DE1952965A1 - New catalysts especially suitable for catalysis of ammoxidation reactions - Google Patents

Description

New catalysts especially suitable for catalysis of ammoxidation reactions

The invention relates to a process for the production of mono-, di- or polynitriles from the corresponding Hydrocarbons and relates in particular to a new catalyst with which such a process can be partially carried out.

Through the well-known reactions, which are designated by the term ammoxyaation, molecules can with at least one nitrile function by catalytic conversion of ammonia and oxygen with a hydrocarbon be prepared according to the following reaction scheme:

R - CH ₅ + ₅ NH + ^3/2 O ₂ - ■} RC fr +

For example, this reaction can produce acrylonitrile from propylene and aromatic nitriles from alkylated aromatic hydrocarbons.

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For example, applying this reaction to p-xylene gives Terephthalonitrile.

The catalysts used so far to carry out the ammoxidation reaction generally contain vanadium or tungsten as the active metal. The so far However, known catalysts all have low mechanical strength and lose some of them Hours of their activity to a large extent.

The catalyst according to the invention, on the other hand, has excellent mechanical properties and lasts for a very long time Has considerable activity over time and shows a remarkably uniform effect on the ammoxidation reaction.

The catalyst according to the invention is characterized in that it is produced by dispersing vanadium pentoxide on and in a crystalline titanium oxide with a square structure of the anatase type
is made.

of the anatase type and a specific surface area of 6-1 Om / g

It is very surprising that the crystalline anatase-type square structure titanium oxide has the best support structure for increasing, regulating and extending the known catalytic activity of vanadium, especially its catalytic activity for the ammoxidation reaction.

The catalysts previously used for ammoxidation were generally by impregnation or precipitation of vanadium or tungsten compounds or a mixture of Vanadium and tungsten compounds made on an aluminum oxide. Partly because of its physical properties, partly because of its crystal structure

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Aluminum oxide (in whatever form it is used) is not an ideal carrier for the active ingredient (vanadium or tungsten), which is less mechanical Strength of the supported catalyst, to local overheating at the active centers and finally to a rapid Shows decrease in the yield of catalyzed reactions and especially of the ammoxidation reaction.

As mentioned, titanium oxide can be used as a carrier for the catalytically active component address these various drawbacks. In addition, the invention is not based on specific ideas about the mechanism of action limited. So the titanium oxide comes safely due to its crystalline structure and its Physical properties play the role of the carrier, but it can also take part in the catalytic during the reaction Be involved in or influence the activity of vanadium.

It is also already known the catalytic activity of the vanadium and tungsten catalysts for ammoxidation reactions can be used, with the help, of various additives, generally made up of different metal compounds exist, modify and to some extent control. These additives that very likely act directly on the active catalytic product, have the effect of increasing the catalytic activity reinforce, inhibit, lengthen or regulate the catalytic converter. It has now been found that the known effect of these various additives on supported catalysts transferred with aluminum oxide as a carrier to the catalysts according to the invention with the titanium oxide carrier described leaves. For example, you can use the catalytic

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effective vanadium compounds oxygen-containing tungsten compounds, oxides of various metals such as magnesium, chromium, manganese, iron, nickel, copper, zinc, molybdenum, silver, tin, tellurium, barium, bismuth, thorium or uranium, which generally act as promoters, or oxide derivatives Add arsenic, antimony or phosphorus, which generally increase the life of the catalyst. For example, it has been found that the selectivity of the vanadium catalyst according to the invention is improved by adding iron oxide in an amount of about 0.2 fo.

The catalysts according to the invention based on vanadium Pentoxide and titanium oxide, as they have been explained above, can finally by known methods with an alumina cement be united. A final product with a very high mechanical strength is thus obtained by hydraulic setting Strength, especially since the carrier for the vanadium oxide, i.e. the titanium oxide, is very hard. That used in this way hydraulic binder gives a very advantageous macroporosity on the order of microns, the free access of the reactants to the allows catalytically active centers and does not interfere with the implementation itself.

The optimal conditions for the action participants Ammoxydationsreaktion may vary depending on the individual case present in R _e. For the reaction of p-xylal with ammonia and oxygen, the maximum p-xylene content is 1.5 % of the gaseous mixture. The ammonia content is preferably about 'Ib f> the gasför-shaped mixture, which ent excess of about 100% compared to the theoretically required amount, "- *

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BATH ORIGINAL

speaks, and the amount of air used is about 25 ¥> i while the rest of the gaseous mixture generally consists of nitrogen or a mixture of nitrogen and water vapor. The temperature used is above 250 C and ^above is preferably from 350 to 450 ^u C, and the applied pressure is between about 0 and 20 bar (gauge pressure).

The invention is illustrated in more detail by the following examples.

example 1

a) Production of a catalyst according to the invention

HO g of VmO ₁ - are dissolved in HCl. To achieve dissolution, the mixture is heated to the boil and further HCl is added in accordance with the evaporation. After cooling, 600 g of TiO ₉ with a specific surface area of 7 m 2 / g are added with stirring until a homogeneous paste is obtained. The paste is then heated ^{to 500 ° C. for 1 hour.} After cooling down, the paste is finely ground and then mixed with 260 g of calcium aluminate cement. A paste is prepared from the mixture by moistening it with water. After drying in air to a residual moisture of 20 Grew .- $ water, the mass is granulated and then molded under pressure. The tablets are watered for 2 hours and then kept in an oven at 200 ^° C. for 4 hours. The finished catalyst is composed of 14% ^V 2 ° 5 » ^6ü & ^Ii0 2 and ²⁶ ^ refractory support material.

The composition of the catalyst can range from 4 to 25 % V ₂ O ₅ , 25 to 70 % _{TiO 2,} and 10 to 60 % refractory supports. Preferably , 15% V ₂ O ₅ »50%, TiO ₂ and 35 % fire-resistant inert substances can be used. use.

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The catalyst described above is used for the ammoxidation of p-xylene in a tubular reactor with a fixed catalyst bed. The results obtained are shown in Table I below. In the table, "I ¹ PN" denotes the terephthalonitrile obtained.

BATH ORIGINAL

Table I.

co ο »

Yersu.cb.8- Reaction VVH feed NH ₅ p-XylOl temperature center U
C. the end duration,
hours pressure,
bar 26 "OO ^N 2 air 80 cm ⁵ / h A
occurs 360 the end
occurs prey
TPN # 2 Atmospheres
pressure ti 160 80 It 21 350 368 *
370 78 12th Il Il Il It ti It 355 367 372 . 80 24 ti It It It It It 355 362 373 80 48 It It Il Il II Il 350 362 372 81 120 Il Tl It It 350 372 81

Remarks:

- the throughput speed is defined by:

O S

VVH = introduced gaseous mixture (l / h _f normal conditions)

Catalyst volume (1)

- The temperatures are in the catalyst at the entry point in the Middle. and measured at the exit point of the reaction mixture;

- The yield is in mol% recovered TPN, based on the imported p-xylene indicated.

cn

b) Comparative experiment

The experiments described above are used for comparison repeated under the same conditions except that in the preparation of the catalyst the titanium oxide thanks to gamma aluminum oxide with a specific surface area of 150 m / g is replaced. The results obtained are listed in Table II below.

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Table II

Yersuchs- Reaction VVH Feed l / h 160 air 80 duration,
Hours: pressure,
Bar: 2600 1 Il 80 Il 1/2 Atmospheres
pressure Il Il Il Il 1 It Il Il Il Il 2 Il Il Il Il Il 5 ti Il Il Il Il 4th It Il U 5 Il

Stress
te

TPN

iSin- middle exit occurs

r cd

• - ίο. -

A comparison of the results listed in Tables I and II shows the advantages of using a "- ■ _ catalyst according to the invention can be achieved instead of a known catalyst.

Example 2 Production of a catalyst according to the invention and

results obtained with it

140 g of V ₂ O ₅ and 2 g of Pe ^ O ₃ are dissolved in HCl. To achieve dissolution, heat to the boil and add more HCl as it evaporates. To. cooling down

558 g TiO ₀ with a specific surface area of 2

2
8 m / g are added with stirring until a homogeneous paste is obtained. The paste is then heated ^{to 500 ° C. for 1 hour.} After cooling, the mass is finely pulverized and then mixed with "260 g of alumina cement. A paste again by moistening with water from the mixture prepared according to T _r ocknen in air to a residual moisture of 20 parts by weight 5 water. Is the mass The tablets are soaked for 2 hours and then kept in an oven for 4 hours at 200 ^° C. The finished catalyst contains -14 f <> V ^ O ₅ , 0.2 <jk Fe ^ O. ,, 5518 fo TiO ^ and 26 ⁶ / ° refractory carrier material _o

In the ammoxidation of p-xylene with this catalyst • At the beginning of the experiment, practically the same results are obtained as with catalyst (a) from Example 1 achieved. After a few hundred hours of operation, however, different aging of the two catalysts is observed *

ORIGINAL INSPECTED

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Claims (5)

Claims -Ί.) Process for the production of nitriles by simultaneous passing a hydrocarbon, ammonia and oxygen over a catalyst, characterized in that one is obtained by impregnating a crystalline titanium oxide with square Structure of the anatase type and a specific surface from 6 to 20 m / g with a solution of vanadium pentoxide and drying the mixture obtained at 500 * 0 obtained catalyst used. 2. The method according to claim 1, characterized in that the catalyst also has at least one promoter or an inhibitor of the ammoxidation reaction contains known metal compound. 3. The method according to claim 1, characterized in that the catalyst 4 to 25 £ & * - # Vanadiurapentoxid and 25 to 70 wt .- ^ of the titanium oxide and that the finely crushed grains of this catalyst by 10 to 60 wt .- $ of an alumina cement, based on the End product, are interconnected. - 4. The method according to claim 1, characterized in that an alkyl aromatic hydrocarbon is ammoxidized and the reaction is carried out at a temperature above 250 ^u C and preferably between 350 and 450 "C. 5. The method according to claim 4 »characterized in that p-xylene is used as the alkyl aromatic hydrocarbon uua the reaction is carried out at a temperature between 360 and 380 ^W C» BATH ORIGINAL 009819/1928