摘要
采用XRD和原子吸收光谱法研究了微波作用下分子筛表面酸性对ZnCl2 与Y分子筛固态相互作用的影响 .结果表明 ,微波辐射可显著促进ZnCl2 在分子筛表面分散 ,其分散阈值与分子筛表面酸性有关 .随着分子筛表面酸量和酸强度增加 ,ZnCl2在分子筛表面的最大分散量减少 ,分散的ZnCl2 与Y分子筛的固态离子交换量也减少 ;NaY型分子筛比HY分子筛更容易发生固态离子交换反应 .考察了微波固相法制备的ZnCl2 /HY催化剂在苯甲醚与乙酰氯酰化反应中的催化性能 .结果表明 ,在分子筛表面分散的ZnCl2 具有更高的催化活性及对甲氧基苯乙酮选择性 .
The effects of surface acid properties of Y zeolite on the solid state interaction between ZnCl2 and Y zeolite with different ion-exchange degrees of Na+ by H+ under microwave irradiation (MWI) were investigated. The XRD patterns indicated that ZnCl2 dispersed completely on the surface of HY-98 zeolite (the number denotes ion-exchange degree) with ZnCl2 loading of 0.45 mmol/g under MWI. The dispersion threshold of Zn-Cl-2 on the surface of HY-98 is in the range from 0.45 to 0.70 mmol/g. With the increase of the acid centers and the acid strength on the surface of Y zeolite, the dispersion threshold of ZnCl2 decreased, which can be attributed to low absorption of microwave energy for low Na+ content in Y zeolite. The ZnCl2/HY samples (ZnCl2 loading 0.45 mmol/g) with different ion-exchange degrees were washed with water completely, and then the amounts of Zn2+ and Na+ in the solution after filtration and retained in the zeolite were analysed by atomic absorption spectroscopy. Zn2+ in the solution and in the zeolite were supposed to be the amounts of ZnCl2 dispered and ion-exchanged by solid state, respectively. The amount of ZnCl2 ion-exchanged by solid state with HY zeolite decreases with the increase of its surface acid properties. It is concluded that the ion-exchange by solid state with NaY zeolite is easier than that with HY zeolite under MWI. ZnCl2/HY catalyst prepared by MWI showed the highest catalytic activity and selectivity for p-methoxyl acetophenone in acylation of anisole and acetyl chloride. The ZnCl2/NaY and ZnCl2/HY-25 samples showed little catalytic activity owing to the ion-exchange by solid state between ZnCl2 and NaY zeolite under MWI during the catalyst preparation. However, when ZnCl2 is dispersed as the predominant status, its catalytic activity increases significantly.
出处
《催化学报》
SCIE
CAS
CSCD
北大核心
2002年第6期567-570,共4页
基金
教育部留学回国人员科研启动基金资助项目 ([2 0 0 1] 498号 )
湖南省教育厅资助项目 (0 1C164 )
