COMPOSITIONS, METHODS AND USES

Abstract

A composition including a pyrolysis oil and, as an additive: (a) one or more nitrogen containing antioxidants is disclosed. An additive composition for a pyrolysis oil including is also disclosed, the additive composition including (a) one or more nitrogen containing antioxidants; and optionally: (b) a copolymer including maleic anhydride derived units and -olefin derived units; and/or (c) the reaction product of a carboxylic acid and a polyamine. Also disclosed is a method of improving including the oxidation stability of a composition including a pyrolysis oil, the method including adding to the composition (a) one or more nitrogen containing antioxidants, and a related use of said nitrogen containing antioxidants. Such methods and uses are also disclosed for the improvement in storage stability of compositions including a pyrolysis oil.

Claims

1. A composition comprising a pyrolysis oil and, as an additive: (a) one or more nitrogen containing antioxidants.

2. The composition according to claim 1 wherein the pyrolysis oil is obtained from the pyrolysis of one or polymers selected from polyethylene, polypropylene, PET, rubber and mixtures thereof.

3. The composition according to claim 1 which comprises a blended fuel oil comprising a pyrolysis oil and a middle distillate fuel oil.

4. The composition according to claim 1, wherein component (a) comprises (i) acylated nitrogen compounds.

5. The composition according to claim 4, wherein component (i) comprises the reaction product of a polyisobutene-substituted succinic acid or succinic anhydride and a polyethylene polyamine.

6. The composition according to claim 1 wherein component (a) comprises (ii) phenylenediamines.

7. The composition according to claim 1 wherein component (a) comprises (iii) substituted hydroxylamines.

8. The composition according to claim 1, further comprising (b) a copolymer comprising maleic anhydride derived units and -olefin derived units.

9. The composition according to claim 8 which comprises a copolymer of maleic anhydride and a mixture of -olefins having 20 to 24 carbon atoms.

10. The composition according to claim 1, further comprising (c) the reaction product of a carboxylic acid and a polyamine.

11. The composition according to claim 9 which comprises the reaction product of one or more fatty acids having 10 to 36 carbon atoms and a polyethylene polyamine having from 2 to 8 nitrogen atoms.

12. An additive composition for a pyrolysis oil comprising: (a) one or more nitrogen containing antioxidants; and optionally: (b) a copolymer comprising maleic anhydride derived units and -olefin derived units; and/or (c) the reaction product of a carboxylic acid and a polyamine.

13. A method of improving the oxidation stability of a composition comprising a pyrolysis oil, the method comprising adding to the composition (a) one or more nitrogen containing antioxidants.

14. The method according to claim 13, further comprising adding to the composition: (b) a copolymer comprising maleic anhydride derived units and -olefin derived units; and/or (c) the reaction product of a carboxylic acid and a polyamine.

15. The method of claim 13, wherein (a) one or more nitrogen-containing antioxidants to improve the oxidation stability of a composition containing a pyrolysis oil.

16. The method of claim 14, wherein the (a) one or more nitrogen-containing antioxidants and (b) a copolymer comprising maleic anhydride derived units and -olefin derived units to improve the oxidation stability of a composition containing a pyrolysis oil.

17. The method of claim 14, wherein the (a) one or more nitrogen-containing antioxidants and (c) the reaction product of a carboxylic acid and a polyamine to improve the oxidation stability of a composition containing a pyrolysis oil.

18. A method of improving the oxidation stability of a composition comprising a pyrolysis oil and one or more nitrogen containing antioxidants, the method comprising adding to the composition: (b) a copolymer comprising maleic anhydride derived units and -olefin derived units; and/or (c) the reaction product of a carboxylic acid and a polyamine.

19. The method of claim 18, wherein the (b) copolymer comprising maleic anhydride derived units and -olefin derived units and/or (c) the reaction product of a carboxylic acid and a polyamine to improve the oxidation stability of a composition comprising a pyrolysis oil and one or more nitrogen containing antioxidants.

20. A method of improving the storage stability of a composition comprising a pyrolysis oil, the method comprising adding to the composition (a) one or more nitrogen containing antioxidants.

21. The method of claim 20, wherein the (a) one or more nitrogen-containing antioxidants to improve the storage stability of a composition containing a pyrolysis oil.

22. A method of improving the storage stability of a composition comprising a pyrolysis oil and optionally one or more nitrogen containing antioxidants, the method comprising adding to the composition: (b) a copolymer comprising maleic anhydride derived units and -olefin derived units; and/or (c) the reaction product of a carboxylic acid and a polyamine.

23. The method of claim 22, wherein the (b) copolymer comprising maleic anhydride derived units and -olefin derived units and/or (c) the reaction product of a carboxylic acid and a polyamine to improve the storage stability of a composition comprising a pyrolysis oil and optionally one or more nitrogen containing antioxidants.

Description

[0127] In some embodiments the diesel fuel composition used in the present invention further comprises a metal deactivating compound. Any metal deactivating compound known to those skilled in the art may be used and include, for example, the substituted triazole compounds of

[0128] FIG. (A) wherein R and R are independently selected from an optionally substituted alkyl group or hydrogen.

##STR00004##

[0129] Preferred metal deactivating compounds are those of formula (B):

##STR00005##

[0130] wherein R.sup.1, R.sup.2 and R.sup.3 are independently selected from an optionally-substituted alkyl group or hydrogen, preferably an alkyl group from 1 to 4 carbon atoms or hydrogen. R.sup.1 is preferably hydrogen, R.sup.2 is preferably hydrogen and R.sup.3 is preferably methyl. n is an integer from 0 to 5, most preferably 1.

[0131] A particularly preferred metal deactivator is N,N-disalicyclidene-1,2-diaminopropane, and has the formula shown in

[0132] FIG. (C);

##STR00006##

[0133] Another preferred metal deactivating compound is shown in

[0134] FIG. (D):

##STR00007##

[0135] Components (a), (b) and (c) are suitably included in the compositions of the first aspect in an amount based on the proportion of pyrolysis oil present in the composition. By this we mean that for a blended fuel, the treat rate of the additive is adjusted to take account of the amount of pyrolysis oil present in a blend. Thus if a component would be added to a neat pyrolysis oil in an amount of 500 ppm, a treat rate of 250 ppm would be used for a blended fuel comprising 50% pyrolysis oil.

[0136] The nitrogen containing antioxidant component (a) is preferably included in the composition of the first aspect in an amount of at least 10 ppm, preferably at least 20 ppm, more preferably at least 50 ppm, for example at least 70 ppm, based in each case on the proportion of pyrolysis oil present in the composition.

[0137] The nitrogen containing antioxidant component (a) may be included in the composition of the first aspect in an amount of up to 10000 ppm, preferably up to 5000 ppm, more preferably up to 2000 ppm, for example up to 1000 ppm, based in each case on the proportion of pyrolysis oil present in the composition.

[0138] Preferably the nitrogen containing antioxidant component (a) is present in the composition of the first aspect in an amount of from 1 to 10000 ppm, preferably 10 to 1000 ppm, preferably 50 to 750 ppm, more preferably 100 to 500 ppm, for example 150 to 400 ppm or 200 to 350 ppm, based in each case on the proportion of pyrolysis oil present in the composition.

[0139] In some embodiments, the nitrogen containing antioxidant component (a) is present in the composition of the first aspect in an amount of from 10 to 500 ppm, preferably 20 to 300 ppm, 50 to 200 ppm or 50 to 175 ppm, based in each case on the proportion of pyrolysis oil present in the composition.

[0140] In preferred embodiments component (a) comprises a mixture of (i) acylated nitrogen compounds, (ii) phenylenediamines and (iii) substituted hydroxylamines. These are suitably present in a ratio of 1 to 4 parts (i): 1 to 4 parts (ii): 2 to 6 parts (iii) by weight.

[0141] In preferred embodiments the composition of the first aspect comprises from 1 to 250 ppm, preferably from 10 to 150 ppm, for example from 50 to 100 ppm of (i) acylated nitrogen compounds; from 1 to 250 ppm, preferably from 10 to 150 ppm, for example from 50 to 100 ppm of (ii) phenylenediamines; and optionally from 1 to 500 ppm, preferably from 50 to 250 ppm, for example from 100 to 150 ppm of (iii) substituted hydroxylamines, based in each case on the proportion of pyrolysis oil present in the composition.

[0142] Copolymer component (b), when present, is preferably included in the composition of the first aspect in an amount of at least 10 ppm, preferably at least 20 ppm, more preferably at least 40 ppm, for example at least 50 ppm, based in each case on the proportion of pyrolysis oil present in the composition.

[0143] Copolymer component (b), when present, may be included in the composition of the first aspect in an amount of up to 10000 ppm, preferably up to 5000 ppm, more preferably up to 1000 ppm, for example up to 500 ppm, based in each case on the proportion of pyrolysis oil present in the composition.

[0144] Preferably the copolymer component (b), when present, is included in the composition of the first aspect in an amount of from 1 to 5000 ppm, preferably 5 to 1000 ppm, preferably 10 to 500 ppm, more preferably 20 to 300 ppm, for example 30 to 200 ppm or 50 to 150 ppm, based in each case on the proportion of pyrolysis oil present in the composition.

[0145] Component (c), when present, is preferably included in the composition of the first aspect in an amount of at least 10 ppm, preferably at least 20 ppm, more preferably at least 40 ppm, for example at least 50 ppm, based in each case on the proportion of pyrolysis oil present in the composition.

[0146] Component (c), when present, may be included in the composition of the first aspect in an amount of up to 10000 ppm, preferably up to 5000 ppm, more preferably up to 1000 ppm, for example up to 500 ppm, based in each case on the proportion of pyrolysis oil present in the composition.

[0147] Preferably component (c), when present, is included in the composition of the first aspect in an amount of from 1 to 5000 ppm, preferably 5 to 1000 ppm, preferably 10 to 500 ppm, more preferably 20 to 300 ppm, for example 30 to 200 ppm or 50 to 150 ppm, based in each case on the proportion of pyrolysis oil present in the composition.

[0148] The metal deactivator (d) may be optionally included in the composition in an amount of from 1 to 1000 ppm, preferably 5 to 500 ppm, for example 10 to 100 ppm.

[0149] In this specification any reference to ppm is to parts per million by weight.

[0150] In preferred embodiments, the first aspect of the present invention provides a composition comprising: a pyrolysis oil; from 100 to 500 ppm, preferably from 200 to 400 ppm of (a) one or more nitrogen containing antioxidants; and optionally from 10 to 400 ppm, preferably from 50 to 200 ppm of: (b) a copolymer comprising maleic anhydride derived units and -olefin derived units and/or (c) the reaction product of a carboxylic acid and a polyamine.

[0151] In some embodiments the composition of the first aspect may be used as a middle distillate fuel oil. Thus the composition may include one or more further additives such as those which are commonly found in diesel fuels. These include, for example, antioxidants, dispersants, detergents, metal deactivating compounds, wax anti-settling agents, cold flow improvers, cetane improvers, dehazers, stabilisers, demulsifiers, antifoams, corrosion inhibitors, lubricity improvers, dyes, markers, combustion improvers, metal deactivators, odour masks, drag reducers and conductivity improvers. Examples of suitable amounts of each of these types of additives will be known to the person skilled in the art.

[0152] According to a second aspect of the present invention there is provided an additive composition for a pyrolysis oil comprising: [0153] (a) one or more nitrogen containing antioxidants; and optionally: [0154] (b) a copolymer comprising maleic anhydride derived units and -olefin derived units; and/or [0155] (c) the reaction product of a carboxylic acid and a polyamine.

[0156] Preferred features of the second aspect are as defined in relation to the first aspect.

[0157] Preferably the additive composition comprises a diluent or solvent. Suitable diluents and solvents will be known to the person skilled in the art.

[0158] Preferred solvents include mixtures of aromatic solvents, for example xylene, aromatic 150 or aromatic 100.

[0159] In one especially preferred embodiment the additive composition of second aspect comprises: [0160] (a) nitrogen containing antioxidants including (i) acylated nitrogen compounds, (ii) phenylenediamines and (iii) substituted hydroxylamines; [0161] (b) a copolymer comprising maleic anhydride derived units and -olefin derived units; and/or [0162] (c) the reaction product of a carboxylic acid and a polyamine; and an aromatic solvent.

[0163] The use of additive component (a), optionally in combination with additives (b) and/or (c), has been found to improve the oxidation stability of pyrolysis oils.

[0164] There are a number of standard tests available for assessing the stability of diesel fuel, including ASTM D4625, ASTM D6468 and ASTM D2274.

[0165] The present inventors have measured the oxidation stability of the compositions of the present invention using the Rancimat test. This test is commonly used to assess the oxidation stability of biodiesel compositions. Like pyrolysis oils biodiesel comprises high levels of components which can be easily oxidised by atmospheric oxidation.

[0166] The Rancimat test is an accelerated oxidation test in which a sample is heated with air bubbling through. Volatile breakdown products pass over into deionised water and the conductivity of the water is measured. The time taken for fuel to breakdown is measured by recording the time at which an increase in conductivity is observed. This is known as the induction period.

[0167] To assess the oxidation stability of the pyrolysis oil compositions of the present invention the inventors followed the Rancimat test method set out in European standard EN 14112, the only difference being the nature of the fuel.

[0168] The use of additive component (a), optionally in combination with additives (b) and/or (c), has been found to improve the storage stability of pyrolysis oils. The storage stability of oils may be assessed using standard tests, such as ASTM D4625.

[0169] According to a third aspect of the present invention, there is provided a method of improving the oxidation stability of a composition comprising a pyrolysis oil, the method comprising adding to the composition (a) one or more nitrogen containing antioxidants.

[0170] The method may optionally further comprise adding to the composition: [0171] (b) a copolymer comprising maleic anhydride derived units and -olefin derived units; and/or [0172] (c) the reaction product of a carboxylic acid and a polyamine.

[0173] According to a fourth aspect of the present invention, there is provided the use of (a) one or more nitrogen-containing antioxidants to improve the oxidation stability of a composition containing a pyrolysis oil.

[0174] The fourth aspect of the present invention may involve the use of (b) a copolymer comprising maleic anhydride derived units and -olefin derived units; and/or (c) the reaction product of a carboxylic acid and a polyamine in combination with (a) one or more nitrogen-containing antioxidants to improve the oxidation stability of a composition containing a pyrolysis oil.

[0175] Preferred features of the third and fourth aspects, including the nature of the composition, and the nature of components (a), (b) and (c) and suitable treat rates thereof, are as defined in relation to the first aspect.

[0176] The method and use of the present invention suitably increase the oxidation stability of a composition comprising a pyrolysis oil as measured by the Rancimat test.

[0177] Preferably the use of (a) a nitrogen-containing dispersant increases the induction time as measured by the Rancimat test of a composition containing a pyrolysis oil by at least 50%, preferably at least 100%, more preferably at least 150%, for example at least 200% or at least 300%.

[0178] The use of (a) a nitrogen-containing dispersant may increases the induction time as measured by the Rancimat test of a composition containing a pyrolysis oil by at least 2 hours, preferably at least 4 hours, suitably at least 6 hours.

[0179] In some embodiments the use of (a) a nitrogen-containing dispersant may increases the induction time as measured by the Rancimat test of a composition containing a pyrolysis oil by at least 8 hours, preferably at least 10 hours, suitably at least 12 hours

[0180] Suitably the use of (b) a copolymer comprising maleic anhydride derived units and -olefin derived units and/or (c) the reaction product of a carboxylic acid and a polyamine in combination with (a) one or more nitrogen-containing antioxidants increases the oxidation induction time as measured by the Rancimat test of a composition comprising a pyrolysis oil by at least 50%, preferably at least 100%, more preferably at least 150%, for example at least 200% or at least 300%.

[0181] Suitably the use of (b) a copolymer comprising maleic anhydride derived units and -olefin derived units and/or (c) the reaction product of a carboxylic acid and a polyamine in combination with (a) one or more nitrogen-containing antioxidants increases the oxidation induction time as measured by the Rancimat test of a composition comprising a pyrolysis oil by at least 2 hours, preferably at least 4 hours, suitably at least 6 hours.

[0182] In some embodiments use of (b) a copolymer comprising maleic anhydride derived units and -olefin derived units and/or (c) the reaction product of a carboxylic acid and a polyamine in combination with (a) one or more nitrogen-containing antioxidants increases the oxidation induction time as measured by the Rancimat test of a composition comprising a pyrolysis oil by more than 8 hours, for example more than 10 hours or more than 12 hours.

[0183] In a fifth aspect the present invention provides a method of improving the oxidation stability of a composition comprising a pyrolysis oil and one or more nitrogen containing antioxidants, the method comprising adding to the composition: [0184] (b) a copolymer comprising maleic anhydride derived units and -olefin derived units; and/or [0185] (c) the reaction product of a carboxylic acid and a polyamine.

[0186] In a sixth aspect the present invention provides use of (b) a copolymer comprising maleic anhydride derived units and -olefin derived units and/or (c) the reaction product of a carboxylic acid and a polyamine to improve the oxidation stability of a composition comprising a pyrolysis oil and one or more nitrogen containing antioxidants.

[0187] Preferred features of the fifth and sixth aspects, including the nature of the composition, and the nature of components (a), (b) and (c) and suitable treat rates thereof, are as defined in relation to the first aspect.

[0188] According to a seventh aspect of the present invention, there is provided a method of improving the storage stability of a composition comprising a pyrolysis oil, the method comprising adding to the composition (a) one or more nitrogen containing antioxidants.

[0189] The method may optionally further comprise adding to the composition: [0190] (b) a copolymer comprising maleic anhydride derived units and -olefin derived units; and/or [0191] (c) the reaction product of a carboxylic acid and a polyamine.

[0192] According to an eighth aspect of the present invention, there is provided the use of (a) one or more nitrogen-containing antioxidants to improve the storage stability of a composition containing a pyrolysis oil.

[0193] This eighth aspect of the invention may involve the use of (b) a copolymer comprising maleic anhydride derived units and -olefin derived units; and/or (c) the reaction product of a carboxylic acid and a polyamine in combination with (a) one or more nitrogen-containing antioxidants to improve the storage stability of a composition containing a pyrolysis oil.

[0194] In a ninth aspect the present invention provides a method of improving the storage stability of a composition comprising a pyrolysis oil and one or more nitrogen containing antioxidants, the method comprising adding to the composition: [0195] (b) a copolymer comprising maleic anhydride derived units and -olefin derived units; and/or [0196] (c) the reaction product of a carboxylic acid and a polyamine.

[0197] In a tenth aspect the present invention provides use of (b) a copolymer comprising maleic anhydride derived units and -olefin derived units and/or (c) the reaction product of a carboxylic acid and a polyamine to improve the storage stability of a composition comprising a pyrolysis oil and one or more nitrogen containing antioxidants.

[0198] The methods and uses of the seventh, eighth, ninth and tenth aspects of the present invention suitably improves the storage stability of a composition comprising a pyrolysis oil as measured by the standard method of ASTM D4625 and/or by said standard method as modified to be conducted at ambient temperature using 200 ml samples of the pyrolysis oil. Said improvement in storage stability suitably results in/is provided by a reduction in the amount of adherent insoluble material produced by the pyrolysis oil on storage, compared to a comparable unadditised pyrolysis oil, and/or a reduction in the total amount of insoluble material produced by the pyrolysis oil on storage, suitably as measured by the methods referred to above.

[0199] In some embodiments, the methods and uses of the seventh, eighth, ninth and tenth aspects provide at least a 30% reduction in the amount of adherent insoluble material produced by the pyrolysis oil on storage, compared to a comparable unadditised pyrolysis oil, suitably at least a 70% reduction, at least an 80% reduction or at least a 90% reduction in said amount of adherent insoluble material, suitably as measured by ASTM D4625 and/or by said standard method modified as described herein.

[0200] In some embodiments, the methods and uses of the seventh, eighth, ninth and tenth aspects provide at least a 30% reduction in the amount of total insoluble material produced by the pyrolysis oil on storage, compared to a comparable unadditised pyrolysis oil, suitably at least a 40% reduction, at least a 50% reduction or at least a 60% reduction in said amount of total insoluble material, suitably as measured by ASTM D4625 and/or by said standard method modified as described herein.

[0201] Preferred features of the seventh, eighth, ninth and tenth aspects, including the nature of the composition, and the nature of components (a), (b) and (c) and suitable treat rates thereof, are as defined in relation to the first aspect.

[0202] Any feature of any aspect of the invention may be combined with any other aspect, as appropriate.

[0203] The invention will now be further described by way of the following non-limiting examples.

EXAMPLE 1

[0204] Additive compositions comprising the following components were prepared:

TABLE-US-00001 TABLE 1 Component Composition 1 Composition 2 Composition 3 PIBSI A 28 15 15 (wt % active) Phenylenediamine 10 15 15 (wt % active) Metal deactivator B 2 (wt % active) Diethylhydroxylamine 25 25 (wt % active) Copolymer C 18 (wt % active) Imidazoline D 18 (wt % active) Aromatic 150 (wt %) 27 27 Aromatic 100 wt % 60

[0205] PIBSI A is polyisobutenyl succinimide obtained from the condensation reaction of a polyisobutenyl succinic anhydride derived from polyisobutene of Mn approximately 750 with a polyethylene polyamine mixture of average composition approximating to tetraethylene pentaamine.

[0206] Metal deactivator B is N,N-disalicyclidene-1,2-diaminopropane.

[0207] Copolymer C an alternating copolymer of maleic anhydride and a mixture of -olefins having 20 to 24 carbon atoms. The number average molecular weight is 15000 Da.

[0208] Imidazoline D is the reaction product of diethylene triamine and tall oil fatty acid.

EXAMPLE 2

[0209] Compositions 1, 2 and 3 from example 1 were dosed into a waste rubber (waste tyre) pyrolysis oil having the following specification:

TABLE-US-00002 TABLE 2 Method Test Result ASTM D4052 API Gravity at 60 F., API 24.2 ASTM D4294 Total Sulfur Content, mg/kg 8800 Total Sulfur Content, % 0.880 (m/m) ASTM D5762 Nitrogen, ppm (m/m) 4800 ASTM D5622 Total Oxygen, % (m/m) 3.00 ASTM D7169 IBP, F. 145 5% Recovered, F. 209 10% Recovered, F. 232 20% Recovered, F. 277 30% Recovered, F. 338 40% Recovered, F. 408 50% Recovered, F. 482 60% Recovered, F. 564 70% Recovered, F. 651 80% Recovered, F. 759 90% Recovered, F. 879 95% Recovered, F. 953 98% Recovered, F. 1010 Recovery, % 100 FBP, F. 1046 ISO 10370 Micro Method Carbon 0.34 Residue, % (m/m) ISO 6245 Ash, % (m/m) 0.001 UOP938 Mercury, ppb (m/m) 4.69 IP 501 Aluminum, mg/kg <5 Silicon, mg/kg <10 Sodium, mg/kg 3 Vanadium, mg/kg <1 Nickel, mg/kg <3 Zinc, mg/kg 12 Iron, mg/kg 10 Manganese, mg/kg <5 Lead, mg/kg <10 Arsenic, mg/kg <1

[0210] The induction period of the base waste rubber pyrolysis oil was measured using the method set out in EN 14112. 500 ppm of compositions 1, 2 and 3 were separately dosed into three further samples of the waste rubber pyrolysis oil and the Rancimat test was repeated.

[0211] The results are shown in table 3:

TABLE-US-00003 TABLE 3 Additive composition Treat rate (ppm) Induction time (h) None 0 2.3 1 500 16.4 2 500 23.3 3 500 >40

EXAMPLE 2

[0212] Additive compositions 1, 2 and 3 from Example 1 were dosed at 500 mg/l into the waste tyre pyrolysis oil having the specification described above to provide oil pyrolysis oil compositions 1, 2 and 3, respectively. These samples were tested for storage stability against an unadditised sample of the waste rubber pyrolysis oil, using a modification of the standard method of ASTM D4625. The standard method was modified by conducting the tests at ambient temperature instead of 43 C. and by using 200 ml samples of the pyrolysis oils instead of 400 ml samples. The method provides amounts of filterable insoluble material, adherent insoluble material and total insoluble material in each sample.

[0213] The amounts of insoluble material recovered (filterable and adherent) for each composition, including the total amounts, are shown in Table 4:

TABLE-US-00004 TABLE 4 Additive composition Filterable Adherent Total (treat rate, insoluble Insoluble Insoluble Oil sample mg/l) (mg/100 mL) (mg/100 mL) (mg/100 mL) Unadditised 0.0107 0.3137 0.3244 1 1 (500) 0.1066 0.0026 0.1092 2 2 (500) 0.1599 0.0044 0.1643 3 3 (500) 0.0980 0.0034 0.1014

[0214] These results show a significant reduction in the amount of adherent insoluble material produced by the plastic pyrolysis oil on storage when the additives of the present invention are used. The results for samples 1, 2 and 3 (at 500 mg/l treat rate) also show a significant reduction in the total amount of insoluble material produced on storage. These additives may therefore be effective in improving the storage stability of a pyrolysis oil.