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Submitted by Isabel Melo (imelo@sa.isel.pt) on 2020-02-13T12:28:34Z No. of bitstreams: 1 Effective_PLAlmeida.pdf: 2814345 bytes, checksum: 6bf343b065cf3469082d8961791ea3bf (MD5) Made available in DSpace on 2020-02-13T12:28:34Z (GMT). No. of bitstreams: 1 Effective_PLAlmeida.pdf: 2814345 bytes, checksum: 6bf343b065cf3469082d8961791ea3bf (MD5) Previous issue date: 2019-10-09 info:eu-repo/semantics/publishedVersion

A combination of catalytic oxidation and extraction was used for the desulfurization of a model diesel containing benzothiophene, dibenzothiophene and 4,6-dimethyldibenzothiophene, or a real diesel sample with a sulfur content of 2300 ppm. The catalysts used were the soluble peroxo compound (nBu4N)3{PO4[WO(O2)2]4} (PW4) and a supported material denoted as PW4@TMA-SBA-15 that was prepared by immobilization of PW4 in an ordered mesoporous silica (SBA-15) derivatized with propyltrimethylammonium groups (TMA). The supported catalyst was characterized by FT-IR, FT-Raman, 31P and 13C MAS NMR spectroscopies, powder X-ray diffraction and scanning electron microscopy. Under optimized conditions (H2O2/S molar ratio = 7, 70 °C, acetonitrile as extraction solvent), both catalysts led to complete desulfurization of the model diesel within a reaction time of 2 h. The desulfurization systems could be recycled 10 times with only a slight decrease in performance being observed between the 9th and 10th oxidative desulfurization cycles. Application of the PW4 system to the real diesel led to an outstanding desulfurization efficiency of 89% after a reaction time of 2 h.

Oxidative desulfurization (ODS) is a method of removing sulfur from diesel fuel that has the potential to complement or even replace conventional hydrodesulfurization processes in oil refineries. One of the most promising variants of ODS is extractive and catalytic ODS (ECODS) in which the organic sulfur compounds in the liquid fuel are oxidized and extracted in situ from the oil phase into an extractant phase. In this study, the desulfurizalion of model and real diesel fuel has been performed in ECODS systems employing two different types of deep eutectic solvents (DESs), prepared by combining polyethylene glycol (PEG) as hydrogen bond donor with tetrabutylammonium chloride (TBACl) or choline chloride (ChCl) as hydrogen bond acceptor. The ECODS systems were evaluated with the complexes [MoO2Cl2(DMB)(2)] (1) and [MoO2Cl2(DEO)] (2) (DMB - N,N-dimethylbenzamide, DEO = N,N'-diethyloxamide) as catalysts and 30 wt% H2O2 as oxidant. The effects of different reaction conditions, such as the amount of catalyst, H2O2 and DES, and reaction temperature, were investigated. The combination of complex 1 with the DES ChCl/PEG showed the best performance for the removal of dibenzothiophene, 4-methyldibenzothiophene and 4,6-di methyldibenzothiophene from a high-sulfur (3000 ppm) model diesel, allowing a desulfurization efficiency of 99.6% to be attained at 70 degrees C within 2 h. By applying the optimized model diesel ECODS systems to the treatment of a commercial untreated diesel with a sulfur content of 2300 ppm. 82% of sulfur compounds could be eliminated. These promising results indicate that DESs are a viable alternative to ionic liquids as extraction solvents in ECODS processes. (C) 2020 Elsevier B.V. All rights reserved. project REQUIMTE-LAQV [FCT (Fundacao para a Ciencia e a Tecnologia)] [UID/QUI/50006/2019] project CICECO-Aveiro Institute of Materials - Foundation for Science and Technology/MCTES [UIDB/50011/2020, UIDP/50011/2020] FCTPortuguese Foundation for Science and TechnologyEuropean Commission [SFRH/BD/102783/2014] European UnionEuropean Commission [SFRH/BD/102783/2014] MCTES European Social Fund through the program POPH of QREN info:eu-repo/semantics/publishedVersion

Highly efficient, deep desulfurization of a multi-component model diesel containing benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) has been achieved by using the peroxophosphomolybdate [(n-C4H9)4N]3{PO4[MoO(O2)2]4} (Q3PMo4) directly as catalyst, and aqueous H2O2 as oxidant. Q3PMo4 behaves as a heterogeneous catalyst in the complete oxidation of the various sulfur compounds to the corresponding sulfones within 3 h at 70 °C, using a relatively low H2O2/S molar ratio of 3.7, and could be recycled for ten times with only a minimal decrease in activity. A study was performed to adapt the catalyst Q3PMo4 for the removal of sulfur from a real untreated diesel while maintaining a low, economically desirable, H2O2/S molar ratio of 3.7. The highest desulfurization performance was achieved in the presence of an extraction solvent during the catalytic oxidative stage, reinforced by two extraction steps before and after sulfur oxidation. Under these conditions, the sulfur content of the real diesel was reduced from 2300 to 500 ppm (78% desulfurization efficiency) after 3 h.

A novel composite has been prepared through the immobilization of the Keggin sandwich-type [Sm(PMo11O39)2]11− anion (SmPOM) on large-pore silica spheres previously functionalized with trimethylammonium groups (TMA). The resulting SmPOM@TMA-LPMS material has been evaluated as heterogeneous catalyst in a biphasic desulfurization 1:1 diesel/extraction solvent system using H2O2 as oxidant. Preliminary experiments were conducted with different extraction solvents, acetonitrile and [BMIM]PF6 ionic liquid. The optimized extractive and catalytic oxidative desulfurization system (ECODS) with [BMIM]PF6 was able to reach complete sulfur removal from a model diesel containing 2100 ppm S in just 60 min (10 min of initial extraction + 50 min of catalytic step). The reutilization of catalyst and extraction phase has been successfully performed without loss of desulfurization efficiency in consecutive cycles, turning the process more sustainable and cost-effective. The remarkable results with simulated diesel have motivated the application of the catalyst in the desulfurization of untreated real diesel and 74% of efficiency was achieved after only 2 h for three consecutive cycles.

Efficient and recyclable liquid–liquid extraction and catalytic oxidative desulfurization (ECODS) systems for the removal of refractory sulfur compounds from liquid fuels are reported that use the cyclopentadienyl molybdenum tricarbonyl complexes [CpMo(CO)3Me] (1), [CpMo(CO)3(CH2-pC6H4-CO2Me] (2) and [CpMo(CO)3CH2COOH] (3) as catalyst precursors. An ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate, was used as both extractant and reaction medium, entrapping the active homogeneous MoVI catalysts that are formed in situ under the operating catalytic conditions (aqueous H2O2 as oxidant, 50 °C). The high sulfoxidation activity of the catalyst formed from 1 was largely responsible for enabling >99% desulfurization within 1 h of a model oil containing 1-benzothiophene, dibenzothiophene, 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene (2000 ppm S). The IL/catalyst phase could be repeatedly recycled with no loss of desulfurization efficiency. By sequentially performing extractive desulfurization and ECODS steps, 83–84% sulfur removal was achieved for untreated real diesel and jet fuel samples with initial sulfur contents of ca. 2300 and 1100 ppm, respectively.

This work presents a successful recycling system based in homogeneous polyoxometalate catalysts to desulfurize model and real diesels. Various Keggin-type polyoxometates entrapped in a room temperature ionic liquid (RTIL) phase were investigated. The desulfurization process here proposed conciliates efficiently an extraction and an oxidative catalytic process under sustainable and moderate conditions (H2O2 as oxidant, 50 °C). The ionic liquid acts as an extraction solvent and also as an effective immobilization medium for the active homogeneous catalysts. The zinc-polyoxometalates presented high stability and high capacity to be recycled for various consecutive cycles with no loss of desulfurization efficiency. Complete desulfurization of model diesel was achieved at short reaction time (3 h). Under the same experimental conditions, 80% of sulfur was removed from real diesel (Sinitial = 2300 ppm).

The complexes [MoO2Cl2(DMB)(2)] (1) and [MoO2Cl2(DEO)] (2) (DMB = N,N-dimethylbenzamide, DEO = N,N'-diethyloxamide) have been evaluated as catalysts in extractive-catalytic oxidative desulfurization (ECOD) of a simulated diesel fuel. Using the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6) as extraction solvent and H2O2 as oxidant, ultra-deep desulfurization (S-content from 3000 ppm to < 10 ppm) was possible within a reaction time of 1-3 h, and the systems Catalyst/[BMIM]PF6 could be recycled for five times without significant decrease in activity. The S-content of a real untreated diesel was lowered by 94.4% from 2300 ppm to 129 ppm after only 2 h of reaction using the ECOD process with 2 as catalyst. REQUIMTE-LAQV [FCT (Fundacao para a Ciencia e a Tecnologia)] [UID/QUI/50006/2019] CICECO - Aveiro Institute of Materials (FCT) [UID/CTM/50011/2019] Centre of Marine Sciences - CCMAR [UID/Multi/04326/2019] FCT/MCTESPortuguese Foundation for Science and Technology FCTPortuguese Foundation for Science and Technology [SFRH/BD/102783/2014] European UnionEuropean Union (EU) [SFRH/BD/102783/2014] MCTES European Social Fund through the program POPH of QREN FCT, I.P.

The zinc-substituted polyoxotungstate [PW11Zn(H2O)O-39](5-) (PW11Zn) has been encapsulated within the aluminium(III) 2-aminoterephthalate NH2-MIL-101(Al) metal-organic framework (MOF) either directly through a one-pot microwave-assisted synthesis or by an impregnation method. The resultant composite materials were characterized by elemental analysis, powder X-ray diffraction, FTIR spectroscopy, and P-31 magic-angle spinning (MAS) NMR spectroscopy. The desulfurization of a model diesel containing three refractory organosulfur compounds (1-benzothiophene, dibenzothiophene, and 4,6-dimethyldibenzothiophene) was studied with the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate as an extractant, the PW11Zn@MOF composites as sulfoxidation catalysts, and aqueous H2O2 as an oxidant. The composite obtained by direct synthesis was the most efficient catalyst and led to almost complete desulfurization of the model diesel under mild conditions. Moreover, the solid catalyst could be recovered readily and recycled without significant loss of desulfurization performance. The application of this system to the treatment of a real diesel sample provided a very good sulfur removal of 83% when combined with liquid-liquid extraction.

This work proposes an alternative technique for the selective extraction of thiols from a \"jet-fuel\" model stream, using the 1-ethyl-3-methylimidazolium triflate ([C(2)mim][CF3SO3]) ionic liquid as extractant, in a hollow fibre membrane contactor. Due to the low distribution ratio of the thiol towards the ionic liquid, observed in single extraction, a regeneration step (stripping with vacuum or a sweep gas) was added to the extraction process, in order to maximize the concentration gradient overcoming thermodynamic constraints. The stripping with a sweep gas allowed for a complete regeneration of the ionic liquid producing a jet-fuel with sulphur content lower than 2 ppm. Since the controlling step of the process is the extraction of thiol from the feed phase to the ionic liquid phase, the increase of the ionic liquid velocity and operating temperature may further enhance the process performance. The results obtained along with the ultra-low sulphur jet-fuel model produced prove the high potential of this integrated process as an alternative method for replacing the current expensive desulphurization process. (C) 2014 Elsevier B.V. All rights reserved.

Made available in DSpace on 2017-12-07T19:57:45Z (GMT). No. of bitstreams: 2 license.txt: 2154 bytes, checksum: 4b0f01eb19f34a0ae8b22225f6f5120c (MD5) Production of ultra-deep sulfur-free diesels using a sustainable catalytic system based on UiO-66(Zr)_10.1039c5cc03958d.pdf: 1011820 bytes, checksum: a1f67332efe0f7ec4a768d545adbf211 (MD5) Previous issue date: 2015

The desulfurization efficiency of various hybrid zinc-substituted polyoxometalates ([PW11Zn(H2O)O39]5−, abbreviated as PW11Zn) was here investigated for the first time and optimized using sustainable systems conciliating successfully the liquid–liquid extraction and the oxidative catalytic process. Initially, the desulfurization studies were performed using a model diesel containing a mixture of the most refractory sulfur compounds and later extended to an untreated real diesel. In both cases, acetonitrile was used as extraction solvent and aqueous H2O2 as oxidant. High level of desulfurization was achieved using model and untreated diesels after few hours. The quaternary ammonium catalysts (TBAPW11Zn and ODAPW11Zn) showed higher catalytic desulfurization efficiency than the ionic liquid catalyst (BMIPW11Zn). The TBAPW11Zn behaved as a homogeneous catalyst immobilized in the extraction solvent, while the ODAPW11Zn with the long carbon chain behaved as a heterogeneous catalyst capable to be recovered from the system. Both quaternary ammonium catalysts showed to be successfully reused/recycled for various consecutive desulfurization cycles.

Submitted by Bella Nolasco (bellanolasco@ua.pt) on 2017-07-26T16:06:19Z No. of bitstreams: 1 A recyclable ionic liquid-oxomolybdenum(VI) catalytic system for the oxidative desulfurization of model and real diesel fuel_10.1039c6dt02065h.pdf: 692592 bytes, checksum: 896be0ecee91d017b0677172ee92729a (MD5) Approved for entry into archive by Bella Nolasco(bellanolasco@ua.pt) on 2017-07-26T16:06:45Z (GMT) No. of bitstreams: 1 A recyclable ionic liquid-oxomolybdenum(VI) catalytic system for the oxidative desulfurization of model and real diesel fuel_10.1039c6dt02065h.pdf: 692592 bytes, checksum: 896be0ecee91d017b0677172ee92729a (MD5) Made available in DSpace on 2017-07-26T16:06:45Z (GMT). No. of bitstreams: 1 A recyclable ionic liquid-oxomolybdenum(VI) catalytic system for the oxidative desulfurization of model and real diesel fuel_10.1039c6dt02065h.pdf: 692592 bytes, checksum: 896be0ecee91d017b0677172ee92729a (MD5) Previous issue date: 2016-08

This work proposes an efficient desulfurization system to produce low sulfur diesel under sustainable and moderate experimental conditions. Treatment of a real diesel with a sulfur content of 2300 ppm led to 80% desulfurization after 2 h. The processes used conciliate liquid-liquid extraction and sulfur oxidative catalysis. The catalytic performance of the commercial Keggin-polyoxomolybdate H3[PMo12O40] (PMo12) was strategically increased by simple cation exchange, using a long carbon chain (ODAPMo12, ODA = CH3(CH2)17(CH3)3N), and by its incorporation into the Metal-Organic Framework (MOF) NH2-MIL-101(Cr), forming a new active heterogeneous PMo12@MOF composite catalyst. Activity of both catalysts was similar, however, the solid catalyst could be easily recovered and reused, and its stability was confirmed after multiple continuous cycles.