Characterization of plasma catalytic decomposition of methane: role of atomic O and reaction mechanism

2021 ◽  
Author(s):  
Yudong Li ◽  
Jingkai Jiang ◽  
Michael Hinshelwood ◽  
Shiqiang Zhang ◽  
Peter Bruggeman ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Gas Phase ◽  
Vibrational Frequency ◽  
Catalyst Surface ◽  
Atmospheric Pressure Plasma ◽  
Catalytic Decomposition ◽  
Fold Increase ◽  
Co2 Absorption ◽  
Ch4 Oxidation ◽  
Frequency Changes

Abstract In this work, we investigated atmospheric pressure plasma jet (APPJ)-assisted methane oxidation over a Ni-SiO2/Al2O3 catalyst. We evaluated possible reaction mechanisms by analyzing the correlation of gas phase, surface and plasma-produced species. Plasma feed gas compositions, plasma powers, and catalyst temperatures were varied to expand the experimental parameters. Real-time Fourier-transform infrared spectroscopy (FTIR) was applied to quantify gas phase species from the reactions. The reactive incident fluxes generated by plasma were measured by molecular beam mass spectroscopy (MBMS) using an identical APPJ operating at the same conditions. A strong correlation of the quantified fluxes of plasma-produced atomic oxygen with that of CH4 consumption, and CO and CO2 formation implies that O atoms play an essential role in CH4 oxidation for the investigated conditions. With the integration of APPJ, the apparent activation energy was lowered and a synergistic effect of 30% was observed. We also performed in-situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) to analyze the catalyst surface. The surface analysis showed that surface CO abundance mirrored the surface coverage of CHn at 25 oC. This suggests that CHn adsorbed on the catalyst surface as an intermediate species that was subsequently transformed into surface CO. We observed very little surface CHn absorbance at 500 oC, while a ten-fold increase of surface CO and stronger CO2 absorption were seen. This indicates that for a nickel catalyst at 500 oC, the dissociation of CH4 to CHn may be the rate-determining step in the plasma-assisted CH4 oxidation for our conditions. We also found the CO vibrational frequency changes from 2143 cm-1 for gas phase CO to 2196 cm-1 for CO on a 25 oC catalyst surface, whereas the frequency of CO on a 500 oC catalyst was 2188 cm-1. The change in CO vibrational frequency may be related to the oxidation of the catalyst.

scholarly journals Ruthenium trisbipyridine as a candidate for gas-phase spectroscopic studies in a Fourier transform mass spectrometer

2004 ◽  
Vol 18 (2) ◽  
pp. 387-396 ◽  
Author(s):  
Jill R. Scott ◽  
Jason E. Ham ◽  
Bill Durham ◽  
Paul L. Tremblay
Keyword(s):  
Fourier Transform ◽  
Gas Phase ◽  
Mass Spectrometer ◽  
Rate Constant ◽  
Optical Detection ◽  
Sinapinic Acid ◽  
Spectroscopic Studies ◽  
Fluorescence Lifetimes ◽  
Fourier Transform Mass Spectrometer

Metal polypyridines are excellent candidates for gas-phase optical experiments where their intrinsic properties can be studied without complications due to the presence of solvent. The fluorescence lifetimes of [Ru(bpy)3]1+trapped in an optical detection cell within a Fourier transform mass spectrometer were obtained using matrix-assisted laser desorption/ionization to generate the ions with either 2,5-dihydroxybenzoic acid (DHB) or sinapinic acid (SA) as matrix. All transients acquired, whether using DHB or SA for ion generation, were best described as approximately exponential decays. The rate constant for transients derived using DHB as matrix was 4×107s−1, while the rate constant using SA was 1×107s−1. Some suggestions of multiple exponential decay were evident although limited by the quality of the signals. Photodissociation experiments revealed that [Ru(bpy)3]1+generated using DHB can decompose to [Ru(bpy)2]1+, whereas ions generated using SA showed no decomposition. Comparison of the mass spectra with the fluorescence lifetimes illustrates the promise of incorporating optical detection with trapped ion mass spectrometry techniques.

scholarly journals Catalytic Performance of Nitrogen-Doped Activated Carbon Supported Pd Catalyst for Hydrodechlorination of 2,4-Dichlorophenol or Chloropentafluoroethane

Molecules ◽  
2019 ◽  
Vol 24 (4) ◽  
pp. 674 ◽  
Author(s):  
Haodong Tang ◽  
Bin Xu ◽  
Meng Xiang ◽  
Xinxin Chen ◽  
Yao Wang ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Liquid Phase ◽  
Gas Phase ◽  
Nitrogen Doping ◽  
Catalyst Surface ◽  
Catalytic Performance ◽  
Atomic Ratio ◽  
Pd Catalyst ◽  
Nitrogen Doped ◽  
The Stability

Nitrogen-doped activated carbon (N-AC) obtained through the thermal treatment of a mixture of HNO3-pretreated activated carbon (AC) and urea under N2 atmosphere at 600 °C was used as the carrier of Pd catalyst for both liquid-phase hydrodechlorination of 2,4-dichlorophenol (2,4-DCP) and gas-phase hydrodechlorination of chloropentafluoroethane (R-115). The effects of nitrogen doping on the dispersion and stability of Pd, atomic ratio of Pd/Pd2+ on the surface of the catalyzer, the catalyst’s hydrodechlorination activity, as well as the stability of N species in two different reaction systems were investigated. Our results suggest that, despite no improvement in the dispersion of Pd, nitrogen doping may significantly raise the atomic ratio of Pd/Pd2+ on the catalyst surface, with a value of 1.2 on Pd/AC but 2.2 on Pd/N-AC. Three types of N species, namely graphitic, pyridinic, and pyrrolic nitrogen, were observed on the surface of Pd/N-AC, and graphitic nitrogen was stable in both liquid-phase hydrodechlorination of 2,4-DCP and gas-phase hydrodechlorination of R-115, with pyridinic and pyrrolic nitrogen being unstable during gas-phase hydrodechlorination of R-115. As a result, the average size of Pd nanocrystals on Pd/N-AC was almost kept unchanged after liquid-phase hydrodechlorination of 2,4-DCP, whereas crystal growth of Pd was clearly observed on Pd/N-AC after gas-phase hydrodechlorination of R-115. The activity test revealed that Pd/N-AC exhibited a much better performance than Pd/AC in liquid-phase hydrodechlorination of 2,4-DCP, probably due to the enhanced stability of Pd exposed to the environment resulting from nitrogen doping as suggested by the higher atomic ratio of Pd/Pd2+ on the catalyst surface. In the gas-phase hydrodechlorination of R-115, however, a more rapid deactivation phenomenon occurred on Pd/N-AC than on Pd/AC despite a higher activity initially observed on Pd/N-AC, hinting that the stability of pyridinic and pyrrolic nitrogen plays an important role in the determination of catalytic performance of Pd/N-AC.

A Fourier transform infrared study of the gas-phase reactions of ozone with chloroethylenes. Detection of peroxyformic acid

1982 ◽  
Vol 86 (10) ◽  
pp. 1858-1861 ◽  
Author(s):  
H. Niki ◽  
P. D. Maker ◽  
C. M. Savage ◽  
L. P. Breitenbach ◽  
R. I. Martinez ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Gas Phase ◽  
Fourier Transform Infrared ◽  
Gas Phase Reactions ◽  
Infrared Study ◽  
Peroxyformic Acid
Sign in / Sign up

Export Citation Format

Share Document