Influence of Hydrogen Pretreatment on the Structure of the Metal-Support Interface in Pt/Zeolite Catalysts

Vaarkamp, Marius; Modica, FS; Miller, J.T.; Koningsberger, DC Diek

doi:10.1006/jcat.1993.1357

Cited by 111 publications

(84 citation statements)

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“…The quality of the fits is similar to those previously reported (28). For Pt/H-LTL, the Pt-Pt coordination number is 5.6 (ca 14 atoms/cluster), whereas the Pt-Pt coordination number is 4.0 (ca 6 atoms/cluster) for Pt/K-LTL.…”

Section: Exafs Multiple Shell Fittingsupporting

confidence: 84%

“…In a vacumn, a decrease in the metal-metal bond distance of approximately 0.1Å has been observed for small metal particles, e.g., Pt/γ -Al 2 O 3 (40), Pt/Y (41), and Ir/γ -Al 2 O 3 (42). By contrast, bulk-like coordination distances are observed for small metal particles covered by chemisorbed hydrogen (28,29,40,42). Chemisorbed hydrogen withdraws electron density from the metal atom which increases the internuclear repulsions and results in an expansion of the metalmetal bond distance.…”

Section: Structural Characterizationmentioning

confidence: 97%

“…The node in the imaginary part for the catalyst around 2.7Å, however, is shifted to lower R. Furthermore, the imaginary parts of the Fourier transforms between about 2.2 to 2.6Å are completely different for the foil and the catalyst. These differences in the Fourier transforms indicate the presence of an additional oxygen scatter in the Pt/H-LTL catalyst (28). Figure 4 shows a comparison of the Fourier transforms (Pt-Pt phase and amplitude corrected) for Pt(S)/H-LTL and Pt(S)/K-LTL catalysts.…”

Section: Exafs Data Analysismentioning

confidence: 99%

“…For Pt/H-LTL, the Pt-Pt coordination number is 5.6 (ca 14 atoms/cluster), whereas the Pt-Pt coordination number is 4.0 (ca 6 atoms/cluster) for Pt/K-LTL. A long Pt-O distance around 2.7Å is characteristic of platinum catalysts reduced at low temperature and is due to the presence of chemisorbed hydrogen between the metal cluster and the support surface (28,30,31). Because of the smaller platinum particle size in Pt/K-LTL, there is a larger Pt-O coordination number, e.g., N = 0.9 for Pt/K-LTL compared to N = 0.5 for Pt/H-LTL.…”

Section: Exafs Multiple Shell Fittingmentioning

confidence: 99%

“…The observed Pt-O distance around 2.7Å is characteristic of platinum catalysts reduced at low temperature and is longer than the sum of the atomic radii for platinum and oxygen. This long distance results from the presence of chemisorbed hydrogen between the metal cluster and the support surface (28,30,31).…”

Section: Structural Characterizationmentioning

confidence: 99%

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The Origin of Sulfur Tolerance in Supported Platinum Catalysts: The Relationship between Structural and Catalytic Properties in Acidic and Alkaline Pt/LTL

Miller¹,

Koningsberger

1996

Journal of Catalysis

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The reactivity, structure, and sulfur tolerance is compared for platinum supported on acidic and alkaline LTL zeolite. In the absence of sulfur, EXAFS spectroscopy indicates that small metallic platinum particles of approximately 6 to 14 atoms/cluster are present. The TOF for neopentane hydrogenolysis and isomerization is ca 100 times higher on the acidic LTL due to the metalsupport interaction. Saturation of the platinum by H 2 S, results in the formation of surface Pt-S bonds with a bond length of 2.33Å. Comparison of the EXAFS results of the sulfur poisoned catalysts, indicates that the S to Pt ratio is lower for platinum on the acidic zeolite. Catalytically, the initial activity (per gram) of both catalysts is greatly reduced after sulfur poisoning due to the loss of exposed platinum, however, the initial neopentane TOFs are nearly unchanged. Because of its higher TOF, the catalytic activity (per gram) of sulfur poisoned, acidic Pt/LTL is comparable to that of nonsulfur poisoned alkaline Pt/LTL. In both sulfur poisoned catalysts the neopentane isomerization selectivity increases compared to the sulfur free catalyst. Although the initial TOFs of the nonsulfur poisoned and sulfur poisoned catalysts are the same, there is a rapid loss in activity due to coke formation in the sulfur poisoned, alkaline LTL, while rate of deactivation by coke in the sulfided, acidic LTL is much lower. The increased sulfur tolerance of acidic supported noble metal catalysts appears to result primarily from the higher intrinsic TOF. In addition, because of its resistance to coke deactivation, the acidic supported sulfur tolerant catalyst is able to maintain stable catalytic activity.

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Section: Exafs Multiple Shell Fittingsupporting

confidence: 84%

Section: Structural Characterizationmentioning

confidence: 97%

Section: Exafs Data Analysismentioning

confidence: 99%

Section: Exafs Multiple Shell Fittingmentioning

confidence: 99%

Section: Structural Characterizationmentioning

confidence: 99%

See 3 more Smart Citations

The Origin of Sulfur Tolerance in Supported Platinum Catalysts: The Relationship between Structural and Catalytic Properties in Acidic and Alkaline Pt/LTL

Miller¹,

Koningsberger

1996

Journal of Catalysis

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Decorated (Coated) Carbon Nanotubes: (X/CNTs)

Bacsa

Serp

2011

Carbon Meta‐Nanotubes

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Metal–Support Interactions

Ruppert

Weckhuysen

2008

Handbook of Heterogeneous Catalysis

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Supported metal catalysts are comprised of small metal nanoparticles dispersed on the surface of a support material. Previously, the role of the support oxide was commonly thought to be limited to provide large metal surface areas. However, it is now generally accepted that the activity and selectivity of these catalysts are dependent on the type and composition of the support used [1][2][3] or even on thermal pretreatment conditions of catalysts consisting of the same metal and support [4]. In other words, the role of the support goes well beyond strictly physical phenomena such as increasing the surface area, and the specific interaction of the support with the active phase often controls the course of a catalytic reaction.Understanding the effect of the support oxide on the properties of metal nanoparticles is a challenging subject because it opens a way towards modeling and tuning of the catalytic properties by a deliberate choice of the support oxide [5][6][7][8]. As a consequence, gaining an insight into the interfacial structure between metal nanoparticles and their support, particularly under relevant reaction conditions, has been an important topic in the field of heterogeneous catalysis for decades [9,10]. Therefore,

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Influence of Hydrogen Pretreatment on the Structure of the Metal-Support Interface in Pt/Zeolite Catalysts

Cited by 111 publications

References 0 publications

The Origin of Sulfur Tolerance in Supported Platinum Catalysts: The Relationship between Structural and Catalytic Properties in Acidic and Alkaline Pt/LTL

The Origin of Sulfur Tolerance in Supported Platinum Catalysts: The Relationship between Structural and Catalytic Properties in Acidic and Alkaline Pt/LTL

Decorated (Coated) Carbon Nanotubes: (X/CNTs)

Metal–Support Interactions

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