(66b) Isomerization of Hexane on Pt-Au Nanoparticles Supported on Zeolites

It is planned to eliminate benzene and its derivatives from petrol and to replace them by methylated hydrocarbons, whence the importance of the isomerization of n-alkanes, which is currently performed in liquid superacid media, since current solid superacids are very rapidly poisoned. We show that some Pt-Au based zeolite catalysts can be useful in this reaction.

Samples were prepared according to reference [1] with 1% w/w of Pt and a ratio Au/Pt=20. UV-Visible, microtomy-EM and EDX spectroscopies show that the particles are essentially in the pores and are bimetallic.

The hydroisomerization of hexane was carried out at 200-350°C in a flow-type fixed-bed reactor. HY, Pt?HY and PtAu-HY are of no interest for this reaction. The efficiency of PtAu-HZSM5 is noteworthy; it is remarkably stable over one week with a selectivity and an activity for methylpentane of about 80% at 260°C. Moreover, cracking is negligeable, the other reaction products being i-C5 and i-C4.

[1] Riahi G., Guillemot D., Polisset-Thfoin M., Khodadafi A., Fraissard J., J. Catal. Today, 72, 115 (2002)