نتایج جستجو برای: brønsted acid and lewis acid catalyst
تعداد نتایج: 16951353 فیلتر نتایج به سال:
چکیده ندارد.
The selective transformation of hexose and pentose sugars to intermediate platform chemicals, such as furans, is an essential step in the conversion of cellulosic and hemicellulosic biomass to biofuels and biochemicals. Yet, many challenges in achieving commercially viable processes remain. In this feature article, we outline challenges that need to be overcome to enable these transformations. ...
Convenient procedure for the synthesis of corresponding pyrano[2,3-d]pyrimidine derivatives were developed via one-pot three-component reaction of aryl aldehyde derivatives, malononitrile with barbituric acids in the presence of copper (II) chloride dihydrate (CuCl2.2H2O) as highly efficient Lewis acid catalyst. This protocol has advantages such as readily and inexpensive catalyst, high reactio...
introduction acetic acid bacteria are large group of obligate aerobic gram negative bacteria with the ability to oxidize ethanol to acetic acid (1). they are widely distributed in natural habitats and classified in family acetobacteraceae. members of this family are useful in industrial production of vinegar(2). acetic acid bacteria (aab) can use substrates as glucose, ethanol, lactate or glyc...
Experimentally, a reversal of chemoselectivity has been observed in catalyzed Diels–Alder reactions α,β-unsaturated aldehydes (e.g., (2E)-but-2-enal) and ketones 2-hexen-4-one) with cyclopentadiene. Indeed, using the triflimidic Brønsted acid Tf2NH as catalyst, reaction gave adduct derived from ketone major product. On other hand, use tris(pentafluorophenyl)borane B(C6F5)3 bulky Lewis catalyst ...
Heterogeneous acid and base catalysts play a crucial role in many important chemical processes. Hard Lewis Brønsted like silica-alumina zeolites have been widely applied numerous reactions; however, developing reusable active soft remain challenge. Herein, we demonstrate for the first time that highly dispersed supported platinum catalyst can act as heterogeneous acid. High turnover numbers reu...
TiCl4/nano-cellulose as a biodegradable and eco-friendly Lewis acid catalyst was synthesized via reaction of nano-cellulose and TiCl4. This catalyst was characterized and used for synthesis of asymmetric highly functionalized tetrahydropyridines via a five-component condensation reaction of p-substituted anilines, aldehydes and ethyl acetoacetate under solvent-free condition. Simple methodology...
A mild and green method has been developed for the preparation of coumarins derivatives through the one-pot reactions. In our study,various phenols and ethyl acetoacetate compound in which we used silica-supported boron sulfonic acid [SiO2/B(SO4H)3] as a new, highly efficient and tri-functional inorganic Brønsted acid catalyst were processed under solvent-free condition and thermal. The catalys...
Heterogeneous catalysts are desired for the conversion of glucose, the most abundant sugar in renewable biomass, but presently their synthesis requires highly toxic chemicals with long synthesis times. We report the conversion of glucose into fructose and 5-hydroxymethylfurfural on a heterogeneous catalyst that is stable and selective and operates in the most environmentally benign solvent, wat...
ZnO modified ZSM-5 and Y zeolites are synthesized by performing atomic layer deposition (ALD) of ZnO to HZSM-5 and HY using diethyl zinc and water as the precursors. The surface area and pore volume of ZSM-5 and Y zeolites are progressively reduced with the increasing number of ZnO ALD cycles. XRD and SEM characterization methods show that highly dispersed ZnO species are deposited on the inter...
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