K_2O对Pt/γ-Al_2O_3上CO选择性氧化反应的助催效应

Selective Oxidation of CO in Hydrogen-rich Stream over K_2O-promoted Pt/γ-Al_2O_3 Catalyst

采用等体积浸渍法制备Pt/γ-Al2O3催化剂,通过添加K2O考察其对改善富氢气氛中CO选择性氧化性能的影响。结果表明,当加入K2O的质量分数为0.034,且采取在负载Pt后再添加的方式时,可显著改善催化剂的低温活性,在120°C时CO转化率可达90%。降低富氢气中CO浓度有助于提高CO转化率。O2/CO增加也可提高CO转化率,但O2/CO的增加并不能提高CO氧化的选择性。为了同时得到CO高转化率和CO氧化高选择性,O2/CO(V∶V)为1.0～1.8。用BET、XRD和CO-TPD等表征方法说明了K2O的助催效应。

γ-Al_2O_3 supported Pt-K_2O catalysts for CO selective oxidation were prepared by using incipient wet impregnation. The catalytic performance of the K_2O promoted Pt/γ-Al_2O_3 catalysts in the selective oxidation of CO in hydrogen rich stream were studied. The results showed that when the K_2O content was 0.034, the activity of catalyst was improved significantly with the CO conversion of 90% at 120 °C. The decrease of CO concentration in hydrogen stream was preferred for obtaining higher conversion of CO at lower temperature. The increase of O_2/CO ratio resulted in the increase of CO conversion, while the (decrease) of O_2/CO did not always increase the selectivity of CO to CO_2. In order to obtain high conversion and higher selectivity, the O_2/CO ratio ranged from 1.0 to 1.8 is desired. The promotion effect of K_2O was characterized by BET, XRD and CO-TPD.