| 2,5-dimethylpiperazine is an important chemical material and pharmaceutical intermediate. It could be used in the synthesis of a number of fine chemicals including Pharmaceuticals, pesticides, dyestuffs, surfactants, etc. 2,5-dimethylpiperazine could be obtained by reduction of 3,6-dimethyl-2,5-diketopiperazine,2,5-dimethylpyrazine or catalytic hydrogenation of lactamide or isopropanolamine. In this thesis, isopropanolamine was used as reactant to form 2,5-dimethylpiperazine in the presence of hydrogenation-dehydrogenation catalysts, e.g. Raney-Ni. The reaction conditions were optimized, such as the amount of the catalyst,reaction temperature,reaction pressure and reaction time. The optimum processing conditions: 2.0～3.0 MPa original hydrogen,reaction temperature 150～170℃, 2.5～5.0 grams of Raney-Ni catalyst per mole and a reaction time of 4 to 6 hours. Under these conditions, the conversion of isopropanolamine was 100 % and the yield of 2,5-dimethylpiperazine was about 70%. The reaction conditions were much moderate compared to references, e.g. the reaction pressure drop from 8.0 MPa to 4.0 MPa and the reaction temperature drop about 50℃. Reaction with Ni-B amorphous alloy catalysts,Ni-B amorphous alloy catalysts with addition of Mo and Cu/SiO2 were also studied. But all of the yields and coversion were much lower. 2,5-dimethylpiperazine, which purity was 90%, was obtained by rectification. And 2,5-dimethylpiperazine of 99 % purity was got by recrystallization. The result ratio of 2,5-dimethylpiperazine against 2,5-dimethylpyrazine could be regulated according to reaction temperature, initial pressure, etc. For example, 2,5-dimethylpyrazine could be obtained by a high yield of 74.5% when reacting at 240℃for 6 h with 1.25 g·mol-1 Raney Ni catalyst and zero initial pressure. |
