Publicação
An environmental approach using niobium supported on zeolites for the catalytic acetalization of glycerol
| Resumo: | Glycerol is produced at a large amount as a by-product or waste stream from biodiesel production. Due to the high growth of biodiesel production, the oversupply of glycerol has become an economic drawback for the development of biofuel itself. Despite of the wide applications of pure glycerol, it is imperative its conversion into value added chemicals. This work reports the results of the acetalization of glycerol with acetone to give solketal, an oxygenated compound useful as chemical and fuel additive for gasoline, diesel and biodiesel over a series of niobium-containing zeolites. NaY, HY, HUSY and HZSM5 were used as the parent zeolites with different amounts of Nb2O5 (Nbx-ZEO, x=5, 10 and 15 wt%), prepared by impregnation method. Selected catalysts were characterized by morphological and structural analyzes: N2 adsorption isotherms, chemical analysis (ICPOES), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The results obtained in the characterization of the heterogeneous catalysts show that the impregnation of the Nb(V) improve the catalytic properties of the materials. The hydrophilic behavior of the parent zeolites: NaY > HY > HUSY > HZSM5 was verified during the reaction. The catalysts were evaluated on the acetalization of glycerol with acetone in a batch reactor using a molar ratio 1:2. The influence of type of catalyst, different reaction temperatures (70 ºC, 40 ºC and room temperature) and catalyst amount were investigated in the selected heterogeneous catalysts. The progress of the reaction was monitored following the variation in intensity of characteristic Raman bands and the quantification was performed by gas chromatography analysis. All parent zeolites and series of Nbx-NaY and Nbx-HY were not active in the conditions tested. When the reaction is performed with Nbx-HUSY and Nbx-HZSM5 catalysts, the results showed good conversion of glycerol into solketal. The best results were obtained with 2 wt% of Nb15-HZSM5 catalyst at 70 ºC with 74 % conversion and 98 % selectivity. However, highly efficient conversion of glycerol to solketal over the Nbx-HUSY/HZSM5 catalysts could be achieved with 10 % of Nb at 40 ºC with highest selectivity (98 %) with 2 wt% of catalyst, showing that our catalysts can be used in moderate temperatures. |
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| Autores principais: | Ferreira, Carla Sofia da Cunha |
| Assunto: | Ciências Naturais::Ciências Químicas |
| Ano: | 2014 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | Glycerol is produced at a large amount as a by-product or waste stream from biodiesel production. Due to the high growth of biodiesel production, the oversupply of glycerol has become an economic drawback for the development of biofuel itself. Despite of the wide applications of pure glycerol, it is imperative its conversion into value added chemicals. This work reports the results of the acetalization of glycerol with acetone to give solketal, an oxygenated compound useful as chemical and fuel additive for gasoline, diesel and biodiesel over a series of niobium-containing zeolites. NaY, HY, HUSY and HZSM5 were used as the parent zeolites with different amounts of Nb2O5 (Nbx-ZEO, x=5, 10 and 15 wt%), prepared by impregnation method. Selected catalysts were characterized by morphological and structural analyzes: N2 adsorption isotherms, chemical analysis (ICPOES), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The results obtained in the characterization of the heterogeneous catalysts show that the impregnation of the Nb(V) improve the catalytic properties of the materials. The hydrophilic behavior of the parent zeolites: NaY > HY > HUSY > HZSM5 was verified during the reaction. The catalysts were evaluated on the acetalization of glycerol with acetone in a batch reactor using a molar ratio 1:2. The influence of type of catalyst, different reaction temperatures (70 ºC, 40 ºC and room temperature) and catalyst amount were investigated in the selected heterogeneous catalysts. The progress of the reaction was monitored following the variation in intensity of characteristic Raman bands and the quantification was performed by gas chromatography analysis. All parent zeolites and series of Nbx-NaY and Nbx-HY were not active in the conditions tested. When the reaction is performed with Nbx-HUSY and Nbx-HZSM5 catalysts, the results showed good conversion of glycerol into solketal. The best results were obtained with 2 wt% of Nb15-HZSM5 catalyst at 70 ºC with 74 % conversion and 98 % selectivity. However, highly efficient conversion of glycerol to solketal over the Nbx-HUSY/HZSM5 catalysts could be achieved with 10 % of Nb at 40 ºC with highest selectivity (98 %) with 2 wt% of catalyst, showing that our catalysts can be used in moderate temperatures. |
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