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.

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) 2 , Na 2 O, KOH, K 2 O, CaO, Ca(OH) 2 , MgO, Mg(OH) 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 2 /g and is used in a fixed-bed reactor at less than 100° C. with an SV of 0.1 to 10 h −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.