ISSN 2070-0504, Catalysis in Industry, 2017, Vol. 9, No. 2, pp. 136–145. © Pleiades Publishing, Ltd., 2017. Original Russian Text © S.V. Budukva, O.V. Klimov, A.S. Noskov, V.A. Golovachev, D.O. Kondrashev, A.V. Kleimenov, R.V. Esipenko, A.P. Kubarev, D.V. Khrapov, 2017, published in Kataliz v Promyshlennosti.
CATALYSIS IN PETROLEUM REFINING INDUSTRY
Reactivation of an Industrial Batch of CoMo/Al2O3 Catalyst for the Deep Hydrotreatment of Oil Fractions S. V. Budukvaa, *, O. V. Klimova, **, A. S. Noskova, ***, V. A. Golovachevb, ****, D. O. Kondrashevb, *****, A. V. Kleimenovb, ******, R. V. Esipenkoc, A. P. Kubarevc, *******, and D. V. Khrapovc, ******** aBoreskov
Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia b PAO Gazprom Neft, St. Petersburg, 190000 Russia cAO Gazprom Neft-Omsk Refinery, Omsk, 644040 Russia *e-mail:
[email protected] **e-mail:
[email protected] ***e-mail:
[email protected] ****e-mail:
[email protected] *****e-mail:
[email protected] ******e-mail:
[email protected] *******e-mail:
[email protected] ********e-mail:
[email protected] Received September 8, 2016
Abstract⎯The results from industrial tests of technology developed earlier for the reactivation of CoMo/Al2O3 catalyst for the deep hydrotreating of diesel fuel, including the oxidative regeneration of the catalyst with subsequent treatment using organic complexing agents, are presented. Samples of the catalyst, fresh and at different stages of its reactivation, are investigated using a set of analytical and physicochemical methods. The chemical composition, textural characteristics, mechanical strength, structure of the active sulfide component (TEM, XPS) are determined. Catalytic tests are performed that include lifetime tests (360 h) in the hydrotreatment of a straight-run diesel fraction. The restoration of the physicochemical and catalytic properties is observed for a sample subjected to oxidative regeneration with subsequent treatment using organic complexing agents. An industrial batch of deep hydrotreatment catalyst reactivated by this technology is loaded into an L-24-6 industrial plant facility and ensures stable purification of straight-run diesel fuel containing up to 10% of light catalytic cracking gas oil to a residual sulfur content of less than 10 ppm. Comparison of the obtained results and data on the industrial operation of fresh catalysts shows that the technology developed by the Institute of Catalysis and PAO Gazprom Neft ensures almost complete restoration of the properties of the deactivated catalysts. Keywords: hydrotreatment, regeneration, reactivation, organic complex agents, catalysts, diesel fuel DOI: 10.1134/S2070050417020027
INTRODUCTION In connection with the adoption by the Russian government the technical regulations “On the Requirements for Automobile and Aviation Gasoline, Diesel and Marine Fuel, Jet Fuel, and Fuel Oil” [1], the domestic oil refining industry has switched to the production of fuels meeting the requirements of the current Euro-5 standard. For the production of such fuels on hydrotreatment units of the L-24-6 and -7 types developed and built in the Soviet Union, catalysts have been replaced with more active (mainly imported) ones, and the temperature of the hydrotreatment process has been raised. At some refineries, the reactor blocks have been reconstructed to increase catalyst loading.
At the same time, the energy consumption per tonne of produced diesel fuel has grown considerably and the catalyst lifetime has been shortened by its accelerated deactivation at elevated temperatures. As a result of operating under such conditions, the catalyst run time is now 9–12 months, after which they are unloaded from the reactor and replaced with fresh ones. In Russia, technologies based only on the oxidative removal of carbonaceous deposits are used for the regeneration of hydrotreatment catalysts. Coke is burned either directly in a hydrotreating reactor, or on the only operating specialized unit at PAO ANK Bashneft (a subsidiary of Bashneft-Ufaneftekhim). The regeneration of modern catalysts using such technolo-
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The most rational solution to the problem is to develop a Russian industrial technology for the reactivation of hydrotreatment catalysts. In [4], we showed that a combination of oxidative regeneration stages and subsequent reactivation with organic complexing agents should result in catalysts that allow the production of Euro-5 diesel fuels at lower temperatures of the hydrotreatment process, compared to those for catalysts regenerated using traditional oxidation technologies. In this work, we consider restoring the activity of an imported CoMo/Al2O3 deep hydrotreatment catalyst using reactivation technology developed jointly by the Boreskov Institute of Catalysis and PAO Gazprom Neft. Catalyst deactivated during industrial operation at the L-24-6 unit of AO Gazprom Neft-Omsk Refinery (AO GPN-OR) was used for industrial tests of the technology.
Table 1. Catalyst samples studied in this work No.
Catalyst
1 2
CoMo-F CoMo-D
3
CoMo-R
4
CoMo-RF
5
CoMo-RFI
137
Description Fresh reference catalyst Sample 1, deactivated during industrial operation on the L-24-6 hydrotreatment unit at PAO GPN-OR Sample 2 after oxidative regeneration Sample 3 after reactivation in the laboratory Sample 3 after industrial reactivation
gies allows us to restore their activity by no more than 90%, resulting in the need to raise the initial temperature of hydrotreatment on regenerated catalysts by at least 10–20°C, in contrast to fresh ones. This means additional energy inputs, reduced yields of target products, and greater consumption of deficit hydrogen due to undesirable gas generation reactions. Since the lifetime of hydrotreatment catalysts is reduced as the initial process temperature rises, shorter lifetimes for catalysts regenerated using oxidation technology are inevitable, resulting in more frequent shutdowns to reload catalyst in hydrotreatment units integrated into the continuous refinery operation scheme. We therefore now have a situation in which any Russian refinery that produces diesel fuel in compliance with the Euro-5 standard must choose one of three unattractive options: 1. Constantly purchasing fresh catalysts, making companies completely dependent on foreign suppliers. Meanwhile, deactivated catalysts that cannot be recycled accumulate in warehouses. 2. Regeneration of catalysts abroad using the specialized units at Porocel or EURECAT [2, 3]. This also results in dependence on foreign service providers. In addition to the cost of regeneration, those of transportation and customs fees are quite high. 3. Regeneration using the outdated oxidation technologies in Russia, and thus continued use of less active regenerated catalysts with the inevitable increase in the temperature of hydrotreatment. This raises the consumption of energy per unit of the final products, lowers the yield of the target product, and shortens the life of a catalyst.
EXPERIMENTAL A list of the catalysts studied in this work is presented in Table 1. The degree of coke removal from the deactivated catalysts as a result of oxidative regeneration was assessed via CHNS analysis conducted on a Vario EL Cube (ELEMENTAR Analysensysteme GmbH). Data for the deactivated and regenerated catalysts are presented in Table 2. The mechanical crushing strength was measured using the Shell SMS 1471 or the analogous ASTM 7084-4 technique (standard ways of determining mechanical strength in the crushing of catalysts and carriers) using a VINCI Technologies Bulk Crushing Strength unit (France). The content of metals and silicon in the catalysts was analyzed by means of atomic emission spectrometry with inductively coupled plasma on a PerkinElmer Optima 4300DV device. The textural characteristics of the catalysts were determined via low-temperature nitrogen adsorption on an ASAP 2400 apparatus (United States). Prior to measuring textural characteristics and performing our elemental analysis, the catalysts were calcined in air at 550°C for 4 h. The results from our measurements are shown in Table 3. The sulfided catalysts were studied by means of transmission electron microscopy (TEM) using an JEM-2010 electron microscope (JEOL, Japan) with a resolution of 0.14 nm at an accelerating voltage of 200 kV. Catalysts unloaded from the reactor after cat-
Table 2. Content (wt %) of carbon, sulfur, nitrogen, and hydrogen in the catalysts Catalyst
С
Н
N
S
CoMo-D CoMo-R
9.146 ± 0.123 0.02 ± 0.010
1.268 ± 0.027 1.144 ± 0.150
0.094 ± 0.024 0.051 ± 0.035
8.905 ± 0.130 0.640 ± 0.321
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Table 3. Main physicochemical characteristics of the studied samples Characteristic Specific surface area* Pore volume* Pore diameter* Average granule length Bulk crushing strength, determined by the Shell SMS 1471 method Active metal content: Mo Co Impurities content: Si Fe Na Ca
Unit of measurement
CoMo-F
CoMo-R
CoMo-RF
CoMo-RFI
m2/g
202
202
199
200
3
cm /g Å mm МPа
0.57 111 5.2 1.08
0.54 108 4.5 1.03
0.58 111 4.5 1.02
0.57 110 4.4 1.07
wt %
11.7 3.20
11.7 3.18
11.5 3.12
11.5 3.10
wt %
0.20 0.01 0.06 0.01
0.49 0.06 0.06 0.01
0.48 0.05 0.06 0.02
0.48 0.05 0.05 0.02
* For catalyst calcined at 550°C over 4 hours.
alytic tests were used for this study. The average length of the sulfide particles and the average number of layers of the sulfide active component in each sample were calculated based on the parameters of more than 500 particles for each catalyst sample. The catalysts were studied by means of X-ray photoelectron spectroscopy (XPS) using a SPECS electronic spectrometer with AlKα radiation (hν = 1486.6 eV). The binding energy scale (Eb) was preliminarily calibrated for the Au4f7/2 (84.0 eV) and Cu2p3/2 (932.67 eV) peaks. The C1s (284.8 eV) line from carbon on the catalyst’s surface was used for calibration. The catalytic properties of the catalyst samples in the hydrotreatment of diesel fuel were studied in pilot plant units at the Boreskov Institute of Catalysis using two procedures whose conditions were as close as possible to the ones currently used on AO GPN-OR L-24-6 and -7 hydrotreating units. Procedure 1. A comparative determination of the activity of the catalysts was performed on a singlereactor unit, in a reactor with a diameter of 16 mm and a length of 530 mm. Catalyst granules (average length, 4.5 mm) with weight equivalent to 10 g of the catalyst calcined at 550°C were placed in the isothermal zone of the reactor, evenly diluting it with particles of 0.1– 0.2 mm silicon carbide. Hydrotreatment was performed at a mass flow rate of 2 h−1, a volume ratio of 500 m3 H2/m3 feed, a pressure 3.8 MPa, and temperatures of 340, 350, and 360°C. Procedure 2. A test of the lifetimes of reactivated CoMo-RF and fresh CoMo-F reference catalyst was conducted on a two-reactor pilot plant. Each reactor (inner diameter, 26 mm; length, 1426 mm) was placed in a tubular furnace with three independent heating
zones, ensuring an isothermal zone in the central part of the reactor. The bulk density of the catalyst was determined according to ASTM D 4164-03, with a difference that the catalyst was predried for 4 h at 120°C. A sample of the granulated catalyst equivalent to a volume of 30.9 cm3 was then placed into the isothermal zone of the reactor and evenly diluted with particles of silicon carbide 0.1–0.2 mm in size. The diluted catalyst layer was placed between two layers of silicon carbide with particle diameters of 3–4 mm. The tests were conducted over at least 14 days using the temperature of the hydrotreating process at which the hydrogenated fuel is purified to a residual sulfur content of less than 10 ppm. The volumetric feed rate was 2.5 h−1, the H2/feed ratio was 500 m3H2/m3 feed, and the pressure was 3.8 MPa. The temperature of the process was chosen experimentally, based on data on the residual sulfur content in the hydrogenate. The sulfur content was determined using a Trace Elemental Xplorer-NS analyzer with a measurement error of ±0.1 ppm. A straight-run diesel fraction provided by AO GPN-OR was used as our feed for hydrotreatment. It contained 3830 ppm (0.383 mass %) of sulfur and 192 ppm of nitrogen, and had a density of 0.862 g/cm3, an initial boiling point of 210°C, and a 95% boiling point of 378°C. In all cases, the catalysts were sulfided in a catalytic reactor directly with a solution of dimethyl disulfide (20 g/L) in straight-run diesel fuel initially containing 0.3 wt % of sulfur. They were sulfide at a pressure of 3.5 MPa and a volume ratio of hydrogen : sulfiding mixture of 300, with a stepwise rise in temperature according to the procedure described in [5]. CATALYSIS IN INDUSTRY
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RESULTS AND DISCUSSION Before deciding to reactivate the industrial batch of catalyst, we had to determine whether catalyst subjected to the oxidative regeneration was suitable for a subsequently complete recovery of activity using the newly developed technology. The main characteristics for determining the possibility of reactivating the catalyst were: 1. the residual content of coke and sulfur; 2. differences between the textural characteristics and mechanical strength of granules of fresh and regenerated catalyst; 3. the average length of the granules; 4. the content of active metals and impurities that were not removed during calcination. The first three characteristics were determined by the conditions of oxidative regeneration; the fourth by the catalyst’s operating conditions in the hydrotreatment unit of AO GPN-OR. Comparing the data from CHNS analysis (Table 2) for the CoMo-D and CoMo-R samples, we can see that the deactivated catalyst was around 9.5% deposits consisting of carbon, nitrogen, and hydrogen, and around 9% sulfur in the form of active metal sulfides, as indicated by the binding energy of the S2p level: 162.0 eV (Table 5). After oxidative regeneration, the content of carbon in the catalyst fell to 0.02%, while that of sulfur fell to around 0.6%. It should be noted that all of the sulfur present in the CoMo-R catalyst was in the form of sulfates, as indicated by the binding energy for the S2p level, obtained via XPS: 169.1 eV. More than 99% of carbon deposits and all sulfide sulfur were thus removed from the catalyst as a result of oxidative regeneration. If the conditions of temperature are violated during oxidative regeneration, catalyst sintering is possible; this leads to substantial changes in a catalyst’s textural characteristics. Harsh mechanical agitation of a catalyst layer can result in lower strength or partial destruction of granules, accompanied by a shortening of their average length. Comparing the data in Table 3 for CoMo-F and CoMo-R samples, we can see that after oxidative regeneration, the specific surface area, volume, and pore diameter remained unchanged within the experimental error. The slightly lower mechanical strength of the CoMo-R sample relative to CoMo-F is entirely logical, since the regenerated sample contained no organic complexing agents that would contribute to an increase in strength. Due to mechanical damage during mixing, the granules were shortened; this was expected, but the resulting average length of 4.5 mm does not limit further use of the catalyst. As a result of oxidative regeneration on the unit in PAO ANK Bashneft (Bashneft-Ufaneftekhim branch), a catalyst was obtained with characteristics of the residual content of carbon deposits and sulfur, texture, CATALYSIS IN INDUSTRY
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strength, and average granule sizes that are not an obstacle to subsequent reactivation. From the data on the content of active metals and impurities that could not be removed during the calcination of CoMo-F and CoMo-R samples (see Table 3), we can see that during the operation of the catalyst on the hydrotreatment unit at AO GPN-OR and its subsequent regeneration, the Co and Mo content remained unchanged within the accuracy of measurement (1 rel %), but the content of Fe and Si grew substantially; this could have a negative effect on restoring the activity of the regenerated catalyst. In order to proceed with the reactivation of the industrial batch of the regenerated catalyst, we performed reactivation experiments in the laboratory with subsequent comparative testing of reactivated and fresh catalysts in hydrotreatment on the pilot plant units. In [4], we described the reactivation of NiMo and CoMo hydrotreatment catalysts with various chelating agents. The greatest recovery of activity was achieved using aqueous solutions that contained citric acid and diethylene glycol or combinations of its esters. Citric acid and diethylene glycol in a specially selected molar ratio were therefore subsequently used as chelating agents. The technique of reactivation was described in detail in [6]. The main characteristics of the catalyst reactivated under laboratory conditions (the CoMoRF sample) are given in Table 3. It can be seen that the reactivated sample had virtually the same textural characteristics and strength as the fresh sample, while containing the same concentrations of active metals and impurities as the CoMo-R sample. The results from comparative testing of catalysts in the hydrotreatment of diesel fuel according to procedure 1 are shown in Fig. 1. From these data, we can see that the deactivated catalyst in the studied temperature range does not allow the production of hydrogenate containing less than 10 ppm of sulfur. The sample after oxidative regeneration (CoMo-R) is also not suitable for obtaining diesel fuel corresponding to the Euro-5 standard and is more than doubly inferior to the reactivated and fresh samples in residual sulfur content. The catalyst reactivated in the laboratory is comparable in activity to the fresh reference sample. It is obvious that for identical textural characteristics and equal contents of active metals, the differences or similarities between the catalytic properties of the studied samples must be determined by the structure of the active sulfide component. A great many physical methods can be used to study this, each of which provides information on a particular parameter. In the world’s scientific literature, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) are the ones most widely used for sulfide catalysts because of their informative and reproducible results. These methods were used in this work to study the structure and morphology of the active component of a catalyst.
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CoMo-F CoMo-D
600
CoMo-R 53.2 CoMo-RF Residual sulfur content, ppm
500 42.0 400
38.3
300
28.5 24.0
200 15.4
15.5
15.4 10.1
100
10.0 5.8
0
350
340
5.7
360
Temperature, °C Fig. 1. Dependence of the residual sulfur content in the hydrogenate as a function of the temperature of diesel fuel hydrotreatment for the reference and reactivated catalysts samples (testing was performed according to procedure 1).
The most typical fragments of microscopic images of the studied catalysts are shown in Fig. 2. No individual cobalt sulfide particles were detected in the images of CoMo-F, CoMo-RF, and CoMo-R samples. If present in a sample, they would easily be detected by TEM [7]. The distribution of the particles of the active sulfide component (the CoMoS phase) based on the length and number of layers in a sample is shown in Figs. 3 and 4, respectively. The average particle length, the number of particles in a sample, and the average number of particles per 1000 nm2 are given in Table 4. The distributions of the CoMoS phase layers according to the length and number of particles in the samples of CoMo-F and CoMo-RF are similar: the particles are evenly distributed over the carrier’s surface in the form of predominantly one- and two-lay-
ered formations. The morphology of the particles for these catalysts (the average length of a layer and the number of layers in sample) is typical of catalysts in which the most active component in hydrodesulfurization is the type II fully sulfided CoMoS phase [7–9]. In the sample after oxidative regeneration (CoMo-R), mostly multilayer associates of the CoMoS phase are observed. This shows that at the stage of sulfidation, the CoMoS phase is formed mainly from massive agglomerates of oxide compounds of active metals (CoMoO4. Co3O4), which in turn form during oxidative regeneration [11–14]. The sulfidation of such compounds is not complete, since the CoMoS phase forms only on the surfaces of particles, while the cores remain in the oxide state or are reduced to metal [15, 16]. The binding energies of the elements of sulfide catalysts are presented in Table 5. Data on the degree of
Table 4. Morphology of CoMoS phase particles in the catalysts, calculated from TEM Catalyst CoMo-F CoMo-RF CoMo-R
Average particle length, nm
Average number of layers in the samples
Average number of particles per 1000 nm2 of surface
3.2 3.1 2.5
1.5 1.6 3.8
31 28 23
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CoMo-F
20 nm CoMo-RF
20 nm CoMo-R
20 nm Fig. 2. TEM images of typical fragments of sulfided catalysts.
sulfur oxidation were obtained from the binding energies for the S2p level, where the value Eb = 162.0 ± 0.1 eV typical of MoS2 (in which sulfur is in state S2−) was observed for all of the studied samples [17, 18]. A binding energy of 228.5 eV is typical of fully sulfided Mo4+ molybdenum in the MoS2 or CoMoS phase of type II [8, 10, 18–20]. These values are identical for fresh and reactivated catalysts, allowing us to assume that most CATALYSIS IN INDUSTRY
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of the molybdenum is in this case part of the CoMoS phase. On the spectrum of the CoMo-R sample, this value is noticeably shifted (by 0.4 eV) to the higher binding energies as a consequence of molybdenum being in the catalyst in the form of compounds with higher oxidation states than Mo4+. For cobalt, the binding energy of the Co2p level of the fresh and reactivated samples corresponds to a binding energy of 778.8 eV. This value of Eb is typical of fully sulfided cobalt in sulfide catalysts [8, 21, 22], but it does not allow us to determine exactly in which form cobalt is present in the sample: that of individual sulfides or that of a bimetallic CoMoS phase. According to the data in [18], the differences between the experimentally obtained binding energies of the (Со2р3/2) and (S2p) levels, and between the (Со2р3/2) and (Mo3d5/2) levels can be used to confirm the presence of cobalt in the CoMoS phase. For different individual cobalt sulfides, ΔEb (Со2р3/2) − (S2p) does not exceed 616.2 eV; for cobalt in the CoMoS phase, typically ΔEb (Со2р3/2) − (S2p) = 617.0 eV and ΔЕb (Со2р3/2) − (Mo3d5/2) = 550.2 eV. The values obtained for the fresh and reactivated samples (see Table 5), ΔЕb (Со2р3/2) − (S2p) = 616.9 eV and ΔЕb (Со2р3/2) − (Mo3d5/2) = 550.2 ± 0.1 eV, lie within the experimental error (0.1 eV), confirming that most of the cobalt in these catalysts is in the form of the CoMoS phase. ΔЕb (Со2р3/2) − (S2p) = 616.7 eV for the deactivated catalyst suggests that during the operation of the catalyst, part of the cobalt was separated to form an individual sulfide. For a sample sulfided after oxidative regeneration, the values ΔЕb (Со2р3/2) − (S2p) = 617.0 eV and ΔЕb (Со2р3/2) − (Mo3d5/2) = 550.2 eV also indicate it contains no individual cobalt sulfides (e.g., Co9S8). According to [17], however, the displacement of the binding energy by 0.3 eV toward higher binding energies indicates there was a considerable amount of oxygen-containing cobalt compounds in its composition. Since the main feature distinguishing the type II CoMoS phase from the relatively inactive CoMoS phase of type I is the presence of oxygen-containing constituents in the latter [8], we may assume that in our case the fresh and reactivated catalysts contained mostly the type II CoMoS phase, and the catalyst sulfided after oxidative regeneration contained a mixture of type I and II CoMoS phases. The TEM and XPS data for the studied catalysts are in good agreement with those on catalyst activity in hydrodesulfurization. For industrial operation, however, the stability of a catalyst is no less important than its activity. To determine its stability, the reactivated catalyst was tested in parallel with a fresh reference sample using procedure 2. The total test time was 360 h, 24 h of which was required to achieve steadystate operation. The remaining 336 h (14 days) were for lifetime testing. The initial test temperature was
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Fraction, % 40 CoMo-F CoMo-RF
35
CoMo-R 30 25 20 15 10 5 0 10
20
30
40
50
60
70
80
Particle length Fig. 3. Distribution of CoMoS phase layers according to length.
Fraction, %
CoMo-F
70 CoMo-RF CoMo-R 60
50
40
30
20
10
0 1
2
3 4 5 Number of layers in the sample
6
7
Fig. 4. Distribution of samples according to the number of layers of the CoMoS phase. CATALYSIS IN INDUSTRY
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Table 5. Binding energies of elements in sulfided catalysts and CoMo-D catalyst ΔСо2р3/2–S2p ΔСо2р3/2–Mo3d5/2
Sample
Mo3d5/2
Co2p3/2
C1s
Al2p
O1s
S2p
CoMo-D CoMo-F CoMo-RF CoMo-R
228.7 228.5 228.6 228.9
778.7 778.8 778.8 779.1
284.8 284.8 284.8 284.8
74.8 74.8 74.8 74.9
531.7 531.7 531.7 531.7
162.0 161.9 161.9 162.1
370°C. The dynamics of the change in the residual sulfur content on the CoMo-F and CoMo-RF catalysts is shown in Fig. 5. At a temperature of 370°C, both catalysts showed virtually the same activity, but a rapid increase in the residual sulfur content (from 8 to 10 ppm) was observed at the end of the test cycle. After raising the temperature to 375°C, the residual sulfur content fell to 7 ppm for the reactivated sample and to 8 ppm for the fresh sample. It should be noted that the reactivated CoMo-RF sample showed slightly higher activity and stability than the fresh CoMo-F reference catalyst under the same reaction conditions throughout the test cycle. This was not accidental, since we had already noted improvement in the performance characteristics of reactivated samples compared to fresh ones in [4, 6].
616.7 616.9 616.9 617.0
550.0 550.3 550.3 550.2
Experimental studies performed in the laboratory and at pilot plant units in the Institute of Coal (Siberian Branch, Russian Academy of Sciences) allowed us to recommend an industrial batch of a catalyst subjected to oxidative regeneration for further reactivation using industrial equipment. Using the technology of the Institute and PAO GPN, the industrial batch of CoMo/Al2O3 catalyst was reactivated on the production line of OOO NPK Sintez (Barnaul). From the main characteristics of this reactivated catalyst given in Table 3, it follows that was basically the same as the catalyst reactivated earlier on a laboratory scale. The reactivated catalyst was loaded into the second stream of the L-24-6 unit at AO Gazprom NneftOmsk Refinery, and commercial operations began in May 2016 with hydrotreatment to produce diesel fuel containing less than 10 ppm of sulfur. CoMo-F
15 370°C
CoMo-RF
375°C
14
Residual sulfur content, ppm
13 12 11 10 9 8 7 5 5
0
41
82
123
164
205
246
287
328
Time, h Fig. 5. Dynamics of the change in the residual sulfur content during diesel fuel hydrotreating at the pilot plant according to procedure 2 for reactivated CoMo-RF and fresh CoMo-F reference catalysts. CATALYSIS IN INDUSTRY
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380
39 38
36 35 34 33
Inlet temperature, °C
Pressure, kg/cm3
375 37
370
365 32 31 30
50000 Circulating hydrogen-containing gas, nm3/h
40
Circulating hydrogen-containing gas Inlet temperature Pressure
360
45000
40000
35000
30000
0
2
4
6
8
10 12 14 Time, day
16
18
20
22
24
Fig. 6. Main hydrotreating parameters on the second stream of L-24-6 unit in PAO Gazprom Neft-Omsk Refinery for the period from 1–22 June 2016.
Residual sulfur content, ppm
Feed 5000 4500 4000 3500 3000 2500 2000 1500 1000
Hydrogenate
15 10 5
0
2
4
6
8
10
12
14
16
18
20
22
24
Time, day Fig. 7. Sulfur content in the feed and hydrogenate on the second stream of the L-24-6 unit of PAO Gazprom Neft-Omsk Refinery for the period 1–22 June 2016.
The production program of AO Gazprom NeftOmsk Refinery did not allow us to perform comparative operation of fresh and reactivated catalysts under completely identical conditions. From the beginning of May 2016 to the present, reactivated catalyst has
been used to hydrotreat different feeds in a wide range of temperatures and conditions. The period of June 1– 22, 2016, best illustrates the possibilities of the reactivated catalyst. During this time, hydrotreatment was performed at a stable volumetric feed rate of 2.33 h−1 CATALYSIS IN INDUSTRY
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and relatively small fluctuations in the composition of the feedstock, a direct summer diesel fraction containing 12.50–13.75 vol % light gas oil (LGO) from catalytic cracking. On average, the feed had a density of 0.8642 g/cm3 and a 95% boiling point of 350°C. The main parameters of hydrotreatment and the content of sulfur in the feed and hydrogenate for the period June 1–22, 2016, are shown in Figs. 6 and 7. From the presented data, we can see that the production of hydrogenate with an average residual sulfur content of 7 ppm from feedstock with an average sulfur content of 3350 ppm was achieved at an average reactor inlet temperature of 367°C. Approximately the same indicators were achieved on the second L-24-6 stream with the hydrotreatment of a similar feed on fresh catalysts in 2013– 2014. At the above values of the volumetric feed velocity, pressure, circulation times, and purity of the hydrogen-containing gas, the hydrotreatment of the feedstock (3300–3450 ppm S, 10 vol % LGO) to obtain a hydrogenate containing less than 10 ppm S was performed at an inlet temperature of 370°C in the initial period of catalyst operation and 378°C in the final period of operation. It should be noted (see Fig. 6) that over 22 days of operation, the temperature of hydrotreatment rose by no more than by 1°C, if at all. This allows us to predict stable operation with such a feed and under such conditions for at least one year.
2. 3. 4. 5.
6. 7.
8.
9. 10.
11. 12.
CONCLUSIONS The most rational way of using the new generation of deactivated hydrotreatment catalysts is to restore their activity by combining the stages of oxidative regeneration and reactivation with organic complexing agents.
13.
Based on a thorough analysis of the physicochemical and catalytic properties of samples of fresh, deactivated, regenerated, and reactivated catalysts for the hydrotreatment of diesel fuel, we studied the dynamics of changes in the characteristics of catalysts during operation and regeneration. The conditions of treatment for the organic complexing agents of catalysts subjected to oxidative regeneration were determined to ensure complete recovery of the catalysts’ activity. An industrial batch of catalyst reactivated using the newly developed catalyst technology is in operation at the L-24-6 hydrotreatment unit of AO Gazprom Neft-Omsk Refinery for the hydrotreatment of mixed summer diesel fuel, showing that the reactivated catalyst allows us to produce hydrotreated diesel fuel with less than 10 ppm of residual sulfur under the same process conditions as fresh catalysts.
14. 15.
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22.
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Translated by A. V. Pashigreva
