Produção de mordenita mesoporosa por síntese direta usando diferentes direcionadores

Abstract

In the present dissertation it was conduced the study of the mesoporous mordenite production by the direct synthesis using hydrothermal media or dry gel convertion. Activated charcoal, starch, carboxymethylcellulose and carbon black were used as mesoporosity templating. To evaluate the effect of these templates, samples were prepared with molar composition of 20 SiO2: 1 Al2O3: 6 Na2O: 600 H2O, by hydrothermal synthesis and 20 SiO2: 1 Al2O3: 4 Na2O, by dry synthesis, following procedures described in the literature and adding different amounts of templates to the synthesis gel. As reagents for the synthesis gel assay, were utilized sodium hydroxide, sodium aluminate, silica (Aerosil 200) and deionized water. The synthesis temperature was 175 ° C, while the synthesis time was 5 days and 3 days for the hydrothermal and dry method, respectively. For characterization of the samples was used X-ray diffraction (XRD), analysis by nitrogen adsorption/desorption measurements and determination of the acidity by temperature programmed desorption of ammonia (NH3-TPD). An evaluation of the samples was carried out using the n-heptane cracking reaction at 380 ° C. By X-ray diffraction, it was observed that the majority of the experiments formated of mordenite phase. The textural properties, particularly the volume of mesopores, improved in most samples synthesized in the presence of the template, however, the values obtained were lower than those defined in the literature for mesoporous materials. The samples showed only a peak of ammonia adsorption in NH3-TPD profiles, related to weak acid sites. Most samples synthesized in the presence of drivers showed an increase in the conversion of n-heptane, while the samples obtained by dry gel convertion showed higher conversion than the hydrothermally synthesized.