Development of the dimethyl ether steam reforming catalysts that suite for generating the CO-free hydrogen

二甲醚(DME)具有毒性小、燃烧无NOx或颗粒物、操作方便等优点，是一种有潜力的新一代清洁燃料。采用溶胶凝胶法制备的催化剂γ-Al_2O_3、SiO_2、Cu/Al_2O_3、Ru/Al_2O_3、Cu/SiO_2等，以及浸渍法制备的铜-锌/Al_2O_3、氧化铜作为工业催化剂。仅在Al_2O_3的情况下生成甲醇。结果表明，γ-Al_2O_3，尤其是路易斯酸中心，对甲醇水蒸气重整有很好的催化作用，生成的甲醇在铜等活性金属催化剂上重整为H_2和CO_2。…此外，还发现，由于γ-Al_2O_3、路易斯酸位和活性金属中心如铜在催化剂表面混合均匀，因此溶胶-凝胶法是制备适用于硫代二甲醚的催化剂的理想方法。作为SRMDE的优良催化剂之一，Cu/Al_2O_3中添加锌、铁、锰均能提高氢产率，但不降低一氧化碳的生成量。CO是由生成的H_2和CO_2发生相反的水煤气变换反应而形成的，因此认为在ppm级或更低级的CO还原是非常困难的。例如，在275wt%的反应温度下，铜-锌(29-1wt%)/Al_2O_3催化剂可将95%的二甲醚转化为H_2和CO_2，其中CO的含量为0.8%。在低温(2 5 0~30 0℃)条件下，我们研制出了性能优良的固体二甲醚催化剂。(2001年至2003年，我们在日本催化学会会议上做了3次发言，在日本化学学会会议上做了7次发言。我们感谢对这项研究的支持。)较少

Dimethyl ether (DME) is a potential clean fuel of the next generation, because of less toxicity, burning without Nox or particulates, and ease of handling. We have studied catalysts which will produce CO-free hydrogen with stream reforming of DME (SRDME) for the use of hydrogen in polymer electrolyte fuel membrane cells.Catalysts prepared by the sol-gel method, such as γ-Al_2O_3, SiO_2, Cu/Al_2O_3, Ru/Al_2O_3, Cu/SiO_2, so on, Cu-Zn/Al_2O_3 prepared by the impregnation method, and CuO-ZnO as a commercial catalyst were used.The Al_2O_3 catalysts prepared by the sol-gel method mainly produced H_2, and in the case only of Al_2O_3 methanol was formed. On the other hand, the Cu/SiO_2 which was excellent for methanol steam reforming and SiO_2 produced no H_2. These results suggest that γ-Al_2O_3, especially the Lewis acid sites, is excellent for hydrolyzing DME into methanol and the methanol produced is reformed to H_2 and CO_2 over active metal for methanol steam reforming, such as copper. … More It is also found that the sol-gel method is excellent for preparing the suitable catalysts for SRDME, because γ-Al_2O_3, the Lewis acid sites, and active metal sites such as copper will be mixed and distributed well on the surfaces of the catalysts. Each addition of Zn, Fe, and Mn into Cu/Al_2O_3 that is one of the excellent catalysts for SRMDE improves the rate of H_2 production ; however, the CO production is not reduced. CO is formed with the opposite water gas shift reaction by generated H_2 and CO_2, therefore it was thought that the CO reduction in the ppm order or less orders is very difficult. However, for example, Cu-Zn(29-1wt%)/Al_2O_3 catalyst converts 95% of DME into H_2 and CO_2 containing 0.8% of CO at the reaction temperature, 275℃. The excellent catalysts for SRDME at low temperature (250-300℃) have been developed.(We had 3 presentations in the conferences of Catalysis Society of Japan, and 7 presentations in the conferences of The Chemical Society of Japan for 2001-2003. We are grateful for support of this research.) Less