CS265445B1 - Method for isolating cobalt salts in the oxonation of propylene - Google Patents

Abstract

A method for isolating cobalt salt in the oxonation of propylene with a synthesis gas containing carbon monoxide and hydrogen under the catalytic action of cobalt carbonyls, whereby the iron carbonyl content of the synthesis gas is reduced by pre-cleaning it at an elevated temperature of 170 to 250 ° C upon hydrolysis of carbonyl sulphide and / or solution washing potassium permanganate and the oxonation desalting residue are washed with dilute 2-8% nitric acid, and cobalt is obtained from the obtained dilute process water solutions by precipitation, sedimentation and re-dissolution with nitric acid.

Description

The invention relates to the isolation of cobalt salts by the oxidation of propylene with a synthesis gas containing carbon monoxide and hydrogen under the catalytic action of cobalt carbonyls, in which a mixture of n-butyraldehyde and i-butyraldehyde is obtained as the main product.

As oxonation catalysts, either cobalt carbonyls alone or heat-resistant cobalt or rhodium carbonyls in the form of complexes are present. The present invention relates only to those cases where the oxonation catalyst is cobalt carbonyls alone.

In established oxonation processes, the cobalt carbonyls contained in the produced oxonation product are isolated, for example, by washing with dilute inorganic acid, and the cobalt salts thus obtained are used to prepare a fresh oxonation catalyst.

In the preparation of oil-soluble cobalt salt, it has been proven to dose an oxonation catalyst containing a cobalt salt in the form of naphthenates, in the form of salts of lauric acid, 2-ethylhexanoic acid, etc. In this process, it is common for cobalt to be lost. According to the journal Neftepererabotka i neftekhimija 1987, No. 4, p. 28, usually up to 280 g of cobalt must be replaced per 1 ton of alcohols produced, obtained from the oxonation product. Given the high prices of cobalt, it is desirable to reduce cobalt losses. In this arrangement, it is also common for the recirculated cobalt salts in the oxonation unit to be contaminated with iron salts, which is undesirable. The increased content of iron salts in the oxonation catalyst increases the formation of undesirable high-boiling fractions, and therefore cobalt salts regenerated from the process usually cannot be used further for the preparation of catalysts.

It has now been found that it is possible to reduce cobalt losses from the previously usual 280 g per ton of oxo-alcohols to a value lower than 70 g of cobalt, e.g. to 50 g/t, while simultaneously reducing undesirable contamination with iron compounds and thereby increasing the usability of the obtained cobalt for the preparation of fresh oxonation catalyst while maintaining a high degree of oxonation selectivity.

The method of isolating cobalt salts during the oxonation of propylene with synthesis gas containing carbon monoxide and hydrogen, prepared from producer gas by its pre-purification including hydrolysis of carbonyl sulfide, under the catalytic action of cobalt carbonyls, prepared from oil-soluble cobalt salt, 2-ethylhexanoic acid, consists, according to the invention, in that the oxonation takes place with the addition of synthesis gas prepared from producer gas by pre-purification including hydrolysis at a temperature of 170 to 250 °C, preferably 180 to 200 °C, with simultaneous saturation of the incoming producer gas with water or steam and/or washing with an aqueous 1 to 5% solution of potassium permanganate at an operating pressure of 2.7 MPa and a temperature of 20 °C, and the distillation residue from the oxonation is washed with diluted 2 to 8% nitric acid and from the obtained diluted solutions of process waters containing cobalt salts, carbonate is precipitated by the addition of a soda solution cobalt(II), after which 70 to 95% of the precipitated cobalt(II) carbonate is separated by sedimentation and the remaining cobalt(II) carbonate is filtered, the filter is washed with 4 to 50% nitric acid or an aqueous solution of cobalt(II) nitrate with a free acid content of 15 to 300 g HNO^/l and the resulting solution is collected.

In this way, it is achieved that cobalt losses during oxonation are reduced to below 70 g Co/t oxo-alcohols and at the same time contamination with iron and nickel compounds is reduced.

The oxonation process therefore includes a new step in the synthesis gas preparation section for oxonation: pre-purification of synthesis gas obtained from producer gas produced by partial oxidation of petroleum residues, with the help of which the content of iron carbonyls is reduced from the usual 4 to 10 mg Fe/m _^ to a value below 1 mg Fe/m^, the remaining cobalt fractions are then isolated from the distillation residue of oxonation (so-called heavy portions of oxonation) using diluted nitric acid, preferably 2 to 8% nitric acid at a temperature of 65 °C, thereby supplementing the already established isolation of cobalt salts from the oxonation product using diluted nitric acid, and cobalt carbonate is precipitated from the obtained diluted cobalt nitrate solutions with a soda solution, after which 70 to 95% of the precipitated cobalt carbonate is separated by sedimentation and the remaining cobalt carbonate is filtered and the filter is subsequently washed with acid. nitric, e.g. 4 to 50% or an aqueous solution of cobalt nitrate with a free acid content of 15 to 300 g HNO^/l.

Pre-purification of the synthesis gas, in which the iron content in the form of iron pentacarbonyl is reduced to a value below 1 mg Fe/m _n, can be ensured either by washing with an aqueous 1 to 5% solution of potassium permanganate at an operating pressure of about 2.7 MPa and a usual temperature of about 20 °C, or in the producer gas by increasing the temperature during the hydrolysis of COS to CO2 and Í^S. In order to increase the removal of the carbonyls of the contained metals simultaneously with the hydrolysis of carbonyl sulfide, it is necessary to increase the hydrolysis temperature from the usual 150 °C at about 2.7 MPa to 170 to 250 °C and at the same time saturate the incoming producer gas with water or water vapor. During operational tests, it has been shown that the required reduction of the iron pentacarbonyl content to a value below 1 mg Fe/m _n of the synthesis gas can be achieved at a temperature of 180 to 200 °C.

Both synthesis gas pre-purification processes, ensuring reduction of the iron pentacarbonyl content to a value below 1 mg Fe/m _n , have been tested and work reliably. The reduction of the metal carbonyl content by hydrolysis of carbonyl sulfide is operationally simpler.

It is possible to operate both pretreatment processes simultaneously. To reduce cobalt losses, all process waters containing cobalt salts are led to a vessel in which cobalt carbonate is precipitated at pH 8.5 by adding 8 to 12% soda solution. After sedimentation of 70 to 95% of the precipitated cobalt carbonate, the remaining cobalt carbonate is filtered from the mother liquor on a sintered corundum filter at approximately 50 °C or on polypropylene fabric filters at various pressure drops.

The preparation of synthesis gas for oxonation according to the invention is shown in the following example.

The incoming producer gas from the partial oxidation of petroleum residues at a pressure of 3.15 MPa is composed of

marriage in % vol. c° ₂ 4.2 WHAT 45.8 ^H 2 48.8 inert 1.16 h ₂ s 0.014 what 0.03 Fe mg/m^ 4.5 Ni mg/m^ 2.5

Individual technological stages:

selective H ₂ S scrubbing and COS hydrolysis temperature during COS hydrolysis (°C) 150 Fe content (mg/m ) 3.5 CO ₂ scrubbing using an aqueous solution of triethanolamine CO ₂ content after scrubbing (% vol.) 1 CO 2 post-scrubbing using an aqueous solution of monoethanolamine CO ₂ content after scrubbing (% vol.) 0.01 Synthesis gas scrubbing with an aqueous solution of up to 5% KMnO.

⁴ 3 Fe content (mg/m _n ) after washing 0.2 to 0.5 Synthesis gas for propylene oxonation CO ₂ content (% vol.) 0.01 Fe content (mg/m _n ) less than 1 e.g. 0.2 to 0.5

180 to 200 0.6

0.01 not performed, or only when necessary

0.01 less than 1 e.g. 0.7

The method applied so far and the method according to the invention can be summarized as follows:

the procedure used so far process according to the invention iron pentacarbonyl removal was not carried out introduced, modification of the hydrolysis of carbonyl sulfide Fe content (mg/m^) in synthesis gas Washing of the oxonation product at approx. 90 °C using 5 under 1 8% nitric acid Co content (g/1) 5.8 4.0 Fe content (mg/1) 1.6 0.3 washing the distillation residue with 2 to 8% nitric acid at approximately 65 °C Co content (mg/1) 15.2 12.0 Fe content (mg/1) 12.4 2.5 cobalt losses (g/t) of oxoalcohols produced 70 50 wastewater from distillation residue washing Co content (g/1) 1.0 1.0 Fe content (g/1) 0.18 0.03

SUBJECT OF THE INVENTION

Claims (2)

Process for the isolation of cobalt salts in propylene oxonation with a synthesis gas containing carbon monoxide and hydrogen prepared from a generator gas by purifying it by hydrolysis under catalysis of cobalt carbonyl prepared from an oil-soluble cobalt salt of 2-ethylhexanoic acid a temperature of 170 to 250 ° C, preferably 180 to 200 ° C, while saturating the incoming generator gas with water or water vapor and / or washed with an aqueous 1 to 5% potassium permanganate solution at an operating pressure of 2.7 MPa and a temperature of 20 ° C; the oxonaoe distillation residue is washed with dilute, e.g. 2 to 8% nitric acid and the obtained diluted cobalt nitrate solutions were precipitated with sodium carbonate solution, then 70-95% of the precipitated cobalt carbonate was separated by sedimentation and the remaining cobalt carbonate was filtered, the filter was washed with 4-50% nitric acid or aqueous solution. cobalt nitrate with a free acid content of 15 to 300 g HNO 3 / l.