METHOD, INCLUDING A HYDROGENATION STEP, FOR TREATING PLASTIC PYROLYSIS OILS

Abstract

The present invention relates to a process for treating a plastics pyrolysis oil, comprising: a) hydrogenation of said feedstock in the presence of at least hydrogen and of at least one hydrogenation catalyst at an average temperature of between 140 and 340 C., the outlet temperature of step a) being at least 15 C. higher than the inlet temperature of step a), to obtain a hydrogenated effluent; b) hydrotreatment of said hydrogenated effluent in the presence of at least hydrogen and of at least one hydrotreatment catalyst, to obtain a hydrotreated effluent, the average temperature of step b) being higher than the average temperature of step a); c) separation of the hydrotreated effluent in the presence of an aqueous stream, at a temperature of between 50 and 370 C., to obtain at least one gaseous effluent, an aqueous liquid effluent and a hydrocarbon-based liquid effluent.

Claims

1. Process for treating a feedstock comprising a plastics pyrolysis oil, comprising: a) a hydrogenation step performed in a hydrogenation reaction section, using at least one fixed-bed reactor containing n catalytic beds, n being an integer greater than or equal to 1, each comprising at least one hydrogenation catalyst, said hydrogenation reaction section being fed at least with said feedstock and a gas stream comprising hydrogen, said hydrogenation reaction section being used at an average temperature of between 140 and 400 C., a partial pressure of hydrogen of between 1.0 and 10.0 MPa abs. and an hourly space velocity of between 0.1 and 10.0 h.sup.1, the outlet temperature of the reaction section of step a) being at least 15 C. higher than the inlet temperature of the reaction section of step a), to obtain a hydrogenated effluent, b) a hydrotreatment step performed in a hydrotreatment reaction section, using at least one fixed-bed reactor containing n catalytic beds, n being an integer greater than or equal to 1, each comprising at least one hydrotreatment catalyst, said hydrotreatment reaction section being fed at least with said hydrogenated effluent obtained from step a) and a gas stream comprising hydrogen, said hydrotreatment reaction section being used at an average temperature of between 250 and 430 C., a partial pressure of hydrogen of between 1.0 and 10.0 MPa abs. and an hourly space velocity of between 0.1 and 10.0 h.sup.=1, the average temperature of the reaction section of step b) being higher than the average temperature of the hydrogenation reaction section of step a), to obtain a hydrotreated effluent, b) optionally, a hydrocracking step performed in a hydrocracking reaction section, using at least one fixed bed containing n catalytic beds, n being an integer greater than or equal to 1, each comprising at least one hydrocracking catalyst, said hydrocracking reaction section being fed at least with said hydrotreated effluent obtained from step b) and/or with the cut comprising compounds having a boiling point greater than 175 C. obtained from step d) and a gas stream comprising hydrogen, said hydrocracking reaction section being used at an average temperature of between 250 and 450 C., a partial pressure of hydrogen of between 1.5 and 20.0 MPa abs. and an hourly space velocity of between 0.1 and 10.0 h.sup.=1, to obtain a hydrocracked effluent which is sent to the separation step c), c) a separation step, fed with the hydrotreated effluent obtained from step b) or with the hydrocracked effluent obtained from step b) and an aqueous solution, said step being performed at a temperature of between 50 and 370 C., to obtain at least one gaseous effluent, an aqueous effluent and a hydrocarbon-based effluent, d) optionally a step of fractionating all or a portion of the hydrocarbon-based effluent obtained from step c), to obtain at least one gaseous effluent and at least one cut comprising compounds with a boiling point of less than or equal to 175 C. and one hydrocarbon-based cut comprising compounds with a boiling point of greater than 175 C.

2. Process according to claim 1, comprising step d).

3. Process according to claim 1, comprising step b).

4. Process according to claim 1, in which the amount of the gas stream comprising hydrogen feeding said reaction section of step a) is such that the hydrogen coverage is between 50 and 1000 Nm.sup.3 of hydrogen per m.sup.3 of feedstock.

5. Process according to claim 1, in which the amount of the gas stream comprising hydrogen feeding said reaction section of step a) is such that the hydrogen coverage is between 200 and 300 Nm.sup.3 of hydrogen per m.sup.3 of feedstock.

6. Process according to claim 1, in which the outlet temperature of step a) is at least 30 C. higher than the inlet temperature of step a).

7. Process according to claim 1, in which at least one fraction of the hydrocarbon-based effluent obtained from the separation step c) or at least one fraction of the naphtha cut comprising compounds with a boiling point of less than or equal to 175 C. obtained from the fractionation step d) is sent into the hydrogenation step a) and/or the hydrotreatment step b).

8. Process according to claim 1, in which at least one fraction of the cut comprising compounds with a boiling point of greater than 175 C. obtained from the fractionation step d) is sent to the hydrogenation step a) and/or the hydrotreatment step b) and/or the hydrocracking step b).

9. Process according to claim 1, comprising a step a0) of pretreating the feedstock comprising a plastics pyrolysis oil, said pretreatment step being carried out upstream of the hydrogenation step a) and comprises a filtration step and/or an electrostatic separation step and/or a step of washing by means of an aqueous solution and/or an adsorption step.

10. Process according to claim 1, in which the hydrocarbon-based effluent obtained from the separation step c), or at least one of the two liquid hydrocarbon-based streams obtained from step d), is totally or partly sent into a steam cracking step e) performed in at least one pyrolysis furnace at a temperature of between 700 and 900 C. and at a pressure of between 0.05 and 0.3 MPa relative.

11. Process according to claim 1, in which the reaction section of step a) uses at least two reactors operating in permutable mode.

12. Process according to claim 1, in which a stream containing an amine is injected upstream of step a).

13. Process according to claim 1, in which said hydrogenation catalyst comprises a support chosen from alumina, silica, silica-aluminas, magnesia, clays and mixtures thereof and a hydro-dehydrogenating function comprising either at least one group VIII element and at least one group VIB element, or at least one group VIII element.

14. Process according to claim 1, in which said hydrotreatment catalyst comprises a support chosen from the group consisting of alumina, silica, silica-aluminas, magnesia, clays and mixtures thereof and a hydro-dehydrogenating function comprising at least one group VIII element and/or at least one group VIB element.

15. Process according to claim 1, which process also comprises a second hydrocracking step b) performed in a hydrocracking reaction section, using at least one fixed bed containing n catalytic beds, n being an integer greater than or equal to 1, each comprising at least one hydrocracking catalyst, said hydrocracking reaction section being fed with the cut comprising compounds having a boiling point greater than 175 C. obtained from step d) and a gas stream comprising hydrogen, said hydrocracking reaction section being used at a temperature of between 250 and 450 C., a partial pressure of hydrogen of between 1.5 and 20.0 MPa abs. and an hourly space velocity of between 0.1 and 10.0 h.sup.=1, to obtain a hydrocracked effluent which is sent to the separation step c).

16. Process according to claim 1, in which said hydrocracking catalyst comprises a support chosen from halogenated aluminas, combinations of boron and aluminium oxides, amorphous silica-aluminas and zeolites and a hydro-dehydrogenating function comprising at least one group VIB metal chosen from chromium, molybdenum and tungsten, alone or as a mixture, and/or at least one group VIII metal chosen from iron, cobalt, nickel, ruthenium, rhodium, palladium and platinum.

17. Product obtained via the process according to claim 1.

18. Product according to claim 17, which product comprises, relative to the total weight of the product: a total content of metallic elements of less than or equal to 5.0 ppm by weight, with a content of iron element of less than or equal to 100 ppb by weight, a content of silicon element of less than or equal to 1.0 ppm by weight, a sulfur content of less than or equal to 500 ppm by weight, a nitrogen content of less than or equal to 100 ppm by weight, a content of chlorine element of less than or equal to 10 ppm by weight.

Description

LIST OF FIGURES

[0229] The information regarding the elements referenced in FIGS. 1 to 2 enables a better understanding of the invention, without said invention being limited to the particular embodiments illustrated in FIGS. 1 to 2. The various embodiments presented may be used alone or in combination with each other, without any limitation to the combination.

[0230] FIG. 1 represents the scheme of a particular embodiment of the process of the present invention, comprising: [0231] a step a) of hydrogenation of a hydrocarbon-based feedstock obtained from the pyrolysis of plastics 1, in the presence of a hydrogen-rich gas 2 and optionally of an amine supplied by the stream 3, performed in at least one fixed-bed reactor including at least one hydrogenation catalyst, to obtain an effluent 4; [0232] a step b) of hydrotreatment of the effluent 4 obtained from step a), in the presence of hydrogen 5, performed in at least one fixed-bed reactor including at least one hydrotreatment catalyst, to obtain a hydrotreated effluent 6; [0233] optionally a step b) of hydrocracking of the effluent 6 obtained from step b), in the presence of hydrogen 7, performed in at least one fixed-bed reactor including at least one hydrocracking catalyst, to obtain a hydrocracked effluent 8; [0234] a step c) of separation of the effluent 8 performed in the presence of an aqueous washing solution 9, making it possible to obtain at least one fraction 10 comprising hydrogen, an aqueous fraction 11 containing dissolved salts, and a hydrocarbon-based liquid fraction 12; [0235] optionally a step d) of fractionation of the hydrocarbon-based liquid fraction 12, making it possible to obtain at least one gas fraction 13, a cut 14 comprising compounds with a boiling point of less than or equal to 175 C. (naphtha cut) and a cut 15 comprising compounds with a boiling point of greater than 175 C. (diesel cut).

[0236] At the outcome of step d), a portion of the cut 14 comprising compounds with a boiling point of less than or equal to 175 C. is sent to a steam cracking process (not represented). Another portion of the cut 14 feeds the hydrogenation step a) (fraction 14a) and the hydrotreatment step b) (fraction 14b). A portion of the cut 15 comprising compounds with a boiling point of greater than 175 C. obtained from step d) feeds the hydrocracking step b) (fraction 15a), another portion 15b constitutes the purge.

[0237] FIG. 2 represents the scheme of another particular embodiment of the process of the present invention, which is based on the scheme of FIG. 1. This scheme comprises notably a second hydrocracking step b) in which the cut 15 comprising compounds with a boiling point of greater than 175 C. obtained from step d) feeds this second hydrocracking step b) (fraction 15a) which is carried out in at least one fixed-bed reactor comprising at least one hydrocracking catalyst and is fed with hydrogen (16). The second hydrocracked effluent (17) is recycled into the separation step c). The other portion of the cut 15 constitutes the purge 15b.

[0238] Instead of injecting the amine stream 3 into the inlet of the hydrogenation step a), it is possible to inject it into the inlet of the hydrotreatment step b), into the inlet of the hydrocracking step U), into the inlet of the separation step c) or else not to inject it, depending on the characteristics of the feedstock.

[0239] Only the main steps, with the main streams, are shown in FIGS. 1 and 2, so as to allow a better understanding of the invention. It is clearly understood that all the equipment required for the functioning is present (vessels, pumps, exchangers, furnaces, columns, etc.), even if it is not shown. It is also understood that hydrogen-rich gas streams (supply or recycle), as described above, may be injected into the inlet of each reactor or catalytic bed or between two reactors or two catalytic beds. Means well known to those skilled in the art for purifying and for recycling hydrogen may also be used.

EXAMPLES

Example 1 (in Accordance with the Invention)

[0240] The feedstock 1 treated in the process is a plastics pyrolysis oil (i.e. comprising 100% by weight of said plastics pyrolysis oil) having the characteristics indicated in Table 2.

TABLE-US-00002 TABLE 2 feedstock characteristics Description/ Methods Unit Pyrolysis oil Density @15 C. ASTM D4052 g/cm.sup.3 0.820 Sulfur content ISO 20846 ppm by weight 2500 Nitrogen content ASTM D4629 ppm by weight 730 Acid number ASTM D664 mgKOH/g 1.5 Bromine Content ASTM D1159 g/100 g 80 Diolefin Content MAV Method.sup.(1) % by weight 10 based on the Maleic Anhydride value Oxygen molecule Combustion + % by weight 1.0 Content Infrared Paraffin Content UOP990-11 % by weight 45 Naphthene Content UOP990-11 % by weight 20 Olefin Content UOP990-11 % by weight 25 Aromatics Content UOP990-11 % by weight 10 Halogen Content ASTM-D7359 ppm by weight 350 Asphaltene Content IFP9313 ppm by weight 380 Chloride Content ASTM D7536 ppm by weight 320 Metal content: ASTM-D5185 P ppm by weight 10 Fe ppm by weight 25 Si ppm by weight 45 Na ppm by weight 2 B ppm by weight 2 Simulated Distillation: ASTM D2887 0% 40 10% 98 30% 161 50% 232 70% 309 90% 394 100% 432 .sup.(1)MAV method described in the article: C. Lpez-Garcia et al., Near Infrared Monitoring of Low Conjugated Diolefins Content in Hydrotreated FCC Gasoline Streams, Oil & Gas Science and TechnologyRev. IFP, Vol. 62 (2007), No. 1, pp. 57-68

[0241] The feedstock 1 is subjected to a hydrogenation step a) performed in a fixed-bed reactor and in the presence of hydrogen 2 and of a hydrogenation catalyst of NiMo type on alumina, under the conditions indicated in Table 3.

TABLE-US-00003 TABLE 3 conditions of the hydrogenation step a) Reactor inlet temperature C. 280 Reactor outlet temperature C. 310 Average temperature (WABT) C. 295 Partial pressure of hydrogen MPa abs 6.4 H.sub.2/HC (volume coverage of hydrogen Nm.sup.3/m.sup.3 300 relative to the feedstock volume) HSV (volume flow rate of feedstock/ h.sup.1 1.0 volume of catalysts)

[0242] The conditions indicated in Table 3 correspond to conditions at the start of the cycle and the average temperature (WABT) is increased by 1 C. per month so as to compensate for the catalytic deactivation.

[0243] At the outcome of the hydrogenation step a), the degrees of conversion (=(initial concentration [0244] final concentration)/initial concentration) observed are indicated in Table 4.

TABLE-US-00004 TABLE 4 conversions of the entities during the hydrogenation step a) Degree of diolefin conversion % >60 Degree of olefin conversion % >60 Retention of silicon % >75

[0245] The effluent 4 obtained from the hydrogenation step a) is subjected directly, without separation, to a hydrotreatment step b) performed in a fixed bed and in the presence of hydrogen 5 and of a hydrotreatment catalyst of NiMo type on alumina under the conditions presented in Table 5.

TABLE-US-00005 TABLE 5 conditions of the hydrotreatment step b) Hydrotreatment average temperature C. 355 (WABT) Partial pressure of hydrogen MPa abs 6.2 H.sub.2/HC (volume coverage of hydrogen Nm.sup.3/m.sup.3 300 relative to the feedstock volume) HSV (volume flow rate of feedstock/ h.sup.1 0.5 volume of catalysts)

[0246] The conditions indicated in Table 5 correspond to conditions at the start of the cycle and the average temperature (WABT) is increased by 1 C. per month so as to compensate for the catalytic deactivation.

[0247] The effluent 6 obtained from the hydrotreatment step b) is subjected to a separation step c): a stream of water is injected into the effluent obtained from the hydrotreatment step b); the mixture is then treated in an acid gas washing column and separating vessels so as to obtain a gas fraction and a liquid effluent. The yields for the various fractions obtained after separation are indicated in Table 6 (the yields correspond to the ratios of the mass amounts of the various products obtained relative to the mass of feedstock upstream of step a), expressed in percentage and noted as % m/m).

TABLE-US-00006 TABLE 6 yields of the various products obtained after separation Gas fraction (NH.sub.3 + % m/m 0.94 H.sub.2S + C1-C4) Liquid fraction % m/m 99.41

[0248] All or part of the liquid fraction obtained can then be upgraded in a steam cracking step for the purpose of forming olefins which may be polymerized for the purpose of forming recycled plastics.

[0249] The process carried out according to the invention results in reduced catalytic deactivations during the hydrogenation step a) and during the hydrotreatment step b) relative to the catalytic deactivations observed according to the prior art.

Example 2 (not in Accordance with the Invention)

[0250] In this example according to the prior art and not in accordance with the invention, the feedstock to be treated is identical to that described in Example 1 (cf. Table 2).

[0251] The feedstock is subjected to a selective hydrogenation step a) performed in a fixed-bed reactor and in the presence of hydrogen and of a selective hydrogenation catalyst of NiMo type on alumina, under the conditions indicated in Table 7.

TABLE-US-00007 TABLE 7 conditions of the selective hydrogenation step a) Reactor inlet temperature C. 130 Reactor outlet temperature C. 138 Average temperature (WABT) C. 134 Partial pressure of hydrogen MPa abs 6.4 H.sub.2/HC (volume coverage of hydrogen Nm.sup.3/m.sup.3 10 relative to the feedstock volume) HSV (volume flow rate of feedstock/ h.sup.1 6 volume of catalysts)

[0252] The conditions indicated in Table 7 correspond to conditions at the start of the cycle and the average temperature (WABT) is increased by 4 C. per month so as to compensate for the catalytic deactivation.

[0253] At the outcome of the selective hydrogenation step a), the degrees of conversion (=(initial concentrationfinal concentration)/initial concentration) observed are indicated in Table 8.

TABLE-US-00008 TABLE 8 conversions of the entities during the selective hydrogenation step a) Degree of diolefin conversion % 35 Degree of olefin conversion % 6 Retention of silicon % <1

[0254] The effluent obtained from the selective hydrogenation step a) is subjected directly, without separation, to a hydrotreatment step b) performed in a fixed bed and in the presence of hydrogen, of a hydrocarbon-based recycle stream and of a hydrotreatment catalyst of NiMo type on alumina under the conditions presented in Table 9.

TABLE-US-00009 TABLE 9 conditions of the hydrotreatment step b) Hydrotreatment average temperature C. 355 (WABT) Partial pressure of hydrogen MPa abs 6.2 H.sub.2/HC (volume coverage of hydrogen Nm.sup.3/m.sup.3 300 relative to the feedstock volume) HSV (volume flow rate of feedstock/ h.sup.1 0.5 volume of catalysts)

[0255] The conditions indicated in Table 9 correspond to conditions at the start of the cycle and the average temperature (WABT) is increased by 2 C. per month so as to compensate for the catalytic deactivation.

[0256] The effluent obtained from the hydrotreatment step b) is subjected to a separation step c): a stream of water is injected into the effluent obtained from the hydrotreatment step b); the mixture is then treated in an acid gas washing column and separating vessels so as to obtain a gas fraction and a liquid effluent. The yields for the various fractions obtained after separation are indicated in Table 10 (the yields correspond to the ratios of the mass amounts of the various products obtained relative to the mass of feedstock upstream of step a), expressed in percentage and noted as % m/m).

TABLE-US-00010 TABLE 10 yields of the various products obtained after separation Gas fraction NH.sub.3 + % m/m 0.85 H.sub.2S + C1-C4 Liquid fraction % m/m 99.50

[0257] The process carried out according to the prior art and not in accordance with the invention results in catalytic deactivations during the selective hydrogenation step a) and during the hydrotreatment step b) which are greater than the catalytic deactivations observed in the process carried out according to the invention during the hydrogenation step a) and during the hydrotreatment step b).