Why are Industrial Applications of Structured Reactors so Scarce

Recently, hydrodynamic aspects of multiphase applications have been studied in detail for the cocurrent and countercurrent flow regimes. Useful correlations were determined and it was found that foams combine high rates and low pressure drop, proving their high potential in multiphase applications [9, 107, 108]. 

Firstly, there are technical reasons concerning catalyst and reactor requirements. In the chemical industry, catalyst performance is critical. Compared to conventional catalysts, they are relatively expensive and catalyst production and standardization lag behind. In practice, a robust, proven catalyst is needed. For a specific application, an extended catalyst and washcoat development program is unavoidable, and in particular, for the fine chemistry in-house development is a burden. For coated systems, catalyst loading is low, making them unsuited for reactions occurring in the kinetic regime, which is particularly important for bulk chemistry and refineries. In that case, incorporated monolithic catalysts are the logical choice. Catalyst stability is crucial. It determines the amount of catalyst required for a batch process, the number of times the catalyst can be reused, and for a continuous process, the run time. 

Structure for gas-phase reactions. In general, efficient deflectors at the inlet and collectors at the outlet of the reactor are needed. A monolithic postreactor seems to be mature technology that requires only a dedicated catalyst. Such a relatively cheap reactor can be installed when retrofitting the plant or designed for new plants. 

Sufficient engineering data for designing reactors for three-phase processes are available. A column reactor with gravitational liquid downflow was industrially proven. An MLR with forced liquid downflow with ejector was also well studied. Dedicated catalysts for particular processes must be, however, worked out. 

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