Examinando por Autor "S. Balula, Salete"

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Improving Oxidative Catalytic Efficiency for Fuels Desulfurization Using Hybrid Materials Based in MOF-808@SBA-15Improving Oxidative Catalytic Efficiency for Fuels Desulfurization Using Hybrid Materials Based in MOF-808@SBA-15
(Wiley, 2024-04-11) C. Fernandes, Simone; Leo, Pedro; Santos-Vieira, Isabel; de Castro, Baltazar; Cunha-Silva, Luis; S. Balula, Salete
This work unveils a route for a new generation of heterogeneous polyoxometalate (POMs) based catalysts associated to the preparation of hybrid materials as a triad of POMs, mesoporous silica (SBA-15) and microporous MOF structures (MOF-808). The prepared catalyst, PMo12@MOF-808@SBA-15, with the main active center the phosphomolybdic acid (PMo12), was successfully applied for the desulfurization of a multicomponent fuel. Its oxidative catalytic performance showed to be considerable superior to the isolated POM@MOF and able to be recycled for more catalytic cycles without active loss. The higher catalytic performance seems to be directly related with the preparation of a more amorphous MOF structure within the channels of SBA-15, in the presence of active POM guests.
MOF-808 as an Efficient Catalyst for Valorization of Biodiesel Waste Production: Glycerol Acetalization
(MDPI, 2023-11-03) Mirante, Fátima; Leo, Pedro; N. Dias, Catarina; Cunha-Silva, Luis; S. Balula, Salete
Glycerol is the main residue in the biodiesel production industry; therefore, their valorization is crucial. The acetalization of glycerol toward fuel additives such as solketal (2,2-dimethyl1,3-dioxolan-4-methanol) is of high interest, promoting circular economy since it can be added to biodiesel or even fossil diesel to improve their quality and efficiency. Straightforward-prepared metal–organic framework (MOF) materials of the MOF-808 family were applied to the valorization of glycerol for the first time. In particular, MOF-808(Hf) was revealed to be an effective heterogeneous catalyst to produce solketal under moderate conditions: a small amount of the MOF material (only 4 wt% of glycerol), a 1:6 ratio of glycerol/acetone, and a temperature of 333 K. The high efficiency of MOF-808(Hf) was associated with the high amount of acid centers present in its structure. Furthermore, its structural characteristics, such as window opening cavity size and pore diameters, were shown to be ideal for reusing this material for at least ten consecutive reaction cycles without losing activity (conversion > 90% and selectivity > 98%). Remarkably, it was not necessary to wash or activate the MOF-808(Hf) catalyst between cycles (no pore blockage occurred), and it maintained structural integrity after ten cycles, confirming its ability to be a sustainable heterogeneous catalyst for glycerol valorization.