溶剂对丙烯环氧化反应活性的影响

Effect of solvent on the propylene epoxidation catalyzed by TS-1

研究了溶剂对钛硅分子筛催化丙烯环氧化反应的影响.研究结果表明,随着溶剂极性增加,活性中间过渡态中的过氧键越易断裂,容易把氧原子传递给丙烯,因此丙烯环氧化反应活性增加.由于TS-1催化剂孔道狭小,产生空间位阻效应,醇溶剂分子越大,活性中间过渡态的形成越困难,反应活性越低.甲醇-丙酮混合溶剂中丙酮含量小于50%时,反应活性与纯甲醇做溶剂相近;混合溶剂中丙酮含量增加到80%时,反应活性略降低;丙酮含量进一步增加,反应活性急剧下降.

Effect of solvent on the propylene epoxidation catalyzed by TS\|1 was studied. It has been shown that the activity of propylene epoxidation increases with the solvent polarity. The cleavage of peroxo bond of the transition state and the transfer of the oxygen atom to propylene may be easier with the increase of solvent polarity. When alcohol with larger molecule is used as solvent, the transition state is difficult to form due to the steric hindrance in the channels of TS\|1, as results in lower activity. The activity of propylene epoxidation nearly doesn't change if the fraction of acetone in the mixed solvent with methanol is less than 50%. But the activity will decreases slightly with the further increase of the fraction of acetone and the activity decreases dramatically if the fraction of acetone exceeds 80%.