Hydrogenation of acetylene in a hydrocarbon stream

Abstract

A system for hydrogenating C3 and C4 acetylenes contained in a hydrocarbon stream produced in a steam cracker, wherein a debutanizer is placed upstream of a depropanizer for more economical processing of the hydrocarbon stream to produce lighter hydrocarbons, wherein the system requires only one stripping column downstream of the hydrogenation to remove residual hydrogen.

Description

Technical Field

[0001] This invention relates to a system for use in a hydrogenation steam cracking process to process C4 acetylenes, such as vinyl acetylene and ethyl acetylene, and C3 acetylenes, such as methyl acetylene and propadiene, contained in the hydrocarbon stream being processed, and more particularly to such a steam cracking method to meet the product specifications required for the respective acetylenes. Background Technology

[0002] In conventional steam cracking processes used to produce lighter hydrocarbons, a depropanizer is located upstream of a debutanizer, which separates the C3-rich acetylene hydrocarbon stream from the C4-rich acetylene hydrocarbon stream. The C4-rich acetylene hydrocarbon stream exiting the depropanizer is fed to the debutanizer, where the C4-rich acetylene hydrocarbons are separated from the C5-rich hydrocarbon stream. 10 The pyrolysis gas stream is separated. Then, the C4 acetylene-rich hydrocarbon overhead from the butanizer is fed to a hydrogenation reactor, where it is hydrogenated by a selective catalyst. The C3 acetylene-rich hydrocarbon overhead from the propanizer is separately fed to a separate hydrogenation reactor for selective hydrogenation of the C3 acetylene-rich hydrocarbon stream.

[0003] In this typical design, two separate stabilization / stripping towers are required—one for removing residual unreacted H2 (hydrogen) from the product stream of the C3 hydrogenation reactor, and one for removing residual unreacted H2 (hydrogen) from the product stream of the C4 hydrogenation reactor.

[0004] U.S. Patent No. 5,090,977 to Exxon Chemical Patents Inc. discloses a process sequence for processing cracked gas from heavy feedstocks, which preferentially produces propylene but not propane, butane, or butene. This method eliminates the need for a depropane tower, resulting in savings in capital and operating costs. Instead of a conventional C3 separator, the method features a depropylene tower, a distillation column designed to separate propylene from propane, butane, and butene. A hydrogenation unit for removing impurities can be placed upstream of the depropylene tower, or the depropylene tower can be divided into two sections with the hydrogenation unit located between them.

[0005] U.S. Patent No. 7,128,827 to Kellogg, Brown & Root LLC discloses the integration of gasoline and light olefin catalytic cracking zones with pyrolysis cracking zones to maximize the efficient production of petrochemical products. By feeding various feed streams and recycle streams to appropriate cracking zones (multiple cracking zones), such as feeding ethane / propane to a steam pyrolysis zone and C4 / C6 olefins to a light olefin cracking zone, the parallel integration of the units allows for the preparation of a monolithic product stream with the highest possible quantities of ethylene and / or propylene. This integration enhances the value of the material balance generated by the integrated unit.

[0006] Additionally, U.S. Patent No. 7,294,749 to Kellogg, Brown & Root LLC describes a low-pressure olefin recovery method and apparatus. Feed gas 300 is compressed 302, 304 and distilled 310 at initial distillation pressure. The overhead stream 312 is below 30 kg / cm³. 2 Cooling 318 at a pressure of 430 psia (430 psia) partially condenses the overhead product. At least a portion of the condensate 320 is refluxed from the primary distillation column 310. The overhead vapor is further cooled 318 and partially condensed, with the condensate 322 sent to the demethanizer 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 provide cooling for the cold section. The expanded vapor 332 from the cold section is recycled to the process gas compressor. The bottom streams 338, 342 from the primary distillation zone and the demethanizer are fractionated into components substantially consisting of ethylene 356, ethane 358, propylene 364, propane 366, C4 346, and C5 346. 5+ The corresponding logistics consist of 348.

[0007] However, the construction of a steam cracking unit with this two-stabilization / stripping tower design for the hydrogenation of acetylene involves significant capital and maintenance costs, which may pose an economic barrier to the construction of systems for oil and gas refining.

[0008] Therefore, it is necessary to reduce the capital costs associated with the preparation of lighter hydrocarbons, especially the capital costs associated with the hydrogenation of acetylene in hydrocarbon streams. Invention Overview

[0010] In one non-limiting embodiment, a system for acetylene in a hydrogenated hydrocarbon stream is provided, the system comprising a propane despan, a butane despan, a C4 acetylene hydrogenation reactor, a C3 acetylene hydrogenation reactor, and a stripping tower, wherein the propane despan is located downstream of the butane despan. In a different non-limiting aspect, there is no stripping tower other than the stripping tower for discharging residual unreacted H2 from the crude butadiene stream.

[0011] In another non-limiting embodiment, a method for selectively hydrogenating acetylene is provided, comprising: C3-C 10The hydrocarbon stream is directed to a butanizer, where the C4 acetylene in the condensed C3-C4 overhead stream is selectively hydrogenated in the C4 acetylene hydrogenation reactor to obtain the reactor outlet stream. This reactor outlet stream is directed to a propanizer downstream of the butanizer. An overhead stream containing a C3 mixture comprising methylacetylene and propadiene is drawn from the propanizer, and a bottom stream containing a crude C4 mixture is drawn from the propanizer. This C3 mixture is directed to a methylacetylene and propadiene (MAPD) ​​reactor, where the methylacetylene and propadiene are selectively hydrogenated to obtain a crude propylene stream. The crude propylene stream is then directed to a stripper. In a different, non-limiting aspect, the stripper is the only stripper and there is no stripper downstream of the C4 acetylene hydrogenation reactor.

[0012] In one different non-limiting embodiment, an ethylene plant is provided, comprising: a system for hydrogenating acetylene in a hydrocarbon stream, said system including a propane despan, a butane despan, a C4 acetylene hydrogenation reactor, a C3 acetylene hydrogenation reactor, and a stripping tower, wherein the propane despan is located downstream of the butane despan. In another different non-limiting aspect of the ethylene plant, there is no stripping tower other than said stripping tower for discharging residual unreacted H2 from the crude butadiene stream.

[0013] Additionally, an upgraded hydrogenated product prepared by the selective hydrogenation method described herein is provided, comprising: independently from about 0.5 to about 2 wt% hydrogenated C4 acetylene; optionally independently from about 0.9 to about 1.6 wt% hydrogenated C4 acetylene. Furthermore, the upgraded hydrogenated product has independently from about 20 wt% to about 60 wt% hydrogenated 1,3-butadiene; optionally, independently from about 40 wt% to about 50 wt% hydrogenated 1,3-butadiene. The upgraded hydrogenated product may also have independently from about 20 wt% to about 60 wt% hydrogenated C3 hydrocarbon; optionally, independently from about 40 wt% to about 50 wt% hydrogenated C3 hydrocarbon. Attached Figure Description

[0014] Figure 1 This is a system flow diagram for acetylene used in hydrogenated hydrocarbon streams. Invention Details

[0016] It has been found that a system for hydrogenating acetylene in a steam cracker, where the debutanizer is located upstream of the depropanizer, eliminates the need for two separate stabilization / stripping towers to remove residual unreacted H2 (hydrogen) from the crude butadiene and crude propylene product streams. In other words, this system and method alters the sequence of the depropanizer and debutanizer, with the debutanizer preceding the depropanizer and downstream of it. This is done because both C4 acetylene (vinylacetylene, ethylacetylene) and C3 acetylene (methylacetylene, propadiene) require hydrogenation to meet the corresponding crude butadiene and crude propylene product specifications. As previously mentioned, in a conventional sequence, this requires two separate stabilization towers—one for crude butadiene and one for crude propylene—to remove unreacted residual hydrogen from the hydrogenation reactor. These two separate towers increase the project's capital costs. Therefore, this system and method saves one tower, resulting in significant cost savings.

[0017] A gas cracker typically includes an ethane feed (or a mixture of ethane and propane) to the pyrolysis system. The cracked gas is then fed to a quenching and condensate recovery system, where it is cooled. The cooled cracked gas enters a compression, acid gas removal, and drying system. The compressed cracked gas then enters a de-ethaner and acetylene reactor system, where C2 and lighter components are separated from C3 and heavier components. The C3 and heavier components form three valuable products: a propylene-rich mixed C3 product, crude butadiene, and pyrolysis gasoline products.

[0018] The preparation of crude butadiene typically involves feeding C3 and heavier components into a propane stripper, followed by a butane stripper to produce a mixed C4 product at the top. The butane stripper topsoil can then be processed in a C4 acetylene reactor system to upgrade the crude butadiene product. This is because reducing or eliminating acetylene can generate a higher market value for the product stream, or the resulting savings in the butadiene unit may outweigh the cost of the C4 acetylene reactor system. However, the C4 acetylene reactor system introduces light-end contaminants that require removal via a separate stripping system.

[0019] In one non-limiting implementation, by Figure 1 The system shown and the method described herein can achieve the hydrogenation of C3 and C4 acetylene contained in the hydrocarbon stream being processed in a steam cracking unit.

[0020] Reference Figure 1 The entire system 10 for acetylene in hydrogenated hydrocarbon streams, and the butane desodane tower 12 receive C3-C4 components. 10Feed 14 of the range of hydrocarbon mixtures. In one embodiment, the C4 and C3 hydrocarbons in the stream may be a mixture of saturates, olefins, dienes, and alkynes. Example feed conditions and operating conditions for C4 acetylene and hydrogen (H2) feeds are provided in Table Y below.

[0021]

[0022] The overhead stream 16 from the butanizer is a mixture of C3 and C4 hydrocarbons, while the bottom stream 18 from the butanizer contains C5-C4 hydrocarbons. 10 The pyrolysis of hydrocarbons into gasoline product streams. It will be understood that the pressure and temperature of the butanizer 12 should be set such that the hydrocarbons in the butanizer overhead stream 16 can be condensed using an available and economical refrigerant. In a non-limiting embodiment, the hydrocarbons are condensed at a pressure of approximately 50 psig (0.3 MPa). If condensation is performed at this pressure, it will be understood that since the butanizer overhead stream 16 contains a mixture of C3 and C4 hydrocarbons, a refrigerant 19 can be used in the butanizer condenser 21, and the temperature of the butanizer overhead stream 16 can be in the range of approximately 40-50°F (approximately 4-10°C), compared to a conventional temperature of 100°F (approximately 38°C). The refrigerant 19 can be a propylene stream from a steam cracker (not shown).

[0023] Continue to refer to Figure 1 The overhead stream 16 of the butanizer, a mixture of C3 and C4 hydrocarbons in the form of saturated hydrocarbons, alkenes, and / or dienes, is pumped to the C4 acetylene selective hydrogenation reactor 22 after being guided through the butanizer reflux drum 20, where C4 acetylene is selectively hydrogenated. In one non-limiting embodiment, the proportion of C3 hydrocarbons in the overhead stream 16 is at least 20% by weight of C3 hydrocarbons and C4 hydrocarbons comprising C4 acetylene and 1,3-butadiene. The molecularly hydrogen-containing stream (not shown) introduced prior to the C4 acetylene selective hydrogenation reactor 22 may have at least 35% by weight of molecular hydrogen, optionally at least 99% by weight of molecular hydrogen, and in another non-limiting form, may be substantially pure molecular hydrogen.

[0024] From start to finish of operation, the temperature at the inlet of the C4 acetylene selective hydrogenation reactor 22 independently ranges from about 50°F (10°C) to about 140°F (about 60°C), and optionally independently ranges from about 78°F (25°C) to about 95°F (35°C). The term “independently” as used herein with respect to parameter ranges means that any range endpoint can be used with any other range endpoint to obtain an acceptable alternative range.

[0025] The C3 and C4 hydrocarbons should be approximately 99% liquid. The evaporation of C3 and C4 hydrocarbons is not used to control the reactor temperature. The total pressure of the C4 acetylene selective hydrogenation reactor 22 is at least the total pressure required to maintain the C3 and C4 hydrocarbons in the liquid phase during hydrogenation. In one non-limiting embodiment, the pressure range is independently from about 300 psi (absolute pressure) (about 2.1 MPa) to about 600 psi (absolute pressure) (about 4.9 MPa); alternatively, it is independently from about 350 psi (absolute pressure) (about 2.5 MPa) to about 400 psi (absolute pressure) (2.8 MPa). Higher pressures are better for the dissolution of hydrogen in the feed, and the pressure should be high enough to maintain liquid-phase hydrocarbons through the C4 acetylene selective hydrogenation reactor 22.

[0026] In one implementation, the C4 acetylene converter outlet components are:

[0027]

[0028] Selective hydrogenation of C4 acetylene is carried out in a fixed bed of catalyst via controlled H2 injection. Unreacted H2 from the reactor effluent is cooled and separated in a separator drum and then sent to the cracked gas compressor suction section.

[0029] The upgraded C3 and C4 effluent streams 24 from the C4 acetylene selective hydrogenation reactor 22 are fed to a depropanizer 26, which separates the bottom crude butadiene product stream 28 from the net depropanizer overhead stream 30. The bottom stream is the bottom crude butadiene product stream 28, while the net depropanizer overhead stream 30 is a mixture of C3 hydrocarbons, which passes through the depropanizer condenser 42. The net depropanizer overhead stream 30 is then pumped from the depropanizer reflux drum 44 to the MAPD (methylacetylene and propadiene) reactor 32 for the selective hydrogenation of C3 acetylene, such as, but not limited to, methylacetylene and propadiene. After selective hydrogenation of C3 acetylene in MAPD reactor 32, the upgraded mixed C3 hydrocarbon stream 34 exiting MAPD reactor 32 reaches C3 stripper 36, where unreacted H2 and light products 38 (generally including methane and trace C2) are discharged. Propylene product 40 is drawn off from C3 stripper 36 as a side-pump. In this non-limiting embodiment, it is understood that since the function of depropanizer 26 is to separate lighter hydrocarbons from C4 hydrocarbons in the stream, it is not necessary to send the crude butadiene product stream 28 from the bottom of depropanizer 26 to a separate stripper to discharge residual unreacted H2.

[0030] In one non-limiting embodiment, the hydrocarbons in the stream contain C3-C 10 The feed 14 for the range of hydrocarbon mixtures can be a mixture of saturated hydrocarbons, alkenes and alkynes.

[0031] Hydrogenation catalysts for selectively hydrogenating C4 acetylene streams (various hydrogenation catalysts) may include, but are not limited to, palladium-based catalysts such as palladium supported on alumina, copper-based catalysts, rhodium-based catalysts, and other such metal-based catalysts. Hydrogenation catalysts for selectively hydrogenating C3 acetylene streams (various hydrogenation catalysts) may include, but are not limited to, palladium-based catalysts such as palladium supported on alumina, copper-based catalysts, rhodium-based catalysts, and other such metal-based catalysts.

[0032] It is understood that the conversion of C4 acetylene can be targeted to meet the specifications of C4 acetylene in the crude butadiene stream. This is achieved through controlled H2 injection, thereby selectively hydrogenating C4 acetylene. The reactor size, circulation rate, pressure, and reactor inlet temperature can all be designed to achieve or exceed the desired conversion of C4 acetylene and 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 length can independently range from about 2 months to about 12 months; alternatively, independently from about 6 months to about 9 months; the space velocity (LHSV) can independently range from about 4 to about 20; alternatively, independently from about 8 to about 16.

[0033] It will also be understood that any hydrogenation of C3 acetylenes, such as methylacetylene and propadiene, in this method, while not intentional, is also beneficial.

[0034] The methods and systems described herein can achieve various objectives, including, but not limited to, the following:

[0035] • Hydrogenate C4 acetylene in a mixed hydrocarbon stream in a manner that substantially maintains the selectivity and conversion rate of hydrogenated C4 acetylene;

[0036] • Hydrogenating C4 acetylene in mixed hydrocarbon streams in a manner that yields improved selectivity and / or conversion; and

[0037] • Hydrogenate C4 acetylene in mixed hydrocarbon streams, reducing the hydrogenation of valuable hydrocarbons such as 1,3-butadiene and propylene.

[0038] Even if only one of these objectives is achieved, such as achieving selectivity and conversion of C4 acetylene in mixed C3 / C4 and C4 streams, the methods and systems described herein are considered effective and successful. If one or more other objectives are also achieved, the methods and systems can be considered even more effective.

[0039] In the foregoing description, the invention has been described with reference to specific embodiments thereof. However, this description should be considered illustrative rather than restrictive. For example, hydrogenation reaction conditions and apparatus, debutanizer and depropanizer conditions, catalysts, and the composition and conditions of hydrocarbon and acetylene streams and hydrogen streams that fall within the claimed or disclosed parameter range but are not specifically specified or attempted in the specific embodiments are contemplated within the scope of the invention.

[0040] This invention can be practiced without the presence of any undisclosed elements. Furthermore, the invention may suitably include, consist of, or consist substantially of the disclosed elements. For example, the system may include, consist of, or consist substantially of: a propane de-propane tower, a butane de-propane unit, a C4 acetylene-rich hydrogenation reactor, a methylacetylene and propadiene (MAPD) ​​reactor, and a stripping tower, wherein the propane de-propane tower is located downstream of the butane de-propane tower.

[0041] In another non-limiting embodiment, a method for selectively hydrogenating acetylene may be provided, the method comprising, substantially comprising, or comprising C3-C 10 The hydrocarbon stream is directed to a butanizer, where the C3-C4 overhead stream is condensed. In a C4 acetylene hydrogenation reactor, the condensed C3-C4 overhead stream is selectively hydrogenated to obtain the reactor outlet stream. The reactor outlet stream is directed to a propaneizer downstream of the butanizer. An overhead stream containing a C3 mixture including methylacetylene and propadiene is extracted from the propaneizer. A bottom stream containing a crude C4 mixture is extracted from the propaneizer. The C3 mixture is directed to a methylacetylene and propadiene (MAPD) ​​reactor, where methylacetylene and propadiene are selectively hydrogenated to obtain a crude propylene stream. The crude propylene stream is then directed to a stripping tower.

[0042] Additionally, an upgraded hydrogenated product prepared by the selective hydrogenation method described herein is also provided, comprising independently from about 0.5 to about 2 wt% hydrogenated C4 acetylene; and optionally independently from about 0.9 to about 1.6 wt% hydrogenated C4 acetylene. Furthermore, the upgraded hydrogenated product comprises independently from about 20 wt% to about 60 wt% hydrogenated 1,3-butadiene; and optionally independently from about 40 wt% to about 50 wt% hydrogenated 1,3-butadiene.

[0043] In another non-limiting embodiment, an ethylene plant may be provided comprising, substantially comprising, or comprising a system for acetylene in a hydrogenated hydrocarbon stream, the system comprising, substantially comprising, or comprising a depropanizer, a debutanizer, a C4 acetylene hydrogenation reactor, a methylacetylene and propadiene (MAPD) ​​reactor, and a stripping tower, wherein the depropanizer is located downstream of the debutanizer.

[0044] The terms “comprising” and “comprises” used throughout the claims should be interpreted as “including but not limited to” and “including but not limited to”, respectively.

[0045] As used in this article, the word “basically” should be interpreted as “to a large extent, but not entirely”.

[0046] As used herein, the singular forms “a”, “an” and “the” are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0047] For the purposes of this document, the term “about” when referring to a given parameter includes the specified value and has a meaning specified by the context (e.g., it includes the degree of error associated with the measurement of the given parameter).

[0048] For the purposes of this document, the term “and / or” includes any and all combinations of one or more of the related listed items.

Claims

1. A system for acetylene in a hydrogenated hydrocarbon stream, the system comprising: Butane removal tower, A C4 acetylene hydrogenation reactor is located downstream of the butane removal tower, wherein the crude butadiene product stream exits from the C4 acetylene hydrogenation reactor. A propane removal tower is located downstream of the C4 acetylene hydrogenation reactor. A methylacetylene and propadiene (MAPD) ​​reactor, located downstream of the propane depropanizer, and The stripping tower, located downstream of the MAPD reactor, receives the crude propylene stream from it. There is no stripping tower other than the stripping tower used to remove residual unreacted H2 from the crude butadiene product stream.

2. The system of claim 1, further comprising a butanizer and a C4 acetylene hydrogenation reactor. The condenser between them is used to condense the overhead stream from the butane debutane tower C3-C4.

3. The system of claim 2, wherein the C4 acetylene hydrogenation reactor is located downstream of the condenser and is configured to selectively hydrogenate and condense the overhead stream of the butane dehydrogenator while keeping the condensed overhead stream of the butane dehydrogenator in the liquid phase.

4. The system of claim 2, wherein a refrigerant is used in the condenser.

5. A method for selectively hydrogenating acetylene using any one of claims 1 to 4, comprising: C3-C 10 Hydrocarbon streams are directed to the butane removal tower; The top stream from the C3-C4 condenser debutane tower; In a C4 acetylene hydrogenation reactor, the selectively hydrogenated and condensed C3-C4 overhead stream... C4 acetylene was used to obtain the reactor outlet stream. The reactor outlet stream is directed to the propane removal tower downstream of the butane removal tower; The overhead product containing a C3 mixture comprising methylacetylene and propadiene is drawn from the depropanizer. flow; Extract the bottom stream containing a crude C4 mixture from the propane stripper; The C3 mixture is directed to the methylacetylene and propadiene (MAPD) ​​reactor and selectively... Hydrogenation of methylacetylene and propadiene yields crude propylene stream; as well as The crude propylene stream is directed to the stripping tower. The stripping tower described therein is the only stripping tower, and no vapor is present downstream of the crude C4 mixture. Tita.

6. The method of claim 5, wherein the overhead stream from the C3-C4 condenser debutanizer is obtained by... It is carried out using a cold medium.

7. The method of claim 5, wherein the C4 acetylene hydrogenation reactor is operated at 10°C to 60°C. It operates at temperatures ranging from 2.1 MPa to 4.9 MPa.

8. An ethylene plant comprising: A system for use in acetylene streams of hydrogenated hydrocarbons, the system comprising: Butane removal tower, A C4 acetylene hydrogenation reactor is located downstream of the butane removal tower, wherein the crude butadiene product stream exits from the C4 acetylene hydrogenation reactor. A propane removal tower is located downstream of the C4 acetylene hydrogenation reactor. A methylacetylene and propadiene (MAPD) ​​reactor, located downstream of the propane depropanizer, and The stripping tower, located downstream of the MAPD reactor, receives the crude propylene stream from it. Furthermore, it does not include any stripping tower other than the stripping tower used to remove residual unreacted H2 from the crude butadiene product stream.

9. The ethylene plant of claim 8, further comprising a condenser between the butane dehydrogenation tower and the C4 acetylene hydrogenation reactor for condensing the butane dehydrogenation tower C3-C4 overhead stream from the butane dehydrogenation tower.

10. The ethylene apparatus of claim 9, wherein a refrigerant is used in the condenser.

11. The ethylene plant of claim 9, wherein the C4 acetylene hydrogenation reactor is located downstream of the condenser and is configured to selectively hydrogenate and condense the overhead stream of the butane dehydrogenator while keeping the condensed overhead stream of the butane dehydrogenator in the liquid phase.

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