We describe herein an efficient microwave-assisted aqueous biphasic dehydration of carbohydrates to 5-hydroxymethylfurfural (HMF). The effects of several alkali metal salts in aqueous phase, organic solvents as an extractive phase and Lewis acids are evaluated on the reaction. Specifically, starting from fructose, the use of bromide salts in aqueous phase and the common organic solvent MeCN or lignocellulose-derived g-valerolactone (GVL) as organic extractors are highly beneficial, leading to excellent HMF yields of up to 91% with HCl as a Brønsted acid catalyst. In conjunction with an isomerization catalyst, the method was applicable to glucose as well as various disaccharides and cellulose, affording HMF in notably good yields, particularly with GVL as an extractor and reusable Amberlyst-38(wet) as an acid catalyst. The exceptionally high HMF yields obtained in aqueous solutions is attributed to the combined effect of the biphasic reaction system and the application of microwaves, which ensures short reaction times and minimized by-product formation thereof.

The effect of salts and Brønsted acids on the Lewis acid (CrCl3⋅6 H2O)‐catalyzed glucose dehydration to 5‐hydroxymethylfurfural (HMF) in aqueous media are described. We show that the reaction with bromide salts in place of chlorides leads to higher HMF yields. The influence of salts can be attributed to the anions in solution, specifically to the bromide anions enhancing the fructose dehydration step. Additionally, we demonstrate that the reaction kinetics are governed strongly by acidity. Although the fructose dehydration step is accelerated by the addition of Brønsted acids, even on a catalytic scale, a significant retardation of the glucose conversion rate results in a substantial drop in HMF yields. The suppression in glucose‐to‐fructose isomerization rate with increasing acidity is ascribed to the restrained formation of the chromium–glucose chelate complex during the reaction.

Lignin, esterified with palmitic and lauric acid chloride, has been studied for the application as coating on fiber-based packaging material. The aim was to improve the barrier properties against water vapor and oxygen of paperboard. The esterification was followed by Fourier transform infrared spectroscopy, 31 P nuclear magnetic resonance spectroscopy, and gel permeation chromatography measurements. The lignin esters were applied on paperboard and formed a continuous film. The moisture barrier property of the coated paperboards was characterized by the water vapor transmission rate (WVTR). A significant decrease in WVTR was observed, for example, 40 g m -2 (for 24 h) for a paperboard coated with 10.4 g m -2 hardwood kraft lignin palmitate. The contact angle of water on the lignin ester coatings was high and stable. For all paperboard samples coated with lignin esters, a significant decrease in oxygen transmission rate was observed. Accordingly, lignin palmitate and laurate have a high potential as a barrier materials in packaging applications.

Solvent-free NaOH catalyzed aldol condensation of biomass-derived 5hydroxymethyl furfural (HMF) and furfural with methyl isobutyl ketone (MIBK) was studied, producing branched C11 and C12 furan compounds in high yields of up to 96%.Through use of a Pd/C and Eu(OTf)3 catalytic system, the condensation products of the bio-based starting materials were further hydrodeoxygenated (HDO) in one-step to biofuel compatible branched alkanes 2-methylundecane (3) and 2-methyldecane (4) in excellent yields of 90% and 98%, respectively. In the one-step HDO developed herein, the variation of solvent had a significant effect on the reaction route and degree of conversion of furans to alkanes in the HDO process. Very high overall yields of alkanes 3 (86%) and 4 (94%) were obtained starting from the biomass-based HMF and furfural.

Naturally occurring hydroxycinnamic acids, such as ferulic and sinapic acids, are known to possess antioxidant activity. In this study, ferulic acid and sinapic acid were covalently attached to oat spelt arabinoxylan and birch wood glucuronoxylan by esterification in a two-step feasible synthesis to generate modified xylans with various degrees of substitution. The obtained derivatives were fully analyzed by FT-IR, NMR, and HPSEC experiments to confirm the esterification of xylans and the degree of substitution. The antioxidative potential of the conjugates was evaluated using the emulsion lipid oxidation test. The results demonstrate that the derivatized xylans inhibited lipid oxidation notably better than the native oat spelt and birch wood xylans. It was found that ferulic acid esters of glucuronoxylan were more efficient antioxidants than those of arabinoxylan and that sinapic acid xylan esters were more efficient than their ferulic acid counterparts.