Characterization and catalytic study of PtGe/Al2O3 catalysts prepared by organometallic grafting

Wootsch, Attila; Paál, Z.; Győrffy, Nóra; Ello, Aimé Serge; Boghian, Irina; Leverd, Julie; Piraúlt-Roy, Laurence

doi:10.1016/j.jcat.2005.11.035

Cited by 19 publications

(24 citation statements)

References 47 publications

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“…These sites could be successfully activated by more surface hydrogen. The relatively high frag (Table 2) and benzene selectivity values were also analogous to earlier results obtained with Ge1/2 [13]. The saturated products formed over GePt/SiO 2 consisted mainly of MCP ( Figure 5) indicating the poorer utilization of higher H 2 pressures to create Pt-H sites necessary to promote opening of the MCP ring to isomers.…”

Section: Discussionsupporting

confidence: 84%

“…Our GePt black catalyst was, however, better than the parent Pt (Figure 9). Its behaviour (Figure 8) was analogous to the second best bimetallic alumina-supported sample, i.e., Ge1/8 [13]. The selectivities on GePt were close to the values measured on GePt/SiO 2 , both as a function of reaction temperature (Tables 2 and 4) and H 2 pressure (Figures 5 and 9).…”

Section: Discussionsupporting

confidence: 72%

“…Our previous study [13] revealed that small amounts of Ge (Ge 1/12 and Ge1/8) increased the catalytic activity of Pt and also the selectivities to saturated products (skeletal isomers and MCP) from hexane. The reason was the selective deposition of small amounts of germanium to platinum into positions where reactions requiring multiple sites (fragmentation [41] and aromatization [14]) would occur.…”

Section: Discussionmentioning

confidence: 96%

“…In the Ge1/2 sample, much higher fraction of the surface was covered with inactive Ge, rendering this sample the least active of the series. Samples Ge1 and Ge2 contained a high fraction of Ge in deeper layers, forming "bulk bimetallic" catalysts which again contained more active surface Pt sites [13], but not necessarily with the same selectivities.…”

Section: Discussionmentioning

confidence: 99%

“…Our recent paper [13] used organometallic grafting for preparing Pt-Ge/Al 2 O 3 catalysts with various Ge content. The amount of Ge added was expressed there in terms of monolayers: e.g., "Ge1/12" means adding 1/12 Ge to Pt while "Ge 1" means 1 monolayer Ge on Pt.…”

Section: Introductionmentioning

confidence: 99%

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Preparation, characterization and catalytic testing of GePt catalysts

Győrffy

Bakos

Szabó

et al. 2009

Journal of Catalysis

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Unsupported and SiO2 supported GePt bimetallic catalysts were prepared by depositing Ge on to Pt underpotentially. Surface-sensitive cyclic voltammetry of Pt black indicated that Ge covered ca. 40-45 % of the Pt surface, whereas XPS showed just ~96 % Pt and ~4 % Ge (normalized to Pt+Ge=100 %). High-resolution Ge map of GePt black obtained by Energy Filtered TEM (EFTEM) showed Ge scattered in the near-surface regions. Both catalysts were tested in hexane (nH) transformation reactions between 543 and 603 K and 60 to 480 Torr H2 pressure (with 10 Torr nH), and compared with the parent Pt catalysts. GePt/SiO2 catalyst was also tested with methylcyclopentane (MCP). Adding Ge to Pt/SiO2 lowered the activity; the opposite effect was observed with GePt black. The selectivities of saturated products on bimetallic catalysts decreased, while those of hydrogenolysis products, benzene and hexenes increased in nH transformations over supported catalyst. The reverse effects were observed over the black samples where addition of Ge prevented accumulation of adventitious carbon. Ring opening was the main reaction with MCP, together with some fragments, benzene and unsaturated hydrocarbons. Ring opening of MCP became more selective with decreasing temperature and increasing hydrogen pressure. Ge on GePt black blocked contiguous Pt sites favoring the formation of coke precursors. The different catalytic behavior of GePt/SiO2 indicated somewhat different Pt-Ge interaction(s).

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Section: Discussionsupporting

confidence: 84%

Section: Discussionsupporting

confidence: 72%

Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Preparation, characterization and catalytic testing of GePt catalysts

Győrffy

Bakos

Szabó

et al. 2009

Journal of Catalysis

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Dehydrocyclization—Heterogeneous

Paál¹

2010

Encyclopedia of Catalysis

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The formation of aromatic rings from alkanes such as hexane, heptane, octane, and so on (aromatization or dehydrocyclization) on oxide catalysts: chromia, lanthana, metals, such as platinum, palladium, and so on, and nonacidic (Na‐ or Ba‐L zeolite) supports is a “monofunctional” route, catalyzed by the active ingredient itself. A bifunctional route prevails in naphtha reforming (platforming) over Pt on acidic supports (eg, alumina). Interactions of Pt with acidic or alkaline support can be important for aromatization. The metallic function can also catalyze the formation of five‐membered ring(s): C5‐cyclization. The effect of added metallic components resulting in bimetallic catalysts (such as PtRe, PtSn, and so on) as well as the effect of nonmetallic components (Cl, S, C, H) is discussed. Aromatization requiring skeletal rearrangement (eg, of alkylpentane feeds) can also take place. Cyclic hydrocarbons may undergo ring enlargement and ring contraction. The same catalyst may promote the formation of a second ring in alkylcyclopentanes. The buildup of aromatic rings is also possible from smaller molecules (ethane, propane, butane) by dehydrocyclodimerization over bifunctional catalysts, such as ZSM 5 zeolites containing Pt, Zn, but first of all Ga (eg, in the CYCLAR process). Aromatics can be produced even from methane (Mo carbide‐ZSM‐5 or Pd‐Co catalysts).

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