TY - JOUR
T1 - The characterization of BaCO3-modified LaOF catalysts for the OCM reaction
AU - AU, Chak Tong
AU - Zhang, Y. Q.
AU - He, H.
AU - LAI, Suk Yin
AU - Ng, C. F.
N1 - Funding Information:
This project was kindly supported by the Hong Kong Baptist University (HKBU) and the Hong Kong Research Grants Council, UGC (HKBC 146/95P). We thank the State Key Laboratory for Physical Chemistry, Xiamen University, for performing (by Mr. R. Q. Long) the in situ Raman experiments. H. H. thanks the HKBU for a Ph.D. studentship.
PY - 1997
Y1 - 1997
N2 - In this paper, BaCO3 is reported to be a good promoter for rhombohedral LaOF. With the addition of 5-20 mol% BaCO3, methane conversion at 800°C was increased by ca. 40% with only slight loss in C2 selectivity. At CH4:O2:N2 = 2.6:1:12 and a contact time of 0.6 g s ml-1, the methane conversion was 36.1%, while the C2 selectivity was 45.3%, giving a C2 yield of 16.4% over the 10 mol% BaCO3/LaOF catalyst at 800°C. Comparing to LaOF, there was a 30% increase in C2 yield. Moreover, similar to the case of BaCO3/LaOBr, the C2H4/C2H6 ratio was enhanced by the presence of 5-20 mol% BaCO3. The loaded barium was found to remain on the surface of the catalyst. XRD, O2-TPD, and CO2-TPD studies revealed that the BaCO3/LaOF catalysts changed greatly in composition, surface site basicity, and active site concentration during OCM reaction. In situ Raman studies disclosed that at 700°C under CH4/O2 (2.6/1), O2-2 species were present on the 10 mol% BaCO3/LaOF catalyst, while none was observed on LaOF. We conclude that the enhancement in methane conversion over the 5-20 mol% BaCO3/LaOF catalysts was due to the generation of surface BaCO3 clusters on LaOF, which could decompose at the temperature range (700-850°C) adopted for OCM reaction to give BaO entities capable of activating O2 to adsorbed O2-2.
AB - In this paper, BaCO3 is reported to be a good promoter for rhombohedral LaOF. With the addition of 5-20 mol% BaCO3, methane conversion at 800°C was increased by ca. 40% with only slight loss in C2 selectivity. At CH4:O2:N2 = 2.6:1:12 and a contact time of 0.6 g s ml-1, the methane conversion was 36.1%, while the C2 selectivity was 45.3%, giving a C2 yield of 16.4% over the 10 mol% BaCO3/LaOF catalyst at 800°C. Comparing to LaOF, there was a 30% increase in C2 yield. Moreover, similar to the case of BaCO3/LaOBr, the C2H4/C2H6 ratio was enhanced by the presence of 5-20 mol% BaCO3. The loaded barium was found to remain on the surface of the catalyst. XRD, O2-TPD, and CO2-TPD studies revealed that the BaCO3/LaOF catalysts changed greatly in composition, surface site basicity, and active site concentration during OCM reaction. In situ Raman studies disclosed that at 700°C under CH4/O2 (2.6/1), O2-2 species were present on the 10 mol% BaCO3/LaOF catalyst, while none was observed on LaOF. We conclude that the enhancement in methane conversion over the 5-20 mol% BaCO3/LaOF catalysts was due to the generation of surface BaCO3 clusters on LaOF, which could decompose at the temperature range (700-850°C) adopted for OCM reaction to give BaO entities capable of activating O2 to adsorbed O2-2.
UR - http://www.scopus.com/inward/record.url?scp=0000031260&partnerID=8YFLogxK
U2 - 10.1006/jcat.1997.1577
DO - 10.1006/jcat.1997.1577
M3 - Journal article
AN - SCOPUS:0000031260
SN - 0021-9517
VL - 167
SP - 354
EP - 363
JO - Journal of Catalysis
JF - Journal of Catalysis
IS - 2
M1 - CA971577
ER -