Supported CoW bifunctional catalyst with high activity and selectivity for hydrocracking alkane

Abstract

Serial CoW-type hydrocracking catalysts supported on different positions of Y zeolite and Al2O3 are prepared to investigate the influences of diffusivity and distance between acid sites and active metal sites on hydrocracking paraffin. The diffusivities of catalysts increase with the ratios of Vmicro/Vmeso due to the larger pressure differences between the micropores and mesopores, which facilitates the external transfer of reactant from meso-Al2O3 to micro-Y zeolite. It is found that the CoW/Y-A catalyst (CoW loading on Al2O3 mixed with Y zeolite) with the worst dispersion of active metals, lowest proportion of WS2 and weakest acidity presents the highest hydrocracking performance, resulting from its superior diffusivity. The CoW/A-Y catalyst (CoW loading on Y zeolite mixed with Al2O3) shows the highest selectivity of isomerized paraffins due to the far distance between acid sites and active metal sites. It also demonstrates that a better diffusivity of the hydrocracking catalyst decreases the selectivity of the isomerization product. Moreover, a far distance between acid sites and active metal sites reduces the stability of the hydrocracking catalyst. These results provide valuable insight regarding the design of hydrocracking catalysts with high activity and selectivity.