DE2222120B2 - METHOD OF MANUFACTURING A PLATINUM CATALYST FOR THE PRODUCTION OF HYDROXYLAMINE - Google Patents

Description

35

The present invention relates to a method of preparing a platinum catalyst for production of hydroxylamine, in which a carrier is mixed with hexachloroplatinic acid and in strong alkaline medium is reduced with formaldehyde.

There are known several processes for the production of hydroxylamine by catalytic reduction of Nitric oxide, nitrogen dioxide, trioxide, nitric acid or nitrate ion in a medium of strong Mineral acid.

Catalysts based on platinum or platinum alloy are used here. The main reaction products are hydroxylamine and ammonia. The best conversions and yields are obtained with catalysts on inert carriers, such as coal, graphite, silica gel or alumina, in a ratio of 0.3 to 15% platinum, in a 10 to 20% hydrochloric or sulfuric acid medium. The working temperature varies between -5 ° C and 100 ° C and the pressure between 1 ata and 10 ata. The ratio between "hydrogen and nitrogen monoxide" also varies between 1:10 and 10: 1, while the ratio between the catalyst and the acid is approx. 0.1 g of platinum per 300 cm ^{3 of} acidic solution. The activation and regeneration of the catalyst begin On the spot by heating the reaction mixture to a temperature which is 10 to 40 ° C higher than the temperature at which the process takes place, accompanied by the five minute to one hour surge of a hydrogen or nitrogen oxide stream, after which the current Generation of the hydroxylamine is resumed by the addition of the mixture of hydrogen and nitrogen monoxide. _>

When regenerating riäüuicat <uysätoren is it has long been known to use suitable reducing agents in the form of hydrazine, formaldehyde, hydrogen, To use formic acid or formates:

In a process for production and regeneration made known by DT-AS 10 88 037 a special catalyst for the production of hydroxylamine from nitrogen oxide and hydrogen by reducing an aqueous platinum (IV) compound in the presence of a carrier, the procedure is as follows: that the platinum (IV) compound is first in a weakly acidic medium by a selective reducing agent transferred into a solution of a platinum (II) compound and then out of the solution transferred to a platinum (II) compound and then from the solution of the platinum (II) compound Platinum is deposited on the support by means of a stronger reducing agent than metal.

In another process for the production and regeneration of an active and selective catalyst for the production of hydroxylamine salts from nitrogen oxide and hydrogen in the presence of acid by reduction with substances which contain metal from the group of platinum metals, known from GDR patent specification 65 788, Particularly Pt in H ₂ PtCl ₆ compound in the presence of carriers, the procedure is such that the reduction process in dilute solutions using not less than 300 l of the reaction solution per 1 kg of the platinum metals in the compound used is most advantageous 6001.

In this process for the preparation and regeneration of a catalyst, there is a reduction the activity by prolonged use the platinum to hexachloroplatinic acid redissolved in order to then after separation of the heavy metal ions acting as catalyst poisons again the production of the catalyst to be supplied. Here, the catalyst has to be prepared anew for each regeneration will. This is a very serious disadvantage, because a lot of work has to be spent on the new manufacture, platinum losses can also occur.

It is the object of the present invention to provide an easily regenerable catalyst To create lifespan and high activity.

The invention consists in adding a protective colloid to the hexachloroplatinic acid solution, which is heated to boiling, and then adding an inert carrier so that the hexachloroplatinic acid is added to the paste obtained at a temperature of -30 to + 100 ^° C., for a minimum of five minutes, with excess formaldehyde is reduced in a strongly alkaline medium, whereupon the paste is left to rest at a temperature of +10 to + 100 ° C for at least five minutes and then filtered, the catalyst on the filter being washed with water, and that the washed and wet catalyst is activated by intensive contact with hydrogen in an acidic medium at a temperature of +20 to 105 ° C for five minutes in the presence of 0.1 mg to 0.1 g of ferric chloride per 1 g of platinum.

The catalyst obtained in this way already has a very high level of activity after its preparation

opened up. It is easy to rest for 2 hours with hydrogen peroxide at a temperature of 50 ° C,

and to regenerate a cation exchanger. after which it is filtered, while the

During the regeneration, the previous catalyst is fed into the filter with water.

gen that - after the activity has decreased, washing is carried out longer until the chlorine ion from the fiI-

Rem use - the catalyst with 15% water disappears.

The washed catalyst is then activated, an acidic cation exchanger is mixed by intensive contact with hydrogen in which, after mixing, 25% sulfuric acid medium is separated off again with the addition of, after which the catalyst is intensively contacted by 1 , 5 mg of ferric chloride at a temperature of 60 ° C., bring with hydrogen in an acidic medium for a period of 30 minutes. The activation takes place in the temperature of + 20 ° to +105 ⁰ C for five minutes hydroxylamine synthesis apparatus, as it is shown in more detail long in the presence of 0.1 mg to 0.1 g remote- in the following example,
chloride is reactivated per 1 g of platinum. After . .
The first regeneration of the catalyst in Example 2
drove even better catalyst properties 15 It becomes a horizontal, cylindrical apparatus for. The regeneration is not only used on a single phase contact, which is limited with one, it can rather be repeated very often central drive shaft without blades and with three. In this case, the catalytic converter-equipped with blades satellite shaft property does not deteriorate. On the contrary: After the first Re- and which has a volume of 22 liters. The catalyst maintains its improved ao: 121 sulfuric acid solution 25 ⁰ Zo, 60 g Pia properties over a long period of time. tin catalyst 10%>, on graphite powder, with an

It is advantageous for the production if there were 1.5 mg of ferric chloride. The catalyst was

Protective colloid gelatin or gum arabic prepared in a according to Example 1 and now its ac-

Amount of 0.05 to 5 g protective colloid per 1 g platinum coating.

be used. a ₅ The air is removed from the apartment by washing

For the activation it is advantageous if this is removed with hydrogen. There is a pressure in the apparatus

takes place with hydrogen in dilute sulfuric acid. of 1.4 ata maintained, the temperature of the reaction

This catalyst is easy to prepare and easy to use by heating the mixture

to prepare. The particularly light conditioning jacket of the apparatus is slowly increased to 60 ° C and

possibility not only saves costs, but leads 30 the agitation, which lasts 30 minutes, started,

also to the fact that in the otherwise known regeneration the catalyst is now activated. He is now in the-

The same way it is cooled down to 25 ° C by restoring a new catalyst, and it starts

tors platinum losses can be avoided. the continuous feeding of the reacting

The activation takes place preferably in hydroxyl gases, hydrogen and nitrogen monoxide, in one

amine synthesis apparatus Fast and favorable results 35 space ratio of 1.8 / 1, as well as the continuous

in terms of activation and synthesis achieved the derivation of the non-reacted

by continuously keeping the gases in contact, a working pressure of 2 ata in the apparatus

Phases, e.g. B. is maintained by planetary movements in a ho-.

rizontally lying device, which with blades If in the liquid mixture of the device a

Carrying satellite waves and with planetary Me- 40 concentration of 97 g HydroxylaminA is achieved,

mechanisms is provided, the continuous supply of sulfur

The invention is illustrated below with the aid of acidity 25 ° / · and the continuous derivation of the

examples of management explained in more detail. The examples are hydroxylamine sulfate solution so that the amount of

write reaction mixture in the apparatus uniformly

1. The preparation of the catalytic converter and its activities are 45.

fourth. The device will operate for 20 days

2. The use of the catalyst in hy- let. In this period of time, a throughdroxylamine synthesis is obtained. average hydroxylamine yield of 90 /

3. The preparation of the catalyst with one over the consumed nitrogen monoxide and one Decrease in activity. So average catalyst activity of 118.0 g

. NO / g Pt.h. The original activity of the catalyst

Example 1 sators experiences a reduction during this time

One prepares for the reduction with formaldehyde of only 35 ° / ».

In an alkaline medium, a solution of 24 ml of hexa- After the catalyst has been separated by abchloroplatinic acid with 6 g of platinum content, which is heated until it is cleared by the boiling removed from the apparatus and in which 54 g of the catalyst is mixed as a carrier, the catalyst according to Example 3 reactivates graphite powder and as a protective colloid 4.15 g alimen- and regenerated. The catalyst treated in this way, distilled gelatin are mixed in. The achieved activity is restored to its original value. Paste is brought into a drying cabinet at 60 ° C. and is again stored in the apparatus for at least 30 minutes. The reduction 60 carried out, where the synthesis of the hydroxylamine begins, then takes place at 0 ^° C. for 30 minutes and is then continued for 10 days. The after-40% formaldehyde in excess with respect to the catalyst subsequently separated has an activity of the theoretically necessary amount with a strong alkali reduction of only 18%.
see medium consisting of sodium hydroxide. As a result, the same kata after the end of the reduction, the presence of two activations and regeneration of chloroplatinum ions can no longer be determined or applications in the synthesis are presented. nomrnen, whereby the synthesis periods are 7 days each

After the reduction, the paste obtained is allowed to contribute. Each time the activity of the catalyst

⁵ . _{t A} In addition, the catalyst has an increased

and its hydroxylamine yield practically reproduced under the audc poisoning and slow previous conditions. ^W1 ° 5. T., α wsvitat during the synthesis process

The spent catalyst, which was removed from the hydroxylamine synthesis apparatus by decanting removed acidic mixture was separated according to Example 2, was agitated with 30 cm 'of hydrogen peroxide 15Vi treated, that afterwards -pasted Se. The catalyst was then used intensively 80 g of strongly acidic cation exchanger mixed as this treatment for the poisoned with metal ions Catalyst is needed.

After its separation from the cation exchanger, the catalyst again underwent a storage regeneration treatment subjected and under the conditions described in Example 1 of the original Activation. , ._,

The prepared and activated or reactivated and regenerated catalyst according to the invention has a increased initial selectivity and activity what to increased hydroxylammy yields - of over 95 »/ ο compared to the nitrogen monoxide consumed - leads.

Poisoning and a slow decrease in activity during the synthesis process

JOTagen _r ^ _eration

_r ^ _eration .

^^ _he number of working periods one placed * ^a ™ ^e catalyst after each Reaktme-

fet that _{its activity} and hydroxyl

Siute regains and that he wears the ^ TSSS ^ iiikende curve in the course of its first use and thus ^^ ίβηαβ reproducibility,
the application of the invention, emalt .P ^ JL ₈₁₀₁ for the synthesis of hydroxylamine ^ ™ kydrieruiig of nitric oxide, etc., durcn α "y _{νοτΐύΧ &} offers:

™ ^ε '^ ° ^Ε selectivity and activity, increased

Resistance to poisoning and increased mechanical iderstanü ^W against β ^ service life;

»O scher Wgmtand ^ _{tivi and} regeneration - _achievements that he has in his

his "« ^ ™ ⁿ £ ^ _how | _he regain with the f ^^ re-use period.

Claims (3)

Patent claims: 1. A process for the production of a platinum catalyst for the production of hydroxylamine, in which a carrier is mixed with hexachloroplantinic acid and reduced in a strongly alkaline medium with formaldehyde, characterized in that a protective colloid and then an inert carrier are added to the hexachloroplatinic acid solution heated to boiling. is mixed that the hexachloroplatinic acid at a temperature of -30 to +100 ⁰ C, minimum of five minutes, is reduced with excess formaldehyde in strongly alkaline medium in the obtained paste, whereafter the paste at a temperature of 10 to 100 ° C for at least for five minutes allowed to rest and is then filtered, the catalyst is washed on the filter with water, that the washed and wet catalyst by intensive ao contacting with hydrogen in an acid medium at a temperature of 20 ° to 105 ⁰ C, at least five minutes long, in the presence of 0.1 mg to 0.1 g of ferric chloride per 1 g of plat is activated in. as 2. The method according to claim 1, characterized in that gelatin or as protective colloid Gum arabic can be used in an amount of 0.05 to 5 g of protective colloid per 1 g of platinum. 3. The method according to claim 1, characterized in that the activation with hydrogen takes place in dilute sulfuric acid.