稀土添加剂对烃类水蒸汽重整镍催化剂性能的影响——水蒸汽吸附的TPD研究

EFFECT OF RARE-EARTH ADDITIVES ON THE CATALYTIC BEHAVIOR OF NICKEL CATALYSTS FOR THE STEAM REFORMING OF HYDROCARBONS--TPD STUDIES ON STEAM ADSORPTION

用程序升温脱附技术,研究了添加稀土的烃类水蒸汽重整催化剂(Ni/α-Al_2O_3)对水蒸汽的吸附性能,同未加稀土的镍催化剂作了对比。结果表明,加有稀土的镍催化剂对水蒸汽的吸附能力主要是稀土的贡献。还原态催化剂对水蒸汽的吸附量比相应的氧化态多1.4倍。发现催化剂对水蒸汽的吸附能力不仅取决于浸渍方式,而且同稀土含量有关。当稀土含量较多时,催化剂表面上呈现出三个能量不同的吸附位。稀土含量少于1.3%时。对提高催化剂吸附水蒸汽的能力已作用不大。含稀土的镍催化剂吸附水蒸汽的能力大,正是其抗结炭性能耐硫性能好的原因。

TPD technique was employed to investigate the adsorption capacity for steam of both rare-earth promoted (1) and unpromoted (2) nickel catalysts for the steam reforming of hydrocarbons. The experimental results show that steam adsorption capacity for (1) is mainly contributed by the rare-earths. After(l) was reduced, more rare-earth centers were exposed on the surface of the catalysts, and therefore the capacity of adsorption for steam in the reduced state is 1-1.4 (?)imes larger than that in the oxidized state. Impregnation mode has a marked influence on the steam adsorption capacity of (1). The steam adsorption capacity of (l)is also related to the content of rare-earths.When the content of rareearths is increased, three different adsoption sites appear on (1). But the effect of rare-earths on steam adsorption capacity becomes negnigible when their contents are reduced to less than 1.3%. As more steam is adsorbed on the surface of(l), its resistance to coking and sulfur poisoning is much better than that of(2).