CA1206481A - Process for the preparation of 3-alkylaminophenols - Google Patents
Process for the preparation of 3-alkylaminophenolsInfo
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- CA1206481A CA1206481A CA000403370A CA403370A CA1206481A CA 1206481 A CA1206481 A CA 1206481A CA 000403370 A CA000403370 A CA 000403370A CA 403370 A CA403370 A CA 403370A CA 1206481 A CA1206481 A CA 1206481A
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- hydrogen
- cyclohexenone
- weight
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-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D295/00—Heterocyclic compounds containing polymethylene-imine rings with at least five ring members, 3-azabicyclo [3.2.2] nonane, piperazine, morpholine or thiomorpholine rings, having only hydrogen atoms directly attached to the ring carbon atoms
- C07D295/04—Heterocyclic compounds containing polymethylene-imine rings with at least five ring members, 3-azabicyclo [3.2.2] nonane, piperazine, morpholine or thiomorpholine rings, having only hydrogen atoms directly attached to the ring carbon atoms with substituted hydrocarbon radicals attached to ring nitrogen atoms
- C07D295/08—Heterocyclic compounds containing polymethylene-imine rings with at least five ring members, 3-azabicyclo [3.2.2] nonane, piperazine, morpholine or thiomorpholine rings, having only hydrogen atoms directly attached to the ring carbon atoms with substituted hydrocarbon radicals attached to ring nitrogen atoms substituted by singly bound oxygen or sulfur atoms
- C07D295/096—Heterocyclic compounds containing polymethylene-imine rings with at least five ring members, 3-azabicyclo [3.2.2] nonane, piperazine, morpholine or thiomorpholine rings, having only hydrogen atoms directly attached to the ring carbon atoms with substituted hydrocarbon radicals attached to ring nitrogen atoms substituted by singly bound oxygen or sulfur atoms with the ring nitrogen atoms and the oxygen or sulfur atoms separated by carbocyclic rings or by carbon chains interrupted by carbocyclic rings
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
Abstract
Abstract of the disclosure:
The invention relates to a process for the pre-paration of 3-alkylaminophenols by catalytic dehydrogena-tion of 3-alkylamino-2-cyclohexenones. The dehydrogenation reaction is carried out in the gas phase at 200 to 500°C
and 0.1 to 10 bar. The catalyst used is preferably a noble metal of the 8th group, in particular palladium, which is applied to a support material.
The invention relates to a process for the pre-paration of 3-alkylaminophenols by catalytic dehydrogena-tion of 3-alkylamino-2-cyclohexenones. The dehydrogenation reaction is carried out in the gas phase at 200 to 500°C
and 0.1 to 10 bar. The catalyst used is preferably a noble metal of the 8th group, in particular palladium, which is applied to a support material.
Description
The invention relates to a process for the pre-paration of 3-alkylaminophenols by catalytic dehydrogena-tion of 3-alkylamino-2-cyclohexenones in the gas phase.
3-Alkylaminophenols are important intermediate products for drugs, dyestuffs (German Offenlegungsschrift
3-Alkylaminophenols are important intermediate products for drugs, dyestuffs (German Offenlegungsschrift
2,458,347), herbicides, optical brighteners and anti-oxidants.
. ~ . ,~2~?,~?3 U.S. Patent ~e~2~e~ describes a process for the preparation of 3-aminophenols, which comprises dehydrogenating
. ~ . ,~2~?,~?3 U.S. Patent ~e~2~e~ describes a process for the preparation of 3-aminophenols, which comprises dehydrogenating
3-amino-2-cyclohexenones in the presence of a dehydrogena-tion catalyst in the liquid phase at 150-300C. In general, an inert solvent boiling between 150 and 300C
is required in this process. Hydrocarbons and poiyglycol ethers are used in particular. In order to achievé high yields,a quantity of solvent which is 5 to 10 times as large as the quantity of 3-amino-2-cyclohexenone is required, and the 3-aminophenols formed must be separated from the solvent by distillation.
- The encumbrance caused by large quantities of solvents, some of which are readily ignitable at the reaction temperatures, is ~ disadvantage in this process.
It has now been ~ound that 3-alkylamino-2-cyclo-hexenones, particularly 3-dimethylamino-2-cyclohexenone, ~ f~
can be vaporized either on their o~"n or in conjunction with an entraining agent and can be dehydrogenated in the gas phase on dehydrogenation catalysts to give 3-alkyl-aminophenols.
The invention therefore relates to a process for the preparation of 3-alkylaminophenols of the general formula I --~ "_ R5 (I) in which the radicals Rl to R5 independently of on.e another can be hydrogen or alkyl groups having up to 12 C
atoms, and R6 denotes an alkyl group having up to 12 C
atoms or, conjointly with R5, denotes an alkylene ring which has 4 to 6 C atoms and which can also contain an oxygen atom or a substituted nitrogen atom, by catalytic lS dehydrogenation of 3-amino-2-cyclohexenones of the general formula II:
~ ~R5 (II) ~2 }I
in which the radicals Rl to R6 have the meaning indicated above, which comprises carrying out the dehydrogenation reaction in the gas phase at 200 to 500C and under a pressure of 0.1 to 10 bar.
The alkyl groups which are suitable for the rad-icals R1 to R6 ln this connection can be straight-chain, ~L2~
b~anched or cyclic and, in the case of Rl to R5 , can further be substi~uted by halogen atoms.
The 3-alkylamino-2-cyclohexenones required as the starting compound for the process according to the inven-tion are readily accessible by reacting the corresponding1,3-cyclohexanediones with primary or secondary amines (U~S. Patent 4,212,823)~
The radicals Rl to R4 are preferably hydrogen, methyl, ethyl, propyl or butyl, in particular hydrogen or methyl. R5 and R6 are preferably methyl or ethyl.
The dehydrogenation catalysts used are ruthenium, rhodium, palladium, osmium, iridium, platinum, copper, silver, gold, iron, cobalt or nickel, preferably ruthenium, rhodium, palladium9 osmium, iridium or platinum. The use of palladium has proved to be particularly advantageous.
--, ...
In general, these elements, in the form of salts, are applied to support materials, such as carbon, aluminum oxide, silicon oxide, chromium oxide, aluminosilicates, zeolites, magnesium oxide, calcium oxide or titanium - 20 oxide. Carbon and sillcon oxide have proved particularly suitable. The quantity of the metal applied is generally between 0.1 and 20% by weight, preferably between 0.1 and 5% by weight. The particles of the support can have any - desired external form; spheres or extruded pieces are preferably used.
Before the start of the reaction, it is generally advantageous to reduce, by passing hydrogen over them at 250-500C or by means of other reducing agents, the salts which have been applied to the support.
The 3-alkylamino~2-cyclohe~enones can be vaporized ..
8~
is required in this process. Hydrocarbons and poiyglycol ethers are used in particular. In order to achievé high yields,a quantity of solvent which is 5 to 10 times as large as the quantity of 3-amino-2-cyclohexenone is required, and the 3-aminophenols formed must be separated from the solvent by distillation.
- The encumbrance caused by large quantities of solvents, some of which are readily ignitable at the reaction temperatures, is ~ disadvantage in this process.
It has now been ~ound that 3-alkylamino-2-cyclo-hexenones, particularly 3-dimethylamino-2-cyclohexenone, ~ f~
can be vaporized either on their o~"n or in conjunction with an entraining agent and can be dehydrogenated in the gas phase on dehydrogenation catalysts to give 3-alkyl-aminophenols.
The invention therefore relates to a process for the preparation of 3-alkylaminophenols of the general formula I --~ "_ R5 (I) in which the radicals Rl to R5 independently of on.e another can be hydrogen or alkyl groups having up to 12 C
atoms, and R6 denotes an alkyl group having up to 12 C
atoms or, conjointly with R5, denotes an alkylene ring which has 4 to 6 C atoms and which can also contain an oxygen atom or a substituted nitrogen atom, by catalytic lS dehydrogenation of 3-amino-2-cyclohexenones of the general formula II:
~ ~R5 (II) ~2 }I
in which the radicals Rl to R6 have the meaning indicated above, which comprises carrying out the dehydrogenation reaction in the gas phase at 200 to 500C and under a pressure of 0.1 to 10 bar.
The alkyl groups which are suitable for the rad-icals R1 to R6 ln this connection can be straight-chain, ~L2~
b~anched or cyclic and, in the case of Rl to R5 , can further be substi~uted by halogen atoms.
The 3-alkylamino-2-cyclohexenones required as the starting compound for the process according to the inven-tion are readily accessible by reacting the corresponding1,3-cyclohexanediones with primary or secondary amines (U~S. Patent 4,212,823)~
The radicals Rl to R4 are preferably hydrogen, methyl, ethyl, propyl or butyl, in particular hydrogen or methyl. R5 and R6 are preferably methyl or ethyl.
The dehydrogenation catalysts used are ruthenium, rhodium, palladium, osmium, iridium, platinum, copper, silver, gold, iron, cobalt or nickel, preferably ruthenium, rhodium, palladium9 osmium, iridium or platinum. The use of palladium has proved to be particularly advantageous.
--, ...
In general, these elements, in the form of salts, are applied to support materials, such as carbon, aluminum oxide, silicon oxide, chromium oxide, aluminosilicates, zeolites, magnesium oxide, calcium oxide or titanium - 20 oxide. Carbon and sillcon oxide have proved particularly suitable. The quantity of the metal applied is generally between 0.1 and 20% by weight, preferably between 0.1 and 5% by weight. The particles of the support can have any - desired external form; spheres or extruded pieces are preferably used.
Before the start of the reaction, it is generally advantageous to reduce, by passing hydrogen over them at 250-500C or by means of other reducing agents, the salts which have been applied to the support.
The 3-alkylamino~2-cyclohe~enones can be vaporized ..
8~
- 4 --directly. In order to ensure the avoi-dance of tarry by-products during the evaporation process, ho~Jever, it is advantageous to use an inert solvent boiling between 50 and 300C as an entraining agent for the starting material~In general, the quantity of solvent is between 10 and 200% by weight, relative to the 3-aminocyclo-hexenone, preferably between 10 and 90% by weight and par-ticularly 20 to 50% by weight. The following are examples of suitable solvents: water, aliphatic or aro-10 matic hydrocarbons, such as toluene and decalin, and ali-phatic and aromatic ethers, such as diphenyl ether or diethylene glycol dimethyl ether.
Water is particularly suitable: while the 3-alkylamino-2-cyclohexenones used as the starting material are readi'y soluble in water, the 3-alkylaminophenols formed in the dehydrogenation reaction are largely insoluble in water. This offers the advantage that the latter can be isolated by filtration and are immediately available for further use, after drying. The unreacted 3-alkylamino-2 cyclohexenone remains dissolved in the water and can bere-used as feed material without further purification.
If water is used as the entraining agent, the dehydrogenation reaction takes place with a higher degree of selectivity in respect of the desired 3-alkylamino-phenols than if organic solvents are used. A high space-time yield of up to 300 g/l.hour is achieved. It is sur-prising that, in the course of this reaction, the water - does not effect hydrolysis of the 3-alkylamino-2-cyclo-hexenones; in p~rticular, 1,3-cyclohexanedione and 8~
resorcinol, the possible by-products, are not formed. The use of water instead of the abovementioned organic sol-vents is also to be preferred from the point of view operatir.g safety; ~later can also bé employed as t~e entraining agent together with organic solvents, pro-vided that the latter are miscible with water, for ex~mple - glycol ethers.
The vaporization of the starting compound is pre-ferably effected by dropwise addition of a mixture ~f the lattçr with an entraining agent on to a heated vaporiza-tion zone located above the catalyst. This vaporization zone is packed with an inert material, such as spheres of glass or stainless steel. The high-boiling 3-alkyl&~no-2-cyclohexenones pass over into the vapor phase at ~
vaporization temperature of 300-500C. It proves ~dv~.-tageous to feed in an inert carrier gas, for example nitro-gen, pre-heated to 300-500C, in order to achieve complete vaporization ~lnd a high selectivlty. The addition of hydrogen to the inert carrier gas counteracts early deposition of carbon on the catalyst and can therefore be recommended. It is preferable to feed in 1~0 to 500 i of nitrogen and 50 to 200 1 of hydrogen per mole of 3-amino-2-cyclohexenone.
The vaporization of the starting compound can also be effected by atomizing a mixture of the latter with the entraining agent, with the aid of a pre-heated stre~n of nitrogen or nitrogen/hydrogen, in a t~Jo-fluid nozzle located above the catalyst.
a ~ The dehydrogenation reaction is carried out at .
~V~;~B~
200 to 500C, preferably 250 to 400C, and under a pressure of 0.1 to 10 bar, preferably 0.5 to 2 bar and especially under normal pressure.
Catalysts which are employed for a prolonged period generally exhibit a slow decline in space-time yield. One of the possible causes of this deactivation is the deposition of carbon on the catalyst. These cata-lysts can be regenerated by burning off the carbon in an oxygen-nitrogen mixture at a temperature of 350 to 500C.
After the carbon has been burnt off, the metal catalysi must be reduced again by passing hydrogen over it.
- The procedure which follows has proved particularly advantageous for carrying out the process according to the invention: ~he reaction is carried out in a vertical reactor, which can be heated externally. The catalyst is located in the middle section of ~his reactor. Above ~his is the vaporization zone, on to which the mixture of starting compound and entraining agent is added dropwise.
Pre-heated nitrogen and hydrogen are passedfrom above over the catalyst. The reaction mixture condenses at the bottom of the reactor. If water is used as the entraining agent, the 3-alkylaminophenol is precipitated in a crystal-line form and is filtered off. If organic entraining agents are used, the products are isolated by distillation.
The following examples are intended to illustrate the invention; the gas rates (l/hour) quoted are in all cases measured under normal conditions~
Exarnple 1 Charcoal having a specific surface area of approx.
. .
. _ _ , . . , ..... . . . .. . .. , ~,, _, 8~
~ - 7 -1,000 m2/g was coated with 0.6% by weight o~ Pt by being impregnated with an aqueous solution of K2PtC16.
40 ml of this catalyst were charged to the middle section of a vertical reactor which can be heated exter-nally, and were reduced at 330C by passing 20 l/hour ofnitrogen and 10 l/hour of ~ydrogen over the catalyst. The starting material, 3-dimethylamino-2-cyclohexenone, was added dropwise, in the form of a 50% strength by weight solution in toluene, on to the vaporization zone above the catalyst and was passed from above over the catalyst in the form of vapor at an LHSV* of 0.9 hours 1 at 330C, together with 20 l/hour of nitrogen and 10 l/hour of hydrogen. The mixture of products obtained at the bottom of the reactor - was analyzed by means of gas chromatography. At a con-15 version of 63%, the yield of 3-dimethylaminophenol was 7%.
~nenthe reaction temperature was increased to 370C, the yield of 3-dimethylaminophenol was 31%, at a conversion of 71%.
*LHSV ( = liquid hourly space velocity) =
liters of solution of starting compound litërs of catalyst x hour ~xample 2 .
Silica having a specific surface area of 100 m2/g was coated with 1% by weight of Pd in the form of palladium 25 acetate and 0.9% by weight of K in the form of potassium hydroxide. 100 ml of this catalyst were charged to the reactor described in Example 1 and were red~lced with hydrogen. A 50% strength by weight solution of 3-dimethyl-amino-2-cyclohexenone in toluene as entraining agent was vaporized, in the presence of 20 l/hour of hyd.ogen, at an LHSV of 0. 25 hours 1 and at a reactor temperature of - 330C, and was dehydrogenated in the gas phase.
- Analysis by gas chromatography indicated a con-
Water is particularly suitable: while the 3-alkylamino-2-cyclohexenones used as the starting material are readi'y soluble in water, the 3-alkylaminophenols formed in the dehydrogenation reaction are largely insoluble in water. This offers the advantage that the latter can be isolated by filtration and are immediately available for further use, after drying. The unreacted 3-alkylamino-2 cyclohexenone remains dissolved in the water and can bere-used as feed material without further purification.
If water is used as the entraining agent, the dehydrogenation reaction takes place with a higher degree of selectivity in respect of the desired 3-alkylamino-phenols than if organic solvents are used. A high space-time yield of up to 300 g/l.hour is achieved. It is sur-prising that, in the course of this reaction, the water - does not effect hydrolysis of the 3-alkylamino-2-cyclo-hexenones; in p~rticular, 1,3-cyclohexanedione and 8~
resorcinol, the possible by-products, are not formed. The use of water instead of the abovementioned organic sol-vents is also to be preferred from the point of view operatir.g safety; ~later can also bé employed as t~e entraining agent together with organic solvents, pro-vided that the latter are miscible with water, for ex~mple - glycol ethers.
The vaporization of the starting compound is pre-ferably effected by dropwise addition of a mixture ~f the lattçr with an entraining agent on to a heated vaporiza-tion zone located above the catalyst. This vaporization zone is packed with an inert material, such as spheres of glass or stainless steel. The high-boiling 3-alkyl&~no-2-cyclohexenones pass over into the vapor phase at ~
vaporization temperature of 300-500C. It proves ~dv~.-tageous to feed in an inert carrier gas, for example nitro-gen, pre-heated to 300-500C, in order to achieve complete vaporization ~lnd a high selectivlty. The addition of hydrogen to the inert carrier gas counteracts early deposition of carbon on the catalyst and can therefore be recommended. It is preferable to feed in 1~0 to 500 i of nitrogen and 50 to 200 1 of hydrogen per mole of 3-amino-2-cyclohexenone.
The vaporization of the starting compound can also be effected by atomizing a mixture of the latter with the entraining agent, with the aid of a pre-heated stre~n of nitrogen or nitrogen/hydrogen, in a t~Jo-fluid nozzle located above the catalyst.
a ~ The dehydrogenation reaction is carried out at .
~V~;~B~
200 to 500C, preferably 250 to 400C, and under a pressure of 0.1 to 10 bar, preferably 0.5 to 2 bar and especially under normal pressure.
Catalysts which are employed for a prolonged period generally exhibit a slow decline in space-time yield. One of the possible causes of this deactivation is the deposition of carbon on the catalyst. These cata-lysts can be regenerated by burning off the carbon in an oxygen-nitrogen mixture at a temperature of 350 to 500C.
After the carbon has been burnt off, the metal catalysi must be reduced again by passing hydrogen over it.
- The procedure which follows has proved particularly advantageous for carrying out the process according to the invention: ~he reaction is carried out in a vertical reactor, which can be heated externally. The catalyst is located in the middle section of ~his reactor. Above ~his is the vaporization zone, on to which the mixture of starting compound and entraining agent is added dropwise.
Pre-heated nitrogen and hydrogen are passedfrom above over the catalyst. The reaction mixture condenses at the bottom of the reactor. If water is used as the entraining agent, the 3-alkylaminophenol is precipitated in a crystal-line form and is filtered off. If organic entraining agents are used, the products are isolated by distillation.
The following examples are intended to illustrate the invention; the gas rates (l/hour) quoted are in all cases measured under normal conditions~
Exarnple 1 Charcoal having a specific surface area of approx.
. .
. _ _ , . . , ..... . . . .. . .. , ~,, _, 8~
~ - 7 -1,000 m2/g was coated with 0.6% by weight o~ Pt by being impregnated with an aqueous solution of K2PtC16.
40 ml of this catalyst were charged to the middle section of a vertical reactor which can be heated exter-nally, and were reduced at 330C by passing 20 l/hour ofnitrogen and 10 l/hour of ~ydrogen over the catalyst. The starting material, 3-dimethylamino-2-cyclohexenone, was added dropwise, in the form of a 50% strength by weight solution in toluene, on to the vaporization zone above the catalyst and was passed from above over the catalyst in the form of vapor at an LHSV* of 0.9 hours 1 at 330C, together with 20 l/hour of nitrogen and 10 l/hour of hydrogen. The mixture of products obtained at the bottom of the reactor - was analyzed by means of gas chromatography. At a con-15 version of 63%, the yield of 3-dimethylaminophenol was 7%.
~nenthe reaction temperature was increased to 370C, the yield of 3-dimethylaminophenol was 31%, at a conversion of 71%.
*LHSV ( = liquid hourly space velocity) =
liters of solution of starting compound litërs of catalyst x hour ~xample 2 .
Silica having a specific surface area of 100 m2/g was coated with 1% by weight of Pd in the form of palladium 25 acetate and 0.9% by weight of K in the form of potassium hydroxide. 100 ml of this catalyst were charged to the reactor described in Example 1 and were red~lced with hydrogen. A 50% strength by weight solution of 3-dimethyl-amino-2-cyclohexenone in toluene as entraining agent was vaporized, in the presence of 20 l/hour of hyd.ogen, at an LHSV of 0. 25 hours 1 and at a reactor temperature of - 330C, and was dehydrogenated in the gas phase.
- Analysis by gas chromatography indicated a con-
5 version of 97% and a yield of 3-dimethylaminophenol of 75%. 6% by weight of cyclohexanone, 4% by weight of phenol and 3% by weight of N,N-dimethylaniline were also ~ormed.
After an operating period of about 50 hours, the 10 catalyst was regenerated at 400-450C by burning off, using 20 l/hour of air. After the subsequent reduction of the catalyst, the same yield of 3-dimethylaminopheno' was obtained as before the regeneration. In a special test run, a catalyst ~ife of 1,000 hours was achieved, 15 regeneration being carried out 11 times.
Example 3 The catalyst and the reactor described in Example 2 were used. A 50% strength by weight aqueous s~lution of 3-dimethylamino-2-cyclohexenone was vaporized and dehy-20 drogenated at 330C in the gas phase. In the course ofthis, an additional 30 l/hour of nitrogen and 10 l/hour of hydrogen were passed through the reactor. Complete conversion was achieved at an LHSV of 0.5 hours 1. The 3-dimethylaminophenol was precipitated from the aqueous 25 solution of product in the form of white-brown crystals.
639 g of the feed material were dehydrogenated in an operating time of 52 hours. After drying, 617 g of 3-dimethylaminophenol were obtained, corresponding to a yield of 98%. The space-time yield was 250 g/l.hour. The 3~2~
g product had a melting point of 70C.
The catalyst was th~n regenerated at 400-450C ~y burning off, using 10 l/hour of air, and was then reduced again.
5764 g of 3-dimethylaminophenol, corresponding to a yield of 96%, were then obtained from 804 g of starting material under the same conditions as before regeneration.
After a further regeneration of the catalyst, a further 595 g of 3-dimethylaminophenol were obtain~d at a yield of 78% in an operating time of 50 hours. The con-version was 95%. The unreacted feed material remained dissolved in the water, while the reaction product was produced in crystalline form and was filtered off.
Example 4 15The reactor described in Example 1 was used.
50 ml of a catalyst containing 1% by weight of Pd and 0.9% by weight of ~ on silica having a specific surface area of 100 m2/g were employed for the dehydrogenation of 3-diethylamino-2-cyclohexenone. The feed material was vaporized in the form of an 80% strength solution in water. In addition 20 l/hour of nitrogen and 10 l/hour of hydrogen were fed in at a reactor ternperature of 350C
and an LHSV of 0.5 hours 1, The conversion was 100%. The 3-diethylaminophenol was precipitated in crystalline form and was filtered off. The yield was 80%.
Example 5 Using the same catalyst and under the same reaction conditions as in Example 4, 3-methylamino-2-cyclohexenone r~ was vaporized in the ~orm of a 40% strength solution in , water, and was dehydrogenated in the gas phase. The reaction product formed an aqueous and an organic phase.
- The 3-methylamino-2-cyclohexenone which had uot reacted remained in the aqueous phase; the conversion was 95%.
After vacuum distillation, the yield of 3-methylaminophenol was 70%.
~xample 6 Under the same conditions as in Example 5, 57 g of 3-dimethylamino-5-methyl-2-cyclohexenone were vaporized in the form of a 50% strength solution in water and were dehydrogenated in the gas phase. At an LHSV of 0.3 hours 1, the conversion was 100%. 41 g of 3-dimethylamino-5-methylphenol, corresponding to a yield of 72%, were obtained after distillation of the organic phase of the reaction i5 product,
After an operating period of about 50 hours, the 10 catalyst was regenerated at 400-450C by burning off, using 20 l/hour of air. After the subsequent reduction of the catalyst, the same yield of 3-dimethylaminopheno' was obtained as before the regeneration. In a special test run, a catalyst ~ife of 1,000 hours was achieved, 15 regeneration being carried out 11 times.
Example 3 The catalyst and the reactor described in Example 2 were used. A 50% strength by weight aqueous s~lution of 3-dimethylamino-2-cyclohexenone was vaporized and dehy-20 drogenated at 330C in the gas phase. In the course ofthis, an additional 30 l/hour of nitrogen and 10 l/hour of hydrogen were passed through the reactor. Complete conversion was achieved at an LHSV of 0.5 hours 1. The 3-dimethylaminophenol was precipitated from the aqueous 25 solution of product in the form of white-brown crystals.
639 g of the feed material were dehydrogenated in an operating time of 52 hours. After drying, 617 g of 3-dimethylaminophenol were obtained, corresponding to a yield of 98%. The space-time yield was 250 g/l.hour. The 3~2~
g product had a melting point of 70C.
The catalyst was th~n regenerated at 400-450C ~y burning off, using 10 l/hour of air, and was then reduced again.
5764 g of 3-dimethylaminophenol, corresponding to a yield of 96%, were then obtained from 804 g of starting material under the same conditions as before regeneration.
After a further regeneration of the catalyst, a further 595 g of 3-dimethylaminophenol were obtain~d at a yield of 78% in an operating time of 50 hours. The con-version was 95%. The unreacted feed material remained dissolved in the water, while the reaction product was produced in crystalline form and was filtered off.
Example 4 15The reactor described in Example 1 was used.
50 ml of a catalyst containing 1% by weight of Pd and 0.9% by weight of ~ on silica having a specific surface area of 100 m2/g were employed for the dehydrogenation of 3-diethylamino-2-cyclohexenone. The feed material was vaporized in the form of an 80% strength solution in water. In addition 20 l/hour of nitrogen and 10 l/hour of hydrogen were fed in at a reactor ternperature of 350C
and an LHSV of 0.5 hours 1, The conversion was 100%. The 3-diethylaminophenol was precipitated in crystalline form and was filtered off. The yield was 80%.
Example 5 Using the same catalyst and under the same reaction conditions as in Example 4, 3-methylamino-2-cyclohexenone r~ was vaporized in the ~orm of a 40% strength solution in , water, and was dehydrogenated in the gas phase. The reaction product formed an aqueous and an organic phase.
- The 3-methylamino-2-cyclohexenone which had uot reacted remained in the aqueous phase; the conversion was 95%.
After vacuum distillation, the yield of 3-methylaminophenol was 70%.
~xample 6 Under the same conditions as in Example 5, 57 g of 3-dimethylamino-5-methyl-2-cyclohexenone were vaporized in the form of a 50% strength solution in water and were dehydrogenated in the gas phase. At an LHSV of 0.3 hours 1, the conversion was 100%. 41 g of 3-dimethylamino-5-methylphenol, corresponding to a yield of 72%, were obtained after distillation of the organic phase of the reaction i5 product,
Claims (6)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the preparation of a 3-alkylaminophenol of the formula I
I
wherein the radicals R1 to R5 independently of one another can be hydrogen or alkyl groups having up to 12 C atoms, and R6 denotes an alkyl group having up to 12 C atoms, or together with R5, denotes an alkylene ring which has 4 to 6 C atoms and which can also contain an oxygen atom or a substituted nitrogen atom, in which a 3-amino-2-cyclohexenone of the formula II
II
wherein the radicals R1 to R6 are as defined above, is dehydro-genated in the gas phase at 200 to 500°C and under a pressure of 0.1 to 10 bar in the presence of a catalyst.
I
wherein the radicals R1 to R5 independently of one another can be hydrogen or alkyl groups having up to 12 C atoms, and R6 denotes an alkyl group having up to 12 C atoms, or together with R5, denotes an alkylene ring which has 4 to 6 C atoms and which can also contain an oxygen atom or a substituted nitrogen atom, in which a 3-amino-2-cyclohexenone of the formula II
II
wherein the radicals R1 to R6 are as defined above, is dehydro-genated in the gas phase at 200 to 500°C and under a pressure of 0.1 to 10 bar in the presence of a catalyst.
2. A process as claimed in claim 1, in which the reaction is carried out in the presence of 10 to 90% by weight, relative to the 3-amino-2-cyclohexenone, of an inert solvent having a boiling point between 50 and 300°C.
3. A process as claimed in claim 2 wherein the inert solvent is water.
4. A process as claimed in claim 1, claim 2 or claim 3 in which the reaction is carried out in the presence of 100 to 500 1 of nitrogen and of 50 to 200 1 of hydrogen, per mole of 3-amino-2-cyclohexenone.
5. A process as claimed in claim 1 in which the catalyst is palladium on a silicon dioxide or carbon support, with a palladium content of 0.1 to 20% by weight.
6. A process for the regeneration of the dehydrogenation catalyst as claimed in claim 5 in which the catalyst is treated with an oxygen-nitrogen mixture at a temperature of 350 to 500°C
and is then treated with hydrogen at 250 to 500°C.
and is then treated with hydrogen at 250 to 500°C.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3120245.4 | 1981-05-21 | ||
| DE19813120245 DE3120245A1 (en) | 1981-05-21 | 1981-05-21 | "METHOD FOR PRODUCING 3-ALKYLAMINOPHENOLS" |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1206481A true CA1206481A (en) | 1986-06-24 |
Family
ID=6132899
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000403370A Expired CA1206481A (en) | 1981-05-21 | 1982-05-20 | Process for the preparation of 3-alkylaminophenols |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0065733B1 (en) |
| JP (1) | JPS57197249A (en) |
| BR (1) | BR8202934A (en) |
| CA (1) | CA1206481A (en) |
| DE (2) | DE3120245A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5202488A (en) * | 1991-04-15 | 1993-04-13 | E. I. Du Pont De Nemours And Company | Method for the manufacture of 3-aminophenol |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2402695C3 (en) * | 1974-01-21 | 1980-05-29 | Hoechst Ag, 6000 Frankfurt | Process for the preparation of 3-aminophenols |
-
1981
- 1981-05-21 DE DE19813120245 patent/DE3120245A1/en not_active Withdrawn
-
1982
- 1982-05-17 EP EP82104302A patent/EP0065733B1/en not_active Expired
- 1982-05-17 DE DE8282104302T patent/DE3260363D1/en not_active Expired
- 1982-05-20 JP JP57084146A patent/JPS57197249A/en active Pending
- 1982-05-20 CA CA000403370A patent/CA1206481A/en not_active Expired
- 1982-05-20 BR BR8202934A patent/BR8202934A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| EP0065733A1 (en) | 1982-12-01 |
| JPS57197249A (en) | 1982-12-03 |
| EP0065733B1 (en) | 1984-07-11 |
| DE3120245A1 (en) | 1982-12-09 |
| BR8202934A (en) | 1983-05-03 |
| DE3260363D1 (en) | 1984-08-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |