Hybrid Multifunctional Reactors

Research activities in past decades have produced new reactor concepts. For example, hybrid (multifunctional) reactors combining reaction and heat or mass transfer are an interesting new option. Progress has also been achieved with monolithic reactors, which are already used commercially in emission control systems. An overview of these developments is given by Moulijn, Makkee, and Van Diepen (2004). Details are given by Westerterp (1992) and Cybyulski and MouUjn (1997). 

The use of miniaturized reactors with characteristic dimensions below about 1 mm, so-called microreactors, is also a currently interesting development. An overview of the basic principles of microreactors is given by Emig and Klemm (2005). Details are found in Hessel, Hardt, and Loewe (2004). Subsequently, short summaries of these new concepts based on the cited literature are given. 

In hybrid systems different processes are coupled, for example, reaction and separation by membranes, adsorption, or distillation. This could lead to a reduction of the investment costs as two different functions are combined in one vessel, and one process step is eliminated. For example, a reactor with a catalyst and a membrane may be used or a distillation column with a catalytic packing, which could also lead to an optimal heat integration. Other benefits depend on the specific reaction. For example, equilibrium-limited reactions would benefit if a product is continuously removed in situ, which leads to an enhanced yield beyond the equilibrium.  

Although membrane reactors certainly open up opportunities, additional challenges have to be faced to design and produce robust modules that allow high rates 

Coupling Reaction and Adsorption A multifunctional reactor may also combine reaction and adsorption. At the laboratory scale, this concept has been apphed for a few reactions, for example, for ammonia and methanol synthesis. Although these processes have been optimized to a high degree of sophistication, improvements 

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Novel processing methods, such as integration of reaction and one or more unit operations in so-called multifunctional reactors and integration of two or more separation techniques in hybrid separations Use of alternative forms and sources of energy for chemical processing Novel methods of process/plant development and operation... 

Stankiewicz and Moulijn further divide PI into two areas equipment and methods. They give an extensive list of equipment examples. The methods are subdivided into multifunctional reactors, hybrid separations, alternative energy sources, and other methods. 

Process intensifying methods, such as the integration of reaction and separation steps in multifunctional reactors (examples reactive distillation, membrane reactors, fuel cells), hybrid separations (example membrane distillation), alternative energy sources, and new operation modes (example periodic operations). 

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