Styrene continuous flow stirred

The styrene conversion for the continuous flow stirred tank experiments was determined utilizing the concentration of the polymer in the feed and the number average degrees of polymerization... 

In the continuous hydrovinylation experiments, the ionic catalyst solution was placed in the reactor R, where it was in intimate contact with the continuous reaction phase entering from the bottom (no stirring was used in these experiments). The reaction phase was made up in the mixer from a pulsed flow of ethylene and a continuous flow of styrene and compressed CO2. 

A continuous polymerization train consisting of two stirred tanks in series is used to copolymerize styrene, rx = 0.41, and acrylonitrile, vy = 0.04. The flow rate to the first reactor is 3000 kg/h and a conversion of 40% is expected. Makeup styrene is fed to the second reactor and a conversion of 30% (based on the 3000 kg/h initial feed) is expected there. What should be the feed composition and how much styrene should be fed to the second reactor if a copolymer containing 58 wt% styrene is desired ... 

Polystyrene can be easily prepared by emulsion or suspension techniques. Harkins (1 ), Smith and Ewart(2) and Garden ( ) have described the mechanisms of emulsTon polymerization in batch reactors, and the results have been extended to a series of continuous stirred tank reactors (CSTR)( o Much information on continuous emulsion reactors Ts documented in the patent literature, with such innovations as use of a seed latex (5), use of pulsatile flow to reduce plugging of the tube ( ), and turbulent flow to reduce plugging (7 ). Feldon (8) discusses the tubular polymerization of SBR rubber wTth laminar flow (at Reynolds numbers of 660). There have been recent studies on continuous stirred tank reactors utilizing Smith-Ewart kinetics in a single CSTR ( ) as well as predictions of particle size distribution (10). Continuous tubular reactors have been examined for non-polymeric reactions (1 1 ) and polymeric reactions (12.1 31 The objective of this study was to develop a model for the continuous emulsion polymerization of styrene in a tubular reactor, and to verify the model with experimental data. 

There are two common types of continuous reactors continuous stirred tank reactors (CSTRs) (53), and plug flow reactors (PFRs). CSTRs are simply large tanks that are ideally well-mixed (such that the emulsion composition is uniform throughout the entire reactor volume) in which the polymerisation takes place. CSTRs are operated at a constant overall conversion. CSTRs are often used in series or trains to build up conversion incrementally. Styrene-butadiene rubber has been produced in this manner. Not all latex particles spend the same amount of time polymerising in a CSTR. Some particles exit sooner than others, producing a distribution of particle residence times, diameters and compositions. 

Pig. 7. Two Continuous stirred tank reactors (CSTR) and a continuous plug flow reactor (CPFR) configuration utilized for continuous mass polymerization of styrene. 

The batch suspension polymerization system considered in the present study, is schematically shown in Figure 1. It consists of a well mixed jacketed vessel. In the suspension polymerization process, liquid styrene is dispersed in the continuous aqueous phase by the combined action of stirring and the use of suspending agents. The reaction takes place in the monomer droplets. For modelling purposes, each droplet can be treated as a small batch bulk polymerization reactor. The heat of polymerization is transferred from the dispersed droplets to the aqueous phase and then to the coolant flowing through the reactor s jacket. 

Raw materials like styrene (potentially purified), and processing aid are fed into the reactor(s). The reactor train usually includes continuous stirred tank reactors (CSTR) and/or plug flow reactors (PFR). 

The reactor train usually includes continuous stirred tank reactors (CSTR) and/or plug flow reactors (PFR). The styrene itself acts as the solvent of the reaction. Moreover, up to 10 % of ethylbenzene is added to ensure a better reaction control. The reactors temperatures are between 110 and 180 °C. The pressure is up to 1 MPa in a PFR, whereas reactions in CSTR are carried out under atmospheric or sub-atmospheric pressure. At the end of the reactor train, the styrene monomer conversion reaches 60 - 90 % solid. 

The continuous stirred-tank reactor is also known as a continuous backmix, bachnaed, or mixed flow reactor. In addition to the catalytic reactors mentioned in the preceding paragraph, the reactors that are used for certain continuous polymerizations, e.g., the polymerization of styrene monomer to polystyrene, closely approximate CSTRs. 

Styrene polymerizes spontaneously on heating by a free-radical mechanism. Some commercial polystyrene is produced by suspension and emulsion polymerization, but the principal route is solution polymerization. This is carried out either in a continuous plug-flow reactor (CPFR) or a continuous stirred tank reactor (CSTR). 

In the polymerization process shown in Fig. Ic [3], a fresh feed of 8% polybutadiene rubber in styrene is added with antioxidant and recycled monomer to the first reactor operating at 124 C and about 18% conversion at about 40% fillage. The agitator is a horizontal shaft on which a set of paddles is mounted. Because the temperature in each compartment can be varied, it is claimed that the linear flow behavior provided by the reactor staging results in more favorable rubber-phase morphology than would be the case if the second reactor were operated as a single continuous stirred tank reactor. 

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