Studies on TiO2/SiO2 and Pd/TiO2/SiO2 Catalysts in Photoreduction of CO2 with H2O to Methanol

The development of industry induced a massive increase in the emission of carbon dioxide into the atmosphere. A large amount of CO2 and its general availability causes that it could be a cheap reactant in a reaction that runs in a way similar to photosynthesis in plants. Pure TiO2 and metal doped TiO2 are the most studied semiconductor catalysts for photoreduction of CO2. The TiO2/SiO2 and Pd/TiO2/SiO2 catalysts were prepared and studied by temperature-programmed desorption, X-ray diffraction analysis, SEM-EDS, temperature-programmed reduction and then used for the methanol synthesis. The photoactivity of Pd/TiO2/SiO2 catalysts in the reduction of CO2 with H2O was tested at room temperature using photoreactor equipped with 16 lamps. The wavelength was characteristic of near ultraviolet. Post-reaction products were identified with gas chromatograph equipped with the flame ionization detector. Pd doping made the catalysts photoactive and the photoactivity of catalysts was changing as follows: 1%Pd/5%TiO2/SiO2 > 1% Pd/10% TiO2/SiO2 > 1% Pd/15% TiO2/SiO2. Optimum ultraviolet radiation time in the photoreduction of CO2 to methanol was 7 h. An addition of Pd does not change the surface of the carrier.