STRUCTURED CATALYSTS BASED ON SINTERED METAL FIBERS FOR 3-PHASE HYDROGENATION: THE DESIGN OF COMPACT REACTOR
Special Symposium - EPIC-1: European Process Intensification Conference - 1
EPIC-1: Poster Session (EPIC - Poster) - P1
Keywords: selective hydrohenation, compact reactor, structured catalyst
Catalytic selective hydrogenation of functional groups in organic molecules is one of the most important chemical reactions used to produce fine chemicals and pharmaceutical products. The performance of the hydrogenation process is strongly dependent on the catalyst activity/selectivity and the interaction of chemical kinetics with mass transfer in the eventual reactor. To avoid internal and external mass transfer limitations and to attain high product selectivity, the micrometer range catalyst particles are required leading to the use of suspension reactors. The most common reactors are the batch wise operated slurry reactors like stirred tanks and loop reactors. The minimum size of the catalyst particles is, however, limited by the separation from the reacting mixture after the reaction. Another problem for the reactor design is related to the heat removal since hydrogenations are highly exothermic reactions. Precise temperature control is required to achieve high selectivity and to prevent run-away.
The efficient heat removal can be provided using micro-structured heat exchangers. In this way a considerable intensification of the hydrogenation process could be attained at high catalyst and reactant concentration. But due to the plugging of micro-channels by catalyst particles, micro-structured heat exchanger is difficult to incorporate in a traditional suspension reactor. Therefore, the heterogeneous catalyst must be immobilized within the reactor and spatially separated from the micro heat exchanger.
A novel approach in the three phase reactor engineering is based on the use of structured catalytic materials. Recently we suggested a reactor design as a bubble column staged by fiber catalysts in the form of woven cloths. As the diameter of the single fiber is usually in the micrometer range, mass transport limitations can be effectively avoided, while the open macrostructure of the material leads to low pressure drop and acts as a micro-mixer to enhance bubble redistribution. Glass fibers as well as activated carbon fiber cloths have shown promising results in this type of reactor, but their low rigidity requires supplemental supporting stages of metal grids.
In this presentation we report the use of Sintered Metal Fibers (SMF) catalysts in the form of porous sheets of ~0.4 mm thickness. These sheets are self-supporting and can be easily shaped into any macro-structured catalytic bed. SMF materials are available on the market from different metallic fibers with diameters of 10-20 µm. Their open structure possesses a high porosity >80% allowing easy passage of reactants without high pressure drop. Furthermore, the high thermal conductivity of metallic SMF ensures isothermal conditions on the catalyst surface even for highly exothermic reactions.
Presented Wednesday 19, 13:30 to 14:40, in session EPIC-1 Poster Session (EPIC - Poster) - P1.
