کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
62638 47648 2007 13 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Mesoporous silica-supported Pd catalysts: An investigation into structure, activity, leaching and heterogeneity
موضوعات مرتبط
مهندسی و علوم پایه مهندسی شیمی کاتالیزور
پیش نمایش صفحه اول مقاله
Mesoporous silica-supported Pd catalysts: An investigation into structure, activity, leaching and heterogeneity
چکیده انگلیسی

Mesoporous silica functionalized by mercaptopropyl trimethoxysilane can be loaded with palladium and the resulting material used as a catalyst for a variety of coupling reactions. The ordered silicate reacts with levels of Pd leaching in the low ppm to ppb range. The catalyst can be re-used multiple times with only moderate loss of activity or structure, depending on the method of incorporation of the thiol. A grafting approach gives a significantly more stable material which is likely insulated from attack by the aqueous base, while incorporation of the thiol by co-condensation gives a material with minimal stability under the reaction conditions. Several heterogeneity tests are performed on the catalyst including three-phase tests and poisoning studies. These indicate that the effective heterogeneity depends strongly on the solvent employed and the reaction conditions. Under non-aerobic conditions with a controlled ratio of sulfur ligand to palladium, low levels of reaction due to homogeneous species are observed, but as the organic content of the solvent is increased, more reaction on an immobilized reagent (as judged through the three-phase test) is observed. In addition, these studies highlight the constraints within which the three-phase test can be an accurate assessment of heterogeneity.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Catalysis - Volume 252, Issue 1, 15 November 2007, Pages 97–109
نویسندگان
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