A microreactor system consisting of membrane-dispersion tube-in-tube microreactors and delay loops was developed for the continuous synthesis of 1-ethoxy-2,3-difluoro-4-iodo-benzene. Because of the high mass and heat transfer in the microreactor system, ortho- and halogen-lithiation could be performed at −40 and −20°C, respectively, which are much higher than the temperature required (−70°C) for the batch reaction. In stirred tanks, the yield of 1-ethoxy-2,3-difluoro-4-iodo-benzene reaches 91.0% in 70 min. Nearly the same yield of 91.3% was achieved within a shorter time of 16 min in the microreactor system. Furthermore, the kinetics of ortho-lithiation calculated by the Gaussian software, were used for the computational fluid dynamics (CFD) simulations of the reaction process in another microreactor system. Thus, a Gaussian-CFD-coupled-method for efficiently predicting reaction kinetics and yield without experiments could be established. The predicted yield reached 88.7% at 1000 s, which is comparable with the experimental yield of 90.1% at 960 s. 相似文献
Synthesis of adipic acid (AA) through the oxidation of cyclohexanol and cyclohexanone (K/A oil) with nitric acid was conducted in a capillary microreactor system. Effects of the temperature, the nitric acid concentration, the volumetric flow rate ratio of nitric acid to K/A oil, and the capillary length on the selectivity and the product yield were investigated systematically to achieve optimal reaction conditions. Notably, a high yield of AA (i.e., 90%) was achieved just in 6 seconds at 85°C with the use of 55 wt% nitric acid. Gas components produced in this oxidation process and its total volumetric flow rate were determined under various operational conditions, which was beneficial for reaction mechanism characterization and process optimization. Finally, a kinetic model was established, which was of crucial theoretical significance and practical value for optimizing the reactor design and better understanding such fast and highly exothermic multiphase processes with abundant gas production. 相似文献
The conventional kinetic analysis of an overall reaction (OR) is limited to a single sequential pathway of molecular steps at a time, based either on the general quasi-steady state (QSS) approach of Bodenstein, or on the much simpler but limited Langmuir–Hinshelwood–Hougen–Watson (LHHW) approach based on assuming a single rate-determining step (RDS), the remaining being quasi-equilibrated (QE). We recently described a new algebraic methodology for deriving the QSS rate expression for a reaction sequence, which allowed interpretation of the final result in an Ohm's law form, i.e., OR rate=OR motive force/OR resistance of an equivalent electric circuit, where the consecutive mechanistic steps represent resistors in series. Here, we propose a similar Ohm's law form of QSS rate for a reaction system involving parallel pathways, whose equivalent electrical circuit derives directly from the reaction route (RR) Graph of its mechanism, as proposed earlier by us. The results are exact for a reaction network with mechanistic steps linear in intermediates concentrations, while they are approximate, albeit accurate, for non-linear step kinetics. We further show how the LHHW methodology, combined with the concept of intermediate reaction might be utilized to obtain the step resistances involved. For illustration, we utilize the relatively simple examples of: (1) the gas-phase hydrogen–bromine non-catalytic reaction (non-linear kinetics), and (2) zeolite catalyzed N2O decomposition reaction (linear kinetics). However, the approach is useful for more complex non-catalytic, catalytic and enzymatic reactions networks as well. 相似文献
With the growth in the use of DFT for predicting elementary catalytic reaction step kinetics, it is desirable to develop approaches that provide the overall reaction (OR) rate in terms of these. Deriving an explicit rate expression for a sequence with three or more steps by solving the quasi-steady-state (QSS) equations, however, is tedious, or infeasible, and the resulting expressions are often unwieldy and difficult to interpret. As a result, the microkinetics approach is favored, providing, however, only numerical results.Here, we provide an alternate approach to obtain the QSS rate expression for a reaction sequence in analogy to an electrical circuit, i.e., OR rate = driving force/overall resistance, where the overall resistance may be obtained in terms of the individual step resistance following the electrical analogy. The individual step resistances, in turn, can be derived readily based on the traditional Langmuir-Hinshelwood-Hougen-Watson (LHHW) approach, by assuming each step in turn to be rate-limiting, combined with the notion of “intermediate reactions” for the formation of the intermediate species. This provides exact expressions for mechanisms with linear (first-order in intermediates) step kinetics in linear sequences, and approximate but accurate expressions in others. Further, it allows insightful conclusions to be drawn about one or more rate-limiting steps in a sequence, and the resulting simplifications. The approach is illustrated with the help of catalytic N2O decomposition (linear kinetics), and the hydrogenation of isobutene (nonlinear kinetics). 相似文献
A novel process concept for the oxidative coupling of methane followed by the oligomerization to liquids has been developed within the frame of the EU integrated project OCMOL. This technology is based on process intensification principles via cutting‐edge structured microreactor technology. It is also a fully integrated industrial process through the re‐use and the recycling of by‐products, in particular CO2, at every process stage. The focus of this contribution is on the reaction engineering aspects of the core steps, i.e., catalysts, kinetics and reactor design for the methane coupling and reforming. 相似文献
The silylation reaction of dextran with 1,1,1,3,3,3-hexamethyldisilazane (HMDS) in DMSO was studied as the first step of the synthesis of new amphiphilic polyester-grafted dextrans. According to the experimental conditions, i.e. dextran molar weight, medium temperature and reaction time, HMDS/OH ratio, addition of a catalyst and co-solvent, partially or totally silylated dextrans were recovered. The highest silylation yields were obtained with the lowest molecular weight dextrans. The increase in temperature medium and/or reaction time, the presence of catalyst or co-solvent favored the protection yield. Whatever the dextran used, complete silylation of the polysaccharide chain could be achieved by adequate selection of the experimental conditions. The thermal properties of resulting silylated polysaccharides were investigated by temperature modulated DSC. It was observed that Tg values of partially silylated dextran were maintained between 120 and 140 °C, independently of the dextran molecular weight. Interestingly, DMSO proved to behave as an efficient plasticizer of (partially) silylated dextrans. The partially silylated dextrans were efficiently used as multifunctional macroinitiators for the controlled ring-opening polymerization (ROP) of lactone. The ROP was then promoted from the remaining hydroxyl groups in the presence of tin or aluminium activator. After polymerization and ultimate deprotection of the silylated dextran backbone, amphiphilic polyester-grafted dextrans were readily recovered. 相似文献
High-purity ethylene carbonate (EC) is widely used as battery electrolyte, polycarbonate monomer, organic intermediate, and so on. An economical and sustainable route to synthesize high-purity ethylene carbonate (EC) via the transesterification of dimethyl carbonate (DMC) with ethylene glycol (EG) is provided in this work. However, this reaction is so fast that the reaction kinetics, which is essential for the industrial design, is hard to get by the traditional measuring method. In this work, an easy-to-assemble microreactor was used to precisely determine the reaction kinetics for the fast transesterification of DMC with EG using sodium methoxide as catalyst. The effects of flow rate, microreactor diameter, catalyst concentration, reaction temperature, and reactant molar ratio were investigated. An activity-based pseudo-homogeneous kinetic model, which considered the non-ideal properties of reaction system, was established to describe the transesterification of DMC with EG. Detailed kinetics data were collected in the first 5 min. Using these data, the parameters of the kinetic model were correlated with the maximum average error of 11.19%. Using this kinetic model, the kinetic data at different catalyst concentrations and reactant molar ratios were predicted with the maximum average error of 13.68%, suggesting its satisfactory prediction performance. 相似文献
Asymmetric sulfoxidation catalyzed by a biomimetic manganese complex under continuous‐flow microreactor is described. The reaction is conducted in microreactor, it can rapidly (<4 min) oxidize a wide scope of sulfides with high yield (up to 91%) and excellent enantioselectivity (up to 99% ee), and allows shorter reaction times, easier scale‐up and lower catalyst loadings than its batchwise counterpart. Additionally, a convenient numbering‐up strategy for the scale‐up of asymmetric sulfoxidation has been developed which enables a direct scaling of the reaction to 5 g affording the corresponding sulfoxides within 20 min.
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