Kinetic Research of O,Oâ²-Dibenzoyltartaric Anhydride Synthesis

Article pubs.acs.org/OPRD

Kinetic Research of O,O′‑Dibenzoyltartaric Anhydride Synthesis: Tartaric Acid and Its O-Acyl Derivatives. Part 12 Paweł Czajka, Halina Hajmowicz, Ludwik Synoradzki, Jerzy Wisialski,* and Krzysztof Zawada Laboratory of Technological Processes, Faculty of Chemistry, Warsaw University of Technology, ul. Noakowskiego 3, 00-664 Warszawa, Poland ABSTRACT: A kinetic study of dibenzoyl-L-tartaric anhydride synthesis was described. The kinetic equation and the dependence of the reaction rate constant on the temperature were determined. It was shown that the reaction is of the pseudo first order. The kinetic data enable the design of a continuous reactor.

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INTRODUCTION Tartaric acid (1) and its derivatives play an important role in asymmetric synthesis. They have been employed as resolving agents,1b,2 chiral building blocks,2a,3 chiral auxiliaries,2a,4 and chiral ligands.2a,5 Interesting but relatively little explored is their use for obtaining of biodegradable, optically active polymers.6 O,O′-Dibenzoyl-L-tartaric acid (5) beside acid 1 belongs to the most often used resolving agents for racemic mixtures of amines or other compounds of basic character also in industry.1a,b For many years, the Laboratory of Technological Processes (LPT) has been a manufacturer of acid 5. The technology was then systematically improved, and the chemistry of acid 1, especially of O-acyltartaric anhydrides and acids, was investigated. A two-stage process of manufacturing of 5 was implemented, consisting of: (1) benzoylation and dehydration of tartaric acid 1, to produce dibenzoyl-L-tartaric anhydride (3) (Scheme 1)

chloride (2) and dissolved or melted benzoic acid (4) with toluene used as solvent, and evolving gaseous hydrochloride. Even though an anhydride 3 was for the first time obtained 130 years ago,7 its synthesis is still the subject of investigation. A complicated heterogenic process consists of series-parallel and consecutive reactions (Scheme 3). Scheme 3. Series-Parallel and Consecutive Reactions To Produce Anhydride 3

Scheme 1. Benzoylation/Dehydration of L-Tartaric Acid (1) To Produce Dibenzoyl-L-tartaric Anhydride (3)

The necessity of using 3 equiv of benzoyl chloride 2 is due to the simultaneous benzoylation of hydroxy groups of acid 1 and dehydration of carboxylic groups of the same, with the formation of anhydride 3 and benzoic acid 4.1h In fact, due to the bad solubility of tartaric acid 1, at the beginning, the process proceeds under the excess of chloride 2, independently of the amount of chloride 2 used. Less than 3 equiv of chloride 2 results in a difficult to separate mixture of products, including unreacted acid 1. The addition of solvent, e.g., toluene, is necessary to prevent too high viscosity and solidification of the system, when nearly all of the chloride 2 has been consumed. Without catalyst the reaction begins >100 °C (no hydrogen chloride releasing was observed at lower

and (2) hydrolysis of anhydride 3, to produce the final product 5 (Scheme 2). The system involved at the first step is especially complicated, hazardous, and highly corrosive. It consists of three phases: solid−acid 1 and anhydride 3, liquid−benzoyl Scheme 2. Hydrolysis of Anhydride 3 To Produce the Acid 5

Received: April 22, 2016 Published: September 12, 2016 © 2016 American Chemical Society

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DOI: 10.1021/acs.oprd.6b00147 Org. Process Res. Dev. 2016, 20, 1702−1708

Organic Process Research & Development

Article

Carrying out kinetic tests in a complex heterogeneous (solid−liquid−gas) and highly corrosive (HCl) system was an intricate task. This required the assurance of the appropriately effective HCl absorption system, isothermal conditions of the process, and the employment of a simple, accurate, and fast method for measuring the reaction progress. A laboratory absorption setup was designed and made to operate under slight under-pressure conditions and to ensure the receipt of HCl in the event of high reaction rates (the start of a batch reaction) (Figure 1). The setup consists of an

temperature), while with catalyst, e.g., sulfuric acid, it already begins at ca. 40 °C.8 A disadvantage of such a method is utilization of only 2 equiv of benzoyl groups, while 1 equiv is lost in benzoic acid 4 which has to be separated. On the other hand, the advantage of such a procedure is the effective separation of anhydride 3 (before its hydrolysis) from the benzoic acid 4 and impurities by straightforward filtration (benzoic acid dissolves in toluene). The filtration cake is anhydride 3. Due to the implementation of the technology in the industry and the real perspective of the annual production exceeding 100 tons, the more cost-effective continuous method for manufacture of anhydride 3 was of interest. There are some advantages of the continuous process, e.g., lower production costs (labor, utilities); it is less hazardous (smaller hold-up of reactants) and easier to control (steady-state conditions), and due to the smaller apparatus size it requires a lower cost of investment. To design a continuous reactor for manufacturing of anhydride 3, it was decided to determine the kinetics of the process, which is needed for design of a reactor working in continuous operation. Due to the fact, that the system is a suspension a concept of stirred tank reactor (or cascade of those) was preliminary selected. While fore the batch reactor the knowledge of reaction time is sufficient, contrary for the design of the continuous rector, the kinetics data are necessary.

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THE KINETIC STUDY CONCEPT The synthesis of anhydride 3 is a complex process. Two possible routes of this process can be assumed. Route 1: Transfer of chloride 2 to the particle surface of acid 1, diffusion of chloride 2 within the solid body to the reaction location (through the layer of the product formed), parallel and followup chemical reactions between acid 1, chloride 2, and particular derivatives with the final formation of 3 (Scheme 3), diffusion of hydrogen chloride from the solid phase to the liquid phase, and desorption of the hydrogen chloride from the liquid; and Route 2: dissolution of acid 1 in the toluene−chloride 2 liquid phase, parallel and follow-up chemical reactions between acid 1, chloride 2 and particular derivatives (Scheme 3), crystallization of anhydride 3, and desorption of the hydrogen chloride from the liquid. It is not possible to state definitely which possibility is true. It is known that the intermediate products, i.e., monobenzoyl-tartaric acid (6), dibenzoyl-tartaric acid (5), and monobenzoyl-tartaric anhydride (7), dissolve better in the toluene−chloride 2 system compared to anhydride 3 and do not crystallize under the process conditions.1h Identifying the rates of individual stages is practically impossible. The reaction cannot be stopped at any of the intermediate stages. The rate of the process, as a whole, is often determined by the slowest stage, but unfortunately its identification is extremely difficult in this case. Due to the complex nature of the process, different processes can be ratelimiting, e.g., diffusion of benzoyl chloride within the grain of acid 3/1, which is dependent on the conversion degree, grain size, temperature, and so forth. The only way is to examine the rate of the process as a whole, though in this manner we will not obtain the complete information about its nature. The process of obtaining anhydride 3 is a solid−liquid−gas heterogeneous process in which the solid particle is not a catalyst.

Figure 1. Schematic diagram of the laboratory kinetic test setup.

absorption column, a hydrochloric acid recirculation pump, an acid buffer tank with an incorporated pH meter, an alkaline protective scrubber, and an injector. This setup allowed the safe discharge of releasing HCl from the reactor and enabled the examination of the process kinetics. The isothermal conditions of the reaction were assured by heating the suspension of acid 1 in chloride 2 with the addition of toluenewithout a catalystup to an appropriate temperature below 100 °C (the start of the “catalystless” reaction). At the preset temperature, the catalyst (sulfuric acid) was added, and measurements were started. The reaction kinetics at 110− 120 °C (process temperature in the batch industrial process and foreseen for the continuous industrial scale process) was determined by the extrapolation of data obtained at lower temperatures. The progress of the reaction was determined basing on the amount of hydrogen chloride releasing in the process, which was one of the reaction products. The amount of HCl was determined from the pH of hydrochloric acid, as measured with a pH meter in the buffer tank (Figure 1). Thanks to this solution, the reaction progress was monitored in a continuous manner. Due to the process temperature fluctuations associated with the endothermic nature of the process and the inertia of the system and the temperature controller, the calculations were made with respect to the so-called nominal temperature, tn, which was the arithmetic mean of the temperatures recorded during the experiment. 1703



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Figure 2. Dependence of conversion 1, α, on the reaction time at various temperatures.

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reaction without the catalyst will start at 100 °C. Assuming that the synthesis of 3 is a pseudo-first order reaction and that the effect of temperature on the rate constant obeys the Arrhenius equation,9 the experimental data were correlated using a relationship of the following type:

RESULTS AND DISCUSSION Six experiments were carried out to determine the dependence of the conversion degree on time for different temperatures from the range of 80−100 °C (Figure 2). A good correlation of experimental data, the dependence of the conversion degree α on time τ, was obtained for the first-order reaction function: α = 1 − exp( −kτ )

⎛ E ⎞ k = k∞ exp⎜ − A ⎟ ⎝ RT ⎠

(1)

which is the solution of the kinetic equation of first order resulting from the component A balance for a periodical reactor (in this case, a pseudo-first order reaction can be considered to occur): r=

dcA = −kcA dτ

(3)

where k∞ is a constant having the sense of the reaction rate constant at an infinitely high temperature (min−1); EA is the activation energy (J·mol−1); R is the gas constant (J·mol−1· K−1); T is the temperature (K), which, as linearized, takes on the form as follows:

(2)

ln k = ln k∞ −

EA RT

where r is the reaction rate (min−1); cA is the concentration of component A (%). Due to the very high correlation coefficients (Table 1) it was considered that this function adequately defined the relationship under examination. To estimate the kinetics of synthesis of anhydride 3 at temperatures of 110−120 °C, it is necessary to make the extrapolation of the data obtained at lower temperatures as the

The data from Table 1 were appropriately converted to the linear eq 4 (Table 2). After making calculations by the least-squares method, the following results were obtained: k∞ = 3.625 × 107; EA = 61985.1 J·mol−1; the correlation coefficient, R2 = 0.9043.

Table 1. Results of the Correlation of Kinetic Experiment Data

Table 2. Data from Table 1 as Converted to the Linear Equation

(4)

tn (°C)

k (min−1)

R2

tn (°C)

k (min−1)

T−1 (K−1)

ln k (−)

80.5 82.1 88.4 88.9 94.2 99.3

0.0215 0.0293 0.0448 0.0489 0.0492 0.0708

0.9882 0.9138 0.9669 0.9660 0.9984 0.9739

80.5 82.1 88.4 88.9 94.2 99.3

0.0215 0.0293 0.0448 0.0489 0.0492 0.0708

0.00283 0.00281 0.00277 0.00276 0.00272 0.00268

−3.8397 −3.5302 −3.1055 −3.0180 −3.0119 −2.6479

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The mass ratio of toluene to tartaric acid λT comes from production experience of Laboratory of Technological Processes.

By using eq 3, the reaction rate constants at temperatures of 110, 115, and 120 °C were calculated (by the extrapolation of the results beyond the experimental region) to obtain k110 = 0.129 min−1, k115 = 0.165 min−1, and k120 = 0.211 min−1 (Figure 3).

λBC = 1.72[kg/kg]

(10)

ρT is the toluene density; ρBC is the tartaric acid density; ρTA is the tartaric acid density.12 For a first-order reaction, the required residence time per stage of the cascade (N-stages) for a given conversion (αD) can be calculated from the equation: 10

τR =

1 k115

11

[(1 − αD)−1/ N − 1] [min]

(11)

For a fill-level of the reactor a = 0.85 m 3/m 3

(12)

size of the reactor can be calculated from the equation VR =

η = 0.93

The experience of the Laboratory of Technological Processes8 shows that the rate of anhydride 3 synthesis is influenced by mixing intensity and tartaric acid particle size. This indicates that the process of mass transfer is limited for those conditions. As the same particle size and similar mixing conditions are used in the production scale, the obtained kinetic data are valid within the range where the mass transfer is the limiting step.

Table 3. Calculated Reactor Cascade Volumes

ESTIMATION OF THE CONTINUOUS REACTOR SIZE In the batch production technology of the anhydride 3, the reactant temperature reaches 120 °C. For the estimation of the reactor size the temperature of 115 °C was assumed. Thus, the reaction rate constant according to eq 3 equals (5)

(6)

Assumed operational hours per year (7)

The concentration of anhydride 3 in the product mixture was calculated from the following equation: 1 c DBTA = 1 [kg/m 3] λBC λT + + ρ ρ ρ TA

BC

T

(8)

where: λBC =

3MBC [kg/kg] M TA

N (−)

τR (min)

VR (L)

ΣVRi (L)

1 2 3 4 5 6 7 PFR

600 54.5 22.1 13.1 9.2 7.0 5.6 27.9

602 55 22 13 9.2 7.0 5.7 23.8

602 110 66 52 46 42.0 39.9 23.8

Table 3 gives also the calculated volume for the plug-flow reactor (PFR) which is 23.8 L and represents the theoretical lowest volume required for the process. The volume of the batch reactor currently used for the production of the anhydride 3 for the capacity of 100 t/y is 1500 L. The use of a single continuous stirred tank reactor (CSTR) with required reactor volume of 602 L would already significantly reduce the reactor size. In a single CSTR the concentration of the reactants and the reaction rate drops immediately to desired final level (perfect back-mixing) which requires a high reactor volume. In a PFR the reaction rate decreases progressively through the system which gives a significantly higher average reaction rate and thus lower required volume.9a Due to the presence of high solids content and gas phase (HCl) the practical realization of a PFR-like reactor would be highly challenging. A compromise between a PFR and a single CSTR is a cascade of CSTRs.13 The back-mixing in the system is reduced what increases the reaction rates and reduces the required reactor volume. The cascade of stirred tank reactors are widely used in the chemical industry, e.g., in production of phosphoric

The production capacity of anhydride 3 is

O = 6000 h/y

(14)

The results of the calculation (for conversion αD = 0.99) are given in Table 3.

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P = 100 t/y

(13)

where MDBTA is the dibenzoyltartaric acid molar mass. The anhydride 3 yield in respect to tartaric acid (from production experience of Laboratory of Technological Processes):

Figure 3. Linearized dependence of rate constant, ln k, on the temperature, 1/T.

k115 = 0.165 min−1

τR M TA P × × a O c DBTAηMDBTA

(9)

MBC is the benzoyl chloride molar mass; MTA is the tartaric acid molar mass. This comes from the reaction equation (Scheme 1) with 3 mol of benzoyl chloride per mole of tartaric acid. 1705



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Table 4. Results of the Experiment for the Predefined Temperature of 88.9 °C time τ (min)

pH (−)

reaction temperature t (°C)

HCl concentration cH+ (mol·dm−3)

conversion degree α (−)

0 2 3 4 5 6 7 8 9 10 11 12 13 14 16 18 20 22 25 28 32 36 41

3.30 2.61 2.43 2.33 2.14 1.98 1.84 1.72 1.68 1.63 1.58 1.55 1.51 1.47 1.44 1.41 1.38 1.36 1.33 1.30 1.28 1.27 1.25

92.0 86.7 85.2 86.1 85.9 86.1 86.9 87.9 88.4 88.8 89.1 89.2 89.6 90.0 90.4 90.3 90.4 90.6 90.4 90.5 90.0 89.6 89.6

0.0005 0.0025 0.0037 0.0047 0.0072 0.0105 0.0145 0.0191 0.0209 0.0234 0.0263 0.0282 0.0309 0.0339 0.0363 0.0389 0.0417 0.0437 0.0468 0.0501 0.0525 0.0537 0.0562

0.0000 0.0312 0.0513 0.0667 0.1077 0.1593 0.2229 0.2964 0.3258 0.3665 0.4122 0.4423 0.4857 0.5333 0.5720 0.6135 0.6580 0.6894 0.7392 0.7927 0.8304 0.8499 0.8904

Table 5. Results of the Experiment for the Predefined Temperature of 94.2 °C time τ (min)

pH (−)

reaction temperature t (°C)

HCl concentration cH+ (mol·dm−3)

conversion degree α (−)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 23 25 29 31 33 35 39 41 43 48 53

2.79 2.41 2.18 2.04 1.89 1.84 1.75 1.66 1.63 1.60 1.56 1.53 1.51 1.49 1.47 1.45 1.43 1.42 1.41 1.39 1.38 1.37 1.35 1.33 1.30 1.28 1.27 1.26 1.25 1.25 1.24 1.22 1.21

95.4 87.1 87.8 87.8 88.6 89.2 90.0 91.2 91.7 92.2 92.9 93.7 94.3 94.7 95.0 95.5 95.6 96.0 96.1 96.3 96.4 96.4 96.6 96.7 96.6 97.0 96.9 96.7 96.8 96.5 96.5 96.6 96.6

0.0016 0.0039 0.0066 0.0091 0.0129 0.0145 0.0178 0.0219 0.0234 0.0251 0.0275 0.0295 0.0309 0.0324 0.0339 0.0355 0.0372 0.0380 0.0389 0.0407 0.0417 0.0427 0.0447 0.0468 0.0501 0.0525 0.0537 0.0550 0.0562 0.0562 0.0575 0.0603 0.0617

0.0000 0.0352 0.0774 0.1163 0.1747 0.1991 0.2508 0.3143 0.3386 0.3646 0.4022 0.4328 0.4543 0.4769 0.5006 0.5254 0.5513 0.5648 0.5785 0.6069 0.6217 0.6367 0.6679 0.7006 0.7525 0.7892 0.8081 0.8275 0.8474 0.8474 0.8677 0.9098 0.9316

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ACKNOWLEDGMENTS Financial support of Warsaw University of Technology, Faculty of Chemistry is gratefully acknowledged. Also we are grateful to the National Centre for Research and Development (NCBR), Poland for share in founding of this this research within the framework of the CHIKADI project PBS2/A1/14/2014. We thank Ms. Renata Przedpełska for assistance in the preparation of this paper.

acid, cyclohexanone oxime, epoxidation of propylene with organic hydroperoxides (Halcon process), and hydroxylamine sulfate (Raschig process).14 In this case, a cascade of CSTRs in the production of anhydride 3 allows the use of stirrers in each stage of the process, which enables to efficiently mixing the high solidcontent suspension. Also HCl product can easily leave the reaction stage through a venting nozzle of each cascade stage, which would be connected to the HCl absorption system. The calculated volumes of the reactors in a cascade system given in Table 3 are significantly lower than the single CSTR reactor. The addition of a cascade stage reduces the required total volume, but at the same time rises the complexity of the system (e.g., need to install the stirrer and instrumentation for each stage). The reduction of the volume decreases with each added stage. A cascade of three CSTRs with a reactor volume of 22 L was selected as the preferred reaction system. The total volume of 66 L is almost 23 times lower than the currently used batch reactor. This significantly reduces the variable costs (e.g., electricity consumption for stirring, steam costs for heating), fixed costs (e.g., maintenance) and process safety risk (hold-up of the corrosive, HCl containing mixture). The investment costs are also significantly reduced. The obtained results encourage the investigation of the operation of the anhydride 3 large-scale production in a continuous manner. The transition of other unit operations (crystallization, filtration, drying) to the continuous manner should be investigated as well, in order to analyze its feasibility.

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REFERENCES

(1) For parts 1−11 see respectively: (a) Synoradzki, L.; Ruśkowski, P.; Bernaś, U. Org. Prep. Proced. Int. 2005, 37, 37−63. (b) Synoradzki, L.; Bernaś, U.; Ruśkowski, P. Org. Prep. Proced. Int. 2008, 40, 163−200. (c) Zachara, J.; Madura, I. D.; Bernaś, U.; Synoradzki, L. Acta Crystallogr., Sect. E: Struct. Rep. Online 2007, E63, o3209. (d) Zachara, J.; Madura, I. D.; Bernaś, U.; Synoradzki, L. Acta Crystallogr., Sect. E: Struct. Rep. Online 2007, E63, o3210. (e) Madura, I. D.; Zachara, J.; Bernaś, U.; Hajmowicz, H.; Kliś, T.; Serwatowski, J.; Synoradzki, L. J. Mol. Struct. 2010, 984, 75−82. (f) Wesela-Bauman, G.; Boinski, T.; Dominiak, P.; Hajmowicz, H.; Synoradzki, L.; Wierzbicki, M.; Woliński, B.; Woźniak, K.; Zawada, K. J. Struct. Chem. 2013, 54 (1), 153−156. (g) Ruśkowski, P.; Synoradzki, L.; Włostowski, M. Arkivoc 2011, No. ix, 142−154. (h) Hajmowicz, H.; Wisialski, J.; Synoradzki, L. Org. Process Res. Dev. 2011, 15, 427−434. i8. (i) Włostowski, M.; Ruśkowski, P.; Synoradzki, L. Org. Prep. Proced. Int. 2012, 44, 401− 454. (j) Madura, I. D.; Zachara, J.; Hajmowicz, H.; Synoradzki, L. J. Mol. Struct. 2012, 1017, 98−105. (2) See for example: (a) Gawroński, J.; Gawrońska, K. Tartaric and Malic Acid in Synthesis; Wiley: New York, NY, 1999. (b) Valdya, N. A. Innovations in Pharmaceutical Technology, December 2001. (c) Evans, G. R. Chemistry Today 2005, 23, 36−39. (d) Fogassy, E.; Nógrádi, M.; Kozma, D.; Egri, G.; Pálovics, E.; Kiss, V. Org. Biomol. Chem. 2006, 4, 3011−3030. (e) Moher, E. D.; Tripp, A. E.; Creemer, L. C.; Vicenzi, J. T. Org. Process Res. Dev. 2004, 8, 593−596. (f) Hobson, L. A.; Nugent, W. A.; Anderson, S. R.; Deshmukh, S. S.; Haley, J. J., III; Liu, P.; Magnus, N. A.; Sheeran, P.; Sherbine, J. P.; Stone, B. R. P.; Zhu, J. Org. Process Res. Dev. 2007, 11, 985−995. (g) Chavan, A. B.; Gundecha, S. S.; Kadam, P. N.; Maikap, G. C.; Gurjar, M. K. Org. Process Res. Dev. 2010, 14, 1473−14. (3) See for example: (a) Ghosh, A. K.; Koltun, E. S.; Bilcer, G. Synthesis 2001, 9, 1281−1301. (b) Coppola, G. M.; Schuster, H. F. αHydroxy Acids in Enantioselective Synthesis; Wiley-VCH: Voting, 2002; p 313. (c) Buschhaus, B.; Bauer, W.; Hirsch, A. Tetrahedron 2003, 59, 3899−3915. (d) Svenson, S.; Tomalia, D. A. Adv. Drug Delivery Rev. 2005, 57, 2106−2129. (e) Buschhaus, B.; Hampel, F.; Grimme, S.; Hirsch, A. Chem. - Eur. J. 2005, 11, 3530−3540. (f) Karlsson, S.; Lindberg, J.; Sörensen, H. Org. Process Res. Dev. 2013, 17, 1552−1560. (4) See for example: (a) Sinkó, B.; Pálfi, M.; Béni, S.; Kökösi, J.; Takaćs-Novák, K. Molecules 2010, 15, 824−833. (b) Paquette, L. A. Handbook of Reagents for Organic Synthesis. Chiral reagents for Asymmetric Synthesis; Wiley: Chichester, 2003; p 317. (c) Ube, H.; Fukuchi, S.; Terada, M. Tetrahedron: Asymmetry 2010, 21, 1203−1205. (5) See for example: (a) Furuta, K.; Miwa, Y.; Iwanaga, K.; Yamamoto, H. J. Am. Chem. Soc. 1988, 110, 6254−6255. (b) Hu, Y.; Yamada, K. A.; Chalmers, D. K.; Annavajjula, D. P.; Covey, D. F. J. Am. Chem. Soc. 1996, 118, 4550−4559. (c) Gao, Q.; Ishihara, K.; Maruyama, T.; Mouri, M.; Yamamoto, H. Tetrahedron 1994, 50, 979−988. (d) Sato, M.; Sunami, S.; Sugita, Y.; Kaneko, C. Chem. Pharm. Bull. 1994, 42, 839−845. (e) Ishihara, K.; Maruyama, T.; Mouri, M.; Gao, Q.; Furuta, K.; Yamamoto, H. Bull. Chem. Soc. Jpn. 1993, 66, 3483−3491. (f) Sugiura, M.; Tokudomi, M.; Nakajima, M. Chem. Commun. 2010, 46, 7799−7800. (g) Harada, T.; Izumi, Y. Chem. Lett. 1978, 7, 1195−1196. (h) Osawa, T.; Sawada, K.; Harada, T.; Takayasu, O. Appl. Catal., A 2004, 264, 33−36. (6) See for example: (a) Akelah, A.; Kenawy, E. R.; Sherrington, D. C. Eur. Polym. J. 1995, 31, 903−909. (b) Schliecker, G.; Schmidt, C.; Fuchs, S.; Kissel, T. J. Controlled Release 2004, 98, 11−23. (c) Marín, R.; Martínez de Ilarduya, A.; Munoz-Guerra, S. J. Polym. Sci., Part A:

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CONCLUSIONS Kinetic studies of the process of synthesis of dibenzoyltartaric anhydride (3) from tartaric acid (1) and benzoyl chloride (2) were carried out. The obtained dependence fit the pseodo-first reaction order. Arhenius equation constants were calculated. The obtained kinetic data form a basis for a design of a continuous reactor. For the desired reaction temperature of 115 °C, a cascade of three stirred tank reactors with volume of 22 L each was suggested as the preferred system to run the reaction in a continuous manner.

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EXPERIMENTAL SECTION Commercially available solvents and reagents were used without further purification. Synthesis of O,O′-Dibenzoyl-L-tartaric Anhydride (3): The Representative Kinetic Experiment. Previously ground acid 1 (31.5 g; 0.21 mol, 200 μm) was added to the mixture of benzoyl chloride (88.5 g; 0.63 mol) and toluene (54.2 g) in 250 mL reaction flask (Figure 1); the stirrer rotation speed was set at 230 rpm. The mixture was heated up to the predetermined temperature, the sulfuric acid (0.98 g; 0.01 mol) was injected, and the process/measurements begun. Variables (pH, temperature, time) were monitored continuously. Examplary results of two experiments are shown in Tables 4 and 5.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected], fax: +48(22)6255317. Notes

The authors declare no competing financial interest. 1707



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Polym. Chem. 2009, 47, 2391−2407. (d) Shibata, Y.; Takasu, A. J. Polym. Sci., Part A: Polym. Chem. 2009, 47, 5747−5759. (7) Anschütz, R.; Pictet, A. Ber. Dtsch. Chem. Ges. 1880, 13, 1175− 1178. (8) Majcher, M. Research on acylation of L-tartaric acid and dehydration of O,O’-diacyl-L-tartaric acid. M. Sc. thesis, Faculty of Chemistry Warsaw University of Technology: Warsaw, 2006. (9) See for example: (a) Levenspiel, O. Chemical Reaction Engineering; Wiley: New York, 1999. (b) Wroński, S.; Pohorecki, R. Kinetics and thermodynamics of chemical engineering processes; WNT: Warszawa, 1977. (10) Perry, R. H.; Green, D. W.; Maloney, J. O. Perry’s Chemical Engineers’ Handbook, 7th ed.; McGraw-Hill: New York, 1997. (11) Carl, L. Yaws’ Handbook of Thermodynamic and Physical Properties of Chemical Compounds; Knovel: New York, 2003. (12) Speight, J. G. Lange’s Handbook of Chemistry, 16th ed.; McGrawHill: New York, 2005. (13) Chen, N. H. Process Reactor Design; Allyn and Bacon: Newton, MA, 1983. (14) Ullmann’s Encyclopedia of Industrial Chemistry, 7th ed.; WilleyVCH: Weinheim, 2011.

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Kinetic Research of O,Oâ²-Dibenzoyltartaric Anhydride Synthesis

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Kinetic Research of O,Oâ²-Dibenzoyltartaric Anhydride Synthesis