γ-Al_2O_3催化尿素法合成二苯甲烷二氨基甲酸甲酯反应研究

SYNTHESIS OF METHYLENE DIPHENYL DICARBAMATE VIA UREA ROUTE CATALYZED BY γ-Al_2O_3

首次尝试以二苯甲烷二胺(MDA)、尿素和甲醇为原料直接合成二苯甲烷二氨基甲酸甲酯(MDC),分别考察了催化剂种类和反应条件对MDC合成反应的影响。结果表明:经400℃焙烧2h的γ-Al2O3对该反应具有较高的催化活性。适宜反应条件为:反应温度180℃,反应时间6h,反应初压1.2 MPa,n(MDA)∶n(尿素)∶n(甲醇)∶n(γ-Al2O3)=1∶3∶50∶0.1。在此条件下,MDA的转化率为81.7%,MDC的收率和选择性分别为26.3%和32.2%。采用液相色谱-质谱联用技术对MDC合成反应的反应路径进行了分析,认为促进中间产物4-氨基-4′-氨基甲酸甲酯二苯甲烷(MMC)向MDC转化是提高MDC选择性的关键。

Methylene diphenyl dicarbamate（MDC）was synthesized using methylene dianiline（MDA）,urea and methanol as starting materials for the first time.The effect of different catalysts and reaction conditions on MDC synthesis was investigated.The results showed thatγ-Al2O3 calcined at 400℃for2hpresented a better catalytic activity.Under the suitable reaction conditions of initial pressure of1.2 MPa,reaction temperature of 180 ℃,reaction time of 6 h,and n（MDA）∶n（Urea）∶n（Methanol）∶n（γ-Al2O3）=1∶3∶50∶0.1,the conversion of MDA was 81.7%,the yield and selectivity of MDC were 26.3% and 32.2% respectively.The reaction route was speculated based onHPLC-MS technique.Results show that promoting the transformation of methyl 4[（4′-aminophenyl）methylene]phenylcarbamate（MMC）toward MDC is a key step to improve the selectivity of MDC.