Purification of feedstock by heat treatment

A process for purifying a feedstock, the process comprising:

• a) providing a feedstock containing impurities, wherein the feedstock comprises:
• one or more of animal fat, tall oil pitch, sludge palm oil or used cooking oil or any combinations thereof;
• b) adding to the feedstock phosphoric acid or sulfuric acid forming an admixture, and adjusting a water content of the admixture as a whole to about 0.05 wt % to about 10 wt %;
• c) heating the admixture to a temperature of 200° C. to 280° C.;
• d) optionally removing water;
• and
• e) removing a separate phase containing impurities from the feedstock from the heated admixture to obtain a purified feedstock.