Process to produce olefins from a catalytically cracked hydrocarbons stream
11267770 · 2022-03-08
Assignee
Inventors
Cpc classification
C10G11/05
CHEMISTRY; METALLURGY
C07C2529/40
CHEMISTRY; METALLURGY
C10G57/00
CHEMISTRY; METALLURGY
International classification
Abstract
Processes to produce olefins from a hydrocarbons stream obtained from a catalytic cracking unit are described. The process includes the integration of metathesis of C.sub.4 olefin process and a hydrocarbon catalytically cracking process to produce commercially valuable products (for example, C.sub.2-3 olefins and a C.sub.5+ gasoline hydrocarbons).
Claims
1. A process for producing olefins, the process comprising: (a) catalytically cracking a hydrocarbons stream consisting essentially of C.sub.5 and C.sub.6 hydrocarbons under conditions sufficient to form a cracked hydrocarbons stream comprising C.sub.5+ gasoline hydrocarbons, and gaseous C.sub.1 to C.sub.4 hydrocarbons; (b) fractionating the cracked hydrocarbons stream to produce at least (1) a first stream comprising C.sub.5+ gasoline hydrocarbons, and (2) a gaseous stream comprising the C.sub.1 to C.sub.4 hydrocarbons and residual C.sub.5+ hydrocarbons; (c) separating the gaseous stream into a gaseous mixed C.sub.4 hydrocarbons stream comprising n-butene and iso-butene, a gaseous C.sub.3 hydrocarbons stream, and a C.sub.5+ gasoline hydrocarbons stream; (d) contacting the gaseous mixed C.sub.4 hydrocarbons stream with a metathesis catalyst under conditions sufficient to produce a second gaseous stream comprising methane, ethylene and/or propylene, and a product stream comprising C.sub.5+ gasoline hydrocarbons; and (e) mixing the step (d) second gaseous stream with the step (c) gaseous C.sub.3 hydrocarbons stream.
2. The process of claim 1, further comprising mixing the C.sub.5+ gasoline hydrocarbons product stream with the C.sub.5+ gasoline hydrocarbons stream.
3. The process of claim 1, wherein separating the gaseous stream of step (c) comprises (i) producing a gaseous product stream comprising C1 and C2 hydrocarbons and a gaseous C3+ hydrocarbons stream comprising gaseous mixed C4 hydrocarbons, gaseous C3 hydrocarbons, and residual C5+ gasoline hydrocarbons; and (ii) separating the gaseous C3+ hydrocarbons stream into the gaseous C3 hydrocarbons stream, the gaseous mixed C4 hydrocarbons stream comprising n-butene and iso-butene, and a second C5+ gasoline hydrocarbons stream.
4. The process of claim 3, wherein the step (a) is performed in a moving catalyst bed.
5. The process of claim 3, wherein the catalytic cracking conditions comprise a temperature of 500-700° C. and a pressure of 0.05 MPa to 0.5 MPa.
6. The process of claim 3, wherein the catalytic cracking conditions comprise an acidic catalyst.
7. The process of claim 6, wherein the acidic catalyst comprises a large pore catalyst.
8. The process of claim 6, wherein acidic catalyst is a Y zeolite, an ultra-stable zeolite Y, or a mixture of both.
9. The process of claim 1, wherein the step (a) is performed in a catalytic cracker unit comprising a fixed catalyst bed, a moving catalyst bed, or fluidized catalyst bed.
10. The process of claim 1, wherein the catalytic cracking conditions comprise water.
11. The process of claim 1, wherein the step (d) metathesis conditions comprise a temperature of 200 to 550° C. and a pressure of 0.1 MPa to 2.0 MPa.
12. The process of claim 1, wherein the step (d) catalyst comprises a Column 6 metal or compound thereof, a noble metal or a compound thereof, or a combination thereof.
13. The process of claim 12, wherein the noble metal is rhenium.
14. The process of claim 1, wherein the step (d) catalyst is molybdenum.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Advantages of the present invention may become apparent to those skilled in the art with the benefit of the following detailed description and upon reference to the accompanying drawings.
(2)
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(5) While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings. The drawings may not be to scale.
DETAILED DESCRIPTION OF THE INVENTION
(6) An alternate process to produce C.sub.5+ gasoline hydrocarbons and methane, ethylene propylene from a gaseous stream produced from catalytically cracking of a C.sub.5-6 hydrocarbons stream has been discovered. The process successfully integrates a self-metathesis of C.sub.4 hydrocarbons process into a catalytically cracking of hydrocarbons process to produce more commercially valuable products from a mixed C.sub.4 hydrocarbons stream. The mixed C.sub.4 hydrocarbons stream used in this process can be produced from the aforementioned hydrocarbon catalytic cracking reaction, thereby providing a sustainable process for value added commercial products such as methane, ethylene, propylene and C.sub.5+ hydrocarbons.
(7) These and other non-limiting aspects of the present invention are discussed in further detail in the following sections with reference to the figures.
(8)
(9) In catalytic cracking unit 104, hydrocarbons stream 102 can be contacted with a hydrocracking catalyst under conditions suitable to produce a cracked hydrocarbons stream 106. Cracked hydrocarbons stream 106 can include C.sub.5+ gasoline hydrocarbons and gaseous C.sub.1 to C.sub.4 (C.sub.1-4) hydrocarbons. Catalytic cracking unit 102 can be any unit capable of cracking hydrocarbons into smaller molecular weight hydrocarbons (i.e., having a lower carbon number than hydrocarbons stream 102). Non-limiting examples of catalytic cracking units include a fixed catalyst bed catalytic cracker, a moving catalyst bed catalytic cracker, or fluidized catalyst bed catalytic cracker. In embodiments when a fluidized bed catalytic cracker is used, the hydrocarbons stream can flow through the catalyst bed in an upwardly or downwardly direction. The hydrocracking catalyst used for cracking the hydrocarbons stream can be an acidic catalyst. Acidic hydrocracking catalysts can include medium pore zeolites, large pore zeolites, and mixtures thereof. Non-limiting examples of medium pore zeolites can include ZSM-5, modified ZSM-5, spray dried ZSM-5, spray dried modified ZSM-5 and the like. Non-limiting examples of large pore zeolite catalyst can include a Y zeolite, an ultra-stable zeolite Y or a mixture of both. Zeolite catalysts can be obtained from commercial vendors such as Grace Catalysts Technologies (U.S.A.), Sigma-Aldrich® (U.S.A.), or Zeolyst International, (U.S.A.). Contacting conditions can include temperature, pressure, residence time and the like. Average temperatures in catalytic cracking unit 104 can range from 500° C. to 700° C., 525° C. to 625° C., 550° C. to 600° C., or any value or range there between. Average pressures in catalytic cracking unit 104 can range from 0.1 MPa to 2 MPa, or 0.5 to 1.5 MPa, or 0.75 to 1.0 MPa or any value or range there between. In embodiments when a fluidized bed catalytic cracker is used, a residence time of hydrocarbons stream 102 in the fixed catalyst bed can be 1 to 10 seconds, or 2 to 9 seconds, or 3 to 8 seconds, or any value or range there between. In a non-limiting example, a C.sub.5-6 hydrocarbons stream can be contacted with a zeolite catalyst and 25 wt. % steam in a fluidized bed reactor at a temperature of 650 to 690° C. to produce first hydrocarbons stream 106 and second hydrocarbons stream 108.
(10) Cracked hydrocarbons stream 106 can exit catalytic cracking unit 104 and enter fractionation unit 108. In fractionation unit 108, cracked hydrocarbons stream 106 can be separated into a plurality of streams that can include gaseous hydrocarbons stream 110 and C.sub.5+ gasoline hydrocarbons stream 112. In some embodiments, C.sub.5+ gasoline hydrocarbons stream 112 can be recycled to catalytic cracking unit 104. Other streams (not shown) that can be produced from fractionation unit 108 include light and heavy cycle oil, heavy hydrocarbons, coke, and the like. The other streams can be sold, transported, recycled, or sent to other processing units. Fractionation unit 108 can be any fractionation unit known in the art capable of separating a hydrocarbons stream. Fractionation unit can include one or more units, one or more distillation plates, etc.
(11) Gaseous hydrocarbons stream 110 can include from C.sub.1 to C.sub.4 hydrocarbons (e.g., methane, ethane, propane, butane, n-butene and iso-butene, propylene, ethane, or mixtures thereof) and residual C.sub.5+ gasoline hydrocarbons. Gaseous hydrocarbons stream 110 can enter gas separation unit 114 and be subjected to conditions to sufficient to hydrocarbons into gaseous C.sub.1-2 hydrocarbon steam 116, gaseous C.sub.3 hydrocarbons stream 118, gaseous mixed C.sub.4 hydrocarbons stream 120, and C.sub.5+ gasoline hydrocarbons stream 122. Gas separation unit 114 can include one or more cryogenic distillation units, membrane units, debutanizers, de-ethanizers, or any known separation unit capable of separating hydrocarbons. Gaseous C.sub.1-2 hydrocarbon steam 116 can include methane and/or C.sub.2 hydrocarbons, preferably ethylene and ethane. In some embodiments, gaseous C.sub.1-2 hydrocarbon steam contains none or substantially no methane. Gaseous C.sub.3 hydrocarbons stream can include propylene and propane. Gaseous C.sub.1-2 hydrocarbon steam 116 and/or gaseous C.sub.3 hydrocarbons stream can exit gaseous separation unit 114 and be stored, transported, sold, or provided to other processing units. Second C.sub.5+ gasoline hydrocarbons stream 122 can be stored, sold, transported to other processing units to be additized or further processed for use as gasoline, combined with other C.sub.5+ gasoline hydrocarbons streams, or combinations thereof. Mixed C.sub.4 hydrocarbons stream 120 can include C.sub.4 alkanes and C.sub.4 olefins. In some embodiments, mixed C.sub.4 hydrocarbons stream includes 0 to 100 vol. % n-butene and/or 0 to 100 vol. % iso-butene.
(12) Mixed C.sub.4 hydrocarbons stream 120 that includes n-butene and iso-butene (mixed butenes) can exit separation unit 114 and enter C.sub.4 metathesis unit 124. In C.sub.4 metathesis unit 124, mixed C.sub.4 hydrocarbons stream 120 can be contacted with a catalyst under conditions sufficient to produce gaseous product stream 126 and product stream 128 that includes C.sub.5+ gasoline hydrocarbons. Gaseous product stream 126 can includes C.sub.2-4 olefins (e.g., ethylene, propylene, butylene, or mixtures thereof) and methane. The conversion of mixed butenes to C.sub.5+ hydrocarbons can be shown in the following chemical equations:
1-C.sub.4H.sub.8+2-C.sub.4H.sub.8.fwdarw.C.sub.3H.sub.6+2-C.sub.5H.sub.10 (1)
Iso-C.sub.4H.sub.8+2-C.sub.4H.sub.8.fwdarw.C.sub.3H.sub.6+H.sub.3C—C(CH.sub.3)═C(H)—CH.sub.2—CH.sub.3 (2)
Iso-C.sub.4H.sub.8+1-C.sub.4H.sub.8.fwdarw.C.sub.2H.sub.4+H.sub.3C—C(CH.sub.3)═C(H)—CH.sub.2—CH.sub.3 (3)
1-C.sub.4H.sub.8+1-C.sub.4H.sub.8.fwdarw.C.sub.2H.sub.4+3-C.sub.6H.sub.12 (4).
Other reactions such as oligomerization, cracking, self-metathesis of isobutylene and isomerization of normal butenes can also occur in C.sub.4 metathesis unit 124. Conditions sufficient to convert the n-butene and iso-butene hydrocarbons into higher molecular weight (i.e., higher carbon number) compounds include a temperature of 200° C. to 550° C., 250° C. to 500° C., 300° C. to 450° C., or 400° C. to 450° C. or any value or range there between and a pressure of 0.1 MPa to 2.0 MPa, 0.5 MPa to 1.5 MPa, or any value or range there between. The catalyst in metathesis unit 116 can be any catalyst capable of catalyzing a C.sub.4 metathesis reaction. The metathesis catalyst can include a metal from Column 6 of the Periodic Table (e.g., W or Mo) or compounds thereof and/or a noble metal (e.g., Rh) or compounds thereof. In a preferred aspect, the catalyst can be W/Rh or Mo/Rh. Non-limiting examples of metathesis catalysts are described in U.S. Pat. No. 6,683,019 to Gartside et al., or can be obtained from commercial vendors such as Aperion synthesis (Poland) or Sigma-Aldrich® (U.S.A.).
(13) Referring to
(14) Referring to
(15) Referring to
EXAMPLES
(16) The present invention will be described in greater detail by way of specific examples. The following examples are offered for illustrative purposes only, and are not intended to limit the invention in any manner. Those of skill in the art will readily recognize a variety of noncritical parameters which can be changed or modified to yield essentially the same results.
Example 1
Catalytically Cracking of a C.SUB.5-6 .Hydrocarbons Stream
(17) A zeolite catalyst was tested for light naphtha cracking using a fluidized bed pilot plant on a single pass. The light straight run naphtha (LSRN) composition is listed in Table 1. Reactor temperature, steam/feed ratio, and residence time are listed in Table 2. Recycle of C.sub.5+ gasoline hydrocarbons stream to the reactor would increase the conversion and yields of light olefins. As can be seen the yields of C.sub.4 is around 11.3 wt. %.
(18) TABLE-US-00001 TABLE 1 Feed (LSRN) Component Wt. % n-pentane 28.8 iso-pentane 11.8 cyclopentane 1.9 n-hexane 24.5 iso-hexane 26.9 cyclohexane 4.6 benzene 1.3 C.sub.7s 0.3 Sum 100
(19) TABLE-US-00002 TABLE 2 Reaction conditions and Product yields Temperature (° C.) 670 Steam/Feed (wt. %) 25 Residence time (seconds) 5 C.sub.5+ gasoline hydrocarbons, wt. % 34.6 Light cycle oil (LCO) + bottoms, wt. % 1.1 C.sub.1-3 alkanes + H.sub.2, wt. % 23 C.sub.2-4 Olefins, wt. % 30 C.sub.4 total (alkanes and olefins), wt. % 11.3 Iso-C.sub.4 olefins, wt. % 3.7 n-C.sub.4 olefins, wt. % 5.4%
Example 2
Simulation of C.SUB.4 .Metathesis Reaction
(20) The self-metathesis reactions of mixed butenes including isobutenes were simulated. The simulation used more than eight reactions. The product distribution is shown in Table 3. It was determined that the yield of C.sub.1-3 olefins was about 23 wt. %.
(21) TABLE-US-00003 TABLE 3 Component Feed (wt. %) Product (wt. %) Ethylene 0.0 3.02 propylene 0.00 20.02 1-C.sub.4 olefin 48.61 5.68 Iso-C.sub.4 olefin 32.23 9.67 butane 19.16 19.15 Total C.sub.5 olefins 0.00 33.38 C.sub.6 olefins 0.00 9.07
Example 3
Integration of Example 1 with Example 2-Catalytic Cracking and C.SUB.4 .Metathesis
(22) The products from the integration of the catalytic cracking process of Example 1 with the C.sub.4 metathesis reaction of Example 2 are shown in Table 4. Inventors:
(23) TABLE-US-00004 TABLE 4 Integration Results C.sub.5+ gasoline hydrocarbons 39.4 Light cycle oil (LCO) + bottoms, wt. % 1.1 C.sub.1-3 alkanes and H.sub.2 23.0 C.sub.2-4 olefins, wt. % 32.6 C.sub.4 total 3.9