Hydrodesulfurization Research Articles

Selective Separation of Thiophene Derivatives Using Metal-Organic Frameworks-Based Membranes.

The removal of sulfur compounds, particularly thiophene derivatives, from oil is crucial due to concerns about environmental issues. Therefore, the deep desulfurization of transportation fuels is currently an urgent problem, and numerous attempts have been made in this direction. Membrane-based desulfurization can be a good alternative to the traditional hydrodesulfurization method, which has several limitations. In this work, the use of membranes containing a metal-organic framework, MOF-5, doped with transition metals (Ag, Cu, Ni), in the adsorptive desulfurization process was studied. The efficiency of membranes was evaluated based on selective removal of thiophene and dibenzothiophene from model oil. Characterization techniques, including scanning electron microscopic (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA), confirmed the successful synthesis and incorporation of metal-organic frameworks (MOFs) into mixed matrix membranes (MMMs). Desulfurization experiments showed that MOF-5/Ag exhibited the highest thiophene adsorption efficiency (86.8%), outperforming MOF-5/Cu and MOF-5/Ni. The enhanced performance is attributed to the strong interaction between silver and sulfur. These findings demonstrate the potential of MOF-based MMMs for efficient and selective desulfurization, offering a viable alternative to traditional hydrodesulfurization (HDS) methods.

Speciation of the Oxide Phase of Molybdenum‐Based HDS Catalysts Enhanced with Organic Additives Using an EXAFS/Raman Coupling Methodology

AbstractThe ability to gain access to the speciation of hydrodesulfurization (HDS) catalysts used for removing sulfur and nitrogen from transportation fuels is becoming a key feature in the understanding and improvement of their catalytic activity with the aim of reducing greenhouse gas emissions of fossil fuels. A novel coupling methodology between Raman spectroscopy and X‐ray absorption spectroscopy (XAS) was developed, which allows for precise qualitative and quantitative analysis of the oxide phase of Mo‐based catalysts. This enabled the detailed study of various impregnation parameters and the characterization of HDS catalysts before sulfidation. To illustrate this methodology, the effects of two additives (triethylene glycol and citric acid) were studied. The results demonstrated that organic additives exert a profound influence on the speciation of oxide precursors of molybdenum‐based catalysts. The presence of these additives enhances the dispersion of Keggin or Dawson heteropolyanions (HPAs) on the support by maintaining a high phosphorus‐to‐molybdenum ratio in solution. This is achieved by two strategies: triethylene glycol (TEG) exhibits a pronounced affinity for alumina hydroxyls, while citric acid compensates for phosphate adsorption through the formation of a stable Mo‐citrate complex.

Unveiling the degradation mechanism of cathodic MoS2/C electrocatalysts for PEMWE applications

Molybdenum dichalcogenides (MoS2) are promising non-noble alternatives to replace platinum (Pt) for Hydrogen Evolution Reaction (HER) electrocatalysis in Proton Exchange Membrane Water Electrolyzers (PEMWE). The knowledge acquired on this class of catalyst for hydrodesulfurization (HDS) reactions has enabled significant advances in designing active MoS2 for HER. However, the stability of MoS2 in the dynamic operating conditions of a PEMWE coupled to renewable energy sources is often overlooked in the literature and is the focus of the present work. Herein, using nano slabs of 2H MoS2 supported on high surface area carbon, we dynamically monitored Mo dissolution trends both under HER conditions and at more anodic potentials to mimic start-ups and shut-downs of a PEMWE device. We report minimal Mo dissolution under HER conditions but it continuously increased with higher electrode potentials. In particular, Mo dissolution peaked during the irreversible oxidation from Mo(IV) to Mo(VI) starting at E = 0.7 VRHE which in turn fully annihilates HER activity. Since no change in Mo and S surface composition was observed, the decline in HER activity was attributed to the continuous exfoliation of the 2D MoS2 stacked layers induced by oxidation/dissolution of Mo. Additionally, our findings indicate that Mo cations can redeposit onto the cathode catalytic layer, forming a Mo blue film primarily composed of Mo(VI) species. This redeposition hampers HER performance by blocking catalytic sites and diminishing the catalyst's overall efficiency. These insights demonstrate the need to avoid excursions above E = 0.6 VRHE for the safe use of MoS2 cathode catalyst in PEMWE.

Enhancing Ultradeep Hydrodesulfurization of Coker Diesel through Adsorptive Predenitrogenation.

The petroleum refining industry places significant challenge in the production of ultralow-sulfur diesel (ULSD) from various middle distillates with high nitrogen concentration in an energy-efficient and cost-effective way to meet strict environmental regulations as coexisting nitrogen compounds significantly inhibit the ultradeep hydrodesulfurization (HDS). Among all of the approaches reported in the literature for this challenge, a combination of adsorptive denitrogenation (ADN) and HDS has attracted great attention. This study focuses on ultradeep HDS of coker diesel (CD) through a synergistic approach combining ADN over a carbon-based adsorbent and the current HDS process. The study found that the predenitrogenation significantly enhanced the HDS reactivity of CD and greatly reduced the start of run temperature for producing ULSD by even 20 °C, depending on the denitrogenation depth. It results in dominantly decreasing energy and H2 consumption in the HDS process, and increasing the lifetime of the catalyst. Furthermore, the predenitrogenation prior to HDS significantly improved the quality of the hydrodesulfurized product by decreasing aromatic content and density, increasing the cetane index, and improving the color and stability of the product as the HDS process for producing ULSD can be conducted at a much lower temperature. The study demonstrated the combination of ADN and HDS for producing ULSD from CD on a pilot unit scale, and the advantages and disadvantages of this combination were discussed in comparison with the conventional HDS process. In addition, it was found that there is a good linear relationship between the logarithm of the product sulfur concentration and the HDS reaction temperature, which can be used conveniently to predict the start-of-run temperature to achieve different sulfur levels.

Hydrodesulfurization and isomerization performance of model FCC naphtha over sulfided Co(Ni)–Mo/Y catalysts

The process of deep hydrodesulfurization (HDS) in gasoline typically results in the saturation of olefins, leading to significant reductions in octane number. In this work, Y-supported Co(Ni)–Mo catalysts that with different Ni–Co content were prepared by the incipient wetness impregnation method, the structure and properties were characterized and analyzed using HRTEM, XPS, H2-TPR, and NH3-TPD. The isomerization of 1-hexene and 1-octene as well as the HDS of thiophene were studied by using model FCC naphtha. The incorporation of Ni was found to enhance the number of MoS2 stacking layers, thereby improving the degree of sulfurization in Mo and subsequently increasing the desulfurization rate, with a maximum achieved desulfurization rate of 94.7%. When employing a Ni/Co ratio of 3:2, optimal synergy between Ni and Co is achieved, resulting in a greater presence of multi-layer stacked II-Co(Ni)MoS active phases. Additionally, appropriate Brønsted acidity levels are maintained to facilitate efficient olefin isomerization while preserving high HDS activity. As a result, the current isomerization yield stands at 58.2%(mass). These understandings shed light on the development of highly HDS and olefin isomerization catalysts.

Parametric analysis on the sulfone adsorption of using iron impregnated bentonite

Abstract Sulfur left in liquid fuel is oxidized during combustion and released into the atmosphere, contributing to the worsening of global warming. To address this, oil refineries make use of hydrodesulfurization (HDS) to reduce sulfur content in the fuel. Alternatives to HDS are being studied due to its extreme operating conditions. An alternative for treating sulfur in fuel is oxidative desulfurization, which converts sulfur to sulfones and can be extracted using adsorption methods. This study focuses on the use of bentonite modified with Fe3+ to improve its adsorptive performance for removing dibenzothiophene sulfone (DBTO) in model oil. The prepared Fe3+-bentonite adsorbents resulted in lower removal of sulfur compared to raw bentonite. This is due to Fe3+ being a hard acid, thus lowering the affinity of bentonite in adsorbing DBTO, which is a soft base. Three parameters were varied in this study, namely adsorption time, adsorbent dosage, and temperature. Results showed that DBTO removal increased with adsorption time as the DBTO molecules occupy more adsorption sites. Increasing adsorbent dosage also increases sulfur removal as it introduces more reaction sites for DBTO removal. The DBTO and bentonite system was also found to be endothermic as desulfurization increased with the temperature rise. With the data collected in this study, it is recommended to explore the possible upscaling of adsorptive desulfurization.

Получение экологичного катализатора на основе четвертичной аммониевой соли гетерополикислоты для глубокой окислительной десульфуризации дизельного топлива

Hydrodesulfurization (HDS) is the most widely used method for fuel oil desulfurization, which can easily remove mercaptan and thiophene from diesel oil, but the removal rate of dibenzothiophene (DBT) and its alkylated derivatives is low. Compared with traditional HDS technology, oxidative desulfurization (ODS) technology has the advantages of less investment, mild reaction conditions, and high ODS activity for DBT and its derivatives. Heteropoly acid (salt)/H2O2 system is highly efficient and the oxidation product of hydrogen peroxide is water, making them green catalysts. A new type of polyoxometalates phase transfer catalyst, [(C16H33(CH3)3)N]3-HPW11VO40, was synthesized through ion exchange method. It was applied to the catalytic oxidative desulfurization of model diesel oil using H2O2 as oxidant. The influencing factors of reaction were investigated in detail. The catalyst exhibits the dibenzothiophene conversion rate of 100% and excellent reusability and retrievability with 99.97% conversion after five times reaction in mild reaction conditions of n(catalyst)/n(DBT)=1/80, n(H2O2)/n(DBT)=8/1, 50 °C, and atmospheric pressure in 3 h. The catalyst could be quickly separated and recycled by centrifugation after reaction and hence be promising in the low-sulfur fuel production.

Atomic decoration of MoS2 using Fe, Co or Ni for highly efficient and selective hydrodesulfurization

Hydrodesulfurization (HDS) is one of the most efficient processes for removing sulfur-containing molecules such as dibenzothiophene (DBT) from oil, whatever fossil based or bio-based. However, hydrodesulfurization using molybdenum sulfides (MoS2) as catalytic active centers and transition metals (X) as promoters is seriously challenged by the insufficient catalytic activity and selectivity because of the separate phases of sulfides, and sparse X-Mo-S active sites, leading to poor synergistic effect between the X promoter and MoS2 active centers. Herein, atomically doped MoS2 catalysts (denoted as XMo, X = Fe, Co or Ni) were synthesized by using polyoxometalate template-based synthetic strategy were proposed. The pre-organized Anderson-type POMs, [XMo6O24H6]n− (X = Fe, Co or Ni), acted as a pre-assembled molecular platform with intimate X-Mo interactions, ensure the uniform formation of X-Mo-S active sites after sulfuration. The promoter atoms, including Fe, Co and Ni, enhanced the efficiency of hydrodesulfurization of MoS2. Particularly, NiMo exhibits the highest HDS activity, while CoMo shows a moderate HDS activity with the highest DDS selectivity (∼85 %). Despite the lowest HDS activities, FeMo with the cheapest Fe promoter, shows good DDS selectivity (∼70 %). Further study reveal NiMo has the most laminated morphology and highest stacking slabs, resulting in the highest HDS activity. Benefiting from the Co(Fe)-Mo-S structure and abundant sulfur vacancy, CoMo and FeMo showed great enhancement in the DDS selectivity. Moreover, the DDS selectivity of these designed catalysts were supported energetically by first principle calculations. This research will expand on the ability to improve the HDS activities and DDS selectivity by precisely engineering catalytic active sites to achieve significant synergistic effect in atomic scale.

Al2O3 Concentration Effect on Deep Hydrodesulfurization of 4,6-Dimethyldibenzothiophene over NiWS/Al2O3-ZrO2 Catalysts.

The Al2O3 concentration effect over NiWS/Al x Zr100-x catalysts was investigated for deep hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT). The sol-gel method changed the wt % Al2O3 concentrations used to synthesize the Al x Zr100-x supports. The NiWS/Al x Zr100-x catalysts were prepared with ammonium metatungstate hydrate and nickel(II) nitrate hexahydrate by sequential incipient impregnation, calcination, and H2S/H2 activation. The catalytic evaluation data fit a pseudo-first-order trend in the 4,6-DMDBT HDS reactions. In the oxide phase, the catalysts presented Ni and W species in tetrahedral (td) and octahedral (oh) coordination, with the oh species prevailing as a function of the Al2O3 amount. The lower amount of Al2O3 can facilitate the "Type II" NiWS phase formation by weakening the interaction of the W-O-Al bond and promoting W and Ni species sulfidation. In the sulfide phase, catalysts with (oh) coordination and surface WO X species promote the formation of WS2 and NiWS species during the catalyst activation step. This species favors the reaction yield, where the hydrogenation route is predominant, with the highest initial reaction rate using the NiWS/Al25Zr75 catalyst. A direct correlation was found between high hydrogenation/hydrogenolysis ratio values and low Al2O3 concentrations.

Recovery of aluminum, vanadium, and nickel from waste desulfurization catalyst residue by roasting and water leaching

The improper disposal of hydrodesulfurization (HDS) catalysts poses significant environmental risks due to the presence of toxic materials and metals. This study investigates a method for recovering valuable resources, specifically aluminum, vanadium, and nickel, from industrial waste HDS catalyst residue. The process involves roasting the HDS residue at 300°C for 120 min with a 1:1 solid-to-liquid (S/L) ratio of residue to sodium hydroxide (NaOH). Subsequent water leaching resulted in the recovery of approximately 99% of Al(III) and V(V). The leaching kinetics of Al(III) and V(V) were found to follow the Shrinking-Core model, described by the equations X = kc.t and 1 − (1 − X)1/2 = kc.t, with activation energies (Ea) of 7.39 kJ/mol and 4.61 kJ/mol, respectively. The leach liquor containing Al(III) V(V) was treated with concentrated hydrochloric acid (HCl) at pH 9.5 to precipitate aluminum salt, while vanadium was extracted using ammonium chloride (NH4Cl) by adjusting the pH to 7.1 at 50°C for 30 min. The residual material was leached with 5% (v/v) sulfuric acid (H2SO4) in the presence of 15% (v/v) hydrogen peroxide (H2O2) to achieve maximum nickel dissolution, resulting in the recovery of 99% of aluminum as Al(OH)3 with 99.8% purity and 99% of nickel as NiSO4.6H2O.

Effects of the depth of hydro desulfurization of raw materials on the yields of catalytic cracking products

The article is devoted to the problem of complex processing of oil feedstock and increasing the output of light petroleum products, in particular, catalytic cracking gasoline. Currently, the oil refining industry of Kazakhstan is faced with the task of complex processing of hydrocarbon raw materials, increasing the depth of processing and output of light petroleum products. In this connection it is urgent to solve the problem of lack of raw materials for oil refineries of the Republic of Kazakhstan. The complexity of solving the problem of processing residues of oils, fuel oil and intermediates of secondary processes lies in the fact that they contain a large amount of various sulfur compounds. This problem concerns not only domestic refineries, for example, oil from Uzbekistan fields contains a relatively large amount of SO2 compounds, which in turn contains about 1.28% sulphur. The high content of sulfur compounds in oil not only negatively affects the quality and environmental friendliness of manufactured products, but also reduces the service life of equipment and oil refineries. In this regard, the preparation and hydrodesulfurization of raw materials is one of the main issues of intensifying the process of catalytic cracking of petroleum raw materials of "PKOP" LLP. The issues of possibility of modernisation of catalytic cracking process units by including the process of hydrodesulphurisation of feedstock in order to improve the quality and yield of light products when using fuel oil and secondary intermediates having a large volume of various sulphur compounds in their composition have been considered by the authors. To evaluate the influence of the depth of hydrodesulfurisation of feedstock on the yields and composition of catalytic cracking products, the cracking of crude and hydrotreated hydrogenated vacuum gas oil mixed with fuel oil was carried out on a laboratory unit. The experiments were carried out on a fluidised catalyst bed at mass feed rates of 2h-1 and 4h-1, catalyst to feed ratio of 3:1 and temperature equal to 5100 C. The analysis of the experimental data obtained showed that preliminary hydrotreating of a mixture of vacuum gas oil and sulfur fuel oil followed by catalytic cracking increases the depth of oil refining and helps to increase the yield of catalytic distillate, improves its quality, which ultimately leads to a decrease in environmental pollution with sulfur compounds.

Modulating the Reaction Pathway of Ni2P/Al2O3 by Introducing Different Noble Metals for Hydrodesulfurization of Diesel.

Regulating the reaction pathway of a hydrodesulfurization (HDS) catalyst to achieve ultradeep desulfurization of diesel is a low-energy-consumption yet effective strategy but remains a tricky challenge. Herein, we present a Ni2P/Al2O3 catalyst with mesoporous properties synthesized by a facile hydrothermal-temperature-programmed reduction and normal impregnation (TPRI) method, and then different precious metals with similar loadings were introduced to prepare M-Ni2P/Al2O3 (M = Pt, Pd) catalysts through incipient wetness impregnation. Their structures were analyzed by a series of characterization methods, and their catalytic performances were examined for 4,6-dimethyldibenzothiophene (4,6-DMDBT) HDS. The correlation characterization results revealed that the kind of precious metals significantly affected the surface acidity and then the metal-support interaction (MSI) between Ni2P and Al2O3. Among them, the Pt-Ni2P/Al2O3 catalyst exhibits superior HDS activity with 88.5% 4,6-DMDBT conversion to Pd-Ni2P/Al2O3 (76.3%) and pristine Ni2P/Al2O3 (58.6%) catalysts under reaction conditions of 3.4 MPa, 340 °C, and LHSV = 4.8 h-1. This should be due to the introduction of Pt, which significantly facilitates the dissociation rate of H2 and the subsequent generation of more active hydrogen species than Pd, thereby promoting the formation of Brønsted acid sites, remarkably facilitating the isomerization (ISO) pathway, and markedly enhancing the 4,6-DMDBT HDS conversion of Pt-Ni2P/Al2O3. This work provides an efficient protocol to tame the reaction pathway and thereafter the catalytic performance of the HDS catalyst in the future.

Synthesis, characterization, and performance evaluation of unsupported tetrametallic CoMoMnAl and CoMoZnAl catalysts for selective hydrodesulfurization (HDS)

New formulations of unsupported tetrametallic catalysts derived from layered double hydroxides (LDH) compounds were synthesized by a constant pH coprecipitation method, characterized, and evaluated in the selective hydrodesulfurization (HDS) of thiophene in the presence of cyclohexene. The layered double hydroxides were prepared using terephthalate (C8H8O2)2- as the interlayer anion with nominal aluminum molar fraction of 0.5, and nominal cobalt to MII (M = Zn or Mn) ratios of 0.2, 0.4 and 0.6. Molybdenum introduction in the LDH precursor was accomplished by an ion exchange process using the heptamolybdate anion. The calcined Mn samples showed a higher surface area than those obtained from Zn. The sulfidation was carried out in situ with a heating ramp up to 673 K and the catalysts were evaluated in a tubular flow reactor. The catalytic evaluation of Zn and Mn-based materials for simultaneous thiophene HDS and cyclohexene hydrogenation (HYD) was conducted at 573 K and 20 bar. The results show that the Zn-based unsupported catalysts synthesized here exhibited higher selectivity for the HDS reaction than an industrial one.

Efficient and selective recovery of Mo and V from spent hydrodesulfurization catalysts via oxidation roasting followed by Na2CO3 and NaOH leaching

Spent hydrodesulfurization (HDS) catalysts containing large amounts of valuable metals, such as Mo and V, are hazardous solid wastes but also valuable secondary resources. However, the current recovery process suffers from the difficulty of balancing the leaching efficiency of Mo and V and their selectivity over Al. This work focused on the effect of phase transformation during roasting operation on the leaching behavior Mo, V, and Al and adopted an oxidation roasting followed by mixed alkali of Na2CO3 and NaOH leaching process to recover Mo and V from spent HDS catalysts. The results indicated that the phase transformation of Mo, V, and Al species during oxidation roasting process played a crucial role in achieving efficient leaching of Mo and V, as well as reducing leaching efficiency of Al. This transformation involved the change in Mo and V species changed from low valent compounds to high valent oxides, and Al2O3 from γ-phase to θ- and α-phases. In addition, efficient and selective leaching of 99.3% Mo and 97.8% V was realized, with only 0.03% Al being dissolved, by roasting the spent catalysts at 700 °C for 2 h and then leaching with a mixed solution of 1.2 mol/L Na2CO3 and 1.6 mol/L NaOH. The efficient and selective leaching of Mo and V can significantly reduce the burden of subsequent separation and purification, which provided an important prerequisite for the development of a new process for the recovery of Mo and V from HDS spent catalysts in alkaline systems.

Enhanced hydrotreating performance of hierarchical NiMo-S/Al2O3 catalysts through ZrO2 incorporation and template-driven structural modulation

A dual template-assisted approach for optimizing support structures to enhance catalytic efficiency in hydrotreating reactions is presented. Catalysts synthesized using activated carbon (AC) templates exhibited significantly higher activity in both hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) compared to those prepared with starch (ST) templates. The unique porous architecture, characterized by well-distributed meso- and macropores, facilitated efficient access of bulky molecules to the active sites. On the other hand, while the reactivity in the selective opening of the naphthenic ring (SONR), which is indicative of hydrocracking functionality, was similar across all catalysts, those modified with Zr exhibited a slight improvement. The catalysts displayed bifunctional characteristics, and their performance was influenced by the amphoteric nature of the support and the specific ratios of active species on the surface. A clear correlation between catalytic activity, selectivity, and the distribution of active sites was established.

Preparation of Ni2P with a Surface Nickel Phosphosulfide Layer by Reduction of Mixtures of Na4P2S6 and NiCl2

AbstractA series of physical mixtures of Na4P2S6 and NiCl2 (P‐NiPS(x), where x represents the P/Ni molar ratio) were employed for the preparation of Ni2P. For comparison, a sulfur‐containing Ni2P catalyst (Ni2P‐S) and a sulfur‐free Ni2P catalyst (Ni2P‐TPR) were prepared by reduction of Ni2P2S6 and a nickel phosphate precursor, respectively. The reduction of the P‐NiPS(x) precursors with P/Ni ratios above 2/3 yielded Ni2P catalysts with a distinct nickel phosphosulfide layer (NiPS(x)), and the Ni2P phase started to form at ca. 200 °C. The reduction of Ni2P2S6 to Ni2P most likely follows a disproportionation mechanism. The P3+ species in Ni2P2S6 disproportionate to PH3 and P5+ during the reduction, and PH3 further reacts with nickel and sulfur species to form Ni2P and the surface nickel phosphosulfide layer. The sulfur atoms in the nickel phosphosulfide phase were in the form of S2−. The introduction of sulfur to Ni2P favored the hydrogenation pathway of the hydrodesulfurization (HDS) of dibenzothiophene (DBT), but hardly affected the direct desulfurization (DDS) pathway and inhibited the hydrogenation of biphenyl. The DDS pathway rate constants of DBT HDS over the Ni2P‐TPR and NiPS(x) catalysts were observed to increase linearly with the increase in their surface Ni atomic concentrations.

Sulfured FeMo carbides and nitrides catalysts upgrade extra heavy crude oil quality

In the context of the energy transition scenario, effective sulfur management is crucial. Enhancing the quality of extra heavy crude oil (EHCO) through catalytic processes, specifically hydrotreatment, is essential for reducing pollutant emissions like SOx into the atmosphere. Traditional hydrotreatment, utilizing MoS2-based catalysts typically on Al2O3 support, faces challenges with EHCO due to its elevated S and N content, which hampers catalyst efficiency. Metal carbides and nitrides exhibit promising electronic structures that confer resistance to deactivation in the presence of heteroatoms. This study compares the catalytic performances of Fe-promoted Mo sulfides, carbides, and nitrides (FeMoS(C,N)) in the thiophene hydrodesulfurization (HDS) reaction, serving as a model molecule for sulfur removal. Subsequently, we investigate the upgrading of a Venezuelan EHCO in terms of pollutant reduction, API gravity, and feedstock aromaticity. Catalysts were prepared from oxide precursors, varying the (Fe/(Fe+Mo)) atomic ratios (x = 0.00, 0.10, 0.33, 0.50, and 1.00), employing a temperature-programmed reaction protocol. Catalytic upgrading of EHCO was conducted in a stirred batch reactor, and the results were compared with a commercial CoMo-based catalyst. FeMoC(N) outperformed the commercial catalyst in sulfur removal. The elemental composition and nitrogen content of the feed remained constant; however, the sulfur content of asphaltenes decreased. Furthermore, the API gravity of crude oil increased when employing FeMoS and FeMoN catalysts, except with FeMoC, possibly linked to dealkylation reactions and the enrichment of lighter fractions with alkanes. FeMoN increased asphaltene aromaticity, while FeMoC decreased it. These results highlight the promise of FeMoC(N) as catalysts for HDS and upgrading heavy feedstocks.

Efficient recovery of all valuable metals from spent HDS catalysts: Based on roasting mechanisms for enhanced selective leaching and separation

Recovery of all valuable metals such as Ni, Mo, V and Al from spent hydrodesulfurization (HDS) catalysts is beneficial to environmental protection and resource recycling. The current recycling process mostly considers the recovery of Mo and V than recovery of Ni and Al, and generates a large amount of difficult-to-decompose Ni-Al residue and wastewater. Aiming at the insufficiency of the current recycling process, in this study, a novel pyro-hydrometallurgical process for efficient and complete recovery of metals from spent HDS catalysts was proposed. The mechanisms of phase transformation during roasting and leaching are investigated by XRD, XPS and SEM in depth. The modulation of the phase transformation of the spent HDS catalyst in the oxidative roasting process is the key to the influence on the leaching of Ni and Al. Inhibition of θ-Al2O3 phase and Ni-Al spinel generation by controlled roasting can achieve efficient leaching of Mo, V, Ni and Al. Subsequently, Mo and V were selectively leached with 2 mol/L Na2CO3, and the alkaline leach residue obtained was treated with 6 mol/L HCl. The results showed that alkaline leaching efficiencies of Mo and V reached 99.73 % and 91.86 % while acid leaching efficiencies of Ni and Al reached 99.71 % and 90.27 %, respectively. The metals of acid leach solution were recovered by using N235, HBL110 and NaAlO2 stepwise. This new process has the advantages of high efficiency and comprehensive metal recovery, high product purity, and low amount of slag and wastewater, and has good prospects for industrial application.

Desulfurising Fuels Using Alcohol-Based Deep Eutectic Solvents Using Extractive Catalytic Oxidative Desulfurisation Method

Removal of sulfur compounds from transportation fuels is a requirement in the worldwide effort to reduce emissions from transportation fuels. Refineries use the hydrodesulfurisation (HDS) process to reduce sulfur compounds in fuels. However, the HDS process requires high hydrogen pressure and temperature, making it costly. An alternative to the HDS process is oxidative desulfurisation via solvent extraction, which requires low-temperature operating conditions. In this regard, deep eutectic solvents (DESs) are attractive for researchers to desulfurise transportation fuels via solvent extraction due to their low-cost. In our study, DESs were synthesised using phenylacetic acid (PAA) and salicylic acid (SAA) as hydrogen bond acceptors (HBAs) and tetraethylene glycol (TTEG) as hydrogen bond donor (HBD) in the mole ratio of 1:2. DESs were characterised by using Fourier transform infrared (FTIR) spectroscopy. Physicochemical properties of DESs, such as density, viscosity and refractive index, were also measured. The synthesised DESs were used to extract organosulfur compounds from model fuel and actual diesel. An oxidation study was carried out for model fuel and diesel, followed by solvent extraction using these synthesised DESs. The extraction efficiency for PAA/TTEG(1:2) and SAA/TTEG(1:2) was achieved as 50.16% and 38.89% for model fuel at a temperature of 30°C using a solvent to feed ratio of 1.0 while for diesel, it was 38% and 37%. However, it increased to 77%, 68% and 54%, 73%, respectively, for PAA/TTEG(1:2) and SAA/TTEG(1:2) when the feedstocks were oxidised. These results showed better extraction performance of DES PAA/TTEG(1:2) than that of SAA/TTEG(1:2) at low temperature 30°C using combined extractive catalytic oxidative desulfurisation. Hence, the DES synthesised using SAA and TTEG in the molar ratio of 1:2 works better as an extraction solvent for removing organic sulfur compounds from fuels at low temperatures.

Regulating the coordination environment of surface alumina on NiMo/Al2O3 to enhance ultra-deep hydrodesulfurization of diesel

Herein, a set of NiMo/Al2O3 catalysts with distinct coordination state of surface alumina were design and prepared by a facile calcination strategy. Various characterization methods were employed to analyze the structural properties of NiMo/Al2O3 catalysts, and the catalytic performances of corresponding catalysts were tested for hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT). The results indicate that the synthesized samples show uniform specific surface area (130 m2·g−1) and pore size (3.5 nm), but varying penta-coordinated aluminum content, which significantly influences the NiMo/Al2O3 catalysts’ surface acidity. Therein, NiMo/Al2O3-600 prepared by calcination at 600 °C exhibits the highest ratio of penta-coordinated aluminum species, which endows more abundant Brønsted acid than that of tetra- and hexa-coordinated aluminum counterparts, thereby substantially promoting the isomerization and direct desulfurization pathways of 4,6-DMDBT HDS, and thereafter considerably boosting the HDS performance of NiMo/Al2O3-600 with 94.5 % 4,6-DMDBT conversion, which is notably higher than that of NiMo/Al2O3-500 (74.4 %) and NiMo/Al2O3-700 (62.7 %).