Structure and reactive properties of Nb-impregnated two-dimensional pillared MWW zeolites for total oxidation of volatile organic compounds

In this work, the structure and reactive properties of niobium (Nb)-impregnated MWW-type materials were evaluated for gas-phase total oxidation of volatile organic compounds, including BTX (benzene, toluene and o -xylene). The role of the type of structure (two or three-dimensional) and the loading of Nb were considered. The results indicated most Nb species with a tetrahedral coordination on the external surfaces of both two- and three-dimensional zeolites, together with a minimal contribution of octahedral extra-framework NbO species. The texture and Nb content played a key role in the gas-phase total oxidation of BTX. With the same Nb content (5 wt%), the pillared zeolite exhibited a higher specific surface, larger pore volume and mesopores between the MWW nanosheets when compared to the MCM-22 zeolites, which resulted in high accessibility of the reactant molecules to the active sites, reflected in higher BTX conversion at lower and higher temperatures (50–300 °C). The best performance was achieved with the pillared zeolite (10 wt% Nb), reaching a BTX conversion at 300 °C of 92%, 69% and 58%, respectively. The catalyst was stable for up to 30 h of reaction.A.J.S. thanks the Cordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES, Brazil; Finance Code 001) and the Programa de Pós-Graduação em Química of the Universidade Federal do Rio Grande do Sul (PPGQ-UFRGS). C.W.L. thanks the PRH 50.1 – ANP/FINEP Human Resources Program for the Visiting Researcher Fellowship. This research used resources of the Advanced Photon Source, a user facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, and was supported by the U.S. DOE under Contract No. DE-AC02-06CH11357 and by the Canadian Light Source and its funding partners. U.D thanks the MAT2017-82288-C2-1-P Project.Peer reviewe

SPEEK-based proton exchange membranes modified with MOF-encapsulated ionic liquid

Ionic liquids (ILs) 1-butyl-3-methylimidazolium hydrogensulfate (BMI.HSO), 1-butylimidazole hydrogensulfate (BImH.HSO) and 3-triethylammonium propane sulfonic hydrogensulfate (TEA-PS.HSO) were encapsulated in UiO-66 (Zr-MOF) framework. These samples were incorporated into sulfonated poly (ether ether ketone) (SPEEK) polymer in different concentrations of IL. The influence of ionic liquid concentration encapsulated in Zr-MOF was evaluated through the morphology and thermal and chemical stability of the modified membranes. The incorporation of 7.5 wt% Zr-MOF in SPEEK produced membranes with high proton conductivity, making this the best mass ratio for the incorporation of the ionic liquids. Contact angle and swelling analysis indicate that the presence of these ionic liquids provides stability to the membrane, preventing it from absorbing high amounts of water. Mass ratios of 2.5 and 5.0 wt% of encapsulated ILs in Zr-MOF were also used. Proton conductivity results show that a higher concentration of ionic liquid generates agglomerates, limiting proton mobility in the membranes. Among the three ionic liquids tested, TEA-PS.HSO presents the best proton conductivity values, between 92 and 140 mS cm. These results indicate that the Zr-MOF/TEA-PS.HSO sample is a good candidate for use in proton exchange membrane for fuel cells