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chemistry

Less pollution

Nanocatalyst created in UFRGS eliminates aromatic compounds from petroleum

A new form of removing petroleum compounds that pollute the environment has come about. The good news comes from nanotechnology, an emergent field in worldwide research, in which work is done atom by atom. Professor Jairton Dupont, of the Federal University of Rio Grande do Sul (UFRGS), has developed a nanocatalyst that permits lowering the concentration of aromatic compounds during the phases of crude oil refining which produces products like gasoline and benzene. Thus, the combustion of gasoline motors, for example, would be more complete without pushing into the air residues that can be cancerigenic and contribute to the formation of acid rain. These nonocatalysts work in the process of catalysis (that modifies the speed of a chemical reaction) that result in cyclohexane, a molecule much less damaging to the environment.

The nanocatalysts recently put together at the Molecular Catalyst Laboratory of UFRGS are groups of particles with around three hundred atoms of iridium – a chemical element in the periodic table which is found in the transition group of metals above rhodium, ruthenium and osmium, with a average diameter of 2 nanometers (a nanometer corresponds to one millionth of a millimeter [1×10-9 m]). These groups, called nanoclusters, are important because they can substitute the organic solvents used in the industrial discharge processes in refineries to eliminate the aromatic compounds. By substituting these organic solvents, the nanocatalysts both lower the industrial costs and solve other problems of operational order in a refinery. Solvents are substances difficult to treat, such as acetone, which serves both to take off nail polish and to purify cocaine – the reason for which its use has been controlled.

The new catalysts are stabilization agents called ionic liquid derivatives of a chemical substance that has received the name imidazole. Developed by a Dupont research group and by professor Roberto de Souza, also of the Chemical Institute of UFRGS and patented in 1996 in conjunction with Petrobras, the ionic liquid prepares and stabilizes the nanoparticles of iridium that catalyze the hydrogenation reactions (addition of hydrogen to the aromatic compounds). A scientific paper with the description of the catalyst and of the mechanism of the reaction was accepted for publishing by the Journal of the American Chemical Society , one of the most prestigious in the world.

In summary, the reaction – very successful on the laboratory experimental scale – occurs in the following manner: the olefins, also by-products in petroleum refining, are added to the ionic liquid, containing the nanocatalyts and gaseous hydrogen. As a result, the aromatics gain atoms of hydrogen and are converted into hydrocarbons. According to Dupont, the final products can be easily removed by decantation, where the hydrogenous product separates itself from the ionic liquid that contains the nanoparticles (catalyst), in a process equivalent to the separation of oil from water. Besides, the catalyst can be recovered and reused and the reactions can be carried out under mild conditions of pressure and temperature (60ºC and only 2 atmospheres). The catalysts normally used for this type of reaction, he stated, work at high temperatures and pressures (300ºC and between 150 to 200 atmospheres).

Understanding chance
Until February, Dupont had the financial support of the Financier of National Petroleum Funds (CTPetro) and at the moment is negotiating the patent and the production on a commercial scale with a large company. “I never even imagined that I would be taking this path”, he says. Nine months ago, by chance, after fifteen years of work on catalysts, he got into nanotechnology when he was intrigued when faced with “a reaction that unexpectedly formed nonometric particles and worked marvelously well”. He spent weeks until he could understand what had been happening and had assured himself that he had discovered heterogeneous “soluble” catalysts. The research in this field is now being responsible for theses and dissertations, as well as having consolidated collaboration with the groups of professors Paulo Fichtner and Sérgio Teixeira of the Physics Institute of UFRGS, who have been participating in the description of the nanoparticles. The group knows that it is not simply enough to eliminate the aromatic compounds. In crude oil there are also sulfur compounds and nitrogenous compounds that also need to be eliminated.

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