The Interaction of Oxides of the Pd/Ce/Zr/Al2O3 Catalysts Prepared by Impregnation Over Alumina and Promoting Effects on Surface Properties

Selective hydrogenation of cinnamaldehyde over Pd (2 wt%) supported on CeO 2, ZrO 2 and CeO 2 -ZrO 2 catalysts is reported for the first time. In general, the olefinic (C=C) group of cinnamaldehyde is preferentially hydrogenated compared to the carbonyl (C=O) group. This selectivity preference could, however, be altered or reversed by adding alkali additives to the catalyst. The influence of additive on the structure and redox properties of the active sites and correlation of that with selective hydrogenation activity is investigated.

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“…The B.E. values of Ce 3d 5/2 and Zr 3d 5/2 are also included in Table 2 and are consistent with the reported values [33].…”

Section: X-ray Photoelectron Spectroscopysupporting

confidence: 87%

“…and Pd 4? states are 335 and 340.6, 337.5 and 342.9, and 338.4 and 343.5 eV, respectively corresponding to the 3d 5/2-3/2 spin-orbit doublet [33][34][35][36]. The binding energy of Zr 3p also falls in the same range.…”

Section: X-ray Photoelectron Spectroscopymentioning

confidence: 83%

Chemoselective Hydrogenation of Cinnamaldehyde over Pd/CeO2–ZrO2 Catalysts

Seemala

Srinivas

2010

Catal Lett

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“…In addition, BET surface areas were measured and resulted in 167.3, 624.6, 669,7, 582.9 and 579.5 for Pd/Ce/Al 2 O 3 , Pd/ SSZ-13 (SAR = 12 and 24) and Pd/BEA (SAR 38 and 300), respectively. According to N 2 physisorption data, it can be seen that the BET surface area of the Pd/Ce/Al 2 O 3 catalyst was lower [20], which is expected since alumina support has lower surface area compared to zeolites in general. Highest BET specific surface areas are revealed for small-pore-sized SSZ-13-based materials [21].…”

Section: Catalyst Characterizationmentioning

confidence: 94%

The Effect of Si/Al Ratio for Pd/BEA and Pd/SSZ-13 Used as Passive NOx Adsorbers

et al. 2018

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The mitigation of cold-start emissions involves the development of passive NO x adsorbers (PNA) systems that store NO x at low temperature, being designed to release the trapped NO x at higher temperatures, where downstream NO x reduction catalysts are efficient. Pd-based zeolites (BEA, SSZ-13) with different SAR (Si-to-Al ratio) were used for PNA investigation, and Pd/Ce/Al 2 O 3 catalyst was used as a reference for comparison. In this study, NO x adsorption is investigated at low temperature (80 °C) and it is released during a temperature ramp (to 400 °C) under various gas feed composition. Moreover, detailed characterization was performed using BET, XRD, XPS, TPO, STEM and ICP-SFMS and the stored NO species was studied using in-situ DRIFTS. The addition of CO to the storage mixture resulted in that for Pd/zeolites with low and medium SAR the binding energy for NO was increased. In addition, NO was stored in larger quantities, especially for the Pd/SSZ-13 samples. However, for Pd/BEA (SAR = 300) no such stable NO species was formed and for Pd/Ce/Al 2 O 3 the CO addition was even negative. Moreover, in-situ NO DRIFTS showed that there was large amount of nitrosyls on ionic palladium for the Pd/zeolites with low and medium SAR, indicating that a significant fraction of the palladium was in ionexchanged positions, while this peak was small for the Pd/BEA (SAR = 300) and non-existing for Pd/Ce/Al 2 O 3. Thus, CO addition is beneficial for Pd species that are in ion-exchanged positions, but this is not the case for Pd particles and this can explain the observations that CO is only beneficial for Pd/zeolites with low and medium SAR. Moreover, experiments with similar SAR [Pd/BEA (SAR = 25) and Pd/SSZ-13 (SAR = 24)], showed that there is larger stability of the stored NO x in the small pore Pd/SSZ-13.

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“…Other experimental techniques corroborate XPS results, showing a beneficial effect of ceria in maintaining Pd in oxidized form and/or shifting PdO decomposition to higher temperature [14,16,38,43,49,57]. The stabilization of oxidized palladium by ceria is often observed also after aging or reducing treatments [14,16,28,45,46,50,52,53,[58][59][60][61], post reaction [22,44,62,63], or during in situ or operando experiments [14,32,38,52,[64][65][66] even in oxygen deficient atmosphere typical of stoichiometric (or rich) operation [14,38,66].…”

mentioning

confidence: 74%