Process for the separation of ortho chlorinated aromatic isomers by selective adsorption

A process is disclosed for separation of ortho chlorotoluene and ortho-dichlorobenzene from their meta and para isomers by use of a specific crystalline aluminophosphate adsorbent which selectively removes the above ortho aromatic isomers. The selectively adsorbed ortho aromatic isomers are removed from the adsorbent through a desorption step.

BACKGROUND OF THE INVENTION 
The field of art to which the claimed invention pertains is chlorinated 
aromatic hydrocarbon separation. More specifically, the claimed invention 
relates to the separation of ortho chlorotoluene and ortho-dichlorobenzene 
from their meta and para isomers by use of a specific crystalline 
aluminophosphate adsorbent which selectively removes the above ortho 
aromatic isomers. The selectively adsorbed ortho aromatic isomers are 
removed from the adsorbent through a desorption step. 
DESCRIPTION OF THE PRIOR ART 
It is known in the separation art that certain adsorbents generally 
comprising crystalline aluminosilicates can be utilized to separate 
certain hydrocarbons from mixtures thereof. In aromatic hydrocarbon 
separation and in particular the separation of C.sub.8 aromatic isomers, 
it is generally recognized that certain crystalline aluminosilicates 
containing selected cations at the zeolitic cationic sites enhances 
selectivity of the zeolite for a given C.sub.8 aromatic isomer. This 
manner of separation is particularly useful when the components to be 
separated have similar physical properties, such as freezing and boiling 
points. 
A number of processes describing the separation of para-xylene from a 
mixture of at least one other xylene isomer utilizing a crystalline 
aluminosilicate adsorbent are shown in U.S. Pat Nos. 3,558,730, 3,558,732, 
3,626,020, and 3,663,638. Other processes which describe the adsorption 
separation of ethylbenzene from a mixture of xylene isomers utilizing a 
crystalline aluminosilicate adsorbent are shown in U.S. Pat Nos. 
3,943,182, 3,997,619, 3,998,901, 4,021,499 and 4,482,776. U.S. Pat. No. 
4,376,226 describes a method of separating ortho-xylene from an aromatic 
hydrocarbon feed stream by use of a crystalline aluminosilicate adsorbent 
CSZ-1. U.S. Pat. No. 4,482,776 discloses a method for separating ortho 
aromatic isomers from a mixture by contacting the feed stream with a bed 
of the crystalline aluminophosphate adsorbent AlPO.sub.4 -5. While the 
separation of dihalobenzene mixtures by adsorption using Na-type zeolites, 
and Ag-K-Y and Ag-Na-Y zeolites, is known in the art, Japanese KOKAI No. 
58/150524 and Japanese KOKAI No. 58/131924, the separation of 
ortho-chlorotoluene or ortho-dichlorobenzene from a feed stream mixture 
containing meta and para isomers of these compounds using a crystalline 
aluminophosphate adsorbent AlPO.sub.4 -5 is not known in the art. 
Ortho-chlorotoluene is used commercially in manufacture of pesticides, 
dyestuffs, pharmaceuticals and as a solvent. Ortho-dichlorobenzene is used 
as a solvent in manufacture of toluene diisocyanates, as a cleaning 
compound and to make 3,4-dichloroaniline, an intermediate for dyes and 
agricultural chemicals. However, availability of these ortho aromatic 
isomers is restricted due to the inability to effectively separate these 
ortho aromatic isomers from their meta and para isomers. 
SUMMARY OF THE INVENTION 
The invention comprises an adsorptive separation process for the separation 
of ortho-chlorotoluene or ortho-dichlorobenzene from mixtures of meta and 
para isomers of these compounds by contacting the chlorinated aromatic 
hydrocarbon feed stream with a bed of the crystalline aluminophosphate 
adsorbent AlPO.sub.4 -5 molecular sieve. A raffinate stream is then 
withdrawn from the bed, this stream containing less of the selectively 
adsorbed ortho isomer. The adsorbed ortho isomer on the bed is then 
desorbed to effect displacement of the ortho isomer, followed by 
withdrawing from the adsorbent bed an extract stream containing the ortho 
aromatic isomer. The AlPO.sub.4 -5 adsorbent is cation exchanged to 
increase the ortho aromatic selectivity of the adsorbent. 
DETAILED DESCRIPTION OF THE INVENTION 
A chlorinated aromatic hydrocarbon feed stream which can be utilized in the 
process of this invention contains mixtures of ortho-, meta-, and 
para-chlorotoluene or ortho-, meta- and para-dichlorobenzene. 
The chlorinated aromatic hydrocarbon feed stream is then contacted with a 
bed of crystalline aluminophosphate adsorbents, entitled AlPO.sub.4 -5, 
having an essential crystalline framework structure whose chemical 
composition expressed in terms of molar ratios of oxides is Al.sub.2 
O.sub.3 :1.0.+-.0.2 P.sub.2 O.sub.5, the said framework structure being 
microporous in which the pores are uniform and in each species having 
nominal diameters within the range of from 3 to 10 Angstroms and an 
intracrystalline adsorption capacity for water at 4.6 torr and 24.degree. 
C. of at least 3.5 weight percent, the adsorption of water being 
completely reversible while retaining the same essential framework 
topology in both the hydrated and dehydrated state. By the term "essential 
framework topology" is meant the spatial arrangement of the primary Al-O 
and P-O bond linkages. No change in the framework topology indicates that 
there is no disruption of these primary bond linkages. 
The present aluminophosphates are prepared by the method described in U.S. 
Pat. No. 4,310,440, incorporated herein by reference. 
The AlPO.sub.4 -5 adsorbent can be combined with a binder, such as natural 
or synthetic clays (e.g. Koalin), inorganic oxides, and lubricants (e.g. 
graphite) and can be in any form acceptable to the separation process such 
as extrudates, spheres, granules or tablets. 
Certain characteristics of adsorbents are highly desirable, if not 
absolutely necessary, to the successful operation of a selective 
adsorption process. Among such characteristics are: adsorptive capacity 
for some weight of the ortho aromatic isomer per weight of adsorbent; and 
the selective adsorption of the ortho aromatic isomer with respect to a 
raffinate component and the desorbent material. 
The process for separating ortho-chlorotoluene toluene or 
ortho-dichlorobenzene from mixtures with their corresponding meta and para 
isomers comprises (a) contacting the mixture of isomers with crystalline 
aluminum phosphate molecular sieve adsorbent, (b) removing from said 
adsorbent a raffinate stream containing less of the ortho isomer than 
contained in the feed, (c) displacing the adsorbed mixture, rich in the 
ortho isomer, with a suitable desorbent, and (d) separating the ortho rich 
adsorbate from the desorbent, for example by distillation. The process can 
be carried either in a batch system or a continuous flow system at ambient 
temperature. 
Examples of the mixtures which can be separated are ortho-chlorotoluene 
from its meta and para isomers, and ortho-dichlorobenzene from its meta 
and para isomers. These are all close boiling mixtures which are costly to 
separate by fractionation. Crystallization can sometimes be used to 
separate the para isomer so the disclosed process provides a complementary 
process for obtaining the ortho isomer. Use of either process would 
provide an improved feedstock for the other. 
Choice of the desorbent is a critical part of the process. Generally a 
material which has an affinity for the adsorbent between that of the ortho 
isomer and that of the remaining isomers is preferred. A second 
requirement is that the desorbent distills at a sufficiently different 
temperature so as to provide easy separation of raffinate and eluent from 
the desorbent. It is sometimes desirable for the desorbent to be higher 
boiling than the raffinate and the product. For optimum performance 
desorbent materials should have a separation factor equal to about 1 or 
less than 1 with respect to all extract components so that all of the 
extract components can be extracted as a class and all raffinate 
components clearly rejected into the raffinate stream. Suitable desorbents 
are toluene, benzene, chlorotoluene, dichlorobenzene, ethyltoluene, and 
chlorobenzene. Preferred desorbents are toluene and chlorobenzene. Toluene 
is more preferred. 
Separation factors can be expressed in terms of the ratio of the two 
components of the adsorbed phase over the ratio of the same two components 
in this unadsorbed phase at equilibrium conditions. Separation factor 
.beta. can be expressed in the following equation: 
##EQU1## 
Where separation factor .beta. of two components approaches 1.0 there is no 
preferential adsorption of one component by the adsorbent with respect to 
the other; they are both adsorbed (or nonadsorbed) to about the same 
degree with respect to each other. As the separation factor becomes less 
than or greater than 1.0 there is preferential adsorption by the adsorbent 
for one component with respect to the other. When comparing the separation 
factor by the adsorbent of one component A over component B, a separation 
factor larger than 1.0 indicates preferential adsorption of component A 
within the adsorbent. A separation factor less than 1.0 would indicate 
that component B is preferentially adsorbed leaving an unadsorbed phase 
richer in component A and an adsorbed phase richer in component B. In the 
separation of ortho aromatic isomers, a separation factor of at least 1.5 
to 2.0 of the ortho aromatic isomer over at least one of the other 
components of the feed stream is preferable. 
It has been found that AlPO.sub.4 -5 molecular sieve selectively adsorbs 
ortho-substituted benzene isomers from mixtures with meta and para 
isomers. This separation cannot be based primarily on molecular size and 
shape because large separation factors are obtained between compounds of 
similar molecular dimension. 
Such selectivity is not common and is reported for only two other sieves, 
cesium- and/or thallium-modified aluminosilicate disclosed in U.S. Pat. 
No. 4,309,313, and disclosed for separation of ortho-xylene in U.S. Pat. 
No. 4,376,226, and a sieve disclosed by D. B. Broughton, Chem. Eng. Prog., 
October, 1977, p 49. 
Results from the measurement of separation factors for 25 compounds 
relative to ortho-xylene indicate that the basis for the selectivity is 
mostly electronic and based on charge distribution. Thus, as electron 
withdrawing groups such as --Cl and --F are added to the ring, or replace 
--CH.sub.3 groups, affinity for the AlPO.sub.4 -5 increases. With the 
exception of benzene.fwdarw.toluene.fwdarw.ortho-xylene, adding a 
--CH.sub.3 group decreases this affinity. Replacement of --CH.sub.3 by 
--C.sub.2 H.sub.5 also decreases this affinity, but for reasons which are 
not apparent. 
To determine other separation capabilities of the AlPO.sub.4 -5 sieve, a 
series of batch, vial tests, were run to determine relative separation 
factors between ortho-xylene and a series of alkyl- and halo-substituted 
and poly-substituted benzenes. 
Ortho-xylene was included as one of the components of the test mixtures so 
that separation factors relative to a common reference, i.e., 
ortho-xylene, could be calculated directly. 
As is the case with other sieves, steric requirements cannot be a critical 
factor affecting selectivity. The pore diameter in AlPO.sub.4 -5 is 8 
.ANG., (ACS Symposium, 218 (1983) p 102)). As shown in Table I below, the 
minimum molecular widths for most of the compounds tested are all less 
than 8 .ANG. and many show only very small differences in width despite 
large differences in relative separation factor. For example, ortho-xylene 
and meta-xylene show the same minimum molecular width and differ by a 
factor of 10 in relative separation factor. 
TABLE I 
______________________________________ 
Minimum Molecular Width of Substituted Benzenes 
and Separation Factors Relative to O--Xylene 
Separation Factor 
Minimum Relative to Ortho 
Compound Width, .ANG.(a) 
Xylene 
______________________________________ 
Benzene 6.8 0.35 
Toluene 6.8 0.550 
para-Xylene 6.8 0.113 
o-Difluorobenzene 
7.2 6.39 
ortho-Xylene 7.6 1.0 
meta-Xylene 7.6 0.069 
Hexafluorobenzene 
7.6 12.1 
o-Chlorotoluene 
7.6 1.633 
m-Chlorotoluene 
7.6 0.179 
1,2,4-Trimethylbenzene 
7.6 0.009 
Durene 7.6 0.26 
o-Bromotoluene 7.8 0.49 
p-Chlorotoluene 0.076 
o-Dichlorobenzene 1.948 
p-Dichlorobenzene 0.291 
m-Dichlorobenzene 0.258 
______________________________________ 
(a) Determined from covalent bond radii and Van der Waals radii of atoms, 
The Nature of the Chemical Bond, L. Pauling, Cornell University Press, 
Ithaca, N.Y., p. 160 (1972). 
Several trends are apparent in Table I. Starting with xylenes, toluene, or 
benzene and either adding chlorine or replacing a methyl group with 
chlorine, and in turn replacing these with fluorine or adding more 
fluorine successively increases the affinity of the adsorbate for the 
AlPO.sub.4 -5. Adding alkyl groups, with the exception of benzene to 
toluene, decreases affinity. These effects can be explained on the basis 
of either withdrawing or contributing electrons to the pi cloud of the 
ring. The differences between ortho, para, and meta isomers are large and 
consistent, but are not consistent with relative basicities. No 
explanation is offered for the large decrease in affinity resulting from 
replacing a methyl group with an ethyl group and the reverse effect in 
replacing an ethyl group with a propyl group. 
Separation factors are tabulated in Table II relative to ortho-xylene. The 
(.beta.) separation factor indicates the relative separation of the ortho 
isomer from the para isomer, i.e., the ortho isomer is adsorbed 
preferentially over the adsorption of the para isomer by the adsorbent 
AlPO.sub.4 -5 
TABLE II 
______________________________________ 
(.beta.) 
Isomers Ethyl- ortho/ 
Compound Ortho meta para benzene 
para 
______________________________________ 
C.sub.8 Aromatics 
1 .068 0.115 .09 8.7 
Chlorotoluene 
1.35 0.179 0.25 -- 5.4 
Dichlorobenzene 
1.75 0.258 0.86 -- 2.03 
Ethyltoluene 
0.06 .01 0.032 -- 1.87 
______________________________________ 
Generally a separation factor (.beta.) of about 2 is regarded as sufficient 
to provide adepuate separation for a process and this criterion is met in 
the above examples. The above runs indicate that chlorotoluene as well as 
dichlorobenzene can be used as a desorbent. Ethyltoluene may also be used, 
although ethyltoluene is not as efficient as chlorotoluene or 
dichlorobenzene. 
In the experimental procedures, a Hewlett-Packard 5880, Level 4 gas 
chromatograph fitted with capillary columns and an auto-sampler was 
employed for all sample analyses. 
The column used was a 60-meter OV-351 fused-silica, glass capillary column 
manufactured by J&W Scientific Corporation, 91 Blue Ravine Road, Folsom, 
Calif. The OV-351 column has several advantages over a Carbowax 20M glass 
capillary column, manufactured by Supelco, Inc. Bellefonte, Pa., which can 
be used. It is very flexible and easily installed, and column stability is 
a definite advantage. The OV-351 column, after a year's service, had no 
significant loss of resolution even though thousands of samples had passed 
through it. 
Cyclododecane was used as internal standard for all analyses. 
Previous work had indicated that adsorbed water may interfere with 
adsorption properties of sieves. Therefore, the AlPO.sub.4 -5 was dried at 
165.degree. C. then heated at 94.degree. C./hr. in a forced draft oven to 
538.degree. C. The temperature was held constant for 8 hours, then lowered 
to 165.degree. C. This calcination procedure was performed on all samples 
overnight prior to experimental use. Immediately prior to experimental 
use, the sample was cooled to room temperature in a N.sub.2 atmosphere dry 
box. Care was taken not to expose the adsorbent to water during all steps 
of experimentation. 
Two methods of testing AlPO.sub.4 -5 for separations were used; batch vial 
experiments to measure separation factors for all the compounds tested, 
and various flow systems to study kinetic effects. 
In a typical batch vial example, one gram of AlPO.sub.4 -5 and .about.3.5 
grams of feed of known composition were sealed in a 15 ml glass centrifuge 
tube fitted with a 12/18 ground glass joint and matching teflon stopper. 
Care was taken so that no sieve or feed was trapped in the joint allowing 
leakage and loss of accuracy. Also, all weighings of feed and adsorbent 
were on a four-place analytical balance to minimize error in this 
extremely sensitive experimental procedure. 
The slurry was allowed to come to equilibrium overnight (16 hours) in an 
oscillating shaker. Each tube was then centrifuged in a Clay-Adams 
four-place clinical centrifuge for approximately five minutes and the 
supernatant liquid removed and analyzed by gas chromatography. From the 
differences in composition of the supernatant liquid compared to the 
feeds, the capacity and selectivity of the adsorbent was calculated. 
The experimental flow system consisted of two Constametric L.C. pumps, 
manufactured by Laboratory Data Control, Riviera Beach, Fla., connected to 
an L.C. column packed with an adsorbent. One pump was used for feed and 
the other for the desorbent. The L.C. columns used were manufactured by 
Bethesda Research Labs, Gaithersburg, Md. Several sizes of columns, 
ranging in size from 30 cm.times.0.90 cm ID to 120 cm.times.0.90 cm ID 
were used. AlPO.sub.4 -5 was packed into columns after soaking for 
approximately 1 hour in toluene to force all gases out so the adsorbent 
bed contained no bubbles during runs. However, even with soaking, some 
bubbles were observed during runs, probably from dissolved gases in the 
liquids coming out of solution. The slurry was then poured into a 
Fischer-Porter bottle and pumped into the top of the column with a 
continuous liquid flow. A vibrator was used to settle the adsorbent bed 
while the slurry was being pumped in. This method of packing the adsorbent 
bed reduced channelling encountered when dry packing an adsorbent bed and 
resulted in a very consistent adsorbent bed. During a run, effluent 
samples were taken continuously and weighed and analyzed. 
In summary, the instant invention comprises an adsorptive separation 
process for separating an ortho aromatic compound selected from the group 
consisting of ortho-chlorotoluene and ortho-dichlorobenzene from a 
chlorinated aromatic hydrocarbon feed stream comprising a mixture of meta 
and para isomers of said ortho aromatic compound which comprises 
contacting said chlorinated aromatic hydrocarbon feed stream with a bed of 
a crystalline aluminophosphate adsorbent of AlPO.sub.4 -5; withdrawing 
from said bed of adsorbent a raffinate stream containing less of the 
selectively adsorbed ortho aromatic compound of the feed stream; desorbing 
the adsorbed ortho aromatic compound with a desorbent to effect 
displacement thereof; and withdrawing from the adsorbent bed an extract 
stream containing the ortho aromatic compound. In more detail, the said 
chlorinated aromatic hydrocarbon feed stream comprises the said ortho 
aromatic compound and a mixture of aromatic hydrocarbons, that is, the 
said feed stream can comprise the said ortho aromatic compound and a 
mixture of benzene and chlorinated aromatic hydrocarbons. Also, the said 
feed stream can comprise the said ortho aromatic compound and a mixture of 
toluene and chlorinated aromatic hydrocarbons. 
The said desorbent is selected from the group consisting of toluene, 
benzene, chlorotoluene, dichlorobenzene, ethyltoluene, and chlorobenzene. 
The said desorbent is probably tolune. 
The following examples are presented to facilitate the understanding of the 
present invention. It is to be understood that these examples are 
presented for the purpose of illustration only and are not intended to 
limit the scope of the invention. 
Although the invented process can be operated without prior purification of 
the feed stream, the invented process is preferably operated with prior 
purifiction of the feed stream to concentrate the desired products of the 
invented process. 
Examples I to IV are presented to exemplify the recovery of ortho-xylene 
from a C.sub.8 feed using toluene as a desorbent. Examples V and VI are 
presented to exemplify the recovery of ortho-chlorotoluene and 
ortho-dichlorobenzene from C.sub.8 feed streams, the data being relative 
to recovery of ortho-xylene using toluene as a desorbent.

EXAMPLE I 
A 30 cm.times.0.9 cm column was packed with 18.35 grams of AlPO.sub.4 -5 
(9044-96, 83% crystalline) in a toluene slurry. The AlPO.sub.4 -5 was &lt;75 
microns. A mixture containing 25% of each of ortho-, meta-, para-xylene 
and ethylbenzene was then pumped through the column at a rate of 0.625 
g/min. at room temperature. After 25 grams of effluent were removed, the 
C.sub.8 aromatic feed was replaced with toluene at a flow rate of 0.678 
g/min and operation continued until substantially all of the C.sub.8 
aromatics had eluted. Weight balances are summarized in Table III as Run 
8528-1. 
EXAMPLE II 
Using the same packed column as in the previous run, an equimolar mixture 
of ortho-, meta-, para-xylene and ethylbenzene was pumped into the column 
at room temperature but at a rate of 0.304 g/min. After 25.3 grams of 
effluent were obtained and the composition had returned to essentially 
that of the feed, the mixed C.sub.8 aromatics were replaced with toluene 
at a rate of 0.303 g/min. until a total of 64.7 grams of aromatics had 
passed through the column and substantially all of the C.sub.8 aromatics 
had eluted. Weight balances are summarized in Table III as Run 8528-4. 
EXAMPLE III 
A 120 cm.times.0.9 cm column was packed with 69.9 grams of AlPO.sub.4 -5 
(67% crystalline) slurried in toluene. An equimolar mixture of ortho-, 
meta-, para-xylene and ethylbenzene was then pumped through the column at 
a rate of 0.669 g/min. at room temperature. The inlet pressure to the 
column was 62 psig. After 91 grams of material had eluted, the mixed 
C.sub.8 aromatic feed was replaced by toluene at a rate of 0.715 g/min. 
After a total of 208 grams of effluent was obtained, and all of the mixed 
C.sub.8 aromatic had eluted, flows were stopped. Weight balances are 
summarized in Table III as Run 8528-23. 
EXAMPLE IV 
The packed column used in the previous runs was flushed with chlorobenzene 
to remove all of the toluene and to saturate the column with 
chlorobenzene. An equimolar mixture of ortho-, meta- and para-xylene and 
ethylbenzene aromatics was then pumped into the column at a rate of 0.727 
g/min. at room temperature. Inlet pressure was 62 psig. After 54.5 grams 
of effluent were collected, the feed was switched to chlorobenzene at a 
rate of 0.681 g/min. After a total of 164 grams of effluent were obtained, 
flows were stopped. Weight balances are summarized in Table III as Run 
8528-28. 
TABLE III 
______________________________________ 
Recovery of Ortho Xylene 
8528-1 8528-4 8528-23 8528-28 
______________________________________ 
Feed, g 
C.sub.8 Feed 
11.99 11.26 40.71 30.53 
O--Xylene Content 
3.00 2.82 10.18 5.11 
Chloro- 
Desorbent Toluene Toluene Toluene 
benzene 
______________________________________ 
Recovery, g 
Forecut 1.10 1.10 4.42 1.60 
Fraction A 0.39 0.92 2.33 2.33 
Fraction B 0.47 0.58 2.06 1.67 
Fraction C 0.72 0.52 0.51 0.55 
Fraction D 0.09 -- -- 
Total 2.68 3.21 9.32 6.15 
Loss, g 0.32 (1.29)a 0.86 (1.04)a 
______________________________________ 
Note: 
a = Gain 
The above data in Table III indicates that as mixed C.sub.8 aromatic is 
fed, the elutant, toluene or chlorobenzene, with which the column is 
saturated, is displaced. Mixed C.sub.8 aromatics then elute. Initially, 
they contain little or no ortho-xylene but composition changes to feed 
composition as the adsorbent becomes saturated with orthoxylene. This 
fraction is labelled Forecut. The next fraction is at feed compositon and 
represents unnecessary feed and operating time. It is being displaced from 
interstitial space in the bed by the elutant. The remaining fractions 
represent C.sub.8 aromatics that the elutant is displacing form the 
adsorbent. They become increasingly rich in ortho-xylene, the more 
strongly adsorbed component, but simultaneously the total C.sub.8 content 
diminishes rapidly. For continuous operation, feed of C.sub.8 aromatics 
would be resumed during this latter phase. The capacities of the sieves 
(for ortho-xylene) are calculated for each of these runs and are shown in 
Table IV below. 
TABLE IV 
______________________________________ 
Capacity of AlPO.sub.4 -5 for ortho-Xylene Flow Runs 
AlPO.sub.4 -5 
Capacity 
Run No. Crystallinity 
Wt. % 
______________________________________ 
8528-1 83% 9.4 
8528-4 83% 10.0 
8528-23 68% 7.3 
8528-28 68% 6.3 
______________________________________ 
The weight % capacity of AlPO.sub.4 -5 for adsorbate as a function of 
percent crystallinity is shown for the different groups of substrates in 
Table IV. In general, the capacity is linear with crystallinity and is 
about 10-11 wt % for the pure crystalline sieve. 
EXAMPLE V 
A series of batch vial experiments were performed to determine that the 
ortho-isomer of chlorotoluene is readily separated from its meta- and 
para-isomers using the AlPO.sub.4 -5 crystalline aluminum phosphate 
molecular sieve. 
In each batch vial experiment, one gram of AlPO.sub.4 -5 and .about.3.5 
grams of feed of known composition were sealed in a 15 ml glass centrifuge 
tube fitted with a 12/18 ground glass joint and matching teflon stopper. 
Care was taken in this procedure so that no sieve or feed was trapped in 
the joint allowing leakage and loss of accuracy. All weighings of feed and 
absorbent were finalized on a four-place analytical balance to minimize 
error. 
The slurry was allowed to come to equilibrium overnight (16 hours) in an 
oscillating shaker. Each tube was then centrifuged in a Clay-Adams 
four-place clinical centrifuge for approximately five minutes and the 
supernatant liquid removed and analyzed by gas chromatography. From the 
differences in composition of the supernatant liquid compared to the 
feeds, the capacity and selectivity of the absorbent was calculated. The 
results are in Table V. 
TABLE V 
______________________________________ 
O--Chlorotoluene and Its Isomers 
Separation Factors Relative to o-Xylene 
2-Chloro- 3-Chloro- 
4-Chloro- 
Sample No. 
Toluene toluene toluene 
toluene 
______________________________________ 
8528-40-1 
0.5843 1.5875 0.4619 -0.1424 
8528-40-2 
0.5922 1.5704 0.3163 -0.0050 
8528-40-4 
0.4987 1.6332 0.0396 0.2688 
8528-40-5 
0.3972 1.7506 -0.1538 
0.1296 
8528-40-6 
0.4475 1.6231 0.2302 0.1286 
Average 0.5040 1.6330 0.1788 0.0759 
______________________________________ 
The above average separation factor of 1.6330 for 2-chlorotoluene versus 
the average separation factors of 0.1788 and 0.0759 for 3-chlorotoluene 
and 4-chlorotoluene, respectively, indicates that the ortho-isomer of 
chlorotoluene is readily separated from its meta- and para-isomers using 
the AlPO.sub.4 -5 crystalline aluminum phosphate molecular sieve. 
EXAMPLE VI 
In the procedure of Example V, 1,2-dichlorobenzene was separated from its 
meta- and para-isomers using AlPO.sub.4 -5 crystalline aluminum phosphate 
molecular sieve. All conditions were duplicated. Results are in Table VI. 
TABLE VI 
______________________________________ 
Ortho-Dichlorobenzene and Its Isomers 
Separation Factors Relative to o-Xylene 
1,2- 1,3- 1,4- 
Dichloro- Dichloro- 
Dichloro- 
Sample No. 
Toluene benzene benzene benzene 
______________________________________ 
8528-40-7 
0.7490 1.8341 0.3297 0.3368 
8528-40-9 
0.5893 2.0138 0.2336 0.2748 
8528-40-10 
0.6184 1.8982 0.2537 0.2895 
5828-40-11 
0.5573 2.0439 0.2154 0.2613 
Average 0.6285 1.9475 0.2581 0.2906 
______________________________________ 
The above average separation factor of 1.9475 for 1,2-dichlorobenzene 
versus the average separation factors of 0.2581 and 0.2906 for 
1,3-dichlorobenzene and 1,4-dichlorobenzene, respectfully, indicates that 
the ortho-isomer of dichlorobenzene is readily separated from its meta- 
and para-isomrrs using the AlPO.sub.4 -5 crystalline aluminum phosphate 
molecular sieve.