Heterogeneous Catalysis
Mostrando 49-60 de 60 artigos, teses e dissertações.
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49. Estudo da Adição do Promotor Cu aos Catalisadores Pt/Al2O3 e Pt/Nb2O5 para a Oxidação Seletiva de CO / Study of the Addition of Cu Promoter to the Pt/Al2O3 and Pt/Nb2O5 catalysts for the Selective Oxidation of CO
The fuel cells are an alternative to generate energy without polluting the environment. They produce electric energy through the reaction of hydrogen with the oxygen from air. The product of the reaction is water. It is an interesting form of generation energy because its a clean technology. The hydrogen used as combustible for the fuel cells is proceeding f
Publicado em: 2005
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50. A Interação substrato-modificador e sua importância para a hidrogenação enantiosseletiva de alfa-cetoésteres
The heterogeneous asymmetric catalysis plays an important and crucial role in many chemical processes and has therefore become a growing and interesting field. The enantioselective hydrogenation of α-ketoesters is one of the best known examples of such process. Methyl pyruvate, which can be converted to (R)- and (S)-methyl lactate with an enantioselecti
Publicado em: 2004
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51. Study of catalytics Pt-In/Nb2O5 in the hydrocarbons conversion / Estudo de catalisadores Pt-In/Nb2O5 na conversão de hidrocarbonetos
Hydrocarbon dehydrogenation is an important industrial process, due to the high demand of unsatured hydrocarbons for industrial processes and products. Unsatured hydrocarbons are used in the manufacture of several products, such as detergents, high octanage gasoline, pharmaceutical products and synthetic rubber. The commercial catalysts employed in the hydro
Publicado em: 2003
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52. Synthesis and Characterization of LaNiO3, LaNi(1-x)Fe xO3 andLaNi(1-x)Co xO3 Perovskite Oxides for Catalysis Application
Mixed metal oxides with perovskite-type structure show a great potential to be used in catalysis, electrocatalysis and electronic ceramics. Perovskites oxides catalysts with the composition LaNiO3, LaNi(1-x)Fe xO3 and LaNi(1-x)Co xO3 (x = 0.4 and 0.7) have been synthesized by the precipitation method to be used in the methane reforming to produce hydrogen an
Materials Research. Publicado em: 2002-09
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53. A Catálise no Brasil nos últimos 25 anos: uma história de sucesso
In the last 25 years the research in catalysis has passed from heterogeneous processes mainly applied to petrochemical industries to homogeneous processes applied to fine chemicals and green chemistry. In this context the Brazilian Chemical Society (SBQ) is playing an important role in the organization of this interdisciplinary area involving researches from
Química Nova. Publicado em: 2002-05
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54. Oxidos mistos e microporosos preparados pelo metodo sol-gel como catalisadores para a oxidação de hidrocarbonetos em fase liquida
Mixed Cr2O3-, CuO-, and Mo2O5 oxides in SiO2 were sintetized by the sol-gel process, using acid catalysis, slow solvent drying, and soft thermal treatment, with slow temperature increase, which favours a narrow micropore distribution. The prepared mixed oxides were characterized by elemental analysis, XRD, nitrogen adsorption - desorption, IR and UV-vis, EPR
Publicado em: 2001
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55. STUDY OF NITRO AND CARBOXY SUBSTITUTED IRONPORPHYRINS: SYNTHESIS, CHARACTERIZATION AND CATALYTIC ACTIVITY IN HYDROCARBON OXIDATION. / Estudo de Ferroporfirinas Nitro e Carboxi Substituídas: Síntese, Caracterização e Atividade Catalítica na Oxidação de Hidrocarbonetos.
In this work, a series of porphyrins and corresponding FeP containing NO2-substituents in the ortho- or COOH-groups in the para- meso-phenyl rings were synthesized and the catalytic activities of such compounds were investigated in both homogeneous and heterogeneous systems. H2(TNMCPP), H2(DNDCPP) and H2(MNTCPP) porphyrins were synthesized through the mixed
Publicado em: 1998
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56. Catalysis-based enantioselective total synthesis of the macrocyclic spermidine alkaloid isooncinotine
A concise and efficient total synthesis of the spermidine alkaloid (-)-isooncinotine (1) incorporating a 22-membered lactam ring is outlined. The approach is largely catalysis-based, involving a selective iron-catalyzed alkyl–aryl cross-coupling reaction of a difunctionalized pyridine substrate, a heterogeneous asymmetric hydrogenation step to set the chir
National Academy of Sciences.
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57. Single-molecule enzymology of RNA: Essential functional groups impact catalysis from a distance
The hairpin ribozyme is a minimalist paradigm for studying RNA folding and function. In this enzyme, two domains dock by induced fit to form a catalytic core that mediates a specific backbone cleavage reaction. Here, we have fully dissected its reversible reaction pathway, which comprises two structural transitions (docking/undocking) and a chemistry step (c
National Academy of Sciences.
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58. Molecular analysis of human argininosuccinate lyase: mutant characterization and alternative splicing of the coding region.
Argininosuccinic acid lyase (ASAL) deficiency is a clinically heterogeneous autosomal recessive urea cycle disorder. We previously established by complementation analysis that 28 ASAL-deficient patients have heterogeneous mutations in a single gene. To prove that the ASAL structural gene is the affected locus, we sequenced polymerase chain reaction-amplified
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59. Compositional genomes: Prebiotic information transfer in mutually catalytic noncovalent assemblies
Mutually catalytic sets of simple organic molecules have been suggested to be capable of self-replication and rudimentary chemical evolution. Previous models for the behavior of such sets have analyzed the global properties of short biopolymer ensembles by using graph theory and a mean field approach. In parallel, experimental studies with the autocatalytic
The National Academy of Sciences.
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60. Facilitation of hammerhead ribozyme catalysis by the nucleocapsid protein of HIV-1 and the heterogeneous nuclear ribonucleoprotein A1.
In order to improve the activity of hammerhead ribozymes in vivo, we have analyzed the effect of several prototypical RNA binding proteins on the ribozyme cleavage reaction: bacteriophage T4 gene 32 protein (gp32), hnRNP A1 (A1) and the nucleocapsid protein of HIV-1 (NCp7). We show that, while gp32 has no effect on the cleavage reaction, A1 and NCp7 affect d