Effect of sonication conditions: solvent, time, temperature and reactor type on the preparation of micron sized vermiculite particles

International audienceThe effects of temperature, time, solvent and sonication conditions under air and Argon are described for the preparation of micron and sub-micron sized vermiculite particles in a double-jacketed Rosett-type or cylindrical reactor. The resulting materials were characterized via X-ray powder diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared (FTIR) Spectroscopy, BET surface area analysis, chemical analysis (elemental analysis), thermogravimetry analysis (TGA) and Laser Granulometry. The sonicated vermiculites displayed modified particle morphologies and reduced sizes (observed by scanning electron microscopy and laser granulometry). Under the conditions used in this work, sub-micron sized particles were obtained after 5 h of sonication, whereas longer times promoted aggregation again. Laser granulometry data revealed also that the smallest particles were obtained at high temperature while it is generally accepted that the mechanical effects of ultrasound are optimum at low temperatures according to physical/chemical properties of the used solvent. X-ray diffraction results indicated a reduction of the crystallite size along the basal direction [001]; but structural changes were not observed. Sonication at different conditions also led to surface modifications of the vermiculite particles brought out by BET surface measurements and Infrared Spectroscopy. The results indicated clearly that the efficiency of ultrasound irradiation was significantly affected by different parameters such as temperature, solvent, type of gas and reactor type

Understanding the physical properties, toxicities and anti-microbial activities of choline-amino acid-based salts:Low-toxic variants of ionic liquids

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Microwaves, Power Ultrasound, and Ionic Liquids. A New Synergy in Green Organic Synthesis

Although the vast majority of organic chemists still cling to conductive heating as a means to promote reactions, major advances have recently been made in this connection. Both dielectric microwave heating (MW) and power ultrasound (US) are being increasingly exploited in organic synthesis, and their combined use is one of the most promising innovations. A long way from pioneering approaches, when domestic MW ovens and US cleaning baths were poorly standardized tools, these techniques now appear in reproducible, high-yield synthetic protocols. Their important contributions towards developing environment-friendly procedures overlap the application domain of room-temperature ionic liquids (RTILs). The synthesis itself of these highly versatile green solvents can be efficiently promoted under US and/or MW irradiation. This review focuses on the advantages arising from the use of these energy sources and their combination with unconventional reaction media such as RTILs. The synergies arising from the combined use of US, MW and RTIL will certainly go a long way to meet the increasing demand for environmentally benign chemical processes

Microwaves, Power Ultrasound, and Ionic Liquids. A New Synergy in Green Organic Synthesis

Although the vast majority of organic chemists still cling to conductive heating as a means to promote reactions, major advances have recently been made in this connection. Both dielectric microwave heating (MW) and power ultrasound (US) are being increasingly exploited in organic synthesis, and their combined use is one of the most promising innovations. A long way from pioneering approaches, when domestic MW ovens and US cleaning baths were poorly standardized tools, these techniques now appear in reproducible, high-yield synthetic protocols. Their important contributions towards developing environment-friendly procedures overlap the application domain of room-temperature ionic liquids (RTILs). The synthesis itself of these highly versatile green solvents can be efficiently promoted under US and/or MW irradiation. This review focuses on the advantages arising from the use of these energy sources and their combination with unconventional reaction media such as RTILs. The synergies arising from the combined use of US, MW and RTIL will certainly go a long way to meet the increasing demand for environmentally benign chemical processes

Synthesis of tetrahydro -β-carbolines via Pictet-Spengler reaction in acidic room-temperature ionic liquids

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