JPH02247134A - Production of methylnaphthalenes - Google Patents

Abstract

PURPOSE:To obtain the title compound having extremely low sulfur and nitrogen contents with a long catalytic life and in high yield by hydrogenating a kerosine fraction to make sulfur and nitrogen contents <= specific concentrations, subjecting the resultant substance to reforming reaction to give a formed oil and recovering the title compound from the formed oil. CONSTITUTION:A kerosine fraction is hydrogenated under a severe condition, sulfur and nitrogen contents are made into <=1ppm, respectively to give a hydrogenated oil, from which n-paraffin is recovered to give raffinate. The raffinate is subjected to reforming reaction. Then methylnaphthalenes are recovered from the prepared formed oil to efficiently give methylnaphthalenes having <=1ppm sulfur content and <=1ppm nitrogen content. Sulfur and nitrogen contents >=the above-mentioned concentrations extremely shorten the catalytic life of the reforming process and exert poisoning actions on zeolite in the following isomerization and adsorption and separation processes in production of 2,6- dimethylnaphthalene useful as a raw material of polyester.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing methylnaphthalenes from severely hydrotreated kerosene fractions.

Methylnaphthalene is used as a solvent, a heating medium for dyeing gears, etc., and is also used as a 2,6-
Dimethylnaphthalene can be produced. This 2,
6-dimethylnaphthalene is used as a raw material for polyesters such as polyethylene naphthalate. This polyester can be formed into synthetic fibers, films, etc. with excellent properties.

[Prior art] Methylnaphthalenes are contained in coal tar or cycle oil of fluid catalytic cracking process, but these oils contain high concentrations of impurities such as sulfur compounds and nitrogen compounds. are doing.

By the way, 2,6- which is the monomer of the above polyester
In the synthesis of dimethylnaphthalene, highly pure methylnaphthalene with a low content of the above-mentioned impurities is particularly desired for reasons such as deterioration of the catalyst, suppression of by-products, and improvement in yield. In particular, when isomerizing to 2,6-dimethylnaphthalene, and when adsorbing and separating 2,6-dimethylnaphthalene using zeolite, etc., this type of species exhibits a poisoning effect on catalysts and adsorbents. It has been found that when methylnaphthalene is used as a raw material, the sulfur content and nitrogen content in the methylnaphthalene must be at least 1 ppm or less.

Among these impurities, nitrogen compounds are removed by methods such as acid or alkali cleaning. Regarding sulfur compounds, methods have been proposed in which they are heat treated with anhydrous aluminum chloride and purified by recrystallization, melt crystallization, etc.
2230737).

[Problems to be solved by the invention] The method of washing with acid or alkali described above cannot sufficiently remove sulfur compounds, and there are also problems in processing the acid or alkali after use. .

On the other hand, even with the method using anhydrous aluminum chloride, sulfur compounds cannot be reduced until the deterioration of the catalyst can be sufficiently suppressed, and there are also problems in waste treatment.

Furthermore, in order to remove the above impurities, direct hydrorefining treatment of coal tar containing methylnaphthalenes, cycle oil of fluid catalytic cracking process, or distillation fractions thereof results in nuclear hydrogenation of methylnaphthalenes. is unavoidable, and the yield of methylnaphthalenes decreases significantly. For this reason, there was a problem in that further dehydrogenation treatment was required, and the manufacturing cost increased significantly.

On the other hand, it has been reported that heavy aromatic compounds are produced by catalytic reforming of kerosene fractions, and that methylnaphthalenes are present in these heavy aromatic compounds. ．． No. 6 (1970), P468
~474]. However, ordinary hydrodesulfurized white kerosene,
The sulfur content is 30 to 40 ppm and the nitrogen content is 4 to 5 ppm, and even if this kerosene fraction is subjected to a reforming reaction, the sulfur content and nitrogen content in the methylnaphthalenes obtained cannot be reduced to 1 ppm or less, Furthermore, it has been found that when such a kerosene fraction is subjected to a reforming reaction, the catalyst is significantly deteriorated and the life of the catalyst is extremely shortened.

[Problems to be Solved by the Invention] In order to solve the above-mentioned problems, the inventor of the present invention has carried out intensive research and has discovered a surprising result by hydrodesulfurizing a kerosene fraction under harsh conditions. Surprisingly, the yield of methylnaphthalenes was found to be increased. The present invention was made based on this knowledge, and an object of the present invention is to provide a method for producing methylnaphthalenes with good yield and a sulfur content and a nitrogen content of 1 ppm or less.

[Means for Solving the Problems] The present invention provides hydrogenated oil in which a kerosene fraction is hydrotreated to reduce the sulfur content and nitrogen content to 1 ppm or less, or normal paraffins are recovered from this hydrotreated oil. The process consists of subjecting the subsequent raffinate to a reforming reaction and then recovering methylnaphthalenes from the resulting product oil.

The above kerosene fraction is 150-300% by distillation separation operation.
It refers to fractions that are distilled in the temperature range of °C, and includes straight-run kerosene fractions obtained by atmospheric distillation of crude oil, as well as thermal cracking, catalytic cracking, and hydrogenation of petroleum fractions and residues. It goes without saying that fractions having the above boiling point range obtained by decomposition, alkylation, other purification treatments, etc. can also be used. This kerosene fraction is first treated under severe hydrotreating conditions to reduce the sulfur and nitrogen content to 1 ppp.
m or less. If it is 1 ppm or more, it will significantly shorten the life of the reforming catalyst in the reforming process, and will also lead to the production of dimethylnaphthalene from the methylnaphthalene, isomerization of the dimethylnaphthalenes, and even
This is because when adsorption separation of , 6- and 2,7-dimethylnaphthalene is performed using a zeolite or the like, the zeolite exhibits a poisoning effect. The conditions for this hydrodesulfurization include, for example, using a catalyst in which one or more of cobalt, nickel, molybdenum, tungsten, etc. is supported on a carrier such as alumina or silica-alumina, and
At a temperature of ~430℃, a pressure of 10~200kg/c♂, a liquid hourly space velocity (LH3V) of 0゜1~15h-'', and a hydrogen circulation rate of 50~140ONn'i/kQ, taking into account oil type, catalyst activity, etc. This is done by selecting appropriate conditions.

Incidentally, raffinate is recovered normal paraffin from the kerosene fraction mentioned above, and recovery of this normal paraffin can be carried out using an adsorption separation method using zeolite or a separation method using urea adduct. Raffinate, a by-product from the process of producing normal paraffin as a raw material, can advantageously be used.

This raffinate contains 50 to 95% normal paraffin.
Those recovered in weight percent are preferably used.

On the other hand, for the reforming reaction, a catalytic reforming method which is widely used as a method for producing high octane gasoline from naphtha fraction etc. can be adopted. In this case, for example,
Using platinum on alumina as a carrier, or a catalyst supporting rhenium, germanium, tin, iridium, ruthenium, etc. in addition to platinum, at a temperature of 400 to 550°C, 1 to 5
0kg/7 pressure, liquid space velocity (LH8V) 0.1~3
h-', hydrogen/oil molar ratio of 0.5 to 2o.

In addition, other modification reaction methods include zeolite or crystalline aluminosilicate, silica, alumina, zirconia, titania, chromia, solid phosphoric acid, or oxides such as indium, lanthanum, manganese, cerium, or tin, or Using an acidic refractory containing a mixture of two or more of these, or a catalyst containing or supporting metals such as platinum, palladium, and rhenium, at a temperature of 250 to 700°C, 1 to 100 kg /
cl'11 pressure, 0.1~20h-''L HS V
, the hydrogen/oil molar ratio can also be carried out under conditions of 0.5 to 20.

Although a reactor in which part of the reforming reaction actor is a fixed bed may be used, it is preferable in terms of efficiency to use a reactor comprising a moving bed to which a continuous catalyst regeneration method is added.

Since the product oil obtained after the reforming reaction contains methylnaphthalenes at a relatively high concentration, it can be extracted by distillation, solvent extraction, ordinary crystallization method, or pressure crystallization method. [Chemical Engineering, 51. (6).

428-433 (1987)). Recovery is preferably carried out by atmospheric distillation, as it is economical.
Highly concentrated methylnaphthalenes can be obtained by collecting the fraction at ~250°C.

[Examples] (Examples 1 to 2, Comparative Examples 1 to 2) Desulfurized kerosene fractions 1 and 2 and desulfurized kerosene fractions having the properties shown in Table 1 obtained by hydrodesulfurizing kerosene fractions under different conditions. The raw material was raffinate obtained by recovering 90% by weight of normal paraffin using zeolite from No. 2, and the pressure was 25 kg/an! using a catalytic reforming catalyst with 0.2% by weight of platinum supported on an alumina carrier. , temperature 490℃, L HS V
A reforming reaction was carried out under conditions of 0°8 h-1 and a hydrogen/oil molar ratio of 6. The properties and methylnaphthalene content of this produced oil are shown in Table 2. In addition, the above-mentioned reforming reaction was carried out over 5 days, and Table 3 shows the change in yield of methylnaphthalenes relative to the raw material oil. This produced oil was distilled under atmospheric pressure and a fraction of 230 to 250°C was collected, and the purity of methylnaphthalene was 92%.

Table 1 Table 2 It is clear from these results that the yield of methylnaphthalenes can be improved by reforming a kerosene fraction with a sulfur content and a nitrogen content of 1 ppm or less. It can be seen that it is possible to suppress the deterioration of the methylnaphthalene production activity of the catalyst.

[Effects of the Invention] The present invention is capable of recovering methylnaphthalenes from a kerosene fraction with a sulfur content and a nitrogen content of 1 ppm or less, or from a product oil obtained by reforming a raffinate obtained by recovering normal paraffin from this kerosene fraction. Therefore, it has the special effect of being able to produce methylnaphthalenes with high yield, long catalyst life, and extremely low sulfur and nitrogen contents.

Claims (2)

[Claims] (1) The kerosene fraction is hydrotreated to reduce the sulfur content and nitrogen content to 1 ppm or less, and the hydrotreated oil is subjected to a reforming reaction, and then methylnaphthalenes are recovered from the resulting product oil. A method for producing methylnaphthalenes. (2) Raffinate is subjected to a reforming reaction after normal paraffin is recovered from the hydrotreated oil which has undergone hydrogenation treatment of a kerosene fraction to reduce the sulfur content and nitrogen content to 1 ppm or less,
A method for producing methylnaphthalenes, which comprises subsequently recovering methylnaphthalenes from the resulting oil.