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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.

International audience; With the depletion of fossil resources, it is essential for the chemical industry to find alternative raw materials for polymers. Polyurethanes can be synthesized from vegetable oils and CO2 via an environmentally friendly, non-isocyanate pathway. Carbonation of epoxidized vegetable oil is a key step allowing the feasibility of this method. Because it requires a high temperature, high pressure and long reaction time to achieve complete conversion, microwave technology (MW) is an interesting approach for the intensification of the carbonation process. However, MW-irradiated batch reactor has multiple issues regarding scale-up. A microwave irradiated continuous-flow recycle batch reactor which can operate at high temperature (130 °C) and moderate pressure (8 bar) was used in the present work. The effect of microwave irradiation on the kinetics of carbonation reaction was studied. A kinetic model was developed to compare quantitatively the performance under microwave and conventional heating (CH). It was found that the activation energy of the carbonation reaction was slightly lower with the use of MW irradiation, where the values for CH and MW are respectively 0.385E + 04 J/mol and 0.338E + 04 J/mol.

Hydrogen peroxide direct synthesis was experimentally studied in three different reactors, namely the batch, semibatch and trickle bed reactors (TBR), using a new promising catalyst based on Pd/K2621. Excellent results were obtained from the experimental point of view, achieving high H2O2 selectivities, around 90% for a short contact time in the batch reactor, 60% in the semibatch reactor and 70% in the TBR. The simplest rate equations compatible with the acknowledged reaction network have been included in a reactor model, which accounts for mass transfer resistances between the gas and the liquid in the liquid–catalyst surface. The corresponding Arrhenius parameters were estimated from direct synthesis experiments for all the reactions and reactors. The models show how the reaction rates change among the batch, semibatch and trickle bed (TBR) reactors. The results suggest how to improve the reactor set-up and reaction performance in continuous operations and how to compare the results between the different reactors and conditions. The sensitivity analysis on the reaction allowed to gain new insights into the reaction rates. The TBR showed how the mass transfer limitations can help to direct the reaction towards the H2O2 synthesis. Remarkably, these results were achieved in the absence of any acids or halide ions, i.e. no known selectivity promoters for direct H2O2 synthesis were applied, thus the kinetics are not affected by the presence of promoters.

In this work, cellulose acetate was synthesized under homogeneous conditions. Cellulose was first dispersed in acetone, acetonitrile, 1,5-diazabicyclo(4.3.0)non-5-ene (DBN) or dimethyl sulphoxide (DMSO) and the resulting suspension was dissolved in an ionic liquid, 1,5-diazabicyclo(4.3.0)non-5-enium acetate [HDBN][OAc] at 70°C for 0.5h. It was possible to dissolve more than 12wt% cellulose with a degree of polymerization in the range of 1000-1100. The dissolved cellulose was derivatized with acetic anhydride (Ac2O) to yield acetylated cellulose. As expected, the use of the co-solvents improved the acetylation process significantly. In fact, cellulose acetates with different properties could be obtained in half an hour, thus facilitating rapid processing. When DBN was used as the dispersing agent (the precursor of the ionic liquid), the problems associated with recycling of the ionic liquid were significantly reduced. In fact, additional [HDBN][OAc] was obtained from the interaction of the DBN and the by-product, acetic acid (from Ac2O). However, the cellulose acetate obtained in this manner had the lowest DS. Consequently, the native cellulose and acetylated celluloses were characterized by means of (1)H- and (13)C-NMR, FT-IR, GPC/SEC and by titration. The cellulose acetates produced were soluble in organic solvents such as acetone, chloroform, dichloromethane and DMSO which is essential for their further processing. It was demonstrated that the ionic liquid can be recovered from the system by distillation and re-used in consecutive acetylation batches.

The public interest in usage of lignocellulosic biomass as a renewable resource has grown strongly during the last decade. Hemicelluloses are the second most abundant constituents of wood biomass, but have yet received less attention, compared to cellulose. In this work hydrolysis of xylan, as an example of hemicelluloses, was studied at moderate temperatures between 70 and 90 °C and pH values ranging from 0.5 to 3 with different liquid (HCl, H 2 SO 4 , triflouroacetic acid, oxalic acid) and solid (Smopex-101) catalysts. Experimental results showed complete cleavage of xylan with xylose yields of up to 95%.

The kinetics of maltose hydrogenation using Ru-containing nanoparticles (NPs) formed in the pores of hypercrosslinked polystyrene (HPS) was studied in this work at 110–140 °C and 2–7 MPa. The concept of two sites and non-competitive adsorption of hydrogen and maltose was used due to large differences in the sizes of molecules. The proposed model was able to describe experimental data with sufficient accuracy.

The isomerisation of β-pinene oxide was studied over supported ionic liquid catalysts (SILCAs) consisting of Lewis acids in immobilized ionic liquid. SILCAs were demonstrated as efficient catalysts ...

Hydrolysis of the hemicellulose arabinogalactan was studied in this work over several functionalized carbon materials, which were specifically treated to increase their acidities. Hydrolytic hydrog ...

International audience; Epoxidation of cottonseed oil by peroxyformic acid (PFA) was studied in a semibatch calorimeter. This liquid–liquid reaction system is composed of different exothermic steps. Thus, a kinetic modeling strategy to diminish the number of parameters to estimate was developed by investigating each reaction system: PFA synthesis and decomposition, ring‐opening and epoxidation. A thermal study was conducted by determining heat capacity of the different organic species, and by analyzing the evolution of global heat‐transfer coefficient with the reaction extent. The epoxidation reaction was performed in a semibatch reactor under isoperibolic mode within an initial temperature range of 50–70°C, an organic phase of 30–34 wt %, a formic acid molar flow rate of 0.02–0.05 mol/min and an addition time of 25–50 min. The interfacial mass transfer was supposed to be faster than the intrinsic reaction kinetics suppressing the use of mass transfer correlation. Nonlinear regression was used to estimate the kinetic and thermal parameters. The kinetic parameters of epoxidation of the three different fatty acids, namely oleic, linoleic, and its intermediate were estimated. The reaction enthalpy of epoxidation was estimated to −230 ± 3.8 kJ/mol, and the reaction enthalpy of ring‐opening was measured to be −90 kJ/mol by Tian–Calvet calorimeter.

Ethyl chloride was synthesized by ethanol hydrochlorination in the temperature range of 240–340 °C. The reaction was performed in two serially coupled microreactors. Besides the main product ethyl chloride, several side-products were formed: ethylene, diethyl ether and acetaldehyde. A maximum ethyl chloride selectivity of 88.5% and 85.3% ethanol conversion were obtained at 300 °C (space time 0.154 s). Higher selectivities and conversions can be obtained at higher space times. Thermodynamic calculations were performed to assess the reversibility of the reactions and the equilibrium composition of the reaction mixture. The developed kinetic model accurately described the concentration profiles of all products in the studied range of temperature and initial reactant concentrations. All reactions were treated as reversible. Adsorption of ethanol and HCl was taken into account in the kinetic modeling. A catalytic effect of HCl concentration on the rates of the dehydration reactions was demonstrated.

The bimetallic Pd–Au catalysts were prepared by simultaneous co-impregnation or consequent impregnation of supports by palladium and gold precursors. The catalytic reactions were performed batch-wise in a Parr stainless steel autoclave and methanol (220 ml) was used as solvent. A series of experiments were conducted to study effects of several variables and conditions on the final H2O2 destruction activity of the catalysts. The factors studied where : the surface chemistry of the support, the amount and ratio of palladium and gold, the catalyst preparation method, the heat treatment of the catalysts in H2 and air, the reaction medium, and reaction temperature. As a conclusion, H2O2 destruction activities of the catalysts were strongly affected by the surface chemistry of the support and the amount and ratio of palladium and gold. Bimetallic catalysts prepared by co-impregnation of Pd and Au were less destructive than the corresponding ones prepared by consequent impregnation. The catalysts supported on activated carbon cloth (ACC) oxidized by nitric acid were considerably less destructive than the corresponding ones on non-oxidized ACC. H2O2 destruction activity of the catalysts on oxidized ACC were highly affected by the heat treatment in H2 and air at different temperatures. Using water instead of methanol as reaction medium substantially speeded up H2O2 destruction. Furthermore, increasing the reaction temperature accelerated destruction of H2O2. Catalytic destruction of H2O2 via its decomposition was considerably low as compared to hydrogenation.

This work is focused on the esterification of fatty acids (commercial oleic mix) with zinc carboxylates (layered metal soap). About 25 experiments were performed, with and without catalyst, yielding a kinetic model based on the Eley–Rideal approach, able to predict fatty acid conversions under different conditions (molar ratio fatty acids/ethanol and temperature). An apparent first order reaction with respect to both reactants with no diffusion limitations was proposed. The activation energy of 80 kJ/mol was found. Fatty acid conversion up to 92% was reached under some conditions and the catalytic yields compared to the blank ones reached 40% in less than 90 min of reaction. This catalyst has shown a unique behavior among all other catalysts available for esterification, acting similarly to a homogeneous catalyst during the reaction but being recovered like a heterogenous catalyst at the end of the process.

Production of fatty alcohols through selective hydrogenation of fatty acids was studied over a 4% ReOx/TiO2 catalyst. Stearic acid was hydrogenated to octadecanol at temperatures and pressures betw ...

BACKGROUND Stricter SO2 emission regulations for power plants and maritime transport encourage a better understanding of the phenomena involved in wet flue gas desulfurization (WFGD) where limestone dissolution is regarded as one of the rate determining steps. RESULTS The dissolution kinetics of two limestone samples was studied in the industrially most relevant pH range 2.4–6. Dissolution experiments were performed under a regime where mechanical stirring did not affect the dissolution rate significantly. Furthermore, a mathematical model was developed by coupling mass transfer and chemical reaction at the surface over the whole range of pH; an analogy of the well-known Langmuir isotherm was applied. The results show that it is possible to accurately model the whole pH range, with a 99.1–99.5% degree of explanation and low relative standard errors ≤2%. CONCLUSION Limestone dissolution was successfully modeled by implementing surface areas measured by physisorption which were also compared with particle size distribution (PSD) measurements. Selected liquid-phase concentrations were measured by means of inductively coupled plasma optical emission spectrometry (ICP-OES) in order to support the proposed mechanism. The samples were characterized by X-ray fluorescence (XRF), X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). A wide range of studies presented in the literature are also described. © 2015 Society of Chemical Industry

Hydrogenation of nitrobenzene (NB) was carried out in methanol solutions (initial concentration 0.8 mol l−1) over a Pd/C catalyst (3 wt.% of Pd; reaction mixture contained 2.2 mg Pd l−1) over the pressure range of 2–4 MPa and temperature 30–70 °C in a laboratory scale batch reactor. Zero order kinetics was observed at hydrogen pressures above 2 MPa Under applied experimental conditions the apparent activation energy was 35 ± 1 kJ mol−1. A detailed analysis of the reaction mixture inspired the hypothesis that a C6H5–NO(H) moiety is formed on the catalyst surface and it undergoes further condensation to azoxybenzene (AOB) releasing water. However, very low concentrations of azobenzene (AB) and hydrazobenzene (HAB) in the reaction mixture indicate that the reaction route to the formation of aniline by hydrogenation of AOB to AB, hydrazobenzene (HAB) and subsequent hydrogenolysis to AN is of low probability. Hydrogenolysis of AOB to C6H5–NO(H) and C6H5–N(H), where the latter is hydrogenated to AN, is more likely. Based on the experimental observations a new reaction scheme for the heterogeneous catalytic hydrogenation of NB was proposed.

The direct synthesis of hydrogen peroxide from molecular hydrogen and oxygen on a supported palladium catalyst was studied at 258–297 K in a laboratory-scale batch reactor. The catalyst was in the form of finely dispersed slurry in methanol/CO 2 to suppress the internal and external mass transfer resistances. Experiments carried out under kinetic control revealed that hydrogen peroxide was successfully formed on the catalyst surface, but it was hydrogenated as the reaction time was prolonged. The mass balances of the components were considered in detail and a reaction mechanism was proposed, based on the competitive adsorption of hydrogen and oxygen on the palladium surface. The surface reactions leading to the formation of hydrogen peroxide and water were assumed to be rate determining, and the rate equations describing direct synthesis, water formation as well as peroxide hydrogenation and decomposition were derived. A special kind of product distribution analysis was used to interpret the kinetic phenomena and to make the estimation of the kinetic parameters very robust. The parameters were estimated by nonlinear regression analysis and the model gave a good fit to the experimental data. The usefulness of the product distribution analysis was clearly demonstrated.

Hemicellulose O-acetyl-galactoglucomannan (GGM) is the main noncellulosic water-soluble polysaccharide in the coniferous softwood Norway spruce, consisting of anhydro-galactose, -glucose, and -mannose. Acid hydrolysis of GGM has been studied in a continuous tube reactor to obtain these sugars under industrially relevant conditions. The reaction was performed under atmospheric pressure at 90°C and 95°C, and hydrochloric acid (HCl) served as catalyst. The influence of the reaction parameters, such as acid concentration (pH), temperature, concentration of the substrate, as well as catalyst and reactant flow rates, has been studied on the conversion efficiency and product distribution. Continuous production of monomeric sugars was achieved without formation of low-molecular by-products. The GGM conversion was high with HCl as catalyst, at 95°C, and a pH of 0.3. The main hydrolysis products were mannose, glucose, and galactose monomers. Minor amounts of sugar dimers were detected among the products. The experimental results are described with a laminar flow model for the continuous reactor.

Application of a trickle bed reactor (TBR) renders a very compact solution to carry out direct synthesis of hydrogen peroxide in water over a carbon supported palladium. The laboratory scale reactor was filled with silica particles (50–70 mesh) physically mixed with 37.5 to 75 mg of 5%Pd/C particles. The reaction conditions applied were 15 °C, 15–28 barg, 0.5 to 6 mL min −1 of liquid and 4.0–4.5 mL min −1 of gas flowrate (86.7/11/2.23 mol% of CO 2 /O 2 /H 2 ). Thus, we demonstrated that the ratio between H 2 and Pd is one of the key factors to achieve optimized, higher yields of hydrogen peroxide. Consequently, low H 2 concentrations lead to low productivities. One of the least studied parameters, addressed here, is the ratio between the bed filling (SiO 2 ) and the catalyst; i.e. the active catalytic species dilution effect. In short, it was found that when the amount of Pd was reduced below 0.094 mg Pd cm −3 SiO 2 the highest productivity of H 2 O 2 could be achieved. The selectivity obtained were between 5.3 and 38.0%, respectively, corresponding to turn-over-frequencies (TOF) ranging from 65 to 921 mmol H 2 O 2 gPd −1 h −1 .

In this study, the promotional effects of gold in Pd–Au bimetallic catalysts supported on activated carbon cloth for direct synthesis of H 2 O 2 has been investigated. The bimetallic catalysts were prepared by simultaneous co-impregnation approach. Direct synthesis was performed batch-wise in a stainless steel autoclave under high pressure (38 bar) at 0 °C and methanol (220 ml) was used as the reaction medium. A series of experiments were conducted to assess the effects of: (i) the surface chemistry of the support and (ii) the amount and ratio of palladium and gold on the surface morphology of the bimetallic catalysts and on their catalytic performances, and (iii) the oxidation state of the metallic components on the activity of the catalysts. Moreover, (iv) the effects of heat treatment of the catalysts in H 2 at 185 °C and in air at 185–275 °C on the surface chemistry of the support, surface morphology of the metallic component, and the performances of the final catalyst were investigated. Almost all of the Pd–Au bimetallic catalysts were more selective than the corresponding Pd monometallic catalysts. The results showed that the surface morphology of the Pd–Au bimetallic catalysts and their catalytic performance were highly influenced by the surface chemistry of the support and the amount and the ratio of Pd and Au in the catalyst. The presence of palladium oxide made the catalysts more selective and active than the corresponding zero-valent palladium (Pd 0 ) catalysts.

BACKGROUND The catalytic direct synthesis of hydrogen peroxide is a highly interesting alternative process to avoid the current anthraquinone route because it implies significant sustainability improvements. Among all the peroxide applications, its use as an electronic chemical requires very low metallic content. The employment of direct synthesis peroxide as raw material for the ultrapurification process has not been investigated before, so its viability is still pending evaluation. RESULTS Although the improvements of catalyst or reactor performance of the direct synthesis process were not defined as objectives of the work, a maximum peroxide concentration of 2.3% was obtained, which is a very good result considering the low pressure used. Some relationships between the measured metallic concentrations in the obtained chemical and the operating conditions have been very useful to identify the most important conditions (selection of appropriate quality chemicals and proper materials for the installation) to promote the production of hydrogen peroxide with low metallic content. The technical competitiveness of this alternative ultrapurification process was clearly demonstrated as the number of required membrane stages (from 1 to 6 depending on the product quality) is lower than that required by the traditional case. Besides, the process can be considered economically viable if the direct synthesis peroxide can be produced with a total cost below 36.5 $ m−3. CONCLUSION Further investigation, specifically focused on holistic approaches, is still necessary in order to assess the total costs of hydrogen peroxide production by direct synthesis. This way, the current available information could be complemented and the competitiveness of this direct route to obtain hydrogen peroxide for electronic grade chemical production could be more clearly defined. © 2015 Society of Chemical Industry

This work concerns a new technique to post-modify the catalytic material intended for use in H2O2 direct synthesis. The catalyst chosen was a commercially available 1 wt.% Pd/C. The catalyst was modified with the so-called Catalyst Wet Pretreatment Method (CWPM) that is used to post-modify prepared catalysts with aqueous solutions of NaBr, in different concentrations. The performance of pristine and the pretreated materials were then compared in the H2O2 direct synthesis and characterized before and after the catalytic tests in order to understand the role of the different concentrations of bromide in the CWPM procedure. The surface features of the different catalysts were analyzed with CO chemisorption (metal dispersion and mean particle size), Transmission Electron Microscopy (TEM, for Pd morphology and Pd particle size distributions), Inductive Coupled Plasma (ICP, for Pd content) and Ion Chromatography (IC, for bromide content). Various features of the materials prepared with the CWPM were correlated with the catalytic performance. It was found that the bromide has an active role in the reconstruction of metal phase and it does not only act as a poison for the most active catalytic sites as often reported in literature. By using this new protocol, the production H2O2 was almost doubled compared to the non-modified material when no direct promoters were added to the reaction environment.

A study on hemicellulose extraction from 10 different tree species was performed using a batchwise operated cascade reactor constituted by 5 units of 200 mL and a buffer vessel of 2000 mL where a flowrate of 150 L h−1 was fully recirculated (close loop operatioin). The experiments were performed at 160 °C, 9 bar and with wood chips particle size of 1.25–2 mm (average solid load of 6.57 g/L). The aim was to identify which wood species were the best candidates to obtain a high yield and/or molecular weight of hemicelluloses. Hydrothermal extractions at different times (from 5 to 80 min) were investigated. The highest yield was obtained with eucalyptus wood (40.3 wt%) after 80 min of extraction. Furthermore, 3 different trends were obtained for molecular weight evolution, where the different tree species can be grouped., MINECO and FEDER Funds, Project CTQ2015-64892-R (BioFraHynery)

The ethyl ester of levulinic acid, ethyl levulinate is a completely bio-based chemical made from levulinic acid, which is a hydrolysis product of cellulose and bio-ethanol. The very precise kinetics of levulinic acid esterification with ethanol was studied in an isothermal batch reactor in the presence of homogeneous (H2SO4) and heterogeneous catalysts (cation exchange resin Smopex-101). The temperature interval of the experiments was 50–70 °C. A kinetic model was proposed for both kinds of catalysts, adopting equilibrium rate expressions in any case. The different role of the catalyst used was considered separately, while a unique equilibrium constant was assumed for each system. The kinetic parameters were successfully determined by non-linear regression analysis. The model gave a very good description to the experimental data. The heterogeneous catalyst was used to demonstrate the feasibility of continuous operation in isothermal fixed bed reactors. The catalyst showed a good stability and high conversions of levulinic acid were obtained in the laboratory-scale fixed bed reactor. The model was able to predict both dynamic and steady-state experimental data.

Levulinic acid (LA) was recognized by the U.S. Department of Energy as one of the top biomass-derived platform molecules, due to its high reactivity and for its low-cost production from lignocellulose wastes. Levulinic acid esters may find applications as alternative green solvents, polymer plasticizers and fragrances [1]. LA esterification with alcohols is an acid catalyzed reaction, promoted by homogeneous catalysts (i.e. sulfuric acid [2]); since recent times a variety of heterogeneous acid catalysts have been used (i.e. zeolites, sulfated metal oxides, silica, sulfonated resins) [2,3]. Amberlyst-15 showed a remarkable high yield to ethyl levulinate, due to the acidity provided by sulfonic groups. In the present work, the kinetics of the levulinic acid esterification with ethanol in the presence of Amberlyst-15 was investigated. Experiments were conducted by evaluating the effect of different operating conditions on the reaction rate (i.e. stirring rate, temperature, catalyst loading and reactants ratio). Through this study it was possible to evaluate the activation energy value (49.39 kJ/mol). The collected experimental data were interpreted with a reliable model taking into account also for the mass transfer phenomena involved in the reaction network, such as eventual fluid-solid and intraparticle mass-transfer limitations. The mixed PDE/ODE system (Eq.1) given by the mass balance equations, was solved with advanced numerical techniques. (1) The results can be considered as good starting point for continuous reactors optimization.

Commercial mixed-phase aluminum oxide was used as a heterogeneous catalyst support, providing slightly basic properties which are well-suited for the condensation of bio-ethanol to C-4 hydrocarbons ...

In the present work a comparison between two different working solutions in the H2O2 catalytic direct synthesis (CDS) was studied in a continuous reactor. The two working solutions (i.e. water and ...

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.

Continuous hydrogenation of glucose to sorbitol was studied in an experimental set-up with parallel screening multiphase reactors. After investigating a range of reaction parameters, the suitable conditions for catalyst screening were found to be 130 °C, 2.0 ml min−1 flow rate and 0.2 mol L−1 glucose concentration. The hydrogen pressure was kept at 20 bar under all reaction conditions investigated. A slate of different ruthenium supported on carbon (active carbon and carbon nanotubes) catalysts was screened. All catalysts showed high (>97.4%) selectivities to sorbitol, while activity and stability varied. Long-term evaluation of the two best catalysts was performed over a 100 h period.

The hydrolytic hydrogenation of hemicellulose arabinogalactan was investigated in the presence of protonic and Ru (1-5 wt.%)-modified USY zeolites (Si/Al ratio = 15 and 30). The use of the purely acidic materials was effective in depolymerizing the macromolecule into free sugars. While the latter partly dehydrated into 5-hydroxymethylfurfural and furfural, the generation of high molecular-weight compounds (aggregates of sugars and humins) was not favored, in contrast to previous evidences over beta zeolites. Application of the bifunctional Ru/USY catalyst, comprising well-dispersed metallic nanopartides on the aluminosilicate support, resulted in the formation of galactitol and arabitol, in the suppression of dehydration side products, and further inhibition of polymerization reactions, which only yielded low molecular-weight oligomers. Detailed analysis of the reaction pathways as well as kinetic modeling of hydrolytic hydrogenation was performed with an advanced reaction mechanism.

The structure sensitivity was studied in the hydrogenation of glucose to sorbitol over supported ruthenium catalysts in a semi-batch reactor. Ruthenium on carbon supports with different ruthenium particle sizes was prepared and evaluated in the hydrogenation experiments. The highest turnover frequency was obtained with a catalyst bearing average ruthenium particle size of ca. 3 nm.

Formic acid production by ethyl or methyl formate hydrolysis was improved using 1-butylimidazole as a complexing agent. The chemical process involved both hydrolysis and complexation steps. The com ...

The degradation of the pharmaceutical compound diclofenac in an aqueous solution was studied with an advanced oxidation method, catalytic ozonation. Diclofenac was destroyed in a few minutes by ozonation but several long-lasting degradation by-products were formed. For this reason, the combination of heterogeneous catalysts and ozonation was applied to eliminate them completely. The kinetics of the diclofenac degradation and the formation of by-products were thoroughly investigated. Loading of Pt on the catalysts resulted in an improvement of the activity. The Mesoporous Molecular Sieves (MCM) were one of the promising catalysts for the degradation of organic pollutants. In this study, six heterogeneous catalysts were screened, primarily MCM-22-100 catalysts with different Pt concentrations loaded via the evaporation-impregnation (EIM) method, and they were applied on the degradation of diclofenac. It was found that the presence of Pt improved the degradation of diclofenac and gave lower concentrations of by-products. The 2 wt % Pt-H-MCM-22-100-EIM demonstrated the highest degradation rate compared to the proton form, 1% or 5 wt % Pt concentration, i.e., an optimum was found in between. Pt-H-Y-12-IE and Pt-&gamma, Al2O3 (UOP)-IMP catalysts were applied and compared with the MCM-22 structure. Upon use of both of these catalysts, an improvement in the degradation of diclofenac and by-products was observed, and the 2 wt % Pt-H-MCM-22-100-EIM illustrated the maximum activity. All important characterization methods were applied to understand the behavior of the catalysts (X-ray powder diffraction, transmission electron microscopy, nitrogen physisorption, scanning electron microscopy, energy dispersive X-ray micro-analyses, pyridine adsorption-desorption with FTIR spectroscopy, X-ray photoelectron spectroscopy). Finally, leaching of Pt and Al were analyzed by inductively coupled optical emission spectrometry.

Kinetic modelling of furfural oxidation with hydrogen peroxide over a fibrous polymer-supported sulphonic acid catalyst was performed. The proposed kinetic model describes the concentration profiles of the reactants, intermediates and products as a function of reaction time at different temperature. Parameter estimation has been performed followed by their statistical analysis showing that the kinetic parameters were statistically well identified.

Wood extractives such as α-pinene oxide and β-pinene oxide are important renewable chemicals for the synthesis of fine chemicals, pharmaceuticals, and value-added intermediates. In this work, catalytic transformations of biomass derived extractives, isomerization of α,β-pinene oxides were studied over supported ionic liquid catalysts (SILCAs). SILCAs consist of catalytic species (e.g., metal nanoparticles or metal complexes) in a thin layer of ionic liquid which is immobilized on a solid support material (e.g., active carbon cloth). The reaction kinetics of the isomerization reactions over supported ionic liquid catalysts were studied and modeled. Mechanistic kinetic models describing the differences in selectivity and activity of the catalysts containing different ionic liquids were developed, and the models described the reaction rates and product distributions very well.

The thorough kinetic study of the solvent-free hydrochlorination of glycerol using gaseous hydrogen chloride in a laboratory-scale semibatch reactor was carried out. A wide set of experiments was performed where reaction temperature (70–120 °C), catalyst concentration (0–50% by moles) and partial pressure (0.25, 0.5, 0.75 and 1.0 atm) were varied. Acetic acid was used as a homogenous catalyst. A more accurate approach was given to the semibatch reactor modeling since it was demonstrated that the liquid volume significantly increased along the reaction. The concentration of HCl was determined experimentally and it was possible to observe the influence of the reaction parameters on the HCl uptake. It was also evidenced that a non-catalytic hydrochlorination takes place in the system and its effect is non-negligible, especially at high temperatures. A new kinetic model was proposed and tested in order to explain the experimental observations. Non-linear regression analysis was successfully applied on the experimental data and the modeling results showed a satisfactory agreement. The model was able to estimate the activation energies for both catalyzed and non-catalyzed experiments. A new concept named Catalyst Modulus was derived from the kinetic equations and then verified with experimental data; the fit of this parameter was very high, thus, pointing out the validity of the model.

A prominent autocatalytic effect in the hydrolysis of hemicelluloses was observed in the presence of heterogeneous cation-exchange catalysts, Amberlyst 15 and Smopex 101. The kinetic models proposed were based on the reactivities of the non-hydrolysed sugar monomer units and the increase of the rate constant as the reaction progresses and the degree of polymerization decreases. General kinetic models were derived and the kinetic parameters, describing the autocatalytic effect, were determined by non-linear regression analysis. The kinetic model explained very well the overall kinetics, as well as the product distribution in the hydrolysis of hemicelluloses.

The enantioselective hydrogenation of ethyl benzoylformate over (−)-cinchonidine (CD)-modified Pt/Al2O3 catalyst in semi-batch and continuous fixed bed reactors was studied as a function of the modifier concentration and reaction temperature. The kinetic results from the semibatch reactor showed a higher enantioselectivity and lower initial rate as the amount of modifier was increased. The results from the fixed bed reactor demonstrates that continuous enantioselective hydrogenation is possible and that continuous feeding of (−)-CD is needed to maintain a high steady-state enantioselectivity.

The isomerisation of α-pinene oxide to campholenic aldehyde, an expensive ingredient utilized by e.g. flavor industry, was studied over Supported Ionic Liquid Catalysts (SILCAs) consisting of catalytically active species residing in ionic liquid. The ionic liquid, in turn, was immobilized on a solid support material. SILCAs were demonstrated as efficient catalysts for the transformation of α-pinene oxide into campholenic aldehyde, with the product distribution and activity being dependent on the nature of the ionic liquid.

Bio-ethanol is well known for its use as a gasoline additive. However, it can be blended in low portions to traditional gasoline although it has a corrosive nature. By taking advantage of modern continuous reactor technology and heterogeneous alumina catalysts, ethanol can be upgraded to 1-butanol in fixed beds. Butanol has more feasible properties as fuel component in comparison to ethanol. Mathematical modeling of reaction kinetics revealed a simple kinetic model could be used to describe the complex reaction process on a Cu/alumina catalyst. The reaction kinetics model is based on five parallel reactions in which ethanol reacts to 1-butanol, acetealdehyde, ethyl acetate, diethyl ether and diethoxyethane, respectively.

There is growing interest in utilizing galactoglucomannan, the main hemicellulose in softwoods, for various applications such as cosmetics, pharmaceuticals, textiles, alimentary, and health products, as well as for the production of fuels. For fuel production and for using the rare sugars as platform chemicals, the hemicelluloses need to be hydrolyzed to sugar monomers, and for this purpose, low-molecular-mass extracts are favorable. However, for the other applications high molecular masses are required, which presents an even greater challenge for extraction. The ability to optimize the extraction process according to the needs of further processing, by using solely water as the solvent, is a key issue in the environmentally friendly utilization of this versatile raw material. The goal of this work is to study how the average molar mass of hemicelluloses extracted from spruce sapwood can be influenced by altering the experimental conditions. The main parameters influencing the extraction and hydrolysis of the hemicelluloses, namely, extraction time, temperature, pH, and chip size, were studied. The results show that it is feasible to develop an extraction process for harvesting spruce hemicelluloses, also of large molar masses, for industrial applications by using pressurized hot water extraction.

Hydrodynamic behavior in a lab-scale Trickle Bed Reactor (I.D. 1.15 cm, L = 30 cm, filled with silica particles of 0.2–0.8 mm) has been investigated. Residence time distribution curves were determined using a step transient response via conductivity measurement varying gas flowrate (0–12 mL/min CO2–H2–O2 at 78–4.0–18 mol.%) and liquid flowrates (methanol 0.5–2.0 mL/min) at −10 °C and atmospheric pressure. We demonstrate that this reactor can be accurately modelled using a combined model of axial dispersion followed by one mixed tank reactor with absolute average deviations lower than 2.6% (maximum deviation of 6.50%). The best results were obtained for a model combining 1-tank reactor with 1.20–6.15 min of residence time in series with a plug flow with residence times from 8.1 to 38.1 min. These values highlight the prevalence of the axial dispersion over the backmixing (exemplified by the mixed tank reactor) with a contribution between 80.3% and 90.1% of the total residence time. The Peclet numbers determined were in the interval of 248.3–699.3, the highest values of Pe were obtained at the highest liquid flowrate indicating the lowest axial dispersion. Correlations with the fraction of liquid flow, gas and liquid Reynolds numbers and the Galilei number are given.

A kinetic model was developed for the enantioselective hydrogenation of ethyl benzoylformate (EBF) on a modified Pt/Al2O3 catalyst. This model was based on the assumption of different numbers of si...

A mathematical model was developed to analyze an exothermic liquid–liquid reaction system using epoxidation of oleic acid by peroxyformic acid formed in situ as an example. Kinetic and thermal parameters were included, mass transfer parameters were eliminated from the model and evaporation/condensation was taken into account. A calorimetric semi-batch reactor under isoperibolic mode was used in the experimental work. Different initial aqueous-phase concentrations of H 2 O 2 [6.5–8.8 mol/l], water [44–45 mol/l], molar flow rate of formic acid [0.02–0.54 mol/min], initial reaction temperature [50–70 °C] and amount of organic phase [34–46 wt.%] were studied. A non-linear regression method was used to estimate kinetic ( e.g. , rate constant at average temperature and activation energy) and thermal parameters ( e.g. , reaction enthalpy) of the epoxidation and ring-opening reactions. The standard reaction enthalpy changes were estimated to be −116 kJ/mol for epoxidation reaction and −50 kJ/mol for the ring opening.

The hydrolytic hydrogenation of hemicellulose arabinogalactan using different beta zeolites as catalysts was studied in this work. The use of bifunctional Ru/β zeolite catalysts leads to formation of valuable polyols (galactitol, arabitol) from hemicellulose. The presence of acid sites enhances hydrolysis of the hemicelluloses into sugars in addition to homogeneous hydrolysis while the Ru catalyzes further hydrogenation into polyols. Using bifunctional catalysts the stability of these polyols can be also enhanced because the side reactions to HMF and furfural were minimized, however formation of high molecular weight compounds (aggregates of sugars and humins) was still quite substantial.

Pressurized hot water extraction of hemicelluloses from spruce sapwood was studied at 120–170 °C using a batchwise-operated cascade reactor, which enables precise sampling as well as very accurate and rapid temperature control. The extraction was performed under identical conditions for two different chip sizes, a 1.25–2.0-mm sieved fraction and handmade 10-mm cubic blocks, to evaluate the influence of chip size on the overall extraction kinetics. The results showed that the extraction rate increases significantly with temperature and that the pH decreases during the extraction, as a result of the liberation of acid groups. The concentration of hydronium ions in the liquid phase was observed to have a linear correlation with conversion depending, however, on the chip size, which shows that the mass transfer of the acid groups differs significantly from that of the bulky hemicelluloses. It also shows that significant amounts of acetyl groups are liberated inside the chips before the hemicelluloses enter th...

Reactive chromatography is a special topic in chemical reaction engineering, consisting of the combination of chemical reaction and chromatographic separation. The main idea is to avoid a further separation unit, by performing reaction and separation in one unique equipment, allowing process intensification. This technology is usually applied in hydrolysis (or esterification) reactions, that undergoes through the reaching of chemical equilibrium. The chromatographic reactor application would lead to complete conversion, by separating reactants and products as the reaction proceeds. Modelling is certainly a delicate issue for chromatographic reactor to optimize the operation conditions, thus different approaches were published. The aim of the present work is to show a novel chromatographic reactor model, were all the physical and chemical phenomena involved and described by a rigorous approach. The fluid-dynamics was treated by axial dispersion approach, and the Peclet number values were obtained from dedicated experiments. The external fluid-solid mass transfer was calculated from existing correlations, demonstrating to be negligible for the modelled chromatographic reactor. The intraparticle mass diffusion was assumed to be the sum of two parallel contributions, i.e. porous and surface diffusivity. The model was tested on literature data for methyl acetate hydrolysis experiments with satisfactory results, obtaining reliable values of the surface diffusivity. A sensitivity analysis was conducted highlighting that the model can predict complete ester conversion and product separation.

A straightforward and reliable method was successfully developed for stainless steel microreactor coating. The importance of this coating method lies in using an already pre-prepared Au/Al2O3 catalyst without incorporation of any binders, addressing the importance of the interplay between the catalyst particle size and slurry viscosity in optimization of the uniformity, stability and thickness of the coating layers. The catalyst and the coated microplatelets were characterized thoroughly using nitrogen adsorption, X-ray Diffraction, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, confocal microscopy, laser diffraction, viscosity measurements, Transmission Electron Microscopy, Energy-dispersive X-ray, Inductively Coupled Plasma- Optical Emission Spectrometry and X-ray Photoelectron Spectroscopy. Moreover, stability of the coating layers was assessed in gas phase partial oxidation of ethanol. Initial increase in the catalyst activity with time on stream was likely due to changes in the gold oxidation state while minor catalyst deactivation could mainly be correlated with coking.

The aqueous phase reforming (APR) of xylitol was studied in a continuous fixed bed reactor over three catalysts: Pt/Al2O3, Pt/TiO2 and Pt-Re/TiO2. The data obtained in the case of the monometallic Pt catalysts was compared to the bimetallic Pt-Re sample. The effect of Re addition on the catalyst stability, activity, product formation and selectivity toward hydrogen and alkanes was studied. The bimetallic catalyst demonstrated a higher selectivity to alkanes compared to the monometallic samples. The monometallic catalyst was more selective toward hydrogen formation. A plausible reaction scheme explaining differences in selectivity toward hydrogen and alkanes was proposed and discussed.