In this memory effect study, hydrotalcite-type compounds in the lamellar double hydroxide-like (LDH)/zeolite A composite material were analyzed using X-Ray Diffration XRD) in situ experiments. Three samples were analyzed: Al,Mg-LDH, Al,Mg-LDH/ZA composite, and a physical mixture (50/50 wt%) of zeolite A and Al,Mg-LDH. The Al,Mg-LDH sample was treated at 500 °C in an O₂ atmosphere and subsequently rehydrated. The Al,Mg-LDH/ZA composites had three treatments: one was performed at 300 °C in a He atmosphere, and two treatments were performed with an O₂ atmosphere at 300 and 500 °C. In the physical mixture, two treatments were carried out under O₂ flow at 500 °C and under He flow at 300 °C. Both went through the rehydration process. All samples were also analyzed by energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The results show that the LDH phase in the Al,Mg-LDH/ZA compounds has memory effects, and thus, the compound can be calcined and rehydrated. For the LDH in the composite, the best heat treatment system is a temperature of 300 °C in an inert atmosphere.

Changing the morphology is an excellent option for altering the textural parameters of SBA-15 materials. This study provides a guide on how the properties of mesoporous structures behave according to their morphology and their contribution to thermal stability. The objective of this work was to synthesize different morphologies (spherical, hexagonal prisms, rice-like grains, rods, and fibers) of SBA-15 materials and evaluate the existing textural changes. The materials were synthesized by varying the temperature of the synthesis gel from 25 °C to 55 °C, with stirring at 300 or 500 rpm. The results of X-ray diffraction, Fourier transform infrared spectroscopy, N₂ adsorption and desorption, and scanning electron microscopy were evaluated. Thermal stability tests were also conducted in an inert atmosphere. The materials were successfully synthesized, and it was observed that they all exhibited different characteristics, such as their ordering, interplanar distance, mesoporous parameter, specific surface area, micropore and mesopore volumes, external mesoporous area, and wall thickness. They also presented different thermal stabilities. The rice grain morphology had the highest specific surface area (908.8 cm²/g) and the best thermal stability, while the rod morphology had the best pore diameter (7.7 nm) and microporous volume (0.078 cm³/g).

Zeolites have a well-ordered crystalline network with pores controlled in the synthesis process. Their composition comprises silicon and aluminum, so industrial residues with this composition can be used for the synthesis of zeolites. The use of zeolites for CO₂ adsorption is feasible due to the characteristics that these materials have; in particular, zeolites with a low Si/Al ratio have greater gas adsorption capacities. In this work, the synthesis of LTA (Linde Type A) zeolites from silica fumes obtained from the industrial LIASA process and light coal ash is presented. We explore three different synthesis routes, where the synthesized materials undergo cation exchange and are applied in CO₂ adsorption processes. Studying the synthesis processes, it is observed that all materials present characteristic diffractions for the LTA zeolite, as well as presenting specific areas between 6 and 19 m²/g and average pore distributions of 0.50 nm; however, the silica fume yielded better synthesis results, due to its lower impurity content compared to the light coal ash (which contains impurities such as quartz present in the zeolite). When applied for CO₂ adsorption, the standard materials after cation exchange showed greater adsorption capacities, followed by the zeolites synthesized from silica fume and, finally, the zeolites synthesized from coal ash. By analyzing the selectivity of the materials for CO₂/N₂, it is observed that the materials in sodium form present greater selectivity when compared to the calcium-based materials.