Hydrogenation of acetylene in hydrocarbon streams.

Abstract

A system for hydrogenating C3 and C4 acetylenes contained in a hydrocarbon stream produced in a steam cracker unit in which a debutanizer is located upstream of a depropanizer to make the processing of the hydrocarbon stream more economical, the system requiring only one stripper tower downstream of the hydrogenation to remove residual hydrogen.

Description

Detailed Description of the Invention

[0001] [Technical field] The present invention relates to a system for the hydrogenation of C4 acetylenes, such as vinyl and ethyl acetylenes, and C3 acetylenes, such as methyl acetylene and propadiene, contained in hydrocarbon streams treated in steam cracking processes, and more particularly to such steam cracking processes required to meet product specifications for the respective acetylenes. [background] In a conventional steam cracking process for producing light hydrocarbons, a depropanizer that separates a C3 acetylene-rich hydrocarbon stream from a C4 acetylene-rich hydrocarbon stream is located upstream of the debutanizer. The C4 acetylene-rich hydrocarbon stream leaving the depropanizer is divided into C5-C 10 The C4 acetylene-rich hydrocarbon overhead from the debutanizer is then sent to a hydrogenation reactor where it is hydrogenated over a selective catalyst. The C3 acetylene-rich hydrocarbon overhead from the depropanizer is sent independently to a separate hydrogenation reactor for selective hydrogenation of the C3 acetylene-rich hydrocarbon stream.

[0002] In this typical design, two separate stabilization / stripper columns are required, one to strip residual unreacted H2 (hydrogen) from the C3 hydrogenation reactor product stream and one to strip residual unreacted H2 (hydrogen) from the C4 hydrogenation reactor product stream.

[0003] One prior process can be found in U.S. Patent No. 5,090,977 to Exxon Chemical Patents Inc., which discloses a process sequence for treating heavy feed cracked gas that preferentially produces propylene to the exclusion of propane, butanes and butenes. The process eliminates the need for a depropanizer, with attendant savings in capital and operating costs. Instead of a traditional C3 splitter, the process features a depropanizer, or distillation column, designed to separate propylene from propane, butanes and butenes. A hydrogenation unit to remove contaminants can be located upstream of the depropanizer, or the depropanizer can be split into two sections with the hydrogenation unit located between the two sections.

[0004] The integration of a gas oil and light olefin catalytic cracking zone with a pyrolytic cracking zone to maximize the efficient production of petrochemicals is disclosed in U.S. Patent No. 7,128,827 to Kellogg, Brown & Root LLC. Parallel integration of units allows for the production of a total product stream containing maximum ethylene and / or propylene by routing various feed streams and recycle streams to the appropriate cracking zones, e.g., ethane / propane to the steam pyrolysis zone and C4C6 olefins to the light olefins cracking zone. This integration increases the value of the mass balance provided by the integrated units.

[0005] Additionally, U.S. Patent No. 7,294,749 to Kellogg, Brown & Root LLC describes a low pressure olefin recovery process and plant. A feed gas 300 is compressed 302, 304 at primary distillation pressure and distilled 310. An overhead stream 312 is compressed at 30 kg / cm to partially condense the top of the column. 2(430 psia) is cooled 318. The primary distillation column 310 is refluxed with at least a portion of the condensate 320. The overhead vapor is further cooled 318 and partially condensed, and the condensate 322 is fed to the demethanizer column 324. The remaining vapor 326 is cooled in the cold section 328, and the resulting liquid is phase separated 330 and expanded 331, 334 to cool the cold section. Expanded vapor 332 from the cold section is recycled to the process gas compressor. The bottoms streams 338, 342 from the primary distillation zone and the demethanizer column consist essentially of ethylene 356, ethane 358, propylene 364, propane 366, C4's 346, and C 5+ The mixture is fractionated into 348 individual streams.

[0006] However, the construction of a steam cracking unit with this two stabilization / stripper column design for acetylene hydrogenation systems requires significant capital and maintenance costs, which may create an economic barrier to the construction of such systems for oil and gas refining.

[0007] Therefore, there is a need to reduce the capital costs associated with the production of light hydrocarbons, and specifically, the hydrogenation of acetylene in hydrocarbon streams. [overview] In one non-limiting embodiment, a system for hydrogenating acetylene in a hydrocarbon stream is provided that includes a depropanizer, a debutanizer, a C4 acetylene hydrogenation reactor, a C3 acetylene hydrogenation reactor, and a stripper column, the depropanizer being downstream of the debutanizer. In a different non-limiting aspect, in addition to the stripper column, there is no stripping column for releasing residual unreacted H2 from the crude butadiene stream.

[0008] In another non-limiting embodiment, C3-C 10A process for selective hydrogenation of acetylene is provided, comprising: directing a hydrocarbon stream to a debutanizer; selectively hydrogenating C4 acetylene in a condensed C3-C4 overhead stream in a C4 acetylene hydrogenation reactor to produce a reactor outlet stream; directing the reactor outlet stream to a depropanizer downstream of the debutanizer; taking an overhead stream from the depropanizer containing a C3 mixture including methylacetylene and propadiene; taking a bottom stream from the depropanizer containing a crude C4 mixture; directing the C3 mixture to a methylacetylene and propadiene (MAPD) ​​reactor to selectively hydrogenate the methylacetylene and propadiene to produce a crude propylene stream; and directing the crude propylene stream to a stripper column. In a different non-limiting embodiment, the stripper column is the only stripper column, and there is no stripper column downstream of the C4 acetylene hydrogenation reactor.

[0009] In another non-limiting embodiment, an ethylene plant is provided that includes a system for hydrogenating acetylene in a hydrocarbon stream, the system including a depropanizer, a debutanizer, a C4 acetylene hydrogenation reactor, a C3 acetylene hydrogenation reactor, and a stripper column, the depropanizer being downstream of the debutanizer. In another non-limiting aspect of the ethylene plant, in addition to the stripper column, there is no stripping column for releasing residual unreacted H2 from the crude butadiene stream.

[0010] Further provided is an upgraded hydroprocessed product produced by the selective hydrogenation process herein, comprising, independently, about 0.5 to about 2 wt.% hydrogenated C4 acetylenes, or, independently, about 0.9 to about 1.6 wt.% hydrogenated C4 acetylenes. Additionally, the upgraded hydroprocessed product has, independently, about 20 wt.% to about 60 wt.% hydrogenated 1,3-butadiene, or, independently, about 40 to about 50 wt.% hydrogenated 1,3-butadiene. The upgraded hydroprocessed product may also have, independently, about 20 wt.% to about 60 wt.% hydrogenated C3 hydrocarbons, or, independently, about 40 wt.% to about 50 wt.% hydrogenated C3 hydrocarbons. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [Detailed Description] It has been found that providing a system for hydrogenating acetylene in a steam cracker in which the debutanizer is located upstream of the depropanizer can eliminate the need for two separate stabilization / stripping columns to release the residual unreacted H2 (hydrogen) present in the crude butadiene and crude propylene product streams. In other words, the present system and process swaps the order of the depropanizer and the debutanizer, with the debutanizer coming first and the depropanizer being placed downstream of the debutanizer. This is done because both C4 acetylenes (vinyl acetylene, ethyl acetylene) and C3 acetylenes (methyl acetylene, propadiene) need to be hydrogenated to meet the specifications of the crude butadiene and crude propylene products with respect to the respective acetylenes. As mentioned above, this requires two separate stabilization columns, one for the crude butadiene and one for the crude propylene, to release the residual unreacted hydrogen in the hydrogenation reactor in the conventional order. These two separate columns would add to the capital cost of the project, therefore this system and process would eliminate one tower, which is a significant cost savings.

[0012] Gas crackers typically include an ethane feed (or a mixture of ethane and propane) to a pyrolysis system. The cracked gas passes to a quench and condensate recovery system where the cracked gas is cooled. The cooled cracked gas is fed to a compression, acid gas removal and drying system. The compressed cracked gas is fed to a de-ethanizer and acetylene reactor system where the C2 and light components are separated from the C3 and heavy components. The C3 and heavy components produce three valuable products: a propylene-rich mixed C3 product, a crude butadiene product, and a pyrolysis gasoline product.

[0013] Producing a crude butadiene product would typically involve sending the C3 and heavier components to a depropanizer and then sending the bottoms to a debutanizer to produce a mixed C4 product at the top of the debutanizer. The debutanizer top can then be processed in a C4 acetylene reactor system to upgrade the crude butadiene product such that reduction or elimination of acetylene may improve the market value of the product stream or may result in savings in the butadiene unit that outweigh the cost of the C4 acetylene reactor system. However, the C4 acetylene reactor system results in light ends contaminants that would need to be removed by an additional stripper system.

[0014] Hydrogenation of C3 and C4 acetylenes contained in the hydrocarbon stream being processed in a steam cracker unit stream may be accomplished, in one non-limiting embodiment, by the system shown in FIG. 1 and by the process described herein.

[0015] Referring to FIG. 1 and the overall system 10 for hydrogenating acetylene in a hydrocarbon stream, the debutanizer 12 is a C3-C 10The feed stream comprises a mixture of hydrocarbons 14 ranging from 0.1 to 1.0 C. In one embodiment, the C4 and C3 hydrocarbons in the stream may be a mixture of saturates, olefins, diolefins, and acetylenes. Example feed conditions for the C4 acetylene and hydrogen (H2) feed are provided in Table Y below along with the operating conditions.

[0016] [Table 1]

[0017] The debutanizer overhead stream 16 is a mixture of C3 and C4 hydrocarbons, while the debutanizer bottoms stream 18 is a mixture of C5-C 10 The debutanizer 12 is a pyrolysis gasoline product stream containing hydrocarbons. It will be appreciated that the pressure and temperature of the debutanizer 12 should be set in a manner that the hydrocarbons in the debutanizer overhead stream 16 can be condensed using an available inexpensive refrigerant. In one non-limiting embodiment, the hydrocarbons are condensed at a pressure of about 50 psig (0.3 MPa). It will be appreciated that since the debutanizer overhead stream 16 contains a mixture of C3 and C4 hydrocarbons when condensed at this pressure, a refrigerant 19 may be used in the debutanizer condenser 21 and the temperature of the debutanizer overhead stream 16 may range from about 40 to 50°F (about 4 to 10°C) as opposed to the conventional temperature of 100°F (about 38°C). The refrigerant 19 may be a propylene stream (not shown) from a steam cracker.

[0018] With continued reference to Figure 1, the debutanizer overhead stream 16, which is a mixture of C3 and C4 hydrocarbons in the form of saturates, olefins, and / or diolefins, is directed through the debutanizer reflux drum 20 before being pumped to the C4 acetylene selective hydrogenation reactor 22 where the C4 acetylenes are selectively hydrogenated. In one non-limiting embodiment, the proportion of C3 hydrocarbons in the debutanizer overhead stream 16 is at least 20 wt% C3 hydrocarbons, the C4 hydrocarbons including C4 acetylene and 1,3-butadiene. The molecular hydrogen-containing stream (not shown) introduced prior to the C4 acetylene selective hydrogenation reactor 22 may have at least 35 wt% molecular hydrogen, alternatively at least 99 wt% molecular hydrogen, or in another non-limiting variation, may be substantially pure molecular hydrogen.

[0019] The inlet temperatures of the C4 acetylene selective hydrogenation reactor 22 are independently within the range of about 50° F. (10° C.) to about 140° F. (about 60° C.) from start to finish of the run, or independently within the range of about 78° F. (25° C.) to about 95° F. (35° C.). As used herein with respect to parameter ranges, the phrase "independently" means that any range endpoint may be used in conjunction with any other range endpoint to provide acceptable alternative ranges.

[0020] The C3 and C4 hydrocarbons should be about 99 percent in the liquid phase. C3 and C4 vaporization is not used to control the reactor temperature. The total pressure of the reactor 22 is at least the pressure required to maintain the C3 and C4 hydrocarbons in the liquid phase during hydrogenation. In one non-limiting embodiment, the pressures independently range from about 300 psia (about 2.1 MPa) to about 600 psia (about 4.9 MPa), or independently range from about 350 psia (about 2.5 MPa) to about 400 psia (about 2.8 MPa). Higher pressures are more favorable for the solubility of hydrogen in the feed and should be high enough to maintain the hydrocarbons in the liquid phase throughout the C4 acetylene selective hydrogenation reactor 22.

[0021] In one embodiment, the outlet components of the C4 acetylene converter are as follows:

[0022] [Table 2]

[0023] Selective hydrogenation is carried out by controlled injection of H2 to selectively hydrogenate C4 acetylene over a fixed bed of catalyst. Unreacted H2 from the reactor effluent is sent to the cracked gas compressor suction after cooling and separation in a separation drum.

[0024] The upgraded C3 and C4 outlet stream 24 from the C4 acetylene selective hydrogenation reactor 22 is sent to a depropanizer 26 which separates a bottom crude butadiene product stream 28 from a final depropanizer overhead stream 30. The depropanizer bottoms stream is a bottom crude butadiene product stream 28 while the final depropanizer overhead stream 30 is a mixture of C3 hydrocarbons and is passed through a depropanizer condenser 42. The final depropanizer overhead stream 30 is then pumped from the depropanizer reflux drum 44 to a MAPD (methyl acetylene and propadiene) reactor 32 for selective hydrogenation of C3 acetylenes such as, but not limited to, methyl acetylene and propadiene. Following selective hydrogenation of the C3 acetylene in the MAPD reactor 32, the upgraded mixed C3 hydrocarbon stream 34 exiting the MAPD reactor 32 proceeds to a C3 stripper column 36 where unreacted H2 and lights 38 (typically including methane and traces of C2) are released, and a propylene product 40 is removed in one form as a side cut from the C3 stripper column 36. It is understood that in this non-limiting embodiment, the crude butadiene product stream 28 exiting the bottom of the depropanizer 26 does not need to be sent to a separate stripping column to release any remaining unreacted H2, since the depropanizer 26 functions to separate the light hydrocarbons from the C4 hydrocarbons in the stream.

[0025] In one non-limiting embodiment, the hydrocarbons in the stream are C3-C 10 The feed may comprise a mixture of hydrocarbons 14 in the range of saturates, olefins and acetylenes. Hydrogenation catalysts useful for selectively hydrogenating the C4 acetylenes in the stream may include, but are not necessarily limited to, palladium-based catalysts, such as, for example, palladium on alumina, copper-based catalysts, rhodium-based catalysts, and other such metal-based catalysts. Hydrogenation catalysts useful for selectively hydrogenating the C3 acetylenes in the stream may include, but are not necessarily limited to, palladium-based catalysts, such as, for example, palladium on alumina, copper-based catalysts, rhodium-based catalysts, and other such metal-based catalysts.

[0026] It is understood that the conversion of C4 acetylenes can be targeted to meet the specifications for C4 acetylenes in the crude butadiene product stream. This is accomplished by controlled injection of H2 to selectively hydrogenate the C4 acetylenes. The reactor size, recirculation rate, pressure, and reactor inlet temperature can be designed to achieve or exceed the desired conversion of C4 acetylenes and to reduce or even minimize the conversion of 1,3-butadiene and propylene present in the crude butadiene stream. In one exemplary embodiment, the desired run times can be independently in the ranges of about 2 months to about 12 months, or independently in the ranges of about 6 to about 9 months, and the ranges of space velocities (LHSV) can be independently in the ranges of about 4 to about 20, or independently in the ranges of about 8 to about 16.

[0027] It will also be understood that any hydrogenation of C3 acetylenes, such as methyl acetylene and propadiene, although not intended, may be beneficial in this process. The processes and systems described herein include hydrogenating C4 acetylenes in a mixed hydrocarbon stream while substantially maintaining selectivity and conversion for hydrogenation of C4 acetylenes; Hydrogenating C4 acetylenes in a mixed hydrocarbon stream to provide improved selectivity and / or conversion; Hydrogenating C4 acetylene in mixed hydrocarbon streams with reduced hydrogenation of valuable hydrocarbons such as 1,3-butadiene and propylene; A variety of goals may be achieved, including, but not limited to:

[0028] The processes and systems described herein are considered effective and successful if only one of these objectives is achieved, such as substantially achieving selectivity and conversion of C4 acetylenes in a C3 / C4 stream mixed with a C4 stream, and may be considered even more effective if one or more of the other objectives are also achieved.

[0029] In the foregoing specification, the invention has been described with reference to certain embodiments thereof. However, this specification should be considered as illustrative rather than restrictive. For example, hydrogenation reaction conditions and equipment, debutanizer and depropanizer conditions, catalysts, and compositions and conditions of the hydrocarbon and acetylene streams, hydrogen streams that are not specifically identified or tested in the specific examples but are within the parameters claimed or disclosed are expected to be within the scope of the invention.

[0030] The invention may be practiced in the absence of elements not disclosed. In addition, the invention may suitably comprise, consist of, or consist essentially of the disclosed elements. For example, the system may comprise, consist of, or consist essentially of a depropanizer, a debutanizer, a C4 acetylene rich hydrogenation reactor, a methyl acetylene and propadiene (MAPD) ​​reactor, and a stripper column, with the depropanizer downstream of the debutanizer.

[0031] In another non-limiting embodiment, C3-C 10There may be provided a process for selective hydrogenation of acetylene comprising, consisting essentially of, or consisting of: directing a hydrocarbon stream to a debutanizer; condensing a debutanizer C3-C4 overhead stream; selectively hydrogenating C4 acetylene in the condensed C3-C4 overhead stream in a C4 acetylene hydrogenation reactor to provide a reactor outlet stream; directing the reactor outlet stream to a depropanizer downstream from the debutanizer; taking an overhead stream from the depropanizer containing a C3 mixture comprising methylacetylene and propadiene; taking a bottoms stream from the depropanizer containing a crude C4 mixture; directing the C3 mixture to a methylacetylene and propadiene (MAPD) ​​reactor; selectively hydrogenating the methylacetylene and propadiene to provide a crude propylene stream; and directing the crude propylene stream to a stripper column.

[0032] Additionally, there may be provided an upgraded hydroprocessed product produced by the selective hydrogenation process herein comprising, independently, about 0.5 to about 2 wt.% hydrogenated C4 acetylenes, or, alternatively, about 0.9 to about 1.6 wt.% hydrogenated C4 acetylenes. Additionally, the upgraded hydroprocessed product has, independently, about 20 to about 60 wt.% hydrogenated 1,3-butadiene, or, alternatively, about 40 to about 50 wt.% hydrogenated 1,3-butadiene.

[0033] Additionally, in another non-limiting embodiment, there may be provided an ethylene plant comprising, consisting essentially of, or consisting of a system for hydrogenating acetylene in a hydrocarbon stream, the system comprising, consisting essentially of, or consisting of a depropanizer, a debutanizer, a C4 acetylene hydrogenation reactor, a methylacetylene and propadiene (MAPD) ​​reactor, and a stripper column, wherein the depropanizer is located downstream of the debutanizer.

[0034] The words "comprising" and "comprises" as used throughout the claims shall be interpreted to mean "including, but not limited to" and "including, but not limited to," respectively.

[0035] As used herein, the term "substantially" is intended to mean "most but not all of what is specified." As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0036] As used herein, the word "about" in connection with a given parameter is inclusive of the explicit value and has the meaning dictated by the context (e.g., includes the degree of error associated with measurement of the given parameter).

[0037] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

Claims

1. 1. A system for hydrogenating acetylene in a hydrocarbon stream, comprising: A propanizer tower; A butanizer; A C4 acetylene hydrogenation reactor having a crude butadiene product stream exiting the reactor. ４ an acetylene hydrogenation reactor; a methylacetylene and propadiene (MAPD) ​​reactor; a stripper column; Equipped with A system in which the depropanizer is downstream of the debutanizer and there is no stripping column in addition to the stripper column to release residual unreacted H2 from the crude butadiene product stream.

2. 2. The system of claim 1, the stripper column is positioned downstream of the MAPD reactor to receive a crude propylene stream therefrom; The MAPD reactor is located downstream of the depropanizer, The MAPD reactor is ４ Located downstream of the acetylene hydrogenation reactor, The system wherein the MAPD reactor is located downstream of the debutanizer.

3. 2. The system of claim 1, The system further comprises a condenser between said debutanizer and said C 4 acetylene hydrogenation reactor for condensing a debutanizer C 3 -C 4 overhead stream from said debutanizer.

4. 4. The system of claim 3, A system wherein a refrigerant is used in the condenser.

5. 1. A process for the selective hydrogenation of acetylene, comprising the steps of: C ３ -C １０ directing the hydrocarbon stream to a debutanizer; Debutanizer C ３ -C ４ condensing the overhead stream; C ４ In the acetylene hydrogenation reactor, the condensed debutanizer C ３ -C ４ C in the overhead stream ４ Selectively hydrogenating acetylene to provide a reactor effluent stream; directing the reactor effluent stream to a depropanizer downstream of the debutanizer; C containing methylacetylene and propadiene ３ removing an overhead stream from the depropanizer containing the mixture; coarse C ４ removing a bottoms stream from the depropanizer containing the mixture; Said C ３ directing the mixture to the methylacetylene and propadiene (MAPD) ​​reactor to selectively hydrogenate the methylacetylene and the propadiene to provide a crude propylene stream; directing said crude propylene stream to a stripper column; Including, the stripper column is a single stripper column and there is no stripper column downstream of the crude C4 mixture; process.

6. 6. The process of claim 5, The debutanizer C ３ -C ４ A process in which condensing the overhead stream is performed against a refrigerant.

7. 6. The process of claim 5, Said C ４ The process wherein the acetylene hydrogenation reactor is operated at a temperature of 10° C. to 60° C. and a pressure of 2.1 MPa to 4.9 MPa.

8. 6. An upgraded hydroprocessed product produced by the process for selective hydrogenation of claim 5, comprising: About 0.5 to about 2 wt. % hydrogenated C ４ Acetylene and about 20 to about 60 weight percent hydrogenated 1,3-butadiene; an upgraded hydroprocessed product comprising:

9. 9. The upgraded hydroprocessed product of claim 8, further comprising: About 20 to about 60 wt. % hydrogenated C ３ Upgraded hydroprocessed products, including hydrocarbons.

10. 1. An ethylene plant comprising:

1. A system for hydrogenating acetylene in a hydrocarbon stream, comprising: A propanizer tower; A butanizer; A C4 acetylene hydrogenation reactor having a crude butadiene product stream exiting the reactor. ４ an acetylene hydrogenation reactor; a methylacetylene and propadiene (MAPD) ​​reactor; a stripper column; A system comprising: An ethylene plant, wherein the depropanizer is downstream of the debutanizer and there is no stripping column to release residual unreacted H2 from the crude butadiene product stream in addition to the stripper column.

11. 11. The ethylene plant of claim 10, the stripper column is positioned downstream of the MAPD reactor to receive a crude propylene stream therefrom; The MAPD reactor is located downstream of the depropanizer, The MAPD reactor is ４ Located downstream of the acetylene hydrogenation reactor, The MAPD reactor is located downstream of the debutanizer.

12. The ethylene plant according to claim 10, further comprising: Debutanizer C from the debutanizer ３ -C ４ the debutanizer and the C column for condensing the overhead stream. ４ An ethylene plant having a condenser between the acetylene hydrogenation reactor and the ethylene plant.

13. 13. The ethylene plant of claim 12, An ethylene plant wherein a refrigerant is used in said condenser.

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