Potassium carbonate and water/alcohol/toluene?
The synthesis you are referring to is outlined here. Potassium Carbonate acts as a drying agent as you said as the later part of the distillation requires a specific temperature to remove the toluene and alcohol.

The water comes from the concentrated sulphuric acid solution added with apidic acid. The residue is also rinsed with alcohol which is a strong indicator that water needs to be removed.