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Патент USA US2118918

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Patented May 31, 1938.
'
2,118,918
UNITED‘ STATES PATENT QFFICE‘
PURIFICATION OF PHTHALIC ANIIYDBIDE
Harold B. Foster, Williamsville, and Elton B.
Punnett, Buffalo, N. Y., assignors to National
Aniline & Chemical Company, Inc., New York,
N. Y., a corporation of New York
>
No Drawing. Application February 9, 1935,
Serial No. 5,842
17 Claims. (C1. 260-—123)
5 partial or selective oxidation by means of oxygen
or oxygen-containing gases in the presence of a
vantageous as purifying agents are carbon and
those metals and metalloids having the proper
ties enumerated above and standing below hy
drogen in the electromotive series, and specifical
ly copper, arsenic, antimony and bismuth.
In the practice of the present invention,
catalyzer and at an elevated temperature, it is
phthalic anhydride contaminated with sulfuric
_ well known that the phthalic anhydride recovered '
anhydride impurities is heated at a temperature
This invention relates to an improvement in
the puri?cation of phthalic anhydride.
In the production of phthalic anhydride by
subjecting naphthalene in the-vapor phase to
from the mixed reaction ,products is contami
10 nated with impurities. The removal of such im
above the melting point of the phthalic anhydride
in the presence of an element of the type referred 10
to, and preferably carbon or ‘copper, whereby said _
impurities are decomposed to form gaseous prod
purities may be accomplished by subjecting the
impure phthalic anhydride‘to treatment with an
agent which is capable of forming decomposition, ucts (such as, for-example, sulfur dioxide, oxides
of carbon, steam, etc.) and/or inert relatively
oxidation or condensation products with the im
15 purities, and subliming or distilling. Sulfuric non-volatile products. While the invention is not 15
anhydride substances, as for example, sulfuric limited to any theoretical explanation, it appears
acid and oleum, are especially effective agents
for this purpose. As a result" of the treatment
with such agents, very small amounts of sulfuric
that the treatment effects a reduction of the
anhydride substances may be carried over with
0d of procedure a mixture of impure phthalic 20
the phthalic anhydride vapors into the sublimed
or distilled phthalic anhydride and be present as
impurities therein. While the presence of such
small amounts of such sulfuric anhydride im
purities in distilled or sublimed phthalic anhy
dride-ordinarily is not harmful and may be
bene?cial for certain industrial uses, the presence '
sulfuric anhydride impurities. In carrying out
the process in accordance with a preferred meth
anhydride and purifying agent is boiled prefer
ably at a temperature within the range of about
250° C. to about 290° C. and at a corresponding
pressure. The gaseous decomposition products
are separated-from the vapors of the phthalic
anhydride by physical means, for example, by
condensing ‘the vapors of phthalic anhydride in
a suitably cooled re?ux condenser which returns
of even such small amounts of such acidic im
the condensed phthalic anhydride to the reaction
purities is objectionable in connection with cer
vessel while allowing the gases produced by the 30
30 tain other industrial uses, as for example, the
decomposition of the sulfuric anhydride impur
manufacture of certain resins.
It is accordingly the principal object of the ities to escape therefrom through a suitable vent.
In order to insure complete removal of the sul
present invention to provide a method for re
moving such sulfuric anhydride impurities from furic anhydride impurities, it is preferred to boil
and reflux the phthalic anhydride for a period
phthalic anhydride containing them.
It has now been found that phthalic anhydride of time after no further gaseous decomposition
products are in evidence in the vapors, as deter
may be freed from said sulfuric anhydride im
purities by treating the phthalic anhydride, in the mined by analysis of the gases issuing from the
liquid state, and at a suitable temperature, with vent. Finally the puri?ed phthalic anhydride is
substances, preferably in a ?nely divided state, vaporized, e. g. distilled at atmospheric pressure
or sub-atmospheric pressure, the latter prefer
which are capable of effecting substantially com
plete decomposition of the sulfuric anhydride ably being employed, and the puri?ed phthalic
impurities to form decomposition products (gas
eous and/or non-volatile) that are easily sepa
rable from phthalic anhydride. Phthalic an
hydride may then be recovered in a puri?ed form,
for example, by distillation or sublimation. The
substances or purifying agents especially em
ployed in accordance with the present invention
5-1‘) comprise the elements which react with sulfuric
acid with formation of sulfur dioxide. Prefer
ably they are relatively non-volatile (with respect
to the phthalic anhydride) and undergo no ap
preciable reaction with the phthalic anhydride
at the temperatures employed.‘ Particularly ad
anhydride collected.
In carrying out the procedure of the inven
tion, the phthalic anhydride may be reduced to
the molten state priorto the addition of the
purifying agent, or the purifying agent may be
added to the phthalic anhydride and the mix
ture then melted. It is desirable, however, that
the purifying agent be in a ?nely divided condi
tion in order to insure its quick and uniform dis
tribution or suspension throughout the molten
phthalic anhydride. The amount of purifying
agent which may be employed may vary consider
ably, since any excess above that required to re
2
8,118,918
act with the sulfuric anhydride impurities does
2. A success for the puri?cation of phthalic
not volatilize or react with the phthalic an
hydride under the conditions of treatment and,
therefore, remains behind as an inert) residue
anhydride obtained by subjecting impure phthalic
when the puri?ed phthalic anhydride is sepa
rated from the decomposition products by vapor
ization, e. g. by distillation. It is preferred, how
ever, to limit the maximum amount of purify
ing agent to about 2 per cent of the weight of
10 the phthalic anhydride to be treated, since such
a quantity has been found to be adequate, in
' most instances, to remove all the impurities ef
fectively without undue waste.
The following example, in which the parts are
15 by weight, is given to illustrate the invention:
Example-100 parts of phthalic anhydride
which has been heated with oleum and distilled,
and which contains a small amount of sulfuric
anhydride impurities, are added to a still which is
20 ?tted with a re?ux condenser and means for
heating and agitating the phthalic anhydride and
which is adapted for conducting all or any of
these operations under either atmospheric or
other pressures. One part of ?nely divided, cal
cined wood-charcoal is added to the charge and
' the resulting mixture is heated under atmospheric
pressure with constant stirring until it boils
gently. The temperature of the re?ux condenser
is controlled so that vapors of phthalic anhydride
are condensed and returned to the still while the
gaseous decomposition products (e. g., sulfur di
oxide, etc.) formed by interaction of the char
coal, with the sulfuric anhydride impurities are
not condensed but are removed through a vent
situated at the top of the re?ux column. Gas
samples are taken from the vent and analyzed
for said gaseous decomposition products. ‘When
the analyses indicate completion of the reaction,
1. e., when no more gaseous decomposition prod
40 ucts are evolved, ther mass is further boiled and '
re?uxed for about 1 hour and then distilled in
vacuo in the usual manner. The puri?ed and dis
tilled phthalic anhydride resulting from this
process is quite suitable for making resins and for
other industrial uses.
anhydride to a purifying treatment with a sul
furic anhydride purifying agent and containing
sulfuric acid impurities which comprises bringing
said phthalic anhydride into contact with a rela
tively non-volatile element that reactswith sul
furic acid with formation of sulfur dioxide, re
acting said element with said impurities, and sep
arating the puri?ed phthalic anhydride from the
resulting decomposition products.
10
3. A process for the puri?cation of phthalic an
hydride obtained by subjecting impure phthalic
anhydride to a purifying treatment with a sul
furic anhydride purifying agent and containing
sulfuric anhydride impurities which comprises
15
heating said phthalic anhydride with an element
that reacts with sulfuric acid with formation of
sulfur dioxide and without affecting said phthalic
anhydride at a reaction temperature, continuing 20
the heating until the sulfuric anhydride impuri
ties are decomposed, and recovering puri?ed
phthalic anhydride.
4. A process for the puri?cation of phthalic an
hydride obtained by subjecting impure phthalic 25
anhydride to a purifying treatment with a sul
furic anhydride purifying agent and containing
sulfuric" anhydride impurities which comprises
boiling said phthalic anhydride at a temperature
of about 250° C. to about 290° C. in intimate con 30
tact with an element that reacts with sulfuric
acid with formation of sulfur dioxide and with
out affecting said phthalic anhydride for a period
of time at least su?icientfto decompose said sul
furic anhydride 'impurities,_1'and recovering puri
35
?ed phthalic anhydride; ,, j
5. A process forfthe-pm'i?cation of phthalic an
hydride obtained by subjecting impure phthalic
anhydride to a purifying treatment with a sul
furic anhydride purifying agent and containing 40
sulfuric anhydride impurities which comprises
intimately contacting said phthalic anhydride at
a temperature above its melting point with a
metal standing between hydrogen and mercury in
the electromotiv series for a period of time at
least su?icienttc ecompose said sulfuric anhy
It will be understood that the invention is not
limited to the example as given, but that changes
may be made without departing from the scope
of the invention. For example, instead of using
dride impurities.
carbon or copper, as indicated above,.?nely di-'
vided antimony, arsenic or bismuth may be used.
anhydride to a purifying treatment with a sul
pressures are preferred. Also, although the use
of temperatures between about 250° C. to about
290' C. are preferred, other temperatures may be
more than about 2 per cent by weight of a metal 55
standing between hydrogen and mercury in the
"
8. A process for the puri?cation of phthalic an
hydride obtained by subjecting impure phthalic
furic anhydride purifying Meat and containing
Further, sub-atmospheric or super-atmospheric sulfuric anhydride impurities which comprises
pressures may be used in place of atmospheric intimately contacting said phthalic anhydride at
pressure; but atmospheric and sub-atmospheric a temperature above its melting point with not
used if desired.
-
electromotive series for a period of time at least
sufficient to decompose said sulfuric anhydride
Furthermore, in place of carbon in the form
of .calcined wood-charcoal, it is also possible to
use other forms of carbon, such as for example,
sugar charcoal, gas black, blood charcoal, animal
impurities, and recovering puri?ed phthalic an
hydride.
7. A process for the puri?cation of phthalic an
hydride obtained by subjecting impure phthalic
charcoal, lamp black, powdered coal, coke, graph
anhydride to a purifying treatment with a sul- . .
ite or the like.
We claim:
furic ‘anhydride purifying agent and containing
sulfuric anhydride impurities which comprises re 05
1. A process for the puri?cation of phthalic
anhydride obtained by subjecting impure phthalic
?uxing said phthalic anhydride in intimate con
tact with a metal standing between hydrogen and
mercury in the electromotive seriesfor a period of
time at least sumcient to decompose said sul
furic anhydride impurities, and separating and
anhydride to a purifying treatment with a sul
phuric anhydride purifying agent and ‘containing
70 sulfuric anhydride impurities which comprises
subjecting said phthalic anhydride to'the action. recovering puri?ed phthalic anhydride. ,
under reaction conditions of ‘a substance that re- .
acts with sulfuric acid with formation of sulfur
8'. A process for the puri?cation of phthalic an
hydrideobtained by subjecting impure phthalic _ .
dioxide for a period of time at least sumcient to
anhydride‘ to a purifying treatment with a sul-i
decompose said sulfuric anhydride impurities.
furic anhydride purifying agent and containing
' - 15 -
3
' 9,118,918
timately contacting said phthalic anhydride at a
sulfuric anhydride impurities which comprises in
timately contacting said phthalic anhydride, at
temperature above its melting point with ?nely
a temperature above its melting point, with ?nely
divided carbon for aperiod of time at least suffi
cient to decompose said sulfuric anhydride im
purities, and vrecovering> puri?ed phthalic an
divided copper for a period of time at least suffi
cient to decompose said sulfuric anhydride im
sulfuric anhydride impurities which comprises in
hydride.
purities.
14. A process for the puri?cation of phthalic
9. A process for the puri?cation of phthalic an
hydride obtained by subjecting impure phthalic
anhydride to a purifying treatment with a sul
furic anhydride purifying agent and containing
sulfuric anhydride impurities which comprises
re?uxing said phthalic anhydride in intimate
contact with ?nely divided, calcined wood-char
15 coal for a period of time at least sufficient to de
compose said sulfuric anhydride impurities.
10. A process for the puri?cation of phthalic
anhydride obtained by subjecting impure phthalic
anhydride, containing sulfuric anhydride impuri
ties, which comprises re?uxing said phthalic an
hydride in contact with about‘ 1 per cent by weight 10
of ?nely divided, calcined wood-charcoal, where
by said sulfuric anhydride impurities are decom
posed, continuing said re?uxing for about one
hour after gaseous decomposition products cease
to be evolved, and then recovering the puri?ed 15
phthalic anhydride.
15. A process for the puri?cation or phthalic
anhydride containing sulfuric acid as an impurity
anhydride to a purifying treatment with a sul
20 furic anhydride purifying agent and containing
which comprises re?uxing said phthalic anhy
re?uxing said phthalic anhydride in intimate con
tact with about 1 per cent by weight of ?nely
divided, calcined wood-charcoal for a period of
25 time at least sufficient to decompose said sulfuric
anhydride impurities, and recovering puri?ed
per cent by weight of ?nely divided calcined wood
charcoal, whereby said sulfuric acid impurity is
decomposed, continuing said re?uxing for about
one hour after gaseous decomposition products
cease to be evolved, and then recovering the puriq
phthalic anhydride.
?ed phthalic anhydride by distillation.
sulfuric anhydride impurities which comprises
I
11. A process for the puri?cation of phthalic
16. A process for the puri?cation of phthalic
anhydride obtained by subjecting impure phthalic
anhydride obtained by subjecting impure phthalic
30 anhydride to a purifying treatment with a sul~
as
furic anhydride purifying agent and containing
sulfuric anhydride impurities which comprises
reacting said phthalic anhydride at a temperature
the molten state, with about 1 per cent by weight
of ?nely divided, calcined wood-charcoal for a
period of time at least su?icient to decompose
said sulfuric anhydride impurities, and recover
above its melting point with not more than about
2% by weight of a substance adapted to decom
' 12. A process for the puri?cation of phthalic
pose the sulfuric anhydride impurities with for
mation of decomposition products easily sep
arable from phthalic anhydride under conditions
adapted to cause decomposition of said sulfuric
anhydride to a purifying treatment with a sul
anhydride impurities until the sulfuric anhydride
impurities are decomposed, and recovering puri-,
furic anhydride purifying agent and containing
?ed phthalic anhydride._
anhydride obtained by subjecting impure phthalic
sulfuric anhydride impurities which comprises in- ,
45
anhydride to a purifying treatment with a sul
furic anhydride purifying agent and containing
sulfuric anhydride impurities which comprises in
timately contacting said phthalic anhydride, in
ing puri?ed phthalic anhydride.
40
dride at a temperature within the range of about
250° C. to about 290° C. in contact with about 1
17. A process‘ for the puri?cation of phthalic
timately contacting said phthalic anhydride, at
anhydride containing sulfuric anhydride impuri-'
a temperature above its melting point, with a
metal standing below hydrogen in the electronic-v
tive series for a period of time at least sumcient
hydride in' contact with not more than about
ties which comprises re?uxing said phthalic an
2% by weight-of ?nely divided carbon until said
to decompose said sulfuric anhydride impuritiea sulfuric anhydride impurities are decomposed,
13. A process for the puri?cation of phthalic . and recovering puri?ed phthalic anhydride.
anhydride obtained by subjecting impure phthalic
50 anhydride to a purifying treatment within sul
. furic anhydride purifying ‘Bent and containing
HAROLD B. FOSTER.
ELTON-B. PUNNE'I'I‘.
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