Continuous solution reactors

This general phenomenon of buildup of solid polymer in static areas of the reactor is common to all continuous solution reactors. A major component of the design is to eliminate regions where this may occur. This is one of the drivers for incorporating agitators in the tower reactors which will be discussed in the next section and has also been a driver for removing heat transfer tubes from the reactor which add wall surface. 

Figure 3.3 summarizes mixing for the various types of continuous solution reactors. Eliminating the wall buildup prevalent in nonradial mixed reactors drives the reactor designer from left to right. The choice from top to bottom depends on the product requirements and the degree of temperature and composition dispersion needed to accomplish them, and the capital cost of multiple control zones in series. 

Solution Polymerization. Solution polymerization of vinyl acetate is carried out mainly as an intermediate step to the manufacture of poly(vinyl alcohol). A small amount of solution-polymerized vinyl acetate is prepared for the merchant market. When solution polymerization is carried out, the solvent acts as a chain-transfer agent, and depending on its transfer constant, has an effect on the molecular weight of the product. The rate of polymerization is also affected by the solvent but not in the same way as the degree of polymerization. The reactivity of the solvent-derived radical plays an important part. Chain-transfer constants for solvents in vinyl acetate polymerizations have been tabulated (13). Continuous solution polymers of poly(vinyl acetate) in tubular reactors have been prepared at high yield and throughput (73,74). 

Both kinetic and equilibrium experimental methods are used to characterize and compare adsorption of aqueous pollutants in active carbons. In the simplest kinetic method, the uptake of a pollutant from a static, isothermal solution is measured as a function of time. This approach may also yield equilibrium adsorption data, i.e., amounts adsorbed for different solution concentrations in the limit t —> qo. A more practical kinetic method is a continuous flow reactor, as illustrated in Fig. 5. 

Application of Wiener type predictive controller to the continuous solution polymerization reactor... 

Table 4 Hydrolysis of continuous flow reactor product solution.

Current single-mode continuous-flow microwave reactors allow the processing of comparatively small volumes. Much larger volumes can be processed in continuous-flow reactors that are housed inside a multimode microwave system. In a 2001 publication, Shieh and coworkers described the methylation of phenols, indoles, and benzimidazoles with dimethyl carbonate under continuous-flow microwave conditions using a Milestone ETHOS-CFR reactor (see Fig. 3.11) [104]. In a typical procedure, a solution containing the substrate, dimethyl carbonate, 1,8-diazabicy-clo[5.4.0]undec-7-ene (DBU) base, tetrabutylammonium iodide (TBAI), and a solvent was circulated by a pump through the microwave reactor, which was preheated to 160 °C and 20 bar by microwave irradiation (Scheme 4.31). Under these condi-... 

Experiments were conducted with a dual catalyst chain shuttling system in a continuous solution polymerization reactor. A series of ethylene-octene copolymers of similar melt index were produced with a composition of ca. 30% (by weight) hard and 70% soft blocks. The level of DEZ was systematically varied to study the effects of CSA ratio on polymer microstructure. 

Saaby S, Knudsen KR, Ladlow M, Ley SV (2005) The Use of a Continuous Flow-Reactor Employing a Mixed Flydrogen-Liquid Flow Stream for the Efficient Reduction of Imines to Amines. Chem Commun 23 2909-2911 Seebach D, Overhand M, Kilhnle FNM, Martinoni D, Oberer L, Hommel U, Widmer H (1996) Beta-Peptides Synthesis by Arndt-Eistert Homologation with Concomitant Peptide Coupling. Structure Determination by NMR and CD Spectroscopy and by X-ray Crystallography. Helical Secondary Structure of a Beta-Hexapeptide in Solution and its Stability Towards Pepsin. Helv Chim Acta 79 913-941... 

Continuous SO3 single-pass sulfonation processes, 23 543-552, 550 Continuous solution polymerization, reactors used for, 23 394-395 Continuous steel casting, 23 266-270 difficulties of, 23 266-267 universality of, 23 269-270 Continuous sterilization, in fermentation, 11 35-36... 

Fig. 5.15b shows a thin-film continuous flow reactor used by Bruno et al. (1991) for determining the dissolution rate of U02 under reducing conditions. A known weight of U02(s) was enclosed into the reactor between two membrane filters (0.22 jum). The reducing conditions of the feed solution were obtained by bubbling H2(g) in the presence of a palladium catalyst. The dissolution rates determined using continu-... 

F. Teymour and W.H. Ray. The dynamic behavior of continuous solution polymerization reactors-IV. Dynamic stabihty and bifurcation analysis of an experimental reactor. Chem. Eng. Sci., 44(9) 1967-1982, 1989. 

Solution of the educts and catalyst are pumped through the system, which is controlled by electronic balances. The actual reaction is performed in 87 ml continuous-flow reactor, from which samples are taken automatically and analyzed by gas chromatography (GC). The analytical data are processed online. 

Fixed-bed reactors Trickle-flow reactor (TFR) This is a tubular flow reactor with a concurrent down-flow of gas and liquid over a fixed-bed of catalyst (Figure 3.10). Liquid trickles down whereas the gas phase is continuous. This reactor is mainly used in catalytic applications. Typical application examples of this reactor type are the following HDS of heavy oil fractions and catalytic hydrogenation of aqueous nitrate solutions. 

In case 2 (middle panel of Fig. 15.9), the initial solution was also determined by beginning with an equilibrium estimate at a reactor temperature of T = 1200 K. Then, through a series of continuations, solutions were determined at temperatures down to 900 K. In this case the solutions are in reasonable agreement with the true solution, although there is some disagreement in the region around 1000 K. 

Silica-supported triflic acid catalysts were prepared by various methods (treatment of silica with triflic acid at 150°C or adsorption of the acid from solutions in trifluoroacetic acid or Freon-113) and tested in the isobutane-1-butene alkylation.161 All catalysts showed high and stable activity (near-complete conversion at room temperature in a continuous flow reactor at 22 bar) and high selectivity to form saturated C8 isomers (up to 99%) and isomeric trimethylpentanes (up to 86%). Selectivities to saturated C8 isomers, however, decreased considerable with time-on-stream (79% and 80% after 24 h). 

A main adimntage of immobilized enzyme is that it can be reused since it can be easily separated from the reaction solution and can be easily retained in a continuous-flow reactor. Furthermore, immobilized enzyme may show selectively altered chemical or physical properties and it may simulate the realistic natural environment where the enzyme came from, the cell. 

The research subject in the given problem is the process of cementation based on squeezing out mercury from salt-acidic solution by means of a less useful metal, such as aluminum. A study of kinetics of the given chemical reaction shows that this process may be effectively conducted in a continuous chemical reactor. Process efficiency is measured by mercury concentration in the solution after refinement. This is simultaneously the system response as it may be measured quite accurately and quantitatively. These three factors influence the cementation process significantly Xi-temperature of solution, °C X2-solution flow rate in reactor, ml/1 and X3-quantity of aluminum g. The factor space is defined by these intervals 50[Pg.341]

Continuous flow reactors allow a new way of catalyst preparation. The fluidic pathways can be used for the transport of impregnation liquid or solid particles if means are supplied to localize the catalysts at defined positions inside the reactor. One possibility is the flow impregnation of wash-coated micro structures with catalyst solutions [38],... 

To demonstrate the synthetic application of this methodology, the authors subsequently demonstrated its use for the preparative kinetic resolutions of a series of 2° alcohols, Table 24, whereby 20 ml solutions of each racemic alcohol were passed through the bioreactor (3.3 h) and found to afford analogous results to those obtained during the initial optimization experiments. The authors successfully demonstrated the use of immobilized and lyophilized enzymes within a continuous flow reactor, presenting a synthetically viable approach to the kinetic resolution of racemic alcohols. 

Employing a stainless-steel continuous flow reactor, Zhang et al. (2004) described the synthesis of gram to kilogram quantities of material for use in early clinical studies. One reaction reported by the authors was the exothermic synthesis of N-methoxycarbonyl-L-ferf-leucine 210, as illustrated in Scheme 61. By continuously adding a solution of methyl chlor-oformate 211 to i-tod-leucine 212, in the presence of aq. NaOH 26, at a reactor temperature of —40°C afforded the target compound 210 in 91% yield with a throughput of 83.0 gh... 

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