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 奈伊尔·A·拉希德 格雷戈里·B·库兹马尼奇 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,本公开涉及通过使用经处理的甲苯代替粗制甲苯在芳烃联合装置中使甲苯和/或苯选择性甲基化来产生对二甲苯的方法和设备。(The present disclosure relates to a method and apparatus for methylating aromatics in an aromatics complex for producing xylene isomer products. More particularly, the present disclosure relates to a process and apparatus for producing para-xylene by selectively methylating toluene and/or benzene in an aromatics complex using treated toluene instead of crude toluene.)

1. A process for the methylation of toluene comprising:

passing the treated toluene stream and the methanol feed stream to a toluene methylation reaction zone to produce a toluene methylation reaction zone product stream;

passing a stream comprising crude a7 and unextracted toluene and an overhead stream from the heavy aromatics column to a transalkylation reaction zone to produce a transalkylation product stream; and

passing the toluene methylation reaction zone product stream and the transalkylation product stream to a benzene column.

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

3. The process of claim 1 wherein an additional methanol stream is passed to the toluene methylation reaction zone.

4. The process of claim 1, wherein the reaction zone comprises at least one reactor.

5. The process of claim 1, wherein the reaction zone comprises no more than four reactors.

6. The process of claim 1, wherein the treated toluene may comprise less than 5% non-aromatics.

7. The process of claim 1, wherein the treated toluene may comprise less than 1% non-aromatics.

8. The process of claim 1, wherein the treated toluene may comprise less than 0.25% non-aromatics.

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

a line in direct communication with the toluene methylation zone comprising treated toluene from the toluene column, a line in direct communication with the toluene methylation zone comprising methanol, wherein the reaction zone is further coupled to a line comprising the reaction zone product stream.

10. The apparatus of claim 9, wherein the treated toluene stream and at least one methanol stream are mixed prior to entering the reaction zone.

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+ components are 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 under 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 recycle of catalysts that are relatively difficult to prepare reproducibly. MFI zeolites are the catalysts mainly used in this process.

Toluene methylation can greatly improve the yield of paraxylene in an aromatics complex. However, toluene methylation catalysts are not effective in treating unextracted toluene. If toluene methylation utilizes unextracted toluene, non-aromatics may accumulate in the toluene methylation loop to near 25% of the feed. This represents a capacity loss of the prior art toluene methylation unit. To avoid this, toluene is traditionally extracted using an aromatics extraction unit, which is a relatively expensive unit to operate.

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 method and apparatus for toluene methylation, wherein toluene methylation can effectively utilize toluene that has passed a transalkylation catalyst once, instead of extracting toluene using an aromatic extraction unit. This treated toluene can then be fed to a toluene methylation unit without accumulating non-aromatics over time. If unextracted toluene is used, non-aromatic build-up occurs, resulting in a 25% reduction in toluene methylation throughput.

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 toluene methylation as demonstrated in the prior art.

Figure 2 illustrates a process and apparatus for toluene methylation in accordance with the claimed invention.

Definition of

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

As used herein, the terms "stream," "feed," "product," "part," 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-aromatics 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 stripper 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 shown in the figures, the process flow lines in the figures may be 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 the accompanying figures. The drawings are simplified illustrations of preferred embodiments of the invention and are 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. Fig. 1 shows the current state of the art. As shown in fig. 1, the process and apparatus 10 includes a first feed stream 12 comprising unextracted toluene and a second feed stream 14 comprising methanol. Unextracted toluene may contain up to 40% by weight of non-aromatic hydrocarbons azeotroped with toluene. The first feed stream 12 and the second feed stream 14 are combined and passed to a toluene methylation reaction zone 16. An additional methanol stream may be fed to the toluene methylation reaction zone 16. It is also contemplated that an additional methanol stream may also be added to the toluene methylation reaction zone 16. The toluene methylation reaction zone 16 can comprise a plurality of reactors. The toluene methylation reaction zone 16 can comprise only one reactor or one reactor with interstage injection points to control reactor exotherm, or the toluene methylation reaction zone 16 can comprise up to four reactors. The toluene methylation reaction zone 16 is operated under standard toluene methylation operating conditions.

The toluene methylation reaction zone product stream 24 exits the toluene methylation reaction zone 16 and contacts stream 18 from the transalkylation zone 20 and is passed to the benzene column 22. Stream 28 from the aromatics extraction unit is also sent to benzene column 22. Benzene stream 26 exits the top of benzene column 22. The benzene column bottoms stream 32 exits the benzene column 22 and enters the toluene column 34. The overhead stream 36 from the toluene column enters the transalkylation zone 20 along with stream 38, the overhead stream from the heavy aromatics column 40. The bottoms stream 42 from the toluene column 34 is sent to the xylene column along with stream 46, the bottoms stream from the reformate stripper column 48. The overhead stream 50 is sent to para-xylene purification and the bottoms stream 52 is sent to the heavy aromatics column 40.

Turning now to fig. 2, many of the units are the same, but here instead of sending the overhead stream from the toluene column 34 to the transalkylation unit 20, the overhead stream from the toluene column is sent to the toluene methylation unit 16 (as shown in line 12), and the fraction from the reformate splitter 48 is sent to the transalkylation unit 20. Instead of extracting toluene using the aromatic extraction unit 30, toluene methylation can effectively utilize toluene that has passed through the transalkylation catalyst once. This treated toluene can then be fed to the toluene methylation unit 16 without accumulating non-aromatics over time. If unextracted toluene is used, non-aromatic build-up occurs, resulting in a 25% reduction in toluene methylation throughput. The treated toluene may comprise 10% or less non-aromatics.

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 present invention is a process for methylating toluene comprising: passing the treated toluene stream and the methanol feed stream to a toluene methylation reaction zone to produce a toluene methylation reaction zone product stream; passing a stream comprising crude a7 and unextracted toluene and an overhead stream from the heavy aromatics column to a transalkylation reaction zone to produce a transalkylation product stream; and passing the toluene methylation reaction zone product stream and the transalkylation product stream to a benzene column. 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 treated toluene stream and 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 toluene methylation 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 treated toluene may comprise less than 5% non-aromatics. 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 treated toluene may comprise less than 1% non-aromatics. 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 treated toluene may comprise less than 0.25% non-aromatics.

A second embodiment of the present invention is an apparatus for methylating toluene comprising: a line in direct communication with the toluene methylation zone comprising treated toluene from the toluene column, a line in direct communication with the toluene methylation zone comprising methanol, wherein the reaction zone is further coupled to a line comprising the reaction zone product stream. 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 treated toluene stream and 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 second embodiment in this paragraph wherein an additional methanol stream is passed to the toluene methylation reaction zone. 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 treated toluene may comprise less than 5% non-aromatics. 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 treated toluene may comprise less than 1% non-aromatics. 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 treated toluene may comprise less than 0.25% non-aromatics.

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.