Applied Catalysis A: General, Vol.161, No.1-2, 227-234, 1997
Effects of Heavy Rare-Earth Addition on Properties of Kl Zeolite-Supported Platinum Reforming Catalyst
A series of Pt-RE-KL catalysts, which containing 0.8 wt% platinum and 0.2 wt% RE (RE=Gd, Tb, Dy, Tm, Yb, Lu), have been prepared by impregnation of the L-type zeolite support with corresponding RE nitrate aqueous solutions. The reforming reactions of rt-hexane, cyclohexane and methylcyclopentane (MCP) on Pt-RE-KL catalysts have been investigated with a plus microcatalytic apparatus. The surface properties and the active sites of these catalysts have also been studied with TPD, TPR and plus-CS2 poisoning test. Our results reveal that those heavy rare earth elements added to Pt-KL catalyst have effect of electronic donation to Pt particles and blocking the accumulation of active Pt particles, and thus can remarkably increase the ability of resistant sulfur poisoning and the aromatic selectivity of n-hexane or MCP conversion on the Pt-KL catalyst. Studies on the relationship between the magnetic properties of catalysts and the activities as well as selectivity of catalysts show that after addition of the RE, the magnetic susceptibilities of Pt-RE-KL catalysts decrease dramatically compared with that of Pt-KL catalyst, while catalytic properties of Pt-RE-KL catalysts are improved, which suggests that the unpaired electron numbers of Pt particles are decreased by RE2O3’s giving electrons to Pt particles, therefore electronic property of catalysts is one of the most important factors affecting the activity of Pt-RE-KL catalysts.