M ALI HAIDER
Articles written in Journal of Chemical Sciences
Volume 129 Issue 11 November 2017 pp 1705-1711 REGULAR ARTICLE
Molybdenum impregnated zeolite catalyst has been well-known for methane conversion into higher hydrocarbons under non-oxidative condition. HZSM-5 & HMCM-22 zeolites are the effective supports for this purpose. However, the catalytic performance of HMCM-22 supported molybdenum catalyst is consideredsuitable than that for HZSM-5 catalyst with high aromatic selectivity due to unique pore structure and framework of MCM-22 zeolite support. Effect of Mo loading over MCM-22 zeolite has been studied for the activity test and observed that 5 wt% metal content over the support (MCM-22) is optimum for the proper tuning of acidic & metallic sites of the catalyst. Effect of silica/alumina ratio (SAR, molar) of MCM-22 zeolite has also been studied and observed that lower SAR (30) is suitable (C₆H₆ selectivity, 37%) comparatively to higher SAR (55)(C₆H₆ selectivity, 18%). Lower GHSV (720 mL/g.h) is effective for higher hydrocarbon production compared to higher GHSV (1200 mL/g.h) due to low residence time. Mo/MCM-22 catalysts with different Mo loading werecharacterized by BET surface area, XRD, Raman spectroscopy and NH₃-TPD analysis. Unique pore systems [10 & 12 membered ring (MR)] and framework of MCM-22 zeolite support are the key factors for effective methane conversion to value added chemicals when loaded with molybdenum.
Volume 129 Issue 11 November 2017 pp 1735-1740 REGULAR ARTICLE
Electrochemical performance of La₀.₈Sr₀.₂MnO₃−δ (LSM) for CO₂ reduction in solid oxide cell is studied by performing impedance spectroscopy measurement and current-voltage characterizations for varying ratio of CO₂/H₂. Ohmic resistance (RΩ) is observed to be slightly increased from 2.59 to 2.70 Ωcm², however; the cathode polarization resistance (R₂) decreased significantly from 16.20 to 4.70 Ω cm² as the H2 percentage increased from 8 to 82%, respectively. As the H₂ content increased in feed gas, the improved polarization resistance indicated an enhanced activity of LSM for CO₂ reduction reaction. Furthermore, the cathode polarization resistance for CO₂/H₂ of 92/08, is observed to be decreased from 16.20 Ω cm² (OCV 0.89 V) to 1.90 Ω cm² (2.0 V) as the applied potential increased in the electrolysis mode of operation. A maximum conversion of CO₂ of 6.0% with 55% of faradaic efficiency for the production of CO is achieved for CO₂/H₂ ratio of 38/62, which is supported by improved current-voltage polarization, i.e., an increase in reduction current from −0.28 to −0.32 A cm−2 (at 2.5 V) as the CO₂/H₂ ratio decreased from 92/08 to 38/62 respectively. These results demonstrate LSM as an active electrocatalyst to reduce CO₂, which could further be improved by increasing the H₂ concentration in the feed composition to the cathode.
Volume 134, 2022
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