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Trimetallic NiMoW/Al2O3 catalysts based on mixed H4[SiMonWn-12O40] (n = 1, 3, 6, and 9) Keggin-type heteropolyacids (HPAs) were synthesized by incipient wetness impregnation of alumina with aqueous solutions of mixed HPAs. For comparison purposes, trimetallic samples were prepared from a mixture of monometallic H4[SiMo12O40] and H4[SiW12O40 ] HPAs with a Mo/W ratio corresponding to the mixed MoW HPAs. The catalysts were sulfided by a liquid phase method and tested in the model reactions of dibenzothiophene hydrodesulfurization and naphthalene hydrogenation, with subsequent addition of quinoline to study the effect of inhibition of target reactions. Further, the catalysts were tested in the hydrotreating of straight-run gas oil to evaluate the efficiency of catalysts on real feedstocks. In order to link catalytic performances with the preparation method and Mo/W ratio, the catalysts were fully characterized by high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, high-angle annular dark-field imaging, and quick X-ray absorption spectroscopy. It was found that the Mo/W atomic ratio of the structure-forming metals in the active phase, deriving from the Mo/W ratio in the HPA precursor, directly affects the ratio of the hydrogenation and hydrodesulfurization performances. For feedstock with a high concentration of N-containing compounds, it is necessary to use mixed NiMoW systems with a high tungsten percentage to reduce the inhibitory effect and ensure the quality of the products. The use of new mixed MoW Keggin HPAs has made it possible to enhance the synergistic effect in trimetallic NiMoW catalysts due to the closer interaction between Mo and W, which increased the sulfidation degree of metals and also contributed to the formation of highly active mixed NiMoWS sites.

Supported and unsupported (with or without Co and Ni promotors) MoS2-based catalysts were prepared using conventional incipient wetness impregnation method on pure and carbonized alumina with an appropriate aqueous solution of a 12-molybdophosphoric heteropolyacid and cobalt or nickel citrate. Unsupported MoS2 catalysts were synthesized by leaching away the supports from MoS2/Al2O3, MoS2/C/Al2O3 and using industrial CoMo/Al2O3 catalyst (named as Et-MoS2-Ind) with HF acid. Catalysts were investigated by low-temperature nitrogen adsorption and transmission electron microscopy techniques to characterize their structure and morphology. Catalysts were tested in hydrodeoxygenation (HDO) of oleic acid (OA) in an autoclave under hydrogen pressure. CoMoS2/Al2O3, NiMoS2/Al2O3, and Et-MoS2-Ind catalysts were also investigated as single and dual catalytic systems, using a bench-scale flow reactor in co-hydroprocessing of mixed feed, containing straight-run gas oil and 15 wt. % of waste sunflower oil. The results of the catalyst tests show that hydrogenation/decarbonylation (HYD/DEC) selectivity in oleic acid HDO strongly depends on catalyst type. The CoMoS2/C/Al2O3 and CoMoS2/Al2O3 catalysts show low HYD/(HYD + DEC) selectivity, equal to 0.55. Unpromoted MoS2/C/Al2O3, MoS2/Al2O3, Et-MoS2-Ind and Ref-MoS2 samples have quite similar HYD/(HYD + DEC) selectivity around 0.85. The highest HYD/(HYD + DEC) selectivity (0.95) was reached over Et-MoS2/C and Et-MoS2 samples, which indicated that HDO had gone through HYD route without any formation of CO and CO2. A double-bed catalyst reactor comprising of the upper-layer bulk Et-MoS2-Ind and the under-layer Co(Ni)–MoS2/Al2O3 catalysts are proposed for the effective co-hydroprocessing of diesel and vegetable oil.

A series of alumina supported CoMo catalysts with different molybdenum surface density was prepared using incipient wet impregnation method and applying H6[Co2Mo10O38H4] (Co2Mo10HPA) as a single oxidic precursor. Dried and sulfided catalysts were characterized by a variety of techniques, such as N2 adsorption, micro-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM). Catalytic properties have been examined in co-hydrotreating of dibenzothiophene and naphthalene using a fixed bed high-pressure flow reactor. It was found that using Co2Mo10HPA as a single precursor enables more than the double increase of maximum metal loading compared to conventional compounds. This also contributed to a significant increase in catalytic activity in hydrotreating.

MoW alumina supported hydrotreating (HDT) catalysts were synthesized by using mixed SiMonW12-n heteropolyacids (HPAs) and also from a mixture of SiMo12 and SiW12 HPAs with the same Mo/W ratios for reference. Gas phase sulfidation of the catalysts prepared from mixed MoW HPAs led to the formation of a mixed phase evidenced by high-angle annular dark-field (HAADF) images, where a core of Mo atoms was surrounded by W atoms. Contrariwise, most of MoS2 or WS2 slabs were observed in the solids prepared from a mixture of the HPAs. This mixed phase induced higher hydrodesulfurization (HDS) of DBT, as well as hydrogenation (HYD) of naphthalene, than it was observed in the case of the reference catalysts. Comparison of activation procedures (gas phase versus liquid phase) confirmed that sulfidation in gas phase led to more efficient catalysts, even in the case of the formation of the mixed slabs. Beneficial effect of the mixed MoWS phase was even more pronounced in the case of the HDS of a more refractory molecule, 4,6-dimethyldibenzothiophene (4,6-DMDBT), which was attributed to the more hydrogenating properties of this mixed phase.

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

Alumina supports were synthesized from aluminum hydroxide produced by the hydrolysis of secondary aluminum butoxide in the presence of the triblock copolymer Pluronic P123 (m-AlOOH) and from the commercial AlOOH pseudoboehmite powder (TH-AlOOH), as well as by mixing of m-AlOOH and TH-AlOOH gel in a ratio of 5:95 (m-TH-AlOOH sample). NiW/Al2O3 catalysts were prepared by impregnation of the synthesized supports with H3PW12O40 heteropolyacid and nickel citrate. Physicochemical properties of the supports and catalysts were investigated by low-temperature nitrogen adsorption, X-ray diffraction, NH3 thermo-programmed desorption, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. Catalytic properties were tested in hydrotreatment of straight-run gas oil and vacuum gasoil on a flow unit. The resulting hybrid support had a non-additively higher average pore radius (75 A) and surface area (307 m2/g) than a conventional alumina support and hence preferred morphology of NiWS active phase (3.8 nm against 6.6 nm with the same stacking number) and an increase in the W sulfidation degree (68% against 54%) and Ni content in NiWS phase (44% against 26%). Therefore, the catalyst on the hybrid support exhibits higher activity in hydrodesulfurization, hydrodenitrogenation and hydrogenation of petroleum feeds, and a lower degree of deactivation and coke formation.

Reactivation of industrial CoMo/Al2O3 hydrotreating (HDT) catalysts was studied. A spent catalyst was used in the ULSD production for about 2.5 years. It was oxidatively regenerated and rejuvenated by organic acids (citric and thioglycolic), glycols (ethylene and triethylene), and dimethylsulfoxide solutions. All solids were characterized by the elemental analysis, N2 physisorption, X-ray powder diffraction, thermogravimetric analysis, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Changes in the active phase composition and morphology during the CoMo/Al2O3 HDT catalyst operation, regeneration and rejuvenation were shown. The rejuvenated catalysts were tested in hydrodesulfurization (HDS) of dibenzothiophene and hydrogenation (HYD) of naphthalene. It was found that oxidative regeneration allowed restoring about 70–85% rel. of initial activity. Rejuvenation with organic chemicals resulted in the complete restoration of HDS and HYD activities. Resulting catalytic activity of the reactivated catalysts depended on the properties of the formed active phase species. These correlations are discussed in the study.

Bimetallic (Me)MoS2 (Me = Nb, Fe, Co, Ni) sulfide systems, both modified and non-modified by potassium, were investigated by the DFT method. Geometric and electronic structures of active sites were compared in terms of CO and hydride hydrogen adsorption. Most of the studied metals are electron density acceptors on the S-edge of the crystallite, which inhibits hydride hydrogen adsorption and deactivates the S-edge. The CO adsorption energy on the Me-edge decreased in the order Fe > Co > Ni. Computational data were verified by experimental tests in syngas conversion. Modification by potassium was shown to hinder σ-bonding of the adsorbed molecule and to stabilize hydride hydrogen.

The purpose of the study was to evaluate carbon effect on Co(Ni)-PMo/C/Al2O3 catalysts in co-hydrotreating (co-HDT) of straight-run gas oil (SRGO) and sunflower oil (SO). The catalysts were prepared using 12-molybdophosphoric heteropolyacid, cobalt tartrate, and Al2O3 or C/Al2O3 (2 wt% of carbon) as a support. The solids were characterized by N2 physisorption, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. The catalytic properties were investigated using a bench-scale flow reactor in co-HDT of mixed feed containing SRGO and 5, 10, and 15 wt% of SO. It was found that Co-РMo catalysts demonstrated higher hydrodesulfurization (HDS) activity in SRGO HDT than its Ni-РMo/C/Al2O3 counterparts. The use of C/Al2O3 led to more active Co-РMo and Ni-РMo catalysts compared with Al2O3 supported ones. Co-PMo samples more significantly lost activities than Ni-PMo after adding SO in the feed. Addition of SO led to an increase in HDS apparent activation energy by 21 kJ mol−1 on Co-РMo and has not affected it in co-HDT of blended feedstock over Ni-PMo. All obtained results showed the high effectiveness of the prepared Ni-РMo/C/Al2O3 catalyst. They showed high HDS, hydrogenation and hydrodenitrogenation activities in co-HDT of the mixed SRGO/SO feedstock as well as catalyst stability against to accelerated deactivation. The possible reasons of the catalytic behavior of the studied samples are discussed based on the characteristics of the freshly sulfided and spent samples as well as determined kinetic parameters.

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

Ni(Co)-PW/Al2O3 catalysts both unmodified and modified with potassium were synthesized with the use of H3PW12O40, CoCO3 or NiCO3, KOH and citric acid. The catalysts were characterized by the techniques such as low-temperature N2 adsorption, temperature-programmed reduction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. The prepared samples were tested in hydrotreating of model FCC gasoline that contained 1000 ppm of sulfur from thiophene and 36 wt.% of n-hexene-1 as a representative olefinic compound. The modification with an alkali metal influenced both the characteristics of the catalyst active phase and catalytic properties of (K)-Ni(Co)-PW/Al2O3 samples. The incorporation of potassium led to some l growth of the linear size of active phase crystallites, to a decrease of reactivity and of the number of active sites, to a strong decrease of CoWS and NiWS particle amounts with a simultaneous rise of separate CoSx and NiSx. The potassium addition also induced a drastic drop of hydrodesulfurization (HDS) and hydrogenation (HYDO) activity with a HDS/HYDO selectivity decrease for Ni- and Co-promoted systems and with a significant increase of the selectivity factor for unpromoted PW/Al2O3. The Ni-promoted catalyst proved to be more sensitive to the potassium modification than the Co-promoted one. So, the modified catalysts can be ranged by activity as follows: KWS

Co x -Co 2 Mo 10 /SiO 2 and Co 2 Mo 10 /Co x /SiO 2 catalysts with various Co/Mo ratios and active species compositions are prepared using H 6 [Co 2 Mo 10 O 38 H 4 ] heteropolyacid, CoCO 3 and citric acid. Catalysts are characterized using the following techniques: low-temperature N 2 adsorption, temperature-programmed reduction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Catalytic activities of the synthesized catalysts are examined in hydrotreating of model fluid catalytic cracking (FCC) gasoline that contains 1000 ppm of sulphur from thiophene and 36 wt.% of n-hexene-1. As the Co/Mo ratio increases, hydrodesulphurization (HDS) and hydrogenation (HYD) activities of the prepared catalysts significantly builds up. The changes of catalytic properties and specifically of the HDS/HYDO selectivity factor of the synthesized CoMo catalysts arise from two effects: an alteration of the promotion degree of CoMoS active phase particles and a hydrogen spillover from CoS x species to active sites. The developed silica-supported CoMo catalysts may be a prospect for selective HDS and hydro-upgrading of FCC gasoline.

Hydrodeoxygenation of glycerol in a flow reactor over a bifunctional Ni/WO3–TiO2 catalyst at 240–255 °C and hydrogen pressure of 3 MPa affords propan-1-ol and propan-2-ol in total yield of 94%.

Catalysts with the common composition KCoMoS/C/Al2O3 were synthesized, characterized by physicochemical methods, and tested in the synthesis of alcohols from CO and H2. It was noted that carbon supported on alumina promoted alcohol synthesis by enhancing the CO conversion and the alcohols/hydrocarbons ratio in comparison to pure alumina. The addition of potassium to CoMoS/C/Al2O3 could substantially affect both the morphology of molybdenum disulfide crystallites and catalyst activity in the synthesis of alcohols. According to quantum chemical calculations, using the density functional theory approach, potassium donates electronic density onto the Co atoms of CoMoS phase active sites. Reduction of metal atoms of active sites leads to a decrease in Lewis acidity and in the CO and H2 adsorption energy as well as promoting the oxidative addition of H2. The influence of ethanol addition to synthesis gas on its conversion and the product composition was examined with a view to checking whether the alkyl intermediate interacted with CO in the presence of potassium. A sharp increase of CO conversion in the presence of ethanol was detected. A reaction network of CO conversion on KCoMoS catalyst active sites to various products depending on the catalyst composition and reaction conditions was suggested.

d-Kx-CoMoP/Al2O3 catalysts with different Mo loading (d) equal to 2, 3 and 5 at Mo/nm2 and varied up to 2 of K/Mo molar ratio (x) were prepared using H3PMo12O40, CoCO3, KOH and citric acid. The catalysts were characterised by low-temperature N2 adsorption, temperature-programmed desorption of NH3, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy and tested in hydrotreating of heavy FCC gasoline. It was found that the introduction of a higher amount of K and Mo in the KxCoMoP catalyst led to enhancement of metal sulfidation and formation of KCoMoS phase species with large sizes. Maximal selectivity factor and low RON less after hydrotreating of FCC gasoline was achieved over 5-K1.5CoMoP catalyst. Both 3-K1.5CoMoP and 2-K1.5CoMoP catalysts contained lower Mo loading had reduced HDS and HYDO activities compared with 5-K1.5CoMoP analog having the same K/Mo ratio. However, 2-K1.5CoMoP and 3-K1.5CoMoP catalysts had a higher selectivity factor, then 5-CoMoP analog having higher Mo loading and similar morphology of active phase species. The introduction of potassium decreased the apparent activation energy and pre-exponential factor of the both HDS and HYDO reactions. It was concluded that the alkali metal changes the properties and concentrations of both types of the active sites on the KCoMoS2 slabs by a similar mechanism.

Hydroprocessing catalysts based on transition metal sulfides have been extensively used worldwide in refineries for upgrading heavy fractions to better quality fuels. The present work reviews the studies dealing with Anderson heteropolyanions (HPAs) and the derived dimeric structure for synthesizing hydrotreating catalysts. The development of new preparation methods based on HPA catalysts led to efficient catalytic systems due to better sulfidation allowed by a better dispersion of the oxidic precursor even at high metallic loadings. The increase of the Co/Mo ratio in the heteropolycompounds up to 0.5 was possible due to the formation of dimer cobalt salt. The association of Co and Mo at the molecular level in the same heteropolycompound preserved after the drying step during the catalyst preparation ensured the efficiency of the promoting effect with a higher quantity of the CoMoS active phase. This HPA-based system was further improved by the simultaneous use of HPAs and chelating agents.

Ni(Co)x-Co2Mo10/Al2O3 catalysts with various (Co+Ni)/(Co + Ni + Mo) atomic ratio (from 0.17 to 0.45) and constant Mo loading (10 wt.%) were synthesised using decamolybdodicobaltate heteropolyacid (Co2Mo10HPA) and cobalt or nickel citrate. The catalysts were characterised using N2 physisorption, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy and tested in the hydrodesulphurisation (HDS) of dibenzothiophene (DBT). It was found that adding the Co(Ni) citrate to Co2Mo10/Al2O3 catalyst significantly altered the active phase morphology. The average slab length increased from 3.0 to 4.1 nm in Cox-Co2Mo10/Al2O3 catalysts and to 3.6 nm in Nix-Co2Mo10/Al2O3 counterparts. The average stacking number of the MoS2 crystallites grew from 1.4 to 2.0 with loading the Co or Ni. Increasing the Co content in the Cox-Co2Mo10/Al2O3 catalysts decreased the Co percentage in the CoMoS phase and led to the growth of Co fraction in cobalt sulphide. With the increase of Ni content in Nix-Co2Mo10/Al2O3 catalysts the Ni percentage in the NiCoMoS phase decreased from 47 to 25 rel.% and the Co percentage in the NiCoMoS phase was constant and equal to ∼62 rel.%. For both series of the catalysts, activity in DBT HDS passed through maximum at 0.33 of the atomic ratio (Co + Ni)/(Co + Ni + Mo). Nix-Co2Mo10S/Al2O3 catalysts indicated higher rate constants in DBT HDS than Cox-Co2Mo10S/Al2O3 counterparts at the same metal content. It was concluded that Ni1-Co2Mo10/Al2O3 sample with minimal Ni/Mo ratio had mixed Ni-Co-Mo sites with high turnover frequencies values.

K-Mo/Al 2 O 3 and K-CoMo/Al 2 O 3 catalysts with various amount of potassium (up to 15 wt. %) were synthesized using H 3 PMo 12 O 40 , CoCO 3 and KOH. The catalysts were characterised by the following techniques: low-temperature N 2 adsorption, Raman spectroscopy, temperature-programmed reduction, temperature-programmed desorption of NH 3 , X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy. Synthesized catalysts were tested in hydrotreating of model fluid catalytic cracking gasoline containing 1000 ppm of sulphur from thiophene and 36 wt. % of n -hexene-1. It was found that potassium incorporation led to the strong changes in both physical-chemical characteristics and catalytic behaviour of sulphide catalysts. Using potassium favoured the growth of average slab length and sulphidation degree of metals with selective formation of CoMoS active phase. Addition of potassium also led to the partial poisoning of the active sites what resulted in decrease of catalyst activities compared with the reference Mo/Al 2 O 3 and CoMo/Al 2 O 3 samples. Olefin hydrogenation was more sensitive to potassium than thiophene hydrodesulphurization what resulted in the growth of the dependence of selectivity factor on potassium content in the catalysts. Obtained results allowed us to suppose that potassium partially inserts in sulphide slabs with changing the nature of active sites and probably with formation of new type of active “KCoMoS” sites.

Furfural derivatives, prepared from vegetable raw materials, have recently become popular as high-performance fuel additives. Special attention is drawn to such compounds as oxygenates. A lot of research has been conducted into creating new substances from furfural, but it is still unclear how exactly they affect physicochemical properties of fuels. This article will demonstrate the possibility of adding furfural derivatives, obtained by their hydrogenation at copper and nickel catalysts with full furfural conversion, to fuel. Their impact on antiknock properties and chemical stability was evaluated. It was noticed that furans are mostly effective in low-octane bases (gasoline HC) at 5–30% wt. concentration. High concentration of potential gum may lead to carbon depositions in the combustion chamber of an engine that requires additional tests.

International audience; Alumina supported MoW hydrotreating catalyst was synthesized by using bimetallic H 4 [SiMo 3 W 9 O 40 ] Keggin heteropolyacid (HPA). Catalysts based on monometallic H 4 [SiMo 12 O 40 ] and H 4 [SiW 12 O 40 ] and their mixture were also studied. Genesis of the active phase was studied during atmospheric gas sulfidation by H 2 S/H 2 of the catalysts by in-situ Quick X-ray absorption spectroscopy (XAS) and High-Angle Annular Dark-Field (HAADF) imaging. The combination of different chemometric tools such as Principal Component Analysis (PCA) and Multivariate Curve Resolution with Alternating Least Squares (MCR-ALS) allowed to determine the number of intermediate species, their chemical nature and concentration profiles during sulfidation. It was found that tungsten sulfidation using bimetallic HPA precursor started at lower temperature, compared to W sulfidation in the monometallic and in the mixture of monometallic HPA catalysts. Simultaneous sulfidation of Mo and W atoms in case of the bimetallic molecular precursor can govern the formation of mixed MoWS 2 phase, which formation during activation was evidenced by HAADF.

K-CoMo/Sup (where Sup = Al2O3, SiO2, TiO2 and ZrO2) catalysts were synthesized using H3PMo12O40, CoCO3, KOH and citric acid. The catalysts were characterized by temperature-programmed reduction (TPR), temperature-programmed desorption of NH3, X-ray photoelectron spectroscopy, transmission electron microscopy. Samples were tested in hydrotreating of model fluid catalytic cracking gasoline and in selective hydrogenation of 1,5-hexadiene and n-heptene-1. The type of used carrier significantly affected the morphology of active phase and catalytic properties. Active sites productivity of K-CoMo/Sup catalysts in hydrodesulfurization (HDS) and olefin hydrogenation (HYDO) reactions as well as HDS/HYDO selectivity correlated with active phase morphology excepting TiO2-supported sample. Productivity of active sites in reactions of selective hydrogenation of diolefin depended on maximum peak reduction obtained from TPR, which in turn was a function of acidity of using supports. The highest HDS/HYDO selectivity was obtained at catalyst which possessed the lowest selectivity towards partial hydrogenation of diolefine compared to complete hydrogenation.

Effects of activated carbon in a carbon-coated alumina (CCA) support, active phase morphology and its composition of Ni 6 -PW 12 S/C x /Al 2 O 3 catalysts in hydrotreating of model compounds were studied. The catalysts were synthesized using 12-tungstophosphoric heteropolyacid, nickel citrate and CCA and characterized with multiple methods: N 2 physisorption, X-ray powder diffraction, H 2 temperature programmed reduction, temperature-programmed desorption of ammonia, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The catalytic properties were determined using a fixed-bed microreactor in hydrotreating of dibenzothiophene, naphthalene and quinoline. It was found that with the increase of carbon content in the CCA up to 5 wt.%, reducible reactivity, sulphidation degree, average length and stacking number of WS 2 crystallites in the catalysts increased. Observed changes can be explained by weakening interaction between metal oxide species and carbon-coated support. Full promotion of the NiWS edges by nickel was achieved in the catalysts supported on the CCA with carbon content equal 0.3 wt.% and more. Activities of the catalysts in dibenzothiophene hydrodesulphurization, naphthalene hydrogenation and quinoline hydrodenitrogenation were essentially depended on the carbon content in the CCA-support. Ni 6 -PW 12 S/C 1 /Al 2 O 3 catalyst showed maximal conversions of the substrates in studied reactions. This result was achieved due to an optimal balance between turnover frequency value of the active sites and their content.

Effect of Ni/W ratio on Ni-CA-PW/Al2O3 hydrotreating catalysts prepared with 12-tungstophosphoric heteropolyacid (PW-HPA) and nickel citrate was investigated. For comparison, the reference samples were prepared using nickel salt of PW-HPA and co-impregnating solution of ammonium metatungstate and nickel nitrate. All synthesized catalysts were characterized by N2 physisorption, X-ray powder diffraction, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The catalytic properties were determined using a fixed-bed microreactor in hydrotreating of dibenzothiophene, naphthalene and quinoline. It was found that with the rise of Ni content in the prepared Ni-PW/Al2O3 catalysts the composition and morphological characteristics of the NiWS active phase species as well as their catalytic properties were changed simultaneously. Turnover frequency (TOF) number in all studied reactions increased with the decrease in both the average length of the NiWS phase species and Ni/W ratio in the (Ni)WS2 edges. Both NiW reference catalysts had active sites with lower TOF values than their counterparts prepared using PW-HPA and nickel citrate. The highest TOF values were achieved at moderate Ni/(Ni + W) ratio equal to 0.24. However, maximal conversions of the reactants were observed over the catalysts with higher Ni/(Ni + W) ratio equal to 0.33–0.45. The possible reasons of these changes are discussed in the paper.

Co 2 Mo 10 /Co x /Al 2 O 3 catalysts were synthesized from the ammonium salt of [Co 2 Mo 10 O 38 H 4 ] 6− anion supported on alumina modified with various amount of cobalt sulphide. The catalysts were analyzed using X-ray powder diffraction, N 2 physisorption, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The catalysts were tested in the hydrodesulphurization (HDS) of dibenzothiophene and 4,6-dimethyldibenzothiophene and the hydrodenitrogenation (HDN) of quinoline. The presence of cobalt sulphide particles on the catalysts surface affects catalytic properties significantly, whereas the structure of the active phase remains constant. The catalytic activity, selectivity and turnover frequency during the HDS and HDN reactions depend on the amount of modifier (cobalt sulphide) in the Co x /Al 2 O 3 supports and can be explained by hydrogen spillover effect. The model of HDS reaction over Co 2 Mo 10 /Co x /Al 2 O 3 catalyst involving hydrogen spillover was established. The obtained results allow us to focus attention on the role of the cobalt sulphide particles on the surface of hydrotreating catalysts.

Genesis of alumina supported hydrotreating (HDT) catalysts prepared with the use of decamolybdodicobaltate heteropolyanion (Co2Mo10HPA) and cobalt citrate during their sulfidation processes and deactivation in diesel HDT has been investigated. The sulfidation stage was studied for two procedures: gas phase sulfidation by H2S/H2 and liquid phase treatment by a mixture of dimethyldisulfide in diesel at various temperatures and durations. The catalysts have been studied by N2 adsorption, thermogravimetric analysis, X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy methods. The catalysts were tested in HDT of mixture of 70 wt.% straight run gas oil with 16 wt.% light cycle oil and 14 wt.% light coker gas oil. Mechanisms of the active phase formation in the course of gas and liquid phase sulfidation processes have been established. It was found that gas phase sulfidation led to formation of the CoMoS active phase with higher cobalt content comparing to liquid sulfidation of the catalyst and initial activity of the gas phase treated catalysts in diesel HDT was also higher than catalysts subjected to liquid sulfidation. Catalytic examination after accelerated deactivation conditions showed that the liquid phase sulfided sample was more resistant to the deactivation. Probably it is due to stabilization of active phase particles by coke formed intensively during liquid phase sulfidation. The results were discussed using the recently developed concept of interlayer dynamics of the active sites of the CoMoS phase.

CoMo/Al 2 O 3 catalysts were synthesised from the ammonium and Co salts of [CoMo 6 O 24 H 6 ] 3− and [Co 2 Mo 10 O 38 H 4 ] 6− anions as well as Co–chelate complexes with nitrilotriacetic, ethylenediaminetetraacetic, citric and tartaric acids. The catalysts were characterised using X-ray powder diffraction, Raman spectroscopy, N 2 physisorption, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The catalysts were tested in the hydrotreating (HDT) of a mixture containing thiophene and n -hexene-1, the hydrodesulphurisation (HDS) of dibenzothiophene and 4,6-dimethyldibenzothiophene and the HDT of diesel. The type of chelating agent significantly affects the structure of the active phase and catalytic properties. The catalytic activity, selectivity and turnover frequency during the HDS and hydrogenation reactions depend on the number and location of CoMoS sites, as well as the shape of the active phase crystallites. New “structure–activity” relationships were established. These approaches yielded catalysts that demonstrated high efficiency towards the deep diesel HDT and selective HDS of a model fluid catalytic cracking gasoline.

Effects of activated carbon of a carbon-coated alumina support and active phase morphology of transition metal sulfide (TMS) catalysts in hydrotreatment (HDT) of S-containing compounds were studied. The catalysts were synthesized from Anderson-type heteropoly compounds and characterized with multiple methods: X-ray powder diffraction, N2 physisorption, temperature-programmed desorption of ammonia, pyridine-adsorbed Fourier transform infrared spectroscopy, H2 temperature-programmed reduction, and high-resolution transmission electron microscopy. The catalysts were tested in hydrodesulfurization (HDS) of thiophene, dibenzothiophene and HDT of diesel. The results suggest that the catalytic activity in HDS and hydrogenation reactions depends on the shape of crystallites of the active phase. The results are interpreted using recently proposed concept of interlayer dynamics. This concept is helpful in establishing structure–activity relations for TMS.

The effect of Co/Mo ratio in the CoMo/Al2O3 hydrotreating catalysts prepared by simultaneous using of the decamolybdodicobaltate heteropolyacid (Со2Мо10HPA) and cobalt citrate was investigated. Synthesized catalysts were characterized by Raman spectroscopy, N2 adsorption, XRD, XPS, HRTEM techniques and were examined in the model reaction of 4,6-dimethyldibenzothiophene (4,6-DMDBT) HDS, in hydrotreating of straight-run gas oil (SRGO) and mixture of 80 vol.% SRGO with 20 vol.% light coker gas oil (LCGO). It was established that Co/Mo ratio in the catalysts significantly influences on the structure of CoMoS phase of type II and catalytic activity. Catalysts with λ = Co/(Co + Mo) = 0.35 had maximal activities in 4,6-DMDBT HDS and diesel HDT and showed the best stability. Increase of the Co/Mo ratio led to simultaneous growing of both average length and stacking number of CoMoS multilayer active phase of the catalysts. Average length increased from 3.0 to 4.0 nm, average staking number increased from 1.4 to 1.6. It was found out that catalysts activity decreased within Co/Mo ratio λ from 0.35 to 0.45. Analysis of textural properties of the catalysts, active phase morphology, phase composition and catalytic activities allowed us to suppose that with increase of Co/Mo ratio blocking the mesopores by sulfides of the active components and by coke species with formation of new micropores would take place. The activity of the best prepared CoMo/Al2O3 catalyst was competitive with the activity of the well-known commercial catalysts for ultra-low sulfur diesel in hydrotreating of SRGO or mixture of SRGO with LCGO.

A new mechanistic model for molybdenum sulfide catalysts with cobalt and nickel promoters under hydrodesulfurization reaction conditions is proposed, which includes dynamic migration of sulfur and promoter atoms between adjacent sulfide layers. These migrations are caused by heterolytic dissociation of gas-phase hydrogen and formation of hydride hydrogen on a promoter atom. Hydride hydrogen adsorbed on a promoter induces electron density transfer from the bonding promoter to Mo, changing its catalytic activity. The proposed concept of dynamic migrations provides new interpretation for the “rim-edge” model, which is based on the formation of two types of active sites: highly active (“rapid”) and less active (“slow”) sites. The “slow” sites are proposed to be associated with a non-promoted cluster on the edge of a MoS2 slab layer (“rim”), which catalyzes hydrogenation. The “rapid” sites are proposed to be associated with a combination of promoted and non-promoted clusters on edges of the same (type I) or adjacent (type II) MoS2 layers. The “rapid” sites catalyze C–S bond hydrogenolysis. Adsorbed hydrogen induces migration of sulfur and promoter atoms between adjacent clusters. This dynamic migration causes a transformation of “rapid” into “slow” sites and vice versa and, therefore, influences catalytic activity. Migration of Co or Ni promoter atoms to Mo sites on the rim is more likely than to Mo sites on the edge of Co(Ni)MoS layers because the former can accept promoter atoms from both upper and lower layers. The proposed model provides critical information for rational design of improved hydrotreating catalysts and selection of preferred catalytic reaction conditions for various types of hydrocarbon feedstocks through optimization of the density and ratio of “rapid” and “slow” catalyst active sites.

The catalysts of the XMo6(S)/Al2O3 and Ni3-XMo6(S)/Al2O3 structures were prepared from heteropolycompounds (HPCs) of Anderson type (where X = Co, Ni, Cr, Mn, Fe, Cu, Zn, Ga). The precursors and synthesized catalysts were characterized by FTIR, XRD, EXAFS, HRTEM techniques. The prepared catalysts were examined in model reactions of thiophene HDS and benzene HYD and in hydrotreating (HDT) of diesel fraction. The correlations between the catalytic activities in HDS and HYD and the heats of thiophene adsorption depending on the nature of the heteroatom prove that it plays an important role in the formation and behavior of the HYD and HDS active sites. It was found that heteropolycompounds are effective precursors of a multilayered active phase of hydrotreating catalysts.

The effect of the intermediate activated carbon covering the alumina carrier on catalytic activity of the supported transition metal sulfides (TMS) prepared from heteropolycompounds (HPCs) in thiophene hydrodesulfurization (HDS), benzene hydrogenation (HYD) and hydrotreating (including HDS of S-containing and HYD of polyaromatic compounds) of diesel oil fractions was investigated. Carbon content on the alumina carrier varied from 0 to 3.8 wt.%. It was found that the structure of carbon coating the alumina surface changes depending on the presence/absence of the active phase on the intermediate activated carbon. Total catalytic activity of the catalysts in HDS and HYD reactions was maximal for carbon content of 1–2 wt.% and fell down for catalysts with 3.8 wt.% of carbon. The specific catalytic activity grew proportionally to the carbon content on the catalyst. The experimental data showed that a rise of the reaction temperature leads to a decrease in the amount of adsorbed hydrogen whose deficiency limits the formation of H 2 S. It was supposed that the intermediate carbon placed between the alumina carrier and the active phase accumulates hydrogen inside carbon pores. Besides, the intermediate C-carrier of the catalysts synthesized from Co(Ni) salts of heteropolycompounds promotes rising of stacking number in nanoslabs of the active CoMoS phase of the second type.

On the basis of the fundamental concepts of catalysis by transition metal sulfides (TMSs) a new dynamic model of the promoted Mo-sulfide catalysts functioning under HDS conditions has been developed. According to the model under hydrogen atmosphere sulfidation degree of the edges of different layers of the slab can vary and surface sulfur can migrate from one layer to a neighboring layer so that average sulfidation state of the slab remains constant under given reaction conditions. The model describes oscillations by sulfur and promoter atoms between the adjacent layers of the slab on the atomic scale level. The driving force of such processes is the heterolytic dissociation of the gas phase hydrogen and formation of hydride hydrogen linked to a promoter atom. This hydride hydrogen triggers an electron transfer from a promoter to Mo with the formation of the vacancy. This model correlates with radioisotopic data and an earlier suggested “forcing out” mechanism and gives some new interpretations of the important statements of the electron theory of promotion and the “rim-edge” model.