Adding a Touch of Green to Gasoline

A project in the works at KACST for the the past 10 years is making great progress in the effort to replace toxic and increasingly banned additives in gasoline with an alternative that offers a range of advantages. “The additive we are developing is easily made, environmentally friendly, non toxic and reduces the emission of harmful polluting gases,” says project leader Mohammed Al-Kinany of KACST National Center for Petrochemicals Technology. To create their additive efficiently, the researchers have also developed a new catalyst with economic and environmentally friendly credentials.

Having successfully moved through the laboratory-scale and pilot phases of the project, in work that began in 2010, the final phases of demonstrating the technology’s potential should be complete by 2020. Hopefully, commercialization will then follow, which could transform gasoline production in Saudi Arabia and worldwide.

The complex chemistry of gas

Most people who fill up their cars with gasoline will give little thought to the complex chemical mixture being pumped into the tank. The fuel is, of course, derived from crude oil; but gasoline contains more than just the mixture of hydrocarbon molecules needed to burn and release the energy that turns a vehicle’s engine and wheels. Additives must be used to optimize the combustion process, especially to achieve a smooth pattern of combustion that avoids undesirable pockets, known as ‘knocking.’

Additives currently used come with a range of problems; the Fuel Additives for the Production of High Efficiency Clean Fuel project at KACST, however, is working to resolve them.

Many existing additives are hydrocarbon molecules containing one or more oxygen atoms. These include the simple alcohol ethanol and more complex molecules, such as a branching molecular structure called methyl tertiary butyl ether (MTBE).

“Rising concern over the environmental impact of MTBE is one of the key scientific driving forces behind our project,” says Al-Kinany. He explains that the U.S. states of California and New York banned MTBE in 2002 and 2004 respectively. In California, the compound was contaminating groundwater supplies. There were also many reports of people exposed to MTBE fumes experiencing symptoms like nausea, dizziness, light-headedness, headaches and nose and throat irritation.

Countries other than the U.S. are also following suit and banning MTBE. Al-Kinany likens the current situation with MTBE to the earlier moves in the 1990s that eventually outlawed the addition of lead to gasoline in most countries.

Existing alternatives to MTBE are flawed however. The production of many additives relies on strong and highly corrosive acids that can be released as aerosols into the environment downwind of oil refineries. As a result, authorities in many industrialized countries have now ceased to license new plants using this polluting technology. Some of the additives also corrode vehicle engines.

These problems provide the backdrop to KACST’s project to find new, efficient and cleaner technologies. The project was set up as part of the Saudi Vision 2030 initiative that, amongst other aims, is intended to develop a more sustainable and environmentally friendly oil industry.

Developing alternatives

KACST researchers have developed their new additive by joining molecules of hydrocarbons, called olefins, that are distinguished from most of the molecules in fuels by the presence of electron-rich chemical bonds linking two carbon atoms. In order to achieve the necessary coupling process — or dimerization — the researchers also had to develop a new catalyst that would allow the necessary chemical reactions to occur at useful rates and without destroying the features of the combined structure.

The solid catalyst developed belongs to a class of compounds known as zeolites. These are minerals composed largely of alumina, oxygen and silica arranged in open crystal frameworks with relatively large accessible cavities within the structure. These spaces can accommodate molecules such as water or other small molecules, and active metal oxides. The name zeolite literally means ‘boiling stone’ in Greek because, although the natural zeolites look like stones, they release copious amounts of internal water as steam when heated.

The unique cavity-filled arrangements of different manufactured zeolites make them useful for catalysing many chemical reactions, including the type targeted by KACST researchers. Unfortunately, many zeolites are rapidly deactivated and lose their chemical selectivity when used. This set the KACST team the challenge of finding a stable metal oxide-supporting zeolite catalyst for their dimerization.

The work has now reached the stage where the researchers have developed an efficient and environmentally friendly zeolite catalyst that can be produced, and can also operate, in conditions that are economically feasible for large-scale use. A patent for the catalyst is now pending, while patent protection for the clean fuel additive has already been granted.

The advantages

Like all the best catalysts, the new one is highly selective, interacting with just the right type of olefins, and linking them together into an ideal branched structure for use as a knock-suppressing additive. The catalyst is non toxic, non corrosive, and can be used repeatedly without significant loss of function.

The additive that is made using the catalyst reduces the emissions of harmful pollutants such as carbon monoxide, carbon dioxide, nitrogen oxides and the carbon particles commonly known as soot. It also reduces fuel consumption, relative to alternatives. An advantage for manufacturers is that it can be made in two steps from just one raw material, unlike the six steps and two raw materials required to make MTBE, for example.

Another crucial advantage of the new process is that it can be operated continuously using chemicals in the gas phase that are readily brought together and pumped through the catalyst system. This is a significant improvement on the current liquid phase methods used to make additives. These methods also use highly toxic and corrosive catalysts and can only make the additives in batches, rather than in continuous production lines.

Although initially developed for gasoline engines, the new additive is also proving useful in the diesel-powered engines used mostly in heavier vehicles such as vans and trucks. “When we tested it in a diesel engine we found it reduced the release of carbon dioxide and damaging particulates,” says Al-Kinany. He emphasizes, however, that more testing is needed to fully assess the potential applications in diesel.

In addition to its core scientific impact, Al-Kinany is keen to point out that the project contributes to the wider development of technical expertise and new technologies for the Saudi kingdom. “This helps to increase societal awareness of the importance of technology in realizing sustainable development and national security aspects of Vision 2030,” he explains.

For the vast oil refining industry in Saudi Arabia to be exploited in the longer term, it will need to adapt to using oil in ways that have less harmful impacts on the environment. KACST Fuel Additives for the Production of High Efficiency Clean Fuel project is taking significant steps in that direction.

1.  Fuel Additives for the Production of High Efficiency Clean Fuel, Review Report  | article