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Catalyst recycling, within flow

Catalyst regeneration also provides a means of maintaining overall catalyst activity within systems with rapid catalyst deactivation. Deactivated catalyst particles can be continuously removed from a reaction zone while regenerated catalyst from a regeneration zone is continuously recycled back to the reaction zone in a flow scheme similar to that shown in Fig. [Pg.329]

As will be shown later the equation above is identical to the mass balance equation for a continuous stirred-tank reactor. The recycle can be provided either by an external pump as shown in Fig. 5.4-18 or by an impeller installed within the reaction chamber. The latter design was proposed by Weychert and Trela (1968). A commercial and advantageously modified version of such a reactor has been developed by Berty (1974, 1979), see Fig. 5.4-19. In these reactors, the relative velocity between the catalyst particles and the fluid phases is incretised without increasing the overall feed and outlet flow rates. [Pg.298]

First, suitable combinations of catalyst 13 and ILs were determined in batch experiments. Using [EMIM][BARF] as IL complete conversion was obtained with 89% ee of (R)-3-phenyl-l-butene. [EMIM][Tf2N] gave lower ee values in the range of 65%. Nevertheless, better availability and easier hand-hng made this the IL of choice for recychng and continuous-flow experiments. In batch-wise recycling experiments of catalyst 13 in ILs, it was found that the products could be readily isolated by extraction with SCCO2. However, the batch mode led to rapid deactivation of the catalyst within three to four cy-... [Pg.102]

Split Ho Recycle. A process flow scheme using the back-flow catalyst/three-stage system is shown in Figure 5. This is basically the reactor scheme which would be used within an H-Oil unit designed to achieve very low sulfur contents. A further aspect of this system, shown in Figure 5, is a split-recycle system. In this way, H2S free-hydrogen would be sent to the third reactor, thereby maintaining an extremely low H2S partial pressure at this critical point in the reactor system. [Pg.112]

Within the context of catalyst separation and recycling, it must be noted that a system where a catalyst needs not to be removed from the reaction vessel is very attractive. One such example occurs in continuous-flow methods [65], by which the immobilized catalyst resides permanently in the reactor, where it transforms the entering starting materials into the exiting products. The retention of a catalyst inside the reaction vessel can be achieved by different techniques, ranging from ultrafiltration through a Mw-selective membrane to immobilization on a silica gel column [66]. [Pg.319]

SCCO2 is delivered to the top of the pre-mixer, where it is mixed with the substrates and any other reactants that are needed for the reaction. The flow of reactants will then be carried by the SCCO2 over the heated catalyst bed where reaction occurs. The products and SCCO2 are then passed through the apparatus to the point where they are expanded to a pressure below the critical point of CO2, to induce phase separation of products [26]. The products may then be separated by gravity from the gaseous CO2, which may be recycled or vented. Clearly, the exact conditions required for reactions within these types of reactors depend on the chemistry. The important point is that the use of the SCF enables the reaction conditions to be controlled more precisely. The presence of the SCF does not necessarily make the catalyst more active, nor does an SCF normally alter the catalytic cycle. But in many cases, overall conversions and selectivities have been found to be at least equal to, if not higher than those obtained by conventional routes. [Pg.376]

Scandium tris(perfluorooctanesulfonyl)methide complex was immobilized in a fluorous phase as a recyclable catalyst for Mukaiyama aldol reaction (2). On the other hand, the catalytic activity of scandium could be significantly increased by the use of a continuous flow system compared with a batch system. For example, in per-fluoromethylcyclohexane, the aldol reaction of benzaldehyde withthe trimethylsilyl enol ether derived from methyl 2-methylpropannoate was completed within seconds in the presence of less than 0.1 mol% of Sc(N(S02CgFi7)2]3 [3]. [Pg.61]

Catalyst may be packed in a fixed bed within the reactor. Uniformly small particles may also be supported by the upward velocity of the reactant stream (gas or liquid), in which case it is called a fluidized bed. Solid catalyst may also be dissolved or suspended in a liquid reaction media, then separated from the products and recycled. Metal catalysts may be made into screens or other shapes across which the reactants flow. It should be remembered, however, that the reaction takes place on the surface of the catalyst if heat is evolved, cooling should be applied there, or the catalyst could be destroyed or deactivated. Most catalysts also become deactivated due to fouling of the surface with by-products and contamination by impurities in the feed stock, called poisons. The... [Pg.259]


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Catalyst recycling

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