助剂和原料气中CO2浓度对CuFeZr催化剂用于合成气制混合醇的影响

摘要

考察了不同助剂(Mn、Zn、Co)对CuFeZr催化剂用于合成气制混合醇的影响.借助BET、XRD、H2-TPR等对其物化性质进行了表征,结果表明,加入助剂可减小颗粒粒径并且增强对CO的吸附能力以及催化剂表面碱性,其中,加入Zn可以增强CuFe间的相互作用,改善CuFeZr催化剂的还原性质,提高对CO的吸附能力,以及提供最强的表面碱性.用固定床反应器对催化剂的反应性能进行了评价,反应结果表明,加入Zn可以显著提高CuFeZr催化剂用于合成气制混合醇的反应活性及醇选择性,使醇时空收率从0.026g/ (gcat·h)提高至0.071g / (gcat·h).由于循环条件下,反应产物CO2同时也是原料气的组成成分,进一步地探究了原料气中CO2浓度对催化剂反应性能的影响.结果表明,加入CO2可提高CO转化率和醇以及烃的收率,但阻碍链增长反应并使得产物烯烷比降低.其中,在所考察浓度范围内,原料气中含有2.5%的CO2最有利于醇和烃的生成尤其是低碳醇和低碳烃的生成.%The effect of various promoting additives (Mn,Zn,Co) on the performance of CuFeZr catalyst in the synthesis of higher alcohol from syngas was investigated.The results of nitrogen physisorption,XRD and H2-TPR characterization show that these additives can reduce the particle size and enhance the surface basicity and the adsorption capacity towards CO.Especially,the doping of Zn in the CuFeZr catalyst can effectively enhance the interaction between Cu and Fe,strengthen the surface basicity,and improve the reducibility and CO adsorption ability.For the synthesis of higher alcohol from syngas over the CuFeZr catalyst,the catalytic evaluation results in a fixed bed reactor illustrate that the activity and selectivity to alcohols are greatly enhanced by the addition of Zn promoter;the space time yield (STY) of ROH is increased from 0.026 to 0.071g/(gcat·h).Meanwhile,it was found that CO2 in the feed can improve the CO conversion as well as the STY to alcohols and hydrocarbons,but suppress the chain growth and decrease the ratio of olefin to paraffin;proper amount of CO2 (2.5%) is beneficial to the formation of alcohols and hydrocarbons of short chains.