Kinetic Study of Methoxycarbonylation of Methylene Dianiline with

ARTICLE pubs.acs.org/IECR

Kinetic Study of Methoxycarbonylation of Methylene Dianiline with Dimethyl Carbonate Using Lead Acetate Catalyst Yixia Pei,†,‡ Huiquan Li,*,† Haitao Liu,† and Yi Zhang† †

Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, 100190, People's Republic of China ‡ Graduate School of Chinese Academy of Sciences, Beijing 100049, People's Republic of China ABSTRACT: Methylene diphenyl dicarbamate (MDC) is a key intermediate in the non-phosgene manufacture of methylene diphenyl diisocyanate. The synthesis of MDC by methoxycarbonylation of methylene dianiline (MDA) with dimethyl carbonate in the presence of lead acetate catalyst, which showed high catalytic activity, was studied. Complete conversion of MDA and 98.10% yield of MDC were achieved under optimum conditions. To quantify the influence of both the temperature and reaction time, the kinetic parameters were investigated in the presence of Pb(OAc)2 3 3H2O. A consecutive reaction model was established by simplifying the methoxycarbonylation process, and the two steps were confirmed to be first-order reactions by the integral test method and the numerical differential method, respectively. The results showed that the activation energies of the two steps are 175.84 and 177.92 kJ/mol, with the frequency factors being 1.91 1020 and 1.98 1020, respectively. Based on the kinetic model obtained, the progress of the reaction can be calculated under given conditions.

1. INTRODUCTION Methylene diphenyl diisocyanate (MDI) is one of the most important raw materials for synthesizing polyurethanes, which have been widely employed as engineering plastics in various applications.1 Traditionally, MDI is synthesized from methylene dianiline (MDA) and phosgene, known as a corrosive and polluting route from both environmental and social points of view. Several routes were proposed to substitute the toxic phosgene in the manufacture of MDI with less noxious starting materials. Recently, research has been focused on the thermal decomposition of methylene diphenyl dicarbamate (MDC); therefore, the synthesis of MDC is an important step in the nonphosgene manufacture of MDI. Dimethyl carbonate (DMC), an environment-friendly chemical, has attracted attention in the past few years as a suitable substrate in non-phosgene organic synthesis. Because MDA is currently manufactured industrially and DMC is currently produced on a large scale by the oxidative carbonylation of methanol, the methoxycarbonylation of MDA with DMC has drawn much attention. Several studies have been devoted to exploring new catalysts for the methoxycarbonylation of MDA with DMC.2-5 Zinc acetates have been studied widely since Baba et al. reported it as a highly active catalyst, giving 98% of MDC yield at 453 K in 2 h.6,7 However, zinc acetate might react with methanol and be converted to ZnO,8 which has no activity in the formation of MDC. Moreover, methanol is a concomitant product in the methoxycarbonylation of MDA with DMC. Consequently, the deactivation of this catalyst is unavoidable and limits its application on an industrial scale. Guo et al. have attempted to resolve the problem of catalyst loss by grafting zinc carboxylate groups (COO(Zn)) onto the pore surface of mesoporous SBA-15; however, the selectivity of the new catalyst to MDC was only 86.5%.9 In the reports of Baba et al., Pb(OAc)2 3 3H2O gave 90% r 2011 American Chemical Society

MDC yield at 453 K in 2 h, second only to that of Zn(OAc)2 3 2H2O.6 However, this result has not received adequate attention and no further research has been conducted on the use of Pb(OAc)2 3 3H2O catalyst in the methoxycarbonylation of MDA with DMC. In fact, lead compounds are active catalysts in the methoxycarbonylation of aromatic amines to produce the corresponding carbamates.10 Pb(OAc)2 is highly selective in the methoxycarbonylation of 2,4-toluenediamine with DMC and gives 98% yield of toluene-2,4-dicarbamate (TDC).11 Therefore, we anticipated that Pb(OAc)2 3 3H2O or Pb(OAc)2 might be an excellent catalyst for the methoxycarbonylation of MDA. Apart from the investigations of different catalysts and formation of intermediates and byproduct by Qiu,12 no further research such as kinetic analysis has been previously reported about the reaction between MDA and DMC. In the present work, we studied the catalytic activity and the stability of lead acetate in the reaction between MDA and DMC. By investigating the optimum conditions for the catalyst, the influence of temperature and reaction time on reaction rates is discussed. To quantify these influences and understand the methoxycarbonylation behavior of MDA in detail, a kinetic study was carried out.

2. EXPERIMENTAL SECTION 2.1. Materials. MDA was commercially obtained and used without further treatment. DMC, of analytical grade, was purified by distillation before use. Pb(OAc)2 was obtained by removal of crystal water from Pb(OAc)2 3 3H2O at 383 K for 4 h. Other Received: August 12, 2010 Accepted: December 19, 2010 Revised: December 6, 2010 Published: January 19, 2011 1955

dx.doi.org/10.1021/ie1017095 | Ind. Eng. Chem. Res. 2011, 50, 1955–1961

Industrial & Engineering Chemistry Research

ARTICLE

Scheme 1. Methoxycarbonylation of MDA with DMC

reagents were commercial A.R. grade products and were used as received. 2.2. Reaction of MDA and DMC. In a typical reaction procedure, MDA, DMC, and catalyst were charged into a 100-mL stainless steel autoclave. After being purged with nitrogen, the autoclave was heated with stirring up to the desirable reaction temperatures and then maintained for a certain time under inert atmosphere. After being cooled to room temperature, the mixture obtained was filtered to separate solid and liquid, both of which were analyzed by high performance liquid chromatography (HPLC, Agilent 1100 series) equipped with a UV detector and ZORBAX Extented-C18 columm (4.6 mm 150 mm, 5 μm). 2.3. Catalyst Separation and Recycling. To investigate the stability of the catalyst, the catalyst should be separated from the reaction system. The experimental procedure was as follows. After the reaction, the mixture in the autoclave was cooled to 355 K and then heating filtration was carried out after 30 min. The filter cake was washed three times using acetone and dried at 383 K for 1 h in a constant temperature oven. Thus, the recycled catalyst was obtained and used for the next synthetic reaction. 2.4. Kinetic Experiments. The kinetic experiments were carried out in a 2-L stainless steel autoclave (KELI Automaton, FCF2-10) with a steel spiral cooler and a straight tube inserted into bottom for sampling. In a typical procedure, raw materials and catalyst were charged into the autoclave, mixed using the stirrer, and then purged with nitrogen. Under inert atmosphere, the autoclave was heated by a thermostat. When the temperature reached 403 K, a sample was taken out through the sampling tube from the autoclave and labeled as the original mixture-component. Beyond 403 K, the reactor was heated to the desirable reaction temperatures within 10 min and timing was set. Experiments were carried out under nearly isothermal conditions, with temperature variation of less than 2 K during each experiment. During the reaction, samples were taken at the following reaction times: 6, 12, 20, 30, 60, 90, 120, and 180 min. The samples were dissolved in acetone immediately, diluted to a constant volume using a methanol-water mixture, and analyzed by HPLC.

3. RESULTS AND DISCUSSION 3.1. Catalyst Selection and Reaction Process. The catalytic activities of Pb(OAc)2 3 3H2O and Pb(OAc)2 for the reaction of MDA and DMC were tested at 443 K for 2 h. The reaction conditions were as follows: 0.6 mol of DMC, 0.03 mol of MDA, and 0.8 mmol of catalyst. Both catalysts showed excellent activity in the synthesis of MDC from MDA and DMC. Pb(OAc)2 3 3H2O gave 95.98%, and Pb(OAc)2 gave 94.51% of MDC yield.

Therefore, further investigation was carried out in the presence of Pb(OAc)2 3 3H2O. The composition of the products was investigated to confirm the progress of reaction. The existence of monocarbamate methyl 4-(40 -aminobenzyl)phenylcarbamate (MMC) gives evidence of a two-step reaction, which is consistent with the report of Qiu etal. with the Zn(OAc)2 catalyst.12 The formation of MDC from MDA and DMC requires the methoxycarbonylation of two amino groups in the MDA molecule in succession, as shown in Scheme 1. Thus, the reaction can be described in the following two steps: (I) the MDA first reacts with DMC to provide MMC, which is an intermediate product, by functionalizing one of the two equivalent amino groups first; (II) MMC reacts with DMC to give the product MDC. In addition to MMC, some byproduct have also been identified in the reaction mixture; however, the corresponding amounts are small. In this context, only MMC and MDC are taken into account. 3.2. Effect of Reaction Condition. Several influencing factors, such as molar ratio, catalyst content, temperature, and reaction time, had been investigated in the methoxycarbonylation of MDA over Pb(OAc)2 3 3H2O catalyst. The results are shown in Figure 1. Because DMC is not only a reactant but also a solvent in the reaction system, DMC must be available in excess. Complete conversion was achieved at 433 K regardless of the ratio; however, the selectivity of MMC and MDC varied with the ratio. When the molar ratio of DMC to MDA was lower than 15, the yield of MDC was low because of the high selectivity of the byproduct.12 From Figure 1A, we can conclude that the optimal molar ratio of DMC/MDA is 20. The investigation of catalyst content on the reaction was carried out at 433 K, and the result is shown in Figure 1B. Complete conversion of MDA was achieved under the reaction conditions, apparently independent of the catalyst content. Nevertheless, the selectivity of MDC increased with increasing content of catalyst to reach a maximum value at a catalyst content of 5.0% (based on MDA, by mass). Accordingly, further investigation was carried out with 5.0% Pb(OAc)2 3 3H2O. To investigate the influence of temperature, the methoxycarbonylation reactions of MDA were carried out at different temperatures for 3 h with 5.0% lead acetate catalyst. From Figure 1C, we can observe that temperature is crucial in this reaction. With increasing temperature, the conversion of MDA increases and then remains constant as it approaches the maximum value. At low temperatures, MDA reacts with DMC slowly, and only 69.4% of MDA is converted when the reaction is conducted at 413 K, with the main reaction product being MMC. As an intermediate, MMC exists in the system in large amounts 1956

dx.doi.org/10.1021/ie1017095 |Ind. Eng. Chem. Res. 2011, 50, 1955–1961


ARTICLE

Figure 1. Effect of reaction conditions on MDC synthesis in the presence of lead catalyst. (A) Reaction temperature: 433 K, reaction time: 3 h, catalyst content: 5.0%; (B) reaction temperature: 433 K, reaction time: 3 h; (C) catalyst content: 5.0%, reaction time: 2 h; (D) reaction temperature: 433 K, catalyst content: 5.0%.

at low temperatures, and the maximal yield of MMC (40.0%) is achieved at 413 K. The formation of MDC is favored over that of MMC at higher temperatures. When the temperature reaches 423 K, the conversion of MDA reaches almost 100%, and MDC is the dominant product. At 433 K, the yield of MDC is 98.1%. With a further increase in the temperature beyond 433 K, the yield of MDC decreases slightly because side reactions could take place easily. The trends indicate that the formation rate of MMC is greater than that of MDC at low temperatures, but the consumption rate of MMC increases with increasing temperature. Figure 1D illustrates the influence of the reaction time on the reaction and gives us an instinctive understanding of the two steps. Under optimum reaction conditions, sharp increases of both reactants and products are observed during the first few minutes. Within 20 min, 91.4% of MDA is converted and complete conversion is achieved in 40 min. The yield of MMC increases rapidly and reaches the maximum level within 20 min, followed by a gradual decrease until 60 min, and then remains constant at a low level with further increase of the reaction time. The MDC yield shows a more moderate trend because of the existence of MMC and reaches a maximum level of 98.1% after 120 min. The existence of small quantities of MMC after 180 min indicated that the reaction between MMC and DMC is reversible, although the equilibrium constant might be large because the concentration of the intermediate MMC is low when the equilibrium is approached.

Figure 2. IR spectra of samples pretreated under different conditions. a, Pb(OAc)2 3 3H2O; b, used catalyst; c, Pb3(CO3)2(OH)2.

3.3. Recycling of the Catalyst. Wang et al. proposed, using X-ray powder diffraction (XRD) analysis,11 that Pb(OAc)2 3 3H2O may be converted into Pb3(CO3)2(OH)2 in the reaction system, and we obtained the same XRD spectrum when testing the used catalyst. However, we made a further identification of the used catalyst and Pb3(CO3)2(OH)2 by Fourier transform infrared spectroscopy, and a significant difference was detected, as shown in Figure 2, indicating that the used catalyst 1957



ARTICLE

the temperature and time influence the reaction degree; hence, the kinetics of the reaction should be studied. Based on the kinetic model, the reaction degree can be calculated using the given reaction temperature and time.

4. KINETICS OF THE METHOXYCARBONYLATION OF MDA

Figure 3. Catalytic activities of the lead catalyst. The catalyst first used is Pb(OAc)2 3 3H2O, followed by used catalyst.

4.1. Establishment of Kinetic Model. The kinetic parameters were studied by measurement of the relationship between reactant concentration and reaction time. Because DMC is available in a large surplus (the molar ratio of DMC to MDA is 20:1), the DMC concentration can be assumed to be quasiconstant.14 To simplify the kinetic model, the reverse reaction of the second step was neglected by assigning a maximal conversion of MMC as 98.1%, according to the experimental results. Consequently, the methoxycarbonylation of MDA can be written in the broadest sense as comprising the following consecutive reactions:15 k1

k2

I

II

MDA sf MMC sf MDC The rate equations of the reactant and the product were considered proportional to the reactant concentration, as represented in eqs 1.1-1.3: consumption rate of MDA : r1 ¼ -

dC1 ¼ k1 Cn1 dt

ð1:1Þ

dC2 ¼ k1 Cn1 - k2 Cm2 ð1:2Þ dt dC3 ¼ k2 Cm2 ð1:3Þ formation rate of MDC : r3 ¼ dt

formation rate of MMC : r2 ¼

Figure 4. Concentration of MDA versus time at different temperatures. Molar ratio of DMC to MDA is 20, catalyst content 5% (based on the mass of MDA), reaction time 2 h.

comprised lead carbonate species and not pure Pb3(CO3)2(OH)2. Under the optimum conditions detailed above, the activities of the used catalyst after recycling four times were tested. The catalytic activity of the used catalyst remained at a high level, and the results are shown in Figure 3. The yield of MDC slightly varied around 97% at first and then decreased to 95%, while the conversion of MDA and the yield of MMC remained invariable. The high catalytic activity of both lead acetate and lead carbonate species may be related to the coordination structure of their carboxyl or carbonate groups.13 Thus, the catalyst PbOAc)2 3 3H2O has a good stability, which is an advantage for applications on the industrial scale. 3.4. Discussion of the Methoxycarbonylation. The results described above show that Pb(OAc)2 3 3H2O is an effective catalyst for the methoxycarbonylation of MDA with DMC. With enough amounts of the catalyst, both temperature and time have a direct influence on the reaction between MDA and DMC. When the temperature is above 403 K, the reaction may be clearly observed. MMC can be obtained with high selectivity at 413 K, and MDC is synthesized selectively above 423 K. Under the optimum temperature of 433 K, the yield of the target product MDC reaches 98.1% after 2 h. In summary, MMC and MDC can be obtained selectively by controlling temperature and time, but we have no idea about how

where C1, C2, and C3 are the concentrations of MDA, MMC, and MDC, respectively; k1 and k2 are the rate constants of the reactions I and II, respectively, and the exponents n and m represent the reaction orders of the reactions I and II, respectively. The dependence of the reaction rate on the temperature can be expressed using Arrhenius relationship (eq 2): E k ¼ A exp RT

ð2Þ

where A is the frequency factor, E is the activation energy, R is the universal gas constant, and T is temperature in Kelvin. It should be noted that the eqs 1.1-1.3 only express a multitude of reaction mechanisms and rates, not the mechanistic model. Therefore, the kinetics mentioned for each reaction step in this study are macroscopic. 4.2. Estimation of Kinetic Parameters for the Reaction of MDA To Form MMC. Isothermal experiments were carried out at four different temperatures, viz. 403, 413, 423, and 433 K, to determine the kinetic parameters for the consumption of MDA. The relationships between MDA concentration and reaction time are shown in Figure 4. First, the reactor order should be confirmed. The data obtained at 423 K were used to determine the value of n by the integral test method. The differential equation described by eq 1.1 was solved by the separation of variables technique and rearranged into the following integral form to retrieve the 1958



ARTICLE

concentration-time relationship for zero-, first-, and secondorder reactions: if n ¼ 0 : C1 ¼ C0 - k1 t ð3.1Þ if if

Figure 5. Plots of ln(C0/C1) versus reaction time.

Table 1. Kinetic Parameters for the Reaction between MDA and DMC temperature (K) k1 (min)

R2

ln k1

403

0.0035

0.9852 -5.744

413

0.0101

0.9978 -4.595

423

0.0386

0.9921 -3.255

433

0.1164

0.9917 -2.151

E1 (kJ/mol) A1 (min-1)

175.84

1.91 1020

n ¼ 1: n ¼ 2:

ln

C0 ¼ k1 t C1

1 1 ¼ k1 t C1 C0

ð3.2Þ ð3.3Þ

where C0 is the initial concentration of MDA. There is a characteristic plot for each integrated rate law, producing a straight line. The straight lines were chosen by considering the regression coefficients of the lines, and the slopes of the straight lines gave the rate constant. Then plots of C1-t, ln C0/C1-t, and 1/C1-t were derived based on the experimental data at 423 K, and results showed that the relationship between ln C0/C1 and time is linear, indicating that the reaction order of the reaction I is one. Figure 5 represents the logarithms of the concentrations as functions of time at different temperatures. A reaction period of approximately 60-120 min is observed in these experiments. It should be noted that only the Arrhenius-controlled conversion regime (i.e, the linear portion) of the curves in Figure 4 was fitted with a regression line. After a critical time, the reactant concentration becomes very low, and measurement errors could significantly influence the calculation, resulting in a deviation from

Figure 6. Concentration profiles for MMC and MDC versus reaction time. Molar ratio: n(DMC)/n(MDA) = 20; catalyst content: 5% (based on the mass of MDA); reaction time: 2 h. 1959



ARTICLE

Table 2. Kinetic Parameters for the Reaction of MMC and DMC temperature (K)

m

ln k2

k2 102 E2 (kJ/mol) A2 (min-1)

403

1.0535 -6.3345

0.1774

413 423

1.0977 -5.1216 0.9260 -3.8915

0.5966 2.0415

433

0.9668 -2.6548

7.0313

177.92

1.98 1020

the kinetic model described by eq 1.1; therefore, the deviating points were eliminated. Using least-squares linear regression, the plots were fitted with a regression line, and a value of the rate constant (k1) was found for each reaction temperature, as listed in Table 1. The value for the activation energy (E1) and the frequency factor (A1) of the reactions I were calculated using the logarithms of the Arrhenius relationship16 (eq 4): ln k ¼ ln A -

E RT

ð4Þ

4.3. Estimation of Kinetic Parameters for the Reaction of MMC To Form MDC. While estimating the kinetic param-

eters k2 and m for the reaction between MMC and DMC, the differential equation described by eq 1.3 was difficult to be solved; hence, the numerical differential method was used.17 According to the integral mean-value theorem, the numerical value of dC3/dt at t þ 0.5Δt min is approximately equivalent to the value of ΔC3/Δt, and the corresponding concentrations of MMC (C2) can be verified by the curves of relationship between concentrations and time. Isothermal experiments were carried out at four different temperatures, viz. 403, 413, 423, and 433 K. The variations in the concentrations of MMC and MDC with the reaction time are shown in Figure 6. The logarithmic form of eq 1.3 is represented as follows: ln r3 ¼ ln k2 þ m ln C2

ð5Þ

Obviously, the relationship between ln r3 and ln C2 can be obtained by linear regression from the experimental and calculated results. The slope of the straight line gives the reaction order m. The intercept of the regression line is the logarithm of the rate constant k2. The value of activation energy (E2) and the frequency factor (A2) of the reaction of MMC and DMC were calculated using eq 4. The kinetic parameters for the synthesis of MDC from MMC and DMC are listed in Table 2. 4.4. Discussion and Application of the Kinetic Equations. The kinetic parameters of the two steps were estimated based on the experimental data by the integral test and numerical differential methods, respectively. Both steps were established to be first-order reactions. Generally, the concentrations relative to time draw much attention. Accordingly, the kinetic equations of the methoxycarbonylation can be expressed as follows: C1 ¼ C0 expð - k1 tÞ C2 ¼ C0

k1 ½expð - k1 tÞ - expð - k2 tÞ k2 - k1

C3 ¼ 0:98ðC0 - C1 - C2 Þ where, k1 = 1.91 10 exp(-175840/RT) and k2 = 1.98 10 exp(-177920/RT). It should be noted that the condensation of MDC can be calculated approximately based on the absence 20

20

Figure 7. Predicted results versus time profiles at different temperatures.

of the reverse reaction of reaction II. The kinetic relations are applicable only on the Arrhenius-controlled stages of the reaction, and the side reactions of MMC have been neglected. The actual complete conversion of MMC cannot be achieved. Therefore, the correction factor for the formation rate of MDC is as assumed 0.98, according to the real maximal yield of MDC. Base on the obtained kinetic model, the reaction proceeding at different temperatures can be calculated. Figure 7 shows the calculated relationships of the product yield with time. In a typical consecutive reaction, the intermediate MMC attains a maximum yield at a certain time point and then decreased. Without consideration of the side reactions, the maximum yield of MDC can be obtained at any temperature with sufficient time. According to the kinetic model, the maximum yield of MDC will be achieved after 6 h at 423 K, and at 443 K, the time required to get the highest yield of MDC is approximately 110 min, which is consistent with the experimental results. Higher temperatures shorten the time interval, but side reactions cannot be neglected in those situations. Figure 8 shows the experimental and predicted results at 423 K, and it shows that the kinetic model is basically consistent with the experimental results. 1960



Figure 8. Experimental and predicted results versus time profiles at 423 K.

According to the model equation, the activation energies of the consecutive steps are 175.84 and 177.92 kJ/mol, respectively. Both steps are endothermic reactions, and the heat of the reaction is relatively large. Because the activation energy of the first step is lower than that of second step, reaction I occurs more easily than reaction II. The rate of reaction I is very high, and MDA can be consumed within a short time. With increasing reaction temperature, the rate constant k2 increases faster than k1, resulting in a short-lived period of the intermediate MMC. Based on the kinetic analysis, the reaction process can be controlled by appropriately adjusting the reaction temperature and time.

5. CONCLUSIONS A non-phosgene route for MDC synthesis via the methoxycarbonylation of MDA with DMC using Pb(OAc)2 3 3H2O catalyst was studied in this work. Under the optimum condition of 433 K for 2 h, MDA was converted completely to MDC, and the yield of MDC reached 98.1%. The kinetics of the reaction between MDA and DMC were investigated for the first time. It is a classical consecutive reaction by simplifying of the reaction model. The activation energies of the two steps are 175.84 and 177.92 kJ/mol, while the frequency factors are 1.91 1020 and 1.98 1020, respectively. Based on the kinetic model obtained, the process can be predicted and the calculated results are consistent with the experimental results. ’ AUTHOR INFORMATION Corresponding Author

*Tel/Fax: þ86-10-6262-1355. E-mail: [email protected].

ARTICLE

weight and chemical structure of soft segment in reaction kinetics of polycarbonate diols with 4,4 0 -diphenylmethane diisocyanate. Eur. Polym. J. 2005, 41 (12), 3051. (2) Carafa, M.; Quaranta, E. Synthesis of Organic Carbamates without Using Phosgene: Carbonylation of Amines with Carbonic Acid Diesters. Mini-Rev. Org. Chem. 2009, 6 (3), 168. (3) Curini, M.; Epifano, F.; Maltese, F.; Rosati, O. Carbamate synthesis from amines and dimethyl carbonate under ytterbium triflate catalysis. Tetrahedron Lett. 2002, 43 (28), 4895. (4) Li, F.; Miao, J.; Wang, Y. J.; Zhao, X. Q. Synthesis of methyl N-phenyl carbamate from aniline and dimethyl carbonate over supported zirconia catalyst. Ind. Eng. Chem. Res. 2006, 45 (14), 4892. (5) Vauthey, I.; Valot, F.; Gozzi, C.; Fache, F.; Lemaire, M. An environmentally benign access to carbamates and ureas. Tetrahedron Lett. 2000, 41 (33), 6347. (6) Baba, T.; Kobayashi, A.; Yamauchi, T.; Tanaka, H.; Aso, S.; Inomata, M.; Kawanami, Y. Catalytic methoxycarbonylation of aromatic diamines with dimethyl carbonate to their dicarbamates using zinc acetate. Catal. Lett. 2002, 82 (3-4), 193. (7) Baba, T.; Kobayashi, A.; Kawanami, Y.; Inazu, K.; Ishikawa, A.; Echizenn, T.; Murai, K.; Aso, S.; Inomata, M. Characteristics of methoxycarbonylation of aromatic diamine with dimethyl carbonate to dicarbamate using a zinc acetate catalyst. Green Chem. 2005, 7 (3), 159. (8) Tonto, P.; Mekasuwandumrong, O.; Phatanasri, S.; Pavarajarn, V.; Praserthdam, P. Preparation of ZnO nanorod by solvothermal reaction of zinc acetate in various alcohols. Ceram. Int. 2008, 34 (1), 57. (9) Guo, X. C.; Qin, Z. F.; Fan, W. B.; Wang, G. F.; Zhao, R. H.; Peng, S. Y.; Wang, J. H. Zinc Carboxylate Functionalized Mesoporous SBA-15 Catalyst for Selective Synthesis of Methyl-4,40 -di(phenylcarbamate). Catal. Lett. 2009, 128 (3-4), 405. (10) Fu, Y.; Baba, T.; Ono, Y. Carbonylation of o-phenylenediamine and o-aminophenol with dimethyl carbonate using lead compounds as catalysts. J. Catal. 2001, 197 (1), 91. (11) Wang, S. P.; Zhang, G. L.; Ma, X. B.; Gong, J. L. Investigations of catalytic activity, deactivation, and regeneration of Pb(OAc)(2) for methoxycarbonylation of 2,4-toluene diamine with dimethyl carbonate. Ind. Eng. Chem. Res. 2007, 46 (21), 6858. (12) Qiu, Z. G.; Wang, J. W.; Kang, M. Q.; Li, Q. F.; Wang, X. K. Formation of intermediate and by-products in synthesis of 4,40 -methylenedimethyl diphenylcarbamate. Catal. Lett. 2008, 124 (3-4), 243. (13) Ma, D.; Wang, G. R.; Wang, Y. J.; Zhao, X. Q. Application of IR Spectrum to the Research on Mechanism of Synthesis of 2,4-Toluene Dicarbamate Catalyzed by Zinc Acetate. Spectrosc. Spectral Anal. (Beijing, China) 2009, 29 (2), 331. (14) Moller, M.; Moritz, H. U. Kinetic investigations of trimethylolpropane-diisocyanate reactions. J. Appl. Polym. Sci. 2006, 101 (6), 4090. (15) Anitescu, G.; Zhang, Z. H.; Tavlarides, L. L. A kinetic study of methanol oxidation in supercritical water. Ind. Eng. Chem. Res. 1999, 38 (6), 2231. (16) Kim, D.; Kim, B. K.; Cho, Y.; Han, M.; Kim, B. S. Kinetics of Polycarbonate Methanolysis by a Consecutive Reaction Model. Ind. Eng. Chem. Res. 2009, 48 (14), 6591. (17) Steel, C.; Naqvi, K. R. Differential Method in Chemical Kinetics. J. Phys. Chem. 1991, 95 (26), 10713.

’ ACKNOWLEDGMENT This work was supported by the Science and Technology Ministry of China (No. 2006BAC02A08) and the Knowledge Innovation Fund of Chinese Academy of Sciences (No. KGCX2YW-215-2). ’ REFERENCES (1) Eceiza, A.; de la Caba, K.; Kortaberria, G.; Gabilondo, N.; Marieta, C.; Corcuera, M. A.; Mondragon, I. Influence of molecular 1961


Kinetic Study of Methoxycarbonylation of Methylene Dianiline with

Recommend Documents