Selective Adsorption for Removing Sulfur from Jet Fuel over Zeolite-Based Adsorbents

Double Unit-Cell Silicogermanate Nanosheets Developed by Salting-Out Mechanism for Biomass Conversion

Zeolite nanosheets with an extremely thin thickness featuring both unique pore systems and low diffusion resistance have the potential to achieve enhanced catalytic performance in the conversion of bulky molecular biomass. The preparation of unit-cell level nanosheets generally requires complex and costly multifunctional surfactants or an organic structure-directing agent (OSDA). Commercially available and environmentally friendly ionic liquids can also direct the structure of zeolite nanosheets by π-π stacking when these kinds of OSDA are used in large amount. Herein, we first report unit-cell-sized silicogermanate nanosheets of NS-IM-20 (UWY topology), 5 nm in thickness, which were synthesized at a relatively low ionic liquid concentration with the assistance of halide ion (Cl-). The Pd-loaded NS-IM-20 nanosheets with a hierarchical porosity and moderate acidity act as promising bifunctional catalysts for selective biomass conversion.

Deep desulfurization of alkylated oil by alumina adsorbents: characteristics and mechanism study

Deep desulfurization of alkylated oil is the primary problem that has long plagued the petroleum refining industry. In this study, alkaline alumina adsorbent microspheres were synthesized by carbonization - hot oil column pelletization method. The adsorption desulfurization performance of as-synthesized adsorbent and three commercial alumina-based adsorbents were systematically evaluated and compared. The results showed that alkaline alumina adsorbent had the optimal adsorption performance with a saturated adsorption capacity of 8.604 mg·g^-1. Meanwhile, FTIR and sulfur speciation analysis indicated that the alkaline alumina adsorbent could deeply remove various sulfides (methyl mercaptan, dimethyl disulfide, hexacarbon sulfide, dibenzothiophene, <i>etc.</i>) from alkylated oil. Furthermore, the adsorption kinetics study manifested that the adsorption of sulfide was dominated by chemical adsorption, supplemented by physical adsorption, and accompanied by competitive adsorption among different sulfides. In addition, the regeneration experiment showed that nitrogen (90 °C) could realize the stable regeneration of the alkaline alumina adsorbent. To ensure stable regeneration performance in industry, it is recommended that the alkaline alumina adsorbent be regenerated once with nitrogen at 90 °C. This study will provide theoretical support for the process optimization of deep desulfurization of alkylated oil and contribute to the high-quality production of clean fuels worldwide.

JP-8 Desulfurization by CuNa-Y zeolite at elevated temperatures has two distinct stages: Chemisorption followed by surface reactions

This study evaluates the performance of continuous flow adsorbers for adsorptive desulfurization. JP-8 fuel with 2,230 ppmw of sulfur was treated in a flow-through adsorber packed with CuNa-Y zeolite pellets and operating at 180 °C and 200 psig with liquid hourly space velocities (LHSV) from 0.13 to 3.24 h^-1. Our results showed that a flow-through adsorber operating at these conditions can effectively reduce the sulfur content of JP-8 to ultra-low values (1-10 ppmw) over the entire LHSV range tested, although the overall performance of the adsorber declined with increasing flow rates as expected. We also observed that the total sulfur removal exceeded the theoretical adsorption limit of our zeolite adsorbent. Detailed characterization of the treated fuel and spent adsorbent via chromatographic and surface analysis techniques revealed that desulfurization occurs in two stages. Sulfur is initially removed via adsorption (chemisorption) on the CuNa-Y zeolite, an assertion supported by simulations with a transient heterogeneous model. As the adsorbent becomes saturated, however, surface chemical reactions start taking place leading to the formation of hydrogen sulfide and polymerization products, and depositing carbon residue on the zeolite. The spent adsorbent was regenerated by treating it with air at 550 or 600 °C, which restored the adsorption capacity of the material to about 90% of its initial value.

Preparation of TiO2/porous glass-H with the coupling of photocatalysis oxidation-adsorption system in the initial position and its desulfurization performance on model fuel

TiO₂/porous glass-H as composite catalysts were synthesized hydrothermally in the presence of H₂O₂ using porous glass microspheres as carriers. The photocatalytic-adsorptive desulfurization of model fuel by composite catalysts was investigated under UV irradiation. The structure and morphology of the composite catalysts were characterized via scanning electron microscopy (SEM), N₂ adsorption, X-ray diffraction (XRD) and ultraviolet-visible spectroscopy (UV-vis). The results showed that TiO₂/porous glass-H exhibited a significantly enhanced photocatalytic-adsorption desulfurization performance due to its enhanced surface area, highly enhanced light absorption, and reduced recombination of photogenerated electron pairs compared with TiO₂/porous glass synthesized in the absence of H₂O₂. The optimized TiO₂ loading was 20% and the reaction temperature was 303.15 K, which could achieve almost 100% sulfur removal when 0.1 g catalyst was applied to a sulfide concentration of 300 mg L⁻¹. Based on the kinetic fitting of the obtained data, it was found that the rate-controlling step of sulfide adsorption on the catalyst was a molecular diffusion process and the adsorption intensity and adsorption capacity of the composite catalyst were significantly improved compared with the porous glass-H in the adsorption thermodynamic curve, and ΔS, ΔH and ΔG of the adsorption process were calculated. In addition, TiO₂/porous glass-H could be regenerated via simple heat treatment, exhibiting similar efficiency as the original TiO₂/porous glass-H after three regeneration cycles.

TiO₂/porous glass-H as composite catalysts were synthesized hydrothermally in the presence of H₂O₂ using porous glass microspheres as carriers.

Adsorption of ciprofloxacin from aqueous solution using surface improved tamarind shell as an economical and effective adsorbent

Antibiotics in water bodies are emerging as an alarming new pollutant because of its persistent and recombinant nature. In recent period of human lifestyle, pharmaceutical products play a vital role in many perspectives. Due to this unpredictable usage of products, the unreacted components release into waterbodies in trace quantities. Eventhough these trace quantities initiate a crisis of developing resistant antibacterial strains which pose health risks to humans and animals. This work reports the batch adsorption of a fluoroquinolone, a fourth-generation antibiotic compound by a biosorbent made by acid-treated tamarind shells. The shells were treated with zinc chloride and hydrochloric acid. The characterization of biosorbent was performed by Fourier transform infrared spectroscopy and field emission scanning electron microscopy. The optimized adsorption parameters of time, pH and temperature were 30 minutes, 6 and 60 °C. The adsorbent can be reused up to seven times with negligible loss in its adsorption capacity. Adsorption followed by Langmuir, Freundlich and Tempkin model where used to determine the correlation coefficient. Pseudo first-order, second-order and intra-particle kinetic model were used to fit the experimental data. The results are best described by pseudo second-order denoting chemisorption and Freundlich isotherm model describing multilayer adsorption.Novelty StatementThe proposed work is to investigate about improved tamarind shell as biomass used in the removal unreacted PPCP components that have been released into aquatic environment.The novelty of this paper lies in that it puts forward a better resource utilization method for treating PPCP component wastewater, and studies the method theoretically from the perspective of mechanism and proves its feasibility.Identifying the maximum adsorption of antibiotic component from wastewater under different conditions and finding the optimum range.In addition to the existing literatures, this study has compared the adsorption efficiency of raw and treated adsorbent material prepared using Tamarind shell.

Desulfurization of liquid fuels using aluminum modified mesoporous adsorbent: towards experimental and kinetic investigations

In this study, a modified mesoporous adsorbent (MSU-S) impregnated by aluminum was used to remove the aromatic sulfur compounds from n-decane as the model fuel. Physical and chemical properties of as-synthesized adsorbent were investigated by XRD (X-Ray Diffraction), SEM (Scanning Electron Microscopy), FTIR (Fourier Transform Infrared spectroscopy) and BET (Brunauer–Emmett–Teller) method. Adsorptive desulfurization of model fuel was studied through batch and continues processes under mild temperature and normal atmospheric pressure. The equilibrium adsorption was modeled by Langmuir, Temkin, and Freundlich and the kinetics of adsorption was studied through first, second and intraparticle diffusion models. It was figured out that Temkin and the pseudo-second-order model were best fitting the adsorption equilibrium and describing the kinetics, respectively.

Recent advances in metal-organic frameworks as adsorbent materials for hazardous dye molecules

Water is vital for the sustenance of all forms of life. Hence, water pollution is a universal crisis for the survival for all forms of life and a hurdle in sustainable development. Textile industry is one of the anthropogenic activities that severely pollutes water bodies. Inefficient dyeing processes result in thousands of tons of synthetic dyes being dumped in water bodies every year. Therefore, the efficient removal of synthetic dyes from wastewater has become a challenging research field. Owing to their tuneable structure-property aspects, metal-organic frameworks (MOFs) have emerged as promising adsorbents for the adsorptive removal of dyes from wastewater and textile effluents. In this perspective, we highlight recent studies involving the application of MOFs for the adsorptive removal of hazardous dye molecules. We also classify the developed MOFs into cationic, anionic, and neutral framework categories to comprehend their suitability for the removal of a given class of dyes.

ECNU-36: A Quasi-Pure Polymorph CH Beta Silicate Composed of Hierarchical Nanosheet Crystals for Effective VOCs Adsorption

A quasi-pure C_H polymorph of microporous zeolite beta, named ECNU-36, was obtained as a highly crystalline silicate using 1,5-bis(tetramethylimidazolium) hydroxide as organic structure-directing agent (OSDA) in fluoride media. An appropriate concentration of free fluoride in the synthetic mother liquor was crucial to purify the C_H -phase. The framework structure of ECNU-36 consists of polymorph C_H (>95 %) and polymorph B, elucidated by a combination of PXRD data, DIFFaX simulation, EDT, and HRTEM techniques. For the first time, the framework structure of beta C_H polymorph was directly confirmed and solved using electron diffraction data. The pure-silica ECNU-36 showed an unusual crystal morphology, composed of stacked nanosheets, with typical 17 nm thickness and exposed {100} facets, which exhibited attractive adsorption performance for hydrocarbons and aromatics.

Simultaneous Adsorption of 4,6-Dimethyldibenzothiophene and Quinoline over Nickel and Boron Modified Gamma-Al2O3 Adsorbent

The simultaneous adsorption of quinoline and 4,6-dimethyldibenzothiophene over adsorbents, based on alumina modified with boron and nickel under ambient temperature and pressure, was studied. The adsorbents were characterized by BET specific surface area, a potentiometric method for the determination of acid strength, electrophoretic migration, and X-ray diffraction. The results showed that the adsorbent containing nickel had better adsorption capacity than the adsorbent modified with nickel and boron, which was attributed to its greater acidity and ability to generate π-complexation between the adsorbent and the molecules. In terms of selectivity, quinoline was more adsorbed than 4,6-dimethyldibenzothiophene in all systems, due to the basic nature of quinoline. The experimental data in all cases were adjusted by three kinetic models (Yoon–Nelson, Yan and Thomas), and the regression coefficients in all models were close to one. Finally, the values of the kinetic constant obtained by the Thomas model were used to relate the adsorption capacity results.

Unraveling How the H2 Treatment Helps Improve the Performances of Cu and Ag Loaded Y Zeolites for Adsorptive Desulfurization

This work seeks for a better understanding on how the gas treatment process affected the structure of metal loaded zeolite Y (MY, M = Ag, Cu) adsorbants and how the structural changes affected the performances of the adsorbents for adsorptive desulfurization. A series of characterization tools including solid-state nuclear magnetic resonance were employed. Compared to the N₂ treatment, the H₂ treatment on the MY adsorbents led to the reduction of the loaded M components to their metallic state and, consequently, brought several structural changes to the zeolitic framework. The structural changes brought by the H₂ treatment can be accounted for the decreased Brönsted acidity over the Lewis acidity of the adsorbents and thus helped in improving their adsorption capacity. This paper provides new insights on how the zeolitic framework changes affected the sulfur adsorption capacity of MY, which is helpful for designing better adsorbents for sulfur removal from oil.

Experimental, kinetic, and thermodynamic studies of adsorptive desulfurization and denitrogenation of model fuels using novel mesoporous materials

The kinetics, equilibrium and thermodynamics studies of adsorptive desulfurization and denitrogenation to eliminate the refractory sulfur and nitrogen compounds like BT, DBT, quinoline and carbazole of model fuel by mesoporous material (MSU-S) and cobalt modified mesoporous material (CoO-MSU-S) adsorbents were carried out. The adsorption performance, capacity and selectivity of the adsorbent toward sulfur and nitrogen compounds were examined. Equilibrium and kinetics experiments confirmed that Co⁺² impregnation would enhance the adsorption capacity of MSU-S. The results demonstrated that CoO-MSU-S led to a considerable improvement in the adsorption performance. The adsorption amounts reached 18.41, 21.20, 39.65 and 24.60 mg.g^-1 for BT, DBT, quinoline and carbazole, respectively. The Langmuir isotherm model showed good fittings with the experimental equilibrium data for benzothiophene, dibenzothiophene and carbazole, and the data for quinoline was expressed well by the Freundlich for CoO-MSU-S adsorbent. Negative Gibbs free energy showed that all sulfur and nitrogen compounds were adsorbed spontaneously. The experimental data revealed that the pseudo-second-order model can describe the kinetics of adsorption of compounds on the adsorbent. The data obtained from the breakthrough curves indicated that DBT < BT < carbazole < quinoline order for the selectivity of modified adsorbent towards the adsorbates.

Adsorption desulfurization performance and adsorption-diffusion study of B2O3 modified Ag-CeOx/TiO2-SiO2

In this work, the adsorption desulfurization performance and adsorption diffusion study of B₂O₃ modified Ag-CeO_x/TiO₂-SiO₂ adsorbent were investigated. The adsorption desulfurization performance was studied by batch and fixed bed tests. The homogeneous surface diffusion model (HSDM) was employed to investigate the adsorption and diffusion behavior of 4,6-dimethyldibenzothiophene (4,6-DMDBT) in diesel. It was found that the addition of B₂O₃ promotes the dispersion of CeO_x species and then further facilitates the dispersion and oxidation of Ag species resulting in higher adsorption desulfurization activity. Ag species are in state of Ag, Ag₂O and Ag₂O₂, among which, Ag₂O and Ag₂O₂ are found to be the active centers. The kinetics of adsorption desulfurization of model diesel fuel was investigated to provide guiding significance for the prediction of breakthrough curves of fixed-bed adsorption columns. The batch kinetic experiment modeled by HSDM model indicates that surface diffusion controls the main rate. The surface diffusion coefficient D_s determined by batch adsorption experiments is independent of operation conditions, which can be used to directly predict the breakthrough behavior in fixed bed adsorption. The modified HSDM model is proposed to describe the breakthrough behavior. Results indicate that the breakthrough time is affected by bed height, flowrate and influent concentration.

Adsorptive desulfurization of liquid hydrocarbons using zeolite-based sorbents: a comprehensive review

Adsorptive desulfurization using modified Y zeolite is an efficient process for the removal of sulfur from transportation fuels.

Desulfurization of JP-8 jet fuel: challenges and adsorptive materials

This review describes ongoing efforts to remove the bulky organosulfur compounds from Jet Propellant 8 (JP-8) that cannot be removed by hydrodesulfurization.

Mesoporous TiO2–SiO2 adsorbent for ultra-deep desulfurization of organic-S at room temperature and atmospheric pressure

Ultra-deep desulfurization is a major requirement for upgrading the quality of fuel and power sources for fuel-cells. A series of mesoporous TiO₂–SiO₂ adsorbents were prepared and investigated for ultra-deep adsorption of benzothiophene (BT) and dibenzothiophene (DBT) from model fuel at ambient conditions. The adsorbents were characterized via SEM, XRD, N₂-BET, FT-IR and NH₃-TPD techniques. The results revealed that the adsorbent containing 40 wt% silica achieved the desulfurization efficiency higher than 99% when the initial sulfur concentration in the model fuel was 550 ppm. The high desulfurization performance of the adsorbent was attributed to its large specific surface and surface acidity. It also achieved a high sulfur adsorption capacity of 7.1 mg g⁻¹ in a fixed-bed test, while its static saturated sulfur capacity was 13.7 mg g⁻¹. The order of selectivity towards the adsorption of different organic sulfurs was DBT > BT&DBT > BT. The kinetics of the adsorption of organic sulfur was studied and the results indicated that the pseudo-second order model appropriately fitted the kinetics data. Furthermore, the used adsorbent can be easily regenerated and the desulphurization efficiency of the recovered adsorbent after five regeneration cycles was still maintained at 94.5%.

Ultra-deep desulfurization is a major requirement for upgrading the quality of fuel and power sources for fuel-cells.