One-pot preparation of nanocrystalline Ag–WO3 catalyst for the selective oxidation of styrene

Abstract

Cationic surfactant cetyltrimethylammonium bromide-mediated water-based preparation of nanocrystalline Ag–WO₃ catalyst has been reported in a one-pot preparation method. This catalyst has been characterized by XRD, XPS, SEM, TEM, STEM-mapping, FTIR, Raman, TGA, and ICP-AES. SEM images displayed the formation of an aloevera-like structure. TEM-images revealed the formation of ultrasmall Ag (with average size 5 nm), anchored on monoclinic WO₃ rods (with diameters in the range between 80 and 120 nm). It was found that the catalyst can effectively oxidize styrene with H₂O₂ as the oxidant. The effects of different reaction parameters have been studied in detail. A styrene conversion of 75% with a styrene-oxide selectivity of 55% and a styrene conversion of >99% with a benzaldehyde selectivity of 88% were accomplished over this catalyst, varying different reaction conditions. The catalyst did not show any leaching for up to five reuses, showing the true heterogeneity of the catalyst. However, significant H₂O₂ decomposition occurs on the catalyst necessitating its usage in four-fold excess.