KR20170013947A - Process for the production of xylene - Google Patents

Abstract

In the production process of para-xylene, a feed comprising a C ₆₊ aromatic carbon pixel is separated into a toluene-containing stream, a C ₈ aromatic hydrocarbon-containing stream and a C ₉₊ aromatic hydrocarbon-containing stream. The toluene-containing stream is contacted with a methylating agent to convert the toluene to xylene to produce a methylated effluent stream. The para-xylene is recovered from the C ₈ aromatic hydrocarbon-containing stream and the methylated effluent stream in the para-xylene recovery section to produce a para-xylene depleted stream, which is then separated from the para-xylene depleted stream Is contacted with the xylene isomerization catalyst under liquid phase conditions effective to isomerize the xylene in the isomerization stream to produce an isomerization stream. The C ₉₊ -containing stream is contacted with a transalkylation catalyst under conditions effective to convert the C ₉₊ aromatic to a C _{8 -aromatic} to produce a transalkylation stream, the transalkylation stream comprising para-xylene recovery Section.

Description

PROCESS FOR THE PRODUCTION OF XYLENE [0002]

Inventor (s) : Mitchell Mollinier, Ground S. Abby Chan, Jeffrey Elle. Andrews, Mr. Timothy. Bender, Robert. Tinzer, Dennis Jay. Stanley, George J. Wagner

Cross-reference to related application

This application claims priority to U.S. Provisional Application No. 62 / 018,726, filed June 30, 2014, and EP 14180052.4, filed on August 6, 2014, All of these applications are incorporated herein by reference in their entirety. Related Applications include U.S. Provisional Application No. 62 / 018,724, filed June 30, 2014 (having attorney case number 2014EM155), and U.S. Serial No. 00000000, filed on Mar. 0, 0 (Attorney Docket No. 2015EM128 .

Field of invention

The present invention relates to a process for the production of xylenes, in particular for the production of para-xylenes.

The main source of xylene is the contact lipid, which is produced by contacting the petroleum naphtha with a hydrogenation / dehydrogenation catalyst on the support. The resulting lipoate is a complex mixture of C ₆ -C ₈ aromatics and paraffins, in addition to a significant amount of heavy aromatic hydrocarbons. After removal of the hard (C _5- ) paraffinic component, the remaining amount of the lipomate is generally separated into C _7- , C ₈ and C ₉₊ containing fractions using multiple distillation steps. The benzene can then be recovered from the _C7- containing fraction to leave a toluene-rich fraction, which is generally added by toluene disproportionation and / or transalkylation using a portion of the _{C9 +} aromatic containing fraction of it can be used to generate the C ₈ aromatics. The C ₈ -containing fraction is fed into a xylene production loop where para-xylene is generally recovered by adsorption or crystallization and the resulting para-xylene depleted stream is treated with catalytic conversion to produce xylene And is isomerized again. The resulting isomerized xylene stream may then be recycled to the para-xylene recovery unit.

Although benzene and toluene are important aromatic hydrocarbons, the demand for xylene, especially para-xylene, surpasses the demand for benzene and toluene, and is now growing at a rate of 5-7% per year. Therefore, there is a continuing need to develop aromatic manufacturing techniques that maximize the production of para-xylene while minimizing the associated capital and operating costs.

According to the present invention, as an improved process for producing para-xylene, optionally with benzene and / or ortho-xylene, a methylation unit is added to the para-xylene production complex to produce toluene and / or To convert the benzene to the additional xylene. The methylation unit produces a C ₈ aromatic product that is para-xylene rich, but has little or no additional ethylbenzene. As a result, the manufacturing and operating costs of the xylene separation section can be reduced, and a less expensive liquid-phase process can be used for at least part of the xylene isomerization section. If necessary, the accumulation of ethylbenzene in the xylenes production loop can be achieved by adding a vapor phase isomerization unit and / or by feeding a portion of the para-xcelene depleted stream to the transalkylation unit and / or by conventional techniques such as distillation, or Membrane, or selective adsorption, or a combination thereof, to remove ethylbenzene from the xylene stream.

Thus, in one aspect, the present invention provides a process for the production of para-xylene, wherein the feed stream comprising C ₆₊ aromatic hydrocarbons is separated into at least a toluene containing stream, a C ₈ aromatic hydrocarbon containing stream and a C ₉₊ aromatic hydrocarbon containing stream In the production process of para-xylene. At least a portion of the toluene containing stream is contacted with the methylating agent under conditions effective to convert the toluene to xylene to produce a methylated effluent stream. Para-xylene is recovered from the C ₈ aromatic hydrocarbon-containing stream and the methylated effluent stream to produce one or more para-xylene depleted streams. Wherein at least a portion of the para-xylene depleted stream is contacted with a xylene isomerization catalyst under liquid phase conditions effective to isomerize the xylene in the para-xylene depleted stream to produce an isomerization stream, And recycled to the xylene recovery stage. At least a portion of the C ₉₊ aromatic hydrocarbon-containing stream is contacted with a transalkylation catalyst under conditions effective to convert the C ₉₊ aromatic to a C _{8 -aromatic} to produce a transalkylation stream and the transalkylation stream is subjected to a toluene methylation step and Para-xylene recovery step.

In a further aspect, the present invention provides an apparatus for producing para-xylene, comprising: a catalytic reformer for producing a reformate stream comprising C ₆₊ aromatic hydrocarbons, a reformate stream comprising at least a toluene-containing stream, a C ₈ aromatic hydrocarbon C ₉₊ aromatic-containing stream and a first separation system, followed by conversion of toluene in the toluene-containing stream with xylene toluene methylation unit for generating a methylation effluent stream, C ₈ aromatic hydrocarbon-containing stream, methylation outlet for separating a hydrocarbon-containing stream A second separation system for recovering para-xylene from the water stream and the transalkylation effluent stream to produce at least one para-xylene depleted stream, isomerizing the xylene in the at least one para-xylene depleted stream to form a first isomerization Liquid phase xylene for producing a stream It was converted to the isomerization unit, a first recirculation system for at least a portion of the isomerized stream to recycle in a second separation system, and the C ₉₊ aromatic C ₉₊ aromatic hydrocarbons contained in the stream to a C _8- aromatic transalkylation effluent stream And a transalkylation unit for producing para-xylene.

1 is a flow diagram of a process for producing para-xylene from a contact lipoate according to a first embodiment of the present invention.
Figure 2 is a flow chart illustrating a process for producing para-xylene from a contact lipid according to a variant of the first embodiment of the present invention.
3 is a flow diagram of a process for preparing para-xylene from a contact lipid according to a further variation of the first embodiment of the present invention.
4 is a flow diagram of a process for producing para-xylene from a contact lipidate in accordance with another further variation of the first embodiment of the present invention.

The present invention describes a process and apparatus for preparing para-xylene from a lipoate or similar aromatic fraction optionally with benzene and / or ortho-xylene. In this process, a methylation unit is added to the para-xylene production complex to convert the toluene and / or benzene in the lipoate fraction to the additional xylene. Since the methylation unit is para-xylene rich, but can produce C ₈ aromatic products with little or no additional ethylbenzene, the manufacturing and operating costs of the xylene separation section can be reduced and the cost of the liquid phase process Can be used in the xylene isomerization section. If desired, the accumulation of ethylbenzene in the xylene production loop can be achieved by adding a vapor phase isomerization unit and / or by feeding a portion of the para-xylene depleted stream to the transalkylation unit and / or by conventional techniques such as distillation, , ≪ / RTI > or selective adsorption, or a combination thereof, to remove ethylbenzene from xylene.

Any method known in the art for adding the methyl group to the phenyl ring can be used in the methylation step of the present process. However, in certain preferred embodiments, the methylation step utilizes a high p-selectivity methylation catalyst, such as those used in U.S. Patent Nos. 6,423,879 and 6,504,072, the entire contents of which are incorporated herein by reference. Such catalysts can be prepared by reacting 2,2-dimethylbutane (such as 2,2-dimethylbutane with a molecular weight of from about 0.1 to about 15 sec ^-1 , such as from about 0.5 to about 10 sec ^-1 , as measured at a temperature of 120 캜 and 2,2-dimethylbutane pressure of 60 torr Lt; RTI ID = 0.0 > diffusion < / RTI > As used herein, the diffusion parameter of a specific porous crystalline material is defined as D / r ² x 10 ⁶ , where D is the diffusion coefficient (cm ² / sec) and r is the crystal radius (cm) The diffusion parameters assumed can be derived from sorption measurements, provided that the plane sheet model describes a diffusion process. Thus, for a given sorbate loading Q, the value Q / Q _∞ (where Q _∞ is the equilibrium sorbate loading) is mathematically related to (Dt / r ² ) ^1/2 , where t is the time (sec) required to reach the sorbate loading Q. The plane A graphical solution for a sheet model is presented by J. Crank, "The Mathematics of Diffusion ", Oxford University Press, Ely House, London, 1967, the entire contents of which are incorporated herein by reference.

The molecular sieves used in the para-selective methylation process are generally medium pore size aluminosilicate zeolites. The mesoporous zeolite is generally defined as having a pore size of from about 5 A to about 7 A such that the zeolite is free to sorb molecules such as n-hexane, 2-methylpentane, benzene and para-xylene. Another general definition for mesoporous zeolites involves the Constraint Index test described in U.S. Patent No. 4,016,218, which is incorporated herein by reference. In this case, the mesoporous zeolite has a constraint index of about 1-12, as measured for the zeolite alone, without introduction of the oxide modifier and before any steaming to adjust the diffusion of the catalyst. Specific examples of suitable intermediate pore zeolites include ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35, ZSM- 11 is particularly preferable.

The mesoporous zeolites described above are very effective in the methylation process of the present invention because the size and shape of the pores of the zeolite prefer para-xylene generation compared to other xylene isomers. Typical forms of such zeolites have an excessive diffusion parameter value in the range of 0.1-15 sec ^-1 mentioned above. However, the required degree of diffusion for the catalyst is achieved by severely straining the catalyst to achieve a controlled reduction of the micropore volume of the catalyst to at least 50%, preferably 50-90%, of that of the unstimulated catalyst . The reduction in micropore volume is induced by measuring the n-hexane adsorption capacity of the catalyst before and after steaming at 90 < 0 > C and 75 torr n-hexane pressure.

The steaming of the zeolite is carried out at a temperature of at least about 950 DEG C, preferably from about 950 DEG C to about 1075 DEG C, most preferably from about 1000 DEG C to about 1050 DEG C for about 10 minutes to about 10 hours, Lt; / RTI >

Prior to steaming, the zeolite is combined with at least one oxide modifier, such as one or more oxides selected from elements of Groups 2 to 4 and Group 13 to 16 of the Periodic Table, to effect the desired degree of diffusivity and the desired controlled reduction in micropore May be desirable. Most preferably, the at least one oxide modifier is selected from boron, magnesium, calcium, lanthanum, and most preferably phosphorus. In some cases, the zeolite may be combined with a combination of more than one oxide modifier, such as phosphorus and calcium and / or magnesium, in this way, the steaming harshness required to achieve the target diffusivity value It may be possible to reduce it. In some embodiments, the total amount of oxide modifier present in the catalyst, as measured on an elemental basis, is from about 0.05 wt% to about 20 wt%, preferably from about 0.1 wt% to about 10 wt% %. ≪ / RTI >

When the modifier comprises phosphorus, incorporation of the modifier into the catalyst is readily accomplished by the methods described in U.S. Patent Nos. 4,356,338, 5,110,776, 5,231,064 and 5,348,643, Are incorporated herein by reference. Treatment with the phosphorus containing compound is readily accomplished by contacting the zeolite present alone or in combination with a binder or matrix material with a solution of an appropriate phosphorus compound followed by drying and calcining to convert the phosphorus to the oxide form . Contact with the phosphorus containing compound is generally carried out at a temperature of from about 25 [deg.] C to about 125 [deg.] C for a time of from about 15 minutes to about 20 hours. The phosphorus concentration in the contact mixture may be from about 0.01 to about 30 weight percent. Examples of suitable phosphorus compounds include, but are not limited to, phosphonic acids, phosphinic acids, phosphorous acids and phosphoric acids, salts and esters of such acids, and phosphorus halides.

After contact with the phosphorus containing compound, the porous crystalline material can be dried and calcined to convert the phosphor to an oxide form. The calcination is carried out in an inert atmosphere or in the presence of oxygen, for example in air at a temperature of from about 150 ° C to 750 ° C, preferably from about 300 ° C to 500 ° C, for 1 hour or more, preferably for 3-5 hours . Similar techniques known in the art can be used to incorporate other modified oxides into the catalyst used in the alkylation process.

In addition to zeolites and modified oxides, the catalyst used in the methylation process may include one or more binders or matrix materials that are resistant to the temperature and other conditions used in the process. Such materials include active and inactive materials such as clay, silica and / or metal oxides such as alumina. The latter may be naturally occurring or may be in the form of a gelatinous precipitate or gel comprising a mixture of silica and a metal oxide. The use of active materials tends to alter the conversion and / or selectivity of the catalyst and is therefore generally undesirable. The inert material functions properly as a diluent to control the conversion amount in a given process, so that the product can be obtained economically or regularly without using any other means for controlling the rate of the reaction. Such materials can be incorporated into naturally occurring clays, such as bentonite and kaolin, to improve the crushing strength of the catalyst under commercial operating conditions. The material, clay, oxide, etc., acts as a binder for the catalyst. It is desirable to provide a catalyst having good crush strength because it is desirable to prevent the catalyst from destroying the catalyst in powder form for commercial use. These clay and / or oxide binders are generally used solely for the purpose of improving the crushing strength of the catalyst.

The naturally occurring clays that can be combined with the porous crystalline material include montmorillonite and kaolin classes, such as subbentonite, and Dixie, McNamee, Goergia and Florida Florida) clay or as other clays in which the major mineral constituents are halloysite, kaolinite, dickite, nacrite or anauxite. . Such clays can be used in the raw state as it is mined, or can be initially treated with calcination, acid treatment or chemical modification.

In addition to the above-mentioned materials, the porous crystalline material can be a porous matrix material, such as silica-alumina, silica-magnesia, silica-zirconia, silica-tori, silica- beryllium, silica- Silica-alumina-zirconia, silica-alumina-magnesia and silica-magnesia-zirconia.

The relative ratio of the porous crystalline material to the inorganic oxide matrix is such that the content of electrons is in the range of about 1 wt% to about 90 wt%, and more typically, when the composite is prepared in the form of beads, To about 80% by weight, based on the total weight of the composition. The matrix material preferably comprises silica or kaolin clay.

The methylation catalyst used in the process of the present invention may optionally be pre-coked. The precoking step can be performed by initially loading the un-corked catalyst into the methylation reactor. Subsequently, as the reaction proceeds, the cork is deposited on the catalyst surface and thereafter cyclically regenerated through exposure to an oxygen-containing atmosphere at elevated temperature to a desired range, typically from about 1 wt% to about 20 wt% %, Preferably from about 1 wt% to about 5 wt%.

The methylation of toluene according to the present process can be carried out by any known methylating agent, but preferred methylating agents include methanol and / or a mixture of carbon monoxide and hydrogen.

Suitable conditions for the methylation reaction are from 350 ° C to 700 ° C. At a temperature of, for example, 500 ° C to 600 ° C, a pressure of 100 to 7000 kPa absolute pressure, a space velocity per weight hour of 0.5 to 1000 hr ^-1 , and a methanol (in the reactor charge) of about 0.2 or more, Toluene. ≪ / RTI > The present process may suitably be carried out in a fixed bed, a moving bed or a fluid bed catalyst. If continuous control of the degree of cork loading is desired, a moving bed or fluidized bed configuration is preferred. Using a mobile bed or fluidized bed configuration, the degree of cork loading can be controlled by varying the severity and / or frequency of subsequent oxidative regeneration in the catalyst regenerator. One example of a fluidized bed process suitable for methylating toluene involves staged injection of a methylating agent at one or more locations downstream of the toluene feed location. Such a process is described in U.S. Patent No. 6,642,426, which is incorporated herein by reference in its entirety.

Using this process, the toluene has a per-pass aromatic conversion of at least about 15 wt% and at least about 75 wt% (based on the total C ₈ aromatics) of trimethylbenzene at a level of less than 1 wt% May be alkylated by methanol to produce para-xylene with selectivity. Some of the unreacted toluene and the methylating agent and the by-product water can be recycled to the methylation reactor and the heavy by-products can be transferred to the fuel batch. The C ₈ fraction is transferred to a para-xylene separation section, which section is typically operated by fractional crystallization or by selective adsorption or both to recover the para-xylene product stream from the alkylation effluent and recover C ₇ and para mainly containing C ₈ hydrocarbons - and Kane xylene depleted residue stream. Since the toluene methylation unit enhances the para-xylene content of the lipoate C ₈ fraction, the size of the para-xylene separation section can be reduced. This is a significant advantage because the para-xylene separation section is one of the most expensive processes in the aromatic complex, both in terms of capital cost and operating cost.

After recovery of the para-xylene from the para-xylene separation section, the remaining para-xylene depleted stream is isomerized back to equilibrium before being recycled back to the para-xylene separation section. In this process, isomerization of the para-xylene depleted stream is carried out alone in the liquid phase isomerization unit, or in a liquid phase isomerization unit connected in parallel with the vapor phase isomerization unit, the units are operated simultaneously or alternately . ≪ / RTI >

Although any liquid phase contact isomerization process known to those skilled in the art may be used in the liquid phase xylene isomerization unit, one preferred contacting system is disclosed in U.S. Patent Application Publication Nos. 2011/0263918 and 2011/0319688 The entire contents of each of which are incorporated herein by reference. Suitable conditions for the liquid phase isomerization process employed herein include a temperature of from about 230 캜 to about 300 캜 and a pressure of from about 1300 to about 3500 kPa selected to maintain a substantially para-xylene depleted stream in the liquid phase. In some embodiments, the weight hourly space velocity (WHSV) may be from about 0.5 to about 10 hr <" ¹ >.

In the case of the present invention, the vapor phase isomerization unit may also utilize any known isomerization catalyst system, but it is also possible to convert some or all of the ethylbenzene in the para-xylene depleted stream as well as to return the xylene to an equilibrium concentration Lt; / RTI > catalyst system. Ethylbenzene removal can be carried out by dealkylation to benzene or by isomerization to xylenes. One preferred vapor phase isomerization process is described in U.S. Patent No. 5,516,956, the entire contents of which are incorporated herein by reference. Suitable conditions for the vapor phase isomerization process include a temperature of about 660 내지 to about 900 ((350 캜 to 480 캜), a pressure of about 50 to about 400 psig (446 to 2860 kPa), a WHSV of about 3 to 50 hr ^-1 , And a molar ratio of hydrogen to hydrocarbons from 0.7 to about 5.

The process may also include converting a C ₉ aromatics, C ₁₀ aromatics and some C ₁₁ aromatics in the lipomate feed to equilibrium xylenes, or by converting them into benzene or toluene transferred from other parts of the process Alkylation units. The xylene in the transalkylation effluent may then be fed to the para-xylene separation section for recovery of the para-xylene, while any benzene or toluene produced in the transalkylation process may be fed to the toluene methylation Is easily supplied to the unit. While any liquid or vapor phase transalkylation unit may be utilized in the present process, one preferred unit utilizes the multi-stage contact system described in U.S. Patent No. 7,663,010, the entire contents of which are incorporated herein by reference. The transalkylation unit, and the entire contents are used to generate the benzene and toluene, using xylene and aromatic C ₉₊ feed as described in U.S. Patent Application Publication No. 2012/0149958 the disclosure of which is incorporated herein by reference, in which the Benzene and / or toluene can be used as feed to the toluene methylation unit to produce a higher para-xylene purity feed to the para-xylene recovery stage. Additionally, some or all of the external benzene or imported benzene feed may be transalkylated with the C ₉₊ aromatic feed to produce toluene and / or xylene. Finally, the C ₉₊ aromatic molecule can be fractionated into a concentrated C ₉₊ stream consisting of propylene benzene and methyl ethylbenzene, which is transalkylated with benzene to produce toluene and ethylbenzene. The toluene and ethylbenzene may then be treated in a toluene methylation unit to generate para-xylene and light olefins by recycling. In addition to the toluene produced by the reforming section and / or the transalkylation section, the imported toluene may also be fed to the toluene methylation unit for the production of incremental para-xylene. Such imported toluene is preferably oxygen stripped, and such an imported toluene storage tank is preferably treated with a nitrogen blanket. Hereinafter, the present invention will be described more specifically with reference to the accompanying drawings.

1 illustrates a process for preparing para-xylene according to a first embodiment of the present invention wherein the naphtha feedstock is fed by line 11 to a contact reformer (e.g., a semi-regenerative reformer, (Continuous contact reformer) 12. The effluent from the contact reformer 12 is a complex mixture of aliphatic and aromatic hydrocarbons and after removing the C ₅ -fraction in a pentane eliminator (not shown), the remaining C ₆₊ fraction is removed from the line 13 To the lipomate divider 15. Hydrogen is also produced in the contact reformer 12 and is present in the gas phase isomerization section described below or in various units within a refinery or in which the cyclohexane unit or aromatic complex is not next to the refinery Is removed via line 14 for use in any other petrochemical process. Alternatively, the hydrogen may be sold as an export, or may be used for fuel, or may be flared.

Optionally separating Wall reformate splitter 15 which may be a distillation column is, in one embodiment, contains C ₆₊ fraction in the line (13) C _6- overhead stream, intermediate stream comprising C ₇ and C-containing bottom ₈₊ Stream. The C ₆ -containing overhead stream may also contain some or all of the toluene and / or C ₈ aromatics present in the line 13 with a non-aromatic n-butanol, depending on the particular economic purpose. In another embodiment (not shown), the lipoate divider 15 _divides the C _{6 +} fraction in line 13 into a C ₇ -containing overhead stream and a C ₈₊ containing Separate into the bottom stream. Again, the C ₇ -containing overhead stream may also contain some or all of the C ₈ aromatics present in line 13, along with the non-aromatic koh boilers, for specific economic purposes.

Returning to FIG. 1, in an alternative embodiment, the C ₆ -containing overhead stream or the C ₇ -containing overhead stream from the lipomate divider 15 is transported via line 16 to the extraction section 17 The extraction section may be a liquid-liquid extraction process, an extraction-distillation type process, or a hybrid thereof. The non-aromatic raffinate is removed from the extraction section 17 via line 18 and can be used in an olefin oligomerization or lipomate alkylation unit or in a steam cracker or refinery gasoline pool, Or as a fuel. Raffinate can also be used as a feed to the aromatic unit, generating additional aromatic molecules while generating hydrogen. The aromatic product from the extraction section 17 is removed via line 19 and optionally pretreated with a clay or molecular sieve catalyst to remove traces of olefins or other low level impurities and then to the benzene column 21 . The entrained water is removed from the aromatic extraction product in the benzene column 21 and the benzene product is collected via line 22, typically as a side stream from the benzene column 21. The benzene column bottom product may contain some trace amounts of xylene and heavy alkyl aromatics, but the toluene is enriched and transferred to the toluene methylation section 31 via line 23. The benzene in line 22 may be recovered for sale or for hydrogenation to produce cyclohexane or may be fed to the toluene methylation section 31 for further xylene production.

The toluene methylation section 31 also contains a C ₇ containing intermediate stream from the lipomate divider 15 via line 32 with a feed of methylating agent, typically methanol (not shown in FIG. 1) or dimethyl ether. . The division between line 16 (the C ₆ -containing overhead stream from the lipomate divider 15) and line 32 (the C ₇ containing intermediate stream from the lipomate divider 15) Aromatics delivered to the toluene methylation section 31 can be used to effectively control the level of non-aromatics transferred to the toluene methylation section 31, since the non-aromatics exiting the lipomate divider 15 through the extraction section 17 through the line 18 are removed via line 18. [ . As such, the additional flow through line 16 will reduce the total non-aromatics content in the feed to the toluene methylation section 31.

In the toluene methylation section 31, toluene from lines 23 and 32, optionally with benzene from column 21, is reacted with methanol to produce xylene and water. In some instances the C ₈ aromatics are also fed to the toluene methylation section 31 via lines 23 and 32 to dealkylate the ethylbenzene from the toluene methylation section 31 to benzene into the section 31, With subsequent methylation of the possible benzene to toluene or xylene.

Toluene can be passed through a toluene furnace and / or heat exchange equipment (not shown) before entering the toluene methylation section 31 to vaporize the toluene and heat it to the temperature required to maintain the methylation reaction The temperature depends on the type of catalyst used in the methylation process. Some catalysts require preheating toluene to 400 ° C, while other catalysts require toluene to be preheated to 600 ° C. Toluene can be heated to such temperatures in process heat exchange equipment and / or furnaces, depending on the heat sink available in the process. Toluene heated to a high temperature, for example a high temperature in a furnace, can reach a temperature at which toluene decomposes toluene with cork or heavy hydrocarbons that can affect the heat transfer rate. This rate of decomposition can be reduced by simultaneously supplying a diluent, such as nitrogen, hydrogen, fuel gas, steam, or a combination thereof, with the toluene at the upstream of the heat transfer equipment. The molar ratio of such diluent to toluene may vary from 0.01 to more than 10. Toluene decomposition may also be controlled using suitable metallurgical techniques for the tube, such as in a convection section or a radiation section, as will be understood by those skilled in the art. Examples include carbon steel, stainless steel, titanium, or other alloys. Special coatings and application can also be used to minimize toluene degradation and minimize corking. In addition, additives may be used to minimize toluene corking.

The efficiency of the methylation reaction is improved as the methylating agent, typically methanol, is distributed very widely within the reactor. The methylating agent may be introduced into the fixed bed or fluidized bed reactor in a number of different ways, for example, through one injection, through several injection points, or even through a sparger arrangement. The methylating agent may be dispersed into the reactor through nozzles that are level with the reaction vessel or through an internal distribution network. The number of flush nozzles in the reactor can be one, several, or multiple. Alternatively, the methylating agent may be introduced into the fixed bed or fluidized bed through an internal distributor. The internal divider may have one starpoint, several starpoints, and a plurality of starpoints. In the case of several stubs or multiple stubs, the divider may contain arteries branching from one or more common headers, and additional partial arteries may branch off from each artery to form a network of arteries. The artery may be designed to have a uniform diameter that is the same or different diameter than the common header, or it may be tapered to various diameters and different lengths. Depending on each common header or vein, there may be one or several nozzles that introduce a methylating agent. The size and length of these nozzles may be similar or different depending on the required distribution of the methylating agent into the reactor. Internal dispensers, arteries and nozzles can be isolated when used in a fluidized bed or fixed bed reactor. The determination of insulation can lead to carbon steel to stainless steel, or to metal engineering requirements that can lead to other types of alloys commonly used in titanium alloys. The bulk temperature of the methylated fluid and the surface temperature inside the distribution network are preferably below the decomposition temperature of the methylating agent and are known to those skilled in the art. The rate of degradation of the methylating agent can be reduced by co-feeding a diluent, such as nitrogen, hydrogen, fuel gas, steam, or a combination thereof. The molar ratio of such diluent to the methylating agent may vary from 0.01 to more than 10. The ideal distribution system for the methylating agent is a fractal dispenser containing a sequence of sizes of arteries and nozzles both radially and axially located throughout the reaction zone. This fractal distribution system can be designed to introduce the methylating agent at the same or different rates on an axial basis within the reactor. The axial distribution may also be controlled such that the rate of the methylating agent has two or more fractal distributors externally controlled from the reactor via common operating methods, such as valves, pumps, restrictive orifices, and the like.

The off-gas from the toluene methylation section 31 is collected by line 33 and may be used in an olefin oligomerization unit or a lipomate alkylation unit or may be transferred to a steam cracker or refinery for olefin recovery , And can be used as a fuel gas. The rest of the product from toluene methylation section 31 is supplied to the xylene distillation column 35 through the line 34, the column is a methylated product para-xylene rich C ₈ aromatics overhead stream and a bottom stream C ₉₊ . Since the amount of C ₉ aromatic less, the distillation column bottom circuit, that is the residence time of the C ₉ aromatic in the reboiler circuit can be very high. Such C ₉ aromatics can then be polymerized or condensed into high-grade hydrocarbon components when exposed to high temperatures for long periods of time, and the components can contaminate the bottom circuit or heat exchanger equipment. Additives can be used to control the rate of excessive polymerization or condensation. Alternatively, another source of C ₉ aromatics may be added to the distillation column to dilute the C ₉ aromatics from the toluene methylation process. These additional sources of C ₉ aromatics may be introduced continuously or introduced in batch or semi-batch mode and may be continuously purged from the system together with the toluene methylated C ₉ aromatics, or in batch or semi-batch mode Lt; / RTI > Additional C ₉ -aromatic sources may be introduced into the distillation column at any location in the distillation column, as can be determined by one skilled in the art.

Prior to the xylene distillation column 35, the product stream from the toluene methylation section 31 can be fed through a toluene distillation column (not shown) to recover unconverted toluene from the xylene and heavy components. New toluene may also be fed through the toluene distillation column. The feed point to the toluene distillation column for the product stream and the fresh toluene may be the same or different, as can be determined by those skilled in the art. In addition, other streams which may be fed into the toluene distillation column, such as naphtha reformer, xylene isomerization unit, disproportionation unit, transalkylation unit, or toluene and any other unit which may contain heavy aromatics, A stream may exist. Toluene from a toluene distillation unit is typically recovered as a liquid overhead product after condensation in a parallel or series configuration, via conventional cooling methods such as air fins, water coolers or process coolers, or a combination thereof. Toluene may also be recovered as a vapor stream either upstream of any refrigeration equipment, overhead of the distillation column, or as a side stream from the distillation column. Likewise, toluene can be recovered as a liquid product from one of the trays in the distillation column, for example, from 3-5 trays under the overhead of the distillation column. This is particularly effective when the distillation column contains component (s) that are harder than toluene, such as water or light hydrocarbons, and the component (s) can reduce the concentration of toluene by dilution. The distillation column separating the toluene from the heavy aromatics and impurities may also be a separating wall column with one or more than one partition. The recovered toluene can then be recycled back to the toluene methylation section 31 and the heavy component can be transported downstream for further processing.

The para-xylene enriched C ₈ aromatics overhead stream from the xylene distillation column 35 is transferred via line 36 to a separation section 37 where the para-xylene product is recovered via line 38 do. The separation section 37 may be based on an adsorption process or a crystallization process or any combination of the two, but may in any case comprise three separate streams, namely one stream with a ~ 20% para-xylene content ₈ parts), preferably ≥ 75% para-one stream having a xylene content (toluene methylation process effluent), and the equilibrium (~ 24%) of the para-one stream having a xylene content (transalkylation and / or the opposite sex Nitration effluent) in the presence of a catalyst. This optimization will result in substantial downsizing of the total separation section 37 as well as significant savings in equipment consumption. Such optimization is described in U.S. Patent Nos. 8,168,845; 8,529,757; 8,481, 798; 8,569,564; 8,580,120; U.S. Patent Application Publication No. 2012/0241384; And feeding the para-xylene enriched stream irrespective of the equilibrium xylene stream as described in U.S. Provisional Patent Application No. 61 / 946,052, the entire contents of which are incorporated herein by reference. Alternatively, the para-xylene enriched product or intermediate product from the adsorption process, having a para-xylene purity of less than 99.7 wt%, may be fed to the crystallization unit to concentrate para-xylene to a higher concentration. Likewise, a crystallization product or intermediate product having a para-xylene purity of less than 99.7 wt% can be fed to the adsorption process to concentrate para-xylene to a higher concentration.

A small amount of toluene will necessarily be present in the xylene feed to the para-xylene separation section 37. When a simulated moving bed (SMB) adsorption unit is used to recover para-xylene, the fraction of toluene present in the xylene feed is fractionated as a "crude" toluene product, which product contains a minor amount of xylene or water . This stream can be transferred directly to the toluene methylation section 31 without any treatment to remove trace amounts of xylene or water because the feed to the toluene methylation section 31 generally improves methanol utilization and provides Because it contains water as a co-feed to inhibit feed preheat coking. The combination of both the adsorption process and the crystallization process in the separation section 37 can include a small SBM unit (not shown) and a small crystallization unit (not shown) operating in series or in parallel, wherein the SMB unit Is mainly devoted to para-xylene separation from an equilibrated xylene stream, and the crystallization unit is mainly devoted to para-xylene separation from a para-xylene enriched stream.

After recovery of para-xylene, the residual liquid phase para-xylene depleted effluent from separation section 37 is collected via line 39 and passed through line 41 to the liquid phase to form a liquid phase xylene isomerization section 42, where the xylenes are isomerized to equilibrium in the isomerization section. The effluent from the liquid phase isomerization section 42 contains para-xylene (~ 24%) close to equilibrium and is fed via line 43 to a xylene rerun column 44, Containing bottom stream from the _lipoate column 15 via line 45. The _{C8 +} The C ₈ rich overhead stream is removed as an overhead from the xylene rylene column 44 and fed via line 46 to the separation sector 37 where the para-xylene product is collected via line 38 .

In some embodiments (not shown), the effluent from the liquid phase isomerization section 42 can be passed directly to the separation section 37 (without separation in the xylene rrhen column 44) The concentration of the heavy aromatics produced over the isomerization section 42 should belong to the specification of the separation process used in the separation section 37. U.S. Patent No. 7,989,672, which is incorporated herein by reference in its entirety, teaches the maximum permissible C ₉₊ aromatics concentration in the crystallization unit, which is also within the limits of a simulated moving bed adsorption process, It may be applied to a hybrid of an adsorption process. In the case of direct feeding from the liquid phase isomerization unit to the simulated moving bed adsorption unit, the C ₉ aromatics treated throughout the adsorption unit take all of the desorbent or slipstream and add the C ₉ aromatics in the desorbent to the heavy bed By treating it over a fractionation tower designed to have a higher boiling point than the desorbent or as a light component, i.e. having a lower boiling point than the desorbent. Examples of desorbents include toluene, paradiethylbenzene or tetralin. Other possible desorbents can also be used depending on the relative selectivity to para-xylene and adsorbed raffinate, i.e. meta-xylene, ortho-xylene and ethylbenzene. U.S. Patent No. 8,697,929, which is incorporated herein by reference in its entirety, discloses that C ₉ aromatics formation can be reduced when dissolved hydrogen is co-fed to a liquid isomerization unit, It is taught that the amount of purge is reduced. In this case, the C ₉ aromatics formation may be low enough to provide adequate separation from the xylene fraction by introducing the liquid phase isomerate into the xylenolrone column 44 or the top tray of the xylene column 35. Any dissolved hydrogen present can be evacuated from the system by those skilled in the art for the production design.

The C ₉ aromatics formation over the liquid phase isomerization catalyst is also a function of the amount of ethylbenz present in the feed. EB EB supply member in the water, or reduction in the liquid isomerization unit will be the formation of a C ₉ aromatic reduce not necessarily required to form an aromatic C ₉ before the absorption unit. The EB can be removed from the liquid phase isomerization unit feed using an EB selective membrane or adsorption technique.

Alternatively, the para-xylene depleted effluent of the separation section 37, collected in line 39, may be fed to the vapor phase xylene isomerization section 48 via line 47 onto the gas phase, In the section, xylene is isomerized to equilibrium. The effluent from the vapor phase isomerization section 48 containing xylenes (~ 24%), close to equilibrium and is fed to the stabilizer column 51 by the line 49, the column in the C ₇ containing over The head stream is removed via line 52 and the C ₈₊ bottoms stream is collected and fed via line 53 to the xylene rrhen column 44. When the vapor phase isomerization process utilized in the isomerization section 48 is an ethylbenzene dealkylation type, the overhead stream in line 52 contains the dealkylation product benzene and some byproduct toluene. When the vapor phase isomerization process utilized in the isomerization section 48 is an ethylbenzene isomerization type, the overhead stream in line 52 contains some benzene and toluene byproducts. In either case, the benzene can be fed to the extraction section 17, sold as a product, or transferred to a cyclohexane unit. Benzene can also be processed in the toluene methylation section 31 or in the transalkylation section (described below) for the preparation of additional xylenes (see other aromatic complex schemes described below). The toluene effluent from the isomerization section 48 will be treated in the toluene methylation section 32 or in the transalkylation section for further xylene production. The combined vapor phase benzene / toluene stream in line 52 can be transferred directly to the toluene methylation unit, thereby reducing fractionation costs and maximizing capital utilization.

The C ₈₊ aromatic bottom stream removed from the stabilizer column 51 via line 53 is fed to the C ₈₊ aromatic containing bottom stream 45 from the _lipoate divider 15 and optionally to the liquid phase isomerization section 42 Is fed to the xylene rylene column 44 together with the effluent from the distillation column. The xylene rerun column (44) is fed to the heavy aromatic C ₉₊ column through the separated aromatics, and aromatic C ₉₊ line 54 55. From these streams, the column also, via line 56, And accommodates a C ₉₊ aromatic stream from the xylene column (35). The heavy aromatic column 55 separates C ₉ aromatics, C ₁₀ aromatics and some C ₁₁ aromatics from the streams 54 and 56 and feeds these components to the transalkylation section 58 via line 57, While the heavy compounds in streams 54 and 56 are collected via line 59 for feeding to the fuel oil pool and / or another hydrocarbon processing unit, which treats the heavy compounds as more desirable and valuable products ). ≪ / RTI >

In the transalkylation section 58, the C ₉ aromatics, C ₁₀ aromatics and some C ₁₁ aromatics are converted to equilibrated xylene directly by conversion to equilibrated xylene or by reaction with benzene or toluene transferred from other parts of the process . Although there are many options for optimizing para-xylene production in the aromatic complexes operating the toluene methylation unit (e.g., toluene methylation section 31) and the transalkylation section (e.g., transalkylation section 58), toluene methylation In a preferred embodiment, all the toluene introduced or produced in the aromatic complex is converted to the toluene methylation section 31 rather than the transalkylation section 58, since it produces a xylene product that is highly selective and para- Lt; / RTI > The toluene source in the complex, illustrated in Figure 1, is a mixture of toluene from the lipoate divider 15 at any line 32, toluene from the benzene column 21 at line 23, The crude toluene from the para-xylene separation section 37, the by-product toluene from the vapor phase isomerization section 48 when the vapor phase isomerization is of the EB dealkylation type, Stream (not shown). Thus, little or no toluene in the effluent from the transalkylation section 58 is recycled to the transalkylation section 58. In a preferred embodiment, the benzene from the benzene column 21 is fed to the transalkylation section 58 (not shown in Figure 1) in an amount that optimizes the ratio of methyl to the ring so that xylene production in the unit is maximized do. Untreated benzene in the transalkylation section 58 may be recovered for sale or hydrogenation to produce cyclohexane or may be fed to the toluene methylation section 31 for further xylene production. The effluent from the transalkylation section (58) is fed to the stabilizer column (51) by line (60).

Optionally, if ortho-xylene production is desired, some or all of the bottom stream from the xylene rylene column 44 may be fed to the ortho-xylene column 62 via line 61. The ortho-xylene product is collected at overhead via line 63, while the ortho-xylene column bottoms graft is conveyed via line 64 to the heavy aromatic column 55. Some or all of the ortho-xylene can be processed over the liquid phase isomerization section 42 or the vapor phase isomerization section 48 or the transalkylation section 58 when excess ortho-xylene is produced above the production demand And produces more para-xylene.

One variation of the process shown in FIG. 1 is shown in FIG. 2, wherein like reference numerals in FIG. 2 are used to indicate elements similar to those shown in FIG. In particular, in the process shown in FIG. 2, the extraction section 17 and the benzene column 21 of FIG. 1 are omitted, since there is no citation for non-aromatic or benzene recovery. Thus, in this variation, after the C ₅ -fraction of the reformer effluent is removed from the pentane remover (not shown), the effluent is fed via line 13 to the lipomate divider section 15, Section separates the C ₆ / C ₇ containing overhead stream from the C _{8 +} containing bottom stream. The C ₆ / C ₇ containing overhead stream is fed to the toluene methylation section 31 via line 16, without the benzene extraction step, and as in the embodiment of FIG. 1, the C _{8 +} 45 to the xylene rylene column 44. [ Another notable change affects the overhead liquid C ₆ / C ₇ stream of the stabilizer column 51, which is collected via line 52. This stream can be recycled to the inlet of the transalkylation section 58 via line 71 or recycled to the inlet of the toluene methylation section 31 via line 72, It can be done in combination. Factors affecting the decision to recycle a portion of the stream 52 to the transalkylation section to the toluene methylation section are the desired catalyst circulation length in the transalkylation section, which is C ₆ / C ₇ in the feed to the transalkylation section Which may be extended by the presence of the same hard component, and the desired methyl / ring ratio in the transalkylation section 58.

Another variation of the process shown in FIG. 1 is shown in FIG. 3, where like reference numerals are used to denote similar elements to those shown in FIG. In particular, in the process shown in FIG. 3, the vapor phase xylene isomerization section 48 of FIG. 1 is omitted. Instead, the para-xylene depleted effluent of the separation section 37 is collected via line 39 and fed to the liquid phase xylene isomerization section 42 in liquid phase via line 41, , Xylene is isomerized to equilibrium. Alternatively, para-xylene depleted effluent of the separation section 37, collected via line 39, is transferred via line 44 to the transalkylation section 58 where the residual ethylbenzene is transferred to the benzene , And some xylene isomerization will take place on the transalkylation catalyst system. Separation section 37 A combination of quantum options for the effluent, i.e., liquid phase isomerization or transalkylation, is acceptable. Transfer of the separation section 37 effluent to one process or to the other process will depend on the ethylbenzene content in the effluent of the separation section 37. Alternatively, the purge stream to the liquid phase isomerization section 42, or the purge stream from that section, may be treated over the toluene methylation section 31, or may be passed over an ethylbenzene isomerization unit (not shown) So that the ethylbenzene concentration can be controlled. Although the extraction section 17 of FIG. 1 and the benzene column 21 are omitted from the embodiment of FIG. 2, the process of FIG. 3 differs from the extraction section 17 of FIG. 1 and the benzene column 21 It is to be understood that the invention may be practiced with such modifications.

A further modification applicable to each of the processes of FIGS. 1 to 3 is shown in FIG. 4, where the xylene column 35 is combined with a xylene rylene column 44 in a single column in FIG. In such embodiments, the toluene methylation section 31. The effluent from the C ₈₊ bottom stream and optionally isomerizing the liquid line section 42 at 43 from the stabilizer column 51 in line 53, Along with the effluent of the distillation column 34, through line 34 to the larger xylene rrhen column 44.

In a variant (not shown) of any of the processes shown in Figures 1-4, the product from the toluene methylation section 31 is fed to a separator drum, which is a liquid hydrocarbon stream, liquid water, and methanol Stream, and an olefin-containing off-gas stream. The separation may be performed in one or more drums, and the cooling, including refrigeration, between the drums consists of air, cooling water, or some suitable refrigerant stream. The drum may be horizontal or vertical, or a combination thereof. The horizontal drum may contain an internal baffle. The horizontal drum may contain a water boot to collect the water. An internal demister pad can be used to minimize liquid carryover by off-gas. The vertical drum may also contain the same features as the horizontal drum, as can be designed by those skilled in the art. Combinations of coolers may also be used to cool the stream between the drums. The refrigerant exchanger may also be located inside the separator drum. The separator drum (s) may be combined with a quench tower to save capital.

The hydrocarbon stream may be further treated through a distillation section, such as a toluene distillation column and / or a xylene distillation column 35, to further separate the hydrocarbons. The water / methanol stream is fed to a methanol stripping column to remove hydrocarbons, methanol and other oxygenated compounds from the water. The resulting stream containing methanol, hydrocarbons and other oxygenated compounds can be recycled back to the toluene methylation section 31. The water stream may contain an acid such as formic acid, acetic acid, etc., which acid may reduce the pH of the stream. The water stream can be neutralized by treatment with caustic, ammonia, sodium carbonate or any other neutralizing agent known to those skilled in the art. The wastewater stream can be treated at or at a different location to the bottom of the methanol stripper as in the reactor effluent. The olefin-containing stream is transferred to further processing to remove contaminants prior to final recovery of valuable olefin components.

In one embodiment, the toluene methylation section 31 comprises a reactor, a regenerator for a catalyst, a catalyst chiller, heat exchanger equipment, and a gas / solid separation equipment. The reactor effluent may contain catalyst particulates, which may be separated by gas / solid separation equipment such as cyclones, centrifuges, gas filters, liquid filters, wash columns, or even columns, tanks or settlers, ≪ / RTI > can be separated from the reactor effluent stream. Such equipment may be located inside the reactor vessel, for example a cyclone or a multiple cyclone, but preferably outside the reactor vessel. The gas / solid separation equipment may be located upstream of any heat exchange equipment used to recover heat from the reactor effluent stream or downstream of the heat exchange equipment. Such heat exchange equipment includes a steam generator that generates steam with a pressure range of 10 psig to 1200 psig, or heat exchange equipment that uses the enthalpy from the reactor effluent stream to heat the process fluid, or a combination thereof. The flue gas from the regenerator may also contain a catalyst fine, which must be reduced to release into the atmosphere. These differentiations can be recovered from the flue gas using a number of different techniques, including cyclones or multiple cyclones, electrostatic precipitators, wash columns, centrifuges, or combinations thereof. The flue gas solid recovery equipment may be upstream or downstream of any process heat exchange equipment, such as a CO boiler, or any other heat exchange equipment commonly used in flue gas services. The catalyst microparticles recovered from the reactor effluent or the regenerator may be returned to the reaction zone or the regenerator zone, or both, either directly or indirectly, for example through an intermediate storage vessel, or may be vented from the system.

The catalyst can be recovered from the regenerator and can be fed to a heat exchanger, also known as a catalyst cooler, to remove heat generated in the regenerator by combustion of cork and other hydrocarbons on the catalyst. The recovery of the catalyst from the regenerator can be carried out at various rates on a continuous or intermittent basis. The cooled catalyst is then fed back to the regenerator. By controlling the flow of catalyst through the catalyst cooler and / or the amount of heat removed, the temperature of the catalyst bed in the regenerator is controlled. Depending on the amount of cork that can be burned in the regenerator, the catalyst cooler can be operated between full speed and full stop. The flow of catalyst recovery from the regenerator can be controlled by a slide valve for controlling the flow of solids including solids fluidized by a suitable vapor stream (aeration medium) injected into the pipe both inside and outside the catalyst cooler It is controlled using other suitable valves. The venting medium can be air, steam, nitrogen, hydrocarbons, and / or other suitable gases, which can also be injected into the catalyst cooler to ensure fluidization of the solids in the catalyst cooler and control the heat transfer coefficient Thereby ensuring proper heat transfer of the high-temperature catalyst to the cooling medium. The catalyst cooler may also be used to preheat the boiler feed water, generate steam at different pressures, preheat and / or vaporize the process stream, or heat the air. The catalyst cooler is typically attached to the regenerator, attached to a separate structure for support, or enclosed (fully recessed) all or part within the regenerator vessel.

Hereinafter, the present invention will be described more specifically with reference to the following non-limiting embodiments.

Example  One

This example demonstrates how the addition of toluene alkylation by a methanol unit increases the para-xylene yield of an aromatic complex based on the same feedstock as conventional aromatic complexes that produce xylene in the reforming and transalkylation sections It is. In this example, it is assumed that all xylene is converted to para-xylene (not produced by ortho-xylene). The results are shown in Table 1 below.

[Table 1]

In Table 1, each aromatic complex utilizes the same feedstock (1245.3 kTa naphtha) quantitatively and qualitatively. Moreover, the reforming section provides the same product slate in all cases, and the product slate is listed in column # 1, which is titled "CCR ". Column # 2, titled "xylene recovery (alone)", shows the preparation of para-xylene only when only the reformer xylene is recovered (no transalkylation unit is used). Column # 3, entitled "Xylene Recovery by Transalkylation, " shows the preparation of para-xylene in a conventional aromatic complex in which the transalkylation unit is added to produce additional xylenes. Column # 4, titled " TAM and xylene recovery by transalkylation, " indicates para-xylene production from an aromatic complex in which toluene alkylation with a methanol unit is added to a conventional aromatic complex with transalkylation.

As can be seen from Table 1, on the basis of the same feedstock and reforming section yields, para-xylene production in conventional aromatic complexes was 560.9 kTa, whereas toluene alkylation by methanol unit was added The production of para-xylene in the conventional complex is 645.1 kTa.

In addition, para-xylene production is often preferred over benzene production due to higher margins. Benzene can be fed to the transalkylation section for further xylene production, but this preparation is limited by the ratio of methyl to the ring. However, when a toluene methylation section is available, all benzene can be converted to xylene and further converted to para-xylene if necessary. Thus, for column # 4, an additional 135.2 kTa of benzene is available for further para-xylene preparation. In this case, the amount of complex para-xylene can be increased to ~ 829 kTa, which is nearly 50% increase in para-xylene production compared to a complex without toluene methylation.

Thus, the combination of toluene alkylation with methanol and transalkylation units in an aromatic complex provides significantly higher para-xylene production than conventional aromatic complexes with the same feedstock and reforming section products. Conversely, achieving para-xylene production similar to conventional aromatic complexes using a combination of toluene alkylation with a methanol unit and a transalkylation unit requires less feed, which allows for a smaller refinery plant section upstream do. In other words, the combination of toluene alkylation with a transalkylation unit by a methanol unit in an aromatic complex allows para-xylene production similar to conventional aromatic complexes using less crude oil.

Although the present invention has been described and illustrated with reference to specific embodiments thereof, those skilled in the art will appreciate that the invention itself provides variations that are not basically illustrated herein. For this reason, reference should be made only to the appended claims to determine the actual scope of the invention.

Claims (20)

As a method for producing para-xylene,
(a1) C ₆₊ containing feed stream containing at least an aromatic hydrocarbon toluene stream, and separating the C ₈ aromatic hydrocarbon-containing stream and a C ₉₊ aromatic hydrocarbon-containing stream,
(b1) contacting at least a portion of the toluene-containing stream with a methylating agent under conditions effective to convert the toluene to xylene to produce a methylated effluent stream,
generating a xylene depleted stream, - to recover the para-xylene one or more - (c1) C ₈ aromatic hydrocarbon-containing stream and an effluent stream from a para-methylated
(d1) contacting at least a portion of the at least one para-xylene depleted stream with a xylene isomerization catalyst under liquid phase conditions effective to isomerize the xylene in the para-xylene depleted stream and produce an isomerization stream,
(e1) recycling at least a portion of the isomerization stream to (c1)
(f1) at least a portion of the C ₉₊ aromatic-containing stream, by converting the C ₉₊ aromatic to an aromatic _8- C under conditions effective to produce a transalkylation stream, contacting the transalkylation catalyst, and
(g1) recycling at least a portion of the transalkylation stream to at least one of (b1) and (cl)
≪ / RTI > The process according to claim 1, wherein the feed stream in (a1) comprises a mixture of C ₆₊ aromatic and aliphatic hydrocarbons produced by removing C ₅ -hydrocarbons from the reformate stream. 3. A process according to claim 1 or 2, wherein the toluene-containing stream is subjected to an extraction treatment to remove the non-aromatics and produce a toluene-containing aromatic stream, wherein the toluene-containing aromatic stream is separated into a benzene stream and a toluene stream, To the step (b1). 3. The process according to claim 1 or 2, wherein the separation step (a1) also produces a benzene containing stream. 5. The process according to claim 4, wherein all of the toluene-containing stream is fed to the contacting step (b1). 5. The process according to claim 3 or 4, wherein the benzene stream or a portion of the benzene containing stream is fed to the contacting step (f1) to optimize the ratio of methyl to the ring. 7. A process according to any one of claims 1 to 6, wherein the separation step (a1) is carried out by means of a separating wall-type distillation column. 8. A process according to any one of claims 4 to 7, wherein at least part of the benzene-containing stream is fed to the contacting step (b1). 9. The process according to any one of claims 1 to 8, wherein the methylating agent comprises methanol. 10. A process according to any one of claims 1 to 9, wherein the contacting step (b1) is carried out at a temperature of 120 占 폚 and 2,2-dimethylbutane pressure of 60 torr (8 kPa) ^{-1 &lt}; / RTI > of a porous crystalline material having a diffusion parameter for 2,2-dimethylbutane. 11. The method of claim 10, wherein the porous crystalline material comprises ZSM-5 that has undergone a pre-treatment with steam at a temperature greater than or equal to 950 < 0 > C. 12. The method according to any one of claims 1 to 11,
(h1) contacting at least a portion of the at least one para-xylene depleted stream with at least a portion of the para-xylene depleted stream to produce an isomerized, ethylbenzene-depleted stream that is isomerized by isomerizing xylene in the para- xylene depleted stream and dealkylating or isomerizing ethylbenzene Contacting it with a xylene isomerization catalyst under vapor phase conditions, and
(i1) isomerizing and recycling at least a portion of the ethylbenzene depleted stream to (c1)
≪ / RTI > 13. The process of claim 12, wherein the vapor phase condition is effective to dealkylate ethylbenzene in the para-xylene depleted stream to produce a by-product toluene stream, the method comprising feeding the by-product toluene stream to contacting step (b1) ≪ / RTI > 14. The process according to any one of claims 1 to 13, wherein at least a portion of the _C7- aromatic in the transalkylation stream is recycled to the contacting step (b1). 15. The process according to any one of claims 1 to 14, wherein part of the _C7- aromatic in the transalkylation stream is recycled to the contacting step (f1). 16. The method according to any one of claims 1 to 15,
(j1) in o from C ₈ aromatic hydrocarbon-containing stream, methylation effluent stream and the transalkylation stream, one or more of - recovering the xylene
≪ / RTI > 17. The method according to any one of claims 1 to 16,
(k1) recovering unconverted toluene from the methylated effluent stream, and
(l1) feeding the unconverted toluene to contact step (b1)
≪ / RTI > As an apparatus for producing para-xylene,
(a2) a contact reformer for producing a lipidate stream comprising a C ₆₊ aromatic hydrocarbon,
(b2) at least lipoic toluene-containing stream to mate stream, C ₈ aromatic hydrocarbon-containing stream and a C ₉₊ first separation system for separating the aromatic hydrocarbon-containing stream,
(c2) a toluene methylation unit for converting the toluene in the toluene-containing stream to xylene to produce a methylated effluent stream,
(d2) C ₈ aromatic hydrocarbon-containing stream, methylation effluent stream and the transalkylation effluent stream from a para-second separation system to produce a xylene depleted stream, and - by the recovery of one or more para-xylene
(e2) a liquid phase xylene isomerization unit for isomerizing xylene in at least one para-xylene depleted stream to produce a first isomerization stream,
(f2) a recirculation system for recirculating at least a portion of the first isomerization stream to a second separation system, and
(g2) C ₉₊ aromatic hydrocarbons containing a transalkylation unit was converted to the C ₉₊ aromatic in the stream with the aromatic _8- C to produce a transalkylation effluent stream
. 19. The method of claim 18,
(h2) a vapor phase xylene isomerization unit for isomerizing xylene in at least one para-xylene depleted stream to produce a second isomerization stream, and
(i2) a second recycle system for recycling at least a portion of the second isomerization stream to a second separation system
Further comprising: 20. The method according to claim 18 or 19,
a third separation system for the recovery of xylene - (j2) C ₈ aromatic hydrocarbon-containing stream, methylation effluent stream and the transalkylation effluent stream from one or more of the ortho
Further comprising:

Images