Synthesis Of ZSM-5 Zeolite And Their Application

ZSM-5 zeolites had been extensively used in petroleum cracking, Catalytic oxidation of methane production of methanol, catalytic reduction of NO and many other industrial processes due to their relative large specific surface area, high hydrothermal stability and specific acidity in the pores, which demonstrated very excellent catalytic performances. However, the ZSM-5 zeolites also had some drawbacks, such as the pore distribution is relative narrow, which limited the transfer of large reactive molecules and caused the carbon deposition, leading to decreased catalytic activity, even inactivation; Besides, the single ZSM-5 zeolites exhibited narrow NO conversion temperature windows in the NH3-SCR process to eliminate NO, which means it is not conductive to practical application. Therefore, according to the above problems, we tried to modify ZSM-5 zeolites to exploit their superior catalytic properties. We mainly had carried on the three following works:1) we employed two steps method to instruct mesoporous in the ZSM-5 pores with the proper concentration of Na Al O2 and HCl solution. The results showed that the obtained ZSM-5 zeolites had a certain amount of mesoporous, and commendably maintained their crystallinity and Si O2/Al2O3 ratios, and presented higher micro-reactivity than the untreated ZSM-5 zeolites.2) We prepared the Zn modified ZSM-5 zeolites to improve their catalytic activity in the NH3-SCR process. Zinc-containing MFI-type ZSM-5 zeolites were synthesized with ammonia coordinated zinc solution as zinc source, n-butyl amine as template and ZSM-5 as seeds by a facile one-step hydrothermal method. We characterized their catalytic performance though the NH3-SCR testing system and found that the single ZSM-5 zeoliles showed high NO conversion in the 300oC~420oC temperature ranges, but the conversion quickly decreased as the temperature rising, while the framework Zn containing Zn-ZSM-5 of 0.73%Zn-ZSM-5 and 1.77%Zn-ZSM-5 samples showed increasing of NO conversion with the increasing of temperatures in the 200oC~550oC temperature ranges, and kept high NO conversion(>90%) in the 400oC~550oC temperature ranges. These results demonstrated that the Zn-ZSM-5 zeolites had high catalytic activity to eliminate NO in NH3-SCR process. Besides, we found that the specific area, morphology and other physical and chemical of these Zn-ZSM-5 zeolites exhibited regular changes with the increasing contents of Zn.3) We synthesized a series of framework Cu contanining Cu-ZSM-5 zeolites by disodium ethylenediaminetetraacetate complexed with copper ions as copper source. The characterization results of XRD and IR showed that the Cu species was successfully incorporated into the ZSM-5 zeolites frameworks; we used N2 absorption-desorption method characterized the textural properties of these Cu-ZSM-5 samples and found that the changes of their specific areas and total pore volumes is very small. Though NH3-SCR testing, these 0.908%Cu-ZSM-5 and 1.51%Cu-ZSM-5 samples showed high NO conversion(over 90%) in the 200 oC~ 370 oC temperature ranges, which illustrated that these Cu-ZSM-5 zeolites had superior catalytic reactivity in the NH3-SCR process at lower temperature ranges.