JP2008106031A - Method for conversion of ethylbenzene and method for production of para-xylene - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ethylbenzene conversion method for converting ethylbenzene in a raw material containing an 8C aromatic hydrocarbon to benzene in a high conversion rate. <P>SOLUTION: The ethylbenzene conversion method comprises bringing a mixed raw material of an 8C aromatic hydrocarbon containing ethylbenzene into contact with an acid type catalyst containing at least one metal selected from the metals of the groups VII and VIII in the presence of H<SB>2</SB>, to convert ethylbenzene to benzene. The raw material comprises an ethyltoluene-containing 9-10C aromatic hydrocarbon and the ethyltoluene is converted to toluene with the conversion of the ethylbenzene. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for converting ethylbenzene and a method for producing paraxylene. More specifically, a method of hydrodeethylating and converting ethylbenzene contained in C8 aromatic hydrocarbons, hydrodeethylating and converting ethylbenzene contained in C8 aromatic hydrocarbons, isomerizing xylene and paraxylene The present invention relates to a method for producing para-xylene and an apparatus for producing the same.

  Of the xylene isomers, paraxylene is the most important. Paraxylene is currently used as a raw material for polyester monomer, terephthalic acid, which is the main polymer, along with nylon. In recent years, demand for it has been strong mainly in Asia.

  Para-xylene is usually obtained by reforming naphtha, then C8 aromatic hydrocarbon mixture obtained by aromatic extraction or fractional distillation, or cracked gasoline by-produced by thermal decomposition of naphtha by aromatic extraction or fractional distillation. Produced from a C8 aromatic hydrocarbon mixture. The composition of this C8 aromatic hydrocarbon mixture raw material varies widely, but usually 10 to 40% by weight of ethylbenzene, 12 to 25% by weight of paraxylene, 30 to 50% by weight of metaxylene, and 12 to 25% by weight of orthoxylene % Is included. Usually, the C8 aromatic hydrocarbon mixture raw material contains a high boiling point component having 9 or more carbon atoms, so this is removed by distillation, and the resulting C8 aromatic hydrocarbon is supplied to the paraxylene separation step, and paraxylene is separated. Collected. However, para-xylene and meta-xylene have boiling points of 138.4 ° C. and 139 ° C., respectively, which are only about 1 ° C., and recovery by distillation separation is industrially very inefficient. Accordingly, there are generally a cryogenic separation method in which separation is performed using a difference in melting point, and an adsorption separation method in which separation is performed using a difference in adsorptivity with a zeolite adsorbent. The paraxylene-poor C8 aromatic hydrocarbons that have left the separation step are then sent to the isomerization step, where they are isomerized mainly to the paraxylene concentration close to the thermodynamic equilibrium composition by the zeolite catalyst, and low boiling point by distillation separation. The by-product is removed and then recycled to a distillation tower mixed with the above-mentioned new C8 aromatic hydrocarbon raw material to remove high-boiling components, and after removing high-boiling components having 9 or more carbon atoms by distillation, paraxylene Paraxylene is separated and recovered again in the separation step. This series of circulating systems is hereinafter referred to as the “separation-isomerization cycle”.

  FIG. 2 shows the flow of this “separation-isomerization cycle”. This “separation-isomerization cycle” is basically a C8 aromatic hydrocarbon mixed raw material obtained from a reformer or the like (hereinafter referred to as a fresh raw material) and a C8 aromatic hydrocarbon contained in a recycled raw material from the isomerization process. Of high boiling point components for separating and removing high boiling point components, paraxylene separation step 2 for separating product paraxylene, C8 aromatic hydrocarbon raw material having a low paraxylene concentration (hereinafter referred to as raffinate xylene) A xylene isomerization step 3 for performing xylene isomerization and ethylbenzene conversion, and a low boiling point component distillation separation step 4 for separating and recovering low boiling components such as benzene and toluene by-produced in the isomerization step. First, the C8 aromatic hydrocarbon mixed raw material is sent to the high boiling point component distillation separation step 1 from the supply line indicated by the stream 5, and the high boiling point component is removed through the line indicated by the stream 7. The C8 aromatic hydrocarbon raw material from which the high-boiling components have been removed is sent to the para-xylene separation step 2 through the line indicated by the stream 6, and the product para-xylene is separated and recovered from the line indicated by the stream 8. The C8 aromatic hydrocarbon raw material having a low paraxylene concentration is sent to the xylene isomerization step 3 through the line shown by stream 9, and ethylbenzene is converted into xylene via benzene or C8 naphthene paraffin as described later. Upon conversion, raffinate xylene with poor paraxylene concentration is isomerized to a paraxylene concentration close to the thermodynamic equilibrium composition. In the isomerization step, hydrogen or a gas containing hydrogen is also sent through the line indicated by the stream 10. C8 aromatic hydrocarbons containing by-products from the isomerization process are sent to the low-boiling component distillation separation process 4 through the line shown by the stream 11, and such as benzene and toluene by-produced in the isomerization process. The low-boiling components are separated and removed through the line indicated by the stream 12, and the paraxylene-rich recycled raw material containing the high-boiling components is sent to the high-boiling component distillation separation step 1 through the line indicated by the stream 13. In this high boiling point component distillation separation step 1, the high boiling point component is removed and recycled to the paraxylene separation step 2 again. In addition, there is an option that incorporates one distillation column into this “separation-isomerization cycle” to produce ortho-xylene together.

  As described above, the C8 aromatic hydrocarbon supplied to the “separation-isomerization cycle” contains a considerable amount of ethylbenzene. However, in the “separation-isomerization cycle”, this ethylbenzene is not removed. In addition, ethylbenzene accumulates during the cycle. If ethylbenzene is removed by any method to prevent the accumulation of ethylbenzene, an amount of ethylbenzene corresponding to the removal rate circulates in the “separation-isomerization cycle”. If this amount of ethylbenzene is reduced, the total amount of circulation is also reduced, so that the amount of utility used in the steps subsequent to the paraxylene separation step is reduced, resulting in great economic merit. In other words, on the same circulation rate basis, it is possible to increase the production of paraxylene according to the decrease in the ethylbenzene concentration during the cycle.

  There are two general methods for removing ethylbenzene, one is a reforming method in which xylene is isomerized in the isomerization process and ethylbenzene is isomerized to xylene, and the other is ethylbenzene in the xylene isomerization process. This is a dealkylation method in which benzene is hydrodealkylated and converted to benzene, and benzene is distilled and separated in a subsequent distillation separation step. However, in the isomerization method, the ethylbenzene conversion rate is only about 20 to 30% due to the equilibrium between ethylbenzene and xylene, whereas the dealkylation reaction is substantially a non-equilibrium reaction. Can be increased. Therefore, at present, a method of removing ethylbenzene by a dealkylation method is common. However, in the isomerization process, no matter how much ethylbenzene is removed by operating at a very high ethylbenzene conversion rate, the C8 aromatic hydrocarbon mixed feed fed to the “separation-isomerization cycle” originally contains ethylbenzene. Therefore, the supply amount to the para-xylene separation step cannot be lowered by the amount of ethylbenzene.

  In order to reduce even the ethylbenzene supply to this “separation-isomerization cycle” substantially and further lower the ethylbenzene supply to the paraxylene separation process, Patent Documents 1 and 2 disclose a method of reducing the supply amount to the paraxylene separation step by dealkylating most of the ethylbenzene in one pass, converting it into benzene, and distilling and separating it. However, the methods described in detail are practically used in order to reduce the concentration of high-boiling components having 9 or more carbon atoms originally contained in fresh raw materials from the viewpoint of preventing catalyst activity deterioration. It is necessary to remove the high boiling point component by distillation separation in advance.

  FIG. 3 is a flow chart showing the embodiment, in which a deethylation / xylene isomerization step 15 in which ethylbenzene is deethylated in one pass in advance, and a low-pressure distillation separation / recovery of benzene converted into ethylbenzene by deethylation. A boiling point component distillation separation step 16 and a high boiling point component separation step 14 for separating and removing the high boiling point component originally contained in the C8 aromatic hydrocarbon mixed raw material are newly added. That is, in order to protect the catalyst used in the deethylation step, a high boiling point component that becomes a catalyst poison in the high boiling point component distillation separation step 14 is removed from the stream 18 through the line indicated by the stream 5 in the stream 18. And the fraction is sent to the deethylation / xylene isomerization step 15 through the line indicated by stream 17. Hydrogen or a gas containing hydrogen is also sent to the deethylation step through a line indicated by a stream 19. C8 aromatic hydrocarbons which are highly ethylethylene deethylated and contain by-products are sent to the low boiling point component distillation separation step 16 through the line shown by stream 20, and benzene and by-products produced in the deethylation step Low boiling components such as toluene are separated off through the line indicated by stream 21 and high boiling components are sent through the line indicated by stream 22 to the previously described “separation-isomerization” cycle. However, in this case, there is a problem that, by newly incorporating the high-boiling component distillation separation step 14 and the low-boiling component distillation separation step 16, the amount of utility usage increases and the merit of introduction is lowered.

  Further, in the case of the above-described embodiment, as a matter of course, the construction cost for newly installing the deethylation process equipment is extra, but the original “separation” is not performed without installing a dedicated deethylation process independently. In the xylene isomerization step in the “isomerization” cycle, a catalyst having not only a normal xylene isomerization ability but also a function of highly deethylating ethylbenzene was introduced, as shown in FIG. The fresh raw material is mixed with the raffinate xylene coming from the para-xylene separation step shown by stream 9 and fed directly to the isomerization step 3, where ethylbenzene is deethylated at a high conversion rate, and this is separated into the low-boiling component distillation separation step 4 After removing low-boiling components containing benzene, the ethylbenzene concentration shown by stream 13 is very low and the paraxylene concentration is high. The recycle material, and wherein the sending the high-boiling components separation step 1 and the p-xylene-separation step 2, a method for producing para-xylene is disclosed in Patent Document 4. This method is called the direct feed method, and it is not necessary to install a separate deethylation process facility, but a simple facility modification such as increasing the number of catalysts in the xylene isomerization process or switching to a highly active catalyst is sufficient. Therefore, it is possible to increase the production of para-xylene with relatively little capital investment. However, according to Patent Document 4, even in this direct feed method, from the viewpoint of preventing the deterioration of catalytic activity, when the fresh raw material contains a high boiling point component having 9 or more carbon atoms, this is distilled and separated. In this case, it is necessary to install the high-boiling component distillation separation step 14, and it is inevitable to increase the capital investment and the amount of utility usage by incorporating this.

  Generally, in order to convert ethylbenzene to a high degree, the reaction temperature is raised or contacted with a highly active catalyst. As the conversion rate of ethylbenzene increases, the yield reduction of xylene becomes obvious. The breakdown of the loss is as follows: (1) Loss of ethylbenzene converted to toluene by dealkylation of benzene and xylene In addition, (2) Loss in which toluene and trimethylbenzene are converted by the disproportionation reaction between xylenes, (3) Non-aromatics such as cycloparaffin, normal paraffin, and isoparaffin through xylene nuclear hydrogenation reaction There is a loss of conversion to chicks. Furthermore, since the non-aromatics produced by the above nuclear hydrogenation reaction are mixed in the benzene obtained by distillation separation, it is necessary to carry out a so-called extraction process such as sulfolane process. Economic disadvantages such as an increase in volume will also come out.

  Patent Document 3 describes that, in the xylene isomerization process, ethylbenzene is converted using a raw material containing C9 and C10 aromatic hydrocarbons, which are high-boiling components, as C9 + aromatic hydrocarbons. There is no disclosure of using ethyltoluene and converting it. That is, in the examples of the document 3, ethylbenzene was converted using a feedstock containing less than 0.01% by weight of C9 + aromatic hydrocarbon, and as a result of this reaction, 0.1% by weight or 0.2% by weight of C9 + aromatic It is described that a reaction product containing hydrocarbons was obtained. According to the explanation of side reactions involving C9 + aromatic hydrocarbons in the same document, the increase in C9 + aromatic hydrocarbons in the above reaction is due to the disproportionation reaction of xylene and ethylbenzene, the production of trimethylbenzene and diethylbenzene, It is thought that side reactions such as the formation of methylethylbenzene and dimethylethylbenzene by transalkylation reaction of xylene have occurred. Patent Document 3 further discloses a method for suppressing xylene loss due to a disproportionation reaction between xylenes by intentionally mixing toluene as an optional case. However, this intentionally mixed toluene is also an important base material with high value used in many applications, such as high octane gasoline base materials and solvents, and raw materials for disproportionation processes. If there is a loss suppression method, it is a component that should avoid mixing into raw materials as much as possible.

Japanese Unexamined Patent Publication No. 01-056626 US Pat. No. 6,342,649 US Pat. No. 5,977,429 Japanese Patent Laid-Open No. 08-14383

  This invention makes it a subject to provide the conversion method of the ethylbenzene which converts the ethylbenzene in the raw material containing a C8 aromatic hydrocarbon into benzene with a high conversion rate.

  In addition, the present invention converts ethylbenzene in a raw material containing C8 aromatic hydrocarbons to benzene and, at the time of isomerizing xylene, has a high ethylbenzene conversion rate and less xylene loss. It is an object to provide a superior method.

  Another object of the present invention is to provide a method for recovering high-purity benzene from a reaction product that has undergone an isomerization step of converting ethylbenzene in a raw material containing C8 aromatic hydrocarbon and isomerizing xylene. To do.

The present inventors have included the ethyltoluene in the raw material is contacted with a strong acid catalyst to catalyst poisons in the presence of H _2, by performing the de-ethylation reaction of ethylbenzene to achieve the above object The present invention has been found.

  That is, the present invention has the following configuration.

(1) C8 aromatic hydrocarbon mixed raw material containing ethylbenzene is brought into contact with an acid catalyst containing at least one metal selected from Group VII and Group VIII metals in the presence of H ₂ , A method for converting benzene, wherein the raw material contains a C9-C10 aromatic hydrocarbon containing ethyltoluene, and the ethyltoluene is converted to toluene together with the conversion of ethylbenzene.

(2) The method for converting ethylbenzene according to the above (1), further comprising recovering benzene having a purity of 99.8% by weight or more by separating benzene produced by the reaction by distillation.

(3) A step of subjecting a C8 aromatic hydrocarbon mixed raw material containing ethylbenzene and xylene to the method described in (1) or (2) above, converting ethylbenzene to benzene and isomerizing xylene, and the reaction obtained A method for producing para-xylene, comprising a step of separating para-xylene from a product.

(4) C8 aromatic hydrocarbon mixed raw material containing ethylbenzene and xylene is subjected to the method described in (3) above, to convert ethylbenzene into benzene and to isomerize xylene, the first deethylation / xylene isomerization Step, a step of separating para-xylene from the reaction product obtained in the first deethylation / xylene isomerization step, and a second xylene isomerization of xylene contained in the separation residue of the separation step A method for producing para-xylene, comprising a step of performing isomerization by attaching to a step and a step of separating para-xylene again from a reaction product of the second xylene isomerization step.

(5) Deethylation / xylene isomerization step in which a C8 aromatic hydrocarbon mixed raw material containing ethylbenzene and xylene is subjected to the method described in the above (3) to convert ethylbenzene into benzene and isomerize xylene; A step of separating para-xylene from the reaction product obtained in the deethylation / xylene isomerization step, and a step of supplying the separation residue of the separation step to the deethylation / xylene isomerization step again. A method for producing para-xylene.

(6) A method for producing paraxylene using a paraxylene production apparatus for performing the first deethylation / xylene isomerization step, the paraxylene separation step, and the second xylene isomerization step described in (4) above. The apparatus comprises a bypass line that does not pass through the first deethylation / xylene isomerization step, and the C8 aromatic hydrocarbon mixed raw material mixed with C9-C10 aromatic hydrocarbons containing ethyltoluene. A method for producing paraxylene, comprising supplying to the paraxylene separation step as necessary.

  According to the present invention, a C9 and C10 aromatic hydrocarbon containing ethyltoluene is mixed with a C8 aromatic hydrocarbon mixed raw material containing ethylbenzene, and this is at least selected from Group VII and Group VIII metals in the presence of hydrogen. By contacting an acid catalyst containing one metal to convert ethylbenzene into benzene and isomerizing xylene, the xylene loss is suppressed and ethylbenzene is highly hydrodeethylated. Can be converted to benzene. The ethyltoluene in the raw material is converted to useful toluene by deethylation and can be recovered as a by-product.

  Moreover, according to this invention, the method of collect | recovering high purity benzene from the reaction material produced | generated by converting the ethylbenzene in the raw material containing C8 aromatic hydrocarbon can be provided. Thereby, after collection | recovery, it can commercialize without passing an extraction process.

  The present invention is characterized in that, in the ethylbenzene deethylation reaction, the C8 aromatic hydrocarbon mixed raw material containing ethylbenzene to be supplied contains ethyltoluene. Usually, ethyltoluene is “separation-isomerization cycle”. Is contained in the high-boiling component of the raw material containing C8 aromatic hydrocarbons supplied to 5 to 15% by weight. For this reason, usually, it is possible to substantially omit the distillation column that has separated the high-boiling components by distillation during the treatment in the deethylation step. FIG. 1 shows an embodiment of a preferred flow for carrying out the present invention, but the high boiling point component distillation separation step 14 shown in FIG. 3 or FIG. 4 of the prior art flow can be omitted.

  That is, according to the present invention, when the ethylbenzene in the raw material supplied in the deethylation step is deethylated, ethyltoluene contained in the feed material containing C9 and C10 aromatic hydrocarbons is removed. By performing ethylation reaction at the same time and converting this to toluene, toluene can be obtained by effectively using ethyltoluene. For example, as in the prior art represented by Patent Document 3, there are many other uses. There is no need to bother useful toluene. Furthermore, the xylene disproportionation reaction or the transalkylation reaction of benzene and xylene deethylated with ethylbenzene, which causes the xylene loss described above, is an equilibrium reaction. The presence of toluene obtained by ethylation suppresses the promotion of these side reactions and reduces xylene loss.

The catalyst used in the method of the present invention is an acid type catalyst obtained by doping a solid acid with a predetermined metal described later, and examples of the solid acid include acid type zeolite. Examples of the zeolite that can be used in the present invention as the acid type zeolite include a pentasil type zeolite. For example, a pentasil type (MFI type) zeolite having pores with a 10-membered oxygen ring (for example, Japanese Patent Publication No. 60-35284). Example 1 on page 4-5 and Example 1 on page 7 of Japanese Examined Patent Publication No. 46-10064 can be used. As the zeolite, both natural products and synthetic products can be used, but synthetic zeolite is preferred. Such a pentasil-type zeolite itself and its manufacturing method are well known, and one example of its synthesis method is also specifically described in the following examples. Even if the zeolite structure is the same, the catalytic performance varies depending on the composition, particularly the silica / alumina molar ratio (SiO ₂ / Al ₂ O ₃ molar ratio), the size of the zeolite crystallites, and the like.

  The preferable range of the silica / alumina molar ratio constituting the zeolite also depends on the zeolite structure. For example, in a synthetic pentasil type zeolite, the preferred silica / alumina molar ratio is 10 to 70, more preferably 20 to 55. This can be achieved by controlling the composition ratio of each component during zeolite synthesis. Further, the silica / alumina molar ratio of the zeolite can be increased by removing aluminum constituting the zeolite structure with an acid aqueous solution such as hydrochloric acid or an aluminum chelating agent such as ethylenediaminetetraacetic acid (EDTA). On the contrary, a preferable silica / alumina molar ratio is obtained by increasing the silica / alumina molar ratio of the zeolite by introducing aluminum into the zeolite structure by treatment with an aqueous solution containing aluminum ions, such as an aqueous aluminum nitrate solution or an aqueous sodium aluminate solution. It is also possible to make it. The silica / alumina molar ratio can be easily measured by atomic absorption, fluorescent X-ray diffraction, ICP (inductively coupled plasma) emission spectroscopy, or the like.

  Since synthetic zeolite is generally a powder, it is preferably molded for use. Examples of the molding method include a compression molding method, a rolling method, and an extrusion method, and the extrusion method is more preferable. In the extrusion method, binders such as alumina sol, alumina gel, bentonite and kaolin and surfactants such as sodium dodecylbenzenesulfonate, span and twin are added to the synthetic zeolite powder as molding aids and kneaded. .

  If necessary, a machine such as a kneader is used. Furthermore, depending on the metal added to the catalyst, a metal oxide such as alumina or titania is added at the time of molding the zeolite, thereby increasing the amount of the metal added to the catalyst or improving the dispersibility. The kneaded material is extruded from the screen. Industrially, for example, an extruder called an extruder is used. The kneaded product extruded from the screen becomes a noodle-like product. The size of the molded body is determined by the screen diameter to be used. The screen diameter is preferably 0.2 to 1.5 mmφ. The noodle-shaped molded body extruded from the screen is preferably treated with a malmerizer to round off the corners. The molded body molded in this way is dried at 50 to 250 ° C. After drying, it is fired at 250 to 600 ° C., preferably 350 to 600 ° C., in order to improve the molding strength.

The molded body thus prepared is subjected to ion exchange treatment for imparting solid acidity. As a method of imparting solid acidity, ion exchange treatment is performed with a compound containing ammonium ions (for example, NH ₄ Cl, NH ₄ NO ₃ , (NH ₄ ) ₂ SO _4, etc.), and NH ₄ ions are added to the ion exchange site of the zeolite After that, it is converted into hydrogen ions by drying and calcination, or directly with an acid-containing compound (for example, HCl, HNO ₃ , H ₃ PO _4, etc.), and hydrogen is added to the ion exchange site of the zeolite. Although there is a method of introducing ions, the latter is preferably subjected to ion exchange treatment with the former, that is, a compound containing ammonium ions, because the latter may destroy the zeolite structure. Alternatively, solid acidity can be imparted to the zeolite by introducing divalent and trivalent metal ions into the zeolite ion exchange site. Examples of the divalent metal ions include alkaline earth metal ions Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , and Ba ²⁺ . Examples of the trivalent metal ions include rare earth metal ions such as Ce ³⁺ and La ³⁺ . It can be used in combination with a method of introducing divalent and / or trivalent metal ions and a method of introducing ammonium ions or direct hydrogen ions, and is sometimes more preferable. The ion exchange treatment is performed by a batch method or a distribution method in which the carrier such as zeolite is treated with a solution containing the above ions, usually an aqueous solution. The treatment temperature is usually from room temperature to 100 ° C.

After the ion exchange treatment in this way, at least one metal selected from Group VII and Group VIII metals is supported as the hydrogenation active metal. By allowing H ₂ to be present in the catalytic reaction system and supporting the hydrogenation active metal, it is possible to prevent deterioration of the catalyst with time. As the hydrogenation active metal, platinum, palladium, rhenium, or the like is preferably used. The preferred loading varies depending on the metal to be loaded. For example, in the case of platinum, it is 0.005 to 0.5% by weight, more preferably 0.01 to 0.3% by weight, based on the whole catalyst. In the case of palladium, 0.05 to 1% by weight is preferably used. In the case of rhenium, the preferred loading is 0.01 to 5.0% by weight, more preferably 0.1 to 2% by weight. When the amount of the hydrogenated metal is increased, the aromatic hydrocarbon is nuclear hydrogenated, which is not preferable. On the other hand, if the amount of hydrogenated metal supported is too small, the hydrogen supply during the deethylation reaction will be insufficient, leading to a decrease in catalytic activity. Therefore, it is necessary to appropriately adjust the metal types and combinations selected, and the supported amounts in accordance with the target performance. These metals are supported by immersing the catalyst in a solution containing at least one of platinum, palladium and rhenium, generally an aqueous solution. Platinum components include chloroplatinic acid and ammonium chloroplatinate, palladium components include palladium acetate, acetylacetone palladium, palladium chloride, palladium nitrate, and rhenium components such as perrhenic acid and perrhenium ammonium. Is done.

  The catalyst thus prepared is dried at 50 to 250 ° C. for 30 minutes or more and calcined at 350 to 600 ° C. for 30 minutes or more before use.

  As the catalyst, one type of catalyst can be used, or two or more types of catalysts can be used in combination.

The catalyst prepared as described above can be carried out according to various conventionally known reaction operations. As the reaction method, any of a fixed bed, moving bed, and fluidized bed method can be used, but the fixed bed reaction method is particularly preferable because of the ease of operation. In these reaction modes, the catalyst is used under the following reaction conditions. That is, the reaction operation temperature is 200 to 500 ° C, preferably 250 to 450 ° C. The reaction operating pressure is from atmospheric pressure to 10 MPa, preferably from 0.3 to 2 MPa. The weight hourly space velocity (WHSV) representing the contact time of the reaction is 0.1 to 50 hr ⁻¹ , preferably 0.5 to 20.0 hr ⁻¹ . The reaction is carried out in the presence of H _{2 and} the molar ratio of H ₂ to feedstock oil is 0.5-10 mol / mol, preferably 1.5-5.0 mol / mol. H ₂ can be present by introducing hydrogen gas into the reaction system. The feedstock oil may be in a liquid phase or a gas phase.

  The ethyltoluene contained in the feedstock oil may be paraethyltoluene, metaethyltoluene, orthoethyltoluene, or an isomer mixture. It is preferred that all of these ethyltoluenes are present in the feedstock in an amount of 1 wt% or more, more preferably 3 wt% or more, more preferably 5 wt% or more. The upper limit is usually preferably 20% by weight or less and more preferably 15% by weight or less. Further, since the C8 aromatic hydrocarbon mixture obtained from naphtha by reforming and fractionation contains ethyltoluene as described above, it may be used as it is. For this reason, it is possible to omit the installation of a distillation column that removes the high-boiling components, which was conventionally required.

  Further, ethyltoluene may be contained in the raw material in a form added to the raw material. When added to the raw material, ethyltoluene alone may be mixed, or may be mixed in the form of a mixture containing this and other C9 to C10 aromatic hydrocarbons and included in the feedstock.

  In the method of the present invention using the above acid type catalyst, ethyltoluene contained in the raw material is removed at a high conversion rate of 50% by weight or more, more preferably 70% by weight or more, and particularly preferably 80% by weight or more. Since ethylation can be performed, a large amount of toluene useful for suppressing xylene loss can be obtained even in a raw material having a low ethyltoluene concentration.

  Furthermore, benzene produced as a by-product by the dealkylation reaction of ethylbenzene is usually purified by distillation separation and extraction separation such as sulfolane process. However, when the above acid type catalyst is used, cyclohexane, methylcyclopentane, normal hexane, etc. Thus, the production of non-aromatic components that have a relatively boiling point close to that of benzene and are difficult to be separated by distillation is small, so that high-purity benzene can be obtained only by distillation separation without the extraction treatment.

  As a formula for estimating the purity of the product benzene obtained by distillation separation from the reaction product liquid composition, for example, the following formula as described in JP-T-2002-504946 has been introduced. The benzene purity in this invention means the benzene purity calculated | required by the purity estimation formula of this product benzene.

Estimated purity of product benzene = ([Benzene concentration] / (a + b + c + d + [Benzene concentration]) x 100 (%))
Here, a to d are defined as follows.
a = 0.1 × [n-C6 paraffin concentration]
b = 0.7 × [methylcyclopentane concentration]
c = 1.0 × [cyclohexane concentration]
d = 1.0 × [C7 naphthene paraffin concentration]

  When rhenium is used as the metal to be included in the acid catalyst, the hydrogenation ability is relatively mild, and the aromatic loss due to nuclear hydrogenolysis is small. The estimated purity of the product benzene defined by the above formula is 99.8% by weight or more, and it is possible to obtain high-purity benzene as a chemical-grade product without further purification such as an extraction process. it can. On the other hand, the toluene obtained from the dealkylation reaction of ethyltoluene is recovered by distillation separation and can be used for effective applications such as gasoline base materials and solvents, or raw materials for the disproportionation process for producing xylene and benzene. .

  Further, in the present invention, by performing the above-described ethylbenzene conversion method using a C8 aromatic hydrocarbon mixed raw material containing ethylbenzene and xylene, not only ethylbenzene is converted into benzene but also xylene can be isomerized (this ethylbenzene). The step of converting benzene into benzene and isomerizing xylene is referred to as “deethylation / xylene isomerization step” or “first deethylation / xylene isomerization step”). Thereby, not only the ethylbenzene conversion rate is high, but also a reaction product with little xylene loss is obtained. Paraxylene can be obtained by separating paraxylene from the reaction product. Separation of para-xylene from the reaction product itself can be performed by a well-known method, for example, a cryogenic separation method using a melting point difference or a zeolite adsorbent using an adsorbent difference. The adsorption separation method can be used.

  Furthermore, in the present invention, raffinate xylene, which is a poor separation residue of para-xylene after separating the para-xylene, may be subjected to xylene isomerization by providing a second xylene isomerization step. There is no particular limitation on the isomerization method performed in the second xylene isomerization step, and it can be performed by a usual method, and the same step as the above-mentioned “deethylation / xylene isomerization step” is performed in the second step. It can also be carried out as a xylene isomerization step. Then, paraxylene can be separated again from the reaction product obtained in the second xylene isomerization step. The second separation residue after the separation of para-xylene may be recycled after being mixed with the C8 aromatic hydrocarbon mixed raw material supplied to the first deethylation / xylene isomerization step again. The isomerization step may be recycled together with the first separation residue to form a “separation-isomerization cycle”.

  In the present invention, a C8 aromatic hydrocarbon mixed raw material containing ethylbenzene and xylene is used, and ethylbenzene is converted into benzene, which is the same step as the first deethylation / xylene isomerization step, and xylene is converted. Para-xylene is separated from the reaction product obtained in the deethylation / xylene isomerization step to be isomerized, and then the separation residue is supplied again to the deethylation / xylene isomerization step to produce para-xylene. can do. This method can also be used in the above-mentioned direct feed method, and the ethyltoluene-containing C8 aromatic hydrocarbon mixed raw material in which the distillation separation treatment of the high boiling point component is omitted is combined with the raffinate xylene after separation of para-xylene. It is mixed and sent to the xylene isomerization step in which the acid catalyst is introduced, ethylbenzene is deethylated at a high conversion rate, and paraxylene can be separated again from the reaction product obtained by isomerizing xylene. That is, when the above acid type catalyst is introduced into the xylene isomerization step, the high boiling point component distillation separation step 14 can be omitted in FIG. 4 showing the concept of a general direct feed method.

  Further, when the first deethylation / xylene isomerization step, para-xylene separation step, and second xylene isomerization step are performed, or when a “separation-isomerization cycle” is further performed, In the para-xylene production apparatus, it is preferable to provide a bypass line that does not pass through the first deethylation / xylene isomerization step, that is, the deethylation / xylene isomerization step bypass line 23 of FIG. .

  This is because when there is an emergency stop due to trouble or the like in the deethylation reaction process, supply of the C8 aromatic hydrocarbon mixed raw material to the “separation-isomerization cycle” via the bypass line By switching, it is not necessary to stop the entire “separation-isomerization cycle” in the subsequent process, and the reduction in production of paraxylene can be minimized. Further, when the above-described deethylation / xylene isomerization step is used as the xylene isomerization step, since the ethylbenzene contained in the C8 aromatic hydrocarbon-containing raw material is also converted at the same time, the first deethylation / xylene Despite skipping the isomerization step, ethylbenzene can be converted at a high conversion rate, and xylene loss can be reduced, so that xylene isomerization can be performed. The influence by not passing through the conversion step can be minimized.

1. Synthesis of pentasil-type zeolite Caustic soda aqueous solution (NaOH content 48.0 wt%, H ₂ O content 52.0 wt%, Toagosei Co., Ltd.) 54.2 grams, tartaric acid powder (tartaric acid content 99.7 wt%, H ₂ O content 0.3 wt%, Kirk Corporation 16.6 grams, dissolved in 698.6 grams of water. To this solution, 9.9 grams of sodium aluminate solution (Al ₂ O ₃ content 13.4 wt%, Na ₂ O content 13.8 wt%, H ₂ O content 43.9 wt%, Sumitomo Chemical Co., Ltd.) was added to obtain a uniform solution. While stirring 111.5 grams of hydrous silicic acid (SiO ₂ content 89.4 wt%, Al ₂ O ₃ content 2.4 wt%, Na ₂ O content 1.6 wt%, NIPSEAL VN-3, Nippon Silica Kogyo Co., Ltd.) In addition, a homogeneous slurry aqueous reaction mixture was prepared. The composition ratio (molar ratio) of this reaction mixture was as follows.

SiO ₂ / Al ₂ O ₃ : 77
OH ^- / SiO _2: 0.3002
A / Al ₂ O ₃ : 5.14 (A: Tartrate)
H ₂ O / SiO ₂ : 25

  The reaction mixture was sealed in a 1000 ml autoclave and then reacted at 160 ° C. for 72 hours with stirring at 250 rpm. After completion of the reaction, washing with distilled water 5 times and filtration were repeated, followed by drying at about 120 ° C. overnight.

  As a result of measuring the obtained product with an X-ray diffractometer using Cu tube and Kα ray, it was found that the obtained zeolite was a pentasil-type zeolite.

  The silica / alumina molar ratio of this pentasil-type zeolite was 49.0 as a result of fluorescent X-ray diffraction analysis.

2. Catalyst production
(1) Production of catalyst A (use of catalyst A is outside the scope of the present invention)
10 grams of pentasil-type zeolite synthesized as described above (calculated from loss of ignition when calcined at 500 ° C. for 20 minutes), hydrous alumina having a pseudo boehmite structure (manufactured by Sumitomo Chemical Co., Ltd.) 30 grams on an absolute dry basis and 60 grams of alumina sol (Al ₂ O ₃ content 10% by weight, manufactured by Nissan Chemical Industries, Ltd.) were added and mixed well. Then, it put into the 120 degreeC dryer and dried until it became clay-like water | moisture content. The kneaded product was extruded through a screen having a 1.2 mmφ hole. The extrudate was dried overnight at 120 ° C., then gradually heated from 350 ° C. to 540 ° C. and calcined at 540 ° C. for 2 hours. 20 grams of this pentasil-type zeolite compact is put into an aqueous solution in which 11 parts by weight of NH ₄ Cl and 5 parts by weight of CaCl ₂ are dissolved per 100 parts by weight of the absolute dry basis of the molded part, and the solid-liquid ratio is 2.0 kg / L in pure water. And contacted for 1 hour at a temperature of 80 ° C. Then, it wash | cleaned with the pure water and washed with the pure water 6 times in batch. The ion-exchanged pentasil-type zeolite molding was dried at 120 ° C. overnight. Prior to the use of the catalytic reaction, a sulfidation treatment was carried out at 250 ° C. for 2 hours in a hydrogen sulfide gas stream, and calcined in the atmosphere at 540 ° C. for 2 hours to obtain Catalyst A.

(2) Production of catalyst B As in the production of catalyst A, a molded body containing pentasil (MFI) type zeolite was prepared, and ammonium ions and calcium ions were exchanged. Twenty grams of the dried product of this ion-exchanged pentasil-type zeolite was immersed in 40 ml of a perrhenic acid aqueous solution containing 80 milligrams of Re at room temperature and left for 2 hours. Stir every 30 minutes. Thereafter, the liquid was drained and dried at 120 ° C. overnight. Prior to the use of the catalytic reaction, sulfiding treatment was performed in a hydrogen sulfide stream at 250 ° C. for 2 hours, and calcination was performed in the atmosphere at 540 ° C. for 2 hours to obtain Catalyst B. As a result of analyzing the Re supported on the catalyst B by ICP emission analysis, the rhenium supported on the catalyst B was 2010 ppm by weight as Re.

Example 1, Comparative Example 1
Each of the catalysts A and B was filled in a reaction tube and subjected to a reaction test. The composition of the four feedstocks used is shown in Table 1 below. In addition, the composition analysis of the feedstock and the reaction product used three gas chromatographs with a hydrogen flame detector. The separation column is as follows.

(1) Gas components (components from methane to n-butane in the gas):
Filler: "Unipak S"("UnipakS") 100-150 mesh,
Column: Stainless steel 4m long, 3mm inside diameter
N ₂ : 1.65kg / cm ² -G
Temperature: 80 ℃

(2) Component having boiling point around benzene in liquid component (from methane dissolved in liquid to n
-Butane and liquid component 2-methyl-butane to benzene component):
Filler 25% polyethylene glycol 20M / carrier "Simalite" 60-80 mesh,
Column: Stainless steel 12m long, 3mm inside diameter
N ₂ : 2.25kg / cm ² -G
Temperature: The temperature was increased from 68 ° C. to 180 ° C. at a rate of 2 ° C./min.

(3) Components with boiling points higher than liquid components benzene (from benzene to heavy-end components):
Spellco wax fused silica capillary; length 60m, inner diameter 0.32mmφ, film thickness 0.5μm
He linear velocity: 23 cm / second temperature; from 67 ° C. to 1 ° C./min, and from 80 ° C. to 2 ° C./min.

  EB represents ethylbenzene, PX represents paraxylene, MX represents metaxylene, OX represents orthoxylene, and ET represents ethyltoluene. C9 + represents a compound having C9 or more carbon atoms. The raw materials A to D are assumed to be a raw material to be put into a deethylation step to be attached before the “separation-isomerization” cycle, and the raw material E is an ethyl toluene and a compound having a carbon number of C9 or more in the direct feed method. The C8 aromatic hydrocarbon mixed raw material to be included is assumed.

  About the said raw material oil, the catalyst A or B was filled in the reaction tube 7.5g, and it was made to react on the following conditions.

Reaction conditions
WHSV (hr ^-1 ): 4.2
Reaction temperature (° C): 405
Reaction pressure (MPa): 0.9
H _{2 /} Feed (mol / mol): 3.5

  Table 2 shows the test results.

  From the results of Example 1, it can be seen that the yield of xylene is improved by treating a raw material containing ethyltoluene using an acid-type zeolite catalyst supporting rhenium, which is a hydrogenation active metal. This is considered to produce toluene by dealkylation of ethyltoluene and to suppress the progress of the transalkylation reaction of xylene and benzene (generated by deethylation of ethylbenzene), which is a side reaction of xylene loss. Furthermore, when ET is added to the raw material by 1% and the yield is improved by 0.2% (comparison between Comparative Example 1-B and Example 1-C), it is generally a large amount of raw material of several tens tons or more per hour. In the industrial production of processing, this yield improvement will have a tremendous economic effect. Further, the reaction product obtained in Example 1 has a low ethylbenzene concentration and a high paraxylene concentration, and the paraxylene production in the “separation-isomerization” cycle, in particular, the paraxylene separation step uses a zeolite-based adsorbent. It can be seen that it is very advantageous in carrying out the adsorption separation used.

  From the results of Comparative Example 1-A, it can be seen that the deethylation activity of ethylbenzene and ethyltoluene is low in the catalyst (catalyst A) that does not support the hydrogenation active metal.

Example 2
In the same manner as in the preparation of Catalyst B, 20 grams of a dried product of a pentasil-type zeolite exchanged with ammonium and calcium was immersed in 40 ml of a chloroplatinic acid aqueous solution containing 4 milligrams of Pt at room temperature and left for 2 hours. Stir every 30 minutes. Thereafter, the liquid was drained and dried at 120 ° C. overnight. Prior to the use of the catalytic reaction, sulfiding treatment was performed in a hydrogen sulfide stream at 250 ° C. for 2 hours, and calcination was performed in the atmosphere at 540 ° C. for 2 hours to obtain Catalyst C. As a result of analysis of Pt supported on the catalyst C by ICP emission spectroscopic analysis, platinum supported on the catalyst C was 169 ppm by weight as Pt.

  About the said raw material oil D, the catalyst C was filled with 7.5g and it was made to react on the same conditions as Example 1. FIG. The results are shown in Table 3 below.

Example 3
Twenty grams of a dried product of pentasil-type zeolite exchanged with ammonium and calcium prepared in the same manner as Catalyst B was immersed in 40 ml of an aqueous palladium chloride solution containing 40 milligrams of Pd at room temperature and left for 2 hours. Stir every 30 minutes. Thereafter, the liquid was drained and dried at 120 ° C. overnight. Prior to the use of the catalytic reaction, a sulfiding treatment was performed at 250 ° C. for 2 hours in a hydrogen sulfide gas stream, followed by calcination in the atmosphere at 540 ° C. for 2 hours to obtain Catalyst D. As a result of analyzing the Pd supported on the catalyst D by ICP emission spectroscopic analysis, palladium supported on the catalyst D was 1480 ppm by weight as Pd.

  About the said raw material oil D, 7.5g of catalyst D was filled into the reaction tube, and it was made to react on the same conditions as Example 1. FIG. The results are shown in Table 3 below.

Example 4
Twenty grams of a dried product of pentasil-type zeolite exchanged with ammonium and calcium exchange prepared in the same manner as Catalyst B was immersed in 40 ml of an aqueous nickel nitrate solution containing 40 milligrams of Ni at room temperature and left for 2 hours. Stir every 30 minutes. Thereafter, the liquid was drained and dried at 120 ° C. overnight. Prior to the use of the catalytic reaction, a sulfidation treatment was performed at 250 ° C. for 2 hours in a hydrogen sulfide gas stream, and calcined in the atmosphere at 540 ° C. for 2 hours to obtain Catalyst E. As a result of analyzing Pd supported on the catalyst E by ICP emission spectroscopic analysis, it was 1680 ppm by weight as Ni supported on the catalyst E.

  About the above raw material oil D, 7.5 g of catalyst E was charged in a reaction tube and reacted under the same conditions as in Example 1. The results are shown in Table 3 below.

Example 5
In the same manner as in the production of catalyst B, 20 grams of a dried product of a pentasil-type zeolite exchanged with ammonium and calcium was immersed in 40 ml of an aqueous rhenium oxide solution containing 200 milligrams of Re at room temperature and left for 2 hours. Stir every 30 minutes. Thereafter, the liquid was drained and dried at 120 ° C. overnight. Prior to the use of the catalytic reaction, sulfidation was performed in a hydrogen sulfide stream at 250 ° C. for 2 hours, and calcination was performed in the atmosphere at 540 ° C. for 2 hours to obtain Catalyst F. As a result of analyzing the Re supported on the catalyst F by ICP emission spectroscopic analysis, the rhenium supported on the catalyst F was 4800 ppm by weight as Re.

  About the said raw material oil E, the catalyst B and F were filled with 7.5g to the reaction tube, and it was made to react on the following conditions. The results are shown in Table 4 below.

Reaction conditions
WHSV (hr ^-1 ): 5.3
Reaction temperature (° C): 390
Reaction pressure (MPa): 0.9
_{H 2 / Feed (mol / mol} ): 2.5

  From Table 4, it can be seen that as the amount of rhenium supported increases, the xylene recovery rate improves. The raw material E is a raw material assuming a case where C9 + removal is omitted in the direct feed method, but it is understood that the raw material E is also effective in the direct feed method.

Example 6
About the catalyst B and the catalyst D of Example 3, the density | concentration was measured by the method (analysis conditions as described in (2) in the sentence of Example 1) of the non-aromatics density | concentration in the reaction liquid. It was measured. As a result, as shown in Table 5 below, the concentrations of cyclohexane and methylcyclopentane, which are contaminant impurities having a boiling point close to that of benzene, are lower when the catalyst B of Example 1 is used and are calculated using the following benzene purity estimation formula. The estimated purity of the product benzene (benzene purity) is as high as 99.8% by weight or more in the examples.

Estimated purity of product benzene = ([Benzene concentration] / (a + b + c + d + [Benzene concentration]) x 100 (%))
Here, a to d are defined as follows.
a = 0.1 × [n-C6 paraffin concentration]
b = 0.7 × [methylcyclopentane concentration]
c = 1.0 × [cyclohexane concentration]
d = 1.0 × [C7 naphthene paraffin concentration]

In the paraxylene production apparatus for performing the first deethylation / xylene isomerization step, the paraxylene separation step, and the second xylene isomerization step, a bypass line that does not pass through the first deethylation / xylene isomerization step It is a conceptual diagram which shows the flow at the time of providing. It is a conceptual diagram which shows the flow of the "separation-isomerization cycle" for general paraxylene manufacture which does not introduce | transduce a deethylation process. It is a conceptual diagram which shows the flow of the "separation-isomerization cycle" for the general paraxylene manufacture which introduce | transduced the deethylation process. General direct feed process flow characterized by mixing fresh raw material with raffinate xylene without introducing a deethylation process and sending it to a xylene isomerization process that has a function of highly ethylating ethylbenzene. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 High boiling component distillation separation process 2 Paraxylene separation process 3 Xylene isomerization process 4 Low boiling component distillation separation process 5 Stream 6 Stream 7 Stream 8 Stream 9 Stream 10 Stream 11 Stream 12 Stream 13 Stream 14 High boiling component distillation separation process 15 Deethylation / xylene isomerization process 16 Low boiling point component distillation separation process 17 Stream 18 Stream 19 Stream 20 Stream 21 Stream 22 Stream 23 Deethylation / xylene isomerization process bypass line

Claims (17)

C8 aromatic hydrocarbon mixed raw material containing ethylbenzene is brought into contact with an acid catalyst containing at least one metal selected from Group VII and Group VIII metals in the presence of H ₂ to convert ethylbenzene into benzene. A method for converting ethylbenzene, wherein the raw material contains a C9 to C10 aromatic hydrocarbon containing ethyltoluene, and the ethyltoluene is converted to toluene together with the conversion of the ethylbenzene.   The method according to claim 1, wherein the concentration of ethyltoluene in the raw material is 1% by weight or more.   The method according to claim 2, wherein the concentration of ethyltoluene in the raw material is 3% by weight or more.   The method according to claim 3, wherein the concentration of ethyltoluene in the raw material is 5% by weight or more.   The method according to any one of claims 1 to 4, wherein ethyltoluene in the raw material is converted at a conversion rate of 50% by weight or more.   The method according to any one of claims 1 to 5, wherein the acid-type catalyst contains at least one metal selected from the group consisting of platinum, palladium and rhenium.   The method according to claim 6, wherein the acid-type catalyst contains rhenium.   The process according to claim 7, wherein the rhenium content in the acid type catalyst is 0.01 wt% to 5 wt%.   The process according to claim 8, wherein the rhenium content in the acid type catalyst is 0.1 wt% to 2 wt%.   The method according to any one of claims 1 to 9, further comprising recovering benzene having a purity of 99.8% by weight or more by separating benzene produced by the reaction by distillation.   The method according to any one of claims 1 to 10, wherein the acid type catalyst is a pentasil type zeolite having a silica / alumina molar ratio of 10 to 70.   A step of subjecting a C8 aromatic hydrocarbon mixed raw material containing ethylbenzene and xylene to the method according to any one of claims 1 to 11 to convert ethylbenzene into benzene and isomerize xylene, and the reaction obtained A method for producing para-xylene, comprising a step of separating para-xylene from a product.   A C8 aromatic hydrocarbon mixed raw material containing ethylbenzene and xylene is subjected to the method according to claim 12 to convert ethylbenzene into benzene and isomerize xylene, and a first deethylation / xylene isomerization step, A step of separating para-xylene from the reaction product obtained in the first deethylation / xylene isomerization step, and xylene contained in the separation residue of the separation step are subjected to a second xylene isomerization step. A method for producing paraxylene, comprising a step of performing isomerization and a step of separating paraxylene again from the reaction product of the second xylene isomerization step. The second xylene isomerization step includes contacting the separation residue with an acid-type catalyst containing at least one metal selected from Group VII and Group VIII metals in the presence of H _2. Item 14. The method according to Item 13.   A C8 aromatic hydrocarbon mixed raw material containing ethylbenzene and xylene is subjected to the method according to claim 12 to convert ethylbenzene into benzene and isomerize xylene, and the deethylation / xylene isomerization step; Production of para-xylene, comprising a step of separating para-xylene from the reaction product obtained in the xylene isomerization step, and a step of supplying the separation residue of the separation step again to the deethylation / xylene isomerization step. Method.   The method according to claim 15, further comprising the step of mixing the separation residue with the C8 aromatic hydrocarbon mixed raw material and supplying the mixed residue again to the deethylation / xylene isomerization step.   A method for producing paraxylene using a paraxylene production apparatus for performing the first deethylation / xylene isomerization step, the paraxylene separation step, and the second xylene isomerization step according to claim 13 or 14. The apparatus comprises a bypass line that does not pass through the first deethylation / xylene isomerization step, and the C8 aromatic hydrocarbon mixed raw material in which C9 to C10 aromatic hydrocarbons containing ethyltoluene are mixed, A method for producing paraxylene, comprising supplying to the paraxylene separation step as necessary.

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