Calcium against the Aromatic Cycle

Calcium against the Aromatic Cycle

Author: ChemCatChem

The methanol-to-olefins (MTO) process is one of the most promising technologies to fulfill the growing demand for ethylene and propylene – primary building blocks in the chemical industry. Since cheap ethylene can be produced from shale gas-based ethane, high selectivity to propylene is one of the main challenges of the MTO process. Another challenge lies in engineering catalysts that are stable towards deactivation by coking.

Both challenges are closely related to the production of methylbenzene derivatives inside the pores of the zeolite used as a catalyst. The so-called aromatic cycle is responsible for the formation of ethylene and coke precursors and competes with the alkene cycle which mostly produces propylene.

Jorge Gascon, Delft University of Technology, the Netherlands, and colleagues addressed both challenges by designing a catalytic system in which the aromatic cycle could be suppressed. The catalyst was obtained by the incorporation of calcium into the commercially available zeolite ZSM-5.

The catalyst was characterized using N2 adsorption and NH3 desorption measurements, X-ray crystallography, scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX), infrared (IR) spectroscopy, and solid-state NMR measurements. The team could show that the incorporation of calcium allows fine-tuning of the zeolite acidity, which in turn leads to improved propylene selectivity and catalyst lifetime.


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