Catalytic combustion of dimethyl ether over Ce-doped cryptomelane-type manganese oxide
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摘要: 通过氧化还原法合成了氧化锰八面体分子筛(OMS-2)，而后浸渍负载一定量的Ce 。 采用TG-DSC、XRD、低温氮气吸附脱附、TEM、FT-IR、Uv-vis、O2-TPD、H2-TPR以及XPS等技术对制备材料的结构和氧化还原性能进行了表征，考察了催化剂的二甲醚催化燃烧反应性能。结果表明，低掺杂量的Ce高度分散在OMS-2中；高含量时存在独立的CeO2。光谱测试结果表明，Ce的掺杂并未对OMS-2的晶型产生影响。XPS结果表明，Ce的掺杂会提高OMS-2中晶格氧的量。 O2-TPD 和H2-TPR 结果表明，制备的催化剂具有比较丰富的氧物种，低温下易还原，因而在二甲醚催化燃烧中表现出了良好的催化活性和热稳定性。起燃温度在160℃左右，完全燃烧温度在170℃左右，反应产物仅有二氧化碳和水，并且反应后催化剂晶型保持不变，没有积炭产生。Abstract: Manganese oxide octahedral molecular sieves (OMS-2) were synthesized by oxidizing MnSO4 with KMnO4 and then doped with Ce. The structure and oxidation activity of the catalysts were characterized by XRD, N2 adsorptiondesorption, TEM, FT-IR, Uv-vis, O2-TPD, H2-TPR and XPS techniques. The catalytic activity for dimethyl ether (DME) combustion was also evaluated. The results showed that the highly-dispersed amorphous CeO2 exited when Ce-doping was low. However, the independent CeO2 formed when Ce-doping exceed 10%. XPS results show that the doped-Ce can improve the lattice oxygen of the catalyst. O2-TPD and H2TPR characterization show that the Ce-OMS-2 catalysts have abundant facile lattice oxygen and can be easily reduced. Ce-OMS-2 display excellent performance in DME catalytic combustion, with a start-off temperature of 160℃ and a complete temperature of 170℃. CO2 and H2O are the only reaction products detected. The used catalyst keeps the same crystalline as the fresh, and there is no carbon deposition detected over the used catalyst.
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Key words:
- Ce-OMS-2 /
- dimethyl ether /
- catalytic combustion
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