Pt catalysts supported on β zeolite ion-exchanged with Cr(III) for hydroisomerization of n-heptane

A series of Pt catalysts supported on Hβ zeolite ion-exchanged with Cr(III) were prepared, characterized by ICP, XRD, BET, NH3-TPD, H2-TPR and H2-chemisorption techniques, and evaluated in hydroisomerization of n-heptane with an atmospheric fixed-bed flow reactor. Pt catalyst supported on Hβ zeolite exhibits both lower selectivity to isomerized products and lower conversion of n-heptane than the counterparts supported on Cr(III)-exchanged Hβ zeolite. The optimal composition for Cr-bearing catalysts is 0.4 wt.% of Pt loading and 0.7 wt.% of Cr loading. This catalyst proves to be highly efficient in the hydroisomerization of n-heptane, giving a very high selectivity to isomerized products: 95.4% coupled with a high conversion of n-heptane: 72.1%. The substantial promotion effect of ion-exchanged Cr(III) species is discussed in relation to catalyst physicochemical properties.

For hydroisomerization of n-heptane, Hβ supported Cr catalyst shows very low conversion () and isomerization selectivity (★). However, when Cr is introduced into Hβ supported Pt catalysts by Cr(III) ion-exchange, remarkable increases in conversion (□) and selectivity to isomerized products (▾) are obtained. The promotion effect of Cr arises from the increased number of strong acid sites, improved Pt dispersion, and enhanced reducibility of Pt.Figure optionsDownload as PowerPoint slide