CA1073674A

CA1073674A - Residual fuel oils

Info

Publication number: CA1073674A
Application number: CA245,279A
Authority: CA
Inventors: Gerardus P. Van Engelen
Original assignee: Shell Canada Ltd
Current assignee: Shell Canada Ltd
Priority date: 1975-03-06
Filing date: 1976-02-09
Publication date: 1980-03-18
Also published as: FR2303063A1; NL7602301A; DE2608971C2; ZA761325B; SE7603024L; SE415106B; JPS51111807A; DE2608971A1; FR2303063B1; JPS605637B2; GB1523597A

Abstract

A B S T R A C T

The invention relates to a residual fuel oil having a potential dry sludge content of not more than 0.1 %w in the case of a residual fuel oil having a viscosity of below about 1,000 Redwood I seconds at 100°F or having a potential dry sludge content of not more than 0.15 %w in the case of a residual fuel oil having a viscosity of above about 1,000 Redwood I
seconds at 100°F, comprising a major proportion of a thermally cracked residue and a diluent and a minor proportion of a dispersant additive, such as a metal salt of an alkyl salicylic acid. Due to the presence of the dispersant additive more severely cracked residues can be used.

Description

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The invention relates to stable residual fuel oils, It is known to prepare stable residual fuels from residues such as thermally cracked, i.e. visbroken, or catalytically processed short or long residues, and diluents such as distillate ~uels or oils, e.g. flashed distillates or gas oils. In general, these fuel oils may be classified into t~o types, namely those having viscosities of below about 15000 Redwood I seconds ~t 100F (type A) and those having viscosities of above about 1,000 Redwood I seconds ~t 100~F
(typ~ B).
Known stable residual ~uel oils are usually characterized by having a potential low dry sludge content. For example, it is usually specified that fuel oils of type A should have a potential dry sludge content of not more than 0.1 %w and that fuel oilæ of type B should have a potential dry sludge content of not more than 0,15 %w. The 15 percentages are based on the weight of the residual fuel oil. Fuel oils having potential dry sludge contents above these values may be described as potentially unstable.
The term "potential dry sludge content" means, insofar as this description is concerned, the potential flocculated asphaltene content 20 Or the fuel oil and does not mean ~ny extraneous matter which may enter the fuel oil during the manu~acture, transport, storage or use thereof. The potential dry sludee content i9 determined by the Shell Hot Filtration Test, which i8 described in the Journal of the Institute of Petroleum Vol. 37, No. 333, pages 596-604, September, 25 1951 after the residual fuel oil has been stored for 24 hours Qt 1 00 C .
In practice, the above specifications place little, if any con~traint on the conditions by which catrlytically processed short or long residues mdy be manufactured since they may be relatively e~sily met when the ~esidues are diluted by the usual range of diluents.
However, these specifications do constrain the conditions by which 3~i7~
thermally cr~cked residues m~y i)e manufactured since severe cracking, e.g. at higher temperature~ and/or for longer residence 1;imes than is usual, may result in cracked residues which when diluted by the usual range of diluents produce potentially unsta~le fuel oils.
This potential instability probsbly results from the higher amolmt of insoluble asphaltenes in severely cracked residues than in other types of residues.
This constraint on the severity of thermal cracking conditions is unfortunate because more se~ere thermal cracking condition~ are often desirable since they result in an increased production of Yaluable distillate fractions, such as middle distillate fractions.
Whether or not the conditions of thermal cracking may be regarded as severe depends upon the nature of the petroleum product being cracked, usually a long or short residue 9 and the nature anld amount of diluent with which it is blended. For example, a long residue derived from B naphthenic crude may be cracked more severely than a lon~ residue derived from a paraffinic crude since the components of the ~ormer are more capable of preventing the flocculation of asphaltenes. As another example, a long residue derived from say a paraffinic crude may be cracked more severely if the cracked residue is to be blended with a middle distillate having a high ~romatics contents than if it is to be blended with a middle di~tillate having a lcw aromatica content since the high aromatics content of the former i8 again more capable of preventing the rlocculating o~ asphaltenes~
Hence, cracking conditions may only he described as severe if ~hen a thermally cracked residue blended with a particular type and amount of diluent produces a potentially unstable residual fuel oil.
In practice, the cracking temperature for normal~v cracked residues i~ about 440C if the residence time is less than about 15 minutes; longer residence times would usu~lly be described as severe cracking. On the other hand, higher cracking temperatures 6``~

may be used for normally cracked residues provided the residence times are shorter, for example a cracking temperature of about 4~0C and a residence time of below 2 minutes would usually be described as normal cracking whereas a residence time of above 2 minutes at this temperature would usually be described as severe cracking.
The applicants have now disc~vered that by using dispersant additives, residual fuel oils are obtained containing a potential dry sludge content which is acceptable or on-specification but which, in the absence of the dlspersant additives, would contain a potential dry sludge content which is unacceptable or off-specification.
The present invention provides a residual fuel oil having a ;-potential dry sludge content of not more than 0.1 %w in the case of a re-sidual fuel oil having a viscosity of below about 1,000 Redwood I seconds at 100F or having a potential dry sludge content of not more than 0.15 %w in the case of a residual fuel oil having a viscosity of above about 1,000 Redwood I seconds at 100F, comprising a thermally cracked residue 20 - 80 %w of a diluent and 0.025 - 10 %w of a dispersant additive, which resiclual fuel oil, in the absence of the additive, would have a potential dry sludge content of above 0.1 %w in the case of a residual fuel oil having a viscosity of below about 1,000 Redwood I seconds at 100F or have a potential dry sludge content of above 0.15 %w in the case of a residual fuel oil having a viscosity of above about 1,000 Redwood I seconds at 100F.
I'he above residual fuel oils may be prepared by a process which comprises adding the additive to the thermally cracked residue, diluent or mixture thereof with the proviso that if the additive is added to the mixture the dry sludge content, if any, of the mixture should be below the specified amounts.
This dry sludge content or the dry sludge content at the moment of addition of the additive is also determined by the aforesaid test with the difference that it is determined just before the moment of addition of the additive and not after storage thereof for 24 hours.
The additives are preferably added to the thermally cracked ~:

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residue before it is mixed ~ith the diluent or added to a stable mixture of the cracked residue and diluent~s) (i.e. to a stable residual fuel oil) before the mixture is blended with further amounts of the same or different diluent(s) which~ in the absence of the additive, would produce a potentially -unstable residual fuel oil. In addition, the additive may be added to the diluent before it is blended with the ~hermally cracked residue. Moreover, the additive may be added to a potentially unstable residual fuel oil pro-vided that the dry sludge content, if any7 at the moment of addition does not exceed the permissable maximum i.e. it has been found that the additives are capable of arresting the further flocculation of asphaltenes even after some flocculation has occurred~
Examples of suitable diluents include cracked cycle oils, kerosene, gas-oils, flashed distillates and long and short residues. The amolmt of diluent in the residual fuel oil may vary between wide limits but usual amounts are from 20 to 80 %w.
Examples of suitable dispersant additives, which may be ash or -ash-less dispersants, include the oil-soluble organic acids or derivatives, such as salts thereof. In general such oil-soluble organic acids include substituted and unsubstituted aliphatic, cycloaliphatic and aromatic acids comprising the carboxylic acids, sulphur-containing acids for example sulphonic acids~ phosphoric acids and the corresponding thio-acids. Phenols and also partial esters of sulphur-containing and phosphorus-containing acids can also be employed.
The sulphonic acids (or salts thereof) which can be employed include the aliphatic-substituted cyclic sulphonic acids in which the aliphatic substituent or substituents contain at least twelve carbon atoms, for example alkylaryl sulphonic acids~ alkylcycloaliphatic sulphonic acids and alkyl-heterocyclic sulphonic acids for example: petroleum sulphonic acids and 29 cycloaliphatic sulphonic acids such as petroleum nap~hane sulphonic acids.

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The phosphorus acids (or salts thereof) which can be employed in the process of the present invention include tri- and pentavalent organic phosphorus acids (and the corresponding thio-acids), such, for example, as the aliphatic, cyclo-aliphatic and aromatic phosphoric and thiophosphoric acids having at least ~welve carbon atoms per molecule.
The phenols (or salts thereof~ which may be used in carrying out the present proc~ss include the octylphenols, dodecylphenols, octadecylphenols, diisopropylphenols, dihexylphenols, and the condensation products of phenols with aldehydes or ketones such as the condensation products of octyl phenol and formaldehyde.
The preferred organic acids or derivatives thereof are the organic carboxylic acids or derivatives of organic carboxylic acids.
Suitable organic carboxylic acids which may be used and/or organic carboxylic acids whose derivatives may be used as additives in the residual fuel oils~ include aliphatic, cycloaliphatic and aromatic carboxylic acids.
Preferred organic carboxylic acids are the alkyl aromatic acids such as the alkyl hydroxy ben~oic acids, e.g. those havin~ at least 8 carbon atoms in the alkyl group, petroleum naphthenic acids, and alkyl(ene) succinic acids such as those haYing at least 25 carbon atoms in the alkyl(ene) group.
Preferred additives include the C8 to C22 allcyl aromatic acids e.g.
the C8 to C22 allcyl salicylic acids. More preferred are the C14 to C18 alkyl salicylic acids.
Other preferred additives include the esters of such alkyl aromatic acids such as those derived from aliphatic and aromatic alcohols e.g. the naphthols. An example of such an additive is alphanaphthol alkyl salicylate.
Other preferred additives include the salts of such alkyl aromatic acids and of a naphthenic acid, in particular a petroleum naphthenic acid.
~uitable metal salts are salts of mono- or polyvalent metals but 29 preferably the metal is in the divalent state. Preferred metal salts are 3~i74 the salts of beryllium, magnesium7 calcium, sb~ntium or barium with metal salts of calcium or magnesium being particularly preferred. Specific examples of such salts include calcium or magnesium alkyl salicylates and calcium petroleum naphthenates. However metal salts of sodium,lithium, copper, zinc, aluminium, tin, chromium, cobalt, manganese, lead or nickel may also be used.
Mixtures of salts may also be used.
The salts may be neutral or basic. By the term "basic" is meant that the ~number of gram equivalents of metal in the salt ls greater than the number of gram equivalents of the acid. The basicity of such salts of poly-valent metals may be expressed in the formula (M-l)x100%, where M s~ands for the number of equivalents of metal and Z for the number of equi~alents of the carboxylic acid, for example per 100 grams of the basic metal salt. The basicity of the salt may be as high as 2,000%, whereas basicities of from 150 to 250% are preferred for basic salts of aromatic carboxylic acids and from 500 to 1,500% for basic salts of cycloaliphatic carboxylic acids.
Other preferred additives include the esters, amides or imides of the aforesaid alkyl(ene) succinic acids, e.g. polyisobutenyl succinic acids, uhich may be derived from such acids or the anhydri~;es thereof, by reac~ion thereof with alcohols, such as pentaerythritol, amines, hydroxyamines, imines etci. Examples of suitable alcohols include the polyols such as trimethylol propane, pentaerythritol etc. and examples of suitable amines include poly-amines such as polyalkylene polyamines e.g. tetrameth~lene pentamine~ Suit~
able esters i.e. alkyl(ene) succinates have a number average molecular weight of from 550 to 750 and suitable amides or imides i.e. alkyl(ene~ succinamides or polyalkyl(ene) succinimides have a number average molecular weight of from

2,000 to 4,000.
Mixtures of the additives may also be used. A particularly suitable mixture is a mixture of alkyl salicylates, e.g. calcium alkyl salicylate, and 9 a polyisobutenyl succinate. Another suitable mixture is a mix~ure of a ~ 3 ~ ~ ~

polyisobutenyl succinate and a polyisobutylene succinimide.
The additives may be added in amounts of up to 10 %w based on weight of res.idual fuel oil but amounts of from 0.01 to 5 %w, particularly from 0.025 to 2.0 ~w, are suitable.
The invention is now illustrated by reference to the following Examples.
In the Examples the residual fuel oils used were: -1) Residual Fuel Oil A comprising :
(I) 62~4 %w of a Kuwait thermally cracked residue prepared from a naphthenic short residue, having a viscosity of 25p00 Redwood I
seconds at 100 F, a density (15/4 C) of 1.0061 and a sulphur content of 4.94 %w, and (II) 37.6 %w of a diluent, comprising 5 pbw of n-hexadecene and 1 pbw of alpha-methylnaphthalene, having a density (15/4 C) of 0.8134 and a viscosity of 32 Redwood I seconds at 100 F.
The residual fuel oil A had a viscosity of 240 Redwood I seconds at 100 F.
2) Residual Fuel Oil B comprising (I) 50 %w of a Cura,cao fuel oil consisting of (a) 60 %w of a Cura~ao thermally cracked residue, prepared from a naphthenic short residue, (b) 18 ~Ow of a light cracked cycle oil, (c) 7 %w of a Bachaquero straight-run residue, and (d) 15 %w of a Sarir heavy gas oil; and (II) 50 %w of a Sarir fuel oil, of paraffinic origin consisting of (a) 50 %w of Sarir long residue, (b) 15 %w of Gamba long residue, and (c) 35 ~w of Sarir heavy gas oil.

29 The residual fuel oil B had a viscosity of 155 Redwood I seconds :~n~3~q~

at lOO F.

3) Residual Fuel Oil C comprising ~I) 47.6 %w of the Kuwait ther~ally cracked residue described above under residual fuel oil A, and (II) 52.4 ~Ow of an Oman heavy gas oil having a viscositv of 50 Uedwood I seconds at 100 F, a density ~15/4C) of 0.869 and a sulphur content of 1.04 ~w. Its initial boiling point was 233 C, its 50 ~Ov boiling point was 347 C and the recovery was 83 % at 370 C.
The residual fuel oil C ha~ a viscosity of 310 Redwood I seconds at 100 F.

4) Residual Fuel Oil D comprising (I) 70.5 %w of the ~uwait thermally cracked residue described above under residual fuel oil A, and ~' (II) 29.5 ~w of a Sarir flashed distillate having a viscosity of 75 Redwood I seconds at 100 F, a specific gravity (70/4 C) of 0.8235 and a sulphur content of 0.17 ~w.
The residual fuel oil D had a viscosity of 2,300 Redwood I seconds at 100 F.
EXAMPLES I TO XIV
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Doped residual fuel oils were prepared by adding one or more of the following additives in xylene to components (I) of the residual Euel oils before dilution thereof with component (II). The amounts of additives used are given in Table I. (The amounts are the amounts of 44 ~w of additive in xylene).
The additives used were as follows: -Additive A. An alkyl salicylic acid wherein the alkyl chain contains from 14 to 18 carbon atoms.
29 Additive B, The neutral calcium salt of the Additive A.
_g_ ' - ' ' ' ' ' ~ ~ ~ 3 ~ ~ ~

Additive C. The basic calcium salt of Additive A having a basicity of about 200 %.
AdditiVe D. The basic magnesium salt of Additive A having a basicity of about 200 %.
Additive E. The alpha-naphthyl ester of Additive Ao Additive F. 1 pbv of Additive A and 1 pbv of an ester of polyisobutenyl succinic anhydride and pentaerythritol wherein the ester has a Mn of about 6~0.
me potential dry sludge content of the undoped residual fuel oils and doped residual fuel oils I to XIV were determined by the Shell Hot Filtra-tion Test as described in the Journal of the Institute of Petroleum Vol. 37, No. 333 pages 596-604, September,1951. The doped or undoped residual fuel oi]s are first heated for 24 hours at 100 C. Care is taken that no extraneous matter had entered the oil. According to the method, Whatma~ No. 50 filter paper (diameter S5 mm) is first dried for 1 hour in a drying oven at about 105 C and stored in a glass container having a ground-in stopper. For analy-sis, one dried filter is weighed on a damped balance. The dried filter paper is placed on a felt disc resting on a perforated plate with a flat, raised edge. This assembly is then mounted over a vacuum flask and a heating jacket placed around the assemblyO Live steam is passed through the heating jacket.
10 g of doped or undoped residual fuel oil are then placed on the filter paper, the flask vacuated and air or nitrogen pressure applied to the filter paper~ as a result of which the fuel oil is filtered. Filtration is continued until air or nitrogen flows through the filter. After filtration is substantially complete water is passed through the heating jacket until the filter is cooled after which it is washed with firstly 5 ml n-heptane and secondly with a large amount of n-heptane whilst the flask is vacuated.
me filter paper is then removed, dried and weighed. The amount of dried sludge is then determined and expressed as ~w, based on weight of residual 29 fuel oil. m e results are expressed in Table I.
~-Trade Mark ~ -10-. .

:1~?~3t;'74 Doped residual fuel oils I, IV, V, VI, IX, XI, XIII and XIV were also examined microscopically (x80 to xlOO) after storage at 100 C for 24 hours and with the exception of doped fuel oil V, in which a small amount of flocculated asphaltenes was observed, no -lOa-.

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flocculated asphaltenes were detected. Microscopic ex~mination of the undoped residual ~uel oils, also after storage at 100C for 24 hours, revealed large amounts of flocculated asphaltenes.
The dry sludge con~ent of residual fuel oil A was also determaned by storing the oil at lOO~C and determining the dry sludge content, as described above, but after increasing ti~e intervals. Just a M er the determination, 1 %w of additive ~ was added to a separated amount of the fuel oil ~nd the potential dry sludge content of the thus doped fuel oil determined ~fter additional storage at 100C for 24 hours. It was found that the additive substantially prevents fu~ther flocculation o~ asphaltenes if the dry slud~e content thereof was below 0.1 %w i.e. in these cases the maximum potential dry sludge content of the doped fuel oil was substantiQlly the same as the dry sludge content of the undoped fuel oil.

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~able I

~xp. Residual Fuel Additive Amount of Dry sludge i~o. Oil type additive') content(%w) (%w of residual -fuel oil) _____ ____ ________ __________ ____________________ _______ - C - - 0.20 I C A 1.0 0.03 II C C 0.4 0.07 III C C o.6 0.04 IV C C 1.0 0.03 V C F 1.0 0.10 VI C F 1.0 0.02 - A - - 0.47 VII A C 0.4 o.o6 VIII A C o.6 0.05 _ B - ~ ~49 IX B C 1.0 o~o8 - D - - 0.17 X D C 0.1 0.07 XI D C 0.2 o.o6 XII D C 1.0 0.05 XIII A ~ 1.0 0.05 XIV A D 1.0 0.05 ========_=================_=====================_==_=========
') Amount of 44 %w additive in xylene.

EXAMPLE XV
A doped residual fuel oil composition was prepared by addin~
basic calcium petroleum naphthenate having a basieity of 1000%
(additive G) to component(I) of re~idual f'uel oi} C before it was diluted with component(II)- The amount used was 1.0 %w o~ 411 ~w additive in xylene based on residual fuel oil. The Shell Hot Filtration Test, as described above, was carried out on the undoped and do~ed residual fuel oils and the results were 0.2 %w and o.o6 %w 0~ dry s.ludge respectively. Microscopic observation of undoped residual fuel oil C and the doped residual ~uel oil after storage at 100C
~10 at 24 hours, revealed a lar~e amount and a small amount of flocculated asphaltenes respectively.

~ 3 EXAMPLES XYI to XVIII
Doped residual fuel oils were prepared by adding one or more of the followin~ additives to components (I) of the residual fuel o.ils before dilu-tion thereof with components(II). The amounts of additives used were 1 %w of 44 % additive in xylene, based on residual fuel oil.
The additives used were as follows.
Additive H. The reaction product of a polyisobutenylsuccinic anhydride and pentaerythritol having a Mn of about 670.
Addditive I. The reaction product of a polyisobuten~lsuccinic anhydride and pentaerythritol having a M of abaut 730.
Additive J~ A mixture of a reaction product of polyisobutenylsuccinic anhy-dride with pentaerythritol and a polyalkylene polyamine, having a molecular weight of about 3000.
The Shell Hot filtration Test, as descr:ibed above, was carried out on the doped and undoped residual fuel oils. The results are give:n in Table II~
Table II

Exp. No. Residual Fuel Additive Dry sludge conten~
Oil Type (a~w) _________ _____________ ________ __________________ -- A -- 0.47 XVI A H 0.06 XVII A I 0.07 __ C - 0.20 XVIII C J 0.08 - ' ' -13- :

. . . , , ,. , . . , . ~ .

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A residual fuel oil having a potential dry sludge content of not more than 0.1%w in the case of a residual fuel oil having a viscosity of below about 1,000 Redwood I seconds at 100°F or having a potential dry sludge content of not more than 0.15%w in the case of a residual fuel oil having a viscosity of above about 1,000 Redwood I seconds at 100°F, comprising a thermally cracked residue 20-80 %w of a diluent and 0.025 - 10 %w of a dispersant additive, which residual fuel oil, in the absence of the additive, would have a potential dry sludge content of above 0.1 %w in the case of a residual fuel oil having a viscosity of below about 1,000 Redwood I
seconds at 100°F or have a potential dry sludge content of above 0.15 %w in the case of a residual fuel oil having a viscosity of above about 1,000 Redwood I seconds at 100°F.

2. A residual fuel oil as claimed in claim 1, wherein said additive is an organic carboxylic acid or a derivative of an organic carboxylic acid.

3. A residual fuel oil as claimed in claim 2, wherein said additive is a C8 to C22 alkyl salicylic acid.

4. A residual fuel oil as claimed in claim 2, wherein said additive is an ester of a C8 to C22 alkyl salicylic acid.

5. A residual fuel oil as claimed in claim 2, wherein said ester is derived from a naphthol.

6. A residual fuel oil as claimed in claim 2, wherein said additive is a normal or basic salt of a C8 to C22 alkyl salicylic acid.

7. A residual fuel oil as claimed in claim 2, wherein said additive is a normal or basic salt of a petroleum naphthenic acid.

8. A residual fuel oil as claimed in claim 6 or claim 7, wherein said salt is a calcium or magnesium salt.

9. A residual fuel oil as claimed in claim 2, wherein said additive is a polyisobutenyl succinate and/or a polyisobutenyl succinimide.

10. A residual fuel oil as claimed in claim 9, wherein the succinate is derived from pentaerythritol.

11. A residual fuel oil as claimed in claim 10, wherein the succinimide is derived from a polyalkylene polyamine.