Date of Award
Master of Science
Thermochemical processing of biomass into liquid chemicals or fuels is a potential way of offsetting excess carbon released from petroleum derived fuel, however thermochemical processing is hindered by the high cost of biomass feedstock. Using municipal solid waste (MSW) as a feedstock can help because it is very cheap and contains significant amounts of organic materials, however the low upfront cost comes with other processing burdens. In particular, polyvinyl chloride (PVC) is a plastic commonly found in MSW that can contribute to equipment wear, environmental harm, and product contamination through release of hydrogen chloride (HCl) when heated. This work looks at using this release of HCl from PVC as an asset instead of a hindrance during thermochemical processing MSW.
The first project co-converted cellulose and PVC in the polar aprotic solvent tetrahydrofuran (THF), with the hypothesis that the HCl released could catalyze conversion of cellulose. It was found that the addition of 2.5 wt% PVC caused an increase from 7% to 36% of levoglucosan at 310 ÃÂ°C. Testing was also done at different temperatures to determine its effect. Raising the temperature from 285 ÃÂ°C to 335 ÃÂ°C increased levoglucosan production from 29% to 38%.
The second project used a mixture of cardboard (CB), PVC, and polyethylene (PE) as feedstock materials because these materials are commonly found in MSW. The goal was to first apply solvent liquefaction, as was done in the first project, but then perform pyrolysis on the residue to further obtain useful chemicals. The hypothesis was that CB and PVC would degrade in the solvent, but PE would not due to its thermally stable nature. Results showed that the addition of PVC decreased the time to peak oil yield from 120 minutes to 60 minutes during solvent liquefaction. When all three feedstock materials were used, the highest oil yield was obtained at 69%, at 45 minutes of reaction time. The most abundant chemical in the liquid was tetrahydrofurfural alcohol, obtained in the CB case at 2.5%. When the residue from the CB+PVC+PE case was pyrolyzed, significant amounts of aliphatic hydrocarbons were obtained from the cracking of the residual PE. Additionally, no chlorinated organic compounds were detected in the residue pyrolysis.
Braden, Joel, "Solvent liquefaction of waste materials" (2018). Graduate Theses and Dissertations. 16321.