甲醇与多聚甲醛反应制备甲缩醛

以甲醇和多聚甲醛为原料、硫酸为催化剂,在甲苯溶剂中合成了甲缩醛。考察了反应温度、原料配比、催化剂用量对甲醇转化率的影响。实验结果表明,较适宜的工艺条件为:反应温度60℃,n(多聚甲醛):n(甲醇)=0.550,催化剂用量(占甲醇的质量分数)5%,反应时间60 min。在此条件下,甲醇的平衡转化率为84.6%,甲缩醛的选择性为97.9%。为提高甲醇的转化率和甲缩醛的收率,将精馏技术应用到甲缩醛合成过程中,并取得了较好的效果。采用精馏技术后,生成的甲缩醛以甲缩醛、甲醇和水的共沸物的形式蒸出,甲醇的平衡转化率达91.8%,甲缩醛的选择性达99.4%;精馏产品的质量组成为甲缩醛91.1%、甲醇6.8%、水2.1%。

Preparation of Methylal from Methanol and Polyoxymethylene

Methylal was synthesized from methanol and polyoxymethylene using sulfuric acid as catalyst and toluene as solvent.Effects of reaction temperature,starting materials ratio and catalyst dosage on methanol conversion were investigated.Under optimal reaction condition:reaction temperature 60℃,n(polyoxymethylene):n(methanol)0.550,catalyst mass fraction 5%(relative to methanol mass)and reaction time 60 rain,methanol equilibrium conversion and selectivity to methylal reach 84.6% and 97.9% respectively.Introduction of reaction distillation into the process greatly enhances the result.Methanol equilibrium conversion and selectivity to methylal rise to 91.8% and 99. 4% respectively.Methylal is obtained from distillate including methanol and water.The latter two are distilled in form of azeotropic mixture.Mass fraction of methylal in distillate is 91.1%,mass fraction of methanol 6.8% and water 2.1%.It is advantageous to carry out the process in organic solvent. Methanol conversion and yield of methylal are high and amount of waste is not much.It is easy to be handled after production.