Redispersion Microreactor System for Phase Transfer‐Catalyzed Esterification

An interdigital mixer‐redispersion capillary assembly was applied to prevent the liquid‐liquid bubbly flow coalescence in microreactors. The redispersion capillary consisted of 1‐mm‐long 0.25 mm inner‐diameter constrictions, placed every 0.50 m along the channel length. The system was tested on the phase transfer‐catalyzed esterification to produce benzyl benzoate. The application of constrictions to prevent coalescence resulted in a better reproducibility and higher conversion compared to a capillary without constrictions. The bubbly flow generated by the interdigital mixer‐redispersion capillary assembly was found to be independent of the redispersion capillary inner diameters (0.50 and 0.75 mm) while being highly dependent on the flow rates. By controlling the total flow rate and the aqueous‐to‐organic ratio, the bubbly flow surface‐to‐volume ratio could be increased up to 230 700 m²m^–3. Compared to the conventional phase transfer‐catalyzed esterification, the continuous operation in the interdigital mixer‐redispersion capillary assembly eliminated the use of solvents and bases, removing an energy‐intensive step of distillation while increasing process safety.     

Modeling,Simulation and Optimized Design of a Microreactor for a Two‐Step Reaction

A two‐step microreactor for the investigation of glucose oxidation is presented. A model is created to pre‐judge the changes in concentrations of the reactants in the straight channels of the microreactor. The structure of the rapid mixing‐reaction units of the microreactor was optimized, and the optimal parameters were found to be p = 1:3, r = 1:1, and w_s = 60 μm. The model and the optimization method can facilitate the design of microreactors.     

Experimental Investigation and Modeling Approach of the Phenylacetonitrile Alkylation Process in a Microreactor

The application of microreaction technology has the potential to intensify chemical processes. It is therefore of great interest to investigate the operating efficiency of a multiphase process such as the alkylation of phenylacetonitrile in a microreactor and to compare the performance to a batch reactor. The undeniable advantages of continuous microreactor systems for this process were demonstrated. Furthermore, the influence of the organic to aqueous phase ratio in the microreactor was investigated. A model of the reaction course was formulated based on experimental data. This model was used in the analysis and modeling of the alkylation process in a microreactor and found to be adequate. The optimal microreactor performance conditions were determined using the numerical optimization technique (Harrington's desirability function) and confirmed by experiments.     

Kinetic study of CO2 fixation into propylene carbonate with water as efficient medium using microreaction system

Carbon dioxide (CO₂) utilization and fixation have become one of the most important research areas nowadays due to the increase of global greenhouse effect. Cyclic carbonate, which is widely used in various fields, can be synthesized by fixation of CO₂ with epoxide in industry. Moreover, the synthesis of cyclic carbonate is a 100% atom economical reaction, which makes it eco-friendly and promising. To enhance the reaction efficiency and safety, a microreaction system was used as the platform for cycloaddition reaction. In this work, tetrabutylammonium bromide (TBAB) was chosen as catalyst, and propylene oxide (PO) as a mode substrate. Interestingly, the addition of water can increase the propylene carbonate (PC) yield and decrease the activation energy considerably, proving water as catalyst promoter for PC synthesis. PC yield and selectivity could reach 91.6% and 99.8%, respectively. The Influence factors and kinetic equation for CO₂ cycloaddition were obtained as well.     

Microreactor Technology as a Tool for the Synthesis of a Glitazone Drug Intermediate

One of the bottlenecks in the pharmaceutical industry is drug production scale‐up, which can be performed by microreactor technology. Such an approach was applied to the synthesis of (Z)‐5‐(4‐hydroxybenzylidene)thiazolidine‐2,4‐dione, a bioactive aromatic heterocyclic compound belonging to the class of glitazones. n‐Propanol was the best solvent and piperidine the best catalyst for the batch reaction, which was completed in only 5.5 h. In the microreactor, the productivity was almost independent of solvent. The microreactor behaved as a plug‐flow reactor and operated at a steady state for ten hours without efficiency loss. The results suggest that microreactors may replace batch reactors in scaling up drug production.     

Residence Time Distribution of a Capillary Microreactor Used for Pharmaceutical Synthesis

The main drivers for application of small-scale reactors in the pharmaceutical industry are the possibility of rapid synthesis and screening of novel drugs as well as the readiness of the scale-up. The characterization of fluid flow pattern was performed through step-up and step-down residence time distribution experiments using a tracer at six different flow rates. Four single-parameter models were considered for representing deviations from ideal plug flow and ideal laminar flow in tubes. The model that provided the best results was the axial dispersion model and the Peclet and Reynolds numbers could be well correlated. Obtained Peclet values from 44 to 244 were close to Pe > 100, in which axial dispersion can be neglected and the reactor can be considered as plug flow reactor.     

A Semi‐continuous Process for the Synthesis of Methyl Carbamate from Urea and Methanol

A semicontinuous process for the synthesis of methyl carbamate from urea and methanol was investigated in the autoclave without the catalyst. Some significant parameters were determined in terms of the methyl carbamate yield. The optimal reaction conditions were found at an initial molar ratio of methanol/urea of 6:1, a reaction temperature of 423 K, a flow rate of fresh methanol at 4 mL/min, a stirring speed of 800 rpm and a reaction time of 6 hours, respectively. A MC yield of 98.7 % was obtained at the optimal reaction conditions. Furthermore, the kinetics of this reaction were researched and the reaction activation energy was obtained as 110.498 kJ/mol. It was demonstrated that removing methanol containing ammonia from the autoclave and replacing it with continuously feeding fresh methanol resulted in a higher reaction rate and a high MC yield.     

Guidance on Safety/Health for Process Intensification including MS Design; Part II: Explosion Hazards

The implementation of process intensification by multiscale equipment will have a profound impact on the way chemicals are produced. The shift to higher space‐time yields for partial oxidation processes using micro‐designed reactors comprises the risk of having a permanent explosive atmosphere in the reaction section. In Part I, it was concluded that spontaneous reaction with hot spots can be presumed if highly exothermic reactions were performed and may cause ignition of an explosive atmosphere. The risk analysis of the situation, based on public information in the literature, leads to the conclusion that microreactors are inherently safe regarding the initiation and propagation of an explosion inside a microchannel by an uncontrolled reaction. The situation is the opposite when a propagating explosion enters the same micro‐designed reactor from one of the outside openings. The external explosion may enter the micro‐designed equipment and destroy it when the same starting conditions are present.     

微反应器中十二烷基苯液相SO_3磺化过程

石油磺酸盐和重烷基苯磺酸盐是三次采油用重要阴离子表面活性剂,其主要成分是烷基苯磺酸盐。本研究以十二烷基苯(DDB)液相SO3磺化为模型反应,研究微反应器内的烷基苯磺酸合成反应过程特性,考察了液体流量、反应温度、磺化剂中SO3含量、反应通道长度、SO3与十二烷基苯物质的量比、微反应器结构、搅拌时间等参数的影响。结果表明,十二烷基苯磺化过程受传质控制,微反应器对反应初始阶段的强化作用明显,在SO3与十二烷基苯物质的量比为1.1时,采用微反应器与釜式反应器串联模式合成十二烷基苯磺酸,收率高达93.7%,为微反应器生产重烷基苯磺酸的路线提供了重要基础。     

Effect of Viscosity on the Hydrodynamics of Liquid Processes in Microchannels

The hydrodynamics of single‐phase liquid flow with relatively high fluid viscosities in a microchannel was investigated experimentally. The results showed that the conventional theory could predict the single‐phase flow with high fluid viscosities in microchannels. Furthermore, the effect of viscosity on the slug flow of two immiscible liquid phases in a microchannel was studied with high‐speed imaging techniques. It was found that a higher dispersed‐phase viscosity quickened the flow pattern transition from slug flow to parallel flow and resulted in smaller slugs. A modified capillary number representing the mutual effects of the viscosities of the continuous phase and the dispersed phase was proposed for predicting the slug sizes in microchannels.     

微通道反应器内氯苯硝化反应研究

在微通道反应器内对氯苯硝化反应进行了研究,考察了氯苯与硝酸的摩尔比、体积流速、反应温度等对单程转化率及选择性的影响。实验选择了较优工艺参数组合:n(氯苯)∶n(硝酸)=1∶1.3,n(硝酸)∶n(硫酸)=1∶3,氯苯体积流速0.5 mL/min,反应温度80℃,氯苯单程转化率达74.8%,n(邻硝基氯苯)∶n(对硝基氯苯)=0.56∶1,时空转化率(STC)达4.07×109mol/(m3.h)。微通道反应器内,时空转化率是常规反应器的3.08×104倍。     

3,6-二氯水杨酸O-甲基化工艺的研究

探讨了以3，6－二氯水杨酸为原料，经O－甲基化反应合成3，6－二氯－2－甲氧基甲酸的工艺。通过正交实验得到O－甲基化反应的最佳工艺条件为：n(3,6－二氯水杨酸）：n（氢氧化钠）＝1：4．5，反应温度100℃，反应压力0．6MPa，保温时间6h，在此条件下，O－甲基化收率为92．6％。     

Guidance on Safety/Health for Process Intensification Including MS Design. Part III: Risk Analysis

The new technology of process intensification by multiscale equipment can significantly contribute to achieve a safer design by going from batch/semi‐batch to continuous operation combined with a reduction of inventory of hazardous substances in critical stages. On the other hand, the shift to higher space‐time‐yields comprises new risks such as runaway reactions with hot spot formation, described in Part I, and handling an explosive atmosphere in the presence of potential permanent ignition sources, described in Part II. A tool was developed for preliminary risk assessments, called HAZOP‐LIKE study, to cover the characteristic features of micro‐designed equipment that are relatively unimportant when handling conventional equipment. Two generic cases concerning liquid/liquid and gas/gas reactions were studied to demonstrate the method.     

浅谈如何实现工艺安全信息的有效应用

工艺安全信息及其有效应用是塔里木油田公司安全文化建设工艺安全管理系统的重要要素之一.工艺安全信息的有效应用就是将与工艺装置有关的工艺物料危害、工艺技术、工艺设备等相关的信息有效应用于工艺安全活动中.工艺安全信息产生于装置生命周期的各个阶段,是进行危害辨识与风险控制的依据,也广泛应用于工艺安全管理系统的其他要素中.工艺安...     

焦化厂蒸氨生产装置技术研究

通过对焦化厂蒸氨系统直接蒸氨、间接蒸氨生产工艺装置的技术研究,选择合理工艺,使氨水中的挥发氨由约0．25％（2．5g／L）降至0．01％（0．1g／L）。     

Kinetics and mechanism of the hydrogenation process – the state of the art

It is just over a century ago that the first industrial hydrogenation plant for edible oils was commissioned. Although at that time several fatty acids had been identified, the analytical characterization of these oils was mainly by physical properties like melting point, density and refractive index and chemical properties like saponification value and iodine value. Some of these properties were used to follow a hydrogenation reaction. Early kinetic studies of the hydrogenation reaction focused on triglycerides but with the advent of GC, fatty acid compositions became so readily available, that kinetic studies switched to the ‘common fatty acid pool’ concept. According to this concept, the rate of reaction of an unsaturated fatty acid in a triglyceride molecule does not depend on the chemical nature of the other fatty acid moieties in this molecule. The concept greatly simplified the understanding of what happens during a hydrogenation reaction and thereby stimulated research. It took more than 50 years before this concept was shown to be an incorrect assumption. Kinetic studies of the hydrogenation process have also been hampered by the lack of an instrument that can measure the hydrogen concentration in oil. That may well be the reason why this concentration has received rather little attention and that its effect on the relative rates of the various, simultaneously proceeding reactions has only fairly recently become clear. Accordingly, the present review will describe the mechanism of the various reactions that occur during the hydrogenation process and highlight the effect of the hydrogen concentration and the triglyceride composition rather than that of the fatty acid composition. It will discuss industrial process conditions rather than laboratory conditions and therefore limit itself to nickel catalysts. It will also paint the most simple picture that is consistent with generally accepted observations.     

A breakthrough technique for the preparation of high-yield precipitated calcium carbonate

Precipitated calcium carbonate (PCC) is conventionally produced through the gas-solid-liquid carbonation route, which consists on bubbling gaseous CO₂ through a concentrated calcium hydroxide (Ca(OH)₂) slurry. However, atmospheric carbonation processes are slow and have low carbonation efficiency. A novel technology based on the combination of supercritical carbon dioxide (scCO₂) and ultrasonic agitation is described here for the preparation of high-yield PCC. The combination of both techniques has demonstrated to produce outstanding improvement for the conversion of Ca(OH)₂ to the stable calcite polymorph of calcium carbonate (CaCO₃). These experiments were carried out at 313 K and 13 MPa using a high-pressure reactor immersed in an ultrasounds cleaner bath. The process kinetics and the characteristics of the precipitated particles using ultrasonic agitation were compared with those obtained under similar experimental conditions using mechanical stirring and non-agitated systems. The crystal characteristics of the samples obtained using the three different agitation techniques were characterized by X-ray diffraction and scanning electron microscopy.     

彩漂液的配方研究及性能测试

彩漂液是含氧的漂白剂,它能有效去除织物上的茶渍、果菜渍、血清、墨水渍等污渍,并且不损织物。通过对彩漂液进行的配方研究及性能测试,结果表明彩漂液的稳定性与稳定剂、溶液的ＰＨ值,表面活性剂有关。经过优选得出的彩漂液配方无论是稳定性还是漂白效果都达到进口同类产品水平。     

An Ionic Liquid as Catalyst Medium for Stereoselective Hydrogenations of Sorbic Acid with Ruthenium Complexes

The ionic liquid 1‐n‐butyl‐3‐methylimidazolium hexafluorophosphate (bmim PF₆) ( 6 ) has been studied as catalyst medium for biphasic homogeneous hydrogenations of sorbic acid ( 1 ). As catalyst we used the Cp*‐ruthenium‐complex [Cp*Ru(η⁴‐CH₃—CHCH—CHCH—COOH) (CF₃SO₃)] which efficiently enables the stereoselective hydrogenation of sorbic acid leading to the formation of cis‐3‐hexenoic acid ( 3 ) in selectivities of up to 90% with turnover frequencies of up to 1100 h^—1. Compared to other biphasic systems the hydrogenation in bmim PF₆ proceeds with enhanced activity. The kinetics can be described with a Michaelis Menten‐equation, and the activation energy for the whole process was determined to be E_A = 78 ± 5 kJ/mol.