No abstract

Tin incorporation in high-silica ZSM-12 zeolite was evaluated using different concentrations of tin and different structure-directing agents (SDA), in order to be used in the glucose isomerization reaction in fructose. The tetraethylammonium hydroxide SDA successfully formed the structure of the high silica zeolite ZSM-12; however, in this system, the addition of Sn prevented the formation of the ZSM-12 zeolite. Therefore, tetraethylammonium bromide was used as SDA, but the syntheses of high-silica ZSM-12 zeolite without and with tin incorporation were not effective. Then methyltriethylammonium chloride was used as SDA, and the high-silica ZSM-12 structure was formed only with the incorporation of tin. The samples with ZSM-12 structure and different concentrations of tin were evaluated in reaction of glucose conversion to fructose. It was found that the sample with the lowest tin content ( Sn / Si = 0 . 005 ) achieved the highest glucose conversion and the highest fructose yield.

A síntese das amostras de mordenita foram realizadas através do método hidrotérmico, utilizando dois tipos diferentes de sementes de cristalização (mordenita e ferrierita), onde foram explorados a variação de alguns parâmetros de síntese, como a razão SiO2/Al2O3 = 20, 60 e 100, e a razão OH/SiO2= 0,2, 0,3 e 0,4, em diferentes tempos de cristalização, à temperatura de 170 °C. As amostras foram caracterizadas por difratometria de raios X (DRX), análises termogravimétricas (ATG), adsorção de nitrogênio a -196 °C (BET) e dessorção à temperatura programada de amônia (DTP-NH3). Constatou-se que a utilização da razão OH/SiO2 = 0,4, em conjunto com as sementes de MOR e FER foram obtidas as amostras mais cristalinas, evidenciando o papel crucial do agente mineralizante OH- no meio.

The possibility of crystallization of ZSM-5 with high Si/Al ratio was evaluated through the combined use of crystallization seeds and organic compounds that are not conventional directing agents for ZSM-5 (ethanol, methylamine, ethylamine, propylamine, butylamine, isopropylamine and diethylamine) in order to find a less toxic and costly route of synthesis. In addition, the influence of the stirring during the crystallization step on the properties of the ZSM-5 obtained in these synthesis conditions was verified. The obtained zeolites were analyzed by X-ray diffractometry in order to understand the effects of the templates. The analyses of NH3-TPD, nitrogen adsorption, SEM, and TG/DTA were performed for the samples with better crystallinity. The procedure was successfully employed for the synthesis of MFI samples using propylamine as an alternative structure-directing agent. Its mean crystallite size ranged from 23 to 24 nm and was efficient in the cracking reaction of n-hexane.

RESUMO