苯酚羟基化合成苯二酚反应过程酚焦油的生成与抑制

对铁基复合氧化物催化苯酚羟基化合成苯二酚反应过程酚焦油的生成反应进行了模拟研究.在含邻苯二酚、对苯二酚和对苯醌的混合水溶液中,邻苯二酚比对苯二酚更容易缩合生成焦油,邻苯二酚能够还原对苯醌,反应时间延长,反应温度提高,加入对苯醌或者催化剂,会促进苯二酚生焦反应.对回收所得废催化剂进行了热失重分析(TG/DrTG),进一步验证了反应过程中沉积在废催化剂上的酚焦油更多的来自于邻苯二酚.红外光谱(IR)分析表明,1620 cm-1吸收峰的产生和强化进一步说明废催化剂上沉积的酚焦油含有典型的C=O结构.在羟基化反应液中加入亚硫酸氢钠可以抑制对苯醌和残留催化剂对苯二酚氧化缩合生成焦油的催化作用,从而减少了反应液中苯二酚的生焦反应.

Formation and Inhibition of Phenolic Tars in Process for Preparation of Diphenols by the Hydroxylation of Phenol

The simulating study of the formation and inhibition of phenolic tars in the process of diphenols preparation by hydroxylation of phenol with iron-based composite oxides as catalyst was conducted. The results show that in the aqueous solution composed of catechol, hydroquinone and benzoquinone, catechol forms phenolic tars easier than hydroquinone. Catechol can reduce benzoquinone. Elongating reaction time, enhancing the reaction temperature and adding benzoquinone or catalyst can promote the tars formation of catechol. The thermogravimetric analysis of the retrieved waste catalyst verifies that, during the reaction process, most of the phenolic tars deposited on the waste catalyst are formed by catechol. The infrared spectrums show that the phenolic tars on the waste catalyst contain the typical structure of C=O bond, and it comes from the further oxidation of catechol. The experiments also show that adding NaHSO3 into the reaction liquid of hydroxylation reaction can inhibit the catalytic effect of benzoquinone and residual catalyst on the phenolic tars formation caused by oxo-condensation of the diphenols and therefore reduce the tars formation of the diphenols in the reaction solution.