Effect of cerium loading on structure and morphology of modified Ce-USY zeolites

Este trabalho descreve detalhadamente o efeito da quantidade de cério na estrutura e morfologia da zeólita NH4USY. Ce-USY (2-25% m/m de CeO₂) foi obtido por impregnação úmida de CeCl₃ seguida de calcinação a 550ºC por 8 h. Em quantidades baixas (2-10%), foi observado que as espécies de cério encontram-se nas posições de troca iônica na rede, enquanto em maiores teores (15-25%) pequenos agregados formaram-se na superfície da HUSY. Difratometria de raios X (XRD) mostrou apenas reflexões relacionadas à HUSY, confirmando a alta dispersão das espécies de cério, porém as análises por espectroscopia Raman com transformada de Fourier (FT-Raman) detectaram CeO_x para os materiais acima de 10%. A reação do CeCl₃ com NH₄USY produziu NH₄Cl, o qual se decompõe em HCl, ocasionando a desaluminização da rede. Os materiais apresentaram um aumento da razão Lewis/Brønsted com o aumento da quantidade de cério, devido a interação do excesso de cério com os grupos OH da USY e consequente formação de espécies CeO_x.

Supercritical extraction of pupunha (Guilielma speciosa) oil in a fixed bed using carbon dioxide

The pupunha (Guilielma speciosa) is the fruit of a palm tree typical of the Brazilian Northern region, whose stem is used as a source of heart of palm. The fruit, which is about 65% pulp, is a source of oil and carotenes. In the present work, an analysis of the kinetics of supercritical extraction of oil from the pupunha pulp is presented. Carbon dioxide was used as solvent. The extractions were carried out at 25 MPa and 323 K and 30 MPa and 318 K. The chemical composition of the extracts in terms of fatty acids was determined by gas chromatography. The amount of oleic acid, a saturated fatty acid, in the CO2 extracts was larger than that in the extract obtained with hexane. The overall extraction curves were modeled using the single-parameter model proposed in the literature to describe the desorption of toluene from activated coal.

Separation of satured and unsaturated fatty acids from palm fatty acids distillates in continuous multistage countercurrent columns with supercritical carbon dioxide as solvent: a process design methodology

In this work the separation of multicomponent mixtures in counter-current columns with supercritical carbon dioxide has been investigated using a process design methodology. First the separation task must be defined, then phase equilibria experiments are carried out, and the data obtained are correlated with thermodynamic models or empirical functions. Mutual solubilities, Ki-values, and separation factors aij are determined. Based on this data possible operating conditions for further extraction experiments can be determined. Separation analysis using graphical methods are performed to optimize the process parameters. Hydrodynamic experiments are carried out to determine the flow capacity diagram. Extraction experiments in laboratory scale are planned and carried out in order to determine HETP values, to validate the simulation results, and to provide new materials for additional phase equilibria experiments, needed to determine the dependence of separation factors on concetration. Numerical simulation of the separation process and auxiliary systems is carried out to optimize the number of stages, solvent-to-feed ratio, product purity, yield, and energy consumption. Scale-up and cost analysis close the process design. The separation of palmitic acid and (oleic+linoleic) acids from PFAD-Palm Fatty Acids Distillates was used as a case study.

High pressure vapor-liquid equilibria of palm fatty acids distillates-carbon dioxide system

Equilíbrio líquido-vapor do sistema destilado ácido do óleo de palma-dióxido de carbono a alta pressão. Foi investigado experimentalmente o equilíbrio líquido-vapor para o sistema Destilado Ácido de Óleo de Palma (PFAD)/Dióxido de Carbono, nas temperaturas de 333, 353 e 373 K e pressões de 20, 23, 26 e 29 MPa, usando-se o método estático. Os dados experimentais do sistema pseudo-binário PFAD/CO₂ foram correlacionados com a equação de estado de Redlich-Kwong do pacote computacional ASPEN. O modelo reproduz bem os resultados experimentais. A seletividade obtida indica que o CO₂ supercrítico é um solvente razoável para a separação em coluna multi-estágio e contínua, do ácido graxo saturado (ácido palmítico) daqueles insaturados (ácido oleico e ácido linoleico) contidos no PFAD.

Desorption of heavy metals from ion exchange resin with water and carbon dioxide

Adsorption and regeneration of ion exchange resins were studied using a subcritical solution of a CO₂-H₂O mixture and a fixed bed column. The commercial Amberlite IRC-50/IRC-86 cation exchange resins and Amberlite IRA-67 anion exchange resin were tested for heavy metals (Pb, Cu, Cd) adsorption from a solution with different initial metal concentrations at different temperatures. After adsorption, the loaded resins were regenerated with water and carbon dioxide at different temperatures and a pressure of 25 MPa. The efficiency of the IRC-50 resin was lower than that of the IRC-86 resin for the adsorption of metals like Cd, Cu and Pb. Results obtained for desorption of these metals indicated that the process could be used for Cd and in principle for Cu. Sorption of metal ions depended strongly on feed concentration. Mathematical modeling of the metal desorption process was carried out successfully as an extraction process. For this purpose, the VTII Model, which is applied to extraction from solids using supercritical solvents, was used in this work.

Influence of solvent on the morphology and photocatalytic properties of ZnS decorated CeO2 nanoparticles

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Thermal investigation and infrared evolved gas analysis of solid trivalent lanthanide and yttrium alpha-hydroxyisobutyrates in N-2 and CO2 atmospheres

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Increased carbon dioxide concentration in the air reduces the severity of Ceratocystis wilt in Eucalyptus clonal plantlets

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

A time series sequestration and storage model of atmospheric carbon dioxide

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Sr2CeO4: Electronic and structural properties

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Increased atmospheric carbon dioxide concentration: effects on eucalypt rust (Puccinia psidii), C:N ratio and essential oils in eucalypt clonal plantlets

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Translucent tin dioxide ceramics obtained by natural sintering

Dense SnO2-based ceramics (relative density >95%) have been obtained by natural sintering at a moderate temperature (less than or equal to 1300 degrees C) with the help of a small amount of manganese, Further thermal treatments above 1500 degrees C result in grain growth and transport of manganese toward the sample surface. If the ceramic is embedded inside alumina powder, the diffusion of Mn out of the sample and into alumina during such heat treatments leads to a manganese-free body (<40 ppm) which is translucent. The transmission in the visible region depends on sample thickness; 61% was achieved for a 0.05 mm thick sample.

Corrosion prevention for Al2O3/SiC/C/MgAl2O4 based ceramics by means of impregnation with cerium-carrying solution

A cerium-carrying solution was developed so as to aprtially fill the open porosity of Al2O3/SiC/C/MgAl2O4 based refractory lining microstructure used in torpedo ladles, thereby enhancing wear resistance. The protection mchanism was cleared up and introduced from the impregnation technique using a cerium-carrying solution.

Effect of the iron doping on the thermal decomposition of the polymeric precursor for the titanium dioxide powder synthesis

The Polymeric Precursor Method has proved suitable for synthesizing reactive powders using low temperatures of calcination, especially when compared with conventional methods. However, during the thermal decomposition of the polymeric precursor the combustion event can be releases an additional heat that raises the temperature of the sample in several tens of degrees Celsius above the set temperature of the oven. This event may be detrimental to some material types, such as the titanium dioxide semiconductor. This ceramic material has a phase transition at around 600 ° C, which involves the irreversible structural rearrangement, characterized by the phase transition from anatase to rutile TiO2 phase. The control of the calcination step then becomes very important because the efficiency of the photocatalyst is dependent on the amount of anatase phase in the material. Furthermore, use of dopant in the material aims to improve various properties, such as increasing the absorption of radiation and in the time of the excited state, shifting of the absorption edge to the visible region, and increasing of the thermal stability of anatase. In this work, samples of titanium dioxide were synthesized by the Polymeric Precursor Method in order to investigate the effect of Fe (III) doping on the calcination stages. Thermal analysis has demonstrated that the Fe (III) insertion at 1 mol% anticipates the organic decomposition, reducing the combustion event in the final calcination. Furthermore, FTIR-PAS, XRD and SEM results showed that organic matter amount was reduced in the Fe (III)-doped TiO2 sample, which reduced the rutile phase amount and increased the reactivity and crystallinity of the powder samples.

The calcium looping cycle study for capturing carbon dioxide applied to the energy generation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)