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

Abstract

Plastic wastes cause well-known harmful effects for the environment and contribute to the depletion of landfill sites. Pyrolysis oil produced from plastic waste materials is considered as an important source to produce monomers, fuel, and chemicals that both circumvent some of the environmental concerns associated with nonrenewable fossil resources and alleviate waste disposal concerns. In order to improve conversion and valorization processes, an advanced molecular description is essential. Such as petroleum crude oils, plastic pyrolysis oils are complex mixtures composed of thousands of chemical species covering a wide range of masses and polarities. Molecular characterizations require the use of high-resolution instruments such as Fourier transform ion cyclotron resonance mass spectrometers. In this study, we report the characterization of plastic pyrolysis oil by the main atmospheric pressure ionization: electrospray ionization (ESI) in positive and negative modes (±), atmospheric pressure photoionization (APPI) in positive mode (+), and atmospheric pressure chemical ionization (APCI) in positive mode (+). A large predominance of hydrocarbon compounds was 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 have 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–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 (−).

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