CS231888B1 - Process for cleaning synthetic gases - Google Patents

Abstract

The invention relates to a method for purifying synthesis gases intended for olefin oxonation, methanol synthesis and other syntheses, in which the contained iron and nickel carbonyls are removed from the gas and at the same time the proportion of contained sulfur compounds is reduced by washing with an aqueous solution of manganous or chromic acid or/and their salts at 5 to 90 °C and at a pressure of 0.1 to 35 MPa.

Description

(54) Synthetic gas purification method

The present invention relates to a process for the purification of synthesis gases for olefin oxonation, methanol synthesis and other syntheses, wherein the contained iron and nickel carbonyls are removed from the gas while reducing the proportion of sulfur compounds present by washing with an aqueous solution of manganese or chromic acid; and their salts at 5 to 90 ° C and at a pressure of 1 to 35 MPa.

The invention relates to the purification of olefin oxonation gases, carbonylations, methanol synthesis and other syntheses in which the iron and nickel carbonyls present are removed from the gas while the proportions of sulfur compounds present are reduced.

Synthesis gases containing carbon monoxide CO and hydrogen H 3 often contain varying amounts of iron and nickel carbonyl. The carbonyls of iron and nickel pass into the synthesis gases either from the gasified feedstock, or from transporting, storage or production equipment, by the effect of carbon monoxide on the steel piping or the internal walls of the production equipment.

In the partial oxidation of oil residues containing small amounts of iron, nickel and other metals, the presence of iron and nickel carbonyl is usual:

3 to 10 mg / m 2 Fe and 3 to 4 mg Ni / m 2 in the form of carbonyl.

In the treatment of this generator gas into synthesis gas for propylene oxonation, the carbonyls present are only partially removed in the hydrogen sulphide H 2 S and CO ₂ scrubbing and in the incorporated carbonyl sulfide hydrolysis stage: in addition, other carbonyls may be formed during the synthesis gas transport.

The presence of iron and nickel carbonyl in the synthesis gas is also determined for synthesis gases that have been produced from natural gas or from primary gasoline by steam reforming.

In this case, the carbonyls entered the syngas during storage, transport and production.

The presence of Fe and Ni carbonyl in the synthesis gas is detrimental to some production processes and it is therefore desirable to remove it from the synthesis gas.

It has now been found that Fe and Ni carbonyls can be removed from the synthesis gases by scrubbing the synthesis gases with an aqueous solution of manganese or chromic acid or a salt thereof simultaneously reducing the residual content of sulfur compounds.

It has been found that the removal of Fe and Ni carbonyl from the synthesis gas is complete even at lower temperatures, e.g. between 5 ° C and 25 ° C. If desired, the scrubbing can also be carried out at elevated temperatures, e.g. pressure of 0.1 to 35 MPa.

It is preferred to remove the carbonyls Fe and Ni from the propylene oxonation synthesis gas which has been produced from the crude generator gas obtained by partial oxidation of the atmospheric petroleum residue.

i At steady-state operation, the propylene oxonation synthesis gas contains Fe / CO / _K in the range of 7 to 20 mg Fe / m ³ and 3 ⁿ Ni / CO / 3 in the range of 3 to 5 mg Ni / m _n

In the propylene oxonation catalysed by cobalt carbonyl, cobalt recycling is an essential part of this process. During this recycling, it is impossible to prevent the iron and nickel compounds from simultaneously separating with the cobalt compounds from the oxo products.

As a result, the recirculated cobalt oxonation catalyst is contaminated especially with iron compounds. Due to the high purchase price for cobalt or cobalt compounds, it is desirable that the cobalt losses during oxonation be as low as possible and therefore distillation residues from propylene oxonation are discarded with nitric acid pens prior to decommissioning.

This wash results in an aqueous solution containing both washed cobalt and washed iron in the form of nitrates. '

Table 1 provides analytical data on the Fe and Co content of the aqueous solution obtained »this table provides analytical data both from the established plant and after the incorporation of a scrubbing gas whereby the contained Fe and Ni carbonyls were removed with an aqueous potassium permanganate solution .

Table 1: Analytical data on the aqueous solution obtained from the washing of oxo-residues with dilute nitric acid.

Sample Content Co g / 1 Content Fe g / l Fe / Fe / CO / ₅ content in synthesis gas mg / n? 1 1,2 0.52 9 2 0.89 0.50 17 3 2.84 1.54 17 · 4 1,2 0.05 not identified / after washing with KMNO ^ solution / 5 1.3 0.03 - dtto 6 2.7 0.1 - dtto

It will be appreciated that the waste cobalt salt solution can be used to prepare the oxonation cobalt catalyst without simultaneously introducing a large amount of undesirable iron compounds.

The removal of Fe and Ni carbonyl from the synthesis gas is shown in Example 1, and a reduction in the sulfur compound content is also shown.

Example 1

800 m ³ / h of synthesis gas was scrubbed at 19 ° C with a 4.7% KMnO 2 solution at 2.5 MPa and further for comparison at 17 ° C with a 1% KMnO 2 solution.

The cleaning process was as follows:

Washing solution KMnO content.

% wt. without washing 4.7% washing 1%

Content of impurities in synthesis gas

Fe mg / m

9,6 Not identified

Ni mg / yyy

3.9 Not identified

S-Compounds mg / nr

0.5

0.9

By increasing the wash temperature, 3 tu below 0.1 mg / m ₂ to above ° C, the sulfur compound content has been reduced to a value. similar results were obtained with solutions which were made alkaline by the addition of soda or potash.

The use of permanganic acid salts in acidic solution was also verified. After acidification with sulfuric acid, the permanganic acid released was the active oxidizing component.

Removing the carbonyl of Fe and Ni with an acidified scrubbing solution requires that the scrubber and the associated auxiliary equipment be stainless steel.

Similarly, aqueous chromic acid solutions or their salts such as potassium, sodium, ammonium can be used to remove carbonyls of Fe and Ni.

Claims (1)

SUBJECT OF THE INVENTION Process for the purification of synthesis gases intended for the oxonation of olefins, for the carbonylation, for the synthesis of methanol and other syntheses, in which the contained iron and nickel carbonyls and residual proportions of sulfur compounds are removed from the gas, characterized in that the gases are scrubbed with an aqueous chromium or their salts at 5 to 90 ° C and at a pressure of from 1 to 35 MPa. Severography, n. P., MOST