CO和氢在Pt/Al_2O_3和Pt/TiO_2催化剂上的吸附态特征  

ADSORPTION FEATURES OF CO AND H_2 ON Pt/AI_2O_3 AND Pt/TiO_2 CATALYSTS

作　　者：谢茂松[1] 郭燮贤[1] 

机构地区：[1]中国科学院大连化学物理研究所催化开放实验室,大连116023

出　　处：《Chinese Journal of Catalysis》1990年第4期278-283,共6页催化学报（英文）

摘　　要：通过对室温氢助CO吸附效应和高温氢助CO吸附效应的研究,发现在Pt/Al_2O_3和Pt/TiO_2催化剂中有两类不同性质的金属担体相互作用,提出了CO的“两位吸附”模型,并从电子因素的角度进行了讨论,表明处于SMSI态的Pt中心带有较多的负电荷。Pt/Al2O3 and Pt/TiO2 catalysts were prepared by impregnation and light-deposition method respectively. Room temperature hydrogen assisted adsorpion (RTHAA) of CO takes place only on Pt/Al2O3, while high temperature hydrogen assisted adsorption (HTHAA) of CO takes place only on Pt/TiO2. When Pt/Al2O3 sample is exposed first to CO and then to H2, the RTHAA effect indicates that the increase of CO uptake is due to the prcadsorbcd H2 at room temperature. If the adsorption order is reversed, the low temperature CO desorption peak becomes smaller and shifts to higher temperature side. The more highly the Pt disperses on the support, the stronger arc the interaction between the Pt and Al2O3 and the RTHAA effect. When Pt/TiO2 is exposed to H2 at 500℃ and CO is then introduced at room temperature, the CO uptake increases and the CO clesorption peak shifts to lower temperature side. It is supposed that on Pt/Al2O3, the C-cnd of CO is adsorbed on one Pt atom, while its O-end ma contact with another Pt atom, which is nearer to the A12O3 support and therefore possesses more positive charge, this is the bi-sitcd CO adsorption model. When H2 is added, H atom replaces the O-cnd of CO to occupy the Pt site previously connec(?)ed to the O-end. Thus CO adsorbs on Pt linearl , and the CO dcsorption peak shifts to higher temperature side. If H2 is introduced prior to CO, the electron-dcfficicncy of Pt atoms can be partially compensated , some CO molecules may adsorb on H-occupied Pt to increase the CO uptake. As we reported before, H-containing Ti species of low valence may be resulted during the Pt/TiO2 is treated in high temperature H2, since some electrons may transfer lo Pt. The HTHAA effect may stem from the valence change of Pt atoms, while the RTHAA effect may involve the direct electronic effect of H2 adsorbed on Pt atoms.

关 键 词：一氧化碳 H2 PT/AL2O3 PT/TIO2 

分 类 号：TQ426.81[化学工程]