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- Polyoxometalate@Periodic mesoporous organosilicas as active materials for oxidative desulfurization of dieselsPublication . Ribeiro, Susana; Almeida, Pedro L.; Pires, João; De Castro, Baltazar; Balula, SaleteNovel material catalysts based in the active zinc-substituted polyoxotungstate ([PW11Zn(H2O)(39)](5-), abbreviated as PW11Zn) were efficiently used in the oxidative desulfurization of real and model diesels. These active catalytic center was strategically immobilized in a less hydrophilic periodic mesoporous organosilicas (PMOs), containing ethane-bridge (PMOE) and benzene-bridge (PMOB) walls, functionalized with (3-aminopropyl)triethoxysilane (aptes). The efficiency of the novel catalytic composites (PW11Zn@aptesPMOE and PM11Zn@aptesPMOB) was studied under oxidative desulfurization system (CODS) without the presence of an extraction solvent and also using a biphasic (diesel/extraction solvent) oxidative desulfurization system (ECODS). Both composites presented higher desulfurization efficiency under the solvent-free system, reaching ultra-low levels of sulfur compounds after only 1 h and using low ratio of H2O2/S = 4. The catalysts could be recycled without loss of activity for ten consecutive cycles. However, after the first desulfurization cycle complete desulfurization was achieved within only 30 min using PW11Zn@aptesPMOE composite. Also, the structure of PW it Zn@aptesPMOE demonstrated to be more stable than PW11Zn@aptesPMOB, probably due to the occurrence of some PW11Zn leaching from the PMOB surface, probably caused by the lower interaction of PW11Zn with the benzene-bridge PMOB wall. The most robust catalyst PW11Zn@aptesPMOE was used to desulfurize a real diesel achieving 75.9% of desulfurization after 2 h. The catalyst was further recycled with success to treat real diesel.
- Desulfurization process conciliating heterogeneous oxidation and liquid extraction: Organic solvent or centrifugation/water?Publication . Ribeiro, Susana O.; Nogueira, Lucie S.; Gago, Sandra; Almeida, Pedro L.; Corvo, Marta C.; De Castro, Baltazar; Granadeiro, Carlos; Balula, SaleteThe present work presents a strategic oxidative desulfurization system able to efficiently operate under sustainable conditions, i.e. using an eco-friendly oxidant and without the need of extractive organic solvents. The catalytic performance of Eu(PW11O39)2@aptesSBA-15 was evaluated for the oxidative desulfurization of a multicomponent model diesel using a solvent-free or biphasic systems. The results reveal its remarkable desulfurization performance achieving complete desulfurization after just 2 h of reaction. Moreover, the composite has shown a high recycling ability without loss of catalytic activity for ten consecutive ODS cycles. Interestingly, under solvent-free conditions it was possible to maintain the desulfurization efficiency of the biphasic system while being able to avoid the use of harmful organic solvents. In this case, a successful extraction of oxidized sulfur compounds was found conciliating centrifugation and water as extraction solvent. Therefore, this work reports an important step towards the development of novel eco-sustainable desulfurization systems with high industrial interest.
- A novel red emitting material based on polyoxometalate@periodic mesoporous organosilicaPublication . Granadeiro, Carlos; Ribeiro, Susana; Kaczmarek, Anna M.; Cunha-Silva, Luis; Almeida, Pedro L.; Gago, Sandra; Van Deun, Rik; De Castro, Baltazar; Balula, SaleteThe first lanthanopolyoxometalate-supported bifunctional periodic mesoporous organosilica (BPMO) composite is here reported. The incorporation of decatunsgstoeuropate anions ([Eu(W5O18)(2)](9-)) within the porous channels of an ethylene-bridged TIVIAPS-functionalized BPMO produced a luminescent material exhibiting a strong red emission under UV irradiation. Photoluminescence studies showed an efficient energy transfer process to the lanthanide emitting center in the material (antenna effect). A significant change in the coordination environment of Eu3+ ions was observed after its incorporation into the TMAPS-functionalized material. The possible reason for this is discussed within the paper.