Dibenzothiophene Hydrodesulfurization Activity Research Articles

Optimization of dendritic TS-1/Silica micro–mesoporous composites for efficient hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene

A novel composite material (TD) composed of TS-1 microcrystalline and dendritic mesoporous silica nanospheres (DMSNs) was successfully prepared. The TD composite material had open pore structure and large specific surface area, which was conducive to the mass transfer of reactants and products. The Ti element in TS-1 could be used as an electron assistant, and the spillover d-electrons were conducive to the improvement of the sulfidation and dispersion of MoS2, thereby forming more type II MoS2 active phases. The incorporation of Ti could bring more Brønsted (B) and Lewis (L) acid, which was conducive to the hydrogenation pathway (HYD) selectivity (41.2%) of dibenzothiophene (DBT) hydrodesulfurization (HDS) and isomerization (ISO) route selectivity (21.9%) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) HDS, thus improve the HDS activity of DBT and 4,6-DMDBT. NiMo/TD-70 (Aging temperature = 70 °C) had the best HDS activities of DBT (99.0%) and 4,6-DMDBT (93.7%) due to its large open pore structure, good acidity, suitable metal-support interaction (MSI) and perfect dispersion of the metallic active sites.

Effect of particle size on the sulfur resistance of nickel phosphide hydrodesulfurization catalysts

The effect of particle size on sulfur resistance of nickel phosphide (Ni2P) catalysts for the hydrodesulfurization (HDS) reaction was probed using Ni2P nanoparticles encapsulated in mesoporous silica (Ni2P@mSiO2). The Ni2P@mSiO2 nanocatalysts, having well-defined particle sizes of 5.9, 11.2 and 17.1 nm, were investigated for the HDS of dibenzothiophene (DBT) in the presence of a co-feed of H2S. The Ni2P@mSiO2 nanocatalysts were characterized by a range of techniques including CO chemisorption to determine active site densities, and sulfur quantification to probe sulfur incorporation during HDS measurements or treatment in a mixture of H2S/H2. The extent of sulfur deactivation depended strongly on Ni2P particle size, with Ni2P@mSiO2-5.9 nm showing little change in DBT HDS activity or turnover frequency (TOF) before and after co-feeding H2S, while Ni2P@mSiO2-17.1 nm exhibited a significant decrease in HDS activity and TOF after co-feeding H2S. Further, the Ni2P@mSiO2-5.9 nm nanocatalyst exhibited stable HDS activity when brought on-stream, while Ni2P@mSiO2-17.1 nm experienced a 40% loss of HDS activity during the initial 3 h on-stream and then stable activity thereafter. The composition of the phosphosulfide phase (NixPySz layer) formed on the surface of the Ni2P particles under HDS reaction conditions also depended strongly on particle size, with the Ni2P@mSiO2-5.9 nm (S/Nisurf = 0.16) having a substantially lower S content than the Ni2P@mSiO2-17.1 nm (S/Nisurf = 0.53). These results indicate that the surface restructuring of Ni2P associated with formation of a phosphosulfide layer is particle size dependent and leads to active sites with significantly different intrinsic activities for the HDS reaction.

Testing conditions for CoMo HDS catalyst in the kinetic region: integrated approach using the math calculations and catalytic experiments

The main idea of the investigation was to define testing parameters with the lowest influence of internal and external diffusion on catalytic activity in hydrodesulfurization of dibenzothiophene. Traditional experimental methods were used to determine the conditions for the influence of internal and external diffusion. Simultaneous change of a linear feedstock rate and a catalyst loading at constant weight hour space velocity were used to determine the process temperature (240–260 °C) at which the impact of external diffusion is minimal. Catalytic tests, including the variation of the catalyst fraction size, were carried out to define the conditions with the lowest influence of internal diffusion. It was found that when the catalyst with the fraction size of 0.1–0.25 mm was used, the fluctuation of sulfur conversion was the smallest. Besides, to validate experimental results, the calculations were performed with mass balance equations and expressions used for HDS modeling. The resulting data and catalytic experiments demonstrated that the lowest influence of internal and external diffusion is achieved at a temperature process less than 260 °C and a catalyst fraction of 0.1–0.25 mm.

Design of improved CoMo hydrotreating catalyst via engineering of carbon nanotubes@alumina composite support

An efficient strategy for the synthesis of nanostructured composite supports for CoMoS hydrotreating catalysts has been proposed. The synthesis concept is based on the growth of multi-walled carbon nanotubes (MWCNTs) on alumina crystallites modified with Fe2Co nanoparticles. The morphology and structural characteristics of the obtained MWCNT@Al2O3 supports were tuned by varying Fe2Co content. A comprehensive analysis using advanced techniques revealed the optimal content and structural characteristics of MWCNTs in composite supports that positively affect the morphology of the sulfide component. It has been established that for the best CoMoS/MWCNT@Al2O3 catalyst, which is characterized by the highest dispersion of sulfide component and CoMoS phase content, the activity in dibenzothiophene hydrodesulfurization and quinoline hydrodenitrogenation significantly exceeds the activity of CoMoS/Al2O3 and CoMoS/MWCNT catalysts. The proposed approach can be applied to improve the activity of both conventionally used hydrotreating catalysts and catalysts for other practically important processes by carefully tuning metal-support interaction.

Is it possible to reactivate hydrotreating catalyst poisoned by silicon?

The feasibility of the reactivation of CoMo/Al2O3 hydrotreating catalysts poisoned by Si compounds has been studied. CoMo/Al2O3 catalysts poisoned with 3, 4 and 5 wt.% of silicon were obtained during hydrotreating of diesel fraction contaminated with decamethylcyclopentasiloxane. Catalysts poisoned by different amount of silicon were regenerated by oxidative treatment and subsequently reactivated using citric acid solution. The catalysts were studied by nitrogen adsorption-desorption method, CHNS analysis, UV–vis, thermal analysis, SEM, HRTEM, XPS. It was shown that the hydrodesulfurization activity of regenerated catalysts decreased with increasing silicon content. According to UV–vis results, the increase in Si content on the spent catalyst leads to the formation of CoOx oxides after oxidative regeneration. Probably, cobalt oxides do not promote MoS2 slabs during sulfidation, convert to inactive Co species and decrease hydrodesulfurization activity. After reactivation procedure, there was the increase in active component particles dispersion, while catalytic activity in hydrodesulfurization of dibenzothiophene and hydrodenitrogenation of quinoline increased. It was established that hydrodesulfurization and hydrodenitrogenation activities of CoMo/Al2O3 catalyst with less than 3 wt.% of Si could be completely restored by reactivation.

CoNiMo/Al2O3 sulfide catalysts for dibenzothiophene hydrodesulfurization: Effect of the addition of small amounts of nickel

Trimetallic CoNiMo hydrodesulfurization (HDS) catalysts were herein synthesized on Al2O3 support through an incipient wetness co-impregnation procedure using ammonium heptamolybdate and cobalt (and nickel) acetate as precursors. CoNiMo catalysts were obtained by adding in a small proportion of nickel with a molar amount representing between 1 and 10% of the total Co atomic loading. This addition of low amounts of nickel allows keeping the (Co + Ni)/(Co + Ni + Mo) molar ratio close to the optimum value of 0.3. The as-formed catalysts were labeled as CoNixMo/Al2O3 with x the relative stoichiometry of Ni compared to Co. Catalysts were then characterized by N2 adsorption-desorption isotherms, X-ray diffraction, ICP-OES spectroscopy, Raman spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Catalysts were tested in the HDS of dibenzothiophene (DBT). Results show a significant impact of adding small amounts of nickel to alumina-supported Co-promoted MoS2 on the final HDS activity. While up to CoNi0.03Mo/Al2O3, the resulting HDS activity is hardly influenced by the addition of nickel, a strong beneficial effect is observed for CoNi0.05Mo/Al2O3 with activity reaching a value of 7.2 × 10−7 mol.gcat−1.s−1. Increasing further, the amount of nickel abruptly decreased the DBT HDS activity. Interpretation of these results is then provided considering the additional role of nickel for improving the intrinsic activity of the HDS sites.

Effect of the Gallium and Vanadium on the Dibenzothiophene Hydrodesulfurization and Naphthalene Hydrogenation Activities Using Sulfided NiMo-V2O5/Al2O3-Ga2O3

The effect of Ga and V as support-modifier and promoter of NiMoV/Al2O3-Ga2O3 catalyst on hydrogenation (HYD) and hydrodesulfurization (HDS) activities was studied. The catalysts were characterized by elemental analysis, textural properties, XRD, XPS, EDS elemental mapping and High-resolution transmission electron microscopy (HRTEM). The chemical analyses by X-ray Fluorescence (XRF) and CHNS-O elemental analysis showed results for all compounds in agreement, within experimental accuracy, according to stoichiometric values proposed to Mo/Ni = 6 and (V+Ni)/(V+Ni+Mo) = 0.35. The sol-gel synthesis method increased the surface area by incorporation of Ga3+ ions into the Al2O3 forming Ga-O-Al bonding; whereas the impregnation synthesis method leads to decrease by blocking of alumina pores, as follows NiMoV/Al-Ga(1%-I) < NiMoV/Al-Ga(1%-SG) < NiMo/Al2O3 < Al2O3-Ga2O3(1%-I) < Al2O3-Ga2O3(1%-SG) < Al2O3, propitiating Dp-BJH between 6.18 and 7.89 nm. XRD confirmed a bulk structure typical of (NH4)4[NiMo6O24H6]•5H2O and XPS the presence at the surface of Mo4+, Mo6+, NixSy, Ni2+, Ga3+ and V5+ species, respectively. The EDS elemental mapping confirmed that Ni, Mo, Al, Ga, V and S are well-distributed on Al2O3-Ga2O3(1%-SG) support. The HRTEM analysis shows that the length and stacking distribution of MoS2 crystallites varied from 5.07 to 5.94 nm and 2.74 to 3.58 with synthesis method (SG to I). The results of the characterization sulfided catalysts showed that the synthesis method via impregnation induced largest presence of gallium on the surface influencing the dispersion V5+ species, this effect improves the dispersion of the MoS2 phase and increasing the number of active sites, which correlates well with the dibenzothiophene HDS and naphthalene HYD activities. The dibenzothiophene HDS activities with overall pseudo-first-order rate constants’ values (kHDS) from 1.65 to 7.07 L/(h·mol·m2) follow the order: NiMoV-S/Al-Ga(1%-I) < NiMo-S/Al2O3 < NiMoV-S/Al-Ga(1%-SG), whereas the rate constants’ values (k) of naphthalene HYD from 0.022 to 2.23 L/(h·mol·m2) as follow: NiMoV-S/Al-Ga(1%-SG) < NiMo-S/Al2O3 < NiMoV-S/Al-Ga(1%-I). We consider that Ga and V act as structural promoters in the NiMo catalysts supported on Al2O3 that allows the largest generation of BRIM sites for HYD and CUS sites for DDS.

Dendritic micro–mesoporous composites with center-radial pores assembled by TS-1 nanocrystals to enhance hydrodesulfurization activity of dibenzothiophene and 4,6-dimethyldibenzothiophene

A novel dendritic composite (TD) with an open center-radial pore structure using TS-1 nanocrystals as microporous precursors was successfully synthesized by a facile method. TS-1 nanocrystals were embedded into the framework of dendritic mesoporous silica nanospheres (DMSNs) to form Si–O–Ti bonds, which was beneficial for generating more S vacancies of MoS2 active phases. The NiMo/TD-2 catalyst had a larger surface area and stronger metal–support interaction, resulting in higher sulfidation and dispersion degrees of MoS2 active phases over the sulfided NiMo/TD-2 catalyst, which was consequently favored to improve the hydrodesulfurization (HDS) activity of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). Furthermore, the NiMo/TD-2 catalyst with an SiO2/TiO2 molar ratio of 150 exhibited higher HDS performance for DBT and 4,6-DMDBT than other NiMo/TD catalysts and the commercial NiMo/Al2O3 catalyst. Moreover, the NiMo/TD-2 catalyst possessed more Brønsted and Lewis acid sites, thus promoting the hydrogenation of DBT and the isomerization of 4,6-DMDBT.

Hydrodeoxygenation and hydrodesulfurization over Fe promoted Ni2P/SBA-15 catalyst

The Fe-doped Ni2P/Fe-SBA-15 was prepared by the temperature programmed reduction method at a relative low temperature of 673 K. The effect of Fe on the catalytic performance for benzofuran (BF) hydrodeoxygenation (HDO) and dibenzothiophene (DBT) hydrodesulfurization (HDS) were investigated. The catalysts were characterized by means of X-ray diffraction (XRD), N2 adsorption-desorption, inductively coupled plasma mass spectrometry (ICP-MS), X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption of ammonia (NH3-TPD), and transmission electron microscope (TEM) and CO uptakes. The results indicate the incorporation of Fe into SBA-15 contributes to the exposure of smaller Ni2P particles (5.6 nm) with an uniform dispersion, along with enhancement of weak and medium acid strengths. Compared with Ni2P/SBA-15, the Fe-doped Ni2P/Fe-SBA-15 exhibited a much higher BF conversion of 91.7% with an improved total deoxygenated product yield of 83.3%. The excellent HDO performance of Ni2P/Fe-SBA-15 can be ascribed to the exposure of highly-dispersed smaller Ni2P particles. Meanwhile, the improved dehydration of 2-EtPh to EB and the high deoxygenated product selectivity can be attributed to the enhanced acidity. As compared to the Ni2P/SBA-15, the Fe-doped Ni2P/Fe-SBA-15 showed a higher DBT HDS activity of 96.3% with the BP formation at a great proportion of 90.3%, indicating that DBT was mainly transformed through the desulfurization pathway during HDS.

Promotional effect of TiO2 on quinoline hydrodenitrogenation activity over Pt/γ-Al2O3 catalysts

The structural and electronic properties of Pt/γ-Al2O3 catalysts for quinoline hydrodenitrogenation were modified by introducing TiO2. The results indicated that the addition of TiO2 enhanced the reducibility of PtOx species, which increased the number of metallic Pt active sites. TiO2 facilitated quinoline hydrodenitrogenation over Pt/γ-Al2O3 catalysts, with an increase in activity from 80.6% to 91.5% at 340 °C and 3 MPa when the TiO2 content was 16.3 wt%; and improved resistance to the inhibiting effects of sulfur species, therefore the hydrodenitrogenation activity decreased less sharply. High activity in dibenzothiophene hydrodesulfurization, i.e., above 91%, was maintained with different sulfur concentrations. Density functional theory calculations confirmed that dibenzothiophene and quinoline had comparable adsorption energies on a metallic Pt surface. We propose that the partially reduced TiO2 mitigated inhibition by dibenzothiophene and enhanced the hydrogenation of quinoline via the formation of electron-rich Pt species.

Effect of cerium content on textural and hydrodesulfurization performance for dibenzothiophene over a bulk Ni2P catalyst

A series of ceria promoted Ni2P catalysts were prepared and evaluated in dibenzothiophene hydrodesulfurization steam. These catalysts were characterized by X-ray diffraction, N2 adsorption–desorption, CO chemisorptions, and X-ray photoelectron spectroscopy. The results showed that the addition of ceria into the bulk Ni2P catalyst was conducive to the formation of the Ni2P phase and contributed to a higher surface area, leading to a better dispersion and smaller crystallite size of Ni2P particles. The CexNi2P catalysts showed higher dibenzothiophene hydrodesulfurization activity than Ni2P catalyst and the Ce0.09Ni2P catalyst showed the highest dibenzothiophene hydrodesulfurization activity. The Ce0.09Ni2P catalyst showed a dibenzothiophene hydrodesulfurization conversion of 94.5% at the reaction conditions of 320°C, 4.0 MPa, a H2/oil ratio of 500 (V/V), and a weight hourly space velocity of 8.0 h−1. The dibenzothiophene was mainly transformed through desulfurization pathway.

Colloidal Synthesis Protocol of Shape- and Dimensionally-Controlled Transition-Metal Chalcogenides and Their Hydrodesulfurization Activities

We present a single-step ligand-directed colloidal synthesis protocol for the selective growth of dimensionally- and shape-controlled niobium disulfide (NbS2) nanostructures. A systematic modulation of the reaction conditions resulted in the development of monolayer nanosheets, which alternatively grew as laterally confined (<100 nm) 2D nanostructures using an appropriate mixture of coordinating ligands with different functional groups. The lateral size reduced to ∼50 nm by increasing the amount of a chalcogen source (carbon disulfide, CS2), which promoted planar growth to form 0D nanohexagons and 1D hexagonal nanorods. A noncoordinating solvent suppressed anisotropic growth and resulted in the formation of 0D nanospheres. Nanohexagons with the highest fraction of corner and edge active sites delivered the highest activity in dibenzothiophene hydrodesulfurization.

Hydrodesulfurization Properties of Dibenzothiophene over NiMo Catalysts Supported on Cubic Fm3m Mesoporous Structure and High-Framework Aluminum-Modified AlKIT-5

The AlKIT-5 sample with Fm3m symmetry order structure and different Si/Al ratios was first synthesized by chemical grafting method. The 27Al NMR result of the AlKIT-5 sample proves that most aluminum species have been incorporated into the silicon framework. The oxidized supports and catalysts were characterized by XRD, N2 adsorption, 27Al MAS NMR, SEM, TEM, Py-FTIR, and Raman spectroscopy, and the series of sulfided catalysts were investigated by XPS and HRTEM. The corresponding NiMo catalysts were obtained by impregnation method, and the hydrodesulfurization activity for dibenzothiophene (DBT) was tested in a high-pressure microreactor under different weight hourly space velocity (WHSV, 10–100 h–1) values. All of the catalysts based on KIT-5 mesoporous material support showed better HDS efficiencies than that of the NiMo/AlMCM-41 catalyst, benefiting from the interconnected large pore structure. The NiMo/AK-10 catalyst exhibited the best HDS activity (99.2%) when the WHSV was 10 h–1, which resulted from...

Highly active P-doped sulfided NiMo/alumina HDS catalysts from Mo-blue by using saccharose as reducing agents precursor

Saccharose (SA) was used as organic additive in simultaneously impregnated P-doped NiMo/Al2O3 hydrodesulfurization (HDS) catalysts (Mo, Ni and P at 12, 3, and 1.6 wt%, respectively). One-pot impregnating solutions were prepared by MoO3 digestion (∼353 K) in diluted aqueous H3PO4, followed by 2NiCO3·3Ni(OH)2·4H2O addition. Saccharose (SA, SA/Ni = 0.5, 1–3) was dissolved in originally emerald-green impregnating solutions which changed to cobalt blue by room-temperature aging (2–4 days, depending on SA concentration) due to Mo-blue formation by partial molybdenum species reduction. After sulfiding of samples impregnated with SA shorter MoS2 slabs of enhanced stacking were observed (by HR-TEM). Ni and Mo dispersion and nickel sulfidability (as determined by XPS) increased with the amount of organic modifier. Enhanced hydrodesulfurization activity in dibenzothiophene HDS was registered for catalyst obtained from Mo-blue precursor as to that of corresponding materials obtained from conventional emerald-green NiMoP impregnating solutions (with or without SA). However, in solids at high saccharose content (SA/Ni = 3) enhanced “NiMoS” phase amount was not reflected in improved activity. Probably, excessive amount of carbonaceous deposits from SA residua decomposition during catalyst activation provoked partially plugged porous network (as determined by N2 physisorption) in sulfided formulations. That fact seemed to limit accessibility of reactant molecules to surface active sites. Mo-blue precursor obtained through monosaccharides partial reduction seemed to play decisive role in obtaining HDS catalysts of improved properties. Saccharose results a highly soluble, cheap and non-toxic environmentally-friendly additive to produce catalysts of enhanced HDS activity.

Synthesis of an Ni2P catalyst supported on Na-MCM-41 with highly activity for dibenzothiophene HDS under mild conditions

A novel and simple method to synthesize supported Ni2P/Na(x)-MCM-41 catalysts (where x is the mass fraction of Na-to-MCM-41 in terms of percentage) at a lower reduction temperature by incorporation of Na was described. The catalysts were characterized by H2 temperature-programmed reduction (H2-TPR), X-ray diffraction (XRD), N2 adsorption–desorption, CO uptake, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The effect of Na on the structure of catalysts and catalytic properties for the dibenzothiophene (DBT) hydrodesulfurization (HDS) was investigated, which confirmed that a suitable amount of Na can promote highly dispersed Ni2P particles. The Na preferentially interacts with phosphate to generate the sodium phosphate and therefore suppresses the formation of stronger P–O–P bonds, which enables the phosphide catalyst to be easily formed at a lower reduction temperature. Compared with conventional phosphate (973–1273 K), the reduction temperature of Ni2P/Na(x)-MCM-41 catalyst was relatively low (773 K). The Ni2P/Na(x)-MCM-41 catalyst with x = 1.0 showed the maximum DBT conversion of 91.6%, which is higher than that of Ni2P/M41 without Na (80.3%).

Comparable investigation of unsupported MoS2 hydrodesulfurization catalysts prepared by different techniques: Advantages of support leaching method

Unsupported molybdenum disulfide catalysts were synthesized from ammonium tetrathiomolybdate with chitosan, hexadecylammonium and Triton X100 as structural agents by leaching of MoS2/Al2O3 and MoS2/C/Al2O3 catalyst supports with HF acid and covering of “FeS” seeds by the MoS2 shell. Activation of the solids was performed under the H2S/H2 flow or by the decomposition of precursors in the presence of a hydrocarbon solvent in an autoclave reactor with varied H2 pressure. X-ray diffraction, N2 adsorption, temperature-programmed reduction, X-ray photoelectron spectroscopy and transmission electron microscopy techniques were used to characterize their structure and morphology. The nature of organic additives and activation conditions affect the surface area, pore size distribution, and morphological characteristics of MoS2 particles. Hydrodesulfurization of dibenzothiophene was performed in an autoclave reactor over unsupported MoS2based catalysts. The catalytic behavior of bulk MoS2 catalysts showed that the hydrogenation pathway prevailed over the direct desulfurization pathway. Higher HYD/DDS selectivity for dibenzothiophene hydrogenation was observed with the bulk molybdenum disulfide catalyst formed by etching of the MoS2/Al2O3 catalyst support. Unsupported Mo sulfide catalysts exhibited high hydrogenation activity in dibenzothiophene hydrodesulfurization and, therefore, might find wide applications in hydroprocessing of heavy feed and co-hydrotreating of petroleum fractions and plant oils.

Comparison of citric acid and glycol effects on the state of active phase species and catalytic properties of CoPMo/Al2O3 hydrotreating catalysts

CoPMo/Al2O3 catalysts were prepared using H3PMo12O40 and Co complexes with citric acid (CA) or non-complexing organic additives such as ethylene glycol (EG), diethylene glycol, triethylene glycol (TEG), glycerol, and a mixture of EG and CA. The catalysts were characterized by low-temperature N2 adsorption, Raman spectroscopy, thermogravimetric analysis, temperature-programmed reduction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. The prepared samples were tested in hydrodesulfurization (HDS) of dibenzothiophene (DBT). The addition of either CA or glycols led to several beneficial effects such as weakening of the slab-support interaction at enhancing the promotion degree, dispersion and stacking number of the CoMoS species. It has been shown that the promotion degree of CoMoS edges increased with a pore volume gain by the additive-impregnated catalysts after their sulfidation. Catalysts with CA, TEG or the EG-CA mixture demonstrated higher activity in DBT HDS. Probable reasons for the found relationships are discussed.

Probing hydrodesulfurization over bimetallic phosphides using monodisperse Ni2-xMxP nanoparticles encapsulated in mesoporous silica

Metal phosphide nanoparticles encapsulated in mesoporous silica provide a well-defined system for probing the fundamental chemistry of the hydrodesulfurization (HDS) reaction over this new class of hydrotreating catalysts. To investigate composition effects in bimetallic phosphides, the HDS of dibenzothiophene (DBT) was carried out over a series of Ni-rich Ni2-xMxP@mSiO2 (M=Co, Fe) nanocatalysts (x≤0.50). The Ni2-xMxP nanoparticles (average diameters: 11–13nm) were prepared by solution-phase arrested precipitation and encapsulated in mesoporous silica, characterized by a range of techniques (XRD, TEM, IR spectroscopy, BET surface area, CO chemisorption) and tested for DBT HDS activity and selectivity. The highest activity was observed for a Ni1.92Co0.08P@mSiO2 nanocatalyst, but the overall trend was a decrease in HDS activity with increasing Co or Fe content. In contrast, the highest turnover frequency (TOF) was observed for the most Co- and Fe-rich compositions based on sites titrated by CO chemisorption. IR spectral studies of adsorbed CO on the Ni2-xMxP@mSiO2 catalysts indicate that an increase in electron density occurs on Ni sites as the Co or Fe content is increased, which may be responsible for the increased TOFs of the catalytic sites. The Ni2-xMxP@mSiO2 nanocatalysts exhibit a strong preference for the direct desulfurization pathway (DDS) for DBT HDS that changes only slightly with increasing Co or Fe content.

Preparation of highly dispersed W/ZrO2–Al2O3 hydrodesulfurization catalysts at high WO3 loading via a microwave hydrothermal method

Abstract A microwave hydrothermal (MWH) method was used to deposit WO 3 onto ZrO 2 –Al 2 O 3 with various ZrO 2 contents to prepare hydrodesulfurization (HDS) catalysts with high WO 3 loading (23 wt%) close to industrial hydrotreating, for achieving high W dispersion and weak W-support interaction. The catalysts with the same WO 3 and ZrO 2 contents were prepared by a conventional impregnation (IM) method as reference. The effects of catalyst preparation methods and ZrO 2 contents on the catalyst property and dibenzothiophene HDS activity were investigated. The results show that the MWH method leads to highly dispersed octahedrally coordinated W species which are weakly linked on ZrO 2 –Al 2 O 3 and easy to be reduced; no bulk WO 3 crystallites are observed even at high ZrO 2 content (50 wt%). Therefore, it causes better sulfidation and shorter WS 2 slabs. Contrarily, the IM method induces W species to agglomerate into bulk WO 3 crystallites which are poorly dispersed and hard to be reduced, which is further aggravated by ZrO 2 . The HDS activity of the MWH-prepared catalysts significantly increases with ZrO 2 up to 40 wt% ZrO 2 . This catalyst shows 2 times higher rate constant and 1.64 times higher efficiency of HDS than the IM-prepared catalyst with the same ZrO 2 content. For the IM-prepared catalysts, the HDS activity slightly increases at small amount of ZrO 2 (10 wt%) and then decreases drastically.

The effect of neodymium content on dibenzothiophene HDS performance over a bulk Ni2P catalyst

Neodymium (Nd)-modified Ni2P catalysts (NdxNi2P, where x is the molar fraction of Nd to Ni2P) have been successfully prepared. An appropriate amount of Nd can dramatically increase the surface area and promote the formation of smaller and highly dispersed Ni2P particles. The NdxNi2P catalyst with x=0.10 exhibited the highest dibenzothiophene hydrodesulfurization activity of 97.4%, which is an increase of 35% when compared with that found for bulk Ni2P.