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[Display omitted] • One-pot citral to menthol transformations over bifunctional Ru/H-Y-80 extrudates. • Long-term experiments in a continuous reactor. • Menthol isomers distribution and Z/E-citral ratio were influenced by Ru size. One-pot transformations of citral were investigated over Ru-catalysts in a batch and a continuous mode over a powder catalyst and extrudates, respectively. Ru/H-Y-80 catalysts were prepared by different impregnation methods to obtain different particle sizes of Ru. The highest yield of isopulegols was 15% and yield of menthols was 3% with stereoselectivity to the desired (±)-menthol isomer of 42% after 5 h over the Ru/H-Y-80 powder catalyst with the smallest metal particles prepared by the incipient wetness impregnation method with six impregnation steps using Ru(NO)(NO 3) 3 as a precursor. This catalyst was synthesized with the Bindzil binder and shaped by extrusion. For comparison, also a catalyst with Ru deposited on the binder was prepared. Addition of 30 wt% Bindzil binder to Ru/H-Y-80 catalyst caused significant catalyst deactivation. Z/E-citral ratio decreased with increasing Ru particle size. Citral conversion and the yield of acyclic hydrogenation products were higher over the powder catalysts containing a mixture of zeolite and binder with a larger distance between the metal and the acid sites, i.e. with Ru deposited on the Bindzil binder. Long-term experiments in the continuous mode revealed comparable catalytic behaviour of both Ru-extrudates with the controlled metal location due to the presence of diffusion regime. The maximum yield of menthols, 6%, with stereoselectivity to the desired (±)-menthol of 73% was obtained during the transient state, below 2 h of time-on-stream. The reuse of Ru/H-Y-80 extrudates was successfully demonstrated. [ABSTRACT FROM AUTHOR]

Although catalyst shaping by extrusion has been industrially applied for decades to suppress the pressure drop, much less emphasis was put on fundamental understanding of extrusion for catalytic pastes and its effect on the properties of the final catalyst bodies. During recent years intensive research efforts have been put on synthesis of extrudates by systematically varying different synthesis parameters, methods of metal modifications, different types of binders and correlating extrudate properties with their performance in several catalytic reactions. The synthesis method of extrudates can have a large impact on properties, relevant for catalysis, including acidity/basicity, the metal location and the particle size as well as textural properties, which can differ from the properties of the corresponding powder catalysts. Furthermore, a binder can interact with the support changing physico-chemical and catalytic properties. The current review summarizes recent developments related to shaping of catalysts by extrusion addressing also such advanced methods to investigate diffusion of liquid reactants inside the extrudates and interconnectivity of pores, as pulse gradient field NMR spectroscopy and fluorescent probe analysis respectively. [Display omitted] • Catalyst shaping by extrusion is reviewed. • Influence of the binder on acidity and catalytic behaviour. • Impact of the metal location in extrudates. [ABSTRACT FROM AUTHOR]