Elements of Two-Stage Unicracking for Maximum Distillate Production

Diesel fuel is projected to be one of the strongest market growth transportation fuels over the next ten years. Availability of more heavy and sour crudes, utilization of refinery configurations for maximum distillate production and more stringent diesel fuel specifications are techno-economic drivers for desiring a hydrocracking process that selectively produces high-quality distillate from tough feeds. UOP's Enhanced Two-Stage Unicracking process is such a hydrocracking process because of the process and catalyst design considerations that are incorporated in its development. The flow scheme and process elements of the Enhanced Two-Stage Unicracking process for maximum diesel production will be discussed. The key factors in producing maximum diesel yields such as choice of first-stage catalyst systems, second-stage catalyst design, sensitivity of diesel yield to contaminants in the second-stage reaction environment, and optimization between first-stage and second-stage conversion and conversion-per-pass are elucidated. The importance of Two-Stage Unicracking in a refinery for diesel production and the enablers for high selectivity to diesel from conversion of difficult feeds with this technology are revealed.