RU2640595C2 - Method for alkylation of aromatic compounds - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: one embodiment includes: (a) providing an aromatic hydrocarbon feedstock containing alkylated aromatic hydrocarbon of, at least, 150 ppm by weight of water and, at least, one organic nitrogen impurity, wherein alkylated aromatic hydrocarbon is benzene; (b) removing water from the aromatic hydrocarbon feedstock in the dewatering zone to produce an anhydrous starting aromatic feedstock having a water content of not more than 20 ppm by weight; (c) contacting the dewatered raw aromatic feedstock with the adsorbent from the clay under conditions comprising a temperature of less than 130°C, so that the adsorbent removes, at least, a portion of the organic nitrogen impurity contained in the feedstock to produce a treated aromatic feedstock; and (d) feeding the treated aromatic feedstock to the alkylation reaction zone and/or the transalkylation reaction zone.

EFFECT: improving the efficiency of cleaning with clay.

11 cl, 1 dwg, 2 tbl, 2 ex

Description

Technical field

The present invention relates to a method for the alkylation of aromatic compounds.

State of the art

Aromatic alkylation processes are of great commercial importance, for example, in the production of ethylbenzene and cumene. Such processes typically include a reaction section and a separation section. In the reaction section, an aromatic compound such as benzene is reacted with an alkylating agent such as ethylene, propylene, butenes, methanol, ethanol, propanol, isopropanol or butanols in the presence of an alkylation catalyst to produce an alkylated aromatic compound. The reaction section may also include allowing the conversion of any polyalkylated compounds to an additional monoalkylated product by reaction with an additional aromatic compound in the presence of a transalkylation catalyst. Unreacted aromatic compound from the reaction section is then recovered in the separation section and recycled back to the reaction section. Fresh aromatic compound may be fed either to the reaction section or to a separation section.

In most modern alkylation processes, the acid catalyst used in the reaction section is a crystalline molecular sieve, such as MCM-22 or zeolite beta. The alkylation reaction may be carried out in the vapor phase, the liquid phase or the mixed phase. More recently, however, there has been an interest in carrying out an alkylation reaction in the at least partially liquid phase, as this leads to a reduction in the production of undesirable by-products.

Water is often found in aromatic feedstocks for alkylation reactions, especially in the case of benzene feedstocks. Thus, commercially available benzene feeds are often saturated with water, for example, when feeds are recycled from the monomeric styrene unit. However, the presence of a high water content may reduce the activity of molecular sieve alkylation catalysts. Therefore, it is natural to subject the aromatic feedstock to a drying step before using it in the alkylation process. For example, in US Pat. 5,030,786 describes the dehydration of an aromatic feedstock in a liquid phase process for converting aromatic compounds to a water content of not more than 100 ppm, and preferably 50 ppm or less, by passing the aromatic feedstock through a molecular sieve dryer.

Other impurities present in the feed for aromatic alkylation reactors include basic compounds, such as basic organic nitrogen compounds. They present a particular problem since they can neutralize active acid sites on a molecular sieve catalyst, which adversely affects both the performance of the catalyst and the life of the catalyst. Even very low nitrogen concentrations in the feed increase the frequency of catalyst regeneration to remove accumulated nitrogen compounds. Since more active zeolite catalysts are used in the conversion reactions of aromatic compounds, the decrease in catalyst life due to nitrogen impurities in the feed should be controlled more carefully. Therefore, in most methods for the alkylation of aromatic compounds, pre-treatment of aromatic raw materials to remove basic organic nitrogen compounds is provided. For example, in US Pat. 6,297,417 discloses a method for the alkylation of aromatic compounds, which involves contacting a benzene feedstock with a solid acid, such as acidic clay or acidic zeolite, in a pre-treatment zone at a temperature between about 130 ° C and about 300 ° C to remove impurities such as organic nitrogen compounds thereby improving the life of the alkylation catalyst.

U.S. Pat. 8,013,199 discloses a method for alkylating an aromatic hydrocarbon stream having impurities in which the hydrocarbon feed is contacted with a first molecular sieve containing a Linde type X molecular sieve and having a Si / Al molar ratio of less than about 5 to remove at least a portion of these impurities and obtaining a stream of partially purified aromatic hydrocarbons; and then contacting said stream of partially purified hydrocarbons with a second molecular sieve containing zeolite Y and having a Si / Al molar ratio of more than about 5 to remove substantially all of the remaining parts of these impurities to produce a fully processed hydrocarbon feed having a reduced amount impurities. A fully processed hydrocarbon feed is contacted with an alkylating agent in the presence of an alkylation catalyst under alkylation conditions to produce a stream of alkylated aromatic hydrocarbons.

U.S. Pat. 6,894,201 discloses a method and apparatus for removing nitrogen compounds from an alkylation substrate such as benzene. A conventional adsorbent layer, such as clay or resin, can be used at ambient temperatures up to 38 ° C to adsorb basic organic nitrogen compounds, and a hot acid molecular sieve adsorbent layer at or above 120 ° C can adsorb weakly basic nitrogen compounds, such as nitriles . Water is believed to facilitate the adsorption of weakly basic nitrogen compounds, and therefore, the water concentration in the hot adsorbent layer is usually set to 20 to 500 ppm by weight by fractionation column.

From the foregoing, it will be understood that the purification of the feedstock of aromatic hydrocarbons brings significant cost and complexity to the alkylation processes of aromatic compounds. Therefore, there is ongoing interest in the development of alternative purification schemes that simplify the entire alkylation process and / or reduce or eliminate the need for expensive molecular sieve adsorbents without compromising catalyst productivity. In accordance with the present invention, it has been found that, under certain conditions, clay treatment can be used to reduce or eliminate the need for more expensive molecular sieve adsorption to remove organic nitrogen compounds from aromatic hydrocarbon feedstocks. It has also been found that by treating a stream of unreacted aromatic compounds recycled from the separation section to the reaction section, the need for processing fresh aromatic hydrocarbon feed can be reduced or eliminated. The recycle stream of aromatics typically has a higher temperature and lower moisture content than fresh hydrocarbon feeds. Both of these two differences increase the performance of some adsorbents, in particular clay, which makes it advantageous for processing a recycled stream of aromatic compounds, instead of supplying fresh hydrocarbon feeds.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a process for the alkylation of aromatic compounds, comprising:

(a) providing a starting aromatic hydrocarbon feed comprising an alkylated aromatic hydrocarbon of at least 150 ppm by weight of water and at least one organic nitrogen impurity;

(b) removing water from the aromatic hydrocarbon feedstock in the dehydration zone to obtain a dehydrated aromatic feedstock having a water content of not more than 20 ppm by weight;

(c) contacting the dehydrated aromatic feedstock with an adsorbent from clay under conditions including a temperature of less than 130 ° C, so that the adsorbent removes at least a portion of the organic nitrogen impurities contained in the feedstock to obtain a processed aromatic feedstock; and

(d) feeding the treated aromatic feedstock to the alkylation reaction zone and / or transalkylation reaction zone.

In one embodiment of the invention, the dehydration zone comprises a distillation column.

It is advisable that the method also includes:

(e) feeding the effluent from the alkylation reaction zone and / or transalkylation reaction zone to a distillation column to remove unreacted aromatic hydrocarbon from said effluent; and

(f) feeding the unreacted aromatic hydrocarbon together with the dehydrated feedstock to the processing unit.

In a further aspect, the present invention provides a process for the alkylation of aromatic compounds, comprising:

(a) passing the aromatic hydrocarbon feed containing a recycle stream of aromatic hydrocarbon and optionally fresh aromatic hydrocarbon through a processing unit containing an adsorbent from clay, under such conditions that the adsorbent from clay removes at least a portion of the impurities contained in the aromatic hydrocarbon feed, with obtaining a stream of processed aromatic hydrocarbon;

(b) supplying at least a portion of the treated aromatic hydrocarbon stream to the alkylation zone;

(c) contacting said treated aromatic hydrocarbon stream in said alkylation zone with an alkylating agent in the presence of an acid alkylation catalyst and under such conditions that at least a portion of the alkylating agent reacts with said processed aromatic hydrocarbon stream to produce an alkylated effluent containing alkylated aromatic compound and unreacted aromatic hydrocarbon;

(d) supplying said alkylation effluent to a separation section to recover at least a portion of the unreacted aromatic hydrocarbon; and

(e) recycling at least a portion of said unreacted aromatic hydrocarbon recovered in (d) as the recycle aromatic hydrocarbon stream indicated in (a).

In yet another aspect, the present invention provides a method for alkylating aromatic compounds, comprising:

(a) passing an aromatic hydrocarbon feed containing a recycle stream of aromatic hydrocarbons and optionally fresh aromatic hydrocarbon through a processing unit containing an adsorbent from clay under conditions where the adsorbent from clay removes at least a portion of the impurities contained in the aromatic hydrocarbon feed to produce a stream refined aromatic hydrocarbons;

(b) supplying at least a portion of the treated aromatic hydrocarbon stream to a transalkylation zone;

(c) contacting said treated aromatic hydrocarbon stream in said transalkylation zone with a polyalkyl aromatic hydrocarbon stream in the presence of an acid transalkylation catalyst and under such conditions that at least a portion of the polyalkyl aromatic hydrocarbon reacts with said processed aromatic hydrocarbon stream to produce a transalkylated effluent containing alkyl aromatic compound, unreacted polyal a potent aromatic hydrocarbon and unreacted aromatic hydrocarbon;

(d) supplying said transalkylation effluent to a separation section to recover at least a portion of the unreacted aromatic hydrocarbon; and

(e) recycling at least a portion of said unreacted aromatic hydrocarbon recovered in (d) as the recycle aromatic hydrocarbon stream indicated in (a).

In a further aspect, the present invention provides a process for the alkylation of aromatic compounds, comprising:

(a) providing a feedstock containing an alkylatable aromatic hydrocarbon, up to 400 ppm by weight of water, at least 0.01% by weight. at least one alkylated aromatic hydrocarbon and at least one organic nitrogen impurity;

(b) passing at least a portion of the feedstock through a processing unit containing clay adsorbent under conditions including a temperature of from 40 ° C to less than 130 ° C so that the adsorbent removes at least a portion of the organic nitrogen impurities contained in the feedstock, to obtain processed feedstock; and

(c) supplying at least a portion of the alkylatable aromatic hydrocarbon from the treated feedstock to the alkylation reaction zone and / or transalkylation reaction zone.

In one embodiment of the invention, at least a portion of the alkylated aromatic hydrocarbon is introduced into the feed into an unreacted alkylated aromatic hydrocarbon recycled from the alkylation reaction zone and / or transalkylation reaction zone.

In another embodiment, at least a portion of the alkylated aromatic hydrocarbon is present in the fresh alkylated aromatic hydrocarbon supplied in the process.

Brief Description of the Drawings

Figure 1 is a flowchart of a method for alkylating an aromatic compound in accordance with a first embodiment of the invention.

Figure 2 is a flow diagram of a method for alkylating an aromatic compound in accordance with a second embodiment of the invention.

Detailed Description of Embodiments

The present invention relates to a method for the alkylation of aromatic compounds in which an alkylated aromatic compound such as benzene is reacted with an alkylating agent such as ethylene or propylene to produce an alkylated aromatic compound such as ethylbenzene or cumene. In the present method, harmful impurities, such as nitrogen-based organic compounds present in aromatic raw materials, are adsorbed using an adsorbent from clay from one or more aromatic streams prior to alkylation and / or transalkylation. In some embodiments of the invention, instead of or in addition to processing fresh aromatic hydrocarbon feedstocks, the removal of impurities affects the recycled flow of aromatic hydrocarbons, which typically has a higher temperature and lower moisture content than fresh aromatic hydrocarbon feedstocks. Thus, the effectiveness of the method of removing impurities can be improved.

Aromatic hydrocarbons that can be alkylated

The term "aromatic" with reference to compounds that can be alkylated, suitable in the present method, should be understood in accordance with its recognized in the art scope, which includes alkyl-substituted and unsubstituted mono- and polycyclic compounds. Aromatic compounds which possess a heteroatom are also suitable provided that they do not act as catalytic poisons under the selected reaction conditions.

Substituted aromatic compounds that can be alkylated in this process must have at least one hydrogen atom directly bonded to the aromatic nucleus. Aromatic rings may be substituted by one or more alkyl, aryl, alkaryl, alkoxy, aryloxy, cycloalkyl, halogen and / or other groups that do not interfere with the alkylation reaction.

Suitable aromatic hydrocarbons include benzene, naphthalene, anthracene, naphthacene, perylene, coronene and phenanthrene, with benzene being preferred.

Typically, alkyl groups that may be present as substituents on the aromatic compound contain from about 1 to 22 carbon atoms, and typically from about 1 to 8 carbon atoms, and most often from about 1 to 4 carbon atoms.

Suitable alkyl substituted aromatic compounds include toluene, xylenes, isopropylbenzene, normal propylbenzene, alpha-methylnaphthalene, ethylbenzene, mesitylene, durene, cymols, butylbenzenes, pseudocumene, o-diethylbenzenebenzene, p-benzene, benzene, benzene, p-benzene, benzene 1,2,3,4-tetraethylbenzene; 1,2,3,5-tetramethylbenzene; 1,2,4-triethylbenzene; 1,2,3-trimethylbenzene, m-butyltoluene; n-butyltoluene; 3,5-diethyltoluene; o-ethyl toluene; n-ethyl toluene; m-propyltoluene; 4-ethyl-m-xylene; dimethylnaphthalenes; ethylnaphthalene; 2,3-dimethylanthracene; 9-ethylanthracene; 2-methylanthracene; o-methylanthracene; 9,10-dimethylphenanthrene and 3-methylphenanthrene. Alkylaromatic hydrocarbons with a higher molecular weight can also be used as starting materials and include aromatic hydrocarbons, such as those obtained by alkylation of aromatic hydrocarbons with olefinic oligomers. Such products are often referred to in the art as alkylates, and they include hexylbenzene, nonylbenzene, dodecylbenzene, pentadecylbenzene, hexyltoluene, nonyltoluene, dodecyl toluene, pentadecyl toluene, etc. Very often, the alkylate is obtained in the form of a fraction with a high boiling point, in which the alkyl group attached to the aromatic core varies in size from about C ₆ to about C ₁₂ .

The reformate or trim thereof, containing substantial amounts of benzene, toluene and / or xylenes, is a particularly suitable aromatic feed for the alkylation process of this invention.

Another suitable aromatic feed for the present alkylation process is a benzene / toluene by-product stream formed in a styrene plant.

Alkylating Agent

The alkylating agent useful in the present process may be any aliphatic or aromatic organic compound having one or more available alkylating aliphatic groups capable of reacting with benzene. Examples of suitable alkylating agents include alkenes; such as ethylene and propylene; alcohols (including monohydric alcohols, dihydric alcohols, trihydric alcohols, etc.), such as methanol, ethanol, isopropanol and n-propanol; aldehydes such as propionic aldehyde; and halides such as ethyl chloride and propyl chloride.

In one embodiment, the alkylating agent comprises an alkene, which may be present as a substantially pure alkene feed or as a dilute feed containing at least one alkane and, typically, at least one alkane having the same number of carbon atoms, like alkene. For example, when the alkene is ethylene, the alkane may be ethane. Typically, diluted alkene feed contains at least 10% of the mass. alkene, for example from about 10 to about 80% of the mass., for example from about 40 to about 80% of the mass. alkene. One particularly suitable feed is a diluted ethylene stream obtained as off-gas from a liquid catalytic cracking unit in an oil refinery.

It should be noted that the feed sources of the alkylating agent can also be purified before being fed into the present process. Such cleaning methods are well known to those skilled in the art.

In one embodiment, the fresh aromatic hydrocarbon feed contains benzene, the alkylating agent contains propylene and / or isopropanol, and the alkylated aromatic compound contains cumene. In another embodiment, the fresh aromatic hydrocarbon feed comprises benzene, the alkylating agent contains ethylene and / or ethanol, and the alkylated aromatic compound contains ethylbenzene.

In one embodiment of the invention, including transalkylation, the fresh aromatic hydrocarbon feed contains benzene, the polyalkyl aromatic hydrocarbon stream contains diisopropylbenzenes, and the alkylated aromatic compound contains cumene. In another embodiment, the fresh aromatic hydrocarbon feed contains benzene, the polyalkyl aromatic hydrocarbon stream contains diethylbenzenes, and the alkylated aromatic compound contains ethylbenzene.

The method of alkylation of aromatic compounds

In the present process, an alkylated aromatic compound is reacted with an alkylating agent (e.g., an alkene feedstock) in an alkylation reaction system. The reaction system contains one or a plurality of series-connected alkylation reaction zones, each of which contains an alkylation catalyst and each, as a rule, is located in one reactor. The alkylation reaction zone or each alkylation reaction zone in the alkylation reaction system preferably operates under conditions effective to initiate the alkylation of the alkylated aromatic compound with an alkylating agent, while providing the alkylated aromatic compound at least partially or mainly in the liquid phase. In one embodiment of the invention, where the alkylated aromatic compound includes benzene, alkene includes ethylene and the alkyl aromatic compound includes ethyl benzene, conditions in the alkylation reaction zone or each alkylation reaction zone include a temperature of from about 120 ° C. to about 270 ° C. and a pressure of from about 500 kPa up to about 8300 kPa. In another embodiment, where the alkylated aromatic compound includes benzene, the alkylating agent includes propylene and / or isopropanol and the alkyl aromatic compound includes cumene, the conditions in the alkylation reaction zone or each alkylation reaction zone include a temperature of from about 40 ° C. to about 300 ° C. and pressure from about 500 kPa to about 8300 kPa. Typically, the molar ratio of the alkylated aromatic compound to the alkylating agent in each alkylation reaction zone is in the range from 100: 1 to 0.3: 1.

In one embodiment, the alkylation catalyst used in the alkylation reaction zone or in each alkylation reaction zone of the alkylation reaction system comprises at least one medium pore molecular sieve having a Permeability Index of 2-12 (as defined in US Patent No. 4,016,218). Suitable mid pore molecular sieves include ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35 and ZSM-48. ZSM-5 is described in detail in US Pat. Nos. 3,702,886 and Re. 29.948. ZSM-11 is described in detail in US Pat. 3,709,979. ZSM-12 is described in US Pat. 3,832,449. ZSM-22 is described in US Pat. 4,556,477. ZSM-23 is described in US Pat. 4,076,842. ZSM-35 is described in US Pat. 4,016,245. ZSM-48 is described in more detail in US Pat. 4,234,231.

In another embodiment, the alkylation catalyst used in the alkylation reaction zone or in each alkylation reaction zone of the alkylation reaction system comprises at least one molecular sieve of the MCM-22 family. As used herein, the term “molecular sieve from the MCM-22 family” (or “material from the MCM-22 family” or “material from the MCM-22 family” or “zeolite from the MCM-22 family”) includes one or more of:

molecular sieves made from a conventional unit cell with a first degree crystalline building block, where the unit cell has a MWW structural topology. (A unit cell is a spatial arrangement of atoms that, when stacked in three-dimensional space, describes a crystal structure. Such crystal structures are discussed in Atlas of Zeolite Framework Types, Fifth edition, 2001, all of which is incorporated by reference);

molecular sieves made from a conventional second-degree building block, being 2-dimensional stacking of such unit cells with the MWW structural topology, form a monolayer with a thickness of one unit cell, preferably with a thickness of one c-unit cell;

molecular sieves made from conventional second-degree building blocks, being layers with a thickness of one or more unit cells, where a layer with a thickness of more than one unit cell is made from stacking, packaging or bonding at least two monolayers with a thickness of one unit cell . The laying of such building blocks of the second degree may be regular, irregular, random or any combination thereof; and

molecular sieves made using any regular or random 2-dimensional or 3-dimensional combination of unit cells having a MWW structural topology.

Molecular sieves from the MCM-22 family include molecular sieves having an X-ray diffraction pattern including a maximum interatomic distance at 12.4 ± 0.25, 6.9 ± 0.15, 3.57 ± 0.07, and 3.42 ± 0.07 angstroms. X-ray diffraction data used to characterize the material is obtained using standard methods using a K alpha copper doublet as incident radiation and a diffractometer equipped with a scintillation counter and connected to a computer as an information collection system.

Materials of the MCM-22 family include MCM-22 (described in US Pat. No. 4,954,325), PSH-3 (described in US Pat. No. 4,439,409), SSZ-25 (described in US Pat. No. 4,826,667), ERB-1 (described in European Patent No. 0293032), ITQ-1 (described in US Patent No. 6,077,498), ITQ-2 (described in International Patent Publication No. WO97 / 17290), MCM-36 (described in US Patent No. 5,250,277), MSM -49 (described in US Pat. No. 5,236,575), MSM-56 (described in US Pat. No. 5,362,697) and mixtures thereof. The related zeolite UZM-8 is also suitable for use as a true alkylation catalyst.

In a further embodiment, the alkylation catalyst used in the alkylation reaction zone or in each alkylation reaction zone of the reaction alkylation system comprises one or more large pore molecular sieves having a Permeability Index of less than 2. Suitable large pore molecular sieves include zeolite beta, zeolite Y, Ultrastable Y (USY), Dealuminized Y (Deal Y), Mordenite, ZSM-3, ZSM-4, ZSM-18 and ZSM-20. Zeolite ZSM-14 is described in US Pat. 3,923,636. Zeolite ZSM 20 is described in US Pat. 3,972,983. Zeolite Beta is described in US Pat. Nos. 3,308,069 and Re. No. 28,341. The low sodium Ultrastable Y molecular sieve (USY) is described in US Pat. Nos. 3,293,192 and 3,449,070. Zealite Dealuminized Y (Deal Y) can be obtained by the method found in US Patent No. 3,442,795. Zeolite UHP-Y is described in US Pat. 4,401,556. Mordenite is a naturally occurring material, but is also available in synthetic forms such as TEM mordenite (i.e. synthetic mordenite obtained from a reaction mixture containing a tetraethylammonium directing agent). TEM mordenite is disclosed in US Pat. Nos. 3,766,093 and 3,894,104.

Preferred molecular sieves for the alkylation reaction include zeolite beta, molecular sieves having a Permeability Index of 2-12, especially ZSM-5, and molecular sieves from the MCM-22 family.

The above molecular sieves can be used as an alkylation catalyst without any binder or matrix, i.e. in the so-called self-bound form. Alternatively, the molecular sieve may be combined with another material that is resistant to the temperatures and other conditions used in the alkylation reaction. Such materials include active and inactive materials and synthetic or natural zeolites, as well as inorganic materials such as clays and / or oxides such as alumina, silica, silica-alumina, zirconia, titanium oxide, magnesia or mixtures thereof and others oxides. The latter can be either of natural origin, or in the form of gel-like precipitates or gels, including mixtures of silica and metal oxides. Clays can also be included with oxide-type binders to modify the mechanical properties of the catalyst or aid in its manufacture. Use of the material in combination with a molecular sieve, i.e. combined with it or present during its synthesis, which itself is catalytically active, can change the conversion and / or selectivity of the catalyst. Inactive materials, respectively, serve as diluents to control the conversion depth so that the products can be obtained economically and orderly without the use of other means to control the reaction rate. These materials can be incorporated into naturally occurring clay, such as bentonite and kaolin, to improve the crush strength of the catalyst under commercial conditions and to function as binders or matrices for the catalyst. The relative proportions of the molecular sieve and inorganic oxide matrix vary widely with sieve contents in the range of from about 1 to about 90 percent by weight, and more usually, in particular when the composite is prepared in the form of balls, in the range of from about 2 to about 80 weight percent of the composition.

Separation of the alkylation effluent

In addition to the desired alkyl aromatic product, the stream from the alkylation reaction typically contains significant amounts of unreacted alkylated aromatic compound (e.g. benzene), and in some cases may also contain polyalkylated aromatic compounds (e.g. di- and triisopropylbenzenes). Thus, the effluent is fed to a product separation system, such as distillation plates, which serves not only to isolate the unreacted aromatic compound and the desired monoalkylated product, but also to separate the polyalkylated compounds. Unreacted aromatic compound is returned to the alkylation section and / or transalkylation section after treatment to remove harmful impurities, such as nitrogen-based compounds, as described below. In one embodiment, a recycle aromatic hydrocarbon stream contains from 0.01 to less than 15 wt.%, For example from 0.1 to 10 wt.%, Of an alkylated aromatic compound.

The feedstock of fresh aromatic hydrocarbon (e.g. benzene) can be fed either to the alkylation section, the transalkylation section or to the separation section. In some embodiments of the invention, fresh aromatic feedstock enters the system to separate the product to reduce the water content of the feedstock to less than 20 ppm by weight, for example, less than 10 ppm by weight. Thus, the aromatic hydrocarbon stream passed through the processing unit may contain fresh as well as recycled aromatic hydrocarbon feed.

Transalkylation

Polyalkylated compounds recovered from the alkylation effluent may be fed to a transalkylation reactor, which is typically separated from the alkylation reactor. In the transalkylation reactor, an additional monoalkylated product is obtained by reacting polyalkylated compounds with an additional aromatic compound in the presence of a transalkylation catalyst. Typically, the transalkylation reactor is operated under such conditions that the polyalkylated aromatic compounds and the alkylated aromatic compound are at least partially or predominantly in the liquid phase.

Suitable conditions for transalkylation of benzene with polyethylbenzenes may include a temperature of from about 100 ° C to about 300 ° C, a pressure of 8000 kPa or less, a space velocity (WHSV), calculated from the total liquid feed to the reaction zone, of from about 0.5 to about 100 h ^-1 and a molar ratio of benzene to polyethylbenzene from about 1: 1 to about 30: 1. Specific conditions for the transalkylation of benzene with polyisopropylbenzenes may include a temperature of from about 100 ° C to about 300 ° C, a pressure of 8000 kPa or less, a space velocity (WHSV), calculated from the total liquid feed to the reaction zone, of from about 0.1 to about 50 h ^-1 and the molar ratio of benzene to polyisopropylbenzene from about 1: 1 to about 20: 1. Specific conditions for the transalkylation of benzene with polybutylbenzenes may include temperatures from 100 to 300 ° C, pressures from 500 to 8000 kPa, space velocity from 0.1 to 50 h ^-1 for general nutrition, and the molar ratio of benzene to polybutylbenzene from 1: 1 to 20 :one.

The transalkylation catalyst may contain one or more of any of the molecular sieves described above with respect to alkylation systems, and may be used with or without a binder or matrix. Typically, however, the transalkylation catalyst is selected from zeolite beta, zeolite Y, Ultrastable Y (USY), Dealuminized Y (Deal Y), mordenite, ZSM-3, ZSM-4, ZSM-5, ZSM-11, ZSM-18, ZSM -20, MCM-22, PSH-3, SSZ-25, ERB-1, ITQ-1, ITQ-2, MCM-36, MCM-49, MCM-56, UZM-8 and mixtures thereof.

Transalkylation effluent separation

The stream leaving the transalkylation system will typically comprise a monoalkylated aromatic compound, unreacted polyalkyl aromatic hydrocarbon and unreacted aromatic hydrocarbon. Thus, the effluent is fed to a product separation system, which serves not only to isolate the unreacted aromatic compound and the target alkylated aromatic compound, but also to separate the unreacted polyalkyl aromatic hydrocarbon. Typically, the same product separation system is used to separate the alkylation effluent and the transalkylation effluent. Unreacted aromatic compound can be returned to remove harmful impurities, such as nitrogen-based compounds, as described below. In one embodiment, the unreacted aromatic compound isolated from the transalkylation stream is combined with the unreacted aromatic compound isolated from the alkylation stream and recycled to remove harmful impurities, such as nitrogen based compounds, as described below.

Aromatic hydrocarbon processing

As noted above, most commercially available starting aromatic hydrocarbons contain significant amounts up to 10 ppm nitrogen by weight of organic nitrogen impurities such as N-methylpyrrolidone (NMP), N-formylmorpholine (NFM), pyridine and dimethylformamide (DMF) . For example, benzene alkylation degree usually contains up to 20 ppm by weight, for example from 0.05 to 2 ppm by weight of nitrogen from organic nitrogen impurities. In addition, the starting aromatic hydrocarbons are also often saturated with water, that is, they may contain from 500 to 1000 ppm by weight of water. For example, the byproduct stream of benzene / toluene from a styrene plant typically contains about 70% toluene, 25% benzene, up to 5% ethylbenzene, about 300 ppm water and a high content (typically from 0, 5 to 10 ppm based on nitrogen by weight of nitrogen compounds.

Since these impurities and especially organic nitrogen compounds can adversely affect the alkylation catalyst and, if present, the transalkylation catalyst, their content should be reduced in the total reaction mixture in contact with the catalyst (s). In the present method, at least part of the necessary reduction in the content of these impurities is achieved by passing a fresh aromatic feedstock, optionally after drying, and optionally in combination with a recycled aromatic stream through a clay processing unit containing one or more clay adsorbents, before the feedstock is supplied to the alkylation reaction zone and / or the transalkylation reaction zone. Clay treatment is usually carried out at a temperature of less than 130 ° C, such as from 40 ° C to less than 130 ° C, for example from 50 ° C to 125 ° C. Under these conditions, clay treatment is effective to remove most of the harmful nitrogen impurities, without contributing to the occurrence of undesirable side reactions. For example, in a cumene plant, residual cumene in a benzene stream passing through a clay processor can be isomerized into n-propylbenzene, which is difficult to separate from the cumene product. As shown in the following Examples, the proposed clay treatment method was found to minimize the isomerization of cumene to n-propylbenzene.

The clay processing unit may comprise a reactor of any conventional design, including a continuous and variable flow reactor, a batch reactor, and a fixed-bed reactor. The processing unit can be made in the form of a separate reactor, which is connected in series with the alkylation / transalkylation reactor. Alternatively, the processing unit may contain only one section of the reactor containing both the treatment zone and the alkylation or transalkylation. Alternatively, a multi-layer reactor may be used in which the first layer contains a treatment unit, in which an alkylating / transalkylating agent is introduced into the second layer and into subsequent layers in a chain of several layers and in which the transalkylation reactor can be placed further in the chain.

By passing the unreacted alkylated aromatic compound through the processing unit, the content of organic nitrogen impurities in the aromatic feed for the alkylation reactor and / or transalkylation reactor can be reduced to less than 0.03 ppm by weight and preferably below measurable levels.

As will be illustrated in the embodiments of the invention shown in the accompanying drawings, the clay processing method of the present invention can be used in various configurations to reduce the level of nitrogen impurities in the aromatic alkylation feedstock. For example, if the aromatic feed is a benzene / toluene by-product stream obtained from a styrene plant, this stream can either be (a) treated with clay to remove nitrogen compounds and then distilled to extract benzene before directing the benzene stream to the plant for the production of ethylbenzene as part of fresh benzene feedstock, (b) distilled and dried to recover dried benzene, which is then treated with clay to remove nitrogen compounds before being sent to the plant on the production of ethylbenzene or (c) distilled to extract benzene, which is then sent to the installation for the production of ethylbenzene and treated with clay as part of the fresh benzene feedstock to remove nitrogen compounds.

As shown in Figure 1, in the method for alkylating aromatic compounds according to the first embodiment of the invention, the alkylation section 11 receives a clay-treated aromatic hydrocarbon stream through line 12 and an alkylating agent stream through line 13. The alkylation section 11 contains one or more reaction zones, where the clay-treated stream aromatic hydrocarbon and the alkylating agent are contacted with an acid alkylation catalyst under such conditions that at least a portion of the alkylating agent enters into reacting an aromatic hydrocarbon to produce an alkylation effluent containing the desired alkylated aromatic compound, unreacted aromatic hydrocarbon, and typically some polyalkyl aromatic compounds. Typically, the conditions in the alkylation section 11 are such that the aromatic hydrocarbon is at least partially in the liquid phase.

The stream leaving the alkylation section 11 is fed via line 14 to the separation section 15, which also receives fresh aromatic hydrocarbon feeds containing organic nitrogen impurities and at least 150 ppm by weight, typically up to 400 hours, through line 16 ./mln by weight of water. The separation section 15 typically comprises a distillation chain comprising a first distillation tower for separating fresh and unreacted aromatic hydrocarbon through line 17, a second distillation tower to extract the desired alkylated aromatic compound through line 18, and a third distillation tower to separate the polyalkyl aromatic compounds through line 19 Usually, the first distillation tower works to remove water impurities introduced into fresh aromatic hydrocarbon feed so that aromatic hydrocarbons leaving the separation section 15 along line 16 contains less than 20 ppm by weight, for example less than 10 ppm by weight, of water. In an alternative embodiment of the invention (not shown), fresh aromatic hydrocarbon feeds are passed through a separate drying section before being fed to separation section 15.

The aromatic stream along line 17 contains organic nitrogen impurities introduced with fresh aromatic hydrocarbon feed and is passed through a clay processing unit 21, which operates at a temperature of from 50 ° C to 125 ° C. The clay processing unit reduces the content of organic nitrogen impurities in the aromatic compound stream to less than 0.03 ppm by mass so that the processed aromatic compound stream exiting the clay processing unit 21 through line 22 can be fed directly to the alkylation section 11 on line 12.

In the illustrated embodiment, a portion of the treated aromatic compound stream exiting the clay processing unit 21 via line 22 also enters the transalkylation section 23 along with polyalkyl aromatic compounds through line 19. The transalkylation section 23 contains one or more reaction zones where the processed aromatic hydrocarbon and a polyalkyl aromatic hydrocarbon are contacted with an acid transalkylation catalyst under conditions such that at least a portion of the polyalkyl aro aticheskogo hydrocarbon stream reacts with the treated aromatic hydrocarbon stream to produce a transalkylation effluent containing the desired alkylated aromatic compound, unreacted polyalkyl aromatic hydrocarbon and unreacted aromatic hydrocarbon. Typically, the conditions in the transalkylation section 23 are such that the aromatic hydrocarbon is at least partially in the liquid phase. The transalkylation effluent is passed through line 24 to a separation section 15 to recover the desired alkylated aromatic compound through line 18 and to separate the unreacted aromatic hydrocarbon and unreacted polyalkyl aromatic hydrocarbon through lines 17 and 19, respectively.

In a second embodiment of the invention, shown in Figure 2, fresh aromatic hydrocarbon feed containing water and organic nitrogen impurities is supplied via line 31 through an optional drying section 32 to the clay processing unit 33. The clay processing unit 33 operates at a temperature of from 50 ° C to 125 ° C and reduces the content of organic nitrogen impurities in the aromatic raw materials so that the processed aromatic stream leaving the clay processing unit 33 through line 34 contains less than 0.03 hours / million by weight of such impurities. The processed aromatic stream is fed through line 34 to an alkylation section 35, which also receives an alkylating agent via line 36, and a transalkylation section 37, which also receives a polyalkyl aromatic hydrocarbon via line 38. The alkylation and transalkylation sections 35, 37 operate as described with reference to Figure 1, to obtain the target alkylated aromatic compounds. The effluent from the alkylation and transalkylation sections 35, 37 is fed through lines 39, 41 to the separation section 42, where the desired alkylated aromatic compound is recovered via line 43 and the unreacted polyalkyl aromatic hydrocarbon is removed via line 38. Unreacted aromatic hydrocarbon is also separated into separation sections 42, and it can be recycled through line 44 through the clay processing unit 33 or through line 45 in the alkylation and transalkylation sections 35, 37.

The invention will now be more specifically described with reference to the following Examples.

Examples

Example 1

дюйма (1,3 см) с общей длиной 24 дюйма (61 см). Блок обработки размещали в рубашке с горячим маслом для подогрева сырья до требуемой температуры на входе и для поддержания температуры блока обработки. Для ароматического сырья использовали резервуар для хранения, а для подачи ароматического сырья в блок обработки использовали поршневой насос. Расход ароматического сырья устанавливали настройками насоса и контролировали с помощью электронного измерителя массы. Условиями эксплуатации блока обработки управляли и контролировали с помощью автоматической системы контроля. Исходное сырье и отходящий поток из блока очистки анализировали с помощью газового хроматографа Hewlett Packard 5890 Series II, снабженного пламенно-ионизационным детектором (FID) и колонкой Chrompack CP-Wax 52СВ, имеющей внутренний диаметр 0,25 мм, толщину пленки 0,5 мкм и длину 60 метров.The test was carried out in a processing unit with a fixed bed made of Schedule 40 Stainless Steel 316 pipe with a diameter

inches (1.3 cm) with a total length of 24 inches (61 cm). The processing unit was placed in a jacket with hot oil to heat the raw material to the required inlet temperature and to maintain the temperature of the processing unit. A storage tank was used for aromatic raw materials, and a piston pump was used to supply aromatic raw materials to the processing unit. The consumption of aromatic raw materials was set by the pump settings and controlled using an electronic mass meter. The operating conditions of the processing unit were controlled and controlled using an automatic control system. The feedstock and effluent from the purification unit were analyzed using a Hewlett Packard 5890 Series II gas chromatograph equipped with a flame ionization detector (FID) and a Chrompack CP-Wax 52CB column having an internal diameter of 0.25 mm, a film thickness of 0.5 μm, and 60 meters long.

Twenty grams of fresh BASF F-24 Clay was loaded into the processing unit. The processing unit was heated in pure benzene and the clay was dried at 125 ° C for four days. Then introduced aromatic raw materials containing 95.5% of the mass. benzene, 4.5% of the mass. cumene, 25 ppm by weight (wtppm) of water and 10 ppm by weight (wtppm) of n-propylbenzene (NPB). The composition of this aromatic feed is similar to that of the recycle benzene stream in the cumene plant, which typically contains some alkyl aromatic compounds in addition to the impurities that were in fresh benzene (e.g. recycle benzene in the cumene plant, typically contains from about 0.1 to about 10% by weight of cumene). The mass hourly space velocity (WHSV) of the feed was 5 h ⁻¹ , the temperature of the processing unit was varied between 95 and 183 ° C., and the pressure at the outlet of the processing unit was maintained between 420 and 450 psi overpressure (PSIG). The effluent from the processing unit was periodically collected and analyzed. The concentrations of NPB in the effluent from the processing unit are shown in Table 1 below.

It should be noted that the amount of NPB obtained in the processing unit increases rapidly with increasing temperature of the processing unit. Since NPB boils in the vicinity of cumene, it cannot be economically separated from cumene once it is formed. Thus, any NPB obtained in the processing unit will contaminate the cumene product and reduce the purity of the cumene product. Depending on the design and operation of the cumene plant, each 1 ppm by weight of NPB obtained in the processing unit can increase the concentration of NPB in the cumene product by 2 to 4 ppm by weight and reduce the purity of the cumene product by the same amount. The estimated increase in NPB content in the cumene product for each temperature of the treatment unit is also listed in Table 1 above.

Thus, it is advisable to operate the processing unit at low temperatures, preferably at 125 ° C. or lower, in order to avoid excessive NPB production in the processing unit and a significant negative effect on the purity of the cumene product.

Example 2

The same experimental setup and control system as described in EXAMPLE 1 was also used in this example. Additionally, the feedstock and effluent from the processing unit were also analyzed for nitrogen.

Twenty grams of fresh BASF F-24 Clay was loaded into the processing unit. The processing unit was heated in pure benzene and the clay was dried at 125 ° C for four days. Then introduced aromatic raw materials containing 98% of the mass. benzene, 2% of the mass. cumene, 6 ppm NPB by mass, 25 ppm water by mass, 5.8 ppm pyridine by mass, 3.8 ppm N-methylpyrrolidone (NMP) by mass and 4.4 ppm N-formylmorpholine (NFM) by weight. The bulk WHSV of the feed was 5 h ⁻¹ , the temperature of the processing unit was maintained between 123 and 125 ° C., and the pressure at the outlet of the processing unit was maintained between 420 and 450 psi overpressure (PSIG). The effluent from the processing unit was periodically collected and analyzed for the content of NPB and nitrogen compounds. The concentrations of NPB and nitrogen compounds determined in the effluent from the processing unit are shown in Table 2 below.

As the above data show, in the present invention, it was possible to efficiently remove nitrogen-containing poisons in the aromatic feedstock over a long period of time. The example also demonstrated that there was no detectable NPB content derived from cumene in the feed.

Although the present invention has been described and illustrated with reference to specific embodiments, those skilled in the art will understand that the invention may relate to variations not necessarily shown herein. For this reason, reference should hereinafter be made solely to the appended claims for the purpose of determining the true scope of the present invention.

Claims (25)

1. The method of alkylation of aromatic compounds, including: (a) providing an aromatic hydrocarbon feed comprising an alkylatable aromatic hydrocarbon of at least 150 ppm by weight of water and at least one organic nitrogen impurity, the alkylated aromatic hydrocarbon being benzene; (b) removing water from the aromatic hydrocarbon feed in the dehydration zone to obtain a dehydrated aromatic feed having a water content of not more than 20 ppm by weight; (c) contacting the dehydrated aromatic feedstock with an adsorbent from clay under conditions including a temperature of less than 130 ° C, so that the adsorbent removes at least a portion of the organic nitrogen impurity contained in the feedstock to obtain a processed aromatic feedstock; and (d) feeding the treated aromatic feedstock to the alkylation reaction zone and / or transalkylation reaction zone. 2. The method according to p. 1, in which the conditions for contacting (a) include a temperature of from 50 ° C to 125 ° C. 3. The method of claim 1, wherein the dehydration zone comprises a distillation column. 4. The method according to p. 3, in which the processed aromatic feedstock is supplied to the alkylation reaction zone, and the method further includes: (e) contacting said treated aromatic feedstock in said alkylation zone with an alkylating agent in the presence of an acid alkylation catalyst and under such conditions that at least a portion of the alkylating agent is reacted with an alkylated aromatic hydrocarbon stream to produce an alkylated aromatic hydrocarbon effluent the compound and unreacted aromatic hydrocarbon; (f) supplying said alkylation effluent to said distillation column to recover at least a portion of the unreacted aromatic hydrocarbon; and (g) contacting the unreacted aromatic hydrocarbon recovered in (f), together with the dehydrated aromatic feedstock, with clay adsorbent in (c). 5. The method according to p. 3, in which the processed aromatic feedstock is supplied to the transalkylation reaction zone, and the method further includes: (h) contacting said treated aromatic feedstock in said transalkylation zone with a polyalkyl aromatic compound in the presence of an acid transalkylation catalyst and under such conditions that at least a portion of the polyalkyl aromatic compound is reacted with an alkylated aromatic hydrocarbon stream to produce a transalkylated effluent containing alkyl aromatic compound and unreacted aromatic hydrocarbon; (i) supplying said transalkylation effluent to said distillation column to recover at least a portion of the unreacted aromatic hydrocarbon; and (j) contacting the unreacted aromatic hydrocarbon recovered in (i), together with the dehydrated aromatic feedstock, with clay adsorbent in (c). 6. The method according to any preceding paragraph, in which the aromatic hydrocarbon feed is supplied to the specified dehydration zone without pre-treatment to remove organic nitrogen impurities. 7. A method of alkylation of aromatic compounds, including: (a) providing a feedstock containing an alkylatable aromatic hydrocarbon, up to 400 ppm by weight of water, at least 0.01% by weight. at least one alkylated aromatic hydrocarbon and at least one organic nitrogen impurity, wherein the alkylated aromatic hydrocarbon is benzene and the at least one alkylated aromatic hydrocarbon is cumene; (b) passing at least a portion of the feedstock through a processing unit containing clay adsorbent under conditions including a temperature of from 40 ° C to less than 130 ° C, so that the adsorbent removes at least a portion of the organic nitrogen impurity contained in the feed raw materials, obtaining processed feedstock; and (c) feeding at least a portion of the alkylatable aromatic hydrocarbon from the treated feedstock to the alkylation reaction zone and / or transalkylation reaction zone. 8. The method according to p. 7, further comprising: (d) removing water from the feedstock in the dehydration zone so that the remainder of the feed to the treatment unit in (b) contains no more than 20 ppm by weight of water. 9. The method of claim 7, wherein at least a portion of the alkylated aromatic hydrocarbon is introduced into the feed into an unreacted alkylated aromatic hydrocarbon recycled from the alkylation reaction zone and / or transalkylation reaction zone. 10. The method of claim 7, wherein at least a portion of the alkylated aromatic hydrocarbon is present in the fresh alkylated aromatic hydrocarbon fed to the method. 11. The method according to any one of paragraphs. 1-5, 7-10, in which the alkylated aromatic hydrocarbon contains benzene.

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