ADSORPTIVE DESULFURIZATION OF LIQUID TRANSPORTATION FUELS VIA NICKEL-BASED ADSORBENTS FOR FUEL CELL APPLICATONS

Open Access
Author:
Clemons, Jennifer Lee
Graduate Program:
Energy and Geo-Environmental Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
May 01, 2009
Committee Members:
  • Chunshan Song, Thesis Advisor
Keywords:
  • fuel processing
  • nickel adsorbents
  • sulfur removal
Abstract:
The objectives of this work are to compare the adsorptive desulfurization capacity of several different types of nickel-based adsorbents and to identify ways for further improving their capacity for removing sulfur from liquid transportation fuels for fuel cell applications. The reforming of liquid fuels to produce hydrogen is a possible intermediate step in moving towards a hydrogen economy, but ultra low sulfur fuels are required since catalysts for fuel reforming and for fuel cell electrode (anode) are sensitive to sulfur poisoning. Traditional methods of removing sulfur, such as hydro-treating, are very costly to create ultra clean fuels, can change the composition of the fuel, and consume large quantities of hydrogen, which are the desired product. Adsorptive desulfurization has great potential to remove sulfur from the readily available liquid fuels, while not affecting the fuel composition. Nickel adsorbents are specifically effective because they are very selective to sulfur. This research will compare three different types of nickel adsorbents. The comparison of these adsorbents should give some insight into how to design the most effective nickel adsorbent for removing sulfur from liquid fuels. The first adsorbent studied in this research is a nickel metal loaded on SiO2Al2O3. The second adsorbent is Raney Nickel which is a highly dispersed nickel supported on an aluminum framework. The final type of adsorbent was prepared in the laboratory by co-precipitation, and has varying nickel metal contents. This adsorbent is supported on aluminum and in some cases contains varying amount of zinc. iv After the three adsorbents have been tested, a comparison on these adsorbents can be shown. The adsorbent performance on jet fuel is highly dependent on the basis. For example, the co-precipitated sample 2/5/1 NiZnAl appears to perform the best with jet fuel on a g-fuel/g-Ads basis. On the basis of fuel processed, the Raney Nickel performs the best. This occurs because the co-precipitated samples are not as dense, and only about 1.7 grams was packed in the same volume as 3 grams of Ni-SiO2Al2O3 and 4.5 grams of Raney nickel. For tests on diesel fuel, there was no difference on the basis. It appears that of all the different physical properties of the adsorbents including surface area, micropore area and average pore size, the most important factor is surface nickel content. Raney nickel has the highest surface nickel content and performs the best followed by Ni- SiO2Al2O3 and then finally the co-precipitated samples.