制备溶液pH对C uO-ZnO/Al_2O_3催化剂前体物相及其CO水汽变换反应活性的影响

用X射线衍射、微分热重分析、程序升温还原、N2吸附、N2O滴定及常压微反活性评价技术考察了制备溶液pH对CuO-ZnO/A l2O3催化剂前体物相、催化剂物性参数及CO水汽变换反应活性的影响。实验结果表明,催化剂前体中主要存在3种物相:Cu2CO3(OH)2、(Cu,Zn)2CO3(OH)2和(Cu,Zn)6A l2(OH)16CO3.4H2O。随着pH的升高,Cu2CO3(OH)2和(Cu,Zn)2CO3(OH)2的含量先增加后减少,而(Cu,Zn)6A l2(OH)16CO3.4H2O的含量则随着pH的升高单调上升。焙烧后的试样中形成的CuO-ZnO固溶体越多,CO水汽变换反应活性越高。实验结果表明,CO水汽变换反应是一个结构敏感型反应。

Influence of Precipitation pH on Phase Composition of Catalyst( CuO -ZnO/Al2O3 ) Precursors and Activity of Catalyst in CO Water Gas Reaction

Effect of precipitation pH on phase composition of catalyst(CuO-ZnO/Al_2O_3)precursors was studied by means of X-ray diffraction,differential thermogravimetry,temperature pregrammed reduction,N_2 adsorption and N_2O titration.Activity of catalyst for CO water gas reaction(WGR)was evaluated in a differential fixed-bed reactor under atmospheric pressure.Precursors of catalysts were prepared by cocurrent coprecipitation.It was found that Cu_2CO_3(OH)_2,(Cu,Zn)_2CO_3(OH)_2 and(Cu,Zn)_6Al_2(OH)_(16)CO_3·4H_2O were main phases of catalyst precursors.At lower pH,Cu_2CO_3(OH)_2 and(Cu,Zn)_2CO_3(OH)_2 were main phases of precursors and their contents decreased with continuous raising of pH,but amount of(Cu,Zn)_6Al_2(OH)_(16)CO_3·4H_2O increased monotonously with raising of precipitation pH.CuO-ZnO solid solution formed during calcination and its amount was direct proportional to catalytic activity in WGR.Activity of catalysts firstly rose with increasing of precipitation pH,then dropped after reaching a maximum at pH=8.Pure CuAl_2O_4 hardly had any catalytic activity for WGR.No correlation had been observed between WGR activity and specific surface area of copper metal.That suggested WGR was a structure-sensitive reaction.