硝酸盐催化碳酸二甲酯与苯酚合成苯甲醚

考察了各种硝酸盐催化剂催化碳酸二甲酯(DMC)与苯酚合成苯甲醚的反应活性及其规律,优化了反应工艺参数,并讨论了反应机理。实验结果表明,在200℃、n(DMC)∶n(苯酚)=2.0、CsNO3催化剂用量为原料质量的1.0%、10h的条件下,苯酚的转化率达98.1%,苯甲醚的选择性达99.2%。分析发现,当硝酸盐阳离子金属的电离能小于600kJ/mol时,硝酸盐具有较好的活性,且电离能与苯酚的转化率近似成线性关系,电离能越小,苯酚的转化率越高;当阳离子金属的电离能大于600kJ/mol时,硝酸盐的活性较低。苯环上引入不同取代基的苯酚的甲基化反应活性不同,供电子基团提高了苯酚的反应活性,而吸电子基团则相反;苯酚活化后生成的苯酚盐的亲核性强弱是影响甲基化反应活性的关键。

Synthesis of Anisole from Phenol with Dimethyl Carbonate over Inorganic Nitrate

Synthesis of anisole by O-methylation of phenol with dimethyl carbonate(DMC)over nitrate catalysts was studied.Under optimal reaction conditions:CsNO3 as catalyst,reaction temperature 200 ℃,n(DMC)∶n(phenol)2.0 and catalyst amount 1.0%(based on mass of raw materials)and reaction time 10 h,phenol conversion and anisole selectivity were 98.1% and 99.2%,respectively.Activity of nitrate catalyst relates to ionization energy of its metallic cation.When the ionization energy was less than 600 kJ/mol,the nitrate would be more active in the methylation,but above 600 kJ/mol the situation was not as promising.Phenol conversion depended almost linearly on ionization energy.The less the ionization energy,the higher the phenol conversion.The substituent groups on phenyl ring influences greatly the reactivity of phenol in O-methylation.Electron donating substituents enhance reactivity of phenol while electron drawing groups attenuate it.Electron density around the oxygen ion of activated phenol is essential to the methylation.