scholarly journals Physicochemical Properties of Mesoporous Organo-Silica Xerogels Fabricated through Organo Catalyst

Membranes ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 607
Author(s):  
Muthia Elma ◽  
Anna Sumardi ◽  
Adhe Paramita ◽  
Aulia Rahma ◽  
Aptar Eka Lestari ◽  
...  
Keyword(s):  
Citric Acid ◽  
Physicochemical Properties ◽  
High Surface ◽  
Water Desalination ◽  
Molar Ratio ◽  
Silica Xerogel ◽  
Catalyst Loading ◽  
Silica Xerogels ◽  
Citric Acid Concentration ◽  
One Step

The physicochemical properties of organo-silica xerogels derived from organo catalyst were pervasively investigated, including the effect of one-step catalyst (citric acid) and two-step catalyst (acid-base), and also to observe the effect of sol pH of organo-silica xerogel toward the structure and deconvolution characteristic. The organo-silica xerogels were characterized by FTIR, TGA and nitrogen sorption to obtain the physicochemical properties. The silica sol–gel method was applied to processed materials by employing TEOS (tetraethyl orthosilicate) as the main precursor. The final molar ratio of organo-silica was 1:38:x:y:5 (TEOS:ethanol: citric acid: NH3:H2O) where x is citric acid concentration (0.1–10 × 10−2 M) and y is ammonia concentration (0 to 3 × 10−3 M). FTIR spectra shows that the one-step catalyst xerogel using citric acid was handing over the higher Si-O-Si concentration as well as Si-C bonding than the dual catalyst xerogels with the presence of a base catalyst. The results exhibited that the highest relative area ratio of silanol/siloxane were 0.2972 and 0.1262 for organo catalyst loading at pH 6 and 6.5 of organo-silica sols, respectively. On the other hand, the organo-silica matrices in this work showed high surface area 546 m2 g−1 pH 6.5 (0.07 × 10−2 N citric acid) with pore size ~2.9 nm. It is concluded that the xerogels have mesoporous structures, which are effective for further application to separate NaCl in water desalination.

scholarly journals Synthesis and Characterization of Trimethylchlorosilane-Modified Silica Xerogel

2020 ◽  
Vol 23 (7) ◽  
pp. 249-254
Author(s):  
Sellen Tanheitafino ◽  
Anis Shofiyani ◽  
Risya Sasri ◽  
Rudiyansyah Rudiyansyah
Keyword(s):  
Contact Angle ◽  
Citric Acid ◽  
Sodium Silicate ◽  
Sol Gel ◽  
Volume Ratio ◽  
Silica Xerogel ◽  
Silica Xerogels ◽  
Modified Silica ◽  
Average Pore ◽  
Pore Size Distributions

Modification of silica xerogel with TMCS (trimethylchlorosilane) reagent has been carried out to improve the hydrophobicity of silica xerogel. Silica xerogel was synthesized based on the sol-gel method using sodium silicate as a precursor, and citric acid as a catalyst, with a mole ratio of sodium silicate and citric acid, was 0.172: 0.004. The sol-gel process was carried out through several stages, i.e., hydrolysis and condensation of sodium silicate to form sol, gelation (sol transition to gel), aging, and drying. Surface modification was performed by studying the effect of TMCS: methanol: petroleum benzine volume ratio of 0.5:1:1, 1:1:1, 1.5:1:1, 2:1:1, and 2.5:1:1 on the characteristics of silica xerogel synthesized. FTIR, SEM, and GSA characterized the synthesized results. The results of FTIR characterization on silica xerogel with volume ratios of 2:1:1 and 2.5:1:1 indicate the presence of the Si‑C group absorption at a wavenumber of 848.68 cm-1 which shows that the formation of silyl groups on the modified silica xerogel surfaces occurs at a TMCS: methanol: petroleum benzine ratio of 2:1:1 and 2.5:1:1. SEM results indicate that the silica xerogels produced are porous. Meanwhile, the GSA analysis results show that the pore size distributions are in the mesoporous region with an average pore radius of 8-13 nm. The greater the volume of TMCS used, the higher the surface area, and the resulting xerogel’s hydrophobicity. Based on the contact angle and seeped time test, the highest hydrophobicity is produced by the material synthesized at a TMCS: methanol: PB volume ratio of 2.5:1:1 with a contact angle of 116.346°.

scholarly journals The Effect of Citric Acid Concentration on the Properties of LaMnO3 as a Catalyst for Hydrocarbon Oxidation

Catalysts ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 226 ◽  
Author(s):  
Zakaria Sihaib ◽  
Fabrizio Puleo ◽  
Giuseppe Pantaleo ◽  
Valeria La Parola ◽  
José Luis Valverde ◽  
...  
Keyword(s):  
Citric Acid ◽  
Physicochemical Properties ◽  
Photoelectron Spectroscopy ◽  
Catalytic Performance ◽  
Morphological Properties ◽  
Molar Ratio ◽  
Hydrocarbon Oxidation ◽  
Total Oxidation ◽  
Propene Oxidation ◽  
X Ray

LaMnO3 (LM) catalysts with a molar ratio of citric acid (CA) to metal (La3+ + Mn2+) nitrates ranging from 0.5 to 2 (LM0.5 to LM2) were synthesized by the citrate sol–gel method with the aim of studying the effect of the citric acid ratio on the physicochemical properties and the catalytic performance in hydrocarbon oxidation. Structural and morphological properties of these catalysts were characterized by X-ray diffraction (XRD) and specific surface area (N2 adsorption) measurements, while the chemical composition was determined by inductively coupled plasma atomic emission spectroscopy (ICP-OES). In the selected samples, additional characterizations were carried out by thermogravimetric and differential thermal analysis (TGA/DTA), Fourier Transform Infrared Spectroscopy (FT-IR), temperature-programmed reduction by hydrogen (H2-TPR), and X-ray photoelectron spectroscopy (XPS). The results showed that the amount of citric acid used significantly influenced the TGA/DTA profile of gels along with the physicochemical properties of the catalysts. The XRD patterns are consistent with the perovskite formation as the main phase. The segregation of a small amount of Mn3O4, detected for molar ratios ranging between 0.5 and 1.5, suggested the formation of a slightly nonstoichiometric LaMn1−xO3 phase with a relatively high content of Mn4+. The catalytic performance was evaluated in the total oxidation of two selected hydrocarbons, toluene and propene, which represent typical volatile organic compounds (VOCs). Typically, three consecutive catalytic cycles were performed in order to reach steady-state performance in toluene and propene oxidation. Moreover, the stability of the catalysts under reaction conditions was investigated through 24-h experiments at 17% of toluene conversion. The catalysts LM1.2, LM1.3, and LM1.5 showed the best catalytic performance in both hydrocarbon oxidations, well comparing with the Pd/Al2O3 used as a reference.

One-Step Hydrothermal Synthesis of MoS2 Nano-Flowers with High Surface Area and Crystalline

2012 ◽  
Vol 531-532 ◽  
pp. 508-511 ◽  
Author(s):  
Yan Juan Li ◽  
Nan Li ◽  
Xiao Yan ◽  
Yue Chi ◽  
Qing Yuan ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Hydrothermal Synthesis ◽  
Surface Area ◽  
Ph Value ◽  
High Surface ◽  
High Surface Area ◽  
Ammonium Molybdate ◽  
Molar Ratio ◽  
Sulfur Source ◽  
One Step

One-step and controlled pH hydrothermal synthesis of transition metal disulfide using double molybdenum sources to synthesize MoS2 nano-flowers at low temperature was first reported. Anhydrous molybdenum pentachloride (MoCl5) and four sulfur ammonium molybdate ((NH4) 6Mo7O24•4H2O) were the molybdenum source and CS (NH2) 2 was the sulfur source. Through hydrothermal method, MoS2 was obtained at 180 °C. The pH value of system was controlled by adjusting the molar ratio of MoCl5 and (NH4) 6Mo7O24•4H2O. The products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), surface area (BET) and transmission electron microscopy (TEM). The results show that the products were hexagonal MoS2 with a high crystalline and flower-like structure consisted of small particles. The thickness of petals is a few to tens of nanometers. By changing the molar ratio of molybdenum sources, the resultant phase from the mixed phase transited to the pure phase and the purity of synthetic MoS2 crystal increaseed.

scholarly journals Preparation, characterization and evaluation of x-MoO3/Al-SBA-15 catalysts for biodiesel production

2021 ◽  
Author(s):  
Joyce S. B. Figueiredo ◽  
Bruno T. S. Alves ◽  
Vitória A. Freire ◽  
José J. N. Alves ◽  
Bianca V. S. Barbosa
Keyword(s):  
Thermal Stability ◽  
Soybean Oil ◽  
Molecular Sieves ◽  
High Surface ◽  
International Standards ◽  
Mesoporous Molecular Sieves ◽  
Biodiesel Production ◽  
Molar Ratio ◽  
Catalyst Loading ◽  
Textural Characteristic

Abstract Biodiesel is an alternative source of renewable energy that can be produced by a transesterification of vegetable oils. Mesoporous molecular sieves, such as SBA-15, due to high surface area and thermal stability are promising precursors for heterogeneous catalysts in the transesterification reaction. In this work, Al-SBA-15 precursor was obtained by direct hydrothermal synthesis, impregnated with different MoO3 contents (5, 10 and 15 wt%) by the pore saturation method, and evaluated as heterogeneous catalyst in the production of biodiesel from a transesterification of soybean oil with methanol. Al-SBA-15 precursor as well as MoO3/Al-SBA-15 catalyst were characterized for its structural characteristic by X-ray diffraction, textural characteristic by N2 adsorption analysis, and thermal stability by thermogravimetric analysis. An experimental planning 22 + 3 CtPt was used to evaluate the influence of MoO3 content and reaction time on biodiesel yield from soybean oil and methanol. The biodiesel content in the final product was obtained by gas chromatography. An average biodiesel yield of 96% was obtained with the catalyst 10%MoO3/Al-SBA-15 under the following reaction conditions: 20:1 methanol/soybean oil molar ratio, and 3 wt% of catalyst loading at 150 °C in 3 h. After five consecutive reaction cycles, the biodiesel yield decreased by about 34%. The density and acidity of the biodiesel produced are within the specified values for commercialization according to international standards. Graphical abstract

Zinc-Modified MCM-22 as Potential Solid acid Catalyst for Friedel–Crafts Alkylation Reaction

2013 ◽  
Vol 11 (1) ◽  
pp. 407-415 ◽  
Author(s):  
Sharad V. Lande ◽  
A. Sakthivel, ◽  
K. V. V. S. B. S. R. Murthy ◽  
Unnikrishnan Sreedharan ◽  
Jagannath Das ◽  
...  
Keyword(s):  
Solid Acid Catalyst ◽  
High Surface ◽  
High Surface Area ◽  
Acid Catalyst ◽  
Systematic Investigation ◽  
Molar Ratio ◽  
Catalyst Loading ◽  
Alkylation Reaction ◽  
Phase Medium ◽  
Alkylation Of Benzene

Abstract In this paper, we report loading of ZnCl2 on microporous medium pore high surface area zeolite, which was achieved by incipient wetness method. The zinc-modified mobil composite material -22 (Zn-MCM-22) was systematically characterized by powder X-ray diffraction, N2 adsorption-desorption analysis, scanning electron microscopy and Fourier transform infrared spectroscopy. The acidity of the materials was studied by temperature programmed desorption of ammonia analysis. The well-characterized Zn-MCM-22 catalyst was investigated for the Friedel–Crafts alkylation of benzene by benzyl chloride in liquid phase medium. A systematic investigation of various operating parameters like effect of different temperature, catalyst loading and reactant molar ratio was carried out. The Zn-MCM-22 found to be promising, further the catalytic activity remains stable over several recycles.

scholarly journals Microwave-Assisted Synthesis of 3,4-Dihydropyrimidin-2(1H)-Ones Using Acid-Functionalized Mesoporous Polymer

2021 ◽  
Author(s):  
Bishwajit Changmai ◽  
Kalyani Rajkumari ◽  
diparjun das ◽  
Samuel Lalthazuala Rokhum
Keyword(s):  
Microwave Irradiation ◽  
Condensation Reaction ◽  
High Surface ◽  
High Surface Area ◽  
Analytical Techniques ◽  
Conventional Heating ◽  
Molar Ratio ◽  
Catalyst Loading ◽  
Microwave Assisted Synthesis ◽  
Mesoporous Polymer

Synthesis and application of acid-functionalized mesoporous polymer catalyst for the synthesis of 3,4-Dihydropyrimidin-2(1H)-ones via Biginelli condensation reaction under microwave irradiation is investigated. Several analytical techniques such as FT-IR, BET, TEM, SEM and EDX were employed to characterize the synthesized polymeric catalyst. High acidity (1.15 mmol g-1 ), high surface area (90.44 m2 g -1 ) and mesoporous nature of the catalyst effectively promoted the synthesis of 3,4-Dihydropyrimidin-2(1H)-ones. Microwave irradiation shows higher yield (89-98 %) as compared to conventional heating (15-25 % yield) under our optimized reaction conditions such as 1:1:1.2 molar ratio of aldehyde/ethylacetoacetate/urea, catalyst loading of 6 wt.% (with respect to aldehyde), the temperature of 80 °C and microwave power of 50 W. The synthesized Biginelli products were fully characterized by 1H and 13C NMR. The reusability of the catalyst was investigated up to 5 successive cycles and it showed great stability towards the synthesis of 3,4-Dihydropyrimidin-2(1H)-ones without any significant depreciation in yields.

One-Step Processing to Fabricate Highly Transparent Superhydrophobic Surface via Granuliform Silica Aerogels

2014 ◽  
Vol 936 ◽  
pp. 1042-1046 ◽  
Author(s):  
Bi Xu ◽  
Jing Jing Ge ◽  
Zai Sheng Cai
Keyword(s):  
Superhydrophobic Surface ◽  
High Surface ◽  
High Surface Area ◽  
Silica Aerogels ◽  
Silica Xerogel ◽  
Methyl Groups ◽  
High Porosity ◽  
Porous Network ◽  
Glass Slides ◽  
One Step

A simple, versatile method has been developed to fabricate the transparent superhydrophobic surface via granuliform silica aerogels. The effect of ageing on the wettability, microstructure morphology and chemical structure of the dried gels has been investigated. Silica aerogel (dried alcogel with ageing) has a 3D porous network exhibiting the high surface area and pore volume. In comparison, large aggregates of silica nanoparticles exist within the backbone of the silica xerogel (dried alcogel without ageing). Both the aerogel and xerogel exhibit analogous chemical composition with abundant of methyl groups on the surface. The rough surface due to the high porosity and low surface energy provided by the methyl groups of aerogel contribute to the superhydrophobicity. Meanwhile, glass slides coated with aerogel film is highly transparent because the roughness created by the aerogel film is limited.

scholarly journals Microwave-Assisted Synthesis of 3,4-Dihydropyrimidin-2(1H)-Ones Using Acid-Functionalized Mesoporous Polymer

2021 ◽  
Author(s):  
Bishwajit Changmai ◽  
Kalyani Rajkumari ◽  
diparjun das ◽  
Samuel Lalthazuala Rokhum
Keyword(s):  
Microwave Irradiation ◽  
Condensation Reaction ◽  
High Surface ◽  
High Surface Area ◽  
Analytical Techniques ◽  
Conventional Heating ◽  
Molar Ratio ◽  
Catalyst Loading ◽  
Microwave Assisted Synthesis ◽  
Mesoporous Polymer

Synthesis and application of acid-functionalized mesoporous polymer catalyst for the synthesis of 3,4-Dihydropyrimidin-2(1H)-ones via Biginelli condensation reaction under microwave irradiation is investigated. Several analytical techniques such as FT-IR, BET, TEM, SEM and EDX were employed to characterize the synthesized polymeric catalyst. High acidity (1.15 mmol g-1 ), high surface area (90.44 m2 g -1 ) and mesoporous nature of the catalyst effectively promoted the synthesis of 3,4-Dihydropyrimidin-2(1H)-ones. Microwave irradiation shows higher yield (89-98 %) as compared to conventional heating (15-25 % yield) under our optimized reaction conditions such as 1:1:1.2 molar ratio of aldehyde/ethylacetoacetate/urea, catalyst loading of 6 wt.% (with respect to aldehyde), the temperature of 80 °C and microwave power of 50 W. The synthesized Biginelli products were fully characterized by 1H and 13C NMR. The reusability of the catalyst was investigated up to 5 successive cycles and it showed great stability towards the synthesis of 3,4-Dihydropyrimidin-2(1H)-ones without any significant depreciation in yields.

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