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Epoxidation of oleic acid and cottonseed oil was conducted in a semibatch reactor with in-situ-formed percarboxylic acid (peracetic acid or perpropionic acid), using hydrogen peroxide as an oxidizi ...

The modeling of chemical reactions studied in small scale, often carried out in Academia, is very important since it gives more information about the system and better possibilities to scale-up the processes in the future. Supported ionic liquid catalysts (SILCAs) have been studied in a number of different processes. However, the modeling of these processes have been studied only in a few cases. In this paper the sample cases are reviewed. These processes include hydrogenation of unsaturated aldehydes as well as isomerization of terpenes, α- and β-pinene oxides.

The present work provides a systematic comparison of solvent-free glycerol hydrochlorination with semibatch and reactive flash distillation technologies. All the experiments were performed at atmospheric pressure and constant flow rate of gaseous HCl in the temperature range of 70 to 120 °C. Both acetic acid and adipic acid were used as homogeneous catalysts, separately, at a concentration of 12% by moles of each. In addition, a series of noncatalytic experiments was investigated. A comparative analysis between reactive flash distillation and semibatch operation suggested that reactive flash distillation only increases the production rate of the desired product 1,3-dichloropropan-2-ol (αγ-DCP) for the highest temperature, i.e. 120 °C. Many aspects of the HCl liquid uptake were also exposed once water was allowed to leave the liquid phase, revealing that water also has a positive influence on the reaction rate because it promotes HCl solubility and hydrolysis. Such an important effect was not predicted by ...

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.

In this work, the friction theory (FT) and free volume theory (FVT) were combined with the electrolyte perturbed-chain statistical association fluid theory (ePC-SAFT) in order to model the viscosity of pure ionic liquids (ILs) and IL/CO2 mixtures in a wide temperature and pressure (up to 3000 bar) range and with viscosities up to 4000 mPa·s. The ePC-SAFT pure-component parameters for the considered imidazolium-based ILs were adopted from our previous work. These parameters were used to calculate the density and residual pressure of the pure ILs. The density and pressure were then used as inputs for pure-IL viscosity modeling using FVT or FT, respectively. The viscosity-model parameters of FT and FVT were obtained by fitting to experimental viscosity data of imidazolium-based ILs and linearized with the molecular weight of the IL-cation. As a result, the FT viscosity model can more accurately describe the experimental viscosity data of pure ILs than the FVT model, at the cost of an increased number of para...

A new kinetic model for the halogenation of polyalcohols (e.g., chlorination of glycerol with gaseous HCl in the presence of homogeneous acid catalysts) was developed. The model is based on a reaction mechanism, which includes esterification and epoxidation steps followed by halogenation steps. The principle of quasi-steady state was applied to the ester and ionic intermediates appearing in the model and rate equations were derived. Furthermore, some simplified cases of the rate equations were considered, such as immediate water removal from the reaction mixture and analytical solutions for the simplified kinetic models were derived. The model was verified against experimental data obtained from laboratory-scale semibatch reactors. The conclusion is that the model worked very well, predicting correctly the glycerol conversion and the product distribution of α-, β-, α,β- and α,γ-chlorinated products. The kinetic model can be used for the design of reactors for homogeneously catalyzed halogenation.

The industrial processes involved in the production of formic acid were reviewed with emphasis on the hydrolysis of methyl formate. The liquid-phase hydrolysis of methyl formate in the absence and ...

The synthesis of dimethyl carbonate from methanol and CO2 catalyzed by ZrO2 doped with KCl was investigated using chemical traps for water to circumvent thermodynamic limitations. The reaction, promoted by magnesium, occurred via the formation of carbonated magnesium methoxide (CMM) which adsorbed on the surface of ZrO2. The surface migration of the oxygen atom of ZrO2 to the surface methoxy groups of CMM resulted in the formation of dimethyl carbonate. The resulting MgO then reacted with methanol forming water and regenerating magnesium methoxide. The water formed reacted with the dehydrating agent, thus shifting the equilibrium toward a higher yield of DMC. The yield of 7.2 mol % DMC and 13.6 mol % conversion of methanol was obtained when methanol reacted with CO2 at 150 °C and 9.5 MPa for 8 h. The plausible reaction pathway is described.

A general mathematical model for the chemical pulping of wood including coupled chemical reactions and diffusion limitations in anisotropic wood chips was developed. The model, which consists of co ...

The kinetics and thermodynamics of alkyl formate hydrolysis in liquid phase were studied in a laboratory-scale autoclave at temperatures between 333 and 383 K using different molar ratios of the reactants. The process was found to exhibit an autocatalytic effect due to the acid formed. More so, the rate of neutral hydrolysis of ethyl formate is faster compared to methyl formate in the uncatalyzed reaction. However, the autocatalytic effect is more pronounced in methyl formate hydrolysis. In addition, the effect of adding a small amount of formic acid as an initial charge upon the equilibrium conversion and kinetics was investigated, and it was found that the addition improved the reaction rate by reducing the induction period but it suppressed slightly the equilibrium conversion. A kinetic model was proposed to explain these experimental trends, and the model agreed well with the experimental results.

The use of ionic liquids in catalysis is attracting interesting attention in chemical engineering. Supported ionic liquid catalyst (SILCA) compounds consist of immobilized catalytic species (e.g., transition metal particles residing in an ionic liquid layer immobilized on a solid support). In this work, the kinetics of SILCA compounds has been studied in detail and a mechanistic kinetic model, which describes the differences in selectivity and activity of the catalysts that contain different ionic liquids, has been developed.

Kinetics and mass transfer for supported ionic liquid catalysts (SILCAs) were studied for complex catalytic hydrogenations of unsaturated aldehydes. The system can be characterized as a gas−liquid−liquid−solid system, where gaseous hydrogen and an unsaturated aldehyde, citral, diffuse from molecular solvent to a thin layer of ionic liquid containing the catalytically active species, metallic palladium nanoparticles. The intrinsic kinetics was determined at 353−423 K (80−150 °C) and pressures ranging from 10 to 50 bar. A kinetic model was proposed that was able to predict the experimental concentration data successfully. In order to obtain more understanding about the importance of mass-transfer and diffusion limitations for these kinds of processes, a number of models describing the concentration profiles of the reactants in the catalysts were developed. The developed reaction-diffusion models revealed important insight into the potential limiting phenomena for this type of reaction systems.

The effect of sonification on d-fructose hydrogenation over several heterogeneous catalysts was investigated. The reaction rate and selectivity were studied at different temperatures, pressures, and ultrasonic power inputs. The ultrasonic effects were clearly catalyst dependent. The sonification during the hydrogenation reaction significantly enhanced reaction rate over Cu/SiO2. In the case of Raney-Ni, just moderate improvements of reaction rates were observed under ultrasound and a slight decrease of catalyst activity by sonification was obtained over Cu/ZnO/Al2O3. Although the choice of catalyst significantly influenced selectivity, no positive influence of acoustic irradiation on selectivity was achieved. The influence of pressure and temperature over Raney-Ni type catalyst was studied under sonification as well. High pressures and temperatures brought just moderate enhancements of reaction rates, while the variation of nominal ultrasonic power input significantly affected the catalyst activity. A cat...

Catalytic hydrogenation of an α,β-unsaturated aldehyde, citral, over different Ni and Pt fiber catalysts as well as a commercial Pt powder catalyst was performed in a batch reactor under pressurized conditions. Active carbon was used as a support material. The influence of the important variables, such as temperature and pressure, was investigated in the batch reactor. The metal loading in the catalyst was varied as well. The catalysts were characterized with scanning electron microscopy, atomic force microscopy, N2-physisorption, temperature-programmed hydrogen desorption, and inductively coupled plasma mass spectroscopy. Four consecutive experiments were carried out with each fiber catalyst in the batch reactor to elucidate eventual catalyst deactivation. The decrease in activity was fairly notable. The results of the kinetic experiments demonstrated the feasibility of utilizing woven active carbon cloths as supports in three-phase metal-catalyzed hydrogenation of citral. The Ni on active carbon cloth (...

Kinetic studies of catalytic three-phase systems are traditionally performed in autoclaves operating batchwise, and the results are described with rate equations based on the simple Langmuir-Hinshelwood concept. This is not sufficient, as complex organic molecules react on the catalyst surface, and more advanced kinetic models and experimental techniques are needed. Semicompetitive and multicentered adsorption models have been applied to kinetic data, and transient step-response experiments have been carried out for various industrially relevant three-phase systems. The theoretical basis of the advanced kinetic concept is described and successfully applied to several industrially relevant processes, such as hydrogenation of aromatic components and aldehydes on commercial catalysts and enantioselective hydrogenation on modified catalyst surfaces.