Synthesis of Chabazite Zeolite via Faujasite Conversion Using 1‐(1‐Methylpropyl)‐4‐aza‐1‐azoniabicyclo[2.2.2]octane Hydroxide as Cost‐Effective Structure‐Directing Agent

Abstract

Cu‐exchanged chabazite zeolite is the state‐of‐the‐art used on‐board catalyst for NOx selective reduction by ammonium (NH3‐SCR), and the zeolite is currently generated in the presence of N,N,N‐trimethyl‐1‐adamantylammonium hydroxide, serving as organic structure‐directing agent (OSDA). The expensiveness of this OSDA increases the catalyst production cost, while its low degradability brings about environmental concerns in post treatment of waste water. Here, a new type OSDA, 1‐(1‐methylpropyl)‐4‐aza‐1‐azoniabicyclo[2.2.2]octane hydroxide, is proposed to direct Faujasite‐to‐Chabazite inter‐zeolite conversion and generate chabazite with Si/Al ratio up to 7.2. The obtained zeolite possesses high hydrothermal stability for the high crystallinity, siliceous framework and low concentrations of Si(2Si, 2Al) sites. The Cu‐form catalyst exhibits better catalytic performance in standard NH3‐SCR process for the tiny crystallite size (35‐258 nm) and formation of highly dispersed copper sites. The synthesis offers a new type of OSDA to fabricate zeolites and expands the toolkit to regulate their physicochemical properties.