DE1007754B - Process for the improvement of iron precipitation catalysts for the catalytic hydrogenation of carbons - Google Patents

Description

Process for improving iron precipitation catalysts for the catalytic carbon dioxide hydrogenation Addition to patent 892437 In patent 892 437 is a process for increasing the grain strength of iron-containing precipitation catalysts described for the catalytic hydrogenation of carbohydrates at normal and elevated pressure, which is characterized in that the precipitated catalyst portion is based on mechanical, chemically or physically obtained iron powder are added.

The catalysts according to the invention are produced in such a way that that the precipitation batch is prepared in a known manner, with one of the as iron powder amount to be added equivalent proportion of iron salt left out of the approach will. The precipitation is then carried out in accordance with the state of the art from the corresponding Fe salts, for example at temperatures between 50 and 1000, using hot alkali hydroxide or carbonate solutions. Immediately afterwards After the precipitation, the prepared amount of iron powder is poured into the precipitated catalyst mass stirred in, expediently using an intensive stirrer, to in as possible A very fine distribution of the iron powder in the precipitated cake in a short time to reach. The amount of iron used in the form of iron powder can up to 75 ovo, however tests have shown that optimal effect then is obtained when the amount of iron powder is about 25 to 500 / a of the total iron content matters.

After the precipitation, the precipitated contact masses are further processed then in a known manner, d. that is, one or more washouts close followed by impregnation according to the intended composition of the catalyst is made. Depending on the one intended for the catalytic converter Partial washout is also beneficial for this purpose. Thereafter it is expedient also a shaping. It has been shown, however, that even by simple Drying a so-called lump catalyst is obtained, the grain strength of which especially after the reduction of those of precipitation catalysts without the addition of iron powder is considerably superior.

In this way, catalysts can be obtained which both in the synthesis of hydrocarbons as well as in the synthesis of oxygen-containing ones Compounds using gases of various compositions in normal and increased pressure without yields with low methane formation and favorable temperatures result.

The reduction or pretreatment of the catalysts of the invention happens in a known manner using reducing gases such as hydrogen, Carbon dioxide or mixtures thereof, with pre- partly a CO: H2 ratio of about 1: 1 to 1: 2 is adhered to. The use of a high gas velocity during the reduction (about 50 to 150 cm / sec.) mainly because it is then also possible to reduce in layer heights of 1 m and more. the Catalysts can be used at normal pressure, but particularly favorably at elevated pressure between 5 and 100 atmospheres, expediently between 1 and 40 atmospheres, are used for the synthesis will. The gas loads can vary within wide limits depending on the purpose and goal of the synthesis can be varied, between 10 and 1000 vol./vol. Catalyst and hour.

It has been found that iron precipitation catalysts for the catalytic Hydrogenation of carbohydrates at normal and elevated pressure, during the production of which the precipitated catalyst fraction by mechanical, chemical or physical means obtained iron powder are added, further improved according to patent 892 437 can be if instead of the metallic iron powder the equivalent amount of powdered iron oxide, expediently Fe 2 O 3, a grain size below 250, preferably below 1 to 10 Ft, of the precipitation solution during or immediately after the precipitation, in any case, however, added before the separation of the precipitate and during the subsequent one Drying, reduction and other post-treatment of the catalyst include heating on calcining temperatures is avoided. It turned out that, surprisingly from the powdered iron oxide through a reducing pretreatment with H2- and / or CO-containing gases produced iron metal catalysts are considerably better and are more active than the previously used powder from only metallic Iron. This even goes so far that even in the case of a non-quantitative reduction of iron oxide powder to iron metal, the catalysts according to the invention already have one have greater activity.

The grain strength is the Heschritten precipitation catalysts also influenced in a particularly favorable sense.

Otherwise the procedure is the same as in patent 892,437.

Example 1 A mixture of the nitrates from iron and copper, dissolved in Water (30 g Fe or 10 g Cu / l) became hot (1000) to a boiling solution of Soda in water (90 g / l) added. The pH after precipitation was 7.5. Immediately afterwards was iron oxide powder (Fe2O0)., Which has a grain size possessed from 0.3 to 5 p. stir in such an amount quickly using a turbo stirrer, that, based on the above 30 g of fur, 10 g is present in the form of iron oxide powder the ratio of Fe from precipitation to Fe powder was 1: 0.33. The catalyst was washed out well with hot condensate (0.30 / 0 based on total Fe and calculated as K2 0 residual alkali) and impregnated with potassium silicate in such a way that, based on Total iron, 3 0 / o K2 0 and 80 / (Si oil were present. After drying at 1100 during 24 hours the mass was crushed (1.5 to 4 mm) and at 2580 during 60 minutes using a linear gas velocity of 1.4 m / sec. with a mixture consisting of 75 ovo H2 and 25 N2. The reduction value was 37 ovo.

In a so-called double tube furnace, the above catalyst has a gas loading of 200 l of water gas / l of catalyst / hour at a synthesis temperature of 2390, synthesis pressure 20 atmospheres, a CO + H2 conversion of 67% corresponding to a CO conversion of 800/0. The methane formation was 60 / o, based on converted CO t H2.

Example 2 A catalyst according to Example 1 was prepared with the following changes: alkali impregnation 5 K2 0 and 25 Si 02, based on total iron, Reduction temperature: 2350. Under the synthesis conditions of Example 1 was at a CO + H2 conversion of 68% was observed at a temperature of 2470. The methane formation was 50/0, based on converted CO + H2. The formation of high molecular weight compounds (> 3200 boiling) was considerably larger (about 400/0) than with this catalyst that in Example 1 (about 25%. The reduction value of this catalyst was 28 0 / o, based on the total iron; since experience has shown that precipitated iron oxide is lighter is reducible than iron oxide powder, only a small part of the iron oxide powder is likely have been reduced to iron.

Example 3 Iron and copper in the form of nitrates and in one concentration 30 g / l each was added hot to a boiling soda solution (85 g soda / l), so that the pH after precipitation was about 9.5.

Immediately afterwards, iron oxide powder (Fe2 00, grain size about 1 to 9 ii) in an amount of 30 g of Fe as a powder, based on 30 g of precipitated Fe, added. After hot filtration and washing out with hot condensate to a residual alkali content of 0,4 ° / o based on total iron and calculated as K2 O, the catalyst mass was impregnated with K2 C 0o in such a way that to 100 parts Total iron 8 parts, calculated as K2 0, were omitted. After drying at 1150 During 24 hours the mass was crushed to a grain size between 1 and 3 mm sieved and at 3150 with a mixture consisting of 75 ovo H2 and 25 0 /, N2 for 2 hours using a 1.4 linear gas velocity m / sec. reduced. Thereafter, the reduction value was about 65%.

At a synthesis pressure of 30 atü using water gas and a catalyst space velocity of 200 1/1 catalyst and hour was at one At a temperature of 2100 a CO + H2 conversion of 63% was found. The methane formation, based on the total converted CO + H2, was 6 0 / o. The liquid reaction product contained over 550/0 of oxygenated compounds, most of which consisted of Alcohols in addition to esters, aldehydes and ketones as well as acid passed. The amount for compounds boiling above 3200 it was 270/0.

Example 4 A catalyst was used as in the example 2 specified composition. A precipitated catalyst mass was produced, which contained 25 parts of copper per 100 parts of iron. After careful washing the remaining alkali to 0.40 / 0, based on the total iron, was with alkali silicate impregnated and after neutralizing with nitric acid a K20: SiO2 ratio set from 1: 5. The alkali content was 5 K20, based on 100 Fe, in the finished product Catalyst.

Half of this approach was exactly analogous to the information in the example 2 processed further (catalyst A).

Part of the remaining dried mass of the approach with a Water content of about 50/0 was determined according to the method of the German patent specification 863 791 ground fine on a ball mill for a long time. After that this became The mass is mixed with the fresh batch available in such a way that 75% of the total iron in the form of the fresh batch, while 25% of the total iron was in the form of the dried material and powdered in a ball mill.

The entire catalyst mass was shaped and dried in the usual way and calcined at 5000 for 1 hour (Catalyst B).

When comparing the catalysts A and B, it was found that under the synthesis conditions of Example 2 at a reaction temperature of 2520 a conversion of 68% was obtained in the first month of operation. Metal formation was 70/0. In the second month of operation, the average reaction temperature was 2560 with a CO + H2 conversion of 670/0. The methane formation was 9%.

This attempt had to be carried out around the middle of the third month of operation be canceled, since partial grain disintegration results in a pressure loss of several Atmospheres had entered.

In contrast, the numbers of the original catalyst A were correspondingly Example 2: 1st month of operation: 68% CO + H2 conversion at one reaction temperature of 2460, methane formation 5 ovo 2nd month of operation: 68 ° / o CO + H2 conversion, reaction temperature 2490, methane formation 6 0 / o.

3rd month of operation: 67% CO + H2 conversion, reaction temperature 2530, methane formation 70/0.

4th month of operation: 67% CO + H2 conversion, reaction temperature 2580, methane formation 100/0.

Even after this time, the experiment did not show any signs an increased pressure loss or a core disintegration.

Claims (1)

PATENT CLAIM: Process for improving iron precipitation catalysts for the catalytic hydrogenation of carbohydrates at normal and elevated pressure, at their Production of the precipitated catalyst portion on mechanical, chemical or physical iron powder obtained by shear ways was added are, according to patent 892 437, characterized that instead of the metallic iron powder, the equivalent amount of powdered Iron oxide, expediently Fe2 03, a grain size below 250i, preferably below 1 to 10 im, the precipitation solution during or immediately after the precipitation, in any case but added before the separation of the precipitate and during the subsequent drying, Reduction and other post-treatment of the catalyst include heating to calcining Temperatures is avoided. Publications considered: German Patent No. 863 791; U.S. Patent No. 1,853,771.