Conversion of Methanol to Olefins over Modified OSDA-Free CHA Zeolite Catalyst

Abstract

Methanol to olefins (MTO) is an essential process that produces olefins from both renewable and fossil fuels resources. Chabazite (CHA) is an efficient catalyst for MTO process due to its distinct properties that promote light olefins (i.e., ethylene and propylene) production. Herein, we report a series of chabazite-based catalysts (OSDA-free with enhanced textural properties) that facilitate the MTO reaction. The synthesized CHA was modified by steam injection (CHA-S), acid treatment (CHA-A), steam and acid treatment (CHA-SA), and metal incorporation (CHA-SA (Mg), CHA-SA (Ca), and CHA-SA (Ba)). The catalysts were characterized by several characterization techniques. The structure was investigated using X-ray diffraction (XRD) and nuclear magnetic resonance, while the morphology and physical properties were studied by field emission scanning electron microscopy (FE-SEM), N2 adsorption/desorption, and ammonia temperature-programmed desorption (NH3-TPD). The catalysts were evaluated at 450 °C until deactivation. CHA modified by only acid treatment showed higher selectivity to olefins from ca. 92 to 95 wt.% but suffered quick deactivation. CHA modified with both steam and then acid treatment was more stable in the MTO process.