کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
10244462 | 47689 | 2005 | 10 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Effects of cerium incorporation into zirconia on the activity of Cu/ZrO2 for methanol synthesis via CO hydrogenation
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موضوعات مرتبط
مهندسی و علوم پایه
مهندسی شیمی
کاتالیزور
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
The effects of Ce incorporation into ZrO2 on the catalytic performance of Cu/ZrO2 for the hydrogenation of CO were investigated. A Ce0.3Zr0.7O2 solid solution was synthesized by forced hydrolysis at low pH. After calcination at 873 K, X-ray diffraction and Raman spectroscopy characterization indicated that the Ce0.3Zr0.7O2 had a tâ³ crystal structure. It was found that 1.2 wt% Cu/Ce0.3Zr0.7O2 exhibited H2 consumption peaks at low temperature (<473 K) during H2-TPR, indicating that a significant fraction (â¼70%) of Ce4+ is reduced to Ce3+. The 1.2 wt% Cu/Ce0.3Zr0.7O2 is 2.7 times more active for methanol synthesis than 1.2 wt% Cu/m-ZrO2 at 3.0 MPa at temperatures between 473 and 523 K and exhibits a higher selectivity to methanol. In situ infrared spectroscopy shows that, analogous to Cu/m-ZrO2, the primary surface species on Cu/Ce0.3Zr0.7O2 during CO hydrogenation are formate and methoxide species. A shift in the band position of the bridged methoxide species indicated that some of these groups were bonded to both Zr4+ and Ce3+ cations. For both catalysts, the rate-limiting step for methanol synthesis is the reductive elimination of methoxide species. The higher rate of methanol synthesis on Cu/Ce0.3Zr0.7O2 relative to Cu/m-ZrO2 was due primarily to a â¼2.4 times higher apparent rate constant, kapp, for methoxide hydrogenation, which is attributed to the higher surface concentration of H atoms on the former catalyst. The increased capacity of the Ce-containing catalyst is attributed to interactions of H atoms with CeO pairs present at the surface of the oxide phase.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Catalysis - Volume 235, Issue 2, 25 October 2005, Pages 368-377
Journal: Journal of Catalysis - Volume 235, Issue 2, 25 October 2005, Pages 368-377
نویسندگان
Konstantin A. Pokrovski, Michael D. Rhodes, Alexis T. Bell,