Initial Reactants Research Articles

Synthesis and characterization of polysulfone based on poly(ethylene terephthalate) waste

The recycling process of Poly(ethylene terephthalate) (PET) wastes is commercially important since it converts a waste material into a value‐added product and also helps to alleviate environmental pollution. PET waste was depolymerized in the presence of ethylene glycol and manganese acetate as a catalyst. Bis(hydroxyethyl terephthalate), (BHET) and other oligomers are predominately the glycolyzed products (GP). These GP products were reacted with a prepared dichlorodiphenylsulfone (DCDPS) in presence of dried potassium carbonate. Two polysulfones (A &B) with different number average molecular weights, 1787 and 3162 g/mol. were obtained, respectively. The chemical structures of the resulting two polysulfones were elucidated using 1HNMR and characterized by the known conventional analysis techniques (e.g. FTIR, GPC, DSC, TGA…). The prepared polysulfone (B) disclosed higher thermal stability with respect to the initial reactants. The originality of this study was derived from the use of waste materials to yield a product that has acceptable high thermal stability which provide many beneficial applications in various industrial fields. POLYM. ENG. SCI., 55:1671–1678, 2015. © 2014 Society of Plastics Engineers

MnO x -Al2O3 catalysts for deep oxidation prepared with the use of mechanochemical activation: The effect of synthesis conditions on the phase composition and catalytic properties

The catalytic activity of alumina-manganese catalysts in the oxidation of CO was studied. The MnOx-Al2O3 catalysts were prepared by an extrusion method with the introduction of mechanically activated components (manganese oxide and its mixtures with aluminum oxide, aluminum hydroxide, and a mixture of a manganese salt with aluminum hydroxide) into a paste of aluminum hydroxide followed by thermal treatment in air or argon at 1000°C. In the majority of cases, the catalysts contained a mixture of the phases of β-Mn3O4 (Mn2O3), α-Al2O3, and δ-Al2O3. The presence of low-temperature δ-Al2O3 suggested the incomplete interaction of manganese and aluminum oxides. It was found that the catalytic activity of MnOx-Al2O3 depends on the degree of interaction of the initial reactants, and its value is correlated with the amount of β-Mn3O4 in the active constituent. The intermediate thermal treatment of components at 700°C negatively affects the catalytic activity as a result of the formation of Mn2O3 and the coarsening of particles, which levels the results of mechanochemical activation. The greatest degree of interaction between Al- and Mn-containing components was reached in the selection of mechanochemical activation conditions by decreasing the size of grinding bodies, optimizing the time of mechanochemical activation, and using the mechanochemical activation of precursor mixtures. As a result of mechanochemical activation, the initial reactants were dispersed, the amounts of MnO2 and Mn2O3 changed, and defects were formed; this strengthened the interaction of components and increased catalytic activity.

Population Balance Modeling of Barium Sulfate Nanoparticle Synthesis via Inverse Microemulsion Including Coagulation Effect

A deterministic model based on the discrete population balance equation (PBE) is used to examine the precipitation of barium sulfate nanoparticles in nonionic inverse microemulsion systems. It is shown that coagulation can have a significant effect at low initial reactants concentration. The simulation results show that a bimodal particle size distribution (PSD) observed in experimental analysis reported in the literature cannot be predicted by neglecting the coagulation effect. A coagulation kernel is proposed that takes into account the effect of interparticle forces through the Fuchs’ stability ratio. The effect of electrolyte concentration on the surfactant headgroup area is also investigated. It is shown that at lower electrolyte concentration, the nucleation and growth rates increase because of higher interdroplet exchange rate. The simulation results show a qualitatively good agreement with experimental data regarding PSD prediction and dynamic evolution of mean particle diameter.

A situ hydrothermal synthesis of SrTiO3/TiO2 heterostructure nanosheets with exposed (0 0 1) facets for enhancing photocatalytic degradation activity

Designingand constructing heterojunction structures based on (001) facets dominated anatase TiO2 has attracted much attention for acquiring higher photocatalytic activity. Here, SrTiO3/TiO2 heterostructure nanosheets with different SrTiO3 contents were fabricated by in situ hydrothermal reaction, in which anatase TiO2 nanosheets with dominant exposed (001) facets were used as templates and initial reactants. Compared with pure TiO2 nanosheets, SrTiO3/TiO2 nanosheets exhibit better photocatalytic activity in degradation of rhodamine B (RhB) owing to the formation of nano–nano heterojunction. More importantly, the SrTiO3/TiO2 composites exhibit excellent photocatalytic stability and outstanding catalytic activity with the increase of utilizing cycles. Particle size and morphology of SrTiO3 nanostructures were found to dominate the photocatalytic activity of SrTiO3/TiO2 composites through regulating the adhesion and aggregation of TiO2 nanosheets as well as the number of reaction active sites. It is the first time to fabricate SrTiO3/TiO2 heterojunction structure on limited two-dimensional nanosheets in situ, which is beneficial for understanding the growth of SrTiO3 from TiO2 in initial period. These results may further promote the applications of SrTiO3/TiO2 composites in environment cleanup, solar cells, sensors and photonic and optoelectronic devices.

Sol–gel combustion synthesis of magnetic MnFe2O4 oxide and FeNi alloy: product dependence on the reduction ability

Based on the sol–gel combustion method, stoichiometric Fe3+, Mn2+, Ni2+ ions and citric acid were chosen as the initial reactants for the preparation of magnetic particles. Due to the different reduction ability of metal ions, completely different magnetic products (MnFe2O4 oxide and FeNi alloy) were obtained by heating the flakes at 600 °C under nitrogen atmosphere. MnFe2O4 particles exhibit superparamagnetic behavior at room temperature, and martensitic phase transformation is observed magnetically at 125 K for FeNi alloy particles.

Synthesis of Symmetrical Disubstituted Bridgehead Adamantane Derivatives

The symmetric bridge disubstituted adamantane derivatives are the key raw materials or intermediates for preparing multisubstituted adamantane derivatives with admantane as the core. With 1-adamantane carboxylic acid that is more efficient and economical as an initial reactant, a series of synthesis technologies of symmetrical disubstituted bridgehead adamantane derivatives which have significant applications, were studied in this work. Those synthesis technologies include the following: 1,3-adamantane dicarboxylic acid (1) was synthesized by 1-adamantane carboxylic acid through Koch-Haaf carbonylation; compound 1 was reduced to get 1,3-adamantane dimethanol(2); compound 2 reacted by bromination in HBr-ZnBr2 system to afford 1,3-dibromomethyl adamantane(3). Meanwhile, compound 2 converted to 1, 3-dichloromethyl adamantane (4) through Apple-Lee reaction. The structures of prepared products were confirmed by IR spectra and H-1 NMR spectroscopy. The possible reaction mechanism was proposed, and the synthesis conditions were discussed and optimized for each technology respectively.

Preparation and characterization of orthorhombic NaNbO3 Long Bar

In this study, we successfully prepared perovskite-type NaNbO3 long bars with orthorhombic phase. At first, one-dimensional sandia octahedral molecular sieves (SOMS) were synthesized by the hydrothermal treatment at 160°C using Nb2O5 and NaOH as the initial reactants. The SOMS exhibited ribbon-like Na2Nb2O6·6/5H2O fiber structures with high length-to-width ratio. Then, the prepared ribbon-like Na2Nb2O6·6/5H2O fibers changed into the perovskite structure by the post-heat treatment at 450°C. The surface morphology and phase structure of the products were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) respectively; the fine structures of the products were investigated by means of Raman spectrum and high-resolution transmission electron microscopy (HRTEM). Furthermore, the mechanism of formation of NaNbO3 long bars was studied based on the experimental data. Our study may provide a new approach for the preparation and investigation of one-dimensional alkali niobate photocatalytic materials and template grain for textured alkali niobium.

Controlled synthesis and novel luminescence properties of string SrWO₄:Eu³⁺ nanobeans.

One-dimensional SrWO4:Eu(3+) nanostructures were prepared by a hydrothermal method. The structures and morphologies of the nanocrystals were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and scanning electron microscopy. The results indicated that the phase compositions, morphologies and sizes and luminescence properties of SrWO4:Eu(3+) are related to the initial reactant content and reaction time, and lower initial reactant content is beneficial for the formation of the string SrWO4:Eu(3+) nanobeans. The photoluminescence properties of SrWO4:Eu(3+) were investigated in detail. In the emission spectra of SrWO4:Eu(3+), the (5)D0→(7)F1 is dominant when the excitation wavelength is 295 nm, while the (5)D0→(7)F2 is dominant when the excitation wavelengths are in the range of 363-537 nm. Obviously, the string SrWO4:Eu(3+) nanobeans have multiple luminescence centers or emitting states. The excitation spectra of SrWO4:Eu(3+) contain several sharp peaks attributed to f-f transitions of Eu(3+) ions and a broad excitation band assigned to the overlap of WO4(3-) absorption and charge transfer transition between Eu(3+) and O(2-). The intensity ratio of the broad excitation band to the sharp excitation peaks changed with the emission wavelength as well as the Eu(3+) content. In addition, Eu(3+) ions occupy higher symmetry sites in SrWO4:Eu(3+) nanocrystals with increasing the particle size of nanocrystals. The effect of Tb(3+) as well as Gd(3+) ions on the photoluminescence of SrWO4:Eu(3+) was also investigated.

Transglycosylation specificity of glycosyl donors in transglycosylation of stevioside catalysed by cyclodextrin glucanotransferase

Specificity of glycosyl donors is a critical issue in transglycosylation of stevioside, the main methodology to improve edulcorant quality of stevioside. The most popular glucanotransferase applied in this reaction is cyclodextrin glucanotransferase (CGTase) that catalyses cyclisation, coupling, hydrolysis and disproportionation simultaneously; which results a crosstalk in the glycosyl donors that comes from initial reactants, reaction intermediates as well as side products in parallel reactions. In this work, the specificity of glycosyl donors was studied to understand the transglucosylation pathways with the designed experiments and material balance analysis on the products using a commercial CGTase. It has been found that cyclodextrins and starches provided the best transglucosylation yield, while the assayed mono- and disaccharides were not effective glycosyl donors to stevioside with the CGTase. It is proposed that α- and β-cyclodextrins performed transglycosylation via coupling to produce intermediates of reducing sugar and followed by disproportionation with stevioside; while starches may perform the transglycosylation combined the cyclodextrins pathway and hydrolysis pathway of starches.

Language-oriented rule-based reaction network generation and analysis: Algorithms of RING

The underlying algorithms of the language interface and post-generation analysis modules in RING, a network generation and analysis tool, are discussed. The front-end is a domain-specific reaction language developed with Silver, a meta-language based on attribute grammars. The language compiler translates user inputs written as a program into internal instructions, catches syntactic and semantic errors, and performs domain-specific optimization to speed up execution. In addition to generating reaction networks, RING allows post-processing analysis options to: (a) obtain reaction pathways and overall mechanisms from initial reactants to desired products using graph traversal algorithms, (b) group together isomers to reduce the size of the network through a novel molecule hashing technique, (c) calculate thermochemical quantities through semi-empirical methods such as group additivity, and (d) formulate and solve kinetic models of the entire or lumped complex network based on a rule-based kinetics specification scheme.

Calcium phosphate based materials starting from calcium carbonate and orthophosphoric acid for the removal of lead(II) from an aqueous solution

Calcium phosphates starting from calcium carbonate and orthophosphoric acid as unconventional and low cost initial reactants were investigated in the removal from aqueous solution of lead(II) as model heavy metal. Sorbent in gel form, which was directly obtained from the reaction of calcium carbonate powder and orthophosphoric acid, and sorbent in powder form, which was obtained by filtration and drying of the gel at room temperature showed the highest reactivity for the removal of lead(II). The sorption capacity could reach up to 1226mg of lead(II) per gram of powder sorbent. On the other hand, the conventional drying overnight at 105°C decreased the reactivity of the sorbent in powder form. The intermediates of the reaction between calcium carbonate and orthophosphoric acid, including brushite (CaHPO4·2H2O), monetite (CaHPO4) and MCPM (Ca(H2PO4)2·H2O) were found to be more active than hydroxyapatite (Ca10(PO4)6(OH)2) which was the final stable product of the reaction between calcium carbonate and orthophosphoric acid. Lead hydroxyapatite (Pb10(PO4)6(OH)2) was the main crystalline phase formed from the contact of calcium phosphate based sorbents with lead(II) nitrate solution. It was only formed at the external surface or surface of open-pores of calcium phosphate particles, highlighted by SEM characterization. The results obtained open new prospects for the design of efficient orthophosphate-based sorbents for the removal of lead(II) and other heavy metals from liquid effluents.

A Series of Enthalpy/Entropy-Driven Reversible Dissolution/Reorganization Equilibriums in the System of Cu(NO3)2–HL–GdX3–H2O (HL = 5-methylpyrazine-2-carboxylic acid; X = Cl, Br, NO3, ClO4)

Five coordination polymers, [Cu(L)2]n (1), {[Cu(L)(Cl)(H2O)]·H2O}2n (2), [KCu(L)(μ-Cl)2]n (3), [Cu(L)(Br)H2O]n (4), and {[Cu0.5(HL)(H2O)](NO3)·H2O}2n (5) (HL = 5-methylpyrazine-2-carboxylic acid) were obtained by reactions of a pyramidal CuII-containing ligand, {[Cu(L)2(H2O)]·3H2O}n (LCu), with Gd(ClO4)3·6H2O, GdCl3·6H2O, GdCl3·6H2O/KCl, GdBr3·6H2O, or Gd(NO3)3·6H2O in water. Structural analysis reveals that the structures of these compounds range from a 0D block to a 2D network with modification of the environment of the CuII ions compared with LCu. Interestingly, there occurred a series of reversible dissolution/reorganization equilibriums between the initial reactants and the final products 1–5, which were determined as enthalpy/entropy driven chemical equilibriums by single crystal X-ray diffraction and microcalorimetry. In addition, the thermal stability of 1–4 and the magnetic property of 2 are discussed.

Nanoparticles of poly(hydroxybutyrate-co-hydroxyvalerate) as support for the immobilization ofCandida antarcticalipase (Fraction B).

This work evaluates the immobilization of Candida antarctica lipase (Fraction B) using poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) nanoparticles as support. The effects of immobilization time (30-150 min) and pH (5-10) on lipase loading were evaluated. The stability of the immobilized enzyme towards temperature (40, 60, and 80 oC), reuse and storage (at 4 oC) were also determined. Furthermore, to assess its potential application in a system of interest, the immobilized lipase was used as a catalyst in the esterification of geraniol with oleic acid. The results indicated a time of 120 minutes and pH of 7 as optimal for immobilization. A 21 hour exposure of the PHBV-lipase derivative to 60 oC showed a 33% reduction of the initial activity while storage at 4 oC led to a residual activity (5% of the original activity). The derivative was used without significant loss of activity for 4 successive cycles. The use of the immobilized lipase as a catalyst in the production of geranyl oleate led to about 88% conversion of the initial reactants to products.

Acrylic acid obtaining by acetic acid catalytic condensation with formaldehyde

Acrylic acid is a bulk product of organic synthesis. Propylene oxidation is main industrial method of its production. Considering substantial costs for oil-derived raw material (propylene), development of alternative acrylic acid production methods are very important. The method of acrylic acid production by acetic acid gas-phase aldol condensation with formaldehyde has fair implementation prospects. In industry formaldehyde and acetic acid are synthesized from methanol produced from synthesis gas, and a feedstock for synthesis gas obtaining is methane or coal. Thus the method allows using non-oil-derived raw materials. The present work is dedicated to the development of efficient catalysts of gas phase aldol condensation of carbonyl compounds. Using of the developed B 2 O 3 –P 2 O 5 –WO 3 /SiO 2 catalyst allows acrylic acid obtaining with high yield. Temperature and contact time effect on the initial reactants conversion and the target product formation selectivity have been studied in the work. Optimal conditions of the condensation process have been determined. The research results implementation would enable diversifying the raw materials base of acrylic monomers production and allow.

Thermal modes of bimolecular exothermic reactions: Concentration limits of ignition

In the present work, the analytical investigation of the phase trajectories structures on the plane: heating rate-temperature for bimolecular exothermic reactions was carried out. This gave a possibility to divide the parametric plane Todes parameter–Semenov parameter into five characteristic regions with various modes of self-heating. It was established that all regions converge at a single point which determines the thermal explosion degeneration conditions. The correlation between Todes parameter, Semenov parameter and concentration ratio of initial reactants at the limit of the thermal explosion degeneration was found. The critical conditions for thermal explosion at any ratio of concentrations of initial reactants were determined. The approach proposed is a general one and allows analyzing both first and second order reactions.

The coloring of geopolymers by the addition of copper compounds

The development of a new coloring technique is desirable to increase the commercial value of geopolymers. Selected copper compounds, i.e. Cu(OH)2, CuO, Cu2O, CuCO3∙Cu(OH)2∙H2O, CuCl2∙2H2O and CuSO4∙5H2O, were added to the initial reactants in order to color the geopolymers in the same manner as naturally occurring minerals. When Cu(OH)2, CuO and Cu2O were used, these compounds remained in the geopolymer matrix following hardening of the material. On the contrary, CuCO3∙Cu(OH)2∙H2O, CuCl2∙2H2O and CuSO4∙5H2O were not detected in the final products. XAFS analyses were performed to investigate the local structure of copper in the geopolymers produced. The results showed that the copper spectra of geopolymers incorporating Cu(OH)2, CuO and Cu2O correspond to those of pure Cu(OH)2, CuO and Cu2O, respectively. However, when CuCO3∙Cu(OH)2∙H2O, CuCl2∙2H2O and CuSO4∙5H2O were added, the copper generated spectra similar to that of the mineral chrysocolla ((Cu, Al)2H2Si2O5(OH)4∙nH2O) than the respective copper compounds.

Structural and electrochemical characteristics of Li x Mn2O4 spinel synthesized using a microwave-assisted method

The structural and electrochemical features of LixMn2O4 spinel synthesized by the microwave-assisted method are discussed. The thermal gravimetric analysis shows that almost 84% of all the initial reactants undergo chemical transformation associated with the weight loss in the course of the microwave-assisted synthesis. The composition of the initial components influences the heating rate negligibly, and the temperature reaches 400°C within around 15 minutes. The X-ray phase analysis shows that the LixMn2O4 samples contain impurities such as MnO2 and Mn2O3, the amount of which decreases with the increase in the lithium content. The electrochemical characteristics of the LixMn2O4 are strongly influenced by the composition of the starting components, which is particularly noticeable upon high discharge rates.

Syntheses based on carbon oxides. XXXV. Carboxylation of resorcin and m-cresol by sodium salt of ethylcarbonic acid

The carboxylation reactions of resorcinol and m-cresol by sodium salt of ethylcarbonic acid were investigated. It was found that carboxylation of resorcinol and m-cresol proceeds regioselectively with formation of b-resorcylic acid and 4-methyl-2-hydroxybenzoic acid respectively. The optimal conditions for the carboxylation reaction of resorcinol by sodiumethylcarbonate were selected: the ratio of initial reactants [resorcinol]:[sodiumethylcarbonate] = 2:1; the temperature of 120 0 C; carbon dioxide pressure of 10 atm; eight-hour duration - at which the yield of b-resorcylic acid reaches 84.5%. For carboxylation reaction of m-cresol by sodium ethylcarbonate: the optimal ratio of initial reactants [m-cresol]:[sodium ethylcarbonate] = 2:1; the temperature of 180 0 C; carbon dioxide pressure of 10 atm; seven-hour duration - at which the yield of 4-methyl-2-hydroxybenzoic acid reaches 55%. The method developed for obtaining b-resorcylic and 4-methyl-2-hydroxybenzoic acids can be used for their industrial production.

Evolution of a Multicomponent System: Computational and Mechanistic Studies on the Chemo‐ and Stereoselectivity of a Divergent Process

The evolution of a ternary molecular system (imine, diene and nitrile) is analyzed to disclose the pathways leading to a divergent synthetic outcome. The Lewis acid catalyzed reaction between cyclohexadiene, 2-phenyl-indol-3-one and acetonitrile yields the imino-Diels-Alder adduct as the major product together with minor amounts of the Mannich-Ritter-amidine product. The experimental and computational data show that the relative orientation of the initial reactants dictates the synthetic outcome. The exo approach between imine and diene leads to the Diels-Alder adduct in a concerted process, whereas the endo mode leads to a polarized intermediate, which is trapped by acetonitrile to yield the multicomponent adduct.

Hydroxyapatite gel for the improved removal of Pb2+ ions from aqueous solution

Hydroxyapatite (Ca10(PO4)6(OH)2, Ca-HA) is a versatile material which can be used in several applications. This study investigated the reactivity of Ca-HA, obtained directly by the one-step synthesis from calcium carbonate and orthophosphoric acid as low-cost initial reactants, in the removal of lead(II) as a model heavy metal. The sorption capacity of synthesized Ca-HA reached at least 750mgg−1, which was much higher than that reported in the literature. This was explained by the favorable effect of the carbonate anion presence in the apatitic structure. Classical stoichiometric lead hydroxyapatite was formed, which was found on the surface of Ca-HA particles. Small amounts of lead oxide were also detected, possibly due to a surface precipitation reaction of lead(II). The crystalline structure of the initial Ca-HA material was destroyed, in relation with the acidic conditions during the sorption experiment, as well as the insertion of lead(II) into this structure. Ionic exchange, surface complexation and dissolution–precipitation all occur and explain lead(II) fixation. The results obtained open a new pathway for the synthesis of low-cost Ca-HA sorbents for environmental purposes.