1 |
Estudo de materiais mesoporosos funcionalizados com diferentes aminas para captura do di?xido de carbono atrav?s do processo de adsor??oBarbosa, Marcela Nascimento 30 September 2013 (has links)
Made available in DSpace on 2014-12-17T15:42:29Z (GMT). No. of bitstreams: 1
MarcelaNB_TESE.pdf: 4650032 bytes, checksum: 4b8ec547749f785718e5f099093fa925 (MD5)
Previous issue date: 2013-09-30 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Intensive use of machinery and engines burning fuel dumps into the atmosphere huge
amounts of carbon dioxide (CO2), causing the intensification of the greenhouse effect.
Climate changes that are occurring in the world are directly related to emissions of
greenhouse gases, mainly CO2, gases, mainly due to the excessive use of fossil fuels. The
search for new technologies to minimize the environmental impacts of this phenomenon has
been investigated. Sequestration of CO2 is one of the alternatives that can help minimize
greenhouse gas emissions. The CO2 can be captured by the post-combustion technology, by
adsorption using adsorbents selective for this purpose. With this objective, were synthesized
by hydrothermal method at 100 ?C, the type mesoporous materials MCM - 41 and SBA-15.
After the synthesis, the materials were submitted to a calcination step and subsequently
functionalized with different amines (APTES, MEA, DEA and PEI) through reflux method.
The samples functionalized with amines were tested for adsorption of CO2 in order to
evaluate their adsorption capacities as well, were subjected to various analyzes of
characterization in order to assess the efficiency of the method used for functionalization with
amines. The physic-chemical techniques were used: X- ray diffraction (XRD), nitrogen
adsorption and desorption (BET/BJH), scanning electron microscopy (SEM), transmission
electron microscopy (TEM), CNH Analysis, Thermogravimetry (TG/DTG) and photoelectron
spectroscopy X-ray (XPS). The CO2 adsorption experiments were carried out under the
following conditions: 100 mg of adsorbent, at 25 ?C under a flow of 100 ml/min of CO2,
atmospheric pressure and the adsorption variation in time 10-210 min. The X-ray diffraction
with the transmission electron micrographs for the samples synthesized and functionalized,
MCM-41 and SBA-15 showed characteristic peaks of hexagonal mesoporous structure
formation, showing the structure thereof was obtained. The method used was efficient reflux
according to XPS and elemental analysis, which showed the presence of amines in the starting
materials. The functionalized SBA -15 samples were those that had potential as best adsorbent
for CO2 capture when compared with samples of MCM-41, obtaining the maximum
adsorption capacity for SBA-15-P sample / A intensa utiliza??o de m?quinas e motores queimando combust?veis despeja na atmosfera
imensas quantidades de di?xido de carbono (CO2), causando a intensifica??o do Efeito Estufa.
As mudan?as clim?ticas que v?m ocorrendo no mundo est?o diretamente relacionadas ?s
emiss?es de gases de efeito estufa, principalmente CO2, devido, sobretudo, ao uso excessivo
de combust?veis f?sseis. A busca por novas tecnologias para minimizar os impactos
ambientais decorrentes deste fen?meno vem sendo investigadas. O sequestro de CO2 ? uma
das alternativas que pode ajudar a minimizar as emiss?es desses gases. O CO2 pode ser
capturado pela tecnologia p?s-combust?o, atrav?s do processo de adsor??o, utilizando
adsorventes seletivos para este fim. Com este objetivo, foram sintetizados, pelo m?todo
hidrot?rmico a 100?C, materiais mesoporosos do tipo MCM-41 e SBA-15. Ap?s as s?nteses os
materiais foram submetidos ? etapa de calcina??o e, posteriormente, funcionalizados com
diferentes tipos de aminas (APTES, MEA, DEA e PEI), atrav?s do m?todo de refluxo. As
amostras funcionalizadas com as aminas foram testadas nos ensaios de adsor??o de CO2 afim
de avaliar suas capacidades de adsor??o, bem como, foram submetidas a diversas an?lises de
caracteriza??o no intuito de avaliar a efici?ncia do m?todo utilizado para a funcionaliza??o
com as aminas. As t?cnicas f?sico-qu?micas utilizadas foram: Difra??o de Raios-X (DRX),
Adsor??o e Dessor??o de nitrog?nio (BET/BJH), Microscopia eletr?nica de varredura (MEV),
Microscopia eletr?nica de transmiss?o (MET), An?lise elementar CNH, Termogravimetria
(TG/DTG) e Espectroscopia fotoeletr?nica de Raios-X (XPS). Os ensaios de adsor??o de CO2
foram realizados nas seguintes condi??es: 100 mg de adsorvente, temperatura de 25 ?C sob
fluxo de 100 mL/min de CO2, press?o atmosf?rica e com varia??o no tempo de adsor??o de
10 a 210 min. Os difratogramas de Raios-X juntamente com as micrografias eletr?nicas de
transmiss?o para as amostras sintetizadas e funcionalizadas, MCM-41 e SBA-15,
apresentaram os picos caracter?sticos da forma??o de estrutura mesoporosa hexagonal,
evidenciando que a estrutura do mesmo foi obtida. O m?todo de refluxo utilizado foi eficiente
segundo as an?lises de elementar e XPS, na qual, mostrou a presen?a das aminas nos
materiais de partida. As amostras funcionalizadas de SBA-15 foram as que tiveram melhor
potencial como adsorvente para captura de CO2 quando comparadas com as amostras de
MCM-41, obtendo a m?xima capacidade de adsor??o para a amostra SBA-15-P
|
2 |
Nickel mediated negishi and oxidative couplings / Couplages de negishi et couplages oxydants à base de complexes de nickelOhleier, Alexia 14 March 2017 (has links)
Ce projet de recherche porte sur la formation de nouvelles liaisons C-C et la production de produits chimiques valorisables grâce à l'utilisation de complexes de nickel chélatés. La première partie de cette thèse est dédiée à des complexes bis-phosphines de nickel employés comme catalyseurs pour le couplage croisé de Negishi. Le précatalyseur [(dcpp)Ni(n2-toluene)] (dcpp = 1,3 bis(dicyclohexylphosphino)propane) permet de coupler efficacement des chloro-arènes avec des organozinciques en utilisant de faibles charges catalytiques (0,2 mol% - 0,1 mol%) et des conditions douces (THF, 60 °C). Une étude mécanistique fondée sur des réactions stœchiométriques et des calculs DFT prouve la présence d'intermédiaires Ni(0)/Ni(II) au cours de la catalyse et exclut tout passage par un mécanisme de type Ni(I)/Ni(III). La seconde partie de ce travail porte sur le couplage oxydant entre l'éthylène et le CO2 sur des complexes de nickel chélatés par des bis-phosphines ou des bis-NHC. Une étude cinétique de l'équilibre entre [(dcpp)Ni(C2H4)] et [(dcpp)nickelalactone] a été réalisée. Le complexe [(dcpp)nickelalactone] peut ensuite être réduit et fonctionnalisé en dérivé du propanol en présence de pinacolborane. Des études mécanistiques et catalytiques préliminaires ont eté menées. De plus, de nouvelles méthodologies de synthèses ont été développées afin d'obtenir les premiers complexes [(bis-NHC)Ni(C2H4)] et [(bis-NHC)nickelalactone]. / The aim of this research project is to promote the formation of new C-C bonds and the production of valuable chemicals by using chelated nickel complexes. The first part of this thesis is dedicated to [nickel(bis-phosphine)] complexes employed as catalysts for Negishi cross coupling reactions. Designed Ni(0) precatalyst [(dcpp)Ni(n2-toluene)] (dcpp = 1,3-bis(dicyclohexylphosphino)propane) promotes efficiently the Negishi cross coupling between aryl chlorides and phenylzinc chloride derivatives at low catalyst loadings (down to 0.2 mol% - 1 mol%) under mild conditions (THF, 60°C). Mechanistic investigations relying on stoichiometric reactions and DFT calculations prove the involvement of Ni(0)/Ni(II) intermediates rather than Ni(I)/Ni(III) species during the catalysis. The second part of this work deals with the oxidative coupling between ethylene and CO2 at bis-phosphine and bis-NHC chelated nickel complexes for the production of value-added chemicals. The equilibrium between [(dcpp)Ni(C2H4)] and [(dcpp)nickelalactone] has been investigated by kinetic studies. The subsequent cleavage of [(dcpp) nickelalactone] by pinacolborane leads to its reductive functionalization into a propanol derivative. Preliminary mechanistic and catalytic investigations have been undertaken. Moreover, new methodologies are provided for the synthesis of the first [(bis-NHC)Ni(C2H4)] and [(bis-NHC)nickelalactone] complexes.
|
Page generated in 0.1322 seconds