Pervaporation Membrane Reactor for Producing Hydroxylamine

Dec 12, 2014 - The longtime experiment demonstrated that the membrane was .... of this reaction but also components coming from ammoximation output, e...
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Pervaporation Membrane Reactor for Producing Hydroxylamine Chloride via an Oxime Hydrolysis Reaction Weidong Zhang,* Xing Su, Zisu Hao, Shaoli Qin, Weihua Qing, and Chunjie Xia State Key Laboratory of Chemical Resource Engineering, Beijing Key Laboratory of Membrane Science and Technology, Beijing University of Chemical Technology, Beijing 100029, PR of China ABSTRACT: A cost-effective route for the synthesis of hydroxylamine chloride (NH2OH·HCl) was proposed by combining ammoximation and oxime hydrolysis reactions (A−O−H route). This route is limited by low equilibrium conversion of oxime hydrolysis, which is a reversible reaction that produces ketone and NH2OH·HCl. A pervaporation membrane reactor (PVMR) was recommended in this route for improving butanoxime hydrolysis conversion by in situ removal of byproduct butanone. Using a PDMS membrane, the effects of feed composition, temperature, and reactant concentration on the PVMR performance were investigated. An enhancement of conversion from about 20% to 84% was achieved. When using a high reactant concentration, NH2OH·HCl can be crystallized in the PVMR. The longtime experiment demonstrated that the membrane was stable in acidic and ionic environments in the reaction mixture.

1. INTRODUCTION Hydroxylamine chloride (NH2OH·HCl) is an important chemical intermediate with various applications in chemical engineering, pharmacy, agriculture, etc.1 The conventional methods for the synthesis of NH2OH·HCl, such as Raschig and NO catalytic reduction, suffered from low yield and many undesirable side reactions, leading to high cost and environmental pollution.2−4 A new route for producing hydroxylamine chloride (NH2OH·HCl) by combining the Ammoximation and Oxime Hydrolysis reaction (A−O−H route) was proposed, as illustrated in Figure 1. In the A−O−H route, oxime was first synthesized using ketone, H2O2, and NH3 by the ammoximation process. Then, the oxime was hydrolyzed with HCl solution by the oxime hydrolysis to produce the desired product NH2OH·HCl, wherein the byproduct ketone was in situ removed and recycled as a reactant in the ammoximation process. In view of the entire process, NH2OH·HCl could be produced by cost-effective materials which were NH3, H2O2, and HCl, with ketone and oxime circulated in the system. Although the ammoximation reaction with very high yield has been already successfully applied on many occasions,5−12 the oxime hydrolysis reaction suffers from severely thermodynamic equilibrium, in which the equilibrium conversion can only reach 10%−20%.13−17 As a result, the proposed A−O−H route would only be a concept unless the small amount of ketone could be effectively removed from its reaction solution, and the equilibrium of oxime hydrolysis reaction could be significantly shifted to the product side. Pervaporation (PV) is a promising separation technique for the separation of liquid mixture by selective transport through a dense membrane.18,19 In these processes, the liquid mixture is exposed to one side of a dense membrane, and a small fraction of the components present a relatively faster permeate rate through the membrane and finally preferentially evaporate at the low-pressure permeate side. Because the separation efficiency in the PV process is governed by the solubilities and diffusivities of components in the membrane, instead of © 2014 American Chemical Society

relative volatility, and only the heat of vaporization of the permeating components has to be supplied, the energy demand of PV is small when compared to traditional separation processes.20,21 By coupling the PV process with a thermodynamicallylimited reaction, the Pervaporation Membrane Reactor (PVMR) technique gained increasing attention in recent years22−24 and has been investigated for many typical thermodynamically-limited reaction systems, such as esterification,25−31 etherification,32−34 acetalization,24,35 etc. It allows to shift the reaction equilibrium and enhance the conversion by in situ removal of byproduct from the reaction mixture.36 In most cases, sufficient enhancements for conversion were achieved, proving the PVMR technique was an efficient approach for this kind of reaction. Additionally, PVMR could be applied in relatively moderate conditions, which may be beneficial for optimizing reaction conditions and lowering the cost of production.37−39 In this regard, by coupling the oxime hydrolysis reaction in a PVMR, the yield of NH2OH·HCl was expected to largely increase due to the in situ removal of the byproduct ketone through a pervaporation membrane.

This work proposed a PVMR-aided A−O−H route for the production of NH2OH·HCl and gave an emphasis on its limited step, i.e. the oxime hydrolysis reaction in PVMR. A butanoxime hydrolysis reaction was selected as a model system (as shown in eq 1), and a PDMS membrane was used in the PVMR. The separation performance of the binary butanoxime/ water mixture and the butanone/water mixture by pervaporation was determined and compared. The performance of the Received: Revised: Accepted: Published: 100

July 14, 2014 November 29, 2014 December 12, 2014 December 12, 2014 DOI: 10.1021/ie502811e Ind. Eng. Chem. Res. 2015, 54, 100−107

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Industrial & Engineering Chemistry Research

Figure 1. Schematic of the A−O−H route for the production of NH2OH·HCl.

PVMR process in the A−O−H route was investigated under different operating parameters, such as upstream components (including TBA, NH3, and butanone), reactant concentration, and temperature. Membrane stability in the reaction mixture was also investigated by the longtime PVMR experiment. To the best of our knowledge, no works have been reported so far regarding the PVMR performance that involved the oxime hydrolysis reaction.

2. EXPERIMENTAL SECTION 2.1. Material. Polydimethylsiloxane (PDMS) with an average molecular weight of 32000 was purchased from Shengzhen Hongyejie Technology Co. Ltd., China. Butanone (≥99%), NaCl (≥99.5%), tert-butyl alcohol (TBA) (≥99.5%), and NH2OH·HCl (≥98.5%) were obtained as analytical reagents from Tianjin Fuchen Chemical Co. Ltd., China. Butanoxime (≥99%) was obtained from Zhejiang Quzhou New Future Chemical Reagent Company, China. PVDF microfiltration membranes, with an average pore size of 0.022 μm and thickness of 95 μm, were from Beijing Beihualiming Company, China and used as supports. Deionized water was used for all the experiments. The membrane used in this work was a lab-made composite membrane with a dense layer of PDMS casting on a porous PVDF support. The method of preparing the composite PDMS/PVDF membranes has already been described elsewhere.40 The thickness of the dense layer prepared was about 43 μm. 2.2. Analysis. The concentrations of butanoxime and butanone in binary aqueous solution were measured by U.V. absorption spectrophotometry with a SHIMADZU 2700 spectrophotometer at the detecting wavelength of 250 and 266 nm, respectively. The NH2OH·HCl concentration in the reaction mixture was determined by the acid−base titration,41 where the butanoxime and butanone were extracted in advance by toluene. For the multicomponent system, the permeate-side samples in PVMR processes were diluted with deionized water and then measured by UV absorption spectrophotometry with the SHIMADZU 2700 spectrophotometer, where the K-factor dual-wavelength method was employed with the detecting wavelength at 255 and 260 nm.42 The pH value of reaction mixture was measured by a UB-7 pH Meter. 2.3. Apparatus and Procedure. Figure 2 shows a schematic diagram of the pervaporation apparatus, which was well used for the PVMR process. The membrane with an effective surface area of 20 cm2 was installed in the middle of the pervaporation apparatus. The feed tank equipped with a

Figure 2. Schematic representation of the PVMR lab unit.

mechanic stirrer was maintained at constant temperature by a water jacket. Sufficient stirring (1500 rpm) of the bulk mixture was found to be enough to avoid concentration polarization effects. The pressure at the downstream side was kept at approximate 5 mmHg, and the permeate stream was condensed using a glass trap cooled with liquid nitrogen. The permeateside pressure was monitored by a manometer. After the system has reached steady state, samples were collected and analyzed periodically. The permeate flux was determined gravimetrically by weighing the glass container before and after permeate collection. The permeate flux J and selectivity αi/j were used for estimation of the pervaporation performance W J= (2) St αi / j =

Pi Pj

(3)

where W was the weight of the permeate, S was the effective area of the membrane, and t was the permeation time interval for the pervaporation; Pi and Pj were the permeability of the membrane for components i and j, respectively, and can be calculated by the method of Guo et al.43,44 In the PVMR process, the butanoxime and the HCl solution were mixed well at an equal molar ratio of acid/butanoxime before adding it into the reactor. Given that the desired product (NH2OH·HCl) existed in the form of a charged molecule, which cannot pass through dense membranes,45,46 the dense PDMS membrane could be used for preferential removal of the byproduct (butanone) from the reaction mixture to enhance conversion. All the PVMR experiments were carried out with a unified ratio of membrane area to reaction volume (S/V ratio) of 16.7 m−1. Simple batch reactor experiments without 101

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Industrial & Engineering Chemistry Research pervaporation were also performed to determine the equilibrium conversion of the butanoxime hydrolysis reaction under the same conditions. Since there were no other side reactions, except for the oxime hydrolysis reaction which occurred in the solution,14 the conversion of butanoxime was equal to the yield of NH2OH·HCl and can be calculated by n Conversion = hc × 100% nox,0 (4)

Table 1. Some of the Physical Properties of Compounds in the Separation System components

solubility parametersa,55 (J/cm3)1/2

molecule volume56 (cm3·mol−1)

butanone butanoxime water

19.1 32.0 47.8

90.1 96.5 18.7

The solution parameter of PDMS is 14.9(J/cm3)1/2 − 15.5 (J/ cm3)1/2. a

where nhc is the molar amount of NH2OH·HCl at time t, and nox,0 is the initial molar amount of butanoxime.

the membrane. Water fluxes in both systems were almost the same and changed a little with feed concentration because of the weak membrane swelling by either butanone or butanoxime. Figure 4 compares the membrane selectivity between pervaporation of butanoxime/water and butanone/water binary

3. RESULTS AND DISCUSSION 3.1. Comparison of the Pervaporation Performances between Butanone/Water and Butanoxime/Water System. Given that the reactant butanoxime and the byproduct butanone are both organophilic, the difference in the permeation rate between butanoxime and butanone through the PDMS membrane would play an important role on the performance of the butanoxime hydrolysis reaction in the PVMR. Figure 3 represents the partial fluxes of butanoxime,

Figure 4. Evolution of the selectivity with feed butanoxime or butanone concentration in pervaporation of butanoxime/water and butanone/water binary mixtures, respectively, 40 °C.

mixtures. The membrane selectivity was used instead of the separation factor because it can eliminate the effect of the driving force and operating conditions when analyzing the membrane performance.50,51 In Figure 4, the selectivities, αke/w (5−6) and αox/w (3−4), were both higher than 1, suggesting the organophilic property of the PDMS membrane. The αke/w were always higher than αox/w, indicating that the PDMS membrane also shows affinity toward butanone rather than butanoxime. The above phenomena demonstrated that the selected PDMS membrane was suitable for the proposed PVMR process, and the byproduct butanone could be preferentially removed to enhance the butanoxime hydrolysis reaction. 3.2. Effects of Upstream Components. 3.2.1. TBA and NH3. The butanoxime hydrolysis reaction mixture in the A−O− H route may contain not only components of this reaction but also components coming from ammoximation output, e.g., reaction solvent, tert-butyl alcohol (TBA), and residual reactant, NH3. In the traditional process, these components are generally separated in advance by an evaporation operation. In this section, we investigated the effects of initial TBA and NH4Cl on the PVMR performance in a condition without traditional evaporation operation. Figure 5 shows the effects of initial TBA and NH4Cl on conversion and NH2OH·HCl concentration in the PVMR process. About 20 wt % TBA and 4 wt % NH4Cl were selected

Figure 3. Evolution of the partial fluxes with feed butanoxime or butanone concentration in pervaporation of butanoxime/water and butanone/water binary mixtures, respectively, 40 °C.

butanone, and water as a function of solute concentration in binary butanone/water and butanoxime/water mixtures. For each system, the partial fluxes were found to increase with increased feed solute content. The butanone flux was much higher at the same feed content than butanoxime by more than 1 order of magnitude. This behavior was mainly attributed to different properties of solubility, diffusivity, and/or transmembrane driven force between different organics.47 Solubility parameter theory is an important factor to evaluate the permeant-polymer mutual solubility, and a solvent with a solubility parameter similar to the polymer will have high solubility.48,49 Table 1 shows that the solubility parameter of butanone (19.1) is closer to the solubility parameter of PDMS (14.9−15.5) than that of butanoxime (32.0) and water (47.8). These results demonstrated that the membrane presents higher affinity to butanone, followed by butanoxime and water. However, water flux was higher than butanoxime flux in the PV process of the butanoxime/water mixture. This was because of the relatively small molecular volume of water, as shown in Table 1, which sharply reduced its diffusion resistance through 102

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PVMR was completely removed by the pervaporation process. Notably, the selected initial butanone concentration of 4.0 wt % (0.56 M) was quite high, indicating that this PVMR could operate with stable productivity in this condition. After 50 h, the low increasing rates of conversion and the NH2OH·HCl concentration were mainly due to the very low permeation rate of butanone. The maximum conversions above 80% were obtained at 80 h because a small amount of reactant butanoxime has been simultaneously removed by the pervaporation process. 3.3. Effect of Temperature. In this section, the effect of temperature on the performance of PVMR was investigated. Figure 7 and Figure 8 show the time dependency of conversion as well as the partial fluxes of butanone and butanoxime at different temperatures. Figure 5. Effects of the initial TBA and NH3 on PVMR conversion and NH2OH·HCl concentration, respectively (initial butanoxime concentration: 0.92 M, temperature: 40 °C).

as typical initial concentrations as referred to by the ammoximation output composition.52,53 Both conversion variation and NH2OH·HCl concentration in these two conditions were found to only slightly change, indicating that the influence of these two components on the PVMR performance were not very important. Thus, the components of TBA and NH3 would not be taken into account below. 3.2.2. Butanone. In order to avoid the introduction of NH4Cl into the final NH2OH·HCl product, excessive butanone should be added to the ammoximation process to make the reactant NH3 completely react. Nevertheless, as one product of the butanoxime hydrolysis reaction, the excessive butanone in PVMR may affect the reaction conversion by shifting the reaction equilibrium. The effect of initial butanone concentration (Cke,0) on the PVMR performance was investigated as illustrated in Figure 6. At the beginning of the PVMR process, the initial conversion at 0 h was found to decrease from 16.7% to 5.0% because the addition of butanone shifted the equilibrium reaction to the reactant side. After 30 h, the conversion and NH2OH·HCl concentration of different initial butanone concentrations were both tending to be the same, because the excessive butanone in

Figure 7. Effect of temperature on PVMR conversion (initial butanoxime concentration: 0.92 M, the dash lines represent the equilibrium conversion).

As shown in Figure 7, equilibrium conversion increases with increased temperature as indicated by the dotted lines, suggesting the butanoxime hydrolysis is an endothermic reaction. Moreover, the conversions in PVMR could rapidly reach equilibrium in just a few minutes at all temperatures and, after that, slowly increased by in situ removal of the butanone.

Figure 6. Effects of initial butanone concentration (Cke,0) on conversion and NH2OH·HCl concentration (initial butanoxime concentration: 0.92 M, temperature: 40 °C).

Figure 8. Effects of temperature on the fluxes of butanone and butanoxime fluxes (initial butanoxime concentration: 0.92 M). 103

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Industrial & Engineering Chemistry Research This phenomenon indicated that the reaction rates were much higher than the removal rates of the byproduct butanone in all conditions. As a result, the transmembrane mass transfer could be considered as the governing step in PVMR. The higher operating temperature was also found to result in a higher increasing rate of conversion in PVMR. This was because increasing the temperature enhanced both reaction rate and separation flux of the byproduct butanone. It took different time ranges from 50 to 100 h to reach maximum conversion, i.e., 80.3%, 82.7%, and 85.4% at 30 °C, 40 °C, and 60 °C, respectively. Based on Figure 8, butanoxime fluxes increased with increased temperature. Nevertheless, their fluxes were about 1 order of magnitude lower than butanone fluxes for all temperatures. This was because most of the butanoxime in the reaction mixture existed as intermediate complexes and cannot pass through the membrane,45 as discussed in Section 3.5. The total amount of butanoxime collected in the permeated side did not change much with varying temperature, which accounted for 11.0%, 11.1%, and 12.0% of the initial butanoxime added to the reaction at temperatures from 30 to 60 °C. The permeated butanoxime, together with butanone, can be returned to the ammoximation step as shown in Figure 1. To further improve the performance of PVMR, the separation performance of butanoxime/butanone should be improved in future work. 3.4. Effect of Reactant Concentration. According to the typical output composition of the ammoximation process,52,53 the initial butanoxime concentrations (Cox,0) in PVMR were estimated at the range of 1 to 2 M at the acid/oxime molar ratio of 1:1. In this section, experiments with initial reactant (butanoxime) concentrations of 0.92 and 1.70 M were selected to investigate the performance of the PVMR processes, and the results were illustrated in Figure 9 and Figure 10.

Figure 10. Effects of initial butanoxime concentration (Cox,0) on the fluxes of butanone and butanoxime (temperature: 40 °C).

rearranging eq 5, the equilibrium conversion, Xeq, can be expressed by eq 6, and it demonstrated that the higher the initial butanoxime concentration is the lower the achieved Xeq is Keq =

C NH2OH·HCl·C ke Cox

=

(Cox,0·Xeq )2 Cox,0·(1 − Xeq )

Equation 5 can be rearranged as 1 Xeq = −0.5 0.5 Keq ·Cox,0 + 1

(5)

(6)

As PVMR proceeded, it was illustrated that the PVMR conversion was found to more slowly increase in Cox,0 of 1.70 M than in that of Cox,0 of 0.92 M. This was because the increase of removal rate of butanone was lower than the increase in Cox,0. However, NH2OH·HCl concentration increased faster in Cox,0 of 1.70 M than that in Cox,0 of 0.92 M because of the same reaction volume in these two conditions. The final conversions in Cox,0 of 0.92 and 1.70 M were 83.1% and 79.7%, respectively, and NH2OH·HCl concentrations in Cox,0 were 75.5 (1.09 M) and 174.4 g/L (2.51 M), respectively. It turned out that the increase in Cox,0 did not affect the final PVMR conversion much, and the high ionic concentration of NH2OH·HCl also did not give any negative impact on the PVMR performance. An experiment on Cox,0 as high as 3.94 M was also carried out. Results show that this PVMR could stably work for 140 h, and the conversion was continuously improved from the equilibrium conversion of 10% to 65%. The high ionic concentration did not deteriorate the PVMR process; even NH2OH·HCl reached its saturation point (about 510 g/L, 7.33 M) and crystallized in the reaction system. Figure 11 showed the crystallization picture of NH2OH·HCl in the PVMR unit. In situ removal of the NH2OH·HCl precipitate in PVMR should be considered to further promote the conversion in the future. 3.5. Membrane Stability. To investigate the tolerance of the PDMS membrane in acidic and ionic environments in the reaction mixture, pervaporation performances for the separation of the butanone/water mixture were compared between a fresh PDMS membrane and a PDMS membrane used in PVMR for over 250 h. The butanone fluxes for the two membranes were found to be similar, i.e., 241.4 g/m2 h for the fresh membrane and 247.7 g/m2 h for the used membrane. This observation indicated that the PDMS membrane offered

Figure 9. Effects of initial butanoxime concentration (Cox,0) on PVMR conversion and NH2OH·HCl concentration (temperature: 40 °C, the dashed lines represent the equilibrium conversion).

Equilibrium conversion (Xeq) was found to decrease with increased initial butanoxime concentrations. This result can be theoretically explained by the formula of equilibrium constant (Keq), shown in eq 5. The formula of Keq was derived from the kinetic characteristics of the butanoxime hydrolysis reaction,14−16 i.e., the first-order kinetics of the forward reaction and the second-order kinetics of the backward reaction. By 104

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Figure 11. Crystallization of NH2OH·HCl in PVMR (initial butanoxime concentration: 3.94 M, temperature: 60 °C).

protonated complex,14−16 which sharply decreased the concentration of H+ in the reaction mixture. All results above indicated that the reaction environment of butanoxime hydrolysis almost had no risk of deteriorating the PDMS membrane in our experimental conditions. Nevertheless, the molar ratio of acid/oxime higher than one was not recommended because PDMS membrane may be deteriorated by the excessive acid.54

excellent stability in this application. The SEM (Figure 12) of the PDMS membrane surfaces also showed that membrane fouling was insignificant.

4. CONCLUSIONS This study aimed to provide a cost-effective technique for NH2OH·HCl production through the A−O−H route and focused on solving its limited step, i.e., oxime hydrolysis reaction, by using the PVMR method. It turned out that the membrane selectivity for butanone/water was higher than that of butanoxime/water by using a PDMS membrane. The upstream composition, containing TBA and butanone, could play a small role on the PVMR performance. Higher than 80% conversion was obtained in all selected operated temperatures ranging from 30 to 60 °C, in which the equilibrium conversions were just about 20%. Increasing initial reactant concentration would extend the reaction time but would not influence the final conversion. When using a high initial reactant concentration of 3.94 M, NH2OH·HCl would crystallize out in PVMR. The PDMS membrane presented excellent tolerance in the butanoxime hydrolysis reaction mixture and stably worked in the PVMR process for at least 250 h without obvious deterioration. However, the PVMR was limited by long reaction time because of the insufficient separation performance for removing butanone from the reaction mixture. With further improvement on membrane material in the future, the proposed PVMR-aided A−O−H route has significant potential for NH2OH·HCl production.

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AUTHOR INFORMATION

Corresponding Author

*Phone: 86-10-64423628. Fax: 86-10-6443-6781. E-mail: [email protected]. Corresponding author address: P.O. Box 1#, NO. 15, N· 3rd Ring Rd East, Beijing 100029, People’s Republic of China.

Figure 12. SEM picture of the PDMS membrane surface: (a) fresh membrane and (b) membrane used in PVMR for over 250 h.

Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors are grateful to the financial support of the National Natural Science Foundation of China (No. 21276011), the National Natural Science Foundation of China (No. 21076012), the Beijing Municipal Natural Science Foundation (No. 3121003), the National High Technology Research and

To clarify the phenomenon above, the H+ concentrations of the reaction mixture were detected and turned out to maintain around 0.1 M throughout the PVMR process. This phenomenon may be attributed to the fact that most of the butanoxime, in the presence of acid solution, were immediately protonated and form butanoxime ion [butanoxime·H]+ or 105

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(16) Ikonomov, N. N. Oxime hydrolysis in hydrochloric acid solutions. J. Serb. Chem. Soc. 1967, 32, 285. (17) Zarakhani, N. G.; Budylina, V. V.; Vinnik, M. I. Kinetics and mechanism of reactions in concentrated acid solutions. X. Kinetics of hydrolysis of cyclopentanone oxime in aqueous solutions of hydrochloric and sulfuric acids. Zh. Fiz. Khim. 1965, 39, 1863. (18) Ten, P. K.; Field, R. W. Organophilic pervaporation: an engineering science analysis of component transport and the classification of behaviour with reference to the effect of permeate pressure. Chem. Eng. Sci. 2000, 55, 1425. (19) Mafi, A.; Raisi, A.; Hatam, M.; Aroujalian, A. A mathematical model for mass transfer in hydrophobic pervaporation for organic compounds separation from aqueous solutions. J. Membr. Sci. 2012, 423−424, 175. (20) Qin, Y.; Sheth, J. P. Pervaporation Membranes That Are Highly Selective for Acetic Acid over Water. Ind. Eng. Chem. Res. 2003, 42, 582. (21) Brazinha, C.; Barbosa, D. S.; Crespo, J. G. Sustainable recovery of pure natural vanillin from fermentation media in a single pervaporation step. Green Chem. 2011, 13, 2197. (22) Lipnizki, F.; Field, R. W.; Ten, P.-K. Pervaporation-based hybrid process: a review of process design, applications and economics. J. Membr. Sci. 1999, 153, 183. (23) Benedict, D. J.; Parulekar, S. J.; Tsai, S.-P. Pervaporation-assisted esterification of lactic and succinic acids with downstream ester recovery. J. Membr. Sci. 2006, 281, 435. (24) Agirre, I.; Güemez, M.; van Veen, H.; Motelica, A.; Vente, J.; Arias, P. Acetalization reaction of ethanol with butyraldehyde coupled with pervaporation. Semi-batch pervaporation studies and resistance of HybSi membranes to catalyst impacts. J. Membr. Sci. 2011, 371, 179. (25) Gubicza, L.; Nemestóthy, N.; Fráter, T.; Bélafi-Bakó, K. Enzymatic esterification in ionic liquids integrated with pervaporation for water removal. Green Chem. 2003, 5, 236. (26) Y Lim, S.; Park, B.; Hung, F.; Sahimi, M.; Tsotsis, T. Design issues of pervaporation membrane reactors for esterification. Chem. Eng. Sci. 2002, 57, 4933. (27) Benedict, D. J.; Parulekar, S. J.; Tsai, S.-P. Esterification of lactic acid and ethanol with/without pervaporation. Ind. Eng. Chem. Res. 2003, 42, 2282. (28) Feng, X.; Huang, R. Y. Studies of a membrane reactor: esterification facilitated by pervaporation. Chem. Eng. Sci. 1996, 51, 4673. (29) Budd, P. M.; Ricardo, N. M.; Jafar, J. J.; Stephenson, B.; Hughes, R. Zeolite/polyelectrolyte multilayer pervaporation membranes for enhanced reaction yield. Ind. Eng. Chem. Res. 2004, 43, 1863. (30) Sarkar, B.; Sridhar, S.; Saravanan, K.; Kale, V. Preparation of fatty acid methyl ester through temperature gradient driven pervaporation process. Chem. Eng. J. 2010, 162, 609. (31) Diban, N.; Aguayo, A. T.; Bilbao, J.; Urtiaga, A.; Ortiz, I. Membrane reactors for in situ water removal: A review of applications. Ind. Eng. Chem. Res. 2013, 52, 10342. (32) Aiouache, F.; Goto, S. Reactive distillation−pervaporation hybrid column for tert-amyl alcohol etherification with ethanol. Chem. Eng. Sci. 2003, 58, 2465. (33) Pera-Titus, M.; Llorens, J.; Cunill, F. Technical and economical feasibility of zeolite NaA membrane-based reactors in liquid−phase etherification reactions. Chem. Eng. Process. 2009, 48, 1072. (34) Kiatkittipong, W.; Assabumrungrat, S.; Praserthdam, P.; Goto, S. A pervaporation membrane reactor for liquid phase synthesis of ethyl tert-butyl ether from tert-butyl alcohol and ethanol. J. Chem. Eng. Jpn. 2002, 35, 547. (35) Agirre, I.; Güemez, M. B.; Motelica, A.; van Veen, H. M.; Vente, J. F.; Arias, P. L. The conceptual design of a continuous pervaporation membrane reactor for the production of 1,1-diethoxy butane. AIChE J. 2012, 58, 1862. (36) Van der Bruggen, B. 3.06-Pervaporation Membrane Reactors. In Comprehensive Membrane Science and Engineering; Drioli, E., Giorno, L., Eds.; Elsevier: Oxford, 2010.

Development Program of China (No. 2008AA062301-04), and Ph.D. Programs Foundation of Ministry of Education (No. 200800100001)

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NOMENCLATURE Ci = concentration for component i (M) Ji = flux through the membrane for component i (g/m2h) Pi = permeability of the membrane for component i (g/(m2· h·Kpa)) Keq = equilibrium constant of oxime hydrolysis reaction (M) ni = molar amount of component i (mole) ni,0 = initial molar amount of component i (mole) Xeq = equilibrium conversion of oxime hydrolysis reaction (%)

Greek Letters

α selectivity Subscripts

i,j eq hc ke ox w

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components equilibrium hydroxylamine chloride ketone oxime water

REFERENCES

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DOI: 10.1021/ie502811e Ind. Eng. Chem. Res. 2015, 54, 100−107

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DOI: 10.1021/ie502811e Ind. Eng. Chem. Res. 2015, 54, 100−107