DE2155562A1 - Process for the preparation of dihydroxybenzenes ^ - Google Patents

Description

Process for the preparation of dihydroxybenzenes The invention relates to a process for the preparation of hydroxybenzenes by aromatic dehydrogenation of oxygenated cyclohexanes such as hydroxy- or ketocyclohexanones or dihydroxy-cyclohexanes to corresponding dihydroxybenzenes.

| US Pat. No. 2,640,084 is a method of manufacture of 1,2-dihydroxybenzene, i.e. pyrocatechol, by ring dehydrogenation of 1,2-dihydroxycyclohexane known. Thereafter, an aqueous solution of dihydroxycyclohexane has the effect of exposed to a Ni-Cu-Cr-SiO2 catalyst in the presence of hydrogen, with which catechol and phenol are obtained in yields of 65% and 25% respectively.

according to Japanese notice 20 847/1964 received an 95% conversion of dihydroxycyclohexane and 90% selectivity with respect to Pyrocatechol using a Ni-Gu-Cr-C catalyst under similar reaction conditions. According to 'Kinetics and Catalysis' 10, 5. 755 (1969), catechol is obtained in one 80% yield using a Pd-C-K2CO3 catalyst with similar reaction conditions.

These known methods represent important and notable techniques dar; however, they are not in the technical mapstab satisfactory. Above all, the selectivity with regard to catechol is unsatisfactory. Also the reactivation of the respective catalysts causes difficulties, according to dap they are lost.

Alumina, silica, silica-alumina and similar substances in synthetic and natural form are known as solid carriers for catalysts. Catalysts, those that carry the catalyst metal components on such carriers can be usually reactivate by calcining in air if the catalytic activity sinks. However, when using the aromatic dehydrogenation of dihydroxytlohexane a catalyst using such a solid acid as a carrier at the same time, dehydration occurs to a marked extent, so dap is a noticeable by-product phenol. When said Ni-Cu-Cr-Si02 catalyst is used, there is a phenol yield of up to 25 5'o compared to a pyrocatechol yield of 65%. Since phenol is a useful compound, this is not necessarily a disadvantage. However, with regard to catechol production, there is a small proportion of by-products preferable. In addition, phenol is easily broken down into benzene. Consequently a solid acid carrier catalyst is not advantageous.

The difficulty explained occurs when using carbon as a carrier. A pyrocatechol yield is achieved with a Ni-Cu-Cr-C catalyst of 85.5 ° / 0 l (95% x 90 S / o) and a pyrocatechol yield with a Pd-C = K2C03 catalyst from 80 o / o. However, a carbon catalyst does not lap itself by calcining reactivate in air once the catalyst has been used up. Under economic It is therefore disadvantageous from viewpoints that such a catalyst is not in can be reactivated easily.

The object of the invention is to provide a method which with a real.tivbaren catalyst a high yield and selectivity ensures the desired dihydroxybenzenes. In addition, this procedure is intended also for the production of catechol from other starting materials - as dihydroxy compounds be useful.

This object is achieved according to the invention in that, under the action of a catalyst which binds nickel and chromium to a calcinable carrier material which essentially contains no acidic constituent, encapsulates an oxygenated cyclohexane of the general formula with R1 and R2 as hydrogen, alkyl or aryl radical, with R as a lower alkyl radical or lower alkenyl radical, with n as an integer between 0 and 4, with the OR² radical in the 2- or 4-position relative to the OR1 radical .

In addition to nickel and chromium, the catalyst contains within the scope of the invention also cobalt and / or copper.

The invention provides when using the metallic catalyst components mentioned and the carrier substances mentioned have a high selectivity with respect to the desired End materials safe.

IMan achieves a catechol yield of 85% or more.

The catalyst used can be reactivated by calcining in air. The starting materials required for the process according to the invention, in particular Hydroxycyclohexanone namely! 2Hydroxycyclohex5none, can easily be obtained by halogenation, in particular chlorination of cyclohexanone and hydrolysis of the halogen compounds formed represent.

1. Oxygenated starting cyclohexanes Usually can be used as starting materials Use compounds of the general formula (I), (II) or (III).

Compounds (I) and (II) By aromatic dehydrogenation of a compound (I) or (ii) the = O radical is converted into an -OH radical. If R 'in -OR' of If hydrogen is different, the dihydroxybenzene formed is obtained within the scope of the invention than a nonether like guaiacol.

Among the substances mentioned are compounds with n = O and R '= H most common. It is also preferable to use the hydroxyl radical of the compound (I) and the keto radical of the compound (II) are in the 2-position. Therefore concerns the following description mainly 2-hydroxycyclohexanone and 2-ketocyclohexanone. In this case the dihydroxybenzene formed is catechol.

However, the method according to the invention is not noticeable by the presence of a substituent R or R 'affects. Change of course individual parameters of the reaction conditions and the selelLtivitat as well as the Yield depending on the presence of substituents R or R '.

Therefore, depending on the respective requirements, a substituted one can also be used Use connection. In some cases, a 4-methyl radical, a 4-vinyl radical, to prefer substituted compounds to an L + allyl radical and a 4-propenyl radical, as they provide usable end products.

The substituent R is a lower alkyl radical or a lower alkenyl radical with fewer than 6 carbon atoms, C1, C2 or C3 radicals are preferred. The attachment of two substituents to a single carbon atom on the cyclohexane ring is inexpedient.

As a substituent R, a lower alkyl radical can be a phenyl radical or a Tolylrest can be used.

Compound (III) Unsubstituted dihydroxycyclohexanes (n = O, R1 = R2 = H), in particular the 1,2-dihydroxy compound, are the most common examples the compound (III). The following description is therefore primarily related on these substances.

The process of the invention, however, is not noticeable by the presence of 2 impaired by substituents R and R, albeit individual parameters of the reaction conditions and the selectivity and the yield according to the dihydroxycyclohexane used vary. As a result, you can also use a substituted compound if necessary use.

The substituent R is a lower alkyl radical or a lower alkenyl radical with fewer than 6 carbon atoms, a C1 radical is preferred C2 residue or a C3 residue. Compounds with two substituents on a single one Carbon atoms of the cyclohexane ring are impractical.

On the other hand, when both of the substituents R 1 and R2 are other than hydrogen are, one should be a lower alkyl radical, a | Phenyl radical or be a tolyl radical. The substituents R1 and R2 can be identical or different. If R1 = H and R = CH3 'in the 1,2-dihydroxy compound, guaiacol is obtained. With 1R1 = R2 = CH3 you get Veratrol.

2. Catalyst Catalyst Components 1The metallic catalyst components are nickel or nickel and cobalt, copper and chromium. Usually they are Weight ratios Ni or Ni + Co: Cu: Cr 100: 0 -j100: 0.1-6, preferably 100: 0-60: 0.5-4.

To improve the selectivity and the life of the catalyst may include a small amount of an alkali sulfate or sulfide and sulfuric acid added to the impregnation of said metal salts with an aqueous solution will. A useful level of sodium, potassium or lithium sulfate is 0.1 - 2.0g per 100g of nickel.

An important feature of the invention is that a calcinable Carrier material essentially without acidic constituents for the metallic catalyst components is used.

Such a carrier does not contain a solid acid and is therefore a neutral or basic solid. Among such carriers are silicon carbide, Corundum and the like are particularly useful. Because the lifespan of what is manufactured with it Catalyst is long; the yield in a use phase of the catalyst up to to reactivate is great; when the activity subsides, there is a reactivation possible with air.

The high yield for the desired end product can be attributed to its use of neutral silicon carbide or electro-corundum as a carrier. if Silica, alumina or similar substances are used as carriers dehydration due to the acidic component of the catalyst (Priority to. Therefore, phenol and benzene are obtained in large proportions as by-products. If, on the other hand, silicon carbide or electro corundum are used as a carrier, will this side reaction is highly suppressed.

(A useful proportion of the metallic catalyst components is between 1 - 35 g per 100 g of the carrier used.

Catalyst preparation From the mentioned catalyst components A catalyst can be produced by a process that is necessary for the preparation of catalysts intended for the dehydrogenation, supports is suitable. Usually a carrier in powder or granule form is combined with a compound in particular an organic or inorganic salt of a catalyst metal impregnated of the type described, which compound is decomposed by heating can. The compound is present as a dispersion, in particular as an aqueous solution. The process product is then heated to decompose the metal compound. Heating in a reducing atmosphere, especially in a hydrogen atmosphere to reduce the material. One can if necessary add a binder in a treatment stage so that the catalyst is in the desired Formation can be shaped.

The sources of these metals are their salts, especially soluble ones Salts, namely water-soluble salts such as nitrates, carbonates, salts of organic acids such as acetates and hydroxides used. If necessary, is used as an excipient for the catalyst uses an alkali sulfate.

In the preparation of the catalyst composition, the IT carrier is used initially with a solution, in particular an aqueous solution of a metal compound or one of two or more metal compounds impregnated; one can use the carrier particles also initially with a pasty mass as enell one or more coat the metal compounds mentioned. Then this mixture is in one Air or nitrogen flow to a temperature between 300 and 000C, preferably between 350 and 4500C, heated so that the mentioned metal compounds decompose. In this treatment stage, a large part of the metal compounds is evidently in Converted to oxides. The mass obtained is then poured into a stream of oxygen a temperature between 350 and 50 ° C heated in a catalyst that works on the described manner is prepared according to the US patent specification 2,640,084, Easily reducible metals such as nickel and copper can be in metallic form, while less easily reducible metals such as chromium are present as oxides. This catalyst can be used as the main active ingredient for the dehydrogenation in which nickel is 2-hydroxycyclohexanone converted into catechol, and caught for dehydration as a side reaction in which 2-hydroxycyclohexanone is converted into phenol via cyclohexanone.

Chromium appears to improve the activity or life of the catalyst and also contributes to dehydration, after which 2-hydroxycyclohexanone transfers Cyclohexanone is converted to phenol; Copper has a compensating effect on the reduction the selectivity of nickel and chromium; an alkali sulphate causes stabilization of nickel, so that the service life is extended.

A carrier for a catalyst in the context of the invention can in the context of the procedure according to the USA patent specification 2,640,084 or according to the Japanese Publication 20 847/1964 can be used.

3. Aromatic dehydrogenation The catalytic dehydrogenation of a - oxygenated cyclohexane according to the general formula (I), (II) or (III) takes place by allowing a fixed bed catalyst or a fluid bed catalyst to act on dihydroxycyclohexane at a temperature between 250 and 5000C, preferably between 300 and 45OOC, in the presence of a diluent or a heat transfer medium 5 as steam and preferably in the presence of hydrogen in a molar ratio Hydrogen / dihydroxycyclohexanone between 1 and 50.

The oxygenated cyclohexane can be used as an aqueous solution or as an aqueous solution Dispersion are initiated. The amount of oxygenated cyclohexane supplied is such that dap the LHSV value for an aqueous solution is between 0.1 and 5 / h, in particular between 0.4 and 2 / h. If the oxygenated cyclohexane as an aqueous solution or as aqueous dispersion is initiated, is a previous complete evaporation unnecessary.

The aqueous solution or dispersion to the extent necessary can be preheated, can be introduced directly into the dehydration room.

If in the context of this description of a catalytic dehydrogenation In the gas phase, the dehydrogenation can also be partially carried out in the liquid phase Phase.

The oxygenated cyclohexane can also be in a state other than an aqueous solution or dispersion are introduced, for example. As a melt, the is evaporated in the dehydration room.

2-Hydrocyclohexanone dimerizes when left to stand, but that Dimer decomposes to 2-hydroxycyclohexanone on heating. Therefore, 2-hydroxycyclohexanone can present as a dimer at the time of introduction into the dehydration chamber. One such a mode of operation is within the scope of the invention.

Since the aromatic dehydrogenation is an endothermic reaction with uptake a large amount of heat is used for heat control of the catalyst layer a fixed bed catalyst requires special attention. To replace the absorbed heat, a heat transfer medium, especially steam, is normally introduced. If the oxygenated cyclohexane is supplied as an aqueous solution, this provides undoubtedly at least water present as a solvent or dispersant part of the steam required. The steam supply to the dehydration room can be carried out in a suitable manner with periodic and intermittent feeding will.

In the condensation product of dehydrogenation are in addition to catechol in aqueous solution phenol as a by-product, unused oxygenated starting cyclohexane and other substances present. The desired catechol can be obtained by solution-1 gain extraction, namely by using a solvent such as ether or Carbon tetrachloride or by another method of operation The extractant is separated from the extract by distillation; then catechol is through Recrystallization or distillation completed, depending on the yield of isolated catechol is higher than 85 mol% For a full understanding of the rationale and usefulness the invention is served by the following individual examples, which explain the concept of the invention and not intended to limit.

Example 1 A catalyst is prepared in the following manner: One aqueous solution with the following compounds in the given proportions will be completed.

Ni (NO3) 2. 6H20 300 g Cu (NO3) 2.3H2O 75 g Cr (No3) 3-9H20 9 g H2S04 0.6 g Na2S ° 4 0.35 g of this aqueous solution are 1000 g of silicon carbide as a carrier added. The resulting mixture is heated with stirring to evaporate water. The preparation is then placed in a stream of air for 4 hours at a temperature of Calcined 4000C. The catalyst obtained is placed in a stream of hydrogen for 2 hours reduced at a temperature of 4000 C before going for the one described below Reaction is used.

Using this catalyst, 2-hydroxycyclohexanone is made under dehydrated following reaction conditions.

Amount of catalyst 50 cm3 Concentration of the starting materials 20% by weight in aqueous LHSV 0.6 h 1 solution Amount of hydrogen introduced (molar ratio based on the starting materials) 10 reaction temperature 3500 ° C. Pyrocatechol is obtained with 94 96 yield, phenol with 2 -o yield and cyclohexanone with 2% yield.

If the activity of said catalyst decreases, the same can fully by calcining in air for a period of about 6 hours at a Temperature of 4000 C are reactivated, whereupon the catalyst for 2 hours in one Hydrogen flow is reduced.

Example 2 The procedure of Example 1 is followed by the modification the use of 250 g nickel nitrate and 50 g cobalt nitrate instead of nickel nitrate performed alone.

One receives catechol in a yield of 90%, phenol in one Yield of 5% and cyclohexanone in a yield of 4%. Example 3 example 3 The procedure of Example 1 is carried out using 2-methoxycyclohexanone carried out as a starting material.

Guaiacol is obtained in a yield of 85%.

Example 4 The procedure of example 1 is carried out with different carrier materials in order to detect the influence of the carrier material. The results of the work are summarized in the following table. Selectivity (mol%) Carrier conversion (%) Catechol phenol cyclohexanone γ-Al2O3 69 15 80 5 Silica 73 18 75 7 Clay Infusorie- 72 23 57 20 Zeolite 70 20 64 16 Electrical 98 94 4 2 corundum SiC 98 96 2 2 -I Example 5) A catalyst is prepared in the following manner by preparing an aqueous solution containing the following compounds.

Ni (No3) 2.6H20 300 g Cu (N03) 2.3H20 75 g Cr (N03) 3.9H20 9g H2SO4 0.6 g Na2S04 0.35 g -This aqueous solution is 1000 g silicon carbide as a carrier admitted. The resulting mixture is heated with stirring to evaporate water. The material obtained is then calcined for 4 hours in a stream of air at 400.degree. Of the The resulting catalyst is in a stream of hydrogen at one temperature for 2 hours of 400 ° C before it is used for a reaction.

Using this catalyst, cyclohexane-1,2-diol is made under dehydrated under the following reaction conditions.

Amount of catalyst 50 cm³ Concentration of the starting materials 20% by weight in aqueous solution LHSV value 0.6 h 1 Amount of hydrogen supplied (molar ratio based on the 10 starting materials) 350 Reaction temperature 350 ° C. Pyrocatechol is obtained in a yield of 94 ,, phenol in a yield of 3% and cyclohexanone in a yield - of 1 O / o Example 6 The procedure of Example 5 is under Repeated use of aluminum-electro corundum instead of silicon carbide.

I catechol is obtained in a yield of 90%, phenol in a yield of 6% and cyclohexanone in a yield of 2%.

Example 7 The procedure of Example 5 is followed using of nickel nitrate and 50 g of cobalt nitrate instead of 300 g of nickel nitrate alone. Pyrocatechol is obtained in a yield of 89 ,, phenol in a yield of 5% and cyclohexanone in a yield of 3%.

Example 8 The procedure of Example 5 is followed using Cyclohexane-1,4-diol was repeated instead of cyclohexane-1,2-diol.

Hydroquinone is obtained in a yield of 93%, phenol in one Yield of 3% and cyclohexanone in a yield of 2%.

Example 9 The procedure of Example 5 is followed using 1,2-dimethoxycyclohexane was repeated instead of cyclohexane-1,2-diol.

Veratrol is obtained in a yield of 85.

Example 10 The procedure of Example 1 is followed by the modification repeated that no copper nitrate is used.

Pyrocatechol is obtained in a yield of 90%, phenol in one Yield of 6% and cyclohexanone in a yield of 3, Example 11 The procedure Example 5 is repeated with the modification that no copper nitrate is used will. vonin One obtains catechol in a yield of 90%, phenol in one yield of 5% and cyclohexanone in a yield of 3%.

Claims (11)

P a t e n t a n s p r ü c h e 1. A process for the preparation of dihydroxybenzenes, characterized in that under the action of a catalyst, the nickel and chromium bonded to a calcinable carrier which contains essentially none of the constituents, an oxygenated cyclohexane of the general formula with R1 and R2 as hydrogen, alkyl or aryl radical, with R as a lower alkyl radical or lower alkenyl radical, with n as an integer between 0 and 4, with the OR2 radical in the 2- or 4-position opposite the OR1 radical . 12. The method according to claim 1, characterized in that dap is used as a carrier Electro-corundum or silicon carbide is used. 3. The method according to claim 1 or 2, characterized in that the catalyst contains cobalt and / or copper. 4. The method according to any one of claims 1 to 3, characterized in that dap an alkali sulfate is used as an accelerator within the catalyst. 5, method according to one of claims 1 to 4, characterized in that that the catalyst holds nickel, copper and chromium, 6. The method according to claim 5, characterized in that a weight ratio in Ni: Cu: Cr of 100: 0 - 100: 0.1 - 6 is used. 7. The method according to any one of claims 1 to 52, characterized in that that the catalyst contains nickel, cobalt, copper and chromium. 8. The method according to claim 7, characterized in that a weight ratio in Ni + Co: Cu: Cr from 100: 0-100: 0.1-6 is used. T 9. Procedure according to one of claims 1 to 8, characterized in that the oxygenated cyclohexane is introduced as an aqueous solution into a catalytic dehydrogenation gas phase. 10. The method according to any one of claims 1 to 9, characterized-marked, dap the catalytic Gaphas dehydrogenation - takes place in the presence of hydrogen, which is added in an amount of 1-50 moles per mole of oxygenated cyclohexane. ! 11. The method according to any one of claims 1 to 10, characterized in, dap as a starting material an oxygenated cyclohexane of the formula (I), (II) or (III) where n = 0 and R1 and R2 are used as hydrogen or methyl radicals.