Multicomponent H2/CO/CO2 adsorption on BaZSM-5 zeolite

A step change response method was used to compare the adsorption behavior of CO2 with that of binary H2/CO2, CO/CO2 and ternary H2/CO/CO2 gas mixtures on BaZSM-5 zeolite. Experiments were conducted with adsorption temperatures from 323 to 473 K and a total pressure of 1 atm. A comparison between single-component CO and CO2 adsorption on BaZSM-5 was also made. The CO2 adsorption capacity was significantly higher than that of CO on BaZSM-5, due to the higher polarity and acidity of CO2. The CO2 adsorption capacity of BaZSM-5 for a H2/CO2 gas mixture was higher than that for single-component CO2 adsorption. TPD and FTIR results showed that the quantity of strongly adsorbed species increased significantly for CO2 adsorption in the presence of H2, compared to that for single-component CO2 adsorption. This effect appears to be due to an interaction between H2 and CO2 on the surface with the Ba cation to form stronger carbonate species. When the CO partial pressure was increased at constant CO/CO2 total pressure, a slight decrease in CO2 adsorption was observed compared to that for single-component CO2 adsorption. On the other hand, a significant decrease in CO uptake could be seen with increasing CO2 uptake. Thus, the smaller adsorption capacity for CO/CO2 gas mixtures compared to each single-component adsorption was probably due to the competitive adsorption of CO2 and CO molecules on weak physisorption sites. The CO adsorption could be described by a single-site Langmuir model and an extended Langmuir model could be applied to describe the CO/CO2 adsorption on BaZSM-5.