摘要
采用共沉淀法，用不同金属盐为Cu源和Zn源合成了一系列CuZnAl水滑石，以此为前体经600℃焙烧后制得相应催化剂．用硝酸盐和醋酸盐合成的水滑石结晶度高，其衍生催化剂比表面积大、Cu的分散性好且易于还原；而用硫酸盐和盐酸盐合成的水滑石结晶度差，其衍生催化剂比表面积小、Cu的分散性差且不易还原．反应评价结果显示，用硝酸盐和醋酸盐制得的催化剂活性高、反应稳定性好；而用硫酸盐和盐酸盐制得的催化剂由于低的Cu表面积以及S和Cl的毒化作用而几乎无催化活性．在醋酸盐制备的催化剂上，产物干气中CO的浓度明显较低，在250℃和WHSV=3．28h^-1的条件下约为0．03％～0．04％，仅为硝酸盐所制催化剂上CO浓度的1／5；在210℃和WHSV=0．5h。的条件下，该催化剂上甲醇几乎完全转化，同时CO浓度降至约0．005％．N2O滴定、CO2程序升温脱附和程序升温还原结果显示，用醋酸盐和硝酸盐制备的催化剂具有极相近的Cu表面积和表面碱性，但前者CuO的还原峰温较后者低近70℃，归因于ZnO与CuO间的强相互作用，这是催化剂具有良好选择性的可能原因．
A series of CuZnAl catalysts for methanol steam reforming have been prepared via pyrogenation of hydrotalcite-like precursors at 600 ℃ , which were synthesized by the traditional Na2CO3/NaOH coprecipitation method using nitrates, acetates, sulfates, and chlorides of copper and zinc as Cu（ Ⅱ ） and Zn（ Ⅲ ） sources. The use of acetates and nitrates facilitated the crystallization of CuZnAl hydrotalcites, and the derived catalysts had large specific surface area, high Cu dispersion, and good reducibility of CuO. The use of sulfates and chlorides inhibited hydrotalcite crystallization, leading to the reduction of the specific surface area and the reducibility of CuO in the corresponding catalysts. The catalysts prepared from acetates and nitrates were highly active and stable for methanol steam reforming, but those prepared from sulfates and chlorides were inactive due to the poisoning of SO4^2- and Cl^- residues. The catalyst prepared from acetates provided much lower CO concentration （0.03%-0.04%） in the dry product gas compared to the catalyst prepared from nitrates （0.2%） with 〉95% methanol conversion at 250 ℃ and WHSV of 3.28 h^-1. Furthermore, CO concentration was reduced to 0.005 % over the catalyst prepared from acetates with 〉95 % methanol conversion when the reaction temperature was decreased to 210 ℃ and WHSV to 0.5 h 1. N20 titration and CO2 temperature-programmed desorption measurements indicated that both of the catalysts from acetates and nitrates possessed close values （-50 m^2/g） of Cu surface area and very similar basic properties. Temperature-programmed reduction results showed that the peak temperature of CuO for the catalyst from acetates was 70 ℃ lower than that for the catalyst from nitrates, which was attributed to the strong interaction between CuO and ZnO. It might be the intrinsic reason for the significant reduction of the CO concentration on the catalyst from acetates.
出处
《催化学报》
SCIE
CAS
CSCD
北大核心
2007年第4期321-326,共6页
基金
国家自然科学基金(20573036
20590366)
上海市科学技术委员会重大项目(05DJ14002)
青年科技启明星计划(05QMX1418)
关键词
氧化铜
氧化锌
氧化铝
水滑石
甲醇
氢
水蒸气重整
燃料电池
copper oxide
zinc oxide
alumina
hydrotalcite
methanol
hydrogen
steam reforming
fuel cell
