Atomic-Level Simulation Study of n-Hexane Pyrolysis on Silicon Carbide Surfaces

Area of Science:

• Materials Science
• Chemical Engineering
• Petrochemistry

Background:

• Ethylene production is vital to the petrochemical industry.
• Ethylene thermal cracking involves high temperatures and coke formation, demanding advanced materials for reactor components like radiant coils tubes (RCTs).
• Developing corrosion-resistant and coking-resistant materials is crucial for efficient and durable RCTs.

Purpose of the Study:

• To evaluate the performance of ceramic materials, specifically silicon carbide (SiC), under severe pyrolysis conditions.
• To understand the coking and stability mechanisms of SiC in ethylene thermal cracking environments.
• To provide insights for the development of novel materials for petrochemical reactors.

Main Methods:

• Utilized reactive force field molecular dynamics (ReaxFF MD) simulations.
• Investigated SiC performance at high temperatures (1500 K and 2500 K).
• Analyzed surface stability, interface behavior, and coke formation on SiC surfaces.

Main Results:

• Beta-silicon carbide (β-SiC) surfaces demonstrated stability at 1500 K.
• Increased temperatures (up to 2500 K) led to interface melting.
• Cross-linked, graphene-like polycyclic aromatic hydrocarbon (PAH) coking structures formed on SiC surfaces at 2500 K, particularly on the carbon-rich side.
• Coking originated from surface atoms after the loss of the hydroxyl layer and subsequent hydrothermal corrosion.
• The SiC substrate accelerated ethylene cracking and influenced intermediate compound formation.

Conclusions:

• SiC exhibits temperature-dependent stability and coking behavior relevant to ethylene thermal cracking.
• The formation of PAH coking structures on SiC surfaces at high temperatures presents challenges.
• This fundamental research offers significant implications for materials science, petrochemistry, and combustion chemistry in the petrochemical sector.