改进型XC502低压甲醇合成催化剂的研究 Ⅱ.催化剂的活性位

Study of a modified low pressure copperbased catalyst XC502 for methanol synthesis

采用ＸＰＳ－Ａｕｇｅｒ、ＸＲＤ和ＦＴＩＲ等方法，对５组分Ｃｕ－Ｚｎ－Ａｌ－Ｍ１－Ｍ２改进ＸＣ５０２铜基低压甲醇合成催化剂进行了表征。ＸＰＳ－Ａｕｇｅｒ结果表明，ＸＣ５０２催化剂出现主峰为３３６．４ｅＶ（Ｃｕ＋），而Ｃｕ－Ｚｎ－Ａｌ催化剂主峰为３３４．９ｅＶ（Ｃｕ０）；ＸＲＤ结果表明，两种工作态催化剂比氧化态新增峰的２θ分别为３６．５°（Ｃｕ＋）和４３．３°（Ｃｕ０），ＸＣ５０２催化剂这两峰的强度比Ｉ３６．５／Ｉ４３．３是Ｃｕ－Ｚｎ－Ａｌ催化剂的２．１倍，说明工作态ＸＣ５０２催化剂单位Ｃｕ０中的Ｃｕ＋含量比Ｃｕ－Ｚｎ－Ａｌ催化剂多；ＦＴＩＲ谱显示，ＸＣ５０２和Ｃｕ－Ｚｎ－Ａｌ两种工作态催化剂新增波数分别为６２２ｃｍ－１和６２７ｃｍ－１的振动峰，此新增峰可能是Ｃｕ＋－Ｏ或Ｃｕ＋－Ｏ－Ｚｎ２＋的振动峰。改进型铜基甲醇合成催化剂的活性位可能是Ｃｕ０－Ｃｕ＋－Ｏ－Ｚｎ２＋／Ａｌ２Ｏ３－ＭＯｘ。

pectroscopic characterization of the active site of a modified low pressure copperbased catalyst XC502, prepared by adding a small amount of metal oxides of the VI B and VB groups to a CuZnAl catalyst for methanol synthesis, is carried out by XPSAuger, XRD and FTIR. The main peaks are detected by XPSAuger to be 336.4eV(Cu+) and 334.9eV(Cu0) on the surfaces of XC502 and the CuZnAl catalyst, respectively. The XRD result shows that two new peaks appear at 2θ=36.5°(Cu+) and 43.3°(Cu0) for those functioning catalysts, but I36.5/I43.3 of XC502 is twice as large as that of the CuZnAl catalyst, showing that the surface of the functioning XC502 catalyst has higher Cu+/Cu0 ratio and valence stability than those of the CuZnAl catalyst. By applying FTIR spectroscopy, bands at 622 cm-1 and 627cm-1 are observed on the functioning XC502 and CuZnAl catalysts, respectively, and the band may be assigned to Cu+OZn2+ bond vibration. In light of the above results, it is suggested that the active site on the functioning XC502 copperbased catalyst for methanol synthesis at low pressure is probably Cu0Cu+OZn2+/Al2O3MOx.