Effects of CuO and La2O3 promoters on the ignition process of NiO/α-Al2O3 catalyst for catalytic partial oxidation of methane to syngas
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摘要: 采用分步浸渍法制备了NiO/α-Al2O3、NiO-CuO/α-Al2O3和NiO-La2O3/α-Al2O3三种催化剂，运用程序升温表面反应（TPSR）技术考察了助剂CuO和La2O3对NiO/α-Al2O3甲烷催化部分氧化（CPOM）反应引发过程的影响。结果表明，无论是否经过预还原处理，NiO/α-Al2O3催化剂在CH4/O2混合气氛下进行程序升温表面反应（CH4/O2-TPSR）时，即使升高到910℃也不能引发CPOM反应。添加助剂CuO或La2O3后，NiO-CuO/α-Al2O3和NiO-La2O3/α-Al2O3催化剂在CH4/O2-TPSR过程中均可以引发CPOM反应。原因分别是CuO促进了CH4对NiO的还原以及抑制了O2对Ni0的再氧化，La2O3减小了Ni晶粒粒径和还原时扩散阻力促进NiO的还原。Abstract: NiO/α-Al2O3, NiO-CuO/α-Al2O3 and NiO-La2O3/α-Al2O3 catalysts were prepared by multistep impregnation method. The effects of CuO and La2O3 promoters on the ignition process of NiO/α-Al2O3 catalyst for catalytic partial oxidation of methane (CPOM) to synthesis gas were studied by temperature-programmed surface reaction (TPSR) technique as well. The results indicated that the CPOM reaction could not be ignited over the NiO/α-Al2O3 catalyst with or without pre-reduction during the CH4/O2-TPSR process till 910℃. The CPOM reaction could be ignited on the NiO-CuO/α-Al2O3 catalysts, which ascribed to the addition of CuO was beneficial to reduction of NiO with CH4 and restraining the re-oxidation of Ni0 by O2. The CPOM reaction could be ignited on the NiO-La2O3/α-Al2O3 catalysts too, which should be due to fact that the addition of La2O3 was beneficial to decrease the diffused resistance during the reduction process for reducing the size of nickel crystal.
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