Initial Reaction Mixture Research Articles

Copolymers of Vinylphosphonic and p‐Methacrylamidobenzoic Acids and their Complexes with Lanthanide Ions

AbstractNew copolymers of vinylphosphonic and p‐methacrylamidobenzoic acids of varying compositions were synthesized via free radical copolymerization. The structure of the obtained polymers was confirmed by NMR and FTIR spectroscopy. As the proportion of vinylphosphonic acid in the initial reaction mixture increased, the yield of the copolymer and its molecular mass both decreased. The synthesized copolymers were found to form stable soluble luminescent complexes in dilute aqueous solutions, with a concentration range of 0.002 to 0.02 mg/ml. An increase in the concentration of vinylphosphonic acid moieties in copolymers was accompanied by a noticeable decrease in the luminescence intensity. The new copolymers’ ability to bind efficiently with lanthanide ions renders them a promising material for the design of polymeric contrast agents, preparations for radioimmunotherapy and photodynamic therapy.

Factors affecting conversion of methane-hydrogen mixtures into nanostructured carbon and hydrogen

At the catalytic decomposition of methane, along with hydrogen, it is possible to obtain carbon nanofibers. The addition of hydrogen to the initial reaction mixture makes it possible to increase significantly the efficiency of the overall process by minimizing the contribution of the catalyst deactivation process caused by coking. As found, the maximum yields of hydrogen and nanostructured carbon over the NiO–CuO/Al2O3 catalyst is achieved at an inlet hydrogen concentration of 13 vol%. The accumulated carbon is represented by well-structured carbon nanofibers, which are resistant to the gasification reaction. The original stacked structure is preserved after the treatment of these fibers in a hydrogen medium. Using numerical methods, the hydrogen productivity at 610 °C was found to be 49.3 mL/(mgcat·h) at an optimal value of the residence time of 5 × 10−3 s.

Enhanced antimicrobial activity of photocatalytic titanium oxide upon formation of composites with polyaniline via an eco-friendly and facile microwave synthesis approach

This study proposes inexpensive antimicrobial polyaniline-titanium oxide (PANI-TiO2) samples prepared through eco-friendly enhanced microwave (MW) synthesis with 93 W applied over 10 min in aqueous 1.25 M hydrochloric acid media (HCl) using potassium iodate (KIO3) as oxidising agent, an approach suitable for industrial scale up production of PANI polymers at room temperature. The PANI-TiO2 samples are produced in the presence of 5–20 wt% of TiO2 in the initial reaction mixture along with aniline monomer by both the enhanced MW method and a classical chemical synthesis (CS) method at room temperature. The nanocomposites showed lower conductivity than pure PANI, slightly higher conductivity was observed in the MW prepared PANI-TiO2 in comparison to CS prepared PANI-TiO2. This result can be correlated with the observation that the optical absorbance of MW PANI-TiO2 samples were notable higher than for CS PANI-TiO2, which may be due to the presence of a greater amount of polarons present in the samples prepared by the enhanced MW method. MW PANI-TiO2 samples were equally active against both Gram-negative E. coli and Gram-positive S. aureus bacteria, in contrast to the CS PANI-TiO2 samples, which could be due to presence of short-chain fragments in the CS samples as confirmed by Fourier-transform infrared (FTIR) spectroscopy. The incorporation of PANI particles in TiO2 showed enhanced antimicrobial activity compared to pure TiO2, with greater antifungal activity. Our study indicates that a facile, low-cost, and green enhanced MW method can be used for preparation of the advanced antimicrobial PANI-TiO2 nanocomposites for biomedical applications.

Promising Directions in Chemical Processing of Methane from Coal Industry. Part 3. Catalytic Tests

For the processing of coal mine methane into hydrogen-containing gas, a catalytic process of methane tri-reforming (СH4 + O2 + CO2 + H2O) was proposed and its component reactions were studied – partial oxidation (СH4 + O2, POM), dry reforming (СH4 + CO2, DRM) and steam reforming (СH4 + H2O, SRM) of methane. Promoted nickel supported on aluminum oxide was used as a catalyst. Experiments were carried out by varying temperature (600–850 ºC), contact time (0.04–0.15 s), linear feed rate (40–240 cm/min) and composition of the reaction mixture (POM – СH4 : O2 : He = 1 : (0.5–0.7) : (3.3–3.4); DRM – СH4 : CO2 : He = 1 : (0.8–1.4) : (2.6–3.2); SRM – CH4 : H2O : He = 1 : (0.8–2.0) : (2.0–3.2)). Optimal reaction conditions were determined to ensure maximum efficiency of hydrogen production by reforming methane-containing mixtures of various compositions (temperature in the range of 800–850 ºC, contact time 0.15 s, linear feed rate 160 cm/min, molar ratio of CH4 : O2 = 1 : 0.5 for POM, CH4 : CO2 = 1 : 1 for DRM and CH4 : H2O = 1 : 1.1 for SRM). The degree of catalyst carbonization during the reactions was reduced (from 3 to 1.5% for POM, from 20.7 to 2.2% for DRM, and from 15.2 to 0.4% for SRM) due to an increase in the O/C molar ratio in the initial reaction mixture. Regulation of H2/CO molar ratio was achieved over a wide range (0.9–6.5). It has been shown that the hydrogen concentration in the resulting hydrogen-containing mixture is determined by the type of process and is equal to 30±5 vol.%.

Dynamic modeling and optimal control of reactive batch distillation: An experimental case study

In the present study, dynamic modeling, optimal operation and control of a reactive batch distillation process is illustrated based on experimental and simulation studies using methyl acetate production case study. An equilibrium stage model, incorporating non-ideal VLE and start-up region of heating, is developed based on data generated on an experimental unit by identifying five input parameters representing uncertainties. The optimal control problem is solved using genetic algorithm, considering the objective function identified on the basis of trend analysis using the developed dynamic model, to find the optimal reflux ratio, heat input to the reboiler, and mole ratio of methanol to acetic acid in the initial reaction mixture. Open-loop and closed-loop implementations clearly illustrate the improved performance with respect to the quantity of methyl acetate in the distillate product with a reasonably high conversion and product purity within reasonably short batch duration, illustrating the successful optimal control implementation experimentally.

One-Step Synthesis of Biphasic, Cavity-forming Polymer Particles via Dispersion Copolymerization of Styrene and Sulfobetaine Methacrylate.

A one-step dispersion copolymerization technique is demonstrated to fabricate biphasic particles as an approach to streamline the production of particles with complex morphology. The model system studies a monomer feed of hydrophobic styrene and hydrophilic, zwitterionic sulfobetaine methacrylate (SBMA) in a water/isopropanol cosolvent mixture. The resulting particles have a core-shell morphology that can be transformed, simply by washing the particles with water, into particles with a single surface opening connected to an interior cavity. Results indicate that particle morphology is dependent on the presence of nanoscopic SBMA-rich aggregates in the initial reaction mixture to act as nucleation sites, forming an SBMA-rich core encased in a styrene-rich shell. Systematic study of the morphology evolution reveals that the difference in monomer solubility profile can be exploited to control compositional drift of the particle composition during copolymerization yielding copolymer with sufficiently different composition to form phase-separated particle morphology. When SBMA is replaced with various ionic comonomers, the cavity-forming morphology is observed when reaction conditions result in low solubility of the comonomer in the cosolvent mixture. Based on these results, design guidelines are developed that may be applied to a variety of systems requiring complex and responsive particles made from chemically distinct comonomer pairings.

Effect of Different Initial CaO/SiO2 Molar Ratios and Curing Times on the Preparation and Formation Mechanism of Calcium Silicate Hydrate.

To better understand the pozzolanic activity in fly ash used as a supplementary cementitious material in cement or concrete, calcium silicate hydrate (C-S-H) has been synthesized by adding silica fume to a supersaturated calcium hydroxide solution prepared by mixing calcium oxide and ultrapure water. Thermogravimetric analysis results have revealed the variation in the weight loss due to C-S-H in the samples and the conversion ratio of calcium oxide (the μCaO value), which represents the proportion of calcium oxide in the initial reaction mixture used to produce C-S-H, with curing time. The weight loss due to C-S-H and the μCaO value were both maximized (13.5% and 90.4%, respectively) when the initial C/S molar ratio was 1.0 and the curing time was 90 d. X-ray diffraction (XRD) analysis has indicated that C-S-H in the samples after curing for 7 d had the composition Ca1.5SiO3.5·xH2O. 29Si magic angle spinning (MAS) nuclear magnetic resonance (NMR) analysis has revealed that the degree of polymerization of C-S-H increased with an increase in curing time for samples with an initial C/S molar ratio of 1.0. The ratio of internal to terminal tetrahedra (Q2/Q1) increased from 2.29 to 4.28 with the increase in curing time from 7 d to 90 d. At curing times ≥ 28 d, a leaf-like C-S-H structure was observed by scanning electron microscopy (SEM). An ectopic nucleation-polymerization reaction process is proposed for the formation mechanism of C-S-H.

Cellulose-g-poly(2-(dimethylamino)ethylmethacrylate) Hydrogels: Synthesis, Characterization, Antibacterial Testing and Polymer Electrolyte Application.

Hydrogels have been investigated due to their unique properties. These include high water content and biocompatibility. Here, hydrogels with different ratios of poly(2-(dimethylamino)ethylmethacrylate) (PDMAEMA) were grafted onto cellulose (Cel-g-PDMAEMA) by the free radical polymerization method and gamma-ray radiation was applied in order to increase crosslinking and content of PDMAEMA. Gamma irradiation enabled an increase of PDMAEMA content in hydrogels in case of higher ratio of 2-(dimethylamino)ethyl methacrylate in the initial reaction mixture. The swelling of synthesized hydrogels was monitored in dependence of pH (3, 5.5 and 10) during up to 60 days. The swelling increased from 270% to 900%. Testing of antimicrobial activity of selected hydrogel films showed weak inhibitory activity against Escherichia coli, Pseudomonas aeruginosa, and Bacillus subtilis. The results obtained by the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) indicate that chemically synthesized hydrogels have good characteristics for the supercapacitor application.

Liquid-Phase-Assisted Catalytic Nitridation of Silicon and In Situ Growth of α-Si3N4.

Si3N4 powders were synthesized with Fe, Co, or Ni as catalysts using Si powder at 1250 °C in a nitrogen atmosphere by liquid-phase-assisted catalytic nitridation synthesis (LPA–CNS). The catalytic effects of the metals on the nitridation of silicon powder were investigated by mixing the powder with 2 wt% by mass of Fe, Co, or Ni in a high-temperature liquid phase in flowing nitrogen. The α-Si3N4 micro-morphology could be effectively changed by adjusting the type of catalyst in the initial reaction mixtures. Fe, Co, and Ni promoted the formation of α-Si3N4 at 1250 °C and controlled the morphology of the α-Si3N4 particles. The hexagonal flakes of α-Si3N4 with a better defined morphology were obtained using Ni as the catalyst, compared to that obtained from the other two catalysts.

Chromatographic and spectrophometric studies of vanadate (+V) reduction by 3–mercaptopropionic acid

The reduction of vanadate (+V) in the presence of 3-mercaptopropionic acid was studied using a chromatographic method for the determination of vanadate (+V) versus vanadyl (+IV) species. Ion chromatography was combined with spectrophotometric investigation of the absorption properties of the solution. The chromatographic method for the separation of vanadate (+V) and vanadyl (+IV) was carried out with an anion exchange column. In the initial reaction mixture containing vanadate (+V) and 3-mercaptopropionic acid, ethylenediaminetetraacetic acid – EDTA was added in an excessive amount relative to the concentration of reactants in the solution. After the ligand exchange reaction, the added EDTA terminates the reduction, allowing redox speciation in the solutions. A strong pH dependence of the reduction rates in the investigated solution was observed. The vanadate reduction seems to proceed in 2 steps: 1) formation of the intermediate vanadate (+V)-thioester; 2) reduction reaction and formation of the vanadyl (+IV)-thiol complex. The obtained results strongly suggest that the reaction of vanadate (+V)-thioester formation is proton catalyzed. It was observed that the overall reduction rates are pH dependent due to the complex vanadate (+V) solution speciation and changes in the ionic form of 3-mercaptopropionic acid.

Correlation of the organic sorbents texture with chromatographic characteristics of monolithic HPLC columns based on 1-vinyl-2-pyrrolidone

Monolithic sorbents based on styrene/divinylbenzene/1-vinyl-2-pyrrolidone copolymer have been synthesized inside the glass tubes with the inner diameter of 2 mm. The effect of the porogenic solvent nature and divinylbenzene content on the textural and chromatographic properties of sorbents was studied. Polypropylene glycol with the molecular weight 2025 g/mol and triblock copolymer Pluronic 10R5 (poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol)) with the molecular weight 2000 g/mol were found to be the most suitable porogenic solvents. The fraction of divinylbenzene in the initial polymerization mixture was shown to affect the textural characteristics of sorbents (specific surface area, pore size and volume). The dependence of hydrodynamic permeability and columns loading capacity on divinylbenzene content in the initial reaction mixture was elucidated. Separation examples for the prepared columns are given.

Anisotropy of the bending strength of LaB6–W2B5 reactive hot-pressed ceramics

Refractory composite ceramic material in the LaB6–W2B5 system with a component ratio of 50 : 50 vol.% was obtained by reactive hot pressing in a graphite mold. A heterophase powder containing lanthanum hexaboride, metallic tungsten, and amorphous boron preliminarily ball-milled for 20 h with tungsten balls was used as the initial reaction mixture. The average particle size of the milled mixture was 2.9 μm. A relative density of 92 % was achieved at a temperature of 1800 °C with isothermal holding for 15 min at 30 MPa in an argon atmosphere. The structure and composition of the LaB6–W2B5 material were studied by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The composition of the ceramics contained two phases – cubic LaB6 lanthanum hexaboride and hexagonal W2B5 tungsten pentaboride. The ceramic structure featured by ordered lamellar W2B5 particles in a LaB6 polycrystalline matrix. During the reactive hot pressing of the LaB6–W–B mixture, the predominant growth of W2B5 crystals along (101) atomic planes was observed. Resulting lamellar W2B5 particles were oriented in the LaB6 matrix perpendicular to the pressing load. Images obtained with electron microscopy were used for the three-dimensional visualization of the LaB6–W2B5 structure. Three-point bending tests were conducted on 3×3×30 mm samples. The dependence of bending strength on the direction of applied breaking load was established. When a breaking load was applied perpendicular to the surface of the lamellar W2B5 particles, the ultimate strength was 420 MPa, while when loaded along the plane of the particles, bending strength increases to 540 MPa. The anisotropy coefficient of ultimate strength was 0.78.

FEATURES OF IN SITU FORMATION OF MIXTURES OF LINEAR POLYMERS

This article is devoted to the analysis of the results of the investigation of the process of forming mixtures of linear polymers formed simultaneously in situ according to different mechanisms. The first mechanism is polyaddition, the second mechanism is radical polymerization. This is one of the possible ways to obtain multicomponent polymer systems. The kinetics of chemical reactions of the formation of components and the phase separation which accompanies these reactions were studied for mixtures of poly(methyl methacrylate) (PMMA) with two polyurethanes (PU) of different chemical nature of both flexible and rigid blocks. PU-1 was synthesized from macrodiisocyanate based on oligo(tetramethylene glycol) with molecular mass 1000 g·mol–1 and hexamethylene diisocyanate taken in the molar ratio 1 : 2 using diethylene glycol as a chain extender. PU-2 was synthesized from macrodiisocyanate based on olygo(propylene glycol) with molecular mass 1000 g·mol–1 and toluylene diisocyanate taken in the molar ratio 1 : 2 using butanediol as a chain extender. The mixture of polystyrene (PS) with PU-2 was studied too. It is established that regardless of the chemical nature of the components, the process of in situ mixture formation is subject to general laws. In particular, the change in the chemical nature of the component formed by the mechanism of polyaddition (mixtures PMMA/PU-1 and PMMA/PU-2) or of the component formed by radical polymerization (mixtures PMMA/PU-2 and PS/PU-2) does not affect the nature of the dependence of the conversion degree of components and the fraction of formed polymers at the beginning of the phase separation on the composition of the initial reaction mixtures. Only the absolute values of these parameters change due to different reactivity and different thermodynamic compatibility of the mixed components.

Hard template synthesis and photocatalytic activity of graphitic carbon nitride in the hydrogen evolution reaction using organic acids as electron donors

Porous graphitic carbon nitride obtained by pyrolysis of melamine in the presence of silica (TEOS in the reaction mixture) has been found to be more active in photocatalytic hydrogen evolution from the aqueous solutions of electron donors (organic acids) under visible light irradiation compared to the bulk analogue. The use of the optimal melamine/TEOS molar ratio in the initial reaction mixtures allows to obtain g-C3N4 characterized by increased mesoporosity due to the formation of smaller particles. It has been shown for the first time that oxalic acid can be used as an environmentally friendly sacrificial donor allowing to reach significantly higher rates of the photocatalytic reaction (up to 300 μmol H2/h*gphotocat.).

Determination of influence of pH on reaction mixture of ferritation process with electromagnetic pulse activation on the processing of galvanic sludge

This paper considers prospects for increasing the level of environmental safety of industrial enterprises as a result of the implementation of resource-saving technology of processing galvanic sludge using the ferritization method. The effectiveness of the use of electromagnetic pulse discharges for resource-saving activation of the ferritization process with the extraction of heavy metal ions from sludge (Fe, Ni, Cu, Zn) has been confirmed. The influence of key parameters of the process such as the pH value of the reaction mixture and the initial concentrations of metals in the solution on the quality of processing galvanic sludge by ferritization has been experimentally investigated. It was determined that with an increase in the pH value from 8.5 to 10.5 the residual concentrations of metal ions decrease to the values of 0.1÷0.25 mg/dm3 regardless of the total initial concentrations. It has been established that the technique of electromagnetic pulse activation ensures an adequate degree of extraction of metal ions of 99.9 %; it also has indisputable energy advantages compared to the thermal method: energy costs are reduced by more than 60 %. That indicates the suitability of purified water for reuse in galvanic production in terms of the requirements for the content of heavy metal ions in it. In addition, the structural studies of ferritization sediment samples have been carried out. The sediment is characterized by the maximum content of crystalline ferromagnetic phases of ferrite. It was established that an increase in the pH of the initial reaction mixture leads to an increase in the ferrite phase in sedimentation: at pH=10.5, phases were detected, which are characterized by a maximum ferrite content (exceeding 76 %). The proposed resource-saving ferritization process prevents environmental pollution, ensures efficient and rational utilization of raw materials and energy in the industry; it also makes it possible to obtain commodity products from industrial waste.

Photocatalytic activity of CdO/ZnO nanocomposite for methylene blue dye and parameters optimisation using response surface methodology

ABSTRACT In this work, CdO/ZnO nanocomposites was synthesised by chemical co-precipitation followed by thermal treatment method, characterised and its photocatalytic activity for the degradation of methylene blue (MB) dye studied. Study of the effects of operational parameters of dye initial concentration, catalyst dose, and pH on the degradation efficiency of the dye was carried out with response surface methodology (RSM) employing the central composite design (CCD) model and that the maximum predicted degradation percentage of the dye obtained was 81.6% at the optimum values of initial catalyst dose, dye concentration and reaction mixture pH of 30 mg, 13 ppm and 10, respectively, under natural sunlight irradiation for a period of 3 h. The measured experimental value at the indicated levels of the factors was 83.14% during the same degradation time and this is in reasonable agreement with the predicted value. Test for reactive radical species showed that HO. and O2 -. are engaged in the decomposition process of the dye. Further, the CdO/ZnO nanocomposite catalyst retained its degradation efficiency by about 96% over 4 consecutive cycles, indicating its stability and potential application for practical decontamination of wastewater from toxic organic pollutants.

Rapid and Sensitive Detection of the Colistin Resistance Gene mcr-3 by Loop-Mediated Isothermal Amplification and Visual Inspection

Objective: The distribution of colistin resistance in mcr-carrying bacteria poses a threat to global public health. In particular, the newly identified mcr-3 allele has spread globally, especially in China, second only to mcr-1. In this study, we aimed to develop a loop-mediated isothermal amplification (LAMP) assay for rapid, sensitive, and visual detection of the presence of the mcr-3 gene. Materials and Methods: A total of 13 clinical bacterial strains and 11 negative strains were used in this study. We designed LAMP Primers, optimized reaction conditions, used three different methods to detect LAMP amplification products: (1) agarose gel electrophoresis, (2) LAMP-hydroxy naphthol blue (HNB) detection, (3) LAMP-SYBR Green I (LAMP-SGI) visual inspection, and evaluated its specificity and sensitivity. Results: The amplification reaction was completed in 1 hr at 62°C under isothermal conditions. The final optimized mixtures contained 100 mM KCl, 100 mM (NH4)2SO4, 20 mM MgSO4, 1% Triton X-100, 1.2 μL HNB, and 0.5 μL SYBR Green I as additives to the initial reaction mixture. LAMP detection, including two visual methods, LAMP-HNB and LAMP-SGI, of mcr-3 possessed the same specificity and a 10-fold higher sensitivity compared with a conventional polymerase chain reaction assay using the same samples. Conclusion: We successfully established an mcr-3 LAMP detection with portability and rapidity of the reaction by the easily distinguishable color changes in the reaction tubes. This visual LAMP assay for mcr-3 detection was simple, time saving, and economical, especially suited to field laboratories.

Ultrasound-assisted enzymatic synthesis of xylitol fatty acid esters in solvent-free conditions

A commercial immobilized lipase was successfully used for the synthesis of five xylityl acyl esters by means of the esterification of free fatty acids (caprylic, capric, lauric and myristic, respectively) with xylitol under solvent-free conditions. Ultrasound-assistance was shown to be a key tool to overcome the handicap imposed by both the mutual immiscibility of fatty acids and xylitol substrates, and the semisolid character of the initial reaction mixtures. In such semisolid systems, ultrasonic irradiation may enable the transport of substrate molecules to the enzyme catalytic-site, leading to the efficient synthesis of xylityl fatty ester (e.g. up to 95% yield after 90 min at 40 °C), with xylityl monoacyl ester and xylitol diacyl ester appearing as the main products (greater than 96%), assessed by HPLC and NMR analyses. The separation of products was carried out by heating and simple centrifugation of the reaction medium, which was possible due to different densities of the resulting fractions.

COMBUSTION SYNTHESIS OF COMPOSITE IN THE Ti-Al-C POWDERS MIXTURE: MODEL AND NUMERICAL SIMULATION

The work uses the basis of conventional combustion theory to propose and study a model of combustion synthesis of a composite material in a three-component powder mixture Ti-Al-C. The model takes into account the dependence of the properties on the composition and structure of the reaction system. The composition of the composite material was analyzed from the reaction initiation stage and to the product cool down. It was shown that the reaction front propagation along the specimen occurs in a stationary regime (with constant rate) for any of the specimens under study. The main synthesis products in the studied concentration range are titanium carbides, titanium aluminide and ternary phases (MAX-phases) Ti2AlC and Ti3AlC2. It was shown that the preliminary heating of the initial reaction mixture prevents the formation of MAX-phases in obtained composites and facilitates the increase in the fraction of carbide phases. Within the framework of the proposed model, the change in an initial porosity of the compact has very little effect neither on the composition evolution of the product. We have found the ranges of concentrations in the initial reaction mixture that provide the prevalence of either intermetallic (TiAl) or MAX-phase (Ti2AlC, Ti3AlC2) in the matrix. The obtained theoretical results are consistent with the experimental results.

Catalyzed-like water enhanced mechanism of CO2 conversion to methanol

Converting carbon dioxide to fine chemicals such as methanol using electrolytic hydrogen could be an efficient way of renewable energy storage. The conversion of CO2 to methanol is a rather complicated multistep process which is usually performed catalytically in gas phase. However, the aqueous phase conversion of CO2 is also feasible in certain conditions. Thus, a catalyzed-like water enhanced mechanism of CO2hydrogenation to methanol has been designed and studied by using the highly accurate W1U composite method. The initial reactant mixture was CO2 + 6H + 8H2O + H3O+, where the hydrogen atoms are added one-by-one to mimic the catalytic effect of a metal surface. The presence of water and H3O+ further enhance the reaction by lowering the reaction barriers. By computing the thermodynamic properties of the reaction mechanism, it was found that the highest relative energy barrier in the most preferred pathway is 212.67 kJ/mol. By taking this into account, the energy efficiency of the pathway has been calculated and it was found to be equal to 92.5%.