乙醇催化氨化合成2-甲基吡啶和4-甲基吡啶

通过对HZSM-5分子筛进行金属修饰制得一系列催化剂,考察了该系列催化剂对乙醇催化氨化合成2-甲基吡啶和4-甲基吡啶的性能,其中Pb6-Fe0.5-Co0.5/ZSM-5(n(Si)∶n(Al)=200)催化剂的活性最高。同时考察了反应温度、n(氨气)∶n(乙醇)和停留时间对合成反应的影响。实验结果表明,在Pb6-Fe0.5-Co0.5/ZSM-5(n(Si)∶n(Al)=200)催化剂作用下,乙醇催化氨化反应的适宜条件为:催化剂用量30mL、0.1MPa、450℃、n(氨气)∶n(乙醇)=6∶1、停留时间19.2s;在此条件下,乙醇转化率达100.0%,2-甲基吡啶和4-甲基吡啶的总收率达到29.0%。催化剂稳定性实验结果表明,反应进行16h后,2-甲基吡啶和4-甲基吡啶的总收率仍可达23.6%。采用空气氧化法再生催化剂可部分恢复催化剂的活性,反应过程中部分催化剂活性组分被还原和生成积碳是导致催化剂活性下降的原因。

Syntheses of 2-Picoline and 4-Picoline by Catalytic Ammoniation of Ethanol

A series of catalysts were prepared through modification of HZSM-5 molecular sieves with several metals and used in ammoniation of ethanol to 2-picoline and 4-picoline.Pb6-Fe0.5-Co0.5/ZSM-5(n(Si)∶n(Al) is 200) catalyst showed good catalytic activity in a fixed-bed reactor.Effects of reaction temperature,mole ratio of ammonia to ethanol and residence time on the catalyst activity were investigated.Under the optimized reaction conditions: catalyst dosage 30 mL,reaction pressure 0.1 MPa,reaction temperature 450 ℃,mole ratio of ammonia to ethanol 6∶1 and residence time 19.2 s,conversion of ethanol and total yield of both 2-picoline and 4-picoline were 100.0% and 29.0%,respectively.The total yield could still reach 23.6% after the catalyst running for 16 h.The catalyst activity could be recovered partially through air oxidation.The fresh and used catalysts were characterized by means of XRD and XPS.The results showed that the main reasons for the catalyst deactivation were formation of Pb0 by reduction of the active species and carbon deposition on the catalyst during the catalyst running.