A multigrain catalyst model for unifunctional multicomponent catalysts

A multigrain catalyst model is developed to describe the simultaneous multicomponent diffusion-cum-reaction taking place in a unifunctional multicomponent catalyst. In this, particles of the more active component are randomly dispersed in a less active near-spherical porous matrix. The catalyst macro-particle is assumed to consist of sub-layers of different thicknesses of active matrix, M, alternating with sub-layers (of different thicknesses) of microspherical particles of the more active component (Z) embedded in the active matrix (the Z + M sub-layer). Cracking of a model compound, 1,3,5-triisopropylbenzene (1,3,5-TIPB), in this catalyst particle is selected as a simple test problem. The concentration profiles of the reactant and the products within the catalyst macro-particle are computed and the effects of important parameters on these are studied

Vapor grown carbon fibers from pyrolysis of hydrocarbons: Modeling of filament growth and poisoning

A kinetic scheme has been proposed as a feasible model to explain the lengthening step in vapor grown carbon fibers from the pyrolysis of hydrocarbons. The two-parameter model assumes that the filaments lengthen by the reaction of a pyrolysis product with the growing filaments, and that the growth process ceases when the catalyst particle attached to the growing filament is poisoned by some reactive species in the gas phase. The model results show that the rate of filament growth is initially high and decreases monotonically. The final average filament length is found to depend only on the ratio of the rate of growth to the rate of poisoning. The model results can satisfactorily correlate the limited experimental data available in the open literature