Hydrotreating in petroleum processing

Abstract

Hydrotreating or catalytic hydrogen treating removes objectionable materials from petroleum fractions by selectively reacting these materials with hydrogen in a reactor at relatively high temperatures and at moderate pressures. These objectionable materials include, but are not solely limited to, sulfur, nitrogen, olefins, and aromatics. The lighter distillates, such as naphtha, are generally treated for subsequent processing in catalytic reforming units, and the heavier distillates, ranging from jet fuels to heavy vacuum gas oils, are treated to meet strict product quality specifications or for use as feedstocks elsewhere in the refinery. Hydrotreating is also used for upgrading the quality of atmospheric and vacuum resids by reducing their sulfur and organometallic levels. Hydrotreaters are designed for and run at a variety of conditions depending on many factors such as feed type, desired cycle length, and expected quality of the products. Until about 1980, hydrotreating was a licensed technology being offered by a fairly large number of companies. From 1980 until the end of the last century, hydrotreating catalysts were becoming more commoditized as the formulations were less differentiated among the various suppliers. Many of the product quality specifications are driven by environmental regulations, and these regulations are becoming more stringent every year. With the advent of ultra-lowsulfur fuel regulations ushering in the first decade of the twenty-first century, however, it was required for hydrotreating research and development to deliver quantum improvements in catalyst performance and process technology. This was accomplished in the form of so-called Type II supported transition metal sulfide (TMS) catalysts, unsupported/bulk TMS catalysts, improved bed grading catalysts and stacking strategies, advanced catalyst loading techniques, improved trickle-flow reactor internals designs, and more effective catalyst activation methodologies.