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The efficient synthesis of dimethylhexane-1,6-dicarbamate(HDC)from 1,6-hexanediamine(HDA)and methyl carbonate over a series of heterogeneous catalysts(e.g.,Mg O,Fe2O3,Mo2O3,and Ce O2)was investigated.The reaction pathway was confirmed as an alcoholysis reaction through a series of designed experiments.Under optimized conditions,100%HDA conversion with 83.1%HDCtotaland 16.9%polyurea was obtained using a onestep with high temperature procedure with Ce O2as the catalyst.A new two-step with variable temperature technology was developed based on the reaction pathway to reduce the polyurea yield.Using the proposed method,the HDCtotalyield reached 95.2%,whereas the polyurea yield decreased to 4.8%.The Ce O2catalyst showed high stability and did not exhibit any observable decrease in the HDC yield or any structural changes after four recycling periods.
The efficient synthesis of dimethylhexane-1,6-dicarbamate (HDC) from 1,6-hexanediamine (HDA) and methyl carbonate over a series of heterogeneous catalysts (eg, MgO, Fe2O3, Mo2O3, and Ce O2) was investigated. The reaction pathway was confirmed as an alcoholysis reaction through a series of designed experiments. Un optimized conditions, 100% HDA conversion with 83.1% HD Cototaland 16.9% polyurea was obtained using a ones with high temperature procedure with Ce O2as the catalyst. A new two-step with variable temperature technology was developed based on the reaction pathway to reduce the polyurea yield. Using the proposed method, the HDC total reduction reached 95.2%, while the polyurea yield decreased to 4.8%. The Ce O2catalyst showed high stability and did not exhibit any observable decrease in the HDC yield or any structural changes after four recycling periods.