(149c) Chlorinating Agents Cause Unexpectedly High Corrosion in the Presence of Acetonitrile.

Sulfuryl chloride (SO₂Cl₂) is a liquid reagent that that can be used as an alternative to chlorine gas in chlorination reactions. Chlorination reactions with SO₂Cl₂ are anhydrous due to its high reactivity with water. SO₂Cl₂ diluted in dichloromethane (DCM) was used in a chlorination of an aryl molecule as part of the process development for a specialty chemical intermediate . In order to optimize the reaction kinetics, the effects of temperature, pressure, and solvent were studied in different reactor types. Acetonitrile was used to enhance the solubility of the starting material. Over the course of these studies, severe corrosion was observed in the Hastelloy C276 reactor when the reaction was conducted with SO₂Cl₂ diluted in a mixture of DCM and acetonitrile (MeCN). Interestingly, the corrosion was negligible when acetonitrile was eliminated from the reaction mixture. Following these findings, a systematic coupon study was conducted without the reaction reagents (i.e., with mixtures of chlorinating agent + DCM + MeCN or chlorinating agent + DCM alone) at two different temperatures using eight alloys and five chlorinating agents. The coupon test confirmed the results from the initial experiments, with unexpectedly high corrosion rates (>100 mils per year) being observed across multiple alloys whenever MeCN was included in the mixture. This presentation will provide an overview of our results and discuss the implications for reagent selection and process safety.