U.S. patent application number 09/777152 was filed with the patent office on 2002-04-18 for process for the removal of dissolved oxygen from phenol.
Invention is credited to Bodiger, Michael, Heydenreich, Frieder, Wagner, Rudolf.
Application Number | 20020045726 09/777152 |
Document ID | / |
Family ID | 7630378 |
Filed Date | 2002-04-18 |
United States Patent
Application |
20020045726 |
Kind Code |
A1 |
Heydenreich, Frieder ; et
al. |
April 18, 2002 |
PROCESS FOR THE REMOVAL OF DISSOLVED OXYGEN FROM PHENOL
Abstract
The present invention relates to a method for avoiding
undesirable discoloration in polycarbonate production by catalytic
removal of dissolved oxygen from phenol by (a) admixing hydrogen
with phenol and (b) passing the phenol stream over ion exchangers
doped with platinum group metals.
Inventors: |
Heydenreich, Frieder;
(Dusseldorf, DE) ; Wagner, Rudolf; (Koln, DE)
; Bodiger, Michael; (League City, TX) |
Correspondence
Address: |
BAYER CORPORATION
PATENT DEPARTMENT
100 BAYER ROAD
PITTSBURGH
PA
15205
US
|
Family ID: |
7630378 |
Appl. No.: |
09/777152 |
Filed: |
February 5, 2001 |
Current U.S.
Class: |
528/196 ;
568/722; 568/723; 568/724 |
Current CPC
Class: |
C07C 37/86 20130101;
Y02P 20/52 20151101; C07C 37/20 20130101; C08G 64/06 20130101; C07C
37/86 20130101; C07C 39/04 20130101; C07C 37/20 20130101; C07C
39/16 20130101 |
Class at
Publication: |
528/196 ;
568/724; 568/722; 568/723 |
International
Class: |
C08G 064/04; C08G
064/00; C07C 037/68; C07C 037/86; C07C 039/16; C07C 039/12 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 10, 2000 |
DE |
10005770.5 |
Claims
What is claimed is:
1. A process for the catalytic removal of dissolved oxygen from
phenol comprising (a) admixing hydrogen with phenol and (b) passing
the phenol stream over an ion exchanger doped with a platinum group
metal to catalyze the reaction
2H.sub.2+O.sub.2.fwdarw.2H.sub.2O.sub.2O.
2. A process according to claim 1 wherein the platinum group metal
is an element selected from the group consisting of ruthenium,
rhodium, palladium, osmium, iridium, and platinum.
3. A process according to claim 1 wherein the platinum group metal
is platinum or palladium.
4. A process according to claim 1 wherein the ion exchanger is an
anion exchanger with weakly and/or strongly basic groups.
5. A process according to claim 4 wherein the anion exchanger is a
strongly basic anion exchanger in the Cl form or a weakly basic
anion exchanger in the free base form.
6. A process according to claim 1 wherein the ion exchanger is a
gel form or macroporous ion exchanger.
7. A process according to claim 1 wherein the ion exchanger
contains 0.3 to 10 g of platinum metal per liter of ion
exchanger.
8. A process for the preparation of oxygen-free phenol comprising
adding hydrogen to the phenol and passing the resultant mixture
over an ion exchanger doped with a platinum group metal.
9. A method for preparing bispenol A comprising reacting acetone
under acidic conditions with phenol prepared by the process of
claim 1.
10. A method for preparing a polycarbonate comprising reacting
phosgene or diphenyl carbonate with bispenol A prepared by reacting
acetone under acidic conditions with phenol prepared by the process
of claim 1.
11. Bisphenol A prepared from oxygen-free phenol obtained by the
process of claim 1.
12. A polycarbonate prepared from oxygen-free phenol obtained by
the process of claim 1.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates to a process for the removal of
dissolved oxygen from phenol by admixing water into the phenol,
which is then passed over metals of the platinum group applied to
supports in order to catalyze the reaction of hydrogen and oxygen
to give water in accordance with the equation:
2H.sub.2+O.sub.2.fwdarw.2H.sub.2O. The invention further relates to
polycarbonate and bisphenol A that are prepared from oxygen-free
phenol prepared by admixing water and subsequently passing the
mixture over ion exchangers doped with platinum metal.
[0002] Phenol is an important unit in the preparation of the
plastic polycarbonate. Phenol is first reacted with acetone under
acid conditions to give bisphenol A. The molar ratio of the
reactants phenol:acetone here is in the range of 8:1 to 14:1,
preferably in the region of 12:1. Bisphenol A is then reacted with
either phosgene or diphenyl carbonate to give polycarbonate in the
following step.
[0003] This plastic is employed in a very wide-ranging spectrum of
uses, inter alia in very demanding fields, such as in the
preparation of high-quality optical materials and of compact discs
and in the electronics field.
[0004] However, discoloration of the plastics often prevent their
use in these applications, even when a very great effort is made to
keep the quality of the starting substances at a high level.
[0005] It has now been found, surprisingly, that discoloration can
be virtually completely avoided if hydrogen is added to the phenol
and the mixture is then passed over a support, preferably an ion
exchanger, doped with at least one metal of the platinum group.
[0006] How the discoloration arises has not yet been clarified in
detail. At the moment, however, it is assumed that discoloration is
caused by the nonselective action of oxygen present in the starting
substances.
[0007] The use of anion exchangers doped with noble metals of the
platinum group as catalysts for the catalytic removal of oxygen
from water, for example, for use in the generation of steam, has
been known for a relatively long time and is already practiced
worldwide. See JP-A 58/079,590 and CN-A 1,098,384. In this process,
hydrogen is fed stoichiometrically to the water in such way that
the oxygen present is reacted away virtually quantitatively.
Residual oxygen values of less than 0.1% of the feed value are
obtainable in this manner.
SUMMARY OF THE INVENTION
[0008] The present invention relates to a process for the catalytic
removal of dissolved oxygen from phenol comprising
[0009] (a) admixing hydrogen with phenol and
[0010] (b) passing the phenol stream over ion exchangers doped with
platinum group metals to catalyze the reaction
2H.sub.2+O.sub.2.fwdarw.2H- .sub.2O.
DETAILED DESCRIPTION OF THE INVENTION
[0011] The platinum metals to be used according to the invention
are the elements of the series ruthenium, rhodium, palladium,
osmium, iridium, and platinum. Palladium and platinum are preferred
for the process according to the invention.
[0012] The ion exchangers to be used according to the invention are
preferably anion exchangers and can contain weakly and/or strongly
basic groups. Strongly basic anion exchangers in the Cl form or
weakly basic anion exchangers in the free base form are
particularly preferred. A crosslinked polymer of ethylenically
unsaturated monomers is used as the base polymer. Examples of
ethylenically monounsaturated monomers are, for example, styrene,
vinyltoluene, ethylstyrene, .alpha.-methylstyrene, and derivatives
thereof halogenated in the nucleus (such as chlorostyrene),
vinylbenzyl chloride, acrylic acid and its salts and esters
(particularly the methyl and ethyl esters), methacrylic acid and
its salts and esters (particularly the methyl ester), and the
nitriles and amides of acrylic and methacrylic acid.
[0013] The polymers are crosslinked, preferably by copolymerization
with crosslinking monomers having more than one (preferably 2 or 3)
copolymerizable C.dbd.C double bonds per molecule. Such
crosslinking monomers include, for example, polyfunctional
vinylaromatics, such as di- or trivinylbenzenes,
divinylethylbenzene, divinyltoluene, divinylxylene,
divinylethylbenzene, or divinylnaphthalene; polyfunctional
allylaromatics, such as di- or triallylbenzenes; polyfunctional
vinyl- or allyl-heterocyclic compounds, such as trivinyl or
triallyl cyanurate or trivinyl or triallyl isocyanurate;
N,N'-C.sub.1-C.sub.6-alkylenediacrylam- ides or -dimethacrylamides,
such as N,N'-methylenediacrylamide or -dimethacrylamide or
N,N'-ethylenediacrylamide or -dimethacrylamide; polyvinyl or
polyallyl ethers of saturated C.sub.2-C.sub.20-polyols having 2 to
4 OH groups per molecule, such as, for example, ethylene glycol
divinyl or diallyl ether or diethylene glycol divinyl or diallyl
ethers; esters of unsaturated C.sub.3-C.sub.12-alcohols or
saturated C.sub.2-C.sub.20-polyols having 2 to 4 OH groups per
molecule, such as allyl methacrylate, ethylene glycol
di(meth)acrylate, glycerol tri(meth)acrylate, or pentaerythritol
tetra(meth)acrylate; divinylethyleneurea, divinylpro-pyleneurea or
divinyl adipate; or aliphatic or cycloaliphatic olefins having 2 or
3 isolated C.dbd.C double bonds, such as hexa-1,5-diene,
2,5-dimethylhexa-1,5-diene, octa-1,7-diene, or
1,2,4-trivinylcyclohexane. Divinylbenzene (as an isomer mixture)
and mixtures of divinylbenzene and aliphatic
C.sub.6-C.sub.12-hydrocarbons having 2 or 3 C.dbd.C double bonds
have proved to be particularly suitable crosslinking monomers. The
crosslinking monomers are in general employed in amounts of 2 to
20% by weight, preferably 2 to 12% by weight, based on the total
amount of polymerizable monomers employed.
[0014] The crosslinking monomers do not have to be employed in pure
form but can also be employed in the form of their technical grade
mixtures of lower purity (such as, for example, divinylbenzene
mixed with ethylstyrene).
[0015] The crosslinked polymers can be further processed to give
anion exchangers in a known manner. The anion exchangers can be
prepared on the one hand by chloromethylation (cf. U.S. Pat. Nos.
2,642,417, 2,960,480, 2,597,492, 2,597,493, 3,311,602, and
2,616,877), preferably with chloromethyl ether, and subsequent
amination (cf. U.S. Pat. Nos. 2,632,000, 2,616,877, 2,642,417,
2,632,001, and 2,992,544) with ammonia, a primary amine, such as
methyl- or ethylamine, a secondary amine, such as dimethylamine, or
a tertiary amine, such as trimethylamine or
dimethylisopropanolamine, at a temperature of as a rule 25 to
150.degree. C.
[0016] On the other hand, the anion exchangers can be prepared by
the aminomethylation process, in which (a) the crosslinked polymers
are reacted with phthalimide derivatives and (b) the resulting
imides are hydrated. The amidomethylation (a) can be carried out by
reaction of the crosslinked polymers with
N-chloromethyl-phthalimide in the presence of swelling agents for
crosslinked polymers and Friedel-Crafts catalysts (DE-A 1,054,715),
the phthalimile derivative being employed in amounts suitable for
the desired level of substitution (0.3 to 2.0 substitutions per
aromatic nucleus) of the aromatic nuclei present in the crosslinked
polymer (or in an excess of up to 20%, preferably up to 10%).
[0017] Suitable swelling agents include halogenated hydrocarbons,
preferably chlorinated C.sub.1-C.sub.4-hydrocarbons. The most
preferred swelling agent is 1,2-dichloroethane.
[0018] Preferred Friedel-Crafts catalysts include, for example,
AlCl.sub.3, BF.sub.3, FeCl.sub.3, ZnCl.sub.2, TiCl.sub.4,
ZrCl.sub.4, SnCl.sub.4, H.sub.3PO.sub.4, HF, and HBF.sub.4. The
catalysts can be employed in amounts of 0.01 to 0.1 mol per mole of
N-chloromethylphthalimide.
[0019] The reaction can be carried out, for example, by a procedure
in which the crosslinked polymer is introduced into a solution of
N-chloromethylphthalimide in a swelling agent and the reactants are
allowed to act in the presence of the catalyst at elevated
temperature, as a rule at 50 to 100.degree. C., preferably 50 to
75.degree. C., until the evolution of hydrogen chloride has
substantially ended. This is in general the case after 2 to 20
hours. After separation of the substituted polymer and liquid
reaction medium and inorganic products, it is advisable to take up
the polymer in aqueous sodium chloride solution and to remove
residues of swelling agent by distillation.
[0020] The hydrolysis (b) of the substituted polymer can be carried
out, for example, by subsequently hydrolyzing the product that has
been isolated with an approximately 5 to 40% strength by weight
aqueous or alcoholic solution of an alkali, such as sodium
hydroxide or potassium hydroxide, or with an approximately 5 to 50%
strength by weight aqueous solution of a mineral acid, such as
hydrochloric acid, hydrobromic acid, or sulfuric acid, in an
autoclave at temperatures between 100 and 250.degree. C. On the
other hand, the intermediate product can also be reacted with a 5
to 50% strength by weight aqueous or alcoholic solution of
hydrazine hydrate at temperatures of 50 to 100.degree. C. In a
preferred embodiment, the solution described last can contain other
alkalis, in particular caustic alkalis, in amounts of 1 to 20% by
weight. The reaction product can be isolated, washed with water and
then heated with an aqueous solution of mineral acid (preferably 5
to 20% strength by weight) to bring the hydrolysis to
completion.
[0021] The aminoalkyl compounds that can be obtained can be
modified by alkylation. Known alkylating agents, such as, for
example, methyl, ethyl, or propyl chlorides and bromides, dialkyl
sulfates, alkylene oxides, halogenohydrins, polyhalogen compounds,
epihalohydrins, and ethyleneimines, can be used for this
purpose.
[0022] The above-mentioned alkylation of the said amino derivatives
can be effected by reaction thereof with alkylating agents in molar
amounts at temperatures of between 20 and 125.degree. C. If, for
example, alkyl halides or dialkyl sulfates are used, it is
advisable to add the amount of an alkaline agent, such as sodium
hydroxide, calcium carbonate, magnesium oxide, and the like,
required for neutralization of the hydrogen halide acids or
alkylsulfuric acids formed. Secondary, tertiary, or quaternary
amino derivatives or mixtures thereof are obtained depending on the
amount of alkylating agent used. A mixture of formaldehyde with
formic acid is another customary alkylating agent which is used in
the form of an aqueous solution, if appropriate in the presence of
mineral acids. The reaction can be carried out with these
alkylating agents at temperatures of between 50 and 120.degree. C.
In the latter case, tertiary amino derivatives are obtained as the
sole reaction products if an excess of alkylating agent is used.
The tertiary amino derivatives can be converted completely or
partly into quaternary derivatives by carrying out a further
reaction with alkylating agents, such as, for example, methyl
chloride, at temperatures of between 10 and 120.degree. C.
[0023] The anion exchangers used can be in gel form or, preferably,
macroporous; those based on polystyrene are preferred. Strongly
basic anion exchangers in the Cl form and weakly basic anion
exchangers in the free base form are particularly preferred.
[0024] Doping of the anion exchangers with platinum metals,
preferably platinum or palladium, can be carried out, for example,
by a procedure in which the platinum metal, preferably platinum or
palladium, in a suitable salt form is taken up by the groups with
ion exchange activity and is then reduced, or reducing substances
are first applied and the platinum metal, preferably platinum or
palladium, is then precipitated on the resin from a suitable
solution. Finally, colloidally dispersed platinum metal that has
already been reduced, preferably platinum or palladium, can also be
taken up adsorptively by the resin from a corresponding solution or
suspension.
[0025] The application process which is particularly preferred in
the present invention starts from the salt form of the resin, which
is first treated with a palladium salt solution (for example, 2 to
20% strength by weight Na.sub.2PdCl.sub.4), the anion on the resin
being exchanged for the anionic palladium complex. The palladium
complex is chiefly distributed in the surface region of the resin
grain, so that the regions which are distinguished by rapid
kinetics are affected above all.
[0026] The reduction of the noble metal bonded ionogenically to the
resin, for example, of palladium to metallic palladium, can be
carried out by reducing agents that are usual for this type of
reduction, such as hydrazine, hydroxylamine, hydrogen, ascorbic
acid, formalin, or formic acid, in strongly alkaline solution at
elevated temperature. Hydrazine or formalin is preferably used.
[0027] The noble metal content, preferably of platinum metal, of
the ion exchangers to be used according to the invention is in
general in the range from 0.3 to 10 g, preferably 0.5 to 1.2 g, per
liter of anion exchanger.
[0028] DE-A 25 24 722 discloses the use of polystyrenes containing
copper ions or cobalt ions for reduction of oxygen dissolved in
water. U.S. Pat. No. 4,789,488 recommends palladium- or
platinum-doped anion exchangers for decreasing the oxygen content
in aqueous systems with hydrogen. In addition to hydrogen, other
reducing agents, such as, for example, hydrazine, have also already
been described for removal of oxygen from water. Cf. F. Martinola
et al., VGB Kraftwerkstechnik 64 (1984), pages 61-63. The use of
metal-doped anion exchangers for simultaneous removal of oxygen and
undesirable ions has also already been discussed. Cf. F. Martinola,
loc. cit.
[0029] It has now been found that this process is very effective in
avoiding discoloration in polycarbonate production by catalytic
reduction of oxygen. The theory described above that the
discoloration is to be attributed to traces of oxygen is thereby
substantiated. Since phenol not only is the main component of the
polycarbonate but is also present in a large excess in the
preparation of bisphenol A and is at the start of the production
sequence it is appropriate to use this process on this starting
material.
EXAMPLE
[0030] Hydrogen at a rate of 50 to 100 l/hour was fed into a phenol
stream having a 10 m.sup.3/hour feed rate in a reactor for the
preparation of bisphenol A. The temperature of the phenol was
50.degree. C. to 80.degree. C.
[0031] The system pressure of the bisphenol A production was in the
range of 3-10 bar at an oxygen feed concentration of 0.1 mg/l to 2
mg/l. The hydrogen-containing stream of phenol was passed through a
reactor upstream of the bisphenol A production which was filled
with a palladized weakly basic anion exchanger (0.5 m.sup.3
Lewatit.RTM. catalyst K3433, manufacturer Bayer AG).
[0032] The height of the resin was 0.5 mm, the specific load was 20
bed volumes/hour and the pressure loss was in the range of 0.08-0.2
bar.
[0033] The oxygen concentration measured in the discharge of the
catalyst bed was only 0.01 to 0.03 mg/l.
[0034] In this procedure, the product discoloration index of the
bisphenol A was 13 to 17 Hazen melt color index.
[0035] If the hydrogen feed was stopped and the stream of phenol
and the catalyst were bypassed, the product discoloration index of
the bisphenol A rose to >17 Hazen melt color index.
[0036] The "Yellowness Index" of the polycarbonate changes
accordingly from .ltoreq.1.7 with phenol treated by the process
according to the invention to .gtoreq.1.7 without the treatment
according to the invention.
* * * * *