Experimental Evaluation of a Membrane Micro Channel Reactor for Liquid Phase Direct Synthesis of Hydrogen Peroxide in Continuous Flow Using Nafion® Membranes for Safe Utilization of Undiluted Reactants

Manuel Selinsek,Manfred Kraut,Roland Dittmeyer

doi:10.3390/catal8110556

Manuel Selinsek, Manfred Kraut + Show 1 more

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https://doi.org/10.3390/catal8110556

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Abstract

In recent years, various modular micro channel reactors have been developed to overcome limitations in challenging chemical reactions. Direct synthesis of hydrogen peroxide from hydrogen and oxygen is a very interesting process in this regard. However, the complex triphasic process (gaseous reactants, reaction in liquid solvent, solid catalyst) still holds challenges regarding safety, selectivity and productivity. The membrane micro reactor system for continuous liquid phase H2O2 direct synthesis was designed to reduce safety issues by separate dosing of the gaseous reactants via a membrane into a liquid-flow channel filled with a catalyst. Productivity is increased by enhanced mass transport, attainable in micro channels and by multiple re-saturation of the liquid with the reactants over the length of the reaction channel. Lastly, selectivity is optimized by controlling the reactant distribution. The influence of crucial technical features of the design, such as micro channel geometry, were studied experimentally in relationship with varying reaction conditions such as residence time, pressure, reactant ratio and solvent flow rate. Successful continuous operation of the reactor at pressures up to 50 bars showed the feasibility of this system. During the experiments, control over the reactant ratio was found to be crucial in order to maximize product yield. Thereby, yields above 80% were achieved. The results obtained are the key elements for future development and optimization of this reactor system, which will hopefully lead to a breakthrough in decentralized H2O2 production.

Highlights

IntroductionSeveral modular micro channel reactors have been developed at the Institute for
In recent years, several modular micro channel reactors have been developed at the Institute forMicro Process Engineering at Karlsruhe Institute of Technology (KIT) to overcome kinetic, heat transfer and mass transfer limitations in challenging chemical reactions and processes [1]
The Nafion ® membranes used in this work were found to introduce a mass transfer resistance as shown by solvent flow rate variations and the influence on product concentration and productivity

Summary

Introduction

Several modular micro channel reactors have been developed at the Institute for. Micro Process Engineering at Karlsruhe Institute of Technology (KIT) to overcome kinetic, heat transfer and mass transfer limitations in challenging chemical reactions and processes [1]. Direct synthesis of hydrogen peroxide from hydrogen and oxygen is a very interesting process in this regard. It is a promising green production route to enable decentralized on-site hydrogen peroxide production for immediate use, e.g., as green oxidizing or bleaching agent since water is the only oxidation by-product. There are three major challenges connected with the direct synthesis process: safety, selectivity and productivity. Safety is an issue, because of the wide concentration range where H2 and O2 form an explosive mixture in the gas phase

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