Primeiramente, agradecer aos meus familiares, em especial aos meus pais, que sempre me apoiaram e foram importantes para a continuidade deste trabalho. Ao Prof. Dr. Gilberto Garcia Cortez pela oportunidade e paciência na orientação necessária para a realização deste mestrado. Ao Dr. José Augusto do INPE pela disponibilização da estrutura do Laboratório Associado de Combustão e Propulsão (LCP) para a síntese dos suportes utilizados neste trabalho. A toda a equipe do LCP-INPE, em especial a Priscila Camargo que me auxiliou no desenvolvimento da metodologia da síntese dos suportes e nas análises de volumetria de nitrogênio. Ao Prof. Dr. Paulo Suzuki, pela colaboração nas análises de difratometria de raios X. À secretária Ana Beatriz, da EEL-USP, sempre muito receptiva pelo atendimento às solicitações e atenção. Aos colegas de mestrado e graduação com os quais tive a oportunidade de fazer amizade. À CAPES pelo apoio financeiro. À Escola de Engenharia de Lorena (EEL-USP) pela oportunidade concedida de realizar o mestrado. RESUMO CRIVELARO, V. M. Síntese de catalisadores baseados em vanádio suportado em aluminas de transição modificadas por metais alcalinos e avaliação catalítica na reação de desidrogenação oxidativa do propano. 2016. 129 p. Dissertação (Mestrado em Ciências)
CRIVELARO, V. M. Synthesis and catalytic evaluation of V2O5/ Nb2O5-Al2O3 catalysts modified with strontium for oxidative dehydrogenation reactions of propane. 2022. 163p. Thesis (Doctoral of
The propane oxidative dehydrogenation (ODH) reaction has been considered as an alternative method for propene production owing to its exothermic nature, which renders it environmentally friendly. The use of alkaline promoters for supported V catalysts can increase propene selectivity and partially inhibit the formation of CO and CO2. Our goal was to evaluate the promoting effect of K and Na and the support effect using gibbsite as precursor for the propane ODH reaction. Catalysts were prepared via co-impregnation of V and alkali metals on a previously prepared alumina support and were characterized using N2 adsorption-desorption, X-ray diffraction, temperature-programmed reduction, and isopropanol decomposition tests to evaluate their acid-base properties. The activity of the synthesized catalysts for the propane ODH reaction was evaluated at the O2:C3H8:He molar ratios of 5:2:4, 6:1:4, and 4:3:4. The addition of alkali metals to the V catalysts increased propane conversion and propene selectivity; moreover, both parameters increased with increasing molar fraction of O2 in the reactants. K doping increased the propene selectivity of the doped catalysts, because it inhibited a large fraction of catalytic surface acidic sites. A high molar fraction of O2 in the reactants facilitated the regeneration of the catalyst, whereas a high reoxidation rate improved catalytic activity and propene selectivity.
RESUMO -O trabalho objetivou sintetizar catalisadores V 2 O 5 /-Al 2 O 3 modificados por sódio ou potássio como promotores para a reação de desidrogenação oxidativa do propano (DOP). Foram usadas as seguintes técnicas de caracterização: volumetria de N 2 , difratometria de raios X (DRX) e redução à temperatura programada (RTP). O íon potássio foi o mais eficiente ao promover uma maior seletividade ao propeno.
The olefins product are more reactive than the corresponding alkanes, and may easily be super-oxidised into CO and CO2 in selective oxidation of alkanes. The proper balance of acid and base sites on the V-based catalyst surface plays a decisive role in limiting the complete oxidation of alkanes. Therefore, our goal was to evaluate the promoting effect of alkali metals and the support effect using boehmite as precursor for the propane oxidative dehydrogenation (ODH) reaction. Catalysts were prepared via co-impregnation of V and Na or K on a synthesized alumina support. The following characterization techniques were used: N2 adsorption-desorption, X-ray diffraction (XRD), temperature programmed reduction (TPR) and isopropanol decomposition testes to evaluate the acid-base character. The catalyst performance in the propane ODH reaction was evaluated at the O2:C3H8:He molar ratios of 5:2:4, 6:1:4, and 4:3:4. The K-doped catalysts exhibited higher propene selectivity owing to the modification of acid-base character that rendered the weaker interaction between olefinic intermediate and more basic catalyst surface. A high molar fraction of O2 of the reaction mixture minimized coke formation and a high reoxidation rate possibly increased catalytic activity and propene selectivity.
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