Effect of ZrO 2 on Catalyst Structure and Catalytic Sulfur-Resistant Methanation Performance of MoO 3 /ZrO 2 –Al 2 O 3 Catalysts

A series of MoO 3 /ZrO 2 –Al 2 O 3 catalysts was prepared and investigated in the sulfur-resistant methanation aimed at production of synthetic natural gas. Different methods including impregnation, deposition precipitation, and co-precipitation were used for preparing ZrO 2 –Al 2 O 3 composite supports. These composite supports and their corresponding Mo-based catalysts were investigated in the sulfur-resistant methanation, and characterized by N 2 adsorption–desorption, XRD and H 2 -TPR. The results indicated that adding ZrO 2 promoted MoO3dispersion and decreased the interaction between Mo species and support in the MoO 3 /ZrO 2 –Al 2 O 3 catalysts. The co-precipitation method was favorable for obtaining smaller ZrO 2 particle size and improving textural properties of support, such as better MoO 3 dispersion and increased concentration of Mo 6+ species in octahedral coordination to oxygen. It was found that the MoO 3 /ZrO 2 –Al 2 O 3 catalyst with ZrO 2 Al 2 O 3 composite support prepared by co-precipitation method exhibited the best catalytic activity. The ZrO 2 content in the ZrO 2 Al 2 O 3 composite support was further optimized. The MoO 3 /ZrO 2 –Al 2 O 3 with 15 wt % ZrO 2 loading exhibited the highest sulfur-resistant CO methanation activity, and excess ZrO 2 reduced the specific surface area and enhanced the interaction between Mo species and support. The N 2 adsorption-desorption results indicated that the presence of ZrO 2 in excessive amounts decreased the specific surface area since some amounts of ZrO 2 form aggregates on the surface of the support. The XRD and H 2 -TPR results showed that with the increasing ZrO 2 content, ZrO 2 particle size increased. These led to the formation of coordinated tetrahedrally Mo 6+ (T) species and crystalline MoO 3 , and this development was unfavorable for improving the sulfur-resistant methanation performance of MoO 3 /ZrO 2 –Al 2 O 3 catalyst.