JPS62250094A - Method for separating and purifying aromatic component - Google Patents

Abstract

PURPOSE:To obtain high-purity BTX readily by superfractionation with most inexpensive energy, by obtaining 6-8C fraction obtained by removing cyclopentadiene from a specific hydrocarbon oil, hydrogenating the fraction at two stages and separating an aromatic component. CONSTITUTION:A hydrocarbon oil (e.g. cracked gasoline prepared as a by- product in production of gaseous olefin by thermal cracking of naphtha, etc.) containing 6-8C aromatic components is distilled to give <=5C fraction and >=6C fraction. Then, 6-8C fraction and a cyclopentadiene-containing fraction are distilled and cyclopentadiene is distilled and separated from the fraction. Then, the 6-8C fraction from which cyclopetadiene is removed is obtained as a bottom product, subjected to hydrogenating and purifying treatment at two stages and the aromatic component is separated. EFFECT:Cyclopentadiene can be recovered in high purity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for separating and refining aromatic components from hydrocarbon oil. Specifically, the present invention relates to a method for separating and refining aromatic components from petroleum-based hydrocarbon oil, such as cracked gasoline, which is a by-product when producing gaseous olefins by thermally cracking naphtha.

[Conventional technology]

In recent years, with the amazing development of the chemical industry, demand has increased for aromatic hydrocarbons such as benzene, toluene, and hxylene (hereinafter referred to as BTX) as well as lower olefins such as ethylene and propylene as basic raw materials. Also, B
Demand from customers to improve the quality of TX is becoming increasingly strict; for example, in the case of benzene, the sulfur content is several ppp.
There is a demand for high-purity products with a freezing point of less than m and a freezing point of more than t, +°C to be supplied at a low price.

Existing BTX production technology generally uses various aromatic component-containing hydrocarbon oils such as coke oven light oil, oil gas light oil, cracked gasoline, and reformed oil as raw materials, and separates and refines the aromatic components from the hydrocarbon oil. This is the process of acquiring BTX through the process, and in special cases, an additional step is added to adjust the BTX production ratio. To explain the production of BTX from cracked gasoline as a typical process of existing BTX production technology, cracked gasoline is subjected to preliminary distillation to obtain 0. The following fractions and the fractions above 0° are separated and aromatic components are concentrated), and the 06 to C8 fractions are subjected to two-stage hydrogenation refining to hydrogenate unsaturated components and hydrogenolyze sulfur compounds, etc. (removal of contaminants), then the hydrogenated oil is treated with a solvent (e.g. sulfolane, NMP) that acts as a solvent for the aromatic components.
etc.) to extract only the aromatic components and separate the non-aromatic components), and finally, the extract is subjected to fractional distillation to separate the BTX components (hereinafter referred to as
extraction process).

[Problem that the invention seeks to solve]

In the above conventional technology, the 06-C3 fraction obtained by preliminary distillation of the cracked gasoline, etc., that is, the fraction rich in aromatic components, is subjected to one-step hydrogenation purification, and the diolefins in the fraction are converted into monoolefins. However, these diolefins, especially dienes such as cyclopentadiene, polymerize during heating or evaporation and form a gum-like substance in heat exchangers, heaters, piping, etc. The problem is that it deposits as a substance or a coke-like substance and eventually blocks these equipment and piping. In addition, during the hydrogenation purification, the diolefin consumes a large amount of hydrogen and has the problem that the operation becomes complicated due to diene number adjustment.

[Means for solving problems]

The present inventors have conducted intensive studies to solve the problems of the conventional technology in the single-stage hydrogenation refining of the pre-distilled fraction of the aromatic component-containing hydrocarbon oil such as cracked gasoline. The 06-C8 fraction obtained by preliminary distillation of the 06-C8 fraction was further distilled and purified to separate and remove cyclopentadiene in the 06-'s M fraction, and then subjected to one-stage water purification treatment, thereby solving the above problems. It was discovered that cyclopentadiene was significantly improved and that cyclopentadiene could be recovered in Manjunka, and the present invention was completed.

That is, the gist of the present invention is to extract 0.0 from a hydrocarbon oil containing 0.6 to C8 aromatic components. The following fractions and fractions of CO or higher were obtained by distillation separation. OL+,, JO, fractions and cyclopentadiene-containing fractions were distilled, and cyclopentadiene-containing fractions were distilled to obtain 06-C, from which cyclopentadiene was separated and removed. The present invention relates to a method for separating and purifying aromatic components, which comprises: distilling a distillate, subjecting it to one-step hydrogenation and purification treatment, and then separating aromatic components.

The present invention will be explained in detail below.

The hydrocarbon oil used as a raw material in the present invention is Oe ~ 0
It is a hydrocarbon oil containing an aromatic component, preferably a hydrocarbon oil containing an aromatic component of 30% by weight or more. Specific examples include petroleum-based light oils such as cracked gasoline and reformed oil, tar-based light oils such as coke oven light oil, and oil gas light oil, with cracked gasoline being particularly suitable.

Cracking gasoline is derived from the thermal cracking or catalytic cracking of petroleum-based hydrocarbon oils, such as naphtha, and its composition and properties vary depending on the manufacturing process, feedstock oil, cracking conditions, cracking process,
It varies depending on the separation conditions etc. A typical example of cracked gasoline is cracked gasoline that is produced as a by-product from plants that produce lower olefins such as ethylene and propylene.

Hereinafter, the case where cracked gasoline is used as a raw material will be specifically explained. In a typical lower olefin production plant, such as an ethylene plant, a petroleum hydrocarbon oil having a final boiling point of about 230"C or less, such as naphtha, kerosene, etc., is used together with lower olefins such as steam pyrene with a boiling point range of 30"C or less. A tr pyrolysis product containing a cracked gasoline fraction at 30° C. is obtained.The cracked gasoline containing a 011 or higher fraction obtained by fractionating a C6 or lower fraction from a nuclear pyrolysis product is Usually, its boiling point is in the range of 30-230 °C, and the aromatic component content is about ?0-f,!% by weight
It is within the range of .

In this case, first, the above-mentioned cracked gasoline is fed to the first distillation column, that is, a light boiling separation column, and the C3 or lower fractions are distilled and separated, and the C1 or lower fractions such as isoprene and cyclopentadiene are removed from the top of the column. The bottoms containing dicyclopentadiene and 06 or higher fractions are extracted from the bottom of the column. The first distillation column is operated under conditions that allow distillation separation of C6 or lower fractions and C06 or higher fractions, that is, a distillation column with 10 or more theoretical plates is used, and the bottom temperature is 1 OO-IZ.

℃, and the tower top pressure is operated under conditions of slightly reduced pressure to slightly increased pressure.

The bottoms from the first distillation column are then fed to the second distillation column, that is, the high-boiling distillation column, and the fractions of 00 and above are separated by distillation, and the dicyclopentadiene and o6 to Oa fractions are separated from the top of the column. The contained fraction is distilled out, and on the other hand, the bottoms containing the fraction of 0° or more is extracted from the bottom. The M,2 distillation column is operated under conditions where the C6-O, fraction and the 00 or more fraction can be separated by distillation, that is,
Using a distillation column with the number of theoretical plates of 10 or more, dicyclopentadiene is preferentially converted to cyclobentadiene by i÷4''
The C%4 top pressure is operated under conditions of slightly reduced to elevated pressure.

In the prior art, the distillate from this co-distillation column was subjected to a two-stage hydrogenation purification treatment, but in the method of the present invention, the distillate is supplied to the third distillation column to convert cyclopentadiene. Distillation separation is performed, and a high-purity cyclopentadiene fraction is distilled out from the top of the column, while a C6-O3 fraction is obtained from the bottom, which contains aromatic hydrocarbons such as benzene, toluene, and xylene. Remove the bottom liquid.

The third distillation column contains cyclopentadiene and 06-0. Under conditions where the fraction can be separated by distillation, that is, using a distillation column with the number of theoretical plates of io or more, the bottom temperature of the column is g.

~/, 20°C, and the tower top pressure is operated under conditions of slightly reduced pressure to increased pressure.

The purity of cyclopentadiene obtained as the distillate of the third distillation column is usually 95% by weight or more, and depending on the selection of distillation conditions, 99% by weight or more can be obtained. It can be used as raw material for medical pears, private shelves, etc.

The bottoms from the third distillation column are then subjected to a one-step hydrogenation refining process to form bottoms, i.e., the fractions containing aromatic components of the 06-08 fractions (hereinafter referred to as aromatic oil). unsaturation contained in, for example, diene compounds excluding cyclopentadiene,
Hydrogenation and purification of monoolefin compounds, sulfur compounds, nitrogen compounds, etc. including styrene type compounds will be carried out.

If the aromatic oil contains unsaturated components, especially diolefins, when the aromatic oil is heated, evaporated, or contacted,
Diolefins are polymerized and used in heat exchangers, evaporators, heaters,
It deposits as a gum-like substance or carbonaceous substance in reactors or piping, etc., eventually clogging these equipment and piping. Hydrogenation methods, polymerization methods, clay treatment methods, etc. have been proposed as methods for removing diolefins, but they can be carried out simultaneously with hydrodesulfurization. The method is simple.

In the first hydrogenation refining treatment, diolefins contained in the aromatic oil, that is, diene compounds and styrene type compounds, are hydrogenated to monoolefins and aromatic components, respectively. In this reaction, a highly active catalyst for selective hydrogenation is used, and operating conditions are adopted to minimize polymerization, condensation, etc. of diene compounds and styrene compounds.

The catalyst used in the primary hydrogenation treatment is basically at least one metal, metal oxide, or metal sulfide selected from the group of elements belonging to Group (a), Group (a) and Group (III) of the Periodic Table. As active ingredients, these are preferably supported on a carrier such as alumina, diatomaceous earth, or calcined clay. For example, palladium is an excellent hydrogenation catalyst in the reduced state, nickel,
Molybdenum, cobalt-molybdenum, and nickel-molybdenum are excellent catalysts in the oxidized or sulfurized state. In particular, cobalt-molybdenum catalysts and nickel-molybdenum catalysts have excellent selectivity in the elR state or sulfided state, and are extremely good primary hydrogenation catalysts that can withstand continuous use for long periods of time. Such a cobalt or nickel-molybdenum catalyst is one in which cobalt or nickel and molybdenum are supported on a carrier such as alumina, diatomaceous earth or calcined clay such that the molar ratio of cobalt or nickel to molybdenum is /: o, r ~ 3. ), the total supported amount of cobalt or nickel and molybdenum is -20 weight S, preferably 3 to 13
Weight x weight.

The primary hydrogenation treatment is carried out at a reaction temperature of 230°C or lower, preferably ts
θ~Here O℃, reaction pressure 1ONs: 0kg7dlc+,
Liquid hourly space velocity (LIISV) / -/ Ohr″″11
This is carried out by contacting the aromatic oil with the catalyst in the presence of hydrogen. In any case, the reaction temperature and pressure are preferably set so that the reaction system can at least partially maintain a liquid phase. As a hydrogen source used for primary hydrogenation treatment,
Examples include reformed gas, off-gas from a lower olefin production plant, or hydrogen concentrate thereof, or hydrogen gas obtained by treating hydrocarbons such as natural gas and petroleum by a steam reforming method or a partial oxidation method. The hydrogen concentration in the primary hydrogenation treatment is preferably about gos or higher, preferably 10X or higher. 1
When using a sulfide-based catalyst for the subsequent hydrogenation treatment, preliminary purification of hydrogen is not particularly required, but when using a palladium-based catalyst, carbon monoxide, which is a poisonous substance of the catalyst,
It is necessary to remove hydrogen sulfide etc. from hydrogen in advance. It is preferable to employ a fixed bed reaction for reaction formation in the primary hydrogenation treatment. In order to carry out the fixed bed reaction in a liquid phase or a gas-liquid mixed phase, either a downflow type or an upflow type can be adopted.

The aromatic oil obtained by the above primary hydrogenation treatment contains impurities such as monoolefin compounds, sulfur compounds, and nitrogen compounds. In order to remove these impurities by hydrogenation purification, a second hydrogenation purification treatment is performed.

At least one metal, metal oxide, or metal sulfide selected from the group is preferably supported on alumina, diatomaceous earth, fired clay, or the like. Especially molybdenum
Preference is given to using alumina, cobal)-molybdenum-alumina and nickel-molybdenum-alumina catalysts in the sulfided state. A-th hydrogen treatment expansion reaction temperature! O ~ 15°C, reaction pressure t o Nt ojtg /dG.

LH8V O,J -t hr-', when an aromatic oil is contacted with the above catalyst in the presence of hydrogen and substantially in the gas phase, K
It's done well. The hydrogen required for the secondary hydrogenation treatment may be the same as that for the primary hydrogenation treatment. The essential difference between primary hydrogenation treatment and primary hydrogenation treatment in reaction conditions is the reaction temperature.
Without gas-liquid separation of the product obtained in the first hydrogenation treatment, the temperature required for the second hydrogenation treatment, that is, 2 kO-1/,
It is desirable to perform the primary hydrogenation treatment by preheating to a temperature of 1°C.

By the primary hydrogenation treatment, monoolefin compounds in the aromatic oil are converted into saturated hydrocarbons, sulfur compounds are converted into hydrocarbons and hydrogen sulfide, and nitrogen compounds are converted into ammonia.

The aromatic oil after the secondary hydrogenation treatment is then sent to a stripper to separate light gases such as hydrogen sulfide and ammonia. Next, the aromatic oil is subjected to a solvent extraction operation using a selective solvent for aromatic components (for example, sulfolane, N-methylpyrrolidone, glycol thread solvent, dimethyl sulfoxide, etc.) to extract only the aromatic components. The extracted extract is subjected to extractive distillation to separate aromatic components, and the aromatic components are subjected to a clay treatment as desired, and then subjected to a fractional distillation operation to separate high-quality BTJI components. do. This fractional distillation operation can be performed using precision distillation, azeotropic distillation, extractive distillation, etc., but precision distillation, which has the lowest energy, produces high-purity BTX, such as freezing point! l-1'C
The above-mentioned high purity benzene can be easily obtained.

[Examples] Next, specific aspects of the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

Example! A C3 or lower fraction was separated by distillation from a pyrolysis product obtained by thermally decomposing naphtha in the presence of steam, and the resulting cracked gasoline containing a C3 or higher fraction was used. The cracked gasoline (containing cyclopentadiene (OPD) i3X, dicyclopentadiene (DOPD) 1./λ, ~C,
The hydrocarbons in the fraction are fed into the center of a 30-stage light-boiling separation column, and the column is operated at a bottom temperature of /, tO ℃, and a reflux ratio of -, and the C6 or lower fraction is removed from the top of the column. The distillate was distilled, and a fraction of 0.6 or higher (containing cyclopentadiene θ% and dicyclopentadiene !, +%) was taken out from the bottom of the column. The C6 to C Hatake fractions and C6 to C Hatake fractions are subsequently fed into the 30-stage high-boiling separation column, which is operated at a bottom temperature of iqo°C and a reflux ratio of 0.4, from the top of the column. Cyclopentadiene 6-4tX
A fraction containing 0.09 and above was distilled out from the bottom of the column.

The distillate from the high-boiling separation column was then fed into the 30-stage third distillation tower, which was operated at a bottom temperature of 90°C and a reflux ratio of 91-3%. Purity cyclopentadiene is recovered by distillation, while the 06-C8 fraction and the fraction containing dicyclopentadiene O,tX ("
"Aromatic oil") was released in a can. The composition and properties of the aromatic oil are shown below.

(1) Aromatic component = Ri O-za S weight X (II) Diene value: ti.

GID Brome number: to-t,.

(IV) Total sulfur content: so-co 00 ppm The above aromatic oil was treated with cobalt-molybdenum-alumina catalyst
It was subjected to a stage hydrogenation purification treatment. The Co-O catalyst has a general formula represented by #Koto-M1-3, and the supporting ratio of cobalt and molybdenum is io weight % as oxides.

The primary hydrogenation treatment was performed at a reaction temperature of 199°C and a hydrogen partial pressure of II! r
kQ/crlG, liquid hourly space velocity/, thr-”, hydrogen/
Aromatic oil (molar ratio) The reaction was carried out under the following conditions: t, 0. In the secondary hydrogenation treatment, the reaction temperature is 310°C and the hydrogen partial pressure is J kk.
The reaction was carried out under the following reaction conditions: g/allc+, hydrogen/aromatic oil (molar ratio) 1.0.

The above two-stage hydrogenation refining treatment of aromatic oil was continuously operated for 100 days, but no coke-like material was observed in the preheater or reactor.

Table 1 shows the composition, properties, and effects of the aromatic oil before and after hydrogenation treatment.

Comparative Example 1 In Example 1, as aromatic oil to be subjected to hydrogenation treatment,
The same procedure as in Example 1 was carried out except that the distillate from the high-boiling separation column (containing 6, q% of cyclopentadiene) was used. When the hydrogenation treatment beam was operated continuously for 0 days, formation of coke-like material was observed at the inlet of the reactor.

Table 1 shows a comparison of the composition, properties, and effects of the aromatic oil after hydrogenation treatment with Example 1.

〔Effect of the invention〕

By the method of the present invention, υC6~0. Efficient and economical separation of aromatic components from hydrocarbon oil containing aromatic components
can do. In the method of the present invention, the formation of gummy substances and coke-like substances in the reactor is suppressed, and a reduction in hydrogen consumption during the hydrorefining process is achieved.

Furthermore, since the hydrogenation load is reduced, the relative activity of STY is improved. In the method of the present invention, deterioration of the catalyst is suppressed and the frequency of regeneration of the catalyst is reduced. Furthermore, in the method of the present invention, cyclopentadiene, which is useful as a raw material for synthesis, can be recovered with high purity.

Patent applicant: Mitsubishi Chemical Industries, Ltd. Agent Patent Attorney Hase - 1 other person

Claims (1)

[Claims] (1) A C_6 to C_8 fraction and a cyclopentadiene-containing fraction obtained by distilling a C_5 or lower fraction and a C_9 or higher fraction from a hydrocarbon oil containing aromatic components of C_6 to C_8. Distillation is performed to obtain a fraction containing cyclopentadiene, and on the other hand, the C_6 to C_8 fractions from which cyclopentadiene has been separated and removed are distilled, and this is subjected to two-stage hydrogenation purification treatment, and then the aromatic components are removed. A method for separating and purifying aromatic components, characterized by separating them.