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S?ntese e caracteriza??o da peneira molecular MCM-41 contendo terras raras na dessulfuriza??o, utilizando tiofeno como mol?cula sondaAlves, Jos? Ant?nio Barros Leal Reis 27 May 2010 (has links)
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Previous issue date: 2010-05-27 / Mesoporous molecular sieves of MCM-41 type are considered as
promising support for metal in the refining processes of petroleum-based
materials as catalysts and adsorbents for environmental protection. In this work,
mesoporous molecular sieves MCM-41 were modified with different rare earth
ions (La, Eu e Yb) for the obtaining nanostrutured materials with catalytic
properties. The catalysts were synthesized by the hydrothermal method at
100oC for 120 h, presenting, all the samples, in the gel of synthesis molar ratio
Si/Ln = 50. The obtained materials after calcination at 500oC for 2 h were
characterized by XRD, surface area BET, TG/DTG, FTIR, and hydrothermal
stability at 700?C. The XRD analysis of the catalysts indicated that the materials
containing rare earth presented characteristic hexagonal structure of the
mesoporous materials of the type MCM-41. The TG curves showed that the
decomposition of the structural template occurs in the materials at temperatures
lower than 500oC. The samples presented variations as the specific superficial
area, average diameter of pores and thickness of the silica wall, as a function of
the nature of the rare earth impregnated in the mesoporous material.
Hydrotermal stability was evaluated through the exposition of the materials to
water vapour at 700?C. The thiophene adsorptions reach a maximum at 80% of
conversion and incorporation of the rare earths showed influence in the
process. Adsorption capacity followed the sequence: Yb-MCM-41 < La-MCM-41
< Eu-MCM-41 < MCM-41 / As peneiras moleculares mesoporosas do tipo MCM-41 s?o
consideradas promissoras como suporte para metais em processos de refino
de materiais a base de petr?leo, como catalisadores e como adsorventes para
prote??o ambiental. Neste trabalho a peneira molecular mesoporosa tipo
MCM-41 foi modificada com diferentes terras raras (La, Eu e Yb) para a
obten??o de materiais nanoestruturados com propriedades catal?ticas. Os
catalisadores foram sintetizados pelo m?todo hidrot?rmico a 100 oC por 120
horas, apresentando, todas as amostras, no gel de s?ntese raz?o molar Si/Ln =
50. Os materiais resultantes, ap?s calcina??o a 500 oC por 2 horas, foram
caracterizados por: DRX, ?rea superficial pelo m?todo de BET, TG/DTG, FTIR
e testes hidrot?rmicos a 700oC. As an?lises de DRX dos catalisadores
indicaram que os materiais contendo as terras raras apresentaram estrutura
hexagonal caracter?stica do material mesoporoso tipo MCM-41. As curvas TG
mostraram que a decomposi??o do direcionador estrutural ocorre nos materiais
em temperaturas inferiores a 500oC. As amostras apresentaram varia??es
quanto ? ?rea superficial espec?fica, di?metro m?dio de poros e espessura da
parede de s?lica, em fun??o da natureza da terra rara impregnada no material
mesoporoso. A estabilidade hidrot?rmica foi avaliada atrav?s da exposi??o dos
materiais a vapor d ?gua a 700oC. A adsor??o de tiofeno atingiu valores
m?ximos de 80% e a incorpora??o das terras raras influenciaram no processo.
A ordem crescente de capacidade de adsor??o seguiu a seguinte seq??ncia:
Yb-MCM-41 < La-MCM-41 < Eu-MCM-41 < MCM-41
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S?ntese e caracteriza??o de peneiras moleculares mesoporosas do tipo MCM-41 e AlMCM-41 a partir de fontes alternativas de s?lica e de alum?nioSilva, Marta L?gia Pereira da 01 June 2009 (has links)
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Previous issue date: 2009-06-01 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The mesoporous molecular sieves of MCM-41 and AlMCM-41 type are considered as promising support for metal in the refining processes of petroleum-based materials as catalysts and adsorbents for environmental protection. In this work the
molecular sieves MCM-41 and AlMCM-41 were synthesized by replacing the source of silica conventionally used, for quartz, an alternative and abundant, and the use of waste from the production of diatomaceous earth, an aluminum-silicate, as a source aluminum, due to abundant reserves of diatomaceous earth in the state of Rio Grande do Norte in the city of Cear?-Mirim, with the objective of producing high-value materials
that have similar characteristics to traditional commercial catalysts in the market. These materials were synthesized by the method of hydrothermal synthesis at 100 ? C for 7
days and subjected to calcination at 500 ? C for 2 hours under flow of nitrogen and air. The molecular sieves were characterized by X-ray diffraction (XRD), differential
thermal analysis (DTA) and thermogravimetric analysis (TG), adsorption of N2 (BET and BJH methods), spectroscopy in the infra red (FTIR), microscopy scanning electron (SEM) and transmission electron microscopy (TEM). The analysis indicated that the synthesized materials showed characteristic hexagonal structure of mesopores materials
with high specific surface area and sort and narrow distribution of size of pores / As peneiras moleculares mesoporosas do tipo MCM-41 e AlMCM-41 s?o consideradas promissoras como suporte para metais em processos de refino de materiais a base de petr?leo, como catalisadores e como adsorventes para prote??o ambiental. Neste trabalho foram sintetizadas as peneiras moleculares MCM-41 e AlMCM-41 atrav?s da substitui??o da fonte de s?lica convencionalmente utilizada, por quartzo, uma fonte alternativa e abundante, e pela utiliza??o do rejeito da produ??o de diatomita, um
alumino-silicato, como fonte de alum?nio, devido a abundante reserva de diatomita no estado do Rio Grande do Norte, no munic?pio de Cear?-Mirim, com o objetivo de produzir materiais de alto valor agregado que apresentam caracter?sticas semelhantes aos catalisadores comerciais tradicionalmente existentes no mercado. Estes materiais foram sintetizados pelo m?todo de s?ntese hidrot?rmica a 100 ?C por 7 dias, e
submetidos a calcina??o a 500 ?C por 2 horas sob fluxo de nitrog?nio e ar. As peneiras moleculares foram caracterizadas por difra??o de raios-X (DRX), an?lises t?rmicas diferencial (DTA) e termogravim?trica (TG), fisissor??o de N2, (M?todos de BET e BJH), espectroscopia na regi?o do infra vermelho (FTIR), microscopia eletr?nica de varredura (MEV) e microscopia eletr?nica de transmiss?o (MET). As an?lises
indicaram que os materiais sintetizados apresentaram estrutura hexagonal caracter?stica dos materiais mesoporosos, com elevadas ordena??o e ?rea superficial espec?fica e
estreita distribui??o de tamanho de poros
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Estudo da regenera??o de aditivos para catalisadores de craqueamento aluminofosfatos (ALPO s)e silicoaluminofosfatos (SAPO s)Silva, Arilson Jos? do Nascimento 12 November 2007 (has links)
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Previous issue date: 2007-11-12 / Heterogeneous catalysts such as aluminophosphate and silicoaluminophosphate, molecular sieves with AEL of ALPO-11 and SAPO-11, were synthesized by the hydrothermal method with the following molar composition: 2.9 Al +3.2 P + 3.5 DIPA
+32.5 H20 (ALPO-11); 2.9 Al +3.2 P + 0.5 Si + 3.5 DIPA +32.5 H20 (SAPO-11) starting from silica (only in the SAPO-11), pseudoboehmite, orthophosphoric acid (85%) and water, in the presence of a di-isopropylamine organic template. The
crystallization process occurred when the reactive hydrogel was charged into a vessel and autoclaved at 170?C for a period of 48 hours under autogeneous pressure. The
obtained materials were washed, dried and calcined to remove the molecular sieves of DIPA. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), thermo gravimetric differential thermal analysis (TG/DTA) and nitrogen adsorption (BET). The acidic properties were determined using adsorption of n-butylamine followed by programmed thermodessorption. This method revealed that ALPO-11 has weaker acid sites due to
structural defects, while SAPO-11 shows an acidity that ranges from weak to moderate.
However, a small quantity of strong acid sites could be detected there. The deactivation
of the catalysts was conducted by the cracking of the n-hexane in a fixed bed continuous
flow microrreator coupled on line to a gas chromatograph. The main products obtained
were: ethane, propane, isobutene, n-butane, n-pentane and isopentane. The Vyazovkin
(model-free) kinetics method was used to determine the regeneration and removal of the
organic template / Foram sintetizados catalisadores heterog?neos do tipo aluminofosfatos e silicoaluminofosfatos pelo m?todo hidrot?rmico a partir de alumina hidratada (pseudobohemita), ?cido fosf?rico 85%, s?lica gel, ?gua e diisopropilamina (DIPA)
usada como direcionador estrutural org?nico. Estes reagentes foram misturados a fim de obter g?is com as seguintes composi??es: 2.9 Al +3.2 P + 3.5 DIPA +32.5 H20; para
ALPO e 2.9 Al +3.2 P + 0.5 Si + 3.5 DIPA +32.5 H20 para SAPO. O processo de cristaliza??o ocorreu ? temperatura de 170 0C durante 48 h, quando foi poss?vel obter as fases puras para ALPO 11 e SAPO 11. Os materiais obtidos foram lavados com ?gua deionizada, secos e calcinados para remover as mol?culas do direcionador. Os materiais foram caracterizados por difra??o de raios-X (DRX), microscopia eletr?nica de varredura (MEV), espectroscopia de absor??o na regi?o do infravermelho (FTIR), an?lise t?rmica via TG/DTG e adsor??o de nitrog?nio (BET). As propriedades ?cidas
foram determinadas usando adsor??o de n-butilamina seguida de termodessor??o programada. Este m?todo revelou que o ALPO 11 possuem s?tios ?cidos fracos devido a defeitos estruturais, j? a amostra SAPO 11 apresenta uma acidez tipicamente fraca a moderada. Entretanto, uma pequena quantidade de s?tios ?cidos fortes foi detectada. A
desativa??o dos catalisadores foi conduzida pela rea??o de craqueamento do n-hexano em um microrreator catal?tico de leito fixo com fluxo cont?nuo acoplado em linha com
um cromat?grafo a g?s. Como principais produtos foram obtidos: etano, propano, isobutano, n-butano,e n-pentano, isopentano. Para determinar a regenera??o e a remo??o
do direcionador org?nico foi aplicado o m?todo cin?tico Vyazovkin (Model Free)
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S?ntese, caracteriza??o e estudo da regenera??o do silicoaluminofosfato-11 (SAPO-11) / Synthesis, characterization and study of the regeneration of silicoaluminophosphate-11 (SAPO-11)Chellappa, Thiago 03 February 2009 (has links)
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Previous issue date: 2009-02-03 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / heterogeneous catalyst such as a silicoaluminophosphate, molecular sieve with AEL (Aluminophosphate eleven) structure such as SAPO-11, was synthesized through the
hydrothermal method starting from silica, pseudoboehmite, orthophosphoric acid (85%) and water, in the presence of a di-isopropylamine organic template. For the preparation of
SAPO-11 in a dry basis it was used as reactants: DIPA; H3PO4; SiO4; Pseudoboehmite and distilled water. The crystallization process occurred when the reactive hydrogel was charged into a vessel and autoclaved at 200?C for a period of 72 hours under autogeneous pressure. The obtained material was washed, dried and calcined to remove the molecular sieves of DIPA. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), nitrogen adsorption (BET) and
thermal analysis (TG/DTG). The acidic properties were determined using adsorption of nbutylamine followed by programmed thermodessorption. This method revealed that SAPO-11 shows an acidity that ranges from weak to moderate. However, a small quantity of strong acid sites could be detected there. The deactivation of the catalysts was conducted by artificial coking followed by the cracking of the n-hexane in a fixed bed with a continuous flow micro-reactor coupled on line to a gas chromatograph. The main products obtained were: ethane, propane, isobutene, n-butane, n-pentane and isopentane. The Vyazovkin (model-free) kinetics method was used to determine the regeneration and removal of the coke / Um catalisador heterog?neo do tipo silicoaluminofosfato, peneira molecular com estrutura AEL (Aluminophosphate eleven), como o SAPO-11, foi sintetizado pelo m?todo
hidrot?rmico a partir de alumina hidratada (pseudobohemita), ?cido fosf?rico 85%, s?lica gel, ?gua e di-isopropilamina (DIPA) usada como direcionador estrutural org?nico. Para a
prepara??o de SAPO-11 em base seca foram necess?rias como reagentes: DIPA; H3PO4:; SiO4; Pseudoboehmita e ?gua destilada. O processo de cristaliza??o ocorreu ? temperatura de 200 0C durante 72 h, quando foi poss?vel obter a fase pura para o SAPO-11. O material obtido foi lavado com ?gua deionizada, seco e calcinado para remover as mol?culas do direcionador. Posteriormente a amostra foi caracterizada por difra??o de raios-X (DRX), microscopia eletr?nica de varredura (MEV), espectroscopia de absor??o na regi?o do infravermelho (FT-IR), adsor??o de nitrog?nio (BET) e an?lise t?rmica via TG/DTG. As propriedades ?cidas foram determinadas usando adsor??o de n-butilamina seguida de termodessor??o programada. Este m?todo revelou que a amostra SAPO-11 apresenta uma acidez tipicamente fraca a moderada. Entretanto, uma pequena quantidade de s?tios ?cidos fortes foi detectada. A desativa??o dos catalisadores foi conduzida pelo coqueamento artificial da amostra, seguida da rea??o de craqueamento do n-hexano em um microrreator
catal?tico de leito fixo com fluxo cont?nuo acoplado em linha com um cromat?grafo a g?s. Como principais produtos foram obtidos: etano, propano, isobutano, n-butano,e n-pentano,
isopentano. Para determinar a regenera??o e a remo??o do coque foi aplicado o m?todo cin?tico Vyazovkin (Model Free Kinetics)
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S?ntese hidrot?rmica e caracteriza??o estrutural de titanatos nanotubulares para aplica??o na captura do di?xido de carbonoSilva, Edjane Fabiula Buriti da 03 August 2012 (has links)
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Previous issue date: 2012-08-03 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Nanostructured materials have been spreading successfully over past years due its size
and unusual properties, resulting in an exponential growth of research activities devoted to
nanoscience and nanotechnology, which has stimulated the search for different methods to
control main properties of nanomaterials and make them suitable for applications with high
added value. In the late 90 s an alternative and low cost method was proposed from alkaline
hydrothermal synthesis of nanotubes. Based on this context, the objective of this work was to
prepare different materials based on TiO2 anatase using hydrothermal synthesis method
proposed by Kasuga and submit them to an acid wash treatment, in order to check the
structural behavior of final samples. They were characterized by X-ray diffraction (XRD),
scanning electron microscopy (SEM), transmission electron microscopy (TEM),
adsorption/desorption of N2, thermal analysis (TG/DTA) and various spectroscopic methods
such as absorption spectroscopy in the infrared (FT-IR), Raman spectroscopy and X-ray
photoelectron spectroscopy (XPS). All the information of characterizations confirmed the
complete conversion of anatase TiO2 in nanotubes titanates (TTNT). Observing the influence
of acid washing treatment in titanates structure, it was concluded that the nanotubes are
formed during heat treatment, the sample which was not subjected to this process also
achieved a complete phase transformation, as showed in crystallography and morphology
results, however the surface area of them practically doubled after the acid washing. By
spectroscopy was performed a discussion about chemical composition of these titanates,
obtaining relevant results. Finally, it was observed that the products obtained in this work are
potential materials for various applications in adsorption, catalysis and photocatalysis,
showing great promise in CO2 capture / Materiais nanoestruturados t?m se difundido com sucesso ao longo dos ?ltimos anos,
isso devido ao seu tamanho e propriedades incomuns, resultando em um crescimento
exponencial das atividades de investiga??o dedicadas ? nanoci?ncia e nanotecnologia, o que
tem estimulado a procura por diferentes m?todos que possam controlar as principais
propriedades dos nanomateriais a fim de adequ?-los para aplica??es de alto valor agregado.
No final da d?cada de 90 um m?todo alternativo e de baixo custo foi proposto a partir da
s?ntese hidrot?rmica alcalina de nanotubos. Baseando-se nesse contexto, o objetivo deste
trabalho foi preparar diferentes materiais ? base de TiO2 anatase utilizando o m?todo de
s?ntese hidrot?rmica proposto por Kasuga e submet?-los em seguida a um tratamento de
lavagem ?cida, com o prop?sito de verificar o comportamento estrutural das amostras finais.
Essas foram caracterizadas por difratometria de raios X (DRX), microscopia eletr?nica de
varredura (MEV), microscopia eletr?nica de transmiss?o (MET), adsor??o/dessor??o de N2,
an?lise t?rmica (ATG/ATD) e diferentes m?todos espectrosc?picos como, espectroscopia de
absor??o na regi?o do infravermelho (FT-IR), espectroscopia Raman e espectroscopia
fotoeletr?nica de raios X (XPS). O conjunto de caracteriza??es se complementou,
confirmando a transforma??o completa do TiO2 anatase de partida em titanatos nanotubulares
(TTNT). Ao observar a influ?ncia que o tratamento de lavagem ?cida exerce na estrutura do
mesmo, conclui-se que os nanotubos s?o formados durante o tratamento t?rmico, pois a
amostra que n?o foi submetida ao processo tamb?m alcan?ou uma transforma??o completa de
fase, conforme os resultados de cristalografia e morfologia, entretanto a ?rea espec?fica deles
? praticamente dobrada ap?s a lavagem ?cida. Por espectroscopia foi realizada uma minusiosa
discuss?o acerca da composi??o qu?mica desses titanatos, obtendo resultados relevantes. Por
fim, ressalta-se que os produtos obtidos nesse trabalho s?o materiais com potencial para
diferentes aplica??es em adsor??o, cat?lise e fotocat?lise, se mostrando promissores na
captura do CO2
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Estudos comparativos do ciclo de regenera??o de diferentes tipos de silicoaluminofosfatosChellappa, Thiago 22 March 2013 (has links)
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Previous issue date: 2013-03-22 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Different types of heterogeneous catalysts of the silicoaluminophosphate type, (SAPO-5, SAPO-11, SAPO-31, SAPO-34 and SAPO-41), molecular sieves with a: AFI, AEL, ATO, CHA and AFO structure, respectively, were synthesized through the hydrothermal method. Using sources such as hydrated alumina (pseudobohemita), phosphoric acid, silica gel, water, as well as, different types of organic structural templates, such as: cetyltrimethylammonium bromide (CTMABr), di-isopropylamine (DIPA), di-n- propylamine (DNPA) and tetraethylammonium hydroxide (TEOS), for the respective samples. During the preparation of the silicoaluminophosphates, the crystallization process of the samples occurred at a temperature of approximately 200 ? C, ranging through periods of 18-72 h, when it was possible to obtain pure phases for the SAPOs. The materials were furthermore washed with deionized water, dried and calcined to remove the molecules of the templates. Subsequently the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), absorption spectroscopy in the infrared region (FT-IR), specific surface area and thermal analysis via TG/DTG. The acidic properties were determined using adsorption of n-butylamine followed by programmed termodessorption. These methods revealed that the SAPO samples showed a typically weak to moderate acidity. However, a small amount of strong acid sites was also detected. The deactivation of the catalysts was conducted by artificially coking the samples, followed by n-hexane cracking reactions in a fixed bed with a continuous flow micro-reactor coupled on line to a gas chromatograph. The main products obtained were: ethane, propane, isobutene, n-butane, n-pentane and isopentane. The Vyazovkin (model-free) kinetics method was used to determine the catalysts regeneration and removal of the coke / Diferentes tipos de catalisadores heterog?neos do tipo silicoaluminofosf?tico, (SAPO-5, SAPO-11, SAPO-31, SAPO-34 e SAPO-41), peneiras moleculares com estrutura: AFI, AEL, ATO, CHA e AFO, respectivamente, foram sintetizados pelo m?todo hidrot?rmico. Utilizando-se de fontes como ? alumina hidratada (pseudobohemita), ?cido fosf?rico, s?lica gel, ?gua e diferentes tipos de direcionadores estruturais org?nicos, tais como o: brometo de cetiltrimetilam?nio (CTMABr), di-isopropilamina (DIPA), di-n-propilamina (DNPA) e hidr?xido de tetraetilam?nio (TEOS), nas respectivas amostras. Durante a prepara??o dos silicoaluminofosfatos o processo de cristaliza??o das amostras ocorreu ? temperatura de aproximadamente 200 ?C, durante per?odos que variaram de 18-72 h, quando foi poss?vel obter as fases puras dos SAPOs. Os materiais obtidos foram lavados com ?gua deionizada, secos e calcinados para a remo??o das mol?culas dos direcionadores. Posteriormente, as amostras foram caracterizadas por difra??o de raios-X (DRX), microscopia eletr?nica de varredura (MEV), espectroscopia de absor??o na regi?o do infravermelho (FT-IR), ?rea de superf?cie espec?fica e an?lise t?rmica via TG/DTG. As propriedades ?cidas foram determinadas usando adsor??o de n-butilamina seguida de termodessor??o programada. Esses m?todos revelaram que ?s amostras dos SAPOs apresentaram uma acidez tipicamente fraca a moderada. Entretanto, uma pequena quantidade de s?tios ?cidos fortes foi tamb?m detectada. A desativa??o dos catalisadores foi conduzida pelo coqueamento artificial das amostras, seguidas das rea??es de craqueamento do n-hexano em um microrreator catal?tico de leito fixo com fluxo cont?nuo acoplado em linha com um cromat?grafo a g?s. Como principais produtos foram obtidos: etano, propano, isobutano, n-butano, n-pentano e isopentano. Para determinar a regenera??o do catalisador e a remo??o do coque foi aplicado o m?todo cin?tico Vyazovkin (Model Free Kinetics) / 2020-02-01
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Avalia??o da s?ntese e caracteriza??o de ze?lita ZSM-5 ausente de direcionador org?nico estruturalCaldeira, Vin?cius Patr?cio da Silva 25 February 2011 (has links)
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Previous issue date: 2011-02-25 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The catalytic processes play a vital role in the worldwide economy, a business that
handles about US$ 13 billion per year because the value of products depends on the catalytic
processes, including petroleum products, chemicals, pharmaceuticals, synthetic rubbers and
plastics, among others. The zeolite ZSM-5 is used as catalyst for various reactions in the area
petrochemical, petroleum refining and fine chemicals, especially the reactions of cracking,
isomerization, alkylation, aromatization of olefins, among others. Many researchers have
studied the hydrothermal synthesis of zeolite ZSM-5 free template and they obtained
satisfactory results, so this study aims to evaluate the hydrothermal synthesis and the
physicochemical properties of ZSM-5 with the presence and absence of template compared
with commercial ZSM-5. The methods for hydrothermal synthesis of zeolite ZSM-5 are of
scientific knowledge, providing the chemical composition required for the formation of
zeolitic structure in the presence and absence of template. Samples of both zeolites ZSM-5 in
protonic form were obtained by heat treatment and ion exchange, according to procedures
reported in the literature. The sample of commercial ZSM-5 was acquired by the company
Sentex Industrial Ltda. All samples were characterized by XRD, SEM, FTIR, TG / DTG /
DSC, N2 adsorption and desorption and study of acidity by thermo-desorption of probe
molecule (n-butylamine), in order to understand their physicochemical properties. The
efficiency of the methods applied in this work and reported in the literature has been proved
by well-defined structure of ZSM-5. According as the evaluation of physicochemical
properties, zeolite ZSM-5 free template becomes promising for application in the refining
processes or use as catalytic support, since its synthesis reduces environmental impacts and
production costs / Os processos catal?ticos desempenham um papel vital na economia mundial, um
neg?cio que movimenta aproximadamente US$13 bilh?es por ano, pois o valor dos produtos
depende dos processos catal?ticos, incluindo os produtos petrol?feros, qu?micos,
farmac?uticos, borrachas sint?ticas e pl?sticos, entre outros. A ze?lita ZSM-5 ? utilizada como
catalisador em rea??es nas ?reas petroqu?mica, petrol?fera e qu?mica fina, destacando-se as
rea??es de craqueamento, isomeriza??o, alquila??o, aromatiza??o de olefinas, entre outras.
Muitos pesquisadores t?m estudado a s?ntese hidrot?rmica da ze?lita ZSM-5 ausente de
direcionador org?nico estrutural e obtiveram resultados satisfat?rios, assim, este estudo visa
avaliar a s?ntese hidrot?rmica e as propriedades f?sico-qu?micas da ZSM-5 com a presen?a e
aus?ncia de direcionador org?nico estrutural, em compara??o com ZSM-5 comercial. Os
m?todos para a s?ntese hidrot?rmica da ze?lita ZSM-5 s?o de conhecimento cient?fico,
fornecendo a composi??o qu?mica necess?ria para a forma??o da estrutura zeol?tica em
presen?a e aus?ncia de direcionador org?nico estrutural. As amostras de ambas as ze?litas
ZSM-5 na forma prot?nica foram obtidas atrav?s de tratamentos t?rmicos e troca i?nica, de
acordo com procedimentos relatados na literatura. A amostra de ZSM-5 comercial foi
concedida pela empresa Sentex Industrial Ltda. Todas as amostras foram caracterizadas por
DRX, MEV, FTIR, TG/DTG/DSC, Adsor??o e dessor??o de N2 e estudo da acidez por
termodessor??o de mol?cula sonda (n-butilamina), a fim de compreender suas propriedades
f?sico-qu?micas. A efici?ncia dos m?todos aplicados no presente trabalho e relatados na
literatura foi comprovada pela estrutura bem definida da ze?lita ZSM-5. Conforme a
avalia??o das propriedades f?sico-qu?micas, a ze?lita ZSM-5 ausente de direcionador org?nico
torna-se promissora para aplica??o em processos de refino ou utiliza??o como suporte
catal?tico, visto que, sua s?ntese reduz os impactos ambientais e custos de produ??o
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Obten??o de ferrita de cobalto atrav?s de dois m?todos de s?ntese: m?todo de complexa??o combinando EDTA/Citrato e m?todo hidrot?rmico / Obtaining cobalt ferrite through two synthesis methods: Complexation Method Conbining EDTA/Citrate and Hydrothermal MethodMedeiros, Indira Aritana Fernandes de 17 December 2013 (has links)
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Previous issue date: 2013-12-17 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / In this work it was synthesized and characterized the cobalt ferrite (CoFe2O4) by
two methods: complexation combining EDTA/Citrate and hydrothermal investigating the
influence of the synthesis conditions on phase formation and on the crystallite size. The
powders were mainly characterized by x-ray diffraction. In specific cases, it was also used
scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), x-ray
fluorescence (XRF) and isotherms of adsorption and desorption of nitrogen (BET method).
The study of the crystallite size was based on the interpretation of x-ray diffractograms
obtained and estimated by the method of Halder-Wagner-Scherrer and Langford. An
experimental design was made in order to assist in quantifying the influence of synthesis
conditions on the response variables. The synthesis parameters evaluated in this study were:
pH of the reaction medium (8, 9 and 10), the calcination temperature (combined complexation
method EDTA/Citrate 600?C, 800?C and 1000?C), synthesis temperature (hydrothermal
method 120?C, 140?C and 160?C), calcination time (combined complexation method
EDTA/Citrate - 2, 4 and 6 hours) and time of synthesis (hydrothermal method 6, 15 and 24
hours). By the hydrothermal method was possible to produce mesoporous powders with high
purity, with an average crystallite size up to 7 nm, with a surface area of 113.44 m?/g in the
form of pellets with irregular morphology. By using the method of combined complexation
EDTA/Citrate, mesoporous powders were produced with greater purity, crystallite size up to
22nm and 27.95 m?/g of surface area in the form of pellets with a regular morphology of
plaques. In the experimental design was found that the hydrothermal method to all the studied
parameters (pH, temperature and time) have significant effect on the crystallite size, while to
the combined complexation method EDTA/Citrate, only temperature and time were
significant / Neste trabalho foi sintetizada e caracterizada a ferrita de cobalto (CoFe2O4)
atrav?s dos m?todos complexa??o combinada EDTA/Citrato e hidrot?rmico, investigando a
influ?ncia das condi??es de s?ntese na forma??o da fase e no tamanho m?dio de cristalito. Os
p?s foram caracterizados principalmente por difra??o de raios-x. Em casos espec?ficos,
tamb?m foi utilizado microscopia eletr?nica de varredura (MEV), espectroscopia de energia
dispersiva (EDS), fluoresc?ncia de raios-x (FRX) e isotermas de adsor??o e dessor??o de
nitrog?nio (M?todo BET). O estudo do tamanho de cristalito foi baseado na interpreta??o dos
difratogramas de raios-x obtidos e estimado atrav?s do m?todo de Halder-Wagner-Langford
(HWL) e de Scherrer. Um planejamento experimental foi realizado com a finalidade de
auxiliar na quantifica??o da influ?ncia das condi??es de s?ntese nas vari?veis-resposta. Os
par?metros de s?ntese avaliados neste trabalho foram: pH do meio reacional (8, 9 e 10),
temperatura de calcina??o (m?todo de complexa??o combinando EDTA/Citrato 600?C,
800?C e 1000?C), temperatura de s?ntese (m?todo hidrot?rmico 120?C, 140?C e 160?C),
tempo de calcina??o (m?todo de complexa??o combinando EDTA/Citrato 2, 4 e 6 hrs) e
tempo de s?ntese (m?todo hidrot?rmico 6, 15 e 24 hrs). Pelo m?todo hidrot?rmico foi
poss?vel produzir p?s mesoporosos com elevado grau de pureza, com tamanho m?dio de
cristalito de at? 7nm, com ?rea superficial de 113,44m?/g e na forma de aglomerados com
morfologia irregular. Ao se utilizar o m?todo de complexa??o combinando EDTA/Citrato
foram produzidos p?s mesoporosos com maior pureza, cristalitos com at? 22nm de tamanho,
27,95m?/g de ?rea superficial e na forma de aglomerados com morfologia regular de placas.
No planejamento experimental foi constatado que no caso do m?todo hidrot?rmico todos os
par?metros estudados (pH, Temperatura e tempo) apresentam efeito significativo no tamanho
de cristalito, enquanto que, para o m?todo de complexa??o combinando EDTA/Citrato,
apenas a temperatura e o tempo foram significativos / 2020-01-01
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Estudo de titanatos nanoestruturados obtidos por tratamento hidrot?rmico de ?xido de tit?nio em meio alcalino / Studies on nanostructured titanates obtained by alkali hydrothermal treatment of titanium oxideMorgado J?nior, Edisson 24 August 2007 (has links)
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Previous issue date: 2007-08-24 / TiTanate NanoTubes (TTNT) were synthesized by hydrothermal alkali treatment of TiO2 anatase followed by repeated washings with distinct degrees of proton exchange. TTNT samples with different sodium contents were characterized, as synthesized and after heattreatment (200-800?C), by X-ray diffraction, scanning and transmission electron microscopy, electron diffraction, thermal analysis, nitrogen adsorption and spectroscopic techniques like FTIR and UV-Vis diffuse reflectance. It was demonstrated that TTNTs consist of trititanate structure with general formula NaxH2−xTi3O7?nH2O, retaining interlayer water in its multiwalled structure. The removal of sodium reduces the amount of water and contracts the interlayer space leading, combined with other factors, to increased specific surface area and mesopore volume. TTNTs are mesoporous materials with two main contributions: pores smaller than 10 nm due to the inner volume of nanotubes and larger pores within 5-60 nm attributed to the interparticles space. Chemical composition and crystal structure of TTNTs do not depend on the average crystal size of the precursor TiO2-anatase, but this parameter affects significantly the morphology and textural properties of the nanostructured product. Such dependence has been rationalized using a dissolution-recrystallization mechanism, which takes into account the dissolution rate of the starting anatase and its influence on the relative rates of growth and curving of intermediate nanosheets. The thermal stability of TTNT is defined by the sodium content and in a lower extent by the crystallinity of the starting anatase. It has been demonstrated that after losing interlayer water within the range 100-200?C, TTNT transforms, at least partially, into an intermediate hexatitanate NaxH2−xTi6O13 still retaining the nanotubular morphology. Further thermal transformation of the nanostructured tri- and hexatitanates occurs at higher or lower temperature and follows different routes depending on the sodium content in the structure. At high sodium load (water washed samples) they sinter and grow towards bigger crystals of Na2Ti3O7 and Na2Ti6O13 in the form of rods and ribbons. In contrast, protonated TTNTs evolve to nanotubes of TiO2(B), which easily convert to anatase nanorods above 400?C. Besides hydroxyls and Lewis acidity typical of titanium oxides, TTNTs show a small contribution of protonic acidity capable of coordinating with pyridine at 150?C, which is lost after calcination and conversion into anatase. The isoeletric point of TTNTs was measured within the range 2.5-4.0, indicating behavior of a weak acid. Despite displaying semiconductor characteristics exhibiting typical
absorption in the UV-Vis spectrum with estimated bandgap energy slightly higher than that of its TiO2 precursor, TTNTs showed very low performance in the photocatalytic degradation of cationic and anionic dyes. It was concluded that the basic reason resides in its layered titanate structure, which in comparison with the TiO2 form would be more prone to the so undesired electron-hole pair recombination, thus inhibiting the photooxidation reactions. After calcination of the protonated TTNT into anatase nanorods, the photocatalytic activity improved but not to the same level as that exhibited by its precursor anatase / Titanatos nanoestruturados, particularmente TiTanatos NanoTubulares (TTNT), foram sintetizados por tratamento hidrot?rmico alcalino de TiO2-anat?sio seguido de repetidas lavagens com diversos graus de troca prot?nica. Amostras de TTNT com diferentes teores de s?dio foram caracterizadas na forma de p? seco e ap?s calcina??o (200-800?C) por difra??o de raios-X, microscopia eletr?nica de varredura e transmiss?o, difra??o de el?trons, an?lise t?rmica, adsor??o de nitrog?nio e t?cnicas espectrosc?picas de infravermelho e de reflet?ncia
difusa no UV-Vis?vel. Demonstrou-se que tais materiais de paredes multilamelares s?o trititanatos de f?rmula geral NaxH2−xTi3O7?nH2O, retendo ?gua entre as lamelas. A remo??o de s?dio da estrutura reduz a quantidade de ?gua contraindo o espa?o interlamelar levando, combinado a outros fatores, ao aumento da ?rea e do volume de poros espec?ficos. Os TTNTs s?o materiais mesoporosos com duas contribui??es principais: poros menores que 10 nm devido ao volume interno dos nanotubos e poros entre 5 e 60 nm devido aos espa?os interpart?cula. A composi??o qu?mica e a estrutura cristalina do TTNT n?o dependem do tamanho de cristalito do TiO2-anat?sio precursor, todavia este par?metro afeta significativamente a morfologia e as caracter?sticas texturais do produto nanoestruturado. Tal depend?ncia foi racionalizada atrav?s de um mecanismo de dissolu??o-recristaliza??o que leva em conta a velocidade de dissolu??o do TiO2 de partida e sua influ?ncia sobre a taxa de crescimento de nanofolhas intermedi?rias em rela??o ? taxa de seu curvamento a nanotubos. A estabilidade t?rmica do TTNT ? definida pelo teor de s?dio e em pequena extens?o pelo tipo de anat?sio de partida. Foi demonstrado que o TTNT ap?s perder a ?gua intercalada entre 100 e 200?C se transforma pelo menos parcialmente num hexatitanato NaxH2−xTi6O13 intermedi?rio ainda nanotubular. A transforma??o t?rmica do tri- e hexatitanato nanoestruturados ocorre em maior ou menor temperatura e segue diferentes rotas dependendo do teor de s?dio. No caso de alto s?dio sinterizam e crescem at? grandes cristais de Na2Ti3O7 e Na2Ti6O13 na forma de bast?es e fitas acima de 600?C. No caso da amostra protonizada evoluem para nanotubos de TiO2(B) que facilmente se convertem em nanobast?es de anat?sio acima de 400?C. Al?m de hidroxilas e acidez de Lewis t?picos dos ?xidos de tit?nio, os TTNTs apresentam uma pequena contribui??o de acidez prot?nica capaz de se coordenar com a piridina a 150?C, e que ? perdida ap?s sua calcina??o e transforma??o ? anat?sio. O ponto isoel?trico do TTNT variou dentro da faixa 2,5- 4,0, indicando o comportamento de um ?cido fraco. Apesar de se revelar um semicondutor exibindo banda de absor??o t?pica no espectro de UV-vis?vel com energia de bandgap ligeiramente superior ao do respectivo TiO2-anat?sio precursor, os TTNTs apresentaram baixo desempenho fotocatal?tico na degrada??o de corantes cati?nico e ani?nico. Concluiu-se que a causa fundamental reside em sua estrutura de titanato lamelar que, em rela??o ? forma TiO2, apresentaria maior probabilidade de recombina??o do par el?tron-lacuna (e-/h+), inibindo as rea??es de fotoxida??o. A transforma??o do TTNT prot?nico ? nanobast?es de anat?sio melhorou a atividade fotocatal?tica, por?m ainda sem atingir o mesmo desempenho do TiO2-anat?sio precursor
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