摘要
用溶胶-凝胶法制备了不同组成的Mg-Co和Mg-Mn-Co复合氧化物,用于催化分解N_2O。在较高活性的Mg-Mn-Co表面浸渍K_2CO_3溶液,制备K改性催化剂。用X射线衍射(XRD)、N_2物理吸附(BET)、扫描电镜(SEM)、H_2程序升温还原(H_2-TPR)、O_2程序升温脱附(O_2-TPD)等技术表征催化剂结构,考察了复合氧化物的组成、K负载量等制备参数对催化剂活性的影响。结果表明,加入助剂K显著提高了催化剂活性,其中,0.02 K/MgMn_(0.2)Co_(1.8)O_4活性较高,有氧无水、有氧有水气氛400℃连续反应50 h,N_2O转化率分别保持97%和60%。有水-无水气氛交替实验表明,有水反应后再进行无水实验,K改性催化剂的稳定性较好。
Mg-Co and Mg-Mn-Co composite oxides with different compositions were prepared by sol-gel method for N_2O catalytic decomposition in the presence of oxygen. Of Mg-Mn-Co catalysts,the one with higher activity was impregnated by K2CO_3 solution to make K-modified catalyst. These catalysts were characterized by X-ray diffraction( XRD),nitrogen physisorption( BET),scanning electron microscopy( SEM),temperatureprogrammed reduction of hydrogen( H_2-TPR),and temperature-programmed desorption of oxygen( O_2-TPD).The effect of preparation parameters such as compositions and potassium loadings on their catalytic activity has been investigated. The results show that K-modified catalysts exhibit better activity and higher resistance tow ards water in contrast to un-modified catalyst due to the weakness of surface metal-oxygen bonds. Among these catalysts,0.02 K/Mg Mn_(0.2)Co_(1.8)O_4 is the most active,over which 97% and 60% conversions of N_2O can be reached at 400 ℃ after continuous running for 50 h under the atmosphere of oxygen-alone and oxygen-steam together,respectively. When the steam is sw itched off,the catalytic activity of 0.02 K/MgMn_(0.2)Co_(1.8)O_4 can be restored to large extent,indicating the good water-resistance of K-modified catalyst.
引文
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