Reactors, chemical immiscible liquids

Polycondensation at room temperature between two or more fast-reacting intermediates is becoming widely used because of its convenience and speed. The interfacial polycondensation system, in particular, which employs two immiscible liquids, is applicable to a wide voriety of chemical structures amides, urethanes, esters, sulfonates, sulfonamides, and ureas. Many products can be made at low temperature which could not be formed by melt methods because of their infusibility or thermal instability. The low temperature procedures are subject to the effect of many variables, but these are readily controlled and acceptable conditions for use with new polymers or intermediates can usually be found. The processes are readily scaled up in simple batch equipment or continuous reactors. Special areas of application are the direct formation of fibers from the reactants and polycondensation on fiber substrates. 

Liquid-phase homogeneous catalytic reactions which are carried out in the absence of a second or even third phase, i.e., a gas or an immiscible liquid, can be treated from a chemical reaction engineering point of view in analogy to other homogenous reactions. If the chemical kinetics of such homogeneous catalytic reactions are known, the reactor performance can easily be predicted with respect to conversion and selectivity. The required procedures have been extensively described in various textbooks, e. g., [1-3]. 

Multiphase Reactors Reactions between gas-liquid, liquid-liquid, and gas-liquid-solid phases are often tested in CSTRs. Other laboratory types are suggested by the commercial units depicted in appropriate sketches in Sec. 19 and in Fig. 7-17 [Charpentier, Mass Transfer Rates in Gas-Liquid Absorbers and Reactors, in Drew et al. (eds.), Advances in Chemical Engineering, vol. 11, Academic Press, 1981]. Liquids can be reacted with gases of low solubilities in stirred vessels, with the liquid charged first and the gas fed continuously at the rate of reaction or dissolution. Some of these reactors are designed to have known interfacial areas. Most equipment for gas absorption without reaction is adaptable to absorption with reaction. The many types of equipment for liquid-liquid extraction also are adaptable to reactions of immiscible liquid phases. 

By process, we mean what occurs inside the reactor. If the material in the reactor is single phase and homogeneous, then the process is a reaction. Such a reaction can occur in a batch, a semi-batch, or a continuous reactor, depending upon our design. However, if the material in the reactor is multiphase, e.g., gas—liquid or two immiscible liquids, then it is a process. In other words, conversion of reactant to product involves more than chemical reaction it involves multiple steps, some of which are physical, such as diffusion across a phase boundary. If diffusion across a phase boundary or diffusion through one of the phases in the reactor is slower than the chemical reaction, then we define the process as diffusion rate limited. If physical diffusion occurs at a much higher rate than chemical reaction, then we define the process as reaction rate limited. ... 

One of the research areas focuses on miCTO-reactors with different catalysts fixed in different compartments within the micro-reactor. This allows a much more efficient use for the chemical pathway of the desired product to take place, as these reactions can take place simultaneously, eliminating the need for many reactors in series, or one reactor that has to be operated in a batch style, replacing the catalyst for each stage, etc. Ideal flow with no build up of product is essential in these reactors to avoid the accumulation of intermediate product, as is being investigated by using methods such as immiscible liquids, etc. 

Although Peligot observed in 1842 that uranyl nitrate is soluble in ether, it was not until materials of high purity were needed for nuclear reactors that extensive applications and developments, both industrial and analytical, were made. The literature on applications of liquid-liquid extraction (solvent extraction) is extensive for details of the various procedures the reader is referred to the original papers and to compilations. " This chapter examines separations involving distribution of a solute between two immiscible phases and chemical equilibria of significance to the distribution ratio. Batch, countercurrent, and continuous liquid-liquid extractions are described in turn, followed by consideration of the factors governing the distribution ratio and finally by some illustrative applications. 

Polymers are produced by polymerization reactions that chemicaliy bond iarge numbers of monomers together. Monomer(s), cataiysts, solvents or fluid carriers, and other secondary chemicals are continually fed into poiymerization reactors. The reaction process is maintained under controlled temperature and pressure. Common categories of polymerization reactions are buik, in which monomers are fed as a pure gas or liquid solution, in which monomers are dissolved in a solvent suspension, in which monomers are suspended in an immiscible medium and emulsion, in which monomers are dispersed as very tiny particles in the carrier. 

In a multiphase stratified flow, the interfaces between immiscible fluids have several characteristics. Firstly, the specific interfacial area can be very large just as droplet-based flow. It can for example be about 10,000 m in a microchannel compared with only 100 m for conventional reactors used in chemical processes. Secondly, the mass transfer coefficient can be very high because of the small transfer distance and high specific interfacial area. It is more than 100 times larger than that achieved in typical industrial gas-liquid reactors. Thirdly, the interfaces of a stratified microchannel flow can be treated as nano-spaces. Simulation results show that the width of the interfaces of a stratified flow is in nanometers, and that diffusion-based mixing occurs at the interface. The interface width can be experimentally adjusted by adding surfactants. Finally, reactants only contact and react with each other at the interface. Therefore, the interfaces supply us with mediums to study interfacial phenomena, diffusion-controlled interfacial reactions and extraction. 

The SFTR reactor uses two immiscible fluid phases (gas or liquid) to create individual micro volumes of previously well-mixed reactants. A static mixer is placed upstream, which ensures efficient and reproducible mixing of the reactants before they enter the reactor. The reactor is believed to be potentially suitable for the forced precipitation of crystals where the mixing step is of major importance in determining their chemical and physical characteristics. Instead of scaling up by increasing vessel size, the SFTR is to be scaled out by replication of similarly sized configurations, as production demands. 

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