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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Synthesis And Characterization Of Co-pb/sba-15 Mesoporous Catalysts

Akca, Burcu 01 September 2006 (has links) (PDF)
Co and Pb are soft oxides, making them useful in partial oxidation catalysis. But it is difficult to prepare high surface area, nanometer size particles due to the low melting point of Pb. In the present study, SBA-15 samples are incorporated with Co and/or Pb at different weight loadings to provide a controlled geometry in nanometer scale via using direct synthesis method. The characterization of the synthesized samples was done by XRD, N2 adsorption isotherms, TEM images and XPS analysis. The increase in the metal loading in SBA-15 causes a decrease in the BET surface area due to the filling of pores with metal atoms. No characteristic peaks of metal oxide was observed up to 15 wt %Pb loading into SBA-15 in the large angle XRD pattern indicating that metal particles are dispersed in the SiO2 structure without accumulating and forming crystals. However, 20 wt%Pb loaded SBA-15 showed more appreciable characteristic peaks, indicating appreciable quantities of crystallites of metal oxide on the surface of silica. The introduction of high amount of cobalt and lead oxides to SBA-15 resulted in the loss of long range order of pores according to the low angle XRD patterns. The hexagonal structure of pores of SBA-15 was v confirmed by TEM images for all samples. XPS analysis indicated that binding energies of O 1s and Si 2p are almost similar in Co or Pb loaded samples, while mixed oxide loaded samples showed slightly higher binding energies which means the structure grows into a different type.
72

Synthesis Of Sba-15 And Incorporation Of Cobalt Oxide Nanoparticles

Sen, Ebubekir 01 October 2006 (has links) (PDF)
Mesoporous materials attracted great interest due to their huge surface area and adjustable pore sizes. One of the important mesoporous materials is SBA-15 and has larger pore size, hydrothermal stability and thicker walls than other mesoporous materials. In this study, SBA-15 is synthesized by using sol-gel technique and cobalt oxide nanoparticles are incorporated in mesochannels by direct method. SBA-15 was produced from the self-assembly of non-ionic triblock co-polymer (Pluronic 123) and tetra ethyl ortho silicate (TEOS). Then cobalt chloride and cobalt nitrate were added at different loading ratios with two different addition sequences / after polymer and after TEOS. The loading ratios are in Si/Co mols and these ratios are / 15, 10, 5, 3, 1.5, 1 and 0.75 in increasing cobalt amount loaded. Characterization of the produced materials was performed by Powder X-Ray Diffraction (PXRD), Infrared (FTIR) analysis. Nitrogen Phisisorption measurements (BET and BJH Methods) were used to examine the textural properties of produced materials. By means of Transmission Electron Microscopy (TEM) the micro structures of materials were investigated. From the PXRD studies it is observed that the long range order of pores is preserved at even high loading amounts for cobalt chloride addition after TEOS. Co3O4 (JCPDS card no: 42-1467) crystallites are observed for Si/Co mol loading ratios 3, 1.5, 1 and 0.75. Above these loading ratios cobalt oxide is highly dispersed in SBA-15-type structure. FTIR studies revealed the formation of condensed silica network. From the Nitrogen Phisisorption measurements it is observed that addition of cobalt salt decreases the BET surface area of produced materials. All Nitrogen Adsorption-Desorption Isotherms are Type-IV, and has H-1 hysteresis which is a fulfillment of mesoporous structures according to IUPAC classification. BET surface area of samples loaded with cobalt chloride after TEOS possessed higher surface area than other samples. TEM images proved that at loading ratios above 3 there were not any cobalt oxide nanoparticles, cobalt oxide is highly dispersed on silica surface whereas at loading ratios 3 and below there were cobalt oxide nanoparticles embedded in the mesochannels for the samples prepared by addition of cobalt chloride after TEOS.
73

Methane Activation Via Bromination Over Sulfated Zirconia/sba-15 Catalysts

Degirmenci, Volkan 01 November 2007 (has links) (PDF)
Methane activation with bromine followed by the condensation of the methyl bromide into higher hydrocarbons or oxygenates is a novel route. However, the selective production of monobrominated methane (CH3Br) at high conversions is a crucial prerequisite. A reaction model was developed according to the kinetic data available in the literature and thoroughly studied to investigate the optimum reactor conditions for selective methane bromination in gas phase. It was concluded that at high methane (&gt / 90%) conversions dibromomethane synthesis was favored at high selectivity (~90%) under the following conditions: T=330 &deg / C, Br:CH4 = 3. Sulfated zirconia included SBA-15 catalysts were prepared and characterized for the catalytic methane activation via bromination. The SBA-15 sol-gel preparation technique was followed and the zirconium was added during the preparation in the form of ZrOCl2&middot / 8H2O with 5-30 mol % ZrO2 with respect to the SiO2 content simultaneously with the silicon source (TEOS). The catalysts were sulfated in 0.25 M H2SO4 solution. The zirconium contents of the catalysts were determined by elemental analysis and 15 wt. % Zr was determined as the highest amount. XRD analysis showed the crystalline zirconia peaks only for high zirconia loadings (&gt / 25 mol % ZrO2) indicating the good distribution of Zr in silica framework at lower loadings. BET surface areas of the sulfated catalysts are in the range of 313-246 m2/g. The porous structures of the catalysts were determined by TEM pictures, which revealed that the increase in Zr content decreased the long range order of pore structure of SBA-15 in agreement with XRD results. The acidities of the catalysts were determined by 1H MAS NMR experiments. Br&oslash / nsted acidity was identified by a sharp 1H MAS NMR line at 10.6 ppm. The highest acidity was observed at 5.2 wt. % Zr loading according to 1H MAS NMR experiments. 29Si MAS NMR analysis showed the formation of Si-O-X linkages (X=H, Zr). Further characterization of Br&oslash / nsted acidity was performed by FT-IR spectroscopy of adsorbed CO at 82 K. The analysis revealed that the Br&oslash / nsted acidity of sulfated catalysts were similar to the acid strength of the conventional sulfated zirconia. In TPD experiments, the basic molecule isopropylamine (IPAm) was adsorbed and decomposition temperature of IPAm was monitored. The temperature decreased from 340 &deg / C to 310 &deg / C in sulfated catalysts, indicating the acidic character of these samples. Catalytic methane bromination reaction tests were performed in a quartz tubular reactor. The results showed that 69% methane conversion was attainable over SZr(25)SBA-15 catalyst at 340 &deg / C. The liquid 1H NMR measurements of the products revealed that &gt / 99% methyl bromide selectivity was achieved.
74

Synthesis Of Mesoporous Catalysts And Their Performance In Pyrolysis Of Polyethylene

Aydemir, Bugce 01 December 2010 (has links) (PDF)
Plastic materials are widely used throughout the world due to their low prices and easy processing methods. A serious problem of environmental pollution is brought with the widespread use of these materials due to their non-biodegradabilty. For this reason, plastic materials are degraded into lower molecular weight liquid and gaseous products which are potential raw materials and fuels for petrochemical industry. The use of catalysts enhances the formation of more valuable hydrocarbons at lower reaction temperatures and residence times. In this study, aluminum containing MCM-41 and tungstophosphoric acid (TPA) loaded SBA-15 materials were synthesized by impregnation of Al and TPA into hydrothermally synthesized MCM-41 and SBA-15, respectively to be used in catalytic degradation of polyethylene. Al was incorporated into MCM-41 framework with different Al/Si ratios using aluminum triisopropylate as the aluminum source and TPA was incorporated to the porous framework of SBA-15 with different W/Si ratios, using tungstophosphoric acid hydrate as the acid source. From XRD analysis, it was observed that introducing acidic compounds did not cause deformations in the regularity and by EDS analysis, it was found out that at lower loadings, acidic compounds were introduced more effectively for MCM-41 materials. Nitrogen adsorption-desorption isotherms showed that the synthesized materials exhibited type IV isotherms. SEM and TEM pictures showed the hexagonal regularly ordered structure of SBA-15 and MCM-41 materials. FTIR analysis of the pyridine adsorbed synthesized materials revealed the existence of Lewis and Br&oslash / nsted acid sites in the synthesized materials. From TGA analysis it was observed that aluminum impregnated MCM-41 samples reduced the temperature of the degradation reaction significantly and TPA loaded SBA-15 samples reduced activation energy of the reaction effectively. In the degradation reaction system, non-catalytic and catalytic degradation experiments of polyethylene were performed. In non-catalytic degradation and catalytic degradation reactions carried out using aluminum containing MCM-41 materials, selectivity of C3 and C4 hydrocarbon gases was high and in catalytic degradation reactions carried out using TPA impregnated SBA-15 materials, selectivity of ethylene was high. In the liquid analysis of non-catalytic degradation reactions, it was observed that the product distribution was mainly composed of hydrocarbons greater than C18. The use of aluminum loaded MCM-41 and TPA loaded SBA-15 materials resulted in a liquid product distribution in the range of C5-C14, which is the hydrocarbon range of gasoline fuel.
75

Surface Functionalization Of Sba - 15 Particles For Amoxicillin Delivery

Sevimli, Filiz F. 01 September 2011 (has links) (PDF)
There are several studies in order to control drug delivery, decrease the toxicity of drugs and also for novel biomedical applications. It is necessary to be able to control the release of the drug within the body by using drug delivery systems. Mesoporous silica compounds have only been discovered twenty years ago and they have already attracted many researchers to study these materials for several applications. SBA-15 particles have a highly ordered regular structure and are a good matrix for guest-host applications. The aim of this study is to be able to address whether the surface functionalization of SBA-15 samples would improve the loading of a drug into these particles. The synthesized SBA-15 particles were surface functionalized by post - grafting synthesis method in order to be used as carrier materials for drug delivery. Amoxicillin was used as a model drug. These mesoporous materials have been characterized using X-ray diffraction (XRD), small-angle X-ray spectroscopy (SAXS), fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), N2 adsorption/ desorption, solid-state silicon nuclear magnetic resonance (Si-NMR), high-performance liquid chromatography (HPLC), ultra-violet (UV) spectroscopy, elemental and thermo gravimetric analysis (TGA). The effect of concentration difference and the type of alkoxysilanes used for the functionalization have been discussed in terms of loading amoxicillin and controlling the delivery. Drug delivery systems have many further applications that still need to be investigated in areas such as neurosciences, cancer and biomedical engineering.
76

Hydrogen Generation From Conventional Fuels Over Mesoporous Mixed Oxide Catalysts Under Time Interrupted Reaction Conditions

Can, Mukaddes 01 April 2011 (has links) (PDF)
In this study, catalytic activity of the Co and/or Pb-SBA-15 mesoporous catalysts in methane partial oxidation reaction was investigated. By using sol-gel, incipient wetness impregnation and post grafting method, SBA-15 samples are incorporated with Co and/or Pb at different weight loadings to provide a controlled geometry in nanometer scale. The characterization of the synthesized samples was done by XRD, N2 adsorption isotherms, FTIR, TEM images, Raman and XPS analysis. In the present study also, gas phase methane partial oxidation modeling and the synthesizing of mesoporous SBA-15 silica with different pore sizes were investigated. For the samples prepared by sol-gel method, XRD analysis showedthat cobalt exists in the form of Co3O4and Pb exist in the form of PbO. BET surface areas of the Co loaded catalysts are in the range of 479.5-640.1 m2/g. However, in Pb loaded samples, higher metal loading decrease the surface area up to 4.63 m2/g. Considering the both Co and Pb containing bi-metallic samples, TEM and BET results revealed that the ordered hexagonal mesostructure was fully destroyed. The samples prepared by incipient wetness impregnation and post grafting method characterized by using BET, TEM, Raman and XPS analysis. According to the BET results all the samples show ordered mesostructure in agreement with TEM results for all Co and/or SBA-15 mesoporous samples. TEM results also revealed that, the Co(5%) Pb(5%)-SBA-15 catalyst prepared by incipient wetness impregnation method possess big cobalt and lead oxide crystallines on the mesoporous structure. Raman analysis results indicated that cobalt exist in Co3O4 form. According to XPS results all samples containing cobalt include Co3O4. The partial oxidation of methane was carried out in a fixed bed flow-type reactor in a temperature range of 50&ndash / 850&deg / C under atmospheric pressure.According to the reaction test results, the 0.5%Rh-Co-SBA15 catalyst shows the highest methane conversion (82%) and H2 selectivity. The non-precious metal show lower reactivities, addition of Pb to the Co-SBA-15 catalyst increases the catalytic activity and decrease the H2 production temperature.
77

En enskild ranking : Hur påverkar den employer branding?

Lillhage, Henrik, Hjelm, Marcus January 2014 (has links)
The amount of prizes, awards and rankings are increasing in today's society. Therefore, it is interesting to look at how these affects companies and their work with employer branding. This thesis is designed to investigate whether there is one ranking in particular that affect companies and how much it affects them. Comparing these with a prize in Japan, taking cultural differences into account, gives us a clear answer. / Mängden priser, utmärkelser och rankingar ökar i dagens samhälle. Därför är det inressant att se till hur dessa påverkar företag och deras arbete med employer branding. Denna uppsats är designad för att udnersöka ifall en specifik ranking påverkar detta arbete och till vilken grad. Det jämförs även med ett pris i Japan där vi med hjälp av kulturella förklaringar finner svaret vi letar efter.
78

S?ntese e caracteriza??o de materiais mesoporosos para a captura de CO2: influ?ncia do ?xido de n?quel / Synthesis and characterization of mesoporous materials for CO2 capture: influence of nickel oxide. thesis of doctorate

Nascimento, Alexsandra Rodrigues do 23 September 2014 (has links)
Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-01-20T21:00:39Z No. of bitstreams: 1 AlexsandraRodriguesDoNascimento_TESE.pdf: 3128857 bytes, checksum: db683b893d3db23b5af91852c4aed0e3 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-01-21T20:23:04Z (GMT) No. of bitstreams: 1 AlexsandraRodriguesDoNascimento_TESE.pdf: 3128857 bytes, checksum: db683b893d3db23b5af91852c4aed0e3 (MD5) / Made available in DSpace on 2016-01-21T20:23:04Z (GMT). No. of bitstreams: 1 AlexsandraRodriguesDoNascimento_TESE.pdf: 3128857 bytes, checksum: db683b893d3db23b5af91852c4aed0e3 (MD5) Previous issue date: 2014-09-23 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / Diversos materiais est?o atualmente em estudo para o processo de captura de CO2, a exemplo dos ?xidos met?licos e ?xidos met?licos mistos, ze?litas, materiais carbon?ceos, estruturas metal-org?nicas (MOF?s), organos?lica e superf?cies de s?lica modificadas. Neste trabalho, analisou-se a capacidade de adsor??o de CO2 em materiais mesoporosos de diferentes estruturas, como o MCM-48 e SBA-15, sem impregna??o e impregnados com n?quel nas propor??es 5 %, 10 % e 20 % (m/m), denominados como 5Ni-MCM-48, 10NiMCM-48, 20Ni-MCM-48 e 5Ni-SBA-15, 10Ni-SBA-15, 20Ni-SBA-15. Os materiais foram caracterizados atrav?s das an?lises de difra??o de raios X (DRX), an?lise t?rmica (TG e DTG), espectroscopia na regi?o do infravermelho com transformada de Fourier (FT-IR), adsor??o e dessor??o de N2 (BET) e microscopia eletr?nica de varredura (MEV) com EDS. O processo de adsor??o foi realizado variando-se a press?o de 100 - 4000 kPa e mantendo-se a temperatura constante e igual a 298 K. Na press?o de 100 kPa, as maiores concentra??es de adsor??o ocorreram para os materiais 5Ni-MCM-48 (0,795 mmol g-1 ) e SBA-15 (0,914 mmol g -1 ) n?o impregnado, e, na press?o de 4000 kPa, para os materiais MCM-48 (14,89 mmol g-1 ) e SBA-15 (9,97 mmol g-1 ) n?o impregnados. Os resultados mostraram que a capacidade de adsor??o varia positivamente com a ?rea espec?fica, no entanto, apresenta uma depend?ncia direta com o tipo e geometria dos canais da estrutura porosa. Os dados obtidos foram ajustados atrav?s dos modelos de Langmuir e Freundlich e os par?metros termodin?micos avaliados foram energia livre de Gibbs e entropia do sistema de adsor??o / Several materials are currently under study for the CO2 capture process, like the metal oxides and mixed metal oxides, zeolites, carbonaceous materials, metal-organic frameworks (MOF's) organosilica and modified silica surfaces. In this work, evaluated the adsorption capacity of CO2 in mesoporous materials of different structures, such as MCM-48 and SBA- 15 without impregnating and impregnated with nickel in the proportions 5 %, 10 % and 20 % (m/m), known as 5Ni-MCM-48, 10Ni-MCM-48, 20Ni-MCM-48 and 5Ni-SBA-15, 10NiSBA-15, 20Ni-SBA-15. The materials were characterized by means of X-ray diffraction (XRD), thermal analysis (TG and DTG), Fourier transform infrared spectroscopy (FT-IR), N2 adsorption and desorption (BET) and scanning electron microscopy (SEM) with EDS. The adsorption process was performed varying the pressure of 100 - 4000 kPa and keeping the temperature constant and equal to 298 K. At a pressure of 100 kPa, higher concentrations of adsorption occurred for the materials 5Ni-MCM-48 (0.795 mmol g-1 ) and SBA-15 (0.914 mmol g-1 ) is not impregnated, and at a pressure of 4000 kPa for MCM-48 materials (14.89 mmol g-1) and SBA-15 (9.97 mmol g-1) not impregnated. The results showed that the adsorption capacity varies positively with the specific area, however, has a direct dependency on the type and geometry of the porous structure of channels. The data were fitted using the Langmuir and Freundlich models and were evaluated thermodynamic parameters Gibbs free energy and entropy of the adsorption system
79

S?ntese e caracteriza??o de complexos de base de schiff com n?quel (ii) ancorados no material mesoporoso SBA-15

Maia, Danielle de Oliveira 23 July 2015 (has links)
Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-05-30T22:35:16Z No. of bitstreams: 1 DanielleDeOliveiraMaia_TESE.pdf: 2480138 bytes, checksum: 11e89b7c4d42403108c704fd453975d5 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-06-01T20:04:06Z (GMT) No. of bitstreams: 1 DanielleDeOliveiraMaia_TESE.pdf: 2480138 bytes, checksum: 11e89b7c4d42403108c704fd453975d5 (MD5) / Made available in DSpace on 2016-06-01T20:04:06Z (GMT). No. of bitstreams: 1 DanielleDeOliveiraMaia_TESE.pdf: 2480138 bytes, checksum: 11e89b7c4d42403108c704fd453975d5 (MD5) Previous issue date: 2015-07-23 / SBA-15 s?o materiais mesoporosos, que possuem uma rede de canais e poros de tamanho bem definido na escala nanom?trica, al?m de outras caracter?sticas, tais como, elevada estabilidade t?rmica e ?rea superficial. Essa arquitetura particular de poros torna esses materiais promissores na ?rea de ancoramento de uma variedade de compostos na matriz da s?lica resultando em aplica??es nas diversas ?reas, dentre elas, na cat?lise. Nesse trabalho, foram sintetizados complexos de Base de Schiff com n?quel (II) para serem ancorados na SBA-15 funcionalizada com 3-cloropropiltrimet?xisilano realizando um estudo da estabilidade t?rmica desses compostos. Ap?s a s?ntese dos complexos, estes foram caracterizados por an?lise elementar (CHN), ponto de fus?o, condutividade, susceptibilidade magn?tica, espectroscopia de absor??o na regi?o do UV-vis?vel, espectroscopia de absor??o na regi?o do infravermelho e an?lises t?rmicas (TG/DTG). A an?lise elementar sugere que os complexos apresentam as seguintes f?rmulas qu?micas gerais: [Ni(C18H19N3O2)].2CH3COO.H2O, [Ni(C20H23N3O2)(2Cl)].2H2O, [Ni(C19H20N3O2)(2Cl)].3H2O, sendo L1= C18H19N3O2, L2= C20H23N3O2, L3 = C19H20N3O2. Na espectroscopia de absor??o na regi?o do UV - vis?vel e infravermelho dos complexos foi evidenciada a coordena??o metal - ligante. Ap?s caracteriza??o dos complexos, estes foram ancorados no material mesoporoso. A caracteriza??o desses materiais foi realizada por difra??o de raios - X, fluoresc?ncia de raios - X, adsor??o e dessor??o de N2, espectroscopia de absor??o na regi?o do infravermelho e an?lises t?rmicas (TG/DTG). No DRX foram observados tr?s picos principais de difra??o, cujos ?ndices de Miller s?o (100), (110) e (200), mostrando que mesmo ap?s a ancoragem, os materiais mesoporosos n?o perderam suas caracter?sticas estruturais. As porcentagens dos elementos (n?quel, cloro e s?lica) encontrados nos materiais atrav?s da an?lise de fluoresc?ncia de raios - x mostraram que os complexos foram ancorados nos poros da s?lica. Atrav?s da adsor??o e dessor??o de N2, foram observadas que os materiais apresentaram isoterma do tipo IV e histerese do tipo H1 caracter?sticos dos materiais mesoporos. Na espectroscopia de absor??o na regi?o do infravermelho, os materiais ancorados apresentaram bandas caracter?sticas dos ligantes (Base de Schiff) e da s?lica evidenciando o sucesso da ancoragem. Na an?lise t?rmica, foram observadas a decomposi??o de ?gua adsorvida, ?gua coordenada, aminas, arom?ticos, ligantes, cloropropiltrimet?xisilano e o aumento na estabilidade t?rmica das s?licas ancoradas com complexos comparado ao complexo livre. / SBA-15 are mesoporous materials, having a network of channels and well defined pore size in the nanometer range, as well as, other features such as high thermal stability and surface area. This particular pore architecture makes these promising materials in the anchoring area of a variety of compounds in the silica matrix resulting in applications in various fields, among them, in catalysis. In this work, complexes were synthesized Schiff base with nickel (II) to be anchored in the functionalized SBA-15 3 ? chloropropyltrimethoxysilane and a study of the thermal stability of these compounds. After synthesis of the complexes, they were characterized by elemental analysis (CHN), melting point, conductivity, magnetic susceptibility, absorption spectroscopy in the UV-visible region absorption, spectroscopy in the infrared region and thermal analysis (TG/DTG). Elemental analysis suggests that the complexes have the general formula chemical: [Ni(C18H19N3O2)].2CH3COO.H2O, [Ni(C20H23N3O2)(2Cl)].2H2O, [Ni(C19H20N3O2)(2Cl)].3H2O, and L1= C18H19N3O2, L2= C20H23N3O2, L3 = C19H20N3O2. In absorption spectroscopy in UV - visible and infrared complexes was evidenced the coordination metal - ligand. After characterization of the complexes, confirming the metal - ligand coordination, they have been anchored in the mesoporous material. The characterization of these materials were made by x- ray diffraction, x- ray fluorescence, N2 adsorption and desorption spectroscopy, the infrared spectroscopy and thermal analysis (TG/DTG). XRD analysis revealed three main diffraction peaks, whose Miller indices are (100), (110) and (200), showing that even after the anchoring, the mesoporous materials do not lose their structural characteristics. The percentages of the elements (nickel chloride and silica) found in the anchored materials through the x-ray fluorescence analysis showed that the complexes were anchored in the pores of the silica. Through adsorption and desorption of N2, we observed that the materials presented isotherm type IV and type H1 hysteresis characteristic of mesoporous materials. In the infrared spectroscopy, the materials showed characteristic bands of ligands (Schiff base) and silica demonstrating the success of the anchor. In the thermal analysis (TG/DTG), there were observed the decomposition of adsorbed water, coordinated water, amines, aromatics, ligands, chloropropyltrimethoxysilane and an increase in thermal stability (removal of ligand) of silicas anchored [Ni(L1)]SBA-15, [Ni(L2)SBA-15 and [Ni(L3)SBA-15 compared of free complexes, showing successful anchoring of complex molecular sieve.
80

Esterifica??o do ?cido oleico utilizando catalisadores ?cidos sulfatados e n?o sulfatados em materiais mesoporosos do tipo SBA-15

Evangelista, Jo?o Paulo da Costa 22 July 2015 (has links)
Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-05-30T22:35:16Z No. of bitstreams: 1 JoaoPauloDaCostaEvangelista_TESE.pdf: 3170006 bytes, checksum: b1459f824b08153ad43dfbda6bced227 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-06-01T20:54:29Z (GMT) No. of bitstreams: 1 JoaoPauloDaCostaEvangelista_TESE.pdf: 3170006 bytes, checksum: b1459f824b08153ad43dfbda6bced227 (MD5) / Made available in DSpace on 2016-06-01T20:54:29Z (GMT). No. of bitstreams: 1 JoaoPauloDaCostaEvangelista_TESE.pdf: 3170006 bytes, checksum: b1459f824b08153ad43dfbda6bced227 (MD5) Previous issue date: 2015-07-22 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Esse estudo prop?s-se a obter biodiesel a partir da esterifica??o do ?cido oleico com os catalisadores Zr-SBA-15, Nb-SBA-15, SO42-/Zr-SBA-15 e SO42-/Nb-SBA-15 obtidos pela inser??o de Zr e Nb no suporte SBA-15 e sulfata??o do suporte impregnado. O suporte SBA-15 foi sintetizado pelo m?todo hidrot?rmico. O catalisador foi incialmente sintetizado pelo m?todo de impregna??o via ?mida, adicionando 4,2 mL de uma solu??o ? 30 % do percursor do metal (Zr e Nb) em cada grama da SBA-15. Ap?s a impregna??o foi realizado o processo de sulfata??o. As condi??es reacionais da s?ntese do biodiesel utilizadas nesse estudo foram: quantidade de catalisador (5% em massa), raz?o molar de metanol:?cido oleico (20:1), tempo reacional (8 h) e temperatura de refluxo (65?C). Os catalisadores foram analisados por: difra??o de raios-X (DRX), an?lise termogravim?trica (TG/DTG), espectroscopia de infravermelho por transformada de Fourier (FTIR), adsor??o/dessor??o de nitrog?nio, microscopia eletr?nica de varredura (MEV), espectroscopia de energia dispersiva (EDS) e teste de acidez para identifica??o da estrutura, composi??o e verifica??o da presen?a de s?tios ?cidos. Os resultados de caracteriza??o indicaram que o suporte SBA-15 preservou a estrutura hexagonal ordenada, ap?s a incorpora??o de Zr e Nb. Observou-se a presen?a de nanopart?culas desses metais dispersas na superf?cie e no interior dos canais microporosos e mesoporosos dos catalisadores Zr-SBA-15 e Nb-SBA-15. Ap?s a sulfata??o, aumentou a quantidade de s?tios ?cidos e a estrutura ordenada foi mantida. Para os catalisadores Zr-SBA-15 e SO42-/Zr-SBA-15 houve a forma??o das estruturas tetragonal e monocl?nica do ZrO2, j? para os demais catalisadores Nb-SBA-15 e SO42-/Nb-SBA-15 formaram-se estruturas amorfas. A atividade catal?tica foi avaliada pela rea??o de esterifica??o do ?cido oleico via rota et?lica, utilizando todos os catalisadores sintetizados. O biodiesel obtido com SO42-/Zr-SBA-15 apresentou propriedades f?sico-qu?micas dentro das normas especificadas pela resolu??o N?7/2008 da ANP e melhor rendimento com 80,7%. Foi verificado que os catalisadores sulfatados, produziram maior rendimento com rela??o aos n?o sulfatados. O suporte SBA-15 n?o apresentou atividade catal?tica. / Fatty acids such as oleic acid, have received particular attention as raw material, due to its abundance, availability and relatively high purity, being considered as potential materials for production of biodiesel. The esterification reaction of oleic acid using heterogeneous catalysts can be a promising alternative for biodiesel production. This study proposes to find a biodiesel through esterification of oleic acid with Zr-SBA-15, Nb-SBA-15, SO42?/Zr-SBA-15 and SO4 2?/Nb-SBA-15 catalysts, obtained by insertion of Zr and Nb in support SBA-15 and sulfation of the impregnated support. SBA-15 support was synthesized by hydrothermal method. Support SBA-15 was synthesized by hydrothermal method. The catalyst was initially synthesized by the wet impregnation method, followed by sulfation process. The catalysts were analyzed: X-ray diffraction (XRD), thermal analysis (TG/DTG), Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption/desorption, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and acidity test to identify the structure, composition and verification the presence acid sites. The characterization results indicated that the SBA-15 support preserved the ordered hexagonal structure after the incorporation of Zr and Nb. It was observed the presence of nanoparticles these metal dispersed on the surface and within the microporous and mesoporous channels of Zr-SBA-15 and Nb-SBA-15 catalysts. After sulfation, increased amount of acid sites and the ordered structure was maintained. For Zr-SBA-15 and SO4 2?/Zr-SBA-15 catalyst was the formation of tetragonal and monoclinic structures of ZrO2, as for the other, Nb-SBA-15 and SO42?/Nb-SBA-15 catalyst were formed amorphous structures. The catalytic activity was evaluated by the esterification reaction of oleic acid via ethyl route, using all the synthesized catalysts. Biodiesel obtained with SO42?/Zr-SBA-15 presented physicochemical properties within the standards specified by the Resolution N? 45/2014 ANP and obtained the best yield with 80.7%. It was found that sulfated catalysts, produced higher yields with respect to nonsulfated. The SBA-15 support showed no catalytic activity.

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