CeO2改性Cu/Al2O3催化剂上甲醇水蒸气重整制氢

研究CeO2改性Cu/Al2O3催化剂上甲醇水蒸气重整制氢反应过程,得到低温活性、氢选择性和稳定性较好的催化剂.Cu/Al2O3催化剂中添加CeO2提高了催化剂的活性和稳定性,当CeO2质量分数为20％时,催化剂活性表现最佳.在反应温度250 ℃,水醇摩尔比为1.0,液体空速为3.28 h －1条件下,甲醇转化率为95.5％,氢气选择性为100％.此外,CeO2通过促进水气转化反应降低了重整气中CO的含量.Cu/CeO2/Al2O3催化剂在200 h的寿命实验中,活性仍保持在90.0％以上,而Cu/Al2O3催化剂在100 h的寿命实验中,活性已很快下降.XRD和TPR分析及表面元素分布结果表明,铜和铈相互作用促进了铜在催化剂表面的高度分散,阻止了铜晶粒团聚、烧结,促使铜晶粒细小化,促进了铜的还原,改善了Cu/CeO2/Al2O3催化剂的性能.

Catalytic Production of Hydrogen from Steam Reforming of Methanol on CeO_2 Promoted Cu/Al_2O_3 Catalysts

Catalytic production of hydrogen by steam reforming of methanol has been studied on a series of co-precipitated CeO2 promoted Cu/ Al2O3 catalysts under atmospheric pressure in a microreactor.Cu/CeO2/Al2O3 catalysts displayed higher activity and stability than that of Cu/ Al2O3 catalysts. Maximum methanol conversion of 95.5％and H2 selectivity of 100％ were obtained at 250 ℃, n(H2O)/n(CH3OH)=1/1,WHSV=3.28 h－1,with the catalyst containing mass fraction 20％ of CeO2.After 200 h of reaction, methanol conversion was still over 90.0％ with CeO2 promoted Cu/ Al2O3 catalyst, while the activity of Cu/ Al2O3 catalyst deactivated rapidly after 100 h of reaction. XRD and TPR results indicated that CeO2 promoter not only greatly improved the surface copper dispersion, and prevented copper crystallites from reuniting or sintering, but also made copper crystallites relatively smaller and promoted copper reduction. In addition, CeO2 could enhance water gas shift reaction, which led to the decrease of CO concentration in the reformed gases. It is suggested that the high activity, selectivity and stability of Cu/CeO2/ Al2O3 catalysts are resulted from higher copper dispersion and smaller copper crystallites, and the synergetic effect between copper and ceria.