化学工程

基于Materials Studio软件进行分子动力学与第一性原理模拟计算，系统地探讨了Pt/Al_2O₃、Pt/TiO₂和Cu/Al_2O₃ 3类催化剂在氨气氧化反应中的作用机制，通过实验验证分析了载体特性与活性组分对催化性能的调控规律。本研究的分子动力学模拟基于Sorption和Forcite板块，揭示了3类催化剂表面对气体分子的吸附与扩散行为。Al_2O₃载体在100—400℃内对NH₃的绝对吸附量显著高于TiO₂载体；NH₃在400℃下，于Cu/Al_2O₃表面表现出最高的扩散系数3.5×10^-8 m²/s。第一性原理计算基于Dmol3板块，对比分析了Pt基与Cu基催化剂的反应路径差异，Pt基催化剂表面NH₃氧化遵循逐步脱氢路径，N—N键形成能垒高达1.347 eV,成为速率控制步骤；而Cu/Al_2O₃通过—NH₂耦合路径(—NH₂→N_2H₄→N₂)直接生成N₂,关键能垒显著低于Pt基体系。本研究揭示了载体酸性位点与金属-载体作用对反应路径选择性的协同调控：Al_2O₃通过强化学吸附提升反应物富集效率，而TiO₂依赖物理吸附促进中间体脱附。

Molecular dynamics and first-principles simulations were employed based on the Materials Studio software to systematically investigate the reaction mechanisms of Pt/Al_2O₃, Pt/TiO₂ and Cu/Al_2O₃ catalysts in ammonia oxidation.Experimental validation was used to analyze the regulatory effects of support properties and active components on catalytic performance.The molecular dynamics simulations, performed using the Sorption and Forcite modules, revealed the adsorption and diffusion behaviors of gas molecules on the surfaces of the three catalyst types. Al_2O₃ support exhibits a significantly higher absolute adsorption capacity for NH₃ within 100-400 ℃ compared to TiO₂ support. NH₃ demonstrates the highest diffusion coefficient of 3.5×10^-8 m²/s on Cu/Al_2O₃ surface at 400 ℃.First-principles calculations, conducted using the Dmol3 module, comparatively analyzed the reaction pathway differences between Pt-based and Cu-based catalysts.Ammonia oxidation on Pt-based catalyst surfaces follows a stepwise dehydrogenation pathway, with N—N bond formation presenting a high energy barrier of 1.347 eV, acting as the rate-determining step.In contrast, Cu/Al_2O₃ directly generates N₂ via —NH₃ coupling pathway(—NH₃ → N_2H₄ → N₂), where the key energy barrier is clearly lower than that in Pt-based systems.This study reveals the synergistic regulation of support acidic sites and metal-support interactions on the selectivity of reaction pathways: Al_2O₃ enhances reactant enrichment efficiency through strong chemisorption, and TiO₂ relies on physical adsorption to promote intermediate desorption.