Abstract Bitumen‐derived asphaltenes are rich in carbon but of low value and contain other elements such as nitrogen, sulphur, oxygen, vanadium, and nickel. Their use as a feedstock for producing carbon fibre (CF) is largely under‐investigated. In this study, electrospinning was used to create asphaltene fibres (AFs), which is a pre ‐ carbon fibre material, from asphaltenes. Various operational parameters were investigated in order to improve the spinning abilities, such as the concentration of asphaltenes in toluene, pumping rate, voltage, and distance between the tip of the needle to the collector. Results indicated that asphaltenes concentrations had the greatest effect on the quality of the produced AFs, with the range of asphaltenes concentrations from 45 to 50 wt.% being suitable for producing the AFs, while voltage, pumping rate, and tip distance had less of an effect on electrospun AF production.
In this study, Fischer‐Tropsch (F‐T) wax and bitumen‐derived hydrotreated heavy vacuum gas oil (HVGO) blends were co‐hydrocracked over a commercial catalyst in an autoclave reactor at a temperature of 360 °C and an initial hydrogen pressure of 4.2 MPa. 100 % F‐T wax and 100 % HVGO were hydrocracked under similar operating conditions as the reference feedstocks. The results revealed that the conversion of 360 °C+ materials decreased from 0.79 g/g (79 mass%) to 0.71 g/g (71 mass%) when the F‐T wax/HVGO blending ratio increased from 0/100 to 25/75 (g/g), then increased dramatically from 0.71 g/g (71 mass%) to almost 1 g/g (100 mass%) when the F‐T wax/HVGO blending ratio continued to increase to 100/0 (g/g). As the F‐T wax/HVGO blending ratio in the feed increased, the contents of cycloparaffins and aromatics decreased, whereas those of iso ‐paraffins and n ‐paraffins in the products increased. The research octane number and the motor octane number of the naphtha fraction also increased from 76 to 95 and from 76 to 82 when the F‐T wax/HVGO blending ratio increased from 0/100 to 100/0 (g/g), respectively. The product obtained from pure F‐T wax, which contained 0.8 g/g (80 mass%) of C 5 –C 11 iso ‐paraffins, was tested for diluent compatibility with Athabasca bitumen. The P‐value at 0.3 L/L (30 vol%) dilution was 2.11, close to that of 2.17 for natural gas condensate. Meanwhile, both the API gravity and viscosity met pipeline specifications, which indicates that the product hydrocracked from F‐T wax is a suitable diluent for bitumen.
9,10-Dihydroplatinaanthracenes with aromatic nitrogen ligands were synthesized, derived from 2,2′-bipyridine, 4,4′-dichloro-2,2′-bipyridine, 4,4′-dimethoxy-2,2′-bipyridine, 4,4′-bis(dimethylamino)-2,2′-bipyridine, 4,4′-di-tert-butyl-2,2′-bipyridine, 1,10-phenanthroline, 2,9-dimethyl-1,10-phenanthroline, 3,4,7,8-tetramethyl-1,10-phenanthroline, and 2,2′-biquinoline. For comparison purposes, the N,N,N′,N′-tetramethylethylenediamine-derived compound was also obtained. A single-crystal X-ray structure determination was carried out on [H2C(C6H4)2]Pt(2,9-dimethyl-1,10-phenanthroline), revealing a pronounced boat conformation of the metallacyclic ring. The diimine-derived compounds are highly luminescent in the solid state at room temperature, as well as in frozen solution. The luminescent complexes are easily prepared by ligand substitution from the new organometallic platinum precursor {[H2C(C6H4)2]Pt(SEt2)}n (n = 2, 3). Spectroscopic data are provided on absorbance and emission in the UV–visible range. In order to obtain insight into orbital energies and the tunability of the optical properties, electrochemical data, as well as DFT and TD-DFT data, were obtained. The lowest-energy absorbances are due to charge transfer from orbitals located largely on the electron-rich metallacyclic ligand with some coefficient on Pt into π* orbitals of the diimine. Computations suggest that the low-energy bands mostly originate from charge transfer from the HOMO−2, HOMO−1, and HOMO to the LUMO (rarely LUMO+1 and LUMO+2) molecular orbitals. Emission maxima range from 536 to 690 nm.
A cationic rhodium-sparteine complex, [((−)-sparteine)Rh(η4-COD)]+ (1+; COD = 1,5-cyclooctadiene) was obtained, isolated as its tetrafluoroborate salt (1BF4), and characterized using X-ray crystallography and multinuclear (1H, 13C) NMR spectroscopy. This is the first structurally characterized sparteine complex of rhodium. The Rh–N bonds are unusually long (2.214(3) and 2.242(3) Å), apparently due to steric repulsion between COD and sparteine. 1H NMR exchange experiments (EXSY) demonstrate a dynamic process that results in an overall 180° rotation of the COD methine protons in solution (CD2Cl2) with a first-order rate constant of 460 s−1 at the coalescence temperature (314 K) and interpolated rate constant of 150 s−1 at 298 K. Temperature-dependent NMR studies yield ΔH‡ = 13.0 ± 0.3 kcal mol−1, ΔS‡ = −5 ± 1 cal mol−1 K−1, such that ΔG‡298 = 14.3 ± 0.3 kcal mol−1. DFT studies (B3LYP) indicate that the loosely bound (−)-sparteine ligand rotates through a pseudo-tetrahedral transition state where both ligands are rotated approximately 90° relative to each other. While both ligands remain bound (η4-COD, κ2-sparteine), bonding to sparteine is weakened much more than bonding to COD in the transition state. DFT computed ΔG‡298 and ΔS‡ values (15.55 kcal mol−1 and −2.67 cal mol−1 K−1, respectively) agree very well with the experimental values. Attempts to find alternative mechanisms involving partial dechelation of COD and (−)-sparteine yielded slightly higher barriers along with positive ΔS values for intermediate formation.
The ring-opening polymerization (ROP) of lactide with DBU (1,8-diazabicyclo[5.4.0] undec-7-ene) is described. Room temperature polymerization using the neutral amine catalyst DBU in the absence of any other initiator produces polymers with narrow polydispersities and shows a linear relationship between molecular weight and conversion. The resulting polymers were characterized and determined to be cyclic. DFT calculations support a mechanistic hypothesis involving a zwitterionic acyl amidinium intermediate.
The ruthenium hydride [RuH(CNN)(dppb)] (1; CNN = 2-aminomethyl-6-tolylpyridine, dppb = 1,4-bis(diphenylphosphino)butane) reacts rapidly and irreversibly with CO2 under ambient conditions to yield the corresponding Ru formate complex 2. In contrast, the Ru hydride 1 reacts with acetone reversibly to generate the Ru isopropoxide, with the reaction free energy ΔG°(298 K) = -3.1 kcal/mol measured by (1)H NMR in tetrahydrofuran-d8. Density functional theory (DFT), calibrated to the experimentally measured free energies of ketone insertion, was used to evaluate and compare the mechanism and energetics of insertion of acetone and CO2 into the Ru-hydride bond of 1. The calculated reaction coordinate for acetone insertion involves a stepwise outer-sphere dihydrogen transfer to acetone via hydride transfer from the metal and proton transfer from the N-H group on the CNN ligand. In contrast, the lowest energy pathway calculated for CO2 insertion proceeds by an initial Ru-H hydride transfer to CO2 followed by rotation of the resulting N-H-stabilized formate to a Ru-O-bound formate. DFT calculations were used to evaluate the influence of the ancillary ligands on the thermodynamics of CO2 insertion, revealing that increasing the π acidity of the ligand cis to the hydride ligand and increasing the σ basicity of the ligand trans to it decreases the free energy of CO2 insertion, providing a strategy for the design of metal hydride systems capable of reversible, ergoneutral interconversion of CO2 and formate.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
A titanium electrode, modified with Ru(OH)x/TiO2, was prepared and observed to mediate both chemical transfer hydrogenation and electrochemical alcohol oxidation. Electro-oxidation of 2-propanol (1.3 M) at room temperature and pH 7.2 exhibits an onset of electrocatalytic current at 1000 mV vs RHE for the two-electron oxidation of 2-propanol to acetone. XPS characterization, cyclic voltammetry, and electrolysis experiments confirm that electrochemically active ruthenium species catalyzed the electro-oxidation of 2-propanol to acetone. These modified electrode surfaces maintain >60% original activity upon reuse, despite low loadings of ruthenium. The applied potentials are consistent with an electrocatalytic mechanism mediated by surface-immobilized Ru–oxo species (1380 mV vs RHE). These results indicate that heterogeneous transfer hydrogenation catalysts can function as alcohol electro-oxidation catalysts.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
