Ni/HY催化剂上2,4-二硝基甲苯催化加氢合成2,4-二氨基甲苯反应动力学研究

Kinetic Study on Hydrogenation of 2,4-Dinitrotoluene to 2,4-Tolylenediamine Catalyzed by Ni/HY Catalysts

在1 L间歇搅拌反应釜中,以Ni/HY为催化剂、乙醇为溶剂,研究了2,4-二硝基甲苯(2,4-DNT)催化加氢合成2,4-二氨基甲苯(2,4-TDA)的反应机理、优化条件及动力学。2,4-DNT催化加氢合成2,4-TDA有两条路线,由于甲基的位阻效应,2,4-DNT会更多地转化为中间产物4A2NT,再生成目标新产物,少部分中间产物为2A4NT。考察了搅拌速度、温度、氢气压力对2,4-DNT的转化率和2,4-TDA产率的影响。条件优化结果表明:当搅拌速度达到600r×min-1时2,4-DNT加氢反应进入本征区;温度、压力对中间产物转化为最终产物的反应速率影响较大。通过本征动力学实验,确定了各反应过程中的反应动力学参数,并计算得到各步骤反应的活化能和吸附热,2,4-DNT生成4A2NT的活化能为31.3 kJ×mol^(-1),吸附热为-29.9 kJ×mol^(-1);4A2NT生成2,4-TDA的活化能为26.4 kJ×mol^(-1),吸附热为-9.3 kJ×mol^(-1);2,4-DNT生成2A4NT的活化能为28.7 kJ×mol^(-1),吸附热为-15.0 kJ×mol^(-1);2A4NT反应生成2,4-TDA活化能为31.0 kJ×mol^(-1),吸附热为-16.8 kJ×mol^(-1)。动力学模拟值与实验值结果拟合效果较好,对实际生产有一定指导意义。

Reaction mechanism, optimization conditions and kinetics of the catalytic hydrogenation of 2,4-DNT to 2,4-TDA with Ni/HY catalysts were investigated in a 1 L batch reactor using ethanol as the solvent. There were two routes using 2,4-DNT to synthesize 2,4-TDA. 2,4-DNT preferred to be converted into intermediate 4 A2 NT（less converted into 2 A4 NT） due to the steric resistance of methyl and then transformed into target products. Effects of stirring rates, reaction temperatures and hydrogen pressure on 2,4-DNT conversion and 2,4-TDA yields were investigated. The results demonstrate that the reaction is under intrinsic regime when the stirring rate is 600 r×min-1. Temperature and pressure have great effects on intermediate conversion. Reaction kinetic parameters were determined based on dynamic studies. The activation energy from 2,4-DNT to 4 A2 NT is 31.3 kJ×mol-1 with adsorption heat of-29.9 kJ×mol-1. The activation energy from 4 A2 NT to 2,4-TDA is 26.4 kJ×mol-1 with adsorption heat of-9.3 kJ×mol-1. The activation energy from 2,4-DNT to 2 A4 NT is 28.7 kJ×mol-1 with adsorption heat of-15.0 kJ×mol-1. The activation energy from 2 A4 NT to 2,4-TDA is 31.0 kJ×mol-1 with adsorption heat of-16.8 kJ×mol-1. The dynamic simulation results are consistent with the experimental results.