Utilização de zeólitas provenientes das cinzas leves do carvão mineral de Candiota-RS como peneiras moleculares para a desidratação do etanol

Abstract

Coal is a Brazilian energy resource that has sufficient reserve to supply the national energy demand for more than 100 years. About 42.9% of the Brazilian coal reserves are located in the Candiota deposits in Rio Grande do Sul. The use of Candiota coal is currently used for the production of energy through direct combustion. However, this type of use in thermoelectric plants is not the most indicated due to the low calorific value (<3200 kcal kg-1) and the high ash content (52 to 59%) of this coal generated in these techniques. The gasification of this coal appears as an attractive option, since it allows greater efficiency in the conversion into electrical energy and reduction in the emission of sulfurous compounds and other gases harmful to the environment. The gasification process has as products the syngas, coal tar and ash and consists of the reaction of the coal with substoichiometric oxygen and steam. The ash, composed mainly of Al and Si, can be used as feedstock for the formation of zeolites. Zeolites are hydrated crystalline structures with uniform channels and cavities of regular size. The most common zeolites are aluminosilicates, which exhibit a negative charge due to the difference in valence of the O and Al atoms present in their structure.Such charges are neutralized by compensating cations, which are commonly alkaline or alkaline earth metals. The presence of these cations gives the zeolites their capacity for cation exchange. In addition, pore size and geometric selectivity allow its use in molecular sieve-type applications. Based on the above, the objective of this work was the synthesis of zeolites using the light ash obtained from the carbonization process of the Candiota/RS mineral coal as well as the application of the product obtained as molecular sieve for the separation of ethanol / water. The material synthesized was identified through XRD as zeolite X, which contains8 Ȧ pore size. With the adjustment of specific mass data in the calibration curve of the initial solutions, it was observed that the zeolitic material allowed the permeation of ethanol through its cavities due to the pore size being larger than the ethanol molecule, besides the loss of ethanol by evaporation into the environment due to its physical properties.