Suitable Synthesis Conditions Research Articles

Effect of synthesis conditions on the properties of 13X zeolites for CO2 adsorption

ABSTRACT The 13X zeolites were successfully synthesized from sodium silicate and sodium aluminate via hydrothermal treatment, and applied to the adsorption of carbon dioxide (CO2). The properties of the 13X zeolites were characterized and tested by powder X-ray diffraction (XRD), N2-physisorption measurements, CO2-temperature programmed desorption (CO2-TPD) and CO2 adsorption measurements. The results demonstrate that H2O/Na2O, Na2O/SiO2, and SiO2/Al2O3 molar ratios have an important influence on the adsorption performance of CO2 because of their different physicochemical properties. The pure 13X zeolite can be obtained with the optimal H2O/Na2O, Na2O/SiO2 and SiO2/Al2O3 molar ratios of 60, 4 and 3 in the preparation process, respectively. The 13X sample prepared with suitable synthesis conditions possesses the highest crystallinity, the maximum values of specific surface area (720.8 m2/g) and pore volume (0.458 cm3/g) and moderate strength of the interaction between 13X and CO2, thus presenting the highest adsorption capacity of CO2 (118.3 mg/g).

Metastable defect phase diagrams as roadmap to tailor chemically driven defect formation

Thermodynamic bulk phase diagrams have become the roadmap used by researchers to identify alloy compositions and process conditions that result in novel materials with tailored properties. Recent experimental studies show that changes in the alloy composition can drive not only transitions in the bulk phases present in a material, but also in the concentration and type of defects they contain. Defect phase diagrams in combination with density functional theory provide a natural route to study these chemically driven defects. Our results reveal, however, that direct application of equilibrium bulk thermodynamics can fail to reproduce experimentally observed defect formation. Therefore, we extend the concept to metastable defect phase diagrams to account for kinetic limitations that prevent the system from reaching equilibrium. We apply this concept to successfully explain the formation of large concentrations of planar defects in supersaturated Fe-Nb solid solutions. We then utilize it to design suitable conditions for synthesis, which we subsequently realized experimentally, successfully validating the formation of the predicted defects in Mg-Al-Ca alloys. The concept offers new avenues for the design of materials performance by tailoring defect structures.

Engineering poly(dehydroalanine)-based gels via droplet-based microfluidics: from bulk to microspheres.

Biomedical applications such as drug delivery, tissue engineering, and functional surface coating rely on switchable adsorption and desorption of specialized guest molecules. Poly(dehydroalanine), a polyzwitterion containing pH-dependent positive and negative charges, shows promise for such reversible loading, especially when integrated into a gel network. Herein, we present the fabrication of poly(dehydroalanine)-derived gels of different size scales and evaluate them with respect to their practical use in biomedicine. Already existing protocols for bulk gelation were remodeled to derive suitable reaction conditions for droplet-based microfluidic synthesis. Depending on the layout of the microfluidic chip, microgels with a size of approximately 30 μm or 200 μm were obtained, whose crosslinking density can be increased by implementing a multi-arm crosslinker. We analyzed the effects of the crosslinker species on composition, permeability, and softness and show that the microgels exhibit advantageous properties inherent to zwitterionic polymer systems, including high hydrophilicity as well as pH- and ionic strength-sensitivity. We demonstrate pH-regulated uptake and release of fluorescent model dyes before testing the adsorption of a small antimicrobial peptide, LL-37. Quantification of the peptide accommodated within the microgels reveals the impact of size and crosslinking density of the microgels. Biocompatibility of the microgels was validated by cell tests.

High-Temperature-Resistant Scale Inhibitor Polyaspartic Acid-Prolineamide for Inhibiting CaCO3 Scale in Geothermal Water and Speculation of Scale Inhibition Mechanism

An excellent high-temperature-resistant scale inhibitor, polyaspartic acid-prolineamide (PASP-Pro), was synthesized by polysuccinimide (PSI) and L-prolineamide (L-Pro), and then characterized by 1H-NMR and FTIR analysis. The inhibition performance of PASP-Pro on CaCO3 precipitation was studied at different temperatures through static tests; at the same time, the influence of PASP-Pro on the crystallization process of CaCO3 was investigated by combining the electrical conductivity test of CaCO3 solution with different CaCO3 scale characterizations. The suitable synthesis and evaluation conditions for PASP-Pro were obtained, and a possible multi-stage scale inhibition mechanism of PASP-Pro for CaCO3 scale was then suggested. PASP-Pro has better thermal stability and high-temperature scale inhibition performance (exceeds 87% after pretreatment at 150 °C) than PASP. In addition, PASP-Pro exhibited a promising anti-scaling property by inhibiting the crystallization of CaCO3; the induction period and the nucleation period of the CaCO3 crystallization process were prolonged nearly four times. It was found from XRD patterns that vaterite, an unstable crystalline phase, gradually emerged with the addition of the scale inhibitors, and the aragonite crystals are clearly observed in SEM images. Finally, the possible multi-stage scale inhibition mechanism of PASP-based inhibitors was proposed, including coating impurities, electrostatic repulsion, and inhibiting dehydration and rearrangement of CaCO3 crystallization.

Synthesis of sulfur-free Co-Mo nitride catalysts for the hydrotreating of atmospheric gasoil and co-processing of rapeseed oil

Sulfur-free transition metal carbide and nitride catalysts have been shown to be reasonable substitutes for sulfidic catalysts for the hydrotreating middle distillates and vegetable oils. However, their catalyst activity is still lower than commercial catalysts. In this paper, we build on our previous research by studying the synthesis and testing of nine sulfur-free Al2O3-supported Co-Mo nitride catalysts for the hydrotreating of atmospheric gasoil and its blends with rapeseed oil (25 wt.%) under industrial conditions (330–350 °C, 5.5 MPa, WHSV 1–2 h−1). Nitration temperatures play the most significant role in the synthesis and activity of the catalyst, obtaining a CoMoNx catalyst whose catalytic behaviour competes with the current commercial sulfidic Ni-Mo or Co-Mo catalysts (reduction of sulfur and nitrogen content up to 99.0 and 84.0%, respectively). Thus, our results allow us to evaluate and define the most suitable synthesis conditions for preparing high activity sulfur-free Al2O3-supported Co-Mo nitride catalysts.

Preparation of Nano-Mg(OH)2 and Its Flame Retardant and Antibacterial Modification on Polyethylene Terephthalate Fabrics.

The multifunctional polyethylene terephthalate (PET) fabrics were successfully prepared through a dip-coating technology to endow the flame retardant and antibacterial properties of PET fabrics, which are extensively used in many fields. The flame retardant and antibacterial agent was synthesized by a double drop-reverse precipitation method and surface-modified by the mixtures of titanate coupling agents and stearic acid to result in a good compatibility of the hydrophilic nano-Mg(OH)2 and the hydrophobic PET fabrics. The results indicated that the suitable synthesis conditions of nano-Mg(OH)2 are: Mg2+ concentration 1.5 mg/mL, reaction temperature 50 °C and reaction time 50 min, and the optimal modification conditions of nano-Mg(OH)2 are: modifier ratio 5/5, modification temperature 70 °C and modification time 40 min. The flame retardant test and the antibacterial test showed that the multifunctional PET fabrics had excellent flame retardant and antibacterial properties.

Synthesis of rhodium catalysts with amino acid or triazine as a ligand, as well as its polymerization property of phenylacetylene

Abstract Three novel rhodium complexes, with l-tyrosine (l-Tyr), l-arginine (l-Arg), or 2,4-diamino-6-phenyl-1,3,5-triazine (Dpt) as a ligand, named as [Rh(cod)(l-Tyr)], [Rh(cod)(l-Arg)], and [Rh(cod)(Dpt)2], respectively, had been synthesized for catalyzing the polymerization of phenylacetylene. Their yields were 62.34, 54.87, and 58.21%, respectively, by the most suitable synthesis conditions at 25°C for 4 h. The structures and purity of these complexes were proved by 1H NMR, element analysis, and scanning electron microscope (SEM). It has been examined that phenylacetylene could be polymerized by the three complexes as catalysts with high degrees of polymerization (n = 368, 385, and 664, respectively) and yields (about 87.62, 88.39, and 59.67%, respectively). In conclusion, compared with traditional [Rh–N] type catalysts, the novel [N–Rh–N] type catalyst ([Rh(cod)(Dpt)2]) gained better catalytic performance. By comparing the yield, Mw, and degree of their polymerization, the polymerization mechanism was found under the [N–Rh–N] type rhodium catalyst system.

Preparation of polyvinyl alcohol-calcium sustained-release agent employed to degrade long-chain fatty acids and improve the performance of anaerobic digestion of food waste

Polyvinyl alcohol (PVA) is a biodegradable material that can be degraded under natural conditions. In this study, a sustained-release agent (SRA) was prepared from calcium compounds and PVA (PVA-Ca) to effectively degrade long-chain fatty acids in food waste (FW) and improve the performance of anaerobic digestion (AD). The most appropriate materials and conditions for synthesizing Ca-SRA were chosen according to the characteristics of the sample and changes in the electrical conductivity of a solution of the SRA. The calcium release kinetics were analyzed by curve fitting. Moreover, analytical methods were used to analyze the formation mechanism of PVA-Ca. Finally, the effect of PVA-Ca on the performance of AD was investigated. The results showed that the most suitable materials for preparing the Ca-SRA were Ca(OH)2 powder and PVA1799. The most suitable synthesis conditions were freezing for 24 h at −20 °C and thawing for 24 h with one freeze–thaw cycle. PVA-Ca achieved rapid release during the first 48 h, which corresponded to first-order kinetics (k = 0.0354 h−1). The release of Ca2+ corresponded to changes in pH and the concentration of volatile fatty acids during hydrolysis and acidification of FW. After PVA-Ca was added, the duration of the system lag phase was significantly shortened to 10 days, the methane yield per unit load was increased from 238.2 to 489.3 mL g−1 volatile solids(VS), and the kinetic constant of AD of FW was 0.083 day−1. Adding PVA-Ca could increase the methane yield by 98.82%. Moreover, the value of T90 was reduced to a maximum of about 16 days. PVA-Ca was successfully employed in the AD of FW for the first time.

Facile phytosynthesis of gold nanoparticles-doped graphene oxide using Mangifera indica leaf extract: Characterization, antibacterial activity, and catalytic reduction of organic dyes

In this study, the gold nanoparticles-doped graphene oxide (AuNPs/GO) was prepared via a biosynthesis path using the Mangifera indica leaf extract. The characterization of produced AuNPs/GO was thoroughly conducted by modern methods such as X-ray diffraction, Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, zeta potential, and so on. The analyses showed that spherical AuNPs were uniformly distributed on the GO sheets with an average diameter of 11–21 nm, proving the successful formation of AuNPs/GO nanocomposite. The initial effects of HAuCl4 volume, reaction time, pH level, the presence of 24-hour-prolonged GO, the amount of GO, and the experiment order were carried out to find the most suitable synthesis conditions and enhance the overall performance of AuNPs/GO. The results indicated that the most appropriate conditions for the fabrication process include 5 mL of extract, 1500 μL of HAuCl4, a reaction time of 120 s, at pH 7, 1500 μL of 24-hour-prolonged GO, and the experiment sequence of adding HAuCl4 to the remaining precursors. The nanocomposite was also discovered to effectively inhibit the growth of both Pseudomonas aeruginosa and Staphylococcus aureus bacteria strains, indicating nearly 100% of bactericidal rates at 50 μg/mL. Meanwhile, the catalytic reduction activity of organic dyes by NaBH4 using the AuNPs/GO support, tested with methylene blue, methyl orange, malachite green, and crystal violet dyes, was also excellent in terms of relatively high efficiency of 99.83, 93.81, 99.85, and 97.93%, respectively. Along with remarkable recovery and reusability confirmed, those results show the highly promising applications of AuNPs/GO in the antiseptics field and treatment of dye-contaminated water sources.

Synthesising copper-carbon nanotube composites through methane diffusion flame

Flame synthesis of carbon nanotubes (CNT) on copper substrate is a novel approach for generating copper-carbon nanotube composites for improving thermal and electrical properties of copper material. The copper substrates were first cleaned and etched with concentrated sulphuric acid. Methane fuel was used in two different laminar flame configurations namely Normal Diffusion Flame (NDF) and Inverse Diffusion Flame (IDF). Under NDF, copper substrate melted due to high temperature blue flame shielding carbon-rich yellow flame in the structure of NDF which was further validated through numerical simulation. Unlike NDF, there is a clear separation between decomposed carbon-rich yellow flame from the oxidising blue flame in IDF that creates two highly differentiated temperature zones. This realises the suitable conditions for CNT synthesis on a copper substrate, generating copper-CNT composites with tubular diameters of 20 nm to 30 nm. This highlights the opportunity of using flame synthesis as a low-costs approach in fabrication of copper-CNT composites.

Synthesis of Diaminoacetic Acid Derivatives as a Promising Scaffold for the Synthesis of Polyheterocyclic Cage Compounds.

Here, we explored in detail an acid-catalyzed condensation of glyoxylic acid or its ethyl ester with several carboxamides of different basicity, or with mesyl amide, to furnish diaminoacetic acid derivatives. The most suitable synthesis conditions and the reaction catalysts were identified. Properties such as structure and basicity of the starting amides were demonstrated to influence the condensation process. Elemental iodine was used for the first time herein as an acid catalyst for the condensation of glyoxylic acid or its ester, which gave access to diaminoacetic acid derivatives in higher yields in most cases, as opposed to p-toluenesulfonic acid (PTSA). An abnormally high activity of mesyl amide when condensed with ethyl glyoxylate was noticed, which may evidence a special impact of the sulfonyl moiety in the amide molecule on the condensation.

Phase-Transition Process in the Hydrothermal Zeolitization of Volcanic Ash into LTA and FAU Structures

AbstractMinerals such as quartz, present widely in various volcanic ashes, remain unaltered throughout the low-temperature hydrothermal process currently used in industry to obtain zeolites, causing an incomplete hydrothermal transformation of the starting solid. This study presents a novel and cost-effective procedure which improves the reactivity of ash toward the generation of zeolite by increasing the availability of silica and alumina components. This method leads to a final product with a large zeolite content. The transformation consisted of an ash-activation step followed by hydrothermal zeolitization. The influence of the structural, chemical, and morphological characteristics of the volcanic ash as well as the effect of the activation procedure on the ash reactivity were studied. A collected sample (VA) and an amorphous fraction obtained after VA sieving (VA40, retained on #40 mesh) were used for zeolite production. These solids were alkaline-treated separately, aged, and reacted under controlled conditions of temperature at autogenous pressure. Throughout the process, the solid phases were characterized by X-ray diffraction, energy dispersive X-ray microanalysis, scanning electron microscopy, Fourier-transform infrared spectroscopy, and N2adsorption-desorption porosimetry measurements. After activation and alkaline aging, the presence of quartz and plagioclase minerals in the natural ash seemed to improve the growth of NaAlSiO4 polymorphs, which in turn were transformed easily to zeolite structures. Even under adequate pretreatment and suitable synthesis conditions, the coarse non-crystalline fraction led to low conversion, while the highest conversions to zeolites A and X were obtained from the natural ash. The outcomes of the present study could be used to improve the conversion levels of other non-conventional aluminosiliceous minerals into zeolites.

Exfoliated Ferrierite-Related Unilamellar Nanosheets in Solution and Their Use for Preparation of Mixed Zeolite Hierarchical Structures.

Direct exfoliation of layered zeolites into solutions of monolayers has remained unresolved since the 1990s. Recently, zeolite MCM-56 with the MWW topology (layers denoted mww) has been exfoliated directly in high yield by soft-chemical treatment with tetrabutylammonium hydroxide (TBAOH). This has enabled preparation of zeolite-based hierarchical materials and intimate composites with other active species that are unimaginable via the conventional solid-state routes. The extension to other frameworks, which provides broader benefits, diversified activity, and functionality, is not routine and requires finding suitable synthesis formulations, viz. compositions and conditions, of the layered zeolites themselves. This article reports exfoliation and characterization of layers with ferrierite-related structure, denoted bifer, having rectangular lattice constants like those of the FER and CDO zeolites, and thickness of approximately 2 nm, which is twice that of the so-called fer layer. Several techniques were combined to prove the exfoliation, supported by simulations: AFM; in-plane, in situ, and powder X-ray diffraction; TEM; and SAED. The results confirmed (i) the structure and crystallinity of the layers without unequivocal differentiation between the FER and CDO topologies and (ii) uniform thickness in solution (monodispersity), ruling out significant multilayered particles and other impurities. The bifer layers are zeolitic with Brønsted acid sites, demonstrated catalytic activity in the alkylation of mesitylene with benzyl alcohol, and intralayer pores visible in TEM. The practical benefits are demonstrated by the preparation of unprecedented intimately mixed zeolite composites with the mww, with activity greater than the sum of the components despite high content of inert silica as pillars.

Investigation of the parameters of carbon nanotube growth on zirconium diboride supported Ni catalyst via CVD

Carbon nanotubes (CNTs) were synthesized on zirconium diboride (ZrB2) through CVD using a Ni catalyst. The influences of the synthesis temperature, time and catalyst amount on the quality and quantity of grown CNTs were studied. The catalyst content determined the temperature at which the CNTs began to grow. When the Ni catalyst content was low, the temperature at which the CNTs began to grow should be higher, and was 1050 °C for 5 wt% Ni content, but was 950 °C for 15 wt% Ni content. Meanwhile, agglomeration of metal atoms was observed if the synthesis temperature was increased until reaching the upper limit temperature for CNT synthesis, which was 1100 °C for 5 wt% and 10 wt% Ni content, but was 1000 °C for 15 wt% Ni content. Increased Ni catalyst content also led to higher catalytic activity as long as the Ni catalyst content did not exceed 15 wt%. Meanwhile, prolonged synthesis time extended the reaction time for the decomposition of C2H2, but resulted in the agglomeration of carbon atoms when the synthesis time was 150 min. The results showed that the uniform distribution of CNTs can be obtained in ZrB2 powder and there was no reaction between ZrB2 and Ni catalyst. The suitable synthesis conditions for obtained uniform size of CNTs grown with a higher degree of graphitization on ZrB2 that identified in this work were: Ni catalyst content of 10 wt%, synthesis temperature of 1050 °C, and synthesis time of 120 min.

Carbon xerogel from 5-methylresorcinol-formaldehyde gel: The controllability of structural properties

Sol-gel-derived porous carbon is an attractive electrode material for various applications because its structure, along with its physical properties, can be tailored to the specified task by selecting suitable precursors and synthesis conditions. To complement oil shale-based sol-gel materials, in the current study, the tunability of the properties of 5-methylresorcinol-formaldehyde (5MR-FA) carbon xerogel is examined. As expected, the porosity of the 5MR-FA carbon xerogel is lower than those of the corresponding carbon aerogels, but the specific surface area in the range of 2–417 m2/g and the electrical conductivity of 0.8 S/cm demonstrate the potential of this xerogel in electrochemical applications as an electrode material. Furthermore, the synthesis conditions and final structure of the resulting carbon were in satisfactory correlation, including with the results of spectroscopy analysis. Na2CO3, which is used as a catalyst in this sol-gel reaction, affects the structure of the resulting carbon. In this study, it was established that the oxidation level of carbon and the short-range structural order and disorder are also influenced by the amount of Na2CO3, which is supported by the trends in the electrical conductivity results.

Borophene-graphene heterostructure: Preparation and ultrasensitive humidity sensing

Heterostructure has triggered a surge of interest due to its synergistic effects between two different layers, which contributes to desirable physical properties for extensive potential applications. Structurally stable borophene is becoming a promising candidate for constructing two-dimensional (2D) heterostructures, but it is rarely prepared by suitable synthesis conditions experimentally. Here, we demonstrate that a novel heterostructure composed of hydrogenated borophene and graphene can be prepared by heating the mixture of sodium borohydride and few-layered graphene followed by stepwise and in situ thermal decomposition of sodium borohydride under high-purity hydrogen as the carrier gas. The fabricated borophene-graphene heterostructure humidity sensor shows ultrahigh sensitivity, fast response, and long-time stability. The sensitivity of the fabricated borophene-based sensor is near 700 times higher than that of pristine graphene one at the relative humidity of 85% RH. The sensitivity of the sensor is highest among all the reported chemiresistive sensors based on 2D materials. Besides, the performance of the borophene-graphene flexible sensor maintains good stability after bending, which shows that the borophene-based heterostructures can be applied in wearable electronics. The observed high performance can be ascribed to the well-established charge transfer mechanism upon H2O molecule adsorption. This study further promotes the fundamental studies of interfacial effects and interactions between boron-based 2D heterostructures and chemical species.

Optimization of synthesizing silver nanoparticles from Trichoderma strains for inhibition of Fusarium oxysporum

With the popularity of green concepts, the use of biological method to synthesize metal nanoparticles is a favored method. Silver nanoparticles (AgNPs) have attracted more and more attention in the control of agricultural diseases, because of their strong antifungal activity and not easy inducing resistance for pathogens. In this study, Trichoderma citrinoviride and Trichoderma velutinous were used to study the most suitable synthesis conditions for AgNPs, and their antifungal activity against Fusarium oxysporum. The silver nanoparticles had an absorbance peak at 400-500 nm, the most suitable synthesis conditions were at standing and light with CL method (mycelium filtrate), AgNO₃ concentration of 2.0 mmol/L, pH of 7, and reaction temperature of 45 °C. AgNPs synthesized by T. citrinoviride and T. velutinous inhibited F. oxysporum, the inhibition effect was better with the increase of silver nanoparticle concentration. When the concentration of AgNPs was 200 mg/L, the antifungal rate from T. citrinoviride and T. velutinous was 33.75% and 36.08%, respectively.

A Review on Titanium Dioxide Based Nanofluids: Synthesis and Stabilizing Techniques in Both “Pure (Single System) and Mixed (Hybrid System) Base Fluids”

Nanofluids have been an attractive field of study due to its important effect on enhancing the thermal conductivity when used in heat transfer applications. Titanium dioxide based nanofluid specifically has been a focus of study due to its distinguished properties as it results in a very good heat transfer enhancement with low viscosity and low-pressure drop while maintaining a very good stability of dispersion for a long time. Also, Titanium dioxide is relatively cheap and non-toxic so using it as a nanofluid will be more economical and safer in many industries. This review represents the most recent synthesis methods of titanium dioxide based nanofluid in both pure and Mixed (hybrid system) base fluids along with the analysis of its properties and the outcome findings. All of which will be discussed in this paper coherently and thoroughly which will be a good reference and makes it easier for other researchers to investigate and choose the suitable synthesis conditions that give them the required nanofluid properties and stability.

Effect of pressure on the order-disorder phase transitions of B cations in AB'1/2B''1/2O3 perovskites.

Perovskite-like oxides AB'1/2B''1/2O3 may experience different degrees of ordering of the B cations that can be varied by suitable synthesis conditions or post-synthesis treatment. In this work the earlier proposed statistical model of order-disorder phase transitions of B cations is extended to account for the effect of pressure. Depending on the composition, pressure is found to either increase or decrease the order-disorder phase transition temperature. The change in transition temperature due to pressure in many cases reaches several hundred kelvin at pressures accessible in the laboratory, which may significantly change the degree of atomic ordering. The work is intended to help in determining how pressure influences the degree of atomic ordering and to stimulate research into the effect of pressure on atomic order-disorder phase transitions in perovskites.

Borophene-graphene heterostructures.

Integration of dissimilar two-dimensional (2D) materials is essential for nanoelectronic applications. Compared to vertical stacking, covalent lateral stitching requires bottom-up synthesis, resulting in rare realizations of 2D lateral heterostructures. Because of its polymorphism and diverse bonding geometries, borophene is a promising candidate for 2D heterostructures, although suitable synthesis conditions have not yet been demonstrated. Here, we report lateral and vertical integration of borophene with graphene. Topographic and spatially resolved spectroscopic measurements reveal nearly atomically sharp lateral interfaces despite imperfect crystallographic lattice and symmetry matching. In addition, boron intercalation under graphene results in rotationally commensurate vertical heterostructures. The rich bonding configurations of boron suggest that borophene can be integrated into a diverse range of 2D heterostructures.