COMBINATION ION EXCHANGE RESIN BED FOR THE SYNTHESIS OF
BISPHENOL A
BACKGROUND OF THE INVENTION
This invention relates to a process for fixed-bed reactors in the production of
bisphenol A, sometimes hereinafter referred to as BPA, which employs a catalytic
combination ion exchange resin bed with low pressure drop, low catalyst breakage
and long catalyst life.
Processes for the synthesis of bisphenol A by ion exchange resin catalysis are
known (see, for example, U.S. Pat. Nos. 4,051,079, 4,391,997, 4,400,555, 4,590,303,
5,395,857, JP-A 8 272 972, EP-A 210 366, etc.).
It is known that, in the industrial production of bisphenol A (BPA), a mixture
of excess phenol and acetone is passed through a cylindrical fixed-bed reactor filled
with divinyl benzene cross-linked sulfonated polystyrene ion exchange resin catalyst.
The direction of flow of the mixture may be either downwards or upwards as
required. Each of these feed directions has advantages and disadvantages. Where the
feed direction is dovrawards, the pressure loss through the ion exchange bed is a
major problem on account of the resulting compressibility of the ion exchange resin
used. The spherical resin particles can be deformed under pressure into a lenticular
shape, thus leading to an exponential reduction in throughput. Firm compression of
the catalyst bed can promote the formation of flow charmels so that flow through the
reactor is not uniform. Accordingly, the quantity of catalyst used as a whole may not
be fully utilized.
A process has now been found in which the catalyst breakage and deactivation
rate in the industrial production of bisphenol A from acetone and phenol in a
cylindrical fixed-bed reactor filled with sulfonic acid ion exchange resin catalysts in
large quantities can be greatly reduced. Because of the reduction of catalyst resin bead
breakage and the substantially lowered rate of catalyst deactivation, the catalyst bed
requires less frequent changeovers minimizing lost production time while, at the same
time, maintaining efficient pressure drop levels.
Hydraulic problems of the type in question have been observed in particular
with ion exchange resin catalysts having a low degree of crosslinking (i.e., less than
2%). On the other hand, these very ion exchange resin catalysts represent an optimum
in regard to catalyst bead integrity, reactivity, selectivity and maintenance of catalyst
activity in the synthesis of bisphenol A.
Although, with ion exchange resin catalysts having a higher degree of
crosslinking (i.e. greater than 2% up to about 4%), the hydraulic problems of the low
degree of crosslink resin beds decrease with increasing degree of crosslinking, the
friability and deactivation rate of such catalysts in the synthesis of BPA also decrease
catalyst life to a considerable extent.
The effect of a higher degree of cross-linked catalyst in BPA syntiiesis is
most pronounced in the catalyst at the portion of the resin catalyst bed which makes
up the upper layer of the resin catalyst bed and which is initially in contact with the
full force of the reactant mixture as it enters the resin catalyst bed. It has been
observed that, the catalyst beads with a higher degree of cross-linking, i.e., greater
than 2% to about 4%, which are at the top of the bed (downstream case), break to a
large extent within a very short period of operation of the resin catalyst bed. This
breakage then leads to extremely high pressure drops because the fractured particles
clog the flow channels through the bed and severely impede its efficient operation.
On the other hand, catalyst beads with a low degree of cross-linking, i.e., 2%
or less, and high intrinsic flexibility when making up the upper layer of the resin
catalyst bed which is initially in contact with the full force of the reactant mixture as it
enters the resin catalyst bed withstand the force of the reactant mixture influx, do not
show perceptible breakage and do not clog the flow channels so that the efficiency of
the resin catalyst bed is maintained and the life of the resin catalyst bed is
substantially extended.
One way of improving the hydraulic quality of lightly crosslinked resin beds is
to cover some of the sulfonic acid groups with cations. Partial covering with -NH3
CH2 CH2 SH or similar systems, as described for example in DE-A 3 619 450 and
U.S. Pat. No. 3,394,089, is particularly advantageous. In addition to embrittlement
and hence greater rigidity of the ion exchange resin, a catalytic effect of the groups in
the synthesis of BPA is also observed. However, the useful life of such systems is
shortened by a factor of approximately 10 compared with unmodified resin systems
by deactivation of the co-catalytic unit and is therefore uneconomical. The necessary
subsequent regeneration of the large quantities of the sulfonated divinylbenzene
cross-linked resin catalyst is time-consuming and expensive and has to be replaced
by an equally large quantity of fresh ion exchange resin to maintain the output of
BPA.
A resin catalyst bed meeting the long felt need for a catalytic combination ion
exchange resin bed with low pressure drop, low catalyst breakage and long catalyst
life has now been found. The desirable characteristics of low breakage, less clogging
and long catalyst life are found with both attached promoter catalysts as well as bulk
promoted catalysts. Further, the shock absorbing layer of ion exchange resin catalyst
with a low degree of cross-linking, i.e., 2% or less, causes a rapid reaction of a high
percentage of acetone fed into the catalyst bed, thus, substantially reducing the
formation of harmful tars and precursers which block the reactive sites on the ion
exchange resin catalyst with a higher degree of crosslinking, i.e., greater than 2% to
about 4%. This enables the more rigid ion exchange resin catalyst with a higher
degree of crosslinking to continue to perform without loss of efficiency for a longer
period of time because of the reduction or elimination of tar build up.
SUMMARY OF THE INVENTION
The ion exchange bed for producing bisphenol A from phenol and acetone in a fixed
bed reactor containing a gel-form or macroporous sulfonic acid ion exchange resin
catalyst bed of the present invention is a resin catalyst bed having an upper layer and
a lower layer wherein:
the lower layer comprises a resin which has a higher degree of crosslinking than the
upper layer, preferably greater than 2%, more preferably, from greater than 2% to
about 4%, and which comprises from 50 to 95%, preferably, from 75 to 85%, of the
bed volume as a whole and
the upper layer of the bed, which comprises from 5 to 50%, preferably, from 15 to
25%, of the bed volume as a whole, comprises either
an unmodified resin having a low degree of crosslinking, preferably 2% or less, or
a resin having a low degree of crosslinking, preferably 2% or less, in which 1 to 35
mol % of the sulfonic acid groups are covered with species containing alkyl-SH
groups by ionic fixing.
DETAILED DESCRIPTION OF INVENTION
The process for preparing bisphenol A from phenol and acetone in a fixed bed reactor
containing gel-form or macroporous sulfonic acid ion exchange resins in the form of a
resin catalyst bed of the present invention comprises a process passing a mixture of
phenol and acetone through a resin catalyst bed having an upper layer and a lower
layer wherein:
the lower layer comprises a resin which has a higher degree of crosslinking than the
upper layer, preferably greater than 2%, more preferably, from greater than 2% to
about 4%, and which comprises from 50 to 95%, preferably, from 75 to 85%, of the
bed volume as a whole and
the upper layer of the bed, which comprises from 5 to 50%, preferably, from 15 to
25% of the bed volume as a whole, comprises either
an unmodified resin having a low degree of crosslinking, preferably 2% or less, or
a resin having a low degree of crossiinking, preferably 2% or less, in which 1 to 35
mol % of the sulfonic acid groups are covered with species containing alkyl-SH
groups by ionic fixing.
In a preferred embodiment, the lower layer of the ion exchange bed has a degree of
crossiinking from equal to or greater than 2% to less than or equal to 4%.
In another preferred embodiment, the lower layer of the ion exchange bed is a resin
in which from 1 to 25 mol % of the sulfonic acid groups are covered with species
containing alkyl-SH groups by ionic fixing
In still another preferred embodiment, the upper layer of the ion exchange bed has a
degree of crossiinking less than or equal to 2%. This upper layer is either an
unmodified resin or a resin in which from 1 to 35 mol % of the sulfonic acid groups
are covered with species containing alkyl-SH groups by ionic fixing.
Ionic fixing is described in DE-A 3 619 450 or in U.S. Pat. No. 3,394,089.
In the practice of the process of the present invention, it is preferred that the flow of
acetone and phenol proceed from above the bed down through the bed. This is the
flow pattern conventionally used in the process for making BPA. However, if for any
reason it is desired to reverse the flow of the phenol and acetone through the bed, i.e.,
pass the phenol and acetone up through the bed from the bottom, the benefits of
longer bed life, lower catalyst breakage and high yields of BPA can still be achieved
merely by reversing the layers so that the resin with the lower cross-link density is on
the bottom and the resin with higher cross-link density is on the top. The key is to
have the resin with the lower cross-link density cover the surface of the bed through
which the phenol and acetone enter the bed to minimize catalyst breakage by
absorbing the impact of the frill force of the incoming phenol and acetone mixture.
Thus, in the description of the present invention it is intended that the upper layer be
construed as the layer through which the phenol and acetone mixture enters the resin
catalyst bed and the lower layer be construed as the layer through which the reacted
mixture exits the resin catalyst bed.
It has been surprisingly found that employing as the upper layer of the resin catalyst
bed a resin with a lower degree of cross-linking and as the lower layer of the resin
catalyst bed a resin with a higher degree of cross-linking, resin catalyst bed life is
extended because catalyst fouling and deactivation and fracturing of the catalyst
resin beads are reduced. Further, employing the resin with a higher degree of cross-
linking in a preferred embodiment of the present invention as the major component of
the resin catalyst bed, provides increased yields of BPA at high production rates.
From the hydraulic point of view, resin beds according to the invention behave
as if the lower rigid resin layer were the sole filling of the reactor, i.e. the capacity of
the reactor is no longer determined by the hydraulics of the filling, but instead by the
acetone conversion which proceeds at a particularly high rate of reaction in the lower
crosslinked top layer of the catalyst resin bed.
In addition to its favorable hydraulic properties in the synthesis of BPA, the
two layer combination bed of the present invention surprisingly shows the excellent
reactivity and selectivity behavior of a resin bed entirely consisting of a lightly
crosslinked ion exchange resin type, having a cross-link density of equal to or less
than 2%.
In a preferred embodiment of the process of the present invention, a mixture of
phenol, recycled mother liquor (consisting of phenol, bisphenol A and secondary
products) and acetone is introduced into the reactor from above through a pipe. The
reactor is normally filled with ion exchange resin to between 50 and 80% of its total
volume. The water-wet ion exchange resin catalyst can be dried or partially dried
prior to charging it to the reactor, the advantage being that dried or partially dried ion
exchange resin catalyst shrinks during the drying stage and does not shrink during
dehydration with phenolic compounds. Hence, more ion exchange resin catalyst can
be charged in the reactor and the 2 catalyst layers will not being disturbed during the
dehydration stage.
In the lower part of the reactor, there is a layer of mineral material as carrier
for the resin bed. The reaction mixture flows downwards through the fixed
bed. The reaction solution exits from the reactor at its lower end and Is then
subjected to further processing.
The feed volume is normally controlled by a pneumatic control valve and a
through flow meter. The feed temperature is In the range from 5(fC to 62''C;
the discharge ten^rature is in the range from 75*C to SS^C. The reactor is
operated under adiabatic conditions. Heat losses are avoided by insulation
and backup heating. The pressure loss through the resin catalyst bed is
measured in the upper part of the reactor. For safety reasons, introduction of
the reaction mixture is stopped when the pressure loss caused by the resin
catalyst bed reaches 2 bar.
The composition by weight of the reaction mixture introduced into the reactor
may vary within the following limits: phenol 75-36% by weight, bisphenol A
and secondary products 12-20% by weight and acetone 2-6% by weight.
Example 1 (Comparison)
A BPA reactor, was charged with sulfonated polystyrene (4% cross-linked
with divinytbenzene) resin ton exchange catalyst
At a reactor feed rat e of 1.0 WHSV, a temperature of 68®C, a pressure drop
of 0.65 bar and a conversion of 96% was obsen/ed. Using a 1.3 WHSV feed
rate, the pressure drop increased to 1.1 bar.
Example 2
The same BPA reactor as employed in Example 1 was charged with an equal
weight of catalyst as In Example 1,90% by weight (on a dry basis) of a
sulfonated polystyrene (4% cross-Jinked with divinylbenzene) catalyst (same
bead size as In Example 1) as a tower layer of the resin catalyst bed and 10%
by weight (on dry
basis) of a sulfonated polystyrene (2% cross-linked with divinylbenzene) catalyst
were charged to the reactor as the upper layer of the resin catalyst bed. Surprisingly,
the pressure drop neither increased nor decreased due to the upper layer of 2%
catalyst. Using the same feed and temperature conditions as described in example 1,
and a feed rate of 1.0 WHSV hour, a pressure drop of only 0.67 bar was observed. At
a 1.3 WHSV feed rate, all other conditions the same, the pressure increased to 1.1 bar.
Example 3 (Comparison)
The ion exchange resin catalyst bed of Example 1 was simulated in a
laboratory scale reactor to illustrate the effect of the direct impact of the BPA
feedstock on a ion exchange resin bed with a top layer of 4% crosslinked resin beads.
5 grams of commercially available 4% cross-linked ion exchange resin catalyst was
charged to the laboratory reactor. A feed mixture typical of feeds employed in the
commercial manufacture of bisphenol-A containing 77% by weight of phenol, 6% by
weight acetone and 17% by weight of bisphenol-A and other compounds present in
bisphenol-A plant recycle streams was charged to the reactor in the downflow mode
at 70°C. and a WHSV of 10 for a period of 16 days. The conversion on the first day
was 4.2 grams per hour. The conversion on the 16th day was 3.4 grams per hour.
Example 4
The ion exchange resin catalyst bed of the present invention was simulated in
a laboratory scale reactor to illustrate the improved BPA catalyst performance
because of reduced ion exchange resin catalyst bead breakage and catalyst fouling
resulting from the direct impact of the BPA feedstock on an ion exchange resin bed
with a top layer of 2% crosslinked resin beads in accordance with the present
invention. 2.5 grams of commercially available 2% cross-linked ion exchange resin
catalyst was charged to the laboratory reactor on top of 2.5 grams of commercially
available 4% cross-linked catalyst previously charged to the laboratory reactor. A
feed mixture typical of feeds employed in the commercial manufacture of bisphenol-
A containing 77% by weight of phenol, 6% by weight acetone and 17% by weight of
bisphenol-A and other compounds present in bisphenol-A plant recycle streams was
charged to the reactor in the downflow mode at 70°C. and a WHSV of 10 for a period
of 16 days. The conversion on the first day was 4.74 grams per hour The conversion
on the 16th day was 4.59 grams per hour.
WHAT IS CLAIMED:
1. In an ion exchange bad for producing bisphenol A from phenol and
acetone in a fixed bed nsador containing a ge^form or macroporous sulfonic
acid ion exchange resin catalyst bed, wherein the reaction mixture enters at
the top of the fixed bed, the improvenrient compriaing a resin catalyst bed
having an upper layer and a lower layer Mierein:
the lower layer comprises a resin which has a higher degree of crosslinKIng
than the upper layer and which comprises 50 to 95% of the bed volume as a
whole and
the upper layer of the bed. which comprises 5 to 50% of the bed volume as a
whole, comprises either
an unmodified resin having a degree of crosslinking of less than, or equal to
2%. or
a resin having a degree ol crosslinking of less than or equai to 2% in which 1
to 35 mol % of the sulfonic acid groups are covered with species containing
alkyi-SH groups by ionic fixing.
2. The ion exchange bed of daim 1 wherein the lower layer has a degree
of crosslinldng finom greater than 2% to (ess than or equal to 4%.
3. TYyo ion exchange bed of daim 2 wherein the lower layer is a resin in
which 1 to 25 mol % of tfte sulfonic add groups are covered with species
containing alliyl-SiH groups by ionic fixing.
4. The ion exchange bed of daim 1 wherein the upper layer has a degree
of crosslinking less than 2%.
5. The km exchange bed of daim 4 wherein the upper layer is an
unmodified resin.
6. The ion exchange bed of claim 4 wherein the upper layer is a resin in
which 1 to 26 mol % of the sulfonic acid groups are covered with species
containing aikyl-SH groups by ionic fixing.
7. The ion exchange bed of daim 1 wherein the lower layer comprises 75
to 85% of the bed volume as a whole and the upper layer comprises 15 to
25% of the bed volume as a whole.
8. In a process for preparing bisphend A from phenol and acetone In a
fixed bed reactor containing geMbrm or macroporous sulfonic acid ion
exchange resins in ttw form of a resin catalyst bed. wherein the reaction
mixture enters at the top of the fixed bed, the improvement which comprises
passing a mixture of phenol and acetone thiX}ugh a nssin catalyst bed having
an upper layer and a tower layer wherein:
the lower layer comprises a resin which has a higher degree of croaslinking
than the upper layer and which comprises 75 to 85% of the bed volume as a
whole and
the upper layer of the bed. which comprises 15 to 25% of the bed volume as a
whole, comprises either
an unmodified resin having a degree of crossiinking of less than or equal to
2%. or
a resin having a degree of crossHnking of less than or equal to 2% in whkrh 1
to 35 moi % of the sulfonk; ackl groups are covered with species containing
alkyl-SH groups by ionic fixing.
9. The pnoceas of daim 8 ^^lerein the bwer layer has a degree of
crossiinking from greater than 2% to less than or equal to 4%.
10. The process of daim 8 wherein the tower layer has 1 to 25 moi % of
the sulfonic add groups are optionally covered with species containing alkyi-
SH groups by Ionic fixing.
11. The process of dahn 7 wherein the upper layer has a degree of
crosslinking less than 2%.
12. The process of daim 11 wherein the upper layer is an unmodified
resin.
13. The ion exchange bed of dalm 11 wherein the upper layer is a resin in
which 1 to 25 mol % of the sulfonic acid groups are covered with species
containing atkyl-SH groups by ionic fixing.
14. The ion exchange bed of claim 6 wherein the lower layer comprises 75
to 85% of the bed volume as a whole arKl the upper layer comprises 15 to
25% of the bed volume as a whole.
15. The process of daim 1 wherein at least one of the layers has been at
least partlaiiy dehydrated.
16. The process of daim 15 wherein both of the layers have been at least
partially dehydrated.
17. The prooees of daim 15 wherein at least one of the layers has been
totally dehydrated.
18. The process of daim 15 wherein both of the layers have been totally
dehydrated.
19. (n a process for preparing bisphenol A from phenol and acetone in a
fixed bed reactor containing gel-form or macroporous sulfonic add ion
exchange resins in the fomn of a resin catalyst bed. wherein the reaction
mixture enters at the (op of the fixed bed, the improvement which comprises
passing a mixture of phenol and acetone through a resin catalyst bad havnig
an uppar layer and a lower layer wherein:
the lower layer comprises a resin which has a higher degree of crossKnking
than the upper layer and which comprises 75 to 85% of the bed volume as a
whole and
the upper layer of the bed. which comprises 15 to 25% of the bed volume as a
whole, comprises either
an unmodified resin having a degree of crosslinking of less than or equal to
2%. or a resin having a degree of crosslinking of less than or equal to 2% in
which 1 to 35 mol % of the sulfonic acid groups covered with species
containing alkyl-SH groups by ionic fixing.
20. The process of claim 19 wherein the lower layer has a degree of
crosslinking from greater than 2% to less than or equal to 4%.
21. The process of daim 20 wherein the lower layer has 1 to 25 mol % of
the sulfonic acki groups opttonally covered with species containing atkyl-5H
groups by ksnic fixing.
22. The process of daim 19 wherein the upper layer has a degree of
crosslinking less than 2%.
23. The prooess of daim 22 wherein the upper layer is an unmodified
resin.
24. The prooesa of daim 19 wherein at least one of the layers has been at
least partially dehydrated.
25. The process of daim 24 wherein both of the layers have been at least
partially dehydrated.
26. The process of claim 24 wherein at least one of the layers has been
totally dehydrated.
27. The process of daim 24 wherein both of the layers have been totally
dehydrated.

The invention is a catalytic ion exchange resin bed with low pressure drop,
low catalyst breakage and low catalyst deactivation as well as an improved process
for the production of bisphenol A employing such a catalytic ion exchange resin bed.