RU2236290C1 - Regeneration of phthalocyanine catalysts with carbon dioxide in above-critical state - Google Patents

Abstract

FIELD: organic synthesis catalysts.

SUBSTANCE: exhausted phthalocyanine catalysts used in the process of carboxylation of propylene oxide with carbon dioxide are regenerated by treatment for 120-180 min with carbon dioxide in above-critical state at 100-150^оС and pressure 200-300 atm. Such treatment allows full restoration of catalytic activity of tert-butyl-substituted phthalocyanine-aluminum chloride, cobalt tert-butyl-substituted phthalocyanine, and dysprosium tert-butyl-substituted phthalocyanine.

EFFECT: increased regeneration efficiency.

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Description

The invention relates to a method for the regeneration of phthalocyanine catalysts used in the synthesis of propylene carbonate from propylene oxide and carbon dioxide.

The restoration of the properties of the catalytic systems used in chemical synthesis is an important problem. This is due to the fact that obtaining new catalytic systems is often associated with significant material costs, as well as environmental problems arising from the disposal of spent catalysts.

Most often, to solve this problem, calcination of the catalytic system with gases (water vapor, air, etc.) is used, heated to a temperature of 300-500 ° C [1]. Often this method cannot be applied in practice due to thermal destruction of the catalyst. In addition, when using this method, a large number of gaseous environmentally harmful emissions are released, the cleaning of which is very expensive. Another method of regeneration is washing the catalyst with organic solvents, alkalis or acids. The application of this method limits the low solubility of many impurities poisoning the catalyst in organic solvents, as well as the instability of the catalyst to acids and alkalis.

In the last twenty years, it has been of great interest to use solvents in the supercritical state for the regeneration of adsorbents and catalysts. This interest is due to the unique dissolving power of substances above their critical point. Carbon dioxide is most often used as a supercritical solvent. This is due to its relatively low critical parameters (P _cr = 73 at, T _cr = 31 ° C), low cost and non-toxicity.

It is known that treatment with supercritical carbon dioxide allows the regeneration of various adsorbents: silica gels [2], activated carbons [3, 4] and polymer sorbents [5]. For example, in [4], the possibility of regenerating activated charcoal used to purify aqueous solutions of impurities of trichlorethylene and o-chlorophenol was studied. It was shown that treatment with supercritical CO ₂ at a temperature of 35 ° C and a pressure of 200 atm makes it possible to completely restore the adsorption properties of coal.

The regeneration of catalysts using CO ₂ in the supercritical state in many cases, is also very effective. Thus, it was shown that treatment with supercritical carbon dioxide allows the zeolites [6] and other porous catalysts [7, 8] to be purified from coke formed during the reactions. The German patent [9] describes a method for the regeneration of rhodium-based catalysts used in the process of carbonylation of methanol, methyl acetate and dimethyl ether.

This patent proposes the use of carbon dioxide for the regeneration of phthalocyanine catalysts after the carboxylation reaction of propylene oxide (I) in the process of producing propylene carbonate (III). The catalyst used in this technology is a phthalocyanine complex supported on an inert carrier Celite 535. Carrier parameters: chemical composition — silicic acid with small amounts of Al, Fe, Mg, Ca; specific surface area is 1-3 m ² / g; bulk density ≈ 0.24 g / cm ³ ; the average pore diameter is 1-3 microns; the diameter of the granules is 60-80 mesh.

It is known [10] that the catalytic reaction of carboxylation of propylene oxide with carbon dioxide is carried out according to the following scheme:

As can be seen from the scheme, polypropylene carbonate (II) is formed during the reaction. As a result, a polymer film gradually appears on the surface of the catalyst. This film covers active centers, which leads to a gradual attenuation of the formation of propylene carbonate (III).

In the proposed method for the destruction and removal of this film uses carbon dioxide in a supercritical state. The regeneration process is carried out as follows: the spent catalyst is loaded into the reactor P, then carbon dioxide is passed through the reactor at a pressure of 200-300 atm and a temperature of 100-150 ° C. Processing is carried out within 120-180 minutes Schematic diagram of the regeneration process is shown in figure 1, figure 2 - dependence of the yield of propylene carbonate on the time of carboxylation.

During the processing of the catalyst system, steady aerosol is observed at the outlet of the reactor. An analysis of the composition of the aerosol, which was carried out by a gas chromatographic method with mass spectral detection, showed the presence of dimers and oligomers of propylene carbonate. After regeneration, the phthalocyanine complex almost completely restored its activity. Comparative characteristics of the starting and reduced catalyst (tert-butyl substituted phthalocyanine aluminum chloride) are shown in FIG. 2

As can be seen from figure 2, the initial ratio of the mass of the obtained propylene carbonate to the mass of the starting propylene oxide (Mpc / op) for the initial (curve 1) and regenerated (curve 2) catalysts practically coincide. Thus, we can conclude that after treatment with carbon dioxide in the supercritical state, the phthalocyanine catalyst completely restores its activity.

Example 1

The catalyst - tert-butyl substituted phthalocyanine-aluminum chloride Pc ^t AlCl (93 mg applied to 2.9 g of Celite 535) with an initial ratio of Mpc / op of 10% was worked out within 24 hours to a Mpc / op ratio of less than 1%. The spent catalyst was placed in a 10 ml reactor and treated for 120 min with supercritical carbon dioxide at a pressure of 300 atm and a temperature of 150 ° C. After processing, the catalyst restored its activity to its original value.

Example 2

The catalyst - phthalocyanine-aluminum chloride PcAlCl (100 mg applied to 2.9 g of Celite 535) with an initial ratio of Mpc / op of 6% was worked out within 16 hours to a ratio of Mpc / op of less than 1%. The spent catalyst was placed in a 10 ml reactor and treated for 120 min with supercritical carbon dioxide at a pressure of 250 atm and a temperature of 150 ° C. After processing, the catalyst restored its activity to its original value.

Example 3

The catalyst - tert-butyl substituted cobalt phthalocyanine Pc ^t Co (100 mg applied to 2.9 g of Celite 535) with an initial ratio of Mpc / op of 6% was worked out within 20 hours to a ratio of Mpc / op of less than 1%. The spent catalyst was placed in a 10 ml reactor and treated for 180 min with supercritical carbon dioxide at a pressure of 250 atm and a temperature of 100 ° C. After processing, the catalyst restored its activity to its original value.

Example 4

The catalyst - diphthalocyanine dysprosium Pc ₂ Dy (110 mg, applied to 3.0 g of Celite 535) with an initial Mpc / op ratio of 5% was worked out within 20 hours to a Mpc / op ratio of less than 1%. The spent catalyst was placed in a 10 ml reactor and treated for 3 hours with supercritical carbon dioxide at a pressure of 250 atm and a temperature of 100 ° C. After processing, the catalyst restored its activity to its original value.

Sources of information

1. Industrial catalytic processes and efficient catalysts. C. Thomas, edited by A.M. Rubinstein. - M.: Mir, 1973, p. 22-27.

2. Van Bommel M.J., de Haan, A.B. Drying silica gels with supercritical carbon dioxide. J. Mater. Sci., 1994, 29 (4), pp. 943-8 (eng.).

3. Srinivasan M.P., Smith J.M., Mc Coy B. Supercritical fluid desorption from activated carbon. J. Chem. Eng. Sci., 1990, 47 (7), pp. 1885-95.

4. Nakai Toshihiro et. al. Adsorption of organic chloro compounds by activated carbon and it's regeneration by supercritical carbon dioxide. Nippon Kogaku Kaishin, 1994 (4), pp371-5 (Japan).

5. U.S. Patent 4,061,566 (Bec 6, 1977).

6. Manos, Georgios et. al. coke Removal from a zeolite catalyst by supercritical fluids. Chem. Eng. Technol, 1991, 14, pp. 73-78.

7. Baptist-Nguyen, Sarh et.al. Coking and Activity of Porous Catalysts in Supercritical Reaction Media. AlchE Jornal, vol. 38, No. 7, pp. 1027-1037, Jul. 1992.

8. US Patent No. 5725756 (Mar 10, 1998).

9. German patent DE No. 3902515 (Aug 02, 1990).

10. Kuran W, Listos T. Macromol. Chem. Phys. 1994, 195, 977.

Claims (5)

1. The method of regeneration of phthalocyanine catalysts used in the reaction of carboxylation of propylene oxide with carbon dioxide, characterized in that to restore the catalytic properties of the spent catalyst is treated with carbon dioxide in a supercritical state at a pressure of 200-300 atm and a temperature of 100-150 ° C for 120- 180 minutes 2. The method according to claim 1, characterized in that the catalyst Pc ^t AlCl is subjected to treatment at a temperature of 150 ° C and a pressure of 300 atm for 120 minutes 3. The method according to claim 1, characterized in that the PcAlCl catalyst is treated at a temperature of 150 ° C and a pressure of 250 atm for 120 minutes 4. The method according to claim 1, characterized in that the Pc ^t Co catalyst is subjected to treatment at a temperature of 100 ° C. and a pressure of 250 atm for 180 minutes. 5. The method according to claim 1, characterized in that the catalyst is subjected to Pc ₂ Dy catalyst at a temperature of 100 ° C and a pressure of 250 atm for 180 minutes

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