Metallic membranes reactor design

Many methods have been proposed to address this issue (see Chapter 9). Beside thermal and chemical resistances of the sealing materials other issues need to be considered as well. One such important issue is the mismatch of the thermal expansion coefficients between the membrane element and the sealing material or joining material. While similar material design and engineering problems exist in ceramic, metal and ceramic-metal joining developmental work in this area is much needed to scale up gas separation units ot membrane reactors for production. The efforts are primarily p ormed by the industry and some national laboratories. 

The main advantages of reactors with composite membrane catalysts arc the higher hydrogen permeability and smaller amount of precious metals in comparison with those presented in Section II. All constructions of the reactors with plane membrane catalyst may be used for composites of thin palladium alloy film and porous metal sheet The design of reactors with composite membranes on polymeric support may be the same as for diffusion apparatus with polymeric membranes (see, for example. Ref. 138). A very promising support for the composite membrane catalysts is hollow carbon fiber [139], once properly thermostable adhesives are found. 

Since Chapter 16 deals with metal-containing membrane reactors and Chapter 17 with inorganic membrane reactors, the design, preparation, activity, and selectivity aspects concerning these types of reactors will not be commented on here. Only aspects relevant to chemical reaction engineering will be discussed. 

Design and engineering of metallic membranes 683 Metallic membrane Catalytic reactor... 

The Batelle process represents the first attempt to recover metals from spent hydro-processing catalysts using electrochemical dissolution in a membrane reactor (Silva, Bray, Matson, 1993). In this process, the spent catalyst is added to a solution containing small (catalytic) amounts of elements that form kinetically active, strongly oxidizing ions such as or Ag +. All these efforts contribute to the developments and design of the ECDS process as well as the metal recovery. 

Nitrite reduction in water is tested as a model reaction. It is shown that nitrite reduction proceeds by both catalytic reduction (with Pd and H2) and by the reactor material itself (i.e., by Fe on CNFs). Eventually, the latter effect will exhaust in time and the reaction will still proceed with the immobilized Pd-catalyst on the CN Fs and the membrane-assisted supply of hydrogen. Results proved that the porous metallic membrane microreactors with carbon nanofibers are suitable materials for the reduction of nitrite and the reactor design is very promising for the multiphase microreactor technologies [lOOj. 

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