GB2245192A

GB2245192A - Preparation of dialkylnaphthalene

Info

Publication number: GB2245192A
Application number: GB9112185A
Authority: GB
Inventors: Hiroshi Ohnuma; Takayoshi Shindo; Mitsuru Suda; Kunio Ohtsuka
Original assignee: Mitsubishi Materials Corp
Current assignee: Mitsubishi Materials Corp
Priority date: 1990-06-06
Filing date: 1991-06-06
Publication date: 1992-01-02
Anticipated expiration: 2011-06-06
Also published as: DE4118494A1; JPH0441446A; FR2663022A1; FR2663022B1; GB2245192B; DE4118494C2; GB9112185D0

Description

BACKGROUND OF THE INVENTION

I. FIELD OF THE INVENTION

This invention relates to a method of preparing dialkylnaphthalene (sometimes referred to herein as DAN) enriched with 2,6--DAN isomer by alkylating naphthalene and/or monoalkylnaphthalene. More particularly, it relates to a catalyst for preparing dialky1naphthalene enriched with 2, 6DAN isomer.

II. DESCRIPTION OF THE RELATED ART

Naphthalene dicarboxylate is obtained by oxidizing dialkylnaphthalene. 2, 6-naphthalene dicarboxylate obtained by oxidation of 2,6dialkylnaphthalene is particularly useful as a raw material for polyester products, such as films, fibers and resins. Dialkylnaphthalene enriched with 2,6-DAN isomer is prepared usually by alkylating naphthalene or monoalkylnaphthalene.

In the reaction, however, it is possible for sub stituent alkyl groups to react and bond among the eight positions of the naphthalene nucleus to thereby form ten possible isomers of DAN. In order to synthesize dialkylnaphthalene enriched with 2,6-DAN isomer at a high yield, i 1 is essential to use a shape selective catalyst with a high degree of stereoregularity.

In the prior art, crystalline alumina silicate zeolite has been proposed as a catalyst for synthesizing dialky1naphthalene enriched with 2,6-DAN isomer by alkylating naphthalene or monoalkylnaphthalene (Japanese Patent Ap plication laid-open sho 61-36232, sho 63-14737, sho 6314738, and sho 63-112527).

In the alkylation of benzene compounds, the above mentioned zeolite exhibits excellent selectivity as a catalyst for producing a desired isomer. This is because the pore size of zeolite is large enough for benzene rings to diffuse within the pores.

However, in the alkylation of naphthalene or monoalkylnaphthalene, it is not easy for naphthalene or monoalkylnaphthalene to diffuse within the pores of the zeolite because their molecular diameters are bigger than that of benzene compounds. This was detrimental in obtaining dialkylnaphthalene enriched with 2,6-DAN isomer at a high yield.

III. SUMMARY OF THE INVENTION

2 An object of this invention is to provide a method for preparing useful dialkylnaphthalene enriched with 2,6DAN isomer at a high yield.

Another object of this invention is to provide a catalyst which exhibits a high degree of selectivity for producing dialkylnaphthalene enriched with 2,6-DAN isomer.

We have discovered that these objects can be achieved by contacting a naphthalene and/or monoalkylnaphthalene with an alkylating agent in the presence of a catalyst consisting of a porous clay intercalation compound.

IV. DESCRIPTION OF THE PREFERRED EMBODIMENT

The in,.entive clay intercalation compound is a compound synthesized by coordinating a separate or guest compound between clay layers. A porous clay intercalation compound is obtained by coordinating this compound in columns or pillars between the clay layers. The coordinating methods include (1) ion exchange between the clay and a metal complex, (2) ion exchange between the clay and particles with positive charges, (3) ion exchange bet-,ieen the clay and organic cations, and (4) ion exchange between the clay and a metal complex followed by hydrolysis between the clay layers.

3 More specifically, the method (1) comprises substituting a portion or all of the cations present between the layers of expandable or laminar clay minerals, such as mica, vermiculite, or smectite, With polynuclear metal hydroxycations to synthesize the intercalation compound. The intercalation compound is heated to dehydrate the polynuclear metal hydroxycations coordinated between the layers. This produces a porous clay intercalation compound having a pore structure created by pillars of cross-linked metal oxides between the layers. Suitable polynuclear metal hydroxycations include: polynuclear aluminum hydroxycations, e.g., [A'6(OH)121 6+; polynuclear zirconium hydroxycations, e.g., [Zr4(OH)8 8+; or polynuclear bismuth hydroxycations, 6+ e.g., [Big(OH),q] The distance between the layers expanded by insertion of the polynuclear metal hydroxycations is substantially the same as the ion radius.

Method (2) can be carried out by treating colloidal particles obtained by hydrolysis of a metallic sa with an alkaline solution, metallic salt, etc. so as to charge them positively, and then coordinate the particles by ion exchange between the clay mineral layers to thereby form a porous body. The pore size can be adjusted by the size of the colloidal particles or the type of clay used.

In method (3) large organic cations, such as, -ween clay mineral amines are coordinated by ion exchange bet it 4 layers to obtain a porous body. The size of pores can be adjusted by the type of organic cation or clay used.

Method (4) includes coordinating metal complexes by method (1) between clay layers. The pore size is controlled by placing the clay in a metal salt solution followed by hydrolyzing the metal salt by heating or adding alkali to form a metal hydroxide between the layers.

As discussed above, the pore size of the clay intercalation compound can be arbitrarily controlled by controlling the type of clay used, the type of compound coordinated between the layers and the reaction conditions for the synthesis of the clay intercalation compound. The porous clay intercalation compound according to the present invention is a porous compound, the pore size of which is larger than the size of 2,6dialkylnaphthalene. The optimum pore size varies depending on the type of alkyl group, which preferably has from 1 to 4 carbon atoms, and is in the range of about ten to 30 angstroms, because porous clay intercalation compounds with much larger pore size than the size of 2,6dialkylnaphthalene exert pore shape selectivity in the alkylation of naphthalene and/or monoalkylnaphthalene. Hence when the inventive catalyst is used in the alkylation of naphthalene and/or monoalkylnaphthalene, dialkylnaphthalene enriched with 2,6-DAN isomer can be synthesized at a yield much higher than when the conventional catalysts are used.

The clay of the porous clay intercalation compound according to the present invention can be either natural or artificial so long as it exhibits ion exchange properties. The compound to be coordinated between the clay layers is preferably a metal hydroxide or oxide because of their high heat resistance and a solid form of the acid. Elements of platinum group, such as, platinum, palladium, rhodium and iridium can be supported on the inventive intercalation compounds. The metal supported catalysts may also be used as a catalyst for alkylating naphthalene and/or monoalkylnaph thalene.

The naphthalene and/or monoalkylnaphthalene starting material for the present invention, may be used alone or in combination. Their purity does not matter. The monoalkylnaphthalene may include a-monoalkylnaphthalenes or -monoalkylnaphthalenes. The alkyl group preferably has from 1 to 4 carbon atoms.

Alkylation agents suitable for use for in the present invention include alcohols, such as, methanol, ethanol, propanol or butanol, or halogenated alkyls, such as, methyl chloride or methyl bromide. They may be used alone or in combination. Many other chain compounds having at least one alkyl group as well as olefins, such as, 6 ethylene, propyrene or butene may also be used as the alkylating agent. The alkylating agent should be used in amounts from about 0.01 to about 10 moles and preferably from 0.05 to 2 moles per mole of naphthalene and/or monoalkylnaphthalene.

The alkylation of naphthalene and/or monoalkylnaphthalene according to the present invention may be performed in the gas or liquid phase.

In the case of the gas phase, the reaction should preferably be carried out at a temperature in the range of from 50 to 600 'C. If the temperature is below 50 OC, the reactivity tends to lower, and if it is above 600 'C, the catalyst tends to deteriorate due to coke precipitation. The reaction can be performed under reduced pressure, atmospheric pressure or higher than atmospheric pressure. Preferably it is carried out under atmospheric or higher pressure, such as, between atmospheric pressure and 50 kg/cm2 in order to keep the catalyst surface wet with the raw material or the resultant product. More preferably, the reaction should be carried out under 1 to 5 kg/cm2 pressure. Hydrogen does not need to be present in the reactiQn system, but when the reaction is carried out in a hydrogen gas stream, deterioration of the catalyst activity can be advantageously prevented. The hydrogen supply should be from 0.1 7 to 20 mole times the naphthalene compound. Gasses, such as, nitrogen, carbon dioxide gas or methane may also be introduced. The reaction is usually conducted in the fixed bed, but it can also be carried out on a fluid bed or moving bed. The weight hourly space velocity (WHSV) should preferably be within the range of 0.1 to 100 h-1, or more preferably within the range of 1 to 20 h-1. WHSV as used herein represents the weight of reactor feed total amount of naphthalene and/or monoalkylnaphthalene and an alkylating agent per unit weight of the catalyst per hour.

In the case of the liquid phase, the reaction is preferably conducted at a temperature in the range of from 100 to 450 'C, pressure in the range of atmospheric pressure to about 50 kg/cm2, and a liquid hourly space velocity (LHSV) in the range of 1 to 20 h-'.

This invention will be described more specifically referring to the following examples.

Example 1 (A) Preparation of porous clay intercalation compound As the clay powder, (1) sodium fluoride tetrasilicic mica (manufactured by Topy Industries Ltd), (2) natural montmorillonite (manufactured and sold under the commercial name "Kunipia F or G" by Kunimine Industries Co. , Ltd) and 8 (3) Li-treated mica were used. The Li-treated mica (3) was obtained by mixing 10. 0 g of mica 0) with 600 ml of 1 M lithium chloride solution for two days, separating and washing the resultant mixture with water, and heating the same for two hours in air at 500 "C.

Aluminum oxide or zirconium oxide was intercalated between the clay powder layers to obtain a porous clay intercalation compound (hereinafter the former is referred to as the "Al-clay catalyst" and the latter as the "Zr-clay catalyst").

(a) Preparation of Al-clay catalysts A 0.2 M aqueous solution of aluminum chloride (AlCl 3 6H20) was rigorously agitated in an agitator provided with rotary vanes, and a 0.1 M aqueous solution of sodium hydroxide (NaOH) was gradually added using a micro-tubing pump at the rate of about 20 cc per hour until the mole ratio of NaOH/AlC'3 became 1.8 to 2.5. After the addition, the resultant mixture was either agitated continuously for another five days at room temperature, or refluxed under heating for two days at 95 OC, to age and stabilize polynuclear aluminum hydroxycations.

Each of the above mentioned clay powders (1), (2) and (3) was added to an aqueous solution of this polynuclear aluminum hydroxycations until the mole ratio of Al/clay became 0.3 - 1.0 mole/100 g and then agitated for five days to 9 cause ion exchange between the sodium ions in the clay layers with the polynuclear aluminum hydroxycations. Subsequently, the resultant product was either centrifuged or filtrated under reduced pressure to separate the powder portion, which was further washed thoroughly with distilled water and dried at 100 - 400 'C to obtain Al-clay catalysts. To enhance the acid strength, some of the Al-clay catalysts were exposed to a C12 gas stream for chlorine treatment. The synthesis conditions of various Al- clay catalysts are given in Table 1.

Table 1

Catalyst Clav OH/Al Al/clay Al aq. sol. cl (Not 1) (mole/- aging conditions treatment g) (temp., time) Al-PTSM (a) TSM 2.5 1.0 room temp. j days none Al-PTSM (b) TSM 2.0 1.0 room temp. 5 days none AI-PTSM (c) TSM 2.0 1.0 room temp. 5 days C12 treatment AlPTSM (d) TSM 1.8 1.0 950C 2 days none Al-PM (a) MT 2.5 0.3 room temp. 5 days none Al-PM (a) LM 1.8 1.0 95C 2 days none Note 1) TSM: Sodium fluoride tetrasilicic mica MT: Montmorillonite MM: Li- treated mica (b) Preparation of Zr-clay catalysts A 0.1 - 0.4 M aqueous solution of zirconium oxychloride (ZrOC128H20) was boiled for one hour and cooled. Each of the above mentioned clay powders was added to separate samples of this solution until the mole ratio of Zr/clay became 0.4 - 1.3 mole/100 g and refluxed at 100 'C for 16 - 24 hours under vigorous agitation in the above mentioned agitator. The resultant product was either centrifuged or filtrated under reduced pressure to separate the powder portion, which was thoroughly washed with distilled water and dried in air heated to 100 - 400 'C to obtain Zr-clay catalysts. The synthesis conditions for the various Zr-clay catalysts are given in Table 2.

Table 2

Catalyst Clay Concentration of Zr/clay Reflux time Zr0C12 aq. sol. (M) (mole/ 100 g) (hr) Zr-PTSM (a) TSM O.i 1.3 24 Zr-PTSM (b) TSM 0.4 1.3 16 Zr-PM (a) MT 0.1 0.4 24 Zr-PM (b) MT 0.4 0.4 16 Zr-PM (a) LM 0.4 1.3 16 (c) Comparative catalyst Commercial silica alumina (manufactured by JGC Corporation) (abbreviated as SA-(I) shown in Table 3) was used as the comparative catalyst. Properties of the clay catalysts (a) and (b) prepared as above and the comparative catalyst (c) are given in Table 3.

12 h Table 3

Catalyst Basal Spacing 0 A) (Note 2) Al/clay catalyst Zr/clay catalyst Comparative catalyst Al-PTSM (a) Al-PTSM (b) Al-PTSM (c) AlPTSM (d) Al-PM (a) Al-KNM (a) Zr-PTSM (a) Zr-PTSM (b) Zr-PM (a) Zr-PM (b) Zr-PU'M (a) SA-(I) Specif ic surf 2 ce area (m /g) (Note 3) 18 18 18 18 18 219 197 269 298 334 18 227 21 191 22 21 23 94 174 212 261 456 Note 2) Measured by X-ray diffractometry Note 3) Measured by BET method (B) Catalyst Runs A selection of clay catalyst (a) and (b) prepared as (A) above, as shown in Table 4 and the comparative catalyst (c) (200 mg of each) were sampled and subjected to the following treatment. About 200 mg of catalyst were charged into a reaction tube with a fixed bed under atmospheric pressure and pre-treated for four hours in a He flow at 400 'C. The reaction temperature was arbitrarily set within the range of from 100 to 400 OC. The starting material naphthalene, the alkylating agent t-butyl alcohol, and the solvent psuedocumene, were mixed at a mole ratio of 1:10:5 and supplied onto the catalyst together with the carrier gas He at the LHSV of about 0.25 h-1. The contact time of the reactor feed was 17 - 18 sec. The product mixture was collected in a condenser attached to the reactor and the liquid sample was analyzed by gas chromatography.

The compositions of the resultant products are shown in Table 4.

1 4 Table 4

Catalyst Reaction temperature ( OC) DtBN 2,6-DtBN/DtBN (mole %) (mole %) (Note 4) (Note 5) Al-PTSM (b) 150 3 86 Al-PTS.M (c) 150 17 83 Al/clay catalyst Al-PM (a) 150 25 83 Al-PMM (a) 150 9 88 Zr-PTSM (b) 150 8 75 Zr/clay catalyst Zr-PM (b) 150 24 80 Comparative SA-(I) 150 1 60 catalyst Note 4) DtBN: Yield of di-t-butylnaphthalene Note 5) 2,6DtBN/DtBN: Ratio of 2,6-DAN isomer to di-t-butylnaphthalene Table 4 indicates that the yield of dialkylnaphthalene by alkylation of naphthalene varies depending on the type of porous clay intercalation compound used, and particularly revealed that dialkylnaphthalene enriched with 2,6,-DAN isomer can be synthesized at a yield much higher than When the conventional catalyst is used.

Example 2

A selection of clay catalyst (a) and (b) prepared as (A) above, as shown in Table 5 and the comparative catalyst (c) (200 mg of each) were sampled and subjected to the following treatment. About 200 mg of catalyst were charged into a reaction tube with a fixed bed under atmospheric pressure and pre-treated for four hours with a He flow at 400 OC. The reaction temperature was arbitrarily set within the range of from 100 to 400 'C, and the starting materials 2-methylnaphthalene and the alkylating agent tbutyl alcohol, were mixed at a mole ratio of 1:5. The mixture was supplied onto the catalyst together with the He carrier gas at a LHSV of about 0.25 h-1. The contact time of the reactor feed was 17 - 18 sec. The product mixture was collected in a condenser attached to the reactor and the liquid sample was analyzed by gas chromatography.

The compositions of the resultant products are shown in Table 5.

16 Table 5

Catalyst Reaction temperature CC) 2,6-MtBN/MtBN (mole %) (mole %) (Note 6) (Note 7) Al-PTSM (a) 150 16 74 Al-PTSM (b) 150 39 77 Al-PTSM (d) 150 39 77 Al-PM (a) 150 25 65 Al-PM (a) 150 92 74 Zr-PTSM (a) 150 48 76 Zr-PTSM (b) 150 77 77 Zr/clay catalyst Zr-PM (a) 150 83 76 Zr-PLM (a) 150 45 72 Comparative SA-(I) 150 68 56 catalyst Note 6) MtBN: Yield of methyl t-butylnaphthalene Note 7) 2,6-MtBN/MtBN: Ratio of 2,6-DAN isomer to methyl tbutylnaphthalene Table 5 indicates that the yield of dialkylnaphthalene in the alkylation of monoalkylnaphthalene varies depending on the type of catalyst of the porous clay intercalation compound, and particularly revealed that dialkyInaphthalene 17 enriched with 2,6-DAN isomer can be synthesized at a yield much higher than when the conventional catalyst is used.

18

Claims

WHAT IS CLAIMED IS:

1. A catalyst for preparing a dialkylnaphthalene having an enriched content of a 2,6-dialkylnaphthalene from a starting material selected from the group consisting of naphthalene, monoalkylnaphthalene and mixtures thereof comprising a porous clay intercalation compound having layers of laminar clay and a compound coordinated between the clay layers in columns which form pores.

2. The catalyst of claim 1 wherein the pores have a size greater than the size of the 2,6-dialkylnaphthalene product.

3. The catalyst of claim 1 wherein the pore size is in the range from about ten to 30 angstroms.

4. The catalyst of claim 1 wherein the coordinating compound is selected from the group consisting of metal oxides, hydroxides and mixtures thereof.

5. A method for preparing a catalyst for use in the preparation of dialkylnaphthalenes comprising reacting a laminar clay having layers with a coordination compound so as to coordinate the coordination compound between.layers of the clay.

6. The method of claim 5 wherein the coordinating compound 1 9 is a metal complex and the coordination is carried out by ion exchange between the clay and the metal complex.

1 7. The method of claim 5 wherein the coordination compound is a particle having a positive charge and the coordination is carried out by ion exchange between the clay and said particle.

8. The method of claim 5 wherein the coordination compound is an organic cation and the coordination is carried out by ion exchange between the clay and the organic cation.

9. The method of claim 5 wherein the coordination compound is a metal complex and the coordination is carried by ion exchange between the clay and the metal complex, and the coordinated compound is placed in a metal salt solution followed by hydrolysis of the metal salt by heating or adding alkali.

10. The method of claim 5 wherein the clay is selected from the group consisting of mica, vermiculite, and smectite.

11. The method of claim 5 wherein the coordination compound is a polynuclear metal hydroxycation.

12. A catalyst prepared by the method of claim 5.

13. A catalyst prepared by the method of claim 6.

A catalyst prepared by the method of claim 7 15. A catalyst prepared by the method of claim 8.

16. A catalyst prepared by the method of claim 9.

17. A catalyst prepared by the method of claim 10 18. A catalyst prepared by the method of claim 11 19. In a method for preparing a dialkylnaphthalene wherein a starting material selected from the group of naphthalene, monoalkylnaphthalene and combinations thereof is contacted with an alkylating agent in the presence of a catalyst, the improvement which comprises the catalyst being the catalyst of claim 1.

20. In a method for preparing a dialkyInaphthalene wherein a starting material selected from the group of naphthalene, monoalkylnaphthalene and combinations thereof is contacted with an alkylating agent in the presence of a catalyst, the improvement which comprises the catalyst being the catalyst of claim 2.

21 21. In a method for preparing a dialkylnaphthalene wherein a starting material selected from the group of naphthalene, monoalkylnaphthalene and combinations thereof is contacted with an alkylating agent in the presence of a catalyst, the improvement which comprises the catalyst being the catalyst of claim 3.

22. In a method for preparing a dialkylnaphthalene wherein a starting material selected from the group of naphthalene, monoalkylnaphthalene and combinations thereof is contacted with an alkylating agent in the presence of a catalyst, the improvement which comprises the catalyst being the catalyst of claim 12.

23. In a method for preparing a dialkylnaphthalene wherein a starting material selected from the group of naphthalene, monoalkylnaphthalene and combinations thereof is contacted with an alkylating agent in the presence of a catalyst, the improvement which comprises the catalyst being the catalyst of claim 13.

24. The method of claim 19 wherein the alkylating agent is an alcohol.

25. The method of claim 19 wherein the alkylating agent is an halogenated alkyl.

22 1 26. The method of claim 19 wherein the contact step with the alkylating agent is carried out in a gas phase at a tem perature in the range of from 50 to 600 'C.

27. The method of claim 19 wherein the alkylating agent is selected from the group consisting of methanol, ethanol, propanol, butanol, methylchloride, methylbromide, and combinations thereof.

28. The method of claim 19 wherein the alkylating agent is present in an amount from about 0.01 to about 10 moles per mole of starting compound.

23 Published 1991 at The Patent Office, Concept House. Cardiff Road, Newport, Gwent NP9 I RH. Further copic, may be obtained from Sales Branch. Unit 6. Nine Mile Point. Cwmfelinfach, Cross Keys. Newport, NP1 7HZ. Printed by Multiplex techniques ltd. St Mary Cray. Kent.