Work package 2.4 - Process and micro-structured reactors for hydrogenation of nitrobenzene to aniline
Principal investigator: Dr. P. Pfeifer (KIT)
Involved researchers: Dr.-Ing. Andreas Kölbl, Dipl.-Chem. Manfred Kraut (KIT)
Main scientific Goals:
In the framework of the Helmholtz Energy Alliance Energy-efficient Chemical Multiphase Processes the Institute of Micro Process Engineering at KIT is carrying out research on the possibilities of utilizing process heat originating from multiphase hydrogenation reactions. Therefore, increased temperature and pressure conditions need to be applied for enabling multiphase conditions. To keep control over the reaction under such severe conditions, process intensification is required with respect to heat and mass transfer. This shall be ensured by the application of microchannel devices.
As a reference process hydrogenation of nitrobenzene to aniline has been selected. Various operating parameters and reactor structures shall be systematically tested for the optimization of mass and heat transfer and the reactor shall be described by simplified methods of modeling.
The optimization of the reactor geometry need to be conducted in the context of maximizing the overall energy efficiency and the following parameters need to be considered for the reaction unit:
1) a decrease of the lateral dimensions will intensify the heat transfer but increase the pressure loss, and
2) the energy required to produce higher interfacial surface is also related to the pressure loss; however, the surface area also depends on the flow regime, and thus on the wetting of the catalyst and reactor surface.
A modular microstructured reactor shall serve as a platform for investigating the reaction up to temperatures of 300 ° C and operating pressures up to 80 bar in order to allow extraction of high-pressure steam from the reaction by indirect heat transfer inside the reactor. Catalyst packings and coatings as well as methods to avoid side reactions on the reactor surface will be compared.
Preliminary results from the heterogeneously catalyzed hydrogenation of nitrobenzene have been obtained in an autoclave reactor at 50 – 80 bar and 200 – 300 °C with extremely low loadings of different catalysts. The tests revealed severe byproduct formation from the reactor wall as well as good performance of Pd-based catalysts.
A novel and flexible design of a microreactor has been developed. This new reactor design can provide different hydrogen feeding options, reactor inner structures and catalyst designs (packed bed and coated structures) while avoiding leakage and even more relevant bypassing effects. Bypassing effects have been a major obstacle in previous reactor designs.
Figure: Novel reactor design with exchangeable hydrogen feeding and microstructure
Direct links to other work-packages:
Work package 1 (KIT)
Work package 2.3 (TU Dresden, FAU Erlangen)
Work package 4.1 (FAU Erlangen)
Work package 4.2 (KIT)
Peter Pfeifer, Martin Cholewa, Andreas Kölbl, Manfred Kraut, Roland Dittmeyer; Contributions of Micro Process Engineering for optimization of heterogeneously catalyzed multiphase processes; Achema 2015.