Molar Ratio Of Urea Research Articles

A photoluminescence study of nitrogen-doped carbon quantum dots/hydroxyapatite (NCQDs/HAp) nanocomposites

ABSTRACT The objective of the present investigation is to functionalise nitrogen-doped carbon quantum dots (NCQDs) with hydroxyapatite (HAp) and study photoluminescence of the composites under ultraviolet radiation. NCQDs were prepared from microwave irradiation of 3:1 molar ratio of urea and citric acid mixture at 750 W for ~5 min. HAp was obtained via wet-chemical process from reacting 1 mol of calcium nitrate with 0.6 mol of ammonium dihydrogen phosphate at ~37°C for 15 h under basic pH (<8). NCQDs/HAp was synthesised from the hydrothermal method by mixing 5–15 mL aqueous solution of NCQDs with 1 g of HAp and autoclaving the mixtures at 100°C for 1 hour. The samples were characterised using diffraction, spectroscopic and microscopic techniques. Pure and nanoscale crystalline NCQDs/HAp composites, with an average particle size of 45 nm, were observed. The NCQDs/HAp resulted in higher photoluminescence than the HAp.

Mineralization of Urea-Formaldehyde Fertilizer and Its Availability to Oil Palm Seedling under the Tropical Environment

Easily dissolved fertilizers release nutrient in excess amount to be assimilated by plant roots. Some portions these fertilizers leach out from the root zone and adversely impact the environment. Controlled-release fertilizers are more favorable to reduce fertilizer loss, labor cost, and environmental impact. Urea-formaldehyde (UF) was synthesized by polymerization of urea and 40% formaldehyde solution using H3PO4 as a catalyst. Three mole ratios of urea:formaldehyde, namely, 1.0:1.0, 1.5:1.0 and 2.0:1.0 were synthesized. Mineralization of the UF was conducted using eight different mixtures, four different moisture, and four incubation periods. The experiment included soil alone, soil with compost, soil with UF (1.0:1.0), soil with UF (1.5:1.0), soil with UF (2.0:1.0), soil with UF (1.0:1.0) and compost, soil with UF (1.5:1.0) and compost, and soil with UF (2.0:1.0) and compost. Moisture of the mixtures was adjusted to 20%, 40% 60% and 80% water holding capacity (WHC) of the soil. The mixtures were incubated at room temperature for 1, 2, 4 and 8 weeks, the released NH4+ and NO3- were extracted by 1 M KCl and analyzed via a distillation method. Rates of mineralization increased with mole ratio of urea and moisture content of the soil. N loss increased with the moisture content. The best performance for the compromised condition was a mole ratio less than 1.5:1.0 (urea:formaldehyde) at 60% WHC. Availability of UF and serpentine-phosphate for oil palm seedlings was conducted using 10 treatments. The experiment consisted of soil without amendment; soil with Multicote; soil with cow manure; soil with cow manure and urea; soil with cow manure and UF (1.0:1.0); soil with cow manure and UF (1.5:1.0); soil with cow manure, MgHPO4 and UF (1.0:1.0); soil with cow manure, MgHPO4 and UF (1.5:1.0); soil with cow manure, serpentine-phosphate and UF (1.0:1.0); and soil with cow manure, serpentine-phosphate and UF (1.5:1.0). All amended soils increased vegetative growth of oil palm seedlings compared with the non-amended soils. Urea and UF increased the N content in seedling leaves, while Multicote, cow manure, MgHPO4, and serpentine-phosphate increased the Mg content. The best performance was found in the combination of cow manure, serpentine-phosphate and the UF with mole ratio of 1.0:1.0.

Unprecedented green chemistry approach: tungstophosphoric acid encapsulated in MOF 199 as competent acid catalyst for some significant organic transformations

In the work, a series of new 12-tungstophosphoric acid (HPW) encapsulated MOF 199 catalysts were synthesized by simple and convenient one step method. The structural and textural properties of the synthesized catalysts were fully characterized by using different techniques such as FTIR, XRD, N2 adsorption–desorption, TEM and SEM. The acidic properties were also studied by using nonaqueous potentiometric titration and FTIR spectra of chemisorbed pyridine techniques. The efficacy of the newly synthesized acid catalysts was tested in the production of 3,4-dihydropyrimidin-2(1H)-one through three-component coupling based Biginelli reaction and biodiesel production through stearic acid esterification reaction. The obtained results indicate that the MOF 199 preserves its structure without any noteworthy changes after the fruitful incorporation of HPW crystals within its cavities. Furthermore, an extraordinary improvement in both Lewis and Bronsted acid sites is observed as a result of the HPW encapsulation process. The catalytic activity results showed that the catalyst displayed excellent performance, where 98.3% of 3,4-dihydropyrimidin-2(1H)-one was obtained over 0.02 g of 50HPWMOF 199 after 2 h at 80 °C using benzaldehyde: ethyl acetoacetate: urea molar ratios of 1:1:1.5. Additionally, 94.1% conversion of stearic acid was observed after 3 h over 0.05 g of 50HPWMOF 199 at ~ 80 °C using stearic acid: ethanol molar ratio of 1:8. Moreover, the catalysts also demonstrated excellent reusability in the investigated organic reactions which can be used many consecutive eras without meaningful loss of their catalytic performance. The achieved high catalytic performance of the synthesized catalysts in the Biginelli and esterification reactions are attributed to uniform HPW distribution inside MOF 199 cavities as well as the Lewis acidity property of MOF 199. The results also demonstrated that the incorporation of HPW crystals within MOF 199 cavities through the encapsulation process is more efficient than the impregnation method.

Addition of cellulose nanofibers extracted from rice straw to urea formaldehyde resin; effect on the adhesive characteristics and medium density fiberboard properties

In this research cellulose nanofibers (CNF) were successfully extracted from rice straw through a chemomechanical method and then mixed with urea-formaldehyde (UF) adhesive for the production of medium density fiberboard (MDF). The industrial grade liquid urea-formaldehyde (UF) resin with formaldehyde: urea molar ratio of 1.15 was modified by adding 0.5, 1.5 and 2 wt % of nanofibrillated cellulose (CNF) based on UF resin solids. The morphology, gel time, viscosity, and the non-volatile solid content of the modified UF adhesive were investigated. Formaldehyde emission and some mechanical properties modulus of rupture (MOR), modulus of elasticity (MOE) and internal bond strength (IB)) of the resulting MDF panels were measured. Solids content and viscosity of the UF adhesive decreased while gel time increased by mixing CNF with the resin. The formaldehyde emission of the panels made with UF containing CNF was lower than that of the panels made from neat UF while MOR, MOE and IB values increased by increasing the CNF content in the panels.

A facile urea-hydrolysis calcination process for the preparation of α -Fe2O3 nanoparticles and α -Fe2O3 nanorods and their fabrication mechanisms

A facile urea-hydrolysis calcination process for the preparation of α-Fe2O3 nanoparticles and α-Fe2O3 nanorods was introduced. The effects of hydrolysis temperature, Fe3+ concentration, and the molar ratio of urea and Fe3+ on nanorod-like precursors and α-Fe2O3 nanomaterials were investigated. The average length and diameter of the nanorod precursors increased with the increasing hydrolysis temperature, Fe3+ concentration, and molar ratio of urea and Fe3+. When the molar ratio of urea and Fe3+ was not less than 5, the α-Fe2O3 nanoparticles were produced. However, when the molar ratio was not greater than 4, the α-Fe2O3 nanorods could be obtained. In addition, the average diameter of the α-Fe2O3 nanoparticles was the largest when the hydrolysis temperature was 85 °C. With the increase in Fe3+ concentration, the average diameter of the α-Fe2O3 nanoparticles was enlarged. The average length and diameter of the α-Fe2O3 nanorods increased with the increase in hydrolysis temperature and Fe3+ concentration. All the results suggested that the rod-like structure of the precursors provided a possibility and the template for the fabrication of α-Fe2O3 nanorods, and the content of Fe3+ in the rod-like precursors played the decisive role in the morphology of the α-Fe2O3 nanomaterials.

Understanding Interfacial Mechanics and Mechanisms of Exfoliation and Stabilization of Graphene Using Urea/Glycerol Solvents

AbstractKnowledge of interfacial mechanics and mechanisms of liquid exfoliation and stabilization of graphene in green solvents is vitally important in advancing preparation and characterization of graphene‐based materials. In this work, molecular dynamics simulations are performed to investigate exfoliation and stabilization of graphene from graphite with the assistance of urea and glycerol hybrid solvents. It is shown that the parallel exfoliation of graphene requires far less external forces as compared with the perpendicular exfoliation. Among different mediums, the 1:2 molar ratio of urea to glycerol solution presents the smallest or even negligible resistive force in both directions due to the less compressed steric hindrance to graphene exfoliation and the optimal hydrogen bonds formed between the binary solvents. During the dispersion process, the urea molecules first wedge into the graphene interlayer and then facilitate the glycerol to diffuse around or inside of the interstice due to hydrogen bonding. The confined solvents form stable layered structure to solvate and stabilize the exfoliated graphene. This work is believed to provide atomic scale understanding of interfacial mechanics and mechanisms of liquid‐phase exfoliation and dispersion of graphene and other 2D materials in low‐cost and environmental‐friendly hybrid solvents.

Effect of the initial F/U molar ratio in urea-formaldehyde resins synthesis and its influence on the performance of medium density fiberboard bonded with them

The formaldehyde to urea molar ratio (F/U) plays an important role on the properties of urea formaldehyde (UF) resins and of the medium density fiber board (MDFs) bonded with them. This work presents a hypothesis that besides the final F/U molar ratio in UF resin preparation, the initial F/U affects both the formaldehyde emission levels and the physico-mechanical properties of the boards. Three initial molar ratios F/U of 1.9, 2.1 and 2.3 in resin synthesis have been examined in this work. The structural changes and thermal curing behavior of UF resins were tracked by 13C NMR and DSC, respectively. At parity of final F/U molar ratio, the resin with initial F/U = 2.1 yielded the highest proportion of linear methylol groups, resulted in the best internal bond strength and lowest thickness swelling of the board. A resin synthesized with the initial F/U = 1.9 provided the highest proportion of total methylene linkages, most methylene ether linkage and lowest free formaldehyde, consistently yielding the lowest formaldehyde emission. These results partially explained why UF resins with lower F/U molar ratios showed relatively poor adhesion when used to manufacture wood-based composites. MDFs bonded with a UF resin having the initial F/U = 2.3 had a relatively good performance with the exception of free formaldehyde, but also showed the best storage stability compared to the other resins having lower initial F/U molar ratios.

Green Extraction of Phenolic Acids from Artemisia argyi Leaves by Tailor-Made Ternary Deep Eutectic Solvents.

The Artemisia argyi leaf (AL) has been used as a traditional medicine and food supplement in China and other Asian countries for hundreds of years. Phytochemical studies disclosed that AL contains various bioactive constituents. Among bioactive constituents, phenolic acids have been recognized as the main active compounds in AL. To the best of our knowledge, no research has been focused on extraction method for the bioactive phenolic acids from AL. Nowadays, deep eutectic solvents (DESs) are emerging as a new type of green and sustainable solvent for efficient extraction of bioactive compounds from natural products. In the present study, an environmentally friendly extraction method based on DESs was established to extract bioactive phenolic acids from ALs. Diverse tailor-made solvents, including binary and ternary DESs, were explored for simultaneous extraction of four phenolic acids (3-caffeoylquinic acid, 3,4-di-O-caffeoylquinic acid, 3,5-di-O-caffeoylquinic acid, and 4,5-di-O-caffeoylquinic acid) from AL. The results indicated that the ternary DES composed of a 2:1:2 molar ratio of choline chloride, malic acid, and urea showed enhanced extraction yields for phenolic acids compared with conventional organic solvents and other DESs. Subsequently, the extraction parameters for the four phenolic acids by selected tailor-made DESs, including liquid–solid ratios, water content (%) in the DESs, and extraction time, were optimized using response surface methodology and the optimal extraction conditions were: extraction time, 23.5 min; liquid–solid ratio, 57.5 mL/g (mL of DES/g dry weight of plant material); water content, 54%. The research indicated that DESs were efficient and sustainable green extraction solvents for extraction of bioactive phenolic acids from natural products. Compared to the conventional organic solvents, the DESs have a great potential as possible alternatives to those organic solvents in health-related areas such as food and pharmaceuticals.

Calorimetric Evaluation of the Operational Thermal Stability of Ribonuclease A in Hydrated Deep Eutectic Solvents

Deep eutectic solvents (DESs), and particularly their mixtures with water, have been postulated as progressive, sustainable biocatalytic media. Currently, however, knowledge of biomolecular stability within DES media, such as protein folding reversibility, remains quite limited. In this Letter, we present the findings of a study of bovine ribonuclease A (RNase A) unfolding/refolding within aqueous media containing 5–35 wt % of illustrative DESs comprising 1:2 molar ratios of choline chloride plus urea (so-called reline), ethylene glycol (ethaline), or glycerol (glyceline). Using differential scanning calorimetry, iterative thermal cycling of RNase A in the presence of reline is shown to result in rapid and complete loss in folding reversibility, tentatively linked to ammonia evolution, whereas the addition of glyceline actually improves the RNase A thermodynamic stability beyond the native, purely aqueous milieu.

Improvement of storage stability of UF resins by adding caprolactam

During storage, the structure of urea-formaldehyde (UF) resins suffers modifications due to reactions between monomers, oligomers, polymer and free formaldehyde, leading to increase in viscosity and decrease in pH. Eventually, viscosity reaches a value that renders the resin unusable, and it must be disposed off. This aging process is accelerated if storage temperature increases.The aim of this work is to obtain UF resins with long storage stability, even when exposed to relatively high temperatures, such as 40 °C. The main strategy adopted was the addition of a chain growth blocker, caprolactam. This monofunctional compound reacts with end groups, blocking them and therefore reducing the polymer's reactivity. In addition, a weak base was added to adjust the pH value, instead of the traditional strong base, sodium hydroxide, therefore hindering the Cannizzaro reaction.The storage stability of UF resins with formaldehyde to urea molar ratio of 1.6–2.0 was monitored by pH and viscosity measurements. Caprolactam was added in different amounts and at different reaction stages. It was found that 10% addition at the beginning of condensation led to the best results, giving a much higher storage stability at 40 °C (2 months when compared to 4 days for a commercial UF resin with low F/U molar ratio). As expected, the resin reactivity decreased with caprolactam addition, demanding for longer pressing times for wood-based panel manufacture. These verified the internal bond strength specification for EN 312 - P2 standard class. Formaldehyde content in the panels was above the E1 class limit when fresh or one month old modified resins were used, implying addition of formaldehyde scavengers. The resin stored for 2 months allowed producing panels within E1 limit. These preliminary results demonstrate the concept that addition of an end-group blocker during UF synthesis is an effective strategy for improving storage stability, encouraging future work on alternative compounds and synthesis conditions optimization.

Optimization of Urea-Glycerin Based NADES-UAE for Oxyresveratrol Extraction from Morus alba Roots for Preparation of Skin Whitening Lotion

: Objective: The oxyresveratrol, polyphenol from Morus alba (Mulberry) roots has been known to have potential skin whitening activities. The application of urea-glycerin-based Natural Deep Eutectic Solvent-Ultrasonic Assisted Extraction (NADES-UAE) method was successful on extraction of polyphenols from plant material. The purpose of this research was to get optimum extraction conditions to enhance oxyresveratrol content and get the best lotion formula based on physical properties evaluation. Methods: The roots were extracted with urea-glycerin-based NADES-UAE method. The NADES-UAE method was employed to determine the optimal extraction condition for two parameters: the molar ratio of urea: glycerin and ultrasonic irradiation time. Oxyresveratrol concentration of the extracts was analyzed with HPLC. Morus alba roots extract was formulated into three formulas of lotion preparation and evaluated based on their physical properties. Results: The optimized conditions for the highest oxyresveratrol concentration from Morus alba roots extract were the molar ratio of urea-glycerin (1:3) and ultrasonic irradiation time as 15 mins. It showed that urea-glycerin UAE method produced Morus alba roots extract with higher oxyresveratrol content than conventional method. Based on physical evaluation from three lotion formulas, formula A was chosen as best formula. Conclusion: This urea-glycerin-based NADES-UAE method was suitable as a green alternative method for the extraction of oxyresveratrol from Morus alba roots because cheaper, faster and easier than conventional extraction method. The lotion preparation which has good physical properties can be applied as a skin whitening cosmetic.Key words: Natural deep eutectic solvent, Ultrasonic assisted extraction, Urea, Glycerin, Oxyresveratrol, Morus alba, Roots extract, Skin whitening.

Controlling the Distribution of Microbially Precipitated Calcium Carbonate in Radial Flow Environments.

Bacterially driven reactions such as ureolysis can induce calcium carbonate precipitation, a well-studied process called microbially induced calcium carbonate precipitation (MICP). MICP is of interest in subsurface applications such as sealing leaks around wells. For effective field deployment, it is important to study MICP under radial flow conditions, which are relevant to near-well environments. In this study, a laboratory-scale radial flow reactor of 23 cm diameter, with a 1 mm glass bead monolayer serving as a porous medium, was used to investigate the effects of fluid flow rates and calcium concentrations on the mass and distribution of MICP by the ureolytic bacterium Sporosarcina pasteurii. Experiments were performed at hydraulic residence times of 14, 7, and 3.5 min and calcium to urea molar ratios of 0.5:1, 1:1, and 2:1. The total amount of CaCO3 precipitated in the reactor increased with increasing residence time and with decreasing Ca2+ to urea molar ratios. Increased bacterial attachment and increased CaCO3 precipitation were observed with distance from the center inlet of the reactor in all experiments. More uniform calcium distribution was achieved at lower flow rates. The relationship between reaction and transport rate (i.e., the Damköhler number) is identified as a useful parameter for the prediction of MICP in radial flow environments.

Luminescent Sol-Gel Glasses from Silicate–Citrate–(Thio)Ureate Precursors

Recent advancements in synthesis and analysis of the composites based on silica and carbon quantum dots have revealed great potential of such systems in bioimaging, sensor, as well as solid-state lighting applications. Most of the synthetic methods for obtaining such materials are still relatively complex and costly. The aim of this work was to study the luminescent properties of silica-based composites prepared by the simple sol-gel method using low-cost silicate–citrate–(thio)ureate precursors. The glassy composites were prepared by acid hydrolysis of ethyl silicate (40%) in aqueous solution of citric acid ureates or thioureates with the citric acid-to-(thio)urea molar ratio of 1:1, 1:1.5 or 1:3. The results of spectrofluorimetric analysis have shown that heat-treated at 270 °C such silica gels upon UV excitation (with an optimum at λexc = 360 nm) emit light in a visible spectrum (400–600 nm). Upon this, photoluminescence efficiency of ureate-derived glasses (quantum yield 70.53% for 1:1.5 sample) appeared to be much higher than that for thioureate-derived glasses (quantum yield 11.25% for 1:3 sample) suggesting that the preparation conditions to obtain the glasses with optimal photoluminescence characteristics are quite different in case of urea and thiourea. Thus, citrate–ureate-derived silica glasses already demonstrate very good potential to be efficient materials for different fluorescence-related applications.

Investigating the effect of synthesis conditions on the formation of urea–formaldehyde microcapsules

In the current study, a set of urea–formaldehyde microcapsules (UFMs) were synthesized at different conditions via the in situ polymerization method. Encapsulation ability of the UFMs was studied by altering the synthesis parameters, such as formaldehyde to urea molar ratio (0.94, 1.88, 2.81), time (1, 4, 7h), temperature (25, 55, 85°C) and pH (3, 7, 11). The capsules were characterized by optical and electron microscopy (OM, SEM and TEM), particle size analysis (PSA), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric/differential thermal analysis (TG/DTA). According to the results, for successful formation of UFMs, the pH value of the synthesis solution must be below 7 and the F/U molar ratio value must exceed 0.94. Effects of temperature and the pH value of the prepared solution were interdependent. To conclude, the results led to determination of the optimum UFM synthesis condition which presented the most effective formation of UFMs. The higher F/U molar ratio as well as higher curing temperatures in UFM-9, increased the UFMs degradation temperature. In order to further investigate the results, the synthesis of the optimized UFM (UFM-Opt.) was conducted, presenting the most effective development of UFMs.

Characterization of the Low Molar Ratio Urea⁻Formaldehyde Resin with 13C NMR and ESI⁻MS: Negative Effects of the Post-Added Urea on the Urea⁻Formaldehyde Polymers.

The structural changes during three-step synthesis of low-molar ratio urea–formaldehyde (UF) resin were tracked by quantitative 13C nuclear magnetic resonance (13C NMR) analysis and electrospray ionization-mass spectrometry (ESI–MS). Condensations that produced polymers were found to be linked by ether bonds in addition to hydroxymethylation reactions at the first alkaline stage with a formaldehyde to urea ratio of 2:1. Considerable formation of branched methylene linkages, with the highest content among all the condensed structures, was the key feature of the acidic stage. Notable changes were observed for the chemical structures and molecular masses of the resin components after the formaldehyde to urea molar ratio was lowered to 1.2 by adding post-urea at the final alkaline stage. Specifically, most of the branched hydroxymethyl groups on the polymers were cleaved, resulting in a significant decrease in the branching degree of the polymers. The performance degradation of the UF resin was attributed to this debranching effect and the production of components with low molecular masses. Based on the observations, the curing pattern of low molar ratio UF resin was postulated and branched polymeric formaldehyde catcher bearing urea-reactivity was proposed.

Morphology and Degradation Kinetics of N-Doped TiO&lt;sub&gt;2&lt;/sub&gt; Nano Particle Synthesized Using Sonochemical Method

Nano particle of N-doped TiO2 with the size of 21.42 nm was successfully created using sonochemical method. Concentration of Nitrogen (N) doping on TiO2 was calculated using mole ratio of Urea and TTiP. Doping variations were performed by doping 5% to 9% N, and did not change the crystallite size and strain. The nanoparticle produced has a polycrystalline structure with a dominant diffraction peak (101). Doping N into TiO2 affects the morphology of particle surface, thus tending to shrink. Results of photo catalysis on liquid samples of MB 20 ppm dye indicate that the addition of N improves the degradation ability of TiO2, with the highest value on sample T5 of 85% and with a rate of degradation kinetics of 0.024 ppm/minute.

Combustion Synthesis and Photoelectrochemical Characterization of Metal Oxynitrides Using GaxZn1-XOyN1-Y as a Model Candidate

Utilization of solar energy is a necessary path forward to deal with the looming energy crisis and worldwide effects of fossil fuel usage. A key component of this utilization is how to store excess solar energy for use on demand. One such method is splitting water into hydrogen and oxygen, both of which can be stored and either burned as fuel or used as feedstock components in industrial processes to synthesize high-value materials. Metal oxynitrides have shown great potential as photocatalysts for overall water splitting applications. Incorporation of nitrogen into metal oxides narrows the band gap to enable absorption of light in the visible spectrum. The typical synthesis of a metal oxynitride, however, requires annealing temperatures at or above 1000 oC and nitridation by flowing pure ammonia gas for anywhere from 1 to 48 hours. Such harsh synthesis conditions can limit the discovery of new candidate materials. In our work, we have prepared an array of gallium zinc oxynitrides (GaxZn1-xOyN1-y) as a model system using a combustion synthesis method and demonstrate that gallium zinc oxynitrides can be synthesized in 30 minutes at 500 oC using this method. X-ray diffraction (XRD), UV-visible spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) are used to characterize the physical properties of the as-synthesized materials. XPS analysis reveals that as much as 50% nitrogen substitution in the metal oxide lattice can be achieved, dependent on the ratio of gallium and zinc nitrates used as precursors. XPS also reveals that the nitrogen valency is that of a nitride material, as would be expected for a substitution into the crystal lattice. Relative atomic concentrations from XPS also reveals that the complex formed is essentially GaN:ZnO. UV-visible spectroscopy reveals that the band gap of the GaxZn1-xOyN1-ymaterials can be controlled simply by altering the precursor ratio. X-ray diffraction measurements reveal shifts in the crystalline peaks from ZnO toward GaN, confirming the incorporation of nitrogen into the lattice. The as-synthesized products are capable of generating photocurrent from visible light irradiation and are able to carry out water splitting in pure water without any co-catalysts, such as Pt, IrO2, or Rh/Cr2O3. Finally, we discuss how to take the results gained from this work and expound upon it to begin the search for new candidate oxynitride materials, including potential high-throughput methods for rapid screening of such candidates. We also discuss the apparent conditions necessary for successful formation of an oxynitride material based on initial experiments with new candidates. Figure caption: Picture of as-synthesized powders from an initial Ga:Zn:urea molar ratio of (A) 1:1:0 and (B) 1:1:10. Figure 1

THE SYNTHESIS OF GLYCEROL CARBONATE FROM BIODIESEL BYPRODUCT GLYCEROL AND UREA OVER AMBERLYST 36

The increasing use of biodiesel as renewable fuels leads to the increasing of glycerol amount as a byproduct of biodiesel production. One of the glycerol derivative products that is environmentally friendly and renewable is glycerol carbonate. Glycerol carbonate is commonly used as a raw material for polymers, surfactants, emulsifiers, lubricants, paints, also used in the cosmetics and pharmaceutical industries. In this study, the research was carried out by using a batch reactor with a three-neck flask equipped with reverse cooling, thermometers, mercury stirrer, and heating mantle with the conditions of the reaction temperature around 373 413 K, mole ratio of reactants of urea: glycerol were 1:0,5, 1:1, 1:1,5, 1:2 and 1:4 and the concentration of catalyst were 1%, 2%, 3%, 4% and 5% respectively. Reaction was done for four hours. The results showed that the formation of glycerol carbonate from glycerol and urea using a catalyst Amberlyst 36 is affected by the catalyst concentration, reaction temperature and the ratio of reactants used. The highest glycerol conversion was obtained at 55.07% at a temperature of 393 K with mole ratio of urea and glycerol 1:0,5 and the percentage of catalyst 3% of the amount of glycerol.

Ca-assisted nitrogen-rich molecular approach for the synthesis of monodisperse tantalum oxide and (oxy)nitride nanocrystals for visible light&amp;ndash;induced water oxidation

The visible-light-induced photocatalytic water oxidation activity without cocatalyst has been demonstrated for the first time on tantalum (oxy)nitride nanocrystals synthesized by a Ca-assisted nitrogen-rich molecular approach. Monodisperse TaON and Ta3N5 nanocrystals were synthesized by using suitable urea /Ta ratios in the presence of Ca2+ions. The as-synthesized (oxy)nitrides are in the form of spherically-shaped and well-defined nanocrystals with an average diameter of ca. 7 nm. Both nanocrystals showed absorption edges in the visible region. The band gap energies of TaON and Ta3N5 nanocrystals were determined from the Tauc’s plots of the UV ­ Vis diffuse reflectance spectra to be 2.27 and 2.08 eV for indirect allowed transitions,respectively. The O2 evolution rate was increased and reached the maximum in the following order: 2.01, 3.32, and 4.66 mol·h¹1 for the samples synthesized with Ca2+/urea molar ratio of 0.10, 0.50, and 0.25, respectively, due to the decrease in the optical band gap. ©2016 The Ceramic Society of Japan. All rights reserved.

Micron-size superparamagnetic iron-oxides watercress with unique MRI properties

In this work, 10-μm-sized superparamagnetic Fe3O4@(α, γ)−Fe2O3 watercress was synthesized by a one-step solvothermal method. Meanwhile, the other two kinds of micron-size hierarchical structures were also obtained by solely altering Fe2+/urea molar ratio in the same solvothermal procedure. It was found that the nuance of reaction parameters during synthesis can greatly alter the morphologies and structures of the obtained products, but it cannot alter their unique superparamagnetic properties at room temperature. Moreover, these large-size Fe3O4@(α, γ)−Fe2O3 products unexceptionally exhibit novel superparamagnetic–ferromagnetic transition around 30 K, indicating that the magnetic arrangement of Fe3O4 and (α, γ)−Fe2O3 components in these architectures are virtually the same. These micron-size iron oxides can beat the superparamagnetic size-limit (25–30 nm) of commonly-used Fe3O4 contrast agents in MRI application.