U.S. patent application number 12/595728 was filed with the patent office on 2012-07-05 for high-performance adsorbents based on activated carbon having high meso- and macropososity.
Invention is credited to Bertram Bohringer, Sven Fichtner, Jann-Michael Giebelhausen.
Application Number | 20120172216 12/595728 |
Document ID | / |
Family ID | 39311596 |
Filed Date | 2012-07-05 |
United States Patent
Application |
20120172216 |
Kind Code |
A1 |
Bohringer; Bertram ; et
al. |
July 5, 2012 |
HIGH-PERFORMANCE ADSORBENTS BASED ON ACTIVATED CARBON HAVING HIGH
MESO- AND MACROPOSOSITY
Abstract
The invention concerns high-performance adsorbents based on
activated carbon of high meso- and macroporosity which are present
in the form of discrete grains of activated carbon, wherein at
least 55% of the total pore volume of the high-performance
adsorbents are formed by pores (i.e. meso- and macropores) having
pore diameters of more than 20 .ANG., the high-performance
adsorbents have a measure of central tendency pore diameter of more
than 25 .ANG., and the high-performance adsorbents have a BET
surface area of at least 1250 m.sup.2/g. These high-performance
adsorbents are obtainable by a novel process comprising specific
two-stage activation, and have, in addition to the aforementioned
properties, an excellent abrasion and bursting resistance, so that
they are useful for a multiplicity of different applications.
Inventors: |
Bohringer; Bertram;
(Wuppertal, DE) ; Fichtner; Sven; (Brandenburg,
DE) ; Giebelhausen; Jann-Michael; (Rathenow,
DE) |
Family ID: |
39311596 |
Appl. No.: |
12/595728 |
Filed: |
January 25, 2008 |
PCT Filed: |
January 25, 2008 |
PCT NO: |
PCT/EP2008/000606 |
371 Date: |
May 31, 2011 |
Current U.S.
Class: |
502/416 ;
2/455 |
Current CPC
Class: |
B01J 20/28057 20130101;
B01D 2253/311 20130101; Y02C 20/40 20200801; B01D 53/02 20130101;
C01B 32/318 20170801; B01J 20/28083 20130101; B01J 20/28085
20130101; Y02C 10/08 20130101; C01B 32/336 20170801; C02F 1/283
20130101; B01J 20/28076 20130101; B01J 20/20 20130101; B01J
20/28019 20130101; A61K 33/44 20130101; C01B 32/382 20170801; A61L
9/014 20130101; B01D 2253/10 20130101; B01D 2253/102 20130101; B01D
2253/306 20130101 |
Class at
Publication: |
502/416 ;
2/455 |
International
Class: |
C01B 31/08 20060101
C01B031/08; C01B 31/10 20060101 C01B031/10; A41D 13/00 20060101
A41D013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 14, 2007 |
DE |
10 2007 012 963.9 |
Oct 25, 2007 |
DE |
10 2007 050 971.7 |
Claims
1. High-performance adsorbents based on activated carbon in the
form of discrete grains of activated carbon, preferably in
spherical form, characterized in that at least 55% of the total
pore volume of the high-performance adsorbents are formed by pores
having pore diameters of more than 20 .ANG., the high-performance
adsorbents have a measure of central tendency pore diameter of more
than 25 .ANG., and the high-performance adsorbents have a BET
surface area of at least 1250 m.sup.2/g.
2. The high-performance adsorbents based on activated carbon as
claimed in claim 1, characterized in that the Gurvich total pore
volume of the high-performance adsorbents is at least 0.8
cm.sup.3/g, particularly at least 1.0 cm.sup.3/g, preferably at
least 1.2 cm.sup.3/g, and/or in that the Gurvich total pore volume
of the high-performance adsorbents reaches values of up to 2.0
cm.sup.3/g, particularly up to 2.5 cm.sup.3/g, preferably up to 3.0
cm.sup.3/g, more preferably up to 3.5 cm.sup.3/g.
3. The high-performance adsorbents based on activated carbon as
claimed in claim 1 and/or 2, characterized in that the Gurvich
total pore volume of the high-performance adsorbents is in the
range from 0.8 to 3.5 cm.sup.3/g, particularly 1.0 to 3.5
cm.sup.3/g, preferably 1.2 to 3.2 cm.sup.3/g.
4. The high-performance adsorbents based on activated carbon as
claimed in one or more of the preceding claims, characterized in
that the carbon black method pore volume of the high-performance
adsorbents which is formed by pores having pore diameters of more
than 20 .ANG. is in the range from 0.4 to 3.3 cm.sup.3/g,
particularly 0.8 to 3.2 cm.sup.3/g, preferably 1.0 to 3.1
cm.sup.3/g, more preferably 1.2 to 3.0 cm.sup.3/g, most preferably
1.2 to 2.8 cm.sup.3/g.
5. The high-performance adsorbents based on activated carbon as
claimed in one or more of the preceding claims, characterized in
that at least 60%, particularly at least 65%, preferably at least
70%, more preferably at least 75%, most preferably at least 80% of
the total pore volume of the high-performance adsorbents is formed
by the pore volume of pores having pore diameters of more than 20
.ANG..
6. The high-performance adsorbents based on activated carbon as
claimed in one or more of the preceding claims, characterized in
that 55% to 95%, particularly 60% to 95%, preferably 65% to 90%,
more preferably 70 to 85% of the total pore volume of the
high-performance adsorbents is formed by the pore volume of pores
having pore diameters of more than 20 .ANG..
7. The high-performance adsorbents based on activated carbon as
claimed in one or more of the preceding claims, characterized in
that the measure of central tendency pore diameter of the
high-performance adsorbents is at least 30 .ANG., particularly at
least 35 .ANG., preferably at least 40 .ANG., and/or in that the
measure of central tendency pore diameter of the high-performance
adsorbents is in the range from 25 to 75 .ANG., particularly 30 to
75 .ANG., preferably 35 to 70 .ANG., more preferably 40 to 65
.ANG..
8. The high-performance adsorbents based on activated carbon as
claimed in one or more of the preceding claims, characterized in
that the BET surface area of the high-performance adsorbents is in
the range from 1250 m.sup.2/g to 2800 m.sup.2/g, particularly 1400
to 2500 m.sup.2/g, preferably 1500 to 2300 m.sup.2/g, more
preferably 1600 to 2100 m.sup.2/g.
9. The high-performance adsorbents based on activated carbon as
claimed in one or more of the preceding claims, characterized in
that the carbon black method pore surface area formed by pores
having pore diameters of more than 20 .ANG. is in the range from
200 to 1000 m.sup.2/g, particularly 250 to 950 m.sup.2/g,
preferably 350 to 900 m.sup.2/g, more preferably 400 to 850
m.sup.2/g.
10. The high-performance adsorbents based on activated carbon as
claimed in one or more of the preceding claims, characterized in
that the carbon black method pore surface area formed by pores
having pore diameters of more than 20 .ANG. comprises up to 30%,
particularly up to 40%, preferably up to 50% of the total pore
surface area of the high-performance adsorbents, and/or in that the
carbon black method pore surface area formed by pores having pore
diameters of more than 20 .ANG. comprises 10 to 50%, particularly
15 to 45%, preferably 20 to 40% of the total pore surface area of
the high-performance adsorbents.
11. The high-performance adsorbents based on activated carbon as
claimed in one or more of the preceding claims, characterized in
that the high-performance adsorbents have a butane adsorption of at
least 30%, particularly at least 35%, preferably at least 40%,
and/or in that the high-performance adsorbents have a butane
adsorption in the range from 30 to 80%, particularly 35 to 75%,
preferably 40 to 70%.
12. The high-performance adsorbents based on activated carbon as
claimed in one or more of the preceding claims, characterized in
that the high-performance adsorbents have an iodine number of at
least 1250 mg/g, particularly at least 1300 mg/g, preferably at
least 1350 mg/g, and/or in that the high-performance adsorbents
have an iodine number in the range from 1250 to 2100 mg/g,
particularly 1300 to 2000 mg/g, preferably 1350 to 1900 mg/g.
13. The high-performance adsorbents based on activated carbon as
claimed in one or more of the preceding claims, characterized in
that the high-performance adsorbents have a methylene blue value of
at least 15 ml, particularly at least 17 ml, preferably at least 19
ml, and/or in that the high-performance adsorbents have a methylene
blue value in the range from 15 to 60 ml, particularly 17 to 50 ml,
preferably 19 to 45 ml.
14. The high-performance adsorbents based on activated carbon as
claimed in one or more of the preceding claims, characterized in
that the high-performance adsorbents have a molasses number of at
least 300, particularly at least 350, preferably at least 400,
and/or in that the high-performance adsorbents have a molasses
number in the range from 300 to 1400, particularly 350 to 1300,
preferably 400 to 1250, most preferably 700 to 1200.
15. The high-performance adsorbents based on activated carbon as
claimed in one or more of the preceding claims, characterized by a
compressive or bursting strength per grain of activated carbon,
particularly per spherule of activated carbon, of at least 5
newtons, particularly at least 10 newtons, preferably at least 15
newtons, and/or characterized by a compressive or bursting strength
per grain of activated carbon, particularly per spherule of
activated carbon, in the range from 5 to 50 newtons, particularly
10 to 45 newtons, preferably 15 to 40 newtons.
16. The high-performance adsorbents based on activated carbon as
claimed in one or more of the preceding claims, characterized by an
abrasion resistance of at least 75%, particularly at least 80%,
preferably at least 85%, more preferably at least 90%, most
preferably at least 95%.
17. The high-performance adsorbents based on activated carbon as
claimed in one or more of the preceding claims, characterized in
that the carbon black method micropore surface area of the
high-performance adsorbents which is formed by pores having pore
diameters of .ltoreq.20 .ANG. is at least 1000 m.sup.2/g,
particularly at least 1100 m.sup.2/g, preferably at least 1200
m.sup.2/g, and/or in that the carbon black method micropore surface
area of the high-performance adsorbents which is formed by pores
having pore diameters of .ltoreq.20 .ANG. is in the range from 1000
to 1800 m.sup.2/g, particularly 1100 to 1600 m.sup.2/g, preferably
1200 to 1500 m.sup.2/g.
18. The high-performance adsorbents based on activated carbon as
claimed in one or more of the preceding claims, characterized in
that the carbon black method micropore surface area of the
high-performance adsorbents which is formed by pores having pore
diameters of 20 .ANG. comprises at least 30%, particularly at least
40%, preferably at least 50% of the total pore surface area of the
high-performance adsorbents, and/or in that the carbon black method
micropore surface area of the high-performance adsorbents which is
formed by pores having pore diameters of .ltoreq.20 .ANG. comprises
50 to 90%, particularly 55 to 85%, preferably 60 to 80% of the
total pore surface area of the high-performance adsorbents.
19. The high-performance adsorbents based on activated carbon as
claimed in one or more of the preceding claims, characterized in
that the weight-based adsorbed N.sub.2 volume V.sub.ads(wt) of the
high-performance adsorbents, determined at a partial pressure
p/p.sub.0 of 0.25, is at least 300 cm.sup.3/g, particularly at
least 350 cm.sup.3/g, preferably at least 375 cm.sup.3/g, and is
particularly in the range from 300 to 800 cm.sup.3/g, preferably
350 to 700 cm.sup.3/g, more preferably 375 to 650 cm.sup.3/g,
and/or in that the volume-based adsorbed N.sub.2 volume
V.sub.ads(vol) of the high-performance adsorbents, determined at a
partial pressure p/p.sub.0 of 0.25, is at least 75
cm.sup.3/cm.sup.3, particularly at least 100 cm.sup.3/cm.sup.3, and
is particularly in the range from 75 to 300 cm.sup.3/cm.sup.3,
preferably 80 to 275 cm.sup.3/cm.sup.3, more preferably 90 to 250
cm.sup.3/cm.sup.3.
20. The high-performance adsorbents based on activated carbon as
claimed in one or more of the preceding claims, characterized in
that the weight-based adsorbed N.sub.2 volume V.sub.ads(wt) of the
high-performance adsorbents, determined at a partial pressure
p/p.sub.0 of 0.995, is at least 400 cm.sup.3/g, particularly at
least 450 cm.sup.3/g, and is particularly in the range from 400 to
2300 cm.sup.3/g, preferably 450 to 2200 cm.sup.3/g, more preferably
750 to 2100 cm.sup.3/g, and/or in that the volume-based adsorbed
N.sub.2 volume V.sub.ads(vol) of the high-performance adsorbents,
determined at a partial pressure p/p.sub.0 of 0.995, is at least
200 cm.sup.3/cm.sup.3, particularly at least 250 cm.sup.3/cm.sup.3,
and is particularly in the range from 200 to 500 cm.sup.3/cm.sup.3,
preferably 250 to 400 cm.sup.3/cm.sup.3, more preferably 275 to 380
cm.sup.3/cm.sup.3.
21. The high-performance adsorbents based on activated carbon as
claimed in one or more of the preceding claims, characterized in
that the high-performance adsorbents or to be more precise the
grains of activated carbon, particularly spherules of activated
carbon, have measure of central tendency particle diameters in the
range from 0.01 to 2.0 mm, particularly 0.01 to 1.0 mm, preferably
0.05 to 0.9 mm, more preferably 0.1 to 0.8 mm, most preferably 0.15
to 0.7 mm.
22. The high-performance adsorbents based on activated carbon as
claimed in one or more of the preceding claims, characterized by an
ash content of at most 1%, particularly at most 0.8%, preferably at
most 0.6%, more preferably at most 0.5%, and/or characterized by a
moisture content of at most 1%, particularly at most 0.5%,
preferably at most 0.2%.
23. The high-performance adsorbents based on activated carbon as
claimed in one or more of the preceding claims, characterized by a
bulk density in the range from 150 to 750 g/l, particularly 175 to
650 g/l, preferably 200 to 600 g/l.
24. The high-performance adsorbents based on activated carbon in
the form of discrete grains of activated carbon, preferably in
spherical form, particularly as claimed in one or more of the
preceding claims, characterized by the following parameters: a pore
volume fraction formed by pores having pore diameters of more than
20 .ANG. which comprises at least 55% of the total pore volume of
the high-performance adsorbents, a measure of central tendency pore
diameter of more than 25 .ANG.. a BET surface area of at least 1250
m.sup.2/g, a methylene blue value of at least 15 ml, and a molasses
number of at least 300.
25. The high-performance adsorbents based on activated carbon,
particularly as claimed in one or more of the preceding claims,
characterized in that the high-performance adsorbents are
obtainable by a process as claimed in claims 26 to 34.
26. A process for producing the high-performance adsorbents based
on activated carbon, as claimed in one or more of the preceding
claims, which process comprises a carbonaceous starting material
being initially carbonized and subsequently activated,
characterized in that the activation is carried out in two stages
wherein the carbonized starting material is initially subjected, in
a first activating step, to an activation in an atmosphere
comprising water vapor, followed by a second activating step of
activation in an atmosphere comprising CO.sub.2.
27. The process as claimed in claim 26, characterized in that the
first activating step is carried out at temperatures of 700 to
1300.degree. C., particularly 800 to 1200.degree. C., preferably
850 to 950.degree. C., and/or for a duration of 5 to 24 hours,
preferably 6 to 15 hours, particularly 6 to 12 hours.
28. The process as claimed in claim 26 and/or 27, characterized in
that the second activating step is carried out at temperatures of
700 to 1300.degree. C., particularly 800 to 1200.degree. C.,
preferably 850 to 950.degree. C., and/or for a duration of 1 to 10
hours, particularly 3 to 8 hours.
29. The process as claimed in one or more of the preceding claims,
characterized in that the atmosphere of the first activating step
comprises or consists of water vapor, particularly a mixture of
water vapor/inert gas, preferably a mixture of water
vapor/nitrogen, particularly where the throughput of water vapor is
25 to 350 m.sup.3/h, particularly 50 to 300 m.sup.3/h, based on
pure water vapor, and/or particularly where the mass-based
throughput of water vapor is 0.01 to 50 l/(hkg), particularly 0.02
to 25 l/(hkg), preferably 0.02 to 5 l/(hkg), reckoned as water and
based on the amount of starting material to be activated with water
vapor.
30. The process as claimed in one or more of the preceding claims,
characterized in that the atmosphere of the second activating step
comprises or consists of CO.sub.2, particularly of pure CO.sub.2 or
a mixture of CO.sub.2/inert gas, particularly a mixture of
CO.sub.2/nitrogen, particularly where the throughput of CO.sub.2 is
10 to 250 m.sup.3/h, particularly 20 to 200 m.sup.3/h, based on
pure CO.sub.2, and/or where the mass-based throughput of CO.sub.2
is 0.001 to 100 m.sup.3/(hkg), particularly 0.01 to 50
m.sup.3/(hkg), preferably 0.05 to 10 m.sup.3/(hkg), reckoned as
pure gaseous CO.sub.2 under activating conditions and based on the
amount of starting material to be activated with CO.sub.2.
31. The process as claimed in one or more of the preceding claims,
characterized in that the first and second activating steps merge
into each other.
32. The process as claimed in one or more of the preceding claims,
characterized in that the first activating step is carried on to
attainment of a predetermined iodine number, particularly to
attainment of an iodine number of at least 1000 mg/g, particularly
at least 1250 mg/g.
33. The process as claimed in one or more of the preceding claims,
characterized in that the carbonization is carried out at
temperatures in the range from 100 to 950.degree. C., particularly
150 to 900.degree. C., preferably 300 to 850.degree. C., and/or for
a duration of 0.5 to 6 hours and/or under an inert or at most
slightly oxidizing atmosphere.
34. The process as claimed in one or more of the preceding claims,
characterized in that the carbonaceous starting material comprises
sulfonated styrene-divinylbenzene copolymers, particularly
sulfonated divinylbenzene-crosslinked polystyrenes, particularly in
grain form, preferably in spherical form, particularly where the
divinylbenzene content of the sulfonated styrene-divinylbenzene
copolymers is in the range from 1% to 20% by weight, particularly
1% to 15% by weight, preferably 2% to 10% by weight, based on the
styrene-divinylbenzene copolymers.
35. The use of the high-performance adsorbents based on activated
carbon as claimed in one or more of the preceding claims for the
food industry, particularly for preparing and/or decolorizing food
products.
36. The use of the high-performance adsorbents based on activated
carbon as claimed in one or more of the preceding claims for the
adsorption of toxins, noxiants and odors, particularly from gas or
air streams, or for purifying or cleaning gases, particularly air
or liquids, particularly water.
37. The use of the high-performance adsorbents based on activated
carbon as claimed in one or more of the preceding claims for use in
adsorptive filtering materials, particularly in the manufacture of
protective apparel.
38. The use of the high-performance adsorbents as claimed in one or
more of the preceding claims as sorptive storage media for gases or
liquids.
39. The use of the high-performance adsorbents based on activated
carbon as claimed in one or more of the preceding claims in the
sector of medicine or pharmacy, particularly as a medicament or
medicament constituent.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a National Stage filing of International
Application PCT/EP2008/000606, filed Jan. 25, 2008, claiming
priority to German Application Nos. DE 10 2007 012 963.9 filed Mar.
14, 2007 and DE 10 2007 050 971.7, filed Oct. 25, 2007. The subject
application claims priority to PCT/EP2008/000606, to German
Application Nos. DE 10 2007 012 963.9 and DE 10 2007 050 971.7 and
incorporates all by reference herein, in their entirety.
BACKGROUND OF THE INVENTION
[0002] The present invention concerns the adsorption arts. More
particularly, the present invention concerns high-performance
adsorbents based on activated carbon of high meso- and
macroporosity and a process for production thereof and also the use
of these high-performance adsorbents, particularly for adsorptive
filtering materials, for the food industry (for example for
preparing and/or decolorizing food products, for the adsorption of
toxins, noxiants and odors, particularly from gas or air streams,
for purifying or cleaning gases, particularly air, and liquids,
particularly water, for application in medicine or to be more
precise pharmacy, and also as sorptive storage media particularly
for gases, liquids and the like.
[0003] Activated carbon has fairly unspecific adsorptive properties
and therefore is the most widely used adsorbent. Legislation as
well as the rising sense of responsibility for the environment lead
to a rising demand for activated carbon.
[0004] Activated carbon is generally obtained by carbonization
(also referred to by the synonyms of smoldering, pyrolysis,
burn-out, etc) and subsequent activation of carbonaceous compounds,
preferably such compounds as lead to economically reasonable
yields. This is because the weight losses through detachment of
volatile constituents in the course of carbonization and through
the subsequent burn-out in the course of activation are
appreciable. For further details concerning the production of
activated carbon, see for example H.v. Kienle and E. Bader,
Aktivkohle and ihre industrielle Anwendung, Enke Verlag Stuttgart,
1980.
[0005] The constitution of the activated carbon produced--finely or
coarsely porous, firm or brittle, etc--depends on the starting
material. Customary starting materials are coconut shells, charcoal
and wood (for example wood wastes), peat, bituminous coal, pitches,
but also particular plastics which play a certain part in the
production of woven activated carbon fabrics for example.
[0006] Activated carbon is used in various forms: pulverized
carbon, splint coal carbon, granulocarbon, molded carbon and also,
since the end of the 1970s, spherical activated carbon
("spherocarbon"). Spherical activated carbon has a number of
advantages over other forms of activated carbon such as pulverized
carbon, splint coal carbon, granulocarbon, molded carbon and the
like that make it useful or even indispensable for certain
applications: it is free flowing, abrasion resistant or to be more
precise dustless, and hard. Spherocarbon is in great demand for
particular applications, for example, because of its specific form,
but also because of its high abrasion resistance.
[0007] Spherocarbon is mostly still being produced today by
multistage and very costly and inconvenient processes. The best
known process consists in producing spherules from bituminous coal
tar pitch and suitable asphaltic residues from the petrochemical
industry, which are oxidized to render them unmeltable and then
smoldered and activated. For example, spherocarbon can also be
produced in a multistage process proceeding from bitumen. These
multistage processes are very cost intensive and the associated
high cost of this spherocarbon prevents many applications wherein
spherocarbon ought to be preferable by virtue of its
properties.
[0008] WO 98/07655 A1 describes a process for producing activated
carbon spherules wherein a mixture comprising a diisocyanate
production distillation residue, a carbonaceous processing aid and
if appropriate one or more further additives is processed into
free-flowing spherules and subsequently the spherules obtained in
this way are carbonized and then activated.
[0009] It is further prior art to produce spherocarbon by
smoldering and subsequent activation of new or used ion exchangers
comprising sulfonic acid groups, or by smoldering ion exchanger
precursors in the presence of sulfuric acid and subsequent
activation, the sulfonic acid groups and the sulfuric acid
respectively having the function of a crosslinker. Such processes
are described for example in DE 43 28 219 A1 and DE 43 04 026 A1
and also in DE 196 00 237 A1 including the German
patent-of-addition application DE 196 25 069 A1.
[0010] However, there are a number of specific applications where
it is not only the geometry or to be more precise the external
shape of the activated carbon which is of decisive importance, but
also its porosity, in particular the total pore volume and the
adsorption capacity on the one hand and the distribution of the
pores, i.e., the fraction of micro-, meso- and macropores in
relation to the total pore volume, on the other.
[0011] There are a number of applications requiring a particularly
high meso- and macroporosity of the activated carbon, i.e., a high
meso- and macropore volume fraction, coupled with an altogether
high total pore volume, for example in relation to the applications
mentioned at the beginning, for example for use in the food
industry, in the manufacture of certain adsorptive filtering
materials (for example for NBC protective apparel), for the
adsorption of toxins, noxiants and odors, particularly from gas or
air streams, for purifying or cleaning gases, such as in particular
air, and also liquids, for application in medicine or to be more
precise pharmacy, in the sorptive storage of gases or liquids and
the like.
[0012] True, the activated carbon known for this purpose from the
prior art does have a certain degree of meso- and macroporosity,
but that degree is not sufficient in all cases. In addition,
increasing porosity is often observed to be accompanied by an
unwelcome, occasionally unacceptable decrease in mechanical
stability or to be more precise abrasion resistance. Nor are the
fraction of the total pore volume which is .alpha.-counted for by
meso- and macropores and the absolute pore volume always sufficient
to ensure adequate performance capability and/or an adequate
impregnatability (for example impregnation with metals or metal
salts) for all applications.
BRIEF SUMMARY OF THE INVENTION
[0013] This invention relates to high-performance adsorbents based
on activated carbon in the form of discrete grains of activated
carbon having: (a) at least 70% of the total pore volume formed by
pores having pore diameters of more than 20 .ANG.; (b) a measure of
central tendency pore diameter (mean pore diameter) of more than 25
.ANG.; (c) a BET surface area of at least 1,250 m.sup.2/g; and (d)
an iodine number of at least 1,250 mg/g. Such adsorbents typically
have a high meso- and macroporosity, (i.e. a high meso- and
macroporous fraction relative to the total pore volume), a large
total pore volume and yet retain high stability to abrasion and
bursting.
[0014] Further aspects of the present invention relate to a process
for producing the high-performance adsorbents based on activated
carbon. The process utilizes a carbonaceous starting material and
involves initially carbonizing and subsequently activating the
starting material. The activation step is carried out in two
stages. The carbonized starting material is initially subjected, in
a first activating step in an atmosphere of water vapor, followed
by a second activation step in an atmosphere that includes
CO.sub.2.
[0015] Further aspects of the present invention relate to a
filtering material based on the high-performance adsorbents
described above.
[0016] Still further aspects of the present invention relate to a
piece of protective apparel that includes the high-performance
adsorbents described above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a graph illustrating a N.sub.2 adsorption isotherm
for a first high-performance adsorbent of the present
invention.
[0018] FIG. 2 is a graph illustrating a N.sub.2 adsorption isotherm
for a second high-performance adsorbent of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0019] It is therefore an object of the present invention to
provide, on the basis of activated carbon, a high-performance
adsorbent which is suitable for the aforementioned fields of
application in particular and which at least substantially avoids
or else at least ameliorates the above-described disadvantages of
the prior art. More particularly, the adsorbent to be provided
according to the present invention should have a high meso- and
macroporosity, i.e., a high meso- and macroporous fraction in
relation to the total pore volume and also a large total pore
volume, yet at the same time also good mechanical stability,
particularly a high stability to abrasion and bursting.
[0020] In the context of the present invention, the term
"micropores" refers to pores having pore diameters of up to 20
.ANG. inclusive, whereas the term "mesopores" refers to pores
having pore diameters in the range of more than 20 .ANG. (i.e.,
>20 .ANG.) to 500 .ANG. inclusive and the term "macropores"
refers to pores having pore diameters of more than 500 .ANG. (i.e.,
>500 .ANG.): [0021] micropores: pore
diameter.sub.micropores.gtoreq.20 .ANG. [0022] mesopores: 20
.ANG.<pore diameter.sub.mesopores.ltoreq.500 .ANG. [0023]
macropores: pore diameter.sub.macropores>500 .ANG.
[0024] By way of a solution to the problem described above, the
present invention proposes--in accordance with a first aspect of
the present invention--high-performance adsorbents based on
activated carbon in the form of discrete grains of activated
carbon, preferably in spherical form, according to claim 1.
Further, in particular advantageous embodiments of the
high-performance adsorbents of the present invention are subject
matter of the corresponding subclaims.
[0025] The present invention further provides--in accordance with a
second aspect of the present invention--the present invention
process for producing the high-performance adsorbents according to
the present invention, as more particularly defined in the
corresponding process claims.
[0026] The present invention yet further provides--in accordance
with a third aspect of the present invention--the present invention
use of the high-performance adsorbents according to the present
invention, as more particularly defined in the corresponding use
claims.
[0027] The present invention accordingly provides--in accordance
with a first aspect of the present invention--high-performance
adsorbents based on activated carbon in the form of discrete grains
of activated carbon, preferably in spherical form, these
high-performance adsorbents being characterized by the following
parameters: [0028] a pore volume fraction formed by pores having
pore diameters of more than 20 .ANG. (i.e., in other words, a meso-
and macropore volume fraction) which comprises at least 55% of the
total pore volume of high-performance adsorbents (This parameter is
interchangeably also referred to as "fraction of external pore
volume in relation to total pore volume".), [0029] a measure of
central tendency pore diameter of more than 25 .ANG.. [0030] a BET
surface area of at least 1250 m.sup.2/g,
[0031] The present high-performance adsorbents or to be more
precise activated carbons, in addition to the aforementioned
properties or to be more precise parameters, particularly a high
meso- and macropore volume fraction (i.e., a high pore volume
fraction due to pores having a pore diameter of more than 20
.ANG.), are further notable in particular for a large total
porosity and a simultaneously large BET surface area.
[0032] As will be shown in what follows, the mechanical strength,
particularly the abrasion resistance and the bursting or to be more
precise compressive strength, of the present high-performance
adsorbents is despite the high total porosity extremely high--in
contrast to comparable high-porosity activated carbons of the prior
art--so that the present high-performance adsorbents or to be more
precise activated carbons are also suitable for applications where
they are exposed to large mechanical loads.
[0033] In relation to all the parameter indications hereinabove and
hereinbelow, it is to be noted that the recited limits, in
particular upper and lower limits, are included, i.e., all
statements of values are to be understood as including the
respective limits, except where otherwise stated in an individual
case. It will further be understood that in an individual case or
in relation to an application it may be necessary if appropriate to
depart slightly from the limits mentioned without leaving the realm
of the present invention.
[0034] The hereinabove and hereinbelow mentioned parameter data are
determined using standardized or explicitly indicated methods of
determination or using methods of determination familiar per se to
one skilled in the art.
[0035] The parameter data concerning the characterization of the
porosity, particularly of the above-specified meso- and macropore
fraction (i.e., the fraction of the total pore volume of the
high-performance adsorbents which is contributed by pores having
pore diameters of more than 20 .ANG.) each follow from the nitrogen
isotherm of the activated carbon measured.
[0036] The measure of central tendency pore diameter is similarly
determined on the basis of the respective nitrogen isotherms.
[0037] The BET method of determining the specific surface area is
in principle known as such to one skilled in the art, so that no
further details need be furnished in this regard. All BET surface
area data are based on the ASTM D6556-04 method of determination.
The present invention utilizes the MultiPoint BET (MP-BET) method
of determination in a partial pressure range p/p.sub.0 of 0.05 to
0.1.
[0038] With regard to further details concerning the determination
of the BET surface area or to be precise concerning the BET method,
reference may be made to the aforementioned ASTM D6556-04 standard
and also to Rompp Chemielexikon, 10th edition, Georg Thieme Verlag,
Stuttgart/New York, headword: "BET-Methode", including the
references cited therein, and to Winnacker-Kuchler (3rd edition),
Volume 7, pages 93 ff, and also to Z. Anal. Chem. 238, pages 187 to
193 (1968).
[0039] As observed above and more particularly specified
hereinbelow, one special feature of the high-performance adsorbents
of the present invention is that they have a very large total pore
volume as determined by the Gurvich method, to provide a very large
adsorptive capacity in which the meso- and macropore volume
fraction (i.e., that is, the pore volume fraction due to pores
having pore diameters above 20 .ANG.) is high, viz. at least 55% of
the total pore volume.
[0040] The Gurvich determination of total pore volume is a method
of measurement/determination known per se in this field to a person
skilled in the art. For further details concerning the Gurvich
determination of total pore volume reference may be made for
example to L. Gurvich (1915), J. Phys. Chem. Soc. Russ. 47, 805,
and also to S. Lowell et al., Characterization of Porous Solids and
Powders: Surface Area Pore Size and Density, Kluwer Academic
Publishers, Article Technology Series, pages 111 et seq.
[0041] The Gurvich total pore volume of the high-performance
adsorbents of the present invention is at least 0.8 cm.sup.3/g,
particularly at least 1.0 cm.sup.3/g, preferably at least 1.2
cm.sup.3/g, and can generally attain values of up to 2.0
cm.sup.3/g, particularly up to 2.5 cm.sup.3/g, preferably up to 3.0
cm.sup.3/g, more preferably up to 3.5 cm.sup.3/g.
[0042] The Gurvich total pore volume of the high-performance
adsorbents of the present invention is generally in the range from
0.8 to 3.5 cm.sup.3/g, particularly 1.0 to 3.5 cm.sup.3/g,
preferably 1.2 to 3.2 cm.sup.3/g.
[0043] Owing to their high meso- and macroporosity, the meso- and
macropore volume of the high-performance adsorbents of the present
invention (i.e., that is, in other words, the pore volume formed by
pores having pore diameters of more than 20 .ANG.) is relatively
high in that in general the carbon black method pore volume of the
high-performance adsorbents of the present invention which is
formed by pores having pore diameters of more than 20 .ANG. (i.e.,
that is, the meso- and macropore volume) is in the range from 0.4
to 3.3 cm.sup.3/g, particularly 0.8 to 3.2 cm.sup.3/g, preferably
1.0 to 3.1 cm.sup.3/g, more preferably 1.2 to 3.0 cm.sup.3/g, most
preferably 1.2 to 2.8 cm.sup.3/g. The pore volume formed by pores
having pore diameters of more than 20 .ANG. is interchangeably also
referred to as "external pore volume".
[0044] Generally at least 60%, particularly at least 65%,
preferably at least 70%, more preferably at least 75%, most
preferably at least 80% of the total pore volume of the
high-performance adsorbents of the present invention is formed by
the pore volume of pores having pore diameters of more than 20
.ANG. (i.e., that is, in other words, by the meso- and macropore
volume).
[0045] Generally 55% to 95%, particularly 60% to 95%, preferably
65% to 90%, more preferably 70 to 85% of the total pore volume of
the high-performance adsorbents of the present invention is formed
by the pore volume of pores having pore diameters of more than 20
.ANG.. The aforementioned percentages thus identify that proportion
of the total pore volume of the high-performance adsorbents of the
present invention which is attributable to the fraction of the
so-called external pore volume (i.e., the pore volume formed by
pores having pore diameters of more than 20 .ANG.).
[0046] The carbon black method of determination is known per se to
one skilled in the art (as is the corresponding analysis, including
plotting and fixing of the p/p.sub.o range), so that no further
details are needed in this regard. In addition, for further details
of the carbon black method of determining the pore surface area and
the pore volume reference may be made for example to R. W. Magee,
Evaluation of the External Surface Area of Carbon Black by Nitrogen
Adsorption, Presented at the Meeting of the Rubber Division of the
American Chem. Soc., October 1994, for example cited in:
Quantachrome Instruments, AUTOSORB-1, AS1 WinVersion 1.50,
Operating Manual, OM, 05061, Quantachrome Instruments 2004,
Florida, USA, pages 71 ff.
[0047] Owing to the high meso- and macroporosity of the
high-performance adsorbents of the present invention, the measure
of central tendency pore diameter is relatively high in that in
general it is at least 30 .ANG., particularly at least 35 .ANG.,
preferably at least 40 .ANG..
[0048] In general, the measure of central tendency pore diameter of
the high-performance adsorbents of the present invention is in the
range from 25 to 75 .ANG., particularly 30 to 75 .ANG., preferably
35 to 70 .ANG., more preferably 40 to 65 .ANG..
[0049] As stated above, it is a further special feature of the
high-performance adsorbents of the present invention that BET
surface area is relatively large and that it is at least 1250
m.sup.2/g, preferably at least 1400 m.sup.2/g, more preferably at
least 1500 m.sup.2/g, most preferably at least 1600 m.sup.2/g.
[0050] In general, the BET surface area of the high-performance
adsorbents of the present invention is in the range from 1250
m.sup.2/g to 2800 m.sup.2/g, particularly 1400 to 2500 m.sup.2/g,
preferably 1500 to 2300 m.sup.2/g, more preferably 1600 to 2100
m.sup.2/g.
[0051] The carbon black method external pore surface area of the
high-performance adsorbents of the present invention (i.e., that
is, the pore surface area formed by pores having pore diameters of
more than 20 .ANG.) is relatively large, because of the high meso-
and macropore fraction, and is generally in the range from 200 to
1000 m.sup.2/g, particularly 250 to 950 m.sup.2/g, preferably 350
to 900 m.sup.2/g, more preferably 400 to 850 m.sup.2/g.
[0052] In general, the carbon black method external pore surface
area of the high-performance adsorbents of the present invention
(i.e., that is, the pore surface area formed by pores having pore
diameters of more than 20 .ANG.) forms up to 30%, particularly up
to 40%, preferably up to 50% of the total pore surface area of the
high-performance adsorbents of the present invention. More
particularly, the carbon black method external pore surface area of
the high-performance adsorbents of the present invention (i.e.,
that is, the pore surface area formed by pores having pore
diameters of more than 20 .ANG.) forms 10 to 50%, particularly 15
to 45%, preferably 20 to 40% of the total pore surface area of the
high-performance adsorbents of the present invention.
[0053] In addition, the high-performance adsorbents of the present
invention have an extremely high butane adsorption and
simultaneously an extremely high iodine number, which fact
characterizes their property of having excellent adsorption
properties with regard to a wide variety of materials to be
adsorbed.
[0054] The ASTM D5742-95/00 butane adsorption of the
high-performance adsorbents of the present invention is generally
at least 30%, particularly at least 35%, preferably at least 40%.
In general, the high-performance adsorbents of the present
invention have an ASTM D5742-95/00 butane adsorption in the range
from 30% to 80%, particularly 35 to 75% preferably 40 to 70%.
[0055] The ASTM D4607-94/99 iodine number of the high-performance
adsorbents of the present invention is generally at least 1250
mg/g, particularly at least 1300 mg/g, preferably at least 1350
mg/g. The high-performance adsorbents of the present invention
preferably have an ASTM D4607-94/99 iodine number in the range from
1250 to 2100 mg/g, particularly 1300 to 2000 mg/g, preferably 1350
to 1900 mg/g. The iodine number can be taken as a measure for
available surface area provided by predominantly larger micropores;
the aforementioned values of the iodine number of the
high-performance adsorbents of the present invention show that the
high-performance adsorbents of the present invention simultaneously
also have a high microporosity.
[0056] Owing to their high meso- and macroporosity, the
high-performance adsorbents of the present invention similarly have
high methylene blue and molasses adsorption numbers which together
can be taken as a measure of available surface area provided
predominantly by meso- and macropores. The methylene blue number or
to be more precise the methylene blue adsorption, which indicates
the amount of methylene blue adsorbed per defined amount of
adsorbents, under defined conditions (i.e., the number of ml of a
methylene blue standard solution decolorized by a defined amount of
dry and pulverized adsorbents), relates to larger micropores and
predominantly smaller mesopores and gives an indication of the
adsorptive capacity of the high-performance adsorbents of the
present invention in relation to molecules comparable in size to
methylene blue. By contrast, the molasses number must be considered
a measure of the meso- and macroporosity and indicates the amount
of adsorbents which is required to decolorize a standard molasses
solution, so that the molasses number gives an indication of the
adsorptive capacity of the high-performance adsorbents of the
present invention in relation to molecules that are comparable in
size to molasses (generally sugar beet molasses). Together,
therefore, the methylene blue and molasses numbers can be
considered a measure of the meso- and macroporosity of the
high-performance adsorbents of the present invention.
[0057] The methylene blue value of the high-performance adsorbents
of the present invention which is determined by following the
method of CEFIC (Conseil Europeen des Federations des Industries
Chimiques, Avenue Louise 250, Bte 71, B--1050 Brussels, November
1986, European Council of Chemical Manufacturers' Federations, Test
Methods for Activated Carbons, Item 2.4 "Methylene blue value",
pages 27/28) is at least 15 ml, particularly at least 17 ml,
preferably at least 19 ml, and is generally in the range from 15 to
60 ml, particularly 17 to 50 ml, preferably 19 to 45 ml.
[0058] The methylene blue value according to the aforementioned
CEFIC method is thus defined as the number of ml of a methylene
blue standard solution which are decolorized by 0.1 g of dry and
pulverized activated carbon. Performing this method requires a
glass vessel with ground stopper, a filter and also a methylene
blue standard solution prepared as follows: 1200 mg of pure
methylene blue dye (corresponding to about 1.5 g of methylene blue
to DAB VI [German Pharmacopeia, 6th edition] or equivalent product)
are dissolved in water in a 1000 ml volumetric flask, and the
solution is allowed to stand for several hours or overnight; to
check its strength, 5.0 ml of the solution are diluted with 0.25%
(volume fractions) acetic acid to 1.0 l in a volumetric flask and
thereafter the absorbance is measured at 620 nm and 1 cm path
length, and it has to be 0.840.+-.0.010. If the absorbance is
higher, it has to be diluted with the computed amount of water; if
it is lower, the solution is discarded and made up fresh. By way of
sample preparation, the high-performance adsorbents in the form of
granular activated carbon are pulverized (<0.1 mm) and then
dried to a constant weight at 150.degree. C. Precisely 0.1 g of the
spherocarbon is then combined with 25 ml (5 ml) of the methylene
blue standard solution in a ground glass flask (A preliminary test
has to be carried out to see whether an initial addition of 25 ml
of methylene blue standard solution with 5 ml additions or an
initial addition of 5 ml of methylene blue standard solution with 1
ml additions can be used.). The flask is shaken until
decolorization occurs. Then, a further 5 ml (1 ml) of the methylene
blue standard solution are added, and the flask is shaken to the
point of decolorization.
[0059] The addition of methylene blue standard solution is repeated
in 5 ml amounts (1 ml amounts) as long as decolorization still
occurs within 5 minutes. The entire volume of the test solution
decolorized by the sample is recorded. The test is repeated to
confirm the results obtained. The volume of the methylene blue
standard solution in ml which are just decolorized is the methylene
blue value of the high-performance adsorbents. It is to be noted in
this connection that the methylene blue dye must not be dried,
since it is heat sensitive; rather, the water content must be
corrected for purely arithmetically.
[0060] The dimensionless molasses number can in principle be
determined either by following the Norit method (Norit N. V.,
Amersfoort, Netherlands, Norit Standard Method NSTM 2.19 "Molasses
Number (Europe)") or alternatively by following the PACS method
(PACS=Professional Analytical and Consulting Services Inc.,
Coraopolis Pa., USA). In the context of the present invention, the
values of the molasses number are determined by following the PACS
method. Thus, the PACS method molasses number of the
high-performance adsorbents of the present invention is at least
300, particularly at least 350, preferably at least 400, and is
generally in the range from 300 to 1400, particularly 350 to 1300,
preferably 400 to 1250, most preferably 700 to 1200.
[0061] Whether by following the Norit method or by following the
PACS method, the molasses number is determined by determining the
amount of pulverized high-performance adsorbents based on activated
carbon that is needed to decolorize a standard molasses solution.
Determination is effected photometrically, and the standard
molasses solution is standardized against a standardized activated
carbon having a molasses number of 245 and/or 350. For further
details in this regard, reference can be made to the two
aforementioned prescriptive methods.
[0062] Despite their high porosity, particularly meso- and
macroporosity, the high-performance adsorbents of the present
invention have a high compressive or bursting strength (resistance
to weight loading) and also an extremely high abrasion
resistance.
[0063] The compressive or bursting strength (resistance to weight
loading) per grain of activated carbon, in particular per spherule
of activated carbon, is thus at least 5 newtons, in particular at
least 10 newtons and preferably at least 15 newtons. In general,
the compressive or bursting strength (resistance to weight loading)
per grain of activated carbon, particularly per spherule of
activated carbon, ranges from 5 to 50 newtons, in particular from
10 to 45 newtons and preferably from 15 to 40 newtons.
[0064] As mentioned, the abrasion hardness of the high-performance
adsorbents of the present invention is also extremely high in that
the abrasion resistance when measured by the method of CEFIC
(Conseil Europeen des Federations des Industries Chimiques, Avenue
Louise 250, Bte 71, B--1050 Brussels, November 1986, European
Council of Chemical Manufacturers' Federations, Test Methods for
Activated Carbons, Item 1.6 "Mechanical Hardness", pages 18/19) is
always 100% or virtually 100%. Similarly, when measured according
to ASTM D3802 abrasion resistances of the high-performance
adsorbents of the present invention of 100% or virtually 100% are
always obtained.
[0065] Therefore, the applicant company has developed a modified
test method on the lines of this CEFIC method in order that more
meaningful values may be obtained. The modified method of
determination provides a better simulation of the resistance of the
sample or to be more precise of the high-performance adsorbents to
abrasion or attrition under near actual service conditions. For
this purpose, the sample is exposed to standardized conditions for
a defined time in a horizontally swinging grinding cup charged with
a tungsten carbide ball. The procedure adopted for this purpose is
as follows: 200 g of a sample are dried for one hour at
(120.+-.2).degree. C. in a circulating air drying cabinet (type:
Heraeus UT 6060 from Kendro GmbH, Hanau) and are subsequently
cooled down in a desiccator over drying agent to room temperature.
50 g of the dried sample are removed and sieved off by means of a
sieving machine equipped with an analytical sieve (for example,
type: AS 200 control from Retsch GmbH, Hanau) at a swing amplitude
of 1.2 mm for ten minutes through an analytical sieve, the
analytical sieve being selected depending on the grain distribution
of the sample to be measured (for example, analytical sieve of mesh
size: 0.315 mm, diameter: 200 mm, height: 50 mm); the subsize grain
is discarded. 5 ml of the nominal grain are filled into a 10 ml
graduated cylinder to DIN ISO 384 (volume: 10 ml, height: 90 mm)
and the weight is accurately determined to 0.1 mg using an
analytical balance (type: BP121S from Sartorius AG, Gottingen,
weighing range: 120 g, accuracy class: E2, readability: 0.1 mg) by
means of a weighing glass having a ground glass lid (volume: 15 ml,
diameter: 35 mm, height: 30 mm) The weighed sample is placed
together with a tungsten carbide grinding ball of 20 mm diameter in
a 25 ml grinding cup with screw action closure (volume: 25 ml,
diameter: 30 mm, length: 65 mm, material of construction: stainless
steel) and then the abrasion test is carried out by means of a
swing mill (type: MM301 from Retsch GmbH, Haan, swing mill with
grinding cup); the grinding cup swings in a horizontal position for
one minute at a frequency of 10 Hz in the swing mill, causing the
grinding ball to impact on the sample and thus create abrasion.
Subsequently, the sample is sieved off by means of a sieving
machine at a swing amplitude of 1.2 mm for five minutes through the
aforementioned analytical sieve, the subsize grain again being
discarded and the nominal grain, which is dependent on the grain
distribution of the relevant sample (e.g. nominal grain greater
than 0.315 mm), being weighed back accurately to 0.1 mg in the
weighing glass with lid. The abrasion hardness is computed as a
mass fraction in % by the following formula: abrasion hardness
[%]=(100.times.back-weighed weight [g])/original weight [g].
[0066] According to this method of determination, modified by the
applicant company by modifying the aforementioned CEFIC standard,
the abrasion resistance of the high-performance adsorbents of the
present invention is at least 75%, particularly at least 80%,
preferably at least 85%, more preferably at least 90%, most
preferably at least 95%.
[0067] As stated above, it is a further special feature of the
high-performance adsorbents of the present invention that they also
have a certain degree of microporosity and thus also a certain
micropore surface area (i.e. surface area which is formed by pores
having pore diameters of .ltoreq.20 .ANG.. In general, the carbon
black method micropore surface area of the high-performance
adsorbents of the present invention which is formed by pores having
pore diameters of .ltoreq.20 .ANG. is at least 1000 m.sup.2/g,
particularly at least 1100 m.sup.2/g, preferably at least 1200
m.sup.2/g, and is generally in the range from 1000 to 1800
m.sup.2/g, particularly 1100 to 1600 m.sup.2/g, preferably 1200 to
1500 m.sup.2/g.
[0068] In general, the carbon black method micropore surface area
of the high-performance adsorbents of the present invention which
is formed by pores having pore diameters of .ltoreq.20 .ANG. is at
least 30%, particularly at least 40%, preferably at least 50% of
the total pore surface area of the high-performance adsorbents of
the present invention. More particularly, the carbon black method
micropore surface area of the high-performance adsorbents of the
invention which is formed by pores having pore diameters of
.ltoreq.20 .ANG. is in the range from 50 to 90%, particularly 55 to
85%, preferably 60 to 80% of the total pore surface area of the
high-performance adsorbents of the present invention.
[0069] Similarly, the weight- and volume-based volume V.sub.ads
(N.sub.2) of the high-performance adsorbents of the present
invention at different partial pressures p/p.sub.0 is very
large:
[0070] The weight-based adsorbed N.sub.2 volume V.sub.ads(wt) of
the high-performance adsorbents of the present invention,
determined at a partial pressure p/p.sub.0 of 0.25, is at least 300
cm.sup.3/g, particularly at least 350 cm.sup.3/g, preferably at
least 375 cm.sup.3/g, and is particularly in the range from 300 to
800 cm.sup.3/g, preferably 350 to 700 cm.sup.3/g, more preferably
375 to 650 cm.sup.3/g.
[0071] In general, the volume-based adsorbed N.sub.2 volume
V.sub.ads(vol) of the high-performance adsorbents of the present
invention, determined at a partial pressure p/p.sub.0 of 0.25, is
at least 75 cm.sup.3/cm.sup.3, particularly at least 100
cm.sup.3/cm.sup.3, and is particularly in the range from 75 to 300
cm.sup.3/cm.sup.3, preferably 80 to 275 cm.sup.3/cm.sup.3, more
preferably 90 to 250 cm.sup.3/cm.sup.3.
[0072] In general, the weight-based adsorbed N.sub.2 volume
V.sub.ads(wt) of the high-performance adsorbents of the present
invention, determined at a partial pressure p/p.sub.0 of 0.995, is
at least 400 cm.sup.3/g, particularly at least 450 cm.sup.3/g, and
is particularly in the range from 400 to 2300 cm.sup.3/g,
preferably 450 to 2200 cm.sup.3/g, more preferably 750 to 2100
cm.sup.3/g.
[0073] In general, the volume-based adsorbed N.sub.2 volume
V.sub.ads(vol) of the high-performance adsorbents of the present
invention, determined at a partial pressure p/p.sub.0 of 0.995, is
at least 200 cm.sup.3/cm.sup.3, particularly at least 250
cm.sup.3/cm.sup.3, and is particularly in the range from 200 to 500
cm.sup.3/cm.sup.3, preferably 250 to 400 cm.sup.3/cm.sup.3, more
preferably 275 to 380 cm.sup.3/cm.sup.3.
[0074] The high-performance adsorbents of the present invention are
based on granular, in particular spherical, activated carbon whose
measure of central tendency particle diameter, determined to ASTM
D2862-97/04, is generally in the range from 0.01 to 2.0 mm,
particularly 0.01 to 1.0 mm, preferably 0.05 to 0.09 mm, more
preferably 0.1 to 0.8 mm, most preferably 0.15 to 0.7 mm.
[0075] The ash content of the high-performance adsorbents of the
present invention, determined to ASTM D2866-94/04, is at most 1%,
particularly at most 0.8%, preferably at most 0.6%, more preferably
at most 0.5%.
[0076] The ASTM D2867-04/04 moisture content of the
high-performance adsorbents of the present invention is at most 1%,
particularly at most 0.5%, preferably at most 0.2%.
[0077] The high-performance adsorbents of the present invention
generally have a bulk density, determined to ASTM B527-93/00, in
the range from 150 to 750 g/l, particularly 175 to 650 g/l,
preferably 200 to 600 g/l.
[0078] In accordance with a particular embodiment of the present
invention, the present invention provides high-performance
adsorbents based on activated carbon in the form of discrete grains
of activated carbon, preferably in spherical form, particularly as
described above, characterized by the following parameters: [0079]
a pore volume fraction formed by pores having pore diameters of
more than 20 .ANG. which comprises at least 55% of the total pore
volume of the high-performance adsorbents, [0080] a measure of
central tendency pore diameter of more than 25 .ANG.. [0081] a BET
surface area of at least 1250 m.sup.2/g, [0082] a methylene blue
value of at least 15 ml, and [0083] a molasses number of at least
300.
[0084] The present invention further provides--in accordance with a
second aspect of the present invention--the present invention
process for producing the high-performance adsorbents according to
the present invention. In accordance with this aspect of the
present invention, the present invention accordingly provides a
process for producing the above-described high-performance
adsorbents based on activated carbon, which process comprises a
carbonaceous starting material being initially carbonized and
subsequently activated, wherein the activation is carried out in
two stages, wherein the carbonized starting material is initially
subjected, in a first activating step, to an activation in an
atmosphere comprising water vapor, followed by a second activating
step of activation in an atmosphere comprising CO.sub.2.
[0085] The high-performance adsorbents of the present invention are
produced using carbonaceous starting materials, in particular
sulfonated styrene-divinylbenzene copolymers, particularly
sulfonated divinylbenzene-crosslinked polystyrenes, preferably in
grain form, more preferably in spherical form. The divinylbenzene
content of the sulfonated styrene-divinylbenzene copolymers used as
starting materials to produce the high-performance adsorbents of
the present invention should particularly be in the range from 1 to
20% by weight, particularly 1 to 15% by weight, preferably 2 to 10%
by weight, based on the styrene-divinylbenzene copolymers. The
starting copolymers can in principle be selected from the gel type
or else from the macroporous type. When unsulfonated starting
materials are used, the sulfonation can be carried out in situ (in
particular before and/or during the carbonization), particularly
using methods known per se to one skilled in the art, preferably by
means of sulfuric acid and/or oleum and/or SO.sub.3; this is
familiar per se to one skilled in the art (cf. also the prior art
described at the beginning). Starting materials which have proven
particularly advantageous are the gel-form or macroporous types of
the corresponding ion exchange resins or of the corresponding
unsulfonated precursors of ion exchange resins which still have to
be sulfonated.
[0086] The carbonization (also known by the synonyms of pyrolysis,
burn-out or smoldering) converts the carbonaceous starting polymers
to carbon; that is, in other words, the carbonaceous starting
material is carbonized. Carbonization of the aforementioned organic
polymeric grains, in particular polymeric spherules, based on
styrene and divinylbenzene which comprise sulfonic acid groups
leads to the detachment of the sulfonic acid groups during the
carbonization to free radicals and thus to crosslinks without which
there would be no pyrolysis residue (=carbon). In general, the
carbonization is carried out under an inert atmosphere (for example
nitrogen) or an at most slightly oxidizing atmosphere. It can
similarly be advantageous for the inert atmosphere of the
carbonization, in particular if it is carried out at comparatively
high temperatures (for example in the range from about 500 to
650.degree. C.) to be admixed with a minor amount of oxygen, in
particular in the form of air (for example 1 to 5%) in order that
an oxidation of the carbonized polymeric skeleton may be effected
and the subsequent activation may thereby be facilitated. In
general, the carbonization is carried out at temperatures of 100 to
950.degree. C., particularly 150 to 900.degree. C., preferably 300
to 850.degree. C. The total duration of the carbonization is
approximately 30 minutes to approximately 10 hours, particularly
approximately 1 hour to approximately 6 hours.
[0087] Following the carbonization, the carbonized intermediate
product is subjected to an activation resulting, at the end of
which, in the present invention's high-performance adsorbents based
on activated carbon in grain form, in particular spherical form.
The basic principle of the activation is to degrade a portion of
the carbon generated during the carbonization, selectively and
specifically under suitable conditions. This gives rise to numerous
pores, fissures and cracks, and the surface area per unit mass
increases appreciably. Activation thus involves a specific burn-out
of the carbon. Since carbon is degraded in the course of
activation, this operation goes hand in hand with a loss of
substance which--under optimal conditions--is equivalent to an
increase in the porosity and in the internal surface area and in
the pore volume. Activation is therefore carried out under
selective or to be more precise policed oxidizing conditions.
[0088] The special feature of how the high-performance adsorbents
of the present invention are produced, as well as the selection of
the starting material described above, resides in the specific
management of the activation process, in particular in the
twostageness of the activation process, wherein the carbonized
starting material is initially subjected, in a first activating
step, to an activation in an atmosphere comprising water vapor,
followed by a second activating step in an atmosphere comprising
CO.sub.2. As the studies carried out by the applicant have
determined it is surprisingly only the separate performance of
these activating steps in the aforementioned order that leads to
the desired products. Reversing the order of the activating steps,
or one conjointly conducted activating step in a water vapor/carbon
dioxide atmosphere leads in contrast to distinctly less
performance-capable products which do not have the desired
properties, particularly not the high total porosity coupled with
high meso-/macropore content and a relatively high absolute
micropore volume and also high mechanical stability. As the studies
by the applicant company have surprisingly shown when the process
is carried out according to the present invention water vapor
activation leads predominantly to the formation of the micropore
fraction, while carbon dioxide activation contributes predominantly
to formation of the meso- and macropores, and surprisingly the
formation of the meso- and macropore volume is not at the expense
of the micropore volume, or vice versa. What is therefore novel and
surprising is in total that this produces a very large total pore
volume coupled with very high stability and abrasion resistance and
also very high meso- and macropore fraction coupled with
simultaneously high micropore fraction (i.e., the formation of
meso- and macropores to the enormous extent in the products of the
present invention does not lead to a reduction in the micropore
fraction, as customary in the prior art). On the contrary, a high
micropore fraction is achieved while the meso-/macropore volume
fraction is also high at the same time.
[0089] The general procedure is for the first activating step to be
carried out at temperatures of 700 to 1300.degree. C., particularly
800 to 1200.degree. C., preferably 850 to 950.degree. C., and/or
for a duration of 5 to 24 hours, preferably 5 to 15 hours,
particularly 6 to 12 hours. Usually, the duration of the first
activation stage can be controlled as a function of the attainment
of a predetermined iodine number; for example, the first activation
stage can be carried out to attainment of an iodine number of at
least 1000 mg/g, particularly at least 1250 mg/g. The atmosphere of
the first activation stage comprises water vapor, particularly a
mixture of water vapor/inert gas, preferably a mixture of water
vapor/nitrogen, or consists thereof. For the aforementioned
reasons, the presence of activating gases other than water vapor,
particularly the presence of carbon oxides (CO.sub.2 for example),
oxygen and/or ammonia, must be foreclosed in the context of the
first activation stage. Good results are obtained when the
throughput or to be more precise the amount used of water vapor is
25 to 350 l/h, particularly 50 to 300 l/h, reckoned as water (i.e.,
liquid water at 25.degree. C. and under atmospheric pressure).
Depending on the amount of starting material to be activated
(=carbonisate previously produced by carbonization), the amount
used or the mass-based throughput of water vapor should
advantageously be 0.01 to 50 l/(hkg), particularly 0.02 to 25
l/(hkg), preferably 0.02 to 5 l/(hkg), reckoned as water (i.e.,
liquid water at 25.degree. C. and under atmospheric pressure) and
based on starting material to be activated with water vapor.
[0090] The general procedure for the second activating step is for
the second activating step to be carried out at temperatures of 700
to 1300.degree. C., particularly 800 to 1200.degree. C., preferably
850 to 950.degree. C., and/or for a duration of 1 to 10 hours,
particularly 3 to 8 hours. The atmosphere of the second activation
stage comprises CO.sub.2, particularly pure CO.sub.2 or a mixture
of CO.sub.2/inert gas, particularly a mixture of CO.sub.2/nitrogen,
or consists thereof, and pure carbon dioxide is particularly
preferred. For the aforementioned reasons, the presence of
activating gases other than CO.sub.2, in particular the presence of
water vapor, must be foreclosed in the context of the second
activation stage. Good results are obtained when the throughput or
the amount used of CO.sub.2 is 10 to 250 m.sup.3/h, particularly 20
to 200 m.sup.3/h (based on pure CO.sub.2). Depending on the amount
of starting material to be activated, the amount used or the
mass-based throughput of CO.sub.2 should advantageously be 0.001 to
100 m.sup.3/(hkg), particularly 0.01 to 50 m.sup.3/(hkg),
preferably 0.05 to 10 m.sup.3/(hkg), reckoned as pure gaseous
CO.sub.2 under activating conditions, particularly at the
respective pressure and the respective temperature, which are
selected for the activation, and based on starting material to be
activated with CO.sub.2.
[0091] The process is typically carried out such that the first and
second activation stages merge into each other (for example by
changing the activating atmosphere within the same apparatus).
[0092] What is surprising is in particular that, first, the way the
activation is carried out according to the present invention
provides exact control of the porosity with regard to the micro-,
meso- and macropore fractions and, secondly, that an extremely high
abrasion resistance and mechanical compressive strength result
despite the high porosity coupled with simultaneously high meso-
and macroporosity and also good microporosity. It was unforeseeable
that this approach selectively generates high meso- and
macroporosity coupled with simultaneously sufficient
microporosity.
[0093] Porosity can be adjusted or controlled to specific values by
varying the previously specified activating conditions. The
high-performance adsorbents of the present invention can thus be
custom tailored so to speak. High-performance adsorbents based on
activated carbon which combine high meso- and macroporosity with
good microporosity and also high stability and abrasion resistance
are not known from the prior art. Another welcome aspect is the
excellent adsorption behavior to molecules of virtually any desired
molecular size due to the presence of all kinds of pores in
relatively large amounts or fractions. Similarly welcome is the
excellent impregnatability of the products of the present invention
with catalysts or to be more precise metals or metal salts.
[0094] The graphs in FIG. 1 and FIG. 2 show N.sub.2 adsorption
isotherms for two different high-performance adsorbents of the
present invention, which were produced under different activating
conditions. The physical-chemical properties of the two
high-performance adsorbents of the present invention are also
summarized in Table 1 below. For comparison, a commercially
available activated carbon from Kureha is also listed therein with
the physical-chemical properties in question.
[0095] The data reported in Table 1 show the superiority of the
high-performance adsorbents of the present invention over a prior
art activated carbon: The combination of high total porosity with
high meso-/macropore volume fraction at high BET surface area and
also good absolute microporosity, high mechanical durability and
excellent adsorption properties is in this combination--as well as
the other physical-chemical parameters--only to be found in the
high-performance adsorbents of the present invention. The present
invention thus makes it possible to produce high-performance
adsorbents based on activated carbon in grain form, in particular
spherical form, which are superior to commercially available
products.
[0096] The inventive high-performance adsorbents "activated carbon
I" and "activated carbon II" recited in Table 1 are each produced
as follows: commercially available dried ion exchanger precursors
based on divinylbenzene-crosslinked polystyrene copolymers having a
divinylbenzene content of about 4% are sulfonated in a conventional
manner at temperatures of 100.degree. C. to 150.degree. C. using a
sulfuric acid/oleum mixture. This is followed in a conventional
manner by carbonization at temperatures up to 850.degree. C. for
four hours under nitrogen and subsequently the induction of
activation. Inventive activated carbon I was produced by performing
the first activation stage ("water vapor activation") for a
duration of about 8.5 hours at about 900.degree. C. with a water
vapor throughput of about 100 m.sup.3/h and the second activation
stage ("carbon dioxide activation") for a duration of about 8.0
hours at about 900.degree. C. with a carbon dioxide throughput of
about 35 m.sup.3/h; in contrast, inventive activated carbon II was
produced by performing the first activation stage ("water vapor
activation") for a duration of about 10.5 hours at about
925.degree. C. with a water vapor throughput of about 125 m.sup.3/h
and the second activation stage ("carbon dioxide activation") for a
duration of about 8 hours at about 925.degree. C. with a carbon
dioxide throughput of about 40 m.sup.3/h. After cooling down to
room temperature, the inventive products recited in Table 1 are
obtained.
TABLE-US-00001 TABLE 1 Comparison of physical-chemical parameters
of two inventive high-performance adsorbents based on spherical
activated carbon on the one hand and commercially available
activated carbon in spherical form from Kureha on the other
Inventive activated carbon I Inventive activated carbon II After
second After second After first activating activating After first
activating activating Commercially step (intermediate step (end
step (intermediate step (end available activated product) product)
product) product) carbon from Kureha Total pore volume (Gurvich)
(p/p.sub.0 = 0.6267 1.7890 0.7510 3.1590 0.5891 0.995)
[cm.sup.3/g]** Measure of central tendency pore diameter 18.08
42.05 19.05 62.75 17.89 [.ANG.] BET (Multipoint, MP) (p/p.sub.0 =
0.05-0.1) 1.387 1.702 1.577 2.013 1.317 (ASTM D6556-04)
[m.sup.2/g]** Carbon black method micropore volume 0.5524 0.5082
0.6211 0.5311 0.5240 [cm.sup.3/g]* Micropore fraction of total pore
volume 88.1 28.4 82.7 16.8 88.95 [%]* Adsorbed N.sub.2 volume
(p/p.sub.0 = 0.25) weight 368 463 422 563 349 based [cm.sup.3/g]**
Adsorbed N.sub.2 volume (p/p.sub.0 = 0.25) volume 233 138 227 101
206 based [cm.sup.3/cm.sup.3]** Adsorbed N.sub.2 volume (p/p.sub.0
= 0.995) 404 1154 484 2037 380 weight based [cm.sup.3/g]** Adsorbed
N.sub.2 volume (p/p.sub.0 = 0.995) volume 256 344 261 365 224 based
[cm.sup.3/cm.sup.3]** Carbon black micropore surface area 1342 1261
1499 1288 1271 [cm.sup.2/g]* Carbon black meso-plus macropore
volume 0.0743 1.2808 0.1299 2.6279 0.07 (= so-called external pore
volume) [cm.sup.3/g]*** Fraction of meso- and macropores in total
11.9 71.6 17.3 83.2 11.1 pore volume (= fraction of so-called
external pore volume in relation to total pore volume) [%]***
Carbon black surface area of meso- and 45 441 78 725 46 macropores
(= so-called external pore surface area) [cm.sup.2/g]*** Pore
surface area fraction of meso- and 3.2 25.9 4.9 36.0 3.5 macropores
in relation to BET surface area (= proportion of so-called external
pore surface area in relation to BET surface area) (MP) [%]***
Adsorbate N.sub.2 N.sub.2 N.sub.2 N.sub.2 N.sub.2 Butane adsorption
(ASTM D5742-95/00) 30.9 42.4 35.4 52.9 29.2 [%] Iodine number 1413
1588 1490 1750 1343 (ASTM D4607-94/99) [mg/g] Methylene blue number
(CEFIC) [ml] 19.9 34.8 27.2 38.9 <10 Molasses number (PACS)
[dimension- 96 1020 142 1174 <100 less] Abrasion resistance
(internal method) [%] 98.22 90.38 99.2 90.04 <90 *micropores:
pores having pore diameters .ltoreq.20 .ANG. **p/p.sub.0 = partial
pressure or partial pressure range ***meso- and macropores:
collective term for all pores with pore diameters >20 .ANG.
[0097] The present invention further provides--in accordance with a
third aspect of the present invention--the present invention use of
the high-performance adsorbents according to the present
invention.
[0098] The high-performance adsorbents of the present invention are
particularly useful for the adsorption of toxins, noxiants and
odors, for example from gas or to be more precise air streams. The
high-performance adsorbents of the present invention are further
useful for purifying and cleaning gases, particularly for purifying
air, and also liquids, such as, in particular, water (for example
drinking water treatment). More particularly, the high-performance
adsorbents of the present invention are useful for impregnation
(for example with catalysts or to be more precise metals or metal
salts).
[0099] The high-performance adsorbents of the present invention are
also useful for example for or in the food industry, particularly
for preparing and/or decolorizing food products.
[0100] The high-performance adsorbents of the present invention can
further be used in adsorptive filtering materials or to be more
precise in the manufacture of adsorptive filtering materials. Such
adsorptive filtering materials are useful in the manufacture of
protective apparel in particular, for example protective suits,
protective gloves, protective underwear, protective footwear, etc.,
in particular for the civilian or military sector (for example NBC
protection).
[0101] The high-performance adsorbents of the present invention are
further useful in the sector of medicine or pharmacy, particularly
as a medicament or medicament constituent.
[0102] The high-performance adsorbents of the present invention can
finally also be used as sorptive storage media for gases and
liquids.
[0103] Owing to their high total porosity coupled with high meso-
and macroporosity and similarly a certain degree of microporosity
and also excellent mechanical stability with excellent adsorptive
properties, the high-performance adsorbents of the present
invention are distinctly superior to comparable adsorbents of the
prior art.
[0104] Further embodiments, modifications and variations of the
present invention are readily discernible and realizable for those
skilled in the art on reading the description without their having
to leave the realm of the present invention. While the invention
has been illustrated and described in detail in the drawings and
foregoing description, the same is to be considered as illustrative
and not restrictive in character, it being understood that only the
preferred embodiment has been shown and described and that all
changes and modification that come within the spirit of the
invention are desired to be protected.
* * * * *