Cu/NiO-MoO_3/SiO_2光催化CO_2与CH_3OH合成碳酸二甲酯的反应性能

Photocatalytic Reaction for Synthesis of Dimethyl Carbonate from CO_2 and CH_3OH over Cu/NiO-MoO_3/SiO_2 Catalyst

采用表面改性法制备了MoO3-SiO2复合氧化物,用等体积浸渍法制备了Cu/NiO-MoO3/SiO2光催化剂,并用XRD,Ra-man,IR,TPD-MS,UV-Vis DRS和光促表面反应研究了催化剂的结构、化学吸附性能、吸光性能和光促CO2与CH3OH合成碳酸二甲酯(DMC)的反应性能.结果表明,Cu和NiO的引入提高了MoO3在SiO2表面的分散度,且Cu和NiO在MoO3-SiO2表面分散均匀;在金属Cu位和Lewis酸位Mo6+(或Ni2+)的协同作用下,CO2在催化剂表面形成活性较高的的卧式吸附态,CH3OH在催化剂表面形成分子吸附态和解离吸附态;NiO与MoO3复合后部分形成了Mo-O-Ni键联,提高了对光的吸收强度;金属Cu的负载扩展了材料在可见光范围的吸收;与热表面催化相比,光催化反应在较低的温度下就能显著进行,并提高了CH3OH的转化率,在110℃常压和空速300 h-1的条件下,CH3OH转化率可达13.9%,DMC选择性可达90.1%.

The Cu/NiO-MoO3/SiO2 catalyst was made by the methods of surface reaction modification and isometric impregnation. The structure, chemisorption and photoabsorption properties of Cu/NiO-MoO3/SiO2 were studied by XRD, Raman, IR, TPD and UV-Vis DRS techniques, and the reaction behavior for the photocatalytic reaction of CO2 and CH3OH to dimethyl carbonate （DMC） was studied by photo-stimulated reaction technique. The results showed that the addition of Cu and NiO greatly increased the dispersion of MoO3 on SiO2, and Cu and NiO could also disperse evenly on the support. The CO2 horizontal state with high activity and the CH3OH molecular and dissociative adsorption states formed on the surface of Cu/NiO-MoO3/SiO2 catalyst under the synergic action of metallic Cu sites and Lewis acid sites （Mo^6＋ or Ni^2＋ ）. The Mo-O-Ni bonds formed and the absorption intensity was enhanced through the coupling of MoO3 and NiO. The absorption region was expanded to visible light after Cu was supported on the coupled semiconductor NiO-MoO3/SiO2. Compared with the thermal surface catalytic reaction, the photo-stimulated surface reaction for synthesis of DMC from CO2 and CH3OH over Cu/NiO-MoO3/SiO2 could proceed at lower reaction temperature and give higher reactant conversion. Under the proper conditions, the CH3OH conversion was up to 13.9% with DMC selectivity of 90.1%.