Adsorption Characteristics of Sol-Gel Gd–Pd/TiO2 Catalysts in Reduction of Nitric Oxide with CH4: DRIFTS and TPD

Watson, Junko M.; Ozkan, Umit S.

doi:10.1006/jcat.2002.3675

Cited by 32 publications

(10 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Many groups had focussed on developing synthesis routes to modified TiO 2 with visible light response by metal, nonmetal doping, and coupling with other semiconductors [5][6][7]. It was also demonstrated that F-doped TiO 2 is effective for enhancing photocatalytic activity.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of fluorine-doped titania-coated activated carbon under low temperature with high photocatalytic activity under visible light

et al. 2008

Journal of Physics and Chemistry of Solids

View full text Add to dashboard Cite

Section: Introductionmentioning

confidence: 99%

Synthesis of fluorine-doped titania-coated activated carbon under low temperature with high photocatalytic activity under visible light

et al. 2008

Journal of Physics and Chemistry of Solids

View full text Add to dashboard Cite

“…Therefore, NO adsorption was combined with DRIFTS to identify monodispersed Pd species in PdLTA. It should be noted that Pd particles generally adsorb very little NO [21,24,25]. Nitrosyl groups on Pd 2+ typically absorb IR radiation with wave numbers of 1800-1881 cm −1 [7,21,[26][27][28][29].…”

Section: Characterizationmentioning

confidence: 99%

“…Note that no major bands were observed in the region of 1700-2700 cm −1 , and this region is therefore not shown for PdAl. The NO adsorption ability is generally low on Pd particles [21,24,25], thus the spectra of PdAl mostly show the NO adsorption on the Al 2 O 3 support. The IR absorbance in the wave number region 1611-1547 cm −1 and 1316 cm −1 is assigned to surface nitrates, whereas the absorbance at the lower wave number 1232 cm −1 corresponds to surface nitrites [34].…”

Section: Catalytic Activity Of Degreened and Aged Samplesmentioning

confidence: 99%

Hydrothermal Aging of Pd/LTA Monolithic Catalyst for Complete CH4 Oxidation

2020

View full text Add to dashboard Cite

Palladium-based catalysts are known to provide high CH4 oxidation activity. One drawback for these materials is that they often lose activity in the presence of water vapor due to the formation of surface hydroxyls. It is however possible to improve the water vapor tolerance by using zeolites as support material. In this study, we have investigated Pd supported on thermally stable LTA zeolite with high framework Si/Al ratio (Si/Al = ~44) for CH4 oxidation and the effect of hydrothermal aging at temperatures up to 900 °C. High and stable CH4 oxidation activity in the presence of water vapor was observed for Pd/LTA after hydrothermal aging at temperatures ≤ 700 °C. However, aging at temperatures of 800–900 °C resulted in catalyst deactivation. This deactivation was not a result of structural collapse of the LTA zeolite as the LTA zeolite only showed minor changes in surface area, pore volume, and X-ray diffraction pattern after 900 °C aging. We suggest that the deactivation was caused by extensive formation of ion-exchanged Pd2+ together with Pd sintering. These two types of Pd species appear to have lower CH4 oxidation activity and to be more sensitive to water deactivation compared to the well dispersed Pd particles observed on the LTA support prior to the hydrothermal aging. By contrast, Pd/Al2O3 was generally sensitive to water vapor no matter of the aging temperature. Although the aging caused extensive Pd sintering in Pd/Al2O3, only minor deterioration of the CH4 oxidation activity was seen. The results herein presented show that Pd/LTA is a promising CH4 oxidation catalyst, however Pd rearrangement at high temperatures (≥800 °C) is one remaining challenge.

show abstract

“…Metallic Pd (Pd 0 ) is more desirable than palladium oxides. 15,16 Pd 0 not only showed superior performance in the adsorption of NO 17,18 but also was beneficial in the activation of H 2 . 19 Therefore, many strategies, such as adding promoters 20−23 or varying supports, 24,25 were developed to modify the valence state of palladium species.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Among supported noble metal (Pt, Pd, Ir) catalysts, palladium-based catalysts were usually used as potential catalysts for industrial application due to their high selectivity. − Catalytic activities of Pd-based catalysts were found to be dependent on the chemical nature of Pd species and types of NO x adsorbed species. Metallic Pd (Pd 0 ) is more desirable than palladium oxides. , Pd 0 not only showed superior performance in the adsorption of NO , but also was beneficial in the activation of H 2 . Therefore, many strategies, such as adding promoters − or varying supports, , were developed to modify the valence state of palladium species.…”

Section: Introductionmentioning

confidence: 99%

Photothermal Synergism on Pd/TiO₂ Catalysts with Varied TiO₂ Crystalline Phases for NO_x Removal via H₂-SCR: A Transient DRIFTS Study

Zhang

Luo

et al. 2022

Ind. Eng. Chem. Res.

View full text Add to dashboard Cite

In this work, photothermal synergism over Pd/TiO2 catalysts with varying rutile and anatase phases was investigated for selective catalytic reduction of NO with H2. In the absence of light, two NO x reduction peaks were observed over Pd/TiO2 catalysts. Pd/TiO2-R exhibited better NO x conversion (65 vs 30%) at 75 °C, while Pd/TiO2-A delivered higher activity (82 vs 40%) at 225 °C. Light excitation exerted a more significant promotional effect over Pd/TiO2-R than over the Pd/TiO2-A catalyst. Diffuse reflectance infrared spectroscopy (DRIFTS) with transient experiments indicated that more nitrates and ammonia species formed on Pd/TiO2-R. For Pd/TiO2-R, bridging, mondentate, and bidentate nitrates served as active NO x adsorbed species at all the investigated reaction temperatures. Ammonia species that originated from the reduction of active NO x species were highly active intermediates, which can react with active NO x species to form N2 and H2O. However, for the Pd/TiO2-A catalyst, bridging and monodentate nitrates were active NO x adsorbed species at 75 °C. The reaction pathway at 225 °C facilitates the reaction between adsorbed NO2 and spiltover hydrogen. From the results of valence band X-ray photoelectron spectroscopy (VBXPS) and UV–vis diffuse reflectance spectroscopy (UV–vis DRS), it could be deduced that the photogenerated holes of both Pd/TiO2 catalysts could activate NO and hydrogen. Moreover, the electrons in the conduction band of the Pd/TiO2-R catalyst had stronger reduction ability, which could combine with O2 to form •O2 –. All these results provided a new insight into the understanding of photothermal synergism in heterogeneous catalysis.

show abstract

Adsorption Characteristics of Sol-Gel Gd–Pd/TiO2 Catalysts in Reduction of Nitric Oxide with CH4: DRIFTS and TPD

Cited by 32 publications

References 47 publications

Synthesis of fluorine-doped titania-coated activated carbon under low temperature with high photocatalytic activity under visible light

Synthesis of fluorine-doped titania-coated activated carbon under low temperature with high photocatalytic activity under visible light

Hydrothermal Aging of Pd/LTA Monolithic Catalyst for Complete CH4 Oxidation

Photothermal Synergism on Pd/TiO₂ Catalysts with Varied TiO₂ Crystalline Phases for NO_x Removal via H₂-SCR: A Transient DRIFTS Study

Contact Info

Product

Resources

About

Adsorption Characteristics of Sol-Gel Gd–Pd/TiO2 Catalysts in Reduction of Nitric Oxide with CH4: DRIFTS and TPD

Cited by 32 publications

References 47 publications

Synthesis of fluorine-doped titania-coated activated carbon under low temperature with high photocatalytic activity under visible light

Synthesis of fluorine-doped titania-coated activated carbon under low temperature with high photocatalytic activity under visible light

Hydrothermal Aging of Pd/LTA Monolithic Catalyst for Complete CH4 Oxidation

Photothermal Synergism on Pd/TiO2 Catalysts with Varied TiO2 Crystalline Phases for NOx Removal via H2-SCR: A Transient DRIFTS Study

Contact Info

Product

Resources

About

Photothermal Synergism on Pd/TiO₂ Catalysts with Varied TiO₂ Crystalline Phases for NO_x Removal via H₂-SCR: A Transient DRIFTS Study