Reaction techniques and processing
The production of MOF substances, including synthesis and downstream processing, requires further development in order to integrate them into industrial application processes. Here synthesis capacities, yield, raw products and energy costs, safety and waste management play a central role. In addition, production strategies have to be developed which enable flexibility concerning the demand on MOF substances in an industrial scale.
The commercial access of MOF substances and their quantitative availability is currently presenting significant obstacles concerning the further application testing of this promising class of compounds. In the context of the MOF2market project, Fraunhofer ICT is therefore dedicated to issues concerning the reaction and process engineering optimization, the upscaling as well as the economic production of these materials. Thereby, synthesis capacity, yields, raw material and energy costs, safety and environmental performance play a central role. Additionally, production strategies that allow maximum flexibility for the preparation of MOF substances in industrial scale need to be developed.
These tasks constitute an important prerequisite in order to make MOF materials available for the production of demonstrators and semi-finished products and thus transfer the MOF research from the academic basis to successful applications with sustainable industrial interest.
For the synthesis of different MOF substances, usual discontinuous batch production methodologies have been consistently converted in continuous processes. This allows - supported by micro-process engineering components - a much more precise control over mass transport and residence time than in conventional batch reactors. Over several development cycles a significant process improvement has been achieved in terms of throughput, product quality and production costs. Typical synthetic capacities are currently in the kg/d range and the corresponding production costs are <1€/g.
A scalable reactor concept was deliberately chosen with the continuous synthesis approach in microfluidic structures. Throughput increase can be achieved by appropriate parallelization of the reactors while maintaining the selected dimensions and thus the optimized mass and heat transfer conditions as well as the optimized residence time. A classic problem in the upscaling of batch processes, namely the modified surface and volume ratios, is thus avoided.
Furthermore, the continuous processing in microreactors ensures a targeted control of the microscopic (crystal form, particle size) and macroscopic morphology of MOFs, through variation of the reaction and process conditions, providing access to customized products.