Effectiveness factors of nth order kinetics in trickle-bed reactors

Goto, S.; Lakota, Ana; Levec, Janez

doi:10.1016/0009-2509(81)80059-0

Cited by 46 publications

(18 citation statements)

References 16 publications

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“…Many investigators have resorted to mathematical models of the single, partially-wetted catalyst to study various interacting processes. Until recently, these diffusion-reaction models were based on the assumption that a single reactant limits the reaction under all wetting conditions throughout the entire pellet: the pseudofirst-order kinetics approximation (Dudukovic, 1977;Ramachandran and Smith, 1979;Herskowitz et al, 1979;Herskowitz, 1981;Goto et al, 1981;Sakornwimon and Sylvester, 1982;Capra et al, 1982). For reasons discussed earlier, these models are incapable of predicting an overall reaction rate maximum at an intermediate liquid flow rate.…”

Section: Introductionmentioning

confidence: 99%

Experimental study of reaction in a partially wetted catalytic pellet

Funk

Harold

1991

AIChE Journal

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Section: Introductionmentioning

confidence: 99%

Experimental study of reaction in a partially wetted catalytic pellet

Funk

Harold

1991

AIChE Journal

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confidence: 97%

Effectiveness of a partially wetted catalyst for bimolecular reaction kinetics

Funk¹,

Harold²,

Ng³

1988

AIChE Journal

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A large number of studies on the effectiveness of a partially wetted catalyst particle have appeared in the literature (for example, Mills and Dudukovic, 1979;Tan and Smith, 1980;Herskowitz, 1981;Goto et al., 1981;Sakornwimon and Sylvester, 1982;Capra et al., 1982;Ring and Missen, 1986). With the exception of work by Goto et al., all these earlier studies considered only a bimolecular reaction with pseudofirst-order kinetics; i.e., first order with respect to the limiting reactant and zero order for the excess reactant. Goto et al. used pseudo-nth-order kinetics. Recently, Beaudry et al. (1987) and Harold and Ng (1 987) demonstrated that pseudofirst-order kinetics can be misleading in that depletion of the supposedly abundant (zeroorder) reactant may occur within the pellet. Also recently, Yentekakis and Vayenas (1987) suggested that bimolecular kinetics, first order with respect to each reactant, is essential for hydrodesulfurization processes.Since zero-order kinetics in actuality loses its physical meaning when the zero-order reactant is no longer in excess and other kinetic expressions are more appropriate for some commercial processes, the objective of this work is to examine the behavior of a single reaction that is first order with respect to both gaseous and liquid reactants. Emphasis is placed on elucidating the interplay between internal diffusion, reaction, and external mass transfer on the partially wetted surface, and to examine the impact of the interplay on catalyst effectiveness. Model DevelopmentA two-dimensional model is developed to describe the isothermal, irreversible reaction between a dissolved gas reactant A and a nonvolatile liquid reactant B within a partially wetted, uniformly active porous catalytic pellet. As illustrated in Figure 1, the pellet has a square cross section with each side of length S and is externally wetted about the four corners. Each of the four identical liquid films is of a uniform depth and covers an equal Correspondence concerning this paper shwld be addrcsscd to K. M. Ng or M. P. Harold. length in both directions from the corresponding corner. The desired wetting efficiency is obtained by adjusting this length from zero to its maximum value of S / 2 , which corresponds to complete wetting. Clearly, this fixed wetting pattern is idealized, as other flow features are present in a trickle-bed reactor (Ng and Chu, 1987). The liquid phase contains the reactants, reaction product(s), and possibly an inert solvent. A gaseous environment, with a constant partial pressure of reactant A, pbA, completely surrounds the wetted pellet.The liquid phase catalytic reaction is given by + uB(,, -Products,,, where g and 1 represent gas and liquid, respectively. The intrinsic reaction rate r is assumed to be first order with respect to A and B; i.e., r = k,CACB Species A and B respectively satisfy the following dimensionless diffusion-reaction equations:The dimensionless variables in Eqs. 2 and 3 are defined as follows:

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“…The problem has been studied for cylindrical particles of finite and infinite length. It is assumed that catalyst pores are completely filled with liquid (Colombo et al, 1976;Goto et al, 1981;Yentekakis and Vayenas, 1987) and that the tracer molecules can penetrate all the accessible pores of the catalyst structure. Furthermore, the catalyst particles are assumed isothermal with a uniform surface activity.…”

Section: Theoretical Studies Cylindrical Modelmentioning

confidence: 99%

“…Using two nonvolatile reactants, the evaluated order of the global reaction rate is higher than one. Goto et al (1981) compared the values of the effectiveness factor given by approximate solutions with the ones obtained from the numerical solution of the relevant partial differential equation for one-half and second-order reactions occurring in catalytic spheres. The correlation between partial wetting and operating parameters has been studied experimentally (Colombo et al, 1976;Morita and Smith, 1978;Mills and Dudukovic, 1981).…”

Section: Introductionmentioning

confidence: 99%