Poisoning of Catalytic Methane Sensors

摘要

Methane sensors using the principle of catalytic oxidation of methane are employed for the determination of methane content in ambient air of coal mines. Certain foreign gases or vapors in the air poison the catalyst of the sensors affecting the sensor response. After a literature search of poison compounds of platinum and palladium oxidation catalysts, experimental studies of catalyst poison kinetics were made for three siloxane compounds, tributyl phosphate, monobromotrifluormethane, and hydrogen sulfide, that were selected as poison vapors. The concentration range of the poison vapors was varied from 3,000 to 0.1 ppb (v/v). Three siloxane vapors produced strong catalyst poison effect followed by tributyl phosphate, hydrogen sulfide, and monobromotrifluoromethane for the high concentration level of the poison vapors. Threshold poison vapor concentrations, where effect of the poison vapors on the sensor is minimal, were determined experimentally. Experimental studies were made further for a prevention method of catalyst poison by adsorption techniques. The use of activated carbon cloth inserted on the sensor head prevented catalyst poisoning efficiently.