Review on evolved gas analysis mass spectrometry with soft photoionization for the chemical description of petroleum, petroleum-derived materials, and alternative feedstocks.
Modern industry strongly relies on the molecular analysis of fossil petroleum and petroleum-derived materials. In the context of a circular economy and carbon neutrality, the chemical description of alternative feedstock materials, such as waste plastic and biomass pyrolysis oils, increases in importance. Moreover, online monitoring of the thermochemical and catalytic conversion processes has gained rising attention. In this framework, evolved gas analysis (EGA) concepts with soft photoionization mass spectrometry (PIMS) were successfully deployed for numerous challenges. On the one hand, photoionization is a highly versatile technique and allows for "soft"ionization of the analyte molecule, preserving the molecular information. On the other hand, multiple evolved gas analysis concepts exist with unique benefits, such as the mass loss information in thermogravimetry coupling, high-throughput in direct inlet probe concepts, or straightforward reactor monitoring, allowing for direct online insights into pyrolytic transformation processes. Hence, this review aims to summarize the recent work in the field of EGA-PIMS. After technical description of the multiple photoionization and thermal analysis concepts, applied studies are summarized, discussed, and evaluated. Besides fossil fuels, studies on alternatives from renewable materials, such as biomass pyrolysis, plastic pyrolysis oils, and recycling processes, are reviewed. Finally, future perspectives on this field are given, highlighting the importance of those soft ionization schemes together with state-of-the-art detection by high-resolution mass spectrometry in the field of energy and fuels research.