RCGI project wants to convert CO2 into third generation ethanol

Develop more efficient catalysts and catalytic processes to generate a chain of transformation of carbon dioxide (CO2), one of the main greenhouse gases (GHG), into products with high added value. This is the goal of the project that has been developed since last year within the scope of the Research Center for Innovation in Greenhouse Gases (RCGI). “We are going to treat CO2 as a raw material, as a kind of building block capable of generating a series of chemical products that can be commercially exploited by industry”, explains Liane Rossi, professor at the Institute of Chemistry at the University of São Paulo ( IQ-USP) and study coordinator.

The first step of the project, which is titled “Development of catalytic routes for transforming CO2 into chemical products and materials”, is to investigate which catalysts are capable of converting CO2 into so-called higher alcohols, that is, those that have at least two carbons in the structure of the molecule, as is the case with ethanol (CH3CH2OH). “We can say that ethanol produced from CO2 would be third generation ethanol, with first generation ethanol being that obtained from sucrose and second generation being that obtained from cellulose. Ethanol, in addition to being used as fuel, can be transformed into chemical products, such as monomers for the production of polymers, or commonly known as plastics”, points out Rossi. “Monomer is the base unit for the production of these polymers. They are macromolecules made from the connection of these base units, forming molecular chains, which is why they are solid and find many applications.”

The researchers' idea is to develop catalytic processes that can be inserted into existing industrial chains, such as ethanol plants, to contribute to the mitigation of CO2 emissions. “In this case, we not only intend to increase the ethanol productivity of the plants by capturing and converting CO2, but to modernize them, transforming them into true biorefineries”, points out Rossi. “The fermentation of sugar cane produces a large amount of CO2, which ends up being emitted into the atmosphere. Capturing this CO2 before it is emitted would represent a much lower cost than sequestering CO2 that is diluted in the atmosphere after it is emitted. Therefore, our objective is to work with CO2 before it is emitted, capturing it at the generating source and converting it through catalysis into alcohols, such as ethanol.”

The first challenge is to obtain alcohols from CO2 and then imagine a market for these alcohols and products derived from them. “There are several research groups that have been thinking about other uses for ethanol, beyond the fuel that powers vehicles. Brazil, which is the second largest ethanol producer in the world, behind only the United States, could gain a lot if it had the technology to do so.”

The project will focus on the generation of four products: acetic acid (which is used to make acetate), propylene (which makes polymers), as well as butadiene and isobutene, two rubber monomers. “The idea is to develop technologies that can strengthen ethanol plants with the aim of increasing alcohol production and creating products derived from third-generation ethanol. From butadiene, for example, synthetic rubbers can be produced that are used in the manufacture of tires.”

According to Rossi, chemical products derived from ethanol produced from CO2 will have the same chemical, physical and mechanical properties as those produced by the petrochemical industry (drop-in chemicals). “This should reduce our dependence on fossil resources and create a circular and beneficial carbon process,” predicts Rossi. According to the researcher, Brazil still does not make extensive use of CO2, and uses little ethanol as a raw material to transform it into products. One of the exceptions, she says, is Braskem, which since 2010 has been manufacturing polyethylene from sugar cane ethanol. “There are also reports of capturing CO2 from fermentation for use in the area of ​​carbonated drinks. But this is very little. We can and must go further in the search for alternatives for capturing and converting CO2.”

Challenges with technology

A chemical engineer who has worked with catalysis for almost two decades at USP, Rossi does not hide her fascination with this technology created in the 2th century. “Catalysis is a segment of chemistry that is present in practically everything we produce today through industrial processes. The synthesis of ammonia, for example, a fundamental compound in the production of fertilizers, is done through catalysis, which combines nitrogen (N2) and hydrogen (HXNUMX)”, she states.

According to the expert, although the technology is old, studies into the catalytic conversion of CO2 have only recently received more attention. “For us scientists, the challenge is to discover the best catalyst for this purpose, fine-tuning the properties of the materials that serve as catalysts”, says Rossi. One of the challenges of catalysis is achieving a high degree of selectivity, which means producing more of the desired product and fewer unwanted byproducts. “When working with the appropriate catalyst, under ideal temperature and pressure conditions, it is possible to direct the reaction to obtain the desired product.”

According to Rossi, in another recent study, carried out in 2020 within the scope of the RCGI, the team of researchers managed to obtain a selectivity of 98% for methanol (CH3OH) and a conversion of 30% of CO2. In other words, 30% of the carbon dioxide used in the process was transformed into methanol, in a chemical reaction with hydrogen, called hydrogenation, without the use of any other additives. “The key point of the technology was to use a titanium oxide and rhenium oxide catalyst, low temperature and high pressure”, points out the researcher.

The objective now is to obtain a result as promising as this for the conversion of CO2 into ethanol, the difference of which is limited to one more carbon than methanol, but it represents a great challenge in terms of the chemistry involved and a great advantage in application. The expert highlights that the project, which lasts three years, seeks to establish the best catalysts for the process. But that doesn't put an end to the story. “In order for the technology to be adopted by industries, it is necessary to verify whether the results obtained in the laboratory are repeated with increased scale and are compensated from a financial point of view. To do this, it is important to attract investors, who can be private, from the industry itself, or public, to turn these ideas into reality.”