UK Catalysis Hub 2024 publication highlights

We have put together a list of publication highlights from 2024 to provide inspiring reading for those long journeys this holiday season.

The effect of pore structure on the local and nanoscale mobility of anisole and guaiacol in commercial zeolite catalysts

PhD student Katie Morton and members of the UK Catalysis Hub, ISIS Neutron and Muon Source and ILL – Institut Laue Langevin have collaborated in work studying the diffusion of lignin derivatives within various zeolite catalysts. By combining Neutron Scattering experiments with Molecular Dynamics simulations, they highlight the importance of studying diffusion across different length/time scales.

Read the full article at https://doi.org/10.1016/j.micromeso.2024.113388

 

 Elucidating the effect of nanocube support morphology on the hydrogenolysis of polypropylene over Ni/CeO2 catalysts

UK Catalysis Hub member Donald Inns has a new paper published. The catalytic hydrogenolysis process offers the selective production of high-value liquid alkanes from waste polymers. Herein, through normalisation of Ni structure, Ni mass and density, and CeO2 crystallite size, the importance of CeO2nanocube morphology in the hydrogenolysis of polypropylene (Mw = 12 000 g mol−1; Mn = 5000 g mol−1) over Ni/CeO2catalysts was determined. High liquid productivities (65.9–70.9 gliquid gNi−1 h−1) and low methane yields (10%) were achieved over two different Ni/CeO2 catalysts after 16 h reaction due to the high activity and internal scission selectivity of the supported ultrafine Ni particles (<1.3 nm). However, the Ni/CeO2 nanocube catalyst exhibited higher C–C scission rates (838.1 mmol gNi−1 h−1) than a standard benchmark mixed shape Ni/CeO2 catalyst (480.3 mmol gNi−1h−1) and represents a 75% increase in depolymerisation activity. This led to shorter hydrocarbon chains achieved by the nanocube catalyst (Mw = 2786 g mol−1; Mn = 1442 g mol−1) when compared to the mixed shape catalyst (Mw = 4599 g mol−1; Mn = 2530 g mol−1). The enhanced C–C scission rate of the nanocube catalyst was determined to arise from a combination of improved H-storage and favourable basic properties, with higher weak basic site density key to facilitate a greater degree of hydrocarbon chain adsorption.

Read the full article at https://doi.org/10.1039/D4TA08111K

 

Metallic sealants increase flux and change selectivity in supported molten-salt membranes

UK Catalysis Hub member Dr Greg Alexander Mutch and collaborators from Newcastle University have had their work published in a new paper in Reaction Chemistry & Engineering. Metallic sealants are widely used with high-temperature membranes. Here we show that their use in supported molten-salt membranes results in order-of-magnitude differences in CO2 flux and introduces O2 co-permeation. The ‘short-circuiting’ effect they introduce has important implications for the design of future experiments, and the interpretation of past work.

Read the full article at https://doi.org/10.1039/D4RE00449C

 

Quantifying CO2 Insertion Equilibria for Low-Pressure Propene Oxide and Carbon Dioxide Ring Opening Copolymerization Catalysts

DPhil Student Katharina Eisenhardt and collaborators from University of Oxford have had their work published in Journal of the American Chemical Society. While outstanding catalysts are known for the ring-opening copolymerization (ROCOP) of CO2 and propene oxide (PO), few are reported at low CO2 pressure. Here, a new series of Co(III)M(I) heterodinuclear catalysts are compared. The Co(III)K(I) complex shows the best activity (TOF = 1728 h–1) and selectivity (>90% polymer, >99% CO2) and is highly effective at low pressures (<10 bar). CO2 insertion is a prerate determining chemical equilibrium step. At low pressures, the concentration of the active catalyst depends on CO2pressure; above 12 bar, its concentration is saturated, and rates are independent of pressure, allowing the equilibrium constant to be quantified for the first time (Keq = 1.27 M–1). A unified rate law, applicable under all operating conditions, is presented. As proof of potential, published data for leading literature catalysts are reinterpreted and the CO2 equilibrium constants estimated, showing that this unified rate law applies to other systems.

Read the full article at https://doi.org/10.1021/jacs.3c13959

 

Nanostructured Solid/Liquid Acid Catalysts for Glycerol Esterification: The Key to Convert Liability into Assets

Researchers from Queen’s University Belfast and members of the UK Catalysis Hub have published a perspective article on the application of nanostructured solid/liquid acid catalysts for upgrading glycerol to glycerol esters. In the present scenario of increasing energy demand and current climate emergency, biorefinery concept has great potential to contribute towards low carbon clean energy for liquid transportation fuels suitable for use in heavy engines such as farm machinery, trucks, and marine shipping sector. However, a major problem associated with biodiesel production is glycerol by-product, which is a liability for biorefinery industry. This perspective article explores the challenges and opportunities in upgrading glycerol to glycerol esters, high energy density biofuel additives. Thus, converting liability into assets by converting glycerol into drop in fuel additives for blending back into the biofuels pool reinforcing the principles of circular economy. The homogeneous catalysts reviewed include mineral acids and Brønsted acidic ionic liquids. The heterogeneous catalysts include solid acid catalysts such as metal oxides, ion-exchange resins, zeolites, and supported heteropoly acid-based catalysts. The techno-economic analysis has shown the process to be highly profitable, confirming the viability of glycerol esterification as a potential tool for economic value addition to the biorefinery industry.

Read the full article at https://doi.org/10.3390/nano14070615

 

Water co-catalysis in aerobic olefin epoxidation mediated by ruthenium oxo complexes

UK Catalysis Hub member Dr Qun Cao and collaborators from Queen’s University Belfast, University of Bath and Technische Universität Darmstadt have had their work published in Chemical Science journal. We report the development of a versatile Ru-porphyrin catalyst system which performs the aerobic epoxidation of aromatic and aliphatic (internal) alkenes under mild conditions, with product yields of up to 95% and turnover numbers (TON) up to 300. Water is shown to play a crucial role in the reaction, significantly increasing catalyst efficiency and substrate scope. Detailed mechanistic investigations employing both computational studies and a range of experimental techniques revealed that water activates the RuVI di-oxo complex for alkene epoxidation viahydrogen bonding, stabilises the RuIV mono-oxo intermediate, and is involved in the regeneration of the RuVI di-oxo complex leading to oxygen atom exchange. Distinct kinetics are obtained in the presence of water, and side reactions involved in catalyst deactivation have been identified.

Read the full article at https://doi.org/10.1039/D3SC05516G