Effect of diffusion factors on the hydrocracking process of vacuum distillates

Abstract

1. It has been shown that with the conduct of the hydrocracking process in fixed and fluidized catalyst beds, there is no significant resistance due to diffusion of the liquid reagents to the catalyst particles; this ensures maintaining the depth of the conversion and of the rate of sulfur removal with a change in the linear velocities, within the limits studied. 2. At small linear velocities of the liquid flow, there is observed incomplete hydrogenation of the decomposition products, as a result of the insufficient access of hydrogen to the active centers of the catalyst. 3. The apparent energy of the conversion reactions in the process of the hydrocracking of vacuum distillates has been determined, and the dependence of the coefficient of utilization of the internal surface of the catalyst on the grain size and on the process conditions has been obtained. 4. Analysis of the effect of diffusion of the reagents in the catalyst particles on the depth of the conversion and on the selectivity permits determining the optimal size of the catalyst particles and, in particular, in carrying out the process in a fixed catalyst bed, recommending a decrease of the grain size to 2–2.5 mm; this permits a decrease in the charge of catalyst by 30–40% while retaining the feed rate of the feedstock and with only a slight increase in the over-all hydraulic resistance of the bed.