Thermodynamic modelling of concentrated sulfuric acid solutions

Abstracts ic acid is an important chemical for the industry. Thus, a proper and reliable thermodynamic model for aqueous sulfuric acid is essential, if the thermodynamic equilibrium calculations will be utilized in the process development and modelling. isting Pitzer models for aqueous H2SO4 are either limited up to 6 molal (37 wt% ) sulfuric acid solution or are too complicated for practical modelling purposes, including 9 to 10 model parameters, with more than 30 terms fitted from experimental data within. ly, a modified Pitzer equation for concentrated aqueous solutions was developed in National Physical Laboratory (UK). The ability of the NPL modification of Pitzer equation to describe the activity and osmotic coefficients of concentrated sulfuric acid solutions up to 15 molal solutions with limited number of Pitzer parameters has been tested and found to be excellent. l sets of Pitzer parameters and four different equations for the dissociation constant of bisulfate ion, K2, were studied at the temperature range 0–55 °C. Four Pitzer parameters were found essential. One 5-parameter set including these four parameters was found to be able to extrapolate the osmotic coefficient up to 40 molal (80 wt%) sulfuric acid solution. There was only a little difference between the studied K2 equations.