Using well-defined analytical criteria, techniques, and tools, 112 products were evaluated and three were selected that stand out with the greatest technical feasibility, market potential, and sustainability

An article published early this year in the Journal of CO2 Utilization shows that Dimethyl carbonate (DMC), acetic acid, and dimethyl ether (DME) are the three products derived from carbon dioxide (CO2) with the greatest developmental potential and the most promise for new studies, according to researchers from the Department of Chemical Engineering of the Polytechnic School of the University of São Paulo (Poli-USP), within the scope of the FAPESP Shell Research Centre for Gas Innovation (RCGI). The conclusion was reached after a study evaluated the best methods and tools for making that choice while taking into consideration multiple criteria. “We attempted to develop our own methodology for making a little more rigorous selection than we found in the literature,” said chemical engineer and doctoral candidate Kelvin André Pacheco, the principal author of the article.

The research group works in a relatively new area of study and process development, which came on the scene as a serious subject of study in 2013, dealing with the conversion of CO2 into other products, based on chemical reactions. “Prior to that time, when we talked about CO2 mitigation, we only mentioned carbon capture and storage (CCS). The CO2 was sequestered and stored in some way,” says Professor Rita Maria de Brito Alves, who also signs the article and is the academic advisor of Pacheco’s Ph.D. program at USP. “But such questions arose as: what do we do with sequestered or captured carbon? Will we store it all? Do we have the capacity for that? What will be the effect of CO2 on the storage sites?”

Therefore, conferences and work in this area began to increasingly deal with carbon capture and utilization (CCU). The use of carbon dioxide without conversion has been known for a long time, with its application, for instance, in solvents, soft drinks, or greenhouses. Lately, however, studies have increasingly sought to chemically convert CO2 into products with greater aggregate value. “It uses CO2 (a waste, a greenhouse gas that causes all of the environmental problems we know) as a raw material, and transforms it into something useful,” Dr. Alves explains. Researchers from all over the world have sought new applications and technologies and, although there are over a hundred possible products derived from carbon dioxide, the process faces enormous challenges.

“The chemical conversion of CO2 into another chemical compound creates an adverse reaction from an energy standpoint. It is difficult to carry out,” points out engineer Antônio Esio Bresciani, a collaborating researcher in the Poli-USP Engineering Department and the RCGI, who is also a co-author of the scientific article. “Another important aspect is that, besides eliminating CO2 emissions, it must be commercially viable. There is no point in creating a reaction for a product that has little or no market value,” he adds. Bresciani also stressed that the methodologies being analyzed attempted to find products that meet these varied criteria, keeping in mind how difficult it is to cause the reaction, the market needed for the product, and its sustainability.

The researchers started with a group of 122 possible products, which were submitted to three selection stages. After defining the criteria and the best multicriteria analysis tools, they carried out an evaluation in which such items as technological maturity of the product, rate of utilization of CO2 molecules, and projected growth – Including price – were studied. From the initial group of 122, a first screening selected 23 and, of those, only eight were kept. From those eight, the researchers selected the three most promising ones.

“These products are projected for a good growth pattern in the industry, as well as intermediary technological maturity,” Pacheco states. “Our objective is to propose the development of processes; to that end, it is important that the product has already achieved a certain degree of maturity, meaning that we have sufficient basic information for the development of a conceptual project, which, in a manner of speaking, will place the process closer to its actual implementation,” Alves adds.

On the other hand, the researchers also assessed the reagents and other necessary substances, besides CO2, for causing the reaction that leads to the products. Many of the processes, for instance, go through the chemical reaction of hydrogenation, which needs to use hydrogen. “In this case, it needs hydrogen from a clean, sustainable, and cheap source,” Ms. Alves explains. “There’s no point in having a product that consumes CO2 but has a production process that demands the emission of an unreasonable amount of carbon dioxide. This proportion must be established in such a way that the process emits less CO2 than it consumes.”

Product applications – The three products derived from CO2 selected by the researchers offer great environmental advantages. dimethyl carbonate (DMC), for example, is currently produced mainly by the conventional route from methane and phosgene, which presents several problems, the principal one being the use of phosgene. This is an extremely toxic gas, which generates highly corrosive hydrochloric acid as a by-product. Therefore, producing DMC from CO2, in the place of phosgene, is a more appropriate method, from an environmental standpoint.

Among the possible applications of DMC is the manufacture of polycarbonate (PC), which is a type of plastic that can substitute glass and is normally generated by the petrochemical industry. The process would take 1,730 tons of CO2 from every 10,000 tons of PC produced because it uses CO2 as a reagent in the production phase of DMC. If all the worldwide production of PC were to use this process, it would lower the amount of CO2 by around 450,000 tons per year. DMC can also be used as a solvent and a fuel additive.

One of the possible applications of Dimethyl ether gas (DME) is to substitute diesel fuel, which would open an enormous market. However, the question of pricing, in comparison with petroleum products needs to be resolved. And the third product, acetic acid, is widely used as a reagent in the chemical industry. It is the precursor of vinyl acetate used to make PVA, which is another type of plastic with numerous applications, such as in adhesives.

The article “Multicriteria decision analysis for screening carbon dioxide conversion products” can be read at: