DEMERUS: Mercaptan removal technologies
(Demerus) was developed by the Scientific and Technical Center «AhmadullinS» in the 90s of the XX century to solve multifaceted problems of mercaptan removal – demercaptanization of natural gas, liquefied hydrocarbon gases, gasoline, kerosene and diesel fractions, gas condensates and light oils. A feature of the proposed technology is the use of a heterogeneous polymer-based phthalocyanine catalyst.
Demercaptanization is the process of removing mercaptans (mercaptan sulfur) from hydrocarbon fractions. For the purification of liquefied hydrocarbon gases (LHG) from mercaptans, alkaline extractive demercaptanization is mainly used, followed by catalytic alkali regeneration. In this case, along with the removal of mercaptans, desulfurization of LPG is carried out.
For the kerosene fraction, the process can be alkaline, but in this case it proceeds directly in a hydrocarbon medium in the presence of a phthalocyanine catalyst, air oxygen and alkali. Removal of mercaptans occurs due to the oxidation of corrosive mercaptans present in kerosene to inert disulfides:
2RSH + 0,5 O2 → RSSR + H2O
Catalytic oxidative demercaptanization is a deodorization process, i. odor removal without changing the total sulfur content in the fraction.
To purify kerosene from mercaptans, a hydrotreatment process is often used, while sulfur compounds, including mercaptans, at high temperature, in the presence of a nickel-molybdenum catalyst and hydrogen, are converted into hydrogen sulfide and sent to the Klaus plant for the oxidation of hydrogen sulfide to elemental sulfur. In the process of hydrotreating kerosene, demercaptanization is accompanied by the removal of sulfur compounds. Purification of gas condensates and light oils is mainly carried out according to the technology of alkaline purification of LPG. The main goal in this case is the removal of corrosive methyl and ethyl mercaptans to prepare gas condensates and light oils for transportation.
Removal of mercaptans – purification of natural (DEMERUS NG process) and liquefied (DEMERUS LPG process) hydrocarbon gases is carried out by extraction with an alkaline solution of mercaptans contained in the raw material to be purified, followed by alkali regeneration in the presence of a heterogeneous KSM catalyst. If carbonyl sulfide (COS) is present in the raw material, the demercaptanization unit is preceded by a regenerative diethanolamine purification unit from COS (DEMERUS LPG+COS technology).
The demercaptanization of the gasoline fraction (DEMERUS NAPHTHA process) is carried out by the method of alkaline oxidative demercaptanization in the presence of a heterogeneous KSM catalyst.
The technology for removing mercaptans from the kerosene fraction (the DEMERUS JET process), used to produce top quality aviation kerosene and white spirit deodorization, is based on alkaline oxidative demercaptanization.
Purification of gas condensates (DEMERUS GASCOND process), used exclusively for their preparation for transportation, is based on extractive alkaline purification of mercaptans with the release of disulfide oil.