AEC05 The Second TSME International Conference on Mechanical Engineering 19-21 October, 2011, Krabi Oxidation Behaviors of Gasohol Deposit Preechar Karin *1 , Olarn Koonsombatkul 2 and Chinda Charoenphonphanich 2 1 International College, King Mongkut’s Institute of Technology Ladkrabang, Bangkok Thailand 10520 2 Department of Mechanical Engineering, Faculty of Engineering, King Mongkut’s Institute of Technology Ladkrabang, Bangkok Thailand 10520 Corresponding Author: Tel: 02 326 4729, Fax: 02 737 2580 E-mail: kkpreech@kmitl.ac.th Abstract Nowadays, the costs of the fossil fuel have continuously increased. To survive from this problem, we need to find the new alternative energy sources to replace the fossil fuel. Ethanol fuel is focused. The side effect when using gasoline or blended ethanol fuel is the adhesion of carbonaceous deposits on the intake port wall will directly result to performance engine because they restrict air flow. Intake deposits have also been shown to affect exhaust emissions, particularly volatile organic compounds (VOCs) and oxide of nitrogen (NO x ). In order to investigate the chemical composition of deposit, scanning electron microscope with energy dispersive spectrometry (SEM-EDS) is used to study. The carbonaceous species of deposit may be in the form of C x H y for gasoline fuel, whereas the carbonaceous species may be C x H y O for blended ethanol fuel. The oxidation kinetics of deposit formed gasoline and blended ethanol fuel are studied by thermo-gravimetric analysis (TGA) and it can be also determined the activation energy for the reaction between deposit and oxygen. The apparent activation energy of deposit formed gasoline and E20 (gasoline 80% + ethanol 20%) fuel are 156 and 149 kJ/mol, respectively. As a result, the lower apparent activation energy of E20 deposit may be expected that there is oxygen molecular inside the deposit. Keywords: Deposit, Thermo-gravimetric analysis, Activation energy. 1. Introduction As gasoline price increases and the emissions of pollutant from the passenger cars or motorcycles into atmosphere are becoming more and more concern. Now, the alternative fuel plays an important role for lessening pollutant emissions from these cars and motorcycles. Among alternative fuels, ethanol is one of fuels employed most widely. The reasons are in the followings. First, it is derived from the direct fermentation of sugars, fermentation of starches and cellulose after chemical or enzymatic pretreatment that can call bio-ethanol.