Characterization of Slow-Pyrolysis Bio-Oils by High-Resolution Mass Spectrometry and Ion Mobility Spectrometry

Bio-oils produced from biomass pyrolysis are an attractive fuel source that requires significant upgrading. Before upgrade strategies can be developed, the molecular composition of bio-oils needs to be better understood. In this work, oily and aqueous fractions of bio-oils produced by slow pyrolysis of two feedstocks, pine shavings (PS) and corn stover (CS), were analyzed by negative electrospray ionization (ESI)-Orbitrap and ion mobility-time-of-flight mass spectrometry (IM-TOF-MS). Analyte ion signal was observed primarily between <i>m</i>/<i>z</i> 80 and 450 in the mass spectra of these samples. Mass defect analysis and collision-induced dissociation (CID) experiments performed on mobility-separated ions indicated a high degree of homology among bio-oil samples produced from both feedstocks. Oxygen-rich species having between 1 and 9 oxygen atoms and with double bond equivalents (DBEs) ranging from 1 to 15 were identified, indicating that catalytic upgrading will likely be required if slow-pyrolysis bio-oils are to be utilized as fuel. IM-MS and IM-MS/MS analysis of ions belonging to select CH₂-homologous series suggest that mass-mobility correlations and post-ion mobility CID mass spectra may be useful in defining structural relationships among members of a given Kendrick mass defect series

Photocatalytic Conversion of Nitric Oxide on Titanium Dioxide: Cryotrapping of Reaction Products for Online Monitoring by Mass Spectrometry

Details of coupling a catalytic reaction chamber to a liquid nitrogen-cooled cryofocuser/triple quadrupole mass spectrometer for online monitoring of nitric oxide (NO) photocatalytic reaction products are presented. Cryogenic trapping of catalytic reaction products, via cryofocusing prior to mass spectrometry analysis, allows unambiguous characterization of nitrous oxide (N₂O) and nitrogen oxide species (i.e., NO and nitrogen dioxide (NO₂)) at low concentrations. Results are presented, indicating that the major photocatalytic reaction product of NO in the presence of titanium dioxide (TiO₂) P25 and pure anatase catalysts when exposed to ultraviolet (UV) light (at a wavelength of 365 nm) is N₂O. However, in the presence of rutile-rich TiO₂ catalyst and UV light, the conversion of NO to N₂O was less than 5% of that observed with the P25 or pure anatase TiO₂ catalysts