Esterification of Octanoic Acid over Solid Acid Catalysts Derived from Petroleum Coke
Date
2021-06-28
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Abstract
Petroleum coke (petcoke) is a solid waste of the oil industry, with limited use due to its high sulfur content (> 6.5 wt%) and other impurities. As a carbon-rich, abundant and inexpensive material, petcoke is a potential resource for carbon-based catalysts. Esterification is a broad, important class of reactions for which carbon-based catalysts have been investigated and applied successfully. The treatment of petcoke (functionalization) with different conditions of temperature, time, and types of acid incorporates surface groups, which are the active sites for the reaction. This study tested the catalytic performance of acid-modified petcoke samples over a model reaction: esterification of octanoic acid with methanol. A commercial catalyst, Amberlyst-15, was used for comparison. The effect of various parameters was evaluated, including stirring speed (200 - 800 rpm), temperature (40 - 80 °C), catalyst loading (1 - 4.5 wt%), and methanol-to-acid molar ratio (40:1 - 10:1). The selectivity of all catalysts was 100% towards the ester yield, with no byproducts from the reaction. The method for the evaluation of catalyst activities was based on kinetic parameters and turnover frequency. The catalytic activity of acidic petcoke samples was comparable to the commercial catalyst in terms of conversion with time at the same reaction conditions, and even higher on a per acid site basis. Based on those results, acid-modified petcoke is a prospective material for catalyzing esterification reactions. Different properties arise from the treatment of petcoke with strong acids. The number of strong acid sites, overall acid strength as well as the surface hydrophobicity all influence the catalytic performance for the esterification reaction. Leaching of active sites was problematic and resulted in almost complete deactivation of the petcoke-derived catalysts. An appropriate balance in the surface hydrophobicity/hydrophilicity and a strong attachment of the active sites to the petcoke surface are required for stability.
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Keywords
esterification, catalysis, petroleum coke
Citation
Schafranski, A. S. (2021). Esterification of Octanoic Acid over Solid Acid Catalysts Derived from Petroleum Coke (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.