CuZnAl水滑石衍生催化剂上甲醇水蒸气重整制氢Ⅱ.催化剂组成的影响

Methanol Steam Reforming over CuZnAl Catalysts Derived from Hydrotalcite Precursor Ⅱ. Effect of Catalyst Composition

以类层柱CuZnAl水滑石为前体，经60012焙烧制备了一系列不同Cu／Zn／Al质量比的催化剂．在250℃、水／甲醇比为1．3和重时宅速为3，28h叫的条件下，考察了Cu／Zn／Al质量比对催化剂甲醇水蒸气重整反应性能的影响．结果发现，最佳Cu／Zn／Al质量比为36．7／13．4／（17～28）．调变Cu的比例不会改变催化剂物相构成和CuO的还原峰温，Cu含量较低的催化剂由于活性位数目少而甲醇转化率低，而Cu含量过高的催化剂甲醇转化率较差可能是因为Cu／Zn比失调，较低或较高的Zn含量会对催化剂物相构成产生影响，这是导致甲醇转化率随Zn含量变化的主要原因．较高的Al含量有利于CuO的分散和增大催化剂的比表面积，因此催化剂上甲醇的转化率明显提高．另外，所制催化剂的Cu／Zn／Al质量比对产物气体的组成没有影响．

A series of catalysts with various Cu/Zn/Al mass ratios were prepared by decomposition of CuZnAl hydrotalcite precursors at 600 ℃ and used for steam reforming of methanol. The effect of the Cu/Zn/Al mass ratio on the catalyst performance for steam reforming of methanol was investigated at 250 ℃ and WHSV of 3.28 h^-1 with a HaO/CH3OH molar ratio of 1.3. Cu/Zn/Al ratio of 36.7/13.4/（ 17 - 28 ） was preferred for achieving good activity. The Cu content barely affected the phase composition of the catalysts and the reduction temperature of the CuO phase. However, the catalysts with much lower or higher Cu content showed low activity because of the less active sites or the unsuitable Cu/Zn ratios. Both higher and lower Zn content led to the phase transformation of the catalysts and therefore the catalysts were less active. Higher Al content facilitated the dis persion of CuO and increased the specific surface area of the catalysts, thereby promoting the activity. In addition, the Cu/Zn/Al ratio hardly affected the gas product composition.