相转移催化合成对氟苯氧丙酸

采用对氟苯酚和3-氯丙酸为起始原料,用聚乙二醇PEG-400和KI双组分催化剂合成对氟苯氧丙酸。本文探讨了原料配比、反应时间和催化剂对产物收率的影响,找到了较佳的合成条件。     

Interfacial mass transfer in extraction of amino acid by aliquat 336 in organic phase

Reactive extraction of L -phenylalanine from alkaline aqueous solution into xylene in the presence of tri-octyl-methyl-ammonium chloride (ALIQUAT 336) as complexing agent was studied using a stirred transfer cell. The study investigated the effects of carrier concentration and temperature on mass transfer rates. Transfer rate across the interface in the presence of surfactant molecules was also studied. A two-film model was proposed by considering film mass transfer resistances at the aqueous and organic phases. The model predicted adequately the experimental time-concentration data at different carrier concentrations and temperatures. The model was modified to take into account the presence of surfactant in the organic phase.     

Oxidation of propionic acid solutions

Wet air oxidation is a process in which organic materials in the aqueous phase are oxidized by air at temperatures between 300°F and 600°F and pressures of 1000-1800 psia. To improve our understanding of the process, its kinetics were studied using a propionic acid solution to simplify both analysis and rate measurements. The aim of the research was to define the regime where the reaction rate is kinetically controlled, to develop a model for the reaction rate and to interpret the model in terms of mechanism. Oxidation appears to proceed homogeneously in the aqueous phase and is probably kinetically controlled between 450° and 550°F. The oxidation appears to take place via two principal routes. Approximately half the propionic acid is oxidized completely to carbon dioxide while the oxidation of the remainder apparently proceeds via acetaldehyde as an intermediate to acetic acid. Acetic acid oxidizes only at a very low rate. A power law rate expression was developed which adequately described the oxidation of propionic acid solutions.     

Desorption of isoamylene from loaded acid liquors

The desorption of 2-methyl-2-butene (isoamylene) from loaded sulphuric acid solutions, having an acid strength of about 60 per cent (w/w) and loading upto 0·45 g mole of isoamylene per g mole of H₂SO₄, was found to be preceded by a fast reaction, which occurred in the film adjacent to the interface. The specific rates of desorption of isoamylene into inert hydrocarbons—n-heptane and toluene and an inert gas—nitrogen, were found to be proportional to the isoamylene concentration j, expressed as g mole of isoamylene per g mole of H₂SO₄, and agreed among themselves at the same value of j.The technique of desorption preceded by a fast reaction was employed for the measurement of effective interfacial area in liquid—liquid and gas—liquid agitated contactors. The absorption of isobutylene into fresh and loaded solutions of sulphuric acid was also used for the measurement of effective interfacial area in gas—liquid agitated contactors for comparative purposes. The values of effective interfacial area for the gas—liquid system obtained by the desorption technique were found to be comparable with those obtained from the absorption of isobutylene in fresh and loaded solutions of sulphuric acid, under otherwise comparable conditions.     

络合萃取法回收生物油加氢水相中的乙酸

应用络合萃取法对生物油加氢水相中的乙酸进行回收,系统地研究了络合剂和稀释剂的种类、络合剂含量对络合萃取效率的影响,以及化学组分不同的生物油加氢水相的络合提取效果。结果表明,选择三辛胺(TOA)为络合剂,异辛醇为稀释剂,络合剂的用量占萃取剂体系体积分数50%~60%,萃取剂与水相体积比为1时,对生物油加氢水相中乙酸的提取效率最高达到84.4%。而且发现水相中其他的有机酸,如丙酸、丁酸和苯酚也被提取了出来。经络合萃取处理后,生物油加氢水相的化学需氧量(COD)大大降低,降低了后续水处理成本。     

络合萃取法分离发酵液中丙酸

利用络合萃取法对模拟溶液和发酵液中的丙酸分离进行研究。络合剂、稀释剂筛选结果表明:选用甲基三辛基氯化胺(MTAC)为络合剂、正辛醇为稀释剂时,萃取受pH值和无机阴离子影响较小,对丙酸具有较高的选择性。以1.2mol/L的MTAC为萃取有机相,有机相/水相(体积比)为3的条件下,萃取15min即能达到平衡;该系统适用于较高浓度丙酸发酵液萃取,经4级萃取丙酸萃取率达86.2%。     

Effect of a water-insoluble organic acid on amine extraction of acetic acid from aqueous solutions. Equilibrium studies

The effect of a water-insoluble organic acid, di(2-ethylhexyl)phosphoric acid (D2EHPA), on the extraction equilibrium of acetic acid from aqueous media with xylene solutions of tri-n-octylamine (TOA) was systematically investigated. In the absence of D2EHPA, the formulation of the extracted species in the organic phase and equilibrium constants for the formation of these species were numerically determined. Synergistic and antagonistic effects on the extraction of acetic acid were observed in the presence of D2EHPA, mainly depending on the concentration of TOA and the concentration ratio of D2EHPA to TOA. Finally, the influence of temperature on the extraction of acetic acid with TOA and/or D2EHPA was investigated.     

Assessment of propionic acid adsorption performance on the phase transformation of calcium sulfate hemihydrate to dihydrate

The adsorption of propionic acid during the transformation process of calcium sulfate hemihydrate to calcium sulfate dihydrate was studied in a batch-type crystallizer with respect to contact time, additive concentration and temperature in pure media, and in the presence of propionic acid used as an additive. The adsorbent was characterized by X-ray diffraction, scanning electron microscopy and thermogravimetric analysis combined with a Fourier-transform infrared spectrometer and a mass spectrometer. The adsorption characteristics were also investigated by means of evaluating the isotherm, kinetic and thermodynamic properties. The results of this investigation showed that propionic acid can serve as a good accelerator for the transformation process from calcium sulfate hemihydrate to dihydrate.     

Three phase partitioning coupled with ultrasound for the extraction of ursolic acid and oleanolic acid from Ocimum sanctum

In this study, three phase partitioning (TPP) is coupled with ultrasound for the extraction of ursolic acid (UA) and oleanolic acid (OA) from Ocimum sanctum leaves and process has been optimized to obtain maximum recovery. TPP is a relatively novel bioseparation technique used for the extraction, concentration and purification of enzymes and natural products. The technique of TPP was explored for the extraction of ursolic acid (UA) and oleanolic acid (OA) from O. sanctum leaves. The influence of various process parameters (pH, ammonium sulfate saturation, crude extract to t-butanol ratio, time and feed loading) on the extraction efficiency was investigated to get highest yield. The optimized conditions were found to be as follows: time – 120 min, pH – 7, ammonium sulfate saturation – 50% w/v, crude extract to t-butanol ratio – 1:1 and feed loading – 7.5% w/v. The highest yield obtained for UA and OA was 79.48% and 80.67% respectively under optimized conditions of TPP. Compared with TPP higher yield (83.36% and 85.58%) was obtained by ultrasound assisted TPP (UATPP) at 40 kHz and 180 W power and the time required was only 14 min as compared to 120 min of TPP. The extraction yield obtained was also compared with conventional solvent extraction and TPP-ultrasound was found to be an attractive technique for the extraction of UA and OA from O. sanctum leaves.     

The production of propionic acid from sugars by fermentation through lactic acid as an intermediate

As an alternative to propionic acid production from sugars by species of propionibacteria, propionic acid may be produced from sugars through lactate as an intermediate. Propionibacteria are actually able to utilize lactate as a substrate much more rapidly than glucose. In this study, Lactobacillus xylosus and Propionibacterium shermanii were utilized to convert glucose and xylose to propionate through lactate as an intermediate. Pure culture batch studies were carried out to obtain fermentation parameters for the two cultures. The pure cultures were then combined in a mixed culture series arrangement designed to prevent nutrient limitation. Finally, propionic acid production from lactate was demonstrated in a cross-linked immobilized cell reactor using lactate added to the medium and produced by L. xylosus in a continuous stirred tank reactor. Productivities of 14 g dm^?3 h^?1 at a 9 min residence time (2·1 g dm^?3 propionate) and 2 g dm^?3 h^?1 at a 9·9 h residence time (19·7 g dm^?3 propionate) were obtained without pH control.     

Estimation of equilibrium parameters using differential evolution in reactive extraction of propionic acid by tri-n-butyl phosphate

The graphical and conventional optimization methods, used for the estimation of equilibrium parameters, do not guarantee the global optimum values. In this study, the equilibrium parameters are estimated using a well proven evolutionary based optimization routine [differential evolution (DE)]. For the estimation of stoichiometry and equilibrium constants, experiments are carried out for the reactive extraction of propionic acid using tri-n-butyl phosphate (TBP) dissolved in n-decane (inert diluent) and 1-decanol (modifier). The number of TBP molecules (n) in the acid:TBP complex and equilibrium extraction constant (K_E) using 1:1 volume ratio of 1-decanol and n-decane as a diluent, are determined through proposed mathematical model using graphical methods as well as the differential evolution algorithm (DE, an optimization routine) and found that the predicted values of distribution coefficient (K_D) using DE are closely matching with the experimental values of K_D. 1:1 complexes between TBP and acid are formed in most of the cases. The enthalpy and entropy of reactive extraction of propionic acid using TBP are also determined and found to be −12.47 kJ mol⁻¹ and −32.42 J mol⁻¹ K⁻¹, respectively. The results of present study will be useful to intensify the recovery of propionic acid from fermentation broth (bio-separation) and aqueous waste stream.     

Design parameters of boric acid production process from colemanite ore in the presence of propionic acid

In this study, three different boric acid production process alternatives which can be performed in the presence of propionic acid and/or calcium propionate were evaluated. The process in which calcium propionate is the recycling component was selected as the best alternative and modeled. Some of the design parameters were determined for the selected process. These parameters are solubility change of boric acid in the presence of calcium propionate at 25 °C, 35 °C and 75 °C, precipitation risk of calcium borate components in concentrated boric acid solutions containing calcium propionate, and the effect of calcium propionate on the solution pH with respect to free sulfuric acid concentration. According to the determined parameters, principal reactions occurred in the process, and other process parameters obtained by industrial practice, mass balances were conducted and all flow rates were calculated. In the process, calcium propionate concentration in production liquor must be kept lower than 3% and the reaction must be carried out without any free sulfuric acid in order to perform the process according to the model.     

Impurity control in the production of boric acid from colemanite in the presence of propionic acid

The most important problem in boric acid production from colemanite ores with H₂SO₄ is the formation of MgSO₄ impurity due to the partial decomposition of clay minerals in the reaction media. Increase of MgSO₄ concentration in solution may be balanced by the discharge of mother liquor which leads to decrease the efficiency of the process. Therefore, the intake rate of MgSO₄ should be lowered for obtaining high purity product in a high yield process. In order to control the intake rate of MgSO₄ impurity, propionic acid, which does not decompose the clay minerals, is used in an acid mixture with H₂SO₄. Batch wise laboratory experiments showed that the higher the propionic acid in reacting acid mixture, the lower the magnesium intake rate. When 10% of required H₂SO₄ replaced by propionic acid, magnesium intake concentration decreased to approximately half of the value obtained in the reaction with H₂SO₄.     

丙酸预处理秸秆的化学降解

选择催化效率高的固体酸SO42-/Fe2O3催化剂催化水解秸秆。用不同浓度的丙酸对秸秆进行预处理,考察了反应温度、反应时间、催化剂与秸秆的质量比以及有机酸的浓度等因素对秸秆水解反应的影响。结果表明:在丙酸浓度为100g/L、温度为120℃、m(催化剂)∶m(秸秆)为2.5∶1的条件下固体酸催化水解秸秆反应1h,得到的总糖含量最高为51.77%,比未经过预处理的总糖含量高6.41%。     

玉米化工醇重组分中有机羧酸络合萃取过程

采用络合萃取技术,以磷酸三丁酯(TBP)为络合剂进行玉米化工醇重组分络合萃取有机羧酸过程研究。探讨了萃取剂浓度、稀释剂的选择、萃取时间、油水比(O/W)、釜残液酸度、萃取级数对萃取平衡常数(D)的影响。结果表明,经四级萃取后,玉米化工醇重组分中有机酸萃取率可达90.7%。     

Synthesis of methoxypoly(oxyethylene)propionic acid

Summary We have investigated the reaction chemistry of methoxypoly(oxyethylene)propionitrile, I, to synthesize methoxypoly(oxyethylene)propionic acid, II. We have found that II can be prepared by converting I first to the corresponding amide. Subsequent hydrolysis of the amide then yields II. Received: 4 March 1999/Revised version: 17 June 1999/Accepted: 17 June 1999     

Batch kinetics and modelling of propionic acid fermentation

Batch propionic acid fermentation kinetics was studied using five different initial concentrations of lactose (i.e., 37 g/L, 45g/L, 50g/L, 57 g/L and 73 g/L) at constant temperature (30°C) and pH (6.5) under anaerobic conditions using Propionibacterium acidipropionici (ATCC 4875). When the initial substrate concentration was 37 g/L, 45 g/L, 50 g/L, 57 g/L and 73 g/L, then, correspondingly, 16 g/L, 19 g/L, 22.25 g/L, 25.3 g/L and 26.3 g/L of propionic acid was accumulated in the fermentation broth. Increasing the supply of lactose in the fermentation medium led to the accumulation of by products succinate, acetate and pyruvate. Maximum propionate yield (0.44 g/g) and comparatively lesser impurities (byproducts) were achieved with 57 g/L initial lactose concentration. The batch growth kinetics was eventually used to develop and test a mathematical model for propionic acid fermentation by P. acidipropionici at pH 6.5 and S_o = 57 g/L. Y_X/S^max was found to be the most sensitive parameter of the model. The same model also successfully simulated the batch kinetics observed at S_o = 37 g/L. However the model failed to simulate the fermentation kinetics observed at S_o = 73 g/L. The developed model can be used for process optimization studies.     

Back extraction of platinum metals from liquid membranes in an electric field

A new method for back extraction of platinum metals from the salts of tertiary amines and quaternary onium bases in the organic phase is proposed. This method allows the back extraction of platinum metals into diluted solutions of mineral acids over one stage. The method involves the passing of direct current through a system in which the extract containing a platinum metal is a liquid membrane. This method allows a practically complete back extraction of the anions PtCl₆ ^2-, RuNOCl₅ ^2- and Ru₂OCl₁₀ ^4- (the latter passes into the aqueous phase without breaking the dimer anion). It was found that when PtCl₆ ^2-, PdCl₄ ^2- and Ru₂OCl₁₀ ^4- are in a liquid membrane based on Oct₃NHCl in 1.2-dichloroethane, under the action of an electric field all these anions are transferred into aqueous 1 M HCl (E > 85%). To provide maximum back extraction of platinum metal anions, it is necessary to use small concentrations of extractants in 1.2-dichloroethane (0.1 M for Oct₃NHCl and 0.03–0.04 M both for Oct₄NCl and Ph₄PCl) over the period of the back extraction. Cyclic voltametry has demonstrated the determining role of chloroions in current transport through the interface of phases I and II.     

气相催化丙酸与甲醛缩合反应制甲基丙烯酸

采用等体积浸渍法制备一系列Cs负载催化剂,采用XRD、ICP和物理吸附等对催化剂进行表征。在固定床反应器中进行气相催化丙酸与甲醛羟醛缩合反应制备甲基丙烯酸,以多聚甲醛解聚液为甲醛源头,考察载体种类、Cs负载量、铯源、反应温度及载气流速等对催化剂催化性能的影响。结果表明,较优的工艺条件为:反应温度340℃,活性组分Cs负载质量分数10%,丙酸与甲醛物质的量比1∶2,载气N2流速60 mL·min^(-1),此条件下,催化剂具有较好的催化活性,甲基丙烯酸收率为26%,甲基丙烯酸选择性为90.4%。     

双水相体系选择性萃取分离对氯扁桃酸对映体

研究了对氯扁桃酸(4-ClMA)对映体在含有羟丙基-β-环糊精(HP-β-CD)的聚乙二醇(PEG)/硫酸铵[(NH_4)_2SO_4]双水相体系中的萃取分配行为。考察了pH、PEG相对分子质量、PEG质量分数、(NH_4)_2SO_4质量分数、HP-β-CD浓度、4-ClMA浓度以及萃取温度对拆分效果的影响。实验结果表明:双水相萃取拆分具有很好的手性分离能力,HP-β-CD对(R)-4-ClMA的识别能力大于对(S)-4-ClMA的识别能力;当pH=6.5,PEG2000的质量分数为20%,(NH_4)_2SO_4的质量分数为20%,HP-β-CD浓度为1 mmol/L,4-ClMA浓度为0.13 mmol/L,萃取温度为25℃时,分离因子α达到1.61,性能因数PfR达到0.065。