The influence of the method for loading platinum precursor and adding
KCl, KCl loading content, calcination temperature, KCl addition proced
ure, various additives, and water washing on the activity and selectiv
ity of Pt/KL catalysts for hexane reforming reaction has been investig
ated. The catalyst preparation methods involve ion exchange (IE), inci
pient wetness impregnation (IWI), and coimpregnation with KCl (IWI-KCl
). The Pt/KL catalysts PrePared by ion ''Change with [Pt(NH3)4]Cl2 fol
lowed by impregnation with KCl (EE-KCl) gave much higher activity and
selectivity for benzene formation than the catalysts prepared by coimp
regnation of KL zeolite with [Pt(NH3)4]Cl2 and KCl. The IE-KCl catalys
t with KCl/Pt molar ratio of 4.5 showed 100.0% conversion of hexane an
d 89.3% yield of benzene at 743 K and 0.2 MPa. The IE-KCl catalysts ex
hibited lower H/Pt ratios than the IE catalyst. The KCl addition proce
dures markedly affected the activity and selectivity of the Pt/KL cata
lyst; the addition of KCl to the IE sample prior to calcination and re
duction was necessary for the catalyst to exhibit the high activity in
benzene formation. It has also been found that the performance of Pt/
KL catalysts is markedly affected by the calcination temperature. With
the IE-KCl catalysts, however, the decrease in the benzene yield caus
ed by high-temperature calcination was not as serious as with the IE c
atalyst. In contrast, with the IWI and IWI-KCl catalysts, the activity
for benzene production was highly sensitive to the calcination at hig
h temperature, drastically decreasing by calcination at 823 K. The Cl
species on the IE-KCl catalysts may have existed in the state of KCl.
(C) 1994 Academic Press, Inc.