Preliminary study on catalytic combustion-type sensor for the detection of diesel particulate matter

Catalytic oxidation and sensing of simulated diesel particulate matter (PM), which consists of hexadecane and carbon black as substitutes of soluble organic fraction (SOF) and soot, respectively, were investigated with Ag and Pt catalysts supported on TiO2 and CeO2. Supported Ag catalysts were active for soot oxidation at temperatures over about 500 °C, while supported Pt catalysts were almost inactive for the soot oxidation. Toward the oxidation of SOF, on the other hand, supported Pt catalysts were more active than supported Ag catalysts. Catalytic combustion-type sensors coated with those catalysts was fabricated, and their sensing characteristics were evaluated. Because of the difficulty to simulate the real sensing condition of PM, employed in this study was the programmed heating of the sensor on which PM or soot was pre-loaded. The results strongly suggest the possibilities to construct the catalytic combustion-type PM sensor and to selectively detect SOF and soot by the proper selection of the catalytic materials and operation temperatures.