Catalytic performances of USY, MOR, and BEA zeolites were compared for the isopropylation of naphthalene by isopropyl alcohol in a high-pressure, fixed-bed reactor. The USY catalyst showed a high conversion of 86% and good stability but a low 2,6-/2,7-DIPN shape selectivity ratio of 0.94. In contrast, over the MOR catalyst, 2,6-DIPN was selectively synthesized with a high 2,6-/2,7-DIPN ratio of 1.75, but low naphthalene conversions and fast deactivation of the catalyst were observed. The USY catalyst was modified by Zn and Fe using the wet impregnation method to enhance the selectivity for 2,6-DIPN. The highest conversion (~95%) and selectivity for 2,6-DIPN (~20%) were achieved with 4% Zn/USY catalyst. It appeared that small metal oxide islands formed in the USY pores to decrease the effective pore size and thus render it mildly shape-selective. Zn loading also decreased the number of strong acid sites responsible for coke formation and increased the number of weak acid sites. The high conversion and stability of Zn-modified catalysts were ascribed to the presence of a suitable admixture of weak and strong acid sites with less coke deposition. The Fe-modified USY catalysts were less effective because the modification increased the number of the strong acid sites.
比较了 USY、MOR 和 BEA
沸石在高压固定床反应器中用
异丙醇对
萘进行异丙基化反应的催化性能。USY 催化剂的转化率高达 86%,稳定性良好,但 2,6-/2,7-二
硝基萘的形状选择性较低,仅为 0.94。相反,在 MOR 催化剂上,2,6-DI
PN 被选择性合成,2,6-/2,7-DI
PN 比率高达 1.75,但
萘转化率低,催化剂失活快。采用湿浸渍法对 USY 催化剂进行了
锌和
铁改性,以提高 2,6-DI
PN 的选择性。在使用 4% Zn/USY 催化剂时,2,6-DI
PN 的转化率(约 95%)和选择性(约 20%)最高。USY 孔中似乎形成了小的金属氧化物岛,从而减小了有效孔径,使其具有轻微的形状选择性。此外,
锌的添加还减少了导致焦
炭形成的强酸位点的数量,增加了弱酸位点的数量。Zn 改性催化剂的高转化率和稳定性可归因于弱酸和强酸位点的适当混合以及较少的焦
炭沉积。
铁改性 USY 催化剂的效果较差,因为改性增加了强酸位点的数量。