Hydrodenitrogenation Activity Research Articles

Enhanced hydrotreating performance of hierarchical NiMo-S/Al2O3 catalysts through ZrO2 incorporation and template-driven structural modulation

A dual template-assisted approach for optimizing support structures to enhance catalytic efficiency in hydrotreating reactions is presented. Catalysts synthesized using activated carbon (AC) templates exhibited significantly higher activity in both hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) compared to those prepared with starch (ST) templates. The unique porous architecture, characterized by well-distributed meso- and macropores, facilitated efficient access of bulky molecules to the active sites. On the other hand, while the reactivity in the selective opening of the naphthenic ring (SONR), which is indicative of hydrocracking functionality, was similar across all catalysts, those modified with Zr exhibited a slight improvement. The catalysts displayed bifunctional characteristics, and their performance was influenced by the amphoteric nature of the support and the specific ratios of active species on the surface. A clear correlation between catalytic activity, selectivity, and the distribution of active sites was established.

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.

Effect of TiO2-Al2O3 support surface properties on active phase structure and hydrodenitrogenation performances of the corresponding NiWS supported catalysts

To explore the effect of the support surface properties on the active phase structure and the hydrodenitrogenation (HDN) catalytic performance of the corresponding hydrotreating (HDT) catalyst, three kinds of TiO2-Al2O3 supports with a Ti/Al molar ratio of 1 but different Ti-Al composite result were prepared by the following methods: the mechanical mixing method (T + A), the ion-exchange method (T/A) and the in-situ synthesis method (TA). The Ti-Al composite results of the supports were characterized by XRD, FTIR, SEM-Mapping and N2 physical adsorption–desorption techniques and the properties of the NiW supported catalysts were determined by XRD, H2-TPR, HRTEM and XPS. The results show that the surface properties of TiO2-Al2O3 composite supports can be modulated by changing the Ti modification method. Among all the three methods, the in-situ synthesis method can achieve the atomic mixing of titanium and aluminum elements to maximize the Ti-O-Al bonds, followed by the ion-exchange method, and finally the mechanical mixing method. Accordingly, the number of Ti-O-Al bonds in the support determines the dispersion, stacking and sulfurization of the active phase. When more Ti-O-Al bonds are present in the support, the higher the dispersion and sulfurization degrees of the active metals and the stacking layer number of the NiWS active phase in the catalyst, thus exhibiting higher HDN activity both for basic and non-basic nitrides. In addition, Ti3+ species can be generated when enough Ti-O-Al bonds are present in the support surface, which also enhance the promotion of the sulfidation degrees of the active metal and the formation of CUS and thus further improve the HDN activity. Generally, the in-situ Ti modification method was considered to be the favorable method for preparing highly active HDT catalysts due to its excellent Ti-Al composite surface properties.

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.

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.

A dye-sensitized solar cells with an efficiency of 10.01% based on the MoP/MoNiP2@Ti3C2 composite counter electrode

Transition metal phosphides are becoming a main study topic in new catalytic materials field due to their similar properties to transition metal nitrides and carbides as well as their excellent reaction activity and catalytic selectivity for deep hydrodesulfurization and hydrodenitrogenation. Mxene, a two-dimensional layered material with high specific surface area and electrical conductivity, plays an important role in accelerating catalytic reduction of triiodide ion in dye-sensitized solar cells (DSSCs). In this work, the MoP/MoNiP2 hybrid was synthesized while adopting Ti3C2 Mxene to realize the intercalation structure of composite with simple conditions, therefore enabling a formation of ‘pillared effect’ in Ti3C2 Mxene. The optimized MoP/MoNiP2@Ti3C2 composite was achieved by adjusting the doping ratio of the two. The DSSCs based on the MoP/MoNiP2@Ti3C2 catalyst with 80 wt% Ti3C2 doping reache an enhancement of power conversion efficiency of 10.01%, much higher than that of the platinum counter electrode (8.22%). Through a suite of morphological and electrochemical analyses, we summarize the reasons for the performance enhancement to the synergistic effect of the MoP/MoNiP2 hybrid and Ti3C2 Mxene, and especially, the unique intercalation structure of MoP/MoNiP2@Ti3C2 with ‘pillared effect’. The MoP/MoNiP2@Ti3C2 counter electrode with perfect electrochemical and photoelectrochemical properties is a promising alternative to the platinum electrode for DSSCs in the future.

A study on the role of Ti/Si atomic ratios in the hydrodenitrogenation activity of NiMo/TiO2-SiO2 catalyst

TiO2-SiO2 composites with different Ti/Si atomic ratios were synthesized by an optimized pre-hydrolysis-co-precipitation method while the corresponding NiMo supported hydrodenitrogenation (HDN) catalysts were prepared by incipient wetness impregnation method. The significant structure of serial TiO2-SiO2 composites was determined by XRD, FT-IR, N2 physical adsorption–desorption and NH3-TPD techniques, and the distributions of TiO2 particles within SiO2 matrix were also illustrated under the help of SEM-EDS. In this work, it can be concluded that the Ti/Si atomic ratio has a large effect on the textural characteristics and the acidity distribution of composites. Among the self-made composites, TS-1 samples (Ti: Si = 1) presented the highest specific surface area (SBET = 230.42 m2/g) and the highest proportion of weak acidity. And then, characterization of the NiMo/TS-n catalysts were performed by H2-TPR, HRTEM and XPS. Among the NiMo/TS-n catalysts, NiMo/TS-1 catalysts presented the particularly favorable dispersion of active metals and the largest proportion of “Ni-Mo-S” active phase. The results of the adsorption tests showed that NiMo/TS-4 catalysts presented the maximum value of adsorption coefficient (ACQ). Compared these ACQ, these adsorption sites of quinoline were attributed to the CUS supported by “Ni-Mo-S” structures as well as the strong acid sites by excessive TiO2 particles. Finally, these catalysts were tested by feeding 1.0 wt% quinoline as the reactant under the constant reaction conditions. However, the results of HDN evaluation showed that NiMo/TS-1 catalyst exhibited the best HDN activity (51.31 %) and the highest value of turnover frequency (TOFQ = 4.77 h−1), which was attributed to the formation of maximum Ti-O-Si bonds providing moderate acidity, appropriate MSI, suitable size of MoS2 slabs and “Ni-Mo-S” active phase having high concentration of CUS and Mo-SH/S2− species.

Unsupported Ni—Mo—W Hydrotreating Catalyst: Influence of the Atomic Ratio of Active Metals on the HDS and HDN Activity

Hydrotreating is one of the largest processes used in a refinery to improve the quality of oil products. The great demand of the present is to develop more active catalysts which could improve the energy efficiency of the process when it is necessary for heavier feedstock to be processed. Unsupported catalysts could solve this problem, because they contain the greatest amount of sulfide active sites, which significantly increase catalysts’ activity. Unfortunately, most of the information on the preparation and properties of unsupported catalysts is devoted to powder systems, while industrial plants require granular catalysts. Therefore, the present work describes a method for the preparation of granular Ni—Mo—W unsupported hydrotreating catalysts and studies the influence of the Ni/Mo/W atomic ratio on their properties. Catalysts have been prepared by plasticizing Ni—Mo—W precursor with aluminum hydroxide followed by granulation and drying stages. Ni—Mo—W precursor and granular catalysts were studied by X-ray diffraction (XRD), nitrogen adsorption–desorption method, high-resolution transmission electron microscopy (HRTEM), and thermal analysis. Granular catalysts were sulfided through a liquid-phase sulfidation procedure and tested in hydrotreating of straight-run vacuum gasoil. It was shown that the Ni/Mo/W atomic ratio influenced the formation and composition of active compounds and had almost no influence on the textural properties of catalysts. The best hydrodesulfurization (HDS) activity was obtained for the catalyst with Ni/Mo/W ratio—1/0.15/0.85, while hydrodenitrogenation (HDN) activity of the catalysts is very similar.

Understanding the effects of feedstock blending and catalyst support on hydrotreatment of algae HTL biocrude with non-edible vegetable oil

The performance of cobalt-molybdenum (CoMo) on hydrotreating of algae HTL biocrude and carinata oil was investigated. Commercial CoMo/Al2O3 (CoMo/Al) and synthesized CoMo supported on Douglas fir biochar (CoMo/DF), sulfided or unsulfided catalysts, were compared for hydrodeoxygenation (HDO), hydrodenitrogenation (HDN), hydrodesulfurization (HDS) and hydrodemetallization (HDM) reactions. Results showed that there lies a synergistic effect when HTL algae biocrude and carinata oil blends are hydrotreated. The yield of the upgraded blend (UB) oils retrieved over alumina catalyst was higher than the individual hydrotreated parent oils. For example, a 9% and 5% increase in yield was noted compared to the average of individual hydrotreated parent oils. The UB produced from sulfided CoMo/Al exhibited superior HDO activity primarily by decarbonylation. This was apparent in increased heating value, carbon addition, higher octane number, and lower total acid number than the oils obtained from the biochar-supported catalysts. Sulfided CoMo/DF catalyzed cracking reactions which lowered the viscosity, followed by high HDN and HDS activity compared to the commercial catalyst. The two supports showed different sorption behaviors. Interestingly, CoMo/DF had an effective sorption mechanism that helped in higher metal removal from the oil. Additionally, presulfiding and DF support exhibited positive results in term of less coke formation. In brief, biochar supports have higher acidic sites, inorganic mineral oxides, ion exchange capacity, high surface area, pore structure and connectivity. All of these make a substantial contribution to its unique catalytic behavior.

Promotion of boron phosphate on the NiMoAl catalyst for hydroprocessing FCC slurry oil

Mesoporous NiMoAl catalysts with boron phosphate (BPO4) modification were synthesized through the complete liquid-phase method. X-ray diffraction (XRD) analysis evidenced the presence of BPO4-AlOOH mixed support in these BPO4-modified NiMoAl samples. The total amount of acid sites declined, but the surface acidity was strengthened by adding BPO4 into the NiMoAl catalyst. It's worth noting that the incorporation of BPO4 could increase the concentrations of Ni and Mo species on the catalyst surface and greatly improve the dispersion of (Ni)MoS2 active phases, as indicated by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) measurements. The catalytic performance of these BPO4-modified NiMoAl catalysts was investigated with the hydroprocessing of fluid catalytic cracking (FCC) slurry oil. The nitrogen-containing compounds removal from the oil was significantly enhanced with increasing the molar ratio of boron phosphate/aluminum. The NM-BPA(0.55) catalyst exhibited the best hydrodenitrogenation (HDN) activity, highlighting the significant impact of Mo sulfidation degree and the dispersion of active metals on HDN performance. The introduction of boron phosphate could also promote the hydrocracking activity of the NiMoAl catalyst, as demonstrated by SARA analysis and simulated distillation of liquid products.

Synthesis of mesoporous TiO2-Al2O3 composites supported NiW hydrotreating catalysts and their superior catalytic performance for heavy oil hydrodenitrogenation

Mesoporous TiO2-Al2O3 composites with different Ti/Al molar ratios were successfully synthesized via pre-hydrolysis co-precipitation method and the corresponding NiW supported hydrotreating (HDT) catalysts were prepared via incipient wetness co-impregnation method. The effects of Ti modification on the physicochemical properties of the prepared supports and catalysts were determined by the characterization techniques such as XRD, FTIR, N2 physical adsorption–desorption, SEM-EDS, ICP-OES, NH3-TPD, H2-TPR, HRTEM and XPS. Finally, quinoline, indole and coker gas oil (CGO) were used respectively as probes to investigate the Ti modification on the hydrodenitrogenation (HDN) performances of the corresponding catalysts. The results show that the TiO2-Al2O3 samples synthesized by the pre-hydrolysis co-precipitation method achieved the level of molecular composition, and the crystalline structures, pore properties and acidity properties of the TiO2-Al2O3 supports varied with the Ti/Al molar ratios. Ti modification can modulate the interaction between the active metals and the supports (MSI), and promote the formation of more so-called “type II” NiWS active phases. Furthermore, the existence of Ti3+ species in catalysts NiW/TA1 and NiW/TA2 enhanced the sulfidation degrees of active metals and weakened the bond energy between the active metals and sulfur atoms and further promoted the formation of more coordinatively unsaturated sites (CUS). The catalytic assessment results show that the HDN activities of the catalysts were effectively improved after Ti modification and the improvement was largely due to the promotion of the cleavage of the C(sp3)-N bond of basic nitrides and the C(sp2)-N bond of non-basic nitrides. The NiW/TA1 catalyst exhibited the highest performance in the HDT process of heavy oil, with a 15.8% and 12.4% improvement in HDN rate and hydrodesulfurization (HDS) rate compared with the unmodified catalyst, respectively, which was mainly attributed to its suitable pore properties, moderate MSI, large number of CUS, moderate stacking and highest active metal sulfidation degree of the active phase.

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.

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.

SRGO hydrotreating over Ni-phosphide catalysts on granulated Al2O3

Ni-phosphides present a promising alternative to the conventional hydrotreatment NiMo sulfides. The hydrotreatment catalysts are supported on Al2O3 granules, and the similarly Al2O3 supported Ni-phosphide catalysts provide an interesting case for comparison. In this work the Ni-phosphide catalysts supported on Al2O3 granules were prepared using two procedures: 1) temperature-programmed reduction of “phosphite”-type precursor in hydrogen flow (TPR_I catalyst), 2) treatment of Ni nanoparticles with triphenylphosphine solution at elevated temperature (LP catalyst). The catalysts were characterized by ICP-AES chemical analysis, N2 physisorption, XRD, TEM, XPS, 27Al MAS NMR. The Ni2P particles were found in LP samples, while TPR method gives the mixture of Ni12P5 and Ni2P particles and amorphous AlPO4 on the alumina surface. The behavior of granulated Ni phosphide and conventional sulfided NiMo/Al2O3 catalysts was compared in hydroprocessing of straight-run gas oil (SRGO) at 340 °C, 4 MPa, V(H2)/V(feed) - 400 Nm3/m3, LHSV - 1,5 h−1. Hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) activity of nickel phosphide catalysts were shown to be lower in comparison with NiMo/Al2O3. Hydrotreating of S-containing model compounds (DBT, 4-MDBT, 4,6-DMDBT) was carried out over TPR_I catalyst, and a negative effect of dimethyl disulfide (DMDS) and acridin additions on the HDS activity was observed.

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.

Novel solution for removing poisonous silica from a Ni-Mo/Al2O3 industrial HDT spent catalyst

During hydrotreating, silica poisoning of catalysts represents a severe problem, because the silicone compounds that are present in coker naphtha feedstocks are adsorbed and transformed on the alumina surface, deactivating it. To provide a solution, in the present work, silica was selectively removed from an industrial Ni-Mo/Al2O3 spent catalyst by applying a depolymerization process with glycerol that resulted in the restoration of silicon retention capacity, hydrodesulfurization and hydrodenitrogenation activities and physical properties of the catalyst. Catalyst samples, before and after the removal of silica compounds, were studied by nuclear magnetic resonance spectroscopy (NMR), N2 physisorption, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), atomic absorption spectroscopy and scanning electron microscopy (SEM).

Effect of Ni loading and impregnation method on the hydrodenitrogenation of coal tar over Ni-Mo/γ-Al2O3

ABSTRACT Ni-Mo/γ-Al2O3 catalysts with different Ni loadings were prepared. They were characterized by X-ray diffraction (XRD), N2 adsorption, IR spectra of adsorbed pyridine (Py-IR), temperature-programmed desorption of ammonia (NH3-TPD), temperature-programmed reduction of H2 (H2-TPR), and high resolution transmission electron microscopy (HRTEM). The hydrodenitrogenation (HDN) performance of catalysts for coal tar were evaluated. The best hydrodenitrogenation activity was observed on the catalysts with a Ni loading of 6.25 wt% and a Ni/(Ni+Mo) ratio of 0.4. Also, the methods of co-impregnation and sequence-impregnation were compared. The denitrification rate of co-impregnation catalyst NiMo-5-co (71.2%) was slightly lower than that of sequence-impregnation catalyst NiMo-5 (71.7%). Disparate product distribution was obtained on NiMo-5-co and NiMo-5. The dispersion of active components, the distribution of pore and acid on catalysts played an important role in HDN process of coal tar.

Silicon doping effect on the properties of the hydrotreating catalysts of FCC feedstock pretreatment

Influence of Si addition at the stage of boehmite preparation on properties of NiMo/Al2O3 catalysts for FCC feedstock pretreatment have been studied. The series of boehmites doped by PDMS at the stage of hydrothermal treatment was prepared. Si/Al molar ratio was 0, 0.01, 0.015 and 0.02. Boehmites were used for supports and catalysts preparation. Boehmites, supports and catalysts have been characterized by XRD, TGA, nitrogen adsorption-desorption, IR spectroscopy, UV–Vis, 29Si MAS NMR, HRTEM, EDX, XPS. Catalysts were tested in hydrotreating of FCC feedstock. It is shown that there are changes in morphology of boehmite particles and textural characteristics of aluminas. Introduction of Si to alumina induces formation of wider mesopores and blocks part of the Lewis acid sites of alumina. Testing of catalysts in hydrotreating of FCC feedstock shows that the catalyst with Si/Al ratio of 0.01 in boehmite has the best combination of hydrodesulfurization and hydrodenitrogenation activities.