Acid-containing activated carbon for adsorbing mercury from liquid hydrocarbons

An activated carbon based adsorbent carrying an acid is provided for eliminating mercury or mercury compounds contained in hydrocarbons. Preferably the activated carbon base is provided with more than 80 ml/g micropore volume having radii less than 8 angstroms. Preferably the acid carried on the activated carbon is hydrochloric acid, sulfuric acid, or phosphoric acid. Hydrochloric acid is most preferred. The active carbon base is preferably manufactured by activating a carbonaceous material in an atmosphere comprising less than 30 vol. % water vapor. The adsorbent can be used to eliminate mercury or mercury compounds contained in hydrocarbons by contacting the adsorbent with the hydrocarbons in liquid phase. Particular hydrocarbons include naphtha and intermediates of oil products or petrochemical products. Minimal amounts of carried acid are desorbed from the adsorbent to the hydrocarbons. The adsorbent is useful to treat hydrocarbons in the oil industry to prevent possible harmful amalgamation due to mercury.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an activated carbon based adsorbent for mercury 
or mercury compounds contained in liquid hydrocarbons, more particularly 
to activated carbon based adsorbents and methods for adsorbing and 
eliminating small amounts of mercury or mercury compounds (hereinafter 
often simplified to "mercury") contained in liquid hydrocarbons, for 
instance naphtha and intermediates of oil products or petrochemical 
products. 
2. Description of the Related Art 
Heretofore, alumina based catalyst carrying palladium, for instance, has 
been used for the hydrogenation process of reforming liquid hydrocarbons, 
such as naphtha. The hydrogenation reaction on the catalyst suffers if 
impurity mercury or mercury compounds are present in the liquid 
hydrocarbons. 
Mercury lends to readily form amalgams with many kinds of metals. For such 
reason, if an apparatus constructed from aluminum based alloys is involved 
in such process, there is harmful risk of corrosion due to amalgamation 
with mercury. Accordingly there has been strong desire for progress in the 
elimination of mercury from such liquid hydrocarbons. 
There has been reported an adsorbent for mercury, based on a porous 
adsorbent carrying sulfur, that eliminates mercury by chemical reaction 
between mercury and sulfur. Further physical adsorption involving no 
chemical reaction with use of a porous adsorbent such as activated carbon, 
zeolite, or alumina is feasible to eliminate inorganic mercury in 
hydrocarbons. However, this method has problems such as inferior 
performance in mercury elimination rate when the adsorption performance 
decreases at a mercury concentration less than 10 bbp. 
In the art disclosed heretofore concerning the adsorbent carrying sulfur, 
the sulfur carrying activated carbon is, for example, prepared by mixing 
activated carbon with fine sulfur particles and heating such mixture at 
110.degree.-400.degree. C. (Japanese patent Application laid-open No. 59 
78915/1984); and can be activated carbon carrying organic sulfur compound 
(Japanese Patent Application laid-open No. 62-114632/1987). Therein, as 
the sulfur compound, the use of solid sulfur or an organic sulfur compound 
such as thiophene is typical. Such porous adsorbents carrying a sulfur 
compound have been intended mainly to eliminate mercury from gases, rather 
than from liquid hydrocarbons. 
Further, such art does not intend to inhibit dissolution or dessorption of 
the sulfur carried by the adsorbents into the liquid hydrocarbon as 
contamination, in addition to eliminating mercury. Liquid hydrocarbons are 
mostly subjected to hydrogenation at the stage of intermediate product 
wherein the contaminant or impurity sulfur contained in such hydrocarbon 
would give serious damage to the catalysts for hydrogenation. Thus there 
are deficiencies in the known art. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide an adsorbent and method for 
effectively adsorbing and eliminating mercury contained small amounts in 
liquid hydrocarbons including an oil product or the intermediate thereof, 
for instance naphtha, without dissolution of a contaminant as sulfur into 
the hydrocarbons. 
My studies on the art heretofore disclosed concerning elimination of 
mercury contained in small amounts in liquid hydrocarbons including the 
oil product or intermediate, for instance naphtha, proves that the 
activated carbon carrying sulfur or organic sulfur compounds does not 
inhibit dissolution of carried sulfur compounds into liquid hydrocarbons 
as far as the process is performed in liquid phase. The dissolution ranges 
from 10 to 400 ppm. Naphtha containing such sulfur concentrations would 
seriously damage catalysts used in a subsequent process. Thus the art 
known is conclusively limited to the gaseous process only, but 
unacceptable for the liquid process. 
Studies based on the activated carbon not carrying either sulfur or sulfur 
compounds have been made. Then, as is known, the activated carbon is a 
kind of unique material having remarkably developed micropore structure 
and is active as a non-polar adsorbent sorbent of nearly all substances. 
The activated carbon exhibits a certain degree of adsorption to inorganic 
mercury dispersed in a solution, and the adsorption of such mercury is 
fairly successful in the case of activated carbon having a limited 
micropore structure, but the activated carbon having such structure with 
no carrier effect is proved to be unsuccessful to adsorb and eliminate 
inorganic or organic mercury contained in a slight amount in liquid 
hydrocarbons to such extent that no harm would substantially ensue in 
subsequent oil process. 
My studies on activated carbon carrying various substances proves that 
carrying hydrochloric acid is found to be remarkably superior to the 
activated carbon with no carrier. In the subject application, superior 
adsorption is confirmed of inorganic and organic mercury in liquid phase, 
but also of such mercury present in small amounts. Further it is confirmed 
that where hydrochloric acid is carried in excess in the preparation, such 
excess hydrochloric acid can be drained out in the preparation stage and 
undrained or carried hydrochloric acid will not dissolve or desorb into 
the liquid phase in the applied adsorption process. 
The studies confirm the effectiveness of acids other than hydrochloric 
acid. Further studies on micropore volume as well as micropore 
distribution suitable to adsorbing and retaining the acids including 
hydrochloric acid sustain the present invention. 
The present invention provides an adsorbent carrying an acid for adsorbing 
mercury contained in liquid hydrocarbons, wherein the activated carbon has 
preferably a micropore volume of more than 80 ml/g defined by the 
micropores whose radii are less than 8 angstroms. Herein, the micropore 
volume is defined as adsorption volume of nitrogen gas measured by the 
instrument BFL, SORP which is converted to a volume of gas at standard 
conditions. This value will be referred to as micropore volume. Where the 
micropore volume defined by adsorbed gas volume may be expressed by 
denotation in liquid nitrogen, this conversion will be obtained by 
assuming that 1 ml of nitrogen gas at standard condition, is equivalent to 
0.001555 ml of liquid nitrogen. 
As for choice of acid carried by the activated carbon, preferred is 
hydrochloric acid, sulfuric acid, or phosphoric acid, and hydrochloric 
acid is the most preferable. As for the activated carbon, the preferred 
preparation is such that carbonaceous material is activated under a 
condition including a water vapor content at less than 30 volume % 
(hereafter a gas composition is expressed by volumetric percentages and 
often denoted by simply %) and cooled down under 300.degree. C. in the 
same atmosphere, or the activated carbon obtained by usual process is 
subjected to treatment under nitrogen gas or carbon dioxide gas with 
substantially no oxygen and/or water vapor at a temperature higher than 
500.degree. C. and cooled down under 300.degree. C. in the same 
atmosphere. 
The present invention includes a preferable method of adsorbing and 
eliminating mercury contained in a slight amount in hydrocarbons including 
an oil product or intermediate thereof, such as naphtha, by containing the 
activated carbon carrying an inorganic acid in a liquid phase. 
DETAILED DESCRIPTION OF THE INVENTION 
The mercury adsorbent of the invention comprises the activated carbon 
carrying an acid, and the base material of activated carbon is provided 
with a specific surface of not less than several hundreds square meters 
per gram and broadly speaking, a carbonaceous material having high 
adsorplivity is acceptable. Source materials include carbonized product of 
coconut shell, phenol resin, and the like or coal. Activation methods 
include such a process as employing a high temperature with water vapor or 
carbon dioxide, or zinc chloride, phosphoric acid, concentrated sulfuric 
acid treatment. 
As for the form, any form of crushed particle or granule is effective, but 
in view of pressure drop, adsorption capacity, and handling convenience in 
exchange of charged loads in field work, particle or granule form is 
preferable. The granules are manufactured as usual by blending 100 parts 
of the carbonaceous material with 30-60 parts of oil pitch, coal tar or 
resin, and by kneading, and molding followed by activation. The activated 
carbon thus obtained is a uinique material acting as a non-polar adsorbent 
exhibiting superior adsorption meeting nearly all liquid or gaseous 
objectives. 
The present invention employs the activated carbon carrying an acid wherein 
the acid is not limitative and a variety of inorganic and organic acids 
exhibit the subject effects wherein preferred is one which adsorbs a large 
amount of mercury and which will not let the acid dissolve or dessolve 
into liquid hydrocarbons during application or will not cause any chemical 
changes. These considerations endorse hydrochloric acid, sulfuric acid, 
phosphoric acid, and the most preferable is hydrochloric acid. 
Improvement in the mercury adsorption attained by the activated carbon 
carrying hydrohiloric acid as compared with the activated carbon with no 
carrier is shown in Table 1, appearing in the following. Example 1 and 
Comparative Example 1, appearing in the following, show mercury 
concentrations contained in light naphtha and mercury adsorptions nearly 
at equilibrium adsorption. The data shows that, in the case of mercury 
concentrations at 100, 10, 1 .mu.g g/kg, adsorbed mercury is 0.95, 0.64, 
0.38 mg/g by the activated carbon carrying hydrochloric acid and 0.14, 
0.03, 0.01 mg/g by the activated carbon carrying no hydrochloric acid. 
This shows the mercury adsorption by carrying hydrochloric acid is 
improved 7, 21, and 38 times, respectively. Based on the same carrier, the 
superiority in mercury adsorption resulting from carrying hydrochloric 
acid on activated carbon is made clear as compared with carrying nothing. 
It is remarkable that the improvement in the adsorption is superior in the 
case of a lower mercury concentration in naphtha, and this result shows 
the inventive adsorbent meets the object of the present invention in view 
of the fact that mercury concentrations contained in the liquid 
hydrocarbons are exceeding low. 
Improvement brought by carrying an acid other than hydrochloric acid, for 
instance, sulfuric acid, phosphoric acid, is shown in Example 11 (sulfuric 
acid) and Example 13 (phosphoric acid) in Table 3. 
With respect to prevention of the carried acid from desorption, the 
prevention by washing out or removal of excess acid after adsorbing an 
inorganic acid including hydrochloric acid, sulfuric acid, phosphoric acid 
is feasible, such inorganic acid molecules adsorbed inside micropores of 
the activated carbon structure are so strongly combined that such acid 
molecules do not readily desorb or become free. This feature is 
particularly remarkable with molecules of hydrochloric acid which have 
such a small molecular size. This acid is highly resistant to desorption 
or liberation into liquid hydrocarbons. On the other hand, it is necessary 
to wash out excess acid after adsorption thereof to avoid the acid 
desorption which will cause possible troubles in subsequent processes. 
Hydrochloric acid is the most preferable in consideration of a minimal 
tendency of desorption and superior performance in the mercury adsorption. 
Turning to the requirement for the activated carbon, a broad range in 
properties is acceptable. However, some difference in performance is found 
wherein the mechanism taken by the activated carbon carrying hydrochloric 
acid in adsorbing mercury is unknown. Nevertheless, the studies on the 
relationship between the specific surface area, micropore volume, 
distribution of the micropores of the activated carbon and the mercury 
adsorption proves that the mercury adsorption is sharply correlated to a 
proportion of the micropore volume having smaller micropore radii. 
In Examples 1, 2, and 3, employed are activated carbons having nearly the 
same micropore volume but different proportions of the micropore volume 
having radii less than 8 angstroms which ranges from Example 1 (largest 
proportion) to 2 and 3. The results indicate that the proportion of the 
micropores having radii less than 8 angstroms is significant. That is, it 
is presumed that mercury is mainly adsorbed into micropores having less 
than 8 angstroms. In view of other results, preferred is the activated 
carbon provided with the micropore volume at more than 80 ml/g having the 
micropore radii less than 8 angstroms. 
Turning to the descriptions about more detailed operations related to the 
present invention. 
As for the activated carbon base carried with hydrochloric acid, a broad 
range is acceptable and the usual manufacturing process therefor is 
already noted. Therein, a general tendency is such that when a degree of 
activation is made higher, a volume of micropore having smaller radii 
decreases. The activation conditions are influential to increase in the 
total micropore volume and to produce the accompanying decrease in the 
smaller micropore proportion. 
As noted before, preferred is the activated carbon provided with the 
micropore volume at more than 80 ml/g having the micropore radii less than 
8 angstroms. In the present invention, measurements on the micropore 
distribution and micropore volume of activated carbon bases are done by 
the instrument commercially named: BEL SORP, Type 28 SA manufactured by 
JAPAN BEL INC. and calculated based on the adsorption isotherm line for 
nitrogen gas. There by tie measurable lower limit for the micropore radii 
is at 3-4 angstroms and upper limit is at 60-70 angstroms. Normally the 
activated carbon has the total micropore volume at 100-500 ml/g and the 
average radius at 12-14 angstroms, and accordingly the invention prefers 
the activated carbon having a high proportion of the micropore volume 
provided with smallest radius range. Therefore, advisable activation 
conditions are those for depressing the tendency of enlarging the average 
micropore radii while enhancing the total micropore volume. 
The activation gas for manufacturing the activated carbon normally contains 
water vapor and carbon dioxide gas and the present invention does not 
limit the content of carbon dioxide, but prefers the water vapor content 
less than 30%. Normally the water vapor not less than 40-60% is employed, 
since the activation rate brought by water vapor is largely higher than 
that by carbon dioxide and thus a gas composition is set to have more 
water vapor content. Compared with the normal condition, the present 
invention prefers a mild condition with slower activation rate. 
Table 1 and Examples 1-5 in the following show that the activated carbon 
activated under the condition including a higher water vapor content 
contains less micropore volume having micropore radii less than 8 
angstroms and in turn performs inferior mercury adsorption. 
The detailed mechanism is unknown for why the activation condition 
containing less water vapor content improves the mercury adsorption, but 
it is presumed that such an activation condition should provide for such 
internal structure that the micropore having smaller radii accounts for 
large proportion, and such micropore portion contributes to the mercury 
adsorption. In order to increase the micropore volume having micropore 
radii less than 8 angstroms, preferred is to set the condition including 
the water vapor content at less than 15% in the activation gas and to 
depress lowering the micropore volume having radii less than 8 angstroms, 
and further preferred is the condition to increase the activation degree. 
The present invention prefers, after the activation, cooling the activated 
carbon under the gas composition unchanged or similar to that for the 
activation until under 300.degree. C. and then taking the activated carbon 
out from the system. Herein, the cooling gas composition unchanged or 
similar to that necessary to the activation means nitrogen gas, carbon 
dioxide gas or mixture thereof or such as substantially contains no oxygen 
and/or water vapor, and accordingly this requirement does not means that 
the activation gas and the cooling gas should have the same composition, 
and "substantially contains no oxygen and/or water vapor" means such 
gaseous condition as does not permit existence of oxygen atoms combined on 
the micropore surface of the activated carbon, in other words, condition 
containing oxygen and water vapor at less than 1-2% . 
Further, the activated carbon preferred in the invention is obtained by 
conversion from the one obtained by the normal or usual activation 
condition. That is, such normal activated carbon is heated in a gas 
composition used for the above mentioned preferable activation condition, 
to a temperature higher than 500.degree. C. and cooled under 300.degree. 
C. in the same gas. Herein, the upper limit of the heat treatment 
temperature is not limitative, however, it is preferred less than 
activation temperature, usually more than 850.degree. C. Then, "activated 
carbon obtained by normal or usual condition" means the one which was 
activated in such a atmosphere as contains water vapor at higher than 15% 
and which is thereafter cooled and taken out into air before enough 
cooling down. 
In the previous description about the conversion, treatment time of the 
normal activated carbon depends upon a temperature wherein 500.degree. C. 
prefers 20-180 min. and 800.degree. C. prefers several min. This 
conversion is thought to bring about such effect due to sintering or 
shrinkage of micropores which comes from the heat effect to carbonaceous 
structure wherein the employment of the heat treatment under such 
circumstance as noted is based on the thought that such would prevent loss 
by oxidation on the carbonaceous surface and enhance the shrinkage in 
micropore radii. 
As for the form of the activated carbon, any form in powder, crushed, 
pellet, particle, fibrous, or honeycomb form is acceptable. The granular 
or molded form is manufactured as usual by blending 100 parts of the 
carbonaceous material with 30-60 parts of oil pitch or coal tar as binder, 
and by kneading, and molding followed by activation. 
The step of carrying or adsorbing an acid to the activated carbon thus 
obtained is feasible by immersing the activated carbon mass into an acid 
solution of interest and letting the acid adsorb into micropores and 
thereafter by washing out excess acid component by water or organic 
solvent for removal. In the case of an inorganic acid, such as 
hydrochloric acid, concentration of the solution is not limitative, but 
0.1N to 3N (normality) is suitable. As for adsorption method, in addition 
to immersing into a solution as noted, impregnation by spraying of such 
acid solution like a shower may be employed. 
It is requisite to remove unadsorbed or excess inorganic acid, such as 
hydrochloric acid, from the activated carbon base after the carrying 
process. The presence of unadsorbed acid would invite dissolution thereof 
into liquid hydrocarbons and give damage to the catalysts used in the 
subsequent oil process or cause harmful corrosion due to amalgamation. The 
washing out is feasible by mild stirring a water or organic solvent based 
solution, wherein the activated carbon is immersed. Thereafter, the 
activated carbon carrying acid may be packed into an adsorption tower 
after sufficient drying or at the state of containing water at about 50% . 
Otherwise, after packing such activated carbon into the adsorption tower, 
back washing by an organic solvent is permitted lo remove the excess acid. 
As noted hereinbefore, the importance in the invention lies in the 
micropores having radii less than 8 angstroms. Acid molecules adsorbed in 
such micropores will not desorb or dissolve out by washing in water or 
organic solvent, further such acid molecules at the state adsorbed in the 
micropores will perform the superior adsorption for mercury and scarcely 
desorb through contact with liquid hydrocarbon. 
In the process of adsorbing hydrochloric acid, for instance, immersing the 
activated carbon mass into 1-2N. Hydrochloric acid solution for about 1 
hour is enough to perform the adsorption noted and in turn the 
hydrochloric acid molecules are so strongly combined by the adsorption 
that such molecules after the washing noted would not desorb through 
contact with liquid hydrocarbons. Test result concerning the desorption 
during immersing into distilled water for long periods of time show trace 
amounts or less than 1 mg/g desorbed as Examples 1-5 show. It is thought 
that hydrochloric acid for the reason of its small molecular size is 
suited to be caught in exceedingly small pores. In view of these results, 
hydrochloric acid is the best in the inorganic acids. 
When the activated carbon carrying acid is immersed in distilled water, 
though the acid molecules are combined strongly, the pH value reading 
decreases a little, and this decreases pH indicates that the carried 
substance is an acid. This decreases in pH becomes clearer if temperature 
is raised more than 60.degree. C. This phenomenon is thought to be a 
result of the nature of a strong acid if there is only a trace amount 
thereof. Normally the activated carbon is manufactured from carbonaceous 
material including coconut shell, coal or charcoal, and plant tissues 
generally contain a trace amount of potassium, sodium and other metallic 
compounds, and these are changed to oxides, for instance potassium oxide, 
through carbonization and activation processes, and such will produce 
metal hydroxide in contact with water and as a result, pH value would be 
led to about 9-10. 
Further, in the case of phenol resin as starting material, such activated 
carbon shows a weak acidity in pH value when immersed in distilled water, 
but this acidity is nearly equal to reading that of distilled water when 
left in air for long time and its pH tends to acidic region, due to 
dissolution of carbon dioxide contained in air, and in the case of the 
phenol resin will not drop further in pH value. However, the activated 
carbon carrying hydrochloric acid or sulfuric acid tends to drop under pH 
6.5 when immersed in distilled water for long time. Accordingly, the 
identification of carrying acid can be readily done by measuring the pH 
value immersed in distilled water. 
There is no limitation about the choice of acids carried on the activated 
carbon base, but preferred is as noted before an inorganic acid including 
hydrochloric acid, sulfuric acid or phosphoric acid, or mixture thereof, 
and the most preferred is hydrochloric acid. 
The present invention includes the method of eliminating mercury contained 
in hydrocarbons. Herein, the hydrocarbon means a broad range of 
hydrocarbons which will be subjected to elimination of mercury by a 
solid-liquid contact process with a mercury adsorbent in solid form, in 
particular mainly naphtha and intermediates of oil products or 
petrochemical products. Typical is naphtha or other intermediate which is 
composed of hydrocarbons having about 6-15 carbon atoms and present in 
liquid phase at ambient temperature, and in addition, liquefied 
hydrocarbons derived from oil (petroleum) or coal may be applied to the 
method of the present invention. 
Further, hydrocarbons having not more than 5 carbon atoms including natural 
gas, ethylene, propylene are in gas form at ambient temperature, but these 
resources may be handled in liquefied form under pressure. Such liquefied 
hydrocarbons may also be applied to the present method, and such 
hydrocarbons present in gas form at ambient temperature may be converted 
to liquid state and then such may be applied to the present method. 
In particular, liquefied hydrocarbons having not more than 5 carbon atoms 
including liquefied natural gas (LNG), liquefied petroleum gas (LPG), 
liquefied ethylene, liquefied propylene, and naphtha, are commercially 
handled in liquid phase and such liquid hydrocarbons may he applied to the 
adsorbent of the present invention. Thus remarkable industrial merit will 
be awarded. The objective liquid hydrocarbon may be a simple one component 
or a blend of a plurality of such components. 
The method for eliminating mercury may be applied to any form of mercury 
contained in liquid hydrocarbons, and such includes solid mercury, 
inorganic mercury compounds, and organic mercury compounds, and there is 
no limitation concerning concentration, that is, the present invention may 
be applied to hydrocarbons containing, a trace or exceedingly small amount 
of mercury. Naphtha usually contains mercury al 0.002-10 mg/kg and such a 
slight level is suited to the present invention which employs the method 
of adsorption. In field practice of eliminating mercury, a preferred 
pretreatment filters the liquid hydrocarbon to remove the sludge contained 
therein together with mercury removable by the filtration as a sludge 
component. 
The present method for eliminating mercury is advantageously feasible in a 
process employing an adsorption tower packed with the activated carbon in 
the form of a fixed bed, wherein a preferred particle size ranges from 
4.75 to 0.15 mm, more preferably 1.70 to 0.50 mm. 
When mercury concentration in a hydrocarbon is at 100 .mu.g/kg, the 
necessary mass of the activated carbon depends upon the allowable 
concentration at an outlet part and the kind of adsorbent. However, 
roughly stated, 0.1-10 g of mercury may be eliminated with use of 1 kg of 
the adsorbent. 
As described above, the inventive activated carbon based adsorbent is 
capable of almost completely eliminating small amounts of mercury 
contained in hydrocarbons by solid-liquid contact with the liquid 
hydrocarbons, and the hydrochloric acid carried on the activated carbon 
scarcely desorbs into the hydrocarbons. Thus the invention is suitable to 
treatment of naphtha and intermediates of oil products or petrochemical 
products.

EXAMPLE 
The invention will be further described by the following examples. 
Example 1 
Coconut shells were carbonized to a carbonaceous substance and then crushed 
to 4-10 mesh (particle size ranges from 1.7 mm to 4.75 mm) which was used 
as raw material to prepare the activated carbon base in particle form. 
This carbonized material was activated at 900.degree. C. by combustion gas 
for liquefied petroleum gas (gas composition: nitrogen 70%, oxygen 0.2%, 
carbon dioxide 19.8%, water vapor 10%) and cooled in the same gas to under 
300.degree. C. The activated carbon was crushed to the particle size from 
10 to 32 mesh (particle size ranges from 0.5 mm to 1.7 mm). The activated 
carbon thus obtained had an ash component (residue after strong 
incineration) of 2.5 wt. %. 
The activated carbon particles obtained above were vacuum deaerated and 
measured of the adsorption isotherm line in nitrogen gas by the instrument 
(BEL SORP Type 28 SA, JAPAN BL INC.) and the total micropore volume and 
radius distribution of the micropores were calculated. The total micropore 
volume was 279 ml/g and the proportion of micropore volume having radii 
less than 8 angstroms was 43% . That is, the micropore volume is 120 ml/g. 
As noted before, herein the micropore volume is always denoted by 
conversion from the nitrogen gas adsorbed amount to the volume at the 
standard condition. If converted to the volume of liquid nitrogen, the 
total micropore volume is 0.434 ml/g and the micropore volume having radii 
less than 8 angstroms is 0.187 ml/g. 
Then, the activated carbon particles were immersed in 1N hydrochloric acid 
aqueous solution for 1.5 hr at room temperature and then washed with 
distilled water and dried at 110.degree. C. for 12 hrs, and then washed 
with light naphtha (C.sub.6 to C.sub.9 hydrocarbons). 
Mercury adsorption was measured at various mercury concentrations by 
contacting the activated carbon carrying hydrochloric acid with light 
naphtha containing mercury and mercury compounds, wherein organic mercury 
accounts for 20% of the total mercury contained in the light naphtha. The 
adsorbent active carbon (10 g) was immersed in the light naphtha with mild 
stirring and after 2 hr. residual mercury concentration in the naphtha and 
mercury adsorption by the active carbon were measured. The mercury 
adsorption performance was evaluated by measuring mercury adsorbed by the 
activated carbon at naphtha mercury concentrations: 100, 10, 1 .mu.g/kg. 
Quantitative determination of mercury was made by atomic adsorption 
analysis. 
Table 1 shows a description of the activated carbon carrying hydrochloric 
acid and the results of mercury adsorption. Under the condition which was 
thought to be at nearly equilibrium, the adsorbed mercury is: 0.95, and 
0.38 mm/g for mercury concentrations of 100, and 1 ng/kg, respectively. 
This result shows that the subject activated carbon has superior mercury 
adsorption. Further, no organic mercury was found in the subject naphtha 
after the adsorption, that is, all organic mercury was adsorbed by the 
subject activated carbon. 
Note: In the Table, organic mercury adsorption is ranked:.largecircle. is 
good, X is fail and overalI mercury adsorption is ranked: .circleincircle. 
is superior, .largecircle. is good, .DELTA. is employable, X is fail. 
TABLE 1 
__________________________________________________________________________ 
Micropores Mercury Adsorption, 
having radii 
Subst- 
by Adsorbent 
less than 
ance 
(mg/g) 
Material Total 
8 angstroms 
Carri- 
Mercury Substance 
Overall 
of Micro- 
Volume ed on 
Content 
Same 
Same 
Adsorpt- 
Dissolved 
Adsorpt- 
Activat- 
Activation Gas 
pore 
Propo- 
Vol- 
Activ- 
in Naphtha 
as as ivity of 
into ion 
ed (Vol %) volume 
rtion 
ume ated 
(100 .mu.g/ 
left 
left 
Organic 
Naphtha 
Perform- 
Carbon 
H.sub.2 O:CO.sub.2 :N.sub.2 :O.sub.2 
(ml/g) 
(%) (ml/g) 
Carbon 
Kg) (10") 
(1") 
Mercury 
(mg/Kg) 
ance 
__________________________________________________________________________ 
Example 
1 Coconut 
10:19.8:70:0.2 
279 43 120 HCl 0.95 0.64 
0.38 
.largecircle. 
Cl.sup.- 
1&gt; 
.circleincircle. 
1 
Shell 
" 2 Coconut 
30:19.8:50:0.2 
282 38 107 HCl 0.73 0.51 
0.28 
.largecircle. 
Cl.sup.- 
1&gt; 
.circleincircle. 
Shell 
" 3 Coconut 
45:19.8:35:0.2 
284 25 71 HCl 0.55 0.41 
0.19 
.largecircle. 
Cl.sup.- 
1&gt; 
.largecircle. 
Shell 
" 4 Coconut 
55:19.8:25:0.2 
280 15 42 HCl 0.31 0.19 
0.08 
.largecircle. 
Cl.sup.- 
5 .DELTA. 
Shell 
" 5 Coconut 
65:19.8:15:0.2 
275 8 22 HCl 0.20 0.08 
0.04 
.largecircle. 
Cl.sup.- 
30 .DELTA. 
Shell 
Comparative 
Coconut 
10:19.8:70:0.2 
279 43 120 - 0.14 0.03 
0.01 
X -- 
-- X 
Example 
1 Shell 
__________________________________________________________________________ 
Examples 2 to 5 
The activation process herein employed activation gases having different 
water vapor contents: 30% (Example 2), 45% (Example 3), 55% (example 4), 
65% (Example 5). Otherwise all 5 conditions were kept the same as those 
employed in Example 1, and thereby the activated carbon was prepared and 
subjected to the step of carrying hydrochloric acid and washed with 
distilled water and light naphtha. Thus adsorbents of activated carbon 
carrying hydrochloric acid were obtained, and these were applied to the 
same mercury adsorption test as noted in Example 1. 
Table 1 shows a description of the activated carbons carrying hydrochloric 
acid and the results of mercury adsorption. The results indicate that the 
water vapor content in the activation gas increases with decrease in the 
micropore volume of the micropores having radii less than 8 angstroms and 
its proportion in the total micropore volume. As for the mercury 
adsorption, each adsorbent performs mercury adsorption, and the adsorbed 
amount decreases with decrease in the volume of micropores 20 having radii 
less than 8 angstroms. 
Comparative Example 1 
The adsorbent composed of the activated carbon prepared in Example 1 and 
with no carrier was employed to test the mercury adsorption. The result is 
shown in Table 1, wherein pH value when the subject activated carbon was 
immersed in distilled water was 8.8. 
The adsorbed mercury amount is exceedingly low as compared with example 1. 
The adsorbents employed in Examples 2-5 have smaller volume of the 
micropores having radii less than 8 angstroms as compared with the 
adsorbent employed in Comparative Example 1 but the mercury adsorption 
performed by Comparative Example 1 is lower than that by Examples 2-5. 
This shows that the carrying hydrochloric acid has large effect in the 
mercury adsorption. 
Examples 6 and 7 
Herein the same carbonaceous material as in Example 1 was employed to 
prepare the activated carbon base, but in the activation process different 
conditions were employed. That is, Example 7 was subjected to milder or 
lower activation to prepare the activated carbon base provided with the 
micropore volume having radii less than 8 angstroms at 82 ml/g. Example 6 
was subjected to stronger or higher activation to prepare the activated 
carbon base provided with the micropore volume having radii less than 8 
angstroms at 108 ml/g. The steps taken subsequently were carrying 
hydrochloric acid and washing, drying to finish the activated carbon 
carrying hydrochloric acid. The mercury adsorption test was carried out in 
the same way as in Example 1. 
A description of the activated carbons carrying hydrochloric acid and 
result of the mercury adsorption are shown in Table 2. Example 7 employed 
lower activation than Example 1, and the activated carbon of Example 7 had 
a total micropore vacuum 117 ml/g, where the proportion of the micropore 
volume having radii less than 8 angstroms was increased to 70%, 
corresponding to a micropore volume of 82 ml/g. Example 6 employed higher 
activation than Example 1, and the activated carbon of Example 6 had a 
total micropore volume of 327 ml/g, where the proportion of the micropore 
volume having radii less than 8 angstroms was decreased to 33%, 
corresponding to micropore volume of 108 ml/g. It is to be noticed that 
this value is lower than that in Example 1. 
TABLE 2 
__________________________________________________________________________ 
Micropores Mercury Adsorption, 
having radii 
Subst- 
by Adsorbent 
less than 
ance 
(mg/g) 
Material Total 
8 angstroms 
Carri- 
Mercury Substance 
Overall 
of Micro- 
Volume ed on 
Content 
Same 
Same 
Adsorpt- 
Dissolved 
Adsorpt- 
Activat- 
Activation Gas 
pore 
Propo- 
Vol- 
Activ- 
in Naphtha 
as as ivity of 
into ion 
ed (Vol %) volume 
rtion 
ume ated 
(100 .mu.g/ 
left 
left 
Organic 
Naphtha 
Perform- 
Carbon 
H.sub.2 O:CO.sub.2 :N.sub.2 :O.sub.2 
(ml/g) 
(%) (ml/g) 
Carbon 
Kg) (10") 
(1") 
Mercury 
(mg/Kg) 
ance 
__________________________________________________________________________ 
Example 
6 
Coconut 
10:19.8:70:0.2 
327 33 108 HCl 0.83 0.58 
0.33 
.largecircle. 
Cl.sup.- 
1&gt; 
.circleincircle. 
1 
Shell 
" 7 
Coconut 
10:19.8:70:0.2 
117 70 82 HCl 0.31 0.15 
0.09 
.largecircle. 
Cl.sup.- 
1&gt; 
.largecircle. 
Shell 
" 8 
Phenol 
10:19.8:70:0.2 
564 25 141 HCl 0.55 0.35 
0.22 
.largecircle. 
Cl.sup.- 
1&gt; 
.largecircle. 
resin 
" 9 
Phenol 
45:19.8:35:0.2 
562 8 45 HCl 0.25 0.15 
0.09 
.largecircle. 
Cl.sup.- 
12 .DELTA. 
resin 
" 10 
Phenol 
30:19.8:50:0.2 
329 45 148 HCl 1.53 1.10 
0.82 
.largecircle. 
Cl.sup.- 
1 .circleincircle. 
0 
resin 
Fiber 
__________________________________________________________________________ 
Further, the mercury adsorption amount in Example 7 is ranked good, and the 
same in Example 6 is superior, and in both examples no organic mercury was 
found in naphtha after the adsorption. 
Examples 8-10 
As the carbonaceous material leading to the activated carbon, carbonized 
particle of phenol resin (Examples 8 and 9) and carbonized fiber of phenol 
resin (Example 10) were employed to prepare the activated carbon base and 
the steps of carrying hydrochloric acid, washing, and drying were carried 
out to finish the activated carbon carrying hydrochloric acid and then the 
mercury adsorption test was conducted in the same way as in Example 1. 
Table 2 shows a description of the activated carbon carrying hydrochloric 
acid and the results of the mercury adsorption test. The adsorbent 
prepared in Example 10 from fibrous phenol resin had very large micropore 
volume having radii less than 8 angstroms at 148 ml/g, and the mercury 
adsorption amounts were 1.53, and 0.82 mg/g for mercury concentrations in 
light naphtha at 100, and 1 .mu.g/kg, respectively. This is a superior 
result. 
Examples 11-13 
Sulfuric acid (Examples 11, 12) and phosphoric acid (Example 13) were 
employed as the acid carried by the activated carbon obtained in Example 1 
and the mercury adsorption test was carried out in the same way as in 
Example 1. Table 3 shows description of such adsorbents carrying such 
inorganic acids and result of the mercury adsorption test. 
TABLE 3 
__________________________________________________________________________ 
Micropores Mercury Adsorption, 
having radii 
Subst- 
by Adsorbent 
less than 
ance 
(mg/g) Adsorp- Overall 
Material Total 
8 angstroms 
Carri- 
Mercury tivity 
Substance 
Adsorp- 
of Micro- 
Volume ed on 
Content 
Same 
Same 
of Dissolved 
tion 
Activat- 
Activation Gas 
pore 
Propo- 
Vol- 
Activ- 
in Naphtha 
as as Organic 
into Per- 
ed (Vol %) volume 
rtion 
ume ated 
(100 .mu.g/ 
left 
left 
Mer- 
Naphtha 
form- 
Carbon 
H.sub.2 O:CO.sub.2 :N.sub.2 :O.sub.2 
(ml/g) 
(%) (ml/g) 
Carbon 
Kg) (10") 
(1") 
cury 
(mg/Kg) 
ance 
__________________________________________________________________________ 
Example 
11 
Coconut 
30:19.8:50:0.2 
282 38 107 H.sub.2 SO.sub.4 
0.42 0.24 
0.15 
.largecircle. 
SO.sub.4 .sup.2- 
1 .largecircle. 
Shell 
" 12 
Coconut 
55:19.8:25:0.2 
280 15 42 H.sub.2 SO.sub.4 
0.20 0.08 
0.02 
.largecircle. 
SO.sub.4 .sup.2- 
20 
.DELTA. 
Shell 
" 13 
Coconut 
30:19.8:50:0.2 
282 38 107 H.sub.3 PO.sub.4 
0.35 0.22 
0.13 
.largecircle. 
PO.sub.4 .sup.3- 
1 .largecircle. 
Shell 
Comparative 
Coconut 
10:19.8:70:0.2 
279 43 120 sulfur 
0.58 0.15 
0.08 
.largecircle. 
sulfur 
380 
X 
Example 
2 Shell 
__________________________________________________________________________ 
The activated carbons employed in Examples 11 and 13 were provided with the 
micropore volume having radii less than 8 angstroms at 107 ml/g and 
performed good adsorption, but as compared with the adsorbent carrying 
hydrochloric acid, the mercury adsorption amount is decreased. In 
addition, dissolution of acidic ions is increased. The activated carbon 
employed in Example 12 was provided with a fairly small micropore volume 
having radii less than 8 angstroms of 42 ml/g, and exhibited a decrease in 
the mercury adsorption. 
Comparative Example 2 
An adsorbent carrying sulfur was compared. Particle activated carbon 
obtained in Example 1 (100 g) was mixed with powdered sulfur (1 g) and 
heated to prepare the adsorbent carrying sulfur at 1% in amount, which was 
subjected to the mercury adsorption test in the same way in Example 1. 
Table 3 shows a description of the adsorbent carrying sulfur and the 
results of the mercury adsorption test. 
This adsorbent carrying sulfur exhibits considerably good mercury 
adsorption, but exhibits a large dissolution of sulfur into naphtha as 
shown in Table 3. Accordingly, in view of the possible trouble or damage 
to catalysts used in oil process, this adsorbent is out of consideration 
as a mercury eliminator for naphtha. 
Example 14 
This illustrates a prototype field operation. A quantity of particle 
activated carbon carrying hydrochloric acid in the form of 10-32 mesh as 
prepared in Example 1 was packed in a adsorption lower (diameter: 25.4 cm, 
height 1 m) and light naphtha containing mercury at 7 .mu.g/kg was passed 
at a flow rate LV value (linear velocity): 0.25 m/min!. The result of 
analysis showed that the light naphtha output from the tower was nearly 
completely freed from mercury including organic mercury. Further the 
amount of chlorine ions dissolved into the naphtha was less than 0.1 mg/kg 
or at a trace level. That is, dissolution of chlorine ion was hardly 
found.