Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Ion-exchange polymer or process of preparing
Reexamination Certificate
2001-04-09
2002-11-26
Zitomer, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Ion-exchange polymer or process of preparing
C521S033000, C568S727000, C568S728000, C568S723000
Reexamination Certificate
active
06486222
ABSTRACT:
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 downwards, 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 channels 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 synthesis 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 —NH
3
CH
2
CH
2
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 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.
In a preferred embodiment, the lower layer of the ion exchange bed has a degree of crosslinking from equal to or greater than 2% to le
Acharya Harish R.
Kissinger Gaylord M.
Peemans Rudy Francois Alain J.
Schlarmann Eduard H.
Shafer Sheldon J.
General Electric Company
Zitomer Fred
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