Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel Full Length Article The role of ethanol as a cosolvent for isooctane-methanol blend Budi Waluyo a , Muji Setiyo a, ⁎ , Saifudin a , I.N.G. Wardana b a Department of Automotive Engineering, Universitas Muhammadiyah Magelang, 56172, Indonesia b Department of Mechanical Engineering, University of Brawijaya, Malang 65141, Indonesia ARTICLE INFO Keywords: Isooctane-methanol blend Ethanol Cosolvent ABSTRACT Methanol has a strong potential to be used as a substitution for fossil fuel due to its several advantages such as the enthalpy of evaporation, high octane numbers and high oxygen content. However, unlike the non-polar gasoline, it is polar and very miscible with water and this leads to the phase separation of the gasoline-methanol blend. Therefore, this study was conducted to understand the role of ethanol in improving the homogeneity and stability of the gasoline-methanol blend. Molecular analysis was conducted through the HyperChem software to simulate important molecular properties of each constituent substance. Isooctane as a single substance was chosen to represent multi-substance gasoline to simplify the analysis of molecular interactions. Experimental tests were also conducted by mixing several fractions of the isooctane-methanol blend, and the ethanol was dripped gradually into separate phases of the mixture. The manual stirring was conducted, then allowed to stay for 120 s on each drop. Visual observation and addition of ethanol drops were stopped after the mixture se- paration phase did not occur. The results showed a certain amount of ethanol (up to 22%) was needed to improve the homogeneity and stability of the isooctane- methanol blend. The ethanol fractions up to 22% v/v needs to be added to block hydrogen bonds between the methanol-water molecules. The addition of ethanol produces new hydrogen bonds that were stronger than the methanol and water bond to improve the homo- geneity and stability of the isooctane-methanol blend. 1. Introduction The depletion of fossil fuel reserves and the deterioration of the environment due to greenhouse effect makes the investigation on the use of alcohol in spark-ignition engines (SI engines) become a focus of sustainable energy research [1]. Several previous studies conducted showed that alcohol produced lower emissions and has good perfor- mance [2]. Moreover, methanol and ethanol are the most potential biofuels to be used as substitutes for gasoline without significant changes in engine structure [3,4]. This has attracted the attention of previous researchers because of their ability to be produced from re- newable energy sources and their oxygen content which enables com- plete combustion [5]. Methanol and ethanol are the leading candidates to replace conventional SI Engine fuels due to some of their physical properties and the similarity in combustion compared to gasoline. The other advantages include high octane numbers, good stoichiometric flame speeds, high octane sensitivity, and high heat evaporation [6,7]. Furthermore, scalability is one of the reasons some researchers have developed methanol as an SI Engine fuel. The ease of being produced from several raw materials makes it a strong alternative for sustainable fuels towards reducing the effects of carbon dioxide from transport activities [8]. Methanol has also been successfully applied to diesel engines through a new combustion scheme which involves gas phase by forming a homogeneous mixture in the combustion chamber (die- sel–methanol dual-fuel/DMDF combustion). Methanol with diesel fuel can operate stably up to a fraction of 30% in practical use [9]. Methanol also has a higher enthalpy of evaporations than ethanol, therefore, it has the potential to produce lower NOx emissions [10]. It can be produced by first converting almost all biomass to synthesis gas in a gasifier, from carbon dioxide and water or water vapor [11]. It can also be produced from carbon dioxide or hydrogen by using renewable energy and other energy sources [12]. Methanol is the simplest mole- cules of the alcohol group and has many similarities with ethanol in physical and combustion properties [8]. Its use in SI engine is also expected to increase the thermal efficiency of combustion [13]. Another advantage of using methanol as a sustainable fuel is the lower boiling point, more oxygen content, and higher evaporation pressure compared to ethanol [14]. However, it has several disadvantages such as cold start problems and lower energy density than ethanol, thus limiting its practical application in SI engine [15]. It is also a hydrophilic liquid with the ability to cause problems when transported through pipes [16]. https://doi.org/10.1016/j.fuel.2019.116465 Received 19 August 2019; Received in revised form 17 October 2019; Accepted 20 October 2019 ⁎ Corresponding author. E-mail address: setiyo.muji@ummgl.ac.id (M. Setiyo). Fuel 262 (2020) 116465 Available online 06 November 2019 0016-2361/ © 2019 Elsevier Ltd. All rights reserved. T