Lignocellulosic biomass is a plentiful and renewable resource for fuels and chemicals. Despite this potential, nearly all renewable fuels and chemicals are now produced from edible resources, such as starch, sugars, and oils; the challenges imposed by notoriously recalcitrant and heterogeneous lignocellulosic feedstocks have made their production from nonfood biomass inefficient and uneconomical. Here, we report that N,N-dimethylacetamide (DMA) containing lithium chloride (LiCl) is a privileged solvent that enables the synthesis of the renewable platform chemical 5-hydroxymethylfurfural (HMF) in a single step and unprecedented yield from untreated lignocellulosic biomass, as well as from purified cellulose, glucose, and fructose. The conversion of cellulose into HMF is unabated by the presence of other biomass components, such as lignin and protein. Mechanistic analyses reveal that loosely ion-paired halide ions in DMA−LiCl are critical for the remarkable rapidity (1−5 h) and yield (up to 92%) of this low...

http://pubs.acs.org/doi/pdf/10.1021/ja808537j

Simple Chemical Transformation of Lignocellulosic Biomass into Furans for Fuels and Chemicals

Mechanism of formation of 5-(hydroxymethyl)-2-furaldehyde from d-fructose and sucrose

All of the lanthanide(III) (La3+–Lu3+) efficiently catalyzed the dehydration of hexose in water at 140 °C to produce 5-hydroxymethyl-2-furaldehyde (HMF) without accompanying further hydrolysis to levulinic acid, which is routinely obtained as a by-product in the conventional Bronsted acid-catalyzed reactions. The relationships between the catalytic activity and the ionic radius (ri) of lanthanides(III) for the dehydration of D-fructose and D-glucose were found to have a double-peak profile maximizing at Pr or Nd (ri 1.00 A) and Er or Yb (ri 0.87 A) with a dip at Sm (ri 0.96 A). Kinetic analyses revealed that the rate-determining step is not the complex formation of lanthanide(III) ion with the saccharide molecule, but a subsequent reaction from the substrate-catalyst complex. Possible reasons why the catalytic activity–ionic radius relationships show a two-peak profile are discussed.

Catalytic Activity of Lanthanide(III) Ions for the Dehydration of Hexose to 5-Hydroxymethyl-2-furaldehyde in Water

Publisher Summary This chapter explains the decomposition of saccharides by heat devoted to the caramelization of saccharides and their pyrolysis above 250°. Caramelization belongs to the group of so-called “browning reactions.” Caramel has a brown color and it originates from various sugars when they are heated, either dry, or in concentrated solutions. The quality of a caramel depends on its source as well as on the parameters of the process of its manufacture. Caramel is manufactured to change and improve the appearance (color) of many food products; the enhancement of the flavor of food is also important. The chemical nature of caramel depends on the conditions of the caramelization and the source, at least in the terminal period of their processing. Ever since it was suspected that caramels are biologically active, the daily uptake levels for them have been calculated and announced. The pyrolysis of sugars has been studied because carbohydrates could be considered as a source of technically important products. Moreover, these studies were intended to contribute to the knowledge of the chemistry of caramelization.

The Thermal Decomposition of Carbohydrates. Part I. The Decomposition of Mono-, Di-, and Oligo-Saccharides

A method for converting a carbohydrate to a furan in a polar aprotic solvent in the presence of a chloride, bromide, or iodide salt or a mixture thereof and optionally in the presence of an acid catalyst, a metal halide catalyst and/or an ionic liquid (up to 40 wt %). The method can be employed in particular to produce furfural or 5-hydroxymethylfurfural.

Laurence Poncini

Papers

Thermolysis of sucrose in dimethyl sulphoxide solution