Hydroisomerization of n-heptane over MoP/Hβ catalyst doped with metal additive

• Doping Ni, Ce or Cr improves the activity of MoP/Hβ for n-heptane hydroisomerization.
• A promoting isomerization of n-heptane is obtained over MoP/Hβ doped with Cr.
• Doping Ni, Ce or Cr leads to improved MoPOx reduction and less blocking of β pores.
• Doping Cr increases the density of strong acid sites on MoP/Hβ.

The bifunctional catalysts of molybdenum phosphide supported on Hβ zeolite (MoP/Hβ) were prepared using a co-impregnation–temperature-programmed reduction method, and catalytically tested in the hydroisomerization of n-heptane. The catalytic conversion and isomerization selectivity of MoP/Hβ were revealed to be higher than those of the control tungsten phosphide sample WP/Hβ and the HMCM22-supported counterpart MoP/HMCM22. Moreover, doping Cr, Ni, or Ce significantly improved the activity of MoP/Hβ; meanwhile, the Cr-promoted catalyst also gave an enhanced selectivity to isomerization products. The catalysts were characterized by X-ray diffraction, Brunauer–Emmett–Teller analysis, temperature-programmed desorption of NH3, and temperature-programmed reduction of H2. Accordingly, it is suggested that the promoting effect of the secondary metal additive is relative to the reduction of MoPOx species, as well as the pores and acid sites of the β zeolite.

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