Search

High-throughput XRD and TGA are used to screen hundreds of candidate Fischer–Tropsch synthesis catalyst samples per month for particle size, reducibility and stability under operating conditions. A series of highly stable catalysts based on Co-Ru-Mg-Al2O3 are identified., Development of heterogeneous catalysts for complex reactions such as Fischer–Tropsch synthesis of fuels is hampered by difficult reaction conditions, slow characterisation techniques such as chemisorption and temperature-programmed reduction and the need for long term stability. High-throughput (HT) methods may help, but their use has until now focused on bespoke micro-reactors for direct measurements of activity and selectivity. These are specific to individual reactions and do not provide more fundamental information on the materials. Here we report using simpler HT characterisation techniques (XRD and TGA) along with ageing under Fischer–Tropsch reaction conditions to provide information analogous to metal surface area, degree of reduction and thousands of hours of stability testing time for hundreds of samples per month. The use of this method allowed the identification of a series of highly stable, high surface area catalysts promoted by Mg and Ru. In an advance over traditional multichannel HT reactors, the chemical and structural information we obtain on the materials allows us to identify the structural effects of the promoters and their effects on the modes of deactivation observed.

© 2016 The Author(s) Published by the Royal Society. All rights reserved.The effectiveness of Mg as a promoter of Co-Ru/γ-Al2O3 Fischer-Tropsch catalysts depends on how and when the Mg is added. When the Mg is impregnated into the support before the Co and Ru addition, some Mg is incorporated into the support in the form of MgxAl2O3+x if the material is calcined at 550°C or 800°C after the impregnation, while the remainder is present as amorphous MgO/MgCO3 phases. After subsequent Co-Ru impregnation MgxCo3-xO4 is formed which decomposes on reduction, leading to Co(0) particles intimately mixed with Mg, as shown by high-resolution transmission electron microscopy. The process of impregnating Co into an Mg-modified support results in dissolution of the amorphous Mg, and it is this Mg which is then incorporated into MgxCo3-xO4. Acid washing or higher temperature calcination after Mg impregnation can remove most of this amorphous Mg, resulting in lower values of x in MgxCo3-xO4. Catalytic testing of these materials reveals that Mg incorporation into the Co oxide phase is severely detrimental to the site-Time yield, while Mg incorporation into the support may provide some enhancement of activity at high temperature.

Selective oxidation of primary carbon-hydrogen bonds with oxygen is of crucial importance for the sustainable exploitation of available feedstocks. To date, heterogeneous catalysts have either shown low activity and/or selectivity or have required activated oxygen donors. We report here that supported gold-palladium (Au-Pd) nanoparticles on carbon or TiO(2) are active for the oxidation of the primary carbon-hydrogen bonds in toluene and related molecules, giving high selectivities to benzyl benzoate under mild solvent-free conditions. Differences between the catalytic activity of the Au-Pd nanoparticles on carbon and TiO(2) supports are rationalized in terms of the particle/support wetting behavior and the availability of exposed corner/edge sites.

Gold catalysis has potential for multiphase oxidation using molecular oxygen but hitherto has been evaluated only in batch autoclaves. The use of continuous flow structured reactors for the oxidation of glycerol under mild conditions using a gold/carbon catalyst is demonstrated. Both monolith and meso-scale structured downflow slurry bubble column designs lead to a significant enhancement in the reaction rate over autoclave studies which is an order of magnitude greater for the gold/carbon coated monolith, and two orders of magnitude for the meso-scale structured downflow slurry bubble column reactor. A change in the reaction products is observed between structured monolith reactor and meso-structured slurry bubble column reactor. The monolith and autoclave data show very high selectivity to glyceric acid, whereas the thin channel slurry bubble column yields approximately equal quantities of dihydroxyacetone and glyceric acid under similar conditions. Since the same batch of catalyst is used for both the autoclave and the meso-scale structured downflow slurry bubble column reactor, the difference in selectivity cannot be attributed to a particle size effect. The difference in selectivity is attributed to enhanced interaction between bubbles and particles from structuring gas-liquid-solid reacting flows in thin channels or capillaries. © 2008 Elsevier B.V. All rights reserved.