Reaction multiphase system

However, a note of caution should be added. In many multiphase reaction systems, rates of mass transfer between different phases can be just as important or more important than reaction kinetics in determining the reactor volume. Mass transfer rates are generally higher in gas-phase than liquid-phase systems. In such situations, it is not so easy to judge whether gas or liquid phase is preferred. 

Example 5.4.4.3b. Optimization of time-profiles for a multireaction and multiphase reaction system (after Marchal-Brassely et al. (1992))... 

Chemical Kinetics, Tank and Tubular Reactor Fundamentals, Residence Time Distributions, Multiphase Reaction Systems, Basic Reactor Types, Batch Reactor Dynamics, Semi-batch Reactors, Control and Stability of Nonisotheimal Reactors. Complex Reactions with Feeding Strategies, Liquid Phase Tubular Reactors, Gas Phase Tubular Reactors, Axial Dispersion, Unsteady State Tubular Reactor Models... 

Mehta VL and Kokossis AC (1988) New Generation Tools for Multiphase Reaction Systems A Validated Systematic Methodology for Novelty and Design Automation, Comput Chem Eng, 22S 5119. 

However, a note of caution should be added. In many multiphase reaction systems, as will be discussed in the next chapter, rates of mass transfer between different phases... 

What we highlight here are some new recent multiphasic reaction systems for catalysis. The systems described here have in common a catalyst-philic phase, which contains, or coats a catalyst (mainly heterogeneous), or in some instances is the catalyst itself (PTC). There are two or three separate phases, and a general composition that can be summarized as liquid-liquid-solid (L-L-S), or liquid-liquid-liquid-solid (L-L-L-S). One of the Ls indicates the liquid-ionic/hydrophilic... 

Reaction Engineering and Reactor Design for Multiphasic Reaction Systems... 

Since the overall reaction rate in the loop reactor is limited by mass transport at the phase boundary, one would expect that the Ru concentration has a weaker influence on the rate of reaction than in the batch reactor. We have carried out experiments at a Ru concentration of 0.005 M as well as at 0.01 M and observed nearly a doubling of the overall reaction rate, giving rise to a reaction order of 0.96 with regard to Ru. The result is somehow surprising, since it can be explained only in terms of a kinetic control of the reaction, like in the batch reactor. On the other hand, previous experiments clearly indicate a mass transport limitation at the L/L-interphase. So the question which arises is how it can be possible that a multiphase reaction system is limited by both mass transport and kinetics ... 

Olefin epoxidation is another synthetic route of great interest that has been the object of several investigations, not only in multiphase reaction systems but also with oxidants other than molecular oxygen, such as inorganic and organic peroxides [55-57]. 

Mehta, VL, Kokossis AC. New generation tools for multiphase reaction systems a validated systematic methodology for novelty and design automation. Comp Chem Eng 1998 22 119. 

The technology also represents a suitable strategy for the preparation of multiphase reaction systems that use phase transfer (bio)catalysts. Giorno et al. [88] reported on the use of membrane emulsification to distribute lipase from Candida rugosa at the interface of stable oil-in-water emulsions. The enzyme itself was used as a surfactant. Shirasu Porous Glassy (SPG) membranes having a nominal pore... 

Aliquiat 336 Pd/C Et3N, KOH, k2co3, NaHC03 100 °C. Multiphasic reaction system aryliodides react up to 10 times faster in the presence of Aliquat 336 product extracted with iso-octane. [60]... 

We first present general criteria for the rational use of MSRs on the basis of fundamentals of chemical reaction engineering [21-24], The main characteristics of MSRs are discussed, and the potential gain in reactor performance relative to that of conventional chemical reactors is quantified (Section 2). Subsequently, the most important designs of fluid-solid and multiphase reaction systems are described and evaluated (Sections 3 and 4). Because microstructured multichannel reactors with catalytically active walls are by far the most extensively investigated MSRs for heterogeneous catalytic reactions, we present their principal design and recent synthetic methods separately in Section 5. 

Bertucco et al. investigated the effect of SCCO2 on the hydrogenation of unsaturated ketones catalyzed by a supported Pd catalyst, by using a modified intemal-recycle Berty-type reactor [63]. A kinetic model was developed to interpret the experimental results. To apply this model to the multiphase reaction system, the calculation of high-pressure phase equilibria was required. A Peng-Robinson equation of state with mixture parameters tuned by experimental binary data provided a satisfactory interpretation of all binary and ternary vapor-liquid equilibrium data available and was extended to multicomponent... 

Bench development of the route (or routes) of choice is pursued aggressively, ideally by both synthesis chemists and chemical engineers, with the former elucidating reaction pathways and byproducts, seeking superior reaction conditions (solvents, catalysts, auxiliary chemicals, temperature, pressure, concentrations, reactant ratios, and approximate kinetics) as well as probing work-up and isolation methods. The engineers work, in collaboration with the chemists, on aspects of the chemistry better suited to their skills (e.g., kinetics and thermochemistry, multiphasic reaction systems... 

Inhomogeneous or multiphase reaction systems are characterised by the presence of macroscopic (in relation to the molecular level) inhomogeneities. Numerical calculations of the hydrodynamics of such flows are extremely complicated. There are two opposite approaches to their characterisation [63, 64] the Euler approach, with consideration of the interfacial interaction (interpenetrating continuums model) and the Lagrange approach, of integration by discrete particle trajectories (droplets, bubbles, and so on). The presence of a substantial amount of discrete particles in real systems makes the Lagrange approach inapplicable to study motion in multicomponent systems. Under the Euler approach, a two-phase flow is described... 

The separation of multiphase reaction system components in tubular turbulent diffuser-confusor devices occurs at high rates of flow. The peripheral area of a tubular turbulent diffuser-confusor device has a pressure gradient, which moves the particles in the opposite direction to the direction of the main flow (circulation zone). A liquid flow rotates in this area and an unusual effect appears centrifugal forces can lead to phase separation, which is mainly caused by the differences in the density of components participating in the dispersing process. Substantial differences in the densities of continuous and dispersed P2 phases and following the Pi < condition... 

The phenomenon of "mass transfer with chemical reaction" takes place v/henever one phase is brought into contact with one or more other phases not in chemical equilibrium with it. This phenomenon has industrial, biological and physiological importance, in chemical process engineering, it is encountered in both separation processes and reaction engineering. In some cases, a chemical reaction may deliberately be employed for speeding up the rate of mass transfer and/or for increasing the capacity of the solvent in other cases the multiphase reaction system is a part of the process with the specific aim of nroduct formation. 

National Natural Science Foundation of China Project guide of NSFC key research program on meso-scale mechanisms and manipulation in multiphase reaction systems [EB/OL], 2013 Beijing, 2013, NSFC. http //www.nsfc.gov.cn/publish/portal0/zdyjjh/006/ infol95.htm. 

Apart from acidic catalysis, ionic liquids have been intensively tested in the last two decades for the immobilisation of homogeneously dissolved transition metal catalysts. Successful catalyst immobilisation techniques are essential for industrial homogeneous catalysis to solve the problem of catalyst/product separation and to recover and recycle the often very expensive dissolved transition metal complexes. Different immobilisation concepts applying ionic liquids have been developed, including the use of organic-ionic liquid multiphase reaction systems and the use of SILP catalysis. These concepts will be described in the following sections. 

Multiphase reaction systems for homogeneous transition metal catalysis consist of one - often polar - phase that contains the dissolved catalyst (the so-called immobilising phase or catalyst phase) and at least one second phase that preferably contains the reaction products. Generally, a suitable catalyst phase must exhibit the following properties ... 

For scientific studies and quality control, detailed characterization of the produced catalytic material is necessary. A key method to test a catalytic material is of course to study its performance in a reaction by a detailed analysis of its reactivity, selectivity, and lifetime. Note in this context that the observable kinetics of a heterogeneous catalyst or a catalyst in any multiphase reaction system is usually a complex interplay of diffusion and reaction processes (for details see Chapter 4). 

We shall discuss in this section the situation where we have two or three phases, which indeed covers the vast majority of multiphase reaction systems. There appears to be a limited number of possible reactor configurations for a given number of phases. In a given two-phase system the number of possible configurations is three ... 

Most of the kinetic analysis of organic reactions in ScCO presented in literature is based on the normal reaction mechanism (in the absence of ScCO ) and use mole fraction for the treatment of data, instead of concentration. The general simplified assumption used implies that CO modifies the phase equilibrium and does not influence the other typical steps in a multiphase reaction system. 

By resolving the structures and dominant mechanisms, it is possible to establish a stability condition reflecting the compromise between different dominant mechanisms for multiphase reaction systems, and the stability condition supplies a mesoscale constraint in addition to mass and momentum conservation equations. The calculation of EMMS model... 

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