Our results point to the weakness in assuming, as is usually done, that the maximum value of PDI for condensation reactions in a well-mixed batch reactor is 2. Thus, if a polymerization reaction is controlled by monitoring the number average molecular weight, the resulting =, can be widely different, depending on whether R was slightly below or above 1. A group attached to a polymer is so low that it is less than the product of the probability 7 of reaction of an A group attached to a polymer and the probability ( I -a) of finding an unreacted B group. Hence, the weight fraction of the species of the type (BBAA), is lower than the weight fraction of the species of the type (BBAA),BB. Thus, the weight fraction of any species containing an even number of units is less than the weight fraction of the next larger species containing one more unit, even when n is large. This disparity in the weight fractions is so large that two separate curves, one each for molecules containing even and odd number of units, may be drawn as done in
Effectiveness Factors and Mass Transfer in Trickle-Bed ReactorsRates of hydrogenation of a-methyl styrene were measured at 40.6OC and 1 atm in a recycle, trickle-bed reactor using a palladium/aluminum oxide catalyst. Data for different hydrogen concentrations in the gas and liquid feed streams suggested that except, at high liquid flow rates, on part of the outer surface of the catalyst the mass transfer limitation was very small, indicating a gas covered type of surface. A procedure was developed for evaluating effectiveness factors for the nonuniform boundary conditions existing when part of the particle surface is covered by gas.
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