Catalyst for co-production of C2-C4 olefin and p-xylene by using C4-C9 alkane and method for co-production of C2-C4 olefin and p-xylene

Abstract

The invention provides a catalyst for co-production of C2-C4 olefins and paraxylene by using C4-C9 alkanes. The catalyst is composed of a catalyst core and a catalyst surface, the inner core of the catalyst is a molecular sieve loaded by a metal oxide, and the surface of the catalyst is a silicon oxide layer; the metal oxide is one or two or more of gallium oxide, zinc oxide, copper oxide, manganese oxide, lanthanum oxide, thorium oxide and iron oxide. The invention also provides a method for co-production of C2-C4 olefin and p-xylene from C4-C9 alkane constructed by using the catalyst. Through the innovative design of the bifunctional catalyst, the problems of poor raw material adaptability, low selectivity and high energy consumption in the traditional process are solved. A method for efficiently converting C4-C9 alkane into low-carbon olefin and p-xylene is constructed by using the catalyst, and a breakthrough solution is provided for high-value utilization of refining byproducts and coal-based light hydrocarbons.

Description

Technical Field

[0001] The present application relates to the fields of petrochemical industry and coal chemical industry, and in particular to a catalyst and a method for preparing C2-C4 olefins and paraxylene. Background Art

[0002] Trienes and triphenyls are essential raw materials in the chemical industry. In traditional petroleum refining chains, the primary mechanisms for producing olefins and aromatics are free radical or carbon ion dehydrogenation and cyclization. Consequently, the efficiency of producing different products from different raw materials varies significantly. Currently, the main sources of trienes include steam cracking, catalytic cracking, light hydrocarbon cracking, and methanol-to-olefins. The main sources of triphenyls include naphtha reforming, light hydrocarbon aromatization, and methanol aromatization. These processes produce large amounts of C4-C9 fractions while producing olefins and aromatics. For a long time, these mixed C4-C9 fractions have not been effectively utilized.

[0003] Taking mixed C5 alkanes as an example, their high saturated vapor pressure results in a low proportion of the gasoline pool. Furthermore, their higher boiling point compared to LPG affects LPG quality. Furthermore, due to the limitations of the reaction mechanism, the olefin yield from n-pentane is much higher than that from isopentane. Consequently, mixed C5 alkanes are difficult to efficiently convert through conventional steam cracking processes, forcing a significant amount of this resource to be used as low-value LPG or as a diluent for ethylene cracking, resulting in significant resource waste.

[0004] It is estimated that of the approximately 120 million tons of C4-C9 alkane fractions produced globally each year, only less than 30% is effectively utilized, and the rest is downgraded. This directly results in the petrochemical industry chain losing more than US$15 billion in economic benefits each year and exacerbates the industry's dependence on high-quality naphtha raw materials. This situation has become a key bottleneck restricting the quality and efficiency improvements of the petrochemical and coal chemical industries. Summary of the Invention

[0005] In response to the above-mentioned problems, this application proposes a catalyst structure based on hydrocarbon pool conversion mechanism modulation and a method for co-producing C2-C4 olefins and para-xylene using C4-C9 alkanes, which significantly improves the selectivity and yield of C2-C4 olefins and para-xylene.

[0006] The specific technical solutions of this application are as follows: A catalyst for co-producing C2-C4 olefins and para-xylene from C4-C9 alkanes, comprising: Catalyst core and catalyst surface; The catalyst core is a molecular sieve supported by a metal oxide, and the catalyst surface is a silicon oxide layer; the metal oxide is one or two or more of gallium, zinc, copper, manganese, lanthanum, thorium and iron oxide.

[0007] Furthermore, the thickness of the metal oxide-supported molecular sieve is 20-50000 nm, and the thickness of the silicon oxide layer is 5-20 nm.

[0008] Furthermore, the metal oxide is 1% to 4% by mass of the catalyst.

[0009] Furthermore, the molecular sieve is one or two or more of ZSM-5, ZSM-11, ZSM-22, Y molecular sieve, β molecular sieve, MCM-22 and MCM-41.

[0010] The present application also provides the use of the above catalyst in the co-production of C2-C4 olefins and para-xylene using C4-C9 alkanes.

[0011] The present application provides a method for co-producing C2-C4 olefins and paraxylene, which comprises: C4-C9 alkanes are contacted with a catalyst to react to generate C2-C4 alkenes and p-xylene, and the reaction temperature is controlled to be 530-570°C.

[0012] Furthermore, the C4-C9 alkane is one or two or more of n-butane, isobutane, n-pentane, isopentane, neopentane, n-hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, n-heptane, n-octane and n-nonane and their isomers.

[0013] Furthermore, the catalyst is the catalyst according to any one of claims 1 to 4.

[0014] Furthermore, the reaction temperature is controlled to be 530-570° C., comprising: The reaction temperature is controlled to be 530-570° C. by controlling the heat released by the exothermic reaction between methanol and the catalyst.

[0015] The present application also provides a method for co-producing C2-C4 olefins and para-xylene using the above method.

[0016] This application addresses the challenges of poor feedstock adaptability, low selectivity, and high energy consumption in traditional processes through an innovative bifunctional catalyst design. This catalyst enables the development of a method for efficiently converting C4-C9 alkanes into C2-C4 olefins and para-xylene, significantly improving the selectivity and yield of these two hydrocarbons. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of this application. The exemplary embodiments and descriptions of this application are intended to explain this application and do not constitute an improper limitation on this application. In the accompanying drawings: Figure 1 The present invention shows a preparation process flow chart of C4-C9 alkanes as starting materials reacting to generate C2-C4 olefins and para-xylene in the presence of a catalyst.

[0018] Reference numerals: 1: reactor; 2: catalyst regenerator; 3: first pipeline; 4: second pipeline; 5: third pipeline; 6: fourth pipeline; 7: fifth pipeline; 8: sixth pipeline; 9: seventh pipeline. DETAILED DESCRIPTION

[0019] The present application is described in detail below in conjunction with the described embodiments. Although specific embodiments of the present application are shown, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0020] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" are open-ended terms and should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present application, but the description is based on the general principles of the specification and is not intended to limit the scope of the present application. The scope of protection of this application shall be as defined by the attached claims.

[0021] The present application provides a catalyst for preparing C2-C4 olefins and para-xylene from C4-C9 alkanes, which includes a catalyst core and a catalyst surface; the catalyst core is a molecular sieve supported by a metal oxide, and the catalyst surface is a silicon oxide layer; the metal oxide is one or two or more of gallium, zinc, copper, manganese, lanthanum, thorium or iron oxide.

[0022] Specifically, the catalyst is loaded on the molecular sieve core by metal oxide to form a synergistic active center, utilizing the metal site to promote the dehydrogenation of C4-C9 alkanes to olefins, while the acidic sites of the molecular sieve induce aromatization reaction to produce p-xylene. The surface-coated silicon oxide layer covers the acidic sites on the outer surface of the catalyst, reducing the excessive activation of the reactants by the strong acidity, thereby inhibiting side reactions and avoiding the formation of coke precursors. At the same time, the hydrophobicity and chemical inertness of silicon oxide reduce the adsorption intensity of olefins and aromatics on the catalyst surface, shortening their residence time, further avoiding the occurrence of side reactions, and the silicon oxide layer maintains structural stability at high temperatures to prevent sintering of metal active components.

[0023] In a specific embodiment, the thickness of the metal oxide-supported molecular sieve is 20 to 50,000 nm, for example, 20 nm, 50 nm, 100 nm, 200 nm, 500 nm, 500 nm, 1000 nm, 2000 nm, 5000 nm, 8000 nm, 10,000 nm, 11,000 nm, 12,000 nm, 15,000 nm, 18,000 nm, 20,000 nm, 21,000 nm, 22,000 nm, 25,000 nm, 28,000 nm, 30,000 nm, 31,000 nm, 32,000 nm, 35,000 nm, 38,000 nm, 40,000 nm, 41,000 nm, 42,000 nm, 45,000 nm, 48,000 nm, or 50,000 nm, or any two of these ranges. This ultra-wide range achieves multi-dimensional performance optimization by regulating the structural properties of the molecular sieve carrier.

[0024] In one embodiment, the thickness of the silicon oxide layer is 5 to 20 nm, for example, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, or 20 nm, or any two thereof. This thickness of silicon oxide layer forms a synergistic effect with the ultrathin structure of the molecular sieve, ensuring the mechanical strength of the molecular sieve framework while passivating the catalyst's external surface acidity, weakening the adsorption of olefins and aromatics, and reducing the rate of coking on the catalyst surface. This extends the catalyst's single-pass life and shortens the catalyst's regeneration cycle.

[0025] In one embodiment, the metal oxide comprises 1% to 4% by mass of the catalyst, for example, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, or any two of these. This ratio, through rigorous optimization of the active component loading, ensures that the metal oxide reaches the critical threshold of monolayer dispersion on the molecular sieve support surface while avoiding clogging of active sites due to excessive loading.

[0026] In a specific embodiment, the molecular sieve is one or two or more of ZSM-5, ZSM-11, ZSM-22, Y molecular sieve, β molecular sieve, MCM-22 or MCM-41.

[0027] The present application also provides a use of the above catalyst in the co-production of C2-C4 olefins and para-xylene using C4-C9 alkanes.

[0028] The present application provides a method for preparing C2-C4 olefins and para-xylene, which comprises: C4-C9 alkanes are contacted with a catalyst to react to produce C2-C4 olefins and para-xylene. The reaction temperature is controlled to be between 530°C and 570°C, for example, within the range of one or any two of 530°C, 535°C, 540°C, 545°C, 550°C, 555°C, 560°C, 565°C, and 570°C. A reaction temperature above 530°C effectively overcomes the energy barrier for alkane dehydrogenation. A temperature limit of 570°C strictly controls the risk of excessive polycondensation of aromatics, thereby improving the selectivity of para-xylene among aromatic products.

[0029] In a specific embodiment, the C4-C9 alkane is one or two or more of n-butane, isobutane, n-pentane, isopentane, neopentane, n-hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, n-heptane, n-octane, n-nonane and isomers thereof.

[0030] In one embodiment, the catalyst is the catalyst described above.

[0031] In one embodiment, the reaction temperature is controlled to be 530-570° C., comprising: The reaction temperature is controlled to be 530-570° C. by controlling the heat released by the exothermic reaction between methanol and the catalyst.

[0032] In one embodiment, the reaction temperature is controlled to be 530-570° C., comprising: The reaction temperature is controlled to be 530-570° C. by controlling the heat generated by the combustion of the coked catalyst.

[0033] Specifically, after methanol is introduced into the reaction system, the dehydration reaction between methanol and the catalyst to produce dimethyl ether instantly releases a large amount of heat. When a C4-C9 alkane feedstock is introduced, its endothermic conversion reaction forms a dynamic heat balance with the exothermic reaction of methanol. By adjusting the methanol feed rate, the temperature fluctuation can be controlled within a range of ±5°C. At the same time, during the catalyst regeneration stage, the waste heat of the regenerated catalyst is transferred to the reaction zone through the circulating catalyst, which can reduce methanol consumption. This coupling mechanism not only eliminates the energy consumption of traditional heating, but also avoids local overheating through dynamic heat balance, thereby reducing the catalyst coking rate. This temperature control strategy achieves the unity of process intensification and energy consumption optimization through the energy matching of the reactants themselves.

[0034] The present application does not limit the reactor used for the reaction, and a tubular reactor, a fluidized bed reactor, an adiabatic reactor or an isothermal reactor can be used.

[0035] The present application also provides C2-C4 olefins and para-xylene obtained by the above-mentioned method for co-producing C2-C4 olefins and para-xylene.

[0036] Use Figure 1 The reaction equipment shown in the figure for co-producing C2-C4 olefins and para-xylene comprises a reactor 1, a catalyst regenerator 2, a first pipeline 3, a second pipeline 4, a third pipeline 5, a fourth pipeline 6, a fifth pipeline 7, a sixth pipeline 8, and a seventh pipeline 9.

[0037] refer to Figure 1 Fresh C4-C9 alkane feedstock enters reactor 1 via the fourth feed line 6, where it reacts with the catalyst heated in catalyst regenerator 2. The resulting C2-C4 olefins and para-xylene enter the subsequent separation system via the fifth feed line 7. Unreacted alkane returns to reactor 1 via the fourth feed line 6 to continue the reaction. Simultaneously, the coked catalyst is transported to the catalyst regenerator 2 via the second feed line 4 and the air transported by the sixth feed line 8 for charring and regeneration. The catalyst then returns to reactor 1 via the first feed line 3, while the flue gas generated by the charring and regeneration is discharged via the seventh feed line 9. Furthermore, methanol feed is introduced into the fluidized bed reactor via the third feed line 5, utilizing the exothermic methanol conversion reaction to provide heat for alkane conversion, achieving self-balancing control of the reaction temperature. Through a reaction-regeneration cycle and recycled feedstock, the entire process achieves efficient and continuous conversion of C4-C9 alkanes into C2-C4 olefins and para-xylene.

[0038] The present application designs a catalyst in which metal oxides are loaded on molecular sieves, and utilizes C4-C9 alkanes to react in contact with the catalyst to achieve efficient conversion of C4-C9 alkanes, with a total selectivity of C2-C4 olefins and para-xylene as high as 60-72%, and a selectivity of benzene and toluene by-products as low as 5-15%. The application also utilizes synergistic optimization of the silica coating and the metal loading amount. The application also greatly reduces system energy consumption through the dynamic heat balance of methanol exotherm and alkane endotherm, and is compatible with pure or mixed C4-C9 alkanes.

[0039] Example Example 1 The catalyst core consists of 3% gallium oxide supported on a 20 nm thick ZSM-5 molecular sieve; the catalyst surface is covered with a 5 nm thick silicon oxide layer. Methanol is introduced into the reactor, where it reacts with the catalyst, which has been heated to 320°C, to produce olefins and aromatics. This reacts with a significant amount of heat, raising the reactor temperature to 550°C. A feedstock consisting of 10% C4 alkanes, 50% C5 alkanes, 30% C6 alkanes, and 10% C7 alkanes is added to the reactor, and the reactor temperature is controlled at 530°C. After 8 hours of conversion of methanol and C4-C7 alkanes over the catalyst, coke forms on the catalyst, and the feedstock conversion rate begins to decline. The coked and deactivated catalyst in the reactor is transferred to a catalyst regenerator to burn the coke. When the temperature in the regenerator reaches 600°C, the regenerated, high-temperature catalyst is returned to the reactor for a cyclic reaction.

[0040] The product composition of the product in the reactor was obtained by gas chromatography analysis, and the selectivity of C2-C4 olefins and p-xylene was calculated to be 65%, and the selectivity of benzene and toluene was 15%.

[0041] Example 2 The catalyst core consists of 4% zinc oxide supported on 20 nm thick ZSM-11 and 50,000 nm thick ZSM-22 molecular sieves in a 1:1 mass ratio. The catalyst surface is covered with a 20 nm thick silicon oxide layer. Methanol is introduced into the reactor, where it reacts with the catalyst, which has been heated to 350°C, to produce olefins and aromatics. This releases a significant amount of heat, raising the reactor temperature to 600°C. A feedstock consisting of 30% C4 alkanes, 30% C5 alkanes, 2% C6 alkanes, 7% C7 alkanes, 20% C8 alkanes, and 11% C9 alkanes is added to the reactor, and the reactor temperature is controlled at 570°C. After two hours of conversion of methanol and C4-C9 alkanes over the catalyst, coking forms on the catalyst, and the feedstock conversion rate begins to decline. The catalyst deactivated by coking in the reactor is transferred to the catalyst regenerator to burn the coke on the catalyst. When the temperature of the catalyst regenerator reaches 650°C, the regenerated high-temperature catalyst is transferred back to the reactor for a circulation reaction.

[0042] The product composition of the product in the reactor was obtained by gas chromatography analysis, and the selectivity of C2-C4 olefins and p-xylene was calculated to be 72%, and the selectivity of benzene and toluene was 8%.

[0043] Example 3 The catalyst core consists of 0.2% gallium oxide and 0.8% lanthanum oxide supported on a 1000 nm thick ZSM-5 and 200 nm thick Y-type molecular sieve in a 4:1 mass ratio. The catalyst surface is covered with an 8 nm thick silicon oxide layer. Methanol is introduced into the reactor, where it reacts with the catalyst, which has been heated to 300°C, to produce olefins and aromatics. This releases a significant amount of heat, raising the reactor temperature to 560°C. A feedstock consisting of 50% n-pentane, 20% isopentane, and 30% neopentane is added to the reactor, and the reactor temperature is controlled at 560°C. After six hours of conversion of methanol and mixed C5 alkanes on the catalyst, coke forms on the catalyst, and the feedstock conversion rate begins to decline. The coked and deactivated catalyst is transferred to a catalyst regenerator to burn the coke. When the temperature in the regenerator reaches 630°C, the regenerated, hot catalyst is returned to the reactor for a cyclic reaction.

[0044] The product composition of the product in the reactor was obtained by gas chromatography analysis, and the selectivity of C2-C4 olefins and p-xylene was calculated to be 60%, and the selectivity of benzene and toluene was 15%.

[0045] Example 4 The catalyst core consists of 1% gallium oxide, 1% thorium oxide, and 2% lanthanum oxide supported on a 100 nm thick beta molecular sieve and a 20 nm thick MCM-41 molecular sieve in a 2:3 mass ratio. The catalyst surface is covered with a 15 nm thick silicon oxide layer. Methanol is introduced into the reactor, where it reacts with the catalyst, which has been heated to 330°C, to produce olefins and aromatics. This releases a significant amount of heat, raising the reactor temperature to 580°C. A feedstock consisting of 50% isopentane, 30% n-hexane, and 20% methylpentane is added to the reactor, and the reactor temperature is controlled at 560°C. After four hours of conversion of methanol and C5-C6 alkanes over the catalyst, coke forms on the catalyst, and the feedstock conversion begins to decline. The deactivated catalyst is transferred to a catalyst regenerator to burn the coke. When the temperature in the regenerator reaches 620°C, the regenerated, hot catalyst is returned to the reactor for a cyclic reaction.

[0046] The product composition of the product in the reactor was obtained by gas chromatography analysis, and the selectivity of C2-C4 olefins and p-xylene was calculated to be 64%, and the selectivity of benzene and toluene was 12%.

[0047] Example 5 The catalyst core consists of 2.5% gallium oxide, 0.5% copper oxide, 0.5% thorium oxide, and 0.5% lanthanum oxide supported on a 15,000 nm thick ZSM-5 and 25,000 nm thick MCM-22 molecular sieve in a 2:3 mass ratio. The catalyst surface is covered with a 15 nm thick silicon oxide layer. Methanol is introduced into the reactor, where it reacts with the catalyst, which has been heated to 320°C, to produce olefins and aromatics. This releases a significant amount of heat, raising the reactor temperature to 580°C. n-Pentane is added as a reaction feedstock, and the reactor temperature is controlled at 555°C. After 5 hours of conversion of methanol and n-pentane on the catalyst, coke forms on the catalyst, and the feedstock conversion rate begins to decline. The deactivated catalyst is transferred to a catalyst regenerator to burn the coke. When the temperature in the regenerator reaches 615°C, the regenerated, hot catalyst is returned to the reactor for a cyclic reaction.

[0048] The product composition of the product in the reactor was obtained by gas chromatography analysis, and the selectivity of C2-C4 olefins and p-xylene was calculated to be 68%, and the selectivity of benzene and toluene was 5%.

[0049] The above description is merely a preferred embodiment of the present application and does not constitute any other form of limitation to the present application. Any technician familiar with the present profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification of the above embodiment based on the technical essence of the present application without departing from the content of the technical solution of the present application shall still fall within the scope of protection of the technical solution of the present application.

Claims

1. A catalyst for co-producing C2-C4 olefins and p-xylene from C4-C9 alkanes, characterized in that: include: Catalyst core and catalyst surface; The catalyst core is a molecular sieve supported by a metal oxide, and the catalyst surface is a silicon oxide layer; the metal oxide is one or two or more of gallium, zinc, copper, manganese, lanthanum, thorium and iron oxide.

2. The catalyst according to claim 1, characterized in that The thickness of the metal oxide-supported molecular sieve is 20-50000 nm, and the thickness of the silicon oxide layer is 5-20 nm.

3. The catalyst according to claim 1, characterized in that The metal oxide accounts for 1% to 4% of the mass of the catalyst.

4. The catalyst according to claim 1, characterized in that The molecular sieve is one or two or more of ZSM-5, ZSM-11, ZSM-22, Y molecular sieve, β molecular sieve, MCM-22 and MCM-41.

5. Use of the catalyst according to any one of claims 1 to 4 in the co-production of C2-C4 olefins and p-xylene from C4-C9 alkanes.

6. A method for co-producing C2-C4 olefins and paraxylene, characterized in that: include: C4-C9 alkanes are contacted with a catalyst to react to generate C2-C4 alkenes and p-xylene, and the reaction temperature is controlled to be 530-570°C.

7. The method according to claim 6, characterized in that The C4-C9 alkane is one or two or more of n-butane, isobutane, n-pentane, isopentane, neopentane, n-hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, n-heptane, n-octane and n-nonane and their isomers.

8. The method according to claim 6, characterized in that The catalyst is the catalyst according to any one of claims 1 to 4.

9. The method according to claim 6, characterized in that Controlling the reaction temperature to be 530-570° C. comprises: The reaction temperature is controlled to be 530-570° C. by controlling the heat released by the exothermic reaction between methanol and the catalyst.

10. The method for co-producing C2-C4 olefins and p-xylene according to any one of claims 1 to 9, wherein C2-C4 olefins and p-xylene are obtained.

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