Heterogeneous reaction system

Terminal and disubstituted internal alkenes react rather slowly with HC1 in nonpolar solvents. The rate is greatly accelerated in the presence of silica or alumina in noncoordinating solvents such as dichloromethane or chloroform. Preparatively convenient conditions have been developed in which HC1 is generated in situ from SOCl2 or (ClCO)2.2 These heterogeneous reaction systems also give a Markovnikov orientation. 

Both homogeneous and heterogeneous reaction systems are frequently encountered in commercial practice. The term homogeneous reaction system is restricted in this text to fluid systems in... 

The comparison among runs (A-l to A-4) shows the sensitivity of oxygen addition to the graft efficiency. The best results in this heterogeneous reaction system are realized when the O2 is introduced slowly so that O B at any time. 

The conditions that must be satisfied by a heterogeneous reaction system in order to be sensitive for segregation and interaction are ... 

Steady states and oscillations in homogeneous-heterogeneous reaction systems (with X. Song and L.D. Schmidt). Chem. Eng. Sci. 46,1203-1215 (1991). 

The grafting reaction of vinyl monomer onto cellulosic fiber is a heterogeneous reaction system. Cellulosic fibers are in a solid phase, and vinyl monomers are in a vapor phase or, as a solute, in a solution phase. Two general methods for initiating grafting reactions are, as follows (1) one-step method monomer is in contact with cellulose when the initiating macrocellulosic radicals are formed or (2) two-step method after formation of the radicals, monomer is contacted with the activated cellulose. 

Imbihl, R., in Optimal Structures in Heterogeneous Reaction Systems (P. J. Plath, ed.), p. 26. Springer-Verlag, Heidelberg, 1989. 

Synthesis in Solid-Liquid Heterogeneous Reaction Systems... 

In heterogeneous reaction systems, the rate of reaction is usually expressed in measures other than volume, such as reaction surface area or catalyst weight. Thus for a gas soUd catalytic reactioa, the dimensions of tltis rate, -/ jj, are the number of moles of A reacted per unit time per unit mass of catalyst (mol/S g catalyst). Most of the introductory discussions on chemical reaction engineering in tins book focus on homogeneous systems. 

Liquid space surrounding active solid. Particularly in heterogeneous reaction system involving a liquid medium, thorough examination of the hydrodynamic flow conditions is appropriate. An example will illustrate this point. 

The many benefits of ultrasound in chemical systems are well-known, and are reported elsewhere in this volume, but perhaps the most striking influence of ultrasound concerns heterogeneous reaction systems, particularly those with a solid-liquid interface where particle size modification, the cleaning of surfaces, or the formation of fresh surfaces are among the beneficial processes. 

Similarly to microwaves, the use ofultrasound can dramatically speed-up chemical reactions and increase the product yield. Table 3.7 shows some examples of such ultrasound effects, both in homogeneous and in heterogeneous reaction systems. More data can be found in the review by Thompson and Doraiswamy [149]. 

Criegee, R., and G. Schjroder. 1960. Direct observation of polymerization in the oleic acid-ozone heterogeneous reaction system by photo electron resonance capture ionization areal mass spectrometry. Chemische Berichte 93 689. 

In the applications where high pressure of residual gases (nonpermeate stream) is required, membranes are well suited. The transport steps involved in a membrane system are very similar to the transport steps involved in a heterogeneous reaction system where first the reactant should be adsorbed on the surface, then diffused into the pellet, and finally the products are desorbed. The permeating component of the gas stream is sorbed in the membrane, diffused through the membrane, and then desorbed on the other side of the membrane. Fundamental research in the area of development of suitable membranes for different gas processing and petrochemical-related industry applications is being carried out in various academic institutions. 

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