Pt supportedβ zeolite catalysts promoted by rare earth elements Ce or La were prepared by the co-impregnation method, and characterized by X-ray diffraction (XRD), BET surface areas( BET), temperature-programmed desorption of ammonia ( NH3-TPD) and H2-chemisorption techniques. Their catalytic activities were evaluated on the hydroisomerization of n-heptane with an atmospheric fixed-bed reactor. The Pt-bearing catalyst doped with Ce or La, especially Ce, was found to exhibit a higher catalytic conversion and much higher isomerization selectivity than the catalyst without the dopant. At the low reaction temperature of 230 ℃, the catalyst with a Pt loading of 0. 4％ and a molar ratio of Ce to Pt of 5: 1 showed a high conversion rate of n-heptane of 61.5％ coupled with a very high selectivity to isomerization products of 96. 7％. In contrast, over the counterpart catalyst without Ce, the conversion rate of n-heptane was 50. 6％ with a low selectivity to isomerization products of 82. 4％. In addition, the same promotion effects of Ce or La were observed on the catalysts, in which dealuminating Hβ zeolite or ultra-stable Y zeolite was pre-coated with phosphotungstic acid as the acidic support. The substantial promotion effect of Ce was suggested in relation to the improved catalyst acidity and the dispersion of the supported Pt.%采用共浸渍法制备稀土元素Ce、La修饰的Pt/Hβ催化剂,通过比表面积测定(BET)、X线衍射(XRD)、NH3程序升温脱附(NH3-TPD)对催化剂进行表征,在连续流动常压固定床反应器上考察催化剂的正庚烷临氢异构化反应性能.结果表明:催化剂中Ce或La的引入提高了正庚烷转化率,同时还在很大程度上提高了异构化产物的选择性.CePt/Hβ催化剂的最佳组成为Pt负载量(质量分数)0.4%,n(Ce):n(Pt)=5:1,催化剂在230℃的反应温度下表现出很高的正庚烷转化率(61.5%)和异构化选择性(96.7%),明显高于相应的Pt/Hβ催化剂性能(50.6%和82.4%).另外,在脱铝β沸石及预先负载杂多酸(磷钨酸)的脱铝Y沸石载体上也发现了Ce或La对其催化性能的促进作用.稀土元素Ce和La通过改善催化剂酸性和Pt分散度而起到了助催化作用.
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