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•Many Rh catalysts were tested for N2O decomposition under diesel conditions.•Rh/CeO2 is the only catalyst with good activity in a wet feed after aging.•Aging does not deactivate ...Rh/CeO2 but significantly increases its activity.•Removal O2 from the catalyst has been demonstrated to be the rate limiting step.
Numerous Rh catalysts were evaluated for N2O decomposition for automotive applications. Some Rh-containing spinel materials exhibit excellent fresh activities in the absence of H2O but become inactive after hydrothermal aging or when tested in a wet feed. Rh catalysts supported on zeolites can be very active in a dry feed even after aging but are extremely sensitive to H2O. Rh/CeO2 is an exceptional catalyst for this reaction in the presence of both H2O and O2. Hydrothermal aging (750 °C/20 h) significantly increases its activity. A similar activity enhancement was found by calcining the support before Rh impregnation. XPS results show a surface enrichment of Rh species on the aged Rh/CeO2 catalyst relative to the fresh catalyst. Aberration corrected STEM images reveal that Rh is buried in the bulk on the fresh catalyst and pulled out onto the surface of the support after thermal treatments. All catalysts are inhibited by H2O with the zeolite-based Rh catalysts being the worst. The aged Rh/CeO2 catalyst is less sensitive to H2O relative to others. DRIFTS data show that H2O sensitivity is related to catalyst hydrophilicity; a high coverage of OH groups on a catalyst reduces its N2O decomposition activity. H2-TPR results show that a Rh/CeO2 catalyst can be readily reduced at < 100 °C. On a reduced Rh/CeO2 catalyst, near complete N2O conversion can be obtained with a lean feed at 250 °C for a duration equivalent to its oxygen storage capacity. The N2O-DRIFTS experiments over a pre-reduced Rh/CeO2 catalyst show that Ce3+ sites are quickly oxidized to Ce4+ upon contacting N2O at room temperature, resulting N2 and adsorbed O, with the latter being an efficient oxidizer. Based on these results, a N2O decomposition mechanism is proposed for the Rh/CeO2 catalyst.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Fluid Catalytic Cracking (FCC) has maintained its crucial role in refining decades after its initial introduction owing to the flexibility it has as a process as well as the developments in its key ...enabler, the FCC catalyst. Boron-based technology (BBT) for passivation of contaminant metals in FCC catalysts represents one such development. In this contribution we describe Fourier Transform Infrared Spectroscopy (FTIR) characterization of boron-containing catalysts to identify the phase and structural information of boron. We demonstrate that FTIR can serve as a sensitive method to differentiate boron trioxide and borate structures with a detection limit at the 1000 ppm level. The FTIR analysis validates that the boron in the FCC catalysts studied are in the form of small borate units and confirms that the final FCC catalyst product contains no detectable isolated boron trioxide phase. Since boron trioxide is regulated in some parts of the world, this novel FTIR methodology can be highly beneficial for further FCC catalyst development and its industrial application at refineries around the world. This new method can also be applied on systems beyond catalysts, since the characterization of boron-containing materials is needed for a wide range of other applications in the fields of glass, ceramics, semiconductors, agriculture, and pharmaceuticals.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Fluid Catalytic Cracking (FCC) is a crucial refining process supplying majority of gasoline used worldwide as well as other key building blocks for chemical industry. Nickel, a contaminant in crude ...oil, deposits on FCC catalysts and induces unwanted dehydrogenation reactions, inhibiting the FCC unit from reaching optimal operation. We describe a new spectroscopic methodology to characterize the impact of boron interaction on nickel in FCC catalysts through a trend analysis of CO DRIFTS for FCC catalysts from boron-based technology. Results obtained by the new method provide direct spectroscopic evidence of boron effect on nickel passivation by decreasing reducibility of nickel.
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•A new DRIFTS-based characterization methodology for evaluation of the state of Ni and its reducibility was developed.•Interference from impurities in FCC catalysts typical in standard CO DRIFTS measurements can be avoided with new method.•Direct spectroscopic evidence of boron effect on nickel passivation by decreasing its reducibility is presented.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Examples on the real-world field application of Raman spectroscopy with systematic analysis of the intensity variation of D and G bands corresponding to the change of excitation laser energy to ...characterize and compare coke species from various industrial processes are presented. The findings indicate the different degree of sp
and sp
hybridized bonding structures of amorphous carbon collected from different industrial processes as well as heavy carbonaceous deposits generated by industrial catalysts. This spectroscopic methodology is practical and highly beneficial in identifying coke formation mechanisms in industrial processes, as well as supporting design strategies to abate the undesired coke formation on industrial catalysts.
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IJS, KILJ, NUK, PNG, UL, UM, UPUK
In this contribution, we present an industrial example on how tailored operando spectroscopic methodologies provide the insights needed for the development of new catalytic technologies and support ...their global utilization. We describe the use of operando spectroscopic methods to investigate how the CO oxidation performance of catalysts is impacted by NOx, H2, temperature, and moisture, as well as the catalyst support. This operando spectroscopic analysis provides mechanistic insights into the current diesel oxidation catalyst (DOC) system and shines light on the material and process development efforts on future DOC catalysts for low-temperature emission control to meet the new regulations. This investigation has shown that at cold-start temperatures, the nitrate growth can occupy the precious metal–alumina support interfacial sites that are critical for O2 dissociation and/or oxygen transfer and hinder CO conversion. Introduction of hydrogen on the catalyst surface can inhibit the nitrate growth, which in turn keeps these critical interfacial sites open.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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