• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1
  • Tagged with
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 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.
1

Catalysts from hydrotalcite dopped with copper in chemical transformation of glycerol / Catalisadores derivados de hidrotalcita dopados com cobre na transformaÃÃo quÃmica do glicerol

SebastiÃo Junior Teixeira Vasconcelos 28 July 2014 (has links)
Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / The hydrotalcites are a class of layered double hydroxides with important physical and chemical properties. The use of this class of compounds in catalysis of specific reactions also requires many studies. The literature has exploited these materials in catalytic reactions in liquid phase with glycerol, particularly in hydrogenolysis reactions. The gas phase reactions with glycerol usually make use of acid catalysts. Thus, both the liquid phase reactions involving catalysts derived from hydrotalcite-like gas phase reactions involving basic catalysts require further study. We developed a study to elucidating the combined effects of basic catalytic sites (MgO and amorphous aluminum oxide) and dehydrogenation (derived from copper oxides) in the hydrogenolysis reaction. The materials used were derived from hydrotalcite oxides, and oxides derivatives containing in its composition 2.5% copper (molar ratio) in relation to the metal network hydrotalcite (Mg and Al). The results obtained for the gas phase show an interrelationship between the sites and the major products of the reaction, acetol and acrolein. Was determined conditions under which one or another product is more favored, with conversions that can reach over 90% and selectivities that exceed 99%. In the liquid phase this interrelationship is more difficult to be demonstrated, given the complications arising from the greater contact time between catalyst and reactants to the point of the major products at the reaction gas phase includes both as reaction intermediates in the liquid phase. In the liquid phase, the predominant carbon chain compounds of higher alcohol and ester functional groups, cyclic compounds but also from various functional groups. / As hidrotalcitas sÃo uma classe de hidrÃxidos duplos lamelares com importantes propriedades fÃsico-quÃmicas. O emprego desta classe de compostos na catÃlise de reaÃÃes especÃficas requer, ainda, muitos estudos. A literatura tem explorado estes materiais na catÃlise das reaÃÃes com glicerol em fase lÃquida, principalmente, em reaÃÃes de hidrogenÃlise. As reaÃÃes em fase gasosa com glicerol normalmente fazem uso de catalisadores Ãcidos, de modo. Deste modo, tanto as reaÃÃes em fase lÃquida envolvendo catalisadores derivados da hidrotalcita como reaÃÃes em fase gasosa envolvendo catalisadores bÃsicos requerem maiores estudos. Desenvolveu-se um estudo com vistas a elucidaÃÃo dos efeitos combinados de sÃtios catalÃticos bÃsicos (MgO e Ãxidos de alumÃnio amorfo) e desidrogenante (Ãxidos derivados do cobre) na reaÃÃo de hidrogenÃlise. Os materiais empregados foram Ãxidos derivados da hidrotalcita, e Ãxidos derivados contendo em sua composiÃÃo 2,5% cobre (proporÃÃo molar) em relaÃÃo aos metais da rede hidrotalcita (Mg e Al). Os resultados obtidos para a fase gasosa evidenciam uma inter-relaÃÃo entre os sÃtios e os produtos majoritÃrios da reaÃÃo, acetol e acroleina. Determinou-se condiÃÃes em que um ou outro produto à mais favorecido, com conversÃes que podem chegar a mais de 90% e seletividades que superam 99%. Em fase lÃquida esta inter-relaÃÃo à mais difÃcil de ser evidenciada, dadas as complicaÃÃes originadas pelo maior tempo de contato entre catalisador e reagentes a tal ponto dos produtos majoritÃrios verificados na reaÃÃo fase gasosa figurarem como intermediÃrios da reaÃÃo em fase lÃquida. Na fase lÃquida, predominam compostos de maior cadeia carbÃnica dos grupos funcionais Ãlcool e Ãster, mas tambÃm compostos cÃclicos de grupos funcionais diversos.

Page generated in 0.0289 seconds