Recirculating inert liquid removal

Figure 1 Recirculating Inert Liquid Removal System. A standard glass cooling apparatus. B liquid reservoir,...

A Recirculating Inert Liquid Heat Removal System. While standard inert atmosphere gloveboxes may be used to perform ambient temperature reactions, the lack of a facility for localized heat removal (as provided externally be running tap water) precludes all syntheses requiring reflux, distillation, or sublimation. This limitation may be eliminated by the installation of a recirculating liquid heat exchange system. 

Their laboratory PVMR consisted of a reservoir in which the reactants were placed together with Nafion pellets, which acted as the catalyst. The liquid in the reservoir was continuously recirculated through the membrane tube, which was placed externally to the reactor. The membrane, itself, was also shown to be catalytic. A flow of inert gas (rather than vacuum) was used to remove the vapors and water from the membrane permeate. For the methanol esterification reaction the improvement in yield was modest (final conversion 77 % vs. 73 % corresponding to equilibrium), because the membrane was not very permselective towards the reaction products. Significant improvements, on the other hand, were observed with the butanol reaction (final conversion 95 % vs. 70 % corresponding to equilibrium), as the membrane is more permselective towards the products of this reaction. Exchanging the acidic protons in the Nafion membranes with cesium ions significantly improved the permselectivity, but also reduced membrane permeance. 

In other cases, the method of removal depends upon the nature of the product, e.g. gases may be (1) vented from the reactor, possibly via a slight reduction In pressure (2) displaced from the electrolyte via inert gas sparging (3) segregated via a solid polymer electrolyte (section 5.2) or recirculated via a gas-liquid separator. Liquid products may be (1) separated by flotation or settlement if they are immiscible and have a markedly different density to the electrolyte or (2) emulsified by mixing, then swept out of the reactor. Solid products can be separated via (I) flotation or settlement (2) fluidization or tangential shear to remove them from the reactor (3) solvent extraction or incorporation into a mercury phase, e.g. amalgamation of metals. 

The best solution appears to be the use of an almost insoluble liquid catalyst held within the pores of a suitable inert support. Supported liquid catalysts are well known and can be used with a continuous catalytic regeneration system similar to that developed for catalytic reforming processes. Haldor Topsoe has successfully tested trifluoromethane sulfonic acid in this way since 1993 with a variety of olefin feeds. " No formal regeneration was necessary apart from periodic removal of some catalyst for reimpregnation and the recovery of dissolved acid from the alkylate. Both catalyst and support are, therefore, recirculated. The small quantity of polymeric by-products formed (acid soluble oil) appears to be less tlm that formed in the sulfuric acid process, but slightly more than in the HF process. 

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