شر ال ع لميمرك ز ال ن Center of Scientific Publications MainPage About the center Journal of KAU Electronic books Saudi Systems Search for Publications Parallel Publication Researches Files New Publications Publications o Scientific books Islamic economy Economy and administration Literature Reviews Geography Computer Science Fire Religion Mathematics and Statistics Geology Piology Educational Science o Seminars and Conferences o Training Courses o Official Printing on Paper o Abstracts and indexes Under publishing Request o Request Order o Subscription جامعة ال م لك ع بدال عزي ز King Abdulaziz University Document Details Document Type Document Title : Article In Conference : Solvent-free oxidation of alcohols by hydrogen peroxide over chromium Schiff base complexes immobilized on MCM-41: optimization of catalytic activity by modificating the local environment of active complexes Solvent-free oxidation of alcohols by hydrogen peroxide over chromium Schiff base complexes immobilized on MCM-41: optimization of catalytic activity by modificating the local environment of active complexes Subject Document Language Abstract : ءك يم يا : English : Oxidation of alcohols to aldehydes and ketones is a ubiquitous transformation in organic synthesis. Recent demand for eco-friendly chemical processes encouraged the development of clean reactions. Hydrogen peroxide as an oxidant are atom efficient and produce water as the only by-product [1]. On the other hand, solvent-free reactions are of general interest due to their potential in combinational chemistry, simple processes, easy work-up, low cost and reduction in noxious waste materials. however, only a limited number of such useful oxidation procedures have been reported. Development of efficient biomimetic heterogeneous oxidation catalysts containing metal complexes, especially the heterogenised transition metal Schiff base complexes is eye-catching for their more accessible synthesis conditions and versatile coordination structures [2]. In the present work, a conventional chromium Schiff Contact Us Visits Of this Page 0 Conference Name Duration Publishing Year base complex was successfully immobilized MCM-41. In order to optimize the catalytic performance of immobilized complexes, a series of typical methyl regulators were further used to finely modify the local environment of active sites in immobilized complex. By changing the kinds and amounts of methyl regulators and their relative position to active sites, a series of methyl-containing immobilized chromium complexes were prepared and used for the selective oxidation of alcohols with 30% H2O2. Elemental analysis and 13C CP/MAS NMR, FTIR and UV spectra showed that the homogeneous chromium complexes had been immobilized on MCM-41, and that the methyl regulators were also successfully introduced. The powder XRD patterns and N2 sorption isotherms displayed that all immobilized complexes still exhibited typical ordered hybrid mesophases. Furthermore, with the introduction of methyl regulators, the surface polarity of immobilized complexes decreased while their hydrophobicity increased. This indicated that the local environment of active sites in immobilized complexes changed significantly. The immobilized complexes were effective catalysts and all exhibited much higher catalytic performance than their corresponding homogeneous analogues. Simultaneously, the catalytic performance of immobilized complexes was closely related to the kinds, amounts and relative localities to active complexes of methyl regulators. Under the optimal reaction conditions, aliphatic secondary alcohols, cyclic alcohols and benzylic alcohols were all oxidized in good yields, and the major products were their corresponding ketones or aldehydes, while primary alcohols were mainly oxidized to carboxylic acid. : Tenth International Symposium on Heterogeneous Catalysis : From : 22/8/1429 AH - To : 26/8/1429 AH From : 23/8/2008 AD - To : 27/8/2008 AD : 1429 AH 2008 AD Article Type Added Date : Article : Sunday, February 22, 2009 Researchers Researcher Name Researcher Name Researcher Dr Email (Arabic) (English) Type Grade Xiaoli Wang Xiaoli Wang Researcher Doctorate Gongde Wu Gongde Wu Researcher Doctorate Junping Li Junping Li Researcher Doctorate Fukui Xiao Fukui Xiao Researcher Doctorate Wei Wei Wei Wei Researcher Doctorate Yuhan Sun Yuhan Sun Researcher Doctorate Files File Name 18552.pdf Type pdf Deanship of Information Technology - King Abdulaziz University. All rights reserved Description