Sol–Gel Process

Landau, Miron V.

doi:10.1002/9783527610044.hetcat0009

Cited by 19 publications

(7 citation statements)

References 274 publications

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“…A second way out is to incorporate titanium atoms in silica-based materials with controlled texture, either by producing small nonporous particles (e.g., via flame spray pyrolysis − ) or by designing materials with larger pores , (e.g., Ti−β zeolites, Ti–MCM-41, TiO 2 –SiO 2 aerogels, Ti–SiO 2 macrocellular foams, and , TiO 2 –SiO 2 xerogels − ). Sol–gel chemistry , represents an important toolbox for the bottom-up preparation of such mesoporous catalysts. , The most significant progress in this direction was obtained thanks to the development of templating strategies (e.g., evaporation-induced self-assembly, EISA , ), or specific drying strategies . However, in these cases, controlling the transition-metal dispersion remains a challenge owing to the different hydrolysis and condensation rates for Ti and Si precursors.…”

Section: Introductionmentioning

confidence: 99%

Aerosol Route to TiO₂–SiO₂Catalysts with Tailored Pore Architecture and High Epoxidation Activity

et al. 2019

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Herein, we present the aerosol-assisted sol − gel preparation of hierarchically porous TiO 2 − SiO 2 catalysts having a spherelike shell morphology and a high Ti dispersion. In order to control the porosity at the micro-, meso-, and macrolevels, we use the evaporation-induced self-assembly (EISA) of a surfactant, possibly combined with polymer beads as hard templates. These catalysts are tested for the epoxidation of cyclohexene with cumene hydroperoxide as the oxidant, and their performance is compared to the reference TS-1 zeolite. The high catalytic performance observed with the catalysts prepared by aerosol stems from their high speci fi c surface area, but also from the short di ff usion path length generated by the meso-/macropore architecture which provides entryways for bulky reactants and products. Besides, these materials can incorporate a higher Ti loading than TS-1 zeolite, while ensuring a good control over the Ti speciation. Thus, the unique features of the aerosol process which is also known to be scalable allow us to prepare catalytic materials with high epoxidation activity, also for bulky olefins.

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Section: Introductionmentioning

confidence: 99%

Aerosol Route to TiO₂–SiO₂Catalysts with Tailored Pore Architecture and High Epoxidation Activity

et al. 2019

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“…Sol-gel processing comprises a series of operations that include chemical reactions and physical processes (dissolution, neutralization, condensation, polymerization, phase transition, phase separation, evaporation, etc.) promoting the formation of porous solids from liquid solutions of molecular precursors (Landau, 2006). Several scienti c investigations have been carried out over the years based on the application of the sol-gel method on RH, RHA, and various waste materials with great success (Ebisike et The recurrent method in these studies consists of dispersing the thermochemical solid waste (ash) in an alkaline solution of sodium hydroxide, where the dissolution of amorphous silica occurs through the conversion into soluble sodium silicate (Eq.…”

Section: Introductionmentioning

confidence: 99%

Silica extraction from rice hull ash through the sol–gel process under ultrasound

Fusinato

Amaral

Irigon

et al. 2022

Environ Sci Pollut Res

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Rice is among the main foods produced in the world and is part of the daily diet of most families. The main waste from rice processing is rice husk (RH), which has been used as biomass for energy generation through combustion. In this process, rice husk ash (RHA) is generated as a residue, and its silica (SiO 2 ) content varies from 85-98%. The present work describes the study of the extraction of silica from RHA by the ultrasoundassisted sol-gel method. An experimental design based on the Response Surface Methodology (RSM) with the symmetrical, second-order Rotational Central Composite Design (RCCD) was applied to determine the best extraction conditions considering extraction time and molar ratio (n) as variables = n NaOH / n Silica ). These optimal conditions were then applied to three ash samples, two obtained by the combustion process in a boiler furnace, with a mobile grate system (RHAC 1 and RHAC 2 ), and one obtained by the pyrolysis process (RHAP) carried out in a xed bed reactor. Results showed that a molar ratio of 4.4, and an extraction time of 107 minutes were the best extraction conditions, leading to a yield of 73.3% for RHAP, 43.9% for RHAC 1 , and 31.1% for RHAC 2 . It was found that the extraction yield and textural properties of the silica obtained depend on the characteristics of the ash used. The silica extracted from RHAC 1 presented a surface area of 465 m 2 .g − 1 , mesopores of 4.69 nm, purity greater than 95%, and an ultra-ne granulometric distribution, reaching nanoparticle dimensions, characteristics comparable to commercially available silicas.

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“…This method provides the possibility to control parameters like texture, morphology, and chemical composition through a cost‐effective procedure, which makes it one of the most employed methods to synthesize metal–oxide nanostructures. [ 32,33 ]…”

Section: Introductionmentioning

confidence: 99%

“…This method provides the possibility to control parameters like texture, morphology, and chemical composition through a cost-effective procedure, which makes it one of the most employed methods to synthesize metal-oxide nanostructures. [32,33] Among different parameters, the most important material properties that a gas sensing material should possess are porous morphology with high surface area and abundant surface oxygen vacancies. ZnO is one of the most reported materials which can be easily obtained by chemical synthesis methods with tunable morphology and present abundant surface oxygen vacancies which results in facile adsorption and desorption of atmospheric oxygen.…”

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confidence: 99%

Carbon Dioxide Detectors based on Al‐ and Ni‐Doped ZnO

Lozano-Rosas

Hernandez

Elizalde-González

et al. 2022

Physica Status Solidi (a)

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Humanity all around the world currently faces two serious challenges: global warming and the COVID-19 pandemic. It is well known that the earth's atmosphere is composed of greenhouse gases that act as a shielding blanket, keeping the global temperature in an optimal range. [1] The three main greenhouse gasses which have presented a significant increment in the course of the industrial period are carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O). [2] CO 2 plays a primary role in global warming because of its production due to a wide range of sources like manufacturing processes, automobiles, human respiration, decomposition, ocean release, etc. [3] In contrast, from December 2019 to date, the COVID-19 pandemic is causing a global impact on every sector of society. [4] One of the strategies of mitigation for the pandemic has been CO 2 concentration monitoring in enclosed spaces to measure indoor ventilation requirements and thus reduce the risk of contagion by the aerosol transmission of the virus. Also, it is clear that CO 2 monitoring has become mandatory to maintain air quality.The values of CO 2 concentration in outdoor ambient air are %400 ppm. [5] Regarding CO 2 concentrations in internal environments, the reality is different depending on the country, specific location, and ventilation system; however, according to the document "Recommendations for operation and maintenance of air conditioning and ventilation systems of buildings and premises for the prevention of the spread of SARS-Cov-2" from Spanish Ministry of Health, for good quality air, it is considered that the concentration of CO 2 in the indoor environment with respect to its concentration in the outdoor environment, should not be higher than 500 ppm. [6] ðCO 2 indoor À CO 2 outdoorÞ < 500 ppm CO 2(1)The first decade of the 21 st century was witness to massive production of sensors, [7] driven principally by the growing concern of global warming. However, new sensing technologies were emerged in the past decade, such as calorimetric sensors (CB), metal-oxide-semiconductor field-effect transistor (MOSFET), conducting polymer sensors, electrochemical sensors (EC), metal-oxide semiconductor (MOS), optical sensors, quartz crystal microbalance (QMB), and surface acoustic wave (SAW). [8] Among these, MOS sensors are mostly investigated, due to their excellent sensitivity, very short response times, low cost, minimal noise, small size, low power consumption for adequate battery life, detection of both oxidizing and reducing gases, easy fabrication, and are excellent candidates for miniaturization with high portability. [9][10][11] There is a wide variety of metal oxides employed for CO 2 detection, including pristine materials:

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Sol–Gel Process

Abstract: The sections in this article are Introduction Physico‐Chemical Basis and Principles of Sol–Gel Processing for the Preparation of Porous Solids Activation of Sol–Gel Precursors Polycondensation Gelation/Aging/Washing Gel Drying/Desolvation Stabilization of Xerogels and Ae… Show more

Cited by 19 publications

References 274 publications

Aerosol Route to TiO₂–SiO₂Catalysts with Tailored Pore Architecture and High Epoxidation Activity

Aerosol Route to TiO₂–SiO₂Catalysts with Tailored Pore Architecture and High Epoxidation Activity

Silica extraction from rice hull ash through the sol–gel process under ultrasound

Carbon Dioxide Detectors based on Al‐ and Ni‐Doped ZnO

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Sol–Gel Process

Cited by 19 publications

References 274 publications

Aerosol Route to TiO2–SiO2Catalysts with Tailored Pore Architecture and High Epoxidation Activity

Aerosol Route to TiO2–SiO2Catalysts with Tailored Pore Architecture and High Epoxidation Activity

Silica extraction from rice hull ash through the sol–gel process under ultrasound

Carbon Dioxide Detectors based on Al‐ and Ni‐Doped ZnO

Contact Info

Product

Resources

About

Aerosol Route to TiO₂–SiO₂Catalysts with Tailored Pore Architecture and High Epoxidation Activity

Aerosol Route to TiO₂–SiO₂Catalysts with Tailored Pore Architecture and High Epoxidation Activity