Methylation of toluene with methanol in sub/supercritical toluene using H-beta zeolite as catalyst

• The synthesis of xylene isomeres were investigated in a continuous sub/supercritical condition on H-beta-zeolite catalyst.
• The optimum conditions for alkylation reaction of toluene include toluene to methanol ratio of 4:1, 623 K, 55 bar and feed flow rate of 0.2 mL min−1.
• Local solute-solute clustering lead to high local concentrations of reagents and increase of reaction rate in high pressures.
• Slower catalyst deactivation occurs compared to normal conditions due to lower surface tension and extraction of the non-volatile materials.

Production of xylene isomers and other alkylbenzene products in normal, near and supercritical toluene using unmodified beta zeolite catalyst and methanol were investigated. The effect of different parameters such as toluene/methanol ratio, temperature, pressure, and flow rate of the reacting materials were investigated. The production optimum conditions for alkylbenzenes are temperature of 623 K, pressure of 55 bar and flow rate of 0.2 mL min−1 using 1 g beta zeolite as catalyst with Si/Al = 38. The selectivity of 47% was achieved for p-xylene production, conversion of methanol and toluene were 100 and 65%, and the production yield and liquid selectivity of xylenes were 72 and 97%, respectively. The catalyst's activity was investigated in a 20 h period and the catalyst were characterized by XRD, TGA, and FT-IR methods.

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