Catalysis Today, Vol.356, 11-17, 2020
Genesis of micropores by thermal activation of Mg-Al layered double hydroxides possessing interlayer organic sulfonates under oxygen-free environments
Microporosity and basic-site density of mixed oxides formed from Mg-Al layered double hydroxides possessing interlayer isethionate (MgAl-Ise) were investigated to seek for a potential application of them to basic catalyst supports for natural gas conversion. The oxide samples were prepared by thermal activation of MgAl-Ise at 500 degrees C in air, 5% O-2 in N-2, N-2, vacuum, H-2 in helium with various concentrations, H-2, and NH3 to investigate effects of gas atmosphere. The N-2 adsorption data show that Mg-Al mixed oxides obtained by thermal activation of MgAl-Ise in H-2, NH3, and N-2 possess substantially larger micropore volumes characterized by N-2 uptake at the relative pressure < 10(-3) than those obtained in oxygen-containing atmospheres. The data indicate that these accessible micropores originate from interlayer spaces and form upon removal of a majority of sulfonates under H-2, NH3, and N-2 treatments. Thermal activation of MgAl-Ise in H-2 and NH3 enhances the concentration of basic sites probed by CO2 relative to that conducted in N-2 by facilitating removal of sulfonate-derived species. Upon conversion of MgAl-Ise to mixed oxides with removal of interlayer sulfonates, the material catalyzes H-2-D-2 exchange reaction.