CS252797B1 - Catalyst for acrylic acid esterification - Google Patents

Abstract

The solution concerns increasing the service life of an ion exchange catalyst for the esterification of acrylic acid or transesterification of acrylic esters in a liquid medium. The increased service life is achieved by swelling the ion exchange in the reaction medium to 2.4 times compared to the dry state. This is related to achieving good permeability of the polymer skeleton of the ion exchange catalyst and thus increased resistance to fouling of the skeleton by products of polymerization of acrylic compounds.

Description

The invention relates to the use of a special ion exchange catalyst, produced in accordance with Czech Patent Application No. AO 214 091, for catalyzing the esterification of acrylic acid or the transesterification of acrylic acid esters in a liquid medium.

In the chemical industry, acidic organic ion exchangers are increasingly being used as heterogeneous catalysts _. They catalyze reactions such as alkoxylation, hydration, dehydration or esterification. A special case of using ion exchange catalysts is the esterification of acrylic acid. The function of the catalyst is threatened here by the possibility of clogging of the ion exchange particles with polymers, which are always formed to a certain extent from the starting acrylic acid and the produced esters. When using ion exchange catalysts in a liquid medium, the reaction does not take place only on the pore walls or on the geometric surface of the ion exchange particles, but mainly takes place inside the polymer mass of the ion exchange. The deposition of acrylic polymers in the polymer skeleton of the ion exchange mass reduces its permeability, thereby slowing down the transport of reactants to the functional groups of the ion exchange, and the result is a gradual decrease in the activity of the ion exchange catalyst. Since the replacement of deactivated catalyst in large-tonnage units causes major production outages, an important property of the ion exchange is the highest possible resistance to polymer fouling and therefore the highest possible service life in the catalytic process. For example, the catalyst from the Japanese company Mitsubishi Petrochemical, used in the acrylic ester production plant in the &SSR, achieves a relatively good service life. In a reactor that processes return streams in the esterification unit, the catalyst needs to be replaced after about 5000 hours of operation. The KASTEL - C - 351 ion exchange from the Italian company Montedison also maintains stable activity for a long time during the esterification of acrylic acid with ethanol. Nevertheless, it is desirable to further increase the resistance of ion exchange to fouling by 2S2 797 soils and thus extend their service life in the catalytic reactor.

The present invention solves the problem of increasing the resistance of an ion exchange catalyst to polymer fouling and thus increasing its service life during the catalytic esterification of acrylic acid or transesterification of acrylic acid esters. It uses the fact that the styrene divinyl benzene sulfone cation exchange resin, produced according to Czechoslovak Patent No. AO 214 091, has a heterogeneous structure of the polymer mass. In the ion exchange resin particle, there are areas with little cross-linking by divinylbenzene and therefore well permeable to reactants. In addition, there are areas with more cross-linked mass, which give the particle the necessary mechanical strength. From the point of view of use in the sense of the invention, the most important new finding is that, in comparison with the previously mentioned foreign ion exchanges, the ion exchange resin according to AO 214 091 has a higher swelling capacity in the reaction medium, i.e. in a mixture of acrylic acid, alcohol, water and the corresponding ester. This ensures greater opening of the polymer skeleton of the ion exchange resin and thus better permeability for the reactants with a positive effect on the service life of the ion exchange resin in the catalytic process. The increased swelling of the ion exchange resin does not endanger the operation of the reactor, because the reactor is filled with the ion exchange resin swollen with water (maximum volume) and the transition to the reaction mixture will cause the catalytic bed to shrink, but to a lesser extent than with the above-mentioned foreign ion exchange resins. Table I shows a comparison of the swelling of foreign ion exchange resins declared for the esterification of acrylic acid and the ion exchange resin designed in accordance with the invention.

Table I - Swelling of ion exchangers, expressed as a ratio:

(volume of swollen ionex/volume of dry ionex)

Ionex (manufacturer country) Swelling in the reaction mixture Swelling in water ionex according to A0-214091 (Czechoslovakia) 2.4 2.8 DIAI0N-PK-216 (Japan) 2.0 2.5 KASTEL- C- 3 51 (Italy) 1.9 2.4

To confirm the suitability of ion exchange resin according to AO 214 091 for esterification

- 3 I

252 797 acrylic acid, the individual ion exchange catalysts were also compared by catalytic test under the same conditions. The test reaction was the esterification of acrylic acid with ethanol. The ion exchange catalyst was stored in an integral flow reactor. The test was carried out for 500 operating hours. The results, summarized in Table II, show that in terms of activity and selectivity, the ion exchange catalyst designed for use according to the invention is comparable to foreign catalysts.

So far, the ion exchange resin produced according to AO 214 091 has been used to catalyze the condensation reaction of acetone with phenol to form diane. Its use for catalyzing the esterification of acrylic acid is suitable in acrylic ester production plants.

Table II - Comparison of catalytic properties of ion exchange resins in the esterification of acrylic acid with ethanol

Ionex (manufacturer country) Concentration at the outlet of ^haa) ethyl acrylate reactor Reaction selectivity (%) ionex according to AO 214 091 (Czechoslovakia) 38.1 98.3 DIAIOK - PK - 216 (Japan) 38.5 97.9 KASTEL - C - 351 (Italy) 38.9 98.0

SUBJECT OF THE INVENTION

Claims (1)

Use of a styrendivinylbenzene sulfonic cation exchanger with a rather homogeneous polymeric structure and increased swellability in the reaction.