Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2000-12-19
2002-07-02
Shippen, Michael L. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C502S158000, C568S727000
Reexamination Certificate
active
06414200
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to silylmethanethiols and their use as promoters in the reaction of hydroxyaromatic compounds with aldehydes and ketones in the presence of an acidic catalyst to afford bisphenols, such as bisphenol A (BPA).
Bisphenols, as exemplified by BPA, are widely employed in the manufacture of polymeric materials and are typically prepared by condensation of a hydroxyaromatic compound with an aldehyde or ketone in the presence of an acidic catalyst. Bisphenol A (BPA) is the principal monomer used in the manufacture of bisphenol A polycarbonate, a commercial engineering thermoplastic material. The manufacture of bisphenol A (BPA) from acetone and phenol is practiced globally on a large scale with hundreds of millions of pounds of BPA produced annually. Typically, phenol is reacted with acetone in the presence of an acidic catalyst and a thiol promoter. The thiol promoter acts to improve the rate and selectivity of BPA formation in the acid catalyzed condensation of phenol with acetone. Many different combinations of acidic catalysts and thiol promoters have been investigated and some thiol promoters such as 3-mercaptopropionic acid have been employed in the commercial scale production of BPA. Notwithstanding earlier research efforts and their attendant impressive process improvements in the manufacture of bisphenols such as bisphenol A, there is a continuing need to improve further both the rate and selectivity of bisphenol formation in the acid catalyzed condensation of hydroxyaromatic compounds with aldehydes or ketones.
BRIEF SUMMARY OF THE INVENTION
In one aspect the present invention relates to A method for making a bisphenol, said method comprising contacting a mixture comprising a hydroxyaromatic compound and a ketone or an aldehyde with an acidic catalyst at a temperature in a range between about 25° C. and about 95° C. in the presence of a silylmethanethiol promoter having structure I:
wherein
R
1
and R
2
are each independently hydrogen, a C
1
-C
40
aliphatic radical, a C
3
-C
40
aromatic radical, a C
3
-C
40
cycloaliphatic radical, or
R
1
and R
2
together form a C
3
-C
40
cycloaliphatic radical or a C
4
-C
40
aromatic radical;
R
3
-R
5
are each independently a C
1
-C
40
aliphatic radical, a C
3
-C
40
aromatic radical, or a C
3
-C
40
cycloaliphatic radical; or
any two of the groups R
3
-R
5
together form a C
5
-C
40
cycloaliphatic radical or C
5
-C
40
aromatic radical; or
the groups R
3
-R
5
together form a C
9
-C
40
cycloaliphatic radical or C
10
-C
40
aromatic radical.
DETAILED DESCRIPTION OF THE INVENTION
The present invention may be understood more readily by reference to the following detailed description of preferred embodiments of the invention and the examples included herein. In this specification and in the claims which follow, reference will be made to a number of terms which shall be defined to have the following meanings.
The term “thiol promoter” as used herein refers to a molecule incorporating a thiol (SH) group. The thiol promoter acts to improve either one of, or both, the rate and selectivity of bisphenol formation when a hydroxyaromatic compound is condensed with an aldehyde or ketone in the presence of an acidic catalyst relative to the same reaction carried out in the absence of the thiol promoter.
The term “silylmercaptan” as used herein refers to a molecule incorporating a thiol (SH) group and a silicon atom. “BPA” is herein defined as bisphenol A and is also known as 2,2-bis(4-hydroxyphenyl)propane, 4,4′-isopropylidenediphenol and p,p-BPA.
“o,p-BPA” is herein defined as o,p-bisphenol A and is also known as 2-(2-hydroxyphenyl)-2-(4-hydroxyphenyl)propane and 2,4′-isopropylidenediphenol.
As used herein the term “aromatic radical” refers to a radical having a valency of at least one and comprising at least one aromatic group. Examples of aromatic radicals include phenyl, pyridyl, furanyl, thienyl, imidazolyl, naphthyl, phenylene and biphenyl groups. The term includes groups containing both aromatic and aliphatic components, for example a benzyl group. Further, a C
3
-C
40
aromatic radical is an aromatic radical comprising between 3 and 40 carbon atoms. The 2-imidazolyl group (i)
illustrates a C
3
aromatic radical.
As used herein the term “aliphatic radical” refers to a radical having a valency of at least one and comprising a linear or branched array of atoms which is not cyclic. The array may include heteroatoms such as nitrogen, sulfur and oxygen or may be composed exclusively of carbon and hydrogen. Examples of aliphatic radicals include methyl, methylene, ethyl, ethylene, hexyl, and hexamethylene groups.
As used herein the term “cycloaliphatic radical” refers to a radical having a valency of at least one and comprising an array of atoms which is cyclic but which is not aromatic. The array may include heteroatoms such as nitrogen, sulfur and oxygen or may be composed exclusively of carbon and hydrogen. Examples of cycloaliphatic radicals include cyclcopropyl, cyclopentyl cyclohexyl and tetrahydrofuranyl groups.
As used herein the term “carbamyl group” refers to a functional group comprising the array of atoms OCONH. For example a carbamyl group is present the product of reaction of an alcohol with an isocyante as illustrated by the compound 1-naphthyl methylcarbamate, CAS No. 63-25-2.
As used herein the term “Boc group” refers to a an amine protecting group comprising the tertiary-butoxycarbonyl moiety. The combination of a nitrogen atom bearing both a hydrogen atom and the Boc group is an example of a carbamyl group.
The instant invention provides a method of preparing a bisphenol, such as bisphenol A, by acid catalyzed condensation of a hydroxyaromatic compound, such as phenol, with an aldehyde, such as butanal, or ketone, such as acetone, in the presence of a silylmethanethiol promoter having structure I.
In one embodiment of the present invention at least one of the groups R1-R5 contains a basic functional group by which the silylmethanethiol promoter may be attached to a solid catalyst such as a sulfonated polystyrene catalyst by virtue of a strong hydrogen bonding interaction between the silylmethanethiol promoter containing said basic functional group and the catalyst. The silylmethanethiol promoter is thus immobilized on the solid catalyst thereby avoiding the necessity of introduction of the silylmethanethiol promoter with the feed stream, and the eventual recovery of the silylmethanethiol promoter from the product stream. Functional groups which are sufficiently basic to facilitate ionic attachment of the promoter to a polymeric acid catalyst include, but are not limited to amino and pyridyl groups. In some instances the thiol promoter does not contain a functional group which is basic per se, yet the thiol promoter does contain a functional group capable of forming one or more hydrogen bonds with sulfonic acid (SO
3
H) or sulfonate (SO
3
−
) groups present in the polymeric acid catalyst, said hydrogen bonds being sufficiently strong to immobilize the thiol promoter on the polymeric acid catalyst. Examples of said functional groups present in the thiol promoter being amido, imido and carbamyl groups as are found in amides, imides and carbamates respectively.
Silylmethanethiols having structure I are known in the chemical
literature and methods for their preparation have been described in, for example, J. Org. Chem. 53(5) 844 (1987); J. Org. Chem. 51(18) 3428 (1986); and Tetrahedron Letters 26 (11) 1425 (1985). In some instances silylmethanethiols having structure I are commercially available as in the case of trimethylsilylmethanethiol which is available from TCI Chemical Company, Portland, Oreg. Other members of this class may be prepared by reaction of a chloromethylsilane having structure II with a sulfur nucleophile such as sodium sulfide, sodium thioacetate or thiourea. Where sodium sulfide is employed the silylmethanthiol I is obtained directly. Where the thioacetate is employed as a nucleophile, acetate derivative III is obtained. The acetate der
Eddy-Helenek Victoria Jean
Spivack James Lawrence
Webb Jimmy Lynn
Wetzel Joseph Richard
Caruso Andrew J.
General Electric Company
Johnson Noreen C.
Shippen Michael L.
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