JP2017524772A - Method for producing BTX and LPG - Google Patents

Abstract

The present invention is a method for producing BTX and LPG comprising the steps of: a) contacting a feed stream comprising C5 to C12 hydrocarbons with a hydrocracking catalyst in the presence of hydrogen in a hydrocracking reactor, Producing a hydrocracked product stream comprising methane, LPG and BTX, b) separating the hydrocracked product stream into a first gas stream and a first liquid stream, c) the first gas Separating the stream to obtain a second gas stream comprising hydrogen and methane and a second liquid stream comprising LPG and BTX, wherein the second liquid stream substantially removes hydrogen and methane. And d) separating the second liquid stream into a third gas stream containing LPG and a third liquid stream containing BTX. c) a portion of the third liquid stream is part of the first gas stream; Adding and absorbing LPG in the first gas stream to obtain a second liquid stream, or a part of the third liquid stream into a gas stream separated from the first gas stream And adding to absorb LPG in the gas stream separated from the first gas stream to obtain a second liquid stream.

Description

  The present invention relates to a method for producing BTX and LPG.

  Aromatic hydrocarbons have a wide variety of uses in the petrochemical and chemical industries. Aromatic compounds are important for many intermediates in commodity petrochemicals and expensive refined chemicals such as polyesters, monomers for engineering plastics, detergents, pharmaceuticals, agricultural products and explosives intermediates It is a raw material. Among them, benzene, toluene and xylene (BTX) are the three basic materials of most intermediates of aromatic derivatives.

  About 70% of the world production of BTX comes from extraction from either reformed gasoline or cracked gasoline (pigas). Reformed gasoline is formed in the catalytic reforming of naphtha, which is a technology mainly aimed at producing gasoline components having a high octane number. Pygas is a liquid byproduct formed in the production of olefins by hydrocracking a liquid feed such as naphtha or light oil. Extraction from reformed gasoline and pie gas is the most economical source of BTX. The composition of BTX depends on its source. Pygas is typically rich in benzene, whereas the major components of reformate gasoline are xylene and toluene. In addition to BTX, LPG is produced during extraction from reformed gasoline or pie gas.

  Patent Document 1 discloses a method for producing BTX from a C5 to C12 hydrocarbon mixture using a hydrocracking / hydrodesulfurization catalyst. According to Patent Document 1, a mixture substantially free of BTX azeotrope is obtained by the method, and therefore chemical BTX can be easily obtained.

  The product stream obtained by the method of Patent Document 1 contains BTX and LPG, methane and unreacted hydrogen. The product stream is separated into methane and unreacted hydrogen as the first separated stream, LPG as the second separated stream, and BTX as the third separated stream.

BTX is separated from the hydrocracked product stream by gas-liquid separation or distillation. A series of distillation steps may be applied. The first distillation step at moderate temperature is to separate most of the aromatic species (liquid product) from the various hydrogen, H ₂ S, methane and LPG. The gas stream from this distillation is further cooled (to about −30 ° C.) and distilled again to separate the remaining aromatic species and most of the propane and butane.

The gaseous product (mainly hydrogen, H ₂ S, methane and ethane) is then further cooled (to −100 ° C.) to separate the ethane and hydrogen, into the gas stream that is recycled to the reactor. Leave H ₂ S and methane. The gaseous product in which this cryogenic cooling takes place must be substantially free of BTX in order to avoid solidification of BTX that would block the system. This separation process requires cryogenic cooling using special equipment, which consumes a large amount of energy.

International Publication No. 2013/182534

  An object of the present invention is to provide a method for producing BTX and LPG by hydrocracking, which consumes less energy.

This task is a method for producing BTX and LPG,
(A) In a hydrocracking reactor, a feed stream containing C5-C12 hydrocarbons is contacted with a hydrocracking catalyst in the presence of hydrogen to produce a hydrocracked product stream containing hydrogen, methane, LPG and BTX. Generating step,
(B) separating the hydrocracked product stream into a first gas stream and a first liquid stream;
(C) separating the first gas stream to obtain a second gas stream containing hydrogen and methane and a second liquid stream containing LPG and BTX, the second liquid stream (D) separating the second liquid stream into a third gas stream containing LPG and a third liquid stream containing BTX. Process,
Having
Step (c)
Adding a portion of the third liquid stream to the first gas stream to absorb LPG in the first gas stream to obtain a second liquid stream;
Or adding a portion of the third liquid stream to the gas stream separated from the first gas stream to absorb LPG in the gas stream separated from the first gas stream, A method is provided that includes obtaining a liquid stream.

  In the method of the present invention, the hydrocracked product stream obtained by step (a) is separated into a first gas stream and a first liquid stream in step (b). The first gas stream includes hydrogen, methane and LPG. The first liquid stream includes BTX. In step (c), LPG is removed from the first gas stream. This removal of LPG from the first gas stream is performed using the BTX produced by the hydrocracking step (a). As a result of step (c), a second liquid stream is formed that includes LPG from the first gas stream and BTX added to the first gas stream. Residual hydrogen and methane from the first gas stream form a second gas stream.

  BTX used in the separation step (c) is obtained by the following separation step (d). In this step (d), LPG and BTX in the second liquid stream are separated from each other as a third gas stream and a third liquid stream. Part of the resulting BTX is fed back to the separation unit used in step (c).

  The separation of step (c) is performed so that the second liquid stream is substantially free of hydrogen and methane. Preferably this second liquid stream consists essentially of LPG and BTX. Thereby, in the next step (d), the second liquid flow can be easily separated into the third gas flow (LPG) and the third liquid flow (BTX). Separation in the step (d) can be easily performed by gas-liquid separation because of the large difference in boiling point between C4 hydrocarbon and benzene. LPG as the desired product is thereby obtained directly. “The second liquid stream is substantially free of hydrogen and methane” means that the total amount of hydrogen and methane in the second liquid stream is less than 1% by weight, preferably less than 0.7% by weight, more preferably Is understood here to mean less than 0.6% by weight, most preferably less than 0.5% by weight.

  It is preferred that the second gas stream primarily comprises hydrogen and methane, i.e., the majority of the heavier hydrocarbons in the first gas stream go to the second liquid stream. The total amount of hydrogen and methane in the second gas stream is at least 60%, preferably at least 65%, more preferably at least 70%, more preferably at least 80%, more preferably at least 90%, More preferably it is at least 95% by weight, more preferably at least 98% by weight. Most preferably, the second gas stream consists essentially of hydrogen and methane, i.e. all of the heavier hydrocarbons in the first gas stream proceed to the second liquid stream. “The second gas stream consists essentially of hydrogen and methane” means that the total amount of hydrogen and methane in the second gas stream is at least 99% by weight, preferably at least 99.3% by weight, more preferably It is understood here to mean at least 99.4% by weight, most preferably at least 99.5% by weight.

  It is preferred that the third gas stream mainly contains LPG. The total amount of LPG in the third gas stream is at least 80 wt%, preferably at least 85 wt%, more preferably at least 90 wt%, more preferably at least 95 wt%, more preferably at least 98 wt%. preferable. Most preferably, the third gas stream consists essentially of LPG. “The third gas stream consists essentially of LPG” means that the amount of LPG in the third gas stream is at least 99% by weight, preferably at least 99.3% by weight, more preferably at least 99.4%. It is understood here to mean that by weight, most preferably at least 99.5% by weight. “The third liquid stream consists essentially of BTX” means that the amount of BTX in the third liquid stream is at least 99% by weight, preferably at least 99.3% by weight, more preferably at least 99.4%. It is understood here to mean that by weight, most preferably at least 99.5% by weight.

In step (b), gas-liquid separation is performed on the hydrocracked product stream. In some cases, the majority of BTX will go to the liquid phase (first liquid stream). However, after a single separation, the gas phase may still contain a significant amount of BTX (especially benzene). In this case, it is preferable to further perform one or more gas-liquid separations in the gas phase until the gas phase contains only a part of BTX. These two cases relate to the two options in step (c):
I) adding a portion of the third liquid stream to the first gas stream to absorb LPG in the first gas stream to obtain a second liquid stream, or II) a third A portion of the liquid stream is added to the gas stream separated from the first gas stream to absorb LPG in the gas stream separated from the first gas stream to obtain a second liquid stream Process.

  As described above, gas-liquid separation of the hydrocracked product stream may be performed such that the first gas stream contains only a portion of BTX. In this case, option I) is preferred for step (c). In option I), the hydrocracked product stream is separated into a first gas stream and a first liquid stream, after which the first gas stream is recycled to the third liquid without further separation. Mixed directly with the stream. This recirculated third liquid stream that has absorbed the LPG in the first gas stream is referred to as the second liquid stream.

  As described above, gas-liquid separation of the hydrocracked product stream may be performed such that the first gas stream contains a majority of BTX. In this case, option II) is preferred for step (c). In option II), the third liquid stream is added after the first gas stream is further separated. In other words, the hydrocracked product stream is separated into a first gas stream and a first liquid stream, after which the first gas stream is separated into yet another gas stream and yet another liquid stream. This further gas stream obtained from the first gas stream is mixed with the recirculated third liquid stream. This recirculated third liquid stream that has absorbed LPG in the gas stream obtained from the first gas stream is referred to as the second liquid stream.

  It is an advantage of the method of the present invention that cryogenic cooling is not required for LPG and methane / hydrogen separation. Instead of cryogenic cooling to separate methane and C2 hydrocarbons, C2 hydrocarbons are absorbed by the added BTX and separated from methane.

  It is yet another advantage of the method of the present invention that no additional solvent is required for the separation because the BTX produced by the method of the present invention is used for the separation.

According to the invention, BTX in liquid form is used to absorb LPG present in the first gas stream. Due to the high affinity between BTX and LPG, LPG present in the first gas stream is absorbed by BTX. Due to the very low affinity between BTX and H ₂ or C1, hydrogen and methane are not absorbed by BTX and therefore remain as a gas stream.

  It should be noted that US Pat. No. 4,212,726 discloses a method for recovering hydrogen gas of increased purity from the effluent of a hydroprocessing process. This process involves the production of a relatively pure stream of hydrogen from the gas phase by gas-liquid separation of the effluent and the use of two absorber liquids.

In U.S. Pat. No. 4,212,726, the absorber liquid consists of a liquid phase hydrocarbon stream obtained from the first gas-liquid separation and a heavier stabilized modified hydrocarbon. Since the purpose of the method of US Pat. No. 4,212,726 is to obtain pure H ₂ , methane in the gas phase is absorbed by the absorber liquid. This is done in US Pat. No. 4,212,726 by the use of a relatively broad range of hydrocarbons as the absorbing liquid, unlike the process of the present invention where substantially only BTX is used as the absorbing liquid. Further, in US Pat. No. 4,212,726, the stream obtained by absorption is separated into a C1-C4 gaseous hydrocarbon fraction stream and a C5 + hydrocarbon fraction stream. Unlike the process of the present invention, the gaseous hydrocarbon fraction needs to be further separated to obtain the desired product consisting mainly of C3 and C4.

  US Pat. No. 7,563,307 describes a process for separating a hydrocarbon gas stream, such as natural gas, by contacting the gas stream with a circulating solvent comprising an internal solvent contained in a feed gas. Note that it is disclosed. In the process, the gas stream is contacted with a solvent in an extraction device to produce a top stream rich in non-absorbing components and a solvent-rich bottom stream rich in absorbing components. Next, the bottom stream of the rich solvent is rapidly vaporized under reduced pressure to regenerate the dilute solvent and recover the absorbing component as a top stream. The regenerated solvent is recycled to the extraction device. A portion of the recycle solvent includes an external solvent added to the system. The second part of the recycle solvent contains the internal solvent contained in the feed gas. US Pat. No. 7,563,307 does not disclose a process for separating the hydrocracked product stream. US Pat. No. 7,563,307 also does not disclose the use of only an internal solvent for recycling. US Pat. No. 7,563,307 also does not disclose the use of a BTX stream to absorb LPG for separation from methane and hydrogen.

  As used herein, the term “C # hydrocarbon” where “#” is a positive integer is meant to represent all hydrocarbons having # carbon atoms. Furthermore, the term “C # + hydrocarbon” is meant to represent all hydrocarbon molecules having # or more carbon atoms. Thus, the term “C5 + hydrocarbon” is meant to represent a mixture of hydrocarbons having 5 or more carbon atoms.

  As used herein, the term “LPG” is an established acronym for the term “liquefied petroleum gas”. LPG generally consists of a blend of C2-C4 hydrocarbons, ie a mixture of C2, C3 and C4 hydrocarbons.

  As used herein, the term “BTX” is well known in the art and relates to a mixture of benzene, toluene and xylene.

  The term “aromatic hydrocarbon” is very well known in the art. Thus, the term “aromatic hydrocarbon” relates to a cyclic conjugated hydrocarbon having a stability (due to delocalization) that is significantly greater than the stability of the virtual localization structure (eg, Keklet structure). The most common method for determining the aromaticity of a given hydrocarbon is a diatropicity in the 1H NMR spectrum, for example a chemical shift in the range of 7.2 to 7.3 ppm for protons in the benzene ring. Is the observation of the existence of

Step (a)
The process according to the invention comprises the step of (a) contacting a feed stream comprising C5 to C12 hydrocarbons with a hydrocracking catalyst in the presence of hydrogen in a hydrocracking reactor. Step (a) may be performed in one hydrocracking reactor or in a plurality of hydrocracking reactors. Step (a) is preferably carried out in at least two hydrocracking reactors arranged in series.

Feed stream The feed stream used in the process of the present invention is a mixture comprising C5-C12 hydrocarbons. This source feed stream preferably comprises at least 40% by weight, more preferably at least 45% by weight, and most preferably at least 50% by weight C5 to C12 hydrocarbons. It is preferred that the feed stream mainly comprises C6-C8 hydrocarbons. The boiling point of this feed stream is preferably in the range of 30 to 195 ° C. Suitable feed streams include, but are not limited to, (thermal) cracked gasoline, straight run naphtha, hydrocracked gasoline, light coker naphtha and coke oven gas oil, FCC gasoline, reformate or mixture thereof. The feed stream may have a relatively high sulfur content, such as cracked gasoline (pigas), straight run naphtha, light coker naphtha and coke oven gas oil and mixtures thereof. Furthermore, it is preferred that non-aromatic species contained in the hydrocarbon feed are saturated (eg, by prior hydrogenation) to reduce the exotherm in the catalyst bed used in the process of the present invention.

  For example, a typical composition of cracked gasoline is 10-15 wt% C5 olefin, 2-4 wt% C5 paraffin and cycloparaffin, 3-6 wt% C6 olefin, 1-3 wt% C6 paraffin and Naphthene, 25-30 wt% benzene, 15-20 wt% toluene, 2-5 wt% ethylbenzene, 3-6 wt% xylene, 1-3 wt% trimethylbenzene, 4-8 wt% di Cyclopentadiene and 10-15 wt% C9 + aromatics, alkyl styrene and indene; for example, Applied Heterogeneous Catalysis: Design, Manufacture, and Use of Solid Catalysts (1987) Table E3 from JF Le Page See .1. However, hydrocarbon mixtures that have been depentanized and adjusted so that all concentrations of C6 to C9 hydrocarbon species are relatively high compared to the previous typical values are also convenient as feed streams in the process of the present invention. Can be used.

  In some embodiments, the feed stream used in the method of the invention is treated to be rich in monocyclic aromatic compounds. As used herein, the term “monocyclic aromatic compound” relates to a hydrocarbon compound having only one aromatic ring. Means and methods suitable for increasing the content of monocyclic aromatics in a mixed hydrocarbon stream, such as the Maxene process, are well known in the art; Bhirud (2002) Proceedings of the DGMK-conference 115 See -122. The feed stream used in the process of the present invention may contain up to 300 ppm by weight of sulfur (ie, the mass of sulfur atoms present in any compound relative to the total mass of the feed).

  In a preferred embodiment, the feed stream is depentanized. This means that the feed stream is substantially free of C5 hydrocarbons. As intended herein, the term “feed stream substantially free of C5 hydrocarbons” means that the feed stream contains less than 1% by weight of C5 hydrocarbons, preferably 0.7% by weight of C5 hydrocarbons. Means less than%, more preferably less than 0.6% by weight of C5 hydrocarbons, most preferably less than 0.5% by weight of C5 hydrocarbons.

  The feed stream can be hydrodesulfurized before hydrocracking.

A feed stream comprising hydrocracking catalyst C5-C12 hydrocarbon is contacted with the hydrocracking catalyst in the presence of hydrogen.

  In a preferred embodiment, the hydrocracking catalyst further has hydrodesulfurization activity. This is advantageous in that there is no need to desulfurize the hydrocarbon feed stream prior to hydrocracking the hydrocarbon feed stream.

  Catalysts having hydrocracking / hydrodesulfurization activity ("hydrocracking / hydrodesulfurization catalyst") are described in Hydrocracking Science and Technology (1996) Ed. Julius Scherzer, AJ Gruia, Pub. Taylor and Francis 13-14 and 17 pages. Hydrocracking and hydrodesulfurization reactions are relatively strong acid functions (which decompose and isomerize and break sulfur-carbon bonds in organic sulfur compounds in the feed) and metal functions ( It proceeds by a bifunctional mechanism that requires hydrogenation of olefins to form hydrogen sulfide). Many catalysts used in hydrocracking / hydrodesulphurization processes are formed by blending various transition metals with solid supports such as alumina, silica, alumina-silica, magnesia and zeolite.

In a preferred embodiment of the present invention, the catalyst, relative to the weight of the total catalyst, 0.01 wt% of the hydrogenation metal, and the pore diameter and 5-200 of silica 5~8Å (SiO ₂₎ pairs A hydrocracking catalyst comprising a zeolite having an alumina (Al ₂ O ₃ ) molar ratio, the process conditions being a temperature of 425-580 ° C., a gauge pressure of 300-5000 kPa and a weight of 0.1-15 h ⁻¹ Includes space velocity.

  In these embodiments, because of the catalyst and conditions used, it is advantageous that the resulting hydrocracked product stream is substantially free of non-aromatic C6 + hydrocarbons. Therefore, chemical BTX can be easily separated from the hydrocracked product stream.

The advantageous effects of these embodiments are obtained by strategic selection of hydrocracking catalysts in combination with hydrocracking conditions. The hydrocracking is performed under process conditions including a temperature of 425-580 ° C., a gauge pressure of 300-5000 kPa and a weight space velocity of 0.1-15 h ⁻¹ . Relatively strong acid function (for example, by selecting a catalyst comprising a zeolite having a pore size and 5-200 of silica 5~8Å (SiO ₂₎ pairs alumina (Al ₂ O ₃₎ molar ratio), and relatively A hydrocracking catalyst having strong hydrogenation activity (eg, by selecting a catalyst containing 0.01 to 1% by weight of metal hydride) is treated with process conditions having a relatively high process temperature (eg, 425- In combination with (by selecting a temperature of 580 ° C.), chemical BTX and LPG can be produced from the hydrocracked product stream.

  The hydrocracking of the feed stream is preferably at a gauge pressure of 300 to 5000 kPa, more preferably at a gauge pressure of 600 to 3000 kPa, particularly preferably at a gauge pressure of 1000 to 2000 kPa, most preferably a gauge. The pressure is 1200 to 1600 kPa. Increasing the reactor pressure can increase the conversion of C5 + non-aromatic compounds, but yields methane and hydrogenation of aromatic rings to cyclohexane species (which can be decomposed into LPG species). Will also increase. This reduces the yield of aromatics as pressure increases, and the resulting benzene at pressures of 1200-1600 kPa, as some cyclohexane and its isomer methylcyclopentane are not fully hydrocracked. The purity of is optimal.

Hydrocracking / hydrodesulphurisation of the feed stream is preferably a weight hourly space velocity of 0.1~15h ^-1 (WHSV), more preferably the weight hourly space velocity of 0.1 to 10 ^-1, and most preferably 2~9h ^{Done at} a weight space velocity of ^-1 . If the space velocity is too high, not all of the azeotropic paraffin component of BTX will be hydrocracked, and therefore the BTX specification cannot be achieved by simple distillation of the reactor product. Too low space velocities increase methane yield at the expense of propane and butane. By selecting the optimal weight space velocity, it has been surprisingly found that a sufficiently complete reaction of the benzene azeotrope takes place to produce BTX that meets specifications without the need for liquid recirculation. .

Thus, such preferred hydrocracking conditions include a temperature of 425-580 ° C., a gauge pressure of 300-5000 kPa and a weight space velocity of 0.1-15 h ⁻¹ . More preferred hydrocracking conditions include a temperature of 450-550 ° C., a pressure of 600-3000 kPa at gauge pressure and a weight space velocity of 0.1-10 h ⁻¹ . Particularly preferred hydrocracking conditions include a temperature of 450-550 ° C., a gauge pressure of 1000-2000 kPa and a weight space velocity of 2-9 h ⁻¹ .

  A particularly suitable hydrocracking catalyst for the process of the invention comprises a molecular sieve, preferably a zeolite, having a pore size of 5 to 8 mm.

Zeolite is a well-known molecular sieve having a specific pore size. As used herein, the term “zeolite” or “aluminosilicate zeolite” relates to an aluminosilicate molecular sieve. An overview of their features can be found, for example, in the chapter on Molecular Sieves in Kirk-Othmer Encyclopedia of Chemical Technology, Vol. 16, pages 811-853; in Atlas of Zeolite Framework Types, 5th edition, (Elsevier, 2001) Is given. It is preferred that the hydrocracking catalyst comprises a medium pore diameter aluminosilicate zeolite or a large pore diameter aluminosilicate zeolite. Suitable zeolites include but are not limited to ZSM-5, MCM-22, ZSM-11, beta zeolite, EU-1 zeolite, zeolite Y, faujasite, ferrierite and mordenite. The term “medium pore zeolite” is commonly used in the field of zeolite catalysts. Accordingly, the medium pore size zeolite is a zeolite having a pore size of about 5 to 6 mm. Suitable convergent-divergent pore size zeolites are 10 ring zeolite, i.e., the pores are formed by rings of ten SiO ₄ tetrahedra. Suitable large pore size zeolites have a pore size of about 6-8 mm and are of the 12 ring structure type. An eight-ring type zeolite is called a small pore size zeolite. In the above Atlas of Zeolite Framework Types, various zeolites based on the ring structure are listed. Most preferably, the zeolite is a ZSM-5 zeolite, which is a well-known zeolite having an MFI structure.

  The silica to alumina ratio of this ZSM-5 zeolite is preferably in the range of 20-200, more preferably in the range of 30-100.

  Zeolite is in hydrogen form: at least some of the original cations associated with it are replaced by hydrogen. Methods for converting aluminosilicate zeolite to the hydrogen form are well known in the art. The first method comprises direct ion exchange using acids and / or salts. The second method comprises base exchange using an ammonium salt followed by calcination.

  In addition, the catalyst composition includes a sufficient amount of metal hydride to ensure that the catalyst has a relatively strong hydrogenation activity. Metal hydrides are well known in the petrochemical catalyst art.

The catalyst composition is preferably 0.01-1% by weight of metal hydride, more preferably 0.01-0.7% by weight, most preferably 0.01-0.5% by weight of metal hydride. 0.01 to 0.3% by mass is more preferable. More preferably, the catalyst composition will contain 0.01-0.1 wt% or 0.02-0.09 wt% metal hydride. In the context of the present invention, when referring to the metal content contained in the catalyst composition, the term “mass%” refers to the mass of the metal relative to the mass of the entire catalyst including the catalyst binder, filler, diluent, etc. %. The metal hydride is preferably at least one element selected from Group 10 of the periodic table of elements. A preferred group 10 element is platinum (Pt). Thus, the hydrocracking catalyst used in the process of the present invention comprises a zeolite having a pore size of 5-8Å and a silica (SiO ₂ ) to alumina (Al ₂ O ₃ ) molar ratio of 5-200, and 0.01 Contains ˜1 wt% platinum (based on total catalyst).

The hydrocracking catalyst composition may further comprise a binder. Alumina (Al ₂ O ₃ ) is a preferred binder. The binder contained in the catalyst composition of the present invention is preferably at least 10% by weight, most preferably at least 20% by weight, preferably up to 40% by weight. In some embodiments, the metal hydride is deposited on a binder, preferably Al ₂ O ₃ .

  According to some embodiments of the invention, the hydrocracking catalyst is a mixture of metal hydride and zeolite on an amorphous alumina support.

According to another embodiment of the invention, the hydrocracking catalyst comprises a metal hydride on a zeolite support. In this case, the metal hydride and zeolite that provide the cracking function are in close proximity to each other, which results in a shorter diffusion distance between the two sites. This allows for high space velocities, which results in a smaller reactor volume and hence lower CAPEX. Thus, in some preferred embodiments, the hydrocracking catalyst is a metal hydride on a zeolite support, and step (b) is conducted at a weight space velocity of 10-15 h- ¹ .

The hydrocracking step is performed in the presence of an excess amount of hydrogen in the reaction mixture. This means that more than stoichiometric amounts of hydrogen are present in the reaction mixture in which the hydrocracking takes place. The molar ratio of hydrogen to hydrocarbon species in the reactor feed (H ₂ / HC molar ratio) is between 1: 1 and 4: 1, preferably between 1: 1 and 3: 1, most preferably Preferably it is between 1: 1 and 2: 1. By selecting a relatively low H ₂ / HC molar ratio, the benzene purity in the product stream can be higher. In this context, the term “hydrocarbon species” means all hydrocarbon molecules present in the reactor feed, such as benzene, toluene, hexane, cyclohexane. It is then necessary to know the feed composition in order to calculate the average molecular weight of this product stream so that an accurate hydrogen feed flow rate can be calculated. An excessive amount of hydrogen in the reaction mixture inhibits the formation of coke, which is thought to result in catalyst deactivation.

The catalyst is 0.01 to 1% by weight of metal hydride, and 5 to 8 mm pore diameter and 5 to 200 silica (SiO ₂ ) to alumina (Al ₂ O ₃ ) moles, based on the total catalyst weight. These are hydrocracking catalysts comprising a zeolite having a ratio, wherein the first process conditions include a temperature of 425-580 ° C., a pressure of 300-5000 kPa at gauge pressure and a weight space velocity of 0.1-15 h ^−1. In this embodiment, the product (hydrocracking product stream) produced by the hydrocracking step of the method of the present invention mainly contains hydrogen, methane, LPG and BTX.

  According to these embodiments of the present invention, chemical BTX can be easily separated from the hydrocracked product stream.

  As used herein, the term “chemical BTX” means less than 5% by weight of hydrocarbons other than benzene, toluene and xylene, preferably less than 4% by weight of hydrocarbons other than benzene, toluene and xylene, More preferably it relates to a hydrocarbon mixture containing less than 3% by weight of hydrocarbons other than benzene, toluene and xylene, most preferably less than 2.5% by weight of hydrocarbons other than benzene, toluene and xylene.

  Furthermore, the “chemical BTX” produced by the process of the present invention comprises less than 1% by weight of non-aromatic C6 + hydrocarbons, preferably less than 0.7% by weight of non-aromatic C6 + hydrocarbons, more preferably It contains less than 0.6% by weight of non-aromatic C6 + hydrocarbons, most preferably less than 0.5% by weight of non-aromatic C6 + hydrocarbons. The most serious contaminants are non-aromatic species whose boiling points are close to those of benzene, including but not limited to cyclohexane, methylcyclopentane, n-hexane, 2-methylpentane and 3-methylpentane.

  Since the boiling point of non-aromatic C6 + hydrocarbons is usually close to that of C6 + aromatic hydrocarbons, the hydrocracking product stream is substantially free of non-aromatic C6 + hydrocarbons in these embodiments. It is a special advantage. Therefore, it may be difficult to separate non-aromatic C6 + hydrocarbons from aromatic C6 + hydrocarbons contained in the hydrocracking product stream by distillation.

  As intended herein, the term “product stream substantially free of non-aromatic C6 + hydrocarbons” means that the product stream contains less than 1% by weight of non-aromatic C6 + hydrocarbons, preferably non-aromatics. Contain less than 0.7% by weight of C6 + hydrocarbons, more preferably less than 0.6% by weight of non-aromatic C6 + hydrocarbons, most preferably less than 0.5% by weight of non-aromatic C6 + hydrocarbons Means.

  It is preferred that the hydrocracked product stream is substantially free of C5 hydrocarbons. As intended herein, the term “hydrocracking product stream substantially free of C5 hydrocarbons” means that the hydrocracking product stream comprises less than 1% by weight of C5 hydrocarbons, preferably C5 hydrocarbons. Is less than 0.7% by weight, more preferably less than 0.6% by weight of C5 hydrocarbons, and most preferably less than 0.5% by weight of C5 hydrocarbons.

  It is preferred that the hydrocarbons of the hydrocracked product stream consist essentially of methane, LPG and BTX. As intended herein, “the hydrocarbons of the hydrocracking product stream consist essentially of methane, LPG and BTX” means that the total amount of methane, LPG and BTX in the hydrocarbons of the hydrocracking product stream is , At least 99% by weight, preferably at least 99.3% by weight, more preferably at least 99.4% by weight, and most preferably at least 99.5% by weight.

Step (b)
During step (b), the hydrocracked product stream is separated into a first gas stream comprising primarily hydrogen, methane and LPG and a first liquid stream comprising primarily BTX. This hydrocracked product stream is separated by standard means and methods suitable for separating gas from the liquid contained in the hydrocracked product stream. The separation may be performed, for example, by flushing, conventional distillation or absorption. The separation in step (b) is preferably performed in a flash chamber. In the flash chamber, the temperature is, for example, between 100 ° C. and 300 ° C., and the pressure is equal to or lower than the pressure in the hydrocracking reactor.

  The first liquid stream is preferably combined with the second liquid stream obtained by step (c), and step (d) is performed on the mixture.

Step (c)
During step (c), the first gas stream is separated to obtain a second gas stream mainly comprising hydrogen and methane and a second liquid stream mainly comprising LPG and BTX. The first gas stream is separated by standard means and methods suitable for separating the gas from the liquid contained in the first gas stream. The separation may be performed, for example, by flushing, conventional distillation or absorption. The separation in step (c) is preferably performed by distillation.

  Step (c) includes absorbing LPG in the gas stream using a portion of the third liquid stream containing primarily BTX. In this way, a second gas stream is obtained that contains only minor amounts of components other than hydrogen and methane.

  It is preferred that a portion of the third liquid stream to be added into the first gas stream is cooled before being added to the first gas stream. Cooling conditions such as temperature and pressure are selected such that the BTX of the third liquid stream remains liquid. Unlike the temperature required for the separation of ethane and methane (eg, -100 ° C), the temperature of the third liquid stream is not very low. Thus, the method of the present invention can be performed in a simpler and less energy consuming manner even when a portion of the third liquid stream to be added to the first gas stream is cooled.

  Cooling a portion of the third liquid stream to be added to the first gas stream has the advantage that the amount of LPG absorbed in the BTX is increased. For example, the third liquid stream to be added to the first gas stream is cooled to a temperature below 0 ° C. The third liquid stream to be added to the first gas stream is preferably −40 ° C. to 0 ° C., more preferably −40 ° C. to −10 ° C., more preferably −40 ° C. to −20 ° C., more preferably Is cooled to a temperature of -40 ° C to -30 ° C, for example -35 ° C. The pressure of the cooled liquid stream may be, for example, 25-50 bar (2.5-5 MPa), for example 30 bar (3.0 MPa). A portion of the third liquid stream to be added to the first gas stream is cooled to a temperature slightly higher than the temperature at which the third liquid stream solidifies before being added to the first gas stream. Most preferred. For example, a portion of the third liquid stream to be added to the first gas stream is 0.5-5 ° C. above the temperature at which the third liquid stream solidifies before being added to the first gas stream. Cooled to high temperature. The temperature at which the third liquid stream solidifies can be readily determined by those skilled in the art depending on the pressure.

  In some embodiments of the present invention, step (c) includes adding a portion of the third liquid stream directly to the first gas stream. This is also described as option (I) elsewhere in this description.

  Step (c) may include compressing the first gas stream and adding a portion of the third liquid stream to the compressed first gas stream. Compressing the first gas stream further improves the separation of components between the second gas stream and the second liquid stream by increasing the absorption of LPG in the BTX.

In another embodiment of the present invention, step (c) is performed in two or more steps. In these embodiments, step (c) comprises
(C1) separating the first gas stream into a gas stream and a liquid stream; and (c2) adding a part of the third liquid stream to the gas stream;
including. This is also described as option (II) elsewhere in this description.

  The liquid stream obtained by step (c1) is preferably combined with the second liquid stream obtained by step (c2), and step (d) is performed on the mixture.

  Step (c2) may include compressing the gas stream of step (c1) and adding a portion of the third liquid stream to the compressed gas stream. Compressing the gas stream of step (c1) further improves the separation of components between the second gas stream and the second liquid stream by increasing the absorption of LPG in the BTX.

  Preferably, at least a portion of the second gas stream is returned to be mixed with the feed stream. In this way, hydrogen that is not consumed during hydrocracking is recycled in the system of the process. This is an economic and environmental advantage.

  In order to control the level of methane in the feed of the hydrocracking reactor, a proportion of the recycle gas stream is removed from the system as a purge. The amount of material purged depends on the level of methane in the recycle stream, which in turn depends on the feed composition. This purge stream has the same composition as the recycle stream. This purge mainly contains hydrogen and methane, so it is suitable for use as a fuel gas or can be further processed (eg, through a pressure swing adsorption unit) to provide a high purity hydrogen stream and methane that can be used as a fuel gas. The streams may be collected separately.

Step (d)
During step (d), the second liquid stream is separated into a third gas stream containing LPG and a third liquid stream containing BTX. The second liquid stream may be separated by standard means and methods suitable for separating the third gas stream containing LPG and the third liquid stream containing BTX from each other. The separation is preferably performed by gas-liquid separation or distillation.

Step (e)
In a preferred embodiment, the method according to the invention further comprises a step (e) of separating benzene from the third liquid stream.

  A third liquid stream is separated into benzene and a liquid stream comprising toluene and xylene, and a (part of) liquid stream comprising toluene and xylene is used to absorb LPG and BTX in step (c). More preferably. The liquid stream containing toluene and xylene contains heavier hydrocarbons than the third liquid stream before separation, so that more effective absorption occurs in step (c) and the separation in step (c) is good become.

  Although the present invention has been described in detail for purposes of illustration, such details are for that purpose only and may be modified by one of ordinary skill in the art without departing from the spirit and scope of the invention as defined in the claims. It will be understood that this can be done.

  It is further noted that the invention relates to all possible combinations of the features described herein and that the combinations of features included in the claims are particularly preferred.

  It is noted that the term “comprising” does not exclude the presence of other elements. However, it will also be understood that a description of a product containing certain components also discloses products made of these components. Similarly, it will also be understood that a description of a method comprising specific steps also discloses a method comprising these steps.

  The invention will be further described with reference to the drawings.

Illustration of an example of a method not according to the present invention Illustration of an example of a method according to the invention

  FIG. 1 shows an illustration of an example of a method not according to the invention. A feed stream comprising C5-C12 hydrocarbons is hydrocracked in the reaction section shown on the left side of the drawing and the resulting hydrocracked product stream comprising hydrogen, methane, LPG and BTX is converted to heat exchanger H. Through -003, it is fed to the separation compartment shown on the right side of the drawing.

  This hydrocracked product stream is supplied to heat exchanger H-003 where it is cooled to, for example, 140 ° C. and then supplied to flash chamber V001. The hydrocracked product stream is separated into a gas stream and a liquid stream in the flash chamber V001. The gas flow from the flash chamber V001 is compressed in the compressor K002 and separated again into a gas flow and a liquid flow, for example, at −100 ° C. in the flash chamber V002. The flash chamber V002 separates most of the C4 + hydrocarbons from the gas stream as a liquid stream. From the flash chamber V002, a gas stream comprising mainly hydrogen and C1-C3 hydrocarbons is directed to a heat exchanger H005 that compresses the gas stream to, for example, 30 bar (3 MPa) and -100 ° C, and then the flash chamber V003, where there is a cryogenic separation between hydrogen, methane and C2-C3 hydrocarbons. A gas stream containing hydrogen and methane is recycled to the reaction zone, where the gas stream is partially recycled and partially purged. The liquid stream leaving the flash chamber V003 containing C2-C3 hydrocarbons is combined with the LPG stream obtained from the liquid stream from the flash chamber V001.

  The liquid flow leaving the flash chamber V001 is supplied to the distillation column C001 through the heat exchanger H006 together with the liquid flow coming from the flash chamber V002. In this distillation column C001, the liquid stream is separated into an LPG stream and a BTX stream. This BTX stream is fed to a distillation column C002 to separate the BTX stream into a light product stream 17, a benzene stream 18 and a toluene / xylene stream 19.

  FIG. 2 shows an illustration of an example of a method according to the invention. The reaction compartment of FIG. 2 is the same as that of FIG.

  In the separation section shown in FIG. 2, the hydrocracked product stream is fed to a flash chamber V001 where it is separated into a gas stream and a liquid stream. The gas flow from the flash chamber V001 is heated in the heat exchanger H003 and separated again in the flash chamber V002. The gas flow from the flash chamber V002 is compressed in the compressor K002 and supplied to the distillation column C003.

  The liquid streams from V001, V002 and C003 pass through heat exchanger H004 and enter distillation column C001, where the liquid stream is separated into LPG and BTX streams. A portion of the BTX stream is fed to distillation column C002 for separation of the BTX stream into a light product stream, a benzene stream and a toluene / xylene stream. A part of the BTX stream is supplied to the upper part of the distillation column C003 through the pump P003. In the distillation column C003, this BTX stream is used to improve the separation between hydrogen, methane and heavier components in the gas mixture fed to C003. As already mentioned, the liquid stream leaving C003 is combined with the liquid stream from V001 and V002 and fed to distillation column C001.

Claims (15)

A method for producing BTX and LPG comprising:
(A) In a hydrocracking reactor, a feed stream containing C5-C12 hydrocarbons is contacted with a hydrocracking catalyst in the presence of hydrogen to produce a hydrocracked product stream containing hydrogen, methane, LPG and BTX. Generating step,
(B) separating the hydrocracked product stream into a first gas stream and a first liquid stream;
(C) separating the first gas stream to obtain a second gas stream containing hydrogen and methane and a second liquid stream containing LPG and BTX, wherein the second liquid stream (D) separating the second liquid stream into a third gas stream containing LPG and a third liquid stream containing BTX. Process,
Having
Step (c)
Adding a portion of the third liquid stream to the first gas stream to absorb LPG in the first gas stream to obtain the second liquid stream; or A part of the liquid flow is added to the gas flow separated from the first gas flow to absorb LPG in the gas flow separated from the first gas flow, and the second liquid Obtaining a flow,
Including the method. Step (c)
(C1) separating the first gas stream into a gas stream and a liquid stream; and (c2) adding a part of the third liquid stream to the gas stream obtained by the step (c1);
The method of claim 1 comprising:   3. Step (c2) comprises compressing the gas stream obtained by step (c1) and adding a portion of the third liquid stream to the compressed gas stream. The method described.   The method of claim 1, wherein step (c) comprises adding a portion of the third liquid stream to the first gas stream.   The method of any one of claims 1-4, wherein the second liquid stream consists essentially of LPG and BTX.   6. The method of any one of claims 1-5, wherein at least a portion of the second gas stream is returned to be mixed with the feed stream.   The method of any one of claims 1 to 6, further comprising the step (e) of separating benzene from the third liquid stream.   The third liquid stream is separated into benzene and a liquid stream comprising toluene and xylene, and the liquid stream comprising toluene and xylene is used to absorb LPG in step (c). 6. The method according to 6.   9. A portion of the third liquid stream to be added to the first gas stream is cooled to a temperature below 0 ° C. before being added to the first gas stream. The method of any one of Claims.   The portion of the third liquid stream to be added to the first gas stream is cooled from -40 ° C to -30 ° C before being added to the first gas stream. 10. The method according to any one of 9 to 9.   The portion of the third liquid stream that is to be added to the first gas stream is 0.5 to less than the temperature at which the third liquid stream solidifies before being added to the first gas stream. The method according to any one of claims 1 to 10, wherein the method is cooled to a temperature of 5 ° C higher. The hydrocracking catalyst of step (a) is 0.01 to 1% by mass of hydrogenated metal, 5 to 8 mm pore diameter and 5 to 200 silica (SiO ₂ ) Comprising a zeolite having an alumina (Al ₂ O ₃ ) molar ratio, wherein step (a) comprises a temperature of 425-580 ° C., a pressure of 300-5000 kPa at gauge pressure and a weight space velocity of 0.1-15 h ^−1. 12. A process according to any one of claims 1 to 11 carried out under process conditions.   13. A process according to claim 12, wherein the metal hydride of the hydrocracking catalyst is at least one element selected from group 10 of the periodic table of elements, preferably Pt.   The zeolite is selected from the group consisting of ZSM-5, MCM-22, ZSM-11, beta zeolite, EU-1 zeolite, zeolite Y, faujasite, ferrierite and mordenite, preferably ZSM-5. 14. A method according to claim 12 or 13.   The feed stream comprises (pyro) cracked gasoline, straight run naphtha, light coker naphtha and coke oven gas oil, FCC gasoline, a reformate or mixture thereof, preferably the feed stream is depentanized. 14. The method according to any one of 14 to 14.