Bennett-Caso Claudia, Leonardi Angelina L, Hambuchen Rachel, Castelblanco Aida, Spagnoletti Jack, Szady Cecily, Wozniak Natasha, Navea Juan G
Chemistry Department, Skidmore College, Saratoga Springs New York 12866-1632, United States.
J Phys Chem A. 2025 Jul 10;129(27):6094-6106. doi: 10.1021/acs.jpca.5c01709. Epub 2025 Jun 3.
Heterogeneous oxidation of hydrocarbons via low-pressure nonthermal plasma has traditionally focused on nonvolatile compounds since volatile or semivolatile hydrocarbons can partition into the plasma, reducing product selectivity. However, adsorption of volatile compounds can prevent the hydrocarbon from vaporizing and reaching the plasma-phase, allowing reactions to take place between free radicals generated via nonthermal plasmas and the volatile or semivolatile hydrocarbon. In this work, we present a state-of-the-art chamber for the heterogeneous reactions between adsorbed hydrocarbons and ground-state oxygen (O( P)) generated via nonthermal plasma. The chamber enabled a hydrocarbon monolayer on an alumina thin film to be exposed to a plasma plume generated with a radio frequency (RF) generator. In situ vibrational spectroscopy of the alumina-coated surface was used to investigate the relative kinetics of two model hydrocarbons, 1-hexene and cyclohexane, chemisorbed onto alumina. Finally, the functionalization of the chemisorbed hydrocarbon on the alumina powder via nonthermal plasma was investigated in situ in order to determine the conditions for an effective oxidation. Our results show a novel and effective method for the reaction with adsorbed volatile compounds with O(P). For the adsorbed compounds, the reaction of adsorbed cyclohexane is twice as fast as adsorbed 1-hexene, which represents a significant change with respect to gaseous phase rates, where 1-hexene reaction with O(P) is approximately 37 times faster than cyclohexane.
传统上，通过低压非热等离子体进行的碳氢化合物非均相氧化主要集中在非挥发性化合物上，因为挥发性或半挥发性碳氢化合物会分配到等离子体中，从而降低产物选择性。然而，挥发性化合物的吸附可以防止碳氢化合物汽化并进入等离子体相，使通过非热等离子体产生的自由基与挥发性或半挥发性碳氢化合物之间发生反应。在这项工作中，我们展示了一个用于吸附态碳氢化合物与通过非热等离子体产生的基态氧（O(³P)）之间非均相反应的先进反应室。该反应室能使氧化铝薄膜上的碳氢化合物单分子层暴露于由射频（RF）发生器产生的等离子体羽流中。利用氧化铝涂层表面的原位振动光谱研究了化学吸附在氧化铝上的两种模型碳氢化合物1-己烯和环己烷的相对动力学。最后，对通过非热等离子体在氧化铝粉末上化学吸附的碳氢化合物进行原位功能化研究，以确定有效氧化的条件。我们的结果表明了一种与吸附态挥发性化合物和O(³P)反应的新颖有效方法。对于吸附态化合物，吸附态环己烷的反应速度是吸附态1-己烯的两倍，这与气相反应速率相比有显著变化，在气相中1-己烯与O(³P)反应的速度比环己烷快约37倍。
