Chlorosulfonation of acetanilide was accomplished within 10 min in up to 96% yield via a highly thermoconductive and corrosion-resistant dual-temperature-zone silicon carbide microchannel reactor. The yield of pilot production was up to 92%. In the first stage, low reaction temperature (40℃) was employed to effect a high sulfonation selectivity at the para position of acetanilide. In the second stage, a higher reaction temperature (100℃) led to a faster formation of chlorosulfonation product. To illustrate the application of this reaction, sulfasalazine with antimicrobial and anti-inflammatory activities was synthesized in total yield of 75% via chlorosulfonation, sulfamide formation, hydrolysis under base conditions, diazotization and coupling with salicylic acid. The two-step continuous reaction helped to solve the problems in batch reactor, such as low temperature leading to slow reaction and high temperature resulting byproducts and/or temperature runaway, the safety concern aroused by heat accumulation, and the polution caused by the use of large excess of chlorosulfonic acid in batch production. The above research provides technical support for the large-scale industrial production of p-acetylaminobenzenesulfonyl chloride and its sulfonamides.

Key words: acetanilide, chlorosulfonation, microchannel reactor, intrinsic safety