Study on the etherification of glycerol to produce glycerol tert-butyl ethers

Abstract

Biodiesel production is rapidly increasing but will only be viable if the inevitable byproduct, glycerol, can be revalorized too. An interesting option is the conversion with tert. butyl alcohol (TBA) into a fuel additive: glycerol tert. butyl ether (GTBE). This oxygen rich ether can improve the combustion, which results in less CO- and soot-exhaust. This thesis investigates the possibilities of mono-GTBE (m-GTBE) as gasoline additive.

First, the etherification of glycerol with TBA is optimized to become a maximal yield of m-GTBE. The temperature (80-110°C), reaction time (2-6h) and catalyst loading relative to glycerol (5-10 wt%) are the observed parameters. After isolation by means of distillation, the m-GTBE is blended with commercial gasoline in percentages of 2.5, 5 and 7.5 v%. Finally, the influence on octane number, density, vapor pressure, boiling range and oxygen content is checked according to ASTM standard test methods.

The temperature affects the yield of m-GTBE positively while the time and catalyst loading show a negative effect. After adding m-GTBE to the gasoline, the octane number has increased, which is a desired effect. The density has increased. The vapor pressure has increased for 5% m-GTBE but decreased for 7.5%. In addition, boiling range and oxygen content augment. These results indicate that m-GTBE could be a potential additive that positively affects the combustion characteristics of gasoline.