Note: Descriptions are shown in the official language in which they were submitted.
CA 02547170 2006-05-25
WO 2005/056733 PCT/US2004/040095
METHOD FOR UPGRADING OF DIESEL
FEED BY TREATMENT WITH SULFURIC ACID
FIELD OF THE INVENTION
[0001] The instant invention relates to a method for upgrading nitrogen-
containing hydrocarbon streams. More particularly, the present invention
relates to a method for producing low-sulfur, low-nitrogen diesel boiling
range
products involving contacting a diesel boiling range feedstream with an acidic
solution to selectively remove heterocyclic nitrogen-containing compounds
before hydrotreating.
BACKGROUND OF THE INVENTION
[0002] Currently, there exists a need to reduce the sulfur and aromatics
content of motor fuels, in particular diesel, to meet current environmental
emission regulations. While both the sulfur and aromatics content of diesel
boiling range feedstreams from which diesel motor fuels are derived can be
reduced to a satisfactory level through the use of catalytic treatments, the
catalytic treatments are severely impeded by nitrogen-containing compounds
present in the feedstream. Thus, many methods for reducing the nitrogen
content in feedstreams, such as those used in sulfur and aromatics reducing
processes, for motor fuel production have been proposed.
[0003] For example, United States Patent Number 3,719,587 teaches the use
of dilute sulfuric acid (0-10 wt°/~) to remove basic nitrogen species
from coal
liquefaction derived naphtha. Unfortunately, hydrotreating catalysts are not
only poisoned by basic nitrogen species, but also by non-basic nitrogen
heterocycles that are abundant in diesel boiling range feedstreams. For this
reason, stronger sulfuric acid has been used to remove substantially all of
the
nitrogen species.
CA 02547170 2006-05-25
WO 2005/056733 PCT/US2004/040095
[0004] Also, United States Statutory Invention Registration H136~, Fraytet,
teaches the use of concentrated sulfuric acid, i.e. at least 95 wt.% sulfuric
acid,
to treat straight run jet fuel boiling range streams. The process requires
that the
sulfuric acid-containing stream be dispersed in the jet fuel in the form of
droplets smaller than about 300 microns. The Fraytet process discloses that
90% or more of the nitrogen can be removed from the jet fuel boiling range
stream. However, as Fraytet points out, separation of the acid from the
feedstream is critical to avoid unwanted secondary reactions from occurring,
such as, for example, polymerization of olefins and reaction of sulfuric acid
with thiophenic species. These unwanted reactions are detrimental in several
ways. First the unwanted side reactions force the practitioner of these
processes to utilize more sulfuric acid because these reactions consume a
portion of the sulfuric acid. Secondly, it degrades the product by forming
high-
boiling polymers from olefinic materials, which become soot-formers in
subsequent combustion. Finally, some of the byproducts from these unwanted
reactions are removed due to solubility in the acid byproduct and lead to an
overall yield loss for the process.
[0005] However it is also known in the art that dispersive contacting
methods such as those of Fraytet have certain drawbacks such as "pepper
sludge" formation. Pepper sludge formation occurs when the tiny droplets of
acid are not readily coalesced or settled in gravity settlers. The dispersed
acidic
material suspended in the feed is thus carried over with the treated feed, and
practitioners of such processes are forced to utilize caustic treatments to
neutralize the pepper sludge and avoid corrosion problems. However, the
"pepper sludge" suspended in the feed also contains nitrogen species that were
removed from the feed. Upon neutralization, the nitrogen species are liberated
CA 02547170 2006-05-25
WO 2005/056733 PCT/US2004/040095
-3-
and return to the feed. Thus, the existence of pepper sludge in dispersive
treatment methods limits the ultimate level of nitrogen reduction that can be
achieved. Therefore, there exists a need in the art for a more effective
nitrogen
removal method for diesel boiling range feedstreams.
[0006] Therefore, there still exists a need in the art for a more effective
nitrogen removal method for diesel boiling range feedstreams which benefits
the hydroprocessing of the diesel boiling range feedstreams, i.e. a process
that
more selectively removes nitrogen-containing heterocycles that poison
hydroprocessing catalysts without incmTing the debits listed above that are
the
result of unwanted chemistry.
SUMMARY OF THE INVENTION
[0007] The instant invention is directed at an improved method for
hydrotreating a diesel boiling range feedstream containing both nitrogen and
sulfur contaminants and having a total acid number. The method comprises:
a) providing a sulfuric acid solution having a sulfuric acid concentration of
at least about 75 wt.%, based on the sulfuric acid solution;
b) contacting a diesel boiling range feedstream containing both nitrogen
and sulfur heteroatoms with the sulfuric acid solution under conditions
effective at removing at least about 85 wt.% of the nitrogen compounds
contained in said diesel boiling range feedstream thereby producing at
least a diesel boiling range product and a used sulfuric acid solution,
wherein the volumetric treat rate of the sulfuric acid solution is greater
than about 0.5 vol.%, based on the diesel boiling range feedstream; and
c) hydrotreating said diesel boiling range product.
CA 02547170 2006-05-25
WO 2005/056733 PCT/US2004/040095
-4-
[0008] In one embodiment of the instant invention the sulfuric acid solution
is a spent sulfuric acid solution obtained from an alkylation process unit
wherein the spent sulfuric acid solution is produced by:
a) combining an olefinic hydrocarbon feedstream containing C4 olefins
with isobutane to form a hydrocarbonaceous mixture; and
b) contacting the hydrocarbonaceous mixture with sulfuric acid under
conditions effective for producing at least an alkylate and a sulfuric acid
solution having an acid concentration of at least about 75 wt.%.
[0009] Another embodiment of the instant invention is directed at an
improved method for hydrotreating a diesel boiling range feedstream
containing both nitrogen and sulfur contaminants and having a total acid
number. The method comprises:
a) providing a sulfuric acid solution having a sulfuric acid concentration of
at least about 75 wt.%, based on the sulfuric acid solution;
b) contacting a diesel boiling range feedstream containing both nitrogen
and sulfur heteroatoms and having a total acid number with the sulfuric
acid solution under conditions effective at removing at least about ~5
wt.% of the nitrogen compounds contained in said diesel boiling range
feedstream thereby producing at least a diesel boiling range product
having a total acid number and a used sulfuric acid solution, wherein the
volumetric treat rate of the sulfuric acid solution is greater than about
0.5 vol.%, based on the diesel boiling range feedstream;
c) contacting said diesel boiling range product with an effective amount of
an acid reducing material selected from caustic and water under
conditions effective at reducing the total acid number of said diesel
boiling range product; and
CA 02547170 2006-05-25
WO 2005/056733 PCT/US2004/040095
=5-
d) hydrotreating said diesel boiling range product.
[0010] In one preferred embodiment, the acid reducing material is water.
[0011] In another preferred embodiment of the instant invention, the
contacting of the diesel boiling range product with water reduces the total
acid
number of the diesel boiling product to at least the total acid number of the
diesel boiling range feedstream.
BRIEF DESCRIPTION OF THE FIGURES
[0012] Figure 1 contains data obtained for Example 2 at 1 vol.% treat rate at
various acid concentrations.
[0013] Figure 2 contains data obtained at 4 vol.% treat rate at various acid
concentrations.
[0014] Figure 3 illustrates the combined impact of acid strength and
treatment volume on the total nitrogen content of the feed.
[0015] Figure 4 shows the combined impact of acid strength and treatment
volume on the total sulfur content of the feed.
[0016] Figure 5 shows the impact of both nitrogen removal and sulfur
removal on yield loss.
CA 02547170 2006-05-25
WO 2005/056733 PCT/US2004/040095
-6-
DETAILED DESCRIPTION OF THE INSTANT INVENTION
[0017] The instant invention is a method for removing nitrogen from diesel
boiling range feedstreams containing both nitrogen and sulfur contaminants.
The present method involves contacting, preferably by a non-dispersive
method, a diesel boiling range feedstream containing both nitrogen and sulfur
contaminants with a sulfuric acid solution thus producing a diesel boiling
range
product. The contacting of the diesel boiling range feedstream with the
sulfuric
acid solution reduces the nitrogen content of the diesel boiling range product
by
at least 85 wt.%. The resulting diesel boiling range product is then
hydrotreated. It should be noted that hydrotreating and hydrodesulfurization
are used interchangeably herein, and the phrase "diesel boiling range
feedstream" is meant to refer to a diesel boiling range feedstream containing
both nitrogen and sulfur contaminants and possessing a Total Acid Number
("TAN"). TAN is a measurement of the acidic content of an oil and is
determined experimentally by titration of the oil with an appropriate base, as
described for example in ASTM method number D664.
[0018] Feedstreams suitable for treatment with the present method boil
within the diesel range. The diesel boiling range includes streams boiling in
the range of about 300°F to about 775°F, preferably about
350°F to about
750°F, more preferably about 400°F to about 700°F, most
preferably about
450°F to about 650°F. These include diesel boiling range
feedstreams that are
not hydrotreated, are a blend of non-hydrotreated diesel boiling range
feedstreams, previously hydrotreated diesel boiling range feedstreams, blends
of hydrotreated diesel boiling range feedstreams, and blends of non-
hydrotreated and hydrotreated diesel boiling range feedstreams.
CA 02547170 2006-05-25
WO 2005/056733 PCT/US2004/040095
[0019] The diesel boiling range feedstreams suitable for treatment with the
present method also contain nitrogen. Typically, the nitrogen content of such
streams is about 50 to about 1000 wppm nitrogen, preferably about 75 to about
800 wppm nitrogen, and more preferably about 100 to about 700 wppm
nitrogen. The nitrogen appears as both basic and non-basic nitrogen species.
Non-limiting examples of basic nitrogen species may include quinolines and
substituted quinolines, and non-limiting examples of non-basic nitrogen
species
may include carbazoles and substituted carbazoles.
[0020] In practicing the instant invention, the above-defined feedstream is
intimately contacted with a sulfuric acid solution. The sulfuric acid solution
used herein contains at least about 75 wt.% sulfuric acid, based on the
sulfuric
acid solution, preferably greater than about 75 wt.%, more preferably about 75
wt.% to about 88 wt.%. The sulfuric acid solution may be obtained through
any means known. It is preferred that the sulfuric acid solution be the spent
acid from an alkylation process unit having a sulfuric acid concentration
within
the above-defined ranges. A typical allcylation process involves combining an
olefinic hydrocarbon feedstream containing C4 olefins with isobutane to
produce a hydrocarbonaceous mixture. This hydrocarbonaceous mixture is
subsequently contacted with sulfuric acid. The sulfuric acid used for
contacting the hydrocarbonaceous mixture is typically reagent grade sulfuric
acid having an acid concentration of at least about 95 wt.%. Preferably the
sulfuric acid has a sulfuric acid concentration of greater than about 97 wt.%.
The hydrocarbonaceous mixture is contacted with the sulfuric acid under
conditions effective at producing at least an allcylate and sulfuric acid
solution.
The sulfuric acid solution so produced comprises at least about 75 wt.%
sulfuric acid, based on the sulfuric acid solution, preferably greater than
about
CA 02547170 2006-05-25
WO 2005/056733 PCT/US2004/040095
_$_
75 wt.%, more preferably about 75 wt. % to about 92 wt.%, about 0.5 to about
wt.% water, with the remaining balance being acid soluble hydrocarbons. It
is more preferred that the effective conditions be selected such that the
sulfuric
acid solution so produced comprises between about 82 and 92 wt.% sulfuric
acid, about 1 to about 4 vol.% water, with the remaining balance being acid
soluble hydrocarbons. However, it is most preferred that the effective
conditions be selected such that the sulfuric acid solution so produced
comprises between about 85 and 92 wt.% sulfuric acid, about 1.5 to about 4
vol.% water, with the remaining balance being acid soluble hydrocarbons.
[0021] It should be noted that it is within the scope of the present invention
to dilute the sulfuric acid obtained from the alkylation unit, or otherwise,
with a
suitable diluent, preferably water, in order to provide a sulfuric acid
solution
having the above-described concentration of sulfuric acid, i.e. at least about
75
wt.% sulfuric acid, based on the sulfuric acid solution, preferably greater
than
about 75 wt.%, more preferably about 75 wt.% to about 88 wt.%. In order to
determine the sulfuric acid concentration once the diluent has been added to
the
sulfuric acid solution, the sulfuric acid content and water content are
measured
by standard analytical techniques. The equivalent acid strength can then be
calculated with the following formula: equivalent wt% sulfuric acid = wt%
sulfuric acid / (wt% sulfuric acid + wt% water). In this formula, the acid
soluble hydrocarbon content of the spent alkylation acid is treated as an
inert
diluent with respect to the sulfuric acid and water content.
[0022] The diesel boiling range feedstream is contacted with the sulfuric
acid solution at an acid volumetric treat rate of greater than about 0.5
vol.%,
based on the diesel boiling range feedstream, preferably about 0.5 to about 20
CA 02547170 2006-05-25
WO 2005/056733 PCT/US2004/040095
-9-
vol.%, and more preferably 0.5 to about 5 vol.%. The contacting can be
achieved by any suitable method including both dispersive and non-dispersive
methods. Non-limiting examples of suitable dispersive methods include
mixing valves, mixing tanks or vessels, and other similar devices. Non-
limiting examples of non-dispersive methods include paclced beds of inert
particles and fiber film contactors such as those sold by Merichem Company
and described in United States Patent Number 3,758,404, which is hereby
incorporated by reference, which involve contacting along a bundle of metallic
fibers rather than a packed bed of inert particles. Preferred contacting
methods
are non-dispersive, and more preferred contacting methods are those that are
classified as dispersive.
[0023] The contacting of the diesel boiling range feedstream with the
sulfuric acid solution occurs under effective conditions. By effective
conditions, it is to be considered those conditions that allow the present
method
to achieve a reduction of nitrogen of greater than about 80 wt.%, preferably
greater than about 85 wt.% more preferably greater than about 92 wt.%.
Effective conditions are also to be considered those conditions that minimize
yield losses during the sulfuric acid solution treatment to about to about 0.5
to
about 6 wt.%, preferably about 0.5 to about 4 wt.%, more preferably about 0.5
to about 3 wt.%.
[0024] The contacting of the diesel boiling range feedstream with the
sulfuric acid solution produces at least a diesel boiling range product that
is
sent to suitable aromatics and sulfur removal processes. Thus, the used
sulfuric
acid solution, which now contains the removed nitrogen species, must be
separated from the diesel boiling range product. The used sulfuric acid
CA 02547170 2006-05-25
WO 2005/056733 PCT/US2004/040095
-10-
solution and the diesel boiling range product can be separated by any means
known to be effective at separating an acid from a hydrocarbon stream. Non-
limiting examples of suitable separation methods include gravity settling,
electric field induced settling, centrifugation, microwave induced settling
and
settling enhanced with coalescing surfaces. However, it is preferred that the
diesel boiling range product and the used sulfuric acid solution be separated,
or
allowed to separate, into layers in a separation device such as a settling
tank or
drum, coalesces, electrostatic precipitator, or other similar device. It is
more
preferred that the above-described fiber-film contactors be used for
separating
the used sulfuric acid solution and the diesel boiling range product produced
by
the present process. The diesel boiling range product can then be withdrawn
from the separation device and passed to a suitable hydrotreating process.
[0025] The diesel boiling range product thus obtained by the present method
will contain substantially less nitrogen, both basic and non-basic, than the
initial diesel boiling range feedstream. By substantially less, it is meant
that
the nitrogen content of the diesel boiling range feedstream is reduced by at
least about 80%, preferably at least about 85%, more preferably at least about
90%. Thus, it can likewise be said that the diesel boiling range product will
have a nitrogen level about 80%, preferably at least about 85%, more
preferably at least about 90% lower than that of the diesel boiling range
feedstream. This will typically result in a diesel boiling range product
having a
nitrogen level of less than about 200 wppm, preferably less than about 100
wppm, more preferably less than about 50 wppm, and most preferably less than
about 20 wppm. The contacting of the diesel boiling range feedstream with the
sulfuric acid solution also typically results in a diesel boiling range
product
CA 02547170 2006-05-25
WO 2005/056733 PCT/US2004/040095
-11-
having a TAN that is higher than the TAN of the diesel boiling range
feedstream.
[0026] The diesel boiling range product will also typically have a sulfur
concentration lower than that of the nitrogen-containing diesel boiling range
feedstream. Thus, the contacting of the diesel boiling range feedstream with
the sulfuric acid solution also reduces the sulfur content of the diesel
boiling
range product. The diesel boiling range product will therefore have a sulfur
content lower than the diesel boiling range feedstream. However, it is
desirable
to minimize the reduction of sulfur to minimize yield losses. Typically the
diesel boiling range product will have a sulfur content about 0.1 to about 25
lower than the diesel boiling range feedstream, preferably about 0.1 to about
15% lower, more preferably about 0.1 to about 10% lower, and most preferably
about 0.1 to about 5 % lower.
[0027] The diesel boiling range product is then hydrotreated to reduce sulfur
levels. Any suitable hydrotreating catalyst can be used to hydrotreat the
diesel
boiling range product. Non-limiting examples of suitable hydrotreating
catalysts are those that are comprised of at least one Group VIII metal oxide,
preferably an oxide of a metal selected from Fe, Co and Ni, more preferably Co
and/or Ni, and most preferably Co; and at least one Group VI metal oxide,
preferably an oxide of a metal selected from Mo and W, more preferably Mo,
on a high surface area support material, preferably alumina. These catalysts
can be arranged in any suitable manner such as, for example, fixed beds. It is
also contemplated that more than one hydrotreating catalyst can be used, and
more than one bed of catalysts can be used, e.g. a stacked bed configuration.
The diesel boiling range product is contacted with the hydrotreating catalysts
CA 02547170 2006-05-25
WO 2005/056733 PCT/US2004/040095
-12-
under conditions effective at removing at least a portion of the sulfur
contained
in said diesel boiling range product. Preferably, that amount of sulfur
necessary to meet current environmental regulatory standards is removed
during the hydrotreating. As previously mentioned, the contacting of the
diesel
boiling range feedstream with the sulfuric acid solution typically results in
a
diesel boiling range product having a TAN that is greater than the TAN of the
diesel boiling range feedstream. Thus, one embodiment of the instant
invention involves contacting the diesel boiling range product, prior to
hydrotreating, with an effective amount of a material selected from caustic
and
water, preferably water. By an effective amount of material, it is meant that
amount of material that reduces the TAN of the diesel boiling range product.
The diesel boiling range product is contacted with the caustic or water under
effective conditions. By effective conditions, it is meant those conditions,
that
when selected, allow for the reduction of the TAN of the diesel boiling range
product. Preferably the effective amount of material and the effective
conditions are selected such that the TAN of the diesel boiling range product
is
equal that of the diesel boiling range feedstream. More preferably the
effective
amount of material and the effective conditions are selected such that the TAN
of the diesel boiling range product is lower than that of the diesel boiling
range
feedstream.
[0028] The above description is directed to preferred embodiments of the
present invention. Those skilled in the art will recognize that other
embodiments that are equally effective could be devised for carrying out the
spirit of this invention.
CA 02547170 2006-05-25
WO 2005/056733 PCT/US2004/040095
-13-
[0029] The following examples will illustrate the improved effectiveness of
the present invention, but is not meant to limit the present invention in any
fashion.
EXAMPLES
EXAMPLE 1
[0030] Two 10 ml samples of a virgin diesel, referred to herein as feed #l,
were pipetted into two glass vials. One sample was combined with 0.1 ml (1
vol.% treat rate) of a reagent grade sulfuric acid solution having a sulfuric
acid
concentration of 96.1wt.%, and the other sample was mixed with the same
sulfuric acid solution but with 0. 2 ml (2 vol.% treat rate). The mixtures
were
shalcen by hand for 60 seconds and then allowed to separate at room
temperature. The two phases, i.e. the diesel boiling range product and the
sulfuric acid solution, separated and the diesel product layers were removed.
The diesel products were weighed and analyzed by ANTED for nitrogen and
sulfur contents. The results of this experiment are contained in Table 1
below.
EXAMPLE 2
[0031] A second diesel boiling range feedstream, referred to herein as feed
#2, was also treated according to the method outlined in Example 1 above. The
second diesel feedstream, however, contained about one-third cracked stock,
i.e
light cat cycle oil and coker gas oil. A 2 liter sample of feed #2 was also
treated in glass separatory funnels with the sulfuric acid solution described
above in Example 1 at a Svol.% treat rate. The results of these experiments
are
contained in Table 1 below.
CA 02547170 2006-05-25
WO 2005/056733 PCT/US2004/040095
-14-
TABLE
1
FeedVolumetricwppm Nitrogenwppm Nitrogen% NitrogenFeed
Treat Ratein Feed in Removal Recovered
Diesel Product
#1 1 vol.% 107 5 95 98%
2 vol.% 107 <2 98+ 98%
#2 1 vol.% 392 158 60 96%
2 vol.% 392 17 96 96%
5 vol.% 392 3 99 96%
[0032] As can be seen in Table 1, both feeds responded well to treatment
with the acidic solution, with nearly quantitative nitrogen removal. Low feed
losses were also observed. The feed recovered was calculated by dividing the
volume of diesel product recovered by the volume of the diesel feedstream and
then multiplying by 100. It was also noted that the acidic solution by product
from feed #2 became more fluid with increased acidic solution treat rates.
EXAMPLE 3
[0033] The experiments contained in Examples 1 and 2 above were repeated
with spent sulfuric acid solution obtained from an alkylation unit. The
composition of the spent alkylation acid was 90 wt% sulfuric acid, 4 wt% water
and 6 wt% acid soluble hydrocarbon (by difference). The equivalent sulfuric
acid concentration is 9&wt.%. The results of these experiments are contained
in
Table 2 below.
CA 02547170 2006-05-25
WO 2005/056733 PCT/US2004/040095
-15-
TABLE
2
Feed Volumetric wppm Nitrogenwppm Nitrogen % Nitrogen
Treat in Feed in Removal
Rate Diesel Product
#1 1 vol.% 107 4 96
2 vol.% 107 1 99
#2 2 vol.% 392 18 95
5 vol.% ~ 392 I 3 99
[0034] As can be seen from Table 2, similar results are obtained by using
the spent alkylation unit acid as are obtained using reagent grade sulfuric
acid.
EXAMPLE 4
[0035] Twenty milliliters of a virgin diesel was equilibrated to 120°F
in a
water bath. The 20 ml sample was combined in a glass centrifuge tube with 0.2
ml (1 vol.% treat rate) of reagent grade sulfuric acid having an acid'
concentration of 96.1 wt.%. This mixture was shaken for 60 seconds and then
subjected to ten minutes of cetrifugation at 1500rpm. The diesel and the
sulfuric acid solution separated rapidly, and the diesel layer was removed and
analyzed by ANTEK for nitrogen and sulfur content.
[0036] This procedure was repeated at several acid concentrations. The acid
concentration was reduced by adding distilled water to the reagent grade
sulfuric acid.
[0037] The results of these experiments are contained in Figure l, herein.
As can be seen in Figure 1, the sulfur content of the feed is unaffected by
the
sulfuric acid treatment until the sulfuric acid solution reaches a sulfuric
acid
concentration of greater than about 80 wt.%. As the concentration of the acid
increases from about 85 to about 94 wt.%, the sulfur loss increases and then
levels off. In contrast, the nitrogen content of the diesel boiling range
product
CA 02547170 2006-05-25
WO 2005/056733 PCT/US2004/040095
-16-
is reduced immediately by treatment with a sulfuric acid solution having an
acid concentration of even 5 wt.% and continues to decrease with increases in
acid strength until the sulfuric acid solution reaches a concentration of
about 50
wt.%. The initial decrease in the total nitrogen concentration represents the
removal of "basic" nitrogen species. However, the "non-basic" nitrogen
species are unaffected by the sulfuric acid treatment until the concentration
of
sulfuric acid in the sulfuric acid solution reaches about 75 wt.%. At 75 wt.%
acid strength, the sulfur species are unaffected.
[0038] Since one of the objects of the instant invention is to remove as much
of the nitrogen as possible from the feed while minimizing yield losses,
Figure
1 suggests that by using a sulfuric acid solution having an acid concentration
within the range of about 75 wt.% to about 85 wt.%, this goal can be achieved.
Though the data indicates that only 10% of the sulfur contained in the diesel
boiling range feedstream is lost when using a sulfuric acid solution having an
acid concentration of about 96 wt.%, this represents the largest single
contributor to yield loss because the removal of sulfur removes the entire
molecule in which the sulfur is contained.
CA 02547170 2006-05-25
WO 2005/056733 PCT/US2004/040095
-1~-
EXAMPLE 5
[0039] Twenty milliliters of a diesel boiling range feedstream containing
about one third craclced stock, i.e., light cat cycle oil and coker gas oil,
was
equilibrated to 120°F in a water bath. The 20 ml sample was combined in
a
glass centrifuge tube with 0.8 ml (4 vol.% treat rate) of reagent grade
sulfuric
acid having an acid concentration of 96.1 wt.%. This mixture was shaken for
60 seconds and then subjected to ten minutes of cetrifugation at 1500rpm. The
diesel and the sulfuric acid solution separated rapidly, and the diesel layer
was
removed and analyzed by ANTEK for nitrogen and sulfur content.
[0040] This procedure was repeated at several acid concentrations. The acid
concentration was reduced by adding distilled water to the reagent grade
sulfuric acid to dilute the acid concentration. Figure 2 contains the results
of
this experiment. As can be seen in Figure 2, treating the diesel containing
cracked stock produced results similar to those that were described with
respect
to Figure 1.
[0041] Figure 3 includes results obtained through this experiment also.
Figure 3 contains the nitrogen-reduction data obtained from treating the
diesel
boiling range feedstream containing cracked stoclc with various treat rates of
sulfuric acid solutions having varied acid concentrations. As can be seen in
Figure 3, nitrogen concentrations decrease with increased acid concentration.
[0042] Figure 4 includes results obtained through this experiment also.
Figure 4 contains the sulfur-reduction data obtained from treating the diesel
boiling range feedstream containing cracked stoclc with various treat rates of
CA 02547170 2006-05-25
WO 2005/056733 PCT/US2004/040095
-18-
sulfuric acid solutions having varied acid concentrations. As can be seen in
Figure 4, sulfur concentrations decrease with increased acid concentration.
[0043] Figure 5 compares the nitrogen and sulfur removal data contained in
Tables 3 and 4 with yield loss from treating the diesel boiling range
feedstream
containing craclced stock with various treat rates of sulfuric acid solutions
having varied acid concentrations. Thus, Figure 5 illustrates the impact on
yield loss from the removal of the nitrogen and sulfur species from the diesel
feedstream. Thus, in viewing Figure 5, one can optimize a nitrogen removal
method while minimizing feed loss.
EXAMPLE 6
[0044] 100 milliliters of virgin diesel having a total acid number ("TAN") of
0.26 mgKOH/g, a nitrogen concentration of 105 wppm, and a sulfur
concentration 1.36 wt.% of was treated with sulfuric acid solution having a
sulfuric acid concentration of 96 wt.%. The virgin diesel was treated by
adding
1 ml of the sulfuric acid solution to the virgin diesel at room temperature,
and
shaking this mixture by hand in a separatory funnel for one minute. The
mixture was then allowed to settle for 10 minutes and the spent acid solution
and diesel boiling range product were decanted to recover the respective
products.
[0045] The diesel boiling range product so recovered was separated into
equal portions that were placed into 50 ml centrifuge tubes. The tubes were
placed in a centrifuge operated at 1500 rpm for ten minutes. Acid sludge was
observed at the bottom of the centrifuge tubes. One of the four samples was
set
CA 02547170 2006-05-25
WO 2005/056733 PCT/US2004/040095
-19-
aside and marked "acid treated, centrifuged only", referred to herein as
"Sample #1" for comparison with the other three samples.
[0046] 25 ml of diesel boiling range product from each respective centrifuge
tube was pipetted into separate 50 ml centrifuge tubes for further treatment.
To
the first 25 ml sample, referred to herein as "Sample #2", 5 ml of distilled
water
was added. To the second and third samples, referred to herein as "Sample #3"
and "Sample 4", respectively, was added 2.5 ml of a 5 wt.% NaOH solution.
Samples 2, 3, and 4 were each shaken for 60 seconds, and then centrifuged for
ten minutes at 1500 rpm. Sample #4 was then further treated by adding 5 ml of
distilled water with subsequent shaking and centrifugation as defined above.
[0047] All of the Samples were submitted Galbraith Analytical Laboratories
for TAN analysis. Sample 2 was observed to have a TAN of 0.37 mg KOH/g,
illustrating that the sulfuric acid treatment increases the TAN of the diesel
boiling range products. Sample #2 had a TAN of 0.25 mg I~OH/g, illustrating
that simple water washing was sufficient to lower the TAN to at least the
level
in the feedstream.
[0048] Sample #3 had a TAN below detection limits, which may be an
erroneous reading due to caustic cai~yover. Sample #4 had a TAN of 0.03 mg
KOH/g, essentially zero. It should be noted that water washing after caustic
treating should minimize or eliminate caustic carryover, and that the nitrogen
concentration of the diesel boiling range products was not reduced by the
caustic and water washing.
CA 02547170 2006-05-25
WO 2005/056733 PCT/US2004/040095
-20-
[0049] Thus, Example #6 illustrates that simple water washing after sulfuric
acid treatment is effective at lowering the TAN of the diesel boiling range
product to at least that of the diesel boiling range feedstream, overcoming
corrosion problems associated with typical acid treating processes.
