Showing papers on "Hydrocarbon published in 2017"

CO2 Reduction Selective for C≥2 Products on Polycrystalline Copper with N-Substituted Pyridinium Additives

Abstract: Electrocatalytic CO2 reduction to generate multicarbon products is of interest for applications in artificial photosynthetic schemes. This is a particularly attractive goal for CO2 reduction by copper electrodes, where a broad range of hydrocarbon products can be generated but where selectivity for C–C coupled products relative to CH4 and H2 remains an impediment. Herein we report a simple yet highly selective catalytic system for CO2 reduction to C≥2 hydrocarbons on a polycrystalline Cu electrode in bicarbonate aqueous solution that uses N-substituted pyridinium additives. Selectivities of 70–80% for C2 and C3 products with a hydrocarbon ratio of C≥2/CH4 significantly greater than 100 have been observed with several additives. 13C-labeling studies verify CO2 to be the sole carbon source in the C≥2 hydrocarbons produced. Upon electroreduction, the N-substituted pyridinium additives lead to film deposition on the Cu electrode, identified in one case as the reductive coupling product of N-arylpyridinium. Pr...

Characterization of Biosurfactant Produced during Degradation of Hydrocarbons Using Crude Oil As Sole Source of Carbon.

Abstract: Production and spillage of petroleum hydrocarbons which is the most versatile energy resource causes disastrous environmental pollution. Elevated oil degrading performance from microorganisms is demanded for successful microbial remediation of those toxic pollutants. The employment of biosurfactant-producing and hydrocarbon-utilizing microbes enhances the effectiveness of bioremediation as biosurfactant plays a key role by making hydrocarbons bio-available for degradation. The present study aimed the isolation of a potent biosurfactant producing indigenous bacteria which can be employed for crude oil remediation, along with the characterization of the biosurfactant produced during crude oil biodegradation. A potent bacterial strain Pseudomonas aeruginosa PG1 (identified by 16s rDNA sequencing) was isolated from hydrocarbon contaminated soil that could efficiently produce biosurfactant by utilizing crude oil components as the carbon source, thereby leading to the enhanced degradation of the petroleum hydrocarbons. Strain PG1 could degrade 81.8% of total petroleum hydrocarbons (TPH) after 5 weeks of culture when grown in mineral salt media (MSM) supplemented with 2% (v/v) crude oil as the sole carbon source. GCMS analysis of the treated crude oil samples revealed that P. aeruginosa PG1 could potentially degrade various hydrocarbon contents including various PAHs present in the crude oil. Biosurfactant produced by strain PG1 in the course of crude oil degradation, promotes the reduction of surface tension (ST) of the culture medium from 51.8 to 29.6 mN m-1, with the critical micelle concentration (CMC) of 56 mg L-1. FTIR, LC-MS, and SEM-EDS studies revealed that the biosurfactant is a rhamnolipid comprising of both mono and di rhamnolipid congeners. The biosurfactant did not exhibit any cytotoxic effect to mouse L292 fibroblastic cell line, however, strong antibiotic activity against some pathogenic bacteria and fungus was observed.

Insights into the Activity and Deactivation of the Methanol-to-Olefins Process over Different Small-Pore Zeolites As Studied with Operando UV–vis Spectroscopy

Abstract: The nature and evolution of the hydrocarbon pool (HP) species during the Methanol-to-Olefins (MTO) process for three small-pore zeolite catalysts, with a different framework consisting of large cages interconnected by small eight-ring windows (CHA, DDR, and LEV) was studied at reaction temperatures between 350 and 450 °C using a combination of operando UV–vis spectroscopy and online gas chromatography It was found that small differences in cage size, shape, and pore structure of the zeolite frameworks result in the generation of different hydrocarbon pool species More specifically, it was found that the large cage of CHA results in the formation of a wide variety of hydrocarbon pool species, mostly alkylated benzenes and naphthalenes In the DDR cage, 1-methylnaphthalene is preferentially formed, while the small LEV cage generally contains fewer hydrocarbon pool species The nature and evolution of these hydrocarbon pool species was linked with the stage of the reaction using a multivariate analysis of

A multi-aromatic hydrocarbon unit induced hydrophobic metal–organic framework for efficient C2/C1 hydrocarbon and oil/water separation

Abstract: Oil spills have led to more and more energy waste and economic losses all over the world. Developing highly hydrophobic materials for efficient oil/water separation has become key in solving this global issue. Here we report a highly hydrophobic porous metal–organic framework, named UPC-21, constructed from a pentiptycene-based organic ligand, for efficient oil/water separation. Large and pure crystals of UPC-21 could be obtained with high yield through a developed “diauxic growth” strategy. Due to the existence of multi-aromatic hydrocarbon units in the central pentiptycene core of the ligand, UPC-21 exhibits high hydrophobicity with a water contact angle of 145 ± 1° and superoleophilicity with an oil contact angle of 0°. Strikingly, oil/water separation measurements reveal that UPC-21 can efficiently separate toluene/water, hexane/water, gasoline/water, naphtha/water, and crude oil/water with a separation efficiency being above 99.0% except for crude oil/water due to its high viscosity and complex composition. Our work presented here may open a new avenue for the application of porous MOF materials.

Characterizing aliphatic moieties in hydrocarbons with atomic force microscopy

Abstract: We designed and studied hydrocarbon model compounds by high-resolution noncontact atomic force microscopy. In addition to planar polycyclic aromatic moieties, these novel model compounds feature linear alkyl and cycloaliphatic motifs that exist in most hydrocarbon resources - particularly in petroleum asphaltenes and other petroleum fractions - or in lipids in biological samples. We demonstrate successful intact deposition by sublimation of the alkyl-aromatics, and differentiate aliphatic moieties from their aromatic counterparts which were generated from the former by atomic manipulation. The characterization by AFM in combination with atomic manipulation provides clear fingerprints of the aromatic and aliphatic moieties that will facilitate their assignment in a priori unknown samples.

Role of the adsorbed oxygen species in the selective electrochemical reduction of CO2 to alcohols and carbonyls on copper electrodes

Abstract: The electrochemical reduction of CO2 into fuels has gained significant attention recently as source of renewable carbon-based fuels. The unique high selectivity of copper in the electrochemical reduction of CO2 to hydrocarbons has called much interest in discovering its mechanism. In order to provide significant information about the role of oxygen in the electrochemical reduction of CO2 on Cu electrodes, the conditions of the surface structure and the composition of the Cu single crystal electrodes were controlled over time. This was achieved using pulsed voltammetry, since the pulse sequence can be programmed to guarantee reproducible initial conditions for the reaction at every fraction of time and at a given frequency. In contrast to the selectivity of CO2 reduction using cyclic voltammetry and chronoamperometric methods, a large selection of oxygenated hydrocarbons was found under alternating voltage conditions. Product selectivity towards the formation of oxygenated hydrocarbon was associated to the coverage of oxygen species, which is surface-structure- and potential-dependent.

Efficient Mechanochemical Synthesis of MOF-5 for Linear Alkanes Adsorption

Abstract: An efficient mechanochemical method was proposed to synthesize MOF-5 with high BET area within minutes. The effects of parameters such as solvents activation, the metal/ligand ratio, grinding speed and time were carefully studied and the optimized MOF-5-B was used to investigate its adsorption properties of linear alkanes (C1–nC7). The results showed that solvents activation played an important role in the formation of MOF-5. Besides, the Zn2+/BDC ratio had a great impact on the formation of crystalline MOF-5, and the appropriate Zn2+/BDC ratio was 3:1 for mechanochemical synthesis of MOF-5. Grinding for 60 min could lead to a better crystallinity and the highest surface area of MOF-5-B. The resulting MOF-5-B possessed BET area of 3465.9 m2·g–1. More importantly, MOF-5-B showed a preferential adsorption for long alkanes over short alkanes at low pressures. The saturated adsorption capacities of nC4–nC7 decreased with the increase of hydrocarbon chain length. The isosteric heats of C1–nC7 increased with th...

Sodium-Containing Spinel Zinc Ferrite as a Catalyst Precursor for the Selective Synthesis of Liquid Hydrocarbon Fuels

Abstract: A microwave-assisted hydrothermal synthesis produces ZnFe2 O4 containing Na residue as a precursor to a CO2 hydrogenation catalyst that displays high CO2 conversion and high selectivity to liquid hydrocarbon products in the gasoline and diesel range with high olefin-to-paraffin ratios. Compared to reference catalysts derived from Fe2 O3 and a ZnO-Fe2 O3 physical mixture, the ZnFe2 O4 -derived catalyst contains well-dispersed iron particles with Zn serving as a structural promoter. A profound effect of the residual Na as an electronic promoter is also observed, which improves the selectivity for C5+ hydrocarbons and olefins. The ZnFe2 O4 -derived catalyst exhibits excellent performance in the CO2 Fischer-Tropsch reaction as it forms the active Hagg iron carbide (χ-Fe5 C2 ) phase readily through the in situ carburization of iron.

Biodegradation of aliphatic and aromatic hydrocarbons using the filamentous fungus Penicillium sp. CHY-2 and characterization of its manganese peroxidase activity

Abstract: The aim of this work was to study the potential of the non-lignolytic filamentous fungus Penicillium sp. CHY-2, isolated from Antarctic soil, for the biodegradation of eight different aliphatic and aromatic hydrocarbons such as octane, decane, dodecane, ethylbenzene, butylbenzene, naphthalene, acenaphthene, and benzo[a]pyrene. Among all the compounds, CHY-2 showed the highest level of degradation for decane (49.0%), followed by butylbenzene (42.0%) and dodecane (33.0%), and lower levels of degradation for naphthalene (15.0%), acenaphthene (10.0%), octane (8.0%), ethylbenzene (4.0%), and benzo[a]pyrene (2.0%) at 20 °C. The addition of carbon sources such as glucose (5 g L−1) and Tween-80 (5 g L−1) enhanced decane degradation by about 1.8-fold and 1.61-fold respectively at 20 °C. The metabolites produced during the degradation of decane were identified by gas chromatography-mass spectrometry (GC-MS). Furthermore, the enzyme manganese peroxidase (MnP) from CHY-2 was purified. MnP was found to consist of monomers with a molecular mass of 36 kDa. The purified MnP had an optimum pH of 5.0 and temperature of 30 °C. The Km and Vmax values of MnP towards Mn2+ were 1.31 μM and 185.19 μM min−1 respectively. These results indicated that the strain CHY-2 can be used for the degradation of hydrocarbons and could have promising applications in treatment of hydrocarbon contaminated sites.

Hydrodeoxygenation of Pyrolysis Oils

Abstract: The hydrodeoxygenation (HDO) of bio-oil derived from white oak wood using non-sulfided catalysts was studied in a two zone continuous flow trickle bed reactor system. The major organic components of the pyrolysis oil were pyrolytic lignin (large phenolic polymers), xylose, levoglucosan, organic acids (primarily acetic acid), and hydroxyacetaldehyde. The first zone was a low temperature zone (130 °C) that contained a Ru/C catalyst. In this zone, carbonyl groups were hydrogenated, producing propylene glycol (from hydroxyacetone), ethylene glycol (from hydroxyacetaldehyde), and sorbitol (from levoglucosan). A more severe hydrotreatment was performed in a second zone containing a bifunctional Pt/ZrP catalyst at a temperature between 300 and 400 °C. In the two-stage HDO, an organic phase was produced that consisted of a distribution of hydrocarbons that were primarily cyclic alkanes (naphthenes) ranging from C7 to C24. The organic phase carbon yield decreased with increasing reaction temperature in the second zone. Catalyst deactivation and reactor plugging by coking occurred under all reaction conditions after 55–72 h time on stream (TOS). After ≈55 h TOS, more than 25 % of the carbon in the original bio-oil was accumulated as coke, with increasing amounts for higher temperatures in the second zone. Hydrotreatment gave rise to >C5 hydrocarbon (gasoline and distillate-range fuel) overall yields between ≈30 and 47 carbon % for all experiments compared to the 79.5 % theoretical yield calculated for the bio-oil feedstock. Coke formation and undesired cracking to C1–C4 hydrocarbon gases were the main causes of lower fuel carbon yields.

On the role of resonantly stabilized radicals in polycyclic aromatic hydrocarbon (PAH) formation: pyrene and fluoranthene formation from benzyl–indenyl addition

Abstract: Resonantly stabilized radicals, such as propargyl, cyclopentadienyl, benzyl, and indenyl, play a vital role in the formation and growth of polycyclic aromatic hydrocarbons (PAHs) that are soot precursors in engines and flames. Pyrene is considered to be an important PAH, as it is thought to nucleate soot particles, but its formation pathways are not well known. This paper presents a reaction mechanism for the formation of four-ring aromatics, pyrene and fluoranthene, through the combination of benzyl and indenyl radicals. The intermediate species and transition structures involved in the elementary reactions of the mechanism were studied using density functional theory, and the reaction kinetics were evaluated using transition state theory. The barrierless addition of benzyl and indenyl to form the adduct, 1-benzyl-1H-indene, was found to be exothermic with a reaction energy of 204.2 kJ mol−1. The decomposition of this adduct through H-abstraction and H2-loss was studied to determine the possible products. The rate-of-production analysis was conducted to determine the most favourable reactions for pyrene and fluoranthene formation. The premixed laminar flames of toluene, ethylbenzene, and benzene were simulated using a well-validated hydrocarbon fuel mechanism with detailed PAH chemistry after adding the proposed reactions to it. The computed and experimentally observed species profiles were compared to determine the effect of the new reactions for pyrene and fluoranthene formation on their concentration profiles. The role of benzyl and indenyl combination in PAH formation and growth is highlighted.