Synthesis of NU‐87 Zeolite via Aging and Dual‐Templating Methods

Abstract

AbstractNU‐87, a kind of high‐silica zeolite with NES topology, was considered as a potential industrial catalyst due to its controllable surface acidity, high thermal/hydrothermal stability, and unique parallel 10‐membered ring (MR) channels connected with 12‐MR cavities. However, the long crystallization time, the poor repeatability of synthesis and the expensive structure‐directing agent (SDA) of decamethonium bromide (DecBr2) used obstruct its industrial applications. In this work, according to the careful study on the influence of synthesis conditions, two methods were developed for synthesis of NU‐87 zeolite. By aging method in the assistance of crystal seeds, the crystallization time of NU‐87 zeolite could be reduced from 10 days to 2.5 days. The interaction between the synthesis precursors and the SDA plays a key role in the synthesis of NU‐87 zeolite. Moreover, NU‐87 zeolite could also be synthesized by a dual‐templating method. 1,3‐propanediamine (PDA) and 1,4‐butanediamine (BDA) could work as the secondary SDAs, which could partially replace the original expensive SDA of DecBr2. In the case of PDA, the DecBr2 could be decreased to 50 % of the original dosage. Finally, the catalytic performance of H‐NU‐87 zeolite was evaluated in the methanol to hydrocarbon reaction. Referred to H‐ZSM‐5, the H‐NU‐87 zeolite presented higher selectivity to gasoline but shorter catalytic life due to its stronger acidity.