Catalytic performances of mesoporous chromium silicates in liquid phase oxidation of toluene

K. Saidi-Bendahou, L. Chérif - Aouali

Abstract


Abstract:The liquid phase oxidation of toluene using peroxide hydrogen (H2O2) as oxidant was investigated over  mesoporous chromium silicates MCrS(n) (n=Si /Cr)  with different Si/Cr molar ratio (Si/Cr =20 and 60).  MCrS (n) were prepared in strong acidic media by assembly of preformed CrS1 precursors with triblock copolymer of the pluronic type (P123) by a two steps  procedures.

They were characterized by X-ray powder diffraction (XRD), N2 adsorption, Fourier-transform infrared spectroscopy (FT-IR), diffuse reflectance ultraviolet-visible spectroscopy (DRUV–vis) and electron paramagnetic resonance spectroscopy (EPR). The catalytic performances were compared with those of CrSBA-15 20

(Si/Cr =20). The MCrS catalysts exhibited higher catalytic activity than CrSBA-15 20, the toluene conversion increased with an increase in chromium content. The oxidation occurred mainly at the aromatic ring, as the cresols isomers were the dominant products. Increasing the chromium content caused a decrease in the selectivity to cresols.

The highest activity was observed over MCrS (20). Moreover, this catalyst was very stable after three cycles of reuse.

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References


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