scholarly journals Ruthenium Catalysts Templated on Mesoporous MCM-41 Type Silica and Natural Clay Nanotubes for Hydrogenation of Benzene to Cyclohexane

Catalysts ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 537 ◽  
Author(s):  
Aleksandr Glotov ◽  
Anna Vutolkina ◽  
Aleksey Pimerzin ◽  
Vladimir Nedolivko ◽  
Gleb Zasypalov ◽  
...  
Keyword(s):  
Specific Activity ◽  
Nitrogen Adsorption ◽  
Halloysite Nanotubes ◽  
High Specific Surface Area ◽  
Ruthenium Catalysts ◽  
Molar Ratio ◽  
Benzene Hydrogenation ◽  
Ru Nanoparticles ◽  
Clay Nanotubes ◽  
Mcm 41

Mesoporous ruthenium catalysts (0.74–3.06 wt%) based on ordered Mobil Composition of Matter No. 41 (MCM-41) silica arrays on aluminosilicate halloysite nanotubes (HNTs), as well as HNT-based counterparts, were synthesized and tested in benzene hydrogenation. The structure of HNT core-shell silica composite-supported Ru catalysts were investigated by transmission electron microscopy (TEM), X-ray fluorescence (XRF) and temperature-programmed reduction (TPR-H2). The textural characteristics were specified by low-temperature nitrogen adsorption/desorption. The catalytic evaluation of Ru nanoparticles supported on both the pristine HNTs and MCM-41/HNT composite in benzene hydrogenation was carried out in a Parr multiple reactor system with batch stirred reactors (autoclaves) at 80 °C, a hydrogen pressure of 3.0 MPa and a hydrogen/benzene molar ratio of 3.3. Due to its hierarchical structure and high specific surface area, the MCM-41/HNT composite provided the uniform distribution and stabilization of Ru nanoparticles (NPs) resulted in the higher specific activity and stability as compared with the HNT-based counterpart. The highest specific activity (5594 h−1) along with deep benzene hydrogenation to cyclohexane was achieved for the Ru/MCM-41/HNT catalyst with a low metal content.

scholarly journals CO2 hydrogenation to dimethyl ether over In2O3 catalysts supported on aluminosilicate halloysite nanotubes

2021 ◽  
Vol 10 (1) ◽  
pp. 594-605
Author(s):  
Alexey Pechenkin ◽  
Dmitry Potemkin ◽  
Sukhe Badmaev ◽  
Ekaterina Smirnova ◽  
Kirill Cherednichenko ◽  
...  
Keyword(s):  
Dimethyl Ether ◽  
Catalytic Properties ◽  
Fixed Bed ◽  
Nitrogen Adsorption ◽  
Halloysite Nanotubes ◽  
Molar Ratio ◽  
Stable Operation ◽  
Bifunctional Catalysts ◽  
Stainless Steel Reactor ◽  
Mcm 41

Abstract This work presents results on CO2 hydrogenation to dimethyl ether (DME) over bifunctional catalysts consisting of In2O3, supported on natural clay halloysite nanotubes (HNT), and HNT modified with Al-MCM-41 silica arrays. The catalysts were characterized by TEM, STEM, EDX-mapping, NH3-TPD, XRD, low-temperature nitrogen adsorption, TPO, and H2-TPR techniques. Catalytic properties of In2O3/HNT and In2O3/Al-MCM-41/HNT in the CO2 hydrogenation to DME were investigated in a fixed-bed continuous flow stainless steel reactor at 10–40 atm, in the temperature range of 200–300°C, at GHSV = 12,000 h−1 and molar ratio of H2:CO2 = 3:1. The best catalyst for CO2 hydrogenation was In2O3/Al-MCM-41/HNT that provided DME production rate 0.15 gDME·(gcat·h)−1 with DME selectivity 53% and at 40 bar, GHSV = 12,000 h−1, and T = 250°C. It was shown that In2O3/Al-MCM-41/HNT exhibited stable operation for at least 40 h on stream.

Synthesis of Nanoporous Materials Al-MCM-41 from Natural Halloysite

NANO ◽  
2015 ◽  
Vol 10 (01) ◽  
pp. 1550005 ◽  
Author(s):  
Yaling Xie ◽  
Aidong Tang ◽  
Huaming Yang
Keyword(s):  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Halloysite Nanotubes ◽  
Nanoporous Materials ◽  
Molar Ratio ◽  
Molar Ratios ◽  
Naoh Solution ◽  
The One ◽  
Mcm 41

Nanoporous materials Al -MCM-41 with varying Si / Al molar ratios have been successfully synthesized from natural clay mineral halloysite nanotubes (HNTs). Hydrothermal treatment of acid-pretreated HNTs and NaOH solution resulted in the one-step synthesis of final nanoporous products by using surfactant. The effects of Si / Al molar ratios (7.7, 61.0 and 176.5) on the surface area, porosity and degree of structural order of Al -MCM-41 materials have been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), N 2 adsorption–desorption measurements and Fourier transform infrared (FTIR) spectra techniques. The results indicated that Si / Al molar ratio had important effect on the characteristics of nanoporous materials, and Al -MCM-41 with an intermediate Si / Al molar ratio of 61.0 exhibited excellent characteristics with high degree of order, high surface area (S BET ) of 1033 m2/g and pore volume of 0.92 mL/g.

scholarly journals Synthesis and characterization of porous silica and polyaniline-porous silica composite materials with high surface area

2014 ◽  
Vol 49 (1) ◽  
pp. 1-8
Author(s):  
US Akhtar ◽  
MK Hossain ◽  
MS Miran ◽  
MYA Mollah
Keyword(s):  
Electron Microscopy ◽  
Pore Size ◽  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Porous Silica ◽  
Nitrogen Adsorption ◽  
High Specific Surface Area ◽  
Molar Ratio ◽  
Cylindrical Pore

Porous silica materials were synthesized from tetraethyl orthosilicate (TEOS) using Pluronic P123 (non-ionic triblock copolymer, EO20PO70O20) as template under acidic conditions which was then used to prepare polyaniline (PAni) and porous silica composites (PAnisilica) at a fixed molar ratio. These materials were characterized by nitrogen adsorption-desorption isotherm measured by Barrett-Joyner- Halenda (BJH) method and pore size distribution from desorption branch and surface area measured by the Brunauer-Emmett-Teller (BET) method, scanning electron microscopy (SEM), transmission electron microscopy (TEM), TEM-energy dispersive X-ray (EDX) and Fourier transform infrared (FT-IR) spectroscopy. The composite maintains its structure even after the polymerization and the polymer is dispersed on the inorganic matrix. The rod-like porous silica was about 1?m to 1.5 ?m long and on an average the diameter was in the range of 300- 500 nm. The SEM and TEM images show well ordered 2d hexagonal pore, high specific surface area (850 m2g-1) and uniform pore size of ca. 6.5 nm in diameter. After incorporation of PAni inside the silica pore, framework of porous silica did not collapse and the surface area of the composite was as high as 434 m2g-1 which was 5.5 time higher than our previous report of 78.3 m2g-1. Due to shrinkage of the framework during the incorporation of aniline inside the silica, the pore diameter slightly increase to 7.5 nm but still showing Type IV isotherm and typical hysteresis loop H1 implying a uniform cylindrical pore geometry. DOI: http://dx.doi.org/10.3329/bjsir.v49i1.18847 Bangladesh J. Sci. Ind. Res. 49(1), 1-8, 2014

Synthesis and Structural Characterization of SiO2-Al2O3 Xerogels

2007 ◽  
Vol 336-338 ◽  
pp. 2286-2289
Author(s):  
Fei He ◽  
Xiao Dong He ◽  
Yao Li
Keyword(s):  
Structural Change ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
Nitrogen Adsorption ◽  
Mesoporous Structure ◽  
Supercritical Drying ◽  
High Specific Surface Area ◽  
Molar Ratio

Low-density xSiO2-(1-x)Al2O3 xerogels with x=0.9, 0.8, 0.7, 0.6 (mole fractions) were prepared by sol-gel and non-supercritical drying. Silica alkogels, which were the framework of binary composite materials, formed from tetraethyl orthosilicate (TEOS) by hydrolytic condensation with a molar ratio of TEOS: H2O: alcohol: hydrochloric acid: ammonia =1: 4: 10: 7.5×10-4: 0.0375. Aluminum hydroxide derived from Al(NO3)3·9H2O and NH4OH acting in the alcohol solution under the condition of catalyst. After filtrating and washing, the precipitation was mixed into silica sols to form SiO2-Al2O3 mixed oxide gels with different silicon and aluminum molar ratio. The structural change and crystallization of the binary xerogels were investigated after heat treatment at 600 for 2 h by the means of X-ray diffraction. Nitrogen adsorption experiment was performed to estimate specific surface area, porous volume and pore size distribution. The structural change of xerogels was observed by FT-IR spectroscopy. The resulting mixed xerogels possess of mesoporous structure which is characteristic of cylindrical pores, high specific surface area of 596-863 m2/g and a relatively narrow pore distribution of 2.8-30 nm. Al2O3 is introduced into the SiO2 phase and some of Al-O-Si bonds form.

Various Morphology of Hierarchical Pore-Structured Compound: MCM-41/Diatomite and its Adsorption Behavior for Methylene Blue

2013 ◽  
Vol 690-693 ◽  
pp. 3533-3540
Author(s):  
Fang Fei Li ◽  
Mao Sheng Xia ◽  
Yin Shan Jiang
Keyword(s):  
Hierarchical Structure ◽  
Catalyst Support ◽  
Nitrogen Adsorption ◽  
High Specific Surface Area ◽  
Sem Analysis ◽  
Structure And Morphology ◽  
Hierarchical Porous ◽  
Hierarchical Pore ◽  
Adsorption Desorption ◽  
Mcm 41

Hierarchical porous materials attract considerable attentions due to their interesting structures and superior adsorption capabilities. In this work, a novel macro- and meso-porous hierarchical material, MCM-41/diatomite, has successfully been synthesized from natural diatomite and tetraethoxysilane by basic hydrothermal method. Nitrogen adsorption/desorption isotherms, low angle XRD and SEM analysis were carried out to character the multiple porous structure and morphology of MCM-41/diatomite. The resultant compound displayed high specific surface area (862~1041 m2/g) and macro-meso-porous hierarchical structure. The morphology of MCM-41/diatomite could be various, such as worm-like, grape-like, flocky, and acaleph-like, due to different ratio between TEOS, PEG, and NaOH. Moreover, the results of adsorption experiments show that some of the resultant MCM-41/diatomite display stronger adsorption capabilities than simply mesoporous MCM-41, due to the macro-meso-porous hierarchical structure, which would further extend the application of MCM-41/diatomite as adsorbent and catalyst support.

A New Method for Plasminogen Standardization

1968 ◽  
Vol 20 (03/04) ◽  
pp. 548-554
Author(s):  
J Gajewski ◽  
G Markus
Keyword(s):  
Proteolytic Activity ◽  
Specific Activity ◽  
Molar Ratio ◽  
Sharp Transition ◽  
Equivalence Point ◽  
Constant Amount ◽  
Residual Level ◽  
Activity Measurements ◽  
Complete Saturation ◽  
Human Plasminogen

SummaryA method for the standardization of human plasminogen is proposed, based on the stoichiometric interaction between plasminogen and streptokinase, resulting in inhibition of proteolytic activity. Activation of a constant amount of plasminogen with increasing amounts of streptokinase yields linearly decreasing activities, as a function of streptokinase, with a sharp transition to a constant residual level. The point of transition corresponds to complete saturation of plasmin with streptokinase in a 1:1 molar ratio, and is therefore a measure of the amount of plasminogen present initially, in terms of streptokinase equivalents. The equivalence point is independent of the kind of protein substrate used, buffer, pH, length of digestion and, within limits, temperature. The method, therefore, is not subject to the variations commonly encountered in the usual determination based on specific activity measurements.

scholarly journals Grafting of (3-Chloropropyl)-Trimethoxy Silane on Halloysite Nanotubes Surface

2021 ◽  
Vol 11 (12) ◽  
pp. 5534
Author(s):  
Asmaa M. Abu El-Soad ◽  
Giuseppe Lazzara ◽  
Alexander V. Pestov ◽  
Daria P. Tambasova ◽  
Denis O. Antonov ◽  
...  
Keyword(s):  
Active Site ◽  
Chemical Engineering ◽  
Coupling Reaction ◽  
Ammonium Hydroxide ◽  
Halloysite Nanotubes ◽  
Chemical Activity ◽  
Molar Ratio ◽  
New Materials ◽  
Experimental Conditions ◽  
Trimethoxy Silane

Modified halloysite nanotubes (HNTs-Cl) were synthesized by a coupling reaction with (3-chloropropyl) trimethoxysilane (CPTMS). The incorporation of chloro-silane onto HNTs surface creates HNTs-Cl, which has great chemical activity and is considered a good candidate as an active site that reacts with other active molecules in order to create new materials with great applications in chemical engineering and nanotechnology. The value of this work lies in the fact that improving the degree of grafting of chloro-silane onto the HNT’s surface has been accomplished by incorporation of HNTs with CPTMS under different experimental conditions. Many parameters, such as the dispersing media, the molar ratio of HNTs/CPTMS/H2O, refluxing time, and the type of catalyst were studied. The greatest degree of grafting was accomplished by using toluene as a medium for the grafting process, with a molar ratio of HNTs/CPTMS/H2O of 1:1:3, and a refluxing time of 4 h. The addition of 7.169 mmol of triethylamine (Et3N) and 25.97 mmol of ammonium hydroxide (NH4OH) led to an increase in the degree of grafting of CPTMS onto the HNT’s surface.

Al-MCM-41 modified with carbonaceous deposits: characterisation by nitrogen adsorption measurements

2000 ◽  
Vol 2 (23) ◽  
pp. 5510-5516 ◽  
Author(s):  
Michal Rozwadowski ◽  
Maria Lezanska ◽  
Jerzy Wloch ◽  
Krzysztof Erdmann ◽  
Roman Golembiewski ◽  
...  
Keyword(s):  
Nitrogen Adsorption ◽  
Carbonaceous Deposits ◽  
Mcm 41

The Influence of Fe/Al Molar Ratio on Microreactor-Based Catalyst Preparation and Carbon Nanotube Preparation

2021 ◽  
Vol 1036 ◽  
pp. 130-136
Author(s):  
Ting Qun Tan ◽  
Lei Geng ◽  
Yan Lin ◽  
Yan He
Keyword(s):  
Carbon Nanotubes ◽  
Catalytic Activity ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Small Diameter ◽  
High Specific Surface Area ◽  
Detection Methods ◽  
Molar Ratio ◽  
High Catalytic Activity

In order to prepare carbon nanotubes with high specific surface area, small diameter, low resistivity, high purity and high catalytic activity, the Fe-Mo/Al2O3 catalyst was prepared based on the microreactor. The influence of different Fe/Al molar ratios on the catalyst and the carbon nanotubes prepared was studied through BET, SEM, TEM and other detection methods. Studies have shown that the pore structure of the catalyst is dominated by slit pores at a lower Fe/Al molar ratio. The catalytic activity is the highest when the Fe/Al molar ratio is 1:1, reaching 74.1%. When the Fe/Al molar ratio is 1:2, the catalyst has a higher specific surface area, the maximum pore size is 8.63 nm, and the four-probe resistivity and ash content of the corresponding carbon nanotubes are the lowest. The higher the proportion of aluminum, the higher the specific surface area of the catalyst and the carbon nanotubes, and the finer the diameter of the carbon nanotubes, which gradually tends to relax. The results show that when the Fe/Al molar ratio is 1:2, although the catalytic activity of the catalyst is not the highest, the carbon nanotubes prepared have the best performance.

Magnetic halloysite nanotubes for yeast cell surface engineering

Clay Minerals ◽  
2016 ◽  
Vol 51 (3) ◽  
pp. 429-433 ◽  
Author(s):  
S.A. Konnova ◽  
Y.M. Lvov ◽  
R.F. Fakhrullin
Keyword(s):  
Surface Engineering ◽  
Halloysite Nanotubes ◽  
Yeast Cells ◽  
Biological Cells ◽  
Intrinsic Properties ◽  
Cell Surface Engineering ◽  
Yeast Cell Surface ◽  
Clay Nanotubes ◽  
Field Manipulation ◽  
Tube Shell

AbstractHalloysite clay nanotubes are safe and biocompatible nanomaterials and their application in biomaterials is very promising. The microencapsulation of yeast cells in the shell of clay nanotubes modifying their properties was demonstrated here. Each cell was coated with a 200–300 nm-thick tube shell and this coating was not harmful for these cells’ reproduction. Synthesis of magnetic nanoparticles on the surfaces of the nanotubes allowed for magnetic-field manipulation of the coated cells, including their separation. Providing nano-designed shells for biological cells is a step forward in development of ‘cyborg’ microorganisms combining their intrinsic properties with functions added through nano-engineering.

Sign in / Sign up

Export Citation Format

Share Document