Mild hydrocracking of vacuum gasoil over NiMo-Beta zeolite catalysts: The role of the location of the NiMo phases and the crystallite size of the zeolite

Mild hydrocracking composite catalysts based on NiMo/gamma-Al2O3-Beta zeolite have been prepared and the influence of the location of the NiMo phases has been studied. A good hydrocracking activity and the highest HDS conversion was found during the hydrocracking of a vacuum gasoil with the composite catalyst where the NiMo is located on the alumina component and then mixed with the zeolite in a proportion of 1: 1 by weight. The crystal size of the beta zeolite had a significative influence on the catalytic behaviour, being better the smaller the crystallite size is. The small crystallite beta-based catalyst displayed a higher hydrocracking activity than conventional USY and silica-alumina-based catalysts, giving a good selectivity towards middle distillates, (C) 1998 Academic Press.