KR20090052361A - Absorption recovery processing of fcc-produced light olefins - Google Patents

Abstract

Treatment techniques and batches are provided for treating heavy hydrocarbon feedstock 212 via hydrocarbon cracking to yield selected hydrocarbon fractions via product recovery based on absorption.

Description

Absorption recovery process of light olefins manufactured by FCC {ABSORPTION RECOVERY PROCESSING OF FCC-PRODUCED LIGHT OLEFINS}

The present invention relates generally to hydrocarbon treatment, and more particularly to the treatment of hydrocarbon-containing materials having a high content of light olefins, such as those produced or formed by the decomposition of heavy hydrocarbon feedstocks or by the decomposition.

Light olefins serve as feedstock for the production of many chemicals. Light olefins have traditionally been produced through processes of catalytic cracking or steam cracking of hydrocarbons such as those derived from petroleum sources. Fluidized catalytic cracking (FCC) of a heavy hydrocarbon stream usually results in fines or particulate solids, whether the starting material is vacuum gas oil, reduced crude or other sources of relatively high boiling hydrocarbons. It is carried out in contact with a catalyst such as consisting of. The catalyst is transported in a fluid-like manner by delivering gas or vapor through the catalyst at a rate sufficient to produce a liquid transport of a given regime. Contact of the oil with the fluidizing material promotes the decomposition reaction.

The decomposition reaction typically deposits coke on the catalyst. The catalyst exiting the reaction zone is usually said to be "consumed", ie partially deactivated by the deposition of coke on the catalyst. The coke consists of hydrogen and carbon and may contain traces of other materials such as sulfur and metals that may enter the process with the starting materials. The presence of coke interferes with the catalytic activity of the spent catalyst. Coke is believed to block acid sites on the catalyst surface where decomposition reactions occur. The spent catalyst is typically conveyed to a stripper to remove adsorbed hydrocarbons and gases from the catalyst for the purpose of removing coke by oxidation with an oxygen containing gas. The remaining catalyst with reduced coke content compared to the spent catalyst in the stripper, hereinafter referred to as regenerated catalyst, is collected and returned to the reaction zone. When coke is oxidized from the catalyst surface, a large amount of heat is released, some of which exit the regenerator with the gaseous product of coke oxidation, commonly referred to as flue gas. The remainder of the heat is discharged from the regenerator with the regeneration catalyst. The fluidization catalyst continues to circulate between the reaction zone and the regeneration zone. Fluidization catalysts not only provide catalytic function but also act as mediators for transferring heat from one zone to another. FCC treatments are described in more detail in US 5,360,533 to Tagamolila et al., US 5,584,985 to Lomas, US 5,858,206 to Castillo and US 6,843,906 to Eng, the contents of each of which are incorporated herein by reference. do. Detailed descriptions of the various contacting zones, regeneration zones and arrangements for catalyst transport between the stripping zones and the various zones are well known to those skilled in the art.

FCC reactors serve to decompose light oil or heavy feeds into a wide range of products. Decomposed steam from the FCC unit is typically used to provide purified oil (CO), including gas streams, gasoline fractions, light cycle oil (LCO) and heavy cycle oil (HCO) components. Enters the separation column in the form of main column. The gas stream may comprise dry gas, ie hydrogen and C ₁ and C ₂ hydrocarbons, and liquefied petroleum gas (“LPG”), often also commonly referred to as wet gas, ie C ₃ and C ₄ hydrocarbons.

In addition to the increased demand and demand for light olefins such as ethylene and propylene for various petrochemical applications, such as for the production of polyethylene, polypropylene, etc., butylene and pentene, which are generally less desirable as gasoline blending components due to environmental considerations, In view of the desire to produce relatively less such heavy olefins, it may be desirable to carry out the decomposition reaction treatment of the heavy hydrocarbon feedstock in order to increase the relative amount of light olefins in the resulting product slate.

Research efforts have developed FCC processes to produce or produce higher relative yields of light olefins, ie ethylene and propylene. This process is disclosed in more detail in US Pat. No. 6,538,169 to Pittman et al., The contents of which are incorporated herein by reference in their entirety. As discussed therein, the hydrocarbon feed stream may be contacted with a mixed catalyst, preferably comprising a regenerated catalyst and a coked catalyst. The catalyst comprises a composition comprising a first component and a second component. The second component comprises a zeolite having a median or less pore size, wherein the zeolite comprises at least 1% by weight of the catalyst composition. Contact at the riser to crack the hydrocarbons in the feed stream to obtain a cracked stream containing hydrocarbon products comprising light olefins and coking catalyst. The cracked stream passes through the ends of the riser so that the hydrocarbon feed stream contacts the mixed catalyst in the riser for an average of 2 seconds or less.

In view of the increased need and demand for light olefins such as ethylene and propylene, there is a need and demand for improved treatments and batches for separating and recovering light olefins from these FCC process effluents.

Summary of the Invention

It is a general object of the present invention to provide an improved process and system for catalytically cracking heavy hydrocarbon feedstocks to obtain selected hydrocarbon fractions.

A general object of the present invention is at least in part through a specific process, such as in the step of contacting a heavy hydrocarbon feedstock with a hydrocarbon cracking catalyst in a fluidization reactor zone to produce a hydrocarbon effluent comprising various cracked hydrocarbon products, including light olefins. Can be achieved with According to one preferred embodiment, the hydrocarbon cracking catalyst is preferably a composition comprising a first component comprising a molecular sieve having a large pore size and a second component comprising a zeolite having a pore size of less than or equal to medium, wherein the pore size is medium. The following zeolite constitutes at least 1.0% by weight of the catalyst composition. The hydrocarbon effluent is separated in the separation zone to form one or more separator liquid streams and separator vapor streams. At least one separator liquid stream comprises a C ₃ + hydrocarbon. The separator vapor stream comprises C ₃ -hydrocarbons. The separator vapor stream to decompose in contact with the first absorbing solvent in an absorption zone recovering the C ₃ + hydrocarbon therefrom and C ₂ - to form a process stream (process stream) containing the hydrocarbon material. The C ₂ -hydrocarbon material may preferably be stripped from one or more separator liquid streams to form a C ₃ + hydrocarbon process stream that is substantially free of C ₂ -hydrocarbons. C ₅ + hydrocarbon material is separated from the C ₃ + hydrocarbon process stream to form a first product process stream comprising C ₅ + hydrocarbon material and a second product process stream comprising C ₃ and C ₄ hydrocarbons. At least a first portion of the first product stream is introduced into the absorption zone, preferably at least as part of the first absorption solvent.

The prior art generally does not provide processing techniques and batches for catalytic light olefins via catalytic cracking of heavy hydrocarbon feedstocks in an effective and efficient manner which may be desirable. More particularly, the prior art generally does not provide such treatment techniques and arrangements that advantageously utilize product recovery based on absorption to produce or obtain a process stream containing a particular desired range of hydrocarbons.

According to another embodiment, a process for catalytically cracking a heavy hydrocarbon feedstock to obtain a selected hydrocarbon fraction comprises contacting the heavy hydrocarbon feedstock in a fluidization reactor zone with a mixed cracking catalyst comprising a regeneration catalyst and a coking catalyst under hydrocarbon cracking conditions. To produce a hydrocarbon effluent stream comprising various hydrocarbon products including light olefins. The catalyst is preferably a composition comprising a first component comprising a large molecular sieve and a second component comprising a zeolite of medium or lower pore size. Zeolites with medium or lower pore sizes make up at least 1.0% by weight of the catalyst composition.

The method further involves separating the hydrocarbon effluent in the separation zone to form at least one separator high pressure liquid stream and separator high pressure vapor stream. At least one high-pressure separator liquid stream and a C ₃ + hydrocarbon. The separator high pressure vapor stream comprises C ₃ -hydrocarbons. The separator high pressure vapor stream is contacted with a first absorbing solvent in the primary absorber to form a first primary absorber process stream comprising mainly C ₂ -hydrocarbons and residual C ₃ + hydrocarbons. First contacting the primary absorber 1 process stream with a second solvent absorbing C ₂ - to form a process stream comprising a process stream and the residual C ₃ + hydrocarbons and a second absorption solvent containing the hydrocarbon material. The C ₂ -hydrocarbon material is stripped from the separator high pressure liquid stream to form a C ₃ + hydrocarbon process stream that is substantially free of C ₂ -hydrocarbons. C ₅ + hydrocarbon material is separated from the C ₃ + hydrocarbon process stream to form a first product process stream comprising C ₅ + hydrocarbon material and a second product process stream comprising C ₃ and C ₄ hydrocarbons. The method involves directing at least a first portion of the first product stream to the primary absorber as most of the first absorbent solvent.

A system is also provided for catalytically cracking heavy hydrocarbon feedstocks to obtain selected hydrocarbon fractions. According to one preferred embodiment, such a system comprises a cracked effluent stream containing hydrocarbon products, including light olefins, in which the heavy hydrocarbon feedstock is contacted with a mixed catalyst comprising a regeneration catalyst and a coking catalyst under hydrocarbon cracking reaction conditions. And a fluidization reactor zone to produce the same.

The system also includes a separation zone for separating the cracked effluent stream to form one or more separator liquid streams and separator vapor streams. At least one separator liquid stream comprises a C ₃ + hydrocarbon. The separator vapor stream comprises C ₃ -hydrocarbons.

The system absorbs C ₃ + C ₂ hydrocarbons, including ethylene from the high pressure separator vapor stream in a first absorption solvent further comprises an absorption zone to form an absorption zone effluent stream comprising hydrocarbons. A stripper is provided that strips the C ₂ -hydrocarbon material from the separator liquid stream to form a C ₃ + process stream that is substantially free of C ₂ -hydrocarbons. Debutanizer for separating C ₅ + hydrocarbon material from a C ₃ + hydrocarbon process stream to form a first process stream comprising C ₅ + hydrocarbon material and a second process stream comprising C ₃ and C ₄ hydrocarbons ) Is provided. The system also includes a process line for introducing at least a first portion of the first product stream into the absorption zone as most of the first absorption solvent.

Reference to “light olefins” as used herein should generally be understood to refer to C ₂ and C ₃ olefins, ie ethylene and propylene, alone or in combination.

Reference to a suitable process stream or light olefin material "substantially free of carbon dioxide" preferably contains generally less than 100 ppm carbon dioxide, preferably less than 10 ppm carbon dioxide, more preferably less than 1 ppm carbon dioxide. It should be understood that these light olefin materials or process streams are generally referred to.

Reference to a process stream “ethylene rich” generally comprises at least 20% ethylene, and at least according to certain preferred embodiments alternatively at least 25% ethylene, at least 30% ethylene, at least 35% Should be understood to refer to such a process stream comprising ethylene, at least 40% ethylene or 40 to 60% ethylene.

Reference to "C _x hydrocarbon" should be understood to refer to hydrocarbon molecules having the number of carbon atoms represented by the subscript "x". Similarly, the term "C _x containing stream" refers to a stream containing C _x hydrocarbons. The term "C _x + hydrocarbon" refers to a hydrocarbon molecule having a number of carbon atoms represented by the subscript "x" or more. For example, “C ₄ + hydrocarbons” includes C ₄ , C ₅ and higher carbon atoms. The term "C _x -hydrocarbon" refers to a hydrocarbon molecule having the number of carbon atoms represented by the subscript "x" or less. For example, “C ₄ -hydrocarbons” include C ₄ , C ₃ and lower carbon number hydrocarbons.

Other objects and advantages will be apparent to those skilled in the art from the following detailed description, which is set forth in conjunction with the appended claims and drawings.

1 is a simplified schematic diagram of a system for catalytically cracking a heavy hydrocarbon feedstock via product recovery based on absorption to obtain selected hydrocarbon fractions, including light olefins, according to one preferred embodiment.

details

Treatment techniques and batches are provided for the efficient and efficient treatment of heavy hydrocarbon feedstocks via hydrocarbon cracking treatments where product recovery based on absorption results in selected hydrocarbon fractions.

FIG. 1 schematically depicts a system for catalytically cracking heavy hydrocarbon feedstocks to obtain light olefins via product recovery based on absorption in accordance with one embodiment of the present invention, generally designated 210. Those skilled in the art and those guided by the teachings provided herein will recognize and understand that the illustrated system is simplified, with the exception of various general or conventional parts of the process equipment, including some heat exchangers, process control systems, pumps, fractionation systems, and the like. will be. It is also to be understood that the process flow shown in the figures may be modified in many respects without departing from the basic overall concept of the invention.

In system 210, a suitable heavy hydrocarbon feedstock stream is introduced via line 212 to fluidization reactor zone 214, where the heavy hydrocarbon feedstock is contacted with a hydrocarbon cracking catalyst zone to produce various hydrocarbon products, including light olefins. A hydrocarbon effluent is produced.

Suitable fluidized catalytic cracking reactor zones for use in the practice of this embodiment provide separator vessels, regenerators, mixing vessels, and pneumatic conveynace zones where conversion occurs, as disclosed in US Pat. No. 6,538,169 to Pittman et al. Described above. It includes a vertical riser. The batch circulates the catalyst and contacts the feed in the manner specified.

More specifically and as described therein, the catalyst typically comprises two components which may or may not be present on the same matrix. The two components are circulated throughout the entire system. The first component may comprise any of the well known catalysts used in the field of fluidized catalytic cracking, such as active amorphous clay type catalysts and / or highly active crystalline molecular sieves. Molecular sieve catalysts are preferred over amorphous catalysts because of the greatly improved selectivity for a given product. Zeolites are the most commonly used molecular sieves in FCC processes. Preferably, the first catalyst component comprises a large pore zeolite such as Y zeolite, active alumina material, adhesive material comprising silica or alumina and inert fillers such as kaolin.

Zeolite molecular sieves suitable for the first catalyst component should have a large average pore size. Typically, molecular sieves with large pore sizes have pores with openings greater than 10 nm and typically greater than 0.7 nm in diameter, defined as 12 membered rings. Large pore pore size index is above 31. Suitable large pore zeolite components include synthetic zeolites such as X- and Y-type zeolites, mordenite and faasite. It has been found that Y zeolites with a low rare earth content are preferred for the first catalyst component. Low rare earth content refers to 1.0 wt% or less of rare earth oxides in the zeolite portion of the catalyst. Octacat ™ catalysts manufactured by W. Grace and Company are suitable low rare earth Y-zeolite catalysts.

The second catalyst component contains a medium or small pore zeolite catalyst exemplified by ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38, ZSM-48 and other similar materials. It includes a catalyst. US 3,702,886 discloses ZSM-5. Other suitable intermediate or small pore zeolites include Ferrilite, Erioneite, and ST-5 developed by Petroleum de Venezuela SA. The second catalyst component preferably disperses the mesoporous or small pore zeolite on a matrix comprising an adhesive material such as silica or alumina and an inert filler material such as kaolin. The second component may also include some other active substance, such as beta zeolite. These catalyst compositions have a crystalline zeolite content of 10 to 25% by weight and a matrix material content of 75 to 90% by weight. Catalysts containing 25% by weight of crystalline zeolite material are preferred. Catalysts with higher crystalline zeolite content can be used if they have satisfactory wear resistance. The zeolites of the intermediate and small pores are characterized by having an effective pore opening diameter of 0.7 nm or less, a ring of 10 members or less, and a pore size index of less than 31.

The total catalyst composition should contain from 1 to 10% by weight of medium to small pore zeolites, preferably at least 1.75% by weight. If the second catalyst component contains 25% by weight of crystalline zeolite, the composition contains 4 to 40% by weight of the second catalyst component, with a content of at least 7% by weight. ZSM-5 and ST-5 type zeolites are particularly preferred because their high coke resistivity can tend to maintain active activity by preserving active decomposition sites while allowing the catalyst composition to pass through a large number of risers. to be. The first catalyst component will constitute the remainder of the catalyst composition. The relative ratio of the first component to the second component in the catalyst composition will not change substantially throughout the FCC unit.

The high concentration of zeolites in the middle pore or small pore of the second component of the catalyst composition further improves the selectivity for light olefins by further degrading the light naphtha range molecules. At the same time, however, the resulting lower first catalyst component still exhibits sufficient activity to maintain conversion of the heavy feed molecules to quite high levels.

Relatively heavy feeds suitable for processing according to the present invention include conventional FCC feedstocks or high boiling feed or residual feeds. Common common feedstocks are hydrocarbon materials, typically prepared by vacuum fractionation of atmospheric residues, with a wide boiling point range of 315 to 622 ° C. (600 to 1150 ° F.), and more typically narrower boiling point ranges of 343 to 551 ° C. (650 to 1025 ° F.). Also suitable are heavy or residual feeds, ie hydrocarbon fractions boiling above 499 ° C. (930 ° F.). The fluidized catalytic cracking treatment of the present invention is suitable for feedstock that is heavier than the naphtha range hydrocarbons that typically boil above 177 ° C (350 ° F).

The effluent or at least a portion thereof is passed from fluidization reactor zone 214 via line 216 to hydrocarbon separation system 220 comprising main column zone 222 and staged compression zone 224. Main column zone 222 is preferably capable of separating the fluidization reactor zone effluent into any fraction, including the main column vapor stream passing through line 226, and the main column liquid stream passing through line 230. A main column separator may be included with the associated main column tower high pressure receiver.

For purposes of illustration and discussion, other fraction lines, including, for example, heavy gasoline streams, light cycle oil ("LCO") streams, heavy cycle oil ("HCO") streams, and refined oil ("CO") streams, are not shown and are shown below. It may not have been described in detail.

Main column vapor stream line 226 is introduced into a staged compression zone 224 such as making up a two stage compression zone. In staged compression zone 224 a high pressure separator liquid stream is formed in line 232 and a high pressure separator vapor stream is formed in line 234. The pressures of these high pressure liquids and high pressure vapors can vary, and in practice this stream is at a pressure in the range of 1375 to 2100 kPag (200 to 300 psig). Compression zone 224 may also form a stream of spill back material composed mostly of heavy hydrocarbon material, which may return to main column zone 222 via line 235.

High pressure separator liquid stream comprises the C ₃ + hydrocarbons substantially free of carbon dioxide. The high pressure separator vapor stream contains C ₃ -hydrocarbons and typically contains large amounts of carbon dioxide.

Separator vapor stream line 234 is introduced via line 237 into an absorption zone, generally designated 236. Absorption zone 236 is C ₃ + a de-butane Chemistry gas material, and a line 230 is the primary absorber 240 from the gas in contact with the main column liquid stream provided by the provided by the separator vapor stream line 242 And a primary absorber 240 that absorbs the individual C ₂ and low boiling fractions. In general, absorption zone 236 suitably includes a primary absorber comprising a plurality of stages having at least one, preferably at least two, intermediate coolers disposed therebetween to assist in achieving the desired absorption. do. In practice, such primary absorbers typically comprise five absorber stages between each pair of intermediate coolers. Thus, according to one preferred embodiment, the primary absorber for achieving the desired absorption preferably comprises at least 15 ideal stages with at least two intermediate coolers suitably arranged therebetween. In another preferred embodiment, suitable preferred primary absorbers for achieving the desired absorption preferably comprise at least 20 or more stages with at least three intermediate coolers suitably disposed therebetween. In another preferred embodiment, suitable preferred primary absorbers for achieving the desired absorption preferably comprise 20 to 25 or more stages with at least four intermediate coolers suitably disposed therebetween. In at least certain preferred embodiments, the broader implementation of the invention is not necessarily limited thereto, and it has been found advantageous to use propylene as a coolant in at least one of the intermediate coolers of such primary absorbers to help achieve the desired absorption. .

Butane gas de-screen and state C ₃ + hydrocarbons in the liquid column or absorbed thereby can be passed through line 243 for further processing according to the present invention as described below in this specification.

Off gas from primary absorber 240 passes through line 244 to secondary or sponge absorber 246. Secondary absorber 246 contacts the off gas with light circulating oil coming from line 250. The light circulating oil absorbs most of the remaining C ₄ and higher hydrocarbons and returns to the main fractionator via line 252. A stream of C ₂ -hydrocarbon is withdrawn as secondary gas from secondary or sponge absorber 246 in line 254 for further processing as described herein below.

The separator liquid stream in line 232 and the contents from line 243 pass through line 260 to stripper 262 which removes most of the light gas and C ₂ in line 264. In practice, such strippers can preferably be operated at pressures in the range of 1650 to 1800 kPag (240 to 260 psig), with a C ₂ / C ₃ molar ratio of less than 0.001 at the stripper tower, preferably C ₂ at the stripper tower. The / C ₃ molar ratio is from 0.0002 to 0.0004.

As shown, C ₂ and light gases in line 264 may be combined with the high pressure separator vapor from line 234, preferably to form line 237 which is supplied to primary absorber 240. Stripper 262 supplies a liquid C ₃ + stream to de-butane exchanger 270 via line 266. According to one preferred embodiment, such a suitable debutane group preferably comprises a condenser (not specifically shown) operated at a pressure in the range of 965-1105 kPag (140-160 psig), with up to 5 mol% on the tower. C ₅ hydrocarbons are present and up to 5 mol% C ₄ hydrocarbons are present at the bottom. More preferably, the relative amount of C ₅ hydrocarbons on the column is 1 to 3 mol% and the relative amount of C ₄ hydrocarbons on the column is 1 to 3 mol%.

A stream of C ₃ and C ₄ hydrocarbons exiting the debutane group 270 is taken on top of the column by line 272 for further processing as described herein below. Line 274 discharges the stream of debutulized gasoline from the debutane 270. According to one preferred embodiment, the stream of debutulized gasoline returned via line 242 to primary absorber 240 acts there as most of the first absorption solvent.

The other portion of the stream of debutulized gasoline passes through line 276 to naphtha splitter 280.

According to one preferred embodiment, naphtha divider 280 is preferably in the form of a dividing wall separating column such as having dividing wall 281 located therein. Such a dividing wall separation column naphtha divider preferably comprises a light fraction stream comprising a compound comprising 5 to 6 carbon atoms, a compound comprising 7 to 8 carbon atoms, for the debutulized gasoline derived therefrom. It is effective for separating into an intermediate fraction stream and a heavy fraction stream comprising a compound comprising more than eight carbon atoms. More specifically, such partition wall separation columns can be operated at condenser pressures generally ranging from 34 to 104 kPag (5 to 15 psig), and in one embodiment 55 to 85 kPag (8 to 12 psig) condenser It is operated at pressure.

These light, medium and heavy fraction streams pass through corresponding lines 282, 284 and 286, respectively, as appropriate for product recovery or further processing as desired.

Returning to the treatment of the stream of C ₂ -hydrocarbons exiting the secondary or sponge absorber 246 in line 254, this stream material is passed through an additional compression zone 290 to compress or discharge drums; Line 292 passing through 294 may be formed. The discharge drum 294 generally consists of heavy components (eg, C ₃ + hydrocarbons liquefied in the discharge drum 294) and forms a knockout stream exiting the line 296. Discharge drum 294 also typically forms a tower stream comprising mainly C ₂ -hydrocarbons with trace amounts (eg, less than 1 wt.%) Of C ₃ + hydrocarbons discharged from line 300.

The columnar stream in line 300 passes through the amine treatment zone 302 as desired to remove CO ₂ therefrom. The use of amine treatment systems for carbon dioxide and / or hydrogen sulfide removal is well known in the art. Such conventional amine treatment systems typically use amine solvents such as methyl diethanol amine (MDEA) to absorb or separate CO ₂ from hydrocarbon stream materials. Strippers or regenerators are typically subsequently used to strip the CO ₂ absorbed from the amine solvent to enable reuse of the amine solvent.

While such amine treatments have generally been found to be effective at removing carbon dioxide from various hydrocarbon containing streams, some of these amine treatments can be applied to streams containing ethylene rich hydrocarbons and carbon dioxide treated at the time of using the system of the present invention. olefin materials can lead to several undesirable problems because they can be absorbed ball and CO ₂ by the amine solvent or equivalent. Such co-absorption of the olefin material preferably reduces the amount of light olefins that can be used to recover from this treatment. In addition, during this subsequent stripper treatment of the amine solvent, polymerization may occur due to the presence of such olefinic materials. Such polymerization can cause decomposition of the amine solvent and may require expensive off-site reclamation processing.

In view of this, it may be desirable to use an amine treatment system that includes or inserts a preliminary stripper disposed between the amine system absorber and the amine system stripper / regenerator. The preliminary stripper disposed between them may preferably serve to separate hydrocarbon materials, including light olefins such as ethylene, from carbon dioxide and amine solvents prior to subsequent processing through the regenerator / stripper.

A stream containing C ₂ -hydrocarbons that are substantially free of carbon dioxide passes through the line 304 to the dryer zone 306 with the water discharged therefrom from line 307. A stream containing stripped hydrocarbons and possibly small amounts (e.g. typically less than 1% by weight) of CO ₂ is conveyed back to the compression zone 224 via line 308 for further processing consistent with the above description. The stream containing CO ₂ is conveyed from the amine treatment zone 302 via line 309.

A stream containing dried C ₂ -hydrocarbon, substantially free of carbon dioxide, is passed via line 310 to an acetylene conversion zone or unit 320. As is known in the art, acetylene conversion zones or units are effective in converting acetylene to form ethylene. Thus, further ethylene-rich process streams exit the line 322 from the acetylene conversion zone or unit 320.

Since additional water may be formed by the acetylene conversion, the process stream in line 322 may be introduced into any dryer unit 324 where water is discharged therefrom from line 326 as needed, resulting in The dry process stream exiting is known in the art for removing CO ₂ , COS, arsine and / or phosphine from line 334 via line 330 and the treated stream from line 336. Passes to any further treatment zone 332 in the form of a CO ₂ , carbonyl sulfide (“COS”), arsine and / or phosphine processor of the bar.

The treated stream in line 336 may preferably be introduced into a demethanizer 340. According to one preferred embodiment, such a suitable demethane group has a temperature of -90 ° C (-130 ° F) or less, more preferably in the range of -90 to -102 ° C, preferably -96 ° C (-130 to -150 ° F). , Preferably a condenser (not shown) operating at a temperature of -140 ° F. In addition, preferred demethane groups for use in the practice of the present invention operate at a methane to ethylene molar ratio of no greater than 0.0005 at the bottom, more preferably at a methane to ethylene molar ratio of 0.0003 to 0.0002 at the bottom.

A stream of methane and hydrogen gas from the demethane is taken from the tower via line 342 for further processing to a pressure swing absorbing unit (not shown) for H ₂ recovery if necessary or for use as fuel.

Line 344 exhausts a stream of demethanated material from demethanizer 340. Delineated material passes through line 344 to ethylene / ethane splitter 346. According to one preferred embodiment, such suitable ethylene / ethane splitters are preferably operated at a pressure in the range of 1930 to 2105 kPag (280 to 305 psig) and preferably up to 0.5% by volume of ethane in the ethylene product stream And preferably a condenser (not shown) which is operated such that less than 0.1% by volume of ethane is present in the ethylene product stream and more preferably less than 0.05% by volume of ethane in the ethylene product stream.

Ethylene / ethane splitter 346 is the vapor stream of the remaining light end, part of ethylene, passing through lines 350, 352 and 354, respectively, for further desired treatment or product recovery as is known in the art. A condensate stream and a bottoms stream of ethane are formed.

Returning to the treatment of a stream containing C ₃ and C ₄ hydrocarbons taken from the debutane group 270 via line 272 over the column, the process stream may contain some significant relative amounts of hydrogen sulfide, 272 may pass through line 362 to a sulfide removal treatment unit 360, as known in the art, preferably in the form of an amine treatment zone. The hydrogen sulfide content of the treated stream is preferably reduced below 20 ppm and hydrogen sulfide is removed via line 364.

If desired, treated stream line 364 may be introduced into zone 366, such as any corrosion treatment, to further remove hydrogen sulfide to a hydrogen sulfide content of 1 ppm or less. Hydrogen sulfide has been found to be removed from the corrosion treatment zone 366 via line 370.

The treated stream with appropriately reduced hydrogen sulphide content is passed through line 372 to mercaptan treatment zone 374 to remove the mercaptan from the stream material via corrosion cleaning as is known in the art. Mercaptan was found to be removed via line 376.

The resulting stream passes through line 380 to C ₃ / C ₄ splitter 382. According to one preferred embodiment, such a suitable C ₃ / C ₄ divider is preferably operated at a pressure in the range of 1650 to 1800 kPag (240 to 260 psig), preferably at a pressure of 1724 kPa (250 psig) Preferably so that up to 5 mol% C ₄ is present in the tower product stream, preferably less than 1 mol% C ₄ is present in the tower product stream, and up to 5 mol% C ₃ is present in the bottom stream. It preferably comprises a condenser (not shown) which is operated such that less than 1 mol% C ₃ is present in the bottoms stream.

C ₃ / C ₄ splitter 382 forms a stream of C ₄ + hydrocarbons passing through line 384 for product recovery or further desired processing as is known in the art.

C ₃ / C ₄ splitter 382 also forms a stream consisting predominantly of C ₃ hydrocarbons passing through line 386.

The stream in line 386 may pass to propylene / propane splitter 390. According to one preferred embodiment, such suitable propane / propylene splitters are operated such that at least 98% by weight, preferably at least 99% by weight, of propylene is withdrawn from the tower stream and propylene in the tower stream is at least 99.5% pure.

Propylene / propane splitter 390 forms a stream of propylene and a stream of propane through lines 392 and 394, respectively, for product recovery or further desired processing as known in the art.

Thus, treatment techniques and batches are preferably provided for obtaining light olefins via catalytic cracking of the heavy hydrocarbon feedstock. More particularly, processing techniques and arrangements are provided that utilize product recovery based on absorption to produce or form process streams containing a certain predetermined range of hydrocarbons.

The present invention as appropriately exemplified herein may be practiced without any member, part, step, component, or raw material not specifically disclosed herein.

In the foregoing Detailed Description, the invention has been described in connection with specific preferred embodiments thereof, and numerous descriptions have been made for purposes of illustration, but additional embodiments are possible and are not limited to the invention without departing from the basic principles thereof. It will be apparent to one skilled in the art that any of the descriptions set forth herein may vary significantly. For example, although the invention has been described above with particular reference to embodiments in which the amine treatment zone 302 is located downstream of the further compression zone 290, those skilled in the art and those guided by the teachings provided herein will appreciate It will be understood that the broader implementation of is not necessarily limited thereto. In certain embodiments, it may be desirable for the amine treatment zone to be located upstream of this additional compression zone.

Claims (10)

Contacting heavy hydrocarbon feedstock 212 in a fluidization reactor zone 214 with a hydrocarbon cracking catalyst to produce a hydrocarbon effluent 216 comprising various cracked hydrocarbon products, including light olefins; Forming a separator vapor stream (234) comprising a hydrocarbon-separation zone 222, the hydrocarbon effluent (216) at least one separator liquid stream 232 and a C ₃ to remove C ₃ + hydrocarbon containing from; Forming a; (254 process stream), the process stream containing the hydrocarbon material-contacting the separator vapor stream (234) from the absorption zone 236 as the first absorption solvent recovering the C ₃ + hydrocarbon therefrom and C _2; Stripping the C ₂ -hydrocarbon material from the one or more separator liquid streams 232 to form a C ₃ + hydrocarbon process stream 266 substantially free of C ₂ -hydrocarbons; C ₅ + hydrocarbon material C ₃ + separated from the hydrocarbon process stream C ₅ + first product process stream (274), and a second product process stream (272) comprising C ₃ and C ₄ hydrocarbons including hydrocarbons Forming a; And Introducing at least a first portion 242 of the first product stream 274 into the absorption zone 236 as at least part of the first absorption solvent. Catalytically cracking the heavy hydrocarbon feedstock to obtain the selected hydrocarbon fraction. The method of claim 1, wherein the contacting of the heavy hydrocarbon feedstock with the hydrocarbon cracking catalyst comprises: mixing the heavy hydrocarbon feedstock in a fluidization reactor zone with a mixed catalyst comprising a regeneration catalyst and a coked catalyst under hydrocarbon cracking reaction conditions; Contacting to produce a cracked stream containing hydrocarbon products, including light olefins, the catalyst comprising a first component comprising a molecular sieve having large porosity and a second component comprising a zeolite having a medium or less pore size; And a zeolite having a median pore size of less than 1.0 wt% of the catalyst composition. The method of claim 1, wherein the first portion (242) of the first product stream introduced into the absorption zone comprises most of the first absorption solvent therein. 2. The light fraction 282 of claim 1, comprising dividing at least a second portion 276 of the first product stream in a dividing wall separation column 280 to include a compound comprising 4 to 6 carbon atoms. And forming an intermediate fraction (284) comprising a compound comprising eight carbon atoms and a heavy fraction (286) comprising a compound comprising more than eight carbon atoms. The process of claim 1, wherein the second product process stream 272 is split in a C ₃ -C ₄ splitter 382 so that the first C ₃ -C ₄ splitter process stream 386 comprising primarily C ₃ hydrocarbons and mainly C Forming a second C ₃ -C ₄ splitter process stream (384) comprising ₄ hydrocarbons. The process of claim 5, wherein propylene is separated from the first C ₃ -C ₄ splitter process stream 386 to form a propylene process stream 392 comprising predominantly propylene and a propane process stream 394 comprising predominantly propane. Further comprising a step. The process of claim 1 wherein the second product process stream 272 comprising C ₃ and C ₄ hydrocarbons comprises a large amount of mercaptan, wherein the method selectively selects at least a portion of the mercaptan from at least a portion of the second process stream. It further comprises the step of removing. The process stream of claim 1, wherein the process stream 254 comprising C ₂ -hydrocarbon material further comprises a large amount of carbon dioxide, the method treating and treating a portion of the process stream comprising at least C ₂ -hydrocarbon material. Removing at least some of the amount of carbon dioxide. The process stream of claim 1, wherein the process stream 254 comprising C ₂ -hydrocarbon material further comprises a large amount of acetylene, the method comprising hydrogenating at least some of the amount of acetylene to form additional ethylene. Further comprising. A fluidized reactor in which heavy hydrocarbon feedstock 212 is contacted in a hydrocarbon cracking reaction condition with a mixed catalyst comprising a regeneration catalyst and a coking catalyst to produce a cracked effluent stream 216 comprising hydrocarbon products, including light olefins. Zone 214; Separation zone 222 to form a hydrocarbon group containing a separator vapor stream (234) at least one separator liquid stream 232 and a C ₃ containing the C ₃ + hydrocarbons to separate the cracked effluent stream; First it absorbs C ₃ + hydrocarbons from the separator vapor stream (234) of the absorption solvent C _2, including the ethylene-absorption zone 236 to form an absorption zone effluent stream (254) containing a hydrocarbon group; A stripper 262 that strips the C ₂ -hydrocarbon material from the separator liquid stream 232 to form a C ₃ + process stream 266 substantially free of C ₂ -hydrocarbons; C ₃ + C ₅ + to separate the hydrocarbons C ₅ + first product process stream (274), and a second product process stream (272) comprising C ₃ and C ₄ hydrocarbons including hydrocarbons from a hydrocarbon process stream A debutanizer 270 for forming; And A process line 242 that introduces at least a first portion of the first product stream 274 into the absorption zone 236 as most of the first absorption solvent. And a system for catalytically cracking the heavy hydrocarbon feedstock to obtain a selected hydrocarbon fraction.

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