Influence of the acidity of USY zeolite on the sulfur tolerance of Pd–Pt catalysts for aromatic hydrogenation
Influence of the acidity of USY zeolite on the sulfur tolerance of Pd–Pt catalysts for aromatic hydrogenation
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DOI：
10.1016/s0920-5861(98)00463-5
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发表时间：
1999-04
期刊：
影响因子：
5.3
通讯作者：
H. Yasuda;T. Sato;Y. Yoshimura
中科院分区：
文献类型：
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作者：
H. Yasuda;T. Sato;Y. Yoshimura
在较宽的SiO_2/Al_2O_3比(5.6~680)范围内，以HY和USY(超稳Y)沸石为载体制备了一系列双金属Pd-铂催化剂(Pd：Pt=4：1)，并用化学分析、X射线衍射、氮气吸附、吡啶吸附红外光谱和CO吸附对其进行了表征。在硫浓度为500ppm的二苯并噻吩加氢存在下，Pd-Pt/HY和Pd-Pt/USY催化剂在553 K、氢压为3.9 Mpa的条件下进行了四氢萘加氢反应。沸石的加氢活性、选择性和耐硫性强烈依赖于沸石的SiO_2/Al_2O_3比。活性随SiO_2/Al_2O_3比例的增加而增加，在SiO_2/Al_2O_3比例为15.0~40范围内达到峰值，然后随着SiO_2/Al_2O_3比例的增加而下降。红外光谱分析表明，对于SiO_2/Al_2O_3比在15.0以上的USY分子筛，其表面存在少量的Brnsted酸中心，而存在强的Lewis酸中心。当SiO_2/Al_2O_3比从15.0-40增加到680时，Pd-Pt/USY催化剂的活性和耐硫性都有所下降，这可能是由于Lewis酸度降低导致Pd-铂的缺电子量减少所致。与Pd-Pt/USY(SiO_2/Al_2O_3=15.0~40)催化剂相比，Pd-Pt/HY和Pd-PT/USY(SiO_2/Al_2O_3=10.7)催化剂的活性较低，可能是由于孔扩散的限制。
A series of bimetallic Pd–Pt (mole ratio Pd:Pt=4:1) catalysts supported on HY and USY (ultrastable Y) zeolites for a wide range of SiO2/Al2O3ratio (5.6–680) was prepared and characterized by chemical analysis, XRD, N2adsorption, IR spectroscopy of pyridine adsorption, and CO adsorption. The hydrogenation of tetralin was done over the Pd–Pt/HY and Pd–Pt/USY catalysts at a hydrogen pressure of 3.9MPa at 553K in the presence of dibenzothiophene at a sulfur concentration of 500ppm. The hydrogenation activity, selectivity, and the sulfur tolerance strongly depended on the SiO2/Al2O3ratio of the zeolites. The activity increased with increasing SiO2/Al2O3ratio, peaked when the ratio was in the 15.0–40 range, and then decreased as the ratio increased further. The IR analysis showed that for the USY zeolites with a SiO2/Al2O3ratio of 15.0 or above, the amount of Brønsted acid sites was extremely small, while strong Lewis acid sites existed on the surface of these zeolites. The decrease in both the activity and the sulfur tolerance of Pd–Pt/USY catalysts when the SiO2/Al2O3ratio increases from 15.0–40 to 680 may be primarily due to the decrease in the amount of electron-deficient Pd–Pt resulting from the decrease in Lewis acidity. Compared with the Pd–Pt/USY (SiO2/Al2O3=15.0–40) catalysts, the activities of the Pd–Pt/HY and Pd–Pt/USY (SiO2/Al2O3=10.7) catalysts were lower, probably because of pore diffusional limitations.