Available at: https://digitalcommons.calpoly.edu/theses/3124
Date of Award
6-2025
Degree Name
MS in Civil and Environmental Engineering
Department/Program
Civil and Environmental Engineering
College
College of Engineering
Advisor
Amro El Badawy
Advisor Department
Civil and Environmental Engineering
Advisor College
College of Agriculture, Food, and Environmental Sciences
Abstract
The effect of household oil and agricultural soil contamination on catalyst performance during polyolefin pyrolysis was simulated on mixed virgin plastic pellets by evaluating contamination influence on mixed plastic degradation temperatures. Three phyllosilicate nanocatalysts including Fulcat435, Fulcat22F and Y-Zeolite were evaluated in this work based on a literature review of catalyzed plastic pyrolysis and these catalysts’ ability to lower plastic decomposition temperature by 50 °C – 100 °C. These findings were confirmed in this research through thermogravimetric analysis of a polyolefin mixture and further developed in furnace experiments containing household oil and agricultural contamination. Household oil contamination deactivated each of the three catalysts evaluated through blockage and poisoning of catalysts active sites. An increase in household oil contamination was directly correlated to a decrease in catalyst performance. As contamination ratio increased, the degradation profile further deviated from the uncontaminated baseline and statistical significance (α = 0.05) increased. It is anticipated, after a contamination ratio of 0.20 (plastic : contamination), the effect of household oil contamination plateaus and degradation profiles would match those similar to uncatalyzed pyrolysis. Experiments performed with Y-Zeolite and Fulcat435 were approximately two times more susceptible to household oil induced catalyst deactivation compared to experiments performed with Y-Zeolite and Fulcat22F. These results indicate that catalysts with smaller surface areas and or greater acid values are less susceptible to catalysts deactivation due to household oil contamination. It is proposed, the tighter phyllosilicate structure of Fulcat22F prevented interaction with larger fatty acid molecules of household oil contamination. Additionally, the greater acid value of Fulcat22F is directly correlated to an increase in active sites composed of Brønsted and Lewis acids. The author proposes these active sites provide extra capacity to catalyze reactions, further suspending complete catalyst deactivation. Although complete deactivation is possible, greater contamination ratios would be required to saturate active sites within Fulcat22F. To confirm this hypothesis, future work should identify potential correlation between phyllosilicate acidity and susceptibility of catalyst deactivation to household oils. The effect of agricultural soil contamination on catalyst performance is uncertain based on the results presented herein as oxygen present in agricultural soil induced combustion reactions increasing plastic degradation. An evaluation of the gas fraction of degradation products is recommended for future work to quantify combustion reactions initiated by oxygen present in agricultural soil contamination. Agricultural soil contamination present in plastic pyrolysis may provide a benefit as carbocation radicals generated from combustion reactions and could further catalyze plastic degradation. However, combustion reactions should be mitigated to preserve the quality of gaseous products. A pre-washing process should be performed if catalyzed pyrolysis is performed to mitigate contamination entering the pyrolysis furnace and maximize catalyst efficiency due to vulnerability of catalysts deactivation from contaminants commonly present in the municipal plastic waste stream.
Included in
Catalysis and Reaction Engineering Commons, Environmental Engineering Commons, Polymer Science Commons