Acetals are chemical compounds found in wines, like port, and give it a unique, sweet smell. In addition, if acetals blend with biodiesel, they can improve its properties.
There is now a project in the works that looks to produce acetals more easily and cheaper, according to the SUPREN research group of the Department of Chemical Engineering and the Environment of the Faculty of Engineering in Bilbao, Spain (UPV/EHU). Their starting point is the alcohol obtained from sugar-rich plants, or glycerol, a bi-product of biodiesel which is also a kind of alcohol. The goal is to come up with an industrial process to obtain the supplements that will improve biodiesel fuel.
If we compare petroleum-based diesel fuel with that based on plants, biodiesel has better properties in terms of oily texture and biodegradation; yet it is worse from the point of view of oxidation, energy potential and contamination.
SUPREN, the Sustainable Process Engineering Group of the Department of Chemical Engineering and the Environment of the Faculty of Engineering in Bilbao (UPV/EHU), is studying the supplements that could overcome these drawbacks. Right now they are looking at acetal production.
From the point of view of chemistry, acetals are the result of the reaction of an alcohol and an aldehyde. They generate naturally in fermentation processes. In many wines like port, acetals are the indicators of quality because of the tremendously special, sweet smell they give the wine. When the liquid pours from glasses into the fuel tank, the acetals improve the properties of the biodiesel when they mix with it: Combustion is more effective and, what is more, it is less polluting because engine performance increases. It is vitally important to come up with a method to obtain acetals easily and cheaply, as a liter of biodiesel may have an acetal content of about 15 percent.
It is easy to produce acetals in a laboratory, but designing an industrial-scale process is quite another matter, according to the UPV/EHU researcher Ion Agirre. He has experimented with the alcohol that is the by-product of sugar-rich plants (sugar cane, beetroot, etc.) and also with glycerol, both of which are alcohols of renewable origin. Glycerol is also an alcohol and is a by-product obtained from the reaction to produce biodiesel. It does see use in products like cosmetic creams, but it is difficult to channel all the glycerol generated in biodiesel production to this use. That is why it would be advantageous to validate this compound in acetal production, Agirre said.
One of the conclusions of the research has been that glycerol-based acetals transmit better properties to the biodiesel in comparison with the alcohols from sugar-rich plants like ethanol or butanol. Research has also occurred to see what would be the most suitable process for producing acetals from the point of view of output. And the conversion level of the reaction would range between 50 percent and 60 percent, in other words, only that quantity of alcohol would convert into acetal. To make the process industrially valid, the aim would be to reach 100 percent output or conversion, and the latest experiments have shown that this is possible. Using a resin as a solid catalyst instead of sulphuric acid, and glycerol and butyraldehyde or acetaldehyde as the starting point, they have obtained outputs of 100 percent, researchers said.
They have used laboratory techniques to achieve these results, but the production of acetals from glycerol using conventional techniques could be feasible.