METHOD FOR CHEMICAL CONVERSION OF A HYDROCARBON FLOW

Abstract

The present invention relates to a chemical conversion method for a hydrocarbon stream. The chemical conversion method of the present invention comprises the following steps: providing a hydrocarbon stream containing an alkane represented by the following structural formula (I) such that at least part of the alkane is converted to a C2-C6 n-alkane in the presence of a catalyst and hydrogen to obtain a conversion product, wherein the catalyst contains a molecular sieve and a non-noble metal hydrogenation active metal component; and performing steam cracking on the conversion product to obtain a cracking product containing ethylene. In the structural formula (I), R is a C2-C6 linear or branched alkyl group. According to the present invention, low-quality ethylene raw materials can be effectively converted into high-quality ethylene raw materials, hydrocarbon streams after hydrogenation conversion can greatly increase the ethylene and triene yield of ethylene plants, the process is simple, the operation difficulty is low, and good economic benefit is achieved.

Description

A method for chemical conversion of hydrocarbon streams Technical Field

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

[0002] Whether it's naphtha derived from crude oil distillation or light naphtha produced through cracking reactions involving molecular sieve catalysts (including hydrocracking and catalytic cracking), the small molecular isoparaffins are rich in 2-methylalkanes (including isopentane, 2-methylpentane, pentane, and 2-methylhexane). While these 2-methylalkanes can be used as gasoline blending components, their saturated vapor pressure limits their availability. Simultaneously, with the continuous development of the chemical industry, ethylene production capacity is also increasing year by year, making the supply of ethylene feedstock a challenge. While 2-methylalkanes can be used as an ethylene feedstock, their molecular structure results in low ethylene and triene yields in the free radical reaction of steam cracking, making them unsuitable as an ethylene feedstock.

[0003] In the existing technology, there are relatively mature processes and supporting catalysts for the conversion of isobutane, which can achieve normalization of isobutane. However, there is no published research on 2-methylalkanes, which have a relatively high carbon number. If these small molecules of 2-methylalkanes can be converted into normal alkanes, their use as ethylene feedstocks could significantly increase ethylene product yields, with broad economic benefits.

[0004] Summary of the Invention

[0005] The inventors 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, improving production flexibility.

[0006] The inventors of the present invention also found that This special structured chain alkane, which exists in large quantities during petroleum processing, consumes much more energy to convert when R=1 than when R>1, and the reaction conditions are more stringent, making it difficult to convert it all together; when R>6, its molecular structure is larger, making it very easy to convert it in conventional hydrocracking processes, and the processing difficulty is relatively low. When R is 2-6, its molecular structure is even smaller, and the reaction difficulty is very high, whether it is the dehydrogenation or cracking of the alkane, and it is difficult to convert it using conventional processing methods. In response to the shortcomings of the existing technology, the present invention provides a conversion method for this type of isoparaffin with a special molecular structure. This method can effectively convert isoparaffins into C2-C6 normal alkanes, and further, when used as ethylene feedstock, can significantly increase the target product yield of the ethylene plant.

[0007] The present invention aims to produce C2-C6 normal alkanes in maximum quantity. In the prior art, C5-C6 isoalkanes are typically converted into normal alkanes, i.e., 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 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 needs to be combined with normal-isomerization 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 ideal feedstocks. The present invention utilizes a specialized catalyst and controlled reaction conditions to simultaneously enhance the normalization and cracking reactions, overcoming the influence of chemical equilibrium on the normalization reaction. This cracking reaction further increases the yield of normal alkanes in the conversion products, making the latter particularly suitable as direct steam cracking feedstock for ethylene production. The present invention was developed with this objective in mind.

[0008] Specifically, the present invention relates to the following aspects.

[0009] 1. A method for chemical conversion of a hydrocarbon stream, comprising the following steps:

[0010] 1) providing a hydrocarbon stream comprising a paraffin represented by the following structural formula (I),

[0011] In the structural formula (I), R is a C2-C6 straight chain or branched chain alkyl group (preferably a C2-C4 straight chain or branched chain alkyl group, more preferably a C2-C3 straight chain alkyl group),

[0012] 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 paraffins 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;

[0013] 3) steam cracking the conversion product to obtain a cracking product containing ethylene.

[0014] 2. 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.

[0015] 3. A method according to any one of the preceding or following aspects, wherein the catalyst further comprises a binder, the binder being generally alumina or silica (preferably alumina), and the content of the binder being 5-65 wt% (preferably 10-35 wt%) based on the weight of the catalyst.

[0016] 4. The method according to any of the preceding or following aspects, wherein the non-precious metal hydrogenation active metal component is selected from one or more of Group VIB non-precious metals, Group VIII non-precious metals, their oxides or sulfides, and more preferably selected from one or more of molybdenum, tungsten, cobalt, nickel, their sulfides or oxides.

[0017] 5. A method according to any of the preceding or following aspects, 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.

[0018] 6. 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.

[0019] 7. The method according to any one of the preceding or following aspects, wherein the specific surface area of ​​the catalyst is 200-400 m 2 / g, and the pore volume is 0.25-0.45mL / g.

[0020] 8. 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).

[0021] 9. The method according to any one 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, and water-to-oil mass ratio 0.2-0.6.

[0022] 10. 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).

[0023] 11. A method according to any of the preceding or following aspects, wherein in the hydrocarbon stream, the content of C7+ hydrocarbons is 0-10 wt% (preferably 0.5-5 wt%), the content of C5-6 isoparaffins is more than 50 wt% (preferably 60-90 wt%, more preferably 70-80 wt%), the content of C5-C6 normal paraffins 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%.

[0024] 12. 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).

[0025] 13. A method according to any of the preceding or following aspects, wherein in the conversion product, the content of C7+ hydrocarbons 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%.

[0026] 14. The process according to any preceding or following aspect, wherein the hydrocarbon stream is a light naphtha component obtained by cracking a hydrocarbon oil feedstock, such as by hydrocracking or catalytic cracking.

[0027] 15. The method according to any one of the preceding or following aspects, wherein step 3) comprises the following steps:

[0028] 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%),

[0029] 3-A-2) steam cracking the separated stream to obtain a cracking product comprising ethylene.

[0030] 16. The method according to any one of the preceding or following aspects, wherein the operating conditions of the first separation include 0.5-10.0 MPaG (preferably 2.0-8.0 MPaG or 2.0-5.0 MPaG) and a temperature of 40-70°C.

[0031] 17. The method according to any one of the preceding or following aspects, wherein step 3) comprises the following steps:

[0032] 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., accounting for more than 95 wt%, more than 98 wt%, more than 99 wt%, or substantially 100 wt%),

[0033] 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);

[0034] 3-B-3) Optionally, the high carbon stream is recycled as a hydrocarbon stream to the step 2) to carry out the conversion reaction,

[0035] 3-B-4) steam cracking the low-carbon stream to obtain a cracking product comprising ethylene.

[0036] 18. The method according to any preceding or following aspect, wherein the operating conditions of the first separation include 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.

[0037] 19. A chemical conversion system comprising the following units:

[0038] 1) a hydrocarbon stream providing unit configured to provide a hydrocarbon stream comprising a paraffin represented by the following structural formula (I),

[0039] In the structural formula (I), R is a C2-6 straight chain or branched chain alkyl group (preferably a C2-4 straight chain or branched chain alkyl group, more preferably a C2-3 straight chain alkyl group),

[0040] 2) a hydrocarbon stream conversion unit configured to convert at least a portion (e.g., 30 wt %, 40 wt %, 50 wt %, 60 wt %, 70 wt %, 80 wt %, or 90 wt % or more of the total amount) of the paraffins 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.

[0041] 3) A steam cracking unit configured to steam crack the conversion product to obtain a cracking product comprising ethylene.

[0042] 20. A hydrocarbon mixture comprising C5-C6 normal alkanes and C2-C3 alkanes, wherein, based on the total weight of the hydrocarbon mixture as 100 wt%, the content of the C5-C6 normal alkanes is 5-30 wt% (preferably 10-25 wt%), and the content of the C2-C3 alkanes is 20-50 wt% (preferably 25-45 wt%).

[0043] Technical Effects

[0044] 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:

[0045] 1. For small molecular isoparaffins, especially isoparaffins with a methyl branch on the second carbon atom of a straight-chain alkane, they are present in large quantities in both crude oil and products obtained after oil processing, and isoparaffins with this molecular structure are much higher than isoparaffins with other molecular structures. This isoparaffin with a special molecular structure has major problems both as a product and in subsequent processing, and is not a high-quality product or raw material. The inventors of the present invention have found that for this isoparaffin with a special molecular structure, by selecting a molecular sieve with a special pore structure and loading a certain amount of hydrogenation metal, the catalyst has strong dehydrogenation performance, which can achieve effective conversion of this isoparaffin, converting more of it into normal alkanes. When used as an ethylene feedstock, the target product yield of the ethylene plant can be greatly improved.

[0046] 2. The conversion process of the present invention is simple. Whether simply modifying existing hydrogenation units (including naphtha hydrogenation, jet fuel hydrogenation, diesel hydrogenation, and wax oil hydrogenation) or building new units, the overall investment is low. Combined with a hydrogenation conversion catalyst with low manufacturing cost, isoparaffins can be efficiently converted into normal paraffins, which has the advantages of low investment and high returns.

[0047] 3. 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 products 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, thereby improving the quality of the ethylene feedstock at a lower hydrogen consumption.

[0048] 4. Flexible adjustment of the hydrocarbon structure of ethylene feedstock can maximize the operational flexibility of the ethylene plant, including flexible adjustment of the yield 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.

[0049] 5. 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.

[0050] 6. The present invention aims to maximize the production of C2-C6 normal alkanes. Conventional methods typically convert C5-C6 isoparaffins into 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 occurrence of both 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 is based on this objective. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] FIG1 is a schematic diagram of a process flow of the process method of the present invention.

[0052] 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.

[0053] FIG2 is a schematic diagram of a process flow of the process method of the present invention.

[0054] 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

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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%.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this specification are based on weight and pressure is gauge pressure.

[0065] 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.

[0066] According to one embodiment of the present invention, a chemical conversion method is provided, in particular a chemical conversion method for hydrocarbon streams or paraffins, which can flexibly adjust the composition of the conversion product. According to the present invention, the weight ratio of C2-C3 hydrocarbons 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) by adjusting the catalyst molecular sieve type, the strength of the acidic center, and the process parameters, thereby obtaining ethylene feedstocks with different hydrocarbon components. For conversion products with a higher content of C2-C3 hydrocarbons, the normal hydrocarbon content is higher, but the conversion process requires more hydrogen consumption; for conversion products with a higher content of C4-C6 normal alkanes, the 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 more excellent technical effect of the present invention, the C4-C6 normal alkanes are more preferably C5-C6 normal alkanes.

[0067] According to one embodiment of the present invention, the chemical conversion method comprises step 1): providing a hydrocarbon stream comprising a paraffin hydrocarbon represented by the following structural formula (I).

[0068] According to one embodiment of the present invention, in structural formula (I), R is a C2-C6 straight-chain or branched alkyl group, preferably a C2-C4 straight-chain or branched alkyl group, and more preferably a C2-C3 straight-chain alkyl group. When R is a C2-C3 straight-chain alkyl group, the paraffin is sometimes also referred to as a C5-C6 isoparaffin. The inventors of the present invention have discovered that when R=1, the energy consumed for its conversion is much higher than when R>1, and the reaction conditions are more stringent, making it difficult to convert it all together. When R>6, its molecular structure is larger, making it very easy to convert it in conventional hydrocracking processes, and the processing difficulty is relatively low. The inventors of the present invention also found that when R has a branched chain, the difficulty of the reaction of simultaneously dehydrogenating two tertiary carbon atoms to form tertiary carbonium ions will increase significantly. The isoparaffins of this molecular structure will not undergo normalization reaction, and there is only one reaction path, the cracking reaction, and its hydrogen consumption will increase significantly. At the same time, due to the complex branched structure, the difficulty of entering the molecular sieve pores also increases, and the cracking difficulty is large. Moreover, due to the presence of two methyl branches, at least one isoparaffin is still produced in the conversion product after the cracking reaction, and the conversion effect is poor. Therefore, in order to make the technical effect of the present invention more excellent, in the hydrocarbon stream, the content of other isoparaffins (such as C5-C6 isoparaffins of other isomeric structures) other than the chain alkane represented by structural formula (I) is controlled as low as possible, for example, generally below 20wt% or below 10wt%, based on the total weight of the hydrocarbon stream as 100wt%.

[0069] According to the present invention, the paraffin or hydrocarbon stream can be produced by any method known in the art. Here, as the production method of the paraffin or hydrocarbon stream, for example, hydrocracking, catalytic cracking or atmospheric and vacuum distillation can be cited, thereby producing the paraffin or hydrocarbon stream. 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. In addition, the hydrocarbon stream can be used for the conversion reaction described below in the present invention after separation (such as distillation or adsorption) or without separation, but from the perspective of raw material acquisition cost, it is preferably not separated.

[0070] According to one embodiment of the present invention, in order to achieve the technical effects of the present invention, in the hydrocarbon stream, the content of the C5-C6 isoparaffins or the paraffins is generally 50 wt% or more (preferably 60-90 wt%, more preferably 70-80 wt%), based on the total weight of the hydrocarbon stream as 100 wt%. According to the present invention, the conversion effect of isoparaffins in the hydrocarbon stream is not only affected by the catalyst type and process conditions, but also by the molecular composition of the feedstock, that is, the feedstock must contain a relatively high amount of isoparaffins. If the isoparaffin content in the feedstock is low, the increase in the normal paraffin content in the conversion product is limited relative to the normal paraffin content in the feedstock, and the increase in the target product when used as an ethylene feedstock is limited; if the isoparaffin content in the feedstock is high, although the normal paraffin content in the conversion product can be greatly increased after conversion, it is difficult to obtain the high isoparaffin content feedstock, and conventional separation methods are difficult to directly obtain, thereby significantly increasing the cost of obtaining the hydrocarbon stream.

[0071] 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 hydrocarbons is generally 0-10 wt% (preferably 0.5-5 wt%), based on the total weight of the hydrocarbon stream being 100 wt%. The inventors of the present invention have found that for the hydroconversion catalyst of the present invention, due to the relatively special pore structure of the molecular sieve, the large molecular isoparaffins and cyclic hydrocarbons in the reactants are difficult to enter the catalyst pores for conversion (for example, the conversion rate is generally less than 10%). Therefore, too high C 7+ The hydrocarbon content will affect the conversion effect of the hydrocarbon stream of the present invention, which is not beneficial to the present invention.

[0072] According to one embodiment of the present invention, there is no particular restriction on the content of C5-C6 normal alkanes in the hydrocarbon stream, but in order to make the technical effect of the present invention more excellent, the content of C5-C6 normal alkanes in the hydrocarbon stream is generally 10-30wt% (preferably 15-25wt%), based on the total weight of the hydrocarbon stream as 100wt%. The inventors of the present invention have found that since there are two reaction pathways in the hydroconversion process, normalization and cracking reaction, the normal alkane content in the hydrocarbon stream has little effect on the cracking reaction, but will affect the normalization reaction. Excessive normal hydrocarbon content will inhibit the normalization reaction. At the same time, a higher ethylene product yield can be obtained when a raw material with a higher normal hydrocarbon content is directly used as an ethylene feedstock, while the improvement in the quality of the hydrocarbon stream after hydroconversion is limited.

[0073] According to one embodiment of the present invention, there is no particular restriction 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 the physical properties of C4-hydrocarbons and C5-C6 hydrocarbons are quite different, especially the boiling point difference is relatively high, which also increases the difficulty of mixing the two streams. In addition, the inventors of the present invention have found that the energy consumed by the conversion of C4-hydrocarbons is much higher than that of C5-C6 isoparaffins, and the reaction performance of C4 hydrocarbons when mixed with C5-C6 isoparaffins is poor (for example, the conversion rate is generally less than 20%). Therefore, if the content of C4 hydrocarbons is too high, it will affect the conversion effect of C5-C6 isoparaffins, which is not conducive to the present invention.

[0074] 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 superior technical effects, 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 as the carbon number of cyclic hydrocarbons increases, their molecular diameter also gradually increases, making it difficult for large cyclic hydrocarbons to enter the catalyst pores for reaction. Furthermore, cyclic hydrocarbons that have not been hydrogenated and enter the ethylene unit will affect the yield of the target product of the ethylene unit, which is detrimental to the present invention.

[0075] According to one embodiment of the present invention, the chemical conversion method includes step 2): allowing at least a portion of the C5-C6 isoalkanes or the paraffins to undergo a conversion reaction in the presence of a catalyst and hydrogen to be converted into C2-C6 normal paraffins to obtain conversion products. 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 isoalkanes or the paraffins. Therefore, the paraffins or the C5-C6 isoalkanes 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 paraffins or isoalkanes are separated from the conversion products and then the conversion reaction is carried out). For example, the conversion rate (preferably single-pass conversion rate) can be 30 wt% or more, 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.

[0076] 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 the chain alkanes or the C5-C6 isoalkanes need to use a molecular sieve with a special pore structure to effectively convert them. At the same time, the catalyst also has strong hydrogenation / dehydrogenation activity. The isoalkanes with this special structure first undergo a dehydrogenation reaction at the hydrogenation center to generate olefins, and the acidic center where the olefin molecules are transferred undergoes a change in molecular structure. If it moves to a strong acid center, it is easier for a cracking reaction to occur; if it moves to a medium-strong acid center, it is easier for a normalization reaction to occur. By selecting molecular sieves with different reaction characteristics, it is possible to strengthen these two reaction paths.

[0077] 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, a liquid hourly volume 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. During the hydrogenation conversion of C5-C6 isoparaffins, both normalization and cracking reactions are typically endothermic reactions. Higher reaction temperatures favor the forward reaction direction. Excessively low reaction temperatures inhibit normalization and cracking reactions, severely impacting the conversion of isoparaffins. C5-C6 isoparaffins are in a gaseous phase at high temperatures. During the gaseous phase reaction, the hydrogen-to-oil ratio is expressed as the hydrogen concentration per unit volume. A higher hydrogen concentration facilitates the combination of hydrogen with reactants, facilitating normalization and hydrogenolysis reactions.

[0078] The inventors of the present invention have found that the chain alkanes or the C5-C6 isoalkanes can show a single-pass conversion rate of more than 40wt%, more than 50wt%, more than 60wt%, more than 70wt%, more than 80wt% or more than 90wt% under the reaction conditions of the present invention. The inventors of the present invention have further found that the conversion reaction is specific to the chain alkanes or the C5-C6 isoalkanes. In addition, for the conversion of chain alkanes with a higher number of carbon atoms (such as R=7 or more), as the carbon number increases, the difficulty of normalization and hardening gradually increases, while the difficulty of cracking reaction gradually decreases. For components with R=7 or more, it is difficult for normalization reaction to occur during the reaction, and excessive cracking reaction will cause a significant increase in hydrogen consumption, resulting in poor conversion effect. In addition, for C 7+ For the conversion of components, for the hydrogenation conversion catalyst of the present invention, since its molecular sieve has a relatively special pore structure, it is difficult for the macromolecular isoparaffins and cyclic hydrocarbons in the reactants to enter the catalyst pores for conversion (for example, the conversion rate is generally less than 10%). Therefore, too high C 7+ The hydrocarbon content can affect the conversion efficiency of the hydrocarbon stream of the present invention. The inventors discovered that during the hydroconversion of low-carbon hydrocarbons, the reactants first undergo a dehydrogenation reaction to form carbonium ions. However, as the molecular weight of hydrocarbon molecules decreases, the bond energy between C—C bonds gradually increases. In other words, the smaller the molecular weight, the more difficult it is for the dehydrogenation reaction to occur. Therefore, under conditions suitable for the conversion of C5-C6 isoparaffins, C4 is less likely to react. Furthermore, to fully react the C4 component, more stringent reaction conditions are required, which can also result in excessive cracking of the C5-C6 isoparaffins, significantly increasing the hydrogen consumption and reducing economic benefits.

[0079] According to the present invention, the catalyst includes molecular sieve and non-precious metal hydrogenation active metal component. According to the present invention, 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. 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 molecular sieve directly affects the reaction characteristics of isoparaffins, and the strong acid center of molecular sieve is more, and cracking reaction is more likely to occur, such as ZSM-5 molecular sieve; and the medium-strong acid center is more, then normalization reaction is more likely to occur, such as mordenite. Therefore, according to the present invention, different reaction pathways can be achieved by selecting the acid strength of the molecular sieve.

[0080] The inventors of the present invention have discovered 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 a supercage structure such as Y molecular sieve 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 the cracking reaction occurs, the large pore structure will lead to excessive production of isobutane, which is not conducive to increasing the yield of normal alkanes in the conversion product.

[0081] 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 hydrocarbons, 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 sieves contain 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 hydrocarbons to C4-C6 normal alkanes in the conversion product can be flexibly adjusted.

[0082] The inventors of the present invention have discovered that the chemical 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 hydrocarbons as the main product. The inventors of the present invention have found that there are two main reaction pathways for C5 and C6 isoparaffins during the hydrogenation conversion process: one is a cracking reaction to convert them into C2-C3 hydrocarbons, and the other is a normalization reaction to generate C4-C6 normal alkanes. Under normal circumstances, these two reactions occur simultaneously. However, by adjusting the acid strength of the molecular sieve and 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. Based on this reaction principle, the production ratio of C2-C3 hydrocarbons and C4-C6 normal 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 non-precious metal hydrogenation active metal component is selected from one or more of Group VIB non-precious metals, Group VIII non-precious metals, oxides thereof, or sulfides thereof, and more preferably selected from one or more of molybdenum, tungsten, cobalt, nickel, sulfides thereof, or oxides thereof. Here, based on the weight of the catalyst, the content of the Group VIB non-precious metal (calculated as oxide) is 5.0-30.0 wt% (10.0-20.0 wt%), and the content of the Group VIII non-precious metal (calculated as oxide) is 0.5-15.0 wt% (preferably 3.0-10.0 wt%). Preferably, the 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 the occurrence of 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. However, 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 even more C2-C3 alkanes.

[0084] 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.

[0085] 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.

[0086] 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 an 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.

[0087] According to one embodiment of the present invention, in the preparation method of the catalyst, the method for loading the 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 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.

[0088] According to one embodiment of the present invention, the conversion product comprises C2-C3 alkanes and C4-C6 normal alkanes (preferably C5-C6 normal alkanes). Generally, preferably, the weight ratio of the C2-C3 alkanes to the C4-C6 normal alkanes (preferably C5-C6 normal alkanes) in the conversion product is generally 0.5:1-8:1 (preferably 0.9:1-5:1).

[0089] According to one embodiment of the present invention, the content of C7+ hydrocarbons in the conversion product is not higher than 5wt% (preferably not higher than 1wt%), 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%. According to the present invention, the conversion reaction substantially does not produce C7+ hydrocarbons, and the methane production is also very low (e.g., less than 5wt%). Since methane is a low-value-added product in the petrochemical process and can only be used as fuel gas; at the same time, since methane has the highest hydrogen content among all molecular structure hydrocarbons, excessive methane generated after hydrogenation conversion will result in a large amount of ineffective loss of hydrogen.

[0090] According to one embodiment of the present invention, depending on the conversion rate, the content of C5-C6 isoparaffins in the conversion product is generally 0-50wt% (preferably 10-40wt%), based on the total weight of the conversion product as 100wt%. The hydroconversion process includes two reaction pathways: normalization and cracking, and normalization is a more ideal reaction pathway because it does not consume hydrogen and does not contain invalid components such as isoparaffins and methane in the conversion product. The normalization reaction is affected by chemical equilibrium, that is, the higher the isoparaffin content, the easier it is to undergo normalization. When the conversion rate is low, although there will be more normalization reactions, the increase in the content of normal paraffins in the product is effective; and when the conversion rate is high, a large amount of isoparaffins undergo cracking reactions, which reduces the concentration of isoparaffins in the reactants and also inhibits the occurrence of normalization reactions.

[0091] According to one embodiment of the present invention, also depending on the conversion rate, the content of C2-C6 normal alkanes in the conversion product is 40-90 wt% (preferably 50-80 wt%), based on the total weight of the conversion product being 100 wt%.

[0092] 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.

[0093] 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 raw materials, C2-C6 normal alkanes are all ideal raw materials. The present invention, by adopting a special 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 products through cracking reactions. The latter are particularly suitable for directly using as steam cracking raw materials to produce ethylene. The present invention is carried out based on this purpose. Typically, a steam cracking unit includes multiple reaction furnaces depending on the feed. This is mainly because the lower the molecular weight of the reaction feed, the higher the cracking temperature, such as gas furnaces and liquid furnaces. 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, there is no need for a second separation, and it directly enters the liquid furnace for conversion. If the C2-C3 content is high, a second 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.

[0094] 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, and there is no 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 conversion of isoparaffins, 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, there is no need for the second separation, and it directly enters the liquid furnace for conversion. If the C2-C3 content is high, a second separation is required, and the products enter the gas and liquid furnaces respectively.

[0095] According to one embodiment of the present invention, step 3) may further include recycling the high-carbon material stream as a hydrocarbon material stream back to step 2) for the conversion reaction. The inventors of the present invention have discovered that the high-carbon material stream contains unreacted C5-C6 isoparaffins and is therefore suitable as a hydrocarbon material stream for further conversion. This recycling step is optional, but preferably essential.

[0096] 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, and water-oil mass ratio 0.2-0.6.

[0097] According to one embodiment of the present invention, a hydrocarbon mixture is also provided, comprising C5-C6 normal alkanes and C2-C3 alkanes. According to the present invention, the hydrocarbon mixture can be obtained as a conversion product by the chemical conversion method described above. According to the present invention, under normal circumstances, as the conversion product, the hydrocarbon mixture is primarily composed of C2-C7 alkanes, and the content of the C2-C7 alkanes is generally greater than 90 wt%, based on the total weight of the hydrocarbon mixture as 100 wt%.

[0098] According to one embodiment of the present invention, based on the total weight of the hydrocarbon mixture as 100wt%, the content of the C5-C6 normal alkanes is 5-30wt% (preferably 10-25wt%), and the content of the C2-C3 alkanes is 20-50wt% (preferably 25-45wt%). The inventors of the present invention have found that the normalization reaction of C5-C6 isoalkanes is affected by chemical equilibrium. When the normal alkanes reach a certain concentration, it is difficult to increase the yield of normal hydrocarbons in the conversion product through the normalization reaction. It is necessary to control an appropriate amount of cracking reaction to increase the yield of normal hydrocarbons in the conversion product. At the same time, although excessive cracking reaction will also result in the generation of a large amount of C2-C3 alkanes, it will also cause some C5-C6 normal alkanes to undergo cracking reactions, consuming too much hydrogen, and the increase in the yield of normal alkanes in the conversion product is limited. The inventors of the present invention also found that, compared with the case of using ZSM-5 molecular sieve, when using mordenite as a molecular sieve with shape-selective catalytic properties, more C5-C6 normal alkanes can undergo normalization reaction, and the yield of C5-C6 normal alkanes in the hydrogenation product is higher. This reaction process does not consume hydrogen, while the yield of propane in the hydrogenation product of the cracking reaction is higher and the hydrogen consumption is higher. Therefore, when using mordenite molecular sieve, the amount of hydrogen consumed in the hydrogenation conversion process is less. At the same time, when the hydrogenation product is used as an ethylene feedstock, propane will generate a large amount of methane during the steam cracking reaction, while the methane yield of C5-C6 normal alkanes is low, which has better economic benefits.

[0099] According to one embodiment of the present invention, a chemical conversion system is provided, comprising a hydrocarbon stream supply 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 details specified in this paragraph, any unspecified details or matters are directly referred to the details 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 are a pressure of 2.5 MPaG and a temperature of 50°C, and the operating conditions of the fractionating tower are 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, and the hydrogen consumption is calculated as the mass percentage of the hydrogen consumption to the feed amount.

[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.

[0116] Table 1

[0117] Table 1

[0118] Table 2

[0119] Table 2

[0120] Example 1

[0121] The chemical conversion method adopts the process shown in Figure 1, including:

[0122] (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;

[0123] (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.

[0124] Example 2

[0125] The chemical conversion method adopts the process shown in Figure 1, including:

[0126] (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;

[0127] (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.

[0128] Example 3

[0129] The chemical conversion method adopts the process shown in Figure 1, including:

[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] Example 4

[0133] The chemical conversion method adopts the process shown in Figure 1, including:

[0134] (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;

[0135] (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.

[0136] Example 5

[0137] The chemical conversion method adopts the process shown in Figure 1, including:

[0138] (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;

[0139] (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.

[0140] Example 6

[0141] The chemical conversion method adopts the process shown in Figure 1, including:

[0142] (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;

[0143] (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.

[0144] Example 7

[0145] The chemical conversion method adopts the process shown in Figure 1, including:

[0146] (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;

[0147] (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.

[0148] Example 8

[0149] The chemical conversion method adopts the process shown in Figure 1, including:

[0150] (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-A2;

[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 directly used as an ethylene feedstock. The process conditions and quality improvement results for this example are shown in Table 3.

[0152] Example 9

[0153] The chemical conversion method adopts the process shown in Figure 1, including:

[0154] (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-A3;

[0155] (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.

[0156] Example 10

[0157] The chemical conversion method adopts the process shown in Figure 1, including:

[0158] (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-A4;

[0159] (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.

[0160] Example 11

[0161] The chemical conversion method adopts the process shown in Figure 1, including:

[0162] (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-A5;

[0163] (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.

[0164] Example 12

[0165] The chemical conversion method adopts the process shown in Figure 1, including:

[0166] (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-A6;

[0167] (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.

[0168] Example 13

[0169] The chemical conversion method adopts the process shown in Figure 1, including:

[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-A1;

[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] Example 14

[0173] The chemical conversion method adopts the process shown in Figure 1, including:

[0174] (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;

[0175] (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.

[0176] Example 15

[0177] The chemical conversion method adopts the process shown in Figure 1, including:

[0178] (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;

[0179] (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.

[0180] Example 16

[0181] The chemical conversion method adopts the process shown in Figure 1, including:

[0182] (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;

[0183] (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.

[0184] Example 17

[0185] The chemical conversion method adopts the process shown in Figure 1, including:

[0186] (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-A4;

[0187] (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.

[0188] Example 18

[0189] The chemical conversion method adopts the process shown in Figure 1, including:

[0190] (1) The raw material 10 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A1;

[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 liquid stream is directly used as an ethylene feedstock. The process conditions and quality improvement results for this example are shown in Table 3.

[0192] Example 19

[0193] The chemical conversion method adopts the process shown in Figure 1, including:

[0194] (1) The raw material 11 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A1;

[0195] (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.

[0196] Example 20

[0197] The chemical conversion method adopts the process shown in Figure 1, including:

[0198] (1) The raw material 12 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A1;

[0199] (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.

[0200] Example 21

[0201] The chemical conversion method adopts the process shown in Figure 1, including:

[0202] (1) The raw material 13 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A1;

[0203] (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.

[0204] Example 22

[0205] The chemical conversion method adopts the process shown in Figure 1, including:

[0206] (1) The raw material 14 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A1;

[0207] (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.

[0208] Comparative Example 1

[0209] The chemical conversion method adopts the process shown in Figure 1, including:

[0210] (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;

[0211] (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.

[0212] Comparative Example 2

[0213] The chemical conversion method adopts the process shown in Figure 1, including:

[0214] (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;

[0215] (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.

[0216] Comparative Example 3

[0217] The chemical conversion method adopts the process shown in Figure 1, including:

[0218] (1) The raw material 9 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with hydroconversion catalyst Cat-A1;

[0219] (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.

[0220] Comparative Example 4

[0221] The chemical conversion method adopts the process shown in Figure 1, including:

[0222] (1) The raw material 9 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A4;

[0223] (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.

[0224] Comparative Example 5

[0225] The chemical conversion method adopts the process shown in Figure 1, including:

[0226] (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-A8;

[0227] (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.

[0228] Comparative Example 6

[0229] The chemical conversion method adopts the process shown in Figure 1, including:

[0230] (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-A9;

[0231] (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.

[0232] Comparative Example 7

[0233] The chemical conversion method adopts the process shown in Figure 1, including:

[0234] (1) The raw material 15 is mixed with hydrogen and sequentially enters the hydroconversion reaction zone; the hydroconversion reaction zone is filled with the hydroconversion catalyst Cat-A1;

[0235] (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.

[0236] Table 3 Quality improvement results

[0237] Table 3 Quality improvement results

[0238] Table 3 Quality improvement results

[0239] Table 3 Quality improvement results

[0240] 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.

[0241] Second embodiment series

[0242] 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.

[0243] 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.

[0244] The preparation method of Cat-A catalyst is:

[0245] (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.

[0246] (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.

[0247] The preparation method of Cat-B catalyst is:

[0248] (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.

[0249] (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.

[0250] The preparation method of Cat-C catalyst is:

[0251] (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.

[0252] (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.

[0253] The preparation method of Cat-D catalyst is:

[0254] (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.

[0255] (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.

[0256] The preparation method of Cat-E catalyst is:

[0257] (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.

[0258] (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.

[0259] The preparation method of Cat-F catalyst is:

[0260] (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.

[0261] (2) 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.

[0262] (3) The catalyst support obtained in steps (1) and (2) 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.

[0263] The preparation method of Cat-G catalyst is:

[0264] (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.

[0265] 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.

[0266] Table 1

[0267] Table 1

[0268] Table 1

[0269] Table 2

[0270] Example 1

[0271] The chemical conversion method adopts the process shown in Figure 1, including:

[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-A1;

[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 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.

[0275] Example 2

[0276] The chemical conversion method adopts the process shown in Figure 1, including:

[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-A2;

[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 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.

[0280] Example 3

[0281] The chemical conversion method adopts the process shown in Figure 1, including:

[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-A3;

[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 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.

[0285] Example 4

[0286] The chemical conversion method adopts the process shown in Figure 1, including:

[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-B1;

[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 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.

[0290] Example 5

[0291] The chemical conversion method adopts the process shown in Figure 1, including:

[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-B2;

[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 directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0294] 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.

[0295] Example 6

[0296] The chemical conversion method adopts the process shown in Figure 1, including:

[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-B3;

[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 directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0299] 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.

[0300] Example 7

[0301] The chemical conversion method adopts the process shown in Figure 1, including:

[0302] (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;

[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 directly used as an ethylene feedstock. The process conditions and conversion results for this example are shown in Table 3.

[0304] 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.

[0305] Example 8

[0306] The chemical conversion method adopts the process shown in Figure 1, including:

[0307] (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;

[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 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.

[0310] Example 9

[0311] The chemical conversion method adopts the process shown in Figure 1, including:

[0312] (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;

[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 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.

[0315] Example 10

[0316] The chemical conversion method adopts the process shown in Figure 1, including:

[0317] (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;

[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 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.

[0320] Example 11

[0321] The chemical conversion method adopts the process shown in Figure 1, including:

[0322] (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;

[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 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.

[0325] Example 12

[0326] The chemical conversion method adopts the process shown in Figure 1, including:

[0327] (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;

[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 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.

[0330] Example 13

[0331] The chemical conversion method adopts the process shown in Figure 1, including:

[0332] (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;

[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] 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.

[0335] Example 14

[0336] The chemical conversion method adopts the process shown in Figure 1, including:

[0337] (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;

[0338] (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.

[0339] 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.

[0340] Example 15

[0341] The chemical conversion method adopts the process shown in Figure 1, including:

[0342] (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;

[0343] (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.

[0344] 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.

[0345] Example 16

[0346] The chemical conversion method adopts the process shown in Figure 1, including:

[0347] (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;

[0348] (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.

[0349] 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.

[0350] Example 17

[0351] The chemical conversion method adopts the process shown in Figure 1, including:

[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-F1;

[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] Example 18

[0355] The chemical conversion method adopts the process shown in Figure 1, including:

[0356] (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-F2;

[0357] (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.

[0358] Example 19

[0359] The chemical conversion method adopts the process shown in Figure 1, including:

[0360] (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-F3;

[0361] (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.

[0362] Example 20

[0363] The chemical conversion method adopts the process shown in Figure 1, including:

[0364] (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-F4;

[0365] (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.

[0366] Example 21

[0367] The method for improving the quality of hydrocarbon streams adopts the process shown in Figure 2, comprising:

[0368] (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;

[0369] (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.

[0370] In this example, about 78 wt% of the total C5-C6 isoparaffins were converted to C2-C3 normal paraffins. The weight ratio of the C4-C6 recycle stream to the feedstock 1 was 0.3:1.

[0371] Example 22

[0372] The method for improving the quality of hydrocarbon streams adopts the process shown in Figure 2, comprising:

[0373] (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;

[0374] (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.

[0375] In this example, about 78 wt% of the total C5-C6 isoparaffins were converted to C2-C3 normal paraffins. The weight ratio of the C4-C6 recycle stream to the feedstock 1 was 0.4:1.

[0376] Example 23

[0377] The method for improving the quality of hydrocarbon streams adopts the process shown in Figure 2, comprising:

[0378] (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;

[0379] (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.

[0380] In this example, about 78 wt% of the total C5-C6 isoparaffins were converted to C2-C3 normal paraffins. The weight ratio of the C4-C6 recycle stream to the feedstock 1 was 0.3:1.

[0381] Comparative Example 1

[0382] The transformation method adopts the process shown in Figure 1, including:

[0383] (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;

[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] Comparative Example 2

[0386] The transformation method adopts the process shown in Figure 1, including:

[0387] (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;

[0388] (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.

[0389] Comparative Example 3

[0390] The transformation method adopts the process shown in Figure 1, including:

[0391] (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;

[0392] (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.

[0393] Comparative Example 4

[0394] The transformation method adopts the process shown in Figure 1, including:

[0395] (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;

[0396] (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.

[0397] Comparative Example 5

[0398] The transformation method adopts the process shown in Figure 1, including:

[0399] (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;

[0400] (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.

[0401] Comparative Example 6

[0402] The transformation method adopts the process shown in Figure 1, including:

[0403] (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;

[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] Comparative Example 7

[0406] The transformation method adopts the process shown in Figure 1, including:

[0407] (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;

[0408] (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.

[0409] Comparative Example 8

[0410] The chemical conversion method adopts the process shown in Figure 1, including:

[0411] (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;

[0412] (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.

[0413] Comparative Example 9

[0414] The process shown in Figure 1 is as follows:

[0415] (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;

[0416] (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.

[0417] Comparative Example 10

[0418] The process shown in Figure 1 is as follows:

[0419] (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;

[0420] (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.

[0421] Comparative Example 11

[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, with a hydrogen-to-oil volume ratio of 20:1; the hydroconversion reaction zone is loaded with hydroconversion catalyst Cat-A1;

[0424] (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.

[0425] Comparative Example 12

[0426] The process shown in Figure 1 is as follows:

[0427] (1) Feedstock 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;

[0428] (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.

[0429] Comparative Example 13

[0430] The process shown in Figure 1 is as follows:

[0431] (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;

[0432] (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.

[0433] Comparative Example 14

[0434] The process shown in Figure 1 is as follows:

[0435] (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-G;

[0436] (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.

[0437] Comparative Example 15

[0438] The process shown in Figure 1 is as follows:

[0439] (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;

[0440] (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.

[0441] Table 3 Transformation results

[0442] Table 3 Conversion results

[0443] Table 3 Conversion results

[0444] 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 hydrocarbons 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.

[0445] Third embodiment series

[0446] In the following examples and comparative examples, the yield is calculated as the mass percentage of the output to the feed amount, and the hydrogen consumption is calculated as the mass percentage of the hydrogen consumption to the feed amount.

[0447] In the following examples and comparative examples, the hydroconversion catalysts are designated as Cat-A, Cat-B, and Cat-C. The hydroconversion catalysts were prepared by conventional active metal saturation impregnation methods. The physicochemical properties of the obtained catalysts are shown in Table 1.

[0448] The preparation method of Cat-A catalyst is:

[0449] (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.

[0450] (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.

[0451] The preparation method of Cat-B catalyst is:

[0452] (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.

[0453] (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.

[0454] The preparation method of Cat-C catalyst is:

[0455] (1) Beta molecular sieve with a SiO2 / Al2O3 molar ratio of 30 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.

[0456] (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.

[0457] The preparation method of Cat-D catalyst is:

[0458] (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.

[0459] (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.

[0460] Table 1

[0461] Table 2

[0462] Example 1

[0463] The chemical conversion method adopts the process shown in Figure 1, including:

[0464] (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-A;

[0465] (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.

[0466] In this example, the hydrogenation product contains 20.2% C5-C6 normal paraffins and 23% C2-C3 hydrocarbons.

[0467] Example 2

[0468] The chemical conversion method adopts the process shown in Figure 1, including:

[0469] (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-A;

[0470] (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.

[0471] In this example, the hydrogenation product contains 16.6% C5-C6 normal paraffins and 30% C2-C3 hydrocarbons.

[0472] Example 3

[0473] The chemical conversion method adopts the process shown in Figure 1, including:

[0474] (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-A;

[0475] (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.

[0476] In this example, the hydrogenation product contains 11.1% C5-C6 normal alkanes and 41.5% C2-C3 hydrocarbons.

[0477] Comparative Example 1

[0478] The chemical conversion method adopts the process shown in Figure 1, including:

[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-B;

[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] In this example, the hydrogenation product contains 2.2% C5-C6 normal paraffins and 60.4% C2-C3 hydrocarbons.

[0482] Comparative Example 2

[0483] The chemical conversion method adopts the process shown in Figure 1, including:

[0484] (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;

[0485] (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.

[0486] In this example, the hydrogenation product contains 17.2% C5-C6 normal paraffins and 14.4% C2-C3 hydrocarbons.

[0487] Comparative Example 3

[0488] The chemical conversion method adopts the process shown in Figure 1, including:

[0489] (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;

[0490] (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.

[0491] In this example, the hydrogenation product contains 15.1% C5-C6 normal alkanes and 10.4% C2-C3 hydrocarbons.

[0492] Table 3

[0493] Table 3

Claims

1. A method for chemical conversion of a hydrocarbon stream, comprising the following steps: 1) feeding a stream of hydrocarbons containing a paraffin alkane represented by the structural formula (I): , (I) where R is a linear or branched C2-C6 alkyl (preferably a linear or branched C2-C4 alkyl, more preferably a linear C2-C3 alkyl), 2) converting at least a portion (for example, 30 wt.% or more, 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 of the total amount) of paraffinic alkanes in a conversion reaction into C2-C6n-alkanes in the presence of a catalyst and hydrogen gas to obtain a conversion product, where the catalyst comprises a molecular sieve and a hydrogenating metal component based on a non-noble metal, 3) steam cracking of the conversion product to obtain a cracking product containing ethylene.

2. The method according to claim 1, wherein the molecular sieve is one or more molecular sieves selected from the group consisting of mordenite, ZSM molecular sieve, SAPO molecular sieve and EU-1 molecular sieve, more preferably one or more molecular sieves selected from the group consisting of mordenite and ZSM molecular sieve, particularly preferably one or more molecular sieves selected from the group consisting 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, especially one or more molecular sieves selected from the group consisting of mordenite and ZSM-5 molecular sieve, preferably with a mass the ratio of mordenite to ZSM-5 molecular sieve in the range of 0-100:100-0 (preferably 10-50:50-10).

3. The method according to claim 1, wherein the non-noble metal hydrogenating component is one or more components selected from the group consisting of a non-noble metal of group VIB, a non-noble metal of group VIII, an oxide or sulfide thereof, more preferably one or more components selected from the group consisting of molybdenum, tungsten, cobalt, nickel, its sulfide or its oxide.

4. The method according to claim 3, wherein the non-noble metal of group VIB (calculated as oxide) is present in an amount of 5.0-30.0 wt.% (preferably 10-20 wt.%), and the non-noble metal of group VIII (calculated as oxide) is present in an amount of 0.5-15.0 wt.% (preferably 3-10 wt.%) by weight of the catalyst.

5. The method according to claim 1, wherein the molecular sieve is present in an amount of 30-80 wt.% (preferably 40-70 wt.%) of the weight of the catalyst.

6. The method according to claim 1, wherein the conversion reaction is carried out under the following conditions: reaction pressure of 0.5-10.0 MPa (eq) (preferably 2.0-8.0 MPa (eq) or 2.0-5.0 MPa (eq)), reaction temperature of 300-500°C (preferably 350-450°C), liquid hourly space velocity of 0.1-15.0 h -1 (preferably 0.5-5.0 h -1 ) and a hydrogen to oil volume ratio of 50:1-2500:1 (preferably 100:1-2000:1 or 100:1-1000:1).

7. The method according to claim 1, wherein the hydrocarbon stream contains C7+ hydrocarbons in an amount of 0-10 wt.% (preferably 0.5-5 wt.%), C 5-6isoalkanes are present in an amount of 50 wt.% or more (preferably 60-90 wt.%, more preferably 70-80 wt.%), C5-C6n-alkanes are present in an amount of 10-30 wt.% (preferably 15-25 wt.%), C4-hydrocarbons are present in an amount of 0-10 wt.% (preferably 2-5 wt.%), and cyclic hydrocarbons are present in an amount of 1-10 wt.% (preferably 2-5 wt.%) of the total weight of the hydrocarbon stream, which is 100 wt.%.

8. The method according to claim 1, wherein the conversion product comprises C2-C3alkanes and C4-C6n-alkanes (preferably C5-C6n-alkanes), and the weight ratio of C2-C3alkanes to C4-C6n-alkanes (preferably C5-C6n-alkanes) is 0.5:1-8:1 (preferably 0.9:1-5:1).

9. The method according to claim 1, wherein the conversion product contains C7+ hydrocarbons in an amount of no more than 5 wt.% (preferably no more than 1 wt.%), C5-C6isoalkanes are present in an amount of 0-50 wt.% (preferably 10-40 wt.%), C2-C6n-alkanes are present in an amount of 40-90 wt.% (preferably 50-80 wt.%), cyclic hydrocarbons are present in an amount of no more than 3 wt.% (preferably no more than 1 wt.%) of the total weight of the conversion product, which is 100 wt.%.

10. The method according to claim 1, wherein step 3) includes the steps of: 3-A-1) separating the conversion product (called a first separation) to obtain a separated stream in which the majority of the total amount is C2+ hydrocarbons (e.g., 95 wt.% or more, 98 wt.% or more, 99 wt.% or more, or substantially 100 wt.% of the total amount), 3-A-2) steam cracking of the split stream to produce a cracked product containing ethylene.

11. The method according to claim 10, wherein the first separation is carried out under conditions including a pressure of 0.5-10.0 MPa(e) (preferably 2.0-8.0 MPa(e) or 2.0-5.0 MPa(e)) and a temperature of 40-70°C.

12. The method according to claim 1, wherein step 3) includes the steps of: 3-B-1) separating the conversion product (called a first separation) to obtain a separated stream, the majority of which is C2+ hydrocarbons (e.g., constituting 95 wt.% or more, 98 wt.% or more, 99 wt.% or more, or substantially 100 wt.% of the total), 3-B-2) separating the split stream (called a second separation) to produce a higher carbon number hydrocarbon stream, the majority of which is C4+ hydrocarbons (e.g., 90 wt.% or more, 95 wt.% or more, 98 wt.% or more, 99 wt.% or more, or substantially 100 wt.% of the total), and a lower carbon number hydrocarbon stream, the majority of which is C2-C3 hydrocarbons (e.g., 90 wt.% or more, 95 wt.% or more, 98 wt.% or more, 99 wt.% or more, or substantially 100 wt.% of the total), 3-B-3) optionally recycling the higher carbon number hydrocarbon stream as a hydrocarbon stream back to step 2) for the conversion reaction, 3-B-4) steam cracking of a lower carbon number hydrocarbon stream to produce a cracked product containing ethylene.

13. The method according to claim 12, wherein the first separation is carried out under conditions including a pressure of 0.5-10.0 MPa(e) (preferably 2.0-8.0 MPa(e) or 2.0-5.0 MPa(e)) and a temperature of 40-70°C, and the second separation is carried out under conditions including a pressure of 0.5-1.5 MPa(e) and a temperature of 30-60°C.

14. A mixture of hydrocarbons containing C5-C6n-alkanes and C2-C3-alkanes, wherein the C5-C6n-alkanes are present in an amount of 5-30 wt.% (preferably 10-25 wt.%), and the C2-C3-alkanes are present in an amount of 20-50 wt.% (preferably 25-45 wt.%) of the total weight of the hydrocarbon mixture, which is 100 wt.%.