کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
61840 47608 2011 8 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Temperature-induced evolution of reaction sites and mechanisms during preferential oxidation of CO
موضوعات مرتبط
مهندسی و علوم پایه مهندسی شیمی کاتالیزور
پیش نمایش صفحه اول مقاله
Temperature-induced evolution of reaction sites and mechanisms during preferential oxidation of CO
چکیده انگلیسی

Active sites responsible for the preferential oxidation of carbon monoxide were investigated using 4 wt.% Cu–CeO2 catalysts prepared by flame spray pyrolysis. Surface redox properties of the catalyst were assessed using a series of temperature-programmed reduction (CO, H2 and mixed) experiments, as well as operando infrared spectroscopy. It was demonstrated that CO and H2 react at identical surface sites, with CO2 formation proceeding simultaneously via three distinct Cun+–CO carbonyl species. The origin of high catalytic selectivity towards CO at below 150 °C stems from the carbonyl stabilization effect on the catalyst surface, preventing adsorption and subsequent oxidation of H2. Under non-selective conditions at higher temperatures, a gradual red-shift and loss of intensity in the carbonyl peak was observed, indicating reduction of Cu+ to Cu0, and the onset of an alternate redox-type oxidation mechanism where CO and H2 compete for the oxidation sites. These results for Cu–CeO2 suggest that improved low-temperature catalytic activity will only be achieved at the expense of reduced high-temperature selectivity and vice versa.

The origin of preferential oxidation (PROX) of CO in the presence of H2 was traced to the carbonyl stabilization on partially-reduced copper oxide surface, at below 150 °C, preventing thus incoming H2 from approaching the oxidation sites.Figure optionsDownload high-quality image (182 K)Download as PowerPoint slide

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Catalysis - Volume 277, Issue 1, 3 January 2011, Pages 64–71
نویسندگان
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