La_2O_3助剂对Co/AC催化剂上费-托合成反应性能的影响

Effect of La_2O_3 Promoter on Reaction Performance of Fischer Tropsch Synthesis over Co/AC Catalyst

通过改变稀土助剂La2O3的负载量,考察了La2O3助剂对活性炭负载Co基催化剂(Co/AC)上费-托合成性能的影响,并通过XRD, SEM, TPR和CO-TPD对催化剂进行了表征. 结果表明, La2O3的加入可提高催化剂的活性,降低产物中甲烷的选择性. 对于15%Co/AC催化剂,加入少量的La2O3(w(La)=0.7%～1.7%)可使CO转化率从27%升高到56%, 甲烷选择性从16.5%下降到7.8%,C5+选择性从55.4%升高到74.7%; 但加入过多的La2O3(w(La)=8.1%～12.4%)时,甲烷选择性反而升高. XRD和SEM结果表明, La2O3的加入提高了催化剂中Co的分散度. TPR和CO-TPD结果表明, La2O3与Co之间存在着相互作用,并使催化剂的还原度下降,尤其是La2O3负载量高的催化剂还原度下降更加明显,导致Co/AC催化剂上CO的高温吸附量的增加.

The effect of La2O3 promoter on the reaction performance of Fischer-Tropsch synthesis over the activated carbon-supported cobalt-based （Co/AC） catalyst was investigated by means of CO hydrogenation, XRD, SEM, TPR and CO-TPD techniques. The results showed that the CO conversion increased from 27 % to 56 %, the selectivity for methane decreased from 16.5 % to 7.8 % , and the selectivity for C5 ＋ increased from 55.4 % to 74.7 % with the addition of small amounts of La2O3 （w（La）= 0.796 - 1.7 % ） to the Co/AC catalyst. However, high La loading （w （La） = 8.1% - 12.4 % ） led to the increase of methane selectivity. The results of XRD and SEM indicated that the existence of La2O3 could enhance the cobalt dispersion on the catalyst surface. The profiles of TPR and CO-TPD illuminated that there was a strong interaction between cobalt particles and La2O3 species, which led to the decrease of the reducibility of Co/AC catalyst, especially for the catalyst sample with high La loading, and the existence of La2O3 resulted in enhancement of CO adsorption at high temperature.