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Partially wetted catalyst performance in the consecutive‐parallel network
Author(s) -
Harold Michael P.
Publication year - 1988
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690340611
Subject(s) - wetting , selectivity , catalysis , chemistry , stoichiometry , limiting , kinetics , chemical engineering , thermodynamics , inorganic chemistry , organic chemistry , physics , mechanical engineering , quantum mechanics , engineering
Abstract In this study the impact of the transport processes and the degree of wetting on the overall selectivity of a single catalytic pellet is examined for the commercially important consecutive‐parallel network A (g) + v B B (l) → v R1 R (l) , A (g) + v R2 R (l) → P (l) . The one‐dimensional formulation applies to catalysts in which the active component is concentrated in a thin porous surface shell coating an impermeable support. Model modifications provide an approximate description of uniformly active catalysts. The kinetics are assumed to be first and zero order with respect to the volatile ( A ) and nonvolatile ( B, R ) components, respectively, as encountered in many olefin hydrogenations. The common literature assumption of volatile reactant limiting reactions is relaxed by accounting for nonvolatile reactant depletion. The depletion can significantly reduce the desired product ( R ) selectivity below its intrinsic value attained under fully wetted, no‐depletion conditions. A model employing the single limiting reactant assumption cannot predict such selectivity variations. The selectivity is shown to be a complex function of the wetting efficiency, the stoichiometry, and the interacting reactions and mass transport processes. In many cases the intrinsic selectivity is attained for wetting efficiencies exceeding a critical value. Increases in the wetting above this value can reduce significantly the production rate of R because of resistance to A supply through the liquid film. Thus, an optimal range of wetting efficiencies exists for which the selectivity is equal to its intrinsic value and overall rates are high. The significance of the main findings with regard to trickle‐bed reactor performance are discussed.