Oxygenation Of Hydrocarbons Research Articles

A Method for Determination of Hydrocarbon and Nitrogenous Biochemical Oxygen Demands in Natural Waters by Manometric Method

The aim of the work was the simultaneous determination of hydrocarbon biochemical oxygen demand - cBOD and nBOD (nitrogen) in the same water sample without using a nitrification inhibitor by the manometric method. Daily measurements of cBOD are determined by recording the pressure drop resulting from the absorption of carbon dioxide released by the oxidation of hydrocarbon organic matter by microorganisms with KOH (potassium hydroxide). Here, the processes of oxidation of mineral substances in water and especially the developing nitrification processes, which absorb oxygen dissolved in water and cause an additional pressure drop in the vessel, are a disturbing factor, for the measurement of which, in the daily 24-hour cycle of registrations, it is recommended to close the absorption hole of the vial with KOH for 8 hours. The 24-hour nBOD and cBOD results are calculated from the result of the pressure drop in these 8 hours. In the paper, in the form of a table, the detailed form of calculation of the recorded results of BODs at two pH-s of a natural water sample within 1-20 days is given. The possibility of anthropogenic impact assessment using this method is shown on the example of natural water. It is concluded that with the proposed method of measuring BODs records the complete and separate results of cBOD are recorded under conditions of developing nitrification in water. All information from both nitrification and BOD-full is recorded simultaneously, which gives a complete picture of the overall oxygen balance in the water. The proposed method is practically applicable and fully comparable with the results obtained by the standard manometric method.

Visible-Light Induced C-H Oxygenation of Hydrocarbons Using Chlorine Dioxide as a Photoredox Catalyst

Photocatalytic oxygenation of benzene occurs in an oxygen-saturated acetonitrile solution containing acridnium ion or quinolinium ion derivatives as a photoredox catalyst, benzene and water under light irradiation to yield phenol and hydrogen peroxide selectively. The benzene radical cation, which is formed by photoinduced one-electron oxidation of benzene with the excited state of catalyst, reacts with H2O to yield phenol.Photocatalytic oxygenation of benzene with oxygen occurs under photoirradiation of an acetonitrile solution of 3-cyano-1-methylquinolinium perchlorate (QuCN+ClO4 –) in an oxygen-saturated acetonitrile (MeCN) containing benzene and H2O with a xenon lamp (500 W) attached with a color-cut glass filter. The selectivity of formation of phenol was 98% with 16% quantum yield after 1 h irradiation, and then 51% of phenol yield after 5 h irradiation. The photocatalytic turnover number (TON) was 7.5. This is the first example of photocatalytic oxygenation of benzene to phenol in a homogeneous system. A preparative gram-scale photocatalytic reaction with benzene (2.3 g, 29 mmol) and QuCN+ (210 mg, 0.8 mmol) in MeCN (200 mL) for 48 h was also examined to afford phenol (1.1 g, 12 mmol) as 41% yield.

Photoredox Oxidation of Alkanes by Monometallic Copper-Oxygen Complexes Using Visible Light Including One Sun Illumination.

Oxygenation of hydrocarbons offers versatile catalytic routes to more valuable compounds, such as alcohols, aldehydes, and ketones. Despite the importance of monometallic copper-oxygen species as hydroxylating agents in biology, few synthetic model compounds are known to react with hydrocarbons, owing to high C-H bond dissociation energies. To overcome this challenge, the photoredox chemistry of monometallic copper (pyrazolyl)borate complexes coordinated by chlorate has been explored in the presence of C1-C6 alkanes with BDEs ≥ 93 kcal/mol. Ethane is photooxidized at room temperature under N2 with yields of 15-30%, which increases to 77% for the most oxidizing tris(3,5-trifluoromethyl-pyrazolyl)borate complex (Cu-3). This complex also promotes the photooxidation of methane to methanol in significant yield (38%) when the photoredox reaction is run under aerobic conditions. Ligand modification alters the reaction selectivity by tuning the redox potential. The ability to activate 1° C-H bonds of C1-C6 alkanes using visible light is consistent with the photogeneration of a powerfully oxidizing copper-oxyl, which is supported by photocrystallographic studies of the tris(3,4,5-tribromopyrazolyl)borate chlorate complex. Mechanistic studies are consistent with the hydrogen atom abstraction of the C-H bond by the copper-oxyl intermediate. We demonstrate for Cu-3 with hexane as an exemplar, that the photoredox chemistry may be achieved under solar conditions of one-sun illumination.

Biosolar Oxygenation of Hydrocarbons by Photocatalytic Artificial Wood

Biosolar Oxygenation of Hydrocarbons by Photocatalytic Artificial Wood

Elucidating the Role of O2 Uncoupling for the Adaptation of Bacterial Biodegradation Reactions Catalyzed by Rieske Oxygenases.

Oxygenation of aromatic and aliphatic hydrocarbons by Rieske oxygenases is the initial step of various biodegradation pathways for environmental organic contaminants. Microorganisms carrying Rieske oxygenases are able to quickly adapt their substrate spectra to alternative carbon and energy sources that are structurally related to the original target substrate, yet the molecular events responsible for this rapid adaptation are not well understood. Here, we evaluated the hypothesis that reactive oxygen species (ROS) generated by unproductive activation of O2, the so-called O2 uncoupling, in the presence of the alternative substrate exert a selective pressure on the bacterium for increasing the oxygenation efficiency of Rieske oxygenases. To that end, we studied wild-type 2-nitrotoluene dioxygenase from Acidovorax sp. strain JS42 and five enzyme variants that have evolved from adaptive laboratory evolution experiments with 3- and 4-nitrotoluene as alternative growth substrates. The enzyme variants showed a substantially increased oxygenation efficiency toward the new target substrates concomitant with a reduction of ROS production, while mechanisms and kinetics of enzymatic O2 activation remained unchanged. Structural analyses and docking studies suggest that amino acid substitutions in enzyme variants occurred at residues lining both substrate and O2 transport tunnels, enabling tighter binding of the target substrates in the active site. Increased oxygenation efficiencies measured in vitro for the various enzyme (variant)-substrate combinations correlated linearly with in vivo changes in growth rates for evolved Acidovorax strains expressing the variants. Our data suggest that the selective pressure from oxidative stress toward more efficient oxygenation by Rieske oxygenases was most notable when O2 uncoupling exceeded 60%.

Simulation of DME-O2 Combustion in a Hollow Cone Impinging Jet Combustor for Direct-Fired Supercritical CO2 Power Cycle

ABSTRACT Combustion is critical in the direct-fired supercritical CO2 power cycle. A hollow cone impinging jet combustor is designed. Instead of methane, dimethyl ether is used as the fuel for the direct-fired supercritical CO2 cycle, with a higher hydrocarbon ratio and oxygen. The dimethyl ether combustion process is simulated by Fluent, based on the k-ε turbulence model and Eddy-Dissipation Concept combustion model, combined with the dimethyl ether combustion mechanism. The effects of the CO2 recycling ratio, the excess oxygen coefficient, and in-combustor pressure are investigated to support improving combustion performance. The results indicate that the recycled CO2 intensifies the movement of the mixture in the combustor, reduces the peak temperature, and makes temperature distribution more uniform. As the excess oxygen coefficient increases, the peak temperature is enhanced, and the combustion is more sufficient. The effect of in-combustor pressure is complex. On the one hand, increasing in-combustor pressure reduces the jet penetration and inhibits the contact between dimethyl ether and O2, leading to a lower peak temperature. On the other hand, it prolongs the residence time of the high-temperature exhaust, making the reaction between dimethyl ether and O2 more sufficient. The optimal operating condition of the combustor is a CO2 recycling ratio of 0.95, an excess oxygen coefficient of 1.20, and an in-combustor pressure of 30 MPa. Moreover, the obtained combustion products parameters, such as temperature, component concentration, and mass flow rate, can guide the performance analysis for the direct-fired supercritical CO2 power cycle.

Electrocatalytic water-to-oxygenates conversion: redox-mediated versus direct oxygen transfer.

Electrocatalytic oxygenation of hydrocarbons with high selectivity has attracted much attention for its advantages in the sustainable and controllable production of oxygenated compounds with reduced greenhouse gas emissions. Especially when utilizing water as an oxygen source, by constructing a water-to-oxygenates conversion system at the anode, the environment and/or energy costs of producing oxygenated compounds and hydrogen energy can be significantly reduced. There is a broad consensus that the generation and transformation of oxygen species are among the decisive factors determining the overall efficiency of oxygenation reactions. Thus, it is necessary to elucidate the oxygen transfer process to suggest more efficient strategies for electrocatalytic oxygenation. Herein, we introduce oxygen transfer routes through redox-mediated pathways or direct oxygen transfer methods. Especially for the scarcely investigated direct oxygen transfer at the anode, we aim to detail the strategies of catalyst design targeting the efficient oxygen transfer process including activation of organic substrate, generation/adsorption of oxygen species, and transformation of oxygen species for oxygenated compounds. Based on these examples, the significance of balancing the generation and transformation of oxygen species, tuning the states of organic substrates and intermediates, and accelerating electron transfer for organic activation for direct oxygen transfer has been elucidated. Moreover, greener organic synthesis routes through heteroatom transfer and molecular fragment transfer are anticipated beyond oxygen transfer.

Assessing the reliability of the forensic technique for the identification study of motor gasoline using gas-liquid chromatography

A new approach to solving the problems of forensic examination of petroleum products, fuels and lubricants associated with establishing whether motor gasoline belongs to a common/different identification set is proposed. A methodology for the identification of gasoline using quantitative results of chromatographic determination of controlled parameters and subsequent evaluation of the results in pairwise compared samples according to the established criteria. The following parameters were selected as controlled indicators: values of research octane number (RON), concentrations of hydrocarbon groups (paraffins, isoparaffins, arenes, naphthenes, olefins) and oxygenates. Their determination was carried out using standardized methods. We used the hardware and software complex of a Chromatek-Crystal 5000 series, including the Chromatek-DHA data processing program. Estimated criteria or decision- making rules regarding the issues posed to an expert were determined to classify gasoline under one product name (generic set), one production technology (group set) or a common source of origin (one production batch, storage tank, etc.). The reliability of the method was assessed using a validation procedure consisted of three stages. We used a collection of AI-92 motor gasoline, selected at gas stations of four oil companies during six months of 2022 in various districts of Moscow. At the first stage, the performer analyzed 12 aliquots of each of four gasoline samples (samples that previously belonged to the common volume) at different times. It was established that the quality indicators of the proposed methodology (standard deviation of the repeatability and reproducibility, expanded uncertainty, limits of the repeatability and reproducibility) for each of the determined controlled indicators did not exceed the permissible errors established by standardized methods. At the second stage of the experiment, the performer combined 12 test samples into four groups from each manufacturer (one production technology) with three samples of different production times (different batches). By comparing the discrepancies in the measured values of the same controlled indicators between pairs of samples within groups and the discrepancy in average indicators between pairs of groups, the contractor identified gasolines manufactured using the same technology; gasolines produced by the same technology, but at different times (different batches) and, with a probability of 95%, gasolines having a common source of origin (previously belonging to a common volume). The conclusions of the validation study matched the original data on the samples, which confirmed the correctness of the developed comparison criteria. At the third stage (blind test), the performer examined seven gasoline samples of, information about the composition and properties of which was not provided to him. The results of the blind test were considered satisfactory. Thus, the validation results indicate the suitability of the methodology for solving forensic identification problems in relation to motor gasoline and the competence of the performer sufficient for implementation of the methodology.

Analysis of Exhaust Gas Emission of Motor Vehicles with Variations of Fuel Types

The discrepancy between the use of vehicle fuel types and the vehicle's technical specifications is expected to affect exhaust emissions. This study aims to examine the effect of using four types of fuel with different octane number specifications on two four-wheeled motor vehicles with an EFI fuel delivery system on exhaust gas emission parameters of carbon monoxide (CO), hydrocarbon (HC), carbon dioxide (CO2) and non-emitting gases Oxygen (O2). With a quantitative experimental approach method using the Automotive Emission Analyzer and simple linear regression analysis, the results showed that the use of variations with octane numbers RON 98, RON 92, RON 90, and RON 88 fuels at the same time as variations in engine speed (1000 – 3000) RPM showed an effect on concentration. HC and CO emissions decreased with each increase in the octane number of fuel, RON 92 fuel with the lowest average CO / HC (0.0013% / 0.46 ppm) and RON 98 with the lowest average CO / HC (0.0026% / 0 ppm). The use of RON 92 fuel is more effective and inexpensive to apply to vehicles with an EFI fuel delivery system (with compression of 1:10/10.2) compared to RON 98 fuel which emits higher CO and HC emissions at low engine speed (1000 -1500) RPM.

Micro-kinetics of ethylene and methane oxidation on platinum

The kinetics of ethylene (C2H4) and methane (CH4) on platinum (Pt) is investigated in an isothermal Pt microtube. A micro-kinetic model of C1 and C2 hydrocarbon oxidation on the Pt(111) surface established using density functional theory is tuned and validated based on experimental results obtained from the Pt microtube. Density functional theory (DFT) modelling is carried out to evaluate the Pt(111) surface coverage of selected species on the thermochemistry and kinetics. The model reasonably predicts the conversion temperature and carbon selectivity of C2H4 and CH4 oxidation under various fuel-oxygen ratios. Micro-kinetic analysis based on this model illustrates that the formation of hydrocarbon oxygenates intermediates is essential, which makes the activity of surface oxygen species decisive in the catalytic activity.

Conceptual and Practical Aspects of Metal-Organic Frameworks for Solid-Gas Reactions.

The presence of site-isolated and well-defined metal sites has enabled the use of metal-organic frameworks (MOFs) as catalysts that can be rationally modulated. Because MOFs can be addressed and manipulated through molecular synthetic pathways, they are chemically similar to molecular catalysts. They are, nevertheless, solid-state materials and therefore can be thought of as privileged solid molecular catalysts that excel in applications involving gas-phase reactions. This contrasts with homogeneous catalysts, which are overwhelmingly used in the solution phase. Herein, we review theories dictating gas phase reactivity within porous solids and discuss key catalytic gas-solid reactions. We further treat theoretical aspects of diffusion within confined pores, the enrichment of adsorbates, the types of solvation spheres that a MOF might impart on adsorbates, definitions of acidity/basicity in the absence of solvent, the stabilization of reactive intermediates, and the generation and characterization of defect sites. The key catalytic reactions we discuss broadly include reductive reactions (olefin hydrogenation, semihydrogenation, and selective catalytic reduction), oxidative reactions (oxygenation of hydrocarbons, oxidative dehydrogenation, and carbon monoxide oxidation), and C-C bond forming reactions (olefin dimerization/polymerization, isomerization, and carbonylation reactions).

Scientific Analysis of Rose Essential Oils: Viewed from Various Perspectives

The use of essential oils in the world each year has increased with the increasing development of modern industries such as the perfume industry, cosmetics, food, aroma therapy and medicine. Essential oils or also known as etheric oils are a large group of vegetable oils in the form of viscous liquids at room temperature but volatile so that they give a distinctive aroma. Some components of essential oils are hydrocarbon compounds (hydrogen-carbon) and oxygen. One source of essential oils can be obtained from rose extract. This study aims to analyze the physical, chemical, and beneficial properties of several components of the rose essential oil. This research approach uses a qualitative approach with a literature study method, then the data were analyzed using descriptive analysis. The results obtained conclude that the essential oil content in roses with the highest percentage is n-nonadekane, -phenylethylacetate, phenylethylalcohol, and 2-Isopropyl-5-methyl-9-methylene-bicyclo-1-decene, -Fernesene, and -cadinene. From these structures there are 2 types of hybrid orbitals, namely sp3 and sp2, when viewed from the type of bond π and σ; whereas if viewed from the isomerism, these structures have skeletal, functional groups, and optical isomers. Some of the constituents in the volatile oil components can be reacted (nucleophilic addition with HCl and electrophilic with bromine). The existence of these differences causes the chemical and physical properties of the structure of the essential oil content to vary according to their usefulness.

Assessment of artificial neural network to identify compositional differences in ultrahigh-resolution mass spectra acquired from coal mine affected soils

This study assessed the applicability of artificial neural networks (ANNs) as a tool to identify compounds contributing to compositional differences in coal-contaminated soils. An artificial neural network model was constructed from laser desorption ionization ultrahigh-resolution mass spectra obtained from coal contaminated soils. A good correlation (R2 = 1.00 for model and R2 = 0.99 for test) was observed between the measured and predicted values, thus validating the constructed model. To identify chemicals contributing to the coal contents of the soils, the weight values of the constructed model were evaluated. Condensed hydrocarbon and low oxygen containing compounds were found to have larger weight values and hence they were the main contributors to the coal contents of soils. In contrast, compounds identified as lignin did not contribute to the coal contents of soils. These findings were consistent with the conventional knowledge on coal and results from the conventional partial least square method. Therefore, we concluded that the weight interpretation following ANN analysis presented herein can be used to identify compounds that contribute to the compositional differences of natural organic matter (NOM) samples.

The bromine mediated electrosynthesis of ethylene oxide from ethylene in continuous flow-through operation

In this work a reactor setup for the bromine mediated, electrochemical oxidation of ethylene oxide from ethylene was developed. This novel design featured a flow-through configuration for the ethylene feed to accommodate the in situ synthesis of the 2-bromoethanol intermediate, creating a low pH at the anolyte to selectively target the bromine evolution. The cell was characterized via chronopotentiometry in 0.5 M KBr electrolyte, using a (i) Pt or (ii) IrO2 coated gas diffusion anodes paired with a Ni foam cathode. Within a current density of 65 to 156 mA/cm2 for Pt and 65 to 133 mA/cm2 for IrO2, the productivity and selectivity of the reactor system was mapped. Throughout all conditions the reactor system retained a Faradaic efficiency of 80 to 90% towards ethylene oxide on both Pt and IrO2 coated gas diffusion anodes and exceeded an equivalent ethylene oxide production of 1 kg/hour/m2 at 156 mA/cm2. Furthermore, the reactor upheld identical selectivity and productivity for 4.5 h without any signs of fading performance. Analysis of the gaseous product phase at this highest current condition showed no CO2 or O2 side products, originating from hydrocarbon overoxidation or oxygen. Based on our findings, the bromine mediated pathway proves to be highly promising as the current best case of the chlorine mediated system achieves a 70% selectivity towards ethylene oxide. Additionally, the anodic catalyst stability was quantified by ICP-MS analysis and scanning electron microscopy coupled with energy dispersive X-ray analysis, which revealed IrO2 to be three orders of magnitude more dissolution resistant compared to Pt and confirm a homogeneous dispersion of the catalyst and binder material on the surface of the gas diffusion electrodes.

Catalytic Oxygenation of Hydrocarbons by Mono-μ-oxo Dicopper(II) Species Resulting from O-O Cleavage of Tetranuclear CuI /CuII Peroxo Complexes.

One of the challenges of catalysis is the transformation of inert C−H bonds to useful products. Copper‐containing monooxygenases play an important role in this regard. Here we show that low‐temperature oxygenation of dinuclear copper(I) complexes leads to unusual tetranuclear, mixed‐valent μ4‐peroxo [CuI/CuII]2 complexes. These Cu4O2 intermediates promote irreversible and thermally activated O−O bond homolysis, generating Cu2O complexes that catalyze strongly exergonic H‐atom abstraction from hydrocarbons, coupled to O‐transfer. The Cu2O species can also be produced with N2O, demonstrating their capability for small‐molecule activation. The binding and cleavage of O2 leading to the primary Cu4O2 intermediate and the Cu2O complexes, respectively, is elucidated with a range of solution spectroscopic methods and mass spectrometry. The unique reactivities of these species establish an unprecedented, 100 % atom‐economic scenario for the catalytic, copper‐mediated monooxygenation of organic substrates, employing both O‐atoms of O2.

Geochemistry of light petroleum from the North of Dongying Depression

With ever-increasing exploration for oils, exploration has inevitably extended into deep layers. Considerable quantity of light oil is discovered from deep Es4 lower layer in the northern steep slope zone of Dongying Depression, Bohai Bay Basin. The oils are characterized by high content of saturated hydrocarbon and low concentration of biomarker and sulphur content. Eleven oil samples and forty-five source rock samples are finely analysed. According to the results of monomer hydrocarbon isotope analysis, carbon and oxygen isotope composition analysis and light hydrocarbon analysis, it is confirmed that the oils in deep strata of northern steep slope zone reach high mature lever. The light oils in the northern steep slope zone have a relationship with deep Es4 lower hydrocarbon source rocks by the results of monomer hydrocarbon isotope and light hydrocarbon analysis. Thermal evolution studies show the top Es4 lower hydrocarbon source rocks have a high thermal evolution level. The top Es4 lower hydrocarbon source rocks have relatively high organic abundance and are dominated by types I-II1 kerogen. This research is helpful for unravelling deep petroleum resources evaluation in this area. The viewpoint will be of great significance in future exploration. Moreover, the views in this paper can also be applied to other basins to explore for deep oil reservoirs.

Self-similar solution of a supercritical two-phase laminar mixing layer

Previous works for a liquid suddenly contacting a gas at a supercritical pressure show the coexistence of both phases and the generation of diffusion layers on both sides of the liquid-gas interface due to local thermodynamic phase equilibrium. A related numerical study of a laminar mixing layer between the liquid and gas streams in the near field of the splitter plate suggests that mass, momentum and thermal diffusion layers evolve in a self-similar manner at very high pressures. In this paper, the high-pressure, two-phase, laminar mixing-layer equations are recast in terms of a similarity variable. A liquid hydrocarbon and gaseous oxygen are considered. Freestream conditions and proper matching conditions at the liquid-gas interface are applied. To solve the system of equations, a real-fluid thermodynamic model based on the Soave-Redlich-Kwong equation of state is selected. A comparison with results obtained by directly solving the laminar mixing-layer equations shows the validity of the similarity approach applied to non-ideal two-phase flows. Even when the gas is hotter than the liquid, net condensation can occur at high pressures while heat conducts into the liquid. Finally, a generalized correlation is proposed to represent the evolution of the mixing layer thickness for different problem configurations.

SYNTHESIS AND PROPERTIES OF METAL-COMPLEX CATALYSTS BASED ON OIL METALLOPORPHYRINS

The study of the properties and use of natural metalloporphyrins in the development of new highly selective methods for the oxygenation of hydrocarbons at moderate temperatures is an urgent problem. The present work is devoted to the extraction of metalloporphyrins from oil residues and the creation on their basis of effective catalytic systems for the oxidation of alkenes. The separation of metalloporphyrins from oil residues was carried out using new bifunctional organic extractants having the nature of keto-alcohols and providing a greater degree of extraction of porphyrins in comparison with the known traditionally used extractants. The results of a study of a number of new bifunctional organic reagents as extractants for the selective extraction of oil porphyrins from asphaltenes are presented, their spectral characteristics are studied, the dependence of the degree of extraction on the mass ratio of the extractant and the crude oil is revealed. The best results were obtained with a mass ratio of 1:30. The isolated mixture of metalloporphyrins is first subjected to demetallization with hydrochloric acid (pH=1–2), turning into a mixture of porphyrins, then, to obtain individual metal porphyrin complexes, the required transition metal ions are introduced into the porphyrin ring by treating the mixture with these metal salts. It was shown that the yield of synthesized oil porphyrins is 42–85 %, depending on the nature of the metal. The composition and structure of the synthesized oil metalloporphyrins containing iron, cobalt, nickel, manganese are established by modern methods of physico-chemical analysis. The catalytic properties of synthesized metalloporphyrins in the epoxidation of unsaturated alkenes have been investigated. Their dioxide adducts were obtained, and a mechanism was proposed for the oxidation of alkenes with the formation of oxinoid structures as a result of the decomposition of the oxygen complexes of metal porphyrins

Secondary reactions of volatiles upon the influences of particle temperature discrepancy and gas environment during the pyrolysis of scrap tyre chips

Pyrolysis process is one of the potential routes to convert waste scrap tyres into high-value resources such as liquid oil that is low in oxygen and high in valuable hydrocarbons. Although many studies have been conducted, the understanding of the fundamental science underpinning the pyrolysis of scrap tyre chip is still far from complete. This paper has examined the mild pyrolysis of scrap tyre chips at 600 °C, in an integrated manner by examining the co-effects of several key parameters including heating rate, volatile residence time, tyre chip size and non-inert gases (CO2 and/or H2O) on the quality of tars. In particular, we aimed to elucidate the influences of particle temperature discrepancy to the surrounding gas environment and reactive gas on the tar yield and properties, under the simulated fixed-bed/rotary kiln condition that is either heated directly by hot flue gas or indirectly by reactor wall. It has been confirmed that, in a simulated fixed-bed reactor with the absence of carrier gas, the particle temperature discrepancy can be correlated exponentially to the secondary cracking extent of volatiles in a temperature discrepancy range of 100 °C. Upon an increase on the temperature discrepancy by either increasing the heating rate or tyre chip size, the inherent long-chain aliphatics preferentially underwent scission, cyclisation and polymerisation, enhancing the yields for both heavy aromatics and methane – rich light gases. The use of carrier gas (i.e. hot flue gas) is beneficial in improving tar yield and aliphaticity. As a convective heating source, it heated particles slowly and also swept out volatile vapours immediately, thereby minimising the secondary reactions. For the two major components, CO2 and steam in hot flue gas, CO2 is rather inert at 600 °C, while steam is reactive enough to reduce the heavy hydrocarbons via steam reforming reaction, upon the catalytic effect of the nascent char derived from scrap tyre chips. The hydrogenation of unsaturated alkene and aromatics was also improved, and even the methanation reaction of CO on the nascent char surface, thus leading to the overwhelming dominance of CH4 in the pyrolysis gas.

Structural, optical and photoconductivity studies of ZnO bicones synthesized by seed-mediated method

ZnO bicones (BC) have been synthesized by a seed-mediated method using polyethylene glycol (PEG) and triethylamine (TEA). As-synthesized ZnO BC has been characterized by X-ray diffraction method (XRD), UV–visible absorption spectroscopy, Photoluminescence spectroscopy (PL), Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Time-dependent Photoconductivity study. XRD pattern of ZnO BC shows hexagonal wurtzite phase structure. The UV–visible absorption spectrum of ZnO BC shows two absorption band edges at 302 nm and 370 nm due to its diameter and length. The PL spectrum of ZnO BC shows rich zinc interstitial defects due to the presence of an intense peak at 423 nm. The FTIR spectrum of ZnO BC confirms the presence of TEA and PEG. SEM and TEM images of ZnO nanostructures confirm the bicones structure as well as the size of the ZnO BC. Photoconductivity study shows that the time-dependent rise and decay curves of ZnO BC has very high photosensitivity in vacuum medium compared to its air medium due to the presence of hydrocarbon functional groups and oxygen deficiency atmosphere.