Search Results (32)

The inclusion of adsorption thermodynamic analysis and performance benchmarking with existing adsorbents reinforces both the theoretical significance and practical applicability of this study. The modified rubber-derived carbon demonstrated a remarkably high DBT adsorption capacity of 254.45 mg/g. These results establish it as a promising alternative to conventional materials such as commercial activated carbon, zeolites, and even metal–organic framework materials. In addition to confirming the superior performance of the adsorbent, the findings provide a deeper understanding of the DBT adsorption mechanism and offer a solid scientific basis for large-scale fuel desulfurization applications. This research highlights the potential of transforming end-of-life tire waste into value-added functional materials and contributes to the advancement of sustainable and efficient desulfurization technologies. Future work should focus on optimizing surface functionalization and regeneration strategies to further improve long-term adsorption stability and practical deployment. Full article

Diesel desulfurization is a critical process for reducing the sulfur content in diesel fuel and mitigating the negative impact of sulfur-containing exhaust gases for the environment. As a cornerstone of the refining industry, desulfurization has garnered significant attention for producing cleaner fuels and reducing pollution. Currently, the primary desulfurization technologies include hydrodesulfurization (HDS), oxidative desulfurization (ODS), biodesulfurization (BDS), adsorptive desulfurization (ADS), and electrochemical desulfurization (ECDS). With the development of global economic competition and the advancement of technological innovation, diesel desulfurization technologies are evolving toward higher efficiency, lower costs, and resource-oriented utilization. This article provides a detailed account of the various desulfurization technologies under investigation and offers an overview of the emerging ultra-deep desulfurization techniques aimed at producing ultra-low-sulfur fuels. Full article

The fuel-cell (FC) power system, utilizing biohydrogen from biomass resources, is a promising alternative to fossil fuels. However, hydrogen sulfide (H₂S) in bio-syngas can severely degrade FC performance and increase environmental impact, necessitating impurity removal. This study investigates a multi-stage desulfurization process using neutralized sediment (NS) and a metal hydride (LaNi₅) as H₂S adsorbents. NS, a mining waste material, can potentially reduce environmental impact when repurposed as an adsorbent, with its performance influenced by pore configuration and Fe content. However, the purified gas does not fully meet FC fuel specifications. To address this, LaNi₅, which selectively absorbs and releases hydrogen, was incorporated to achieve higher purification levels. In our study, H₂S adsorption tests were conducted using two fixed-bed flow reactors heated to 250 °C, where a gas mixture containing 196 ppm of H₂S flowed through the system. The proposed multi-stage system achieved a breakthrough time of 182.5 h with purified gas remaining under 0.1 ppm and an adsorption capacity of 16.4 g/g-sorbent. These results demonstrate the high desulfurization performance achieved using NS and LaNi₅. Full article

Currently, the key challenge of the oil-refining industry worldwide is to produce environmentally friendly fuel in large volumes to meet market demand, which is due to strict environmental standards governing the permissible sulfur content in fuel. Natural gas, refinery gas, and coal gas contain acid gases such as hydrogen sulfide and carbon dioxide. These compounds must be removed from the gas stream because of the toxicity of H₂S and to prevent the acid gas-induced corrosion of pipelines and facilities. Hydrogen sulfide is released as a result of various industrial processes, and its removal is critical because this compound can cause corrosion and environmental damage even at low concentrations. Sulfur compounds are also present in natural gas, biofuels and other fuel gases used in power plants. This article proposes new adsorbents of natural and waste origin and presents the results of their testing for the removal of acid gases. This paper also considers methods for the preparation of adsorbents from waste and procedures for the removal of sulfur-containing compounds. Using agricultural, industrial waste to produce activated sorbents not only solves the problem of waste disposal but also reduces the cost of desulfurization, contributing to the creation of sustainable and environmentally friendly technologies. The Review Section comprehensively summarizes current research on hydrogen sulfide removal in gas cleaning processes using agricultural and industrial waste as highly efficient adsorbents. In the Experimental Section, 10 composite materials based on natural raw materials and wastes, as well as 6 commercial adsorbents, were synthesized and tested under laboratory conditions. The choice of materials for the adsorbent production was based on the principles of environmental friendliness, availability, and cost-effectiveness. The developed materials based on modified sludge from water treatment plants of thermal power plants are effective sorbents for the purification of gas emissions from petrochemical enterprises. For industrial use, it is necessary to solve the problems of increasing the economic attractiveness of sorbents from waste, the ability of regeneration, the competitive adsorption of pollutants, the use of indicator sorbents, the optimization of operating conditions, and safe waste disposal. Full article

The environmental and health impacts of sulfur compounds in fuel oil have prompted considerable research interest in oxidative desulfurization (ODS) technology. Tetrahedrally coordinated titanium has been demonstrated to exhibit excellent activity in the context of oxidative desulfurization processes. However, further improving the catalytic property of the tetrahedrally coordinated titanium remains a challenging endeavor. In the context of ODS processes conducted at near room temperatures, the improvement of conversion remains a subject of considerable challenge. In this study, hierarchically porous titanosilicate hollow spheres were synthesized by using TS-1 zeolite precursors as Ti and Si sources to obtain the catalyst with only tetrahedrally coordinated titanium. The synthesized materials were characterized through transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), ultraviolet–visible diffuse reflectance spectroscopy (UV-Vis), and nitrogen adsorption analysis. These techniques confirmed the formation of hollow spherical hierarchically porous structures with Ti species uniformly incorporated in tetrahedral coordination and the presence of five-member rings of TS-1 zeolite. As a result, the hierarchically porous titanosilicate hollow spheres demonstrated excellent catalytic performance in ODS, achieving complete dibenzothiophene (DBT) removal within 15 min and a high turnover frequency (TOF) of up to 123 h⁻¹ at 30 °C. Full article

The oxidative desulfurization (ODS) of heavy fuel oil (HFO) offers a promising solution for desulfurizing marine fuels under mild conditions, in line with current environmental regulations. While most studies focus on model or light fuels, explaining deactivation through leaching or sulfone adsorption, the deactivation mechanisms of catalysts in HFO remain poorly understood. In this work, Mo-based catalysts supported on alumina were extensively characterized before and after catalytic reactions, and regeneration through air calcination was considered. Techniques such as XRD, Raman spectroscopy, XRF, and TGA, alongside catalytic testing with H₂O₂ as an oxidant, revealed that Mo surface speciation significantly impacted both activity and deactivation. Contrary to well-dispersed polymolybdates, crystalline MoO₃ induced low activity and hindered regeneration. No leaching of the active phase was demonstrated during the reaction. Sulfone adsorption had minimal impact on deactivation, while non-sulphur compounds appeared to be the key contributors. Regeneration outcomes were found to be molybdenum content-dependent: 10Mo/Al recovered its activity, while 20Mo/Al formed inactive phases, like Al₂(MoO₄)₃. Using an organic oxidant (tBHP) during ODS influenced the regeneration, as it prevented Al₂(MoO₄)₃ formation and redispersed crystalline MoO₃, enhancing performance. These findings advance understanding of catalyst deactivation and suggest strategies to extend catalyst life in the ODS of HFO. Full article

Various Keggin-type heteropolyoxometalate catalysts with structural defects and surface acidity were synthesized by immobilizing 12-phosphotungstic acid (HPW) on mesoporous SBA−15, to produce near-zero-sulfur diesel fuel. As the calcination temperature increased, the W=O and the corner-shared W–O–W bonds in the Keggin unit partially broke, creating oxygen defects, as evidenced by the Rietveld refinement and in situ FTIR characterization. All the catalysts contained Lewis (L) and Brønsted (B) acid sites, with L acidity predominant. The relative intensity of the IR band (I₉₈₀) of W=O bond inversely correlated with the number of L acid sites as the calcination temperature varied, suggesting that oxygen defects contributed to the Lewis acid sites formation. In the oxidation of dibenzothiophene (DBT) in a model diesel within a biphasic system, DBT conversion exceeded 99% under the optimal reaction conditions (reaction temperature 70 °C, reaction time 60 min, H₂O₂/sulfur molar ratio 8, H₂O₂/formic acid molar ratio 1.5, catalyst concentration 2 mg/mL). The influence of fuel composition and addition of indole and 4,6-DMDBT on DBT oxidation were also evaluated. Indole and cyclohexene negatively impacted the DBT oxidative removal. Oxygen defects served as active centers for competitive adsorption of sulfur compound and oxidant. Both L and B acid sites were involved in transferring O atom from peroxophosphotungstate complex to sulfur in DBT, resulting in DBTO₂ sulfone, which was immediately extracted by polar acetonitrile. This study confirms that structural defects and surface acidity are crucial in the deep oxidative desulfurization (ODS) reaction, and in enabling the simultaneous oxidation and separation of refractory organosulfur compounds in a highly efficient model diesel. Full article

Fuel gas desulfurization is an important technological step toward achieving environmental neutrality in industrial production. The presence of sulfur compounds in fuel not only significantly increases the rate of corrosion processes, but also increases the amount of sulfur oxides in flue gases. Adsorption technologies are actively used to purify fuel. Materials that are mainly chosen as sorbents are determined by economic feasibility. These materials include bentonite clays. The paper presents an analysis of scientific works on the possible methods of using bentonite clays in industry. Due to its natural properties, this material has high adsorption properties. The authors present experimental laboratory studies to determine the adsorption efficiency of bentonite clay with a carbon substrate. Results on the adsorption capacity after regeneration of the composition are also presented. Based on the data obtained, the adsorption unit was calculated, and the process flow diagram was designed. Full article

With increasingly stringent emission limits on sulfur and sulfur-containing substances, the reduction and removal of sulfur compounds from fuels has become an urgent task. Emissions of sulfur-containing compounds pose a significant threat to the environment and human health. Ionic liquids (ILs) have attracted much attention in recent years as green solvents and functional materials, and their unique properties make them useful alternatives to conventional desulfurization organic solvents. This paper reviews the advantages and disadvantages of traditional desulfurization technologies such as hydrodesulfurization, oxidative desulfurization, biological desulfurization, adsorptive desulfurization, extractive desulfurization, etc. It focuses on the synthesis of ionic liquids and their applications in oxidative desulfurization, extractive desulfurization, extractive oxidative desulfurization, and catalytic oxidative desulfurization, and it analyzes the problems of ionic liquids that need to be solved urgently in desulfurization, looking forward to the development of sulfuric compounds as a kind of new and emerging green solvent in the field of desulfurization. Full article

In recent years, due to the rapid growth of mankind’s demand for energy, harmful gases (SOx) produced by the combustion of sulfur-containing compounds in fuel oil have caused serious problems to the ecological environment and human health. Therefore, in order to solve this hidden danger from the source, countries around the world have created increasingly strict standards for the sulfur content in fuel. Adsorption desulfurization technology has attracted wide attention due to its advantages of energy saving and low operating cost. This paper reviewed the latest research progress on various porous adsorption materials. The future challenges and research directions of adsorption materials to meet the needs of clean fuels are proposed. Full article

The removal of sulfur- and nitrogen-containing compounds present in fuels is and will be crucial to accomplish actual strict regulations to avoid environmental and humanity health adversities. The conventional hydrodesulfurization and hydrodenitrogenation processes conducted by refineries are limited due to severe operating conditions, and even more importantly, they are inefficient for simultaneously removing nitrogen- and sulfur-containing compounds in fuels. On the other hand, non-hydrogen technologies are beneficial in terms of mild operating conditions, and during the last two decades, some successful works have shown that these can be highly effective at efficiently removing both sulfur- and nitrogen-containing compounds from liquid fuels. For more than four decades, extensive research (thousands of publications since the 1980s) has been dedicated to developing remote desulfurization technologies without taking into consideration the presence of a complex fuel matrix, or even taking into account the presence of other harmful pollutant elements, such as nitrogen. Even more recently, several effective non-hydrogen denitrogenation processes have been reported without considering the presence of sulfur compounds. This review paper is a reflection on the limited work that has been successfully performed to simultaneously remove sulfur- and nitrogen-containing compounds from fuels. An evaluation of different methodologies (adsorption, extraction, oxidative (photo)catalysis, ultrasound-assisted oxidation) is presented here. Furthermore, this review intends to define new future strategies that will allow the design of more suitable and economical technologies, effectively conciliating desulfurization and denitrogenation processes to produce more sustainable fuels. Full article

Production of renewable fuels from gasification is based on catalytic processes. Deep desulfurization is required to avoid the poisoning of the catalysts. It means the removal of H₂S but also of organic sulfur species. Conventional cleaning consists of a several-step complex approach comprising catalytic hydro-treating followed by H₂S removal. In this work, a single-stage process using a zinc and nickel oxide sorbent has been investigated for the removal of organic sulfur species present in syngas. The process is called reactive adsorption and comes from the refinery industry. The challenge investigated by CIEMAT was to prove for the first time that the concept is also valid for syngas. We have studied the process at a lab scale. Thiophene and benzothiophene, two of the main syngas organic sulfur compounds, were selected as target species to remove. The experimental study comprised the analysis of the effect of temperature (250–450 °C), pressure (1–10 bar), space velocity (2000–3500 h⁻¹), tar components (toluene), sulfur species (H₂S), and syngas components (H₂, CO, and full syngas CO/CO₂/CH₄/H₂). Operating conditions for removal of thiophene and benzothiophene were determined. Increasing pressure and temperature had a positive effect, and full conversion was achieved at 450 °C, 10 bar and 3500 h⁻¹, accompanied by simultaneous hydrogen sulfide capture by the sorbent in accordance with the reactive adsorption desulfurization (RADS) process. Space velocity and hydrogen content in the syngas had little effect on desulfurization. Thiophene conversions from 39% to 75% were obtained when feeding synthetic syngas mimicking different compositions, spanning from air to steam-oxygen-blown gasification. Toluene, as a model tar component present in syngas, did not strongly affect the removal of thiophene and benzothiophene. H₂S inhibited their conversion, falling, respectively, to 2% and 69% at 350 °C and 30% and 80% at 400 °C under full syngas blends. Full article

A new type of catalyst was synthesized by immobilizing heteropolyacid on ionic liquid-modified mesostructured cellular silica foam (denoted as MCF) and applied to the oxidative desulfurization of fuel. The surface morphology and structure of the catalyst were characterized by XRD, TEM, N₂ adsorption–desorption, FT-IR, EDS and XPS analysis. The catalyst exhibited good stability and desulfurization for various sulfur-containing compounds in oxidative desulfurization. Heteropolyacid ionic liquid-based MCF solved the shortage of the amount of ionic liquid and difficult separation in the process of oxidative desulfurization. Meanwhile, MCF had a special three-dimensional structure that was not only highly conducive to mass transfer but also greatly increased catalytic active sites and significantly improved catalytic efficiency. Accordingly, the prepared catalyst of 1-butyl-3-methyl imidazolium phosphomolybdic acid-based MCF (denoted as [BMIM]₃PMo₁₂O₄₀-based MCF) exhibited high desulfurization activity in an oxidative desulfurization system. The removal of dibenzothiophene could achieve levels of 100% in 90 min. Additionally, four sulfur-containing compounds could be removed completely under mild conditions. Due to the stability of the structure, sulfur removal efficiency still reached 99.8% after the catalyst was recycled six times. Full article

Desulfurization of organic sulfur in the fuel oil is essential to cut down the emission of sulfur dioxide, which is a major precursor of the acid rain and PM_2.5. Currently, hydrodesulfurization is regarded as a state-of-art technology for the desulfurization of fuel oil. However, due to the stringent legislation of the fuel oil, the deep desulfurization technology is urgent to be developed. Adsorptive desulfurization method is promising due to the high selectivity and easy operation. The development of efficient adsorbent is important to advance this technology into industrial application. In this work, the five types of metal-organic frameworks (MOFs), including Cu-BTC, UMCM-150, MIL-101(Cr), UIO-66, and Cu-ABTC were synthesized for the adsorption of dibenzothiophene (DBT), a typical organic sulfur compound in the fuel oil. The experimental results revealed that the adsorption capacity of the five MOFs followed the order of Cu-ABTC, UMCM-150, Cu-BTC, MIL-101(Cr), and UIO-66, which adsorption capacities were 46.2, 34.2, 28.3, 26.3, and 22.0 mgS/g, respectively. The three types of Cu-based MOFs such as Cu-ABTC, UMCM-150, and Cu-BTC outperformed the Cr-based MOFs, MIL-101, and Zr-based MOFs, UIO-66. Since the surface area and pore volumes of the Cu-based MOFs were not the greatest among the tested five MOFs, the physical properties of the MOFs were not the only limited factor for the DBT adsorption. The π-complexation between DBT and linkers/metal in the MOFs was also important. Kinetic analysis showed that the DBT adsorption onto the five tested MOFs follows the pseudo-second-order kinetics, confirming that the chemical π-complexation was also contributed to the DBT adsorption. Furthermore, the operation parameters such as oil-adsorbent ratio, initial sulfur concentration and adsorption temperature for the DBT adsorption onto Cu-ABTC were optimized to be 100:1 g/g, 1000 mgS/L and 30 °C, respectively. This work can provide some insights into the development of efficient adsorbent for the organic sulfur adsorption. Full article

The negative environmental and industrial impacts of the presence of sulfur compounds such as benzothiophene in fuels have led to a greater interest in desulfurization research. In this work, carbon from palm waste sources was modified with trihexYl(tetradecyl)phosphonium dicyanamide-ionic liquid and characterized by SEM, EDS, XRD and FTIR to assess surface properties. Then, the prepared carbon and carbon modified with ionic liquid were evaluated for the adsorption of benzothiophene by investigating the effects of time. The equilibrium occurred after 120 min, recording adsorption capacities of 192 and 238 mg/g for carbon and carbon modified with ionic liquid, respectively. The effect of the adsorbent dose on the adsorption of benzothiophene was evaluated, indicating that the maximum adsorption capacities were obtained using a dose of 1 g/L for both carbon and carbon modified with ionic liquid. The kinetic investigation for the adsorption of benzothiophene onto carbon and carbon modified with ionic liquid indicated that the second-order kinetic model is well fitted with the adsorption data rather than the first-order kinetic model. The equilibrium investigations for the adsorption of benzothiophene onto carbon and carbon modified with ionic liquid with Langmuir and Freundlich isotherm models reveals that the Freundlich model is the most suitable for describing the adsorption process, suggesting a multilayer adsorption mechanism. The desulfurization process showed a high impact on environmental safety due to the possibility of regenerating and reusing the prepared adsorbents with promising results up to five cycles. Full article