Electrocatalytic hydrogenation of glucose and xylose using carbon fiber supported Au nanocatalysts

Recent evidences have shown catalyst structure sensitivity of electrocatalytic hydrogenation (ECH) of organic molecules in aqueous phase. In this study, ECH of glucose and xylose was investigated using gold nanoparticles (AuNPs) on activated carbon fiber (CF) support as catalyst. CF supported AuNPs catalysts (CF/AuNPs) were synthesized by deposition-precipitation method and were characterized by physicochemical (SEM, TEM, XRD, N2 physisorption, ICP-OES) and electrochemical methods. Chemical or thermal pre-treatment of CF prior to Au deposition resulted in different AuNPs size distributions. The activity towards glucose or xylose ECH were observed to be dependent on the particle size of AuNPs and the applied potential. Compared to a polycrystalline Au catalyst, higher reaction rates for glucose and xylose ECH were observed for a CF/AuNPs catalyst with a higher surface area. This indicates that the activity of Au towards glucose and xylose ECH is dependent on the surface area and particle size, and particle size control can be achieved by simple chemical or thermal pretreatment of the catalyst support.</p

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

13th International Conference on Renewable Resources and Biorefineries (RRB-13)

In literature, there are several examples of studies concerning the extraction of hemicellulose with pressurized hot water from lignocellulosic materials, however there is not any detailed investigation, which compares the extraction efficiency from different species, analyzing the characteristics of the extracted hemicelluloses. The main hypothesis that we wanted to test is weather there exists a clear relationship between biomass structure, e.g. determined via TGA model analysis, and the quality of the hemicellulose extracted. Fractionation of the wood from 10 different tree species was carried out in a batchwise operated cascade reactor, where mass transfer effects are negligible, at a constant temperature of 160ºC. The concentration of hemicellulose extracted from the species was analyzed at 5 different extraction times by calculating and comparing the yields of the extractions. The molecular weights of the oligomers obtained during various extraction times were measured and a direct correlation with the pH of the extracted solution was identified. The content of lignin and cellulose in the various species was also determined, to understand if the composition has an influence on the extraction process

Fully bio-based films based on purified biopolymer fractions from hydrothermal extraction of discarded carrots

Flexible 100 % bio-based films were produced from discarded carrots fractions. The main ingredient was purified high molecular weight fractions of hemicelluloses and pectins previously obtained by hydrothermal treatment and ultrafiltration/diafiltration. A fraction of lignin-containing cellulose nanofibers was used as an additive. These nanofibers were obtained from the residual pulp of the hydrothermal treatment after a mechanical treatment. Low content of lignin-cellulose nanofibers (< 5 % w/w) improved oxygen permeability (up to 29 %) but worsened water vapor permeability and tensile properties. A higher addition of lignin-cellulose nanofibers (5-25 % w/w) allowed to recover the properties of the reference film (without fibers) and provided a higher hydrophobicity, increasing the water contact angle from 79.9° to 125.8°. The study of the influence of the molecular weight (67.77-102.75 kDa) and composition of the hemicellulose and pectin fraction in films containing 1 % lignin-cellulose nanofibers showed that a higher molecular weight decreased oxygen permeability (from 48.18 to 41.14 cm3·µm/m2/kPa/day), increased water vapor permeability (from 21.56 to 24.01 g·mm/m2/kPa/day) and decreased hydrophobicity (from 86.84° to 71.10°). Tensile stress was higher with higher pectin content and lower molecular weight (from 1.13 to 2.84 MPa), while elongation was higher with higher hemicellulose content (from 5.92 to 15.28 %). The obtained films had acceptable properties for food packaging and high hydrophobicity, with the great advantage of being 100 % from agri-food waste by applying environmentally friendly processes and without the need for chemical modification.Grupo de Tecnologías a Presión (PressTech)Agencia Estatal de Investigación (Gobierno de España) and FEDER Funds EU [PID2019-105975GB-I00 (MICINN/FEDER, EU)]Junta de Castilla y León - Consejería de Educación and FEDER Funds [CLU-2019-04

Evolution of Specific Heat Capacity with Temperature for Typical Supports Used for Heterogeneous Catalysts

International audienceHeterogeneous catalysts are widely used in the chemical industry. Compared with homogeneous catalysts, they can be easily separated from the reaction mixture. To design and optimize an efficient and safe chemical process one needs to calculate the energy balance, implying the need for knowledge of the catalyst’s specific heat capacity. Such values are typically not reported in the literature, especially not the temperature dependence. To fill this gap in knowledge, the specific heat capacities of commonly utilized heterogeneous catalytic supports were measured at different temperatures in a Tian–Calvet calorimeter. The following materials were tested: activated carbon, aluminum oxide, amberlite IR120 (H-form), H-Beta-25, H-Beta-38, H-Y-60, H-ZSM-5-23, H-ZSM-5-280, silicon dioxide, titanium dioxide, and zeolite 13X. Polynomial expressions were successfully fitted to the experimental data

Upcycling of carrot waste into pectin-arabinogalactan and lignin-cellulose films via hydrothermal treatment, ultrafiltration/diafiltration, and casting

Discarded carrots were valorized to obtain different films. The pulp was subjected to hydrothermal treatment (140 and 180 °C) at pilot scale, with one and with several flow-through reactors in series, allowing the extraction of pectin-containing arabinogalactan (P-AG) of very high molecular weight. Ultrafiltration and diafiltration allowed obtaining purified fractions with molecular weights be-tween 3.48-102.75 kDa. The solid residue from the hydrothermal process was subjected to mechanical treatments to obtain lignin-containing cellulose nanofibers (L-CNFs). The P-AG film had a better oxygen barrier (67.73 vs. 239.83 cm3·µm/m2/kPa/day) and the L-CNFs film had a higher tensile strength (7.74 vs. 3.14 MPa). The combination of both fractions showed that L-CNFs should be added in percentages higher than 15 % (w/w) so that their presence does not harm the P-AG based film. There was a synergistic effect on hydrophobicity when mixing both fractions, reaching a 57.5 % higher water contact angle (125.8 °). As for the P-AG sample, a higher molecular weight decreased the oxygen permeability up to 14.6 % (41.14 cm3·µm/m2/kPa/day) but increased the water vapor permeability up to 11.4 % (24.01 g·mm/m2/kPa/day). The tensile strength was up to 150.9 % higher at lower molecular weight and higher pectin content (2.84 MPa) due to the high degree of branching of the arabinogalactan. Elongation was up to 157.9 % higher at higher arabinogalactan content (15.28 %). For the first time, purified fractions of P-AG and L-CNFs from carrot waste were obtained and used for film formation. The films had acceptable properties for food-packaging.Grupo de Tecnologías a Presión (PressTech)Instituto de Bieconomía de la Universidad de ValladolidAgencia Estatal de Investigación (Gobierno de España) and FEDER Funds EU [PID2019-105975GB-I00 (MICINN/FEDER, EU)] Junta de Castilla y León - Consejería de Educación and FEDER Funds [CLU-2019-04

Sorption enhanced catalysis for CO₂ hydrogenation towards fuels and chemicals with focus on methanation

Hydrogen produced by the electrolysis of water using sustainable electricity will play an increasingly important role as an energy and a feedstock vector. Shifting from fossil to renewable resources means that new industrial platforms have to be set up to provide carbon-based fuels and bulk base chemicals to replace the current fossil resources based routes. The global demand cannot be met by indirect use of carbon dioxide via biomass necessitating the use from point sources or direct air capture, which changes the value of CO2 from waste to commodity chemicals. The production of chemicals by hydrogenation of CO2 is typically hampered by the thermodynamic conversion being far from 100% under currently viable reaction conditions. The equilibrium can, however, be shifted to increase conversion by removing one of the reaction products, namely water, from the reaction mixture with sorbents like zeolites. Prerequisite to conversion enhancement and process intensification is the close proximity of sorption and catalytic sites. This review presents the state of the art in synthesis and application of these, in fact, bifunctional materials.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Large Scale Energy StorageChemE/Materials for Energy Conversion & Storag