Temperature-programmed sensing for gas identification using the cataluminescence-based sensors

A new method of gas identification utilizing the difference in the cataluminescence (CTL) intensities during transition from physisorption to chemisorption state on the catalyst is proposed. By stepwise heating of the catalyst from 100 to 450 °C in atmosphere containing sample gas, the peak CTL intensity ( I P) and the steady state CTL intensity ( I SS) are observed. I P is the CTL intensity under the catalytic oxidation of adsorbate physisorbed on the catalyst previously, and I SS is that from gases diffused from the gas phase to the catalyst surface continuously. The ratio of I P/ I SS depends on the types of gases. The accumulation process of the physisorbed molecules is investigated, and the adsorbed amount increases with elapse of time on the porous catalyst. The values ( I PA and I SSA) for sensor A and those ( I PB and I SSB) for sensor B are measured. A good linearity in the CTL intensity versus gas concentration is obtained. Using values of I PA/ I SSA and I SSB/ I SSA for various gases with various concentrations, we can discriminate 11 types of gases, methanol, ethanol, 1-propanol, 1-butanol, acetone, pinene, linalool, diacetyl, n-butyric acid ethyl ester, acetic acid n-amyl ester and n-nonyl aldehyde.