Oxidative desulfurization of fuel oils-catalytic oxidation and adsorptive removal of organosulfur compounds

The syntheses and evaluation of oxidovanadium(IV) complexes as catalysts for the oxidation of refractory organosulfur compounds in fuels is presented. The sulfones produced from the oxidation reaction were removed from fuel oils by employing molecularly imprinted polymers (MIPs). The oxidovanadium(IV) homogeneous catalyst, [V ͥ ͮ O(sal-HBPD)], as well as its heterogeneous polymer supported derivatives, poly[V ͥ ͮ O(sal-AHBPD)] and poly[V ͥ ͮ O(allylSB-co-EGDMA)], were synthesized and fully characterized by elemental analysis, FTIR, UV-Vis, XPS, AFM, SEM, BET and single crystal XRD for [V ͥ ͮ O(sal-HBPD)]. The MIPs were also characterized by elemental analysis, FTIR, SEM, EDX and BET. The catalyzed oxidation of fuel oil model sulfur compounds, thiophene (TH), benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT), was conducted under batch and continuous flow processes at 40°C by using tert-butylhydroperoxide (t-BuOOH) as oxidant. The continuous flow oxidation process presented the highest overall conversions and very high selectivity for sulfones. Maximum oxidation conversions of 71%, 89%, 99% and 88% was achieved for TH, BT, DBT and 4,6-DMDBT respectively when poly[V ͥ ͮ O(allylSB-co-EGDMA)] was employed at a flow-rate of 1 mL/h with over 90% sulfone selectivity. The process was further applied to the oxidation of hydro-treated diesel containing 385 ± 4.6 ppm of sulfur (mainly dibenzothiophene and dibenzothiophene derivatives), and this resulted to a high sulfur oxidation yield (> 99%), thus producing polar sulfones which are extractible by polar solid phase extractants. Adsorption of the polar sulfone compounds was carried-out by employing MIPs which were fabricated through the formation of recognition sites complementary to oxidized sulfur-containing compounds (sulfones) on electrospun polybenzimidazole (PBI) nanofibers, cross-linked chitosan microspheres and electrospun chitosan nanofibers. Adsorption of benzothiophene sulfone (BTO₂), dibenzothiophene sulfone (DBTO₂) and 4,6-dimethyldibenzothiophene sulfone (4,6-DMDBTO₂) on the various molecularly imprinted adsorbents presented a Freundlich (multi-layered) adsorption isotherm which indicated interaction of adsorbed organosulfur compounds. Maximum adsorption observed for BTO₂, DBTO₂ and 4,6-DMDBTO₂ respectively was 8.5 ± 0.6 mg/g, 7.0 ± 0.5 mg/g and 6.6 ± 0.7 mg/g when imprinted chitosan nanofibers were employed, 4.9 ± 0.5 mg/g, 4.2 ± 0.7 mg/g and 3.9 ± 0.6 mg/g on molecularly imprinted chitosan microspheres, and 28.5 ± 0.4 mg/g, 29.8 ± 2.2 mg/g and 20.1 ± 1.4 mg/g on molecularly imprinted PBI nanofibers. Application of electrospun chitosan nanofibers on oxidized hydro-treated diesel presented a sulfur removal capacity of 84%, leaving 62 ± 3.2 ppm S in the fuel, while imprinted PBI electrospun nanofibers displayed excellent sulfur removal, keeping sulfur in the fuel after the oxidation/adsorption below the determined limit of detection (LOD), which is 2.4 ppm S. The high level of sulfur removal displayed by imprinted PBI nanofibers was ascribed to hydrogen bonding effects, and π-π stacking between aromatic sulfone compounds and the benzimidazole ring which were confirmed by chemical modelling with density functional theory (DFT) as well as the imprinting effect. The home-made pressurized hot water extraction (PHWE) system was applied for extraction/desorption of sulfone compounds adsorbed on the PBI nanofibers at a flow rate of 1 mL/min and at 150°C with an applied pressure of 30 bars. Application of molecularly imprinted PBI nanofibers for the desulfurization of oxidized hydro-treated fuel showed potential for use in refining industries to reach ultra-low sulfur fuel level, which falls below the 10 ppm sulfur limit which is mandated by the environmental protection agency (EPA) from 2015

Kinetics of oxidation of D-arabinose and D-xylose by vanadium (V) in the presence of manganese II as homogeneous catalyst

<div align="justify">Kinetics of oxidation of D-arabinose and D-xylose by acidic solution of vanadium (V) ions in the presence of manganese (II) has been reported. First-order dependence of the reaction rate was observed on [sugars] and [H+] at low concentrations throughout the oxidation reaction and a zero-order dependence on [sugar] and [H+] was observed at high concentrations. First-order kinetics with respect to [Mn (II)] was also observed throughout the oxidation for both sugars. The results indicate the effect of Cl- concentration is negligible. The reaction rates increase with the ionic strength of the medium. Various activation parameters were evaluated and provide further support to the proposed mechanism. Formic acid was reported as one of the oxidation products of these sugars. </div

Biomimetic photocatalysts for the transformation of CO2: design, properties, and mechanistic insights

The increase in the CO2 concentration in the atmosphere due to the intensive burning of fossil fuels, for the energy needs of our modern society, has strongly contributed to global warming. One of the promising strategies to fight this menace is to capture atmospheric CO2 and convert it into value added products, including fuels and chemicals. Among the methods developed for the transformation of CO2, the sunlight-activated photocatalytic conversion appears as a renewable and easy to use method. For this purpose, it is required to have at disposal proper materials to act as catalysts and light absorbing materials to harvest sun energy, and then to combine these components with an electron carrier in an efficient way in order to access the desired fuels by photocatalytic sustainable CO2 conversion. Among the efforts in research dedicated to the production of solar fuels, studies focused on the design and development of bio-based photocatalytic systems as an alternative to conventional photocatalytic systems have emerged in the literature in the last decade. The objective of this review is to show the readers the recent advances in the fabrication of bio-based photocatalysts for the transformation of CO2 into value added products. This review specifically focuses on the conversion of CO2 into carbon monoxide, methanol, formic acid/formate, and acetic acid, which are the main target products described. Methods adopted to enhance the selectivity and efficiency of the bio-derived photocatalysts developed are also discussed, and a section is dedicated to computational investigations. Finally, the current challenges and perspectives in the development and use of these novel and greener photocatalysts are presented

Bottom-up approach synthesis of core-shell nanoscale zerovalent iron (CS-nZVI): Physicochemical and spectroscopic characterization with Cu(II) ions adsorption application

Single pot system in chemical reduction via bottom-up approach was used for the synthesis of core shell nanoscale zerovalent iron (CS-nZVI). CS-nZVI was characterized by a combination of physicochemical and spectroscopic techniques. Data obtained showed BET surface area 20.8643 m2/g, t-Plot micropore volume 0.001895 cm3/g, BJH volume pores 0.115083 cm3/g, average pore width 186.9268 Å, average pore diameter 240.753 Å, PZC 5.24, and pH 6.80. Surface plasmon Resonance from UV-Vis spectrophotometer was observed at 340 nm. Surface morphology from SEM and TEM revealed a spherical cluster and chain-like nanostructure of size range 15.425 nm �97.566 nm. Energy Dispersive XRF revealed an elemental abundance of 96.05% core shell indicating the dominance of nZVI. EDX showed an intense peak of nZVI at 6.2 keV. FTIR data revealed the surface functional groups of Fe–O with characteristics peaks at 686.68 cm�1, 569.02 cm�1 and 434 cm�1. In a batch technique, effective adsorption of endocrine disruptive Cu(II) ions was operational parameters dependent. Isotherm and kinetics studies were validated by statistical models. The study revealed unique characteristics of CS-nZVI and its efficacy in waste water treatment

Nanomaterials as catalysts for CO2 transformation into value-added products: A review

International audienceCarbon dioxide (CO2) is the most important greenhouse gas (GHG), accounting for 76% of all GHG emissions. The atmospheric CO2 concentration has increased from 280 ppm in the pre-industrial era to about 418 ppm, and is projected to reach 570 ppm by the end of the 21st century. In addition to reducing CO2 emissions from anthropogenic activities, strategies to adequately address climate change must include CO2 capture. To promote circular economy, captured CO2 should be converted to value-added materials such as fuels and other chemical feedstock. Due to their tunable chemistry (which allows them to be selective) and high surface area (which allows them to be efficient), engineered nanomaterials are promising for CO2 capturing and/or transformation. This work critically reviewed the application of nanomaterials for the transformation of CO2 into various fuels, like formic acid, carbon monoxide, methanol, and ethanol. We discussed the literature on the use of metal-based nanomaterials, inorganic/organic nanocomposites, as well as other routes suitable for CO2 conversion such as the electrochemical, non-thermal plasma, and hydrogenation routes. The characteristics, steps, mechanisms, and challenges associated with the different transformation technologies were also discussed. Finally, we presented a section on the outlook of the field, which includes recommendations for how to continue to advance the use of nanotechnology for conversion of CO2 to fuels

Step-scheme photocatalysts: promising hybrid nanomaterials for optimum conversion of CO2

The appealing prospect of photocatalysts as an environmentally friendly method for converting atmospheric CO2 into value-added products is undeniable, and scientists are working hard to further enhance their performance. This review outlines the most recent developments in the synthesis, characterization, computational insights, and emerging application of Step-scheme (S-scheme) photocatalysts in CO2 transformation into value added products. The review begins with a survey of different generations of heterojunctions and the challenges associated with each heterojunction generation. S-scheme heterojunctions are therefore suggested as a solution to the drawbacks of type-II and Z-scheme family heterojunctions, and the underlying reaction mechanism of S-scheme is critically outlined. The different synthesis approaches for the design of S-scheme heterojunctions are discussed. Following this, direct characterization techniques and emerging computational methods to identify the charge transfer mechanism in S-scheme heterojunctions are presented. Furthermore, emerging applications of S-scheme photocatalysts in CO2 transformation into value-added products are critically surveyed from recent literature. Finally, the current challenges and prospects of the S-scheme heterojunction photocatalyst are discussed