Abstract
The monolacunary Keggin-type [PW11O39]7− (PW11) heteropolyanion was immobilized on porous framework of mesoporous silicas, namely SBA-15 and an ethylene-bridged periodic mesoporous organosilica (PMOE). The supports were functionalized with a cationic group (N-trimethoxysilypropyl-N, N, N-trimethylammonium, TMA) for the successful anchoring of the anionic polyoxometalate. The PW11@TMA-SBA-15 and PW11@TMA-PMOE composites were evaluated as heterogeneous catalysts in the oxidative desulfurization of a model diesel. The PW11@TMA-SBA-15 catalyst showed a remarkable desulfurization performance by reaching ultra-low sulfur levels (<10 ppm) after only 60 min using either a biphasic extractive and catalytic oxidative desulfurization (ECODS) system (1:1 MeCN/diesel) or a solvent-free catalytic oxidative desulfurization (CODS) system. Furthermore, the mesoporous silica composite was able to be recycled for six consecutive cycles without any apparent loss of activity. The promising results have led to the application of the catalyst in the desulfurization of an untreated real diesel supplied by CEPSA (1,335 ppm S) using the biphasic system. The system has proved to be a highly efficient process by reaching desulfurization values higher than 90% for real diesel during three consecutive cycles.
Highlights
Over the last years, ordered mesoporous silicas (OMS) have attracted researchers’ attention in catalysis, due to its long range order, high surface areas and well-defined pore size (2–50 nm) (Esquivel et al, 2014; Wang et al, 2014)
The synthesis of the terminal silane (TMA)-functionalized silica supports and the preparation of the PW11-based composites is represented in Scheme 1
The synthesis of ethylene-bridged Periodic mesoporous organosilicas (PMOs) has been performed by co-condensation of the bridged bis-silane [1,2-bis ethane; BTEE] and the terminal silane (TMA) in the presence of the micelles of the surfactant (Pluronic P123) in acid medium
Summary
Over the last years, ordered mesoporous silicas (OMS) have attracted researchers’ attention in catalysis, due to its long range order, high surface areas and well-defined pore size (2–50 nm) (Esquivel et al, 2014; Wang et al, 2014). Different mesoporous silica families (SBA-n, PMOs, etc.) have been used to create active heterogeneous catalysts, some of these having Keggin-type polyoxometalates (POMs) as active centers (Zhu et al, 2009). The morphology of these silica based materials and the functional groups present at their surface are crucial to the structural robustness of these catalysts. The functional organic moieties in PMOs are present at the surface and in the channel walls, which are responsible for the structural features of the material (rigidity/flexibility) (Van Der Voort et al, 2013). The unique properties of PMOs make them suitable candidates for catalytic applications; the number of reports found in the literature is rather scarce and, in particular, its application in oxidative desulfurization is still inexistent (Karimi et al, 2012)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
