Synthesis and evaluation of the cobalt-promoted NiO/CaO.2Al2O3 catalysts in CO2 methanation reaction: Effect of different promoters

Abstract

This work is concentrated on designing of CO2 methanation process over nickel-based catalysts doped by different promoters (CuO, Cr2O3, Co3O4, Fe2O3, and MnO2) supported on CaO.2Al2O3 powder. The CaO-Al2O3 powder was fabricated by mechanochemical method, and catalysts were synthesized via a wet impregnation procedure. The characterization properties of all samples were tested by XRD, BET, TPR, FESEM, and EDS-mapping analyses. The optimum amount of NiO was selected at 10 wt% along with CaO:Al2O3 as support with the molar ratio of 1:2. The Co-doped catalyst showed the lowest pore size (9.4 nm) and the highest surface area (106 m2.g−1) among the promoted catalysts. The results exhibited that the Co3O4(3)-NiO(10)/CaO.2Al2O3 catalyst possessed superior catalytic performance in the CO2 methanation reaction. The results illustrated that the increase in cobalt oxide percentage up to 3 wt% improved catalytic performance. However, further augmentation in the Co3O4 from 3 to 7 wt% diminished the specific surface area. According to the performance tests, carbon dioxide conversion and methane selectivity were 83.1% and 99.5% at 450 °C under operating conditions (GHSV = 18,000 ml.gcat−1.h−1 and H2:CO2 = 4:1) over this catalyst. The processing conditions including calcination temperature, reduction temperature, GHSV, feed ratio, and long-term stability test were also examined over the selected catalyst. Outcomes revealed that CO2 conversion increased with a decrement in calcination temperature from 650° to 450°C. Also, chosen catalyst reduced at 650 °C showed the highest performance. Besides, catalytic performance enhanced by raising feed ratio (H2:CO2) from 2:1 to 5:1 and decreased with augmentation of GHSV from 12,000 to 30,000 ml.gcat−1.h−1. Moreover, Co3O4(3)-NiO(10)/CaO.2Al2O3 catalyst possessed high stability during 14 h time on stream.