Literatura académica sobre el tema "M-PTC"

Metallophilic (metal-metal) interactions are weak interactions between closed-shell (d10, s2) or pseudo-closed-shell (d8) metal cations. This type of interaction is generally believed to be responsible for various intriguing structures, luminescence, catalysis and magnetism. To gain a better understanding of metallophilic interactions, both experimental and computational investigations have been carried out in this thesis. Chapter 1 gave an up-to-date literature review on the definition, significance, and methods of estimating metallophilic interactions. The disputed nature and strength of metallophilic interactions encouraged us to further understand them. Chapter 2 focused on aurophilic interactions between AuI cations. Aurophilic interactions were observed in the solid state, but not well expressed in solution. Further experimental and computational results suggested that the strength of aurophilic interactions were weaker than electrostatic interactions. The nature of aurophilic interactions arose from orbital interactions rather than dispersion. Chapter 3 presented the study of metallophilic interactions between group 10 metal centres, including PtII-PtII, PdII-PdII and NiII-NiII. A series of cyclometalated square-planar metal complexes with different metals or substituents were prepared. PtII-PtII interactions were found to be stronger than PdII-PdII and NiII-NiII interactions. The dimerization constants of the Pt-containing complexes increased in line with increasing electron-withdrawing ability. Chapter 4 investigated the solvent-induced and thermally dependent colour changes of the Pt-containing complexes synthesised in chapter 3. Metallophilic interactions were proposed to be important in influencing the luminescence properties.

The diploma thesis is focused on the study of chemical reaction products in prebiotic atmospheres. The theoretical part deals with the main theories of composing the atmosphere of the early Earth, hypotheses of the origin of life and genetic code in the form of RNA, the atmosphere of the moon Titan and the basic characteristics of the gliding arc discharge, and the analytical techniques used in the diploma thesis. In the experimental part, study of products was carried out by experimental atmospheric simulations in a special stainless steel reactor in various mixtures of gases N2, CH4, CO2 and O2. The electrical discharge for atmospheric simulation was generated by an electrode configuration for the gliding arc discharge and glow discharge. Detection and identification of chemical reaction products was performed by Gas Chromatography with Mass Spectrometry (GC-MS) and Flame Ionization Detector (GC-FID), Testo 350 M/XL and Proton Transfer Reaction Mass Spectrometry (PTR-MS). A theoretical kinetic model was created to predict and confirm the detected products. During the experiments, the dependence of the product intensity on changes in the composition of the gaseous mixture and the applied value of the electric current was also observed.

Made available in DSpace on 2014-12-17T15:42:31Z (GMT). No. of bitstreams: 1 AnneMichelleGPS.pdf: 4577671 bytes, checksum: 19f54b9da1543ee4a1008ce93d607ec1 (MD5) Previous issue date: 2007-10-04<br>Bifunctional catalysts based on zircon oxide modified by tungsten (W = 10, 15 and 20 %) and by molybdenum oxide (Mo= 10, 15 e 20 %) containg platinum (Pt = 1%) were prepared by the polymeric precursor method. For comparison, catalysts the tungsten base was also prepared by the impregnation method. After calcinations at 600, 700 and 800 ?C, the catalysts were characterized by X-ray diffraction, fourier-transform infrared spectroscopy, thermogravimetric and differential thermal analysis, nitrogen adsorption and scanning electron microscopy. The profile of metals reduction was determined by temperature programmed reduction. The synthesized catalysts were tested in n-heptane isomerization. X-ray diffractogram of the Pt/WOx-ZrO2 and Pt/MoOx-ZrO2 catalysts revealed the presence of tetragonal ZrO2 and platinum metallic phases in all calcined samples. Diffraction peaks due WO3 and ZrO2 monoclinic also were observed in some samples of the Pt/WOx-ZrO2 catalysts. In the Pt/MoOx-ZrO2 catalysts also were observed diffraction peaks due ZrO2 monoclinic and Zr(MoO4)2 oxide. These phases contained on Pt/WOx-ZrO2 and Pt/MoOx-ZrO2 catalysts varied in accordance with the W or Mo loading and in accordance with the calcination temperature. The infrared spectra showed absorption bands due O-W-O and W=O bonds in the Pt/WOx-ZrO2 catalysts and due O-Mo-O, Mo=O and Mo-O bonds in the Pt/MoOx-ZrO2 catalysts. Specific surface area for Pt/WOx-ZrO2 catalysts varied from 30-160 m2 g-1 and for the Pt/MoOx-ZrO2 catalysts varied from 10-120 m2 g-1. The metals loading (W or Mo) and the calcination temperature influence directly in the specific surface area of the samples. The reduction profile of Pt/WOx-ZrO2 catalysts showed two peaks at lower temperatures, which are attributed to platinum reduction. The reduction of WOx species was evidenced by two reduction peak at high temperatures. In the case of Pt/MoOx-ZrO2 catalysts, the reduction profile showed three reduction events, which are attributed to reduction of MoOx species deposited on the support and in some samples one of the peak is related to the reduction of Zr(MoO4)2 oxide. Pt/WOx-ZrO2 catalysts were active in the n-heptane isomerization with high selectivity to 3-methyl-hexane, 2,3- dimethyl-pentane, 2-methyl-hexane among other branched hydrocarbons. The Pt/MoOx-ZrO2 catalysts practically didn't present activity for the n-heptane isomerization, generating mainly products originating from the catalytic cracking<br>Catalisadores bifuncionais a base de ?xido de zirc?nio modificado por ?xidos de tungst?nio (W = 10, 15 e 20 %) ou molibd?nio (Mo= 10, 15 e 20 %) contendo platina (Pt = 1 %) foram preparados pelo m?todo dos precursores polim?ricos. Por compara??o, catalisadores a base de tungst?nio tamb?m foram preparados pelo m?todo de impregna??o. Ap?s calcina??es a 600, 700 e 800 ?C, os catalisadores foram caracterizados por difra??o de raios-X, espectroscopia de absor??o na regi?o do infravermelho, an?lise termogravim?trica, an?lise t?rmica diferencial, adsor??o de nitrog?nio e microscopia eletr?nica de varredura. Os perfis de redu??o dos metais foram determinados por redu??o a temperatura programada. Os catalisadores sintetizados foram testados na isomeriza??o do n-heptano. Os difratogramas de raios-X dos catalisadores Pt/WOx-ZrO2 e Pt/MoOx-ZrO2 revelaram a presen?a do ZrO2 tetragonal e da platina met?lica em todas as amostras calcinadas. Picos de difra??o referentes ao WO3 e ao ZrO2 monocl?nico tamb?m foram observados em algumas das amostras dos catalisadores Pt/WOx-ZrO2. Nos catalisadores do tipo Pt/MoOx-ZrO2 tamb?m foram observados picos de difra??o referente ao ZrO2 monocl?nico e ao ?xido Zr(MoO4)2. O aparecimento destas outras fases contidas nos catalisadores Pt/WOx-ZrO2 e Pt/MoOx-ZrO2 variaram de acordo com o teor de W ou Mo e de acordo com a temperatura de calcina??o. Os espectros de absor??o na regi?o do infravermelho exibiram bandas de absor??o referentes as liga??es O-W-O e W=O nos catalisadores Pt/WOx-ZrO2 e referentes as liga??es O-Mo-O, Mo=O e Mo-O nos catalisadores Pt/MoOx-ZrO2. A ?rea superficial espec?fica dos catalisadores Pt/WOx-ZrO2 variou de 30-160 m2 g-1 e para os catalisadores do tipo Pt/MoOx-ZrO2 variou de 10-120 m2 g-1. O teor de metais (W ou Mo) e a temperatura de calcina??o exercem uma influ?ncia direta no valor da ?rea superficial espec?fica das amostras. Os perfis de redu??o dos catalisadores Pt/WOx-ZrO2 exibiram dois picos a baixas temperaturas, os quais s?o atribu?dos a redu??o da platina. A redu??o das esp?cies WOx foi evidenciada por dois picos de redu??o a altas temperaturas. No caso dos catalisadores Pt/MoOx-ZrO2, os perfis de redu??o mostram tr?s eventos de redu??o, os quais s?o atribu?dos a redu??o das esp?cies MoOx depositadas no suporte e em algumas amostras um dos picos ? relacionado com a redu??o do ?xido Zr(MoO4)2. Os catalisadores Pt/WOx-ZrO2 foram ativos para a isomeriza??o do n-heptano com alta seletividade a 3-metil-hexano, 2,3-dimetil-pentano e 2-metil-hexano entre outros hidrocarbonetos ramificados. Os catalisadores Pt/MoOx- ZrO2 praticamente n?o apresentaram atividade para a isomeriza??o do n-heptano, gerando principalmente produtos oriundos do craqueamento catalitico

Catalisadores bifuncionais a base de óxido de zircônio modificado por óxidos de tungstênio (W = 10, 15 e 20 %) ou molibdênio (Mo= 10, 15 e 20 %) contendo platina (Pt = 1 %) foram preparados pelo método dos precursores poliméricos. Por comparação, catalisadores a base de tungstênio também foram preparados pelo método de impregnação. Após calcinações a 600, 700 e 800 ºC, os catalisadores foram caracterizados por difração de raios-X, espectroscopia de absorção na região do infravermelho, análise termogravimétrica, análise térmica diferencial, adsorção de nitrogênio e microscopia eletrônica de varredura. Os perfis de redução dos metais foram determinados por redução a temperatura programada. Os catalisadores sintetizados foram testados na isomerização do n-heptano. Os difratogramas de raios-X dos catalisadores Pt/WOx-ZrO2 e Pt/MoOx-ZrO2 revelaram a presença do ZrO2 tetragonal e da platina metálica em todas as amostras calcinadas. Picos de difração referentes ao WO3 e ao ZrO2 monoclínico também foram observados em algumas das amostras dos catalisadores Pt/WOx-ZrO2. Nos catalisadores do tipo Pt/MoOx-ZrO2 também foram observados picos de difração referente ao ZrO2 monoclínico e ao óxido Zr(MoO4)2. O aparecimento destas outras fases contidas nos catalisadores Pt/WOx-ZrO2 e Pt/MoOx- ZrO2 variaram de acordo com o teor de W ou Mo e de acordo com a temperatura de calcinação. Os espectros de absorção na região do infravermelho exibiram bandas de absorção referentes as ligações O-W-O e W=O nos catalisadores Pt/WOx-ZrO2 e referentes as ligações O-Mo-O, Mo=O e Mo-O nos catalisadores Pt/MoOx-ZrO2. A área superficial específica dos catalisadores Pt/WOx-ZrO2 variou de 30-160 m2 g-1 e para os catalisadores do tipo Pt/MoOx-ZrO2 variou de 10-120 m2 g-1. O teor de metais (W ou Mo) e a temperatura de calcinação exercem uma influência direta no valor da área superficial específica das amostras. Os perfis de redução dos catalisadores Pt/WOx-ZrO2 exibiram dois picos a baixas temperaturas, os quais são atribuídos a redução da platina. A redução das espécies WOx foi evidenciada por dois picos de redução a altas temperaturas. No caso dos catalisadores Pt/MoOx-ZrO2, os perfis de redução mostram três eventos de redução, os quais são atribuídos a redução das espécies MoOx depositadas no suporte e em algumas amostras um dos picos é relacionado com a redução do óxido Zr(MoO4)2. Os catalisadores Pt/WOx-ZrO2 foram ativos para a isomerização do n-heptano com alta seletividade a 3-metil-hexano, 2,3-dimetil-pentano e 2-metil-hexano entre outros hidrocarbonetos ramificados. Os catalisadores Pt/MoOx- ZrO2 praticamente não apresentaram atividade para a isomerização do n-heptano, gerando principalmente produtos oriundos do craqueamento catalitico. _________________________________________________________________________________________ ABSTRACT: Bifunctional catalysts based on zircon oxide modified by tungsten (W = 10, 15 and 20 %) and by molybdenum oxide (Mo= 10, 15 e 20 %) containg platinum (Pt = 1%) were prepared by the polymeric precursor method. For comparison, catalysts the tungsten base was also prepared by the impregnation method. After calcinations at 600, 700 and 800 ºC, the catalysts were characterized by X-ray diffraction, fourier-transform infrared spectroscopy, thermogravimetric and differential thermal analysis, nitrogen adsorption and scanning electron microscopy. The profile of metals reduction was determined by temperature programmed reduction. The synthesized catalysts were tested in n-heptane isomerization. X-ray diffractogram of the Pt/WOx-ZrO2 and Pt/MoOx-ZrO2 catalysts revealed the presence of tetragonal ZrO2 and platinum metallic phases in all calcined samples. Diffraction peaks due WO3 and ZrO2 monoclinic also were observed in some samples of the Pt/WOx-ZrO2 catalysts. In the Pt/MoOx-ZrO2 catalysts also were observed diffraction peaks due ZrO2 monoclinic and Zr(MoO4)2 oxide. These phases contained on Pt/WOx-ZrO2 and Pt/MoOx-ZrO2 catalysts varied in accordance with the W or Mo loading and in accordance with the calcination temperature. The infrared spectra showed absorption bands due O-W-O and W=O bonds in the Pt/WOx-ZrO2 catalysts and due O-Mo-O, Mo=O and Mo-O bonds in the Pt/MoOx-ZrO2 catalysts. Specific surface area for Pt/WOx-ZrO2 catalysts varied from 30-160 m2 g-1 and for the Pt/MoOx-ZrO2 catalysts varied from 10-120 m2 g-1. The metals loading (W or Mo) and the calcination temperature influence directly in the specific surface area of the samples. The reduction profile of Pt/WOx-ZrO2 catalysts showed two peaks at lower temperatures, which are attributed to platinum reduction. The reduction of WOx species was evidenced by two reduction peak at high temperatures. In the case of Pt/MoOx-ZrO2 catalysts, the reduction profile showed three reduction events, which are attributed to reduction of MoOx species deposited on the support and in some samples one of the peak is related to the reduction of Zr(MoO4)2 oxide. Pt/WOx-ZrO2 catalysts were active in the n-heptane isomerization with high selectivity to 3-methyl-hexane, 2,3- dimethyl-pentane, 2-methyl-hexane among other branched hydrocarbons. The Pt/MoOx-ZrO2 catalysts practically didn't present activity for the n-heptane isomerization, generating mainly products originating from the catalytic cracking.