scholarly journals Aluminum oxide carrier for a catalyst for low-temperature isomerization of hydrocarbons

2020 ◽  
Vol 15 (3) ◽  
pp. 58-69
Author(s):  
N. Tagandurdyyeva ◽  
N. V. Maltseva ◽  
T. A. Vishnevskaya ◽  
V. N. Narayev ◽  
A. Yu. Postnov
Keyword(s):  
Low Temperature ◽  
Polyvinyl Alcohol ◽  
Aluminum Oxide ◽  
High Selectivity ◽  
Ph Value ◽  
Strength Properties ◽  
Isomerization Reaction ◽  
Preparation Conditions ◽  
Constant Ph ◽  
Extrusion Method

Objectives. Determine the necessary conditions for obtaining a granulated η-Al2O3 carrier, investigate its structural and strength properties, and evaluate its activity for the model n-butane isomerization reaction.Methods. Samples containing bayerite structure aluminum trihydroxide were synthesized by precipitation from aqueous solutions of aluminum nitrate with ammonia under isothermal conditions at a constant pH value. The samples of the granulated carrier were obtained using an extrusion method when the composition of molding pastes was varied by tuning the ratio of bayerite- and η-Al2O3 -containing components and introducing polyvinyl alcohol.Results. The influence of the preparation conditions on the structural and strength properties of the active Al2O3 granules is evaluated. Samples of the aluminum oxide carrier were tested for a model reaction of low-temperature isomerization of n-butane, demonstrating a sufficiently high selectivity and reasonable prospects for use as catalysts for low-temperature isomerization of hydrocarbons.Conclusions. Increasing the content of the polyvinyl alcohol in the molding paste from 0.4 to 1.8 wt % is accompanied by an increase in the predominant sizes of the mesopores in the range of 10–50 nm and pores in the range of 50–80 nm, explaining the high values of all recorded parameters for the process of isomerization of n-butane.

scholarly journals Self-Assembly of the Bio-Surfactant Aescin in Solution: A Small-Angle X-ray Scattering and Fluorescence Study

2019 ◽  
Vol 3 (2) ◽  
pp. 47 ◽  
Author(s):  
Carina Dargel ◽  
Ramsia Geisler ◽  
Yvonne Hannappel ◽  
Isabell Kemker ◽  
Norbert Sewald ◽  
...  
Keyword(s):  
Low Temperature ◽  
Small Angle ◽  
Self Assembly ◽  
Ph Value ◽  
Micelle Formation ◽  
X Ray ◽  
X Ray Scattering ◽  
Transmission Electron ◽  
Constant Ph ◽  
Ray Scattering

This work investigates the temperature-dependent micelle formation as well as the micellar structure of the saponin aescin. The critical micelle concentration ( c m c ) of aescin is determined from the concentration-dependent autofluorescence (AF) of aescin. Values between c m c aescin , AF (10 ∘ C) = 0.38 ± 0.09 mM and c m c aescin , AF (50 ∘ C) = 0.32 ± 0.13 mM were obtained. The significance of this method is verified by tensiometry measurements. The value determined from this method is within the experimental error identical with values obtained from autofluorescence ( c m c aescin , T ( WP ) (23 ∘ C) = 0.33 ± 0.02 mM). The structure of the aescin micelles was investigated by small-angle X-ray scattering (SAXS) at 10 and 40 ∘ C. At low temperature, the aescin micelles are rod-like, whereas at high temperature the structure is ellipsoidal. The radii of gyration were determined to ≈31 Å (rods) and ≈21 Å (ellipsoid). The rod-like shape of the aescin micelles at low temperature was confirmed by transmission electron microscopy (TEM). All investigations were performed at a constant pH of 7.4, because the acidic aescin has the ability to lower the pH value in aqueous solution.

Influence of Wood Flour Additive on Porous Structure and Strength Properties of Moulded Alumina

2015 ◽  
Vol 670 ◽  
pp. 139-143 ◽  
Author(s):  
Tatiana Bugrova ◽  
Anastasia Tatarkina ◽  
Ilya Zhukov ◽  
Grigory Mamontov
Keyword(s):  
Low Temperature ◽  
Porous Structure ◽  
Pore Volume ◽  
Wood Flour ◽  
Catalyst Support ◽  
Strength Properties ◽  
Porous Catalyst ◽  
Preparation Conditions ◽  
Granule Strength ◽  
20 Nm

The moulded Al2O3 materials prepared by mixing of thermochemically activated aluminum trihydroxide (TCA ATH) with wood flour were proposed to be used as promising porous catalyst support for various processes. A series of Al2O3 supports with different wood flour loading (0, 2 and 5 %wt.) were studied by SEM, low-temperature N2 sorption, XRD, granule strength and water-absorbing capacity. It was shown that supports were characterized by porous structure with mesopore sizes of 2-20 nm and specific surface area of 159-186 m2/g. The increase of the amount of wood flour leads to increase of the share of pore volume with wider than 10 nm and the decrease of the strength of alumina granules. Thus, optimization of preparation conditions allows obtaining alumina materials with desired porous structure.

Effect of Temperature on the Structure and Mechanical Properties of Mechanically Alloyed Al-Nio Composite

2014 ◽  
Vol 59 (1) ◽  
pp. 121-126
Author(s):  
M. Zygmunt-Kiper ◽  
L. Blaz ◽  
M. Sugamata
Keyword(s):  
Mechanical Properties ◽  
Aluminum Oxide ◽  
Aluminum Matrix ◽  
Hot Extrusion ◽  
Effect Of Temperature ◽  
Compression Tests ◽  
Mechanically Alloyed ◽  
Structure Morphology ◽  
High Purity Aluminum ◽  
Extrusion Method

Abstract Mechanical alloying of high-purity aluminum and 10 wt.% NiO powders combined with powder vacuum compression and following hot extrusion method was used to produce an Al-NiO composite. Mechanical properties of as-extruded materials as well as the samples annealed at 823 K /6 h, were tested by compression at 293 K - 770 K. High mechanical properties of the material were attributed to the highly refined structure of the samples. It was found that the structure morphology was practically not changed during hot-compression tests. Therefore, the effect of deformation temperature on the hardness of as-deformed samples was very limited. The annealing of samples at 823 K/6 h induced a chemical reaction between NiO-particles and surrounding aluminum matrix. As a result, the development of very fine aluminum oxide and Al3Ni grains was observed.

Ultra-precision grinding of 4H-SiC wafer by PAV/PF composite sol-gel diamond wheel

2021 ◽  
Vol 13 (9) ◽  
pp. 168781402110449
Author(s):  
Kaiping Feng ◽  
Tianchen Zhao ◽  
Binghai Lyu ◽  
Zhaozhong Zhou
Keyword(s):  
Surface Roughness ◽  
Low Temperature ◽  
Polyvinyl Alcohol ◽  
Feed Rate ◽  
Hot Pressing ◽  
Phenolic Resin ◽  
Sol Gel ◽  
Diamond Wheel ◽  
Sic Wafer ◽  
Better Than

To eliminate the deep scratches on the 4H-SiC wafer surface in the grinding process, a PVA/PF composite sol-gel diamond wheel was proposed. Diamond and fillers are sheared and dispersed in the polyvinyl alcohol-phenolic resin composite sol glue, repeatedly frozen at a low temperature of −20°C to gel, then 180°C sintering to obtain the diamond wheel. Study shows that the molecular chain of polyvinyl alcohol-phenolic resin is physically cross-linked to form gel under low-temperature conditions. Tested by mechanical property testing machines, microhardness tester, and SEM. The results show that micromorphology is more uniform, the strength of the sol-gel diamond wheel is higher, the hardness uniformity is better than that of the hot pressing diamond wheel. Grinding experiments of 4H-SiC wafer were carried out with the prepared sol-gel diamond wheel. The influence of grinding speed, feed rate, and grinding depth on the surface roughness was investigated. The results showed that by using the sol-gel diamond wheel, the surface quality of 4H-SiC wafer with an average surface roughness Ra 6.42 nm was obtained under grinding wheel speed 7000 r/min, grinding feed rate 6 µm/min, and grinding depth 15 µm, the surface quality was better than that of using hot pressing diamond wheel.

scholarly journals Influence of Bitumen Type and Asphalt Mixture Composition on Low-Temperature Strength Properties According to Various Test Methods

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2118 ◽  
Author(s):  
Marek Pszczola ◽  
Cezary Szydlowski
Keyword(s):  
Tensile Strength ◽  
Low Temperature ◽  
Cooling Rate ◽  
Strength Properties ◽  
Test Methods ◽  
Asphalt Mixtures ◽  
Bending Test ◽  
Mixture Composition ◽  
Tension Stress ◽  
Strength Reserve

In regions with low-temperatures, action transverse cracks can appear in asphalt pavements as a result of thermal stresses that exceed the fracture strength of materials used in asphalt layers. To better understand thermal cracking phenomenon, strength properties of different asphalt mixtures were investigated. Four test methods were used to assess the influence of bitumen type and mixture composition on tensile strength properties of asphalt mixtures: tensile strength was measured using the thermal stress restrained specimen test (TSRST) and the uniaxial tension stress test (UTST), flexural strength was measured using the bending beam test (BBT), and fracture toughness was measured using the semi-circular bending test (SCB). The strength reserve behavior of tested asphalt mixtures was assessed as well. The influence of cooling rate on the strength reserve was investigated and correlations between results from different test methods were also analyzed and discussed. It was observed that the type of bitumen was a factor of crucial importance to low-temperature properties of the tested asphalt concretes. This conclusion was valid for all test methods that were used. It was also observed that the level of cooling rate influenced the strength reserve and, in consequence, resistance to low-temperature cracking. It was concluded that reasonably good correlations were observed between strength results for the UTST, BBT, and SCB test methods.

scholarly journals The effects of low-temperature storage on the viability of Lactobacillus casei and the stability of antibacterial activity in green grass jelly synbiotic drinks

2020 ◽  
Vol 21 (8) ◽  
Author(s):  
SAMSUL RIZAL ◽  
Suharyono Suharyono ◽  
Fibra Nuariny ◽  
Julfi Restu Amelia
Keyword(s):  
Antibacterial Activity ◽  
Lactic Acid ◽  
Low Temperature ◽  
Lactic Acid Bacteria ◽  
Lactobacillus Casei ◽  
Pathogenic Bacteria ◽  
Ph Value ◽  
Low Temperature Storage ◽  
The Stability ◽  
Temperature Storage

Abstract. Rizal S, Suharyono, Nurainy F, Amela JR. 2020. The effects of low-temperature storage on the viability of Lactobacillus casei and the stability of antibacterial activity in green grass jelly synbiotic drinks. Biodiversitas 21: 3826-3831. Synbiotic drinks from green grass jelly have shown antibacterial activity against pathogenic bacteria. These are usually stored at low temperatures to maintain their characteristics. The aim of this study was to determine the effect of storage at low temperature of 10°C on the viability of lactic acid bacteria (Lactobacillus casei) and the stability of the antibacterial activity in synbiotic drinks made of green grass jelly. Antibacterial activity of green grass jelly synbiotic drink was conducted against pathogenic bacteria (Staphylococcus aureus, Salmonella sp., Bacillus cereus, and Escherichia coli). The products were stored for 28 days at 10°C temperature. Observations on the antibacterial activity, pH value, total acid, and total lactic acid bacteria were carried out every 7 days. Antibacterial activity was evaluated using agar well diffusion method. The results showed that storage at low temperature (10 ± 2°C) for 28 days decreased the antibacterial activity and pH value but sharply increased total lactic acid bacteria (at 0 to 7 days of storage) in green grass jelly synbiotic drinks. Salmonella sp. showed the highest inhibition caused by the antibacterial agents in green grass jelly synbiotic drinks while the lowest inhibition was found on Staphylococcus aureus. During storage at low temperature, green grass jelly synbiotic drinks had a total of lactic acid bacteria that ranged from 9.51 to 10.10 (Log CFU/mL) or equal to 3.24x109-1.26x1010 CFU/mL; a total of lactic acid that ranged from 0.48% to 0.87%; and pH values that ranged from 3.78 to 4.08.

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