JPH02247136A - Production of dimethylnaphthalene - Google Patents

Abstract

PURPOSE:To obtain the subject compound having extremely reduced sulfur and nitrogen contents with a long catalyst life by hydrogenating a kerosine distillate to reduce sulfur and nitrogen contents to <= specific concentrations, reforming the product and subsequently recovering the subject compound from the produced oil. CONSTITUTION:A kerosine distillate is hydrogenated under a severe condition to reduce the sulfur and nitrogen contents thereof to <=1ppm, and the hydrogenated oil or a raffinate remained after normal paraffin is recovered from the hydrogenated oil is reformed. Dimethyl naphthalenes are recovered form the produced oil to obtain the dimethyl naphthalenes having sulfur and nitrogen contents of <=1ppm in good yields. The sulfur and nitrogen contents higher than the above-mentioned concentrations remarkably shorten the catalyst life in the reforming process and further poison zeolite in an isomerization process and an adsorptive separation process when 2,6- and 2,7-dimethyl naphthalenes useful as the raw materials for polyesters are especially produced.

Description

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

Dimethylnaphthalenes, especially 2,6-5 and 2,7-
By oxidizing dimethylnaphthalene, 2,6-1
and 2,7-naphthalene dicarboxylic acid, which is used as a raw material for polyesters such as polyethylene naphthalate. This polyester can be molded into synthetic fibers, films, etc. with excellent properties, but an inexpensive industrial production method for 2,6-1 and 2°7-dimethylnaphthalene has not yet been established.

[Prior Art] Dimethylnaphthalenes are contained in coal tar or cycle oil of a fluid catalytic cracking process, and methods for recovering them by distillation have been proposed (for example, in JP-A No. 6
0-69042). However, in the method of recovering dimethylnaphthalenes from coal tar and cycle oil of a fluid catalytic cracking process, since high concentrations of sulfur compounds and nitrogen compounds are present in the cycle oil, these compounds are converted into dimethylnaphthalenes. It gets mixed in. By the way, these sulfur compounds and nitrogen compounds are used when dimethylnaphthalenes as other substituted compounds are isomerized to 2,6-1 and 2,7-dimethylnaphthalene, and also in 2,6- and 2,7-dimethylnaphthalenes. It exhibits a poisoning effect when methylnaphthalene is adsorbed and separated using zeolite, etc. Therefore, the sulfur content and nitrogen content in dimethylnaphthalenes should be reduced to at least 1
It was found that it is necessary to keep the amount below ppm. When hydrorefining treatment is performed to ensure this, treatment under harsh conditions is required, nuclear hydrogenation of dimethylnaphthalenes is unavoidable, and the yield of dimethylnaphthalenes is significantly reduced. Therefore, there was a problem that further dehydrogenation treatment was required, which significantly increased manufacturing costs.

On the other hand, it has been reported that heavy aromatic compounds are produced by catalytic reforming of kerosene fractions, and that dimethylnaphthalenes are present in these heavy aromatic compounds [Journal of Japan Petroleum Institute, Vol. 13. No. 6 (1970), P46
8~4741° However, ordinary hydrodesulfurized white kerosene has a sulfur content of 30~40 ppm and a nitrogen content of 4~5 ppm.
However, even if this kerosene fraction is subjected to a reforming reaction, it is not possible to reduce the sulfur and nitrogen contents in dimethylnaphthalenes to 1 ppm or less, and furthermore, it is not possible to reduce the sulfur and nitrogen contents in the dimethylnaphthalenes obtained by subjecting this kerosene fraction to a reforming reaction. It was found that this significantly deteriorated the catalyst and shortened its lifespan.

[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, it has been found that the yield of dimethylnaphthalenes is increased. The present invention was made based on this knowledge, and an object of the present invention is to provide a method for producing dimethylnaphthalenes 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 a hydrogenated oil in which a kerosene fraction is hydrotreated to have a sulfur content and a nitrogen content of 1 ppm or less, or normal para-3=fin from this hydrotreated oil. The process consists of subjecting the recovered raffinate to a reforming reaction, and then recovering dimethylnaphthalenes from the resulting product oil.

The above kerosene fraction is 150-300% by distillation separation operation.
It refers to the fraction distilled in the temperature range of 0C, and includes straight-run kerosene fraction obtained by atmospheric distillation of crude oil, as well as thermal cracking, catalytic cracking, and hydrocracking of petroleum fractions and residues. It goes without saying that fractions having the above boiling point range obtained by , 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 ppm or less. this is,
If it is more than 1 ppm, it will significantly shorten the life of the reforming catalyst in the reforming process, and also cause the isomerization of dimethylnaphthalenes using the subsequent zeolite catalyst, and even
, 6- and 2. This is because when dimethylnaphthalene is adsorbed and separated using a zeolite or the like, it exhibits a poisoning effect on the zeolite. 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 0'C, a pressure of 10 to 200 kg/c, a liquid hourly space velocity (LH3V) of 0.1 to 15 h-', a hydrogen circulation rate of 50 to 140 ON%/kit, taking into account oil type, catalyst activity, etc. Based on the above, conditions are selected as appropriate.

Raffinate is normal paraffin recovered from the above-mentioned kerosene fraction, and recovery of this normal paraffin can be carried out using an adsorption separation method using zeolite or a separation method using urea adduct, and it can be used as a raw material for detergents. Raffinate, which is a by-product from the process of producing normal paraffin, may 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 carrying rhenium, germanium, soot, iridium, ruthenium, etc. in addition to platinum, at a temperature of 400 to 550 °C, 1 to 5
0kg/c pressure, liquid hourly velocity (LH8V) 0.1~
It can be carried out under the conditions of 3h-1 and a hydrogen/oil molar ratio of 0.5 to 20.

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 /
It can also be carried out under the conditions of LH8V of cllI pressure peak of 0.1 to 20 h-+ and hydrogen/oil molar ratio 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 dimethylnaphthalenes 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 performed by distillation as it is economical.
By collecting the fraction at 0°C, a high concentration of dimethylnaphthalenes can be obtained.

2,6-1 and 2゜7-dimethylnaphthalenes are separated and recovered from the dimethylnaphthalenes by known means such as adsorption separation using zeolite, crystallization, separation by complex compound formation, etc., and the recovered residual liquid is It is isomerized using an isomerization catalyst or the like and recycled for the separation and recovery.

[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. Using a raffinate obtained by recovering 90% by weight of normal paraffin using zeolite from No. 2 as a raw material, using a catalytic reforming catalyst in which 0.2% by weight of platinum was supported on an alumina carrier, the pressure was 25 kg/cJ, the temperature was 490°C, A reforming reaction was carried out under the conditions of LH8V at 0°8 h-1 and hydrogen l oil at a molar ratio of 6. The properties and dimethylnaphthalene 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 dimethylnaphthalenes relative to the raw material oil. This produced oil was distilled under atmospheric pressure and a fraction of 255 to 265°C was collected, and the purity of dimethylnaphthalene was 94%.

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

[Effects of the Invention] The present invention recovers dimethylnaphthalenes 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 dimethylnaphthalenes 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 dimethylnaphthalenes are recovered from the resulting oil. A method for producing dimethylnaphthalenes. (2) A reforming reaction is carried out on the raffinate after recovering normal paraffin 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 dimethylnaphthalenes, which comprises subsequently recovering dimethylnaphthalenes from the resulting oil.