Stripping reactor

Figure A3.14.12. The first experimental observation of a Turing pattern in a gel strip reactor. Solutions containing separate components of the CIMA/CDIMA reaction are flowed along each edge of the strip and a spatial pattern along the horizontal axis develops for a range of experimental conditions. (Reprinted with pennission from [38], The American Physical Society.)...

Despite our personal skepticism, a sample of / was obtained (8) and tested in a bench test unit that simulates continuous vapor stripped reactor operation (9). The... 

As in the original Monsanto process involving homogeneous catalysis and catalyst recycle, the product is removed as a liquid, because the gas phase of a stripping reactor would contain a low concentration of the high-boiling acetic acid. In the Acetica process, no catalyst recycle is needed, as the solid catalyst stays in the reactor. 

Fig. 12.2 Continuously fed unstirred reactor (CFUR). Sketch of (a) gel strip reactor and (b) disk reactor. The grey rectangle represents the gel and its support. Patterns are viewed from the top...

Two stripping solutions were prepared from deionized water and reagent grade sulfuric acid of either 400 or 250 g/1 H2SO4 concentration. This solution made up stream Al 1 which was fed directly into the galvanic stripping reactor with the return strip solution A9. A high acid concentration was utilized to produce a more concentrated iron solution and the low concentration was utilized to study the effect of the pH. 

After stripping, the A10 aqueous exit solution containing mainly ferrous sulfate, was split into the product stream, Al 2, and the return stream, AlO, going into the galvanic stripping reactor. Therefore streams A9, AlO, and A12 have the same chemical composition but different volumes and flow rates. The iron was allowed to build up in these streams until a steady state was reached. 

Unreacted NH3 and CO2 are separated from the urea solution in the high-pressure separator and in two to three steam-heated carbamate strippers at successively lower pressures. The off-gas from the separator and the first-stage stripper is absorbed in the high-pressure absorber by a side stream of partially stripped reactor effluent from the high-pressure separator. Heat evolved in the absorber reaction is removed (to increase absorption capacity) by the addition and expansion of part of the liquid ammonia feed at this point. Pure gaseous ammonia from the top of the absorber is also recycled to the urea reactor after being condensed. 

Some economic aspects, including rhodium catalyst cost, are treated in section 8.2. Catalyst performance aspects are treated in sections 8.3 (activity, selectivity) and 8.4 (stability, loss routes for Rh and ligand). In 8.5 and 8.6, several commercial processes are described. Four generic, industrially used process types are described in 8.5, viz. processes using a stripping reactor, a liquid recycle, a two-phase reaction, and an extraction after a one-phase reaction. In 8.6, interesting, current developments in a few petrochemical product areas are shortly discussed. 

Type I Stripping reactor process/Rh containment in reactor... 

Figure 3. Process type I stripping reactor (gas recycle process Union Carbide)...

This process has been developed for propene hydroformylation by Mitsubishi Chemical and Union Carbide/Davy Process Technology [32, 33, 36], as improvement of the stripping reactor concept. Product is now removed from the reactors via the liquid phase and carefully evaporated from the catalyst. The uncoupling of reactor and product/catalyst separation... 

Fig. 8. The Gel Strip Reactor and the first Turing pattern in the CIMA reaction, (a) Sketch of the reactor. Reagents well mixed in reservoirs A and B diffuse into the gel from the longest edges (b) Contrast enhanced picture of the pattern Several rows of clear spots. Dark regions correspond to reduced state colored dark blue. Clear regions correspond to oxidized state (c) Enlarged picture of the region of patterns. Scale is in mm. Experimental conditions temperature 7°C boundary feed concentrations [NaC102] = 2.6 x 10 M, [KI] = 3 x 10 M, [NaOH] = 3 X 10 M, [Na2S04] = 3 x IQ- M, [CH2(COOH)2] = 9 x 10" M, [H2SO4] = 10" M.

In the first set of experiments, we used a gel strip reactor , a geometry shown to be convenient as mentioned above. The core of our reactor is a thin strip of polyacrylamide gel 20 mm long, 1 mm thick, 3 mm wide (Figure 8a). The gel strip is squeezed between a white bottom plate and a Plexiglas cover... 

Fig. 11. Perspective view of a 3-D Tliring pattern in a gel strip reactor 3 mm thick. Partial view. The edges of the gel strip are underlined.

We have seen in Section 2.3 that to recover the uniformity of the control parameters in the plane of observation, one can resort to the disc reactor as initially proposed by the group in Austin [50,51]. A schematic representation of the disc reactor is given in Figure 12a. The piece of gel is now a flat disc fed by the two circular faces. Observations are made perpendicularly to the feed surfaces. The rows of patterns in the gel strip reactor correspond to planes filled with patterns in the disc reactor. As mentioned in Section 2.3, the pattern is still localized and tridimensional. 

Fig. 16, Travelling wave pattern. Strip reactor made of agarose gel (2% dry material) loaded with Thiodfene (6 g/liter of gel)[65]. All feed concentrations are as in Figure 15. The whole wave pattern moves from left to right at constant speed parallel to the feed surfaces. The bar inside the picture represents 1 mm.

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