Hollow reactors

Studying cyclopentane pyrolysis processes, Frey [72] has found that in a hollow reactor about 5.4% of olefins and diolefms are formed, among which only 2.7% are formed by cyclopentadiene and 66.5% of cyclopentane remain unconverted. Thermal degradation of cyclopentane was thoroughly studied by Japanese scientists [73]. 

The results of studies of this reaction in a hollow reactor show high selectivity up to 640 °C in the range of 4-EP volume rate from 0.065 to 0.78 h 1 and at 4-EP 20% aqueous H202 = 1 3 [94], Under optimal conditions at 620 °C, 4-VP yield equals 20.9% with 92% selectivity. Injection of quartz granules to the reactor raises the yield to 44.3% and selectivity to 96%. This is because the total surface on which, probably, the chain initiation reaction ... 

Besides, it is advisable to carry out the direct synthesis of phenylchlorosilanes not in hollow reactors in the fluidised layer, but in mechanically agitated reactors where the contact time of chlorobenzene and contact mass increases approximately 10-fold this seems to have a favourable effect on the yield of diphenyldichlorosilane. Thus, the direct synthesis of phenylchlorosilanes with the mechanical mixture of silicon and copper promoted by zinc oxide and cadmium chloride produces a condensate, which after the separation of unreacted chlorobenzene contains 25-30% of phenyltrichlorosilane and 50-55% of diphenyldichlorosilane. This condensate is rectified to extract phenyltrichlorosilane by the technique described above at the third rectification stage it yields diphenyldichlorosilane. 

Hollow-fiber module Hollow-fiber reactor Hollow fibers... 

In this case study, an enzymatic hydrolysis reaction, the racemic ibuprofen ester, i.e. (R)-and (S)-ibuprofen esters in equimolar mixture, undergoes a kinetic resolution in a biphasic enzymatic membrane reactor (EMR). In kinetic resolution, the two enantiomers react at different rates lipase originated from Candida rugosa shows a greater stereopreference towards the (S)-enantiomer. The membrane module consisted of multiple bundles of polymeric hydrophilic hollow fibre. The membrane separated the two immiscible phases, i.e. organic in the shell side and aqueous in the lumen. Racemic substrate in the organic phase reacted with immobilised enzyme on the membrane where the hydrolysis reaction took place, and the product (S)-ibuprofen acid was extracted into the aqueous phase. 

Hollow fiber reactors [7] and dialysis reactors [8] avoid shear stress by separating cells and flowing media. In both reactors nutrient supply takes place by diffusion through the capillary wall or the dialysis membrane. 

The main disadvantage of all these systems is the Hmitation of scale-up. Monoclonal antibodies are produced by multiplying the hollow fiber systems and stirred tank reactors with membrane aeration are known up to 100 liter. Small quantities of product can be produced by these systems but they are not suitable for real industrial scale-up. 

There are a variety of routes currently utilized to fabricate a wide range of hollow capsules of various compositions. Among the more traditional methods are nozzle reactor processes, emnlsion/phase-separation procednres (often combined with sol-gel processing), and sacrificial core techniques [78], Self-assembly is an elegant and attractive approach for the preparation of hollow capsules. Vesicles [79,80], dendrimers [81,82], and block hollow copolymer spheres [83,84] are all examples of self-assembled hollow containers that are promising for the encapsnlation of various materials. 

The next two chapters concern nanostructured core particles. Chapter 13 provides examples of nano-fabrication of cored colloidal particles and hollow capsules. These systems and the synthetic methods used to prepare them are exceptionally adaptable for applications in physical and biological fields. Chapter 14, discusses reversed micelles from the theoretical viewpoint, as well as their use as nano-hosts for solvents and drugs and as carriers and reactors. 

Cross-flow ultrafdtration equipment.—The device used is shown in Figure 1. It included a glass reactor (R) with temperature, pH and stirring control, a Minitan pump (P) (Millipore, Bedford, USA), a Harp hollow fiber membrane cartridge (M) (Romicon-Supelco, Bellefonte, USA) with a cut-off of 2000 daltons, and a permeate exit (f) for fraction collection. The retentate (r) was returned to the reactor. 

Remarks Dead-end reactor with a hollow shaft or a nuiltistirrer system possible Internals like disc-donuts or perforated plates can be inserted Internal gas circulation without pumping device possible... 

A gas-inducing agitator system is an alternative to a multistirrer system. It contains a hollow shaft with orifices above the liquid level and a hollow impeller. A typical hollow impeller consists of a tube that is, at the centre, connected to the hollow shaft. Both ends of the impeller are cut at 45 so that, at rotation, the open portions of the tube are at the near side of the stirrer. There are several modifications of this design. Obviously, there is a minimum impeller speed at which the onset of gas induction occurs. Loop reactors are also successfully used. 

Hollow-fiber membrane reactor Hydrolysis of sunflower oil Lipase from Rhizopus sp. 122... 

The production process for (S)-phenylalanine as an intermediate in aspartame perpetuates the principle of reracemization of the nondesired enantiomer (Figure 4.5) in a hollow fiber/ liquid membrane reactor. Asymmetric hydrolysis of the racemic phenylalanine isopropylester at pH 7.5 leads to enantiopure phenylalanine applying subtilisin Carlsberg. The unconverted enantiomer is continuously extracted via a supported liquid membrane [31] that is immobilized in a microporous membrane into an aqueous solution of pH 3.5. The desired hydrolysis product is charged at high pH and cannot, therefore, be extracted into the acidic solution [32]. 

Ricks, E.E., Estrada-Vades, M.C., McLean, T.L. and Iacobucci, G.A. (1992) Highly enantioselective hydrolysis of (/ ,Sl-phenylalanine isopropyl ester by subtilisin Carlsberg. Continuous synthesis of (Sl-phenylalanine in a hollow fibre/liquid membrane reactor. Biotechnology Progress, 8, 197-203. 

Osorio-Lozada, A., Surapaneni, S., Skiles, G. and Subramanian, R. (2008) Biosynthesis of drug metabolites using microbes in hollow fiber cartridge reactors case study of diclofenac metabolism by Actinoplanes sp. Drug Metabolism and Disposition The Biological Fate of Chemicals, 36, 234-240. 

Enzyme membrane reactor for production of diltiazem intermediate. A solution of the racemic ester in organic solvent enters the port at the bottom of the reactor and flows past the strands of microporous, hollow-fiber membrane that contain an enzyme. The enzyme catalyzes hydrolysis of one enantiomer of the ester that undergoes decarboxylation to 4-methoxyphenylacetaldehyde (which in turn forms a water-soluble bisulfite complex that remains in the aqueous phase). The other enantiomer of the ester remains in the aqueous stream that leaves the reactor via the port at the top. Courtesy of Sepracor, Inc. 

An immobilized-enzyme continuous-flow reactor incorporating a continuous direct electrochemical regeneration of NAD + has been proposed. To retain the low molecular weight cofactor NADH/NAD+ within the reaction system, special hollow fibers (Dow ultrafilter UFb/HFU-1) with a molecular weight cut-off of 200 has been used [32],... 

Natural nuclear reactors, 17 589 25 397 Natural organic polymers, manufactured fibers produced from, 24 616 Natural photocatalytic processes, in the environment, 19 100-101 Natural plant growth regulators, 13 22-28 Natural polymer hollow fibers, 16 23... 

Spinning basket reactor, 21 352, 353 Spinning-cup atomizers, 23 659 Spinning-cup sulfur burner, 23 660 Spinning machines, 19 749 Spinning processes, hollow-fiber, 16 7-12 Spinning pump, for olefin fiber extrusion, 11 231... 

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