Note: Descriptions are shown in the official language in which they were submitted.
PROCESS FOR PRODUCING DIARYL CARBONATE
BACKGROUND OF THE INVENTION
The present invention relates to a process for producing a
diaryl carbonate. More particularly, the present invention
relates to a process for producing a diaryl carbonate according
to the disproportionation reaction of an alkylaryl carbonate.
It has been already known to obtain diphenyl carbonate by
disproportionation of an alkylphenyl carbonate [Japanese Patent
Publication No. 1~8537/1983 (USP 4,045,~164)]. However, in this
method, a catalyst selected from among Lewis acids and transition
metal compounds capable of forming Lewis acids is used, and
specifically AlX3, TiX3, UX4, VOX3, VX5, ZnX2, FeX3, SnX4 are
included, wherein X is a halogen, an acetoxy group, an alkoxy
group, or an aryloxy group. Such Lewis acids are highly
corrosive to the metallic materials of reaction vessels,
pipelines and valves. Thus methods using these Lewis acids
involve a problem when industrially practiced.
Further, it has been also praposed to conduct such a method
using a catalyst consisting of a mixture of a Lewis acid and a
protonic acid [Japanese Laid-open Patent Application No.
173016/1985 (USP 1l,609,501)~ lowever, in this method, because
a protonio acLd is uaed in addition to a Lewis acid, not only the
problem of corro.sion becomes more serious, but also separation
and recovery of the catalyst are difficult.
2 ~ J
Also, some proposals have been made to use organic tin
compounds or organic titanium compounds as a catalyst in such
methods [Japanese Laid-open Patent Publications Nos . 169444/1985
(USP ~,554,110), 169l~45/l985 (USP 4,552,704), 265062/1989,
265063/1989), but these organic tin compounds or organic titanium
compounds are difficult to separate completely from the products
whereby it is very difficult to obtain the diaryl carbonate with
high purity. One irnportant use of a diaryl carbonate is its use
as a monorner ror prod~cing polycarbonate, and in this case, if an
organic tin compound or an organic titanium compound is present,
even in a small amount, in the diaryl carbonate, the physical
properties of the polycarbonate thus produced will be lowered.
Therefore, the diaryl carbonate produced by the methods using
such catalysts cannot be effectively used as the monomer for
producing the polycarbonate.
Further, it has been also proposed to use in such a method a
catalyst selected from a compound containing Sc, Cr, Mo, W, Mn,
Au, Ga, In, Bi, Te, and lanthanoid (Japanese Laid-Open Patent
Application No. 265064/1989). However the yield of the desired
diaryl carbonate is low in this method.
SUMMARY OF TH~ INVENTION
The above-identified problems have been eliminated by the
present invention which provides a process for produclng a diaryl
carbonate, which comprises disproportionating an alkylaryl
carbonate to a diaryl carbonate and a dialkyl carbonate in the
presence of a lead catalyst.
' $ ~ ~
DETAILED DESCRIPTION OF THE INVENTIO~
The process o~ the present invention is represented by the
reac~ion (I) as shown below:
O O
Il 11
2R - O - C - O - Ar = Ar - O - C - O - Ar ~
o
ll ....................... (I)
R - O - C - O - R
(wherein R represents an alkyl group such as an aliphatic group,
an alicyclic group, an aralkyl group, and Ar represents an aryl
eroUP which is an aromatic group).
The alkylaryl carbonate to be used as the starting material
of the present invention is a compound shown on the left side of
the above reaction (I). As R, for example, aliphatic groups
including various isomers such as methyl, ethyl, propyl, butyl,
pentyl, hexyl, heptyl, octyl, nonyl and the like; alicylic groups
such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl,
methylcyclobutyl, cyclohexylmethyl and the like; aralkyl groups
such as benzyl, phenethyl and the like are preferred. As Ar,
unsubstituted aromatic groups such as phenyl, naphthyl, pyridyl,
etc.; substituted aromatic groups represented by the following
f'ormulae are preferred:
~ R~- ~ ( R~-~ - ~ - ( R~
(wherein R' represents a sub.stltuent such as lower alkyl group,
all<oxy group, acyl group, halogen, aryloxy group, aromatic group,
nitro group, cyano group, aralkyl group, etc., Q is an integer of
1 to 5, m is an integer of' 1 to 7, n is an integer of 1 to 4, and
'3 ~
wl.~n Q, m and n are each an integer of 2 or more, and R' may be
either the same or dif'ferent). Also, in R, those wherein one or
more hydrogen is subst1tuted with a substituent such as halogen,
alkoxy group having 1 ~o 10 carbon atoms, cyano group, etc. can
be also used.
A particularly preferable alkylaryl carbonate is one where
the alkyl group is a lower aliphatic group having 1 tG l~ carbon
atoms such as rnethyl, ethyl, propyl, butyl, and where the aryl
group i3 phenyl eroup or a sub,stituted phenyl group having 7 to
15 carbon atoms with a sub.stituent having 1 to 9 carbon atoms
such as methyl, dirnethyl, ethyl, t-butyl., 2-phenyl-2-methylethyl,
etc.
'rhe lead catalyst to be used in the present invention may
be lead containing material or a compound containing lead, but
particularly preferable are basic or neutral lead compounds.
Examples of such lead compounds preferably used may include lead
oxides such as PbO, PbO2, Pb304; lead sulfides such as PbS, PbS2,
PbS3; lead halides such as PbC12, PbBr2, PbI2, 3PbBr2-2PbO,
PbC12-Pb(OH)2 etc.; lead hydroxides such as Pb(OH)2, Pb302(0H)2,
Pb2~PbO2(0H)21, Pb20(0H)2, etc.; plumbites such as Na2PbO2,
K2PbO2, NaMPbO2, KHPbO2, etc.; plumbates such as Na2PbO3,
Na2H2PbOIl, K2PbO3, K2[Pb(OH)6], K~PbOIl, Ca2PbO4, CaPbO3, etc.;
carbonates of lead or lead compounds and basic salts thereof such
as PbC03, 2PbC03 Pb(0~1)2' PbC03 PbC12~ 2pbco3-pbsol~-pb(oH)
etc.; lead salts of' orgarlic acLds such as Pb(OCOCH3)2,
Pb(OCOCH3)1l~ Pb(~C~CH3)2-PbO-3H20, etc.; organ:ic lead compounds
such as BullPb, Phl~Pb, Bu3PbCl, Ph3PbBr, Ph3Pb (or Ph6Pb2),
2~ 3
~_3PbOH, Ph2PbO, etc. (Bu and Ph represent a butyl group and a
phenyl group, respectively); lead alkoxides or lead aryloxides
Such as Pb(~CH3~2' Pb(~C2H5)2~ (CH30)pb(oph)~ Pb(OPh)2, etc.;
alloys of lead such as Pb-Na, Pb-Ca, Pb-Ba, Pb-Sn, Pb-Sb, etc.;
lead ores such as galena, boulagerite, etc., and hydrates o~
these coMpounds and so on. Of course, these lead compounds may
be also those which are reacted with the organic compounds
existing in the reaction systern such as alkylaryl carbonates,
diaryl carbonates, dialkyl carbonates, or hydrolyzed products of
these cornpounds (alcohols, aromatic hydroxy compounds, etc.), and
may be also those subjected to heat treatment with the starting
material, the products or alcohols or aromatic hydroxy compounds
prior to the reaction.
Among these, particularly preferred catalysts are lead and
lead compounds such as powdery lead, fine particulate or powdery
lead-sodium alloys, various lead oxides, lead hydroxides, lead
carbonates and basic lead carbonates, plumbites and plumbates,
lead acetates and basic lead acetates, lead alkoxides and lead
aryloxides. These lead and lead compounds can be also pretreated
by being reacted with organic compounds which exist in the
re~ction system, or by being subjscted to a heat treatrnent with
the starting material, with the products or with a]cohols or
aromatic hydroxy compounds and used as the catalyst system. In
the present invention, when these particularly preferred
catalysts are used, not only can a diaryl carbonate be obtained
in high yield and high s~lectivity, but also the diaryl carbonate
can be easily separated frorn the catalysts used. More
Q~ ~' ~'
s~ecifically, the diaryl carbonate thus produced is generally
separated and purified by distillation under reduced pressure
from the reaction mixture, and none of the lead components of
these particularly preferred catalysts is distilled off together
with the diaryl carbonate, because there is entirely no or very
little vapor pressure of the lead components under such
distillation conditions. Accordingly, a highly pure diaryl
carbonate free from any lead components can be obtained. This is
one of the excellent features of the present invention.
The catalyst of the present invention is excellent in
producing a diaryl carbonate in a high yield with high
selsctivity, and further it has also the specifio feature that
there is no problem of corrosion of the metallic materials of the
installation caused by the prior art use of a Lewis acid, because
the lead and lead compounds constituting the catalyst are neither
Lewis acids nor transition metal compounds which can form Lewis
acids.
The catalyst comprising such lead materials or lead compounds
can be used either singly or as a mixture of two or more kinds.
The amount of the lead catalyst to be used in the present
invention is not particularly limited, but may be generally used
in the range of from 0.00001 to 100 moles, preferably from 0.001
to 2 moles per mole of the alkylaryl carbonate used.
Since the reactlon of the present invention is an equilibrium
reaction as shown by the reaction (I), by removing at least one
of the diaryl carbonate or the dia:Lkyl carbonate which are the
reaction products ~rom the reaction system, the reaction can
f, ~ J ~ 3
better progress.
Since the reaction of the present invention is generally
carried out in liquid phase or gas phase, it is preferable to
progress the reaction while distilling off the component with the
lower boiling point of the reaction products. The order of the
boiling points of ~he starting materials and the products are
generally diaryl carbonate > alkylaryl carbonate > diall<yl
carbonate, or dialkyl carbonake > alkylaryl carbonate > diaryl
carbonate, and thus it is easy to distill off one of the
products. A dialkyl carbonate of which the alkyl group comprises
a lower aliphatic group such as methyl, ethyl, propyl, butyl,
etc. has a low boiling point, and therefore can be easily
distilled off from the reaction system. In such meaning, an
alkylaryl carbonate having a lower aliphatic group may be
preferably used.
For effectively distilling off the lower boiling components,
there may be preferably employed the method in which an inert
gas such as nitrogen, helium, carbon dioxide, etc. or a lower
hydrocarbon gas or mi~ture thereof is introduced into the
reaction system, and the method is performed under reduced
pressure. These methods may be also used in combination. In the
case of a tank type reactor, it is also a preferable method to
perform effective stirring to increase the interfacial area
between the gas and llquid phases, or to promote the interfacial
renewal, while in the case of a tower type reactor, it is also a
preferable method to rnake an apparatus with a large interfacial
area between the gas and llquid phases.
2~ J~3 eJ
The reaction of the present invention is generally carried
out at about 50 to about 400 ~C, preferably in the range of from
about oO to about 300 ~C. The reaction time which may vary
depending on the reaction system employed and o~her reaction
condition.s chosen is typically about one minute to about 50
hours. The reaction pressure may be either reduced pressure,
normal pressure or in the range of ~rom about 0.01 I<g/cm~ to
about 50 kg/cm2.
The procet~s of the present invention can also be practiced
wlth or without the use of solvent. When a solvent is used, it
is also a preferable method to distill off the lower boiling
products together with a part of the solvent. Examples of such
solvent may include aliphatic hydrocarbons such as pentane,
hexane, heptane, octane, nonane, decane, undecane, tridecane,
etc.; aromatic hydrocarbons such as benzene, toluene, xylene,
ethylbenzene, styrene, etc.; alicyclic hydrocarbon~ such as
cyclohexane, methylcyclohexane, etc.; halogenated hydrocarbons
sucn as methyl chloride, methylene chloride, chloroform, carbon
tetrachloride, dichloroethane, chlorobenzene, dichlorobenzene,
etc.; nitrilies such as acetonitrile, propionitrile,
benzonitrile, etc.; ketones such as acetone, methyl ethyl
ketone, acetophenone, etc.; ethers such as diethyl ether,
tetrahydro~uran, dioxane, diphenyl ether. etc.
The process of the present invention can be practlced by
either a batch systetn or a continuous system.
DRTAILED DESCRIPT:L~N OF TllE P~EEERRED EMBODIMENTS
The preserlt invention is described in more detail by
re~erring to tl1e ~ollowin~ examples, which shoulcl not be
-- 8
.Isidered as limiting in any way the sense of the present
invention.
Example 1
Pre-treatment of the catalyst is performed by heating 2 g Or
PbO and 10 g of rnethylphenyl carbonate under a small amount of
nil;rogen streaM at about 180~C for one hour. Subsequently, by
distilling off unreacted methylphenyl carbonate and most o~ the
diphenyl carbonate formed at about 150~C under a reduced pressure
of about 0.5 mm Hg, 2.5 g of a pale yellow solid is obtained. To
thi.s is added 76 g (0.5 mole) of rnethylphenyl carbonate, and the
whole amount is transferred into a 200 ml four-necked flask
equipped with a stirring device, a reflux condenser, a gas
introducing inlet reaching lower level than the liquid surface,
and a thermometer. The reaction is carried out by dipping the
flas~ in an oil bath of 190 - 195~C under stirring, while
introducing dry nitrogen at a rate of 80 N ml/min. Through the
jacket of the reflux condenser is conveyed water at a temperature
of about 90~C, and the reaction is carried out while distilling
off dimethyl carbonate by-produced, and refluxing methylphenyl
carbonate and the diphenyl carbonate formed to return them into
the reactor. The results are shown in Table 1. Selectivity of
anisole which is the by-product is 1 ~ or less even after 3
hours.
. 9
Table 1
Reaction time Methylphenyl carbonate Diphenyl carbonate
(min.)conversion (~) ~ield (%) Selectivity (%)
56.6 56.2 99.3
7ll.5 73.9 99.2
120 85.5 84.7 99.1
180 90.~ 89.9 99.0
Three hours later, the system i9 gradually brought under
reduced pressure to distill off unreacted methylphenyl earbonate.
Subsequently, in place of the reflux condenser, a packe-l column
ith an inner diarneter of 2 em and a height of 30 cm (paeked with
6 mm~ Diekson paekings made of stainless steel) is rnounted, and
distillation is performed under redueed pressure to give 45 g of
diphenyl carbonate (purity 99.99 %) which is distilled out at
1B4 - 185 ~C/17 mm Hg. When metal analysis in the diphenyl
earbonate is eondueted by ICP (Induetively eoupled diseharge
speetrometry) method, no lead is detee'ced at all.
Comparative example 1
The disproportionation reae'cion of methylphenyl earbonate
(76 g, 0.5 mole) is carried out in the same manner as in Example
1, by using of 3.8 g of Ti(OC6H5)4 as the catalyst proposed in
USP 4,045,46ll. As a result, the conversion of methylphenyl
earbonate after 3 hours is :found to be 60.3 %, and the yield of
diphenyl carbonate 56.1 % and .lts selec~ivity 93.0 %. Anisole
whieh is the by-produet is found to be forrned ac a seleetivity o:f
6.2 %. Subsequently, sirnilarly as in Example 1, unreaeted
- 10 -
nl_~hylph~nyl carbonate is distilled off, and 23 g of diphenyl
carbonate (purity 99.0 %) is obtained by reduced pressure
distillation. When metal analysis in the diphenyl carbonate is
conducted by the ICP method, 150 ppm of Ti is detected.
Example 2 - 11
According to the same procedure as in Example 1 except for
using various lead cornpounds or lead in place of PbO, the
reactions from methylphenyl carbonate (76 g) to diphenyl
carbonate are carried out. The results of the reactions after
2 hours are listed in Table 2. In these Examples, the catalyst
is used in an amount of 5 mmol or 5 mg-atom as lead. The Pb-Na
alloy used in Example 3 contained 90 % by weight of Pb. In
Examples 2, 3, 7, 8 and 9, the reaction is carried out directly
without pre-treatment of the catalyst.
Table 2
Methylphenyl Diphenyl carbonate
Example Catalyst carbonate Yield (%) Selectivity(%)
conversion (%)
2 Powdery Pb 52.3 51.8 99.0
3 Fine particulate
Pb-Na alloy 88.2 81.1 92.0
4 PbO2 86 5 85.7 99.1
Pb304 82.3 81.ll 98.9
6 Pb(OH)2 87.8 87.1 99.2
7 2PbC03-Pb~OH)2 85.6 83.3 97.3
8 Pb(OAc)2 Pb(OH)2 8Ll~5 82.0 97.0
9 Pb(OAc)2~3~l20 85.0 82.0 96.5
Na2PbO3 80.2 79.4 99 0
11 PbC03 83.0 82.0 98.8
- 1 1 -
~ 3~
Examples 12 - 17
The reactions are carried out in the same manner as in
Example 1 except for using various alkylaryl carbonates in place
of methylphenyl carbonate, and the results of the reactions
after 2 hours are shown in Table 3.
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?, ~) ,3 ~
Table 3
Example R - OCO - Ar Diaryl carbonate
R Ar Yield (,~) Selectivity (,~)
12C2H5 ~> 76.5 9~.5
13 3 7 ~ CH3 70.2 97.0
CH3
1 4 3 <~ C - CH3 8 6 . 0 99 . O
CH3
CH
15CH3 ~ C ~> 88.5 98 .8
CH3
1 63 ~ CQ 8 4 . 0 97 . O
17CH3 ~ OC~13 85.8 97 .5
- 13 -
2 ~ ' $ ~, ~
However, in Examples 12 and 13, ~he reaction temperature is
205 - 210 ~C, and an oil of about 130 ~C is circulated through
the reflux condenser.
Example 18
Into a flask equipped with a stirrer and a gas outlet is
charged 578 g of phenol, and the flask is dipped in an oil bath.
The oil bath is heated to ;~bout 110 ~C, and 100 g o~ PbO is added
little by little under stirring. The oil bath is heated to reach
190~C in 3 hours. Water and phenol are distilled off. When the
amount of dlstilled liquid becomes 406 g, distillation is
stopped, and after cooled to about 110 ~C, 300 ml of toluene is
added and the mixture is cooled to room temperature. As a
result, pale yellow crystals are precipitated. By
recrystallization of the crystals by use of 350 ml of toluene,
120 g of crystals are obtained. The Pb content in the crystals
is found to be 52.7 ~ by ICP analysis. Tne crystals are
identified to be Pb(OC6H5)2.
The reaction is carried out in the same manner in Example
1 except for using 2 g of Pb(OC6H5)2, 100 g of n-butylphenyl
carbonate, making the reaction temperature 205 - 210 ~C, the
reaction pressure 80 mm Hg, and passing oil at a temperature of
about 140 ~C through the jacket of the reflux condenser. One
hour later, the conversion of n-butylphenyl carbonate i9 found to
be 80.a %, and the yield of diphenyl carbonate i9 ~~0.0 ~, with
its selectivity being 99.1 %.
According to the present invention, by use of a lead
d $ '~ ~
catalyst, a diaryl carbonate can be produced in a high yield
with high selectivity, and the problems of corrosion, etc. of the
apparatus caused by the use of a catalyst such as Lewis acid has
been solved. Furthermore, according to the present inventLon, a
highly pure diaryl carbonate required for the production of
polycarbonate with high qualitles can be easily obtained.
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