Formation of strong electron—acceptor centers in reduced Ga- and PT—Ga zeolites

Mechanism of the decomposition of adsorbed methanol over a Pd/α,β-Ga2O3 catalyst

“…Then, it seems reasonable to suggest, once more, that H S atoms are transferred from Ga 2 O 3 to Pd by reverse spillover, where they finally recombine and desorb as H 2 (g). Lastly, we emphasize again that the oxygen atoms able to transform methoxy species to formate groups are provided by the support; furthermore the reducibility of gallium oxide is enhanced by the presence of noble metals, such as Pd [14,28] or Pt [40]. Thus, in like manner as on clean gallia, surface oxygen atoms of the support react with methoxy groups to yield dioxymethylene species which further transform to formate groups on the Pd/gallia catalyst.…”

A highly efficient Ga/ZSM-5 catalyst prepared by formic acid impregnation and in situ treatment for propane aromatization

“…The characterization of XPS is effective for the chemical states of the elements on the surface of the zeolites. Already published studies 21,25,39,40 have reported that the XPS technique is used to characterize the states of Ga in nonframework or extra-framework positions on the surface of the catalysts. Fig.…”

Preparation of Oxide, Sulfide and Other Chalcogenide Clusters in Molecular Sieves

“…Gallium oxide was shown by transmission electron microscopy to be deposited mainly on the external surface of H-ZSM-5 [97,99,103,104], and this has been confirmed by hexane adsorption measurements [105], XPS [100], and by IR spectroscopy using CO as a probe molecule [98]. A reductive treatment of zeolite H-ZSM-5 modified by gallium oxide led to a better dispersion of gallium within the zeolitic pores as detected by STEM images, IR spectroscopy and XPS [94,97,98,100,101,103,104,106]. The formation of a mobile Ga 2 O species was proposed which is believed to migrate into the zeolitic channels where it can undergo a solid-solid reaction with acidic OH groups [94,97,98,103,104,[107][108][109].…”

“…These catalysts and physical mixtures of Ga 2 O 3 and H-ZSM-5 differ only by the dispersion of gallium oxide and by the average distance between the acid sites of the zeolite and the gallium species [95]. For ion exchange or impregnation, aqueous solutions of gallium nitrate are usually applied, but the treatment of zeolite ZSM-5 under hydrothermal conditions with sodium gallate solution, formed from Ga 2 O 3 and aqueous NaOH, has been reported as well [100,101]. Extensive reaction studies have been carried out; however, the number of investigations concerning the stability of the host framework during catalyst preparation or the structure and location of the guest oxide is smaller.…”

“…The formation of a mobile Ga 2 O species was proposed which is believed to migrate into the zeolitic channels where it can undergo a solid-solid reaction with acidic OH groups [94,97,98,103,104,[107][108][109]. For a sample containing 1.75 wt.% of gallium, Shpiro et al estimated the amount of reduced gallium to be about 30% [101].…”