WO1991005751A1

WO1991005751A1 - Selective diethylation of naphthalene to 2,6-diethylnaphthalene

Info

Publication number: WO1991005751A1
Application number: PCT/US1990/005916
Authority: WO
Inventors: Jere D. Fellmann; Pascale Massiani; Herbert Exner; Paul R. Wentrcek; Robert J. Saxton
Original assignee: Catalytica, Inc.
Priority date: 1989-10-17
Filing date: 1990-10-16
Publication date: 1991-05-02
Also published as: KR920703482A; EP0496831A1; CA2066205A1; EP0496831A4; JPH05504332A

Abstract

The selective alkylation of naphthalene or 2-ethylnaphthalene to diethylnaphthalene while maximizing the yield of the 2,6-diethylnaphthalene isomer is achieved by carrying out the reaction in the presence of a shape selective catalyst such as the zeolite catalyst ZSM-12.

Description

SELECTIVE DIETHYLATION OF NAPHTHALENE

TO 2,6-DIETHYLNAPHTHALENE

Related Application

This is a continuation-in-part of U.S. Serial No. 07/422,784 filed October 17, 1989, the entirety of which is incorporated by refernece.

TECHNICAL FIELD OF THE INVENTION This invention relates to the production of 2,6-diethylnaphthalene by the alkylation of naphthalene compounds. We have found that certain acidic zeolite catalysts (such as ZSM-12, SAPO-11, and EU-1) may be employed to maximize the yield of this isomer which is useful as a precursor to

2,6-dicarboxynaphthalene, the latter compound being an important monomer for the production of polyester film.

BACKGROUND OF THE INVENTION The compound 2,6-dicarboxynaphthalene is a key monomer used as a precursor for polyester film. As such, the search for an inexpensive source of 2,6-dicarboxynaphthalene has been the object of intense investigation.

Alkylaromatic compounds may be converted to their analagous aromatic carboxylic acids by free radical oxidation using various catalytic combinations of cobalt, manganese and bromide salts in an acetic acid solvent. This technology has been commercialized for the conversion of p-xylene to terephthalic acid. Alkyl aromatics, where the alkyl group is either ethyl or isopropyl, should be oxidizable to the corresponding carboxylic acid using the same or similar catalyst systems. The preferential synthesis of particular isomers of a dialkylnaphthalene has been the subject of investigation by numerous research groups. In Applicants' own U.S. Patent Application Serial No. 254,284, filed on October 5, 1988, the preparation of 2,6-diisopropylnaphthaleπe was described using a specific group of twelve-ring zeolite catalysts. In European Patent Application Serial No. 317,907 and its corresponding

U.S. Patent No. 4,891,448, the Dow Chemical Company teaches the use of acidic mordenite zeolite catalysts to produce para-isomers useful in the preparation of thermotropic liquid crystal polymers. German Patent Application No. DE 370,3291 A discloses and claims the use of ZSM-5 as a preferred catalyst for the conversion of methanol and naphthalene or 2-methylnaphthalene into 2,6-dimethylnaphthaIene.

Japanese Patent Application No. 63-211243 teaches that 2-methylnaphthalene can be alkylated with propylene, using a non-shape selective solid acid catalyst to yield 2-methyl 6-isopropylnaphthalene in high yield. U.S. Patent No. 4,873,385 shows the selective production 2,6- diethylnaphthalene via a transalkylation process. The reaction includes the liquid phase contact of at least one of naphthalene or 2-ethylnaphthalene with at least one of 1 ,4-diethylbenzene; 1,2,4-triethylbenzene, at least one tetraethylbenzene, or pentaethylbenzene as the ethylating agent at a level of from one to about ten moles of the ethylating agent per mole of the feed in the presence of a Lewis acid catalyst selected from the group consisting of aluminum chloride, aluminum bromide, tantalum chloride, antimony fluoride, or red oil. The catalyst is introduced at a level of from about 0.01 to about one mole of the catalyst per mole of the feed (for red oil, based on the content of aluminu i chloride content of the red oil) and the reaction is then carried out at a temperature in the range of from about 10°C to about 100°C.

A Japanese patent, namely Japanese Patent No. 51-6953 filed on behalf of Mitsubishi Chemical Co., describes the diethylation of naphthalene using the non-shape selective catalyst AICI₃. The ethylation reaction takes place in contact with the catalyst at 135°C over nine hours. The amount of the desired 2,6-diethylnaphthalene produced was between 17% and 20% of the total dialkylate yield. The ratio of the 2,6/2,7-diethylnaphthalene isomers was observed to be approximately one. This result is consistent with other efforts conducted in this area. More specifically, prior work in producing diisopropylnaphthalene indicated that non-shape selective catalysts (when operated at equilibrium) gives a 2,6/2,7 ratio of about one with the amount of the 2,6 isomer not exceeding 39% of the total dialkylates present. The observation that the total dialkylate mixture comprises approximately 20% 2,6-diethylnaphthalene isomer seems reasonable since it is possible to achieve more dialkylate isomers when dealing with ethyl substitution than isopropyl substitution. It is not possible to alkylate adjacent carbon atoms on the naphthalene ring with isopropyl groups ~a problem which does not exist when dealing with ethyl substitution. As a result, three additional isomers are possible with diethylnaphthalene than are possible with diisopropylnaphthalene.

It is an object of this invention to improve upon the selectivity of producing 2,6-diethylnaphthalene while avoiding the necessity for operating at severe processing conditions.

It is an additional object of this invention to provide a shape selective catalyst whose pore size and configuration is such that it maximizes the yield of the desired 2,6-diethylnaphthalene isomer relative to the sum of other dialkylate species while minimizing the formation of higher substituted species.

We have found that when either the non-shape selective catalysts or zeolite catalysts having inappropriate pore dimensions are replaced by a shape selective catalyst having a longest pore dimension between about 5.6 A and 7.0A, preferably 5.6A to 6.4A, such as the zeolites ZSM-12, SAPO-11, and EU-1 as the acidic crystalline molecular sieve of choice, the selectivity of 2,6-diethylnaphthalene is enhanced.

SUMMARY OF THE INVENTION

This invention is a process in which naphthalene or 2-ethylnaphthalene is reacted with ethylene or ethanol in the presence of an acidic zeolite catalyst, preferably ZSM-12, EU-1, or SAPO-11 (and most preferably ZSM-12) under conditions sufficient to convert the naphthalene or 2-ethylnaphthalene to 2,6-diethylnaphthalene.

DETAILED DESCRIPTION OF THE INVENTION The ethylation of naphthalene would be expected to proceed in a step-wise manner much like the way in which the isopropylation of naphthalene is conducted. The ethylation reaction should be slower than the propylation reaction since the initial ethylation reaction step is the acid-catalyzed formation of a carbonium ion. Although some literature exists concerning naphthalene isopropylation, the literature addressing naphthalene ethylation is quite sparse. As a result, we considered it important first to determine the equilibrium product distribution for the naphthalene ethylation reaction so that a basis for improvement via shape selective synthesis using zeolite catalysts could be established. Equilibrium in alkylation reactions occurs when isomerization between alkylated species to the most thermodynamically stable product distribution occurs faster than the alkylation. Generally, equilibrium mixtures are obtained at low feed rates of olefin so that alkylation (and not isomerization) is the limiting step.

For non-shape selective catalysis, equilibrium represents the highest yield for the 2,6- isomer since the 2,6- and 2,7- isomers are the β, β isomers and are the preferred form at equilibrium. The ratio of the 2,6/2,7 isomers is expected to be about one.

As noted previously, since steric interference between ethylene groups in diethylnaphthalene is smaller than between isopropyl groups in diisopropylnaphthalene, the total number of possible diethylnaphthalene isomers is greater than the number of diisopropylnaphthalene isomers. The total number of diisopropyl isomers observed is seven and for diethylnaphthalene the number of isomers is ten. The existence of this large number of isomers not only adds to the complexity of the system but also lowers the absolute amount of the 2,6 and 2,7 isomers produced at equilibrium. For example, due to steric constraints, the β isomer in the total monoalkylate using AICI₃ at equilibrium is 98.5% the for isopropylation reaction but only 90.5% for the ethylation reaction. See G.A. Olah et al., J. Amer. Chem. Soc. 98, 1839 (1976). We found equilibrium conditions to result in a 2,6/2,7 ratio very near 1.0 and a DEN content of 17% to 22%.

As previously noted, the present invention is a process for producing 2,6-diethylnaphthalene using a suitable shape selective catalyst. A suitable shape selective catalyst is one having a longest pore aperture dimension between about 5.6A and about 7.0 A, preferably between 5.6A and 6.4A.

Examples of molecular sieves with their longest pore aperture dimension in the desired range are shown in the following table. Of these, ZSM-12, SAPO-11, and EU-1 are synthetic zeolites and, as such, are more widely available.

Cancrinite, partheite, and stilbite are naturally occurring zeolites and their purity, stability, and availability vary. It is quite possible that offretite and MAPSO-46 could be selective catalysts but they are also difficult to obtain. The preferred zeolites are ZSM-12, EU-1, and SAPO-11. Most preferred is the zeolite catalyst ZSM-12. The pore structure of ZSM-12 consists of linear, non-interpenetrating channels which are formed by twelve-member rings and possess pore aperture dimensions of 5.5A X 5.7A x 6.2A. See Jacobs, P.A., et al., "Synthesis of High Silica Aluminosilicate Zeolites", Studies in Surface Science and Catalysis, No. 33, Elsevier, 1987, page 301. See also Meier, W.M., "Atlas of Zeolite Structure Types", 2nd. Ed., Structure Commission of the International Zeolite Association, 1987. The term "dimension" is preferred over "diameter" because the latter term implies a circular opening, which is not always accurate in describing crystalline molecular sieves. When citing the term "pore aperture dimension or width" we mean (for non-circular zeolite openings) the longest dimension of the pore. For example, ZSM-12 is an irregularly shaped zeolite with pore aperture dimensions of 5.5A x 5.7A X 6.2A. Likewise, SAPO-11 has pore aperture dimensions of 3.9A x 6.3A. SO for ZSM-12, the "pore aperture dimension" is 6.2A; for SAPO-11, 6.3A; for EU-1 the dimension is 5.7A.

Shape selective reactions occur when the zeolite framework and its pore structure allow substrate molecules of a given size and shape to reach active sites located in the intracrystalline free space and allow product molecules of a given size and shape to diffuse out of the intracrystalline free space. It is, therefore, important to characterize accurately the pore structure that is encountered in the various crystalline molecular sieve frameworks.

Crystalline sieve structures are often defined in terms of the number of the tetrahedral units [J. atoms). For example, in sodalite, the silica and alumina tetrahedra are linked together to form a cubooctahedron, an octahedron truncated perpendicularly to all C₄-axes. The sodalite unit is built from 4- and 6-member oxygen rings. A more complete characterization of zeolites can be found in E.G. Derouane, "Diffusion and Shape-Selective Catalysis in Zeolites", Intercalation Chemistry. Ed. by M. Stanley Whittingham (Academic Press 1982). SAPO-11 belongs to the family of silicoaluminophosphate molecular sieves, first reported in 1984 in U.S. Patent No. 4,440,871. The pore structure of SAPO-11 consists of linear, non-interconnected channels which are limited by 10- membered rings and possess pore aperture dimensions of 3.9A and 6.3A. See Bennett, J.M., et al.. Zeolites, j (1987) 160. See also Meyer, W.M., and Olson, D.H., "Atlas of Zeolite Structure Types", 2nd Ed., Structure Commission of the International Zeolite Association. Butterworths, 1987.

It should be noted that ZSM-12 and EU-1 are available in cationic form. Calcination may be necessary if the zeolite contains an organic template; only an ion exchange with an ammonium cation followed by calcination under suitable conditions is needed then to convert these to the hydrogen form. The catalysts may be optimized to yield greater selectivities of the desired diethylnaphthalene without substantially altering its pore aperture dimensions. One such modification to the preferred catalysts is dealumination. The dealumination of acidic crystalline molecular sieve materials may be achieved by exposing the solid catalyst to acid mixtures such as HF up to 2.0 N (preferably up to 1.5 N) and HN0₃ (up to 16 N). The desired degree of dealumination will dictate the strength of acid used and the time during which the crystalline structure is exposed to the acid. Other methods of dealumination are via steam treatment followed by a mild acid treatment and calcination.

The preferred steam treatment parameters are as follows:

Parameter Range Preferred Most Preferred

Temperature (°C) 300-1000 400-850 450-750

Total pressure (ATM) 0.001-15 0.001-5 0.2-2

Length of time 0-24 hrs. 10 min.-4 hrs. 20 min.-2 hrs.

For additional methods of preparing aluminum deficient zeolites see J. Scherzer, "The Preparation and Characterization of Aluminum-Deficient Zeolites", Thaddeus E. Whyte et al.. "Catalytic Materials: Relationship between Structure and Reactivity", at pp. 156-160, ACS Symposium Series 248 (American Chemical Society, 1984). We have found that although a wide variety of dealuminated zeolitic materials are initially suitable for the isopropylation reaction, only certain materials retain that suitability for prolonged periods. For instance, dealumination techniques employing strong acid leaches typically produce catalysts which initially are very active but short lived. In certain circumstances such an activity profile might be desirable but, typically, a catalyst with a longer life is preferred.

One method of dealumination which has been found to produce such a preferred material is a steam treatment (in one or more stages) followed by a mild acid leach.

A dealuminated crystalline molecular sieve may be calcined at temperatures between 400°C and 1000°C, preferably between 400°C and ^'

700°C. Calcination serves to dehydrate or "heal" Si-OH bonds (or "nests") after dealumination. Healing these nests provides for a more uniform pore structure within the crystalline material leading to structural stability and, ultimately, resulting in improved selectivity and lifetime. The calcination conditions of a catalyst can critically effect the catalytic activity. The selected calcination gas (for example, oxygen or nitrogen) can effect catalyst species differently. In general, calcination temperatures for crystalline molecular sieve catalysts can vary from 300°C to 1000°C. For a zeolite such as ZSM-12, the optimal temperature ranges were found experimentally to lie between 400°C and 1000°C. In the case of organic residues present on the catalyst surface the calcination temperature and the calcination gas are both important. When organic residues are present, an atmosphere (preferably nitrogen) is used so that a minimal amount of water results when bringing the catalyst to calcination temperature. After a period of time sufficient to carbonize the organic residue, the atmosphere is changed to oxygen at a temperature sufficient to combust the carbonized residue to C0₂ while minimizing water formation.

In using the preferred zeolites ZSM-12, SAPO-11, and EU-1, it was surprisingly found that they would form 2,6-diethylnaphthalene in high yield by the combination of ethylene with naphthalene or 2-ethylnaphthalene under equilibrium conditions. The synthesis procedure in creating ZSM-12 was described in Jacobs, et al., supra, page 303. Typically, the Si/AI ratio of these catalysts are in the range of from five to 2000, preferably from ten to 1000, more preferably from 20 to 500, and most preferably from 20 to 100. Additionally, we have found that the ZSM-12 particle diameters are preferably less than about 4.0 j_m, preferably 0.1 μ to 3.75 μ .

In order to convert the as-synthesized ZSM-12 into the active acidic form, it is first calcined at temperatures between 400°C to 1000°C for 0.5 to eight hours in flowing air or oxygen. Preferably, the calcining temperature is from 400°C to 700°C. Subsequently, any residual cations are removed by either ion exchange with NH₄CI (0.01 N to 6 N) at temperatures between 20°C to 100°C for ten to 300 minutes or by treatment with strong acids such as HCI, HN0₃, H₂SO_A etc. (0.01 N to 6 N) at temperatures between 20 to 100°C for ten to 30 minutes. After ion exchange the catalyst may be dried in air at temperatures between 50°C to 200°C for one to 20 hours and then activated by calcining in air or nitrogen at temperatures between 400°C to 1000°C for 0.5 to eight hours. Preferably, the calcining temperature is between 400°C to 700°C. A catalyst treatment according to the present invention, involves catalyst external surface acid site removal or blockage. The reason for external surface acid site removal or blockage is that by deactivating the external surface of zeolite catalyst will increase its shape selective character as otherwise, the external surface acts as a non-shape selective catalyst. An additional reason for external surface acid site blockage or removal relates to coking on the catalyst surface. With an acid catalyzed reaction such as the ethylation of naphthalene, coke will form at the catalyst pore mouth over time. This buildup will cause the pores to become less accessible to substrate molecules, and eventually closes the pores, rendering these channels inactive.

It is desirable to deactivate external surface acid sites to prevent non-shape selective reactions on the external surface. External surface acid site deactivation can be obtained by either acid site blockage or acid removal. The acidic sites on the external sufrace of the catalyst may be deactivated by contacting the catalyst with a deactivatiing agent selected from the group selected from the halogen, hydridic, and organic derivatives of Groups IMA, IVA, IVB, and VA. One major limitation of both techniques, however, is that the deactivating agent should be selected to preclude internal surface diffusion. This limitation is easily met by the use of deactivation agents in either liquid or gas phase, whose molecules are too large to fit within even the largest pores of known zeolites. One such molecule is triphenylchlorosilane. See Martens, J.A. et al., Zeolites, 1984, 4, April, pp. 98-100. Additionally, the surface may be deactivated by precoking with one of the substitutes or another precoking agent.

In another embodiment of external surface acid site modifications, the intracrystalline pores may be filled with a hydrocarbon to obtain an internally protected catalyst. Thereafter, either an aqueous acid or complexing agent, which is insoluble in the hydrocarbon contained within the intracystalline pore, is contacted with the protected catalyst. Once the external surface has been deactivated, then the hydrocarbon is removed from said intracrystalline pores. In EP 86543, a non-polar organic substance is added to the zeolite to fill its pores. Subsequently, a deactivating agent solution (in polar solvent) is introduced to the catalyst. Alkali metal salt solutions, acting as ion exchange atoms to remove the acidic proton associated with aluminum, are described as suitable deactivating agents. See also U.S. Patent No. 4,415,544 which teaches the use of paraffin wax to seal off the pores prior to surface treatment with hydrogen fluoride, which remove the aluminum. The naphthalene compound may be in liquid form or in a solution. The alkylating agent may be in a liquid or gaseous form and, depending upon the reaction device chosen, may be added continuously or in a single batch at the beginning of a reaction cycle in the batch reactor. The catalyst may be also in the particulate or granular form and may be placed in a fluidized bed, a stirred bed, a moving bed, or a fixed bed. The catalyst may be in suspension or in a spouted bed. Reactive distillation columns may also be utilized.

The ratio of alkylating agent to naphthalene compound should be between 0.01 and 100 and preferably between 1.0 and 10.0. The reaction is preferably carried out in the liquid state and the temperature should be between 100°C and 400°C, preferably between 225°C and 350°C and the pressure should be between one to 100 atmospheres. The amount of catalyst is easily determinable and in general should be enough to promote the reaction to produce a product having, in general, a 2,6-diethylnaphthalene product in excess of that expected on an equilibrium catalyst such as silica/alumina. Typically the weight ratio of aromatic compound to catalyst would be in the range of 1:1 to 200:1. Some optimization within that range would obviously be appropriate.

Separation of the 2,6-DEN product may be by standard techniques such as a distillation, crystallization, adsorption, or the like. When employing a silica-alumina catalyst for naphthalene alkylation, it became evident that regardless of how the ethylene was fed to the system, the distribution of products was indicative of a non-shape selective catalyst.

Throughout the reaction, the percentage of any one isomer of diethylnaphthalene remained essentially unchanged. At low conversions, the amounts of diethylnaphthalene were very low and other GLC peaks overlapped with that of the 2,6 isomer. This resulted in artificially high selectivity values for the 2,6 isomer. At higher conversions, the amount of the 2,6 isomer was approximately 17% or 19% to 22%.

The ethylating agent may be ethylene, ethanol, ethyl ether, ethyl chloride, or other suitable ethylating materials. Preferably the agent is ethylene, optionally with added water.

Conditions Used in the Examples A stirred autoclave reactor was chosen for this work. It is conveniently operated and was suitable for the purposes of screening for selectivity improvements. The catalysts were tested in a 300 cc Autoclave Engineers autoclave.

The reaction used gaseous ethylene. The ethylene feed rate was regulated via a mass flow controller or a pressure regulator. By regulating the ethylene feed rate, the system could be operated between ethylene-limited conditions and ethylene-rich conditions. The former conditions simulate an equilibrium limited reaction. The latter conditions simulate a kinetically controlled reaction.

The analytical results were obtained by gas chromatography. In testing a catalyst, 90 g naphthalene and from 0.5 g to 5.0 g of catalyst were charged and gaseous propylene was fed at either a constant flow from a mass flow controller or through a pressure regulator. In all cases unless noted, periodic samples were withdrawn and analyzed by GLC. The reactor temperature could be varied between 40 ^βC and 355°C although the reaction temperature varied from 225°C and 350° C. The ethylene pressure may be from 0.1 to 100 atmospheres, preferably one to ten atmospheres.

All data expressed in the tables are as mole percent selectivity. The methods used in this study to calculate the parameters used for comparing catalyst performance are as follows:

Moles "X" Peak Area of "X"

Number of Carbons in "X" Mole Percent "X" = Moles "X" x 100

Sum of Moles of all Species in Sample

Mole Percent Moles "X" x 100 Selectivity Sum of Moles of All Alkylated Species in Sample

% Conversion = 100 - Mole Percent Substrate in Sample

% 2,6/DEN Moles 2.6 DEN x 100

Sum of Moles of Dialkylates in Sample

2,6/2,7 Moles 2.6

Moles 2,7

It was recognized that for comparative purposes on issues dealing solely with selectivity that a more useful measure of performance other than selectivity to the 2,6 DEN isomer was needed. Instead, a more convenient measure of relative performance was devised, that is, the 2,6/2,7 ratio gave an assessment of the primary objective, which was to produce more 2,6 than 2,7. The percentage of 2,6-DEN/dialkylates gave a measure of the amount of desired isomer produced among all dialkylates.

EXAMPLES Example 1 : Comparative This Example shows the value of the 2,6/2,7 ratio and the percent 2,6 in total DEN isomers at equilibrium. An experiment using the method noted above conducted with silica/alumina showed that these values were 1.0 and between 17% to 22% respectively (Figure 1) for the ethylation of naphthalene. On the basis of these data, a shape selective effect is evident if either the 2,6/2,7 ratio and the percent 2,6/DEN is greater than 1.0 and 22%, respectively. However, the more reliable parameter is the 2,6/2,7 ratio.

In an attempt to confirm the presence of a shape selective effect for the catalysts of Table 1, several zeolites were selected. A sample of SAPO-11 was r stained from Union Carbide and a sample of EU-1 was prepared according to ^ irature procedures. A sample of ZSM-11 was also prepared according to literature methods. Other comparative catalysts were mordenite and zeolite β. Mordenite was commercially available and used as received in its acidic form. Zeolite β was prepared according to literature references.

Samples of ZSM-11, ZSM-12, SAPO-11, EU-1, and mordenite were tested for alkylation activity in the diethylation of naphthalene. No attempt was made to optimize these catalysts before testing.

.6-DEN/Total PEN'S

Figure 2 shows a comparison of the results of the diethylation reaction using all these catalysts. Clearly, ZSM-12 shows shape selectivity with an initial value for 2,6/2,7 equals 1.7.

ZSM-11 shows no indication of shape selective catalysis since 2,6/2,7 < 1.0. Mordenite showed much higher activity indicating that the internal active sites are accessible but still no shape selectivity (i.e. 2,6/2,7 approximately equals one). SAPO-11 did show evidence of shape selectivity. The 2,6/2,7 ratio (approximately equals 1.1) was nearly constant over the run. This was also evident even at very low conversion where the selectivity to 2,6-DEN is highest supporting the concept that SAPO-11 is not the optimum catalyst but is adequate for producing 2,6-DEN. The results with EU-1 were interesting in that the 2,6/2,7 ratio was observed to be quite low initially but rising to a maximum 2,6/2,7 equals 1.3. As the conversion increased the 2,6/2,7 ratio fell in value. The rise and fall of the 2,6/2,7 as a function of conversion is typically seen with shape selective catalysts operating in batch mode. These data show that shape selective effect for ZSM-12, SAPO-11, and EU-1 present; ZSM-12 is preferred.

Example 2:

This Example shows the effect of the performance on ZSM-12 catalyst when it is synthezised in nearly the same particle size but different silica/alumina ratios. The catalysts were tested in the stirred autoclave at 325°C, 30 psi ethylene, and a naphthalene/catalyst ratio of 30:1. Samples were withdrawn and analyzed. The results of these analyses are shown below:

Zeolite ZSM-12

ZSM-12

Example 3:

This Example shows the effect of dealumination on the performance of the preferred ZSM-12 catalyst. The catalyst was treated with 0.5 N HF in 16 N at about 100°C HN0₃ for two hours. After drying and calcining, the catalyst was tested in the same manner as in Example 2.

The ZSM-12 catalyst having the higher silica/alumina ratio clearly performs better.

Example 4:

The effect of higher levels of dealumination with larger particles on the performance of the ZSM-12 catalyst is shown below. The catalyst was treated with 1.0 N HF in 16 N HN0₃ at about 100°C for two hours. After drying and calcining the catalyst was tested as outlined above.

The higher silica/alumina ratio catalysts gave a higher performance even with the larger catalyst particle size.

Example 5:

This Example shows the synthesis of ZSM-12 in various particle sizes. At 165°C and a constant gel water content, the particle size was varied by changing the silica/alumina ratio in the starting gel. The source of the various reactants were: silica equals colloidal Si0₂, alumina equals AI(N0₃)₃ hydrate. In the synthesis, 160 g water and 3.36 NaOH were combined and stirred. To this solution 29.6 g triethylmethylammonium bromide was dissolved and 3.36 g of AI(N0₃)₃ was added and dissolved by stirring. To this solution 42 g of 30% colloidal Si0₂ was added. This gel was placed in a Teflon lined autoclave and heated to 165°C for several days. The crystallized ZSM-12 was isolated by filtration and washed with water. The bulk ICP analysis showed that the crystallized ZSM-12 has a silica/alumina ratio which is quite similar to the stoichiometry used in the synthesis. In all cases, the zeolite was 100% cr'stalline and free from major contaminants. The table below also shows that changes in both the water content and the silica/alumina ratio can dramatically affect the particle size. Table Example Gel Stoichiometry fAI:Si:H-0 Si/AI Particle Size fSEM)

1 23:2400 2 35:2400 3 50:2400 4 75:2400 5 33:8700 6 1400:9000

The ZSM-12 obtained from the reaction mixture is in the template-sodium form. In order to activate the catalyst it was calcined in air at 650°C for eight hours. Subsequent ion exchange with 5 N NH₄CI for two hours at 100°C yielded the ammonium form which after drying at 110°C for two hours followed by calcination at 650°C for twelve hours (both in air) yields the acid form.

Example 6: This Example shows the diethylation of naphthalene with ethylene using

ZSM-12 catalysts synthesized in Example 5 and run according to the process discussed below.

A ca. 15 μm catalyst was prepared and the DEN reaction showed that the catalyst deactivated rapidly. Undoubtedly the path length is too long. Coking predominated. This result shows that large particle diameter ZSM-12 is not desirable in this reaction.

Claims

WE CLAIM AS OUR INVENTION:

1. A process for producing diethylnaphthalene enriched in

2,6-diethylnaphthalene, which process comprises the steps of: a. providing naphthalene or 2-ethylnaphthalene and an ethylating agent to an alkylation reactor containing an acidic zeolite catalyst having a large pore aperture diameter between 5.6A and 7.0A; and b. reacting the naphthalene or 2-ethylnaphthalene with an ethylating agent in said alkylation reactor in the presence of the catalyst under conditions sufficient to convert at least a portion of said naphthalene or 2-ethylnaphthalene to 2,6-diethylnaphthalene.

2. The process of Claim 1 where the acidic zeolite is selected from ZSM-12, EU-1, and SAPO-11.

3. The process of Claim 1 where the ethylating agent is selected from ethylene, ethanol, ethyl ether and ethyl chloride.

4. The process of Claim 3 where the ethylating gent comprises ethylene.

5. The process of Claim 2 where the percentage of 2,6-diethylnaphthalene in the diethylated isomers is greater than

20%.

6. The process of Claim 5 where the reaction produces both 2,6-diethylnaphthalene and 2,7-diethylnaphthalene and the ratio of the 2,6/2,7 isomers is greater than one.

7. The process of Claim 2 where said catalyst exhibits an Si/AI ratio between approximately five to 2000.

8. The process of Claim 7 where said catalyst exhibits an Si/AI ratio between approximately ten to 1000.

9. The process of Claim 8 where said catalyst exhibits an Si/AI ratio between approximately 20 to 500.

10. The process of Claim 9 where said catalyst is calcined at a temperature between 400°C and 1000°C.

11. The process of Claim 2 where the acidic sites on the external surface of said zeolite catalyst are deactivated by contacting the catalyst with a deactivating reagent selected from the group consisting of the halogen, hydridic and organic derivatives of Groups IIIA, IVA, IVB, and VA.

12. The process of Claim 2 where the acidic sites on the external surface of said catalyst are deactivated by a process comprising the steps of: a. filling the intracystalline free pore volume of said catalyst with a hydrocarbon to obtain an internally protected catalyst; b. treating said internally protected catalyst with an aqueous acid or complexing agent which is insoluble in the hydrocarbon contained within the intracrystalline pores; and, c. removing said hydrocarbon to recover said catalyst.

13. The process of Claim 2 where the external acidic sites are deactivated by precoking.

14. The process of Claim 2 further comprising the step of oxidizing the 2,6-diethylnaphthalene to produce 2,6-dicarboxynaphthalene.

15. A process for producing diethylnaphthalene enriched in 2,6-diethylnaphthalene, which process comprises the steps of: a. providing naphthalene or 2-ethylnaphthalene and an ethylating agent to an alkylation reactor containing an acidic zeolite ZSM-12; and b. reacting the naphthalene or 2-ethylnaphthalene with an ethylating agent in said alkylation reactor in the presence of the catalyst under conditions sufficient to convert at least a portion of said naphthalene or

2-ethylnaphthalene to 2,6-diethylnaphthalene.

16. The process of Claim 15 where the ethylating agent is selected from ethylene, ethanol, ethyl ether and ethyl chloride.

17. The process of Claim 16 where the ethylating gent comprises ethylene.

18. The process of Claim 15 where the percentage of 2,6-diethylnaphthalene in the diethylated isomers is greater than

20%.

19. The process of Claim 18 where the reaction produces both 2,6-diethylnaphthalene and 2,7-diethylnaphthalene and the ratio of the 2,6/2,7 isomers is greater than one.

20. The process of Claim 15 where said catalyst exhibits an silica/alumina ratio between approximately ten to 1000.

21. The process of Claim 20 where said catalyst exhibits an silica/alumina ratio between approximately 20 to 500.

22. The process of Claim 21 where said catalyst is calcined at a temperature between 400°C and 1000°C.

23. The process of Claim 15 where the acidic sites on the external surface of said zeolite catalyst are deactivated by contacting the catalyst with a deactivating reagent selected from the group consisting of the halogen, hydridic and organic derivatives of Groups MIA, IVA, IVB, and VA.

24. The process of Claim 15 where the acidic sites on the external surface of said catalyst are deactivated by a process comprising the steps of: a. filling the intracystalline free pore volume of said catalyst witn a hydrocarbon to obtain an internally protected catalyst; b. treating said internally protected catalyst with an aqueous acid or complexing agent which is insoluble in the hydrocarbon contained within the intracrystalline pores; and, c. removing said hydrocarbon to recover said catalyst.

25. The process of Claim 15 where the external acidic sites are deactivated by precoking.

26. The process of Claim 15 where the catalyst has a particle diameter less than about 4.0 μm.

27. The process of Claim 26 where the particle diameter is between 0.1 and 3.75 μm.

28. The process of Claim 15 additionally comprising the step of oxidizing the 2,6-dimethylnaphthalene to produce 2,6-dicarboxynaphthalene.

29. A process for producing diethylnaphthalene enriched in 2,6-diethylnaphthalene, which process comprises the steps of: a. providing naphthalene or 2-ethylnaphthalene and an ethylating agent to an alkylation reactor containing a catalyst comprising a shape selective catalyst having pore aperature dimensions between 5.1A and about 7.0A, and b. reacting the naphthalene or 2-ethylnaphthalene with an ethylating agent in said alkylation reactor in the presence of the catalyst under conditions sufficient to convert at least a portion of said naphthalene or 2-ethylnaphthalene to a stream where the percentage of 2,6-diethylnaphthalene is greater than 20%.

30. The process of Claim 29 where the ethylating agent is selected from ethylene, ethanol, ethyl ether and ethyl chloride.

31. The process of Claim 30 where the ethylating gent comprises ethylene.

32. The process of Claim 29 where the reaction produces both 2,6-diethylnaphthalene and 2,7-diethylnaphthalene and the ratio of the 2,6/2,7 isomers is greater than one.

33. The process of Claim 29 where said catalyst exhibits a silica/alumina ratio between approximately five to 2000.

34. The process of Claim 33 where said catalyst exhibits a silica/alumina ratio between approximately ten to 1000.

35. The process of Claim 34 where said catalyst exhibits a silica/alumina ratio between approximately 20 to 500.

36. The process of Claim 29 where said catalyst is calcined at a temperature between 400°C and 1000°C.

37. The process of Claim 29 where the acidic sites on the external surface of said catalyst are deactivated by contacting the catalyst with a deactivating reagent selected from the group consisting of the halogen, hydridic and organic derivatives of Groups IIIA, IVA, IVB, and VA.

38. The process of Claim 29 where the acidic sites on the external surface of said catalyst are deactivated by a process comprising the steps of: a. filling the intracystallline free pore volume of said catalyst with a hydrocarbon to obtain an internally protected catalyst; b. treating said internally protected catalyst with an aqueous acid or complexing agent which is insoluble in the hydrocarbon contained within the intracrystalline pores; and c. removing said hydrocarbon to recover said catalyst.

39. The process of Claim 29 where the external acidic sites are deactivated by precoking.

40. The process of Claim 29 where the the catalyst has a particle diameter less than about 4.0 μm.

41. The process of Claim 40 where the particle diameter is between 0.1 μm and 3.75 μm.

42. The process of Claim 29 additionally comprising the steps of oxidizing the 2,6-dimethylnaphthalene to produce 2,6- dicarboxynaphthalene.