DE2006347C3 - Process for the preparation of a catalyst - Google Patents

Description

25th

The invention relates to a method of manufacture a catalyst for a direct ammonia synthesis from gaseous hydrogen and nitrogen.

The industrial processes used to date for the synthesis of ammonia are the Haber-Bosch process, the Claude method and the Mont Cenis method. The main catalyst for the first two Process an iron oxide catalyst and in the latter process a cyanoferrate complex salt used. All of these catalysts have in common that they essentially consist of iron compounds exist as a catalytically active component and optionally of activators and that they only after a reduction treatment should be used.

Traces of oxygen or carbon monoxide also act as catalyst poisons on these catalysts and lead to a decrease in the catalytic effectiveness.

In addition, a catalyst for the treatment of petroleum distillates, especially acidic petroleum distillates, known to be obtained by separating phthalocyanine from aqueous or alkaline solution Activated carbon is produced.

The process for the production of catalysts according to the invention, which, however, is completely so in its kind is new and leads to catalysts that differ from the catalysts used up to now Have compositions, is characterized in that you have an excess amount at least one of the alkali metals with one or more transition metal phthalocyanines, one or several transition metal porphyrins or with graphite at one above the melting point of the Can react alkali metals lying temperature.

The term "excess amount" usually denotes an amount that is greater than that the equimolar ratio of alkali metal to transition metal phthalocyanine or porphyrin or graphite corresponding amount is.

The catalyst complex compounds produced in this way belong to the group of electron donor acceptor complexes, in which the transition metal phthalocyanines, the transition metal porphyrins and graphite are the electron acceptors and the alkali metals which are electron donors.

The term alkali metals includes the following metals: lithium, sodium, potassium, rubidium

and cesium.
The transition metal phthalocyanines are z. B. the

Phthalocyanines of iron, nickel,! Cobalt, tungsten, Platinum, titanium, manganese, chromium, zirconium, hafnium, Vanadium, molybdenum, osmium, palladium, ruthenium, Rhodium and iridium.

These transition metal porphyrins are z. B. Porphyrins of iron, nickel, cobalt, tungsten, platinum, iridium, osmium, titanium, manganese, chromium, zirconium, Hafnium, vanadium, molybdenum, palladium, ruthenium and rhodium.

The catalysts according to the invention absorb a considerable amount of gaseous substances Hydrogen and nitrogen and put a mixture of gaseous hydrogen and nitrogen catalytically in ammonia. An ammonia formation does not take place, however, if the gas mixture only over Alkali metals, only via transition metal phthalocyanines, only via transition metal porphyrins, or only is passed over graphite. In addition, the catalysts according to the invention as well as the known catalysts the process of ammonia decomposition vice versa. The highest ammonia yield is therefore at low temperatures and high Pressing, so achieved on the side of high equilibrium concentration of ammonia.

The catalysts according to the invention can for example by one of the following methods getting produced:

An excess of at least one of the alkali metals is mixed with at least one of the transition metal phthalocyanines, at least one of the transition metal poirphyrins or with graphite at a temperature mixed, which is above the melting point of the alkali metal or the alkali metals.

When using transition metal phthalocyanines or transition metal porphyrins, the Alkali metal or the alkali metals and the transition metal phthalocyanines or transition metal porphyrins deposited on a carrier with a large surface, and the mass thus obtained is at a Heat-treated at a temperature above the melting point of the alkali metal or alkali metals.

The catalysts of the invention consist of complex compounds between the alkali metals and the transition metal phthalocyanines, the transition metal porphyrins or graphite and are can be produced by one of the aforementioned processes.

Activators do not need to be added to activate the catalysts of the invention another reducing treatment with hydrogen. In addition, the catalytic effectiveness decreases of the catalysts according to the invention does not decrease in the presence of gaseous oxygen.

The exemplary embodiments reported below serve to illustrate the invention.

example 1

0.5 g of metallic sodium were on the inner wall of a glass, serving as a reaction vessel U-tube was deposited, and 0.1 g of iron phthalocyanine was then evaporated onto this layer. These precipitated substances were then heat-treated at 200 ° C. in a vacuum, with

a deeply colored complex of iron phthalocyanine sodium formed. A mixture of gaseous hydrogen and nitrogen was introduced into the reaction vessel with the complex thus formed and circulated at a rate of 12.2 ml / min. The volume of the circulation system was about 140 mL. The surface area of the complex catalyst, determined by the BET method, was about 1 m ² / g; the ammonia collected in a cold trap was quantitatively analyzed using gas chromatography and infrared spectrometry. The results are shown in Table I. When the catalyst obtained in this way was exposed to 10 to 20 atmospheric Hg of oxygen or carbon monoxide, its catalytic activity was practically not changed.

Table I.

Partial pressure N ₂ H ₂ 30th Reaction
temperature Ammonia- NHj / Nj *) of the initiated (cm Hg) 30th yield after Gas 10 30th (° C) 20 hours
(ml under 10 30th 110 normal 0.02 10 to. 170 conditions) 0.07 10 240 0.26 0.27 30th 260 0.92 0.36 240 3.64 0.05 4.60 1.80

*) In this and in all the following tables, “NH3 / N2” denotes _{the ratio of the amount of NH 3 formed} to the amount of N _{2 used.}

Example 2

The catalysts were prepared in the same way as in Example 1, 0.5 g of the various alkali metals being reacted with 0.2 g of the various transition metal phthalocyanines in the list shown in Table II. Table II also shows the results of the ammonia synthesis carried out using the corresponding catalysts, the surface area of the catalysts again being about 1 m ² / g.

Table II Example 3

0.5 g of metallic sodium and 0.2 g of iron phthalocyanine were deposited on 0.1 g of activated carbon with a surface area of about 600 m ² / g and converted to the catalyst. The results of the ammonia synthesis carried out with this catalyst are shown in Table III Reaction system was about 140 mL

Table HI

Partial pressure of
initiated
Gas
N ₂ IH ₂
(cm Hg) 45
45 Reaction
temperature
CC) Ammonia VniislKtitr NH ₃ ZN ₂ 10
15th 25th
50 after 20 hours
(ml under normal 0.015
0.06 03

20th

Example 4

The catalysts were prepared in the same manner as described in Example 1, with 0.5 g metallic sodium and 0.2 g of transition metal tetraphenylporphine in the table IV Composition were implemented. The results the ammonia synthesis carried out with the catalysts shown in this way are summarized in Table IV. The volume of the reaction system was about 140 ml.

35

40

Table IV catalyst

Partial
print of the H ₂ 30th Rcak- ammonia NHj / N ₂ one (cm Hg) 45 functional
tempe- yield catalyst guided
Gaw 10 45 rature after
20 hours 10 45 (ml under N ₂ 15th 45 ( ⁰ C) Normai- 0.24 10 45 240 conditions) 0.36 K-FePc *) 10 200 3.2 0.42 Na-CoPc **) ... 10 240 10 0.19 Na-CoPc **) ... 240 18th 0.07 Na-WPc **) .... 240 5.8 0.17 Na-PtPc **) .... 240 2.1 Na-ClTiPc **) .. 5.2

Na-ClFe- (HIMetra- phenylporphine

Na-ClMn- (Ill) -tetra-

50 phenylporphine

110
240

240

Example p

Ammonia yield

after 20 hours

(ml under Normal conditions)

0.2 8.2

0.8

NH ₃ / N ₂

0.01 0.41

0.04

Pc = phthalocyanine.

*) The volume of the reaction system is about 100 ml. * ♦) The volume of the reaction system is about 210 ml.

A graphite-alkali metal complex catalyst was prepared by reacting about 2 g of graphite powder obtained with about 2 g of alkali metal in a vacuum at 300 ° C in a glass U-tube.

In the reaction vessel, which is kept at a certain temperature, a hydrogen-nitrogen mixture is circulated at a rate of 12 ml / min. The volume of the recirculation system is approximately 114 ml. The surface of the complex, was determined by the BET method using nitrogen _s was about 500 m ² / g. The reaction product, the ammonia, was collected in a glass U-tube, which was used as a cold trap and was built into the circulation system and was cooled with liquid nitrogen, and was then

then analyzed with the aid of infrared spectrometry and gas chromatography. The results are reproduced in Table V.

The presence of oxygen and carbon monoxide made the activity of the complex practical barely changed.

Table V

Partial
print of the killed
ises
H ₂
Hg) React Ammonia-
loot NH ₃ ZN ₂ catalyst gelci
Ga
N ₂
(cm 9.2 üons-
tempe-
rature
( ⁰ Q after
12 hours
(ml under
normal
conditionseii) 0.24 K graphite 5.8 9.2 300 1.9 0.27 Na graphite 5.8 300 2.1

Example 6

In the same manner as described in Example 5, the catalyst was prepared from one gram of an alkali metal and two grams of graphite. The results of the ammonia synthesis carried out with these catalysts are shown in Table VI. The surface area of the catalyst was about 20 m ² / g, and the volume of the reaction system was about 310 ml.

Table VI

Partial
print of the
cin ~ H ₂ 24 React Ammonia
yield NH ₃ ZN ₂ catalyst guided
Gas (cm Hg) 24 lions
tempe-
rature after
20 hours
(ml under N ₂ 8th 24 Nonnal 8th 38 ( ⁰ C) conditions) 0.002 K graphite 8th 306 0.06 0.004 12th 325 0.11 0.008 350 0.23 0.008 Rb graphite 300 0.39

Claims (3)

Patent claims: 1. A process for the preparation of a catalyst, characterized in that S an excess amount of at least one of the alkali metals with one or more transition metal phthalocyanines, one or more transition metal porphyrins or with graphite at one above the melting point of the Can react alkali metals lying temperature 2. The method according to claim 1, characterized in that the alkali metal is on a carrier precipitates, the transition metal phthalocyanine or porphyrin precipitated on this Layer is evaporated and the conversion to the catalyst by a subsequent tempering in Vacuum. 3. Use of the catalysts according to Claim 1 and 2 for the synthesis of ammonia.