基于改性Ni/γ-Al_2O_3催化剂的电催化甲烷水蒸气重整的研究

提出了电催化作用下甲烷水蒸气催化重整的新工艺。基于工业常规Ni基催化剂,采用等体积浸渍法,以Ni为活性组分,γ-Al_2O_3为载体,MgO、CaO为助剂,制备了Ni/γ-Al_2O_3、Ni-MgO/γ-Al_2O_3和Ni-CaO/γ-Al_2O_3催化剂,考察了电流强度、重整温度、水蒸气与甲烷的物质的量比(水碳比,S/C)对不同催化剂的CH_4转化率、H_2产率、CO选择性和催化剂稳定性的影响。结果表明,电催化工艺有着良好的普适性,电流的引入能够提升CH_4转化率、增加H_2产率,尤其在低温下电流的促进作用显著。在三种催化剂中,Ni-CaO/γ-Al_2O_3催化效果最佳,在电流为4.5 A、S/C为3、重整温度为700℃时,CH_4转化率就高达95%以上。稳定性测试表明,电流的通入还能显著提高催化剂的稳定性,延缓催化剂的积炭失活。通过对催化剂的分析表征,发现电流的通入提升了催化剂中NiO的还原程度,同时抑制了反应过程中NiC_x向石墨炭的转化,从而可延缓催化剂因积炭覆盖反应活性位点而造成的失活。

Research on electro-catalytic steam reforming of methane with modified Ni/γ-Al2O3 catalysts

A novel electro-catalytic technique for catalytic methane steam reforming was developed. Based on the conventional industrial Ni-based catalyst, aseries of catalysts, including Ni/γ-Al₂O₃, Ni-MgO/γ-Al₂O₃ and Ni-CaO/γ-Al₂O₃, were prepared using incipient wetness impregnation method with Ni as the active component, γ-Al₂O₃ as the carrier, and MgO or CaO as the promoter. Experiments were performed to investigate the effects of electric current intensity, reforming temperature, and molar ratio of water vapor to methane (water/carbon ratio, S/C) on CH₄ conversion, H₂ yield, CO selectivity and catalyst stability. The results indicated that the electro-catalytic technique had good adaptability, and the introduction of electric current could improve the CH₄ conversion and increase the H₂ yield. Such effects were more intensive at lower reforming temperatures. Among the three catalysts, Ni-CaO/γ-Al₂O₃ catalyst exhibited the best catalytic efficiency, with the CH₄ conversion over 95% under conditions of 4.5 A, S/C of 3, and 700℃. Stability tests of the catalysts showed that the electric current could improve the stability of catalysts and delay the deactivation caused by coke deposition. The characterization results proved that the presence of electric current enhanced the reduction degree of NiO in the catalyst and inhibited NiC_x conversion to graphite carbon, resulting the delay of catalyst deactivation caused by carbon deposition over reactive sites.