Diesel Hydrotreating Process

Diesel hydrotreating (DHT) or catalytic hydrogen treating is mainly to reduce undesirable species from straight-run diesel fraction by selectively reacting these species with hydrogen in a reactor at elevated temperatures and at moderate pressures. With the advent of ultra-low-sulfur fuel regulations ushering in the first decade of the twenty-first century, however, it was required for hydrotreating (HDT) research and development to deliver quantum improvements in catalyst performance and process technology. In order to successfully produce ultra-low-sulfur diesel (ULSD), essentially all of the organo-sulfur species must be removed including the substituted dibenzothiophenes (DBTs) and other refractory sulfur species. Multiple reactions occur in parallel on the HDT catalyst surface including hydrodesulfurization (HDS), hydrodenitrogenation (HDN), and aromatic saturation/hydrogenation (HDA). Feeds for DHT unit typically have a nominal distillation range of 300-700 °F. Different process design and flow schemes can be employed for DHT depending on the process objectives and characteristics of the feed being processed.