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Titanosilicate
A titanosilicate, also called titanium silicate or silicotitanate, is a silicate mineral where some portion of the silicon atoms have been replaced by titanium(IV) atoms. The term most commonly refers to the zeolitic polymorph, also called titanium silicalite, which is a heterogeneous catalyst in industrial chemistry. Applications Titanosilicate catalysts are commonly used in oxidation reactions that employ hydrogen peroxide as an oxidant. The production of propylene oxide by epoxidation of propylene is a major industrial application. Epoxidation by is considered a greener alternative to epoxidation via propylene chlorohydrin, but this reaction of and propylene competes with many side reactions. The formation of titanium coordination complexes in the zeolite structure improves selectivity for the epoxide. Synthesis Titanosilicates can be prepared via crystallisation of silica and titanium dioxide with quaternary ammonium cations as a structure-directing agent. The silic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silicalite
Silicalite is an inorganic compound with the formula SiO2. It is one of several forms ( polymorphs) of silicon dioxide. It is a white solid. It consists of tetrahedral silicon centers and two-coordinate oxides. It is prepared by hydrothermal reaction using tetrapropylammonium hydroxide followed by calcining to remove residual ammonium salts. The compound is notable in being ca. 33% porous. It is useful because the material contains (SiO)10 rings that allow sorption of hydrophobic molecules of diameter 0.6 nm. A commercially important modification of silicalite is titanium silicalite. With the formula Si1−xTixO2, it consists of silicalite with Ti doped into some Si sites. Unlike conventional polymorphs of titanium dioxide, the Ti centers in titanium silicalite have tetrahedral coordination geometry. The material is a useful catalyst for the reaction of hydrogen peroxide with propylene to give propylene oxide Propylene oxide is an epoxide with the molecular formula C3H6O ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silicate Mineral
Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, the crystalline forms of silica (silicon dioxide, ) are usually considered to be Silicate mineral#Tectosilicates, tectosilicates, and they are classified as such in the Dana system (75.1). However, the Nickel-Strunz system classifies them as oxide minerals (4.DA). Silica is found in nature as the mineral quartz, and its polymorphism (materials science), polymorphs. On Earth, a wide variety of silicate minerals occur in an even wider range of combinations as a result of the processes that have been forming and re-working the crust for billions of years. These processes include partial melting, crystallization, fractionation, metamorphism, weathering, and diagenesis. Living organisms also contribute to this carbonate–silicate cycle, geologic cycle. For example, a type of plankton ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crystallisation
Crystallization is a process that leads to solids with highly organized atoms or molecules, i.e. a crystal. The ordered nature of a crystalline solid can be contrasted with amorphous solids in which atoms or molecules lack regular organization. Crystallization can occur by various routes including precipitation from solution, freezing of a liquid, or deposition from a gas. Attributes of the resulting crystal can depend largely on factors such as temperature, air pressure, cooling rate, or solute concentration. Crystallization occurs in two major steps. The first is nucleation, the appearance of a crystalline phase from either a supercooled liquid or a supersaturated solvent. The second step is known as crystal growth, which is the increase in the size of particles and leads to a crystal state. An important feature of this step is that loose particles form layers at the crystal's surface and lodge themselves into open inconsistencies such as pores, cracks, etc. Crystallizati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Versalis
Versalis (''Polimeri Europa'' till 5 April 2012) is a wholly owned subsidiary of Italian oil supermajor Eni specializing in the production of chemicals. With more than 7,000 employees and a production of about 5.6 million tons of chemical products in 2023, it is by far the largest chemical company in Italy and one of the largest in Europe. History The history of Versalis dates back to the Enrico Mattei's management era of Eni. In 1953 Mattei obtained full control of Anic, a company specializing in synthetic fuels by coal hydrogenation, and initiated a massive investment program in order to turn it into the chemical and agrichemical arm of Eni. In 1957, following the discovery of substantial natural gas fields off the Adriatic coast, a major fertilizer and petrochemical plant was completed in Ravenna, than in 1960 started producing PVC. Two years later another large plant was set up in Gela, Sicily, close to some offshore oil fields. Other chemical plants were built in Pistic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MCM-41
MCM-41 (Mobil Composition of Matter No. 41) is a mesoporous material with a hierarchical structure from a family of silicate and alumosilicate solids that were first developed by researchers at ExxonMobil, Mobil Oil Corporation and that can be used as catalysts or catalyst supports.Reichinger, M. (2007) ''Poröse Silikate mit hierarchischer Porenstruktur: Synthese von mikro-/mesoporösem MCM-41 und MCM-48 Materialien aus zeolithischen Baueinheiten des MFI-Gerüststrukturtyps'' Dissertation Ruhr-Universität Bochum (in German) Structure MCM-41 consists of a regular arrangement of cyli ...[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
