Temperature excursions in catalytic monoliths

Abstract

The application of monolithic catalysts to automotive emission control has frequently been complicated by unexplained thermal degradation phenomena. This paper reports experimental and theoretical studies aimed at the understanding of how heat is generated and distributed in catalytic monoliths during an exothermal, mass transfer limited reaction.Theoretical considerations indicate that under certain operating conditions the steady state solid catalyst temperature can exceed the adiabatic reaction temperature. It is also shown that the catalyst overtemperature is influenced by the nature of the reactive species and by the geometry of the catalyst. These predictions have been verified by experiments in a novel tubular reactor. j L. LOUIS HEGEDUS General Motors Research Laboratories Warren, Michigan 48090 (0, -0,) -2 pivi = 0 or $5.00 for photocopies.

Adequacy of lumped parameter models for SCR reactors with monolith structure

“…Considerable work has been done on modeling and analyzing general monolith (or catalytic wall) reactors (Carberry and Kulkarni, 1973;Votruba et al, 1975a;Smith and Carberry, 1975;Hlavacek and Votruba, 1976;Heck et al, 1974;Hegedus, 1975;Young and Finlayson, 1976a, b;Pereira et al, 1988). Since this class of reactors has been applied mostly to automotive catalytic converters (Taylor, 1984) and to catalytic combustors (Trimm, 1980;Pfefferle and Pfefferle, 1988), emphasis has been placed primarily on the analysis of strong thermal effects, multiplicity of steady states, and other phenomena associated with very fast exothermic reaction conditions, that is, in a purely diffusional regime.…”

Optimal design of catalytic converters for minimizing cold-start emissions

“…Articles by Hegedus [1], Heck et al [2], Young and Finlayson [3] and Boersma et al [4] are amongst the first that describe both the experimental and modeling work on catalytic monoliths. Review articles by Cybulski and Moulijn [5], Groppi et al [6] and books by Becker and Pereira [7], Hayes and Kolaczkowski [8] summarize the recent progress.…”

The Effect of Catalytic Washcoat Geometry on Light-off in Monolith Reactors

“…Good reviews of the plethora of publications dealing with catalytic combustion in monolith reactors, including modelling at various levels of sophistication, have been published [13][14][15][16][17]. One-dimensional [18][19][20] and two-dimensional models [21] have been used. The use of three-dimensional models is less reported, likely as a result of their computational complexity and expense.…”