Synthesis of fatty acid methyl esters via direct transesterification with methanol/carbon dioxide mixtures from spent coffee grounds feedstock

The feasibility of in situextraction and transesterification of spent coffee ground oil into fatty acid methyl esters with supercritical methanol has been investigated in the temperature range 473–603 K, and in the pressure range 10.0–30.0 MPa. At 30.0 MPa and 603 K, a fatty acid methyl esters (FAME) yield of 84.9% was obtained. Carbon dioxide was added to methanol with the aim of reducing the operating temperature and pressure. It was demonstrated that at a reaction temperature of 573 K, pressure of 10.0 MPa and a CO2/MeOH molar ratio of 0.11, a FAME yield of 93.4% was obtained.