Compatibility of di- and tri-tert-butyl glycerol ethers with gasoline

Abstract

Di- and tri-tert-butyl glycerol ethers (DTBGE and TTBGE) can be produced at high yields via etherification of glycerol with isobutene over cost effective and commercially available solid acid catalysts. These ethers have a potential to replace methyl-tert-butyl ether, an environmentally unfriendly gasoline oxygenate. In this study, we first synthesized fuel additive mixtures consisting of different concentrations of DTBGE and TTBGE and then determined the fuel characteristics of the fuel surrogates prepared by blending these mixtures with a reference gasoline fuel. Density, kinematic viscosity, and water solubility of the GTBE mixtures dropped with increasing TTBGE concentration, corresponding to a decrease in the number of hydroxyl groups in the ether mixtures. Blending 3.45 vol% GTBE in gasoline resulted in an increase in octane number from 95 to 96 and a decrease in vapor pressure from 57 to 55 kPa, whereas density and oxidation stability of the GTBE-gasoline blends remained within the fuel specifications. Results indicated that DTBGE alone is not compatible with gasoline, there is a need of TTBGE content in the fuel blends for better compatibility. We then compared the power and emissions by conducting fuel performance tests in an engine dynamometer using the reference gasoline, 3.45 vol% MTBE-blended gasoline, and 3.45 vol% GTBE-blended gasoline (34 wt% TTBGE, 62 wt% DTBGE, 1 wt% MTBGE, and 3 wt% isobutene oligomers). Our results illustrate that GTBE is an alternative gasoline additive to MTBE as their blends provide similar torque values, specific fuel consumption, and mean emissions of CO2, CO, NOx, and total hydrocarbon emissions (THC).