阅读说明：本技术 用于在芳烃联合装置中使芳烃甲基化的方法和设备 (Method and apparatus for methylating aromatics in an aromatics complex ) 是由 帖木儿·V·沃斯科博伊尼科夫 詹邓阳 约翰·Q·陈 埃德温·P·博尔丁格 于 2018-12-05 设计创作，主要内容包括：本公开涉及在用于产生二甲苯异构体产物的芳烃联合装置中使芳烃甲基化的方法和设备。更具体地,本公开涉及通过在芳烃联合装置中使甲苯和/或苯选择性甲基化而产生对二甲苯的方法。(The present disclosure relates to a method and apparatus for methylating aromatics in an aromatics complex for producing xylene isomer products. More specifically, the present disclosure relates to a process for producing para-xylene by selective methylation of toluene and/or benzene in an aromatics complex.)

1. A process for the methylation of toluene comprising:

passing a toluene feed stream and a plurality of methanol feed streams to a reaction zone to produce a reaction zone product stream;

separating the reaction zone product stream and passing the reaction zone product stream to a stripper to produce an effluent gas stream, an overhead stream comprising toluene and xylenes, a sidedraw comprising xylenes, and a bottoms stream comprising C9+, specifically a diphenylmethane component; and

passing the C9+ stream to a transalkylation zone comprising a transalkylation catalyst comprising at least one zeolite of the MWW or mordenite type.

2. The process of claim 1, wherein the toluene stream and at least one methanol stream are mixed prior to entering the reaction zone.

3. The process of claim 1, wherein one additional methanol stream is passed to the reaction zone.

4. The process of claim 1, wherein two additional methanol streams are passed to the reaction zone.

5. The process of claim 1, wherein three additional methanol streams are passed to the reaction zone.

6. An apparatus for the methylation of toluene, comprising:

a plurality of lines comprising toluene in direct communication with the reaction zone, wherein the reaction zone is further coupled to a line comprising a reaction zone product stream;

the reaction zone product stream is in direct communication with a stripper to produce a line comprising a vent gas stream, an overhead line comprising toluene and xylenes, a side draw line comprising xylenes, and a bottoms line comprising C9+, specifically a diphenylmethane component; and is

The bottom line comprising the C9+ stream is in direct communication with a transalkylation zone comprising a transalkylation catalyst comprising at least one zeolite of the MWW or mordenite type.

7. The apparatus of claim 6, wherein the reaction zone comprises at least one reactor.

8. The apparatus of claim 6, wherein the reaction zone comprises no more than four reactors.

9. The apparatus of claim 6, wherein the reaction zone is operated at a temperature of 200 ℃ to 400 ℃.

10. The apparatus of claim 6, wherein the reaction zone is operated at a pressure of 103kPa (15psig) to 2758kPa (400 psig).

Technical Field

The present disclosure relates to a method and apparatus for methylating aromatics in an aromatics complex for producing xylene isomer products. More specifically, the present disclosure relates to a process for producing para-xylene by selective methylation of toluene and/or benzene in an aromatics complex.

Background

Xylene isomers are produced in large quantities from petroleum as a feedstock for a variety of important chemicals. The most important xylene isomer is the main feedstock for polyesters, namely para-xylene, which continues to enjoy high growth rates due to a large fundamental demand. Ortho-xylene is used to produce phthalic anhydride, which supplies a high volume but relatively mature market. Meta-xylene is used less, but its use in products such as plasticizers, azo dyes and wood preservatives is increasing. Ethylbenzene is typically present in xylene mixtures and is sometimes recovered for styrene production, but is generally considered to be a less desirable component of C8 aromatics.

Among the aromatic hydrocarbons, xylene is comparable in overall importance to benzene as an industrial chemical feedstock. Xylenes and benzene are produced from petroleum by reforming naphtha but cannot be used in sufficient quantities, so conversion of other hydrocarbons is required to increase the yield of xylenes and benzene. Typically, toluene is dealkylated to produce benzene or selectively disproportionated to produce benzene and recover the C8 aromatics of the individual xylene isomers therefrom.

Handbook of methods for refining Petroleum (H) published in 1997 by the McGraw-Hill group_{ANDBOOK OF}P_ETROLEUMR_EFININGP_ROCESSES) (second edition), Meyers, discloses an aromatics complex flow scheme, and is incorporated herein by reference.

A conventional aromatics complex sends toluene to a transalkylation zone to produce the desired xylene isomers via transalkylation of toluene with a9+ component. The a9+ component is present in both the reformate bottoms stream and the transalkylation effluent.

Methylation of toluene or benzene with an oxygenate such as methanol has been proposed as a route to xylene production, and the ratio of methyl to phenyl in an aromatic complex is increased to maximize xylene production. Toluene methylation operating in the gas phase has poor feed (especially oxygenate) utilization, low aromatics per pass conversion, and poor catalyst stability over time periods of hours, days, and weeks, thus requiring frequent regeneration. Typically, to selectively produce para-xylene targets, toluene methylation is operated, which requires operation at severe process conditions (i.e., high temperatures) where the decomposition of methanol to COx and H2 via significant amounts of diluents (such as H2O, H2) is significant and thus requires recycling of the catalyst, which is relatively difficult to prepare reproducibly. MFI zeolites are the catalysts mainly used in this process.

Accordingly, it is desirable to provide improved methods and apparatus for methylating aromatics, such as toluene and benzene, in an aromatics complex. Furthermore, it would be desirable to provide an economical and efficient process and apparatus for toluene and/or benzene methylation that operates under mild conditions, promotes high feedstock utilization, and wherein higher than equilibrium paraxylene/xylenes can be achieved without dilution. Additionally, it is desirable to reduce the overall cost of operating and/or introducing such methylation units in an aromatics complex. Furthermore, other desirable features and characteristics of the present subject matter will become apparent from the subsequent detailed description of the subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the subject matter.

Disclosure of Invention

The present subject matter relates to methods and apparatus for methylating toluene and/or benzene in an aromatics complex for producing xylene isomers. More particularly, the present disclosure relates to a process and apparatus for methylating toluene at mild reaction conditions (i.e., a combination of low temperature and high pressure).

In the foregoing, all temperatures are shown in degrees celsius and all parts and percentages are by weight unless otherwise indicated. Other objects, advantages and applications of the present invention will become apparent to those skilled in the art from the following detailed description and the accompanying drawings. Additional objects, advantages and novel features of the example will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following detailed description and the accompanying drawings, or may be learned by production or operation of the example. The objects and advantages of the concepts may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

Drawings

Figure 1 shows a process and apparatus for methylating toluene at mild reaction conditions (i.e. a combination of low and high temperatures).

Definition of

As used herein, the term "stream" may include various hydrocarbon molecules and other materials.

As used herein, the terms "stream," "feed," "product," "fraction," or "portion" may include various hydrocarbon molecules such as straight and branched alkanes, cycloalkanes, alkenes, alkadienes, and alkynes, and optionally other substances such as gases, e.g., hydrogen, or impurities such as heavy metals, as well as sulfur and nitrogen compounds. Each of the above may also include aromatic hydrocarbons and non-aromatic hydrocarbons.

As used herein, the term "overhead stream" may mean a stream withdrawn at or near the top of a vessel (such as a column).

As used herein, the term "bottoms stream" can mean a stream withdrawn at or near the bottom of a vessel (such as a column).

Hydrocarbon molecules may be abbreviated as C1, C2, C3, Cn, where "n" represents the number of carbon atoms in one or more hydrocarbon molecules, or abbreviations may be used as adjectives for non-aromatic hydrocarbons or compounds, for example. Similarly, aromatic compounds may be abbreviated as a6, a7, A8, An, wherein "n" represents the number of carbon atoms in one or more aromatic molecules. In addition, the superscript "+" or "-" may be used for one or more hydrocarbon symbols of the abbreviation, such as C3+ or C3-, including one or more hydrocarbons of the abbreviation. By way of example, the abbreviation "C3 +" means one or more hydrocarbon molecules having three or more carbon atoms.

As used herein, the term "unit" may refer to a region that includes one or more items of equipment and/or one or more sub-regions. Items of equipment may include, but are not limited to, one or more reactors or reactor vessels, separation vessels, distillation columns, heaters, exchangers, piping, pumps, compressors, and controllers. In addition, an equipment item such as a reactor, dryer, or vessel may also include one or more zones or sub-zones.

The term "column" means one or more distillation columns for separating the components of one or more different volatile substances. Unless otherwise specified, each column includes a condenser at the top of the column for condensing a portion of the top stream and refluxing it back to the top of the column, and a reboiler at the bottom of the column for vaporizing a portion of the bottom stream and returning it to the bottom of the column. The feed to the column may be preheated. The top or overhead pressure is the pressure of the overhead vapor at the vapor outlet of the column. The bottom temperature is the liquid bottom outlet temperature. Unless otherwise indicated, net overhead and net bottoms lines refer to the net lines to the column from any column downstream of reflux or reboil. The stripping column may omit a reboiler at the bottom of the column and instead provide the heating requirements and separation power for the liquefied inert medium (such as steam).

As depicted, the process flow lines in the figures are referred to interchangeably as, for example, lines, pipes, feeds, gases, products, effluents, parts, portions, or streams.

The term "transfer" means the transfer of a substance from a conduit or container to an object.

Detailed Description

The following detailed description is merely exemplary in nature and is not intended to limit the application and uses of the described embodiments. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.

A description of the apparatus of the present invention is presented with reference to figure 1. Fig. 1 is a simplified diagram of a preferred embodiment of the present invention, and is not intended to unduly limit the broad scope of the description provided herein and the claims that follow. Certain hardware, such as valves, pumps, compressors, heat exchangers, instrumentation and controls, have been omitted because such hardware is not necessary for a clear understanding of the present invention. The use and application of such hardware is well within the skill of the art.

Various embodiments described herein relate to methods and apparatus for methylating toluene and/or benzene in an aromatics complex for producing xylene isomers. As shown in fig. 1, the process and apparatus 10 includes a first feed stream 12 comprising toluene and a second feed stream 14 comprising methanol. The first feed stream 10 and the second feed stream 12 are mixed and passed to the reaction zone 18 via line 16. An additional methanol stream can be fed to reaction zone 18 via line 20 and line 22. It is also contemplated that additional methanol streams may also be added to reaction zone 18. Passing multiple streams of methanol to the reaction zone 18 maximizes the toluene to methanol ratio and minimizes the temperature rise due to the exothermic heat of reaction. Reaction zone 18 can include a plurality of reactors. Reaction zone 18 may include only one reactor or one reactor with interstage injection points to control reactor exotherm, or reaction zone 18 may include up to four reactors. Reaction zone 18 is operated at a temperature of from 200 ℃ to 400 ℃. The reaction zone 18 is operated at a pressure of from 15psig to 400 psig.

The reaction zone product stream 24 exits the reaction zone 18 and passes to a separator 26. The reaction zone product stream 24 comprises toluene, para-xylene, and water. Separator 26 separates stream 24 into stream 28 and stream 30. Stream 28 passes to stripper 32. Stream 30 passes to methanol stripper 34, which provides methanol recycle stream 36 to reaction zone 18. Methanol stripper product stream 38 exits methanol stripper 34 and enters wastewater treatment. Sending the methanol to methanol stripper 34 purifies the recycled product methanol, which facilitates lower methanol conversion.

The stripper 32 produces an overhead stream 40 comprising a discharge to fuel gas, an overhead stream 42 comprising toluene and benzene recycled back to the first feed stream 12, a side draw 44 comprising para-xylene, toluene, ortho-xylene, meta-xylene, and some C9-C10, and a bottoms stream 46 comprising C9+ (which comprises diphenylmethane). The bottom stream 46 is passed to a transalkylation unit 48, which also receives a stream 50 comprising benzene and C9+ and potentially toluene. The transalkylation unit comprises a transalkylation catalyst comprising at least one zeolite of the MWW type or the mordenite type. The transalkylation unit product stream 52, now containing para-xylene, exits the bottom of the transalkylation unit 48 and may be passed to a benzene column, a toluene column, a xylene column, a para-xylene separation zone, or an isomerization zone.

TABLE 1

The data in Table 1 are at 3hr^-1At a weight hourly space velocity of 335 ℃, at a temperature of 335 ℃, and at a pressure of 400 psig. For clarity, ITN is defined as indan-tetralin-naphthalene and DMP is defined as diphenylmethane. The results in table 1 show how the a7-a9+ feed, initially containing 6.23% diphenylmethane, after passing over the transalkylation catalyst under transalkylation conditions contained only 0.14% diphenylmethane, i.e. cracking of diphenylmethane was close to 98%. This enables the a9+ fraction of the toluene methylation product to be recycled to the transalkylation unit, thereby increasing xylene yield as a whole and improving the economics of the aromatics complex. There is evidence that in small amounts (<0.1%) of the polynuclear aromatics present in the A9+ fraction of the toluene methylation product (hereinafter "PNA") were not converted, but adsorbed or somehow accumulated on the transalkylation catalyst. This indicates that for stable operation of the transalkylation unit, those PNAs should be removed from the feed by conventional distillation or adsorption.

While the invention has been described in connection with what is presently considered to be the preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

Detailed description of the preferred embodiments

While the following is described in conjunction with specific embodiments, it is to be understood that this description is intended to illustrate and not limit the scope of the foregoing description and the appended claims.

A first embodiment of the invention is a process for toluene methylation comprising passing a toluene feed stream and a plurality of methanol feed streams to a reaction zone to produce a reaction zone product stream; and separating the reaction zone product stream and passing the reaction zone product stream to a stripper to produce a vent gas stream, an overhead stream comprising toluene and xylenes, a sidedraw comprising xylenes, and a bottoms stream comprising C9+, specifically a diphenylmethane component; and passing the C9+ stream to a transalkylation zone comprising a transalkylation catalyst comprising at least one zeolite of the MWW or mordenite type. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the toluene stream and the at least one methanol stream are mixed prior to entering the reaction zone. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein an additional methanol stream is passed to the reaction zone. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein two additional methanol streams are passed to the reaction zone. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein three additional methanol streams are passed to the reaction zone. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the reaction zone comprises at least one reactor. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the reaction zone comprises no more than four reactors. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the reaction zone is operated at a temperature of from 200 ℃ to 400 ℃. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the reaction zone is operated at a temperature of from 250 ℃ to 350 ℃. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the transalkylation zone is operated at a temperature of from 300 ℃ to 500 ℃. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the transalkylation zone is operated at a pressure of 1379kPa (200psig) to 4137kPa (600 psig). An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the reaction zone is operated at a pressure of from 103kPa (15psig) to 2758kPa (400 psig). An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the reaction zone is operated at a pressure of 345kPa (50psig) to 1379kPa (200 psig). An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the overhead stream comprising toluene is recycled back to the toluene feed stream. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising separating a methanol stream from the reaction zone product stream and recycling the methanol stream back to the methanol feed stream.

A second embodiment of the invention is an apparatus for the methylation of toluene comprising a plurality of lines comprising toluene in direct communication with a reaction zone, wherein the reaction zone is further coupled to a line comprising a reaction zone product stream; the reaction zone product stream is in direct communication with a stripper to produce a line comprising a vent gas stream, an overhead line comprising toluene and xylenes, a side draw line comprising xylenes, and a bottoms line comprising C9+, specifically a diphenylmethane component; and said bottom line comprising a C9+ stream is in direct communication with a transalkylation zone comprising a transalkylation catalyst comprising at least one zeolite of the MWW or mordenite type. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the reaction zone comprises at least one reactor. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the reaction zone comprises no more than four reactors. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the reaction zone is operated at a temperature of from 200 ℃ to 400 ℃. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the reaction zone is operated at a pressure of from 103kPa (15psig) to 2758kPa (400 psig).

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent and can readily ascertain the essential characteristics of the present invention without departing from the spirit and scope thereof, to make various changes and modifications of the invention and to adapt it to various usages and conditions. Accordingly, the foregoing preferred specific embodiments are to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever, and is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

In the foregoing, all temperatures are shown in degrees celsius and all parts and percentages are by weight unless otherwise indicated.