Design of Fixed Bed Catalytic Microreactors

Abstract

permeation process could be accounted for by assuming that the activation energy is changed by an amount proportional to the stored mechanical energy. An estimate of the stored energy per unit volume may be obtained by taking the product of t (eq 8) with the mean stress, , defined as the value of the local stress (eq 7) at the mid-radial portion, i.e., at x = 3.18 cm. In addition, if the volume

A new technique for the determination of contact time distribution (CTD) from tracers experiments in heterogeneous systems

“…Within the framework of fixed-beds catalytic reactors modelling, Shinnar and co-workers (Shinnar et al, 1972;Shinnar, 1986;Silverstein and Shinnar, 1975) have defined and used another concept of contact time distribution (CTD) by considering the reactor as a combination of a mobile phase and a stagnant phase. This is an example of multi-zones system where a residence time distribution is associated to each of them (Aris, 1984;Gibilaro, 1979).…”

Dispersion and diffusion influences on yield in complex reaction networks

“…Consider a reactor with a residence time distribution close to that of a plug flow reactor so that its Laplace transform can be represented as (Silverstein and Shinnar, 1975)…”

“…Many papers have examined the influence of axial dispersion or residence time distribution on the conversion or yield in reactors in which first-order reactions occur. Many investigators studied the conditions leading to optimal yield for specific reaction networks and kinetic parameters (Tichacek, 1963;Kipp and Davis, 1968;Chung and Howell, 1970;Glasser et al, 1973;Wan and Ziegler, 1973;Silverstein and Shinnar, 1975;Dang, 1984).…”

“…It is shown that in a packed-bed reactor, the fractional yield loss is smaller than:where m -1 is the number of reaction steps involved in converting a reactant to the desired product, 08' is the dimensionless variance of the residence time density function, Bi,,, is the Biot number, p2 = [( V,/S,)*(I / (DJ)], and T is the average residence time.predicting the minimal length a laboratory reactor should have for specified operating conditions so that the yield of a desired product will not deviate by more than some specified value from that of a full scale reactor.Tichacek (1963) developed a rule of thumb that for two consecutive reactions, the maximum fractional reduction in the yield of an intermediate due to axial dispersion is approximately equal to 1/Pe = D,,/uL, where D, is the axial disperison coefficient. Glasser et al (1973) and Silverstein and Shinnar (1975) conjectured that for n isothermal, irreversible, first-order, consecutive reactions, the maximal fractional yield loss of the mth species due to axial dispersion occurs when the rate constants of the first m reactions are equal. This led to a prediction that the maximal fractional yield loss of the mth species due to a small deviation from plugflow is(1)…”

“…Tichacek (1963) developed a rule of thumb that for two consecutive reactions, the maximum fractional reduction in the yield of an intermediate due to axial dispersion is approximately equal to 1/Pe = D,,/uL, where D, is the axial disperison coefficient. Glasser et al (1973) and Silverstein and Shinnar (1975) conjectured that for n isothermal, irreversible, first-order, consecutive reactions, the maximal fractional yield loss of the mth species due to axial dispersion occurs when the rate constants of the first m reactions are equal. This led to a prediction that the maximal fractional yield loss of the mth species due to a small deviation from plugflow is…”