A chemist at the Ontario-based University of Guelph has developed a technique to use red mud as a catalyst to reduce the acid level in bio oil, making it more amenable to use as heating oil or as an input into the refining sector.

Bio oil is manufactured through the pyrolysis process, which involves the flash heating of biomass in the absence of air. The resulting substance can be ultimately used as a replacement for crude oil. However, high acid levels result in bio oil that is unstable, corrosive and impossible to store. According to Marcel Schlaf, an associate professor of chemistry at the University of Gluelph who made the discovery, these problems occur because bio oil does not come out of the pyrolysis process as a mixture of stable compounds. Rather, it’s a mixture of compounds that can react with one another. Those reactions are catalyzed by the acids present in the mixture, he said.

"When you pyrolysize biomass to bio oil, two components that you inevitably end up making in your bio oil are formic acid and acetic acid," Schlaf said. "On a weight by weight percentage, [these acids could comprise] up to 15 percent of your bio oil." The first problem, Schlaf continued, is that these substances obviously make the overall bio oil acidic. "However, there is another problem, because in addition to those acids in the bio oil, you will have a variety of aldehydes, ketones, and phenol components." Although bio oil initially comes out of the pyrolysis process as a fairly free flowing liquid, these components, catalyzed by acids, start to undergo reactions similar to those used to manufacture phenol resins. "Essentially you are getting condensation reactions that take place in the bio oil. The moment bio oil is made, it starts to condense with itself, and this process of condensation reactions is catalyzed by the acids present," Schlaf continued.

To solve this problem, Schlaf discovered that red mud could be used to break down the acidic components in the bio oil, making it more stable. Red mud is a high alkaline waste byproduct of the Bayer process, which is used to refine bauxite into aluminum oxide. It typically contains a significant amount of iron oxide. Approximately 70 million tons of red mud is produced annually.

The process developed by Schlaf involves mixing bio oil with red mud, and then heating it for a few hours. "Basically, you are brining your red mud into intimate contact with the bio oil and some agitation, and you heat it to 350 degrees," he said. "That process destroys the formic acid…turning it into a mixture of carbon dioxide, hydrogen, water and carbon monoxide. It’s nice because when you have formic acid and you decompose it, you can ultimately decompose it into carbon dioxide and hydrogen, which means the formic acid internally generates hydrogen, which in turn can be used…to reduce some of the aldehydes and ketones present in your oil to the corresponding alcohols." This makes these substances less reactive. Bio oil upgraded through the red mud process has been shown to be stable for at least 90 days, Schlaf said.

To date, Schlaf and his team have been evaluating the process on the bench scale. So far the work looks promising, he said. The next step would be to evaluate the process on a slightly larger pilot scale. To do this, Schlaf is working to form a collaboration with the University of Western Ontario’s Institute for Chemicals and Fuels from Alternative Resources. The team is also hoping to involve commercial partners in the process. "We’ve demonstrated the chemistry, and engineering is the next step," Schlaf said. "We’ll have to see if we can actually make this work on a larger scale. I can’t do that myself, and we’ll have to secure funding, but we are working on it."