沉淀剂对ZnCr氧化物催化剂合成异丁醇性能的影响

为开发高选择性和稳定性的异丁醇合成催化剂,选用了不同的沉淀剂,通过共沉淀法制备了系列ZnCr基氧化物催化剂。采用N_2吸附-脱附、X射线衍射(XRD)、程序升温还原(H_2-TPR)等手段对催化剂织构参数、体相结构、还原性能等进行表征,并研究了其CO加氢制异丁醇的催化性能。表征数据表明:使用碱性较弱的沉淀剂时,制得的催化剂比表面积较大,ZnO和Cr_2O_3形成非计量比尖晶石Zn_xCr_(2/3(1-x))O结构,且颗粒分散度较好,被还原能力较强。使用强碱性沉淀剂时,制得的催化剂比表面积较小,出现相分离现象,且被还原能力较差。研究结果表明,使用(NH_4)_2CO_3沉淀剂制备的ZnCr催化剂表现出了最佳的催化性能。该催化剂在390℃,10000h~(-1),12MPa时,CO单程转化率可达15.3%,醇选择性90.3%,异丁醇选择性33.5%。

Effect of Precipitants on the Performance of ZnCr Oxide Catalysts in the Isobutanol Synthesis

In order to develop highly selective and stable catalysts for the synthesis of isobutanol,different precipitants were selected and a series of ZnCr based oxide catalysts were prepared by co-precipitation method.The texture parameters,structure and reduction properties of the catalysts were characterized by N2 adsorption-desorption technique,X-ray diffraction (XRD) and temperature-programmed reduction (H2-TPR).The catalytic performance of CO hydrogenation to isobutanol was studied.The characterization results indicate that when weak base is used as the precipitant,the non-stoicheiometric spinel ZnxCr2/3(1-x)O is formed,which has large specific surface area,and exhibits good dispersion and reducibility.When strong base is used as the precipitant,the specific surface area of the prepared catalyst is small,the reducibility is poor,and the phase separation is observed.It was found that the ZnCr catalyst precipitated by (NH4)2CO3 shows the best catalytic performance.ZnCr-(NH4)2CO3 catalyst could achieve 15.3％ CO conversion,90.3％ alcohols selectivity,and 33.5％ isobutanol selectivity at the condition of 390 ℃,10 000 h-1 and 12 MPa.