CuO-NiO/Al_20_2催化剂上N-甲基哌嗪合成研究

Synthesis of N-methylpiperazine over CuO-NiO/Al_2O_3 Catalysts

以共沉淀法制备铜、铝系复合氧化物作为催化剂,二乙醇胺和甲胺为原料,合成了N-甲基哌嗪.利用高压反应釜对其进行活性评价,发现CuO-NiO/Al2O3活性最高.并对铜、铝、镍摩尔比、沉淀剂种类、沉淀方式、焙烧温度等条件进行了优化.结果表明:催化剂中理想的Cu、Al、Ni摩尔比为1:1:3.2,沉淀剂为氢氧化钠,沉淀方式为并流,焙烧温度为500℃.该条件下N-甲基哌嗪的选择性为27.7%,二乙醇胺的转化率达89.8%.另外通过对使用前后催化剂进行表征分析发现催化剂失活原因为表面高聚物的附着和对孔道的堵塞.

Copper, aluminum-based composite metal oxides was prepared by coprecipitation method and as the catalyst in synthesis of the N-methylpiperazine while the starting materials are diethanolamine and methylamine. Compared the activity of the catalysts in autoclave and found that copper, aluminum and nickel composite metal oxides has the highest activity. The molar ratio of copper, aluminum and nickel, different coprecipitators, precipitants order and the calcining temperature have been optimized. Experimented results showed that ： the ideal molar ratio of copper, aluminum and nickel is 1 ： 1 ： 3.2, coprecipitator is NaOH, precipitants order is cocurrent, and the best calcining temperature lies around 500 ℃. Under this condiction the conversion of diethanolamine and the yield of N-methylpiperazine were 89.8% and 27.7% respectively. Meanwhile, the reason of deactivation for the catalysts was that some oligomeric compounds deposited on the catalyst surface and blocked active site via comparing the catalyst unused and used by token analyzing.