Kinetic Studies on the Conversion of Levoglucosan to Glucose in Water Using Bronsted Acids as the Catalysts

Fast pyrolysis is as a promising and versatile technology to depolymerize and concentrate sugars from lignocellulosic biomass. The pyrolysis liquids produced contain considerable amounts of levoglucosan (1,6-anhydro-beta-D-glucopyranose), which is an interesting source for glucose (GLC). Here, we report a kinetic study on the conversion of levoglucosan (LG) to GLC in water using sulfuric and acetic acid as the catalysts under a wide range of conditions in a batch setup. The effects of the initial LG loading (0.1-1 M), sulfuric and acetic acid concentrations (0.05-0.5 M and 0.5-1 M, respectively), and reaction temperatures (80-200 degrees C) were determined. Highest GLC yields were obtained using sulfuric acid (98 mol %), whereas the yields were lower for acetic acid (maximum 90 mol %) due to the formation of byproducts such as insoluble polymers (humins). The experimental data were modeled using MATLAB software, and relevant kinetic parameters were determined. Good agreement between experimental and model was obtained when assuming that the reaction is first order with respect to LG. The activation energies were 123.4 kJ mol(-1) and 120.9 kJ mol(-1) for sulfuric and acetic acid, respectively

Valorization of humin type byproducts from pyrolytic sugar conversions to biobased chemicals

The pyrolytic sugar fraction, obtained by an aqueous extraction of pyrolysis oil, is an attractive source for sugar-derived platform chemicals. However, solids (humin) formation occurs to a significant extent during hydrolysis and subsequent acid-catalyzed conversion processes. In this study, we report investigations on possible conversion routes (pyrolysis, liquefaction) of such humin byproducts to biobased chemicals. Experiments were carried out with a model humin made from a representative technical pyrolytic sugar and the product was characterized by elemental analysis, GPC, TGA, HPLC, GC-MS, FT-IR and NMR. The obtained humin sample is soluble in organic solvents (dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), and isopropanol (IPA)), in contrast to typical more condensed humins from glucose and fructose, allowing characterization using NMR and GPC. All analyses reveal that the humins are oligomeric in nature (M-w of about 900 g/mol) and consist of sugar and furanic fragments linked with among others (substituted) aliphatic, ester units and, in addition, phenolic fragments with methoxy groups. The humins were used as a feed for catalytic pyrolysis and catalytic liquefaction experiments. Catalytic pyrolysis experiments (mg scale, programmable temperature vaporizer (PTV)-GC-MS, 550 degrees C) with HZSM-5 50 as the catalyst gave benzene-toluene-xylene-naphthalene-ethylbenzene mixtures (BTXNE) in 5.1 wt% yield based on humin intake. Liquefaction experiments (batch reactor, 350 degrees C, 4 h, isopropanol as both the solvent and hydrogen donor and Pt/CeO2 (4.43 wt% Pt) catalyst) resulted in 80 wt% conversion of the humin feed to a product oil with considerable amounts of phenolics and aromatics (ca. 24.7 % based on GC detectables in the humin oil). These findings imply that the techno-economic viability of pyrolysis oil biorefineries can be improved by converting humin type byproducts to high value, low molecular weight biobased chemicals

Experimental and Kinetic Modeling Studies on the Conversion of Sucrose to Levulinic Acid and 5-Hydroxymethylfurfural Using Sulfuric Acid in Water

We here report experimental and kinetic modeling studies on the conversion of sucrose to levulinic acid (LA) and 5-hydroxymethylfurfural (HMF) in water using sulfuric acid as the catalyst. Both compounds are versatile building blocks for the synthesis of various biobased (bulk) chemicals. A total of 24 experiments were performed in a temperature window of 80–180 °C, a sulfuric acid concentration between 0.005 and 0.5 M, and an initial sucrose concentration between 0.05 and 0.5 M. Glucose, fructose, and HMF were detected as the intermediate products. The maximum LA yield was 61 mol %, obtained at 160 °C, an initial sucrose concentration of 0.05 M, and an acid concentration of 0.2 M. The maximum HMF yield (22 mol %) was found for an acid concentration of 0.05 M, an initial sucrose concentration of 0.05 M, and a temperature of 140 °C. The experimental data were modeled using a number of possible reaction networks. The best model was obtained when using a first order approach in substrates (except for the reversion of glucose) and agreement between experiment and model was satisfactorily. The implication of the model regarding batch optimization is also discussed

Experimental and modeling studies on the acid-catalyzed conversion of inulin to 5-hydroxymethylfurfural in water

Inulin is considered as an attractive feed for the synthesis of 5-hydroxymethylfurfural (HMF), an important biobased platform chemical with high application potential. We here report a systematic study to optimize the HMF yield from inulin in a batch reactor for reactions in water using sulphuric acid as the catalyst. The latter was selected on the basis of a screening study with seven organic- and inorganic Bronsted acids (H2SO4, HNO3, H3PO4, HCl, trifluoroacetic acid, maleic acid and fumaric acid). The effect of process conditions such as temperature (160-184 degrees C), inulin loading (0.05-0.17 g/mL), sulphuric acid concentration (0.001-0.01 M) and reaction time (0-60 min) on HMF and levulinic acid (LA) yields were determined experimentally and subsequently modeled using non-linear multivariable regression. The highest experimental HMF yield was 39.5 wt% (50.6 mol%) and was obtained at 170 degrees C, an inulin loading of 0.17 g/mL, a sulphuric acid concentration of 0.006 M and a reaction time of 20 min. Agreement between experiments and model for both HMF and LA yield was very satisfactorily. (c) 2016 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved

Kinetic Studies on the Conversion of Levoglucosan to Glucose in Water Using Brønsted Acids as the Catalysts

Fast pyrolysis is as a promising and versatile technology to depolymerize and concentrate sugars from lignocellulosic biomass. The pyrolysis liquids produced contain considerable amounts of levoglucosan (1,6-anhydro-β-d-glucopyranose), which is an interesting source for glucose (GLC). Here, we report a kinetic study on the conversion of levoglucosan (LG) to GLC in water using sulfuric and acetic acid as the catalysts under a wide range of conditions in a batch setup. The effects of the initial LG loading (0.1–1 M), sulfuric and acetic acid concentrations (0.05–0.5 M and 0.5–1 M, respectively), and reaction temperatures (80–200 °C) were determined. Highest GLC yields were obtained using sulfuric acid (98 mol %), whereas the yields were lower for acetic acid (maximum 90 mol %) due to the formation of byproducts such as insoluble polymers (humins). The experimental data were modeled using MATLAB software, and relevant kinetic parameters were determined. Good agreement between experimental and model was obtained when assuming that the reaction is first order with respect to LG. The activation energies were 123.4 kJ mol^–1 and 120.9 kJ mol^–1 for sulfuric and acetic acid, respectively

Conversion of levoglucosan to glucose using an Choar tor acidic heterogeneous Amberlyst 16 catalyst:Kinetics and packed bed measurements

Levoglucosan (1,6-anhydro-beta-D-glucopyranose) is an anhydrosugar found in significant amounts in pyrolysis liquids obtained from lignocellulosic biomass. Levoglucosan (LG) is an attractive source for glucose (GLC), which can be used as a feedstock for biofuels (e.g. bioethanol) and biobased chemicals. Here, we report a kinetic study on the conversion of LG to GLC in water using Amberlyst 16 as the solid acid catalyst at a wide range of conditions in a batch set-up. The effects of the reaction temperature (352-388 K), initial LG intake (100-1000 mol m(-3)), catalyst loading (1-5 wt%), and stirring rate (250-1000 rpm) were determined. The highest GLC yield was 98.5 mol% (388 K, 5 wt% Amberlyst 16, C-LG,C-0 = 500 mol m(-3) at 500 rpm stirring rate and t = 60 min). The experimental data were modelled and relevant kinetic parameters were determined using a first order approach including diffusion limitations of LG inside the Amberlyst particles. Good agreement between experiments and kinetic model was obtained. The activation energy was found to be 132.3 +/- 10.1 kJ mol(-1). Experiments in a continuous packed bed set-up for up to 30 h show that catalyst stability is good. In addition, the steady state LG conversion (73 mol%) and the GLC selectivity were in line with the kinetic model obtained in the batch reactor. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved

Naphthol-derived Betti bases as potential SLC6A14 blockers

Betti bases (aminobenzylnaphthols) have not been studied extensively to explore their possible pharmacological applications. Our group prepared a small and focused library of twenty-three Betti bases from the multicomponent reaction of 2-naphthol with primary or secondary cyclic amines and representative aromatic aldehydes. The compounds were prepared in 52-90% yield using environmentally friendly procedures. The E-factor and the atom economy for our process were 3.92 and 94%, respectively. The study of the anti-proliferative activity against human solid tumor cell lines pointed out that these Betti bases represent privileged scaffolds and could be used for the development of pharmacologically-active compounds in cancer therapeutics. The 50% growth inhibitory (GI50) values of the most potent compounds were in the low micromolar range. Fourteen of these Betti bases were less active in HBL-100 breast cancer cells than towards the breast cancer cell line T-47D. A subset of these Betti bases was further tested against the human breast cancer cell lines MCF-7 and MDA-MB-453. The results indicated a correlation in the sensitivity of T-47D cells to Betti bases. We explored computationally the interaction of the Betti bases with SLC6A14, a Na+- and Cl-- dependent influx transporter of both neutral and cationic amino acids that is overexpressed in T-47D cells. SLC6A14 is inhibited by α-methyl-tryptophan, which blocks cell growth via deprivation of amino acid influx. The docking studies indicated that our Betti bases might behave as tryptophan mimetics, blocking this solute carrier transporter and inducing the anti-proliferative effects. Importantly, these Betti bases showed good cytotoxic selectivity towards cancer cells with no activity against normal human fibroblast cells BJ-hTERT.peer-reviewe

Practical chain-end reduction of polymers obtained with ATRP

A practical and user-friendly strategy for the chain-end reduction of halogen terminated polymers that employs hydrogen gas and heterogeneous catalysis (palladium on carbon) is reported. Quantitative dehalogenation of a wide variety of monomer families (polystyrenes, polyacrylates, and polymethacrylates) with either chlorine or bromine chain-ends is observed. The utility of this chain-end reduction is further highlighted by mild reaction conditions, simple purification, and compatibility with a wide range of solvents. (Figure presented.)

Controlled Formation and Binding Selectivity of Discrete Oligo(methyl methacrylate) Stereocomplexes

The triple-helix stereocomplex of poly(methyl methacrylate) (PMMA) is a unique example of a multistranded synthetic helix that has significant utility and promise in materials science and nanotechnology. To gain a fundamental understanding of the underlying assembly process, discrete stereoregular oligomer libraries were prepared by combining stereospecific polymerization techniques with automated flash chromatography purification. Stereocomplex assembly of these discrete building blocks enabled the identification of (1) the minimum degree of polymerization required for the stereocomplex formation and (2) the dependence of the helix crystallization mode on the length of assembling precursors. More significantly, our experiments resolved binding selectivity between helical strands with similar molecular weights. This presents new opportunities for the development of next-generation polymeric materials based on a triple-helix motif