Martes, 16 de septiembre de 2014
Mordenite

Autor: Fernandes, L. D.

A commercial Na-mordenite sample underwent ion exchange with HCl. The ion-exchanged sample was sequentially submitted to hydrothermal treatments at 823, 873 and 923 K, each followed by acid leaching of the extraframework alumina (EFAL) generated. Six mordenite samples, presenting different framework and extraframework compositions, were obtained. These samples were used to prepare bifunctional catalysts by mixing them with Pt/Al2O3 in different proportions. The generated samples presented distinct platinum contents and were tested in the hydroisomerization reaction of ethylbenzene. A maximum xylene selectivity at about 0.45 wt% of platinum was observed. Normally, the total activity increased as the platinum content increased; this effect was more pronounced in the samples which presented lower mesoporosity. The most dealuminated sample, which presented a high mesoporosity, did not show any change in activity with the increase in platinum content.

Autor: Vigil de la Villa, R.

[EN] A natural mordenite-type zeolite from Palmarito ore deposit (Cuba) was studied along the reaction with a saturated lime solution at 40 °C in order to determine its pozzolanic activity. Ca(OH)2 is an alkali activating agent that simulates the release of lime from ordinary portland cement during the hydration reaction. Formation of C–S–H-like phases with very low Ca/Si ratio (below 0.8) was observed in agreement with previous studies, however, the transformation of the original mordenite into a heulandite–clinoptilolite-type secondary zeolite was also detected. A thermodynamic approach was used to evaluate the stability of the zeolite minerals and showed that clinoptilolite is the most stable zeolite that forms under the experimental alkaline conditions. The results indicate that not all Ca2+ consumed from solution is used in the pozzolanic reaction. Calcium aluminates hydrates were not detected as products of the alkali-activated reaction.

Autor: Pinar, Ana Belén

Ferrierite synthesis from gels containing a mixture of two template molecules, in the absence of inorganic cations and in fluoride media, is described. One of them is a bulky structure-directing agent (SDA), 1-benzyl-1-methylpyrrolidinium cation (bmp), and the other one is a small organic cation acting as a co-template. We present here the results obtained with tetramethylammonium (TMA) and quinuclidinium (Qui) compounds as co-templates in a gel containing bmp cation as SDA. It has been observed that in both cases co-templates exert a marked effect on the nature of the synthesis products

Autor: Benito García, R.

[EN]: The mordenite are deposit of Los Escuellos is formed of horizontal interbedded volcanic bentonitised materials from hydromagmatic activity.

Autor: Boveri, M.

A systematic study of both acid and steam dealumination of mordenite has been carried out aiming to obtain a mordenite featuring high acid strength active sites along with a secondary mesoporous system, in order to maximize both catalytic performance and time-on-stream stability of the material in solid-acid catalyzed alkylation of benzene with 1-dodecene. Detailed assessment of the textural (XRD, N2 adsorption–desorption) and acid (FTIR of pyridine adsorption) properties of the obtained materials was performed.

It has been found that catalysts obtained by combined steam dealumination and acid washing show a dramatic increase in the intrinsic activity and a significantly lower tendency to suffer deactivation when compared to the parent zeolite and samples obtained by acid treatments. This improved behaviour of the steam-treated sample is attributed to its increased mesoporous surface area, lower acid sites concentration and less hydrophilic surface.