- 220 views
- 342 downloads
Oil Upgrading by Molecular Rearrangement and Cracking: A Study Using Model Compounds and Natural Chabazite
-
- Author / Creator
- Rocha Aguilera, Gonzalo
-
As demand for fuel increases, new technologies that can convert heavy oil and bitumen into light fuels are needed. Natural zeolites have been proven to catalyze reactions that decrease molecular weight, density, nitrogen, and metals content as well as vacuum residue content when mixed with raw oil sands at cracking conditions. Chabazite is an abundant and inexpensive natural zeolite with high acidity and a platy morphology that could be used for a new upgrading process for bitumen and heavy oils. In this work, model compounds were used to determine the mode of action of the chabazite towards nitrogen compounds, porphyrins, alkanes and substituted aromatics. Sulfur compounds were not studied here since previous studies suggest that the chabazite is not highly active towards such compounds. Indole and octaethylprophyrin (OEP) (in Ni and vanadyl form) were used as model compounds for nitrogen and metals. Both compounds were used in solution with 1-methylnaphthalene as solvent. Using indole as model compound, 43% indole removal and 17% nitrogen removal was achieved. Ni and vanadyl octaethylprophyrin were also used and the chabazite was able to remove up to 47.5% vanadium. Hexadecane was also used and a conversion up to 10.1% was achieved. All those reactions were done at 400 oC for 1 hr using a catalyst load of 10%. Cumene was reacted at 300 oC for 4 hr giving a maximum conversion of 25.1%. Up to 90% nickel removal was obtained at room temperature at equilibrium. The main reaction observed in those systems was transalkylation. Cumene, indole, OEP and the solvent underwent transalkylation reactions. Other reactions observed were opening of the pyrrolic ring, demetalation of porphyrins and cracking. With this observation, reactions were made using artificial oil sands. The addition of 2,2,4-trimethylpentane as methyl groups donor increased the conversion of the vacuum residue contained in the artificial oil sands Reaction paths for the nitrogen and metals removal were proposed. For indole, the non-basic nitrogen was converted to basic nitrogen (aniline) and then adsorbed into the surface of the chabazite. Metals were removed through demetalation of the porphyrin and adsorption. During this study, it was also observed that chabazite is more active than zeolite Y for cumene cracking while zeolite Y is more active towards hexadecane cracking. It was also observed that both Lewis and Brønsted-Lowry acid sites play different roles. Indole seems to preferentially adsorb into Brønsted-Lowry acid sites preventing them from participating in further reactions. Cumene-indole conjugated products, however, were observed. The role of the water was also studied but no definitive conclusions were drawn. Water seems to affect preferentially the Brønsted-Lowry acid sites. It also seems to adsorb competitively thus preventing some molecules from adsorption. It also increases the dispersion of the catalyst and reduces coke formation. The results presented in this study opens the possibility to create a new oil upgrading process through simultaneous cracking and molecular rearrangement using cheap and abundant material such as natural zeolites. More studies on the addition of alkyl-donating molecules to increase the activity of the zeolite are recommended. It is also suggested to study the activity of the chabazite towards different feeds including vacuum residue, asphaltenes and heavy gas oil.
-
- Graduation date
- Fall 2015
-
- Type of Item
- Thesis
-
- Degree
- Doctor of Philosophy
-
- License
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.