Alkane Chain Research Articles

Insight into the mechanisms for pyrolyzing organic macromolecular structure of subbituminous coal by comparing the extraction and flash pyrolysis

Investigating the organic structure of coal is an essential basic research for producing clean fuels and value-added fine chemicals by the clean and efficient utilization of coal. As a consequence, the structural characteristics of organic macromolecular in subbituminous coal (SBC) were analyzed at different levels using multiple destructive and non-destructive technical strategies. Correspondingly, the pyrolysis mechanisms of SBC organic macromolecular structure were investigated to understand through the molecular level correlation group component from extraction portion (EP) and flash pyrolysis (FP). In detail, solid-state 13C nuclear magnetic resonance analysis indicates that carbon skeleton of SBC mainly consists of aliphatic carbons (48.5%) and aromatic carbons (50.3%). The number of substituents on each aromatic ring in SBC is up to 2 on average and aliphatic linkages connect 3–4 aromatic rings. X-ray photoelectron spectrometer analysis exhibits that the >C–O- groups, pyrrolic, and sulfonic sulfurs of organic components are the most abundance O-, N-, and S-containing species, which is consistent with Fourier transform infrared and solid-state 13C nuclear magnetic resonance. The destructive analysis with thermogravimetric implies that organic macromolecular structure in SBC consists different types of covalent bonds (>Cal-X) with different strength. Furthermore, the contents of chain alkanes (CAs, 17.4%), arenes (62.7%), and oxygen-containing organic species (OCOSs, 18.0%) in EP from SBC (EPSBC), while the CAs (53.1%), alkenes (7.4%), arenes (27.3%), and OCOSs (7.5%) in FP of SBC (FPSBC). Comprehensive comparative analysis of detectable small molecule species from EPSBC and FPSBC further indicate that the cleavage > Cal-X bridge bonds of organic macromolecular structure in SBC attack by active hydrogen (H‧) through the pyrolysis reaction to obtain more alkenes, CAs, alkanols, and phenols.

ANALYSIS OF THE COMPOSITION AND STRUCTURE OF HEAVY OILS ACCORDING TO NMR SPECTROSCOPY

The results of studies of 1H and 13C NMR spectroscopy of heavy oil samples from the Timan Pechersk, Volga Ural oil and gas basins are presented. Knowledge of the chemical composition and physicochemical properties of crude oil, along with the particularities of geological and geochemical conditions is of paramount importance for solving the problems of the origin of crude oil and its subsequent processing. Information on the chemical composition of oil allows you to combine samples of crude oil from various fields before refining to achieve the necessary commercial and technical characteristics. 59.7-60.5% of β-CH3 groups were found in the samples, in β-CH2 and CH-groups to the aromatic ring, as well as the content of CH2- and CH-groups of saturated compounds. Dividing 13C NMR spectra into ranges shows a high content of methyl groups with the number of CH-groups in the alkyl fragments and CH and CH2-alkyl groups of naphthenic moieties attached to CH-group being 14.37-24.17%. A specific range of values is from 9.4 to 11.4 ppm. indicates methyl substituted octane, nonane or decane. It was found that the content of primary and secondary carbon atoms was in the range from 59.4-60.7%. The studied samples possess branched alkane chains. Comparison of the content of aromatic / aliphatic components allows us to determine the sample of the Volga Ural basin as a sample with a high content of aromatic component. The content of aromatic fragments varies in a wider range of 17-25.9%. From the data of 1H NMR-spectra of samples of heavy oils with different origin, viscosity and treatment it was found that crude and refined oils can differ in the content of olefin signals. For citation: Kolchina G.Yu., Poletaeva O.Yu., Leontev A.Yu., Movsumzade E.M., Loginova M.E., Kolchin A.V. Analysis of the composition and structure of heavy oils according to NMR spectroscopy. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 6. P. 94-101. DOI: 10.6060/ivkkt.20236606.6783.

Disclose effect and mechanism of external electric field on RP-1 fuel pyrolysis

To explore the combustion efficiency of aviation fuel in an electric field, a ReaxFF molecular dynamics and density functional theory calculation was performed to study the electric field effect on 3-component RP-1 (methylcyclohexane, n-dodecane, and isododecane) pyrolysis. The electrostatic potential, charge natural population analysis and molecular structure were discussed under electric fields of various directions and strengths. The chemical reaction kinetics and species were analyzed under a wide range of electrostatic fields and temperatures. The key reaction energy of RP-1 components and motion statistics were discussed. The analysis revealed significant changes in molecular charge density and structure, which predicted possible cracking sites. Cyclohexane and chain alkanes exhibited opposite trends of decomposition rates depending on the field strength and temperature. The different trends were detail analyzed by reaction pathways and product distribution. Newly cracking way appeared under electric field. The decomposition reaction barrier was reduced by the electric field overall. While the motion of molecules was inhibited with the field increasing, which decrease the molecular potential energy. This work conducted a comprehensive analysis about effect of external electric field on the RP-1 mixture fuel pyrolysis. offering a potential solution for improving combustion efficiency.

Design and synthesis of isosorbide‐based copolycarbonates with high transparency and low hygroscopicity for optical applications

AbstractPoly(isosorbide carbonate) (PIC) is an example of the shift from fossil to bio‐based feedstocks in polymeric materials. However, the naturally high hygroscopicity of isosorbide may lead to the bad dimensional stability of its polymers, limiting its application. This work aims to develop a series of isosorbide‐based copolycarbonates by introducing hydrophobic groups, such as alkane chains and aromatic rings, into the polymer backbone via one‐pot melt polycondensation. As expected, the molecular structure and steric hindrance of the comonomer have a remarkable effect on the water absorption of the copolycarbonates. Among the comonomers, tricyclo[5.2.1.0(2,6)]decanedimethanol with an alkane skeleton bridge effectively reduces the saturation water absorption by 61% compared to PIC. The water absorption mechanism and kinetics of the copolycarbonates are investigated. Moreover, the incorporation of comonomers in PIC not only exhibits stronger hydrophobicity, but also significantly improves its optical properties. Copolycarbonates obtained have a light transmittance of 92% and a refractive index of 1.5394, which are higher than those of PIC, along with better thermal stability, flexibility, and lower glass transition temperature. This work provides a new strategy for the design of isosorbide‐based polycarbonates for use in optics.

A Novel Graphene Based Bi-Function Humidity Tolerant Binder for Lithium-Ion Battery.

Binders play a critical role in rechargeable lithium-ion batteries (LIBs) by holding granular electrode materials, conductive carbons, and current collectors firmly together to form and maintain a continuous electron conduction phase with sufficient mechanical strength. In the commercial LIBs, the dominant binder is polyvinylidene fluoride for the cathode (LiCoO2 , LiFePO4 , LiNix Coty Mnz O2 , etc.) and carboxyl methylcellulose/styrene-butadiene rubber for the anode (graphite and Li4 Ti5 O12 ). However, these polymer binders have several drawbacks, particularly, a lack of electronic and lithium-ion conductivities. Here, a novel organic/inorganic hybrid conductive binder (LAP-rGO) for both the anode and cathode of LIBs is reported. The binder consists of 2D reduced graphene oxide sheets with anchored long alkane chains. Electrodes prepared using this binder exhibit sufficient high bond strength, fast electrolyte diffusion, high rate charge/discharge performance, and excellent cycling stability. Around 130 mAh g-1 capacity enhancement at 5C is demonstrated for LiFePO4 and Li4 Ti5 O12 electrodes owing to the combined improvement in electron and lithium ion transportation. LAP-rGO bond graphite anode shows specific capacity beyond its theoretical value. Electrode slurries prepared using this new binder have superior processing and coating properties that can be prepared under a high humidity and dried using less energy.

P‐12.12: Development and Application of High Birefringence Liquid Crystal Materials

The development of new liquid crystal optoelectronic devices, including laser phase modulation, microwave and terahertz devices, requires liquid crystal materials with high birefringence. In this paper, three new molecular design strategies are proposed, including the introduction of olefin chain, lateral fluorine substitution and new ring core. Four new series of isothiocyanate liquid crystal compounds with high birefringence, low melting point and wide nematic temperature range were synthesized. Based on these new liquid crystal compounds, a liquid crystal mixture with nematic temperature range of ‐40~146 ºC and birefringence of 0.42 was developed. At 19 GHz, the new liquid crystal mixture shows excellent dielectric properties, with dielectric anisotropy of 1.28 and dielectric loss of 0.0087. The new liquid crystal mixture also has very low viscoelastic coefficient. The results at 1550nm and 60 ºC show that the response speed can reach 3.6 milliseconds with 2π phase modulation in the reflection mode.

Effect of Beeswax on hydrophobicity, moisture resistance and transparency of UV curable linseed oil based coating for compostable paper packaging

Compostable bio-sourced moisture barrier coating is among the most emerging material alternative to non-degradable single use plastics liner in paper packaging applications. In the current work, highly unsaturated linseed oil is epoxidized and acrylated to form UV curable bio-acrylate resin (Acrylated Linseed Oil) to be used as bio-coating material for paper substrate to improve its barrier properties. Beeswax has been proposed as an excellent barrier to water vapour permeability, the hydrophobicity being imparted by esters of long chain fatty alcohols, acids and long chain alkanes present within. Beeswax is incorporated into AELO resin to enhance the water and moisture barrier property of the coating due to its hydrophobicity and food compatibility. The addition of beeswax has significantly reduced the Water Vapour Transmission Rate (WVTR) to 20 g/m2.day.atm while improving the Water Contact Angle (WCA) to 111° for 10 wt% beeswax loading. Further, the WCA remains above 90° even after 50 cycles of abrasion revealing the durability of the coating. The hydrophobicity is further reinstated by the SEM images which show microscale roughness imparted by uniformly dispersed beeswax. Beeswax thus improves hydrophobicity both by virtue of its composition and the surface roughness imparted. Improved transparency (>95% UV–vis transmittance), higher thermal stability (T5 >250 °C, T10 >300 °C), and reasonable glass transition temperature of the bio-coatings reveals its wide application in the field of packaging. The compostability of the coating in soil and paper repulpability after removal of the coating, both explored its potential in paper-based food packaging by replacing single use plastics.

Atomically Dispersed Pt-Doped Co3 O4 Spinel Nanoparticles Embedded in Polyhedron Frames for Robust Propane Oxidation at Low Temperature.

This study adopts a facile and effective in situ encapsulation-oxidation strategy for constructing a coupling catalyst composed of atomically dispersed Pt-doped Co3 O4 spinel nanoparticles (NPs) embedded in polyhedron frames (PFs) for robust propane total oxidation. Benefiting from the abundant oxygen vacancies and more highly valent active Co3+ species caused by the doping of Pt atoms as well as the confinement effect, the optimized 0.2Pt-Co3 O4 NPs/PFs catalyst exhibits excellent propane catalytic activity with low T90 (184 °C), superior apparent reaction rate (21.62×108 (mol gcat -1 s-1 )), low apparent activation energy (Ea = 17.89kJ mol-1 ), high turnover frequency( 811×107 (mol gcat -1 s-1 )) as well as good stability. In situ diffuse reflectance infrared Fourier transform spectroscopy and density functional theory calculations indicate that the doping of Pt atoms enhances the oxygen activation ability, and decreases the energy barrier required for CH bond breaking, thus improving the deep oxidation process of the intermediate species. This study opens up new ideas for constructing coupling catalysts from atomic scale with low cost to enhance the activation of oxygen molecules and the deep oxidation of linear short chain alkanes at low temperature.

Microstructure evolution and mechanical performance of tetrahedral amorphous carbon coatings with dense droplets during annealing

Tetrahedral amorphous carbon (ta-C) coatings with approximately 50% sp3C were deposited onto cemented carbide alloy YG6 and Si wafers via direct vacuum cathode arc (DVCA) evaporation at different substrates temperatures. Coated specimens were annealed in a 5 Pa argon atmosphere. The micromorphology and chemical bonding structure of these coatings with different treatments were characterized using field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The mechanical performance was tested using a nanoindenter and film stress instrument. The obtained ta-C coatings contained dense droplets of various sizes (“abnormal particles” (An-Ps)). The densities of the An-Ps were controlled by the graphite cathode target arc rather than the substrate temperature, and their ID/IG ratios were close to their counterpart coating matrix. Increasing the substrate temperature was beneficial for increasing the sp2C fraction and the number of aromatic ring sp2C sites. Growth, coalescence, and leveling-diffusion of aggregates in the coating matrix and An-Ps occurred during annealing, which was related to the existing state of the sp2C sites, including the olefinic chain and aromatic ring. The residual stress variation with annealing temperature also depended on the sp2C state. The residual stress in the coating increased during annealing when the number of aromatic ring sp2C sites exceeded a certain critical value.

Heterojunction of SnO2/Sn nanoparticles coated by graphene-like porous carbon as ultrahigh capacity anode of lithium-ion batteries

SnO2-based anode of lithium-ion batteries (LIB) suffers from excessive volume expansion and low conductivity, resulting in very poor capacity stability and rate capability. To solve the problems, three kinds of SnO2/Sn@carbon heterostructures were synthesized by a salt template following calcination using tartaric acid, p-phthalic acid and ethylenediamine tetraacetic acid with different carboxyl groups as carbon sources, respectively. The acidity, carbon atoms number and position affect the ratio of SnO2/Sn, the morphology and content of derived carbon, the advantage crystal plane and the surface defects of SnO2. The carbon atoms located at carboxyl are transformed to CO and formed pores, and the carbon atoms at alkane chain are polycondensed and transformed to amorphous carbon during annealing process. The SnO2/Sn@C derived from tartaric acid (SnO2/Sn@TA) has the largest ratio of SnO2/Sn, which fixed on graphene-like porous carbon, exposed the most surface defects and more high energy crystal plane. The specific structure ensures structural stability and ultrahigh capacity, lower Li+ diffusion barrier energy and super rate capability. It exhibits the charge/discharge capacity of 1059.7/1064.4 mAh g−1 at 2 A g−1 after 1500 cycles and super rate performance of 399.3/404.5 mAh g−1 at 6 A g−1, which are superior to most reference data.

Microscopic stabilization mechanism of nanoparticle-laden droplets under external electric fields: A molecular dynamics study

Electric dehydration process of crude oil is frequently accompanied by water droplet breakup, resulting in efficiency reduction of oil-water separation. To reveal the microscopic stabilization mechanism of nanoparticle-laden droplet, molecular dynamics (MD) simulations were adopted to investigate the electro-deformation and breakup dynamics. Good qualitative and quantitative agreements were observed between the present simulations and the literature experiments. The effects of electric fields (electrocapillary numbers and frequencies) and nanoparticles (concentrations and types) on the droplet stability were analyzed in terms of intermolecular total interactions. The analysis of quantum chemical calculations and weak interactions shows that stable hydrogen bonds can be formed between the silicon dioxide (SiO2) and water (H2O) molecules, enhancing droplet stability. The droplet stability under alternating current (AC) electric fields are higher than that under direct current (DC) electric fields, and the stability increases with increasing AC frequencies. At the total interactions of the nanoparticle-laden droplet system after switch-off electric field stronger than that after switch-on electric field, fast droplet recovered process was observed. The modified SiO2 NPs can efficiently enhance droplet stability, and high nanoparticle (NP) concentrations lead to high droplet stabilities. Eventually, the ranking of NP-laden droplet stabilities is roughly consistent with that of droplet pair electrocoalescence efficiencies, i.e., CAC (SiO2 modified with 6 carboxylic acid chains) > CAAL (SiO2 modified with 3 carboxylic acid chains and 3 alkane chains) > ALC (SiO2 modified with 6 alkane chains) > SiO2. The results of this work will be potentially valuable for optimizing the design of compact and efficient oil-water separators.

Preparation of Amphiphilic Chitosan-Loaded Bentonite Adsorbent and Its Performance in Removing Organic Matter from Coking Wastewater

An amphiphilic chitosan-loaded bentonite adsorbent (C18CTS-BT) was prepared for the efficient removal of organic matter from coking wastewater. The structure and surface morphology of adsorbents were characterized by FT-IR, XRD, and SEM. The removal of those organics by C18CTS-BT was investigated by comparing the adsorption performances of C18CTS-BT with bentonite (BT) and chitosan-loaded bentonite (CTS-BT). The results showed that compared with BT and CTS-BT, C18CTS-BT showed the performance advantages of having a low dosage, wide pH range, and short adsorption equilibrium time. The optimized treatment process was as follows: the adsorbent dosage was 1.5 g·L-1, the adsorption time was 60 min, and the pH of the system was 7.0. The chemical oxygen demand (COD) of the coking wastewater treated with BT, CTS-BT, and C18CTS-BT decreased from 342 mg·L-1 in the raw water to 264 mg·L-1, 218 mg·L-1, and 146 mg·L-1, corresponding to COD removal rates of 22.81%, 36.26%, and 57.31%, respectively. The results of GC-MS analysis also confirmed that C18CTS-BT could remove most of the organic compounds in coking wastewater, especially long-chain alkanes and their derivatives. The hydrophobic modification of the adsorbent material can effectively improve the removal performance of organic compounds from coking wastewater.

Atomistic MD Simulations of n‐Alkanes in a Phospholipid Bilayer: CHARMM36 versus Slipids

AbstractLinear alkanes (n‐alkanes) are chemically the most simple linear hydrophobic molecules in nature. Studying the incorporation of n‐alkanes into lipid membranes is therefore a good starting point toward understanding the behavior of hydrophobic molecules in lipid membranes and to assess how accurately molecular dynamics models describe such systems. Here, the miscibility and structure of different n‐alkanes—n‐decane (C10), n‐eicosane (C20), and n‐triacontane (C30)—in dipalmitoylphosphatidylcholine membranes are investigated using two of the most used force fields for lipid membrane molecular dynamics simulations (CHARMM36 and Slipids). The n‐alkanes are miscible in the membrane up to a critical volume fraction, ϕc, that depends on the force field interaction parameters used. ϕc is dependent on alkane chain length only for the model with more disordered chains (Slipids). Below ϕc, a comparison with 2H nuclear magnetic resonance (NMR) spectra indicates that a more realistic structure of the longer alkane molecules (C20 and C30) is obtained using the Slipids force field. On the other hand, for the shorter alkane (C10), Slipids simulations underestimate molecular order and CHARMM36 simulations enable a precise prediction of its experimental spectrum. The predicted 2H NMR spectra are highly sensitive to 1–4 electrostatic interactions, and suggest that a reduction of the partial charges of the longer alkanes and acyl chains in CHARMM36 results in a better performance. The results presented indicate that lipid membranes with incorporated alkanes are highly valuable systems for the validation of force fields designed to perform lipid membrane simulations.

Unveiling the effect of molecular chain length on the thermal energy storage capacity and transition temperature of alkane-based phase change composites

Thermal energy storage systems based on phase-change materials (PCMs) have garnered significant attention, because they can overcome intermittency issues related to renewable energy sources. However, the energy storage capacity and phase-change temperature of phase-change composites largely depend on the PCM type and molecular weight, in addition to the supporting material type, and experimental studies on the thermal properties of PCMs with different molecular chain lengths are scarce. In this study, phase-change composites were prepared by the vacuum impregnation method using boron nitride (BN) as the support and n-alkanes of different chain lengths–dodecane (C12H26), and docosane (C22H46)–as the PCMs to study the effect of the alkane chain length on the thermal energy storage density and phase-change temperature. The BN@C22 composite exhibited greater latent heat storage capacity (125.11 kJ/kg) than the BN@C12 composite (70.84 kJ/kg), indicating the low confinement effect of the BN support on the long-chain n-alkane. In contrast, the BN functional groups and shorter-chain n-alkane had strong intermolecular interactions, which compromise the energy storage density for seepage resistance and shape stability. Both PCM composites exhibited good chemical compatibility between the two components, improved thermal durability, and insignificant leakage rate (up to 98.7% leakage resistance capability), while BN@C12 showed higher shape stability. The thermal performance of the as-prepared PCM composites, including their phase-transition temperature (range: −9.54 to + 43.53 °C), illustrates their potential for various thermal management applications, including indoor temperature-control systems. This study provides fundamental guidelines for tuning the working temperature range and improving the efficiency of thermal management systems.

Guiding Metal Organic Framework Morphology via Monolayer Artificial Defect-Induced Preferential Facet Selection.

Guiding metal organic framework (MOF) morphology, especially without the need for chemical additives, still remains a challenge. For the first time, we report a unique surface guiding approach in controlling the crystal morphology formation of zeolitic imidazole framework-8 (ZIF-8) and HKUST-1 MOFs on disrupted alkanethiol self-assembled monolayer (SAM)-covered Au substrates. Selective molecule removal is applied to generate diverse SAM matrices rich in artificial molecular defects in a monolayer to direct the dynamic crystal growth process. When a 11-mercaptoundecanol alkanethiol monolayer is ruptured, the hydroxyl tail groups of surface residue molecules act as nucleating sites by coordination with precursor metal ions. Meanwhile, the exposed alkane chain backbones stabilize a particular facet of MOF nuclei in the dynamic growth by slowing down their crystal growth rates along a specific direction. The competitive formation between the [110] and [100] planes of ZIF-8 ultimately regulates the crystal shapes from rhombic dodecahedron, truncated rhombic dodecahedron, and truncated cube to cube. Similarly, changeable morphologies of HKUST-1 crystals are also achieved from cube and tetrakaidekahedron to octahedron, originating from the competitive selection between the [100] and [111] planes. In addition to the artificial matrix preferred orientation of initial nucleation, parameters such as temperature also play a crucial role in the resulting crystal morphology. Standing on the additive-free MOF crystal morphology growth control, porous architectures prepared in this approach can act as templates for ligand-free metal (Au, Ag, and Cu) nanocluster synthesis. The nanocluster-embedded MOF structures represent distinct crystal morphology-dependent optical properties, and interestingly, their fluorescence emission can be highly enhanced by facet-induced nanocluster packing alignments. These findings not only provide a unique thought on MOF crystal morphology guidance but also pave a new route for the accompanied property investigation and further application.

Aggregation and crystallization of small alkanes.

We present a computer simulation study of the aggregation and ordering of short alkane chains using a united atom model description. Our simulation approach allows us to determine the density of states of our systems and, from those, their thermodynamics for all temperatures. All systems show a first order aggregation transition followed by a low-temperature ordering transition. For a few chain aggregates of intermediate lengths (up to N = 40), we show that these ordering transitions resemble the quaternary structure formation in peptides. In an earlier publication, we have already shown that single alkane chains fold into low-temperature structures, best described as secondary and tertiary structure formation, thus completing this analogy here. The aggregation transition in the thermodynamic limit can be extrapolated in pressure to the ambient pressure for which it agrees well with experimentally known boiling points of short alkanes. Similarly, the chain length dependence of the crystallization transition agrees with known experimental results for alkanes. For small aggregates, for which volume and surface effects are not yet well separated, our method allows us to identify the crystallization in the core of the aggregate and at its surface, individually.

Low-temperature oxidation of n-octane and n-decane in shock tubes: Differences in time histories of key intermediates

The impact of chain length on the time histories of key intermediate species that form upon first-stage ignition was studied experimentally in a shock tube using multi-color laser absorption diagnostics. CO, CH2O, OH, and composite time histories of heavier carbonyls were measured simultaneously during the low temperature oxidation of n-octane & n-decane in the temperature range of 720–860 K, and pressure range of 4.1–5.8 atm. The test mixtures were 0.64% & 0.6% fuel in oxygen, respectively. A two-color diagnostic was also developed and used in tandem with other diagnostics to quantify the evolution of temperature during oxidation. To our knowledge, this work reports the first measurement of CH2O, OH, and temperature during oxidation of C8 or heavier hydrocarbon fuels at low temperatures. The measured time histories were also compared against the predictions of two recent detailed kinetic models. Significant differences in the measured and predicted first-stage ignition delay times, absolute concentration of species post-ignition and the maximum rate of formation of species were observed. Our measurements will serve as targets for further refinement of these detailed kinetic models and in the development of rate rules for similar classes of fuels. The measurements also revealed significant differences in the relative reactivity of n-octane and n-decane. Taken together with previous speciation studies conducted in n-heptane, we observe a strong correlation between the species time histories, reactivity, and chain length of straight chain alkanes. This observation lends further support to the selection of CO and CH2O as target species for development of Low-Temperature Hybrid Chemistry (HyChem) models for real transportation and aviation fuels in future.

Effect of Secondary Oxidation of Pre-Oxidized Coal on Early Warning Value for Spontaneous Combustion of Coal

The indicative ability of a gas indicator for the spontaneous combustion of coal is affected by the secondary oxidation of oxidized coal, from old goafs, entering a new goaf through air leakages. This phenomenon can affect the accuracy of early warning systems regarding the spontaneous combustion of coal in a goaf. In this research, three kinds of coal were selected to carry out a spontaneous combustion simulation experiment in which a temperature-programmed experimental device was used to analyze the behavior of the index gas towards raw coal and oxidized coal, for which the latter was oxidized at 70 °C, 90 °C, 130 °C, and 150 °C. The results show that the chain alkane ratio in the secondary oxidation process and the trends of oxygen, CO, and C2H4 concentrations are the same as those in the primary oxidation process. On the other hand, the temperature at which C2H4 initially appears, during secondary oxidation, is lower than in primary oxidation. The CO produced in the early stage of secondary oxidation is greater than the CO produced, at the same temperature, in primary oxidation. In this regard, the usage of C2H4 concentration as an indicator with which to judge the occurrence of the spontaneous combustion of coal would allow for an earlier response. In the secondary oxidation process, the temperature of the extreme value of the alkene ratio appears higher than in primary oxidation. The presence of a higher pre-oxidation temperature and a higher proportion of secondary oxidation gas will affect an indicator’s judgement when the primary oxidation enters the severe oxidation stage. The gas produced by secondary oxidation will affect the early warning of the spontaneous combustion of coal in the coal mine goaf, which should be considered in the establishment of an early warning system.

Effects of Chain Alkanes on Restraining Water Re-Adsorption of Dried Indonesian Lignite

Effects of Chain Alkanes on Restraining Water Re-Adsorption of Dried Indonesian Lignite

Recovery utilization of triolein for producing short chain alkane by combining biocatalysis and inorganic catalysis

ABSTRACT The production of waste cooking oil (WCO) has been increasing year by year and brought the serious environmental problems. A considerable research effort has been focused on the reuse of WCO. Utilizing the triolein existing in great quantity on olive oil and rapeseed oil is an effective strategy to realize the reuse of WCO. This work introduces a novel process for producing short-chain alkane from triolein based on the convenience of products separation. The continuous process including the hydrolysis of triolein into fatty acid by lipase, the oxidation of fatty acid for producing short-chain fatty acid, and the light-driven decarboxylation of short chain fatty acids was established to produce alkane. The feasibility of the proposed process was demonstrated using model substances. The influences of various operational parameters on hydrolysis, oxidation, and decarboxylation using model substances were studied systematically. The optimized yields of the hydrolysis, oxidation, and decarboxylation reactions were 78.7%, 52.1%, and 78.9%, respectively. The free lipase is reused under the optimal condition and observed that 31.9% decay in catalytic activity even 5 cycles. Immiscible reaction systems are used to facilitate separation of products. The decarboxylation with decarboxylase (CvFAP) for short-chain fatty acid lead to higher alkane yields in 15 min. In addition, the octane yield of 16.2% using triolein as the raw material was obtained in the continuous process. Although this approach results in a low total yield of gasoline, it highlights the potential applications in the production of hydrocarbon fuel with WCO.