2984-50-1Relevant articles and documents
Oxide-Supported Titanium Catalysts: Structure-Activity Relationship in Heterogeneous Catalysis, with the Choice of Support as a Key Step
Larabi, Cherif,Norsic, Sébastien,Khrouz, Lhoussain,Boyron, Olivier,Szeto, Kai Chung,Lucas, Christine,Taoufik, Mostafa,De Mallmann, Aimery
, p. 4608 - 4617 (2020)
The reactions of tetrakis(neopentyl)titanium, TiNp4 (1), with the surface of three solid oxides, silica, silica-alumina, and alumina, all partially dehydroxylated at 500 °C under vacuum were achieved. The resulting supported organometallic species react with dihydrogen to form the corresponding supported hydrides. The preparation of supported titanium hydrides on alumina is described here in detail, and the species obtained were extensively characterized by FTIR, solid-state NMR and EPR spectroscopy, and mass-balance analysis. The supported titanium hydride species were tested in three important reactions for petrochemistry: epoxidation of 1-octene, depolymerization of Fischer-Tropsch waxes, and polymerization of ethylene. The activities of titanium hydrides supported on alumina were compared to those of their silica- and silica-alumina-supported analogues.
Polyoxometalate-catalysed epoxidation of 1-octene with hydrogen peroxide in microemulsions coupled with ultrafiltration
Lambert, Arnold,Plucinski, Pawel,Kozhevnikov, Ivan V.
, p. 714 - 715 (2003)
Epoxidation of 1-octene with hydrogen peroxide catalysed by amphiphilic salts of peroxo tungstophosphate {PO4[WO(O2)2]4}3- in water-in-oil microemulsions is an efficient and environmentally benign reaction which, coupled with ultrafiltration, shows the potential for continuous production of epoxides.
Effect of Tetrahedral Ti in Titania-Silica Mixed Oxides on Epoxidation Activity and Lewis Acidity
Imamura, Selichiro,Nakai, Tohru,Kanai, Hiroyoshi,Ito, Tomoyasu
, p. 1261 - 1266 (1995)
The states of Ti in titania-silica mixed oxides have been studied by varying the Ti content.EXAFS analyses indicated that the amount of tetrahedral Ti species increased with a decrease in the Ti content reaching a maximum at 10 to 20 molpercent of Ti while octahedrally coordinated Ti predominated in the high Ti content region (Ti >/= 50 molpercent).Tetrahedral Ti species catalyse the epoxidation of oct-1-ene and cyclohexene using tert-butyl hydroperoxide as an oxidant.Lewis acid sites of the titania-silica also originated from the tetrahedral Ti species.Both epoxidation activity and Lewis acidity of the titania-silica were well explained by the coordinative unsaturation of the tetrahedral Ti site.
Are Highly Stable Covalent Organic Frameworks the Key to Universal Chiral Stationary Phases for Liquid and Gas Chromatographic Separations?
Cui, Yong,Jia, Wenyan,Li, Yanan,Yu, Ziyun,Yuan, Chen,Yuan, Li-Ming,Zi, Min
, p. 891 - 900 (2022/02/03)
High-performance liquid chromatography (HPLC) and gas chromatography (GC) over chiral stationary phases (CSPs) represent the most popular and highly applicable technology in the field of chiral separation, but there are currently no CSPs that can be used for both liquid and gas chromatography simultaneously. We demonstrate here that two olefin-linked covalent organic frameworks (COFs) featuring chiral crown ether groups can be general CSPs for extensive separation not only in GC but also in normal-phase and reversed-phase HPLC. Both COFs have the same 2D layered porous structure but channels of different sizes and display high stability under different chemical environments including water, organic solvents, acids, and bases. Chiral crown ethers are periodically aligned within the COF channels, allowing for enantioselective recognition of guest molecules through intermolecular interactions. The COF-packed HPLC and GC columns show excellent complementarity and each affords high resolution, selectivity, and durability for the separation of a wide range of racemic compounds, including amino acids, esters, lactones, amides, alcohols, aldehydes, ketones, and drugs. The resolution performances are comparable to and the versatility is superior to those of the most widely used commercial chiral columns, showing promises for practical applications. This work thus advances COFs with high stability as potential universal CSPs for chromatography that are otherwise hard or impossible to produce.
Green solvent free epoxidation of olefins by a heterogenised hydrazone-dioxidotungsten(vi) coordination compound
Bikas, Rahman,Heydari, Neda,Lis, Tadeusz,Shaterian, Maryam
, p. 4813 - 4827 (2022/02/19)
A new mononuclear tungsten coordination compound, [WO2L(CH3OH)] (1), was synthesized by the reaction of WCl6 and H2L (H2L = (E)-4-amino-N′-(5-bromo-2-hydroxybenzylidene)benzohydrazide) in methanol. Bo