酸处理的纳米ZSM-22沸石负载Pt催化剂对正十二烷的加氢异构化性能

Hydroisomerization Performance of Acid-Treated Nanosized ZSM-22 Zeolite Supported Pt Catalyst on n-Dodecane

采用铵交换-稀硝酸脱铝相结合的方法处理针状形貌ZSM-22(De-HZSM-22)和纳米ZSM-22(De-HZSM-22-NA)沸石,并以De-HZSM-22、De-HZSM-22-NA和铵交换的针状形貌ZSM-22(HZSM-22)沸石为载体,采用等体积浸渍的方法制备Pt催化剂(Pt/De-HZSM-22、Pt/De-HZSM-22-NA和Pt/HZSM-22),研究其对长链烷烃正十二烷的加氢异构化性能。通过X射线衍射、N_(2)吸附-脱附、氨气程序升温脱附、氢气程序升温还原、透射电子显微镜等手段对催化剂进行系列表征。结果表明:Pt/De-HZSM-22-NA与Pt/De-HZSM-22的催化活性相当,均低于Pt/HZSM-22。但是Pt/De-HZSM-22-NA具有更高的异构体选择性,在反应压力2.0 MPa、H_(2)体积流量为40 mL/min、质量空速2.5 h^(-1)的条件下,320℃时得到最佳的异构体收率为80.0%,高于Pt/HZSM-22(300℃,70.2%)和Pt/De-HZSM-22(320℃,71.6%)的最佳收率;对应地,Pt/De-HZSM-22-NA的裂化选择性为10.8%,低于Pt/HZSM-22的21.6%和Pt/De-HZSM-22的21.1%。

The needle-shaped ZSM-22(De-HZSM-22)and nano-ZSM-22(De-HZSM-22-NA)zeolites were treated by ammonium exchange in combination with the dilute nitric acid dealumination method.Additionally,De-HZSM-22,De-HZSM-22-NA and the ammonium-exchanged needle-shaped ZSM-22(HZSM-22)zeolites were used as carriers for preparing Pt catalysts(Pt/De-HZSM-22,Pt/De-HZSM-22-NA and Pt-HZSM-22)with incipient wetness impregnation method,aiming to study their hydroisomerization performance on long-chain alkane n-dodecane.The catalysts were characterized by X-ray diffraction,N_(2)adsorption-desorption,temperature-programmed desorption of ammonia,temperature-programmed reduction of H_(2),and transmission electron microscope.The results show that the Pt/De-HZSM-22-NA and Pt/De-HZSM-22 have equivalent catalytic activity,both lower than that of Pt/HZSM-22 catalyst.However,Pt/De-HZSM-22-Na has a higher isomer selectivity.When the reaction pressure is 2.0 MPa,H_(2) volume flow rate is 40 mL/min,MHSV is 2.5 h^(-1) and the temperature is 320℃,the optimum isomer yield ratio is 80.0%,which is higher than that of Pt/HZSM-22(300℃,70.2%)and Pt/De-HZSM-22(320℃,71.6%).Correspondingly,the cracking selectivity of Pt/De-HZSM-22-NA is 10.8%,which is lower than that of Pt/HZSM-22(21.6%)and Pt/De-HZSM-22(21.1%).