酸活化蒙脱土催化乙二胺合成哌嗪和三乙烯二胺

Synthesis of piperazine and triethylenediamine from ethylenediamine over acid activated montmorillonite catalyst

以硝酸活化钠基蒙脱土制备了系列酸活化蒙脱土催化剂,考察了不同活化时间及活化温度的酸活化蒙脱土催化乙二胺(EDA)反应性能的影响。采用N2吸附-脱附、XRD、FTIR、NH3-TPD、XRF等方法对催化剂进行了表征。表征结果显示,随着酸活化时间的延长及活化温度的升高,酸活化蒙脱土中Al含量逐渐降低,层状结构逐渐坍塌,平均孔径逐渐增大,孔径分布向大孔径区偏移,酸性逐渐增大后减小,导致EDA转化率先升高后降低,哌嗪(PIP)选择性先降低后升高,三乙烯二胺(TEDA)和烷基吡嗪类产物选择性先升高后降低。实验结果表明,通过改变蒙脱土的活化条件,可在一定范围内对蒙脱土的酸性、组成和结构进行可控调变,实现较宽范围内EDA转化率、PIP及TEDA选择性的可变调节。催化剂MMT-16-104催化EDA分子内脱水效果最佳,在EDA转化率达78.6%时,PIP与TEDA总选择性最高达87.2%。

The natural Na-type montmorillonite was activated in nitric acid aqueous solution to obtain the acid activated montmorillonite catalyst.The effects of acid activation time and temperature of acid activated montmorillonite on ethylenediamine(EDA)reaction were investigated.The catalysts were characterized by N2 adsorption-desorption,XRD,FTIR,NH3-TPD,and XRF.The characterization results showed the content of aluminium decreased,the layer structure collapsed,the average pore size increased,the pore size distribution widened,the acidity increased to the maximum and then decreased with the increase of activation time and temperature of the acid activated montmorillonite.The changes of the acid activated montmorillonite catalyst resulted in that the conversion of EDA and the selectivity to triethylenediamine(TEDA)and alkylpyrazines increased to the maximum and then decreased,and at the same time,the selectivity to piperazine(PIP)decreased to the minimum and then increased.Because the acidity,textural properties and composition of the acid activated montmorillonite can be tuned by acid activation conditions,EDA conversion and PIP and TEDA selectivity can be controlled within a wide range.87.2%PIP and TEDA selectivity at the EDA conversion 78.6%was achieved over the optimum catalyst MMT-16-104.