Adsorptive Removal of Sulfur Containing Compounds from Marine Fuel using Metal Loaded Zeolite Y
Lobb, Jake Robert
Wong, Michael S
Master of Science
The removal of sulfur containing compounds from liquid fuels is becoming increasingly important. The International Maritime Organization (IMO), the governing body that regulates international maritime trade, has recently passed regulation that significantly decreases the total allowable sulfur content in fuels in order to reduce SOx emissions from merchant vessels. Furthermore, certain applications, such as the operation of fuel cells, require exceptionally low sulfur fuel in order to mitigate catalyst poisoning in the reformer. To this end, the two fuels that were investigated in this work were Intermediate Fuel Oil 380 (IFO380), a common heavy marine fuel, and Jet Propellant 8 (JP – 8), a military logistic fuel desirable for use with fuel cells. The primary desulfurization method used at refineries is hydrodesulfurization (HDS), which is highly effective for sulfur removal of aliphatic sulfur compounds, but remains inefficient at removing refractory sulfur compounds. Therefore, alternative desulfurization methods have been heavily researched which aim to more efficiently remove these compounds after the refining process. In this work, adsorptive removal of sulfur compounds via a batch reactor was chosen for investigation using sodium zeolite Y loaded with copper or nickel (NaY, CuY, and NiY, respectively). It was found that adsorptive desulfurization with metal loaded zeolite Y is capable of removing sulfur compounds from IFO380. The sulfur removal decreased as follows: CuY = NiY > NaY. The sulfur removal, however, was limited as compared to the JP – 8 results. Presumably, the decreased performance was due to the active sites in the zeolite being inaccessible to the large sulfur compounds that likely exist in IFO380, including the significant amount of sulfur contained by the asphalthenes in the fuel. A two-step batch reactor desulfurization technique was used to adsorb sulfur compounds in JP – 8, with the most effective two – step series being CuY – CuY. It was concluded that CuY is the most effective adsorbent for this fuel due to its bonding mechanism allowing it to selectively remove sulfur compounds over competing non-sulfur compounds. Prior to conducting desulfurization experiments, the adsorbents are activated at high temperature under helium gas. During activation, it is well known that the Cu2+ ions within the CuY partially reduce to Cu+. However, there is much disagreement in literature as to the extent of this reduction and which activation conditions contribute. This work investigates the reducibility of copper species within CuY, after various activation conditions under inert gas or reducing agent, using hydrogen – temperature programmed reduction. Through this method, the location of Cu2+ species within the zeolite frame work can be determined, as well as the relative amounts of Cu2+, Cu+, Cu0, and CuO that exist. It was shown that the reducibility of copper species is a strong function of activation temperature and gas and not a function of activation time.