Effect of ethanol on the isomerization of n-heptane over Pt/SAPO-11 and Pt/ZSM-22 catalysts

The hydroisomerization of n-heptane over the Pt/SAPO-11 and Pt/ZSM-22 catalysts prepared by the impregnation methods was systematically investigated in the presence of ethanol. The physicochemical properties, adsorption and reaction behaviors, and active acid sites were studied by X-ray diffraction, N₂-adsorption, C₂H₅OH-TPD and C₂H₅OH-FTIR techniques. A negative impact of alcohol was observed; the activity and selectivity to isomers decreased with the increase of the ethanol amount. Nevertheless, the effect of ethanol on the hydroisomerization over the Pt/SAPO-11 was weaker than that over the Pt/ZSM-22, showing that Pt/SAPO-11 is more resistant to oxygenated compounds due to the presence of a large amount of P-OH groups in SAPO-11. The effect of ethanol on the isomerization of n-heptane occurs through its dehydration into water over the catalysts.