What are the requirements of methanol synthesis catalysts for raw gas purification?

The feed gas must be purified to remove oil, water, dust particles, iron carbonyl, chlorides, and sulfides from it, with the elimination of sulfides being particularly important. Therefore, removal must be carried out inside the synthesis tower; processes such as dust removal, desulfurization, decarburization, and rough refining must be installed before the synthesis unit to remove toxic substances present in the feed gas that could harm the catalysts, thereby ensuring their proper functioning. In particular, sulfides have a very harmful effect on methanol production. The sulfur content in the feed gas should be below 50 mg/kg. Copper-based catalysts have strict requirements regarding sulfur content; the sulfur level in the feed gas must be below 0.06 mg/kg according to the ICI method, and below 0.150 mg/kg according to the Lurgi method. Furthermore, the amount of inert gases (methane, nitrogen, rare gases) in the raw materials should be as low as possible; otherwise, it will reduce the methanol synthesis rate, cause buildup in the synthesis system, increase venting, and result in waste of raw materials!