Using a novel, reusable carbon material derived from old rubber tires, an Oak Ridge National Laboratory (ORNL)-led research team has developed a simple method to convert used cooking oil into biofuel. The team’s approach combines modified, recovered carbon with sulfuric acids, which is then mixed with free fatty acids in household vegetable oil to produce usable methyl ester biofuel.
The study, done with collaborators Wake Forest University and Georgia Institute of Technology and detailed in Chemistry Select, provides a pathway for inexpensive, environmentally benign and high value-added waste tire-derived products—a step toward large-scale biofuel production, according to ORNL co-author Parans Paranthaman.
Many inexpensive biofuel feedstocks, including those containing free fatty acids (FFAs) in high concentrations, are typically disposed of as waste due to our inability to efficiently convert them into usable biofuels. Here we demonstrate that carbon derived from waste tires could be functionalized with sulfonic acid (-SO3H) to effectively catalyze the esterification of oleic acid or a mixture of fatty acids to usable biofuels.
Waste tires were converted to hard carbon, then functionalized with catalytically active -SO3H groups on the surface through an environmentally benign process that involved the sequential treatment with L-cysteine, dithiothreitol, and H2O2. When benchmarked against the same waste-tire derived carbon material treated with concentrated sulfuric acid at 150 ˚C, similar catalytic activity was observed. Both catalysts could also effectively convert oleic acid or a mixture of fatty acids and soybean oil to usable biofuels at 65 ˚C and 1 atm without leaching of the catalytic sites.—Hood et al.
In previous ORNL studies, carbon powders have proven useful in developing lithium-ion, sodium-ion and potassium-ion batteries and supercapacitors. The patent-pending, waste oil-to-biofuel conversion adds a new approach to waste tire recycling initiatives.
Z. D. Hood, S. P. Adhikari, Y. Li, A. K. Naskar, L. Figueroa-Cosme, Y. Xia, M. Chi, M. W. Wright, A. Lachgar, M. P. Paranthaman (2017) “Novel Acid Catalysts from Waste-Tire-Derived Carbon: Application in Waste–to-Biofuel Conversion” Chemistry Select 2, 4975 doi: 10.1002/slct.201700869