Enhanced Oxidative Reactivity for Anthracite Coal via a Reactive Ball Milling Pretreatment Step

Reactive ball milling in a cyclohexene solvent significantly increases the oxidative reactivity of an anthracite coal, due to the combined effects of particle size reduction, metal introduction, introduction of volatile matter, and changes in carbon structure. Metals introduced during milling can be easily removed via a subsequent demineralization process, and the increased reactivity is retained. Solvent addition alters the morphological changes that occur during pyrolysis and leads to a char with significantly increased reactivity. When the solvent is omitted, similar effects are seen for the milled product, but a significant fraction of the char is resistant to oxidation

Polyphosphazene Elastomers Containing Interdigitated Oligo‑<i>p</i>‑phenyleneoxy Side Groups: Synthesis, Mechanical Properties, and X‑ray Scattering Studies

The range of polyphosphazene-based elastomers has been expanded through the use of phenoxy or oligo-<i>p</i>-phenyleneoxy minor cosubstituent side groups with majority 2,2,2-trifluoroethoxy side groups. Specifically, polymers with both trifluoroethoxy and low ratios of phenoxy, <i>p</i>-phenylphenoxy, <i>p</i>-diphenylphenoxy, or <i>p</i>-triphenylphenoxy cosubstituents, can generate noncrystalline, noncovalently cross-linked elastomers. These are formed through the steric interactions of the oligo-<i>p</i>-phenyleneoxy side groups. Small-angle X-ray scattering (SAXS) analysis of polymers containing <i>p</i>-diphenylphenoxy or <i>p</i>-triphenylphenoxy cosubstituents suggests that these macromolecules contain microdomains caused by the phase separation of the trifluoroethoxy and aryloxy groups, through stacking or agglomeration of the aryloxy units, and that those serve as noncovalent cross-linking points. Moreover, annealing of the polymers at elevated temperatures (150 °C) causes a decrease in the average spacing between the aryloxy aggregates and has a direct effect on the mechanical properties, similar to the toughening caused by increases in the cross-link density in conventional elastomers

Role of Carbon Order in Structural Transformations and Hydrogen Evolution Induced by Reactive Ball Milling in Cyclohexene

Demineralized Summit (DS) anthracite, DS annealed at 1673 K, and graphite are used to explore the effect of precursor order on structural transformations and H2 evolution that result during reactive ball milling. Carbon structure was assessed before and after milling with temperature-programmed oxidation, X-ray diffraction (XRD), ultraviolet Raman spectroscopy, N2 adsorption, He density, and solvent swelling. Graphite milled in cyclohexene is primarily nanocrystalline graphite, with 8 wt % amorphous content leading to low-temperature oxidation, swelling, increased surface area and mesoporosity. Milling the disordered DS leads to signs of increased sp2 clustering, increased cross-linking, a significant ultramicroporosity with pores less than 8 Å, and low-temperature H2 evolution. The carbon fraction of annealed DS behaves similarly to graphite in the mill

Characterization of carbon-coated core-shell iron nanoparticles annealed by oxygen and nitrogen

Nanocomposites consisting of nanoparticles of iron oxide (Fe3O4) and iron carbide (Fe3C) with a core-shell structure (Fe core, Fe3O4 and/or Fe3C shells) coated with additional graphite-like carbon layer dispersed in carbon matrix have been synthesized by solid-phase pyrolysis of iron-phthalocyanine (FePc) and iron-porphyrin (FePr) with a pyrolysis temperature of 900°C, and post-annealing conducted at temperatures ranging from 150°C to 550°C under controlled oxygen- and/or nitrogen-rich environments. A comprehensive analysis of the samples’ morphology, composition, structure, size, and magnetic characteristics was performed by utilizing scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-STEM) with elemental mapping, X-ray diffraction analysis (XRD), and magnetic measurements by utilizing vibrating sample magnetometry (VSM). The effect of the annealing process on magnetic performance and efficient control of the hysteresis loop and specific absorption rate (SAR) are discussed

Catalytic Transfer Hydrogenolysis of Switchgrass Lignin with Ethanol Using Spinel-Type Mixed-Metal Oxide Catalysts Affords Control of the Oxidation State of Isolated Aromatic Products

Chemical reductions of lignin are useful to remove oxygen and create product slates that can function as renewable platform molecules for new fuels and chemicals. Catalytic transfer hydrogenolysis (CTH) is an underexplored method to reduce lignin that obviates the use of dangerous and nonrenewable hydrogen gas. While noble metals are used extensively as catalysts for transfer hydrogenation, sustainability remains a major challenge to their deployment. In this work, we synthesized mixed-metal oxides of earth-abundant Co and Ni and characterized the catalysts using powder X-ray diffraction (XRD). Catalyst reactivity for the CTH of acetophenone was also assessed. Among the catalysts tested, spinel NiCo2O4 demonstrated the highest conversion of acetophenone (75%) and the highest selectivity for ethylbenzene (90%); thus, we applied it to valorize switchgrass lignin, extracted under mild operating conditions by cosolvent enhanced lignocellulosic fractionation (CELF). The catalytically depolymerized lignin showed an increase in the number of selectively deoxygenated monomeric compounds. As demonstrated using 2D-NMR spectroscopy, the lignin displayed highly reduced aliphatic carbons, resulting from the catalyst-mediated reduction reaction at the Cα sites. These results are critical to the further development of the lignin-first biorefinery as they demonstrate the use of sustainable catalyst materials and mild transformation conditions to generate and refine a suite of new bioproducts