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Project titleDeveloping materials based on mixed Mo, W and Ni oxides as components of bulk hydroprocessing catalysts

Research area 03 - CHEMISTRY AND MATERIAL SCIENCES, 03-601 - Chemistry of new inorganic functional and nano-dimensional materials

Keywordsbulk catalyst, sulfides, nickel, molybdenum, tungsten, hydroprocesses, hydrogenation, heteroatomic compounds, sulfur, nitrogen

Annotation
Currently, a wide variety of difficult-to-convert hydrocarbon feedstocks are involved in processing in Russia - from distillates obtained during the processing of alternative natural feedstocks (heavy oil and bitumen) to liquid products obtained from the disposal of plastic waste. At the same time, there is a constant tightening of ecological standards for the quality of oil products. One of the characteristic of oil products is the content of sulfur and nitrogen compounds. It is necessary to hydrotreated oil fractions to decrease sulfur and nitrogen to the required level. To maintain the energy efficiency of the hydrotreatment process, when the hydrocarbon composition of the feedstock becomes heavier, it is necessary to use more active catalysts that provide a product meeting modern environmental quality standards. In addition, Russian refineries use mostly imported catalysts for hydrotreatment processes. Taking into account the rapid development of the foreign market of catalysts for oil refining processes, it is possible to overcome import dependence by developing and putting into operation competitive domestic hydrotreating catalysts. Thus, the development of new methods for the preparation of highly active hydrotreating catalysts is extremely important at the present time. Ni(Co)-Mo(W) sulfide systems supported on porous alumina carrier are often used as hydroprocessing catalysts. There are many ways to increase activity of this system, however, the main principle is reduced to finding a way to synthesize the largest amount of the active sulfide phase. Foreign manufacturers suggest to use bulk sulfide catalysts as an alternative to supported catalysts. In this case, the proportion of the active component in the volume of the catalyst increases many times. The use of such systems is possible individually throughout the reactor, or as one of the layers in the reactor, for example, as an upper layer before the main catalyst layer. In the case of using such catalyst as the main layer in the hydrotreating reactor, one can expect a significant decrease in the process temperature due to much higher activity of the bulk catalyst compared to the supported system. On the other hand, such catalyst should significantly increase the amount of absorbed hydrogen per ton of feedstock. In the case of using this bulk catalyst as one of the layers in the reactor, and in particular before the main catalyst layer, one can expect a significant improvement in the composition of the feedstock before its interaction with the main catalyst layer. In this case, the prospects for involving a larger amount of heavy hydrocarbon raw materials, including secondary oil refining processes, open up. It should be noted that there are practically no studies devoted to the synthesis and investigation of massive hydroprocessing catalysts in the open scientific and patent literature. In this project, it is proposed to develop approaches to the synthesis of materials consisting of mixed complex oxides of transition metals Ni, Mo and W, which are the precursor of the active sulfide Ni-Mo-W phase. And also to study the influence of the structure of complex oxides Ni, Mo and W on the features of the formation of mixed sulfides and their catalytic activity in the reactions of hydrogenation, hydrodesulfurization and hydrodenitrogenation of a model mixture and heavy oil feedstock. Previously, our group was engaged in the development of catalytic systems based on Co(Ni)-Mo(W) sulfides deposited on alumina. Numerous works have been related to the synthesis of active phase precursors, the synthesis of alumina and aluminosilicate supports, the optimization of the properties of supports, and the optimization of catalyst synthesis parameters. In this work, the accumulated long-term experience of the scientific team in the field related to this work will be used. The results of this work can be further used by enterprises involved in the development, production and operation of catalysts.

Expected results
The following results are planned to be ontained in this project: 1. The main conclusions on the most perspective compounds - precursors of complex oxides Ni, Mo and W, that will provide the formation of bulk porous oxide structure selectively transromed to the sulfide active component will be made on the base of scientific and paten literature about bulk hydroprocessing catalysts. 2. Development of a technique for obtaining a precursor of complex of mixed complex oxides of Ni, Mo and W. 3. Development of a method for obtaining a granular and tableted bulk NiMoW catalyst using the method of extrusion of a plastic paste containing NiMoW material, followed by heat treatment of the obtained granules and tablets. 4. Establishment of the main regularities of the influence of the conditions for obtaining a plastic paste of mixed complex oxides of Ni, Mo and W, the conditions of heat treatment of extrudates, on the textural and strength properties of a massive NiMoW catalyst, the structure and morphology of mixed oxides of nickel, molybdenum and tungsten. 5. Establishment of the main regularities of the influence of the sulfidation conditions of the mized oxides of nickel, molybdenum and tungstem on the chemical composition, morphology of active component sulfides and catalytic activity of NiMoWS systems in hydrogenation, hydrodesulfurization and hydrodenitrogenation reactions in hydrotreating condition of heavy oil fractions. The complex investigation of the prepared bulk NiMoW catalysts at all preparation stages will be carried out using modern physico-chemical methods. Availability of pilot units for testing the obtained catalysts in fixed-bed flow reactors will provide to perform the correct comparison of the obtained bulk catalysts with traditional supported catalysts in order to show the evident advantages of bulk catalysts as well as to establish the dependence between changes of catalysts properties and its catalytic activity in target reactions. The obtained results will be useful for scientific community since there are no works devoted to the synthesis and detailed study of the properties of bulk catalysts in the open scientific and patent literature at present. The approaches used in present work for the synthesis of bulk NiMoW catalysts are available for industrial application and do not require significant technological reconstruction of the equipment of catalysts plants. Due to the high demand for the introduction of new domestic catalysts that will make it possible to obtain high-quality marketable petroleum products at low energy costs, this work will be extremely useful for specialists in the field of synthesis of catalysts for oil refining. Since there are no domestic analogues of bulk catalysts for catalytic hydrogenation processes at present.

Annotation of the results obtained in 2022
1. The influence of preparation techniques of NiMoW precursor, which are suitable for synthesis of bulk catalysts, on their catalytic properties was studied at the first stage of the project. The method of hydrothermal treatment of active phase precursor in the solution, the method of direct precipitation, as well as the method of synthesis of active phase precursors in the solution followed by spray drying of the obtained suspension, were chosen. According to literature data, these methods are the most perspective ways for synthesis of NiMoW precursor. Synthesis of NiMoW oxide precursors by coprecipitation method, hydrothermal synthesis and spray drying of the solution of initial Ni, Mo and W compounds was carried out. Hydrothermal synthesis of NiMoW precursor was performed by the method described in [US 20070084754]. Synthesis of complex trimetallic oxides by direct precipitation was carried out by the procedure given in [https://doi.org/10.1016/S0167-2991(03)80246-X]. The third way of synthesis of trimetallic precursor included spray drying of the obtained suspension and was earlier described in [https://doi.org/10.1016/j.apcata.2007.01.008]. For the method of hydrothermal synthesis, initial reagents and temperature of the treatment (95, 150 and 170°С) were varied. In all cases, molar Ni/Mo/W ratio was 1/0.5/0.5. Thus, 6 samples of NiMoW precursors were prepared. It was established that preparation procedure of the precursor significantly influenced its particles morphology. Particles of the prepared samples was similar to stacked plates (in the case of hydrothermal synthesis), small balls < 2.5 mkm (for direct precipitation method) or spherical particles of greater size (up to 10 mkm) (for spray drying method). In the case of hydrothermal treatment synthesis and spray drying method for preparation of NiMoW precursor, fine distribution of active metals was observed by of energy dispersive X-ray spectroscopy. 2. In addition, it was found that the synthesis method had a significant effect on the phase composition of the active phase precursor. The use of ammonium metatugstate and ammonium paramolybdate as the precursors of active metals for hydrothermal treatment synthesis is more attractive, because of the formation of lower amount of individual oxides. The sample prepared by direct precipitation contains Ni-Mo particles, which are not doped by W. It resulted to the decrease of the amount of NiMoW mixed sulfide phase. XPS data emphasize the sample prepared by spray drying method. This catalyst contained the highest amount of Mo and W in the sulfide state comparing to other samples. The observed changes in the precursor properties further influenced activity of catalysts in hydrodesulfurization and hydrodenitrogenation reactions. The sample prepared by direct precipitation demostrated the lowest activity. The samples prepared by hydrothermal treatment showed similar activity, but the following tendency was observed. The increase in crystallinity of Ni-containing phase resulted in the decrease in hydrodesulfurization and hydrodenitrogenation activities. The best activity amlng all samples was demostrated by the one prepared by spray drying. 3. A study of the effect of thermal treatment of trimetallic precursors on the phase and chemical composition of granular bulk catalysts was made. The precursors were prepared by mixing a NiMoW precursor obtained by spray drying with pseudoboehmite as a binder and a nitric acid solution as a plasticizing agent. The obtained kneading paste was extruded to obtain granules with a cross section in the form of a trilobe. The precursor heat treatment temperature was varied in the range of 110–500°C. It has been found that at a heat treatment temperature of the NiMoW precursor below 300°C, it is not possible to obtain a plastic extrudable paste. It was also found that the catalyst mostly contains X-ray amorphous particles at a heat treatment temperature below 400°С. When evaluating the activity in the reactions of hydrodesulfurization and hydrodenitrogenation, this sample proved to be more active. 4. The preparation method of granular bulk catalysts was developed. The synthesis procedure was based on the preparation of the kneading phase suitable for extrusion via spinneret with trilobe holes with cross-section diameter 1.3±0.1 mm. To prepare kneading paste, the mixing of the precursor and pseudoboehmite in the mixer followed by the addition of nitric acid solution for plasticizing was carried out. During selection of optimal synthesis conditions, the type of binding agent and its weigth portion (0-30 wt.%) were varied. It was established that the lowest content of pseudoboehmite for preparation of granulat catalyst is about 30 wt. %. 5. The influence of the type of platicizing agent used for preparation of the kneading paste suitable for extrusion on the structure and composition of the active phase precursor was studied. Solutions of nitric acid, phosphoric acid, acetic acid and citric acid and diethylene glycole were used as plasticizing agents. The study of the properties of the obtained samples showed that the choice of a plasticizing agent has little effect on the textural characteristics of the catalysts and their phase composition. However, the sample obtained using nitric acid had a larger pore volume, which characterized it as the most promising. Variation of the plasticizer had a greater effect on the value of bulk crushing strength (BCS). The highest BCS value was obtained for the sample prepared by plasticization with acetic acid, which is also an advantage of this sample as an exploited catalyst. 6. The influence of heat treatment temperature of granular bulk catalysts on their textural properties, strength characteristics and phase composition was studied. The precursors synthesized by spray drying were used as trimetallic compounds for granular catalysts. Preparation of granular catalysts is described in section 4. The obtained extrudates were calcined at a temparature in the range of 120-500°C. It was established that the increase in the treatment temperature resulted in the increase in specific surface area, pore volume and the amount of mesopores with sized <7 nm. In addition, the increase in heat treatment temparature leads to the decrease in BSC value for the catalysts. According to XRD data, varioation of temperature from 120 to 300°С does not result in strong changes of phase composition as well as poorly crystallized phases of active metals did not observed. The increase in temperature of the treatment to 400°C leads to the formation of γ-Al2O3. The sample calcined at 500°С also demonstrates reflections of alumina phase and intensive peaks from α-NiMoO4 phase. It was found that drying at 120°С results in changes in the structure of nickel-citrate complexes. Heat tratment at >300°С led to partial destruction of amorphous organic precursors, which contain citrate complexes and nitrate ions with the formation of coke (carbon) depositions of not clear nature. In this case, a uniform distribution of active metal ions in coke deposits was observed. Complete decomposition of amorphous organic precursors in the sample occurred at temperatures above 450°C. Nickel in the catalyst calcined at 500°C was in the structure of nickel molybdate, nickel oxide, and possibly nickel tungstate. The activity of the obtained samples was evaluated in the hydrotreatment of straight-run VGO. The best results were shown by the catalyst heat-treated at 300°C.

Publications

1. Nadeina K.A. , Budukva S.V. , Vatutina Y.V. , Mukhacheva P.P. , Gerasimov E.Y. , Pakharukova V.P. , Klimov O.V. , Noskov A.S. Unsupported Ni—Mo—W Hydrotreating Catalyst: Influence of the Atomic Ratio of Active Metals on the HDS and HDN Activity Catalysts, 12, 12, 1671 (year - 2022) https://doi.org/10.3390/catal12121671

2. Nadeina K.A. , Budukva S.V. , Vatutina Y.V. , Mukhacheva P.P. , Gerasimov E.Y. , Pakharukova V.P. , Prosvirin I.P. , Larina T.V. , Klimov O.V. , Noskov A.S. , Atuchin V.V. Optimal Choice of the Preparation Procedure and Precursor Composition for a Bulk Ni–Mo–W Catalyst Inorganics, № 2, V. 11, P. 1-23 (year - 2023) https://doi.org/10.3390/inorganics11020089