Eight Dawson‐type polyoxometalates were successfully prepared and used in an octanal/air oxidative desulfurization (ODS) system for model oil. Among which, the classical 2:18 polyoxometalate ...K6α‐P2W18O62·14H2O exhibited the best catalytic performance with a sulfur removal ratio of 99.63%. Then, K6α‐P2W18O62·14H2O was supported on graphene oxide (GO) to afford K6P2W18O62/GO using the hydrothermal method. Due to the in situ adsorption of the supported catalysts in the ODS process, the sulfur removal ratio was 96.10% without extraction treatment. Compared with the octanal/air ODS system using pure GO as an adsorbent for the oxidation products, the sulfur removal ratio increased from 89.21 to 96.10%, and the n‐octanal/S molar ratio decreased from 24 to 4. To facilitate the recycling of the catalyst and avoid catalyst loss, K6α‐P2W18O62·14H2O was supported on magnetic graphene oxide (mGO) to afford K6P2W18O62/mGO. The results showed that the supported catalyst could be easily recovered with the aid of an external magnetic field, while maintaining high catalytic activity during five cycles of reuse with little catalyst loss. Furthermore, all the prepared materials were analyzed by a series of characterizations, and the reaction mechanism of the studied system was proposed through contrast tests and GC‐MS characterization analysis.
In situ ultra‐deep desulfurization of fuel oil was achieved by the combination of catalytic air oxidation and adsorption.
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•An amphiphilic particles ODS catalyst was successfully prepared.•The stable Pickering emulsion was formed in bi-phase ODS system.•Impressive desulfurization performance was achieved ...in model oil and real oil.•Demulsification of the system was easily achieved by centrifugation.•The catalyst could be recycled for 5 times with little catalytic inactivation.
Phosphotungstic active component (PW12O403−) was supported on the bi-component carbon-organosilica Janus particles to prepare an amphiphilic catalyst for oxidative desulfurization, and it was analyzed by a series of characterization. Its catalytic performance in different systems including n-octane/acetonitrile, n-octane/BimPF6, n-octane/BimBF4, n-octane/methanol, and n-octane/water, was evaluated. According to the results, the stable Pickering emulsion was formed in n-octane/acetonitrile system which exhibited the best desulfurization performance, corresponding to the final desulfurization ratio of 99.86%. Compared with the conventional bi-phase system using H3PW12O40 as catalyst, the desulfurization ratio was sharply increased. Besides, the prepared amphiphilic catalyst could be easily recovered by centrifugation, which was unattainable for the conventional amphiphilic heteropoly acid catalyst. The desulfurization ratio could achieve above 98% even after the catalyst was reused for 5 times. Due to its excellent catalytic performance for the model oil with different initial sulfur content and different sulfur-containing compounds, good recyclability, and outstanding selectivity, the prepared catalyst was evaluated for real oil desulfurization, and a satisfactory result was achieved. The excellent desulfurization performance was attributed to the micrometer-scale droplets formed in Pickering emulsion to result in good mixing.
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•Catalytic emulsion stabilizer for ODS was prepared using green GO and mSiO2.•The structure and property of prepared materials were detailed analyzed.•Bi-phase ODS system was ...converted to stable Pickering emulsion using the material.•ODS performance was sharply increased due to the enlarged contact area.•The material showed high catalytic activity, selectivity and magnetic recyclability.
A series of amphiphilic particles were prepared using Janus graphene oxide (GO) and magnetic SiO2-NH2 (mSiO2-NH2) as starting materials. Then, H3PW12O40 (HPW) was supported on the particles through the interaction between surface amino groups and HPW to obtain catalytic emulsion stabilizers for oxidative desulfurization. The characterization analysis showed that the prepared materials exhibited the sheet structure of GO which was connected by several core–shell microspheres of mSiO2 on one side, and the other side of the materials was grafted by carbon chains to increase hydrophobicity. The catalytic performance of prepared materials increased with the grafted carbon chain length, and the one grafted by hexadecylamine had the best performance with a final desulfurization ratio of 99.21%. That was because it had the most appropriate amphipathy, which can convert the bi-phase system into a stable Pickering emulsion with enlarged contact area between oil and extractant, thus largely promoting mass transfer even without stirring. With the excellent magnetism, the catalytic emulsion stabilizers can be magnetically separated to realize the emulsion breaking, thus easily recycling the catalyst and value-added reaction products after reaction.
On the basis of the comprehensive utilization of the Na–Mg salt deposit, a new process to produce NaCl and ammonium carnallite (MgCl2·NH4Cl·6H2O) by using NH4Cl and the solution left after the ...preparation of potassium salt as raw materials was proposed. For this, the phase equilibrium of the quaternary system NaCl–MgCl2–NH4Cl–H2O at 25 and 0 °C was studied. The solubilities of the quaternary system NaCl–MgCl2–NH4Cl–H2O were measured by an isothermal method, and the corresponding phase diagrams were drawn out. From the phase diagrams: there are four solid phase crystalline zones, which correspond to NaCl, MgCl2·6H2O, NH4Cl, and MgCl2·NH4Cl·6H2O respectively. NaCl and MgCl2·NH4Cl·6H2O have larger crystalline zones at 25 °C than at 0 °C, and NH4Cl has a smaller crystalline zone at 25 °C than at 0 °C. It indicates that NaCl and MgCl2·NH4Cl·6H2O are easy to crystallize out. On the basis of the analysis and calculation of the phase diagrams, the appropriate conditions for the process were identified. In the process, the NaCl could be prepared at 25 °C, and the ammonium carnallite could crystallize out at 0 °C when NH4Cl was added into the remaining solution. The solubilities of the studied system were calculated based on the extended Pitzer model, and the results showed that the calculated values were closed to the experimental results.
The solubilities of the quaternary system K2SO4–MgSO4–(NH4)2SO4–H2O were measured by isothermal method at 25 °C and their dry salt phase diagrams were plotted. The results indicated that, at 25 °C, ...the solubility phase diagram of this quaternary system consists of seven crystallization regions, those are single-salt crystallization region MgSO4·7H2O, (NH4)2SO4, and K2SO4, complex salt crystallization region MgSO4·(NH4)2SO4·6H2O, MgSO4·K2SO4·6H2O, solid solution crystallization region (K1−n, NH4n)2SO4 (n:0.143–0.893) and (K1−n, NH4n)2SO4·MgSO4·6H2O (n:0.552–0.973), respectively. The extended Pitzer model was derived and applied to the phase equilibrium calculation of system K2SO4–MgSO4–(NH4)2SO4–H2O and its sub-systems at 25 °C. The results showed that the calculated values were consistent with experimental results well. The study on the quaternary system K2SO4–MgSO4–(NH4)2SO4–H2O provides a foundation for the N–Mg–K–S compound fertilizers preparation.
•Determination of the phase equilibrium of K2SO4–MgSO4–(NH4)2SO4–H2O system at 25 °C.•Dry salt phase diagram of this system was investigated and analyzed.•A new K–Mg–N compound fertilizers was generated.•Calculation of the phase equilibrium of the above system by Pitzer model.•The calculated results are consistent with the experimental data well.
The solubilities of quaternary system Na2SO4–MgSO4–(NH4)2SO4–H2O at 60 °C were measured by the isothermal method, and the corresponding phase diagram was studied. The analysis of the phase diagram ...shows that there are five crystalline fields, MgSO4·6H2O, Na2SO4·MgSO4·4H2O, Na2SO4, (NH4)2SO4, and MgSO4·(NH4)2SO4·6H2O, respectively. MgSO4·(NH4)2SO4·6H2O, and Na2SO4 crystalline fields are larger than other crystalline fields, which indicates that MgSO4·(NH4)2SO4·6H2O and Na2SO4 are crystallized out easily. On the basis of the analysis and calculation of the phase diagrams of the quaternary system Na2SO4–MgSO4–(NH4)2SO4–H2O and ternary system Na2SO4–(NH4)2SO4–H2O at 60 °C, a technology was designed to produce Mg–N compound fertilizers and Na2SO4 using (NH4)2SO4 as a salting-out agent to separate bloedite, which is easy to operate, fast to reach phases equilibrium, and can gain anhydrous Na2SO4 directly. On the basis of the Pitzer model of electrolyte solution theory, the solubilities of Na2SO4–MgSO4–(NH4)2SO4–H2O system at 60 °C were calculated. The results showed that calculated values were well consistent with experimental results.
•Determination of phase equilibrium of Na2SO4–MgSO4–(NH4)2SO4–H2O system at 25°C.•Phase diagram of this system was investigated and analyzed.•A new technology to produce Mg–N compound fertilizers was ...proposed.•The advantage of recycling mother liquid, steady production and energy saving.
Bloedite (Na2SO4·MgSO4·4H2O) is a kind of abundant natural resources. So far, it has not been developed and utilized effectively. In order to process and develop bloedite, a new technology to produce Na2SO4 and Mg–N compound fertilizers by a (NH4)2SO4 salting-out method to separate bloedite was proposed, the phase equilibrium of the quaternary system Na2SO4–MgSO4–(NH4)2SO4–H2O at 25°C was studied. The solubilities of the quaternary system Na2SO4–MgSO4–(NH4)2SO4–H2O were measured using isothermal method, and the phase diagram of this system was investigated. According to this phase diagram, there are six solid phases crystalline zones, which correspond to MgSO4·7H2O, MgSO4·Na2SO4·4H2O, Na2SO4·10H2O, Na2SO4·(NH4)2SO4·4H2O, (NH4)2SO4 and MgSO4·(NH4)2SO4·6H2O respectively. MgSO4·(NH4)2SO4·6H2O has the largest crystalline zone among these crystalline zones, which indicates that the double salt MgSO4·(NH4)2SO4·6H2O is the most easily to crystallize out. Based on the analysis and calculation of the phase diagrams, a new technology to produce Mg–N compound fertilizers and Na2SO4·10H2O using bloedite and (NH4)2SO4 as raw materials shows the advantage of non-evaporation of water and low energy consumption.
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•Pickering emulsion system for CODS was established by bifunctional materials.•The bifunctional material with anisotropic Janus structure was favor for reaction.•Interphase mass ...transfer was sharply enhanced in emulsion.•High sulfur removal was achieved without stirring.•Catalyst showed high catalytic activity, selectivity and recyclability.
The mass transfer resistance atliquid (oil)-liquid (extractant)interface seriouslylimits the reaction rate and desulfurization efficiency in extraction-catalytic oxidative desulfurization (ECODS), and the catalyst is difficult to be recycled in the homogeneous system. Herein, we demonstrated a renewable Pickering emulsion system with enlarged interfacial contact area to overcome the mass transfer resistance. The bifunctional materials were designed based on Janus graphene oxide (GO) 2D-sheets, amino-modified SBA-15 (NH2-SBA-15) mesoporous microspheres and H3PW12O40 (HPW), as both catalysts and emulsion stabilizers to establish the catalytic emulsion system. Excellent amphiphilicity was endowed by the anisotropic Janus structure of prepared materials, which could convert the oil/extractant bi-phase into a stable Pickering emulsion. The interfacial contact area was skillfully enlarged in emulsion due to formed micro emulsion droplets and empty channels between the droplets, and the catalyst could be easily recycled by centrifugation. Besides, the unique properties of catalyst including large specific surface area, adequate exposed catalytic active sites and high pore volume could also shorten the reaction path and facilitate the rapid diffusion of reactants and products. This opens the door to the application of Pickering emulsion in ECODS fields based on the design of bifunctional materials.
