Mn and Mg dual promoters modified Ni/α-Al2O3 catalysts for high temperature syngas methanation

Mn and Mg doped Ni/α-Al2O3 catalysts were prepared by impregnation method for high temperature syngas methanation. The catalysts were characterized by N2 adsorption-desorption, XRD, HRTEM, H2-TPR, CO-TPD, CO2-TPD, CO pulse chemisorption and XPS. Compared to single promoter doped catalysts, dual promoters doped catalysts exhibited better high temperature activity. In particular, an optimal catalyst with Mn, Mg content of 2 wt% (2Mn2Mg) achieved almost 100% CO conversion and 97.5% CH4 selectivity at 500 °C, 2.0 MPa, and a WHSV of 12,000 mL·g− 1·h− 1, and showed good stability in stability test. Mn and Mg species could help to form a moderated interaction between NiO with support in co-impregnation process, which inhibited Ni agglomeration in high temperature, improved the Ni dispersion, and enhanced the CO/CO2 adsorption capacity. Meanwhile, the Ni electron cloud density increased by electron transfer from promoters, which facilitated the dissociation of CO on the catalyst surfaces. In addition, the impregnation sequence and promoters loading was also investigated.