3.2.4. Chemi-Sorption

The basicity of S-shell catalysts was characterized by CO2 temperature-programmed desorption (CO2-TPD) experiments on a PCA-1200 chemi-adsorption analyzer provided by Biaode electronic technology CO.,LTD (Beijing, China). For each test, the sample was placed in a quartz reactor, pretreated in He flow at its preparation temperature for 1 h, and cooled down in He flow to 80 ◦C. After the saturated adsorption of CO2, the sample was purged with He at 80 ◦C for 45 min to remove the physically adsorbed CO2. The desorption of CO2 was carried out in He flow from 80 ◦C to 800 ◦C at a heating rate of 10 ◦C/min.

The acidity of the solid base catalysts was measured with NH3-TPD on the same catalyst characterization system as we used in CO2-TPD. For each test, the sample was placed in a quartz reactor. Before the measurement, the sample was purged with He flow at 120 ◦C for 2 h. After the saturated adsorption of NH3 at 120 ◦C, the sample was maintained at 100 ◦C in He flow for 45 min to remove the physically adsorbed ammonia. The desorption of NH3 was conducted in He flow from 100 ◦C to 800 ◦C at a heating rate of 10 ◦C/min.
