(352t) Quantitative Substance-Property Relationships Method for Boiling Point and Critical Properties of Substances, Refrigerants, Petroleum, Coal-Liquids, Natural Products

This particular session at the 2017 AIChE Meeting in St Paul Minneapolis, Minnesota was dominated by the need to have predictive methods for estimating normal boiling point (Tb) and critical properties (Tc, Pc, Vc) of pure substances (organic and inorganic) as opposed to the multiplicity of group contribution methods that are based on structural groupings of the pure substances. A comprehensive investigation was carried out and the result is that the method of correlating critical properties of poorly characterized pseudocomponents (such as petroleum fractions, heavy-oils, coal-liquids and natural products) by mathematical expression of molecular weight, normal boiling point and specific gravity have limited applications for isomers, PNA characterization assay and extrapolation to high-molecular-weight compounds (such as squalane, n-alkane (nC₂₁- nC₁₂₂), lubricants, bitumen and Krytol GPL).

A comprehensive research literature was conducted on vapor-liquid critical properties of elements and compounds which started with Andrews (1869), Heilborn (1891), Young (1899), Wohl (1914) and Meissner-Redding (1942) reviews to Kobe-Lynn (1953), Kudchadker et al. (1968), Mathews (1972) compilations and spanning over a century, a fitting epitaph in the memorial issue in honor of Kenneth Marsh and the data of Douglas Ambrose (National Physical Laboratory (NPL) Teddington, England) is the creation of Quantitative Substance-Property Relationships (QSPR) method. Likened to the namesake bearing the same acronym QSPR for critical property estimation from molecular structure but lacking the measurable molecular descriptors, here QSPR method is based on adaptation of the Law of corresponding states (LCS) that physical properties should behave similarly (excluding chemical activity and regardless of polarity, size, shape, structure or bonding) for identical values of substance-property relationships (Mw/Tc, Tb/Tc, Mw/Pc). Thus, the LCS provides integrated property in QSPR method for substances (refrigerants, organic, inorganic, isomers and esters), elements, compounds (silicon compounds, large n-alkane, lubricants, bitumen) and pseudocomponents (petroleum fractions, coal-tar liquids, lipids and natural products).

Consequently, the group-contributors in the prototype formalism introduced in 1955 by Lydersen theory are replaced by measurable substance-property relationships for predicting an internally consistent property for missing critical property data in the latest Ambrose et al. (JCED 2015) compilations and for the tabulation by Ihmels (JCED 2010). The procedure of QSPR method is initiated by the knowledge of structural formula or molar mass and then physical properties (Tb, Tc, Pc, Vc, Zc) are established. The QSPR precision is limited by accuracy of measured critical property data but the correctly predicted property trends guaranteed applications to infinite chain length and high-molecular-weight fluids. The QSPR virtue provides accurate estimation for Vc and Zc using measured or estimated (Mw, T_c, P_c). Thus, remedy the most elusive necessity of molecular descriptor for critical volume V_c. The QSPR model results based on either experimental or estimated values of (Tb, Tc, Pc) are more accurate than the Lydersen brand of group contribution techniques.