The main production processes of ethyl mercaptan (EM) can be divided into traditional methods and emerging technologies. The core differences lie in the selection of raw materials, reaction conditions and environmental protection. The following is a brief description of the main processes:
1. Anhydrous ethanol method
Principle: Using anhydrous ethanol, fuming sulfuric acid and sodium hydrosulfide as raw materials, ethyl mercaptan is generated through multi-step reactions.
Reaction process:
Ethanol reacts with fuming sulfuric acid to generate ethyl sulfuric acid;
Ethyl sulfuric acid is neutralized with sodium carbonate to generate sodium ethyl sulfate;
Sodium ethyl sulfate reacts with sodium hydrosulfide to finally generate ethyl mercaptan.
Features: The process is mature, but the route is long, the yield is low (60%-65%), and it is highly corrosive and has great environmental pressure.
2. Ethyl chloride method
Principle: Ethyl chloride reacts directly with sodium hydrosulfide to generate ethyl mercaptan.
Reaction formula:
C2H5Cl+NaSH→C2H5SH+NaCl
Features: The yield is high (more than 80%), but high-pressure equipment is required, and the source of ethyl chloride is limited, and the labor intensity is high. Representative manufacturer Arkema S.A. of France.
3. Ethanol/ethylene gas phase catalytic method
Principle: Ethanol or ethylene reacts with hydrogen sulfide in the gas phase under the action of a catalyst (such as alumina-loaded tungstic acid) to produce ethyl mercaptan.
Reaction conditions: Normal pressure or low pressure (0.6-3.0 MPa), high temperature (360-380℃), catalysts can improve selectivity and yield (70%-79%).
Features: Raw materials are easily available and can be produced continuously, but hydrogen sulfide is highly toxic and corrosive to equipment.
Representative manufacturer Chevron Phillips Chemical
4. Catalytic hydrogenation (emerging technology)
Principle: Ethanol and hydrogen are directly hydrogenated and sulfided under the action of a catalyst (such as cobalt/nickel oxide) to produce ethyl mercaptan.
Features: Mild reaction conditions (low temperature and low pressure), few by-products, in line with the trend of green production, but industrial applications are still being promoted.
5. Biotransformation (laboratory stage)
Principle: Use microorganisms or enzymes to catalyze the reaction of ethanol and sulfide to produce ethyl mercaptan.
Features: The raw materials are renewable (such as biomass ethanol) and environmentally friendly, but large-scale production has not yet been achieved.
Process comparison and trend
Traditional processes (such as anhydrous ethanol method and ethyl chloride method) are gradually being eliminated due to environmental issues, especially in China where some companies have been shut down.
Gas phase catalytic method and catalytic hydrogenation method have become mainstream due to high efficiency and continuous production, especially suitable for large chemical companies. Bioconversion and membrane separation and purification technologies represent the future direction, but further breakthroughs in technical bottlenecks are needed.
