Performance of Bimetallic Additives (Fe–Co, Mn–Co, Cu–Co, and Zn–Co) Modified Na₂S/AC Deoxidizers in Removal of O₂ from Low-Concentration Coalbed Gas
2019
Zhang, Yuhua | Pan, Hongyan | Lin, Qian | Liu, Fuxin | Zhang, Guoxiang | Hu, Pingfeng
In this study, the deoxidizer Na₂S was modified by different transition bimetals (Fe–Co, Mn–Co, Cu–Co, and Zn–Co) and Fe–Co ratios as auxiliary. The obtained deoxidizers were characterized by X-ray diffraction, N₂ adsorption/desorption, X-ray photoelectron spectroscopy, and H₂-TPR; their deoxidizing activity for the removal of O₂ from low-concentration coalbed gas (CBM) were studied. Results showed that reactive oxygen species (O£–) content in Na₂S deoxidizer, as well as unit effective deoxidization capacity (QO₂) and conversion rate of (CNₐ₂S), increased after modification with Fe–Co, Mn–Co, and Cu–Co. The higher the O£– content in deoxidizers, the higher the activity of the deoxidizers for the removal of O₂ from CBM was. Fe/Co–Na₂S/activated carbon (AC) had the highest amount of O£– content, larger pore volume, and less impurity species with small crystal size, and this made it the largest QO₂ (63.74 mL/g) and CNₐ₂S (87.24%) at 200 °C and 1 atm. Although the deoxidizer Zn/Co–Na₂S/AC modified with Zn–Co had larger O£– content, QO₂ and CNₐ₂S of this deoxidizer is the lowest due to the presence of more impurities CoS₂, CoO, and NaOH with larger crystal size on its surface. These impurities blocked the pores of the deoxidizer Zn/Co–Na₂S/AC and inhibited both mass transfer and reaction of reactants through the material, resulting in declined activity. The deoxidizer Fe/Co (0.33/1)–Na₂S/AC showed higher deoxidizing activity when the Fe–Co ratio was 0.33/1.
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