Molecular interaction of quinoline with coal-liquid fractions

A direct calorimetric method has been used to determine simultaneously the molar enthalpy, ΔH^o, and equilibrium constant, K, for the interaction of quinoline (Qu) with coal-derived asphaltenes (A), acid/neutral (AA) and base (BA) components of A, silylated asphaltenes (A(TMS)) and heavy oil (HO) fractions in solvent C₆H₆. Solvent fractionated A and HO fractions were from three centrifuged-liquid product (CLP) samples prepared in the 450 kg ($\text{≈}\text{1}\text{2}$ U.S. ton) per day Process Development Unit at Pittsburgh Energy Research Center, at different process conditions from the same feed coal, Kentucky hvAb. For a given system, Qu-A (AA or BA), Qu-HO, the almost constant value of K and rectilinear variation of ΔH^o with the phenolic oxygen content of coal-liquid fractions have been attributed to the dominance of hydrogen-bonding effects, involving phenolic OH, over other types of molecular interactions in solution. In the Qu-A(TMS) system, ?ΔH^o values increase with decrease in molecular weight of A(TMS), while ?ΔS^o values increase with increase in aromaticity of the A fraction. The degree of complexation, in absence of OH groups, is much smaller than with the Qu-A system.