【摘要】 在离子交换法制备的Ni改性HZSM-5的基础上,采用等体积浸渍法引入不同含量的H3PO4改性,制备了磷镍复合改性的HZSM-5并用于乙醇脱水制乙烯。采用XRD、N2吸附脱附、PyTPD、27Al MAS NMR等表征手段考察了改性对分子筛的影响。结果显示:P添加后促进了骨架铝的脱离,导致强酸量进一步减少,提高了催化剂的使用寿命。活性评价结果表明,以8%磷酸改性的催化剂催化效果最好。然后考察了反应条件对其催化乙醇脱水制乙烯的影响,得到最适宜反应条件为温度260℃、质量空速1.5 h-1、进料乙醇体积分数为50%。在此条件下进行了稳定性测试,50 h内乙醇转化率大于97%,乙烯选择性高于98%,和仅用镍改性相比稳定性显著提高。更多还原

【Abstract】 Based on the Ni-modified HZSM-5 synthesized via ion-exchange method,a series of phosphorus-nickel modified HZSM-5 catalysts were prepared by impregnating the Ni-HZSM-5 with phosphoric acid aqueous solution. The influence of modification on the structure and acid properties of HZSM-5 was investigated by means of X-ray diffraction( XRD),N2 physisorption,temperature programmed desorption of pyridine( Py-TPD) and27 Al nuclear magnetic resonance(27Al MAS NMR). The results indicated that the addition of phosphoric acid promoted the dealumination from framework,and reduced the amount of strong acid,which was responsible for the enhancement of anti-carbon deposition ability and extension of its service life. The results of catalytic activity test revealed that the catalyst with H3PO4 content of 8%( 3-PN-Z) showed the best performance. The effect of operating parameters on the dehydration of ethanol to ethylene over 3-PN-Z was also investigated and the optimal reaction conditions obtained were 260 ℃,1. 5 h- 1( WHSV) and 50%( volumetric fraction) of ethanol concentration. The stability evaluation showed that during the initial 50 hours,the ethanol conversion and ethylene selectivity kept higher than97% and 98% respectively,which was better than the Ni-modified HZSM-5 catalyst.更多还原