In this project funded by the Chemical Catalysis program of the Chemistry Division, Professors Mark Bussell and Takele Seda of Western Washington University, Professor Stephanie Brock of Wayne State University and Professor S. Ted Oyama of Virginia Tech are investigating the fundamental properties of a new class of materials for the removal of impurities from petroleum and other oils. The new materials, composed of metals bonded to phosphorus, are known as metal phosphides and have been shown capable of removing sulfur, nitrogen and oxygen impurities from both petroleum and other oils made from plant or food sources. The need for such removal catalysts is high because all these oils contain substantial impurities, and removing them must be done in such a way that stringent environmental standards are met. By working collaboratively, the researchers on this project are probing the role of particle size, shape and composition on the fundamental catalytic properties of metal phosphides, providing new information for the improvement and commercialization of these promising catalysts. The development of a new generation of catalysts based on metal phosphides would have positive economic and environmental impacts in the U.S. and globally. The collaborative team consisting of PI Bussell and co-PI Seda, faculty members at a predominantly undergraduate institution, co-PI Brock, a faculty member at an urban research university, and co-PI Oyama, who has joint appointments at large U.S. and Japanese research universities, embraces a diverse range of participants. The faculty and students involved in this project are participating in K-12 outreach to educate and recruit the next generation of STEM talent to address the range of energy issues facing the world.
Transition metal phosphides have the potential to be highly active hydrodesulfurization (HDS) and hydrodeoxygenation (HDO) catalysts. While metal phosphides represent a promising next generation catalyst for hydrotreating applications, until the effects of active site density, surface composition, and mechanism of resistance to poisoning/deactivation are known, the prospects for improvement and commercialization of such phosphide catalysts face significant challenges. The aims of this project are to determine the roles of particle size, particle shape and composition in determining the activity and selectivity of metal phosphide nanoparticles encapsulated in mesoporous oxide shells for the HDS and HDO reactions. Pre-formed particles are being investigated because they can be prepared as nearly monodisperse samples in sizes ranging from 2-30 nm, and as spherical or rod-shaped single crystallites, thereby enabling quantification of the active site density (and thus turnover frequencies (TOFs)) as well as assessment of the relative activity of different crystal faces. Each member of the collaborative team brings unique characterization capabilities for investigating the structural details of the well-defined metal phosphide nanoparticle catalysts. The proposed research activities with core-shell nanocatalysts will allow us to probe the fundamental chemistry of HDS and HDO over metal phosphides, providing new information for the improvement and commercialization of these promising catalysts.