Study On Photocatalysis Of Synthesizing Glycine Directly From CO₂ And CH₃NH₂

Photocatalysis of synthesizing glycine directly from CO₂ and CH₃NH₂ has a great significance in synthesis-chemistry, utilization of CO₂ and protection of environment. In this thesis, a photocatalytic reaction technology has been applied to this reaction system. A series of metal modified coupled-semiconductor materials Cu/Fe₂O₃ -TiO2 were prepared by sol-gel method. The chemical composition, surface structures, energy band edge position amd their influence rule on photon absorption properties, chemiadsorption properties, photocatalytic activities were systematically investigated by DTA-TG, TPR, XRD, TEM, BET, IR, Raman, UV-vis and photocatalytic reaction.The metal modified coupled-semiconductor Cu/Fe₂O₃ -TiO₂ have high surface area over 80 m2/g. And the coupled-semiconductor Fe₂O₃ -TiO2 with particle sizes around 10nm. Metallic Cu clusters are dispersed in a high degree on the surface of coupled-semiconductor. Three kinds of active sites of metallic sites Cu, Lewis acid sites Fe3+ and Ti4+, Lewis base sites surface O- and bridge-O2- appeared on the surface of materials.The coupled-semiconductors Fe₂O₃-TiO2 have excellent photon absorption property in 250⁴00nm. The absorptance of visible light obviously increase after metel Cu supported, the absorptance in 400¹100nm over 60%. CO₂ mainly form the high active horizontal state Cu-C(O)O→Ti4+ with the synergistic effects of metallic site Cu and Lewis acid sites Ti4+. And CH₃NH₂ can be mainly chemiadsorbed on the Lewis base site Fe-O- with H in methyl.The photocatalytic reaction results indicate that the photocatalytic performance is influenced by the content of Fe₂O₃ in the coupled-semiconductors. 1%Cu/10% Fe₂O₃-TiO2 has the best photocatalytic performance. Under the conditions of radiation of UV light (wavelength 365nm, intensity 0.65mw/cm2), 200℃, space velocity 200 h-1 and CO₂:CH₃NH₂=1:1, the conversion of CH₃NH₂ reach 1.35% and the selectivity to glycine is 92.0%.Based on the experimental results, a mechanism for direct-synthesis of glycine from CO₂ and CH₃NH₂ and the synergetic effects of"light-surface-thermal"in photocatalytic reaction have been proposed.