Mechanism study of anisole synthesis from o-methylation of phenol with DMC over KBr catalyst
-
摘要: 结合原位FT-IR，热力学分析及反应规律研究了KBr催化剂上碳酸二甲酯（DMC）氧位甲基化苯酚合成苯甲醚的反应机理。FT-IR显示KBr催化剂高于100℃活化苯酚生成酚盐，但至200℃也不活化DMC。共吸附的FT-IR及反应数据均显示苯甲醚高于150℃时生成。反应中检测到少量羰基甲氧基化产物苯基甲基碳酸酯（MPC）先于苯甲醚而生成，结合热力学计算及MPC分解转化的实验结果分析，生成MPC的反应是与生成苯甲醚的甲基化反应并行的可逆副反应。甲基化反应的机理为苯酚先被去质子化而形成酚盐，高于150℃时，酚盐的酚氧负离子亲核进攻DMC的甲基碳而生成苯甲醚。Abstract: The o-methylation of phenol with DMC to anisole over KBr catalyst was studied by in-situ FT-IR, thermodynamic analysis and reactivity test. FT-IR showed that phenol was activated to generate phenolate over 100℃ while DMC was not activated even at 200℃ by KBr catalyst. Anisole was formed over 150℃ on KBr catalyst as FT-IR and reactivity data revealed. Small amount of carboxymethylation product methyl phenyl carbonate (MPC) was detected and its formation was earlier than that of anisole. Thermodynamic analysis and MPC decomposition experiment showed that the reaction of MPC formation was a parallel and reversible side reaction. Methylation reaction mechanism was thus suggested as phenol was activated by KBr to form phenolate, a strong nucleophilic reagent, which attacked DMC methyl carbon to generate anisole when temperature was higher than 150℃.
-
Key words:
- dimethyl carbonate (DMC) /
- phenol /
- o-methylation /
- anisole /
- in-situ FT-IR /
- reaction mechanism
-
点击查看大图
计量
- 文章访问数: 2563
- HTML全文浏览量: 47
- PDF下载量: 978
- 被引次数: 0
下载:
