Hydrodesulfurization Performance Research Articles

Study of the impregnation of NiMo assisted by chelating agents for hydrodesulfurization-supported catalysts over mesoporous silica

Abstract

The influence of hydrothermal crystallization temperature on a novel FDU-12 mesoporous composite assembled by ZSM-5 nanoclusters and its hydrodesulfurization performance for DBT and FCC diesel

A novel FDU-12 composite assembled by the ZSM-5 nanoclusters, which contained the primary and secondary building units of ZSM-5 zeolites, was synthesized successfully by in-situ assembly crystallization method. The influence of hydrothermal crystallization temperature on the properties of FDU-12 materials was studied comprehensively. The as-synthesized materials and catalysts, named as ZF-T and NiMo/ZF-T, were characterized by various methods, including XRD, nitrogen physisorption, pyridine-FTIR, H2-TPR, HRTEM and XPS characterization. The characterization results showed that NiMo/ZF-T series catalysts exhibited the satisfactory pore properties, more moderate metal-support interaction, preferable dispersion and sulfidation degree of Mo species than those of the commercial NiMo/Al2O3, which led to better hydrotreating performance than those of NiMo/Al2O3 (except NiMo/ZF-140 °C). Moreover, when the hydrothermal crystallization temperature was 110 °C, the obtained NiMo/ZF-110 °C catalyst achieved the best HDS and HDN efficiencies of 98.6% and 99.5%, respectively, which could be mainly ascribed to the synergistic effects of the largest specific surface area, the best dispersion and the highest sulfidation degree of Mo species as well as its appropriate acidic properties and moderate metal-support interaction.

Effect of sulfiding conditions on the hydrodesulfurization performance of the ex-situ presulfided CoMoS/γ-Al2O3 catalysts

The influence of sulfiding conditions in the ex-situ presulfidation process on the morphology and performances of CoMoS/γ-Al2O3 catalysts was studied in details for hydrodesulfurization (HDS) of dibenzothiophene. Surface and bulk characterization using XRD, HRTEM, XPS, TPR and FT-IR confirmed that the sulfiding agent mixture of (NH4)2S and elemental S effectively react with the supported Mo oxide to form intermediate thiosalts from mononuclear ammonium thiomolybdates to polynuclear ammonium thiomolybdates, namely the formed thiosalts from (NH4)2MoS4 to (NH4)2Mo2S12 and (NH4)2Mo3S13,which weaken the strong interaction between the γ-Al2O3 support and Mo oxide, resulting in maximum sulfidation of Mo oxide species. Mo species tend to agglomerate as the number of Mo nuclear increases, which further induces significant changes in the morphology of MoS2 particles. Such observation was further correlated with HDS activity and selectivity. The CoMoS/γ-Al2O3 catalyst with (NH4)2Mo2S12 as intermediate exhibits suitable slab lengths and stacking numbers of MoS2 slabs with optimal compromisebetween the Mo dispersion and ratios of edge sites to rim sites, and show the highest HDS activity. Therefore, a tailor-made catalyst with excellent HDS performance could be developed by adjusting the sulfiding conditions through ex-situ presulfidation method.

Effect of preparation method of nanosized zeolite HY-Al2O3 composite as NiMo catalyst support on diesel HDS

Two NiMo catalysts using the nanosized zeolite HY-Al2O3 composite (labeled as NYA) prepared by mechanical mixing method and sol-gel method as the support were prepared and characterized by XRD, BET, TPD, HTPR, HRTEM and FT-IR spectroscopy. The former catalyst possessed larger pore volume and specific surface area, more acid amount, superior reducibility of metal phase and higher dispersion of edge and corner Mo atoms, and showed higher hydrodesulfurization (HDS) performance. Compared with the former catalyst, the latter catalyst had more MoO3 to be converted to active type-II NiMoS phase, possessed higher stacking degree and bigger length of MoS2 slabs, and showed lower active phase dispersion. Although the sol-gel method was beneficial to increase the precursor ratio of type-II NiMoS phase, the poor pore structure caused by this method inhibited this advantage and reduced the catalytic activity of the catalyst.

Dependence of Morphology, Dispersion and Hydrodesulfurization Performance of Active Phases in NiMo/SBA‐15 on Loading Method

AbstractWith the aim of exploring the dependence of morphology, dispersion and hydrodesulfurization (HDS) activity of active phases over SBA‐15 on loading method, four NiMo/SBA‐15 catalysts have been prepared by two different Mo introduction strategies with varying MoO3 contents (13 and 19 wt.% in each approach, respectively). One of the approaches is the conventional incipient wetness impregnation (IM) and the other is a new‐proposed Mo‐based inorganic‐organic hybrid nanocrystals as the precursor with hydrothermal‐assisted (HA) loading method. The results show that metal species are severely aggregated at a high concentration by IM method, leading to the poorly distributed MoS2 slabs with large sizes and ultra‐high stacking layers. While in case of the HA approach, the organic molecules surrounding the Mo species can isolate Mo species effectively to prevent them from aggregation and greatly improve the dispersion of active phases, even at high MoO3 loadings. Therefore, the HDS activity is improved as increasing the amounts of MoO3 for the catalyst prepared with HA method because of the more active sites accessible to the reactants, however, HDS activity is decreased for the catalyst acquired by the IM method due to the serious metal aggregation. It is demonstrated that the HA method is favorable for the better dispersion of active phases over SBA‐15 with the help of organic molecules leading to the effective MoS2 morphology with remarkably enhanced catalytic activity, and such superiority of the HA approach is more prominent at high MoO3 loadings.

Effect of partial Mo substitution by W on HDS activity using sulfide CoMoW/Al2O3–TiO2 catalysts

A series of Al2O3–TiO2-supported trimetallic CoMoW catalysts were prepared with the aim to study the effect of Mo substitution by W on the catalyst performance in deep hydrodesulfurization (HDS) reaction. The oxide catalyst precursors were characterized by N2 physisorption, temperature-programmed desorption of NH3 (TPD-NH3), temperature-programmed reduction (TPR), diffuse reflectance spectroscopy (DRS UV–vis) and Raman spectroscopy. Sulfided catalysts were characterized by X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM), and tested in the dibenzothiophene (DBT) hydrodesulfurization (HDS) reaction carried out in a batch reactor at T = 320 °C and total H2 pressure of 5.5 MPa. It was found that partial substitution of Mo by W leads to enhancement of catalyst metal and acid functions. The W-rich catalyst (W/Mo atomic ratio of 1.2) exhibited the best catalytic behavior and a larger selectivity toward HYD route products than W-free CoMo counterpart. The catalyst structure-activity correlation suggested that this is due to the combined effects of the best dispersion of metal oxides, the enhance of the catalyst acidity, a lower stacking of Mo(W)S2 layers and the formation of mixed “Co–Mo(W)–S” phase. In contrast, the less active phase (CoMo2S4) was formed on the surface of the conventional CoMo catalyst. For all catalysts, The HDS reaction proceeds via direct desulfurization (DDS) and hydrogenation (HYD) reaction routes, the former being the main reaction route.

Synthesis of Mesoporous γ-Al₂O₃ with Spongy Structure: In-Situ Conversion of Metal-Organic Frameworks and Improved Performance as Catalyst Support in Hydrodesulfurization.

Over the past decades, extensive efforts have been devoted to modulating the textural properties, morphology and microstructure of γ-Al2O3, since the physiochemical properties of γ-Al2O3 have close correlations with the performance of hydrotreating catalysts. In this work, a spongy mesoporous γ-alumina (γ-Al2O3) was synthesized using Al-based metal-organic frameworks (Al-MOFs) as precursor by two-step pyrolysis, and this Al-MOF-derived γ-Al2O3 was used as hydrodesulfurization (HDS) catalyst support, to explore the effect of support on the HDS performance. Compared with industrial γ-Al2O3, the spongy alumina displayed well-developed porosity with relatively high surface area, large pore volume, and abundant weak Lewis acid sites. Based on catalyst characterization and performance evaluation, sulfurized molybdenum and cobalt molecules were able to incorporate and highly disperse into channels of the spongy mesoporous alumina, increasing the dispersion of active catalytic species. The spongy γ-Al2O3 was also able to enhance the diffusion efficiency and mass transfer of reactant molecules due to its improved texture properties. Therefore, the corresponding catalyst presented higher activities toward HDS of dibenzothiophene (DBT) than that from industrial alumina. The spongy mesoporous γ-alumina synthesized by Al-MOFs provides a new alternative to further develop novel γ-alumina materials with different texture and various nanoporous structures, considering the diversity of MOFs with different compositions, topological structures, and morphology.

Three-Dimensional NiS-MoS2/Graphene Heterostructured Nanohybrids as High-Performance Hydrodesulfurization Catalysts

A simplistic and scalable method for constructing three-dimensional (3D) highly porous aerogels composed of in situ formed NiS nanoparticles anchored onto two-dimensional (2D) MoS2/graphene assembly was reported. This process involves simple hydrothermal treatment followed by moderate thermal annealing. The as-synthesized nanohybrids were deeply investigated using several characterization techniques. The favorable interfacial interactions promoted the graphene surface to control the aggregation of layered MoS2 and uniform decoration of in situ formed NiS nanoparticles was achieved in the resulting nanohybrids. The resulting nanostructured 3D NiS-MoS2/graphene assembly produced synergistic effects and displayed remarkably enhanced hydrodesulfurization (HDS) performance toward dibenzothiophene conversion. The content of NiS cocatalyst controls the hydrogen spillover in the resulting nanoheterojunction catalysts and exhibits an enhanced HDS performance. The presented synthetic approach can be applied into th...

Optimal Synthesis of Hierarchical Porous Composite ZSM-5/SBA-16 for Ultradeep Hydrodesulfurization of Dibenzothiophene and 4,6-Dimethyldibenzothiophene. Part 2: The Influence of Aging Temperature on the Properties of NiMo Catalysts

ZSM-5/SBA-16 (ZS) supports were prepared using the two-step hydrothermal crystallization method. The effect of the aging temperature on the structural properties of the series ZS supports was studied. The prepared samples were analyzed by X-ray diffraction, scanning electron microscopy, N2 physisorption, 27Al magic angle spinning nuclear magnetic resonance, H2 temperature-programmed reduction, Raman, X-ray photoelectron spectroscopy, pyridine–Fourier transform infrared spectroscopy, and high-resolution transmission electron microscopy. The hydrodesulfurization performances of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) were examined at T = 340 °C and PH2 = 4 MPa. The NiMo/ZS-45 catalyst synthesized at the aging temperature of 45 °C exhibited the best catalytic activities of DBT and 4,6-DMDBT, which were attributed to its regular shape, well-organized pore structure, high sulfidation degree, and a compromise between the acidity and metal–support interaction (MSI, Mo–O–Si). Moreover, the possible DBT and 4,6-DMDBT HDS reaction networks over NiMo/ZS-45 were proposed.

Size‐Controllable Synthesis of NiMoS Nanoflowers for Hydrodesulfurization – Space‐Confinement Effect of Silica Nanospheres

The edge sites of NiMoS are highly catalytically active and are preferred over the surfaces. However, the stacking of the NiMoS layers is thermodynamically favored and limits the exposure of the active surface. Herein, we engineer the nanoflower structure to expose surface active sites through the synthesis of NiMoS nanoflowers assembled from ultrathin nanosheets. The well‐controlled fabrication of small NiMoS nanoflowers under the assistance of small silica nanospheres exposes abundant active sites. The exposed active sites and high surface area lead to superior hydrodesulfurization performance.

Effects of gallium addition to mesoporous alumina by impregnation on dibenzothiophene hydrodesulfurization performances of the corresponding NiMo supported catalysts

The effects of gallium (Ga) modification on mesoporous Al2O3 (MA) were studied, focusing on the morphology changes of the active phases and the application as catalyst support for catalytic performances for dibenzothiophene (DBT) hydrodesulfurization (HDS). MA samples with wide mesopore size distribution (MA-W), double mesopore size distribution (MA-D) and single mesopore size distribution (MA-S) were synthesized from the boehmite sol–gel via a hydrothermal synthesis method. The synthesized MA-S sample was modified with Ga2O3, and the corresponding sulfide NiMo supported catalysts were prepared. The as-synthesized samples were characterized by XRD, N2 physisorption, NH3-TPD, H2-TPR, HRTEM and XPS. Superior catalytic performance was observed over the NiMo/MA-S-2Ga catalyst due to the moderate interaction between the active metals and the supports; the superior morphology for Ni promoted MoS2 crystals, the highest sulfidation degree, the largest proportion of the NiMoS phase and the enhanced hydrogenation activity caused by the introduction of Ga species.

The development of catalysts and their stacking technology for diesel ultra-deep hydrosulfurization

The CoMo type and NiMo type catalysts with high amounts of Bronsted (B) acid sites, referred to as FHUDS-5 and FHUDS-6 respectively, were investigated for their hydrogenation performances including alkylation, hydrodesulfurization (HDS), and hydrodenitrogenation (HDN). The results demonstrated that, as hydroprocessing different diesel feedstocks, appropriate types of catalyst or their stacking system should be considered to achieve optimal HDS performance. As processing the feedstock with high sulfur content but low contents of nitrogen and aromatics, the CoMo type FHUDS-5 exhibited the highest HDS efficiency. On the other hand, the NiMo type catalyst FHUDS-6 presented the highest HDS and HDN efficiency as processing the feedstock with high amounts of nitrogen and aromatics. As processing the feedstock with medium contents of nitrogen and aromatics, the catalysts stacking system of FHUDS-6/FHUDS-5 presented the highest HDS efficiency due to their synergistic effects. The commercial applications for these hydroprocessing catalysts for the ultra-deep HDS on diesel at different refinery plants were also reported.

Optimal Synthesis of Hierarchical Porous Composite ZSM-5/SBA-16 for Ultradeep Hydrodesulfurization of Dibenzothiophene and 4,6-Dimethyldibenzothiophene. Part 1: The Influence of Inorganic Salt on the Properties of NiMo Catalysts

Series ZSM-5/SBA-16 (ZS) composites were prepared using various inorganic cations as additives, and the associated catalysts were tested for dibenzothiophene and 4,6-dimethyldibenzothiophene hydrodesulfurization (HDS). The structure–function relationship was investigated through various characterization methods. The NiMo/ZS–Mg catalyst using MgCl2 as an additive displayed higher HDS reaction rate constant and turnover frequency values, which could be attributed to its major acidity, higher metal–support interaction (MSI), higher sulfidation degree, higher dispersion degree, moderate stacking number, and shorter stacking length of sulfide Mo species, of which the higher acidity and higher MSI contributed more to the improvement of its HDS performance. Besides, the possible HDS pathways on the NiMo/ZS–Mg catalyst were provided.

Nondestructive construction of Lewis acid sites on the surface of supported nickel phosphide catalysts by atomic-layer deposition

In this paper, we have developed a new strategy to construct the acidic sites on the surface of supported transition-metal phosphide catalysts, which could precisely control the deposition of the Al2O3 atomic layer through atomic-layer deposition (ALD). A series of supported nickel phosphide catalysts decorated with Al2O3 film were prepared and characterized. The results show that Al2O3 film was deposited on the surface of the catalyst via AlOSi bonding, which does not affect or alter the characteristics of the as-prepared nickel phosphide phase. Most importantly, among all the Ni2P-based catalysts, the Ni2P/SiO2-ALD catalyst with 10 Al2O3 layers possesses the optimal performance in hydrodesulfurization and hydrodearomatization reactions. In particular, superior hydrogenation performances were considered to be strongly related to a synergistic effect between nickel phosphide and the modulated acidic property. This precise stepwise ALD strategy opens a convenient route and provides a prospective design guideline for constructing high-performance hydrogenation catalysts.

Effect of surface modification temperature on the hydrodesulfurization performance of Ni2P/MCM-41 catalyst

Highly active MCM-41-supported nickel phosphide catalysts for hydrodesulfurization (HDS) were synthesized by surface modification, in which the surface of supported Ni2P catalysts were directly modified at different temperatures by air instead of being passivated by an O2/N2 mixture. In addition, the prepared catalysts need not be activated under high temperature in H2 flow prior to the HDS reaction as in the conventional method. X-ray diffraction, X-ray photoelectron spectroscopy, N2-adsorption specific surface area measurements, CO chemisorption and transmission electron microscope were used to characterize the resulting catalysts. The effect of modification temperature on HDS performance of the catalysts was investigated. The results showed that the surface modification could promote the formation of smaller and more uniform Ni2P particles and the exposure of more Ni atoms. The modification method is simple and energy-saving, and the catalyst modified by air at 150 °C presents a dibenzothipohene conversion of 95.4%, which is 6.8% higher than that of a catalyst passivated by O2/N2 mixture followed by high-temperature and H2 pretreatments.

Morphology-performance relation of (Co)MoS2 catalysts in the hydrodesulfurization of FCC gasoline

The morphology-performance relation is of great importance for designing a catalyst with high performance in the selective hydrodesulfurization (HDS) of fluid catalytic cracking (FCC) gasoline. Herein, we report a simple one-pot hydrothermal method to prepare the unsupported MoS2 catalysts with controlled morphology by adjusting the pH values and using different precursors. It is found that smaller MoS2 crystallites are produced when the pH value decreases in the synthetic process. With the increased MoS2 crystallite size, the HDS selectivity factor (SF) increases from 1.46 to 1.52 for non-promoted MoS2 catalysts, and from 13.96 to 19.69 for Co-promoted MoS2 catalysts. On the other hand, for MoS2 catalysts with similar stacking, the MoS2 with longer slab length exhibits improved HDS selectivity (SF from 2.90 to 2.99). These results confirm that the slab length instead of the stacking for MoS2 particles is more important to influence the HDS selectivity. Due to the fact that the corner sites could catalyze both HDS and HYD reactions while edge sites only catalyze the HDS reaction, thus increasing the edge/corner ratio by preparing (Co)MoS2 catalysts with longer MoS2 slab length is an efficient way to improve the selectivity in the selective HDS of FCC gasoline.

Controllable Synthesis of Spherical Al-SBA-16 Mesoporous Materials with Different Crystal Sizes and Its High Isomerization Performance for Hydrodesulfurization of Dibenzothiophene and 4,6-Dimethyldibenzothiophene

Series Al-SBA-16 supports with different crystal sizes were fabricated by adding different inorganic salts to the synthesis system and used as the catalyst support for dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) hydrodesulfurization (HDS). The supports and the corresponding catalysts were well analyzed in depth to investigate their structure–property relationship. NiMo/AS-Mn catalyst with the smallest crystal sizes, the largest BET surface areas, and the highest total acid and Bronsted acid content displayed the highest kHDS of 4,6-DMDBT and DBT. HYD was the preferential route for the DBT HDS over NiMo/AS-Mn, while ISO was the preferential pathway for 4,6-DMDBT HDS. Moreover, the DBT and 4,6-DMDBT HDS reaction networks over NiMo/AS-Mn were proposed.

Self-Assembly of Hierarchically Porous ZSM-5/SBA-16 with Different Morphologies and Its High Isomerization Performance for Hydrodesulfurization of Dibenzothiophene and 4,6-Dimethyldibenzothiophene

ZSM-5/SBA-16 (ZS) composite materials with different morphologies were synthesized successfully. The series supports were utilized to prepare NiMo/ZS for dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) hydrodesulfurization (HDS) reactions. Series ZS supports and NiMo/ZS were well characterized to investigate their structure–property relationship. The NiMo/ZS catalyst (NiMo/ZS-3) with uniform morphology and well-ordered pore channels showed the maximum kHDS and TOF values of DBT and 4,6-DMDBT HDS. The kHDS value (13.9 × 10–4 mol g–1 h–1) of DBT over NiMo/ZS-3 was more than 2 times greater than that over the reference NiMo/ZS-M catalyst (5.5 × 10–4 mol g–1 h–1), 3 times greater than that over the NiMo/SBA-16 catalyst (4.4 × 10–4 mol g–1 h–1), and almost 4 times greater than that over the NiMo/ZSM-5 catalyst (3.5 × 10–4 mol g–1 h–1). Furthermore, the kHDS value (8.4 × 10–4 mol g–1 h–1) of 4,6-DMDBT over NiMo/ZS-3 was more than 3 times greater than that over the reference NiMo/ZS-M catalys...

Ultradeep Hydrodesulfurization of Feedstock Containing Cracked Gasoil through NiMo/γ-Al2O3 Catalyst Pore Size Optimization

The importance of ultra-deep hydrodesulfurization (HDS) of the cracked and straight run gasoil blend necessitate an extensive study on HDS catalyst optimization. Herein, we report a CO2 assisted neutralization of NaAlO2 aqueous solution conducted in a semi-batch membrane dispersion microstructured reactor, as a novel method to synthesize pseudoboehmite powders with different textural properties. A number of γ-Al2O3 catalyst supports as well as NiMo catalysts with the average pore sizes of 6.3 (5.2) to 21.5 (18.6) nm and 5.0 (3.7) to 20.3 (17.2) nm are prepared using the as synthesized pseudoboehmite powders. XRD analysis shows the sizes of all pseudoboehmite and γ-Al2O3 supports crystalline are in the nanoscale range. NH3 TPD results reveal that about half of the total NH3 (1.76 mmol NH3/g) is adsorbed on the surface of γ-Al2O3 support due to presence of strong acidic cites. FTIR spectrometer confirms formation of MoO4−2 species. The effects of catalyst pore size on HDS performance of the straight run gas...

Interfacial Engineering of NiMo/Mesoporous TiO2 Catalyst with Carbon for Enhanced Hydrodesulfurization Performance

1 and 5 wt% initial introduced contents of carbon (denoted as 1C/TiO2 and 5C/TiO2, respectively) were used to engineer the interfacial properties of mesoporous TiO2 for studying its hydrodesulfurization (HDS). The physical structure, surface properties and dispersion state of active species of samples were characterized by various technologies. The results showed that there was no obvious difference in physical structure of supports and catalysts before and after interfacial engineering. The carbon species formed on the surface of 1C/TiO2 was only graphitic carbon, whereas that of 5C/TiO2 was composed of mixed graphitic carbon and amorphous carbon. H2S-TPD results displayed that H2S adsorption–desorption behavior was mainly influenced by the different states of carbon species: H2S easily desorbed from 1C/TiO2 surface but strongly adsorbed on 5C/TiO2 surface. This was because H2S had a strong adsorption on amorphous carbon, but a weak one with the graphitic carbon. Sulfided active species were well formed in both 1C/TiO2 and 5C/TiO2 supported catalysts. The dibenzothiophene (DBT) conversion was increased to 98% on the 1C/TiO2 supported catalyst, but was decreased to 50% on the 5C/TiO2 supported catalyst, significantly different from the conversion of the pristine TiO2 supported catalyst (65%). It was found that the H2S adsorption–desorption behavior was closely related to the kind of interfacial carbon, which further influenced the HDS performance of mesoporous TiO2-supported HDS catalyst.