DE2012939C3 - Catalyst for the reforming of hydrocarbons with water vapor - Google Patents

Description

The invention relates to catalysts for reforming hydrocarbons with water vapor.

GB-PS 1039206 describes catalysts that Contains uranium and nickel. There is no information about the addition of barium. Furthermore, there is no information about a certain ratio between nickel and uranium as well as information on the total permissible weight of nickel and uranium on the catalyst carrier.

GB-PS 944207 describes catalysts for removing oxygen from gas mixtures. These Catalysts contain copper as an essential component, while the catalysts according to the invention contain no copper.

The invention relates to a catalyst for the reforming of hydrocarbons with steam, with a catalyst support on its Surface is a mixture of nickel oxide and / or nickel together with one or more oxides of uranium as well as with a barium component, obtainable by impregnating the carrier with thermally decomposable nickel and uranium compounds and calcination of the impregnated support, the characterized in that the weight ratio of uranium to nickel on the catalyst support is 0.62 up to 0.74: 1 and the total weight of nickel and Uranium on the catalyst support, calculated as metals, constitutes not less than 2 and not more than 20% by weight of the catalyst and that the barium content of the catalyst, expressed as barium oxide, is not more than 20% by weight and the barium either by impregnating the support with barium hydroxide or a compound which becomes Heat decomposes to barium oxide, barium hydroxide, barium carbonate or barium uranate, or through Mixing the carrier with barium oxide or a compound that turns into barium oxide when heated decomposed, is introduced, and that the mixture formed is calcined.

The nickel and the uranium can be used in both

menial form as well as in compounds. When reforming methane, the total weight of nickel and uranium on the catalyst is preferably 5 to 10%, for example 7%, the end. In the case of higher hydrocarbons, e.g. B. naphtha, makes the total weight of the nickel and uranium usually 10 to 20% by weight, preferably 15-20% by weight, for example 18% by weight. So if the uranium to nickel ratio is 0.63 to 0.64: 1, the catalyst contains about 7% uranium in the form of an oxide (e.g. UO ₁ , U ₃ O ₈ or U ₄ O ₉ ) and about 11% nickel in the form of nickel oxide. The carrier on the surface of which the active ingredients are formed is preferably α-alumina. Other carriers can also be used den, for example γ-alumina, molecular sieves, zirconium silicates, silicon carbide, silicic acid and natural Clays and aluminum silicates.

The term "catalyst" as used in the description refers to either the catalyst in its active form or on a catalyst in an easily activated form, wherein the activation often takes place under the conditions of the reaction to be catalyzed. In the present case, Nickel oxide is not an active catalytic component.

But if it is reduced to nickel, the reduction can take place under the conditions of the steam reforming reaction, the catalyst is activated. Under The term "thermally decomposable compounds" used in the description should not contain any residues

or groups that can poison the catalyst, e.g. B. sulfides, halides or arsenic compounds.

The barium component contains one or more compounds, such as barium oxide, barium hydroxide,

for example barium carbonate, barium uranium and compounds that decompose into the specified compounds when heated. The barium component is expediently made by impregnating the catalyst support Barium hydroxide or a compound used in

Heating decomposed to barium oxide, barium hydroxide, barium carbonate or barium uranate, built-in.

However, a preferred catalyst according to the invention can also be prepared by a catalyst carrier that contains barium oxide in a Amount of not more than 20% by weight based on the catalyst, is produced by barium oxide or a compound that decomposes to barium oxide when heated, with the other component or the other components of the catalysis

6 »gate bearer» ttew. with a connection or with Compounds that decompose to this component or components when heated, mixed, whereupon the mixture thus formed, if necessary

and then the nickel and uranium components of the catalyst on the surface of the catalyst carrier.

The catalyst expediently contains a small amount of potassium oxide, preferably not more than 2% by weight of potassium. The amount of "available" potassium is preferably 0.6 to 1.2%, e.g. 0.8%, although the catalyst is also effective at potassium concentrations of 0.2 to 0.3% by weight. The term "available potassium" means the potassium present in the catalyst, which cannot be extracted by water or sootic acid, but which can be extracted by hydrochloric acid. An equivalent amount of lithium oxide can be used in place of the potassium oxide. The presence of the barium component in the catalyst means that only a small amount (e.g. 0.5%) of lithium or potassium oxide needs to be incorporated into the catalyst, and these compounds can be used before, simultaneously with or after the addition of the nickel and uranium components are added. So a salt, e.g. B. a nitrate of lithium or, preferably of potassium, can be used to impregnate the catalyst or the catalyst support.

When the catalyst support is alpha-alumina, it may be preferable that the support contain not more than 0.07% by weight of sodium calculated as sodium oxide based on the weight of the support. When such a carrier is used, it is also desirable that sulfur be present in amounts less than 50 ppm and silicon, calculated as SiO ₂ , be present in amounts less than 0.14% by weight.

The alkali metal compound, based on the alkali metal equivalent, is preferably in amounts of no more than 0.15 to 3%, preferably no more than about 0.2%.

Those used to apply the active component of the catalyst to the catalyst surface Processes are customary in the manufacture of catalysts. In this context, the GB-PS 1039206 and BE-PS 699949 pointed out, in which processes for the preparation of catalysts with similar components as the catalysts according to the invention are described; in particular, the following general processes for the preparation of catalysts are described there:

The catalyst can be obtained by impregnating a carrier with an aqueous solution of nickel and uranium salts, optionally together with a potassium or lithium salt, the salts being heated in the oxides of the corresponding metals can be converted (e.g. nitrates), can be produced. The impregnated support can then, after the addition of the barium component, be used to produce a catalyst be heated according to the invention. Soaking can be done in one stage or with just one metal at a time be performed.

To apply the uranium component, the carrier can be impregnated with a uranium salt from an aqueous solution and dried, after which the impregnated carrier is brought into an ammonia solution in order to convert the uranium salt into ammonium diuranate, whereupon the diuranate is thermally decomposed to uranium oxide,

If necessary or desired, a binder can be incorporated into the catalyst.

Good catalysts can be obtained, if

a salt of a carboxylic acid, preferably the acetate of nickel and / or uranium, which is on the support surface is located, a regulated decomposition at a temperature of not more than 650 ° C and

is subject to. This working method is described in BE-PS 700310. But it can also do that in the BE-PS 700311 described method are used. In the latter case, the Catalyst after its formation a reduction and

ίο then an oxidation in the presence of reducing agents or oxidizing gases, e.g. B. subjected to hydrogen and air, with smaller crystallites obtained will. Preferably, the barium component of the catalyst is prior to the formation of the nickel

and uranium components or their precursors are added to the carrier on the carrier surface. The carrier can with an aqueous solution of a barium compound, e.g. B. a carboxylic acid salt, such as barium acetate, or preferably soaked in barium hydroxide

will. When heated to around 300 ° C, the hydroxide becomes at least partially decomposed to the CWd. Will the acetate used is essentially obtained on heating to a temperature of about 550 ° C Barium carbonate.

As soon as the barium compound is incorporated into the carrier by this method, the carrier can be coated with nickel and uranium compounds, e.g. B. with nickel and uranium nitrate, which can then be decomposed to the metal oxides. If nitrates are used, the decomposition can take place by heating the catalyst to about 650 ° C.

According to another preferred method, the catalyst support is impregnated with the salts at the same time, z. B. with the acetates of nickel, uranium and barium, which are present in an aqueous solution. The oxides of nickel and uranium can be formed by heating the impregnated catalyst will; if acetates are used, temperatures of about 500 to 610 ° C are used.

According to a third preferred method, the carrier is first in a solution of the nickel and Uranium compounds, e.g. B. nickel and uranium nitrate, which are then decomposed to form the metal oxides to build. A barium compound in solution is applied to this impregnated carrier, for example a carboxylic acid salt such as barium acetate or, preferably, barium hydroxide. The barium compound can then be partially decomposed to the oxide by heating the support.

According to a fourth preferred process, the catalyst is prepared by, in a suspension a thermally decomposable salt of barium, e.g. B. the hydroxide or a carboxylic acid salt, such as the acetate of barium, together with the other components of the carrier in powder form, e.g. B. powdered Aluminum dioxide, is mixed. Di «; Calcination is preferably carried out at a relatively high temperature, so that a thorough Decomposition is guaranteed. In those cases where

μ Barium hydroxide used as a precursor for the barium oxide is, the Calciniertempertaur is preferably above 1500 ° C, z. B, at about 1650 "C, will If barium acetate is used, the aging temperature is preferably about 1500 ° C.

In any case it will be the proportions of the components determined on the carrier by the concentration of the soaking solution and the duration of the soaking. The catalyst according to the invention is used to

formation of hydrocarbons, in particular of methane and higher hydrocarbons, such as naphtha, with water vapor, usually in the Vapor phase, used. The temperature at which the process is carried out is preferably about 650 to 750 "C. The catalyst is preferably in the form of rings, spheres or hollow cylinders.

example 1

Barium hydroxide and powdered clay are mixed together in a suspension, shaped, and calcined at a temperature of 1650 ° C.

The carrier obtained in this way is then impregnated with a solution of nickel and uranium nitrate and then heated to 600 ° C., a catalyst containing 1.0% by weight of barium oxide being obtained.

Ll c 13 μ ic ι L

Example 1 is repeated with the difference that potassium nitrate is added to the suspension, with 0.2% potassium equivalents are present as potassium oxide in the carrier.

Example 3

Example 1 is repeated with the difference that barium acetate is used instead of barium hydroxide will. The calcination is carried out at a temperature of 1500 ° C.

Example 4

Example 3 is repeated with the difference that potassium nitrate is added to the suspension, wherein 0.2% potassium equivalents are present in the carrier.

Example 5

Shaped corundum supports are immersed in a bath containing an aqueous solution of nickel and uranium nitrate. The impregnated carrier is calcined at 650 ° C. in order to convert the metal nitrates into the corresponding oxides and then imnräoniprt with pinpr wäRriqpn RariiimhvrlroYirllöciino

After calcining at 300 ° C., a catalyst is obtained which contains 10.8% by weight of nickel, 6.7% by weight of

Contains uranium and 0.8% by weight of barium oxide. Application example

The catalyst prepared according to Example 5 is poured into a reaction tube. At 420 ° C, water vapor in an amount of about 82 kg / hour, and naphtha in an amount of about 18 liters / hour. passed into the reactor. The initial temperature is 160 ^° C.

The plant was in operation for 1700 hours. Thereafter , the reactant flow rate was gradually increased to about 73 liters / hour. Fast evaporator distillate flow and about 196 kg / hour. Increased water vapor. The pressure in the reactor was about 31.5 bar.

The gas formed had the following composition:

62% 13.83% 9.76% 16.67% 0.0059% 0.002% 0.002%

hydrogen

methane
CO
CO,

CJhJ

CjH ₈

The naphtha used had a final boiling point Λΐη 123 ° C.

In the case of steam reforming reactors, the catalysts according to the invention are particularly advantageous compared to other nickel-uranium catalysts, since a significantly lower carbon deposition occurs, as can be seen from the drawing. The drawing shows that in catalysts with a Uranium / nickel ratio from 0.62 to 9.74: i the resistance of the catalyst is most favorable to carbon deposition, the latter being the latter Parameter on the curve is given as the reciprocal time it takes for a pressure differential to develop of about 7.0 bar is required. If the proportion of active metals is not more than 20% by weight rle «catalyzer makes up, κη the catalyzer has one stronger structure, and its manufacture is more economical.

For this 1 sheet of drawings

Claims (2)

Claims; 1, catalyst for the reforming of hydrocarbons with water vapor, with a Catalyst support, on the surface of which there is a mixture of nickel oxide and / or nickel together with one or more oxides of uranium as well as with a barium component, obtainable by impregnating the carrier with thermally decomposable nickel and uranium compounds and calcination of the impregnated carrier, characterized in that - the weight ratio of uranium to nickel on the catalyst support 0.62 to 0.74: 1 and the total weight of nickel and uranium on the catalyst support, calculated as metals, not less than 2 and not more than 20% by weight of the catalyst, and that - the uranium content of the catalyst, expressed as barium oxide, not more than 20% by weight and the barium either by impregnating the support with barium hydroxide or a compound which decomposes to barium oxide, barium hydroxide, barium carbonate or barium uranate when heated - or by mixing the carrier with barium oxide or a compound that decomposed on heating to barium oxide, is introduced, and that the mixture formed calcinierc. will. 2. Use of the catalyst according to claim 1 for reforming hydrocarbons with steam.