Initial Concentrations Of Reagents Research Articles

Hirshfeld surface analyses, NCI–RDG and effect of surfactant on the size of Co3O4 nanostructures obtained from cobalt(II) nano-complex

Nanostructures of the compound [Co(O2CCH3)2(2-apy)2] (1) (2-apy = 2-Aminopyridine) have been synthesized by a sonochemical process at different of concentrations cobalt acetate tetrahydrate and 2-aminopyridine ligand. The smallest nanostructures of compound 1 are produced in low concentrations of initial reagents. Co3O4 nanoparticles were prepared from thermal decomposition in oleic acid as a surfactant and direct calcination of compound 1 at different temperatures. The effect of calcination temperature and oleic acid, as a surfactant, was investigated on the particle size distribution of the products. The compounds were studied by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), UV–vis, FT-IR spectroscopy, thermal analyses (TGA and DTA) and elemental analyses. Hirshfeld surface analyses and Noncovalent interaction reduced density gradient (NCI-RDG) calculations of compound 1 were illustrated and discussed in order to quantify the order and nature of intermolecular interactions in the crystal network. Hirshfeld surface analysis indicated that there are other types of intermolecular contacts in Crystal, including H…H, H…O, C…H, H…N, C…C and C…N interactions, and the contributions of these interactions are 55.4%, 19.7%, 19.2%, 4.1%, 1.4% and 0.2%, respectively.

Silica–Resorcinol–Melamine–Formaldehyde Composite Aerogels as High-Performance Thermal Insulators

Here, we report the gelation and supercritical drying of ethanol-based silica–resorcinol–melamine–formaldehyde (RMF) composite aerogels with relative concentrations of initial reagents ranging from neat silica to neat RMF alcogels. The as-prepared materials are subsequently supercritically dried with carbon dioxide. Their properties include a thermal conductivity in the 15–20 mW·m–1·K–1 range even with a silica content as low as 20%wt. The possible reasons behind this interesting insulation performance and the mechanisms leading to the underlying gel structure are discussed in depth. A focus is made on the different gelation modes happening between the RMF and silica phases, from a coating of silica surfaces with RMF species to discontinuous RMF particles within a silica backbone and a continuous RMF backbone with isolated silica particles. The implications in terms of mechanical properties and thermal conductivity are elaborated upon. The initial ratio of silica–RMF species in this ethanol-based synthesis affects the micro- and macrostructure of the composites, resulting in materials with drastically different pore structures and thus an interesting array of possibilities for a new class of silica-organic composite aerogels, based on a sol–gel process.

Ultrasound Irradiation Assisted Synthesis of Luminescent Nano Amide-Functionalized Metal-Organic Frameworks; Application Toward Phenol Derivatives Sensing.

Two nano amide-functionalized metal-organic frameworks (MOFs) with molecular formula [Co(oba) (bpta)]·(DMF)2 TMU-50 and [Co2(oba)2 (bpfn)]·(DMF)2.5 TMU-51 obtained under ultrasonic method without any surfactants. The only difference between the two selected amide functionalized pillar ligands, N,N′-bis(4-pyridinyl)-terephthalamide (bpta), and N,N′-bis-(4-pyridylformamide)-1,5-naphthalenediamine (bpfn), is related to the naphthyl group, which led to the different luminescence properties of the nano frameworks. In this study, the special ability of the luminescent nano MOFs were investigated to sensitize nitroaromatic compounds. Due to its unique and porous framework, Nano TMU-50 shows a good sensitivity towards nitro phenol by strong fluorescence emission with a detection limit of 2 × 10–3 mM−1. Both nano MOF structures were characterized via many analyses such as powder X-ray diffraction, Field Emission Scanning Electron Microscopy (FE-SEM), elemental analysis, and FTIR spectroscopy. Moreover, the effect of a number of important parameters including initial reagent concentrations, power of ultrasound, time on morphology, and size of nano structures were examined. According to the fluorescence titration results, the activated nano-TMU-50 detected NP selectively with a quick response.

EPR monitoring of aniline polymerization: Kinetics and reaction mechanism

The possibility of using EPR spectroscopy to monitor the current concentration of polyaniline and control the kinetics of aniline polymerization is shown. Kinetic measurements were carried out for various temperatures, initial concentrations of reagents. Autocatalysis was detected in all cases. It was shown that the order of polyaniline-catalyzed oxidation of aniline changes from the first to the second as a result of a decrease in the monomer concentration. A new approach to deriving an equation for the rate of oxidative polymerization of aniline and its derivatives is proposed taking into account the physical adsorption and chemisorption of the monomer, and the reaction mechanism is considered.

Crystal structures and evaluated of structural transformations of three novel Lead(II) halide/pseudohalide coordination polymers: Effect of sonochemical synthesis conditions on morphology and particle size

A thermal gradient method (branched tube) was applied to synthesize three novel lead (II) mixed-ligand coordination polymers, [Pb(NNO) (HNNO) (I3)]n (1), [Pb(NNO) (SCN)]n (2) and [Pb(PNO) (I)]n (3), (HPNO ​= ​picolinic acid N-oxide and HNNO ​= ​nicotinic acid N-oxide) which were structurally characterized by single crystal X-ray diffraction. The thermal behavior of 1, 2 and 3 was identified by thermogravimetric analysis. Compounds 2 and 3 were also prepared by an ultrasonic process and their characterizations were carried out by IR spectroscopy, powder X-ray diffraction and scanning electron microscopy. Mechanochemical transformations of compounds 3 and [Pb(PNO) (SCN)] (4) were investigated by replacement of their anions. The particle size and morphology of compounds 2 and 3 were examined by changing the initial concentration of reagents, time and ultrasonic power.

Process Comparison for Caffeine Degradation: Fenton, Photo-Fenton, UV/H2O2 and UV/Fe3+

The fenton, photo-fenton, UV/H2O2 and UV/Fe3+ processes were applied as advanced oxidative treatments in the degradation of caffeine. Parameters such as pH, initial reagent concentration and artificial and natural radiation were evaluated. The tests carried out indicated that the photo-fenton process studied here had its best performance at pH ~ 4.4; however, at pH without adjustment and near to neutral (~ 6.1), the result was also satisfactory at the end of the reaction (~ 51%). The degradation of caffeine, under the conditions studied with artificial radiation, was superior to natural radiation. In addition, it was found that H2O2 was the reagent that most influenced the experimental results obtained, and when studied separately, it was noted that natural pH conditions present excellent results of caffeine degradation. Comparing the artificial radiation used (125 and 250 W), there was no significant influence on the degradation of caffeine. Other parameters analyzed for both the photo-fenton reaction and the UV/H2O2 reaction were the aquatic matrix and, for comparison, the degradation of another emerging pollutant, ibuprofen. In general, the results obtained showed that the UV/H2O2 reaction is promising in the degradation of pollutants such as caffeine.

Perturbation on dynamics of ferroin-catalyzed Belousov–Zhabotinsky reaction by monomer N-isopropylacrylamide and poly(N-isopropylacrylamide)

The present study pertains to the study of ferroin-catalyzed Belousov–Zhabotinsky (BZ) oscillatory chemical reaction having catechol as an organic substrate in aqueous acid media at 30 ± 0.1 °C under stirred batch conditions. The above system shows oscillations within narrow range of concentration of initial reagents which was monitored potentiometrically in oxidation reduction mode. The system shows a long induction time and a good number of oscillations at 30 ± 0.1 °C. The temperature dependence of the above system was studied. Activation parameters have been calculated, and the results showed good agreement with Arrhenius equation. Thermosensitive polymer, Poly(N-isopropylacrylamide) (PNIPAA), was synthesized by conventional method, and the polymer was characterized by different techniques. The catechol-based BZ system with ferroin as a catalyst was perturbed with N-isopropylacrylamide (NIPAA) monomer and the PNIPAA. Both NIPAA and PNIPAA affected mostly the induction time and number of oscillations. Comparative studies of catechol systems based on Ce(IV) and Mn(II) as metal catalysts were also carried out both in the presence and absence of NIPAA and PNIPAA to explore its oscillatory behavior.

Solving the problem of planning a chemical experiment based on genetic algorithms

The article is devoted to the task of planning an experiment in chemistry and chemical technology. The problem statement of finding the optimal ratio of the initial substances of reaction is defined. A genetic algorithm for solving this problem is proposed. The algorithm is tested on the example of the reaction of aminomethylation of thiols using tetramethylmethanediamine. The optimal initial concentrations of reagents are calculated to obtain the maximum yield of the target reaction product.

Ultrasound-assisted synthesis of a stable Co(II) coordination polymer as heterogeneous catalyst for CO2 transformation

A stable benzimidazole-containing Co(II) coordination polymer namely [Co(L)0.5(oba)]n (1) (H2oba = 4,4′-oxybis(benzoate), L = 1,6-bis(5,6-dimethylbenzimidazolyl) hexane) was successfully synthesized by ultrasonic technique under mild conditions. In especial, the effects of initial reagent concentration, irradiation time and ultrasonic power on the morphology and size of micron scale 1 were discussed in detail. Micron scale 1 appeared exceptional solvent and pH stabilities. Further, as a heterogeneous Lewis catalyst, 1 exhibited a highly activity and recyclability for CO2 transformation by cycloaddition with epoxide under room temperature.

Sonication-assisted synthesis of a strawberry-like nano-structure triphenyltin(IV) adduct as precursor for preparation of nano-sized SnP2O7: Crystal structure and DFT calculations

A triphenyltin(IV) adduct of phosphoramide with a formula of [Sn(Ph)3Cl(L1)] (C1), L1 = N-phenyl-N´,N´´-bis(pentamethylene) phosphoric triamide, has been synthesized and characterized by elemental analyses and IR spectroscopy. In the crystal structure, the tin(IV) environment adopts a distorted trigonal bipyramidal geometry with three phenyl groups in the equatorial plane, one chloro atom and the oxygen atom of ligand at the axial sites. Hirshfeld surface analysis and fingerprint plots were used to investigat of the intermolecular interactions, responsible for the crystal architecture. The complex was also prepared under ultrasonic irradiation (C1a) and characterized by elemental analyses, IR, and X-ray powder diffraction (XRPD). The effects of two different concentrations of initial reagents on the size and morphology of the nanomaterial were studied by scanning electron microscopy (SEM), which shows that C1a grown as nano-strawberry morphology. The calcination of triorganotin complex in air atmosphere led to production of nano-structured tin pyrophosphate. The thermal stabilities of the single crystal and of the nano-crystalline form were investigated by thermal gravimetric and differential thermal analyses. The structural and electronic properties of L1, C1 and similar molecules were evaluated by density functional theory (DFT) calculations. Parameters derived from NBO and QTAIM analyses suggest that the nature of Sn-O interaction is electrostatic with a small amount of covalent character and donor-acceptor delocalization from the ligand oxygen atom to the tin center. Moreover, the electronic parameters including HOMO-LUMO orbitals, bond gap, chemical hardness-softness, electronegativity, and electrophilicity were calculated.

Optimizing the Fenton Based Pre-Treatment of Landfill Leachate Using Response Surface Methodology

Mixing of xenobiotic substances with the household waste decreases the biodegradability of leachate generated from municipal landfill sites. In various parts of the world, where solar energy is pervasive, solar photo Fenton-based pre-treatment of municipal landfill leachate can be considered as a potential pre-treatment method to improve its biodegradability. Therefore, this paper reports a laboratory study conducted to compare the efficiency of Fenton and Solar Photo Fenton processes to pre-treat leachate from municipal solid waste landfill site of Chandigarh, India. The operating parameters such as pH and initial concentrations of reagents (i.e., H2O2 and Fe2+) were optimized using a three level multivariate Box-Behnken statistical approach in combination with response surface methodology. After 2 h of treatment, at the optimal conditions of pH 3.4, [H2O2] = 2.73 g/L and [Fe2+] = 63.71 mg/L, 86.21% degradation of Chemical Oxygen Demand (COD) was observed after solar photo Fenton-based treatment. On the contrary, the final COD removal obtained using Fenton process at the optimal conditions, pH 5, [H2O2] = 2.66 g/L, [Fe2+] = 47.29 mg/L, was 59.19%. Further, this study showed that the Fenton based pre-treatment can enhance the biodegradability of landfill leachate. After pre-treatment, the Biological Oxygen Demand (BOD5) to COD ratio of landfill leachate improved from 0.13 to 0.57 and 0.49 for solar photo Fenton process and Fenton process, respectively. Findings of this study will trigger the broader interest of the auditory comprising policy makers and scientists to treat the leachate using renewable sources and prevent contamination of groundwater.

Oxidative Destruction of Phenol in Aqueous Solution by Cotreatment with UV Radiation and Hydrogen Peroxide

The oxidative degradation of aqueous solutions of phenol by radiation with ultraviolet light and combined treatment with ultraviolet radiation and hydrogen peroxide has been studied. It has been found that the degree of oxidation of phenol by ultraviolet irradiation can be as high as 99.9%. It has been demonstrated that the initial pollutant and reagent concentrations have a significant effect on the degree of conversion and the rate of oxidation process. For the first time, the kinetic effect of phenol degradation has been experimentally revealed when phenol enters into the aqueous medium preliminarily irradiated with ultraviolet light. The products of the oxidative degradation of phenol have been identified and quantified.

Study of the Formation Process of Memristor Structures Based on Copper Sulfide

An alternative to the currently existing elemental basis for creating dynamic random-access memory and flash memory is memristor structures, i.e., two-electrode systems, whose operation is based on the resistance switching effect. In this paper, the results of studying the specific features of the production of memristor structures on the basis of copper sulfide as a promising material providing high-efficiency performance of the structures are reported. The process of copper sulfurization is considered. In this process, the surface region of the copper layer is transformed into sulfide, and the remaining part of the layer is used as the active electrode for the later formed memristor structure. It is shown that, as the concentrations of the initial chemical reagents is increased, the surface roughness of the sulfide layer significantly increases. The sulfide growth rate at optimal initial concentrations of the chemical reagents is ~30 nm/min. In studies of memristor structures, it is established that, as the copper sulfide thickness is increased, the ratio between the resistances in the low- and high-resistance states increases from 11.2 to 12.5. In the memristor structures formed in the study, the time of switching from the high- to low-resistance state is about 1.3 μs, whereas the time of switching from the low- to high-resistance state is 0.9 μs.

Ultrasonic-assisted synthesis of the nanostructures of a Co(II) metal organic framework as a highly sensitive fluorescence probe of phenol derivatives.

Nanostructures of a metal-organic framework with chemical formula, [Co(BDC)(L*)]n.DMF (TMU-40), BDC = 1,4-benzendicarboxylate, L* = 5,6-dipyridin-4-yl-1,2,3,4-tetrahydropyrazine, under ultrasonic irradiation at ambient temperature and atmospheric pressure were prepared and characterized by Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Sonication time, concentration of initial reagents and ultrasonic generator power effects on the size and morphology of nano-structured compounds were studied. TMU-40 (for Tarbiat Modares University) displayed a good potential as a luminescent sensor against phenol derivatives consist of phenol, 4-aminophenol, 4-methylphenol and 4-chlorophenol. Nano-sized TMU-40 showed the better sensing performance in comparison to its bulk phase. The nano TMU-40 displayed very selective and sensitive in detection of phenol derivatives. The detection limit amounts of 15 nM and 63 nM were achieved for 4-aminophenol in nano TMU-40 and bulk TMU-40, respectively. The special structure and fluorescent character of L* ligand and high surface area of nano MOF provide an effective interaction between MOF and phenolic analytes to selectively and sensitively detect of the analyte molecules.

Comparative study of K2SO4 production by wet conversion from phosphogypsum and synthetic gypsum

This paper proposes a very attractive process for K2SO4 production via the wet conversion of phosphogypsum (PG) and K2CO3. A parallel study of the conversion of two synthetic types of gypsum by K2SO4 was performed in order to compare their reactivity with that of PG.We remark that PG is more reactive and yields the desired results while commercial types of gypsum react slowly and generate unwanted secondary products. The factors affecting the PG conversion processes such as the initial concentration of reagents, the reaction time and the reaction temperature was studied to optimize the reaction conditions. X-ray diffraction (XRD) was used to characterize the PG conversion at different conditions while the other techniques (Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), scanning electron microscopy (SEM), flame photometer (FP), inductively coupled plasma mass spectrometry (ICP-MS) and thermogravimetric analysis (TGA)) were applied to prove the quality of the final products.Based on the obtained results, the reaction is carried out with stoichiometric proportions between PG and K2CO3. The maximal conversion of PG is attained at 80°C; this temperature corresponds to the higher solubility of K2SO4, which is 1.2mol/l.

Two Synthetic Replicators Compete To Process a Dynamic Reagent Pool.

Complementary building blocks, comprising a set of four aromatic aldehydes and a set of four nucleophiles-three anilines and one hydroxylamine-combine through condensation reactions to afford a dynamic covalent library (DCL) consisting of the eight starting materials and 16 condensation products. One of the aldehydes and, consequently, all of the DCL members derived from this compound bear an amidopyridine recognition site. Exposure of this DCL to two maleimides, Mp and Mm, each equipped with a carboxylic acid recognition site, results in the formation of a series of products through irreversible 1,3-dipolar cycloaddition reactions with the four nitrones present in the DCL. However, only the two cycloadducts in the product pool that incorporate both recognition sites, Tp and Tm, are self-replicators that can harness the DCL as feedstock for their own formation, facilitating their own synthesis via autocatalytic and cross-catalytic pathways. The ability of these replicators to direct their own formation from the components present in the dynamic reagent pool in response to the input of instructions in the form of preformed replicators is demonstrated through a series of quantitative 19F{1H} NMR spectroscopy experiments. Simulations establish the critical relationships between the kinetic and thermodynamic parameters of the replicators, the initial reagent concentrations, and the presence or absence of the DCL and their influence on the competition between Tp and Tm. Thus, we establish the rules that govern the behavior of the competing replicators under conditions where their formation is coupled tightly to the processing of a DCL.

Optimization of synthesis conditions of HgS thin films

The mercury sulfide (HgS) films were obtained on glass substrates via the chemical deposition method. The aqueous solutions of mercury(II) nitrate, thiourea and trisodium citrate were used. X-ray and elemental analysis of the film sample were made. The effect of concentrations of initial reagents, deposition duration and temperature on the mass of HgS coatings was investigated and their thickness were calculated. The optical and morphological properties of HgS coating were examined. Keywords : mercury sulfide, thin films, chemical deposition, optical properties.

Biodiesel production using calcium‐based catalyst from venus shell: Modeling of startup production in an industrial reactor

Calcium oxide‐based catalyst was produced from Venus shell by fast fluidized bed calcination for biodiesel synthesis. The kinetics of biodiesel synthesis was found to be a pseudo‐first‐order reaction at the experimental conditions. The obtained kinetic parameters were used for modeling the startup operation of biodiesel production in an industrial continuous stirred tank reactor (CSTR). The model was found to agree well with the reagent concentration and temperature profiles in a real production practice during biodiesel production. The variations of initial temperature, initial reagent concentration in the reactor was investigated. It was found that the reagent concentration and temperature oscillated around the final steady state. From safety operation perspective, the first 4 h were found to be the most unsteady period during continuous production. The initial concentration of waste fry oil (WFO) was also found to be critical to the safe operation of CSTR. A violation of the settings for safe operation of CSTR will be triggered once the initial concentration of WFO in CSTR reaches 500 mol m−3. © 2018 American Institute of Chemical Engineers Environ Prog, 38:e13053, 2019

Ultrasound and solvothermal synthesis of a new urea-based metal-organic framework as a precursor for fabrication of cadmium(II) oxide nanostructures

Dramatic advances in nanostructured MOFs have been strongly promoted by the introduction and development of new synthetic methods that control the size, morphology, and nano/microstructure. High intensity ultrasound method suggests an environmentally friendly, facile and versatile synthetic method to these nanostructured materials that are complicated to synthesize by commonly used methods. Both Solvothermal and sonochemical methods were used to synthesize the new urea-based metal-organic framework [Cd(L1)(DMF)3] (1). Compound 1 was structurally characterized by using X-ray crystallography and spectroscopically by different techniques. The effect of concentration of the initial reagents, time of sonication and sonication power on size and morphology has been studied. The results indicate that decreasing concentration of initial reagents, along with increasing ultrasonic radiation time, cause a dramatic effect on the size and morphology of compound 1. Calcination of the nano-sized plate-like particles of compound 1 at 550 °C under air atmosphere yields CdO nanoparticles.

Polymer Degradation in a Solution: Monitoring and Predicting Quality Parameters

The experimental study of polymer degradation processes in a solution is carried out. A mathematical description of the time dependences of the main polymer structural characteristics, i.e., the number average Mw and the weight average Mn molecular weight and the polydispersity coefficient Kp are obtained. For the model adequacy to be tested and the calculation error to be estimated, linear polymers—SKD-ND rubbers— are used as experimental samples. The change in the polymer molecular weight distribution (MWD) and its parameters are studied by gel permeation chromatography. The resulting dependences can be used for the process control systems. The developed mathematical description relates the controllable and control parameters in the structure (initial reagent concentrations, the reagent ratio, reaction temperature, etc.). However, the complete reconstruction of the mode of the MWD and its time dependence cannot be achieved.