Nascent Decomposition Pathways of CH₄ Pyrolysis in Gas-Phase Metal Halides.

Area of Science:

• Chemical kinetics
• Catalysis
• Computational chemistry

Background:

• Methane pyrolysis is a key process for producing hydrogen and carbon materials.
• Understanding catalytic mechanisms is crucial for optimizing methane conversion.
• Gas-phase metal halides offer potential as catalysts for methane decomposition.

Purpose of the Study:

• To investigate the nascent decomposition pathways of methane pyrolysis catalyzed by gas-phase zinc chloride (ZnCl2).
• To determine the catalytic activity and identify key reactions in the methane pyrolysis network.
• To explore and compare the catalytic potential of various gas-phase metal halides for methane decomposition.

Main Methods:

• Combined quantum mechanical (QM) and microkinetic modeling.
• Simulation in a constant pressure batch reactor at 1273 K.
• Sensitivity analysis of the reaction network.

Main Results:

• ZnCl2 catalyzes methane pyrolysis with an apparent activation energy of 227 kJ/mol.
• The complex reaction network simplifies to four key reactions governing initial methane decomposition rate.
• Gas-phase CuCl2 and NiCl2 exhibit the highest catalytic activity among the investigated metal halides.

Conclusions:

• Gas-phase ZnCl2 is an effective catalyst for methane pyrolysis, with a well-defined kinetic model.
• CuCl2 and NiCl2 are promising catalysts for efficient methane decomposition.
• The study provides fundamental insights into metal halide-catalyzed methane pyrolysis mechanisms.