三乙烯二胺合成催化剂的表征和反应机理的研究

以N β 羟乙基哌嗪为原料对三乙烯二胺的合成进行了深入研究。采用DTA、BET、XRD等对催化剂进行了系列表征,发现焦磷酸钡的生成使催化剂具有较高的机械强度和较大的孔径(20 5nm),从而有利于脱水反应的进行,提高了Ba Sr 2催化剂的活性和稳定性。通过SEM和XPS分析,发现积碳是造成催化剂失活的主要原因,而且发现水蒸气能使催化剂再生,再生后的催化剂仍能使三乙烯二胺的收率达到88%以上,并且仍具有200h以上的使用寿命。基于磷酸盐催化剂的酸性本质和温度对反应的影响,推测了反应的机理,认为在三乙烯二胺的生成过程中经历了磷酸酯中间体和由稳定的椅式构象向船式构象转化的过程。

Characterization of Catalysts for the Synthesis of Triethylenediamine and Studies of the Reaction Mechanism

Synthesis of triethylenediamine from N-β- hydroxyethylpiperazine is studied.The alkaline earth metal phosphate catalysts are characterized by means of DTA,BET and XRD.Formation of barium pyrophosphate affords the catalyst relatively high mechanical strength and bigger pores(20 .5 nm),which is in favor of the dehydration reaction and contributes a lot to the activity and stability of the Ba-Sr-2 catalyst.By SEM and XPS analyses it is found that carbon deposit is the main reason for catalyst deactivation,and the deactivated catalyst can be recovered by steam.The regenerated catalyst can also give triethylenediamine in over 88% yield and has a service life of more than 200 hours.The reaction mechanism is deduced on the basis of the acidic character of the catalyst and the influence of temperature on the reaction.Triethylenediamine is obtained via the phosphate ester intermediate and the transformation of the more stable chair conformation to the boat conformation.