Diesel fuel is essential intercontinentally, as it plays critical roles for industry, agriculture, military, and healthcare sectors. Hence, the storage stability of diesel is an essential aspect of maintaining daily operations globally. As the nitrogen-containing compounds (NCCs) are known to facilitate storage stability failure of diesel, their chemical characterization is vital. In this work, (+) electrospray ionization coupled to an orbitrap mass spectrometer was employed to qualitatively characterize ionized NCCs derived from stable and unstable diesels, and from sediment obtained from the unstable diesel fuel. Remarkably, up to 40 and 63 individual homologue ion series (ions sharing the same general molecular formula, each representative of at least one chemical class (e.g., pyrroles, quinolines, carbazoles)) were detected in diesel fuel and sediment, respectively. Hence, this work provided more comprehensive qualitative information for diesel fuels and sediments than previously documented. Upon comparison of diesel fuels, important compositional differences were observed, notably greater abundances of NCCs with the general formula of C x H y NO and C x H y NO2 in the unstable diesel. Upon analysis of sediment, ions of the general formula of C x H y N, C x H y NO, C x H y NO2, C x H y NO3, and C x H y N2O2 were detected. Interestingly, NCCs of smaller alkyl carbon number showed greater propensity to contribute to sediment formation. Additional stress studies using ASTM D5304 were completed on copper-doped and nondoped diesel fuels. Upon stressing the nondoped and copper-doped stable diesel fuels, oxidized NCCs clearly increased in abundance, especially for the copper-doped diesels, demonstrating its significance for accelerating oxidative reactions. Additional qualitative data was reported for the NCCs detected in fuels and sediments and by individual ion series (i.e., range and average molecular masses) as well as Kendrick Mass Defect plots. Overall, the reported qualitative information showcased the proficiency of the orbitrap at providing vital information for enhancing our current understanding of diesel storage stability.
A class of bio-based bifunctional phthalonitrile (PN) resins composed of cinnamaldehyde derivatives, aminophenol, and end-capped with a PN moiety is detailed. The cinnamic-imine PN (CIPN) resins were synthesized by utilizing environmentally friendly solvents methanol (MeOH) and acetone at ambient temperatures. Characterization of the resins was conducted via proton (1H) and carbon (13C) nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), infrared spectroscopy (IR), mechanical analysis, single crystal X-ray diffraction (XRD), and rheometry. The CIPN resins were self-curing due to the vinylic, imine, and PN moieties present and displayed a range of viscosities from 153-1546 cP at 225 °C. The resulting CIPN polymers were prepared by post-curing up to 380 °C and exhibited excellent thermal stability with T d5% above 510 °C up to an 80% char yield. Moderate brittleness ranging from an initial storage modulus (G' at 25 °C) of 86-1295 MPa was observed among the CIPN resins. This combination of properties suggests that the bifunctional CIPN resins are excellent materials for high temperature thermosets in composite applications.
A number of mechanistic schemes exist attempting to outline the processes involved in the reforming of carbon in solid oxide fuel cells (SOFCs) using ex situ techniques at temperatures and in environments that are far from those used under operational conditions and therefore not necessarily reflective of true events. I n situ vibrational spectroscopies (Raman and Fourier transform infrared emission, FTIRE) and near infrared thermal imaging (NIRTI) techniques are uniquely suited to probe the processes occurring in SOFCs in real time under operando conditions. In this study these methodologies are coupled to electrochemical data and employed to elucidate and compare the mechanisms underlying the partial oxidation reforming reactions. This process seems to be governed by the reformer’s affinity for the Ni-anode surface. We argue that high affinity for the anode surface reported for O, resulting from the surface dissociation of O 2 , result in slow oxidation of carbon possibly due to competition with the more favorable formation of NiO.
