X-ray absorption spectroscopic study on the states of gallium and platinum in Pt/Ga/H-beta zeolites

In situ Ga K edge XANES study of the activation of Ga/ZSM-5 prepared by chemical vapor deposition of trimethylgallium

“…Table 1 lists the corresponding EXAFS fit parameters. The structure analysis of the [23,24]. The data are also in good agreement with a separate XANES analysis of the edge, giving Ga(t)/ Ga(o) = 0.73.…”

Characterization of bifunctional Pt/H[Ga]ZSM5 and Pt/H[Al]ZSM5 catalysts

“…These results clearly demonstrate the effect of the supported platinum on the "degalliation" process (equivalent to the dealumination of aluminosilicate zeolites) of these Pt/H[Ga]ZSM5 catalysts, a phenomenon that could be associated to the mobility of gallium in this solids as a consequence of thermal effects, but basically due to the formation of stable chemical species between platinum and gallium, which have been proposed as bimetallic (Pt-Ga) by Chao et al [19]. Therefore, it was suggested that the non-sintering of the supported metallic phase (dispersion is over 80% in the present solids) and the low hydrogenating activity of the solids are a direct consequence of the formation of these species.…”

“…It has also been found that in systems consisting of physical blends of Ga 2 O 3 and protonic zeolites, as well as in zeolites exchanged with aqueous solutions of Ga 3+ precursor salts, gallium migrates from the surface into the framework of the zeolite structure, to occupy tetrahedral positions; this phenomenon has been attributed to the mobility of gallium when it is subjected to thermal treatments [19]. If gallium can migrate from the surface into the crystalline zeolitic structure, the reverse process could also take place; in this regard, Ga 3+ has been found to migrate from framework sites toward the solid surface in Ga-loaded zeolites.…”

Supported platinum–gallium catalysts for selective hydrodechlorination of CCl4

“…The reduction and migration of gallium are dramatically promoted by interacting with Pt in both Ga/H-ZSM-5 and Ga-silicate supported platinum catalyst [55], in good agreement with the TPR results in our case, where PtGa assemblies or PtGa alloys were supposed to be formed on the catalyst surface. It is reported that for Pt/Ga/H-beta zeolites, the GaPt bimetallic species are formed with inter-atomic distance of 2.51-2.54Å upon reduction as determined by EXAFS analyses, and the sintering of Pt are prevented to aggregate into large particles by the Ga [51]. Thus, the dependence of dispersion on the Ga loading as shown in Table 4 can be well understood by considering the formation of PtGa assemblies, where Ga atoms may cover or be attached on the surface of Pt particles or even be incorporated into the Pt lattice to form PtGa alloys, and a similar preventing effect is expected to occur during the forming of Pt particles as in the case of reference [51].…”

“…The ratio of A line to B line slightly increases upon the Ga loading, indicative of an increase in the amount of the Pt sites involved in the Pt-F interaction due to the Ga addition. It is found that Ga atom can migrate and then be incorporated into Pt cluster during the process of reduction in the case of a Pt/Ga/H-Beta zeolite [51]. Ga can diffuse into the crystal lattices of platinum metal to form PtGa alloys of various compositions [52].…”