KR20170031729A - Aromatics production process - Google Patents

Abstract

The para-xylene in the manufacturing method of, an aromatic C ₆₊ to at least one feed comprising the hydrocarbon feed to the dividing wall distillation column to the feed containing C _7- aromatic hydrocarbon stream, aromatic hydrocarbon-containing stream and a C ₈ C _{9 +} Aromatic hydrocarbons containing stream. This document, the C ₈ aromatic hydrocarbon stream containing at least a portion of the para-xylene is fed to the recovery unit, the C ₈ aromatic hydrocarbons from the stream containing para-xylene is recovered and para-xylene is removed, a stream is generated. At least a portion of the para-xylene-depleted stream is contacted with a xylene isomerization catalyst in a xylene isomerization zone under conditions effective to isomerize the xylene in the para-xylene-depleted stream and produce an isomerized stream. And the isomerized stream is at least partially recycled to the para-xylene recovery unit.

Description

AROMATICS PRODUCTION PROCESS &

Relevant Application Cross Reference

This application claims priority to and claims the benefit of United States Provisional Application No. 62 / 037,645, filed August 15, 2014, which is incorporated herein by reference in its entirety.

Technical field

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

Benzene, toluene and xylene (BTX) are important aromatic hydrocarbons with steadily increasing demand worldwide. The demand for xylene, especially para-xylene, has increased in proportion to the demand for polyester fibers and films, and is growing at a rate of 5 to 7% per year in general. Benzene is a very valuable product used as a chemical raw material. Toluene is also a valuable petrochemical product used as an intermediate and solvent in chemical manufacturing processes and as a component of high octane gasoline. However, in many modern aromatic complexes, some or all of the benzene and / or toluene is further converted to xylene by transalkylation or methylation or a combination thereof.

The main source of benzene, toluene, and xylene (BTX) is catalytic reforming oil, which is prepared by contacting petroleum naphtha with a hydrogenation / dehydrogenation catalyst on the carrier. The resulting reformate is a complex mixture of paraffins and the desired C ₆ to C ₈ aromatics, in addition to a significant amount of heavier aromatic hydrocarbons. After removal of the hard (C _5- ) paraffin component, the remainder of the reforming oil is usually separated into C _7- , C ₈ and C ₉₊ containing fractions using multiple distillation steps. Then benzene can be recovered from the fractions containing the C _7- remaining toluene-rich fraction which is usually used for the production of more C ₈ aromatic C ₉₊ by-containing fraction portion and a transalkylation or methylation. The C ₈ -containing fraction is generally fed into a xylenes production loop in which para-xylene is recovered by adsorption or crystallization and the resulting para-xylene-free stream is catalytically converted to xylenes isomerized again into an equilibrium distribution, Level, otherwise ethylbenzene accumulates in the xylene production loop.

Although contact technology has become more efficient at achieving the desired chemical reaction to reduce the loss of valuable aromatic molecules while maximizing para-xylene production, it has been shown to achieve hardware cost and energy savings to reduce overall para- There is a continuing need to do.

Summary of the Invention

According to the present invention, it is believed that the separating wall distillation column provides an effective and energy efficient means for the separation of hydrocarbon streams, especially C ₇ , C ₈ , and C ₉₊ containing fractions, which are encountered in certain para-xylene production complexes Found.

In a first embodiment, at least one feed comprising C ₆₊ aromatic hydrocarbons is fed to a separate wall distillation column to separate the feed into a C ₇ -aromatic hydrocarbon-containing stream, a C ₈ -aromatic hydrocarbon-containing stream and a C ₉₊ aromatic hydrocarbon Containing stream. The at least a portion of the C ₈ aromatic hydrocarbon-containing stream is then fed to a para-xylene recovery unit to recover para-xylene from the C ₈ aromatic hydrocarbon-containing stream to produce a para-xylene-free stream, In the zone, the para-xylene-depleted stream is contacted with a xylene isomerization catalyst under conditions effective to isomerize the xylene in the para-xylene-depleted stream and produce an isomerized stream. At least a portion of the isomerized stream is then recycled to the para-xylene recovery unit.

In another embodiment, the present process, C _7- removing at least a portion of the aliphatic hydrocarbon from the hydrocarbon-containing stream to produce a C _7- aromatic hydrocarbon-enriched stream, and a C _7- aromatic hydrocarbon by supplying enriched stream to the separation unit C Further comprising separating the _7- aromatic rich stream into a benzene containing stream and a toluene containing stream. At least a portion of the toluene-containing stream and at least a portion of the _{C9 +} hydrocarbon-containing stream are contacted with the transalkylation catalyst under conditions effective to produce a xylene-containing transalkylation product fed to the para-xylene recovery unit.

Preferably, the present process, (a1 or a2, or from a3) C ₈ to at least a portion of the aromatic hydrocarbon-containing stream, para-located upstream of the xylene recovery unit C ₈ at least a portion of the ethylbenzene, the aromatic hydrocarbon-containing stream To an ethylbenzene removal unit operated under conditions effective to remove the ethylbenzene. Preferably, the conditions in the ethylbenzene removal unit are effective to substantially maintain the C ₈ aromatic hydrocarbon-containing stream in the gaseous phase, and the conditions in the xylene isomerization zone are to maintain the para-xylene- .

In a third embodiment, a feed comprising a mixture of C ₆₊ aliphatic and aromatic hydrocarbons is provided in a distillation column to separate the feed into a C ₇ -hydrocarbon-containing stream and a C ₈₊ hydrocarbon-containing stream. At least a portion of the aliphatic hydrocarbons are removed from the C ₇ -hydrocarbon-containing stream to produce a C ₇ -aromatic hydrocarbon-rich stream, which is fed to a separation unit from which benzene is recovered and a toluene-containing stream is produced. C ₈ at least a portion of the hydrocarbon-containing stream is contacted with the ethylbenzene dealkylation catalyst at conditions effective to de-alkylation of ethylbenzene in the hydrocarbon-containing stream C ₈₊ and create a dealkylation effluent containing benzene and a C ₈₊ hydrocarbon And the dealkylation effluent is separated into a C ₇ -aromatic hydrocarbon-containing stream, a C ₈ -aromatic hydrocarbon-containing stream and a C ₉₊ aromatic hydrocarbon-containing stream in a separate wall distillation column. The C ₈ aromatic hydrocarbon-containing stream is then transferred to the para-xylene recovery unit to recover the para-xylene from the C ₈ aromatic hydrocarbon-containing stream and the para-xylene-free stream, Contacting the xylene isomerization catalyst under conditions effective to isomerize the xylene in the para-xylene-depleted stream and produce an isomerized stream, and the isomerized stream is recycled to the separation wall distillation column. At least a portion of the toluene-containing stream and at least a portion of the _{C9 +} hydrocarbon-containing stream are contacted with the transalkylation catalyst under conditions effective to produce a xylene-containing transalkylation product fed to the separation unit.

1 is a flow chart of a process for producing para-xylene from a contact reforming passage according to a first embodiment of the present invention.
2 is a flow chart of a process for producing para-xylene from a contact reforming flow path according to a second embodiment of the present invention.
3 is a flow chart showing a process for producing para-xylene from a contact reforming passage according to a modification of the second embodiment of the present invention.
4 is a flow chart of a process for producing para-xylene from a contact reforming passage according to a third embodiment of the present invention.
5 illustrates the separation wall fractional distillation column system for separation of the _{C 7- / C 8 / C 9} + stream from the aromatic complex.
6 illustrates a conventional two-column fractional distillation system for separation of the _{C 7- / C 8 / C 9} + stream from the aromatic complex.
Figure 7 shows a third fraction splitter fractional distillation system for separation of the _{C 7- / C 8 / C 9} + stream from the aromatic complex.

Detailed Description of the Embodiments

The production of para-xylene from the contact reforming flow requires a number of expensive fractional distillation steps. In order to reduce capital and operating costs, the present invention utilizes one or more separate wall distillation columns to separate various C _{6 +} hydrocarbon fractions into at least a C ₇ -aromatic hydrocarbon containing stream, a C ₈ aromatic hydrocarbon containing stream, and a C ₉₊ aromatic hydrocarbon Stream. Benzene can then be recovered from the C ₇ -aromatic hydrocarbon-containing stream while toluene can be used to generate additional xylene by transalkylation with at least the C ₉₊ aromatic hydrocarbon-containing stream portion. The C ₈ aromatic hydrocarbons containing stream and the additional xylenes produced by the transalkylation are then fed into a para-xylene production loop comprising a para-xylene recovery unit and a xylene isomerization unit. The ethylbenzene moiety contained in at least the reformate feed can be removed by dealkylation in the upstream or downstream of the para-xylene recovery unit to benzene or isomerization to xylene.

As the name implies, the term "separation wall distillation column" means a particular known type of distillation column comprising a separation wall. The separating wall vertically bisects a portion of the interior of the distillation column but does not extend to the top or bottom of the column, allowing the column to be recirculated and re-circulated similar to a conventional column. The separating wall provides a fluid-impermeable baffle separating the interior of the column. The column inlet is located on one side of the separating wall and one or more side draws are located on the opposite side. The separating wall may allow the column side having no inlet to function in a more stable and minimized variation in inlet flow rate, condition or composition. Because of this increased stability, the column can be designed and operated such that one or more side draw streams have a different composition than the overhead stream or bottom stream and are removed from the column.

The ability to produce three or more product streams from a single column can enable component separation with fewer distillation columns and can reduce capital and operating costs. A separate wall distillation column may be used as the only distillation column or a plurality of separate wall distillation columns may be used in series or parallel connection. Separated wall distillation columns may also be used with one or more conventional distillation columns. Embodiments of the present invention may be particularly applicable when the optimum feed position into the column is over the optimum side draw position. In a conventional distillation column, when the feed position is above the side draw position, the downward flow of the liquid feed in the column has a significant effect on the side draw composition. Variations in the feed flow rate, conditions, or composition of the feed stream change the side draw composition and make it very difficult to create a stable side draw stream.

In some embodiments, as shown in Figures 1, 2, 3, and 5, a split-wall distillation column may be used in place of a conventional reforming oil-splitter to remove residual C ₅ aliphatic hydrocarbons from the contact- The C _{6 +} hydrocarbon stream is fractionally distilled.

In some embodiments, as shown in FIG. 4, the feed to the separation wall distillation column is produced when the ethylbenzene is removed, in part, by dealkylation from a C ₈₊ aromatic fraction from a conventional reforming _oil- To the C _{6 +} aromatic hydrocarbon stream and, in part, from the effluent from the xylene isomerization unit.

Thus, the present separation wall distillation column provides a cost effective separation system for the various feed and product streams encountered in modern para-xylene production complexes.

The present invention will now be described more specifically with reference to the accompanying drawings.

1 shows a process for producing para-xylene according to a first embodiment of the present invention wherein a contact reformate feed stream containing aromatics is fed to the depentanizer section 12 by line 11 C _5- fraction is removed. The pentane and harder hydrocarbons are removed via line 13 and the C ₆₊ bottoms fraction is fed via line 14 to the separation wall distillation column 15 to form C ₇ , C ₈ , and C ₉₊ aromatics Containing stream. The separated fuel gas in the separating wall distillation column 15 is collected via line 20.

The C ₇ -containing stream from the separate wall distillation column 15 is transferred via line 16 to an extractive distillation or liquid-liquid extraction unit 17 where the aliphatic hydrocarbons are removed via line 18 to form benzene- And leaving the toluene-rich stream, this stream is fed via line 19 to the olefin saturation zone 21. The olefin saturation zone 21 can be any other means effective in removing olefin contaminants in the aromatic stream, including a clay processor or any hydrogenation, including a contacting process. The effluent from the olefin saturation zone 21 is fed via line 22 to an additional separating wall distillation column 23 from which benzene is collected via line 24 and toluene is fed via line 25 To the transalkylation unit 26 and the C ₈₊ fraction is fed via line 27 to the xylene distillation column 28.

C ₈ aromatic hydrocarbon containing stream that is recovered from the reformate separation wall column 15 is fed to the olefin saturation zone 37 by a line 29. The olefin saturation zone 37 may be a clay processor or any other means effective to remove olefin contaminants in the aromatic stream, optionally with hydrogenation, including a contacting process. The effluent from the olefin saturation zone 37 is fed to the xylene distillation column 28 via line 38. Preferably, the stream at line 38 is much harder than the stream at line 27, so that the effluent from the olefin saturation zone 37 is separated from the feed point of the C _{8 +} fraction in line 27 Above which it is fed to the column 28 above.

Xylene distillation column 28 separates the overhead stream removed from the C ₉₊ feed to the distillation column (28). This overhead stream is then fed via line 39 to para-xylene separation section 41 where para-xylene is typically separated by adsorption, crystallization or a combination thereof and recovered via line 42. The remaining toluene in the overhead stream is removed from the para-xylene separation section 41 and fed via line 43 to the transalkylation section 26 while the remaining para-xylene-free stream is passed through line 40 to the ethyl Benzene removal and xylene isomerization section (44). When para-xylene is separated by adsorption, the adsorbent used preferably contains zeolite. Typical adsorbents used include natural or synthetic crystalline aluminosilicate zeolites such as zeolite X or Y or mixtures thereof. These zeolites are preferably exchanged by cations such as alkali or alkaline earth or rare earth cations. The adsorption column is preferably a pseudo-mobile phase column (SMB), and desorbents such as, for example, paradiethylbenzene, paradifluorobenzene, diethylbenzene or toluene or mixtures thereof are used.

In ethylbenzene removal and xylene isomerization section 44, ethylbenzene removal is preferably carried out in the vapor phase and by dealkylation with benzene or isomerization to xylene. Where the preferred mechanism is dealkylation to benzene, any conventional contacting process for the dealkylation of ethylbenzene may be used. However, in one preferred embodiment, the dealkylation is carried out using a medium pore size zeolite (having a limiting index of 1 to 12 as defined in U.S. Patent No. 4,016,218) and a catalyst comprising a hydrogenation component, optionally with a non-acidic binder such as silica Lt; / RTI > Examples of suitable intermediate pore size zeolites are ZSM-5 (U.S. Pat. No. 3,702,886 and Re. 29,948); ZSM-11 (U.S. Patent No. 3,709,979); ZSM-12 (U.S. Patent No. 3,832,449); ZSM-21 (U.S. Patent 4,046,859); ZSM-22 (U.S. Patent No. 4,556,477); ZSM-23 (U.S. Patent 4,076,842); ZSM-35 (U.S. Patent 4,016,245); ZSM-38 (U.S. Patent No. 4,406,859); ZSM-48 (U.S. Patent No. 4,397,827); ZSM-57 (U.S. Patent 4,046,685); And ZSM-58 (U.S. Patent No. 4,417,780). Examples of suitable hydrogenation components include Group 8-10 metals (i.e., Pt, Pd, Ir, Rh, Os, Ru, Ni, Co, and Fe), Group 14 metals (i.e., Sn and Pb) , Sb and Bi), and oxides, hydroxides, sulfides or free metals of the Group 7 metals (i.e. Mn, Tc and Re). Precious metals (i.e. Pt, Pd, Ir, and Rh) or Re are the preferred hydrogenation components. Combinations of such noble metal or non-noble metal catalyst forms, such as a combination of Pt and Sn, may be used. As used herein, the numbering system for the families of the Periodic Table of Elements is as disclosed in Chemical and Engineering News, 63 (5), 27 (1985).

In a preferred embodiment, the dealkylation catalyst is prepared by contacting the catalyst with a selective activator such as at least one organosilicon in the liquid carrier, followed by calcination of the selectively activated catalyst at a temperature of from 350 to 550 DEG C, prior to introduction into the dealkylation reactor Or activated in situ in the reactor. Since the selective activation procedure changes the diffusion characteristics of the catalyst, the catalyst requires more than 50 minutes to adsorb 30% of the equilibrium capacity of ortho-xylene at 120 ° C and an ortho-xylene partial pressure of 4.5 ± 0.8 mm of mercury. One example of a selective activated ethylbenzene dealkylation catalyst is disclosed in U.S. Patent No. 5,516,956, the entire content of which is incorporated herein by reference.

Suitable conditions for the gas-phase dealkylation of ethylbenzene with the catalysts described above include a temperature of from about 400 ℉ to about 1000 ((204 캜 to 538 캜), a pressure of from about 0 to about 1,000 psig (100 to 7000 kPa) A weight hourly space velocity (WHSV) of 200 hr <" ¹ >, and a molar ratio of hydrogen to hydrocarbons from about 0.5 to about 10. Preferably, these conversion conditions include a temperature of about 660 ℉ 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 about 50 hr ^-1 , And a molar ratio of hydrogen to hydrocarbons of about 0.7 to about 5. The WHSV is based on the weight of the catalyst composition, i. E., The total weight of the active catalyst and, if used, its binder. The conversion conditions are such that in the ethylbenzene removal section 44 the C ₈ aromatic hydrocarbon containing feed is substantially gaseous.

In ethylbenzene removal and xylene isomerization section 44, xylene isomerization is also preferably carried out in the vapor phase. Although any gas phase isomerization process known to those skilled in the art may be utilized to perform xylene isomerization in section 44, one preferred contacting system is a mesopore size < RTI ID = 0.0 > Zeolite is used. Thus, in one embodiment, the xylene isomerization catalyst requires less than 50 minutes to adsorb 30% of the equilibrium capacity of ortho-xylene at an ortho-xylene partial pressure of 120 ° C and mercury 4.5 ± 0.8 mm.

The xylene isomerization conditions used in the ethylbenzene removal and xylene isomerization section 44 are such that the xylene in the para-xylene-depleted stream is isomerized and thereby the para-xylene is higher in concentration than the para- And is selected to produce an isomerized stream. Suitable conditions include a temperature of about 660 ℉ 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 about 50 hr ^-1 , 5 < / RTI > hydrocarbons. The WHSV is based on the weight of the catalyst composition, i. E., The total weight of the active catalyst and, if used, its binder.

One preferred process for ethylbenzene removal and operation of the xylene isomerization section 44 is disclosed in U.S. Patent No. 5,516,956.

The effluent from the ethylbenzene removed and xylene isomerization section 44 is fed to the dividing wall distillation column 15 through the line 45 is separated into a C _7-, C ₈ and C ₉₊ aromatic hydrocarbon-containing stream.

Reformate separation wall C ₉₊ aromatic hydrocarbon-containing stream is recovered from the distillation column 15 is fed to the heavy aromatic distillation column 49 via line 48, and the column is also xylene distillation column via line 51, Lt; RTI ID = 0.0 > 28 < / RTI > The heavy aromatic distillation column 49 contains a C ₉ / C ₁₀ / hard C ₁₁ containing fraction which is removed from the line 52 and the C ₉₊ aromatic hydrocarbon fed by lines 48 and 51, and separated into pools, containing C ₁₁ + fraction that is fed to the fuel oil pool or topping column. The C ₉ / C ₁₀ / hard C ₁₁ containing fraction 52 is then passed through an olefin saturation zone, such as optionally any other means for the removal of olefin contaminants, including clay treatment or any hydrogenation, And then fed to the transalkylation unit 26 together with the toluene-rich stream fed via lines 25 and 43. In FIG. 1, the olefin saturation zone is shown integrated with a transalkylation zone and a single unit 26, but the purpose of this schematic view is not limited. One of ordinary skill in the art knows that olefin saturation can be carried out in a unit that is located upstream from and separates from the transalkylation unit. Also, because olefin saturation is performed only when necessary, only stream 52 passes through the olefin saturation zone, for example, if stream 52 requires olefin removal and the olefin content in stream 25 is such that olefin removal is unnecessary.

Although any transalkylation process known to those skilled in the art may be used, one preferred process utilizes the multi-stage contact system disclosed in U.S. Patent No. 7,663,010, which is incorporated herein by reference in its entirety. Such a system comprises (i) a first catalyst comprising a first molecular sieve containing from 0.01 to 5% by weight of at least one source of a first metal element of group 6-10 of the periodic table and a limiting index of from 3 to 12, and (ii) ) A second catalyst comprising a second molecular sieve having 0 to 5 wt% of at least one source of a second metal element of group 6-10 of the periodic table and a limiting index of less than 3, wherein the first catalyst or the second The weight ratio of catalyst is in the range of 5:95 to 75:25 and the first catalyst is located upstream of the second catalyst.

Examples of suitable molecular sieves having a limiting index of from 3 to 12 used in the first catalyst are ZSM-5, ZSM-11, ZSM-22, ZSM-23, ZSM-35, ZSM-48, ZSM- -58, and ZSM-5 is preferred. Examples of suitable molecular sieves having a limiting index of less than 3 used in the second catalyst include zeolite beta, zeolite Y, ultra-stable Y (USY), dealuminated Y (Deal Y), mordenite, ZSM- 4, ZSM-12, ZSM-18, NU-87, and ZSM-20, with ZSM-12 being preferred. Specific examples of metals useful for each of the first and second catalysts include iron, ruthenium, osmium, nickel, cobalt, rhenium, molybdenum, tin, and precious metals such as platinum, rhodium, iridium or palladium.

The dealkylation process may be carried out in any suitable reactor, including a radial flow reactor, a fixed bed reactor, a continuous downflow reactor or a fluid bed reactor. The conditions on the first and second catalysts may be the same or different, but are generally in the range of from 100 to 1000 占 폚, preferably from 300 to 500 占 폚; A pressure in the range of 790 to 7000 kPa-a (kilo-Pascal absolute), preferably in the range of 2170 to 3000 kPa-a, a molar ratio of hydrogen to hydrocarbons of from 0.01 to 20, preferably from 1 to 10; And a WHSV in the range of 0.01 to 100 hr ^-1 , preferably 1 to 20 hr ^-1 .

The effluent from the transalkylation unit 26 is fed via line 54 to a stabilizer 55 where the light gas is collected and removed via line 56. The sidestream from the stabilizer 55 is recycled to the pentane pentane 12 via line 57 and the stabilizer bottom pentane is optionally fed via line 58 via the olefin saturation zone 21 to benzene / toluene / C _{8 +} < / RTI > separation wall column 23.

Compared to a conventional aromatic complex using a conventional distillation unit instead of a separate wall column section 15, one advantage of the embodiment shown in FIG. 1 is that most of the C ₉₊ content of the reformate C ₈ fraction fed to the xylenes loop Can be removed. To a lesser extent, the same advantage applies to isomeric C ₈ fractions which are eliminated with reduced C ₉₊ fractions (if present). From the reformer section and the isomerization section C ₈ aromatic fraction is because both the C ₉₊ is removed, the xylene column 28 at a feed tray which is located the C ₈ aromatic fraction derived from the transalkylation unit above the feed tray, fed Lt; / RTI > This is illustrated by placing the stream of line 38 on the stream of line 27 in FIG. In the case of the specification within the C ₉₊ species content in the stream of line 38 separating section 41, the xylene column 28, as shown by some or all of the dashed lines 70 in the stream Can be bypassed and fed directly to the separation section 41. Depending on the degree of fractionation performed in the separation wall column section 15 and the tolerance of the separation section 41 for the C ₉₊ compound, one or both of the above options may be considered. These options reduce the overall energy consumption of the xylene column 28 compared to conventional aromatic complexes without a separate wall column.

In a variant (not shown) of the process shown in FIG. 1, the ethylbenzene removal and xylene isomerization section 44 is divided into two separate reactors located downstream of the para-xylene separation section 41. The two reactors may be arranged in parallel or in series, where the ethylbenzene removal reactor, when arranged in series, is usually upstream of the xylene isomerization reactor. In this variant, the ethylbenzene removal reactor can be operated under conditions that are significantly different from the xylene isomerization reactor. For example, the ethylbenzene removal reactor can be operated in a substantially gas phase while the xylene isomerization reactor can be operated in a substantially liquid phase to reduce xylene losses during the isomerization process.

2 shows a process for the preparation of para-xylene according to a second embodiment of the present invention, in which the C _{6 +} hydrocarbon stream remaining after the removal of the C ₅ -aliphatic hydrocarbons from the contact reformate stream is fractionally distilled A separating wall distillation column is used instead of the reforming oil separator. Thus, in a second embodiment, a contact reformate feed stream containing aromatics is fed to the depentanizer section 112 by line 111 to remove the C ₅ -fraction. The pentane and harder hydrocarbons are removed via line 113 while the C ₆₊ bottoms fraction is fed via line 114 to the separation wall distillation column 115 to produce C ₇ , C _8, and C ₉₊ aromatics Containing stream.

C ₇ stream is transferred via line 116 to an extractive distillation or liquid-liquid extraction unit 117 where the aliphatic hydrocarbons are removed via line 118 leaving a benzene and toluene-rich stream, Is supplied to the olefin saturation zone (121) The olefin saturation zone 121 can be any other means effective for removal of olefin contaminants in the aromatic stream, including a clay processor or any hydrogenation, including a contacting process. The effluent from the olefin saturation zone 121 is fed via line 122 to an additional separating wall distillation column 123 from which benzene is collected via line 124 and toluene is fed via line 125 To the transalkylation unit 126 and the C ₈₊ fraction is fed via line 127 to the xylene distillation column 128 and preferably to the bottom of the xylene distillation column 128.

2, the C ₈ aromatic hydrocarbon-containing stream recovered from the reformate separating wall column 115 is passed through line 129 to the xylene isomerization section and the Is fed separately to the ethylbenzene removal reaction section 131 located upstream of the xylene distillation column 128. Optionally, the C ₈ aromatic hydrocarbon-containing stream in line 129 may be subjected to an ethylbenzene removal reaction section 131 (e. G., A < RTI ID = 0.0 > ). ≪ / RTI >

As in the embodiment of FIG. 1, ethylbenzene removal can be carried out in either vapor or liquid phase, but is preferably carried out in the vapor phase and is carried out by dealkylation with benzene or isomerization to xylene. Where the preferred mechanism is dealkylation to benzene, suitable and preferred catalysts and conditions for dealkylation are disclosed in connection with the FIG. 1 embodiment.

Ethylbenzene removal is supplied to the section 131, de-heptane exchanger 133 the effluent via line 132 from, the from which the fuel gas is removed through line _{(134), C 6 / C} 7 stream line Is passed to the deheptane section 112 via line 135 and the xylene enriched effluent is passed through line 136 to the olefin saturation zone 137 and generally comprises a clay processor or optionally a hydrogenation process, Lt; RTI ID = 0.0 > olefinic < / RTI > The effluent from the olefin saturation zone 137 is fed to the xylene distillation column 128 via line 138, preferably above and above the heavier C _{8 +} fraction of line 127.

The overhead stream of the xylene distillation column 128 is then fed via line 139 to the para-xylene separation section 141 where the para-xylene is typically separated by adsorption or crystallization or a combination thereof, ). ≪ / RTI > The remaining toluene is removed from the para-xylene separation section 141 and fed via line 143 to the transalkylation section 126 while the remaining para-xylene-free stream is passed through line 140 to the xylene isomerization section (144). The para-xylene separation section 141 is substantially similar to the para-xylene separation section 41 described above.

The xylene isomerization section 144 may operate in a gaseous or liquid phase, but preferably in a liquid phase. Although any liquid contact isomerization process known to those skilled in the art may be utilized in the xylene isomerization section 144, one preferred contact system is disclosed in U.S. Patent Application Publication Nos. 2011/0263918 and 2011/0319688, The entire contents of which are incorporated herein by reference.

The conditions in the xylene isomerization section 144 are that the isomerization of the xylene in the para-xylene-depleted stream while maintaining the para-xylene-depleted stream in a substantially liquid phase, The concentration of xylene is chosen to produce a higher isomerized stream. Suitable conditions include a temperature of about 230 캜 to about 300 캜, a pressure of about 1300 to about 2100 kPa, and a weight hourly space velocity (WHSV) of about 0.5 to about 10 hr ^-1 .

The effluent from the xylene isomerization section 144 is fed via line 145 and recycled to the xylene column 128 via line 161 and recycle to the deheptane 133 via line 146 , Or to the ethylbenzene removal reaction section 131 via line 147. The routing of the xylene isomerization section effluent of line 145 between line 161, line 146 and line 147 can be optimized according to the ethylbenzene content and the overall composition of the effluent.

Reformate separate streams containing C ₉₊ aromatic hydrocarbons Wall recovered from the distillation column 115 is supplied by the heavy aromatic distillation column 149, via line 148, the column is also xylene distillation column via line 151 Lt; RTI ID = 0.0 > 128 < / RTI > Heavy aromatic distillation column 149 is fed through line 153 to the C ₉ / C ₁₀ / hard C ₁₁ containing fraction removed from line 152 by the C ₉₊ aromatic hydrocarbons fed by lines 148 and 151, and separated into pools, containing C ₁₁ + fraction that is fed to the fuel oil pool or topping column. The C ₉ / C ₁₀ / hard C ₁₁ containing fraction 152 is then passed through an olefin saturation zone, such as optionally any other means for the removal of olefin contaminants, including clay treatment or any hydrogenation, And then fed to the transalkylation unit 126 along with the toluene enriched stream fed via lines 125 and 143. In FIG. 2, the olefin saturation zone is shown as being integrated with a transalkylation zone and a single unit 126, but the purpose of this schematic view is not limited. One of ordinary skill in the art knows that olefin saturation can be carried out in a unit that is located upstream from and separates from the transalkylation unit. Also, since olefin saturation is performed only when necessary, only stream 152 passes through the olefin saturation zone, for example, if stream 152 requires olefin removal and the olefin content in stream 125 is such that olefin removal is unnecessary. Suitable transalkylation processes are described above in connection with the FIG. 1 embodiment.

Although any transalkylation process known to those skilled in the art may be used, one preferred process utilizes the multi-stage contact system disclosed in U.S. Patent No. 7,663,010, which is incorporated herein by reference in its entirety. Such a system comprises (i) a first catalyst comprising a first molecular sieve containing from 0.01 to 5% by weight of at least one source of a first metal element of group 6-10 of the periodic table and a limiting index of from 3 to 12, and (ii) ) A second catalyst comprising a second molecular sieve having 0 to 5 wt% of at least one source of a second metal element of group 6-10 of the periodic table and a limiting index of less than 3, wherein the first catalyst or the second The weight ratio of catalyst is in the range of 5:95 to 75:25 and the first catalyst is located upstream of the second catalyst.

Examples of suitable molecular sieves having a limiting index of from 3 to 12 used in the first catalyst are ZSM-5, ZSM-11, ZSM-22, ZSM-23, ZSM-35, ZSM-48, ZSM- -58, and ZSM-5 is preferred. Examples of suitable molecular sieves having a limiting index of less than 3 used in the second catalyst include zeolite beta, zeolite Y, ultra-stable Y (USY), dealuminated Y (Deal Y), mordenite, ZSM- 4, ZSM-12, ZSM-18, NU-87, and ZSM-20, with ZSM-12 being preferred. Specific examples of metals useful for each of the first and second catalysts include iron, ruthenium, osmium, nickel, cobalt, rhenium, molybdenum, tin, and precious metals such as platinum, rhodium, iridium or palladium.

The dealkylation process may be carried out in any suitable reactor, including a radial flow reactor, a fixed bed reactor, a continuous downflow reactor or a fluid bed reactor. The conditions on the first and second catalysts may be the same or different, but are generally in the range of from 100 to 1000 占 폚, preferably from 300 to 500 占 폚; A pressure in the range of 790 to 7000 kPa-a (kilo-Pascal absolute), preferably in the range of 2170 to 3000 kPa-a, a molar ratio of hydrogen to hydrocarbons of from 0.01 to 20, preferably from 1 to 10; And a WHSV in the range of 0.01 to 100 hr ^-1 , preferably 1 to 20 hr ^-1 .

The effluent from the transalkylation unit 126 is fed via line 154 to a stabilizer 155 where the light gas is collected and removed via line 156. The side stream from the stabilizer 155 is recycled to the pentane pentane 112 via line 157 and the stabilizer bottom pentane is fed via line 158 and optionally through the olefin saturation zone 121 to the benzene / Toluene / _C8 < ₊ > separation wall column 123.

As in the FIG. 1 embodiment, if the C 9 + species content in the stream of line 138 is within specification of the separating section 141, some or all of this stream may be _fed to the separator section 141 as shown by dashed line 170 Can be fed directly to the separation section 141 bypassing the xylene column 128.

Figure 3 illustrates various possible variations of the process shown in Figure 2, wherein like numerals refer to like parts. In one such variant, the isomerized C ₈ aromatics recycle stream 147 (see FIG. 2) to section 131, taken downstream of the isomerization unit 144, is located upstream of the isomerization unit 144 Is replaced by a C ₈ aromatic recycle stream 163 (see FIG. 3) from which the para-xylene removed is taken. When the catalyst used in the ethylbenzene removal section 131 is selectively activated as described above, the xylene loss tends to increase with the para-xylene concentration in the feed, since the molecules of ethylbenzene and para-xylene Because they are similar in size. Therefore, as the diffusion of ortho and meta-xylene into the catalytic pore is limited, the para-xylene as well as ethylbenzene readily reacts at the catalytically active sites, thereby increasing xylene losses. However, since the effluent from the separation section 141 is removed from para-xylene, adding it via line 163 to the feed to the ethylbenzene removal section 131 will reduce the para-xylene content in the feed to The xylene loss through the ethylbenzene removal section 131 is reduced.

Another variation of the second embodiment shown in Figure 3 is to direct a portion of the effluent from the isomerization section 144 directly through the line 162 to the para-xylene separation section 141. If the liquid isomerization section 144 operates under conditions with little or no benzene yield or if this benzene yield does not affect the performance of the para-xylene separation section 141, It may be advantageous to recycle a portion of the effluent from the isomerization section 144 directly through the line 161 to the xylene column 128. In addition, when the liquid isomerization section 144 is operated with little or no benzene yield and little or no C ₉₊ aromatic yield, or when these yields do not affect the performance of the para-xylene separation section 141 It may be advantageous to directly recycle a portion of the effluent from the isomerization section 144 through the line 162 to the para-xylene separation section 141, as already shown in Fig. The benzene yield and _{C9 +} aromatic yield from liquid isomerization are typically related to the operating temperature of the unit and also to the ethylbenzene content of the unit feed. Thus, the efficiency of the catalyst in the ethylbenzene removal section 131 and the state of the catalyst in the liquid isomerization unit 144 (the liquid isomerization catalyst is generally at a lower temperature at the beginning of the cycle and at a higher temperature Depending on the type of adsorbent and desorbent used in the para-xylene separation section 141, the distribution of the liquid isomerization effluent through lines 146, 161 and 162 may be optimized. Such recirculation 162 and 161 may also be implemented with other process systems contemplated herein.

In a further variant shown in Fig. 3, the gaseous ethylbenzene removal reaction, supplied by an olefin saturation zone, such as any other means for the removal of olefin contaminants, optionally including clay treatment or any hydrogenation, Section 131 is replaced by the vapor ethylbenzene removal and xylene isomerization section. Thus, in addition to ethylbenzene dealkylation with benzene or ethylbenzene isomerization with ethylbenzene isomerization to xylene, xylene isomerization is also carried out in section 131. A suitable example of an ethylbenzene removal / xylene isomerization integrated system is disclosed in the aforementioned U.S. Patent No. 5,516,956. Some of the xylene isomerization is carried out in section 131 and is then fed to the deoxygenator 133 via line 132 and then to the section 141 via lines 136, 138, and 139, The effluent of the distillation column 131 has a higher para-xylene concentration than in the system shown in Fig. This means that a smaller separation unit 141 is needed since the para-xylene to xylene ratio is higher than in the scheme shown in Fig. The concept of adding a xylene isomerization function to the ethylbenzene removal section is also applicable to other process systems contemplated herein.

Another modification of the process shown in FIG. 3, shown in FIG. 3, is to add optional bypass 164 from stream 138 to liquid isomerization section 144. If stream 138 contains little or no para-xylene, xylene in stream 138 is isomerized prior to recycling the xylene through line 161 to xylene column 128 and separation section 141 Is advantageous to reduce the amount of traffic in these sections and the associated operating costs. This alternative is more particularly suitable if the isomerization efficiency in section 131 is low because the xylene isomerization catalyst is loaded in the section 131 with little or no loading so the main function of the section 131 is to remove ethylbenzene And stream 129 is highly diluted with stream 163.

Another modification of the process shown in FIG. 3, shown in FIG. 3, is to optionally add a stream 165 from the xylene column 128 to the effluent line 140 from the separation section 141. When the stream 165 is collected at the ortho-xylene enriched position of the xylene column 128, recycle to the liquid isomerization section 144 is carried out such that the stream with a low para-xylene content circulates through the separation section 141 To be equilibrated to the equilibrium xylene, thereby reducing the amount of transport through the separation section and associated operating costs. This variant is also applicable to other process systems contemplated herein.

Another modification of the process shown in FIG. 3, shown in FIG. 3, is to add an optional bypass stream 166 from the stream 148 to the olefin saturation and transalkylation section 126. In the reformate, which can result in a low end point of the oil stream 111, if the stream 148 in the C ₁₁ + When the content is low, the line to bypass at least a portion of the heavy aromatics column 149 of the stream 148 Can be directed to olefin saturation and transalkylation section 126 through line 166 to reduce the amount of transport through the heavy aromatic column 149 and associated operating costs. This variant is also applicable to the schemes shown in Figs. 1, 2 and 4. As noted above, in FIG. 3, the olefin saturation zone is shown integrated with a transalkylation zone and a single unit 126, but the purpose of this schematic view is not limited. Those skilled in the art know that olefin saturation can be carried out in a unit that is located upstream of the transalkylation unit and is separate from it. In addition, since olefin saturation is performed only as needed, for example, if streams 152 and 166 require olefin removal and the olefin content in stream 125 is such that olefin removal is unnecessary, then only streams 152 and 166 are in the olefin saturation zone Lt; / RTI >

3 is to separate the isomerization recycle stream from the two isomerization sections, namely, the vapor isomerization section 131 and the liquid isomerization section 144. The recycle stream is the C ₉ in accordance with the aromatic content can be supplied at different supply point of xylene column 128 (the line for supplying the vapor phase the isomerization effluent to the xylene column 128 in Fig. 3 (138) and after (See line 161 for feeding the liquid isomerization effluent to the xylene column 128), reducing the size and energy consumption of the column.

4 shows a process for producing para-xylene according to a third embodiment of the present invention. Here, a conventional reforming oil-type separator is used in which a C ₅ aliphatic hydrocarbon remaining after removal of C ₅ -aliphatic hydrocarbons from a contact- _{The 6+} hydrocarbon stream is fractionally distilled. Thus, in a third embodiment, the reformate feed stream containing aromatics is fed to the depentanizer section 202 by line 201 to remove the C ₅ -fraction. The pentane and harder hydrocarbons are removed via line 203 while the C ₆₊ bottoms fraction is fed via line 204 to a conventional reforming oil splitter 205 to form C _7- and C ₈₊ aromatic hydrocarbon Stream.

The C _{7 -stream} from reforming oil splitter 205 is transferred via line 206 to an extractive distillation or liquid-liquid extraction unit 207 where aliphatic hydrocarbons are removed via line 208 to produce benzene and toluene-rich Leaving a stream which is fed via line 209 to the olefin saturation zone 211. The olefin saturation zone 211 can be any other means effective for removal of olefin contaminants in the aromatic stream, including a clay processor or any hydrogenation, including a contacting process. The effluent from the olefin saturation zone 211 is fed via line 212 to a separate wall distillation column 213 from which benzene is collected via line 214 and toluene is passed through line 215 to the trans- Alkylation unit 216 and the C ₈₊ fraction is fed via line 217 to a xylene distillation column 218.

The _{C8 +} aromatic hydrocarbon-containing stream recovered from reforming oil splitter 205 may be recovered by olefin saturation zone, such as any other means for the removal of olefin contaminants, optionally including clay treatment or any hydrogenation, , And is supplied via line 219 to the ethylbenzene removal section 221. The removal of ethylbenzene in section 221 is preferably carried out by dealkylation of benzene and hard (C ₂ ) gases in the gas phase as described above. Alternatively, ethylbenzene removal can also be carried out by isomerization to xylene.

Ethylbenzene removed and fed to additional separation wall distillation column 223 of the effluent from the section 221, via line 222, an therefrom fuel gas is removed through line _{(224), C 6 / C} 7 stream de-pentane exchanger section 202 to be transferred via line (225), C ₉₊ aromatic stream is fed to a heavy column 226 via line 227, xylene rich C ₈ stream line 228 To the olefin saturation zone 229, generally optionally with hydrogenation, to any process for the removal of olefin contaminants, including the contacting process. The effluent from the olefin saturation zone 229 is also fed via line 231 to the para-xylene separation section 232 which is fed via line 233 with an overhead from a xylene distillation column 218. Para-xylene is typically separated by adsorption or crystallization or a combination thereof in a para-xylene separation section 232 and recovered via line 234. The remaining toluene is removed from the para-xylene separation section 232 and fed via line 235 to the transalkylation section 216 while the remaining para-xylene-free stream is passed through line 237 to the xylene isomerization section (236).

Although any xylene isomerization process known to those skilled in the art may be utilized in the xylene isomerization section 236, one preferred process is disclosed in U.S. Patent Application Publication Nos. 2011/0263918 and 2011/0319688, The entire contents of which are incorporated herein by reference.

The effluent from the xylene isomerization section 236 is recycled to the separated wall distillation column 223 via line 239 via line 239 or to the ethylbenzene removal section 221 via line 241, Lt; RTI ID = 0.0 > a < / RTI > If the ethylbenzene removal section 221 is operated at a very high conversion rate (greater than about 50%), then the slip stream passed through line 241 to the ethylbenzene removal section is very low and most of the isomerization section effluent Through line 239 to the separating wall distillation column 223.

The C ₉₊ stream from the separating wall distillation column 223 is fed via line 227 to the heavy aromatic distillation column 226 which also passes through the line 242 from the xylene distillation column 218 to the bottoms stream . The heavy aromatic distillation column 226 is fed to the gasoline pool through line 244 and the C ₉ / C ₁₀ containing fraction removed from line 243 by the C ₉₊ aromatic hydrocarbons fed by lines 227 and 242 C ₁₁ -containing fraction. The C ₉ / C ₁₀ -containing fraction 243 is then passed through an olefin saturation zone, optionally followed by a clay treatment or any other means for the removal of olefin contaminants, including the contacting process with optional hydrogenation, 215 to the transalkylation unit 216 together with the toluene-rich stream. In FIG. 4, the olefin saturation zone is shown integrated with a transalkylation zone and a single unit 216, but the purpose of this schematic view is not limited. One of ordinary skill in the art knows that olefin saturation can be carried out in a unit that is located upstream from and separates from the transalkylation unit. Also, because olefin saturation is performed only when necessary, only stream 243 passes through the olefin saturation zone, for example if stream 243 requires olefin removal and the olefin content in stream 215 is such that olefin removal is unnecessary.

Although any transalkylation process known to those skilled in the art may be utilized in the transalkylation unit 216, one preferred process utilizes the multi-stage contact system disclosed in U.S. Patent No. 7,663,010, as described above for the Figure 1 embodiment.

The effluent from the transalkylation unit 216 is fed via line 245 to a stabilizer 246 where a light gas is collected and removed via line 247. The sidestream from the stabilizer 246 is recycled to the pentane pentane 202 via line 249 and the stabilizer bottoms optionally is passed through the olefin saturation zone 211 via line 248 to a separate wall distillation column 213).

In the second and third embodiments shown in Figures 2 to 4, the ethylbenzene removal is carried out in sections 131 and 221 for the rich C ₈ aromatic mixture recovered from the fractional distillation of the reformate and the xylene isomerization Is carried out in dedicated sections (144, 236) for para-xylene-free stream. This arrangement allows the isomerization of a large amount of para-removed xylene stream to be carried out in liquid phase (without addition of a gas phase isomerization unit) by separating the ethylbenzene removal from the xylene isomerization, while the EB elimination is less EB-enriched stream. Thereby, when both contact reactions are carried out in the same unit 44 as shown in Fig. 1, it is possible to remove the para-xylene from the para-xylene separating sections 141 and 232 necessary for isomerization of para- The cost associated with the liquid effluent cost is reduced. In addition, separating the ethylbenzene removal from xylene isomerization reduces the cost of the catalyst, since the liquid isomerization catalyst is generally metal free while the gaseous isomerization catalyst contains a noble metal such as rhenium or an expensive noble metal. In addition, the conditions for each process can be independently set, maximizing its yield and efficiency through plant useful life, so that the overall xylene loop efficiency can be increased.

According to a fourth embodiment (illustrated in Fig. 7 described below), the system shown in Figs. 1-3 comprises a first separating wall column 15,115 as three fractions, C7 _- fraction, as a side-draw may be modified by replacing a conventional distillation column, which enables the separation of the C ₉₊ fraction as a C ₈ fraction and a bottom fraction. When C ₈ oil is supplied to the EB removal section 131 (FIG. 2 or 3) or 211 (FIG. 4), this method transfers more C _{9 out} of the C ₈ fraction to the ethylbenzene removal unit . As some of the C ₉ components are dealkylated to toluene, the toluene / C ₉₊ ratio in the transalkylation feed increases and the benzene / PX ratio in the aromatic complex also increases, indicating that the contact system of the EB removal unit is EB If a heavier feed can be processed without significantly affecting the removal efficiency, it may be advantageous if more benzene production is aimed at. In this case, the C ₉₊ oil fraction may contain some residual C ₈ aromatics and must therefore be transported to a heavy aromatic distillation column or a xylene distillation column.

Some configuration options are not disclosed herein but fall within the scope of this disclosure, namely: (a) in the scheme shown in the following figures, the separation wall column 23 of FIG. 1, the separation wall column of FIGS. 2 and 3 123, and the separating wall column 213 of FIG. 4 may be replaced by a conventional arrangement of benzene and toluene columns; (b) In the schemes shown in the following figures, the separating wall column 15 of FIG. 1 and the separating wall column 115 of FIGS. 2 and 3 correspond to the conventional arrangement of hard modifying oil splitters and heavy reforming Can be replaced by a u-splitter column; (c) In the schemes shown in Figures 2 and 3 below, EB removal unit 131 (Figure 2) or EB removal and xylene isomerization unit 131 (Figure 3) May be located between the separation wall column 115 in the stream 114 and the depolymerizer 112 instead of downstream of the column 115; (d) Similarly, in the schemes shown in FIG. 4 below, the EB removal unit 221 may optionally be coupled to a reforming oil splitter (not shown) in the stream 204 instead of downstream of the reforming oil- Can be located between the desolvation unit (205) and the depentanizer (202).

The present invention will now be described more specifically with reference to the following non-limiting examples.

Example 1

This embodiment shows the advantage of using a separation wall column (FIG. 5) in comparison with the conventional hard and heavy reforming oil splitters (FIG. 6) in the configuration scheme shown in FIGS. 1-3.

This example is based on a 85 wt% rich C ₆₊ aromatic hydrocarbon stream obtained from the modification of a naphtha feed having the following carbon number distribution:

Referring to Figure 5, a rich C _{6 +} aromatic hydrocarbon stream (stream 301) at 220 t / h is fed to a separating wall column 302, operating at a pressure of 1.4 kPa, a condenser temperature of 83 ° C, and a re- . The separating wall column (DWC) 302 includes 58 theoretical plates including a condenser (No. 1 plate) and a reboiler (No. 58 plate). The DWC technique involves placing a vertical divider between the feed or reservoir of the three product towers and the product side. On the feed side, the separation of the low boiling point and high boiling point fraction occurs, and on the product side the intermediate boiling fraction is separated. The prefractionator side of the DWC distributes the intermediate key between the top and bottom so as to allow great flexibility in composition matching at the top and top of the main column.

In the embodiment shown in Figure 5, the vertical wall 303 in the separating wall column 302 extends from tray 11 down to tray 37 and each tray is divided into two sections, Into the supply and withdrawal zones. The rich C ₆₊ aromatic hydrocarbon feed stream 301 is introduced into the separating wall column 302 in plate 13 at the feed zone side of the wall section. Dividing wall column 302 as a liquid distillate from the plate C _7- fraction (stream 304) times 1, C ₈ fraction (stream 305) as a side-draw from the plate 23 of the take-out area of the side wall 303, and the C ₉₊ fraction (stream 306) to be produced as a bottom product. Condensation is carried out using an air cooler which removes 30 MW of heat and the boiling is carried out at a minimum of 214 ° C, preferably on a heating medium which provides 33.3 MW of heat above 15 ° C of the column bottom temperature of the separating wall column 302 .

The fractional distillation performance of the separation wall column 302 is summarized below:

Toluene recovery (defined as toluene in C- ₇ fraction (stream 304) divided by toluene in feed (stream 301)) is 99.9 wt%.

The C ₈ aromatic recovery (defined as EB + PX + MX + OX in C ₈ fraction (stream 305) divided by EB + PX + MX + OX in the feed (stream 301) is 99 wt%.

The C ₉ aromatics content in the C ₈ oil (stream 305) is 5% by weight.

In order to achieve the separation performance described above, conventional fractionation requires the use of two distillation columns run in series as shown in FIG. Thus, referring to FIG. 6, a rich C _{6 +} aromatic hydrocarbon feed (stream 401) at 220 t / h is fed to plate 15 of the first distillation column 402. This first distillation column 402 contains 29 theoretical plates and is operated at a pressure of 1.4 kPa, a condenser temperature of 83 DEG C and a re-boiling temperature of 175 DEG C. Condensation is carried out using an air cooler to remove 26.7 MW, and the cost is ensured by a heating medium which provides 29.6 MW of heat at a minimum of 180 ° C, preferably above 15 ° C of the column bottom temperature of the first column. The first distillation column 402 allows the _C7- oil (stream 403) to be recovered as a liquid distillate on the first plate and the _{C8 +} oil (stream 404) as the bottom product.

The fractional distillation performance of the first distillation column 402 is summarized below:

Toluene recovery (defined as toluene in C- ₇ fraction (stream 403) divided by toluene in feed (stream 401) is 99.9 wt%.

The C ₈ aromatic recovery (defined as EB + PX + MX + OX in C _{8 +} fraction (stream 404) divided by EB + PX + MX + OX in the feed (stream 401) is 99.5 wt%.

The bottoms product (stream 404) of the first distillation column 402 comprises a second distillation column 405 comprising 29 theoretical plates and operating at a pressure of 1.4 kPa, a condenser temperature of 144 캜 and a reboiling temperature of 197 캜, . Condensation is carried out using an air cooler to remove 13.7 MW and the cost is ensured by a heating medium which provides 19.5 MW of heat at a minimum of 202 ° C, preferably above 15 ° C of the column bottom temperature of the second column. A second distillation column 405 is a C ₈ fraction (stream 406) in the plate 1 as a liquid distillate and the C ₉₊ fraction (stream 407) to be recovered as the bottom product.

The fractional distillation performance of the second distillation column 405 is summarized below:

The C ₈ aromatic recovery (defined as EB + PX + MX + OX in C ₈ fraction (stream 406) divided by EB + PX + MX + OX in the feed (stream 404) is 99.5 wt%.

The C ₉ aromatics content in the C ₈ oil (stream 406) is 5% by weight.

Thus, the fractional distillation performance of a system consisting of a tandem bisection column (FIG. 6) is similar to the fractional distillation performance of the separation wall column (FIG. 5). Compared with the conventional configuration shown in Fig. 6, however, the separation wall column shown in Fig. 5 is more energy efficient because the heat required to perform the same fractional distillation performance is reduced from 49.1 MW to 33.3 MW. An additional advantage of the separating wall column over conventional arrangements is that the fractionation system hardware (number of columns, reboiler, etc.) needed to achieve the desired fractional distillation performance is reduced in half.

Example 2

Referring now to FIG. 7, this embodiment illustrates the effect of using a three-oil distillation column instead of a separating wall column as the reforming oil splitter 15, 115 in the configuration scheme shown in FIGS. 1-3.

In the embodiment of FIG. 7, a rich C _{6 +} aromatic hydrocarbon feed (stream 501) at 220 t / h contains 58 theoretical plates and has a pressure of 1.4 kPa, a condenser temperature of 83 ° C and a re- Is fed to the twentieth plate of a three-oil distillation column (502) operated in a distillation column. The third fraction distillation column 502 as a liquid distillate from the plate C _7- fraction (stream 503) times 1, C ₈ fraction (stream 504) as a side-draw from the plate 40 times, and the C ₉₊ fraction (stream 505) as a bottom product. Condensation is carried out using an air cooler to remove 31 MW and the cost is ensured by a heating medium which provides 33.7 MW of heat at a minimum of 207 ° C, preferably above 15 ° C of the column bottom temperature of the distillation column.

The fractional distillation performance of the three-oil distillation column 502 is inferior to that achieved with the separation wall column of Example 1, which is summarized below:

Toluene recovery (defined as toluene in C- ₇ fraction (stream 503) divided by toluene in feed (stream 501) is 99.9 wt%.

The C ₈ aromatic recovery (defined as EB + PX + MX + OX in C ₈ fraction (stream 504) divided by EB + PX + MX + OX in the feed (stream 501) is 87 wt%.

The C ₉ aromatics content in the C ₈ oil (stream 504) is 15% by weight.

However, the ethylbenzene recovery (defined as EB in the C ₈ fraction divided by EB in the feed) (98% by weight) achieved with a three-oil distillation column was comparable to that obtained with the separation wall column of Example 1 (98.5% by weight) Similar.

The performance of the distillation schemes of Example 1 and Example 2 are summarized in the following Table 1, where Qr denotes the heat requirement.

Other documents, including all patents, test procedures, and priority documents referred to herein, are hereby incorporated by reference in all jurisdictions to the extent that the disclosure is not inconsistent with the present invention and is permitted to include.

Having particularly described the exemplary embodiments disclosed herein, it is to be understood that various other modifications, additions and / or modifications may be apparent to and readily made by those skilled in the art without departing from the spirit and scope of the disclosure. The scope of the claims appended hereto is therefore not intended to be limited to the embodiments and descriptions disclosed herein, and the claims are intended to cover all such features, modifications, Should be construed to include all features of novelty as far as possible.

Where numerical lower limits and numerical upper limits are recited herein, ranges from any lower limit to any upper limit are contemplated and are clearly within the scope of the present invention. The term "comprising" is synonymous with the term "containing ". Likewise, where a composition, element, or group of elements is followed by a linking phrase "comprising ", the phrase " consisting essentially of" Means the same composition or group of components having a linking phrase of "phosphorus" and vice versa.

Claims (25)

As a method for producing para-xylene,
(a1) feeding at least one feed comprising C ₆₊ aromatic hydrocarbons to a separation wall distillation column to convert the feed to a C ₇ -aromatic hydrocarbon-containing stream, a C ₈ aromatic hydrocarbon-containing stream and a C ₉₊ aromatic hydrocarbon- Separating;
generating a stream of xylene is removed by supplying a xylene recovery units, para from the C ₈ aromatic hydrocarbon-containing stream - - (b1) at least a portion of the C ₈ aromatic hydrocarbon stream containing para-xylene and para recovered;
(c1) in a xylene isomerization zone, at least a portion of the para-xylene-depleted stream is treated with a xylene isomerization catalyst in a condition effective to isomerize the xylene in the para-xylene-depleted stream and produce an isomerized stream ; And
(d1) recycling at least a portion of the isomerized stream to the para-xylene recovery unit
≪ / RTI > The process according to claim 1, wherein the at least one feed to (a1) comprises a mixture of C ₆₊ aromatic and aliphatic hydrocarbons produced by removing C ₅ -hydrocarbons from the reformate stream. 3. The method of claim 2,
(e1) removing at least a portion of the aliphatic hydrocarbons from the C7 _- aromatic hydrocarbon-containing stream to produce a C7 _- aromatic hydrocarbon-rich stream
≪ / RTI > The method of claim 3,
(f1) feeding at least a portion of the C7 _- aromatic hydrocarbon-rich stream to a separation unit to recover benzene therefrom to produce a toluene-containing stream;
(g1) contacting at least a portion of the toluene-containing stream and at least a portion of the _{C9 +} aromatic hydrocarbon-containing stream with a transalkylation catalyst under conditions effective to produce a xylene-containing transalkylation product; And
(h1) feeding at least a portion of the transalkylation product to a separation unit of (f1)
≪ / RTI > The process according to claim 4, wherein the separation unit (f1) comprises an additional separation wall distillation column. 6. The method according to any one of claims 1 to 5,
(i1) C ₈ further comprising: at least a portion of the aromatic hydrocarbon-containing stream supplied to the ethylbenzene removal zone; And
(j1) it is subjecting the stream containing C ₈ aromatic hydrocarbons in the conditions effective to remove at least a portion of the ethylbenzene in the C ₈ aromatic hydrocarbon-containing stream from the ethylbenzene removal zone in contact with a first catalyst
≪ / RTI > The process according to claim 6, wherein the conditions in the ethylbenzene removal zone are effective to maintain the C ₈ aromatic hydrocarbon-containing stream substantially in the vapor phase. 8. A process according to claim 7, wherein the ethylbenzene removal zone is located upstream of the para-xylene recovery unit. 8. A process according to claim 7, wherein the ethylbenzene removal zone is located downstream of the para-xylene recovery unit. The process according to claim 8 or 9, wherein the ethylbenzene removal zone also contains a second catalyst effective to isomerize xylene in the C ₈ aromatic hydrocarbon-containing stream under the conditions. 11. The process according to any one of claims 1 to 10, wherein the conditions of the xylene isomerization zone are effective to keep the para-xylene-depleted stream substantially in liquid phase. 11. The process according to any one of claims 1 to 10, wherein the conditions of the xylene isomerization zone are effective to maintain the para-xylene-depleted stream substantially in the vapor phase. As a method of producing para-xylene and benzene,
(a2) feeding a feed comprising a mixture of C ₆₊ aliphatic and aromatic hydrocarbons to a separate wall distillation column to separate said feed into a C ₇ -hydrocarbon-containing stream, a C ₈ -hydrocarbon-containing stream and a C ₉₊ -hydrocarbon-containing stream ;
(b2) removing at least a portion of the aliphatic hydrocarbons from the C7 _- hydrocarbon-containing stream to produce a C7 _- aromatic hydrocarbon-rich stream;
(c2) feeding at least a portion of the C7 _- aromatic rich stream to a separation unit to separate the _C7- aromatic rich stream into a benzene containing stream and a toluene containing stream;
(d2) at least a portion of the stream containing C ₈ hydrocarbons, para-xylene to produce the stream is removed by feeding the para-xylene recovery unit from the stream containing C ₈ hydrocarbon-recovery of para-xylene;
(e2) in a xylene isomerization zone, at least a portion of the para-xylene-depleted stream is subjected to a reaction with a xylene isomerization catalyst and a xylene isomerization catalyst under conditions effective to isomerize the xylene in the para- Contacting;
(f2) recycling at least a portion of the isomerized stream to the para-xylene recovery unit;
(g2) contacting at least a portion of the toluene-containing stream and at least a portion of the _{C9 +} hydrocarbon-containing stream with a transalkylation catalyst under conditions effective to produce a transalkylation product containing xylene; And
(h2) feeding at least a portion of the xylene in the transalkylation product to the para-xylene recovery unit
≪ / RTI > The process according to claim 13, wherein the feed to (a2) is produced by removing _C5- hydrocarbons from the reformate stream. The method according to claim 13 or 14,
supplying the ethylbenzene removal zone which is located upstream of the xylene recovery unit - (i2) at least a portion of the C ₈ aromatic hydrocarbon-containing stream from the (a2), para; And
(j2) (d2) prior to the step of contacting the C ₈ aromatic hydrocarbon stream containing at conditions effective to remove at least a portion of the ethylbenzene in the C ₈ aromatic hydrocarbon-containing stream from the ethylbenzene removal zone with a first catalyst
≪ / RTI > The method of claim 15 wherein the method of producing ethylbenzene removal zone will also containing an effective catalyst for the second reason to nitride the xylene in the C ₈ aromatic hydrocarbon-containing stream under the above conditions. Claim 15 according to any one of claims 16, wherein the conditions of the ethylbenzene removal zone is a manufacturing method effective in maintaining a substantially gaseous phase C ₈ aromatic hydrocarbon-containing stream. 18. The method according to any one of claims 13 to 17,
(k2) feeding at least a portion of the para-xylene-depleted stream from (d2) to an ethylbenzene removal zone upstream of the xylene isomerization zone; And
(l2) contacting the para-xylene-depleted stream with the first catalyst under conditions effective to remove at least a portion of the ethylbenzene in the para-xylene-depleted stream in the ethylbenzene removal zone before (e2)
≪ / RTI > 19. The process of claim 18, wherein the conditions of the ethylbenzene removal zone are effective to maintain the para-xylene-depleted stream substantially in the vapor phase. 20. The process according to any one of claims 13 to 19, wherein the conditions of the xylene isomerization zone are effective to maintain the para-xylene-free stream in a substantially liquid phase. 14. The method of claim 13 according to any one of claim 20, wherein the separation unit is fed to the at least a portion of the transalkylation product from (g2) (c2) the separation unit separates the xylene from the transalkylation product, and C _7- Containing stream is effective to separate the aromatic-rich stream into a benzene-containing stream and a toluene-containing stream. 22. A production process according to any one of claims 13 to 21, wherein the separation unit (c2) comprises an additional separation wall distillation column. 23. The method of claim 22,
(m2) removing the _{C8 +} hydrocarbon residue stream from the further separation wall distillation column; And
(n2) supplying at least a portion of the _{C8 +} hydrocarbon residue stream to the para-xylene recovery unit
≪ / RTI > As a method of producing para-xylene and benzene,
(a3) feeding a feed comprising a mixture of C ₆₊ aliphatic and aromatic hydrocarbons to a distillation column to separate the feed into a C ₇ -hydrocarbon-containing stream and a C ₈₊ hydrocarbon-containing stream;
(b3) removing at least a portion of the aliphatic hydrocarbons from the C7 _- hydrocarbon-containing stream to produce a C7 _- aromatic hydrocarbon-rich stream;
(c3) feeding at least a portion of the C7 _- aromatic hydrocarbon-rich stream to a separation system to recover benzene therefrom to produce a toluene-containing stream;
(d3) C ₈₊ hydrocarbon-containing stream, de-alkylation of ethylbenzene to benzene and C ₈₊ ethyl at least a portion of the C ₈₊ hydrocarbon-containing stream at conditions effective to produce a dealkylation effluent containing benzene hydrocarbons dealkylation Contacting the catalyst with the catalyst;
(e3) separating a dealkylation effluent de-alkylation to provide water to the dividing wall distillation column effluent to C _7- aromatic hydrocarbon-containing stream, C ₈ aromatic hydrocarbon-containing stream and a C ₉₊ aromatic hydrocarbon-containing stream;
generating a stream of xylene is removed (f3) C ₈ aromatic hydrocarbon stream containing at least a portion of the para-xylene recovery unit and supplied to the para from C ₈ aromatic hydrocarbon-containing stream, - and recovering the p-xylene;
(g3) contacting at least a portion of the para-xylene-depleted stream with a xylene isomerization catalyst under conditions effective to isomerize the xylene in the para-xylene-depleted stream and produce an isomerized stream;
(h3) recycling at least a portion of the isomerized stream to the separation wall distillation column;
(i3) contacting at least a portion of the toluene-containing stream and at least a portion of the _{C9 +} hydrocarbon-containing stream with a transalkylation catalyst under conditions effective to produce a transalkylation product containing xylene; And
(j3) feeding at least a portion of the transalkylation product to a separation system of (c3) effective to separate xylene from the transalkylation product from (i3)
≪ / RTI > 25. The process according to claim 24, wherein the separation system of (c3) comprises an additional separation wall distillation column.

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