U.S. patent application number 09/782776 was filed with the patent office on 2002-02-07 for removal of impurities from hydrocarbon streams.
Invention is credited to Mesher, Shaun A., Reid, John S., Szymanski, Thomas.
Application Number | 20020014439 09/782776 |
Document ID | / |
Family ID | 25127148 |
Filed Date | 2002-02-07 |
United States Patent
Application |
20020014439 |
Kind Code |
A1 |
Reid, John S. ; et
al. |
February 7, 2002 |
Removal of impurities from hydrocarbon streams
Abstract
The invention provides a method of purifying hydrocarbon streams
from metallic impurities which comprises passing the stream through
media comprising alumina with relatively minor amounts of calcia
and magnesia.
Inventors: |
Reid, John S.; (Wooster,
OH) ; Szymanski, Thomas; (Hudson, OH) ;
Mesher, Shaun A.; (Calgary, CA) |
Correspondence
Address: |
Saint-Gobain Corporation
1 New Bond Street
P.O. Box 15138
Worcester
MA
01615-0138
US
|
Family ID: |
25127148 |
Appl. No.: |
09/782776 |
Filed: |
February 13, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09782776 |
Feb 13, 2001 |
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09476898 |
Jan 3, 2000 |
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6207612 |
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Current U.S.
Class: |
208/251R ;
585/830 |
Current CPC
Class: |
B01J 20/041 20130101;
B01J 20/08 20130101; B01J 20/28054 20130101; B01J 2220/42 20130101;
B01J 2220/58 20130101; C10G 25/003 20130101; C07C 7/12 20130101;
B01J 20/28057 20130101 |
Class at
Publication: |
208/251.00R ;
585/830 |
International
Class: |
B01D 047/00 |
Claims
We claim:
1. A method for the removal of metals from a hydrocarbon stream
which comprises contacting the hydrocarbon stream with an absorbent
media comprising from 50 to 97% by weight of alumina and from 50 to
3% by weight of alkaline earth metal oxides selected from calcium
and magnesium oxides present in calcia to magnesia weight ratios of
from 10:1 to 50:50, said media having a BET surface area of at
least 100 m.sup.2/gm.
2. A method according to claim 1 in which the absorbent media have
an apparent porosity of from 60 to 80%.
3. A method according to claim 1 in which the media comprise less
than 1% of other metallic or metallic oxide impurities.
4. A method according to claim 1 in which the removal is conducted
at a temperature of from 20.degree. C. to 450.degree. C.
5. A method according to claim 4 in which the removal is conducted
at a temperature of from 250.degree. C. to 350.degree. C.
Description
[0001] This Application is a continuation-in-part of application
Ser. No. 09/476,898 filed Jan. 3, 2000 which describes the
discovery of certain media useful in the separation of certain
acidic impurities from crude hydrocarbon flows. This Application
arises from the discovery of another important application for such
media in the removal of metallic impurities from hydrocarbon
streams.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to the treatment of
hydrocarbon streams using adsorbent material that is effective to
remove troublesome metallic components often present in such
streams.
[0003] Hydrocarbon streams generated within a refinery often
contain metallic impurities in the form of organic or inorganic
compounds of the metal or in the form of the metal itself. These
metallic impurities can cause significant problems such as catalyst
deactivation, degradation of properties of metals used in the
processing equipment, environmental pollution and toxic
contamination. It is therefore highly desirable to remove these
materials form the streams to avoid or mitigate such effects.
SUMMARY OF THE INVENTION
[0004] The invention provides a method of removing metallic
impurities from a hydrocarbon stream which comprises contacting the
stream with media which comprise from 50 to 96% by weight of
alumina and from 50 to 4% by weight of alkaline earth metal oxides
selected from calcia and magnesia in CaO:MgO proportions by weight
of from 90:10 to 50:50, and have a BET surface area of at least 100
m.sup.2/gm. The hydrocarbon stream is preferably contacted with the
media at a temperature between 20.degree. C. and 450.degree. C. and
preferably between 250.degree. C. and 350.degree. C.
[0005] The metals removed from petroleum streams using the media
according to the invention include lead, copper, aluminum, silicon,
iron, chromium, zinc, magnesium, nickel, sodium, calcium, vanadium,
mercury phosphorus and manganese. As a general rule the hydrocarbon
stream contains hydrocarbons with five or more carbon atoms.
[0006] The term "media" as used herein is intended to ceramic
materials having the above composition in the shape of pellets,
balls, rods or other shapes having sufficient porosity, (as
reflected in the surface area), to cause the metallic impurities to
be physically trapped within the pores of the medium, adsorbed on
to the surface of the pores of the medium, or, more usually to
react chemically with the material of the medium to produce
components that are not further transported by the flow of which
the impurity was a component.
[0007] The proportions of the components are calculated of the
basis of the weights of components added initially
stoichiometrically adjusted to the oxides that remain after firing
to produce the media of the invention. In general terms this gives
a reasonably accurate translation as can be seen from the following
chart.
1 Boehmite CaCO.sub.3 MgCO.sub.3 .fwdarw. Al.sub.2O.sub.3 CaO MgO
90 8.2 1.8 92.2 6.6 1.2 60 36 4 65.9 31.1 3.0 96 3.6 0.4 97.1 2.6
0.3 96 2.0 2.0 97 1.6 1.4
[0008] The first three formulations were made using dolomitic
limestone and the fourth used plain dolomite. As can be seen the
relative proportions do not change very significantly when going
from the precursor materials to the final fired product.
[0009] The media can have any desired shape depending on the
application. They can for example be in the form of short rods or
pellets, hollow cylinders, rings, saddles and the like. A
particularly useful shape is described in U.S. Pat. No. 5,304,423.
Alternatively they can have the form of monoliths with multiple
through passages that can be assembled into beds. Such monolith
media are however often less preferred for applications such as
those primarily intended for the media of the present
invention.
[0010] It is believed that a major component mechanism for the
removal of the metal from the hydrocarbon stream is based on the
reaction of the metal with the media. When both the metal and the
media are both polar in a non-polar liquid, (the hydrocarbon
stream), the adsorption of the metal on the media surface is
accelerated. Heat has been shown to accelerate this process. The
activity of the media can be regenerated through removal of
chemically retained impurities. This can be done by back-flushing a
bed comprising media whose activity has declined with hot, (about
150.degree. C. for example), steam. Removal that is essentially
complete by continuing the steam treatment fo about eight hours.
Prior to reactivation as outlined above it is desirable to remove
heavy hydrocarbon residues trapped within the pores of the media
using a hydrocarbon solvent such as toluene or an aromatic-rich
solvent such a XYSOL.TM. (available from Trysol Canada Ltd. Of
Calgary, Canada), preferably heated to a temperature of about
300.degree. C.
[0011] It has been found that the use of a hot methanol wash, (at
about 150.degree. C. for example), between the solvent wash and the
steam treatment helped clear out any residual oil and helps the
steam penetrate the pores. The same effect can be achieved by the
incorporation of a proportion of methanol in the steam. While
methanol is particular effective, it is believed that any low
molecular weight alcohol, such as ethanol or (n- or iso-) propanol
could be substituted.
[0012] The media can be made by a method which comprises a) forming
an aqueous slurry mixture of from 50-97% by weight of a hydrated
alumina component, such as for example a boehmite, with from 50 to
3% by weight of a mixture of calcium carbonate and magnesium
carbonate wherein the relative weight proportions of the calcium
and magnesium carbonates are from 10:1 to 50:50, the weights of the
boehmite and carbonate mixture being based on the solids weight in
the slurry;
[0013] b) peptizing the slurry by addition of an acid;
[0014] c) extruding the peptized slurry to form the desired media
shapes; and
[0015] d) drying to remove water and then firing the shapes at a
temperature of 650 to 850.degree. C.
[0016] The hydrated alumina component can be selected, for example,
from any of the commercial boehmite products which are commonly
assigned the formula AlOOH or more accurately
Al.sub.2O.sub.3.H.sub.2O.
[0017] The mixture of calcium and magnesium carbonates is
conveniently supplied by a powdered form of dolomite or preferably
dolomitic limestone, which is a mixture of dolomite, (in which the
calcium and magnesium metal atoms are present in nominally equal
numbers) and calcite, with the calcite predominating and a few
percentage points of impurities such a s silica and iron. When
calcined during the firing stage this mixture decomposes to the
respective oxides. The products of the invention could therefore,
in theory, be made by incorporating the oxides or hydroxides into
the boehmite slurry. This would however require more acid to
peptize the slurry and thus is a less preferred option.
[0018] To aid dispersion of the carbonates in the boehmite sol, it
is preferred that they be supplied in the form of a powder of about
50 microns average particle size or finer. A commercial dolomitic
limestone that is commercially available from National Lime and
Stone Company under the trade name Bucyrus Microfine, (99% passing
through 325 mesh screen), is particularly suitable. This material
contains the calcium and magnesium carbonates in a roughly 6:1
weight ratio
[0019] The acid added to cause peptization of the slurry, which is
essentially a dispersion of the calcium/magnesium-containing
component in a boehmite sol, can be any of those generally know to
peptize such sols. Because the firing would lead to decomposition
of the acid, it is preferred that mineral acids such as nitric,
hydrochloric or sulfuric acids be avoided and a strong organic acid
such as acetic or, better, formic acid is used to cause
peptization. The peptized sol in effect becomes a stable gel which
can be formed, for example by extrusion, to produce shapes that
will retain their shape during drying and firing. Enough is
preferably added to reduce the pH to 5 or lower.
[0020] The drying of the shapes is preferably carried out under
conditions that will allow the water to be removed without
disruption of the shape. This implies drying at a fairly low
temperature of about 100.degree. C. (though up to 50.degree. C.
higher can be used in most circumstances) for prolonged periods of
up to two days though usually a drying period of 10-24 hours is
adequate.
[0021] Firing of the dried shapes should be long enough to form
calcium and magnesium oxides from their respective carbonates and
to drive off any bound water and convert the boehmite to the gamma
alumina form of some other intermediate allomorph or amorphous
form. It is however preferred that the firing should not be under
conditions that would lead to the formation of the alpha form or
sintering since this leads to a loss of porosity and leaves the
alumina in a less active form. The firing temperature therefore is
preferably at a maximum temperature of from 500 to 800.degree. C.
and for a period until no further loss of weight occurs. Generally
heating at the firing temperature for 30 minutes to 5 hours is
enough to decompose essentially all the carbonate and drive off all
the bound water.
[0022] The surface area of the fired product is at least 100
m.sup.2/gm such as above about 200 m.sup.2/gm and preferably from
200 to 250 m.sup.2/gm.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0023] The invention is now further described with particular
reference to the following non-limiting examples which illustrate
the capabilities of the media of the invention for effective
removal of contaminants from hydrocarbon streams.
[0024] In the Examples that follow analysis was done using ICP with
identification of the individual elements carried out by Metro Tech
System Ltd. of Calgary, Canada.
[0025] Examples 1-4 all use a hydrocarbon stream identified by an
API gravity of 48 containing various amounts of metallic
contaminants. This stream was pumped through a heated stainless
steel column 25 cm in length and 1.27 cm in diameter, packed with 8
gm of the media. In each case the media had the following
properties. The BET surface area of the media obtained was measured
at 219 m.sup.2/gm, the apparent porosity was 78.5%, the water
absorption was 103.4%, the apparent specific gravity was 3.54 gm/cc
and the material density was 0.76 gm/cc. Analysis of the material
showed 92.2% by weight of alumina, 6.6% by weight of calcia and
1.2% by weight of magnesia.
EXAMPLE 1
[0026] In a first run of the hydrocarbon stream which contained 24
ppm of iron, 2 ppm of zinc and 2 ppm of lead was passed through the
above media at a flow rate of 3.1 mL/min. The initial temperature
was held at 273.9.degree. C. and after 60 hours the temperature was
raised to 301.7.degree. C. and after 120 hours the temperature was
raised again to 315.6.degree. C. The amounts of metals removed, as
a percentage of the ppm of the element in the flow, after the
specified number of hours is as indicated in the following Table
1.
2 TABLE 1 HOURS LEAD IRON ZINC 6 100 87 100 12 100 85 100 24 24 81
100 36 14 88 100 48 38 95 100 60* 100 98 100 72 100 98 100 84 100
100 100 96 33 96 100 108 39 97 100 120* 38 100 100 132 39 100 100
144 39 100 100 156 96 99 100 162 100 96 100 174 78 91 100 186 100
100 100 198 83 93 100 200 91 99 100 *indicates temperature
raised.
EXAMPLE 2
[0027] After 200 hours the column was cleaned using toluene and
regenerated with steam as described above. This run was conducted
at 315.6.degree. C. and the flow rate was again 3.1 mL/min. The
hydrocarbon stream contained the same level of the same impurities
as were used in Example 1. The results are presented in Table 2
with the percentage of the ppm of the element present that have
been removed indicated in each column.
3 TABLE 2 HOURS LEAD IRON ZINC 6 100 100 100 12 100 100 100 24 100
100 100 36 100 100 100 48 100 100 100 60 100 100 100 72 100 100 100
84 100 100 100 96 100 100 100 108 100 100 100 120 100 100 100 132
100 100 100 144 100 100 100 156 100 100 100 162 100 100 100
EXAMPLE 3
[0028] After the run lasting 162 hours described in Example 2, the
hydrocarbon flow was changed to one containing the following
metallic impurities: iron--116 ppm; zinc--2 ppm; lead--3ppm;
aluminum--223 ppm; magnesium--49 ppm; sodium--38 ppm; calcium--57
ppm and manganese--1 ppm.
[0029] The run was continued for 24 hours under the same conditions
described in Example 2. Samples removes at 12 and 24 hours
indicated that 100% of each of the impurities had been removed at
each interval.
EXAMPLE 4
[0030] In this Example the influence of temperature is explored ion
the removal of various elements. The same experimental arrangement
as was used in the prior Examples was used but with a new charge of
media and a hydrocarbon flow containing: mercury--6 ppm;
copper--2.6 ppm; iron--8.9 ppm; zinc--0.1 ppm; and phosphorus--8.2
ppm.. The flow was continued at a rate of 3.1 mL/min. for six hours
at temperatures changed as indicated in Table 3 below.
4TABLE 3 HOURS 1 3 5 6 TEMP (.degree. C.) 110 210 280 280 Mercury
50% 66% 77% 85% Copper 81% 96% 100% 100% Iron 0% 30% 100% 100% Zinc
100% 100% 100% 100% Phosphorus 100% 100% 100% 100%
EXAMPLE 5
[0031] In this Example evaluation was carried out in a pilot plant
using a hydrocarbon stream due for reprocessing. The API gravity of
the stream was 45-50, the water content was 1-10% and the solids
level was 1-3%. The base water and sediment were removed and the
flow was then pumped through two heat exchangers and a line heater
to raise the temperature to between 248.9.degree. C. and
315.6.degree. C. The hot flow was then passed through a bed
containing approximately 1.87 m.sup.3, (66 cubic feet), of the same
media used in the prior Examples. The volume of flow processed was
between 25 and 38 per day. The pressure on the flow was 517
kN/m.sup.2 to 620 kN/m.sup.2, (75 to 90 psi), at which pressure at
least 50-60% is in the vapor form. The vapor stream is separated
and not passed through the media bed. The vapor and the liquid bed
were recombined after passing the liquid component through the bed
and sent on to a fractionating tower. After a total of 2300 barrels
had been processed the percentage of the metals removed was as
follows:
[0032] phosphorus--98%; sodium--72%; iron 95%; aluminum--97%;
copper--92%; zinc--99%; calcium--94%; magnesium--98%; silicon--77%;
lead--49%; and chromium 89%.
[0033] A sample taken after 1900 barrels had been processed
contained iron, calcium, sodium, magnesium, aluminum, silicon and
phosphorus. After passage through the bed the percentages of these
elements removed was as follows: calcium--90%; sodium--73%;
magnesium--98%; aluminum--95%; iron--92%; silicon--15%; and
phosphorus--96%.
EXAMPLE 6
[0034] In this Example the hydrocarbon flow was a Northern Alberta
crude containing zinc, nickel, sodium and vanadium. A sample from
this source was placed in an autoclave with 10 gm of the same media
used in the previous Examples. The autoclave was heated to
300.degree. C. under 689 kN/m.sup.2, (100 psi), nitrogen pressure.
After 30 minutes the sample was analyzed and it was found that 45%
of the nickel, 21% of the sodium, 76% of the sodium and 24% of the
vanadium had been removed.
* * * * *