METHOD FOR PURIFYING HYDROCARBON FEEDSTOCK IN AN AQUEOUS MEDIUM AND USE THEREOF

Abstract

Method for purifying a composition comprising a plastic liquefaction oil comprising a treatment by a strong base in the presence of water followed by washing with water. The method is useful for reducing the concentration of heteroelements and in particular of alkali or alkaline earth metal cations in said composition with a view to making it compatible for introduction as a feedstock in conversion methods such as steam cracking, catalytic cracking on a fluidised bed, catalytic hydrogenation or hydrocracking, in particular without deactivation of catalysts used in these methods.

Claims

1. Method for reducing the concentration of heteroatoms in a composition comprising a plastic liquefaction oil containing at least 20 ppm by weight of chlorine as measured according to the standard ASTM D7359-18, comprising: (a). placing said composition in contact with 0.1-50% by weight of a strong base comprising an alkali or alkaline-earth metal cation, in the presence of water, for 1 minute to 20 minutes at a temperature of at most 450 C., (b). washing the product coming from step (a) with water at neutral or acidic pH, (c). the product coming from the washing of step (b) undergoes a catalytic hydrogenation in one or two steps.

2. Method according to claim 1, wherein the composition further comprises an oil of pyrolysis or of hydrothermal liquefaction of biomass, in particular an oil of pyrolysis or of hydrothermal liquefaction of biomass such as of Panicum virgatum, a tall oil, a used food oil, an animal fat, a vegetable oil such as a colza, canola, ricin, palm, soybean oil, an oil extracted from an alga, an oil extracted from a fermentation of oleaginous microorganisms such as oleaginous yeast, an oil of pyrolysis or of hydrothermal liquefaction of biomass such as a lignocellulosic biomass such as an oil of pyrolysis of wood, of paper and/or of cardboard, an oil obtained by pyrolysis or hydrothermal liquefaction of ground used furniture, an oil of pyrolysis of elastomers for example of optionally vulcanised latex or of tires, as well as mixtures thereof.

3. Method according to claim 1, comprising between step (a) and (b) a step of separation between the strong base comprising the alkali or alkaline earth metal cation in solution in the water and the product coming from placing said composition in contact.

4. Method according to claim 3, wherein the separation step is carried out by (i) centrifugation, (ii) decantation, or (iii) by the combination of these two steps.

5. Method according to claim 3, wherein the strong base in solution in the water separated during the separation step is sent back, partly or in totality, into the step (a) of placing in contact.

6. Method according to claim 3, wherein the separation step is preceded by a step of separating the solids by (i) filtration, (ii) centrifugation or (iii) a combination of the two steps.

7. Method according to claim 1, wherein the placing in contact is carried out for a duration of 1 minute to 20 minutes, preferably 1 minute to 16 minutes, at a temperature of 50 to 450 C., preferably 50 to 350 C. or 90 to 350 C., more preferably 150 to 350 C., even more preferably 50 to 250 C. or 50 to 225 C. or 50 to 200 C., and at an absolute pressure of 0.1 to 100 bar, preferably 1 to 50 bar.

8. Method according to claim 1, wherein the strong base is chosen from LiOH, NaOH, CsOH, Ba(OH).sub.2, Na.sub.2O, KOH, K.sub.2O, CaO, Ca(OH).sub.2, MgO, Mg(OH).sub.2 and mixtures thereof.

9. Method according to claim 1, wherein, before the placing in contact of step (a), said composition is subjected to (i) a filtration, (ii) washing with a polar solvent, (iii) a distillation, (iv) a decantation, or (v) to the combination of two, three of four of steps (i) to (iv).

10. Method according to claim 1, wherein the catalytic hydrogenation of step (c) is carried out in a first step (c-1) in which the product coming from the placing in contact is hydrogenated at a temperature of between 2 and 200 C., preferably between 3 and 90 C. in the presence of hydrogen at an absolute pressure of between 5 and 60 bar, preferably between 20 and 30 bar and in the presence of a hydrogenation catalyst comprising Pd (0.1-10% by weight) and/or Ni (0.1-60% by weight) and/or NiMo (0.1-60% by weight), and in a second step (c-2) in which the effluent coming from step (c-1) is hydrogenated at a temperature of between 200 and 450 C., preferably between 20 and 340 C. in the presence of hydrogen at an absolute pressure of between 20 and 140 bar, preferably between 30 and 60 bar and in the presence of a hydrogenation catalyst comprising NiMo (0.1-60% by weight) and/or CoMo (0.1-60% by weight).

11. Method according to claim 1, wherein the product coming from step (b) or the effluent coming from step (c) is (d) purified by passing over a solid adsorbent in order to reduce the content of at least one element out of F, Cl, Br, I, O, N, S, Se, Si, P, As, Fe, Ca, Na, K, Mg and Hg and/or the content of water.

12. Method according to claim 11, wherein the adsorbent is used in regenerative or non-regenerative mode, at a temperature lower than 400 C., preferably lower than 100 C., more preferably lower than 60 C. chosen from: (i) a silica gel, (ii) a clay, (iii) a crushed clay, (iv) apatite, (v) hydroxyapatite and combinations thereof, (vi) an alumina for example an alumina obtained by precipitation of boehmite, a calcinated alumina such as Ceralox from Sasol, (vii) boehmite, (viii) bayerite, (ix) hydrotalcite, (x) a spinel such as Pural or Puralox from Sasol, (xi) a promoted alumina, for example Selexsorb from BASF, an acidic promoted alumina, an alumina promoted by a zeolite and/or by a metal such as Ni, Co, Mo or a combination of at least two of them, (xii) a clay treated with an acid such as Tonsil from Clariant, (xiii) a molecular sieve in the form of an aluminosilicate containing an alkali or alkaline earth cation for example the sieves 3A, 4A, 5A, 13X, for example marketed under the brand Siliporite from Ceca, (xiv) a zeolite, (xv) an activated carbon, or the combination of at least two adsorbents, the adsorbent or the at least two adsorbents retaining at least 20% by weight, preferably at least 50% by weight of at least one element out of F, Cl, Br, I, O, N, S, Se, Si, P, As, Fe, Ca, Na, K, Mg and Hg and/or of the water.

13. Method according to claim 12, wherein the adsorbent is regenerative, has a specific surface area of at least 200 m.sup.2/g and is used in a fixed-bed reactor at less than 100 C. with an SV of 0.1 to 10 h.sup.1.

14. Method according to claim 1, wherein at least a part of the product coming from step (b) or of the effluent coming from step (c) or (d) is: (e) treated in a steam cracker, and/or (f) treated in a fluidised-bed catalytic cracker, and/or (g) treated in a hydrocracker, and/or (h) treated in a catalytic hydrogenation unit, and/or (i) used as such or separated into flows usable for the preparation of fuels and combustibles such as GPL, gasoline, diesel, heavy fuel oil and/or for the preparation of lubricants.

Description

DESCRIPTION OF THE INVENTION

EXAMPLES

[0098] The embodiments of the present invention are illustrated by the following non-limiting examples.

Example 1: Purification of a Plastic Pyrolysis Oil in the Presence of a Strong Base and Water Followed by Washing with Water

[0099] The physico-chemical characteristics of the plastic pyrolysis oil used are described in table 1, below:

TABLE-US-00001 TABLE 1 Pyrolysis oil HPP2 Density (g/mL) 0.800 Kinematic viscosity (15 C., mm.sup.2/s) 2.1 Distillation, initial boiling point ( C.) 69 Distillation, 50% ( C.) 214 Distillation, final boiling point ( C.) 451 Silicon (mass ppm) 82 Chlorine (mass ppm) 96 Oxygen (mass %) 0.87 Nitrogen (ppm weight) 206

Trial Protocol:

[0100] A 1.5 L autoclave made of AISI-316L grade stainless steel equipped with mechanical stirring is loaded with the pyrolysis oil HPP2, a strong base in the form of NaOH and water, the strong base being dissolved in the water before its introduction into the autoclave (table 2). The sum of the volume of pyrolysis oil and of the volume of water introduced is approximately 600 mL at ambient temperature, without taking into account the possible effects of variation in volume during their mixture. The autoclave is closed and the headspace in the autoclave is swept with nitrogen for 30 minutes. The autoclave is then heated under autogenous pressure with stirring at a speed of 400 to 1500 rpm at a temperature of 225 C. for a duration of 1 minute, 10 minutes or 20 minutes according to the trials, once the target temperature has been reached. The speed of temperature rise is set to 30 C./10 minutes.

TABLE-US-00002 TABLE 2 Trial 1 2 3 Pyrolysis oil HPP2 HPP2 HPP2 Volume ratio water/feedstock 0.024 0.024 0.024 Temperature ( C.) 225 225 225 Time (min) 1 10 20 Volume of water (mL) 13.8 13.8 138.0 Mass of NaOH (g) 14.0 14.0 138.0 Mass of pyrolysis oil (g) 467.2 467.2 368.0 Initial volume pyrolysis oil (mL) 584 584 460 NaOH concentration in pyrolysis oil 3 3 3 (% m/m) NaOH concentration in water (% m/m) 50 50 50 Initial density (g/mL) 0.8 0.8 0.8 Final pressure in the autoclave (bar) 10 8 12

[0101] After the reaction, the autoclave is cooled to ambient temperature then, for trials 1 and 2, the mixture is unloaded and washed three times with water with, at each washing, a volume ratio of water/feedstock=40/60, to eliminate the residues of strong base and the impurities soluble in water. The resulting purified and washed pyrolysis oil is analysed to measure the content of residual impurities (table 3). For trial 3, the mixture unloaded from the autoclave is divided into two parts. The first part is washed with water in the same conditions as for trials 1 and 2 and the resulting purified and washed pyrolysis oil is analysed (trial 3A in table 3). The second part is decanted in order to recover the organic phase, which is then centrifuged. The resulting decanted and centrifuged pyrolysis oil is analysed (trial 3B in table 3).

TABLE-US-00003 TABLE 3 Trial 1 2 3A 3B Initial silicon (ppm weight) 80 80 80 80 Final silicon (ppm weight) <2 <2 <2 <2 Silicium reduction (%) >97 >97 >97 97 Initial chlorine (ppm weight) 115 115 115 115 Final chlorine (ppm weight) 32 24 23 23 Chlorine reduction (%) 72 79 80 80 Initial oxygen (% weight) 0.90 0.90 0.90 090 Final oxygen (% weight) 0.12 0.13 0.11 0.47 Oxygen reduction (%) 87 86 88 48 Initial nitrogen (ppm weight) 192 192 192 192 Final nitrogen (ppm weight) 31 29.8 30.0 43.6 Nitrogen reduction (%) 84 84 84 77 Initial sodium (ppm weight) <2 <2 2.5 <2 Final sodium (ppm weight) <2 <2 <2 1536

[0102] The data of table 3 shows that the use of sodium hydroxide in the presence of water followed by washing allows to considerably reduce the impurities initially contained in the pyrolysis oil as well as the sodium introduced by the treatment with sodium hydroxide, even for a short duration of treatment with sodium hydroxide.

[0103] In particular, it was observed that in the absence of washing, for example after a simple decantation/centrifugation, the content of sodium in the pyrolysis oil is high, in particular greater than 1000 ppm, which is not acceptable for a later catalytic treatment.

[0104] The pyrolysis oil can be either used as such, or optionally dried on an adsorbent such as a molecular sieve or an anhydride salt, for example Na.sub.2SO.sub.4, then is distilled under reduced pressure in order to eliminate any possible trace of solid, for example of strong base, of adsorbent residue, of anhydride/hydrated salt or of gums.

Example 2: Purification of a Plastic Pyrolysis Oil in the Presence of a Strong Base and Water Followed by Washing with Water

[0105] Another pyrolysis oil HPP8 was placed in contact with sodium hydroxide according to a trial protocol similar to that of example 1 in conditions gathered together in table 4. 450 g of HPP8 oil were thus placed in contact for 20 minutes at 180 C. with 22.5 g of NaOH dissolved in water.

TABLE-US-00004 TABLE 4 Pyrolysis oil HPP8 Volume ratio water/feedstock 0.05 Temperature ( C.) 180 Time (min) 20 Volume of water (mL) 22.5 Mass of NaOH (g) 22.5 Mass of pyrolysis oil (g) 450 Initial volume pyrolysis oil (mL) 563.2 NaOH concentration in pyrolysis oil (% m/m) 5 NaOH concentration in water (% m/m) 50 Initial density (g/mL) 0.799 Final pressure in the autoclave (bar) 8

[0106] After the reaction, the autoclave is cooled to ambient temperature, then the mixture is unloaded and washed three times with water with, at each washing, a volume ratio of water/feedstock=40/60, to eliminate the residues of strong base and the impurities soluble in water.

[0107] The data of table 5 shows that the use of sodium hydroxide in the presence of water followed by washing allows to considerably reduce the impurities initially contained in the pyrolysis oil as well as the sodium introduced by the treatment with sodium hydroxide, even for a temperature of treatment with sodium hydroxide lower than 200 C.

TABLE-US-00005 TABLE 5 Trial 4 Initial silicon (ppm weight) 93 Final silicon (ppm weight) <2 Silicium reduction (%) >98% Initial chlorine (ppm weight) 470 Final chlorine (ppm weight) 79 Chlorine reduction (%) 83% Initial oxygen (% weight) 1.49 Final oxygen (% weight) 0.22 Oxygen reduction (%) 85% Initial nitrogen (ppm weight) 1820 Final nitrogen (ppm weight) 157 Nitrogen reduction (%) 91% Initial sodium (ppm weight) Final sodium (ppm weight)

Example 3: Hydrotreatment in Two Steps and Steam Cracking of the Product of Example 1

[0108] One of the purified and washed pyrolysis oils of example 1 (coming from trials 1, 2 or 3A) or of example 2 (trial 4) can be hydrotreated in two steps according to the following procedure:

[0109] The purified and washed pyrolysis oil can be introduced into a first hydrotreatment section (HDT1) substantially to hydrogenate the diolefins and is operated in liquid phase. This step can comprise a plurality of reactors in series and/or parallel if guard reactors are used upstream or downstream of the first hydrogenation reactor. These guard reactors can allow to reduce the concentration of certain undesirable chemical species and/or of elements such as chlorine, silicon and the metals. Particularly undesirable metals include Na, Ca, Mg, Fe and Hg.

[0110] A second hydrotreatment section (HDT2) is dedicated to the hydrogenation of the olefins and to demetallation (HDM), desulphurisation (HDS), denitrification (HDN) and deoxygenation (HDO). HDT2 is operated in gas phase. This section consists of one or more reactors operated in series, lead-lad or parallel.

[0111] Since the hydrotreatment reactions in the sections HDT1 and HDT2 are exothermal, a quenching with cold hydrogen can be used to moderate the temperature increase and control the reaction.

[0112] Insulated guard reactors, in lead-lag, series and/or parallel are possible according to the nature and the quantity of the contaminant in the flow to be treated.

[0113] In the hypothesis in which the treatment of example 1 does not allow to obtain a sufficient reduction in impurities, guard reactors to eliminate the chlorine and the silicon can be operated in gas phase. The silicon can thus be trapped on the upper bed of a reactor of the section HDT2 or separately, upstream or downstream by the treatment of the hot gases exiting the section HDT2.

[0114] The chlorine and the mercury can be separated by guard reactors in liquid or gas phase.

[0115] There can be intermediate quenchings between the beds or between the reactors HDT1 and HDT2 or no quenching. In the latter case, a recycling of a part of the flow exiting HDT1 or HDT2 must be carried out to control the temperature. A strict control of the temperature in HDT1 must be carried out, in order to avoid the plugging of the reactor and the degradation of the catalytic hydrogenation conditions.

[0116] The operating pressure in each of the hydrotreatments HDT1 and HDT2 is 5-60 bar, preferably 20-30 bar for HDT1 and 20-140 bar, preferably 30-60 bar for HDT2, typically 30-40 bar for HDT2.

[0117] Typical temperature range at the inlet of HDT1 at cycle start (SOR: start of run): 150-200 C. The catalyst for HDT1 usually comprises Pd (0.1-10% weight) and/or Ni (0.1-60% weight) and/or NiMo (0.1-60% weight).

[0118] Typical temperature range at the inlet of HDT2 at cycle start (SOR: start of run): 200-340 C. Typical temperature range at the outlet of HDT2 (SOR): 300-380 C., up to 450 C. The catalyst for HDT2 usually comprises an NiMo (any type of commercial catalyst for refinement or petrochemical use), potentially a CoMo in the very last beds at reactor bottom (any type of commercial catalyst for refinement or petrochemical use).

[0119] The upper bed of HDT2 must be operated preferably with an NiMo having a hydrogenating capacity as well as a capacity for trapping silicon. An upper bed of this type can be considered to be an adsorbent as well as a metal trap also having an HDN activity and a hydrogenating capacity. An example of an acceptable upper bed for this function comprises the commercially available NiMo catalyst adsorbents such as ACT971, ACT981 from Axens or equivalents from Haldor Topsoe, Axens, Criterion, etc. It is possible to have two separate beds in a reactor HDT2, with a quenching between the two beds or between the two reactors, if the two beds are in two distinct reactors, or no quenching at all. Ideally, the intermediate quenching is carried out via the cold effluent of HDT2 or by an addition of cold hydrogen, that is to say at a temperature generally ranging from 15 to 30 C., in order to control the exotherm of HDT2. A dilution by recycling of the flow of hydrocarbon towards the upper bed of HDT2 is not recommended because of the increased risks of fouling of the bed. The feedstock arriving on the catalyst of HDT2 should be totally vapourised at all times, including in variable state as is the case during the start-ups. The sending of liquid hydrocarbons onto the upper bed of a reactor HDT2 can generate fouling and an increase in the pressure difference between the inlet and the outlet of said reactor HDT2 and lead to premature stoppage.

[0120] According to the metals present in the pyrolysis oil to be hydrotreated, a hydrodemetallation catalyst, for example commercial, can be added onto the upper bed of the section HDT2 in order to protect the lower catalytic beds against deactivation.

[0121] The hydrotreated pyrolysis oil exiting the section HDT2 can be used as such or fractioned according to the distillation temperature ranges, to feed a steam cracker, an FCC, a hydrocracker, a catalytic reformer or a pool of fuels or combustibles such as GPL, gasoline, jet, diesel, fuel oil.

[0122] Alternatively, the treated pyrolysis oil exiting the section HDT2 undergoes an additional step of purification by passing over a capture mass such as an adsorbent, for example (i) a silica gel, (ii) a clay, (iii) a crushed clay, (iv) apatite, (v) hydroxyapatite and combinations thereof, (vi) an alumina for example an alumina obtained by precipitation of boehmite, a calcinated alumina such as Ceralox from Sasol, (vii) boehmite, (viii) bayerite, (ix) hydrotalcite, (x) a spinel such as Pural or Puralox from Sasol, (xi) a promoted alumina, for example Selexsorb from BASF, an acidic promoted alumina, an alumina promoted by a zeolite and/or by a metal such as Ni, Co, Mo or a combination of at least two of them, (xii) a clay treated with an acid such as Tonsil from Clariant, (xiii) a molecular sieve in the form of an aluminosilicate containing an alkali or alkaline earth cation for example the sieves 3A, 4A, 5A, 13X, for example marketed under the brand Siliporite from Ceca, (xiv) a zeolite, (xv) an activated carbon, or the combination of at least two adsorbents, the adsorbent or the at least two adsorbents retaining at least 20% by weight, preferably at least 50% by weight of at least one element out of F, CI, Br, I, O, N, S, Se, Si, P, As, Fe, Ca, Na, K, Mg and Hg and/or of the water. Ideally, the adsorbent is regenerative, has a specific surface area of at least 200 m.sup.2/g and is used in a fixed-bed reactor at less than 100 C. with an SV of 0.1 to 10 h.sup.1.