Síntese, caracterização e aplicação de catalisadores mistos contendo cobalto e cobre

AUTOR(ES)

Daniela dos Santos Barbalho

DATA DE PUBLICAÇÃO

2007

RESUMO

Studies on the use of catalysts have been directed to develop new processes taking into consideration the economic point of view (for example, substitution for cheaper raw materials) as well as the green chemistry aspects. The majority of supported catalysts is prepared by the impregnation method of the metallic salt over a material of high specific surface area (support). Afterward, the material undergo calcination, where occurs the metallic oxide attachment on the support surface. Typically, these catalysts are heterogeneous. Some basic properties of the catalysts are extremely important. One of them is that it does not change either the equilibrium composition or the equilibrium constant. Another property is that they are specific and selective for the reaction of interest. A catalyst does not have stoichiometric relation with the formed products. In general, the amount of catalyst necessary to run a reaction is small. Moreover, the catalyst decreases the energy of activation of a reaction. Its application in syntheses is increasing quickly, as for instance in esterification reactions (ethanol + acetic acid  ethyl acetate + water). Because of the low equilibrium constant value for that reaction, there is a great need to accelerate that process. In order to achieve better results, one should remove the water or work with excess reagents. The efficient withdrawal of the water needs a high rate of the reaction, that is, a very active catalyst such as sulfuric acid should be used. The target of this work is to prepare and to examine the efficiency of catalysts based on cobalt and copper oxides (in three mass ratios: 1%; 5%; and 10%) supported on silica or alumina, for the esterification reaction of acetic acid with ethanol. The catalysts were characterized by XRD, FTIR and DRIFTS. The catalytic tests were monitored by GC/FID. It was observed up to 70% conversion for ethyl acetate. It was also studied the leaching process of the metals and their relation with the conversion.

ASSUNTO(S)

catalisadores óxidos metálicos quimica inorganica lixiviação esterificação

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