Reactor evaporator concept

A recent technology improvement, based on the concept of reactor-evaporator, affords higher productivities in the industrial production of DMC, making it easier to scale up to large capacity plants. 

Another centrifugal evaporator concept was proposed by Porter and Ramshaw (1988). Unlike the unit described above, this uses a large number of plates located normal to the rotating shaft, and is designed to accommodate a wider range of separations than that of the above apparatus. As described in Chapter 4 and in the context of spinning disc reactors in Chapter 5, the enhanced evaporation (and condensation) heat transfer coefficients on spinning disc surfaces are of considerable benefit. 

As depicted in Scheme 2.4, the concept of the reactor-evaporator is adopted the catalyst is kept inside the reactor, from which the products are vaporized, largely taking advantage of the heat of reaction (AH = —74 kcal mol ), and are removed from the reaction system together with the excess gas leaving the reactor [120]. 

Besides this early example another application was reported in 1988 by Ven-turello and coworkers [10]. They disclosed the use of aminopropyl-function-alized silica gel as a suitable catalyst in Knoevenagel condensations under continuous flow conditions (Scheme 4). Good yields were obtained when aromatic aldehydes, cyclohexanone, and acetophenone were condensed with ethyl acetoacetate, ethyl cyanoacetate or malononitrile [11,12]. The concept was based on a conventional column reactor which was equipped with a vertical double-jacket thermostat. The catalyst was introduced into the column while the reactants were placed on the top of the column. Toluene was passed through the column and the products were conveniently obtained by evaporation of the solvent. 

The reactor is cooled by 3 secondary sodium circuits each of them having one SG of modular concept. Each SG is composed of the economizer-evaporator, the superheaters and the resuperheaters stages each of them is composed of 12 modules. Forty-seven modules from 2 SG s superheater and resuperheater have to be repaired. A superheater module has the S shape and is composed of a 27 m long-( ) 200 mm shell, containing 7 water vapour tubes (Fig. 1). The sodium flows around the tubes. The tubes are maintained by regularly spaced grids. 

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... 

A concept for a methanol (or ethanol) fuel processor based upon steam reforming and membrane separation was presented by Gepert et td. [400]. As shown in Figure 5.33, the alcohol/water mixture was evaporated and converted by steam reforming in a fixed-bed catalyst, into which palladium capillary membranes were inserted. The retenate then entered the combustion zone, which was positioned concentrically around the reformer bed at the reactor wall. Air was fed into the combustion zone and residual hydrogen, carbon monoxide and unconverted methanol combusted therein. The sealing of the membranes at the reactor top was an issue solved by air-cooled elastomers. 

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