Mesoporous FeAlMCM-41: an improved catalyst for the vapor phase tert-butylation of phenol Original Research Article

A range of iron and aluminum-containing mesoporous molecular sieves FeAlMCM-41 with different nSi/(nFe+nAl) ratios have been synthesized hydrothermally and characterized in detail by physicochemical methods, viz. X-ray diffraction (XRD), N2 adsorption, elementary analysis, UV-Vis, ESR and 27Al MAS NMR spectroscopy. UV-Vis and ESR spectroscopy suggest that iron is present in tetrahedral coordination and imparts Brønsted acidity. The catalyst FeAlMCM-41 (nSi/nAl=40; nSi/nFe=40) showed superior performance in the acid-catalyzed tert-butylation of phenol employing tert-butanol as the alkylation agent. At a reaction temperature of 200 °C, a phenol conversion of 70.1% and a selectivity of ca. 75% for 4-tert-butylphenol (4-TBP) were observed. The catalyst FeAlMCM-41(nSi/nMe=50) shows a phenol conversion of 55.4% at a reaction temperature of 180 °C, which is significantly higher as compared to AlMCM-41(56) and FeMCM-41(50). Over these catalysts, phenol conversions amounted to 35.9 and 21.1%, respectively.