Gaining Molecular Insights into Porous Niobium-based Catalysts for One-pot Biomass Upgrading

As a sustainable source of organic carbon, biomass is playing an increasingly important role in our energy landscape. Lignocellulose, as the main component of woody biomass, is composed of cellulose, hemicellulose, and lignin. The upgrading of renewable lignocellulosic biomass is particularly attractive to bridge future gaps in the supply of chemical fuels and feedstocks. However, due to the complexity of the molecular structure of lignocellulosic biomass, particularly for the lignin portion, and its notorious resistance to chemical transformation, energy-efficient and cost-effective production of liquid fuels and chemical feedstocks from lignocellulose remains a highly challenging task worldwide.

Recently, a family of porous Nb-based catalysts (Ru, Pt or Pd loaded porous NbOPO4 or Nb2O5) have exhibited an outstanding performance for the conversion of lignocellulosic biomass (190 oC, 5 MPa H2, 20 h) and bulk lignin (250 oC, 0.5 MPa H2, 20 h) into alkanes and arenes, respectively, via one-pot reactions. These reactions enable the complete removal of oxygen from biomass to produce liquid hydrocarbons and avoid chemical pre-treatment to the raw biomass materials, thus leading to potential energy savings in the biomass refinery based upon these novel catalysts.

However, to date, little information on the catalytic active site or mechanism is known for these systems and little effort has been devoted to investigating the structural changes of these catalysts upon cycling reactions, where decreased activity/selectivity was often seen. Gaining in-depth understanding on the reaction mechanism and catalysts stability is of fundamental importance for the development of improved catalytic systems.

This proposal will systematically investigate the binding dynamics, activation and conversion of the substrate molecules on the surface of the catalysts by a combination of spectroscopic, crystallographic and computational approaches. In particular, inelastic neutron scattering, a very powerful but rarely used spectroscopic technique, will be applied extensively to gain molecular details on these catalytic upgrading reactions of renewable biomass for the production of liquid fuels and high value aromatic chemicals. More importantly, the stability and details on structural degradation of the catalysts will be studied in situ under flow conditions via time-resolved X-ray crystallography and a range of chemical analytic approaches.

The essential goal of converting biomass (esp. for the cellulose and hemicellulose portion) into liquid hydrocarbon fuels is the complete removal of oxygen through the cleavage of C-O bonds during the one-pot reaction. This project will determine the most stable reaction intermediate/s on the surface of catalysts and the stepwise pathway for the rate-determining steps (esp. for the cleavage of C-O bonds) within the entire conversion. In this way, we will understand the unique feature of these porous Nb-based catalysts in cleaving the C-O bonds to achieve the complete removal of oxygen from the system.

The success of this project will not only gain in-depth understanding of the catalytic mechanism for some highly important but challenging biomass upgrading reactions, but also afford key insights into the design of new catalysts with improved structural stability and catalytic activity. This proposal involves multiple collaborations with Central Facilities and will strengthen the links between neutron scattering and catalysis.

We aim to deliver world-leading research in catalysis and functional materials for energy conversion. The proposed project aims to gain in-depth understanding into the origins of a family of porous Nb-based catalysts for their exceptionally high activity in the catalytic biomass upgrading to produce liquid hydrocarbon fuels and valuable chemical feedstocks. The proposed investigations will deliver fundamental scientific and technological advances to provide improved catalysts and/or catalytic processes to address key industrial challenges in bio-refinery, chemicals, and catalysis sectors, with potential academic, economic and societal impact.

In the short term, this project will deliver world-leading research in porous Nb-based catalysts for bio-refinery, whilst longer-term the delivery of a comprehensive in situ characterisation technique for solid catalysts involving neutron and X-ray scattering will impact across a wide spectrum of heterogeneous catalysis, one of the UK Research Council Grand Challenge. We will work closely with key industry and academic collaborators to identify the commercial opportunities that can be addressed by developing innovative catalytic processes and catalysts. One of the key features of this project is that it will greatly strengthen the links between neutron scattering and catalysis, promoting the application of neutron scattering in a wider range of heterogeneous catalysis for the study of binding dynamics of substrate molecules and their reaction pathways, offering direct benefits to academia working in this field.

For the production of liquid fuels, the replacement of oil-based routes by renewable biomass has huge potential economic advances. This proposal aims to promote the economic benefits on biomass utilisation by developing efficient and effective routes for biomass conversion. This project will afford insights into the design of new catalysts and/or catalytic systems with improved activity, selectivity, and stability. All of these will deliver impact by providing key knowledge into our recently discovered one-pot biomass conversions, thus promoting new catalytic processes leading to improved utilisation of sustainable biomass. These topics lie fully within the "Eight Great Technologies" and will have clear economic and environmental impact. This is because this project contributes new technologies to reduce our reliance on crude oil through efficient biomass conversions to feedstocks and liquid fuels and thus in accord with the UK renewable energy strategy (15% of energy from renewables by 2020). The project will also deliver a well-trained early career researcher with expertise in deep characterisation of catalytic processes available for the broad catalysis community.

In order to maximise the societal impact of our work, we will communicate and engage with the private and public sectors, academia, and the public through a series of activities coordinated by University of Manchester (UoM) and UK Central Facilities. Engagement opportunities with both industry and the general public will be generated by using university business development team and social media. We will aim to generate industrial interest in our research through press releases accompanying key publications to showcase our research. This will be achieved via active communications with journalist (e.g., BBC, Reuters, The Economist), media outlets, Press Offices at various Central Facilities to maximise the public awareness of our research outcomes. The PI has been interviewed by journalists from BBC, TheEngineer and the Economist for the research outputs in porous materials. We will use the existing extensive programme of outreach, schools and public engagement activities currently undertaken at the UoM/Diamond/ISIS to further raise public awareness of our research.