Lim Norleakvisoth, McFarland Eric, Gordon Michael J
Department of Chemical Engineering, University of California, Santa Barbara, California 93106, United States.
J Am Chem Soc. 2025 Jan 8;147(1):397-408. doi: 10.1021/jacs.4c11174. Epub 2024 Dec 20.
AC plasmas directly excited within liquid hydrocarbons were investigated for the production of hydrogen and unsaturated C hydrocarbon in a recirculating liquid "jet" flow configuration. Arc discharges were excited at two different frequencies (60 Hz and 17.3 kHz) in C-C hydrocarbons (hexane, cyclohexane, benzene, toluene, and xylene) to produce H, CH, CH, and CH, along with liquid and solid carbon byproducts. AC frequency was seen to modify the plasma properties and gas bubble formation dynamics, significantly influencing the efficiency and reaction pathway. Higher discharge frequency increased energy efficiency more than 2-fold by minimizing thermal losses and favored the production of hydrogenated compounds due to shorter reactant-plasma contact times. Further optimization of hexane conversion was achieved by introducing fluid flow around the plasma electrodes, which led to competitively low specific energy requirements (SERs) of 3.2 kWh/kg CH, 4.9 kWh/kg CH, and 24.3 kWh/kg H. The effect of hydrocarbon feed chemistry was analyzed, showing that hexane and cyclohexane are preferable for C hydrocarbon syntheses, whereas aromatic hydrocarbons produce more H. Gas bubble dynamics and liquid/solid products were analyzed using high-speed imaging, optical emission spectroscopy (OES), gas chromatography-mass spectrometry (GC-MS), scanning electron microscopy/transmission electron microscopy (SEM/TEM), and Raman spectroscopy. This work contributes to the understanding of plasma conversion mechanisms within liquids and demonstrates the potential for the energy-efficient transformation of hydrocarbons with plasma in unique reaction environments.
研究了在液态烃中直接激发的交流等离子体，以在循环液体“喷射”流配置中生产氢气和不饱和碳氢化合物。在碳氢化合物（己烷、环己烷、苯、甲苯和二甲苯）中以两种不同频率（60赫兹和17.3千赫兹）激发电弧放电，以产生H、CH、CH和CH，以及液体和固体碳副产物。发现交流频率会改变等离子体特性和气泡形成动力学，显著影响效率和反应途径。较高的放电频率通过最小化热损失使能量效率提高了两倍多，并且由于反应物与等离子体的接触时间较短，有利于氢化化合物的生产。通过在等离子体电极周围引入流体流动，实现了己烷转化率的进一步优化，这导致了具有竞争力的低比能量需求（SERs），分别为3.2千瓦时/千克CH、4.9千瓦时/千克CH和24.3千瓦时/千克H。分析了烃类进料化学的影响，结果表明己烷和环己烷更适合用于碳氢化合物合成，而芳烃产生更多的H。使用高速成像、光发射光谱（OES）、气相色谱-质谱（GC-MS）、扫描电子显微镜/透射电子显微镜（SEM/TEM）和拉曼光谱对气泡动力学和液体/固体产物进行了分析。这项工作有助于理解液体中的等离子体转化机制，并证明了在独特反应环境中利用等离子体对烃类进行节能转化的潜力。
