铝源对Ni/Al2 O3催化剂结构及其CO2-CH4重整性能的影响

以三种不同铝源采用溶液燃烧法制备了系列Ni/Al_2O_3催化剂,通过XRD、H_2-TPR、NH_3-TPD、N_2吸附-脱附、TGDTG和TPH等分析方法对反应前后催化剂进行了表征,研究了铝源对Ni/Al_2O_3催化剂结构、表面性质及其CO_2-CH_4重整性能的影响。结果表明,以Al(NO_3)_3·9H_2O为铝源制备的NiNO-AlNO催化剂比表面积较大,达102 m~2/g;高温还原峰面积大,峰型更为弥散;且载体Al_2_O_3具有一定的结晶性。而以Al_2(SO_4)_3·18H_2O和AlCl_3·6H_2O为铝源制备的NiNO-AlSO和NiNO-AlCl催化剂,其载体以无定型Al_2O_3存在,活性组分Ni晶粒粒径大、分散性差,还原峰面积较小,与载体的相互作用较弱。其中,由于硫酸铝较为稳定,需要在更高温度下才能转化为Al_2O_3,且所制备NiNO-AlSO催化剂中残留有含硫物质,使得其表面酸性较强。评价结果显示,NiNO-AlNO催化剂活性较高,稳定性好,CH4转化率为31.21%,CO_2转化率为48.97%。积炭分析结果发现,NiNO-AlNO催化剂表面积炭量最少,沉积炭主要以无定型态存在,具有良好的抗积炭性能。

Effect of aluminum source on the structure and performance of Ni/Al2O3 catalysts in CO2-CH4 reforming

Three Ni/Al₂O₃ catalysts were prepared with different aluminum sources by the solution combustion method and characterized by XRD, H₂-TPR, NH₃-TPD, N₂ sorption, TG-DTG and TPH. The effect of aluminum source on the structure and performance of Ni/Al₂O₃ catalysts in CO₂-CH₄ reforming was then investigated. The results show that the NiNO-AlNO catalyst with Al(NO₃)₃·9H₂O as aluminum source owns a large surface area of 102 m²/g and a wide and intense high-temperature reduction peak; besides, the Al₂O₃ support displays certain crystallinity. In contrast, the NiNO-AlSO and NiNO-AlCl catalysts, prepared with Al₂(SO₄)₃·18H₂O and AlCl₃·6H₂O sources, respectively, are composed of amorphous Al₂O₃ as support and crystal Ni as active component; the Ni species is poorly dispersed and present as large grains, with a small reduction peak and weak interaction with the support. In particular, because of the high stability of Al₂(SO₄)₃ and difficulty in converting Al₂(SO₄)₃ to active Al₂O₃ at high temperature, certain sulfur-containing substances are preserved and the resultant NiNO-AlSO catalyst shows strong surface acidity. The catalytic evaluation results indicate that the NiNO-AlNO catalyst exhibits high activity and stability in the CO₂-CH₄ reforming; the conversions of CH₄ and CO₂ are 31.21% and 48.97%, respectively. The carbon deposition analysis illustrates that the content of deposited carbon (present mainly in the amorphous form) on the NiNO-AlNO catalyst is rather low, suggesting a high resistance against carbon deposition.