Análise da performance de zeólitas modificadas na adsorção seletiva e separação da mistura glicose-frutose

• Ano de defesa: 2000
• Autor(a) principal: Martinelli, Ana Luísa Saavedra
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Estadual de Maringá; Brasil; Programa de Pós-Graduação em Engenharia Química; UEM; Maringá, PR; Departamento de Engenharia Química
• Palavras-chave em Português: Frutose; Zeólitas; Análise; Glicose Frutose; Separação da mistura; Adsorção seletiva; Brasil.; Engenharias; Engenharia Química
• Link de acesso: http://repositorio.uem.br:8080/jspui/handle/1/3745

Fructose is one of the most important natural sugar found mainly in fruit and honey. It is one of the products of the sucrose hydrolysis together with its isomeric, the glucose. In a scale of sweetness it is 1,3 - 1,8 times sweeter than sucrose and 2,4 times sweeter than glucose. Because of its organoleptic and technical qualities, fructose can be used as a sucrose substitute in jams, chocolates, glacé silks and creams, biscuits, mixture for diet cakes, jellies, puddings, diet and usual candies, gums and diet soft drinks. The use of fructose started to expand as syrup with high meaning of fructose (high-fructose syrups, HFS), produced through enzymatic isomerization of glucose deriving initially from hydrolysis of corn starch. In Brazil, the most economically feasable method to produce fructose is from enzymatic inversion of sucrose. In both methods the final solution will be constituted basically of fructose and glucose. Several works and patents have proposed the separation of the glucose-fructose mixture using zeolite in the calcic and baric forms. The goal of this work was to evaluate the efficacy of the A and X zeolite exchanged with ions of calcium, barium and potassium in the selective adsorption of the fructose and separation of glucose-fructose mixture. The ionic exchanges were carried out in batch reactor under agitation for a 24 hours period. The adsorption isotherms of fructose were determined to the A and X zeolites in the sodic form and to exchange zeolite with calcium, barium and potassium ions. For the zeolite that showed the highest capacities of fructose adsorption and lower values of Kd, it was also determined the adsorption isotherms of glucose. It was observed that all the isotherms behaved like Langmuir isotherms. The maximum capacity of adsorption of fructose was lower to the zeolite of starting Na-A (110 mg fructose/g of zeolite) and Na-X (134 mg fructose/g of zeolite). Among the studied zeolite, the zeolite Ca-X showed the highest fructose adsorption capacity (791 mg de frutose/g de zeólita) and the lower glucose adsorption capacity (192 mg de frutose/g de zeólita), besides the value of Kd was relatively low compared to exchanged zeolite. Because of that, this zeolite was used in the separation of the synthetic mixture of glucose-fructose in column. Two columns, with different quantities of zeolite were tried. The chromatographic separation was made using the step type injection. From the adsorption curves of pure solutions of fructose and glucose, for both columns, were determined the medium residence times, the adsorption equilibrium constants of glucose and fructose and the degree of separation of the mixture. The results obtained were close to the ones obtained in previous works by other researchers. In both columns it was verified the selectivity in relation to the fructose. The degree of separation of the mixture was bigger in the column 2 (40 g)what evidences a higher selectivity of zeolite in relation to the fructose, but the capacity of fructose adsorption was higher in the column 1 (23 g) what can be explained by of the lower bed porosity. Because of the high degree of separation obtained by column 2, this column was used to carried out the separation of the fructoseglucose equimolar mixture. The mixture separation tests (adsorption and desorption), proved the separation of the mixture, however in a lower degree than the glucose and fructose adsorption test made in boat-load, probably, because of the synergistic effects between the molecules of the two sugar.