Development of a device to measure hydrogen in the presence of moist chlorine : influence of a novel menbrane

Abstract

Recently, an amperometric sensor attached with a hydrogen-selective membrane made of epoxy vinyl ester based resin, Derakane 470-300, coated on a Teflon sheet, has been proposed to measure hydrogen concentration in the presence of moist chlorine. The response of the sensor is not satisfactory. The Derakane layer gives a slow response time, and the brittleness of the resin makes the thin membrane easy to crack. The cracking allows Cl2 to get into the sensor and nullifies the principle of the sensor. As result, a sandwich membrane having an active layer less than 0.10 mm thick between two sheets of Teflon was introduced in this study. It was believed that the sandwich technique would enhance transmembrane flux and physical strength of the membrane. However, no research has been carried out on the ability of the thin-active-layer membrane to withstand chlorine. Thus, sandwich membranes of two types of Derakane resin; 470-300 and 8084 were prepared. The H2 and Cl2 permeability coefficients of the membranes in H2-Ar atmosphere and Cl2 atmoshere at 25, 50 and 80C were determined. Mixed gas experiments were carried out at 80C to determine the effect of the presence of chlorine on the permeation of hydrogen through the membrane. The selectivity was calculated by the permeability ratio of hydrogen and chlorine. From the experimental results, both types of membrane allow chlorine to pass through but Derakane 8084 showed higher selectivity for hydrogen than Derakane 470-300 in the range of temperature studied. A decrease in hydrogen and chlorine permeability coefficients was found in the experiment of 5% H2 and 95% Cl2 mixed gas system. The permeability coefficient of hydrogen is lower in 5% H2/Cl2 than in the mixed gas containing 1% H2 whereas the chlorine permeability coefficient is higher.