Espectroscopia e relaxometria de RMN aplicadas em estudos envolvendo a síntese de biodiesel por catálise heterogênea

• Ano de defesa: 2023
• Autor(a) principal: Fernandez, Joycel Verde
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal do Espírito Santo; BR; Doutorado em Física; Centro de Ciências Exatas; UFES; Programa de Pós-Graduação em Física
• Palavras-chave em Português: Catalisadores alcalinos heterogêneos; RMN-DT; Cinzas; Reuso; subject.br-rjbn; Física
• Link de acesso: http://repositorio.ufes.br/handle/10/16959

This work describes the use of NMR spectroscopy and relaxometry methods in research involving the synthesis of biodiesel from oils of vegetable origin. In the first part of the work, solid state 13C and 31P NMR methods were used to characterize biochars and ash from coffee husk, which were used as heterogeneous catalysts to produce biodiesel from the transesterification reaction between methanol and. commercial and fried soybeans oils. The results showed the presence of different inorganic compounds, mostly phases containing Ca and K, several carbonates, and specifically the compound K2Ca(CO3)2, which was identified in all catalysts. Biodiesel conversions obtained using the biochars samples had values above 66 % and for the activated biochar sample (PC700_CA) the value was 74 %. However, ash catalysts had conversions to biodiesel above 90 %. This effect was related to the high concentrations of K and Ca salts (fairchildite and buetschliite) in the ashes. Reuse tests conducted with the ash catalyst showed a significant reduction in efficiency after the second cycle, due to the partial removal of active phases containing mainly K. Calibration methods, using DTG and NMR-TD techniques, were constructed to quantify the biodiesel concentrations obtained by the catalysts. The efficiencies of the calibration methods showed better performances for the ash catalysts. In conclusion, coffee husk represents a cheap and viable source with regard to the preservation of the environment for the production of biodiesel via heterogeneous catalysis, without the need for chemical modifications. Such methods proved to be efficient for the quantification of biodiesel concentrations in liquid solutions, allowing the detection and quantification of contamination or adulteration of vegetable oil in biodiesel samples. These methods are recommended for use with other sources of oils.