scholarly journals Effects of Different Variables on the Formation of Mesopores in Y Zeolite by the Action of CTA+ Surfactant

2018 ◽  
Vol 8 (8) ◽  
pp. 1299 ◽  
Author(s):  
Juliana Silva ◽  
Edilene Ferracine ◽  
Dilson Cardoso
Keyword(s):  
Active Sites ◽  
Cetyltrimethylammonium Bromide ◽  
Morphological Characteristics ◽  
Textural Properties ◽  
Alkaline Treatment ◽  
Y Zeolite ◽  
Usy Zeolite ◽  
Large Molecules ◽  
Structural Selectivity ◽  
Modified Zeolites

Zeolites are microporous crystalline aluminosilicates with a number of useful properties including acidity, hydrothermal stability, and structural selectivity. However, the exclusive presence of micropores restricts diffusive mass transport and reduces the access of large molecules to active sites. In order to resolve this problem, mesopores can be created in the zeolite, combining the advantages of microporous and mesoporous materials. In this work, mesospores were created in the Ultrastable USY zeolite (silicon/aluminum ratio of 15) using alkaline treatment (NaOH) in the presence of cetyltrimethylammonium bromide surfactant, followed by hydrothermal treatment. The effects of the different concentrations of NaOH and the surfactant on the textural, chemical, and morphological characteristics of the modified zeolites were evaluated. Generating mesoporosity in the USY zeolite was possible through the simultaneous presence of surfactant and alkaline solution. Among the parameters studied, the concentration of the alkaline medium had the greatest influence on the textural properties of the zeolites. The presence of Cetyltrimethylammonium Bromide (CTA+) prevented the amorphization of the structure during the modification and also avoided desilication of the zeolite.

Modification of Y Zeolite with Alkaline Treatment: Textural Properties and Catalytic Activity for Diethyl Carbonate Synthesis

2013 ◽  
Vol 52 (19) ◽  
pp. 6349-6356 ◽  
Author(s):  
Shouying Huang ◽  
Pengzhen Chen ◽  
Bing Yan ◽  
Shengping Wang ◽  
Yongli Shen ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Textural Properties ◽  
Alkaline Treatment ◽  
Diethyl Carbonate ◽  
Y Zeolite

scholarly journals INVESTIGATION ON PRE-TREATMENT PROCESS IN MICROCRYSTALLINE CELLULOSE (MCC) FROM OIL PALM EMPTY FRUIT BUNCH (EFB)

2018 ◽  
Vol 3 (1) ◽  
pp. 87-96
Author(s):  
Muhammad Arif Fahmi Supian ◽  
Khairatun Najwa Mohd Amin ◽  
Saidatul Shima Jamari ◽  
Shahril Mohamad
Keyword(s):  
Microcrystalline Cellulose ◽  
Morphological Characteristics ◽  
Alkaline Treatment ◽  
Empty Fruit Bunch ◽  
Characteristic Peak ◽  
Reinforcing Agent ◽  
Good Potential ◽  
The Mean ◽  
The Difference ◽  
Pre Treatment

In this study, microcrystalline cellulose (MCC) was extracted from empty fruit bunch (EFB) with alkaline treatment, bleaching and acid hydrolysis treatment and its properties were compared with commercial MCC. Two conditions were optimized in this study which are fiber consistency and sodium hydroxide (NaOH) concentration in alkaline pretreatment. The obtained optimum consistency and alkaline concentration are 5% and 20%respectively. The physicochemical and morphological characteristics, elemental composition and size distribution of the obtained alpha cellulose and MCC were analyzed in this work. Fourier transform infrared spectroscopy (FTIR) analysis provided clear evidence that the characteristic peak of lignin and hemicellulose were absent in the spectrum of the alpha cellulose and MCC. The difference in surface morphology and aggregation between alpha cellulose, MCC and commercialized MCC were observed by scanning electron microscopy (SEM). The mean length of approximately 251.3 μm, 41.4 μm and 138.6 μm were measured for alpha cellulose, MCC and commercialized MCC respectively. Thus, the isolated MCC from EFB has a good potential to be utilized as reinforcing agent in green composites and may be a precursor for future roselle derived nanocellulose, and thus a promising subject in nanocomposite research.

scholarly journals Comparative study on photocatalytic activity of transition metals (Ag and Ni)-doped ZnO nanomaterials synthesized via sol–gel method

2020 ◽  
Vol 7 (2) ◽  
pp. 191590 ◽  
Author(s):  
A. K. Azfar ◽  
M. F. Kasim ◽  
I. M. Lokman ◽  
H. A. Rafaie ◽  
M. S. Mastuli
Keyword(s):  
Photocatalytic Activity ◽  
Active Sites ◽  
Sol Gel ◽  
Textural Properties ◽  
High Photocatalytic Activity ◽  
Factors Affecting ◽  
Gel Method ◽  
Sol Gel Method ◽  
Zno Nanomaterials ◽  
Almost All

Ag and Ni/ZnO photocatalyst nanostructures were successfully synthesized by a sol–gel method. In this work, the photocatalyst sample was systematically studied based on several factors affecting the performance of photocatalyst, which are size, morphology, band gap, textural properties and the number of active sites presence on the surface of the nanocatalyst. X-ray diffraction revealed that Ag/ZnO nanomaterials experienced multiple phases, meanwhile for Ni/ZnO the phase of nanomaterials were pure and single phase for stoichiometry less than 5%. Field emission scanning electron microscope (FESEM) showed almost all of the synthesized nanomaterials possessed a mixture of nanorods and spherical-like shape morphology. The Ag/ZnO showed high photocatalytic activity, producing at least 14th trials of nanocatalyst reusability on degradation of methyl orange under UV irradiation. Interestingly, this phenomenon was not observed in larger surface area of Ni/ZnO nanomaterials which supposedly favour photocatalytic activity, but instead producing poor photocatalytic performance. The main reasons were studied and exposed by temperature-programmed desorption of carbon dioxide (TPD–CO 2 ) which showed that incorporation of Ag into ZnO lattice has enhanced the number of active sites on the surface of the nanocatalyst. Whereas incorporation of Ni in ZnO has lowered the number of active sites with respect to undoped ZnO. Active sites measurement is effective and significant, providing opportunities in developing an intensive study as an additional factor.

scholarly journals Probing the pore structure of hierarchical EU-1 zeolites by adsorption of large molecules and through catalytic reaction

2020 ◽  
pp. 174751982093659
Author(s):  
Zaibin Guo ◽  
Wenming Hao ◽  
Jinghong Ma ◽  
Ruifeng Li
Keyword(s):  
Adsorption Kinetics ◽  
Fumed Silica ◽  
Active Sites ◽  
Main Reaction ◽  
Catalytic Transformation ◽  
Pore System ◽  
Large Molecules ◽  
Silicon Source ◽  
Kinetics Of ◽  
And Diffusion

The adsorption of toluene and 1,3,5-trimethylbenzene and the catalytic transformation of 1,3,5-trimethylbenzene are applied as probing approaches to characterize the pore system of hierarchical EU-1 zeolites prepared using organofunctionalized fumed silica as the silicon source. The adsorption and diffusion of toluene and 1,3,5-trimethylbenzene are significantly improved in the hierarchical EU-1 zeolites compared with the conventional microporous EU-1 zeolite. The adsorption kinetics of toluene and 1,3,5-trimethylbenzene suggested that introducing mesopores significantly increases the rate of adsorption and improved the diffusion of large molecules. In the catalytic transformation of 1,3,5-trimethylbenzene, the conversion of 1,3,5-trimethylbenzene on the hierarchical EU-1 zeolites is doubled compared with the conventional microporous EU-1 zeolite, due to the improved diffusion of bulky molecules and enhanced accessibility of active sites in the hierarchical EU-1 structure. Although isomerization is the main reaction, differences are observed in the product ratios of isomerization to disproportionation between the hierarchical EU-1 zeolites and the microporous counterpart with different times on stream. The transformation of 1,3,5-trimethylbenzene over the hierarchical EU-1 zeolites has a higher isomerization to disproportionation ratio than that over the microporous EU-1 zeolite; this is due to the increased mesoporosity.

Carbon Dioxide Hydrogenation to Methanol over Cu/ZnO-SBA-15 Catalyst: Effect of Metal Loading

2017 ◽  
Vol 380 ◽  
pp. 151-160 ◽  
Author(s):  
Sara Faiz Hanna Tasfy ◽  
Noor Asmawati Mohd Zabidi ◽  
Maizatul Shima Shaharun ◽  
Duvvria Subbarao ◽  
Ahmed Elbagir
Keyword(s):  
Catalytic Activity ◽  
Carbon Source ◽  
Active Sites ◽  
Low Cost ◽  
Fixed Bed ◽  
Textural Properties ◽  
Catalytic Performance ◽  
Hydrogenation Reaction ◽  
Supported Metal Catalysts ◽  
Metal Loading

Utilization of CO2 as a carbon source to produce valuable chemicals is one of the important ways to reduce the global warming caused by increasing CO2 in the atmosphere. Supported metal catalysts are crucial to produce clean and renewable fuels and chemicals from the stable CO2 molecules. The catalytic conversion of CO2 into methanol is recently under increased scrutiny as an opportunity to be used as a low-cost carbon source. Therefore, a series of the bimetallic Cu/ZnO-based catalyst supported by SBA-15 were synthesized via an impregnation technique with different total metal loading and tested in the catalytic hydrogenation of CO2 to methanol. The morphological and textural properties of the synthesized catalysts were determined by transmission electron microscopy (TEM), temperature programmed desorption, reduction, oxidation and pulse chemisorption (TPDRO), and N2-adsorption. The CO2 hydrogenation reaction was performed in a microactivity fixed-bed system at 250oC, 2.25 MPa, and H2/CO2 ratio of 3. Experimental results showed that the catalytic structure and performance were strongly affected by the loading of the active site. Where, the catalytic activity, the methanol selectivity as well as the space-time yield increased with increasing the metal loading until it reaches the maximum values at a metal loading of 15 wt% while further addition of metal inhibits the catalytic performance. The higher catalytic activity of 14% and methanol selectivity of 92% was obtained over a Cu/ZnO-SBA-15 catalyst with a total bimetallic loading of 15 wt%. The excellent performance of 15 wt% Cu/ZnO-SBA-15 catalyst is attributed to the presence of well dispersed active sites with small particle size, higher Cu surface area, and lower catalytic reducibility.

scholarly journals The Binding Characteristics of Sediment-Derived Dissolved Organic Matter with Ceftazidime: A Microstructural and Spectroscopic Correlation Study

2021 ◽  
Author(s):  
Xuewei Cai ◽  
Kemin Qi ◽  
Xiaoli Zhang ◽  
Xiaoyun Xie ◽  
Zhaowei Wang
Keyword(s):  
Active Sites ◽  
Surface Composition ◽  
Yellow River ◽  
Binding Capacity ◽  
High Surface ◽  
Average Molecular Weight ◽  
Morphological Characteristics ◽  
Correlation Study ◽  
Chemical Compositions ◽  
Binding Characteristics

Abstract This research focused on the characterization of sediment-derived DOM (SDOM) extracted from sediment of Yellow River and the binding behaviors of ceftazidime (CAZ) with the presence of SDOM. The morphology, surface composition and structure of SDOM and the complexation between SDOM and CAZ in terms of component features, binding capacity and sequence were studied by multiple approaches. Results showed that SDOM was in situ autochthonous-dominated with a low weight-average molecular weight and aromaticity. The multiple morphological characteristics, high surface oxygen contents (53.49%) and more aliphatic of SDOM were further confirmed. Studies on SDOM-CAZ interaction suggested that the functional groups and chemical compositions of SDOM were susceptible to CAZ. In more detail, the aromatic protons and aliphatic protons of CAZ impacted significantly and the binding between CAZ and SDOM might relate to noncovalent. The protein-like fractions were considered to primary participant and the aromatics and amides as mainly active sites interaction with CAZ. These findings have significant implications on the environmental fate of cephalosporin antibiotics and that of sediment-derived DOM.

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