沸石催化剂上醇的醚化反应

ETHERIFICATION OF ALCOHOLS OVER ZEOLITE CATALYSTS

研究了乙醇、正丁醇、仲丁醇和正戊醇在ＺＳＭ５和Ｂｅｔａ沸石上的醚化反应。用ＮＨ３ＴＰＤ和ＩＲ测定了ＺＳＭ５沸石的表面酸性，讨论了沸石表面Ｂ酸和Ｌ酸与醚化活性的关系。结果表明，乙醇的脱水反应既可以在Ｂ酸中心上进行，也可以在Ｌ酸中心上进行；既可以在强酸中心上进行，亦可以在弱酸中心上进行。但在Ｌ酸或弱酸中心上需要更高的反应温度。对结构不同的醇，其脱水活性顺序为：乙醇＞仲丁醇＞正丁醇＞正戊醇；生成醚的选择性顺序为：乙醇＞正丁醇＞仲丁醇＞正戊醇。实验结果还表明，由于沸石的孔结构效应，分子体积较大的醚的生成将受到抑制。

The etherification reactions of ethanol, 1butanol, 2butanol and 1pentanol over HZSM5, NaZSM5L and Hβ zeolites in a flow reactor are described The surface acidity measured by NH 3TPD and IR is discussed The correlation between the activity and B acid sites, L acid sites is suggested The results indicat that the dehydration of ethanol to ethyl ether and ethylene can take place both at the B acid sites and L acid sites, while the dehydration over L acid sites is only carried out at the higher reaction temperature The dehydration of ethanol can be catalyzed both by acid sites of strong and weak The dehydration on weak acid sites demand a higher reaction temperature than that on strong acid sites At identical reaction conditions, the activity trend of various alcohols is: ethanol>2butanol>1butanol>1pentanol, and the selectivity trend to ethers is: ethanol>1butanol>2butanol>1pentanol Inside of zeolites the formation of bulky ethers is inhibited owing to the smaller size of the pores