PNNL

Abstract

The gas-phase hydrolysis of thionyl chloride (SOCl2) has been investigated at 297 K and 309 K in a mixing chamber using FTIR spectroscopy. Reagent concentrations of ~80 ppmv SOCl2 at 1, 18, 45 and 63% relative humidity (RH) were studied at 309 K, while humidities of ~3, 6, 10, 12, 18, 34, 48, 68 and 85% were used in the 297 K studies, all at a total pressure of ~1 atm in synthetic air. In each experiment, an aliquot of SOCl2(g) was rapidly introduced into a chamber at fixed RH, quickly reaching a maximum and then decreasing exponentially as monitored by time-resolved infrared spectroscopy. The only observed reaction products were HCl(g) and SO2(g) which were formed in a molar ratio of ~2:1. The exponential SOCl2 decay curves directly showed the reaction to be first order in SOCl2, and together with the RH-dependent data reveal the reaction to be first order in H2O as well. The 297 K and 309 K hydrolysis rate constants were measured as 5.0 ? 1.3 x 10-21 and 4.3 ? 1.5 x 10-21 cm3/molecule-sec, respectively. Confirming previous results, SOCl2 absorbed only at lambda