A combined process and system for the catalytic cracking of olefins to produce low-carbon olefins
By pretreating and enriching C4 feedstock and light gasoline feedstock, the boiling points of olefins and alkanes are altered, the olefin concentration is increased, and unreacted materials are recycled. This solves the problem of high energy consumption in existing technologies and achieves the effect of reducing energy consumption and production costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA NAT PETROLEUM CORP
- Filing Date
- 2021-12-31
- Publication Date
- 2026-06-30
AI Technical Summary
Existing olefin catalytic cracking technology has high energy consumption in refineries, leading to increased production costs and limiting its widespread application.
By pretreating and enriching C4 feedstock and light gasoline feedstock, impurities are removed and the boiling points of olefins and alkanes are changed. After increasing the olefin concentration, catalytic cracking is carried out. Combined with the recycling of unreacted materials, energy consumption is reduced.
This reduces energy consumption in olefin catalytic cracking reactions, lowers production costs, and improves the economic efficiency of the plant.
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Figure CN116410049B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the petrochemical field, and in particular to a combined process and system for the catalytic cracking of olefins to produce low-carbon olefins. Background Technology
[0002] From the perspective of propylene supply and demand, on the one hand, there is a shortage of domestic propylene resources, and the output cannot meet the demand. The growth of effective propylene production capacity lags behind the growth of demand from downstream derivative industries. On the other hand, traditional propylene production is relatively monopolistic. Downstream supporting facilities of propylene producers can basically consume the propylene output, and the domestic propylene circulation cannot meet the needs of other downstream enterprises, resulting in a large demand gap.
[0003] Propylene mainly originates from catalytic cracking units in refineries, steam cracking units in ethylene plants, methanol-to-olefins (MTO) units, and propane dehydrogenation units. Steam cracking units, catalytic cracking units, and MTO units produce large quantities of C4-C8 olefin fractions as byproducts. Converting these to propylene is an excellent way to increase propylene production, alleviating the supply-demand imbalance and improving the economic benefits for petrochemical companies. Currently, relatively mature olefin catalytic cracking technologies include UOP's OCP process and the Shanghai Research Institute of Petrochemical Technology's OCC process, primarily used to process mixed C4 fractions with high olefin content from MTO units, achieving olefin content exceeding 90%. Refinery catalytic cracking units can produce large quantities of C4 and light gasoline, typically with an olefin content of 50-65%, also suitable as feedstock for olefin catalytic cracking. Converting these to low-carbon olefins can bring significant economic benefits to enterprises. However, compared to the mixed C4 from MTO, the olefin content of refinery-grade C4 and catalytic light gasoline after etherification is lower, resulting in a large amount of unreacted material circulating within the system, increasing energy consumption and production costs, and hindering the widespread application of olefin catalytic cracking technology in refineries.
[0004] Patent CN101205162A discloses a combined process for producing olefins using refinery C4, employing a special distillation method (such as extractive distillation) to separate butene and butane. However, while using a special near-distillation method to separate butene and butane can increase the olefin content at the inlet of the olefin catalytic cracking reactor, it also suffers from high energy consumption. Summary of the Invention
[0005] This application provides a combined process and system for the catalytic cracking of olefins to produce low-carbon olefins, in order to solve the technical problem of high energy consumption in existing processes.
[0006] In a first aspect, this application provides a combined process for the catalytic cracking of olefins to produce low-carbon olefins, characterized in that the process includes the following steps:
[0007] The C4 feedstock and light gasoline feedstock are pretreated to remove impurities, resulting in pretreated C4 feedstock and first olefin-rich feedstock.
[0008] The pretreated C4 feedstock is enriched to change the boiling points of the olefins and alkanes, resulting in a second olefin-rich feedstock and an alkane-rich feedstock.
[0009] The first olefin-rich feedstock and the second olefin-rich feedstock are subjected to catalytic cracking to obtain reactive oil and gas.
[0010] The reaction oil and gas are separated to obtain ethylene, propylene, and recycled materials.
[0011] Optionally, the mass fraction of olefins in the C4 feedstock is 30% to 100%, and the mass fraction of olefins in the light gasoline feedstock is 30% to 100%.
[0012] Optionally, the enrichment method includes reactive distillation and the addition of an acidic catalyst.
[0013] Optionally, the temperature of the reactive distillation is 30–100°C, and the pressure during the reactive distillation is 0.5–2 MPa.
[0014] Optionally, the temperature of the first catalytic cracking is 500–650°C, and the reaction pressure of the catalytic cracking is 0.02–0.2 MPa.
[0015] Optionally, a molecular sieve catalyst may be added during the first catalytic cracking.
[0016] Optionally, the process further includes:
[0017] The recycled material is reused in the catalytic cracking process.
[0018] Secondly, this application provides a system for the combined process described in the first aspect, the system comprising:
[0019] The raw material pretreatment unit is connected to the feed pipeline and is used to process the C4 raw material and light gasoline raw material in the feed pipeline.
[0020] An olefin enrichment unit, connected to the raw material pretreatment unit, is used to enrich and separate the pretreated C4 raw material.
[0021] An olefin catalytic cracking unit, together with the olefin enrichment unit and the feedstock pretreatment unit, is used to catalytically crack olefin-rich feedstock.
[0022] The product separation unit is connected to the olefin catalytic cracking unit and is used to separate the components obtained from the olefin catalytic cracking unit.
[0023] Optionally, the outlet end of the product separation unit is connected to the inlet end of the olefin catalytic cracking unit, for catalytic cracking and recycling of the recycled material obtained in the product separation unit.
[0024] Optionally, the olefin catalytic cracking unit includes a fixed-bed reactor.
[0025] The technical solutions provided in this application have the following advantages compared with the prior art:
[0026] The method provided in this application pre-treats C4 feedstock and light gasoline feedstock to remove impurities, and then enriches C4 olefins. Through the enrichment process, the boiling points of the olefins and alkanes are changed, making it easier to separate the second olefin-rich feedstock and the alkane-rich feedstock, thus reducing the energy consumption of separation. The concentration of the second olefin-rich feedstock is increased, and the first olefin-rich feedstock and the second olefin-rich feedstock are simultaneously subjected to catalytic cracking, which helps to reduce the investment in olefin catalytic cracking equipment, reduce the energy consumption of the olefin catalytic cracking process, thereby reducing production costs and making it more competitive. Attached Figure Description
[0027] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.
[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0029] Figure 1 A schematic flow diagram of a combined process for producing low-carbon olefins by catalytic cracking of olefins, provided for an embodiment of this application;
[0030] Figure 2 This is a schematic diagram of a system structure for the catalytic cracking of olefins to produce low-carbon olefins, provided as an embodiment of this application.
[0031] The components include: 1. Raw material pretreatment unit; 2. Olefin enrichment unit; 3. Olefin catalytic cracking unit; 4. Product separation unit; 5. C4 feedstock; and 6. Light gasoline feedstock. Detailed Implementation
[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0033] In a first aspect, this application provides a combined process for the catalytic cracking of olefins to produce low-carbon olefins, characterized in that the process includes the following steps:
[0034] S1. Pre-treat the C4 feedstock and light gasoline feedstock to remove impurities, and obtain pre-treated C4 feedstock and first olefin-rich feedstock;
[0035] Specifically, pretreatment can remove trace amounts of impurities such as water and metals. The light components of C4 materials may include: n-butane, isobutane, 1-butene, isobutene, 2-trans-butene, 2-cis-butene, and butadiene.
[0036] S2. The pretreated C4 raw material is enriched to change the boiling point of the olefins and alkanes, resulting in a second olefin-rich material and an alkane-rich material.
[0037] Specifically, the pre-treated C4 feedstock is enriched to change the boiling point of the olefins from -7 to 5°C to >100°C, so that the effective component concentration of the subsequent separated second olefin-rich feedstock is above 90%, which facilitates the subsequent first catalytic cracking and reduces the overall energy consumption of the process.
[0038] S3. Catalytically crack the first olefin-rich feedstock and the second olefin-rich feedstock to obtain reactive oil and gas;
[0039] Specifically, the reacting oil and gas contains a class of low-carbon olefins such as ethylene and propylene.
[0040] S4. Separate the reaction oil and gas to obtain ethylene, propylene and recycled materials.
[0041] Specifically, the reaction oil and gas can be separated to obtain heavy components, which include alkanes, unreacted olefins and aromatics, and the recycled material is unreacted C4 feedstock.
[0042] In some embodiments, the mass fraction of olefins in the C4 feedstock is 30% to 100%, and the mass fraction of olefins in the light gasoline feedstock is 30% to 100%.
[0043] In this embodiment, the reason for controlling the mass fraction of olefins in the C4 feedstock and light gasoline feedstock to be 30% to 100% is to control the cycle ratio. If the mass fraction of olefins is less than 30%, it will cause the adverse effects of an excessively high cycle ratio and excessive energy consumption.
[0044] In some embodiments, the enrichment process includes reactive distillation and the addition of an acidic catalyst.
[0045] In this embodiment, reactive distillation is used for enrichment to change the boiling point difference between olefins and alkanes. An acidic catalyst is added during enrichment because it has high enrichment efficiency. The acidic catalyst can be solid phosphorus, molecular sieve, or ion exchange resin.
[0046] In some embodiments, the temperature of the reactive distillation is 30–100°C, and the pressure during the reactive distillation is 0.5–2 MPa.
[0047] In this embodiment, the reason for controlling the reaction distillation temperature to be 30–100°C is that the reaction efficiency is high, and the reason for controlling the reaction distillation pressure to be 0.5–2 MPag is that the reaction efficiency is high.
[0048] In some embodiments, the temperature of the first catalytic cracking is 500–650°C, and the reaction pressure of the catalytic cracking is 0.02–0.2 MPa.
[0049] In this embodiment, the reason for controlling the temperature of the first catalytic cracking at 500-650°C is that the reaction selectivity is good, and the reason for controlling the reaction pressure of the catalytic cracking at 0.02-0.2 MPag is that it is beneficial to the production of low-carbon olefins.
[0050] In some embodiments, a molecular sieve catalyst is added during the first catalytic cracking.
[0051] Specifically, adding a molecular sieve catalyst has the beneficial effects of reducing the severity of the reaction and improving the distribution of reaction products. The molecular sieve catalyst includes any one of ZSM-5, MCM-22 and SAPO-34.
[0052] In some embodiments, the process further includes:
[0053] The recycled material is reused in the catalytic cracking process.
[0054] In this embodiment, the recycled material includes unreacted C4 feedstock, which is then subjected to catalytic cracking again. This can improve the yield of low-carbon olefins and allow the C4 feedstock to be directly subjected to catalytic cracking, thereby improving economic efficiency and avoiding resource waste.
[0055] Secondly, this application provides a system for the combined process described in the first aspect, the system comprising:
[0056] The raw material pretreatment unit is connected to the feed pipeline and is used to process the C4 raw material and light gasoline raw material in the feed pipeline.
[0057] An olefin enrichment unit, connected to the raw material pretreatment unit, is used to enrich and separate the pretreated C4 raw material.
[0058] An olefin catalytic cracking unit, together with the olefin enrichment unit and the feedstock pretreatment unit, is used to catalytically crack olefin-rich feedstock.
[0059] The product separation unit is connected to the olefin catalytic cracking unit and is used to separate the components obtained from the olefin catalytic cracking unit.
[0060] Specifically, the product separation unit can be equipped with an independent separation system, such as using low-temperature oil absorption separation to obtain polymer-grade ethylene and polymer-grade propylene, or using conventional absorption stabilization and gas separation to obtain polymer-grade propylene and ethylene-rich dry gas. Alternatively, it can be combined with an existing catalytic cracking unit, MTO unit, or propane dehydrogenation unit to share the product separation system.
[0061] In some embodiments, the outlet end of the product separation unit is connected to the inlet end of the olefin catalytic cracking unit, for catalytic cracking and recycling of the recycled material obtained in the product separation unit.
[0062] In this embodiment, the product separation unit outlet is connected to the olefin catalytic cracking unit inlet, which allows for the reuse of recycled materials and reduces costs.
[0063] In some embodiments, the olefin catalytic cracking unit includes a fixed-bed reactor.
[0064] In this embodiment, a fixed-bed reactor refers to a reactor in which granular solid catalysts or solid reactants are packed into a bed of a certain height. Gas or liquid materials flow through the gaps between the particles through the stationary fixed bed, while a heterogeneous reaction process is achieved, which can improve selectivity.
[0065] The method of the present invention will now be described in detail with reference to embodiments, comparative examples and experimental data.
[0066] Example 1
[0067] Using olefin-rich feedstocks from refineries as raw materials, low-carbon olefins such as ethylene and propylene can be produced at low cost. This embodiment provides a combined process for producing low-carbon olefins through catalytic cracking of olefins in a refinery, the main steps of which include:
[0068] S1. Pre-treat the C4 feedstock and light gasoline feedstock to remove impurities, obtaining pre-treated C4 feedstock and first olefin-rich feedstock; specifically, pre-treatment can remove trace amounts of water, metals, and other impurities. The light components of the C4 feedstock may include: n-butane, isobutane, butene-1, isobutene, trans-butene-2, cis-butene-2, and butadiene.
[0069] S2. The pretreated C4 raw material is enriched to change the boiling point of the olefins and alkanes, resulting in a second olefin-rich material and an alkane-rich material.
[0070] S3. Catalytically crack the first olefin-rich feedstock and the second olefin-rich feedstock to obtain reactive oil and gas; specifically, the reactive oil and gas contains a type of low-carbon olefin such as ethylene and propylene.
[0071] S4. The reacted oil and gas are separated to obtain ethylene, propylene, and recycled material. Specifically, the recycled material is unreacted C4 feedstock.
[0072] S5. The recycled material is reused in the catalytic cracking process, and the reaction continues.
[0073] The C4 feedstock contains 30%–100% olefins by mass, and the light gasoline feedstock contains 30%–100% olefins by mass. The enrichment process includes reactive distillation with the addition of an acidic catalyst. The reactive distillation temperature is 30–100°C, and the pressure during reactive distillation is 0.5–2 MPa. The first and second catalytic cracking temperatures are 500–650°C, and the reaction pressure during catalytic cracking is 0.02–0.2 MPa.
[0074] This application provides a system for the combined process described in the first aspect, the system comprising:
[0075] The raw material pretreatment unit 1 is connected to the feed pipeline and is used to process the C4 raw material 5 and light gasoline raw material 6 in the feed pipeline.
[0076] Olefin enrichment unit 2 is connected to the raw material pretreatment unit and is used to enrich and separate the pretreated C4 raw material.
[0077] The olefin catalytic cracking unit 3, together with the olefin enrichment unit and the feedstock pretreatment unit, is used to catalytically crack olefin-rich feedstock; the olefin catalytic cracking unit includes a fixed-bed reactor.
[0078] Product separation unit 4 is connected to the olefin catalytic cracking unit and is used to separate the components obtained from the olefin catalytic cracking unit. The outlet end of the product separation unit is connected to the inlet end of the olefin catalytic cracking unit and is used to catalytically crack and recycle the recycled material obtained from the product separation unit.
[0079] Specifically, the feedstock consisted of 34,748 kg / h of post-etherified C4 and 21,325 kg / h of catalytic light gasoline. The post-etherified C4 contained 49% olefins, and the catalytic light gasoline contained 61% olefins, resulting in a total olefin concentration of 54%. After pretreatment and olefin enrichment, the post-etherified C4, along with the catalytic light gasoline, was used as feedstock in the olefin catalytic cracking reactor, increasing the olefin concentration to 78%. The reaction occurred at 550°C and 0.3 MPa, followed by separation to obtain 5,155 kg / h of polymer-grade ethylene and 18,698 kg / h of polymer-grade propylene. The overall selectivity (based on olefins) reached 17.2% and 62.2%, respectively, with an energy consumption of 817.5 kg C / t olefins. If, after enrichment, the olefin concentration of the feedstock entering the olefin catalytic cracking reactor was 64%, the energy consumption would be 942 kg C / t olefins.
[0080] Example 2
[0081] Using olefin-rich feedstock from an MTO (Metal-to-Olefins) unit as raw material, low-carbon olefins such as ethylene and propylene can be produced at low cost. This embodiment provides a combined process for the catalytic cracking of olefins to produce low-carbon olefins, the main steps of which include:
[0082] S1. The C4 feedstock is pretreated to remove impurities, resulting in pretreated C4 feedstock and a first olefin-rich feedstock. Specifically, pretreatment can remove trace amounts of water, metals, and other impurities. The light components of the C4 feedstock may include: n-butane, isobutane, 1-butene, isobutene, 2-trans-butene, 2-cis-butene, and butadiene.
[0083] 82. The pretreated C4 raw material is enriched to change the boiling points of the olefins and alkanes, resulting in a second olefin-rich material and an alkane-rich material.
[0084] S3. Catalytically crack the first olefin-rich feedstock and the second olefin-rich feedstock to obtain reactive oil and gas; specifically, the reactive oil and gas contains a type of low-carbon olefin such as ethylene and propylene.
[0085] S4. The reacted oil and gas are separated to obtain ethylene, propylene, and recycled material. Specifically, the recycled material is unreacted C4 feedstock.
[0086] S5. The recycled material is reused in the catalytic cracking process, and the reaction continues.
[0087] The C4 feedstock contains 30%–100% olefins by mass. The enrichment process includes reactive distillation with the addition of an acidic catalyst. The reactive distillation temperature is 30–100°C, and the pressure during reactive distillation is 0.5–2 MPa. The first and second catalytic cracking processes are performed at temperatures of 500–650°C, and the reaction pressure during catalytic cracking is 0.02–0.2 MPa.
[0088] This application provides a system for the combined process described in the first aspect, the system comprising:
[0089] The raw material pretreatment unit 1 is connected to the feed pipeline and is used to process the C4 raw material 5 in the feed pipeline;
[0090] Olefin enrichment unit 2 is connected to the raw material pretreatment unit and is used to enrich and separate the pretreated C4 raw material.
[0091] The olefin catalytic cracking unit 3, together with the olefin enrichment unit and the feedstock pretreatment unit, is used to catalytically crack olefin-rich feedstock; the olefin catalytic cracking unit includes a fixed-bed reactor.
[0092] Product separation unit 4 is connected to the olefin catalytic cracking unit and is used to separate the components obtained from the olefin catalytic cracking unit. The outlet end of the product separation unit is connected to the inlet end of the olefin catalytic cracking unit and is used to catalytically crack and recycle the recycled material obtained from the product separation unit.
[0093] Specifically, C4 etherified feedstock with a flow rate of 24,000 kg / h and an olefin content of 76% was used as feedstock. After pretreatment and olefin enrichment, the C4 etherified feedstock was used as feedstock for the olefin catalytic cracking reactor, increasing the olefin concentration to 99%. The reaction took place at 550°C and 0.3 MPa, and after separation, 3,180 kg / h of polymerization-grade ethylene and 11,812 kg / h of polymerization-grade propylene were obtained. The overall selectivity (based on olefins) reached 17.5% and 65.0%, respectively, with an energy consumption of 646.7 kg Cd / ton of olefins. If, after enrichment, the olefin concentration of the feedstock entering the olefin catalytic cracking reactor was 86%, the energy consumption would be 686.5 kg Cd / ton of olefins.
[0094] Comparative Example 1
[0095] Using olefin-rich feedstocks from refineries as raw materials, low-carbon olefins such as ethylene and propylene can be produced at low cost. This comparative example provides a combined process for producing low-carbon olefins through catalytic cracking of olefins in a refinery, the main steps of which include:
[0096] S1. Pre-treat the C4 feedstock and light gasoline feedstock to remove impurities, obtaining pre-treated C4 feedstock and first olefin-rich feedstock; specifically, pre-treatment can remove trace amounts of water, metals, and other impurities. The light components of the C4 feedstock may include: n-butane, isobutane, butene-1, isobutene, trans-butene-2, cis-butene-2, and butadiene.
[0097] S2. Catalytically crack the first olefin-rich feedstock and the C4 feedstock to obtain reactive oil and gas; specifically, the reactive oil and gas contains a type of low-carbon olefin such as ethylene and propylene.
[0098] S3. The reacted oil and gas are separated to obtain ethylene, propylene, and recycled material. Specifically, the recycled material is unreacted C4 feedstock.
[0099] S4. The recycled material is reused in the catalytic cracking process and the reaction continues.
[0100] The mass fraction of olefins in the C4 feedstock is 30%–100%, and the mass fraction of olefins in the light gasoline feedstock is 30%–100%. The temperatures of the first and second catalytic cracking are 500–650°C, and the reaction pressure of the catalytic cracking is 0.02–0.2 MPa.
[0101] Specifically, the feedstock consisted of 34,748 kg / h of post-etherified C4 and 21,325 kg / h of catalytic light gasoline, with the post-etherified C4 containing 49% olefins and the catalytic light gasoline containing 61% olefins. The pretreated post-etherified C4, along with the catalytic light gasoline, was used as feedstock in the olefin catalytic cracking reactor. The reaction occurred at 550°C and 0.3 MPa, followed by separation to obtain 4,956 kg / h of polymer-grade ethylene and 18,622 kg / h of polymer-grade propylene. The overall selectivity (based on olefins) reached 165% and 62%, respectively, with an energy consumption of 1078.9 kg of standard coal per ton of olefins.
[0102] Comparative Example 2
[0103] Using olefin-rich feedstock from an MTO (Metal-Oxide-Transfer) unit as raw material, low-carbon olefins such as ethylene and propylene can be produced at low cost. This comparative example provides a combined process for producing low-carbon olefins through catalytic cracking of olefins in a refinery. The main steps include:
[0104] S1. Pre-treat the C4 feedstock and light gasoline feedstock to remove impurities, obtaining pre-treated C4 feedstock and first olefin-rich feedstock; specifically, pre-treatment can remove trace amounts of water, metals, and other impurities. The light components of the C4 feedstock may include: n-butane, isobutane, butene-1, isobutene, trans-butene-2, cis-butene-2, and butadiene.
[0105] S2. Catalytically crack the first olefin-rich feedstock and the C4 feedstock to obtain reactive oil and gas; specifically, the reactive oil and gas contains a type of low-carbon olefin such as ethylene and propylene.
[0106] S3. The reacted oil and gas are separated to obtain ethylene, propylene, and recycled material. Specifically, the recycled material is unreacted C4 feedstock.
[0107] S4. The recycled material is reused in the catalytic cracking process and the reaction continues.
[0108] The mass fraction of olefins in the C4 feedstock is 30%–100%, and the mass fraction of olefins in the light gasoline feedstock is 30%–100%. The temperature of the first catalytic cracking and the second catalytic cracking is 500–650°C, and the reaction pressure of the catalytic cracking is 0.02–0.2 MPa.
[0109] Specifically, C4 etherified feedstock with a flow rate of 24,000 kg / h was used as the raw material, wherein the olefin content of the C4 etherified feedstock was 76%. After pretreatment and olefin enrichment, the C4 etherified feedstock was used as the feedstock for the olefin catalytic cracking reactor, where it reacted at 550 °C and 0.3 MPa. After separation, 3,101 kg / h of polymerization-grade ethylene and 11,765 kg / h of polymerization-grade propylene were obtained. The total selectivity of the reaction (based on olefins) reached 17.0% and 64.5%, respectively, and the energy consumption was 732.4 kg of standard coal / ton of olefins.
[0110] As can be seen from the examples and comparative examples, based on olefins, the raw materials used in Comparative Example 1 and Example 1 are the same, and the raw materials used in Comparative Example 2 and Example 2 are the same. The examples significantly reduced energy consumption compared to the comparative examples. The energy consumption of the examples was 646.7-817.5 kg of standard coal / ton of olefins, while the energy consumption of the comparative examples was 732.4-1078.9 kg of standard coal / ton of raw materials. This shows that the enrichment of C4 olefins can achieve the effect of reducing energy consumption.
[0111] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0112] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.
Claims
1. A process for the catalytic cracking of olefins to produce lower olefins, characterized in that, The process includes the following steps: The C4 feedstock and light gasoline feedstock are pretreated to remove impurities, resulting in pretreated C4 feedstock and first olefin-rich feedstock. The pretreated C4 raw material is enriched to change the boiling point of olefins and alkanes, so that the boiling point of the olefins changes from the original -7~5℃ to >100℃, to obtain a second olefin-rich material and an alkane-rich material, wherein the effective component concentration of the second olefin-rich material is above 90%. The first olefin-rich feedstock and the second olefin-rich feedstock are combined and then subjected to catalytic cracking to obtain reactive oil and gas. The reaction oil and gas are separated to obtain ethylene, propylene and recycled materials; The mass fraction of olefins in the C4 feedstock is 30% to 100%, and the mass fraction of olefins in the light gasoline feedstock is 30% to 100%. The enrichment method includes reactive distillation with the addition of an acidic catalyst. The reactive distillation temperature is 30-100°C, and the pressure during reactive distillation is 0.5-2 MPag. The acidic catalyst is any one of solid phosphorus, molecular sieve, and ion exchange resin.
2. The process according to claim 1, characterized in that, The catalytic cracking temperature is 500~650℃, and the catalytic cracking reaction pressure is 0.02~0.2MPag.
3. The process according to claim 1, characterized in that, Molecular sieve catalysts are added during the catalytic cracking process.
4. The process according to claim 1, characterized in that, The process further includes: reusing the recycled material in the catalytic cracking process.