The synthesized ZSM-5 zeolite aggregate of Si/Al = 150 denoted as sample Z was treated with different concentration of sodium carbonate solution (0.2 mol/L and 0.6 mol/L), the treated samples were denoted as ZA1 and ZA2 respectively. In addition, sample Z also was treated with alkali solution containing CTAB (0.05 mol/L) denoted as ZAC1 and ZAC2 respectively. Their catalytic activities were investigated in MTP reaction.<br/>After alkali modification with CTAB, due to adjustment of textural properties, catalytic performance of the catalyst eventually improved in the MTP reaction. Because of the low alkali concentration, the textural properties of ZA1 and ZA2 remain unchanged compared with sample Z. While after adding CTAB into sodium carbonate solution, ZAC1 and ZAC2 contain more micropores and mesopores with diameter of ~3 nm, and the ZAC1 and ZAC2 present hollow structure as shown in Fig.1. In the <sup>29</sup>Si NMR test, ZAC1 and ZAC2 contain more proportion of Si(0Al) species which means CTAB played main role of reassembling the dissolved silicon species. CTAB distributed in the entire ZSM-5 particle region leading to the desilication in the inner area of the particle and reassemble of dissolved silicon species at the outside area then the hollow structure was generated. And the new micropores and 3 nm mesopores were formed during the reassemble processing.<br/>For all the samples, sample Z, ZA1 and ZA2 possess the same catalytic lifetime (100h), while the lifetime of ZAC1 and ZAC2 prolonged to 180h and 150h respectively which is attributed to the finely tuned texture property, such as the increased micropore surface area, the newly formed 3 nm mesopores and the hollow structure. Comparing to sample Z， ZAC1 performs high propylene selectivity increasing from 38% to 45% and the low HTI (hydrogen transfer index) decreasing from 0.15 to 0.05.

Hollow structure of ZSM-5 aggregate prepared by desilication with surfactants: A superior MTP catalyst

255th National Meeting (2018)

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