Polyorganosiloxane catalyst

Details Polyorganosiloxane catalyst Polyorganosiloxane catalyst

2000-04-04

2001-05-08

Shaver, Paul F. (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Silicon containing

C502S158000, C502S168000, C528S030000, C568S727000

Reexamination Certificate

active

06229037

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polyorganosiloxane catalyst, more specifically a polyorganosiloxane catalyst with both of a sulfonic acid group-containing hydrocarbon group and a mercapto group-containing hydrocarbon group. Such catalyst is used as the catalyst for producing bisphenol A by the dehydration-condensation of acetone and phenol.
2. Description of the Related Art
Bisphenol A [2,2-bis(4′-hydroxyphenyl)propane] is generally produced continuously in the mode of so-called flow reaction on fixed bed, comprising passing acetone and phenol of an excess of 8-fold to 15-fold in molar ratio to solid catalysts.
Conventionally, a technique using cation exchange resin or mercapto-modified cation exchange resins as such solid catalysts has been known, and in the mercapto-modified cation exchange resins, the mercaptoalkylamine are partially neutralized and mercapto group is fixed on cation exchange resins.
Concerning solid catalysts other than the ion exchange resin catalysts, additionally, a technique using polyorganosiloxane catalysts with both of a sulfonic acid group-containing hydrocarbon group and a mercapto group-containing hydrocarbon group as solid catalysts is described for example in U.S. Pat. No. 5,631,338, U.S. Pat. No. 5,789,628, EP-A-765,897, and EP-A-856,505. Compared with ion exchange resin catalysts, the polyorganosiloxane catalysts are known to have very high catalytic activity and selectivity.
These polyorganosiloxane catalysts are generally porous substances synthetically produced by so-called sol-gel process comprising hydrolysis of alkoxysilanes of different types and subsequent dehydration-condensation; and the porous substances comprise a macro-porous region of a pore size of 200 angstroms or more and a meso-porous region of a pore size within a range of 20 to 200 angstroms. The mean pore size in the meso-porous region is generally 20 to 100 angstroms. So as to recover high catalytic activity, generally, the specific surface area is 500 to 1500 m
2
/g; and the total amount of the sulfonic acid group-containing hydrocarbon group and the mercapto group-containing hydrocarbon group is generally about 2.5 to 8.5 &mgr;mol per unit surface area (1 m
2
).
In case that polyorganosiloxane catalysts are used for flow reaction on fixed bed to produce bisphenolA, additionally, it has been known that the catalyst life of the polyorganosiloxane catalysts can be prominently improved by adding a trace amount of water to the starting materials acetone and phenol, as in the case of the use of mercapto-modified cation exchange resin catalysts described in Japanese Patent Laid-open No. 172241/1994 for flow reaction on fixed bed.
However, the serious problem of the polyorganosiloxane catalysts, namely the continuous decrease of the catalytic activity thereof as the reaction time passes even by the addition of water to the raw materials, has not yet been overcome. Thus, the polyorganosiloxane catalysts have not yet been applied industrially.
As described above, the currently known polyorganosiloxane catalysts cannot be applied in practice because the deterioration of the catalysts, namely the continuous decrease of the catalytic activity as the reaction time passes, is serious. When such catalysts are charged as they are on fixed bed, problematically, the frequency of the exchange of the catalyst is increased, involving the elevation of the production cost of the resulting product, which is industrially disadvantageous.
Accordingly, it is a purpose of the invention to provide a catalyst with the deterioration thereof under suppression.
SUMMARY OF THE INVENTION
The present inventors have made investigations so as to overcome such problems. Consequently, the inventors have found that, by modifying the total amount (active site amount) of the sulfonic acid group-containing hydrocarbon group and the mercapto group-containing hydrocarbon group in a polyorganosiloxane catalyst with both of the sulfonic acid group-containing hydrocarbon group and the mercapto group-containing hydrocarbon group, unexpectedly, the reduction of the active site amount extremely suppresses the deterioration of the catalyst, with almost no deterioration of the high catalytic activity. More specifically, the inventors have found that by controlling the active site amount within an appropriate range per unit surface area of the polyorganosiloxane catalyst, the deterioration of the catalyst can significantly be suppressed, with no deterioration of the catalytic activity, so that bisphenol A can continuously be produced at a high yield and a high selectivity. Thus, the invention has been achieved.
That is, the invention relates to a polyorganosiloxane catalyst with both of a sulfonic acid group-containing hydrocarbon group and a mercapto group-containing hydrocarbon group, wherein the total amount of the sulfonic acid group-containing hydrocarbon group and the mercapto group-containing hydrocarbon group is regulated within a range of 0.5 to 2.0 &mgr;mol per unit surface area (1 m
2
) of the polyorganosiloxane catalyst and a process for producing bisphenol A comprising the dehydration-condensation of acetone and phenol in the presence of said polyorganosiloxane catalyst.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The polyorganosiloxane catalyst with a sulfonic acid group-containing hydrocarbon group and a mercapto group-containing hydrocarbon group in accordance with the invention means a polyorganosiloxane described in U.S. Pat. No. 5,631,338, EP-A-765,897, and EP-A-856,505, wherein the polyorganosiloxane is of a structure such that the sulfonic acid group-containing hydrocarbon group and the mercapto group-containing hydrocarbon group are partially bonded via carbon-silicon bonding or mercapto group-silicon bonding directly to the silicon atoms in the silica matrices comprising siloxane bonds.
Theoretically, the total amount (hereinafter referred to as active site amount) of the sulfonic acid group-containing hydrocarbon group and the mercapto group-containing hydrocarbon group in the polyorganosiloxane catalyst with both of the sulfonic acid group-containing hydrocarbon group and the mercapto group-containing hydrocarbon group can be modified up to about 8.00 mmol/g; however, a too large amount of the sulfonic acid group-containing hydrocarbon group makes the resulting polyorganosiloxane water soluble, so that the polyorganosiloxane can never be used as a solid catalyst. Furthermore, the increase of the active site amount induces great reduction of the specific surface area, with the resultant severe deterioration of the catalytic activity. So as to recover a polyorganosiloxane with a high catalytic activity, therefore, the total amount of the sulfonic acid group-containing hydrocarbon group and the mercapto group-containing hydrocarbon group, namely the active site amount, is generally 3.0 mmol/g or less. On a unit surface area basis, the value is converted to a range of 2.0 to 6.0 &mgr;mol/m
2
in case that the specific surface area is 500 to 1500 m
2
/g.
In accordance with the invention, importantly, it is found that the catalytic life of the polyorganosiloxane catalyst can be improved while the high activity of the polyorganosiloxane catalyst is retained, by further reducing theactive siteamounttoa farlowervalue. More specifically, by controlling the active site amount within a range of 0.3 to 2.0 &mgr;mol/m
2
, preferably within a range of 0.5 to 1.6 &mgr;mol/m
2
, more preferably within a range of 0.6 to 1.3 &mgr;mol/m
2
per unit surface area of a polyorganosiloxane catalyst, the resulting polyorganosiloxane catalyst can retain a high catalytic activity while the deterioration thereof is suppressed. Additionally, the specific surface area of the catalyst is in no way with any specific limitation, but preferably, the specific surface area thereof is preferably within a range of 500 to 1500 m
2
/g, more preferably within a range of 600 to 800 m
2
/g.
In accordance with the invention, any hydrocarbon group with at least one s

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