Co负载量对Co/TiO2催化CO2甲烷化性能影响

Effect of the Co Loading Amount on the Performance of Co/TiO2 Catalyst for CO2 Methanation

摘要:

采用沉淀-沉积法制备出Co负载量为w(Co)=10%、15%、20%和25%的Co/TiO2催化剂（w为质量分数），并用于CO2甲烷化反应。通过XRD、TEM、N2吸附-脱附、H2程序升温还原(H2-TPR)和CO2程序升温脱附(CO2-TPD)对催化剂进行了表征与测试。结果表明，Co负载量的增加影响了催化剂的Co3O4晶粒尺寸、比表面积、孔径以及催化剂的还原性能，且Co物种与TiO2载体发生了强相互作用。其中Co负载量为w(Co)=20%的Co/TiO2催化剂的Co颗粒尺寸约为8 nm，比表面积及孔径分别为40.9 m2/g和6.96 nm，且Co分散度达10.1%，从而更有利于CO2甲烷化反应。此外，w(Co)=20%的Co/TiO2催化剂表面具有最大的中强碱位量（28 μmol/g），从而可活化更多的CO2。活性测试结果表明，当反应条件为温度400 ℃、压力0.5 MPa、原料气空速3600 mL/(gcat·h)、V(H2)/V(CO2)=4时，w(Co)=20%的Co/TiO2催化剂的活性最好，其CO2转化率和CH4选择性可分别达到69.9%和98.3%，且在20 h内保持稳定。

Abstract:

Co/TiO2 catalysts with different Co loading amount (w(Co)=10%, 15%, 20% and 25%) were prepared by using a deposition- precipitation method, and applied to the CO2 methanation process, and were characterized by the XRD, TEM, N2 adsorption-desorption, H2-temperature program reduce (H2-TPR), and CO2-temperature program desorption(CO2-TPD). The results showed the crystallite size of the Co3O4, the BET surface area, and the reducing properties were affected by the increase of the cobalt loading amount, and the metal-support interaction was observed between the Co species and the TiO2. The Co/TiO2 catalyst with the Co loading amount of w(Co)=20% exhibited a smaller Co particle size of 8 nm and a good Co dispersion of 10.1%, and the BET surface area and the pore size were 40.9 m2/g and 6.96 nm, respectively. which would favor the CO2 methanation. From the CO2-TPD results, a maximum medium basicity of 28 μmol/g was observed on the Co/TiO2 catalyst with the Co loading amount of w(Co)=20%, which indicated more CO2 molecule were activated on the catalyst surface. The activity test indicated the Co/TiO2 catalyst with the Co loading amount of w(Co)=20% exhibited the highest activities when reacted at 400 ℃ and 0.5 MPa with a gaseous hourly space velocity of 3600 mL/(gcat·h), and the CO2 conversion and CH4 selectivity was 69.9% and 98.3%, respectively, and the Co/TiO2 catalyst kept stable in 20 h.