对硝基甲苯合成对羟基苯甲醛工艺研究

以对硝基甲苯为原料，采用氧化还原、重氮化水解反应，通过改变物料摩尔比、反应时间等工艺参数，研究了合成对羟基苯甲醛的最佳工艺条件。在由对硝基甲苯氧化还原成对氨基苯甲醛及后处理时，易产生大量聚合物，实验主要从减少或消除聚合度以及寻求重氮化过程的最佳工艺条件出发。结果表明，Na2Sx中硫指数为5、乙醇与水的体积比大于1、反应时间为3h、后处理速度快等可减少大量的聚合物．硫酸与对氨基苯甲醛摩尔比为2．2～2．4：1、酸化时间0．5h、重氮化时间1～1．5h时可提高对羟基苯甲醛的收率，由PNT制备PAB时收率可达93．2％，由PAB制备PHB时最高产率为77．1％。

The Study of Synthesis Technology of P-Hydroxybenzaldehyde from P-Nitrotoluene

P-hydroxybenzaldehyde was synthesized from p-nitrotoluene by redox reaction,diazotization reaction and hydrolysis reaction.The reaction condition was optimized by changing the technological parameters such as mole ratio of raw materials and reaction time.Polymer was easy to produce when p-nitrotoluene was redoxed to p-aminotenzaldehyde and after-treatment of p-aminotenzaldehyde.Experiment was arranged to find out the best technology conditions to reduce or eliminate the polymer.Experimental results showed that the polymer was reduced greatly under the following reaction conditions: sulfur index 5,the proportion of ethanol and water is greater than 1,reaction time 3 h,the quick speed during after-treatment and so on.That the yield of p-hydroxybenzaldehyde was improved under the following reaction conditions: mole ratio of H2SO4 and p-aminotenzaldehyde 2.2～2.4:1,acidification time 0.5 h,diazotization time 1～1.5 h.