Catalisadores heterogêneos aplicados à reação de Biginelli
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2017-03-07
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Universidade Federal de Goiás
Resumo
The Biginelli reaction involves the cyclocondensation of three reagents in the presence of an
acid catalyst to obtain dihydropyrimidinones (DHPMs).This compound and its analogues are
widely known to possess various pharmacological properties, such as antibacterial, antiinflammatory,
antifungal, antiviral, anticancer and antihypertensive. This reaction is usually
carried out via homogeneous catalysis, which presents, however, some difficulties, such as
regeneration of the catalyst and difficult separation of the final product, thus becoming an
obstacle for industrial use. In the present work, it was proposed the use of two classes of
heterogeneous catalysts, which are: metal oxides and acid carbons in order to achieve
attractive characteristics in the Biginelli reaction, as a reduction of reaction time and increase
in yield. The acidic carbons were prepared by carbonization by impregnation of agroindustrial
residues with sulfuric acid at a temperature of 200 °C in the mass ratio of 1:10
(precursor: H2SO4) for 6 h. The pure HY-340 and Nb2O5 were both tested and chemically
treated with a solution of 30% sulfuric acid. The catalysts were characterized by X-ray
diffraction (XRD), infrared spectroscopy (FTIR), thermogravimetric (TG), differential
thermal analysis (DTA), textural adsorption/desorption analysis of N2 at -196 °C and
desorption of ammonia at programmed temperature (DTP-NH3), scanning electron
microscopy (SEM) and X-ray Dispersive Energy Spectrometry (EDS). The contents of C, N,
O and S present on the surface of the coals were quantified by Elementary Analysis
(CHNS-O). Exploratory catalytic tests were carried out to define the best experimental
conditions of solvent, temperature, molar ratio and amount of catalyst. The results obtained
allowed to establish the best experimental conditions for the realization of the Biginelli
reaction. Thus, the following parameters were adopted to evaluate the performance of the
different catalysts. These are: 5% catalyst content (by mass), molar ratio of 1 Benzaldehyde:
1,5 Methyl acetoacetate: 1,5 Urea, without solvent and temperature of 130 °C. The best
catalyst was Nb2O5 treated with sulfuric acid, whereby a yield of 94% of
dihydropyrimidinones (DHPMs).
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Citação
NASCIMENTO, L. G. Catalisadores heterogêneos aplicados à reação de Biginelli. 2017. 88 f. Dissertação (Mestrado em Engenharia Química) - Universidade Federal de Goiás, Goiânia, 2017.