Naphtha hydrotreating process

Abstract

A naphtha hydrotreating process containing a first step in the presence of the first catalyst containing a support; a second step in the presence of the second catalyst containing a support and an active phase, which active phase contains a Group 9 or 10 metal and a Group 6 metal; a third step in the presence of the third catalyst containing a support and an active phase, which active phase contains a Group 6 metal; wherein the content of Group 6 metal of the third catalyst is less than the content of Group 6 metal of the second catalyst; the ratio of the loaded specific surface area of the first catalyst to that of the second catalyst is greater than or equal to 1.20; the ratio of the loaded specific surface area of the third catalyst to that of the second catalyst is greater than 1.07.

Claims

1. A naphtha hydrotreating process performed in the presence of at least a first catalyst, a second catalyst and a third catalyst, each of said catalysts having a loaded specific surface area, L.sub.1, L.sub.2 and L.sub.3, respectively, corresponding to the specific surface area by mass multiplied by the loaded density of the respective catalysts, said process comprising three successive steps through each of which the naphtha is passed through: a first step a) in the presence of the first catalyst having loaded specific surface area L.sub.1, said first catalyst comprising a support and optionally an active phase, said active phase containing at least one Group 6 metal and optionally at least one Group 9 or 10 metal; a second step b) in the presence of the second catalyst having loaded specific surface area L.sub.2, said second catalyst comprising a support and an active phase, said active phase containing at least one Group 9 or 10 metal and at least one Group 6 metal; a third step c) in the presence of the third catalyst having loaded specific area L.sub.2, said third catalyst comprising a support and an active phase, said active phase containing at least one Group 6 metal and optionally at least one Group 9 or 10 metal; wherein a hydrotreated naphtha is produced, and wherein the content of Group 6 metal of the third catalyst is less than the content of Group 6 metal of said second catalyst; the ratio L.sub.1/L.sub.2 is greater than or equal to 1.20; the ratio L.sub.3/L.sub.2 is greater than 1.07.

2. The process according to claim 1, in which said first catalyst comprises an active phase, and wherein the content of Group 6 metal of said first catalyst is less than the content of Group 6 metal of said second catalyst.

3. The process according to claim 2, in which the active phase of the first catalyst contains at least one Group 9 or 10 metal, and wherein the content of Group 9 or 10 metal of said active phase of the first catalyst is greater than or equal to 0.5% by weight and less than 3% by weight; the content of Group 9 plus 10 metal of said active phase of the first catalyst is less than the content of Group 9 plus 10 metal of said second catalyst.

4. The process according to claim 2, in which the active phase of the first catalyst contains at least one Group 9 or 10 metal, and wherein the content of Group 9 or 10 metal of said first catalyst is greater than or equal to 3% by weight and less than or equal to 9% by weight; the content of Group 9 plus 10 metal of the first catalyst is greater than the content of Group 9 plus 10 metal of said second catalysts.

5. The process according to claim 1, in which said first catalyst consists of a support without an active phase.

6. The process according to claim 1, in which the active phase of the third catalyst contains at least one Group 9 or 10 metal, and wherein the content of Group 9 plus 10 metal of the third catalyst is less than the content of Group 9 plus 10 metal of said second catalyst.

7. The process according to claim 1, in which the liquid hourly space velocity of the first step is less than or equal to 20 times the overall liquid hourly space velocity and greater than or equal to 1.33 times the overall liquid hourly space velocity.

8. The process according to claim 1, in which the liquid hourly space velocity of the second step is less than or equal to 4 times the overall liquid hourly space velocity and greater than or equal to 1.33 times the overall liquid hourly space velocity.

9. The process according to claim 1, in which the liquid hourly space velocity of the third step is greater than or equal to 5 times the overall liquid hourly space velocity and less than or equal to 20 times the overall liquid hourly space velocity.

10. The process according to claim 1, in which the first or third catalyst contains molybdenum alone, or nickel and molybdenum, or cobalt and molybdenum, or nickel and cobalt and molybdenum.

11. The process according to claim 1, in which the second catalyst contains nickel and molybdenum, or cobalt and molybdenum, or nickel and cobalt and molybdenum.

12. The process according to claim 1, in which said naphtha comprises hydrocarbons comprising from 10 to 50 000 ppm by weight of one or more sulfur-based compounds.

13. The process according to claim 1, in which said naphtha comprises a cracked naphtha feedstock, alone or as a mixture with a different naphtha feedstock.

14. The naphtha hydrotreating process according to claim 1, which produces a hydrodesulfurized naphtha, further comprising an optional step of hydrogenation of diolefins, producing a naphtha with a reduced content of diolefins; a step of separation of at least part of the hydrodesulfurized naphtha to remove H.sub.2S and optional production of an LPG fraction or of an uncondensable stream; an optional step of separating the hydrodesulfurized naphtha into at least two naphtha fractions.

15. A naphtha hydrotreating reactor comprising a reaction section containing at least three catalysts, said catalyst being loaded onto first, second and third successive layers of catalyst and each of said catalysts having a loaded specific surface area L.sub.1, L.sub.2 and L.sub.3, respectively, corresponding to its specific surface area by mass multiplied by its loaded density, the first layer of catalyst contains the first catalyst comprising a support and optionally an active phase, said active phase containing at least one Group 6 metal and optionally at least one Group 9 or 10 metal; the second layer of catalyst contains the second catalyst comprising a support and an active phase, said active phase containing at least one Group 9 or 10 metal and at least one Group 6 metal; the third layer of catalyst contains the third catalyst comprising a support and an active phase, said active phase containing at least one Group 6 metal and optionally at least one Group 9 or 10 metal; and wherein the content of Group 6 metal of the third catalyst is less than the content of Group 6 metal of the second catalyst; the ratio L.sub.1/L.sub.2 is greater than or equal to 1.20; the ratio L.sub.3/L.sub.2 is greater than 1.07.

16. The naphtha hydrotreating reactor according to claim 15, which is a fixed catalytic bed reactor with axial flow.

17. The naphtha hydrotreating process according to claim 3, wherein the content of Group 6 metal of said first catalyst is greater than or equal to 0.5% by weight and less than or equal to 6% by weight.

18. The naphtha hydrotreating process according to claim 4, wherein the content of Group 6 metal of said first catalyst is greater than 6% by weight and less than or equal to 10% by weight.

19. The naphtha hydrotreating process according to claim 3, wherein the the ratio L.sub.1/L.sub.2 is greater than or equal to 1.35; and the ratio L.sub.3/L.sub.2 is greater than or equal to 1.35.

Description

LIST OF FIGURES

(1) FIG. 1 represents an embodiment of a hydrotreating reactor R which may be used in the unit and/or the process according to the invention.

DESCRIPTION OF THE EMBODIMENTS

(2) As shown in the FIGURE, the hydrotreating reactor R was loaded using a dense loading device with three layers of catalyst: a first layer of first catalyst C.sub.1, a second layer of second catalyst C.sub.2 and a third layer of third catalyst C.sub.3. The layers of inert or active grading upstream or downstream of the layers of catalyst are not shown. The hydrotreating reactor R is run in descending flow with a naphtha feedstock fed via an inlet line I at the top of the reactor and collected at the reactor outlet via an outlet line O.

(3) Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.

(4) In the foregoing and in the examples, all temperatures are set forth uncorrected in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated.

(5) The entire disclosures of all applications, patents and publications, cited herein and of corresponding application No. FR 1903928, filed Apr. 12, 2019 are incorporated by reference herein.

EXAMPLES

(6) Naphtha hydrotreating catalysts supported on alumina having the following properties are used in the examples. All the catalysts are loaded without any control of their distribution (sock-loaded).

(7) Table 1 below indicates the properties of the hydrotreating catalysts used.

(8) TABLE-US-00001 Specific Loaded surface area specific by mass Ni content Mo content surface area Name Type (m.sup.2/g) (weight %) (weight %) (10.sup.6m.sup.2/m.sup.3) A Calcined 175 4.0 15.5 128 B Calcined 280 2.4 9.5 176 C Calcined 230 1.8 6.9 113 D Calcined 320 0.9 3.5 176 E With booster additive 155 4.2 18.0 127 F Calcined 248 8.2 7.0 154 G Calcined 320 0 3.5 176 H Calcined 290 0 0 206 K Calcined 180 3.2 13.5 122 L With booster additive 165 2.4 9.5 132

(9) For all the examples, the targeted specifications for the hydrotreated naphtha are 0.5 ppm by weight of sulfur and 0.5 ppm by weight of nitrogen.

Example 1

(10) A coker naphtha feedstock of a delayed coker unit is treated in a first stage in order to hydrogenate all of its diolefins and is then sent to the naphtha hydrotreating unit. The feedstock requires harsh hydrotreating conditions on account of its composition and also of the nature and type of its impurities.

(11) Table 2 below indicates the properties of the feedstock 1.

(12) TABLE-US-00002 Coker naphtha feedstock Density, kg/m.sup.3 750 Sulfur content, weight % 1.0 Nitrogen content, ppm by weight 150 Bromine number, g/100 g 75 Maleic anhydride value, mg of maleic 4 anhydride/g Silicon content, ppm by weight 4

(13) The naphtha hydrotreating of feedstock 1 having the properties described in Table 2 (downstream of the removal of diolefins) is simulated considering several configurations of catalytic bed in a hydrotreating reactor under the conditions described in Table 3, which indicates the properties of the catalytic bed configurations:

(14) TABLE-US-00003 TABLE 3 Catalyst load 1 Catalyst load 2 Catalyst load 3 Catalyst load 4 (comparative) (invention) (comparative) (invention) Volume Volume Volume Catalyst (volume %) Catalyst (volume %) Catalyst (volume %) Catalyst Volume Bed 1 B 50% B 50% K 50% B 50% Bed 2 A 50% A 40% A 40% A 40% Bed 3 D 10% D 10% G 10% LHSV (h.sup.−1) 2.0 2.0 2.0 2.0 Partial 4.0 4.0 4.0 4.0 pressure of hydrogen (MPa) L.sub.1/L.sub.2 1.38 1.38 0.95 1.38 L.sub.3/L.sub.2 1.00 1.38 1.38 1.38

(15) The following simulation results are obtained as indicated in Table 4 below:

(16) TABLE-US-00004 TABLE 4 Catalyst load 1 Catalyst load 2 Catalyst load 3 Catalyst load 4 (comparative) (invention) (comparative) (invention) WABT, start of run (° C.) 280 280 280 280 WABT, end of run (° C.) 310 330 330 325 Service life of the catalyst Base Base +34% Base −20% Base +20% load, % of the base case Silicon scavenged, kg 4106  4194  3536  4194 

(17) As shown in Table 4, when the three catalysts used for the naphtha hydrotreating reaction are loaded according to the invention, as in the catalyst loads 2 and 4, the service life of the catalyst load is increased by 34% and 20%, respectively, relative to the comparative load with only two layers (catalyst load 1).

(18) As shown in Table 4, not only do the catalyst loads 2 and 4 according to the invention make it possible to use the catalyst load for longer than the comparative load with only two layers, but also the catalyst can function at a higher WABT temperature, while at the same time maintaining its performance. Specifically, the WABT end of run is increased by 20° C. for load 2 and by 15° C. for load 4 relative to load 1.

(19) The silicon scavenged during the service life of the catalyst load is increased by 88 kg for the loads 2 and 4 relative to the comparative load 1 with only two layers. Consequently, the silicon scavenging capacity of the catalyst loads according to the invention is increased so as to prevent the silicon from reaching the end of the run.

(20) The comparative load 3 corresponds to a load in which the metal content criteria of the first, second and third catalysts are satisfied, but the ratio of the loaded specific surface areas L.sub.1/L.sub.2 is less than 1.20. The results indicate a 20% decrease in the service life of the catalyst load. Furthermore, the silicon scavenging capacity is reduced to 3536 kg/h instead of 4194 kg/h for the load according to the invention.

Example 2

(21) A conventional naphtha feedstock consisting of a mixture of straight-run naphtha and of coker naphtha is sent to a naphtha hydrotreating unit. The feedstock does not require harsh hydrotreating conditions on account of its composition and also of the nature and type of its impurities.

(22) Table 5 below indicates the properties of the feedstock 2.

(23) TABLE-US-00005 Naphtha feedstock 2 Density, kg/m.sup.3 750 Sulfur content, weight % 0.1 Nitrogen content, ppm by weight 10 Bromine number, g/100 g 8 Anhydride value, mg of maleic 2.5 anhydride/g Silicon content, ppm by weight 0.4

(24) The naphtha hydrotreating of feedstock 2 having the properties described in Table 5 is simulated considering several configurations of catalytic bed in a hydrotreating reactor under the following conditions:

(25) Table 6 below describes the properties of the four catalytic bed configurations.

(26) TABLE-US-00006 Catalyst load 5 Catalyst load 6 Catalyst load 7 Catalyst load 8 (comparative) (invention) (invention) (invention) Volume Volume Volume Volume Catalyst (volume %) Catalyst (volume %) Catalyst (volume %) Catalyst (volume %) Bed 1 D 20 D 20 G 20 H 20 Bed 2 C 75 C 75 C 75 C 75 Bed 3 C 5 D 5 D 5 D 5 LHSV (h.sup.−1) 10 10 10 10 Partial 1.0 1.0 1.0 1.0 pressure of hydrogen (MPa) L.sub.1/L.sub.2 1.56 1.56 1.56 1.82 L.sub.3/L.sub.2 1.00 1.56 1.56 1.56

(27) The simulation results are obtained according to Table 7 below:

(28) TABLE-US-00007 Catalyst load 5 Catalyst load 6 Catalyst load 7 Catalyst load 8 (comparative) (invention) (invention) (invention) WABT, start of run (° C.) 270 270 275 285 WABT, end of run (° C.) 320 335 335 335 Service life of the catalyst Base Base +30% Base +20% Base +6% load, % of the base case Silicon scavenged, kg 472 490 490 580

(29) As shown in Table 7, when the three catalysts used for the naphtha hydrotreating reaction are loaded according to the invention, as in the catalyst loads 6, 7 and 8, the service life of the catalyst load is increased relative to the comparative load with only two layers (catalyst load 5), by 30%, 20% and 6%, respectively.

(30) As shown in Table 7, not only does the catalyst load according to the invention make it possible to use the catalyst load for longer than the comparative load with only two layers, but also the catalyst can function at a higher WABT temperature, while at the same time maintaining its performance. Specifically, the WABT end of run is increased by 15° C. for loads 6, 7 and 8 relative to load 5.

(31) Furthermore, the silicon scavenged during the service life of the catalyst load is increased by 18 kg relative to the comparative load 5 for loads 6 and 7, and by 108 kg for load 8. Consequently, the silicon scavenging capacity of the catalyst loads according to the invention is increased so as to prevent the silicon from reaching the end of the run.

(32) The process according to the invention is still advantageous even when the feedstock to be treated does not require harsh hydrotreating conditions.

Example 3

(33) A coker naphtha feedstock of a delayed coker unit having a high arsenic content is treated in a first stage in order to hydrogenate all of its diolefins and is then sent to the naphtha hydrotreating unit.

(34) The feedstock requires harsh hydrotreating conditions to treat the simultaneous contamination with arsenic and silicon.

(35) Table 8 below indicates the properties of the feedstock 3.

(36) TABLE-US-00008 Coker naphtha feedstock 3 Density, kg/m.sup.3 750 Sulfur content, weight % 1.0 Nitrogen content, ppm by weight 150 Bromine number, g/100 g 75 Maleic anhydride value, mg of maleic 4 anhydride/g Silicon content, ppm by weight 3 Arsenic content, ppm by weight 40

(37) The naphtha hydrotreating of feedstock 3 having the properties described in Table 8 (but downstream of the removal of the diolefins) is simulated considering several configurations of catalytic bed in a hydrotreating reactor included in the reaction section of a hydrotreating unit.

(38) Table 9 below indicates the properties of the three catalytic bed configurations.

(39) TABLE-US-00009 Catalyst load 9 Catalyst load 10 Catalyst load 11 (comparative) (invention) (comparative) Volume Volume Volume Catalyst (volume %) Catalyst (volume %) Catalyst (volume %) Bed 1 F 20% F 20% F 20% Bed 2 E 65% E 65% E 65% Lit 3 E 15% B 15% L 15% LHSV (h.sup.−1) 2.0 2.0 2.0 Partial pressure of 4.0 4.0 4.0 hydrogen (MPa) L.sub.1/L.sub.2 1.21 1.21 1.21 L.sub.3/L.sub.2 1.00 1.21 1.04

(40) The simulation results obtained are indicated in Table 10 below:

(41) TABLE-US-00010 Catalyst load 9 Catalyst load 10 Catalyst load 11 (comparative) (invention) (comparative) WABT, start of run (° C.) 285 285 285 WABT, end of run (° C.) 310 330 325 Service life of the catalyst Base Base +1.3% Base −0.3% load, % of the base case Silicon scavenged, kg 2778 2815 2769 Arsenic scavenged, kg 34.7 35.2 34.6

(42) As shown in Table 10, when the three catalysts used for the naphtha hydrotreating reaction are loaded according to the invention, as in the catalyst load 10, the service life of the catalyst load is increased by 1.3% relative to the comparative load (catalyst load 9 in which the second and third layers consist of the same catalysts).

(43) As shown in Table 10, not only does the catalyst load 10 according to the invention make it possible to use the catalyst load for longer than the comparative load 9, but also the catalyst can function at a higher WABT temperature, while at the same time maintaining its performance. Specifically, the WABT end of run is increased by 20° C. for load 10 relative to load 9.

(44) The silicon scavenged during the service life of the catalyst load is increased by 37 kg for the catalyst load 10 relative to the comparative load 9. The silicon scavenging capacity of the catalyst loads according to the invention is increased so as to prevent the silicon from reaching the end of the run.

(45) The arsenic scavenged during the service life of the catalyst load is slightly improved relative to the comparative load 9.

(46) The comparative load 11 corresponds to a load in which the metal content criteria of the first, second and third catalysts are satisfied, but the ratio of the loaded specific surface areas L.sub.3/L.sub.2 is less than 1.20. The results show a small decrease in the service life of the catalyst load (0.3%) and a relative decrease in the silicon scavenging capacity (−9 kg/h relative to the comparative load 9). In the comparative load 11, the amount of silicon scavenged is even slightly smaller than the amount scavenged with the comparative load 9 with only two layers.

(47) The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

(48) From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.