Investigation of CO and CO2 adsorption on tetragonal and monoclinic zirconia
Investigation of CO and CO2 adsorption on tetragonal and monoclinic zirconia
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DOI：
10.1021/la001723z
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发表时间：
2001-07-10
期刊：
影响因子：
3.9
通讯作者：
Bell, AT
中科院分区：
文献类型：
--
作者：
Pokrovski, K;Jung, KT;Bell, AT
采用红外光谱和程序升温脱附技术研究了CO和CO2在四方晶系和单斜晶系ZrO 2上的吸附行为。在这项研究中，制备了表面积为20和187 m2/g的四相ZrO 2（t-ZrO 2）和表面积为19和110 m2/g的单斜ZrO 2（m-ZrO 2）样品。m-ZrO 2的CO2吸附容量比t-ZrO 2高一个数量级以上。在m-ZrO 2上观察到的主要物种是HCO 3-和m-和b-CO 3 2-，而在t-ZrO 2上观察到的主要物种是p-和b-CO 3-。m-ZrO_2对CO_2的高吸附容量是由于其表面羟基的浓度和碱性较高，Zr-4（+）阳离子的刘易斯酸性较强，O_2-阴离子的Leu碱性较强。取决于吸附温度，m ZrO 2的CO吸附容量比t-ZrO 2的CO吸附容量高5- 10倍。在450 K以下，CO被吸附为HCO 3-和CO 32-物种上的两种多晶型的ZrO 2。在较高温度下，仅观察到CO 32-和HCOO物种。m-ZrO_2的CO吸附容量高于t-ZrO_2，这是因为m-ZrO_2上的吸附中心强度较大。
The adsorption of CO and CO2 on tetragonal and monoclinic ZrO2 was investigated using infrared spectroscopy and temperature-programmed desorption spectroscopy. For this study, samples were prepared of tetragonal ZrO2 (t-ZrO2) with surface areas of 20 and 187 m(2)/g and of monoclinic ZrO2 (m-ZrO2) with surface areas of 19 and 110 m(2)/g. The CO2 adsorption capacity of m-ZrO2 is more than an order of magnitude higher than that of t-ZrO2. The principal species observed on m-ZrO2 are HCO3- and m- and b-CO32- whereas the principal species observed on t-ZrO2 are p- and b-CO3-. The higher CO2 adsorption capacity of m-ZrO2 is attributed to the higher concentration and basicity of the hydroxyl groups on this polymorph, as well as the stronger Lewis acidity of Zr-4(+) cations and the stronger Leu is basicity of O2- anions. Depending on the adsorption temperature, the CO adsorption capacity of m ZrO2 is 5- to 10-fold higher than that of t-ZrO2. Below 450 K, CO is adsorbed as HCO3- and CO32- species on both polymorphs of ZrO2. At higher temperatures, only CO32- and HCOO species are observed. The CO adsorption capacity of m-ZrO2 is higher than that of t-ZrO2 because of the greater strength of the adsorption centers on this phase.