The effects of hydrogen treatment on Zn/HZSM-5 catalysts to the evolution of zinc species and their activity in n-pentane aromatization were studied. By heating Zn/HZSM-5 catalysts under inert atmosphere, most of zinc species appeared as (ZnOH)(+). The XPS and IPA-TPD results showed that using H-2 as a treatment gas, the hydro dehydroxylation of (ZnOH)(+) generated (ZnH)(+) species with the recovery of some Bronsted acid sites. It was found that under the hydrogen atmosphere, the H-2 molecule was dissociated on this Zn species and generated the H-2-chemisorbed Zn species. Compared with HZSM-5 catalyst, the presence of (ZnOH)(+) species improved the aromatics selectivity from 11% to 22%. Nevertheless, after pre-treating Zn/HZSM-5 with H-2, the formation of H-2-chemisorbed Zn species remarkably increased the BTX aromatics selectivity to 31%. It was found that the H-2-chemisorbed Zn species was not stable in the absence of H-2 however it could be regenerated upon H-2 treatment. (C) 2016 Elsevier B.V. All rights reserved.