DE19757570B4 - Process for the preparation of bisphenol A - Google Patents

Abstract

A process for the preparation of bisphenol A from phenol and acetone in acidic ion exchange resins as catalyst-containing fixed bed reactors in which the ion exchange bed is rinsed with phenol at intervals, between 30 to 3500 m ³ Eduktstrom per m ^{3 of} catalyst resin passed through the reactor between two rinses and the Temperature of the phenol used is 40 to 150 ° C.

Description

The The present invention relates to a method for increasing the Space-time yield in the production of bisphenol A in fixed bed reactors.

method for the synthesis of bisphenol A (BPA) by ion exchange catalysis are known, e.g. from US Pat. No. 4,391,997, US Pat. No. 4,400,555, US Pat. No. 4,590 303 or EP-A 210 366. It is known for the large-scale production of BPA is a mixture of phenol and acetone by a sulfonic acid To conduct ion exchange resins on polystyrene-based filled fixed bed reactor and subsequently to feed the workup. The product flow can either be from top to bottom or from down through the reactor. Both feed directions have advantages and disadvantages. When feeding from above, the Pressure loss through the catalyst bed is a significant problem because throughput limitation is required. The compressive stress of the catalyst measured at the top of the reactor may be certain Do not exceed limits (e.g., 1.5 bar with 4% cross-linked ion exchangers or 1.2 bar in case of 2% cross-linked ion exchangers), otherwise it would lead to a irreversible deformation of the catalyst comes. Will the in the Reactor fed educt amount increased, so the pressure in the Reactor. The amount fed in can only be increased until the limit pressure is reached. This determines the capacity and thus the space-time yield the entire plant. With increasing operating time, it should be noted that at constant feed through the catalyst bed in the reactor caused pressure loss gradually rises so that the fed quantity must be reduced to the limit pressure not To exceed.

Out DE 1 244 796 It is known that the catalytic activity of the cation exchange resins can be increased if the resin is treated with a mercapto alcohol prior to use. EP 559 372 A describes a process for preparing BPA in which at least a portion of the phenol is contacted prior to reaction with a strong acid cation exchange resin and a strong base anion exchange resin and / or a portion of the product mixture and / or a portion of the mother liquor prior to recycling to the reaction mixture is contacted with a strongly acidic cation exchange resin and a strongly basic anion exchange resin. EP 305 774 A discloses a thiazoline-modified ion exchanger which comprises drying known acidic ion exchange resins having very high to quantitative neutralization of the acid groups, then rinsing with the phenol to be used for BPA preparation, and finally neutralizing with thiazolines above the melting point of the phenol.

It it has now been found that this creeping increase of the pressure loss can be eliminated by the ion exchange bed with Purged phenol becomes. After this flushing can restore the original one high amount of reactant are fed into the reactor. The through the rinsing process Conditional loss of production will be back within a short time compensated. Furthermore was found that the flush also a positive effect on the selectivity and reactivity of the fixed beds Has.

The invention therefore relates to a process for the preparation of bisphenol A in acidic ion exchange resins as catalyst-containing fixed bed reactors, in which the ion exchange bed is rinsed at intervals with phenol. The interval is preferably selected so that 30 to 3500 m ³ , particularly preferably 90 to 600 m ³ feed stream per m ^{3 of} catalyst resin are passed through the reactor between two rinses. The ion exchange bed can be flushed with phenol from above, from below or alternately successively from above and below. The preferred practice is to rinse from below or alternately successively from below and from above. Based on the amount of ion exchange resin, the amount of phenol to be used for the rinse is 0.1 to 20 times, preferably 0.3 to 5 times, the catalyst volume. The temperature of the phenol used should be 40 to 150 ° C, preferably 45 to 120 ° C. During the rinsing process, the reactor can be rinsed once or even several times in succession. After the rinsing process, the amount of reactants fed into the reactor can again be increased by up to 35%, which entails a corresponding increase in productivity.

In the reactor, a mixture of phenol, recycled mother liquor (consisting of phenol, bisphenol A and by-products) and acetone is passed from above to the reactor via a line. The reactor is usually filled to 40 to 95% of its volume with ion exchanger. The ion exchange resin has a low crosslinked (0.5-5%) sulfonated polystyrene matrix. The preparation of the ion exchanger from the water-moist form is carried out by dehydration with phenol. In phenol-moist form, the catalyst resin usually has a particle size distribution of 0.3 to 1.0 mm. In the lower conical part of the reactor there is a layer of gravel and sand, which supports the ionic structure scherbettes serves. The reaction mixture flows from top to bottom through the fixed bed. So that the reactor is constantly flooded, the pipeline of the product solution is passed back to the reactor via the reactor outlet. Thereafter, the product mixture flows into a template and from there for further work-up. The quantity control for the feed is made via a pneumatic control valve and a flow meter. The reaction mixture is pumped from a tank with a centrifugal pump into the reactor. The feed temperature is due to the process between 50 and 65 ° C, the discharge temperature in the range of 57 to 90 ° C. The reactor is driven adiabatically; Heat losses are avoided by insulation and an applied heat tracing. The reactor pressure is measured in the feeding line.

The Composition of the reaction mixture at the beginning of the reaction may vary depending on the process in the following areas: phenol 75 to 85% by weight, bisphenol and by-products 12 to 17% by weight, Acetone 2 to 5 wt .-%. Usually is the reaction mixture to accelerate the reaction and increase the Catalyst selectivity Cocatalyst added, z. B. mercaptopropionic acid.

example 1

The reactor diameter is 5.70 m, the reactor volume 150 m ³ , the ion exchange resin is Lewatit SC 102 ^® (Bayer AG), the volume of the catalyst filling 108 m ³ , the catalyst height is 4.25 m.

The original feed quantity of reaction solution into the reactor is 18,000 kg / h, the reactor pressure is 0.95 bar. Over a period of 100 days, the feed amount had to be lowered from 18,000 kg / h to 14,000 kg / h, since the reactor pressure had reached the maximum permissible limit pressure of 1.2 bar over time. The reaction mixture at the exit of the reactor contained 0.36 wt.% Acetone (acetone breakthrough). After 100 days, the phenol rinse was carried out by the feed of the reaction solution to the reactor was turned off and the reactor located in the reaction solution (thereof about 50 m ³ ) by means of a reduced nitrogen pressure of about 1.5 bar within 2 hours from the Reactor over the line (7) is pressed to the workup template. After that, the nitrogen was turned off and the reactor slowly expanded. Then 30 m 3 60 ° C warm phenol were driven over a further 2 h into the reactor from below. The further filling of the reactor with 20 m ^{3 of} phenol was again fed from above into the reactor over 2 h. Thereafter, reaction mixture was returned to the reactor. The first feed rate was 8000 kg / h and was then increased within 48 h to 18000 kg / h. The acetone breakthrough was at the same level as before the rinse, despite the feed rate of about 4000 kg / h at 0.37 wt%, ie the reactivity of the catalyst bed was markedly improved. The reactor pressure was then only 0.9 bar at the high feed. After just 3 days, the infeed caused by the rinsing process and thus reduced production was made up for.

Example 2

The procedure was as in Example 1, with the only difference that the volume of the catalyst filling was only 70 m ³ and the catalyst height accordingly 2.65 m. Again, the feed amount over time of 18000 kg / h had to be lowered to 14000 kg / h, in order not to exceed the maximum allowable limit pressure of 1.2 bar. After the rinsing process initially 10500 kg / h reaction mixture were fed, the load was then increased within 48 h to 18000 kg / h; the reactor pressure increased to 0.9 bar. The acetone punctures are 0.41 wt .-% before rinsing and 0.43 wt .-% after the rinsing process despite the differing by 4000 kg / h feed quantities at the same level.

Claims (3)

A process for the preparation of bisphenol A from phenol and acetone in acidic ion exchange resins as catalyst-containing fixed bed reactors in which the ion exchange bed is rinsed with phenol at intervals, between 30 to 3500 m ³ Eduktstrom per m ^{3 of} catalyst resin passed through the reactor between two rinses and the Temperature of the phenol used is 40 to 150 ° C. Method according to claim 1, where the for the flushing amount of phenol to be used 0.1 to 20 times the catalyst volume is. Method according to claim 1, in which the ion exchange bed successively from below and from above purged with phenol becomes.