U.S. patent application number 12/316948 was filed with the patent office on 2010-06-24 for purification of ultralow sulfur diesel fuel.
Invention is credited to Lawrence M. Candela, Gopalakrishan Juttu, Mark P. Kaminsky, David W. Leyshon, Allen B. Quakenbush.
Application Number | 20100155302 12/316948 |
Document ID | / |
Family ID | 42264493 |
Filed Date | 2010-06-24 |
United States Patent
Application |
20100155302 |
Kind Code |
A1 |
Kaminsky; Mark P. ; et
al. |
June 24, 2010 |
Purification of ultralow sulfur diesel fuel
Abstract
The invention is a method of purifying an ultralow sulfur diesel
fuel which contains polycyclic aromatic color bodies. The method
comprises contacting the ULSD fuel in the liquid phase with a
coal-based activated carbon adsorbent having a surface area ranging
from 800 to 1500 m.sup.2/g and containing pores having pore size
greater than 20 .ANG., and recovering a purified diesel product
having a decreased color bodies content.
Inventors: |
Kaminsky; Mark P.;
(Friendsville, TX) ; Leyshon; David W.; (West
Chester, PA) ; Juttu; Gopalakrishan; (Glenn Mills,
PA) ; Quakenbush; Allen B.; (Friendswood, TX)
; Candela; Lawrence M.; (Havertown, PA) |
Correspondence
Address: |
LyondellBasell Industries
3801 WEST CHESTER PIKE
NEWTOWN SQUARE
PA
19073
US
|
Family ID: |
42264493 |
Appl. No.: |
12/316948 |
Filed: |
December 18, 2008 |
Current U.S.
Class: |
208/212 ;
208/250 |
Current CPC
Class: |
C10G 45/02 20130101;
C10G 67/06 20130101; C10G 2400/04 20130101; C10G 25/003
20130101 |
Class at
Publication: |
208/212 ;
208/250 |
International
Class: |
C10G 45/00 20060101
C10G045/00; C10G 29/00 20060101 C10G029/00 |
Claims
1. A method of purifying an ultralow sulfur diesel fuel containing
polycyclic aromatic color bodies, which comprises contacting the
ultralow sulfur diesel fuel in the liquid phase with a coal-based
activated carbon adsorbent having a surface area ranging from 800
to 1500 m.sup.2/g and containing pores having pore size greater
than 20 .ANG., and recovering a purified diesel product having a
decreased polycyclic aromatic color bodies content.
2. The method of claim 1 wherein the ultralow sulfur diesel fuel
has a color greater than 2.5 as measured by ASTM D 6045.
3. The method of claim 1 wherein the purified diesel product has a
color less than 2.5 as measured by ASTM D 6045.
4. The method of claim 1 wherein the carbon adsorbent has a surface
area ranging from 800 to 1200 m.sup.2/g.
5. The method of claim 1 wherein at least 10 percent of the total
pore volume of the carbon adsorbent is in pores having a pore size
greater than 20 .ANG..
6. The method of claim 1 wherein at least 30 percent of the total
pore volume of the carbon adsorbent is in pores having a pore size
greater than 20 .ANG..
7. The method of claim 1 wherein the carbon adsorbent is a
granulated activated carbon.
8. The method of claim 1 wherein the contacting is performed at a
temperature within the range of about 10.degree. C. to 60.degree.
C.
9. A process for producing an ultralow sulfur diesel fuel,
comprising: (a) hydrodesulfurizing a diesel fuel stream in the
presence of the supported hydrodesulfurization catalyst to produce
an ultralow sulfur diesel fuel having a color greater than 2.5 as
measured by ASTM D 6045; (b) contacting the ultralow sulfur diesel
fuel having a color greater than 2.5 in the liquid phase with a
coal-based activated carbon adsorbent having a surface area ranging
from 800 to 1500 m.sup.2/g and containing pores having pore size
greater than 20 .ANG.; and (c) recovering an ultralow sulfur diesel
product having a color less than 2.5 as measured by ASTM D
6045.
10. The method of claim 9 wherein the carbon adsorbent has a
surface area ranging from 800 to 1200 m.sup.2/g.
11. The method of claim 9 wherein at least 10 percent of the total
pore volume of the carbon adsorbent is in pores having a pore size
greater than 20 .ANG..
12. The method of claim 9 wherein at least 30 percent of the total
pore volume of the carbon adsorbent is in pores having a pore size
greater than 20 .ANG..
13. The method of claim 9 wherein the carbon adsorbent is a
granulated activated carbon.
14. The method of claim 9 wherein the contacting is performed at a
temperature within the range of about 10.degree. C. to 60.degree.
C.
Description
FIELD OF THE INVENTION
[0001] This invention relates to the purification of an ultralow
sulfur diesel fuel.
BACKGROUND OF THE INVENTION
[0002] The presence of sulfur compounds in diesel fuel is
undesirable as they result in a serious pollution problem.
Combustion of diesel fuel containing these sulfur impurities
results in the release of sulfur oxides which are noxious and
corrosive. Federal legislation, specifically the Clean Air Act of
1964 as well as the amendments of 1990 and 1999, has imposed
increasingly more stringent requirements to reduce the amount of
sulfur released to the atmosphere. As a result, the United States
Environmental Protection Agency lowered the sulfur standard for
diesel fuel to 15 parts per million by weight (ppmw), effective in
2006.
[0003] The most common method of removing sulfur from diesel fuel
is hydrodesulfurization, in which the diesel fuel is reacted with
hydrogen gas at elevated temperature and high pressure in the
presence of a catalyst. See, for example, U.S. Pat. No. 5,985,136.
Catalysts for the production of ultralow sulfur diesel (ULSD) fuel,
having less than 15 ppm sulfur and typically 4-8 ppm sulfur,
include supported cobalt-molybdenum or nickel-molybdenum
catalysts.
[0004] Numerous methods have been taught in the prior art for
removing various impurities in hydrocarbon streams. For instance,
U.S. Appl. Pub. No. 2004/0129608 discloses a process for
decolorizing and removing some trace impurities such as indanes,
naphthalenes, phenanthrenes, pyrene, and alkylbenzenes from fuel
streams, in particular gasoline. The process comprises contacting
the fuel stream with a decolorizing carbon. U.S. Pat. No. 4,977,871
discloses a system for the selective removal of polynuclear
aromatic hydrocarbons containing 3 or more aromatic rings from
lubricating oil. In particular, U.S. Pat. No. 4,977,871 teaches
that wood and peat based carbons are significantly more effective
in the removal of these polynuclear aromatic hydrocarbons. The
prior art also teaches the use of promoted carbon adsorbents, which
may include various metals or other promoters, for the purification
and decolorization of hydrocarbon fuel. For instance, U.S. Pat.
Appl. Pub. No. 2007/0184976 discloses an activated carbon useful in
purification and decolorization of hydrocarbon fuel, which includes
within its pore structure a polymerized phosphate. None of these
prior art documents teach the purification of an ultralow sulfur
diesel fuel.
[0005] In sum, new methods for purifying ultralow sulfur diesel
fuel are needed. Particularly required are processes which
effectively decrease the amount of polycyclic aromatic color bodies
in the ULSD fuel. We have discovered an effective, convenient
method to remove color bodies from ultralow sulfur diesel fuel.
SUMMARY OF THE INVENTION
[0006] The invention is a method for purifying an ultralow sulfur
diesel fuel which contains polycyclic aromatic color bodies. The
method comprises contacting the ULSD in the liquid phase with a
coal-based activated carbon adsorbent having a surface area ranging
from 800 to 1500 m.sup.2/g and pores having a pore size greater
than 20 .ANG., and recovering a purified diesel product having a
decreased color bodies content. The invention also includes a
process for extending the life of a supported hydrodesulfurization
catalyst used in the production of an ultralow sulfur diesel fuel.
This process comprises hydrodesulfurizing a diesel fuel stream in
the presence of the supported hydrodesulfurization catalyst to
produce an ultralow sulfur diesel fuel having a color greater than
2.5 as measured by ASTM D 6045, and then contacting the colorized
ULSD fuel with a coal-based activated carbon adsorbent having a
surface area ranging from 800 to 1500 m.sup.2/g and pores having a
pore size greater than 20 .ANG. to reduce color.
DETAILED DESCRIPTION OF THE INVENTION
[0007] Ultralow sulfur diesel fuel (diesel fuel having less than 15
ppm sulfur, by weight, and preferably less than 10 ppm sulfur) is
typically produced by a hydrodesulfurization method to remove
sulfur from diesel fuel. The diesel fuel is reacted with hydrogen
gas at elevated temperature and high pressure in the presence of a
catalyst. See for example U.S. Pat. No. 5,985,136. Typical
hydrodesulfurization catalysts include supported cobalt-molybdenum
or nickel-molybdenum catalysts.
[0008] Ultralow sulfur diesel fuel (ULSD), as produced
commercially, contains significant amounts of polycyclic aromatic
hydrocarbons such as naphthalene, acenaphthalene, fluorene,
anthracene, phenanthrene, pyrene, and the like (e.g., 10-30, and
usually 15-20, weight percent polycyclic aromatic hydrocarbons
based on the total amount of ULSD). Although the amount of
polycyclic aromatic hydrocarbons in ULSD is large, only a small
portion of the polycyclic aromatic hydrocarbons are polycyclic
aromatic color bodies. As discussed by X. Ma et al. in Energy &
Fuels, Vol. 10, 1996, p. 91-96, the polycyclic aromatic color
bodies which are the major components of fluorescence color in
desulfurized diesel are anthracene, fluoranthene, and their
alkylated derivatives. These color bodies are first excited by UV
light in the 320-400 nm range and then emit visible light in the
400-550 cm.sup.-1 range.
[0009] We have found that a color problem associated with these
color bodies is related to catalyst deactivation and polycyclic
aromatic hydrocarbon-type color bodies in the feed to the ULSD
hydrotreater. As the hydrodesulfurization catalyst deactivates with
time onstream, the average bed temperature needs to be increased to
maintain desulfurization activity. As the bed temperature reaches
about 376.degree. C. or above, the color of the diesel fuel
increases and approaches 2.5-3 or greater (as measured by ASTM D
6045). The maximum specification for ULSD is 2.5. Ultimately, the
ULSD reactor run ends when the ULSD fuel fails to meet the color
specification, even though the catalyst is still performing well in
terms of desulfurization. The current invention thus also includes
a process to extend the life of a supported hydrodesulfurization
catalyst used in the production of an ultralow sulfur diesel fuel,
thus extending ULSD reactor runs.
[0010] The total amount of polycyclic aromatic color bodies
contained in an ultralow sulfur diesel fuel to be treated by the
process of the invention is typically greater than 30 ppm, and
preferably less than 1000 ppm, giving the ultralow sulfur diesel
fuel a color greater than 2.5 as measured by ASTM D 6045.
[0011] In order to reduce the level of polycyclic aromatic color
bodies in the ultralow sulfur fuel, the ultralow sulfur diesel fuel
is contacted in the liquid phase with a carbon adsorbent. In
accordance with the present invention, the impure ultralow sulfur
diesel fuel is contacted in the liquid phase with a carbon
adsorbent whereby polycyclic aromatic color bodies are retained on
the carbon adsorbent and a purified ultralow sulfur diesel product
reduced in polycyclic aromatic color bodies content is conveniently
separated.
[0012] The carbon adsorbent useful in the invention is a coal-based
activated carbon adsorbent having a surface area ranging from 800
to 1500 m.sup.2/g. The coal-based activated carbon adsorbent
preferably has a surface area ranging from 800 to 1200 m.sup.2/g.
The coal-based activated carbon adsorbent also contains pores
having a pore size greater than 20 .ANG. (Angstrom). Preferably, at
least 10 percent of the total pore volume of the coal-based
activated carbon is from pores having a pore size greater than 20
.ANG.. More preferably at least 30 percent, even more preferably at
least 50 percent, and most preferably at least 90 percent, of the
total pore volume is from pores having a pore size greater than 20
A. Pore volume from pores having a pore size greater than 20 .ANG.
can be measured by the BJH (Barrett, Joyner, Hallenda) Method.
Molasses number is another often used method to measure the total
pore volume from pores having a pore size greater than 20 .ANG.. A
high molasses number (e.g., a molasses number greater than about
200) is typically indicative of a substantial amount of pores
having a pore size greater than 20 .ANG..
[0013] Specific commercially available coal-based activated carbons
useful in the invention include Calgon Corporation's SGL.RTM. and
CAL.RTM. granular carbons and NORIT.RTM. GAC 1240 and RBHG 3. We
have found that coal-based activated carbon is significantly more
effective than other carbons, in contrast with U.S. Pat. No.
4,977,871 which teaches that wood and peat based carbons are
significantly more effective in the removal of polynuclear aromatic
hydrocarbons from lubricating oil.
[0014] The coal-based carbon adsorbent may be in granular,
pelleted, or powdered form. Adsorption is preferably carried out by
passing the impure ultralow sulfur diesel fuel through a bed of
granular carbon adsorbent or pelleted carbon adsorbent.
Alternatively, powdered carbon adsorbent can be slurred in the
impure ultralow sulfur diesel fuel and separated by filtration.
Granular carbon adsorbent is particularly preferred.
[0015] The invention may be carried out in a continuous or
batch-wise fashion in accordance with known procedures. Continuous
operation is preferred, as is the use of a plurality of adsorbent
contact zones. When a plurality of adsorbent contact zones is used,
one zone may be in use while adsorbent in a second zone is
regenerated or changed out. The use of three contact zones is
particularly preferred, with two zones in use at the same time, one
a lead contact zone and the second a polishing zone, while the
third zone is regenerated or changed out.
[0016] The adsorptive contact is preferably carried out at moderate
temperatures. Suitable temperatures are in the range of about
0.degree. C. to 100.degree. C., preferably 10.degree. C. to
60.degree. C. Flow rates of about 0.005 to 50 volumes of ultralow
sulfur diesel fuel per volume of adsorbent per hour are preferred,
more preferably about 0.01-0.6. In general, slower feed flow rate
reduces product impurity at a given bed-volume. Therefore, flow
rate may be optimized depending on the volume of adsorbent utilized
in the method.
[0017] The carbon adsorbent retains the impurities adsorbed thereon
and purified diesel fuel product can be separated. Initially, there
can be substantially complete removal of the polycyclic aromatic
color bodies and the recovered ultralow sulfur diesel fuel is of
exceptional color purity. Over the course of time, the contact
solids gradually become less effective for the removal of these
impurities.
[0018] Thus, when the separation efficiency of the carbon adsorbent
has fallen below a desired point, for instance as demonstrated by a
color level greater than 2.5, the carbon adsorbent contact
materials are preferably regenerated, as by contact with a heated
vapor stream such as nitrogen, stream, or air at a temperature of
at least 200.degree. C. or by wash with a solvent such as mixed
xylenes, methanol, acetone or water. It is advantageous to employ a
plurality of parallel contact zones such that while one zone is
being regenerated, the feed is passed through another zone
containing fresh or regenerated adsorbent so that optimum
impurities removal can be achieved.
[0019] Following the purification method, a purified diesel fuel
product having a decreased polycyclic aromatic carbon bodies
content is recovered. Preferably, the purified diesel fuel product
has an equilibrium color in solution of less than 2.5, according to
ASTM D 6045.
[0020] The invention also includes a process for extending the life
of a supported hydrodesulfurization catalyst used in the production
of an ultralow sulfur diesel fuel. This process comprises first
hydrodesulfurizing a diesel fuel stream in the presence of the
supported hydrodesulfurization catalyst until the ultralow sulfur
diesel fuel produced has a color greater than 2.5 as measured by
ASTM D 6045, thus above the maximum specification. The ULSD having
a color greater than 2.5 is then contacted with a coal-based
activated carbon adsorbent having a surface area ranging from 800
to 1500 m.sup.2/g and pores having a pore size greater than 20
.ANG. to reduce color, and recovering an ultralow sulfur diesel
product having a color less than 2.5 as measured by ASTM D 6045 in
the procedure detailed above. The supported hydrodesulfurization
catalyst is preferably a supported cobalt-molybdenum or
nickel-molybdenum catalyst. See, for example, U.S. Pat. No.
5,985,136.
[0021] The following examples merely illustrate the invention.
Those skilled in the art will recognize many variations that are
within the spirit of the invention and scope of the claims.
EXAMPLE 1
Adsorption Runs with Coal-Based Activated Carbon Compared to
Wood-Based Carbon
[0022] ULSD (56-58 g) having a color in solution of 2.9, as
measured by ASTM D 6045, is placed in a 250-mL beaker. A coal-based
carbon adsorbent (Calgon CAL.RTM. 12.times.40 granulated activated
carbon, having surface area between 800 to 1500 m.sup.2/g, and a
molasses number of 230 min.) or a wood-based carbon adsorbent
(NORIT.RTM. Darco G 60/80), in varying amounts for each adsorption
run, is placed in the beaker and the mixture is stirred overnight.
The adsorbent is filtered (with a Buchner funnel, 3 micron filter
paper) and the final equilibrium color is measured according to
ASTM D 6045. The results of Examples 1A-1D using Calgon.RTM. CAL
12.times.40 adsorbent and Comparative Examples 1E-1H using Darco G
60/80 adsorbent are shown in Table 1.
COMPARATIVE EXAMPLE 2
[0023] ULSD (58 g) having a color in solution of 4.5-5.1, as
measured by ASTM D 6045, is placed in a 250-mL beaker. Adsorbent
(0.58 g), in an amount equivalent to 1 weight percent based on the
amount of ULSD, is placed in the beaker and the mixture is stirred
overnight. Calgon CAL.RTM. 12.times.40 is used for Example 2A and a
carbon molecular sieve (Carbosieve.RTM. SII, 60/80 mesh, a product
of Sigma-Aldrich) is used for Comparative Example 2B. The adsorbent
is filtered (with a Buchner funnel, 3 micron filter paper) and the
final equilibrium color is measured according to ASTM D 6045. The
results are shown in Table 2. Carbosieve.RTM. SII is a molecular
sieve carbon with very small pore size, the majority being less
than 10 .ANG..
COMPARATIVE EXAMPLE 3
[0024] The procedure of Example 2 is repeated with a ULSD having a
color in solution of 3.1 and with a variety of adsorbents, in
amounts equivalent to 10 weight percent based on the amount of
ULSD. Example 3A uses Calgon CAL.RTM. 12.times.40 adsorbent,
Example 3B uses Calgon SGL.RTM., Comparative Example 3C uses
Amberlyst.RTM. A15, Comparative Example 3D uses Amberlyst.RTM. A35,
Comparative Example 3E uses kaolin clay, Comparative Example 3F
uses fuller's earth clay, and Comparative Example 3G uses silica
gel. The results are shown in Table 3.
[0025] The results show that coal-based carbon adsorbents are much
more effective than wood-based carbon adsorbents (and other
adsorbents) at removing color bodies from ULSD. The results also
show that it is important that the adsorbent contains pores having
a pore size greater than 20 .ANG. to be effective at removing color
bodies. This indicates that too small a porosity is ineffective
when trying to adsorb large (tri- and tetracyclic) color
bodies.
TABLE-US-00001 TABLE 1 Adsorption Run Data for Coal vs Wood-based
Carbons Amount Amount Wt. % Adsorbent ULSD Adsorbent Final Change
in Total Color Run (g) (g) in ULSD Color Color.sup.1 Change.sup.2
1A 5.8 58 10 0.4 2.5 25 1B 0.58 58 1 0.9 2 200 1C 0.0583 58 0.1 1.6
1.3 1293 1D 0.01 58 0.0172 2 0.9 5220 1E* 5.8 58 10 0.6 2.3 23 1F*
0.582 58 1 1.2 1.7 169 1G* 0.05 56.37 0.089 1.9 1 1127 1H* 0.01
56.63 0.0177 2.5 0.4 2265 .sup.1Change in Color = Initital ULSD
Color (2.9) - Final Color (post-adsorbent). .sup.2Total Color
Change = Change in Color .times. Amount ULSD/Amount Adsorbent.
*Comparative Example
TABLE-US-00002 TABLE 2 Adsorption Run Data for Coal-based Carbons
vs Carbon Molecular Sieve ULSD Change in Run Feed Color Final Color
Color.sup.1 2A 4.5 2 2.5 2B* 5.1 5.2 -0.1 .sup.1Change in Color =
Initial ULSD Feed Color - Final Color (post-adsorbent).
*Comparative Example
TABLE-US-00003 TABLE 3 Adsorption Run Data for Coal-based Carbons
vs Carbon Molecular Sieve Change in Run Final Color Color.sup.1 3A
0.4 2.7 3B 0.5 2.6 3C* 2.1 1 3D* 2.3 0.8 3E* 1.6 1.5 3F* 0.9 2.2
3G* 1.8 1.3 .sup.1Change in Color = Initial ULSD Color (3.1) -
Final Color (post-adsorbent). *Comparative Example
* * * * *