Mariana M.V.M. Souza

Aqueous-phase reforming of glycerol using Ni–Cu catalysts prepared from hydrotalcite-like precursors

Ni–Cu catalysts derived from hydrotalcite-like compounds were prepared with 20 wt% of NiO and 0, 5 and 10 wt% of CuO, and evaluated in the aqueous-phase reforming of glycerol. The catalysts were characterized by chemical composition, textural analysis, crystalline structure, reducibility and acidity. The reaction was performed in a continuous flow reactor with a solution of 10 vol% glycerol, at 250 °C/35 atm and 270 °C/50 atm. The maximum glycerol conversion at 250 °C/35 atm was 70% and total conversion of glycerol was achieved at 270 °C/50 atm with Cu-containing catalysts. In the gas phase, the H2 selectivity was around 40% and CO selectivity was very low at 250 °C/35 atm. The addition of Cu decreased the CH4 formation. The main products formed in the liquid phase were acetol and lactic acid and a small quantity of propanoic acid. The Cu-containing catalysts showed higher formation of acetol, which was correlated with their higher acidity. Characterization of the spent catalysts revealed a sintering of the metal particles, although no deactivation was observed during 6 h of reaction.

Synthesis Gas Production from Natural Gas on Supported Pt Catalysts

Abstract Auto-thermal reforming of methane, combining partial oxidation and reforming of methane with CO2 or steam, was carried out with Pt/Al2O3 Pt/ZrO2 and Pt/CeO2 catalysts, in a temperature range of 300–900°C. The auto-thermal reforming occurs in two simultaneous stages, namely, total combustion of methane and reforming of the unconverted methane with steam and CO2, with the O2 conversion of 100% starting from 450°C. For combination with CO2 reforming, the Pt/CeO2 catalyst showed the lowest initial activity at 800°C, and the highest stability over 40 h on-stream. This catalyst also presented the best performance for the reaction with steam at 800°C. The higher resistance to coke formation of the catalyst supported on ceria is due to the metal-support interactions and the higher mobility of oxygen in the oxide lattice.

Production of synthesis gas from natural gas using ZrO2-supported platinum

Reforming of methane with steam, partial oxidation of methane and a combination of both reactions were camed out using Pt/Al2O3, Pt/ZrO2 and Pt/10%ZrO2/Al2O3 catalysts, in temperature range between 350–900°C. For steam reforming, the H2/CO product ratio is strongly influenced by the water-gas shift reaction, with the Pt10Zr sample showing the highest activity and stability. When oxygen is present in the feed, the total combustion is the main reaction at low temperatures. The catalyst with 10% of ZrO2 also presented the best performance for partial oxidation and oxy-steam reforming.

Surface characterization of zirconia-coated alumina as support for Pt particles

ZrO 2 /Al 2 O 3 samples were prepared by impregnation of the alumina powder with a solution of zirconium hydroxide in nitric acid, containing ZrO 2 in the range of 1-20 wt%. Platinum was impregnated by incipient wetness technique, using an aqueous solution of H 2 PtCl 6 . The surface coverage of zirconia on alumina, as probed by XPS and ISS, increased up to 10 wt% of ZrO 2 and above this concentration crystallites of zirconia nucleated, which decreases the BET surface area. XRD measurements indicated that the average size of these crystallites was about 1 nm. ISS data of Pt/ZrO 2 and Pt/10%ZrO 2 /Al 2 O 3 catalysts, after reduction at 773 K indicated an increase in the surface population of Zr atoms which are able to catch CO. This interaction was also probed by FTIR spectra of CO adsorbed on Pt/ZrO 2 catalyst, where an intense band at 2130 cm -1 , associated to CO adsorption on Pt-ZrO x interface, was observed.

Production of hydrogen from steam reforming of glycerolusing nickel catalysts supported on Al2O3, CeO2 and ZrO2

Abstract Nickel catalysts supported on Al2O3, CeO2 and ZrO2 were prepared by wet impregnation method and evaluated in steam reforming of glycerol. The catalysts were characterized by chemical composition, textural analysis, crystalline structure and reducibility. The structural characterization of the catalysts revealed a good dispersion of Ni particles using the Al2O3 support, needing higher reduction temperature. The reactions were performed at 500°C with 10 vol.% glycerol solution in a continuous flow reactor. All catalysts showed conversions close to 100%. The selectivity to gas products and formation of liquid by-products were found to be dependent on the type of support. The H2 selectivity showed the following trend: ZrO2 > Al2O3 ≈ CeO2. The catalyst supported on CeO2 showed low activity for water-gas shift reaction, with the highest CO selectivity. All catalysts presented a low formation of CH4. In the liquid phase some by-products were identified (hydroxyacetone, acetic acid, lactic acid, acetaldehyde, acrolein and ethanol) and secondary reaction routes were proposed. Coke formation was higher on Ni/Al2O3 catalyst, but no deactivation was observed during 8 h of reaction.

Synthesis of Sr-doped LaMnO3 and LaCrO3 powders by combustion method: structural characterization and thermodynamic evaluation

Manganita de lantânio dopada com estroncio (LSM) e cromita (LSC) em po, bem como as correspondentes amostras nao dopadas, foram sintetizadas pelo metodo de combustao, usando dois diferentes combustiveis (ureia e glicina). A ignicao da mistura reacional com ureia leva mais tempo e a temperatura maxima e maior do que usando glicina, para as amostras dopadas. Os calculos teoricos de calor de reacao e temperatura de chama adiabatica indicam condicoes favoraveis a combustao. No entanto, a calcinacao e uma etapa essencial para uma boa cristalizacao da fase perovskita. Os padroes de difracao de raios X mostraram a formacao apenas da fase perovskita para as amostras sintetizadas com ureia. Os tamanhos de cristalitos estao na faixa de 19-25 nm, com valores menores quando a ureia e usada como combustivel. Analises de microscopia eletronica de varredura mostraram a presenca de aglomerados, formados por particulas finas de diferentes formas. A analise termogravimetrica revelou que a perda de peso e muito maior para as manganitas, com queima completa dos orgânicos em 850-900 oC.

Atual estágio de desenvolvimento da tecnologia GTL e perspectivas para o Brasil

Although the production of liquid fuels from coal, natural gas (CTL and GTL processes) and other carbon sources has been discovered 90 years ago, the interest was renewed in the last years motivated by stranded gas reserves and by petroleum market instability. This review intends to show the scenario of these technologies nowadays, discussing the applied technologies, the steps in an industrial plant, the ways to produce syngas and liquid fuels, the catalysts used, the type of reactors and the operating plants with their respective capacities, besides the technical, economical and environmental viability, challenges and perspectives for Brazil.

Tar removal from biomass gasification streams: processes and catalysts

Biomass gasification is a technology that has attracted great interest in synthesis of biofuels and oxo alcohols. However, this gas contains several contaminants, including tar, which need to be removed. Removal of tar is particularly critical because it can lead to operational problems. This review discusses the major pathways to remove tar, with a particular focus on the catalytic steam reforming of tar. Few catalysts have shown promising results; however, long-term studies in the context of real biomass gasification streams are required to realize their potential.

Removal of boron from oilfield wastewater via adsorption with synthetic layered double hydroxides.

Hydrotalcite is a layered double hydroxide (LDH) consisting of brucite‐like sheets of metal ions (Mg‐Al). In this work, hydrotalcites were synthesized, and boron removal from oilfield wastewater was evaluated. LDHs were synthesized using the co‐precipitation method. The calcined products (CLDHs) were obtained by heating at 500°C and characterized using X‐ray diffraction, X‐ray fluorescence, thermogravimetric analysis and the specific surface area (BET). The affinity of LDHs for borate ions was evaluated for calcined and uncalcined LDHs as a function of contact time, initial pH of the oilfield wastewater (pH ∼ 9) and the LDH surface area. The tests were conducted at room temperature (approximately 25ºC). The results indicated that 10 min were needed to reach a state of equilibrium during boron removal for calcined LDHs due to the high surface area (202.3 m2 g−1) regardless of the initial pH of the oilfield wastewater, which resulted from the high buffering capacity of the LDHs. The adsorption capacity increased as the adsorbents levels increased for the range studied. After treatment of the oilfield wastewater containing 30 mg L−1 of boron with Mg‐Al‐CO3‐LDHs, the final concentration of boron was within the discharge limit set by current Brazilian environmental legislation, which is 5 mg L−1. Pseudo–first‐order and pseudo–second‐order kinetic models were tested, and the latter was found to fit the experimental data better. Isotherms for boron adsorption by CLDHs were well described using the Langmuir and Freundlich equations.

Study of the mechanism of the autothermal reforming of methane on supported Pt catalysts

Autothermal reforming of methane was investigated on Pt/CeO2, Pt/ZrO2 and Pt/Ce-ZrO2 catalysts. Temperature programmed surface reaction experiments (TPSR) showed the reaction proceeds through an indirect mechanism. A carbon removal mechanism was observed for the catalysts that presented oxygen storage capacity, favoring the stability of the catalyst in the reaction.