Showing papers on "Aldose published in 2016"

Production of alpha-hydroxy carboxylic acids and esters from higher sugars using tandem catalyst systems

Abstract: The present disclosure is directed to methods and composition used in the preparation of alpha-hydroxy carboxylic acids and esters from higher sugars using a tandem catalyst system comprising retro-aldol catalysts and Lewis acid catalysts. In some embodiments, these alpha-hydroxy carboxylic acids may be prepared from pentoses and hexoses. The retro-aldol and Lewis catalysts may be characterized by their respective ability to catalyze a 1,2-carbon shift reaction and a 1,2-hydride shift reaction on an aldose or ketose substrate.

Catalytic conversion method of aldose into ketose

Abstract: The invention provides a method for simultaneous isomerism of aldose into corresponding ketose and epimer aldose. The method uses the aldose as a substrate, and selects oxidation modified carbon nanotube supported with iron, aluminum, calcium, magnesium, molybdenum, chromium, and manganese elements of carbon nanotubes, or graphene as a catalyst. When the catalyst is mixed with the substrate aldose to not only catalyze aldehyde ketone isomerism to obtain corresponding ketose but also catalyze isomerism of C2 to obtain a corresponding C2 isomerism aldose catalyst, so as to realize simultaneous isomerism by one catalyst to obtain two rare functional sugars. The method has the advantages of high isomerism efficiency, simple operation conditions, reutilization of catalyst, small energy consumption, green, low cost, and potential in industrial mass production.

Differentiation of the Coordination Chemistry of Metal Chlorides in Catalytic Conversion of Glucose in Ionic Liquids

Abstract: Catalytic aldose isomerization to ketose is an important reaction for the utilization of cellulosic biomass. However, a fundamental understanding and knowledge base involved in this reaction remains lacking in the literature. In this chapter, we provide a focused review of the most studied solvent-based catalytic system involving metal halides for glucose isomerization to fructose and further to 5-hydroxymethhylfurfral (5-HMF). Results from studies by different physical techniques are critically reviewed. A differentiation of the coordination chemistry of different metal chlorides obtained by various physical techniques is established to rationalize the drastically different catalytic pathways by the metal chloride catalysts. The performance of metal chloride catalysts for the isomerization of aldose to ketose is found to correlate with their coordination chemistry. Solvents play an important role in determining the coordination structures for the metal ions, which critically affect the catalysis of the metal chloride precursors. Undesired side products are related to the reaction pathways corresponding to the nature of the coordination of metal ions with different oxygen sources in the substrates and the products.