Formation of a Third Liquid Phase and Its Reuse for Dibenzyl Ether Synthesis in a Tetraalkylammonium Salt Phase Transfer Catalytic System

This paper describes the formation of a third liquid phase in a phase transfer catalytic system in the presence of benzyl alcohol and potassium hydroxide, where dodecane and tetraalkylammonium bromide serve as organic solvent and catalyst, respectively. In this kind of system, a symmetrical ether (dibenzyl ether) was synthesized from benzyl chloride and benzyl alcohol at 323 K. In particular, the investigation demonstrates that the observed reaction rate constant depends on the length of the alkyl group of the catalyst. Tetrabutylammonium bromide exhibits the highest catalytic activity among the catalysts explored. With respect to the reuse of the third liquid phase, the results confirm that there is no decrease in phase transfer catalytic activity in three consecutive runs.     

Synergetic Effect of Tetrabutylammonium Bromide and Polyethylene Glycol as Phase Transfer Catalysts in Third Liquid Phase for Benzyl-n-Butyl Ether Synthesis

This study intends to clarify the forming characteristics of third liquid phase in phase transfer catalytic system in the presence of n-butanol and potassium hydroxide when tetrabutylammonium bromide, polyethylene glycol and their mixture serve as phase transfer catalyst, respectively. At 323 K, the three catalytic systems were applied to yield benzyl-n-butyl ether from benzyl chloride and n-butanol, and they performed distinct reaction activity. Among them, a combination of two kinds of catalyst results in a synergetic effect in reaction activity.     

INFLUENCE OF MIXING INTENSITY ON THE MASS TRANSFER COEFFICIENT ACROSS LIQUID-LIQUID INTERFACES

The influence of mixing intensity on the liquid-liquid mass transfer have been investigated using a binary system (water/n-butanol) in a modified stirred cell type contactor which overcomes the shortcomings associated with the previous contactors. It is observed that the mass transfer coefficient is affected by the degree of mixing intensity in both phases. The dependence of the aqueous and organic mass transfer coefficients on the mixing rate is about the same when both phases are agitated at the same speed and these coefficients become asymptotic values for the coefficients obtained at non identical agitation rate in both phases.     

Numerical simulation of influence of mass transfer on phase transfer catalytic reaction

Mass transfer with chemical reaction by liquid/liquid phase tranfer catalysis (LLPTC) for an isothermal batch reactor was analyzed. The results for the phase transfer catalyzed reaction system can be generally described by a pseudo first-order hypothesis, whereas the reaction system can be controlled by simultaneous mass transfer of the catalysts between two liquid phases and chemical reaction in the organic phase. The mass transfer limitation is mainly from the mass transfer step of QX from the organic phase to the aqueous phase. The concept of catalyst-effectiveness vs. physically meaningful parameters in a liquid/liquid phase transfer catalyzed reaction is introduced. The catalyst effectiveness is increased as the mass transfer factors increase, the ratio of reaction rate coefficients of aqueous forward reaction to organic increases, and the equilibrium constant in the aqueous solution increases.     

相转移催化合成N,N-二乙基氨基乙基-4-甲基苄基醚

以二乙氨基乙醇和对甲基氯化苄为原料,以四丁基溴化铵为相转移催化剂,合成了N,N－二乙基氨基乙基－4－甲基苄基醚,产率最高可达87．78％。考察了催化剂、温度、反应时间以及氢氧化钠用量对反应的影响,确定了最佳反应条件。产物经过沸点、折光率、红外光谱、氢质子核磁共振谱认证。     

苄基-2-萘基醚的相转移催化合成研究

以四丁基溴化铵为相转移催化剂,2-萘酚和氯化苄为原料合成苄基-2-萘基醚,采用单因素实验法,得到最佳配比为2-萘酚∶氯化苄∶催化剂∶氢氧化钠=1∶1.05∶0.028∶1.10(摩尔比)。在最佳反应温度100°C下反应1.5h,苄基-2-萘基醚的收率可达到85.32%以上,产品纯度达到99.6%以上。     

Phase transfer catalysis of alkaline hydrolysis of n-butyl acetate: Comparison of performance of batch and micro-reactors

The hydrolysis of n-butyl acetate with aqueous sodium hydroxide was studied in the batch mode as well as in the continuous mode in a micro-reactor. The progress of the reaction was analyzed both with and without a phase transfer catalyst. The concentration of the unreacted sodium hydroxide in the aqueous phase was determined by titration with hydrochloric acid to monitor the progress of the reaction. The performance of the two systems is studied for different operating conditions, i.e. concentrations of reactants, stirring speeds (in batch mode) and flow rates (in continuous mode). Conditions are identified when the performance of the micro-reactor system is superior to that of the batch system. To understand this better the performance of a 1 mm channel and a 0.4 mm channel are compared with that of the batch reactor.     

对苯二酚二苄醚合成的新工艺

采用对苯二酚与氯化苄在适量还原剂 Na2 S2 O4存在下 ,用相转移催化剂催化合成对苯二酚二苄醚的新工艺 ,最佳工艺条件为 :对苯二酚 :氯化苄 :氢氧化钠 =1∶ 3∶ 2 ,还原剂用量为 5 % ,氢氧化钠浓度为 3 3 % ,反应温度 70～ 75°C,反应时间 3 h。此法革除了反应溶剂 ,改善了产品的色泽 ,缩短了反应时间 ,收率 96 .5 5 % ,mp1 2 4 .5～ 1 2 5°C。     

BENZYL ACETATE FROM PHASE TRANSFER CATALYZED ACETATE DISPLACEMENT OF BENZYL CHLORIDE

The overall production rate equation of benzyl acetate by L-L phase transfer catalyzed acetate displacement of benzyl chloride were derived. The experimental results of the effects of stirring speed, structure and amount of catalyst, reaction temperature, amount of sodium acetate, and phase volume-ratio on the production rate of benzyl acetate are elucidated with the rate equation. Benzyltributylammonium chloride is the recommended catalyst. The apparent activation energy of the displacement of benzyl chloride with the ion pairs of benzyltributylammonium acetate is 8.13kcal/mol. Sodium sulfate is a suitable salt to improve the partition coefficient of the phase transfer catalyst. The cocatalyst, sodium iodide, can greatly improve the production rate of benzyl acetate when its amount do not exceed 3 mol% of the substrate, benzyl chloride. Under the conditions of 5mol% benzyltributylammonium chloride, phase volume-ratio 0.429, stirring speed 520 rpm, reaction temperature 70°C, and 50% aqueous sodium acetate, about 80% yield of benzyl acetate can be obtained within 2 hrs. of reaction time.     

Highly Selective Extraction and Transport through a Bulk Liquid Membrane of L-Cysteine Using [K • DC18C6]+ Complexes

It is shown that dicyclohexyl-18-crown-6 (DC18C6) dissolved in chloroform can extract efficiently and selectively the anionic form of L-cysteine from aqueous solutions containing potassium ions. This ability depends on the aqueous phase pH and type of the salt used in this phase. Under optimized conditions L-cysteine can be quantitatively extracted into the organic phase. In such conditions there was no detectable extraction of amino acids tryptophan, tyrosine, leucine, methionine, arginine, asparagine, aspartic acid, glycine, serine, and threonine. The transport of L-cysteine from potassium chloride/potassium hydroxide solution across a bulk liquid membrane containing DC18C6 dissolved in chloroform has been investigated. The parameters influencing the transport efficiency such as the pH of the feed phase, the kind and concentration of the receiving phase, carrier concentration, the kind of organic diluents, and time were examined and optimized. An efficient stripping at the membrane/stripping phase interface was found using hydrochloric acid as strippant. Selectivity of the proposed system was evaluated by performing a series of competitive transport experiments on the binary mixtures containing L-cysteine with the competitor amino acids noted earlier. This investigation exhibits excellent transport selectivity of the process towards L-cysteine with respect to the examined amino acids.     

微波作用下壳聚糖的O-苯甲基化反应

在微波辐射下 ,壳聚糖与氯甲苯在相转移催化剂和NaOH水溶液中能迅速地发生反应 ,生成相应的O -苯甲基化产物 ,取代度可达 0 .6 5。     

氧化石墨烯/自湿润流体脉动热管的传热特性

以氧化石墨烯分散液(浓度为0.5mg/mL)和正丁醇水溶液(质量分数为0.5%)的混合溶液(体积比2:5)为工质,充液率为50%,对不同加热功率条件下环路脉动热管稳定运行的传热特性进行实验研究,并与正丁醇水溶液和去离子水的传热性能进行对比,分析了混合溶液在脉动热管稳定运行时冷热端温差和传热热阻的变化特点,探究了氧化石墨烯对自湿润流体传热性能的影响。研究结果表明:在自湿润流体中加入氧化石墨烯能够强化脉动热管的传热特性,但是和脉动热管的加热功率密切相关;在低加热功率下,氧化石墨烯对自湿润流体脉动热管的传热特性没有强化作用;随着加热功率的增加,强化作用明显增强,而当加热功率过大时,强化作用又会逐渐减弱。     

乙醇和正丁醇添加剂对喷雾冷却的影响

喷雾冷却是高功率电子器件冷却领域最具有发展前景的散热方式。利用在去离子水中添加不同浓度低醇类（乙醇、正丁醇）添加剂以提升喷雾冷却换热性能的方法,搭建了喷雾冷却实验平台并就添加剂浓度对传热特性的影响进行了实验研究。实验结果表明在去离子水中加入乙醇和正丁醇,存在强化换热的最佳添加剂浓度。在还未达到最佳浓度值之前,添加剂浓度越高,喷雾冷却换热效果越好。乙醇的最佳浓度为4%,正丁醇的最佳浓度为0.5%。     

BENZYL ALCOHOL FROM PHASE TRANSFER CATALYZED WEAKLY ALKALINE HYDROLYSIS OF BENZYL CHLORIDE

The chemical and mass transfer processes were formulated and explained for the system initially composed of BzCl/BzR₃”NCI, R'COONa, H₂O. The effects of the size of the alkyl group of benzyltrialkylammonium chloride, the pH of the aqueous phase, the concentration of the pH controlling agent, aqueous NaOH, the stirring speed, the reaction temperature, the amounts of the cocatalysts, sodium formate and sodium acetate, and the initial volume-ratio of benzyl chloride to water on the product distribution and the production rate of benzyl alcohol were investigated experimentally.

The experimental results show that the pH of the aqueous phase is the most important factor. With sodium formate as the cocatalyst it should be controlled within 7.2-7.7, while with sodium acetate it should be within 9.5-10. Under the suitable pH and 110°C and other suitable conditions, 95% yield of benzyl alcohol can be obtained within 3 hrs of reaction time.     

Heat Transfer Studies in an Agitated Vessel During Aqueous Alkaline Depolymerization of Poly(Ethylene Terephthalate) (PET) Waste

Depolymerization reactions of poly(ethylene terephthalate) (PET) waste in aqueous sodium hydroxide solution were carried out in a batch reactor at 150°C at atmospheric pressure. Disodium terephthalate (terephthalic acid salt) and ethylene glycol (EG) remain in the liquid phase. Terephthalic acid (TPA) salt was converted into TPA. The produced monomeric products (TPA and EG) were recovered. Various design parameters were estimated. Design of a batch reactor was undertaken for depolymerization of PET waste in aqueous sodium hydroxide solution. As expected, the Reynolds numbers, Prandtl numbers, Nusselt numbers, coil-side heat transfer coefficients, and overall heat transfer coefficients were consistent with the fluid velocities. It shows excellent potential for commercialization of the depolymerization of PET waste.     

Dehydrogenation of 11α‐hydroxy‐16α, 17‐epoxyprogesterone by encapsulated Arthrobacter simplex cells in an aqueous/organic solvent two‐liquid‐phase system

BACKGROUND: Arthrobacter simplex cells immobilised in sodium cellulose sulfate/poly‐dimethyl‐diallyl‐ammonium chloride microcapsules were used for the microbial dehydrogenation of 11α‐hydroxy‐16α,17‐epoxyprogesterone to 11α‐hydroxy‐16α,17α‐epoxypregn‐1,4‐diene‐3,20‐dione in an aqueous/organic solvent two‐liquid‐phase system, which is a key reaction in the production of glucocorticoid pharmaceuticals. The aim of the study was to establish a suitable aqueous/organic solvent two‐liquid‐phase system for performing semi‐continuous production in an airlift loop reactor by encapsulated A. simplex cells with the addition of suitable surfactants to achieve a higher yield of the product. RESULTS: n‐Hexane was selected as the most suitable organic solvent. In optimised Tween‐80 emulsion feed mode the conversion in the airlift loop reactor was as high as 97.54% when the time of reaction was 2 h, and the reaction time was greatly shortened. In semi‐continuous production the cultivation with immobilised cells was carried out for five batches in total. The conversion in each batch was above 95% and the enzymatic activity still remained quite high after five batches of biotransformation. CONCLUSION: The results showed that performing the conversion by this method shortened the reaction time and increased the productivity, thus demonstrating the great potential of the method for the dehydrogenation of 11α‐hydroxy‐16α,17‐epoxyprogesterone. Copyright © 2008 Society of Chemical Industry     

A LIMITATION OF REUSING THE CATALYST IN TRI-LIQUID-PHASE CATALYTIC SYSTEMS

This work demonstrates important factor influencing the reusability of the phase transfer catalyst in the third liquid phase in addition to the role of the possible loss of catalyst due to the dissolution of the catalyst into the aqueous and organic phases. When the catalyst might react with the byproducts, in addition to reacting with the organic substrate and aqueous nucleophile, it would lose its catalytic activity. The substitution reaction between the organic substrate and an aqueous nucleophile (sodium phenolate) with tetra-n-butylammonium bromide as a phase-transfer catalyst was employed as a model reaction and was performed in a batch reactor. Three organic substrates, including allyl bromide, n-butyl bromide, and ethyl 2-bromoisobutyrate, were tested. Each of the third liquid phases formed in these tri-liquid-phase catalytic systems was utilized three times to observe the change in the activity of the catalyst. The catalyst in the third liquid phase can be reused without any loss of its catalytic activity when allyl bromide or n-butyl bromide is utilized as the organic substrate; however, the catalytic activity declines when ethyl 2-bromoisobutyrate is the organic reactant. Therefore, the organic reactant plays a crucial role in determining whether the catalyst can be reused or not.     

A LIMITATION OF REUSING THE CATALYST IN TRI-LIQUID-PHASE CATALYTIC SYSTEMS

This work demonstrates important factor influencing the reusability of the phase transfer catalyst in the third liquid phase in addition to the role of the possible loss of catalyst due to the dissolution of the catalyst into the aqueous and organic phases. When the catalyst might react with the byproducts, in addition to reacting with the organic substrate and aqueous nucleophile, it would lose its catalytic activity. The substitution reaction between the organic substrate and an aqueous nucleophile (sodium phenolate) with tetra-n-butylammonium bromide as a phase-transfer catalyst was employed as a model reaction and was performed in a batch reactor. Three organic substrates, including allyl bromide, n-butyl bromide, and ethyl 2-bromoisobutyrate, were tested. Each of the third liquid phases formed in these tri-liquid-phase catalytic systems was utilized three times to observe the change in the activity of the catalyst. The catalyst in the third liquid phase can be reused without any loss of its catalytic activity when allyl bromide or n-butyl bromide is utilized as the organic substrate; however, the catalytic activity declines when ethyl 2-bromoisobutyrate is the organic reactant. Therefore, the organic reactant plays a crucial role in determining whether the catalyst can be reused or not.     

超声波相转移催化合成对羟基苯甲酸苄酯

采用超声波相转移催化技术,以四丁基溴化铵为相转移催化剂,先将对羟基苯甲酸和碳酸钾成盐,再使对羟基苯甲酸钾盐、氯化苄在水和二甲苯的二相体系中酯化合成对羟基苯甲酸苄酯。经正交实验确定最佳条件:超声功率160W,超声温度85~90℃,超声时间1h,氯化苄与对羟基苯甲酸摩尔比为2:1,四丁基溴化铵与对羟基苯甲酸摩尔比为0.02:1,二甲苯与水体积比为1:4。产率可达90.3%。     

Interfacial mass transfer in stripping of phenylalanine in a liquid-liquid extraction process

Stripping of L-phenylalanine from organic phase containing ALIQUAT 336 (tri-octyl-methyl-ammonium chloride) as complexing agent was studied using a stirred transfer cell. The study investigated the effects of concentration of the stripping agent, potassium chloride, in strip solution and temperature on mass transfer rates. A two-film model based on organic and aqueous phases mass transfer resistances was proposed to estimate mass transfer coefficients and it predicted adequately the experimental time-concentration data at different conditions studied. A comparison of mass transfer coefficients for stripping and previously published results on extraction for the same system was made.