Catalisadores de MoO3 suportados em estrutura micromesoporosa para uso na produção de biodiesel.

Abstract

The rise in oil prices due to the recent conflicts between Russia and Ukraine, together with uncertainties about the future depletion of oil and the environmental impacts caused by this fuel, makes it necessary to search for alternative sources of energy. Biodiesel is an alternative to petroleum diesel because it is produced from renewable sources and causes less pollution in the atmosphere. This biofuel can be obtained mainly through the transesterification reaction using vegetable oils or animal fats with a short chain alcohol in the presence of catalysts. The heterogeneous catalyst may be the most viable, as it can enable reuse in industrial processes. Micro mesoporous materials are relevant for heterogeneous catalysis, as they combine the benefits of microporous materials, such as zeolites that have high acidity and selectivity and mesoporous materials that have high surface area. The insertion of metal oxides in catalytic supports proved to be efficient because the existence of acidic sites in these metal oxides favors many chemical reactions. This work aimed to evaluate molybdenum trioxide (MoO3) catalysts supported on H-ZSM-5/SBA-15 micro mesoporous structure in the production of biodiesel and to investigate the best reaction conditions using a 23 + 3 CtPt factorial design. Factorial design was used to evaluate the influence of the amount of MoO3 (wt.%), reaction time and methanol: oil molar ratio on biodiesel production. For this, ZSM-5 in ammoniacal form was introduced by the seed method during the synthesis of SBA-15. Molecular sieve SBA-15 was synthesized by hydrothermal synthesis using TEOS as a source of silica and triblock copolymer P123 as a targeting agent. The diffractograms confirmed the obtaining of the micro mesoporous support and the x_MoO3/H-ZSM-5/SBA-15 catalysts (where x= 6, 9 and 12 wt.%). From the textural properties, it was observed that the increase in MoO3 content decreased the specific areas and pore diameters of the catalysts. The Raman spectra of the catalysts indicated three vibration modes corresponding to the MoO3 species in the porous structure. Statistical analysis (ANOVA) indicated that the Methanol:oil molar ratio was the most significant parameter in the yield of methyl esters. The maximum biodiesel yield was obtained when using the catalyst 6_MoO3/HZSM-5/SBA-15 with a methanol:oil molar ratio of 20:1 and reaction time of 4h, which resulted in 79.2% yield.