Average Number Of Carbon Atoms Research Articles

Carbon Dioxide Pressure and Catalyst Quantity Dependencies in Artificial Photosynthesis of Hydrocarbon Chains on Nanostructured Co/CoO Surfaces.

In this study, we investigated the influence of pressure and the quantity of Co/CoO catalyst on an artificial photosynthesis process that converts CO2 and H2O into hydrocarbons (CnH2n+2, where n ≤ 18). The adsorption of CO2 and H2O on Co/CoO surfaces proved to be pivotal in this photo-catalytic reaction. Photoexcited carbon dioxide and water molecules ((CO2)* and (H2O)*) generated by illuminating the catalyst surface led to the formation of alkene hydrocarbon molecules with carbon numbers following an approximate Poisson distribution. The optimal pressure was found to be 0.40 MPa. Pressure less than 0.40 MPa resulted in low CO2 adsorption, impeding excitation for photosynthesis. At greater pressure, oil/wax accumulation on Co/CoO surfaces hindered CO2 adsorption, limiting further photosynthesis reactions. The average number of carbon atoms in the hydrocarbons and hydrocarbon yield were correlated. The amount of Co/CoO was also found to affect the hydrocarbon yield. Our study contributes to the understanding of Co/CoO-catalyzed photosynthesis and suggests that an open-flow system could potentially enhance the productivity of long-chain hydrocarbons.

Polycyclic aromatic hydrocarbon size tracers

ABSTRACT We examine the dependence of polycyclic aromatic hydrocarbon (PAH) band intensity ratios as a function of the average number of carbon atoms and assess their effectiveness as tracers for PAH size, utilizing the data, models, and tools provided by the NASA Ames PAH Infrared Spectroscopic Data base. To achieve this, we used spectra from mixtures of PAHs of different ionization fractions, following a size distribution. Our work, congruent with earlier findings, shows that band ratios that include the 3.3 μm PAH band provide the best PAH size tracers for small-to-intermediate sized PAHs. In addition, we find that band ratios that include the sum of the 15–20 μm PAH features (I$_{\Sigma _{15-20}}$) and the 6.2 or 7.7 μm bands also serve as good tracers for PAH size in the case of small-to-intermediate sized PAHs, for objects under a similar PAH size distribution as with the presented models. For different PAH size distributions, the application of a scaling factor to the I6.2/I$_{\Sigma _{15-20}}$ ratio can provide estimates for the size of the small-to-intermediate PAH population within sources. Employment of the I6.2/I$_{\Sigma _{15-20}}$ and I7.7/I$_{\Sigma _{15-20}}$ ratios can be of particular interest for JWST observations limited only to ∼5–28 μm MIRI(MRS) coverage.

Spectral variations among different scenarios of PAH processing or formation

ABSTRACT We examine the variations in the spectral characteristics and intensities of polycyclic aromatic hydrocarbons (PAHs) in two different scenarios of PAH processing (or formation): (1) small PAHs are being destroyed (or equivalently large PAHs are being formed, referred to as SPR, i.e. small PAHs removed), and (2) large PAHs are being destroyed (or equivalently small PAHs are being formed, referred to as LPR, i.e. large PAHs removed). PAH emission was measured considering both the presence and absence of plateau components. The variation in the PAH band intensities as a function of the average number of carbon atoms 〈NC〉 has the highest dynamic range in the SPR case, suggesting that smaller PAHs have higher impact on the PAH band strengths. The plateaus show overall declining emission with 〈NC〉, and their higher dynamic range in the SPR case also suggests that smaller PAHs are mainly contributing to the plateau emission. The 7.7/(11.0 + 11.2) $\mu$m PAH band ratio presents the least amount of variance with the lowest dynamic range, rendering this ratio as the better choice for tracing PAH charge. The 3.3/(11.2 + 11.0) $\mu$m PAH band ratio is the only ratio that has both a monotonic variance and fully separated values among the SPR and LPR scenarios, highlighting its efficiency as PAH size tracer but also allowing the characterization of the dominant scenario of processing or formation in a given region or source. We present new PAH charge–size diagnostic diagrams, which can provide insights into the average, maximum, or minimum NC within astrophysical sources.

Effect of Temperature on the Graphitizability and Electrochemical Properties of a Quang Ninh Natural Anthracite Used As Anode in Li/Na-Ion Batteries

In this research, natural anthracite coal (ATC) originated from Vang Danh - Quang Ninh province in Viet Nam was firstly chemically purified and then calcined in inert gas (Ar) at 800 oC for different periods (t = 2, 3 and 6 h) to remove all the impurities and enrich the carbon content. The purity and graphitized structure of treated coal proved significantly while evaluating its structural parameters (the lateral crystallite size - La, stacking crystallite height - Lc, the average number of layers per carbon crystallite - Naverage, and the average number of carbon atoms per aromatic lamellae - n)1, 2 and morphology. After purification step, ATC possesses relatively high carbon content (96.0%) and its impurities were mostly removed. The structure of heat-treated ATC samples is like hard carbon. Besides, its graphene interlayer spacing is larger than that of graphite. These features seem to be potential for application of ATC as negative electrode materials for both Li and Na rechargeable batteries.In batteries testing, using ATC calcined at 800 oC for 3 hours as anode material in lithium half-cell exhibited a quite good specific capacity (170.1 mAh g-1), which is much higher than the value obtained for commercial hard carbon (162.2 mAh g-1). Moreover, Coulombic efficiency of ATC is almost absolute (99.8%). In sodium half-cell, the sample calcined at 800 oC for 2 hours gave much smaller specific capacity of 130.5 mAh g-1 than hard carbon one (280 mAh g-1). Nevertheless, Coulombic efficiency of ATC anode in lithium half-cell and sodium half-cell throughout 100 cycles remained absolutely at 99.6%, while their values for hard carbon anode were 99.9% and 99.7%, respectively. References Abou-Rjeily, J.; Laziz, N. A.; Autret-Lambert, C.; Outzourhit, A.; Sougrati, M.-T.; Ghamouss, F., Towards valorizing natural coals in sodium-ion batteries: impact of coal rank on energy storage. Scientific Reports 2020, 10 (1), 1-10.Manoj, B.; Kunjomana, A., Study of stacking structure of amorphous carbon by X-ray diffraction technique. Int. J. Electrochem. Sci 2012, 7 (4), 3127-34. Acknowledgement This work is supported by Viet Nam National University Ho Chi Minh City (VNUHCM) under grant number B2020-18-06

Linking Characteristics of the Polycyclic Aromatic Hydrocarbon Population with Galaxy Properties: A Quantitative Approach Using the NASA Ames PAH IR Spectroscopic Database

Utilizing the data and tools provided through the NASA Ames PAH IR Spectroscopic Database (PAHdb), we study the PAH component of over 900 Spitzer-IRS galaxy spectra. Employing a database-fitting approach, the average PAH size, the PAH size distribution, and PAH ionization fraction are deduced. In turn, we examine their connection with the properties of the host galaxy. We found that PAH population within galaxies consists of middle-sized PAHs with an average number of carbon atoms of = 55, and a charge state distribution of ∼40% ionized—60% neutral. We describe a correlation between the 6.2/11.2 μm PAH ratio with the ionization parameter (), a moderate correlation between the 8.6/11.2 μm PAH ratio and specific star formation rate, and a weak anticorrelation between γ and M *. From the PAHdb decomposition, we provide estimates for the 3.3 μm PAH band, not covered by Spitzer observations, and establish a correlation between the 3.3/11.2 μm PAH ratio with N C. We further deliver a library of mid-IR PAH template spectra parameterized on PAH size and ionization fraction, which can be used in galaxy spectral energy distribution fitting codes for the modeling of the mid-IR PAH emission component in galaxies.

Influence of operating conditions on the main characteristics of a cobalt Fischer-Tropsch catalyst

Three stages of extraction of the contents of the porous space of cobalt catalysts, continuously operating for different periods of time (Time on stream (TOS) is from 40 to 800 h) in a Fischer-Tropsch fixed bed reactor, were performed to identify carbon-containing compounds using chromatographic analysis. At each stage of extraction, the surface of the samples under study was investigated by SEM and BET methods. It was determined that during operation, as a result of accumulation of linear alkanes in the pores of the catalyst with an average number of carbon atoms from 20 to 25 and a decrease in the specific surface area, the reaction rate reduces by 25-30 %. With the help of oxidative treatment, it was found that elemental carbon is contained in the porous space of the spent catalysts.

A study on the effects of compositional variations of biodiesel fuel on its physiochemical properties

The objective of the present work is to alter the composition of palm biodiesel and study its effects on fuel properties. As the fatty acid methyl ester composition of biodiesel has an influence on its properties, it can be varied to alter the properties as desired. Palm biodiesel was blended with various neat methyl esters on a 10%, 15% and 20% volume basis. Kinematic viscosity, heating value, density and surface tension of the 34 prepared biodiesel samples were determined and the trends followed were studied to establish the effects. The viscosity of biodiesel decreased with a decrease in methyl oleate concentration and the degree of unsaturation. An 80% palm +20% methyl octanoate blend exhibited the least viscosity. The heating value of the sample was found to be influenced by the changes in the methyl esters’ chain length, the average number of single bonds and the average number of double bonds. Apparently, 80% palm +20% methyl stearate has the highest heating value. Not great appreciable change in density was found, but the surface tension of the blends prepared was influenced by changes in the average number of carbon atoms. An 80% palm +20% methyl octanoate mix exhibited the least surface tension of the fuel blends. Based on the measured composition and property data, a multi-linear regression approach was used to develop correlations to predict the properties of biodiesel from its composition, which is validated using samples other than those used as inputs to develop the model. Further, ANN is used to predict the properties of biodiesel fuels based on their composition. The present investigation could further be extended to study the effects of compositional variations of biodiesel on other properties, which would help in arriving at an ideal biodiesel composition for automotive engine applications.

A comparative study on the fuel properties of biodiesel from woody essential oil depending on terpene composition

The essential oils from four Korean domestic gymnosperm species (red pine, white pine, cypress, and cedar) were examined in this study to understand the fuel characteristics based on their terpene compositions. The elemental composition, heating value, density at 20 °C, energy density, flash point, and kinematic viscosity at 40 °C of each woody essential oil were analyzed based on their terpene composition. The major elements in all woody essential oils investigated in this study were carbon, hydrogen, and oxygen. The woody essential oils were composed of more than 80% carbon and less than 10% oxygen due to the presence of terpene derivatives (terpene alcohols and terpene acetates). With respect to minor elements, sulfur contents did not satisfy the quality standard (10 ppm). Among the four woody essential oils, both red pine oil and white pine oil showed slightly lower higher heating values (HHVs; 44.09 MJ/kg and 44.13 MJ/kg, respectively) than diesel fuel. There was a negative correlation between oxygen content and HHV. Density was raised by an increase in the average number of carbon atoms and/or the terpene derivative contents and ranged from 0.875 g/mL for red pine oil to 0.924 g/mL for cedar oil. Based on their higher densities than diesel fuel and although they had lower HHVs, higher energy densities (38.59–39.18 MJ/L) were observed, with the exception of cypress oil. All the woody essential oils satisfied the quality standard for flash point (>40 °C). These flash points should consider both the average number of carbon atoms and terpene derivatives. In contrast, the kinematic viscosity of the essential oils was only affected by the number of carbon atoms. Cedar oil (6.1 mm2/s) had the largest kinematic viscosity followed by cypress oil (2.7 mm2/s), white pine oil (1.6 mm2/s), and red pine oil (1.4 mm2/s). By considering all assessed properties, a terpene mixture similar to the essential oil from red pine oil or white pine oil was deemed the most appropriate alternative biodiesel candidate though its viscosity and sulfur content must be improved.

Structural characterization of asphaltenes derived from nigerian bitumen using the x-ray diffraction technique

ABSTRACTPetroleum asphaltenes consist of complex hydrocarbon molecules that pose a marked difficulty in the production of crude oils. They tend to flocculate and precipitate during oils refinery and this stimulates considerable interest in the elucidation of their molecular structure for improved processing. In this investigation, five bitumen samples obtained from oil sand outcrops at five localities in Nigeria were used. These were treated with n-pentane that necessitates the precipitation of asphaltene. The different asphaltene samples were analyzed by the x-ray diffraction technique to obtain their various structural parameters. The parameters were determined from the peaks of the gamma (γ) band, graphene (c = c) or (002) band and the (10) or (11) band in the diffraction spectra of the respective samples. Slight variations in the distance between the aliphatic chains and the distance between the aromatic sheets were observed for three of the samples, while the remaining two presented significant variations in the structural parameters. Variations in the average number of carbon atoms per aromatic units correspond to the variation in the size and number of aromatic units and aliphatic chains. The variations consequently determined the level of processing necessary to improve the heavy oil (bitumen).

Effect of fatty acid composition on ignition behavior of straight vegetable oils measured in a constant volume combustion chamber apparatus

Straight vegetable oils attracted attention several times as alternative fuel for mobile machinery. Certain efforts have already been undertaken to enable the usage of the high viscous oils in compression ignition engines. While physical properties are well specified for different kind of oils, only few information is available on the ignition behavior of vegetable oils under modern engine like conditions. Therefore, the ignition behavior of nine different vegetable oils and two oil mixtures was investigated using the Advanced Fuel Ignition Delay Analyser (AFIDA). The AFIDA is a modern constant volume combustion chamber apparatus equipped with a high pressure injection system. Analysis was performed at combustion chamber temperatures ranging from 796K to 967K and at air density levels of 4.7kg/m3, 9.3kg/m3 and 17.7kg/m3. Ignition behavior was correlated to the structure indices average number of carbon atoms and average number of double bonds. Both were calculated using the fatty acid composition of the oils. Ignition delay decreased with rising temperature and air density. Coconut oil ignited first at every temperature except for the lowest air density level. Start of combustion was always last for linseed oil, followed by camelina and soybean oil. Ignition delay increased linearly with rising average number of double bonds and decreasing average number of carbon atoms. The effect of the average number of double bonds on ignition delay was more pronounced than that of carbon chain length. Fatty acids with two or more carbon-carbon double bonds led mostly to a stronger increase in ignition delay compared to those with only one double bond.

Characterization of Highly Oxidized Molecules in Fresh and Aged Biogenic Secondary Organic Aerosol.

In this work, highly oxidized multifunctional molecules (HOMs) in fresh and aged secondary organic aerosol (SOA) derived from biogenic precursors are characterized with high-resolution mass spectrometry. Fresh SOA was generated by mixing ozone with a biogenic precursor (β-pinene, limonene, α-pinene) in a flow tube reactor. Aging was performed by passing the fresh SOA through a photochemical reactor where it reacted with hydroxyl radicals. Although these aerosols were as a whole not highly oxidized, molecular analysis identified a significant number of HOMs embedded within it. HOMs in fresh SOA consisted mostly of monomers and dimers, which is consistent with condensation of extremely low-volatility organic compounds (ELVOCs) that have been detected in the gas phase in previous studies and linked to SOA particle formation. Aging caused an increase in the average number of carbon atoms per molecule of the HOMs, which is consistent with particle phase oxidation of (less oxidized) oligomers already existing in fresh SOA. HOMs having different combinations of oxygen-to-carbon ratio, hydrogen-to-carbon ratio and average carbon oxidation state are discussed and compared to low volatility oxygenated organic aerosol (LVOOA), which has been identified in ambient aerosol based on average elemental composition but not fully understood at a molecular level. For the biogenic precursors and experimental conditions studied, HOMs in fresh biogenic SOA have molecular formulas more closely resembling LVOOA than HOMs in aged SOA, suggesting that aging of biogenic SOA is not a good surrogate for ambient LVOOA.

Emission behaviour of vegetable oil fuel compatible tractors fuelled with different pure vegetable oils

The emission behaviour of pure vegetable oils to be used as a fuel was researched using two vegetable oil fuel compatible tractors. The tractor engines were equipped with a common-rail and pump-line injection system. For the research eight different vegetable oils, one vegetable oil mixture and diesel fuel were used. Vegetable oils are basically triacylglycerides and can be characterised by the two structure indices average number of carbon atoms (AC) and average number of double bonds (ADB). The results show that both tractors can be operated with vegetable oils and diesel fuel at about the same level of efficiency. Specific test cycle emissions of nitrogen oxides (NOX) tend to be higher while specific carbon monoxide (CO), hydrocarbon (HC) and particle mass (PM) emissions tend to be lower with the vegetable oils compared to diesel fuel.The emission behaviour of the two tractors was influenced by the type of vegetable oil used.The differences were dependent on the operation mode. At average and high load operation points the emissions of CO, HC and PM were at the same level, whereas the NOX emissions were rising with increasing ADB of the vegetable oils. At low load and idle operation the emissions of CO, HC and PM were rising with increasing unsaturation respectively increasing ADB of the vegetable oils. The observed increase of NOX at average and high load could not be recognized anymore at low load and idle and is even reversed for one tractor. This indicates deteriorated combustion with increasing unsaturation of the vegetable oils at idle and low load.

A new method for the prediction of flash points for ternary miscible mixtures

The flash point is one of the most important physicochemical parameters used to characterize the fire and explosion hazard for flammable liquids. The flash points of ternary miscible mixtures with different components and compositions were measured in this study. Four model input parameters, being normal boiling point, the standard enthalpy of vaporization, the average number of carbon atoms and the stoichiometric concentration of the gas phase for mixtures, were employed and calculated based on the theory of vapor–liquid equilibrium. Both multiple linear regression (MLR) and multiple nonlinear regression (MNR) methods were applied to develop prediction models for the flash points of ternary miscible mixtures. The developed predictive models were validated using data measured experimentally as well as taking data on flash points of ternairy mixtures from the literature. Results showed that the obtained average absolute error of both the MLR and the MNR model for all the datasets were within the range of experimental error of flash point measurements. It is shown that the presented models can be effectively used to predict the flash points of ternary mixtures with only some common physicochemical parameters.

Structural characterization of graphene layers in various Indian coals by X-Ray Diffraction technique

The results of the structural investigation of three Indian coals showed that, the structural parameters like fa & Lc increased where as interlayer spacing d002 decreased with increase in carbon content, aromaticity and coal rank. These structural parameters change just opposite with increase in volatile matter content. Considering the 'turbostratic' structure for coals, the minimum separation between aromatic lamellae was found to vary between 3.34 to 3.61 A° for these coals. As the aromaticity increased, the interlayer spacing decreased an indication of more graphitization of the sample. Volatile matter and carbon content had a strong influence on the aromaticity, interlayer spacing and stacking height on the sample. The average number of carbon atoms per aromatic lamellae and number of layers in the lamellae was found to be 16-21 and 7-8 for all the samples.

Flash points measurements and prediction for binary miscible mixtures

Flash point is one of the most important parameters used to characterize the potential fire and explosion hazards for flammable liquids. In this study, flash points of twenty eight binary miscible mixtures comprised eighteen flammable pure components with different compositions were measured by using the closed cup apparatus. The obtained experimental data are further employed to develop simple and accurate models for predicting the flash points of binary miscible mixtures. Based on the vapor–liquid equilibrium theory, the normal boiling point, the standard enthalpy of vaporization, the average number of carbon atoms, and the stoichiometric concentration of the gas phase were selected as the dominant physicochemical parameters that were relevant to the overall flash point property of liquids. With these parameters for pure components as well as the compositions of mixtures, the new form of characteristic physicochemical parameters for mixtures were developed and used as the input parameters for the flash point prediction of mixtures. Both the modeling methods of multiple linear regression (MLR) and multiple nonlinear regression (MNR) were employed to model the possible quantitative relationships between the parameters for mixtures and the flash points of binary miscible mixtures. The resulted models showed satisfactory prediction ability, with the average absolute error for the external test set being 2.506 K for the MLR model and 2.537 K for the MNR model, respectively, both of which were within the range of the experimental error of FP measurements. Model validation was also performed to check the stability and predictivity of the presented models, and the results showed that both models were valid and predictive. The models were further compared to other previously published models. The results indicated the superiority of the presented models and revealed which can be effectively used to predict the FP of binary miscible mixtures, requiring only some common physicochemical parameters for the pure components other than any experimental flash point or flammability limit data as well as the use of the Le Chatelier law. This study can provide a simple, yet accurate way for engineering to predict the flash points of binary miscible mixtures as applied in the assessment of fire and explosion hazards and the development of inherently safer designs for chemical processes.

Biodegradation of Coal Minerals by Gluconic Acid and its Effect on the Stacking Structure of Carbon: An Investigation

Leaching of minerals (Silicates, Calcium, Aluminum) from bituminous coal by gluconic acid of varying concentration was carried out and the chemical mechanism was studied. Stacking structural parameters of the coal like aromaticity, rank, number of aromatic layers, carbon atoms per aromatic lamellae, stacking height and lattice spacing were determined using X-ray analysis. An ordering of lattice was noticed with gluconic acid leaching and is maximum for 20% and 40% concentration. The number of lyers and average number of carbon atoms per lamellae are found to be varying from 6-7 and 11-17 respectively. The mineral content (Al and Si) shows systematic decrease with increase in concentration of leachant. The optimum demineralization is noticed for the successively leached coal sample with glucoinc acid and mild Hydrofluoric acid.

Systematic investigations of graphene layers in sub-bituminous coal

Coal is the plentiful and widely and universally used fuel. However, its structural characteristic makes a perception that it is only worthwhile for generating energy via combustion. Herein we report a simple method to synthesize nanometre-sized graphene sheets with amorphous carbon addends on the edges from sub-bituminous coal. The X-ray analysis reveals the presence of crystalline carbon in the amorphous background. The average number of carbon atoms and aromatic layers was estimated as ∼21 and 8. The interlayer spacing d 002 for the aromatic lamellae of samples leached using HF and acetic acid, are found to be 0.352 and 0.376 nm, respectively. The oxidation of coal structure resulted in nanometre sized graphene having lateral size of 4.19 nm and stacking height of 2.3 nm. The Raman spectrum analysis confirmed the formation of finite sized, less defective graphene nanolayers with leaching. The crystalline carbon within the coal matrix displaced with chemical leaching, resulting nano-meter sized graphene sheets. The results also established that with HF leaching, carbon in coal becomes more stacked and ordered compared to organic acid leached coal.

Electrochemical properties of novel porous carbon based material synthesized from polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are interesting compounds from both fundamental and applied research points of view, because these molecules can be considered as well-defined cut-outs of graphene. Starting from relatively small PAHs it is possible to electrochemically synthesize in one easy step electroactive films consisting of larger PAH molecules. In the present work benzo(a)pyrene was used as the monomer and by potential cycling in propylene carbonate, porous films were obtained consisting of PAH molecules with an average number of carbon atoms in the range 40–60, evidenced by Raman and infrared spectroscopy. Electrochemical activity during oxidation of the resulting amorphous poly(benzopyrene) (PBP) films was determined in propylene carbonate and acetonitrile by in situ conductance measurements and electrochemical impedance spectroscopy. Additionally, based on impedance spectra a new equivalent circuit was proposed which accurately describes the electrochemical properties of the synthesized PBP films. The model was verified by comparing calculated conductivity values with experimental values obtained from in situ conductance measurements. It was found that PBP films exhibit fast ion transport with electrical conductivity of ∼6.6mScm−1. The results presented in this work imply that PBP is an interesting material for electrochemical applications.

Structural Study of Asphaltenes from Iranian Heavy Crude Oil

In the present study, asphaltene precipitation from Iranian heavy crude oil (Persian Gulf off-shore) was performed using <i>n<i/>-pentane (<i>n<i/>-C<sub>5<sub/>) and <i>n<i/>-heptane (<i>n<i/>-C<sub>7<sub/>) as light alkane precipitants. Several analytical techniques, each following different principles, were then used to structurally characterize the precipitated asphaltenes. The yield of asphaltene obtained using <i>n<i/>-pentane precipitant was higher than asphaltene precipitated with the use of <i>n<i/>-heptane. The asphaltene removal affected the <i>n<i/>-C<sub>5<sub/> and <i>n<i/>-C<sub>7<sub/> maltene fractions at temperatures below 204°C, as shown by the data obtained through the simulated distillation technique. Viscosity of heavy oil is influenced by the asphaltene content and behavior. The viscosity dependence of the test heavy oil on the shear rate applied was determined and the flow was low at y. above 25 s<sup>-1<sup/> . The reconstituted heavy oil samples were prepared by adding different amounts of asphaltenes to the maltenes (deasphalted heavy oil) and asphaltene effects were more pronounced at the low temperature of 25°C as compared with those at the higher temperatures. According to the power law model used in this study the flowability of the test heavy oil exhibited a pseudoplastic character. Structural results obtained from Fourier Transform InfraRed (FTIR) spectroscopy showed the presence of the different functional groups in the precipitated asphaltenes. For instance, the presence of different hydrocarbons (aliphatic, aromatic and alicyclic) based on their characteristics in the FTIR spectra was confirmed. Resins are effective dispersants, and removal of this fraction from the crude oil is disturbing to the colloidal nature of heavy oil; asphaltene flocculation and precipitation eventually occur. Appearance of pores in the Scanning Electron Microscopy (SEM) images was used as an indicator of the resin detachment. With the use of <sup>1<sup/>H and <sup>13<sup/>C Nuclear Magnetic Resonance (NMR) spectroscopy, two important structural parameters of the asphaltenes were determined. Namely, the aromaticity (fa) and the average number of carbon atoms per alkyl side chain (<i>n<i/><sub><i>carbon<i/><sub/>), where <i>f<sub>a<sub/><i/> for <i>n<i/>-C<sub>5<sub/> asphaltenes was lower (0.39) than that obtained with <i>n<i/>-C<sub>7<sub/> solvent (0.49). Additionally, the <i>n<i/><sub><i>carbon<i/><sub/> parameter values were 7.7 and 5.7 for <i>n<i/>-C5 and <i>n<i/>-C<sub>7<sub/> asphaltenes, respectively. Structural recognition of the oil constituents is the prerequisite of different techniques usable for heavy oil upgrading.

Graphical method to select vegetable oils as potential feedstock for biodiesel production

AbstractChemical compositions of 80 vegetable oils were collected from literature and the properties of the obtainable biodiesel (methyl esters) have been predicted by empirical relationships. The purpose has been to check the viability of predicting if a biodiesel could meet the EN 14214 standards knowing only the fatty acid profile (FAP) of the parent oil. Two parameters were used in this investigation: (i) average number of carbon atoms in the fatty acid chains, (ii) average number of double bonds (CC) per molecule. Two new empirical relationships have been proposed to predict the viscosity and the cetane number of biodiesel from the two parameters. The range of values of the two parameters leading to biodiesel meeting the EN 14214 standard for viscosity, cetane number, iodine value, and cold filter plugging point have been graphically obtained by overlapping the corresponding level surfaces.Practical applications: This work provides biodiesel producers with indications of the quality of biodiesel without the need for analytical testing of the product (indeed, of the product itself). Only the fatty acid profile of the starting vegetable oil is required. The quality of biodiesel can be estimated by using a chart developed in this work, allowing to estimate, e.g. if the biodiesel meets the European standards. The work can be useful to rapidly screen oil seed crops in studies of genetic engineering that require high throughput.