Effects of Pyrosulfate on Sulfated Oxide Supports

With the support of the Chemical Catalysis program in the Division of Chemistry, Professor Matthew P. Conley of the University of California, Riverside is studying new catalysts for challenging chemical bond cleavage and formation reactions. Catalysts are important in a variety of reactions that activate inert bonds. The catalysts studied will be metal oxide materials containing anions, with a focus on zirconium oxide containing sulfate and pyrosulfate anions. This catalyst is used industrially in hydrocarbon refining and has a rich and complex history. Most literature assigns the unique reactivity of this material to strong acid sites present from sulfate anions, while other reports suggest that pyrosulfate anions are the reactive centers that promote catalysis. This work shows that the pyrosulfate anion is responsible for activation of inert carbon-hydrogen and carbon-carbon bonds in paraffins. This property is extended to activation of the inert bonds in polymer waste, a stream containing vast amounts of polyethylene and polypropylene that are difficult to recycle. The products of these reactions are processible oils that can be further functionalized using know catalytic technologies. Through these, and related studies, the chemistry of oxides containing pyrosulfate anions will help define this interesting class of catalytic materials. As part of this effort. Professor Matthew P. Conley also hosts high school students from a nearby high school to engage them in an academic research environment and to inspire them to pursue studies in STEM fields. With the support of the Chemical Catalysis program in the Division of Chemistry, Professor Matthew P. Conley of the University of California, Riverside is studying the surface chemistry of sulfated zirconium oxide (SZO) materials. When considering the chemistry of SZO towards alkanes, the dominant view in the available literature is that Brønsted sites mediate all reactivity. This proposal provides a new mechanistic model to describe how alkanes interact with SZO; pyrosulfates behave as adsorbed SO3, a very strong Lewis acid capable of activating C–H bonds. The insights from this mechanistic proposal, supported by preliminary data, resulted in the formulation of a simple anion doped oxide as a catalyst for chain cleavage in polypropylene waste. Thus, a simple oxide can facilitate a reaction that is usually performed by a highly reactive organometallic or supported metal nanoparticle catalysts. The results from this mechanistic model also extends to other H-atom transfer reactions that, to the best of our knowledge, are unprecedented in the chemistry of SZO. Professor Matthew P. Conley’s group will also host students from a nearby high school to involve them in this project to help retain them in STEM fields. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.