Síntese Da Peneira Molecular McM-41 Derivada Da Cinza Da Casca Do Arroz

Abstract

Artigo submetido em abril de 2013 e aceito em outubro de 2013 RESUMOAs peneiras moleculares MCM-41 têm atraído grande interesse devido as suas propriedades de alta área específica, volume e diâmetro de poros controláveis. Estes materiais são aplicados em diversos ramos da indústria química como adsorventes, suportes catalíticos e catalisadores heterogêneos em vários processos. , com dimensões e volume de poros dentro das especificações de materiais mesoporosos, sendo estas prorpriedades semelhantes ao MCM-41 sintetizado com a sílica gel comercial, comprovando que a cinza da casca do arroz pode ser utilizada como fonte alternativa de sílica na síntese de peneiras moleculares do tipo MCM-41. PALAVRAS-CHAVE:MCM-41, síntese hidrotérmica, sílica, cinza da casca do arroz SYNTHESIS OF MCM-41 MOLECULAR SIEVE DERIVED FROM RICE HUSK ASH ABSTRACTMCM-41 molecular sieves attracted great interest due their properties, as high specific surface area, controllable diameter and pore volume. These materials have been applied as adsorbents, catalyst supports, and heterogeneous catalysts in various branches of the chemical industry. In this work, MCM-41 was synthesized from rice husk ash, natural and chemically treated, as alternative sources of silica, called CCA-MCM-41 and CCAL-MCM-41, respectively, with the aim of reusing this residue and produce a lower cost mesoporous material. The materials were synthesized by the hydrothermal method from a gel composition: CTAMBr 1,0 mol L -1 ; SiO 2 4,0 mol L -1 ; Na 2 O 1,0 mol L -1 ; H 2 O 200 mol L -1 ; and characterized by XRF, XRD, FT-IR and specific surface area determination by the BET method. The materials showed high specific surface area (905 m 2 g -1 ), with dimensions and pore volume within the specifications of mesoporous materials, which are proprieties similar to MCM-41 synthesized with commercial silica gel, proving that rice husk ash can be used as an alternative source of silica for the synthesis of MCM-41 molecular sieves.

Comparison of Kinetic Study of CTMA+ Removal of Molecular Sieve Ti-MCM-41 Synthesized with Natural and Commercial Silica

“…The XRD patterns of the synthesized samples are similar to MCM-41 materials reported in literature 1,10,19 . Both samples showed high intensity of peaks.…”

“…According to results of Table 1, that show the values of apparent activation energy for conversion levels from 5 to 90 %, the presence of titanium in the MCM-41 favor minor apparent activation energy values for CTMA + removal from the porous system of Ti-MCM-41 (SG) and (RHA) compared to RHA-MCM-41 and MCM-41 synthesized by Braga et al 10 and Souza et al 15 , that found values of Ea of 221 and 166 kJ mol -1 , respectively 15,17 . In previous study Fontes et al 1 observed that the increase of Ti in MCM-41 resulted in a gradual decrease apparent activation energy for CTMA + removal, which confirm the lower Ea values to the Ti-MCM-41 (SG) and (RHA) when compared to other MCM-41 of literature 18 .…”

“…The iso and nonisomorphic substitutions usually enhance catalytic activity in processes of commercial interest such as: hydrocarbon catalytic cracking isomerization, hydrodesulphurization, oxidation reactions, hydroxylation and epoxidation of aromatics, olefins and phenols 9 . Many authors [10][11][12] have used the rice husk ash (RHA) as silica source in the synthesis of various mesoporous materials (ZSM-5, MCM-41, MCM-48, SBA-15) using different extraction methods of silica. This agricultural waste has attracted great interest from researchers due to its high silicon content (>90%) of low cost that can be use as Si source in different silica based materials.…”

Some Features of Liquid Crystalline Oxadiazoles

“…The enantioselective segregation has been obtained in the smectic and nematics phases of other banana oxadiazoles, without introducing any chiral species, by a Japanese group [30]. This sort of segregation is rather important for drugs, because the stereoisomers of chiral drugs often exhibit pronounced differences in their properties, so pronounced that it is necessary to study each stereoisomer separately [31]. This is the reason why the pharmaceutical research has converged to use single enantiomers as substitutes for their racemates.…”

MCM-41 Derived from Freshwater Sponge Silica as Support for HPW Applied in the Esterification of Oleic Acid

“…As desvantagens destes precursores de sílica são o elevado custo e seu efeito tóxico ao meio ambiente. [19][20][21] No entanto, vários estudos têm mostrado a utilização de outros materiais ricos em silício (resíduos) na síntese de peneira moleculares. Chiarakorn e colaboradores 22 utilizaram cinza de casca de arroz, Zhou e colaboradores 23 utilizaram silicatos de solos e Zhu e colaboradores 24 utilizaram sílica ativa (microssílica).…”