Article pubs.acs.org/EF
Catalytic Upgrading of in Situ Coal Pyrolysis Tar over Ni-Char Catalyst with Different Additives Jiangze Han,†,‡ Xiaoxing Liu,† Junrong Yue,† Bingfeng Xi,† Shiqiu Gao,*,† and Guangwen Xu*,† †
State Key Laboratory of Multi-phase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China ‡ University of Chinese Academy of Sciences, Beijing 100049, China ABSTRACT: Ni-char catalyst doped with different additives was used to catalytically upgrade coal pyrolysis tar in situ generated in a laboratory-scale dual-stage reactor. The additives including Fe, Mg, Ce, Zr were all beneficial to the catalytic activity for tar cracking. The best result of tar upgrading was achieved with Ce−Ni-char at a Ce-to-Ni molar ratio of 0.4. The upgrading test at 500 °C over a layer of such a catalyst (20% of the tested coal mass) increased the light tar (boiling point 360 °C) in the tar was cracked through catalytic upgrading. Comparing with the upgrading over the Ni-char catalyst, adding Ce according to a Ce-to-Ni molar ratio of 0.4 further increased the light tar fraction and yield by 11.9% and 8.9%, respectively. While no obvious acidic sites were identified for pure char in its NH3-TPD spectrum, the existence of both weak Lewis and strong Bronsted acidic sites was proved for Ni-char. The Ce additive facilitated the uniform dispersion of Ni on char so that only more weak Lewis acid sites were detected on Ce−Ni-char to have its better activity for upgrading of tar. Via XRD and SEM-EDS analyses it was demonstrated that element Ni was present on all the tested Ni-char catalysts, but Ce existed in its oxide form of CeO2 for the Ce−Ni-char catalyst. The Ce additive into Ni-char catalyst also suppressed the deposition of coke or carbon on the catalyst, so the Ce−Ni-char showed the better probability for repeated use in tar upgrading.
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[email protected]. Phone: +86 10 82544885, Fax: +86 10 82629912. (S.G.) *E-mail:
[email protected]. (G.X.) 4940
dx.doi.org/10.1021/ef500927d | Energy Fuels 2014, 28, 4934−4941
Energy & Fuels
Article
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dx.doi.org/10.1021/ef500927d | Energy Fuels 2014, 28, 4934−4941
