稀土对ZSM-5分子筛芳烃烷基化反应性能的影响

THE EFFECT OF RARE-EARTH ON THE ALKYLATION PERFORMANCE OF ZEOLITE ZSM-5 CATALYST

本文制备了含不同稀土量的改性ZSM-5分子筛催化剂,考察了它们的甲苯乙醇乙基化反应性能,发现在稀土含量大于4％时,催化剂具有较好的反应稳定性。选择了含稀土4％的改性催化剂,比较了反应条件对催化剂性能的影响,并选择出较佳的反应条件为:WHSV=1.5h^(-1)、370 C、甲苯/乙醇=2(摩尔比)。在此条件下作了200h的乙基化反应,该催化剂表现出良好的稳定性。

The aromatic alkylation to form directly para-dialkylbenzene is an ad- vanced catalytic process. It has many advantages especially in energy saving and productivity increasing than the conventional process in industry. So this subject has been carring by many catalytic researchers since zeolite ZSM-5 was synthesised in the 1970s and has made great progress. Now the main problem of this process is its reaction stability. Coke deposition is the cause for deactivity of this alkylation catalyst. From early exploration of the effects of the properties of zeolite acidity and pore size on the coke deposition, we found that the rare-earth compound may restrain the dehydrogenation of organic compounds on the zeolite surface and enhance the alkylation stability. In this paper we further study the effect of the rare-earth compound on the properties of zeolite ZSM-5 catalyst in the toluene alkylation with ethanol. The reaction stability is the main parameter in our discussion. The experiment results show that the adding of rare-earth compound is favor for reaction stability. When the content of rare-earth is more than 4%, the reaction stability can not be changed greatly. The effect of operating conditions on the reaction properties are also studied and the suitable ones are se- lected. The selective catalyst containning 4% rare-earth oxide has good reaction stability du- ring the 200 hours TOS.