Production and use of H2O2 for atom-efficient functionalization of hydrocarbons and small molecules

Abstract

H2O2 is a relatively benign and selective oxidant, which has motivated research into scalable methods for H2O2 production and the design of catalysts to perform oxidations with H2O2. The energy intensive anthraquinone oxidation process is the standard for H2O2 production, however, alternatives such as electrocatalytic oxygen reduction and the direct synthesis of H2O2 have significant potential. Recent publications have investigated the reactor design, the mechanism for H2O2 formation, and the synthesis of increasingly selective catalysts and have demonstrated the role of proton–electron transfer in H2O2 formation and improving selectivities by alloying transition metals. H2O2 is a relatively unstable molecule which readily decomposes over a catalyst, making it difficult to use H2O2 for many oxidation reactions selectively. As such, there is extensive research on the use of H2O2 for different oxidation reactions, with the most common being olefin epoxidation. Olefin epoxidation is readily catalyzed by transition metal substituted zeolites, polyoxometallates, metal oxides, and homogeneous coordination compounds. These catalysts activate H2O2 to form many reactive intermediates, which possess selectivities for the epoxidation of olefins that reflect electronic properties of the reactive intermediate and the substrate. Ideally, H2O2 could be used for epoxidations within a single reactor (i.e., tandem catalysis), which would reduce costs from purification and transportation of H2O2. However, performing these reactions together typically provides poor epoxidation selectivities due to over-oxidation products. These chemistries are industrially relevant and present many unanswered questions of fundamental interest that warrant future investigation.