Combined solid base/hydrogenation catalysts for industrial condensation reactions

Solid base catalysts of the type Na/SiO2 have been developed for the fixed-bed vapour-phase aldol condensation of aldehydes (n-butanal and n-hexanal) which can run continuously at high activity (n-butanal maximum conversion 58%) and selectivity. These industrially significant reactions can be also be combined with hydrogenation steps using either a single bed or dual bed system. Using a Pd/Na/SiO2 catalyst the saturated aldehyde product can be selectively produced over a single bed without hydrogenating the original feedstream. The Pd/Na/SiO2 catalyst has a higher initial conversion (82%) than the Na/SiO2 catalyst but deactivates more rapidly. A dual bed system using a conventional CuO/ZnO hydrogenation catalyst can be used to produce a mixed stream of alcohols. (C) 2002 Elsevier Science B.V. All rights reserved.