CH3 Functional Groups Research Articles

Experimental and theoretical analyses of nano-silver for antibacterial activity based on differential crystal growth temperatures.

The modulation of antimicrobial properties of nanomaterials can be achieved through various physical and chemical processes, which ultimately affect subsequent properties. In this study, the antibacterial potential of nano-silver was investigated at 0.5, 1.0, 2.0, and 3.0g/L, and its differential temperature synthesis was achieved at 20, 50, and 70°C using the solvent evaporation method. Nano-silver particles exhibited FCC (octahedral) crystalline structure with crystallite sizes ranging between 28 and 39nm calculated using XRD analysis. Moreover, irregular and non-uniform surface morphology was evident from SEM micrographs. The UV-Vis absorbance spectrum of nano-silver exhibited wave maxima at 433nm, while the FTIR analysis depicted different modes of vibration indicating the CH, OH, C≡C, C-Cl, and CH2 functional groups attached to the surface. Lastly, nano-silver caused prominent inhibition (12.5mm) in the Escherichia coli growth, particularly at 70°C synthesis temperature and 3.0g/L dose. It is concluded that both the nano-silver crystal growth temperature and dose contributed substantially to bacterial growth inhibition linked with subsequent size, shape-dependent properties.

Collective influence of substrate chemistry with physiological fluid shear stress on human umbilical vein endothelial cells.

In the treatment of cardiovascular diseases, vascular scaffold materials play an extremely important role. The appropriate substrate chemistries and 15 dynes/cm2 physiological fluid shear stress (FSS) are both required to ensure normal physiological activity of human umbilical vein endothelial cells (HUVECs). The present study reported the collective influence of substrate chemistries and FSS on HUVECs in the sense of its biological functions. The CH3 , NH2 , and OH functional groups were adopted to offer a variety of substrate chemistries on glass slides by the technology of self-assembled monolayers, whereas FSS was generated by a parallel-plate fluid flow system. Substrate chemistries on its own by no means had noticeable effects on eNOS, ATP, NO, and PGI2 expressions, while FSS stimuli enhanced their production. While substrate chemistries, as well as FSS, were both exerted, the releases of ATP, NO, and PGI2 were dependent on substrate chemistries. Study of F-actin organization and focal adhesions (FAs) formation of HUVECs before FSS exposure proves that F-action organization and FAs formation followed similar chemistry-dependence. Hereby proposed a feasible mechanism, that is, the F-actin organization and FAs formation of HUVECs are controlled by substrate chemistries, further advancing the modulation of FSS-triggered responses of HUVECs.

Evaluation of characteristics and microbial community of anaerobic granular sludge under microplastics and aromatic carboxylic acids exposure

The influences of polyether sulfone (PES) microplastics and different structures aromatic carboxylic acids such as benzoic acid (BA), phthalic acid (PA), hemimellitic acid (HA), and 1-naphthoic acid (1-NA) on the performances and characteristics of anaerobic granular sludge as well as the microbial community were investigated. The chemical oxygen demand (COD) removal efficiency was the highest in the experimental group with 40 mg/L BA, reaching 90.1%. The inhibitory effect of aromatic carboxylic acids addition on the 2,3,5-triphenyltetrazolium chloride (TTC) activity was more obvious than that on 2-para (iodo-phenyl)-3(nitrophenyl)-5(phenyl) tetrazolium chloride (INT) activity. Compared with the control group (only 0.5 g/L PES microplastics, 60.6 mg TF·g TSS·h−1), the inhibition effect of TTC activity was 32.5 mg TF·g TSS·h−1 and 44.3 mg TF·g TSS·h−1 in the 40 mg/L HA and 40 mg/L 1-NA experimental groups, respectively. When aromatic carboxylic acids were added, the activities of acetate kinase and coenzyme F420 in the anaerobic granular sludge decreased. The excitation-emission matrix (EEM) fluorescence spectra indicated that loosely bound extracellular polymeric substances (LB-EPS) began to decay. After the addition of different aromatic carboxylic acids, the CC and CH functional groups of the anaerobic granular sludge increased, suggesting that aromatic carboxylic acids migrated to the surface of anaerobic granular sludge, such a transfer would lead to changes in anaerobic granular sludge performance. High-throughput sequencing technology showed that the dominant microbial communities in the anaerobic granular sludge were Proteobacteria, Methanothrix, and Methanomicrobia. After the addition of aromatic carboxylic acids, the relative abundances of Proteobacteria, Methanobacterium, and Methanospirillum increased. In the presence of PES, 1-NA had the most serious toxicity to the anaerobic granular sludge.

Ekstraksi Glukomanan dari Umbi Gembili (Dioscorea esculenta L.)

Gembili bulbs (Dioscorea esculenta L.) have a fairly high carbohydrate content, so they can potentially be a new source of glucomannan compounds. This study aims to determine the yield and glucomannan characteristics of Gembili bulbs at different extraction times and temperatures. Glucomannan was obtained by extraction with water at temperatures of 45, 60, 75, 90, and 105oC for 45, 60, 75, 90, and 105 minutes, and precipitated with isopropyl alcohol. The results showed that the highest yield was obtained at the extraction time of 90 minutes and a temperature of 105oC of 53.09%. The glucomannan of Gembili bulb has a molecular weight of 1,865 x 104 g/mol with ash and water content values of 0.866% and 10.45%, respectively. The results of identification of functional groups with an FTIR spectrophotometer showed that there was a functional group stretching vibration of glucomannan compounds, including the –OH group at a wavenumber of 3431 cm-1 and -C-O-C (glycosidic bond) at a wavenumber of 1020.34 cm-1 and bending vibration of -CH functional groups on wavenumber of 850.61 cm-1.

Identification of Surface Functional Group on Activated Carbon from Waste Sago

Activated carbon is a powerful adsorption material which mainly used as pollutants adsorption. The adsorption properties own derived from the main functional groups or chemical atoms derived from the activation processes. In this study, the activated carbon was prepared from waste sago and activated using two different chemicals activation agents called phosphoric acid and potassium hydroxide. The aim of this study was to identify the surface functional group on waste sago activated carbon produced. The results showed that activated carbon with phosphoric acid activator contained OH, C=C, CO and CH functional groups, while activated carbon with potassium hydroxide activator contained O-H, C≡C, C=C, C-O and C-H functional groups. These results lead to support the recommendations for the development of the application of waste sago activated carbon made as adsorbents in the purification of lead (II) and cadmium (II) wastewater.

Exploration of bioactive prospects of a polysaccharide fraction from Termitomyces heimii against colorectal cancer and broad spectrum bacteria

Termitomyces heimii is a highly cherished wild edible mushroom in India for its pleasant delicacy, rich proximate compositions and profound ethno medicinal applications. A water soluble crude polysaccharide fraction (THP-I) was isolated from dried fruit bodies of T. heimii and purified by GPC. The 1H- NMR spectrum of THP-I exhibited anomeric protons within chemical shifts (δH) between 3.40 to 4.0, indicating that the compound possess –CH and –CH2 functional groups, which resonate with the oxygen atoms of the –OH group, confirmed it as a polysaccharide. THP-I exhibited the MIC values of 62.5 and 125 <mu>g/ml against Staphylococcus aureus and Shigella flexneri respectively. DPPH and FRAP assays showed effective radical scavenging potential by THP-I. In vitro cytotoxicity of THP-I was evaluated by MTT assay and showed notable cellular toxicity against HCT cells at a dose concentration 200 <mu>g/ml. It is first time reported herein that, THP-I has effectively diminished hyperplasia in 1, 2-dimethylhydrazine (DMH) induced colon cancer of Swiss albino rats along with sprouting of goblet cells. Through the present study it is evident that polysaccharide from T. heimii exhibited manifold bioactivities and therefore could be exploited further for its undiscovered potential applications.

Study of organic-matter intercalated vermiculitic phases in the hydromorphic red earth sediments

Al-hydroxy intercalated vermiculitic phases have been widely observed in pedogenic environment, but soil organic intercalations have rarely been reported. In the present study, mixed-layer illite–vermiculite (I/V) with organic matter (OM) intercalation under hydromorphic conditions in the Xuancheng red earth sediments was investigated in order to better understand the interlayer components occurring in mixed-layered clay minerals and the formation of this unusual OM interlayered mixed-layer clay species. Selective extraction of organic fillings by ammonium ethylene diamine tetraacetic acid (EDTA) and acid ammonium oxalate (NH4OX) showed that the components associated with organic complexes in the interlayer space of the 2:1 clays are mainly Fe- and A1-(oxy)hydroxides, which block substantial swelling after ethylene glycol solvation and complete collapse after heating. The OM interlayer filling contains CH3(CH2), CO, COO-, and NH functional groups and are resistant to H2O2 extraction although the binding intensity to the interlayer surface may change. Upon heating to ~300 °C the OM filling escapes from the interlayer space which causes the collapse of the 2:1 clay species. Alteration of primary illite during pedogenesis causes release of K and intercalation of hydrated cations in the interlayer space, and also leaching of Al and Fe. There is accumulation of exchangeable cations and Al and Fe oligomers in the interlayer region, which affects the behavior of I/V clays on glycolation and heating. Hydromorphic conditions favor the transformation of organic polymers into small size organic acids, and thus, favor the intercalation of interlayer OM filling into the 2:1 clays. Pedogenesis processes involves both the weathering of clay minerals and the decomposition of OM, leading to formation of interlayer clay-organic complexes in a hydromorphic soil.

Adsorptive interaction of antibiotic ciprofloxacin on polyethylene microplastics: Implications for vector transport in water

Abstract This study investigates the adsorption behavior of Ciprofloxacin (CPX) antibiotic on polyethylene (PE) microplastics through batch adsorption experiments under various environmental conditions, i.e., ionic strengths, pH and in the presence of dissolved organic matter (DOM). The adsorption of CPX showed a gradual increase with increasing pH reaching the maximum adsorption at pH 6.5–7.5 and then decreased, which is likely due to the redistribution of CPX species with pH. The overall CPX adsorption capacity of PE microplastics decreased with an increase in the ionic strength revealing the hydrophobic and electrostatic interactions. Fourier-transform infrared spectra (FTIR) bands ascribable to −CH2 and −CH3 functional groups exhibited non-polar hydrophobic properties of PE microplastics. CPX adsorption kinetics data were compatible with the parabolic diffusion model and the Elovich model in the presence of humic acid, suggesting that the adsorption was assisted through diffusion-controlled processes. The isotherm equilibrium data fitted well for Hill and Dubinin–Radushkevich models implying multilayer adsorption through physical adsorption processes on the heterogeneous PE microplastics surface. Hence, PE microplastics could be a potential vector to transport CPX in a natural aquatic environment where the adsorption mechanism is being influenced primarily by the pH, ionic strength, DOM of the water system, and the properties of the plastic.

Remediation of Pb (II) ions from Kagara gold mining effluent using cotton hull adsorbent

Fixed-bed column adsorption experiment was conducted to remove lead ions from Kagara mining wastewater using unmodified Cotton Hull Adsorbent (CHA). Analysis of the wastewater effluent revealed that it contains as high as 85 mg/L lead ions. The Fourier Transform Infra-red, Brauneur-Emmet-Teller and Scanning Electron Microscopy characterization of the CHA revealed the presence of O-H, CO, C = O, CO-H and CH2 functional groups, surface area of 139.8 m2/g and porous micrograph of the adsorbent. The column flow experiment indicated that the maximum adsorption capacity of the carbon is 27.65 mg/g. Analysis of the experimental data using dynamic adsorption models revealed that Thomas model had insignificant difference between the average values of the experimental and the model's data. More so, it revealed high correlation coefficient of 0.77 to 0.96 signifying that Thomas model fitted adequately to the experimental data. This study has revealed that Kagara mining effluent which predominantly contains Pb ions can be sufficiently treated with unmodified cotton hull adsorbent before discharging it to the ecosystem.

Impact of lubricating base oil on diesel soot oxidation reactivity

In this study, the surface functional groups types and concentrations, graphitization degree, and oxidation reactivity of exhaust soot samples generated by a heavy-duty engine when employing neat diesel and four base oil dosed mixtures as the fuel was compared. Fourier transform infrared (FTIR), Raman spectroscopy and Thermal gravimetric analyzer (TGA) were used to characterize particle physicochemical properties. Four lubricating base oils were blended in diesel at a mass ratio of 0.5% and 1.0% for combustion. It was found that although the chemical compositions of these four base oils were different, the aliphatic CH functional groups content, graphitization degree and oxidation reactivity of exhaust soot exhibited similar trends. The combustion of base oil was found to change the graphitization degree of emitted soot and lead to soot with a more disordered nanostructure. The soot particles derived from base oil blended fuels had higher aliphatic CH groups concentration than those from neat diesel. Soot oxidation reactivity analyses showed that soot generated from base oil blended fuels had lower characteristic temperatures and lower activation energy than that from neat diesel. Besides, there was a clear correlation between the soot graphitization degree, relative concentration of aliphatic CH groups and its oxidation reactivity.

Synthesis, characterization, and application of β-cyclodextrin-based ion-imprinted polymer for selective sequestration of Cr(VI) ions from aqueous media: Kinetics and isotherm studies

Toxic chromium(VI) is a menace to the environment and humans. Its tendency to transform into chromium(III) complicates its removal. An ion-imprinted polymer (IIP) synthesized by encapsulating 1,5′-diphenylcarbazide (DPC) ligand into the β-cyclodextrin cavities then held into position by 4-vinylpyridine and ethylene glycol dimethacrylate functional monomers (γ-MPS/β-CD/DPC/VP) were employed to investigate Cr(VI) removal efficacy. The corresponding non-imprinted polymer was also prepared, but the template ion was omitted. The inclusion of DPC ligand into the polymeric matrix was responsible for the pronounced selectivity observed due to the high affinity of DPC towards Cr(VI). Characteristic peaks at 3318, 1718, 1258 and 940 cm−1 apportioned to the –OH, CO, C–N, and Si–O–CH3 functional groups were observed in the FTIR spectra. The maximum Langmuir adsorption capacity obtained at 25 °C was 15.61 mg/g for IIP. The optimum solid/liquid ratio achieved at equilibrium time (240 min) was 10 g/L. The IIP selectivity order was Cr(VI)>Cr(III)>Co(II)>Zn(II)>Ni(II).

Transformation of functional groups during lignite heat-treatment and its effects on moisture re-adsorption properties

The surface functional groups of lignite are thought to be the significant factor influencing the moisture re-adsorption behavior of dried coal. Several lignite samples with different surface functional groups were prepared by thermal treatment from 160 °C to 240 °C in N2 and air. In situ FTIR and chemical titration methods were carried out to measure the functional groups of the raw coal and dried samples, and the results from these two methods were compared. FTIR spectra were deconvoluted to reveal the transformation of different functional groups, e.g. CH3, CH2, CH, anhydrides, esters, aldehydes, carboxylic acid, quinones, and ketones. The moisture re-adsorption behaviors of the heat-treated coals under relative humidity of 75% at 25 °C were measured, and the effect of functional groups on moisture re-adsorption property was investigated. The results showed that CHx functional groups decreased dramatically, especially in air, when heat-treating temperature was higher than 200 °C. For the CH, CH2, and CH3 functional groups, their decomposition activation energies are 29.6, 44.2 and 19.3 kJ·mol−1, and their oxidation activation energies are 65.9, 36.1 and 36.5 kJ·mol−1, respectively. In air, when the heat-treating temperature raised to 240 °C, aromatic esters, aliphatic esters and anhydrides all sharply increased. The quinones were probably produced from the transformation of phenolic hydroxyl (Ar-OH) at 240 °C in air. Moreover, coal samples heat-treated in N2 and air showed different equilibrium moisture capacity, which can be attributed to the different contents of hydrophilic groups. The contents of ketones, aldehydes, COOH and Ar-OH had a good linear relationship with equilibrium moisture capacity. The hydrophilic abilities of ketones, aldehydes, COOH and Ar-OH in lignite are higher than that of quinones, esters and anhydrides.

Confirmation of supramolecular structure and its impact on nonlinear optical properties of Bis(4-methylbenzylammonium) tetrabromido zincate: A new semiorganic crystal

Supramolecular structure exhibits good nonlinear optical (NLO) properties due to the enhanced proton transfer process. Semiorganic Bis(4-methylbenzylammonium) tetrabromido zincate (4MLTBZ) crystal was developed by functionalizing 4-methylbenzylamine (4MLBA) with hydrobromic acid and zinc bromide. Amine group of 4MLBA gets protonated by H+ cation of hydrobromic acid. Zinc bromide was linked with 4MLBA through CH ⋯Br and NH ⋯Br interactions which forms supramolecular structure and crystallized noncentrosymmetric space group Pna21. Raman and FTIR spectral analysis provides the evidence for the protonation of amine (NH3+) group. Raman spectrum reveals the coordination of ZnBr4 in 4MLTBZ crystal structure through the observed ZnBr vibrations between 50 and 400 cm−1. The impact over the shift in vibrational frequencies of NH and CH functional groups due to CH ⋯Br and NH ⋯Br interactions were discussed. The ‘CarbonHydrogen’ frame work of 4MLTBZ crystal was established by 1H NMR and 13C NMR spectroscopy. The UV–Vis–NIR spectrum of 4MLTBZ showed very good transparency in the region from 260 nm to 1100 nm. The enhanced SHG efficiency and third order nonlinear optical susceptibility (χ3) are interpreted through hydrogen bonds.

Terminal chemical functions of polyamidoamine dendrimer surfaces and its impact on bone cell growth

Besides their use for drug and gene delivery, dendrimer molecules are also favorable for the design of new surface coatings for orthopedic and dental implants due to the wide variety of functional terminal groups and their multivalent character. The purpose of this work was to observe how covalently immobilized polyamidoamine (PAMAM) dendrimer molecules with different terminal chemical groups influenced serum protein adsorption and osteoblast behavior. To this end, fifth-generation PAMAM dendrimers were immobilized on silicon surfaces with an anhydride-containing silane coupling agent which results in positively charged terminal NH2-groups. Coatings with a net negative charge were generated by introduction of terminal CO2H- or CH3-groups. Surface characterization was performed by static and dynamic contact angle and zeta potential. The in vitro studies with human MG-63 osteoblastic cells focused on cell adhesion, morphology, cell cycle, apoptosis and actin formation within 24 h. This work demonstrated that cell growth was dependent on surface chemistry and correlated strongly with the surface free energy and charge of the material. The positively charged NH2 surface induced tight cell attachment with well-organized actin stress fibers and a well spread morphology. In contrast, CO2H- and CH3-functional groups provoked a decrease in cell adhesion and spreading and indicated higher apoptotic potential, although both were hydrophilic. The knowledge about the cell-material dialogue is of relevance for the development of bioactive implants in regenerative medicine.

Effects of exhaust gas recirculation on the functional groups and oxidation characteristics of diesel particulate matter

The effects of EGR on the carbon-containing functional groups in PM were determined by X-ray absorption near-edge spectroscopy. A TG analyzer was used to determine the effects of EGR on the components and oxidative activity of PM. The results show that the use of EGR in the diesel engine had a minor influence on the types of carbon-containing functional groups in the PM; however, it did affect their relative contents. As the EGR rate increased, the aromatic and graphitized carbon contents of the PM gradually decreased, and the contents of the oxygen-containing and aliphatic CH functional groups increased, which strongly promoted the oxidative activity of the PM. The percentage of soot in the PM decreased with the use of EGR, while the percentages of water and volatile organic matter increased. In addition, the volatile emission temperature TSOF1 gradually decreased, and the trends in the initial volatile combustion temperature TSOF2, the soot ignition temperature Ti, and the burnout temperature Th were consistent with that in the volatile emission temperature. Both the combustion and burnout characteristic indices gradually increased as the EGR rate grows. Instead, the activation energy decreased dramatically, and the energy required for PM to react decreased with the increase of EGR rate.

Chemical functional group descriptor for ignition propensity of large hydrocarbon liquid fuels

The chemical functional group approach is investigated to verify the fundamental applicability of low-dimensional descriptors in the prediction of global combustion behavior, as described by homogeneous reflected shock ignition delay times. Three key chemical functional groups, CH2, CH3 and benzyl-type, are used to represent n-alkyl, iso-alkyl, and aromatic functionalities, respectively. To examine whether such descriptors can appropriately reflect the influences of these functionalities on ignition delay, Quantitative Structure-Property Relationship (QSPR) regression analysis is performed with the formulation of analytical models based on a fundamental Arrhenius-type description. The models are trained using literature measurements of reflected shock ignition delay times for stoichiometric fuel/air mixtures at 20 atm. Sensitivity analyses applied to the QSPR regression models show that the CH2 functional group dominates chemical kinetic behaviors at low temperature, while the chemical kinetic impacts of CH2, CH3, and benzyl-type functional groups all diminish as temperature increases. Further analyses of constant-volume adiabatic ignition delay predictions using detailed chemical kinetic models demonstrate influences of n-alkyl, iso-alkyl, and aromatic functionalities at both low and high temperature, consistent with those found for the QSPR regression models. Finally, 1H and 13C Nuclear Magnetic Resonance (NMR) spectroscopy is used to directly quantify the chemical functional group compositions of both petroleum-derived and alternative jet fuels. Combining the QSPR model with NMR spectra interpretation, the applicability of current approach as an expeditious tool to accurately characterize the ignition propensity of real transportation fuels is demonstrated by comparison with experimental measurements.

Reaction of Pentanol isomers with OH radical – A theoretical perspective

ABSTRACTThe stability of all the three isomeric forms of Pentanol has been examined with relative energy analysis. Even though 2-Pentanol is predicted to be most stable isomeric form, all the three isomeric forms undergo hydrogen atom abstraction reaction with OH radical. Among the proposed 18 different hydrogen atom abstraction reaction, the abstraction from CH2 and CH functional group is found to be a favourable reactive site with low energy barrier in M06-2X/6-311+G(d,p) level of theory. Wiberg bond order analysis shows all the abstraction reactions are concreted but not synchronic in nature. Using force analysis, the calculated work done of individual reaction regions illustrates that structural rearrangements drive the reaction with higher contribution to the energy barrier. The rate constant calculated at M06-2X method for the most favourable reaction is well matched with available experimental data. Using the reported atmospheric OH concentration (1 × 106 molecules/cm3), the life time of 1-Pentanol, 2-Pentanol and 3-Pentanol has calculated to be 18.66, 0.36 and 2.86 days, respectively.

High Intensity Broad Spectrum LEDs in the Near Infrared Range

IR LEDs are widely used in the near-infrared (NIR) spectroscopy, especially in hand-held devices for the detection and measurement of organic materials, allowing faster and cheaper examinations. The -OH, -NH and -CH functional groups found in organic substances can frequently be detected by spectroscopy through absorbance measurement at the resonance wavelength of valence-bond vibrations. The measured wavelengths are 4-2.5 μm, while signal to noise ratio of photon detectors is low due to thermal noise at room temperature. The 1st-3rd harmonic absorption bands are located in the range of the NIR, where smaller signals can be measured effectively in practice. The LEDs have tunable narrow wavelength range therefore they are suitable for such measurements as radiation sources. Further advantages of LEDs compared to incandescent lamps are small dimensions, high efficiency, and low power consumption. In order to tune the emission wavelength of the LED, the composition of the semiconductor light-emitting layer has to be properly set. The change in chemical composition will generally affect the lattice constant too. The crystal defects caused by lattice-mismatch often reduce the efficiency. The emission wavelength is tunable in the quaternary GaInAsP/InP material system meanwhile the lattice-constant remains unchanged. Absorption band of the organic materials is generally broader than the emission spectrum of the LED, therefore a broader emitter is preferred. To achieve this, a number of solutions are known. One of these is to use multiple layers with different composition, where the primary light comes from the active layer at the p-n junction of the diode, then excites the second smaller band gap layer producing longer wavelength secondary light by photoluminescence. The transmitted part of the primary light, together with the secondary light, results in a broader spectrum. This method is not yet implemented in this material system, so my work is focused mainly on this approach.

Hydrothermal dewatering of a Chinese lignite and properties of the solid products

A lignite from Shengli mine in Chinese Inner Mongolia was upgraded by hydrothermal dewatering (HTD). The effects of the HTD process on the solid product yield and the removal rate of elements, organics and inorganics in this coal were determined. The moisture re-adsorption capacities and spontaneous combustion behaviors of coal products from the HTD process were studied, using the saturated salt solution and wire basket reactor methods respectively. FT-IR, XRD, CO2 adsorption, mercury intrusion porosimetry (MIP) and helium pycnometry were carried out to characterize the physicochemical properties of samples. The results show that during the HTD process, organic matter was removed due to the loss of CH3, CH2, and O-containing functional groups, while the inorganic matter was mainly removed in the forms of Ca- and Fe-containing minerals. The amounts of both organic and inorganic matter removed increased with temperature. The equilibrium moisture contents of the hydrothermally dewatered coals at 30°C in the relative humidity range 11–97% were lower than those of the raw coal. They decreased as the HTD temperature rose, probably due to the increase in the loss of hydrophilic O-containing functional groups and decrease in surface area with the increasing of HTD temperature. Moreover, the critical ignition temperature (Tcr) of all the hydrothermally dewatered coals, as measured by wire basket spontaneous combustion experiments, was lower than that of raw coal.

Predicting the phase behavior of fatty acid methyl esters and their mixtures using the GC-SAFT-VR approach

Biodiesel fuels, which consist of a blend of long chain fatty acid methyl esters, have attracted increased interest in recent years as possible alternates to fuels derived from petroleum. An understanding of the thermophysical properties and phase behavior of these molecules are therefore important to the investigation and design of biodiesel processes; however, such data is limited, making the development of molecular based modeling approaches that can accurately and reliably determine the thermophysical properties of fatty acid methyl esters an important research area. Here we apply the group contribution based statistical associating fluid theory for potential of variable range (GC-SAFT-VR) equation of state to the study of long chain fatty acid methyl esters that comprise biodiesel fuels. With minimal reliance on experimental data, the GC-SAFT-VR equation of state offers a predictive approach that allows for the description of hetero-segmented chains that can correlate and predict the phase behavior of pure associating and non-associating fluids and their mixtures. Model parameters for the CO, CH3, CH2, CHCH2, OCH2, and OCH3 functional groups and their cross interactions were taken from earlier work and used here in a transferable fashion to predict the thermophysical properties and phase behavior of pure fatty acid methyl esters and their mixtures with other fatty acid methyl esters, alcohols, and carbon dioxide. It is shown that the GC-SAFT-VR approach can be used as a purely predictive tool without fitting any new model parameters) to accurately predict the phase behavior of the fatty acid methyl ester fluids and their mixtures studied.