Vapour–liquid critical properties of components of biodiesel. 3. Methyl esters of linoleic, linolenic, and erucic acids

• Critical properties of some unsaturated fatty acid methyl esters were measured.
• These compounds are components of biodiesel.
• Pulse-heating method with ultralow residence times was used.

The critical temperatures and the critical pressures of methyl esters of linoleic, linolenic, and erucic acids have been measured by the pulse-heating technique. Triglycerides of these acids are a considerable fraction of many vegetable oils. The critical temperatures of methyl esters of acids from stearic (C18:0) to linolenic (C18:3) remain almost equal, which correlates well with the fact that the normal boiling temperatures of these esters are practically equal too. The critical pressure monotonically increases in this series. Experimental critical properties have been compared with estimations made by the group-contribution methods of Wilson and Jasperson (WJ), Marrero and Gani (MG), Nannoolal, Rarey, and Ramjugernath (NRR). All the group contribution methods considered in this study predict the critical temperatures of the esters investigated well enough. For the critical pressures, the NRR method gives the best estimation, next are the WJ and MC methods. The acentric factors of the esters studied have been estimated.