Synthesis of Uniform Mesoporous Zeolite ZSM-5 Catalyst for Friedel-Crafts Acylation

Heman Smail,Kafia Shareef,Zainab Ramli,Abdul-Sattar Nizami,Jabbar Gardy,Mohammad Rehan

doi:10.3390/chemengineering3020035

Abstract

This work highlights how the treatment of ZSM-5 (parent Zeolite Socony Mobil–5, Si/Al = 23) with different surfactant templates and alkaline solution, improved the catalytic performance in the Friedel-Crafts acylation of anisole with a propionic anhydride to obtain p-methoxypropiophenone. The modified microporous to mesoporous zeolite catalysts were characterized using different analytical techniques, including X-ray diffraction (XRD), nitrogen porosimetry, Fourier-transform infrared spectroscopy (FT-IR), temperature-programmed desorption (ammonia-TPD) and field emission scanning electron microscopy (FE-SEM) to analyze the crystallographic structure, surface acidity, surface area, porosity, morphology, and particle size. The results showed that the formed mesoporous zeolite by NaOH solution had smaller mesopores (ca. 3.7 nm) as compared to the mesoporous zeolites obtained by surfactant templates, such as, CTAB (ca. 14.9 nm), TPAOH (ca. 11.1 nm) and mixture of CTAB/TPAOH (ca. 15.2 nm). The catalytic acylation reaction was conducted in a batch glass reactor at various temperatures and the products were analyzed using off-line gas chromatography–mass spectrometry (GC-MS). It was found that the activity of treated ZSM-5 with mixed surfactant templates (CTAB/TPAOH) exhibited enhanced selectivity towards the main product (p-methoxypropiophenone) by a factor 1.7 or higher than unmodified ZSM-5 due to its increased surface area by 1.5 times and enhanced acid sites.

Highlights

The Friedel-Crafts acylation is one of the most vital organic reactions in the preparation of substituted aromatic ketones in pharmaceutical, fragrance, cosmetics and agrochemical industries
The catalyst activity and selectivity of zeolite H-Beta, H-ZSM-5, H-Y, and NH4-Y catalysts in the acylation reaction of anisole with acetic anhydride were compared by Freese et al [5]
They reported a lower catalytic activity of H-ZSM-5 compared to H-Y and H-Beta catalysts with only 14% of conversion; this is due to smaller intersection channels in ZSM-5 [8]

Summary

Introduction

The Friedel-Crafts acylation is one of the most vital organic reactions in the preparation of substituted aromatic ketones in pharmaceutical, fragrance, cosmetics and agrochemical industries. Catalysts such as strong mineral acids (H2SO4 and HF) and metal halides (and FeCl3 and AlCl3) have been used in the conventional acylation method [1]. The catalyst activity and selectivity of zeolite H-Beta, H-ZSM-5, H-Y, and NH4-Y catalysts in the acylation reaction of anisole with acetic anhydride were compared by Freese et al [5] They reported a lower catalytic activity of H-ZSM-5 compared to H-Y and H-Beta catalysts with only 14% of conversion; this is due to smaller intersection channels in ZSM-5 [8]

Methods

Results

Conclusion