Organonitrogen compounds, even though they occur at low levels, are undesirable because they cause poisoning of downstream catalysts.
HDN is effected as general hydroprocessing, which traditionally focuses on hydrodesulfurization (HDS) because sulfur compounds are even more problematic.
[1] Typical organonitrogen compounds in petroleum include quinolines and porphyrins and their derivatives.
The total nitrogen content is typically less than 1% and the targeted levels are in the ppm range.
In HDN, the organonitrogen compounds are treated at high temperatures with hydrogen in the presence of a catalyst, the net transformation being:[2] The catalysts generally consist of cobalt and nickel as well as molybdenum disulfide or less often tungsten disulfide supported on alumina.