Raney Nickel for the Desulphurization of FCC Gasoline

Abstract

Abstract This study is being performed as part of a graduate thesis project at the University of Northern British Columbia. We are attempting to develop an alternative method for removing sulphur compounds from the fluid catalytically cracked stream of gasoline (FCC gasoline). As of January 1, 2005, Canada developed new regulations for the amount of total sulphur in fuel, thereby limiting the total sulphur to 30 ppmw. This paper reports on our work using Raney nickel for the removal of sulphur-containing compounds from FCC gasoline. Raney nickel is activated with an alkaline solution, then reacted with the FCC gasoline to form a nickel sulfide precipitate. Simply by varying the reaction time, a maximum reduction of 80% sulphur concentration can be seen at 60 min. Similarly, by varying the temperature, a maximum reduction of 99% sulphur concentration was obtained at a reaction temperature of 50 °C. Finally, sequential reaction experiments indicated a maximum reduction in sulphur concentration of 97% in the treated FCC gasoline using two consecutive additions of Raney nickel. These reactions are being performed on a laboratory scale but indicate that Raney nickel is very effective at removing sulphur from FCC gasoline. Introduction The removal of sulphur from fossil fuels has become a major concern. Currently, the most common way of removing sulphur from fossil fuels is by hydrotreating. However, it is an expensive process. As of January 1, 2005, Canada legislated that the sulphur content in gasoline be lowered to 30 ppmw from 150 ppmw with the hopes of further lowering the sulphur levels in future years. The purpose of this project was to develop an alternative method for removing sulphur from gasoline, specifically, fluid catalytically cracked gasoline (FCC gasoline) Raney nickel is one of the most common metal catalysts and was discovered by Murray Raney in 1927. In general, Raney nickel is comprised of sponge-like particles and it is this porous structure that makes Raney nickel a high capacity catalyst or rapid reactant for the removal of sulphur(1). Raney nickel is prepared by reacting an alkaline solution with a nickel-aluminum alloy(1). The activation is typically carried out by the addition of a sodium hydroxide solution. This leaching process causes the nickel-aluminum (Ni-Al) alloy to be more porous, have a higher surface area, and become activated(2). The activation process oxidizes the aluminum and generates hydrogen gas, which activates the nickel portion of the catalyst(3). Equation (Available In Full Paper) Some of the hydrogen remains adsorbed on the nickel, making it a low temperature hydrogenation catalyst. Therefore, nickel catalysts have been used widely in hydrogenation, hydrotreating, and in steam-reforming reactions(4). In particular, Raney nickel has been used in industry for the hydrogenation of organic compounds(2) and the determination of trace amounts of sulphur in organic Mixtures(5). There were several methods developed to determine trace amounts of sulphur in petroleum distillates(6). These methods were previously used in the laboratory analysis of sulphur levels in fuels.