Hydrocracking catalysts silica-alumina

This work is a contribution to the understanding of the effect of spillover hydrogen in a type of catalyst of considerable industrial importance, namely that composed of transition metal sulfides and amorphous acidic solids. This is typically the case of sulfided CoMo supported on silica-alumina used for mild hydrocracking. 

The acid component of a hydrocracking catalyst can be an amorphous oxide, e.g., a silica-alumina ora zeolite, eg., USY. This component usually serves as a support for the metal compound responsible for the hydrogenation function. The metal compound can be a noble metal, e.g., Pt or Pd, or a mixture of sulfides, e.g., of Ni/Mo, NiAV, or Co/Mo. The relative amounts of the respective compounds have to be thoroughly balanced to achieve an optimum performance. 

In a detailed kinetic study, Sridhar and Ruthven [256], using nickel supported on Kieselghur (58% Ni), alumina (14% and 40% Ni) and silica-alumina (5% Ni), showed that over all four catalysts the rates of both hydrogenation and hydrocracking could be correlated according to the power rate law equation... 

Hydrocracking Pd on zeolite in an amorphous matrix NiMo on silica-alumina, various other dual-function catalysts (adiabatic fixed beds)... 

The acid function of the catalyst is supplied by the support. Among the supports mentioned in the literature are silica-alumina, silica-zirconia, silica-magnesia, alumina-boria, silica-titania, acid-treated clays, acidic metal phosphates, alumina, and other such solid acids. The acidic properties of these amorphous catalysts can be further activated by the addition of small proportions of acidic halides such as HF, BF3, SiFit, and the like (3.). Zeolites such as the faujasites and mordenites are also important supports for hydrocracking catalysts (2). 

Silica-alumina and zeolites are used commercially in hydrocracking catalysts. Ni-Mo on silica-alumina is a better HDN catalyst than Ni-Mo/Al203 and is used in the first reactor of a two-stage hydrocracking process (/). 

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