Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2001-11-27
2004-05-04
Reddick, Judy M. (Department: 1713)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C521S033000, C568S728000
Reexamination Certificate
active
06730816
ABSTRACT:
The present invention relates to a catalyst composition for significantly increasing the productivity of fixed-bed reactors in the production of bisphenol-A.
Industrial production of bisphenol-A (BPA) currently involves a process whereby 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 by reactor design. Each feed direction has its own advantages and disadvantages. Typically, the flow of the viscous reactant mixture is down-flow. Where the feed directions is downwards, the pressure drop through the sulfonic acid resin catalyst bed is a major problem limiting the throughput of reactants and products, which ultimately limits the production of bisphenol-A. The pressure drop is caused by a variety of factors, including the viscosity and density of both reactants and products, particle size and particle size distribution of catalyst and the compressibility of the catalyst. The compressibility of the sulfonic acid catalyst appears to be an important factor relating to the pressure drop level. The spherical catalyst particles can be compressed/deformed under pressure into a variety of non-spherical or lenticular shapes and a loss in bed void fraction, leading to an exponential reduction in throughput. Moreover, compression of the catalyst bed under pressure can promote the formation of flow channels so that flow through the reactor is not uniform. As a result, the quantity of catalyst used as a whole may not be fully utilized.
An optimized catalyst system for the synthesis of bisphenol-A has been disclosed by Berg et. al. in U.S. Pat. No. 5,395,857. Berg et. al. disclose sulfonic acid catalyst beds for increasing the volume/time yield of fixed-bed reactors in the production of bisphenol-A from phenol and acetone in cylindrical fixed-bed reactors filled with gel-form or macroporous sulfonic acid ion exchange resin catalysts, characterized in that the lower layer of the bed consists of a resin having a low degree of cross-linking (=2%) and makes up 75 to 85% by volume of the bed as a whole and the upper layer of the bed, which makes up 15 to 25% by volume, consisting either of a resin having a higher degree of cross-linking (=2% to =4%), in which 1 to 25 mole % of the sulfonic acid groups may be covered with species containing alkyl-SH units (ionic fixing) or of a resin having a low degree of cross-linking (=2%), in which 1 to 25 mole % of the sulfonic acid groups are covered with species containing alkyl-SH units (ionic fixing).
Yet another catalyst system for the synthesis of bisphenol-A has been disclosed by Kissinger et al. in the International Publication No. WO 00/50372A1. Kissinger et al. discloses an improved process for the production of bisphenol-A employing a catalytic ion exchange resin bed in which the lower portion of the bed is filled with a resin which has a higher degree of crosslinking than the upper layer and the upper portion of the bed is filled with an unmodified resin having a low degree of crosslinking or a resin having a low degree of crosslinking in which 1 to 35 mol % of the sulfonic acid groups are covered with species containing alkyl-SH groups by ionic fixing.
A reactor system for bisphenol-A is also disclosed in International Publication No. WO 97/34688 in which the reactor is operated in an upflow mode with a fixed bed catalyst and randomly distributed reactor packing, employing lightly cross-linked ion exchange resin catalysts, typically containing no greater than 2 to 4% divinylbenzene cross-linking.
It is preferred that in both reactor systems, the catalysts are sulfonated aromatic resins comprising cross-linked polymers, typically polystyrene/divinyl benzene (PS/DVB) copolymers, having a plurality of pendant sulfonic acid groups. In both types of reactor systems, when the catalyst contains 1 to 3% cross-linking, catalyst compression and the resulting pressure drop becomes more limiting than the acetone reaction rate. The compressibility of the catalyst particles can be decreased by increasing the amount of cross-linking material (divinyl benzene) used in the copolymerization. However, as taught in U.S. Pat. No. 5,395,857, increasing the amount of cross-linking material decreases the reactivity and selectivity of the bisphenol-A catalyst to produce BPA.
A process has been discovered in which the pressure drop 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 significantly reduced. According to the present invention, catalyst compressibility can be substantially decreased by cross-linking the PS/DVB copolymer with sulfone bridges during the sulfonation process. Surprisingly, the sulfone cross-linking does not have a negative effect on the activity and selectivity of the catalyst in bisphenol-A production. The sulfonation process used to introduce sulfone cross-linking has also been found to introduce additional sulfonic acid groups so that the average styrene aromatic ring contains more than one sulfonic acid group. The catalysts used in the process of the present invention provide an unexpected combination of desired performance properties in the synthesis of bisphenol A: reactivity, selectivity, compressibility and hydraulic characteristics.
According to present invention, a high productivity catalyst for bisphenol-A has been discovered which comprises strongly acidic cation-exchange resin spheres produced from a polystyrene/divinylbenzene (PS/DVB) copolymer sulfonated under conditions to introduce sulfone cross-linking. Surprisingly, the sulfone cross-linking improves the resistance to deformation but does not have a negative effect on the activity and selectivity of the catalyst in bisphenol-A production. The catalysts used in the process of the present invention provide an unexpected combination of desired performance properties in the synthesis of bisphenol A: reactivity, selectivity, compressibility and hydraulic
The bisphenol-A catalyst of the present invention is characterized in that the spherical catalyst particles substantially resist deformation under pressure as compared to currently known bisphenol-A catalysts and posses higher reactivity as compared to currently known bisphenol-A catalysts.
According to present invention, a high productivity catalyst for bisphenol-A has been discovered which comprises strongly acidic cation-exchange resin spheres produced from a polystyrene/divinyl benzene (PS/DVB) copolymer sulfonated under conditions to introduce sulfone cross-linking.
The spherical bisphenol-A catalyst particles were formed by suspending a mixture of styrene and divinylbenzene monomers and initiators in an aqueous liquid, and subsequently polymerizing the mixture to produce spherical copolymer beads, that when sulfonated to introduce sulfonic acid groups and sulfone crosslinking give a catalyst of surprisingly high reaction rates and low deformation when used to catalyze the conversion of phenol with acetone to bisphenol-A.
The process by which the catalyst is made, comprises suspending a mixture of styrene and divinylbenzene monomers and a free-radical polymerization initiator into an aqueous suspending medium that is agitated to form monomer droplets, heating the droplets to a temperature above the activation temperature of the polymerization initiator until the droplets polymerize, separating the resulting polymer beads from the suspending medium, drying the beads, functionalizing the beads with strongly acidic cation-exchange groups and sulfone cross-links. The process of making such types of ion exchange resin catalysts of uniform particle size without sulfone cross-linking is disclosed by Lundquist in U.S. Pat. No. 5,233,096.
The monounsaturated vinyl aromatic monomers useful in preparing the cross-linked copolymer beads of the present invention include
Johnson Stephen E.
Reddick Judy M.
Rohm and Haas Company
Ziar Witold Andrew
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