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 H-2/CO2, CO/CO2 and ternary H-2/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 H-2, compared to that for single-component CO2 adsorption. This effect appears to be due to an interaction between H-2 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. (c) 2006 Published by Elsevier B.V.