Avaliação de argilas regionais e obtenção de zeólita X para utilização em catálise

• Ano de defesa: 2008
• Autor(a) principal: Frederico, Carlos Wellington
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Palavras-chave em Português: Argilas; Caulim; Zéolita X; Catalisadores
• Link de acesso: http://www.repositorio.ufc.br/handle/riufc/61313

Local clays are characterized by several types of analytical techniques: chemical analysis, which showed a Si/AI ratio and the possible Si and Al substitutes as well as the exchangeable cations; scanning electron microscopy (SEM), which showed the textural properties of the clay and allowed us to qualify the types of elements present in the material; thermogravimetric analysis (TG), which was valuable in recognizing the thermal decomposition ranges as result of hygroscopic water losses and combined water, dehydration and total weight loss; cationic exchange capacity (CEC), showing a value of 121 meq for vermiculite, 140.2 and 140.8 meq for montmorillonite and 6.5 and 25.3 meq for white and gray kaolins, respectively; infrared, which showed the vibrational modes with the respective wave lengths and their correlation with the clays properties and, specially, the X-ray diffraction analyses which allowed us to identify the following phases: vermiculite-PI as RM92.36Feo.48A10.16)(A11.28Si2.72)010(OH)2(H20)6Mg], contaminated with other phases such as riqueterite, iron riqueterite, calcium carbonate and tremolite; montimorilonite as [Cao.2(A1,M9)25i4010(OH)2.4H20] contaminated with graphite; nantrolite as [Na0.33Fe2+3(Si,A1)4010(OH)2.xH20] contaminated with quartz and tricasilite; gray kaolinite-PI as [Al2(Si205)(OH)4] contaminated with muscovite; and white kaolinite-PB as [Al2(Si205)(OH)4] without any other mineral phase as contaminant. Zeolite X with structure of the type faujazite is obtained by modifying the structure of a clay, like white kaolinite-PB, by means of kaolinite calcination, adjustment of the Si/AI ration through dealuminization with sulfuric acid, hydrothermal treatment at 70 °C with sodium hydroxide, aging for 18 h followed by crystallization during 5 h. The main advantages of this process are the decrease of the work temperature (70°C) of the gel formation during the synthesis, the process being carried out at low pressure, the obtaining of only one crystallographic phase and for being an outstandingly reproductive method. This work is complemented with isonnerisation tests of noctane by using nickel and platinum catalysts supported on zeolite X, which gave rise to an average conversion value of 66.8% and whose selectivity was favourable to the cracking process for all the used catalysts except for the standard one, Pt/Y, which showed higher isomerisation. The main products obtaining by means of reaction of hydroisomerization with the catalyst Ni/NaX, which promoted the highest conversion rate were: C-(C) = 2,4-dimethylhexane with 7.6% by isomerization; E-(C) = 2- methylpentane with 7.2%, F-(C5) = isopentane with 6.1% and H-(C4) = isobutane with 5.7% by cracking.