催化学报

催化学报 ›› 2007, Vol. 28 ›› Issue (4): 321-326.

• 研究论文 • 上一篇    下一篇

CuZnAl水滑石衍生催化剂上甲醇水蒸气重整制氢Ⅲ. 合成水滑石用金属盐的影响

汤颖,刘晔,路勇,朱萍,何鸣元   

  1. 华东师范大学化学系, 上海市绿色化学与化工过程绿色化重点实验室, 上海 200062
  • 收稿日期:2007-04-25 出版日期:2007-04-25 发布日期:2011-03-28

Methanol Steam Reforming over CuZnAl Catalysts Derived from Hydrotalcite PrecursorsⅢ. Effect of Metal Salts Adopted for Hydrotalcite Synthesis

TANG Ying, LIU Ye, LU Yong*, ZHU Ping, HE Mingyuan   

  1. Shanghai Key Laboratory of Green Chemistry and Chemical Processes, Department of Chemistry, East China Normal University, Shanghai 200062, China
  • Received:2007-04-25 Online:2007-04-25 Published:2011-03-28

PDF

811

被引次数

19

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=3.28 h-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=0.5 h-1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.

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

Abstract: 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(Ⅱ) 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 SO2-4 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. N2O titration and CO2 temperature-programmed desorption measurements indicated that both of the catalysts from acetates and nitrates possessed close values (～50 m2/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.

Key words: copper oxide, zinc oxide, alumina, hydrotalcite, methanol, hydrogen, steam reforming, fuel cell