Non-aromatic Hydrocarbons Research Articles

ВЛИЯНИЕ СТРОЕНИЯ ЦИКЛИЧЕСКИХ УГЛЕВОДОРОДОВ НА ТЕМПЕРАТУРУ САМОВОСПЛАМЕНЕНИЯ

Using experimental data available in the literature the impact of the molecular structures of cycloalkanes and aromatic hydrocarbons on the auto-ignition temperature is analyzed. Based on contemporary studies of auto-ignition kinetic processes of cyclic nonaromatic and aromatic hydrocarbons, the connection between chemical structure, bond strength in the molecule and features of radical mechanisms of oxidation processes with the auto-ignition temperature is shown. It is noted that unsubstituted cycles usually have the highest auto-ignition temperature. The increase in the structure of substituents the number of methyl groups and double bonds capable to conjugate with benzene ring contributes to an index increase. Alkyl side chains located in the ortho-position, as well as the elongation of the chain of alkyl radicals attached to the ring, reduce the auto-ignition temperature. Polycyclic aromatic structures have a lower auto-ignition temperature than structurally similar benzene derivatives.

Year-round measurement of atmospheric volatile organic compounds using sequential sampling in Dronning Maud Land, East-Antarctica

Antarctica is considered the most pristine environment on Earth but is also characterized by its unique conditions such as the strong polar vortex and extreme cold. A detailed understanding of volatile organic compounds (VOCs) and the atmospheric oxidation reactions they undergo is essential to document biogeochemical cycles and to better understand their impact on radiative forcing. This research aims to provide a unique dataset of oxygenated (O)VOCs occurring in the Antarctic troposphere and provide insights into their temporal behavior. A home-made sequential sorbent tube auto sampler was deployed at the atmospheric observatory of the Princess Elisabeth station (71.95° S, 23.35° E, 1390 m asl) to collect 20 samples during the period from December 2019 to October 2020. The samples were analyzed consecutively by TD-GC-MS followed by direct thermal desorption of samples in a high-resolution PTR-Qi-TOFMS.Concentrations of 70 VOCs allocated to 4 different chemical groups (halogenated compounds, non-aromatic hydrocarbons, sulfur-containing compounds, and oxygenated aromatic and non-aromatic compounds) were determined. The results show temporal patterns for compounds such as bromoform (14 ± 6 ng/m3) and OVOCs such as furaldehyde (24 ± 9 ng/m³), amongst others, which are attributed to the seasonality of atmospheric conditions. Products of the atmospheric oxidation process show linear correlation indicating their mutual relationship and association with a common parent compound.The usage of an autonomous autosampler in the extreme conditions of Antarctica was demonstrated and proved to be a powerful tool in the sampling of air in such a remote location. The novel approach of using two analytical techniques boasts increased sensitivity and a broad range of compounds that can be detected, yielding the first dataset of its kind for Antarctica.

Extraction of methylcyclohexane−toluene mixture using imidazolium ionic liquids

Separation of aromatics from non-aromatic hydrocarbons was exemplified assuming the liquid-phase extraction process for methylcyclohexane−toluene model mixture separation using the newly tested 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMim][NTf2]) ionic liquid (IL). For this process a separation unit was proposed consisting of separation part represented by a counter-current extraction column and regeneration part including a vacuum evaporator and a vacuum distillation column. Separation of feed composed of 10 mole% of toluene in methylcyclohexane was considered in the designed separation unit. Designed separation efficiency of the unit was based on the following specifications: minimum methylcyclohexane and toluene content in the product streams of 99.5 mole% and the purity of regenerated extraction solvent recycled to the extraction column above 99 mole%.Mathematical model of a counter-current extractor was compiled and its operation was simulated in the Matlab environment. In extractor simulations, proprietary phase equilibrium data were employed. Ternary liquid–liquid equilibrium (LLE) of the methylcyclohexane−toluene−[EMim][NTf2] system was estimated experimentally, from which the model parameters of the original NRTL equation were evauated and used for the ternary phase equilibrium description.Aspen Plus was used to design a separation unit for the title hydrocarbons mixture separation, including the extraction solvent regeneration. Simulation of the proposed separation unit operation was focused not only on its separation efficiency but also on the evaluation of the unit energetic requirements.Results of the unit design calculations (parameters of individual equipment, heat duties) obtained for the tested ionic liquid [EMim][NTf2] were confronted with the simulation results obtained for two ILs recommended in the literature for the non-aromatic–aromatic hydrocarbon mixture separation, namely 1‑butyl‑3-methylimidazolium tetracyanoborate [BMim][TCB] and 1-hexyl-3-methylimidazolium tetracyanoborate [HMim][TCB]. Based on the energetic analysis, the heat integration of the suggested separation unit was carried out for ionic liquid [HMim][TCB], which appeared to be the most efficient extraction solvent among those tested in this study, The heat integration resulted in about 71% reduction of the heat demand of the proposed separation unit.

ОПРЕДЕЛЕНИЕ СОДЕРЖАНИЯ АРОМАТИЧЕСКИХ УГЛЕВОДОРОДОВ В МИНЕРАЛЬНЫХ МАСЛАХ МЕТОДОМ ЯМР-РЕЛАКСАЦИИ

Molecular group composition analysis of mineral oils is helpful to predict the performance of a future lubricant and to assess the compatibility of plasticizer oil with rubbers. The method of pulsed low-frequency NMR relaxation was used to determine the molecular group composition of 11 mineral oil samples, and the ratio of aromatic and non-aromatic hydrocarbons in them was calculated. NMR measurements were performed on a Chromatec-Proton 20M NMR analyzer with a 1H resonance frequency of 20 MHz. The method used consists in recording free induction decay signals, reconstructing the total signal amplitude, estimating the relative signal amplitude per unit mass of the sample, and calculating the proportion of aromatic hydrocarbons in the sample. The results were compared with those obtained by the standard chromatographic method. A high degree of correlation (R2 = 0.99) was observed between the results.

Pyrolysis-GCMS of Spirulina platensis: Evaluation of biomasses cultivated under autotrophic and mixotrophic conditions.

Microalgae are autotrophs and CO2 fixers with great potential to produce biofuels in a sustainable way, however the high cost of biomass production is a challenge. Mixotrophic growth of microalgae has been presented as a great alternative to achieve economic sustainability. Thus, the present work reports the energetic characterization of S. platensis biomasses cultivated under autotrophic (A) and mixotrophic conditions using cheese whey waste at different concentrations, 2.5 (M2.5), 5.0 (M5) and 10.0% (M10), in order to analyze the potential production of valuable chemicals and bio-oil by TGA/DTG and Py-GC/MS. The biochemical compositions of the studied biomasses were different due to the influence of different culture mediums. As the whey concentration increased, there was an increase in the carbohydrate content and a decrease in the protein content, which influenced the elemental composition, calorific value, TGA and volatile compounds evaluated by Py-GC/MS at 450°C, 550°C and 650°C. Sample M10 had lower protein content and formed a smaller amount of nitrogenates compounds by pyrolysis at all temperatures evaluated. There was a reduction of 43.8% (450º), 45.6% (550ºC) and 23.8% (650ºC) in the formation of nitrogenates compounds in relation to sample A. Moreover, the temperature also showed a considerable effect in the formation of volatile compounds. The highest yields of nitrogenates compounds, phenols and aromatic and non-aromatic hydrocarbons were observed at 650ºC. The oxygenated, and N and O containing compounds decreased as the temperature increased. Hydrocarbons such as toluene, heptadecane and heneicosane were produced by S.platensis pyrolysis, which makes this biomass attractive for production of high quality bio-oil and valuable chemicals. Therefore, the results showed that it is possible to decrease the formation of nitrogen compounds via manipulation of growth conditions and temperature.

Waste tyres valorisation through gasification in a bubbling fluidised bed: An exhaustive gas composition analysis

Waste tyres gasification in a bubbling fluidised bed reactor is evaluated by means of a complete characterisation of the product gas. The experiments are carried out at two temperatures, 700 and 850 °C, and various equivalence ratios (ER) while using air as a gasifying. Additionally, the effect of steam is also studied at 850 °C. High temperature and low ER increase the production of H2, CH4, and C2H4. Steam addition mainly affects H2 and CO production. Low carbon conversion (CC) into gas and cold gas efficiency (CGE) are obtained, increasing with temperature and ER. The lower heating value (LHV) of the gas decreases with the ER because of the higher partial combustion rates. LHV values range between 12 MJ/Nm3 with steam addition at ER = 0.13 and 850 °C to 5.3 MJ/Nm3 at ER = 0.33 and 700 °C using air only. Along with a major permanent gas (CO2, CO, H2, CH4, and C2Hn), up to 25 short-chain hydrocarbons (non-aromatic hydrocarbons ranging from C3 to C6+) and two light aromatics are present in the product gas. Among short-chain hydrocarbons, C3 and C4 compounds are present in the highest yields. All these minor hydrocarbon species (i.e., C3 to C6+), not usually reported in biomass or waste gasification studies, yield up to 13 %vol. on a N2-free basis. Their contribution to the gasification performance is important because they account for half of the energy content in the product gas. Therefore, it is important to consider them in the gasification process, not only for energy purposes but also for the chemical industry.

Highly efficient separation of benzene + cyclohexane mixtures by extraction combined extractive distillation using imidazolium-based dicationic ionic liquids

Benzene (BEN) and cyclohexane (CYH), which have very close boiling points and a binary azeotrope, are the most difficult binary components in the separation of aromatic and non-aromatic hydrocarbons. This study further explored the separation mechanism and industrial application prospects of BEN ​+ ​CYH mixtures separated by a dicationic ionic liquid (DIL) [C5(MIM)2][NTf2]2 based on experimental research. The calculation results of the Conductor-like Screening model Segment Activity Coefficient (COSMO-SAC) model show that selectivity and solvent capacity of the DIL are significantly improved. The effects of different anions and cations on the microstructure distribution and diffusion behavior of BEN ​+ ​CYH system were investigated by quantum chemistry (QC) calculations and molecular dynamics (MD) simulations. The results indicate that the anion [NTf2]− has low polarity, uniform charge distribution, and a dual role of hydrogen bonding and π-π bonding, and the cation [C5(MIM)2]2+ has stronger interaction with BEN and higher selectivity than conventional cations. The liquid-liquid extraction and extractive distillation (LLE-ED) process using an optimized 65 mol/mol DIL ​+ ​35 mol/mol H2O mixed solution as the extractant was proposed, which solved the problem of low product purity in the LLE process and high energy consumption in the ED process. Under the best operating conditions, the purity of CYH product was 99.9%, the purity of BEN product was 99.6%, the recovery rate of BEN reached 99.9%, and the recovery rate of DIL reached 99.9%. The heat-integrated LLE-ED process reduced total annual cost by 21.6%, and reduced CO2 emissions by 48.0%, which has broad industrial application prospects.

Toxic Toys Threaten the Health of the Children: An Appraisal of Potential Literature

Children are considered highly susceptible due to their exposure to the environmental pollutants from the toys, playing dough and paint colors. Despite of graving nature of problem, few studies are conducted on the associated risk factors and environmental pollutants. The current review put an effort on exploration the studies of environmental pollutants in children play products and its related effects on children’s health. The methods of pollutant’s detection were also discussed. The studies covered showed environmental toxicants including a wide range of heavy metals, volatile organic compounds, nonaromatic hydrocarbons, and Bisphenol A and flame retardants. Few studies has reported Chromium (555±144mg/kg) in Chinese-manufactured play dough, Cadmium (10±1.4 mg/kg) in the toy paints of China, and lead (293.8±184.5 mg/kg) in the toy paint of USA. Therefore, a dire need of research and strong legislation is needed to create awareness to protect the health of children. Keywords: Exposure, environmental pollutants, health effects, risk factors

Experimental study on combustion and unregulated emission characteristics of a diesel engine fueled with light hydrocarbon/diesel blends

Rigorous emission regulations are provoking to pursue substitute of diesel with clean and sustainable alternative fuels to work out the problem of the regulated and unregulated emissions and diesel depletion. In this paper, the partial load characteristics of emission especially unregulated and combustion characteristics of a six-cylinder compression ignition diesel engine fueled with conventional diesel and 85% light hydrocarbon (LHC)-diesel blends were investigated and compared at the load points of 50%, 75% and 100% and the speed of 1000 rpm. Gas chromatography-mass spectrometry (GC–MS) technology was utilized to identify components of both tested fuel and unregulated emissions. The cylinder pressure, pressure rise rate, indicated power, heat release rate and emissions were comparatively analyzed between these two fuels. The gaseous pollutants including NOx, CO and total hydrocarbon (THC) are determined by gas analyzer. Based on the experimental results, blending LHC extend the ignition delay period, thus leading to its combustion phase lag behind that of diesel fuel by 3°CA. Significant reduction in specific NOx and CO emissions was noted while THC emission is higher in engine fueling LHC/diesel blends. The dominant unregulated pollutants primarily include organosilicon compounds (OSC), aromatic compounds (AC), and non-aromatic hydrocarbons and their derivatives (NAHC). The determinant factors on OSC emissions are summarized into the content of antifoaming agents in lubricants and the load conditions. The AC emissions of both fuels have an ascending tendency with the increase of load and the AC emissions of LHC/diesel blends are obviously less than that of pure diesel. The NAHC emissions usually appear under higher load conditions with regard to LHC blends and the content is far lower than that of diesel. In a word, blending diesel with LHC significantly contributes to improve both combustion and emission characteristics.

Taming the stilbene radical anion.

Radical anions appear as intermediates in a variety of organic reductions and have recently garnered interest for their role as mediators for electron-driven catalysis as well as for organic electron conductor materials. Due to their unstable nature, the isolation of such organic radical anions is usually only possible by using extended aromatic systems, whereas non-aromatic unsaturated hydrocarbons have so far only been observed in situ. We herein report the first isolation, structure and spectroscopic characterization of a simple aryl substituted alkene radical anion, namely that of stilbene (1,2-diphenyl ethylene), achieved by encapsulation between two [K{18c6}] cations. The formation of the radical anion is accompanied by Z → E isomerization of the involved double bond, also on a catalytic scale. Employing the linear iron(i) complex [Fe(NR2)2]- as a reductant and coordination site also allows for this transformation, via formation of an iron(ii) bound radical anion. The use of the iron complex now also allows for Z → E isomerization of electron richer, simple alkenes bearing either mixed alkyl/aryl or even bis(alkyl) substitution.

Controlling hydrocarbon oligomerization in phosphorus-modified CHA zeolite for a long-lived methanol-to-olefin catalyst

The catalytic performance of phosphorus-modified CHA zeolites, synthesized by direct phosphorus modification using tetraethylphosphonium as a phosphorus-modifying agent (P-MA), was investigated for the methanol-to-olefin (MTO) reaction. Comparative catalytic testing in the MTO reaction revealed that the phosphorus modification effectively prolonged the catalyst lifetime while hardly affecting the ethene and propene selectivities. The initial ethene and propene selectivities over CHA zeolite with P/Al ratio of 0.44 were 28.7 and 37.5 C %, respectively, and the catalytic life time improved from 4 to 7 h compared with the catalyst without phosphorus modification. The relative amount of non-aromatic hydrocarbons retained in the zeolite catalysts with respect to those of the aromatic ones increased with increasing degree of phosphorus modification. This demonstrates that the suppression of excess oligomerization of the hydrocarbon species results in a prolonged lifetime in the phosphorus-modified catalyst.

Pyrolysis technology for Cortaderia selloana invasive species. Prospects in the biomass energy sector

Cortaderia selloana (CS), is an invasive and exotic species that is generating significant invasive problems in the Iberian Peninsula ecosystems. The objective of this research was to study this plant potential thorough a pyrolytic process helping to reduce its expansion. Stems and leaves were subjected to conventional and flash pyrolysis. These processes were carried out in an original design oven using a 25 °C/min heating ramp at a 750 °C temperature and during 60 min at the pyrolysis temperature for conventional pyrolysis and with 750 °C and 850 °C pyrolysis temperatures for flash. Gas-fraction obtained by flash pyrolysis had higher HHV data when compared with conventional ones (∼17 MJ/kg vs ∼5 MJ/kg) due to their less CO2 and higher CO, CH4 and H2. The greater bio-oil yield was obtained for CSS-P (33.58%). The composition of conventional pyrolysis bio-oils had an overbearing of nonaromatic and monoaromatic hydrocarbons nature whereas bio-oils from flash pyrolysis were composed mainly of polycyclic aromatic hydrocarbons. Bio-char fraction was higher in CSL than CSS with HHV similar to lignite and bituminous coals (22.74–29.12 MJ/kg). After done the quantification and characterization of the fractions, it was concluded that a possible energetic valorization of Cortaderia selloana biomass was possible.

Detonation Nanodiamonds: A Comparison Study by Photoacoustic, Diffuse Reflectance, and Attenuated Total Reflection FTIR Spectroscopies.

The qualitative analysis of nanodiamonds by FTIR spectrometry as photoacoustic (FTIR–PAS), diffuse-reflectance (DRIFT), and attenuated total reflection (ATR) modalities was evaluated for rapid and nondestructive analysis and comparison of nanodiamonds. The reproducibility and signal-gathering depth of spectra was compared. The assignment of characteristic bands showed that only six groups of bands were present in spectra of all the modalities with appropriate sensitivity: 1760 (C=O stretch, isolated carboxyl groups); 1640–1632 (H–O–H bend, liquid water); 1400–1370 (non-carboxyl C–O–H in-plane bend and CH2 deformation); 1103 (non-carboxyl C–O stretch); 1060 (in-plane C–H bend, non-aromatic hydrocarbons and carbohydrates); 940 cm−1 (out-of-plane carboxyl C–O–H bend). DRIFT provides the maximum number of bands and is capable of measuring hydrogen-bonded bands and CHx groups. ATR provides the good sensitivity for water and C–H/C–C bands in the range 2000–400 cm−1. FTIR–PAS reveals less bands than DRIFT but more intense bands than ATR–FTIR and shows the maximum sensitivity for absorption bands that do not appear in ATR-IR spectra and are expedient for supporting either DRIFT or FTIR–PAS along with depth-profiling. Thus, all three modalities are required for the full characterization of nanodiamonds surface functional groups.

Free-volume theory coupled with modified group-contribution PC-SAFT for predicting the viscosities. I. Non-associated compounds and their mixtures

The modified group contribution PC-SAFT (Fluid Phase Equilibria, 2016.430: p. 33–46, https://doi.org/10.1016/j.fluid.2016.09.020) has been combined with the Free Volume theory (FVT) to estimate fluid viscosities. The proposed model does not require critical constants or acentric factor of fluid as input parameters, while the correlation of the FVT parameter triplet is used to estimate the viscosity of n-alkanes, (up to n-C64H130), aromatics, non-aromatic hydrocarbons and small gases. The universal FVT parameters working with mg-SAFT for n-alkanes were used to predict the viscosity of heavy molecules at extreme pressure condition (up to 5000 bar). For all cases, an overall average relative deviation is around 3% compared to experimental data. The new approach empowers mg-SAFT with new predictive ability, allowing to simultaneously calculate fluid phase equilibria and viscosity with the same degree of accuracy.In addition, a new, simple and effective mixing rule was also proposed. It can yield very satisfactory predictions for liquid viscosity of several binary and multi-component mixtures from atmospheric to high pressure, with an overall average deviation of 2.46% for 87 considered mixtures.

Raman Spectroscopic Investigation of Olefins in Saturated Hydrocarbons and Self-Tuning Model Development

Based on systematized collection of Raman spectra of about 40 monounsaturated olefins, spectral patterns and invariant relations were established that formed the basis of the method for determining total olefins (total unsaturation per 100 carbon atoms) and their main classes in solutions of saturated hydrocarbons. Self-tuning of the model by calculating the proportion of spectrally unresolvable C=C components using the intensity of conjugated methyl groups increased its accuracy. In terms of repeatability, speed and cost-effectiveness of the analysis, the Raman-method is superior to standard methods of gas and adsorption chromatography and other modern spectralcorrelation methods. The accuracy and stability of the results repeatability is confirmed by more than annual series of parallel comparisons with the data of known method. It is shown that five types of olefins in paraffin model solutions are sufficient to construct calibration curves in units of the number of C=C bonds per 100 carbon atoms. These units make it possible to transform the data to the iodine scale and unify the calibration model for different fractions regardless of the hydrocarbon chain length. The Raman technique can be extended to analyze other mixtures of nonaromatic hydrocarbons and be used for remote control of processes via fi ber optic cables in industrial production.

CHROMATOGRAPHIC MASS-SPECTROMETRIC STUDY OF VOLATILE EMISSIONS OF ETHER-BEARING PLANTS FOR CHEMICAL SAFETY ASSESSMENT OF THEIR USE IN ENCLOSED SPACES

Issues of improving the environment are now among the most important for the population of large administrative and industrial cities. Improving the quality of the environment and creating comfortable living conditions for people using environmentally friendly methods is the one of most up-to-date directions in environmental health. Improving the quality of the internal environment of the premises involves the use of various modern technical life support systems to regulate parameters of the environment. However, existing methods of cleaning and air conditioning of public and industrial premises not only fail to provide the required quality of cleaning, but also can often lead to the appearance of toxic substances, promote deionization of air and deterioration of its quality according to by biological indices. Both to clean and improve the air and give it the properties that are favorable for the life-activity of a person, phytodesign methods are used. The most popular in the gardening of interiors are tropical, subtropical and aromatic plants. Their application is due to their release in the process of vital activity in the environment of biologically active substances - phytoncides, which can improve the air composition, reduce the number of bacteria, fungi, viruses and have a therapeutic effect. Chromatographic-mass-spectrometric studies of the composition of volatile organic components of ether-bearing plants of phytocomposites, when used for artificial illumination of phytolamps with narrow spectral red and blue light, have shown that 26 organic compounds have been identified in the composition of volatile discharges of phytomodule plants grown under natural illumination. The greatest contribution to the component composition of the mixture was made by saturated hydrocarbons (36%). The contribution of oxygen-containing compounds, including phenols, was 13%, aldehydes and cyclic non-aromatic hydrocarbons -12 and 11% respectively. Despite the usefulness of additional artificial lighting for plants, an increase in the amount of substances has been established with the formation of new compounds and an increase in the total content of the identified substances. There was an increase in the content of toxic phenol (by 14 times), benzaldehyde (by 10 times) and acetophenone (by 7 times). The most hygienic significance was the group of terpenic hydrocarbons, which belongs to the group of readily convertible substances, as well as groups of oxygen-containing compounds (aldehydes, ketones, phenols, ethers), which belong to the naturally occurring entities of the toxic and dangerous groups of chemicals. More than 50% of the identified compounds did not have hygienic standards, it is not possible to assess their danger or safety for human health. The use of ether-bearing plants in closed rooms requires the chemical-analytical control of the composition of volatile emissions and the establishment of optimal conditions (saturation of plants in the room, room volume, the presence of conditioning or ozonizing units, temperature regime, humidity, etc.) in order to provide the chemical safety for human health.

A PC-SAFT model for hydrocarbons I: Mapping aromatic π-π interactions onto a dipolar free energy

Aromaticity is an important property of many petroleum derived streams. Traditional thermodynamics tools (e.g., cubic equations of state) do not provide any special treatment to these aromatic hydrocarbons. A feature which discriminates aromatics from paraffins is that aromatic rings exhibit anisotropic π-π interactions. Accounting for this key difference between aromatic and non-aromatic hydrocarbons in an equation of state will allow for a level of predictability which is not possible with our current tools. By mapping the anisotropy of π-π attractions onto a dipolar free energy, we develop a simple and powerful treatment of aromatic hydrocarbons within the PC-SAFT equation state. We demonstrate that this approach provides a substantial increase in performance over the standard non-polar treatment of aromatic molecules. The methodology developed is used to develop a generalized hydrocarbon model in instalment II of this series.

A Method for the Quantitative Analysis of a Key Component in Complex Mixtures Using Raman Spectroscopy Based on Peak Decomposition.

Raman spectroscopy has been increasingly used in industrial production processes for analytical purposes. However, the quantitative analysis of complex mixtures based on their Raman spectra remains a problem, especially when not all of the spectra of pure components in the mixture are available. In this work, a method for the quantitative analysis of a key component in complex mixtures based on peak decomposition is introduced. The proposed method only requires the spectrum of the main component in the mixture before analysis. The spectra of the mixture are decomposed to the contributions of the main component and a group of parametric Lorentzian functions. Then, the representative peaks of the key component are extracted. Finally, a calibration model is established. This method is applied to a complex mixture containing m-xylene, o-xylene, p-xylene, ethylbenzene, methylbenzene, three trimethylbenzenes, non-aromatic hydrocarbons, etc. to determine the concentration of o-xylene in the mixture. Experiments demonstrate that the proposed method performs better than the commonly-used partial least squares (PLS), especially when the number of training samples is very small.

The capability of organic compounds to swell acrylonitrile butadiene O-rings and their effects on O-ring mechanical properties

As interest in replacing petroleum-derived aviation fuels with resilient, alternative fuels increases, the ability to derive correlations between the chemical compositions of aviation fuels and their properties and performance becomes more important. In this work, correlations between the exact chemical structures of organic compounds and their ability to increase the volume and decrease the tensile strength of Buna-N o-ring seals were explored. Buna-N o-ring seals are a representative group of essential seals in the hydraulic and pneumatic components of aircraft fuel delivery systems. They are utilized to prevent fuel leakage within the pumps, metering devices, and connectors. To measure the volume swell percent of o-ring seals caused by various organic compounds, a test rig was assembled that suspended o-ring seals in neat Sasol IPK (isoparaffinic kerosene) or in Sasol IPK doped individually with an organic compound at 8% by volume. Of the aromatic compounds tested, ethylbenzene and indane swelled o-ring seals most effectively, with volume swell percent values of 3.1 ± 0.2% and 2.8 ± 0.1%, respectively. In comparison, the approved aviation fuel Jet A/HEFA has volume swell percent value of 2.2 ± 0.2%. Alkylbenzenes with a smaller number of alkyl groups, less branching in the alkyl groups, and shorter alkyl chains caused greater swelling and greater decrease in the tensile strength for o-ring seals. Naphthene-containing aromatic compounds (i.e., indane and tetralin) swelled o-ring seals more effectively than alkylbenzenes with the same number of carbons (i.e., n-propylbenzene and n-butylbenzene). Therefore, steric hindrance seems to have an important impact on the ability of these compounds to swell o-rings. Nonaromatic unsaturated hydrocarbons, such as cyclohexene, were also found to swell o-ring seals to some extent. On the other hand, saturated hydrocarbons, such as cyclohexane, contributed to minimum or no swelling. Tensile strengths of intact o-rings were measured using an MTS Insight Electromechanical Testing Instrument. Aromatic compounds that facilitated greater swelling of o-ring seals also caused greater decrease in the tensile strength. For example, ethylbenzene and sec-butylbenzene, with volume swell percent values of 3.1 ± 0.2% and 0.9 ± 0.1%, respectively, reduced the o-ring tensile strength from 15.4 MPa to 13.6 MPa and 14.9 MPa, respectively. Additional experiments demonstrated that volume swell and tensile strength of o-ring seals are reversible properties. Hence, a decrease in tensile strength for o-ring seals does not imply irreversible damage. Overall, the extent of volume swelling and the lowering of tensile strength for o-ring seals was found to depend on the exact chemical structure of the organic compound.

Response of microbial community structure and metabolic profile to shifts of inlet VOCs in a gas-phase biofilter

The effects of inlet VOCs (Volatile Organic Compounds) shifts on microbial community structure in a biofiltration system were investigated. A lab-scale biofilter was set up to treat eight VOCs sequentially. Short declines in removal efficiency appeared after VOCs shifts and then later recovered. The number of OTUs in the biofilter declined from 690 to 312 over time. At the phylum level, Actinobacteria and Proteobacteria remained dominant throughout the operation for all VOCs, with their combined abundance ranging from 60 to 90%. The abundances of Planctomycetes and Thermi increased significantly to 20% and 5%, respectively, with the intake of non-aromatic hydrocarbons. At the genus level, Rhodococcus was present in the highest abundance (≥ 10%) throughout the experiment, indicating its wide degradability. Some potential degraders were also found; namely, Thauera and Pseudomonas, which increased in abundance to 19% and 12% during treatment with ethyl acetate and toluene, respectively. Moreover, the microbial metabolic activity declined gradually with time, and the metabolic profile of the toluene-treating community differed significantly from those of other communities.