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• Greener and safer production of epoxidized vegetable oil. • Positive effect of semibatch operation on the reaction performance. • Kinetic modelling based on plausible mechanism for the alumina catalyzed epoxidation. Heterogeneously catalyzed epoxidation of vegetable oils by hydrogen peroxide represents a greener route for the production of epoxides and a thermally safer reaction route compared to the classical Prileschajew epoxidation approach. The epoxidation kinetics of the heterogeneous system formed by aluminium oxide catalyst, hydrogen peroxide and methyl oleate as a model compound was studied with semibatch experiments in laboratory scale. It was found that semibatch operation improved the performance significantly compared to classical batch operation, a low and constant volumetric flowrate of hydrogen peroxide increased the final oxirane yield considerably. A semibatch reactor model and a kinetic model were developed, featuring the reaction temperature, the reactant molar ratio, the catalyst loading and the mass flow rate as the most significant experimental parameters. The mathematical model was able to well describe the experimental data. The approach can be applied to other liquid–solid catalyst systems in future in order to optimize the semibatch operation policy for complex reaction systems. [ABSTRACT FROM AUTHOR]

Aqueous phase reforming (APR) can be used as an efficient method to purify and obtain added value from rather dilute side/waste streams of process waters containing e.g. alcohols or sugar alcohols. Such side streams often have none or even negative value due to purification costs, which contributes to the economy of the process. Xylitol was here used as a model compound. The desired product in the current study was hydrogen, which can be used for valorizing by-products via hydroprocessing or as a bioenergy source. In addition to hydrogen, some alkanes were also obtained, which are prime sources of bio-energy for power production. The current work focused especially on the influence of the reaction conditions (temperature, pressure and inert gas flow) on the xylitol conversion and hydrogen selectivity, which has not been reported previously. The influence of reaction conditions on the aqueous phase reforming of xylitol on Pt/Al 2 O 3 catalyst was studied in a trickle-bed reactor. Selectivity to hydrogen was dependent on gas flow through the reactor, especially the absence of any gas resulted in a low selectivity. A higher reaction temperature and a higher inert gas flow gave a better xylitol conversion, while an increase of the overall pressure had an opposite effect on conversion. The activation energy for xylitol conversion was determined for the first time being 79.3 kJ/mol. The results demonstrate that aqueous phase reforming is a viable method for energy efficient value added processing of sugar alcohol containing dilute side streams in modern bio-refinery applications. • Biohydrogen and some alkanes were obtained for use in biofuels, biochemicals and bioenergy production. • Practically full conversion was achieved in a trickle bed reactor system. • The liquid-to-gas ratio and operating pressure influenced significantly the conversion and to some extent also selectivity. • Temperature influenced the conversion significantly, however, the influence on selectivity was not very significant. • The activation energy for xylitol conversion was determined for the first time being 79.3 kJ/mol. [ABSTRACT FROM AUTHOR]

• Ethene oxychlorination over CeO 2 was performed in a microreactor. • CeO 2 catalyst was prepared without any promotors by deposition-precipitation. • The effect of the reactant concentration on the activation energy was revealed. • The previously developed reaction network over ceria was completed. • Kinetic modelling was successfully carried out based on the proposed mechanism. Oxychlorination of ethene was conducted in a microreactor (150–375 °C) over a thin layer of CeO 2 prepared in the current work with the specific surface area of 80 m2/g and compared with the same reaction in millireactors (250–500 °C). The kinetic analysis revealed influence of the ethene concentration on the apparent activation energy which was different in micro- and millireactors. The previously developed reaction network was completed by including two parallel reactions for formation of ethylchloride and vinylchloride and two consecutive reactions accounting for formation of dichloroethane and vinylchloride via ethyl chloride. The reaction orders with respect to HCl and O 2 in the microreactor were comparable with the literature data for millireactors. Kinetic modeling was successfully carried for all reactants by using a steady state model of a packed bed reactor. [ABSTRACT FROM AUTHOR]

• Oxidation of arabinose on extrudates or foams containing gold. • Tandem reactor system comprising a fixed bed and a stirred tank. • High selectivity to arabinonic acid. • Mathematical model comprising intrinsic kinetics, gas –liquid and liquid–solid mass transfer. Oxidation of arabinose was investigated in a tandem reactor system comprising a fixed bed of gold catalysts supported on extrudates or solid foams and a stirred tank allowing operation under constant pH of 8. Powder catalyst containing 3 wt% Au deposited on γ-alumina was extruded with γ-alumina and attapulgite or sepiolite as a binder or deposited on the solid open-cell aluminum foam after anodic oxidation pretreatment. Alternatively, deposition precipitation of gold with urea from HAuCl 4 precursor was done directly on the extruded support or the solid foam. The presence of gold was essential for catalytic activity which in the applied reactor set-up was strongly limited by mass transfer. Arabinose was rather selectively (ca. 90–95% at full conversion) oxidized to arabinonic acid giving besides arabinolactone other by-products. A mathematical model was developed for the open foam catalyst structures and the extrudates, comprising intrinsic kinetics deduced from batch experiments and the mass transfer within the solid catalyst. [ABSTRACT FROM AUTHOR]

The purpose of this work was to investigate biomass-derived ethanol dehydrogenation into acetaldehyde using several mono- and multicomponent (CuO, ZnO and Cr 2 O 3 )-containing catalysts supported on industrial size Al 2 O 3 beads. The catalysts, prepared with either solution combustion or incipient wetness method, were characterized by using various physico-chemical methods, such as EDXA, SEM-EDXA, TEM, XRD, XPS, pyridine adsorption desorption FTIR, and ζ-potential measurements. The results revealed that the multicomponent catalysts exhibited superior activity compared to the metal oxide catalysts containing only one metal oxide. In addition, the most selective catalyst towards acetaldehyde formation, with 50% selectivity at 55% conversion of ethanol at 300 °C and WHSV 1 h −1 was CuO Cr 2 O 3 /Al 2 O 3 prepared by using the solution combustion method, indicating that this inexpensive and rapid catalyst preparation method is promising for other applications. [ABSTRACT FROM AUTHOR]

Partial oxidation of ethanol to acetaldehyde was carried out over gold catalysts supported on various oxides and zeolites by deposition precipitation. The special focus of this work was on the influence of H-Y zeolite surface charge on Au cluster size and loading linking it to activity and selectivity in ethanol oxidation and comparing with other studied catalysts. The catalysts were characterized by nitrogen physisorption, transmission electron microscopy (TEM), scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDXA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and zeta potential measurements. pH of the solution governed the Au NPs size within the range of 5.8–13.2 nm with less negatively charged surfaces leading to formation of smaller clusters. Au loading on H-Y zeolite with silica to alumina ratio of 80 was increased by raising the pH. In fact, H-Y-12 and H-Beta-25 were selective towards diethyl ether while acetaldehyde was the prevalent product on less acidic H-Y-80. The results demonstrated strong dependency of the catalytic activity on the Au cluster size. Namely turn over frequency (TOF) decreased with an increase in metal size from 6.3 to 9.3 nm on H-Y-80. Selectivity towards acetaldehyde and ethyl acetate did not change significantly on H-Y-80 within 6.3–9.3 nm Au particle size range. On Al 2 O 3 support, however, selectivity towards acetaldehyde increased considerably upon diminishing Au average particle size from 3.7 to 2.1 nm. [ABSTRACT FROM AUTHOR]

Benzodioxinols, compounds with 6-membered heterocycles containing two oxygen atoms, exhibit promising analgesic activity. In the current study, synthesis of dioxinol via two-step approach including Prins cyclization of isopulegol with benzaldehyde to tetrahydropyran and its ring-rearrangement to dioxinol was investigated. Different acidic and basic catalysts were studied in the second step and the highest selectivity toward dioxinol was achieved using mesoporous Ce-composite material. [ABSTRACT FROM AUTHOR]

The density, viscosity and hydrogen solubility of selected sugars ( l -arabinose, d -galactose, d -maltose and l -rhamnose) were determined at different temperatures (generally 60, 90 and 130 °C). The role of internal diffusion resistance in porous catalyst layers for sugar hydrogenation was confirmed by numerical simulations based on kinetic data and physical properties. The simulations suggested the use of small catalyst particles or structured catalysts in continuous hydrogenation of the sugars to sugar alcohols. Continuous hydrogenation of l -arabinose was carried out in a laboratory-scale fixed bed reactor with ruthenium catalysts on three different supports (active carbon clothes, carbon nanotubes on sponge-like metallic structures, conventional active carbon catalyst particles). It was proved that continuous hydrogenation is a feasible alternative to batch technology for sugar hydrogenation over conventional catalyst particles and structured catalysts: l -arabinose was converted to arabitol with a very high selectivity. [ABSTRACT FROM AUTHOR]

• Glycerol hydrochlorination was studied in a gas–liquid semibatch reactor. • The presence of Ester intermediates was confirmed. • The non-isothermal nature of the process was verified. • The mechanistic and kinetic results provides the basis of rational reactor design. A homogeneously catalyzed gas–liquid process, glycerol hydrochlorination was studied in a semibatch reactor with gaseous hydrogen chloride (HCl) as a continuous phase and acetic acid as homogeneous catalyst. Several experiments were conducted varying the temperature in the jacket of the reactor in the range 70–115 °C and the catalyst mole fraction between 0 and 15 mol-%. The effects of HCl on the kinetics was investigated by changing the partial pressure of HCl in the range 0.25–1 atm by diluting HCl with inert gas, while the absolute pressure of the reactor was remained constant at atmospheric pressure. The experiments revealed new information about this particular reaction system. Considerable changes in the reactor temperature occurs, temperature changes close to 20 °C, which are an effect of the absorption process of gaseous HCl. The HCl uptake in the liquid phase exhibits a strange behavior at the beginning of the reaction, associated to the appearance of water and the temperature change during the experiments. The experiments also revealed that a part of the catalyst is transformed into esters in the presence of glycerol and 3-chloro-1,2-propanediol (α-MCP), particularly at high catalyst concentrations. These esters were detected and an improved gas-chromatographic method was developed to analyze these quantitatively. In long run, the esters are converted back to the original catalyst, acetic acid, as the reaction stops because of lack of glycerol. The information provided by the experiments in this work gives better understanding of the reaction mechanism and thus they are the basis for a rational design of glycerol hydrochlorination reactors. [ABSTRACT FROM AUTHOR]

• Arabinose was successfully oxidized to arabinonic acid in a slurry reactor. • Dispersed gold nanoparticles were used as catalyst. • Oxygen solubility in the reaction solution was measured. • Extensive kinetic study of the oxidation process was conducted, revealing the effect of oxygen pressure and pH. • A kinetic model was developed and used to describe the experimental data. Sugar acids obtained by oxidation of sugars are very valuable molecules which are used as chelating agents, binders as well as ingredients in pharmaceuticals. Arabinonic acid was prepared by oxidation of arabinose on gold nanoparticles deposited on an aluminium oxide carrier. A systematic reaction kinetic study was conducted to reveal the influence of oxygen partial pressure and pH on reaction rate and product selectivity. Experiments were carried out in a laboratory-scale semi-batch reactor which was operated at 70 °C and oxygen partial pressures 0.125–1.0 atm. The pH of the aqueous sugar solution was 6–8. Oxygen was continuously flowing through the semibatch slurry reactor and the pH was kept constant by adding NaOH during the experiments. The oxygen solubility in the reaction mixture was determined in separate experiments. A reaction mechanism was proposed for the formation of arabinonic acid (main product) and arabinolactone (intermediate by-product). The surface reaction of competitively adsorbed arabinose and oxygen was assumed to be rate determining for the arabinose consumption. For the formation of arabinonic acid from arabinolactone, the rate determining step was presumed to be the reaction between arabinolactone and sodium hydroxide. The reactor was described with the perfect backmixing model and the component mass balances were solved numerically during the estimation of kinetic parameters by nonlinear regression analysis. The kinetic model gives new insights in the reaction mechanism and described the experimental data very well. The model has potential for application in the oxidation of other monomeric sugars, too. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nonanoic acid esterification promoted by Amberlyst-15 and Amberlite IR120. • Amberlyst-15 is more active than Amberlite IR120. • Internal mass transfer limitation was always present. • Amberlite IR120 shows a more ideal fluid-dynamics than Amberlys-15. • The industrial feasibility was successful in PBR with Amberlite IR120. Nonanoic acid is considered a feedstock of growing interest due to the promising applicability of its derivatives. It can be obtained from vegetable oils, one of the products of oleic acid oxidation. Recently, a very interesting application of the ester obtained from nonanoic acid esterification with 2-ethylhexanol was found. In fact, it showed excellent properties as solvent for varnishes. The aim of this work was the kinetic investigation of the nonanoic acid esterification with 2-ethylhexanol in batch and continuous reactors, promoted by Amberlyst-15 and Amberlite IR120 resins, and to demonstrate the technical feasibility of the mentioned technology in flow systems. A mathematical model was developed to simulate the collected experimental data taking into account all the phenomena appearing in the system: intrinsic kinetics, mass transfer and flow pattern. Experiments were also conducted in the continuous packed bed reactor to compare the catalyst performances and validate the results obtained in the batch reactor. The best nonanoic acid conversion (85%) was obtained fixing T = 363 K, Q = 4.17·10−9 m3/s with an alcohol:acid molar ratio of 5:1 using Amberlyst-15 as heterogeneous catalyst. [ABSTRACT FROM AUTHOR]

Zinc-modified alumina catalysts for methyl chloride synthesis were prepared with varying zinc loadings: from 2.4 to 21.1 wt%. The influence of the zinc loading, zinc precursor and the pH of the impregnation on the physico-chemical properties of the catalyst, and on the catalyst activity and selectivity for methyl chloride (MeCl) synthesis was investigated. The prepared catalysts were thoroughly characterized by FTIR, TEM, physisorption and EDX. On the alumina surface, both molecular and bulk zinc species are created upon zinc loading. The surface area of the catalyst decreases steadily with zinc loading. Bulk zinc species dominate on the catalyst starting at a zinc loading of 9.4 wt% and the amount of Lewis acid sites (LAS) decreases. A shift in the acid site type takes place upon zinc modification. Sites assigned to stronger LAS are eliminated while zinc-based weaker acid sites started to predominate. The shift in acidity increases the selectivity and activity of methyl chloride synthesis, which was demonstrated in a series of experiments in a laboratory-scale fixed bed reactor. [ABSTRACT FROM AUTHOR]

Highlights: [•] Activity, selectivity and stability have been tested for all catalysts. [•] Influence of zinc modification on surface area and pore volume was investigated. [•] Activity and selectivity have been correlated with the catalysts acid properties. [•] Zinc species on the catalyst surface have been characterized by EDX, TEM and XPS. [•] Spent catalysts were characterized by N2-physisorption, FTIR, EDX and XRD. [ABSTRACT FROM AUTHOR]

One-pot continuous synthesis of menthols both from citronellal and citral was investigated over 5 wt% Ni supported on H-Beta-38-sepiolite composite catalyst at 60–70 °C under 10–29 bar hydrogen pressure. A relatively high menthols yield of 53% and 49% and stereoselectivity to menthol of 71–76% and 72–74% were obtained from citronellal and citral respectively at the contact time 4.2 min, 70 °C and 20 bar. Citral conversion noticeably decreased with time-on-stream under 10 and 15 bar of hydrogen pressure accompanied by accumulation of citronellal, the primary hydrogenation product of citral, practically not affecting selectivity to menthol. A substantial amount of defuctionalization products observed during citral conversion, especially at the beginning of the reaction (ca. 1 h), indicated that all intermediates could contribute to formation of menthanes. Ni/H-Beta-38-sepiolite composite material prepared by extrusion was characterized by TEM, SEM, XPS, XRD, ICP-OES, N 2 physisorption and FTIR techniques to perceive the interrelation between the physico-chemical and catalytic properties. [Display omitted] • one-pot continuous synthesis of menthols from citronellal and citral. • 5 wt% Ni supported on H-Beta-38-sepiolite composite catalyst. • menthols yield of 53% and 49% from citronellal and citral. • stereoselectivity to menthol ca. 70–75%. [ABSTRACT FROM AUTHOR]

• Aqueous phase reforming of real hemicellulose hydrolysates was performed. • The best results were obtain with a tailored bimetallic Pd-Pt/sibunit catalyst. • Complete conversion was achieved for C5 and C6 sugars and formic acid. The current work focuses on studying the aqueous phase reforming (APR) of pine and birch hydrolysate obtained from waste wood by using organic acids available from biorefineries. Processing of representative synthetic mixtures was utilized in the work in order to support data interpretation related to the influence of different chemical compound and processing parameters on the APR of the actual hydrolysates. It was shown, that hydrogenation of the hydrolysates prior to APR was not feasible in the presence of formic acid, which ruled out one potential processing route. However, it was successfully demonstrated that birch and pine hydrolysates could be directly processed obtaining close to full conversion. The best results were obtained with tailored bimetallic Pd-Pt/sibunit catalyst in a trickle bed reactor system in the temperature range 175 °C–225 °C. [ABSTRACT FROM AUTHOR]

[Display omitted] • One-pot citral to menthol transformations over bifunctional Ru/H-Y-80 extrudates. • Long-term experiments in a continuous reactor. • Menthol isomers distribution and Z/E-citral ratio were influenced by Ru size. One-pot transformations of citral were investigated over Ru-catalysts in a batch and a continuous mode over a powder catalyst and extrudates, respectively. Ru/H-Y-80 catalysts were prepared by different impregnation methods to obtain different particle sizes of Ru. The highest yield of isopulegols was 15% and yield of menthols was 3% with stereoselectivity to the desired (±)-menthol isomer of 42% after 5 h over the Ru/H-Y-80 powder catalyst with the smallest metal particles prepared by the incipient wetness impregnation method with six impregnation steps using Ru(NO)(NO 3) 3 as a precursor. This catalyst was synthesized with the Bindzil binder and shaped by extrusion. For comparison, also a catalyst with Ru deposited on the binder was prepared. Addition of 30 wt% Bindzil binder to Ru/H-Y-80 catalyst caused significant catalyst deactivation. Z/E-citral ratio decreased with increasing Ru particle size. Citral conversion and the yield of acyclic hydrogenation products were higher over the powder catalysts containing a mixture of zeolite and binder with a larger distance between the metal and the acid sites, i.e. with Ru deposited on the Bindzil binder. Long-term experiments in the continuous mode revealed comparable catalytic behaviour of both Ru-extrudates with the controlled metal location due to the presence of diffusion regime. The maximum yield of menthols, 6%, with stereoselectivity to the desired (±)-menthol of 73% was obtained during the transient state, below 2 h of time-on-stream. The reuse of Ru/H-Y-80 extrudates was successfully demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: Selective synthesis of methyl chloride from methanol and hydrochloric acid was performed in an alumina-coated microreactor. Conversions from 4% to 83% were achieved in the investigated temperature range of 280–340°C. This demonstrated that the reaction is fast enough to be successfully performed in a microreactor. A model based on kinetic experiments and thermodynamic calculations was developed for the system. The influence of the reactant adsorption on the catalyst surface was investigated performing transient experiments and comparison of kinetic models. A model taking into account HCl adsorption on the catalyst surface was able to describe the data most precisely. Kinetic models advanced in this work were compared with a previously published model. With the obtained kinetic parameters, a selectivity analysis was performed. The activation energy for the methyl chloride and dimethyl ether formation was 108kJ/mol and 118kJ/mol respectively. The former value is ca. two fold higher than the previously published, indicating a sign for diffusion limitations in previous studies. A detailed modeling of the diffusion in the porous catalyst layer confirmed that the kinetic constants determined in the microreactor represent the intrinsic kinetics and that methyl chloride formation is limited by diffusion starting from catalyst coating thicknesses of 50μm. [Copyright &y& Elsevier]

Abstract: H2O2 direct synthesis over two bimetallic, palladium-gold catalysts based on sulfated ceria (PdAu-CeS) and on sulfated zirconia (PdAu-ZS) has been studied in a continuous, trickle-bed reactor, at −10°C and 10bar. Three different liquid flow rates and seven different gas flow rates were used. The combined effect of liquid and gas flow rates, with two different H2/O2 ratio (2/18 and 4/16) in the gas feed, has been studied, by independent variations. The highest H2/O2 ratio always increases production rate and selectivity. In the case of 4/16 ratio, PdAu-CeS catalyst shows an enhancement in selectivity only, while the increase in H2O2 production rate is not significant compared to the 2/18 ratio case. PdAu-ZS catalyst shows a remarkable gain in both selectivity and production rate when the 4/16 ratio in gas feeding is used, outperforming the PdAu-CeS catalyst. The enhancement of the catalytic activity is more pronounced in the case of PdAu-ZS, compared to PdAu-CeS, when the highest H2/O2 ratio is used. A selectivity up to 90% has been measured on PdAu-ZS with the higher H2/O2 ratio and larger liquid flow rates. The maximum production rate measured is 6μmol/min (i.e. a productivity 0.18mol H2O2 gPd −1 h−1) with 1ml/min liquid flow rate and 2.7ml/min gas flow rate again on PdAu-ZS. [Copyright &y& Elsevier]

• Industrial xylan was converted into xylitol in a continuous reactor. • Isothermal single flow through using two catalyst beds was utilized. • The selectivity of the process was enhanced compared to conventional processes. • Over 90% yield was achieved. Xylan obtained from birch (betula pendula) by a novel semi-industrial scale aqueous based method was used for studying the hydrolysis and consecutive hydrolysis-hydrogenation processes in continuous reactors. Dowex 50WX2-100 was chosen as the hydrolysis catalyst based on the results of catalyst screening performed previously in batch reactor. It was also observed to perform well in continuous reactor converting xylan to xylose in high yield under the studied reaction conditions. The influence of several reaction parameters were investigated for optimization. Similar experimental conditions used in the hydrolysis were then applied for studying one flow through hydrolysis and hydrogenation of the semi-industrial xylan. A consecutive catalyst bed consisting of ruthenium on carbon was introduced into the continuous reactor downstream from the hydrolysis bed to hydrogenate monosaccharides to xylitol. Hydrogen was co-fed into the reactor with the xylan solution. Reaction parameters, including temperature, residence time and hydrogen pressure, were varied to maximize the xylitol yield. The developed continuous process was demonstrated to be highly selective and efficient for the valorization of the semi-industrial xylan by yielding over 90% xylitol under optimal experimental conditions. It was noticed, that co-feeding hydrogenation decreased the degradation of monosaccharides during hydrolysis, thus improving the selectivity towards the target product and enabling remarkable process intensification. Moreover, mathematical modelling was performed for the hydrolysis and one flow through hydrolysis and hydrogenation processes. The models take into account the consecutive reaction pathways and the influence of the experimental conditions. Good fits of the model to the experimental data were obtained. The conversion of this novel, well characterized wood-based xylan to produce xylose or xylitol in continuous reactors has not been studied previously. The current work contributes significantly to understanding the processing of real feedstock in one flow through employing consecutive reactions and provides necessary data for process intensification. Graphical Abstract [Display omitted]. [ABSTRACT FROM AUTHOR]

Abstract: Hydrogen assisted n-octane-SCR under lean conditions over a 1.91wt.% Ag/alumina catalyst was studied. The kinetic behaviour of the catalytic reaction at 200°C at steady state conditions was examined in the concentration range: , 0.5 and 1vol.%, P NO =375, 500 and 1000ppm, P octane =187.5, 375 and 500ppm and , 3 and 6vol.%. The results showed that all the rates increased along the increasing H2 concentration with the reaction order equal to 0.4 in NO and 1.4 in octane at 0.5vol.% hydrogen concentration. Moreover it was observed that the effect of hydrogen was more predominant on the NO to N2 reduction than varying reactant (NO, C8H18) concentration. The main mechanistic effect of hydrogen in significantly improving the low temperature performance of silver/alumina catalysts in HC-SCR cannot only be attributed to the reduction of surface nitrates with hydrogen suggesting its involvement in the catalytic cycle of NO reduction. [Copyright &y& Elsevier]

• Theoretical concepts of semibatch technology for kinetic studies were presented. • The approach is based on gradual addition of a homogeneous catalyst. • The success of the method was demonstrated with a consecutive esterification process. • The method is generally applicable for homogeneously catalyzed liquid-phase processes. Experimental measurements of the reaction kinetics of complex consecutive and parallel-consecutive reactions is a challenge, because the reaction rates of the sequence are often very different, the primary reactions being much more rapid while the secondary and tertiary reactions might be much slower requiring very long kinetic experiments. An approach to surmount this dilemma is proposed for homogeneously catalyzed liquid-phase reactions by adding the catalyst gradually into the reaction mixture: in this way the primary reactions are slowed down but the secondary and tertiary reactions are accelerated. A mathematical model for this approach was developed and complex reaction systems were simulated numerically in the Damköhler space. The applicability of the approach was illustrated with experimental data obtained for the formation of mono- and diesters from carboxylic acids and dialcohols in the presence of homogeneous strong acid catalysts. Acetic acid and ethylene glycol were used as reagents in the experimental work and aqueous hydrogen chloride was the homogeneous catalyst. Rate equations for this reaction systems were derived based on molecular mechanisms and the kinetic parameters in the rate equations were estimated with regression analysis. Simulation of the esterification model illustrated the benefits of the proposed experimental semibatch approach for complex reaction systems. [ABSTRACT FROM AUTHOR]

Hexadecane hydrocracking was investigated over bifunctional Ru-containing micro- and mesoporous USY zeolites at 250°C under 45 bar in the presence of hydrogen in a batch reactor. A comparative study was performed using the Ru-free zeolites in the protonic form. The highest yield of jet-fuel products, C 9 - C 15 , being 26% at 71% conversion, was obtained with 2.5 wt% Ru deposited on a hierarchical micro-mesoporous USY zeolite, e.g. a material possessing secondary porosity, where a superior combination of acidity and mesoporosity was created by treatment of the parent zeolite with aqueous sodium hydroxide and tetrapropylammonium hydroxide. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrocracking of hexadecane to jet fuel components H- proton and metal Beta zeolites with different acidity. • Extensive catalyst characterization by physico-chemical methods. • Mildly acidic 2.5 wt% Ru-H-Beta-300 afforded 24% yield of the jet fuel components and 89% liquid mass balance closure. Hydrocracking of hexadecane to produce jet fuel components was investigated over proton and metal modified Beta zeolites with different acidity. They were characterized by a range of physico-chemical methods. The initial catalyst screening was performed at 210 °C under 40 bar hydrogen showing that the most promising catalysts were 2.5 wt% Pt-H-Beta-25 and 2.5 wt% Ru-H-Beta-300, which were also tested at 240 °C under 45 bar hydrogen. The results revealed that the yield of jet fuel components was maximally 27% over 2.5 wt% Pt-H-Beta-25. This catalyst gave, however, only 55% mass balance closure to the liquid phase products, while a mildly acidic 2.5 wt% Ru-H-Beta-300 afforded 24% yield of the jet fuel components and 89% liquid mass balance closure. [ABSTRACT FROM AUTHOR]

Epoxidation of two butane isomers (1-butene and isobutene) on the commercial titanium silicate (TS-1) catalyst was studied in a laboratory-scale trickle bed reactor. The transient step response technique was used as the main tool in the investigation. The transient responses revealed different dynamics of product formation in continuous operation. The study of isomers showed the impact of the molecular structure on the transient and stationary states of the system. The four-carbon chain present in 1-butene displayed a dynamic behavior with a prominent maximum of the conversion as a function of time-on-stream. On the contrary, the behavior of isobutene was displayed to be closer to ethene and propene under similar conditions reaching a steady state after ca. 2 h. The structure of the epoxide was an important factor in order to achieve a high epoxide selectivity. In isobutene epoxidation, the primary product 1,2-epoxy-2-methylpropane was highly reactive, giving a spectrum of parallelly formed byproducts. Therefore, the selectivity of the epoxide from isobutene was limited to ca. 70%. In the epoxidation of 1-butene, 1,2-epoxybutane was displayed to be a highly stable product with a selectivity close to 99%. Based on the transient and stationary data, a reaction mechanism was proposed for the epoxidation and ring-opening reactions present in the system., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Sugar alcohols are obtained by hydrogenation of sugars in the presence of ruthenium catalysts. The research effort was focused on the development of solid foam catalysts based on ruthenium nanoparticles supported on active carbon. This catalyst was used in kinetic experiments on the hydrogenation of l-arabinose and d-galactose at three temperatures (90, 100, and 120 °C) and two hydrogen pressures (20 and 40 bar). Kinetic experiments were carried out with binary sugar mixtures at different d-galactose-to-l-arabinose molar ratios to study the interactions of these sugars in the presence of the prepared solid foam catalyst. The solid foam catalyst preparation comprised the following steps: cutting of the open-cell foam aluminum pieces, anodic oxidation pretreatment, carbon coating, acid pretreatment, ruthenium incorporation, and ex situ reduction. The carbon coating method comprised the polymerization of furfuryl alcohol, followed by a pyrolysis process and activation with oxygen. Incorporation of ruthenium on the carbon-coated foam was done by incipient wetness impregnation (IWI), using ruthenium(III) nitrosyl nitrate as the precursor. By applying IWI, it was possible to prepare an active catalyst with a ruthenium load of 1.12 wt %, which gave a high conversion of the sugars to the corresponding sugar alcohols. The catalysts were characterized by SEM, HR-TEM, TPR, and ICP-OES to interpret the catalyst behavior in terms of activity, durability, and critical parameters for the catalyst preparation. Extensive kinetic experiments were carried out in an isothermal laboratory-scale semibatch reactor to which gaseous hydrogen was constantly added. High selectivities toward the sugar alcohols, arabitol and galactitol, exceeding 98% were obtained for both sugars, and the sugar conversions were within the range of 53-97%, depending on temperature. The temperature effect on the reaction rate was very strong, while the effect of hydrogen pressure was minor. Regarding the sugar mixtures, in general, l-arabinose presented a higher reaction rate, and an acceleration of the hydrogenation process was observed for both sugars as the ratio of d-galactose to l-arabinose increased, evidently because of competitive interactions on the catalyst surface., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Hydrodeoxygenation (HDO) of isoeugenol (IE) was investigated using bimetallic iridium-rhenium and platinum-rhenium catalysts supported on alumina in the temperature and pressure ranges of 200-250 °C and 17-40 bar in nonpolar dodecane as a solvent. The main parameters were catalyst type, hydrogen pressure, and initial concentration. Nearly quantitative yield of the desired product, propylcyclohexane (PCH), at complete conversion in 240 min was obtained with Ir-Re/Al 2 O 3 prepared by the deposition-precipitation method using 0.1 mol/L IE initial concentration. High iridium dispersion together with a modification effect of rhenium provided in situ formation of the IrRe active component with reproducible catalytic activity for selective HDO of IE to PCH. The reaction rate was shown to increase with the increasing initial IE concentration promoting also HDO and giving a higher liquid phase mass balance. Increasing hydrogen pressure benefits the PCH yield., Competing Interests: The authors declare no competing financial interest.

Measurements of the zeta potential of solid heterogeneous supports are important for preparation of metal supported catalysts and for shaping zeolites into extrudates. In the current work, different types of heterogeneous support materials such as SiO₂, Al₂O₃, and a range of beta zeolites of different silica- to-alumina ratio were analysed. It was observed that parameters such as temperature, pH and acidity significantly affect the zeta potential. In several instances, depending on the materials’ acidity and microstructure, maxima in zeta potential were observed. The solid materials were thoroughly characterized using XRD, SEM, EDX, TEM, nitrogen physisorption, Al-NMR and FTIR with pyridine before zeta potential measurements.

Amidation of renewable feedstocks, such as fatty acids, esters, and Chlorella alga based biodiesel, was demonstrated with zeolites and mesoporous materials as catalysts and ethanolamine, alaninol, and leucinol. The last two can be derived from amino acids present in alga. The main products were fatty alkanol amides and the corresponding ester amines, as confirmed by NMR and IR spectroscopy. Thermal amidation of technical-grade oleic acid and stearic acid at 180 °C with ethanolamine were non-negligible; both gave 61% conversion. In the amidation of stearic acid with ethanolamine, the conversion over H-Beta-150 was 80% after 3 h, whereas only 63% conversion was achieved for oleic acid; this shows that a microporous catalyst is not suitable for this acid and exhibits a wrinkled conformation. The highest selectivity to stearoyl ethanolamide of 92% was achieved with mildly acidic H-MCM-41 at 70% conversion in 3 h at 180 °C. Highly acidic catalysts favored the formation of the ester amine, whereas the amide was obtained with a catalyst that exhibited an optimum acidity. The conversion levels achieved with different fatty acids in the range C12-C18 were similar; this shows that the fatty acid length does not affect the amidation rate. The amidation of methyl palmitate and biodiesel gave low conversions over an acidic catalyst, which suggested that the reaction mechanism in the amidation of esters was different., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The effect of five different wood particle size fractions between 0.5 and 12.5 mm on hot-water extraction of acetylated water-soluble hemicelluloses from spruce wood with a batch extraction setup at 170 °C was investigated. Extraction kinetics, with regard to particle size, was also studied. The purpose was to intensify the hemicellulose extraction for high molar mass hemicelluloses at high yield and purity. About 30% of the wood was dissolved and basically all the hemicelluloses could be extracted. The average molar masses of the extracted hemicelluloses decreased rapidly during the first 10 min of the extraction, but were not much affected by the difference in wood particle sizes. Smaller particles resulted in higher extraction rates. The reaction order was established to be of pseudo-first order for particles above 2mm and 1.5st order for particles smaller than 2mm. The effective diffusion coefficient was determined to be 9.11×10(-10) m(2)/s., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Solid imidazolium-based poly(ionic liquid)s with variable molecular weights that contain the poly[2-(1-butylimidazolium-3-yl)ethyl methacrylate] (BIEMA) cation and different counter anions were evaluated in terms of CO2 capture and compared with classical ionic liquids with similar counter anions. In addition to poly(ionic liquid)s with often-applied ions such as BF4 (-) , PF6 (-) , NTf2 (-) , trifluoromethanesulfonate (OTf(-) ) and Br(-) , for the first time [BIEMA][acetate] was synthesised, which revealed a remarkably high CO2 sorption performance that exceeded the poly(ionic liquid)s studied previously on average by a factor of four (12.46 mg gPIL (-1) ). This study provides an understanding of the factors that affect CO2 sorption and a comparison of the CO2 capture efficiency with the frequently used sorbents. Moreover, all the studied sorbents were reusable if regenerated under carefully selected conditions and can be considered as suitable candidates for CO2 sorption., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A novel heating efficiency analysis of the microwave heated stop-flow (i.e. stagnant liquid) and continuous-flow reactors has been presented. The thermal losses to the surrounding air by natural convection have been taken into account for heating efficiency calculation of the microwave heating process. The effect of the load diameter in the range of 4-29 mm on the heating efficiency of ethylene glycol was studied in a single mode microwave cavity under continuous flow and stop-flow conditions. The variation of the microwave absorbing properties of the load with temperature was estimated. Under stop-flow conditions, the heating efficiency depends on the load diameter. The highest heating efficiency has been observed at the load diameter close to the half wavelength of the electromagnetic field in the corresponding medium. Under continuous-flow conditions, the heating efficiency increased linearly. However, microwave leakage above the propagation diameter restricted further experimentation at higher load diameters. Contrary to the stop-flow conditions, the load temperature did not raise monotonously from the inlet to outlet under continuous-flow conditions. This was due to the combined effect of lagging convective heat fluxes in comparison to volumetric heating. This severely disturbs the uniformity of the electromagnetic field in the axial direction and creates areas of high and low field intensity along the load Length decreasing the heating efficiency as compared to stop-flow conditions.

In the present work pyrolysis of pure pine wood and softwood carbohydrates, namely cellulose and galactoglucomannan (the major hemicellulose in coniferous wood), was conducted in a batch mode operated fluidized bed reactor. Temperature ramping (5 degrees C/min) was applied to the heating until a reactor temperature of 460 degrees C was reached. Thereafter the temperature was kept until the release of non-condensable gases stopped. The different raw materials gave significantly different bio-oils. Levoglucosan was the dominant product in the cellulose pyrolysis oil. Acetic acid was found in the highest concentrations in both the galactoglucomannan and in the pine wood pyrolysis oils. Acetic acid is most likely formed by removal of O-acetyl groups from mannose units present in GGM structure.

The potential of different catalytic after treatment techniques to meet future diesel emission standards, which are strongly shifted toward urban driving conditions including cold start, are critically discussed in this Account and evaluated for their suitability for commercial applications. The dominating techniques in this field are NO(x) storage, urea-selective catalytic reduction (SCR), and HC-SCR. Each of these techniques have significant disadvantages such as sulfur sensitiveness and regeneration requirements of NO(x)-storage materials, infrastructure issues and formation of ammonium nitrate (at low temperatures) for urea-SCR, and low-temperature activity of HC-SCR catalysts. Ways to overcome these disadvantages in commercial applications may involve optimized regeneration strategies, reactor modifications, flow reversal, closed-loop NO(x) feedback systems, nonthermal plasma, and/or hydrogen-assisted catalyses, etc.