Complete Decomposition of Benzene, Toluene, and Particulate Matter Contained in the Exhaust of Diesel Engines by Means of Thermally Excited Holes in Titanium Dioxide at High Temperatures

Abstract

We previously reported on a decomposition system of organic wastes by the use of thermally excited holes in TiO2 at high temperatures. A good feature of our system is that it makes use of a large number of holes formed, for example, at 350 °C for the oxidation of organic wastes. In this investigation, we aim at applying this technology to the complete decomposition of benzene, toluene, and particulate matter (PM) included in the exhaust of diesel engines. Special attention has been paid to the adsorption process of benzene and toluene onto the surface of TiO2, as well as to their subsequent decomposition, as studied by thermal analysis, Raman spectroscopy, and ESR in consideration of the specific surface of TiO2 powders. Both benzene and toluene are found to completely decompose into H2O and CO2 at about 350 °C, via fragments of ethylene, butene, propene, and butadiene. On the other hand, PM appears more difficult to decompose due to its powdered form. However, PM was finally confirmed to be decomposed when the mixture of PM and TiO2 was heated under a pressure of about 280 N/m2 at about 350 °C.