Selective Liquid Phase Adsorption of 5‑Hydroxymethylfurfural on Nanoporous Hyper-Cross-Linked Polymers

Hydroxymethylfurfural (HMF) is considered a high potential biogenic platform chemical that can be produced from carbohydrates by hydrothermal or acid-catalyzed dehydration processes. Its separation from polar liquid phase reaction mixtures still remains a challenge on the way to commercialization. Recently, liquid phase adsorption of HMF has been considered a viable and energy efficient method. While conventional adsorbents show competitive adsorption in the reaction mixture, we herein report for the first time the highly selective adsorption of HMF from aqueous solutions on nanoporous hyper-cross-linked polymers (HCP). Excess adsorption isotherms of fructose (F), HMF, and its follow-up products levulinic acid and formic acid were measured under equilibrium conditions, and the data were modeled accordingly. Additionally, the desorption behavior was investigated. Overall, the evaluated HCP as well as similar nonpolar adsorbents exhibit great potential for future process development regarding efficient adsorptive separation technologies for the utilization of renewable feedstock

ReO_<i>x</i>/TiO₂: A Recyclable Solid Catalyst for Deoxydehydration

Deoxydehydration (DODH) enables the transformation of two adjacent hydroxyl functions into a C–C double bond: e.g., facilitating synthesis of 1,3,5-hexatriene from sorbitol. Here we report the first stable heterogeneous catalyst for DODH based on ReO_<i>x</i> supported on TiO₂. ReO_<i>x</i>/TiO₂ exhibits not only catalytic activity and selectivity comparable to those of previously described molecular rhenium catalysts but also excellent stability without deactivation over at least six consecutive runs. X-ray absorption spectroscopy (XAFS) measurements indicate a mixture of Re­(VII), Re­(IV), and Re(0) species at a ratio of 0.47:0.27:0.25, remaining comparatively stable during catalysis

Selective Production of Glycolic Acid from Cellulose Promoted by Acidic/Redox Polyoxometalates via Oxidative Hydrolysis

The direct conversion of cellulose to glycolic acid (GA) with a high yield of up to 75% is realized using acidic/redox polyoxometalates (POMs) as catalysts in a one-pot reaction. Analysis of the reaction pathway and mechanism for the three POMs H3PMo12O40 (H3PMo), H3PW12O40 (H3PW), and H5PMo10V2O40 (H5PMoV2) by density functional theory calculations and experiments shows that H3PMo is especially promising. Activation of O2 to •O2– and 1O2 via one-electron transfer assists the depolymerization process of cellulose by acidic/redox H3PMo. The reduced form [PMo10VIMo2VO39]5– plays a crucial role in GA production due to its high activity and ability to stabilize the intermediates of the retro-aldol reaction. H3PMo was furthermore complexed by the ionic liquid 1-(3-sulfonic group) propyl-3-methyl imidazolium (MIMPS), which enables easy recovery from the reaction solution due to temperature-responsive properties of the complexes. [MIMPS]H2PMo provides an outstanding GA selectivity of 61% under aerobic conditions and is comparable to the homogeneous H3PMo. Activity and selectivity to GA could be improved to 100 and 75%, respectively, by performing the reaction in the microwave at 190 °C for 2 min. The work deepens the insight on cellulosic biomass transformation over POMs by acidic/oxidative synergetic catalysis and contributes to the effort of designing highly active, selective, and multifunctional catalysts

Pharmakoökonomie - Besteht ein Bedarf bei Studierenden der Medizin für interdisziplinäre Seminare mit Studierenden der Wirtschafts- und Rechtswissenschaften?

To ensure a high efficiency of 5-hydroxymethylfurfural (HMF) synthesis, improved solvents for the extraction of HMF from a reactive aqueous solution were identified using the predictive thermodynamic model COSMO-RS. Utilizing COSMO-RS as a basis for a systematic solvent selection has the advantage of potentially saving significant time and effort by computationally screening several thousand possible solvents. Factors including temperature, concentration, and fructose addition were used for experimental validation of the predictive power of COSMO-RS. Continuous extraction experiments confirmed also kinetics and phase separation to be important for technical implementation. COSMO-RS predicted <i>o</i>-propylphenol and <i>o</i>-isopropylphenol to have partition coefficients as high as 10.02 and 9.82, which are roughly five times higher than the partition coefficient of the previously known, most effective solvent: 2-methyltetrahydrofuran (<i>P</i>_HMF = 2). Therefore, the identification of <i>o</i>-propylphenol and <i>o</i>-isopropylphenol as improved solvents constitutes a significant efficiency improvement for the extraction, and by extension for the entire HMF synthesis