Thermodynamic Analysis of Isomerization Equilibria of Chlorotoluenes and Dichlorobenzenes in a Biphasic Reaction Systems Containing Highly Acidic Chloroaluminate Melts

Abstract

Thermodynamics and kinetics of the isomerization of chlorotoluenes and dichlorobenzene to the technically desired meta-isomers have been studied in the presence of highly acidic chloroaluminate melts with alkali metal and organic imidazolium cations. Enthalpies of four isomerization processes in reacting systems of chlorotoluenes and dichlorobenzene were obtained from temperature dependencies of the corresponding equilibrium constants in the liquid phase. Experimental reaction enthalpies, enthalpies of vaporization, and absolute vapor pressures of chlorotoluenes and dichlorobenzene have been used for the validation of quantum-chemical methods to predict thermodynamic functions of the four reactions under study successfully. Values of the standard Gibbs energies of formation, standard enthalpies and entropies of formation of chlorotoluenes and dichlorobenzenes in the liquid and in the gas phase have been derived. These values allow optimization of liquid-liquid biphasic manufacturing technologies for halogen-substituted benzenes.

Isomerization and Redistribution of 2,5-Dichlorotoluene Catalyzed by AlCl3 and Isomerization Thermodynamics

“…Reaction equilibriums were obtained when the catalyst loading was 50% at 392. 15 (Table 1). At the equilibrium, the total dichlorotoluene yield was ca.…”

“…According to the second law method (equilibrium constant measurement), for a general chemical reaction in the liquid phase, the true thermodynamic equilibrium constant, K a , is defined as the ratio of the activity, a i , of product and reactant under equilibrium condition. Verevkin et al 15 suggested that the activity coefficients of monochlorotoluenes (or dichlorobenzenes) are identical. In our present research, the activity coefficients of the dichlorotoluene isomers are considered identical.…”

“…Isomerization reactions of xylene, dichlorobenzenes, and monochlorotoluene have been investigated over various catalysts, such as Pt/Fe-ZSM-5, 9 La 2 O 3 -(MgO-) modified HMCM-22, 10 HZSM-5, 11 EU-1 zeolite, 12 hierarchical ZSM-5, 13 and AlCl 3 -LiCl 14,15 catalysts. Interestingly, the Lewis acidic AlCl 3 -LiCl catalyst exhibited good catalytic activity for the isomerization of 1,4-dichlorobenzene to 1,3dichlorobenzene.…”

“…Interestingly, the Lewis acidic AlCl 3 -LiCl catalyst exhibited good catalytic activity for the isomerization of 1,4-dichlorobenzene to 1,3dichlorobenzene. 14,15 For the isomerization of dichlorotoluene, Hβ and Hβ-supported metallic Ag and Cu catalysts effectively catalyzed the isomerization of 2,5-DCT to 2,6-DCT and 2,4-DCT. 16 Although the isomers of 2,5-DCT are high-value chemicals, the isomerization of 2,5-DCT has rarely been investigated.…”

“…16 Although the isomers of 2,5-DCT are high-value chemicals, the isomerization of 2,5-DCT has rarely been investigated. 16 Metal chlorides, such as AlCl 3 , FeCl 3 , CrCl 3 , CrCl 2 , LiCl, SbCl 5 , and SnCl 4 , containing an empty orbital to accept the electrons are conventionally used as the Lewis acidic catalysts for the chlorination, [17][18][19] isomerization, 14,15,20 dehydration, 21,22 alkylation, and acylation reactions. The Lewis acidic metal chloride catalysts could effectively catalyze the isomerization reactions of monochlorotoluenes and dichlorobenzenes at relatively lower reaction temperatures of 140-200 o C. 14,15 However, Hβ and Hβ-supported metallic Ag and Cu The conversions of 2,5-DCT and product yields were the average values of the equilibrium data obtained at different catalyst loadings.…”