Note: Descriptions are shown in the official language in which they were submitted.
1334193
The present invention relates to an adsorbent composition
for removing mercury from hydrocarbons, especially from liquid
hydrocarbons, and a method for removing mercury from a liquid
hydrocarbon containing mercury.
For example, a natural gas liquid (NGL), liquid
hydrocarbons recovered from natural gas, contains mercury in
amounts ranging from several ppb (parts per billion) to several
thousands ppb depending on its district of production. The
mercury causes an amalgamation corrosion of aluminum used for
construction of equipments, and induces poisoning and
deterioration of activity of catalysts when natural gas liquid
containing mercury is used as a raw material in a successive
catalytic reaction.
Mercury in natural gas liquid generally exists in the forms
of elemental mercury, ionized mercury and ionizable mercury
compounds. All of them are requested to be removed. Further,
organic mercury compounds are contained in some natural gas
liquid depending on its district of production, and its removal
is also necessary.
Heretofore, most of the processes for removal of mercury
have dealt with industrial sewages or exhaust gases of
incinerators in general.
1334193
As for the natural gas, the following two methods have been
proposed:
a) cooling-condensation method, and
b) adsorption (absorption) method.
The former method is employed in natural gas liquefaction
plants. However, the method is not applicable for removal of
mercury from liquid hydrocarbons such as natural gas liquid,
because the method includes cooling step by adiabatic expansion
which is employable to gaseous material only.
The latter method uses various adsorbents; for example, an
alumina or a zeolite impregnated with silver, an activated
charcoal or a molecular sieve impregnated with potassium iodide
or sulfur or the like. There are, however, such problems in
them that some of them are expensive or some of them are small
in adsorption capacity, inherently or as the results of
reduction of the mercury adsorbing capacity due to co-adsorption
of hydrocarbons.
On the other hand, adsorbents comprising heavy metal
sulfides as mercury adsorbents have already been proposed. USP
4,094,777 proposed a method for removal of mercury employing
copper sulfide and USP 4,474,896 proposed polysulfide-containing
adsorbent compositions for use in the adsorption of elemental
mercury consisting essentially of a support; a cation selected
from the group consisting of antimony, arsenic, bismuth,
cadmium, cobalt, copper, gold, indium, iron, lead, manganese,
molybdenum, mercury, nickel, platinum, silver, tin, tungsten,
titanium, vanadium, zinc, zirconium and mixtures thereof; and a
polysulfide. 1334 1 93
- The former method using copper sulfide is mentioned in the
patent specification to be able to remove mercury from gaseous
or liquid hydrocarbons. However, its practical object is
oriented to natural gas consisting mainly of methane containing
negligible amount of liquid hydrocarbons having five or more
carbon atoms with around 19 ~g/m3 of mercury. However, the
effects of the method for liquid hydrocarbons such as natural
gas liquid or naphtha fraction containing mercury in higher
content is not disclosed at all.
In our experiment, it has been found that Hg adsorbing
capacity of copper sulfide per the copper atom is small contrary
to our expectation.
As for the latter method using polysulfides of heavy
metals, adsorption of other type mercury than elemental mercury
has not been mentioned. Further, preparation or handling of
such metal polysulfides appears to be very troublesome, because
the preparation of the polysulfides will be realized only by
using special agents.
It is an object of the present invention to obviate or
mitigate at least one of the above-mentioned disadvantages.
1 334 1 ~3
Embodiments of the present invention will now be
~ described with reference to the accompanying drawings:
FIG.1 shows the relation of the value of Hg atom adsorbed
per Mo atom in the adsorbent in the ordinate left and the amount
of Hg adsorbed by 1 gram of the adsorbent in the ordinate right
against Co/Mo atomic ratio in the Co-Mo-sulfide adsorbent,
respectively. FIG.2 shows the relation of the value of Hg atom
adsorbed per Mo atom in the adsorbent in the ordinate left and
the amount of Hg adsorbed by 1 gram of the adsorbent in the
ordinate right against Mo content (as metal) in the Co-Mo-
sulfide adsorbent, respectively. FIG.3 shows the relation of
the value of Hg atom adsorbed per Mo atom in the adsorbent in
the ordinate left and the amount of Hg adsorbed by 1 gram of the
adsorbent in the ordinate right against Ni/Mo atomic ratio in
the Ni-Mo-sulfide adsorbent, respectively. FIG.4 shows the
relation of the value of Hg atom adsorbed per Mo atom in the
adsorbent in the ordinate left and the amount of Hg adsorbed by
1 gram of the adsorbent in the ordinate right against Mo content
(as metal) in the Ni-Mo-sulfide adsorbent, respectively.
Accordingly, the present invention provides an adsorbent
co~position for removing mercury from hydrocarbons
comprising multi-
component metal sulfides supported on a carrier wherein one of
metal components is molybdenum of 3-15 weight-% calculated as
molybdenum metal in final product and another metal component is
selected from a group of cobalt and nickel, the atomic ratio of
these to molybdenum being in the range of o.o5 103~.41 93
~ The combination of nickel or cobalt with molybdenum
provides advantages such as lowering of initiation temperature
of sulfurization of metal components, and the prevention of
sintering of metals due to dispersion of cobalt or nickel in
molybdenum sulfide crystal to give a highly dispersed sulfide on
a carrler.
The highly dispersed sulfide on a carrier provides not only
the increase of the adsorbing capacity of molybdenum sulfide for
elemental mercury but also increase of the ability of adsorbing
organic mercury compounds and ionized mercury by the adsorbent.
The adsorbent may contain other metallic or inorganic
components additionally.
As the carrier, particle materials comprising silica,
alumina, silica-alumina, zeolite, ceramics, glass, resins, an
activated charcoal, etc. can be employed; among which alumina is
most preferred.
The carrier may be preferably selected from materials with
a large specific surface of 5-400 m2/g, preferably of 100-250
m2/g, for giving a better contacting efficacy, though these are
not critical.
The adsorbent may be prepared by sulfurization of the metal
components in a state supported on a carrier.
The metal components may be supported on a carrier by a
impregnation method, a blending method or a coprecipitation
method.
A typical method of preparation is as follows; an aqueous
~ 1 334 1 93
solution of molybdenum compound and cobalt compound is
impregnated to alumina as carrier, then dried, followed by
calcining at 450-500C for 0.1-2 hours and sulfurized finally.
For example, ammonium paramolybdate [(NH4)6Mo7o24-4H2o] for
molybdenum, ammonium cobalt chloride [NH4Cl CoCl2 6H20] for
cobalt and ammonium nickel chloride [NH4Cl NiCl2 6H20] for
nickel can be used as metal sources.
The sulfurization of the adsorbent can be conducted by
using a mixture of hydrogen and hydrogen sulfide, in which
hydrogen sulfide is contained preferably in 0.1-10 volume-%.
The treatment temperature is 200-450C, preferably 300-400C.
By the way, cobalt-molybdenum catalyst or nickel-molybdenum
catalyst which is generally used for desulfurization process of
kerosene or light oil (VGO) in typical refinery firms, where the
spent catalysts are discharged. These spent catalysts can
adsorb mercury in liquid hydrocarbons effectively, because they
become fully sulfurized in use. Accordingly, utilization of the
spent catalysts as the adsorbent may be quite advantageous for
reducing the procurement cost of adsorbent.
The contact of a liquid hydrocarbon containing mercury with
the adsorbent is preferably conducted at temperatures below
200C. Temperatures above 200C may release mercury from the
adsorbent or may cause problems such as evaporation or cracking
of the liquid hydrocarbon.
Though the contact of liquid hydrocarbons containing
mercury and the adsorbent can be conducted using arbitrary
methods, a fixed bed flowing method which enables a continuous
operation is preferable. l 3341 93
The present invention can be most preferably adopted for
removal of mercury from liquid hydrocarbons, for example,
natural gas liquid recovered from natural gas or liquid
hydrocarbons obtained by liquefaction of gases produced as a by-
product of petroleum.
The adsorbent composition of the present invention may be
applicable for removing mercury from natural gas.
The present invention will be illustrated hereunder in more
detail by examples.
Examples and Comparative Examples
[Preparation of adsorbents]
Ammonium paramolybdate [(NH4)6Mo7O24 4H20] for molybdenum,
ammonium cobalt chloride [NH4Cl CoCl2 6H20] for cobalt and
ammonium nickel chloride [NH4Cl NiC12 6H20] for nickel were used
as metal sources.
To y-alumina carrier particles, aqueous solution containing
a measured amount of each metal component was impregnated by the
pore-filling method, and they were dried at 110C for 12 hours,
then they were calcined at 500C for 4 hours.
When metal content cannot fully be carried on by one time
impregnation, the supplemental impregnation should be conducted
after the calcination.
The calcined particles were graded in the range of 0.25-
0.30 mm in diameter by 48-60 mesh sieves.
Finally, to obtain an adsorbent, sulfurization of the
graded particles was conducted at 350C for 2 hours by passing
T334193
through a hydrogen gas containing 2 volume % of hydrogen
sulfide. After the sulfurization, the adsorbent was stored and
handled in the atmosphere of nitrogen to prevent the oxidation
by the air.
In this manner, adsorbents containing various amounts of
molybdenum sulfide with cobalt sulfide or nickel sulfide were
prepared.
[Measurement of adsorbed Hg]
A forced circulation batch type experimental apparatus
equipped with a raw material tank, a constant capacity pump and
a column to be filled with an adsorbent was used.
As the raw material, a model liquid was prepared by
dissolving in light naphtha 2 ppm (parts per million) of
elemental mercury.
Into a column for the experimental apparatus, 30 mg
(milligrams) of an adsorbent was filled and the model liquid was
passed through the column at a linear velocity of 3 cm
(centimeter) per second with circulation. The concentration of
Hg in the model liquid was measured continuously. When the
concentration of Hg in the model liquid did not show more
decrease, it was judged that the adsorbent reached to the
saturation point.
When the Hg adsorbing capacity of the adsorbent was still
large enough to decrease the Hg content in the model liquid to
100 ppb or below, the model liquid was exchanged to a new one
and the experiment was continued up to reaching the saturation
point.
[Test 1]
~ The experiments were made to find the sa~r4atli~93 amount of
Hg adsorbed per 1 gram of each adsorbent comprising sulfide of
Mo, Mo Co or Co respectively. The results are shown in Table 1.
In Table 1, the amounts of Mo sulfide and Co sulfide are shown
as the wt.% of metal per the adsorbent.
Table 1
experiment adsorbent composition saturated amount of Hg
No. adsorbed by adsorbent
wt.% Co/Mo mg Hg Hg atom
atomic ratio /9 adsorbent /Mo atom
2 4.0 0.7 0.3 69 1 0.83
mg Hg ¦ Hg atom
/9 adsorbent I /Co atom
3 0 10.3 22 0.06
The experiment 2 showed that combination of Co and Mo
remarkably increased the Hg adsorbing capacity compared to the
experiment 1 wherein molybdenum sulfide only was used. The
cobalt sulfide only also showed a small absorbing capacity per
cobalt atom as shown in experiment 3.
[Test 2]
To search a preferable ratio of cobalt to be added to
- _ 1 334 1 93
molybdenum, adsorbents containing 7.0 wt.% (as metal) of
molybdenum sulfide and various amounts of cobalt sulfide were
tested. The results are shown in Table 2 and in FIG. 1.
Table 2
i
experiment adsorbent composition saturated amount of Hg
No. adsorbed by adsorbent
wt.% Co/Mo mg Hg Hg atom
atomic ratio /9 adsorbent /Mo atom
Mo Co 0
7.0 0.4 0.1 104 0.71
6 7.0 2.1 0.5 117 1 0.80
7 ! 7.0 4.0 1.0 1 83 0.57
With the increase of cobalt, the Hg adsorbing capacity
molybdenum sulfide per Mo atom and the saturating amount of Hg
adsorbed per 1 gram of the adsorbent were increased to reach a
peak at about 0.5 of the atomic ratio of Co/Mo, and then
decreased gradually.
From FIG.1, it can be observed that Hg adsorbing capacity
of molybdenum sulfide per Mo atom and the saturating amount of
Hg adsorbed per 1 gram of the adsorbent were remarkably larger
than those of the adsorbent comprising Mo sulfide only, in the
range of 0.05-0.9, especially in the range of 0.1-0.8 of the
atomic ratio of Co/Mo.
[Test 3] l 3341 93
To search a preferable amount of Mo to be supported on a
carrier, adsorbents comprising various amounts of Mo in a
constant Co/Mo atomic ratio of 0.3 were tested respectively.
The results are shown in Table 3 and in FIG. 2.
Table 3
~ experimentl adsorbent composition ~ saturated amount of Hg
lO No. ~ adsorbed by adsorbent
~ wt.% Co/Mo mg Hg , Hg atoml
15 ~ ~ ~ ~atio¦ /9 adsorbent /Mo atom
4.0l 0.7 ~ 0.3 69 0.83
8 5.0 0.9 0.3 84 1 0.81
10.0 1.8 0.3 129 1 0.62
12.0 2.2 0.3 lS0 0.60
11 20.0 3.7 0 3 166 0.40
With the increase of Mo content, the amount of Hg which is
adsorbed per 1 gram of the adsorbent was increased, but became
almost constant when the Mo content became over 15 wt.% as
metal.
However, the Hg adsorbing capacity of molybdenum sulfide
per Mo atom was decreased linearly.
From FIG.2, it can be observed that the suitable amount of
_~ 1 334 1 93
Mo sulfide to be supported on a carrier is in the range of 3-15
wt.% (as metal), preferably in the range of 4-12 wt.% (as metal)
per the adsorbent.
[Test 4]
The experiments were made to find saturating amount of Hg
adsorbed per 1 gram of each adsorbent comprising sulfide of Mo,
Mo Ni or Ni. The results are shown in Table 4. In Table 4 and
following tables, the amounts of Mo sulfide and Ni sulfide are
shown as the wt.% of metal per the adsorbent.
Table 4
¦experiment ¦ adsorbent composition saturated amount of Hg
15 l l adsorbed by adsorbent
wt.%Ni/Mo mg Hg ¦ Hg atom
,atomic ratio /9 adsorbent /Mo atom
Mo ¦ Ni
1 4.0 0 0 47 0.56
4.0 0.7 0.3 71 0.85
l ~ ¦ mg Hg ¦ Hg atom
¦ ¦ /9 adsorbent ¦ /Ni atom
13 0 9.8 38 0.11
The experiment 12 showed that combination of Ni and Mo
remarkably increased the Hg adsorbing capacity of molybdenum
sulfide per Mo atom and the saturating amount of Hg adsorbed per
1 gram of the adsorbent compared to the experiment 1 wherein
1 334 1 93
molybdenum sulfide only was used. The nickel sulfide only
showed a small absorbing capacity per nickel atom as shown in
experiment 13.
[Test 5]
To search a preferable ratio of nickel to be added to
molybdenum, adsorbents comprising 7.0 wt.% (as metal) of
molybdenum sulfide and various amounts of nickel sulfide were
tested. The results are shown in Table 5 and in FIG. 3.
Table 5
¦experlment ¦ adsorbent composition ~ saturated amount of Hg
15 1 ~ adsorbed by adsorbent
wt.%Ni/Mo I mg Hg I Hg atom
latomic ratiol /9 adsorbent I /Mo atom
Mo ¦ Ni ,,
~ 4 7.0 0 0 75 ' 0.51
14 7.0 0 4 0.1 107 0.73
7.0 2.1 0.5 1 120 0.82
16 7.0 q.0 1.0 88 0.60
With the increase of nickel sulfide, the Hg adsorbing
capacity of molybdenum sulfide per Mo atom and the saturating
amount of Hg adsorbed per 1 gram of the adsorbent were increased
to reach a peak at about 0.5 of the atomic ratio of Ni/Mo, and
then decreased gradually.
From FIG.3, it can be observed that Hg adsorbing capacity
of molybdenum sulfide per Mo atom and the satl~a~l~n~a3Ount of
Hg adsorbed per 1 gram of the adsorbent were remarkably larger
than those of the adsorbent comprising Mo sulfide only, in the
range of 0.05-0.9, especially in the range of 0.1-0.8 of the
atomic ratio of Ni/Mo.
[Test 6]
To search a preferable amount of Mo to be supported on a
carrier, adsorbents comprising various amounts of Mo in a
constant Ni/Mo atomic ratio of 0.3 were tested. The results are
shown in Table 6 and in FIG. 4.
Table 6
experiment ¦ adsorbent composition saturated amount of Hg
15 No. I adsorbed by adsorbent
wt.% Ni/Mo mg Hg ¦ Hg atom
atomic ratio /9 adsorbent ~ /Mo atom
Mo I Ni . l I
12 4.0l 0.7 0.3 71 ~ 0.85 .
17 5.0 1.0 0.3 88 0.85
18 10.0 1.8 0.3 139 0.67
19 12.0 2.1 0.3 153 0.61 .
20.0 3.8 0.3 183 1 0.44
With the increase of Mo content, the amount of Hg which is
adsorbed per 1 gram of the adsorbent was increased, but the
'' - 1 334 1 q3
increasing rate became sluggish when the Mo content became over
- 15 wt.% as metal.
On the other hand, the Hg adsorbing capacity of molybdenum
sulfide per Mo atom was decreased linearly.
From FIG.4, it can be observed that the suitable amount of
Mo sulfide to be supported on a carrier is in the range of 3-15
wt.% (as metal), preferably in the range of 4-12 wt.% (as metal)
per the adsorbent.
[Test 7]
Using conventional CuS or FeS adsorbent, saturating amount
of Hg caught by these adsorbents were measured. The results are
shown in Table 7.
Table 7
experiment ~ adsorbent saturated amount of Hg
No. I composition adsorbed by adsorbent
sulfide I wt.% mg Hg I Hg atom
as metal /9 adsorbentl /Metal atom
21 Cu 8.4 80 0.44
22 ¦ Fe 1 8.8 17 ¦ 0.05
The conventional CuS adsorbent and FeS adsorbent showed
smaller adsorbing capacities of Hg compared to the adsorbents of
the present invention.
[Test 8]
To investigate the types of mercury which can be adsorbed
by the adsorbent of the present invention, model liquids were
1334193
-
prepared by dissolving in light naphtha each o~ ~h~r~r~
- dichloride [HgCl2], diethylmercury [(C2Hs)2Hg] or mercury
methylchloride [CH3HgCl] to make Hg content 2 ppm, respectively.
Each of the model liquids was contacted with an adsorbent
composed of multi-component metal sulfides supported on y-alumina
carrier wherein the binary metal sulfide is consisted of
molybdenum sulfide corresponding to 6.4 wt.% of molybdenum metal
per the adsorbent and cobalt sulfide corresponding to 2.8 wt.%
of cobalt metal per the adsorbent (Co/Mo atomic ratio is 0.7).
The results are shown in Table 8.
Table 8
experiment mercury compounds ¦saturated amount of Hg
No. ladsorbed by adsorbent
mg Hg/g adsorbent
23 HgCl2 42
24 (C2H5)2H9 30
CH3HgCl 18
Table 8 shows that inorganic mercury compound (HgCl2) and
organic mercury compounds ((C2Hs)2Hg and CH3HgCl) in liquid
hydrocarbons can be caught by the adsorbent of the present
invention though the saturated amount of Hg adsorbed by the
adsorbent is smaller than that for elemental mercury.
16
