Desulfurization Reaction Research Articles

Effect of methane presence on catalytic heavy oil partial upgrading

In this work, several heavy crudes with wide viscosity range from 1200 to 120,000 cP at 15.6 °C were partially upgraded with a specially designed catalyst under CH4 atmosphere. All these reactions were conducted using a batch mode high temperature and high-pressure Parr reactor. This technique was proved to be suitable for the heavy oil feeds with varied properties, confirming its generality for industrial practice. Upgrading under CH4 demonstrated much better performance than that under N2 when the reaction conditions kept the same, confirming the role played by methane on facilitating heavy ends conversion during heavy oil partial upgrading. Furthermore, the effect of methane presence was further investigated through comparing with its N2 counterpart at the similar asphaltene conversion by tuning the reaction time and temperature. Although it is well expected that coke yield and gas yield increased yet liquid yield decreased along with upgrading reaction proceeding, the reaction under CH4 showed noticeably lower coke and gas yield while higher liquid yield than its counterpart under N2 at comparable asphaltene conversion, strongly indicating the methane’s effect on effective suppression of thermal over-cracking of heavy crude, which is beneficial for achieving more high value-added liquid products. Moreover, the properties of the oil products derived from different atmospheres including viscosity, density, TAN (total acidic number), AMW (average molecular weight) and sulfur content were studied and compared. All these indexes showed a decreasing trend with increasing asphaltene conversion. The values for viscosity, density and AMW were higher under CH4 than those under N2, while the TAN and sulfur content were lower when methane was present, implying the possible methane incorporation and its role played on promoting deoxygenation and desulfurization reactions. The research outcomes derived from this study further evidence the technical advantages of heavy crude partial upgrading under methane, thus providing a more cost-effective and environmentally friendly alternative to hydrotreating for processing heavy oil.

Visible-light-assisted efficient removal of sulfur from high sulfur coal under mild conditions

ABSTRACT In order to find a green and effective chemical desulfurization method, the photocatalytic technology and oxidative desulfurization were combined to minimize the sulfur content in coals. In this paper, 30% H2O2 was mixed with raw coal, demineralized coal, and removal pyrite coal at a ratio of 5:1 (ml: g), the oxidative desulfurization reaction was carried out with visible light irradiation for different times, and compared with the experimental results without light irradiation under the same condition. IC was used to characterize the SO4 2- content in the filtrate of the reaction mixture, and the chemical method was used to determine the forms of sulfur in coal samples before and after desulfurization, FTIR was used to characterize the change of sulfur-containing functional group content in coal samples before and after desulfurization. And the photochemical characterization of raw coal, demineralized coal and removal pyrite coal were carried out to explore the photochemical properties of different coal samples, further explored the reasons for the promoting effect of visible light irradiation on H2O2 oxidation desulfurization. The experimental results showed that the desulfurization efficiency can be significantly enhanced by visible light irradiation. Under the optimum conditions, the desulfurization rate can reach 67.68%, most of the pyrite and part of organic sulfur in coals were effectively removed. The pyrite in coal was the main reason for the promotion of H2O2 oxidative desulfurization by visible light irradiation.

Investigation on Desulfurization of Rejected Electrolytic Manganese Metal Scrap: Experiment and Mathematical Modeling

To improve the recycling efficiency of rejected electrolytic manganese metal (EMM) scrap that contains excessive sulfur, a high-temperature experiment and mathematical model reflecting the mechanism of sulfur transfer from the molten manganese metal to the molten slag were elaborated. A MoSi2 electrical resistance furnace filled with argon protective gas was first employed to perform the desulfurization experiment at 1673 K (1400 °C). Four different fluorine slags with the CaO content ranging from 0 to 20 pct were used in the experiment. A mathematical model of the rejected EMM scrap desulfurization, based on the two-film theory, was established. It adequately described the thermodynamics and kinetics of the rejected EMM scrap desulfurization reaction. In particular, it captured the influence of the interfacial tension between the molten slag and molten manganese for the sulfur transfer process. A comparative analysis of measured and calculated results proved the model feasibility: it took into account the effects of the holding temperature, slag CaO content, the initial sulfur content in rejected EMM scrap, and slag/manganese mass ratio on the desulfurization efficiency. The results indicate that CaO could promote the desulfurization of the manganese metal. The sulfur removal ratio is 58.01 pct with a CaO-free slag at 1673 K (1400 °C), while the ratio increases to 84.58 pct if the CaO content rises to 20 pct. At higher temperatures, the CaO content in the slag can be appropriately reduced. High slag/manganese mass ratios were found to benefit the sulfur removal, while the CaO content in the slag could be adjusted according to the initial sulfur content in the rejected EMM scrap.

Electronic Regulation of Bromophenyl Grafted Metal‐Free Carbon Nitride Catalysts for Enhanced Utilization of H2S

AbstractDeveloping metal‐free heterogeneous catalysts with high efficiency for the elimination of H2S into eco‐friendly products are very important for both fundamental catalytic science and industrial chemistry. Herein, we design a new modified carbon nitride catalyst engrafted with Br‐substituted aromatic heterocycle (CNU−Br) through a simple copolymerization and exfoliation method. CNU−Br exhibits excellent H2S conversion efficiency, high sulfur selectivity, and outstanding stability in the catalytic desulfurization reaction, which is better than most of the reported catalysts. The experiments and theoretical calculations show that the grafting of bromophenyl groups into the fundamental carbon nitride structural network leads to π‐delocalization, surface modification, as well as enhances the basicity of the structural active N sites. The regulation of the H and S affinity of CNU−Br that mediate the facile cleavage of H2S hydrogen‐sulfur bonds and the release of S atoms in thermodynamics. Furthermore, the superior surface area and mass transfer over CNU−Br accelerate the adsorption and oxidation of H2S in kinetics compared with the ordinary carbon nitride.

Comprehensive Composition, Structure, and Size Characterization for Thiophene Compounds in Petroleum Using Ultrahigh-Resolution Mass Spectrometry and Trapped Ion Mobility Spectrometry.

Thiophene compounds are the main concern of petroleum desulfurization, and their chemical composition and molecular configuration have critical impacts on thermodynamic and kinetic processes. In this work, atmospheric pressure chemical ionization (APCI) was employed for effective ionization of thiophene compounds in petroleum with complex matrix, in which carbon disulfide was used for generating predominant [M]+• ions without the need of derivatization as for electrospray ionization. APCI coupled with ultrahigh-resolution mass spectrometry (UHRMS) was successfully applied to the composition characterization of thiophene compounds in both a low boiling petroleum fraction and a whole crude oil. APCI coupled with trapped ion mobility spectrometry (TIMS) was developed to determine the shape and size of thiophene compounds, providing configuration information that affects the steric hindrance and diffusion behavior of reactants in the desulfurization reaction, which has not been previously reported. Moreover, the comprehensive experimental structural data, expressed as the collision cross section (CCS) of the ions as surrogates of molecules, provided clues to the factors affecting the desulfurization reactivity of thiophene compounds. Further exploration showed that not only qualitative analysis of thiophene compounds can be achieved from the correlation between m/z and CCS, but also molecular size was found to be correlated with CCS that can be used as structural analysis. Overall, the molecular composition and dimension analysis together can provide substantial information for the desulfurization activity of thiophene compounds, facilitating the desulfurization process studies and catalyst design.

Role of Surface Paramagnetic Oxygen Species in the Desulfurization Reactions on Zinc Oxide

Surface paramagnetism of the ZnO(1010) facet is a well-known property of this surface and has been explained by the ionosorption of negatively charged oxygen species, which play a significant role...

Effective Desulfurization and Alumina Digestion of High-Sulfur Bauxite by New Roasting Process with Conveying Bed

A new roasting process with a conveying bed was constructed and used to remove sulfur of high-sulfur bauxite. Roasting temperature, phase transformation, microcrystal, specific surface area of high-sulfur bauxite, and the mechanism of the reaction during the roasting process were analyzed. The digestion properties of roasted bauxite were also investigated. The results showed that the sulfur in high-sulfur bauxite can be efficiently removed by roasting in the conveying bed at 520–720 °C for 2 s. Major reactions of high-sulfur bauxite during roasting were the dehydration of minerals, desulfurization of pyrite, sulfation of SO2, and decomposition of sulfate. The rate of mineral dehydration reaction was significantly slower than that of the desulfurization reaction. The specific surface area of roasted ore greatly increased, and the microcrystal of Al-O mineral was refined, which was conducive to Al2O3 digestion. The mass fraction of sulfide sulfur in high-sulfur bauxite was reduced from 1.20% to 0.01%, and the relative digestibility of alumina reached more than 99% when roasting at 600 °C for 2 s. This paper provides revelations and instructions for the process development and application of high-sulfur bauxite.

Desulfurization Characteristics of Fuel-Born Alkali and Alkali Earth Metal Compounds in Coal Ashes from Lab-Scale Experiment to Real-Scale Monitoring of CFBC and PC Boiler.

Previous research findings and experiential accounts have provided evidence that specific components of coal ash play a catalytic role in the dry desulfurization of flue gas such that their contributions need to be considered for determining the optimal amount of desulfurizing agent such as limestone. The purpose of this study was to quantify the desulfurization characteristics of coal ash in a 500 MW pulverized coal combustion (PC) boiler as well as a 1000 MW circulating fluidized bed combustion (CFBC) boiler. In parallel with a year-long data collection of coal blends and emission characteristics, a series of temperature-controlled fixed bed (lab scale) experiments were conducted for 11 individual (but representative) coal samples. The results indicated that desulfurization by fly ashes appeared to proceed roughly in proportion to the total alkali (TA) contents of the ash, which were consistent with our preliminary test result of the CFBC boiler. In the PC boiler, however, the desulfurization reaction seemed to be very kinetically limited, apparently deactivating the TA components. We developed a practical equation for a priori prediction of SO2 concentration based on the sulfur content of coal blends.

Effect of particle size on in-situ desulfurization for oxy-fuel CFBC

Oxy-fuel circulating fluidized bed combustion (Oxy-CFBC) has been widely recognized as an economically promising way to capture carbon dioxide by injecting pure O2 and recycling CO2 from the flue gas because Oxy-CFBC has the advantages of fuel flexibility, in-situ desulfurization and NOx emission reduction. In this study, domestic limestone samples with a particle size range of 0–1 mm (0–75 μm, 75–106 μm, 106–212 μm, 212–300 μm and 500–1000 μm) were reacted in a thermogravimetric analyzer (TGA) under 60% CO2/40% O2 and 80% CO2/20% O2 at 1073 K and 1123 K for a direct desulfurization reaction. The surface and cross-section of limestone and CaSO4 samples with different conversion ratios were analyzed using a field emission scanning electron microscope (FE-SEM) and an energy dispersive spectrometry (EDS). FE-SEM images and EDS analysis of limestone and CaSO4 showed that direct desulfurization reaction starts from surface and progresses to center of particles, and the layer of CaSO4 expands into the whole particle. Since the experimental conditions of all particles were the same, the difference in CaSO4 conversion ratio by particle size confirmed through the TGA results depends only on the specific surface area. Also, the CaSO4 layer was formed at a uniform thickness regardless of the particle size.

A Radiometric Technique for Monitoring the Desulfurization Process of Blister Copper.

In this paper, a novel optical technique for following the progress of the blister copper desulfurization process is presented. The technique is based on the changes observed in the continuous spectrum of the visible–near-infrared (VIS–NIR) radiation that the blister melt emits while the chemical reactions of the sulfur elimination process are taking place. Specifically, the proposed technique uses an optical probe composed of an optical fiber, a collimating lens, and a quartz tube, which is immersed in the melt. This optical probe provides a field of view of the blowing zone where the desulfurization reaction occurs. The experimental results show that the melt VIS–NIR total irradiance evolves inversely to the SO2 concentration reported by a gas analyzer based on differential optical absorption spectroscopy. Furthermore, the blister copper spectral emissivity as well as the total emissivity observed throughout the process show strong correlation with the sulfur content during desulfurization reaction.

In-Situ Heavy Oil Aquathermolysis in the Presence of Nanodispersed Catalysts Based on Transition Metals

The aquathermolysis process is widely considered to be one of the most promising approaches of in-situ upgrading of heavy oil. It is well known that introduction of metal ions speeds up the aquathermolysis reactions. There are several types of catalysts such as dispersed (heterogeneous), water-soluble and oil soluble catalysts, among which oil-soluble catalysts are attracting considerable interest in terms of efficiency and industrial scale implementation. However, the rock minerals of reservoir rocks behave like catalysts; their influence is small in contrast to the introduced metal ions. It is believed that catalytic aquathermolysis process initiates with the destruction of C-S bonds, which are very heat-sensitive and behave like a trigger for the following reactions such as ring opening, hydrogenation, reforming, water–gas shift and desulfurization reactions. Hence, the asphaltenes are hydrocracked and the viscosity of heavy oil is reduced significantly. Application of different hydrogen donors in combination with catalysts (catalytic complexes) provides a synergetic effect on viscosity reduction. The use of catalytic complexes in pilot and field tests showed the heavy oil viscosity reduction, increase in the content of light hydrocarbons and decrease in heavy fractions, as well as sulfur content. Hence, the catalytic aquathermolysis process as a distinct process can be applied as a successful method to enhance oil recovery. The objective of this study is to review all previously published lab scale and pilot experimental data, various reaction schemes and field observations on the in-situ catalytic aquathermolysis process.

Synthesis BiVO4 modified by CuO supported onto bentonite for molecular oxygen photocatalytic oxidative desulfurization of fuel under visible light

A highly photocatalytic activity of bismuth vanadate (BiVO4) modified by CuO was synthesized loaded onto the bentonite (BTT) and applied to photocatalytic oxidative desulfurization of model oil. The photocatalyst was characterized by XRD, SEM, EDS, FT-IR, XPS and UV–vis DRS. The influences of the mass ratio of cata./model oil, the flow rate of molecular oxygen and the irradiation time on the photocatalytic oxidative desulfurization of model oil were investigated by using molecular oxygen as the oxidant. The sulfur removal performances and products of the photocatalytic oxidative desulfurization of benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) in model oil under visible light were also discussed. The results showed that the photocatalytic activity of CuO modified BiVO4/BTT for organic sulfur compounds under visible light was significantly higher than that of BiVO4 and BiVO4/BTT. Its oxidative desulfurization reactions for BT, DBT, 4-6DMDBT were the pseudo-first-order reaction, and the desulfurization activity as well as apparent activation energy followed the order of DBT > 4,6-DMDBT > BT. The photocatalytic oxidative desulfurization mechanism of CuO-BiVO4/BTT was analyzed through the calculated band gap, valence band and conduction band position. The recycling experiment presented that DBT removal by CuO-BiVO4/BTT still reached 81.5% after ten cycles.

Size modulation of MIL-125 nanocrystals to promote the catalytic performance towards oxidative desulfurization.

The Ti-based metal-organic framework (Ti-MOF) MIL-125 with tunable crystalline size in the range of ca. 50 nm to 1500 nm was synthesized by the coordination modulation method using trans-cinnamic acid (CA) as a modulator. The coordination modulation also induced hierarchical porosity and structure defects on the nanocrystals. A significant size-dependent catalytic activity towards the oxidative desulfurization (ODS) reaction was observed for these MIL-125 nanocrystals. In particular, the MIL-125 nanocrystals with a mean size of ca. 50 nm exhibit dramatically enhanced catalytic performance for the bulky sulfur compound 4,6-dimethyldibenzothiophene (4,6-DMDBT) compared to the microcrystals. It is demonstrated that the size modulation of MIL-125 is an effective approach to promote its performance for the catalysis of bulky molecules.

Assembly of polyoxometalate-thiacalix[4]arene-based inorganic-organic hybrids as efficient catalytic oxidation desulfurization catalysts.

Self-assembly of polyoxometalates, Ni(ii)/Ag(i) cations and tetra-[5-(mercapto)-1-methyltetrazole]-thiacalix[4]arene (L) yielded three inorganic-organic hybrids, namely, [Ni3L2(CH3OH)6(H2O)4][PMo12O40]2·3CH3OH·2H2O (1), [Ni3L2(CH3OH)6(H2O)4][PW12O40]2·3CH3OH·2H2O (2) and [Ag3L(PMo12O40)] (3). In hybrids (1) and (2), Ni(ii) cations are linked by L ligands to produce layered frameworks, and H bonds among the [PMo12O40]3-/[PW12O40]3- anions and L ligands lengthen the structures to form 3D supramolecular architectures. Hybrid (3) exhibits a 3D architecture, of which Ag(i) cations not only coordinated with the N and O atoms of L ligands and [PMo12O40]3- anions simultaneously, but also connected each other by Ag-Ag interactions. It is worth mentioning that 1 and 3 as recyclable catalysts show excellent heterogeneous catalytic activity in oxidation desulfurization reactions.

Preparation, properties and modification mechanism of vulcanized eucommia ulmoides gum modified asphalt

To understand effects of vulcanized eucommia ulmoides gum (EUG) on properties of asphalt, and to reveal modification mechanism of vulcanized EUG on asphalt, the vulcanized EUG modified asphalt was prepared, and the changes in different performances of asphalt were characterized. Test results indicate that as the vulcanized EUG content increases, the anti-rutting performance and crack resistance of asphalt materials are improved. Vulcanized EUG content of 10 wt% is proposed to modify asphalt. The vulcanized EUG absorbs some light components in asphalt to swell. Desulfurization and degradation reactions occur to produce more and smaller EUG molecules, improving its compatibility with asphalt.

Ultra-deep oxidative desulfurization of real fuels by sandwich-type polyoxometalate immobilized on copper ferrite nanoparticles, Fe6W18O70 ⊂ CuFe2O4, as an efficient heterogeneous nanocatalyst

In order to obtain the clean gasoline, we report on the synthesis and characterization of a new heterogeneous nanocatalyst comprised of the sandwich-type polyoxotungstate [(FeW9O34)2Fe4(H2O)2]−10 (Fe6W18O70) clusters and copper ferrite (CuFe2O4) nanoparticles. The materials were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible (UV–vis), and scanning electron microscopy (SEM). The Fe6W18O70⊂CuFe2O4 nanocatalyst catalyzed the oxidative desulfurization (ODS) reactions of hazardous sulfur-containing compounds by H2O2-CH3COOH as oxidant. The nanocatalyst exhibited an exceptionally high catalytic performance in the ultra-deep ODS of simulated fuels and real gasoline. The experimental results revealed that the oxidation reaction efficiencies were up to 95% at the temperature of 35 °C and the contact time of 1 h. Particularly, the removal (%) of thiophene (C4H4S), benzothiophene (C8H6S), and dibenzothiophene (C12H8S) from simulated fuels over Fe6W18O70⊂CuFe2O4 nanocatalyst could reach 98%, 99%, and 99%, respectively. Moreover, the heterogeneous nanocatalyst could be easily recovered and reused multiple times by filtration with no obvious loss of activity. The present study will lead to the widespread catalytic application of Fe6W18O70⊂CuFe2O4 material in the efficient and feasible ODS of petroleum fractions.

Polyoxometalate-Based Organic–Inorganic Hybrids as Heterogeneous Catalysts for Cycloaddition of CO2 with Epoxides and Oxidative Desulfurization Reactions

Self-assembly of polyoxometalates, transition metal salts, and 2,6-bis(2′-pyridyl)-4-hydroxypyridine (LOH) obtained four organic–inorganic hybrids [Co2.5(LOH)(LO)2(H2O)2(PW12O39)]·3CH3CN·2OH (1), [...

Highly efficient Co(II) porphyrin catalysts for the extractive oxidative desulfurization of dibenzothiophene in fuel oils under mild conditions

Co(II) porphyrins have been utilized as efficient and selective catalysts for the extractive oxidative desulfurization reaction on the refractory dibenzothiophene (DBT) in [Formula: see text]-dodecane (model middle distillate fuel oil). The acetonitrile was taken as extracting polar solvent and H2O2 was used as oxidant. The reaction optimization was done with respect to DBT:catalyst molar ratio; DBT:H2O2 molar ratio; extracting solvent: CH3CN/[Formula: see text]-dodecane volume ratio; reaction temperature and time. Under the optimized conditions, a maximum of [Formula: see text]98% DBT removal was achieved by using the meso-tetrakis(4[Formula: see text] methoxyphenyl)porphyrinatocobalt(II) as catalyst under mild conditions at 50[Formula: see text]C.

Synthesis and Characterization of Mechanically Alloyed, Nanostructured Cubic MoW Carbide

Carbides are used extensively as cutting tools, forming dies, and recently in catalysis applications, among other industrial applications. In this work, the synthesis and characterization of a nanostructured MoW bimetallic carbide were carried out by mechanical alloying with a mixture of elemental powders with a nominal composition of W1.5Mo6C2.5 at different grinding times as follows: 25, 50, and 75 h in a low-energy ball mill at a speed of 500 rpm and 125 and 150 h in a high-energy ball mill at a speed of 1500 rpm. The formation of a solid solution was observed at 150 h of milling; the nanostructured bcc MoW carbide corresponded to the main phase in the sample, besides the presence of the nanostructured MoW alloy as a secondary phase with an average crystal size of 40.8 nm. The phases and morphology at every stage of milling were studied by: X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and Vickers hardness. As the milling time increased, the hardness of these particles increased from 10.5 to 31.48 GPa for the powder particles milled for 150 h. The samples obtained at 125 and 150 h of milling were evaluated during catalytic aqua-thermolysis of heavy oil to analyze fuel desulfurization properties by Fourier transform infrared (FTIR) techniques. The results showed the breaking of S-S bonds, indicating the existence of a desulfurization reaction of heavy oil.

Defect Engineering on Boron Nitride for O2 Activation and Subsequent Oxidative Desulfurization.

The rational design of highly active hexagonal boron nitride (h-BN) catalysts at the atomic level is urgent for aerobic reactions. Herein, a doping impurity atom strategy is adopted to increase its catalytic activities. A series of doping systems involving O, C impurities and B, N antisites are constructed and their catalytic activities for molecular O2 have been studied by density functional theory (DFT) calculations. It is demonstrated that O2 is highly activated on ON and BN defects, and moderately activated on CB and CN defects, however, it is not stable on NB and OB defects. The subsequent application in oxidative desulfurization (ODS) reactions proves the ON and C-doped (CB , CN ) systems to be good choice for sulfocompounds oxidization, especially for dibenzothiophene (DBT). While the BN antisite is not suitable for such aerobic reaction due to the extremely stable B-O* -B species formed during the oxidation process.