直接反应法合成异丙醇钇中AlCl3的催化作用

The AlCl_3 catalyzing effect on the preparation of yttrium isopropoxide by the direct reaction of yttrium with isopropanol

在用直接反应法合成稀土金属醇盐的反应中,传统上一直以I2或Hg2+系列盐(如HgCl2,Hg(C2H3O2)2和HgI2等)或其混合物做催化剂.对某些金属合成反应会存在反应速率低、产率低的问题.通过以无水AlCl3做催化剂、金属钇薄片和异丙醇为原料,加热回流直接反应,成功地合成了异丙醇钇.反应中放出大量H2和红外吸收光谱分析结果证明产物确为异丙醇钇.实验证明以无水AlCl3做催化剂可以大大提高反应速率和产率.实验和理论分析揭示了无水AlCl3的催化机理:无水AlCl3与异丙醇作用生成了HCl和可表示为AlCl2(OPri).2AlCl3.PriOH的中间产物,使整个体系的酸性提高,从而加速了反应的进行.AlCl3催化机理完全不同于I2和Hg2+系列盐类,这里H+为氧化剂,起重要作用.使用无水AlCl3替代传统催化剂可以解决I2做催化剂对某些反应的效率低下问题,或Hg2+系列盐类的毒性问题.

Traditionally, iodine or Hg^2＋ series salts, such as mercury chloride （HgCl2）, mercury iodinate （Hgl2） etc. have been always employing as catalysts in the synthesis of metal alkoxides via the direct reaction of metal with alcohols. But this sort of methods results in impure products, low velocity of reaction, and poor yield for some of metal alkoxides synthesis, for the catalysis of iodine is weaker, and mercury salts are very virulent. Aluminium chloride （AlCl3） catalyzing effect on the preparation of yttrium alkoxides by the direct reaction of yttrium with isepropanol had beon studied. A great deal of hydrogen is given out during the synthesis reaction. IR analysis indicated that the product was yttrium isepropoxide. When AlCl3 was allowed to react with isepropanol, resulted in the formation of products of composition AlCl2（OPr^i）·2AlCl3·Pr^iOH and HCl, leading to decreasing of pH of the system and increasing the velocity of the reaction. Hydrogen ion H^＋is an oxidant in these reactions; its mechanism is very different from I2 and Hg^2＋ series salts in alcohol-aluminium-alkoxides system. AlCl3 could be the most appropriate substitute for iodine and mercury chloride in the future because of its innocuity and strength.