کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
10244783 | 47702 | 2005 | 19 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Dehydrogenation of isopropyl alcohol on carbon-supported Pt and Cu-Pt catalysts
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
مهندسی شیمی
کاتالیزور
پیش نمایش صفحه اول مقاله
![عکس صفحه اول مقاله: Dehydrogenation of isopropyl alcohol on carbon-supported Pt and Cu-Pt catalysts Dehydrogenation of isopropyl alcohol on carbon-supported Pt and Cu-Pt catalysts](/preview/png/10244783.png)
چکیده انگلیسی
The kinetics of isopropyl alcohol (IPA) dehydrogenation over carbon-supported Pt and three bimetallic CuPt catalysts were examined and compared with previous results for carbon-supported Cu. Adsorption of H2 and CO, dissociative chemisorption of N2O, and the titration of adsorbed O atoms by H2 and CO were used to determine surface compositions and metal dispersion. Monometallic platinum catalysts had a higher specific activity than monometallic Cu catalysts and the bimetallic catalysts; for example, at 448 K and 14 Torr IPA, for an activated carbon heat treated at 1223 K as the support, the turnover frequency (TOF) on the Pt catalyst was 0.11 sâ1, the TOF on the Cu catalyst was 0.020 sâ1, and the TOFs on the three bimetallic catalysts were between 0.006 and 0.043 sâ1. Reaction orders were typically between 0 and 12 for IPA and slightly negative for acetone and H2. Increasing the Cu loading reduced the number of surface Pt atoms, and the kinetic behavior became similar to that of monometallic copper catalysts. The apparent activation energy for acetone production from IPA on Pt/C was 6.8 kcalâmolâ1, compared with 21 kcalâmolâ1 for the monometallic Cu/C catalysts. Apparent activation energies for the CuPt/C catalysts (7-9 kcalâmolâ1) were comparable to those of Pt/C at lower temperatures and decreased further to â¼3kcalmolâ1 above 443 K. This decrease is not due to diffusional limitations and can be explained by a decrease in the surface coverage of IPA. A Langmuir-Hinshelwood model invoking cleavage of the alcohol OH bond to form a surface isopropoxide species as the rate-determining step fit the data well and accounted for the shift in the apparent activation energy. Physically meaningful values of enthalpies and entropies of adsorption were obtained from the fitting parameters contained in the L-H rate expression. Additional evidence for adsorbed IPA and acetone was provided by infrared spectra of the catalysts obtained under reaction conditions.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Catalysis - Volume 233, Issue 1, 1 July 2005, Pages 147-165
Journal: Journal of Catalysis - Volume 233, Issue 1, 1 July 2005, Pages 147-165
نویسندگان
R.M. Rioux, M.A. Vannice,