New catalysts make H2O2 in one-step process

CARDIFF UNIVERSITY researchers have developed a new, lower-cost group of catalysts to directly manufacture hydrogen peroxide in a one-step process.

Hydrogen peroxide, a disinfectant and bleaching agent, is conventionally produced indirectly from anthraquinone in a large-scale multi-stage process. The final product is highly concentrated and must be diluted for use. Hydrogen peroxide is useful for water purification, and researcher Simon Freakley, from the Cardiff Catalysis Institute, explains that the team’s new catalyst could be used for producing hydrogen peroxide on demand from hydrogen and oxygen on a much smaller scale than usual. This could allow clean drinking water to be produced at small, decentralised plants in remote or disaster-stricken regions of the world.

The research was led by Cardiff professor Graham Hutchings, who in 2015 was part of the team which won the IChemE Award for Innovative Product of the Year, for a gold catalyst to make vinyl chloride monomer. He has also worked on a gold and palladium catalyst which can produce hydrogen peroxide directly from oxygen and hydrogen and it was this work which formed the basis of the current project. Gold and palladium are extremely expensive and the team sought to replace the gold with cheaper metals.

Hutchings and the team made the catalyst using a wet impregnation method to produce a palladium and tin based catalyst supported on titanium dioxide. The optimum catalyst was found to have 3% palladium and 2% tin. Smaller palladium particles were found to facilitate further hydrogenation of the hydrogen peroxide, breaking it down. The team added a calcination step in air at 500?C, which encapsulated the palladium nanoparticles in a tin oxide surface layer, effectively suppressing this reaction. The calcination step, however, was found to lower the activity of the catalyst, so they also carried out a further reoxidation step.

The final catalyst has a selectivity of 95% to make hydrogen peroxide and shows no degradation activity.

Hutchings adds: “Rather than replace the current industrial process, we envisage this catalyst being used where low concentrations of hydrogen peroxide are required. For example, we could see our catalyst being used in decentralised water purification systems in which the speedy, on-demand production of hydrogen peroxide would be essential.”

He and the team also created catalysts in the same basic design from other metals, including nickel, zinc, gallium, indium and cobalt. Although these showed lower activity than the tin catalyst, the team says that it proves the possibility of making selective, reusable catalysts with reduced precious metal content.

The researchers say they are in discussions with industry to develop the catalysts further.

Science DOI: 10.1126/science.aad5705