NiMoS Phase Research Articles

Structural, mechanical and tribocorrosion behaviors of Mo-Ni-Si alloys

Mo-Ni-Si alloys were fabricated using arc melting, and their structural and tribocorrosion behaviors were investigated. The results revealed that the alloys have good comprehensive mechanical properties and tribocorrosion resistance with increasing Mo content. The alloys exhibit lower friction coefficients and wear rates owing to the creation of the MoO3-NiO-SiO2 passivation layer. The wear rates of the alloys were approximately one-tenth of that of 0Cr18Ni9. During the tribocorrosion tests, the OCP values of the alloys are inversely related to the friction coefficient, which is attributed to the synergistic effect of wear and corrosion. The main tribocorrosion mechanisms for Mo-Ni-Si alloys are pure wear and preferential tribocorrosion of the NiMo phase, whereas the wear loss of 0Cr18Ni9 is dominated by corrosion-induced wear.

Suppression of inactive sites in NiMo@amorphous alumina catalysts for hydrodesulfurization reaction: Effect of Ga doping

Hydrodesulfurization (HDS) reaction activity depends on the formation of active NiMoS (completely sulfided multilayer type 2 sites) and inactive NiAl2O4/NixSy phases on the catalyst surface. These inactive phases not only itself inactive for the reaction but also hinder the formation of active NiMoS phases. In addition, the formation of strong Mo-O-Al bonds also lowers the reducibility of the catalyst, suggesting lesser catalytic activity (type 1 sites, partially sulfided single-layer sites). To this end, we report the formation of NiMo/Ga doped amorphous alumina (A-Al2O3) catalysts prepared by the colloidal synthesis method. A-Al2O3 was chosen as a support because it has lower surface energy, better physicochemical properties, and enhanced acidic sites than the crystalline alumina phase, which favours the formation of type 2 sites or weak metal-support interaction (completely sulfided multilayer NiMoS sites). Further, the Ga doping in A-Al2O3 support substitute the tetrahedral Al sites and form GaAl2O4 phases by reducing NiAl2O4 inactive sites, and the free Ni decorate the edges of MoS2 to form HDS active NiMoS sites. Therefore, NiMo/Ga doped A-Al2O3 catalyst (at 1 wt% Ga loading) reported enhanced HDS catalytic activity (25%), HDS reaction rate constant (kHDS-2.15 times) and turn over frequency (TOF-1.3 times) than the conventional NiMo/γ-Al2O3 catalysts.

Mechanochemical approach for the preparation of technical catalysts

Technical catalysts are shaped as pellets, extrudates, beads, and monoliths. Most often, they are composed of a mixture of oxides used as carriers for metallic phases. The latter are usually incorporated by wet impregnation; a method with a strong environmental impact due to the production of liquid wastes and toxic gases. Owing to such issues, this work presents alternatives for preparing technical catalysts using reactive grinding to mix its components. Particularly, we prepared a series of catalytic extrudates used in the hydrocracking of tetralin. These extrudates were composed of a bimetallic NiMo active phase, an acidic HY zeolite, and boehmite as a binding agent. A 25 wt% combination of HY zeolite with boehmite was used as the carrier for the NiMo active phase. The need for the inclusion of a calcination step for the preparation of the carrier was examined as well as the need for the use of a simultaneous or sequential impregnation process for incorporating the metallic NiMo phase into the carrier. In general, we demonstrate that there is no need for calcining the carrier. Indeed, non-calcined carriers produced catalysts with higher mechanical resistance than the catalysts whose carrier was calcined. In addition, we found that the simultaneous impregnation of NiMo yields materials with better catalytic properties than both their sequentially impregnated and wet-impregnated counterparts. This tendency was ascribed to the preservation of the crystallinity of the zeolite; a better dispersion and exposure of the HY zeolite within the matrix of the carriers which preserve its acidity when the NiMo phase is present. Overall, we also demonstrated that an adequate fluency of the extrusion pastes can be achieved using only water as lubricant. These findings are of course a step forward in the search for less environmentally harmful processes for catalysts manufacturing.

3D Printing Technique Fortifies the Ultradeep Hydrodesulfurization Process of Diesel: A Journal of NiMo/Al2O3-MMT.

In this contribution, we rationally designed and controllably fabricated a NiMo/Al2O3-montmorillonite (3D-NiMo/Al2O3-MMT) monolithic catalyst via a 3D printing strategy with economical montmorillonite (MMT) as a binder. The catalytic performance of the resulting NiMo/Al2O3-MMT for 4,6-dimethyldibenzothiophene (4,6-DMDBT) hydrodesulfurization (HDS) was evaluated. The experimental results unveil that the 3D-NiMo/Al2O3-MMT monolithic catalyst exhibits robust stability and exceptional HDS activity with 99.2% 4,6-DMDBT conversion (residual 4 ppm of S), which is remarkably superior to that of conventional NiMo/Al2O3 (61.5%), NiMo/MMT (63.2%), and even NiMo/Al2O3-MMT (76.5%) prepared by the mechanical-mixing method. This should be ascribed to the synthetic effect between the MMT binder and the Al2O3 substrate, which effectively weakens the interaction between the Mo species and the Lewis acids on the original Al2O3 surface, thereby significantly increasing the content of reducible Mo species and considerably facilitating the formation of more highly active NiMoS phase (Type II) with optimal average stacking layers and thereafter remarkably enhancing the ultradeep HDS activity of the 3D-NiMo/Al2O3-MMT monolithic catalyst.

Activating MoS2 by site-selective Ni incorporation for efficient and robust alkaline hydrogen evolution

In this work, a surface engineering strategy has been developed to implant atomic Ni mostly enriched in 1 nm thickness of MoS2 nanosheets, and suppresses the segregation of undesired NiSx. Notably, this structural regulation not only creates additional edges exposed at the inert basal plane of MoS2 nanosheets, but also increases the catalytic ability of edge sites by forming dominant NiMoS phase. As such, a low overpotential of 95 mV is achieved to deliver a current density of 10 mA cm−2, which is 242 mV decrease than unmodified MoS2, together with 86.5% preservation of initial capacity after 100 h test. Theoretical calculations further identify the activated catalytic sites both in Mo-edge and S-edge, and the specific atomic configurations enable the synergistic effect to optimize the adsorption-desorption of H∗, and is responsible for the remarkably improved hydrogen evolution reaction (HER) activity.

Active phase morphology engineering of NiMo/Al2O3 through La introduction for boosting hydrodesulfurization of 4,6-DMDBT

Herein, we designed and constructed a mesoporous LaAlOx via a solvent evaporation induced self-assembly protocol. The structure and physicochemical property of the corresponding NiMo supported catalyst was analyzed by a set of characterizations, and its catalytic activity was investigated for hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene. It has confirmed that the incorporation of La profoundly facilitate the generation of “Type II” NiMoS phase by weakening the interaction of Mo–O–Al leakage and promoting the sulfidation of both Ni and Mo oxides as well as changing the morphology of Ni promoted MoS2 slabs, thereafter boosting the HDS performance substantially. The finding here may contribute to the fundamental understanding of structure-activity in ultra-deep desulfurization and inspire the advancement of highly-efficient HDS catalyst in future.

Relation between NiMo(O) Phase Structures and Hydrogen Evolution Activities of Water Electrolysis

Relation between NiMo(O) Phase Structures and Hydrogen Evolution Activities of Water Electrolysis

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.

Resurrection of the spent NiMo/Al2O3 catalyst for diesel hydrofining

Spent catalysts from the hydrofining process are hazardous wastes, while their appropriate utilization can also bring enormous environmental and economic benefits. Herein, a chemical resurrection method was developed to resurrect and recycle the industrial spent NiMo/Al2O3 hydrofining catalyst. The spent catalysts are calcined to remove the carbon deposit followed by the treatment with citric acid (CA) and ethylene glycol (EG). The results show that the calcination can also accelerate the aggregation and inerting of the active phase. However, the redispersion and reactivation of the inactive phases over the spent catalysts are realized through formation of metal complex with the citric acid, which weaken the interaction between Mo species and support. It increases reducibility of the Mo species and then improve the sulfurization degree of the resurrected catalyst. Besides, the average length of MoS2 is reduced while the stacking number is increased. The ethylene glycol further regulates the reducibility of Ni and Mo species to promote the formation of NiMoS phase with high activity instead of Ni3S2. Consequently, the average length of the MoS2 is reduced while the average stacking number of MoS2 and content of the NiMoS phase are increased over the resurrected catalyst compared with the spent catalyst. It recovers the hydrodesulfurization activity of the resurrected catalyst to a level higher than that over the spent and industrially regenerated catalyst.

Modulating the active phase structure of NiMo/Al2O3 by La modification for ultra‐deep hydrodesulfurization of diesel

AbstractHerein, a series of mesoporous NiMo/LaAlOx with various La contents were constructed through a solvent evaporation‐induced self‐assembly protocol, and their catalytic activities were investigated for hydrodesulfurization (HDS) of 4,6‐DMDBT. It has been confirmed that the incorporation of La influences the electronic structure and morphology of NiMoS active phase. The lower amount of La (x ≤ 1.0 wt.%) could facilitate the formation of “Type II” NiMoS phase by weakening the interaction of Mo‐O‐Al leakage and promoting the sulfidation of both Mo and Ni species as well as increasing the ratio of “Type II” NiMoS phase, thereafter boosting the HDS performances. Further increasing La incorporation, however, leads to the generation of inactive NiSx phase and decrease of NiMoS active phase proportion, the HDS activities of corresponding catalysts were suppressed. NiMo/LaAlOx‐1.0 exhibits the highest activity for 4,6‐DMDBT HDS because of its moderate metal‐support interaction, optimal morphology and the largest proportion of “Type II” NiMoS active phase.

Effects of Al introduction methods for Al-SBA-15 on NiMoS active phase morphology and hydrodesulfurization reaction selectivities

A series of Al-SBA-15 were synthesized with three Al introduction methods and different Si/Al molar ratios. The introduction methods included the direct synthesis (DS), post-synthesis grafting (PG) and impregnation synthesis (IM) method. The Si/Al molar ratios of Al-SBA-15 materials were 20, 10 and 5 respectively. The corresponding NiMoS catalysts were performed by hydrodesulfurization (HDS) recations of dibenzothiophene (DBT) to analyze reaction behavior. The characterization results of N2-physisorption, X-ray diffraction and 27Al NMR presented that the Al introduction method has a direct effect on the physical and chemical properties of Al-SBA-15. PG method could introduce most of Al atoms into the framework of parent- material, which was opposed to the IM method. The DS method could better maintain the pore structure advantages of the Al-SBA-15. The PG-NiMo catalyst had the strongest metal-support interaction, and the NiMoS slabs presented the lowest average stacking number over this catalyst. The reaction results showed that DS-NiMo catalyst obtained the highest HDS activity, and PG-NiMo catalyst presented the highest HDS hydrogenolysis selectivity of DBT. It is speculated that the frame-work Al has strong metal interaction with metal oxide precursor, and the morphology of NiMoS Phase has important effect on the selectivity of DBT HDS.

Tetradecylamine-induced assembly of Mo and Al precursors to prepare efficient NiMoS/Al2O3 catalysts for ultradeep hydrodesulfurization

Novel alumina-supported Ni-Mo hydrodesulfurization (HDS) catalysts were prepared via assembly of Mo and Al precursors induced by tetradecylamine (TDA). Compared with conventional impregnation, this assembly method improves Mo dispersion, weakens metal-support interactions, enhances Ni modification at MoS2 edge sites, and produces more NiMoS phases on Al2O3. The optimal NiMoS microstructure was obtained by modulating the TDA/Mo ratio in the assembly. A microstructure-activity correlation indicated that the S vacancies at the NiMoS corner sites favored σ-adsorption and direct desulfurization of 4,6-dimethylbenzothiophene (4,6-DMDBT), and those at the NiMoS edge sites promoted C-S breaking in hydrogenated derivatives of 4,6-DMDBT. Among these catalysts, NiTMo-2.0/Al2O3, which had the most corner and edge S vacancies, exhibited the highest reaction rate constant of 5.89 × 10−7 mol·g−1·s−1 and the highest desulfurization ratio of 99.5% in HDS of 4,6-DMDBT.

Modification of HDT catalysts of FCC feedstock by adding silica to the kneading paste of alumina support: Advantages and disadvantages

The effect of Si incorporation at the stage of alumina preparation on physico-chemical properties and catalytic performance of NiMo/Al2O3 catalysts for FCC feedstock pretreatment has been studied. Silicon was added to alumina support by kneading. Si/Al molar ratio was 0–0.16. Supports and catalysts were characterized by XRD, MAS NMR spectroscopy, Raman and IR spectroscopies, nitrogen adsorption-desorption, HRTEM, UV-Vis DRS, XPS. Introduction of Si changes textural characteristics of supports and leads to the decrease in acidity of parent alumina caused by blocking of a part of surface OH groups by deposits of silicon compounds. Silicon addition promotes the formation of small amount of strong LAS and strong BAS. Incorporation of Si facilitates segregation of Ni from the NiMoS phase. Testing of catalysts in VGO hydrotreating shows that addition of silicon to alumina support by kneading improves hydrodesulfurization activity of catalysts. However, an improvement in HDN activity was not achieved.

Role of the solvent evaporating temperature on the NiMo/TiO2-Al2O3 catalyst and the hydrodesulfurization performance for 4,6-dimenthyldibenzothiophehe

Binary TiO2-Al2O3 serial composites(TA-x) and the NiMo supported catalysts(NiMo/TA-x) were successfully synthesized at different solvent evaporation temperatures,. The materials were characterized by several advanced characterization techniques, and the catalytic hydrodesulfurization (HDS) performances were evaluated. The results revealed that the synthesized TA-x serial composites are amorphous mixtures of TiO2 and Al2O3 with highly ordered two-dimensional hexagonal mesopores. Both the mesostructures and the acidities of the synthesized TA-x composites changed at different evaporation temperature of the solvent. The metal-support interaction(MSI), the existence states and the coordination states of the Mo precursors can be modulated by the changes in the physicochemical property of the TA-x composites caused by the solvent evaporating temperature. A moderate solvent evaporation temperature is favorable for the doping of Ni species into the MoS2 slab and Mo sulfidation degree, thus enhancing the proportion of the NiMoS active phases. Catalyst NiMo/TA-60 exhibits superior activity and the highest direct desulfurization(DDS) pathway selectivity due to the excellent acidity and pore structure property, the highest dispersion and the highest Mo sulfidation degree, a moderate MSI, the highest efficiency in the formation of NiMoS phase and the highest proportion of corner Mo atoms. Moreover, the rate constants of the specific HDS pathways can be correlated with the specific types of active sites: the DDS pathway (kDDS) is closely related to the proportion of corner active sites and the hydrogenation desulfurization pathway (kHYDS) is closely related to the proportion of brim sites. The activity of a single corner active site is found to be approximately 100 times that of a single edge active site. These findings are promising in the design of HDS catalysts for inferior distillates.

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.

Rapid solidification and physical properties of a refractory Mo-Ni alloy under containerless microgravity condition

<p indent="0mm">The solidification kinetics and physical properties of Mo-48%Ni alloy were studied using the free fall technique. The cooling rate and undercooling of this alloy both increased exponentially as the droplet diameter decreased, and they could reach <sc>2.41×10⁴ K s⁻¹</sc> and <sc>322 K</sc> (0.19 <italic>T</italic>_L), respectively. The high cooling rate significantly suppressed the subsequent solid state transformation process. The primary NiMo phase exhibited a morphological transition from coarse dendrite to a remarkably refined structure, and the regular lamellar (Ni+NiMo) eutectics changed into anomalous eutectic. The maximum length of the primary NiMo phase fell from 142.2 to <sc>28.4 μm</sc>, whereas its volume fraction initially rose and then fell, with a maximum of 60.1%. Moreover, the variation in the Mo content of the primary phase coincided well with that of the eutectic structure. As regards mechanical properties, the nanoindentation measurements indicated that the elastic moduli of the primary phase and the eutectic structure both showed a downward trend along with the microstructure evolution. The eutectic hardness decreased monotonously from 14.1 to <sc>8.7 GPa</sc>, whereas the primary phase hardness increased slightly from 8.0 to <sc>8.5 GPa</sc> and finally fell to <sc>5.4 GPa</sc>. In addition, the growth morphology of the (Ni) solid solution within the eutectic structure was shown to have an obvious effect on the magnetic properties of the Mo-48%Ni alloy. As the rate of cooling increased, the saturation magnetization and residual magnetization diminished. The alloy’s coercivity increased from 11.8 to <sc>25.7 A m⁻¹</sc>, indicating enhancement of the temperature resistance induced by microstructure refinement. The rapid solidification under space simulation conditions affected the mechanical and magnetic properties of the Mo-48%Ni alloy to a certain degree.

Co-processing of hydrodeoxygenation and hydrodesulfurization of phenol and dibenzothiophene with NiMo/Al2O3–ZrO2 and NiMo/TiO2–ZrO2 catalysts

Abstract The influence of Al2O3–ZrO2 and TiO2–ZrO2 supports on NiMo-supported catalysts at a different sulfur concentration in a model hydrodeoxygenation (HDO)-hydrodesulfurization (HDS) co-processing reaction has been studied in this work. A competition effect between phenol and dibenzothiophene (DBT) for active sites was evidenced. The competence for the active sites between phenol and DBT was measured by comparison of the initial reaction rate and selectivity at two sulfur concentrations (200 and 500 ppm S). NiMo/TiO2–ZrO2 was almost four-fold more active in phenol HDO co-processed with DBT than NiMo/Al2O3–ZrO2 catalyst. Consequently, more labile active sites are present on NiMo/TiO2–ZrO2 than in NiMo/Al2O3–ZrO2 confirmed by the decrease in co-processing competition for the active sites between phenol and DBT. DBT molecules react at hydrogenolysis sites (edge and rim) preferentially so that phenol reacts at hydrogenation sites (edge and edge). However, the hydrogenated capacity would be lost when the sulfur content was increased. In general, both catalysts showed similar functionalities but different degrees of competition according to the highly active NiMoS phase availability. TiO2–ZrO2 as the support provided weaker metal-support interaction than Al2O3–ZrO2, generating a larger fraction of easily reducible octahedrally coordinated Mo- and Ni-oxide species, causing that NiMo/TiO2–ZrO2 generated precursors of MoS2 crystallites with a longer length and stacking but with a higher degree of Ni-promotion than NiMo/Al2O3–ZrO2 catalyst.

A perspective on the catalytic hydrogenation of aromatics by Co(Ni)MoS phases

Hydrogenation of aromatics by catalytic hydroprocessing is necessary in the upgrading of fossil hydrocarbons into fuels and bases for petrochemistry. In this paper the meaning and applicability are discussed of the “rim-edge” model, the outstanding hydrogenation activities of NiMoS supported on NiSx, and the effect of doping by the hard anion-forming elements phosphorous, boron, and fluorine.

Role of 3D Alumina Foam Support on the Formation and Dispersion of Active NiMoS Phase for Hydrodesulfurization Application

The role of 3D alumina foam support (Al-F) and titania-modified alumina foam support (Al-F-Ti-X, where X represents the weight ratio of Al-F/TiO2) on the dispersion and catalytic activity of NiMo m...

Ni–Mo sulfide nanosized catalysts from water-soluble precursors for hydrogenation of aromatics under water gas shift conditions

Abstract The unsupported catalysts were obtained during hydrogenation by in situ high-temperature decomposition (above 300 °C) of water-soluble metal precursors (ammonium molybdate and nickel nitrate) in water-in-oil (W/O) emulsions stabilized by surfactant (SPAN-80) using elemental sulfur as sulfiding agent. These self-assembly Ni–Mo sulfide nanosized catalysts were tested in hydrogenation of aromatics under CO pressure in water-containing media for hydrogen generation through a water gas shift reaction (WGSR). The composition of the catalysts was determined by XRF and active sulfide phase was revealed by XRD, TEM and XPS techniques. The calculations based on TEM and XPS data showed that the catalysts are highly dispersed. The surfactant was found to affect both dispersion and metal distribution for Ni and Mo species, providing shorter slab length in terms of sulfide particle formation and stacking within high content of NiMoS phase. Catalytic evaluation in hydrogenation of aromatics was performed in a high-pressure batch reactor at T = 380–420 °С, p(CO) = 5 MPa with water content of 20 wt.% and CO/H2O molar ratio of 1.8 for 4–8 h. As shown experimentally with unsupported Ni–Mo sulfide catalysts, the activity of aromatic rings depends on the substituent therein and decreases as follows: anthracene&gt;&gt;1-methylnaphthalene≈2-methylnaphthalene&gt;1,8-dimethylnaphthale-ne&gt;&gt;1,3-di-methylnaphthalene&gt;2,6-dimethylnaphthalene≈2,3-dimethylnaphthalene&gt;2-ethyl-naphthalene. The anthracene conversion reaches up to 97–100% for 4 h over the whole temperature range, while for 1MN and 2MN it doesn’t exceed 92 and 86% respectively even at 420 °С for 8 h. Among dimethyl-substituted aromatics the higher conversion of 45% was achieved for 1,8-dimethylnaphthalene with 100% selectivity to tetralines at 400 °С for 6 h. Similar to 1- and 2-methylnaphtalenes, the hydrogenation of asymmetric dimethyl-substituted substrate carries out through the unsubstituted aromatic ring indicating that steric factors influence on the sorption mechanism over active metal sites. The catalysts were found to be reused for at least six cycles when the hydrogenation is sulfur-assisted preventing metal oxide formation. It was established, that at the first 2–3 h known as the induction period, the oxide catalyst precursors formed slowly by metal salt decomposition, which reveals that it is the rate-determining step. The sulfidation is rather fast based on high catalytic activity data on 2MN conversion retaining at 93–95% upon recycling.