【作者】 赵春；

【导师】 钟顺和；

【作者基本信息】 天津大学 ， 工业催化， 2003， 硕士

【摘要】 CO2和C2H4直接合成丙烯酸，是重要的原子经济型反应之一。本论文将光促表面反应技术应用于这一反应体系，设计并用混合溶胶凝胶法制备了Cu/ZnO-TiO2系列固体材料，采用DTA-TG、TPR、XRD、TEM、BET、IR、UV-Vis和光促表面反应等技术系统地考察了固体材料的制备工艺、化学组成和表面构造对其吸光能力、化学吸附性质和光促表面催化反应性能的影响规律。用溶胶凝胶法制得的Cu/ZnO-TiO2系列固体材料是由晶粒粒径10nm左右的锐钛矿型TiO2以及少量ZnTiO3 和ZnO组成的化学混合物，Cu以金属状态高度分散于固体材料表面，固体材料的比表面积大于80m2/g，其表面存在金属位Cu，Lewis酸位Zn2＋和Ti4＋，Lewis碱位Zn-O-、Zn-O-Ti和Ti-O-Ti键中的桥氧。n-p复合型ZnO-TiO2半导体材料在250-400nm紫外光区域内具有优异的吸光性能，其吸收率可达85％以上；负载金属Cu后其对可见光的吸收明显增加，同时紫外光的吸收限发生较大蓝移。CO2在固体材料表面金属位Cu及Lewis酸位的协同作用下可形成双齿吸附态、剪式吸附态以及高活性的卧式吸附态；C2H4以端位H和C吸附在在表面金属位Cu和Lewis碱位Zn-O-上，形成非解离双点吸附态；表面金属Cu位是CO2和C2H4的共同吸附位，导致二者之间存在一定的竞争吸附；光促表面催化反应实验结果表明，固体材料中ZnO的含量对其光催化反应性能有较大影响，组成为1%Cu/20%ZnO-TiO2的固体材料性能最优，反应产物为丙烯酸、乙醛和CO；反应温度、空速及反应物组成对该固体材料反应性能有一定影响，在主波长365nm、光强为10mw/cm2的紫外灯照射下及温度100℃、空速200 h-1和CO2:C2H4=1:1的操作条件下，取得了CO2转化率为1.25%，C2H4转化率为1.23%，生成丙烯酸的选择性超过90%的优良成果；根据以上实验结果，探讨了光促CO2与C2H4合成丙烯酸表面催化反应的机理、Cu/ZnO-TiO2固体材料中各组分的作用、以及光促表面反应过程中“光－表面－热”的协同效应。更多还原

【Abstract】 Direct synthesis of crylic acid from CO2 with C2H4 is important one of the atom-economic reaction, and the technology of photo stimulated surface catalytic reaction (PSSCR) has been used to this reaction system at first time. In this work, a series of Cu/ZnO-TiO2 solid materials were prepared by sol-gel method, and their preparation conditions, chemical composition and surface structure, chemisorption properties, absorptivity of UV light and photoreaction behaviors were investigated by techniques of DTA-TG, TPR, TEM, BET, XRD, IR, UV-vis and PSSCR-GC. The Cu/ZnO-TiO2 solid materials are composed of anatase TiO2, ZnTiO3 and ZnO with particle sizes around 10nm and surface area over 80m2/g, and metallic Cu clusters are dispersed in a high degree on the surface of solid materials. Three kinds of active sites of Lewis acid sites Zn2+ and Ti4+, Lewis base sites surface O- and bridge-O2- and metallic sites Cu appeared on the surface of these solid materials.The ZnO-TiO2 n-p coupled semiconductors can absorb UV light of 250-400 nm effectively with the absorptance over 85%. The absorbance of visible light obviously increase and UV absorbance limit shift to shorter wavelength region after Cu supported on ZnO-TiO2. CO2 can be chemisorbed on the Cu and Lewis acid sites of material surface to form bidentate, bridge and shearing adsorption states, while C2H4 can be chemisorbed on the Cu and Lewis base site to form undissociated intermediate. There exist competitive adsorption between CO2 and C2H4 on Cu.The PSSCR performance is influenced by the content of ZnO in the Cu/ZnO-TiO2 solid materials. The solid material, 1%Cu/20%Zn-TiO2, has the best PSSCR performance and the products are crylic acid, aldehyde and CO. The reaction temperature, space velocity, and reactant component have obvious effects on the PSSCR. IUnder the conditions of radiation of UV light (wavelength 365nm, intensity 10mw/cm2), 100℃, space velocity 200 h-1 and CO2:C2H4=1:1, the conversions of CO2 and C2H4 reache1.25% and 1.23% respectively, and the selectivity to crylic acid is over 90%;Based on the experimental results, a PSSCR mechanism for direct-synthesis of crylic acid from CO2 and C2H4, the action of each component in the solid material and the synergetic effects of “light-surface-thermal” in PSSCR process has been proposed.更多还原