Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA 70803, USA.
Phys Chem Chem Phys. 2011 Aug 28;13(32):14735-41. doi: 10.1039/c1cp20856j. Epub 2011 Jul 11.
A 10% Co-4% Re/(2% Zr/SiO(2)) catalyst was prepared by co-impregnation using a silica support modified by 2% Zr. The catalyst was characterized by temperature programmed reduction (TPR), in situ XRD and in situ XANES analysis where it was simultaneously exposed to H(2) using a temperature programmed ramp. The results showed the two step reduction of large crystalline Co(3)O(4) with CoO as an intermediate. TPR results showed that the reduction of highly dispersed Co(3)O(4) was facilitated by reduced rhenium by a H(2)-spillover mechanism. In situ XRD results showed the presence of both, Co-hcp and Co-fcc phases in the reduced catalyst at 400 °C. However, the Co-hcp phase was more abundant, which is thought to be the more active phase as compared to the Co-fcc phase for CO hydrogenation. CO hydrogenation at 270 °C and 5 bar pressure produces no detectable change in the phases during the time of experiment. In situ XANES results showed a decrease in the metallic cobalt in the presence of H(2)/CO, which can be attributed due to oxidation of the catalyst by reaction under these conditions.
采用浸渍法制备了一种 10%Co-4%Re/(2%Zr/SiO(2))催化剂，载体采用 2%Zr 改性的二氧化硅。采用程序升温还原（TPR）、原位 XRD 和原位 XANES 分析对催化剂进行了表征，同时在程序升温条件下用 H(2)对其进行了原位处理。结果表明，大晶粒 Co(3)O(4)分步还原，中间产物为 CoO。TPR 结果表明，高度分散的 Co(3)O(4)的还原是通过 H(2)溢流机制促进还原铼来实现的。原位 XRD 结果表明，在 400°C 下还原后的催化剂中存在 Co-hcp 和 Co-fcc 相。然而，Co-hcp 相更为丰富，与 Co-fcc 相比，它被认为是 CO 加氢反应的更活性相。在 270°C 和 5 巴压力下进行 CO 加氢反应，在实验时间内，各相中未检测到明显变化。原位 XANES 结果表明，在 H(2)/CO 存在下，金属钴的含量减少，这可以归因于在这些条件下催化剂的氧化反应。
