Nanoscale Catalytic Materials for Sulfur Removal from Fossil Fuels
February, 2008
Understanding and optimizing the properties solid state materials plays a key role in a number of important technologies, including those in energy-related science and engineering. As crude oil prices approach $100/barrel, the need for careful utilization of fossil fuel resources has been heightened. A number of factors influence the price of crude oil, including a long-term concern that sources of conventional crude oil are being substantially depleted. Reflecting the depletion of crude oil reserves, a growing fraction of crude oil imports into the U.S. is synthetic crude derived from Canadian oil sands. There are significantly higher sulfur and nitrogen impurity levels in crude oil derived from the oil sands than in Arabian crude oils. The high impurity levels in heavy and unconventional crude oils present major challenges to the petroleum industry at a time that environmental regulations in the United States, Japan and in many western European countries are dramatically lowering allowable sulfur levels in transportation fuels.
Research in Professor Bussell’s laboratory focuses on the development of new catalytic materials for the removal of S impurities from fossil fuels via the hydrodesulfurization (HDS) process. While the catalysts currently used in industry are based on metal sulfides (e.g. MoS2), work in the Bussell laboratory focuses on the development of a new generation of catalysts based on metal phosphides (e.g. Ni2P). Nanoscale metal phosphide particles are deposited on a high surface area silica support using conventional catalysis preparation and cutting-edge nanosynthesis methods, the latter via collaboration with Prof. Stephanie Brock of Wayne State University. As shown in the transmission electron microscopy (TEM) images below, the conventional preparation method yields a range of Ni2P particle sizes (dark blobs) while the nanoscience preparation yields nearly monodisperse Ni2P particles of 10.2 nm diameter. Initial HDS activity measurements show the Ni2P nanoparticle catalyst to be nearly as active as a highly optimized, conventionally prepared catalyst. This collaborative project, which as already yielded one research article published in Advanced Functional Materials, is now focusing on probing the relationship between metal phosphide particle size, shape and composition and HDS activity.
Left: Comparison of thiophene HDS activity vs. time for a conventionally prepared Ni2P/SiO2 catalyst and a silica-supported Ni2P nanoparticle catalyst. Right: TEM micrographs of the conventional and nanoparticle Ni2P/SiO2 catalysts.
