纳米铁基催化剂在CO2加氢制烃中的性能

摘要

使用尿素沉淀凝胶、机械混合和等体积浸渍相结合的方法,制备了一系列的纳米尺寸FeK-M/y-Al2O3 (M=Cd,Cu)催化剂,采用扫描电镜(SEM)、透射电镜(TEM)、N2物理吸附、X射线衍射(XRD)光谱和H2程序升温还原(H2-TPR)仪对催化剂进行表征,并在小型固定床反应器上考察其对CO2加氢反应的催化性能.结果表明:3 MPa,400 ℃,3600 h-1,H2/CO2摩尔比为3的条件下,15％(w,下同)Fe1 0％WK/-Al2O3催化剂可稳定运行100h以上,CO2转化率为51.3％,C2+烃类的选择性达62.6％.Fe含量降至2.5％时,c2+烃类的选择性仍能达到60.0％.随着K含量由0％增加至10％,低碳烯烃选择性增加,烯烷比增加至3.6.Cd和Cu助剂可促进Fe物种的还原,改善目的产物的分布,其中Cu的加入使低碳产物烯烷比增至5.4,Cd的加入使C5.产物选择性增加了12％.%Combining co-precipitation-gelation, mechanical mixing and impregnation methods, a series of catalysts of FeK-M/y-AlzO3(M=Cd or Cu) have been attained. The catalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 physisorption, X-ray diffraction (XRD) and temperature-programmed reduction of hydrogen (Hi-TPR). The hydrogenation of carbon dioxide over these catalysts was also investigated in a fixed bed. Given a reaction time of 100 h, CO; conversion over a 15%Fe/10%K/y-AI2O3 catalyst reached 51.3 %, with a selectivity towards C;. of 62.6 % at 3 MPa, 673 K, a space velocity of 3600 h' and at a molar ratio of H2/CO2 of 3. At the lower Fe content of 2.5%, the selectivity towards C:. was still greater than 60.0%. Increasing the potassium content from 0% to 10%, increased the selectivity towards d-C; and the molar ratio of Cj-C;/C2-C! increased to 3.6. The addition of Cd and Cu improved the reduction and catalytic activities. Specifically, Cu improved the molar ratio of Ca-C; /C:-CS from 3.6 to 5.4, and the Cd increased the selectivity of C5+by 12%.