钴铝水滑石焙烧产物催化剂上NO的直接分解

DIRECT DECOMPOSITION OF NITRIC OXIDE UPON CATALYST DERIVED FROM CALCINED Co Al HYDROTALCITE LIKE COMPOUND

研究了 以钴铝 水滑石焙 烧产物复 合钴铝 氧化物为 催化 剂直 接分 解 Ｎ Ｏ ． 当 钴铝 复合 氧化物以还 原态存 在时，其脉 冲催化 分解活性 在４５０ ℃时 为 １００ ％ ， 相 同条 件下 Ｃｕ Ｚ Ｓ Ｍ５ 催 化剂 的活性只有 ４５ ％ ． Ｘ Ｒ Ｄ 和 Ｔ Ｐ Ｒ 表征表明 ，焙烧温 度不太 高的情况 下，钴铝 复合氧化 物中已含 有不 少的铝酸钴尖 晶石（ Ｃｏ Ａｌ Ｏ２） ， 它 还原后 生 成高 分 散态 的 金 属钴 ，这 可 能是 它 分 解 Ｎ Ｏ 活性 高 的原 因．另外，加 入少量 Ｐｔ 或 Ａｇ 可以 极大地 提高催化 剂的稳定 性，这 可能 是由 于 Ｎ Ｏ 的 分解 产物 Ｏ２ 优先吸附在 Ｐｔ 或 Ａｇ 的 表面，从 而避免了 因 Ｃｏ 吸附 Ｏ２ 而 失活．

Direct catalytic decomposition of NO over complex oxide of cobalt and aluminum derived from calcined Co Al hydrotalcite like compound is studied. It is found that the decomposition activity of such catalysts in reduction state is 100% (tested by micro pulse reaction method at 450 ℃), while that of CuZSM 5 catalyst is 45% in the same condition . XRD and TPR characterization results show that there is a large quantity of CoAlO 2 spinel in the Co Al complex oxide phase. When CoAlO 2 is reduced, it may produce highly dispersed metallic Co, this may be the reason why this kind of catalyst possesses high activity for direct decomposition of NO. In addition, the stability of catalyst is improved prominently by adding small amount (<1%) of Pt or Ag to the catalyst. It is suggested that oxygen, the product of NO decomposition, is adsorbed firstly on Pt or Ag, so that the adsorption of oxygen on Co surface which may cause the deactivation of catalyst is prevented.