DE919289C - Process for the catalytic hydrogenation of carbons using iron catalysts precipitated from sulfuric acid solutions - Google Patents

Description

(WiGBl. P. 175)

ISSUED OCTOBER 18, 1954

R 5761 IVd 112 ο

In the hydrogenation of carbon monoxide over iron catalysts, it is known that using from normal pressure, but above all from increased pressure, and from a wide variety of catalysts Composition on the one hand, more or less large amounts of oxygen-containing compounds, mainly alcohols, but also almost exclusively hydrocarbons can. To date, melt catalysts, sintered catalysts and precipitation catalysts have been used for this purpose.

In the preparation of the precipitation catalysts, the iron and any activators to be added are generally introduced in the form of their nitrate solutions. The nitrates are easily soluble, result from precipitation with alkali compounds, ζ. B. soda or potash, easily filterable precipitates and very active catalysts after the reduction. Among other things, the use of nitrates is also advantageous because the residual alkali remaining in the precipitated catalyst mass does not contain any troublesome admixtures during the precipitation and can be easily removed _{by careful washing with H 2 O.}

The disadvantage of the precipitation catalysts mentioned are the high costs of those used for precipitation Nitrate solutions. It is always necessary to put the appropriate metals in excess nitric acid to solve, eliminating such catalysts with the high cost of the used Are contaminated with nitric acid. In addition, considerable losses arise in the dissolving process itself

of nitric acid. Thought has already been given to the mother liquor running off after the precipitation evaporate and recover the valuable alkali nitrate. However, this procedure is not cheap.

It has been found that the catalytic carbohydrate hydrogenation using from sulfuric acid solutions precipitated iron catalysts can be carried out favorably if catalysts are used that are made from Ferro - SuIf at solutions without the addition of ferric compounds or Oxidation mediators for the precipitation solution were precipitated, with the precipitation of about 10 to 50%, predominantly about 25 to 35% of the iron present has been converted into the trivalent form, while washing out the resulting precipitate using ion-exchanging agents Solutions, preferably of readily soluble ammonia compounds, has taken place and during ao the leaching, pre-drying and drying a further oxidation of the remaining divalent Iron to trivalent iron has been carried out with an ample supply of air in such a way that in the end over 70%, preferably over 80%, of the total iron was present as trivalent iron to have. Iron sulfate falls in numerous chemical processes, e.g. B. in pickling processes, in the production of titanium white etc., as a cheap waste product. The impurities contained in this sulfate are irrelevant and do not disturb.

Care must be taken when producing catalysts using iron sulfate that practically no more sulfur in the form of sulfate is present in the finished catalyst is, since the reduction produces sulphide and the hydrogen sulphide which is formed immediately the Would poison the catalyst.

The process for the preparation of catalysts using iron sulfate requires that at least a part of the divalent iron is converted into the trivalent iron. For this purpose, the iron sulfate is dissolved in hot water, the concentration of des.Fe ^{11 being} between 5 and 100, advantageously between 20 and 60 g Fe per liter. Now, if necessary, with the addition of activators, such as. B. copper, silver or calcium heated. The alkali solution to be used for precipitation, for example soda solution, is also heated. Immediately before the start of the precipitation, an oxygen-containing gas, ζ. Β a strong stream of air, blown through the hot soda solution. The purpose of this measure is to convert the ferrous hydroxide formed during the precipitation at least partially into ferric hydroxide. The air flow, which may have been heated to temperatures between 80 and 100 ° by a preheater, is dimensioned so that an amount of about 10 to 50, expediently 20 to 30 cbm / hour is blown through the solution per kilogram of iron. Immediately thereafter, the precipitation is carried out in a known manner by adding the heated sulfate solution to the hot alkali solution and terminated for about 2 to 6 minutes. During this time, the air flow is blown through at the specified speed. Experience has shown that about 25 to 30% of the iron in the precipitated contact mass is obtained in the form of trivalent iron with this method of operation. The temperatures during the precipitation are about 50 to 100 °, preferably 60 to 95 °, the temperatures of the alkaline or iron solution not necessarily having to be the same.

For the production of a good and highly active catalyst using ferrous sulfate, the removal of the alkali adsorptively bound to the iron hydroxide, which is now in the form of sulfate, is of decisive importance. For this purpose, it is not sufficient, for example when using iron nitrate solutions, to simply rewash the precipitated contact mass with hot condensate. It is absolutely necessary to add ion-exchanging solutions to the condensate used for washing out in order to achieve a considerably easier removal of the sulfate ions through ion exchange. Ammonia compounds of the ammonium nitrate, carbonate and acetate type have proven particularly suitable as ion-exchanging solutions, but numerous other readily soluble ammonia compounds can also be used for this purpose; NH ₃ is also suitable, depending on the type of catalyst.

It is advantageous to adjust the concentration of the ion-exchanging solutions at the beginning of the washout In the condensate it should not be selected too high, as a large part is still present in the first stage of washing the adsorptively bound alkali sulfate can be removed by washing out with condensate alone can. Only in the last stage of the washout is it necessary to measure the amount of, for example To increase ammonium carbonate or nitrate. The concentration of ion exchange solutions in the wash water can vary between 0.2 and 20%, preferably with wash water washed out, which contain amounts of exchangers of about 0.2 to 2%.

Sulfur contents in the catalyst of not more than 0.1, especially below 0.05%, have not been found to be proved to be disturbing.

The further measures in the preparation of the catalyst using iron sulfate are practically the same as in the prior art using iron nitrate solution correspond. The well-washed catalyst mass is according to the intended Purpose impregnated, possibly shaped and dried at temperatures around 100 to 100 °, so that the water content of the finished catalyst is about 3 to 5%.

It is essential, however, that all these measures are carried out with a large amount of oxidizing agents Media, especially air, are carried out, so that the blown dry the washed Contact mass in the filter press using a lot of air at an elevated temperature

is carried out and that the final drying in the dryer also takes place with ample admission of air, so that at the end over 70%, predominantly over 80% of the total ^{iron is} present as Fe III. In the case of small amounts of precipitation, for example on the suction filter, good oxidation is achieved if the slurrying and washing out of the precipitated contact material is carried out in thin layers.

Dust and chips are removed from the finished grain by sieving and can then be reduced using hydrogen, carbon dioxide, nitrogen or mixtures of these gases. The temperatures here are in the range from 150 to 350 ⁰ , expediently from 220 to 320 ⁰ . A high flow velocity in the reduction of more than 50 cm, advantageously more than 1 m, is generally favorable. The layer height during the reduction can be below 30 cm, expediently 30 and 100 cm, or even significantly higher. If necessary, the reduction can even take place in the synthesis furnace itself. The catalysts according to the invention can also contain certain amounts of carrier substance, e.g. B. kieselguhr, Al ₂ O ₃ , Tonsil (trade name), activated bleaching earth, etc. contain. For carrying out the synthesis it has been found that catalysts prepared according to the invention, which predominantly lead to the formation of oxygen-containing compounds, especially alcohols, should have at least 50%, preferably more than 60%, of their iron content in the form of metallic iron .

On the other hand, a higher content of hydrocarbons can be achieved in the synthesis products, when using according to the invention produced, appropriately composed Catalysts have a content of less than 50%, preferably less than 30%, of free iron in the reduced catalyst is observed.

When using the catalysts according to the invention, the synthesis can be carried out either in one stage or in multiple stages and either in a straight pass or in a cycle. When working in several stages, it is advantageous to partially remove the carbon dioxide formed between the individual stages. The synthesis pressures should be 1 to over 100 atmospheres, expediently 20 to 40 atmospheres. The synthesis temperatures are between about 150 and 300 ⁰ . The gas loading can be varied within wide limits from about 10 volumes of gas per volume of catalyst and hour to over 500 volumes of gas per volume of catalyst and hour. The gas composition can vary between 0.5 to 2 H, and higher, based on 1 CO. The contact layer heights can be 5 m, but also more, up to about 12 m.

example 1

A solution consisting of iron sulphate and copper sulphate, which contains 5 parts copper per 100 parts iron and whose concentration was 40 parts iron in 1000 parts water, was brought to the boil and poured into soda solution at 80 ° (concentration 90 g Na ₂ CO ₃ per liter). A stream of air was blown through during the precipitation. The amount of air was 600 liters per 25 g of iron, and the blowing time was 3.5 minutes. Immediately thereafter, the mother liquor was freed by sharp suction and initially washed twice with a boiling amount of condensate corresponding to twelve times the amount of iron present. Finally, the contact mass was washed out three times by slurrying in an ammonium carbonate solution which contained 5 to 10 g of ammonium carbonate dissolved in 1500 ecm. 1500 ecm washing solution was used three times per 25 g of iron. After the last washout, the sulfur content in the finished catalyst was only 0.02%. Of the total Fe, 28% was now present as Fe ¹¹¹ , the remainder as Fe ¹¹ . The contact mass was then impregnated in a potassium carbonate solution in such a way that 8 parts of alkali, calculated as K ₂ O, accounted for 100 parts of iron.

The catalyst, dried for 24 hours with air circulation and comminuted to a particle size of 2 to 4 mm, now had an Fe ^{II content of 88%!} . It was then ^{reduced at 300 °} for 1 hour with a mixture consisting of 75% hydrogen and 25% nitrogen, using a linear gas velocity of 1.4 m (measured cold). According to this, the catalyst had a reduction value of 68% free iron.

If this catalyst was used for the synthesis at a synthesis pressure of 30 atm and a gas loading of 100 volumes of gas per volume of catalyst and hour with water gas, a conversion of 60% CO + H _{2 was} obtained at 205 °. The methane formation of this catalyst was approximately between 4.5 and 6. The yield of oxygen-containing compounds was 50%, based on the total liquid product.

Example 2

A solution consisting of iron sulfate and copper sulfate containing 2 parts of copper per 100 parts of iron, and their concentration was 45 parts of iron in 1000 parts of water, was heated to 90 ⁰ and by pouring into sodium carbonate solution of 75 ⁰ no (concentration 68 g Na ₂ CO ₃ per liter) at a _pH value of 7.2 hot like. A stream of air was blown through the precipitation apparatus during the precipitation. The amount of air was 650 liters per 25 g of iron and the blowing time was 4.5 minutes. Calcium carbonate was then added with vigorous stirring in an amount, calculated as CaO, of 10%, based on the iron present. Immediately thereafter, the mother liquor was freed by sharp suction and initially washed out with a boiling amount of condensate corresponding to 12 times the amount of iron present. Finally, the contact mass was washed out twice by slurrying in an ammonium carbonate solution which initially contained 4 and then 10 g of ammonium carbonate dissolved in 1500 ecm. Of the

The sulfur content after the last washout was 0.05%. Of the total iron, 28.5% was now present as Fe ¹¹¹ , the remainder still as Fe ¹¹ . The catalyst was then impregnated with a clay / waterglass solution in such a way that 3 parts of K ₂ O and 7.6SiO ₂ accounted for 100 parts of iron.

The at 105 ^0-dried for 24 hours under air circulation, and to a grain size of i, from 5 to 3 mm crushed catalyst had a content of Fe ¹¹¹ of 91% and was then at 305 ° for 90 minutes with a mixture consisting of 75% H ₂ and 25% N ₂ , using a linear gas velocity of 1.4 m (calculated cold). The reduction value was 35%. If this catalyst was used for the synthesis at a synthesis pressure of 10 atm and a gas loading of 100 volumes of gas per volume of catalyst and hour with water gas (CO: H ₂ = 1: 1.2), a CO + H ₂ - was obtained at 215 ° 66% conversion achieved. The resulting liquid product contained 40% of hydrocarbons boiling above 320 ^0. Oxygen-containing compounds were only present to a small extent.

Claims (7)

Patent claims: i. Process for the catalytic hydrogenation of carbohydrates using iron catalysts precipitated from sulfuric acid solutions, characterized in that catalysts are used which are made from ferrous sulfate solutions precipitated without the addition of remote compounds or oxidation mediators to the precipitation solution were, with their precipitation about 10 to 50, predominantly about 25 to 35% of the iron present has been converted into the trivalent form during the leaching of the obtained iron Precipitation using ion exchange solutions, preferably of easily soluble ammonia compounds, has taken place and during the washout, pre-drying and drying, further oxidation of the remaining divalent iron to trivalent iron Iron has been carried out with an ample supply of air in such a way that at the end over 70%, preferably over 80%, of the total iron was present as trivalent iron. 2. The method according to claim 1, characterized in that that the concentration of ion-exchanging solutions in the wash water in the The course of leaching was increased. 3. The method according to claim 1 and 2, characterized in that washing water with a Ion-exchange solution content of 0.2 to 20%, preferably 0.2 to 2%, for use came. 4. The method according to claim 1 to 3, characterized in that to achieve a possible high yield of oxygen-containing compounds these catalysts 2 to 15%, predominantly 4 to 12%, alkali, based on Fe in the form of hydroxide, oxide, carbonate or Salts of volatile or decomposable acids. 5. The method according to claim 1 to 4, characterized characterized in that in order to achieve a high yield of oxygen-containing compounds those catalysts are used which have at least 50%, preferably more than 60%, of their iron content in the form of metallic Had iron. 6. The method according to claim 1 to 3, characterized characterized in that to achieve the highest possible yield of hydrocarbons those catalysts are used in which alkali salts are not used for impregnation volatile acids, e.g. B. boric acid, phosphoric acid, silica, tungstic acid, etc. applied have been, the proportion of the acid component over 1 percent by weight, based on iron, expediently above 10 percent by weight, and the alkali amounts 1 to 10 percent by weight, expediently 1 to 7 percent by weight, based on iron. 7. The method according to claim 1, 2, 3 and 6, characterized in that in order to achieve a high yield of hydrocarbons those catalysts are used which have a content of less than 50%, preferably less than 30% free iron. © 9558 10.54