Jt Gleaves

Uniformity in a thin-zone multi-pulse TAP experiment: numerical analysis

Abstract The thin-zone TAP reactor (TZTR) model of a multi-pulse experiment is computationally validated based on a more general three-zone reactor model. The analysis is focused on the uniformity of gaseous and surface concentrations in the catalyst zone, which is a key property of TZTR model. It is shown that if the TZTR model is valid for the first pulse in a multi-pulse experiment then it is valid for all subsequent pulses. For a typical reactor packing (the ratio of the thin-zone thickness to the length of reactor is 1/30) and with the first pulse conversion up to 97%, the gaseous and surface concentration profiles can be considered uniform and characterized by their spatial average values only. The reaction rate in the catalyst zone may also be characterized by its spatial average value and directly related to the spatial average gaseous and surface concentrations, in the same way as an elementary rate is related to concentrations. As a result of these unique characteristics, the TZTR may be considered a “perfectly-mixed” reactor even at high conversion.

Multi-zone TAP-reactors theory and application: II. The three-dimensional theory

The rigorous three-dimensional theory for a TAP (Temporal Analysis of Products) Knudsen pulse response experiment is developed for the combined diffusion and reaction cases for multi-zone packing, in order to determine the domain of validity of the commonly used one-dimensional model. The analysis is based on a specific modification of the transfer matrix formalism previously introduced for one-dimensional TAP-reactor models. The outlet flux can be written as a sum of three independent terms: one corresponding to the one-dimensional solution, a term accounting for axially symmetric radial nonuniformity, and a term needed for a fully three-dimensional model. The theory provides a method for estimating the accuracy of the one-dimensional model and for finding the domain of its validity. The theory is illustrated by the diffusion-only case for a one-zone reactor. It is shown that the one-dimensional model is valid for aspect ratios L/R>3.5.