CS243846B1 - A method for isolating cobalt salt in the oxonation of propylene - Google Patents

Abstract

Method for isolating cobalt during the oxonation of propylene with synthesis gas containing carbon monoxide and hydrogen, in which the incoming synthesis gas is washed with a 1 to 5% aqueous solution of potassium permanganate and, in addition to the known method for isolating cobalt from oxonation products separated by distillation, the distillation residue from the oxonation product is washed with dilute nitric acid, preferably 8%, cobalt is precipitated as cobalt carbonate, which sediments and the mother liquors from the sedimentation are filtered and the cobalt carbonate obtained is dissolved with nitric acid or a cobalt nitrate solution.

Description

(54) Method for isolating cobalt salt during propylene oxonation

Method for isolating cobalt during the oxonation of propylene with synthesis gas containing carbon monoxide and hydrogen, in which the incoming synthesis gas is washed with a 1 to 5% aqueous solution of potassium permanganate and, in addition to the known method for isolating cobalt from oxonation products separated by distillation, the distillation residue from the oxonation product is washed with dilute nitric acid, preferably 8%, cobalt is precipitated as cobalt carbonate, which sediments and the mother liquors from the sedimentation are filtered and the cobalt carbonate obtained is dissolved with nitric acid or a cobalt nitrate solution.

The present invention relates to the oxonation of propylene with synthesis gas containing carbon monoxide and hydrogen, in which a mixture of n-butyraldehyde and i-butyraldehyde is obtained as the main product.

Either cobalt carbonyls alone or complex, heat-resistant cobalt or rhodium carbonyls are used as enrichment catalysts.

Oxonation processes usually proceed in such a way that the cobalt carbonyls contained in the produced oxonation product are isolated, for example by washing with dilute organic acid, and the cobalt salts thus obtained are used to prepare a fresh oxonation catalyst.

When preparing the Oil-Soluble Cobalt Salt, it has proven effective to dose an oxonation catalyst containing cobalt salt in the form of naphthenates, in the form of lauric acid salt, 2-ethylhexanoic acid, etc.

In this process, it is common for cobalt to be lost in the amount of 70 to 90 g per ton of oxo-alcohols produced. Due to the high price of cobalt, efforts are being made to reduce cobalt consumption. In this arrangement, it is also common for cobalt salts to be contaminated with iron compounds, which is undesirable.

It has now been found that it is possible to reduce cobalt losses from the usual 70 to 80 g of cobalt per ton of oxo-alcohols to a value lower than 60 g/t, e.g. 40 g/t, while simultaneously reducing undesirable contamination with iron compounds, thereby increasing the usability of the obtained cobalt for the preparation of fresh cobalt catalyst while maintaining a high degree of process selectivity.

The method of isolating cobalt salts during the oxonation of propylene with synthesis gas containing carbon monoxide and hydrogen, catalyzed by cobalt carbonyls, prepared from an oil-soluble salt of 2-ethylhexanoic acid to a residual value of less than 50 g Co/t of oxoalcohols while simultaneously reducing their contamination with iron and nickel compounds according to the invention consists in that, in addition to the known isolation of cobalt salts from the oxoproducts of distillation separated from the residues, the remaining cobalt portions in the distillation residue are isolated from the oxonation product, in which the iron content has been reduced to a value below 5 mg Fe/l by washing the gas entering the oxonation with a 1 to 5% solution of potassium permanganate, by washing with dilute, preferably 8% nitric acid at 5 to 95 °C at atmospheric pressure, and from the obtained dilute solutions of cobalt nitrate, cobalt carbonate is precipitated with a soda solution, after which 70 to 95% The precipitated cobalt carbonate is separated by sedimentation and the remaining cobalt carbonate is filtered and the filter is washed with 4 to 5% nitric acid or with an aqueous solution of cobalt nitrate with a free acid content of 15 to 300 g HNO ₃ /l.

In this arrangement, care is taken to ensure that all wastewater containing cobalt salts is led to a vessel in which cobalt carbonate is precipitated at pH 8.5 by adding 12% soda solution. After sedimentation of 70 to 95% of the precipitated cobalt carbonate, the remaining cobalt carbonate is filtered from the mother liquor by filtration on a sintered corundum filter at 50 °C or on a polypropylene fabric filter at various pressure drops of 0.05 MPa, 0.1 MPa,

0.2 MPa.

The method applied so far and the method according to the invention can be more clearly stated as follows:

removal of cobalt compounds from the oxonation product at approx. 90 °C using 8% nitric acid Co content g/1 Fe content mg/l method used so far input output 0.7 0.02

0.5 method according to the invention input output 0.7 0.02

0.5 removal of Fe and Ni carbonyls from synthesis gas content Fe/m^ mg content Ni/m^ mg washing of distillation residue with 8% nitric acid content Co g/1 content Fe mg/1 filtration of mother liquors sedimentation tanks content Co/1 mg content Fe/1 mg quality of oxonation catalyst content Co g/1 cobalt losses per l.t of oxoalcohols g/t not performed

20.0 20.0

3.7 3.7 the method used so far is not being implemented

0.23 0.23

52 not implemented

11

1.8 1.8

2.1

20.0 0 3.7 0 method according to the invention

0.23 O O 0

0 0 0

2.1

The process according to the invention is illustrated by the following examples.

Example

Synthesis gas in the amount of 3,850 m^/h, pre-cleaned in a monoethanolamine scrubber, with the composition

«2 50 % obj. WHAT 48 % obj. C0 ₂ 1 í obj. inert 1 obj. sulfur content 3, .6 mg/m^

is freed from the contained Fe and Ni carbonyls at a pressure of 2.5 MPa and at a temperature of 25 to 50 °C in a washing machine by washing with an aqueous solution of potassium permanganate. The potassium permanganate solution is replaced with a fresh solution after it is used up. A solution of 1 to 5% is used.

Analytical data:

entry exit Fe content (mg/mj) 20.0 0.0 Ni content mg/iRj) 3.7 0.0 content S mg/mj| 3.6 3.0

The synthesis gas purified in this way is further compressed and fed into the oxonation reactor.

Example 2

The distillation residue obtained after distilling off water, toluene, n-butyraldehyde, i-butyraldehyde, C ₄ oxo-alcohols, referred to as heavy oxonation fractions, is passed in an amount of 490 kg/hour.

into a flow-through stirred vessel in which it is washed with 8% nitric acid at a rate of 50 |/h.

Working on at temperature 60°C, usual and Analytic data: entry exit contents Pe mg/1 0.065 0.0 contents What mg/1 0.300 0.0 contents Ni mg/1 0.012 0.0 Example 3

A mixture of process waters from washing the oxonation product, from washing heavy portions of oxonation and waters from the preparation of the oxonation catalyst containing 0.5 to 0.9 g Co/l is fed in an amount of 4 ^m3 /h into a standing vessel with the addition of 12% aqueous soda solution to a final pH of 8.5.

The obtained suspension is allowed to sediment for about one hour at 70 °C. Already during sedimentation, the mother liquor is gradually drained from the top of the sedimentation tank through the drain fittings. 3 drain fittings were installed on the tank.

The second fitting from the top is opened until the mother liquor above the first fitting is drained. This procedure is continued until the cobalt carbonate settles. In order to increase its quantity for subsequent handling, another batch of aqueous solutions of cobalt and soda salts is poured into the sedimentation tank and the gradual draining of the mother liquor is repeated. This procedure is repeated five times in total until about 80 kg of cobalt carbonate is collected at the bottom of the tank. .

The discharged mother liquor from all discharge fittings and from all batches is led to the installed filter.

The tests verified filtration on a sintered corundum or sintered glass filter at 50 °C and on a polypropylene fabric filter at various pressure drops: 0.05 MPa, 0.1 MPa and 0.2 MPa.

The cobalt carbonate trapped on the filters is dissolved with 84% nitric acid and the filter is thus ready for further filtration. Dissolution has also been tried with 4 to 50% nitric acid or with an aqueous solution of cobalt nitrate containing 0.2 to 30 g Co/l and free HN0 ₃ 15 to 300 g/l.

Claims (1)

OBJECT OF THE INVENTION Process for the isolation of cobalt salts in propylene oxonation with a synthesis gas containing carbon monoxide and hydrogen, cobalt-catalyzed carbonyls prepared from an oil-soluble cobalt salt of 2-ethylhexanoic acid to a residual value of less than 60 g Co / t oxoalcohols by isolating cobalt salts from oxo products by distillation from residues, characterized by isolating the remaining portions of cobalt in the distillation residue from the oxonation product in which the iron content was reduced to below 5 mg Fe / l by washing the synthesis gas entering the oxonation 1 Up to 5% potassium permanganate solution, scrubbing with dilute, preferably 8% nitric acid at 5 to 95 ° C at atmospheric pressure and precipitating cobalt carbonate with soda solution from the dilute cobalt nitrate solutions obtained, followed by 70 to 95% of the cobalt carbonate precipitated. The residue is separated by sedimentation and the remaining cobalt carbonate is filtered, and the filter is washed with nitric acid 4 to 50% or an aqueous solution of cobalt nitrate having a free acid content of 15 to 300 g ΗΝΟ ^ / Ι. Severography, n. P., MOST Price 2,40 Kčs