Here [Pf ] is the concentration of growing centres ending in monomer x and kx y is the absolute rate coefficient of reaction of P with monomer y. Two difficulties arise in anionic polymerization. In hydrocarbon solvents with lithium and sodium based initiators, [Pf ] is not the total concentration of polymer units ending in unit x but, due to self-association phenomena, only that part in an active form. The reactivity ratios determined are, however, unaffected by the association phenomena. As each ratio refers to a common active centre, the effective concentration of active species is reduced equally to both monomers. In polar solvents such as tetrahydrofuran, this difficulty does not arise, but there will be two types of each reactive centre Pf, one an anion and the other an ion-pair. Application of eqn. (22) will give apparent rate coefficients as discussed in Section 4 if total concentrations of Pf are used. Reactivities can change with concentration if defined on this basis. [Pg.53]

You will be solving for Ca ), but you cannot evaluate the rate of reaction in Eq. (8.45) because you do not know Ca.s- You need a mass balance relating the rate of mass transfer to the catalyst to the rate of reaction. One form of that is Eq. (8.46), where is a mass transfer coefficient in units of m/s, determined from correlations derived in fluid mechanics and mass transfer courses, a is the surface area exposed per volume of the reactor (m /m ), and k is a rate of reaction rate constant (here rn /kmol s). Other formulations are possible, too [Pg.132]

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