UREP-17 Cycle

Funding Agency

Project No


Roles of Additives in the Enhancement of the GTL Diesel Fuel Blends

The Gas-To-Liquid (GTL) technology is the catalytic conversion process of natural gas into synthetic liquid fuels, one of which is GTL diesel, utilizing Fischer-Tropsch synthesis (FTS) chemistry. Diesel fuel is one of the most essential fuels due to the variety of applications and uses of diesel engines.  Diesel engines are pivotal to many fields such as transportation and construction due to the use of diesel fuel in heavy trucks, trains, boats, and barges to name a few. All Gas-to-liquid (GTL) fuels are ultra-clean and environmentally benign fuels with low emissions of carbon monoxide and particulates upon combustion. Nevertheless, the lack of sulfur and aromatics in the GTL diesel fuel, compared to conventional diesel, negatively impacts certain important physical characteristics such as lubricity and density. Therefore, these fuels are improper for use in existing diesel engines [1]. The lubricity issue is significant for GTL diesel, as it does not match the global standards. The aim of this research project was to design and optimize new generation ultra clean GTL diesel compliant with global standards. The enhancement of GTL diesel lubricity, which serves as the major property drawback, was desired to be carried out without compromising any other physical property. The goal was to keep other properties within ranges appropriate for existing engines and specified in American Society for Testing Materials (ASTM) standards. For this study, four lubricity enhancement biodiesel additives were selected. Blends were tested for fuel characteristics and physical properties. The tests include vapor pressure, viscosity, flash point, pour point, cloud point, distillation performance, heat content and lubricity.

Since Qatar has the largest GTL plant in the world, this research is essentially significant and relevant. It also enriches Qatar’s scientific research culture and serves the world by creating cleaner fuels for a cleaner environment.


Testing Method

Reason of Selection


ASTM D4052

Indirect measure of average fuel molecular weight

Flash Point


Important safety measure for the fuel. Identifies the tendency to flammability.

Cloud Point


Cold flow property of fuel and an estimation of crystallization of fuel in cold conditions

Pour Point

D 5949

Flow characteristics, like pour point, can be critical for the correct operation of lubricating oil systems, fuel systems, and pipeline operations.

Vapor Pressure

D 6378

This test method can be applied in online applications in which an air saturation procedure prior to the measurement cannot be performed

Cetane Index(calculated)

D 4737

The cetane number provides a measure of the ignition characteristics of diesel fuel oil in compression ignition engines.

Viscosity Distillation curves

ASTM D7042

Measure of flow properties of fuel
The distillation (volatility) characteristics of hydrocarbons have an important effect on their safety and performance, especially in the case of fuels and solvents. The boiling range gives information on the composition, the properties, and the behavior of the fuel during storage and use. Volatility is the major determinant of the tendency of a hydrocarbon mixture to produce potentially explosive vapors


ASTM D6078

Evaluation of lubricity of diesel fuel using a scuffing load ball-on-cylinder lubricity evaluator.