Cu- and Ni-Grafted Functionalized Mesoporous Silica as Active Catalyst for Olefin Oxidation

Abstract

Mesoporous silica has been functionalized with 3‐aminopropyl triethoxy silane (3‐APTES), followed by Schiff‐base condensation with 2‐hydroxy‐1‐naphthaldehyde. Incorporation of copper and nickel by covalent grafting onto the Schiff‐base loaded materials gives two heterogenized catalysts namely, Cu–Cat and Ni‐Cat, respectively. The materials have been characterized by PXRD analyses, nitrogen sorption studies, TEM, TGA, FT‐IR, UV‐visible and solid state MAS‐NMR spectroscopy. The metal‐contents in the samples are estimated using ICP‐AES studies. Cu–Cat and Ni‐Cat have been used as active catalyst in the oxidation of various olefins e. g. styrene, α‐methyl styrene, cyclohexene, trans stilbene and cyclooctene in the presence of tert‐butyl hydroperoxide as the oxidant in acetonitrile under mild conditions. Different products have been analyzed by gas chromatography and gas chromatography‐mass spectrometry. The results show high conversion of the substrates, moderate to good product selectivity and high TOFs of the reactions. The catalysts are recycled without deteriorating their activities and heterogeneous nature.

Recent Investigation on Epoxidation of Styrene with Hydrogen Peroxide by Heterogeneous Catalysis

“…Hence, it is necessary to pay attention to the heterogeneous process of styrene epoxidation. [10] Above all, heterogeneously catalyzed styrene oxidation with H 2 O 2 as oxidant is the optimum strategy. The properties of catalysts and related reaction parameters determine that it yields styrene oxide from superoxide radical or benzaldehyde (the main product) from hydroxyl radical.…”

The Ozone and Hydroperoxide Teamwork: Synthesis of Unsymmetrical Geminal Bisperoxides from Alkenes

“…However, the simultaneous use of such reagents could be disrupted by a number of side processes caused by interactions of the oxidants with each other and with the starting alkene. For example, the treatment of alkenes with hydroperoxides leads to oxygen transfer with the formation of epoxides and oxidative cleavage with the formation of carbonyl compounds (Scheme b) . In addition, ozone is generated from pure oxygen and enters the reaction mixture with an oxygen stream.…”

“…For example, the treatment of alkenes with hydroperoxides leads to oxygen transfer with the formation of epoxides and oxidative cleavage with the formation of carbonyl compounds (Scheme 1b). 38 ozone is generated from pure oxygen and enters the reaction mixture with an oxygen stream. This can also lead to undesirable olefin oxidation into carbonyl compounds or acids under oxygen in the presence of radical initiators (Scheme 1c).…”

Self-Assembly of a Pd4Cu8L8 Cage for Epoxidation of Styrene and Its Derivatives

“…In recent years, scientists confined the metal complexes into solid support to produce heterogeneous catalysts and used eco-friendly oxidants (such as tert -butyl hydroperoxide (TBHP), hydrogen peroxide, and O 2 ) for epoxidation of styrene. Although some catalysts showed a good performance upon the conversion of styrene, the selectivity for styrene oxide was very poor. − Thus, it is still necessary to develop new, green, and efficient heterogeneous catalysts.…”

“…The mechanism of copper complexes as catalysts for the reaction of epoxidation has been well studied in the literature. 22,25,43,44 As shown in Scheme S1, the possible reaction mechanism is as follows. (1) The anion of TBHP coordinates to the copper(II) center, which replaces the weakly coordinated water or DMSO.…”