Kinetics and extraction of phenol in phase-transfer catalyzed reaction

Under two-phase conditions, the feasibility of extracting/removing phenol from aqueous alkaline medium via reaction with allyl bromide dissolved in dichloromethane was investigated using phase-transfer catalysts in a stirred cell. The effects of the concentrations of base, reactant and catalyst, and temperature were also evaluated to obtain the optimum reaction conditions. According to these results, the extractive efficiency of phenolic substances varied strongly with increasing base concentration. The specific extraction rate, diffusivity, mass transfer coefficient and distribution coefficient of an intermediate product were determined to explain the reaction mechanism by the proposed theoretical model. During reaction, the concentration of the intermediate product in the organic phase was also measured, and a simulation method was used to examine the mass transfer behavior of the intermediate product in the liquid-liquid system.     

相转移催化法制备丙烯酸烯丙酯

以丙烯酸钠与氯丙烯(ALC)为原料,在相转移催化剂存在下合成出丙烯酸烯丙酯(ALA)粗产品,经离心、干燥、蒸馏等纯化手段得ALA产品。最佳反应条件为:以四丁基溴化铵为相转移催化剂,用量为反应物物质的量的4%,VALC∶V水=1∶1,在40℃下反应1.75 h,ALA产率达94%以上,纯度达98%以上。     

相转移催化法合成7-羟基黄酮的研究

以2,4-二羟基苯乙酮与苯甲酰氯在相转移催化剂四丁基硫酸氢铵催化下,一锅法反应,得到7-羟基黄酮(Ⅲ),产品收率60%,对Ⅲ的反应机理进行了推测,对于Ⅲ质谱表征结果进行了分析。以间苯二酚(Ⅰ)与冰醋酸反应,制得原料2,4-二羟基苯乙酮(Ⅱ),产品收率达到70%。     

Kinetic study of reaction of hexachlorocyclophosphazene with phenol by triphase catalysis

The kinetics of the substitution reaction of hexachlorocyclotriphosphazene, (NPCl₂)₃, with phenol to synthesize the partially substituted (phenoxy) chlorocyclotriphosphazene was investigated by using triphase catalysis in an organic phase/alkaline solution. The relative reaction-rate constants and the corresponding energies, enthalpies, and entropies of activation of the sequential substitution were also estimated. The diffusional limitations involve both ion diffusion in the aqueous phase and organic reactant diffusion in the organic phase within the catalyst pellet. The particle diffusion and intrinsic reactivity limit the substitution reaction in the organic phase. The diffusion of the aqueous phase in the ion-exchange step is the main rate-limiting factor.     

相转移催化法一步合成丙烯酸缩水甘油酯

采用相转移催化法合成了丙烯酸缩水甘油酯,研究了反应物摩尔比、反应时间、反应温度及碱的用量和浓度对产物收率的影响.结果表明,在40％的氢氧化钾乙醇溶液中,以十六烷基三甲基氯化铵为相转移催化剂,环氧氯丙烷与丙烯酸钠摩尔比为3.0∶1,反应温度80～90℃,反应时间为2.5h,产率可达88.0％.     

乙基香兰素的相转移催化合成

报道了应用相转移催化技术合成中间体邻乙氧基苯酚及最终产物乙基香兰素,考察了反应温度、时间、物料配比等因素对合成的影响,确定了最佳反应条件,邻乙氧基苯酚反应的最佳温度60℃;合成乙基香兰素最佳温度55～60℃。研究结果显示聚乙二醇作为相转移催化剂合成邻乙氧基苯酚,四丁基溴化胺相转移催化合成乙基香兰素,其结果均优于以往报道,邻乙氧基苯酚最高收率可达75.5%,乙基香兰素最高收率可达70%。     

Synthetic opportunities of gas-liquid phase-transfer catalysis

A concise survey of gas-liquid phase-transfer catalysis is reported, showing the main features of the method, and, in particular, discussing the influence of the temperature and pressure, catalyst selection and nature of the solid bed on the outcome of the reaction. Some new results concerning the malonate synthesis and the halide-exchange on hydrocarbons are reported: the former shows that the monoalkylated ester can be selectively obtained by using the polyethyleneglycol “Carbowax 6000” as a catalyst adsorbed over potassium carbonate, whilst the latter refers to a true catalytic process, which can proceed indefinitely without renewing the catalytic bed. The influence of the catalyst percentage on the reaction equilibrium is also discussed. The advantages and the problems of gas-liquid phase-transfer catalysis are reviewed, together with its analogies to classic phase-transfer catalysis and gas chromatography.     

Phase-transfer catalysis of the reaction of α-bromo-p-xylene with iron carbonyls

The carbonylation of α-Bromo-p-xylene (BrCH₂C₆H₄CH₃, BX) with iron pentacarbonyl (Fe(CO)₅) by phase-transfer catalysis was studied in an organic solvent/alkaline solution. The reaction mechanism was corrected and clarified. The concentrations of base, reactant and catalyst, volume ratio, the kind of catalysts, organometals and solvents were evaluated to find the optimum condition in this reaction. The technique of phase-transfer catalysis has a dramatic accelerating effect on the reaction. In examining eight kinds of phase-transfer catalysts, tetra-n-butylammonium cation and tetra-n-butylphosphonium cation were found to be the best for increasing the yield of bis(p-methylbenzyl) ketone ((p-CH₃C₆H₄CH₂)₂CO, BMBK). The amount of phase-transfer catalyst, the concentration of NaOH, the molar ratio of BX to Fe(CO)₅ and the volume ratio of aqueous to organic phase affected the product selectivity.     

相转移催化法合成烯丙基缩水甘油醚

以烯丙醇和环氧氯丙烷为原料，采用相转移催化法，合成了烯丙基缩水甘油醚。研究了反应时间、反应温度、投料比及固体碱的用量对反应收率的影响。在n(烯丙醇)∶n(环氧氯丙烷)∶n(固体碱)∶n(催化剂)=1∶1.5∶1.5∶0.005、反应时间1 h、反应温度50～60 ℃时，烯丙醇缩水甘油醚收率可达88%。     

相转移催化法合成1-(2,3-环氧丙基)-2-甲基-5-硝基咪唑

在相转移催化剂四丁基溴化铵存在下,奥硝唑与碱性溶液反应,脱去HCl,得到1-(2,3-环氧丙基)-2-甲基-5-硝基咪唑。研究了碱性溶液种类、碱性溶液的浓度、催化剂加入量、反应温度对目标产物收率的影响。结果表明,较佳反应条件为:奥硝唑∶四丁基溴化铵(质量比)=0.6,碱性溶液为5%NaOH水溶液,反应温度15℃,反应时间1 h,在此条件下,目标产物收率83.9%,纯度99.4%。对目标产物进行了IR及1H NMR表征,并对催化反应机理进行了分析。     

Liquid-solid-liquid phase-transfer catalysis in sequential phosphazene reaction: kinetic investigation and reactor design

The reactor design and kinetics of the substitution reaction of hexachlorocyclotriphosphazene, (NPCl₂)₃, with phenol to synthesize the partially substituted (phenoxy)chlorocyclotriphosphazene was investigated by using triphase catalysis in an organic phase/alkaline solution. Two reactors, the slurry reactor and the fixed-bed reactor were proposed to evaluate a liquid-solid-liquid triphase reaction. The design problems of these reactors were evaluated to obtain the best performance. A cross type “+” Teflon magnetic stirrer was put in the bottom of the slurry reactor that can reduce the liquid flow rate to prevent solid catalyst to flow out of the reactor. Because the mass-transfer rate for the first and second degree of the substitution of the series phosphazene reaction were slow, they reacted in situ with sodium phenolate in the interior of the resin to form the two to five degrees of the substituted products. The kinetic parameter of the phosphazene reaction was influenced by the particle diffusion of the reactant. The effectiveness factor and Thiele modulus of the system and the diffusivity of the reactants were also obtained. The relationship of the coverage of catalyst onto the interfacial area between the two phases with the reaction-rate constant was studied.     

Thermoregulated phase transfer ligands and catalysis. III. Aqueous/organic two-phase hydroformylation of higher olefins by thermoregulated phase-transfer catalysis

A series of poly(ethylene oxide)-substituted triphenylphosphines, Ph_3−mP[C₆H₄-p-(OCH₂CH₂)_nOH]_m (PEO-TPPs; 1a m=1, 1b m=2, 1c m=3; N=m×n=8–25), have been prepared by the ethoxylation of mono-, di-, and tri-p-hydroxytriphenylphosphines. PEO-TPPs demonstrate an inverse temperature-dependent solubility in water, and possess distinct cloud points range from 26°C to 90°C.

Based on the clouding property of PEO-TPPs, a new line of aqueous/organic two-phase catalysis termed the thermoregulated phase-transfer catalysis (TRPTC) has been described. That is, the catalyst transfers into the organic phase to catalyze a reaction at a higher temperature, and returns to the aqueous phase to be separated from the products at a lower temperature. Application of this novel strategy to the rhodium-catalyzed two-phase hydroformylation of higher olefins gave desirable results with an average turnover frequency of 180 h⁻¹ for 1-dodecene. The TRPTC is suitable for carrying out a reaction with extremely water-immiscible substrate in the aqueous/organic two-phase system. Thus, the application scope of the classical two-phase catalysis has been widened.     

Improvement of the phase-transfer catalysis method for synthesis of glycidyl ether

A convenient procedure for the synthesis of aliphatic alkylglycidyl ether has been studied. It has been found that the improved preparation of the alkylglycidyl ether can be achieved by using fatty alcohol such as octanol and octadecanol with epichlorohydrin in the presence of phase-transfer catalyst (PTC) such as 1-alkyloxypropan-2-ol-3-trimethyl ammonium methylsulfate, 1-alkyloxypropan-2-ol-3-methyldiethanolammonium methylsulfate, alkyloxy-2-hydroxypropyldimethylamine and alkyloxy-2-hydroxypropyldiethanolamine, tetrabutylammonium bromide, etc. without water and other organic solvents. This method, carried out in solid phase/organic phase (reactants and product themselves), has the following merits: (i) producing the solid by-products such as sodium chloride and sodium hydroxide which are easily removed by simple filtration, (ii) saving the amount of reactants used such as sodium chloride and phase-transfer catalyst, and (iii) increasing the yields of glycidyl ethers. The yields of octylglycidyl ether and octadecylglycidyl ether are 92.0 and 91.7%, respectively. The amount of sodium hydroxide used can be saved by from 1.5 to 0.7 molar ratio with respect to octanol in comparison with those in the conventional method using PTC.     

三相相转移催化合成对苯二甲酰氯的研究

合成制备了既有聚醚链段又有季铵盐的新型聚合物固载相转移催化剂,并以之用于对苯二甲酸合成标题化合物.考察了催化剂、氯化亚砜、甲苯等的用量对反应收率的影响,得到了适宜的合成工艺条件为:n(TPA):n(SOCl2):n(PhCH3):n(PTC)=1:3:3:0.06,反应温度85 ℃,反应时间6 h.在该条件下,对苯二甲酰氯收率>89.6%,HPLC法测定纯度>99.6%,该聚合物固载相转移催化剂可重复使用6次以上.     

Kinetics for benzoylation of sodium 4-acetylphenoxide via third-liquid phase in the phase-transfer catalysis

In this research, the kinetics for synthesizing 4-acetylphenyl benzoate (R^*COOR) from benzoylation of sodium 4-acetylphenoxide via third-liquid phase-transfer catalysis was investigated. The reaction rate was observed to be strongly dependent on agitation speeds in the third-phase catalytic reaction. By forming the third-liquid phase, the observed reaction can be greatly enhanced to give a product yield of 100% in a duration of 3 min at 20 °C and 200 rpm. If a third-liquid phase was not formed in the liquid–liquid system, the reaction rate is very slow and the product yield is only 2% in 3 min at 20 °C. The reaction conducted in third-liquid phase-transfer catalytic system is faster than that in LLPTC system by 25–28 times. The amount of catalytic intermediate (QOR) in the third-liquid phase was about 50% of the catalyst initially added and kept about 30% of it remained after 1 min, and only small amounts of a catalytic intermediate residing in the organic phase were observed during the reaction using methyl t-butyl ether as the solvent. The concentration of catalytic intermediate slightly decreased with increasing reaction time, while the molar ratio of QOR to benzyl tri-n-butylammonium cation in the third-liquid phase remained almost constant after 1 min and increased with increasing agitation speeds. The experimental results were well described by the pseudo-first-order kinetics. The present work shows an effective method to synthesize 4-acetylphenyl benzoate.     

相转移催化合成N,N-二烷基氨基乙基-4-乙氧基苄基醚

用相转移催化法合成了标题化合物,产率69%～82%。适宜的反应条件是:以4-乙氧基氯化苄、二烷基氨基乙醇为原料,在固体氢氧化钠作用下,四丁基溴化铵为相转移催化剂,甲苯为溶剂,物质的量比n(R1R2NCH2CH2OH):n(EtOArCH2Cl):n(NaOH):n(PTC)=1:1:2:0.05,反应时间2h,温度70℃。产物经过沸点、元素分析、红外光谱、氢质子核磁共振谱给予确证。     

Kinetics of PdO combustion catalysis

The kinetics of the catalytic combustion of methane by supported palladium oxide catalysts (2 wt.-% Pd/La₂O₃·11A1₂O₃ and 5 wt.-%Pd/ γ-A1₂0₃ were examined for several oxygen partial pressure levels over the temperature range from 40–900°C using temperature-programmed reaction and slow ramp and hold temperature-time transient techniques. Combustion rates were measured by differential reaction in a fixed bed of powdered catalyst at lower temperatures (200–500°C). Also, by preparing the catalysts as thin (ca. 10 μm) coatings on an alumina tube and conducting the experiments with very high flows of dilute methane and oxygen in helium, the rate measurements were extended up to 900°C without significant contribution from gas phase reactions. The specific combustion activity of supported PdO shows a persistent hysteresis between 450 and 750°C, i.e., the rate of combustion between these temperature limits depends strongly on whether the catalyst is cooling from above 750°C or heating from below 450°C. This region is also notable for negative apparent activation energy in the rate of methane oxidation, i.e., the rate increases with decreasing temperature during reoxidation of the Pd metal and decreases with increasing temperature (especially with low oxygen partial pressure) prior to decomposition of the bulk oxide. Detailed time-temperature transient kinetic analyses were performed for supported PdO catalysts within the 450–750°C temperature range. The hysteresis in methane combustion rate is caused by a higher activation energy for reduction of oxygen chemisorbed on metallic Pd and by suppressed reoxidation of Pd metal relative to PdO decomposition.     

多金属氧酸盐催化合成缩醛（酮）的研究进展

作为具有出色催化性能的绿色催化剂多金属氧酸盐,在催化合成缩醛（酮）反应领域展现出了广阔的应用前景。首先简要地介绍了多金属氧酸盐的性质及其应用;然后综述了近几年来多金属氧酸盐及负载多金属氧酸盐催化剂在催化合成缩醛（酮）反应中的研究现状,包括活性炭、硅胶、二氧化钛、分子筛等载体;并对其未来的发展方向进行了展望。     

The removal of dichloromethane from atmospheric pressure air streams using plasma-assisted catalysis

Plasma-assisted catalysis was used for the destruction of 500 ppm of dichloromethane, CH₂Cl₂ (DCM), in gas streams of air using a non-thermal, atmospheric pressure plasma utilising a dielectric packed bed. The combination of plasma and catalyst gave improved destruction of DCM. Eight catalysts which including alumina, TiO₂ and various zeolites were investigated with the finding that alumina in a one-stage reactor configuration and TiO₂ and HZSM-5 in two-stage configurations gave the best DCM destructions. The sodium zeolites are capable of reducing by 50% the unwanted NO_x by-products, formed by plasma processing in air. The nature of the catalyst is important in terms of the destruction efficiency, end-product selectivity and NO_x reduction.     

油酸存在下的聚氨酯(脲)固化动力学

采用差示扫描量热法(DSC)研究了油酸存在下聚氨酯(脲)固化过程反应动力学参数.利用Kissinger法求得不同油酸含量固化反应的表观活化能Ea,Crane方程计算该体系的固化反应级数n.结果表明,加入油酸后固化体系的活化能减小,油酸为聚氨酯(脲)固化反应的催化剂;油酸质量分数为0.9%时,固化反应的E.为27.91 ...