Method for improving quality of hydrocarbon stream

Abstract

A method for improving the quality of a hydrocarbon stream. The method comprises the following steps: providing a hydrocarbon stream containing a C5-C6 isomeric alkane, wherein the content of the C5-C6 isomeric alkane in the hydrocarbon stream is 60-90 wt%; and subjecting at least part of the C5-C6 isomeric alkane to a conversion reaction in the presence of a catalyst and hydrogen, to convert same into a C2-C6 normal alkane, so as to obtain a conversion product, wherein the catalyst comprises a molecular sieve and a non-precious-metal hydrogenation active metal component. The converted hydrocarbon stream can greatly improve the yields of ethylene and triene in an ethylene device.

Description

A method for improving the quality of hydrocarbon streams Technical Field

[0001] The present invention relates to the technical field of petrochemical industry, in particular to a method for improving the quality of hydrocarbon streams. Background Art

[0002] During petroleum processing, C5 and C6 isoparaffins are typically obtained through cracking processes such as crude oil separation or hydrocracking. However, due to their small molecular weight, high interatomic bond energy, and weak molecular polarity, conventional cracking processes such as hydrocracking or catalytic cracking hinder further chemical reactions. Currently, there are two main approaches to utilizing C5 and C6 isoparaffins: one is direct use as a gasoline blending component, but due to the influence of saturated vapor pressure, the amount of such components added to gasoline blending is relatively low; the other is use as a feedstock for steam cracking to produce ethylene. However, the inventors have discovered that the yields of ethylene and trienes during thermal cracking of isoparaffins are relatively low, making them unsuitable as high-quality ethylene feedstocks.

[0003] During the production process of an ethylene plant, a series of complex chemical reactions occur after the raw materials undergo high-temperature cracking, leading to varying degrees of coking on the inner walls of the cracking furnace's radiant section tubes and the inner walls of the quench boiler casing. As the coke layer continues to thicken, the heat transfer resistance of the tubes increases, and the heat outside the tubes cannot be promptly transferred to the cracked raw materials inside, seriously affecting the cracking depth of the raw materials. In addition, the temperature of the outer surface of the tubes continues to rise, which may cause local overheating and shorten the life of the tubes. When the temperature exceeds the maximum design temperature of the tube material, the furnace must be shut down and de-coked. Therefore, if the ethylene feedstock contains no or low levels of sulfides, sulfur injection is required during the reaction to prevent coking of the tubes. If the ethylene feedstock contains a certain amount of sulfides, sulfur injection is also required during the reaction to reduce the operating costs of the plant.

[0004] When isoparaffins are used as ethylene feedstock, their ethylene yield and triene yield are both low. Therefore, effectively converting isoparaffins into normal paraffins can significantly increase the yield of high-value products in the ethylene plant. Among normal paraffins, low-carbon paraffins (including ethane and propane) are better cracking raw materials. They are easy to separate and have high ethylene product yields. However, more hydrogen is consumed in the process of obtaining ethane and propane through hydrogenation. 4+ Due to the presence of isomers, normal alkanes can also achieve higher ethylene yields, while also consuming less hydrogen during the hydroconversion process. However, separating isomeric hydrocarbons of the same carbon number is more difficult, and the hydrogenated product often contains isomeric hydrocarbons, resulting in a lower ethylene yield than when using lower alkanes as feedstock. The hydroconversion process allows for flexible adjustment of the ratio of lower alkanes to normal alkanes in the hydrogenated product, significantly improving operational flexibility.

[0005] With the rapid development of my country's chemical industry, the production capacity of ethylene has increased year by year. Therefore, the demand for ethylene raw materials has also continued to increase. How to broaden the selection range of ethylene raw materials and how to obtain high-quality ethylene raw materials have become urgent issues that need to be solved in the development of the ethylene industry.

[0006] Summary of the Invention

[0007] In response to the shortcomings of the existing technology, the present invention provides a method for the hydrogenation conversion of C5 and C6 isoparaffins, which can effectively convert isoparaffins with poor cracking performance into C2-C6 normal paraffins with better cracking performance, thereby significantly improving the ethylene and triene yields of the ethylene plant. The triene yield refers to the mass yield of ethylene, propylene and butadiene.

[0008] The inventors of the present invention have also discovered that organic sulfur in the ethylene feedstock obtained through a hydrogenation process is converted into hydrogen sulfide during the hydrogenation reaction, and the hydrogen sulfide is removed during product separation. Therefore, the sulfur content in the ethylene feedstock is generally low, and sulfur injection is required before entering the ethylene cracking furnace to prevent coking of the furnace tubes. If a portion of the hydrogen sulfide is retained in the hydrogenated product during the separation process, sulfur injection can be reduced or even eliminated before entering the ethylene cracking furnace when the hydrogenated product is used as an ethylene feedstock, thus achieving high-value utilization of the waste gas.

[0009] The inventors of the present invention have further discovered that small-molecule isoparaffins undergo two primary reactions during hydrogenation: cracking and normalization. The cracking reaction converts isoparaffins of the same carbon number into normal alkanes, while the normalization reaction converts isoparaffins of the same carbon number into normal alkanes. By adjusting the catalyst and process conditions, the molecular composition of the hydrogenation products can be flexibly adjusted, thereby enhancing production flexibility.

[0010] The purpose of the present invention is to maximize the production of C2-C6 normal alkanes. In the prior art, C5-C6 isoalkanes are usually converted into normal alkanes, that is, only the normalization reaction occurs, suppressing the occurrence of the cracking reaction. The entire normalization reaction process requires a lower reaction temperature and a lower hydrogen-to-oil volume ratio. However, the normalization reaction is affected by chemical equilibrium. After the concentration of normal alkanes in the product reaches a certain proportion (about 30%), the normalization reaction will be inhibited, making it difficult to increase the yield of normal alkanes in the product by adjusting the reaction process. This route needs to be combined with normal-isomer separation, and after separating the normal alkanes, the unconverted isoalkanes are further converted. However, for steam cracking to produce ethylene, C2-C6 normal alkanes are all ideal raw materials. The present invention uses a dedicated catalyst and controls the reaction conditions to simultaneously strengthen the occurrence of normalization and cracking reactions, breaking the influence of chemical equilibrium on the normalization reaction. The cracking reaction further increases the yield of normal alkanes in the conversion product, the latter being particularly suitable for direct use as a steam cracking feedstock to produce ethylene. The present invention is based on this purpose.

[0011] Specifically, the present invention relates to the following aspects.

[0012] 1. A method for improving the quality of a hydrocarbon stream, comprising the steps of:

[0013] 1) providing a hydrocarbon stream containing C5-C6 isoparaffins, wherein the content of the C5-C6 isoparaffins in the hydrocarbon stream is 60-90 wt% (preferably 70-80 wt%), based on the total weight of the hydrocarbon stream being 100 wt%,

[0014] 2) converting at least a portion (e.g., more than 30 wt%, more than 40 wt%, more than 50 wt%, more than 60 wt%, more than 70 wt%, more than 80 wt%, or more than 90 wt%) of the C5-C6 isoparaffins into C2-C6 normal paraffins in the presence of a catalyst and hydrogen to obtain a conversion product, wherein the catalyst comprises a molecular sieve and a non-precious metal hydrogenation active metal component;

[0015] 3) steam cracking the conversion product to obtain a cracking product containing ethylene.

[0016] 2. The method according to any one of the preceding or following aspects, wherein the hydrocarbon stream has an initial boiling point of 10-30°C (preferably 15-25°C) and a final boiling point of 50-100°C (preferably 55-70°C).

[0017] 3. The process according to any one of the preceding or following aspects, wherein the sulfur content of the hydrocarbon stream is 50-5000 mg / kg (preferably 200-1000 mg / kg), based on the total weight of the hydrocarbon stream.

[0018] 4. The method according to any one of the preceding or following aspects, wherein the hydrocarbon stream contains C 7+ The content of hydrocarbons is 0-10 wt% (preferably 0.5-5 wt%), the content of C5-C6 normal alkanes is 10-30 wt% (preferably 15-25 wt%), the content of C4-hydrocarbons is 0-10 wt% (preferably 2-5 wt%), and the content of cyclic hydrocarbons is 1-10 wt% (preferably 2-5 wt%), based on the total weight of the hydrocarbon stream being 100 wt%.

[0019] 5. A method according to any of the preceding or following aspects, wherein the conversion product comprises C2-C3 alkanes and C4-C6 normal alkanes (preferably C5-C6 normal alkanes), and the weight ratio of the C2-C3 alkanes to the C4-C6 normal alkanes (preferably C5-C6 normal alkanes) is 0.5:1-8:1 (preferably 0.9:1-5:1).

[0020] 6. A method according to any of the preceding or following aspects, wherein the content of C7+ hydrocarbons in the conversion product is not higher than 5 wt% (preferably not higher than 1 wt%), the content of C5-C6 isoparaffins is 0-50 wt% (preferably 10-40 wt%), the content of C2-C6 normal paraffins is 40-90 wt% (preferably 50-80 wt%), and the content of cyclic hydrocarbons is not higher than 3 wt% (preferably not higher than 1 wt%), based on the total weight of the conversion product being 100 wt%.

[0021] 7. The process according to any one of the preceding or following aspects, wherein the hydrocarbon stream is a light naphtha component obtained by cracking a hydrocarbon oil feedstock, such as by hydrocracking or catalytic cracking.

[0022] 8. The method according to any of the preceding or following aspects, wherein the molecular sieve is selected from one or more of mordenite, ZSM molecular sieve, SAPO molecular sieve and EU-1 molecular sieve, more preferably selected from one or more of mordenite and ZSM molecular sieve, particularly preferably selected from one or more of mordenite, ZSM-5 molecular sieve, ZSM-11 molecular sieve, ZSM-12 molecular sieve, ZSM-22 molecular sieve, ZSM-23 molecular sieve, ZSM-35 molecular sieve, Beta molecular sieve and ZSM-38 molecular sieve, in particular selected from one or more of mordenite and ZSM-5 molecular sieve (particularly preferably, the weight ratio of mordenite to ZSM-5 molecular sieve is 0-100:100-0, preferably 10-50:50-10).

[0023] 9. The method according to any one of the preceding or following aspects, wherein the catalyst further comprises a binder (preferably alumina), and the content of the binder is 5-65 wt% (preferably 10-35 wt%) based on the weight of the catalyst.

[0024] 10. The method according to any one of the preceding or following aspects, wherein the non-noble metal hydrogenation active metal component is selected from one or more non-noble metals of Group VIB and Group VIII of the Periodic Table of Elements.

[0025] 11. A method according to any one of the preceding or following aspects, wherein the Group VIB non-noble metal is selected from one or more of molybdenum and tungsten (particularly preferably molybdenum), and the Group VIII non-noble metal is selected from one or more of cobalt and nickel (particularly preferably nickel).

[0026] 12. A method according to any of the preceding or following aspects, wherein, based on the weight of the catalyst, the content of the non-noble metal of Group VIB (calculated as oxide) is 5.0-30.0 wt% (preferably 10-20 wt%), and the content of the non-noble metal of Group VIII (calculated as oxide) is 0.5-15.0 wt% (preferably 3-10 wt%).

[0027] 13. The method according to any one of the preceding or following aspects, wherein the content of the molecular sieve is 30-80 wt% (preferably 40-70 wt%) based on the weight of the catalyst.

[0028] 14. The method according to any one of the preceding or following aspects, wherein the catalyst has a specific surface area of ​​200-400 m 2 / g, and the pore volume is 0.25-0.45mL / g.

[0029] 15. The method according to any of the preceding or following aspects, wherein the reaction conditions of the conversion reaction include: a reaction pressure of 0.5-10.0 MPaG (preferably 2.0-8.0 MPaG or 2.0-5.0 MPaG), a reaction temperature of 300-500° C. (preferably 350-450° C.), a liquid hourly volume space velocity of 0.1-15.0 h -1 (Preferably 0.5-5.0h -1 ), the volume ratio of hydrogen to oil is 50:1-2500:1 (preferably 100:1-2000:1 or 100:1-1000:1).

[0030] 16. The method according to any one of the preceding or following aspects, wherein step 3) comprises the following steps:

[0031] 3-A-1) separating the conversion products (referred to as a first separation) to obtain a separated stream consisting primarily of C2+ hydrocarbons (e.g., greater than 95 wt%, greater than 98 wt%, greater than 99 wt%, or substantially 100 wt%),

[0032] 3-A-2) steam cracking the separated stream to obtain a cracking product comprising ethylene.

[0033] 17. The method according to any one of the preceding or following aspects, wherein the operating conditions of the first separation include a pressure of 0.5-10.0 MPaG (preferably 2.0-8.0 MPaG or 2.0-5.0 MPaG) and a temperature of 40-70°C.

[0034] 18. The method according to any one of the preceding or following aspects, wherein step 3) comprises the following steps:

[0035] 3-B-1) separating the conversion products (referred to as the first separation) to obtain a separated stream consisting primarily of C2+ hydrocarbons (e.g., greater than 95 wt%, greater than 98 wt%, greater than 99 wt%, or substantially 100 wt%),

[0036] 3-B-2) separating the separated stream (referred to as the second separation) to obtain a high-carbon stream composed primarily of C4+ hydrocarbons (e.g., accounting for 90 wt% or more, 95 wt% or more, 98 wt% or more, 99 wt% or more, or substantially 100 wt% of the total amount) and a low-carbon stream composed primarily of C2-C3 hydrocarbons (e.g., accounting for 90 wt% or more, 95 wt% or more, 98 wt% or more, 99 wt% or more, or substantially 100 wt% of the total amount);

[0037] 3-B-3) Optionally, the high carbon stream is recycled as a hydrocarbon stream to the step 2) to carry out the conversion reaction,

[0038] 3-B-4) steam cracking the low-carbon stream to obtain a cracking product comprising ethylene.

[0039] 19. A method according to any of the preceding or following aspects, wherein the operating conditions of the first separation include a pressure of 0.5-10.0 MPaG (preferably 2.0-8.0 MPaG or 2.0-5.0 MPaG) and a temperature of 40-70°C, and the operating conditions of the second separation include a pressure of 0.5-1.5 MPaG and a temperature of 30-60°C.

[0040] 20. The method according to any of the preceding or following aspects, wherein the operating conditions of the steam cracking include: reaction temperature 750-900°C, reaction pressure 0.1-0.5 MPaG, water-oil mass ratio 0.2-0.6, and system sulfur content 100-200 mg / kg.

[0041] 21. A system for improving the quality of a hydrocarbon stream, comprising the following units:

[0042] 1) a hydrocarbon stream providing unit configured to provide a hydrocarbon stream containing C5-C6 isoparaffins, wherein the content of the C5-C6 isoparaffins in the hydrocarbon stream is 60-90 wt% (preferably 70-80 wt%), based on the total weight of the hydrocarbon stream being 100 wt%, and

[0043] 2) a hydrocarbon stream conversion unit configured to convert at least a portion (e.g., more than 30 wt%, more than 40 wt%, more than 50 wt%, more than 60 wt%, more than 70 wt%, more than 80 wt%, or more than 90 wt%) of the C5-C6 isoparaffins into C2-C6 normal paraffins in the presence of a catalyst and hydrogen to obtain a conversion product, wherein the catalyst comprises a molecular sieve and a non-precious metal hydrogenation active metal component.

[0044] 3) A steam cracking unit configured to steam crack the conversion product to obtain a cracking product comprising ethylene.

[0045] Technical Effects

[0046] Compared with the prior art, the method and system provided by the present invention can achieve one of the following technical effects or a combination of all or part of them:

[0047] 1. for hydrocracking reaction, molecule is less, more difficult to cracking reaction, particularly as small molecule hydrocarbons such as C5 and C6, need to ensure that reactant has certain residence time in catalyst pore, simultaneously, when taking production normal paraffin as purpose product, need the molecular sieve of catalyst to have straight pore structure, like this also more conducive to the generation of normal paraffin, therefore, when processing the raw material rich in C5 and C6 isoparaffins, need to select the catalyst of special pore structure. The inventor has found after deliberation, the molecular sieve with shape selectivity, it has extraordinary reactivity to the reaction of molecule directly less (comprising normal paraffins and short-chain isoparaffins), can effectively convert C5 and C6 isoparaffins. The hydrocarbon stream containing C5 and C6 isoparaffins can significantly improve the triolefin yield of steam cracking ethylene device after hydroconversion, improves the economic benefit of ethylene device.

[0048] 2. The processing capacity of an ethylene plant is based on the ethylene yield, that is, the higher the ethylene yield, the less raw materials the ethylene plant consumes. Raw material costs account for more than 60% of the processing costs of an ethylene plant. Therefore, increasing the ethylene yield can significantly reduce the processing costs of an ethylene plant.

[0049] 3. The C5 and C6 isoparaffin content in the hydrocarbon stream is controlled at 60-90%. Since the hydroconversion process mainly includes two reactions, normalization and cracking, and the normalization reaction does not consume hydrogen, it is a more ideal reaction path. The inventors have found that the normalization reaction of isoparaffins is affected by chemical equilibrium. A high content of normal paraffins in the reactants will inhibit the normalization reaction. At the same time, too low an isoparaffin content will cause the loss of normal paraffins in the raw material, causing the C5 and C6 normal paraffins in the raw material to be converted into isoparaffins or small molecular normal paraffins, which will deteriorate the product quality or cause unnecessary hydrogen consumption. In the current petroleum processing process, hydrocracking and catalytic cracking, which follow the positive carbon ion reaction mechanism, will have a large amount of isoparaffins in their C5 and C6 products, but the isoparaffin content does not exceed 90%. If you want to obtain a raw material containing higher isoparaffins, special separation methods are required, including adsorption separation and distillation, and these separation methods all require high energy consumption, which greatly increases the processing cost.

[0050] 4. During steam cracking to produce ethylene, the sulfur content of the feedstock must be controlled to a certain level. If the sulfur content is too low, sulfur injection is required before the cracking furnace, otherwise it will accelerate coking in the ethylene cracking furnace, affecting the operating cycle and cracking efficiency. Excessive sulfur content in the feedstock increases the cost of subsequent desulfurization. When producing ethylene feedstock through hydrogenation, by processing the feedstock and controlling the appropriate sulfur content in the hydrogenation product, the sulfur content of the feedstock in the ethylene plant can be effectively controlled, reducing or even eliminating the amount of sulfur injection required in the ethylene cracking furnace.

[0051] 5. During the hydrogenation reaction of hydrocarbon streams, organic sulfides are converted into hydrogen sulfide. This hydrogen sulfide is a valueless product for the hydrogenation unit and may even require removal through separation methods such as stripping. The removed hydrogen sulfide also requires subsequent harmless treatment. However, when the hydrogenation product containing a certain amount of hydrogen sulfide is used as an ethylene feedstock, it can solve the problem of ethylene sulfur injection and realize the high-value utilization of the non-beneficial component.

[0052] 6. When C5-C6 isoparaffins are used directly as ethylene feedstock, the yields of ethylene and trienes are relatively low. Through hydrogenation conversion, the ratio of C2-C3 light alkanes and C4-C6 normal alkanes in the hydrogenation product can be flexibly adjusted. Based on the two different reaction pathways of C5-C6 isoparaffins, by adjusting the acid strength of the catalyst's acidic center, the two different reaction pathways of cracking and normalization can be flexibly adjusted. If the hydrogen cost is low or the hydrogen surplus is high, more C2-C3 light alkanes can be produced, which greatly increases the yield of the target ethylene product; if the hydrogen cost is high or the hydrogen surplus is low, more C4-C6 normal alkanes can be produced, improving the quality of the ethylene feedstock at a lower hydrogen consumption.

[0053] 7. Flexible adjustment of the structural composition of ethylene olefin streams can maximize the operational flexibility of the ethylene plant, including flexible adjustment of the yields of the main target products of the ethylene plant, ethylene, propylene, butadiene and aromatics. The product structure can be adjusted according to changes in market demand to improve the market competitiveness of the ethylene plant.

[0054] 8. The hydrogenation conversion products have a high content of C2-C6 normal alkanes, especially C2-C3 small molecular normal alkanes, which can achieve a better ethylene yield during the steam cracking process. At the same time, the C4-C6 normal alkanes in the conversion products are also greatly improved compared with the raw materials, and can be used directly as ethylene raw materials.

[0055] 9. The present invention aims to maximize the production of C2-C6 normal alkanes. Prior art methods typically convert C5-C6 isoparaffins to normal alkanes, meaning only the normalization reaction occurs, suppressing the cracking reaction. The entire normalization reaction process requires a lower reaction temperature and a reduced hydrogen-to-oil volume ratio. However, the normalization reaction is affected by chemical equilibrium. Once the concentration of normal alkanes in the product reaches a certain proportion (approximately 30%), the normalization reaction is inhibited, making it difficult to increase the yield of normal alkanes in the product by adjusting the reaction process. This route requires combining normal-isomer separation, separating the normal alkanes and then converting the unconverted isoparaffins. However, C2-C6 normal alkanes are ideal feedstocks for steam cracking to produce ethylene. The present invention utilizes a specialized catalyst and controls reaction conditions to simultaneously enhance the normalization and cracking reactions, disrupting the influence of chemical equilibrium on the normalization reaction. The cracking reaction further increases the yield of normal alkanes in the conversion product, making the latter particularly suitable for direct use as a steam cracking feedstock for producing ethylene. The present invention was developed with this objective in mind. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] FIG1 is a schematic diagram of a process flow of the process method of the present invention.

[0057] In Figure 1, 1-hydrocarbon stream, 2-hydrogen, 3-hydrogenation reaction zone, 4-hydrogenation reaction zone effluent, 5-high-pressure separator, 6-gas stream hydrogen-rich gas, 7-liquid stream.

[0058] FIG2 is a schematic diagram of a process flow of the process method of the present invention.

[0059] In Figure 2, 1-hydrocarbon stream, 2-hydrogen, 3-hydrogenation conversion reaction zone, 4-hydrogenation conversion reaction zone effluent, 5-high-pressure separator, 6-gas stream hydrogen-rich gas, 7-liquid stream, 8-fractionation tower, 9-gas phase product, 10-liquid phase product. DETAILED DESCRIPTION

[0060] The specific embodiments of the present invention are described in detail below. However, it should be noted that the protection scope of the present invention is not limited by these specific embodiments, but is determined by the claims in the appendix.

[0061] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In the event of conflict, the definitions in this specification will prevail.

[0062] When this specification uses the prefix "well known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, the objects introduced by the prefix include those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become generally recognized in the art to be suitable for similar purposes.

[0063] In the context of the present invention, all numerical values ​​for parameters (eg, amounts or conditions) are to be understood as being modified in all instances by the term "about," regardless of whether "about" actually appears before the numerical value.

[0064] In the context of the present invention, unless otherwise specified, the various devices used in the present invention may use structures conventionally selected in the art without particular limitation.

[0065] In the context of the present invention, “substantially” means that deviations that are acceptable or reasonable to those skilled in the art are allowed, such as deviations within ±5%, within ±2%, within ±1%, within ±0.5% or within ±0.1%.

[0066] In the context of the present invention, the measurement method of the initial boiling point and the final boiling point is in accordance with the ASTM D86 measurement method.

[0067] In the context of the present invention, the method for measuring sulfur content is in accordance with GB / T380.

[0068] In the context of the present invention, the term "C2-C6 normal alkanes" refers to normal alkanes with carbon atoms ranging from 2 to 6. It should be specifically clarified that while alkanes with carbon atoms ranging from 2 to 3 are not distinguished between normal alkanes and isoalkanes, for the sake of convenience, alkanes with carbon atoms ranging from 2 to 3 are also considered normal alkanes. Furthermore, unless otherwise specified, the term may refer to any one or more normal alkanes with carbon atoms ranging from 2 to 6, or to all normal alkanes with carbon atoms ranging from 2 to 6.

[0069] In the context of the present invention, cyclic hydrocarbons refer to hydrocarbons having a ring structure in their molecular structure, such as cycloalkanes and aromatic hydrocarbons.

[0070] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this specification are based on weight and pressure is gauge pressure.

[0071] In the context of the present invention, any two or more embodiments or aspects of the present invention may be arbitrarily combined, and the technical solutions thus formed belong to part of the original disclosure of this specification and also fall within the scope of protection of the present invention.

[0072] According to one embodiment of the present invention, a method for improving the quality of a hydrocarbon stream is provided. Here, "improving the quality" refers to changing the chemical composition of the hydrocarbon stream through chemical conversion to make it more easily converted into high-value-added products such as ethylene through steam cracking.

[0073] According to one embodiment of the present invention, the method includes the step of providing a hydrocarbon stream containing C5-C6 isoparaffins. According to the present invention, the hydrocarbon stream can be manufactured by any method known in the art, as long as it meets the requirements of the present invention for the hydrocarbon stream. As the manufacturing method of the hydrocarbon stream, for example, hydrocracking, catalytic cracking or atmospheric and vacuum distillation can be cited. Preferably, the initial boiling point of the hydrocarbon stream is 10-30°C (preferably 15-25°C), and the final boiling point is 50-100°C (preferably 55-70°C). More preferably, the hydrocarbon stream is a light naphtha component obtained by hydrocracking a hydrocarbon oil feedstock.

[0074] According to one embodiment of the present invention, in order to achieve the technical effects of the present invention, the content of the C5-C6 isoparaffins in the hydrocarbon stream is generally 60-90 wt%, preferably 70-80 wt%, based on the total weight of the hydrocarbon stream being 100 wt%. The inventors of the present invention have discovered that the isoparaffin content in the hydrocarbon stream must have a certain ratio. If the isoparaffin content is too low, the proportion of normal paraffins in the product will be limited, and it will also cause cracking of some normal paraffins, resulting in hydrogen loss. If the isoparaffin content is too high, conventional separation methods cannot be achieved, and adsorption separation or distillation is required, which consumes a lot of energy.

[0075] According to one embodiment of the present invention, the C 7+ There is no particular limitation on the content of hydrocarbons, but in order to make the technical effect of the present invention more excellent, the C 7+ The content of hydrocarbon is generally 0-10 wt% (preferably 0.5-5 wt%), based on the total weight of the hydrocarbon stream being 100 wt%. 7+A high content of hydrocarbons will carry a certain amount of aromatic hydrocarbons, but aromatic hydrocarbons are difficult to be effectively converted under the conversion reaction conditions of the present invention (for example, the conversion rate is generally less than 10%) and appear as reaction inert components. 7+ Too high a hydrocarbon content will significantly inhibit the conversion activity of the hydrocarbon stream of the present invention, which is disadvantageous to the present invention.

[0076] According to one embodiment of the present invention, there is no particular limitation on the content of C5-C6 normal alkanes in the hydrocarbon stream. However, to achieve even greater technical benefits, the content of C5-C6 normal alkanes in the hydrocarbon stream is generally 10-30 wt% (preferably 15-25 wt%), based on 100 wt% of the total weight of the hydrocarbon stream. The inventors of the present invention have discovered that a high content of normal alkanes in the hydrocarbon stream inhibits the conversion reaction of isoparaffins, and the increase in normal alkanes after conversion is limited, thus having little impact on the ethylene yield.

[0077] According to one embodiment of the present invention, there is no particular limitation on the content of C4-hydrocarbons in the hydrocarbon stream, but in order to make the technical effect of the present invention more excellent, the content of C4-hydrocarbons in the hydrocarbon stream is generally 0-10wt% (preferably 2-5wt%), based on the total weight of the hydrocarbon stream as 100wt%. The inventors of the present invention have found that C4-hydrocarbons are gaseous at room temperature and pressure and have limited solubility in C5-C6 hydrocarbons. Therefore, in order to obtain a hydrocarbon stream with a high C4-hydrocarbon content, a special manufacturing method is required, which will significantly increase the manufacturing cost of the hydrocarbon stream of the present invention. In addition, the inventors of the present invention have found that compared with C5-C6 isoparaffins, C4 hydrocarbons are more difficult to be effectively converted under the conversion reaction conditions of the present invention (for example, the conversion rate is generally less than 20%). Therefore, an excessively high content of C4 hydrocarbons will significantly inhibit the conversion activity of the hydrocarbon stream of the present invention, which is not conducive to the present invention.

[0078] According to one embodiment of the present invention, there is no particular limitation on the content of cyclic hydrocarbons in the hydrocarbon stream. However, to achieve a more superior technical effect of the present invention, the content of cyclic hydrocarbons in the hydrocarbon stream is generally 1-10 wt% (preferably 2-5 wt%), based on 100 wt% of the total weight of the hydrocarbon stream. The inventors of the present invention have discovered that cycloalkanes with relatively low carbon numbers can be converted, while cycloalkanes and aromatic hydrocarbons with relatively high carbon numbers are difficult to effectively convert under the process conditions of the present invention. These components, when introduced into an ethylene plant, can affect the ethylene yield of the ethylene plant, which is detrimental to the present invention.

[0079] According to one embodiment of the present invention, the method comprises converting at least a portion of the C5-C6 isoparaffins into C2-C6 normal alkanes by a conversion reaction in the presence of a catalyst and hydrogen to obtain a conversion product. Here, the so-called at least a portion, for example, is more than 30wt%, more than 40wt%, more than 50wt%, more than 60wt%, more than 70wt%, more than 80wt% or more than 90wt% of the total amount. According to the present invention, there is no particular limitation on the conversion rate of the C5-C6 isoparaffins. Therefore, the C5-C6 isoparaffins can achieve this conversion rate (single-pass conversion rate) after a single conversion reaction, or can achieve this conversion rate after multiple recycling (for example, the unreacted C5-C6 isoparaffins are separated from the conversion product and then subjected to the conversion reaction).

[0080] According to a preferred embodiment of the present invention, the hydrocarbon stream is a sulfur-containing hydrocarbon stream. According to the present invention, a sulfur-containing conversion product is obtained by converting the sulfur-containing hydrocarbon stream. The inventors of the present invention have discovered that a portion of the hydrogen sulfide generated by the conversion remains in the conversion product during the separation process. Therefore, when the conversion product is used as a feedstock for ethylene cracking, such as steam cracking of the sulfur-containing conversion product, sulfur injection prior to entering the ethylene cracking furnace can be reduced or even eliminated, thereby achieving high-value utilization of the waste gas.

[0081] According to the present invention, the sulfur content of the hydrocarbon stream is 50-5000 mg / kg (preferably 200-1000 mg / kg), relative to the total weight of the hydrocarbon stream. The inventors of the present invention have found that too low a sulfur content in the hydrocarbon stream can easily cause the hydrogenation catalyst to continuously lose sulfur during the reaction process, change the valence state of the hydrogenation component, and thus cause catalyst deactivation. At the same time, too low a sulfur content cannot transfer the sulfur in the hydrocarbon stream to the hydrogenated product, and cannot solve the sulfur injection problem of the ethylene unit. If the sulfur content in the hydrocarbon stream is too high, it will increase the difficulty of removing it during the hydrogenation reaction, especially for low-pressure reaction processes, which greatly increases the difficulty of hydrodesulfurization. When excessive sulfides remain in the hydrogenated product and enter the ethylene unit, it will also cause the sulfur content of the ethylene product to increase, increasing the difficulty of subsequent removal.

[0082] According to one embodiment of the present invention, the conversion reaction can be a hydrogenation normalization reaction to obtain a conversion product with C4-C6 normal alkanes as the main product, or it can be a hydrocracking reaction to obtain a conversion product with C2-C3 alkanes as the main product. The inventors of the present invention have found through research that C5 and C6 isoalkanes can undergo unimolecular reactions and bimolecular reactions during the conversion reaction of the present invention, wherein the unimolecular reaction can convert isoalkanes into normal alkanes, and only a small amount of isoalkanes can directly undergo cracking reactions, while the bimolecular reaction refers to two small molecular isoalkanes being spliced ​​into a long-chain isoalkanes and then undergoing cracking reactions. As described below in this specification, the inventors of the present invention have found that by selecting a molecular sieve with shape-selective catalytic properties, especially a molecular sieve with a special straight pore structure and containing more medium-strong acid or strong acid, and then loading a suitable hydrogenation metal, it is possible to flexibly control the occurrence of unimolecular reactions and bimolecular reactions. Furthermore, since the normalization reaction is affected by the concentrations of n-alkanes and isoalkanes in the reactants, i.e., a high concentration of n-alkanes in the reactants inhibits the normalization reaction, limiting the increase in the n-alkanes ratio in the conversion product. Therefore, to obtain conversion products with higher n-alkanes content, a certain amount of cracking reaction must be ensured. The inventors of the present invention have also discovered that while the cracking reaction and the normalization reaction generally occur simultaneously, by adjusting the acid strength of the molecular sieve and the acid center, it is possible to enhance these different reaction processes. Strong acid centers favor the cracking reaction, while medium-strong acid centers favor the normalization reaction. Based on this reaction principle, the production ratio of C2-C3 alkanes and C4-C6 n-alkanes in the conversion product can be flexibly adjusted. The inventors of the present invention have also found through research that the content of isoalkanes in the raw materials also has a direct impact on the conversion process. For the cracking reaction, although there is no restriction on whether the reactants are normal alkanes or isoalkanes, the higher the isoalkanes content in the raw materials, the greater the probability of the cracking reaction, and the more obvious the improvement in the quality of the conversion product; while for the normalization reaction, the reactants are only isoalkanes, and the normalization reaction is affected by chemical equilibrium. The higher the isoalkanes content, the more conducive it is for the conversion reaction to proceed in the normalization direction.

[0083] According to one embodiment of the present invention, the reaction conditions of the conversion reaction include: a reaction pressure of 0.5-10.0 MPaG (preferably 2.0-8.0 MPaG or 2.0-5.0 MPaG), a reaction temperature of 250-500°C, preferably 300-500°C or 350-450°C, and a liquid hourly space velocity of 0.1-15.0 h -1 (Preferably 0.5-5.0h -1), the hydrogen-to-oil volume ratio is 10:1-2500:1, preferably 50:1-2500:1, 100:1-2000:1 or 100:1-1000:1). The inventors of the present invention have discovered that in the hydrogenation conversion process of C5-C6 isoparaffins, both the normalization reaction and the cracking reaction are typical endothermic reactions. The higher the reaction temperature, the more favorable the chemical reaction is in the forward direction. Too low a reaction temperature will inhibit the occurrence of normalization and cracking reactions, seriously affecting the conversion of isoparaffins. C5-C6 isoparaffins are in a gaseous state at high temperatures. During the gas-phase reaction process, the hydrogen-to-oil ratio is expressed as the hydrogen concentration per unit volume. A higher hydrogen concentration is favorable for the combination of hydrogen and reactants, which is conducive to the occurrence of normalization and hydrogenolysis reactions.

[0084] The inventors of the present invention have found that C5-C6 isoparaffins can exhibit a single-pass conversion rate of 40 wt% or more, 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or 90 wt% or more under the reaction conditions of the present invention. 7+ The conversion of components, large molecular cycloalkanes with higher carbon numbers are difficult to enter the catalyst pores for ring-opening reaction, and the cracking reaction of aromatics must first undergo hydrogenation saturation of aromatics. The hydrogenation saturation of aromatics is directly affected by the reaction pressure. In order to obtain a better conversion effect of isoparaffins, the present invention uses a lower reaction pressure, which is not conducive to the hydrogenation saturation of aromatics, and therefore has a poor conversion effect on aromatics. The inventors of the present invention have found that in the hydrogenation conversion process of low-carbon hydrocarbons, the reactants must first undergo a dehydrogenation reaction to generate positive carbon ions. As the molecular weight of the hydrocarbon molecules decreases, the bond energy between the C-C bonds gradually increases, that is, the smaller the molecular weight, the more difficult it is to undergo dehydrogenation reaction. Therefore, under the suitable conversion conditions for C5-C6 isoparaffins, C4 is difficult to react. If the C4 component is to react fully, more harsh reaction conditions are required, which will also cause excessive cracking of C5-C6 isoparaffins, a significant increase in reaction hydrogen consumption, and reduced economic benefits.

[0085] According to one embodiment of the present invention, the conversion reaction is carried out in the presence of a catalyst, and the catalyst includes molecular sieves and non-precious metal hydrogenation active metal components. According to the present invention, the molecular screening is from one or more of mordenite, ZSM molecular sieve, SAPO molecular sieve and EU-1 molecular sieve, more preferably selected from one or more of mordenite and ZSM molecular sieve, particularly preferably selected from one or more of mordenite, ZSM-5 molecular sieve, ZSM-11 molecular sieve, ZSM-12 molecular sieve, ZSM-22 molecular sieve, ZSM-23 molecular sieve, ZSM-35 molecular sieve, Beta molecular sieve and ZSM-38 molecular sieve, particularly selected from one or more of mordenite and ZSM-5 molecular sieve. Here, based on the weight of the catalyst, the content of the molecular sieve is 30-80wt% (preferably 40-70wt%). The inventors of the present invention have found that the acid strength of the molecular sieve directly affects the reaction characteristics of isoparaffins. Molecular sieves with more strong acid centers are more prone to cracking reactions, such as ZSM-5 molecular sieves; while those with more medium-strong acid centers are more prone to normalization reactions, such as mordenite. Therefore, according to the present invention, different reaction paths can be achieved by selecting the acid strength of the molecular sieve. The inventors of the present invention have found that in the conversion process of C5-C6 isoparaffins, the pore structure of the molecular sieve directly affects the reaction effect. For example, molecular sieves with supercage structures such as Y molecular sieves have large pores, and the residence time of small molecular isoparaffins in the catalyst pores is short, making it difficult to react effectively. At the same time, when a cracking reaction occurs, the large pore structure will lead to excessive isobutane generation, which is not conducive to improving the yield of normal paraffins in the conversion product.

[0086] The inventors of the present invention have discovered that there are two main reaction pathways in the hydroconversion process, one is the cracking reaction that converts to C2-C3 alkanes, and the other is the normalization reaction that generates C4-C6 normal alkanes. Generally, these two reactions occur simultaneously, but by adjusting the molecular sieve and the acid strength of the acid center, it is possible to strengthen the different reaction processes. Strong acid centers are conducive to the occurrence of cracking reactions, while medium-strong acid centers are conducive to the occurrence of normalization reactions. For example, mordenite contains more medium-strong acids, and its normalization reactions are more frequent; while ZSM-5 molecular sieve contains more strong acids, and its cracking reactions are more frequent. According to the present invention, by changing the weight ratio of the mordenite to the ZSM-5 molecular sieve between 0-100:100-0 (preferably 10-50:50-10), the weight ratio of C2-C3 alkanes to C4-C6 normal alkanes in the conversion product can be flexibly adjusted. To this end, according to the present invention, by adjusting the catalyst molecular sieve type, acidic center strength, and process parameters, the weight ratio of C2-C3 alkanes to C4-C6 normal alkanes in the conversion product can be flexibly adjusted within the range of 0.5:1-8:1 (preferably 0.9:1-5:1), thereby obtaining ethylene feedstocks with different hydrocarbon components. For conversion products with a higher C2-C3 alkane content, their normal hydrocarbon content is higher, but the conversion process requires more hydrogen consumption; for conversion products with a higher C4-C6 normal alkane content, hydrogen consumption is lower during the reaction, and the quality of the ethylene feedstock can also be improved. Here, from the perspective of achieving a better technical effect of the present invention, the C4-C6 normal alkanes are more preferably C5-C6 normal alkanes.

[0087] According to one embodiment of the present invention, the non-precious metal hydrogenation active metal component is selected from one or more of the non-precious metals of Group VIB and Group VIII of the Periodic Table of Elements. Preferably, the non-precious metal of Group VIB is preferably selected from one or more of molybdenum and tungsten (particularly preferably molybdenum), and the non-precious metal of Group VIII is preferably selected from one or more of cobalt and nickel (particularly preferably nickel). Here, based on the weight of the catalyst, the content of the non-precious metal of Group VIB (calculated as oxide) is 5.0-30.0wt% (10.0-20.0wt%), and the content of the non-precious metal of Group VIII (calculated as oxide) is 0.5-15.0wt% (preferably 3.0-10.0wt%). Preferably, the non-precious metal hydrogenation active metal component of the present invention does not contain precious metals such as Pt. The inventors of the present invention have discovered that, compared to non-precious metals, precious metal components have stronger hydrogenation / dehydrogenation properties, enabling dehydrogenation reactions at lower reaction temperatures, converting C5-C6 isoparaffins into C5-C6 normal paraffins. However, it is well known that cracking reactions are primarily affected by reaction temperature; lower reaction temperatures and stronger hydrogenation properties inhibit cracking reactions. Therefore, using precious metal catalysts in an operation mode focused on normalization makes it difficult to produce significant amounts of C2-C3 alkanes. Using non-precious metal catalysts, due to their relatively weak dehydrogenation properties, requires higher reaction temperatures for the reaction to occur. Consequently, a significant amount of cracking reactions also occur simultaneously with the normalization reaction, producing more C2-C3 alkanes.

[0088] According to one embodiment of the present invention, the catalyst further comprises a binder. The binder may be selected from conventional materials in the art, including but not limited to aluminum oxide and silicon oxide, with aluminum oxide being preferred. The binder content is 5-65 wt% (preferably 10-35 wt%) based on the weight of the catalyst.

[0089] According to one embodiment of the present invention, the specific surface area of ​​the catalyst is 200-400m 2 / g, and the pore volume is 0.25-0.45mL / g.

[0090] According to one embodiment of the present invention, the catalyst can be prepared according to conventional methods in the art. The preparation method includes preparing a carrier and loading a non-precious metal hydrogenation-active metal component, wherein the carrier preparation process is as follows: the molecular sieve and the binder are mechanically mixed, formed, and then dried and calcined to form a catalyst carrier. Conventional conditions can be used for drying and calcining the carrier. The drying conditions are: drying at 100°C-150°C for 1-12 hours. The calcination conditions are: calcining at 450°C-550°C for 2.5-6.0 hours.

[0091] According to one embodiment of the present invention, in the preparation method of the catalyst, the method for loading the non-precious metal hydrogenation active metal component is a conventional method, such as a kneading method, an impregnation method, etc., preferably an impregnation method. The impregnation method can be a saturation impregnation method, an excess impregnation method, or a complex impregnation method, that is, the catalyst support is impregnated with a solution containing the desired non-precious metal hydrogenation active metal component, and then dried and calcined to obtain the first catalyst. The drying conditions are: drying at 100°C-150°C for 1-12 hours. The calcination conditions are: calcining at 450°C-550°C for 2.5-6.0 hours.

[0092] According to one embodiment of the present invention, from the perspective of the balance between quality improvement effect and energy consumption, the content of C7+ hydrocarbons in the conversion product is not higher than 5wt% (preferably not higher than 1wt%), the content of C5-C6 isoparaffins is 0-50wt% (preferably 10-40wt%), the content of C2-C6 normal paraffins is 40-90wt% (preferably 50-80wt%), and the content of cyclic hydrocarbons is not higher than 3wt% (preferably not higher than 1wt%), based on the total weight of the conversion product as 100wt%.

[0093] According to a preferred embodiment of the present invention, if the hydrocarbon stream contains sulfur, the conversion product also contains sulfur. Preferably, substantially all of the sulfur contained in the hydrocarbon stream is retained in the conversion product. To this end, the conversion product typically has a sulfur content of 50-1000 mg / kg (preferably 100-200 mg / kg), based on the total weight of the conversion product.

[0094] According to one embodiment of the present invention, step 3) may include the following steps: separating the conversion product (referred to as the first separation) to obtain a separated stream consisting primarily of C2+ hydrocarbons (e.g., accounting for more than 95 wt%, more than 98 wt%, more than 99 wt%, or substantially 100 wt% of the total). Here, C2+ hydrocarbons refer to hydrocarbons with 2 or more carbon atoms. To this end, according to the present invention, the purpose of the first separation is to separate and remove hydrogen from the conversion product. This hydrogen may be hydrogen generated during the conversion reaction or unreacted hydrogen, so as to prevent hydrogen from adversely affecting the subsequent steam cracking step. According to the present invention, there are no particular limitations on the first separation, as long as it can effectively separate hydrogen from the conversion product. Furthermore, the first separation can be performed in any gas-liquid separation device conventionally known in the art, such as a flash tank, and is not particularly limited. According to the present invention, the operating conditions of the first separation generally include a pressure of 0.5-10.0 MPaG (preferably 2.0-8.0 MPaG or 2.0-5.0 MPaG) and a temperature of 40-70°C. In addition, according to the present invention, the separated hydrogen can be recycled back to the step 2) as a circulating material to perform the conversion reaction.

[0095] According to one embodiment of the present invention, the step 3) may further include the following steps: separating the separated stream (referred to as the second separation) to obtain a high-carbon stream mainly composed of C4+ hydrocarbons (e.g., accounting for more than 90wt%, more than 95wt%, more than 98wt%, more than 99wt% or substantially 100wt% of the total amount) and a low-carbon stream mainly composed of C2-C3 hydrocarbons (e.g., accounting for more than 90wt%, more than 95wt%, more than 98wt%, more than 99wt% or substantially 100wt% of the total amount). Here, the C4+ hydrocarbons refer to hydrocarbons with a carbon number of 4 or more, covering C4-C6 isoalkanes and C4-C6 normal alkanes, while C2-C3 hydrocarbons cover ethane and propane. To this end, according to the present invention, the purpose of the second separation is to effectively separate the hydrocarbons with a carbon number of 4 or more from the hydrocarbons with a carbon number of 2 and 3 in the separated stream. However, the second separation is not intended to separate any isomers. For example, the second separation is not intended to separate C4-C6 isoparaffins from C4-C6 normal paraffins in the separated stream, which is a major feature of the present invention. The purpose of the present invention is to maximize the production of C2-C6 normal paraffins. The prior art typically converts C5-C6 isoparaffins to normal paraffins, meaning that only normalization occurs, suppressing the occurrence of cracking reactions. The entire normalization reaction process requires a lower reaction temperature and a lower hydrogen-to-oil volume ratio. However, the normalization reaction is affected by chemical equilibrium. After the concentration of normal paraffins in the product reaches a certain proportion (approximately 30%), the normalization reaction is inhibited, making it difficult to increase the yield of normal paraffins in the product by adjusting the reaction process. This route requires combining normal-isomer separation with the separation of normal paraffins and further conversion of unconverted isoparaffins. However, for steam cracking to produce ethylene, C2-C6 normal alkanes are ideal raw materials. The present invention, by using a dedicated catalyst and controlling the reaction conditions, simultaneously strengthens the occurrence of normalization and cracking reactions, breaks the influence of chemical equilibrium on the normalization reaction, and further increases the yield of normal alkanes in the conversion product through the cracking reaction. The latter is particularly suitable for directly using it as a steam cracking feedstock to produce ethylene. The present invention is based on this purpose. The inventors of the present invention have found that, generally, steam cracking units include multiple reaction furnaces depending on the feed. This is mainly because the reaction feed with a lower molecular weight requires a higher cracking temperature, such as a gas furnace and a liquid furnace. During the isoparaffin conversion process, the distribution of the conversion products can be flexibly adjusted according to different needs. If the C2-C3 content in the conversion product is low, no secondary separation is required and it directly enters the liquid furnace for conversion. If the C2-C3 content is high, a secondary separation is required and the products enter the gas and liquid furnaces respectively.The present invention is not a normalization reaction in the traditional sense, that is, the conversion of isoparaffins into normal paraffins of the same molecular weight. During the conversion process, in order to obtain a higher yield of normal paraffins, a certain amount of cracking reaction will be accompanied. The generated C2-C3 alkanes are very easy to separate from the liquid phase product. The liquid phase product obtained after the conversion is significantly reduced compared with the fresh feed, and the proportion of normal paraffins will be greatly increased. At this time, performing normal-isomer separation will lead to a significant increase in energy consumption and reduce the overall economic benefits.

[0096] According to the present invention, there is no particular limitation on the second separation, as long as it can effectively separate the C4+ hydrocarbons from the C2-C3 hydrocarbons, and the second separation can be carried out in any gas-liquid separation device conventionally known in the art, such as a distillation tower, without particular limitation. According to the present invention, the operating conditions of the second separation include a pressure of 0.5-1.5 MPaG and a temperature of 30-60°C. During the isoparaffin conversion process, the distribution of the conversion products can be flexibly adjusted according to different needs. If the C2-C3 content in the conversion product is low, the second separation is not required and the product directly enters the liquid furnace for conversion. If the C2-C3 content is high, the second separation is required and the products enter the gas and liquid furnaces respectively.

[0097] According to one embodiment of the present invention, step 3) may further include recycling the high-carbon feed stream as a hydrocarbon feed stream back to step 2) for the conversion reaction. The inventors of the present invention have discovered that the high-carbon feed stream contains unreacted C5-C6 isoparaffins and is therefore suitable as a hydrocarbon feed stream for further conversion. This recycling step is optional, but preferably essential.

[0098] According to one embodiment of the present invention, the step 3) may further include the following steps: steam cracking the separated stream or the low-carbon stream to obtain a cracking product containing ethylene. The inventors of the present invention have found that the low-carbon stream or the separated stream can be directly used as a raw material for steam cracking without any additional treatment (such as by separation to enrich normal alkanes, or by separation to remove any light components or heavy components). Here, the steam cracking can be carried out in any manner conventionally known in the art and is not particularly limited. Generally speaking, the operating conditions of the steam cracking include: reaction temperature 750-900°C, reaction pressure 0.1-0.5MPaG, water-oil mass ratio 0.2-0.6. According to the present invention, preferably, in the steam cracking, the amount of sulfur injection is to control the sulfur content in the raw material to 100-200mg / kg. According to this preferred embodiment of the present invention, since the conversion product, the separated material stream or the low-carbon material stream substantially retains all the sulfur contained in the sulfur-containing feed hydrocarbon, the sulfur injection demand of the steam cracking can be reduced by at least 50%. In the most preferred case, the steam cracking can completely eliminate the need for additional sulfur injection, and only the sulfur contained in the conversion product, the separated material stream or the low-carbon material stream can be used to meet the steam cracking demand.

[0099] According to one embodiment of the present invention, a system for improving the quality of a hydrocarbon stream is provided, comprising a hydrocarbon stream providing unit and a hydrocarbon stream conversion unit. According to the present invention, the system is specifically configured to implement the method described earlier in this specification. Therefore, except for the contents specified in this paragraph, any other contents or matters not specified herein are directly referred to the contents or matters described earlier in this specification with respect to the method, and are not particularly limited.

[0100] The present invention will be further described below with reference to the accompanying drawings, but the present invention is not limited thereto.

[0101] According to Figure 1, hydrocarbon stream 1 is mixed with hydrogen 2 and enters hydroconversion reaction zone 3. The effluent 4 of the hydroconversion reaction zone enters high-pressure separator 5. The separated gaseous stream hydrogen-rich gas 6 is recycled, and the liquid stream is used as ethylene feedstock.

[0102] According to Figure 2, the hydrocarbon stream 1 is mixed with hydrogen 2 and enters the hydroconversion reaction zone 3. The effluent 4 of the hydroconversion reaction zone enters the high-pressure separator 5. The separated gaseous stream hydrogen-rich gas 6 is recycled. The liquid stream 7 enters the distillation tower for separation to obtain a gaseous product 9 as an ethylene feedstock. The liquid product 10 is circulated to the inlet of the hydroconversion reaction zone 3.

[0103] Example

[0104] The present invention is further described in detail below using examples and comparative examples, but the present invention is not limited to these examples.

[0105] In the following examples and comparative examples, the operating conditions of the high-pressure separator 5 include a pressure of 2.5 MPaG and a temperature of 50°C, and the operating conditions of the fractionating tower include a pressure of 1.0 MPaG and a temperature of 40°C.

[0106] First embodiment series

[0107] In the following examples and comparative examples, the yield is calculated as the mass percentage of the output to the feed amount. The ton-of-oil processing benefit refers to the profit obtained from processing 1 ton of raw materials, and is calculated as (ethylene product price - raw material and hydrogen price - processing energy consumption) / processing volume. The ton-of-oil processing benefit is based on the raw materials being directly used as ethylene raw materials without hydrogenation conversion.

[0108] In the following examples and comparative examples, each hydroconversion catalyst is represented by Cat-A followed by a number, such as Cat-A1, Cat-A2, Cat-A3, etc. The hydroconversion catalyst was prepared by a conventional active metal saturation impregnation method. The physicochemical properties of the obtained catalyst are shown in Table 1.

[0109] The preparation method of Cat-A1 to Cat-A3 catalysts is as follows:

[0110] (1) Mordenite with a SiO2 / Al2O3 molar ratio of 15 was selected and mechanically mixed with a binder, molded, dried at 120°C for 10 hours, and calcined at 500°C for 4 hours to prepare a catalyst carrier.

[0111] (2) The catalyst carrier obtained in step (1) was easily impregnated with the active component, dried at 120°C for 10 hours, and calcined at 500°C for 4 hours to prepare a hydrogenation catalyst.

[0112] The preparation method of Cat-A4 to Cat-A7 catalysts is as follows:

[0113] (1) ZSM-5 with a SiO2 / Al2O3 molar ratio of 10 was selected and mechanically mixed with a binder, molded, dried at 120°C for 10 hours, and calcined at 500°C for 4 hours to prepare a catalyst carrier.

[0114] (2) The catalyst carrier obtained in step (1) was easily impregnated with the active component, dried at 120°C for 10 hours, and calcined at 500°C for 4 hours to prepare a hydrogenation catalyst.

[0115] The properties of the raw materials are shown in Table 2. Among them, the raw material 5 needs to be obtained by adsorption separation or distillation of the isoparaffin raw material.

[0116] Table 1

[0117] Table 2

[0118] Example 1

[0119] The process shown in Figure 1 is as follows:

[0120] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A1;

[0121] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is directly used as an ethylene feedstock. The process conditions and quality improvement results for this example are shown in Table 3.

[0122] In this example, about 49 wt% of the total amount of C5-C6 isoparaffins were converted into C2-C6 normal paraffins.

[0123] Example 2

[0124] The process shown in Figure 1 is as follows:

[0125] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A2;

[0126] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is directly used as an ethylene feedstock. The process conditions and quality improvement results for this example are shown in Table 3.

[0127] In this example, about 45 wt% of the total amount of C5-C6 isoparaffins are converted into C2-C6 normal paraffins.

[0128] Example 3

[0129] The process shown in Figure 1 is as follows:

[0130] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A3;

[0131] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is directly used as an ethylene feedstock. The process conditions and quality improvement results for this example are shown in Table 3.

[0132] In this example, about 34 wt% of the total amount of C5-C6 isoparaffins are converted into C2-C6 normal paraffins.

[0133] Example 4

[0134] Use the process shown in Figure 1. It includes:

[0135] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A4;

[0136] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is directly used as an ethylene feedstock. The process conditions and quality improvement results for this example are shown in Table 3.

[0137] In this example, about 64 wt% of the total amount of C5-C6 isoparaffins are converted into C2-C6 normal paraffins.

[0138] Example 5

[0139] The process shown in Figure 1 is as follows:

[0140] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A5;

[0141] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is directly used as an ethylene feedstock. The process conditions and quality improvement results for this example are shown in Table 3.

[0142] In this example, about 60 wt% of the total amount of C5-C6 isoparaffins are converted into C2-C6 normal paraffins.

[0143] Example 6

[0144] The process shown in Figure 1 is as follows:

[0145] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A6;

[0146] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is directly used as an ethylene feedstock. The process conditions and quality improvement results for this example are shown in Table 3.

[0147] In this example, about 52 wt% of the total amount of C5-C6 isoparaffins are converted into C2-C6 normal paraffins.

[0148] Example 7

[0149] The process shown in Figure 2 is as follows:

[0150] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A4;

[0151] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is separated in a fractionating tower to obtain C2 and C3, which are used as ethylene feedstock. The remaining stream is cracked. The process conditions and quality improvement results for this example are shown in Table 3.

[0152] In this example, about 78 wt% of the total amount of C5-C6 isoparaffins are converted into C2-C3 normal paraffins.

[0153] Example 8

[0154] The process shown in Figure 2 is as follows:

[0155] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A5;

[0156] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is separated in a fractionating tower to obtain C2 and C3, which are used as ethylene feedstock and then recycled to C4-C6 for cracking. The process conditions and quality improvement results for this example are shown in Table 3.

[0157] In this example, about 78 wt% of the total amount of C5-C6 isoparaffins are converted into C2-C3 normal paraffins.

[0158] Example 9

[0159] The process shown in Figure 2 is as follows:

[0160] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A5;

[0161] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is separated in a fractionating tower to obtain C2 and C3, which are used as ethylene feedstock and then recycled to C4-C6 for cracking. The process conditions and quality improvement results for this example are shown in Table 3.

[0162] In this example, about 78 wt% of the total amount of C5-C6 isoparaffins are converted into C2-C3 normal paraffins.

[0163] Example 10

[0164] The process shown in Figure 1 is as follows:

[0165] (1) Raw material 2 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A1;

[0166] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is directly used as an ethylene feedstock. The process conditions and quality improvement results for this example are shown in Table 3.

[0167] In this example, about 34 wt% of the total amount of C5-C6 isoparaffins are converted into C2-C6 normal paraffins.

[0168] Example 11

[0169] The process shown in Figure 1 is as follows:

[0170] (1) The raw material 3 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A4;

[0171] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is directly used as an ethylene feedstock. The process conditions and quality improvement results for this example are shown in Table 3.

[0172] In this example, about 65 wt% of the total amount of C5-C6 isoparaffins are converted into C2-C6 normal paraffins.

[0173] Example 12

[0174] Use the process shown in Figure 1. It includes:

[0175] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A1;

[0176] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is directly used as an ethylene feedstock. The process conditions and quality improvement results for this example are shown in Table 3.

[0177] In this example, about 27 wt% of the total amount of C5-C6 isoparaffins were converted into C2-C6 normal paraffins.

[0178] Example 13

[0179] The method for improving the quality of hydrocarbon streams adopts the process shown in Figure 2, comprising:

[0180] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A4;

[0181] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the C2 and C3 obtained from the liquid stream are separated and used as ethylene feedstock. The remaining stream (referred to as the C4-C6 recycle stream) is cracked. The process conditions and quality improvement results for this example are shown in Table 3.

[0182] In this example, about 78 wt% of the total C5-C6 isoparaffins are converted into C2-C3 normal paraffins. The weight ratio of the C4-C6 recycle stream to the feedstock 1 is 0.3:1.

[0183] Example 14

[0184] The method for improving the quality of hydrocarbon streams adopts the process shown in Figure 2, comprising:

[0185] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A5;

[0186] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the C2 and C3 obtained from the liquid stream are separated and used as ethylene feedstock for the C4-C6 cycle. The process conditions and quality improvement results for this example are shown in Table 3.

[0187] In this example, about 78 wt% of the total C5-C6 isoparaffins are converted into C2-C3 normal paraffins. The weight ratio of the C4-C6 recycle stream to the feedstock 1 is 0.4:1.

[0188] Example 15

[0189] The method for improving the quality of hydrocarbon streams adopts the process shown in Figure 2, comprising:

[0190] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A6;

[0191] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the C2 and C3 obtained from the liquid stream are separated and used as ethylene feedstock for the C4-C6 cycle. The process conditions and quality improvement results for this example are shown in Table 3.

[0192] In this example, about 78 wt% of the total C5-C6 isoparaffins are converted into C2-C3 normal paraffins. The weight ratio of the C4-C6 recycle stream to the feedstock 1 is 0.3:1.

[0193] Comparative Example 1

[0194] The process shown in Figure 1 is as follows:

[0195] (1) The raw material 4 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A1;

[0196] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is directly used as an ethylene feedstock. The process conditions and quality improvement results for this example are shown in Table 3.

[0197] Comparative Example 2

[0198] The process shown in Figure 1 is as follows:

[0199] (1) The raw material 4 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A4;

[0200] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is directly used as an ethylene feedstock. The process conditions and quality improvement results for this example are shown in Table 3.

[0201] Comparative Example 3

[0202] The process shown in Figure 1 is as follows:

[0203] (1) The raw material 5 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A1;

[0204] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is directly used as an ethylene feedstock. The process conditions and quality improvement results for this example are shown in Table 3.

[0205] Comparative Example 4

[0206] The process shown in Figure 1 is as follows:

[0207] (1) The raw material 5 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A4;

[0208] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is directly used as an ethylene feedstock. The process conditions and quality improvement results for this example are shown in Table 3.

[0209] Comparative Example 5

[0210] The process shown in Figure 1 is as follows:

[0211] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A7;

[0212] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is directly used as an ethylene feedstock. The process conditions and quality improvement results for this example are shown in Table 3.

[0213] Comparative Example 6

[0214] The process shown in Figure 1 is as follows:

[0215] (1) The raw material 6 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A1;

[0216] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is directly used as an ethylene feedstock. The process conditions and quality improvement results for this example are shown in Table 3.

[0217] Comparative Example 7

[0218] The process shown in Figure 1 is as follows:

[0219] (1) The raw material 7 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A1;

[0220] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is directly used as an ethylene feedstock. The process conditions and quality improvement results for this example are shown in Table 3.

[0221] Comparative Example 8

[0222] The process shown in Figure 1 is as follows:

[0223] (1) Raw material 1 and hydrogen are mixed and sequentially fed into the hydroconversion reaction zone at a reaction temperature of 250°C; the hydroconversion reaction zone is loaded with hydroconversion catalyst Cat-A1;

[0224] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is directly used as an ethylene feedstock. The process conditions and quality improvement results for this example are shown in Table 3.

[0225] Comparative Example 9

[0226] The process shown in Figure 1 is as follows:

[0227] (1) Raw material 1 and hydrogen are mixed and sequentially fed into the hydroconversion reaction zone at a reaction temperature of 200°C; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A1;

[0228] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is directly used as an ethylene feedstock. The process conditions and quality improvement results for this example are shown in Table 3.

[0229] Comparative Example 10

[0230] The process shown in Figure 1 is as follows:

[0231] (1) Raw material 1 and hydrogen are mixed and sequentially fed into the hydroconversion reaction zone, with a hydrogen-to-oil volume ratio of 20:1; the hydroconversion reaction zone is loaded with hydroconversion catalyst Cat-A1;

[0232] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is directly used as an ethylene feedstock. The process conditions and quality improvement results for this example are shown in Table 3.

[0233] Comparative Example 11

[0234] The process shown in Figure 1 is as follows:

[0235] (1) Raw material 1 and hydrogen are mixed and sequentially fed into the hydroconversion reaction zone, with a hydrogen-to-oil volume ratio of 5:1; the hydroconversion reaction zone is loaded with hydroconversion catalyst Cat-A1;

[0236] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is directly used as an ethylene feedstock. The process conditions and quality improvement results for this example are shown in Table 3.

[0237] Comparative Example 12

[0238] The process shown in Figure 1 is as follows:

[0239] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with a solid acid catalyst;

[0240] (2) The effluent from the hydroconversion reaction zone in step (1) is separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream is directly used as an ethylene feedstock. The process conditions and quality improvement results for this example are shown in Table 3.

[0241] Table 3 Quality improvement results

[0242] Table 3 Quality improvement results

[0243] Table 3 Quality improvement results

[0244] Table 3 Quality improvement results

[0245] By comparison, it can be seen that the method of the present invention can effectively convert low-quality ethylene raw materials into high-quality ethylene raw materials. The hydrocarbon stream after hydrogenation conversion can greatly improve the ethylene and triene yields of the ethylene plant. In addition, the process is simple, the operation difficulty is low, and it has very good economic benefits.

[0246] Second embodiment series

[0247] In the following examples and comparative examples, the yield is calculated as the mass percentage of the output to the feed amount. The ton-of-oil processing benefit refers to the profit obtained from processing 1 ton of raw materials, and is calculated as (ethylene product price - raw material and hydrogen price - processing energy consumption) / processing volume. The ton-of-oil processing benefit is based on the raw materials being directly used as ethylene raw materials without hydrogenation conversion.

[0248] In the following examples and comparative examples, each hydroconversion catalyst is represented by Cat-A followed by a number, such as Cat-A1, Cat-A2, Cat-A3, etc. The hydroconversion catalyst was prepared by a conventional active metal saturation impregnation method. The physicochemical properties of the obtained catalyst are shown in Table 1.

[0249] The preparation method of Cat-A1 to Cat-A3 catalysts is as follows:

[0250] (1) Mordenite with a SiO2 / Al2O3 molar ratio of 15 was selected and mechanically mixed with a binder, molded, dried at 120°C for 10 hours, and calcined at 500°C for 4 hours to prepare a catalyst carrier.

[0251] (2) The catalyst carrier obtained in step (1) was easily impregnated with the active component, dried at 120°C for 10 hours, and calcined at 500°C for 4 hours to prepare a hydrogenation catalyst.

[0252] The preparation method of Cat-A4 to Cat-A6 catalysts is:

[0253] (1) ZSM-5 with a SiO2 / Al2O3 molar ratio of 10 was selected and mechanically mixed with a binder, molded, dried at 120°C for 10 hours, and calcined at 500°C for 4 hours to prepare a catalyst carrier.

[0254] (2) The catalyst carrier obtained in step (1) was easily impregnated with the active component, dried at 120°C for 10 hours, and calcined at 500°C for 4 hours to prepare a hydrogenation catalyst.

[0255] The preparation method of Cat-A7 catalyst is:

[0256] (1) Mordenite with a SiO2 / Al2O3 molar ratio of 15 was selected and mechanically mixed with a binder, molded, dried at 120°C for 10 hours, and calcined at 500°C for 4 hours to prepare a catalyst.

[0257] The properties of the raw materials are shown in Table 2. Among them, the raw material 5 needs to be obtained by adsorption separation or distillation of the isoparaffin raw material.

[0258] Table 1

[0259] Table 2

[0260] Example 1

[0261] The process shown in Figure 1 is as follows:

[0262] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A1;

[0263] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0264] In this example, about 47 wt% of the total amount of C5-C6 isoparaffins were converted into C2-C6 normal paraffins.

[0265] Example 2

[0266] The process shown in Figure 1 is as follows:

[0267] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A2;

[0268] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0269] In this example, about 38 wt% of the total amount of C5-C6 isoparaffins are converted into C2-C6 normal paraffins.

[0270] Example 3

[0271] The process shown in Figure 1 is as follows:

[0272] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A3;

[0273] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0274] In this example, about 31 wt% of the total amount of C5-C6 isoparaffins were converted into C2-C6 normal paraffins.

[0275] Example 4

[0276] The process shown in Figure 1 is as follows:

[0277] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A4;

[0278] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0279] In this example, about 59 wt% of the total amount of C5-C6 isoparaffins were converted into C2-C6 normal paraffins.

[0280] Example 5

[0281] The process shown in Figure 1 is as follows:

[0282] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A5;

[0283] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0284] In this example, about 53 wt% of the total amount of C5-C6 isoparaffins were converted into C2-C6 normal paraffins.

[0285] Example 6

[0286] The process shown in Figure 1 is as follows:

[0287] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A6;

[0288] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0289] In this example, about 46 wt% of the total amount of C5-C6 isoparaffins are converted into C2-C6 normal paraffins.

[0290] Example 7

[0291] The process shown in Figure 2 is as follows:

[0292] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A4;

[0293] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was separated in a fractionating tower to obtain C2 and C3, which were used as ethylene feedstock. The remaining stream (referred to as the C4-C6 recycle stream) was cracked. The process conditions and conversion results for this example are shown in Table 3.

[0294] In this example, about 78 wt% of the total amount of C5-C6 isoparaffins are converted into C2-C3 normal paraffins.

[0295] Example 8

[0296] The process shown in Figure 2 is as follows:

[0297] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A5;

[0298] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was separated in a fractionating tower to obtain C2 and C3, which were used as ethylene feedstock and then recycled to C4-C6 for cracking. The process conditions and conversion results for this example are shown in Table 3.

[0299] In this example, about 78 wt% of the total amount of C5-C6 isoparaffins are converted into C2-C3 normal paraffins.

[0300] Example 9

[0301] The process shown in Figure 2 is as follows:

[0302] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A5;

[0303] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was separated in a fractionating tower to obtain C2 and C3, which were used as ethylene feedstock and then recycled to C4-C6 for cracking. The process conditions and conversion results for this example are shown in Table 3.

[0304] In this example, about 78 wt% of the total amount of C5-C6 isoparaffins are converted into C2-C3 normal paraffins.

[0305] Example 10

[0306] The process shown in Figure 1 is as follows:

[0307] (1) Raw material 2 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A1;

[0308] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0309] In this example, about 39 wt% of the total amount of C5-C6 isoparaffins were converted into C2-C6 normal paraffins.

[0310] Example 11

[0311] The process shown in Figure 1 is as follows:

[0312] (1) The raw material 3 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A4;

[0313] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0314] In this example, about 36 wt% of the total amount of C5-C6 isoparaffins are converted into C2-C6 normal paraffins.

[0315] Example 12

[0316] The process shown in Figure 1 is as follows:

[0317] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A1;

[0318] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0319] In this example, about 28 wt% of the total amount of C5-C6 isoparaffins were converted into C2-C6 normal paraffins.

[0320] Example 13

[0321] The process shown in Figure 1 is as follows:

[0322] (1) The raw material 7 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A1;

[0323] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0324] In this example, about 47 wt% of the total amount of C5-C6 isoparaffins are converted into C2-C6 normal paraffins.

[0325] Example 14

[0326] The process shown in Figure 1 is as follows:

[0327] (1) The raw material 8 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A1;

[0328] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0329] In this example, about 47 wt% of the total amount of C5-C6 isoparaffins are converted into C2-C6 normal paraffins.

[0330] Comparative Example 1

[0331] The process shown in Figure 1 is as follows:

[0332] (1) The raw material 4 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A1;

[0333] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0334] Comparative Example 2

[0335] The process shown in Figure 1 is as follows:

[0336] (1) The raw material 4 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A4;

[0337] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0338] Comparative Example 3

[0339] The process shown in Figure 1 is as follows:

[0340] (1) The raw material 5 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A1;

[0341] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0342] Comparative Example 4

[0343] The process shown in Figure 1 is as follows:

[0344] (1) The raw material 5 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A4;

[0345] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0346] Comparative Example 5

[0347] The process shown in Figure 1 is as follows:

[0348] (1) The raw material 6 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A1;

[0349] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0350] Comparative Example 6

[0351] Use the process shown in Figure 1. It includes:

[0352] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A7;

[0353] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0354] Table 3 Transformation results

[0355] Table 3 Conversion results

[0356] Table 3 Conversion results

[0357] Table 3 Conversion results

[0358] By comparison, it can be seen that the method of the present invention can effectively convert the sulfide in the raw material into hydrogen sulfide, and selectively retain it in the conversion product. When the conversion product is used as an ethylene raw material, the amount of sulfur injection can be reduced or even eliminated, thereby realizing high-value utilization of worthless components.

[0359] Third embodiment series

[0360] In the following examples and comparative examples, the yield is calculated as the mass percentage of the output to the feed amount. The ton-of-oil processing benefit refers to the profit obtained from processing 1 ton of raw materials, and is calculated as (ethylene product price - raw material and hydrogen price - processing energy consumption) / processing volume. The ton-of-oil processing benefit is based on the raw materials being directly used as ethylene raw materials without hydrogenation conversion.

[0361] In the following Examples and Comparative Examples, each hydroconversion catalyst is designated by a number, such as Cat-A, Cat-B, or Cat-C, such as Cat-A1, Cat-A2, and Cat-A3. The hydroconversion catalysts were prepared using a conventional active metal saturation impregnation method. The physicochemical properties of the resulting catalysts are shown in Table 1.

[0362] The preparation method of Cat-A catalyst is:

[0363] (1) Mordenite with a SiO2 / Al2O3 molar ratio of 15 was selected and mechanically mixed with a binder, molded, dried at 120°C for 10 hours, and calcined at 500°C for 4 hours to prepare a catalyst carrier.

[0364] (2) The catalyst carrier obtained in step (1) was easily impregnated with the active component, dried at 120°C for 10 hours, and calcined at 500°C for 4 hours to prepare a hydrogenation catalyst.

[0365] The preparation method of Cat-B catalyst is:

[0366] (1) A ZSM-5 molecular sieve with a SiO2 / Al2O3 molar ratio of 10 was selected and mechanically mixed with a binder, formed, dried at 120°C for 10 hours, and calcined at 500°C for 4 hours to prepare a catalyst carrier.

[0367] (2) The catalyst carrier obtained in step (1) was easily impregnated with the active component, dried at 120°C for 10 hours, and calcined at 500°C for 4 hours to prepare a hydrogenation catalyst.

[0368] The preparation method of Cat-C catalyst is:

[0369] (1) A ZSM-35 molecular sieve with a SiO2 / Al2O3 molar ratio of 20 was selected and mechanically mixed with a binder, formed, dried at 120°C for 10 hours, and calcined at 500°C for 4 hours to prepare a catalyst carrier.

[0370] (2) The catalyst carrier obtained in step (1) was easily impregnated with the active component, dried at 120°C for 10 hours, and calcined at 500°C for 4 hours to prepare a hydrogenation catalyst.

[0371] The preparation method of Cat-D catalyst is:

[0372] (1) SAPO-34 molecular sieve with a SiO2 / Al2O3 molar ratio of 0.5 was mechanically mixed with a binder, formed, dried at 120°C for 10 hours, and calcined at 500°C for 4 hours to prepare a catalyst support.

[0373] (2) The catalyst carrier obtained in step (1) was easily impregnated with the active component, dried at 120°C for 10 hours, and calcined at 500°C for 4 hours to prepare a hydrogenation catalyst.

[0374] The preparation method of Cat-E catalyst is:

[0375] (1) Select Y molecular sieve with a SiO2 / Al2O3 molar ratio of 15 and mechanically mix it with a binder, shape it, dry it at 120℃ for 10 hours, and calcine it at 500℃ for 4 hours to prepare a catalyst carrier.

[0376] (2) The catalyst carrier obtained in step (1) was easily impregnated with the active component, dried at 120°C for 10 hours, and calcined at 500°C for 4 hours to prepare a hydrogenation catalyst.

[0377] The properties of the raw materials are shown in Table 2. Among them, the raw material 5 needs to be obtained by adsorption separation or distillation of the isoparaffin raw material.

[0378] Table 1

[0379] Table 1

[0380] Table 2

[0381] Example 1

[0382] The process shown in Figure 1 is as follows:

[0383] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A1;

[0384] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0385] In this example, about 33 wt% of the total C5-C6 isoparaffins were converted into C2-C6 normal paraffins, and the weight ratio of C2-C3 hydrocarbons to C4-C6 normal paraffins in the reaction effluent was 0.9:1.

[0386] Example 2

[0387] The process shown in Figure 1 is as follows:

[0388] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A2;

[0389] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0390] In this example, about 37 wt% of the total C5-C6 isoparaffins were converted into C2-C6 normal paraffins, and the weight ratio of C2-C3 hydrocarbons to C4-C6 normal paraffins in the reaction effluent was 1.4:1.

[0391] Example 3

[0392] The process shown in Figure 1 is as follows:

[0393] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A3;

[0394] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0395] In this example, about 42 wt% of the total C5-C6 isoparaffins were converted into C2-C6 normal paraffins, and the weight ratio of C2-C3 hydrocarbons to C4-C6 normal paraffins in the reaction effluent was 2.1:1.

[0396] Example 4

[0397] The process shown in Figure 1 is as follows:

[0398] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-B1;

[0399] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0400] In this example, about 62 wt% of the total C5-C6 isoparaffins were converted into C2-C6 normal paraffins, and the weight ratio of C2-C3 hydrocarbons to C4-C6 normal paraffins in the reaction effluent was 5:1.

[0401] Example 5

[0402] The process shown in Figure 1 is as follows:

[0403] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-B2;

[0404] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0405] In this example, about 57 wt% of the total C5-C6 isoparaffins were converted into C2-C6 normal paraffins, and the weight ratio of C2-C3 hydrocarbons to C4-C6 normal paraffins in the reaction effluent was 4.4:1.

[0406] Example 6

[0407] The process shown in Figure 1 is as follows:

[0408] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-B3;

[0409] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0410] In this example, about 52 wt% of the total C5-C6 isoparaffins were converted into C2-C6 normal paraffins, and the weight ratio of C2-C3 hydrocarbons to C4-C6 normal paraffins in the reaction effluent was 3.9:1.

[0411] Example 7

[0412] The process shown in Figure 1 is as follows:

[0413] (1) Feedstock 1 and hydrogen are mixed and sequentially fed into the hydroconversion reaction zone; the hydroconversion reaction zone is sequentially loaded with hydroconversion catalysts Cat-B1 and Cat-A1 along the feedstock flow direction;

[0414] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0415] In this example, about 48 wt% of the total C5-C6 isoparaffins were converted into C2-C6 normal paraffins, and the weight ratio of C2-C3 hydrocarbons to C4-C6 normal paraffins in the reaction effluent was 3.2:1.

[0416] Example 8

[0417] The process shown in Figure 1 is as follows:

[0418] (1) Feedstock 1 and hydrogen are mixed and sequentially fed into the hydroconversion reaction zone; the hydroconversion reaction zone is sequentially loaded with hydroconversion catalysts Cat-B1 and Cat-A1 along the feedstock flow direction;

[0419] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0420] In this example, about 44 wt% of the total C5-C6 isoparaffins were converted into C2-C6 normal paraffins, and the weight ratio of C2-C3 hydrocarbons to C4-C6 normal paraffins in the reaction effluent was 2.3:1.

[0421] Example 9

[0422] The process shown in Figure 1 is as follows:

[0423] (1) Feedstock 1 and hydrogen are mixed and sequentially fed into the hydroconversion reaction zone; the hydroconversion reaction zone is sequentially loaded with hydroconversion catalysts Cat-B1 and Cat-A1 along the feedstock flow direction;

[0424] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0425] In this example, about 40 wt% of the total C5-C6 isoparaffins were converted into C2-C6 normal paraffins, and the weight ratio of C2-C3 hydrocarbons to C4-C6 normal paraffins in the reaction effluent was 2.5:1.

[0426] Example 10

[0427] The process shown in Figure 1 is as follows:

[0428] (1) Feedstock 1 and hydrogen are mixed and sequentially fed into the hydroconversion reaction zone; the hydroconversion reaction zone is sequentially loaded with hydroconversion catalysts Cat-B1 and Cat-A1 along the feedstock flow direction;

[0429] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0430] In this example, about 38 wt% of the total C5-C6 isoparaffins were converted into C2-C6 normal paraffins, and the weight ratio of C2-C3 hydrocarbons to C4-C6 normal paraffins in the reaction effluent was 1.8:1.

[0431] Example 11

[0432] The process shown in Figure 1 is as follows:

[0433] (1) Feedstock 1 and hydrogen are mixed and sequentially fed into the hydroconversion reaction zone; the hydroconversion reaction zone is sequentially loaded with hydroconversion catalysts Cat-B1 and Cat-A1 along the feedstock flow direction;

[0434] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0435] In this example, about 36 wt% of the total C5-C6 isoparaffins were converted into C2-C6 normal paraffins, and the weight ratio of C2-C3 hydrocarbons to C4-C6 normal paraffins in the reaction effluent was 1.3:1.

[0436] Example 12

[0437] The process shown in Figure 1 is as follows:

[0438] (1) Raw material 2 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A1;

[0439] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0440] In this example, about 42 wt% of the total C5-C6 isoparaffins were converted into C2-C6 normal paraffins, and the weight ratio of C2-C3 hydrocarbons to C4-C6 normal paraffins in the reaction effluent was 2.2:1.

[0441] Example 13

[0442] The process shown in Figure 1 is as follows:

[0443] (1) The raw material 3 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-B1;

[0444] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0445] In this example, about 56 wt% of the total C5-C6 isoparaffins were converted into C2-C6 normal paraffins, and the weight ratio of C2-C3 hydrocarbons to C4-C6 normal paraffins in the reaction effluent was 4.1:1.

[0446] Example 14

[0447] Use the process shown in Figure 1. It includes:

[0448] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A1;

[0449] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0450] In this example, about 25 wt% of the total C5-C6 isoparaffins were converted into C2-C6 normal paraffins, and the weight ratio of C2-C3 hydrocarbons to C4-C6 normal paraffins in the reaction effluent was 0.7:1.

[0451] Example 15

[0452] The process shown in Figure 1 is as follows:

[0453] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-C;

[0454] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0455] In this example, about 28 wt% of the total C5-C6 isoparaffins were converted into C2-C6 normal paraffins, and the weight ratio of C2-C3 hydrocarbons to C4-C6 normal paraffins in the reaction effluent was 0.8:1.

[0456] Example 16

[0457] The process shown in Figure 1 is as follows:

[0458] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-D;

[0459] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0460] In this example, about 26 wt% of the total C5-C6 isoparaffins were converted into C2-C6 normal paraffins, and the weight ratio of C2-C3 hydrocarbons to C4-C6 normal paraffins in the reaction effluent was 0.7:1.

[0461] Comparative Example 1

[0462] The process shown in Figure 1 is as follows:

[0463] (1) The raw material 4 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A1;

[0464] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0465] Comparative Example 2

[0466] The process shown in Figure 1 is as follows:

[0467] (1) The raw material 4 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-B1;

[0468] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0469] Comparative Example 3

[0470] The process shown in Figure 1 is as follows:

[0471] (1) The raw material 5 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A1;

[0472] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0473] Comparative Example 4

[0474] The process shown in Figure 1 is as follows:

[0475] (1) The raw material 5 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-B1;

[0476] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0477] Comparative Example 5

[0478] The process shown in Figure 1 is as follows:

[0479] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A4;

[0480] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0481] Comparative Example 6

[0482] The process shown in Figure 1 is as follows:

[0483] (1) The raw material 6 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A1;

[0484] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0485] Comparative Example 7

[0486] The process shown in Figure 1 is as follows:

[0487] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-E;

[0488] (2) The effluent from the hydroconversion reaction zone in step (1) was separated into a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas was recycled, and the liquid stream was directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0489] Comparative Example 8

[0490] The process shown in Figure 1 is as follows:

[0491] (1) Raw material 1 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A1;

[0492] (2) The effluent from the hydroconversion reaction zone in step (1) is subjected to gas-liquid separation to form a hydrogen-rich gas and a liquid stream. The hydrogen-rich gas is recycled, and the liquid stream undergoes normal-isomer separation, with the normal paraffins serving as the ethylene feedstock and the isoparaffins being recycled to the hydroconversion reaction zone. The process conditions and conversion results for this example are shown in Table 3.

[0493] Table 3 Transformation results

[0494] Table 3 Conversion results

[0495] Table 3 Conversion results

[0496] By comparison, it can be seen that the method of the present invention can achieve selective conversion of isoparaffins, and can flexibly adjust the ratio of C2-C3 alkanes to C4-C6 normal alkanes in the conversion products, thereby achieving flexible adjustment of the ethylene product structure and improving the product flexibility of the ethylene plant.

Claims

1. A method for improving the quality of a hydrocarbon stream, comprising the following steps: 1) providing a hydrocarbon stream containing C5-C6 isoparaffins, wherein the content of the C5-C6 isoparaffins in the hydrocarbon stream is 60-90 wt% (preferably 70-80 wt%), based on the total weight of the hydrocarbon stream being 100 wt%, 2) converting at least a portion (e.g., more than 30 wt%, more than 40 wt%, more than 50 wt%, more than 60 wt%, more than 70 wt%, more than 80 wt%, or more than 90 wt%) of the C5-C6 isoparaffins into C2-C6 normal paraffins by a conversion reaction in the presence of a catalyst and hydrogen to obtain a conversion product, wherein the catalyst comprises a molecular sieve and a non-precious metal hydrogenation active metal component, 3) steam cracking the conversion product to obtain a cracking product containing ethylene.

2. The process of claim 1, wherein the sulfur content of the hydrocarbon stream is 50-5000 mg / kg (preferably 200-1000 mg / kg), based on the total weight of the hydrocarbon stream.

3. The method of claim 1, wherein the content of C7+ hydrocarbons in the hydrocarbon stream is 0-10wt% (preferably 0.5-5wt%), the content of C5-C6 normal alkanes is 10-30wt% (preferably 15-25wt%), the content of C4- hydrocarbons is 0-10wt% (preferably 2-5wt%), and the content of cyclic hydrocarbons is 1-10wt% (preferably 2-5wt%), based on the total weight of the hydrocarbon stream being 100wt%.

4. The method of claim 1, wherein the conversion product comprises C2-C3 alkanes and C4-C6 normal alkanes (preferably C5-C6 normal alkanes), and the weight ratio of the C2-C3 alkanes to the C4-C6 normal alkanes (preferably C5-C6 normal alkanes) is 0.5:1-8:1 (preferably 0.9:1-5:1).

5. The method according to claim 1, wherein the content of C7+ hydrocarbons in the conversion product is not higher than 5wt% (preferably not higher than 1wt%), the content of C5-C6 isoparaffins is 0-50wt% (preferably 10-40wt%), the content of C2-C6 normal paraffins is 40-90wt% (preferably 50-80wt%), and the content of cyclic hydrocarbons is not higher than 3wt% (preferably not higher than 1wt%), based on the total weight of the conversion product being 100wt%.

6. The method of claim 1, wherein the molecular sieve is selected from one or more of mordenite, ZSM molecular sieve, SAPO molecular sieve and EU-1 molecular sieve, more preferably selected from one or more of mordenite and ZSM molecular sieve, particularly preferably selected from one or more of mordenite, ZSM-5 molecular sieve, ZSM-11 molecular sieve, ZSM-12 molecular sieve, ZSM-22 molecular sieve, ZSM-23 molecular sieve, ZSM-35 molecular sieve, Beta molecular sieve and ZSM-38 molecular sieve, in particular selected from one or more of mordenite and ZSM-5 molecular sieve (particularly preferably, the weight ratio of mordenite to ZSM-5 molecular sieve is 0-100:100-0, preferably 10-50:50-10).

7. The method of claim 1, wherein the non-precious metal hydrogenation active metal component is selected from one or more of non-precious metals of Group VIB and Group VIII of the Periodic Table of Elements, preferably, the non-precious metal of Group VIB is selected from one or more of molybdenum and tungsten (particularly preferably molybdenum), and the non-precious metal of Group VIII is selected from one or more of cobalt and nickel (particularly preferably nickel).

8. The method of claim 7, wherein the content of the non-noble metal of Group VIB (calculated as oxide) is 5.0-30.0 wt% (preferably 10-20 wt%), and the content of the non-noble metal of Group VIII (calculated as oxide) is 0.5-15.0 wt% (preferably 3-10 wt%), based on the weight of the catalyst.

9. The method of claim 1, wherein the content of the molecular sieve is 30-80 wt% (preferably 40-70 wt%) based on the weight of the catalyst.

10. The method of claim 1, wherein the reaction conditions of the conversion reaction include: The reaction pressure is 0.5-10.0MPaG (preferably 2.0-8.0MPaG or 2.0-5.0MPaG), the reaction temperature is 300-500°C (preferably 350-450°C), and the liquid hourly volume space velocity is 0.1-15.0h -1 (Preferably 0.5-5.0h -1 ), the volume ratio of hydrogen to oil is 50:1-2500:1 (preferably 100:1-2000:1 or 100:1-1000:1).

11. The method of claim 1, wherein said step 3) comprises the following steps: 3-A-1) separating the conversion product (referred to as the first separation) to obtain a separation stream mainly composed of C2+ hydrocarbons (e.g., accounting for more than 95 wt%, more than 98 wt%, more than 99 wt% or substantially 100 wt%) of the total amount, 3-A-2) steam cracking the separated stream to obtain a cracking product comprising ethylene.

12. The method of claim 11, wherein the operating conditions of the first separation include a pressure of 0.5-10.0 MPaG (preferably 2.0-8.0 MPaG or 2.0-5.0 MPaG) and a temperature of 40-70°C.

13. The method of claim 1, wherein said step 3) comprises the following steps: 3-B-1) separating the conversion product (referred to as the first separation) to obtain a separation stream mainly composed of C2+ hydrocarbons (e.g., accounting for more than 95 wt%, more than 98 wt%, more than 99 wt% or substantially 100 wt%) of the total amount, 3-B-2) separating the separated stream (referred to as the second separation) to obtain a high-carbon stream consisting mainly of C4+ hydrocarbons (e.g., accounting for more than 90wt%, more than 95wt%, more than 98wt%, more than 99wt% or substantially 100wt% of the total amount) and a low-carbon stream consisting mainly of C2-C3 hydrocarbons (e.g., accounting for more than 90wt%, more than 95wt%, more than 98wt%, more than 99wt% or substantially 100wt% of the total amount). 3-B-3) Optionally, the high carbon feed stream is recycled as a hydrocarbon feed stream to the step 2) for the conversion reaction, 3-B-4) steam cracking the low-carbon stream to obtain a cracking product comprising ethylene.

14. The method of claim 13, wherein the operating conditions of the first separation include a pressure of 0.5-10.0 MPaG (preferably 2.0-8.0 MPaG or 2.0-5.0 MPaG) and a temperature of 40-70°C, and the operating conditions of the second separation include a pressure of 0.5-1.5 MPaG and a temperature of 30-60°C.

15. The method of claim 1, wherein the operating conditions of the steam cracking include: The reaction temperature is 750-900°C, the reaction pressure is 0.1-0.5MPaG, the water-oil mass ratio is 0.2-0.6, and the sulfur content of the system is 100-200mg / kg.

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