Coal fly ash derived zeolite: a solid-state base for convenient synthesis of diphenyl ethers

Abstract

Worldwide, the ever-rising demand for coal in power plants has increased coal fly ash (CFA) production. Its disposal is a major environmental problem. CFA zeolitization offers a possible alternative for converting this hazardous solid waste into high-value products. This work uses the fusion-assisted ultrasonication method to synthesize zeolite. The material was characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) techniques. The synthesized zeolite, sodalite was mesoporous with a surface area of 22.13 m² g⁻¹ and an average pore size of 7 nm. This was used and optimized as a solid-state base for synthesizing diphenyl ethers (DPEs). The yields of twelve diphenyl ethers with aldehyde, chloro, methoxy, methyl and nitro groups ranged from 35 to 91%. The methodology offers an advantage over conventional processes in providing single-step synthesis of DPEs with electron-withdrawing groups on both rings.