A process for producing alkyl esters useful in biofuels and lubricants by transesterifying
glyceride- or esterifying free fatty acid-containing substances in a single critical
phase medium is disclosed. The critical phase medium provides increased reaction
rates, decreases the loss of catalyst or catalyst activity and improves the overall
yield of desired product. The process involves the steps of dissolving an input
glyceride- or free fatty acid-containing substance with an alcohol or water into
a critical fluid medium; reacting the glyceride- or free fatty acid-containing
substance with the alcohol or water input over either a solid or liquid acidic
or basic catalyst and sequentially separating the products from each other and
from the critical fluid medium, which critical fluid medium can then be recycled
back in the process. The process significantly reduces the cost of producing additives
or alternatives to automotive fuels and lubricants utilizing inexpensive glyceride-
or free fatty acid-containing substances, such as animal fats, vegetable oils,
rendered fats, and restaurant grease.
