High Desulfurization Performance Research Articles

Controllable fabrication of persimmon wood-inspired macroporous (a%Co-Mn)1.5Al0.5Ox, high desulfurization performance and analysis of deactivation kinetic mechanism

The removal of H2S that seriously threaten the environment and human health is of great significance in enhancing coal cleaning utilization. Herein, a series of persimmon wood-inspired macroporous (a%Co-Mn)1.5Al0.5Ox (a = 0, 3, 6, 10, 15, 20) sorbents were constructed by the self-assembly of vacuum-assisted sol–gel procedure, and their desulfurization efficiency was evaluated on a fixed-bed reactor at 600–800 °C. Among cobalt-doping sorbents, the breakthrough sulfur capacity (BSC, 272.2 mg g−1) and effective utilization (EU, 81.5%) over (15%Co-Mn)1.5Al0.5Ox is greatly high than the value (138.08 mg g−1) over ZnCoO4/SAPO-34@SBA-15, and slightly lower than BSC (286.2 mg g−1) and EU (92.3%). The magnification SEM images of (15%Co-Mn)1.5Al0.5Ox revealed that regularly straight macroporous channel structure inherited from persimmon wood effectively promoted the rapid diffusion of H2S molecules and accelerated the rate of sulfur/oxygen exchange on the interface of the channel wall. In the meantime, the results studied by the deactivation kinetics model also confirm invariable rate constants (ka, kd) with high correlation coefficients due to higher stability and renewable ability of (15%Co-Mn)1.5Al0.5Ox.

Reactive adsorption desulfurization of FCC gasoline over self-sulfidation adsorbent

NiSO4/ZnO-Al2O3-SiO2 adsorbent, as a novel reactive adsorption desulfurization (RADS)adsorbent, has self-sulfidation ability and high desulfurization performance when treating model fuel. However, the RADS performance of the adsorbent under FCC gasoline feedstock is not well understood. Here, we compare the performance of the adsorbent under FCC gasoline with model fuel to test the effect of the hydrocarbon composition of the feedstock. The complex composition of FCC gasoline makes it sensitive to the nickel loading amount of the adsorbent. Under the influence of specific surface area and pore structure, the adsorbent loaded with 3 wt% nickel shows better desulfurization activity when treating FCC gasoline. As hydrocarbons in FCC gasoline compete with sulfur compounds for active Ni sites, the reaction conditions have been tested and optimized to achieve deep desulfurization while maintaining low olefin loss to ensure the octane number of the product. By experimental tests and characterization, it has been proved that NiSx and NiO acted as active Ni sites of the adsorbent. Based on these observations, the mechanism of RADS of FCC gasoline over NiSO4/ZnO-Al2O3-SiO2 adsorbent has been proposed, which provides theoretical support for the development of new adsorbents and the optimization of RADS process.

A facile fabrication of highly dispersed CeO2/SiO2 aerogel composites with high adsorption desulfurization performance

A simple, low energy consumption and environment-friendly strategy was used to prepare highly dispersed CeO2/SiO2 aerogel composites with different molar ratio of Si/Ce via sol-gel method and subsequently drying under the ambient pressure, in which the oxidation of Ce3+ species into Ce4+ species could be achieved by adding H2O2. The structural and surface properties of adsorbents were analyzed by XPS, XRD, FT-IR, Py-IR, SEM, XRF and N2 adsorption-desorption isotherm. The adsorption desulfurization performances of CeO2/SiO2 for thiophenic compounds from simulated gasoline and model aromatic products were investigated and compared by the breakthrough and batch adsorption experiments. As a result, the weak Lewis acid centers appeared on the surface of CeO2/SiO2. Among them, CeO2/SiO2 with a Si/Ce of 25 performed best, the adsd by Duanpacity for TP from simulated gasoline (n-heptane) was 10.9 mg-S/gads, followed by model aromatic products (benzene, 10.6 mg-S/gads; p-xylene, 10.1 mg-S/gads), however, the difference between them was slight, attributed to the formation of S-Ce bonding instead of C-Ce bonding. The very weak competitive adsorption of benzene and p-xylene with thiophene originated from the weak Lewis acid-base interaction. After the fourth solvent washing regeneration, the breakthrough adsorption capacity of regenerated CeO2/SiO2-25 still remained 60% of the fresh one. The equilibrium adsorption data of CeO2/SiO2-25 for thiophene were well fitted by Langmuir and Freundlich model, and the adsorption for TP was more favorable at the higher temperature. The adsorption process of CeO2/SiO2-25 was well fitted by pseudo-second-order kinetic model, which was spontaneous, endothermic and the freedom degree increased. The solvent (n-heptane, benzene, p-xylene) hardly influence the adsorption behavior of TP on CeO2/SiO2.

Radiofrequency-driven selective oxidation of H2S on hierarchical metal-free catalyst containing defects

Hierarchical all carbon metal-free catalyst with controlled macroscopic shape based on the carbon nanotubes decorated carbon felt (CNT@CF) has been prepared. The catalyst was further treated under gaseous nitric acid to generate structural defects on its surface (o-CNT@o-CF). The as-synthesized catalyst was evaluated in the partial oxidation of H2S by oxygen into elemental sulfur in a fixed-bed reactor under a direct and non-contact inductive heating mode. The catalytic results indicate that the o-CNT@o-CF catalyst exhibits an extremely high desulfurization performance under inductive heating mode. The high desulfurization performance was attributed to the high effective heat management inside the catalyst through inductive heating along with a short diffusion length associated with the nanoscopic dimension of the carbon nanotubes. The catalyst also displays a high stability as a function of time on stream.

Study on the production of low sulfur petroleum coke

ABSTRACT High-quality low sulfur petroleum coke (LSPC) (sulfur content <0.5 wt.%) can be used to produce graphite electrode, which has high market demand and economic value. In this work, the sulfur distribution of delayed coking (DC) reaction of vacuum residue (VR) and ebullated-bed hydrotreating unconverted oil (UCO) was studied. The effects of different hydrotreating catalysts and different hydrotreating depths on the sulfur transfer of the coking reaction of UCO were investigated. The economic index of producing low sulfur petroleum coke was put forward, and the equation for predicting the sulfur content of petroleum coke was established. According to the economic index, it is suitable to use the catalyst with high desulfurization performance and low ring-opening performance to hydrogenate VR to produce LSPC. Meanwhile, it is not economical to adopt higher hydrogenation depth. According to the prediction equation, for UCO with a Conradson carbon residue (CCR) content of 25 wt.%, its sulfur content should be less than 0.25 wt% to produce high-quality low sulfur petroleum coke.

Preparation of Porous Carbon Materials Derived from Hyper-Cross-Linked Asphalt/Coal Tar and Their High Desulfurization Performance

The development of simple and highly effective desulfurization technology is attracting more and more interests in both industrial and academic fields. Here, a new family of precursors were prepared based on hyper-cross-linked asphalt and coal tar building blocks. Thanks to the pre-introduced porous structure, the precursors were converted into carbons with high surface area and large micropore volume via a uniform carbonization process. The synergistic effects of high surface area, abundant microporous structure and the introduced polar functional groups endow the carbon materials with high desulfurization performance. The results of repeated experiments show that the adsorption capacities of five carbonized samples are higher than 40 mg S g-1, and the theoretical maximum adsorption capacity reaches 44.7 mg S g-1. Particularly, the adsorption equilibrium of all the carbonized samples can be reached in 5 min. Moreover, the recycle adsorption performance was also studied. Toluene exhibits the best elution effect among three eluents (iso-octane, para-xylene and toluene) and the adsorption capacity remains 89% of the initial adsorption capacity after two adsorption-desorption cycles. It is believed that both innocent treatment of byproducts from petroleum industry and their high-value application for deep desulfurization in liquid hydrocarbon fuels benefit to the environmental protection and sustainable development.

Reactive adsorption desulfurization of thiophene over NiMo/ZnO, a new adsorbent with high desulfurization performance and sulfur capacity at moderate temperature

3Ni7Mo/ZnO adsorbent was synthesized by a two-step impregnation method for reactive adsorption desulfurization (RADS) experiments.

Fabrication of oxygen-defective tungsten oxide nanorods for deep oxidative desulfurization of fuel

Owing to the increasingly serious environmental issues caused by the sulfur burnt in fuel, desulfurization has become an important topic. In this work, an amphiphilic oxygen-defective tungsten oxide was synthesized by a colloidal chemistry method. The amphiphilic property and oxygen defects were well characterized, and the structure of the oxygen-defective tungsten oxide catalyst was investigated. In addition, the catalyst was employed in oxidative desulfurization system of fuel, and deep desulfurization was achieved. It was found that the very high oxidative desulfurization performance of oxygen-defective tungsten oxide catalyst resulted from both the amphiphilic property and oxygen defects. This work can provide a strategy for preparation of highly active metal oxide catalysts with oxygen defects in oxidative desulfurization reaction of fuel.

Adsorptive on-board desulfurization over multiple cycles for fuel-cell-based auxiliary power units operated by different types of fuels

On-board desulfurization is essential to operate fuel-cell-based auxiliary power units (APU) with commercial fuels. In this work, both (i) on-board desulfurization and (ii) on-board regeneration performance of Ag-Al2O3 adsorbent is investigated in a comprehensive manner. The herein investigated regeneration strategy uses hot APU off-gas as the regeneration medium and requires no additional reagents, tanks, nor heat exchangers and thus has remarkable advantages in comparison to state-of-the-art regeneration strategies. The results for (i) show high desulfurization performance of Ag-Al2O3 under all relevant operating conditions and specify the influence of individual operation parameters and the combination of them, which have not yet been quantified. The system integrated regeneration strategy (ii) shows excellent regeneration performance recovering 100% of the initial adsorption capacity for all investigated types of fuels and sulfur heterocycles. Even the adsorption capacity of the most challenging dibenzothiophene in terms of regeneration is restored to 100% over 14 cycles of operation. Subsequent material analyses proved the thermal and chemical stability of all relevant adsorption sites under APU off-gas conditions. To the best of our knowledge, this is the first time 100% regeneration after adsorption of dibenzothiophene is reported over 14 cycles of operation for thermal regeneration in oxidizing atmospheres.

One-Pot Hydrothermal Synthesis, Characterization, and Desulfurization Performance of ZnFe2O4/AC Composites

ZnFe2O4/AC composites were prepared by the one-pot hydrothermal method using the activated carbon (AC) as a carrier. The synthesis conditions were optimized by a single-factor experiment. The structural, textural, and surface properties of the adsorbent have been comprehensively characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, Brunauer–Emmett–Teller (BET) measurements, and X-ray photoelectron spectroscopy (XPS) analysis. The SO2 removal capacities of the composites were investigated via testing the adsorption capacity at the self-made desulfurization equipment. The results show that the adsorption capacity of ZnFe2O4/AC composites is much higher than that of the AC and ZnFe2O4 samples, respectively. The composite overcomes the disadvantages of the traditional sintering, showing a very high desulfurization performance. The breakthrough time was 147 min, and the sulfur adsorption capacity could reach 23.67% in the desulfurization performance test.

Synthesis, characterization and application of some non-halogen ionic liquids as green solvents for deep desulfurization of diesel oil

Some non-halogen ionic liquids (1-n-butyl-3-methylimidazolium hydrosulphates ([BMIM][[HSO4]), 1-n-butyl-3-methylimidazolium acetate ([BMIM][CH3COO]), 1-n-butyl-3-methylimidazolium dibutyl phosphate ([BMIM][DBP]), 1-n-octyl-3-methylimidazolium hydrosulphates ([OMIM][HSO4]), and 1-n-octyl-3-methylimidazolium acetate ([OMIM][CH3COO])) were synthesized, characterized, and used as solvents for extraction of sulfur compounds in model oils. All investigated ionic liquids show high desulfurization performance from the model oils. The influence of factors such as the structures of ionic liquid anions and cations, and the structure of sulfur compounds on the deep desulfurization was investigated. Some ionic liquids with high, mild and low desulfurization ability ([OMIM][CH3COO], [BMIM][DBP], and [BMIM][[HSO4], respectively) were used as solvents to extract sulfur compounds in diesel oil. The residual sulfur contents in diesel oil meet Euro III and Euro IV standards after five or six extraction cycles corresponding to a desulfurization efficiency of approximately 97%. The combination of oxidation reagents and [BMIM][HSO4] or [BPy][HSO4] increases the desulfurization efficiency. The used ionic liquids were recovered by re-extraction of sulfur compounds and oxidation products of DBT from ionic liquid phase to ethyl acetate or cyclohexane. The formation of sulfones and sulfoxides during oxidative desulfurization was confirmed by FT-IR spectra of ethyl acetate that was used to recover ionic liquids. The slight decrease in desulfurization efficiency of recovered ionic liquids shows their high potential of reusability. Used ethyl acetate and cyclohexane were recovered by distillation and sulfur compounds can be used for other purposes. The extraction process was performed at room temperatures and under normal pressures; no high hydrogen pressure was needed.

High performance of Fe nanoparticles/carbon aerogel sorbents for H2S Removal

To solve the effect of the strong reduction gas, sintering problem and improve the desulfurization activity. Fe nanoparticles (NPs) into carbon aerogel desulfurizers were fabricated with by 50%Fe/C700 precursor and their performance for H2S removal in hot coal gas was studied. The Fe nanoparticles loading in mesoporous carbon aerogels with larger specific surface area and pore volume sorbent were designed and firstly applied to remove H2S with high efficiency in hot coal gas. The H2S removal experiments were conducted in the temperature range of 500–650°C using hot coal gas containing 0.2vol% H2S. We explored the optimum temperature conditions and the influence of textural parameters of carbon aerogels and tested the Fe nanoparticles desulfurizers with 10–20% H2 and 10–20% CO. The fresh, used, regenerated samples were characterized by N2 adsorption, X-ray diffraction, high-resolution scanning electron microscope techniques (HRSEM) and high resolution transmission electron microscopy (HRTEM). The results confirmed that Fe nanoparticle sorbent had high desulfurization performance. This work could provide a new direction and new field in hot coal gas desulfurization and would be important to research on the development sector of the coal industry.

Adsorptive Desulfurization: Fast On-Board Regeneration and the Influence of Fatty Acid Methyl Ester on Desulfurization and in Situ Regeneration Performance of a Silver-Based Adsorbent

Adsorptive on-board desulfurization units require a high desulfurization and regeneration performance for a wide range of fuels to keep them small and ensure long maintenance intervals. A novel thermal regeneration strategy was investigated in this work, fulfilling all requirements for in situ on-board regeneration. In this strategy, a temperature-controlled flow rate (TCFR) of air was used to control the temperature inside the adsorber. With this dynamic approach, the regeneration time was reduced significantly in comparison to other thermal regeneration strategies. The novel regeneration strategy was tested using Ag–Al2O3 as an adsorbent to desulfurize a benzothiophen (BT)-enriched road diesel (300 ppmw of total sulfur). A commercial diesel containing fatty acid methyl ester (FAME) was used to evaluate the fuel flexibility regarding desulfurization and regeneration performance. In the case of 6.63 wt % FAME and 300 ppmw of sulfur, the breakthrough adsorption capacity of sulfur decreased from 1.04 to 0.1...

Density functional theory study of adsorption of benzothiophene and naphthalene on silica gel

The adsorptive removal of sulfur-containing compounds such as thiophene and dibenzothiophene derivatives from transportation fuels has received extensive attention because of the economical and environmental advantages of adsorptive removal compared to the hydrodesulfurization process. Metal-ion-exchanged zeolites have been known to exhibit high desulfurization performance. However, zeolites induce side reactions because of their strong acidity. Accordingly, silica-based adsorbents showing lower acidity have potential for the desulfurization adsorbent. In this study, to facilitate the development of efficient desulfurization adsorbents, the mechanisms of benzothiophene and naphthalene adsorption onto silica surface were investigated using density functional theory (DFT) in conjunction with experimental approaches. Both the computational and the experimental results suggested that the sites at which benzothiophene and naphthalene adsorb onto silica gel are different types of silanol groups. The adsorption sites of benzothiophene at the initial stage were vicinal-type and/or geminal-type silanols and the final adsorption sites were isolated-type silanols. In addition, the results of DFT calculations suggest that multilayer adsorption might occur. In contrast, the adsorption sites of naphthalene at the initial stage were vicinal-type silanols. Afterward, multilayer adsorption through a T-shape interaction might occur successively on the silica surface.

Hot Gas Clean‐Up with Dolomites: Effect of Gas Composition on Sulfur Removal Activity

In this study high temperature desulfurization performance of dolomite was investigated for coal‐derived gases. Experimental results indicated that dolomite was active and could be effectively used for gas desulfurization at temperatures greater than 1023 K. However, due to thermodynamic equilibrium restrictions, in the presence of water vapour the H2S concentration could not be reduced below 150–200 ppmv by dolomite. Thermodynamics predicts that water vapour can adversely affect the chemical equilibrium between H2S and calcium oxide. The presence of CO2 in the gas stream did not have a suppressing effect on the sulfidation reactions, whereas it tended to depress the calcination of CaCO3 to CaO. During the dolomite‐based sulfur removal process, both the water‐gas shift and reverse water‐gas shift reactions could also occur depending on the reacting gas compositions. The Boudouard reaction could take place and proceed at 1023 K depending on the CO/CO2 ratio in the feed stream. This was dictated by the thermodynamic characteristics of the reaction. COS formation was observed due to the reactions taking place between H2S and CO/CO2 during H2S removal by dolomite. Trace amounts of methyl mercaptan were also detected in the reactor effluent gases during H2S removal. Methyl mercaptan formation might be attributed to the reactions taking place between H2S, H2, and CO and/or CO2.

Efficient oxidative desulfurization of diesel fuel using amide-based ionic liquids

A series of Brønsted acidic ionic liquids having a protonated amide- or lactam-based cation were synthesized and investigated as extractants and catalysts in the extraction combined with oxidative desulfurization (ECODS) of both model oil and diesel fuel, with hydrogen peroxide (H2O2, 30wt%) as oxidant. Each of them showed obvious removal of benzothiophene (BT) and dibenzothiophene (DBT) in model oil. Among them, [HCPL][TFA] exhibited the best performance by completely removing BT and DBT in a short time. The detailed structure and conformation of [HCPL][TFA] were investigated by 1H NMR and FTIR as well as theoretical calculation. HCPL+ cation was verified to exist in an enol form, which was supposed to contribute to high desulfurization performance by improving the formation of peroxides. In the end, two kinds of diesel were used to evaluate its desulfurization performance. [HCPL][TFA] can reduce the S-content of real hydrogenated diesel from 659.7ppm to 8.62ppm with 98.69% S-removal efficiency after two ECODS processes. Furthermore, the total S-content of straight-run diesel fuel was reduced to 89.36ppm from 11,034ppm with a similar S-removal rate. The results of GC-PFPD before and after each ECODS process indicated that almost all the original S-compounds in diesel had been converted to their corresponding oxidation products. The desulfurization performance was actually restricted by extraction capability.

Nitrogen-doped carbon nanotubes decorated silicon carbide as a metal-free catalyst for partial oxidation of H2S

Hierarchical metal-free catalyst based on the CVD synthesis of nitrogen-doped carbon nanotubes decorated silicon carbide (N-CNTs/SiC) macroscopic host structure has been prepared. The catalyst was evaluated in the partial oxidation of H2S by oxygen into elemental sulfur in a fixed-bed reactor. The catalytic results indicate that the N-CNTs/SiC catalyst exhibits an extremely high desulfurization performance even under severe reaction conditions such as low temperature, high space velocity and at low O2-to-H2S molar ratio. The high desulfurization performance was attributed to the high effective surface area of the catalyst along with a short diffusion length associated with the nanoscopic dimension of the carbon nanotubes. The N-CNTs/SiC catalyst also displays a high stability as a function of time on stream which could be attributed to the strong anchoring of the nitrogen doping within the carbon matrix. The extrudates shape of the SiC support allows the direct macroscopic shaping of the catalyst for use in conventional fixed-bed reactor without facing problems linked with catalyst handling, transportation and pressure drop across the catalyst bed as encountered with nanoscopic carbon-based catalyst.

Enhancing FCC gasoline desulfurization performance in a polyphosphazene pervaporative membrane

Nowadays, pervaporation is widely investigated as a promising process in FCC (fluid catalytic cracking) gasoline deep desulfurization, in which the membrane plays a decisive role. In this work, a membrane with high desulfurization performance was initiated and its pervaporation performance was evaluated using FCC model gasoline composed of thiophene and heptane. The membrane was prepared from chlorine incompletely substituted poly [bis (phenoxy) phosphazene] (Cl-PBPP) followed by simple self-crosslinking at room temperature. Compared with previous jobs, the Cl-PBPP is 12times increased in pervaporation separation index. Moreover, via self-crosslinking the trade-off effect is eliminated. The highest enrichment factor and flux of Cl-PBPP membrane for separating thiophene from heptane are 5.6 and 1.38kg/(m2h), respectively. The obtained results are promising for industrial trial.

DFT study of the interaction between ethanethiol and Fe-containing ionic liquids for desulfuration of natural gasoline

The interaction between ethanethiol molecule and either anhydrous FeIII chloride anions or 1-butyl-3-methylimidazolium ([BMIM]+) cations of ionic liquids (ILs) was investigated using Density Functional Theory approach and results were correlated with our previous experimental results on extractive desulfurization (EDS), where ILs containing anionic FeIII species show excellent performance to remove sulfur compounds from natural gasoline, especially when there exists an excess of FeCl3 in the [BMIM]+[FeCl4]− IL since this mixture contains binuclear anions [Fe2Cl7]−, whose Fe―Cl―Fe bonds are larger and less strong than Fe―Cl bonds of mononuclear anions [FeCl4]−, being then the former bonds activated for ethanethiol chemisorption. Molecular frontier orbitals and Mulliken atomic charges reveal that the high desulfurization performance could be due to a Dewar–Chatt–Duncanson-like mechanism of electron donation–backdonation among ethanethiol sulfur and transition metal centers of [Fe2Cl7]− anions, and this mechanism is promoted because of the symmetry affinity among the ethanethiol HOMO and the atomic orbital t2g on Fe sites in [Fe2Cl7]− LUMO. On the other hand, when there is no excess of FeCl3, EDS increases with the size of N-alkyl substitutes in [BMIM]+ due to ethanethiol physisorption by these cations.

Effect of surfactant modification on the desulfurization performance of Zn/Ti-PILCs adsorbent

Various surfactants were added during the synthesis of pillared clays Ti-PILCs to modify their structure and properties. Zn supported on the surfactant-modified Ti-PILCs (Zn/Ti-PILCs) was used as a desulfurization adsorbent and its performance in desulfurization of a model diesel oil containing dibenzothiophene (DBT) was investigated. The results showed that the capability of Zn/Ti-PILCs for DBT selective adsorption is enhanced by the surfactant modification. Especially, Zn/Ti-PILCs-CTAB obtained through modification with hexadecyl-trimethyl-ammonium bromide (CTAB) (CTAB/Ti molar ratio being 0.5) exhibits high desulfurization performance with a DBT removal rate of 96.3%. The characterization results of nitrogen sorption indicated that the surfactants added during the pillaring process can increase the surface area of the resultant Ti-PILCs and improve their pore distribution by enhancing the amounts of mesopores (1–4 nm).