The characterization of coke on spent catalysts is key to understanding deactivation mechanisms in hydrocarbon transformations. In this paper we report the comprehensive characterization (using laser Raman spectroscopy, 13C MAS NMR, temperature-programmed oxidation, XPS, and carbon K-edge NEXAFS) of coke on a series of spent Pt-Re re-forming catalysts as a function of time on stream and position in the catalytic bed. Laser Raman spectroscopy is shown to be rather insensitive to the carbon species present, while 13C MAS NMR finds that the carbon is present primarily as aromatic carbon. The TPO data are consistent with the coke being present on the alumina support and not to a large extent covering the metallic Pt-Re nanoclusters, but the data do suggest the presence of more than one type of coke present. The carbon K-edge NEXAFS data, however, clearly differentiate the types of coke species present. In the more coked samples the features ascribed to graphite become more pronounced, together with an increase in the aromaticity, as judged by the intensity of the π* peak. With increasing amounts of carbon on the catalyst there is also a concomitant decrease in the σ* C–H peak, indicating that the carbon is becoming less hydrogenated. By using a linear combination of C NEXAFS spectra for n-hexane, benzene, and broadened highly oriented pyrolytic graphite (HOPG), we estimate the compositional change on the coke species, verifying the aliphatic to aromatic conversion. The data indicate that a good model for the deposited coke is that of highly defected, medium-sized rafts with a short-range polycyclic aromatic structure which have a variety of points of contact with the alumina surface, in particular with the O atoms. In agreement with the NMR, there is evidence for the C–O functionality from the presence of a shoulder in the C NEXAFS spectra that is ascribed, as a result of DFT calculations, to a 1s → π* transition of the carbon atoms bound to the oxygen of a phenoxide-like species bound to the alumina surface. These data confirm earlier Soxhlet extraction studies and show that extraction process did not substantially change the character of the coke from what it was while still in contact with the catalyst surface.

Biomass conversion, especially the development of bioprivileged molecules utilizing integration of biological and chemical processes, has shown potential to produce novel chemicals with enhanced properties. Here, organic corrosion inhibitors based on triacetic acid lactone (TAL) and 4-hydroxycoumarin (4HC) have been synthesized in good yield and tested for corrosion inhibition on mild steel in both sulfuric acid and hydrochloric acid. Sixteen novel corrosion inhibitors derived from TAL and 4HC were efficiently synthesized, and 12 of them showed high corrosion inhibition efficiency as confirmed by electrochemical impedance spectroscopy (giving values greater than 78%) and polarization analysis. While TAL-based compounds showed good corrosion inhibition performance, the 4HC-based compounds showed further improvement in corrosion inhibition performance. Scanning electron microscopy analysis of the mild steel coupon in the presence of selected inhibitors showed that corrosion was significantly diminished, with complementary X-ray photoelectron spectroscopy analysis suggesting that the inhibitor molecules strongly adsorbed on the steel surface. Quantum chemical calculations showed poor correlation between calculated parameters and the performance of these molecules. This large set of corrosion inhibitors containing a dozen promising corrosion inhibitors is useful for future rational design of corrosion inhibitors. The results demonstrate a new direction for the development of bioprivileged molecules.

The efficient conversion of a living anionic polymer chain end to a macrochain transfer agent suitable for reversible addition–fragmentation chain transfer (RAFT) polymerization is reported. Conversion to the macrochain transfer agent efficiency reached as high as 97% by capping the polyanion with alcohol, coupling with α‐bromoisobutryl bromide, followed by atom‐transfer radical addition–fragmentation with bis(thiobenzyl)disulfide to add the chain transfer agent functionality. To our knowledge, this is the most efficient marriage of anionic and reversible addition–fragmentation transfer polymerization reported to date, and can be carried out under common industrial processing conditions. The combination of these polymerization methods broadens the scope of commercially accessible block copolymers by exploiting the advantages of both RAFT and anionic polymerization chemistries.

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