کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
9607891 46026 2005 13 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Isomerization of n-hexane over mono- and bimetallic Pd-Pt catalysts supported on ZrO2-Al2O3-WOx prepared by sol-gel
موضوعات مرتبط
مهندسی و علوم پایه مهندسی شیمی کاتالیزور
پیش نمایش صفحه اول مقاله
Isomerization of n-hexane over mono- and bimetallic Pd-Pt catalysts supported on ZrO2-Al2O3-WOx prepared by sol-gel
چکیده انگلیسی
The catalytic performance of mono- and bimetallic Pd (0.6, 1.0 wt.%)-Pt (0.3 wt.%) catalysts supported on ZrO2 (70, 85 wt.%)-Al2O3 (15, 0 wt.%)-WOx (15 wt.%) prepared by sol-gel was studied in the hydroisomerization of n-hexane. The catalysts were characterized by N2 physisorption, XRD, TPR, XPS, Raman, NMR, and FT-IR of adsorbed pyridine. The preparation of ZrW and ZrAlW mixed oxides by sol-gel favored the high dispersion of WOx and the stabilization of zirconia in the tetragonal phase. The Al incorporation avoided the formation of monoclinic-WO3 bulk phase. The catalysts increased their SBET for about 15% promoted by Al2O3 addition. Various oxidation states of WOx species coexist on the surface of the catalysts after calcination. The structure of the highly dispersed surface WOx species is constituted mainly of isolated monotungstate and two-dimensional mono-oxotungstate species in tetrahedral coordination. The activity of Pd/ZrW catalysts in the hydroisomerization of n-hexane is promoted both with the addition of Al to the ZrW mixed oxide and the addition of Pt to Pd/ZrAlW catalysts. The improvement in the activity of Pd/ZrAlW catalysts is ascribed to a moderated acid strength and acidity, which can be correlated to the coexistence of W6+ and reduced-state WOx species (either W4+ or W0). The addition of Pt to the Pd/ZrAlW catalyst does not modify significantly its acidic character. Selectivity results showed that the catalyst produced 2MP, 3MP and the high octane 2,3-dimethylbutane (2,3-DMB) and 2,2-dimethylbutane (2,2-DMB) isomers.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Applied Catalysis A: General - Volume 290, Issues 1–2, 18 August 2005, Pages 97-109
نویسندگان
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