Process for preparing 2-methylnaphthalene

A process for producing 2-methylnaphthalene from a feedstock containing 1-methylnaphthalene by contacting the feedstock with a catalyst composition, in which the process comprising isomerization of 1-methylnaphthalene, wherein the catalyst composition comprising a synthetic zeolite characterized by an X-ray diffraction pattern including interplanar d-spacing as set forth in Table A of the specification.

FIELD OF THE INVENTION 
This invention relates to a process for preparing 2-methylnaphthalene 
(2-MN) from 1-methylnaphthalene(1-MN) by using catalysts for isomerization 
of 1-MN. 
BACKGROUND OF THE INVENTION 
The compound 2-MN as well as 1-MN are contained in coaltar which is 
produced by coking of coal or in LCO(light cycle oil) which is obtained 
from the oil refining process. Concerning 2-MN, it is quite useful raw 
material, for example, 2-MN is used as a starting material in 
manufacturing Vitamin K of pharamaceuticals, or a precursor of 
2,6-dimethylnaphthalene in the manufacture of heat resisting polyester 
resins. 
By contrast, the effective use of 1-MN has not been developed in the 
industry, therefore the following methods to isomerize 1-MN to 2-MN have 
been proposed. V. Solinas et al. reported a process for isomerization of 
1-MN in the presence of Y-zeolite as a catalyst Applied Catalysis, 
9(1984), p109-117!. Z. Popova et al. disclosed isomerization of 1-MN to 
2-MN by using a zeolite H-ZSM5 React. Kinet. Catal. Lett., Vol.52, No. 1, 
p51-58 (1994)!. 
However, a catalitic life of each process was so short that the catalytic 
activity is reduced quickly by coking in the reaction. 
Japanese Laid-open Hei5-201890 shows a process to isomerize 1-MN by 
employing a zeolite on which metals such as Ni or Pd etc. are carried, 
over feeding Hydrogen gas in a reactor. According to this process, the 
catalytic life can be extended, however, the preparing process of the 
catalyst is complicated and is not desirable economically, and it also 
produces unfavorable byproduct (other alkylnaphthalenes except 1-MN and 
2-MN) such as dimethylnaphthalene, ethylnaphthalene and so on. 
SUMMARY OF THE INVENTION 
The present invention has been made in view of the foregoing situation and 
it intends to provide a process for preparing 2-methylnaphthalene, in 
which an employed catalyst exhibits high selectivity of 2-MN and low 
conversion rate to undesirable byproduct as well as long catalytic 
activity. 
Provided herein is a process for producing 2-MN from a feedstock containing 
1-MN by contacting said feedstock with a catalyst composition, said 
process comprising isomerization of 1-MN, wherein said catalyst 
composition comprising a synthetic zeolite characterized by an X-ray 
diffraction pattern including interplanar d-spacing as set forth in Table 
A. 
TABLE A 
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interplanar d-spacing 
relative intensity 
(.ANG.) I/I.sub.o .times. 100 
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12.36 .+-. 0.4 M-VS 
11.03 .+-. 0.2 M-S 
8.83 .+-. 0.14 M-VS 
6.18 .+-. 0.12 M-VS 
6.00 .+-. 0.10 W-M 
4.06 .+-. 0.07 W-S 
3.91 .+-. 0.07 M-VS 
3.42 .+-. 0.06 VS 
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*The relative intensities are given in terms of the symbols: W = weak, M 
medium, S = strong, VS = very strong. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present inventors have made earnest studies to utilize 1-MN 
effectively, as a result, have accomplished the present invention by 
employing a particular catalyst in the isomerization of 1-MN. 
The particular catalyst is a zeolite which comprises a synthetic porous 
crystalline material characterized by an X-ray diffraction pattern 
including interplanar d-spacing can be set forth in the Table A. 
The zeolite is known as MCM-22 and the entire contents of application Ser. 
No. 5,001,295 are incorporated herein by reference. 
Isomerization conditions include a temperature of between 300.degree. to 
400.degree. C., and preferably between 350.degree. and 400.degree. C., and 
a pressure of between 0 to 100 kg/cm.sup.2.G and preferably 5 to 50 
kg/cm.sup.2.G. 
The reaction is accomplished utilizing a feed weight hourly space velocity 
(WHSV) of between 0.1 to 500 hr.sup.-1, and suitably 0.5 to 10 hr.sup.-1. 
In case WHSV is too high, contacting time between a feedstock and the 
catalyst is not enough and the conversion rate of 1-MN is low. On the 
contrary, when WHSV is too low, it means the reactor requires to be large 
in the volume to accommodate much more catalyst, or the supply of the 
feedstock should be decreased in amount, therefore productivity in the 
isomerization is reduced. 
In the isomerization of the present invention, the content of 1-MN in a 
feedstock is desirable to be more than 35 weight %, more preferably the 
content of 1-MN is more than 50 weight %. The feedstock can be supplied 
into a reactor in the liquid or gaseous phase, and gaseous phase is 
preferable. 
Furthermore, the present invention provides a process for producing 2-MN 
from a feedstock containing 1-MN by contacting the feedstock with the 
catalyst MCM-22, comprising a step for isomerization of 1-MN to produce 
2-MN, and a step for separation of 2-MN from the product in the 
isomerization. 
As a method for separation of 2-MN, any method which is known for 
separation of isomers, such as distillation, crystallization, adsorption 
or extraction, can be used. However, to obtain high yield of 2-MN from the 
mixture of MN isomers, distillation and crystallization are preferable. 
In this process, it is recommendable to recycle 1-MN fraction which is 
separated from the product as a feedstock for isomerization. 
The present invention will now be explained refering to examples.