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Патент USA US3047624

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United States Patent O?ice
1
3,047,614
Patented July 31, 1962 ~
2
than the aqueous phase. This will result in phase inver
‘
3,047,614
.
sion. In an intermediate situation, concentrations of the
various components present may be such that the con
1
CONDENSATE RECOVERY IN OXIDATION
OF ALKYL BENZENES
Robert E. Pennington and James K. Nickerson, Baytown,
Tex., assignors, by mesne assignments, to, Esso Re
search and Engineering Company, Elizabeth, N.J., a
corporation of Delaware
densate will comprise a single phase containing both the
alkyl benzene and water components in contrast to the _
separate water and oil phases that would normally be
expected or else the water phase and oil phase will have
approximately equal speci?c gravities and will not sepa
Filed July 5, 1960, Ser. No. 40,775 ,
8 Claims. (Cl. 260—475)
10
rate. Still further, the changes in composition required
to bring about the above-noted changes in the speci?c
This invention relates to an improved method for the
gravity relationship are slight so that even minor changes ‘
continuous processing of the off gas formed during the
in the composition of the condensate will result in majorv
production of a carbomethoxy benzene by the liquid phase
changes in the observed settling rates thereof. As a con
catalytic oxidation of an alkyl benzene with molecular _ sequence, unless special precautions are taken, it will notv
oxygen in the presence ofmethanol. More particularly, 15 be possible to obtain dependable phase separation of the .
this invention relates to an improved method for process
condensate with a supernatant alkyl benzene condensate
ing the vaporized e?luent from a reaction zone wherein
an alkyl benzene is catalytically oxidized with molecular
oxygen in liquid phase in the presence of methanol in
phase during continuous operations.
It has been found that the vapor from a reaction zone
wherein an alkyl benzene is catalytically oxidized with
order to dependably and rapidly resolve the vaporized 20 molecular oxygen in the presence of methanol may be
effluent into an off-gas fraction, an aqueous fraction and ~
an alkyl benzene condensate fraction.
In the oxidation-esteri?cation reaction it has been found
to be necessary to remove at least a major portion of the
water that is formed ‘during the reaction so that the re
action mixture will contain, for example, not more than
about 5 weight percent of water. This is conveniently
accomplished by conducting the reaction at a temperature
whichis near the boiling point of Water for the pressure
cooled to liquefy condensable components therein, and
the condensed liquids may be separated from the off-gas
and resolved into an aqueous fraction and an alkyl ben
zene off-gas condensate fraction in the presence of addi
tional quantities of water over and above the amount of
water normally present in the vapor. Thus, phase sepa
ration may be obtained in dependable fashion by adding
water to the condensate in signi?cant quantities, e.g., by
adding from about 5 to 50 weight percent of Water based
employed. However, volatilization of the water will also
on the total weight of the condensate or, on a different
result in volatilization of other components of the re
basis, about 15 to 100 weight percent of'water based on
the weight of the aqueous phase). The oil phase may be
recycled and the aqueous phase may be fractionated (e.g.,
action mixture to a signi?cant extent whereby unre
acted methanol, methanol oxidation products, unreacted
alkyl benzene and alkyl benzene conversion products
by distillation) to obtain the methanol contained therein ,
with the volatilizedwater and o? gas components (e.g.,
for recycle. Methanol oxidation products may also be
recovered. The remainder of the aqueous phase may be
nitrogen, carbon monoxide, carbon dioxide). Because
of'the comparatively large quantity of unreacted or par
and alkyl benzene conversion products dissolved therein.
‘are vaporized and leave the reaction zone together
rejected, even though it has some unreacted alkyl benzene
tially reacted material present in the vapor, it is desirable
This is a practical means of operation, but certain
to process this vapor for the recovery of valuable com 40 problems still exist in connection with the water stream for
rejection. This is related to the fact that a certain amount
ponents thereof. It has been discovered, however, that
this presents serious problems, particularly where recycle
of the aromatic feed stock and its derivatives remain dis
type operations are employed.
solved or entrained or both in the aqueous phase and are
When the vapor from the reaction zone is cooled to a
not returned to the reaction zone with the oil phase. In
temperature sufficient to liquefy the condensable com 45 the distillation column, the major portion ‘of the aromatic
ponents thereof, the thus-obtained condensate will com
feed. stock is surprisingly carried overhead with the
methanol and in this way may ?nd its way back to the
prise a mixture of water, methanol, methanol oxidation
products, alkyl benzene and alkyl benzene conversion
reactor. This is not the case with the aromatic oxidation
products. It might ordinarily be expected that the metha
esteri?cation derivatives which are considerably higher in
nol, methanol oxidation products and water would sepa 50 boiling point. These materials appear in the bottoms
rate from the alkyl benzene and alkyl benzene conversion
stream and unless some recovery means are adopted, will
products in order to provide a heavy aqueous phase which
be lost with the discarded water.
could be separated from the alkyl benzene condensate
This loss may be somewhat minimized by operating in i
phase by, any suitable phase separation technique such as
a manner wherein the injection water is drawn from the
gravity settling. However, the presence of large quanti 55 distillation column bottoms with no fresh water. intro
ties of methanol in the aqueous phase tends to decrease
duced. Thus, the volume of the aqueous stream discarded
the speci?c gravity‘of the aqueous phase, Whereas the
is reduced to only the water of reaction originally present
concentration of alkyl benzene conversion products in the
in the condensate from the reactor 01f gases.
alkyl benzene phase tends to increase the speci?c gravity
The losses of desirable materials may be further re
of the alkyl benzene condensate phase. Thus, the normal 60 duced by the following procedures of the present inven
speci?c gravity differential that exists with respect to water’
tion. In accordance with this procedure, the aqueous
and oil will tend to be minimized with respect to the
bottoms are contacted in a mixing zone ‘with the oil layer
components of the condensate and, as a consequence, even
from the phase separation zone. After being settled, these
under the most favorable conditions, the driving force for
materials are decanted with the oil layer now being re
phase separation, i.e., the dilference between the speci?c 65 turned to the reactor, part of the water being used as in
gravity of the oil phase and the Water phase) will be
jection water to bring on the initial phase separation, and
significantlyreduced whereby long settling times will be
excess water being rejected from this zone. As ‘an alter
required.
Moreover, even a moderate increase in the
nate, fresh injection water may be used and all the aqueous
concentration of the alkyl benzene conversion products
phase from the second decanter rejected from the system.
in the alkyl benzene condensate phase will actually cause 70 The alkyl benzene feed stock to be used in accordance
the normal speci?c gravity differential to be reversed and
with the present invention is an alkyl benzene containing
the alkyl benzene condensate phase will become heavier
one or a plurality of C1 to C4 alkyl groups attached direct
3
1y to the benzene ring. By way of example, the starting
materials may comprise methyl benzenes such as toluene,
xylenes, trimethyl benzenes, tetramethyl benzenes, penta
methyl benzene or hexamethyl benzene or a corresponding
ethyl, n-propyl, isopropyl, butyl, or isobutyl benzene.
Polyalkyl benzenes containing a plurality of alkyl groups
of varying chain lengths may also be utilized such as, for
example, a cymene, 1-methyl-3-butyl benzene, l-methyl
4~tertiary-butyl benzene, etc. A single isomer, a plurality
Within the reaction zone 200‘ the alkyl benzene, the
molecular oxygen present in the air, and the methanol
are catalytically reacted in liquid phase under suitable
operating conditions including, for example, a tempera
ture within the range of about 350° to 550° F. a residence
time in the range of about 0.2 to 2 hours, and a pressure
within the range of about 500‘ to 1000 p.s.i.g. such that
at least about 1 weight percent of methanol (and pref
erably l to 15 weight percent) is present in the liquid
of isomers or a plurality of alkyl benzenes of different 10 reaction mixture. Any suitable polyvalent metal salt
which is soluble in the reaction mixture may be used as
molecular weight may be utilized.
The ‘alcohol feed material is methanol.
the catalyst, as exempli?ed by the acetates, naphthenates,
formates, etc., of cobalt, manganese, etc. The catalyst
The preferred starting materials are the methyl benzenes
may be added by way of a catalyst charge line 18 con
and methanol, because less oxygen is required, because
less by-product water is formed, and because workup of the 15 trolled by a valve 20.
For purposes of description, it may be assumed that
reaction mixture is simpli?ed.
the alkyl benzene is a xylene. It will be understood,
The oxidizing medium to be employed is molecular
however, that any other suitable ‘alkyl benzene, as de
oxygen and a preferred oxygen charge stream is ‘air. How
scribed above, could be used.
ever, it is within the scope of the present invention to
utilize puri?ed molecular oxygen or molecular oxygen
diluted with another inert gas such as carbon dioxide.
The catalyst that is used is a salt of a polyvalent heavy
metal which is soluble in the liquid reaction mixture as
exempli?ed by the salts (e.g., the naphthenates, acetates,
bromides, etc.) of cobalt and manganese, etc. The cata
If the cit gas in line 220 contains an excessive amount
of the heavier xylene conversion components (e.g.,
methyl toluates, monomethyl phthalates, dimethyl phthal
iates, etc.) valve 222 is closed and the off gas is passed
by a branch line 226 controlled by valve 228 to a pre
25 cooler 230 wherein the vapors are cooled to a tempera
lyst concentration should preferably be within the
ture, for the pressure employed, sufficient to substantially
range from about 1 to about 10,000 ppm. of soluble
polyvalent heavy metal based on the total weight of the
reaction mixture. Catalyst promoters are optionally em
selectively liquefy only the heavier xylene conversion
products such as the methyl toluates, monomethyl phthal
ployed and, more particularly, soluble bromine salts such
as cobalt bromide, ammonium bromide, manganese bro
mide, etc. or hydrobromic acid are employed because of
their high promotional activity, both with respect to the
oxidation reactions ‘and with respect to the esteri?cation
reactions that are involved.
ates and dimethyl phthalates. This procedure will be
employed particularly in situations wherein the xylene
type components of the off-gas contain in excess of more
than about 30' weight percent of the heavy xylene con
version products in the condensate. From precooler 230,
the partially condensed material is charged by Way of a
35 line 232 ‘to a drum 234 wherein the condensed heavy
The term “recycle type operation” as used in this ap
Xylene partial conversion products are separated from the
plication means a continuous operation wherein products
remainder of the vapor. The heavy xylene partial con
of the conversion operation (both liquid and vapor) are
version product may be withdrawn by way of a line 236
continually processed exteriorly of the reaction zone for
leading back to liquid product line 214.
the removal of nonreactive components of the reaction 40
Within the cooler 224 the remaining portion of the
mixture and wherein unreacted alcohol, unreacted alkyl
condensable cit-gas, is cooled to a temperature, for the
benzenes and alkyl benzene conversion products are re
pressure employed, su?icient to liquefy the condensable
turned to the reaction zone.
components of the vapor of the line 220. The resultant
The term “alkyl benzene conversion products” as used
o? ‘gas condensate stream is passed by way of a line 250
herein is intended to include those aromatic type reaction
to a drum 252 wherein the tail gas is withdrawn by way
products that are formed in the reaction zone including
of a vent‘ line 254. The condensate is discharged from
the reaction products of ‘alkyl benzene with the oxygen
‘drum 252 by way ‘of a line 256 containing a pressure
only, as well as the reaction products (such as oxidation
reducing valve ‘258 leading to a separator 262.
Water
esteri?cation) of alkyl benzene, oxygen and methanol. \ is added to the condensate in any desired manner such
Also, since the alkyl benzene will ordinarily contain small 50 as, for example, by way of a water charge line 263 con
quantities of aromatic type impurities, the term “alkyl
trolled by a valve 100 leading to- the line 256. Within
benzene conversion products” is also intended to include
the separator 262 the condensate and added water are
conversion products of the aromatic impurities. Accord
resolved into a lower aqueous phase comprised principally
ingly, for the purpose of this application, the term “alkyl
of water, methanol and methanol oxidation products
benzene conversion products” is de?ned as the aromatic 55 which are discharged by way of a line 264 for further
conversion products of the alkyl benzene feed stock and
processing and a supernatant xylene phase which is dis
‘aromatic impurities contained therein ‘and comprising
charged by way of a line 269‘.
aromatic alcohols, aromatic aldehydes, aromatic acids,
The aqueous phase is charged by way of line 264 to
methyl esters of aromatic acids, partial methyl esters of
a suitable distillation zone illustrated schematically in the
polybasic aromatic acids, etc.
60 drawing as a single distillation column 106 wherein the
The term “methanol oxidation products” as used herein
means reaction products of methanol and oxygen includ
ing formaldehyde, formic acid, methyl formate and
methylal.
The invention will be further illustrated with respect
to the accompanying drawing wherein:
The sole FIGURE isa schematic ?ow sheet illustrating
one embodiment of the present invention.
Turning now to the drawing, there is schematically dis
closed a reactor 2%‘ to which an alkyl benzene, air, and
methanol are respectively charged by lines 202, 206, and
210.
A liquid product line 214 containing a pressure reduc
aqueous stream 264 is separated into a light overheads
fraction 108 composed principally of methanol and meth
anol oxidation products (and also containing some water
and unreacted xylenes feed stock) ‘and a bottoms water
fraction 110 composed principally of water and contain
ing some xylene conversion products.
It is generally desirable to recover methanol from the
overheads fraction 108 for recycle although it may be
‘discarded from the system by way of a discard line 112
controlled by a valve 114. Thus, the overheads 108
may suitably be charged to a second distillation column
116 where it is separated into an overheads fraction 118
composed of methanol and methanol oxidation products
ing valve 216 leads to a ‘?ash zone 218, and an off gas
and abottoms fraction 120 composed principally of meth
line 220 control-led by a valve 222 leads to a cooler 224. 75 anol and containing some unreacted xylenes. The bot
A
35,047,614
toms fraction 120 is preferably recycled to the reaction
zone 200 by way of a suitable recycle line (not shown)
in order to supply at least a portion of the methanol
requirements for the system.
water charge line 150 con-trolled by a valve 152 in order
to insure positive phase separation.
The oil from separator 148 may ‘be withdrawn by way
of a line 90 controlled by valve 92 for recycle to the reac
tion zone zoo. Alternately, it may be charged by Way
of the line 154 controlled by a valve 156 to a suitable
The water fraction- 110 from the distillation column
106 is charged by way of a branch line 122 to a suitable
mixing device such as a ba?ie plate incorporator 124.
mixing device such as a baffle plate incorporator 158
It is generally desirable to charge substantially all of the
for a purpose to be described.
The water phase from separator 148 may be discharged
bottoms fraction 110 to the mixer 124 although, if desired,
a portion of the water may be purged from the system 10 by way of a line 160 controlled by a valve 162 leading
The supernatant xylene phase 269‘ from the separator
to charge line 264 which feeds into distillation column
11-06 in order to recover xylenes and xylene conversion
262 is also charged to the mixer '124 and the two streams,
products contained therein. Alternately, the water phase
after being thoroughly commingled, are discharged by
may be charged by way of a branch line 164 controlled
by way of a purge line 126 controlled by a valve 128.
way of a line 130 leading to a separation zone 132 wherein 15 by valve 166 to a distillation zone illustrated schematically‘
in the drawing as a single fractionator 168 wherein the
phase separation is accomplished. The supernatant xy
water fraction may be separated into an overhead
lene phase containing a major amount of the xylene
methanol oxidation fraction 170, a methanol distillate
conversion products initially present in the Water ?'ac
fraction 172 (containing unreacted xylenes) and a bot
tion'110 is withdrawn by way of a recycle line 134 which
suitably leads to the alkyl benzene charge line 202.
20 toms water fraction discharged by way of a line 174
controlled by a valve 176 and‘ containing dissolved
The water fraction is discharged ‘from separator 132
xylene oxidation products. Although the water fraction "
by way of a line 136 controlled by a valve 137. All of
174 may be discharged from the system, if desired, it is
the water may be discarded from the system by way of
preferable to treat the same for recovery of xylene con
line 136. Preferably, however, at least a portion of the
water in line 136 is routed by way of a branch line 138 25 version Products therein. For example, the fraction 174
may be charged by Way of a line 178 controlled by a
controlled by a valve 140 leading to the water charge
valve 180 to incorporator 124 for processing the mixture
line 263.
110 to the distillation column 106. Alternately, the water.
As the result of this operation, a signi?cant portion
fraction 174 may be charged by Way of a branch line 182
of the xylene conversion products that would normally
controlled by a valve 184 to the baffle plate incorporator
be lost from the ‘system by water fraction 110 are recov
158 wherein it is brought into intermediate contact with
ered by way of a recycle stream 134, thereby improving
the oil phase 154. The resultant mixture is discharged
the selectivity'of the process and-thereby abating a poten
from incorporator 158 by way of a line 186 to a separator
tial pollution problem.
188 wherein phase separation occurs. The supernatant .
The liquid product stream withdrawn by line 214 (con
taining pressure reduction valve 216) from the reactor 35 oil phase is withdrawn by way of a line 190 for recycle
to the reactor 200. The water phase is discharged by
200 will comprise not only dicarbomethoxy benzene, un-.
reacted xylene and xylene conversion products, but also
free methanol, methanol oxidation products and, normal
way of a line 192 controlled by a valve 194._ If desired,
a portion of the water in the line 192 may be charged by
way of a recycle line 196 controlled by a valve ‘198 to the
water charge line 150 for the line 144.
It will be understood that modi?cations of the process
‘shown in the drawing may be made and that the process
ly, at least a minor amount of water.
In order to facilitate the processing of the liquid prod
uct stream 214, it is desirable in many instances to sepa
rate the stream 214 into a heavy fraction containing a
heavy oxidate stream containing a concentrated amount
shown in the drawing is by way of illustration only. For
example, all or a portion of the fresh alkyl benzene feed
of dicarbomethoxy benzene and a lighter fraction sub
stantially free from the dicarbomethoxy benzene and 45 stock may be charged to the process by way of a line 400
controlled by a valve 402 leading to the charge line 256
other dibasic materials.
.
for the separator 262 in order to improve the phase sepa
The initial separation may conveniently be accom
ration to be accomplished in the zone 262. Similarly,
plished in the ?ash zone 218 wherein the ?ashing con
all or a portion of fresh alkyl benzene feed stock could be
ditions are adjusted so as to vaporize a substantial amount
charged by way of a line 404, controlled by a valve 406
of the unreacted xylene and substantially all of the water,
leading to the charge line 144 for the separator 148 in
unreacted methanol and methanol oxidation products over
order to promote phase separation in the separator 148.
head as ?ashed liquid product by way of a line 266 lead
It will also be understood that the water to be added
ing to a condenser 270. In this situation, the heavy oxi
to the charge streams to the separators 148 and 262 may
date is discharged by Way of a line 272 for further proc
be added directly to the separators by suitable lines (not
essing. Suitable means such as trays 102 at the top of
shown) or at any other upstream point from the sep
zone 218 may be provided in order to prevent excessive
arator 262 and downstream from reaction zone 200 and
carryover of heavy oxidate into line 266.‘
?ash zone 218.
Di?iculties will be encountered in processing the vapor
The invention will be further illustrated by the follow
ized reaction product in the line 266 because of the spe
60 ing speci?c examples which are given by way of illustra
ci?c gravity problem.
1
tionvand not as limitations on the scope of this inven
‘Within the cooler 270 the condensable components are
tion. Where parts are given, they are parts by weight.
lique?ed, and the resultant ?ashed liquid product con
densate stream is then charged by way of a line 288 to
a manifold 104.
From manifold 104 the condensate is preferably routed
by way of a branch line 142 controlled by a valve 143
to the charge line 256 for the separator 262 in order to
improve the e?iciency of the process by processing the
65
EXAMPLE I
Initiate a continuous total recycle process for the pro
duction of dimethyl terephthalate from paraxylene, meth
anol, and oxygen in equipment for continuous reactions
as schematically shown in the drawing. Pressure the re
actor to about 700 p.s.i.g. with air and charge freshly
condensate 288 in admixture with the o?’ gas condensate 70 prepared p-xylene (98.6 percent purity) to the reaction
256. However, the condensate 288 may be separately
zone 200 through the line 202, the fresh xylene containing
processed, if desired. Thus, for example, the condensate
an amount of cobalt naphthenate su?icient to provide
may be routed from manifold 104 by way of a line 144
about 5 parts per million of dissolved cobalt in the liquid
controlled by a valve 146 to a phase separator 148.
phase. Charge air at the rate of about 0.4 part per part
Water will also be added to the line 144 by way of a 75 of p-xylene. After initiation of the oxidation reaction,
8,047,614
8
said reaction zone, said off gas stream and said liquid
reaction mixture stream comprising normally liquid com
charge methanol by way of line 210 in the ratio of about
0.4 part of methanol per part of p-xylene. Start recycle
operations in the manner shown schematically in the
ponents including Water of reaction, unreacted methanol,
methanol oxidation products, unreacted alkyl benzene, and
drawing.
Thus, process an off gas stream after removal through
the oif gas line 229 by cooling in the cooler 224 in or
alkyl benzene conversion products, and wherein at least
der to condense lique?able components followed bypsep
condensate fraction comprising water of reaction, unre
aration of the tail gas from the condensate in drum 252.
Charge the condensate by way of line 256 to‘ a separator
acted methanol, methanol oxidation products, unreacted
alkyl benzene and alkyl benzene conversion products, by
262 and add about 25 weight percent of Water to the con
densate by way of a line 263.
~
10 continuously charging said condensate fraction to a ?rst
Within the separator 252 the condensate resolves by
gravity separation into a supernatant xylene condensate
to said separation zone in an amount su?icient to cause
a portion of said reaction products are recovered as a
separation zone, continuously charging additional Water
separation of said condensate fraction and said added
water into a lower phase comprising water, methanol and
methanol oxidation products and a supernatant phase
phase 269 in which is charged to mixer 124 and an aque
ous fraction 264 which was fractionated in a distillation
zone 106 for the recovery of methanol. Methanol re
comprising unreacted alkyl benzene and alkyl benzene
conversion products, the improvement which comprises
covered by line 120 is recycled to the reaction zone 2.09.
Water from the line 110 is charged to mixer 124.
The oil phase and water phase after being thoroughly
commingled in mixer 124 is passed through line 130 to
separator 132 and separated therein into an oil phase
and an aqueous phase.
2,0
In a representative run con
fractionating said lower water phase into a heavy water
fraction and a light overhead fraction comprising meth
anol and methanol oxidation products, continuously ad
mixing said heavy water fraction with said supernatant
phase in a second separation zone wherein there is formed
an alkyl benzene phase comprising unreacted alkyl ben
ducted in this fashion, the compositions for the fractions
110, 269, 134 and 136 were found by analysis to be
zene and alkyl benzene conversion products and a water
those set forth in Table I.
phase substantially free of alkyl benzene conversion prod
nets, and recycling said alkyl benzene phase to said re
Table I
action zone.
STREAM ANALYSES
2. A method as in claim 1 wherein said condensate
fraction is recovered from said off gas stream.
(110)
(269)
(134)
(136)
3. A method as in claim 2 wherein at least a portion
Column Oil From Oil From Aqueous 30
Bottoms,
Component
First
Wt. per- Decant,
cent
Second
From
Decant,
Second
of said water phase is contacted with said condensate frac
tion.
4. ‘In a continuous method for the production of a di
Wt. per- Wt. per- Decant,
cent
cent
Wt. per
cent
methyl phthalate by the catalytic liquid phase oxidation of
35 a xylene in a reaction zone with molecular oxygen in the
Dimethylterephthalate .... __
Monomethyltcrephthalate. __
Methyl p-Toluate __________ _p-Toluic Acid ______ _-
p-Tolualdehyde_
p Tolyl Alcohol
0. 4
0. 1
1. 9
0. 6
5. 2
0. 4
23. 6
2. 4
5. 9
1. 1
27. 7
3. 3
0.2
0. 1
0.2
0. 6
0.0
0.0
0.0
0. 0
18. 9
1. 3
75. 5
1. 4
0. 4
53. 7
3. l
0.0
3. 9
0. 1
0. 5
4. 4
0. 1
0. 8
1. 1
0. 3
56. 7
1. 8
0.0
2. 1
0. 0
0. 0
0.0
0.0
0.0
0. 0
0. 1
0. 2
0. 3
presence of methanol under reaction conditions includ
ing a temperature within the range of about 350° to about
0. 0
0.1
0.0 40
1. 6
0.3
1. 1
0. 6
0. 0
17. 2
1. 5
77. 5 HA Cu
550° F. and a pressure within the range of about 500
to about 1000 p.s.i.g. and wherein reaction product
streams, including an o? gas stream and a liquid product
stream, are continuously withdrawn from said reaction
zone, said off gas stream and said liquid product stream
comprising normally liquid components including water
of reaction, unreacted methanol, methanol oxidation
products, unreacted xylene and xylene conversion prod
ucts, methyl toluate and heavier xylene conversion prod
ucts, wherein ?rst condensate from said oil gas is re
From Table I it can be calculated that 80 percent of
the aromatic materials in the fraction 110 were recovered
as a part of the second oil fraction 134.
covered which comprises said normally liquid components,
EXAMPLE II
By way of contrast, it was attempted to recover the
aromatic materials from the line 110 by a stream strip
ping-azeotropic technique. Thus, a sample of the ma
product stream is separated into a heavy liquid fraction
containing said dimethyl phthalate and a vapor fraction
at least a portion of said methyl toluate and heavier xylene
conversion products are removed from said ?rst conden
sate to provide a ?rst condensate fraction, said liquid
comprising said normally liquid components including
terial in the line 110 was re?uxed in a well stirred one
liter round bottom ?ask ?tted with a condenser and a de
methyl toluate and heavier xylene conversion products,
canting leg on the re?ux return. At the outset, an oil
layer was obtained which ?oated on the water layer. This
material was withdrawn and after further re?uxing a new
said heavy liquid fraction and the remainder of said heavy
liquid fraction is recycled to said reaction zone, said
said dimethyl phthalate is continuously recovered from
vapor fraction is condensed to provide a second conden
oil layer formed which sank below the water layer. Thus, 60 sate, at least a portion of said methyl toluate and heavier
xylene products are removed from said second conden
the phase separation obtained would be undependable for
sate to provide a second condensate fraction, and where
continuous operations. To further demonstrate the limi
in from about 5 to 50 weight percent of additional water
tations of this technique, vigorous re?uxing was main
is added to said ?rst and second condensates, the im
tained for a period of about four hours and then after
provement which comprises admixing said ?rst conden
cooling, the oil phase from the re?ux vessel (which sep
sate fraction and said second condensate fraction before
arates from the water when cooled) and the oil layer
‘adding said water, separating said admixture after add
from the decanter were weighed. Only about 40 per
ing said water into a water phase containing unreacted
cent of the oil material had been stripped overhead.
methanol and methanol oxidation products and a super
What is claimed is:
1. In a continuous method for the production of a car
bomethoxy benzene by the catalytic liquid phase oxida
tion of a ‘C1 to C4 alkyl benzene in a reaction zone with
molecular oxygen in the presence of methanol and where
in reaction products, including an off gas stream and a
70 natant xylene phase comprising unreacted xylene and
xylene conversion products, fractionating said lower water
phase into a Water fraction containing xylene conversion
products and a methanol fraction comprising methanol
and methanol oxidation products, continuously mixing
liquid product stream, are continuously withdrawn from 75 said water fraction with said supernatant xylene phase,
8,047,614
charging said mixture to a second separation zone, sep
10
7. vA method in accordance with claim 6 wherein the
arating said mixture into said supernatant xylene phase
and said water fraction, and recycling said xylene phase
water admixed with said condensate stream amounts to
to said reaction zone.
8. In a process of recovering a condensate stream from
the oxidation-esteri?cation reaction between a methyl ben
zene, molecular oxygen, and methanol, wherein said con
5. A method in accordance with claim 1 wherein the
alkyl benzene is a methyl benzene.
6. In a continuous method of producing a dirnethyl
phthalate by the catalytic liquid phase reaction of a xylene
about 5 to about 50 weight percent of said condensate.
densate stream comprises unreacted methanol, unreacted
‘methyl benzene, methyl benzene conversion products,
in a reaction Zone with molecular oxygen and methanol
methanol conversion products and water of reaction, and
under conditions including a temperature within the range 10 wherein water in amounts from about 5% to about 50%
of about 350° F. to about 550° F. and a pressure within
by weight based on said condensate stream is added to
the range of about 500 p.s.i.g. to about 1000 p.s.i.g.,
said stream whereby a methyl benzene supernatant phase
wherein reaction products including an off gas condensate
and a methanol containing lower aqueous phase are
staream and a ?ashed liquid product condensate stream
formed, said aqueous phase containing at least a portion
are continuously recovered from said reaction zone, and 15 of said ‘methyl benzene conversion products, the improve
wherein water is admixed with at least one of said con
ment which comprises fractionating said aqueous phase
densate streams whereby said admixed stream is separated
to remove methanol therefrom and contacting said frac
tionated aqueous phase v with said supernatant phase
into a supernatant xylene phase and a lower aqueous
phase, the improvement which comprises fractionating
whereby said methyl benzene conversion products are ab
said lower aqueous phase into a water fraction containing 20 sorbed by said supernatant phase.
xylene conversion products and a methanol fraction, con
tacting said water fraction with said supernatant xylene
References Cited in the ?le of this patent
phase whereby said xylene conversion products are re
UNITED STATES PATENTS
moved from said water, and recycling said supernatant
2,879,289
xylene phase to said reaction zone.
25
Johnson _____________ __ Mar. 24, 1959
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