Hydrogen Peroxide Production from Elements and Usage in Olefin Epoxidation

The chemical industry is one of the major contributors to negative environmental impacts. Intensive research efforts have therefore been undertaken to transform this sector to mitigate climate change and ensure a more sustainable future. An important part of research activities in industrial chemistry is the development of new processes that provide environmentally friendly alternatives to established chemical processes while increasing efficiency and saving resources.

An example of such a development is the direct synthesis of hydrogen peroxide (DSHP), which represents an environmentally friendly alternative to the current large-scale anthraquinone process, which is considered as an inefficient and hazardous technology. In the DSHP, hydrogen peroxide (H2O2) is produced directly from hydrogen and oxygen with an atom efficiency of 100%.

Despite its great potential, DSHP has not yet been implemented industrially, as the thermodynamically favored formation of water and the degradtion of hydrogen peroxide during the reaction suppress the H2O2 selectivity. Numerous studies have aimed to overcome these challenges through catalyst development, mechanistic invetigation and optimization of process parameters. Another strategy to enhance the feasibility of DSHP is its combination with subsequent reactions, either indirectly as on-site H2O2 production or directly in one-pot systems. Such implementations of combined processes can drastically enhance overall efficiency by reducing time, space, energy demand and associated costs.

In this work, a novel process to produce propylene oxide was developed, which combines DSHP with the hydrogen peroxide to propylene oxide (HPPO) process in a single reactor unit. For this one-pot system, bifunctional catalysts were designed to enable both reactions to proceed simultaneously. The synthesis of the gold-palladium (AuPd) catalysts on titanium silicate was varied and optimized to improve catalysts’ physico-chemical properties, which were extensively investigated by catalyst characterization.

A compromise of the reaction parameters of DSHP and HPPO enabled the operation of the combined reaction. First insights into the reaction system were obtained through step response experiments and individual operation of the elementary reactions on AuPd/TS-1. Critical reaction parameters were identified by variation of the reaction parameters, and the catalyticperformance of the synthesized catalysts was evaluated in the combined system. Catalysts with larger metal nanoparticles and gold-rich alloy compositions exhibited improved propylene oxide selectivity but reduced overall activity.

Further, Ti-MWW catalysts with varying Si/Ti ratios and calcination conditions were synthesized and evaluated in epoxidation of propylene in acetonitrile and methanol solvents. Their performance was compared with commercial TS-1 as a reference catalyst to assess the influence of structure, chemical composition, and reaction medium on catalytic behavior.