Process and composition for stabilized distillate fuel oils

This invention relates to processes and compositions for stabilized distillate fuel oils, such as straight-run diesel fuel, which comprise an effective stabilizing amount of (a) N-(2-aminoethyl)piperazine, (b) triethylenetetramine, and (c) N,N-diethylhydroxylamine.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to stabilized distillate fuel oils. More 
particularly, this invention relates to inhibiting color deterioration and 
particulate formation in distillate fuel oils, such as straight-run diesel 
fuel. 
2. Description of the Prior Art 
Various middle distillate fuel oils tend, with time, to deteriorate. 
Normally, distillate fuel oils are stable during standing. However, some 
distillate fuel oils that contain abnormally high levels of organic acid 
and sulfur containing species can be quite unstable and may deteriorate. 
This deterioration usually results in the formation of sediment, sludge, 
or gum and objectionable color deterioration during transportation and 
storage. This fuel oil deterioration is caused, in part, by the presence 
of oxygen in the storage tank containing the fuel oil. Resulting oxidation 
of the fuel oil manifests itself in the appearance of darker colors, gum 
and the like. Sediment formation may cause clogging of fuel system 
equipment such as filters, screens, nozzles, burners and other associated 
equipment. This problem may be further aggravated when cracked material is 
blended with distillate fuels. Discoloration of distillate fuel oils is 
objectionable for various reasons, including customers' preference for 
light colored fuel oils because discoloration may indicate that 
deterioration has occurred. 
Suggestions of the prior art for stabilizing fuel oils include U.S. Pat. 
No. 2,672,408, Bonner, which discloses the use of oil-soluble 
water-insoluble amines, the general formula of which can be represented 
as: N(R).sub.3, wherein R can be hydrogen or the same or different 
hydrocarbon radicals with at least one R being a non-aromatic hydrocarbon 
radical, for protection of particular blends of liquid hydrocarbons 
against discoloration. Also, U.S. Pat. No. 2,742,349, McCoy, discloses the 
use of arylamine antioxidants and sundry. substances derived from the 
class of piperazines for protecting various organic materials from 
deterioration in the presence of oxygen. U.S. Pat. No. 2,945,749, Andress, 
discloses the use of a tertiary alkyl, primary, monoamine having from 
about 4 to 24 carbon atoms and in which the primary nitrogen atom is 
directly attached to a tertiary carbon atom, for inhibiting fuel oil 
deterioration in storage. U.S. Pat. No. 3,017,258, Pollitzer, teaches the 
use of the reaction product of an amine compound, having at least 12 
carbon atoms and a straight chain of at least three carbon atoms attached 
to the nitrogen atom, with an epihalohydrin compound for retarding 
deterioration of burner oil. U.S. Pat. No. 3,049,414, Kruyff, discloses a 
process for stabilizing the color of gasoline comprising the steps of 
washing the gasoline with a liquid characterized as being free of heavy 
metals and capable of dissolving pyridine; washing with alkaline aqueous 
solution, characterized as being free of heavy metals; removing 
substantially all the free alkali; and then adding an organic nitrogenous 
base, all of whose carbon-carbon bonds are saturated. U.S. Pat. No. 
3,129,699, teaches the use of heterocyclic polyamine salts of organic 
acids to improve the ignition characteristics of diesel fuel. Also, U.S. 
Pat. No. 3,198,730, Goodrich, discloses the use of a solid sulfuric acid 
catalyst composition for treatment of catalytically cracked hydrocarbon 
distillates boiling up to and including the gas oil boiling range. 
Additionally, U.S. Pat. No. 3,490,882, Dunworth, relates to stabilized 
petroleum distillate fuel oils containing N,N-dimethylcyclohexylamine and, 
optionally, an N,N'-di(orthohydroxyarylidene)-1, 2-alkylenediamine. U.S. 
Pat. No. 3,640,692, Rakow, et. al., discloses a stabilized distillate 
hydrocarbon fuel oil composition comprising a major proportion of a 
distillate hydrocarbon fuel and a minor proportion of a stabilizer 
comprising (a) an additive selected from the group consisting of (1) an 
amide plus a Schiff base; (2) an amide containing a Schiff base group; and 
(3) an amide containing a Schiff base group in combination with either an 
amide or a Schiff base; and (b) a cyclohexylamine selected from the group 
consisting of N,N-dimethylcyclohexylamine and dicyclohexylamine. Also, 
U.S. Pat. No. 3,701,641, discloses a stabilized distillate hydrocarbon 
fuel oil composition comprising a major proportion of a distillate 
hydrocarbon fuel and a minor proportion of a stabilizing additive 
comprised of (a) a polyamine having 2 to about 6 amino groups and 
containing about 24 to 50 carbons; (b) 
N,N'-disalicylidine-1,2-propylenediamine, and (c) a cyclohexylamine 
selected from the group consisting of N,N-dimethylcyclohexylamine and 
dicyclohexylamine. Of particular interest is U.S. Pat. No. 3,818,006, 
Klemchuk, which discloses the use of sundry substituted hydroxylamines for 
stabilizing diverse organic materials against oxidation. Additionally, 
U.S. Pat. No. 4,509,952, relates to an alkyldimethylamine ranging from 
C.sub.4 -C.sub.20 alkyl which may be added to a distillate fuel as a 
stabilizer to prevent fuel oil degradation. However, none of these prior 
art references disclose the unique and effective mixture of 
N-(2-aminoethyl)piperazine, triethylenetetramine and 
N,N-diethylhydroxylamine for inhibiting the color degradation and 
particulate formation of distillate fuel oils. 
SUMMARY OF THE INVENTION 
This invention relates to processes for stabilizing distillate fuel oil 
which comprises adding to the distillate fuel oil an effective stabilizing 
amount of a mixture of (a) N-(2-aminoethyl) piperazine, (b) 
triethylenetetramine, and (c) N,N-diethylhydroxylamine. This invention 
also relates to stabilized distillate fuel oil compositions comprising 
distillate fuel oil and an effective stabilizing amount of (a) 
N-(2-aminoethyl)piperazine, (b) triethylenetetramine, and (c) 
N,N-diethylhydroxylamine. More particularly, the processes and 
compositions of this invention relate to inhibiting particulate formation 
and color deterioration of distillate fuel oils. Generally, the total 
amount of the mixture of (a), (b), and (c) is from about 1.0 part to about 
10,000 parts per million parts of the fuel oil. It is preferred that the 
weight ratio of (a):(b) is from about 1:3 to about 3:1, the weight ratio 
of (a):(c) is from about 1:3 to about 3:1, and the weight ratio of (b):(c) 
is from about 1:3 to about 3:1. This mixture of (a), (b), and (c) provides 
an unexpectedly higher degree of stabilization of distillate fuel oils 
than the individual ingredients comprising the mixture. It is therefore 
possible to produce a more effective stabilizing composition and process 
than is obtainable by the use of each ingredient alone. Because of the 
enhanced stabilizing activity of the mixture, the concentrations of each 
of the ingredients may be lowered and the total amount of (a), (b), and 
(c) required for an effective stabilizing treatment may be reduced. 
Accordingly, it is an object of the present invention to provide processes 
and compositions for stabilizing distillate fuel oils. It is another 
object of this invention to inhibit particulate formation in distillate 
fuel oils. It is a further object of this invention to inhibit color 
deterioration of distillate fuel oils. These and other objects and 
advantages of the present invention will be apparent to those skilled in 
the art upon reference to the following description of the preferred 
embodiments.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention pertains to a process for stabilizing distillate fuel 
oil, such as straight-run diesel fuel, which comprises adding to the 
distillate fuel oil an effective stabilizing amount of a mixture of (a) 
N-(2-aminoethyl)piperazine, (b) triethylenetetramine, and (c) 
N,N-diethylhydroxylamine. The amounts or concentrations of these three 
components of this invention can vary depending on, among other things, 
the tendency of the distillate fuel oil to undergo deterioration or, more 
specifically, to form particulate matter and/or discolor. While from the 
disclosure of this invention it would be within the capability of those 
skilled in the art to find by simple experimentation the optimum amounts 
or concentrations of (a), (b), and (c) for any particular distillate fuel 
oil, generally the total amount of the mixture of (a), (b), and (c) which 
is added to the distillate fuel oil is from about 1.0 part to about 10,000 
parts per million parts of the distillate fuel oil. Preferably, the 
mixture of (a), (b), and (c) is added in an amount from about 1.0 part to 
about 1,500 parts per million. It is also preferred that the weight ratios 
of: (a):(b) is from about 1:3 to about 3:1; (a):(c) is from about 1:3 to 
about 3:1; and (b):(c) is from about 1:3 to about 3:1, based on the total 
combined weight of these three components. Most preferably, the weight 
ratio of (a):(b):(c) is about 2:1.5:1.5 based on the total combined weight 
ratio of these three components. 
The aforementioned three components, (a), (b), and (c), are all presently 
available commercially. The components can be added to the distillate fuel 
oil by any conventional method. The three components can be added to the 
distillate fuel oil as a single mixture containing all three compounds or 
the individual components can be added separately or in any other desired 
combination. The mixture may be added either as a concentrate or as a 
solution using a suitable carrier solvent which is compatible with the 
components and distillate fuel oil. The mixture can also be added at 
ambient temperature and pressure to stabilize the distillate fuel oil 
during storage. 
The present invention also pertains to a stabilized distillate fuel oil 
composition comprising a major portion of distillate fuel oil, such as 
straight-run diesel fuel, and a minor portion of an effective stabilizing 
amount of (a) N-(2-aminoethyl) piperazine, (b) triethylenetetramine, and 
(c) N,N-diethylhydroxylamine. Generally, the total amount of (a), (b), and 
(c) is from about 1.0 part to about 10,000 parts per million parts of the 
distillate fuel oil and, preferably, the total amount of (a), (b), and (c) 
is from about 1.0 part to about 1,500 parts per million parts of the 
distillate fuel oil. It is also preferred that the weight ratios of: 
(a):(b) is from about 1:3 to about 3:1; (a):(c) is from about 1:3 to about 
3:1; and (b):(c) is from about 1:3 to about 3:1, based on the total 
combined weight of these three components and, most preferably, the weight 
ratio of (a):(b):(c) is about 2:1.5:1.5 based on the total combined weight 
of these three components. 
The distillate fuel oils of this invention are those fuels produced by 
distillation of fuel oils, such as straight-run diesel fuel, as 
distinguished from fuel products produced by cracking or reforming 
processes. More particularly, the distillate fuel oils of this invention 
are those fuel oils having hydrocarbon components distilling from about 
300.degree. F. to about 700.degree. F., such as kerosene, jet fuel and 
diesel fuel. Preferably, the distillate fuel oil is straight-run diesel 
fuel. 
The processes and compositions of the instant invention effectively 
stabilize the distillate fuel oils, particularly during storage. The term 
"stabilize" as used herein means that particulate formation in the 
distillate fuel oil and color deterioration of the distillate fuel oil are 
inhibited. The term "particulate formation" is meant to include the 
formation of soluble solids, sediment and gum. 
In order to more clearly illustrate this invention, the data set forth 
below was developed. The following examples are included as being 
illustrations of the invention and should not be construed as limiting the 
scope thereof. 
EXAMPLES 
There are several accelerated test methods that are used by refineries for 
determining the stability of diesel fuels. Some of the most widely 
accepted test methods are the 110.degree. F. dark storage test (one week 
to three months), DuPont F21-61, UOP test method 413, 80.degree. C. test, 
ASTM D-2274 test, and the 216.degree. F. test. It was observed that some 
diesel fuels respond positively to selected chemical additives under 
specific conditions. In some cases, additives that were effective under 
accelerated test conditions (e.g., 216.degree. F., 300.degree. F.), were 
occasionally found to perform poorly under the more moderate 110.degree. 
F. test. This observation agrees with those found in the recent 
literature. See Stavinoha, L. L., et. al., "Accelerated Stability Test 
Techniques for Diesel Fuels," October, 1980. Stability data obtained using 
the 216.degree. F. or 300.degree. F. accelerated tests are considered to 
be only qualitative indicators of the performance expectations of an 
additive under the highly regarded 110.degree. F. storage test condition. 
It is widely accepted among researchers that seven days at 110.degree. F. 
is equivalent to one month's storage at 72.degree. F. Although the results 
of the 110.degree. F. dark storage test are generally accepted as the only 
valid data in correlating data from these conditions to those from actual 
storage, some current manufacturers continue to rely on stability data 
from the more accelerated conditions. 
The effect of the components to inhibit color degradation of a straight-run 
diesel fuel derived from a 50% San Joaquin Valley crude and 50% North 
Alaska crude was tested using the conditions of the 216.degree. F. 
accelerated test method. Four-ounce glass bottles were filled with 100 mLs 
of the diesel fuel. The samples were then spiked with the appropriate 
treatments. The glass bottles were capped but not tightly sealed to allow 
for the samples to be exposed to air during the test. The bottles were 
then transferred to an oil bath whose temperature was maintained at 
216.degree. F..+-.2.degree. F. during the duration of the test. The oil 
temperature recovered to 216.degree..+-.2.degree. F. within 15 minutes 
after the samples were placed in oil. The bath oil level covered at least 
three-fourths of the sample. The test was allowed to run for the time 
periods specified below. The samples were then removed and stored in the 
dark for two hours. The color of the samples was determined by visual 
comparison with known standards according to the ASTM-D- 1500 procedure, 
which involved matching the color of the fuel samples with ASTM-1500 color 
numbers. The results are based on a scale of 0.5 to 8.0 wherein increasing 
values indicate increasing darkness of the sample. The results obtained 
are reported in Table I below. 
TABLE I 
______________________________________ 
ASTM COLOR # 
TETA.sup.1 DEHA.sup.2 
AEP.sup.3 
a b 
______________________________________ 
CONC. -- -- -- 3.4.sup.4 
3.8.sup.4 
ACTIVE 150 150 200 1.5 
PPM 75 75 100 1.8 
100 100 300 1.8 
75 75 150 2.5 
250 250 1.5 1.8 
125 125 2.0 2.5 
250 250 1.7 
125 125 2.3 
166.6 166.6 166.6 2.0 
83.3 83.3 83.3 2.3 
______________________________________ 
ASTM Color: 
.sup.a 21/2 hours at 216.degree. F. 
.sup.b 21/2 hours at 216.degree. F. plus 24 hours at 72.degree. F. 
.sup.1 Triethylenetetramine 
.sup.2 N,N--diethylhydroxylamine 
.sup.3 N--(2aminoethyl)piperazine 
.sup.4 Controluntreated sample 
The results reported in Table I indicate that the combination of the three 
components of this invention, N-(2-aminoethyl)piperazine (AEP), 
triethylenetetramine (TETA), and N,N-diethylhydroxylamine (DEHA), is 
effective in inhibiting color deterioration of the straight-run diesel 
fuel. 
Additional tests were conducted to determine the effect of the components 
and their concentration to inhibit both discoloration and solids formation 
of a straight-run diesel fuel derived from 50% San Joaquin Valley crude 
and 50% North Alaska crude using the 110.degree. F. dark storage test. 100 
mLs of the diesel fuel were transferred into glass bottles. Caps were 
secured on the bottled samples but not tightly in order to expose the fuel 
to atmospheric conditions. The samples were placed in an oven set at 
110.degree. F. for 14 days. The samples were then removed from the oven 
and allowed to cool to room temperature. After each sample had cooled, it 
was poured into a separatory funnel and filtered (dispersed) through a 
tared Gooch crucible containing two glass-fiber filter papers. The 
ASTM-D-1500 procedure was used to determine the color of the filtrant. The 
sample container was washed with the rinsings (about 50 mL) of a 
heptane/acetone solvent (50/50). The separatory funnel and filter washing 
were also worked through the crucible. The crucible was dried in an oven 
(100.degree. C.) for one hour, cooled in a dessicator and the precipitate 
was weighed. The results obtained are reported in Table II below. 
TABLE II 
______________________________________ 
Color Level 
Concentration Level of Quantity of 
of Diesel Fuel.sup.4 
Precipitate 
Active Agent (ppm) ASTM Color (mg/50 
AEP.sup.1 
TETA.sup.2 
DEHA.sup.3 
Other Number mLs) 
______________________________________ 
-- -- -- Blank.sup. 
6.0 52.4 
-- -- -- Blank.sup. 
6.0 50.7 
-- -- -- Blank.sup.5 
6.0 126.5 
400 300 300 2.5 31.2 
200 150 150 .sup.6 
3.7 87.4 
200 150 150 .sup.5 
3.7 108 
200 -- -- -- 5.0 16.3 
-- 150 -- -- 6.0 37.2 
-- 150 -- .sup.7 
6.0 25.1 
-- -- 150 -- 4.3 42.0 
-- -- 300 -- 4.3 43.2 
200 150 -- -- 5.6 32.3 
200 -- 150 -- 3.7 41.8 
200 -- 300 -- 2.5 58.3 
-- 150 150 -- 5.0 33.8 
-- 150 300 -- 2.8 41.0 
______________________________________ 
.sup.1 N--(2aminoethyl)piperazine 
.sup.2 Triethylenetetramine 
.sup.3 N,N--diethylhydroxylamine 
.sup.4 Determined after 14 days at 110.degree. F. in an ambient 
atmosphere. 
.sup.5 Sample exposed to air after 1, 7 and 14 days; after each exposure, 
filtrations were performed. These filtrations yielded a combined weight o 
precipitate. 
.sup.6 Sample exposed to air after 7 and 14 days; after each exposure, 
filtrations were performed. These filtrations yielded a combined weight o 
precipitate. 
.sup.7 A second sample was prepared and examined after 13 days of heated 
storage. 
The results reported in Table II demonstrate the unique and exceptionally 
effective relationship of the components of this invention since the 
samples containing N-(2-aminoethyl)piperazine, triethylenetetramine and 
N,N-diethylhydroxylamine show better overall effectiveness in stabilizing 
the diesel fuel (inhibiting both color degradation and solids formation) 
than was obtainable in using each of the components individually. 
Further tests were conducted to determine the effect of the components of 
this invention to inhibit both color deterioration and sediment formation 
of the straight-run diesel fuel described above using the 110.degree. F. 
dark storage test for a seven day test period. The results obtained are 
reported in Table III below. 
TABLE III 
______________________________________ 
Quantity of Sediment 
ASTM Color 
Treatment (mg/100 mLs) Number 
______________________________________ 
Control Avg. 
6.6 4.3 
A 0.4 3.5 
B 1.0 2.5 
______________________________________ 
A = UOP130; a dispersant material manufactured by UOP of Des Plaines, IL, 
which is believed to be the reaction product of a tallowamine with 
epichlorohydrin. 
B = 
N--(2aminoethyl)piperazine:triethylenetetramine;N,N--diethylhydroxylamine 
(2:1.5:1.5) 
While this invention has been described with respect to particular 
embodiments thereof, it is apparent that numerous other forms and 
modifications of this invention will be obvious to those skilled in the 
art. The appended claims and this invention generally should be construed 
to cover all such obvious forms and modifications which are within the 
true spirit and scope of the present invention.