Catalyst for dehydrogenation of cyclohexanol to cyclohexanone and method thereof

 

(57) Abstract:

The invention relates to the field of catalysts. Describes a catalyst for the dehydrogenation of cyclohexanol to cyclohexanone containing copper as the active component and aluminum oxide with a BET surface, measured according to DIN 66131, of at least 30 m2/g, and the method of its production, including the application of copper to the medium - alumina with the above characteristics by impregnation, deposition, dry mixing or current-free copper coating and calcination. The technical result - obtaining a catalyst with high activity and selectivity. 2 S. and 1 C.p. f-crystals, 1 table.

The invention relates to the production technology of cycloalkanones, and more particularly to a catalyst for the dehydrogenation of cyclohexanol to cyclohexanone, and how to obtain it.

Cyclohexanone is an important preliminary step in obtaining polyamide 6 and 6,6, made in krupnoseriynom scale using catalytic dehydrogenation of cyclohexanol. The question catalytic dehydrogenation of cyclohexanol there are two technological variants. When high-temperature version of the cyclohexanol de the Lack of dehydrogenation at high temperatures is low selectivity valuable products concerning the possibility of their conversion to cyclohexanol, since at high temperatures, flows a significant number of adverse reactions, such as digitalizacija of cyclohexanol to cyclohexene, or the reaction of dimerization, such education cyclohexylcyclohexanes. The formation of by-products require costly rework and reduces the efficiency of the method.

For dehydrogenation of cyclohexanol at low temperatures are primarily used catalysts based on copper. These catalysts make it possible to reduce the reaction temperature to about 240 - 280oWith, thus providing increased selectivity for cyclohexanone. However, the degree of conversion at relatively low temperatures, due to the equilibrium, as a rule, not very high.

One of these classes of low-temperature catalysts contains a composition consisting of copper and ceramic media that can be presented or silicon oxide, or alumina, or a mixture of these two oxides. The copper content of these catalysts can be up to 50 wt.%. In addition, these catalysts may contain as promoters minor amounts of alkali metals.

For example, we know about use the patent in the UK 1081491), copper/lithium/silicon oxide (patent application USSR 465217) and copper/potassium/aluminum oxide (patent application USSR 522853). Mentioned catalysts based on copper are in most cases so that the active ingredient (copper) or applied on the pre-made media by precipitation of salts of copper, or by soaking the corresponding solution of copper salts, or components of the catalyst, deposited together. Another possibility for the manufacture of catalysts based on copper is a dry mixture of components with subsequent calcination.

From the publication of Chang and others, Appl. Catal. A 103 (1994), pp. 233-42 aware of during madnani, or deposition of copper on the carrier with a reducing agent in the presence of complexing agents, in the manufacture of catalysts based on copper for dehydrogenation of cyclohexanol without oxidation. As the carrier used is aluminum oxide surface 22.6 m2/, Chang selectivity depends on the acidity of the medium: acidic media such as aluminum oxide or silicon oxide - have a catalytic effect on adverse reactions similar to reactions degidratatsii to cyclohexanol or dimerization, Appl. Cat. A: vol. 83, 2 (1992), pp. 201-11), this measure leads to both decreased activity. The advantage of the increased activity of the catalysts based on copper compared to high-temperature catalysts, thus, again partially lost due to the use of additives of alkali or alkaline earth metals.

Described in Appl. Cat. A 103 (1994), pp. 233-42 catalysts are not suitable for use in large industrial scale, because they are presented in the form of a powder. Making them by pressing in the form of molded products, such as tablets, compounded by poor tabletiruemogo of this powder. In addition, low hardness made thus molded products leads to the low wear resistance in the reactor, connected with the increase of the pressure loss with increasing duration of the reaction. Thus, in General, their use in large technical scale is not possible.

Another disadvantage of the use of aluminum oxide as the material of the carrier is a weak correlation with the active component (copper), which resulted in too quickly begins agglomeration of the active component associated with the loss Catalytica a high degree of conversion, it would be necessary to raise the operating temperature of the dehydrogenation reaction in the reactor, resulting, of course, and the sintering process, and the consequent deactivation of the catalyst would have continued to progress.

The fundamental task of the present invention was to create a catalyst that does not have the above disadvantages. In particular, the catalyst should have a high service life and to ensure the dehydrogenation of cyclohexanol to cyclohexanone with a high yield of the target product and high selectivity at relatively low reaction temperatures, and would prevent the need for constant temperature control of the reaction. In addition, the catalyst would have to allow processing without the high cost in the molded product in the form of tablets, rods, rings, cylinders, and the possibility of its further use on the basis of high hardness and wear resistance.

The objective of the invention is solved by the proposed catalyst for dehydrogenation of cyclohexanol to cyclohexanone containing copper as the active component and aluminum oxide with a BET surface, measured according to DIN 66131, of at least 30 m2/,

2/g by impregnation, deposition, dry mixing or during copper plating and calicivirus.

Preferably used is aluminum oxide surface on BET 50 - 300 m2/g, particularly preferably 100 to 250 m2/, Such vysokopoligonalnaya-alumina commercially available (for example, company Alcoa).

When applying the active component by impregnation of the carrier is impregnated with an aqueous solution of copper salts (mainly nitric, sulfuric, acetic or hydrochloric acid), dried and then soaked in the form calicivirus.

When the deposition is usually mixed aqueous solution of salt of copper (see above) in the presence of media precipitator, ensuring the formation of insoluble copper compounds. For the deposition of copper is mainly used soda. Then the usual way is produced by drying and calcining.

When a dry mixture usually mix the media with the desired salt of copper and then produce calcination.

Following receipt form consists of the manufacture of the catalyst by means of a current-free selection of copper (madnani) in the Pris is eh at first put some rare-earth metal (platinum, rhodium, iridium, gold or palladium), mainly palladium, i.e. create centers of crystallization, and then allocate the copper on the carrier surface of complex shape using a reductant.

To prevent premature deposition of copper is usually necessary when high pH values is added, as a rule, some strong complexing agents of the type of ethylenediaminetetraacetate, its alkali metal salts of the type of sodium leads to compounds, which, as well as Ethylenediamine or venotrain. Recovery (or copper) occurs, as a rule, with the help of reductant type of formaldehyde or formate sodium, are known to produce copper (0) from a solution of copper salts.

According to conducted to date observations particularly fine particles of copper are obtained when, during its allocation. Their value, determined by x-ray diffraction, is mostly less than 50 nm, and mostly less than 20 nm.

Regardless of the method of deposition of copper on the carrier, calcining the resulting powder or the respective molded articles are made at 250 - 450oFrom within 1 to 24 hours in air or in an atmosphere of inert gas, it is better

Obtained during the selection or other methods described catalyst in powder form is pressed, usually with adulteration tabletiruemyh additives in molded products (tablets, rods, rings, wheels, sprockets, pieces, beads, pellets or extruded billet, preferably tablets. As tabletiruemyh additives can be used with commonly used excipients, such as graphite, magnesium stearate, methyl cellulose (type Walocel"), copper powder or a mixture of them.

The copper content in the catalyst is usually selected in the range from 0.01 to 50.0%, preferably 2 to 30%, most preferably 5 to 20% by weight of the total catalyst.

The surface of the catalyst according to BET (measured according to DIN 66131) is usually not less than 30 m2/g, preferably 50 to 300 m2/g, most preferably 100 to 250 m2/,

The dehydrogenation of cyclohexanol to cyclohexanone is produced, as a rule, in the gas phase at 180 - 400oWith, preferably 200 - 350oWith and most preferably 220 - 260oC. typically, the pressure is in the range of 50 kPa to 5 MPa, optimum performance is achieved at atmospheric pressure.

In quality the I, you can use pure cyclohexanol. Commonly used mixture consists of cyclohexanol (50 - 100%, preferably 60 to 99%, optimally 96 wt.%) and cyclohexanone (50 - 0%, preferably 40 to 1%, optimally 4 wt.%). Cyclohexanone and cyclohexanol are usually obtained by oxidation of cyclohexane with a subsequent increase in the concentration of cyclohexanol due distillatively distillation of cyclohexanone and other boiling components.

Typically, recovery of the catalyst with hydrogen is performed before the reaction. This procedure is in General so that diluted with an inert gas (preferably nitrogen) flow of hydrogen is conducted through the catalyst at a certain temperature, preferably 120 to 300oC. the Percentage of hydrogen content in gas-reducing agent is then usually rises to the disappearance of the characteristic temperature changes.

Further, in accordance with the preferred form of the method is passed a gaseous feedstock through the catalyst, it is desirable that the volumetric flow rate was 0.1 to 100,0 h-1preferably 0,1 - 20,0 h-1. Raw materials can be mixed with an inert gas (nitrogen) or with steam. The product of the dehydrogenation in the usual way (see,working.

Further in accordance with another preferred form of the method are extracted from the mixture leaving the reaction zone, hydrogen, and add it to the gas mixture entering the reaction zone. In the following it is advisable to keep the reaction mixture in the circulation loop to achieve a desired degree of conversion.

The claimed catalyst can operate due to their high activity at much lower temperatures than the catalysts used in large-scale industrial production. He has a short phase molding, high selectivity and degree of conversion, close to equilibrium. In addition, considerable deactivation occurs only after a considerably longer period of use than the time taken currently known catalysts.

The claimed catalyst has good teletrauma ability, sufficient hardness, a high degree of conversion at low temperatures, high selectivity to cyclohexanol and a good life.

Examples

Example 1 - Production of catalyst

To a mixture consisting of 27,27 g 11% (by mass) solution of palladium nitrate (calculated by palla, the average molecular weight of 25,000 g/mol); the resulting solution was heated for 4 hours under reflux. Thus obtained Sol ("palladium Sol") contains 0,34 wt.% palladium (based on the total weight of palladium Zola).

To 20,6 ml prepared by the aforementioned method palladium Zola add 23 ml of water and 125 g of aluminum oxide (firm Alcoa, surface BETH 156 m2/g, water absorption of 0.35 ml/g of aluminum oxide). Then the impregnated carrier is dried in the air. Pre-treated and dried carrier is suspended in 3894 ml of freshly prepared solution consisting of 0.1 molar concentration of Cu(SLA)2; of 0.2 molar concentration of sodium ethylenediaminetetraacetate; and 0.2 molar concentration of formaldehyde and 0.0125 molar concentration of pyridine. Under strong stirring set with 35% (by weight) sodium hydroxide solution the pH value equal to 12.5. Thus, there is a change in color from gray-black to red-brown. This suspension is heated to 70oC, and the pH value is maintained in the range from 12 to 12.5 by further adding sodium hydroxide (caustic consumption of soda is about 400 ml). Then after reaching a temperature of 70oWith peremeshivajutsa and washed with water until the establishment in normal water pH values (filtrate has a weak blue color). Then the washed solid is dried for 16 hours at a temperature of 110oWith under a nitrogen blanket and then calcined for 2 hours at a temperature of 300oC.

Constructed in this way catalyst contains 16.5 wt.% copper and 0.046 wt.% sodium, calculated on the total weight of the gray-black catalyst.

X-ray analysis of the crystalline components gives the following results: aluminum oxide (19 nm) oxide copper (13,0 nm), copper oxide (traces).

Manufacturing tablets

(thickness 5 mm, diameter 3 mm)

100 g made the above image of the powder catalyst is pre-compacted with 1% (by weight) of copper powder "FFL" (company" North-German enterprise for the allocation of precious metals", 10914) and 1% (by weight) magnesium stearate (firm Riedel de Han, 4162757), respectively, of the weight of the catalyst, into the cylinders (length 20 mm, diameter 1 mm), which is then pressed through a die plate with a mesh size of 1.6 mm and pressed when applying 2% graphite in tablet thickness of 5 mm and a diameter of 3 mm

Lateral pressure tablets is 53 N, the standard deviation of 16 H (measured by the device by "Frank", type 81557).

Example 2 the catalyst Test

the I in 200 ml of catalyst, which is activated before the reaction with hydrogen. Before downloading the raw material, the catalyst was activated at 120oWith flow 150 l of nitrogen per hour and 1.5 liters of hydrogen per hour. When the temperature rises by more than 10oWith the supply of hydrogen is stopped. Then the temperature stepwise increase (increments of 20oC) to achieve 240oWith the amount of hydrogen constant support. Then at a temperature of 240oTo carry out the activation of the catalyst flow 150 l of nitrogen per hour and 7.5 l of hydrogen per hour. After activation of the catalyst used for the mixture anal/anyone (96% of cyclohexanol, 4% cyclohexanone), with a volumetric hourly rate of approximately 0.7 hours-1. The products exiting the reactor are subjected to gas chromatographic analysis. The results are presented in the following table.

Comparative example

When performing the test, perform the operations described in example 1 with the only difference that for the dehydrogenation using commercial copper catalyst (catalyst CU 940 firm Prokatalyse).

The claimed catalyst shows already at temperatures >230oWith the conversion, close to equilibrium, while at the same time a very high selectivity of >99%.

When this temperature is URS approximately 240oWith the conversion rate can be increased without loss of selectivity of about 60%. But at this temperature is only a very slow loss of activity.

As can be seen from the results for the comparative experiment the temperature adjustment must be made after 168 hours, in order to maintain the conversion rate, while for the claimed catalyst such adjustment is necessary only approximately 600 hours. In addition, the temperature used in the comparative example, are approximately 40oWith higher than in the example of the claimed catalyst. Finally, it should be pointed out that the indicators of selectivity in the example of the claimed catalyst are optimal, which is unexpected when using aluminum oxide surface by BET at least 30 m2/,

1. Catalyst for dehydrogenation of cyclohexanol to cyclohexanone containing copper as the active component and the alumina as a carrier, characterized in that it contains aluminum oxide with a BET surface, measured according to DIN 66131, of at least 30 m2/,

2. A method of producing a catalyst for dehydrogenation of cyclohexanol to cyclohexanone under item 1, is less than 30 m2/g by impregnation, deposition, dry mixing or during copper plating and calicivirus.

3. The method according to p. 2, characterized in that the catalyst is subjected to molding, in particular, tablets, rods, rings, cylinders.

 

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