Quantification of the available acid sites in the hydrocracking of nitrogen-containing feedstocks over USY shaped NiMo-catalysts

Abstract

The inhibition of Brønsted acid sites by nitrogen-containing molecules was quantified under industrially relevant hydrocracking conditions. This was achieved by testing bifunctional catalysts based on HUSY zeolite in cyclohexane hydroconversion. For ammonia partial pressures within 0.2-2.8kPa, the percentage of inhibited Brønsted sites was superior to 98% at 623K. Significant reduction in the ammonia content caused rather moderate variations on the number of available sites. Conversely, a temperature raise from 600 to 640K triplicated the vacant Brønsted sites due to the significant endothermicity of ammonia desorption. The inhibiting effect of ammonia can be therefore easily modulated by temperature.