Application of liquid-phase plasma for the production of hydrogen and carbon from the plasma-induced cracking of liquid hydrocarbons

A study was conducted on the decomposition reaction of liquid hydrocarbons induced by liquid plasma and photocatalyst. This study is to obtain useful resources by recycling waste liquid-hydrocarbons. Titanium dioxide and TiO2-doped with a metal (and nitrogen atoms) were used as photocatalysts individually in the study. First, H2 and carbon were simultaneously produced in the decomposition reaction of liquid hexane and benzene induced by liquid plasma. Notably, only H2 was obtained as a gaseous product, and no carbon dioxide was produced in this reaction. However, when photocatalyst was injected into this decomposition, the corresponding reactivity improved. In particular, the amount of H2 and carbon produced increased in the order of: the amount of H2 and carbon produced with N/Ni/TiO2 > Ni/TiO2 > TiO2 photocatalyst, respectively, when the photocatalyst was added in an equal amount to the reactant of the decomposition. The highest carbon yield and hydrogen evolution under these experimental conditions were about 1 %/(g center dot h) and about 180 L/(g center dot h), respectively. This order is because the strong visible light generated by liquid plasma discharge improved the photoreactivity of the N/Ni/TiO2 photocatalyst that has a high sensitivity to visible light and narrow band gap. Carbon particles produced from the decomposition reaction of liquid hexane and benzene, respectively, induced by liquid plasma and photocatalyst were small and uniform, with a size of 10 nm or less. In addition, the BET surface area of the carbon produced in this reaction was greater than 500 m2/g, and the properties of the carbon particles were almost the same regardless of the lapse of reaction time. Hence, this decomposition reaction of liquid hexane and benzene, respectively, induced by liquid plasma and photocatalyst was judged to be forming an efficient technology that can simultaneously obtain high-purity hydrogen energy and useful basic materials from liquid hydrocarbons.