Glycerol Chlorination Research Articles

Glycerol chlorination reaction mechanism

AbstractA new reaction mechanism for the glycerol chlorination is proposed. This mechanism is based on theoretical calculations within density functional theory combined with polarizable continuum model . Two possibilities were investigated, the first is the SN2 chlorination forming mono‐ and dichlorinated products and the second one is through an ester intermediate formed by glycerol esterification in the presence of acetic acid as catalyst. Our results indicate that the first chlorination reaction can occur in the absence of the catalyst and the main product is 3‐monochloropropane‐1,2‐diol (1‐MCP). The inhibitory role of water in the second chlorination is also revealed, that is, water formation suppresses the second chlorination when reaction is conducted in the absence of a carboxylic acid. In the presence of the catalyst, oxonium species are formed as reaction intermediates and the main products are 1‐MCP and 1,3‐dichloropropan‐2‐ol (1,3‐DCP). Our results are in agreement with the experimental data, which indicate that the 1,3‐DCP is the main product when an acid catalyst is employed and, also, there is no significant formation of 2‐monochloropropane‐1,2‐diol and 1,2‐dichloropropan‐3‐ol .

SELECTIVE CHLORINATION OF GLYCEROL TO 3-CHLORO-1,2-PROPANEDIOL CATALYZED BY BRØNSTED ACIDIC IONIC LIQUIDS

Abstract Bronsted acidic ionic liquids composed of 1-butyl-3-methylimidazolium, triethylbutylammonium, and 1-butylpyridinium cation counterparts and HSO4‾ and H2PO4‾ anion counterparts were used as the catalysts for the selective chlorination of glycerol with hydrogen chloride to 3-chloro-1,2-propandiol. From the perspective of the glycerol conversion and product yields, the catalytic activities of the ionic liquids containing HSO4‾ were higher than the ionic liquids containing H2PO4‾. As compared with the carboxylic acid catalysts, Bronsted acidic ionic liquids favored the catalytic chlorination of glycerol to 3-chloro-1,2-propandiol. When the glycerol chlorination was catalyzed by the Bronsted acidic ionic liquids at 110 oC for 12 h with the catalyst loading of 0.75 mol·kg‾1 glycerol, the 3-chloro-1,2-propandiol yield was more than 81% at the complete conversion of glycerol.

Chlorination of glycerol with HCl to 1,3‐dichloro‐2‐propanol catalyzed by aliphatic carboxylic acids

AbstractGlycerol oversupplied in biodiesel production can be used as a renewable raw material for producing high‐valued chemicals, such as 1,3‐dichloro‐2‐propanol (1,3‐DCP), propanediol, acrolein, and acrylic acid. Catalytic chlorination of glycerol to 1,3‐DCP is an alternative to propylene chlorination. The catalytic activities of various aliphatic carboxylic acid catalysts for the catalytic chlorination of glycerol with HCl to 1,3‐DCP were investigated. When monocarboxylic acids, such as acetic, propanoic, butyric, and hexylic acids, were used as the catalysts, the monocarboxylic acids with the carbon numbers of 3 and 4 favored the glycerol chlorination to 1,3‐DCP. When dicarboxylic acids, such as oxalic, malonic, succinic, and adipic acids, were used as the catalysts, the dicarboxylic acids with long carbon chain favored the glycerol chlorination to 1,3‐DCP. The highest yield of 1,3‐DCP of 88.6% was obtained over adipic acid catalyst after reacting at 110 °C for 14 h. When hydroxylcarboxylic acids, such as citric, malic, and lactic acids, were used as the catalysts, the 1,3‐DCP yields were approximately half of those over monocarboxylic and dicarboxylic acid catalysts with the same carbon number, respectively. The steric hindrance effect of carboxylic acids played an important role in glycerol chlorination to 1,3‐DCP as compared with their acid strengths. © 2015 Curtin University of Technology and John Wiley & Sons, Ltd.

Mechanism of chemical activation of sodium chloride in the presence of amino acids

Sodium chloride has been shown to promote chlorination of glycerol during thermal processing. However, the detailed mechanism of this reaction is not well understood. Preliminary experiments have indicated that the reaction mixture should contain an amino acid and it should be dissolved thoroughly in water in order to induce chlorination. These observations are consistent with the process of dissociation of sodium chloride and its re-association with amino acid and eventual formation of the chlorinating agent in the form of the hydrochloride salt. Release of HCl from this salt can be manifested in chlorination and hydrolytic reactions occurring during thermal processing. The generation of HCl at room temperature from a mixture of sodium chloride and glycine was confirmed through spectrophotometric monitoring of the pH. Hydrolytic and chlorination reactions were demonstrated through monitoring of formation of HMF and chlorinated products under pyrolytic conditions using glucose or sucrose and amino acid mixtures.

Glycerol chlorination in a gas-liquid semibatch reactor: New catalysts for chlorohydrin production

Glycerol from biodiesel production can be an important industrial feedstock for chemical commodities as it can be used in the food, cosmetic, pharmaceutical and tobacco industries. However, crude glycerol derived from biodiesel production has a low value because of impurities. The purification of this glycerol into a high grade involves high costs and is not economically feasible for small and medium size plants. The glycerol conversion into chlorohydrins was studied using new homogeneous catalysts and hydrochloric acid as chlorination agent. This is an interesting alternative route to epichlorohydrin and then to epoxy resins. The behavior of two series of homologous catalysts, glycolic acid series (glycolic acid, di-glycolic acid and thio-glycolic acid) and amminoacid series (glutamic acid, aspartic acid and cysteine), were investigated for their activity and selectivity. Glycolic acids were more active than amminoacids. The p K a values had a strong influence on selectivity (mono-chlorohydrins/di-chlorohydrins) for the amminoacid series, which was not observed for the glycolic acids. A kinetic model and reaction mechanism developed in a previous work were used for interpreting the kinetic runs. Glycerol chlorination in the presence of aminoacids and glycolic acids as catalyst was studied. The data were interpreted with a gas-liquid kinetic model and the kinetic and mass transfer parameters were obtained

Kinetic Model for Homogeneously Catalyzed Halogenation of Glycerol

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.

10.2478/s11814-009-0329-x

A kinetic model for the chlorination of glycerol with hydrochloric acid in the use of acetic acid as catalyst is presented in this study. The model is based on a comprehensive chlorination mechanism, taking the formation of 1,3-dichloro-2-propanol and 2,3-dichloro-1-propanol into account while ignoring the formation of any intermediate in the chlorination system. Simulations were carried out under different chlorination conditions to calculate the concentrations of the main chemical species in the reaction system. The validity of the model was examined via a comparison of the calculated data with the experimental data on the chlorination of glycerol with hydrochloric acid at 363–393 K. The results show the model is capable of describing the chlorination performance with good agreement with experimental data.

Kinetic model of glycerol chlorination with hydrochloric acid

A new reaction model for dichloropropanol (DCP) synthesis from glycerol chlorination is proposed based on the models reported by Tesser et al. (2007) and Luo et al. (2009). Two reaction steps, glycerol to glycerol-1-acetate and α-MCP to 3-chloropropandiol-1-acetate, were defined as reversible reactions and other reaction steps were defined as irreversible processes. Using the experimental data reported by Luo et al. (2009), the values predicted in this study were compared with the previous model reported by Luo et al. (2009) using both the average absolute deviation (AAD) and root mean square deviation (RMSD). The AAD and RMSD of the new model were 31% and 33% lower than that of the existing one, respectively. Overall, the proposed model for glycerol chlorination is superior to the previous model.

New Process for Producing Epichlorohydrin via Glycerol Chlorination

The strong growth of biodiesel production occurring in the last years has determined the availability of a great amount of the byproduct glycerol. Many researches in the world are therefore oriented to find new possible uses for glycerol also with the aim of reducing the cost of biodiesel. In this paper the chlorination of glycerol with gaseous hydrochloric acid to obtain 1,3-dichlorohydrin and then epichlorohydrin will be described. All the advantages of this process will be examined and discussed. The behavior of the different proposed catalysts (normally compounds containing carboxylic acid groups), the reaction kinetics, the effect of the catalyst concentration, the effect of HCl pressure, the vapor−liquid phase equilibria of the reaction products in the reaction environment, and the most convenient operative conditions have been studied, concluding with useful suggestions for the design of the industrial plants.

A kinetic model for glycerol chlorination in the presence of acetic acid catalyst

A kinetic model for the chlorination of glycerol with hydrochloric acid in the use of acetic acid as catalyst is presented in this study. The model is based on a comprehensive chlorination mechanism, taking the formation of 1,3-dichloro-2-propanol and 2,3-dichloro-1-propanol into account while ignoring the formation of any intermediate in the chlorination system. Simulations were carried out under different chlorination conditions to calculate the con- centrations of the main chemical species in the reaction system. The validity of the model was examined via a com- parison of the calculated data with the experimental data on the chlorination of glycerol with hydrochloric acid at 363- 393 K. The results show the model is capable of describing the chlorination performance with good agreement with experimental data.

Investigation of the kinetics and mechanism of the glycerol chlorination reaction using gas chromatography-mass spectrometry

As a primary by-product in biodiesel production, glycerol can be used to prepare an important fine chemical, epichlorohydrin, by the glycerol chlorination reaction. Although this process has been applied in industrial production, unfortunately, less attention has been paid to the analysis and separation of the compounds in the glycerol chlorination products. In this study, a convenient and accurate method to determine the products in glycerol chlorination reaction was established and based on the results the kinetic mechanism of the reaction was investigated. The structure of main products, including 1,3- -dichloropropan-2-ol, 2,3-dichloropropan-1-ol, 3-chloro-1,2-propanediol, 2-chloro- 1,3-propanediol and glycerol was ascertained by gas chromatography-mass spectrometry and the isomers of the products were distinguished. Apidic acid was considered as the best catalyst because of its excellent catalytic effect and high boiling point. The mechanism of the glycerol chlorination reaction was proposed and a new kinetic model was developed. Kinetic equations of the process in the experimental range were obtained by data fitting and the activation energies of each tandem reaction were 30.7, 41.8, 29.4 and 49.5 kJ mol-1, respectively. This study revealed the process and mechanism of the kinetics and provides the theoretical basis for engineering problems.

From glycerol to chlorohydrin esters using a solvent-free system. Microwave irradiation versus conventional heating

Esterification–chlorination of glycerol provides chlorohydrin esters in high yields. A ratio of reagents close to equivalence can be used, so that atom economy of the reaction is optimized. The reaction can be carried out using either classical or microwave heating, and no solvent is required. 2-Chloro-1-(chloromethyl)ethyl esters can be obtained in high regioisomeric relationship when either low or moderate temperature is used. In contrast, microwave irradiation allows the use of higher reaction temperatures that render mixtures of both regioisomers in variable relationships. Kinetic control of the process is proposed for classical heating, and experimental results are analyzed with the aid of ab initio calculated values. Non-thermal phenomena can be used to explain the high efficiency of microwave irradiation at low temperature.

Direct preparation of dichloropropanol from glycerol and hydrochloric acid gas in a solvent-free batch reactor: Effect of experimental conditions

Solvent-free direct preparation of dichloropropanol (DCP) from glycerol and hydrochloric acid gas was carried out in a batch reactor with a variation of reaction conditions (agitation speed, reaction time, reaction temperature, and reaction pressure), amount of H3PW12O40 catalyst, and amount of water absorbent (silica gel blue). The reaction was conducted at high agitation speed in order to avoid mass transfer limitation between glycerol and hydrochloric acid gas. In the direct preparation of DCP from glycerol and hydrochloric acid gas, DCP formation was increased with increasing reaction time, reaction temperature, and reaction pressure. Chlorination of glycerol occurred via the following consecutive reaction steps: glycerol→monochloropropanediol (MCPD)→dichloropropanol (DCP)→trichloropropane (TCP). Reaction rate decreased in the order of first-step reaction>second-step reaction>third-step reaction. The presence of H3PW12O40 catalyst and water absorbent (silica gel blue) enhanced the formation of DCP. DCP formation was increased with increasing the amount of H3PW12O40 catalyst and water absorbent (silica gel blue). Strong Bronsted acid site of H3PW12O40 catalyst and water removal from the reaction system favorably served in improving DCP formation.

Effect of reaction conditions on the catalytic performance of H3PW12O40 heteropolyacid catalyst in the direct preparation of dichloropropanol from glycerol in a liquid-phase batch reactor

Direct chlorination of glycerol to dichloropropanol (DCP) was conducted in a liquid-phase batch rector using homogeneous H3PW12O40 heteropolyacid (HPA) catalyst. The effect of reaction conditions (reaction time, reaction pressure, reaction temperature, and catalyst amount) on the catalytic performance of H3PW12O40 in the direct preparation of DCP from glycerol was examined. The optimum reaction pressure and reaction temperature were found to be 10 bar and 130 °C, respectively. The reaction temperature was more crucial than the reaction pressure in improving the selectivity to DCP. Selectivity to DCP increased with increasing reaction time and with increasing catalyst amount. Acid sites of H3PW12O40 catalyst favorably devoted to the chlorination of glycerol. H3PW12O40 served as an efficient catalyst in the direct preparation of DCP from glycerol under the mild reaction conditions.

Kinetics of Glycerol Chlorination with Hydrochloric Acid: A New Route to α,γ-Dichlorohydrin

The growing availability of glycerol, as a consequence of the increase in biodiesel production (for which glycerol is a byproduct), is rapidly saturating the market, and consequently, a great interest is now addressed to the development of new process routes for alternative uses of glycerol. Among the various possibilities, our attention has been focused on the glycerol chlorination reaction, with the aim to produce α,γ-dichlorohydrin. This compound can then subsequently be converted into epichlorohydrin, which is an important intermediate in the production of epoxy resins. α,γ-dicholorhydrin, together with α,β-dichlorohydrin, is currently synthesized starting from propylene via allyl chloride. In the present paper, the kinetics of glycerol chlorination with gaseous hydrochloric acid, for the production of α,γ-dichlorohydrin, has been investigated by means of a jacketed glass reactor operated in batch conditions for the substrate (glycerol) and continuously for the hydrochloric acid. Different organic acids have been tested as catalysts with good performances in terms of both activity and, in particular, selectivity toward the desired 1,3-dichlorinated product. A reaction mechanism has been proposed and a consequent kinetic model has been developed in order to quantitatively describe the experimental data collected at various temperatures (80−120 °C), and the kinetic parameters have been evaluated. A generally good agreement between the experimental data and the theoretical model has been found.