Phenol alkylation with methanol: Effect of sodium content and ammonia selective poisoning of an HY zeolite

Sodium exchange and ammonia selective poisoning of the acid sites of an HY zeolite (Si/Al = 20) were carried out and their effects on the catalytic properties for the alkylation of phenol with methanol (200 degrees C, 1 atm and N-2/reactants molar ratio of 4) were evaluated. Results show that the reaction is highly sensitive to the number and strength of the acid sites of the catalyst. A decrease in the number of acid sites by sodium exchange of the protons or by ammonia selective poisoning produces important changes in the selectivity of the reaction. In fact, a high increase in the anisole/cresol ratio is observed as the percentage of exchanged sodium in the zeolite increases, while the ammonia selective poisoning shows that at low desorption temperatures (less than or equal to 250 degrees C) only anisole is formed while at higher desorption temperatures both anisole and cresols were observed. These results show that anisole formation requires sites with lower acid strength compared to those necessary for cresol formation.