Nowadays, tert -butylated phenols are very valuable industrial chemicals. For example, derivatives of this compounds are intermediates for pesticides, fragrances, flavoring compounds, pharmaceutical intermediates and chromans. These compounds are also used in metallic detergents (phenates), lubricating oils and variety of resins, wire enamels, printing inks, phosphate esters, antioxidants, co-stabilizer of polyvinyl chloride, UV adsorbent, dyes and agrochemicals. Among heterogeneous catalysts, MCM-41 molecular sieves have attracted much research attention owing to their high surface area, thermal and hydrothermal stability and ordered meso porous nature. In the present study, Al-MCM-41 with various SiO 2 /Al 2 O 3 ratio was synthesized and modified by impregnation with phosphoric acid. The catalysts extensively characterized by XRD, BET, FT-IR, Si-MAS-NMR and the acidity of the catalysts were measured by pyridine adsorbed FT-IR spectroscopy. Their catalytic performance was examined in the vapor phase alkylation of phenol with tert -butyl alcohol in the temperature range of 110-220 ?C. Then we studied the amount of H 3 PO 4 loaded on the surface of catalysts. The vapor phase t -butylation of phenol over H 3 PO 4 /Al-MCM-41 revealed that 30 %wt. H 3 PO 4 /Al-MCM-41 (70) is more active than the other catalysts. The effect of molar ratio, space velocity, time on stream and H 2 O on conversion and selectivity of 4- t -butyl phenol (4-TBP) over the best catalyst were studied and the results are discussed. In the best conditions, we observed high selectivity of 4-TBP (79.1%) and phenol conversion of 78.6%. Finally alkylation of phenol with tert -butyl alcohol was investigated over H-Al-MCM-41(70), 15%H 3 PO 4 /ZSM-5(60), 30%H 3 PO 4 /Si-MCM-41, 15%H 3 PO 4 / ZrO 2 -TiO 2 . The results reveal that 30%wt H 3 PO 4 /Al-MCM-41 shows a good selectivity and activity in t -butylation of phenol.
