DFT study of phenol alkylation with propylene on H-BEA in the absence and presence of water

Water reduces the activation barrier of the rate-limiting step of phenol alkylation with propylene in H-BEA. This, in turn, increases the transition-state theory rate coefficient by two orders-of-magnitude, suggesting much faster alkylation.

FEATURES OF PHENOL ALKYLATION WITH HIGHER ALPHA – OLEFINS ON MACROPOROUS SULFOCATIONITES

The features of phenol alkylation by higher alpha-olefins to obtain monoalkylphenols (MAP) using commercial industrial samples of macroporous sulfocationites are considered: Tulsion-66 and Amberlist 36 dry, which are in different price categories and differ significantly in geometric dimensions: pore diameter at Tulsion-66 = 450-500 A; at Amberlist 36 dry =240 A; pore volume (cm3/g) 0.35 and 0.2, respectively. The thermodynamic analysis of a complex mixture of simultaneously occurring reversible reactions of the formation of target monoalkylphenols (the sum of ortho - and para - isomers) and by-products (dialkylphenols and alkylphenyl ether) in the range of 383-408 K was performed. It was found that to obtain 97-98% equilibrium monoalkylphenols yield, it is necessary to have a 4-6 fold molar excess of phenol with respect to olefins. It is not recommended to raise the temperature above 408 K, as this leads to a significant increase in by-products. In the course of kinetic studies, the optimal concentration of sulfocationites was established - 20% for the initial mixture, providing maximum rates for the selected samples under the same conditions while maintaining selectivity for the target monoalkylphenols at the level of 97-98%. Thus, at T=383 K, the phenol/olefin ratio =6: 1, the reaction rate on Tulsion-66 is 1.6-1.7 times higher than on Amberlist 36 dry. The activation energies estimated from experimental data in the studied temperature range had values (kJ/mol) : 14.64±1.89 on Tulsion-66 and 26.53±3.2 on Amberlist 36 dry. Differences in the reactivity of the investigated sulfocationites confirm the known theoretical positions, according to which the reaction rate during ion exchange catalysis depends on the ratio of the sizes of reacting molecules and catalyst pores.