Roles of Pt and alumina during the combustion of coke deposits on propane dehydrogenation catalysts

Mongkhonsi, Tharathon; Prasertdham, Piyasan; Saengpoo, Atchara; Pinitniyom, Nonglak; Jaikaew, Bualom

doi:10.1007/bf02707096

Cited by 7 publications

(12 citation statements)

References 12 publications

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“…After the first cycle, coke combustion occurs at a much lower temperature for Pt/γ-Al 2 O 3 than for Pt-Sn/γ-Al 2 O 3 , suggesting that carbon deposits are in the proximity of the Pt sites in the Pt catalyst, whereas for the Pt-Sn catalyst, carbon deposits are likely located on the alumina support because combustion occurs at a higher temperature. 22 After the 10th cycle, coke combustion temperatures have changed for both catalysts, and the combustion profiles are now similar. In a previous study of olefin metathesis catalysts, we demonstrated by EFTEM how the coke can be present on the alumina support and not block the active sites.…”

Section: Resultsmentioning

confidence: 92%

“…The results show that the extent of deactivation of Pt/γ-Al 2 O 3 and Pt-Sn/γ-Al 2 O 3 could not be correlated with coke deposits, as is commonly assumed in the literature. 22 , 24 , 30 , 39 , 40 This is because the coke can be effectively transported to the support, as suggested previously, 19 , 29 , 41 , 42 allowing the active sites to continue functioning.…”

Section: Introductionmentioning

confidence: 74%

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Role of Sn in the Regeneration of Pt/γ-Al₂O₃ Light Alkane Dehydrogenation Catalysts

et al. 2016

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Alumina-supported Pt is one of the major industrial catalysts for light alkane dehydrogenation. This catalyst loses activity during reaction, with coke formation often considered as the reason for deactivation. As we show in this study, the amount and nature of carbon deposits do not directly correlate with the loss of activity. Rather, it is the transformation of subnanometer Pt species into larger Pt nanoparticles that appears to be responsible for the loss of catalytic activity. Surprisingly, a portion of the Sn remains atomically dispersed on the alumina surface in the spent catalyst and helps in the redispersion of the Pt. In the absence of Sn on the alumina support, the larger Pt nanoparticles formed during reaction are not redispersed during oxidative regeneration. It is known that Sn is added as a promoter in the industrial catalyst to help in achieving high propene selectivity and to minimize coke formation. This work shows that an important role of Sn is to help in the regeneration of Pt, by providing nucleation sites on the alumina surface. Aberration-corrected scanning transmission electron microscopy helps to provide unique insights into the operating characteristics of an industrially important catalyst by demonstrating the role of promoter elements, such as Sn, in the oxidative regeneration of Pt on γ-Al2O3.

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Section: Resultsmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 74%

Role of Sn in the Regeneration of Pt/γ-Al₂O₃ Light Alkane Dehydrogenation Catalysts

et al. 2016

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“…This adverse effect is also prominent on Pt-or Cr-based systems, [19] which, however, can easily be regenerated by oxidation with air. [20] Propane conversions in our experiments are rather low (< 5 %), however, the formation rate of propylene over b-Mo 2 C in the pseudo-steady state is among the highest reported at 500 8C ( Figure 1).…”

Section: Resultsmentioning

confidence: 44%

“…Although the carbide phase is stable, deposition of carbonaceous species as shown in a quasi in situ Raman experiment (Figure 2) leads to a rapid decrease in activity with time on stream at the higher temperatures. This adverse effect is also prominent on Pt‐ or Cr‐based systems,19 which, however, can easily be regenerated by oxidation with air 20. Propane conversions in our experiments are rather low (<5 %), however, the formation rate of propylene over β ‐Mo 2 C in the pseudo‐steady state is among the highest reported at 500 °C (Figure 1).…”

Section: Resultsmentioning

confidence: 59%

Carbon Dynamics on the Molybdenum Carbide Surface during Catalytic Propane Dehydrogenation

Frank¹,

Cotter²,

Schuster³

et al. 2013

Chemistry A European J

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The effect of the gas-phase chemical potential on surface chemistry and reactivity of molybdenum carbide has been investigated in catalytic reactions of propane in oxidizing and reducing reactant mixtures by adding H2, O2, H2O, and CO2 to a C3H8/N2 feed. The balance between surface oxidation state, phase stability, carbon deposition, and the complex reaction network involving dehydrogenation reactions, hydrogenolysis, metathesis, water-gas shift reaction, hydrogenation, and steam reforming is discussed. Raman spectroscopy and a surface-sensitive study by means of in situ X-ray photoelectron spectroscopy evidence that the dynamic formation of surface carbon species under a reducing atmosphere strongly shifts the product spectrum to the C3-alkene at the expense of hydrogenolysis products. A similar response of selectivity, which is accompanied by a boost of activity, is observed by tuning the oxidation state of Mo in the presence of mild oxidants, such as H2O and CO2, in the feed as well as by V doping. The results obtained allow us to draw a picture of the active catalyst surface and to propose a structure-activity correlation as a map for catalyst optimization.

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“…Improvement in catalytic activity has been reported by using Pt-Sn on Al 2 O 3 [9] and ZSM-5 as support [21][22][23][24][25]. The interaction of tin on the performance of Pt-Sn catalysts has been extensively investigated [26][27][28][29][30][31][32]. Tin modifies the electronic density of Pt [33] and decreases the size of platinum leading to reduction in coking formation [34][35][36].…”

Section: Introductionmentioning

confidence: 99%

Influence of operating conditions, Si/Al ratio and doping of zinc on Pt-Sn/ZSM-5 catalyst for propane dehydrogenation to propene

Nawaz

Tang

Wei

2009

Korean J. Chem. Eng.

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The direct catalytic dehydrogenation of propane to propene is an important route to enhance propene production. In the present experimentation the focus was to investigate the influence of incipient operating conditions, Si/Al ratio of zeolite support and effect of zinc doping on Pt-Sn/ZSM-5 catalyst performance. The catalysts were extensively investigated by reaction tests in a continuous plug-flow quartz micro-reactor. The experimental data shows that the manipulation of operating parameters significantly improves the reaction performance, while huge dynamicity is observed in product distribution. Reaction temperature, 600 o C is found to be most suitable, while increasing the weight hourly space velocity (WHSV), propene selectivity improves at the expense of lower conversion. The OPE was drawn to observe overall reaction network. It was found that the acidity of zeolitic support plays a more important role in achieving desired product selectivity than additional metallic content. Accordingly, the Si/Al ratio of the ZSM-5 zeolite the pro-pene selectivity was enhanced, leading to remarkable improvement in the total olefins selectivity which was remarkably improved owing to a suppression of secondary reactions. At Si/Al ratio 300, the selectivity of propene and total olefins becomes stable at 73% and 90% respectively. The doping of Zn on Pt-Sn/ZSM-5 improves only propene selectivity, but is severely affected by quick deactivation.

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Roles of Pt and alumina during the combustion of coke deposits on propane dehydrogenation catalysts

Cited by 7 publications

References 12 publications

Role of Sn in the Regeneration of Pt/γ-Al₂O₃ Light Alkane Dehydrogenation Catalysts

Role of Sn in the Regeneration of Pt/γ-Al₂O₃ Light Alkane Dehydrogenation Catalysts

Carbon Dynamics on the Molybdenum Carbide Surface during Catalytic Propane Dehydrogenation

Influence of operating conditions, Si/Al ratio and doping of zinc on Pt-Sn/ZSM-5 catalyst for propane dehydrogenation to propene

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Roles of Pt and alumina during the combustion of coke deposits on propane dehydrogenation catalysts

Cited by 7 publications

References 12 publications

Role of Sn in the Regeneration of Pt/γ-Al2O3 Light Alkane Dehydrogenation Catalysts

Role of Sn in the Regeneration of Pt/γ-Al2O3 Light Alkane Dehydrogenation Catalysts

Carbon Dynamics on the Molybdenum Carbide Surface during Catalytic Propane Dehydrogenation

Influence of operating conditions, Si/Al ratio and doping of zinc on Pt-Sn/ZSM-5 catalyst for propane dehydrogenation to propene

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Role of Sn in the Regeneration of Pt/γ-Al₂O₃ Light Alkane Dehydrogenation Catalysts

Role of Sn in the Regeneration of Pt/γ-Al₂O₃ Light Alkane Dehydrogenation Catalysts