Decomposition Of Hydrocarbons Research Articles

Microwave-catalyzed pyrolysis of waste engine oil using steel slag catalyst: Structure design and insights into the intrinsic mechanism of active catalytic sites and microwave absorption functions

As an industrial waste rich in metal elements, steel slag (SS) has the potential for application as a catalytic material. However, the presence of large amounts of silicates and ferrates is one of the main reasons for the low catalytic properties of SS. In this work, SS was converted into catalysts with multi-metal oxide fractions by regulating the pH of the pretreatment process and using microwave calcination technology. By targeted design of oxygen vacancy (OV) number, specific surface area, and grain size, the steel slag catalyst (SSC) showed catalytic and microwave absorption functions, which could quickly convert waste engine oil (WEO) into light fuel. When the pH of the pretreatment was 8, SSC contained an abundance of metal oxides (such as Fe2O3, Fe3O4, and MnFe2O4), and the specific surface area could reach 237.3 m2/g. The abundant OV defect structure also contributed to the enhanced catalytic properties of the SSC. The light hydrocarbon (C5-C20) composition of the WEO increased from 15.11% to 86.24% at 500℃ in the presence of the bifunctional catalyst. Density functional theory calculations showed that the OV was the key to enhancing the catalytic and microwave absorption functions of the SSC. OV could be used as the activity site to promote the decomposition of heavy hydrocarbons by breaking CH bonds. Meanwhile, defect-induced polarization caused by OV promoted the transfer of carriers in the microwave field, thus enhancing the microwave absorption properties of the catalyst. This work provided a new perspective on the design of bifunctional catalysts for the preparation of microwave pyrolysis.

Large improvement of the tensile strength of carbon nanotube films in harsh wet environments by carbon infiltration

Carbon nanotube (CNT) materials show large degradation in tensile strength when they are exposed in chemically active environments due to the loss of inter-tube bonding. Here, we report the suppression of such degradation by chemical vapor infiltration of amorphous carbon into CNT films. The amorphous carbon generated by the thermal decomposition of the gaseous hydrocarbon of acetylene is firmly bonded on the CNT sidewalls and intersections. Based on the improved inter-tube bonding and restriction of inter-tube sliding, the tensile strength of the film is improved to be 3 times of the original level. More importantly, the bonding is so strong and stable that the high tensile strength remains with little loss even in harsh wet environments such as boiling alcoholic, acidic, alkaline solutions and seawater. Such harsh environments-tolerant properties, which were rarely observed before, could open new windows for the CNT/C composite material to be applied from functional devices to structural components under extreme corrosive conditions.

Experimental characterization of TIAGO torch discharges: surface wave discharge behavior and (post-)discharge kinetics

The Torche à Injection Axial sur Guide d’Ondes source—better-known as the TIAGO torch—is a particular type of microwave-induced plasma that has become a focus of technological and scientific interest due to its outstanding features. Moreover, the TIAGO torch device arouses interest thanks to its remarkable performance in many challenging areas, such as green energy generation and graphene production by hydrocarbon decomposition. Although it has not been experimentally demonstrated to date, discharges generated by a TIAGO torch have been theoretically predicted to be surface wave discharges (SWDs), a kind of plasma leading the development of new materials. Therefore, deeper and fundamental research on this device is needed to optimize the implementation of plasma technology in these fields. In this study, the axial distribution of gas temperature, electron density and intensity of the main atomic and molecular emissions have been studied by optical emission spectroscopy when feeding the discharge with different input power values (200, 400 and 600 W). A complete axial characterization of both the dart and the plume regions is depicted and, according to the data obtained for the main plasma parameters, different regions can be identified, with the radiation zone being reported for the first time at atmospheric pressure. The kinetics of both the dart and the plume are discussed and an experimental verification of TIAGO torch behavior as a SWD is presented for the first time.

Clean treatment and resource utilization of oilfield wastewater using supercritical water gasification

Unconventional oil and gas resources are expected to be recovered efficiently by multi-component supercritical thermal fluid (MCSCTF) which is generated based on supercritical water gasification (SCWG) of oilfield wastewater and hydrogen oxidation technology. In this paper, SCWG experiments of oilfield wastewater were performed under 550–750 °C, 2–15 min, 21–29 MPa, and feedstock concentration of 2–10 wt%. High temperatures, extended residence times, and low concentrations encouraged the production of gases. There was no significant change in SCWG as the pressure changed. The highest H2 yields and carbon gasification efficiency (CE) were 52.31 mol/kg and 97.59%, respectively. The SCWG mechanism was summarized to describe the conversion details. The SCWG of oilfield wastewater has the fastest initial rate to present a trend of deceleration and the activation energy of CE was calculated as 135.7 kJ/mol. The reason for gasification deceleration was explained by the proposed gaseous product kinetics. Small molecules and saturated hydrocarbons etc. (Int 1) can be quickly decomposed while the decomposition of phenols and aromatic hydrocarbons etc. (Int 2) is slower. Inhibition of Int 2 generation and enhanced Int 2 decomposition is the key to total gasification. This work is useful for reactor design and process intensification.

Experimental and Modeling Investigation on the Pyrolysis of n-Decane Initiated by Nitropropane. Part I: 1-Nitropropane.

Initiators can accelerate the pyrolysis of hydrocarbon fuels, thereby reducing the required reaction temperature in the hypersonic vehicle heat exchanger/reactor. Nitro-alkanes are considered as efficient initiators due to their lower energy barrier of the C-N bond cleavage reaction. To research the mechanism of the initiation effect of nitro-alkanes on the decomposition of hydrocarbon fuel, synchrotron radiation vacuum ultraviolet photoionization-mass spectrometry (SVUV-PIMS) was employed to experimentally study the pyrolysis of n-C10H22, 1-C3H7NO2, and their binary mixtures in a flow tube under pressures of 30 and 760 Torr. The species identified and measured in the experiments included alkanes, alkenes, dialkenes, alkynes, nitrogen oxides, benzene, and free radicals, which revealed the mechanism of n-decane and 1-C3H7NO2 pyrolysis, as well as the interactions of the two fuels. Experiments show that the presence of 1-C3H7NO2 reduces the initial decomposition temperature of n-C10H22, and the increased pressures could achieve a stronger promoting effect on the conversion of n-C10H22. A detailed kinetic model containing 1769 reactions and 278 species was established and validated based on the mole fraction distributions of n-C10H22, major pyrolysis species, and important intermediates measured in pure fuel and initiated pyrolysis. The kinetic model can accurately predict the experimental data, and the mechanism of 1-C3H7NO2-initiated pyrolysis of n-C10H22 is analyzed with the model. The effect of 1-C3H7NO2 on the consumption of n-C10H22 and selectivity of cracked products is highlighted.

Thermal Decomposition of Synthetic Cage Hydrocarbons and Their Mixtures

The kinetics of thermal decomposition of cage hydrocarbons, specifically exo-tricyclo[5.2.1.02.6]decane (exo-TCD) and exo,endo-tetracyclo[5.3.1.02,6.08,10]undecane (TCU-1, a monocyclo­propanated analog of exo-TCD), as well as their mixture (1 : 3 w/w) has been investigated. These compounds were compared in terms of thermal stability. The molar concentrations of the resultant gaseous products were determined experimentally. The equilibrium composition of the decomposition products was quantified, and the thermal effects of the thermal decomposition under thermodynamic and kinetic reaction control were identified.

Degradation potential and pathways of methylcyclohexane by bacteria derived from Antarctic surface water

Cycloalkanes pose a tremendous environmental risk due to their high concentration in petroleum hydrocarbons and hazardous effects to organisms. Numerous studies have documented the biodegradation of acyclic alkanes and aromatic hydrocarbons. However, insufficient attention has been paid to studies on the microbial degradation of cycloalkanes, which might be closely linked to psychrophilic microbes derived from low-temperature habitats. Here we show that endemic methylcyclohexane (MCH, an abundant cycloalkane species in oil) consumers proliferated in seawater samples derived from the Antarctic surface water (AASW). The MCH-consuming bacterial communities derived from AASW exhibited a distinct species composition compared with their counterparts derived from other cold-water habitats. We also probed Colwellia and Roseovarius as the key active players in cycloalkane degradation by dilution-to-extinction-based incubation with MCH as sole source of carbon and energy. Furthermore, we propose two nearly complete MCH degradation pathways, lactone formation and aromatization, concurrently in the high-quality metagenome-assembled genomes of key MCH consumer Roseovarius. Overall, we revealed that these Antarctic microbes might have strong interactions that enhance the decomposition of more refractory hydrocarbons through complementary degradation pathways.

Thermal Decomposition of Synthetic Cage Hydrocarbons and Their Mixtures

Thermal Decomposition of Synthetic Cage Hydrocarbons and Their Mixtures

Study of Heptane and Toluene Decomposition during High-Energy Processing in a Planetary Mill Together with Titanium Powder

Molecular spectroscopy in the UV and IR ranges is used to perform a comparative study of the decomposition of toluene and heptane during mechanical activation with titanium. It is shown that high-energy mechanical processing is effective for obtaining low-molecular-weight alkanes, the amounts of which are largely determined by the nature of the hydrocarbons. The effect the mill carrier’s speed of rotation has on the depth of hydrocarbon decomposition and the composition of products of the mechanical processing of the liquid phase is considered. It is shown that at a speed of 600 rpm, heptane begins to decompose at short periods of mechanical activation (MA), while toluene is stable up to 30 h MA. Considerable structural and chemical transformations occur in toluene after only 20–30 h of mechanical treatment at a speed of 890 rpm.

The Influence of Remediation with Bacillus and Paenibacillus Strains and Biochar on the Biological Activity of Petroleum-Hydrocarbon-Contaminated Haplic Chernozem

The effect of bacterial strains on certain genera, both independently and in combination with biochar in various options, on petroleum hydrocarbon decomposition in chernozem and the restoration of the ecological state of the soil were studied. To simulate petroleum hydrocarbon contamination, petroleum hydrocarbons were introduced into soil in the amount of 5% of soil weight. Strains of Bacillus and Paenibacillus bacteria (in recommended and increased doses × 100) and biochar (1% of soil weight) were introduced into contaminated soil separately and together. It was found that after 30 days, the oil content decreased with the joint introduction of an increased dose of Bacillus, Panibacillus and biochar by 64%, as well as with the inoculation of biochar with Bacillus and Panibacillus bacteria at the recommended dose by 67%. The introduction of biochar, inoculated with BP and BP × 100, contributed to an increase in the intensity of CO2 emission compared to the background by 5–10%. With the joint introduction of BP + B, stimulation was 70%, with an increase in the concentration of BP × 100–115%. The preparation BP and BP × 100 introduced with biochar stimulated the activity of the enzyme by 49 and 61%; with the preinoculation of BP in biochar, stimulation was 27% relative to the background value. The most informative biological indicators when introducing ameliorants of biochar, Bacillus and Paenibacillus were the total number of bacteria, the length of the barley roots and the catalase activity, demonstrating the greatest sensitivity. The results of the study should be used for the remediation and biomonitoring of the state of oil-contaminated soils.

Thermo-mechanical analysis of hydrogen permeation in lubricated rubbing contacts

Exploring the fundamental mechanisms of hydrogen generation from a lubricated rubbing contact is a critical step to mitigate premature failure of mechanical elements. This work employs an in-situ hydrogen uptake technique and molecular dynamics simulations to study the thermo-mechanical effects on the hydrogen generation in lubricated contacts. The hydrogen uptake is measured on AISI 52100 bearing steel at temperature of 27 ◦C and 85 ◦C under applied pressure of 140 kPa and 350 kPa. Experimental measurements are modeled through atomic simulations using the reactive force field potential. The hydrogen generation associated with the Poly Alpha Olefin decomposition is studied through calculating the pair distribution function. Findings demonstrate enhancing hydrocarbon decomposition with increasing temperature and pressure, while a critical pressure is required for the decomposition process at the ambient temperature. The critical pressure for lubricant degradation is reduced with increasing the temperature. This study highlights the incorporation of thermo-mechanical effects on the hydrogen generation for the design and development of lubricated rubbing contacts.

Current Synthetic Methodologies of Carbon Nanotubes: A Review

Abstract:Carbon Nanotubes (CNTs) possess a unique one-dimensional molecular geometry with a large surface area. Recently, CNTs have become a thrust area of research as they play a crucial role in molecular engineering due to their excellent mechanical, electrical, and thermal properties. CNTs have a wide range of applications in various fields due to their unique properties. The Multiple Walled Carbon Nanotubes (MWCNTs) are thermally, mechanically, and structurally stronger than single-walled carbon nanotubes (SWCNTs). The sublimation of carbon in an inert atmosphere is the basis of synthetic methods of CNTs like the solar method, laser ablation, and electric arc discharge. Specific chemical methods like CVD, electrolysis, catalytic decomposition of hydrocarbons, heat treatment of a polymer, ball milling, etc., can also be used to prepare CNTs. Attempts have been made in the present review to discuss all synthetic methods of CNTs, their discoverers, the importance of techniques, various parameters that affect the process in detail, and the mechanism for the growth of CNTs. This article aims to provide a comprehensive pathway for researchers who deal with the synthetic methodology of carbon nanotubes. This review is also interesting for readers of material science and nanochemistry.

Formation of Graphite Materials by Decomposition of Liquid Hydrocarbons Heated to High Temperatures

The possibility of forming materials, blanks and products made of graphite by decomposition of liquid hydrocarbons heated to high temperatures has been shown. Optimal modes for growing bulk products in liquid hydrocarbons have been determined. It is presented the Raman spectra of the obtained of graphite materials samples with the signs of presence of carbon nanostructures of various types in these materials.

Comparative analysis of industrial ethane pyrolysis methods for the ethylene production

The thermal decomposition of hydrocarbons in tubular furnaces is the main technology for the production of ethylene. Also, there are some alternative pyrolysis types, such as catalytic pyrolysis, oxidative dehydrogenation, pyrolysis with direct heating. This paper summarizes ethylene production via the most used pathways of this process and the comparison of pyrolysis methods is also discussed.

Biological Activity of Leached Chernozem under Oil and Sodium Chloride Pollution and the Effect of Treatment with Halotolerant Oil-Destructing Bacteria

Soil contamination with oil is often accompanied by pollution by oilfield wastewater, which contains a significant amount of NaCl, which enhances the negative impact of hydrocarbons on soil, plants, and soil microbiota. Therefore, for the biotechnological purification of soils subjected to such combined pollution, hydrocarbon-oxidizing bacteria resistant to salinity should be used. In a model experiment, the effect of artificial pollution with oil (5%) and sodium chloride (1 and 3%) and their combinations, as well as bioremediation using halotolerant hydrocarbon-oxidizing bacteria on the biological activity of leached chernozem (Luvic Chernozem) was studied. Soil contamination with all types of pollution increased its phytotoxicity, while bacterization did not have a positive effect on this indicator in the presence of NaCl and with combined pollution, but contributed to a decrease in toxicity for plants of oil-containing soil. The most sensitive to the presence of oil and/or NaCl were actinomycetes, the number of which decreased by 1–2 orders of magnitude. The introduction of microorganisms increased the decomposition of hydrocarbons, including in complex polluted soil by 10.5–31.8%. In general, the presence of pollutants reduced the activity of soil enzymes. Bacterization contributed to some increase in the level of catalase in soil with oil, restored urease activity in oil-containing soil and under the combined action of pollutants, and increased invertase activity under combined pollution.

Decay of oil residues in the soil is enhanced by the presence of Spartina alterniflora, with no additional effect from microbiome manipulation

Recent work has suggested that the phytoremediation potential of S. alterniflora may be linked to a selection by the plant for oil-degrading microbial communities in the soil, in combination with enhanced delivery of oxygen and plant enzymes to the soil. In salt marshes, where the soil is saline and hypoxic, this relationship may be enhanced as plants in extreme environments have been found to be especially dependent on their microbiome for resilience to stress and to respond to toxins in the soil. Optimizing methods for restoration of oiled salt marshes would be especially meaningful in the Gulf of Mexico, where there is a persistently high threat of petroleum contamination. One favorable strategy for restoration of oiled sites might include planting S. alterniflora with a microbiome that has been pre-selected for an oiled environment. We examined this strategy with a two-year greenhouse experiment and found that planting S. alterniflora in an oiled environment enhances decomposition of oil residues without a clear negative impact on plant growth. Manipulation of the S. alterniflora microbiome through soil inoculation and through exposure to oil residues, elicited a detectable response of soil prokaryote communities to the presence of oil, while only demonstrating an analogous response in fungal communities in the plant roots and leaves. Yet, manipulation of the plant microbiome did not change plant morphology or relative decomposition of polycyclic aromatic hydrocarbons (PAHs) in the soil. Therefore, despite evident relationships between the plant, microbes, and oil, manipulation of the microbiome may not be a worthwhile addition to S. alterniflora phytoremediation strategies. Nevertheless, our work adds support for replanting S. alterniflora in oiled salt marshes as an effective strategy for reducing oil residues in salt marshes, in addition to the re-vegetation and erosion reduction benefits demonstrated by others.

Evolution of Chemical Component and Physical Properties of Datong Long-Flame Coal After Superheated Water Vapor Pyrolysis

ABSTRACT Datong long-flame coal from China was pyrolysis with superheated water vapor at 300°C to 536°C. Chemical and physical changes of long flame coal, including composition, weight loss, pore fracture structure, density, and water absorption were tested, and the qualitative and quantitative relationships among these changes were analyzed. superheated water vapor pyrolysis removes moisture and volatile components from long flame coals and increases the fixed carbon content. After superheated water vapor pyrolysis, the O/C and H/C atomic ratios of long flame coal decreased due to the decomposition of oxygen-containing functional groups and chain aliphatic hydrocarbons. superheated water vapor pyrolysis increased the porosity of long flame coal by material removal and matrix fracture. Material removal occurs throughout the pyrolysis process but matrix fracture occurs only at the initial stage of the conversion of solid organic matter to oil and gas products. The expansion of pore fractures in long flame coal caused a significant decrease in apparent density and an increase in water absorption. Quantitative analysis revealed the forced water absorption of long flame coal was quadratically polynomial with respect to porosity.

Modeling Formic Acid Combustion

Nowadays, the knowledge of the gas-phase chemistry of formic acid is paramount for several industrial sectors, including energy supply and the production of bulk chemicals. In this work, a simplified kinetic mechanism and a detailed kinetic mechanism deriving from a rate-based selection algorithm were developed and tested against experimental data available in the literature. The former contains 141 species and 453 reactions, whereas the latter comprises 90 species and 1047 reactions. A focus on a low initial temperature (i.e., up to 500 K) was provided by comparing the numerical estimations with laminar burning velocity and jet-stirred measurements at several conditions. A good agreement among numerical predictions and experimental data was observed, especially for the simplified kinetic mechanism. The accuracy of the generated mechanism allowed for further analysis of the chemistry of the system, enlightening some determining aspects of the chemistry of formic acid. The produced mechanism can be also intended as per seed mechanism for the generation of kinetic models focused on the chemistry of biofuels. Indeed, the characterization of chemical aspects of formic acid occurring in an oxidative environment is crucial due to its relevance as an energy vector as well as an intermediate compound in the decomposition of larger hydrocarbons and bio-oils.

In-situ decomposition of hydrocarbons from wood cell wall enables configuration of highly active and hierarchical catalyst for hydrogen evolution reaction

Molybdenum carbide has been demonstrated as a promising alternative to noble metal catalysts toward green and efficient hydrogen conversion. However, the suboptimal hydrogen adsorption free energy (∆GH*) and complex carbon reduction procedures remain crucial challenges. Herein, a gas-phase reaction approach based on the in-situ decomposition of hemicellulose and cellulose from natural wood was proposed for the design of highly active Mo2C nanoparticles that are tightly rooted into the hierarchical N-doped carbonized wood (denoted as Mo2C/N-CW). As expected, the Mo2C/N-CW catalyst exhibited low hydrogen evolution reaction (HER) overpotential (98 mV at 50 mA cm−2) and outstanding long-term durability. The theoretical findings show that the conjunction between Mo2C and N-CW can modulate the ∆GH* to the desired level, thereby improving the HER activity. The proposed approach enabled by the decompositions from natural biomass to construct high-performance electrocatalysts opens a novel perspective for the efficient production of hydrogen energy.

Analysis of diesel hydrocarbon decomposition using efficient indigenous bacterial isolate: Bacterial growth and biodegradation kinetics

Analysis of diesel hydrocarbon decomposition using efficient indigenous bacterial isolate: Bacterial growth and biodegradation kinetics