Process for the hydrotreatment of renewable materials, with an optimized gas recycle

Abstract

A process for the hydrotreatment of a feed obtained from renewable sources in which the total stream of feed F is divided into a number of different part-streams of feed F1 to Fn equal to the number of catalytic zones n, where n is 1 to 10. The mass flow rate of hydrogen sent to the first catalytic zone represents more than 80% by weight of the total mass flow rate of hydrogen used. The effluent from the reactor outlet undergoes at least one separation step. A portion of the liquid fraction is recycled to the catalytic zones in a manner such that the local recycle ratio for each of the beds is 2 or less, and the local dilution ratio over each of the beds is less than 4.

Claims

1. A process for the hydrotreatment of a feed obtained from renewable sources to produce paraffinic hydrocarbons which is carried out in the presence of hydrogen in a fixed bed reactor having a plurality of catalytic zones disposed in series and each catalytic zone comprising at least one hydrotreatment catalyst, said process comprising: a) dividing a liquid feed stream F into a plurality of different part-streams of liquid feed, F1 to Fn, respectively, wherein the number of part-streams of liquid feed is equal to the number of catalytic zones n in said fixed bed reactor, Z1 to Zn, respectively, and n is a whole number in the range of 2 to 10; b) injecting a first part-stream of liquid feed F1 into a first catalytic zone Z1, and injecting a second part-stream of liquid feed F2 into a second catalytic zone Z2 and so on if n is greater than 2; c) hydrotreating each part-stream, F1 to Fn, in each catalytic zone, Z1 to Zn, respectively, in the presence of hydrogen at a temperature in the range of 180 C. to 400 C., at a pressure in the range of 0.1 MPa to 15 MPa, at an hourly space velocity in the range of 0.1 h.sup.1 to 10 h.sup.1, and with a ratio of flow rate of hydrogen to flow rate of liquid feed in the range of 150 to 1500 Nm.sup.3/m.sup.3 to produce at least one effluent containing paraffinic hydrocarbons discharged from said reactor, wherein the mass flow rate of hydrogen sent to the first catalytic zone Z1 represents more than 80% by weight of the total mass flow rate of hydrogen used in the hydrotreatment process, hydrotreated product and hydrogen-containing gas are discharged from each catalytic zone, and, except for the nth catalytic zone, the hydrotreated product and hydrogen-containing gas from each catalytic zone are introduced into the next catalytic zone in the series, and the hydrotreated product and hydrogen-containing gas from the nth catalytic zone form said at least one effluent discharged from said reactor; d) separating said effluent from c) in at least one separation step in order to separate at least one gaseous fraction containing hydrogen and at least one liquid fraction containing paraffinic hydrocarbons; e) dividing at least a portion of said at least one liquid fraction containing paraffinic hydrocarbons from d) into a plurality of liquid recycle streams, RL1 to RLn, and recycling a first liquid recycle stream RL1 to the first catalytic zone Z1, and recycling a second liquid recycle stream RL2 to the second catalytic zone Z2 and so on if n is greater than 2; and f) optionally dividing at least a portion of said gaseous fraction containing hydrogen from d) into a plurality of gaseous recycle streams, RG1 to RGn, and optionally recycling a first gaseous recycle stream RG1 to the first catalytic zone Z1, and optionally recycling a second gaseous recycle stream RG2 to the second catalytic zone Z2 and so on if n is greater than 2; wherein each of the catalytic zones has a local recycle ratio which is defined as the weight ratio between (i) the total weight of the liquid recycle stream introduced to the catalytic zone plus any the liquid recycle streams introduced into any previous catalytic zone in the series, if present, and (ii) the part-stream of liquid feed introduced into the catalytic zone, and wherein said local recycle ratio of each catalytic zone is >0 to 2; wherein the first catalytic zone of the series receives a liquid diluting stream and optionally a gaseous diluting stream, wherein the optional gaseous diluting stream is the first gaseous recycle stream from f); wherein each of the other catalytic zones, Z2 to Zn, in the series receives liquid and gaseous diluting streams, wherein said liquid diluting streams are: (1) the part-stream(s) of liquid feed streams introduced into each of the previous catalytic zones in the series, if present, (2) the liquid recycle streams from e) introduced into each of the previous catalytic zones in the series, if present, and (3) the liquid recycle stream from e) introduced into the catalytic zone, and said gaseous diluting streams are: (4) the hydrogen-containing gas discharged from the previous catalytic zone in the series, if present, (5) the optional gaseous recycle streams from f) introduced into each of the previous catalytic zones in the series, if present, and (6) the optional gaseous recycle stream from f) introduced into the catalytic zone; and wherein each of the catalytic zones has a local dilution ratio defined as the weight ratio between (I) the total quantity of liquid and gaseous diluting streams introduced into the catalytic zone and (II) the part-stream of liquid feed introduced into the catalytic zone, and wherein said local dilution ratio of each catalytic zone is >0 to less than 4.

2. The process according to claim 1, wherein the liquid feed obtained from renewable sources is selected from vegetable oils, oils from algae or algal oils, fish oils, spent cooking oils, and fats of vegetable or animal origin, and mixtures thereof, and comprises triglycerides, free fatty acids, and/or esters.

3. The process according to claim 1, wherein the mass flow rate of hydrogen sent to the first catalytic zone Z1 represents more than 90% by weight of the total mass flow rate of hydrogen used in the hydrotreatment process.

4. The process according to claim 3, wherein 100% by weight of the total mass flow of hydrogen used in the hydrotreatment process is sent to the first catalytic zone Z1.

5. The process according to claim 1, wherein the local recycle ratio of each of the catalytic zones is >0 to 1.7.

6. The process according to claim 3, wherein the local recycle ratio of each of the catalytic zones is >0 to 1.5.

7. The process according to claim 1, wherein said hydrotreatment catalyst in each catalytic zone comprises at least one metal from group VIII selected from nickel and cobalt, used alone or as a mixture, optionally in association with at least one metal from group VIB selected from molybdenum and tungsten, used alone or as a mixture, and a support selected from the group formed by alumina, silica, silica-aluminas, magnesia, clays and mixtures thereof.

8. The process according to claim 1, wherein separation d) is carried out in a high temperature high pressure separator and wherein said effluent from c) is separated into a gaseous fraction comprising hydrogen, CO, CO2, H.sub.2S, light gases, water, and at least some paraffinic hydrocarbons and a liquid fraction containing paraffinic hydrocarbons, wherein said gaseous fraction is then sent to a low temperature high pressure separator to separate said gaseous fraction into a further gaseous fraction comprising hydrogen, CO, CO2, H.sub.2S, light gases and water and a further liquid fraction containing paraffinic hydrocarbons.

9. The process according to claim 1, wherein separation d) is carried out in two separation steps, the first separation step being carried out in a low temperature high pressure separator, followed by a second separation step for separation of at least a portion of water formed during hydrodeoxygenation reactions occurring in said hydrotreatment process.

10. The process according to claim 1, wherein said gaseous fraction separated in separation d) is recycled to c).

11. The process according to claim 1, further comprising subjecting at least a portion of the liquid fraction containing paraffinic hydrocarbons obtained from separation d) to hydroisomerization in the presence of a hydroisomerization catalyst to produce a hydroisomerization effluent.

12. The process according to claim 11, wherein said hydroisomerization is performed at a temperature in the range of 150 C. to 500 C., at a pressure in the range of 1 MPa to 10 MPa, at an hourly space velocity in the range of 0.1 h.sup.1 to 10.sup.1, and at a hydrogen flow rate such that the volume ratio of hydrogen/hydrocarbons is in the range of 70 to 1000 Nm.sup.3/m.sup.3 of feed.

13. The process according to claim 11, wherein the hydroisomerization catalyst comprises: (a) at least one metal from group VIII selected from platinum activated in its reduced form, palladium activated in its reduced form, nickel in its sulphide form, and cobalt in its sulphide form, and/or (b) at least one metal from group VIB selected from molybdenum and tungsten, and at least one molecular sieve or amorphous mineral support.

14. The process according to claim 11, further comprising subjecting the hydroisomerization effluent to at least one separation step and at least one step for fractionation in order to obtain a gaseous cut, a gasoline cut and at least one middle distillates cut containing kerosene and/or diesel.

15. The process according to claim 1, wherein at least a portion of said gaseous fraction containing hydrogen from d) is divided into a plurality of gaseous recycle streams, RG1 to RGn, and a first liquid gaseous recycle stream RG1 is recycled to the first catalytic zone Z1, and a second gaseous recycle stream RG2 is recycled to the second catalytic zone Z2 and so on if n is greater than 2.

16. The process according to claim 1, wherein the local dilution ratio of each of the catalytic zones is >0 to <3.8.

17. The process according to claim 1, wherein the local dilution ratio of each of the catalytic zones is >0 to <3.5.

18. The process according to claim 1, wherein the local dilution ratio of each of the catalytic zones is >0 to <3.

19. The process according to claim 1, wherein said hydrotreatment process is conducted at a temperature in the range of 200 C. to 350 C., at a pressure in the range of 0.5 to 10 MPa, at an hourly space velocity in the range of 0.1 to 5 h.sup.1, and with a ratio of flow rate of hydrogen to flow rate of liquid feed in the range of 400 to 1200 Nm.sup.3/m.sup.3.

20. The process according to claim 1, wherein the first catalytic zone Z1 has an inlet and an outlet, and the temperature at the inlet to said first catalytic zone Z1 is more than 180 C., and the temperature at the outlet from said first catalytic zone Z1 is less than 350 C.

21. The process according to claim 20, wherein each of the catalytic zones has an inlet and an outlet, and the temperatures at the inlet to each of the catalytic zones following the first catalytic zone is higher than that temperature at the inlet of the preceding catalytic zone.

22. The process according to claim 21, wherein the temperature at the outlet of each of the catalytic zones following the first catalytic zone Z1 is below 400 C.

23. The process according to claim 21, wherein a difference in temperature between the outlet temperature and the inlet temperature for each catalytic zone is in the range 1 C. to 80 C.

24. The process according to claim 1, wherein for catalytic zones Z2 to Zn the flow rate of the part-streams of liquid feed injected into each catalytic zone is a higher proportion of the liquid feed stream F than the flow rate of the part-stream of liquid feed injected into the previous catalytic zone.

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1 represents a general layout of a process in accordance with the invention comprising n catalytic zones. In this particular embodiment n is 4 and thus there are 4 catalytic zones, Z1 to Z4.

(2) The crude feed, also known as the fresh feed F, is injected into the line 1 represented in FIG. 1. The feed is distributed into various streams F.sub.1, F.sub.2, F.sub.3, and F.sub.4 supplying the various successive catalytic zones Z1, Z2, Z3, and Z4, respectively. The gas recycle RG is mixed with a hydrogen-rich gas 2. The stream RG (conduit 13) is subdivided into various streams RG.sub.1, RG.sub.2, RG.sub.3 and RG.sub.4. The liquid recycle stream 17 is subdivided into several streams RL.sub.1, RL.sub.2, RL.sub.3, and RL.sub.4. The feed stream F.sub.1 is mixed with a liquid and gas recycle stream RL.sub.1 and RG.sub.1 via the conduits 15, 16 and 17 before said stream of feed F.sub.1 is sent to the first catalytic zone Z1. Similarly, the stream of feed F.sub.2, liquid recycle stream RL.sub.2 and optional gas recycle stream RG.sub.2 in the case in which 100% of the mass flow of hydrogen used in the hydrotreatment process is not sent to the first catalytic zone Z1, are sent to second catalytic zone Z2, and so on up to the 4.sup.th-catalytic zone Z4.

(3) The hydrotreated effluent is withdrawn via the line 11 and sent to a first separator 8 to separate a gaseous stream 20 and a paraffinic liquid stream 19, the gaseous stream being sent to a second separator 9 so as to separate a gaseous stream RG which is recycled via the conduit 13, and a liquid stream which is sent to a final separation step 12. The separator 12 can be used to separate water (not shown), a gaseous stream 22, and a second liquid paraffinic stream 21, a portion 18 of which is recycled, R, via the conduit 16 before being subdivided and sent to the various catalytic zones of the reactor. The other portion of the liquid stream 21 is collected and mixed in the conduit 10 with the liquid stream 19 obtained from the separation 8 for sending to the hydroisomerization step (not shown in FIG. 1), or for recycling.

(4) FIG. 2 represents the streams entering and leaving the hydrotreatment reactor. The fresh feed F is divided into various streams F1, F2 and F3 and sent respectively to the zones Z1, Z2 and Z3. The stream of feed F1 enters the catalytic bed of catalytic zone Z1 as a mixture with a gas recycle RG1, a makeup of hydrogen and a liquid recycle RL1. The stream of feed F2, gas recycle stream RG2, and liquid recycle stream RL2 are sent to the catalytic bed of catalytic zone Z2, and stream of feed F3, gas recycle stream RG3, and liquid recycle stream RL2 are sent to the catalytic bed of catalytic zone Z3.

(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 application No. FR 15/57053, filed Jul. 24, 2015 are incorporated by reference herein.

EXAMPLES

Example 1 (not in Accordance with the Invention)

(8) Example 1 is not in accordance with the invention, because the mass flow of hydrogen sent to the first catalytic zone Z1 represents 35% by weight of the total mass flow of hydrogen used in the hydrotreatment process.

(9) The feed to be treated was a palm oil with the principal characteristics shown in Table 1a. This feed had already undergone a treatment with phosphoric acid and a treatment with bleaching clay using protocols known to the person skilled in the art.

(10) TABLE-US-00001 TABLE 1a Characteristics of the treated feed (palm oil) Treated feed Palm oil Density at 15 C. (kg/m.sup.3) 915.5 Oxygen (% by wt) 11.34 Hydrogen (% by wt) 12.0 Sulphur (ppm by wt) 1.7 Nitrogen (ppm by wt) 1.5 Phosphorus (ppm by wt) <0.5 Magnesium (ppm by wt) <0.5 Sodium (ppm by wt) <0.5 Iron (ppm by wt) <0.5

(11) 100 g/h of this feed was to be treated in a hydrotreatment reactor constituted by 2 catalytic beds.

(12) Each catalytic zone was constituted by one bed of catalyst. The catalyst used was identical in the two catalytic zones of the hydrotreatment step and comprised 4% by weight of NiO, 21% by weight of MoO.sub.3 and 5% by weight of P.sub.2O.sub.5 supported on a gamma alumina. Said catalyst had a Ni/Mo atomic ratio equal to 0.4.

(13) The supported catalysts were prepared by dry impregnation of the oxide precursors in solution, then sulphurized in situ prior to the test at a temperature of 350 C. using a straight run gas oil feed supplemented with 2% by weight of sulphur from dimethyldisulphide (DMDS). After in situ sulphurization in the unit under pressure, the feed described in Table 1a, obtained from a renewable source constituted by palm oil, was sent to each of the two catalytic zones.

(14) The method for the preparation of the catalysts does not limit the scope of the invention.

(15) The total palm oil feed (F=100 g/h) was divided into two streams, one stream F1 of 40 g/h injected into the zone Z1, and a second stream of 60 g/h injected into the zone Z2.

(16) The quantity of liquid recycle used was injected integrally with the feed over the zone Z1 at a flow rate RL1=90 g/h.

(17) The gas injected with the feed was entirely composed of hydrogen. This hydrogen was injected as a whole with the two feed streams supplying zones Z1 and Z2, at a flow rate such that at the inlet to each of the catalytic zones, the same ratio was obtained: RG1/F1=RG2/F2=700 Nm.sup.3/m.sup.3.

(18) Thus, the mass flow rate of hydrogen sent to the first catalytic zone Z1 represented 35% by weight of the total mass flow rate of hydrogen used in the hydrotreatment process.

(19) The total operating pressure was 50 bar rel (5 MPa rel).

(20) Table 1b indicates the flow rates of each of the two streams of feed, as well as the liquid recycle ratios and the degrees of dilution for each of the two catalytic zones.

(21) TABLE-US-00002 TABLE 1b Operating conditions for hydrotreatment section and characteristics of effluent produced Formula for Parameter calculation Value Flow rate of feed, zone Z1 (F1) (g/h) 40.0 Flow rate of feed, zone Z2 (F2) (g/h) 60.0 Total flow rate of feed (F) (g/h) 100.0 Liquid recycle flow rate (RL1) (g/h) 90 Liquid recycle flow rate (RL2) (g/h) 0.0 Flow rate of gas, zone Z1 (RG1) (g/h) 2.73 Flow rate of gas, zone Z2 (RG2) (g/h) 4.10 Liquid recycle ratio zone Z1 (TR1) (g/g) RL1/F1 2.25 Liquid recycle ratio zone Z2 (TR2) (g/g) (RL1 + RL2)/F2 1.5 Dilution ratio zone Z1 (TD1) (RL1 + RG1)/F1 2.32 Dilution ratio zone Z2 (TD2) (RL1 + RG1 + RL2 + 2.28 RG2 + F1)/F2 Temperature at inlet, zone Z1 ( C.) 230 Temperature at outlet, zone Z2 ( C.) 312 Mean temperature ( C.) 273 Delta T1 = T, outlet Z1 T, inlet Z1 83 Delta T2 = T, outlet Z2 T, inlet Z2 70 Characteristics of effluent produced Flow rate of hydrocarbons produced (g/h) 81.0 Density at 15 C. (kg/m3) 785.5 Oxygen (% by wt) <0.2

(22) Oxygen was completely eliminated during this hydrotreatment step. A liquid product essentially composed of hydrocarbons in a yield of 81.0% by weight was obtained.

Example 2 (in Accordance with the Invention)

(23) The same feed as in Example 1 was treated in a hydrotreatment reactor constituted by two catalytic zones each comprising the same catalyst as in Example 1. In Example 2 of the invention, the mass flow rate of hydrogen sent to the first catalytic zone Z1 represented 80% by weight of the total mass flow rate of hydrogen used in the hydrotreatment process.

(24) The same protocol for activation of the catalyst by sulphurization was applied, and the total operating pressure was 50 bar rel (5 MPa rel).

(25) Table 2 indicates the flow rates of each of the two streams of feed, as well as the liquid recycle ratios and the degree of dilution for each of the two catalytic zones.

(26) The same quantity of liquid product was recycled (R=90 g/h) but, in contrast to Example 1, part of this recycle was sent to the catalytic zone Z1 (RL1=72 g/h) and part of it was sent to the catalytic zone Z2 (RL2=18 g/h). The nature and the gas flow recycled to the hydrotreatment reactor was generally identical to that of Example 1 (100% hydrogen, RG1=5.46 g/h, corresponding to a ratio of the volume of H.sub.2/volume of feed at the reactor inlet of 700 Nm.sup.3/m.sup.3). In contrast, this gaseous flow was distributed in a different manner, since the mass flow of hydrogen sent to the first catalytic zone Z1 represented 80% by weight of the total mass flow of hydrogen.

(27) TABLE-US-00003 TABLE 2 Operating conditions for the hydrotreatment section Yield and characteristics of the effluent produced Formula for Parameter calculation Value Flow rate of feed, zone Z1 (F1) (g/h) 40.0 Flow rate of feed, zone Z2 (F2) (g/h) 60.0 Total flow rate of feed (F) (g/h) 100.0 Liquid recycle flow rate (RL1) (g/h) 72 Liquid recycle flow rate (RL2) (g/h) 18 Flow rate of gas, zone Z1 (RG1) (g/h) 5.46 Flow rate of gas, zone Z2 (RG2) (g/h) 1.36 Liquid recycle ratio zone Z1 (TR1) (g/g) RL1/F1 1.80 Liquid recycle ratio zone Z2 (TR2) (g/g) (RL1 + RL2)/F2 1.50 Dilution ratio zone Z1 (TD1) (RL1 + RG1)/F1 1.94 Dilution ratio zone Z2 (TD2) (RL1 + RG1 + RL2 + 2.28 RG2 + F1)/F2 Temperature at inlet, zone Z1 ( C.) 220 Temperature at outlet, zone Z2 ( C.) 313 Mean temperature ( C.) 269 Delta T1 = T, outlet Z1 T, inlet Z1 76 Delta T2 = T, outlet Z2 T, inlet Z2 65

Example 3 (in Accordance with the Invention)

(28) The same feed as in Example 1 was treated in a hydrotreatment reactor constituted by two catalytic zones each comprising the same catalyst as in Example 1. In Example 3 of the invention, the mass flow rate of hydrogen sent to the first catalytic zone Z1 represented 100% by weight of the total mass flow rate of hydrogen used in the hydrotreatment process.

(29) The same protocol for activation of the catalyst by sulphurization was applied, and the total operating pressure was 50 bar rel (5 MPa rel).

(30) Table 3 indicates the flow rates of each of the two streams of feed, as well as the liquid recycle ratios and the degrees of dilution for each of the two catalytic zones.

(31) The same quantity of liquid product was recycled (R=90 g/h) but, in contrast to Example 1, part of this recycle was sent to the catalytic zone Z1 (RL1=60 g/h) and part of it was sent to the catalytic zone Z2 (RL2=30 g/h).

(32) The nature and the gas flow rate recycled to the hydrotreatment reactor was generally identical to that of Example 1 (100% hydrogen, RG1=6.83 g/h, corresponding to a ratio of the volume of H.sub.2/volume of feed at the reactor inlet of 700 Nm.sup.3/m.sup.3). In contrast, this gaseous flow was distributed in a different manner, since all of it was sent to the catalytic zone Z1.

(33) TABLE-US-00004 TABLE 3 Operating conditions for the hydrotreatment section Yield and characteristics of the effluent produced Formula for Parameter calculation Value Flow rate of feed, zone Z1 (F1) (g/h) 40.0 Flow rate of feed, zone Z2 (F2) (g/h) 60.0 Total flow rate of feed (F) (g/h) 100.0 Liquid recycle flow rate (R1) (g/h) 60.0 Liquid recycle flow rate (R2) (g/h) 30.0 Flow rate of gas, zone Z1 (R1g) (g/h) 6.83 Flow rate of gas, zone Z2 (R2g) (g/h) 0.00 Liquid recycle ratio zone Z1 (TRL1) (g/g) RL1/F1 1.50 Liquid recycle ratio zone Z2 (TRL2) (g/g) (RL1 + RL2)/F2 1.50 Dilution ratio zone Z1 (TDL1) (RL1 + RG1)/F1 1.67 Dilution ratio zone Z2 (TDL2) (RL1 + RG1 + RL2 + 2.28 RG2 + F1)/F2 Temperature at inlet, zone Z1 ( C.) 215 Temperature at outlet, zone Z2 ( C.) 313 Mean temperature ( C.) 266 Delta T1 = T, outlet Z1 T, inlet Z1 73 Delta T2 = T, outlet Z2 T, inlet Z2 65 Characteristics of effluent produced Flow rate of hydrocarbons produced (g/h) 83.0 Density at 15 C. (kg/m3) 786.3 Oxygen (% by wt) <0.2

(34) Examples 1 to 3 demonstrate that implementing the present invention means that a low recycle ratio can be employed in all of the catalytic zones due to application of a high flow rate of hydrogen to the inlet to the first bed, in contrast to Example 1, not in accordance with the invention, in which the hydrogen was distributed over the catalytic beds in a uniform manner and in which the exothermicity was not controlled, the temperature differences between the outlet and inlet for the catalytic beds being too high.

(35) Furthermore, good management of the exothermicity in Examples 2 and 3, in accordance with the invention, mean that a lower mean bed temperature was employed compared with Example 1 which was not in accordance with the invention, which meant that deactivation of the catalyst was reduced, and thus the service life of the catalyst was longer.

(36) 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.

(37) 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.