A product of vegetable-origin, manufactured from oil-bearing plants, particularly soybeans, biodiesel represents 3% of the diesel sold at Brazil’s fuel pumps and puts the country in third place in the world with a production of 557,000 m3 between January and July this year, behind Germany and the United States. But the increase in production has not been accompanied by technological evolution. Even abroad the biodiesel production process still reveals problems for a biofuel that theoretically should be produced more efficiently and cleanly. Two of these problems are the excessive use of water in the process and the use of catalysts, like caustic soda (NaOH) or potassium hydroxide (KOH), substances that are used to accelerate the transformation of vegetable oil into biofuel. The two catalysts are major contaminants of soil and water if they are not suitably disposed of, a problem that has warranted the attention of two studies that came up with a solution in the form of new catalysts. They can be transformed into a technological alternative for this process, making production more efficient and sustainable from the environmental point of view.
In the Department of Physics and Chemistry at the Federal University of Itajubá (Unifei), Professor Alvaro Antonio Alencar de Queiroz and student Rafael Silva Capaz, from the environmental engineering course, have developed an inorganic nanostructured alkaline catalyst called CNK47. With this catalyst it is possible to carry out the catalysis in the biodiesel production process, reusing the substance in up to five different production sessions until it reaches saturation point. Unlike conventional homogeneous catalysts, CNK47 is solid and does not mix with the product. It can be reused several times and it is not necessary to wash the biodiesel to remove the remains of the catalyst, as happens in the conventional situation. When caustic soda is used in biodiesel production, for example, 500 liters of water are needed to fully clean every 1000 liters of biodiesel. In addition to the danger of contamination, any caustic soda remaining in the fuel can make it highly corrosive for engines. So a change in catalyst can lead to a saving of millions of liters of water. “CNK47 is formed by nanospheres and nanopores of silica, with a high potassium content and made available in the form of powder”, says Professor Queiroz, from the Institute of Exact Sciences of Unifei.
The new catalyst is installed in a reactor with a column impregnated with CNK47, in a continuous flow system in which the oil, already mixed with alcohol (in the transesterification process necessary for producing biodiesel), in this case methanol, passes through the catalyst, which does not dissolve, before being transformed into biodiesel and glycerin, a by-product of the manufacture of biodiesel (see Pesquisa FAPESP nº 149). The nanostructure of the product, like any other nanometric (a measure equivalent to a millimeter divided by 1,000,000) material has a high surface area because a large part of the molecules existing in the nanopores are, in this case, in contact with the mixture of oil and alcohol, which facilitates the chemical reaction.
“Our studies were carried out in a laboratory with soybean oil and methanol (the two most widely used ingredients in Brazil). The ideal thing now is to do the experiment on pilot projects on an industrial scale, with larger quantities of product, which is already being done by a company from Sao Paulo. They have been carrying out tests since September this year but because of a confidentiality agreement we can’t disclose the company’s name”, says Queiroz. After confirming the results on an industrial scale an international patent will be drawn up by Unifei and the company. The work became known when it won first place in the awards at the 16th Mineira Society of Science and Ttechnology Engineers in 2007.
Another heterogeneous catalyst was invented by researchers from the Federal University of São Carlos (UFSCar) and the University of Ribeirão Preto (Unaerp). With this one, also, there is a concern about making the process cleaner and reducing stages in biodiesel production by eliminating the use of water. It is formed from a composite of silicates, clays, aluminum and zeolytes, a type of porous mineral that serves as the basis of the catalyst. “Zeolytes have nanometric pores like a molecular sieve where the chemical reaction occurs”, says Professor Dílson Cardoso, from the Department of Chemical Engineering at UFSCar. He has already been working for 28 years with catalysis, mainly linked to industrial processes in the areas of fuels and fine chemistry.
“Nine years ago we started working with catalysts for liquid fuels and we’ve developed one that increases the octane level in gasoline, a factor that improves the quality of this fuel.” It’s a product to be used in refineries for obtaining gasoline that improves vehicle performance.
“In 2006, with the start of biodiesel production in Brazil, we decided to also use zeolytes in the transesterification reaction, which is necessary for the production of this fuel, because we had experience in using this mineral and even a patent for a zeolytic sieve-based catalyst for use in chemical and pharmaceutical industries. We developed another catalyst for producing biodiesel and we’ve already lodged a patent request with the National Institute of Industrial Property (INPI)”, says Cardoso, whose co-authors are PhD students Leandro Martins, with a FAPESP scholarship, and Demian Fabiano, from the National Council for Scientific and Technological Development (CNPq). “Now we’re working on the product’s stability so that it can be reused several times”, says Cardoso.
The heterogeneous catalysts formulated by Queiroz and Cardoso have many advantages over conventional products, like not needing to use water in the process and eliminating effluents that are harmful to the environment, but also there are some difficulties to be overcome. Among the disadvantages Queiroz points to the need for high temperatures for the process developed at Unifei, which needs 80° C to function, a factor that requires expenditure on energy from electricity or other sources. Cardoso’s catalyst functions at 50°C. The synthesis process of these substances also requires high temperatures. The CNK47 catalyst was synthesized at 600°C for 24 hours. “It’s still dear to do this in the country, particularly in small quantities.” Even with difficulties the future for biodiesel production is promising and dependent on new technologies and on the evolution of research and inventions, as shown by the recent studies of these two groups of researchers.
Catalytic process based on molecular sieves for transesterification reactions that are useful in the production of biodiesel (nº 06/60875-7); Modality Intellectual Property Support Program (Papi); Coordinator Dílson Cardoso – UFSCar; Investment R$ 6,000.00 (FAPESP)