In situ X-ray photoelectron spectroscopy study of gallium-modified MFI zeolite

An in situ XPS investigation of calcined and reduced GaMFI was conducted both at room temperature and at 823 K. In the reduced GaMFI most of gallium is distributed at room temperature inside the zeolite channels in the form Ga+ compensating cations. At high temperatures and under ultra-high vacuum conditions the formation of metallic gallium was observed, most likely as a result of the disproportionation of Ga+ cations. During this disproportionation Ga3+ compensating cations are also formed. In the presence of hydrogen the disproportionation of Ga+ is reversible.