金负载量对低温水煤气变换Auα-Fe_2O_3催化剂结构和性能的影响

INFLUENCE OF Au LOADING ON THE STRUCTURE AND CATALYTIC PERFORMANCE OF Au/α-Fe_2O_3 CATALYSTS FOR LOW-TEMPERATURE WATER-GAS SHIFT REACTION

采用共沉淀法制备了低温水煤气变换Au α Fe2O3催化剂。通过正交实验优化催化剂的还原活化条件,考察了金负载量对催化剂性能的影响。采用BET、XRD、UV VIS、XRF、H2 TPR和O2 TPO等表征手段对催化剂的结构进行分析,并与其催化性能进行关联。结果表明,(1)采用10% H2 N2还原气将催化剂在150℃原位还原9h,其催化活性最高;(2)金的最佳负载量为8 00%,此时在催化剂制备过程中金的流失量较少,金粒子较小,也有利于抑制催化剂在反应过程中烧结;(3)TPR TPO结果表明,金的负载量为8 00%时,Au α Fe2O3催化剂具有较易被还原、不易被氧化的性质,从而显示出最高催化活性。(4)Au α Fe2O3催化剂中的金以单质金(Au0)形式存在;其高活性与Au0 Fe3O4间的协同作用有关。

In this paper, supported Au/α-Fe_2O_3 catalyst for low-temperature water-gas shift reaction(WGSR) was prepared through co-precipitation method. The reduction procedure was optimized to activate the category of gold catalysts, which involves rhombization of reduction conditions, i.e. reductive gas composition, reduction temperature, and reduction time, using 8.00%Au/α-Fe_2O_3 catalyst as sample. It was found that the sample, pre-reduced under 150?℃ for 9?h in reductive gas flow (10% -H_2/N_2) , exhibits the higher activity. Then the influence of gold loading on the ultimately WGSR activity of Au/α-Fe_2O_3 catalyst was investigated due to the precious cost of gold, wherein its loading was controlled through adjusting the atomic ratio Au/Fe. The 8.00%Au/α-Fe_2O_3 catalyst shows the highest activity. The structure of Au/α-Fe_2O_3 catalysts with different gold loadings were studied by BET, XRD, XRF, UV-VIS, H_2-TPR and O_2-TPO characterization techniques. The introduction of gold during co-precipitation may suppress catalyst sintering during WGS reaction. During the preparation, the loss of gold will occur; the loss becomes more serious if the designed gold amount is increased. Moreover it will lead to the aggregation of gold particle, which was revealed by XRD and UV-VIS results. The Au/α-Fe_2O_3 catalysts with optimal Au loading (8.00%) shows the highest activity owing to the present of moderate Au^0 particle and the α-Fe_2O_3 support holding susceptible reduction but resistant to oxidation, revealed by the TPR-TPO results. Therefore, the high catalytic activity of the investigated catalyst was attributed to the synergism between Au^0 and Fe_3O_4.