Influence Of Reaction Conditions Research Articles

Self-supported Ni2P nanotubes coated with FeP nanoparticles electrocatalyst (FeP@Ni2P/NF) for oxygen evolution reaction

Bimetallic phosphides have been widely investigated as electrocatalysts for oxygen evolution reaction (OER) due to their efficient activity and environmental friendliness. While the reasonable design and controllable synthesis of bimetallic phosphide with typical nanostructure is still a great challenge. Hence, we put forward a novel and straightforward way for constructing FeP nanoparticles coated Ni2P ultrathin nanotube arrays on the surface of Ni foil (FeP@Ni2P/NF), which is synthesized through two steps of electrodeposition and subsequent in-situ phosphorization process. The obtained FeP@Ni2P/NF shows excellent electrochemical activity for OER, and it only needs potential of 1.52 V vs. RHE to reach the current density of 50 mA cm−2 in an alkaline media. The excellent electrocatalytic activity of FeP@Ni2P/NF mainly benefits from: (i) the synergistic effect between FeP and Ni2P promoting electron transfer; (ii) the formation of the unique 3D ultrathin nanotube arrays increasing the quantity of active sites and avoiding the agglomeration of catalysts during testing. In addition, the influence of reaction condition on the electrochemical activity for OER has also been investigated through altering the phosphorization temperature of precursor.

Cobalt chromium-layered double hydroxide, α- and β- Co(OH)2 and amorphous Cr(OH)3: synthesis, modification and characterization

Cobalt-chromium layered double hydroxide (CoCr LDH), α- and β- Co(OH)2 and amorphous Cr(OH)3 have been synthesized under different reaction conditions. The obtained CoCr LDH was modified by stearic acid (SA) and sodium stearate (SS). The obtained samples have been characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), Ultraviolet-visible- (UV-Vis), Fourier transform infrared- (FTIR) and Energy-dispersive X-ray- (EDX) spectroscopy. The influence of reaction conditions on product composition, structural and optical properties of the samples have been discussed in detail. The basal spacing of CoCr-LDH increased from 7.366 Å to 7.428 Å and 25.214Å after the intercalation by stearic acid and sodium stearate, respectively. The average particles size by SEM analyze was estimated to be approximately 100–150 nm and 30–50 nm for CoCr-LDH0.6M(90°C) and CoCr-LDH0.6M(90°C)/SS nanostructures, respectively. Mixed hydroxides like α- and β- Co(OH)2 have been obtained along with LDH at lower pH value (pH ∼ 7). The number of diffraction peaks corresponding to β-Co(OH)2 has increased with relatively decreasing of Co2+ ions in the reaction medium. At high chromium concentrations (Co2+:Cr3+ = 1:3 and 1:5), amorphous Cr(OH)3 were formed in the experiment.

DEVELOPMENT AND RESEARCH OF PACKAGING PAPER MODIFIED BY TITANIUM DIOXIDE NANOPARTICLES

Research is conducted on the development of paper packaging materials with antibacterial properties using titanium dioxide nanoparticles. Titanium dioxide nanoparticles are synthesized by the hydrolysis of titanium tetrachloride in an alkaline medium, adjusting the pH value with an aqueous solution of ammonia at a temperature of 30 to 60°C. The influence of reaction conditions on the synthesis of titanium dioxide nanoparticles and the pH of the medium are studied and the optimal synthesis conditions are found. The processing parameters of paper packaging materials with aqueous solutions of titanium dioxide nanoparticles, which give them antimicrobial properties, are determined. Using electron-scanning microscopy and energy dispersive microanalysis, it is shown that untreated packaging paper contains 64.69% of C and 35.31% of O; after modification with a solution of titanium dioxide nanoparticles, titanium dioxide particles, which are distributed quite unevenly depending on the initial concentration of titanium dioxide nanoparticles, form on 16.46–21.14% of the surface of the treated paper. The packaging materials modified by the proposed composition show strong resistance to the action of microorganisms. The use of the developed antimicrobial food packaging reduces losses and preserves the quality and safety of food products during transportation, storage, and sales.

Influence of reaction conditions on solvolysis of organosolv lignin using water and green organic co-solvents as reaction medium

This study investigated the non-catalyzed solvolysis of sulphur free organosolv lignin using mixtures of organic solvents (methanol, ethanol and 2-methyltetrahydrofuran) and water with emphasis on the novel biphasic 2-methyltetrahydrofuran (2-MTHF)/water reaction medium. The effect of co-solvents, co-solvent-to-water ratio and temperature were studied. 2-MTHF proved to be effective co-solvent with water that significantly suppressed char formation and also demonstrated promising protection effect on monoaromatic compounds. The yield of solvolyzed lignin (SL) and char were in the range of 40.0–88.6% and 10.4–0.1% respectively, based on initial amount of dried lignin. The yield of monoaromatics maximized to 67.2 mg g−1 of lignin at 310 °C and 60 min with syringol, syringaldehyde, 4-methylsyringol, 1,2,3-trimethoxy-5-methyl benzene and guaiacol as the main compounds.

The Influence of Reaction Conditions on DNA Multimerization During Isothermal Amplification with Bst exo- DNA Polymerase.

Methods for isothermal amplification of nucleic acids are gained more attention in the last two decades. For isothermal amplification, DNA polymerases with strand displacement activity are required, and Bst exo- is one of the most commonly used polymerases. However, Bst exo- is able to cause nonspecific DNA amplification through multimerization, which leads to a set of undesirable by-products. In this study, circumstances that facilitate DNA multimerization by Bst exo- polymerase have been determined. We found that an essential requirement for multimerization is the presence of short (50-60 bp) DNA duplexes formed through primer extension after annealing on the template or in homo- and heterodimers. The highest multimerization efficiency is observed for Bst 2.0 polymerase in buffers with a high salt concentration and/or in the presence of reducing agents (for example, β-mercaptoethanol). Multimerization occurs mainly at 55-60 °С, while specific isothermal amplification is more efficient at 60-65 °С. The SYBR Green I intercalating dye inhibits multimerization with Bst LF and Bst 2.0 polymerases in concentrations above 0.25×, whereas inhibition with Bst 3.0 polymerase occurs only above 1.25×. The obtained results allow to elaborate accurate and reliable methods for isothermal amplification of nucleic acids.

Hafnium-Doped Mesoporous Silica as Efficient Lewis Acidic Catalyst for Friedel-Crafts Alkylation Reactions.

The development of an efficient solid catalyst for Friedel–Crafts (FC) reactions is of great importance to organic synthetic chemistry. Herein, we reported the hafnium-doped mesoporous silica catalyst Hf/SBA-15 and its first use for Friedel–Crafts alkylation reactions. Catalysts with different Si/Hf ratios were prepared and characterized, among which Hf/SBA-15(20) (Si/Hf = 20:1) was the most active catalyst, offering up to 99.1% benzylated product under mild reaction conditions. The influences of reaction conditions on the product were systematically investigated and compared. Pyridine-IR characterization of the catalyst showed that Lewis acid formed the primary active sites for the Friedel–Crafts alkylation reaction. X-ray photoelectron spectroscopy (XPS) characterization revealed that the electron shift from the Hf center to the silica framework resulted in a more active Lewis metal center for FC reactions. Moreover, the catalyst was successfully applied to the alkylation reaction with different alcohols and aromatic compounds. Finally, the Hf/SBA-15(20) catalyst also showed good recyclability in the recycling runs, demonstrating its high potential of being used for large scale FC reactions in the industry.

Isoindole based fluorophore for the sensitive fluorimetric determination of isobutyl gamma aminobutyric acid

The present work deals with the development and validation of a selective and highly sensitive spectrofluorimetric method for determination of 3-isobutyl gamma amino butyric acid (3-isobutyl GABA). The drug is selectively condensed with o-phthalaldehyde in presence of 2-mercaptoethanol to form a highly fluorescent isoindole derivative. The fluorescent intensity of the obtained fluorophore was monitored at 431 nm (λex = 335 nm). The influence of reaction conditions was investigated in order to enhance the sensitivity of the proposed procedure. At the optimized reaction condition the fluorescence intensity was found to be in linear relationship with drug concentration in the range of 0.025 0.125 μg ml−1. The quantitation and detection limits were 15.5 and 4.6 ng ml−1, respectively. The guidelines of the International Conference on Harmonization (ICH) were followed in order to validate the suggested procedure. The developed method was employed for the analysis of pharmaceutical preparations containing the cited drug. The obtained data were compared with those from the reported method. Good agreement was found between both methods in respect to the accuracy and precision. Moreover, the proposed method utilizes low cost reagents, and has high sensitivity. These advantages give the method the ability to be a good alternative for determination of cited drug in routine analysis.

Synthesis and Swelling Behavior of Poly(acrylic acid)/Graphite Oxide Superabsorbent Composite

Poly(acrylic acid)/graphite oxide superabsorbent composite was prepared by solution intercalation polymerization of acrylic acid and graphite oxide using N,N-methylene-bis-acrylamide as a cross-linker and potassium persulfate as an initiator. The composite was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscope, powder X-ray diffraction and differential scanning calorimetry. The influence of reaction conditions on water and saline absorption of superabsorbent was studied in details. Water retention properties of the composite were also discussed. The improvement of absorption capacities and the retention rates with the incorporation of graphite oxide was found.

An Overview of Light Olefins Production via Steam Enhanced Catalytic Cracking

Steam thermal cracking is an established technology for the production of light olefins, such as ethylene and propylene. The shift to lighter, ethane-based feeds means that propylene production from steam crackers will be lower than the corresponding ethylene production. Therefore, alternative technologies have to be developed to produce more propylene to make up for the shortfall from steam cracking. This review looks at the steam catalytic cracking technology, which combines both catalytic cracking and steam cracking to maximize the production of light olefins. This review looks at the effect of catalyst and technology applied in fluid catalytic cracking reactors to enhance light olefins production. The influence of reaction conditions and the reaction mechanism are also presented. The graphical abstract shows the feed and steam being fed into the FCC unit from which light olefins and gasoline are produced as the desired products.

Acid catalyzed acetalization of aldehydes with diols resulting into the formation of fragrant cyclic acetals

The influence of reaction conditions (amount and type of the catalyst, the reaction temperature, the type of the solvent) on the reaction course of the acetalization of aldehydes with diols was tested in this paper. The optimization of reaction conditions was performed on model reaction, acetalization of 2-methylpentanal by 2-methyl-2-propyl-1,3-propanediol leading to the formation of fragrant compound 2-(1-methylbutyl)-5-methyl-5-propyl-1,3-dioxane (Troenan). p-Toluenesulfonic acid was used as an active homogeneous catalyst. It appeared to be advantageous not to use any solvent in the reaction. Using 0.3 wt% of the catalyst the almost total conversion of 2-methylpentanal was achieved after 240 min of reaction at room temperature while the selectivity to the desired product was about 98%. The optimized reaction conditions were applied to the preparation of four cyclic fragrant acetals (namely 2-hexyl-1,3-dioxolane, 2-hexyl-4-methyl-1,3-dioxolane, 2-benzyl-5-hydroxy-1,3-dioxane and 2-(1-methylbutyl)-5-methyl-5-propyl-1,3-dioxane) in larger scale; and these were sensory evaluated after purification step. Prepared heterogeneous catalysts, acid modified montmorillonite (MMT) K-10 (treated by H2SO4, HNO3, and HCl) were successful in the model reaction. The conversion of 2-methylpentanal over 90% was achieved using acid modified MMT after 300 min of reaction at room temperature, the selectivity to the desired product was about 98%. MMT/H2SO4 can be used in the model reaction four times without any change in the reaction course, what makes it promising for the further application.

Supercritical water oxidation of ammonia with methanol as the auxiliary fuel: Comparing with isopropanol

The co-oxidation behavior of methanol on ammonia in supercritical water was investigated in a continuous tubular reactor under a range of methanol concentration (10–800 mmol/L), ammonia concentration (50–400 mmol/L), oxidation coefficient (1.05–1.7) and preheating temperature of 400 and 415 °C. Calculation based on a mechanism-based model for supercritical water oxidation of methanol/ammonia showed that the synergy between the kinetics action to supply radicals and the thermal action to elevate the reaction temperature of methanol would improve the efficient decomposition of ammonia at relatively moderate reaction conditions. Specifically, near complete conversion of ammonia (97.5%) can be achieved at [CH3OH]0 = 800 mmol/L, preheating temperature of 415 °C and oxidation coefficient of 1.5. The influence of reaction conditions on the co-oxidation behavior and the formation of nitrate were examined experimentally. Methanol and isopropanol served as the auxiliary fuel for ammonia were compared by the positive effect and exothermic performance, which reached that methanol was superior to isopropanol.

Influence of Reaction Conditions and Promoting Role of Ammonia Produced at Higher Temperature Conditions in Its Synthesis Process over Cs‐Ru/MgO Catalyst

AbstractCs promoted Ru/MgO catalyst was prepared by an impregnation method using Ru(NO3)3 and Cs(NO3)2 as precursor compounds. The activity measurements for ammonia (NH3) synthesis were carried out in a fixed‐bed flow reactor. A reactant stream of H2 and N2 was used for NH3 synthesis. The influences of reaction temperature, pressure and H2/N2 ratio on the performance of the catalyst were investigated in detail. The relative concentration of H2 and N2 in the reactant stream highly influenced the catalytic activity. The remarkably higher rate of NH3 synthesis was observed for the higher H2/N2 ratio at 400 °C and lower H2 concentration in the reactant stream improved the catalytic activity at lower temperature conditions. A sharp increase in the catalytic activity of Cs−Ru/MgO with an increase in pressure was observed at 400 °C for a reactant stream with higher H2 concentration. Relatively less interaction of H2 with the surface of the catalyst is suggested in the presence of NH3 produced during the reaction conducted at elevated temperature conditions. This less susceptibility for H2 adsorption on the active sites of the catalyst is a plausible reason for a higher rate of NH3 synthesis at higher temperature conditions. We modified the Temkin equation model by considering the adsorbed species on the surface of the catalyst affecting NH3 synthesis.

Chemical Versatility of [FeFe]-Hydrogenase Models: Distinctive Activity of [μ-C6H4-1,2-(κ2-S)2][Fe2(CO)6] for Electrocatalytic CO2 Reduction

The [FeFe]-hydrogenase model, [(μ-bdt)Fe2(CO)6] (1, bdt = benzene-1,2-dithiolato), displays distinctive activity from its analogous complex, [(μ-edt)Fe2(CO)6] (2, edt = ethane-1,2-dithiolato), for electrochemical CO2 reduction in acetonitrile with methanol or water as proton source. The maximum turnover frequency of 195 s–1 estimated for 1 is more than 4800 times higher than that of 2. The influence of reaction conditions on faradaic yield and product selectivity was investigated. Controlled potential electrolysis experiments of 1 under optimal conditions gave a good faradaic yield of 88%, with formic acid as major product (selectivity ≈81%) together with a small amount of CO (selectivity ≈ 11%) and H2 (selectivity ≈ 8%). Density functional theory calculations suggest a mechanism of bimetal synergistic catalysis for electrochemical CO2 reduction by 1.

A new method to prepare mesoporous silica from coal gasification fine slag and its application in methylene blue adsorption

Mesoporous silica materials are often restricted from large-scale industrial production due to their high preparation costs. This study used the solid waste coal gasification fine slag (FS) as the silica source, utilizing the simple acid leaching technology, successfully produced mesoporous glass microspheres (MGS) with specific surface area of 364 m2/g and pore volume of 0.339 cm3/g. The porous structure was confirmed by TEM. Moreover, the influences of reaction conditions on the specific surface area and pore structure were thoroughly investigated. The methylene blue adsorption test on the prepared mesoporous microspheres showed a maximum adsorption capacity of 140.57 mg/g. This research provides a new method for the industrial production of mesoporous silica.

Electronic Effects of the Backbone on Bis(imino)pyridyliron(II)‐Catalyzed Ethylene Polymerization

A series of bis(imino)pyridyl iron(II) complexes 1–5 with electron‐donating and ‐withdrawing substituents on the backbone of the ligand have been synthesized and characterized. Activated with methylaluminoxane (MAO), ethylene polymerization by these iron(II) complexes was investigated in detail, involving the electronic effect and influence of reaction conditions on catalyst activity and polymer molecular weight. The electronic perturbations exert great influence on the catalytic activity of ethylene polymerization. Complexes bearing electron‐withdrawing substituents in the 4‐position of the pyridine ring showed the better activity than analogues bearing electron‐donating substituents. However, no clear trend was observed for the dependence of polymer molecular weight on these substituents. In particular, the binuclear iron(III) complex 2′ we obtained by accident displayed a similar catalytic behavior compared to its iron(II) analogue complex 2.

Methyltrioxorhenium as a Lewis Acid in the Prins Cyclization of Benzaldehyde and Isoprenol

Methyltrioxorhenium (MTO) as a Lewis acid was used in the acid catalyzed reaction of benzaldehyde and isoprenol leading to the formation of 4-methyl-2-phenyl-tetrahydro-2H-pyran-4-ol. The influence of reaction conditions on the reaction course was investigated. Under optimal reaction conditions (70 °C, a molar ratio of reactants 1:1, 1 wt% of MTO, no solvent, 100 mol% of water) the selectivity to desired product was 76%. The addition of water to the reaction mixture evoked the decrease of the reaction rate and slight increase of selectivity (without water addition the selectivity was approximately 70%). The typical composition of isomers of the desired product was cis:trans = 30:70. The mechanism of Prins cyclization using methyltrioxorhenium as the catalyst was offered. This mechanism explains the low concentration of intermediate hemiacetal in the reaction mixture using MTO as the catalyst. MTO was also heterogenized on silica, alumosilicate and alumina support. Characterization confirmed the successful attachment and homogeneous distribution of MTO on the supports, but kinetic measurement showed high leaching of MTO from pure silica and aluminosilicate support. MTO/alumina was reused with a low decrease of conversion.

Kinetic parameter estimation and simulation of trickle-bed reactor for hydrodenitrogenation of whole-fraction low-temperature coal tar

ABSTRACTA kinetic model of whole-fraction low-temperature coal tar (LTCT) hydrodenitrogenation (HDN) was established and applied to a bench-scale trickle-bed reactor (TBR). The gPROMS software was used for parameter estimation, and nonlinear regression method was used to get the kinetic parameters: Ea = 98,173; k0 = 1.7 × 106; n = 1.56; α = -0.16; m = 0.5; tc = 12,196; β = 1.06. The concentration of nitrogen compounds in the liquid phase at different axial positions of TBR was obtained. At the same time, the order of influence of reaction conditions on HDN was temperature, LHSV, and pressure. The effectiveness factors at different positions of the catalyst bed were analyzed, and the influence of different reaction conditions on the effectiveness factor was studied.

Phase controllable synthesis of NaMgF3:Yb3+, Er3+ nanocrystals with effective red upconversion luminescence

Synthesizing and controlling lanthanide ions doped upconversion luminescent nanocrystals with effective emission have been researched to satisfy the demand for different applications. In this work, the influence of reaction conditions on crystal composition and upconversion luminescence properties of NaMgF3:Yb3+, Er3+ nanocrystals have been explored with XRD and upconversion emission spectra. The experimental results demonstrate that lanthanide ions concentration has great impact on the growth of samples, i.e., a low concentration leads to cube NaMgF3 nanocrystals, while a high concentration facilitates impurity NaYbF4 microtube. Adjusting reaction parameters is also crucial for controlling NaMgF3 crystal structure by shortening reaction time and reducing reaction temperature. In addition, the well-dispersed NaMgF3:Yb3+, Er3+ nanocrystals with different red-to-green ratios have been achieved successfully by changing the reaction parameters, resulting in the upconversion luminescence from orange to red, and the single-band red UC luminescence can be observed in NaMgF3:0.5Yb3+, 0.5Er3+ nanocrystals. This study explains the formation mechanism of NaMgF3:Yb3+, Er3+ nanocrystals and gains the effective red luminescence, which may be helpful to synthesize other similar upconversion nanocrystals in colour display, bioimaging and so on.

Co-pyrolysis of lignocellulosic biomass with low-quality coal: Optimal design and synergistic effect from gaseous products distribution

Co-pyrolysis of lignocellulosic biomass and low-quality coal can alternate fossil fuel partially and utilize biomass on a commercial scale. Gaseous products from co-pyrolysis process can be widely applied in industries due to the advantage in transportation and compression. Thus, investigation of synergistic effect and optimal design about gas products is essential for efficiently and comprehensively design of the process. In this research, three model compounds of lignocellulosic biomass (cellulose, hemicellulose, lignin) and wheat straw were co-pyrolyzed with a kind of low-quality coal via a drop tube furnace. Based on the component insight of biomass and response surface methodology, synergetic effects from gas distribution were investigated. The influence of reaction condition (biomass ratio and pyrolysis temperature) on the yield and high heat value (HHV) of gaseous products were explored. Optimal result for the objective of the highest effective gas yield during co-pyrolysis were obtained. Results revealed that both positive and negative synergic effects on yields and composition of pyrolysis gas were presented. When pyrolysis temperature was 600 °C, both wheat straw and three model compounds promoted the formation of H2 and CO. Negative effects on CO2 were observed when co-pyrolysis of cellulose/wheat straw with coal at the temperature of 600 °C to 800 °C. Whether positive or negative synergy existed depended on the mixing ratio, temperature and combined action of lignin, hemicellulose, and cellulose. For coal and hemicellulose mixtures, the mixing ratio of 0.03 and temperature of 936 °C can get the highest yield of H2 (20.56 mmol/g). Moreover, the maximum yield of CO and CO2 was obtained at cellulose mixing ratio of 0.99 and 0.98 at 787 °C and 626 °C, respectively. Based on the view of biomass composition, the results can be used to optimize the gaseous products distribution during co-pyrolysis of coal and biomass.

New thermally stable condensation polymers containing central ketal moieties derived from malonaldehydetetramethyl acetal and dihydroxyaromatic compounds

A number of new condensation polymers with acetal units in the main chain and having linear and ladder-form structure and high thermal stability were synthesized by solution polycondensation of dihydroxyaromatic compounds with malonaldehydetetramethyl acetal as a reactive protected 1,3-dicarbonyl compound. Optimal conditions for polycondensation were obtained via study of the model compounds. In order to obtain high molecular weight polymers, general investigations on the influence of reaction conditions, such as monomer concentration and reaction temperature were carried out. All polymers were obtained in high yields and moderate inherent viscosity ranging from 0.25 to 0.41 dL/g. The proposed chemical structures of condensation polymers were confirmed by 1H-NMR, 13C-NMR, FTIR spectroscopies, TGA, and DSC. Thermal analysis indicated that these polymers are stable up to 360 °C, and a 10% weight loss (T10) were recorded on the TG curves in the temperature range of 381–411 °C in nitrogen atmosphere, indicating their good thermal stability.