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Chemical transformation of enzymatic hydrolysis lignin (EHL) with catalytic solvolysis to fuel commodities under mild conditions

Periodic Reporting for period 1 - EHLCATHOL (Chemical transformation of enzymatic hydrolysis lignin (EHL) with catalytic solvolysis to fuel commodities under mild conditions)

Reporting period: 2020-11-01 to 2022-04-30

The EHLCATHOL project, Horizon 2020 H2020-LC-SC3-2018-2019-2020 (BUILDING A LOW-CARBON, CLIMATE RESILIENT FUTURE: SECURE, CLEAN AND EFFICIENT ENERGY), with a topic Chemical transformation of enzymatic hydrolysis lignin (EHL) with catalytic solvolysis to fuel commodities under mild conditions, was designed based on the state-of-the-art of catalytic solvolysis of lignin and the important results of the consortium members obtained in the past decade. Specifically, they were the first to achieve complete conversion of technical lignin to fuel-range precursor molecules. However, they as well as others in follow-up works encountered typical challenges in scaling up this process, such as, recondensation of the monomers during distilling the products, a relatively low lignin-to-solvent ratio in the feed, low reaction rates and yields of desired products. The key to overcome these challenges enroute to commercialization of this promising approach is to build up the needed fundamental knowledge about the underlying chemistry and process steps aimed to optimization towards specific product classes.

The EHLCATHOL project is aimed to boost 2G Advanced Bioethanol Technologies, which utilizes lignocellulose, the material making up the cell wall of land-based plants, to produce fuel-grade ethanol. The solar synthesis of green leaves consumes CO2 and H2O and produces a large amount of lignocellulose, which is a promising feedstock for obtaining renewable fuels and chemicals. Bioethanol production via fermentation of non-edible lignocellulose biomass has been demonstrated at the commercial scale at all continents in the past decade. As such, it is also expected to contribute to the EU’s 2050 carbon neutral renewable fuel goals. Nevertheless, fermentation primarily converts saccharide polymers, i.e. cellulose and hemicellulose, to fuel ethanol, leaving EHL as a waste. Therefore, the profitability of 2G bioethanol plants is hampered by the lack of efficient methods to valorise EHL, i.e. transforming the current waste by-product from which mostly energy is recovered into more valuable products, such as fuel blends. Furthermore, even for energy crops, the amount of lignin in dried biomass can be in the 10-15 wt% range. The mid-to-long term target of the 2G bioethanol technology is to utilize forestry and agricultural residues, which contain lignin in larger amounts, roughly 35-45% in terms of energy content. It can therefore be foreseen that, as the efficiency and scale of the 2G bioethanol technology is improved, the switch of the feed to lignin-rich biomass would make EHL utilization even more demanding.
EHLCATHOL gathers the most promising teams in Europe to carry out the tasks aimed at adding more value to EHL. Prof. Beller and Prof. Rajenahally from the Leibniz-Institut für Katalyse (LIKAT) investigate the key reaction mechanism of the EHL catalytic solvolysis reaction suppressing recondensation reactions of the monomeric reaction products obtained during solvolysis and in consequent separation steps (WP2). Prof. Chen’s team of Norges Teknisk-Naturvitenskapelige Universitet (NTNU) focuses on tuning of different fuel-cuts with suitable C-C coupling, hydrogenation, alkylation and isomerization catalytic tools (WP5). Prof. Dyson of École Polytechnique Fédérale de Lausanne (EPFL) aims to reveal, using operando spectroscopy techniques, the mechanism of the key steps of catalysed solvolysis and solvolysis oil regulation reactions, and the roles of capping agents (WP3). Aalto university (Prof. Li) and Technische Universiteit Eindhoven (Prof. Hensen) teams work on the different aspects of catalyst development, reactor and process configurations of the EHL solvolysis process (WP1&7). Dr. Boot leads the VERTORO team to take care of the reaction at the bench-scale, sample delivery, separation and scale-up (WP4). Dr. Battin-Leclerc, Director of Research of Centre National de la Recherche Scientifique (CNRS) in Nancy, and her team focus on the fuel combustion properties and the related pollutant formation of the refined EHL solvolysis products, and of the separated commodity fuels (WP6). To efficiently implement the EHLCATHOL project, we designed WP8-11 to take care of Exploitation, Dissemination, Communication, Project Management and Ethics issues.

The EHLCATHOL has been successfully implemented during the first 18 months. The major outcomes in this period provide a solid base for achieving the goals of the whole project and indicate that the work formulated in the WPs and associated Tasks are well on track and efficiently going forward towards their individual goals in the form of defined deliverables.
The major scientific and technological outputs and their impacts of this M18 milestone are summarized as follows:

We successfully enhanced the catalytic reaction rate of lignin solvolysuis by developing novel and improved catalysts. Modifications were made in terms of catalyst composition, preparation techniques as well as using novel promoters and supports. We also enhanced the reaction rate and effectively lowered the reaction temperature by using novel solvents compatible with later fuel use and cascade catalysis in the reaction.
Our work on capping and elimination of functional groups of model compounds provides new understanding on the reaction mechanism of both the solvolysis and the upgrading steps. Based on advanced techniques such as operando NMR and FTIR, further understanding about reaction mechanism is obtained with an additional benefit that the use of advanced operando spectroscopy under demanding biomass conversion conditions is now possible. The mechanisms of guaiacol hydrogenation and the capping reaction steps for too reactive functional groups have been investigated in detail; such knowledge is very useful to the design of new solvolysis and upgrading catalysts.
WP4 has established litre-scale catalytic solvolysis and successfully supplied to other WPs samples of solvolysis products in this past period. WP6 has successfully started combustion testing and made a detailed literature survey of the combustion performance of oxygenated aromatic compounds. WP7 explored the possibility of further lowering the reaction temperature and obtained data on the solubility and dissolution of different EHL and other technical lignin samples. WP7 also investigated the feasibility of flow-through reaction and designed a reaction system.

As part of WP8, four EHL producers, spread across the globe from Brazil to India, agreed to join the project Advisory Board (AB). Their participation can be seen as a testament to the importance of the overarching EHLCATHOL objective, which is to generate more value for EHL. The AB members will furthermore be providing EHL samples to the consortium, thereby securing that the project team has sufficient and industrially relevant feedstock to work with. As one of the most important dissemination activities of the project in the past period, we successfully organized a symposium on catalytic solvolysis of lignocellulose during the ACS Spring Meeting & Expo in San Diego in March 2022.

In addition, we have carefully analysed the materialized risks and the mitigation measures in the past 18 months, especially the challenges arisen due to the recent COVID-19 pandemic. The recent political crisis also brings new challenges but may accelerate renewable energy developments.
Chemical transformation of EHL with catalytic solvolysis to fuel commodities under mild conditions