Zeolite topology effects in the alkylation of phenol with propylene

• The reaction pathway for the gas phase alkylation of phenol with propylene catalyzed by zeolites was established.
• Zeolite pore topology was demonstrated to strongly influence product selectivity.
• Larger zeolite pores gave more di-alkylated products.
• For reactions occurring in the micropores, *BEA was the most selective for 2-isopropylphenol.

The zeolite catalyzed gas phase alkylation of phenol with propylene is studied with an aim to maximize the production of 2-isopropylphenol instead of the usual focus with zeolites of producing the para product, in this case 4-isopropylphenol. The reaction pathway studies show that 2-isopropylphenol and 4-isopropylphenol are the primary products of the alkylation reactions, as expected. Additionally, it is determined that 3-isopropylphenol and 4-isopropylphenol do not participate in secondary reactions once they are formed, while 2-isopropylphenol and isopropylphenyl ether are more likely to de-alkylate than isomerize in secondary reactions. Of the zeolite topologies studied (FAU, BEA, MOR, MFI, TUN, MEL, MWW, MTT, CHA), maximum 2-isopropylphenol selectivity is obtained when the reactions are not restricted in the zeolite pores and the conversion occurs predominantly on the external surface. For intrazeolitic reactions, BEA zeolite maximizes the 2-isopropylphenol selectivity by balancing diffusion and steric limitations with secondary reactions producing di-alkylated products. The sensitivity of the product selectivity to zeolite pore size when the reaction occurs mainly in the pores suggests this reaction could be used as a test to estimate the pore size of an unknown zeolite.

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