Investigation of ketal-acetin mixture synthesized from glycerol as a renewable additive for gasoline-ethanol fuel blend: Physicochemical characterization and engine combustion, performance, and emission assessment

Abstract

Fossil fuel combustion in internal combustion engines, especially gasoline engines, leads to urban air pollution and contributes to greenhouse gas emissions and climate change. Ethanol has long been considered a promising option to replace gasoline and reduce the amount of associated pollution. Despite its advantages of improving fuel combustion and reducing pollutants, increasing nitrogen oxide emission is an environmental issue caused by using a high percentage of ethanol in fuel. Another challenge the biofuel industry faces is the crude glycerol produced as a by-product of the biodiesel production process, which requires a high-technology purification line, restricting biodiesel production capacity. Considering both challenges, the present study valorized glycerol into a fuel bio-additive, i.e., a ketal-acetin mixture, and developed gasoline-ethanol fuel formulations containing the synthesized bio-additive. To this end, the additive was synthesized through two-stage reactions, i.e., synthesizing acetin mixture using acetic acid and then ketalizing using acetone at specific reaction conditions. Afterward, different fuel samples were analyzed through a physicochemical study and tested in a spark-ignition engine setup. According to the results observed, adding a 2.5% ketal-acetin mixture to gasoline fuel containing 20% ethanol could improve brake power and thermal efficiency, especially at higher engine speeds. At higher engine speeds, there was a decrease in the brake specific fuel consumption values of the fuel sample containing a 2.5% ketal-acetin mixture. At the same time, besides maintaining the positive effects of ethanol presence in reducing engine exhaust emissions such as carbon monoxide and unburned hydrocarbons, this fuel blend reduced nitrogen oxides mean values by 34.5%.