The kinetic behavior of the heterogeneous esterification of propionic acid with n-butanol over an acidic cation-exchange resin, Amberlyst 35, was investigated. The experiments were conducted in a fixed-bed reactor at temperatures from 353.15 to 393.15 K and molar ratios of feed θBo (n-butanol to propionic acid) from 0.5 to 2. The equilibrium conversion of propionic acid was found to increase with increasing reaction temperature and feed composition θBo. Gas-bubble formation was observed when the reaction temperatures were higher than 373.15 K at atmospheric pressure. The kinetic data at temperatures from 353.15 to 373.15 K and θBo from 0.5 to 2 were correlated with the quasi-homogeneous, the Langmuir−Hinshelwood, the Eley−Rideal, and the modified Langmuir−Hinshelwood models, respectively. The Langmuir−Hinshelwood model yielded the best representation for the kinetic behavior of the liquid−solid catalytic esterification over Amberlyst 35.

The Patel-Teja equation of state was incorporated with Eyring's theory to form the Eyring-Patel-Teja viscosity model, in which both the excess activation free energy of flow and the density of a liquid mixture were calculated with the aid of the equation of state. The model correlated viscosities to a grand average absolute deviation of 2.1% for 60 nonaqueous binaries, when the one-parameter van der Waals one-fluid mixing rules were used for the equation constants of such mixtures. With the two-parameter Redlich-Kister type mixing rule of a m , the Eyring-Patel-Teja model correlated viscosities to a grand average absolute deviation of 4.5% for 15 aqueous binaries. This new model is applicable to elevated pressures and, with the binary interaction parameters as determined from binary mixtures, also successfully predicted ternary viscosities. The binary interaction parameters could be estimated from a rather limited data source of mixture viscosities (one data point for a nonaqueous system and two data points for an aqueous system).

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