Compositional and Structural Analysis of Silica Gel Fractions from Municipal Waste Pyrolysis Oils

Abstract

Hydrocarbon-rich pyrolysis oils produced from landfill waste and recycled plastics are potential sources for fuels and chemicals. It is well established that feedstock composition significantly affects pyrolysis oil composition and, hence, its potential uses. For example, plastics waste pyrolysis oils contain a high concentration of hydrocarbons, whereas biomass pyrolysis oils have high oxygen content. Previous studies have shown that the addition of plastics to a biomass feedstock increases the hydrocarbon content; however, a detailed analysis of hydrocarbons and polar species from pyrolysis oils produced from “real world” mixed municipal waste materials has not yet been done. Here, the silica gel fractions from unsorted landfill waste and mixed recycled plastics pyrolysis oils are analyzed by two-dimensional gas chromatography (GC × GC), field ionization mass spectrometry (FI-MS), Fourier transform infrared spectroscopy (FT-IR), and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Gravimetric results show that the plastics pyrolysis oil has a much greater concentration of saturated hydrocarbons than the more aromatic landfill pyrolysis oil. GC × GC and FI-MS for the saturated hydrocarbons show a range of alkanes, cycloalkanes, olefins, and 1-ring aromatics. Molecular elemental compositions from FT-ICR MS were correlated with structural assignments from GC × GC to expand the structural understanding of the aromatic hydrocarbons from plastics and landfill pyrolysis oils and showed that the aromatic hydrocarbons from the landfill are both peri- and cata-condensed. In contrast, plastics pyrolysis oil consists of polyphenyls and cata-condensed aromatic hydrocarbons. The polar species from the plastics pyrolysis oil contain more alcohol functionalities than the landfill pyrolysis oil, which contains non-carboxyl carbonyl functional groups. Improved structural understanding of both pyrolysis oils will provide better understanding of their properties and potential uses.

Molecular Characterization of a Mixed Plastic Pyrolysis Oil from Municipal Wastes by Direct Infusion Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

“…Fourier transform ion cyclotron resonance (FTICR) mass spectrometers with a high magnetic field offer the best performances in terms of resolution, mass accuracy, and dynamic range. − Over the past 20 years, it has been widely used to decipher ultracomplex mixtures. − In the case of plastic pyrolysis oil, two studies using FTICR-MS reported their molecular characterization with atmospheric pressure photoionization (APPI). This enabled the characterization of hydrocarbon compounds and a part of oxygenated compounds defined as alcohols. , However, as stated before, the molecular characterization of other heteroatom-containing species such as nitrogen species is also important in order to anticipate their impact on the refining process. − Depending on the ionization method, different ionization selectivities can be obtained in order to detect specific families of compounds. Electrospray ionization (ESI) is known to be selective of basic and acidic compounds using the positive and negative ion modes, respectively, while APPI and atmospheric pressure chemical ionization (APCI) are less selective and allow for the detection of low-polarity species. , …”

“…This enabled the characterization of hydrocarbon compounds and a part of oxygenated compounds defined as alcohols. 39,40 However, as stated before, the molecular characterization of other heteroatom-containing species such as nitrogen species is also important in order to anticipate their impact on the refining process. 41−43 Depending on the ionization method, different ionization selectivities can be obtained in order to detect specific families of compounds.…”

Liquid fuel from waste tires: novel refining, advanced characterization and utilization in engines with ethyl levulinate as an additive

“…The exciting principle behind twodimensional GC Â GC TOFMS is the separation of mixtures by the polarity of species compared to one-dimensional GC-MS separation based on the compounds' boiling point. [28][29][30]36 There are very few studies in the literature regarding the analysis of tire oil fractions using this advanced chromatographic technique. Ngxangxa reported that TPO is a complex mixture of C 6 -C 24 compounds, including paraffins, terpenes, monocyclic and PAHs, heterocyclic compounds, etc.…”

Speciation and Semiquantification of Nitrogen-Containing Species in Complex Mixtures: Application to Plastic Pyrolysis Oil

“…Each was previously characterized using different analytical methods such as gas chromatography (GC), 21 , 23 − 26 infrared spectroscopy (IR), 27 nuclear magnetic resonance (NMR), 19 and mass spectrometry (MS). 12 , 16 , 25 Because pyrolysis oil is of particular interest for the recovery of monomers, the material chosen in this study is a pyrolysis oil produced from real municipal wastes made up of different plastic types. Owing to the high molecular complexity of such samples, the necessity of using very-high-resolution mass spectrometry such as Fourier transform ion cyclotron resonance (FTICR) to characterize plastic oils has been demonstrated.…”

“…Owing to the high molecular complexity of such samples, the necessity of using very-high-resolution mass spectrometry such as Fourier transform ion cyclotron resonance (FTICR) to characterize plastic oils has been demonstrated. 12 , 25 , 28 Specifically, in a previous study, the presence of nitrogen-containing species in the plastic pyrolysis oil was highlighted by electrospray ionization (ESI). 29 Nitrogen-containing species form due to the presence of antioxidant additives such as hindered amine light stabilizers (HALS) and nitrogen-containing polymers such as polyamides in the plastic waste.…”