原位漫反射红外光谱研究CO、CO_2在Rh-Mn-Li/SiO_2催化剂上的化学吸附

In-situ DR-FTIR of CO and CO_2 Chemisorptive Properties over Rh-Mn-Li/SiO_2 Catalyst

在温度25-300℃和压力0.1-3.0 MPa范围内,利用原位漫反射红外光谱法研究了CO和CO2在Rh-Mn-Li/SiO2催化剂上的化学吸附。在0.1 MPa和25℃时CO在该催化剂上存在线式、孪生和桥式吸附,以桥式吸附为主,3种吸附均能快速达到吸附平衡。压力保持0.1 MPa,温度由25℃升至300℃时,线式比桥式先脱附,至265℃时,3种吸附基本脱附完全;当温度维持205℃不变而压力逐步由0.1升至3.0 MPa时,线式吸附增量较少,桥式吸附增量较多;CO2在0.1 MPa,25℃时就能发生快速的解离吸附,即CO2→CO＋O,其吸附行为表现为CO的线式吸附,但吸附峰与纯CO吸附时不同;当温度稳定在25℃而压力逐步升至2.5 MPa时,不仅CO2吸附量增大,而且其2052 cm^-1吸附峰有向高波数移动的趋势。

In-situ DR-FTIR technique is employed to investigate the chemisorption of CO and CO2 on Rh-Mn-Li/SiO2 catalyst at 25-300 ℃ and 0. 1-3.0 MPa. The results show that there are linear, twin and bridged CO on the surface of catalyst. The linear, twin and bridged CO can reach adsorption equilibrium quickly at 0.1 MPa and 25 ℃. Linear CO desorbs earlier and quicker than twin and bridged CO with the progressive heating from 25 to 300 ℃ at 0.1 MPa, and the three types of adsorption disappear at 265 ℃. At 205 ℃, the adsorption amount of linear CO and bridged CO increases with the pressure from 0. 1 to 3.0 MPa, but the adsorption amount of bridged CO is more than that of linear CO. At 0. 1 MPa and 25 ℃, CO2 can decompose into CO and then CO adsorbs quickly, namely, CO2→CO＋O, but the wave numbers of the adsorptive CO from decomposed CO2 are different from the pure CO, which demonstrates the effect of [O] on CO adsorption. With the pressure of CO2 from 0.1 to 3.0 MPa at 25 ℃, the total adsorption amount increases and the band at 2 052 cm^-1 shifts towards higher frequency.