Note: Descriptions are shown in the official language in which they were submitted.
L-2lo8s
3q~7
ORGANO TRANSITION METAL SALT/ASHLESS
DETERGENT-DISPERSANT/PHENOLIC ANTIOXIDANT COMBINATIONS
Backaround of the Invention
Field of the Inven~ion
____
This invention relates to hydrocarbon-soluble
compositions containing a transition me~al salt of an or
ganic acid, a hydrocarbon solubie ashless dispersant, and a
phenolic antioxidant. Typically, it relates to such compo-
sitions wherein the organic acid is a carboxylic, sulfonic
or phosphorus acid, the ashless dispersant is a nitrogen or
non-nitrogen containing ester d:ispersan~ and the antioxidant
is a hindered phenol. It also relates to hydrocarbon sys-
tems containing the aforesaid compositions, such as lub-
ricants based on oils of lubricating viscosity and hydro-
carbon fuels,
Prior ~rt
The ~reatment of hydrocarbon systems such aslubricants based on lubricating oils of lubricating Vi5-
cosity (e.g., greases, lubricating oils and the like) and
hydrocarbon`fuels of both the solid and normally liquid type
with transition metals and transition metal-containing com-
pounds, both organic and inorganic~ is well known to the
art. Such treatments are used to increase the systems' re-
sistance to oxidative deterioration, promote their conver-
sion to cohe.Rlve films in the case of paints and lacquersand improve their combustion as, for example t fu ls.
Among the organic txansition metal compounds that
3 ~'t~
-- 2 --
have been used for such purposes are carboxylate and sul-
fona~e salts and mixtures of such sal~s. For example, U.S.
Patent 4,162,986 to Alkaitis, et. al. describes transition
metal salts of mixed organic carboxylic and sulfonic acids
or a second carboxylic acid and their use as catalysts,
an~i knock agents, combustion improvers, smoke suppressants,
curing agents, driers, micronutrient sources, lubricant
additives, and the like.
U.S. Patent 3,762,890 to Collins describes hydro-
lyzable mangane~e soaps~ stabilized by the inclusion ofpropionic acid and the use of such materials as siccatives
fox paints, varnishes and inks, stabilizers in various
plastics and additives for greases and lubricating oils as
well as smoke-suppressing and anti-corrosion additives for
15 ~uel and fuel oils.
U.S. Patent 3,723,152 to Alkaitis, et. al. de-
scribes basic cobalt salts of carboxylic acids and their use
as drier compositions for oil vehicles.
Other patents such as U.S. Patent 4,202,671 to
20 Diehl, et. alO describe the use of organic magnesium com-
pounds as fuel conditioners for the reduction of fuel re-
quirements and emiss~ons.
Incxeasing concern with pollution and the xising
cost of hydrocarbon-based fuels and lubricants ha~ promoted
25 continued interest in the use of transikion metal compounds
in such systems~ It has been found, however, that such u~e~
sometimes causes deleterious as well as beneficial effects.
Among the deleterious effects are promotion of ssdiment and
sludge, particularly in lubricants and fuel oils. Such
30 deposits can inter~ere with storage and transport of the oil
by promoting corrosion and interfering with pumps, meters
and associated equipment.
Therefore, it is an ob~ect of the present inven-
tion to provide hydrocarbon-soluble composi~ions containing
35 organic transition metal salts in combination with ashless
dispexsants, and phenolic antioxidants which provide an
optimum balance between beneficial and deleterious effects.
Other o~jects will be apparent to those of skill in the art
upon reading this disclusure.
Summary of the Inven~ _
It has now been found that useful hydrocarbon-
soluble compositions comprise (A) one or more transition
metal salts of at least one organic acid, (B) at least one
hydrocarbon soluble ashless dispersant and (C) at least one
phenolic antioxidant.
~ydrocarbon systems such as lubricant and fuel
compositions (such as distillate fuel composi~ions compris-
ing a ma~or amount of hydrocaxbon fuel and a minor amount of
the aforedescribed salt/dispersant/antioxidant composi-
tions), as well as additive concentrate compositions, are
15 also within the scope of the invention.
Detailed Description of the Invention
(A) The transition metal salts.
The transition metals in the organic salts of this
invention are chosen from the group consisting o copper,
20 scandium, titanium, vanadium, chromium, manganese, iron, co-
bal~, nickel and mixtures of two or more of these. Mangan-
ese salts and salts containing manganese in admixture with
other metals are most commonly u~ed. Often sal~s containing
only manganese are used. Lead salts can also be used.
- The organic acids used to make the transition
metal salts used in this invention con~ain carbon atoms and
include carboxylic acids, particularly those containing from
1 to 30 carbon atoms, sulfonic acids, particularly those
containing an aromatic ring structure (e.g., benzene ring)
30 substituted with one or more alkyl groups of 4 to about 22
carbon atoms, and phosphorus acids, containing within their
structures one or more organic groups of 1 to about 30 or
more carbon atoms.
Such carboxylic, sulfonic and phosphorus acids are
35 well known to the art. Tha carboxylic acids can be mono- or
polycarboxylic acids (if the latter, typically they are di-
or tricarboxylic acids). Monocarboxylic acids include Cl-7
lower acids (acetic, propionic, etc.) and higher C8+
acids (e.g., octanoic, decanoic, etc.) as well as the well
known fatty acids o:E about 12-30 carbon atoms. The fatty
acids are often mixtures of straight and branched chain
acids containing, for example, from 5 to about 30% straight
chain acids and about 70 to about 95% (mole) branched chain
acids. Other commercially available fatty acid mixtures
containing much higher proportions of straight chain acids
are also useful. Mixtures produced from dimerization of
unsaturated fatty acids can also be used.
Higher carboxylic acids include the well known
dicarboxylic acids made by alkylating maleic anhydride or
its derivatives. The products of such reactions are hydro-
carbon substi~uted succinic acids, anhydrides, and the like.
Lower molecular weight dicarboxylic acids, such as the
polymethylene bridged acids (glutaric, adipic, and the
like), can also be used to make the salts of this invention
as well as the lower molecular weight substituted succinic
acids such as -tetrapropenyl succinic acid and its analogs of
to about C30 substituted acids.
Higher molecular weight substituted succinic
anhydrides, acids, and analogs useful in making the salts
of this invention have been described in a number of patents,
particularly those dealing with acylated compounds useful
as dispersants. Typical high molecular weight acids are
those made by reacting a poly(isobutene) fraction having
between 30 and 400 (usually 50-250) carbon atoms with maleic
anhydride. Such materials are described in U.S. Patents
3,172,892, 3,219,666, and 3,272,746. Other mono-
carboxylic acids of similar molecular weight can be made
by alkylating acrylic acid and its analogs. Mixtures of
such acids can also be used.
Useful salts can also be made from carbocycli~
carboxylic acid and even acidic hydroxy compounds such as
alkylated phenols. Such materials are disclosed in U . S .
Patent 4,100,082, particularly columns 15-17.
-- 5
The '082 patent just idPntified also describes a
number of sulfonic acids which are useful in making the
salts of this invention particularly in col~s 12-14.
Transition metal salts made from phosphorus acids
are also useful in this invention. Such phosphorus acids
have been disclosed in a number of U.S. patents and other
literature. Exemplary of the former is U.S. Patent
4,191,658 which discloses pho~phorus acid salts of the
formula
x3
Rl(Xl)~
P-X M
R2 (X2) b/
wherein M i9 a transition metal as described above; each
and R2 is a hydrocarbon radical; each of Xl, x2, X3 and X4
is oxygen or sulfur; and each of a and b is 0 or 1.
Typically, the organic acids used to make the
salts of this invention are carboxylic acid, sulfonic acid,
or mixtures thereof. A particularly useful group of such
salts are those described in U.S. Patent 4,162,986 to
A~kaitis, et al.
It should be noted that the transition metal salts
used in this invention are often overbased; that is, they
~5 contain more khan sufficien~ m~tal to neutralize the acid
present. In other words, they contain in excess of one
equivalent of metal per equivalent of acid derived moiety.
~8~3~7
-- 6 ~
Such salts are known to the art. See, for example, the just
cited ~,162,986 patent as well as the :Eollowing U~S.
Patents: 3,~27,979 to Plotrowski, et. al., 3,312,618 to
LeSuer, et. al., 3,616,904 and 3,616,905 to Asseff, et. al.,
2,595,790 to Norman, et. al., and 3,725,~1 to Murphy, et.
al
(B) The ashless dispersants.
The ashless dispersants useful in the present
invention are known to the art and are those dispersants
commonly used in lubricants based on oils of lubricating
viscosity and hydrocarbon fuels such as normally li~uid
hydrocarbon fuels. Ashless dispersants are those which
leave little or no (metallic) residuQ or ash on combustion.
Generally, this means that they are substantially metal free
though they may contain, in addition to carbon, oxygen,
hydrogen and, often, nitrogen elements such as phosphorus,
sulfur, boron, etc.
Generally, the ashless dispersants of the present
invention contain only C, H, O, and N. Occasionally, ester
type dispersants (see below) can contain only C, H, and O.
More complex ashless dispersants, while still metal free,
may also contain other elements, such as sulfur, boron r
phosphorus, and the like. Typically, however, the ashless
dispersants used in this invention are of the nitrogen-
containing or nitrogen-free ester type.
Many types of ashless dispersants are known; see,
for example, the descriptions in ~lLubricant Additives -
Recent Developments" and the earlier "Lubricant Additives",
both by M.W. Ranney, published by Noyes Data Corporation,
Park Ridge, New Jersey, 1978 and 1973, respectively.
Among the more commonly available and, therefore,
useful hydrocarbon-soluble ashless dispersants are:
~c~
3~
(1) Acylated nitrogen-containing dispersants such
as those described in U.S. Patent 4,100,082, particularly
those at columns 18-20.
These dispersants are made by reaction of an
acylating agent (e.g. carboxylic acid or anhydride) with an
amino compound such as an amine, polyamine, or other
compound containing an -~H- group. Typical acylating agents
include the substituted succinic acids described above and
in the '082 patent. Other useful acylating agents have
been described in detail in many other patents, such as
UOS. Patent 4,234,435 which describes in detail both
acylating agents and amino-containing and non-amino-
containing compounds which can be used to prepare ashless
dispersants.
The acylated ashless dispersants useful in the present
invention can be of either the high or low molecular weight
type. In addition to portions from amino compounds, they
may also incorporate portions from mono- and poly- alcohols,
including amino hydroxy compound groups such as the well
known amino alcohols. Typical ashless dispersants
include those made from alkylene polyamines having 2 to 7
amino groups and 1 to 6 alkylene groups, each containing 2
to 4 carbon atoms. The commercially available ethylene
polyamines are useful reagents in this regard.
Lower molecular weight acylated nitrogen-containing
compounds are also useful as dispersants in the
compositions of this invention. Such compounds are made
from the aforedescribed amino compounds and mono- and
dicarboxylic acid acylating agents containing about 12 to
about 20 carbon atoms. Such dispersants often contain
imida~oline groups and are known to the art; see, for
example, U.S. Patents 3,405,064 and 3,240,575.
.~
High molecular weight acylated nitrogen-containing
ashless dispersants wherein an amino and alcohol compound
(or amino-alcohol) both are acylated are also known and
useful in the compositions of this invention; these are
described in U.S. Patent 4,136,043.
(2) High molecular weight nitrogen-free esters.
These esters, as indicated above, are made by
reactlng the aforedescribed acylating agents (e.g. poly-
(isobutene)) succinic anhydride with polyols and mono-
alcohols and are well known; see, for example, U.S. Patent
3,522,179 A
(3) Hydrocarbyl substituted amines.
Hydrocarbyl substituted amines useful as ashless
dispersants are known in the art; see, for example, U.S.
15 Patents 3,275,554, 3,438,7~7, 3,454,555, and 3,565,804.
A discussion of such materials also appears in the
aforementioned '082 patent.
(4) Nitrogen-containing condensates of phenols,
aldehydes and amino compounds.
Condensates made from reacting a phenol, aldehyde
(such as formaldehyde) and amino compounds ~such as those
described above) are useful as ashless dispersants in the
compositions of this invention. These materials are often
generically known as Mannich condensates. Generally, they
are made from reacting a hydrocarbon suhstituted phenol
(e.g., an alkylated phenol having an alkyl group of about
34-400 carbon atoms), formaldehyde and an amino or poly-
amino compound having at least one -NH- group. A number
of such materials are known to the art; see, for example,
the aforementioned '082 patent, particularly columns
21-22, and the references cited therein.
1~
3~7
(C) The phenolic antioxidants
As noted throughvut this specifica~ion and ap-
pended claims, the compositions of the present invention are
hydrocarbon soluble. To ensure this solubility, it is
necessary that the antioxidants used in combination with the
above descxibed tran~ition metal salts of organic acids,
component (A) and the ashle~s dispersants, component (~), be
compatible with said components and not cau~e precipita~ion
of the compo~ition~ and particularly the tran~ition metal
alt component. Antioxidants which were fo~nd to be com-
patible with the other components in the composition~
described and claimed herein and not cause precipitation of
the transition metal ~alt component comprise the class of
antioxidants commonly referred to as phenolic antioxidants
and preferably th~ hindered phenoli antioxidants. As used
herein, tne term "hindered phenolic antioxidants" means
phenolic antioxidant~ characterized by having at least one
substituent in at least one position oxtho to the phenolic
hydroxyl group. Specifically, the hindered phenols useful
in preparing the organo transition metal salt/ashless de-
tergent-di~persant/ phenolic antioxidant combination~ of
this invention ar~ hindered phenols and hindered bisphenols
corresponding to the general formulae
~H
X ~R ( I I )
wherein said R groups are hydrogen cr aliphatic hydrocarbon
radicals con aining from 1 to about 8 carbon atoms with the
proviso that at least one of said R groups is said aliphatic
nydrocarbon radical in a position ortho to the phenolic hy-
droxyl group and wherein X is a radical selected from thegroup consisting of alkylidene radicals containing from 1 to
about 4 carbon atoms and thio (-S-) and dithio (-S~S-) rad-
icals.
With re~pect to the hindered phenols and hindered
bisphenols defined immediately above the term "aliphatic
hydrocarbon" means saturated alkyl and cycloalkyl hydro-
carbons and by the term "alkylidene radical" is meant di-
valent hydrocarbon radicals derived from alkyl radicals in
which two hydrogen atoms are removed from the same carbon.
Among the hindered phenol~ and hindered bisphenols
useful in preparing the compositions of the present inven-
tion the preferred phenols are those in which at least one
of ~aid R group~ in the formulae above is a branched-chain
alkyl xadical, especially a~ the alpha carbon in said rad-
ical, in a position ortho to the phenolic hydroxyl group.
Particularly preferred hinderad phenols and hindered bis-
phenols are those in which two of ~aid R groups in the
formula àbove are branched-chain alkyl radicals, especially
at the alpha carbon in said radical, in both positions ortho
to the phenolic hydroxyl group.
Representative, but non-limited examples of
hindered phenols and hindered bisphenols corresponding to
the above formulae and useful in preparing the hydrocarbon
soluble compositions of this invention include 2-tert-
butylphenol; 2~ethyl-6-methylphenol; 2,6-di-tert-butyl-
phenol; 3-methyl-2,6-bis(l-methylethyl)phenol; 4-methyl-2,6-
di-tert-butylphenol; 3-methyl-2,6-bis(l-methylpropyl)phenol;
2-butyl-6-ethylphenol; 4-butyl-2,6-di tert-butylphenol; 4-
tert-butyl-2,6-dimethylphenol; 6-tert-butyl-2,3-d~methyl-
phenol; 2-tert-butyl-4-methylphenol; 2-cyclohexyl-6-tert-
butylphenol; 2-cyclohexyl-6-ter~-butyl-4-methylphenol; 2-
tert-butyl 4,6-dimethylphenol; 2,2'-methylenebis(4,6-di-
tert-bukylph~nol); 4,4'-methylenebis~2,6-di-tsrt~butyl
phenol~; 2,2'-methylenebis ~4,6-bis~ dimethylpropyl)-
phenolJ; 4,4'-methylenebis~2,6-bis(2-methylhexyl)phenol];
3,3'-m~thylenebis(2,6-di-tert-butyl-4-methylphenol); 4,4'-
propylideneb~s(2~tert-butylphenol); 2,2l-propylidenebis(6-
tert-butyl-4-methyl-phenol); 2,2'-ethylidenebls(4,6-di-~ert-
butylphenol); 4,4'-ethylidenebis(2,6-di-tert-butylphenol)i
4,4'-ethylidenebis(2-tert-butyl~6-methylphenol~; 2,2'-
butylidenebis(4,6-di-tert-butylphenol); 4,4'-butylidenebis-
(2-tert-butyl-3-methylphenol); 4,4'-butylidenebis(2-tert-
butyl-6-methylphenol); 2,4,6-~ri-tert-butylphenol; 2,4,6~
tris~l,l^dimethylbutyl)-~henol; 2,2'-thiobis(2,6-di-tert-
butylphenol); 4,4'-thiobis(2,6-di-tert-butylphenol); 3,3'-
thiobis(2,6-di-tert-butyl-4-methylphenol); 4,4'-~2-tert-
butyl-6-methylphenol); 4,4'-dithiobis(2,6-di-tert-butyl-
phenol); 4,4'-dithiobis(2,6-diisopropylphenol); 2,2'-di-
thiobis-[6-tert-butyl-4-methylphenol); 4,4'-dithiobist2-
tert-butyl-6-methylphenol) and the like.
The phenolic antioxidants described hereinabove
can be employed either singularly or as mixtures of two or
more of said phenolic antioxidants. Preferred phenolic
antioxidants for use in preparing the composi~ions of this
invention include 2,6-di-tert-bu~yl-4-methylphenol; 2,6-di-
tert-butylphenol; 2,6-di-tert-butylphenol, 2-tert-butyl
phenol; 4,4'-methylenebis(2,6-di-tert-butylphenol) and mix-
tures thereof.
The hydrocarbon-soluble compositions of this in~
vention are made by combining (A3 one or more of the afore-
descxibed transition metal salts of organic acids with (B)at least one of the aforedescribed hydrocarbon-soluble ash-
less dispersants and the combination of (A) and (B) with (C)
at least one of the aforedescribed phenolic antioxidants.
It should b.f~ noted that "hydrocarbon soluble" in describing
this invention means that the material in ~uestion has a
3~7
- 12 -
solubility at 25C. of at least 0.001 part~ by weight in the
hydrocarbon system in which it is to function. The combin-
ation of the materials (A) and (~ can be e~fected in any
convenient manner. Usually, it is advantageous to avoid
combining the salt and the dispersant directly since pre-
cipitation problems can thus be avoidedO Therefore, it is
common to combine either the dispersant or the salt with an
inert, solvent diluent and then combine this material with
the other and/or auxiliary agents. The solvent/diluents
used in the composition of this invention are usually hy-
drocarbyl in nature although they may contain small amounts
of other hetero elements and are often highly aromatic to
promote solubility. Auxiliary agents used in the composi-
tions of this invention include dyes, metal deactivators,
and, particularly, demulsifying agents which inhibit the
tendency of the dispersant and/or the salt to promote emul-
sion formations in the vehicles it i5 used ~o treat, such
as fuel oils, lubricants and the like. Many such demul-
sifying agents are known; see, for example, Encyclopedia of
Chemical Technology - Kirk-Othmer, Volume 8, pages 151 et
seq. and Volume 19, pages 507 et seq. (1965). Typical de-
mulsifying agents are surface active agents containing hy-
drophilic and lipophilic portions in the molecule. Such
agents are often made by reacting a hydroxy compound, such
as a phenol or alcohol, with materials such as ethylene
oxide and propylene oxide and ~heir mixtures in various
proportions.
As indicated above, the compositions of this in-
vention are used to treat lubricants based on lubricating
oils of lubricating ivscosity and hydrocarbon fuels. The
lubricating oils are typically hydrocarbon in nature al-
though they n.ay contain non-hydrocarby portions, such as
synthetic ester, ether, and similar oils.
The fuels treated with the compositions of thiq
invention include both solid and normally liguid fuels.
Among the solid fuels are coal, shale, peat, wood, organic
13 -
refuse, charcoal and the like. Liquid fuels encompass the
lighter petroleum fractions such as gasoline, kero~ene, and
the like, as well as other fractions such as middle dis-
tillaie fuel oils. Typical middle distillate fuel oils
which can be treated with the compositions in this invention
include No. 1, 2, and 4 fuel oils as defined by ANSI/ASTM
Standard D-396-97 and other such materials. Combinations of
such fuel oils with straight run, vacuum run, and other
specially treated residual oils can also be advantageously
treated with the combinations of the present invention,
The concentration of the compositions of this in--
vention in the treated lubricant or oil compositions is such
that the trea~ed lubricant or oil compositions contain about
1-500, preferably 5-350 ppm (by weight) transition metal*,
about 5-1000, preferably 10-800 ppm (by weiyht) ashless
dispersant and about 1-50, preferably 1-25 ppm (by weight)
phenolic antioxidant. In fuel oiLs, particularly, the
composition is used to produce a transition metal concen-
tration at about 5-200 ppm (by weight), an ashless dis-
persant concentration of about 15-450 ppm (by weight) and a
phenolic antioxidant concentration of about 1-15 ppm (by
weight).
EXAMPLES
A known ashless acylated nitrogen-containing dis-
per~ant iQ prepared by reacting a mixture of poly(isobutene)
:-~ substituted succinic anhydride acyla~ing agent (having a
substituent wi~h an Mn equal to about 1,OOO) with a commer-
cial mixture of ethylene polyamineQ averaging in composition
triethylene tetra-amine. The reaction is carried out in
aromatic solvent/diluent and the proportion of acid to
polyamine, by weight, i9 approximately 100 to 9; water and
other low-boiling products and impurities are removed by
heating to give the desired ashless dispersant having a
* The concentration of salt is expressed in terms of metal
alone.
33~
nitrogen content of about 2% ~by weight).
Exam~le 2
An intermediate composition is prepared by com-
bining by weight the following: an overbased manganese
carboxylate* (containing 40% by weight Mn) - 10.82 parts,
the ashless dispersan~ of Example 1 - 14.43 parts, a first
demulsifier** - 0.18 parts, a second demulsifier (3) - 0.14
parts, and aromatic solvent (4) - 74.43 par-ts. * Sold by the
Mooney Chemical Company as Mooney 910. ** An Ethoxylated/
Propylated Hydroxy Compound available as TOLAD 285 from The
Tretolite Division of Petrolite Corporatio~, St. Louis,
Missouri~ (3) ~n Ethoxylated Propoxylated Pentaerythritol
available as NALCO 5RD-648 from the Nalco Chemical Company
o~ Houston, Texas. (4) HI-SOL Aromatic Solvent having a
Kauri Gum-Butanol value of 95, The above combination is
made by using ~he aromatic solven~ in such a way as to avoid
direct combination of the concentrated carboxylate and
ashless dispersant. The combination has a specific gravity
at 15.6 of 0.94, a pour point of -57C., and a manganese
content of 4.3-4.6 percent by weight.
Example 3
A hydrocarbon soluble compo~ition is prepared by
combining 475.0 parts by weight of the intermediate compo-
sition of Example 2 with 25.0 parts by weight of the pheno~
lic an~ioxidant t 4,4'-methylenebis(2,6-di-tert-butylphenol)
under constant agitation at room temperature. Ag~tation is
continued until a clear solution is obtained.
~.
A hydrocarbon soluble composition is prepared by
combining 4~7.5 parts by weight of the intermediate compo-
sition of Example 2 with 12,5 parts by weight of the phe-
nolic antioxidant, 2,6-di-tert-butyl 4-methylphenol under
constant agi~ation at room tempera~urel Agitation is con-
tinued until a clear solution is obtained.
~
Two hydrocarbon soluble compositions are prepared
as follows: to one portion of 475.0 parts by weight of the
- 15 -
composition of Example 2 is combined 25.0 parts by weight of
a mixture of phenolic antioxidan~s comprised of 85.0 weight
percent of 2,4,6-tri-tert-butylphenol and 11.0 weight per-
cent of 2,6-di-ter~-butylphenol and available from the Ethyl
Corporation as Ethyl 735 and to another portion of 475.0
parts by weight of the composition of Example 2 is combined
25.0 parts by weight of a mixture of phenolic antioxidants
comprised of 75.0 weight percent of 2,4,6-di-tert-butyl-
phenol, 12.0 weight percent of 2,6-di-tert-butylphenol and
7.4 weight percent of 2-tert-butylphenol and available from
the Ethyl Corporation as Ethyl 733. In both preparations
the blending is carried out under constant agitation at room
temperature and said agitation is continued until clear
solutions are obtained,
~
The compositions of Examples 3, 4, and 5 are used
to treat a typical commercially available No. 2 middle dis-
tillate fuel oil. The treatment level in each instance is 1
part composition to 4600 parts by weight of fuel oil. This
treatment level is equivalent to 10.7 parts per million
manganese per part of fuel. The treated fuel is used to op-
erate a commercial boiler.
