The aim of this work was to study the hydrothermal synthesis of Si and SiAlMCM-41 performed under both autogenic pressure and refluxing conditions. XRD data showed that the MCM-41 phase may be formed by both processes and that the synthesized material in the presence of Al and/or under reflux presents the hexagonally arrangement of less ordered mesopores. However, as verified by XRD and physisorption data, the order was improved with higher synthesis times. 29 Si and 1 H-29 Si C/P MAS NMR spectra showed that a great part of the Si atoms exists as silanol groups which originate resonance peaks at-110,-100 and-91 ppm. The presence of Al atoms may generate Si(3Si, Al) and Si(2Si, 2Al) environments which might be contributing to resonance peaks at-100 and-91 ppm. The 27 Al MAS NMR spectrum of the as synthesized AlSiMCM-41 showed a resonance peak of tetrahedral framework aluminum close to 53 ppm and two others, one close to 14 ppm attributed to Al(H2O)6 +3 species and the other a weak signal close to 32 ppm attributed to pentacoordinated Al. 27 Al MAS NMR spectra of the calcined sample showed a peak at 0 ppm corresponding to an hexacoordinated extra-framework aluminum formed during calcination.
<p align="justify">A indústria de ácido fosfórico gera anualmente milhões de toneladas de fosfogesso, que é disposto em pilhas a céu aberto por não existir um destino onde haja seu consumo em grandes quantidades e que seja economicamente viável. Cada vez mais, vêm sendo realizados estudos de sua aplicação nas mais variadas áreas industriais, principalmente na construção civil. Este trabalho tem como foco o estudo da aplicação do fosfogesso na fabricação de materiais cerâmicos.</p><p align="justify">Abstract</p><p align="justify">The phosphoric acid industry annually generates millions of tons of phosphogypsum which is arranged in piles in the open because there is a destination where there is consumption in large quantities and economically feasible. Increasingly, studies have been carried out their application in various industrial areas, mainly in construction. This work focuses on the study and application of phosphogypsum in the manufacture of ceramics.</p>
Hydrothermal Synthesis of Cerium Aluminophosphate.-Molecular sieves CeAlPO-11 of composition Ce 0.04 Al 0.97 P 1.01 O 4.04 are prepared hydrothermally at 170 • C from Al(OH) 3 , H 3 PO 4 , and hydrated Ce 2 O 3 using (iPrO) 2 NH as organic template. The structure is similar to that of AlPO-11 zeolites. Incorporation of Ce 3+ into the aluminum phosphate matrix leads to an increase of the BET surface area from 104.8 m 2 /g for AlPO-11 to 188.4 m 2 /g. -(ARAUJO, A. S.; DINIZ, J. C.; SILVA, A. O. S.; MELO, R. A. A.; J. Alloys Compd. 250 (1997) 1-2, 532-535; Dep. Quim., Univ. Fed. Rio Grande do Norte, 59078 Natal, RN, Brazil; EN)
-Propane oxidation and reduction of NO to N 2 with propane under oxidative conditions on a Cu-Al-MCM-41 mesoporous molecular sieve and Cu-ZSM-5 zeolites were studied. Both types of catalysts were prepared by ion exchange in aqueous solutions of copper acetate and characterised by X-ray diffraction (XRD), nitrogen sorption measurement, diffuse reflectance ultra-violet spectroscopy (DRS-UV), diffuse reflectance infra-red Fourier transform spectroscopy (DRIFTS) of the adsorption of CO on Cu + and temperature-programmed reduction with hydrogen (H 2 -TPR). The NO reduction was performed between 200 and 500 o C using a GHSV = 42,000 h -1. H 2 -TPR data showed that in the prepared Cu-Al-MCM-41 all the Cu atoms are on the surface of the mesopores as highly dispersed CuO, which results in a decrease in specific surface area and in mesopore volume. H 2 -TPR together with DRIFTS data provided evidence that in Cu/ZSM-5 catalysts, Cu atoms are found as two different Cu 2+ cations: Cu α 2+ and Cu β
2+, which are located on charge compensation sites, and their thermo-redox properties were different from those of Cu atoms in Cu-Al-MCM-41. The specific activity of the Cu 2+ exchangeable cations in Cu-ZSM-5, irrespective of their nature, was much greater than that of the Cu 2+ in Cu-Al-MCM-41, where they are found as CuO.
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