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|Title:||Reações de etanol sobre hidrotalcitas calcinadas|
|Author:||Villanueva, Sandra Bizarria Lopes|
|Advisor:||Sprung, Renato, 1945-|
|Abstract:||Resumo: Materiais do tipo hidrotalcita MgI-xAlx(OH)2(COl)x/2.Y H20 foram sintetizados, calcinados, caracterizados e testados cataliticamente na conversão do etanol. As sínteses foram realizadas com proporções de alumínio correspondentes a valores de x variando de 0,25 e 0,33. Ambos os materiais mostraram diftatogramas típicos de hidrotalcitas, áreas superficiais BET de cerca de 50 m2g-1 e 60 m2g-I, e volumes de mesoporos de 0,16cm3g-1 e 0,38 cm3g-|
Abstract: Hydrotalcite-like compounds, Mg1-xAlx(OH)2(Col")xl2.y H20, were synthesized, calcined, characterized, and tested as catalysts for the vapor phase conversion of ethanol. Two hydrotalcite-like compounds were synthesized by varying the fraction x of aluminum in the starting solutions from 0,25 to 0,33. Both materiaIs yielded X-ray diffraction pattems typical ofhydrotalcites, with BET surface areas ofabout 50 and 60 m2g1 and mesopore volumes of 0,16 and 0,38 cm3g-1, respectively. Micropore volumes were negligible. When calcined at temperatures ranging from 500 to 1000°C, the materiaIs flrst yielded aluminum and magnesium double hydroxides for temperatures up to 800°C. By increasing the calcination temperature, the double hydroxides were progressively decomposed into magnesium hydroxide and a magnesium aluminate spinelic phase. The BET surface areas were increased up to about 200 m2g-1 and the mesopores volumes, to 0,68 cm3g-1. Catalytic tests were performed at 350°C and atmospheric pressure by passing 1,96 gIh ethanol diluted in nitrogen at a molar ratio of 1:2 through a fixed bed of calcined hydrotalcite partieles. Ethylene, acetaldehyde, ethyl ether and n-butanol were identifled as the reaction products. The ratio of ether to n-butanol was elose to one for alI the hydrotalcite samples utilized. The global yield of the condensation products, ether and nbutanol, was maximum for materiaIs calcined at 650°C, about 80%, and decreased continuously with increasing calcination temperatures. Acetaldehyde yield was maximum for materiaIs calcined at 1000°C. Total conversions of ethanol were slightly higher when using samples with higher aluminum content (x=0,33); samples calcined at 650°C yielded the highest ethanol conversion, about 14%. No conversion changes were detected over 150 minutes of reactor operation. Catalytic tests performed with magnesium oxide, obtained by calcination of synthesized magnesium hydroxide, yielded acetaldehyde and traces of ethylene. Total conversion of ethanol was typically 1 % after strong catalyst deactivation
|Appears in Collections:||FEQ - Dissertação e Tese|
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