Preparation of NiFe-CeLaOx/HAP catalyst and its performance and mechanism for high-efficiency methanation of coal pyrolysis gas

The coexistence of CO, CO2, H2, and trace sulfur in coal pyrolysis gas hinders efficient methanation, as traditional catalysts easily deactivate via sulfur poisoning, carbon deposition, and active component sintering. This study prepared hydroxyapatite (HAP) support hydrothermally, then loaded Ni-Fe active components and CeO2-La2O3 composite promoters via incipient wetness impregnation, constructing a catalyst with their synergistic effect for efficient multi-component coupled methanation. HAP’s PO43 − and Ca2 + sites anchor active components and promoters via interfacial interactions, forming a stable “metal-promoter-support” ternary interface. Catalytic mechanisms were analyzed using XRD, XPS, SEM, TEM, H2-TPR, CO2-TPD, BET, and FT-IR. The results were as follows: (1) When the Ni/Fe molar ratio is 1:1, the Ce/La molar ratio is 1:1, and the total Ni/Fe metal loading is 15%, CO and CO2 conversions reach 97.22% and 94.54%, respectively, with CH4 selectivity >99%. Moreover, the activity retention rate remains 90% after 800 h of continuous operation. (2) After introducing 100 ppm H2S, the CO and CO2 conversions stabilize at 82.01% and 80.07%, respectively, after 200 h, maintaining 85% of the initial activity. When H2S introduction is stopped after 500 h, the CO and CO2 conversions recover to 83.85% and 81.93%, respectively, with the activity restoring to 87% of the initial value. With the introduction of 200 ppm H2S, the conversions drop to 77.07% and 75.01%, respectively, after 500 h.