杂多酸催化剂上乙苯的氧化脱氢

本文研究了H₃PW₁₂O₄₀及其Na⁺、Al³⁺、Cd²⁺、La³⁺盐对乙苯氧化脱氢反应的催化活性。发现活性与酸强度和酸量之间没有直接的关系。杂多酸及其盐类在反应开始阶段均存在一段活性增长期,简称为"增活期"。增活期内催化剂表面的积炭量逐渐增加,积炭物的H/C比逐渐减小。用质谱法、薄板层析法检知了积炭物中有醌类物质存在,提出了积炭物中的醌类基团是氧化肥氢的活性中心的观点。

THE OXIDATIVE DEHYDROGENATION OF ETHYLBENZENE ON HETEROPOLYACID

The experimental results showed that H₃PW₁₂O₄ and its salts are effective catalysts for oxidative dehydrogenation of ethylbenzene to styrene. The selectivity was as high as 98% at 18% conversion.Their activities were nearly the same regardless of their differences in acid strength and acidity. The most important feature of this reaction system appeared that the catalytic activity increases with reaction time in the beginning period, the "Break-in"period.During the "Break-in" the H/C ratio of coke decreases, while the amount of coke formed on the catalyst surface increases. some quinoid compounds were detected by thin layer chromatography and mass spectrometry and they are considered to be the active sites of tbe oxidative dehydrogenation of ethylbenzene.