Process for paraffin cracking

Abstract

Processes for cracking petroleum products such as paraffins and olefins to produce light olefins with increased olefin yield are described. The paraffin-rich feed stream is cracked in an olefin cracking reactor. Light olefins are removed from the olefin cracking effluent stream. A C4-C5 stream from the olefin cracking reactor effluent is cracked in a paraffin cracking reactor, and the paraffin cracking reactor effluent is passed to the olefin cracking reactor.

Description

[0001] Priority Claim

[0002] This application claims priority to U.S. Non - Provisional Patent Application Serial No. 18 / 394,291, filed on December 22, 2023, which claims priority to U.S. Provisional Patent Application Serial No. 63 / 436,069, filed on December 29, 2022, the entire contents of which are incorporated herein by reference. Background Art

[0003] Light olefins are used as feedstocks for producing a variety of chemicals. Light olefins, mainly ethylene and propylene, are used as feedstocks in the production of plastics and petrochemicals. Typically, light olefins are produced by steam cracking or catalytic cracking. However, the limitations associated with conventional methods of preparing light olefins have led to a situation where the demand for light olefins exceeds the supply.

[0004] Integrating the olefin cracking process (OCP) into refining and petrochemical complexes has led to an increase in the paraffin content of the feed streams. These feed streams have a relatively low olefin content, and thus the recycle streams have an even lower olefin content.

[0005] There is a need for improved methods for producing light olefins. Brief Description of the Drawings

[0006] Figure 1 Exemplary methods provided herein are schematically illustrated.

[0007] Figure 2 Exemplary methods provided herein are schematically illustrated.

[0008] Figure 3 Exemplary methods provided herein are schematically illustrated.

[0009] Figure 4 Exemplary methods provided herein are schematically illustrated.

[0010] The drawings shown herein are illustrative of exemplary embodiments provided herein and are not intended to limit the scope of the invention as covered by the claims.

[0011] Like reference symbols in the various drawings represent like elements. Detailed Description

[0012] The present invention relates to a process for producing light olefins such as ethylene and propylene. The process uses a staged OCP reactor to increase light olefin yield by cracking a recycle stream rich in paraffins in a first stage and then sending the first stage effluent together with a fresh paraffin-rich feed to a second stage. Due to the low olefin content of the recycle, the paraffin cracking in the first stage should be greater. Then the first stage effluent and the fresh feed are preferentially cracked in the second stage. The process improves the conversion of olefin feed to lower hydrocarbons at an improved weight hourly space velocity (WHSV) to reduce overcracking of the feed and subsequent formation of excessive heavy materials. The process also offers cost effectiveness in terms of lower capital and operating expenditures.

[0013] The olefin cracking process (OCP) cracks paraffins and olefins to produce light olefins such as ethylene and propylene. The olefin feed contains diolefins and monoolefins. The recycle stream recovered from the separation process after the olefin cracking reactor is lean in light olefins. The olefin-lean stream has a higher paraffin content than the fresh feed (e.g., paraffin-containing feedstock or olefin-containing feed or a combination thereof) and the mixed feed. The depleted olefin vapor is suitable for cracking under more severe conditions to convert paraffins into olefins, thereby increasing the total olefin yield of the process.

[0014] The feed stream contains a mixture of C 4+ olefins and paraffins greater than or equal to 30 wt%. The feed stream can contain cracked petroleum products derived from petroleum sources such as heavy petroleum feedstocks, e.g., feedstocks containing vacuum gas oil or topped crude.

[0015] The process can optionally include selectively hydrogenating an olefin-containing stream to saturate diolefins and acetylenes. The selective hydrogenation will result in 50% to 99% of the diolefins and acetylenes being converted to olefins. The saturation step can be applied to the fresh feed stream or the recycle stream in the OCP process, or the mixed fresh feed and recycle stream can be treated in a single selective hydrogenation step. Typical selective hydrogenation conditions include a temperature between 40 °C and 140 °C and a pressure in the range of 1.4 MPa(a) to 4.1 MPa(a). In some embodiments, the hydrogenation catalyst can comprise nickel, palladium, platinum, silver, tungsten disulfide, colloidal molybdenum on activated carbon or molybdenum trioxide or a combination thereof.

[0016] The paraffin-rich feed stream can be heated before entering the olefin cracking reactor, and / or the paraffin-rich recycle stream can be heated before entering the paraffin-rich reactor, and / or the paraffin cracking reactor effluent stream can be heated before entering the olefin cracking reactor. The temperature of one or more of these streams can be raised to the desired inlet temperature of the reactor involved. Any suitable heater can be used. Suitable heaters include, but are not limited to, for example, heat exchangers, flame heaters, electric heaters, or combinations thereof.

[0017] In some embodiments, the paraffin-rich feed stream and the paraffin-rich recycle stream can be heated with separate flame heaters or electric feed heaters. Alternatively, a single flame heater or electric feed heater with separate tube passes can be used to heat the paraffin-rich feed stream and the paraffin-rich recycle stream.

[0018] In some embodiments, the paraffin-rich feed stream and / or the paraffin-rich recycle stream can be heat-exchanged with the olefin reactor effluent stream. In some embodiments, the heat exchanger can be used in combination with a flame heater or an electric heater.

[0019] In some embodiments, the paraffin cracking reactor effluent stream can be mixed with the paraffin-rich feed stream, and the mixed stream can be heated in a heater and / or a heat exchanger before being sent to the olefin cracking reactor.

[0020] The paraffin cracking reactor effluent stream and the paraffin-rich feed stream are sent to the olefin cracking reactor either separately or as a mixed stream. When the streams are sent separately, they can be introduced at different locations in the olefin cracking reactor.

[0021] The paraffin-rich feed stream and the paraffin-rich recycle stream are sent to the olefin cracking reactor. The olefin cracking reactor inlet temperature is typically in the range of 560 °C to 620 °C or 570 °C to 590 °C. C 4+ Olefin cracking forms light olefins (i.e., ethylene and propylene). The reaction is endothermic, and the reactor outlet temperature is typically in the range of 490 °C to 550 °C or 520 °C to 540 °C. The pressure at the olefin cracking reactor outlet is typically in the range of 20 kPa(g) to 140 kPa(g).

[0022] The olefin reactor effluent stream contains C4 to C 10 olefins and 10 wt% or more of C4 to C8 paraffins.

[0023] The olefin cracking reactor effluent stream can be separated into one or more streams. In some embodiments, it is separated into an olefin product stream comprising ethylene and propylene and any hydrogen, and a C4-C5 stream comprising butane and pentane. The C4-C5 stream will also contain some C4-C5 olefins. In some embodiments, there may also be a heavy stream comprising C 6+ hydrocarbons and aromatic compounds. Other separations can be utilized as are known to those skilled in the art.

[0024] In some embodiments, the olefin reactor effluent stream is compressed prior to separation. The olefin reactor effluent stream can be compressed to a pressure in the range of 1.4 MPa(a) to 2.8 MPa(a).

[0025] The C4-C5 stream can be split into two parts, namely a recycle stream rich in paraffins and a purge stream. In some embodiments, the purge stream is removed to control the olefin content in the mixed feed (the paraffin-rich feed stream and the paraffin-rich recycle stream). In some embodiments, the paraffin-rich recycle stream is adjusted to achieve 40 wt% - 60 wt% olefins in the mixed feed to the reactor. In some embodiments, 30 wt% to 80 wt% of the C 4-5 paraffins in the olefin reactor effluent are in the paraffin-rich recycle stream and 20 wt% to 70 wt% are in the purge stream.

[0026] The paraffin-rich recycle stream depleted in olefins can be heated as described above and sent to a paraffin cracking reactor where the paraffins are cracked. Since there is no (or a reduced amount of) olefins in the paraffin cracking reactor, this arrangement provides enhanced paraffin cracking.

[0027] The paraffin cracking reactor typically operates in a temperature range of 490 °C to 620 °C and a pressure range of 135 kPa(a) to 1050 kPa(a).

[0028] The paraffin cracking reactor effluent contains ethylene and propylene converted from the paraffins in the paraffin-rich recycle stream, C4-C 10 olefins, and a reduced level of paraffins compared to the paraffin-rich recycle stream entering the paraffin cracking reactor.

[0029] The paraffin cracking reactor effluent is sent to an olefin cracking reactor which maximizes the conversion of olefins to light olefins. 10 wt% to 60 wt% of the olefins are converted to light olefins in the olefin cracking reactor.

[0030] The catalysts in the olefin cracking reactor and the paraffin cracking reactor can be the same, or they can be different.

[0031] Any suitable olefin cracking catalyst can be used. Suitable olefin cracking catalysts include, but are not limited to, zeolites, alumina and silica, faujasite, or combinations thereof. In some embodiments, the olefin cracking catalyst comprises a zeolite that comprises a silica rock having a silica to alumina ratio greater than 200, the zeolite being steam treated, pickled, and loaded with an alkaline earth metal selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), or mixtures thereof. In some embodiments, the alkaline earth metal loading ranges from 0.1 weight (wt)% to 2 wt% of the catalyst. The catalyst may optionally also comprise a binder. In some embodiments, the binder comprises from 10 wt% to 75 wt% of the total weight of the catalyst. In some embodiments, the catalyst is calcined.

[0032] In some embodiments, the catalyst in the olefin cracking reactor or the paraffin cracking reactor or both comprises a silica rock having a silica to alumina ratio greater than 200, and wherein the silica rock is steam treated, pickled, and loaded with an alkaline earth metal.

[0033] In some embodiments, the catalyst in the olefin cracking reactor comprises a catalyst comprising a silica rock having a silica to alumina ratio greater than or equal to 200, and wherein the catalyst in the paraffin cracking reactor comprises an acidic catalyst.

[0034] Any suitable paraffin cracking catalyst can be used. Suitable paraffin cracking catalysts can include any of the above olefin cracking catalysts. Additionally, suitable paraffin cracking catalysts include acidic catalysts. Suitable acidic catalysts include, but are not limited to, zeolites having a structure of one of the following classes: MFI, MEL, ITH, IMF, TUN, FER, BEA, FAU, BPH, MEI, MSE, MWW, UZM-8, MOR, OFF, MTW, TON, MTT, AFO, ATO, and AEL. The three-letter codes indicating zeolite classes are as defined by the Structure Commission of the International Zeolite Association and are maintained at http: / / www.iza-structure.org / databases.

[0035] In some embodiments, the paraffin cracking catalyst comprises a silica rock having a silica to alumina ratio less than 200.

[0036] The paraffin cracking reactor and the olefin cracking reactor can be located in separate vessels. Alternatively, they can be located as separate beds in a single vessel.

[0037] Figure 1 An embodiment of a method 100 for producing light olefins is shown. A paraffin-rich feed stream 105 is heated in a first feed heater 110. The heated paraffin-rich feed stream 115 is sent to an olefin cracking reactor 120, where the olefins in the paraffin-rich feed stream 105 are cracked into light olefins.

[0038] The olefin cracking reactor effluent stream 125 is transferred to a separation zone 130. The olefin cracking reactor effluent stream 125 can optionally be compressed before separation. The separation zone 130 includes one or more fractionation towers, where the olefin cracking reactor effluent stream 125 is separated into an olefin product stream 135 containing ethylene and propylene, a C4-C5 stream 140 containing butane and pentane, and a heavy stream 145 containing C 6+ hydrocarbons.

[0039] The olefin product stream 135 is recovered, and the heavy stream 145 can be purged.

[0040] The C4-C5 stream 140 is split into a paraffin-rich recycle stream 150 and a purge stream 155.

[0041] The paraffin-rich recycle stream 150 is sent to a second feed heater 160, where the paraffin-rich recycle stream is heated. The heated paraffin-rich recycle stream 165 is sent to a paraffin cracking reactor 170, where the paraffins are cracked into olefins.

[0042] The paraffin cracking reactor effluent stream 175 is mixed with the heated paraffin-rich feed stream 115 to form a mixed stream 180. The mixed stream 180 is sent to the olefin cracking reactor 120.

[0043] Alternatively, the first feed heater 110 and the second feed heater 160 can be replaced by a single feed heater having separate tube passes (not shown).

[0044] Figure 2 An alternative embodiment of an olefin cracking method 200 is shown. In this embodiment, a selective hydrogenation reactor 205 and a first heat exchanger 210 and a second heat exchanger 215 are added.

[0045] The paraffin-rich feed stream 105 is selectively hydrogenated in the selective hydrogenation reactor 205. The hydrogenated feed stream 220 is heated in the first heat exchanger 210 by heat exchange with the olefin cracking reactor effluent stream 125 to form a partially heated hydrogenated feed stream 225 and a first partially cooled olefin cracking reactor effluent stream 230.

[0046] A partially heated hydrogenated feed stream 225 is sent to a first feed heater 110 to form a heated paraffin-rich feed stream 115. The heated paraffin-rich feed stream 115 is sent to an olefin cracking reactor 120, where the olefins in the paraffin-rich feed stream 105 are cracked into light olefins.

[0047] A portion 235 of the olefin cracking reactor effluent stream 125 is sent to a second heat exchanger 215, where this portion exchanges heat with the paraffin-rich recycle stream 150 to form a partially heated paraffin-rich recycle stream 240 and a second partially cooled olefin reactor effluent stream 245.

[0048] The first partially cooled olefin reactor effluent stream 230 and the second partially cooled olefin reactor effluent stream 245 are mixed into a mixed cooled olefin reactor effluent stream 250.

[0049] The mixed cooled olefin reactor effluent stream 250 is sent to a separation zone 130. The olefin cracking reactor effluent stream 125 may optionally be compressed before separation. The separation zone 130 includes one or more fractionation towers, where the olefin cracking reactor effluent stream 125 is separated into an olefin product stream 135 containing ethylene and propylene, a C4-C5 stream 140 containing butane and pentane, and a heavy stream 145 containing C 6+ hydrocarbons.

[0050] The olefin product stream 135 is recovered, and the heavy stream 145 may be purged.

[0051] The C4-C5 stream 140 is split into a paraffin-rich recycle stream 150 and a purge stream 155.

[0052] The partially heated paraffin-rich recycle stream 240 is sent to a second feed heater 160, where the partially heated paraffin-rich recycle stream is heated. The heated paraffin-rich recycle stream 165 is sent to a paraffin cracking reactor 170, where the paraffins are cracked into olefins.

[0053] The paraffin cracking reactor effluent stream 175 is mixed with the heated paraffin-rich feed stream 115 to form a mixed stream 180. The mixed stream 180 is sent to the olefin cracking reactor 120.

[0054] Optionally, the first feed heater 110 and the second feed heater 160 may be replaced by a single feed heater having separate tube passes (not shown).

[0055] Figure 3 An embodiment of a method 300 for producing light olefins is shown. Method 300 is similar to Figure 1Method 100 in [reference]. In this method, instead of directly sending the paraffin cracking reactor effluent stream 175 to the olefin cracking reactor 120, it is mixed with the paraffin-rich feed stream 105 to form a mixed stream 305. The mixed stream 305 is sent to the first feed heater 110, and the heated mixed stream 310 is sent to the olefin cracking reactor 120. This provides additional heating for the paraffin cracking reactor effluent stream 175. By achieving a high inlet temperature of the paraffin cracking reactor effluent stream 175 to the olefin cracking reactor 120, the additional heating increases the conversion rate in the olefin cracking reactor 120. Alternatively, the temperature of the paraffin cracking reactor effluent stream 175 can be increased in a third feed reactor (not shown).

[0056] Figure 4 An embodiment of a method 400 for producing light olefins is shown. Method 400 is similar to Figure 2 Method 200 in [reference]. In this method, instead of directly sending the paraffin cracking reactor effluent stream 175 to the olefin cracking reactor 120, it is mixed with a partially heated hydrogenation feed stream 225 to form a mixed stream 305. The mixed stream 305 is sent to the first feed heater 110, and the heated mixed stream 310 is sent to the olefin cracking reactor 120. This increases the conversion rate in the olefin cracking reactor 120 by achieving a high inlet temperature of the paraffin cracking reactor effluent stream 175 to the olefin cracking reactor 120. Alternatively, the temperature of the paraffin cracking reactor effluent stream 175 can be increased in a third feed reactor (not shown).

[0057] The present invention will be further described with reference to the embodiments described herein; however, it should be understood that the present invention is not limited to such embodiments.

[0058] Example

[0059] Example 1

[0060] In Example 1, in the presence of a silicalite catalyst, a blend of 60 wt% isobutane (i-C4) and 40 wt% isobutene (iC4=) was subjected to catalytic cracking. The catalyst contains crystalline silicalite zeolite, where the silicalite has a silica-to-alumina ratio greater than 400, by steam treatment and pickling, followed by drying and calcination. The feedstock was passed over the catalyst at a temperature of 580 °C, a weight hourly space velocity (WHSV) of 6 h -1 and a total hydrocarbon pressure of 10 psig. The conversion rate, expressed as the average olefin conversion rate and paraffin conversion rate over the period when the test reached steady state, is given in Table 1. In addition, Table 1 includes the amounts of ethylene and propylene (wt%) in the reaction effluent.

[0061] Conversion rate of olefins = 100 * (olefins in feed - olefins in effluent) / olefins in feed Conversion rate of paraffins = 100 * (paraffins in feed - paraffins in effluent) / paraffins in feed.

[0062] Table 1

[0063]

[0064] Example 2

[0065] Example 1 was repeated using light coker naphtha as the feedstock, the composition of which is given in Table 2. All test conditions were the same as in Example 1. As shown in Table 1, although the olefin conversion rate was comparable to that in Example 1, being 64 wt% vs. 67 wt%, the paraffin conversion rate was significantly higher, i.e., 33.6 wt% vs. 2.4 wt%. Compared with shorter-chain paraffins (isobutane), the C5-C6 longer-chain paraffins present in light coker naphtha (Table 2) were more prone to cracking over the cracking catalyst.

[0066] Supporting the high paraffin conversion rate observed with a light coker naphtha feed having 44 wt% C4-C7 paraffins was the very high reaction endotherm recorded during the testing of Example 2, i.e., 24 °C, compared to an endotherm of only 14 °C in Example 1 using a feed having 60% isobutane, which is also included in Table 1. As mentioned, isobutane, and generally shorter-chain paraffins, are more difficult to crack.

[0067] Table 2

[0068] Composition wt% C4P 2.010 C4O 1.391 C4DO 0.033 C5P 20.637 C5O 20.713 C5DO 1.122 C5N 1.357 C6P 20.798 C6O 24.183 C6DO 0.396 C6N 2.822 C7P 0.662 C7O 1.731 C7DO 0.364 C7N 0.055 A6 0.428 A7 0.015 Heavier compound 1.282

[0069] Where P = paraffin, O = olefin; N = naphthene; DO = diolefin; A = aromatic compound

[0070] Multiple embodiments of the present invention have been described. However, it should be understood that various modifications can be made without departing from the essence and scope of the present invention. Therefore, other embodiments are within the scope of the following claims.

[0071] The term "column" means one or more distillation columns for separating one or more components having different volatilities. Each column can include a condenser at the top of the column to condense the overhead vapor and reflux a portion of the overhead stream back to the top of the column.

[0072] The term "stream" can contain various hydrocarbon molecules and other substances.

[0073] The term "heavies" means heavy hydrocarbons such as C 9+hydrocarbons and may also include unreacted oil containing C 9+ hydrocarbons in the reactor or reaction chamber.

[0074] As used in this specification and the claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0075] Unless specifically stated or obvious from the context, as used herein, the term "or" is understood to be inclusive and encompasses both "or" and "and."

[0076] Unless specifically stated or obvious from the context, as used herein, the term "about" is understood to be within the normal tolerances in the art, e.g., within 2 standard deviations of the mean. (The use of the term "about") can be understood to be within 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the specified value. Unless the context clearly dictates otherwise, all numerical values provided herein are modified by the term "about."

[0077] Unless specifically stated or obvious from the context, as used herein, the terms "substantially all," "substantially most of," "substantially all of," or "most of" encompass at least 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 99.5% or more of the reference amount of the composition.

[0078] This specific embodiment is merely exemplary in nature and is not intended to limit the various embodiments or their applications and uses. The drawings have been simplified by removing various devices or apparatuses commonly used in the OCP method for this nature, including but not limited to internals of the vessel, temperature and pressure control systems, connections to a computer, and the computer (or other storage device) for controlling the system for implementing the methods provided herein, flow control valves, recirculation pumps, etc., which are not particularly required to illustrate the performance of the exemplary methods provided herein. The illustration of the exemplary methods in the drawings provided herein is not intended to limit the invention to the specific embodiments described or depicted herein.

[0079] Any pipeline, conduit, unit, device, container, surrounding environment, area for practicing a method as provided herein may be equipped with one or more monitoring components, including sensors, measuring devices, data capture devices or data transmission devices. Signals, method or status measurements, and data from the monitoring components can be used to monitor conditions in, around, and related to the method equipment. Signals, measurements, and / or data generated or recorded by the monitoring components can be collected, processed, and / or transmitted through one or more networks or connections, which can be private or public, general or dedicated, direct or indirect, wired or wireless, encrypted or unencrypted, and / or combinations thereof. In an alternative embodiment, sensors are present on all pipelines or flows such that corresponding parameters can be monitored and / or controlled as desired or needed.

[0080] Signals, measurements, and / or data generated or recorded by the monitoring components can be transmitted to one or more computing devices or systems. In an alternative embodiment, the methods provided herein include using a computing device or system, which can include at least one processor and a memory storing computer-readable instructions that, when executed by the at least one processor, cause the one or more computing devices to perform a method that can include one or more steps. For example, one or more computing devices can be configured to receive data related to at least one device associated with the method from one or more monitoring components. One or more computing devices or systems can be configured to analyze the data. Based on the data analysis, one or more computing devices or systems can be configured to determine one or more recommended adjustments to one or more parameters of one or more of the methods described herein. One or more computing devices or systems can be configured to transmit encrypted or unencrypted data that includes one or more recommended adjustments to one or more parameters of one or more of the methods described herein.

[0081] Details of one or more exemplary embodiments of the invention are set forth in the accompanying drawings and the foregoing description. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

[0082] The entire contents of each patent, patent application, publication, and document cited herein are hereby incorporated by reference. The citation of the foregoing patents, patent applications, publications, and documents is not an admission that any of the foregoing is relevant prior art, nor does it constitute any admission as to the content or date of these publications or documents. The mere incorporation of these documents by reference should not be construed as an assertion or admission that any part of the content of any document is considered necessary material to meet the statutory disclosure requirements of any national or regional patent application. Nevertheless, the right is reserved to rely on any such document, where appropriate, to provide material that is considered necessary by the examining authority or court for the subject matter claimed.

[0083] Modifications may be made to the foregoing without departing from the basic aspects of the present invention. Although the present invention has been described in detail with reference to one or more specific embodiments, those of ordinary skill in the art will recognize that changes may be made to the embodiments specifically disclosed herein, and such modifications and improvements are still within the scope and spirit of the present invention. The present invention, as appropriately and illustratively described herein, may be practiced without any element not specifically disclosed herein. Thus, for example, in each instance herein, any one of the terms "comprising," "consisting essentially of," and "consisting of" may be replaced with any one of the other two terms. Accordingly, the terms and expressions employed have been used as terms of description rather than of limitation, and do not exclude equivalents or portions thereof of the features shown and described, and it is recognized that various modifications are possible within the scope of the present invention. Embodiments of the present invention are set forth in the following claims.

[0084] Specific embodiments

[0085] While the following is described in conjunction with specific embodiments, it should be understood that the description is intended to illustrate rather than limit the scope of the foregoing description and the appended claims.

[0086] A first embodiment of the present invention is a method that includes cracking a feed stream comprising C 4+ olefins and paraffins in an olefin cracking reactor in a cracking zone to form an olefin cracking reactor effluent stream, wherein the olefin reactor effluent stream comprises ethylene, propylene, C4 to C 10 olefins, and 10 wt% or more of C4 to C8 paraffins, separating the olefin reactor effluent stream into at least an olefin product stream comprising ethylene and propylene, and a C4-C5 stream comprising butane and pentane; dividing the C4-C5 stream into a paraffin-rich recycle stream and a purge stream; cracking the paraffin-rich recycle stream in the paraffin cracking reactor in the cracking zone to form a paraffin reactor effluent stream, the paraffin reactor effluent stream comprising ethylene and propylene, C4-C 10Olefins and alkanes at a reduced level compared to the alkane-rich recycle stream; and cracking the alkane reactor effluent stream in the olefin cracking reactor; whereby the olefin reactor effluent stream contains a greater level of ethylene and propylene than the olefin reactor effluent stream from an olefin cracking zone without an alkane cracking reactor. One embodiment of the present invention is one, any, or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, further comprising heating the feed stream before cracking the feed stream; or heating the alkane-rich recycle stream before cracking the alkane-rich recycle stream in the alkane cracking reactor; or both. One embodiment of the present invention is one, any, or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, wherein the feed stream or the alkane-rich recycle stream or both are heated in a feed heater or by heat exchange with the olefin reactor effluent stream or by both of the above methods. One embodiment of the present invention is one, any, or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, wherein the feed stream and the alkane-rich recycle stream are heated in a single feed heater having separate tubes. One embodiment of the present invention is one, any, or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, further comprising mixing the feed stream and the olefin reactor effluent stream to form a mixed stream; heating the mixed stream before cracking the feed stream and the alkane reactor effluent stream in the olefin cracking reactor, wherein cracking the feed stream and the alkane reactor effluent stream includes cracking the mixed stream. One embodiment of the present invention is one, any, or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, further comprising compressing the olefin reactor effluent stream before separating the olefin reactor effluent stream. One embodiment of the present invention is one, any, or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, wherein the olefin cracking reactor and the alkane cracking reactor are separate beds in a single reaction vessel. One embodiment of the present invention is one, any, or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, wherein the olefin cracking reactor and the alkane cracking reactor are in separate vessels. One embodiment of the present invention is one, any, or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, wherein the feed stream and the alkane reactor effluent stream are fed at different locations in a single reaction vessel. One embodiment of the present invention is one, any, or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, wherein the olefin cracking reactor and the alkane cracking reactor contain the same catalyst.One embodiment of the present invention is one, any, or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, wherein the olefin cracking reactor and the paraffin cracking reactor contain different catalysts. One embodiment of the present invention is one, any, or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, wherein the olefin cracking reactor or the paraffin cracking reactor or both contain a catalyst, and the catalyst contains silicalite having a silica to alumina ratio greater than 200, and wherein the silicalite is steam-treated, pickled, and loaded with an alkaline earth metal. One embodiment of the present invention is one, any, or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, wherein the olefin cracking reactor contains a catalyst, the catalyst contains silicalite having a silica to alumina ratio greater than 200, and wherein the paraffin cracking reactor contains a catalyst including an acidic catalyst. One embodiment of the present invention is one, any, or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, wherein the operating temperature of the olefin cracking reactor ranges from 560 °C to 620 °C. One embodiment of the present invention is one, any, or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, wherein the operating temperature of the paraffin cracking reactor ranges from 490 °C to 620 °C. One embodiment of the present invention is one, any, or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, further comprising selectively hydrogenating the feed stream before feeding the paraffin-rich feed stream to the olefin cracking reactor.

[0087] A second embodiment of the present invention is a method comprising cracking a feed stream comprising C 4+ olefins and paraffins in an olefin cracking reactor in a cracking zone to form an olefin cracking reactor effluent stream, wherein the olefin reactor effluent stream comprises ethylene, propylene, C4 to C 10 olefins and 10 wt% or more of C4 to C8 paraffins, compressing the olefin reactor effluent stream; separating the compressed olefin reactor effluent stream into at least an olefin product stream comprising ethylene and propylene, a C4-C5 stream comprising butane and pentane, and a heavy stream comprising C 6+ hydrocarbons; dividing the C4-C5 stream into a paraffin-rich recycle stream and a purge stream; cracking the paraffin-rich recycle stream in the paraffin cracking reactor in the cracking zone to form a paraffin reactor effluent stream, the paraffin reactor effluent stream comprising ethylene and propylene, C4-C 10Olefins and paraffins at a reduced level compared to the paraffin-rich recycle stream; cracking the paraffin reactor effluent stream in the olefin cracking reactor; and heating the feed stream before cracking the feed stream, or heating the paraffin-rich recycle stream before cracking the paraffin-rich recycle stream in the paraffin cracking reactor, or both; whereby the olefin reactor effluent stream contains a greater level of ethylene and propylene than the olefin reactor effluent stream from an olefin cracking zone without a paraffin cracking reactor. One embodiment of the present invention is one, any, or all of the previous embodiments in this paragraph to the second embodiment in this paragraph, wherein the feed stream and the paraffin reactor effluent stream are fed at different locations in a single reaction vessel. One embodiment of the present invention is one, any, or all of the previous embodiments in this paragraph to the second embodiment in this paragraph, wherein the olefin cracking reactor or the paraffin cracking reactor or both contain a catalyst, and the catalyst contains silica rock having a silica-to-alumina ratio greater than 200, and wherein the silica rock is steam-treated, pickled, and loaded with an alkaline earth metal. One embodiment of the present invention is one, any, or all of the previous embodiments in this paragraph to the second embodiment in this paragraph, wherein the olefin cracking reactor contains a catalyst, the catalyst contains silica rock having a silica-to-alumina ratio greater than 200, and wherein the paraffin cracking reactor contains a catalyst including an acidic catalyst.

[0088] Although no further detailed description is provided, it is believed that those skilled in the art can utilize the present invention to the greatest extent by using the foregoing description and can easily determine the basic features of the present invention without departing from the essence and scope of the present invention to make various changes and modifications thereto and adapt it to various uses and conditions. Accordingly, the foregoing preferred specific embodiments should be construed as merely illustrative and in no way limiting the remainder of the disclosure, and are intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

[0089] In the foregoing, all temperatures are shown in degrees Celsius, and all parts and percentages are by weight unless otherwise indicated.

Claims

1. A method, the method comprising: In the olefin cracking reactor (120) in the cracking zone, cracking a feed stream (105) containing C 4+ olefins and paraffins to form an olefin cracking reactor effluent stream (125), wherein the olefin reactor effluent stream (125) contains ethylene, propylene, C4 to C 10 olefins and 10 wt% or more of C4 to C8 paraffins: Separating the olefin reactor effluent stream (125) into at least an olefin product stream (135) comprising ethylene and propylene and a C4-C5 stream (140) comprising butane and pentane; Dividing the C4-C5 stream (140) into a paraffin-rich recycle stream (150) and a purge stream (155); Crack the paraffin-rich recycle stream (150) in the paraffin cracking reactor (170) in the cracking zone to form a paraffin reactor effluent stream (175) that contains ethylene and propylene, C4-C 10 olefins and has a reduced level of paraffins compared to the paraffin-rich recycle stream (150); And Cracking the paraffin reactor effluent stream (175) in the olefin cracking reactor (120); Whereby the olefin reactor effluent stream (125) contains a higher level of ethylene and propylene than the olefin reactor effluent stream from an olefin cracking zone without a paraffin cracking reactor.

2. The method according to claim 1, the method further comprising: Heating the feed stream (105) before cracking the feed stream (105); Or Heating the paraffin-rich recycle stream (150) before cracking the paraffin-rich recycle stream (125) in the paraffin cracking reactor (170); or Both.

3. The method according to any one of claims 1 to 2, the method further comprising: Mixing the feed stream (105) and the paraffin reactor effluent stream (175) to form a mixed stream (305); And Heating the mixed stream (305) before cracking the feed stream (105) and the paraffin reactor effluent stream (175) in the olefin cracking reactor, wherein cracking the feed stream (105) and the paraffin reactor effluent stream (175) includes cracking the mixed stream (305).

4. The method according to any one of claims 1 to 2, the method further comprising: Compressing the olefin reactor effluent stream (125) before separating the olefin reactor effluent stream (125).

5. The method according to any one of claims 1 to 2, wherein the olefin cracking reactor (120) and the paraffin cracking reactor (170) are separate beds in a single reaction vessel; or wherein the olefin cracking reactor (120) and the paraffin cracking reactor (170) are in separate vessels.

6. The method according to any one of claims 1 to 2, wherein the feed stream (105) and the paraffin reactor effluent stream (175) are fed at different locations in a single reaction vessel.

7. The method according to any one of claims 1 to 2, wherein the olefin cracking reactor (120) or the paraffin cracking reactor (170) or both contain a catalyst, and the catalyst comprises a silica rock having a silica to alumina ratio greater than 200, and wherein the silica rock is steam-treated, pickled and loaded with an alkaline earth metal.

8. The method according to any one of claims 1 to 2, wherein the olefin cracking reactor (120) contains a catalyst, the catalyst comprises a silica rock having a silica to alumina ratio greater than 200, and wherein the paraffin cracking reactor (170) contains a catalyst having an acidic catalyst.

9. The method according to any one of claims 1 to 2, wherein the operating temperature of the olefin cracking reactor (120) ranges from 560 °C to 620 °C; or wherein the operating temperature of the paraffin cracking reactor (170) ranges from 490 °C to 620 °C; or both of the above cases.

10. The method according to any one of claims 1 to 2, the method further comprising: selectively hydrogenating the feed stream (105) before feeding the feed stream (105) to the olefin cracking reactor (120).

Images