Search

Non-thermal plasma has been proposed as a promising technique for the reformation of fossil fuel into cleaner fuel. Despite recent achievements in the economic and technical development of plasma-assisted reforming techniques, a better understanding of thermochemistry and electron-induced chemistry is required to optimize the performance of the relevant systems. We study the relative importance of electron-induced chemistry and thermochemistry for C5H12 (model gasoline) activation and products formation using a temperature-controlled dielectric barrier discharge (DBD) reactor. Important mechanical insight is obtained from the comparison between high-temperature and low-pressure conditions under similar reduced field intensities. In a tested range of background temperatures (303 < T < 623 K), we found that the conversion of C5H12 in the DBD depended only on electron-induced chemistry for the Ar/C5H12 and He/C5H12 mixtures, while it was affected by both electron-induced chemistry and thermochemistry for the N2/C5H12 mixture. However, the consecutive reactions from the initiation to the product always depended upon the corresponding thermochemistry for a given temperature. Due to an enhanced electron density and electron energy in the Ar/C5H12 and He/C5H12 DBD, increased C5H12 conversion was observed when compared to N2/C5H12. More importantly, cleaner products were produced from the Ar/C5H12 and He/C5H12 DBD because He and Ar were not involved in the product formation reaction pathways. We also found that extensive thermochemical involvement is favorable for enhancing the performance of plasma-assisted C5H12 reforming. Our findings may not only be useful for a greater understanding of the plasma-assisted reforming process but also helpful in designing a cost-effective plasma reformer. [ABSTRACT FROM AUTHOR]

The catalytic activity of a transition metal (host) oxide can be influenced by doping with a second cation (dopant), but the key factors dominating the activity of the doped catalyst are still controversial. Herein, CeO2 doped with Ni, Mn, and Y catalysts prepared using aerosol pyrolysis were used to demonstrate the positive, negative, and additive effects on CO oxidation as a model reaction. Various characterization results indicated that Ni, Mn, and Y had been successfully doped into the CeO2 lattice. The catalytic activities of each catalyst for CO conversion were in the order of Ni–CeO2 > Mn–CeO2 > CeO2 > Y–CeO2. Operando DRIFTS-MS and various characterization methods were applied to reveal the intrinsic nature of the doping effects. The accumulation rate of the surface bidentate carbonates determined the CO oxidation. A definition to evaluate the doping effect was proposed, which is anticipated to be useful for developing a rational catalyst with a high CO oxidation activity. The CO oxidation reactivities displayed strong correlations with the surface factors obtained from operando DRIFTS-MS analysis and the structure factors from XPS and Raman analyses. [ABSTRACT FROM AUTHOR]

This study proposes a novel four-way plasma-catalytic removal of particulate matter, nitrogen oxides, hydrocarbons, and carbon monoxide without external heating using a pulsed dielectric barrier discharge reactor combined with Au/CaSO4/γ-Al2O3 catalyst balls. With the optimized amount of Au and CaSO4, over 90% of particulate matter, 40% of nitrogen oxides, and nearly 100% of hydrocarbons were removed from the diesel engine exhaust, while the increase of carbon monoxide concentration due to the oxidation of particulate matter and hydrocarbons and the decomposition of carbon dioxide were minimized. Importantly, the performance of the plasma-catalytic reactor was maintained without decline for the duration of the experiment (7 h) with an attractive cost/performance ratio. These findings offer a new approach to the simultaneous treatment of diesel exhausts and provide a novel concept for the design of a practical and compact after-treatment device for the diesel engine exhaust gases. [ABSTRACT FROM AUTHOR]

The activities for nonthermal plasma-induced oxidation of diesel particulate matter (DPM) with various metal sulfates were investigated. It was found that the metal sulfates, MgSO4, K2SO4, and CaSO4·2H2O, enhanced the energy yield of DPM oxidation while other sulfates, Na2SO4, Fe2(SO4)3, and Al2(SO4)·8H2O, did not affect the energy yield. The addition of water vapor caused a promotion of DPM oxidation regardless of a metal sulfate was presented. The effect of temperature and sulfate adding amount was also investigated. The metal sulfates enhanced DPM oxidation is possibly due to the adsorption of O atoms onto the sulfates. The positive effects of H2O might be thought of as due to the formation of reactive OH radicals and the promotion of the hydrolysis of the oxygen-containing compounds on DPM surface. [ABSTRACT FROM PUBLISHER]

Plasma-assisted dry reforming of methane has attracted much research attention because this process simultaneously utilizes greenhouse, methane and carbon dioxide, to produce hydrogen-rich syngas at a relative low temperature. Although it is generally recognized that the gas composition of reactant has great effect on the methane conversion and products distribution, systematic studies that clarify the roles that electron-induced chemistry and thermochemistry play are needed for a full understanding of reactant effect. Here, we compared the reforming performance by varying the ratio of CO2/CH4 or O2/CH4 at the similar reduced field intensity (E/N) in a temperature-controlled dielectric barrier discharge reactor to elaborate the role of electron-induced chemistry and thermo-chemistry in the dry reforming process. By conducting optical emission spectrum measurement, the enrichment of O atoms was observed at the increased CO2/CH4 or O2/CH4 ratios. At T = 293 K, methane conversion was only dependent on the electron-induced chemistry regardless of the specific reactant gas composition. At a relative high temperature condition, however, thermochemistry could become pronounce when sufficient O atoms were added into the dry reforming process. In contrast, the chemical pathways to the products were overall controlled by the thermochemistry at the tested background temperatures. Due to the conversion of carbon-based products into the carbon dioxide, the conversion of carbon dioxide was influenced by the thermochemistry when the concentration of O atoms was high. Our findings may improve the understanding of reactant effect and the designs of plasma-reformer. [ABSTRACT FROM AUTHOR]