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
موضوعات مرتبط
مهندسی و علوم پایه مهندسی شیمی کاتالیزور
پیش نمایش صفحه اول مقاله
Effects of cerium incorporation into zirconia on the activity of Cu/ZrO2 for methanol synthesis via CO hydrogenation
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 t″ 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 (∼70%) 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 ∼2.4 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
نویسندگان
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