Catalyst deactivation by multilayer coking: A kinetic model

Local effective diffusivity in a pellet deactivated by multilayer coking

“…While the local effective diffusivity can be expressed in terms of the local coke content Cc, the average effective diffusivity cannot be expressed in terms of the total coke content of the pellet, as we shall soon see. According to the multilayer kinetic model (Klingman and Lee, 1986), the local coke content C , ( z ) normalized with respect to its "monolayer" coke content Q is related to the fraction of catalyst deactivated y for the case of infinite number of layers allowed by:…”

“…Since the parameters Q and Ep are known from the data of activity vs. total coke content obtained under diffusion-free conditions, which are detailed elsewhere (Klingman and Lee, 1986), the problem is again that of determining a and p. The definition of a, which is the inverse of the total coke content required to fill the pores, enables one to determine a from the measurements of porosity and total coke content. Thus the problem is simply that of determining 0.…”

“…The intrinsic relationship between catalytic activity and the amount of coke deposits, which is applicable in the absence 2022 December 1994 of diffusion limitation, has been developed (Klingman and Lee, 1986) based on a multilayer kinetic model. The kinetic model, which accounts for the multilayer nature of coke growth is applicable in its concept and approach to any type of coking, although the specific results are applicable to a class of coking in which an energetically uniform surface is involved in both the main and coking reactions.…”