Enhanced stability of Pt@S-1 with the aid of potassium ions for n-hexane and n-heptane aromatization

As a typical high-efficient alkane aromatization catalyst, Pt/KL is prone to deactivation due to the sintering growth of Pt on the outer surface of KL and the channel blockage caused by carbon deposition , which is further exacerbated by the one-dimensional channel structure of KL. Therefore, a series of encapsulated catalysts combining the three-dimensional channel structure advantages of S-1 with the role of potassium are prepared and evaluated. It is shown that the encapsulated catalyst KPt@S-1-02 modified by moderate potassium exhibits extremely superior stability and no significant deactivation is observable after n-heptane aromatization for 180 h under harsh conditions. On the one hand, encapsulation structure enables a strong anti-agglomeration ability of Pt and the topological structure of S-1 endows the encapsulation catalysts less susceptible to channel blockage, which has been demonstrated by HAADF-STEM and N 2 -adsorption. On the other hand, characterizations involving NH 3 -TPD, CO-DRIFT and HAADF-STEM verify that the modification by an appropriate amount of K can inhibit acid sites of catalysts and improve Pt dispersion and electron density, thus enhance the stability of catalysts. However, excessive K can serve as weak acid sites, poison of active sites and inhibitor of H 2 adsorption on Pt surface, leading to deactivation of the catalyst.