Synthesis and modification of phyllosilicate by Schiff base Molybdenum complexes: characterization and catalytic application in epoxidation of alkenes

An aminopropyl-functionalized magnesium phyllosilicate (AMP clay) contains a trioctahedral smectite with an organic propyl amine group. Therefore, the interest in the use of organically modified clays has increased with time. In fact, they possess the swelling ability, high cation exchange capacity, high layer aspect ratio, high specific surface area, film formation and adsorptive properties [1]. In particular, smectites appear to be good candidates in industry, agriculture, environmental remediation, catalysis, coatings, ceramics, and polymer materials due to their submicron size [2]. Epoxidation reactions represent a high added value for transformation of olefins. As a result, the technology of olefin epoxide production is an area with great development potential [3]. Molybdenum (II) complexes have been used to synthesize effective catalysts for the epoxidation of olefins using tert-butyl hydroperoxide (TBHP) as oxidant, a process which starts with the oxidation of the precursor complex to an active species of molybdenum (VI) [4]. An aminopropyl-functionalized magnesium phyllosilicate clay was synthesized. The surface of AMP was further reacted with aldehydes (salicylaldehyde) in order to form Schiff base chelating ligands with N-donor groups incorporated in the layer surface. After that the product was reacted with MO2(acac)2 and was used them as heterogeneous catalysts in epoxidation of some alkenes. It was found that the optimized conditions with over 95% yield for epoxidation of allkenes was 20 mg of catalyst, 2 ml C2H4Cl2 as solvent and 0.4 ml THBH as oxidant at 80 °C after 90 min. The final products were thoroughly characterized by fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM) along with energy dispersive X-ray (EDX) Spectroscopy, thermogravimetric and differential thermal analysis (TG/DTA) and X-ray photoelectron spectroscopy (XPS).