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Carbon adsorbents from petroleum residues
(‘urhon Printed
Vol. 2’). No. 7. pp. XhS-869. m Great Brltam
1441
CopyrIght
0UllX-h223!Y I $3.(X + .I)(1 ” 1991 Pcrgamon Press plc
CARBON ADSORBENTS FROM PETROLEUM RESIDUES Yu. V. POKONOVA Lensoviet
Institute
of Technology,
Moscovsky
Avenue
26. 198013 Leningrad.
(Received 4 December 1989; accepted in revised form 2 October
U.S.S.R.
1990)
Abstract-Data are presented on utilizing petroleum asphaltite as an addition to the charge and a binder when obtaining adsorbents as well as the products of their thermal and chemical modification. High effective microporous adsorbents have been produced whose sorption indices are higher than industrial ones. They may be used as carriers of hemosorbents, clarifying carbons. and for selective isolation of the noble metals from multicomponent solutions. The new adsorbents may be useful for air purification in rooms, for keeping the required temperature in food storage, as well as for cleaning nuclear power plant gas effluents. Key Words-Carbon binder.
adsorbents,
sorption
capacity.
(asphaltene concentrate) obtained during petrol deasphaltizing of tar represents raw material for petroleum chemistry and is the basis for producing radioresistant ion exchangers, the agents of nonsulphur vulcanization, fillers, macromolecular initiators, and so on[l]. This article describes experiments on the use of asphaltite as a binder and charge component. The success of the undertaking is promoted by a high yield of the coke residue containing a substantial number of heteroatoms and free lasting radicals. asphaltite
2. EXPERIMENTAL
RESULTS AND DISCUSSION
2.1 Utilization of petroleum
residues as
charge additions
Without being modified, petroleum residues were used both for charge addition in the amount of 8 to 15% and as a binder instead of conventional wood resin. In this way, 8 to 15% of asphaltite added to bitumen coal dust significantly affects the properties of adsorbents (Table 1). By utilizing asphaltites, carbon adsorbents can be produced which, in parameters of microporous structure (W,,, by 0.35 to 0.37 cm’ig), substantially exceed industrial active carbons produced from bitumen coal dust and wood resin by similar methods (Table 2). The combination of the developed microporous structure with sufficient strength and developed meso- and macroporosity characteristic for coals produced when utilizing petroleum asphaltites allows them to be recommended instead of the industrial adsorbents for adsorption of dissolved substances with small molecules, concentrations being relatively small (iodine extraction from oil well waters, water cleaning to remove disagreeable smell. etc.) as well as for removing organic solvent vapours CAR
for aurum,
asphaltite.
air purification,
from air, petrol extraction from natural gases, and for other purposes. The samples (3-5%) with a low activation level possess molecular-sieve properties. Medium activation level samples (20-30%) have a narrow distribution of micropores (B, x 10h = 0.4) and possess increased sorption capacity with respect to poorly sorbed gases exceeding AG-2 coal by 2 to 2.5 times and adsorbent from sapropel coal (SKT) by 1.2 to 1.3 times. High activation level samples possess sorption capacity 1.5 times greater with respect to the noble metals when extracting them from solutions. By selecting the group compound of petroleum asphaltite, a porous structure can be formed. The utilization of petroleum residues as an additive does not solve the problem of the new raw material. To introduce petroleum residues into the charge, they have to be transformed into a nonfusible state. This can be achieved in two ways: either thermochemically by low-temperature carbonization or chemically by copolycondensation[l,2].
1. INTRODUCTION Petroleum
selectivity
2.2 Utilization of petroleum low-temperature
residues after
carbonization
From a semicoke of petroleum residues, in particular from asphaltites, crushed macroporous lowquality adsorbents can be produced[5] fit for preliminary cleaning of high-concentration solutions. By combining semicoke with wood resin, top-quality granulated carbon adsorbents can be produced following known industrial procedures. Their characteristics exceed those of industrial activated carbon (Table 3). An interesting and important mechanism was found: In the process of forming the porous structure of adsorbents the group compound of asphaltites subjected to low-temperature carbonization and not their nature is of crucial importance. Thus, semicoke-based adsorbents from asphaltites
29:7-C 865
866
Y. v.
POKONOVA
Table 1. Technical data of carbon adsorbents from asphaltite added to bitumen coal dust Charge content (mass %)
Adsorbent
1 2 3 4 5 6 A(-$2
Asphaltite
8 8 8 8 13 14 _
Yield (%)
Wood resin
Coal dust
30 30 29 29 28 28 _
:: 63 63 59 59 _
Under carbonization
Under activation
72 72 69 69 72 72 _
54.5 27.2 68.0 30.6 46.3 34.9 -
differing by asphaltene content extracted from tars of various petroleums, but close in group content, possess similar parameters of porous structure. This arose from the fact that native asphaltenes from petroleums of various fields have a relatively formed structure[l], forming semicokes rather close in composition and structure. With considerable resin-oil content in asphaltites the formation of semicoke structure will be different. In the process of heat treatment of oils and resins the developing asphaltenes are more aromatized than the starting ones, and as a result the coke produced has a higher C/H ratio, which means a regulated and condensed structure[ 1,2]. In the course of thermal destruction of less condensed semicoke (C/H = 2.2) the split of peripheral structural blocks occurs, which is beneficial for developing a mostly mesoporous structure. In the course of the thermal destruction of semicoke with a more condensed (C/H = 2.4) and regulated structure formed to a large extent by oils and resins, the structural blocks split probably to a considerably lesser degree, the formation of gaseous productshydrogen and C,-C., alkanes being more. Therefore, the microporous structure develops more. Consequently, the amount of meso- and micropores as well as the distribution of micropores can be purposefully controlled by selecting raw materials for semicoking[ 11. The semicoke asphaltite samples with minimum asphaltene content possess the biggest vol-
Table 2. Characteristics
Total
39.2 19.6 47.0 21.1 33.3 25.0
Bulk density
Content (%)
Strength (mass %)
(kg/m3)
0
80 65 88 70 86 84 70
480 390 507 390 466 430 550
15.02 16.42 12.95 15.91 11.48 12.52 1.30
of copolycondensation
The high reactivity of resinous-asphaltene compounds[ 1,2] offers a means of producing hard crosslinked products in a short period of time without increasing temperature (i.e., to change over to the nonfusible state by a simple non-power-intensive method). For this purpose resinous-asphaltene matter is dissolved in acidated furfural. The minor amount of catalyst remaining in copolycondensate
of carbon adsorbents
from asphaltite added to
B, . lo6
Benzene
Toluene
Sorption activity by iodine in powder-like form (%)
1.30 0.99 0.95 1.21 0.84 1.12 0.74 0.67
159 181 162 215 140 153 135
154 180 160 207 138 161 124 -
91 107 87 112 88 92 87
Static activity (g/L)
Adsorbent
Micro
Meso
Macro
1 2 3 4 5 6 AR-3 AG-2
0.25 0.29 0.23 0.30 0.24 0.28 0.29 0.29
0.04 0.08 0.07 0.10 0.05 0.05 0.06 0.05
0.31 0.33 0.23 0.32 0.32 0.32 0.27 0.24
0.33 0.25 0.28 0.27 0.33 0.42 0.19 0.20
11.0 15.6 9.8 15.0 11.6 14.0 13.4
2.3 Changing petroleum residues by means
Structural constants WI, (cm’/g)
1.0 0.7 0.9 0.65 1.0 0.88 1.40
ume of micropores (V,,,ic, to 0.21 cm3/cm3), whereas the samples of semicoke asphaltite with the maximum asphaltene content possess the biggest volume of mesopores (Vm, to 0.22 cm3/cm3). The developed mesoporous structure of a sample with 60.5% activation level offers a means of utilizing it as hemosorbent and immunosorbent (Table 4). Such an adsorbent almost twice exceeds BAU carbon in its sorption properties and is not worse than SKT adsorbent. It can be successfully used in medical practice for removing such dangerous toxines as bilirubin from blood. In this case, the increased mechanical strength of the sample (to 78%) is very important as it ensures less attrition of adsorbent in the course of operation. UAT-I-60.5 adsorbent holds three times more y-globulin on its surface than BAU and 10 times more than SKT in alcoholic solutions, 10 and 1.5times more in alcoholic-rivanol solutions, respectively.
of porous structure and sorption properties bitumen coal dust
Volume of pores (cmj/cm’)
N + S Ash
Carbon adsorbents from petroleum residues Table 3. Properties of high activation level carbon adsorbents from asphaltite semicokes Adsorbent from semicoke
Indices Activation level. % C/H ratio Heteroatom content, % Ash content, % Density, g/cm’ Strength, % Volume of pores, cm’icm’ Micro Meso Macro Specific surface of mesopores, m/g Structural constant W,,,. cm’ig B, x 1Oh Sorption capacity, gidm Benzene Toluene Iodine, % Methylene blue, % Separation criteria CH,-Xe CO,-Xe t*For
industrial
70.0 7.92 12.9
5.32 5.4
8.5 0.41 78
13.4 70
0.21 0.20 0.32 167
0.29 0.06 0.27 48
0.32 1.75
0.19 0.74
213 198 86 70 1.43 0.63
adsorbent
Industrial adsorbent AR-3
The adsorbents which have the most narrow distribution of micropores by the size of pores (B,lOh = 0.4), the activation level being 20 to 30%, feature increased sorption capacity for poorly sorbed gases. In this they exceed AG-2 carbon by 2.5 times and SKT by 1.3 to 1.4 times (Table 5). Copolycondensates of petroleum residues of shale phenols and furfural have a considerable sorption capacity and selectivity in gold and silver extraction as compared to industrial adsorbents[4]. With the increase of activation level from 6 to 32%, sorption capacity and selectivity increase, reaching a maximum when activation level is 32%. With all activation levels, milled adsorbents exceed KAD-iodine carbon; with 15% activation level the milled copolycondensate is compared with AM-2B anionite; and with 20% activation level it exceeds SKT (Table 6). Selectivity with respect to gold with activation level of 20 to 24% is approximately equal to selectivity of SKT and KAD-iodine carbons. Compared to AM-2B anionite the milled adsorbent is more selective starting from 10% activation level.
135 124 75 60
2.4 Molding process for granular adsorbents
1.62(1.12)* 0.83(1.28)*t
AG-2, in parentheses
867
for
BAU. does not require rinsing of the product. In this reaction acid tars can be also utilized[3]. To produce granulated adsorbents as a charge base, milled furanoformolites can be used.
For a low activation level of adsorbents, CO2 volumes retained exceed those with CH, by 10 to 50 times and with Xe by 9 times, despite the fact that the last possesses 1.4 times greater polarizability. Consequently, these samples incorporate clearly marked molecular-sieving properties.
For conducting the molding process when obtaining granulated adsorbents, asphaltite was used as a binder in the solution (1: 2 ratio) of petroleum fractions containing 60% of mono- and poly-arenes. Thirty-nine percent of this solution was added to coal dust stirred at 65 to 70°C and forced through 2 to 2.5 mm dies. The granules obtained were carbonized at 450 to 500°C. The yield of carbonizates amounted to 74% and had a high mechanical strength of 93%. the total volume of pores being 0.25 cm3/g. Carbonizates were activated in a rotary drum-type electric furnace in CO, at 800 to 850°C. The adsorbents obtained have a C/H ratio from 5.51 to 8.03 and rise of oxygen content to 13%. The data shown in Table 7 indicate that the samples with a low activation level have molecular-sieve properties for materials with
Table 4. Sorption capacity of carbon adsorbents from asfaltite semicokes used as hemosorbents Adsorbent
Indices Capacity by caffeine- benzoat, mgicmj Equilibrium concentration of caffeinebenzoat in solution, mg/cm3 Selectivity factor in distribution of caffeine-benzoat between adsorbent and solution Adsorption of y-globulin (alcoholic solution), mgig Desorption of -y-globulin, % Adsorption of y-globulin (alcoholicrevanol solution), mgig Desorption of y-globulin, % Adsorption of polyglobulin, mg/g Desorption of polyglobulin, %
Produced from semicoke, with 60.5% of activation level
SKT
BAU
130
129
89
.05
0.5
0.5
260
258
166
135
75
158
46 I18
91 58
84 108
35 64 14
99 43 25
93 60 67
868
y. v.
POKONOVA
Table 5. Characteristics of carbon adsorbents produced from furanoformohtes
Activation level (mass %)
Bulk density (g/cm)
16.7 0.487 23.2 0.479 28.2 0.472 36.3 0.442 47.5 0.390 55.2 0.369 AR-3 0.550 Industrial adsorbents
Volume of pores (cm3/cm3) Strength (mass %) Micro Meso 90 90 90 88 83 80 70
0.13 0.14 0.15 0.16 0.17 0.18 0.29
0.04 0.04 0.06 0.07 0.08 0.09 0.06
Structural constants
Characteristic Static activity energy of (g/L) adsorption, E B, x lo6 (kJ/mol) Benzene Toluene
Macro
W,,
0.28 0.28 0.29 0.29 0.30 0.32 0.27
0.16 0.17 0.19 0.21 0.27 0.30 0.19
0.45 0.43 0.39 0.46 0.62 0.64 0.74
28.68 29.18 30.48 28.05 24.16 23.57 22.44
98 103 109 129 139 160 135
Sorption activity by iodine (%; in milled state)
89 98 102 117 135 141 125
75 77 80 82 86 90 75
Note: For AR-3 for the second microporous structure W,, = 0.18; B2 x 106 = 3.42; Eo2 = 7.75. dimensions less than 0.7 mm. With the activation level increase, a microporous structure (W,, = 0.35 cm3/g) develops and adsorption properties are higher than those of the industrial adsorbents (see Table 8), which is determined not only by a porous structure but also by surface polarity. They may be recommended for trapping vapours of organic solvents from air, for extracting petrol from natural gases, and adsorption of dissolved matter from water solutions.
3. CONCLUSION
A special feature of petroleum residual raw material is its substantial reactivity determined by a highly condensed structure replaced by a great number of alkyl radicals-the structure which is capable of light self-catalyzed oxidation with the formation of surface oxygen functional groups[ 1,2]. Considerable content of heteroorganic compounds prevents the structure from complete regulation, facilitates oxidation processes, the availability of transitional valency metals (particularly nickel and vanadium), and is beneficial for self-catalysis. The components of light oxidation susceptibility, with sulphur content, are capable of forming strong and weak acid groups in the oxidation process. Stable free radicals, as well as those formed during thermal dealkylation
and dearylation, comprise an additional source of functional groups formation. Adsorbents will acquire the properties of strong amphoteric ionexchangers in combination with thermally stable cyclic compounds with nitrogen content. The developing and already available starting functional groups with oxygen content and basic nitrogen content by nondivided electron pairs participate in common system P of electronic clouds of graphite-like aromatic plates, thus increasing the adsorption field of micropores. Therefore, for the adsorbents produced from petroleum residues, surface polarity plays an important role and should be taken into consideration when predicting sorption ability of adsorbents. We have proposed functional empirical dependence which takes into account structural constants (volume of micropores Wo,, width of their distribution, B,) as well as surface polarity characterized by heteroatom content. For small polarizable gases (for example, nitrogen) the dependence is as follows: V, = A . W% . By (0
+ S + ~~o+.T+N.
For all remaining variants the dependence is simpler: V, = A . Bys (0
+
s+
~V)W+S+N
Table 6. Sorption kinetics of cyanic complexes of metals by carbon adsorbents from copolycondensates shale phenols, and industrial adsorbentst
of asphaltite,
Activation level of adsorbent (%)
Au
Ag
cu
Zn
Ni
co
Sum
Selectivity factor Au (%)
6 15 20 24 32 SKT KAD-iodine AM-2B
2.3 3.8 5.7 6.8 7.8 5.5 3.6 3.7
0.6 0.7 1.2 1.4 2.0 1.4 0.8 0.3
46.6 40.4 60.0 54.3 67.2 47.5 22.5 34.2
14.0 16.6 23.0 20.5 26.0 29.5 27.5 53.2
0.3 0.4 0.6 0.4 1.5 3.0 1.5 0.6
0.1 0.1 0.5 0.5 0.4 0.3 0.3 0.4
63.9 61.9 91.0 83.9 104.9 76.2 56.2 92.4
3.6 6.1 6.3 8.1 7.4 7.2 6.4 4.0
Sorption capacity (mg/g)
tAnion exchange resin AM-2B; period of contact 120 hours.
Carbon adsorbents from petroleum residues Table 7. Characteristics
of porous structures of carbon adsorbents obtained from coal dust using asphaltitc as a binder True
Density
ActnatIon lcvcl
)
(%
Bulk
869
(g/cm’)
density
Water
hydroxide
BCIlZClK
volumes
of pores
(cm’lcm’)
CarbOll
Methyl
Carbon
Methyl
Seeming
Total
(g/cm’)
tetrochloridc
hydroxide
Water
Bcnzcnc
tctrochloridc
0.0
(1 74
LIX
1.76
1 .x3
I.63
1.56
0.33
0.36
0.27
0.24
1.4
0.73
1.17
,180
1.X6
I .70
I.59
0.35
0.37
0.31
0.26
3.2
0.72
I.15
1 .X6
1.88
I .7Y
1.62
0.3x
0.3’)
0.35
0.20
22.5
0.63
I .Ol
I .Y6
I.‘)7
I.‘)6
1.Y5
0.48
0.49
0.4x
0.38
53.4
O.Sl
0.x2
I.99
2.00
l.YY
I.99
0.5’)
0.59
0.5’)
0.5Y
Table 8. Characteristics of sorption properties of carbon adsorbents obtained from coal dust using asphaltite as a binder Volume
of pores
(cm’icm’)
Structural
constants
Sorption
activity
(g/L)
Clarifying
ability
(9;)
Bulk Activation lcvcl
(76)
density
Strength
(g/cm’)
(S)
Micro
Mew
w,,, cm’ig
Macro
Mcthylcnc B,
10”
Bcnzol
Tolucne
Iodine
Molasses
hluc
7.4
0.720
93
0.10
0.02
0.23
0.03
0.59
71
20
34
22.5
0.632
02
0.20
0.02
0.26
0.24
0.51
I35
77
82
YO
7
53.4
o.sox
XX
0.28
0.03
0.28
0.35
0.77
IYW
1.53
YX
75
75
?Thc
indlcea
of industrial
adsorbent
AR-A
arc in compliance
with
the order
in the tahlc:
156,
143, 88. Y5. 62
allows prediction of sorption properties mination of their parameters.
where
and deter-
v,< = volume of the gas to be adsorbed 0, s, N = oxygen, sulphur, nitrogen content,
o/c REFERENCES
ciw, cifi = power indices, determining
structure I. Yu. V. Pokonova. Chemistry of Petroleum High-Molecular Compounds (in Russian). Leningrad State Univer-
effect %+s+\. = power, In article
determining
[5] the values
heteroatom
of constant
factor
effect. A
and
indices of a power are given: ow
on
%..iiN.
Stable dependencies of holding capacity in gases upon structure and polarity of adsorbents’ surfaces
sity Publishers (1980). 2. Yu. V. Pokonova. A. A. Gaile, V. G. Spirkin ef al., Chemistry of Petroleum (in Russian), Khimiya, Leningrad (1984). 3. Yu. V. Pokonova, New Ion Exchangers und Ad.~orhents from Petroleum Raw Material (in Russian), Institute of Technology, Leningrad (1980). 4. Yu. V. Pokonova and A. I. Grabovsky Khimiya Twerdogo Topliva (in Russian) (6), 77 (1986). 5 Yu. V. Pokonova, E. V. Shepelevskaya and M. S. Olei_ nik, Zhurnal Prikladnoi Khimii (in Russian) 55(2), 276 (1982).
Vol. 2’). No. 7. pp. XhS-869. m Great Brltam
1441
CopyrIght
0UllX-h223!Y I $3.(X + .I)(1 ” 1991 Pcrgamon Press plc
CARBON ADSORBENTS FROM PETROLEUM RESIDUES Yu. V. POKONOVA Lensoviet
Institute
of Technology,
Moscovsky
Avenue
26. 198013 Leningrad.
(Received 4 December 1989; accepted in revised form 2 October
U.S.S.R.
1990)
Abstract-Data are presented on utilizing petroleum asphaltite as an addition to the charge and a binder when obtaining adsorbents as well as the products of their thermal and chemical modification. High effective microporous adsorbents have been produced whose sorption indices are higher than industrial ones. They may be used as carriers of hemosorbents, clarifying carbons. and for selective isolation of the noble metals from multicomponent solutions. The new adsorbents may be useful for air purification in rooms, for keeping the required temperature in food storage, as well as for cleaning nuclear power plant gas effluents. Key Words-Carbon binder.
adsorbents,
sorption
capacity.
(asphaltene concentrate) obtained during petrol deasphaltizing of tar represents raw material for petroleum chemistry and is the basis for producing radioresistant ion exchangers, the agents of nonsulphur vulcanization, fillers, macromolecular initiators, and so on[l]. This article describes experiments on the use of asphaltite as a binder and charge component. The success of the undertaking is promoted by a high yield of the coke residue containing a substantial number of heteroatoms and free lasting radicals. asphaltite
2. EXPERIMENTAL
RESULTS AND DISCUSSION
2.1 Utilization of petroleum
residues as
charge additions
Without being modified, petroleum residues were used both for charge addition in the amount of 8 to 15% and as a binder instead of conventional wood resin. In this way, 8 to 15% of asphaltite added to bitumen coal dust significantly affects the properties of adsorbents (Table 1). By utilizing asphaltites, carbon adsorbents can be produced which, in parameters of microporous structure (W,,, by 0.35 to 0.37 cm’ig), substantially exceed industrial active carbons produced from bitumen coal dust and wood resin by similar methods (Table 2). The combination of the developed microporous structure with sufficient strength and developed meso- and macroporosity characteristic for coals produced when utilizing petroleum asphaltites allows them to be recommended instead of the industrial adsorbents for adsorption of dissolved substances with small molecules, concentrations being relatively small (iodine extraction from oil well waters, water cleaning to remove disagreeable smell. etc.) as well as for removing organic solvent vapours CAR
for aurum,
asphaltite.
air purification,
from air, petrol extraction from natural gases, and for other purposes. The samples (3-5%) with a low activation level possess molecular-sieve properties. Medium activation level samples (20-30%) have a narrow distribution of micropores (B, x 10h = 0.4) and possess increased sorption capacity with respect to poorly sorbed gases exceeding AG-2 coal by 2 to 2.5 times and adsorbent from sapropel coal (SKT) by 1.2 to 1.3 times. High activation level samples possess sorption capacity 1.5 times greater with respect to the noble metals when extracting them from solutions. By selecting the group compound of petroleum asphaltite, a porous structure can be formed. The utilization of petroleum residues as an additive does not solve the problem of the new raw material. To introduce petroleum residues into the charge, they have to be transformed into a nonfusible state. This can be achieved in two ways: either thermochemically by low-temperature carbonization or chemically by copolycondensation[l,2].
1. INTRODUCTION Petroleum
selectivity
2.2 Utilization of petroleum low-temperature
residues after
carbonization
From a semicoke of petroleum residues, in particular from asphaltites, crushed macroporous lowquality adsorbents can be produced[5] fit for preliminary cleaning of high-concentration solutions. By combining semicoke with wood resin, top-quality granulated carbon adsorbents can be produced following known industrial procedures. Their characteristics exceed those of industrial activated carbon (Table 3). An interesting and important mechanism was found: In the process of forming the porous structure of adsorbents the group compound of asphaltites subjected to low-temperature carbonization and not their nature is of crucial importance. Thus, semicoke-based adsorbents from asphaltites
29:7-C 865
866
Y. v.
POKONOVA
Table 1. Technical data of carbon adsorbents from asphaltite added to bitumen coal dust Charge content (mass %)
Adsorbent
1 2 3 4 5 6 A(-$2
Asphaltite
8 8 8 8 13 14 _
Yield (%)
Wood resin
Coal dust
30 30 29 29 28 28 _
:: 63 63 59 59 _
Under carbonization
Under activation
72 72 69 69 72 72 _
54.5 27.2 68.0 30.6 46.3 34.9 -
differing by asphaltene content extracted from tars of various petroleums, but close in group content, possess similar parameters of porous structure. This arose from the fact that native asphaltenes from petroleums of various fields have a relatively formed structure[l], forming semicokes rather close in composition and structure. With considerable resin-oil content in asphaltites the formation of semicoke structure will be different. In the process of heat treatment of oils and resins the developing asphaltenes are more aromatized than the starting ones, and as a result the coke produced has a higher C/H ratio, which means a regulated and condensed structure[ 1,2]. In the course of thermal destruction of less condensed semicoke (C/H = 2.2) the split of peripheral structural blocks occurs, which is beneficial for developing a mostly mesoporous structure. In the course of the thermal destruction of semicoke with a more condensed (C/H = 2.4) and regulated structure formed to a large extent by oils and resins, the structural blocks split probably to a considerably lesser degree, the formation of gaseous productshydrogen and C,-C., alkanes being more. Therefore, the microporous structure develops more. Consequently, the amount of meso- and micropores as well as the distribution of micropores can be purposefully controlled by selecting raw materials for semicoking[ 11. The semicoke asphaltite samples with minimum asphaltene content possess the biggest vol-
Table 2. Characteristics
Total
39.2 19.6 47.0 21.1 33.3 25.0
Bulk density
Content (%)
Strength (mass %)
(kg/m3)
0
80 65 88 70 86 84 70
480 390 507 390 466 430 550
15.02 16.42 12.95 15.91 11.48 12.52 1.30
of copolycondensation
The high reactivity of resinous-asphaltene compounds[ 1,2] offers a means of producing hard crosslinked products in a short period of time without increasing temperature (i.e., to change over to the nonfusible state by a simple non-power-intensive method). For this purpose resinous-asphaltene matter is dissolved in acidated furfural. The minor amount of catalyst remaining in copolycondensate
of carbon adsorbents
from asphaltite added to
B, . lo6
Benzene
Toluene
Sorption activity by iodine in powder-like form (%)
1.30 0.99 0.95 1.21 0.84 1.12 0.74 0.67
159 181 162 215 140 153 135
154 180 160 207 138 161 124 -
91 107 87 112 88 92 87
Static activity (g/L)
Adsorbent
Micro
Meso
Macro
1 2 3 4 5 6 AR-3 AG-2
0.25 0.29 0.23 0.30 0.24 0.28 0.29 0.29
0.04 0.08 0.07 0.10 0.05 0.05 0.06 0.05
0.31 0.33 0.23 0.32 0.32 0.32 0.27 0.24
0.33 0.25 0.28 0.27 0.33 0.42 0.19 0.20
11.0 15.6 9.8 15.0 11.6 14.0 13.4
2.3 Changing petroleum residues by means
Structural constants WI, (cm’/g)
1.0 0.7 0.9 0.65 1.0 0.88 1.40
ume of micropores (V,,,ic, to 0.21 cm3/cm3), whereas the samples of semicoke asphaltite with the maximum asphaltene content possess the biggest volume of mesopores (Vm, to 0.22 cm3/cm3). The developed mesoporous structure of a sample with 60.5% activation level offers a means of utilizing it as hemosorbent and immunosorbent (Table 4). Such an adsorbent almost twice exceeds BAU carbon in its sorption properties and is not worse than SKT adsorbent. It can be successfully used in medical practice for removing such dangerous toxines as bilirubin from blood. In this case, the increased mechanical strength of the sample (to 78%) is very important as it ensures less attrition of adsorbent in the course of operation. UAT-I-60.5 adsorbent holds three times more y-globulin on its surface than BAU and 10 times more than SKT in alcoholic solutions, 10 and 1.5times more in alcoholic-rivanol solutions, respectively.
of porous structure and sorption properties bitumen coal dust
Volume of pores (cmj/cm’)
N + S Ash
Carbon adsorbents from petroleum residues Table 3. Properties of high activation level carbon adsorbents from asphaltite semicokes Adsorbent from semicoke
Indices Activation level. % C/H ratio Heteroatom content, % Ash content, % Density, g/cm’ Strength, % Volume of pores, cm’icm’ Micro Meso Macro Specific surface of mesopores, m/g Structural constant W,,,. cm’ig B, x 1Oh Sorption capacity, gidm Benzene Toluene Iodine, % Methylene blue, % Separation criteria CH,-Xe CO,-Xe t*For
industrial
70.0 7.92 12.9
5.32 5.4
8.5 0.41 78
13.4 70
0.21 0.20 0.32 167
0.29 0.06 0.27 48
0.32 1.75
0.19 0.74
213 198 86 70 1.43 0.63
adsorbent
Industrial adsorbent AR-3
The adsorbents which have the most narrow distribution of micropores by the size of pores (B,lOh = 0.4), the activation level being 20 to 30%, feature increased sorption capacity for poorly sorbed gases. In this they exceed AG-2 carbon by 2.5 times and SKT by 1.3 to 1.4 times (Table 5). Copolycondensates of petroleum residues of shale phenols and furfural have a considerable sorption capacity and selectivity in gold and silver extraction as compared to industrial adsorbents[4]. With the increase of activation level from 6 to 32%, sorption capacity and selectivity increase, reaching a maximum when activation level is 32%. With all activation levels, milled adsorbents exceed KAD-iodine carbon; with 15% activation level the milled copolycondensate is compared with AM-2B anionite; and with 20% activation level it exceeds SKT (Table 6). Selectivity with respect to gold with activation level of 20 to 24% is approximately equal to selectivity of SKT and KAD-iodine carbons. Compared to AM-2B anionite the milled adsorbent is more selective starting from 10% activation level.
135 124 75 60
2.4 Molding process for granular adsorbents
1.62(1.12)* 0.83(1.28)*t
AG-2, in parentheses
867
for
BAU. does not require rinsing of the product. In this reaction acid tars can be also utilized[3]. To produce granulated adsorbents as a charge base, milled furanoformolites can be used.
For a low activation level of adsorbents, CO2 volumes retained exceed those with CH, by 10 to 50 times and with Xe by 9 times, despite the fact that the last possesses 1.4 times greater polarizability. Consequently, these samples incorporate clearly marked molecular-sieving properties.
For conducting the molding process when obtaining granulated adsorbents, asphaltite was used as a binder in the solution (1: 2 ratio) of petroleum fractions containing 60% of mono- and poly-arenes. Thirty-nine percent of this solution was added to coal dust stirred at 65 to 70°C and forced through 2 to 2.5 mm dies. The granules obtained were carbonized at 450 to 500°C. The yield of carbonizates amounted to 74% and had a high mechanical strength of 93%. the total volume of pores being 0.25 cm3/g. Carbonizates were activated in a rotary drum-type electric furnace in CO, at 800 to 850°C. The adsorbents obtained have a C/H ratio from 5.51 to 8.03 and rise of oxygen content to 13%. The data shown in Table 7 indicate that the samples with a low activation level have molecular-sieve properties for materials with
Table 4. Sorption capacity of carbon adsorbents from asfaltite semicokes used as hemosorbents Adsorbent
Indices Capacity by caffeine- benzoat, mgicmj Equilibrium concentration of caffeinebenzoat in solution, mg/cm3 Selectivity factor in distribution of caffeine-benzoat between adsorbent and solution Adsorption of y-globulin (alcoholic solution), mgig Desorption of -y-globulin, % Adsorption of y-globulin (alcoholicrevanol solution), mgig Desorption of y-globulin, % Adsorption of polyglobulin, mg/g Desorption of polyglobulin, %
Produced from semicoke, with 60.5% of activation level
SKT
BAU
130
129
89
.05
0.5
0.5
260
258
166
135
75
158
46 I18
91 58
84 108
35 64 14
99 43 25
93 60 67
868
y. v.
POKONOVA
Table 5. Characteristics of carbon adsorbents produced from furanoformohtes
Activation level (mass %)
Bulk density (g/cm)
16.7 0.487 23.2 0.479 28.2 0.472 36.3 0.442 47.5 0.390 55.2 0.369 AR-3 0.550 Industrial adsorbents
Volume of pores (cm3/cm3) Strength (mass %) Micro Meso 90 90 90 88 83 80 70
0.13 0.14 0.15 0.16 0.17 0.18 0.29
0.04 0.04 0.06 0.07 0.08 0.09 0.06
Structural constants
Characteristic Static activity energy of (g/L) adsorption, E B, x lo6 (kJ/mol) Benzene Toluene
Macro
W,,
0.28 0.28 0.29 0.29 0.30 0.32 0.27
0.16 0.17 0.19 0.21 0.27 0.30 0.19
0.45 0.43 0.39 0.46 0.62 0.64 0.74
28.68 29.18 30.48 28.05 24.16 23.57 22.44
98 103 109 129 139 160 135
Sorption activity by iodine (%; in milled state)
89 98 102 117 135 141 125
75 77 80 82 86 90 75
Note: For AR-3 for the second microporous structure W,, = 0.18; B2 x 106 = 3.42; Eo2 = 7.75. dimensions less than 0.7 mm. With the activation level increase, a microporous structure (W,, = 0.35 cm3/g) develops and adsorption properties are higher than those of the industrial adsorbents (see Table 8), which is determined not only by a porous structure but also by surface polarity. They may be recommended for trapping vapours of organic solvents from air, for extracting petrol from natural gases, and adsorption of dissolved matter from water solutions.
3. CONCLUSION
A special feature of petroleum residual raw material is its substantial reactivity determined by a highly condensed structure replaced by a great number of alkyl radicals-the structure which is capable of light self-catalyzed oxidation with the formation of surface oxygen functional groups[ 1,2]. Considerable content of heteroorganic compounds prevents the structure from complete regulation, facilitates oxidation processes, the availability of transitional valency metals (particularly nickel and vanadium), and is beneficial for self-catalysis. The components of light oxidation susceptibility, with sulphur content, are capable of forming strong and weak acid groups in the oxidation process. Stable free radicals, as well as those formed during thermal dealkylation
and dearylation, comprise an additional source of functional groups formation. Adsorbents will acquire the properties of strong amphoteric ionexchangers in combination with thermally stable cyclic compounds with nitrogen content. The developing and already available starting functional groups with oxygen content and basic nitrogen content by nondivided electron pairs participate in common system P of electronic clouds of graphite-like aromatic plates, thus increasing the adsorption field of micropores. Therefore, for the adsorbents produced from petroleum residues, surface polarity plays an important role and should be taken into consideration when predicting sorption ability of adsorbents. We have proposed functional empirical dependence which takes into account structural constants (volume of micropores Wo,, width of their distribution, B,) as well as surface polarity characterized by heteroatom content. For small polarizable gases (for example, nitrogen) the dependence is as follows: V, = A . W% . By (0
+ S + ~~o+.T+N.
For all remaining variants the dependence is simpler: V, = A . Bys (0
+
s+
~V)W+S+N
Table 6. Sorption kinetics of cyanic complexes of metals by carbon adsorbents from copolycondensates shale phenols, and industrial adsorbentst
of asphaltite,
Activation level of adsorbent (%)
Au
Ag
cu
Zn
Ni
co
Sum
Selectivity factor Au (%)
6 15 20 24 32 SKT KAD-iodine AM-2B
2.3 3.8 5.7 6.8 7.8 5.5 3.6 3.7
0.6 0.7 1.2 1.4 2.0 1.4 0.8 0.3
46.6 40.4 60.0 54.3 67.2 47.5 22.5 34.2
14.0 16.6 23.0 20.5 26.0 29.5 27.5 53.2
0.3 0.4 0.6 0.4 1.5 3.0 1.5 0.6
0.1 0.1 0.5 0.5 0.4 0.3 0.3 0.4
63.9 61.9 91.0 83.9 104.9 76.2 56.2 92.4
3.6 6.1 6.3 8.1 7.4 7.2 6.4 4.0
Sorption capacity (mg/g)
tAnion exchange resin AM-2B; period of contact 120 hours.
Carbon adsorbents from petroleum residues Table 7. Characteristics
of porous structures of carbon adsorbents obtained from coal dust using asphaltitc as a binder True
Density
ActnatIon lcvcl
)
(%
Bulk
869
(g/cm’)
density
Water
hydroxide
BCIlZClK
volumes
of pores
(cm’lcm’)
CarbOll
Methyl
Carbon
Methyl
Seeming
Total
(g/cm’)
tetrochloridc
hydroxide
Water
Bcnzcnc
tctrochloridc
0.0
(1 74
LIX
1.76
1 .x3
I.63
1.56
0.33
0.36
0.27
0.24
1.4
0.73
1.17
,180
1.X6
I .70
I.59
0.35
0.37
0.31
0.26
3.2
0.72
I.15
1 .X6
1.88
I .7Y
1.62
0.3x
0.3’)
0.35
0.20
22.5
0.63
I .Ol
I .Y6
I.‘)7
I.‘)6
1.Y5
0.48
0.49
0.4x
0.38
53.4
O.Sl
0.x2
I.99
2.00
l.YY
I.99
0.5’)
0.59
0.5’)
0.5Y
Table 8. Characteristics of sorption properties of carbon adsorbents obtained from coal dust using asphaltite as a binder Volume
of pores
(cm’icm’)
Structural
constants
Sorption
activity
(g/L)
Clarifying
ability
(9;)
Bulk Activation lcvcl
(76)
density
Strength
(g/cm’)
(S)
Micro
Mew
w,,, cm’ig
Macro
Mcthylcnc B,
10”
Bcnzol
Tolucne
Iodine
Molasses
hluc
7.4
0.720
93
0.10
0.02
0.23
0.03
0.59
71
20
34
22.5
0.632
02
0.20
0.02
0.26
0.24
0.51
I35
77
82
YO
7
53.4
o.sox
XX
0.28
0.03
0.28
0.35
0.77
IYW
1.53
YX
75
75
?Thc
indlcea
of industrial
adsorbent
AR-A
arc in compliance
with
the order
in the tahlc:
156,
143, 88. Y5. 62
allows prediction of sorption properties mination of their parameters.
where
and deter-
v,< = volume of the gas to be adsorbed 0, s, N = oxygen, sulphur, nitrogen content,
o/c REFERENCES
ciw, cifi = power indices, determining
structure I. Yu. V. Pokonova. Chemistry of Petroleum High-Molecular Compounds (in Russian). Leningrad State Univer-
effect %+s+\. = power, In article
determining
[5] the values
heteroatom
of constant
factor
effect. A
and
indices of a power are given: ow
on
%..iiN.
Stable dependencies of holding capacity in gases upon structure and polarity of adsorbents’ surfaces
sity Publishers (1980). 2. Yu. V. Pokonova. A. A. Gaile, V. G. Spirkin ef al., Chemistry of Petroleum (in Russian), Khimiya, Leningrad (1984). 3. Yu. V. Pokonova, New Ion Exchangers und Ad.~orhents from Petroleum Raw Material (in Russian), Institute of Technology, Leningrad (1980). 4. Yu. V. Pokonova and A. I. Grabovsky Khimiya Twerdogo Topliva (in Russian) (6), 77 (1986). 5 Yu. V. Pokonova, E. V. Shepelevskaya and M. S. Olei_ nik, Zhurnal Prikladnoi Khimii (in Russian) 55(2), 276 (1982).