JPH0461855B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention efficiently converts dimethylnaphthalene (hereinafter referred to as DMN) containing ethylnaphthalene into 2,6-dimethylnaphthalene (hereinafter referred to as 2,6-
The present invention relates to a method for manufacturing DMN (abbreviated as DMN). An application has already been filed for a method for isomerizing DMN on a zeolite whose main cavity has a 10-membered oxygen ring (Japanese Patent Application No. 57-196578). It has been found that isomerization between -β progresses and isomerization from 2,7-DMN to 2,6-DMN is possible. However, in commercial processes, DMN-containing fractions such as petroleum-based (FCC light cycle oil) and coal-based sources are used as DMN raw materials, but in addition to DMN, these raw materials also contain ethylnaphthalenes (1-substituted There are 2-substituted and 2-substituted forms, both of which are combined together.
(abbreviated as EN) and paraffins (including alkylbenzenes). Therefore, in order to obtain 2,6-DMN from these raw materials, it is necessary to convert or remove EN and paraffins into DMN, but it is technically extremely difficult to convert these into DMN. . Extraction, adsorption separation, and the like are already known methods for removing paraffins. Therefore, the present inventors conducted intensive studies on methods for removing EN, and when the catalyst used for the isomerization reaction of DMN was brought into contact with EN, a disproportionation reaction mainly occurred, and naphthalene and diethylnaphthalene were mainly removed. found that it can be generated. Naphthalene (hereinafter abbreviated as NL) and diethylnaphthalene (isomers exist, but collectively abbreviated as DEN)
2,6- isomers have a large boiling point difference from DMN isomers, so they can be separated by distillation, and 2,6-
As a method for separating DMN, a complex separation method, an adsorption separation method, etc. are known. By combining these results and known techniques, it has become possible to create an economical 2,6-DMN production process using FCC light cycle oil or the like as a raw material, which was virtually unusable in the past. The present invention will be explained in detail below. The raw materials used in the method of the present invention include DMN
Petroleum-based or coal-based mixtures containing ENs and paraffins (including alkylbenzenes) in the same boiling point range as these can be used, but it is preferable that the concentration of DMNs be as high as possible. Further, it is preferable to remove as much paraffin as possible in advance. The concentration of ENs is not particularly critical, but economically it is preferably equal to or lower than the concentration of DMNs. Preferably, the DMN fraction containing EN, which is distilled and separated from the recycled oil of the above-mentioned FCC process, is used. Further, the residue containing EN after separating the desired isomer from the isomerized products of these dimethylnaphthalene fractions is also used as a raw material for the method of the present invention. The catalyst used in the method of the present invention is a zeolite whose main cavity has a 10-membered oxygen ring at the entrance. Such zeolites are known, and representative ones include ZSM-5, 8, and 11 zeolites published by Mobil Corporation. This type of zeolite usually has a pentasil structure and its silica/alumina molar ratio is usually 12 or more. Zeolites generally have a skeletal structure composed of silica-alumina, but there are also zeolites in which iron, chromium, and other metals form part of the skeletal structure, that is, they are included as non-exchangeable metals. Although any zeolite can be used in the method of the present invention, aluminosilicate whose skeleton is composed of silica-alumina is usually used. These zeolites are used in the reaction in their acid form. As is well known, acid type zeolites have polyvalent cations such as protons and rare earth ions as cations. It is usually used in the reaction as hydrogen-type zeolite. Note that zeolite may be used as it is, or may be molded together with clay compounds such as silica, alumina, kaolin, and other auxiliaries. The zeolite used as a catalyst in the method of the present invention, whose main cavity has a 10-membered oxygen ring at the entrance, has an acid content that differs depending on the manufacturing conditions. According to studies by the present inventors, the amount of acid at 300°C determined by the gaseous base adsorption method shown in Japanese Patent Application No. 57-196578 is 0.1 m
It is advantageous to use mol/g or more,
It has been found that it is particularly preferable to use an acid with an acid content of 0.45 mmol/g or more. The method of isomerizing DMN containing EN according to the method of the present invention may be carried out in either a gas phase or a liquid phase. The gas phase method will be described below. The reaction is usually carried out using a fixed bed reactor, but it can also be carried out using a fluidized bed, moving bed or the like. The reaction temperature is
The temperature is 250 to 550°C, preferably 300 to 450°C, and the pressure is 0.1 to 100 atm, preferably room temperature to 20 atm. Raw materials can be used alone or in hydrogen, nitrogen, carbon dioxide,
Alternatively, dilute with water vapor and contact. The total gas hourly space velocity is 100 to 10000hr ^-1 under standard conditions (NTP),
Preferably, it is about 500 to 5000 hr ^-1 , and the liquid weight space velocity (WHSV) of the raw material is usually 0.01 to 100 ml/g.
−cat・hr, preferably 0.1 to 10ml/g−cat・hr
It is. Next, the liquid phase method will be described. The reaction is usually carried out using a suspended bed or fixed bed reactor.
The reaction temperature is usually 250-550℃, preferably 300-450℃
℃, and the pressure is normal pressure to 50 ki, as long as it is sufficient to keep the raw material in a liquid phase state, excessive pressure is not necessary and is specified based on economic or technical considerations. In the case of a suspended bed, either a batch method or a flow method can be used. The charging ratio of catalyst in the raw material is usually 0.0 to 50% by weight, preferably 1 to 20% by weight.
The reaction time is about 0.1 to 10 hours.
For a fixed bed, the liquid hourly space velocity (LHSV) of the feedstock is
It is appropriately selected within the range of 0.1 to 100hr ^-1 . DMN
is brought into contact with a catalyst alone or in an atmosphere of hydrogen, nitrogen, carbon dioxide, or the like. Thus, in the present invention, the EN-containing
The DMN is isomerized to remove at least a portion of the light boilers, high boilers and 2,6-DMN from the reaction mixture, and at least a portion of the remaining fraction is recycled to the isomerization reaction zone. Here, light boilers include NL produced by disproportionation of EN, methylnaphthalenes (hereinafter abbreviated as MN) or gas fractions produced as by-products, and high boilers include trimethylnaphthalenes, etc. (hereinafter abbreviated as TMN) and DEN, etc.
Both light boiling substances and high boiling substances refer to substances that can be separated from DMN by distillation. The remaining fraction is 2,6-
This is a DMN fraction from which at least a portion of DMN has been removed, and unreacted EN, and is difficult to separate from 2,6-DMN by distillation. A preferred embodiment of the present invention is shown in Figure 1. First, from the raw materials paraffin and 2,6-
Separate the DMN. Separation of paraffins is known, and for example, the extraction method disclosed in Japanese Patent Publication No. 16963/1988 can be applied. Adsorption separation using zeolite is also possible. A method for separating 2,6-DMN from a DMN mixture can be carried out, for example, in accordance with the method described in Japanese Patent Publication No. 52-945. As mentioned above, paraffins and 2,6-
After separating DMN, an isomerization reaction is performed. NL produced by disproportionation of EN during the isomerization reaction, and light components such as by-product MN and gas are removed by distillation, and then the DMN fraction and high It is boiled
The TMN and DEN fractions are separated by distillation.
The DMN fraction contains 2,6-DMN and other
It is difficult to separate DMN and unreacted EN etc. by distillation, so at least a part of 2,6-DMN is removed by the method disclosed in the above-mentioned Japanese Patent Publication No. 52-945. separate,
The remaining fraction is recycled to the isomerization reaction zone along with fresh feedstock. According to the method of the present invention, ENs contained in the raw material DMN, which are difficult to separate by distillation, are converted into light boiling substances such as NL and high boiling substances such as DMN, so they are mixed into the product. EN can be reduced and fed back to the isomerization reaction zone without special methods of separating it from the DMN mixture. EXAMPLES The present invention will be explained in more detail with reference to examples below, but the present invention is not limited to the following examples unless it exceeds the gist thereof. In addition, the conversion rate and selectivity in the examples are as follows:
It was calculated using the following formula based on the following components detected by gas chromatography. Detected components: naphthalene, α and β-methylnaphthalene, α and β-ethylnaphthalene, dimethylnaphthalene isomers, conversion rate (%) = total gas chromatography detected components (mo
l) - Recovered raw material (mol) / Total gas chromatography detection component (mol) x 100 Selectivity (%) = Each detection component (mol) / Total gas chromatography detection component (mol) - Recovered raw material (mol) x 100 Example 1 () Synthesis of zeolite In a stainless steel pressure vessel with an internal volume of 100, colloidal silica (silica content 20.4% by weight) 32.471
Kg, water 18.8Kg, and diglycolamine
7.228Kg was added and stirred. Add to this 10kg of water and sodium aluminate (90.3% by weight)
A solution of 499.3 g and 726 g of sodium hydroxide was added, and the mixture was heated to 160° C. for 3 days under sealed acid and stirring. The obtained product was washed with about 100 Kg of water and dried at 130°C. The obtained product is
The silica/alumina ratio is 27, and the diffraction pattern by powder X-ray diffraction analysis is similar to that described in Example 1 of JP-A-56-92114, and the entrance of the main cavity is a pentasil composed of a 10-membered oxygen ring. It was confirmed that it was type zeolite. () Conversion to acid type zeolite 36g of the above zeolite was charged into an aqueous solution of 53.3g of ammonium chloride dissolved in 200ml of water.
Reflux was carried out for 2 hours. After that, the same refluxing operation was repeated two more times. Then, it was washed with demineralized water until chlorine ions were removed (chlorine ions were detected using a 0.1N silver nitrate aqueous solution). Thereafter, it was dried at 130°C, molded using a powder tablet molding machine, and then crushed and sized into 10 to 20 meshes. This was heated and calcined in air at 500°C for 3 hours to obtain an acid type zeolite. () Reaction 10ml of acid type zeolite obtained above (5.7
g) was packed into a reactor made of SUS316 with an inner diameter of 19 mm and equipped with a heating furnace. β- _{ethylnaphthalene} ( ^β-
EN) and _H2 gas at β-EN; 9ml/hr (53m
mol/hr), H ₂ /β-EN; 12.5/1 (mol), and the reaction product liquid was collected 90 to 120 minutes after the start of the reaction. A portion of the reaction product liquid was extracted and analyzed by gas chromatography. The results are shown in Table-1. Example 2 A reaction was carried out in the same manner as in Example 1, except that the raw materials shown in Table 2 were used. Table 2 of the results
Shown below. Example 3 A glass reactor with an inner diameter of 19 mm was filled with 7.3 ml (4.2 g) of the catalyst prepared in Example 1, and a reaction was carried out at normal pressure. The raw materials used in Example 2 were used. The reaction conditions were 350℃, raw material 1.33g/hr (7.81mmol/
hr), H ₂ ; 2.8/hr (NTP), 30 to 60 minutes after the start of the reaction, the reaction product liquid was collected, a portion was extracted, and analyzed by gas chromatography. Table 2 of the results
Shown below.

【table】

[Table] The boiling points of the components in the fractions obtained in Example 2 and Example 3 are as follows.

[Table] Therefore, NL and MN are considered light boilers, and TMN
and DEN can be separated from EN and DMN fractions by distillation as high boilers. The method for separating 2,6-DMN from EN and DEN fractions uses ammonium Y-type (SK-41: manufactured by Union Carbide) and sodium X-type (13-X: manufactured by Union Carbide) zeolites as adsorbents. The others are Example 5 described in Japanese Patent Publication No. 52-945
It can be implemented in accordance with the Toluene is used as a desorption agent, and ammonium Y-type and sodium X-type zeolites are used as adsorbents in a weight ratio of 7:3. When separated at a temperature of 120° C., 1,7-DMN is first desorbed, then 2,6-DMN, and then other components are desorbed. The 1,7-DMN component is 2,6-
The DMN is mixed with the other separated components and the toluene is separated and recycled to the isomerization reaction zone.

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing an embodiment of the present invention.

Claims (1)

[Claims] 1. Dimethylnaphthalenes containing ethylnaphthalenes are catalytically isomerized with a zeolite whose main cavity has a 10-membered oxygen ring at the entrance, and at least one of light-boiling substances, high-boiling substances and 2,6-dimethylnaphthalene is extracted from the reaction mixture. A method for producing 2,6-dimethylnaphthalene, characterized in that at least a portion of the remaining fraction is recycled to an isomerization reaction zone.