OPTIMIZED METHOD FOR PROCESSING PLASTIC PYROLYSIS OILS FOR IMPROVING THEIR USE

Abstract

A process for treating plastics pyrolysis oil by a) selectively hydrogenating a feedstock in the presence hydrogen and a selective hydrogenation catalyst, at a temperature between 100 and 150° C., a hydrogen partial pressure between 1.0 and 10.0 MPa abs. and an hourly space velocity between 1.0 and 10.0 h.sup.−1, to obtain a hydrogenated effluent; b) hydrotreating the hydrogenated effluent in the presence of hydrogen and a hydrotreating catalyst, at a temperature between 250 and 370° C., a hydrogen partial pressure between 1.0 and 10.0 MPa abs. and an hourly space velocity between 0.1 and 10.0 h.sup.−1, to obtain a hydrotreating effluent; c) separating the hydrotreating effluent in the presence of an aqueous stream, at a temperature between 50 and 370° C., to obtain at least one gaseous effluent, a liquid aqueous effluent and a liquid hydrocarbon effluent; e) recycling at least one fraction of the product obtained.

Claims

1. A process for the treatment of a feedstock comprising a plastics pyrolysis oil, comprising: a) a stage of selective hydrogenation carried out in a reaction section fed at least with said feedstock and a gas stream comprising hydrogen, in the presence of at least one selective hydrogenation catalyst, at a temperature between 100 and 250° C., a hydrogen partial pressure between 1.0 and 10.0 MPa abs. and an hourly space velocity between 1.0 and 10.0 h.sup.−1, to obtain a hydrogenated effluent; b) a hydrotreating stage carried out in a hydrotreating reaction section, employing a fixed-bed reactor having n catalytic beds, n being an integer greater than or equal to 1, each comprising at least one hydrotreating catalyst, said hydrotreating reaction section being fed at least with said hydrogenated effluent resulting from stage a) and a gas stream comprising hydrogen, said hydrogenated effluent resulting from stage a) and said gas stream comprising hydrogen being introduced into the hydrotreating reaction section at the level of the first catalytic bed of said section, said hydrotreating reaction section being used at a temperature between 250 and 430° C., a hydrogen partial pressure between 1.0 and 10.0 MPa abs. and an hourly space velocity between 0.1 and 10.0 h.sup.−1, to obtain a hydrotreating effluent; c) a separation stage, fed with the hydrotreating effluent resulting from stage b) and an aqueous solution, said stage being operated at a temperature between 50 and 370° C., to obtain at least one gaseous effluent, an aqueous effluent and a hydrocarbon effluent; d) optionally a stage of fractionating all or part of the hydrocarbon effluent resulting from stage c), to obtain at least one gas stream and at least one hydrocarbon stream; e) a recycling stage comprising a phase of recovery of a fraction of the hydrocarbon effluent resulting from the separation stage c) or a fraction of the or of at least one of the hydrocarbon stream(s) resulting from the optional fractionation stage d), to constitute a recycle stream, and a phase of recycling said recycle stream to at least the selective hydrogenation stage a), the hydrotreating stage b) or stages a) and b).

2. The process as claimed in claim 1, in which the hydrotreating reaction section of stage b) is additionally fed with at least one fraction of the recycle stream resulting from stage e) which is (are) introduced into said hydrotreating reaction section as a mixture with the hydrogenated effluent resulting from stage a), separately from said hydrogenated effluent resulting from stage a) or according to the two modes as a mixture and separately from said hydrogenated effluent.

3. The process as claimed in claim 1, in which the reaction section of stage a) is additionally fed with at least one fraction of the recycle stream resulting from stage e), either as a mixture with said feedstock or separately from the feedstock, or also according to the two modes as a mixture and separately from the feedstock.

4. The process as claimed in claim 1, comprising said fractionation stage d).

5. The process as claimed in claim 1, comprising a stage a0) of pretreatment of the feedstock comprising a plastics pyrolysis oil, said pretreatment stage being carried out prior to the selective hydrogenation stage a) in an adsorption section, operated in the presence of at least one adsorbent, and/or in a solid/liquid separation section, said pretreatment stage being fed with said feedstock and operating at a temperature between 0 and 150° C., preferably between 5 and 100° C., and at a pressure between 0.15 and 10.0 MPa abs., preferably between 0.2 and 1.0 MPa abs., to obtain a pretreated feedstock which feeds stage a).

6. The process as claimed in claim 1, in which the selective hydrogenation stage a) is carried out at a temperature between 110 and 200° C., preferably between 130 and 180° C.

7. The process as claimed in claim 1, in which the amount of hydrogen of the gas stream employed in stage a) is between 1 and 200 Sm.sup.3 of hydrogen per m.sup.3 of feedstock, preferably between 1 and 50 Sm.sup.3 of hydrogen per m.sup.3 of feedstock, in a preferred way between 5 and 20 Sm.sup.3 of hydrogen per m.sup.3 of feedstock.

8. The process as claimed in claim 1, in which the reaction section of stage a) employs at least two reactors preferably operating in permutable mode.

9. The process as claimed in claim 1, in which said at least one selective hydrogenation catalyst comprises a support, preferably chosen from the group consisting of alumina, silica, silica-aluminas, magnesia, clays and their mixtures, and a hydrodehydrogenating function comprising at least one element from Group VIII, preferably chosen from the group consisting of nickel and cobalt, and/or at least one element from Group VIb, preferably chosen from the group consisting of molybdenum and tungsten.

10. The process as claimed in claim 9, in which said at least one selective hydrogenation catalyst comprises less than 1% by weight of nickel, expressed as nickel oxide NiO with respect to the weight of said catalyst, and less than 5% by weight of molybdenum, expressed as molybdenum oxide MoO.sub.3 with respect to the weight of said catalyst, on an alumina support.

11. The process as claimed in claim 1, in which n is between 2 and 10, and an additional gas stream comprising hydrogen is introduced into the inlet of each catalytic bed starting from the second catalytic bed of the hydrotreating reaction section of stage b).

12. The process as claimed in claim 1, in which the amount of hydrogen of the gas stream employed in stage b) is between 50 and 1000 Sm.sup.3 of hydrogen per m.sup.3 of fresh feedstock which feeds stage a), preferably between 50 and 500 Sm.sup.3 of hydrogen per m.sup.3 of fresh feedstock which feeds stage a), in a preferred way between 100 and 300 Sm.sup.3 of hydrogen per m.sup.3 of fresh feedstock which feeds stage a).

13. The process as claimed in claim 1, in which said at least one hydrotreating catalyst comprises a support, preferably chosen from the group consisting of alumina, silica, silica-aluminas, magnesia, clays and their mixtures, and a hydrodehydrogenating function comprising at least one element from Group VIII, preferably chosen from the group consisting of nickel and cobalt, and/or at least one element from Group VIb, preferably chosen from the group consisting of molybdenum and tungsten.

14. The process as claimed in claim 1, in which said at least one hydrotreating catalyst exhibits a specific surface of greater than or equal to 250 m.sup.2/g, preferably of greater than or equal to 300 m.sup.2/g.

15. The process as claimed in claim 1, additionally comprising a steam cracking stage f), carried out 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.

Description

LIST OF THE FIGURES

[0119] The particulars of the elements referenced in FIGS. 1 to 3 makes possible a better understanding of the invention, without the latter being limited to the specific embodiments illustrated in FIGS. 1 to 3. The various embodiments presented can be used alone or in combination with one another, without limitation of combination.

[0120] FIG. 1 represents the diagram of a specific embodiment of the process of the present invention, comprising: [0121] a stage a) of selective hydrogenation of a hydrocarbon feedstock resulting from the pyrolysis of plastics 1, in the presence of a hydrogen-rich gas 2, of a fraction R1 of a recycle stream R and optionally of an amine supplied by the stream 3, carried out in at least one fixed-bed reactor comprising at least one selective hydrogenation catalyst, to obtain an effluent 4; [0122] a stage b) of hydrotreating the effluent 4 resulting from stage a), in the presence of hydrogen 5 and of two fractions R2 and R3 of a recycle stream R, carried out in at least one fixed-bed reactor comprising at least one hydrotreating catalyst, to obtain a hydrotreated effluent 6; [0123] a stage c) of separation of the effluent 6 carried out in the presence of an aqueous washing solution 7 and making it possible to obtain at least one fraction 8 comprising hydrogen, an aqueous fraction 9 containing dissolved salts, and a liquid hydrocarbon fraction 10; [0124] the recycling of a part R of the hydrocarbon fraction 10 resulting from stage c), said part R constituting the recycle stream and being divided into three fractions R1, R2 and R3, to feed the selective hydrogenation stage a) (fraction R1) and the hydrotreating stage b) (fractions R2 and R3).

[0125] Instead of injecting the amine stream 3 at the inlet of the selective hydrogenation stage a), it is possible to inject it at the inlet of the hydrotreating stage b), at the inlet of the separation stage c), or else not to inject it, depending on the characteristics of the feedstock.

[0126] FIG. 2 represents another specific embodiment of the process according to the invention. In the embodiment shown in FIG. 2, the liquid hydrocarbon fraction 10, obtained on conclusion of stage c), is sent to a fractionation stage d) which makes it possible to obtain at least one gaseous fraction 11, a fraction comprising naphtha 12 and a hydrocarbon fraction 13. A part R of the hydrocarbon fraction 13 resulting from stage d) constitutes the recycle stream which feeds the hydrotreating stage b).

[0127] FIG. 3 represents an alternative form of the implementation of the process according to the invention represented in FIG. 1. In the embodiment shown in FIG. 3, the hydrocarbon feedstock resulting from the pyrolysis of plastics 1 undergoes a pretreatment stage a0), prior to the selective hydrogenation stage a). The then pretreated feedstock 14 feeds the selective hydrogenation stage a). Furthermore, the liquid hydrocarbon fraction 10 obtained on conclusion of stage c) is sent to a fractionation stage d) making it possible to obtain at least one gaseous fraction 11, a fraction comprising naphtha 12 and a hydrocarbon fraction 13. A recycle stream R, consisting of a part of the hydrocarbon fraction 13, is divided into three fractions R1, R2 and R3, to feed the selective hydrogenation stage a) (fraction R1) and the hydrotreating stage b) (fractions R2 and R3).

[0128] Only the main stages, with the main streams, are represented in FIGS. 1 to 3, in order to make it possible for the invention to be better understood. It is clearly understood that all the items of equipment required for the operation are present (drums, pumps, exchangers, furnaces, columns, and the like), even if not represented. It is also understood that gas streams rich in hydrogen (supply or recycle), as described above, can be injected at the inlet of each reactor or catalytic bed or between two reactors or two catalytic beds. Means well known to a person skilled in the art for the purification and recycling of hydrogen can also be employed.

[0129] On conclusion of stage d), the fraction comprising naphtha 12 and/or the hydrocarbon fraction 13 is/are sent to a steam cracking process.

EXAMPLES

Example 1 (in Accordance with the Invention)

[0130] The feedstock 1 treated in the process is a plastics pyrolysis oil (that is to say, comprising 100% by weight of said plastics pyrolysis oil) exhibiting the characteristics indicated in table 2.

TABLE-US-00002 TABLE 2 Characteristics of the feedstock Pyrolysis Description Methods Unit 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 Diolefins content from MAV % by weight 10 the Maleic Anhydride Method.sup.(1) Value Content of oxygen Combustion + % by weight 1.0 compounds Infrared Content of paraffins UOP990-11 % by weight 45 Content of naphthenes UOP990-11 % by weight 20 Content of olefins UOP990-11 % by weight 25 Content of aromatics UOP990-11 % by weight 10 Content of halogens ASTM-D7359 ppm by weight 350 Content of asphaltenes IFP9313 ppm by weight 380 Chloride content ASTM D7536 ppm by weight 320 Content of metals: 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% ° C. 40  10% ° C. 98  30% ° C. 161  50% ° C. 232  70% ° C. 309  90% ° C. 394 100% ° C. 432 .sup.(1)MAV method described in the paper: C. López-García et al., Near Infrared Monitoring of Low Conjugated Diolefins Content in Hydrotreated FCC Gasoline Streams, Oil & Gas Science and Technology - Rev. IFP, Vol. 62 (2007), No. 1, pp. 57-68

[0131] The feedstock 1 is subjected to a selective hydrogenation stage a) carried out in a fixed-bed reactor and in the presence of hydrogen 2 and of a selective hydrogenation catalyst of the NiMo-on-Alumina type, under the conditions indicated in table 3.

TABLE-US-00003 TABLE 3 Conditions of the selective hydrogenation stage a) Temperature ° C. 150 Hydrogen partial pressure MPa abs. 6.4 H.sub.2/HC (Hydrogen coverage by volume, with respect Sm.sup.3/m.sup.3 10 to the volume of feedstock) HSV (flow rate by volume of feedstock/volume of h.sup.−1 6 catalysts)

[0132] On conclusion of the selective hydrogenation stage a), all of the diolefins initially present in the feedstock were converted.

[0133] The effluent 4 resulting from the selective hydrogenation stage a) is subjected directly, without separation, to a hydrotreating stage b) carried out in a fixed bed and in the presence of hydrogen 5, of a hydrocarbon recycle stream R and of a hydrotreating catalyst of NiMo-on-Alumina type under the conditions presented in table 4.

TABLE-US-00004 TABLE 4 Conditions of the hydrotreating stage b) Hydrotreating temperature ° C. 355 Hydrogen partial pressure MPa abs. 6.2 H.sub.2/HC (Hydrogen coverage by volume, with respect Sm.sup.3/m.sup.3 300 to the volume of feedstock) HSV (flow rate by volume of feedstock/volume of h.sup.−1 0.5 catalysts)

[0134] The effluent 6 resulting from the hydrotreating stage b) is subjected to a separation stage c) in which a stream of water is injected into the effluent resulting from the hydrotreating stage b); the mixture is subsequently treated in an acid gas washing column and knockout drums. The liquid effluent obtained is then sent to a fractionation stage d) which comprises a stripping column. The yields of the various fractions obtained after separation and fractionation are shown in table 5 (the yields being corresponding to the ratios of the amounts by weight of the various products obtained, with respect to the weight of feedstock upstream of the stage a), expressed as percentage and denoted % w/w).

TABLE-US-00005 TABLE 5 Yields of the various products obtained after separation and fractionation NH.sub.3 + H.sub.2S % w/w 0.35 C.sub.1-C.sub.4 Fraction % w/w 0.50 IP-150° C. Fraction % w/w 28.10 150° C.+ Fraction % w/w 71.40 IP+ Fraction (mixture of the IP-150° C. and % w/w 99.50 150° C.+ fractions)

[0135] A part of the 150° C.+ fraction is recycled to the hydrotreating stage b) in the form of a recycle stream. The amount of 150° C.+ fraction is adjusted so that the ratio by weight of the recycled fraction to the fresh feedstock 1 is 1.

[0136] It appears that the temperature difference between the inlet and the outlet of the hydrotreating reaction section, the hydrotreating temperature (or mean hydrotreating temperature, WABT) being adjusted to 355° C., is reduced in comparison with a process in accordance with the invention but not comprising recycling of a fraction of the hydrocarbon effluent obtained. This means that the recycling of a fraction of the hydrocarbon effluent obtained makes it possible to control the temperature in the hydrotreating reaction section in which the reactions involved are highly exothermic.

[0137] The characteristics of the IP-150° C. and 150° C.+ liquid fractions (and also the IP+ fraction which is the sum of the IP-150° C. and 150° C.+ fractions) obtained after the separation stage c) and a fractionation stage are presented in table 6:

TABLE-US-00006 TABLE 6 Characteristics of the IP-150° C., 150° C.+ and IP+ fractions IP-150° C. 150° C.+ IP+ Analysis (method) Fraction Fraction Fraction Density @ 15° C. g/cm.sup.3 0.750 0.827 0.804 (ASTM D4052) Content of: Sulfur (ASTM D5453) ppm by weight <2 <10 <10 Nitrogen (ASTM ppm by weight <0.5 <5 <5 D4629) Fe (ASTM D5185) ppb by weight Not <50 <50 detected Total metals ppm by weight Not <1 <1 (ASTM D5185) detected Chlorine (ASTM ppb by weight Not <25 <25 D7536) detected Paraffins (UOP990-11) % by weight 68 65 66 Naphthenes % by weight 30.5 33 32 (UOP990-11) Olefins (UOP990-11) % by weight Not Not Not detected detected detected Aromatics % by weight 1.5 2 2 (UOP990-11) Simulated Distillation(ASTM D2687)  0% ° C. 25 150 25  5% ° C. 32 162 53  10% ° C. 40 174 92  30% ° C. 82 226 155  50% ° C. 108 281 227  70% ° C. 126 346 305  90% ° C. 142 395 391  95% ° C. 146 404 398 100% ° C. 150 432 432

[0138] The IP-150° C. and 150° C.+ liquid fractions both exhibit compositions compatible with a steam cracking unit since: [0139] they do not contain olefins (monoolef ins and diolefins); [0140] they exhibit contents of chlorine element which are very low (respectively a not detected content and a content of 25 ppb by weight) and below the limit required for a steam cracker feedstock (≤50 ppb by weight); [0141] the contents of metals, in particular of iron (Fe), are themselves also very low (contents of metals not detected for the IP-150° C. fraction and <1 ppm by weight for the 150° C.+ fraction; contents of Fe not detected for the IP-150° C. fraction and 50 ppb by weight for the 150° C.+ fraction) and below the limits required for a steam cracker feedstock (≤5.0 ppm by weight, very preferably ≤1 ppm by weight for metals; ≤100 ppb by weight for Fe); [0142] finally, they contain sulfur (<2 ppm by weight for the IP-150° C. fraction and <10 ppm by weight for the 150° C.+ fraction) and nitrogen (<0.5 ppm by weight for the IP-150° C. fraction and <5 ppm by weight for the 150° C.+ fraction) at contents which are far below the limits required for a steam cracker feedstock (≤500 ppm by weight, preferably ≤200 ppm by weight for S and N).

[0143] It also appears that the mixture of the two liquid fractions, named IP+, also exhibits very low contents of olefins and of contaminants (in particular of metals, chlorine, sulfur, nitrogen), making the composition compatible with a steam cracking unit.

[0144] The IP-150° C. and 150° C.+ liquid fractions obtained are thus subsequently sent to a steam cracking stage where the liquid fractions are cracked under different conditions (cf. table 7). The IP+ mixture can also be sent directly to a stage of steam cracking according to the conditions mentioned in table 7.

TABLE-US-00007 TABLE 7 Conditions of the steam cracking stage Pressure at furnace exit MPa abs. 0.2 Temperature at furnace exit of IP-150° C. fraction ° C. 800 Temperature at furnace exit of 150° C.+ fraction ° C. 790 Temperature at furnace exit of IP+ fraction ° C. 795 Steam/IP-150° C. fraction ratio kg/kg 0.6 Steam/150° C.+ fraction ratio kg/kg 0.8 Steam/IP+ fraction ratio kg/kg 0.7 Furnace residence time of IP-150° C. fraction s 0.3 Furnace residence time of 150° C.+ fraction s 0.3 Furnace residence time of IP+ fractions s 0.3

[0145] The effluents from the various steam cracking furnaces are subjected to a separation stage which makes it possible to recycle the saturated compounds to the steam cracking furnaces and to obtain the yields presented in table 8 (yield=% by weight of product with respect to the weight of each of the fractions upstream of the steam cracking stage, denoted % w/w).

TABLE-US-00008 TABLE 8 Yields of the steam cracking stage IP-150° C. 150° C.+ IP+ Fractions Fraction Fraction Fraction H.sub.2, CO, C.sub.1 % w/w 7.8 7.9 8.1 Ethylene % w/w 33.7 34.2 34.8 Propylene % w/w 18.3 18.6 19.0 C.sub.4 cut % w/w 14.6 14.8 15.1 Pyrolysis gasoline % w/w 19.8 19.4 18.8 Pyrolysis oil % w/w 5.7 5.1 4.2

[0146] By considering the yields obtained for the various IP-150° C. and 150° C.+ liquid fractions (and their IP+ mixture) during the process for the treatment of the pyrolysis oil (cf. table 5), it is possible to determine the overall yields of the products resulting from the steam cracking stage with respect to the initial feedstock of plastics pyrolysis oil type introduced in stage a):

TABLE-US-00009 TABLE 9 Overall yields for the process followed by the steam cracking stage IP-150° C. 150° C.+ IP+ Fractions Fraction Fraction Fraction H.sub.2, CO, C.sub.1 % w/w 2.2 5.6 8.0 Ethylene % w/w 9.5 24.4 34.7 Propylene % w/w 5.2 13.3 18.9 C.sub.4 cut % w/w 4.1 10.6 15.1 Pyrolysis gasoline % w/w 5.6 13.9 18.7 Pyrolysis oil % w/w 1.6 3.6 4.2

[0147] When the IP+ liquid fraction is subjected to a steam cracking stage, the process according to the invention makes it possible to achieve overall yields by weight of ethylene and propylene respectively of 34.7% and 18.9%, with respect to the amount by weight of initial feedstock of plastics pyrolysis oil type. When the IP-150° C. and 150° C.+ fractions are sent separately to the steam cracking unit, the process according to the invention makes it possible to achieve overall yields by weight of ethylene and propylene respectively of 33.9% (=9.5+24.4) and 18.5% (=5.2+13.3), with respect to the amount by weight of initial feedstock of plastics pyrolysis oil type.

[0148] Furthermore, the specific sequence of stages upstream of the steam cracking stage makes it possible to limit the formation of coke and to avoid the problems of corrosion which would have appeared if the chlorine had not been removed.

Example 2 (in Accordance with the Invention)

[0149] In this example, the fractionation stage includes, in addition to a stripping column, a distillation section so as to obtain a diesel cut which can be incorporated directly in a diesel pool, that is to say corresponding to the specifications required for a diesel and in particular the specification of T90 D86 at 360° C.

[0150] The feedstock to be treated is identical to that described in example 1 (cf. table 2).

[0151] It is subjected to the selective hydrogenation stage a), the hydrotreating stage b) and the separation stage c) carried out under the same conditions as those described in example 1. The liquid effluent obtained on conclusion of the separation stage c) is sent to a stripping column, as in example 1. On conclusion of the stripping column, the two IP-150° C. and 150° C.+ fractions are obtained, as in example 1. They have the same characteristics as those of example 1 (cf. table 6). The 150° C.+ fraction is sent to a distillation column where it is distilled into two cuts: a 150-385° C. cut and a 385° C.+ cut. A part of the 385° C.+ cut is recovered to constitute a recycle stream R which is sent to the hydrotreating stage b).

[0152] Similarly to the process described in example 1, the temperature difference between the inlet and the outlet of the hydrotreating reaction section is limited in comparison with a process without recycle.

[0153] Table 10 gives the overall yields of the various fractions obtained on conclusion of the separation stage c) and the fractionation stage d) (which comprises a stripping column and a distillation column).

TABLE-US-00010 TABLE 10 Yields of the various products obtained after separation and fractionation NH.sub.3 + H.sub.2S % w/w 0.35 C.sub.1-C.sub.4 Fraction % w/w 0.50 IP-150° C. Fraction % w/w 28.10 150-385° C. Fraction % w/w 60.90 385° C.+ Fraction % w/w 14.63

[0154] Table 11 gives the characteristics of the 150-385° C. and 385° C.+ cuts, and the EN-590 commercial specifications of a diesel.

TABLE-US-00011 TABLE 11 Characteristics of the 150-385° C. and 385° C.+ cuts, and EN-590 commercial specifications 150-385° C. 385° C.+ EN-590 Characteristics Units Cut Cut Specifications Density @ 15° C. g/cm.sup.3 0.824 0.844 0.820-0.845 Content of: Sulfur ppm by weight <10 <10 <10 Nitrogen ppm by weight <5 <5 Cetane Number D613 55.4 — >51 Cetane Index D4737A 54.4 — >46 Aromatics % by weight 2 2 <11 Simulated Distillation D2887  0 ° C. 152 377  5 ° C. 160 381  10 ° C. 171 383  30 ° C. 216 391  50 ° C. 263 398  70 ° C. 318 404  90 ° C. 369 420  95 ° C. 380 426 100 ° C. 390 429 Distillation D86  0 ° C. 181 402  5 ° C. 187 403  10 ° C. 193 396  30 ° C. 225 389  50 ° C. 262 384  70 ° C. 305 387  90 ° C. 344 394  95 ° C. 355 398 <360° C. 100 ° C. 358 395

[0155] Table 11 shows that the 150-385° C. cut has the qualities required to be sent directly to the diesel pool.

Example 3 (not in Accordance with the Invention)

[0156] In this example, the hydrocarbon feedstock of pyrolysis oil type identical to that used in example 1 is sent directly to a steam cracking stage.

[0157] The yields by weight of the various products obtained are calculated with respect to the initial feedstock (see table 12).

TABLE-US-00012 TABLE 12 Yields of the steam cracking stage H.sub.2, CO, C.sub.1 % w/w 7.7 Ethylene % w/w 33.1 Propylene % w/w 18.0 C.sub.4 cut % w/w 14.4 Pyrolysis gasoline % w/w 20.3 Pyrolysis oil % w/w 6.5

[0158] The yields of ethylene and propylene, obtained after direct steam cracking of the pyrolysis oil (process not in accordance with the invention) and presented in table 12, are lower than those obtained after steam cracking of a feedstock resulting from the treatment according to the process of the invention of the same plastics pyrolysis oil of example 1 (cf. table 8), which demonstrates the advantage of the process according to the invention. Additionally, the treatment of pyrolysis oil directly in a steam cracking furnace (example 2) resulted in increased coke formation, requiring premature shutdown of the furnace.