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Cleave and couple: Fully sustainable catalytic conversion of renewable resources to amines

Periodic Reporting for period 5 - CatASus (Cleave and couple: Fully sustainable catalytic conversion of renewable resources to amines)

Période du rapport: 2021-06-01 au 2023-04-30

Amines are ubiquitous in the chemical industry, omnipresent in polymer chemistry, medicinal chemistry or as fine/commodity chemicals. The aim of this interdisciplinary research program was to deliver groundbreaking approaches in catalysis that are necessary to establish an entirely biomass valorization platform to amines.
Lignocellulose is produced in large (~160MT/year) quantities as part of agricultural and forestry waste, (not competing with food), but currently it is not valorized because of its challangeing structure. The development of entirely novel waste-to-value chains has significant environmental and economic benefits overall, whilst also creating revenues for various other stakeholders in the European Bioeconomy.
Importantly, the project identifes fundamentally novel approaches in catalysis - combining valrious fields (homogeneous, heterogeneous, nanoscale catalysis). Focus is devoted to catalysts, relying on cheap, Earth-abundant materials in contrast to methods that use expensive, noble metals that are scarce and will run out in the coming decades. Moreover, the project will seek to bridge fundamental research directly with industrial relevance by identifying concrete building blocks, products which can be valorised and are interesting for industrial partners.
The CatASus project has delivered groundbreaking scientific results related to the catalytic valorization of lignocellulosic biomass to amines. By forging new methods of depolymerization of lignocellulosic biomass to platform chemicals (cleave), and subsequent coupling of these platform chemicals preferantially with amines (couple) we were able to access new sustainable value chains towards bio-based products. For both these key focus areas, specific catalytic methods have been developed.

WP1> Lignin depolymerization: Lignin-first biorefining has emerged as a new enabling method that unlocks the potential of native lignin and delivers high yield and selectivity of aromatic monomers. This project has significantly contrinuted to establihing this new field of biorefining, introducing 2 main methods, namely 'reductive catalytic fractionation' and 'diol assisted fractionation' which relies on stabilization of reactive intermediates during acidolysis. (examples for papers: on RCF: Nature Catalysis, 2018, 1, 82-92; On acidolysis: J. Am. Chem. Soc., 2016,138(28), pp 8900–8911. A perspective paper [Nature Rev Chem, 2020, 4, 311–330].

During the course of research, as proposed in the DOA we have engaged in catalyst development, method development, mechanistic elucidation, model compound studies, lignini studies, and moving entirely to raw lignocellulosic biomass.

WP2> The catalytic valorization of the cellulose fraction proceeded hand-in-hand with lignin chemistry, matching the actual biorefinery approach established. Overall, the project introduced full sustainable biorefinery concepts whereby both the efficient valorization of lignin, cellulose and hemicellulose are targeted. This involved in specific cases the conversion of cellulosics to HMF derivatives, for example towards bio-based polymers [Nature Comm., 2022, 13, 33762022], or the conversion of cellulose to aviation fuels by catalytic depolymerization and C-C coupling reactions [Nature Catalysis 2018, 1, 82].

WP3> The the development of homogeneous /and heterogeneous catalytic methods for diverse N-alkylations of ligncellulose derived platform chemicals was developed. We have identified a range of ho catalytic methods for the direct coupling of amines/and or ammonia with bio-based platfrom chemicals. {Science Advances 2017, 2017, 3 (12), eaao6494], biologically active molecules: [ACS Cent. Sci. 2019, 5, 10, 1707-1716].
Another important research area was to provide specific amines for the production of bio-based polymers. [Chem Catalysis 2021, 1, 7, 1466-1479]

WP4 – This work package deals with the integration of all developed catalytic methods, and placing these into overall biorefinery concepts, which has been accomplished beyond expectations and well-beyond state of the art. Specific products classes, and collaborations with polymer chemist, medicinal chemists, separation chemistry, biological activity testing were established. Original concept: Cleave and couple has been put forward and discussed in talks and perspective articles: [Z. Sun, K. Barta, Chem Commun, 2018, 54, 7725-7745.]

The project results were broadly presented on scientific conferences, and meetings and >30 invited talks and seminars. The PI was appointed Chair of Gordon Conference of Lignin valorization 2022, and the Chair of EuChemSoc Division Green and sustainable chemistry.
Research awards for the work done were: NCCC conference award for early carrer scientist in 2019, the prestigious ACS Sustainable Chemistry and Engineering Lectureship award 2020, Styria innovation award 2021.
The result lead to the successful aquiry of the ERC PoC Grant PURE in 2019, as well as the EIC Transition Grant PureSurf 2021.
The project has unlocked the potential of lignocellulosic biomass for the sustainable production of well-defined bio-based products, ranging from fine chemicals, biologically active compounds, polymers, surfactants and aviation fuels. This was achieved by addressing the two key challanges pertinent to this goals: CLEAVE: efficient depolymerization of lignocellulosic biomass to well-defined platform chemicals and COUPLE: sustainable and waste-free pathways to end products, chiefly amines, crucially important in the chemical industry. Overall sustainable and energy efficient pathways were developed, displaying high atom economy. The progress in each 4 specific work packages exceeded the initial expectations and went well-beyond SOA. The results have been communicated at > 40 intational conferences and the PI has received research awards.

The depolymerization of lignin to well-defined aromatic chemicals was a significant challange, this project has significantly contributed to solving the depolymerization challange by delivering novel well-defined aromatic platform chemicals, relying on the stabilziation of reactive intermediates. Initially, there were no studies addressing the sustainable catalytic conversion of lignocellulosic biomass to amines. This project has forged selective N-alkylation protocols able to directly couple platform chemicals to amines. Hydrogen borrowing methods allow for the direct catalytic conversion of alcohols to amines delivering only water as side-products.

At the beginning of the project there were no specific proposals of bio-based products from lignocellulose, apart from high temperatue conversion to complex mixtures or pyrolysis to pyrolyiss oils leading to biofuels or cellulosic ethanol. In this project we have created new chemical space and have convincingly shown that sustainable pahtywas to new, emerging bio-based products can be proposed and such bio-based products find applicatons in many crucially important industrial segments, such as pharmaceuticals, polymers, surfactants, and alternative biofuels such as aviation fuels. The project progressed this field well-beyond the state of the art, and has established many important breakthougghs that are now internationally recognized as impactful research areas, followed up by many resarch groups internationally.
Towards valuable products from lignin