scholarly journals Al-ZSM-5 Nanocrystal Catalysts Grown from Silicalite-1 Seeds for Methane Conversion

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 485
Author(s):  
Hyun Su Kim ◽  
Su Kyung Kang ◽  
Haoxiang Zhang ◽  
Elsa Tsegay Tikue ◽  
Jin Hyung Lee ◽  
...  
Keyword(s):  
Rapid Growth ◽  
Methane Conversion ◽  
Crystal Size ◽  
Reaction System ◽  
Seed Crystal ◽  
Catalyst Stability ◽  
Synthesis Time ◽  
Seed Crystals ◽  
Synthesis Conditions ◽  
Methane Dehydroaromatization

This study evaluated Al-ZSM-5 nanocrystals grown from silicalite-1 seed crystals as catalysts for the methane dehydroaromatization (MDA) reaction. Silicalite-1 seed crystals sized between 30 and 40 nm were used to grow Al-ZSM-5 under various synthesis conditions. The size of Al-ZSM-5 was significantly affected by the Si/Al ratio (SAR), synthesis time, and silica nutrients/seed crystal ratio (NSR). Larger crystals were obtained with an increased SAR in the synthesis sols. Gradual growth of Al-ZSM-5 occurred with synthesis time, although the growth in crystal size ceased at 5 h of synthesis at 120 °C, indicating the rapid growth of Al-ZSM-5 aided by the silicalite-1 seeds. Precise tuning of Al-ZSM-5 size was possible by changing the nutrient/silicalite-1 seed ratio; a higher NSR led to larger crystals. Two representative Al-ZSM-5 crystals with SARs of 35 and 140 were prepared for catalyst testing, and the crystal sizes were tailored to <100 nm by controlling NSR. The MDA reaction was conducted in the presence of the prepared Al-ZSM-5. The catalyst size exhibited distinct differences in catalyst stability, while the SAR of catalysts did not produce noticeable changes in the catalyst stability of the Al-ZSM-5 crystals and commercial zeolites in this reaction system.

Catalysts for hydrogenation of CO2 into components of motor fuels

2020 ◽  
pp. 1-18
Author(s):  
Yu.V. Bilokopytov ◽  
◽  
S.L. Melnykova ◽  
N.Yu. Khimach ◽  
◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Heterogeneous Catalysts ◽  
Fossil Fuels ◽  
Catalyst Stability ◽  
Co2 Conversion ◽  
Active Components ◽  
Synthesis Conditions ◽  
Hydrogenation Of Co2 ◽  
Mesoporous Zeolites ◽  
Motor Fuels

CO2 is a harmful greenhouse gas, a product of chemical emissions, the combustion of fossil fuels and car exhausts, and it is a widely available source of carbon. The review considers various ways of hydrogenation of carbon dioxide into components of motor fuels - methanol, dimethyl ether, ethanol, hydrocarbons - in the presence of heterogeneous catalysts. At each route of conversion of CO2 (into oxygenates or hydrocarbons) the first stage is the formation of CO by the reverse water gas shift (rWGS) reaction, which must be taken into account when catalysts of process are choosing. The influence of chemical nature, specific surface area, particle size and interaction between catalyst components, as well as the method of its production on the CO2 conversion processes is analyzed. It is noted that the main active components of CO2 conversion into methanol are copper atoms and ions which interact with the oxide components of the catalyst. There is a positive effect of other metals oxides additives with strong basic centers on the surface on the activity of the traditional copper-zinc-aluminum oxide catalyst for the synthesis of methanol from the synthesis gas. The most active catalysts for the synthesis of DME from CO2 and H2 are bifunctional. These catalysts contain both a methanol synthesis catalyst and a dehydrating component, such as mesoporous zeolites with acid centers of weak and medium strength, evenly distributed on the surface. The synthesis of gasoline hydrocarbons (≥ C5) is carried out through the formation of CO or CH3OH and DME as intermediates on multifunctional catalysts, which also contain zeolites. Hydrogenation of CO2 into ethanol can be considered as an alternative to the synthesis of ethanol through the hydration of ethylene. High activation energy of carbon dioxide, harsh synthesis conditions as well as high selectivity for hydrocarbons, in particular methane remains the main problems. Further increase of selectivity and efficiency of carbon dioxide hydrogenation processes involves the use of nanocatalysts taking into account the mechanism of CO2 conversion reactions, development of methods for removing excess water as a by-product from the reaction zone and increasing catalyst stability over time.

scholarly journals Investigation and Characterization of Synthesis Conditions on Sucrose-ammonium Dihydrogen Phosphate (SADP) Adhesive: Bond Performance and Chemical Transformation

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4078 ◽  
Author(s):  
Shijing Sun ◽  
Min Zhang ◽  
Kenji Umemura ◽  
Zhongyuan Zhao
Keyword(s):  
Chemical Analysis ◽  
Chemical Transformation ◽  
Raw Material ◽  
Synthesis Process ◽  
Dihydrogen Phosphate ◽  
Ammonium Dihydrogen Phosphate ◽  
Synthesis Time ◽  
Synthesis Conditions ◽  
Renewable Chemicals ◽  
Bond Performance

Sucrose is one of the most abundantly available renewable chemicals in the world, and it is expected to be utilized as a raw material for wood-based material products. Herein, a novel adhesion system that was based on sucrose and ammonium dihydrogen phosphate (ADP) was synthesized into an adhesive with 80% solid content, and this eco-friendly was utilized on the fabrication of plywood. The effects of the synthesis conditions on the plywood bond performance and synthesis mechanism were investigated. The optimal synthesis conditions were as follows: the mass proportion between sucrose and ADP was 90/10, the synthesis temperature was 90 °C, and the synthesis time was 3 h. The bonding performance of the plywood that was bonded by optimal SADP adhesive satisfied the GB/T 9846-2015 standard. The chemical analysis was performance tested by using High-Performance Liquid Chromatography (HPLC), Attenuated Total Reflection-Fourier Transform Infrared Spectra (ATR-FTIR), and Pyrolysis Gas Chromatography and Mass Spectrometry (Py-GC/MS) to understand the chemical transformation during the synthesis process. The chemical analysis results confirmed that the hydrolysis and conversation reaction of sucrose occurred in the synthesized SADP adhesive, and ADP promoted the pyrolysis efficiency of sucrose.

Relationship between growth rate and undercooling in Pt-added Y1Ba2Cu3O7−x

1996 ◽  
Vol 11 (5) ◽  
pp. 1114-1119 ◽  
Author(s):  
A. Endo ◽  
H. S. Chauhan ◽  
Y. Nakamura ◽  
Y. Shiohara
Keyword(s):  
Experimental Data ◽  
Growth Rate ◽  
Parabolic Equation ◽  
Growth Rates ◽  
Crystal Size ◽  
Experimental Conditions ◽  
Seed Crystals ◽  
Cooling Method ◽  
Increasing Trend ◽  
Good Agreement

Y1Ba2Cu307−x (Y123) crystals were grown by two different methods, the constant undercooling solidification and the continual cooling method, with top seeding by Sm123 seed crystals in order to investigate a relationship between undercooling (ΔT) and a growth rate (R). The crystals of Y123 with a sharp faceted interface, which consisted of {100} and {001} faces, grew epitaxially from the seed. It was found that the growth rates of {100} face (Ra) and that of {001} face (Rc) showed an increasing trend with increasing ΔT, and Rc was faster than Ra within these experimental conditions, ΔT < 20 K. The relation between R and ΔT follows the parabolic equation, viz. Ra ∝ ΔT1.9 and Rc ∝ ΔT1.3 for {100} and {001} faces, respectively. The simulated crystal size using the R and ΔT relations obtained from the constant undercooling method showed good agreement with experimental data by the continual cooling.

Anatase titania nanoparticles for covering P3HT microfibers: Morphological properties

2015 ◽  
Vol 1737 ◽  
Author(s):  
Evelyn B. Díaz-Cruz ◽  
Diego Hernandez ◽  
M.E. Nicho-Díaz ◽  
Omar Martínez-Alvarez ◽  
Hailin Zhao-Hu ◽  
...  
Keyword(s):  
Solar Cells ◽  
Hydrothermal Treatment ◽  
Crystal Size ◽  
Bulk Heterojunction ◽  
Sol Gel ◽  
Titania Nanoparticles ◽  
Morphological Properties ◽  
High Concentration ◽  
Synthesis Conditions ◽  
Anatase Titania

ABSTRACTAnatase titania has been widely used for several applications such as photocatalysis and solar cells. Sol-gel is a conventional route to obtain amorphous titania and, either post-annealing or a post-hydrothermal treatment are necessary to obtain anatase crystalline phase. It is well known that the synthesis conditions affect in the particle size, surface area and grain size of the titania. In this work regular nanoparticles of anatase titania (TiO2) were obtained by an easy ultrasound-assisted synthesis; the nanoparticles were undergone to either a hydrothermal treatment at 130 °C and/or to an annealing at 450°C. Nanoparticles powder with a crystal size of about 8-10 nm were re-dispersed in aqueous solution at different concentrations (5 to 20mg/mL). Poly (3-hexylthiophene) (P3HT) microfibers were immersed into the TiO2 nanoparticles solution for 24 h and they were dried at 80°C for 1 h in order to form the bulk heterojunction. P3HT:TiO2 heterojunctions were characterized by SEM and EDS. According to SEM results at low concentration (5 mg/mL), the covering of the P3HT microfibers is poor and at high concentration (20 mg/mL) the microfibers were seen cracked. The best homogeneous covering onto the P3HT microfibers was obtained at 10mg/mL of titania nanoparticles; it could be the optimal concentration to build bulk heterojunction for hybrid solar cells.

scholarly journals Deactivation and Regeneration of Mo/ZSM-5 Catalysts for Methane Dehydroaromatization

2009 ◽  
Vol 12 (1) ◽  
pp. 1 ◽  
Author(s):  
E.V. Matus ◽  
O.B. Sukhova ◽  
I.Z. Ismagilov ◽  
V.I. Zaikovskii ◽  
M.A. Kerzhentsev ◽  
...  
Keyword(s):  
Reaction Time ◽  
Reaction Temperature ◽  
Methane Conversion ◽  
Formation Rate ◽  
Space Velocity ◽  
Molybdenum Content ◽  
Stable Operation ◽  
Carbonaceous Deposits ◽  
Methane Dehydroaromatization ◽  
The Stability

The methane dehydroaromatization (DHA) was studied over a series of impregnated Mo/ZSM-5 catalysts with different molybdenum contents (1-10 wt.%). It was shown that total methane conversion was decreased by 30% during 12 h of DHA reaction. The benzene formation rate was increased from 0.5 to 13.9 mol C<sub>6</sub>H<sub>6</sub>/(g<sub>Mo</sub>·s) when the molybdenum content in the catalyst was lowered from 10 to 1 wt.%. The deactivated Mo/ZSM-5 catalysts were studied by a group of methods: N<sub>2</sub> adsorption, XRD, TGDTA, HRTEM and XPS. The content and condensation degree (C/H ratio) of the carbonaceous deposits was found to increase with an increase of either of the following parameters: molybdenum content (1-10 wt.%), reaction temperature (720-780 °C), space velocity (405-1620 h<sup>-1</sup>), reaction time (0.5-20 h). The stability of Mo/ZSM-5 catalysts in reaction-regeneration cycles was better when the time on stream was shorter. The regeneration conditions of deactivated Mo/ZSM-5 catalysts providing their stable operation under multiple reaction-regeneration cycles have been selected.

scholarly journals Synthesis of Molecularly Imprinted Polymer via Emulsion Polymerization for Application in Solanesol Separation

2020 ◽  
Vol 10 (8) ◽  
pp. 2868 ◽  
Author(s):  
Guojie Zhao ◽  
Jing Liu ◽  
Minghong Liu ◽  
Xiaobin Han ◽  
Yulong Peng ◽  
...  
Keyword(s):  
Emulsion Polymerization ◽  
Molecularly Imprinted Polymers ◽  
Current Method ◽  
Synthesis Process ◽  
Cross Linking ◽  
Adsorption Effect ◽  
Synthesis Time ◽  
Molecularly Imprinted ◽  
Imprinted Polymers ◽  
Synthesis Conditions

High-purity solanesol can be used for pharmaceutical applications, but the current method for purifying solanesol has high cost and difficult continuous operation, and the use of molecular imprinting to purify natural products is a hot research topic of current research. Solanesol molecularly imprinted polymers were synthesized via emulsion polymerization for the first time. The morphology of the SSO-MIPs was observed with a scanning electron microscope, and the effects of the synthesis time, initiator dosage, functional monomer dosage, and cross-linking agent dosage on the adsorption effects under high-temperature and rapid synthesis conditions were discussed. The results demonstrate that the optimum synthesis conditions were a ratio of the template molecules to the functional monomers to the cross-linking agents of 1:8:30 (mol:mol:mol), 10 mg of the initiator, and a synthesis temperature of 70 °C. The imprinting factor of SSO-MIPs synthesized under the optimized process was found to reach 2.51, and the SSO-MIPs synthesized by this method exhibited a good adsorption effect, emitted less pollution during the synthesis process, and are convenient for demulsification. This research reports a reliable method for the synthesis of solanesol molecularly imprinted polymers.

Growth of High Quality 4H-SiC Crystals in Controlled Temperature Distributions of Seed Crystals

2012 ◽  
Vol 717-720 ◽  
pp. 13-16
Author(s):  
Hiroshi Tsuge ◽  
Shinya Sato ◽  
Masakazu Katsuno ◽  
Tatsuo Fujimoto ◽  
Wataru Ohashi
Keyword(s):  
Crystal Surface ◽  
Surface Condition ◽  
Large Diameter ◽  
Growth Conditions ◽  
Seed Crystal ◽  
Seed Crystals ◽  
Temperature Distributions ◽  
Edge Part ◽  
Defect Densities

Large diameter 4H-SiC single crystal wafers with higher quality are required to improve the yields of devices fabricated onto the SiC wafers. For crystal growths with higher quality, it is important to prepare seed crystals with lower defect densities. In particular, the edge part of the seed has to be prepared with considerable care because the crystallinity of the enlarged part of grown crystals depends much upon the surface condition of the seed crystal during radial expansion growth. We found that growth with fewer defect and micropipe densities, specifically at the periphery of the crystal, is possible by utilizing in-situ etching process for the seed crystal surface. We have also performed intense numerical calculations of the temperature distribution around the seed surface, and discussed growth conditions which cause the in-situ etching effective to improvement of the crystallinity in enlarged crystals.

Cortical bone growth and maturational changes in dwarf rats induced by recombinant human growth hormone

1996 ◽  
Vol 270 (1) ◽  
pp. E51-E59 ◽  
Author(s):  
D. A. Martinez ◽  
M. W. Orth ◽  
K. E. Carr ◽  
R. Vanderby ◽  
A. C. Vailas
Keyword(s):  
Growth Hormone ◽  
Bone Formation ◽  
Cortical Bone ◽  
Rapid Growth ◽  
Crystal Size ◽  
Bone Growth ◽  
Recombinant Human Growth Hormone ◽  
Bone Collagen ◽  
Bone Maturation ◽  
Hydroxyapatite Crystal

The growth hormone (GH)-deficient dwarf rat was used to investigate recombinant human (rh) GH-induced bone formation and to determine whether rhGH facilitates simultaneous increases in bone formation and bone maturation during rapid growth. Twenty dwarf rats, 37 days of age, were randomly assigned to dwarf plus rhGH (GH; n = 10) and dwarf plus vehicle (n = 10) groups. The GH group received 1.25 mg rhGH/kg body wt two times daily for 14 days. Biochemical, morphological, and X-ray diffraction measurements were performed on the femur middiaphysis. rhGH stimulated new bone growth in the GH group, as demonstrated by significant increases (P < 0.05) in longitudinal bone length (6%), middiaphyseal cross-sectional area (20%), and the amount of newly accreted bone collagen (28%) in the total pool of middiaphyseal bone collagen. Cortical bone density, mean hydroxyapatite crystal size, and the calcium and collagen contents (microgram/mm3) were significantly smaller in the GH group (P < 0.05). Our findings suggest that the processes regulating new collagen accretion, bone collagen maturation, and mean hydroxyapatite crystal size may be independently regulated during rapid growth.

scholarly journals Further Exploration of Sucrose-Citric Acid Adhesive: Synthesis and Application on Plywood

Polymers ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1875 ◽  
Author(s):  
Shijing Sun ◽  
Zhongyuan Zhao ◽  
Kenji Umemura
Keyword(s):  
Citric Acid ◽  
Research Direction ◽  
Synthesis Temperature ◽  
Solid Content ◽  
National Standard ◽  
Synthesis Process ◽  
Synthesis Mechanism ◽  
Synthesis Time ◽  
Synthesis Conditions ◽  
Bond Performance

The development of eco-friendly adhesives is a major research direction in the wood-based material industry. Previous research has already demonstrated the mixture of sucrose and citric acid could be utilized as an adhesive for the manufacture of particleboard. Herein, based on the chemical characteristics of sucrose, a synthesized sucrose-citric acid (SC) adhesive was prepared, featuring suitable viscosity and high solid content. The investigation of synthesis conditions on the bond performance showed that the optimal mass proportion between sucrose and citric acid was 25/75, the synthesis temperature was 100 °C, and the synthesis time was 2 h. The wet shear strength of the plywood bonded with SC adhesive, which was synthesized at optimal conditions and satisfied the China National Standard GB/T 9846-2015. The synthesis mechanism was studied by both 13C NMR analysis and HPLC, and the chemical composition manifesting caramelization reaction occurred during the synthesis process. The results of ATR FT-IR indicated the formation of a furan ring, carbonyl, and ether groups in the cured insoluble matter of the SC adhesive, which indicated dehydration condensation as the reaction mechanism between sucrose and citric acid.

Synthesis of Large ZSM-5 Crystals under High Pressure

2000 ◽  
Vol 658 ◽  
Author(s):  
Xiqu Wang ◽  
Allan J. Jacobson
Keyword(s):  
High Pressure ◽  
Elevated Temperature ◽  
Strong Correlation ◽  
Crystal Size ◽  
Silicate Solution ◽  
Synthesis Temperature ◽  
Organic Template ◽  
Uniform Size ◽  
Synthesis Conditions ◽  
Temperature And Pressure

ABSTRACTThe synthesis temperature for silicalite-I (MFI) can be raised to 300°C by applying high pressure to stabilize the structure-directing organic template. The elevated temperature and pressure favor theformation of crystals with improved quality. Prismatic silicalite-I crystals with a uniform size of about 0.7× 0.2 × 0.2 mm have been obtained by heating a gel prepared from TMA-silicate solution, TPABr andsodium hexafluorosilicate at 250°C under a pressure of 80 MPa. The influence of synthesis conditions on the crystal sizes has been studied by systematically changing temperature, pressure and gel compositions. Underthe specific conditions of 250°C and 80 MPa, a strong correlation was found between the crystal size andthe F/Si mole ratio of the starting gel, which enables the preparation of uniform crystals of silicalite-I with preset dimensions.

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