Hydrogen Free Selective Hydrogenation: Step Changing Innovation in Catalysis by Gold

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This project sets out the ambitious goal of achieving atom efficiency and enhanced catalytic activity in "hydrogen free" hydrogenation in continuous flow operation. The work brings together two established research groups with expertise in heterogeneous catalyst preparation, characterisation and reaction engineering (Keane, Chemical Engineering, Heriot-Watt University) and catalytic surface science (Baddeley, Chemistry, St. Andrews University). The synergy that results from this collaboration allows innovation with respect to catalyst design and optimisation with the integration of fundamental and in situ surface science measurements into catalyst synthesis/characterisation and testing. Prior work has established ultra-selectivity in nitro- and carbonyl- group reduction over supported Au catalysts. However, reaction rates were appreciably lower than standard non-selective (Pt, Pd and Ni) metal catalysts due to the activation energy barrier for H2 dissociative adsorption on Au. Gold promoted hydrogenation is conducted in excess H2 that remains unreacted, resulting in fundamental process inefficiency and unsustainability. We propose an innovative coupling of catalytic dehydrogenation (as a source of reactive hydrogen) with hydrogenation. Preliminary data provide proof of concept for the coupling of 2-butanol dehydrogenation with furfural hydrogenation (to furfuryl alcohol) over physical mixtures of oxide supported Au and Cu. We have recorded (orders of magnitude) enhanced H2 utilisation in the coupled system and elevated selective hydrogenation rate relative to the single component Au catalyst. Furfural is a biomass derived heterocyclic aldehyde that can serve as a non-petroleum based renewable feedstock. The target furfuryl alcohol product is a high value chemical used to manufacture resins/rubbers/adhesives and as a chemical building block for drug synthesis. Our proposed coupling reaction is step changing and closes the sustainability gap in terms of unreacted hydrogen. As Au in effect 'borrows' hydrogen generated in situ via Cu promoted dehydrogenation, the coupled system circumvents the use of compressed H2, which has important safety implications for large scale chemical production.We have set out to gain a fundamental understanding of coupled dehydrogenation/ hydrogenation through a programme of surface science measurements involving STM, RAIRS, XPS, TPD and DRIFTS analysis that will provide critical information on reactant/product surface interactions. The work will first focus on reaction coupling over supported Au and Cu physical mixtures, addressing sensitivity to metal particle size and electronic character, the role of the metal/support interface, hydrogen spillover, transport and reactivity. The molecular-level mechanistic understanding provided by the surface science methodologies coupled with a determination of the influence of the gas phase species on surface composition (MEIS) will inform synthesis of supported bimetallics (Au-Cu) with a programme of rational catalyst design directed at achieving the catalyst formulation that delivers the optimum hydrogen utilisation efficiency. Collaboration with Syngenta and Sasol Technology UK as industrial partners will ensure that the work delivers real commercial impact. The ultimate deliverable is a catalytic process than can deliver 100% selectivity at elevated rates in the sustainable hydrogen free hydrogenation of renewable furfuran platform reactants.This proposal fits well with the EPSRC shaping capability agenda, notably the "catalysis" theme, underpinning "energy efficiency", "sustainability" and "frontier manufacturing" priorities. Moreover, the work tackles head on the "Dial-a-Molecule-100% Efficient Synthesis" Grand Challenge with a programme of work directed at the "catalytic paradigms for 100% efficient synthesis" theme.