Three-zone TAP reactor

Figure 8.18. Three-zone TAP reactor (D. Constales, G. S. Yablonsky, G. B. Marin and J. T. Gleaves, Multi-zone TAP-reactors theory and application. Ill Multi-response theory and criteria of instantaneousness, Chemical Engineering Science, 59 (2004) 3725).

Three-zone TAP reactor with quadrupole mass spectrometer L one i =/-zone 2 = zone 3 Reprinted from Shekhtman, S.O., Yablonsl, G.S., Chen,S., Cleaves, J.T., 1999. Thin-zoneTAP-reactor—theory and application. Chem. Eng. Sci. 54, 4371—4378, Copyright (1999), with permission from Elsevier. 

In the three-zone TAP reactor, it is difficult to maintain a uniform profile of the catalyst surface composition because of the gas concentration gradient, which is the driving force for the diffusion transport in the reactor. This nonuniformity of the catalyst surface composition becomes significant particularly in multipulse experiments. 

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... 

In general, no second-order correction can ensure 0 L convergence, but in the special case where b,if eff,i = fi),3f eff,3 (most notably, whenever the first and last zones have the same physical characteristics, even if their lengths differ), some terms in the general solution s second derivative with respect to L2 at 0 vanish, and then the corrected values (after elimination of Deff,3) will ensure an 0 L discrepancy between the three-zone TAP reactor and the TSTR reactor. Note that all parameters are now influenced by k ... 

The most common TAP microreactor is the three-zone TAP reaetor (Fig. 5.2). In this reactor the active catalyst zone is sandwiched between two inert zones, which consist of packed beds of inert particles, typically quartz. 

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

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 TAP reactor equation used by workers in this field [3,4] divides the reactor into three zones. Each zone is governed by the diffusion equation (with a different difiusivhy), and the zones are connected by Danckwerts-type boundary conditions. Thus ... 

The zone transfer matrix calculated in the Laplace domain for a single zone in the one-dimensional model exactly expresses its behavior as a component of any system built from such a zone, not only as part of a TAP reactor. We now study what happens if we were to consider concentric situations in two and three dimensions instead. Let d denote the dimension (d= 1, 2, or 3). Then the spatial PDE, Eq. (5.123), takes the following form for radial situations... 

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