JPH07119424B2 - Heavy naphtha reforming method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for reforming heavy naphtha for producing a gasoline base material.

BACKGROUND ART Gasoline for automobile engines is required to have a uniform octane number distribution. This is because if the octane number distribution is non-uniform, a knocking phenomenon will occur, and if this knocking becomes severe, the output will decrease.

On the other hand, the octane number distribution of reformed gasoline, which is a typical base material of gasoline, is not uniform. This is in the reformed gasoline
This is because the octane numbers of C ₆ and C ₇ fractions are lower than those of other carbon number fractions. If the reaction conditions are increased to increase the octane number of the C ₆ and C ₇ fractions, especially if the reaction temperature is increased, the octane number will improve, but the yield of hydrocracked gas as a by-product will increase. As a result, the amount of hydrogen generated will decrease, and the yield of reformed gasoline will decrease.

Conventionally, in order to solve such a problem, for example, according to Japanese Patent Laid-Open No. 2-84488, after distilling heavy naphtha, C
_{The 5 to} C ₆ fraction is directly used as a gasoline base material or subjected to an isomerization reaction, and the C _{7 to} C ₈ fraction is subjected to an aromatization reaction, and further,
A method has been proposed in which a C ₈₊ fraction is subjected to a usual catalytic reforming reaction to produce a gasoline base material. Note that C
_{The 8+} fraction means a hydrocarbon having 8 or more carbon atoms, and so on.

[Problems to be Solved by the Invention] According to the invention disclosed in Japanese Patent Laid-Open No. 2-84488 described above, C
There is a step of carrying out an isomerization reaction of ₇ fractions with C _{5 to} C ₆ fractions. However, this is not preferable for the following reason.

First, a fraction having a carbon number of 7 or more is decomposed into an LPG fraction, which causes a reduction in gasoline yield. Second, as the thermodynamic equilibrium reveals,
With the above isomerization of paraffinic hydrocarbons, the octane number required value of gasoline cannot be sufficiently satisfied.

An object of the present invention is to provide a method for reforming heavy naphtha, which has a high octane number and provides a gasoline base material having an improved octane number distribution.

[Means for Solving the Problems] The method for reforming heavy naphtha according to the present invention has a boiling point range of 60 to 20.
A step of separating the heavy naphtha at 5 ° C. into a C ₆ fraction, a C _{6 to} C ₇ fraction containing at least 70% by volume or more of the C ₇ fraction and a C ₈₊ fraction, and the above C ₆ to At least 1 C ₇ cut
Halogenated L containing metals of Group VIII of the periodic table
B step of contacting with a catalyst composed of type zeolite to aromatize and then separating the C ₅₊ effluent, and after catalytically reforming the mixture of the C ₆ fraction and the C ₈₊ fraction , and having a c separating the C ₅₊ effluent, the d mixing the C ₅₊ effluent of the process c and C ₅₊ effluent of said step b.

The heavy naphtha is a heavy naphtha obtained by fractionating naphtha in the entire boiling range into light naphtha and heavy naphtha (boiling point 60 to 205 ° C.), and contains hydrocarbons having 5 to 11 carbon atoms. .

Specifically, isopentane, n-pentane, cyclopentane, 2,3-dimethylbutane, 2-methylpentane, 3
-Methylpentane, n-hexane, methylcyclopentane, 2,4-dimethylpentane, benzene, cyclohexane, 2-methylhexane, 3-methylhexane, 1-trans-2-dimethylcyclopentane, n-heptane,
Methylcyclohesican, ethylcyclohexane, toluene, 2-methylheptane, 3,4-dimethylhexane, 3
-Methylheptane, 1,3-dimethylcyclohexane, n
-Octane, ethylbenzene, ethylcyclohexane,
1,1,4-trimethylcyclohexane, m-xylene, p
-Xylene, o-xylene, 3-methyloctane, n-
Nonane, 1,2,4-trimethylbenzene and n-decane are the main components.

The step a can be performed by a one-stage treatment using one fractionation tower or a two-stage treatment using two fractionation towers.

That is, in the one-stage treatment using one fractionation tower, the heavy naphtha as a raw material is supplied to the middle stage of the fractionation tower, and the C ₆ fraction from the top and the C ₈₊ fraction from the bottom are _removed. Extract each and mix these. Further, a C _{6 to} C ₇ fraction is taken out from a distillation tray slightly above the middle stage of the fractionating tower and is supplied to an aromatization reaction device together with hydrogen. In addition, if the C ₆ fraction and the C _{6 to} C ₇ fractions are respectively refluxed to the fractionation tower, the effect of the fractionation is further improved.

The operating conditions in this fractional distillation are as follows. ()
Is a preferable condition.

Distillation tray ... 20-80 stages (30-65 steps) Temperature ... 60 to 250 ° C. (110 to 180 ° C.) Pressure ^{... 0~20kg / cm 2 · G (} 1.5~3.5kg / cm 2 · G) reflux ratio ... 0~4.5mol / mol (0.3~3.5mol / mol) also in fractionating tower 2 tower 2-stage process using, the partial heavy naphtha in the first column to the C _7- fraction and C ₈₊ fraction Stay and in the 2nd tower, this C _7-
The fraction is fractionated into a C ₆ fraction and a C _{6 to} C ₇ fraction. After this, C _{6 to} C ₇
The fraction is fed to the aromatization reactor. Remaining C ₆ cut and C
_{The 8+} fractions are mixed and _subjected to conventional catalytic reforming to separate the C ₅₊ effluent from the product.

Benzene has a high antiknock property, but is known to be a harmful substance. Further, benzene in gasoline becomes a polycyclic aromatic hydrocarbon in engine exhaust gas, and therefore its carcinogenicity is regarded as a problem. Therefore, in the production of gasoline, it is desirable to suppress the formation of benzene as much as possible, and when separating C _{6 to} C ₇ fractions from heavy naphtha, reduce the content of C ₆ fractions as much as possible to reduce C ₇ fractions. To aromatize.

In the step b, the C _{6 to} C ₇ fraction obtained from the heavy naphtha fractionation column is dehydrocyclized using a platinum-supported L-type zeolite catalyst in the aromatization reactor under the following reaction conditions. It mainly produces hydrogen and aromatic hydrocarbons.

. i The reaction conditions [() Preferred conditions] Temperature ... 400 to 550 ° C. (four hundred and thirty to five hundred and thirty ° C.) Pressure ... atmospheric ^{~35kg / cm 2 · G (2~10kg} / cm 2 · G) WHSV ... 0.1~10hr - ¹ (0.5 to 5 hr ^-1 ) Hydrogen / Oil feedstock ... 0 to 20 mol / mol (0 to 10 mol / mol) ii. Catalyst As the catalyst, a zeolite catalyst containing at least one metal of Group VIII of the periodic table is used. The zeolite catalyst includes X-, Y-, and L-type zeolite, and L-type zeolite is preferable.

L-type zeolite composition: 0.9-1.3M _{2 / n} O ・ Al ₂ O ₃・ 5.0〜7.0SiO ₂・ 0-9H ₂
O (in the formula, M represents an alkali metal or an alkaline earth metal, and n represents a valence of M) The specific composition is disclosed in JP-B-58-57408. As the carrier of this zeolite, one subjected to halogenation treatment such as fluorination treatment or chlorination treatment is used. Of these, L-type zeolite treated with CFC is particularly preferable.

Amount of metal supported: 0.1 to 5.0% by weight of the total catalyst, preferably
0.3 to 1.5% by weight Loading method: Various methods can be used to load platinum or the like on zeolite, but generally, vacuum impregnation method, atmospheric pressure impregnation method, dipping method, ion exchange method, etc. may be used. .

Supported metal: For example, as a platinum source when platinum is used,
There are various types, specifically ammine platinum chloride, chloroplatinic acid, chloroplatinate, tetraammine platinum hydroxide,
Examples thereof include dinitrodiamine platinum.

In the step b, the C _{6 to} C ₇ fraction is aromatized, the reaction product is cooled, and then the reaction product is separated into a C ₅₊ effluent and a gas product in a gas-liquid separation tank. To do.

The C5 ₊ effluent is a mixture of hydrocarbons predominately aromatic hydrocarbons. Specifically, isobutane, n-butane,
Isopentane, n-pentane, 2-methyl-2-butene, cyclopentane, 2,3-dimethylbutane, 2-methylpentane, 3-methylpentane, n-hexane, 2-
Methyl-2-pentene, methylcyclopentane, 2,4-
Dimethylpentane, benzene, 3,3-dimethylpentane, cyclohexane, 2-methylhexane, 3-methylhexane, 1-trans-2-dimethylcyclopentane, dimethylcyclopentane, n-heptane, 1-heptene, methylcyclohexane, 4 -Methyl-1-hexene, 2,4-dimethylhexene, ethylcyclopentane,
It is a mixture of toluene and the like.

The gas product in this step is used as a recycled gas or a hydrogen-containing gas.

The catalytic reforming of the mixture of the C ₆ fraction and the C _{8 +} fraction in the step c is carried out using a platinum-supported alumina catalyst which is a usual reforming catalyst, and a heavy naphtha at a reaction temperature of about 470 to 520. A gasoline base material with a high octane number is obtained by catalytically reforming at ℃. In addition to platinum, the platinum-supported alumina catalyst may contain a metal selected from the group consisting of rhenium, iridium and the like. Usually this catalyst is
It is called a bifunctional catalyst and promotes various reactions such as hydrocarbon isomerization reaction, dehydrogenation reaction, aromatization reaction, and hydrocracking reaction.

[Example] A method for reforming heavy naphtha according to an example of the present invention will be described with reference to FIG.

As shown in FIG. 1, the apparatus used in the present example is equipped with a fractionation tower 1, an aromatization reaction apparatus 2, a catalytic reforming reaction apparatus 3 and a gas-liquid separation tank 4.

Using this apparatus, heavy naphtha was reformed as follows.

First, a raw material naphtha having a C _{4 to} C ₁₀ fraction a is sent to a fractionation tower 1 and divided into a light naphtha having a C _{4 to} C ₆ fraction b and a heavy naphtha having a C _{6 to} C ₁₀ fraction c. I stayed. This heavy naphtha
It is obtained by fractional distillation of raw material naphtha in the entire boiling range and then desulfurization. Its properties are as follows.

Properties of heavy naphtha Specific gravity (15/4 ℃) …… 0.738 Distillation property (℃) Initial boiling point …… 87 5% Distillation temperature …… 95 10% Distillation temperature …… 96 20% Distillation temperature …… 98 30% Distillation temperature …… 100 40% Distillation temperature …… 103 50% Distillation temperature …… 105 60% Distillation temperature …… 109 70% Distillation temperature …… 113 80% Distillation temperature …… 120 90% Distillation temperature …… 131 95% Distillation temperature …… 139 97% Distillation temperature …… 143 End point …… 149 Composition (% by volume) Paraffin hydrocarbon …… 58.3 Olefin hydrocarbon …… 0.0 Naphthene hydrocarbon …… … 31.4 Aromatic hydrocarbons …… 10.3 Fraction (% by volume) C ₅ ………… 0.1 C ₆ ………… 12.3 C ₇ ………… 51.5 C ₈ ………… 25.3 C ₉₊ ………… 10.8 Next, the heavy naphtha was sent to the fractionation tower 1 and fractionated under the following conditions. From the middle of the fractionation column 1, C ₆ -C ₇ fraction g of 40 wt% with respect to the supplied heavy naphtha is obtained, the C ₆ -C ₇
Fraction g was sent to the next aromatization reactor. Further, C ₆ fraction e obtained from the top of the fractionation tower 1 and C ₈₊ obtained from the bottom of the fractionation tower 1
The fraction f was mixed and then sent to the catalytic reforming reactor 3.

Number of distillation trays …… 60 stages Temperature top …… 117 ℃ Bottom …… 168 ℃ Pressure top …… 1.6kg / cm ² · G Bottom …… 2.0kg / cm ² · G Reflux ratio Top (C ₆ fractions) ... 3.3 mol / mol side cut (C _{6 to} C ₇ fractions) ... 0.3 mol / mol Next, the C _{6 to} C ₇ fraction g obtained from the middle stage of the fractionation tower 1 is used as a by-product gas. It was supplied to the aromatization reactor 2 together with hydrogen of h, and the reaction was carried out under the following conditions using a 1.0 wt% platinum-supported chlorofluorocarbon-treated L-type zeolite catalyst (see JP-A-62-57653). Then, the reaction product was sent to the gas-liquid separation tank 4.

Reaction conditions Reaction temperature …… 460 ℃ Reaction pressure …… 5kg / cm ²・ G WHSV …… 2hr ^-1 Hydrogen / stock oil ratio… 5mol / mol Gas-liquid separation condition Temperature …… 5 ℃ Pressure …… 4kg / cm ²・G Reaction Result Feedstock Product oil Composition (% by volume) Paraffin hydrocarbons… 67.4 23.6 Olefin hydrocarbons… 0.0 0.0 Naphthene hydrocarbons… 12.6 0.9 Aromatic hydrocarbons… 20.0 75.5 Fractions (volume%) C ₅ …… 0.0 2.6 C ₆ …… 2.9 8.4 C ₇ …… 91.8 87.0 C ₈ …… 5.3 2.0 Research method Octane number (-) 46 101 Selectivity of aromatic formation (%) 73 * Selectivity = Aromatic product (number of moles) On the other hand, C ₆ fraction e obtained from the top of the fractionating tower 1 and C ₈ obtained from the bottom of the fractionating tower 1 ₊ mixture i fraction f is sent to catalytic reforming reactor 3 with hydrogen in the product gas h, where commercial reforming catalyst (platinum-carrying alumina catalyst ) Were reacted under the following conditions using a. The reaction results were as follows. Then, the reaction product was sent to the gas-liquid separation tank 4.

Reaction conditions Reaction temperature Average temperature of each catalyst layer …… 515 ℃ Average temperature of all catalyst layers… 497 ℃ Reaction pressure …… 18kg / cm ² · G WHSV …… 1hr ⁻¹ Hydrogen / feed oil ratio …… 6mol / mol gas Liquid separation conditions Temperature …… 25 ℃ Pressure …… 15kg / cm ² · G Reaction results Raw oil Produced oil Composition (% by volume) Paraffin hydrocarbons… 55.8 33.8 Olefin hydrocarbons… 0.0 0.0 Naphthene hydrocarbons… 33.2 3.9 Aroma Group hydrocarbons …… 11.0 62.3 Fraction (% by volume) C ₅ …… 0.0 8.1 C ₆ …… 25.4 28.6 C ₇ …… 0.0 5.0 C ₈ …… 52.4 46.7 C ₉₊ …… 22.2 11.6 Research method Octane number (-) 58 100 selection of the aromatic product (%) 42 then, according to this embodiment by mixing a C ₅₊ effluent d from C ₅₊ effluent d and catalytic reforming reaction step from the aromatization reaction process A gasoline base material was obtained. This gasoline base material had a research octane number of 100.

Comparative Example 1 As shown in FIG. 2, as compared with the above example, an isomerization reaction device 5 was added, and a C ₆ fraction obtained from the top of the fractionation tower 1 in this isomerization reaction device 5 was added. The isomerization reaction was performed on e. Other devices and steps are substantially the same as those in the above-mentioned embodiment.

The isomerization reaction was performed under the following conditions.

Composition of C ₆ fraction (% by volume) Paraffinic hydrocarbons …… 40.8 Olefinic hydrocarbons …… 0.0 Naphthenic hydrocarbons …… 51.0 Aromatic hydrocarbons …… 8.2 Catalyst… Platinum supported amorphous catalyst Reaction conditions Reaction temperature… … 250 ℃ Operating mode Separation of unreacted materials and properties of recycled reaction products to reaction zone Octane number of research method… 88 Catalytic reforming reaction was also carried out in the same manner as in the above example, but specific conditions and reaction results Was as follows:

Reaction conditions Reaction temperature Average temperature of each catalyst layer …… 515 ℃ Average temperature of all catalyst layers …… 491 ℃ Reaction pressure …… 18kg / cm ² · G WHSV …… 1hr ^-1 Hydrogen / feed oil ratio… 6mol / mol Gas-liquid Separation conditions Temperature …… 25 ℃ Pressure …… 15kg / cm ² · G Reaction results Feedstock Product oil composition (% by volume) Paraffin hydrocarbons… 59.4 23.5 Olefin hydrocarbons… 0.0 0.0 Naphthene hydrocarbons… 28.2 4.0 Aromatic Hydrocarbons 12.4 72.5 Fraction (% by volume) C ₅ …… 0.0 7.5 C ₆ …… 0.0 8.1 C ₇ …… 0.0 7.1 C ₈ …… 70.3 62.0 C ₉₊ …… 29.7 15.3 Research method octane number (−) 56 103 Aromatic production selectivity (%) 48 In this comparative example, the C ₅₊ effluent d from the isomerization reaction step,
To obtain a gasoline base according to the present comparative example a mixture of C ₅₊ effluent d from C ₅₊ effluent d and catalytic reforming reaction step from the aromatization reaction process. This gasoline base material had a research octane number of 100.

Comparative Example 2 As shown in FIG. 3, a gasoline base material was obtained by carrying out only catalytic reforming reaction on heavy naphtha.

This catalytic reforming reaction was carried out in the same manner as in the above example, but the specific conditions and reaction results were as follows.

Reaction conditions Reaction temperature Average temperature of each catalyst layer …… 515 ℃ Average temperature of all catalyst layers ・ ・ ・ 499 ℃ Reaction pressure …… 18kg / cm ² · G WHSV …… 1hr ^-1 Hydrogen / raw material ratio ・ ・ ・ 6mol / mol Gas-liquid separation Conditions Temperature …… 25 ℃ Pressure …… 15kg / cm ² · G Reaction results Feedstock Oil composition (% by volume) Paraffin hydrocarbons… 58.3 40.5 Olefin hydrocarbons… 0.0 0.4 Naphthene hydrocarbons… 31.4 5.7 Aromatic carbonization Hydrogen… 10.3 53.4 Fraction (volume%) C _4- …… 0.0 2.0 C ₅ …… 0.1 5.9 C ₆ …… 12.3 17.5 C ₇ …… 51.5 46.1 C ₈ …… 25.3 22.7 C ₉₊ …… 10.8 5.8 Research method Octane number (−) 53 97 Aromatic formation selectivity (%) 42 In this comparative example, C ₅₊ effluent d from the catalytic reforming reaction step d
A gasoline base material was obtained. This gasoline base material had a research octane number of 97.

As can be seen from the above Examples and Comparative Examples, according to this Example, the heavy naphtha is a C ₆ fraction e, and C _{6 to} C ₇ fractions g and C containing at least 70% by volume or more of C ₇ fraction. each separated into ₈₊ fraction f, since C ₆ -C ₇ fraction g was adapted to aromatization by contacting the platinum-supporting flon disposal L-type zeolite catalyst having a low octane number under relatively mild conditions C Aromatic hydrocarbons having a high octane number can be produced from the _{6 to} C ₇ fraction g. On the other hand, the C ₆ fraction e and the C ₈₊ fraction f are mixed and the mixture is _subjected to a catalytic reforming reaction to obtain a C ₅₊ effluent, and the C _{6 to} C ₇ fraction C _Since the gasoline base material is produced together with the ₅₊ effluent, the non-uniformity of the octane number distribution is improved, and the gasoline base material having a high octane number can be produced. Therefore, by using the gasoline base material according to the present embodiment, the knocking phenomenon of the automobile engine is reduced.

On the other hand, according to Comparative Example 1, the same octane number as that of the Example is obtained, but a step of subjecting the C ₆ fraction e to the isomerization reaction is required. Becomes complicated. Further, an isomerization reaction device for this is required, and the device as a whole becomes complicated.

Further, according to Comparative Example 2, since only the catalytic reforming process is performed, the process itself is simple, but the octane number of the obtained gasoline base material is low.

EFFECT OF THE INVENTION According to the method for reforming heavy naphtha according to the present invention, a gasoline base material having a high octane number and an improved octane number distribution can be obtained.

[Brief description of drawings]

FIG. 1 is a process diagram showing a method for reforming heavy naphtha according to an embodiment of the present invention, FIG. 2 is a process diagram showing a method for reforming heavy naphtha according to Comparative Example 1, and FIG. 3 is a comparison. It is a process drawing which shows the reforming method of the heavy naphtha which concerns on Example 2. 1 ... Fractionation tower, 2 ... Aromatization reactor, 3 ... Catalytic reforming reactor, 4 ... Gas-liquid separation tank, 5 ... Isomerization reactor.

Claims (1)

[Claims] 1. A heavy naphtha having a boiling point range of 60 to 205 ° C. is separated into a C ₆ fraction, a C _{6 to} C ₇ fraction and a C ₈₊ fraction containing at least 70% by volume or more of the C ₇ fraction. a step and at least one of the above C _{6 to} C ₇ fractions in Periodic Table No. VIII
A step of aromatizing by contacting with a catalyst comprising a halogenated L-type zeolite containing a Group 3 metal, and then separating the C ₅₊ effluent, the C ₆ fraction and the C ₈₊ fraction after the mixture of catalytic reforming, it has a c separating the C ₅₊ effluent, the d mixing the C ₅₊ effluent of the process c and C ₅₊ effluent of said step b A method for reforming heavy naphtha, characterized by: