Soraia Teixeira Brandão

Cracking and hydrocracking of triglycerides for renewable liquid fuels: alternative processes to transesterification

Os processos industriais mais utilizados na producao de combustiveis liquidos semelhantes ao diesel usam catalisadores homogeneos basicos atraves das metanolise e etanolise de oleos tais como os de soja, canola, palma entre outros. Desse modo, se obtem o biodiesel. Por sua vez, transformacoes termo-cataliticas usando as facilidades existentes nas refinarias de petroleo sao alternativas que merecem atencao devido a sua viabilidade economica. De fato, tres processos industriais ja estao em funcionamento e novos projetos estao em fase final para comercializacao. O presente trabalho analisa os experimentos ja realizados por pesquisadores brasileiros nas areas do craqueamento, do craqueamento catalitico e do hidrocraqueamento catalitico dos oleos vegetais puros ou modificados. A partir dos resultados descritos, sao sugeridas novas direcoes destas pesquisas para os proximos anos. The most used industrial processes for the production of liquid fuels like diesel type are based on the methanolysis and ethanolysis of various oil reactants, such as palm, soybean and rapeseed oils, in the presence of homogeneous base catalysts. However, thermal and catalytic transformations of vegetable oils using available reactors and industrial processes are possible alternatives and deserve attention. In fact, three industrial processes are operating and new projects are announced. The present work analyses the experimental studies performed up to now by Brazilian researchers in the field of cracking, catalytic cracking and hydrocracking of pure or modified vegetable oils. From the published results, some research areas for the near future are suggested.

Palladium-supported catalysts in methane combustion: comparison of alumina and zirconia supports

Palladium catalysts supported on alumina and zirconia were prepared by the impregnation method and calcined at 600 and 1000 oC. Catalysts were characterized by BET measurements, XRD, XPS, O2-TPD and tested in methane combustion through temperature programmed surface reaction. Alumina supported catalysts were slightly more active than zirconia supported catalysts, but after initial heat treatment at 1000 oC, zirconia supported palladium catalyst showed better performance above 500 oC A pattern between temperature interval stability of PdOx species and activity was observed, where better PdOx stability was associated with more active catalysts.

Combustion of Methane Using Palladium Catalysts Supported in Alumina or Zirconia

In this work, catalysts based on palladium supported on alumina and zirconia were prepared by wet impregnation method and calcined at 600 °C and 1000 °C. All the samples were characterized by surface area measurements (BET), X-ray diffraction (XRD), X-ray photoelectronic spectroscopy (XPS), and temperature desorption of oxygen (O2-TPD), and were tested in the combustion of methane using temperature-programmed surface reaction (TPSR). The results indicated that alumina supported catalysts calcined at 600 °C were slightly more active than zirconia supported catalysts, but after heat treatment at 1000 °C, palladium catalyst supported on zirconia presented better performance above 500 °C. The O2-TPD pattern of temperature between the range of stability of PdOx species and activity was observed, where a better PdOx stability was associated with more active catalysts. The aim of this study is to understand the behavior of the Pd catalysts in the combustion of methane by analyzing the effect of the support (alumina or zirconia) and of the heat treatment (600 °C or 1000 °C) using a simple experimental approach.

Characterization of TiLaNa Catalysts in the Oxidative Coupling of Methane

Publisher Summary Recently, many efforts have been directed toward the direct conversion of methane to chemicals. One of the most promising ways seems to be the oxidative coupling of methane (OCM), making methane react with oxygen in the presence of oxide catalysts to give mainly C2+ hydrocarbons. The aim of the study described in the chapter was to characterize the catalyst surface to obtain information about gas–solid interactions in situations as close as possible to the OCM working conditions. Preliminary results coming from surface characterization techniques performed on TiLaNa catalysts are reported. The catalyst surface may be regarded as a CO2 acceptor forming carbonate species, mainly of La but also of Na, because of its surface enrichment with respect to the bulk. These partially reversible carbonate species seem to depress the selectivity to C2 hydrocarbons. Some X-ray photoelectron spectroscopy (XPS) peak shifts were observed in the catalysts with respect to the single oxides: studies are still under way to determine whether the surface is a mixture of one-component oxides or a single ternary compound.

Catalytic combustion of methane over PdO-CeO2/Al2O3 and PdO-CeO2/ZrO2 catalysts

Publisher Summary Hydrocarbon combustion is one of the most important processes for heat and energy generation; however, it results in polluting emissions of nitrogen oxides and carbon monoxide. Methane is one of the most commonly used fuel, and the development of more efficient and less pollutant processes of its combustion (complete combustion at lower temperatures) is a priority. In this context, catalytic combustion offers an alternative to flame combustion because of its ability to promote combustion at lower temperatures than conventional flame combustion, thus reducing residual emissions of NOx, CO, and unburned hydrocarbons. Noble metal catalysts are considered extremely active for the total oxidation of hydrocarbons, and palladium is described in literature as the most active for methane combustion. The active phase of noble metal catalysts is usually dispersed on supports such as SiO2, Al2O3, ZrO2, TiO2, and zeolites. Alumina is most commonly used because of its high surface area, whereas zirconia presents high thermal stability because of its oxygen-rich surface. This is interesting for palladium-based catalysts because it promotes PdO thermal stability, which is the active phase for methane combustion. This chapter describes the preparation, characterization, and activity tests in methane combustion using palladium and cerium supported on alumina and zirconia catalysts.

Oxidative coupling of methane over alkali-promoted Ti-La oxide catalysts. Effect of bulk and surface properties on catalytic performance

The reactivity of lanthanum titanate catalysts is investigated in the oxidative coupling of methane (OCM) under lean-oxygen conditions. The catalyst performances are influenced by the catalyst preparation method and by the amounts of the alkali dopant. A transient method was also used to study the mobility of lattice oxygen species under OCM reaction conditions. It is found that (i) in the absence of gas phase oxygen the sample does not possess lattice oxygen species which participate in the reaction; (ii) the alkali doping does not appreciably modify the mobility of lattice oxygen; and (iii) the role of the alkali promoter in the reaction is that of modifying the surface acid/base and oxidizing properties.

Supported ‖Cp‖2ZrCl2 as catalyst for ethylene polymerization

This work studied the heterogenization of biscyclopentadienyl-zirconium dichloride ([Cp] 2 ZrCl 2 ) on silica surface and the use of the heterogenized catalyst for ethylene polymerization. A supported metallocene catalyst with polymerization activity comparable with the homogeneous species was developed; this catalyst was anchored on silica previously, thermally and chemically, treated. Other procedures that yielded high activity catalyst are also presented. Trimethylaluminum (TMA) was investigated as a co-catalyst for ethylene polymerization with the supported catalysts prepared in this work. The supported catalysts when activated with a co-catalyst composed of equal parts of TMA and methylalumoxane (MAO) had activity about twice as that using of the pure MAO as co-catalyst; oppositely, TMA at any concentration had always a deleterious effect on the homogeneous metallocene activity.