Two-step hydrocracking process for the production of naphtha comprising a hydrogenation step carried out upstream of the second hydrocracking step

Abstract

The present invention is based on the use of a two-step hydrocracking process for the production of naphtha, comprising a step of hydrogenation placed upstream of the second hydrocracking step, the hydrogenation step treating the unconverted liquid fraction separated in the distillation step in the presence of a specific hydrogenation catalyst. Furthermore, the hydrogenation step and a second hydrocracking step are carried out under specific operating conditions and in particular under temperature conditions that are very specific with respect to one another.

Claims

1. A process for producing naphtha from a hydrocarbon feedstock containing at least 20% by volume of compounds boiling above 340° C., said process comprising at least the following steps: a) a step of hydrotreating said feedstocks in the presence of hydrogen and at least one hydrotreating catalyst, at a temperature of between 200° C. and 450° C., under a pressure of between 2 and 25 MPa, at a space velocity of between 0.1 and 6 h.sup.−1 and with an amount of hydrogen introduced wherein a litre of hydrogen/litre of hydrocarbon volume ratio is between 100 and 2000 Nl/l, b) a step of hydrocracking at least one portion of the effluent resulting from step a), the hydrocracking step b) taking place, in the presence of hydrogen and at least one hydrocracking catalyst, at a temperature of between 250° C. and 480° C., under a pressure of between 2 and 25 MPa, at a space velocity of between 0.1 and 6 h.sup.−1 and with an amount of hydrogen introduced wherein a litre of hydrogen/litre of hydrocarbon volume ratio is between 80 and 2000 Nl/l, c) a step of high-pressure separation of the effluent resulting from the hydrocracking step b) to produce at least a first gaseous effluent and a first liquid hydrocarbon effluent, d) a step of distilling at least one portion of the liquid hydrocarbon effluent resulting from step c) carried out in at least one distillation column, from which step the following are drawn off: a gaseous fraction, at least one fraction comprising converted hydrocarbon products having at least 80% by volume of products boiling at a temperature below 250° C., and an unconverted liquid fraction having at least 80% by volume of products having a boiling point above 175° C., e) optionally a purging of at least one portion of said unconverted liquid fraction containing HPNAs, having at least 80% by volume of products having a boiling point above 175° C., before the introduction thereof into step f), f) a step of hydrogenating at least one portion of the unconverted liquid fraction having at least 80% by volume of products having a boiling point above 175° C. resulting from step d) and optionally purged, said step f) taking place in the presence of hydrogen and a hydrogenation catalyst, at a temperature TR1 between 150° C. and 470° C., under a pressure of between 2 and 25 MPa, at a space velocity of between 0.1 and 50 h.sup.−1 and with an amount of hydrogen introduced wherein a litre of hydrogen/litre of hydrocarbon volume ratio is between 100 and 4000 Nl/l, said hydrogenation catalyst comprising at least one metal from group VIII chosen from nickel, cobalt, iron, palladium, platinum, rhodium, ruthenium, osmium and iridium alone or as a mixture and not containing any metal from group VIB and a support chosen from refractory oxide supports, g) a second step of hydrocracking at least one portion of the effluent resulting from step f), said step g) taking place, in the presence of hydrogen and at least one second hydrocracking catalyst, at a temperature TR2 of between 250° C. and 480° C., under a pressure of between 2 and 25 MPa, at a space velocity of between 0.1 and 6 h.sup.−1 and with an amount of hydrogen introduced wherein a litre of hydrogen/litre of hydrocarbon volume ratio is between 80 and 2000 Nl/l, and in which the temperature TR2 is at least 10° C. higher than the temperature TR1, h) a step of high-pressure separation of the effluent resulting from the hydrocracking step g) to produce at least a second gaseous effluent and a second liquid hydrocarbon effluent, and i) recycling, to said distillation step d), at least one portion of the liquid hydrocarbon effluent resulting from step h).

2. The process according to claim 1, in which said hydrocarbon feedstocks are selected from the group consisting of VGOs, vacuum distillates (VDs), gas oils resulting from direct distillation of crude, gas oils resulting from conversion units, gas oils resulting from FCC units, gas oils resulting from coker units, gas oils resulting from visbreaking units, feedstocks originating from units for extraction of aromatics from lubricating oil bases; feedstocks resulting from solvent dewaxing of lubricating oil bases, distillates originating from desulfurization, distillates originating from hydroconversion of ATRs (atmospheric residues), distillates originating from hydroconversion of VRs (vacuum residues), distillates originating from hydroconversion of deasphalted oils, feedstocks resulting from biomass and mixtures thereof.

3. The process according to claim 1, in which the hydrotreating step a) takes place at a temperature of between 300° C. and 430° C., under a pressure of between 5 and 20 MPa, at a space velocity of between 0.2 and 5 h.sup.−1 and with an amount of hydrogen introduced wherein a litre of hydrogen/litre of hydrocarbon volume ratio is between 300 and 1500 Nl/l.

4. The process according to claim 1, in which the hydrocracking step b) takes place at a temperature of between 330° C. and 435° C., under a pressure of between 3 and 20 MPa, at a space velocity of between 0.2 and 4 h.sup.−1 and with an amount of hydrogen introduced wherein a litre of hydrogen/litre of hydrocarbon volume ratio is between 200 and 2000 Nl/l.

5. The process according to claim 1, in which the following are drawn off from the distillation step d): at least one fraction comprising converted hydrocarbon products having at least 80% by volume of products boiling at a temperature below 190° C., and an unconverted liquid fraction having at least 80% by volume of products having a boiling point above 190° C.

6. The process according to claim 1, in which the following are drawn off from the distillation step d): at least one fraction comprising converted hydrocarbon products having at least 80% by volume of products boiling at a temperature below 175° C., and an unconverted liquid fraction having at least 80% by volume of products having a boiling point above 175° C.

7. The process according to claim 1, in which the hydrogenation step f) takes place at a temperature TR1 of between 180° C. and 320° C., under a pressure of between 9 and 20 MPa, at a space velocity of between 0.2 and 10 h.sup.−1 and with an amount of hydrogen introduced wherein a litre of hydrogen/litre of hydrocarbon volume ratio is between 200 and 3000 Nl/l.

8. The process according to claim 1, in which the hydrocracking step g) takes place at a temperature TR2 of between 320° C. and 450° C., under a pressure of between 9 and 20 MPa, at a space velocity of between 0.2 and 3 h.sup.−1 and with an amount of hydrogen introduced wherein a litre of hydrogen/litre of hydrocarbon volume ratio is between 200 and 2000 Nl/l.

9. The process according to claim 1, in which step g) is carried out at a temperature TR2 at least 20° C. higher than the temperature TR1.

10. The process according to claim 9, in which step g) is carried out at a temperature TR2 at least 50° C. higher than the temperature TR1.

11. The process according to claim 10, in which step g) is carried out at a temperature TR2 at least 70° C. higher than the temperature TR1.

12. The process according to claim 1, in which the hydrogenation step f) is carried out in the presence of a catalyst comprising nickel and alumina.

13. The process according to claim 1, in which the hydrogenation step f) is carried out in the presence of a catalyst comprising platinum and alumina.

14. The process according to claim 1, which consists of the following steps: a) a step of hydrotreating said feedstocks in the presence of hydrogen and at least one hydrotreating catalyst, at a temperature of between 200° C. and 450° C., under a pressure of between 2 and 25 MPa, at a space velocity of between 0.1 and 6 h.sup.−1 and with an amount of hydrogen introduced wherein a litre of hydrogen/litre of hydrocarbon volume ratio is between 100 and 2000 Nl/l, b) a step of hydrocracking at least one portion of the effluent resulting from step a), the hydrocracking step b) taking place, in the presence of hydrogen and at least one hydrocracking catalyst, at a temperature of between 250° C. and 480° C., under a pressure of between 2 and 25 MPa, at a space velocity of between 0.1 and 6 h.sup.−1 and with an amount of hydrogen introduced wherein a litre of hydrogen/litre of hydrocarbon volume ratio is between 80 and 2000 Nl/l, c) a step of high-pressure separation of the effluent resulting from the hydrocracking step b) to produce at least a first gaseous effluent and a first liquid hydrocarbon effluent, d) a step of distilling at least one portion of the liquid hydrocarbon effluent resulting from step c) carried out in at least one distillation column, from which step the following are drawn off: a gaseous fraction, at least one fraction comprising converted hydrocarbon products having at least 80% by volume of products boiling at a temperature below 250° C., and an unconverted liquid fraction having at least 80% by volume of products having a boiling point above 175° C., e) optionally a purging of at least one portion of said unconverted liquid fraction containing HPNAs, having at least 80% by volume of products having a boiling point above 175° C., before the introduction thereof into step f), f) a step of hydrogenating at least one portion of the unconverted liquid fraction having at least 80% by volume of products having a boiling point above 175° C. resulting from step d) and optionally purged, said step f) taking place in the presence of hydrogen and a hydrogenation catalyst, at a temperature TR1 between 150° C. and 470° C., under a pressure of between 2 and 25 MPa, at a space velocity of between 0.1 and 50 h.sup.−1 and with an amount of hydrogen introduced wherein a litre of hydrogen/litre of hydrocarbon volume ratio is between 100 and 4000 Nl/l, said hydrogenation catalyst comprising at least one metal from group VIII chosen from nickel, cobalt, iron, palladium, platinum, rhodium, ruthenium, osmium and iridium alone or as a mixture and not containing any metal from group VIB and a support chosen from refractory oxide supports, g) a second step of hydrocracking at least one portion of the effluent resulting from step f), said step g) taking place, in the presence of hydrogen and at least one second hydrocracking catalyst, at a temperature TR2 of between 250° C. and 480° C., under a pressure of between 2 and 25 MPa, at a space velocity of between 0.1 and 6 h.sup.−1 and with an amount of hydrogen introduced wherein a litre of hydrogen/litre of hydrocarbon volume ratio is between 80 and 2000 Nl/l, and in which the temperature TR2 is at least 10° C. higher than the temperature TR1, h) a step of high-pressure separation of the effluent resulting from the hydrocracking step g) to produce at least a second gaseous effluent and a second liquid hydrocarbon effluent, and i) recycling, to said distillation step d), at least one portion of the liquid hydrocarbon effluent resulting from step h).

15. The process according to claim 1, in which the hydrocracking step g) takes place at a temperature TR2 of between 330° C. and 435° C., under a pressure of between 9 and 20 MPa, at a space velocity of between 0.2 and 3 h.sup.−1 and with an amount of hydrogen introduced wherein a litre of hydrogen/litre of hydrocarbon volume ratio is between 200 and 2000 Nl/l.

16. The process according to claim 1, in which the hydrogenation step f) is carried out in the presence of a catalyst consisting of nickel and alumina.

17. The process according to claim 1, in which the hydrogenation step f) is carried out in the presence of a catalyst consisting of platinum and alumina.

18. The process according to claim 1, in which the following is drawn off from the distillation step d): at least one fraction comprising converted hydrocarbon products having at least 80% by volume of products boiling at a temperature below 175° C.

19. The process according to claim 1, in which the following is drawn off from the distillation step d): an unconverted liquid fraction having at least 80% by volume of products having a boiling point above 220° C.

20. The process according to claim 1, in which the following is drawn off from the distillation step d): an unconverted liquid fraction having at least 80% by volume of products having a boiling point above 250° C.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 illustrates an embodiment of the invention.

(2) The VGO-type feedstock is sent a via the pipe (1) to a hydrotreating step a). The effluent resulting from step a) is sent via the pipe (2) to a first hydrocracking step b). The effluent resulting from step b) is sent a via the pipe (3) to a high-pressure separation step c) to produce at least a gaseous effluent (not represented in the FIGURE) and a liquid hydrocarbon effluent which is sent a via the pipe (4) to the distillation step d). The following are drawn off from the distillation step d): a gaseous fraction (5), optionally a light petroleum fraction (6) having at least 80% by volume of products having a boiling point between 20° C. and 80° C., a fraction comprising the converted hydrocarbon products having at least 80% by volume of products boiling at a temperature below 250° C. (7) and an unconverted liquid fraction having at least 80% by volume of products having a boiling point above 175° C. (8).

(3) At least one portion of the unconverted liquid fraction containing HPNAs is purged in a step e) via the pipe (9).

(4) The purged unconverted liquid fraction is sent via the pipe (10) to a hydrogenation step f). The hydrogenated effluent resulting from step f) is sent a via the pipe (11) to the second hydrocracking step g). The effluent resulting from step g) is sent a via the pipe (12) to a high-pressure separation step h) to produce at least a gaseous effluent (not represented in the FIGURE) and a liquid hydrocarbon effluent which is recycled via the pipe (13) to the distillation step d).

(5) 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.

(6) 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.

(7) The entire disclosures of all applications, patents and publications, cited herein and of corresponding French application No. 19/00.208, filed Jan. 9, 2019, are incorporated by reference herein.

EXAMPLES

(8) The following examples illustrate the invention without limiting the scope thereof.

(9) Example no. 1 not in accordance with the invention: basic case of a two-step hydrocracking process comprising no hydrogenation step

(10) A hydrocracking unit treats a vacuum gas oil (VGO) feedstock described in Table 1:

(11) TABLE-US-00001 TABLE 1 Type VGO Flow rate t/h 37 Density — 0.92 Initial boiling point (IBP) ° C. 304 Final boiling point (FBP) ° C. 554 S content wt % 2.58 N content ppm by 1461 weight

(12) The VGO feedstock is injected into a preheating stage and then into a hydrotreating reactor under the following conditions set out in Table 2:

(13) TABLE-US-00002 TABLE 2 Reactor R1 Temperature ° C. 375 Total pressure MPa 14 Catalyst — NiMo on alumina HSV h.sup.−1 1.67

(14) The effluent from this reactor is subsequently injected into a second “hydrocracking” reactor R2 operating under the conditions of Table 3:

(15) TABLE-US-00003 TABLE 3 Reactor R2 Temperature ° C. 390 Total pressure MPa  14 Catalyst — Metal/zeolite HSV h.sup.−1  3

(16) R1 and R2 constitute the first hydrocracking step, the effluent from R2 is then sent to a separation step composed of a train for recovery of heat and then for high-pressure separation including a recycle compressor and making it possible to separate, on the one hand, hydrogen, hydrogen sulfide and ammonia and, on the other hand, the liquid hydrocarbon effluent feeding a stripper and then an atmospheric distillation column in order to separate streams concentrated in H.sub.2S, a “Light Naphtha” light petroleum cut (of which 97% by volume of the compounds have a boiling point of between 27° C. and 80° C.), a “Heavy Naphtha” heavy petroleum cut (of which 96% by volume of the compounds have a boiling point of between 80° C. and 175° C.) and an unconverted liquid fraction (UCO) (of which 97% by volume of the compounds have a boiling point above 175° C.). A purge corresponding to 2% by weight of the flow rate of the VGO feedstock is taken as distillation bottoms from the unconverted liquid fraction.

(17) Said unconverted liquid fraction is injected into a hydrocracking reactor R3 constituting the second hydrocracking step. This reactor R3 is used under the following conditions set out in Table 4:

(18) TABLE-US-00004 TABLE 4 Reactor R3 Temperature (TR2) ° C. 330 Total pressure MPa  14 Catalyst — Metal/zeolite HSV h.sup.−1  2

(19) This second hydrocracking step is carried out in the presence of 150 ppm of equivalent sulfur and 7 ppm of equivalent nitrogen, which originate from the H.sub.2S and NH.sub.3 present in the hydrogen and from the sulfur- and nitrogen-containing compounds still present in said unconverted liquid fraction.

(20) The effluent from R3 resulting from the second hydrocracking step is subsequently injected into the high-pressure separation step downstream of the first hydrocracking step then into the distillation step.

(21) Example No. 2 in Accordance with the Invention:

(22) Example 2 is in accordance with the invention in so far as it is a two-step hydrocracking process that maximizes the production of the “Heavy Naphtha” fraction (according to Example 1) in which a step of hydrogenation in the presence of a hydrogenation catalysts consisting of Ni and of an alumina support is carried out upstream of the second hydrocracking step in a hydrogenation reactor RH and in which the temperature TR1 in the hydrogenation step is at least 10° C. below the temperature TR2 of the second hydrocracking step.

(23) The hydrotreating step in R1, first hydrocracking step in R2 and second hydrocracking step in R3 are carried out on the same feedstock and under the same conditions as in Example 1. A purge corresponding to 2% by weight of the flow rate of the VGO feedstock is also taken as distillation bottoms from the unconverted liquid fraction.

(24) The unconverted liquid fraction resulting from the distillation is sent to a hydrogenation step carried out in a reactor RH placed upstream of the hydrocracking reactor R3 in which the second hydrocracking step is carried out. In this case, the temperature TR1 in the hydrogenation step is 60° C. below the temperature TR2 of the second hydrocracking step.

(25) The operating conditions of the hydrogenation step in the hydrogenation reactor RH used upstream of the hydrocracking reactor R3 are set out in Table 5.

(26) TABLE-US-00005 TABLE 5 Reactor RH Temperature (TR1) ° C. 270 Total pressure MPa  14 Catalyst — Ni/Alumina HSV h.sup.−1  2

(27) The catalyst used in the reactor RH has the following composition: 28 wt % Ni on gamma alumina.

(28) The hydrogenated effluent resulting from RH is then sent to the second hydrocracking step carried out in the reactor R3 before being sent to the high-pressure separation then being recycled to the distillation step.

(29) Example No. 3 in Accordance with the Invention:

(30) Example 3 is in accordance with the invention in so far as it is a two-step hydrocracking process that maximizes the production of the “Heavy Naphtha” fraction (according to Example 1) in which a step of hydrogenation in the presence of a hydrogenation catalyst consisting of Pt and of an alumina support is carried out upstream of the second hydrocracking step in a hydrogenation reactor RH and in which the temperature TR1 in the hydrogenation step is at least 10° C. below the temperature TR2 of the second hydrocracking step.

(31) The hydrotreating step in R1, first hydrocracking step in R2 and second hydrocracking step in R3 are carried out on the same feedstock and under the same conditions as in Example 1. A purge corresponding to 2% by weight of the flow rate of the VGO feedstock is also taken as distillation bottoms from the unconverted liquid fraction.

(32) The unconverted liquid fraction resulting from the distillation is sent to a hydrogenation step carried out in a reactor RH placed upstream of a hydrocracking reactor R3 in which the second hydrocracking step is carried out. In this case, the temperature TR1 in the hydrogenation step is 55° C. below the temperature TR2 of the second hydrocracking step.

(33) The operating conditions of the hydrogenation step in the hydrogenation reactor RH used upstream of the hydrocracking reactor R3 are set out in Table 6.

(34) TABLE-US-00006 TABLE 6 Reactor RH Temperature (TR1) ° C. 275 Total pressure MPa  14 Catalyst — Pt/Alumina HSV h.sup.−1  2

(35) The catalyst used in the reactor RH has the following composition: 0.3 wt % Pt on gamma alumina.

(36) The hydrogenated effluent resulting from RH is then sent to the second hydrocracking step carried out in the reactor R3 before being sent to the high-pressure separation then being recycled to the distillation step.

(37) Example No. 4 in Accordance with the Invention:

(38) Example 4 is in accordance with the invention in so far as it is a two-step hydrocracking process that maximizes the production of the “Heavy Naphtha” fraction (according to Example 1) in which a step of hydrogenation in the presence of a hydrogenation catalyst consisting of Ni and of an alumina support is carried out upstream of the second hydrocracking step in a hydrogenation reactor RH and in which the temperature TR1 in the hydrogenation step is at least 10° C. below the temperature TR2 of the second hydrocracking step.

(39) The hydrotreating step in R1, first hydrocracking step in R2 and second hydrocracking step in R3 are carried out on the same feedstock and under the same conditions as in Example 1. This time, a purge corresponding to 1% by weight of the flow rate of the VGO feedstock is taken as distillation bottoms from the unconverted liquid fraction.

(40) The unconverted liquid fraction resulting from the distillation is sent to a hydrogenation step carried out in a reactor RH placed upstream of a hydrocracking reactor R3 in which the second hydrocracking step is carried out. In this case, the temperature TR1 in the hydrogenation step is 60° C. below the temperature TR2 of the second hydrocracking step.

(41) The operating conditions of the hydrogenation step in the hydrogenation reactor RH used upstream of the hydrocracking reactor R3 are set out in Table 7.

(42) TABLE-US-00007 TABLE 7 Reactor RH Temperature (TR1) ° C. 270 Total pressure MPa  14 Catalyst — Ni/Alumina HSV h.sup.−1  2

(43) The catalyst used in the reactor RH has the following composition: 28 wt % Ni on gamma alumina.

(44) The hydrogenated effluent resulting from RH is then sent to the second hydrocracking step carried out in the reactor R3 before being sent to the high-pressure separation then being recycled to the distillation step.

(45) Example 5—Process Performance

(46) Table 8 summarizes the performance of the processes described in Examples 1 to 4 in terms of “Heavy Naphtha” yield, cycle time of the process and overall conversion of the process. The conversion of coronene (HPNA with 7 aromatic rings) carried out in the hydrogenation step is also reported.

(47) TABLE-US-00008 TABLE 8 1 (not in 2 (in 3 (in 4 (in accordance accordance accordance accordance with the with the with the with the Examples invention) invention) invention) invention) Scheme R3 alone RH + R3 RH + R3 RH + R3 Catalyst in — 28% Ni/ 0.3% Pt/ 28% Ni/ RH alumina alumina alumina Purge (%) 2 2 2 1 TR1 (° C.) — 270 275 270 TR2 (° C.) 330  330 330 330 Coronene 0 91 76 91 conversion (%) (1) “Heavy Base Base Base Base + 1 Naphtha” point yield Cycle time Base Base + 7 Base + 4 Base + 5 months months months Overall 98  98 98 99 conversion (%)

(48) The coronene conversion is calculated by dividing the difference in the amounts of coronene measured upstream and downstream of the hydrogenation reactor by the amount of coronene measured upstream of this same reactor. The amount of coronene is measured by high-pressure liquid chromatography coupled to a UV detector (HPLC-UV), at a wavelength of 302 nm for which coronene has a maximum absorption.

(49) These examples illustrate the advantage of the process according to the invention which makes it possible to obtain improved performance in terms of cycle time, “Heavy Naphtha” yield or overall conversion of the process.

(50) 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.

(51) 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.