WO2009032480A1

WO2009032480A1 - Integrated process for the production of hydroxylated aromatic hydrocarbons

Info

Publication number: WO2009032480A1
Application number: PCT/US2008/072758
Authority: WO
Inventors: Anna Fornlin
Original assignee: Dow Global Technologies Inc.
Priority date: 2007-08-29
Filing date: 2008-08-11
Publication date: 2009-03-12
Also published as: TW200920732A

Abstract

An integrated process for the production of a hydroxylated aromatic hydrocarbon such as phenol. The process includes (A) contacting hydrogen peroxide with a mixture of an aromatic hydrocarbon such as benzene and an alkyl cyanide such as acetonitrile in the presence of a catalyst to form the hydroxylated aromatic hydrocarbon and water, wherein at least a portion of the aromatic hydrocarbon, alkyl cyanide, and hydrogen peroxide are from step (C); (B) separating the hydroxylated aromatic hydrocarbon, water, and any by¬ products from unreacted aromatic hydrocarbon and alkyl cyanide; and (C) using the aromatic hydrocarbon and alkyl cyanide from step (B) as a solvent in the production of hydrogen peroxide in step (A).

Description

INTEGRATED PROCESS FOR THE PRODUCTION OF HYDROXYLATED AROMATIC HYDROCARBONS

Background of the invention

This invention pertains to an integrated process for the production of hydroxylated aromatic hydrocarbons such as the production of phenol from benzene and hydrogen peroxide.

Phenol is a well known commercial product. One way of making phenol involves hydroxylating benzene using hydrogen peroxide. A need exists for improved methods of phenol production that are more efficient and less costly.

Summary of the Invention

This invention provides a solution to one or more of the problems and disadvantages discussed above.

In one broad respect, this invention is an integrated process for the production of a hydroxylated aromatic hydrocarbon, comprising: (A) contacting hydrogen peroxide with a mixture of an aromatic hydrocarbon and an alkyl cyanide in the presence of a catalyst to form the hydroxylated aromatic hydrocarbon and water, wherein at least a portion of the aromatic hydrocarbon, alkyl cyanide, and hydrogen peroxide are from step (C); (B) separating the hydroxylated aromatic hydrocarbon, water, and any by-products from unreacted aromatic hydrocarbon and alkyl cyanide; and (C) using the unreacted aromatic hydrocarbon and alkyl cyanide from step (B) as a solvent in the production of hydrogen peroxide in step (A).

In certain embodiments, the catalyst is a zeolite; the catalyst is a ZSM-5 zeolite; the catalyst is a ZSM-5 zeolite that contains iron and aluminum; the hydroxylated aromatic hydrocarbon is phenol; the aromatic hydrocarbon is benzene; the temperature during the contacting step (B) is in the range from about 50 to about 150 degrees Centigrade (⁰C); the temperature during the contacting step (B) is in the range from about 80 ⁰C to about 130 ⁰C; the alkyl cyanide is acetonitrile; the benzene conversion is in the range from about 5 percent (%) to about 25 %; the phenol conversion is at least about 97 %; and combinations thereof.

In another broad respect, this invention is an integrated process for the production of phenol, comprising: (A) contacting hydrogen peroxide with a mixture of an benzene and acetonitrile in the presence of a catalyst to form phenol and water, wherein at least a portion of the benzene, acetonitrile, and hydrogen peroxide are from step (C); (B) separating the phenol, water, and any by-products from unreacted benzene and acetonitrile; and (C) using the benzene and acetonitrile from step (B) as a solvent in the production of hydrogen peroxide in step (A).

In another broad respect, this invention is an integrated process for the production of phenol, comprising: (A) contacting hydrogen peroxide with a mixture of a benzene and an acetonitrile in the presence of a zeolite catalyst to form phenol and water, wherein at least a portion of the benzene, acetonitrile, and hydrogen peroxide are from step (C); (B) separating the phenol, water, and any by-products from unreacted benzene and acetonitrile; and (C) using the benzene and acetonitrile from step (B) as a solvent in the production of hydrogen peroxide in step (A).

In another broad respect, this invention is an integrated system for the production of a hydroxylated aromatic hydrocarbon, comprising: (A) a hydroxylation reactor where hydrogen peroxide is contacted with a mixture of an aromatic hydrocarbon and an alkyl cyanide in the presence of a catalyst to form the hydroxylated aromatic hydrocarbon and water, wherein at least a portion of the aromatic hydrocarbon, alkyl cyanide, and hydrogen peroxide are from the hydrogen peroxide reactor (C); (B) a separator where the hydroxylated aromatic hydrocarbon, water, and any by-products are separated from unreacted aromatic hydrocarbon and alkyl cyanide; and (C) a hydrogen peroxide reactor where the unreacted aromatic hydrocarbon and alkyl cyanide from separator (B) are used as a solvent mixture in the production of hydrogen peroxide.

In another broad respect, this invention is a process for the manufacture of an integrated system for the production of a hydroxylated aromatic hydrocarbon, comprising: (A) providing a hydroxylation reactor where hydrogen peroxide is contacted with a mixture of an aromatic hydrocarbon and an alkyl cyanide in the presence of a catalyst to form the hydroxylated aromatic hydrocarbon and water, wherein at least a portion of the aromatic hydrocarbon, alkyl cyanide, and hydrogen peroxide are from the hydrogen peroxide reactor (C); (B) providing a separator where the hydroxylated aromatic hydrocarbon, water, and any by-products are separated from unreacted aromatic hydrocarbon and alkyl cyanide; and (C) providing a hydrogen peroxide reactor where the unreacted aromatic hydrocarbon and alkyl cyanide from separator (B) are used as a solvent mixture in the production of hydrogen peroxide.

This invention provides a number of advantages. The use of a mixture of aromatic hydrocarbon such as benzene and alkyl cyanide such as acetonitrile in the hydroxylation reaction helps provide very high yield to phenol. Likewise, use of a ZSM-5 catalyst doped with iron and aluminum helps provide a high yield to phenol. The use of a mixture of aromatic hydrocarbon and alkyl cyanide as the solvent for the direct production of hydrogen peroxide provides reduced costs of production as well as purification of hydrogen peroxide which is produced directly in the aromatic hydrocarbon/alkyl cyanide stream from oxygen and hydrogen where the reaction selectivity of hydrogen to hydrogen peroxide is generally higher than 60%. The main undesired reaction product is water which is in low amounts; hence the outlet stream of hydrogen peroxide in the aromatic hydrocarbon/alkyl cyanide stream can be used directly as feed to the hydroxylation reactor.

Brief Description of the Drawings

Figure 1 is a representative block diagram of the integrated process of this invention.

Detailed Description of the Invention

The contacting of the aromatic hydrocarbon with the hydrogen peroxide in the presence of a catalyst to effect hydroxylation (oxidation to form a hydroxy group) of the aromatic hydrocarbon can occur in a variety of reactors. Typically, the reactor is a fixed bed. In one embodiment the process is conducted in plug flow fashion. Effluent from the direct hydrogen peroxide synthesis unit is sent to the hydroxylation reactor. The flow of reactants over the catalyst is typically in the range from about 0.1 to about 10 WHSV, more typically from about 0.5 to about 5 WHSV, and in one embodiment is from about 1 to about 3 WHSV. It should be noted that WHSV is the liquid hourly space velocity and defines the weight of liquid per weight of catalyst per hour. In one embodiment, excess hydrogen peroxide is employed in the hydroxylation reactor, with some decomposing to oxygen and water during the hydroxylation. Typically, there is no residual hydrogen peroxide in the hydroxylation reactor outlet stream, but there can be oxygen present which is removed and purged as a gas stream. The temperature at which the hydroxylation occurs will vary depending on the type of aromatic compound being hydroxylated. Typically the temperature is in the range from 50 ⁰C to 150 ⁰C. In one embodiment, the temperature is in the range from about 80 ⁰C to about 130 ⁰C for hydroxylation of benzene.

The aromatic hydrocarbons that can be used in the practice of this invention may vary. Typically the aromatic hydrocarbon has from 6 to about 30 carbons. The aromatic hydrocarbon can include non-aromatic groups, such as alkyl groups. Representative examples of such aromatic hydrocarbons include but are not limited to benzene, toluene, ethyl benzene, xylene, diphenyl, diphenyl methane, diphenyl ethane, naphthalene, anthracene, and combinations thereof. In one embodiment, the aromatic hydrocarbon is benzene.

The alkyl cyanide compounds are generally of formula: R-CN, where R is alkyl of from 1 to about 10 carbons. The alkyl can be substituted in the 1 position or can be substituted at other positions of the alkyl chain. In one embodiment, the alkyl cyanide used in this invention is acetonitrile (methyl cyanide).

The relative amounts of aromatic hydrocarbon and alkyl cyanide used can vary. The ratio of alkyl cyanide to aromatic hydrocarbon can vary from about 0.1 :1 to about 10:1. In one embodiment, the ratio of alkyl cyanide to aromatic hydrocarbon is in the range from about 0.5:1 to about 2:1. In one embodiment, the ratio of alkyl cyanide to aromatic hydrocarbon is about 1.5:1 . It should be appreciated that aromatic hydrocarbon that has been hydroxylated reduces the amount of aromatic hydrocarbon in the mixture of aromatic hydrocarbon and alkyl cyanide. Thus, make-up aromatic hydrocarbon will need to be added in the integrated process to maintain the desired ratio of aromatic hydrocarbon to alkyl cyanide.

The catalyst that is used in the hydroxylation of the aromatic hydrocarbon with hydrogen peroxide can vary widely. Well known catalysts such as various zeolites (e.g., ZSM-5, mordenite, and so on) can be used, as well as silicate catalysts such as titanium silicate. The catalysts can be doped with a variety of other compounds using well known techniques. Representative examples of such other compounds include Be, Ti, V, Mn, Fe, Co, Zn, Zr, Rh, Ag, Sn, Sb, Al, B, and combinations thereof. Such compounds and any other promoters or materials can be used as would be apparent to one of skill in the art.

The ratio of aromatic hydrocarbon to hydrogen peroxide in the hydroxylation reactor can vary widely. In general, the ratio of aromatic hydrocarbon to hydrogen peroxide is in the range of from about 0.1 :1 to about 1 :1. In one embodiment, the ratio of hydrogen peroxide to aromatic hydrocarbon is in the range from about 0.5:1 to about 0.7:1.

In the process of this invention, the conversion of benzene to phenol is typically in the range from about 5 percent (%) to about 25%. More typically, the conversion is in the range from about 7% to about 20%. In one embodiment of this invention, the conversion is at least 10%. Benzene conversion (in %) is defined as 100 x (benzene converted in the reactor / total benzene fed to the reactor).

In the process of this invention, the phenol selectivity is typically at least about 90 percent. More typically, the phenol selectivity is at least about 94 percent. In one embodiment of this invention, the phenol selectivity is at least about 97 percent.

The effluent from the hydroxylation reactor is subjected to separation. Thus, water, hydroxylated aromatic hydrocarbon, and any by-products produced in the hydroxylation reaction are separated from the unreacted aromatic hydrocarbon and the alkyl cyanide. This separation can be accomplished using standard techniques, such as distillation, crystallization or solidification of product coupled with decanting or filtration, extraction, or other conventional method. The hydroxylated aromatic hydrocarbon may be further purified downstream.

The aromatic hydrocarbon and alkyl cyanide effluent from the separation is then used as a solvent system in the hydrogen peroxide reactor. The production of the hydrogen peroxide can be conducted using conventional techniques. In general, hydrogen, oxygen, and a catalyst and co-catalyst are charged to the hydrogen peroxide reactor where hydrogen peroxide formation occurs. The hydrogen and oxygen are used in quantities that provide a non-explosive mixture. The benzene and alkyl cyanide solvent system is capable of dissolving hydrogen peroxide and water formed during the synthesis of the hydrogen peroxide. The catalyst can also be present as a fixed bed, trickle bed, or the like. Representative examples of references that disclose hydrogen peroxide synthesis include published US Patent Application No. 2003/0083510, incorporated herein in their entirety by reference.

Known catalysts can be used for the reaction in the production of the hydrogen peroxide. These are catalysts with one or more elements of the Groups VIII and/or Ib of the periodic system, especially elements from the series Ru, Rh, Pd, Ir, Pt and Au, with Pd and Pt particularly preferred. The catalytically active element or elements are usually bound to a particulate carrier, but can also be made as a coating with sufficiently great active surface on a monolithic carrier with channels, or on other flat carriers. Carrier-bound noble metal catalysts are particularly preferred as they are suitable for use in trickling bed reactors as a fixed bed with predetermined particle size. The particle size of suitable carriers is in the general range of about 0.01 to about 5 mm, and especially in the range of abut 0.05 to about 2 mm. The noble metal content in the carrier/catalyst combination is generally from about 0.01 to about 10 percent by weight.

Suitable carrier materials, other than activated carbon, are water-insoluble oxides, mixed oxides, sulfates, phosphates, and silicates of alkaline earth metals, Al, Si, Sn, and metals of the third to sixth subgroups (Ilia to Via). Activated carbons are generally preferred carriers, but in selection care should be taken that they have the minimum effect of decomposing hydrogen peroxide. Of the oxides, SiO₂, AI₂O₃, SnO₂, TiO₂, ZrO₂, Nb₂O₅, and Ta₂O₅, are preferred, and, of the sulfates, barium sulfate.

Thus, representative examples of suitable catalysts include catalysts composed of palladium, platinum, alloyed or non-alloyed combinations of palladium, platinum, with or without promoters such as silver or gold, and so on, which can be present on a support material such as silica, alumina, titanium dioxide, zirconium dioxide, and zeolites where the catalyst may be in the form of powder, extrudates, granules, and so on.

Referring now to Figure 1 , a block diagram of the integrated process of this invention is shown. For purposes of Figure 1 , the aromatic hydrocarbon is benzene, the alkyl cyanide is acetonitrile, and phenol is produced. In Figure 1 , there is shown an integrated process, generally indicated as numeral 10, which includes a reactor for the direct synthesis of hydrogen peroxide 20, a hydroxylation reactor 30 for the oxidation of benzene to phenol, and a separation unit 40. With respect to hydrogen peroxide reactor 20, benzene and acetonitrile (recycle stream) from separation apparatus 40 is provided, via line 44, to the reactor 20. Hydrogen and oxygen are provided to the hydrogen peroxide reactor 20 via lines 21 and 22, respectively. A suitable catalyst is supplied to the reactor 20 via line 23. Alternatively, the catalyst is a fixed bed that has been previously installed. Hydrogen peroxide is thus made directly in the reactor 20. The hydrogen peroxide and mixture of benzene and acetonitrile is then introduced into oxidation reactor 30 via line 24.

In oxidation reactor 30 (which may also be referred to as a hydroxylation reactor), make-up benzene is provided to reactor 30 via line 31. A suitable hydroxylation catalyst is supplied to the reactor 30 via line 32. Alternatively, the oxidation catalyst is a fixed bed that has been previously installed. In reactor 30, the benzene contacts the hydrogen peroxide in the presence of the hydroxylation catalyst to form phenol and water. The reactor can be operated continuously or batch-wise. In either case, effluent from the reactor 30, which contains benzene, acetonitrile, phenol, water, and any undesired by-products are sent via line 33 to the separation unit 40. Hydrogen peroxide can be used in the hydroxylation reactor owing to parallel decomposition to oxygen (O₂) and water during the hydroxylation reaction. Oxygen is removed and purged via outlet purge line 34.

In separation apparatus 40, the water, any by-products, and phenol are separated and removed via lines 41 , 42, and 43, respectively. It should be appreciated that the separation unit 40 may include one or more individual apparatus to accomplish the desired separations, and that separation unit 40 is intended to represent a block step. The benzene and acetonitrile effluent from the separation unit 40 is sent to hydrogen peroxide reactor 20 via line 44.

The following examples are provided as being illustrative of the present invention, and are not to be construed as limiting the scope of the present invention or claims hereto. Unless otherwise denoted, all percentages are by weight.

Example 1 - 5

The following table shows the results from a hydroxylation reactor where the effluent was treated to remove phenol and the resulting stream containing unreacted benzene and acetonitrile was sent to a hydrogen peroxide production unit, with the effluent from the hydrogen peroxide production unit being fed to the hydroxylation reactor. The catalyst was present in the hydroxylation reactor in a plug flow arrangement. The data provided in the table was based on 2 week runs, where there was no catalyst deactivation or iron leaching observed. In all runs the co-solvent was acetonitrile and the acetonitrile to benzene ratio was 1.5:1 . In all runs the amount of catalyst was 4 grams.

Further modifications and alternative embodiments of this invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the manner of carrying out the invention. It is to be understood that the forms of the invention herein shown and described are to be taken as illustrative embodiments. Equivalent elements or materials may be substituted for those illustrated and described herein, and certain features of the invention may be utilized independently of the use of other features, all as would be apparent to one skilled in the art after having the benefit of this description of the present invention.

Claims

What is claimed is:

1. An integrated process for the production of a hydroxylated aromatic hydrocarbon, comprising: (A) contacting hydrogen peroxide with a mixture of an aromatic hydrocarbon and an alkyl cyanide in the presence of a catalyst to form the hydroxylated aromatic hydrocarbon and water, wherein at least a portion of the aromatic hydrocarbon, alkyl cyanide, and hydrogen peroxide are from step (C);

(B) separating the hydroxylated aromatic hydrocarbon, water, and any by- products from unreacted aromatic hydrocarbon and alkyl cyanide; and

(C) using the unreacted aromatic hydrocarbon and alkyl cyanide from step (B) as a solvent in the production of hydrogen peroxide in step (A).

2. The process of claim 1 , wherein the catalyst is a zeolite.

3. The process of claim 1 , wherein the catalyst is a ZSM-5 zeolite.

4. The process of claim 1 , wherein the catalyst is a ZSM-5 zeolite that contains iron and aluminum.

5. The process of claim 1 , wherein the hydroxylated aromatic hydrocarbon is phenol.

6. The process of claim 1 , wherein the aromatic hydrocarbon is benzene.

7. The process of claim 1 , wherein the temperature during the contacting step (B) is in the range from about 50 to about 150 degrees Centigrade.

8. The process of claim 1 , wherein the temperature during the contacting step (B) is in the range from about 80 to about 130 degrees Centigrade.

9. The process of claim 1 , wherein the alkyl cyanide is acetonitrile.

10. The process of claim 1 , wherein the benzene conversion is in the range from about 5 to about 25 percent.

1 1 . The process of claim 1 , wherein the phenol conversion is at least about 97 percent.

12. An integrated process for the production of phenol, comprising:

(A) contacting hydrogen peroxide with a mixture of benzene and acetonitrile in the presence of a catalyst to form the phenol and water, wherein at least a portion of the benzene, acetonitrile; and hydrogen peroxide are from step (C);

(B) separating the phenol, water, and any by-products from unreacted benzene and acetonitrile, and

(C) using the benzene and acetonitrile from step (B) as a solvent in the production of hydrogen peroxide in step (A).

13. The process of claim 12, wherein the catalyst is a zeolite.

14. The process of claim 12, wherein the catalyst is a ZSM-5 zeolite.

15. The process of claim 12, wherein the catalyst is a ZSM-5 zeolite that contains iron and aluminum.

16. The process of claim 1 , wherein the temperature during the contacting step (B) is in the range from about 50 to about 150 degrees Centigrade.

17. The process of claim 1 , wherein the temperature during the contacting step (B) is in the range from about 80 to about 130 degrees Centigrade.

18. The process of claim 1 , wherein the benzene conversion is in the range from about 5 to about 25 percent.

19. The process of claim 1 , wherein the phenol conversion is at least about 97 percent.

20. An integrated process for the production of phenol, comprising: (A) contacting hydrogen peroxide with a mixture of benzene and acetonitrile in the presence of a zeolite catalyst to form the phenol and water, wherein at least a portion of the benzene, acetonitrile, and hydrogen peroxide are from step (C);

(B) separating the phenol, water, and any by-products from unreacted benzene and acetonitrile; and (C) using the benzene and acetonitrile from step (B) as a solvent in the production of hydrogen peroxide in step (A).

21 . The process of claim 20, wherein the catalyst is a ZSM-5 zeolite that contains iron and aluminum.

22. The process of claim 20, wherein the temperature during the contacting step (B) is in the range from about 50 to about 150 degrees Centigrade.

23. The process of claim 20, wherein the temperature during the contacting step (B) is in the range from about 80 to about 130 degrees Centigrade.

24. The process of claim 20, wherein the benzene conversion is in the range from about 5 to about 25 percent.

25. The process of claim 20, wherein the phenol conversion is at least about 97 percent.

26. An integrated system for the production of a hydroxylated aromatic hydrocarbon, comprising:

(A) a hydroxylation reactor where hydrogen peroxide is contacted with a mixture of an aromatic hydrocarbon and an alkyl cyanide in the presence of a catalyst to form the hydroxylated aromatic hydrocarbon and water, wherein at least a portion of the aromatic hydrocarbon, alkyl cyanide, and hydrogen peroxide are from the hydrogen peroxide reactor (C);

(B) a separator where the hydroxylated aromatic hydrocarbon, water, and any by-products are separated from unreacted aromatic hydrocarbon and alkyl cyanide; and

(C) a hydrogen peroxide reactor where the unreacted aromatic hydrocarbon and alkyl cyanide from separator (B) are used as a solvent mixture in the production of hydrogen peroxide.

27. A process for the manufacture of an integrated system for the production of a hydroxylated aromatic hydrocarbon, comprising:

(A) providing a hydroxylation reactor where hydrogen peroxide is contacted with a mixture of an aromatic hydrocarbon and an alkyl cyanide in the presence of a catalyst to form the hydroxylated aromatic hydrocarbon and water, wherein at least a portion of the aromatic hydrocarbon, alkyl cyanide, and hydrogen peroxide are from the hydrogen peroxide reactor (C); (B) providing a separator where the hydroxylated aromatic hydrocarbon, water, and any by-products are separated from unreacted aromatic hydrocarbon and alkyl cyanide; and

(C) providing a hydrogen peroxide reactor where the unreacted aromatic hydrocarbon and alkyl cyanide from separator (B) are used as a solvent mixture in the production of hydrogen peroxide.