Note: Descriptions are shown in the official language in which they were submitted.
~01)~6~
PROCFSS FOR ~N~ANCING T~ CET~NE
NUMBER ~ND COLOR OE DI~SEL FUEL
EIELD OE THE INVENTION
This invention provides a process for upgrading a
diesel oil by treatment of a diesel oil with a nitroge-
nous treating agent to increase the cetane rating and
improve the color of the treated oil, and blending the
treated oil with an untreated diesel oil to obtain in
the diesel fuel blend a cetane increase, good color,
good stability and useful levels of Ramsbottom carbon.
More particularly, in an embodiment of the present
process, the extent of nitrogen addition to the treated
diesel oil used in the diesel fuel blend and the blend
ratio of treated to untreated diesel oil are controlled
in one embodiment to insure that the concentration o
added nitrogen in the final blended diesel fuel product
does not exceed about 300 ppm in the case of virgin
diesel oil stocks, or about 450 ppm in the case of
hydrotreated diesel oil stocks.
; BACKGROUND OF THE INVENTION
It has long been known that the cetane number of
diesel oils can be improved either by adding a
nitrogen-containing fuel additive, or by treatment with
a nitrogenous oxidizing agent. Oils in the diesel
13~1~0~4
boiling point range having the proper physical charac-
teristics such as pour point, cloud point, viscosity
and volatility can be obtained by nitrating the diesel
fraction in order to increase the cetane number.
However, it is well known that the nitration of such
oils tends to increase the Ramsbottom carbon content
and to decrease the stability of the fuels by forming
an insoluble sediment. The insoluble sediment produces
a haze and eventually a deposit while the fuels are in
storage. While many attempts to eliminate the
disadvantage of poor stability characteristics have
been made and solvent extraction, including alkali
scrubbing, has been employed to improve stability,
conventional solvent extraction has proven unsatisfac-
tory to provide acceptable stability in the case of
nitrogen-treated fuels.
Solvent extraction with certain organic solvents,
such as those described in United $tates patents
4,643,820 and 4,746,420,
is effective to improve stability and reduce Ramsbottom
carbon content, but a ma~or portion of the cost of
upgrading diesel oil by this method is incurred in the
solvent extraction process. A method of improving the
cetane rating of substandard diesel oils that does not
1~
~3~ 64
-- 3
require an expensive solvent extraction step to meet
diesel fuel product specifications for stability and
Ram~bottom carbon is particularly desirable.
It is known to enhance the cetane number of diesel
oil using oxidative processes. Regarcling the use of
nitration to improve the cetane number of diesel oil~,
British Patent No. 491,648 teache~ contacting a diesel
oil with a nitrating agent in order to increase its
ce-tane number. The disclosure in British Pa-tent
No~ 4gl,648 is that the nitrated oil can be used alone
or in a blend with untreated diesel oil. Extraction
with solvents including acetone, methyl and ethyl
alcohols, ethylene dichloride and aniline is described
for obtaining concentrates of nitrated petroleum
components. However, by contacting a diesel oil with a
nitrating agent, stability is decreased and Ra~sbottom
carbon is increased, and these de~iciencies are
combined with poor process yields when the product is
extracted using the solvents disclo~ed. While
recognizing the problem of sedimentation and poor
stability, this British Patent contains no suggestion
as to how these problems can be reduced or eliminated.
U.S. Patent No. 39135,680 discloses oxidation of a
sour petroleum fraction with nitrogen dioxide followed
by washing with water and alkali, to desulfurize diesel
06~
-- 4 --
oils and improve cetane. The disclosure is that the
product obtained, however, tends to have an
objectionable color resulting from the nitrogen dioxide
treatment, and subsequent sulfuric acid treatment,
vacuum distillation or clay treating is considered
essen-tial to completely remove materials formed during
oxidation. Unfortunately, this reduces or eliminates
the increase in cetane number. Due to its high
Ramsbottom carbon content, the product of this process
forms substan-tial coke in the still upon distillation.
A proces~ is described in U.S. Patent 3,164,546
for producing diesel fuels having improved cetane
number and odor, by treating the oil with nitrogen
dioxide, washing with aqueous alkali and/or solvent
extraction, followed by a water wash. Solvents
disclosed as suitable for the solvent extraction step
are nitromethane, dimethylformamide, pyridine,
acetonitrile, glycolonitrile, ethylene glycol,
ethanolamine and phenol. No reference is made,
however, to the important stability and Ramsbottom
carbon content specifications, which are by far the
most difficult product specifications to meet for a
diesel fuel product when employing nitrogenous treating
agents. Furthermore, extraction reduces yields of
product.
.
~3~00~
-- 5
U.S. Patent No. 2,333,817 discloses oxidation of
diesel oils by nitrogenous compounds followed by hexane
dilution and filtering to improve cetane and prevent
sediment formation. Such a product does not pass
present~day indu~try standards for stability ~although
haze formation is reduced) and it does not meet
Ramsbottom carbon ~pecifications. From the
exemplification it appears this techni~ue is only
applicable to cycle oils.
These methods have generally apparently employed
nitration or an oxidation treatment for cetane
improvement of diesel oils, but lt is also ~nown that
the cetane number of diesel oils can be increased by
adding various nitrated hydrocarbon derivatives to the
oils, including amyl nitrate, octyl nitrate, and the
nitrate ester "dopes" disclosed in British Patent No.
491,648. Other nitrogen-containing additives for
improving cetane are disclosed in U.S. Patent No.
4,398,505. Use of these derivatives is generally
disadvantageous since they are expensi~e and must be
separately prepared, handled and ~tored.
U.S. Patent No. 2,184,440 relates to methods of
increasing the cetane number of blended diesel fuels by
blending diesel fuels from different sources, one of
which is a high sulfur crude, and treating the blended
130006~L
fuel with sodium plumbite and a large excess of
elemental sulfur. Alternatively, a distillate fuel
stock can be treated with ~odium plumbite and an excess
amount o elemental sulfur over that reguired to
sweeten the 6tock, and distilled to obtain a sweetened
condensate, with the bottoms being further reduced and
added to an untreated diesel fuel to increase the
cetane number of the blend. The reduced bottoms
amounting to about 1 to 6% of the original distillate
fuel stock are added in amounts of about 0.5 to 5% to
diesel fuels to raise their cetane number, e.g., by 2
to 19 over untreated diesel fuel.
U.S. Patent No. 2,104,919 provides a means to
achieve a stabilized fuel by blending straight-run and
cracked stocks. The disclosure of this patent states
that typically fuel oils produced by blending
straight-run components and cracked residues have a
tendency to form a carbonaceous sludge on storage, and
the precipitation of sludge in such fuels containing 10
to 80% heavy cracked residues is inhibited by mildly
oxidizing the straight-run component before blending,
e.g., by blowing air at 250-400C therethrough for l/2
to 12 hours.
U.S. Patent No. 2,317,96~ disclose~ a die~el fuel
containing substantial portions of chemically combined
~30~t~6~
-- 7 --
reactive oxygen through treatment with air, oxygen or
an oxyyen carrying gas, to produce by partial oxidation
a petroleum fuel having a volatility greater than that
of kerosene and relatively free from asphaltic and
resinous components and from large proportions of
aromatics, to an "oxygen factor" of 800 to 1450 by air
blowing, removal of acids produced by oxidation, and
blending with a diesel fuel to produce a diesel fuel
blend having increased cetane. Blends of 2.5% oxidized
oil to 97.5% by volume sulfur dioxide-treated petroleum
distillate and of 20% by volume of oxidized oil to 80%
by volume of a clean gas oil distillate are disclosed.
U.S. Patent No. 2,365,220 discloses a method
similar to that o U.S. Patent 2,317,968. The
disclosure is of the preparation of a diesel fuel, in
which a diesel fuel of predominately paraffinic
character is oxidized using air, oxygen or an oxygen
carrying gas to produce an oil having an "oxygen
factor" of higher than 5, acidic reaction products are
rsmcved, and the resulting oxidized stock is blended
with from 2/5 to 20 time~ its volume of a clean diesel
petroleum hydrocarbon distillate.
U.S. Patent No. 2,521,698 discloses that the fuels
produced by the methods of U.S. Patent Nos. 2,317,968
and 2,365,220 are unstable and corrosive, and that the
~31DOl)~
-- 8 --
stability and corrosiveness of such cetane-enhanced
diesel fuels can be improved with a loss of about 25%
of cetane enhancement, by subjecting the oxidized
diesel fuel to acid treatment with a strong acid, such
as sulfuric or nitric acid, in a concentration of at
least 0.1 pound per gallon of ox$dized stock, followed
by alkali wash and blending of the treated oxidized
stock with diesel fuel. A concentrated oxygenated
cetane-improving additive is also disclosed, prepared
from the bottoms of the distilled oxidized diesel
stock.
U.S. Patent 4,280,818 discloses oxidizing a
hydrocarbon oil with aqueous nitric acid in a weight
ratio of about 1:0.1 to 1:10 of hydrocarbon to acid and
separating the aqueous phase from the oxidized
hydrocarbon phase. The disclosure is that the oxidized
hydrocarbon phase can be extracted and the product
obtained blended with a polar solvent to produce a fuel
mixture.
U.S. Patent No. 3,284,342 discloses oxidation of
residue using a number of oxidants including nitrogen
oxides, followed by a thermal treatment to reduce the
sulfur content of the residue, in which both s-teps can
be promoted with catalysts. When applied to diesel
oil, this process produces substantial carbonaceous
01~6~
deposits in the thermal treating still, and is
unsatisfactory for commercial use.
U.S. Patent 3,135,680 discloses a process for
refining petroleum fractions in the diesel oil boiling
range to produce diesel fuel with enhanced cetane
number and odor by treating the fractions with nitrogen
dioxide followed by a clay treatment to remove odor.
A process of deodorizing and desulfurizing light
petroleum distillatss by treatment with nitrogen
dioxide ollowed by alkali wash and water wash is
disclosed in U.S. Patent No. 3,267,027. This process
i~ unsuitable for producing diesel fuels of acceptable
stability and Ramsbottom carbon content.
U.S. Patent No. 3,244,618 discloses a process for
sweetening petroleum hydrocarbons by treating the
hydrocarbon fraction with molecular oxygen in the
presence of a catalytic amount of a nitrogen oxide.
Application of this process to diesel fuel results in a
product with inferior cetane enhancement.
U.S. Patent No. 2,004,849 discloses the use of an
oxidant, hydrogen peroxide, in combination with
sulfuric acid to effect sulfur removal from
hydrocarbons, without substantial loss of aromatics.
However, this process is ineffective for improving the
cetane of di~sel fuel.
1~0(1 ~4
-- 10 --
Processes for treating petroleum 6tocks by
oxidation ~ollowed by solvent extraction have been
described for various purposes.
For example, a process for producing a fuel
composition by oxidizing a hydrocarbon oil with aqueous
nitric acid, followed by extraction with acetone,
methyl ethyl ketone, cyclohexanone, methanol, ethanol,
normal propanol, isopropanol, ethyl acetate,
tetrahydrofuran, dioxane, or a combination of an
alcohol and a ketone, an alcohol and water, a ketone
and water or a combination o alcohols is disclosed in
U.S. Patent No. 4,280,~18.
Although the oxidation/extraction methods
described above have met with some success in improving
petroleum diesel fueLs, the known approaches toward
oxidation to remove a portion of the original sulfur
content as gaseous sulfur oxide~, and to convert a
portion of the original sulfur content into sulfoxides
and/or sulfones followed by extraction with appropriate
solvents to achieve a desired low sulfur raffinate have
not completely eliminated problems of in~tability and
unacceptable Ramsbottom carbon for diesel fuels, and
have the disadvantage of an expensive solvent
extraction step, resulting in low yields.
13006)6A
-- 11 --
The methods described above when applied to
petroleum stocks for use as diesel fuels basically have
the disadvantages that (a) oxidative desulfurization
methods involving nitrogenous oxidizing agents often
result in increased gum and sedimentation, and reduce
the stability of the fuels produced, (b) the oxida-
tively treated fuel~ are not useful as diesel fuel
blendstocks due to poor stability and high Ramsbottom
carbon content, and (c) solvent extraction, while
effective to im~roVe stability and Ramsbottom carbon
content, is expen~ive and of low product yield~ in
comparison to oxidative treatment alone where the
oxidized product alone can be blended to improve diesel
fuels.
While many conventional methods of improving
diesel cetane number by oxidation with nitrogenous
oxidizing agents exist, they are generally inadequate
to meet other product specifications. Particularly,
diesel fuels produced by nitrogeneous oxidation and
solvent extraction can in svme cases meet sulfur and
cetane requirements for fuels, but are unsatisfactory
with respect to the important specifications of
stability and Ramsbottom carbon content. Processes
employing sulfuric acid or clay in conjunction with
nitrogeneous oxidizing agents are inefective to retain
~O~O~i4
- 12 -
a high cetane rating when pxacticed to control
Ramsbottom carbon and stability. Distillative methods
are commercially unfeasible due to the presence of
substantial carbonaceous deposits in the still, and
when thermal trea-ting is applied to diesel fuel to
reduce sulfur content of the residue, this process also
produces substarltial carbonaceous deposits in the
thermal treating still. Often acceptable color levels
in the product, particularly after storage, are not
achievable.
Apart from the failure o conventional oxida-tive
cetane enhancement methods to provide diesel fuels of
sufficient stability and Ramsbottom carbon content,
these methods, like the oxidative desulfurization
methods, employ solvents which result in poor yields?
re~uiring unacceptably high solvent-to-oil ratios.
Alternatively, the sol~ent~ used in some methods reduce
or entirely eliminate the advantage of cetane
enhancement obtained by oxidation.
While certain of the patents cited above refer to
oxidation of diesel stocks to improve cetane~ and the
use o ~uch oxidatively enhanced stocks in blends with
unoxidized diesel fuels, these patents fail to
recognize the importance of limiting the nitrogen
content of the final blend to achieve acceptable
~L3~00Ç;g~
stability or Ramsbottom carbon content in the final
blend. Furthermore, there is no appreciation of the
remarkable increase of cekane in the treated por-tion
and in the final blend when nitrogen treatment and
blending are controlled according to the present
process. Finally, thare is no recognition o~ the
further benefits of selected alkaline wash agents in
imparting improved color stability while retaining the
foregoing attributes.
SUMMARY OF T~E INVENTION
An object of the invention i8 to provide a process
for enhancing the cetane number o a diesel fuel.
Another object of the invention is to provide a
process for increasing the cetane number and improving
the color of a diesel fuel e.g., preventing the
development of color in the blend product over
development of color in the blend product not subjected
to the proces~ of this invention comprising treating
the diesel oil with a nitrogenous treating agent,
separating unreacted nitrogenous treating agent,
treating the diesel oil with an inorganic alkali, and
then blending the treated diesel oil with an untreated
diesel oil in specific proportions to produce a blended
diesel fuel having an unexpectedly increased cetane
number and with marked improvement in the color of the
~30006~L
- 14 -
blended diesel fuel, compared to blending the treated
oil without use of an alkali treating agent.
A further object of this lnvention is to provide a
blended diesel fuel with improved cetane number and
appropriate stability and Ramsbottom carbon.
An even further object of this invention is to
provide a blended diesel fuel in which the amount of
additive which might be added to enhance even ~urther
the stability o~ the blended diesel fuel is minimized.
Also, an object of thi~ invention is to provide a
process for producing a blended diesel fuel having good
storage stability and color along with useful levels of
Ramsbottom carbon.
When the alkali used for treatment is ln an
aqueous solution form, a further object of the
invention is to minimize the chemical oxygen demand in
treatment of the spent alkali wash water for release in
the environment or for recycle/reuse.
In one embodiment of this invention, this
invention provide3 a process for the enhancement of the
cetane number of and improvement in color developed on
storage of a diesel fuel comprising:
(1) treating a diesel oil with a nitrogenou~
treating agent in a nitrogen amount,
equivalent on a 100% nitric acid basis, to
~..3~
- 15 -
about 10 weight percent or less of the diesel
oil feed;
(2) separating unreacted nitrogenous treating
agent from the diesel oil of step (1~;
(3) treating the diesel oil of step (2) with an
inorganic alkali to produce a treated diesel
oil; and
(4) blending the treated diesel oil of step (3)
wlth an untreated diesel oil to produce a
blended diesel uel ~uch that the nitrogen
added content in the blended diesel fuel is
(a) about 300 ppm or less of nitrogen added
when the diesel oil treated in step (1)
is obtained from virgin diesel oil
stock, or
(b) about 450 ppm or less of nitrogen added
when the diesel oil treated in step (1)
is obtained from hydrotreated diesel oil
stock.
In a further embodiment of this invention~ this
invention provides a process for the enhancement of the
cetane number of and improvement in color developed on
storage of a non-fungible diesel fuel comprising:
(1) treating a first diesel oil with a
nitrogenous treating agent in a nitrogen
~3()0~4
- ~6 -
amount, equivalent on a 100% nitric acid
basis, to about 10 weight percent or les~ of
the diesel oil feed;
(2) separating unreacted nitrogenous treating
agent rom the diesel oil of step (1);
(3) treating the diesel oil of step (2) with an
inorganic alkali to produce a treated dieseL
oil; and
(4) blending the treated diesel oil of step (3)
with a second diesel oil which has not been
treated as in step (1) above to produce a
blended diesel fuel such that the nitrogen
added content in the blended diesel fuel is
about 1,000 ppm or less of nitrogen added,
and
: ~ wherein the first diesel oil treated in step (1)
and/or the second diesel oil blended in step (4)
and/or the blended product o step (4) is a
non-fungible diesel fuel.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 is a graph showing the relationship
between ASTM color and age of the diesel fuel blend
: ' produced by the process of this invention.
Eigure 2 is a graph showing the relationship
between Nalco stability and amount of stability
0~4
- 17 -
improviny additive present in a diesel fuel blend
produced by the process of this invention.
Figure 3 is a graph showing the relationship
be-tween Ramsbottom carbon and nitrogen added to the
diesel oil blend.
Figure 4 is a graph showing the relationship
between stability and nitrogen added to the blended
diesel fuel.
Figure 5 i8 a graph showing the average blending
cetane numbers of blended diesel fuel products for
varying amounts of treated diesel fuel in the blend.
Figure 6 is a graph showing the calculated pool
cetane of blended diesel products produced.
DETAILED DESCRIPTION OE THE INVENTION
As indicated above, the process of this invention
involves, in particular, enhancement of the cetane
number of a diesel fuel and improvement in color
developed on storage. The process basically comprises:
(1) treating a diesel oil with a nitrogenous
treating agent in a nitrogen amount,
e~uivalent on a 100~ nitric acid ba~is, to
about 10 weight percent or less to the diesel
oil feed;
(2) separating unreacted nitrogenous treating
agent from the diesel oil of step (l);
- 18 -
(3) treating the diessl oil of step (2) with an
inorganic alkali to produce a treated diesel
oil; and
(4) blending the treated oil of step (3) with a
diasel oil which has not been so treated as
in step (1) to produce a blended diesel fuel
such that the nitrogen added content in the
blended diesel fuel
(a) is about 300 ppm or less of nitrogen
added when the diesel oil treated in
step (1) is a diesel oil obtained from
virgin diesel oil s~ock, or
(b) is about 450 ppm or less of nitrogen
added when the diesel oil treated in
step (1) is a diesel oil obtained from
hydrotreated diesel oil stock.
In the first step of the process of this
invention, a diesel oil is treated by contacting such
with a nitrogenous treating agent in a nitrogen amount
equivalent to about 10 weight percent or less on the
diesel oil feed of nitric acid based on the nitrogen
content of a 100% concentration nitric acid.
If desired, the feed oil can first be subjected to
pretreatment, 8uch as by washing to remove phenols or
other corrosive components of the oil, filtering to
~00~4
-- 19 --
remove gum or sediment, or heating or treatment with
H2S04 as conventionally used. In the fir~t step of the
process of the invention, the treating agent is a
nitrogenous treating agent. The term "nitrogenous
treating agent" is used herein to mean any known
nitrogen-containing oxidizing compound including, e.g.,
a gas containing at least one nitrogen oxide with more
than one oxygen atom for each nitrogen atom, a liquid
containing at least one nitrogen oxide with more than
one oxygen atom for each nitrogen atom, nitric acid and
nitrous acid.
The treating gas used can be a gas containing only
such a nitrogen oxide or can be one which contains
mixtures of such nitrogen oxides. Furthermore, the
treating gas can be one which also contains other
components such as oxygen, nitrogen, lower nitrogen
oxides, i.e., nitrogen oxides containing only one
oxygen atom or less than one oxygen atom per nitrogen
atom in the oxide. For efficiency, preferably the
treating gas will be one which contains only nitrogen
oxides with more than one oxygen atom for each nitrogen
atom but mixtures with other gases such as oxygen,
nitrogen, as well as inert gases such as air, helium
and helium with air can be employed if desired.
Suitably the treating gas will contain at least 0.5% by
~3~ i4
- 20 -
volume of at least one nitrogen oxide with more than
one oxygen atom for each nitrogen atom, but the
concentration can be reduced if the flow rate of
treating agent is increased for a longer time.
Nitrogen dioxide or its dimer N204 can be
advantageously employed, alone or in a admixture with
air.
The nitrogenous treating liquid used can be li~uid
ni-trogen oxides as defined above, nitric or nitrous
acid either concentrated or in admixture with up to
about 90% water by weight. Preferably the liquid
nitrogenous treating agent is an a~ueous solution of
nitric acid containing about 50 to 90% by weight nitric
acid.
However, the above described concentrations, e.g.,
nitrogenous treating agent concentrations, are not
limiting and are given merely for exemplification.
Basically any concentration can be used as long as the
nitrogenous treating agent is present in sufficient
amounts to achieve in the blended product the nitrogen
added amounts for the process of the invention when the
treated diesel oll is blended with the untreated diesel
oil.
When liquid nitric acid is used as a nitrogenous
treating agent in the present invention, it may
~3~0~
- 21 -
advantageou~ly be used in combination with other
organic or inorganic acids. Suitable inorganic acids
include sulfuric and phos~horic acids, and suitable
organic acids include, e.g., acetic and formic acids.
The organic and inorganic acid may be used alone or in
combination. Typically, an inorganic acid can be added
to the aqueous nitric acid solution used as a trea-ting
agent in an amount of fxom about 5 to 200% by weight of
the nitric acid solution, and an organic acid can be
added in an amount from about 5 to 200% by weight of
the nitric acid æolution. Preferred combinations of
nitric and au~iliary acids include nitric and sulfuric,
nitric and acetic, and nitric and formic acids.
When liquid nitrous acid is used as a nitrogenous
treating agent in the present invention, it may
advantageously be uæed in combination with other
organic or inorganic acids. Suitable inorganic acids
include sulfuric and phosphoric acids, and suitable
organic acids include, e.g., acetic and formic acids.
The organic and inorganic acid may be used alone or in
combination. Typically, an inorganic acid can be added
to the aqueous nitrouæ acid æolution used as a treating
agent in an amount of from about 5 to 200% by weight of
the nitrous acid ~olution, and an organic acid can be
added in an amount from about 5 to 200% by weight of
1~ 0~4
- 22 -
the nitrou~ acid solution. Preferred combinations of
nitrous and auxiliary acids include nitrous and
sulfuric, nitrous and acetic, and nitrous and formic
acids. Mixtures of nitric acid and nitrous acid can
also be used.
In the first step o the process of this
invention, a diesel oil such as atmoæpheric gas oil is
reacted with a nitrogenous treating agent in the form
of a liquid or gas. The contacting of the diesel oil
with the treating liquid can be accompli~hed by any
means conventional in the art or contacting two liquid
reactants, e.g., by injecting the acid mixture under
the surface of agitated oil contained in a reactor.
When a treating gas is employed, the treating gas can
be contacted with the diesel oil using any conventional
means for contacting a gaseous reactant with a liquid
reactant. Suitable examples of such means for
contacting a gaseous reactant with a liquid reactant
include dispersing the gas as bubbles in the li~uid,
trickling the liquid over an inert solid bed with gas
passing also over the bed co-currently or
countercurrently to the liquid flow, the latter type
flow being preferred.
It is important in the first step of the process
of thi~ invention to control the operating parameters
130~ Ei4
- 23 -
during the reaction of the diesel oil with the treating
gas or liquid to insure that the nitrogenous treating
agent is employed in a nitrogen amount e~uivalent to
about 10 weight percent or less, preferably 6 weight
percent or less, more preferably 5 weight percent or
less, of nitric acid based on the nitrogen content of
100% nitric acid. In accordance with the process of
the present invention, by conducting step (1) in this
manner and in combination with steps ~2) and (3)
described hereinafter, this results in a product of
extremely high cetane value which may be advantageously
blended into a dlesel pool without deleterious effects
on Ramsbottom carbon and ~tability. This important
processing control as to the reaction of the diesel oil
with the nitrogenous treating agent is described in
more detail below.
As used herein, the term "nitric acid
e~uivalent-to-oil ratio" (acid-to-oiL ratio, A/0)
refers both to the weight of water-free nitric acid to
the weight of diesel oil feedstock and to the weight of
undiluted gaseous or liquid nitrogenous treating agent
to the weight of diesel oil feedstock, and is from
about 0.0002 to 0.10, preferably from about 0.0005 to
0.05, for the acids and from 0.0002 to 0.10, preferably
0.0005 to 0.05, for the nitrogen oxides. The control
5~
- 24 -
of the trea-tment may be achieved by controlling the
water content of the acid in the reactor, by
controlling the mixture of nitrogenous gas and air or
inert gas used or by controlling temperature, time and
degree of agitation. The treatment can also be
controlled and improved by the copresence of sul~uric
acid through itF9 effect on water availability or other
auxiliary acid mixed with the treating agent. This
control of the amount of nitrogenous treating agent to
the total weight of the diesel oil feed in step (1) can
be easily maintainéd.
The reaction of the first step of the present
invention can be performed at any temperature from
about -40 to about 200C, or less, moet preferably from
about 25 to 90~C. The reaction time is not
particularly limited, and may include9 for example, any
time from about 1 minute to about 3 weeks. This first
step o the present invention may be conducted at
atmospheric pressure or at greater or lower pressures
as de~ired. Advantageously, the reaction step is
conducted using conventional agitation means, such as a
stirrer or such as a pumparound reactor.
Since a nitrogenous treating agent is used in the
first step of the present invention, typically an
increase in nitrogen compound content over that
~3~
- 25 -
originally present in the diesel oil will be observed.
While not desiring to be bound by theory, the reason
for the increase in observed nitrogen compound content
is believed to be that nitration and esterification of
the diesel oil substrate can occur resulting in an
increase in the heteroatom nitrogen compound content.
~ ecause of the complexity o the reactions
involved, the treating agent~ may well do more than
oxidize or nitrate compounds contained in the diesel
oil in the process according to the invention. Hence,
the first step is variously described herein as
"nitrogenation" or simply "nitrogen treatment" or more
simply "treatment", which refers to any reaction of the
nitro~enous treating agent and diesel oil or its
components, without limitation, and without reliance on
any particular reaction or reaction mechanism.
Contact times on the order of less than about 120
minutes and weight ratios of nitrogenous treating agent
to diesel oil feed o less than about 0.1 are desirable
not only from the standpoint of efficiency hut also
from the standpoint of economics. Particularly
preferably, a contact time of ahout 30 minutes in
combination with a weight ratio of nitrogenouæ trea-ting
agent to diesel oil feed of about 0.05 or less can be
o~
- 26 -
advantageously employed for maximum yield of diesel oil
with improved ce-tane rating and useful stability.
However, because of the known :relationship of
nitrogenous treating agent to cetane number, it i9
often advantageous when using a nltrogenous treating
agent to carefully control the minimum amount of
nitrogen compounds added to the diesel feed in order to
insure a suficient cetane number in the diesel fuel
produced.
Depending on the nature of the nitrogenous
treating agent employed, one ~killed in the art can
easily determine the amount o nitrogenous treating
agent to use to ensure the proportion employed i 6 a
nitrogen amount equivalent to 10 weight percent or less
nitric acid based on the weight of the diesel oil fed
as a eed stock in step (1) of the process of this
invention.
The process of this invention is applicable to the
upgrading of diesel oil which can be derived from any
source, for example, a conventional petroleum crude oil
or crude oil fraction containing sulfur, aromatic,
olefinic and naphthenic compounds as impuritles. The
term "die~el oil" as used herein is broadly deEined to
include any hydrocarbon having a nominal boiling range
of about 350F to 700F which can be upgraded by the
1~0~4
- 27 -
process o this invention to meet commercial
speciications for a diesel fuel and the term "diesel
fuel" is ~enerally used to describe the upgraded
product, although the terms can be used
interchangeably.
The process of this invention is basically not
limited in term~ of the source of the diesel oil, but
is applicable to any diesel oil from petroleum, coal,
shale, tar sands, etc.
In the process for upgrading diesel oils accord:ing
to the invention, particular product specifications may
vary over a range. Based upon the disclosure contained
herein, the present process may be readily applied and
modified by one skilled in the art to produce a blended
diesel fuel having particular desired specifica-tions,
particularly with respect to the basic criteria of
cetane, stability, Ramsbottom carbon and sulfur
content, density and boiling range. Furthermore, the
process of this invention can be employed in
combination with conventional techniques for meeting
product specifications as desired, e.g., by addition of
chemical additives such as corrosion inhibitors,
stabilizer~ and the like.
Fuel stability is measured by a number of
accelerated tests, one of which is the Nalco 300F
~o~!Ei4
- 28 -
test. For satisfactory stabili.ty in commercial storage
and use, a transportation fuel must exhibit a Nalco
rating of about 7.0 or lower. A rating of about 7.0 is
the upper level of acceptability for commercial use,
although a lower limit is desirable. The applicable
Nalco test is well known in the art, and the test can
be simply performed, for example, by placing 50 ml of
oil to be tested in a tube 3 cm in diameter, heating
the tube in a 300F bath for 90 minutes, and then
cooling the oil. The oil i~ then filtered using a
micropore filter with a number 1 filter paper, the
filter and the filter paper are washed with heptane,
and the residue remaining is compared with standard
samples to determlne the stability rating. If a fuel
has a Malco rating exceeding 7, it may often be blended
with other ~tocks or treatsd with economic levels of
chemical additives to bring it into specificat1on.
This approach can be smployed with the blended fuel
product produced by the process of this invention as
well.
In addition to management of the above criteria of
stability and cetane number, Ramsbottom carbon content
is an important ~uality speciication for diesel fuels,
since fuels high in Ramsbottom carbon cause fouling
problems when used in diesel engine~. In an acceptable
~30~ 4
- 29 -
diesel fuel, the Ramsbottom carbon content is
preferably less than about 0.3 weight per cent, as
determined by the method disclosed in ASTM D 524, prior
to addition of any nitrate additives for cetane
improvement.
Nonfungible fuels also have commercial importance,
such as dedicated uses for railroad engines and the
like. In these applications, fuel specifications, for
example, Ramsbottom carbon and stability can be grea-tly
relaxed from those discussed above, such as permitting
a Ramsbottom carbon content o, for example, about 1 to
about 10%. For these cases, the present inven-tion
still finds important applicabillty at appropriately
elevated levels o nitrogen added.
While not desiring to be bound by theory, it is
currently believed that the complex process according
to the pre~ent invention for upgrading diesel oils by
contact with a nitrogenous treating agent probably
involves nitrogen addition to paraffins, olefins,
naphthenes and aromatics to form nitrates, esters,
amines, azides, indoles and the like.
As indlcated above, the process of this invention
can be employed on an atmospheric gas oll fraction
derived from li~uid petroleum crude sources.
Atmospheric gas oil is one component used in diesel oil
~1~31)~
- 30 -
blending, and may contain an off-specification sulfur
content for use as a diesel fuel. Typically, ~ulfur as
a heteroatom i9 present as thiol.s, di~ulfides,
sulfides, thiophenes, and mercaptans, and nitrogen is
present a~ substituted pyridines and pyrroles, and
other compounds. A typical analy~is of atmospheric gas
oils is set forth in Table 1 below.
13~
- 31 -
Table 1
Properties of Atmospheric Gas
0i1 (AGO) and of Liqht CYcle Oil (LC~
Stock H Stock I LCO
Gravity, API 33.1 34.2 17.65
Sulfur, wt.% 0.5 0.460.77
Nitrogen, ppm 156 191 679
Ramsbottom carbon, % 0.156 0.105 0.620
Nalco* 1 2 2
Cetane Number 46.0 41.0 22.7
D86 Distillation, F
start 290 250 430
5% 410 380 465
10% 435 395 490
30% 487 450 530
50% 517 490 550
70% 550 540 570
90% 602 600 625
95% 676 640 650
After the completion of the treatment of the
diesel oil With the nitrogenous treating agent in
step (1) of the process of this invention, unreacted
nitrogenous treating agent is separated from the diesel
* trade mark
- 32 -
fuel in step (2). Where excess nitrogenous treating
agerlt is separated, this can be achieved by decanting
of the residue phase, by strippin~ of the nitrogeneous
treating agent, or by other techniques well known to
one skilled in the art or combinations of these
physical removal techniques.
In step (3) of the process of this invention, the
diesel oil from step (2) is treated with an inorganic
alkali preferably an alkali metal hydroxide or a~monium
hydroxide or mixtures thereof. Preferably a solution,
e.g., an aqueous solution, of the inorganic alkali is
employed. Where a solution is employed, a suitable
concentration of alkali in the alkali solution is about
0.01 to about 5 M, more preferably 0.05 to 2.0 M, even
more preferably 0.5 to 2.0 M, and most preferably 0.5
to 1.0 M. The alkali solution is used in a weight
ratio to the diesel oil of step (2) of about 0.01 to
l:l, preferably 0.08 to 0.5:1, most preferably 0.08 to
0.15:1.
A preferred inorganic alkali is ammonium hydroxide
since it has been found, as is shown in the examples
yiven hereinafter, that the chemical oxygen demand
(COD) of the wash separated from the diesel oil in
step (2) in treatment for environmental release or
reuse is markedly reduced.
- 33 - ~
The treating of the treated diese]. oil from
step (2) with the inorganic alkali can be achieved by
simply mixing the diesel fuel obtained in step (2) with
the alkali. Any conventional means for achieving
effective contact, such as co-current or countercurrent
flow or a simple addition with agita~ion, can be
employed to treat in step (3) the diesel oil from step
(2). Although not essential, if desired, the diesel
oil of step (3) can be subjected to a water washing
step prior to use of the treated diesel oil of step (3)
to produce the diesel fuel blends of ~tep (4).
In the next step (4) of the process of this
invention, the treated diesel fuel so obtained is then
mixed with a diesel oil which has not been BO treated,
herein "untreated diesel oil", to produce a blended
diesel fuel.
Examples of untreated diesel oils which can be
used and mixed with the treated diesel fuel obtained in
step (3) include any diesel oil with a boiling range of
about 350F to about 700F. While in the process of
this invention, any untreated diesel oil as previously
described can be blended with the treated diesel fuel
obtained in Step (3) above to achieve cetane
enhancement and improved color development on storage,
it would be obviou~ to one skilled in the art that the
~3~ 4
- 34 -
properties of the untreated diesel oil to be blended
must be taken into account such that when the blend
product is produced, other specifications required for
a commercial fuel, such as sulfur content, Ramsbot-tom
carbon content, stability, and the like, are met.
In order to enhance the cetane number of the
ultimate diesel fuel blend, the nitrogen content added
into the blended diesel fuel comprising the mixture of
the treated diesel uel and the untreated diesel oil is
carefully controlled in accordance with the ollowing
parameters.
SpeciEically, where the diesel oil feed to step
(l) is obtained from virgin diesel oil stocks, such as
atmospheric gas oil, the amount of nitrogen added into
the blended diesel fuel is about 300 ppm nitrogen or
less, generally 150 ppm or less, more generally 100 ppm
or less..
Where the diesel oil feed to step (1) is obtained
from a diesel oil from hydrotreated diesel oil stocks,
such as an atmospheric gas oil treated with hydrogen in
the presence of a cataly~k at a temperature exceeding
about 600F and a pressure exceeding about ~00 psi, the
amount of nitrogen added into the diesel fuel blend is
about 450 ppm nitrogen or less, generally 300 ppm
nitrogen or less, more generally 200 ppm or less. The
1~ 4
- 35 -
minimum amount of treated diesel oil prepared in
steps (1), (2) and (3) which i~ employed in the blended
product produced in step (4) is at lea~t about 5 ppm
nitrogen added, whether the diesel oil ~tock treated in
step (1) is from virgin diesel oil stocks or
hydrotreated diesel oil stocks.
Where the blended diesel product is to be used as
a nonungible fuel, i.e., where the fuel i5 produced
for a specific end use and thus adherence to normal
specifications of a fungible commercial diesel fuel are
not of concern, then the diesel oil feed to step (1)
can be any refinery stock having appropriate properties
such that when subjected to the process of this
invention provides blends meeting nonfungible
specifications in the final product blend. In this
case, the nitrogen added due to the treated diesel oil
of step (3) in the blended product can be such that the
diesel fuel blend contains about 1000 ppm or less of
added nitrogen, generally 800 ppm or less of added
nitrogen, more generally 600 ppm or less of added
nitrogen
Use of the treated diesel oil in the blend
produced with more than the above described levels of
nitrogen added to the blend results in the inability to
- 36 -
meet the desired blended product specifications for a
diesel fuel.
The diesel oil stocks used to which the present
invention is applicable can vary widely, and
specifically can contain initial nitrogen levels from
as little as about 5 ppm up to levels of about 1000
ppm. Surprisingly, even though it is conventionally
believed there is a relationship of cetane to nitrogen
level of a fuel, it has now been found that as a result
of this invention it is no-t the total nitrogen content
of the product blend which is relevant to simultaneous
control of cetane, Ramsbottom carbon, and stability of
the fuel product. Without regard to the nitrogen
content of the ultimate blend obtained, the amount of
added nitrogen i8 the relevant parameter to be
controlled. Added nitrogen is defined herein as the
nitrogen content of the final blended product after
step (4) less the nitrogen content of the untreated
diesel oil stock used in step (4) before addition of
treated diesel oil obtained from step (3).
Regarding the blendability of Ramsbo-ttom carbon
content, it must be recognized that ASTM procedures
reguire that the fueL first be distilled, and the
carbon measurement then be made on the 10% bottoms
remaining (by pyrolysis). This is because the
Q~
Ramsbottom carbon precursors are normally found in the
bottom cut of the die~el fuel. By concentrating these
precusors by distillation, the precision of the carbon
measurement is greatly improved. If another low
Ramsbottom stock is blended, Ram6bottom carbon is not
necessarily reduced because that blend-stock is
distilled out before carbon measurement. Blending a
heavier stock with the high carbon content stock ~so
that the bottom 10% i~ relatively dilute in
carbon-forming compounds) might be contemplated but
this would violate the ASTM end point specifications on
the diesel fuel. Fur~hermore, for nitrogenated stocks
produced in the process of thè present invention, the
nitrogen compounds are known to be polymerization
catalysts for carbon formation, so that small amounts
produce signiicant Ramsbottom carbon even when
diluted.
As to stability of diesel fuels, the stability of
diesel fuels and blends of diesel fuels are generally
improved by the addition of certain stability addi-
tives. Use ul additives include alkyl amines in either
a petroleum or polymeric solvent. The amine functional
groups in these additives are predominantly found in
high molecular weight molecules containing either
branched chain alkyl or allyl groups. Dupont, UOP, and
13~
- 38 -
Ethyl Corporation produce additive~ of this general
composition, although the specific compositions of such
additives are generally proprietary. sorg-warner
Chemicals market~ an additive which has a phenolic base
structure, while Petrolite Corporation produces an
alkylamine-iodine base additive ~n an acrylate polymer
and xylene solvent as stability additives to diesel
fuels. Table 2 summarizes known compositional details
of these commercially available additives.
It has also been found that when conventional
stability additives are employed with the blended
diesel fuel product produced by the process of the
present invention, the levels required to achieve
acceptable stability results are unexpectedly reduced.
More specifically, the Petrolite commercially
available stability additive (Petrolite T-363),
provided the best stability improvement response for a
given stability additive level. Reduction of the ASTM
D 2274 oxidation stability rating by 47%, 67% and 81%,
using stability additive levels of 60, 100 and 150 ppm
(based on the blended diesel fuel product obtained in
this invention) at 3% by weight of the diesel oil
product of step (3) in the blend diesel fuels of step
(4), re~pectively were aGhieved, with only 60 to 80 ppm
being re~uired to provide an adequate stability.
1~0~
Similar stability improvements at 6tability additive
levels in the 60 to 80 ppm range were also achieved
wi-th other Petrolite additives and would be expected
over the entire range to 150 ppm.
Although the other amine based commercially
available additives, e.g., those produced by Dupont,
UoP, and Ethyl improved stability, this improvement was
less than that achieved with the preferred commercially
available Petrolite products for the same additive
level. However, acceptable stability could be achieved
at a higher ppm level than for Petrolite.
A reduction in the stability additive requirement
to about 25% to 75%, more typically 33% to 50%, for the
blended product produced in the present invention,
where the product of step (3) used to produce such
blend of step (4) is subjected to the inorganic alkali
treatment as in step (3) in comparison with a blended
product produced where the product used in producing
the blend of step (4) is not so subjected to an alkali
treatment as in step (3). The inorganic alkali
treatment of step (3), therefore, reduces the stability
additive level re~uirement from, for example, about 60
to 80 ppm down to about 20 to 40 ppm level, to give a
suitable stability based upon a product blend with a
blending of 3% by weight of the diesel oil of step (3)
13(J 0~
- 40 -
in producing the diesel uel bl~nd of step (4) of thiæ
invention.
As a result, it can be seen that the process of
this invention provides the ability to reduce the
amount of stability additive to levels of about 25% to
75%, more typically 33% to about 50%, of the amount of
stability additive which would be employed in the
absence of the inorganic alkali treatment of step (3)
of the process of this invention.
~3~ 64
- 41 -
Table 2
Compo~itional Summary o
CommerciallY Available StabilitY Additives
Additive TyPe Chemical Compo~ition
Petrolite T-260 Organic amines
Petrolite T-316 Organic amines
Petrolite T-362 Organic amines
Petrolite T-363 Alkyl amine-iodine base with
acrylate polymer in xylene
Petrolite T-386 Organic amines
UOP Polyflo T121 N-~l-methylheptyl) ethanol amine
N,N' di~alicylidene-1,2-propane-
dlamine in a naphtha solvent
UOP Polyflo T122 Polyamino polyol
N-(l-methylheptyl) ethanol a~m:Lne
N,N' disalicylidene-1,2-propane
dlamine in a naphtha ~olvent
UOP AID T2525 High molecular weight amine
polymer and petroleum solvent
UOP Polyflow T120 Similar to Polyflo T121, but
without a copper deactivator.
Dupont E'uel Oil Additive $~3 Organic amine
Borg Warner Ultranox 226 2,6-di-t-bukyl-4~methylphenol
Borg Warner Ultranox 236 4,4'-thio-bi~(2-t-butyl-5-
methylphenol)
Borg Warner Ultranox 246 2,2'-methylene-bis(4-methyl-6-
t-butyl phenol)
Borg Warner.Ultranox 254 polymeric 2,2,4-trimethyl-1,2-
dihydroguinoline
Borg Warner Ultranox 256 polymeric ~3terically hindered
phenol
- 42 -
Figure 1 shows the effect of storage on the
blended diesel fuel resulting from step (4) of the
process of the present invention as a function of ASTM
color (D-1500) in relation to time where the treated
diesel oil of step (1) is washed with water or is
treated with an agueous sodium hydroxide solution. It
is surpising that by using the aqueous alkali solution
treatment after the treatment with nitrogenous treating
agent in step (1) and separation of excess nitrogenous
treating agent in step ~2) but prior to blending in
step (4) results in the marked improvement in color of
the blended diesel fuel on storage. This is
particularly true since treatment with inorganic alkali
in the form of an a~ueous solution does not appear to
initially have much effect on the color of the dlesel
oil obtained in step (3).
Considering the background of stability and color
formation of diesel oils, the mechanisms are not well
known except in general terms. It is, however,
recognized that trace levels of contaminants, such as
nitrogen compounds, play an important role in sediment
formation, often as catalysts. They may also play a
role in color development. As a result, as to
stability, dilution of an unstable fuel by a stable
fuel does not generally improve stability appreciably.
~3~)0~
- 43 -
Upon dilution by a stable uel, there are still
suffi~ient quantitie~ of these initi~tors to cause
stability problems. Increased color on storage may
also result. As a re6uLt, the conventional method to
attack stability pxoblems has been to use a range of
antioxidants, with the choice of the appropriate
antioxidants being selected empirically (governed by
which mechanism is operative or a given stock).
Unfortunately, for nitrogenated stocks, uneconomic
levels o additives have been required in the past.
It has also been found in this invention that when
such stability improvqng additives are used, the amount
thereof necessary in the blended diesel fuel produced
by the proceæs of this invention can be markedly
reduced. Thi~ effect i8 6hown in Figure 2 discussed
below.
Figure 2 demonstrates that the amount of stability
additive to the diesel fuel blend obtained in step (4)
of the process o this invention can be markedly
reduced by using the treatment with inorganic alkali of
step (3) of the process of this invention. For
example, the amount of additive, Petrolite T-363 in
(ppm) to achieve a particular Nalco stability for the
alkali treatment using an aqueous solution of ammonium
hydroxide is markedly reduced in comparison with the
~L300~
- 44 -
amount of additive required for the same Nalco
s-tability where the treatment in step (3) of the
process of this invention i~ simply a water wash.
Figures 3, 4, 5 and 6 clearly show graphically the
above advantages of the process of thi~ invention in
terms of cetane enhancement and stability of the
blended fuel product obtained in accordance with the
trea-tment with nitrogenous treating agent step, the
removal of excess nitrogeneous treating agent step and
the blending step as disclosed in parent application
Serial No. 832,196, iled February 24, 1986, the
disclosure of which is incorporated herein by
reference. The addition o the alkali treatment step
between separation of the nitrogeneous treating agent
step and the blending step as in this invention does
not substantially change the nature of the improvements
in cetane number enhancement achieved but additionally
provides the ability to unexpectedly minimize color
development of the diesel fuel blend as shown in
Figure 1 and reduce the amount of any affirmatively
added stability enhancer which might be used as shown
in Figure 2. As long as the nitrogen added levels
adhered to set forth in step (4) above are as to the
relationship of the amount of treated diesel oil o
step (3), used in the blend of step (4~, the same
136~ 4
- 45 -
general cetane enhancements achieved in the process of
said parent application Serial No. 832 J 196 are achieved
with the process of this invention and surprisingly the
amount of color developed on storage of the blend of
step (4) i5 minimized as shown in Figure 1 hereof. The
presence or absence of an alkali treatment step does
not substantially affect the cetane enhancement,
characteristics achievable, etc.
To illustrate the cetane enhancement, stability,
etc., characteri#tics achievable in the process of this
invention, reference more specifically is made to
Figures 3 to 6 below~
To obtain the data shown in Figures 3 and 4, the
diesel oil of step (2) was blended with an untreated
oil to produce a blend product. Since the oil of step
(2) contained nitrogen at levels of 2000 to 4000 ppm,
the this oil was employed in the blend at about 2% to
15% by weight of the total blend. Analogous results to
those shown in Figures 3 and 4 are achieved when an
alkali treated oil of step ~3) is used to produce a
blend product. The prior art has variously reported
cetane number improvements of 5 to 20 numbers. Figure
shows blending cetane number~ achieved generally
corresponding to data with less than about 15% by
weight treated oil in the blend. Since the di~sel oil
130~4
- 46 -
feed had a cetane number of about 40, the product oil
of step (2) or of step (3) would be e~pected to have a
cetane number o~ 45 to 60. Quite aurprisingly, cetane
numbers of 60 to 220 are achieved when blend
proportions of lesa than 15% by weight of the oil
obtained in step (2) or in step (3) are used in
producing the diesel fuel blend product. However, it
is to be emphasized the blend proportion used in Eigure
was employed only for purposes of illustration.
Various other combinations of treating reactor
variables and blend proportions to provide appropriate
levels of added nitrogen as herein defined can be
employed.
As will be discussed below, the line through the
data of Figure 5 may be used to describe the cetane
number of oils produced in step ~2) and by analogy in
step (3) of the present invention. For these runs,
this corresponds to blend proportions of less than 15%
by weight. When the cetane of the final blend of
diesel fuel obtained is calculated from the curve shown
in Figure 5 to eliminate scatter, the resulta of
Figure 6 are obtained. In view of the very ~mall
amounts of step (2) and by analogy of step (3) oil
used, it is very surprising that a large improvement in
cetane of the blended diesel fuel product is achieved.
0~;4
- 47 -
In particular, a 3 cakane number increase in the diesel
fuel hlend produced is obtained. Furthermore, it is
particularly surprislng that the maximum in the cetane
curve resides in the blend region where Ramsbottom
carbon content and stability are simultaneously
controlled.
Figures 1 through 6 indicate surprising and
unobvious results, particularly by considering the
weight of the combination o these effects. It is
surprising that blends with added nitrogen having
acceptable Ramsbottom carbon also provide blends of
acceptable stability, with large cetane improvement and
with a maximum cetane in regions of excellent stability
and Ramsbottom carbon as well as improved blend color
development on storage, i.e., less color developed, as
discussed above.
The treated diesel oil from step (1) of the
process of this invention can typically contain from
2000 to 4000 ppm nitrogen. The measured cetane ratings
of such treated oils generally is 44 to 50 with an
initial cetane rating of 40 for the diesel oil feed to
step (1), with an improvement over step (1) diesel oil
feed (40 cetane) of 4 to 10 cetane numbers, similar to
that which would be expected rom the prior art. If
the nitrogen added data are considered for an untreated
~3~)0~)~4
- 4~
feed o 100 ppm nitrogen to produce the diesel uel
blend, simple calculations reveal that less than about
20% by weight and usually less than about 10% by weight
of treated diesel oil can be accommodatled in the blend.
With such a low blend percentage o treated diesel oil,
it would not be expected that the blended diesel fuel
product could have a cetane improvement beyond about 1
number ba~ed on conventional knowledge. Nevertheless,
a surprisingly large cetane improvement was obtained.
Further, if the cetane i8 measured of the blended
diesel fuel product, the blending cetane value of the
step (2) and by analogy of step (3) diesel oil can be
back-calculated from the well-known linear blending
equation. The surprisingly large cetane improvement of
the diesel fuel blend produced leads to extremely large
apparent blending cetane ratings for the diesel oil
product obtained from step (2) or step ~3). Whereas
conventionally, cetane improvements of the die~el oil
product of steps (1), (2) and (3) of about 10 cetane
numbers might be predicted and such valu~s were indeed
measured for pure diesel oil product of step ll), the
blending cetane values of the diesel oil product
obtained after conducting steps (1), (2) and (3) are
markedly increased.
~ 3(~0~Ç~4
- 49 -
With these dilute dies~l blends, little cetane
improvement would have been expected. However, as
shown in Figure 5, the effective cetane rating of the
diesel oil product used in the blend produced becomes
surprisingly large for the~e dilute blend~. Not only
do these blends exhibit useful Ramsbottom carbon and
stability under the nitrogen added criteria of the
present invention, but a~so the cetane level of the
diesel fuel blend i8 maximized as shown in Figure 6.
The blended diesel fuel obtained in accordance
Wit}l the process of this invention can be used in any
application wherein a diesel fuel meeting commercial
specifications is desired. For example, the blended
diesel fuel can be used as fuel for automotive, motor
truck, railroad or marine diesel uses.
The following examples are given to illustrate the
process of this invention in greater detail. ~owever,
these examples are not to be construed as limiting the
scope of the present invention but rather are given to
merely illustrate the present invention. Unless
otherwise indicated herein, all parts, percents, ratios
and the like are by weight.
Example 1
To provide the data of Figures 3 through 6, diesel
oils were fed to a treating reactor, consisting of
- 50 -
individual stocks selected from those shown in Table 2
for each run~ These products were decanted to separate
a re~idu~ phase a~ discussed below to produce a treated
diesel oil. This oil was then blended with individual
stocks A, B, or C selected from those described in
Table 3 shown below to produce a blended diesel fuel.
The designations in Figure 3 show the nontreated diesel
fuel used to blend with the treated diesel oil. Note
that the treating reactor die~el oil feed, ~tocks A
through G of Table 3, contained widely varying amounts
of nitrogen.
In each one o the runs, about 500 grams o diesel
oil was placed in a 1000 ml volume reactor which
consisted of a beaker with a septum on the side.
Nitric acid was used as the nitrogenous treating agent.
The septum was about 1 inch from the bottom surface of
the reactor for nitric acid injection. A measured
~uantity of 90% nitric acid (5.5g for 0.01 A/0, 16.5g
for 0.03 A/0, 2.75 for 0.05 A/0, and 33g for 0.06 A/0)
was placed in a syringe and mounted on an in~ection
pump. Here, A/0 designates the acid to oil weight
ratio used. The oil was stirred with a lab size
stirrer at 1000 RPM. The temperature o the mixture
was controlled at specific levels between 25C and 80C
for these runs. Acid was injected over a 30 minute
~3003~
period. After the acid injection, the reaction mixture
was further stirred for an additional 30 minutes to
ensure consumption of residual acid in the mixture. A-t
the completion of the treatment, the oil was separated
from the residue formed by simple decantation. The
separated oil was weighed~ water washed and filtered.
A specified amo~nt of oil was blended with one of the
untreated diesel oils shown in Table 3. Depending on
the A/0 ratio and treatment temperature used, different
percent blends were made to be able to generate the
relationships among variables shown in Eigures 3 to 5.
Samples of the blended products were analyzed for
cetane number (ASTM D613), Ramsbottom carbon (ASTM
D524~, and Nalco stability. With 0.01 A/0 ratio
usually the nitrogen content of the treated oil is
about 1500 to 2000 ppm; with A/0 = 0.03 the nitrogen
content of the treated oil is about 3000 to 4000 ppm
and for A/0 = 0.05 the nitrogen content of treated oil
is about 5000 to 6000 ppm. With A/0 = 0.01, 5 to 10
percent blends were made (N added = 75 - 150 ppm).
With A/0 = 0.03, 3 to 5 percent blends were made (N
added = 100 - 150 ppm) and with A/0 = 0.06, 1 to 2
percent blends were made (N added ~ 60 - 120 ppm) The
results obtained are shown graphically in Figures 3 -to
5.
~OO~
- 52 -
Tablo 3
Propertles of VariouJ Dlesel Oil 5tot:ks
Low Pressure ~loderate Pre3sure Ill~h Pre3~uro
Strai~ht Run Dle~el _ydrotreated ~59~ Hydrotreated
E F ~; C_ A B D
Gravity,API 34.637.6 32.4 38.8 36.3 34.2 30.8
Sul~ur, wt% 1.070.72 1.08 0.09 0.60 0.46 0.0
Nitrogen ~ ppm200 150 93 96 191 256 87
llam~bottom
t~arbon % O.IZ90.144 0.139 0.122 0.111 0.105 0.107
N~lt70 - - 2 4 1 2 2
Cetane Number 58 53 48 39.2 41.7 41 38.8
D86 D1stlllat1On, F
Start216 300 270 405 Z50 380
5% 418 408 440 41~ 380 410
10% 4~12 446 468 440 395 426
30% 532 501 520 485 450 480
50% 55a 529 550 508 490 519
70% 584 562 580 558 540 550
90% 618 619 640 619 600 610
95% 636 - - 645 640 635
comParative ExamPle 1
~30a~
- 53 -
500 grams of (Stock H as disclosed in Table 1)
diesel oil was placed in a 1000 ml volume reactor which
consisted of a beaker with a septum on the side. The
sep-tum was about 1 inch from the bottom surface of the
reactor for nitric acid injection. Mitric acid was
used as the nitrogeneous treating agent. 21.4 grams of
a 70% aqueous solution of nitric acid was placed in a
syringe and mounted on an injection pump. This
quantity of acid corresponds to an acid-to-oil weight
ratio of 0.03:1 (based on 100% nitric acid). The oil
was stirred with a lab size stirrer at 1000 rpm. The
temperature of the reactor was controlled at 85C
throughout the treatment step with nitrlc acid. The
nitric acid was injected over a 15 minute period.
After the acid injection, the reaction mixture was
further stirred for an additional 60 minutes to ensure
consumption of residual acid in the mixture. At the
completion of the nitric acid treatment, the oil was
separated rom the residue formed by simple decantation
to remove any excess nitric acid. The separated oil
was weighed, and filtered. A portion of the treated
oil was water washed with a water-to-oil weight ratio
of 0.1:1 followed by filtration.
A specified amount of the water washed oil was
blended into a diesel oil pool which contained 30
~3~ i4
- 54
volume percent o LC0, the characteristics of which are
shown in Table 1. The blends were made according to
the nitrogen content of the treated oil to obtain 100
ppm nitrogen added to the pool which corresponded to at
least a 2 cetane number enhancement to produce a diesel
~uel blend. Samples of the ble~ded product6 were
analyzed for Nalco stability and color (ASTM-D 1500).
The Nalco stability rating of this blend wa5 13 which
is substantially higher than acceptable for a fungible
diesel fuel. The immediate ASTM color reading for this
diesel fuel blend was 1.5 which Was the same color
reading a~ that of the die~el oil pool beore addition
of the treated diesel oil. After 3 days storage of the
blend, the ASTM color was measured to be 4.0, which is
greater than a diesel fuel meeting commercial
specifications of 3. The results o color testing with
longer storage time are shown graphically in Figure 1.
Example 2
Another portion of the decanted treated oil
obtained as discussed in Comparative Example l above
was treated with a 1 M aqueous solution of sodium
hydroxide with a 60dium hydroxide to oil weight ratio
of 0.1:1. After the separation of the aqueous phase,
the product was filtered and blended into a diesel oil
pool as described in Comparative Example 1 above
~L30~
- 55 -
(containing 30 volume percent LC0) with a blend ratio
to obtain 100 ppm nitrogen added to the diesel oil
pool.
Samples of the blend were analyzed for Nalco
stability and ASTM color as described above. The Nalco
stability rating of this blend wa~ 3, a value generally
acceptable for a commercial diesel fuel. The immediate
ASTM color readin~ for this blend wa3 the same as the
diesel oil pool before addition of the treated oil.
After 3 days storage, the blend ASTM color was 2 . 5 .
The resul ts o~ the color test~ With ~torage time for
this blend are also shown graphically in Figure 1.
Substantial improvement in the storage color of the
blend with time ca~ be seen from the results in
Figure 1.
Comparative Example 2
500 grams of a diesel oil (Stock I) was treated
With 21.4 g of a 70% nitric acid aqueous solution
according to the procedure set forth in the Comparative
Example 1. After decantation, a portion of the treated
oil was water washed wlth a water-to-oil weight ratio
of 0.1:1. The washing procedure was as follows: 100 g
of treated oil was mixed with 10 g of water. The
mixture was placed in a separatory funnel and shaken
or 30 seconds. The mixture was allowed to settle for
~:~o~
- 56 -
10 minutes after which the two phases were separated.
The produc-t oil was then filtered. A speciied amount
of the treated oil was blended into a commercially
available sample of diesel oil pool which contained
LCO. The percent blends were made according to the
nitroqen level of the treated oil in order to obtain
100 ppm nitrogen added to the diesel oil pool.
Different level~ of Petrolite T-363 as a stability
additive (a commercially available stability additive
believed to be a mixture of alkyl amines and al}cyl
amine iodine complexes) were added to this blend and
the Nalco stabilikies were measured. The results
obtained are shown graphically in Figure 2.
Example 3
Another portion of the treated oil obtained as
described in Comparative Example 2 after decantation
was treated with a 1 M solution of a~monium hydroxide
with a weight ratio of 0.1:1 to the oil according to
the procedure of Compartive Example 2. After
separation of the two phases, the product was filtered
and blended into a diesel oil pool as described in
Comparative Example 2 above with a blend ratio to
obtain 100 ppm nitrogen added to the diesel oil pool.
Different levels of Petrolite T-363 as a stability
additive were added to this blend and the Nalco
OOfiA
- 57 -
stabilities were measured. The results obtalned are
shown graphically in Figure 2. Figure 2 clearly
demonstrates th~ reduction in the amount of stability
additive required upon alkali treatment of the treated
oil after decantation to remove excess nitrogenous
treating agent.
When the above procedures of Example 3 were
repeated using aqueou~ solutions of sodium hydroxide or
potassium hydroxide, similar re~ults were obtained.
Example 4
500 qrams of a diesel oil ~Stock H) was treated
with 21.4 g o a 70% aqueous nitric acid solution
according to the procedures outlined in Comparative
Example 1.
The treated oil after decantation to remove excess
nitrogenous treating agent was treated with aqueous
solutions of different inorganic alkali compounds. The
inorganic alkali compounds used were: 1 M sodium
hydroxide, 1 M potassium hydroxide, 1 M ammonium
hydroxide. For comparison, treatment was also
conducted with a water wash. The treatments were done
according to the procedure set forth in Comparative
Example 2 above. The a~ueous phase from each treatment
was analyzed for chemical oxygen demand (COD). The
results obtained are shown in Table 4 below. The oil
~.~0~4
- 58 -
pha~e from the washes was filtered and the nitrogen
content was measursd. Compared with the nitrogen
measurements on the unwashed oil, the percent nitrogen
reduction of each treatment was calculated. The
results obtained are also shown in Table 4.
Table 4
% Nitrogen
TreatmentCOD (mq/l) Reduction
Water 11794
Sodium Hydroxide183311 20.27
Potassium Hydroxide 145984 18.70
Ammonium Hydroxide 40309 11.08
These results in the above examples demonstrate
that an improvement in cetane number of a diesel fuel
blend can be obtained, when the t~eated oil added to
the blend is treated with a solution of an inorganic
alkali and such is then blended with an untreated
diesel oil. The blend so produced has good storage
stability and color and possesses useful levels of
Ramsbottom carbon. Further, these results show that
the amount of stability additives which may be used in
such blends is reduced due to the inorganic alkali
treatment.
While the invention has been described in detail
and with reference to specific embod~ments thereof, it
Ç;4
-- ss --
will be apparent to one skilled in the art that various
changes or modification~ can be made therein without
departing from the scope and spirit thereof.
