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应用氢化学吸附、透射电镜和选区电子衍射考察了Pt/Al_2O_3,PtSn/Al_2O_3催化剂经过n-C_4H_(10)反应积炭及氧烧炭循环后的晶粒、结构及表面吸附性质。发现多次循环后催化剂晶粒发生烧结,烧结程度为Pt/Al_2O_3>PtSr/Al_2O_3(分浸)>PtSn/Al_2O_3(络合)。选区电子衍射分析进一步揭示了双金属PtSn催化剂的活性组分物相的变化。络合法制备的PtSn催化剂经过循环处理后,双金属结构遭到破坏出现游离的Pt和Sn,催化剂氢吸附量呈现波动而降至很低。通过与无积炭直接氧化-还原循环的对比,表明积炭-烧炭循环中表面含炭物是引起烧结及双金属结构变化的主要因素。
The chemical composition, structure and surface adsorption properties of Pt / Al 2 O 3 and PtSn / Al 2 O 3 catalysts after n-C_4H_ (10) reaction and oxygen-carbon cycle were investigated by means of hydrogen chemisorption, transmission electron microscopy and selected area electron diffraction. It is found that the catalyst grains sinter after repeated cycles, and the degree of sintering is Pt / Al 2 O 3> PtSr / Al 2 O 3 (immersion)> PtSn / Al 2 O 3 (complexation). The selected area electron diffraction analysis further reveals the phase change of the active component of the bimetallic PtSn catalyst. The complexed PtSn catalyst after recycling treatment, the bimetallic structure was destroyed by the emergence of free Pt and Sn, the hydrogen adsorption capacity of the catalyst showed a drop to very low. The comparison of direct oxidation-reduction cycle with no-carbon shows that the surface carbon content in the carbon deposition-carbonization cycle is the main factor that causes the sintering and bimetallic structure to change.