Note: Descriptions are shown in the official language in which they were submitted.
L945
The use of certain lactones or lactone reaction products as rust
and corrosion inhibitors in hydrocarbon oil compositions is known. Thus,
such a material as tetrapropenylsuccinic acid lactone has exhibited
effectiveness as a rust inhibitor in gasoline.
The alkenylsuccinic acid lactones have been prepared by reacting
an alkenylsuccinic acid with a hydrating mineral acid, such as 50 percent
sulfuric acid, dilute hydrochloric acid or dilute sulfuric or phosphoric
acid. In general, the reaction has been conducted at an elevated temper-
ature ranging up to about 212F. and in the presence of a nonpolar solvent,
such as hydrocarbon i.e. naphtha, kerosene or the like. A feature of the
known process is that the catalyst for the reaction has been employed in a
hydrating environment, i.e. in an aqueous solution, such as 50 percent
aqueous sulfuric acid or other dilute aqueous mineral acids.
The conventional method for preparing a lactone reaction product
is relatively inefficient and produces a low yield of the desired product.
In particular, the conventional method gives a poor yield of a lactone
reaction product in which the alkenyl radical on the alkenylsuccinic acid
reactant is a high molecular weight radical having from about 300 to 3,000
average molecular weight.
United States 3,248,187 discloses a hydrocarbon oil composition
which has been inhibited against rust by the addition thereto of a lactone
reaction product. This reference discloses the process of reacting an
alkenyl succinic acid in the presence of a dilute aqueous mineral acid and
a hydrocarbon solvent at an elevated temperature to produce an alkenyl
substituted lactone reaction product.
The method of the invention which is effective for preparing a
relatively high molecular weight alkenyl substituted lactone reaction
product comprises reacting an alkenylsuccinic acid in which the alkenyl
radical has an average molecular weight ranging from about 300 to 3,000 in
the presence of a protonating agent and under substantially anhydrous
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reaction conditions at an elevated temperature up to about 100 C. until a
substantial proportion of the alkenylsuccinic acid has been converted to
the lactone reaction product.
~ lus, the invention provides a method for preparing a high
molecular weight alkenyl-substituted lactone reaction product which
comprises admixing an alkenylsuccinic acid, said alkenyl radical having an
average molecular weight ranging from about 300 to 3,000 with a protonating
agent or electron pair acceptor in a concentration sufficient to provide
from about 0.25 to 1.5 moles of protons or electron pair acceptors per mole
of said alkenylsuccinic acid to form an essentially anhydrous mixture and
reacting said mixture under essentially anhydrous reaction conditions at an
elevated temperature up to about 100C. until infrared spectra at about
5.66 and 5.74 micro meters indicates the conversion of said alkenylsuccinic
acid to said lactone reaction product.
The invention further provides a motor fuel composition comprising
a mixture of hydrocarbons in the gasoline boiling range containing a minor
amountof the lactone reaction product prepared according to the method of
the invention.
In carrying out the method of the invention, a high molecular
weight alkenylsuccinic acid, in which the alkenyl radical has a molecular
weight ranging from about 300 to 3,000, is advantageously admixed with an
electron pair acceptor or a protonating agent to form a reaction mixture.
The protonating agent is generally a concentrated mineral acid and can be
added next to the alkenylsuccinic acid-containing reaction mixture. The
temperature of the reaction mixture is then raised up to about 100 C. to
promote lactone formation while maintaining substantially anhydrous reaction
conditions. The reaction is continued under these conditions for sufficient
time to effect conversion of a substantial portion of the reactant to a
laclone reaction product. It is convenient to follow the process of the
reaction by withdrawing samples during the reaction and subjecting them ~o
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infrared radiation. The formation of alkenyl substituted 5 and 6 membered
ring lactone reaction products is shown by infrared radiation at 5.66 and
5.74 micrometer regions. Thus, by utilizing the infrared analysis or
correlated reaction times, it is possible to insure conversion of a major
portion or substantially all of the alkenylsuccinic acid to a lactone
reaction product.
The alkenylsuccinic acid reactant employed in this process is
represented by the following formula:
R - CH - COOH
CH2 - COOH
in which R represents an alkenyl radical having an average molecular
weight ranging from about 300 to 3,000. A more preferred reactant is an
alkenylsuccinic acid in which the alkenyl radical has an average molecular
weight from about 700 to 2,000. The most preferred reactants are those al-
kenylsuccinic acids in which the alkenyl radical has an average molecular
weight ranging from about 800 to 1,200.
It will be understood that the prescribed alkenylsuccinic acid
reactant can be prepared from the corresponding alkenylsuccinic anhydride.
Specifically, an alkenylsuccinic anhydride and water can be reacted in
equimolar amounts to form the prescribed alkenylsuccinic acid reactant in
accordance with known methods. Thus, the present invention contemplates
that an alkenylsuccinic anhydride can be employed as a precursor to the
reactant in this process by undergoing the hydrolysis reaction noted.
This process is also conveniently conducted by dissolving the
prescribed alkenylsuccinic acid in an inert non-hydrating solvent such as a
hydrocarbon solvent. A suitable solvent is a mineral oil having an SUS
viscosity at 100F. ranging from about 50 to about 1,000. Other suitable
hydrocarbon solvents for this process include kerosene, benzene, ~ylene and
the like.
The interesterification reaction or formation of a lactone
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reaction product in the present invention is conducted in the presence of
an acid catalyst. The catalyst may be any protonating agent or electron
pair acceptor i.e. any material which can provide a hydrogen ion or accept a
pair of electrons to catalyze the reaction. The protonating agent or
electron pair acceptor employed should provide from about 0.25 to 1.5 moles
of protons or electron acceptors per mole of the alkenylsuccinic acid being
reacted although smaller or larger amounts can be employed with compromises
in efficiency and/or economy. It is preferred to employ a protonating agent
or electron pair acceptor which provides from about 0.5 to 1 moles of proton
or electron pair per mole of alkenylsuccinic acid. These ranges can be also
expressed as 0.25 to 1.5 or 0.5 to 1 equivalents of acid per mole of the
alkenylsuccinic acid moiety.
A variety of protonating agents or electron pair acceptors can be
employed in the present process. Included among these are the mineral
acids such as sulfuric acid and perchloric acid. Organic acids including
p-toluene sulfonic acid hydrate, electron pair acceptors such as boron
trifluoride etherate, and solid acid catalysts such as sulfonic acid ion
exchange resins are suitable. There appears to be criticality in the
catalyst since formic acid, oxalic acid and aqueous hydrochloric acid are
either inoperative or have little effect on the process.
The reaction is normally conducted at a temperature ranging from
about 25C. up to about 100C. with a range from about 60 to ~100 C. being
especially suitable. A preferred temperature range for this process is from
about /0 to 98C. Highly efficient conversions have been realized
e~mploying a temperature in a preferred range, namely from about 85 to 95C.
A temperature of 100C. or above should be avoided because these temperatures
tend to decrease conversion and lead to the production of undesirable
reaction products.
A critical feature of the process of this invention for the
production of a high molecular weight alkenyl substituted lactone reaction
product is that it be conducted under substantially anhydrous conditions.
The reactant, solvent and the catalyst or the protonating agent must all
be selected so as to insure substantially anhydrous and preferably
essentially anhydrous reaction conditions. By substantially anhydrous
reaction conditions is meant that the reaction mixture should contain no
more than about 5 percent water. It is preferred that this mixture contain
no more than about 2 percent water with the most preferred situation being
an essentially anhydrous reaction mixture. The surprising improvement in
yield of high molecular weight alkenyl substituted lactone reaction product
is attributed to the use of the described substantially anhydrous reaction
conditions.
The following example illustrates a known lactone process
employing an unconventional high molecular weight polyisobutenylsuccinic
acid:
EXAMPLE I
POLYISOBUTENYLSUCCINIC ANHYDRIDE REACTION
USING AQUEOUS MINERAL ACID
To a solution of 126 g. of a 50 wt.% oil solution of crude
polyisobutenylsuccinic acid (prepared from polyisobutene of 1300
molecular weight and maleic anhydride by thermal alkenylation with about
50% unreacted polyisobutene) in 125 ml. of hexane, 100 g. of 50 wt.% sulfuric
acid in water was added. The mixture contained about 0.025 moles of
polyisobutenylsuccinic acid and about 0.5 moles of sulfuric acid or about
1.0 moles of available protons. After stirring one hour at about 25C. an
aliquot is diluted with water, extracted with hexane, and the hexane extract
separated. Infrared analysis of the residue obtained by evaporation of the
hexane under nitrogen with mild heating shows lactone and anhydride formation
to an incomplete degree. After four hours the temperature of the mixture
was 29C. and an infrared analysis as above showed much less anhydride and
lactone formation compared to the one-hour sample.
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The mixture was then heated to reflux. The mixture temperature
was about 74C. Infrared analysis after 80 minutes of refluxing (method as
above) indicated small amounts of lactone and anhydride were formed, but
that the starting material, polyisobutenylsuccinic acid was predominately
unchanged. After 17 hours and 20 minutes of refluxing, infrared analysis
indicated relatively little change in reaction mixture composition as compared
to the 80-minute reaction mixture composition.
The mixture was cooled to room temperature and washed with water
and co-solvents until the wash water was about a pH of 5. The organic
phase was separated and flash evaporated. The residue was held at 95C. at
about 20 mm Hg pressure for about 12 hours to remove solvent traces. By
infrared analysis the final product appears to be largely
polyisobutenyl succinic acid with a small amount of anhydride present and
little if any lactones. The amount of lactones present cannot be greater
than 15 mole % and are probably less than 5 mole %.
Upon repeating this ex~mple, no change was noted in the starting
material by infrared analyscs at 15, 30 60 and 90 minutes in the initial
phase (25C) described above and this work was discontinued.
The following examples illustrate the novel process of this
invention:
EXAMPLE II
A mixture of 126 g. (0.025 mole) of crude polyisobutenylsuccinic
acid (containing about 50% unreacted polyisobutene of about 1300 average mole-
cular weight) in a 50 wt.% mineral oil solution and 1.25 g. (0.0125 mole)
of sulfuric acid is mixed at 90C~ for three hours. The infrared spectrum
of the product indicates high conversion to five and six membered lactones.
The yield of lactones is greater than 85 mole %.
EXAMPLE III
A mixture of 2,570 g. (1.0 mole) of crude polyisobutenyl succinic
anhydride (containing about 50% unreacted polyisobutene of about 1300
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average molecular weight) and 25 g. (0.25 mole) of about 96% aqueous
sulfuric acid and 18 g. (1.0 mole) of water were heated and stirred at 90C.
for about one hour and then allowed to cool to room temperature. The
mineral acidity can be removed by extraction but the product can be used
without further purification. Infrared analysis indicates high conversion
to lactones as in Example II.
EXAMPLE IV
A mixture of 1058 g. (0.5 mole) of crude polypropenylsuccinic
anhydride (containing about 50% unreacted polypropene of about 850 average
molecular weight) were heated to about 90C. with stirring. Over a period
of about four minutes, 21.5 g. of a solution consisting of 12.5 g. of
about 96% sulfuric acid and 9.0 g. (0.5 mole) of water were added
dropwise. After four hours the mixture was allowed to cool. This product
has similar strong lactone absorptions in its infrared spectrum to
Example I and gave the following analysis.
ASTM D-94 Saponification Number 94.5
ASTM D-974 Total Acid Neut. Number 55.0
Iodine Number 7.8
Average Molecular Weight
(by vapor pressure osmometry) 955
EXAMPLE V
A mixture of 270 g. (1.0 mole) of tetrapropenylsuccinic anhydride,
18.0 g. (1.0 mole) of water, and 51.5 g. (0.5 mole) of about 96% sulfuric
acid and 100 ml. of xylene were heated to reflux at atmospheric pressure
for two hours and allowed to coo~. The product was mixed with ethyl ether
and hexane and the organic phase extensively washed with water until the pH
of the aqueous extract was repeatably between 4 and 5. The organic
raffinate was filtered through diatomaceous earth, flash evaporated, and
stripped of traces of solvent in a vacuum oven to obtain 260.1 g. of
product. The infrared spectrum of the product indicated high conversion to
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five and six membered lactones by strong absorptions at 5.66 and 5.74
micrometers.
EXAMPI,E_VI
A mixture of 377.5 g. (0.05 mole) of crude polyisobutenylsuccinic
anhydride (containing about 31% unreacted polyisobutene of about 400
average molecular weight) 12.5 g. (0.125 mole) of about 96% sulfuric acid,
and 9.0 g. (0.5 mole) of water were heated to about 90C. with stirring for
one hour and allowed to cool. The product was washed free of mineral
acidity by extraction and weighed 360.9 g. after handling-solvent
evaporation. The product exhibited the same strong lactone absorptions in
its infrared spectrum as the product of Example II.
Examples II through VI illustrate the effectiveness of the novel
process of this invention for providing a substantial yield of high
molecular weight alkenyl substituted lactone reacticn products in contrast
to prior methods. The lactone reaction products of this process are
particularly effective as dispersants in motor fuel compositions.
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