Preparation, characterization and catalytic testing of GePt catalysts

Abstract

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).

Doping Platinum with Germanium: An Effective Way to Mitigate the CO Poisoning

“…Other studies show that the addition of GeO 2 to Pt/C changes the adsorption properties of CO on the platinum surface, [36] and that bimetallic PtGe/C catalyst presents an easier CO oxidation as well as a higher electrocatalytic activity in methanol oxidation [37] . Ge can boost the catalytic performance of Pt for dehydrogenation reactions or naphtha reforming too, and prevents the formation of undesired coke deposits [38–45] . Nevertheless, studies on the potential promotional effect of Ge are still very scarce, and it is unclear what effect Ge exerts on Pt in such catalytic processes.…”

Hydrogenation of p-chloronitrobenzene over NiPtB nanoalloy catalysts

“…Bimetallic catalysts [1][2][3][4][5][6][7][8] are the subject of considerable interest in heterogeneous catalysis, because their catalytic properties can be superior to those of monometallic catalysts for many reactions. It is now widely acknowledged that the addition of a second metal provides a method to control the activity, selectivity, and stability of the catalysts in certain reactions.…”

Pt:Ge ratio as a lever of activity and selectivity control of supported PtGe clusters in thermal dehydrogenation

“…Germanium too has been tested as a promoter for Pt in reactions such as naphtha reforming or larger alkane and cycloalkane dehydrogenation reactions. [21][22][23][24][25][26][27][28] In the past, we predicted that germanium could be an adequate alloying agent to tune the selectivity and sintering resistance of Pt sub-nanoclusters in the ethane dehydrogenation reaction. 29 This finding was later proven experimentally.…”