ChemInform Abstract: Heterogeneous Solid Catalysts and Related Catalytic Mechanisms for Epoxidation of Olefins with H₂O₂

Abstract

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Studies on Obtaining Diglycidyl Ether from Allyl-Glycidyl Ether over the Mesoporous Ti-SBA-15 Catalyst

“…The formation of 3A12PD as the main product in this process can be explained taking into account the acidic character of the mesoporous Ti-SBA-15 material. This character is mainly connected with: (1) the silanol groups located on the surface of this catalyst [19,38], (2) the species of Ti present on the surface of the catalyst -tetrahedral Ti(IV) active sites, titanium-containing species in the form of dimmers or very small oligomers [38][39][40][41], and (3) the active species of titanium with hydrogen peroxide which are formed during the oxidation process, for example, five-membered active complexes -titanium hydroperoxo species with the specific structure, which are formed from tetrahedral Ti(IV) active sites, protic solvent (for example, methanol or water), and hydrogen peroxide and are present on the surface of the catalyst [42]. Among others, the formation of 3A12PD can also be under influence of the active species of titanium with hydrogen peroxide which are formed during the oxidation process and some of them can have the acidic character.…”

“…A few structures have been proposed until now for explanations of the structures of these active species. Among these structures are: the peroxide structure, the hydroperoxide structure, and superoxide structures (radical species) [40,[42][43][44][45][46][47][48][49]. Indeed, mainly the hydroperoxide structure was described as the structure responsible for the epoxidation of olefinic compounds [45,47].…”

“…In the medium in which epoxidation takes place, the excess of olefins causes that the peroxide structure is converted to hydroperoxide structure [45]. Hydroperoxide structures in the presence of protic solvent create the five-membered active complexestitanium hydroperoxo species which are composed from tetrahedral Ti(IV) active sites, protic solvent (in case of these studies, from water), and hydrogen peroxide [40,42,50,51]. Bhaumik et al [42] described that under the influence of the titanium hydroperoxo species undergoes acid-catalyzed cleavage of the oxirane rings in the epoxide compounds; this reaction has considerable SN1 character and the nucleophilic attack is easy to occur at the more crowded carbon atom that can best accommodate the positive charge.…”

Effect of Temperature and Reaction Time on the Synthesis of Butadiene Monoepoxide Using Iron Complex as an Efficient Catalyst

“…Epoxides are an important class of industrial chemicals that have been widely used as raw materials for production of epoxy resin, paints, surfactants, medicines and so on, or the efficient intermediates in organic syntheses [1][2][3][4]. Their selective synthesis is attractive to both academic research and industrial production [5][6][7].…”

Pd(II) anchored to modified Fe3O4 nanoparticles as a new magnetically recoverable catalyst for epoxidation of styrene

“…Various modified MNPs were introduced in the drug delivery with unique features [4][5][6]. Modified MNPs also widely have been studied in the catalyst designing [7][8][9].The epoxidation of olefins as an important chemical processes gives epoxides [10,11] which widely used as the starting materials or intermediates for the production of epoxy resins, paints, surfactants and medicines. Excellent selectivity can be obtained for the epoxidation of olefins using a heterogeneous silver catalyst [12], but typically chlorinated hydrocarbons and nitrogen oxides have to be added to quench unfavorable by-product formation, and this makes the process nongreen in this respect.…”