A new method to construct hierarchical ZSM-5 zeolites with excellent catalytic activity

Abstract

Desilicication and dealuminzation with weak alkaline solution and acid liquor is an effective way to construct hierarchically mesoporous without damaging its crystallinity and preserving its acidity in ZSM-5 zeolites. We investigated the influence of the concentration of NaAlO 2 , treatment time, temperature and the concentration of HCl on the crystallinity of ZSM-5 and characterized the products with XRD, SEM, XRF, BET, NH 3 -TPD, etc. The results showed that the appropriate concentration of NaAlO 2 solutions extract selectively silicon from the framework of the zeolites while a small portion of aluminum would patch some parts of vacancies produced by the removal of silicon, then the HCl would dealuminize to maintain the SiO 2 /Al 2 O 3 ratios, which preserved the crystallinity of ZSM-5 perfectly. Furthermore, the micro-reaction activity tests displayed that the obtained products had higher catalytic than the parent zeolites because of their optimized hierarchical micro-mesoporous.

Effects of different porous fillers on interfacial properties of poly (vinyl alcohol) hybrid films

“…According to the XRD patterns shown in Figure 3(a), the four porous fillers are seen highly crystalline, which are almost identical to the diffraction patterns reported in the literatures for UiO‐66, 36 ZIF‐8, 37 ZSM‐5, 38 and Hβ 39 . For the unfilled PVA film, it exhibits a fairly broad characteristic peak at around 2θ = 20°, reflecting a typical semi‐crystalline feature of polymer materials, and the broad peak is seen to keep well in its all hybrid films with a filler loading of 20 wt% as shown in Figure 3b.…”

Strategies to Enhance the Catalytic Performance of ZSM-5 Zeolite in Hydrocarbon Cracking: A Review

“…High aluminum content could stabilize the surrounding silicon atoms preventing their dissolution, which leads to few mesopores, while, for low aluminum content, large number of the zeolites could be dissolved resulting in low productivity and large pores [91]. Yuan et al [92] developed a new method to prepare the hierarchical ZSM-5 zeolite by post-treatment with different concentration of sodium aluminum solution (NaAlO 2 ). It is a more moderate alkaline etching method compared with NaOH etching method.…”

Catalytic Conversion of 1‐butene over Modified Versions of Commercial ZSM‐5 to Produce Clean Fuels and Chemicals

“…In the former case, mesoporosity is formed by hard templating (e. g. carbonaceous or polymeric compounds), soft templating (e. g. surfactants, organosilanes), or indirect templating methods (e. g. steam‐assisted and solid‐phase crystallization) . In top‐down approaches, mesoporosity is introduced by strategically removing framework atoms from pre‐made zeolites; e. g. desilication via alkaline treatment, and dealumination via acid treatment or steaming at high temperature . The top‐down strategies are advantageously cheaper, relatively easy to reproduce and scale‐up for larger production .…”

“…[36][37][38] In top-down approaches, mesoporosity is introduced by strategically removing framework atoms from pre-made zeolites; e. g. desilication via alkaline treatment, [39][40][41][42] and dealumination via acid treatment or steaming at high temperature. [39,[42][43][44][45] The top-down strategies are advantageously cheaper, relatively easy to reproduce and scale-up for larger production. [23,28,46] Zeotypes based on the MFI, [39,43,47] MOR, [24,48] FAU [49] and TON [50] topologies were prepared via topdown strategies.…”