La_2O_3助剂对Co/SiC催化费托合成反应的影响

Effect of La_2O_3 additive on the catalytic performance of Co/SiC catalysts for Fischer-Tropsch synthesis

采用等体积浸渍法在Si C上浸渍质量分数为0.2%~4.0%的La_2O_3,制备了15%Co/La_2O_3-Si C催化剂,利用N2吸附-脱附、XRD、H2-TPR、XPS等分析方法对制备的催化剂进行了表征,研究了催化剂催化费托合成反应的性能。实验结果表明,La_2O_3的加入减弱了钴与载体之间的相互作用,提高了催化剂的还原度,且钴与La_2O_3的相互作用使催化剂的分散度显著提高;随着La_2O_3加入量的增加(0.2%~2.0%(w)),CO的转化率从68.4%提高到91.0%;气态产物中CH4的选择性从6.5%增加到13.9%,C2~4的选择性从5.2%增加到9.4%,C5+选择性从87.7%降至75.5%;液态烃产物中汽油含量(w)从64.0%增加到了84.7%,而煤油、柴油、润滑油和石蜡的含量均呈降低趋势;含2.0%(w)La_2O_3的催化剂具有最佳的稳定性。

0.2%-4.0%mass fraction of La2O3 were coated on SiC by incipient wetness impregnation method.15%Co/La2O3-SiC catalysts were prepared by the same impregnation method using cobalt nitrate as the cobalt source.The catalysts were characterized by N2 adsorption-desorption,XRD,H2-TPR,XPS and other analytical methods.The performances for the catalytic reaction of Fischer-Tropsch synthesis were studied.The results indicated that the addition of La2O3 weakened the interaction between cobalt oxide and SiC,and increased the degree of reduction of the catalysts.Moreover,there was the interaction between cobalt species and La2O3,which increases the dispersion of catalyst.The activity evaluation results of catalysts showed that the CO conversion increased from 68.4%of Co/SiC to 91.0%of 15%Co/2.0%La2O3-SiC.The selectivity of CH4 in gaseous products increases from 6.5%to 13.9%,C2-4 increases from 5.2%to 9.4%,and C5+decreased slightly from 87.7%to 75.5%with the increase of La2O3.In liquid products,the mass percentage of gasoline increased from 64.0%to 84.7%with the addition of La2O3.The percentage of kerosene,diesel,lubricating oil and paraffin wax showed a downward trend.The catalyst with 2.0%(w)La2O3 showed the best catalytic stability.