Acrylonitrile Concentration Research Articles

Polymerization of acrylonitrile in dimethyl carbonate: A kinetic and mechanistic study

For the first time, a new polymerization medium, dimethyl carbonate (DMC), was used for the polymerization of acrylonitrile (AN), and polyacrylonitrile (PAN) powder was obtained successfully. The effects of polymerization factors, including monomer concentrations, temperature and initiator concentrations on the structures and properties of PAN powders were investigated by nuclear magnetic resonance spectroscopy (NMR), total internal reflectance Fourier transform infrared spectrometer (FTIR), wide-angle X-ray diffractometer (WXRD) and thermal gravimetric analyzer (TGA). The polymerization kinetic and mechanistic study of PAN with DMC as the polymerization medium were discussed in details. There are three key achievements in this paper. First, the kinetic equation of PAN polymerization with DMC as a medium was established: Rp = K[ABVN]0.92[AN]6.78. This result shows that the Rp is highly dependent on the AN concentrations. Second, the chain transfer constant of DMC was measured to be 4.57 × 10−4 at 60 °C, and the chain transfer constant increases with polymerization temperature. Lastly, the structures and properties of PAN powders prepared with H2O, tetrahydrofuran (THF) and DMC as media were compared. The results showed that the PAN prepared with DMC as a medium by free radical polymerization had a higher conversion, molecular weight and better crystalline property compared to THF. These findings indicate that DMC is a promising medium for manufacturing high quality PAN powder by free radical polymerization.

Graft Copolymerization of Acrylonitrile onto Banana Cellulose Fiber

The graft co-polymerization of acrylonitrile monomer (AN) onto banana cellulose fiber (BCF) was carried out using ceric ammonium nitrate (CAN)/oxalic acid (OA) as redox pair in the aqueous nitric acid medium at 90 ºC. The effect of different reaction conditions on the grafting has been studied by determining the grafting parameters, i.e. concentration of acrylonitrile, ceric ammonium nitrate, oxalic acid, nitric acid, reaction time and temperature were carefully optimized to achieve the highest rate of grafting polymerization (RG), highest percent grafting yield (%GY) and grafting efficiency (%GE). All the reagents enhanced the RG%, GY% and %GE, with an increase of concentration up to a certain extent and then found to decline, except for the concentration of nitric acid. The grafting parameters were also increased with time/duration and temperature. The water retention value (WRV) of the grafted co-polymer was also measured. Activation parameters such as energy of activation (Ea), enthalpy change (ΔH), entropy change (ΔS) and free energy change (ΔG) can also be reported by using the Arrhenius plot. The evidence of grafting can also be predicted by the FTIR spectral analysis, moreover, the organic reaction mechanism has been proposed.

Evaluation and modeling of acrylonitrile migration from polypropylene for food packaging.

This study validated an analytical technique using headspace gas chromatography with flame ionization detection to quantify acrylonitrile monomer with a quantification limit of 0.10±0.04µg kg-1 . Subsequently, the acrylonitrile migration from polypropylene granules was evaluated in food simulants water and ethanol (50% v/v) and at two temperatures (20±1°C and 44±2°C) for up to 6weeks, representing the service time of a bottle. From the experimental data obtained, pseudo-second-order kinetics were adjusted to represent the acrylonitrile migration into the simulants. For water, equilibrium concentrations of 13.58 and 16.58µg kg-1 at 20 and 44°C, respectively, were obtained, while for 50% ethanol, 15.07 and 16.40µg kg-1 were obtained for the same temperatures. The experimental results and the values estimated from the migration kinetics indicate that the maximum acrylonitrile concentration will not exceed the tolerable specific limit established in regulations. PRACTICAL APPLICATION: The migration of compounds such as acrylonitrile can be a drawback resulting in an undesirable reduction in the shelf life of liquid foods packaged in bottles made of materials such as polypropylene. In this paper, acrylonitrile migration kinetics and a methodology are proposed to determine whether the tolerable migration limits are ever reached, which can serve as a tool for producers of this type of packaging of food to predict shelf life.

In Situ Analysis of the Effect of Tetraakylammonium Salts on the Selectivity and Efficiency of Acrylonitrile Electrohydrodimerization

Traditional chemical manufacturing processes are primarily powered by fossil-fuel combustion, and often require operation at elevated temperatures and pressures. Introducing electrosynthesis as an alternative to thermal processes at industrial scale can allow direct integration of renewable electricity with chemical manufacturing, accelerating the decarbonization of large-scale chemical processes. However, there are major challenges that must be addressed before implementing organic electrosynthesis on an industrial level, such as the low solubility of organic reactants in aqueous electrolytes and the existence of multiple reaction pathways that lead to undesired byproducts. In this presentation, we will discuss our work on electrolyte design strategies to enhance the performance of adiponitrile (ADN) electrosynthesis. ADN is a large volume precursor of hexamethylenediamine, which is a monomer used in Nylon 6,6 manufacturing. The most commonly used method for ADN production, the thermochemical hydrocyanation of 1,3-butadiene, is energy intensive and uses hydrogen cyanide, a highly toxic reactant. Alternatively, ADN can be produced electrochemically via the hydrodimerization of acrylonitrile (AN), which is the largest and most successful industrial organic electrochemical process. In this reaction, the addition of tetraalkylammonium (TAA) salts as supporting electrolytes in large concentrations has been widely accepted to enhance the solubility of organic reactants. It has been hypothesized that TAA ions boost the selectivity towards ADN by increasing the AN concentration in the electrical double layer (EDL). Recent studies by our group explored the effect of the molecular size and concentration of TAA ions on the selectivity and efficiency of ADN production. Resulting trends suggest that the reaction is strongly limited by mass transport of organic reactants to the EDL at high current densities. Despite these advances, the local effects of TAA ions on the concentration of reactants and intermediates in the EDL remain unclear. Inspired by prior demonstrations, we developed a spectroelectrochemical method for quantitatively assessing the concentration of species at the electrode/electrolyte interface. This method relies on an electrochemical flow cell integrated with an attenuated total reflection (ATR) Fourier-transform infrared (FTIR) spectrometer to quantify concentrations of reactive species in the near-electrode region. Our results demonstrate that the presence of TAA ions increases the local concentration of AN at the electrode, and that applied potential increases TAA ion concentration. These results provide insights into the effects of supporting ions and potential in organic electrosynthesis selectivity.Figure caption: Schematic view of the enhancement of acrylonitrile (AN) concentration in the electrical double layer (EDL) by the addition of Tetrabutylammonium (TBA) ions to the aqueous electrolyte. Figure 1

Nitrogen–Fluorine co-doped TiO2/SiO2 nanoparticles for the photocatalytic degradation of acrylonitrile: Deactivation and regeneration

In this study, we investigated the deactivation kinetics and mechanism of N–F–TiO2/SiO2 nanopowder as a model photocatalyst for the purpose of facilitating the photocatalytic degradation of acrylonitrile (AN) in aqueous environment. Prior research has already displayed the proficient degradation of AN through the utilization of N–F–TiO2/SiO2 catalysts, revealing a degradation efficiency of 81.2% within a span of 6 min at an initial AN concentration of 10 mg/L. Multiple variables including the initial AN concentration, illumination intensity, and initial pH value were extensively analyzed during the degradation process. The kinetics of photocatalytic degradation of AN, facilitated by the N–F–TiO2/SiO2 photocatalyst, were modeled by fitting the pseudo first-order reaction kinetics to each individual factor. Furthermore, the adverse effect of catalyst poisoning during the photocatalytic breakdown of AN using the N–F–TiO2/SiO2 photocatalyst was analyzed through a range of different techniques including SEM, XPS, BET, XRD, TG, and NH3-TPD. The incorporation of findings from these diverse techniques revealed that, the primary factors contributing to the photocatalyst's poisoning were as follows: (i) During the degradation process, the build-up of intermediate molecules on active sites hindered their functionality, leading to a decrease in the efficiency of the photocatalytic reaction, (ii) Carbonaceous deposits formed when the catalyst's pore structure was obstructed by pollutants or intermediate products that had not undergone timely photocatalytic breakdown and (iii) The persistent erosion of active sites due to hydraulic forces resulted in inadequate performance of the N–F–TiO2/SiO2 photocatalyst in aqueous solutions. A comprehensive analysis of the deactivation kinetics was conducted, deciding in the formulation of a detailed poisoning mechanism for the N–F–TiO2/SiO2 photocatalyst. Additionally, we explored the catalysts regeneration, involving thermal treatment, ultrasonic irradiation, and catalyst reloading. This study not only advances our insight into the waning performance of catalysts in aqueous media but also establishes a conceptual framework for extrapolating analogous deactivation dynamics in other catalysts, grounded in precedent experimental knowledge. This research contributes to the development of a deactivation model for catalysts in the aqueous environment, based on existing experimental research, providing a theoretical framework for understanding the deactivation process of photocatalysts.

Characteristics of Hazardous Substances Extracted from Laundry Water for Fire Protection Suit Exposed to Fire

(1) Background: It is well known that various toxic substances, including carcinogens, are generated at the fire scenes, so it is very important for firefighters to wear comprehensive personal protective equipment. The extent of the type and amount of harmful substances contained in the washing water of fire protection suits (FPS) exposed to fire scenes have not yet been confirmed. The purpose of this study is to evaluate the characteristics of harmful substances contained in wash water extracted from FPSs exposed to fire. (2) Methods: The study design was a simulation-based experimental study. To evaluate the degree of contamination exposure of FPSs, 10 sets of fire suits were classified into four groups as follows: newly supplied, field use, one fire exposure, and two consecutive fire exposures. In the experimental environment, after exposing three to four groups of FPSs to residential fire conditions. they were sealed in a plastic bag in the experimental space. The washing water for FPSs was extracted through manual washing in the order of Groups 1 to 4, and 24 items were analyzed according to the water pollution process test standards. (3) Results: According to the results of the FPS laundry analysis, the concentration of acrylonitrile in laundry was higher when exposed to fire twice than when exposed to fire once. Moreover, there was a dose–response relationship, and the risk of cumulative toxicity was shown. Naphthalene and diethylhexyl phthalate (DEHP) were detected to be high in the washing water of Group 3 FPSs exposed to incomplete combustion fire. Of the 24 items that were analyzed for in the water, four item exceeded the standard for sewage discharge facilities in accordance with the Water Environment Conservation Act. Copper and its compounds exceeded the standards by 3.4 times, antimony 4.8 times, acrylonitrile 26.0 times, and DEHP 4.1 times, respectively. (4) Conclusions: Therefore, when removing FPSs after firefighting activities, care should be taken to avoid contaminating the skin. In addition, facilities that wash FPS that have been exposed to a fire scene must have a sewage treatment and purification facility. However, if emergency decontamination of FPSs is conducted at the fire scene, the concentration of toxic substances contained in laundry can be reduced. In the case of large-scale fire, there is a risk of water pollution near the fire scene, so it is necessary to prepare a national countermeasure. The results of this study can be applied to the revision of regulations related to the building of the fire departments, reduction of water pollution, and water environment policy.

Comparison of Carcinogen Biomarkers in Smokers of Menthol and Nonmenthol Cigarettes: The 2015-2016 National Health and Nutrition Examination Survey Special Sample.

The US FDA announced its commitment to prohibiting menthol as a characterizing flavor in tobacco. The relationship between cigarette menthol and exposure to toxic substances in mainstream tobacco smoke is not well characterized. Data from the National Health and Nutrition Examination Survey (NHANES) 2015 to 2016 special sample were used to study markers of 26 harmful and potentially harmful constituents (HPHC) in tobacco smoke. These include urine metabolites of polycyclic aromatic hydrocarbons (PAH), volatile organic compounds (VOC), and heavy metals in exclusive menthol (n = 162) and nonmenthol (n = 189) cigarette smokers. Urine metabolites of 7 PAHs, 15 VOCs, and 4 heavy metal biomarkers were compared by menthol status. Multivariable analyses were conducted on creatinine-adjusted concentrations. There were no significant differences in cotinine levels or in 22 of 26 HPHCs. Among the urine metabolites of PAHs, the levels of 1-hydroxyphenanthrene were about 16% lower in menthol smokers. Among the urine metabolites of VOCs, menthol cigarette smokers presented significantly lower concentrations of acrylamide, N,N-dimethylformamide, and acrylonitrile. Menthol and nonmenthol smokers presented similar levels of heavy metals. Menthol did not affect the levels of cotinine and the nicotine metabolite ratio in urine. Menthol and nonmenthol cigarettes deliver similar levels of most HPHCs. Findings on toxicity are similar for menthol and nonmenthol cigarettes.

Гигиеническая оценка детских одноразовых подгузников, изготовленных с применением инновационных материалов

Background : It is of current importance to develop an algorithm for assessing chemical and physical safety of products for children and adolescents made with such innovative materials as organic cotton, bamboo, fibers and threads containing silver ions used for children’s underwear, materials impregnated with marigold extract for insoles of children’s footwear, and diapers from plant raw materials. The institute conducts testing and scientific substantiation of children’s goods made using innovative technologies. Objective : To assess safety of diapers made with innovative materials (ECO-diapers). Materials and methods: We conducted physicochemical, toxicological and organoleptic testing of 200 samples of medium size disposable baby ECO-diapers made with innovative materials. Results : The results of chemical and toxicological tests of ECO-diapers in a model aqueous environment showed that the formaldehyde concentration in aqueous extracts of the diaper samples ranged from 0.08 ± 0.020 to 0.1 mg/dm 3 ; toxicity index values – from 74.1 to 89.1 %; pH – from 0.35 to 0.5 units, and the total phenolic content – from < 0.005 to 0.024 ± 0.002 mg/dm 3 , thus being within permissible limits. Measured concentrations of acetaldehyde, acrylonitrile, acetone, benzene, hexane, methyl and propyl alcohols, toluene, ethyl acetate, lead, arsenic, zinc, chromium were also below threshold values. Chemical testing of the samples of baby diapers in a model air environment with exposure duration of 4, 12, and 24 hours detected migration of chemicals already after four hours of exposure, which did not change following 12 and 24 hours. The value of water absorption capacity, which is one of the main indicators of functional benefit of diapers, ranged from 307.6 ± 30.8 g to 355.5 ± 35.5 g and significantly exceeded the established standard (not less than 240.0 g for medium size diapers) owing to the use of innovative materials in the production of ECO-diapers. Conclusions : Our findings demonstrate the necessity to develop special methodological approaches to measuring breathability of ECO- and traditional diapers, to regulate smell by including this organoleptic quality criterion in the list of safety requirements, and to limit exposure duration in a model air environment to four hours.

Immunological and genetic indices in workers under long-term exposure to low-doses of acrylonitrile

Introduction. Nowadays there is very relevant research on the study of the characteristics of the impact on the health of workers of low levels of harmful factors (acrylonitrile) of production during long-term exposure. Aim of the study was to examine peculiarities of immunologic and genetic indices in workers under the long-term exposure to acrylonitrile in low doses. Materials and methods. Our research object was working area air (MPCw.ar.=0.5 mg/m3) and biological media (blood and exhaled air) of workers employed at industrial rubber manufacture. Acrylonitrile was determined via a non-invasive procedure in exhaled air with samples being concentrated on sorption tubes that were then analyzed with capillary gas chromatography. Blood samples were examined to determine contents of malonic dialdehyde, lymphocytes (absolute and relative activated T-lymphocytes CD3+CD25+, absolute and relative activated T-lymphocytes CD3+CD95+), cytokines (VEGF), oncomarkers (PSA), and adrenals hormones; to do that, we applied ELISA tests and flow cytometry. Results. Acrylonitrile was established to occur in working area air in concentrations varying within MPCw.ar. range (0.007-0.015 mg/m3) being 2-3 times higher than in air inside offices at the same enterprise. We obtained statistically significant linear dependence between concentrations of acrylonitrile in the air exhaled by workers (y) and their working experience (x) that was given with the following equation: y=0.00046+0.00027x. According to the results of the laboratory examination of the workers, violations of the antioxidant defense were established. Contents of malonic dialdehyde and steroid hormones including progesterone, estradiol, and hydrocortisone that were pathogenetically linked to each other were authentically up to 3.2 times higher in the test group than in the reference one (p&lt;0.05). Risk for antioxidant protection disorders such as elevated malonic dialdehyde contents in blood plasma might occur in the test group was 1.58 times higher than in the reference one. Conclusion. We revealed certain peculiarities in polymorphism of PPARGC1A Gly482Ser rs8192678 gene, the variability of which contributes to the formation of pathology of the cardiovascular, endocrine systems, oncoproliferative states that increase the likelihood of these undesirable events.

Hygienic Assessment of Disposable Baby Diapers Made with Innovative Materials

Background: It is of current importance to develop an algorithm for assessing chemical and physical safety of products for children and adolescents made with such innovative materials as organic cotton, bamboo, fibers and threads containing silver ions used for children’s underwear, materials impregnated with marigold extract for insoles of children’s footwear, and diapers from plant raw materials. The institute conducts testing and scientific substantiation of children’s goods made using innovative technologies. Objective: To assess safety of diapers made with innovative materials (ECO-diapers). Materials and methods: We conducted physicochemical, toxicological and organoleptic testing of 200 samples of medium size disposable baby ECO-diapers made with innovative materials. Results: The results of chemical and toxicological tests of ECO-diapers in a model aqueous environment showed that the formaldehyde concentration in aqueous extracts of the diaper samples ranged from 0.08 ± 0.020 to 0.1 mg/dm3; toxicity index values – from 74.1 to 89.1 %; pH – from 0.35 to 0.5 units, and the total phenolic content – from &lt; 0.005 to 0.024 ± 0.002 mg/dm3, thus being within permissible limits. Measured concentrations of acetaldehyde, acrylonitrile, acetone, benzene, hexane, methyl and propyl alcohols, toluene, ethyl acetate, lead, arsenic, zinc, chromium were also below threshold values. Chemical testing of the samples of baby diapers in a model air environment with exposure duration of 4, 12, and 24 hours detected migration of chemicals already after four hours of exposure, which did not change following 12 and 24 hours. The value of water absorption capacity, which is one of the main indicators of functional benefit of diapers, ranged from 307.6 ± 30.8 g to 355.5 ± 35.5 g and significantly exceeded the established standard (not less than 240.0 g for medium size diapers) owing to the use of innovative materials in the production of ECO-diapers. Conclusions: Our findings demonstrate the necessity to develop special methodological approaches to measuring breathability of ECO- and traditional diapers, to regulate smell by including this organoleptic quality criterion in the list of safety requirements, and to limit exposure duration in a model air environment to four hours.

The thermal oxidation of hydrogenated acrylonitrile-co-butadiene rubber from ambient to 150 °C

Hydrogenated acrylonitrile-co-butadiene (HNBR) elastomers containing three concentrations of acrylonitrile (34, 39 and 50 wt%) and less than 1% residual double bond content were heat aged up to 150 °C. Fourier transform Infrared (FTIR) spectroscopy, elemental analysis and liquid proton Nuclear Magnetic Resonance (NMR) were used to analyze the thermo-oxidized samples. FTIR clearly shows the development of esters, ketones, carboxylic acids and secondary alcohols upon heat aging which were confirmed by NMR. The acrylonitrile content was not affected by the employed heat aging conditions. Using the carbonyl growth index and time-temperature superposition (T-TS), the long term thermo-oxidative kinetics possessed three distinct regions: 23-85 °C, 85-100 °C and 100-150 °C. The slower oxidation kinetics between 85 and 100 °C in combination with an induction period shown by T-TS likely contributes to the enhanced oxidative heat aging resistance of HNBR. Activation energies increased with temperature and lower acrylonitrile levels. A series of reaction mechanisms has been put forth to explain functional group development or loss during oxidative heat aging.

2,5-Dimethylfuran/Acrylonitrile as Latent Monomer for Sequence-Controlled Copolymer and Sequence-Dependent Thermo-Responsivity.

Sequence control has attracted increasing attention for its ability of regulating polymer property and performance. Herein, the sequence-controlled polymer containing acrylonitrile (AN) is achieved by using 2,5-dimethylfuran/acrylonitrile adduct as a latent monomer. The temperature-dependent retro Diels-Alder reaction is engaged in controlling the release of AN during RAFT polymerization, that is, regulating the instant AN concentration via a non-invasive and in situ manner. Such control over the instant AN concentration and particularly the molar ratio of comonomer pair leads to the simultaneous change of monomer units in "living" polymeric chain, thus resulting in the sequence-controlled polymeric structures. By delicately manipulating the polymerization temperature, diverse sequence-on-demand structures of AN-containing copolymers, such as poly(AN/methyl methacrylate), poly(AN/styrene), poly(AN/butyl acrylate), poly(AN/N,N-dimethylacrylamide), and poly(AN/N-isopropylacrylamide) are created. Meanwhile, this study presents an initial attempt in tuning the thermal responsivity of poly(AN/N-isopropylacrylamide), which is closely correlated to the sequence of polymer structure. More importantly, the polymer with averagely distributed AN units results in the higher thermal sensitivity. Therefore, the synthetic strategy proposed in this work offers a promising platform for accessing the sequence-controlled copolymers containing AN structures, thus expanding the investigation on the relationship between the polymer structures and correlated properties.

Ce(IV)-ion initiated grafting of 1,3 galactomannan biopolymer with acrylonitrile

Galactomannans based biopolymers are common constituents of ungerminated seeds of numerous leguminous plants present in endosperm of seeds. They are highly valuable in industries due to their ability to modify the flow behavior of aqueous solutions viz. thicken, suspend, gel, stabilize, swell and film formation. Consequently, they have diverse applications in food and non-food due to their biocompatibility, biodegradability, sustainability and abundance. Cassia occidentalis, an annual weed occurring throughout India is a rich source of seed galactomannans (∼30% endosperm). The gum derived from seed endosperm can be potentially utilized in a number of industries to replace the conventional expensive gums. However, the extracted gum has considerable disadvantages such as uncontrolled hydration, changes in viscosity during storage, pH-dependent solubility, lower shelf life etc, thereby, limiting their vast industrial applications. Intriguingly, these limitations can be overcome by functionalization of hydroxyl groups. Therefore, grafting onto C. occidentalis seed gum was carried out with acrylonitrile in presence of ceric ammonium nitrate under inert atmosphere. The reaction conditions were optimized by varying concentration of CAN, nitric acid, acrylonitrile, reaction temperature and time. The grafted gum was characterized using FTIR, TGA, DTG, X-Ray and SEM analysis.

Influence of monomeric concentration on mechanical and electrical properties of poly(styrene‐co‐acrylonitrile) and poly(styrene‐co‐acrylonitrile/acrylic acid) yarns electrospun

AbstractTwo series of copolymers were synthesized by emulsion polymerization: poly(styrene‐co‐acrylonitrile) P(S:AN) and P(S:AN‐acrylic acid) P(S:AN‐AA). The monomeric concentrations in both series were: 0:100, 20:80, 40:60, 50:50 (wt%:wt%), and 1 wt% of AA. The copolymers were dissolved in N,N‐dimethylformamide (4–10 wt%) and were electrospun. Polymeric yarns were collected using a blade collector. The synthesized and fabricated materials were characterized by known techniques. Mechanical and electrical properties of polymeric yarns indicated a dependence of monomeric concentration. Elastic modulus increases as acrylonitrile concentration increases (up to 30 MPa). Yarns were submitted to degradation process into saline solution, where the acrylic acid content kept a constant elastic modulus at long times. The electrical current into yarns was higher when the concentration is 50:50 wt%:wt% (1.2 mA). The cytotoxicity results showed a cell viability close to 100% for yarns without AA.

Coverage-dependent acrylonitrile adsorption and electrochemical reduction kinetics on Pb electrode

Electrochemical dimerization of acrylonitrile (AN) is an environmentally friendly approach to manufacture adiponitrile (ADN), the key raw material of nylon-6,6. Despite its significance in industry, the studies on the mechanism and kinetics of AN conversion on cathode are relatively limited. Herein we investigated the adsorption and electrochemical reduction of AN on Pb electrode under different coverage by the combination of experiments and density function theory (DFT) calculations. Under various reaction conditions, it was observed that when decreasing the bulk concentration of AN, the generation of ADN decreases as expected while that of the saturated propionitrile (PN) increases on the contrary, indicating a coverage-dependent kinetic behavior. Theoretical analysis revealed high AN coverage on Pb surface could inhibit the formation of H and repel the contacting of C=C with active site, both of which is against the generation PN and favorable for ADN. A kinetic model was then developed for the cathodic reaction by taking the impact of temperature, potential and surface coverage into account, which gives good agreement in a wide range of operation conditions.

Catalytic peroxidation of acrylonitrile aqueous solution by Ni-doped CeO2 catalysts: characterization, kinetics and thermodynamics

Acrylonitrile is one of the major pollutants of acrylonitrile–butadiene–styrene resin industry wastewater present in high concentration. In the current study, the treatment of acrylonitrile from aqueous solution was performed by catalytic peroxidation using Ni-doped CeO2 catalysts. Various catalysts with different loadings of nickel were synthesized by co-precipitation method and further characterized by X-ray diffraction, Fourier transform infrared spectroscopy, liquid nitrogen adsorption–desorption technique, transmission electron microscopy, scanning electron microscopy with energy-dispersive X-ray, thermogravimetric analysis and X-ray photoelectron spectroscopy. The effects of various parameters such as catalyst dose, pH, nickel loading, H2O2/acrylonitrile molar ratio, initial concentration of acrylonitrile, temperature and reaction time on acrylonitrile removal were studied. Maximum acrylonitrile removal of 84.12% was observed at optimum operating conditions of pH = 6.5, catalyst dosage = 500 mg/L, nickel loading = 2.5 wt.%, stoichiometric molar ratio (H2O2/acrylonitrile) = 1, temperature = 298 K and reaction time = 3 h. Acrylonitrile degradation kinetics was investigated using power law model and non-competitive Langmuir–Hinshelwood model in which non-competitive Langmuir–Hinshelwood isotherm model better fitted for acrylonitrile degradation using Ni-doped CeO2 catalyst. Thermodynamic study of the parameters has also been presented.

Molecular Simulations and Experimental Characterization of Fluorinated Nitrile Butadiene Elastomers with Low H2S Permeability

The elastomer seals that are used in the processing of sour gas in the oil and gas industry must be able to withstand chemical degradation by corrosive materials such as hydrogen sulfide present in the sour gas. Nitrile rubbers, including hydrogenated nitrile butadiene (HNBR), are commonly used because they have low glass transition temperatures, good low-temperature sealing ability, and excellent resistance to swelling by hydrocarbons. They are, however, prone to chemical modifications, including chain scission, cross-linking, and sulfur incorporation, that result in changes in mechanical properties after contact with H2S. Fluoroelastomers are promising alternatives but have higher glass transition temperatures than nitrile rubbers, which affect their low-temperature performance. The approach of free-radical grafting of a semifluorinated alkyl methacrylate, 1H,1H,2H,2H-perfluorooctyl methacrylate (F6H2MA), to HNBR, to improve its resistance to H2S was investigated. The effects of grafting density of F6H2MA on the solubilities and diffusion coefficients of H2S, and carbon dioxide, which is also present in sour gas, were studied using molecular dynamics and Monte Carlo simulations. The influence of acrylonitrile concentration in the copolymer was characterized. Simulated dilatometry and differential scanning calorimetry measurements showed that the grafting of F6H2MA to HNBR did not result in a significant increase in the glass transition temperature of the copolymer. H2S permeability through the fluorinated HNBR showed a significant decrease with an increase in F6H2MA concentration. The results of molecular simulations were corroborated by measurement of mechanical properties of elastomer samples aged in a sour-gas environment at 250 °F and 1000 psig for 24 h. Gravimetric and volumetric swelling, as well as mechanical properties of the aged samples, was measured for comparison with the original unaged samples. The degrees of swelling and mechanical property deterioration after aging were significantly suppressed by grafting HNBR with even low concentrations of the semifluorinated methacrylate.

ACTIVATION ENERGIES OF THERMO-OXIDIZED NITRILE RUBBER COMPOUNDS OF VARYING ACRYLONITRILE CONTENT

ABSTRACT The thermo-oxidative behavior of carbon black–reinforced sulfur-cured nitrile rubber compounds with varying acrylonitrile (ACN) content (18–49 wt%) was investigated. Accelerated heat aging was carried out from 40 °C to 115 °C for various aging times. Ambient aging was also included. Samples were tested for hardness, 10% tensile stress, tensile strength, elongation at break, network chain density by equilibrium solvent swell, and toluene-soluble fraction. Diffusion-limited oxidation affected data at high temperatures and was eliminated for time-temperature superposition. Linear Arrhenius kinetic behavior was confirmed throughout the whole temperature range, and calculated activation energies varied from 75 to 93 kJ/mol. Activation energies calculated through the hardness data were found to increase steadily with ACN concentration, whereas the other test responses showed less direct correlation, likely because of the influence of the underlying NBR microstructure, which changes as a function of ACN content. The high-temperature thermo-oxidative process consists of both oxidative crosslinking and chain scission reactions. Sulfur reversion and alkyl radical recombination reactions are likely prevalent at low temperatures during the buildup of hydroperoxides up to 60 °C. The shelf life of nitrile rubbers strongly depends on their ACN level, with lower ACN nitriles being more susceptible to degradation, leading to shorter shelf lives, than higher ACN-containing nitriles.

Adsorptive Removal of Lead Ions in Aqueous Solution by Kapok-Polyacrylonitrile Nanocomposites

Abstract In this study, the naturally hydrophobic kapok fibers were modified with polyacrylonitrile (PAN) to reverse its wetting property for adsorption of lead (Pb) ions in aqueous solution. Increasing the initial amount of the acrylonitrile (AN) monomer in solution resulted in thicker PAN coating on the surface of the kapok fibers after in situ polymerization. Consequently, the static water contact angle of the nanocomposite was reduced to zero. The kapok-PAN nanocomposites were then used for adsorption of lead (Pb) II in aqueous solution. Adsorption capacities for Pb(II) increased from 22.05 to 26.81 mg/g with higher AN concentration. Hydrolysis of the kapok-PAN nanocomposite was performed by immersing in a sodium hydroxide (NaOH) solution, which results to significantly enhanced adsorption of about 78.34 mg/g.

Acute and chronic toxicity effects of acrylonitrile to the juvenile marine flounder Paralichthys olivaceus.

Acrylonitrile (ACN) spills in marine environment have the potential to cause ecological hazards and consequences, but currently little is known about the disruptive effects of ACN on marine organisms. In the present study, we investigated the lethal and sublethal effects of ACN on juvenile flounder Paralichthys olivaceus. The results showed that the 96-h LC50 of ACN to P. olivaceus juveniles was 6.07mg/L. The fish were then exposed to different sublethal concentrations (0.1, 0.2, and 0.4mg/L) of ACN for 28days and then transferred to clean seawater and keep in clean seawater for 14days to simulate the conditions of a spill incident. Biomarkers (EROD, GST, SOD, AChE activity, and levels of LPO and DNA alkaline unwinding) were tested in liver and brain. The weight gain rates and specific growth rate of juvenile marine flounder exposed to ACN (≥ 0.1mg/L) for 28days decreased significantly, indicating that ACN had an inhibitory effect on juvenile growth. Deformity of fish tails was observed on individuals exposed to the highest concentration (0.4mg/L ACN) for 14days, and the malformation rate was 38% after 28-day exposure. The present study provides the first evidence that ACN causes inhibition of AChE activity in fish brain. Furthermore, the results showed that ACN can significantly inhibit SOD activity and cause lipid peroxidation and DNA damage in fish brain. The results indicated that brain is more sensitive to ACN toxicity compared to liver and provides a suitable tissue for biomonitoring. The biomarkers measured during the depuration period showed that the effects caused by ACN were reversible when the exposure concentration was lower than 0.4mg/L. These results highlight the adverse effects of ACN in brain of fish, which should be considered in environmental risk assessment. Biomarkers including AChE activity, LPO, and DNA damage of brain tissue should be included in fish bioassays for toxic effect assessment of ACN spills.