Green and selective epoxidation of alkenes catalysed by new TiO₂–SiO₂SBA mesoporous solids

Abstract

New catalysts TiO 2 -SiO 2 (Ti-SBA) with pore sizes of 37 and 65 Å have been synthesized by grafting titanium on a structured mesoporous SBA15 (SBA for Santa BArbara and 15 for hexagonal structure) by means of titanium tetrachloride in the gas phase. These catalysts have been tested in the selective epoxidation of cyclooctene, cyclohexene, (R)-limonene and a-pinene. Whatever the oxidant, hydrogen peroxide (H 2 O 2 ), tert-butyl hydroperoxide (TBHP) or cumyl hydroperoxide (CHP), the selectivity is 100%. However, the yield is low with H 2 O 2 and the catalyst is partially leached out. In the case of TBHP and CHP the epoxide yields can reach practically 100% and no leaching of titanium is observed after four successive reaction cycles. An effect of pore size on the epoxidation kinetics of a-pinene and cyclooctene has been found.

Grafting of Molecularly Ordered Mesoporous Phenylene‐Silica with Molybdenum Carbonyl Complexes: Efficient Heterogeneous Catalysts for the Epoxidation of Olefins

“…[49][50][51][52][53] One exception concerns titanium-containing SBA-15 catalysts, which were 100% selective to epoxide formation for all three of the above oxidants (Table 2); however, a relatively high reaction temperature of 80 8C and a reaction time of 24 h were required to reach an epoxide yield of almost 100% (with TBHP as the oxidant). [54] The selective aerial oxidation of limonene at ambient temperature in the presence of manganese salen or porphyrin complexes grafted on organo-functionalized SBA-15 was recently reported by Srinivas and co-workers, [55] with the best results being 95-100% limonene oxide selectivity at 62-64% conversion (8 h, Table 2). …”

Remarkable effect of ordered mesoporous carbon support in tantalum oxide-catalyzed selective epoxidation of cyclooctene

“…The epoxidation of olefin is one of the most important reactions for both bulk and fine chemicals [1,2]. After pioneering works using Ti-zeolites such as TS-1 [3], mesoporous mixed oxide catalysts with larger pores (e.g., Ti substituted mesoporous silica) were developed to expand its applicability to this reaction [4][5][6][7][8][9][10]. Another approach has been done by immobilization of active molecular complexes (e.g., Ti, Mo, Mn, W) onto heterogeneous supports via organic anchors [11][12][13].…”

Zeolites as Catalysts for the Synthesis of Fine Chemicals

“…Thus, Chiker et al [140,141] prepared mesoporous silica SBA-15 samples functionalized with titanium as catalysts for the epoxidation of pinene with TBHP as oxidant on refluxing from acetonitrile. For instance, using a Ti-SBA15 with pore diameter of 61Å and a Si/Ti ratio of 17.8, the epoxide was produced with 100% selectivity at 91% conversion, with an efficiency of the oxidant of 93%.…”