Date of Award


Document Type


Degree Name

Master of Science (MS)


Chemical Engineering


Leonardite and lignite were carboxylated by the Kolbe-Schmitt reaction in order to increase the acidity and hence the cation exchange capacity. A larger carboxyl group content would increase solubility and effectiveness in commercial application such as a thinner for oil-well drilling fluids.

The carboxylation was performed in a heated autoclave under a high carbon dioxide pressure. The Kolbe-Schmitt reaction was used in an anhydrous medium and in a slurry medium and in a modification developed by Marasse using anhydrous potassium carbonate. The reaction material consisted of moisture free, fine powdered potassium salts of leonardite and lignite. Temperature was varied from 100°C to 180°C and the initial carbon dioxide pressure from 225 psig to 900 psig. The time of reaction was also varied between 4 and 24 hours. The extent of reaction was evaluated from changes in total acidity, hydroxyl acidity and carboxyl acidity of the treated material.

The maximum increase obtained in carboxyl acidity was 39 percent and that in total acidity was 89 percent of the increase predicted on the basis of complete ortho substitution to all existing hydroxyl groups. The optimum conditions found were at 150°C temperature and a pressure of 1060 psig for 8 hours.