hydroprocessing

Hydroprocessing is a family of refinery processes that use hydrogen to upgrade petroleum fractions. It encompasses hydrodesulfurization, hydrodenitrogenation, and hydrodemetallization, which remove sulfur, nitrogen, oxygen, and metals, as well as saturate aromatics to improve stability, cold flow properties, and overall product quality. A related set of operations, hydrocracking, uses hydrogen and bifunctional catalysts to crack heavy feeds into lighter products while saturating and upgrading them.

Catalysts and operation: Hydroprocessing typically relies on sulfide catalysts such as cobalt-molybdenum (Co-Mo) or nickel-molybdenum (Ni-Mo) supported on alumina or silica-alumina. Hydrocracking employs bifunctional catalysts with metal sites for hydrogenation and acid sites for cracking. Conditions are high pressure and temperature, with hydrogen partial pressures ranging from tens to over 100 bar and temperatures roughly 300–450°C, tailored to the specific feed and desired products. Hydrogen is circulated through the reactor to sustain the reaction and capture sulfur as hydrogen sulfide.

Feeds and products: Common feeds include vacuum gas oil, heavy gas oils, and residua. Products typically comprise lighter, more valuable fractions such as naphtha, kerosene, diesel, and jet fuel, with substantially reduced sulfur, nitrogen, and metal contents. HDS lowers sulfur to meet environmental fuel specifications; HDN reduces nitrogen compounds; HDM removes metals that can deactivate downstream catalysts.

Applications and implications: Hydroprocessing is essential for meeting regulatory sulfur limits, improving fuel stability and combustion properties, and enabling downstream upgrading. It requires a reliable hydrogen supply and high-pressure equipment but is central to modern refinery operation. The process also extends to upgrading renewables and bio-oils through hydrotreated pathways.