Patent Application
20190031967
The disclosed subject matter relates to processes and systems for recovering C5 hydrocarbons, integrated with pygas treatment.
Pygas, also known as pyrolysis gas, can be formed in the cracking furnaces of various refinery processes. Pygas can include alkanes, alkenes, alkynes, aromatics, naphthenes, alkyl aromatics and/or polyaromatics. After being formed in the cracking furnaces, pygas can be distilled through one or more fractional distillation columns to remove lighter hydrocarbons.
C5 hydrocarbons can be separated from pygas while olefins are converted to alkanes. The separated C5 stream can be returned to the cracking furnace as feedstock. This process can cause the conversion of certain C5 hydrocarbons, e.g., isoprene and cyclopentadiene, to what can be less valuable chemicals such as isopentane and cyclopentane.
Therefore, there remains a need for improved techniques for integrating the processing of pygas with the utilization of C5 hydrocarbons including isoprene and cyclopentadiene.
The disclosed subject matter provides processes and systems for recovering isoprene, pyperylene and cyclopentadiene from pygas.
In certain embodiments, processes for treating pygas can include depentanizing the pygas to produce a C5 stream and a C6+ stream and contacting the C6+ stream with a first catalyst to form one or more hydrotreatment products. Example processes can further include separating the C5 stream to form a product stream and a raffinate stream. The processes can also include contacting the raffinate stream with a second catalyst to produce alkanes. In certain instances, the pygas stream, the C5 stream, and/or the C6+ stream can be introduced into or contacted with a sulfur removal unit (e.g., a sulfur removal adsorption bed, amine treatment unit, etc.) to remove sulfur containing compounds (e.g., mercaptains, carbon sulfides, hydrogen sulfide, etc.) from these streams prior to coming into contact with the first and/or second catalysts. Removal of sulfur containing compounds from these streams can help protect the first and/or second catalysts from deactivation. In preferred instances, the sulfur removal unit can be positioned just before the C5 stream and/or the C6+ stream enter the hydrogenation reactor/unit or the hydrotreatment reactor/unit, respectively.
In certain embodiments, the first and/or second catalyst is a hydrogenation catalyst. For example the second catalyst can be a C5 or C4/C5 hydrogenation catalyst.
In certain embodiments, the product stream can include isoprene, piperylene, and/or dicyclopentadiene.
In certain embodiments, the process can further include deoctanizing the hydrotreatment products to form a benzene, toluene, and/or xylene stream and a C9+ hydrocarbon stream. The processes can further include cracking the alkanes to produce feedstock.
The presently disclosed subject matter also provides processes for treating pygas which can include depentanizing the pygas to produce a C5 stream and a C6+ stream. Example processes can further include contacting the C6+ stream with a first catalyst to form hydrotreatment products and separating the C5 stream to form a product stream and a raffinate stream. The process can additionally include separating the raffinate stream to form a C4 raffinate stream and a C5 raffinate stream and contacting the C5 raffinate stream with a second catalyst to produce alkanes.
In certain embodiments, the second catalyst is a C5 hydrogenation catalyst.
The presently disclosed subject matter also provides systems for processing pygas which can include a first distillation column configured to separate pygas to produce a C5 stream and C6+ stream and a hydrotreatment unit, coupled to the first distillation column, configured to hydrotreat the C6+ stream to form one or more hydrotreatment products. Example systems can also include a second distillation column, coupled to the hydrotreatment unit, configured to produce a benzene, toluene, and/or xylene stream and a C9+ hydrocarbon stream and a separations unit, coupled to the first distillation column, configured to produce a C5 raffinate stream and a isoprene, piperylene, cyclopentadiene stream. The system can further include a hydrogenation reactor, coupled to the separations unit, which can include a catalyst to convert the C5 raffinate stream into alkanes. In certain aspects, the system can also include at least one, two, three, or more sulfur removal units (e.g., a sulfur removal adsorption bed, amine treatment unit, etc.) to remove sulfur containing compounds (e.g., mercaptains, carbon sulfides, hydrogen sulfide, etc.) from the pygas stream, the C5 stream and/or the C6+ stream. For example, a sulfur removal unit can be coupled to and positioned between the separations unit and the hydrogenation reactor. Alternatively, or additionally, a sulfur removal unit can be coupled to and positioned between the first distillation column and the hydrotreatment unit. Even further, a sulfur removal unit can be coupled to the first distillation column such that the pygas is first treated to remove (e.g., reduce) sulfur containing compounds prior to entering the first distillation column.
In certain embodiments, the first distillation column is a depentanizer column. The second distillation column can be an deoctanizer column, and the hydrogenation reactor can be a three bed deep hydrogenation reactor.
The presently disclosed subject matter provides methods and systems for recovering C5 hydrocarbons from pygas. The presently disclosed subject matter also provides methods for recovering isoprene and cyclopentadiene from pygas. For the purpose of illustration and not limitation,
In certain embodiments, a method 100 for recovering isoprene and cyclopentadiene from pygas includes depentanizing the pygas to produce a C5 stream and a C6+ stream. The pygas of the presently disclosed subject matter can originate from various sources, for example other chemical processes, e.g., ethylene production or the cracking of naphtha, butanes, or gas oil. The pygas can include alkanes, alkenes, alkynes, aromatics, naphthenes, alkyl aromatics, and polyaromatics. For example, the pygas can include cyclopentadiene and/or dicyclopentadiene.
As used herein, the term “about” or “approximately” means within an acceptable error range for the particular value as determined by one of ordinary skill in the art, which will depend in part on how the value is measured or determined, i.e., the limitations of the measurement system. For example, “about” can mean a range of up to 20%, up to 10%, up to 5%, and or up to 1% of a given value.
In certain embodiments, the method can include separating a C5 stream from the pygas 101. In certain embodiments, the C5 fraction can be recovered from the pygas by distillation, i.e., in a fractional distillation column. The distillation column can be a depentanizer column. The C5 fraction can include aliphatic and aromatic hydrocarbons, e.g., pentanes, pentenes, pentynes, cyclopentanes, cyclopentenes, and/or cyclopentadiene. In certain embodiments, a stream containing C6+ hydrocarbons is also recovered, e.g., by distillation.
In certain embodiments, the method can further include contacting the C6+ hydrocarbon stream with a first catalyst to form hydrotreatment products 102. For example, the C6+ stream can be contacted with a catalyst, e.g., in a hydrotreatment reactor. In certain embodiments, the catalyst is any hydrogenation catalyst known in the art. In certain embodiments, the catalyst can include nickel, platinum, and/or palladium supported on alumina or the like. In certain embodiments, the C6+ hydrocarbon stream can be introduced into or contacted with a sulfur removal unit (e.g., a sulfur removal adsorption bed, amine treatment unit, etc.) to remove sulfur containing compounds (e.g., mercaptains, carbon sulfides, hydrogen sulfide, etc.) from the stream prior to coming into contact with the first catalyst. In certain embodiments, the method can further include recovering benzene, toluene, and/or xylene from the hydrotreatment products, e.g., in a distillation column. The distillation column can be a deoctanizer column. In certain embodiments, the method can further include recovering C9+ hydrocarbons from the hydrotreatment products, e.g., in a distillation column. The distillation column can be the same deoctanizer column and can operate from between about 80° C. to about 200° C. of temperature and pressures from between about 1 bar to about 10 bars.
In certain embodiments, the method 100 can further include separating the C5 stream to form a product stream and a raffinate stream 103. For example, a product stream can be recovered from the C5 stream by separation, i.e., in a separations unit via a series of separations, including, but not limited to, extractive distillation. The product stream can include chemicals such as isoprene, piperylene and cyclopentadiene. In certain embodiments, the cyclopentadiene is dimerized to dicyclopentadiene (DCPD).
In certain embodiments, the raffinate stream includes the remaining C5 and/or C4 hydrocarbons. In certain embodiments, the C4 hydrocarbons can be recovered from the raffinate stream, e.g., in a hydrotreatment reactor. The C4 hydrocarbons can be recycled to a cracker furnace. Alternatively, in other embodiments, the C4 hydrocarbons are not separated from the raffinate stream and the raffinate stream is contacted with a second catalyst to produce alkanes 104. In certain embodiments, the raffinate stream can be introduced into or contacted with a sulfur removal unit (e.g., a sulfur removal adsorption bed, amine treatment unit, etc.) to remove sulfur containing compounds (e.g., mercaptains, carbon sulfides, hydrogen sulfide, etc.) from the stream prior to coming into contact with the second catalyst.
In certain embodiments the second catalyst is a C4/C5 hydrogenation catalyst. Hydrogenation catalysts can include, but are not limited to, nickel, palladium and platinum on an aluminum support or the like. In certain embodiments, the alkanes are further processed to obtain feedstock, e.g., in a cracker furnace.
The presently disclosed subject matter further provides systems for processing pygas. The system can include one or more distillation columns, e.g., depentanizer and/or deoctanizer columns, and one or more reactors which can include one or more catalysts. For the purpose of illustration and not limitation,
In certain embodiments, a system 200 for recovering dicyclopentadiene from pygas includes a pygas stream 201. To preserve the C5 valuable chemicals, a depentanizer column 202 is placed before the hydrotreatment reactor 204, C5 hydrocarbons are separated in the overhead stream from the C6+hydrocarbons of pygas in the depentanizer column. The depentanizer column can be a distillation column. Although not show in
The bottom stream of the depentanizer column is removed as C6+ hydrocarbons 203. In certain embodiments, the depentanizer column's overhead stream is coupled to a separations unit 208 for separating the C5 stream to recover isoprene, piperylene and cyclopentadiene 213 from the stream. In certain embodiments, the cyclopentadiene 213 is dimerized to dicyclopentadiene (DCPD) as a final product. In certain embodiments, the separations unit 208 is also coupled to a hydrogenation reactor 210 for separating the remains of the C5 stream (referred to as raffinate) 209 before C4 is recycled back 212 to the cracker 211. In certain embodiments, the reactor 210 includes a catalyst. In other embodiments the catalyst can be a C4 hydrogenation catalyst or a C4/C5 hydrogenation catalyst that is capable of hydrogenating mixed raffinate streams of C4-C5 hydrocarbons. In certain embodiments, the reactor 210 is a three bed deep hydrogenation reactor that converts all hydrocarbons to alkanes. Although not shown in
“Coupled” as used herein refers to the connection of a system component to another system component by any means known in the art. The type of coupling used to connect two or more system components can depend on the scale and operability of the system. For example, and not by way of limitation, coupling of two or more components of a system can include one or more joints, valves, fitting, coupling, transfer lines or sealing elements. Non-limiting examples of joints include threaded joints, soldered joints, welded joints, compression joints and mechanical joints. Non-limiting examples of fittings include coupling fittings, reducing coupling fittings, union fittings, tee fittings, cross fittings and flange fittings. Non-limiting examples of valves include gate valves, globe valves, ball valves, butterfly valves, needle valves and check valves.
In certain embodiments, a system 200 includes processing of the C6+ hydrocarbons of pygas, extracted from depentanizer column bottom 203. In certain embodiments, the depentanizer column bottom is coupled to a pygas hydrotreatment unit 204 which includes a catalyst. In further embodiments, the pygas hydrotreatment unit 204 can be coupled to a deoctanizer for separating a C9+ hydrocarbon stream 206 and a benzene, toluene, and/or xylene stream 207. The deoctanizer column can be a distillation column.
The distillation columns, e.g., a depentanizer or deoctanizer, for use in the presently disclosed subject matter can be any type known in the art to be suitable for fractional distillation. The one or more distillation columns can be adapted to continuous or batch distillation. The one or more distillation columns can be coupled to one or more condensers and one or more reboilers. The one or more distillation columns can be stage or packed columns, and can include plates, trays and/or packing material. The one or more distillation columns can be coupled to one or more transfer lines. The one or more distillation columns can be made of any suitable material including, but not limited to, aluminum, stainless steel, carbon steel, glass-lined materials, polymer-based materials, nickel-base metal alloys, cobalt-based metal alloys or combinations thereof. The presently disclosed systems can further include additional components and accessories including, but not limited to, one or more gas exhaust lines, cyclones, product discharge lines, reaction zones, heating elements and one or more measurement accessories. The one or more measurement accessories can be any suitable measurement accessory known to one of ordinary skill in the art including, but not limited to, pH meters, flow monitors, pressure indicators, pressure transmitters, thermos-wells, temperature-indicating controllers, gas detectors, analyzers and viscometers. The components and accessories can be placed at various locations within the system.
The methods and systems of the presently disclosed subject matter provide advantages over certain existing technologies. Exemplary advantages include a decrease in capital and separation energy costs due to the saving of an additional depentanizer column. Also, due to the separation of valuable chemicals from the C5 stream, there is less hydrogen required for the hydrogenation reactor. In addition, when the C4/C5 hydrogenation catalyst is a three bed hydrogenation reactor which can perform deep hydrogenation, the C4/C5 hydrocarbons recycled to the cracker are totally hydrogenated and therefore have a low tendency to form coke in the cracker. The diversion of a C5 hydrocarbon stream from the hydrotreater reactor also offloads the pygas reactor capacity by about 25-40% allowing an aromatics plant to process more aromatics using the same reactor unit. Another benefit of the presently disclosed subject matter is that the same depentanizer column used after pygas hydrotreatment unit can be used upstream without modification. Yet another benefit of the presently disclosed subject matter is that the C4/C5 hydrogenation reactor can be a 3 stage reactor which can perform deep hydrogenation of C5 unsaturated hydrocarbons. This is unlike pygas hydrogenation which usually utilizes one or two stage reactors to avoid hydrogenating aromatic products. The deep hydrogenation of C5 and C4 hydrocarbons ensures that only alkanes are recycled to cracker. This reduces coke formation in cracker tubes and gives longer cycle time.
In addition to the various embodiments depicted and claimed, the disclosed subject matter is also directed to other embodiments having other combinations of the features disclosed and claimed herein. As such, the particular features presented herein can be combined with each other in other manners within the scope of the disclosed subject matter such that the disclosed subject matter includes any suitable combination of the features disclosed herein. The foregoing description of specific embodiments of the disclosed subject matter has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosed subject matter to those embodiments disclosed.
It will be apparent to those skilled in the art that various modifications and variations can be made in the systems and methods of the disclosed subject matter without departing from the spirit or scope of the disclosed subject matter. Thus, it is intended that the disclosed subject matter include modifications and variations that are within the scope of the appended claims and their equivalents.
This application claims the benefit of priority of U.S. Provisional Patent Application No. 62/316,045, filed Mar. 31, 2016, which is hereby incorporated by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2017/051766 | 3/28/2017 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62316045 | Mar 2016 | US |
