丙烯氧化反应的Redox机理

以流动床微分反应器研究了Bi_2MO_3O_(12)-Bi_2O_3催化剂上的丙烯氧化动力学。丙烯和氧的分压范围分别为0.05—0.95atm和0.07—0.80atm。当氧和丙烯分压低于0.30atm时, 丙烯醛的生成速度对丙烯为一级对氧为0.5级。表观活化能为30.1 kcal mol~(-1)。当丙烯和氧分压高于0.30atm时, 丙烯醛生成反应的动力学不能用幂速度方程描述。丙烯醛的生成速度对丙烯和氧分压存在着极大值。热脱附实验表明, 在低于150 ℃时, 分子态丙烯可以吸附于氧化态催化剂。但当温度高于300 ℃时, 丙烯则不以分子态吸附, 且脱附物为丙烯醛、一氧化碳和二氧化碳。在广阔的温度区(25—500 ℃)氧皆不以分子态处于催化剂上。因此, 建议了以表面双位反应为速控步骤的氧化还原机理。

REDOX MECHANISM OF PROPYLENE OXIDATION OVER Bi2Mo3O12-Bi2O3 CATALYST

The kinetics of propylene oxidation over Bi_2Mo_3O_(12)-Bi_2O_3 catalyst in a differ ential flow reactor has been investigated. The partial pressures of propylene and oxygen coverd the range of 0.05-0.95 atm and 0.07-0.80 arm, respectively. Kee ping their partial pressures less than 0.30 atm, the rate of acrolein formation took first order for propylene and 0.5 order for oxygen. The apparent activation energy was 30.1 kcal/mol. On the other hand, the kinetics of acrolein formation did not follow any power rate equation when the partial pressure of propylene or oxygen became larger than 0.30 atm. A maximum rate of acrolein formation appeared....