Determination of water content of nitrogen containing hydrogen sulfide by Karl Fischer coulometric titration

Abstract

Measuring the water content in natural gas is important for safety; however, complex matrixes make the results inaccurate. Natural gas contains hydrogen sulfide (H2S), which react with iodine (I2), causing Karl Fischer coulometric titration (KFCT) to give higher results. The KFCT method for the determination of water content of nitrogen containing H2S was investigated. A chilled mirror hygrometer offered a reference water content to calibrate the KFCT. The interfering of H2S was reduced by subtracting I2 consumed by H2S according to the reaction mechanism of ISO 10101; however, the modified results remained higher. A possible reaction mechanism with a stoichiometry of H2S to I2 of 1:2.5 was proposed. The improved KFCT method had an error of water content no more than (3 + 2%·x) mg/kg (x, water content in mg/kg) and had the potential of online monitoring of natural gas.