Abstract
The reforming of hydrocarbons has gained much interest as a means to upgrade low-grade fuels and to produce value-added chemicals. Plasmas have been considered one of the potential ways to reform fuels to achieve more effective and cleaner combustion, particularly by producing various hydrocarbons, hydrogen carriers, and oxygenates as well as syngas. Here, we employed a submerged microwave plasma jet of argon to investigate its potential to transform n-heptane. We found that the product selectivities were mainly governed by the effective gas temperature, which we adjusted by changing the energy density of the argon stream. The transformation of n-heptane by this method mostly produced ethylene and acetylene, which is different than the products produced by pyrolysis or a chemical equilibrium composition. Such unique selectivities could be attributed to the rapid quenching of the microwave plasma jet upon direct contact with the colder liquid. The transformation of n-heptane was significantly affected by the interactions between the microwave plasma jet and the liquid n-heptane. To support our results, we include a detailed chemical analysis and discussion of the physical characterization of the microwave plasma jet using optical emission spectroscopy.
Highlights
The reforming of fuel has been of special interest ever since the Fischer–Tropsch process, i.e., the liquefaction of syngas from coal, was first introduced in the early 20th century
In our previous studies on the basic reforming processes of methane—partial oxidation, dry reforming, and steam reforming—using a temperature-controlled dielectric barrier discharge (DBD) reactor,9–11 we found that the gas temperature mainly controlled the product selectivity, and the reactant conversion was initiated by electron-induced chemistry, depending on electron temperature and density
We experimentally investigated a submerged microwave plasma jet (MWPJ) of argon in liquid n-heptane to study its transformation capability with liquid substance and to prove its unique character in controlling product selectivity due to the rapid quenching of chemical reactions caused by heat interaction with the liquid
Summary
The reforming of fuel has been of special interest ever since the Fischer–Tropsch process, i.e., the liquefaction of syngas from coal, was first introduced in the early 20th century. Since the early 2000s, nonthermal plasmas have been considered as a promising method for the on-board production of hydrogen-rich syngas, because plasma devices are compact and respond quickly.. Recent advances in the field of in-liquid discharges have inspired the exploration of the reforming of liquid hydrocarbons.. Recent advances in the field of in-liquid discharges have inspired the exploration of the reforming of liquid hydrocarbons.12–16 These approaches practically do not require the evaporation of liquid fuels; these can accommodate various kinds of feedstock and scitation.org/journal/jap save the energy for the evaporation as compared to gas phase plasma methods. Studies have shown that the product composition of in-liquid plasma processes to transform liquid hydrocarbons can be tailored by adding chemical additives.. Studies have shown that the product composition of in-liquid plasma processes to transform liquid hydrocarbons can be tailored by adding chemical additives. methane and carbon dioxide were found to selectively increase the production of lighter hydrocarbons and oxygenates, respectively, in the reforming of n-dodecane and n-heptane. there exist at least two ways to control the product composition: by controlling the reaction temperature and the choice of chemical additives
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