Reactions Amenable to Inorganic Membrane Reactors

Much of the research and development activity on inorganic membrane reactors in recent years has been directed toward hydrogenation or dehydrogenation of hydrocarbons, especially the latter, and other reactions involving production or depletion of hydrogen. This can be attributed to a number of factors. 

First of all, hydrocarbons constitute a major force in the very important petroleum and petrochemical industry. Generation or consumption of hydrogen, a very valuable commodity chemical, is one of the key steps in many chemical processes. Even a modest success in the improvement of reaction conversion, yield or selectivity by the use of a membrane reactor can represent a substantial economic benefit due to the volume of streams involved. 

Secondly, many if not most of these high temperature reactions are equilibrium limited. Therefore, the removal of one of the reaction products (often hydrogen) by the use of an inorganic membrane displaces the reaction equilibrium toward more product formation, thus increasing the reaction conversion as has been demonstrated extensively. This favorable effect of equilibrium displacement or shift is particularly pronounced for those reactions where the stoichiometric coefficient of the product to be removed is high. 

The organic polymer membranes have an upper operating limit of approximately 200 C due to their thermal stability. Below this temperature, there exist organic polymer membranes suitable for homogeneous catalytic reactions in some compatible solvents. This temperature also represents the lower limit for most heterogeneously catalyzed reactions [Armor, 1992]. 

As mentioned in Chapter 8, the understanding of how the material composition of a dense membrane interplays with the operating conditions and the reaction components is far from being sufficient for reliable design of a dense membrane reactor, particularly 

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In view of the state-of-the-art developments in inorganic membranes, those reactions amenable to inorganic membrane reactors are characterized. The effects of space time in isothermal and non-isothermal membrane reactors are reviewed. 

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