Abstract
Microstructured membrane reactors present a promising approach to master the productivity and safety challenges during the direct synthesis of hydrogen peroxide. However, various mass transport processes occur in this complex system. In order to gain a deeper understanding of these processes, the saturation and desaturation behaviour of the liquid reaction medium with the gaseous reactants is investigated experimentally to examine possible cross-contamination. Moreover, the employed PDMS membrane’s permeances to hydrogen and oxygen are researched at different pressures, by using a variable-pressure/constant-volume setup for the behaviour at ambient pressure and a constant-pressure/variable-volume setup for the behaviour at elevated pressures. A mathematical model in MATLAB is applied to simulate the results. It is shown that a certain desaturation of the gasses through the membrane occurs, and the results are underlined by the modelled ones using a solution-diffusion model in MATLAB. Thus a constant flushing of the gas channels of the reactor is required for safety reasons. Moreover, the measured permeance values indicate that the species transport is mainly limited by the diffusion in the liquid phase and not the membrane resistance.
Highlights
Oxidation reactions play an important role in the synthesis of platform chemicals for the manufacturing of various everyday products (Goor et al, 2000; Wilson et al, 2017)
The longdistance transport associated with this centralized production of H2O2 requires an energy-intensive concentration of the aqueous peroxide solutions up to 70 wt.% H2O2, which stands in contrast with typical end-user requirements of dilute solutions with less than 9 wt.% H2O2
The cross-contamination observed underlines the importance of employing a reactor design in which the gas channels are flushed with H2 (O2) to maintain process safety by avoiding the accumulation of O2 (H2) in regions with limited convection
Summary
Oxidation reactions play an important role in the synthesis of platform chemicals for the manufacturing of various everyday products (Goor et al, 2000; Wilson et al, 2017). The AO process has severe drawbacks, like a high energy demand (Campos-Martin et al, 2006) or the generation of gaseous, liquid and solid waste, which negatively affect the sustainability of the process (Yi et al, 2016). The longdistance transport associated with this centralized production of H2O2 requires an energy-intensive concentration of the aqueous peroxide solutions up to 70 wt.% H2O2, which stands in contrast with typical end-user requirements of dilute solutions with less than 9 wt.% H2O2. It poses a potential safety hazard (Yang et al, 2018) and increases the chemical’s price (CamposMartin et al, 2006)
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