CS230865B1 - Method of reactivation of catalyst of oxidation of ethylene into ethylene oxide - Google Patents

Abstract

Reactivating a silver-based catalyst with promoters and activators, as a rule, it is done on carriers by being on catalyst acts by solvent (aqueous -acetone or aqueous-alcoholic solution) and / or oxalic acid solution. solvent as a rule, in another catalyst the catalyst is removed and the catalyst is exposed temperature of 100 to 500 ° C (150 - 350 ° C) in the atmosphere synthesis or inert gas s 10 to 100 vol. carbon dioxide.

Description

The invention relates to reactivation, resp. the recovery of a catalyst of oxidation of ethylene to silver-based ethylene oxide, optionally together with promoters and activators using physical and chemical methods, using available chemicals.

It is known to prepare a silver catalyst for the oxidation of ethylene to ethylene by impregnating α-alumina with silver lactate and treating it at a temperature of 270 to 350 ^° C in an atmosphere containing more than 70% by volume. of carbon dioxide and 1 to 20 vol. oxygen for 7 to 10 h (U.S. Pat. No. 3,943,069; U.S. Pat. No. 1,440,332). The actual production of ethylene oxide is in turn carried out with molecular oxygen or oxygen-containing gas on the silver catalyst, wherein in the reaction gas, in addition to ethylene, ethane, methane, oxygen, nitrogen with argon, it is about 5% by volume. carbon dioxide, respectively. between 1 and 9% vol. (NSR Pat. 2,505,414, 2,219,748). This is quite understandable because the by-product of ethylene oxidation is carbon dioxide. The higher carbon dioxide content in the synthesis process reduces the production of the catalyst. However, even under these conditions, both the overall quality of the catalyst and its selectivity are reduced. The silver catalyst must be reactivated. Known reactivation with aqueous-alcoholic alkali metal solutions, in particular cesium and rubidium salts (U.S. Pat. No. 1,578,133, 1,571,123, U.S. Pat. No. 4,033,903, U.S. Pat. No. 2,611,856, and 2,636,680 J. however, the process of reactivating or regenerating the silver ethylene oxide oxidation catalyst to ethylene oxide by acting at a temperature of 150 to 500 ° C under a synthesis gas atmosphere is particularly effective in the passivation of the catalyst by sulfur compounds and by higher hydrocarbons or by products of oxidation and condensation of higher hydrocarbons. as a rule, essentially oxygen-reacted and / or corrosive, and can additionally be impregnated with a solution of the promoter elements (cf. No. 222,335J). However, it does not exhaust all possibilities of reactivating the poisoned catalyst. and extends them to other addicts Specific reduction of activity and selectivity of silver catalyst of oxidation of ethylene to ethylene oxide.

According to the present invention, the method for reactivating the catalyst of oxidation of ethylene to ethylene oxide, based on silver, optionally together with promoters and activators, is generally carried out by treating the catalyst with an organic solvent or a mixture of organic solvents boiling up to 150 ° C. singly or in the mixture is an aliphatic alcohol, a ketone, an amine and optionally water and / or a solution of oxalic acid at a concentration of 0.05 to 10% by weight, whereby further solvent is pumped off and solvent residues removed and / or the catalyst exposed to temperature 100 to 500 ° C and a synthesis or inert gas atmosphere containing 10 to 100 vol. carbon dioxide.

The advantage of the process of reactivating the catalyst according to the invention is that it can be carried out not only on the selected catalyst from the reactor, but also directly in the catalytic bed of the reactor or the reactor. in ethylene to ethylene oxide oxidation reactors. Furthermore, the full operational safety of the reactivation procedures and the technical availability of the chemicals required for reactivation. Last but not least, the advantage is that the reactivation process can be used to reactivate virtually all commercially available silver-based catalysts for the oxidation of ethylene to ethylene oxide by all known processes, both for "oxygen" and "air" technology.

Suitable solvents include water, aqueous acetone solution, aqueous alcoholic solution, optionally acetone alone, methyl ethyl ketone, low molecular weight aliphatic alcohol itself, such as methanol, ethanol, less suitable, but also propanol, isopropyl alcohol, tert-butyl alcohol is also useful. The synthesis gas or inert gas shall contain at least 10% vol. carbon dioxide, wherein in addition to the generally known and technically available inert gases, such as nitrogen, argon, helium and the like, carbon monoxide can also be present as an additive or even an inert gas component. However, carbon dioxide itself is most suitable. It is preferable whether carbon dioxide alone or synthesis carbon dioxide, respectively. inert gas containing more than 10% by weight replace carbon dioxide during reactivation. This method of reactivation can be applied in addition to activation according to U.S. Pat. 222 335, resp. after thermal activation according to the invention and additionally doping the catalyst with alkali metal compounds. In the case of reactivators, a temperature of more than 500 ° C is inappropriate, especially in the case of highly efficient catalysts, since agglomeration of silver particles and sublimation of the activators are already occurring.

Further details and advantages of the reactivation method of the present invention are evident from the examples.

Example 1

Into a microreactor of a stainless steel test apparatus having an internal diameter of a 4 mm microreactor equipped with a temperature sensor, 0.4 g (0.35 cm ³ ) of fresh silver grain catalyst of 0.5-0.63 mm containing 10 wt. silver on a macroporous ceramic support. A gas volume velocity of 1430 h ^-1 is applied for testing. The synthesis gas composition is as follows (in% by volume): 7.3 oxygen, 3.6 carbon dioxide, 33.5 ethylene and the remainder being nitrogen with other inert materials.

The catalyst is activated for 5 h in a syngas stream at a temperature of 280 ° C. Then, with said synthesis gas, the oxygen conversion of 40% is achieved at a temperature of 241 ° C, the selectivity to ethylene oxide reaching 52%.

A similar catalyst is exploited 4 years in the industrial scale and has deactivated to a similar sample of 0.4 g (0.35 cm ^3] of the test apparatus with the same synthesis gas and space velocity of 1430 h ^_1 a conversion of 40% and oxygen at a temperature of 324 ° C, the selectivity to ethylene oxide being 37%.

This catalyst with markedly reduced activity is reactivated in a laboratory microreactor in a stream of carbon dioxide at 340 ° C for 24 h. The temperature of the microreactor and the catalyst is then reduced and the carbon dioxide is exchanged for synthesis gas at a volume rate of 1430 h ^-1 . Oxygen conversion of 40% is achieved at 282 ° C, with selectivity to ethylene oxide reaching 44%.

Example 2

Reactivation of the near-deactivated catalyst (four-year explosive specified in Example 1) is first carried out in the syngas stream specified in Example 1 at a volumetric rate of 1500 h ^-1 and a temperature of 340 ° C for 24 h. 40% oxygen is achieved at 279 ° C, with an ethylene oxide selectivity of 42%, then the catalyst is reactivated at a temperature of 340 ° C in a stream of carbon dioxide for a further 24 hours to further increase the activity and selectivity of the catalyst. dioxide synthesis gas space velocity of 1500 tr ¹ 40% oxygen conversion was achieved at 274 ° C, the selectivity to ethylene oxide increases to 47%.

Example 3

The almost deactivated catalyst specified in Example 1 was impregnated with an aqueous acetone oxalic acid solution (oxalic acid content of 1.3 wt%) for 24 h at 25 ° C. After removal of the oxalic acid solution, the catalyst is dried for 2 h at 120 ° C and for 24 h at 330 ° C in a syngas stream whose composition is specified in the example.

1. Following this reactivation, an oxygen conversion of 40% is achieved at a temperature of 288 ° C and a selectivity to ethylene oxide of 56%.

Example 4

Nearly deactivated silver catalyst specified in Example 1 in amount e

0.35 cm ³ is mixed with 20 cm ^{3 of} acetone, which is left to react for 24 h at 25 ° C. The acetone is then removed and treated with 10 cm @ ^{3 of} acetone three times at half-hour intervals with stirring. After removal of acetone, the catalyst is dried for 2 hours in an oven at 120 ° C and then in the reactor for 24 hours at 315 to 335 ° C under the synthesis gas flow specified in Example 1. The oxygen conversion of 40% is achieved at 314 ° C, the selectivity to ethylene oxide being 44 percent.

Example 5

The reactivation of the nearly deactivated catalyst specified in Example 1 is carried out similar to Example 4, but diethylamine is used instead of acetone. Following this reactivation, the oxygen conversion of 40% is achieved at 229 ° C, with a selectivity to ethylene oxide of 42%.

Example 6

The deactivated catalyst specified in Example 1 is reactivated initially for 24 h at 340 ° C in a syngas stream whose composition is specified in Example 1 and in a carbon dioxide stream at 340 ° C for 24 h. After cooling 0.7 cm ^{3 of} catalyst, it is impregnated four times with 1.4 cm ³ of a cesium-acetone aqueous solution (177 mg CsCl in 28 cm ^{3 of} water and 680 cm ^{3 of} acetone). After removal of the impregnation solution, the catalyst is dried in an oven at 120 ° C for 16 h. It is then dried in the reactor at 330 ° C for 12 h. After reactivation, oxygen conversion of 40% at 294 ° C and selectivity to ethylene oxide of 51% are achieved.

Example 7

The reactivation of the near-deactivated catalyst specified in Example 1 is carried out similar to Example 4, but methanol is used instead of acetone. After this reactivation, a selectivity for ethylene oxide of 50% and an oxygen conversion of 40% were obtained at 305 ° C.

Example 8

The procedure is similar to that in Example 7 except that an aqueous solution of ethanol with conc. 76% wt. Using the reactivated catalyst at 301 ° C, the conversion of oxygen per pass was 40% and the selectivity to ethylene oxide was 52%.

Claims (2)

1. Method for reactivating a catalyst of oxidation of ethylene to ethylene oxide, based on silver, optionally together with promoters and activators, usually on supports, characterized in that it is impregnated on the catalyst with an organic solvent or a mixture of organic solvents boiling up to 150 ° C. singly or in the mixture is an aliphatic alcohol, a ketone, an amine and optionally water and / or a solution of oxalic acid at a concentration of 0.05 to 10% by weight, OF THE INVENTION in another solvent is pumped off and the solvent residues are removed and / or the catalyst is subjected to a soaking temperature of 100-500 ° C and a synthesis or inert gas atmosphere containing 10-100% by volume. carbon dioxide. 2. A process according to claim 1, wherein the solvent residues are removed by evaporation and / or by gas purging, preferably by carbon purging gas purging.