Germany-based chemical company Grillo-Werke has successfully functionalized methane to high-purity methanesulfonic acid (MSA) by direct sulfonation of methane with sulfur trioxide. Start of large-scale production is planned for 2019.
Methanesulfonic acid is a strong acid that is not oxidative; it is readily biodegradable and toxicologically unproblematic. MSA is used in electroplating (as an environmentally friendly alternative to other acid electrolytes used in plating processes); electronics; electrochemical; industrial cleaning; and pharmaceutical applications. It can also be used as a catalyst to accelerate the esterification process.
|MSA applications. Source: BASF. Click to enlarge.|
Grillo solved the challenge of methane’s limited reactivity using a tailored reaction environment and specific activators. The process has been continuously optimized and now achieves almost full conversion at mild reaction conditions, the company said.
Grillo says that the Grillo-Methane-Sulfonation (GMS) process is highly cost-competitive. It is based on natural gas and sulfur trioxide (SO3) as feedstocks and is free of environmentally problematic intermediate and by-products.
Background. Development of commercial production of C1 through to C4 alkanesulfonic acids—including MSA—came out of work in the 1940s at Standard Oil of Indiana. The original method used an initial NOx-catalyzed air oxidation of an alkyl mercaptan (an organic sulfur compound composed of an alkyl group and a thiol group) followed by a secondary stripping procedure which removed residual NOx from the sulfonic acid product.
A strong market for the acids did not develop until the early 1980s, as major electronic components producers began using MSA as an electrolyte for Sn/Pb solder electroplating.
Air oxidation of mercaptans is inexpensive, but suffers from several practical problems including poor product quality and the potential for explosions. A practical short-chain alkanesulfonic acid preparation was developed by Pennwalt Corporation in 1967, using the direct chlorine oxidation of an aqueous emulsion of a mercaptan. Other approaches used anodic oxidation of mercaptans and/or disulfides, but with problematic economics.
BASF has become BASF the world’s leading manufacturer of methanesulfonic acid, which is marketed world-wide under the Lutropur trademark, with a total capacity of 30,000 tonnes per year.
BASF produces its methanesulfonic acid via a proprietary continuous process that does not employ chlorine and which yields a product with very high purity.
Michael D. Gernon, Min Wu, Thomas Buszta and Patrick Janney (1999) “Environmental benefits of methanesulfonic acid. Comparative properties and advantages” Green Chem., 1, 127-140 doi: 10.1039/A900157C