The partial oxidation of methane over Pd/Al2O3 catalyst nanoparticles studied in-situ by near ambient-pressure x-ray photoelectron spectroscopy

Near ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) is used to study the chemical state of methane oxidation catalysts in-situ. Al2O3{supported Pd catalysts are prepared with different particle sizes ranging from 4 nm to 10 nm. These catalysts were exposed to conditions similar to those used in the partial oxidation of methane (POM) to syn-gas and simultaneously monitored by NAP-XPS and mass spectrometry. NAP-XPS data show changes in the oxidation state of the palladium as the temperature in- creases, from metallic Pd0 to PdO, and back to Pd0. Mass spectrometry shows an increase in CO production whilst the Pd is in the oxide phase, and the metal is reduced back under presence of newly formed H2. A particle size effect is observed, such that CH4 conversion starts at lower temperatures with larger sized particles from 6 nm to 10 nm. We find that all nanoparticles begin CH4 conversion at lower temperatures than polycrystalline Pd foil

Catalyseurs et procédés catalytiques utilisés dans la production des grands intermédiaires pétrochimiques. Situation actuelle et futur Catalysts and Catalytic Processes Used for the Production of the Major Petrochemical Building Blocks. Present Situation and the Future

La pétrochimie représente une part modeste du marché des catalyseurs, mais les dix dernières années ont vu des améliorations substantielles des catalyseurs et des procédés utilisés. Ces améliorations ont permis de mieux répondre à la demande en grands intermédiaires pétrochimiques. Cette évolution est bien illustrée par les hydrogénations, autour du vapocraquage destiné à produire des oléfines, par le reformage catalytique et les procédés satellites destinés à produire des aromatiques et par les nouveaux procédés de déshydrogénation, métathèse, oligomérisation. . . qui permettent de mieux équilibrer le marché des oléfines. <br> Petrochemicals account for a modest share of the market for catalysts, but there have been substantial improvements in the catalysts and processes used in the last ten years. These improvements have brought about a better response to the demand for major petrochemical building blocks. This trend is clearly illustrated by hydrogenations in the field of steam cracking to produce olefins, by catalytic reforming and satellite processes to produce aromatics, and by new processes such as dehydrogenation, metathesis and oligomerization which provide better balance to the market for olefins