Hydrodesulfurization Activity Research Articles

A new approach to synthesize supported ruthenium phosphides for hydrodesulfurization

Supported noble metal ruthenium phosphides were synthesized by one-step H2-thermal treatment method using triphenylphosphine (TPP) as phosphorus sources at low temperatures. Two phosphides RuP and Ru2P can be prepared by this method via varying the molar ratio of metal salt and TPP. The as-prepared phosphides were characterized by X-ray powder diffraction (XRD), low-temperature N2 adsorption, CO chemisorption and transmission electronic microscopy (TEM). The supported ruthenium phosphides prepared by new method and conventional method together with contradistinctive metallic ruthenium were evaluated in hydrodesulfurization (HDS) of dibenzothiophene (DBT). The catalytic results showed that metal-rich Ru2P was the better active phase for HDS than RuP and metal Ru. Besides this, ruthenium phosphide catalyst prepared by new method exhibited superior HDS activity to that prepared by conventional method.

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.

Formation of Rh<sub>2</sub>P Supported on Na-form Zeolites and Catalytic Activity for Hydrodesulfurization

Formation of Rh<sub>2</sub>P Supported on Na-form Zeolites and Catalytic Activity for Hydrodesulfurization

Effects of pH and chelating agent on the NiWS phase formation in NiW/γ-Al2O3 HDS catalysts

In this article, NiW/γ-Al2O3 samples were prepared by consecutive impregnations of a W/γ-Al2O3-based catalyst with aqueous solution of nickel salt. The structural control of the nickel ion precursor in the impregnation solution was achieved by the addition of 1,2-cyclohexanediamine-N,N,N′,N′-tetraacetic acid (CyDTA) as a chelating agent. The influence of pH of this aqueous solution on the NiWS phase formation in the sulfided catalysts was investigated. Coordination structures of the Ni–CyDTA complexes were evaluated by FT-IR and DRS UV–Vis spectroscopies. Sulfided catalysts were characterized by X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM) and tested in hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) carried out in a batch reactor at 593 K and total H2 pressure of 55 bar. Spectroscopic characterization by DRS UV–Vis showed the predominance of the [Ni(CyDTA)]2− species in solution. Following the impregnation and drying steps, the [Ni(CyDTA)]2− complex showed no apparent changes of its structure, independent of the pH value of impregnation solution. The Ni/W/γ-Al2O3 catalysts ex [Ni(CyDTA)]2− complex exhibited high stability. The presence of CyDTA delayed the reduction of Ni and caused a remarkable decrease of the W-support interaction, thus increasing the formation of NiWS phase upon catalyst sulfiding. The catalyst activity–structure correlation demonstrated that the catalyst activity and selectivity is linked with formation of the most active NiWS phase having single or double WS2 slab structures. The catalyst prepared with [Ni(CyDTA)]2− complex at pH of 4.0 exhibited the largest initial HDS activity, which was approximately triple compared with the CyDTA-free counterpart. For all catalysts, the HDS reaction proceeded via hydrogenation (HYD) and direct desulfurization (DDS) reaction routes, the former being the main reaction route. The addition of chelating agent led to an increase of the selectivity toward HYD route products.

Single-walled carbon nanotubes supported Ni–Y as catalyst for ultra-deep hydrodesulfurization of gasoline and diesel

To obtain ultra-deep hydrodesulfurization (HDS) on the fluid catalytic cracking (FCC) gasoline and diesel, a novel catalyst has been prepared by an arc discharge method. This nickel yttrium (Ni–Y) bi-metallic catalyst is attached on single-walled carbon nanotubes (SWCNTs) and it shows higher HDS activities than that of mono-metal catalyst. Our results demonstrate that the content of SWCNTs has important effect on HDS when the Ni–Y/SWCNTs are oxidized by heat treatment. In addition, further results found that prepared in the He atmosphere by arc discharge, the oxidized Ni–Y/SWCNTs have the best HDS performance due to the high yield of SWCNTs and the much smaller size of Ni–Y nanoparticles. When the Ni–Y/SWCNTs, oxidized at 200°C, are used in the continuous HDS reaction with FCC gasoline as feedstock, the S content of the hydrotreated product is reduced from 259mg/L to less than 1mg/L starting from the sixth hour to thirty second hour in reaction.

Competitive HDS and HDN reactions over NiMoS/HMS-Al catalysts: Diminishing of the inhibition of HDS reaction by support modification with P

Individual and simultaneous hydrodesulfurization (HDS) of dibenzothiophene (DBT) and hydrodenitrogenation (HDN) of carbozole reactions have been studied in the presence of hydrogen (P=55bar) at 310°C in a batch reactor over a series of sulfided NiMo/P/Al-HMS catalysts modified with phosphorus (0.5–2.0wt%). Both oxidic precursors and sulfide catalysts have been characterized by specific surface area, XRD, Raman, TPD-NH3, HRTEM, XPS and IR spectroscopy of adsorbed pyridine. Regardless of the reaction studied, all P-containing catalysts showed higher activity than that to the P-free one. The catalyst modified with optimized amount of P (1wt%) the best HDS activity and exhibited a lowest inhibition factor during simultaneous HDS and HDN, which was close to that of a commercial NiMo/Al2O3 sulfide catalyst. This was linked with formation of irregular MoS2 structures having high concentration of brim sites as well as with its largest total acidity.

The hydroxyapatite nanotube as a promoter to optimize the HDS reaction of NiMo/TiO2 catalyst

A composite containing TiO2 whiskers (TiO2(w)) and hydroxyapatite nanotube (nHA) with mosaic structure functioned as a support was successfully synthesized by a facile route. The TiO2(w) was prepared from potassium titanate and the novel single-crystalline hydroxyapatite nanotubes were synthesized via a distinctive biomimetic route. Properties of support and catalyst were characterized by SEM, TEM, XRD, FT-IR of adsorbed pyridine (in situ FT-IR), BET, TPR, and NH3-TPD. Catalytic activity of NiMo/TiO2(w)-nHA, and the effect of nHA contents on hydrodesulfurization (HDS) activity was performed. Results indicated the incorporation of nHA can weaken the Lewis acidity of TiO2 supports and decrease acidity of the NiMo/TiO2(w)-nHA catalyst. The addition of moderate nHA has weak influence on the textural and structural properties of the catalyst. NiMo/TiO2(w)-nHA exhibits higher HDS catalytic activity than that of NiMo/TiO2(w) catalyst under mild conditions of low temperature and pressure (280°C and 2MPa), and the catalytic performance of NiMo/TiO2(w)-nHA-0.1 is the best. The synergistic effects between TiO2(w) and nHA and acidity regulation contribute to improve the HDS catalytic activity of the nHA-doped samples.

The tuning of pore structures and acidity for Zn/Al layered double hydroxides: The application on selective hydrodesulfurization for FCC gasoline

Co–Mo catalysts applied on the hydrodesulfurization (HDS) for FCC gasoline were prepared with Zn–Al layered double hydroxides (LDHs) to improve their performances, and the effects of pore structures and acidity on HDS performances were studied in detail. A series of Zn–Al/LDHs samples with different pore structures and acidities are synthesized on the bases of co-precipitation of OH−, CO2−, Al3+, and Zn2+. The neutralization pH is a main factor to affect the pore structures and acidity of Zn–Al/LDHs, and a series of Zn–Al/LDHs with different pore structures and acidities are obtained. Based on the representative samples with different specific surface areas (SBET) and acidities, three CoMo/LDHs catalysts were prepared, and their HDS performances were compared with traditional CoMo/Al2O3 catalysts. The results indicated that catalysts prepared with high SBET possessed high HDS activity, and Brönsted acid sites could reduce the thiol content in the product to some extent. All the three catalysts prepared with LDHs displayed little lower HDS activity but higher selectivity than CoMo/Al2O3, and could restrain the reactions of re-combination between olefin and H2S which could be due to the existence of Brönsted acid sites.

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.

NiMo catalysts supported on graphene-modified mesoporous TiO2 toward highly efficient hydrodesulfurization of dibenzothiophene

The graphene-covered mesoporous TiO2 (SBET>90m2g−1) were successfully prepared by using graphene oxide (GO) as graphene source via one-step hydrothermal reduction, and then were prepared supported NiMo catalysts for hydrodesulfurization (HDS) of dibenzothiophene (DBT). The active species were incorporated by incipient impregnation. Compared with the unmodified NiMo/TiO2 catalyst, all modified catalysts exhibited higher HDS activity under mild conditions of 280°C, 2.0MPa, liquid hourly space velocity of 4h−1 and hydrogen/feed ratio of 400 (V/V). Among of them, the catalyst with the appropriate mass ratio of rGO/TiO2(0.5) showed the highest DBT conversion of 99.9%. The prepared catalysts were characterized by various techniques (N2 adsorption-desorption, XRD, Raman, Pyridine FT-IR, NH3-TPD, H2-TPR, CO uptake, SEM and TEM). The enhanced HDS activity can be ascribed to (i) The incorporation of rGO (reduced graphene oxide) induces proper enhanced Lewis acidity of the modified catalysts, which promotes the adsorption of DBT molecules and facilitates the hydrogenation route. (ii) The introduction of rGO changes the HDS product (H2S) desorption behaviors, accelerating H2S desorption rate from catalyst surface and promoting the efficiency of catalyst immediately.

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.

MgO Nanosheet Assemblies Supported CoMo Catalyst with High Activity in Hydrodesulfurization of Dibenzothiophene

A magnesium oxide nanosheet assembly (NS-MgO) with high surface area (255 m2/g) and nanopore volume (0.30 cm3/g) was prepared by a pressure-assisted carbonation method at large scale. After loading of cobalt and molybdenum (CoMo) species and followed by sulfidation, the NS-MgO supported CoMo catalyst (Co-MoS2/NS-MgO) exhibits high activity (94.2%) and good nitrogen tolerance in the hydrodesulfurization (HDS) of dibenzothiophene (DBT), compared with a conventional γ-alumina-supported CoMo catalyst (64.1%). These results are attributed to the difference in the basicity of the NS-MgO and γ-Al2O3 supports. The large amount of the middle strong basic sites on NS-MgO can avoid the polymerization of Mo species and form small Mo oxide clusters. After sulfidation, the small MoS2 clusters with shorter lengths and less stacking formed on the NS-MgO contribute to an increase in the sites available for Co promotion, resulting in the Co-MoS2/NS-MgO catalyst with high HDS activity.

Synthesis of metallic Ni-Co/graphene catalysts with enhanced hydrodesulfurization activity via a low-temperature plasma approach

Graphene sheets (GS) supported monometal (Ni, Co) or bimetal (Ni-Co) nanoparticle composites have been conveniently prepared with the assistance of dielectric barrier discharge (DBD) plasma at low temperature. Both graphene oxide and the metal ions (Ni2+, Co2+) can be simultaneously reduced during the DBD plasma treatment in H2 atmosphere, which gives rise to the uniformly distributed metal nanoparticles on the surface of GS. The graphene-based catalysts are used in the catalytic hydrodesulfurization (HDS) of carbonyl sulfide (COS). It is revealed that the bimetallic Ni-Co/GS catalyst exhibits outstanding performance for higher COS conversion compared with the monometal catalysts, suggesting the synergetic effect between Ni and Co active species in the HDS reaction. The presented strategy demonstrates a new pathway for the preparation of graphene-based catalysts with high HDS catalytic performance.

Selectivity enhancement of CoMoS catalysts supported on tri-modal porous Al 2 O 3 for the hydrodesulfurization of fluid catalytic cracking gasoline

Abstract To improve the selectivity performance of CoMoS catalysts applied to the hydrodesulfurization (HDS) of fluid catalytic cracking (FCC) gasoline, a series of CoMoS/Al 2 O 3 catalysts was prepared with alumina of different pore structures, and their HDS performance was evaluated with a real FCC gasoline. This study indicated that CoMoS/Al 2 O 3 catalysts prepared with micro- or meso-porous alumina possessed high HDS activity but low selectivity, whereas macro-porous alumina enhanced the selectivity of CoMoS catalysts. The enhanced HDS selectivity was due to the tuning of the MoS 2 slabs and the weakening of the internal diffusion resistance. Based on the above results, the optimal CoMoS/Al 2 O 3 catalyst was prepared with the alumina of the tri-modal pore distribution at approximately 5–8 nm, 15–20 nm, and 90–100 nm. The optimal catalyst displayed a balanced HDS activity and selectivity in contrast to the reference catalyst prepared with K- and P-modified Al 2 O 3 .

Influence of the solution pH in impregnation with citric acid and activity of Ni/W/Al2O3 catalysts

The impregnation parameters setting is an essential strategy to find efficient active phase precursors in heterogeneous catalysts due to the close connection between the chemistry of impregnated aqueous solution and the nature of metal-support interactions. In this work, the effect of impregnation solution pH on active NiWS phase formation was studied. Ni/W/Al2O3 catalysts were prepared by impregnation of a W/Al2O3-based catalyst using aqueous nickel-citric acid (CA) solutions (CA/Ni=2) at different pH values (0.3, 3.4, 5.1 and 8.7). The citric acid presence and the impregnation pH influenced the NiWS phase formation. Citric acid provided isolation to supported metal species avoiding strong metal-support interactions, delaying nickel reduction at higher temperatures and decreasing WS2 sintering when compared with a free-citric acid catalyst. An increase of 2.2 times in NiWS fraction was related to these citric acid features. Furthermore, the solution pH influenced the aqueous and supported nickel speciation. Dispersed nickel species were associated with AlO-Ni-Cit surface complexes generated by the adsorption of [Ni(HCit)(Cit)(H2O)4]3− or [Ni(Cit)2(H2O)4]4− over alumina surface. In turn, these surface complexes were associated with a higher W sulfidation. 3-fold increases in Ni/W/Al2O3 catalytic activity for hydrodesulfurization of 4,6-dimethyldibenzothiophene were reached by the presence of citric acid and a pH of nickel-citric acid solution around 5. Therefore, the active NiWS species formation in Ni/W/Al2O3 catalysts was improved with citric acid addition and furthermore, it was notably optimized by the control of the nickel species via tuned impregnation pH.

Modeling the kinetics of sulfidation over NiMo/Al2O3 catalyst for thiophene hydrodesulfurization

A kinetic model has been developed for the sulfidation of NiMo/Al2O3 hydrodesulfurization (HDS) catalyst, which quantitatively establishes a relationship between the HDS activity and sulfidation conditions. The model parameters were estimated by fitting a series of experimental thiophene HDS conversion data over the catalysts sulfurized under different operations. The results show that the developed model satisfactorily predicts the HDS conversion with a total average relative deviation of less than 4 %. Moreover, parametric studies were made to validate the accuracy of the model. The comparison results show that the proposed model is fairly effective in simulating the sulfidation process. It is expected that the model will be used to guide the sulfidation research of supported Mo-based catalysts and to optimize laboratory/pilot-plant sulfiding procedures.

Effect of basic nitrogen compounds on gas oil hydrodesulfurization and deposit formed on the catalyst

The authors studied the effect of the composition of cracked gas oils on the hydrodesulfurization to obtain clean diesel fuel. The required reaction temperature for sulfur specification of diesel fuel using a feedstock mixed with residue desulfurization gas oil (RDS-GO) was equivalent to that using light cycle oil (LCO). RDS-GO has a high content of basic nitrogen compounds, whereas LCO has a high content of aromatic hydrocarbons that are known to inhibit the hydrodesulfurization of gas oil. Using two-dimensional gas chromatography, LCO was found to contain polyaromatic hydrocarbons and non-basic nitrogen compounds, such as indoles and carbazoles, whereas RDS-GO contained monoaromatic hydrocarbons and basic nitrogen compounds, such as anilines. In a deactivation test conducted over 2300h, the feedstock mixed with RDS-GO showed a lower deactivation rate than LCO. Raman spectroscopy, 13C NMR, and electron energy-loss spectroscopy in transmission electron microscopy showed that the deposits formed on the used catalysts during the deactivation test with the feedstock mixed with LCO contained more aromatic compounds than those with RDS-GO. The coke in the deposits from the feed containing RDS-GO was expected to be more anisotropic than that from the LCO. The improved hydrodesulfurization activity observed with RDS-GO was attributed to its characteristic components, which are thought to inhibit the growth of coke on the catalyst.

An Investigation of Ni2P Single Crystal Surfaces: Structure, Electronic State and Reactivity

Ni2P has demonstrated high catalytic activity for hydrodesulfurization and has recently been employed as a catalyst in a variety of other reactions. We have thoroughly reviewed the literature concerning Ni2P single crystal surfaces, with the aim of determining the relationship between surface structure and catalytic properties. Published results to date indicate that Ni2P single crystal surfaces exhibit reconstructed structures, and so the bulk terminated structure may not be stable. We have also reviewed the surface structures and electronic states of (1 × 1) and reconstructed Ni2P(0001) and (\(10\overline{1} 0\)). Based on these reviews, this paper presents general rules regarding stabilization of the Ni2P surface structure and discusses the role of phosphorus in the single crystal surfaces.

Preparation of Alumina-supported Cobalt–molybdenum Catalysts by Sol-gel Method and Hydrodesulfurization Activities

Al2O3-supported Co and Mo catalysts were prepared by the sol-gel method, in which Co and/or Mo species were added at the hydrolysis of Al tri-s-butoxide. XRD patterns, N2 adsorption and desorption, amounts of NO adsorption and NO species by FT-IR were measured to characterize the catalysts. Catalysts with active components Co and Mo separately supported by the sol-gel method had higher activity for hydrodesulfurization of dibenzothiophene. Mo-Co/Al2O3, in which Mo species was supported on Co/Al2O3 by the sol-gel method, showed the highest activities at lower temperature, indicating that the Co species was effectively dispersed on Al2O3 during the preparation of Co/Al2O3. Catalysts in which Co and Mo species were simultaneously supported had lower activity, indicating that both Co and Mo species were dispersed and reduced interaction between Co and Mo. Co-Mo/sol-gelAl2O3, with the Co species supported on Mo/sol-gelAl2O3, showed the highest activity among sol-gelAl2O3 supported CoMo catalysts, indicating that the Mo species was effectively dispersed during the preparation of Mo/sol-gelAl2O3. Biphenyl was selectively obtained. NO adsorption measurement showed that the amount of NO adsorbed was almost same for Mo-Co/Al2O3 sulfided once or twice. In contrast, sol-gelCoMo/Al2O3, with the Co and Mo added simultaneously by the sol-gel method, showed significant decrease in NO adsorption after second sulfiding, which would be related to the lower stability of sol-gelCoMo/Al2O3 prepared by the sol-gel method. Al2O3-supported Co-Mo catalysts prepared using the sol-gel method had relatively high surface areas (282-544 m2/g) and relatively smaller pore sizes (3.7-6.3 nm).

Surface Carbon Activated NiMo/TiO2 Catalyst Towards Highly Efficient Hydrodesulfurization Reaction

By adopting molecular self-assembly, the surface of mesoporous TiO2 whiskers (TiO2(w)) was modified with 18 alkyl phosphate as carbon source. This method was successfully used to form a carbon heterogeneous monolayer on titania surface (TiO2(w)–C) under N2 atmosphere. Novel NiMo/TiO2(w)–C catalysts were prepared by incipient-wetness impregnation. The carriers and catalysts were characterized by N2 adsorption–desorption measurements, NH3-temperature-programmed desorption, Raman Spectra, Fourier transform infrared, scanning electron microscopy, temperature-programmed reduction, and H2S-temperature-programmed desorption. The catalytic activity of TiO2(w)–C as a support, together with the effect of carbon content on hydrodesulfurization (HDS) activity of NiMo/TiO2(w)–C was investigated. The results showed that NiMo/TiO2(w)–C exhibited higher HDS catalytic activity under conditions of low temperature and pressure (280 °C and 2 MPa). Under such mild reaction conditions, NiMo/TiO2(w)–C-0.5 with carbon loading of 0.5 % showed the highest HDS result (100 %). The improved activity of NiMo/TiO2(w)–C-0.5 can be attributed to the TiO2(w) modifying with trace amounts of carbon, which would increase the total acid sites and suppress the carbon deposition on the surface of catalyst. Additionally, the generated carbon nanoparticles can weaken the interaction between TiO2(w) and the HDS product (H2S) and then improve H2S desorption from the catalyst surface, which lead to the outstanding HDS activity.