Thesis (M.Eng.)--Chulalongkorn University, 2005

Each type of titanium dioxide has different photocatalytic activity on photooxidation of ethylene. Titanium dioxide synthesized via sol-gel method type I (prepared in nitric acid and water) yielded the most conversion of ethylene and less for that synthesized via sol-gel method type II (prepared in ethanol and water), solvothermal method and JRC-TIO1, respectively. When gold was deposited. For titanium dioxide synthesized via sol-gel method type I and type II including solvothermal method, conversion of ethylene decreases with increasing of pH values due to decreasing of amount of Ti[superscript 3+] affected from gold nanoparticles confirmed by Electron Spin Resonance results (ESR) and decreasing of active gold nanoparticles confirmed by Transmission Electron Microscope results (TEM). However, JRC-TIO1 titanium dioxide yielded more conversion of ethylene when it was deposited with gold nanoparticles. The highest conversion could be obtained at pH value of 9 at which the average particle size of gold nanoparticles were less than 5 nm and gave high activity for the reaction at the surface of titanium dioxide.