نتایج جستجو برای: natural catalysts

تعداد نتایج: 513446  

Journal: :Chemical science 2015
Yang Zheng Li Deng

An unprecedented highly diastereoselective and enantioselective aldol reaction of α-alkyl azlactones and aliphatic aldehydes was achieved with cinchona alkaloid catalysts. To our knowledge, this reaction provides the first useful catalytic asymmetric access toward β-hydroxy-α-amino acids bearing alkyl substituents, which are structural motifs embedded in many natural products.

1999

Ammonia (NH3) is produced from atmospheric nitrogen and hydrogen from a hydrocarbon source. Natural gas is the most commonly used hydrocarbon feedstock for new plants; other feedstocks that have been used include naphtha, oil, and gasified coal. Natural gas is favored over the other feedstocks from an environmental perspective. Ammonia production from natural gas includes the following processe...

2017
Jan Wallbaum Daniel B Werz

A variety of novel imidazolidinone-based organocatalysts with bulky substituents were synthesized under mild reaction conditions starting from easily accessible substrates. Different natural and unnatural amino acid methyl amides were cyclized with aromatic carbaldehydes to yield two diastereomeric MacMillan-type catalysts. Special emphasis was put on bulky residues such as mesityl and pyrene m...

2018
Ramesh Karunagaran Campbell Coghlan Cameron Shearer Diana Tran Karan Gulati Tran Thanh Tung Christian Doonan Dusan Losic

Rapid depletion of fossil fuel and increased energy demand has initiated a need for an alternative energy source to cater for the growing energy demand. Fuel cells are an enabling technology for the conversion of sustainable energy carriers (e.g., renewable hydrogen or bio-gas) into electrical power and heat. However, the hazardous raw materials and complicated experimental procedures used to p...

2008
M. Foix C. Guyon P. Da Costa M. Tatoulian

Introduction Nowadays, almost all major chemicals are produced by catalytic processes. Among them, heterogeneous catalysis plays a very active role, because of environmental concerns. The use of plasmas for catalysis is now well developed and some authors have used plasma treatment in a low pressure system to replace the thermal calcination of the catalysts [1]Fluidized bed reactors offer the p...

Journal: :Journal of the American Chemical Society 2015
Jennifer M Howell Kaibo Feng Joseph R Clark Louis J Trzepkowski M Christina White

Nitrogen heterocycles are ubiquitous in natural products and pharmaceuticals. Herein, we disclose a nitrogen complexation strategy that employs a strong Brønsted acid (HBF4) or an azaphilic Lewis acid (BF3) to enable remote, non-directed C(sp(3))-H oxidations of tertiary, secondary, and primary amine- and pyridine-containing molecules with tunable iron catalysts. Imides resist oxidation and pro...

Journal: :polyolefins journal 2015
helmut g. alt

eethylene polymerization catalysts became available in an enormous variety. the challenge in this research is to find catalysts that are able to connect ethylene molecules in such a way that not only linear chains are produced but variations like branched materials that possess very interesting mechanical properties like linear low density polyethylene (lldpe). in this contribution, three diffe...

Journal: :Catalysts 2021

Co–Fe–Al catalysts prepared using coprecipitation at laboratory scale were investigated and extended to pilot for high-calorific synthetic natural gas. The with different metal loadings analyzed BET, XRD, H2-TPR, FT-IR. An increase in the loading of showed low spinel phase ratio, leading an improvement reducibility. Among catalysts, 40CFAl catalyst afforded highest C2–C4 hydrocarbon time yield,...

Journal: :Green Energy & Environment 2023

Among challenges implicit in the transition to post–fossil fuel energetic model, finite amount of resources available for technological implementation CO2 revalorizing processes arises as a central issue. The development fully renewable catalytic systems with easier metal recovery strategies would promote viability and sustainability synthetic natural gas production circular routes. Taking Ni N...

Journal: :Chembiochem : a European journal of chemical biology 2014
Thomas Heel John A McIntosh Sheel C Dodani Joseph T Meyerowitz Frances H Arnold

Recent work has shown that engineered variants of cytochrome P450BM3 (CYP102A1) efficiently catalyze non-natural reactions, including carbene and nitrene transfer reactions. Given the broad substrate range of natural P450 enzymes, we set out to explore if this diversity could be leveraged to generate a broad panel of new catalysts for olefin cyclopropanation (i.e., carbene transfer). Here, we t...

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