Macroporous CoMo Alumina Pellets for Hydrotreating of Heavy Oil

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Meso/macroporous CoMo alumina pellets for hydrotreating of heavy oil Ekaterina Vasilievna Parkhomchuk, Anton Igorevitch Lysikov, Alexey Grigorievitch Okunev, Pavel Dmitrievitch Parunin, Victoria Sergeevna Semeikina, Artem B. Ayupov, Valentina Alexandrovna Trunova, and Valentin N. Parmon Ind. Eng. Chem. Res., Just Accepted Manuscript • Publication Date (Web): 13 Nov 2013 Downloaded from http://pubs.acs.org on November 13, 2013

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Industrial & Engineering Chemistry Research

Meso/macroporous CoMo alumina pellets for hydrotreating of heavy oil

Ekaterina Vasilievna Parkhomchuka,b,*, Anton Igorevitch Lysikova,b, Alexey Grigorievich Okuneva,b, Pavel Dmitrievich Paruninb, Victoria Sergeevna Semeikinab, Artem Borisovich Ayupova, Valentina Alexandrovna Trunovac, Valentin Nikolaevich Parmona,b

a – Boreskov Institute of Catalysis SB RAS, Lavrentieva ave. 5, Novosibirsk 630090, Russia b – Novosibirsk State University, 2 Pirogova st., Novosibirsk 630090, Russia c – Nikolaev Institute of Inorganic Chemistry SB RAS, 3 Lavrentieva st., Novosibirsk 630090, Russia * – Corresponding author, Boreskov Institute of Catalysis SB RAS, 5 Lavrentieva st., Novosibirsk 630090, Russia, Tel./Fax: (383)333-16-17; e-mail: [email protected]

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Abstract CoMo catalysts supported on meso/macroporous alumina have been designed for hydrotreating of heavy oil. Pellets were prepared from pseudoboehmite and polystyrene colloidal crystals with subsequent CoMo compounds supporting on alumina. Supports, fresh and spent catalysts were characterized by crushing tests, X-ray diffraction, scanning and high-resolution transmission electron microscopies, N2 sorption and pycnometric techniques, mercury porosimetry and different methods of elemental analyses. The hydrotreating experiments were carried out at 380-420 °C and 70 bar in presence of CoMo catalysts supported on meso/macroporous or reference mesoporous alumina. Viscosity, desulfurization extent, micro carbon residue and asphaltenes content were determined for the reaction products. CoMo compounds supported on meso/macroporous Al2O3 had transformed to the layered sulfides under the influence of reaction medium, while no significant changes of supported compounds were observed for reference mesoporous catalyst. Bimodal meso/macroporous catalyst had increased activity in hydrodemetallization and hydrodesulfurization reactions compared with mesoporous analogue. Keywords: Polystyrene spheres; Meso/macroporous alumina; CoMo catalysts; Hydrodemetallization; Hydrodesulfurization; Heavy oil

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Introduction Advanced technologies for residue hydroprocessing are now extremely necessary1. However heavy oil fractions contain high amounts of sulfur and other contaminants that must be at least partially removed before further processing. Hydroconversion of heavy oils is a well-established upgrading process which requires specific hydrotreating catalysts designed to desulfurize the feed and to remove contaminants2. Catalytic hydroprocessing includes a range of different reactions: hydrodemetallization (HDM), hydrodesulfurization (HDS), hydrodeasphaltenization (HDAs), during which high molecular weight molecules react with catalytic sites. In this view catalytic activity and selectivity in conversion of heavy and extra-heavy oil fractions is mainly determined by porous structure of the catalyst3-5. An increase in the average mesopore size from 3 nm to 20 nm of alumina support improves the capacity of catalysts for metals and sulfur6, and macroporosity of the catalyst also increases its life time especially in the conversion of oils with high metal content7. For preparing meso- and macroporous structure of catalysts different methods may be used. Some of them are hydrothermal treatment, acidic or basic treatment8-11, the others use surfactants as structure directing agents or 1,3,5-trimethylbenzene as swelling agent and result in more controllable mesoporosity12-15. In the last decades a method for synthesis of inorganic supports with regular macroporous structure based on polymeric template has been widely developed16-18. Dual templating with polymer beads and surfactants leads to bimodal meso/macroporosity19-20. For obtaining hierarchical pore structure of alumina a mix of propylene oxide with polyethylene oxide21 or colloidal crystal22-26 consisting of polymeric monodisperse spheres with the diameter being controllably varied from 50 nm to 1500 nm are used. Catalysts based on these supports with regularly ordered porosity may provide higher efficiency and stability of the catalytic sites compared with the conventional analogues. In these methods aluminum salt solutions, aluminum isopropoxide, aluminum tri-n-butoxide and alumina suspensions are used for producing of alumina. In this paper meso/macroporous alumina pellets were prepared by mixing of pseudoboehmite with polystyrene colloidal crystals with subsequent paste extrusion, drying and calcination.

It is a simple method of obtaining the catalyst support having a bimodal

meso/macroporous structure and characteristics required for industrial use. CoMo oxides were 3



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chosen for supporting on alumina since CoMo catalyst exhibits better hydrogenolysis activity and suppressed hydrogenation activity as compared with NiMo catalyst27. The object of this paper is to elucidate an influence of catalyst texture on the in situ sulfidation reaction, as well as on the activity in HDM and HDS of heavy oils. Bimetallic Co-Mo complex prepared using citric acid was applied as a precursor of supported active component, because catalytic sites prepared with this technique have been found to have the superior activity in hydrotreatment of diesel fuels28. 2. Experimental 2.1. Chemicals The following chemicals were used: stabilized styrene (pure grade, Angara reaktiv), NaOH

(analytical

grade,

Reakhim),

potassium

persulfate

K2S2O8

(98%,

Aldrich),

pseudoboehmite AlOOH (Promyshlennye katalizatory), HNO3 (reagent grade, Reakhim), ammonium heptamolybdate tetrahydrate (NH4)6(Mo7O24)·4H2O (Alfa Aesar), cobalt(II) nitrate hexahydrate Co(NO3)2·6H2O (analytical grade, Reakhim),

citric acid C6Н8О7·H2O (reagent

grade), 95 %-ethanol and distilled H2O. High purity hydrogen (99.99 %) was supplied from the cylinder. Crude Tatar Oil has been used for hydrotreatment experiments. Its properties are listed in Table 1. 2.2. Catalyst preparation 2.2.1. PS template preparation Polystyrene

(PS)

spheres

were

synthesized

using

emulsifier-free

emulsion

polymerization technique as described elsewhere29. Polymerization was carried out at constant temperature of 90 оС under continuous stirring at stirrer speed of 245 rpm and continuous nitrogen purge during 24 hours. PS template was formed by centrifugation at relative acceleration of 160 g and dried in air. PS template was washed by ethanol and dried in air before using. 2.2.2. Support synthesis For the template synthesis of alumina granules, 150 g of dry AlOOH powder was mixed with 75 g of PS to obtain Al2O3-S1 sample or with 50 g of PS to obtain Al2O3-S2 sample. 4


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Distilled water (40 mL) acidified with HNO3 was then added to the mixture, and the mixture was stirred for 30 min. The reference sample of conventional alumina, Al2O3-S3, was obtained in the absence of the PS template under the same conditions. The mixtures were extruded to produce 2 x 5 mm cylindrical granules that then were dried in air for 1 day and heat treated for 4 h at 900 °C, the heating rate being 100 °C h-1. Just before impregnating procedure, the supports were dried at 120 °C during 30 min. 2.2.3. Catalyst synthesis Before the impregnation step, the water capacity of all supports had been determined. The impregnation was carried out by the required amount of impregnating solution, calculated with taking into account the water capacity of the support (0.6 cm3/g and 0.3 cm3/g for Al2O3-S2 and Al2O3-S3 samples, respectively), without any solution excess. The impregnating solution containing cobalt and molybdenum compounds was prepared from (NH4)6(Mo7O24)·4H2O, citric acid and Co(NO3)2·6H2O30. For this purpose the required amount of reagents were placed in water with the Co:Mo:citric acid molar ratio of 1:2:1.2. The solution was prepared with stirring at temperature (80 ± 5) ºC and pH = 2.0. Prior to impregnating the reactor containing the support was evacuated to 5 Torr and heated to 80 ºC, then the required amount of the impregnating solution was introduced and the reactor was exposed to vacuum and temperature of 80 ºC during 30 min. The impregnated support was dried at room temperature for 24 hours and calcined in air at 450 ° C for 4 hours. Two samples CoMo/Al2O3-S2 and CoMo/Al2O3-S3 were obtained from templated and conventional alumina supports, respectively. 2.3. Catalyst characterization The crushing strength of alumina granules was determined by measuring the breaking force for a sample compressed between two parallel plates using a MP-9S testing machine. In the lateral crushing strength measurements, the cross-sectional area of the granule was taken to be S = DH, where D is the granule diameter (cm) and H is the granule length. In the axial crushing strength measurements, the cross-sectional area of the granule was calculated as S = πD2/4. The crushing strength was calculated as the arithmetic mean of 30 replica measurements whose spread did not exceed the maximum allowable value, which was 0.6 kg cm-2 at a confidence level of 0.95. The crushing strength data for three alumina supports are presented in Table 2. 5



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Measurement of the true density of the supports and catalysts were conducted after thorough drying (calcination and cooling in a desiccator) using an instrument Ultrapycnometer1200e (Quantachrome Instruments, USA). The measurement was reproduced at least three times, the result was taken as the arithmetic mean. The true density data for alumina supports and CoMo catalysts based on these supports is presented in Table 2. X-ray diffraction patterns were recorded on an diffractometer Bruker D8 Advanced (2011, Germany) using CuKα monochromatic radiation (λ = 1.5418 Å) with step of 2θ = 0.05° and storage time of 1-2 s at each point using the linear detector Lynexeye (1D). Scanning electron microscopy (SEM) images were obtained on a JSM_6460LV microscope at the accelerating voltage of 15–20 kV. Transmission electron microscopy (TEM) micrographs were obtained with a JEM-2010 instrument at lattice resolution 1.4 Å and acceleration voltage 200 kV. Analysis of the local elemental composition (in atomic %) was carried out by using an energy-dispersive EDX spectrometer equipped with Si(Li) detector (energy resolution 130 eV). Atomic percentages were then converted to weight % for all samples. Measurements of N2 adsorption at the liquid nitrogen temperature (77.4 K) were performed after degassing the samples in vacuum of 6 mTorr at 200 °C for 4 h with Autosorb6B-Kr instrument (Quantachrome Instruments, USA). The specific BET surface area was calculated on the branch of the adsorption isotherm in the range of relative pressure of 0.05-0.20. The volume of micropores and the total surface of mesopores were calculated by αS-method using N2 adsorption isotherm at 77 K on alumina C31. The pore size distribution was calculated by BJH method using the software supplied with the instrument. Mercury porosimetry for some samples was carried out on AutoPore IV 9500 porosimeter (Micromeritics). The elemental composition of the catalysts was determined by the inductive coupled plasma optical emission spectroscopy (ICP-OES) as well as X-ray fluorescent analysis with synchrotron radiation (SRXRF). The last method was carried out on the station of SRXRF elemental analysis (storage ring VEPP-3, Siberian Synchrotron and Terahertz Radiation Center, Budker Institute of Nuclear Physics SB RAS, Novosibirsk, Russia) with the involvement of equipment belonging to the shared research center "SSTRC" and supported by the Ministry of Education and Science of the Russian Federation. The conditions of VEPP-3 were the following: Eex = 2 GeV, B =2T, and Ie=100 mA. All spectra obtained were processed by AXIL program (Canberra Packard, 6


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Benelux). The concentrations of chemical elements in the samples were calculated by the external standard method with standard reference material 1633a (Coal fly ash). 2.5. Hydrotreating tests 2.5.1 Reaction setup The heavy oil hydrotreating experiments were carried out using the lab scale Berty reactor. The reactor of 50 ml internal volume was produced by Autoclave Engineers, USA (Fig. 1a). Typical catalyst loading of 2-4 g was supported in the basket with wire mesh plugs. The outer wall of the basket has a flow fields for oil recirculation. Continuous stirring with recirculation pump impeller provides gradientless conditions in the reactor interior. The hydrogen is introduced into the reactor via high pressure line equipped with an intermediate pressure buster which compensates pressure drop in buffering cylinder (Haskel Gas booster AGT-32/62). Forward pressure control valve supports the preset total pressure in the reactor. The oil is supplied using a “Teledyne Isco” 500D syringe pump. The product gas and liquid are fed to a thermostated separator of 200 ml internal volume. The gas products are vented through the forward pressure control valve and mass flow controller, which controls outlet gas flow rate. The liquid products are purged through a sequence of two pneumatically actuated high pressure valves with an intermediate liquid collector. Figure 1a depicts the setup flow diagram. 2.6. Reaction product and catalyst analyses after hydrotreating tests Reaction products deposited on the samples CoMo/Al2O3-S2 and CoMo/Al2O3-S3 after hydrotreating tests were subjected to extraction by benzene in a Soxhlet extractor for 48 hours, after that one part of the catalysts were characterized by TEM and elemental analysis (ICP, SRXRF). The other part was calcined in air at 450 ° C for 4 hours and characterized by lowtemperature N2 adsorption, mercury porosimetry and XRD methods. The sulfur content in the oil before and after hydrotreating tests was determined by using an X-ray fluorescence analyzer HORIBA SLFA 2100 according to the GOST R 50442-92 (ASTM 4294) method. The amount of carbon residue formed after evaporation and pyrolysis of petroleum material have been measured under conditions specified in ASTM D 4530. The micro carbon residue fraction was determined as the ratio of the coke weight to the weight of sample oil. C, H analyses were performed with a Vario Cube analyzer following the standard method ASTM D5291. The 7



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asphaltenes content was determined according to standard method GOST 17789. Briefly run through the process. 5 ml of heavy oil were dissolved in 10 ml of toluene under vigorous mixing, then 200 ml of hexane was added to the solution. The precipitate was filtered, washed and dried. The asphaltenes content was determined as a ratio of the precipitate mass to the mass of the heavy oil sample. Viscosity measurement was carried out in a cryostate LOIP LT-912 monitoring the time t of expiration of the fixed sample volume through the calibrated nozzle, according to GOST-6258 (ASTM D 445) procedure. Using the calibration factor of f = 18.062 mPa the dynamic viscosity was calculated as η = f ⋅ t .

3. Results and discussion 3.1. Textural properties of the supports According to SEM analysis templated alumina has macroporous structure throughout the granule unlike reference conventional Al2O3 (Fig. 2,3). Highly ordered arrangement of macropores are scattered in irregular macroporosity of templated samples. Such regular structures are partially formed due to the method of pellet preparation consisting in mixing of dry powders of pseudoboehmite and polystyrene colloidal crystals with subsequent adding of acidified water to form a paste. Some PS crystals are not only covered, but partially impregnated by the peptized mixture resulting in ordered arrangement of alumina macropores, but generally macropores with a wide size disribution are formed as a result of PS template combustion and CO2 emission during calcination procedure. If PS colloidal crystals were impregnated by dissolved aluminum precursor it would be possible to obtain a regular macroporosity throughout a sample, however the periodic structure of the support possibly is not a crucial criteria in catalytic approach. It should be noted that a reliable texture data for macroporous alumina samples may be obtained only by combination of low-temperature N2 adsorption and mercury porosimetry methods. Combined texture data shows that PS template synthesis of alumina results in the formation of bimodal meso/macroporous structure of the sample (Table 3). Mesoporosity is formed due to the density increase from 3.01-3.06 g cm-3 for AlOOH to 3.43-3.46 g cm-3 for Al2O3 (Table 2), while macroporosity remains after PS template removing. On the basis of 8


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experimental data, relative volumes of meso- and macropores in templated samples may be estimated, not taking into account a thermal shrinkage of alumina. If the polystyrene density is ca. 1.1 g cm-3, then for the sample Al2O3-S1 a real volume of obtained granules is 75/1.1+150/3.0 = 118.2 cm3, the volumes of macropores and solid AlOOH phase are 68.2 and 50 cm3, respectively. During transformation of AlOOH to Al2O3 the solid phase shrinks to volume of 37.2 cm3, therefore contribution of meso- and macropores is 16 and 84 %, respectively, in relation to the total pore volume. Estimated absolute values of meso- and macropores for such a sample should be 0.10 and 0.53 cm3/g, respectively. According to the texture data from Table 3 contribution of mesoporosity to the total pore volume for templated samples Al2O3-S1 and Al2O3-S2 is higher than 16 % and is in the range of 25 to 42 % due to several reasons. The first one is an imperfectly regular structure of macropores, and as a result thicker walls than filling the space between the tightly packed PS spheres (Fig. 3). The other reason is a presence of nitric acid in the initial synthetic mixture, which results in more developed mesoporosity after the sample calcination that is evidently observed for conventional sample Al2O3-S3 from the texture data. Mercury porosimetry data, presented in the Fig. 4, clearly shows a bimodal porosity of the templated alumina relative to the conventional one. The mean macropore size in the sample Al2O3-S1 obtained using PS template at the higher weight ratio of PS template/AlOOH is 146 nm (Table 2), which is significantly higher than the mean pore size of 113 nm in the sample Al2O3-S2, obtained at the lower weight ratio of PS template/AlOOH. As a result the specific surface area increases from 132 to 187 m2g-1, respectively. The mean mesopore size of all samples may be considered as the same and equals 10 nm (Fig. 5). Two templated alumina supports were produced but only the sample Al2O3-S2 with the smaller weight ratio of PS template/AlOOH was chosen for the catalyst synthesis due to the high porosity and relatively good crushing strength (Table 2). CoMo impregnating procedure results in mesopore volume decrease in both alumina samples Al2O3-S2 and Al2O3-S3 according to the porosimetry techniques (Fig. 4,5). This is apparently due not so much to the volume of supported phase, but to the exposure of alumina to the acidic impregnating mixture at elevated temperature. Macroporous structure of templated alumina sample also changes: the average size and a specific volume of macropores are reduced. 9



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Hydrotreating tests at temperatures below 420 oC and a pressure below 90 atm does not result in any significant change of the catalyst texture (Fig. 4,5).

3.2. Phase and elemental composition of the catalysts Phase composition of alumina supports obtained in absence and in presence of PS template is the same and corresponds to δ-Al2O3, whose broad peaks are observed on the XRD patterns (Fig. 6). Observed patterns are attributed to δ-phase of Al2O3 due to splitting of reflexes 220 and 400, which is not observed in case of γ-phase. However the mixture of δ-Al2O3 and γAl2O3 in the catalysts can’t be denied. According to TEM analysis (Fig. 7) all CoMo/Al2O3 samples consist of agglomerates of alumina particles with the size ranging from 10 nm to several microns. Particles with the size of 20 nm have a plate shape with rounded edges. The hydrotreating tests don’t change the morphology of alumina particles for both CoMo/Al2O3-S2 and CoMo/Al2O3-S3 samples. EDX data show that the active component, supported on templated catalyst CoMo/Al2O3S2 as well as on conventional catalyst CoMo/Al2O3-S3 before the hydtotreating tests, represents the small particles with a size of 0.3 - 0.5 nm in the form of CoMoO4 (Fig. 7). Distinguishable CoMoO4 reflections are observed on the XRD patterns of the templated sample CoMo/Al2O3-S2 and only a small peak in the angular region of 25-27

o

is observed for

the conventional sample CoMo/Al2O3-S3, indicating the trace amount of CoMoO4. These data agree with the elemental analyses of the catalysts (Table 4). It can be seen that when impregnated with solution of the same concentration the templated support makes it possible to impregnate a larger amount of active component than a conventional support due to a favorable porosity and the larger water uptake. After the oil hydrotreating procedure and consecutive regeneration, CoMoO4 reflections in the XRD patterns of the sample CoMo/Al2O3-S2 become narrower resulted from the increase of the particle size. It is obvious from HRTEM that CoMo component supported on the macroporous CoMo/Al2O3-S2 undergoes a change after the hydrotreating reaction, i.e. converts to Co-Mo-S package with variations of size and number of layers in the package. But after the reaction no any changes are observed for the patterns of conventional mesoporous sample

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CoMo/Al2O3-S3, that corresponds with the idea of sihnificant diffusion difficulties of reactants in the internal catalyst volume under the reaction conditions (Fig. 6). According to EDX analysis, the sample CoMo/Al2O3-S2 contains 2.1 wt.% of vanadium. It was impossible to fix any phase containing V on the HRTEM images, thus one can assume that V-containing phase covers a sample in the form of substantially uniform film transparent for HRTEM. The presence of unevenly coating of amorphous carbon in the form of particles with a size of 10 nm is observed for the sample CoMo/Al2O3-S2. It is well known, that with respect to feed composition, vanadium is mainly concentrated in heavy fractions as vanadyl porphyrins and is associated with other large molecules containing condensed poly-aromatic rings32. Thus, the vanadium deposition inside the macro CoMo/Al2O3-S2 catalyst provides the direct evidence of the easily accessible catalyst internal surface for the oil macromolecules, that in the case of mesoporous CoMo/Al2O3-S3 cannot enter to the pores of 10 nm in size. Taking into account very similar chemical nature of both catalysts, we account the observed phenomenon entirely to the different porous structure of the catalysts.

3.3.Hydrotreating tests The performance of prepared CoMo/Al2O3 catalysts was evaluated in hydrocracking of heavy crude oil at reaction temperature of 380-420 °C, liquid hourly space velocity (LHSV) of 0.8771.175 h-1, hydrogen feed rate of 1000 cm3-H2(n.c.)/cm3-oil and total pressure of 70 bar. These operating conditions are typical for hydrotreatment of heavy oil27. The products of catalytic heavy oil hydrotreatment were analyzed for viscosity, sulfur content and micro carbon residue (Table 5). Measured viscosities of the hydrotreated products are much lower than the viscosity of the feed oil. The hydrotreatment temperature is found to have a major influence on the viscosity. Increase in hydrotreatment temperature from 380 °C to 420 °C induces 3 fold drop in viscosity values measured at 25 °C. Other factors such as porous structure of the catalysts and oil feed rate seems to have minor influence over products viscosity. Both of the temperature dependence and absolute viscosity values nearly coincide for meso- and meso/macroporous catalysts at the same temperature (Fig. 8). The apparent activation energy for viscosity dependence on temperature,

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which can be calculated from the slope in Arrhenius plot (Fig. 8) also decreases at higher reaction temperature (Table 5). Similar behavior has been found for changes in micro carbon residue content. Hydrotreatment at 380 °C slightly decreases the residue content from 9.3 in feed oil to 8 in hydrotreatment products for both meso- and meso/macroporous catalysts (Table 5). Thus, close micro carbon residue content and viscosity values let us think that the both catalysts have similar moderate activity in hydrogenation of the hydrocarbon macromolecules. These findings correlate with the data of Rana et al27 who found CoMo catalysts much less active in HDAs reaction as compared to NiMo catalyst. On the contrary, desulfurization extent is very sensitive to the catalyst porous structure. Only 13 % drop of sulfur content was found for mesoporous CoMo/Al2O3-S3 catalyst. Macroporous CoMo/Al2O3-S2 under similar conditions demonstrated 32 % of sulfur removal. At the higher reaction temperature 420 °C, the desulphurization extent was even higher, reaching 68 %. The following tests on stability of the macroporous catalyst were carried out. A series of hydrotreating experiments in presence of the same catalyst without its regeneration was as follows: 1) LHSV 0.87 h-1, temperature 420 oC during 108 h, 2) LHSV 0.87 h-1, temperature 380 oC during 96 h, 3) LHSV 1.75 h-1, temperature 380 oC during 96 h, 4) LHSV 0.87 h-1, 420 o

C during 130 h. The product properties: viscosity, sulfur content and micro carbon residue were

analyzed after the each stage. The differences between the product properties after the first and the last stages were insignificant and the granules were not crumbled. Putting together the results of the desulphurization and the data on vanadium content in the catalysts after test, one may conclude that macroporous catalyst has increased activity in HDM and HDS reaction as compared to the catalyst without macroporosity. Open porous structure of macroporous catalyst, which was prepared using templated synthesis procedure, contained wide pore mouth that can be easily penetrated by the macromolecules of heavy hydrocarbon fractions. It makes the catalyst internal surface and the active component in the interior of the catalyst grain accessible for large reagent molecules, enhancing the overall reaction rate. One more advantage of new catalytic system may be the increased metal retention capacity, which is based on their increased pore volume. This guess will be tested in our further research.

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4. Conclusions Synthesis of alumina using polymeric templates consisting of packed polymeric spheres allowed to produce a controllable macroporosity of the support without changing surface chemical properties and texture characteristics in mesopore range. Depending on the required strength of the catalyst, one can select the most appropriate support with the optimal values of strength and porosity. Macroporous structuring of the support resulted in increase of active site content of the catalyst available for heavy oil components containing sulfur and metals. Alumina-supported compounds were CoMoO4 particles with a size of 0.3-0.5 nm that under the influence of the reaction medium in bimodal meso/macroporous support became larger, transforming to the layered sulfides. No any changes of the supported compounds were observed for conventional mesoporous alumina-based catalyst, which means a low availability of active sites on mesoporous support for reactants of heavy oil. The both CoMo-catalysts had a similar moderate activity

in

hydrogenation

of

the

hydrocarbon

macromolecules.

Meanwhile,

the

meso/macroporous catalyst had increased activity in HDM and HDS reactions as compared to the mesoporous analogue, which demonstrates improved transport and diffusion properties of the templated catalyst.

Acknowledgements The authors thank O.A. Bulavchenko, E.Yu. Gerasimov, M. Melgunov for their help in catalyst characterization. Financial support by Department of Science and Education (projects №14.515.11.0043 and №8440) is gratefully acknowledged.

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Captions for Tables 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Table 1. Feed oil characteristics. Table 2. Crushing strength and true density of conventional and templated alumina-based granules. Table 3. Textural properties of alumina-based supports and CoMo catalysts according to low temperature nitrogen adsorption data and mercury porosimetry. Table 4. Sulfur and metal content (wt.%) of the catalysts before and after the hydrotreating tests, as determined by X-ray fluorescence analysis (XF), inductive coupled plasma (ICP) optical emission spectroscopy, X-ray fluorescent analysis with synchrotron radiation (SRXRF) spectroscopy and energy-dispersive X-ray (EDX) spectrometry. Table 5. Sulfur, micro carbon residue content and viscosity of the hydrotreatment products.

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Table 1. Feed oil characteristics. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

Density at 15 °C

Viscosity, St

Fractional composition, wt. %

kg m-3

API

25 °C

80 °C

Nafta 360 °C

967.5

14.75

3.6

0.16

0

21.2

78.8

Micro carbon residue, wt. %

Elemental composition, wt. %

C

H

S

V

Ni

9.3

81.2

11.0

3.4

0.013

0.067

15


Asphaltenes, wt.%

10.2


Page 16 of 32

Table 2. Crushing strength and true density of conventional and templated alumina-based granules. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

Al2O3-S1

Crushing strength, kg cm-2 True density, g cm-3

Al2O3-S2

Al2O3-S3

CoMo/ Al2O3-S2

CoMo /Al2O3-S3

lateral 10.4

32.6

32.9

-

-

axial 55.3

93.0

153

-

-

3.43

3.46

3.68

3.62

-

16


Page 17 of 32


Table 3. Textural properties of alumina-based supports and CoMo catalysts according to low temperature nitrogen adsorption data and mercury 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

porosimetry. Mean pore size, nm

1.22

Mesopore volume by N2, cm3 g-1 0.29

0.56

0.84

0.36

11.8; 113

126

0.34

0.62

0.25

9.8, 123

96

103

0.29

0.60

0.25

9.8, 111

Al2O3-S3

222

168

0.58

0.34

0.54

10.4

CoMo /Al2O3-S3

114

132

0.31

0.32

0.27

10.7

CoMo /Al2O3-S3 spent

118

120

0.35

0.32

0.34

9.8

Sample

BET surface area, m2 g-1

Pore surface Total pore Pore volume by Hg, m2 g-1 volume by N2, by Hg, cm3 g-1 cm3 g-1

Al2O3-S1

132

157

0.31

Al2O3-S2

187

194

CoMo /Al2O3-S2

125


17


11.9; 146


Page 18 of 32

Table 4. Sulfur and metal content (wt.%) of the catalysts before and after the hydrotreating tests, as determined by X-ray fluorescence analysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

(XF), inductive coupled plasma (ICP) optical emission spectroscopy, X-ray fluorescent analysis with synchrotron radiation (SRXRF) spectroscopy and energy-dispersive X-ray (EDX) spectrometry. S

Mo

Co

V

XF

ICP

SRXRF

EDX

ICP

SRXRF

EDX

ICP

SRXRF

EDX

ICP

SRXRF

CoMo /Al2O3-S2

0

10.2

12.4

20.9

3.53

8.01

3.9

0

0.0

0

0

0.06


5

7.53

10.9

9.4

2.32

8.03

5.1

0.22

0.06

2.1

0.18

0.3

CoMo /Al2O3-S3

0

4.85

4.0

9.1

1.73

2.34

3.0

0

0

0

0

0.02


0.35

2.3

3.9

7.1

0.44

3.09

3.2

0.06

0.04

0

0.1

0.06

18


Ni

Page 19 of 32


Table 5. Sulfur, micro carbon residue content and viscosity of the hydrotreatment products. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

Hydrotreatment conditions

S, wt. %

HDS conversion,

Micro carbon

Viscosity, St

Apparent Ea,

%

residue, wt%

at 25 °C

kJ/mole

Catalyst

Temperature, °C

LHSV, h-1

CoMo/Al2O3-S2

380

0.877

2.31

32

8.01

1.7

48 ± 1

CoMo/Al2O3-S2

380

1.175

1.46

57

n.d.

1.8

43 ± 1

CoMo/Al2O3-S2

420

0.877

1.08

68

7.70

0.48

34 ± 0.5

CoMo/Al2O3-S3

380

0.877

2.96

13

7.95

1.7

44 ± 1

19



Page 20 of 32

1 2 Captions for figures 3 4 5 Fig. 1. The hydrotreating lab-scale setup: a) the gas and liquid line scheme; b) drawing of the Berty stationary 6 7 basket reactor. 8 9 Fig. 2. SEM images of the latitude (a) and longitude (b) cross-sections of the sample Al O -S1, obtained in the 2 3 10 11 presence of the PS template. 12 13 14 Fig. 3. SEM images of the granule sections of alumina support: Al2O3-S2 (a), Al2O3-S3 (c), and CoMo catalysts: 15 CoMo/Al2O3-S2 (b), CoMo/Al2O3-S3 (d). In the insets photos of Petri dishes with granules of the appropriate samples 16 17 are shown. 18 19 20 Fig. 4. Mercury intrusion curves for the alumina supports (black), fresh CoMo-catalysts (blue) and spent catalysts 21 22 calcined in air after the hydrotreating tests (red): meso/macrporous (solid) and mesoporous (dash-dot) samples. 23 Curves are normalized with respect to the Al2O3 weight content. 24 25 26 Fig. 5. Nitrogen adsorption (solid) – desorption (open) isotherms of the alumina supports (black), fresh CoMo27 28 catalysts (blue) and spent catalysts calcined in air after the hydrotreating tests (red): meso/macrporous (left panel) 29 30 and mesoporous (right panel) samples. In the insets the pore size distributions for the appropriate samples are 31 shown. 32 33 34 Fig. 6. XRD patterns of the alumina supports (black), fresh CoMo-catalysts (blue) and spent catalysts calcined in 35 36 air after the hydrotreating tests (red): meso/macroporous (a) and mesoporous (b) ones. 37 38 Fig. 7. TEM images of the meso/macroporous CoMo catalysts: fresh CoMo/Al2O3-S2 (a), spent CoMo/Al2O3-S2 (b), 39 40 and mesoporous CoMo catalysts: fresh CoMo/Al2O3-S3 (c), spent CoMo/Al2O3-S3 (d). In the insets atomic distributions 41 42 for the appropriate samples are shown. 43 44 Fig. 8. Arrhenius plot for a viscosity of the crude oil and hydrotreatment products. 45 46 47 48 49 50 51 52 53 54 55 56 57 20 58 59 60 ACS Paragon Plus Environment

Page 21 of 32

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Stirrer Basket

Reactor case

a

b

Fig. 1. The hydrotreating lab-scale setup: a) the gas and liquid line scheme; b) drawing of Berty stationary basket reactor.

21



Page 22 of 32

a 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

b

Fig. 2. SEM images of latitude (a) and longitude (b) cross-sections of the sample Al2O3-S1, obtained in the presence of the PS template.

22


Page 23 of 32


1 2 a b 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 c d 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 Fig. 3. SEM images of the granule sections of alumina support: Al2O3-S2 (a), Al2O3-S3 (c), and CoMo catalysts: 45 46 CoMo/Al2O3-S2 (b), CoMo/Al2O3-S3 (d). In the insets photos of Petri dishes with granules of the appropriate samples 47 48 are shown. 49 50 51 52 53 54 55 56 57 23 58 59 60 ACS Paragon Plus Environment

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Cummulative volume, cm3 g-1


Page 24 of 32

Al2O3-S2

0,8

fresh CoMo/Al2O3-S2 spent CoMo/Al2O3-S2 Al2O3-S3

0,6

fresh CoMo/Al2O3-S3 spent CoMo/Al2O3-S3

0,4

0,2

0,0 10

100

1000

10000

100000

Pore diameter, nm

Fig. 4. Mercury intrusion curves for the alumina supports (black), fresh CoMo-catalysts (blue) and spent catalysts calcined in air after the hydrotreating tests (red): meso/macrporous (solid) and mesoporous (dash-dot) samples. Curves are normalized with respect to the Al2O3 weight content.

24


0,09 0,08

400

0,07

400

dV/dd


dV/dd

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Volume adsorbed, cm3 g-1

Page 25 of 32

0,09 0,08 0,07

0,06

0,06

0,05

0,05

0,04

0,04

0,03

0,03

0,02

0,02

300

0,01

0,01

0,00

0,00 6

8

10

12

14

16

18

20

6

8

10

12

14

18

20

Al2O3-S3

200

Al2O3-S2

200

16

Pore size, nm

Pore size, nm

fresh CoMo/Al2O3-S3

fresh CoMo/Al2O3-S2

spent CoMo/Al2O3-S2

spent CoMo/Al2O3-S2

100

0

0 0,0

0,2

0,4

0,6

0,8

1,0

0,0

0,2

0,4

0,6

0,8

1,0

Relative pressure Fig. 5. Nitrogen adsorption (solid) – desorption (open) isotherms of the alumina supports (black), fresh CoMocatalysts (blue) and spent catalysts calcined in air after the hydrotreating tests (red): meso/macrporous (left panel) and mesoporous (right panel) samples. In the insets the pore size distributions for the appropriate samples are shown.

25



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

a

b δ − δ-Al2O3

* − CoMoO4 δ − δ-Al2O3

* * * **** δ δ * * δ δ *

δ

δ

*

δ δ

δ

δ

δ

δ δ

30

40

δ

δ δ δ

δ

400

220

20

Page 26 of 32

50

60

20

70

30

2θ, degrees

40

50

60

70 2θ, degrees

Fig. 6. XRD patterns of the alumina supports (black), fresh CoMo-catalysts (blue) and spent catalysts calcined in air after the hydrotreating tests (red): meso/macroporous (a) and mesoporous (b) ones. XRD pattern of the control sample δ-Al2O3 is presented by green line (b).

26


Page 27 of 32

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


a

b

c

d

Fig. 7. TEM images of the meso/macroporous CoMo catalysts: fresh CoMo/Al2O3-S2 (a), spent CoMo/Al2O3-S2 (b), and mesoporous CoMo catalysts: fresh CoMo/Al2O3-S3 (c), spent CoMo/Al2O3-S3 (d). In the insets atomic distributions for the appropriate samples are shown.

27



4

lg(η), log(mPa s)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 32

Feed Tatar oil -1 o Macroporous catalyst at LHSV 0,877 h and 380 C -1 o Macroporous catalyst at LHSV 1,175 h and 380 C -1 o Mesoporous catalyst LHSV 0,877 h at 380 C -1 o Macroporous catalyst at LHSV 0,877 h and 420 C

3

2

0,33

0,34

0,35

0,36

0,37

0,38

0,39

0,40

0,41

0,42

-1

1000/RT, (kJ/mol)

Fig. 8. Arrhenius plot for a viscosity of the crude oil and hydrotreatment products.

28


Page 29 of 32

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


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Macroporous CoMo Alumina Pellets for Hydrotreating of Heavy Oil

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