PtSnZn/ZSM-5-ZSM-11-Al_2O_3催化剂上FCC汽油制苯、甲苯和二甲苯

以全馏分流化催化裂化(FCC)汽油为原料,在小型固定床反应装置上考察了添加ZSM-5-ZSM-11共晶分子筛(简称CDM分子筛)对PtSnZn/Al2O3催化剂催化FCC汽油芳构化制苯、甲苯和二甲苯(BTX)的性能、抗积碳和反复再生性能的影响,并与工业重整催化剂PS-Ⅵ进行了对比。实验结果表明,添加CDM分子筛可有效提高PtSnZn/Al2O3催化剂的芳构化活性和稳定性;在460～560℃、0.4MPa、重时空速0.3h-1、H2与原料油的体积比100的条件下连续运行72h,随运行时间的延长和反应温度的升高,PtSnZn/CDM-Al2O3催化剂上液体产物中BTX的质量分数从47.1%逐渐增至63.1%。NH3-TPD表征结果显示,CDM共晶分子筛为催化剂提供了较稳定的酸性中心。PtSnZn/CDM-Al2O3催化剂反复再生10次后,活性无明显下降,且再生过程中无需补氯。TG和程序升温氧化分析结果显示,PtSnZn/CDM-Al2O3催化剂上的积碳量明显低于PS-Ⅵ催化剂,且高温区积碳量很少,使催化剂具有良好的稳定性。

Aromatization of FCC Gasoline to BTX Aromatics over PtSnZn/ZSM-5-ZSM-11-Al2O3 Catalysts

A series of Pt-based catalysts supported on ZSM-5-ZSM-11-Al2O3 were prepared and applied to aromatization of fluid catalytic cracking gasoline to benzene,toluene and xylene(BTX) in a fixed bed reactor. It was found that the catalytic activity and stability of the catalyst could be improved through introduction of ZSM-5-ZSM-11 zeolite to PtSn/Al2O3. Under the reaction conditions of PtSnZn/ZSM-5-ZSM-11-Al2O3 as catalyst,460-560 ℃,0.4 MPa,WHSV 0.3 h-1 and V(H2):V(Oil) 100,BTX mass fraction in C+5 liquid products increased from 47.1% to 63.1%,which was much better than that over industrial PS-Ⅵ catalyst. NH3-TPD measurement indicated that the ZSM-5-ZSM-11 zeolite could provide stable acid sites which were necessary for the aromatization. At the same time little activity loss was found on the PtSnZn/ZSM-5-ZSM-11-Al2O3 catalyst even after regeneration 10 times. TG and O2-TPO analyses revealed that amount of the carbonaceous deposit on the Pt-Sn-Zn/ZSM-5-ZSM-11-Al2O3 was lower than that on PS-Ⅵ,which could lead to the higher catalyst stability.