Hydrotretning

Hydrotretning, or hydro-treating, is a catalytic refining process used to remove impurities such as sulfur, nitrogen, and oxygen compounds from hydrocarbon fractions and to saturate unsaturated hydrocarbons. The primary aim is to improve product quality, stability, color and odor, and to prepare feeds for further upgrading or for use as clean fuels.

The process operates by contacting a hydrocarbon feed with hydrogen in the presence of a sulfided catalyst, typically cobalt-molybdenum (Co-Mo) or nickel-molybdenum (Ni-Mo) on an alumina or silica-alumina support. The treatment occurs in one or more fixed-bed reactors at elevated temperature and pressure, usually around 250–450°C and 20–100+ bar. Key reactions include hydrodesulfurization (removal of sulfur as H2S), hydrodenitrogenation (removal of nitrogen as ammonia), and hydrodearomatization (saturation of aromatics). At higher severities, hydrocracking and hydroisomerization may also take place to adjust boiling range and product yields.

Applications and outcomes: Hydrotreating is applied to naphtha, kerosene, diesel and residual oils to meet sulfur specifications and to improve feed quality for downstream processing. The process yields products with lower sulfur and nitrogen contents and with more saturated hydrocarbons, enhancing stability and performance.

Plant and safety considerations: Hydrogen handling and the production of H2S require appropriate equipment and safety measures. Offgas with H2S is treated in acid-gas removal units and sulfur recovery systems. Hydrotreating is distinct from hydrocracking, which adds cracking activity through acidic sites; hydrotreating focuses on impurity removal and saturation with limited cracking.