Final Report Summary - FUSION (FUndamental studies of tranSport in Inorganic Nanostructures)
'Fundamental studies of transport in inorganic nanostructures (Fusion) represents a problem-based approach to the development of ultra-high performance, high temperature, gas separation materials based on newly emerging porous, inorganic materials, associated fabrication processes and, in a key way, fundamental molecular-level phenomena.
In this latter case, very important theoretical advances made in laboratories associated with this project have provided insights into the controlling, molecular-level phenomena important in ultra-thin, nano-porous, inorganic material (NPIM) performance. To fully and rapidly exploit these and other fundamental advancements, there exists a need to develop a framework for the design and performance testing of porous inorganic membranes for selected gas separations.
To leverage the maximum impact of these new discoveries and developments for ultra-thin NPIMs, major gas separation challenges were taken as case studies for investigation, including the high temperature separation of CO2 / air, SOx / air, NOx / air, O2 / N2 and H2 / CH4 gas mixtures. Taking the case of the separation of CO2 / air as an example, the successful removal of CO2 from gas streams has, not only, huge commercial implications in the production of a purified CO2 gas stream as a product or raw material, but it necessarily has very significant environmental ramifications, particularly in the light of EU obligations under the Kyoto Protocol.
The core science and technology objectives of this project can be summarised as follows:
- General: to provide a coherent picture of the molecular mechanisms controlling the structure and function of novel, ultra-thin (around 10 nm), nanoporous, inorganic materials.
- Particular: the application of controlled-structure, ultra-thin, nano-porous inorganic materials (in either membrane or coated powder form) to high temperature (500-1,000 K) gas separation activities of major importance, i.e. the high temperature separation of CO2 / air, SOx / air, NOx / air, and H2 / CH4 gases.
The materials chosen for such high temperature applications are amorphous metal oxides (AMOs), structured mesoporous silicas (SMSs) and zeolites, chosen by virtue of their unique high temperature resilience, amenability to thin film processing and the promise of nano-structure architecture control. More specifically, these objectives can be described as follows:
- the development of simulation tools for the accurate modelling of the high temperature gas sorption and transport properties of ultra-thin NPIMs;
- the development of experimental techniques for measuring the gas separation performance of ultra-thin NPIMs;
- the development and application of experimental in-situ characterisation procedures to determine the stability of these novel material forms to extended operation;
- the assessment of the performance of these novel material forms under 'real' process and economic constraints;
- the development of simulation tools for the accurate modelling of the high temperature gas sorption and transport properties of ultra-thin NPIMs;
- the development of experimental techniques for measuring the gas separation performance of ultra-thin NPIMs;
- the development and application of experimental in-situ characterisation procedures to determine the stability of these novel material forms to extended operation;
- the assessment of the performance of these novel material forms under 'real' process and economic constraints.
The state-of-the-art is under constant review as part of this project. In light of this, it is clear that the core objectives of the project still represent a clear scientific and technological advancement. It is clear from the literature that high temperature gas separation remains a key challenge, particularly for the separation of molecular species very similar in size (CO2/N2, for example, which have kinetic diameters of 3.3 Å/3.64 Å, respectively) where molecular size, and not sorption effects, is key for separation. The theoretical developments that underpin this work provide an alternative means to this end, whereby non-percolating effects for ultra-thin nano-porous membranes leverage significantly small molecular size differences.
Scientific achievements and results
As a result of the work performed during this project, the following scientific achievements may be highlighted:
1. The development of computational routines for the simulation of supported membrane synthesis via CVD:
a. A novel technique has been developed for the simulation of the formation of boro-silicate glass extendable to the modelling of other etched amorphous metal oxides.
b. A novel kinetic Monte Carloroutine has been developed which replicates the experimental synthesis method of CVD for Si(OH)4 and TEOS. This can be easily extended to other precursor agents.
2. The development of routines for the modelling of the synthesis of MCM-based materials including functionalisation:
a. Techniques have been developed which can mimic the synthesis routes for a variety of MCM materials
b. Techniques have been developed for the surface functionalisation of MCM-based materials, thus allowing the rapid testing of these materials for CO2 and other gas capture technologies.
3. The development of molecular models for ZSM-5 zeolites, including accounting for the presence of different ions in zeolite cages.
4. A number of techniques have been tested for their application in the preparation of nano-thin selective layers of amorphous metal oxides for high temperature gas separation:
a. Physical vapour deposition (PVD) in the form of magnetron sputtering proved inadequate for membrane formation, producing layers of too high a density and low integrity.
b. Atmospheric pressure plasma liquid deposition (APPLD) provided for smooth coatings, well controlled thickness and several optimisation parameters for membrane development.
5. A suite of characterisation routines have been developed specifically for the characterisation of porous, nano-thin layers deposited via a variety of techniques. These include a novel AFM-masking technique for determining coating thicknesses, and surface roughness, SEM and FIB for determining surface and cross-sectional structure and refractive index techniques for determining density.
7. A methodology has been devised for the high-through-put screening of functionalised MCM-based materials for gas adsorption properties:
a. Multiple functionalisations have been tested for CO2 adsorption.
b. A number of candidates have been identified for future developmental work, including experiment, for pressure-swing applications.
8. A specially constructed rig has been developed for the testing of planar, membrane geometries at a variety of temperatures and pressures. This includes:
a. a membrane testing apparatus
b. a specially design membrane holder.
9. Over 500 membrane tests have been conducted on membranes prepared by both PVD and APPLD techniques:
a. Optimised APPLD deposition conditions have been established for the synthesis of high quality membranes.
b. Selectivities of 8:1 for CO2 / N2 and 100:1 for He / N2 at 673 K have been achieved. Currently, no technology is able to achieve this degree of separation at this elevated temperature.
Conclusion
The Fusion project represented an ambitious endeavour aiming to advance the technology for high temperature CO2 capture through membrane technology.
Substantial advancement has been made in the development of techniques for the manufacture of membranes currently representing the state-of-the-art in CO2 / N2 elevated temperature capture (8:1 at 673 K). Researchers were confident the this can be substantially improved upon with further modification to deposition equipment and process optimisation. Indeed, theoretical predictions suggest that an order or magnitude improvement is possible.
A second significant achievement is the development of software tools and techniques for the molecular modelling of deposited layer synthesis (amorphous metal oxides) of membranes (as mentioned above) and the synthesis of functionalised MCM-based materials. Together with techniques applied for modelling sorption and transport properties in these model materials, a suite is now available for the rapid testing of a wide variety of material modification, speeding up the discovery and ultimately the implementation of successful capture technologies.
In this latter case, very important theoretical advances made in laboratories associated with this project have provided insights into the controlling, molecular-level phenomena important in ultra-thin, nano-porous, inorganic material (NPIM) performance. To fully and rapidly exploit these and other fundamental advancements, there exists a need to develop a framework for the design and performance testing of porous inorganic membranes for selected gas separations.
To leverage the maximum impact of these new discoveries and developments for ultra-thin NPIMs, major gas separation challenges were taken as case studies for investigation, including the high temperature separation of CO2 / air, SOx / air, NOx / air, O2 / N2 and H2 / CH4 gas mixtures. Taking the case of the separation of CO2 / air as an example, the successful removal of CO2 from gas streams has, not only, huge commercial implications in the production of a purified CO2 gas stream as a product or raw material, but it necessarily has very significant environmental ramifications, particularly in the light of EU obligations under the Kyoto Protocol.
The core science and technology objectives of this project can be summarised as follows:
- General: to provide a coherent picture of the molecular mechanisms controlling the structure and function of novel, ultra-thin (around 10 nm), nanoporous, inorganic materials.
- Particular: the application of controlled-structure, ultra-thin, nano-porous inorganic materials (in either membrane or coated powder form) to high temperature (500-1,000 K) gas separation activities of major importance, i.e. the high temperature separation of CO2 / air, SOx / air, NOx / air, and H2 / CH4 gases.
The materials chosen for such high temperature applications are amorphous metal oxides (AMOs), structured mesoporous silicas (SMSs) and zeolites, chosen by virtue of their unique high temperature resilience, amenability to thin film processing and the promise of nano-structure architecture control. More specifically, these objectives can be described as follows:
- the development of simulation tools for the accurate modelling of the high temperature gas sorption and transport properties of ultra-thin NPIMs;
- the development of experimental techniques for measuring the gas separation performance of ultra-thin NPIMs;
- the development and application of experimental in-situ characterisation procedures to determine the stability of these novel material forms to extended operation;
- the assessment of the performance of these novel material forms under 'real' process and economic constraints;
- the development of simulation tools for the accurate modelling of the high temperature gas sorption and transport properties of ultra-thin NPIMs;
- the development of experimental techniques for measuring the gas separation performance of ultra-thin NPIMs;
- the development and application of experimental in-situ characterisation procedures to determine the stability of these novel material forms to extended operation;
- the assessment of the performance of these novel material forms under 'real' process and economic constraints.
The state-of-the-art is under constant review as part of this project. In light of this, it is clear that the core objectives of the project still represent a clear scientific and technological advancement. It is clear from the literature that high temperature gas separation remains a key challenge, particularly for the separation of molecular species very similar in size (CO2/N2, for example, which have kinetic diameters of 3.3 Å/3.64 Å, respectively) where molecular size, and not sorption effects, is key for separation. The theoretical developments that underpin this work provide an alternative means to this end, whereby non-percolating effects for ultra-thin nano-porous membranes leverage significantly small molecular size differences.
Scientific achievements and results
As a result of the work performed during this project, the following scientific achievements may be highlighted:
1. The development of computational routines for the simulation of supported membrane synthesis via CVD:
a. A novel technique has been developed for the simulation of the formation of boro-silicate glass extendable to the modelling of other etched amorphous metal oxides.
b. A novel kinetic Monte Carloroutine has been developed which replicates the experimental synthesis method of CVD for Si(OH)4 and TEOS. This can be easily extended to other precursor agents.
2. The development of routines for the modelling of the synthesis of MCM-based materials including functionalisation:
a. Techniques have been developed which can mimic the synthesis routes for a variety of MCM materials
b. Techniques have been developed for the surface functionalisation of MCM-based materials, thus allowing the rapid testing of these materials for CO2 and other gas capture technologies.
3. The development of molecular models for ZSM-5 zeolites, including accounting for the presence of different ions in zeolite cages.
4. A number of techniques have been tested for their application in the preparation of nano-thin selective layers of amorphous metal oxides for high temperature gas separation:
a. Physical vapour deposition (PVD) in the form of magnetron sputtering proved inadequate for membrane formation, producing layers of too high a density and low integrity.
b. Atmospheric pressure plasma liquid deposition (APPLD) provided for smooth coatings, well controlled thickness and several optimisation parameters for membrane development.
5. A suite of characterisation routines have been developed specifically for the characterisation of porous, nano-thin layers deposited via a variety of techniques. These include a novel AFM-masking technique for determining coating thicknesses, and surface roughness, SEM and FIB for determining surface and cross-sectional structure and refractive index techniques for determining density.
7. A methodology has been devised for the high-through-put screening of functionalised MCM-based materials for gas adsorption properties:
a. Multiple functionalisations have been tested for CO2 adsorption.
b. A number of candidates have been identified for future developmental work, including experiment, for pressure-swing applications.
8. A specially constructed rig has been developed for the testing of planar, membrane geometries at a variety of temperatures and pressures. This includes:
a. a membrane testing apparatus
b. a specially design membrane holder.
9. Over 500 membrane tests have been conducted on membranes prepared by both PVD and APPLD techniques:
a. Optimised APPLD deposition conditions have been established for the synthesis of high quality membranes.
b. Selectivities of 8:1 for CO2 / N2 and 100:1 for He / N2 at 673 K have been achieved. Currently, no technology is able to achieve this degree of separation at this elevated temperature.
Conclusion
The Fusion project represented an ambitious endeavour aiming to advance the technology for high temperature CO2 capture through membrane technology.
Substantial advancement has been made in the development of techniques for the manufacture of membranes currently representing the state-of-the-art in CO2 / N2 elevated temperature capture (8:1 at 673 K). Researchers were confident the this can be substantially improved upon with further modification to deposition equipment and process optimisation. Indeed, theoretical predictions suggest that an order or magnitude improvement is possible.
A second significant achievement is the development of software tools and techniques for the molecular modelling of deposited layer synthesis (amorphous metal oxides) of membranes (as mentioned above) and the synthesis of functionalised MCM-based materials. Together with techniques applied for modelling sorption and transport properties in these model materials, a suite is now available for the rapid testing of a wide variety of material modification, speeding up the discovery and ultimately the implementation of successful capture technologies.
