【摘要】 用共沉淀法制备一系列六铝酸盐催化剂样品(LaMeAl11O19,Me=Mn、Fe、Co、Ni、Ni、Ce),采用X-射线衍射(X-ray diffraction,XRD)、比表面积测试法(Brunauer-Emmett-Teller,BET)和X-射线光电子能谱(X-rayphotoelectron spectrometry,XPS)等方法对样品结构进行表征,并通过生物质气化气中可燃气体成分(CH4/CO/H2)的模拟燃烧试验,考察不同过渡金属离子取代对催化剂结构特征及催化燃烧活性的影响。利用原位红外(in-situ DRIFT)方法研究了气体在催化剂表面反应的机制。结果表明,焙烧后催化剂形成具有相同的MP结构、但化学组分不同的六铝酸盐,且具有较大的比表面积。LaMeAl11O19催化剂对模拟生物质气化气中可燃成分燃烧均具有一定的催化活性,添加Mn离子时催化剂对甲烷的催化燃烧活性最好。各可燃气体起燃温度自低至高为CO、H2、CH4。150℃时CO已在催化剂表面发生吸附,250℃出现气相CO2的吸附峰,同时检测到反应气中H2被催化剂内部晶格氧所氧化生成的水分子吸附峰。气相CH4的吸附峰在反应开始(150℃)时就已形成,其强度和位置不随温度和时间变化。更多还原

【Abstract】 A serie of hexaaluminate catalyst samples(LaMeAl11O19,Me=Mn、Fe、Co、Ni、NiCe) were prepared by co-precipitation method,and characterized by means of X-ray diffraction(XRD),Brunauer-Emmett-Teller(BET) and X-ray photoelectron spectrometry(XPS) to investigate the effects of different transitional metal ions substitution on the structures.The combustion experiments of CH4/CO/H2simulated biomass gasified products were carried out in a bench-scale quartz reactor to investigate the catalytic combustion activities of catalysts.Moreover,the surfaces of catalyst samples were examined by in-situ DRIFT experiments.The results indicate that the calcinations of precursors at 1 200 ℃ could result in the formation of final MP structures and higher specific surface areas.In the structures of LaMeAl11O19 catalyst samples,the valence states of concerned elements are La3+,Al3+,O2respectively.When the other transitional metal ions were introduced,the Fe ion is trivalent,and Co and Ni ions are both divalent,whereas the Mn ion is either divalent or trivalent.All substituted LaMeAl11O19 catalyst samples show certain catalytic combustion activities for the CH4/CO/H2mixed gases.Particularly,the Mn-substituted LaMeAl11O19 catalyst demonstrates the best catalytic combustion activity of methane,followed by Fe-substituted catalyst.and doping of Ce can obviously improve the catalytic activity.The order of the ignition temperture from low to high were CO,H2,CH4.Among the gaseous components in mixed gas,CO could be adsorbed on the catalyst surface at 150 ℃,when temperature increased to 250 ℃,the adsorption peak of gaseous CO 2(at 2 359 cm-1) appeared,and the adsorption peak of water,which is produced via the oxidation of H 2 by the lattice oxygen in solid catalyst,could be detected.The adsorption peak of gaseous CH 4(at 3 016 cm-1) is formed at the beginning(150 ℃) of reaction,and its position and intensity did not change with temperature and time.更多还原