A new catalyst should make it possible to produce sustainable fuels for aircraft. Jet fuel from plants: A team in the USA has developed a process to produce sustainable aviation fuel (SAF). It is based on a common catalyst material.
The team from the US Department of Energy's National Renewable Energy Laboratory (NREL), the Massachusetts Institute of Technology (MIT), and Washington State University used lignin to produce the SAF. Lignins are biopolymers that occur in the cell walls of plants and ensure that the cells lignify. Lignin has not been used to make biofuels because it is difficult to chemically break down and convert into useful products, NREL said.
The oxygen has to go
The team presented a method to remove the oxygen from the lignin so that the resulting hydrocarbons can be used as jet fuel. It uses molybdenum carbide as a catalyst to reduce the oxygen content to about 1 percent.
Jet fuel is a mixture of different hydrocarbon molecules, including aromatics and cycloalkanes. These components are not produced in current commercial processes. Instead, SAFs are blended with conventional hydrocarbon fuels. The new process makes it possible to produce fuels that are 100 percent sustainable.
However, lignin oils produced in previous research projects had an oxygen content of 27 to 34 percent. In the case of aircraft fuel, however, this must be less than half a percent. Up to now, catalysts have been used to reduce the oxygen content, which contains expensive precious metals but have proved to be of little use. Lignin is already used in other fuels. In the European Union, for example, there is a project for lignin-based marine fuels.
The team described their process in the journal Joule. The paper points to the urgency of using SAFs as the aviation industry commits to drastically reducing carbon emissions. At the same time, the consumption of aviation fuel is rising sharply. A reduction in carbon dioxide emissions can only be achieved with the massive use of SAFs.