Catalytic Synthesis of Hydrogen Peroxide in a Capillary Microreactor
Advancing the chemical engineering fundamentals
Chemical Reaction Engineering: Practical Applications (T2-2c)
Keywords: hydrogen peroxide, microreactor, water electrolysis
Hydrogen peroxide (H2O2) is used for pulp bleaching and washing of semiconductor substrate. H2O2 is commercially produced by the so-called anthraquinone method. This method involves auto-oxidation of anthraquinone, which results in the presence of large amounts of organic contaminants in solution due to the decomposition of the anthraquinone and the organic solvents.
Direct synthesis of H2O2 from H2 and O2 as an alternative has been investigated. However, it is very difficult to realize the direct synthesis of H2O2 on a large scale because of explosive properties, unless a safe control system can be established. Microreactor is capable of generating hydrogen peroxide on demand by direct synthesis of H2 and O2 that could be generated by water electrolysis.
In this study, the properties of H2O2 production were investigated in a slurry reactor containing Pd/C catalyst. H2 and O2 produced in a solid polymer electrolyte (SPE) water electrolyzer were used as starting materials. Then, H2O2 production was carried out in a capillary microreactor with electrodes for water electorlysis, Pd/C catalyst was coated on the inner wall of capillary tube.
The maximum rates of production of H2O2 were observed at a reaction temperature of 10 oC in the slurry reactor. The production rates of H2O2 were sharply increased in the presence of added methanol. Results show that H2O2 production is significantly influenced by the solubility of the gas. Meanwhile, excessive catalyst and hydrogen facilitate the decomposition of the accumulated H2O2, resulting the decrease in the production rate of H2O2. In addition, H2O2 production was performed in a catalytic slurry reactor in which a pair of platinum electrodes was inserted. The in-situ feed of hydrogen and oxygen into the reactor improved H2O2 production. This could be explained by an increase in gas solubility due to fine bubbles or the electrochemical generation of H2O2.
A micro-electrolyzer was connected to a capillary tube (inner diameter = 1mm). Pd/C catalyst was coated on the inner wall of the capillary tube. Reaction solution was fed into the micro-electrolyzer by tube-pump. H2 and O2 were evolved during water electrolysis and then the slug flow was formed in the capillary tube. H2O2 formation was observed in the solution recovered from the capillary tube.
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Presented Tuesday 18, 15:00 to 15:20, in session Chemical Reaction Engineering: Practical Applications (T2-2c).
