New Process for Producing Epichlorohydrin via Glycerol Chlorination

Aug 5, 2009 - through the reactor and the distillate accumulator, the unreacted. HCl flows into a series of alkaline trap solutions for its complete n...
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Ind. Eng. Chem. Res. 2010, 49, 964–970

New Process for Producing Epichlorohydrin via Glycerol Chlorination E. Santacesaria,* R. Tesser, M. Di Serio, L. Casale, and D. Verde Dipartimento di Chimica dell’UniVersita` “Federico II” di Napoli, Italy

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. 1. Introduction In biodiesel production, about 10% by weight of glycerol is obtained as byproduct. Therefore, by increasing the amount of biodiesel produced the availability of glycerol increases, too. It will be imperative, therefore, to find new uses for glycerol suitable to consume the large amounts of this substance derived from the biodiesel production also with the aim of reducing the overall costs. There are only two possible strategies to solve this problem: to use glycerol as raw material for obtaining commodities or to use glycerol for producing fuels additives. For this purpose, the use of glycerol for producing acrolein and acrylic acid1-4 is an example of the first type, while, the glycerol etherification (5,6) is an example of the second one. In this paper we will study, in particular, the glycerol chlorination by using gaseous HCl to obtain as main product 1,3-dichlorohydrin, which is an important intermediate for synthesizing epichlorohydrin used in the production of epoxy resins. Epichlorohydrin is normally produced in industry starting from 1,2- (70%) and 1,3-dichlorohydrins (30%) that are obtained in a mixture using propylene as raw material. The predominance of 1,2-dichlorohydrin is a drawback of this process, because, the reaction rate for obtaining epichlorohydrin from this isomer is about 20 times slower than from 1,3-dichlorohydrin, and this has negative consequences on the reactor sizing (a reactive distillation column) and on the formation of undesired byproduct.5,6 The reaction of glycerol with hydrochloric acid, in the presence of carboxylic acids as catalyst, occurs in two steps giving mainly 1-monochlorohydrin with small amounts of 2-monochlorohydrin. The entrance of a second chlorine in the last compound is strongly inhibited, and 1,3 dichlorohydrin is obtained almost exclusively in the second chlorination step. In the first papers and patents published on the subject, acetic acid was used as catalyst and HCl in aqueous phase as reagent. In this condition the reaction rates were very slow. Different patents7-10 and papers11,12 have recently been published on glycerol chlorination and the construction of some industrial plants has recently been announced. All these papers and patents, published more recently, suggest the use of gaseous HCl and carboxylic acids as catalyst, other than acetic acid, because they have boiling points higher than that of acetic acid at 117 °C. In the presence of gaseous HCl the reaction is faster and by using the new proposed catalysts the loss of catalyst by evaporation is avoided * To whom correspondence should be addressed. E-mail: [email protected].

or minimized. All the occurring reactions have been studied in a previous work11 and there a kinetic approach, based on a reliable reaction mechanism, has been developed. For this purpose, a reaction scheme of the following type can be considered:

A comparison of the kinetic behavior of different catalysts have already been made in the mentioned work,11 but in the present work this aspect will be further deepened with the aim to find a correlation between the structure of the catalyst and the observed activities and selectivities. Moreover, the possibility of a continuous operation will also be demonstrated on experimental bases. At last, kinetic runs performed in total refluxing conditions, that have been used for determining the kinetic laws and related parameters11 have been compared with other runs performed in HCl stripping conditions, by condensing, collecting, and analyzing the stripped compounds along the run. The most abundant stripped compound was 1,3-dichlorohydrin because of its relatively high volatility, demonstrating in this way the possibility of a continuous operation with product recovery at a high degree of purity. By using the kinetic approach developed in a previous work,11 and with the vapor-liquid equilibrium data described by UNIFAC model, in this paper we simulated the kinetic runs performed in stripping conditions by using a commercial process simulator (ChemCad 5.2), obtaining a good agreement between calculated and experimental measurements for both the reactor and the distillate reservoir. Finally, by using the kinetic and modeling approach, also developed in previous literature work,5,6 we quantitatively show and discuss the advantage of using a feed stream of 1,3dichlorohydrin instead of the mixture 1,2- (70%) and 1,3dichlorohydrins (30%), normally used in the process via propene for producing epichlorohydrin. 2. Experimental Section 2.1. Reactants and Apparatus. All the reactants have been purchased by Aldrich Co. at the maximum available degree of purity with the exception of gaseous hydrochloric acid that has been purchased in a bomb from Air Liquide Italia Co.

10.1021/ie900650x  2010 American Chemical Society Published on Web 08/05/2009

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Figure 1. Experimental apparatus: (1) jacketed reactor made of Pyrex glass or in hastelloy steel, with a capacity of 700 mL; (2) thermostat for the circulation of thermal fluid (glass reactor) of electrical heating system (steel reactor); (3) peristaltic pump; (4) valve for performing samples withdrawal of the reaction mix; (5) cylinder of hydrochloric acid; (6) vertical condenser for total reflux operation; (7) horizontal condenser for stripping operation; (8) bottle for collecting the condensed reaction product; (9) bubbler provided with a porous disk for introducing gaseous HCl, which ensures effective contact between the gas and liquid phases; and (10) system for suppressing the excess HCl (two or three Drechsel bottles, arranged in series, each containing a solution of sodium hydroxide).

The scheme of the used experimental apparatus is reported in Figure 1. As reactor body, both a jacketed glass reactor and a hastelloy steel reactor have been used, this last in the case of runs in the condition of elevated pressure. The reactor is operated in continuous mode for what concerns the flow of HCl and in batch modality regarding glycerol and catalyst. After flowing through the reactor and the distillate accumulator, the unreacted HCl flows into a series of alkaline trap solutions for its complete neutralization. In this device both total reflux and stripping runs can be performed. More details about the reactor and the operative procedure for experimental runs can be found elsewhere.11 2.2. Analysis. On the collected samples a first neutralization operation is performed in order to eliminate the dissolved HCl and the acid used as catalyst. On about 3 cm3 of sample, 0.5 g of calcium carbonate is added in a vial and the mixture is kept at 100 °C for 30 min in order to remove also the water formed by the reaction. Subsequently, the solid is removed by centrifugation and the composition is determined by GC analysis. The GC analytical method is the following: column, CHROMPACK CP Wax; stationary phase, 100% polyethyleneglycol; length, 30 m; i.d., 0.25 mm; film thickness, 0.25 µm; FID detector; helium as gas carrier; injector temperature, 250 °C; detector temperature, 280 °C; temperature ramp, 1 min at 40 °C; heating rate, 20 °C/min to 100 °C, then 40 °C/min up to 200 °C, then hold for 4 min. The sample of the reaction mixture is first diluted with methanol in a volumetric ratio of 1:20 and 1 µL of solution is injected into the GC. 2.3. Experimental Runs. Catalytic Screening: Runs in Total Reflux Conditions. To extend the catalytic screening started in our previous work,11 in the present paper we have tested other compounds containing carboxylic groups as catalysts in the glycerol chlorination reaction. The tested catalysts and the experimental conditions adopted are summarized in Table 1 together with the obtained results in terms of products distribution (1; 2; 1,3; and 1,2 isomers) after 3 h of reaction. In each run related to the reported catalysts, different samples of liquid phase have been taken during the reaction and analyzed accordingly to the GC method previously described. Two examples of the evolution with time of the experimental

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products’ molar concentration are reported in Figures 2 and 3, corresponding to the runs in the presence of respectively tartaric and malonic acid. The first catalyst is one of the more selective in the production of monochlorohydrin,13 while, the second is active and selective in giving 1,3-dichlorohydrin.7 For all the catalysts reported in Table 1 similar experimental data have been collected. Moreover, runs at different temperatures have been made only for malonic and tartaric acid, developing a kinetic approach based on a reasonable reaction mechanism. At last, some kinetic runs have been made with acetic acid with different catalyst concentrations and different HCl pressures (these last runs were performed in semibatch conditions). Runs in Stripping Conditions. Two runs have been performed by using the HCl stream as stripping agent through the condenser (Nr. 7) in Figure 1 and using malonic acid as catalyst. In the run at 100 °C only the final composition of the distillate reservoir have been determined, while, for the run at 110 °C, the distillate has been analyzed at different intervals of time during the run. The aim of such runs was the evaluation of the possibility to selectively recover the desired reaction product that is 1,3-dichlorohydrin. The experimental results related to the stripping runs are reported in Table 2 together with the other adopted operating conditions. As an example, in Figure 4 and 5, the composition-time profiles are reported for, respectively, the liquid phase in the reactor and the products recovered in the distillate after condensing. Runs under Pressure in Semibatch Conditions. A recent paper published by Bell et al.,12 has reported a detailed behavior of the reaction of glycerol with HCl at different pressures from 15 to 110 psi in semibatch conditions. It is very interesting to observe that the pressure of HCl has a great effect on both the glycerol consumption rate and the products distribution. By simply increasing the HCl pressure from 20 to 50 psi they show a dramatic change of behavior because in the first case a negligible amount of 1,3-dichlorohydrin is formed with a conversion of glycerol of about 60% reaching a plateau, while, at the higher pressure 1,3-dichlorohydrin becomes predominant and glycerol is totally converted in about 30 min. It must be pointed out that the authors used wet glycerol containing 9% by weight of water. The presence of water very probably affects the equilibrium of the reaction at low HCl pressure. We confirmed this finding, and in Figure 6 there is a comparison between an experimental run performed at atmospheric pressure with flowing HCl and a run performed under constant pressure of 5.5 bara. In the first case water is slowly removed from the system considering that the condenser was cooled with water at 15-20 °C, and this explain the fast glycerol conversion, while, on the other hand, the formation of 1,3-dichlorohydrin is strongly promoted by the HCl pressure. In Figure 7, the instantaneous feed of hydrochloric acid along the time for this run is reported. The flow of HCl is necessary to maintain the total pressure inside the reactor at the prefixed value of 5.5 bara and represents, indirectly, a measurement of the hydrochloric acid consumption rate. It is interesting to observe that in the first part of the run the decrease in the HCl consumption rate is almost linear while, subsequently, the ration rate is slower and a tenuous decrease of HCl consumption proceeds through the rest of the run. All these observations suggest that HCl concentration in the liquid phase is not linear with the pressure and that gas-liquid mass transfer is very probably operative especially in the initial part of the run. Both these aspects require further investigations.

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Table 1. Experimental Runs for Catalyst Screening: Products Distribution after 3 h of Reactiona products distribution after 3 h of reaction (mol %) catalyst

pKa

amount of catalyst (g)

Gly

1

2

1,3

1,2

acetic acidb malonic acidb propionic acidb adipic acid succinic acidb citric acidb levulinic acidb pivalic acidb benzoic acidb trichloroacetic acidb tartaric acid fumaric acid oxalic acid maleic acid formic acid chloro-succinic acid EDTAc

4.75 2.84 4.87 4.43 4.20 3.13 4.59 5.10 4.19 0.70 3.03 3.05 1.25 1.88 3.74 2.67 2.00

10.00 18.00 13.00 24.85 20.00 34.00 20.60 18.00 13.90 13.60 25.50 20.30 15.40 20.30 7.00 25.60 10.52

0.86 0.57 0.00 0.00 1.86 5.15 0.39 88.05 86.34 82.91 14.14 5.91 34.15 5.50 24.15 5.82 46.39

63.01 55.85 49.88 21.93 60.88 70.45 60.04 9.19 12.38 15.08 78.43 85.08 60.06 76.08 66.63 82.16 44.69

5.98 7.24 8.77 4.94 6.84 6.49 6.98 1.65 1.27 2.01 7.42 7.99 5.53 9.38 7.86 7.94 4.93

29.82 35.87 41.00 72.23 30.05 17.61 32.20 1.11 0.00 0.00 0.00 1.02 0.23 8.78 1.32 4.08 3.84

0.33 0.46 0.35 0.89 0.37 0.26 0.37 0.00 0.00 0.00 0.00 0.00 0.01 0.30 0.04 0.00 0.13

a Other experimental common conditions: T ) 100°C, HCl flow rate ) 24 g/min, glycerol loaded ) 200 g, catalyst concentration ) 8% by moles, reaction time ) 3 h, total reflux conditions except for HCl. b Results taken from Tesser et al. 2007. c Run under HCl pressure of 6 bara.

Figure 2. Evolution in time of the experimental product distribution for the run with tartaric acid at T ) 100 °C: (9) glycerol; (2) 1-monochlorohydrin; (b) 2-monochlorohydrin; (0) 1,3-dichlorohydrin; (1) 1,2-dichlorohydrin.

Figure 3. Evolution in time of the experimental product distribution for the run with malonic acid at T ) 100 °C: (9) glycerol; (2) 1-monochlorohydrin; (b) 2-monochlorohydrin; (0) 1,3-dichlorohydrin; (1) 1,2dichlorohydrin.

Pseudocontinuous Runs. Finally, with the aim to demonstrate the possibility to perform the 1,3-dichlorohydrin production process in continuous modality, a specific run was performed in which the continuous conditions were simulated by withdrawing portions of reactive mixture followed by a corresponding addition of fresh glycerol (containing dissolved catalyst). This operation was repeated at intervals of time of 1 h. The reaction was conducted with malonic acid as catalyst, at 100 °C and atmospheric pressure, under a continuous flow of HCl, and a clear distillate was collected. The overall composition of the reaction products (reactor + distillate) is reported in Table 3 together with other experimental conditions adopted for the run.

and other catalysts, having higher boiling points, have been tested and proposed in different patents and papers.7-11 In the already mentioned previous work11 malonic acid catalyst was considered for a detailed kinetic approach, and an hypothesis of reaction mechanism was presented there. In particular, the reaction mechanism, used for the kinetic model development, was a mechanism assumed valid for all the OH substitutions with chlorine: a first acid-catalyzed OH esterification followed by an alkyl-oxygen bond scission favored by vicinal OH group that restores the catalytic species as in the reaction scheme reported below. It must be pointed out that chlorination of catalyst molecules was not evidenced by using GC-MS analysis. However, from the results reported in Table 1, it is evident that some catalysts, tested in the present work, have shown a remarkable selectivity toward the production of monochlorohydrins. Moreover, the concentration profiles reported in Figure 2 show a particular behavior according to which dichlorohydrins concentration remains quite low in the initial part of the run. After an induction period, a sensible increase in 1,3-dicholorohydrin production has been observed while 1-monochlorohydrin begins to decrease. These experimental observations cannot be explained on the basis of the previously

3. Results and Discussion In a previous work11 catalysts screening was performed by comparing the activities of different carboxylic acids (see in Table 1 catalysts marked with superscript b) in the formation of chlorohydrins from glycerol with respect to acetic acid that was the first catalyst proposed in the literature.14-16 Acetic acid has the drawback of a relatively low boiling point (117 °C)

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Table 2. Mole % Composition in the Reactor and in the Distillate Accumulator for Runs at 100 and at 110 °C. Catalyst: Malonic Acid T ) 100 °C reactor t (min)

Gly

0 30 60 120 180 240 300

100 1.62 0.00 0.00 0.00 0.00

a

1

2

T ) 110 °C reactor

1,3

1,2

0

0

0

0

76.15 56.48 39.10 30.15 24.88

6.18 7.74 9.71 10.52 11.69

16.05 35.24 50.41 58.36 62.34

0.00 0.54 0.78 0.97 1.09

T ) 110 °C distillate tank

Gly

1

2

1,3

1,2

Gly

1

2

1,3

1,2

100 39.20 12.60 1.11 1.54 0.05 0.06

0 53.71 75.40 60.20 42.86 31.87 31.11

0 5.80 7.30 7.92 12.15 12.98 18.57

0 1.29 4.74 30.30 42.55 53.84 48.82

0 0.00 0.00 0.47 0.90 1.26 1.43

0 0 0 0 0 0 0

0 18.47 21.55 5.53 6.89 2.40 1.78

0 0.00 1.64 0.27 0.85 0.49 0.27

0 81.13 76.08 93.30 91.40 96.11 96.92

0 0.40 0.73 0.90 0.86 0.99 1.03

Note: Composition in the distillate tank for run at 100 °C after 300 min of reaction: Gly ) 0; 1 ) 3.62; 2 ) 0.52; 1,3 ) 94.90; 1,2 ) 0.96.

Table 3. Overall Mole % Composition (Reactor + Distillate) for the Pseudocontinuous Runa reaction time (h)

glycerol

1-monochlorohydrin

2-monochlorohydrin

1,3-dichlorohydrin

1,2-dichlorohydrin

0 1 2 3 4 5 6 7 8 9

100.00 5.18 0.19 1.08 3.89 1.88 0.60 0.89 3.18 1.06

0.00 60.79 46.20 34.87 22.33 16.70 14.35 15.60 17.03 15.13

0.00 6.31 6.27 7.44 6.85 8.40 8.33 9.40 10.06 8.82

0.00 27.33 46.77 55.83 66.07 71.94 75.60 72.87 68.58 73.76

0.00 0.38 0.57 0.78 0.86 1.09 1.12 1.24 1.15 1.22

a Run operative conditions: initial charge of glycerol, 260.6 g; total glycerol added, 84,52 g; catalyst malonic acid, 8% molar with respect to glycerol; temperature, 100 °C; atmospheric pressure, continuous flow of hydrogen chloride.

proposed reaction mechanism and a different mechanistic hypothesis must be introduced considering diversifications between the first and the second chlorination reaction.

In this case we have supposed that both monochlorohydrin and dichlorohydrin production proceed through the formation of two ester species of different reactivity in which the catalyst is distributed. For this purpose, a simplified scheme of the following type can be written: Keq2

1-monochlorohydrin + catalyst {\} ester2 + water Keq1

glycerol + catalyst {\} ester1 + water The values of the two equilibrium constants Keq1 and Keq2 are of paramount importance for the selectivity of the catalyst toward monochlorinated or dichlorinated products. If Keq1 ≈ Keq2 the formation of mono and dichlorohydrins follows a reaction-in-series mechanism according to that proposed by

Tesser et al.11 On the contrary, when Keq1 . Keq2 the catalyst gives mainly monochlorohydrin because the catalyst gives mainly the ester1 as intermediate. Then, it is interesting to observe that, with some exceptions, the catalysts having pKa greater than 4 are selective to dichlorohydrin, while, the catalysts with pKa between 1.2 and 3 are more selective to monochlorohydrins. More acidic carboxylic acids, like for example trichloroacetic acid, are not active in the reaction. Very probably it is necessary to form esters for promoting the reaction, but the ester formed must be not too stable to allow the subsequent reaction steps. Clearly pKa is not the only factor influencing the selectivity, because the presence of more than one carboxylic group in the same molecule and/ or the presence of other functional groups are also important. More deepened mechanistic studies are clearly necessary for a fine-tuning of the interpretation of the selectivity-structure relationship. The selectivity to monochlorohydrins open a perspective to the industrial production and use of monochlorohydrins and glycidol that could become building blocks for many other syntheses on the basis of the most general interest to find new uses for glycerol. The two runs in which a stripping operation has been performed by means of the HCl stream itself (Table 2 and Figures 3 and 4) have been simulated by means of a commercial process simulation package (Chemcad 5.2). The reference scheme and the equation for the material balance related to the stripping system are reported in Figure 8. The vapor-liquid equilibria of the system have been described by means of the UNIFAC model for liquid phase activity coefficients while the kinetics parameters have been taken from our previous investigation.11 The simultaneous description of liquid phase reaction and multicomponent vapor-liquid phase partition, allow a satisfactory accuracy in the prediction of the experimental data collected for both the reactor and the flashed condensed composition. It is interesting to observe that the stripping operation allows the recovery of a product with a molar composition above 95% in 1,3-dichlorohydrin. It is obvious, that a rectification will give better performances. Rectified 1,3-

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Figure 4. Composition profiles for the run at 110 °C in the reactor. (9) glycerol; (b) 1-monochlorohydrin; (1) 2-monochlorohydrin; (2) 1,3dichlorohydrin; ([) 1,2-dichlorohydrin. Comparison between the experimental data and Chemcad prediction.

Figure 5. Composition profiles for the run at 110 °C in the distillate accumulator: (2) 1,3 dichlorohydrin, (b) 1-monochlorohydrin. Comparison between the experimental data and Chemcad prediction.

dichlorohydrin could be advantageously employed in a epichlorohydrin production process as will be shown in the following paragraph. Finally, a confirmation of the feasibility of the 1,3-dichlorohydrin production process in continuous modality has been obtained from a pseudocontinuous run for which results are reported in Figure 9. From this plot we can appreciate that, after about 5 h of operation, the overall product concentrations (reactor + distillate) are quite stationary and, in particular, the desired 1,3-dichlorinated product is obtained at a concentration level of about 70%. Simulation of Epichlorohydrin Production Process. The conventional process for epichlorohydrin production, via propene, starts from a mixture of dichlorohydrin isomers of which the molar composition is around 70% of 1,2 isomer and 30% of 1,3-dichlorohydrin.5,6 Starting from this mixture, by HCl elimination in alkaline conditions, the desired epichlorohydrin product is formed and, simultaneously, monochlorohydrin and subsequently glycidol can be formed as by products. The overall reactions scheme is reported in Figure 10.

Figure 6. Comparison of runs at different pressure: (9) glycerol at 1 bar; (b) 1,3-dichlorohydrin at 1 bar; (2) glycerol at 5.5 bara; (1) 1,3dichlorohydrin at 5.5 bar. Glycerol, 150 g; catalyst acetic acid, 7.82 g.

Figure 7. Instantaneous consumption rate of HCl in the semibatch run under pressure. Total pressure kept at 5.5 bara; glycerol, 150 g; catalyst acetic acid, 8 g.

Figure 8. Reference scheme for the material balance used in the simulation of stripping runs: (R) reactor, (D) distillate accumulator, (V) liquid phase volume.

To better emphasize the advantages involved in the use of glycerol chlorination, promoted by catalysts that are selective toward the production of 1,3-dichlorohydrin, a simulation has been made for comparing the yields of the two process alternatives. The first one is the reactive distillation (pilot scale) of the mixture with the traditional composition (1,3-/ 1,2-, 30/70%) and the second one is the same unit operation performed on pure 1,3-dichlorohydrin. The simulation of epichlorohydrin reactive column has been performed with a

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column. The yield is defined as the ratio between the distilled epichlorohydrin and the fed dichlorohydrins. It is interesting to observe that, from the plot reported in Figure 11, a higher epichlorohydrin yield is obtainable also at low reflux ratios with a feed that is constituted by pure 1,3-dichlorohydrin. A confirmation of the superiority of a process based on this kind of feed to the epichlorohydrin reactive column section is evident also if we consider the trend of epichlorohydrin yield for the case of 30/70% mixture: only at a very high reflux ratio is a good product yield obtained, but it is not comparable. 4. Conclusions

Figure 9. Overall % molar concentration profiles (reactor + distillate) for the run in pseudocontinuous conditions.

Figure 10. Reactions scheme for epichlorohydrin production.

In this work the basis of a production process of epichlorohydrin from glycerol was developed. The kinetics and mechanism of the first stage of the process, glycerol conversion to chlorohydrins, was deepened and different carboxylic acids, not previously tested, were used as catalyst for this first reaction step. A rough correlation was found between the value of pKa of the catalyst and its selectivity toward mono- (pKa < 3) or dichlorinated (pKa > 4) compounds. Some explorative runs were performed also under HCl pressure. A pseudocontinuous run was performed in order to verify the feasibility of industrial continuous operation. Finally, a run in stripping conditions was reported that satisfied the scope of a continuous recovery of the products from the reaction mixture. This last approach was particularly promising, allowing the recovery of a product with a molar concentration of 1,3-dichlorohydrin higher than 95%. The possible industrial exploitation of these results were investigated by comparing the traditional epichlorohydrin production process starting from propene, with the proposed process starting from glycerol that allows the selective recovery of 1,3-dichlorohydrin. In the last case, the reactive column used for epichlorohydrin production, could be operated with lower reflux ratio, maintaining high product yield.

Literature Cited

Figure 11. Comparison between reactive distillation for epichlorohydrin production: (2) feed mixture, 1,2-dichlorohydrin (70%)/1,3-dichlorohydrin (30%); (b) feed only 1,3-dichlorohydrin.

commercial process simulation package (Chemcad 5.2) by introducing the kinetic expression and parameters taken from Carra` et al.5,6 In both the process alternatives considered, the reactive column has been simulated with the following specifications: total pressure, 1 bar; reboiler heat duty, 17000 kcal/h; 15 theoretical plates; liquid holdup, 0.02 L/stage. The comparison between the two different feeds to the column, reported in Figure 11, is made by plotting the epichlorohydrin yields as a function of the reflux ratio adopted in the reactive

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ReceiVed for reView April 23, 2009 ReVised manuscript receiVed July 15, 2009 Accepted July 16, 2009 IE900650X