Charlotte Mase is currently conducting a PhD in analytical chemistry at COBRA laboratory in collaboration with TotalEnergies. She works on the molecular characterization of pyrolysis oils (plastic or biomass) and new sources of energies by ultra-high-resolution mass spectrometry.
Plastic wastes cause well known harmful effects for environment and contribute to the depletion of landfill sites. Pyrolysis oil produced from plastic waste materials is considered as an important source of monomers, fuel and chemicals that both circumvent some of the environmental concerns associated with non-renewable fossil resources and alleviate waste disposal concerns. In order to improve conversion and valorization processes, an advanced molecular description is essential. Such as crude oil, plastic oils are complex mixture including thousands of chemical species covering a wide range of mass and polarity. The most powerful technique for the analysis of this type of sample, in terms of mass accuracy and resolving power, is Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry (FTICR). It allows assigning a unique molecular formula to each m/z signal. Besides, the use of different ionization sources ensures an extensive molecular description and enables to assess the efficiency of different catalytic chemical treatments. Electrospray source (ESI) ionizes compounds with medium to high polarity. On the contrary, atmospheric pressure photoionization (APPI) allows the characterization of less polar compounds and in particular aromatics whereas atmospheric pressure chemical ionization (APCI) affords the ionization of aliphatic species. For this purpose, this study reports the molecular characterization of plastic pyrolysis oil by the main atmospheric pressure ionization. A large predominance of hydrocarbons compounds were observed in APPI (+) and APCI (+). Moreover, the use of both sources highlighted different types of molecules such as paraffins, diolefins and more particularly triolefins which had not yet been reported. Basic and neutral nitrogen containing species (N1 and N2 classes) were highlighted by ESI (+) and ESI (−) respectively. Oxygen containing species O1 to O4 were identified principally by ESI (−) but also in APPI (+) and APCI (+) and attributed as carboxylic acid and alcohol functional species. The same functionality of oxygen is founded in NxOy compounds observed in ESI (+) and ESI (−). The plastic pyrolysis oil molecular composition will be compared with petroleum fractions.