Os processos industriais mais utilizados na produção de combustíveis líquidos semelhantes ao diesel usam catalisadores homogêneos básicos através das metanólise e etanólise de óleos tais como os de soja, canola, palma entre outros. Desse modo, se obtém o biodiesel. Por sua vez, transformações termo-catalíticas usando as facilidades existentes nas refinarias de petróleo são alternativas que merecem atenção devido a sua viabilidade econômica. De fato, três processos industriais já estão em funcionamento e novos projetos estão em fase final para comercialização. O presente trabalho analisa os experimentos já realizados por pesquisadores brasileiros nas áreas do craqueamento, do craqueamento catalítico e do hidrocraqueamento catalítico dos óleos vegetais puros ou modificados. A partir dos resultados descritos, são sugeridas novas direções destas pesquisas para os próximos 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.
In
this paper, two biosystems based on filamentous fungi and Pd
nanoparticles (NPs) were synthesized and structurally characterized.
In the first case, results concerning the integration and distribution
of Pd-NPs on Phialomyces macrosporus revealed that
nanoparticles are accumulated on the cell wall, keeping the cytoplasm
isolated from abiotic particles. However, the Penicillium sp. species showed an unexpected internalization of Pd-NPs in the
fungal cytosol, becoming a promising biosystem to further studies
of in vivo catalytic reactions. Next, we report a
new solution-based strategy to prepare palladized biohybrids through
sequential reduction of Pd2+ ions over previously harvested
fungus/Au-NP composites. The chemical composition and the morphology
of the biohybrid surface were characterized using a combination of
scanning electron microscopy, transmission electron microscopy, and
photoelectron spectroscopy. The deposition of Pd0 over
the fungal surface produced biohybrids with a combination of Au and
Pd in the NPs. Interestingly, other chemical species such as Au+ and Pd2+ are also observed on the outermost wall
of microorganisms. Finally, the application of A. niger/AuPd-NP biohybrids in the 3-methyl-2-buten-1-ol hydrogenation reaction
is presented for the first time. Biohybrids with a high fraction of
Pd0 are active for this catalytic reaction.
Recebido em 4/8/11; aceito em 6/2/12; publicado na web em 15/5/12Palladium catalysts supported on alumina and zirconia were prepared by the impregnation method and calcined at 600 and 1000 °C. Catalysts were characterized by BET measurements, XRD, XPS, O 2 -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 °C, zirconia supported palladium catalyst showed better performance above 500 °C A pattern between temperature interval stability of PdOx species and activity was observed, where better PdOx stability was associated with more active catalysts.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.