Development of a Surrogate Mixture for Algal-Based Hydrotreated Renewable Diesel

Abstract

In this study, the chemical composition and physical properties of an algal-based hydrotreated renewable diesel (HRD) fuel were used to develop a surrogate mixture containing commercially available hydrocarbons. Analysis of the chemical composition of the algal HRD showed a small quantity of low-molecular-weight components and a high quantity of four high-molecular-weight components: n-pentadecane, n-hexadecane, n-heptadecane, and n-octadecane. Using these four components, a fifth branched component was added to match the physical properties of the algal HRD. Candidates for the fifth component were 2-methyloctane, 2-methylnonane, isooctane, and isododecane. The isooctane- and isododecane-based surrogates were tested in a Yanmar engine along with algal HRD and petroleum F76 diesel to assess the start of ignition, start of combustion, ignition delay, maximum rate of heat release, and overall combustion duration. The surrogate that best matches the physical properties of the flash point, density, viscosity, and surface tension as well as most closely reflecting the combustion metrics is one containing isododecane, n-pentadecane, n-hexadecane, n-heptadecane, and n-octadecane.