RESUMO
We have developed a simple and effective route for the high yield extraction of sugars from cellulosic based biomass. This process uses a combination of a cellulose decrystallization step with a mixture of phosphoric and sulfuric acid, followed by a hydrolysis step producing sugars (xylose and glucose) with yields of approximately 90%.
Assuntos
Biomassa , Carboidratos/química , Ácidos Fosfóricos/química , Ácidos Sulfúricos/química , CristalizaçãoRESUMO
We have recently developed an improved synthetic route to 1,1,2,2-tetrafluoroethanesulfonic acid (HCF2CF2SO3H, TFESA) and explored the applications of this newly available superacid in catalysis. Low volatility, ease of handling, and a convenient 1H NMR handle make this acid an attractive alternative to triflic acid. TFESA can also be converted to several of its derivatives: anhydride, sulfonyl chloride, and sulfonyl fluoride, which provide a good entry point for the synthesis of aryl sulfonates. We prepared several aryl esters of 1,1,2,2-tetrafluoroethanesulfonic acid (aryl tetraflates) and showed that they can be used in a number of palladium-catalyzed coupling reactions (Suzuki, Heck, and Buchwald-Hartwig couplings). While the reactivity of tetraflates lies between that of triflates and chlorides, tetraflates appear to be more thermally stable. Additionally, the presence of a hydrogen atom in the tetraflate group facilitates monitoring of reactions and characterization of derivatives.
Assuntos
Sulfonatos de Arila/síntese química , Hidrocarbonetos Fluorados/química , Ácidos Sulfônicos/química , Sulfonatos de Arila/química , Catálise , Espectroscopia de Ressonância Magnética/métodos , Estrutura Molecular , EstereoisomerismoRESUMO
Perfluorinated sulfonic acids have been immobilised into mesoporous silica frameworks by a one-step process, representing the first example of the successful incorporation of charged silanes using this route, and have been shown to be excellent catalysts for Brønsted acid catalysed transformations.
Assuntos
Polímeros de Fluorcarboneto/química , Dióxido de Silício/química , Catálise , Polímeros de Fluorcarboneto/síntese química , Estrutura Molecular , Porosidade , Propriedades de Superfície , Fatores de TempoRESUMO
High catalytic activity is demonstrated for the formation of linear alkylbenzenes using a perfluorosulfonic acid catalyst in supercritical fluid reaction media: enhanced alkylation activity is observed in fluoroform (CHF3) compared to carbon dioxide.
