Effects of CeO₂ on the XPS valence band spectra of coal under the combustion initialization stage at 400°C

Abstract

In order to get the catalytic mechanism of CeO₂ on graphite and coal at 400°C, the morphologies of coal, graphite, and CeO₂ before and after combustion were analyzed through X-ray photoelectron spectroscopy (XPS). It is found that the particle size of coal is mostly between 11.727 and 64.79 μm, while the particle size of CeO₂ is between 1.937 and 11.79 μm. The agglomeration of coal and CeO₂ can be seen by scanning electron microscopy (SEM) after reaction. XPS results show that with the addition of CeO₂, the intensity of binding energy gets stronger, but there is no energy peak transition. Comparing the character of coal with and without the addition of CeO₂, it can be seen that the C-C bond fractures first at 400°C, while the C-H energy-band takes electrons at the same time to be far away from the Fermi level, and the O 2s, O 2p, and C sp hybrid orbitals are all excited. Adding CeO₂ can enhance the activity of the whole coal. In addition, through XPS analysis, combined with the oxygen transfer theory and the electron transfer theory, the catalytic mechanism of CeO₂ for pulverized coal combustion could be obtained.

Keywords

coal combustion / cerium oxide / valence bands / catalysis / binding energy / X-ray photoelectron spectroscopy / pulverized fuel

References

[1] Xu Y, Dou YB. Application of rare earth oxides as catalyst on pulverized coal in blast furnace and catalytic mechanism. J. Chin. Rare Earth Soc., 2009, 27(5): 635.

[2] Ganduglia-Pirovano MV, Hofmann A, Sauer J. Oxygen vacancies in transition metal and rare earth oxides: Current state of understanding and remaining challenges. Surf. Sci. Rep., 2007, 62(6): 219.

[3] Devener B v, Anderson SL. Break down and combustion of JP-10 fuel catalyzed by nanoparticulate CeO₂ and Fe₂O₃. Energy Fuels, 2006, 20(5): 1886.

[4] Issa M, Petit C, Brillard A, Brilhac JF. Oxidation of carbon by CeO₂: effect of the contact between carbon and catalyst particles. Fuel, 2008, 87(6): 740.

[5] Gong XZ, Guo ZC, Wang Z. Reactivity of pulverized coals during combustion catalyzed by CeO₂ and Fe2O3. Combust. Flame, 2010, 157(2): 351.

[6] Wu ZH, Xu L, Wang ZZ, Zhang ZR. Catalytic effects on the ignition temperature of coal. Fuel, 1998, 77(8): 891.

[7] Gong XZ, Guo ZC, Wang Z. Variation on anthracite combustion efficiency with CeO₂ and Fe₂O₃ addition by differential thermal analysis (DTA). Energy, 2010, 35(2): 506.

[8] Chen Y, Mori S, Pan WP. Studying the mechanisms of ignition of coal particles by TG-DTA. Thermochim. Acta, 1996, 275(1): 149.

[9] Faúndez J, Arenillas A, Rubiera F, García X, Gordon AL, Pis JJ. Ignition behaviour of different rank coals in an entrained flow reactor. Fuel, 2005, 84(17): 2172.

[10] Wall TF, Gupta RP, Gururajan VS, Zhang DK. The ignition of coal particles. Fuel, 1991, 70(9): 1011.

[11] Zhang DK, Wall TF, Tate AG. The reactivity of pulverized coal char particles: experiments using ignition, burnout and DTG techniques and partly burnt chars. Fuel, 1992, 71(11): 1247.

[12] Chang HZ, Wang CG, Zeng FG, Li J, Li WY, Xie KC. XPS comparative analysis of coal macerals with different reducibility. J. Fuel Chem. Technol., 2006, 34(4): 389.

[13] Kozlowski M. XPS study of reductively and nonreductively modified coals. Fuel, 2004, 83(3): 259.

[14] Xiang J, Hu S, Sun LS, Xu MH, Li PS, Su S, Sun XX. Evolution of carbon and oxygen functional groups during coal combustion. J. Chem. Ind. Eng., 2006, 57(9): 2181.

[15] Yang ZY, Zhou AN, Zhang H, Zhang Q. XPS Analysis of shenfu coal with different density fraction under UV catalytic photo oxidation. J. Chin. Univ. Min. Technol., 2010, 39(1): 98.

[16] Liu SF, Wang PM, Li ZJ, Lo IM. An FTIR and XPS study of immobilization of chromium with fly ash based geopolymers. Spectrosc. Spectral Anal., 2008, 28(1): 67.