Determination and Correlation of Vapor–Liquid Equilibria for the Phosphoric Acid + Water + Cyclohexane + Ethanol System

Abstract

The production of phosphoric acid by wet processes is quite energy consuming. The adoption of azeotropic distillation in the evaporation process, using cyclohexane as an entrainer, may be potentially economical. The vapor–liquid equilibria (VLE) data were determined by ebulliometric method for the following systems at 20, 40, 60, 80, and 101.3 kPa: (1) phosphoric acid + water + ethanol; (2) phosphoric acid + water + cyclohexane + ethanol; (3) phosphoric acid + water + cyclohexane. The electrolyte NRTL parameters for the following pairs were correlated from the VLE data by using Aspen Plus as a tool: H3PO4–H2O, H+[H2PO4]−–H2O, H3PO4–C2H6O, H3PO4–C6H12, and H+[H2PO4]−–C6H12. The VLE data and the obtained parameters may provide basic data for the enhancement of phosphoric acid by azeotropic distillation.

Determination and Correlation of Vapor–Liquid Equilibria for the Nitric Acid + Water, Nitric Acid + Water + Phosphoric Acid, and Nitric Acid + Water + Phosphoric Acid + Sulfuric Acid System

“…To validate the reliability of the dynamic equilibrium cell, the isobaric VLE data for a well-studied water (2) + phosphoric acid (3) binary system at several pressures were measured and compared with those obtained from the literature. , The maximum deviation (MD) and root-mean-square deviation (RMSD) shown in Table for the temperature ( T ) are only 0.33 and 0.19 K, respectively. The results presented in Figure show that the experimentally obtained VLE data agree well with the literature data, which indicates that the apparatus, procedure, and analysis method used are reliable.…”

“…Boiling points of phosphoric acid solutions at several pressures: experimental results are compared with the literature data. , …”

“…At low or moderate pressures, the term exp[ v i l ( p i – p i s )/ RT ] is approximately equal to 1, and the vapor phase could be treated as the ideal phase, ,,, which results in ϕ̂ normalv i = 1 , ϕ̂ normals i = 1 ; thus, eq can be rewritten as follows: y i p = p i normals γ i x i where p i s is the saturation vapor pressure of the pure component i at temperature T (in Kelvin), and it can be calculated by extended Antoine eq , ln ( p i s / kPa ) = C 1 i + C 2 i T + C 3 i + C 4 i T + C 5 i ln nobreak0em.25em⁡ T + C 6 i T C 7 i 0.25em for 0.25em C <...…”

“…At low or moderate pressures, the term exp­[ v i l ( p i – p i s )/ RT ] is approximately equal to 1, and the vapor phase could be treated as the ideal phase, ,,, which results in , ; thus, eq can be rewritten as follows: where p i s is the saturation vapor pressure of the pure component i at temperature T (in Kelvin), and it can be calculated by extended Antoine eq , where C 1 i to C 7 i are the coefficients of pure components i and C 8 i and C 9 i represent the limits of the temperature range, which were retrieved from the Aspen databank and given in Table .…”

“…In addition, Messnaoui also simulated the phosphoric acid concentration process and calculated the activity coefficient of species in aqueous solution using the electrolyte NRTL model. Based on this, Li concentrated phosphoric acid using ethanol and cyclohexane as the entraining agents and modeled the boiling point of the system using the NRTL model. Finally, the model with better predictive performance is obtained.…”