Thin-zone TAP reactor

Chapter 5 is devoted to the basic reactor models used in chemical engineering the batch reactor, the CSTR, the plug-flow reactor, and the TAP reactor with its modification, the thin-zone TAP reactor. Special attention is paid to the reaction-diffusion reactor, the detailed analysis of which opens up wide perspectives for the understanding of different types of reactors, such as catalytic, membrane and biological reactors. 

A small amount of a chemical substance is injected into the reactor during a small time interval. In a conventional pulse reactor, the substance is pulsed into an inert steady carrier-gas stream. The relaxation of the outlet composition following the perturbation by this pulse provides information about the reaction kinetics. In the TAP reactor, no carrier-gas stream is used and the substance is pulsed directly into the reactor. Transport occurs by diffusion only, in particular by well-defined Knudsen diffusion. The Knudsen diffusion coefficient does not depend on the composition of the reacting gas mixture. In a thin-zone TAP reactor (TZTR), the catalyst is located within a narrow zone only, similar to the differential PFR. 

The thin-zone TAP reactor (TZTR) configuration (Fig. 5.3) was a proposal by Shekhtman et al. (1999). In a TZTR, the thickness of the catalyst zone is made very small compared to the total length of the reactor. Thus, the change of the gas concentration across the thin catalyst zone is... 

Thin-zone TAP reactor. Reprinted from Shekhtman, S.O., Yablonsky, G.S., Chen, S., Cleaves, J.T., 1999. Thin-zone TAP-reactor—theoy and application. Chem. Eng. Sci. 54, 4371—4378, Copyright (1999), with... 

Schematic of three-zone, thin-zone TAP reactor.

The validity of the reciprocal relations was shown by Yablonsky et al. (201 lb) using the technique of Temporal Analysis of Products (TAP) developed by Cleaves in 1988 (Cleaves et al., 1988 see Chapter 5). The reactor used was a so-called thin-zone TAP reactor (TZTR), in... 

We can refine this analysis comparing different cases with cascades of three model reactors, namely CSTRs, plug-flow reactors (PFRs), and TAP reactors (including thin-zone TAP reactors), for which the models are presented in Chapters 3 and 5. All results of our analysis are given in Table 8.1. 

The experiment must be isothermal and uniform in chemical composition (i.e., present perfect mixing). Temperature gradients may be minimized by intensive heat exchange, dilution of the active material, or rapid recirculation of fluid phase. The reaction zone may be minimized in order to render the reactor gradientless, such as in the cases of differential plug flow reactor (Section 10.4.1.1) or thin-zone TAP reactor (TZTR) (Section 10.6.1.2). 

S. O. Shekhtman and G. S. Yablonsky, Thin-zone TAP reactor versus differential PFR analysis of concentration nonuitiformity for gas-solid systems. Industrial 8c Engineering Chemistry Research, vol. 44, pp. 6518-6522, 2005. 

S. O. Shekhtman, G. S. Yablonsky, S. Chen, and J. T. Cleaves, Thin-zone TAP-reactor - theory and application. Chemical Engineering Science, vol. 54, pp. 4371-4378, 1999. 

Consider a three-zone TAP reactor in which an irreversible (adsorption) reaction occurs, and for which the middle zone is intended to be thin (the TZTR). The transfer matrix Mi for the first zone is given by... 

This has motivated the introduction of the thin-sandwiched TAP reactor (TSTR), an ideal reactor offering a far superior approximation from the asymptotic viewpoint, while retaining the property of concentration uniformity in the reactive zone that is essential for application of the Y procedure (see Yablonsky et al., 2(X)2). 

Dudukovic [70, 71], Rothaemel and Baems [72], Gleaves et al. [73], Soick et al. [74] and others. Quinta Ferreira et al. [75] discussed tiie influence of convective flow in large pores. Van der Linde et al. [76] present a detailed method of solution of the system of partial differential equations which model the TP reactor. Shekhtman et al. [69] developed a model of a so-called "thin-zone reactor" in which the concentration gradients across the short catalyst bed can be neglected, and diffusion and reaction can be separated. A very general model was presented by Garayhi and Keil [112-115] which comprises the TAP reactor as a special case, and which considers also multicomponent diffusion within the pores as well as the possibility to include arbitrarily complicated systems of reaction equations. 

We also assume that for every inactive diffusion zone, the effective diffusion coefficientDeff is the same. We apply the general model of the TAP reactor as a system of partial differential equations (see Chapter 5). In the Laplace domain, each zone is represented by a zone transfer matrix (Constales et al., 2006). The thin zone of activity k corresponds to the matrix ... 

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