Abstract: Effects of a series of n-alkanol additives on the phase stability of methanol–straight-run gasoline blends were studied by testing phase separate temperature of these blends and analyzing linear regression equation of curves related with n-alkanol amount–phase separate temperature. Results show that the positive effects of C4-C10 n-alkanol on the phase stability of methanol–straight-run gasoline blends are better than that of low carbon number alcohol. Those effects are relative to HLB values of n-alkanol and the volume fraction of methanol (MVF) in the system. The most effective additive to maintain a stable system for M15 and M85 blends (MVF of 15% and 85%, respectively, following the same) is n-hexanol, so does n-decanol for M30, M50 and M65 blends. Under medium MVFs, for blends with same MVF, its phase stability can be improved with the decrease of n-alkanol HLB value; for blends with high MVF or low MVF, there is always an optimum n-alkanol HLB value to maintain a stable system. For systems adding the same n-alkanol, with the increase of MVF in the blends, the phase stability of the system weakens gradually.

Key words: methanol–straight- run gasoline blends, phase stability, linear regression, HLB value