selection, several catalyst achieved the targeted productivity and lifetime. Using these optimized catalysts, an extensive experimental dataset has been acquired which has been used to develop a microkinetic model. This micro-kinetic model is capable to describe the effects of operating conditions and catalyst properties on the observed ethylene oligomerization kinetics. Additionally, an industrial oligomerization reactor based on these micro-kinetics has been designed ‘in-silico’. A pilot-plant has been used to investigate the possibilities op upscaling.

Process integration
Each of the different processes described in previous paragraphs, i.e. methane conversion, separation, syngas to liquid and oligomerization has been tested in separate, dedicated units. These tests aimed at proving the objectives set for the reactions and the catalysts, i.e. selectivity, yield, conversion and lifetime. These tests also resulted in data for the integrated process engineering and its economic evaluation. The individual test units have been hosted by the following partners:
• OCM and RM unit: multi-bed reactor with structured heat-exchangers hosted by BTS and micro-structured reactor hosted by IRCE.
• Separation unit hosted by SINTEF.
• Syngas to liquids unit hosted by HTAS.
• Oligomerization unit hosted by CEPSA.

Toolkit for material and reactor design
The design and building of a number of different reactors for testing of OCM catalysts, testing of ethylene oligomerization catalysts and the measuring of reaction kinetics (including a novel NMR reactor) have been targeted. The formation of micro-kinetic models to aid the other technical SP’s has been included. Selection of standard catalysts for other SP’s, as well as their large scale preparation and forming by innovative coating methods has been incorporated in to this area of the project. It also included the realisation of two microstructured laboratory prototype reactors allowing the combination of the exothermic OCM and endothermic dry reforming reactions at a quasi-auto-thermal regime with staged oxygen dosing. Investigations into separation materials have also been performed.

Process engineering and economic evaluation
The concept for the fully-integrated OCMOL process has been finalized based on a plant capacity of 100 kTon/year of methane, and considering different combinations of valorization scenarios and corresponding flow sheets. An estimate of equipment costs has been made for the most favorable combinations. Life Cycle Assessment and a Net Present Value analysis have been performed based on different assumptions concerning methane cost. CO2 emissions per ton of product have been used as a meaningful environmental Key Performance Indicator. Other greenhouse gases have been shown to play a less important role. The potential savings in CO2 emissions have been quantified.

4.1.3.1. Methane conversion (Oxidative coupling and reforming)
The subproject on methane conversion, i.e. methane oxidative coupling and reforming, comprised 4 major activities ranging from catalyst synthesis and innovation over (micro)kinetic modelling to reactor design. The latter was split up in multi-bed reactors and coated microstructured reactors.

Catalyst development and testing

• Methane oxidative coupling (OCM)
OCM catalysts have mainly been developed by IRCE and JM while in a later stage also RUB got involved in the synthesis of a novel class of catalysts based on NaWMnSi. While IRCE has screened a wide panel of catalysts with varying amounts of Sr, La, Li and Sn supported on different carriers, JM has focused on alternative synthesis methods which allowed tuning the size of the catalyst crystallites. Micro-emulsions as well as flame spray pyrolysis were used for this purpose and, e.g. adequate control of the La2O3 crystallite size with the micro-emulsion temperature was achieved. The best OCM catalyst as identified from the screening by IRCE comprised 1%Sr and 10%La deposited on CaO. With this OCM catalyst a stable activity in terms of methane conversion and C2 yield could be achieved. It was mainly attributed to the formation of monodentate carbonates on the La which were converted into more stable bidentate carbonates in the presence of Sr. A Sr excess, however, resulted in too high amounts of bidentate carbonates with a negative impact on the OCM performance.

• Methane reforming (RM)
RM catalysts have mainly been investigated by BIC and also JM. Various complex mixed oxides have been synthesized and tested in the reforming of model as well as realistic feeds consisting of natural gas. A Ru promoted perovskite made of Pr, Fe and Ni have been found to be one of the best performing catalyst compositions in dry reforming of natural gas for 60h. Equilibrium conversion could be achieved during this time period. Moreover, a promoted version of this catalyst, i.e. additionally containing La, Mn and Cr as well as some yttrium stabilized zirconia, exhibited stable, kinetically controlled performance. Particular attention has also been paid to potentially remaining oxygen traces in the reformer feed, leading to so-called ‘oxy’ dry reforming. The enhanced performance of a Pt promoted Pr loaded ceria zirconia has been evidently demonstrated.

Kinetics model development
To ensure an effective start of the project, literature based, global models have been initially constructed for OCM as well as for RM by UGENT. Quite rapidly these global models have been replaced by more advanced, micro-kinetic models. In particular for OCM a one-dimensional, heterogeneous reactor model has been implemented by UGENT that has been enhanced compared to its original version in terms of accounting for radical profiles within the catalyst pores. The model allowed a detailed assessment of the contribution of catalytic and homogeneous reactions to methane activation and methyl radical coupling respectively. Data acquired by RUB have been adequately simulated by UGENT using this model. The model also allowed accounting for varying catalyst properties by virtue of the catalyst descriptors. The latter parameters provided a quantitative explanation for the differences in catalytic behaviour exhibited by 5 alternative catalysts ranging from the very first (Sn)LiMgO based catalysts over the SrLaCaO ones to the more innovative NaWMnSiO2. Higher hydrogen abstraction enthalpies from methane and higher oxygen chemisorption heats on the catalyst surface could quantitatively capture the differences between the well performing SnLiMgO and NaWMnSiO2 catalysts. For RM a more detailed kinetic analysis has been performed by BIC based on transient data.

Reactor design and implementation
The design and actual construction of a non-integrated multi-bed test reactor with structured heat exchangers design proved to be particularly challenging because of the extreme operating conditions, mainly required for OCM. Adequate sealing proved to be such an issue that only welding could be identified as a suitable technique. BTS, in collaboration with IMM, designed a 5-step unit in which the heat generated by OCM was in sufficient transferred to the RM side to sustain the reaction.

Coated microstructured reactor development
A plate-heat-exchanger microreactor has been developed by IMM using wet-chemical etching and laser cutting. It comprised an array of 40 microchannels which have been coated with a catalyst for either dry reforming or oxidative coupling of methane by JM and IRCE. Prior to OCM catalyst coating, the corresponding channels have been coated with an innovative enamel protection layer. By stacking the different types of plates on top of each other alternating layers of RM channels, OCM channels, and channels for oxygen dosing have been achieved. Similar to the laboratory prototypes developed, this demonstrator comprised two heating plates at the top and bottom which can be used for the heating-up procedure. For reactor operation, the educt gases have been heated to 850°C using microstructured pre-heaters and have been then fed into the reactor. Autothermal operation of the microreactor has been successfully achieved.

4.1.3.2. Separation processes
Three key challenges concerning separation have been ultimately addressed in the project:
1. Achievement of a purified stream of ethylene as a feed into the sensitive oligomerization
2. Providing an oxygen feed stream for the reforming step
3. Aiming at more energy efficient separation of methane prior to the oxygenates step.

The results of the research activities have been based on development and screening of materials with relevant properties, with further consideration of their potential for application in sorbent or membrane based separation.

With respect to achieving the purified stream of ethylene, a novel material with unusually high selectivity in the separation of the product ethylene from by-products of similar size has been discovered. IRCE characterized this material, ENI supported this development with modelling and the PSA results were obtained at SINTEF. A "Molecular Sieve" with silver as part of its composition (AgA) and pore dimensions similar to the size of the ethylene molecule has been able to completely exclude the undesirable ethane molecule from entering the pores.

Regarding the oxygen feed stream, the enrichment of the CO2 stream by oxygen separated from air allowed to adjust the content of oxygen in the RM inlet stream in order to achieve heat balance between the endothermic RM and exothermic OCM, resulting in a global autothermal process. High oxygen permeability and stable performance of asymmetric supported membranes have been achieved by BIC due to a positive role played by developed perovskite–fluorite interfaces with specific structure and composition.

For the separation of methane, the key challenge was to find a sorbent able with the affinity to separate the relatively inert methane molecule from a mixture with hydrogen and CO. Another "Molecular Sieve" (ZSM-5) has been shown experimentally by SINTEF to in fact to have higher affinity for methane over the other two molecules, though not to the level desired. This has meant carrying out detailed modelling studies by ENI to see if a viable commercial process can be based on this level of affinity.

4.1.3.3. Syngas to liquids

Syngas to Oxygenates
One of the targets of OCMOL was to design a syngas to oxygenate (STO) process utilising the syngas produced in the preceding reforming step, which has a H2/CO ratio close to one, with conversion efficiency above 95%. Thermodynamics play a crucial role to meet this goal. The combination of methanol and DME synthesis provides an important enhancement to the conversion of syngas, enabling a remarkable efficiency at pressures significantly below those required for methanol synthesis. However, the equilibrium conversion is still limited and recycle is required in order to reach the targeted 95% syngas conversion levels.

In this work, HTAS portfolio of proprietary DCK-10 series of composite catalysts have been applied using a molar feed composition close to the near-ideal blend coming from the reformer unit at 50 bar. The once-through syngas conversion was 83%, with DME concentrations between 25-30 mol% in the product stream. Process studies varying the ratio of recycle to makeup gas (R/M) for different reaction pressures and product separation temperatures showed that the targeted 95% steady state conversion may be reached with an R/M ratio of one at 50 bar. The product separation has been carried out efficiently at below 5°C, resulting in a product liquid phase composed of DME and CO2. Due to the high solubility of CO2 in DME, the separation step provided a suitable means of rejecting CO2 from the synthesis loop. Thus, the gaseous phase has been recycled directly back to the oxygenate synthesis reactor without an additional CO2 removal unit, significantly reducing capital costs.

Oxygenates to liquids
The oxygenates to liquids (OTL) process has been carried out over zeolite or zeotype catalysts. Zeolite and zeotype materials have a high specific surface area and contain pores of molecular dimensions. These pores lead to shape selectivity, by restricting the maximum size of products that may be formed in, and diffuse out of, the pores. Today, two main processes exist for converting oxygenates (methanol and dimethyl ether) to hydrocarbons; i.e. the methanol to olefins (MTO) process, which produces only linear alkenes and alkanes; and the methanol to gasoline (MTG) process, which produces a mixture of alkanes, alkenes and aromatic products, well suited for conventional gasoline production. The MTG process may be optimised for propene production (the MTP process) by changing catalyst composition and reaction conditions, but even then lead to a high fraction (> 15 %) of aromatic products. The goal of the OCMOL process has been to produce an aromatics-free gasoline mixture of products. Inspiration for the work was found in mechanistic studies of oxygenate to hydrocarbons reaction, which indicated that the process is an autocatalytic reaction proceeding via a dual-cycle mechanism, where one cycle involves alkene intermediates, and the other cycle involves aromatic intermediates.

The idea was to employ a catalyst with too narrow pore size to allow for aromatics formation. A total of four zeolites, all having 1-dimensional 10-ring channels, were identified by UiO and were tested by UiO/HTAS for this purpose.

The reaction temperature was 400-450 C. Their pore sizes ranged from 4.5×5.2 Å (H-ZSM-23) to 5.6×5.3 Å (H-ZSM-48). Two of the catalysts, H-ZSM-22 and H-ZSM-23, were selective towards aliphatic C5+ hydrocarbons: C5+ hydrocarbon yields up to 55 %, corresponding to selectivities between 40 and 70 C%, have been observed depending on the conversion. Moreover, the selectivity towards aromatic hydrocarbons was inferior to 2 % at all measured conversions, and the main by-products over H-ZSM-22 and H-ZSM-23 were C2-C4 alkenes. It is also worth noting that an optimal C5+ aliphatics yield of 53-55 % has been observed for both topologies at 90–95 % methanol conversion. On the other hand, H-EU-1 and H-ZSM-48 both produced more than 15% aromatics yield at 90 % conversion. This result illustrated that subtle changes in pore size may lead to significant selectivity differences in zeolite catalysts.

The ultimate goal of OCMOL was an overall selectivity of more than 75 % aliphatic C5+ hydrocarbons in the syngas to liquids process. Process optimisation towards this goal was attempted by co-feeding C2-C4 hydrocarbons withy methanol. This approach led to effluent compositions very close to those obtained when feeding methanol alone. This result strongly suggests that net C5+ aliphatics selectivity close to 100 % may be achieved with modest product recycling. A micro-kinetic model has been constructed by UGENT in order to perform a contribution analysis. This led to the identification of the main reaction pathways and catalyst descriptors to tune the catalyst activity, selectivity and stability. This micro-kinetic model has been expanded further by including diffusion effects and has been used to simulate an industrial unit.

Even though the product distribution from H-ZSM-22 and H-ZSM-23 is highly interesting, two issues need to be further addressed in the OTL process; that is, the low activity and short life-time before regeneration is required due to coke formation, of both catalysts. The two issues are related: The OTL reaction is autocatalytic and a critical contact time is needed to produce sufficient products that the autocatalytic reaction dominates. If the critical contact time represents X % of the total contact time, then only (100 – X) % of the catalyst bed contributes efficiently to product formation. A less rapid catalyst deactivation was observed when co-feeding alkenes to the methanol feed. This effect may (in part) be due to a shorter critical contact time resulting from the product co-feed.

Future studies of the OTL process should focus on catalyst optimisation. Recent studies have pointed to catalyst morphology as a key factor for activity and conversion capacity optimisation of zeolite catalysts. In particular, an increase in the accessible fraction of the zeolite crystal by nano-sized crystals or hierarchical pore systems has been highlighted. For H-ZSM-22 and H-ZSM-23 that usually crystallise as needle-like structures, a change in catalyst morphology towards shorter channels would be particularly advantageous. Finally, studies of other zeolites have pointed to acid site density as an important parameter for catalyst deactivation. Thus, increasing the Si/Al ratio by steaming and/or acid treatment might also lead to enhanced methanol conversion capacity for the selected catalyst structures. Exchanging the H-ZSM-22 and H-ZSM-23 zeolites with zeotypes which offer lower acid strength and possibly sites that prevent coke formation could lead to further OTL process improvements on a longer time-scale.

Syngas to liquids
The synthesis of gasoline from syngas as part of the OCMOL process has been shown by HTAS to be feasible by integrating STO with OTL. The products from the oxygenate reactor has beendirected to a separator where mainly DME and CO2 have been condensed and subsequently sent to the oxygenate-to-liquids reactor. A recycle stream of CO and hydrogen has also been implemented in the layout with the aim of increasing the conversion of syngas. To further reduce the concentration of reactants, the oxygenates-rich stream has been mixed with a recycle stream from the post-OTL process separation step. This recycle stream contained a high fraction of light alkenes, which may react to form higher hydrocarbons and improve the gasoline yield. The addition of light alkenes improved both the gasoline yield and prolonged the lifetime of the catalyst.

Since the conversion of oxygenates into hydrocarbons is a strongly exothermic reaction, and less than 100% conversion gives the highest gasoline yields over H-ZSM-22 or H-ZSM-23 catalysts, the use of a fluidized bed reactor would be beneficial. Fluidization of the catalyst provides an excellent means for controlling the reaction temperature, ensuring homogeneous reaction conditions along the catalytic bed and minimizing the risk for a runaway or hot spots, in addition to allowing stable operation at less than 100% conversion. Further, the application of a fluidized bed process enables continuous regeneration of the catalyst particles in a separate regenerator, which is particularly relevant for catalysts suffering from rapid deactivation such as H-ZSM-22 and H-ZSM-23.

In summary, the full conversion of syngas via DME/MeOH with light olefin recycle into higher hydrocarbons can give a gasoline product with in C5+ and C4+ yields superior to 70 wt% and 80 wt%, respectively, of the total hydrocarbon product. In addition, the final product stands out by its low content in aromatics. The topology of H-ZSM-22 and H-ZSM-23 inhibits the formation of aromatic compounds, which makes this process very attractive for producing environmentally friendly gasoline.

4.1.3.4. Oligomerization

Catalyst Development and Testing
A major scientific and technological challenge in this subproject has been the development of an efficient heterogeneous (solid) catalyst for the oligomerization of ethylene (OLI) to liquids as a greener alternative to the current technologies based on homogeneous systems. The developed catalyst should have targeted a minimum productivity to liquid oligomers (as fuel precursors) of 5 mmol/(kgcat•s) and a lifetime of, at least, 60 h in a continuous operation mode. Identification of potential catalyst poisons that might be present in the ethylene stream leaving the OCM reactor and their impact on the catalytic performance has also been a relevant aspect of the catalyst development. This has helped defining the required purity of the ethylene stream entering the OLI reactor and, hence, the targets of the preceding separation steps as contemplated in the overall OCMOL process scheme.

To this purpose, a strategy has designed which involved the synthesis and fast screening, at different operating conditions, of an initial library of potential catalyst candidates by CSIC-ITQ, JM, IRCE and ENI. The library comprised about hundred catalysts from different families of materials including, for instance, nickel loaded on micro and mesoporous aluminosilicates, supported ionic liquids, supported heteropolyacids, and more sophisticated structures like MOFs (Metal-Organic-Frameworks). This initial screening study allowed to identify the most suitable catalysts for performing the oligomerization of ethylene to liquids at mild reaction conditions. In particular, three catalysts consisting of nickel loaded on nanocrystalline zeolite beta (Ni-Beta), amorphous silica-alumina (Ni-ASA), and Al-MCM-41 having an ordered arrangement of uniformly-sized mesopores (Ni-Al-MCM-41) outperformed the catalytic behavior of the other materials. Further optimization of these materials in subsequent stages of the project resulted in a Ni-Al-MCM-41 catalyst which, under appropriate reaction conditions, successfully accomplished the targets of productivity and lifetime. In fact, the productivity to liquid oligomers for the optimized Ni-Al-MCM-41 surpassed the initial target of 5 mmol/(kgcat•s) by ca. 24% in average during the 60 h run.

The most critical impurities present in the ethylene stream leaving the OCM reactor were identified by CSIC-ITQ to be CO and CO2. In particular it has been concluded from the poisoning studies that CO is a strong poison for the Ni-based oligomerization catalyst and must, thus, be eliminated from the stream entering the OLI reactor while CO2 concentration must be reduced to the minimum technically feasible levels.

Recently, development of in situ techniques and introduction of operando studies of fixed-bed heterogeneous catalytic reactors have hugely improved the knowledge of solid catalysts, allowing to establish a correlation between catalyst properties and catalyst behavior under reaction conditions. Particularly, in the context of OCMOL project, operando magnetic resonance (MR) spectroscopy has been used by CAM to follow OLI reaction over a reference Ni-SiO2-Al2O3 catalyst at standard OLI conditions (high temperature and pressure). The ratio of aliphatic-to-olefinic peak intensities changed with time on stream. Using this ratio determined from MR spectra and Schulz-Flory theory, conversion and product distribution have been calculated as a function of TOS. Besides, by means of volume selective spectroscopy conversion and product distribution has also been studied as a function of position with the bed. Additionally, operando MR results can be integrated into kinetic study of heterogeneous catalyst owing to the ability of this technique to perform time-resolved studies at sub-second timescales.

Kinetics Model Development
Concerning the kinetic modeling for OLI process, a Single-Event Microkinetic (SEMK) model has constructed by UGENT. For the single-event methodology, reaction families are defined rather than lumping species into pseudo components in order to reduce the number of model parameters. The final SEMK model developed was able to simulate the oligomerization kinetics of ethylene on a bifunctional catalyst and includes both the reaction occurring on the metal-ion and the acid functions, satisfactorily describing the experimental data. Based upon this micro-kinetic model, a tool for determining optimal catalyst properties and reaction conditions has been built.

Reactor Development
A simulation model for an industrial reactor for ethylene oligomerization including the SEMK model has been constructed by UGENT, accounting for transport limitations and the formation of liquids due to condensation of heavy olefins. A multi-fixed bed adiabatic operation with inter-bed cooling has been employed. Finally, according to the design parameters previously obtained, a pilot plant for ethylene oligomerization based in a fixed bed reactor has been designed and assembled by CEPSA. This pilot plant has been used as test unit to prove that the oligomerization step within OCMOL project has been able to convert an ethylene-rich stream separated from OCM effluent into liquid fuels (branched with controlled degree of branching). The simulation model for and industrial OLI reactor has been used for predicting the optimal reaction operation in this pilot plant, including feedstock composition, temperature and pressure.

Selected Ni-SiO2-Al2O3 catalysts have been formed and tested in the pilot plant. Reaction conditions have been optimized in order to maximize the productivity lo liquid oligomers and lifetime.

4.1.3.5. Process integration
Oxidative Coupling of Methane and Reforming

• Multi-bed reactor with structured heat-exchangers design
At the heart of the OCMOL process is an integrated autothermal reactor that combines the oxidative coupling of methane (OCM) into ethylene and ethane (C2) and methane reforming by CO2 (RM) to produce syngas. The reactor concept has been based on heat integration of the exo- and endothermic reactions. For the industrial reactor, this could be accomplished in a fixed-bed heat-exchanger configuration. This device acted simultaneously as a reactor and a heat-exchanger. The multi-bed structured reactor has been developed by BTS and transferred to ICT-IMM where it has been constructed and successfully operated at ICT-IMM.

Experimental evaluation of the first stage has been carried out at nitrogen concentrations of 2 and 20 % and a feed composition of CO2/CH4/H2O 2:1:1.5. The catalyst performance has been checked at WHSV values in the range of 50 to 200 L/h g catalyst resulting in methane conversions from 45 to 70 %. The RM catalyst did not show any indication of deactivation.

In further experiments, the demonstrator has been evaluated by a stepwise adjustment of the gas composition in a single reactor stage to simulate all stages of the demonstrator. The initial feed contained 20 % N2 and ratio of CO2/CH4/H2O of 2:1:1.5. The total flow rate has been adjusted to 25 L/min. A methane conversion of 52 % has been achieved after the first RM stage. By the subsequent RM stages, the overall methane conversion has been increased to 79, 91, and finally 96 %. The diminishing increase in conversion with each stage has also been reflected by a steady rise of the temperature at the reformer outlet. The product gas compositions seemed to be mainly affected by the reforming reactions and the reverse WGS. At the third RM stage, the hydrogen consumption by the reverse WGS exceeded the hydrogen formation by the reforming reactions resulting in a slight decrease of the molar hydrogen flow.

• Coated micro-structured reactor development
The integration of a micro-structured reactor has been realized by using structured metallic platelets on which both OCM and RM catalysts have been coated. The thin catalyst layers minimize internal diffusion limitations and the microstructured channels minimized the pressure drop. Based on the results achieved with the laboratory prototypes developed in Toolkit for material and reactor design SP, a small-scale demonstrator has been developed and manufactured by ICT-IMM. The demonstrator has been realized as a plate-heat-exchanger reactor. Wet-chemical etching and laser cutting have been employed to manufacture the microstructured plates required for this reactor. The microstructure has been realized as an array of 40 microchannels. These channels have been coated with a catalyst for either dry reforming or oxidative coupling of methane by JM and IRCE. Additionally, the OCM channels have been coated with a protection layer prior to the catalyst coating. By stacking the different types of plates on top of each other a stack has been achieved having alternating layers of RM channels, OCM channels, and channels for oxygen dosing. For oxygen dosing flip side of the plates having OCM channels have been structured by wet-chemical etching and laser cutting in such a way that small apertures have been obtained allowing to feed the oxygen directly into the microchannels. The parameters of the laser cutting process have been optimized to reduce the diameter of the apertures and to minimize the remaining melt. Mixing of oxygen and methane takes place inside the microchannels very close to the layer of the OCM catalyst. For operating the reactor, the educt gases have been heated to 700°C with the help of microstructured pre-heaters and were then fed into the reactor. The reactor can be operated at temperatures up to 850°C and pressures up to 10 bar. This unit has been tested at IRCE. The experiments in the test unit over the Mn/W/Na/Si catalyst gave a C2 selectivity of close to 30% at 800°C.

Separation Processes
The development of separation processes for OCMOL has resulted in the proposal of following scenario for the separation of the OCM stream to produce a feed to the oligomerization step.
The key step to be demonstrated is the vacuum swing adsorption (VSA) process for the separation of ethylene from the stream after removal of water, CO and CO2. This test has been carried out at in a larger scale pressure swing adsorption (PSA) at SINTEF unit that is conditioned to measure the ternary separation of CH4, C2H6 and C2H4. The selected adsorbent is zeolite 4A. A mass of 127 grams has been packed in a column with 0.56m length and 0.0254m external diameter. The initial activation of the zeolite has been carried out under helium at 573 K overnight.
The initial results from the breakthrough curves in the unit indicate that it is possible to separate the olefin from the paraffin, though one of the main issues to be addressed is the regeneration pressure.

Syngas to Liquids
In the syngas to liquids part of OCMOL the syngas to oxygenate (STO) process converts the syngas produced in the preceding reforming step, which has a H2/CO ratio close to one, with conversion efficiency of over 95%. The formed oxygenates (DME/MeOH) are subsequently converted in the oxygenate to liquids (OTL) process with an overall selectivity of more than 75 % aliphatic C5+ hydrocarbons. The synthesis of environmental friendly gasoline from syngas is feasible by integrating STO with OTL and was demonstrated by HTAS. The products from the oxygenate reactor have been directed to a separator where mainly DME and CO2 have been condensed and subsequently sent to the oxygenate-to-liquids reactor. A recycle stream of CO and hydrogen has also been implemented in the layout with the aim of increasing the conversion of syngas. To further reduce the concentration of reactants, the oxygenates-rich stream has been mixed with a recycle stream from the post-OTL process separation step. This recycle stream contains a high fraction of light alkenes, which may react to form higher hydrocarbons and improve the gasoline yield. The addition of light alkenes improved both the gasoline yield and prolonged the lifetime of the catalystThe Syngas to liquids test has been performed in two separate steps (two independent reactors). STO has been demonstrated in an existing (dedicated) unit at HTAS, while a new, custom made reactor has been built for the OTL reaction, which enabled operation in fixed-bed and fluid-bed mode (small bench scale). Fixed-bed (1 and 20 bar) vs. fluid-bed operation has been evaluated. The feed gas compositions for the two separate steps have been chosen on the basis of the experimental results obtained in syngas to liguid SP in combination with process calculations to mimick the recycle streams. A minimum of 5 regeneration-reaction cycles of OTL catalyst have been performed.

Oligomerization
A pilot plant has been built at the CEPSA facilities to test the catalyst provided by JM at a larger scale. The unit consisted of a fixed bed reactor which is heated by an electrical furnace. The reactor was capable of operating at temperatures up to 550 ºC and pressures up to 50 atm. A double loop control has been designed for better temperature control. The reactor feed system included three independent gas feed modules (ethylene, nitrogen, methane/CO2) and one liquid feed module (in case water is to be added). The maximum catalyst volume per reactor was 100 ml with a product vessel capacity of 9 liters. All reactor materials have been made of SS316L. The unit had an integrated and accurate safety and alarm system. The pilot plant has been fully automated and all the control strategy has been executed on a dedicated process computer. Outlet gases and vaporized liquids have been analyzed by an online chromatograph. The pilot plant has been used to select the best preindustrial catalyst provided by JM in terms of activity, selectivity and life time. The OCMOL target was to obtain a productivity of C5+ liquids (gasoline and kerosene) of at least 5 mmol/(g•s), with a catalyst stability of at least one week without deactivation. After measuring experimentally the activity, it was also necessary to study the regeneration of the catalyst. Due to the production of long chain oligomers and the relatively low working temperatures, the catalyst tended to deactivate and a regeneration process was necessary. Such regeneration studies has been carried out in the pilot plant using the usual methods of purging with inert gas and temperature and/or combustion of hydrocarbons with air. Thanks to these studies a regeneration protocol has been achieved that fully recovers the activity and selectivity of the catalyst. This would allow, if required, working in a dual catalyst bed system, one in reaction mode and the other in regeneration mode.

4.1.3.6. Toolkit for material and reactor design
Catalyst Development and Testing
This task included the design and building of a number of reactors for use in other sub projects of the OCMOL process.

• Test rigs
Johnson Matthey (JM) has created a high throughput rig with 8 quartz reactors for the purpose of testing OCM catalysts. The rig has been able to carry out testing at high temperature (900oC), atmospheric pressure and allowed the use of various different feed gases. A micro-GC connected in series allowed the quantitative and qualitative analysis of the products. A program was developed in order to control the rig so the system is fully automated. This rig was used to screen a number of powder and formed OCM catalysts.

CSIC-ITQ designed and constructed a reaction system comprising a bench scale fixed-bed reactor and associated analytics. This reaction system has been used for screening ethylene oligomerization catalysts and for evaluating the impact of impurities (CO, CO2, and methane) on the catalytic performance. The reactor was able to operate under a wide range of reaction conditions: T= ambient-600ºC, P= 1-35 bar, and WHSV= 0.1-10 h-1.

RUB has designed and constructed a test bench for kinetic investigations on the challenging OCM reaction. Analytical methods for quantitative determination of all reaction components have been developed. A specific fixed bed reactor has been designed and constructed. Automation allowed tracing catalyst induction during long time experiments. Measurements over aged catalysts enabled collection of reliable kinetic data while varying several process parameters. The test bench yielded data, which served as basis for the development of a micro-kinetic model for the OCM reaction by UGENT.

A reactor set-up for intrinsic kinetics measurement was constructed by UGENT. This set-up has specifically been designed to operate over a very wide range of conditions without running into transport limitations. For this set-up, the main focus was on OCM kinetics measurement. Therefore, the set-up was designed to operate safely at temperatures up to 1173 K and pressures up to 2.0 MPa. Particular attention was paid to the inertness of the reactor material. A high-temperature fluidized sand bath has been employed to ensure the reactor’s optimal isothermal operation. OCM kinetics data sets at higher total pressures, which are unique within OCMOL, have been acquired thanks to this set-up.

A rig was built by CAM comprising of a reactor with a magnetic resonance imaging system. The study of ethylene oligomerization within the OCMOL programme using the high temperature/high pressure MRI compatible reactor has provided the scientific community with the first non-invasive, spatially resolved measurements of chemical speciation and mass transport behaviour at realistic (operando) reactor conditions. Two-dimensional spatial images have shown that liquid products are produced with increasing carbon number towards the exit of the reactor. The analysis of the magnetic resonance spectral data have shown that it has been possible to use this information in conjunction with well-established theories, such as Schulz-Flory, to calculate conversion and selectivity with time-on-stream. In addition, new information, using spatially resolved chemical shift imaging has shown it is possible to apply these theories locally as opposed to globally with time-on-stream. Furthermore, CAM has measured, for the first time, effective diffusion coefficients of the liquid products within the catalysts pellets themselves during reaction; these values can be used directly to: (i) check the validity of micro-kinetic models and: (ii) as starting values for process design and optimisation.

• Micro-kinetic based catalyst design
A general platform for micro-kinetic model based catalyst design has been developed by UGENT. The 3 following elements constituted the crucial support for this platform: detailed reaction networks, thermodynamics and kinetics equations. Detailed reaction networks have been generated for oxygenates to liquids conversion and ethylene oligomerization thanks to the (further) development of the in-house automated reaction network generation tool, i.e. ReNGeP. The thermodynamics for both before-mentioned reactions have been typically obtained by using Bensons’ group additivity method, which is also implemented in an in-house software tool. A dedicated reaction network and corresponding thermodynamics for oxidative coupling of methane has been constructed in a tailor-made manner. The determination of the kinetics equations was based upon the reaction network generated and were generally determined by the law of mass action.

A systematic methodology has been proposed and demonstrated for a simpler benchmark reaction, i.e. n-hexane hydroisomerization. This methodology allowed facilitating the whole procedure for kinetic model construction, its regression to experimental data and the subsequent statistical analysis of the results obtained. The proposed modeling methodology pursued an adequate compromise between statistical significance and physical meaning of the kinetic model and the corresponding parameters and typically results in models of an appropriate complexity. It comprised the following activities: (i) data analysis, aiming at qualitative information on the reaction mechanism and corresponding rate equations, (ii) model regression to quantify this information via optimal parameter values and (iii) validation of the statistical significance and physical meaning of the parameter estimates.

• Catalyst preparation scale-up
IRCE screened a multitude of OCM catalysts formulations and established the peak performing material among the samples tested. Catalyst poisoning by constituents of steel has been observed and model case studies identified an enamel based protective coating as partial solution to the problem.

In Month 6 of the project an OCM standard catalyst (1% Sr/ La2O3) has been selected from literature. After catalyst testing has been carried out it has been decided to change the standard catalyst in M18 (10% La/ 20% Sr/ CaO) of the project. Large batches of each have been produced by JM for use by partners. Forming of these standard catalysts in to an industrially useable state has been carried out. The formed catalysts have been tested on the high-throughput rig to determine their activity as OCM catalysts.

Reforming catalysts have been selected as standard catalysts for the OCMOL project. At M6 a commercial Ni catalyst, HiFUEL 110 has been selected and at M18 a new catalyst containing a precious metal has been chosen. These have been distributed to partners as needed, including samples in the form of pellets. The M18 reforming catalyst has been coated on to platelets for use in the reactor manufactured by IMM.

A standard catalyst for ethylene oligomerization, Ni on silica-alumina, has been selected from literature and kept as the standard ethylene oligomerization catalyst throughout the project. This powder has been subsequently formed by JM for use by partners. In particular, formed catalysts have been tested by CEPSA in the pilot plant and utilized by the University of Cambridge for NMR studies to help to elucidate the ethylene oligomerization mechanism.

Separation Materials Development and Testing
Efforts from IRCE concerned the operation of a thermally coupled microstructured reactor integrating the OCM reaction as heat source and the reforming reaction as heat sink.

ENI assessed options for the numerical modelling of sorption based separation steps. Since a commercial package predicted data in an appropriate way, it has been decided to adopt the latter solution rather than proceeding to internal code development.
Reactor and process
This work package has been centred on the creation of two micro-structured laboratory prototype reactors allowing the combination of the exothermic OCM reaction and endothermic dry reforming reaction at a quasi-auto-thermal regime with staged oxygen dosing.

RUB tested the OCM reaction in a microstructured steel reactor configuration with distributed oxygen supply. The intense drop in OCM performance associated with the use of a steel based reactor has been observed. Therefore, a poisoning study, investigating the impact of different steel components on the OCM reaction has been conducted. It has been shown that Cr has a strong detrimental effect regarding the performance in OCM reaction. Most partial oxidation products (C2H6, C2H4 and CO) were converted to CO2. Cr forms easily volatile oxide species, especially when oxygen is present. Complementary model experiments investigated the OCM catalyst performance in an inert tubular quartz reactor with distributed oxygen supply. The beneficial effect of a distributed oxygen supply has been demonstrated. The challenging task remains the design of a Cr-free microstructured reactor capable of operating at high temperatures.

Two laboratory prototypes have been developed and manufactured by IMM. The first prototype has been realised as a plate-heat-exchanger reactor consisting of 75 plates each having 40 parallel microchannels. The microchannels have been coated with a catalyst for either dry reforming or oxidative coupling of methane by JM and IRCE. In the case of the OCM-part of the prototype, methane and oxygen are separately fed into the reactor. Inside the microchannels, the oxygen is admixed at single stage via small apertures with the methane. For operating the prototype, microstructured pre-heaters have been connected with the reactor inlets allowing it to heat up the feeds up to 850°C. The prototype has been used for the investigation of the thermal coupling of RM and OCM by IRCE.

The second prototype has been employed by RUB to investigate the effect of the staged dosing on the selectivity of OCM. For this purpose, the second prototype consisted of three microstructured plates to carry out the OCM reaction and to dose oxygen into channels at three stages. With regard to the dimensions of the microchannels, the section for the OCM reaction has been derived from the plate-heat-exchanger reactor. The plates comprising the reaction channels have been coated with a protection layer and the OCM catalyst by RUB and IRCE. The microstructured plate used for dosing provides three discrete stages along the reactor allowing it to feed the oxygen into the microchannels via small apertures.

4.1.3.7. Process engineering and economic evaluation
Engineering Concept for Process Steps
Block flow diagrams have been developed for the five process steps by LE:
1. Oxidative coupling of methane
2. Dry methane reforming
3. Separation steps which comprise three different PSA as well as water separation and compression steps.
4. Oxygenates synthesis and Oxygenates to liquids
5. Ethylene oligomerization.

Finally a process simulation has been performed integrating the discrete process steps. The simulation has been done using the standard simulation software UniSim which is available at LE. This simulation has been further developed along the project to reach the most sustainable design considering different aspects such as economic constraints and achieved performances (conversion and selectivity) during the experimental phase of the project.
Economic Evaluation of the Process Steps
The economic study has been based on the calculation of fixed capital investment as well as cost of production defined by the process simulation.

Two cases have been considered by LE:
The first case represented the results obtained during the OCMOL project from the laboratory phase, while the second case represented results which could be possibly achieved with additional R&D efforts.

Both cases showed that the project could be economic. For middle investment and in combination with the production of higher value chemicals like e.g. alpha-olefins, the net present value (NPV) is positive after 8 years.
By producing gasoline, the NPV is also positive after 8 years, but only with reduced investment. This could be achieved with the current performances obtained during the project (case 1) but by suppressing the recovery of ethylene and its further oligomerization.
Finally following recommendations have been made to improve the competitiveness of OCMOL:
• The investment has to be as low as possible by economizing expensive separation steps.
• The production of liquids via methane coupling and ethylene oligomerization has to be very effective in order to compensate the additional capital cost due to the recovery of ethylene and its further oligomerization.
• The process has to be economic at much lower capacities of 100 kt/year, which is currently not possible by using state of the art technologies.
• The product stream should present several alternatives allowing maximum profitability by adapting the outcome (gasoline/diesel fuels and/or petrochemicals) to fluctuations of the market demand.

Life Cycle Assessment
This study by LE has been based on the carbon footprint associated with the OCMOL process. A cradle-to-gate approach has been taken and a partial product life cycle from resource extraction (cradle) to the factory gate (i.e. before it is transported to the consumer) has been performed. The emissions related to the transport and the usage of the final synthetic fuels produced by the OCMOL process, have been considered not to be different from other conventional fuels.
Three impact categories have been identified where the OCMOL process may contribute to the improvement of the environmental impact:
1. Energy consumption
2. Emissions
3. Transportation.
Emissions related to energy consumption from the OCMOL process are inherently low because of its heat integration. Since oxidative coupling is generating heat that can be used for reforming no extra furnace needs to be installed. The only emissions that were related to energy were due to the consumption of electricity.

The OCMOL process has been designed to be CO2 neutral. Apart from fugitive emission no other emissions are expected. CO2 emissions will also be considerably reduced with the recycling of released CO2 from the OCM into the RM step. With a carbon efficiency of 92% obtained so far, the corresponding CO2 emissions have been estimated around between 578 and 606 kg CO2/ton of final product and slightly lower than the value of 823 kg CO2/ton found for a natural gas-to-synthetic diesel process.
The impact of logistics, which depends on the distance between a gas field and the OCMOL plant, is low when the process is build close to the gas field. Gas transport can be avoided and replaced by a much more efficient transport of liquid. It has been estimated that each extra kilometer of gas transport corresponds to 0,1 kg CO2/Ton of final product. Of course it is not always possible to construct an OCMOL plant close to a remote gas field due its deep-sea location or due to extreme climate conditions. In these cases OCMOL still can reduce the carbon footprint when the plant is constructed in the neighbourhood of the nearest gas storage terminal. In all cases the carbon footprint will be lower than bringing the feedstock via pipelines over a large distance to the market.

4.1.3.8. Conclusion

OCMOL aims at the exploitation of small stranded gas (including shale gas) reserves with a capacity of approximately 100 kT/year. Close to zero CO2 emissions and cost efficiency have been the driving force of the RTD developments on process intensification and innovative technologies. These developments allow in turn the construction of small units which could be implemented on scattered sites without transportation issue as the produced liquids will be easily stored and transported under ambient conditions.
The OCMOL process was found to be potentially viable. The cost effectiveness was compared with existing technologies. The milestones related to the competitiveness of the integrated process have been achieved, in particular with respect to CO2 emissions.
Beyond the potential economic advantage, the flexibility offered by the OCMOL process also contributes to its competitiveness, since both gasoline and diesel have been targeted as end products, with a higher quality than conventional liquid fuels. In addition, possible by-products, such as ethylene, -olefins and syngas are high-value feedstocks, adding more flexibility to the project according to local market demands.
The environmental impact of the process has also been significantly reduced mainly via the autothermal coupling of exothermic and endothermic reactions leading to a reduction of the overall energy consumption and the recycling of produced CO2 at every stage of the process. The estimated CO2 emissions have been lower than the reported value for a natural gas-to-synthetic diesel process.
In general, effective progress has been achieved for a number of key aspects of the integrated project. Some expected breakthroughs on other sections were not achieved. These challenges did not jeopardize the interest of the OCMOL concept, but underlined the requirement to continue research and development in this domain with focus on oxidative coupling of methane.
Potential Impact:
4.1.4.1. Strategic impact of the OCMOL project for the European Union

Economic pressure on crude oil makes the synfuel production strategic for the EU
The EU is currently the world’s largest importer of oil and gas. The dependency on raw materials for energy production makes the EU vulnerable to the price variations. This vulnerability has been profoundly proven during the last two years with the dramatic increase of the crude oil price. Due to high price of crude oil and refined petroleum products, nonconventional liquids become more and more interesting to displace petroleum in the traditional supply mix.
Stranded gas reserves represent a great potential unexploited so far

The estimated proven gas reserves are approximately 180 trillion (1012) Nm3. One third of these proven reserves are constituted by stranded gas reserves that remain unexploited because they are economically not attractive due to local market saturation or high exploitation/transportation costs.

A lack of processes adapted to the exploitation of small capacity reservoirs


Nowadays, the main processes used to transform gas into liquids are the Liquefied Natural Gas (LNG) processes and the Gas-to-Liquids (GTL) processes.

• LNG processes bring about a physical transformation of the natural gas into liquefied gas by cooling it down to -163 °C at a pressure of 0.1 MPaG. However LNG processes involve high investments costs for the equipment and the means of transportation when it comes to small capacity reservoirs.

• Gas-to-liquid processes consist of two processes:

 Fischer Tropsch (FT) synthesis, based on the partial oxidation of methane followed by conversion to liquids. Due to high investment costs FT synthesis is not competitive on small reservoirs.

 MTG and TIGAS processes, producing high quality gasoline directly from methanol. These processes require also a quite large capacity to be economically viable.

It can be concluded that neither the LNG nor the GTL processes are suited for the exploitation of small capacity reservoirs. Within this frame, it appears necessary to develop a new concept relevant to the exploitation of stranded gas reservoirs.
OCMOL: a flexible industrial solution for producing high quality fuels from small scattered and/or remote natural gas reservoirs

• A cost-effective and competitive process:

OCMOL targets specifically the exploitation of small stranded gas (including shale gas) reserves, since the process is designed for a capacity in the range of 100kT/year. Close to zero CO2 emissions and cost efficiency have been the driving force of the RTD developments on process intensification and innovative technologies (novel nanostructured materials, intensified reactors and integrated heat exchangers for higher liquids productivity and reduction of energy consumption). These developments allow the construction of relatively small units which could be implemented on various scattered sites without transportation issue as the produced liquids can be easily stored and transported under ambient conditions.

Based on a scaling-out strategy (multiplying the number of small units) rather than a scaling-up strategy (which involves RTD efforts with a lot of uncertainties and investments), the OCMOL process was found to be potentially viable. The contribution of the process engineering companies belonging to the consortium ensured this cost effectiveness by steady comparison with existing technologies and definition of RTD guidelines in accordance with the economic constraints. The milestones related to the final economic evaluation of the integrated process and the validation of its competitiveness were achieved. OCMOL was found to be competitive by producing gasoline but only with reduced investment. This could be achieved by suppressing the recovery of ethylene and its further oligomerization. Another attractive alternative would be to produce pure chemicals; in this case the investment is higher but also the expected revenue, which makes this process more interesting.

Beyond possible economic advantage, the flexibility offered by the OCMOL process in terms of outputs also contributes to its competitiveness. Indeed, both gasoline and diesel are targeted as end products. Moreover, these end-products are expected to have a greater quality than conventional liquid fuels, since natural gas contains lower impurities than crude oil. In addition, by-products such as ethylene, alpha-olefins and syngas are high-value feedstocks for the whole petrochemical industry, adding more flexibility to the project addressing local market demands.

The environmental impact of the process is also significantly reduced mainly via the autothermal coupling of exothermic and endothermic reactions leading to a reduction of the overall energy consumption. Moreover, CO2 emissions were found to be lower with the recycling of produced CO2 at every stage of the process. From the model prediction the optimal carbon efficiency obtained was 92% which corresponds to emissions between 578 and 606 kg CO2/ton of final product. Obtained emissions are slightly lower than the 823 kg CO2/ton published in the literature for a natural gas-to-synthetic diesel process.

CO2 emissions are also minimised due to the avoidance of gas transportation and its replacement by a much more efficient transport of liquid. It has been estimated that each extra kilometer of gas transportation corresponds to 0.1 kg CO2/Ton of final product. Off course it is not always possible to construct an OCMOL plant close to a remote gas field due its deep-sea location or due to extreme climate conditions. In these cases OCMOL still can reduce the carbon footprint when the plant is constructed in the neighborhood of the nearest gas storage terminal. In all cases, the carbon footprint will be lower than bringing the feedstock via pipelines over a large distance to the market.

In general, effective progress was achieved for a number of key aspects of the integrated project. Some expected breakthroughs on other sections like the C2 yield from the OCM reactor were not achieved but were in line with the pre-existing knowledge in the domain. However, these remaining challenges did not jeopardize the overall demonstration of the interest of the OCMOL concept, but underscored the need to continue on this domain under the efficient strategy allowed by the EC support.

4.1.4.2. OCMOL enhances the competitiveness of European stakeholders in strategic industries
Innovative and eco-friendly catalysts (JM): the OCMOL project will be beneficial to JM principally in two ways: firstly it will help the development of low carbon chemical processing technologies and secondly it would allow alternative catalytic alkane/alkene activation technologies to be commercialized. Since the reduction of greenhouse gases is one of JM core environmental targets, the re-use of produced CO2 is significant.

New business on structured reactors (BTS): BTS being active in the field of micro-structured reactors, the development of an integrated reactor (along with ICT-IMM Fraunhofer) for an exo- and endothermic reaction system is a significant product improvement.

New processes for the fuel production (BTS, HTAS, CEPSA): BTS is also involved in the process development and exploitation of alternative resources. As a result, the novel OCM concept will open new business opportunities. The oligomerization process leading to a high quality fuel is significant for CEPSA, leader in activities relating to petroleum and petrochemistry. The innovative OCMOL route for producing gasoline/diesel will bring great benefits and reinforce its position on the fuel market. HTAS is a catalyst and technology company, dedicated to developing novel processes based on the combination of fundamental science and reaction engineering. The development of an integrated syngas-to-oxygenates and oxygenates-to-liquid process and the corresponding manufactured catalysts are closely aligned with HTAS’ current strategy to further expand its business in the synfuels area.

Process integration and turnkey processing units (LE, HTAS, ENI, INEOS): LE is one of the leading design and engineering companies for the construction of air separation, olefins, natural gas and syngas plants worldwide; the outcome of the process integration will bring new innovative technologies to its core businesses and establish their market position as technology leader. Moreover, since ENI’s goal is to address the exploitation of small hydrocarbon fields, it is profoundly interested in the overall integrated process. HTAS has also a strong tradition in process development with particular emphasis on integration and process intensification. Thus, the integration of syngas production and syngas conversion to oxygenates and liquids are among HTAS core competencies. INEOS as global manufacturer of petrochemicals, specialty chemicals and oil products will benefit from the project outcome to make strategic decisions with respect to its process portfolio.

4.1.4.3. OCMOL reinforces the European knowledge base on cutting-edge sciences
Understanding of the behaviour of nanostructured catalysts (IRCE, BIC, UIO, CSIC-ITQ): for IRCE (regarding OCM and RM catalysts), knowledge has been extracted from the screening strategies, in terms of: i) discovery of new formulas adapted to micro-structured coatings and confinements, ii) relationship between catalytic descriptors and intrinsic physicochemical characteristics of the tested materials. BIC has gained further knowledge on i) innovative coating methods and formulas for methane RM, ii) supported asymmetric membranes for oxygen separation. For oxygenates to liquid catalysts (UIO), improved understanding has been gained on the influence of topology and composition of nanostructured catalysts on reaction selectivity, with emphasis on limiting the yield of aromatic compounds and increasing catalyst life-time. Regarding oligomerization catalysts (CSIC-ITQ), understanding has been gained on the following issues: i) influence of the nature of metal/ligand couple on the carbon-range of produced oligomers, ii) influence of nature of ligand on the electronic properties of metal, iii) effect of chemical nature (acid-base characteristic) and porosity of support on the activity/selectivity and stability (leaching) of the anchored organometallic catalyst.

Interfacing of advanced reaction engineering and catalysis (RUB, BIC): The work of RUB targeted on identifying and answering new challenges for catalysis arising from new intensified reactors at the interface of engineering and chemistry. Experiments have confirmed the beneficial effect of staged oxygen supply in terms of significantly improved C2 yields at OCM conditions. This new mode of reactor operation introduced a new challenge of catalyst poisoning by steel constituents, most probably chromium, that needs to be further addressed. BIC has considerably augmented its know-how in the field of membrane reactor technology.
Modelling of catalytic complex behaviour (UGENT, CAM): The use of catalyst descriptors in micro-kinetic models enabled, not only to develop fundamental relationships between catalyst physicochemical properties and performance by structure-activity relationships, but also to define the optimal combination of catalyst properties, process conditions and reactor design. The developed simulation tool necessary for model based catalyst design can be used in a high-throughput (HT) environment. Moreover, the development and application of a unique in-situ characterization technique (MRI) can spark significant progress in this field.

Understanding of advanced separation processes (SINTEF, ENI): The design and screening of a range of novel candidate systems has produced extensive knowledge on : i) routes to novel materials and the understanding of designing hybrid formulations, ii) the correlation of the structure-composition of materials with their performance in separation of complex mixtures, iii) formulation of hybrid systems for applications under realistic testing setups (membranes, PSA units).

Control of coupled reactions in integrated reactor (ICT-IMM Fraunhofer): ICT-IMM Fraunhofer has expanded its significant knowledge in the field of micro-structured reactors in the framework of OCMOL. Regarding the process control of the coupled reactions, knowledge has been increased regarding the coupling of exothermic and endothermic reactions in a single reactor.

4.1.4.4. OCMOL provides significant contributions to the community social objectives
Environmental issues

Currently, low-carbon technologies constitute a rapidly growing international market. Boosting investments in this market is strategic for EU in order to avoid a loss of competitiveness against the US and Japan. OCMOL has tackled this issue through the development and integration of sustainable processing units for natural gas conversion into liquid fuels and petrochemicals. Indeed, the OCMOL project proposes a fully integrated industrial process which is self-sufficient with the re-use and the recycling of CO2 at every stage, leading to near zero CO2 emissions (578 - 606 kg CO2/ton of final product).

Moreover, the end-products of the OCMOL process will exhibit higher quality than that of the conventional processes. Typical impurities originating from crude oil (metals, S and N-based) will be absent or present in negligible amounts, enabling to comply more easily with fuel norms.

Energy savings:

Substantial improvement has been achieved concerning the catalytic activity and stability in specific processes, such as natural gas Dry Reforming (85 % CH4 conversion, 60 h stability at 800 0C) which will help reduce the overall energy needed to manufacture the desired products.
Moreover, energy consumption from the OCMOL process was shown to be inherently low (~1GJ/ton) because of its heat integration. Since oxidative coupling generates heat that can be used for the reforming no extra furnace needs to be installed, resulting in a more efficient heat transfer.
Safety and health

The OCM process was shown experimentally to proceed safely at pressures up to 15 barg. Inflammability issues of CH4/O2 are not critical in the developed confined micro-reactor configuration. Moreover, by means of a staged supply of oxygen into the reaction mixture, the maximum oxygen concentration inside the reactor can be decreased.
Education and training
Apart from the scientific and socio-economic challenges addressed by OCMOL and the knowledge generated, the project has attracted young scientists to join the project, who constitute a potential source of highly trained personnel for European industry as well as for the scientific community. Furthermore 9 internal traineeships and 10 external training courses, addressed to junior and experienced scientists, were organised. Some of these courses will be continued in the future.

4.1.4.5. Dissemination and Exploitation of outputs

Within the frame of the project, an active communication plan was set up to raise awareness of scientists and industrials about the benefits linked to the OCMOL developments. Within this scope, the numerous research outputs produced throughout OCMOL lifetime have been disseminated in peer-reviewed journals and books (36 publications and at least 8 to follow) and at major international scientific events (126 participations of OCMOL partners). A book on GTL technologies will be published soon in collaboration with NEXT-GTL project. OCMOL partners have participated by contributing a chapter relevant to their duties in the framework of OCMOL project. The OCMOL website (www.ocmol.eu) has been continuously updated with the main results of the project and announcements of events, organized by the consortium (congresses, workshops, summer schools…), articles, press releases and other dissemination material (presentations, leaflets, posters, pictures …). A video illustrating the concept and main results of the project can be also found on the OCMOL website as well as on YouTube. The OCMOL website will remain accessible.

OCMOL results can have a strong impact on EU market. Thus, exploitation and protection of outcomes has been a major point of attention during the lifetime of the project. OCMOL consortium has identified 59 potential exploitable results, 3 of which will lead to patent applications. The other 56 results pertaining to software tools, test rigs, kinetic models etc. that have been developed within OCMOL will be exploited in the near future in various ways, i.e. through further internal research and IPR protection, making and selling, licensing or providing services such as consultancy, training etc.

List of Websites:
www.ocmol.eu