Reactivity ratios continuous stirred tank

In addition to the above investigations, free-radical high-pressure polymerizations should also be studied in continuously operated devices for three reasons. (1) Because of the wealth of kinetic information contained in the polymer properties, product characterization is mandatory. Sufficient quantities of polymer, produced under well defined conditions of temperature, pressure, and monomer conversion, are best provided by continuous polymerization, preferably in a continuously stirred tank reactor (CSTR). (2) Copolymerization of monomers that have rather dissimilar reactivity ratios, such as in ethene-acry-late systems, will yield chemically inhomogeneous material if the reaction is carried out in a batch-type reactor up to moderate conversion. To obtain larger quantities of copolymer of analytical value, the copolymerization has to be performed in a CSTR. (3) Technical polymerizations are exclusively run as continuous processes. Thus, in order to stay sufficiently close to the application and to investigate aspects of technical polymerizations, such as testing initiators and initiation strategies, fundamental research into these processes should, at least in part, be carried out in continuously operated devices. 

The error-in-variables method was used to estimate the reactivity ratios. This method was developed by Reilly et al. (57, 58), and it was first applied for the determination of reactivity ratios by O Driscoll, Reilly, and co-workers (59, 60). In this work, a modified version by MacGregor and Sutton (61) adapted by Gloor (62) for a continuous stirred tank reactor was used. The error-in-variables method shows two important advantages compared to the other common methods for the determination of copolymer reactivity ratios, which are statistically incorrect, as for example, Fineman-Ross (63) or Kelen-Tiidos (64). First, it accounts for the errors in both dependent and independent variables the other estimation methods assume the measured values of monomer concentration and copolymer composition have no variance. Second, it computes the joint confidence region for the reactivity ratios, the area of which is proportional to the total estimation error. 

The use of a continuous stirred tank reactor permits one to apply the instantaneous copolymer equation for reactivity ratios estimation. 

Gloor, P. Estimation of Reactivity Ratios Using the Error-in-Variables Method and Data Collected from a Continuous Stirred Tank Reactor, MIPPT-Report, McMaster University, Hamilton, Ontario, Canada, 1987. 

The polymerization section consists of a series of continuously stirred tank reactors (24,25). The solvent (25) (usually cyclohexane) and monomers are fed into the reactor and an initiator as well as a randomizer [usually tetrahydrofuran (THF)] is added. The function of the randomizer is to make sure that no blocks are formed from a single monomer (Hall, Oxolanyl Cyclic Acetals as Anionic Polymerization Modifiers 68). This is because the reactivity ratios of the monomers are not ideal. Usually the reaction temperature is kept less than 110°C to prevent deactivation of the growing chain ends (25). Once polsrmerization is complete, alcohol is added to terminate the polymerization reaction and the polymer solution is transferred to holding tanks to be blended to increase imiformity. Subsequent steps of washing and filtering remove all the unreacted monomers, THF, and other chemicals. 

The styrene and acrylonitrile can be copolymerized by free radical methods using a continuous stirred tank reactor (CSTR). The reactivity ratios r,2 and rj, can be taken as 0.04 and 0.41, respectively. Construct a first-order Markov model using the dyad probabilities derived in Section 11.1. 

In addition to processes involving gas-liquid reactions, stirred-tank reactors can also be used for single (liquid)-phase reactions. Moreover, their operation is not limited to the continuous mode, and they can be easily adapted for use in semibatch and batch modes. The absence of a gas phase does not pose important structural and operational differences from those stated earlier for multiphase systems. However, in the case of single-phase operation, the aspect ratio is usually kept lower ( 1) to ensure well mixing of the reactive liquid. Regardless of the number of phases involved, stirred-tank reactors can approach their ideal states if perfect mixing is established. Under such conditions, it is assumed that reaction takes place immediately just... 

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