Study On The Co-production Of Piperazine And N-alkylpiperazine

Piperazine and N-monoalkylpiperazines are important pharmaceuticalintermediates and they are mainly obtained by the catalytic amination of alcohols.Based on the modification of the Cu-based catalysts, the synthesises ofhomopiperazine and piperazine are investigated and then the co-production processfor piperazine and N-monoalkylpiperazine is established.1. The modification of the Cu-based catalysts was first conducted because of thedeactivation and Cu20Cr10La10/γ-Al2O3catalyst exhibited the best activation,selectivity and stability among the modified catalysts.Therefore, Cu₂₀Cr₁₀La₁₀/γ-Al₂O₃was applied to the synthesis of piperazine using N-β-hydroxyethyl-1,2-ethylenediamine as the starting materials. Additionally, the reaction parameters wasoptimized and under the optimum conditions （170℃,3MPa hydrogen pressure,0.30mL/min feed rate）, piperazine was obtained with a yield of98.6%. And thesatisfied results for the synthesises of hexahydro-1H-azepine, piperidine andpyrrolidine over Cu₂₀Cr₁₀La₁₀/γ-Al₂O₃were obtained. The catalysts werecharacterized by XRD, XPS, NH₃-TPD and H2-TPR. It was found that Cu0was theactive sites of the reduced Cu-based catalysts and the introduction of Cr and La couldimprove the Cu0dispersion. Additionally, the addition of La neutralizes the strong acidsites and decreases the amount of the acid sites which facilitated the desorption ofamino compounds on the surface of catalysts and inhibited the carbon deposition.These may improve the lifetime of the catalyst.2. Alcohols was used as the alkylation agents by investigated the co-production ofpiperazine and N-monoisopropylpiperazine. And the Cu₂₀Cr₁₀La₅/γ-Al₂O₃catalystwas the best catalyst by investigating the effect of the amount of La on the catalyticperformance and it was found that the diameters of Cu0decreased with the increase ofthe amount of La. Additionally, the distribution of the products was found to bemarkedly dependent on the reaction temperature by optimization of the reactionconditions. Piperazine and N-monoisopropylpiperazine can be obtained with76.0%and15.8%yield respectively at180℃and3MPa with1:4molar ratio ofN-β-hydroxyethyl-1,2-ethylenediamine to isopropanol at complete conversion. Andthe catalyst showed good stability over100h. 3. The co-production of piperazine and N-alkylpiperazine could be achievedusing ethanol, propanol, butanol,1-hexanol, cyclohexanol, benzyl alcohol,sec-butanol,3-pentanol and methanol as the alkylation agents except fordiisopropylcarbinol over Cu₂₀Cr₁₀La₅/γ-Al₂O₃. Additionally, it was found that theamount of N-alkylpiperazine would be higher when primary alcohol was used as thealkylation agent rather than secondary alcohol, the steric hindrance of the hydroxylgroup was higher and benzene groups could conjugate with the carbonyl groupformed by the dehydrogenation of the alcohol. Therefore, the co-production ofpipeazine and N-alkylpiperazine was eatablished.