Reactive Chromatography Research Articles

Solid‐Phase Reactive Chromatography (SPRC): A New Methodology for Wittig and Horner–Emmons Reactions on a Column under Microwave Irradiation

AbstractA new methodology named solid‐phase reactive chromatography (SPRC), which combines reaction, separation, and purification into a single unit for the preparation of small samples, is described. This method was illustrated in the synthesis of some natural bioactive compounds, namely, methoxylated analogues of resveratrol, alkylresorcinols, and 5‐aryl‐2,4‐pentadienoates, over a column of alumina‐KF under microwave irradiation by using the Wittig and Horner–Emmons reactions. This approach permitted the preparation of the target olefins with high purity and good to excellent yields in short reaction times.

Reactive Chromatography for the Synthesis of 2-Ethylhexyl Acetate

Reactive chromatography (RC) combines reaction and chromatography in a single unit. Due to simultaneous separation of products it can be advantageously used for reversible reactions to obtain the enhanced performance. It is a promising alternative to reactive distillation when the components are temperature sensitive and less volatile. In the present work, we study the application of RC for the synthesis of 2-ethylhexyl acetate through esterification of acetic acid with 2-ethylhexanol. Amberlyst-15 has been used as a catalyst/adsorbent. Several aspects such as reaction kinetics, multicomponent adsorption equilibria, and reaction-separation study using fixed bed chromatographic reactor are covered. The kinetics was studied in a stirred batch reactor. The effects of various parameters such as speed of agitation, particle size, temperature, mole ratio of reactants, and catalyst loading have been investigated. Kinetic modeling was performed using modified activity based Langmuir-Hinshelwood-Hougen-Watson (LHHW) model. Non-reactive binary adsorption experiments were performed to determine the parameters of Langmuir adsorption isotherm by minimizing the errors between the experimental and predicted breakthrough curves. Further, the reactive chromatography experiments were performed to obtain the reactive breakthrough curves which indicate a clear potential for the use of reactive chromatography for this reaction. The obtained data has been compared with the predictions of mathematical model of the chromatographic reactor.

The back-titration of chemisorbed atomic oxygen on copper by carbon monoxide investigated by microcalorimetry and transient kinetics

The back-titration of atomic oxygen chemisorbed on metallic copper using carbon monoxide is investigated by microcalorimetry. Results from simulations based on a microkinetic model of the back-titration are used for processing of microcalorimetric data. In addition, surface oxidation of copper by nitrous oxide is investigated by microcalorimetry. The results are compared with results obtained by nitrous oxide reactive frontal chromatography and by static oxygen adsorption studied by microcalorimetry. The heat of adsorption of nitrous oxide on copper amounts to 304 kJ mol−1, and the heat of adsorption of carbon monoxide on surfaceoxidized copper is in the range from 120 to 70 kJ mol−1.

Esterification of acrylic acid with methanol by reactive chromatography: Experiments and simulations

The esterification of acrylic acid with methanol using Amberlyst 15 as a stationary phase has been investigated using a chromatographic reactor. Several experimental runs at various operating conditions have been conducted on a batch column. A classical reactive chromatography model including lumped kinetics, a linear driving force transport model and a heterogeneous kinetic model for the catalytic reaction has been developed. The additional dispersion of concentration fronts due to density gradient effects has been accounted for in the model. The model parameters have been determined in a fast and reliable way by directly fitting the batch column experiments. In general, a good agreement between experimental and calculated results is obtained. The evaluation of the covariance of the fitted model parameters reveals important insights about the system behavior. Based on the detailed batch column model, a complete model of a simulated-moving-bed reactor has been implemented and its optimal point of operation for the synthesis of methyl acrylate from acrylic acid has been determined. Particularly when considering the low-operating temperature, we can regard this process as a possible competition for current technologies.

Chromatographic Reactors: Esterification of Glycerol with Acetic Acid Using Acidic Polymeric Resins

Reactive chromatography is an attractive method for chemical synthesis because chemical reactions and product separation occur simultaneously in the same unit. In this work, the synthesis of triacetine, starting from glycerol and acetic acid, using reactive chromatography on acidic polymeric resins is investigated. The study proceeds first to the characterization of the adsorption equilibria of the involved multicomponent mixtures and then to the study of the kinetics of the relevant reactions using a batch reactor. Next, the separation−reaction process is investigated using a fixed-bed chromatographic column. The obtained data are compared with the predictions of a mathematical model, whose kinetic and equilibrium parameters were estimated from the batch experiments mentioned above. It is shown that, although this synthesis requires three steps in series, the chromatographic reactor can produce high-purity (i.e., food-grade) triacetine with high conversions. It is found that the presence of water in the ...

The effect of additives on Cu/HZSM-5 catalyst for DME synthesis

The addition of ZnO or ZrO2 into CuO/HZSM-5 was investigated for DME synthesis from syngas by using the reactive frontal chromatography method, TPR and in situ TPR. These promoters enhanced the catalytic activity of Cu/HZSM-5 and promotion with ZnO and ZrO2 produced a maximum activity, which could be explained by the improvement of the dispersion of Cu and the promotion of CuO reduction. The Cu+ species existing during the reaction have been detected, based on which a Cu0 ↔ Cu+1 redox cycle model was put forward.

A New Reaction-Separation Unit: The Simulated Moving Bed Reactor

Process intensification is one of the most promising tools for improving current technologies. This requires dealing in most cases with complex systems where many different and often interacting physicochemical phenomena take place simultaneously. Continuous reactive chromatography, implemented through the simulated moving bed reactor technology, represents a novel example of such an intensified process. In this case, only a detailed description of the selective polymer swelling and reaction kinetics enables the modeling and the understanding of the behavior of the chemical production process. The optimization of the unit reveals its major economic limitation to arise from the sorptive properties of the currently available stationary phase. Based on a proper understanding of the unit operation, it is possible to design new stationary phases, tailor-made for specific reacting systems, which allow the performance of the process to be significantly improved.

Continuous reactive chromatography

Reactive “simulated moving bed” chromatography (SMBR) is a continuous and counter-current operation combining chemical reaction and adsorptive separation within one single apparatus. Its application promises substantial improvements in process performance, especially for equilibrium limited reactions involving heat-sensitive products, as, for example, fine chemicals or pharmaceuticals. In this work, a general approach towards the design of a SMBR process is illustrated using the synthesis of methyl acetate, catalyzed by a sulfonated poly(styrene–divinylbenzene) resin, as a model system. Starting from a suitable mathematical representation of the experimentally determined adsorption thermodynamics and reaction kinetics, a model for a reactive chromatographic column is developed and validated. Based on an extension of this model, the SMBR process is investigated through numerical simulation, in order to identify the governing design parameters and to devise an efficient strategy towards process optimization both in terms of productivity and desorbent requirement. Finally, the feasibility of the process for the model system is proved experimentally using a SMBR unit of mini-plant scale.

The detailed kinetics of the adsorption of hydrogen on polycrystalline copper studied by reactive frontal chromatography

The coverage-dependent sticking probabilities of molecular hydrogen on polycrystalline copper supported on alumina have been determined in the temperature range 213–273 K by analysis of the hydrogen frontal adsorption line shape. In this temperature range the initial sticking probabilities increase from 8× 10−13 (213 K) to 1.3× 10−10 (273 K). The overall activation energy to adsorption has been found to be 42 kJ mol−1. The application of reactive frontal chromatography for the measurement of hydrogen sticking probabilities on copper is a novel variant of the N2O reactive frontal chromatographic method, developed for the measurement of copper surface areas. Its use here shows that reactive frontal chromatography may be applied generally to any adsorbate/adsorbent system involving activated adsorption and low sticking probabilities.

Dynamics of a Chromatographic Reactor: Esterification Catalyzed by Acidic Resins

Reactive chromatography, i.e., coupling chemical reaction and selective sorption, allows us to drive the chemical reaction beyond equilibrium and to separate its products. Chromatographic reactors exhibit a complex dynamical behavior, whose analysis is the objective of this work. The synthesis of ethyl acetate and water from ethanol and acetic acid on a commercial polystyrene−divinylbenzene acidic resin is considered. The results of experiments run in a laboratory-scale chromatographic reactor are reported. Experimental data are in good agreement with the results obtained using a fully predictive equilibrium dispersive model. This exploits an accurate description of both the multicomponent sorption equilibria on the resin, based on the extended Flory−Huggins model, and the kinetics of the heterogeneously catalyzed chemical reaction. The chromatographic reactor exhibits a rather rich dynamical behavior, which is a consequence of the dual role, as a catalyst and as a selective sorbent, played by the resin. In particular, it is characterized by the development of composition fronts traveling along the fixed bed column at well-defined propagation velocities. By interpreting the obtained results in terms of these classical nonlinear chromatography concepts, a deep insight into the dynamical behavior of the chromatographic reactor can be achieved. These findings can be usefully summarized in a master plot which allows us to identify the different dynamic regimes in the operating parameter space.

Chemochromatography: Its use for the separation of nikkomycins X and Z

A novel mode of reversed-phase high-performance liquid chromatography in which the mobile phase reacts chemically with the compounds to be separated was developed. Nikkomycin X and nikkomycin Z, two natural isomeric nucleoside peptide antibiotics, move as a single peak on a C 18 reversed-phase column using an aqueous trifluoroacetic acid mobile phase. Addition of sodium bisulfite (1.0%) to the mobile phase results in the formation of a polar bisulfite addition product with nikkomycin X, but not with nikkomycin Z, inside the HPLC column. This type of reactive chromatography, or chemochromatography, led to the analytical and preparative separation of nikkomycins X and Z which are normally very intractable to separation by conventional chromatographic techniques.

The chemical nature of adsorption centers in modified carbon-silica adsorbents prepared by the pyrolysis of alcohols

The investigations concerned the surface properties of carbon-silica adsorbents prepared through the pyrolysis of n-heptyl and benzyl alcohols and their mixtures on the surface of silica gels. IR spectroscopy, gas adsorption chromatography and reactive chromatography were used in the studies. On the basis of the results obtained two different methods are proposed for the modification of the surface properties of carbon-silica absorbents. In the first method additional pyrolysis of the carbon deposit with or without partial hydrogenation of the deposit with or without partial hydrogenation of the deposit at elevated temperature takes place, while the other method consists of chemical modification of the carbon-silica adsorbents with silanes. This is possible due to the mosaic structure of the adsorption centers of these adsorbents. Linear relationships were observed between the adsorption heats of hydrocarbons and the amount of carbon deposited on the silica gel surface.

Reactive Thin-Layer Chromatography for the Evaluation of Cotton Finishes

A technique of thin-layer chromatography is described wherein cellulose-reactive materials are cured on the cellulose adsorbent prior to development. The technique should prove useful as a rapid means of evaluating the reactivity or mechanism of action of cotton finishing agents.