Thiophene Hydrodesulfurization Research Articles

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.

Bifunctional Ni2P/SAPO-11 catalyst for simultaneous hydroisomerization of 1-hexene and hydrodesulfurization of thiophene

A bifunctional Ni2P/SAPO-11 catalyst for the upgrading of fluidized catalytic cracking (FCC) gasoline was constructed to achieve the simultaneous removal of sulfur and prevention of octane number loss. In the preparation of Ni2P/SAPO-11, a modification with an ammonia post-treatment led to improved dispersion and high catalytic performance. Adsorption and kinetic study demonstrated that thiophene preferentially and more strongly occupied the Ni2P sites, so as to inhibit the undesired saturation of 1-hexene and facilitate the parallel skeletal isomerization on Ni2P/SAPO-11. The concerted synergy of Ni2P crystallites for hydrodesulfurization and moderate Brønsted acid sites of SAPO-11 for isomerization led to full conversion of thiophene and 1-hexene with 74 % selectivity to branched isomers at 320 °C and 1.5 MPa.

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.

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.

In-Situ Sulfurization Synthesis of Three-Dimensional Porous CoMoS/CMF Catalysts for Thiophene Hydrodesulfurization

In-Situ Sulfurization Synthesis of Three-Dimensional Porous CoMoS/CMF Catalysts for Thiophene Hydrodesulfurization

Microporosity and Catalytic Activity for Hydrodesulfurization of Pharmacosiderite Mo4P3O16 Synthesized at a Moderate Temperature.

Pharmacosiderite Mo4P3O16 (Pharma-MoPO) consists of [Mo4O4] cubane unit and [PO4] tetrahedral to form an open framework with a microporous structure similar to that of LTA-type zeolite. Although attractive applications are expected due to its microporous structure and redox-active components, its physicochemical properties have been poorly investigated due to the specificity of its synthesis, which requires a high hydrothermal synthesis temperature of 360 °C. In this study, we succeeded in synthesizing Pharma-MoPO by hydrothermal synthesis at 230 °C, which can be applied using a commercially available autoclave by changing the metal source. Through the study of the solids and liquids obtained after hydrothermal syntheses, the formation process of Pharma-MoPO under our studied synthesis conditions was proposed. Advanced characterizations provided detailed structural information on Pharma-MoPO, including the location site of a countercation NH4+. Pharma-MoPO could adsorb CO2 with the amount close to the number of cages without removing NH4+. Pharma-MoPO exhibited stable catalytic activity for the hydrodesulfurization of thiophene while maintaining its crystal structure, except for the introduction of sulfide by replacing lattice oxygens. Pharmacosiderite Mo4P3O16 was successfully obtained by hydrothermal synthesis at a moderate temperature, and its microporosity for CO2 adsorption and catalytic properties for hydrodesulfurization were discovered.

Hydrodesulfurization of Thiophene in n-Heptane Stream Using CoMo/SBA-15 and CoMo/AlSBA-15 Mesoporous Catalysts

Heterogeneous catalysts containing cobalt and molybdenum supported on mesoporous materials types SBA-15 and AlSBA-15 were synthesized for application in the HDS reactions of thiophene in the n-heptane stream. The materials were synthesized by the hydrothermal method using Pluronic P123 as a template. The calcined SBA-15 and AlSBA-15 supports were submitted to co-impregnation with solutions of cobalt nitrate and ammonium heptamolybdate, aiming for the production of 15% in mass of metal loading with an atomic ratio of [Co/(Co + Mo)] = 0.45. The obtained materials were dried and calcined to obtain the mesoporous catalysts in the forms of CoMo/SBA-15 and CoMo/AlSBA-15. The catalysts were characterized by XRD, TG/DTG, SEM, and nitrogen adsorption. From XRD analysis, it was verified that after the decomposition of the cobalt and molybdenum salts, MoO3, Co3O4, and CoMoO4 oxides were formed on the supports, being attributed to these chemical species, the activity for the HDS reactions. The catalytic activity of the obtained catalysts was evaluated in a continuously flowing tubular fixed-bed microreactor coupled on-line to a gas chromatograph, using an n-heptane stream containing 12,070 ppm of thiophene (ca. 5100 ppm of sulfur) as a model compound. The synthesized catalysts presented suitable activity for the HDS reaction, and the main obtained products were cis- and trans-2-butene, 1-butene, n-butane, and low amounts of isobutane. The presence of 1,3-butadiene and tetrahydrothiophene (THT) was not detected. A mechanism of the primary and secondary reactions and subsequent formation of the olefins and paraffins in the CoMo/SBA-15 and CoMo/AlSBA-15 mesoporous catalysts was proposed, considering steps of desulfurization, hydrogenation, dehydrogenation, THT decyclization, and isomerization.

N-octyltrimethylammonium bromide-assisted self-assembly of CoMo precursors to prepare CoMoS/Al2O3 catalysts for highly selective hydrodesulfurization of thiophene

A novel (C11H26N)2Co(MoS4)2 complex was prepared via the n-octyltrimethylammonium bromide-assisted self-assembly of CoMo precursors for the selective hydrodesulfurization (HDS) of thiophene. The complex was generated by the interaction between the negatively charged CoMo compound and the positively charged n-octyltrimethylammonium ions. Then positively charged bimolecular layers were formed owing to van der Waals forces between the C11H26N+ and the complex, and they were anchored on the negatively charged γ-Al2O3. Compared with CoMoS/γ-Al2O3 catalysts prepared by impregnation, the optimal CoMoN-0.3/γ-Al2O3 catalyst exhibited better performance for selective HDS due to the enhanced Mo dispersion, the close contact between Co and Mo, and the increased amount of CoMoS phases on γ-Al2O3. Among these catalysts, the optimal CoMoN-0.3/γ-Al2O3 catalyst with the highest concentration of CoMoS phases exhibited the highest HDS reaction rate constant of 6.95 × 10-6 mol·g−1·s−1 and the best selective factor of 26.1 for the selective HDS of thiophene with 1-hexene.

In situ synthesis of mesoporous NiS2-MoS2 sphere-flower hybrid for hydrodesulfurization of thiophene and 4,6-dimethyl-dibenzothiophene

A series of new NiS2-MoS2-x (x = 0–0.5) sphere-flower hybrids with different Ni/Mo molar ratios, synthesized via a one-pot hydrothermal method, were used as catalysts for hydrodesulfurization (HDS) of thiophene (TP) and 4,6-dimethyl-dibenzothiophene (4,6-DMDBT). The characterizations show that the microstructure of MoS2, including the size of MoS2 nano-flowers, the length of MoS2 slabs, and the number of defects, was regulated by changing Ni/Mo ratios. Increasing the Ni/Mo ratio in the NiS2-MoS2-x catalysts significantly boosts their HDS activity, with the optimum ratio being 0.2. In addition, the NiS2-MoS2-0.2 catalyst exhibits the best direct desulfurization performance, which is associated with the minimum ratio of average slab length (Lav) to average stacking number (Nav) as well as the highest concentration of Ni-promoted Mo sites and sulfur vacancies. Moreover, Ni-containing NiS2-MoS2-x catalysts, characterized by a highly stable sphere-flower configuration, exhibit superior structural stability and catalytic durability than the Ni-free NiS2-MoS2-0 catalyst.

Nanocrystalline Sulfided NiMoW Catalyst Supported on Mesoporous Aluminas for the Hydrodesulfurization of 4,6-Dimethyldibenzothiophene

Tri-metallic NiMoW catalysts prepared by impregnating mesoporous aluminas (pore sizes of ~9 nm and surface areas of ~225 m2/g) obtained by sol-gel (NiMoW/Al) and hydrothermal (NiMoW/AlHYDT) processes were investigated in the hydrodesulfurization (HDS) of thiophene and 4,6-dimethyldibenzothiophene (4,6-DMDBT) at H2 pressures of 1 MPa and 5.0 MPa, respectively. The supports and catalysts were characterized by N2 physisorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM). The NiMoW/AlHYDT catalyst, which was the most active in both test HDS reactions, was characterized by a pore size of 7.5 nm, whereas the pore size of the catalyst on sol-gel alumina (NiMoW/Al) was only 4.8 nm. Moreover, the NiMoW/AlHYDT catalyst exhibited reduction peaks shifted to a lower temperature during TPR, indicating weaker metal support interactions, a higher degree of Mo (79%) and W (48%) sulfidation, and an optimal layer slab length distribution of Mo(W)S2 nanocrystals preferentially between 2–4 nm with an average layer stacking of 1.7 compared to the NiMoW/Al counterpart.

Venezuelan red mud: an environmental passive with catalytic applications in the reaction of thiophene hydrodesulfurization

Venezuelan red mud: an environmental passive with catalytic applications in the reaction of thiophene hydrodesulfurization

Melamine foam-supported CoMo catalysts with three-dimensional porous structure for effective hydrodesulfurization of thiophene

The performance of the hydrodesulfurization (HDS) catalysts is generally subjected to the characteristics of supports. In this work, the melamine foam (MF) was employed as the support for fabricating a series of three-dimensional porous (3DP) CoxMo/MF supported HDS catalysts. The properties of the obtained HDS catalysts were characterized by XRD, TG, SEM, TEM, and low-temperature N2 adsorption–desorption techniques. The characterization results demonstrated that the CoxMo/MF supported catalysts possessed the 3DP structure, in which the metal oxides were attached to the prismatic pillars of the MF framework. The activity test results illustrated that the thiophene conversion over the Co2.0Mo/MF catalyst could reach 96.96% under 1 MPa and 360 °C. The unique 3DP structure with rich meso-/macropores, low average length and average stacking of crystalline MoS2 promoted the HDS activity of the Co2.0Mo/MF catalyst. This research shows the potential application of MF support in the field of catalysis and provides the possible direction for the further development of the supported HDS catalysts.

Simultaneous hydrodesulfurization of thiophene and benzothiophene over NiMoS catalysts supported on γ-Al2O3 composites containing ZSM-5

Alumina composites containing microporous ZSM-5 (Z-5) and mesoporous ZSM-5 (MZ-5), corresponding to xZA and xMZA, were developed by incorporating Z-5 and MZ-5 into γ - Al2O3, respectively. The two series of NiMoS/xMZA and NiMoS/xZA catalysts were prepared with these two composites as supports, respectively, and were used for the simultaneous hydrodesulfurization (HDS) of thiophene (T) and benzothiophene (BT). The results show that NiMoS/xMZA series catalysts exhibit higher HDS activity than that of NiMoS/xZA and NiMoS/γ-Al2O3, and the HDS activity of NiMoS/xMZA catalysts increases with the increase of MZ-5. The high HDS activity can be mainly attributed to the synergistic effects of the efficient diffusing pore channels, high dispersion of type II NiMoS phases, suitable acidity, and moderate Mo-support interaction. Moreover, the product distribution of HDS shows that the NiMoS/xMZA catalysts possess the dominant direct desulfurization (DDS) selectivity and the selectivity increases with the increase of MZ-5 content due to more corner sites and suitable Brønsted (B) acid sites, whereas the NiMoS/xZA catalysts perform more excellent hydrogenation (HYD) selectivity, and the selectivity increases with the increase of Z-5 content because of the existence of more edge sites. Based on this, the possible reaction network for T and BT hydrodesulfurization over the catalysts are proposed.

On the electronic properties and catalytic activity of MoS2–C3N4 materials prepared by one-pot reaction

MoS2–C3N4 composite materials with Mo content from 0.3 to 9 wt% have been prepared by means of one-pot synthesis from ammonium thiomolybdate (NH4)2MoS4 and urea-thiourea mixture. The solids were characterized by several physical techniques and tested in the thiophene hydrodesulfurization model reaction (HDS) and in photocatalytic hydrogen evolution reaction (PHER). Transmission electron microscopy (TEM) and X-ray absorption spectroscopy (XAS) show that even at the smallest Mo contents the solids contain individual MoS2 and C3N4 phases. As attested by powder X-ray diffraction (XRD), addition of (NH4)2MoS4 impacts the properties of obtained C3N4, probably at the growth stage, leading to more disordered carbon nitride phase. However, the materials demonstrate electronic properties close to a superposition of two separate MoS2 and C3N4 phases, as follows from the results of UV–visible diffuse reflectance spectroscopy (UV–vis DRS) combined with Ultraviolet and X-ray photoelectron spectroscopies (UPS, XPS). The band alignment diagram constructed from the UV–vis DRS, XPS and UPS data is of staggered type, the valence band edge of MoS2 being located above that of C3N4. Composite materials have high thiophene HDS activity, increasing in step with the Mo content, which proves fine dispersion of MoS2 phase and good availability of MoS2 edges to the reactants. By contrast, PHER activity first increases and then decreases with the Mo loading, reflecting on the competition between the ability of MoS2 to promote associative desorption of hydrogen and its role as a charge carriers recombination sink.

Single-source approach to amorphous RuS2 materials supported on SBA-15 and their catalytic activity for thiophene hydrodesulfurization

Single-source approach to amorphous RuS2 materials supported on SBA-15 and their catalytic activity for thiophene hydrodesulfurization

Global trends in technologies and nanomaterials for removal of sulfur organic compounds: Clean energy and green environment

• Various Technologies for sulfur organic compounds removal from fuels were reviewed. • Several nanomaterials used in desulfurization of thiophenes were discussed. • Trending catalysts used in hydrodesulfurization of thiophenes were reviewed. • Trends in desulfurization technologies to achieve complete sulfur removal were highlighted. Sulfur compounds, which commonly exist in substantial amounts in produced oil, gasoline, diesel, and jet fuel, cause a wide range of negative consequences including pollution, reduced engine efficiency, severe corrosion of pipelines, reactors, and equipment, as well as the poisoning of catalysts. Consequently, strict environmental rules and constraints are in place to keep the amount of sulfur in the air to a bare minimum. To achieve this objective, desulfurization or removal of sulfur is applied commonly in most refinery plants. In this review, numerous methods, adsorbents and catalysts used for the elimination of sulfur compounds are investigated. The review presents an overview of the emerging technologies for ultra-deep desulfurization to obtain ultra-low-sulfur fuels. The development of robust adsorbents and nanomaterials with ideal regeneration approaches is required to establish the capabilities of desulfurization processes. This review is expected to provide essential references and future directions for developing desulfurization technologies and materials for practical applications.

A Facile Synthesis of Highly Efficient MXene Supported CoMoS Catalysts for Hydrodesulfurization

AbstractIn this study, ammonium tetrathiomolybdate (ATM) and 2D‐layer MXene support were used to prepare more efficient MoS2 catalysts with cobalt promoter for the elimination of sulfur atoms in thiophene. A series of well‐dispersed and highly active MoS2 and Co−Mo−S phase on MXene catalysts were derived by thermal activation of precursors varying promoter cobalt to molybdenum molar ratio up to 0.6. The physicochemical properties of synthesized catalysts were characterized by XRD, TPR, SEM/EDS, XPS, HRTEM, and Raman spectroscopy. The as‐prepared MoS2/MXene and Co−MoS2/MXene catalysts were examined for thiophene hydrodesulfurization (HDS) at 300–400 °C. The synergetic effect between Co and few‐layer MoS2 on MXene, enhanced their HDS activity to ∼ 20.6 mmol g−1 h−1 with an excellent turnover frequency of about 55 h−1 achieved on Co−MoS2/MXene catalysts, which were 8‐fold higher than the conventional CoMoS/alumina catalyst. Co−MoS2/MXene catalysts produce high butenes selectivity ∼73% at low temperature, whereas, at high‐temperature alkane levels were increased ∼42% in CoMoS phase through hydrogen activation. Hence, the few‐layer MoS2 obtained from ATM and promoter Co intercalated MXene catalysts enhances the rate of C−S bond cleavage in HDS, and the result is scrubbing a large volume of sulfur atoms in clean fuel processes.

The evolution of NiMo unsupported catalysts with 3DOM structure for thiophene hydrodesulfurization

The microstructure changes of unsupported hydrodesulfurization (HDS) catalysts could significantly influence their properties, including the morphology, the dispersity of active components, and HDS activity. In this work, three-dimensionally ordered macroporous (3DOM) NiMo unsupported catalysts were fabricated using the polymethyl methacrylate (PMMA) colloidal crystal template with the assistance of citric acid in 95% ethanol solution. The TG/DTG, XRD, SEM, HRTEM, low-temperature N2 adsorption-desorption, and H2-TPR techniques were employed to intensively characterize the obtained unsupported catalysts. The characterization results indicated that all catalysts possessed a well-defined 3DOM structure, which could not only provide abundant active sites and high specific surface area but also enhance the contact efficiency between the active sites and reactants. Furthermore, among the prepared 3DOM unsupported catalysts, the 3DOM NiMo-1 exhibited an excellent thiophene conversion rate of 99.4% under the reaction conditions of 360 °C and 1.0 MPa. This research provided an evolution direction for designing the high-efficient unsupported HDS catalysts.

Role of Phosphorus and Triethylene Glycol Incorporation on the Activity of Model Alumina‐Supported CoMoS Hydrotreating Catalysts

AbstractEnvironmental regulations concerning fuel‐related sulfur emissions are currently experiencing worldwide expansion. This is motivating the research and development of improved hydrotreating (HDT) catalysts with carefully engineered synthesis methods that maximize activity as ultimate goal. In this contribution, the effect of phosphorus doping and triethylene glycol (TEG) incorporation on the genesis of the CoMoS phase of model HDT catalysts is assessed. Following a surface‐science approach, α‐Al2O3 single crystals with four orientations: C(0001), A(11 0), M(10 0), and R(1 02) are used as model supports of the traditional γ‐Al2O3 support for the study of active phase‐support interactions at the molecular scale. The model catalysts are prepared by traditional impregnation of a solution containing metal and phosphorus precursors and TEG. The catalysts are characterized in the sulfide phase by XPS, XAS, TEM, and AFM, revealing that the calcination step is key in the emergence of distinctive metal‐support interactions, which are directly related to the nature of alumina surface sorption sites. In addition, TEG incorporation on dried catalysts increases metal sulfidation and enhances promotion with respect to non‐additivated systems, especially at mild sulfidation temperatures. The catalytic activity of the model catalysts is tested in a thiophene hydrodesulfurization reaction, revealing the following activity trend with respect to alumina surface orientations: A ≫ M >R , C(0001). This trend is identical to the one observed for non‐phosphorus doped non‐TEG additivated model systems, confirming the predominance of surface effects on the catalytic activity over those exerted by P and TEG. By transposing these results to the industrial γ‐Al2O3 support, the (100) facet would provide surface sites that lead to better performing catalysts. This could result in the development of novel supports, engineered to expose surface sites that maximize hydrotreating activity.

Characterization and HDS activity of Mo and NiMo sulfided catalyst prepared by thioglycolic acid assisted hydrothermal deposition method

Dispersed NiMo sulfide catalysts were synthesized by hydrothermal deposition method with the assistance of thioglycolic acid (TGA) as sulfiding agent ex situ at 160 °C. The prepared samples were characterized by SBET, XRD, SEM, FTIR, XPS, TPR/TPS, TPD-NH3. The catalyst activity was investigated during hydrodesulfurization (HDS) of thiophene (TH) at 340 °C. XRD and XPS methods showed that this hydrothermal synthesis of Mo and NiMo solids yielded sulfide crystalline phases with high bulk and surface S/Mo ratio. Re-sulfidation of the Ni-containing samples led to an increase in surface area, which was thus able to redisperse the NiMo sulfide active sites. The results of temperature programmed sulfidation measurements combined with mass spectrometric analysis (TPS-MS) of the catalysts revealed the formation of a fraction of TGA species that remained in the pores of the sample with the highest TGA content. In the NiMo catalyst prepared at TGA/Mo molar ratio of four, this TGA enhanced the amount of NiMoS phase in the catalyst and positively affected the HDS activity.