Avaliação de catalisadores superácidos de SO4 2-/ZrO2 destinados à reação de esterificação do óleo de algodão para produção de biodiesel.

Abstract

The objective of this research was to obtain two zirconia by combustion reaction (named ZS and ZSY), evaluating two impregnation methods of the sulfate ion on the surface of the synthesized zirconia sample (ZS), in order to obtain a sulfated catalyst with maximum possible acidity, that is, low pH. Initially, the samples ZS and ZSY were obtained by combustion reaction in batch of 15 g of the product, used IVzirconium n-propoxide and urea as precursor to produce ZS and zirconium npropoxide IV, hexahydrate yttrium nitrate and urea in the production of ZSY. The synthesized sample (ZS) has shown the formation of the monoclinic majority phase with traces of the tetragonal phase, with a crystallite size of 25.35 nm and a crystallinity of 77.6%, and the sample ZYS has shown the tetragonal phase as the majority and the monoclinic phase as secondary, with crystallite size of 17.79 nm and crystallinity of 76.6%. For the sulfated samples, the same related phases were also observed in the samples ZS and ZSY with the following crystallite and crystallinity sizes: 25.56 nm and 77.3% for the sample ZS-IMA and 26.63 nm and 76.5% for the sample ZSY-IMA. The impregnation method of the sulfate ion on the surface of the selected sample (SZ) that presented the best pH index was the IMA, being 2.2 compared to 3.6 of the IFM method (discarded). The best sulfation method used in the sample ZS was also used in the synthesized sample ZSY and in a commercial sample (ZC) of monoclinic phase, provided by Saint-Gobain Zirpro company, for comparison purposes. Both samples presented homogeneous morphology, consisting of fine particles of approximately spherical shapes, nanometric (with particle sizes varying between 44 and 58 nm, according to MEV, DG and BET) and more accentuated compaction after sulfation by MEV images. Chromatographic analysis indicated conversions of ethyl esters of 27.57; 28.31 and 32.16% for the non-sulfated samples and variations from 80.36 to 99.60% for the sulfated samples, respectively. The results indicated that the differentiation in both impregnation methods was essential for the choice of the best impregnation method of the sulfate ion in ZrO2, which contributed significantly to choice the best impregnation method, and with this, to course the research. The variations in reaction times made it possible to identify the catalyst (ZSY) that favored the catalytic process, achieving a conversion average of ethyl esters of 98.57%, 3.11% higher than the target stipulated by the Petroleum, Natural Gas and Biofuels National Agency (Agência Nacional de Petróleo, Gás Natural e Biocombustíveis – ANP). The reuse had a mean decrease in the ester content of approximately 6.05% for each cycle of reuse of the catalyst,which can be compensated by the addition of less sulfate ion in the reuse catalyst, when compared to the impregnation of the sulfate ion in an original catalyst (without reuse).