Investigation of Co-doped Mn oxide catalyst for NH3-SCR activity and SO2/H2O resistance
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摘要: 采用共沉淀法制备了一系列不同物质的量比的钴掺杂锰氧化物催化剂，并对其进行了系统表征。讨论了钴掺杂锰的氧化物催化剂的NH3-SCR催化活性和抗水抗硫性能。结果表明，锰钴物质的量比为1∶1的Co(1)-MnOx催化剂的催化性能最好，在100−275 ℃时实现了大于90%的NOx转化率，并且耐水性和耐硫性较好。Co(1)-MnOx催化剂呈现出球状结构，拥有相对较大的表面积。钴掺杂锰增加了催化剂表面的高价金属离子和化学吸附氧含量。Co(1)-MnOx催化剂具有丰富的活性物种和酸性位点，降低了催化剂的表观活化能。Abstract: A series of Co-doped Mn oxide catalysts with different Co/Mn molar ratios were prepared by co-precipitation method, which was systematically characterized by XRD, SEM, H2-TPR and NH3-TPD etc. Co-doped Mn oxide catalysts are evaluated for NH3-SCR activity and resistance to SO2 and/or H2O, and the Co(1)-MnOx catalyst with Mn/Co molar ratio of 1∶1 performs the best catalytic performance, which achieved higher than 90% NOx conversion in the temperature range of 100−275 °C and possessed better SO2 and H2O resistance. The Co(1)-MnOx catalyst presented a sphere-like structure possessing a relatively large surface area. Doping of cobalt greatly improved the high-valent metal ions and chemisorbed oxygen content of Co(1)-MnOx catalyst surface, and the catalyst possessed abundant active species and acid sites and apparent activation energy of the catalyst was reduced, which makes Co(1)-MnOx a highly effective NH3-SCR catalyst.
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Key words:
- selective catalytic reduction /
- cobalt-doping /
- manganese /
- synergistic effect
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Figure 1 (a) XRD patterns of all the prepared catalysts calcined at 400 °C, (b) XRD patterns of Co(1)-MnOx calcined at 300, 400, 500, 600 °C
Figure 2 SEM images of (a), (b) CoOx and (c), (d) Co(1)-MnOx catalysts calcined at 400 °C
Figure 3 Adsorption-desorption profiles of N2 (a) and distribution of pore size (b) for MnOx, CoOx and Co(1)-MnOx catalysts
Figure 6 (a) Mn 2p, (b) Co 2p and (c) O 1s XPS profiles of Co(1)-MnOx and MnOx catalysts
Figure 7 (a) NOx conversion, (b) N2O selectivity, (c) N2 selectivity, (d) NH3 conversion and (e) NO2 selectivity of MnOx, CoOx, and Co(y)-MnOx
Figure 10 (a) NOx conversion, (b) N2O selectivity, (c) N2 selectivity, (d) NH3 conversion and (e) NO2 selectivity of Co(1)-MnOx calcined at different temperatures
Figure 11 Effect of H2O and SO2 at 150 °C on NH3-SCR performance of Co(1)-MnOx catalyst: (a) SO2 resistance test, (b) H2O resistance test，(c) H2O + SO2 resistance test
Table 1 MnOx, CoOx and Co(1)-MnOx catalysts structural parameters
Catalyst BET surface area/(m2·g–1) Average pore diameter/nm Pore volume/ (cm3·g–1) MnOx 131 3.72 0.23 Co(1)-MnOx 158 6.28 0.31 CoOx 117 6.80 0.29 
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Table 2 Surface element concentrations and relative atomic concentrations of Co(1)-MnOx and MnOx catalysts
Catalyst Surface atoms concentration/% Relative concentration ratios/% O Mn Co Oα/(Oα+Oβ) Mn4+/Mn Co3+/Co Co(1)-MnOx 70.54 16.48 12.97 58.20 37.34 33.26 MnOx 53.95 10.42 − 49.70 33.14 −
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