Development of Novel Catalytic Materials for Hydrodesulfurization
in Manufacturing of Super-Clean Fuels
Catalytic materials play a crucial role in the chemical industry, as they are widely used in many chemical processes such as molecular hydrogenation, oxidative dehydrogenation, epoxidation, isomerization, disproportionation, polymerization, etherification, addition and decomposition. Control of active composition, surface area and porosity, in combination with acidity and high-temperature stability of surface modified supports, promise years of fertile research and technological development.
In connection to petroleum manufacturing, environmental protection is another important issue we have to face today. In recent years, the push to create clean technologies for conventional chemical industries has been moved to a higher gear. In the area of air pollution control, the legislation concerning the exhaust emissions from automobiles as well as from many other chemical processes is being continuously strengthened. To meet this move, cleaner fuels and other energy sources, i.e., with lower contents in nitrogen and sulfur species, are being demanded.
In the petroleum industry, as an example, regulation of sulfur content of gas and oil was limited to 0.2 % (by weight) in 1992. The limit was further reduced to a level of less than 0.05% in October 1997, and may be reduced again as little as 0.005 % in the near future. This non-stop improvement in emission standards requires more active catalytic materials (catalysts) to be developed. At present, all major oil-companies world-wide are developing a newer generation of hydrodesulfurization (HDS) catalysts, as a strategic move to a higher level competition in both chemical technology and sale market.
Improvements in catalyst performance and operation have to be reached within a competitive cost structure for the hydrodesulfurization application. In this regard, the development of new cost effective catalyst technology and its proper operation is an urgent task for petrochemical research. Recently, the Chemical and Process Engineering Centre (CPEC), a University Research Centre under the National University of Singapore (NUS) has started the above HDS project with Shell (Netherlands) and CRI Criterion (Singapore). With the support from the National Science and Technology Board (NSTB), the Economic Development Board (EDB) and CRI Criterion (Singapore), this three-year project will examine the existing catalytic materials and develop new material combinations and novel processing techniques for the super clean fuels production, aiming at a sulfur content of 0.005 wt.% or less. The project will also be in collaboration with other overseas Universities active in this area.
Over the past few years, novel processing techniques for metal oxide materials have been developed at NUS, which include HDS related catalysts. In particular, CoO, Co3O4, CoAl2O4, Ru/Al2O3, MgAl/Al2O3, CoAl/Al2O3 Co/ZrO2, Ni/ZrO2, Co/Ni/ZrO2, MoO2, MoO3, and PbMoO4 have been synthesized. In addition to these active catalysts, new generation-catalyst carriers of ZrO2, Al2O3, SiO2-ZrO2 with a large surface area and controlled porosity have been prepared. As this class of catalytic materials is closely related to the commercial catalysts (e.g., Co/Mo/Al2O3 and Ni/Mo/Al2O3) for hydrodesulfurization, the existing work at NUS can be easily extended to the development of new generation hydrodesulfurization catalysts for super-clean petroleum production.
Figure 1: X-ray diffraction method for determination of HDS catalyst structures.