Spectroscopic Solubility Study of Citric Acid in n-Propanol

Citric acid is a very common chemical in a variety of industrial chemical processes and consumer products. One notable use is as a chelating agent in Co-Mo impregnation solutions for distillate hydrotreating catalysts, where it greatly increases the catalysts efficacy in removing sulfur and nitrogen from light petroleum fractions. However, citric acid is commonly added to such a degree that the resulting solution has very high concentrations of citric acid which dramatically increases solution viscosity which can reduce catalyst quality when the impregnation process is brought to production scale. One possible method to maintain the positive activity benefits while reducing the viscosity of the impregnation solution is to add a small amount of non-aqueous solvent to the impregnation solution to reduce the amount of free citric acid. A crucial figure to consider in the selection of such a solvent is how soluble citric acid is in the system. However, figures for the solubility of citric acid in organic solvents are both scarce and contradictory, possibly due to the gravimetric method of analysis used previously. This project seeks to establish the solubility of citric acid in n-propanol using in-situ UV-Vis spectroscopy at different temperatures and derive the thermodynamic quantities associated with the dissolution process using Van’t Hoff analysis