Effect of Ni Precipitation Method on CO Methanation over Ni/TiO2 Catalysts

Abstract

A Ni/TiO2(TBT) catalyst was prepared through in situ precipitation, using tetrabutyl titanate(TBT) as the TiO2 precursor, and was studied in CO methanation. A Ni catalyst supported on commercial TiO2 was also prepared through post precipitation and studied to compare the influence of Ni precipitation conditions on the catalyst’s performance. To gain insight on their structure and physicochemical properties, the catalysts were characterized with N2-adsorption, X-ray diffraction, transimission electron microscopy, H2 temperature programmed reduction and temperature programmed desorption. The results showed that the in situ precipitation method was beneficial to the dispersion of Ni and the formation of more active sites on the Ni/TiO2 catalyst. In addition, the density of the metal- support boundary and its interaction with the active component were also increased. These characteristics of Ni/TiO2(TBT) led to a lower light-off temperature and a suppression of Ni sintering during CO methanation. As a consequence, the Ni/TiO2(TBT) exhibited better catalytic behavior, with a CO conversion of 99.4% and CH4 selectiv-ity of 90.4% under the following conditions: p=1 MPa, t=320 °C, n(H2)/n(CO)=3, gas hour space velocity (GHSV)=2×104 mL·g–1·h–1. The life test results of the two catalysts showed that Ni/TiO2(TBT) was more stable and the catalytic activity remained at its initial level after being used for 30 h.