First-stage hydrocracking: process and catalytic aspects

Abstract

First-stage hydrocracking is a fixed-bed, catalytic process, which is implemented industrially with the prime objective of reducing organonitrogen, organosulfur and organooxygen compounds from the feedstock, and for lowering the aromatics concentration. Additionally, a part of the feedstock may be cracked. The most difficult step is generally the hydrodenitrogenation (HDN) reaction. The essential factors in HDN, and the consequences for other hydrotreating and hydrocracking reactions, are discussed. Considerable attention is paid to inhibition effects of nitrogen compounds. These effects are not only important from a process point of view, but also influence developments of first-stage hydrocracking catalysts. Recent trends in catalysts are reviewed with an emphasis on those showing improved cracking activity compared to conventional NiMo/alumina systems.