Hydrodenitrogenation Of Quinoline Research Articles

Rational design of titanium-doped Y zeolite for hydrodenitrogenation of aromatic N-heterocyclic compounds

Ti modified Y zeolites with different Ti content were synthesized by in-situ hydrothermal crystallization method and used as the support of hydrodenitrogenation (HDN) catalyst. The forms of Ti species in the zeolites and the effect of Ti incorporation on the active metal states of the corresponding catalysts were investigated by XRD, UV–Vis DRS, XPS, HAADF-STEM, ICP-OES, Py-FTIR, H2-TPR, HRTEM, and DFT calculation. The results show that the incorporation of in-situ Ti species into Y zeolite led to a decrease in the Brønsted acid sites (BAS) /Lewis acid sites (LAS) value of the corresponding catalyst, but effectively enhanced the stacking layer number of the WS2 active phase by weakening the interaction between the active metals and the supports, which is manifested in the improvement of the hydrogenolysis activity and the decrease of the hydrogenation activity of the catalyst. When the hydrogenolysis activity and hydrogenation activity in the catalyst match to a certain extent, that is, the BAS/LAS value and the stacking layer number of the active phase reach an appropriate value, the HDN catalyst exhibited the highest catalytic activity. The NiW/Y-0.1Ti catalyst with suitable amount of BAS and stacking layer number of active phase showed the maximum kHDN values (11.7 × 10-4 mol·g−1·h−1 and 3.9 × 10-4 mol·g−1·h−1) and TOFs (1.91 h−1 and 1.04 h−1) of quinoline and indole HDN.

Three-dimensionally ordered macroporous ZSM-5 zeolite supported high-dispersed Ni2P: Highly active catalyst for quinoline hydrodenitrogenation

Zeolite catalysts have shown significant advantages in hydrogenation reactions due to their ordered pore structure and abundant acid sites. Common zeolites exhibit pore accessibility limited to microporous states, which restricts their application in diffusion-limited processes. In this study, a steam-seeding-assisted colloidal crystal template (SSAC) method was used to prepare ZSM-5 zeolite with a three-dimensionally ordered macroporous (3DOM) structure, which was then loaded with nickel phosphide for hydrodenitrogenation reactions. SEM and TEM characterization demonstrated that the prepared zeolite material possessed a highly ordered 3DOM structure with interconnected macropores. XRD, FT-IR, and BET analysis indicated that the macroporous zeolite material exhibited a typical MFI structure, mesoporous channels, and a higher specific surface area. The high external surface area facilitated the formation of uniformly sized Ni2P nanoparticles on the zeolite surface. The introduction of macroporous structures also leads to suitable Brönsted acid and Lewis acid sites in zeolite materials. The resultant Ni2P/3DOMZSM-5 catalyst exhibited higher reaction rate constants and TOF (10.87×10−2 μmolg−1s−1 and 1.5×10−3s−1, respectively) compared to other zeolite catalysts and commercial catalysts.

Elucidation of C–N bond cleavage mechanism in quinoline hydrodenitrogenation over Pt-based catalysts

C–N bond breaking is a difficult but crucial step in the quinoline removal of coal-based liquids. Noble metal catalysts have higher C–N bond breaking activity, but their surface bond breaking mechanism is unclear. Atomic layer deposition creates more metal-oxide sites and generates different active species, which facilitates the mechanism study. For this reason, we used atomic layer deposition to deposit TiO2 on the catalyst surface and suggested a more complete C–N bond breaking mechanism in this study. The particle size and pore structure of the catalyst did not change significantly after the deposition, and the hydrogen adsorption was reduced when there were too many layers deposited and the surface Pt sites were occupied to a high degree. TiO2 is extremely susceptible to reduction to Ti3+ under hydrogen, and can change the nature of the electron density of Pt through oxygen vacancies, creating Ti3+-Ptδ− sites that are prone to protonation reactions. That means, the occurrence of these protonation reactions not only easily breaks the C–N bond, but also accelerates the rate of C–N bond cleavage due to the increased H coverage on the surface of the xcTi-PtAl catalysts. And the Ti3+-Ptδ− sites in catalyst had a stronger adsorption effect on the nitrogen-containing compounds, which in turn lowered the energy barriers of bond cleavage. It is concluded that protonation is a necessary step before the C–N bond can be broken. The subsequent steps were showed by the DFT calculations that the nitrogen-containing compounds adsorbed on the Ti3+-Ptδ− sites undergo β-H fracture after the protonation reaction, with the elimination reaction cleaving the C–N bond. The xcTi-PtAl catalysts by atomic layer deposition of Ti not only improve the C–N bond breaking performance, but also improve bond breaking stability by a factor of four compared to the Pt/Al2O3 catalysts.

Hydrothermally synthesized mesoporous titanium-containing Y zeolites with different titanium contents and their high activity for hydrodenitrogenation of quinoline and indole

Herein, the effect of in-situ Ti modification on the physicochemical properties of the TixY zeolites and the corresponding NiW supported TixY-A catalysts, as well as on the catalytic performances for aromatic N-heterocyclic compounds hydrodenitrogenation (HDN) was investigated. The existing forms of Ti atoms in the Y zeolites and the active metal states of the corresponding catalysts were investigated by XRD, ICP-OES, SEM, FTIR, UV–Vis DRS, CP-MAS NMR, N2 physical adsorption–desorption, Py-FTIR, H2-TPR, HRTEM, XPS and DFT calculation. The results show that the Ti atoms can be effectively introduced into the Y zeolite framework by the in-situ hydrothermal crystallization method. With the increase of TiO2/Al2O3 molar ratio in the Y zeolite, the amount of Brønsted acid sites of the zeolite tended to decrease constantly, but the reducibility of the catalyst and the stacking layer number as well as the sulfidation degree of the NiWS active phase continued to be enhanced. The highest quinoline and indole conversions of 86.5 % and 46.9 % at 320 °C, 4.0 MPa, 300 H2/oil (v/v), and 10 h−1 LHSV, as well as the highest TOFs of 2.24 h−1 and 1.04 h−1, the highest kHDN values of 12.4 × 10−4 mol·g−1·h−1 and 3.6 × 10−4 mol·g−1·h−1, and the highest denitrogenated product selectivities of 46.1 % and 66.2 % under quinoline and indole conversions of about 15 % and 50 % respectively have been achieved in catalyst NiW/Ti0.1Y-A due to the perfect matching of its hydrogenation and hydrogenolysis performance, which was mainly derived from the remarkable synergistic effect between the Brønsted acid sites of the Y zeolite and the NiWS active phase of the catalyst.

In situ synthesis of Co modified SAPO-5 molecular sieves and the application in quinoline hydrodenitrogenation of their NiWS supported catalysts

To improve the hydrodenitrogenation (HDN) ability of conventional Al2O3-based catalysts, SAPO-5 molecular sieves with different cobalt (Co) contents were synthesized by one-pot hydrothermal method and doped as catalyst supports. The characterization results show that the Co atoms can be effectively introduced into the skeleton of SAPO-5 molecular sieve, which improved the amount of Brønsted acid site and modulated interaction between the active metals and the support (MSI). Moreover, the introduction of Co atoms also promoted the dispersion and sulfidation of the NiW active metals, resulting in more NiWS edge active sites, which contributed to the accessibility of nitrogen-containing compounds to the active center and the hydrogenation conversion performance. Together with the synergistic effect of C-N bond breaking by matching Brønsted acid between Co-modified SAPO-5 molecular sieve and the NiWS active phase, the hydrodenitrogenation activity of the catalyst was substantially improved. Hence, the catalysts containing Co modified SAPO-5 molecular sieves exhibited higher HDN activity compared with that of containing unmodified SAPO-5 molecular sieve. Among all the catalysts investigated, the NiW/CSA-3 was found to show the highest HDN performance due to the highest number of Brønsted acid sites in the Co modified SAPO-5 molecular sieve and the maximum sulfidation degree of the active phase.

Kinetics of simultaneous hydrodesulfurization and hydrodenitrogenation reactions using CoMoP/Al2O3 and NiMoP/Al2O3

Hydrodesulfurization (HDS) is a key reaction to achieve diesel production at the specified low sulfur levels and is highly affected by a competing reaction involving nitrogen removal through hydrodenitrogenation (HDN). This work evaluated kinetic parameters of simultaneous reactions of HDS of dibenzothiophene (DBT) and HDN of quinoline (Q) using CoMoP/Al2O3 and NiMoP/Al2O3 catalysts under operational conditions that allow a wide range of reagent conversions. Estimated parameters were evaluated using rigorous statistical analysis. Good fits for the evaluated experimental data were provided by both power-law and Langmuir-Hinshelwood models. Turnover frequency values highlight adsorption and competition effects between nitrogen-containing compounds and sulfur-containing compounds. NiMoP catalyst showed higher hydrogenating power than CoMoP, with larger absolute value of the estimated adsorption enthalpy (−120 kJ.mol−1 for NiMoP and −75 kJ.mol−1 for CoMoP), suggesting strong adsorption of nitrogen compounds. A catalyst with more hydrogenating power is also more capable of performing both HDN and HDS reactions simultaneously.

Ni2P/Beta@SBA-16 core-shell catalyst with tunable shell thickness for the hydrodenitrogenation of quinoline

A series of core-shell structural hydrodenitrogenation (HDN) catalyst supports, using H-Beta zeolite nanoparticles as the core and tunable mesoporous materials SBA-16 thin film thickness as shell, were designed and controllably synthesized. The corresponding Ni2P catalyst were prepared, and their catalytic performances were tested for quinoline HDN. It was found that the high external surface area provided by the mesoporous shell layer of the core-shell catalyst favored the formation of Ni2P nanoparticles with more uniform particle size. The Py-IR result indicates that the SBA-16 shell thickness plays an important role in influencing the ratio of the amount of Bronsted and Lewis acid sites on the catalyst. The H2-TPR results indicates that the introduction of core-shell structure can adjust the metal-support interactions (MSI) of materials. The core-shell support with suitable shell thickness (70 nm) exhibits a wide pore structure, large surface area and sufficient amounts of Lewis and Bronsted acid sites. These properties contribute to the formation of tiny and size homogeneous (4.6 nm) Ni2P nanoparticles. Smaller Ni2P particles present more active sites, which increases catalytic activity. The Ni2P/H-Beta@SBA-16–2 catalyst with the most suitable shell thickness exhibited a higher reaction rate constant and TOF for HDN reaction of quinoline.

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.

Substituent Effects of the Nitrogen Heterocycle on Indole and Quinoline HDN Performance: A Combination of Experiments and Theoretical Study.

Hydrodenitrogenation (HDN) experiments and density functional theory (DFT) calculations were combined herein to study the substituent effects of the nitrogen heterocycle on the HDN behaviors of indole and quinoline. Indole (IND), 2-methyl-indole (2-M-IND), 3-methyl-indole (3-M-IND), quinoline (QL), 2-methyl-quinoline (2-M-QL) and 3-methyl-quinoline (3-M-QL) were used as the HDN reactant on the NiMo/γ-Al2O3 catalyst. Some key elementary reactions in the HDN process of these nitrogen compounds on the Ni-Mo-S active nanocluster were calculated. The notable difference between IND and QL in the HDN is that dihydro-indole (DHI) can directly convert to O-ethyl aniline via the C-N bond cleavage, whereas tetrahydro-quinoline (THQ) can only break the C-N single bond via the full hydrogenation saturation of the aromatic ring. The reason for this is that the -NH and C=C groups of DHI can be coplanar and well adsorbed on the Ni-Mo-edge simultaneously during the C-N bond cleavage. In comparison, those of THQ cannot stably simultaneously adsorb on the Ni-Mo-edge because of the non-coplanarity. Whenever the methyl group locates on the α-C or the β-C atom of indole, the hydrogenation ability of the nitrogen heterocycle will be evidently weakened because the methyl group increases the space requirement of the sp3 carbon, and the impaction of the C=C groups on the Ni-S-edge cannot provide enough space. When the methyl groups are located on the α-C of quinoline, the self-HDN behavior of 2-M-QL is similar to quinoline, whereas the competitive HDN ability of 2-M-QL in the homologs is evidently weakened because the methyl group on the α-C hinders the contact between the N atom of 2-M-QL and the exposed metal atom of the coordinatively unsaturated active sites (CUS). When the methyl group locates on the β-C of quinoline, the C-N bond cleavage of 3-methyl-quinoline becomes more difficult because the methyl group on the β-C increases the steric hindrance of the C=C group. However, the competitive HDN ability of 3-M-QL is not evidently influenced because the methyl group on the β-C does not evidently hinder the adsorption of 3-M-QL on the active sites.

Insight into the hydrodenitrogenation mechanism of quinoline on the MoP(010) surface with and without the effect of sulfur

The nitrogenous aromatic compounds such as quinoline in coal-based crude oil not only generate photochemical smog, but also inhibit the activity of catalyst to a certain extent. The hydrodenitrogenation (HDN) mechanism of quinoline including hydrogenation and ring opening was investigated by using the density functional theory (DFT) on the MoP(010) surface. The favorable pathway is that quinoline generates 1,2,3,4-tetrahydroquinoline (THQ1) through hydrogenation, and then undergoes CN bond cleavage through the Hoffman elimination mechanism (E2). In addition, the effect of S in coal-based crude oil on quinoline HDN was also investigated. The introduction of S leads to the transfer of more electrons from the uppermost surface of MoP(010) to the S, which improves the HDN activity for the MoP(010) surface by reducing the hydrogenation energy barrier for the quinoline to THQ1. The microkinetic analysis indicates that the actual temperature (650 K) is more favorable for the HDN of quinoline on the MoP(010) surface.

Preparation of Beta-KIT-5 composite material supported ternary metal catalyst and its hydrodenitrogenation performance of quinoline

A series of Beta-KIT-5 (BK-x) composite materials with different Si/Al ratios were synthesized successfully with the nano-assembly method, and NiMoW catalysts were prepared for quinoline hydrodenitrogenation (HDN) reaction. The characterization results showed that BK composite materials possessed the ordered three-dimensional face-centered-cubic mesoporous structure and Beta topological structure; moreover the Beta structure units were embedded into the framework of KIT-5 material. The addition of Beta seed solution modified the textural properties and interaction between the support and active metals, thus improving the distribution of active metal species and enhancing the acidity of NiMoW catalysts, especially for Brønsted acid sites. The catalytic performance displayed that the NiMoW/BK-3 catalyst exhibited the highest HDN efficiency and maximum kHDN (21.6×10−5 mol g−1h−1), which was attributed to the excellent structural properties, moderate acid sites and suitable dispersion of Mo(W)S2 stacking slabs.

Charge effects on quinoline hydrodenitrogenation catalyzed by Ni–Mo–S active sites-A theoretical study by DFT calculation

The charge distribution on Ni–Mo–S active sites can affect hydrodenitrogenation (HDN) activity. In this study, a series of model Ni–Mo–S were developed with various charge distributions. For comparison, the charge distribution effects on quinoline HDN were studied. The results show that a lack of electrons and extra protons can both lower the orbital eigenvalue of the Ni–Mo–S, leading to stronger adsorption of nitrogen-containing compounds and inhibition of ammonia desorption. Electron deficiency will improve the generation of active hydrogen on the active sites but inhibit hydrogen transfer to the nitrogen compounds; extra protons can provide H+ to the nitrogen compounds, which will flexibly transfer between the nitrogen compound and active sites, thus improving the cleavage of the C–N bond.

Products, pathways, and kinetics for catalytic hydrodenitrogenation of quinoline in hydrothermal condition

The purpose of this study is to investigate reaction mechanism and kinetics of catalytic hydrodenitrogenation (HDN) of quinoline under hydrothermal conditions (300 °C, 350 °C, and 400 °C), using Ni-Ru/γ-Al2O3 catalyst and formic acid (FA) as hydrogen donor. 1,2,3,4-tetrahydroquinoline, decahydroquinoline, aniline, methyl aniline, 2-hexene, and toluene were primary products. Quinoline conversion fits a first-order kinetics, with an activation energy of 41.72 kJ/mol. A possible reaction network of HDN of quinoline was developed and the corresponding kinetic model captures nearly all the temporal variation of all major products’ concentration. The kinetic modeling results indicated that the dehydrogenation of 1,2,3,4-tetrahydroquinoline to quinoline is the rate-determining step with high energy barrier of 174.6 kJ/mol. Reaction rate analysis showed 2-hexene as the major denitrogenated product is mainly derived from hydrogenation of aniline and its formation rate from decahydroquinoline is higher than the path from aniline derivatives. Sensitivity study revealed that hydrogenation from quinoline to decahydroquinoline has a strong influence on the whole reaction process. Both catalyst durability test and catalyst characterizations demonstrated that the Ni-Ru bimetallic catalyst was relatively unstable under supercritical water conditions, probably due to the joint influences of partial agglomeration of active metal and hydrolysis of supporter γ-Al2O3.

Hydrodenitrogenation of Quinoline with high selectivity to aromatics over α-MoC1-x

The hydrodenitrogenation (HDN) with a low hydrogen consumption in the hydroprocessing of crude oils derived from carbon resources is still a challenge. Here, a molybdenum carbide (α-MoC1-x) catalyst with a high selectivity to aromatic compounds was reported, using the HDN of quinoline as a model reaction. This process was characterized by low hydrogen consumption. The prepared α-MoC1-x had a much larger specific surface area (107.6 m2•g−1) than β-Mo2C (6.8 m2•g−1). Under the catalysis of α-MoC1-x, the conversion and the denitrification rate of quinoline could both reach 99%, and the highest selectivity of the total aromatics reached 48.5% at 360 °C, which was 10.7% higher than that on β-Mo2C. The cleavage of CC bonds of side chain of Propylbenzene (PB) and Propylcyclohexane (PCH) occurred, producing several unexpected products with unusual high selectivity. A new possible reaction network of quinoline hydrodenitrogenation was drawn, and the reaction mechanism was discussed based on the experiments and DFT (density functional theory) calculations.

Influence of Ni on the active phase and hydrodenitrogenation and hydrodesulfurization activities of MoS2 catalysts

To obtain type II active phase with higher activity, MoS2-based catalysts were prepared by thermal decomposition of ammonium tetrathiomolybdate. The influence of Ni adding way and decomposition atmosphere on the microstructures of MoS2 slabs, chemical state of surface elements, as well as hydrodesulfurization and hydrodenitrogenation activities were investigated. Results indicated that simultaneous impregnation of Mo and Ni precursors caused in situ deposition of amorphous NiMoS4 over the support surface, which subsequently facilitated the substitution of Mo atoms by Ni atoms at MoS2 edges. Accordingly, these decorated catalysts exhibited higher dispersion of MoS2 slabs with more suitable slab length (3–5 nm) and stacking number (2–4), which attributed to larger numbers of rim and corner active sites exposed at the edges. These active sites were essential in hydrogenation and hydrogenolysis reactions. In comparison with N2 atmosphere, thermal decomposition in H2 atmosphere was more conducive to the substitution of Mo atoms by Ni atoms at MoS2 edges, which provided more active Ni-Mo-S structures for the adsorption, activation and hydrogenolysis of quinoline and dibenzothiophene molecules. The catalyst prepared by thermal decomposition of NiMoS4 in H2 atmosphere showed superior activities in the quinoline hydrodenitrogenation with 23.8% conversion and in the dibenzothiophene hydrodesulfurization with 93.3% conversion, under the conditions of 340°C, 3 MPa, a weight hourly space velocity of 23.4 h−1, H2/oil volume ratio of 600 and 0.1 g of NMS-H2 catalysts.

Core-shell meso-beta@mesoporous aluminosilicate supported Ni2P catalyst for the hydrodenitrogenation of quinoline: Effect of core shell structure on Ni2P particle size

A core–shell structured material with a mesoporous aluminosilicate (MAS) shell and mesopore-containing beta zeolite (meso-beta) core was synthesized by self-assembly using triblock copolymer (P123) as template. The corresponding Ni2P catalyst for quinoline hydrodenitrogenation (HDN) was prepared by the hypophosphite disproportionation method. The core–shell support exhibits a wide pore structure, large surface area, suitable amounts of Lewis and Bronsted acid sites, and a large number of acidic hydroxyl groups exist at the interface of MAS and meso-beta. These properties contribute to the formation of very small (4.7 nm) Ni2P clusters. Furthermore, the micropores of the zeolite core can anchor the Ni2P nanoparticles and prevent nanoparticle aggregation. The smaller Ni2P particle size can expose more active sites and thus results in higher catalytic activity. The obtained Ni2P/meso-beta@MAS catalyst exhibits a higher reaction rate constant and TOF (12.37 × 10-2 μmolg−1s−1 and 1.7 × 10−3s−1, respectively) for the quinoline HDN reaction compared to a silica-supported Ni2P catalyst (6.18 × 10−2 μmolg−1s−1 and 1.5 × 10−3s−1, respectively) and Ni2P/H-beta catalyst (6.81 × 10−2 μmolg−1s−1 and 1.4 × 10−3s−1, respectively).

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.

Boosting hydrodesulfurization activity of CoMo/Al2O3 catalyst via selective graphitization of alumina surface

The positive effect of alumina surface graphitization by CVD with ethylene on the activity of CoMo catalysts in hydrodesulfurization has been demonstrated. X-ray diffraction, Raman spectroscopy, High-resolution transmission electron microscopy, X-ray photoelectron spectroscopy and nitrogen physisorption showed that alumina surface graphitization does not significantly change the morphology and textural characteristics of the support. However, it has a significant impact on the morphology of supported sulfide component resulting in the formation of particles with a shorter slab length (2.9 vs 3.3 nm) and higher stacking number (2.4 vs 2.1) as compared to the sample based on γ-Al2O3. The results of CoMoS/γ-Al2O3 and CoMoS/[email protected]γ-Al2O3 catalysts testing in hydrotreating reactions demonstrated a similar activity in hydrodenitrogenation of quinoline and 1.7 times higher activity of CoMoS/[email protected]γ-Al2O3 in hydrodesulfurization of dibenzothiophene. Higher hydrodesulfurization activity of CoMoS/[email protected]γ-Al2O3 sample is attributed to improved dispersion of the supported sulfide component and enhanced promotion of MoS2 by cobalt. Thus, the simple CVD approach presented here allows selective modification of the surface of commercially available alumina supports with a layer of graphite-like carbon and can be used to improve the activity of conventional hydrotreating catalysts.

Single-Pot Synthesis of NiMo-Al2O3 Catalyst for Quinoline Hydrodenitrogenation

Mesoporous NiMo-Al2O3 catalysts were synthesized without the structure-directing agent by a single-pot method and were studied for quinoline hydrodenitrogenation (HDN). These catalysts were charact...

Effect of Zr on catalytic performance of unsupported Ni(Zr)Mo and Ni(Zr)W sulfide catalysts for quinoline hydrodenitrogenation

To increase the dispersion of active species and full utilization of active metals are of great importance for hydrodenitrogenation (HDN) performance of unsupported hydrotreating catalysts. Herein, a series of unsupported Ni(Zr)MoS and Ni(Zr)WS catalysts were prepared from Ni(Zr) layered double hydroxide (LDH) precursors. The Zr species remarkably promote the dispersion and reducibility of NiMo and NiW composite species. Also, the total HDN rate constants are increased from 2.42 h−1 to 9.18 h−1 for Ni(Zr)MoS and from 5.68 h−1 to 23.0 h−1 for Ni(Zr)WS, and exhibit a maximum at a Zr/Ni atomic ratio of about 0.04. The HDN selectivities indicate that the Zr species increase the number of superficial active sites without affecting their structure. The present work shows that the crystallinity of LDH precursors is crucial to the structure of unsupported sulfide catalysts, and a suitable amount of Zr could be a dispersive promoter to increase the HDN activity.