No abstract

The influence on gas-phase catalytic glycerol dehydration of crystal size (S: small, or L: large crystals), acidity, and synthesis procedure for isomorphous incorporation of gallium (Ga-S; Ga-L) or aluminum (Al-S; AlL) in MFI zeolites was studied. The main product observed was acrolein, with the undesirable parallel formation of deactivating coke molecules such as polyglycols and polyaromatics. The GaS zeolite showed the best performance in this reaction, as it provided a combination of adequate accessibility to the microporous system and weak Brønsted acid sites. The chemical and structural properties of the fresh MFI zeolites were studied by X-ray diffraction, nitrogen sorption measurements, scanning electron microscopy, temperature-programmed desorption of NH 3 , X-ray photoelectron spectroscopy, and 27 Al and 29 Si MAS-NMR. Solid-state 13 C MAS-NMR and thermogravimetric analyses of the spent MFI zeolites confirmed the differences in the nature and amounts of the carbonaceous deposits formed. The polyglycols were preferentially formed on the external surface of the zeolite crystals, as expected due to the greater exposed area. On the other hand, the polyaromatic compounds formed were more abundant inside the micropores of the MFI zeolites, especially those composed of larger crystals and with a greater number of strong Brønsted acid sites.

A magnetic ZSM-5 zeolite with a core–shell type structure was synthesized, fully characterized and had its catalytic activity evaluated on the valorization of bio-derived furfuryl alcohol.

An array of Pd, Fe and Ir exchanged β-zeolites were synthesized, fully characterized, and their catalytic activity evaluated in converting bio-derived compounds to value-added platform chemicals.

Cu and Fe species formed during the preparation of Cu/ and Fe/ZSM-5 catalysts by ion exchange were studied. XRD, SEM, H2-TPR, DRS-UV-VIS, EPR, Mössbauer Spectroscopy (MÖSS) and chemical analysis (AAS) were used to sample characterization. Cu/ZSM-5 catalysts, irrespective of their Si/Al ratio and Cu content, showed a reduction peak at around 210°C, which was attributed to the reduction of Cu+2 to Cu+1. The reduction peak of Cu+1 to Cu0 shifted to higher temperatures with the increase of Si/Al ratio or with the diminution of Cu/Al ratio, evidencing that isolated Cu cations present a higher interaction with the zeolite structure. The MÖSS data showed the presence of Fe+3 species in charge-compensation sites and a higher content of hematite (Fe2O3) in the catalysts prepared in aqueous medium. The EPR analysis also evidenced the Cu+2 and Fe+3 presence in Cu and Fe/ZSM-5 catalysts, respectively