RU2555842C1 - Copper-chromium-zinc catalyst for heterogeneous reactions - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: a copper-chromium-zinc catalyst for heterogeneous reactions, which includes copper, chromium, zinc and aluminium oxides and an additional component is disclosed. The catalyst contains, as the additional component, 0.5-5 wt % of a silicon compound with respect to the oxide and the catalyst is formed via heat treatment of aluminium hydroxide together with compounds of said components, and has a porous structure with total specific pore volume of not less than 0.25 cm³/g and content of mesopores with a diameter of 10-40 nm higher than 60%, and the catalyst has the following composition, with respect to oxides, wt %: CuO 50.0-57.0; Cr₂O₃ 11.0-16.0; ZnO 9.5-13.0; SiO₂ 0.5-5.0; aluminium oxide - the balance.

EFFECT: forming a copper-chromium-zinc catalyst having high strength, thermal stability and which can be used in different chemical processes.

6 cl, 2 tbl, 8 ex

Description

The invention relates to the chemical industry, namely to the improvement of industrial copper-zinc catalyst for low-temperature conversion of carbon monoxide and the expansion of its scope for other processes.

Copper-zinc catalyst for the low-temperature conversion of carbon monoxide (NTK-4) has the following composition, wt.%: CuO 37.5-55.0; ZnO 9.0-25.5; Cr ₂ O ₃ 6.0-15.0; Al ₂ O ₃ (Catalysts of the nitrogen industry. Catalog, NIITEKHIM, Cherkassy, 1989, 11-12. Catalysts used in the nitrogen industry. Catalog, NIITEKHIM, Cherkassy, 1979).

It is known to use this catalyst for other reactions (patent RU 2066679 C1, C07C 211/48, B01J 23/86, publ. 09/20/1996). It was proposed to carry out N-alkylation of aniline with methanol on industrial catalysts for low-temperature conversion of carbon monoxide NTK series at 180-220 ° C in the presence of hydrogen. The proposed method allows for the conversion of aniline to 99.2% and the yield of the target N-methylaniline to 97.7% to simplify the production technology by eliminating the stage of preparation of a special catalyst, carrying out the process at a lower temperature and prolonging the period of active operation of the catalyst without regeneration.

The disadvantage of the catalyst is its low strength, which leads to the need for its frequent regeneration and reduction of its service life.

It is known to use the NTK-4 catalyst for producing aniline (patent RU 2135461 C1, C07C 211/46, C07C 209/36, publ. 08.27.1999).

It was proposed to carry out the hydrogenation of nitrobenzene to aniline on industrial oxide alumino-zinc-chromium methanol synthesis catalysts DV-8-2 or low-temperature conversion of carbon monoxide NTK-4, NTK-4m, NTK-8 at a temperature of 155-240 ° C and atmospheric pressure. The proposed method allows for the conversion of nitrobenzene close to 100% and the yield of aniline 99.2-99.8% to simplify the production technology by eliminating the stage of preparation of a special catalyst, carrying out the process at a lower temperature and prolonging the period of active operation of the catalyst without regeneration.

The disadvantage of this catalyst in this process is its insufficiently high strength, which also leads to a decrease in its service life.

It is known to use the NTK-4 catalyst for the production of n-alkylanilines (patent RU 2152382 C1, C07C 211/48, C07C 209/36, publ. 10.07.2000).

An improved method for producing N-alkylaniline by reductive N-alkylation of nitrobenzene with alcohol is carried out on industrial catalysts for the low-temperature conversion of carbon monoxide NTK series at 150-300 ° C in a hydrogen atmosphere. The molar ratio of the starting components is nitrobenzene: alcohol: hydrogen is 1: (1-5) :( 3-10), respectively. As alcohols, C1-C8 alcohols of normal, branched or cyclic structure can be used.

The disadvantage of this catalyst in this process, as in the above, is its insufficiently high strength, which leads to a decrease in its service life.

It is known to use a copper-zinc catalyst for methanol synthesis and carbon monoxide conversion (a.s. SU 671077, B01J 23/72, B01J 23/86, B01J 37/16, publ. 10.08.2008).

A method for producing a catalyst for methanol synthesis and carbon monoxide conversion involves mixing zinc, chromium, copper and aluminum compounds, followed by treatment with a reducing agent and drying.

The disadvantage of this catalyst in this process, as in the above, is its insufficiently high strength.

The closest technical solution is the catalyst for low-temperature conversion of carbon monoxide disclosed in patent RU 2175265 C1, B01J 23/80, B01J 23/78, B01J 23/84, B01J 23/883, B01J 23/885, B01J 37/04, C01B 3/16, publ. 10/27/2001.

The proposed catalyst for low-temperature conversion of carbon monoxide includes copper oxides, zinc, a modifying metal compound and aluminum oxide containing at least one compound of an element selected from the group K, Na, Si, Fe, Ca, Ba, or a mixture thereof, in an amount of 0.01 -2.0 wt.% In terms of oxide, and as a modifying compound, the catalyst contains at least one metal compound selected from the group Ni, Mn, Cr, Zr, Na, Ti, Mg, or a mixture thereof, in an amount of 0, 1-15 wt.% In terms of oxide, and the catalyst has the following composition, wt.%: CuO 35.0-61.0; ZnO 12.0-29.0. At least one compound of a modifying metal from the group: Ni, Mn, Cr, Zr, Na, Ti, Mg, or a mixture thereof 0.1-15.0. Alumina containing at least one compound of an element selected from the group: K, Na, Si, Fe, Ca, Ba or a mixture thereof, in an amount of 0.01-2.0 wt.% - the rest.

This catalyst has a higher strength than the above catalysts, however, its composition is quite complex. In addition to modifying compounds, the catalyst contains a carrier, which is obtained by introducing in a special way the necessary elements into it, which leads to a significant complication of the method for its preparation. The catalyst has insufficient strength for use in various processes.

The task of the invention is the creation of a copper-zinc catalyst with enhanced strength and thermal stability for use in various processes.

The problem is solved using a copper-zinc catalyst for heterogeneous reactions, including oxides of copper, chromium, zinc, aluminum and an additional component. The catalyst contains as an additional component a silicon compound in terms of 0.5-5 wt.% Oxide, and is formed during the heat treatment of aluminum hydroxide together with the compounds of the above components, and has a porous structure with a total specific pore volume of at least 0.25 cm ³ / g and a fraction of mesopores with a diameter of 10-40 nm more than 60%, and the catalyst in terms of oxides has the following composition, wt.%:

CuO  50.0-570 Cr ₂ O ₃  11.0-160 Zno  9.5-130 SiO ₂  0.5-50 aluminium oxide  rest

Preferably, the catalyst is in the form of cylindrical granules obtained by extrusion in the form of uniformly sized cylinders with a diameter of 3-8 mm.

Preferably, the catalyst has a specific surface area of at least 60 m ² / g while maintaining it up to a temperature of 500 ° C.

Preferably, the catalyst has a mechanical crush strength of at least 5 MPa along the generatrix of the granule while maintaining it to a temperature of 500 ° C.

Preferably, the catalyst contains silica in an amount of 2-3 wt.%.

Preferably, the catalyst is used to produce aniline or low temperature carbon dioxide conversion, methanol synthesis, N-alkylaniline synthesis.

At present, in Russia, the NTK-4 copperchromic zinc catalyst is prepared by tabletting. The main disadvantage of this catalyst is its short life due to the loss of mechanical strength, especially in the presence of water vapor.

The proposed catalyst is obtained by mixing components comprising copper, chromium, zinc, silicon and aluminum hydroxide, when mixed, a uniform distribution of the catalyst components over the granule occurs. The catalyst is obtained by extrusion molding.

An unexpected result was the production of a copper-zinc catalyst, which has increased strength and has a total specific pore volume of at least 0.25 cm ³ / g and mesopores with a diameter of 10-40 nm. Obtaining a catalyst with such properties allows you to use it for many chemical processes, for example:

1) obtaining aniline;

2) low temperature conversion of carbon monoxide;

3) methanol synthesis;

4) synthesis of N-alkylaniline.

The following examples illustrate the invention. The specific surface area is determined by the BET method, the pore volume is determined by water adsorption, the crushing strength is determined on an MP-9C device.

Example 1

In a paddle mixer load aluminum hydroxide pseudoboehmite structure in the amount of 15-25% in terms of the finished catalyst, carry out its peptization with nitric acid. The acid module is 0.12-0.14. Then powdered components are loaded - oxides of copper, chromium, zinc and silicon in quantities necessary to obtain a finished catalyst of the following composition, wt.%:

CuO 53 Cr ₂ O ₃ 13.5 Zno 10 SiO ₂ 2 Al ₂ O ₃ rest

The dry components are uniformly mixed with wet aluminum hydroxide, in the presence of water, the mass is brought to a uniform pasty state. The resulting paste is extruded through a die with a hole diameter of 5 mm, cut into granules 5-6 mm long, which are dried at a temperature of 120 ° C for 4 hours. The calcination of the catalyst is carried out in a stream of air at a temperature of from 400 to 500 ° C. The specific surface area of the finished catalyst is 73 m ² / g, the crushing strength along the generatrix is 6.2 MPA, the total pore volume is 0.27 cm ³ / g, and the proportion of the pore volume with a radius of 10 to 40 nm is 70%.

Examples 2-7 are similar to example 1, the difference is that the components were loaded into the mixer in an amount corresponding to the composition of the catalyst, wt.%.

Example 2

CuO 54.5 Cr ₂ O ₃ 12.5 Zno 11.7 SiO ₂ 5 Al ₂ O ₃ rest

The characteristics of the catalyst are presented in table 1.

Example 3

CuO 51.8 Cr ₂ O ₃ 14.0 Zno 12,2 SiO ₂ 1.05 Al ₂ O ₃ rest

The characteristics of the catalyst are presented in table 1.

Example 4

CuO 52.3 Cr ₂ O ₃ 16,0 Zno 12.9 SiO ₂ 3,5 Al ₂ O ₃ rest

The characteristics of the catalyst are presented in table 1.

Example 5

CuO 55,4 Cr ₂ O ₃ 12.0 Zno 10.3 SiO ₂ 2.7 Al ₂ O ₃ rest

The characteristics of the catalyst are presented in table 1.

Example 6

CuO 51.5 Cr ₂ O ₃ 15.1 Zno 9.0 SiO ₂ 0.5 Al ₂ O ₃ rest

The characteristics of the catalyst are presented in table 1.

Example 7

CuO 57.0 Cr ₂ O ₃ 14.5 Zno 11.8 SiO ₂ 0.5 Al ₂ O ₃ rest

The characteristics of the catalyst are presented in table 1.

Example 8 (prototype)

To aluminum hydroxide containing Na ₂ O in an amount of 0.03%, oxygen-containing compounds Cu, Cr, Zn are added in an amount necessary to obtain CuO — 52%, ZnO — 9.96%, Cr ₂ O ₃ —12 nitric acid is added (the acid module is 0.75), the mass is stirred for 30 minutes, extruded, dried at 110 ° C and calcined at 450 ° C for 6 hours.

From table 1 it is seen that the proposed catalyst is characterized by high mechanical strength and specific surface area. The proportion of pore volume from 10 to 40 nm, providing a high catalyst activity, is at least 70% of the total pore volume.

To copper-containing catalysts used in the processes of low-temperature conversion of carbon monoxide with water vapor, the synthesis of aniline and others, stringent requirements are placed on:

1. Activities.

2. Thermostability, ie activity should be maintained when the catalyst overheats to 350-400 ° C.

3. Stability, ie to the stability of the catalyst to the effects of the reaction medium.

4. Mechanical strength.

Mechanical strength is of particular importance when loading the catalyst into a tubular reactor, such as aniline synthesis. The catalyst in such a reactor should provide a steady pressure drop across the tube, that is, have good strength and not collapse during operation. Therefore, the proposed catalyst was repeatedly exposed to high temperatures of 500 ° C for four hours to verify the preservation of its properties.

The characteristics of the samples (specific surface and crushing strength along the generatrix) after heat treatment at 500 ° C are shown in table 2.

Table 2 shows that the proposed catalyst has high thermal stability and maintains a high specific surface area and mechanical strength up to 500 ° C, which allows it to be used with high efficiency for many heterogeneous reactions in which a copper-zinc catalyst was previously used. The proposed catalyst was tested in the following reactions:

1. Hydrogenation of nitrobenzene to aniline at a temperature of 160-240 ° C and atmospheric pressure.

The catalyst showed the following results:

Nitrobenzene conversion - 99.8%

Aniline yield - 99.8%

2. Low temperature conversion of carbon monoxide. The activity of the catalyst is characterized by a constant reaction rate (cm ³ / g · s) at temperatures of 180 ° C, 200 ° C, 225 ° C, at a space velocity of 5000 h ^-1 and a steam: gas ratio of 0.7: 1, volume fraction N ₂ - 23.1%, H ₂ - 55.6%, CO - 12.5%, CO ₂ - 9.4%. The reaction rate constant is at temperatures:

180 ° C - 2.6

200 ° C - 4.2

225 ° C - 6.2

The technical result of the invention is the creation of a copper-zinc catalyst with increased strength and thermal stability and the possibility of its use in various chemical processes.

Claims (6)

1. Copper-zinc catalyst for heterogeneous reactions, including oxides of copper, chromium, zinc, aluminum and an additional component, characterized in that the catalyst contains silicon compounds as an additional component in terms of oxide, 0.5-5 wt.% And formed during the heat treatment aluminum hydroxide together with the compounds of the above components and having a porous structure with a total pore volume of at least 0.25 cm ³ / g and a mesopore diameter fractions 10-40 nm greater than 60% and the catalyst is based on the following oxides composition, wt.%:
CuO 50.0-57.0 Cr ₂ O ₃ 11.0-16.0 Zno 9.5-13.0 SiO ₂ 0.5-5.0 aluminium oxide rest 2. The copper-chromzinc catalyst according to claim 1, characterized in that it has the form of cylindrical granules obtained by extrusion in the form of uniformly sized cylinders with a diameter of 3-8 mm 3. The copper-chromzinc catalyst according to claim 1, characterized in that it has a specific surface area of at least 60 m ² / g while maintaining it up to a temperature of 500 ° C. 4. The copper-chromzinc catalyst according to claim 1, characterized in that it has a mechanical crushing strength along the generatrix of the granule of at least 5 MPa while maintaining it to a temperature of 500 ° C. 5. The copper-chromzinc catalyst according to claim 1, characterized in that it contains silicon dioxide in an amount of 2-3 wt.%. 6. Copper-zinc catalyst according to any one of paragraphs. 1-5, characterized in that the catalyst is used to obtain aniline, low-temperature conversion of carbon dioxide, the synthesis of methanol, the synthesis of N-alkylaniline.