Study On Mid-East Interact Photocatalytic Reaction For Synthesis Of Methanol From CO₂ And H₂O On Nd～(3+) Doped TiO₂ Catalysts

As an Earth's ultimate power supply and friendly energy source for environment, lightcan activate reaction molecule directly to enhance the conversion of reactants and theselectivity of products. Since synthesis of methanol from CO₂ and H₂O is very difficultfor thermal surface catalysis, application for photo stimulating surface reaction techniqueinto the reaction system is of great value in both theory and application.Nano-particles of TiO₂ doped with various transition metal ions and rare earth metalions were prepared through two different ways: iso-volume impregnation method andSol-Gel processing. In the part of ion doping, the influence factors of doping methods,species, dopant amount and calcination temperature on the crystal structure andphotoactivity were systematically studied. The influences of ion doping on thephotoactivity of nano-TiO₂ were evaluated by photocatalytic reaction for the synthesis ofmethanol from CO₂ and H₂O. Then, our work was focused on the study of neodymium,copper and iron, which were found to be more excellent in improving the catalytic activityof TiO₂. Both transition metal and rare earth metal were used to modify titania by doping.X-ray diffraction (XRD), TEM, UV-Vis diffuse reflection spectra, IR and FT-Raman wereused to characterize the doped and undoped TiO₂ samples. The phase composition,surface structure, chemisorbing ability and photon absorbing of the simple ion doped andtransition metal-rare earth metal ions doped samples were carfully compared. And theaction mechanism of the ions was discussed. The effect of parameters, such as reactiontemperature, CO₂ pressure, irradiation time and concentration of catalysts on theproduction of methanol were explored.The metal particles of catalysts prepared by sol-gel method are homogeneouslydispersed with a narrow size distribution. It presents higher activity for the synthesis ofmethanol from carbon dioxide and water compared with the catalysts prepared byiso-volume impregnation method. The results implied that Nd³⁺ doping inhibited theanatase to rutile phase transformation and restrained the growth of grain size. Moreover,Nd³⁺-TiO₂ catalyst exhibited red shift in UV absorption remarkably, and the sensitivity tovisible light was enhanced. The good cooperative actions of transition metal ions and rareearth metal ions greatly improved the photocatalytic activity of the titenia. With the catalyst of 1%Cu²⁺-0.2%Nd³⁺-TiO₂ the methonal yield was 420.2μmol/g-cat.following the UV irradiation of 8h, which was 2.3 times as the methanol yield as0.2%Nd³⁺-TiO₂, and 7.8 times as 1%Cu²⁺-TiO₂.The least square method was employed for optimizing the doping amount of ions ofthe catalyst, which was found has the practical value to deal with the relations between thedoping quantity and the catalytic activity.