Acetyl Group Migration in Xylan and Glucan Model Compounds as Studied by Experimental and Computational Methods

It was recently demonstrated by us that acetyl groups in oligosaccharides can migrate not only within one saccharide unit but also between two different saccharide units. Kinetics of this phenomenon were previously investigated in both mannan model compounds and a naturally occurring polysaccharide. In addition to mannans, there are also several other naturally acetylated polysaccharides, such as xyloglucans and xylans. Both xyloglucans and xylans are some of the most common acetylated polysaccharides in nature, displaying important roles in the plant cells. Considering the various biological roles of natural polysaccharides, it could be hypothesized that the intramolecular migration of acetyl groups might also be associated with regulation of the biological activity of polysaccharides in nature. Consequently, a better understanding of the overall migration phenomenon across the glycosidic bonds could help to understand the potential role of such migrations in the context of the biological activity of polysaccharides. Here, we present a detailed investigation on acetyl group migration in the synthesized xylan and glucan trisaccharide model compounds by a combination of experimental and computational methods, showing that the migration between the saccharide units proceeds from a secondary hydroxyl group of one saccharide unit toward a primary hydroxyl group of the other unit

Reductive N-methylation of amines using dimethyl carbonate and molecular hydrogen: Mechanistic insights through kinetic modelling

[EN] Kinetic analysis of ruthenium-catalyzed reductive N-methylation of amines using dimethyl carbonate as C1 source and molecular hydrogen as reductant has been performed. Kinetic equations have been derived and kinetic modelling has been performed for experimental data generated previously at a constant hydrogen pressure as well as for additional experiments performed at different hydrogen pressures. The study has revealed interesting kinetic features related to an induction period strongly influenced by temperature. A kinetic model has been proposed based on advanced reaction mechanism featuring transformation between different type of catalytic species and inactivation of them during the reaction. Kinetic modelling was done for all data sets together showing excellent correspondence between calculations and experiments.Cabrero Antonino, JR.; Adam-Ortiz, R.; Wärnå, J.; Murzin, DY.; Beller, M. (2018). Reductive N-methylation of amines using dimethyl carbonate and molecular hydrogen: Mechanistic insights through kinetic modelling. Chemical Engineering Journal. 351:1129-1136. https://doi.org/10.1016/j.cej.2018.06.174S1129113635

Acetyl group migration across the saccharide units in oligomannoside model compound

Acetylated oligosaccharides are common in nature. While they are involved in several biochemical and biological processes, the role of the acetyl groups and the complexity of their migration has largely gone unnoticed. In this work, by combination of organic synthesis, NMR spectroscopy and quantum chemical modeling, we show that acetyl group migration is a much more complex phenomenon than previously known. By use of synthetic oligomannoside model compounds, we demonstrate, for the first time, that the migration of acetyl groups in oligosaccharides and polysaccharides may not be limited to transfer within a single monosaccharide moiety, but may also involve migration over a glycosidic bond between two different saccharide units. The observed phenomenon is not only interesting from the chemical point of view, but it also raises new questions about the potential biological role of acylated carbohydrates in nature.Peer reviewe

Brønsted acid catalyzed Prins-Ritter reaction for selective synthesis of terpenoid-derived 4-amidotetrahydropyran compounds

A number of SO3H-functionalized solids (biochar, montmorillonites, carbon and halloysite nanotubes) has been studied as catalysts in the cascade Prins-Ritter reaction of (-)-isopulegol with benzaldehyde and acetonitrile for synthesis of octahydro-2H-chromene amides (as 4R- and 4S-isomers). A high selectivity to these products at 30 °C in the presence of H2O was observed on catalysts modified with chlorosulfonic acid (CSA) reaching 84% (4R/4S of 5.7) in the case of biochar, while a relatively large amount of octahydro-2H-chromenols (up to 31%), products of Prins condensation, was formed on the materials functionalized by 2-(4-chlorosulfonylphenyl)ethyltrimethoxysilane (CSP). Although Prins condensation proceeds efficiently on weak acid sites, the Prins-Ritter reaction requires sulfated materials with strong (0.33 – 5.8 mmol/g) Brønsted acidity. Catalysts functionalized by CSP were stable, while for the materials modified with chlorosulfonic acid, leaching of -SO3H groups was observed. Nonetheless, on resistant Bioсhar-CSP, selectivity to the amides at 30 °C (67%) was higher than that with the commercial Amberlyst-15 (47%), and triflic acid at − 25 °C (62%). Similar selectivity to the desired products on Biochar-CSA (-SO3H groups) and H2SO4 (81–84%) as well as on Biochar-CSP (-PhSO3H) and with p-toluenesulfonic acid (67–70%) was observed. DFT calculations and experimental results showed that at 30 °C formation of 4S-amide thermodynamically is more beneficial than of alcohols and dehydration products. However, addition of water results in a sharp increase in the reaction rate and 4R-amide selectivity due to a change to the kinetic control, leading eventually to both high yields and stereoselectivity. The proposed reaction pathways also were confirmed by kinetic modelling.This work is part of the scientific activity of the Institute of Chemistry of New Materials, funded by the National Academy of Sciences of Belarus. Julián E. Sánchez thanks to Pontificia Universidad Javeriana for providing computational powder and to Universidad Jaume I (Pla de Promoció de la Investigació de la Universitat Jaume I) for the Post Doctoral Fellowship. Part of this work (synthesis and charaterization of sulfonic-acid catalysts presented in Fig. 2) was funded by the Portuguese funds through Fundação para a Ciência e a Tecnologia (FCT/MCTES) in the framework of the projects UIDB/50006/2020, UIDP/50006/2020. A.F.P. is also grateful to FCT for funding through the Individual Call to Scientific Employment Stimulus 2020.01614.CEECIND/CP1596/CT0007

Interactions between Iron and Nickel in Fe–Ni Nanoparticles on Y Zeolite for Co-Processing of Fossil Feedstock with Lignin-Derived Isoeugenol

A set of low-cost monometallic Fe, Ni, and bimetallic Fe–Ni bifunctional H–Y-5.1 catalysts with different metal ratios were synthesized by sequential incipient wetness impregnation. The catalysts were characterized in detail by N$_2$ physisorption, Fourier transform infrared spectroscopy with pyridine, inductively coupled plasma optical emission spectroscopy, X-ray diffraction (XRD), transmission and scanning electron microscopy (TEM–SEM), magic angle spinning nuclear magnetic resonance, X-ray photoelectron spectroscopy (XPS), Mössbauer spectroscopy, magnetic measurements, temperature-programmed reduction (TPR), and X-ray absorption spectroscopy (XAS). The results revealed that introduction of Fe led to a decrease of strong acid sites and an increase of medium Brønsted acid sites, while introduction of Ni increased the number of Lewis acid sites. The particle size of iron was approx. 5 nm, being ca. fourfold higher for nickel. XPS demonstrated higher iron content on the catalyst surface compared to nickel. Both Mössbauer spectroscopy and magnetic measurement confirmed the ferromagnetic behavior of all catalysts. In addition, the results from XRD, TEM, XPS, XAS, and magnetization suggested strong Fe–Ni nanoparticle interactions, which were supported by modeling of TPR profiles. Catalytic results of the co-processing of fossil feedstock with lignin-derived isoeugenol clearly showed that both product distribution and activity of Fe–Ni catalysts strongly depend on the metals’ ratio and their interactions. Key properties affected by the Fe–Ni metal ratio, which played a positive role in co-processing, were a smaller medial metal nanoparticle size (<6 nm), a lower metal–acid site ratio, as well as presence in the catalyst of fcc FeNi alloy structure and fcc Ni doped with Fe

Oxidation of glucose and arabinose mixtures over Au/Al2O3

Oxidation of a mixture of glucose and arabinose over 1% Au deposited on alumina was investigated in a semi-batch reactor varying pH, temperature and partial pressure of oxygen. Elevation of the latter enhancing the rate induced also losses in selectivity to aldonic acids. A kinetic model representing the catalytic oxidation reactions of arabinose and glucose along with respective isomerization to fructose and ribulose was developed. Calculations based on the model were able to describe experimental data in a reliable way

Citral-to-Menthol Transformations in a Continuous Reactor over Ni/Mesoporous Aluminosilicate Extrudates Containing a Sepiolite Clay Binder

One-pot continuous synthesis of menthols from citral was performed over 5 wt % Ni supported on a mesoporous aluminosilicate catalyst with sepiolite as a binder at 70 degrees C with a selectivity of 75% to menthols. Catalyst deactivation with time-onstream resulted in a decrease of the conversion and selectivity to menthols at the expense of higher selectivity to isopulegols. Stereoselectivity to isopulegols and menthols only slightly changed with conversion and TOS. A kinetic model capable of describing experimental data for transformations of citral to menthol in a continuous mode was developed. It was based on a detailed reaction network and also comprised deactivation on both metal and acid sites. Numerical data fitting confirmed a good correspondence between the experimental data and calculations

Catalytic decomposition of formic acid in a fixed bed reactor – an experimental and modelling study

Formic acid is one of the key components in green chemistry being involved in energy storage, production of chemical intermediates and fuel components. Therefore the knowledge of its stability is of crucial importance and a systematic study of its decomposition is needed. The kinetics of formic acid decomposition to hydrogen and carbon dioxide was investigated in a laboratory-scale fixed bed reactor at 150–225 °C and atmospheric pressure. Palladium nanoparticles deposited on porous active carbon Sibunit were used as the heterogeneous catalyst. The catalyst was characterized by nitrogen physisorption and high-resolution transmission electron microscopy. The average palladium nanoparticle size was 5–6 nm. The impacts of mass transfer resistance and formic acid dimerization were negligible under the reaction conditions. Prolonged experiments revealed that the catalyst had a good stability. Hydrogen and carbon dioxide were the absolutely dominant reaction products, whereas the amounts of carbon monoxide and water were negligible. The experimental data were described with three kinetic models: first order kinetics, two-step adsorption-reaction model and multistep adsorption-decomposition model of formic acid. The multistep model gave the best description of the data.</p

Production of Cycloalkanes in Hydrodeoxygenation of Isoeugenol Over Pt- and Ir-Modified Bifunctional Catalysts

Hydrodeoxygenation of isoeugenol was investigated at 200 °C under 3 MPa total pressure in dodecane as a solvent, in hydrogen, over bifunctional Pt‐ and Ir‐modified Beta zeolites and mesoporous materials. As a comparison, Pt and Ir supported on Al2O3, SiO2 and mesoporous MCM‐41 were also tested. The catalysts were characterized by XRD, CO pulse chemisorption, transmission electron microscopy, scanning electron microscopy, nitrogen adsorption and FTIR pyridine adsorption desorption. The results revealed that the most active and selective catalyst was Pt‐H‐Beta‐300, which exhibits the lowest acidity and largest crystal size of Beta zeolite among the studied Pt‐ and Ir‐modified Beta zeolites. Complete conversion of isoeugenol and 89 % selectivity to propylcyclohexane was obtained with this catalyst in 240 min. The overall deoxygenation selectivity was 100 %, giving dialkylated cyclohexanes as the second major product. The catalyst was regenerated, reduced and reused in the hydrodeoxygenation of isoeugenol with almost the same performance as the fresh catalyst. Thermodynamic analyses and kinetic modelling of the data were also performed.</p

Tillämpade intelligenta system inom välfärdsteknologi och digital hälsa. Nulägesanalys

Rapporten ger en översikt över tillämpade intelligenta system inom välfärdsteknologi och digital hälsa och vad de senaste trenderna är inom dessa områden. Begrepp som artificiell intelligens, maskininlärning, välfärdsteknologi, digital hälsa, bärbara enheter (wearables) och m-hälsa förklaras inledningsvis för att ge läsare en bakgrund. Visioner och trender i nuläget inom digital hälsa lyfts fram och exempel ges på digital teknik och intelligenta system som förutspås kunna förändra hälso- och sjukvården i framtiden