Method for preparing low-carbon olefin from C4 hydrocarbon
By co-catalyzing the cracking of C4 hydrocarbons with 12-membered and 8-membered ring molecular sieve catalysts and methanol, the problems of high energy consumption at high temperatures and low yield of low-carbon olefins have been solved, realizing the preparation of low-carbon olefins with low energy consumption and high yield, thus improving resource utilization and economic benefits.
Patent Information
- Application Number
- CN202410713378.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-06-04
- Publication Date
- 2025-12-05
AI Technical Summary
In existing technologies, the preparation of low-carbon olefins by catalytic cracking of C4 hydrocarbons requires high reaction temperatures, resulting in high energy consumption and low yield of low-carbon olefins. Furthermore, the residual C4 resources are not utilized at a high value, leading to resource waste.
Catalysts including twelve-membered and eight-membered ring molecular sieves are used to co-catalyze the cracking of C4 hydrocarbons with methanol at 240-430℃. Through the negative hydrogen transfer reaction mechanism, thermal coupling is achieved, which reduces the reaction temperature and increases the yield of low-carbon olefins.
This technology enables the efficient and low-energy production of low-carbon olefins, improves the yield of low-carbon olefins, reduces the generation of dry gas and coke, extends catalyst life, and enhances resource utilization and economic benefits.
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Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of petroleum chemical industry, and particularly relates to a method for preparing low-carbon olefins from carbon four hydrocarbons. BACKGROUND
[0002] The carbon four hydrocarbon resources from oil refinery devices in China are very rich and low in price. At present, the carbon four hydrocarbons from refineries are used in MTBE (methyl tert-butyl ether) devices and alkylation devices, and the components such as isobutylene and butene have been used, and the remaining residual carbon four is mainly composed of n-butane and isobutane. This part of residual carbon four after etherification and alkylation has no high-value utilization way, and is often burned as fuel, causing resource waste, low benefit and becoming a focus of attention of enterprises. The demand for low-carbon olefins such as ethylene and propylene is huge, and the preparation of high-value low-carbon olefins from low-cost carbon four hydrocarbons can greatly improve the economic benefit of oil refineries.
[0003] In the prior art, when carbon four hydrocarbons are used as raw materials to prepare low-carbon olefins through catalytic cracking reaction, a relatively high reaction temperature is usually required, which not only has high energy consumption, but also generates a large amount of dry gas and coke, affecting the yield of low-carbon olefins. SUMMARY
[0004] The main purpose of the present application is to provide a method for preparing low-carbon olefins from carbon four hydrocarbons, which has low energy consumption and high yield of low-carbon olefins.
[0005] The present application provides a method for preparing low-carbon olefins from carbon four hydrocarbons, comprising the following steps:
[0006] The raw material system comprising carbon four hydrocarbons and methanol is subjected to catalytic cracking reaction at 240-430 DEG C to obtain low-carbon olefins.
[0007] The catalyst for the catalytic cracking reaction comprises at least one twelve-membered ring molecular sieve and at least one eight-membered ring molecular sieve.
[0008] The proportion of the twelve-membered ring molecular sieve in the catalyst is 10-45%, and the proportion of the eight-membered ring molecular sieve is 55-90%.
[0009] The molecular sieve comprises at least one of FAU, MOR and BEA and at least one of CHA, AEI and AFX.
[0010] The average particle size of the catalyst is 0.5-3 mm.
[0011] The reaction temperature of the catalytic cracking reaction is 300-400 DEG C.
[0012] The method as described above, the carbon four hydrocarbon includes the residual carbon four hydrocarbon after etherification and / or alkylation.
[0013] The method as described above, the carbon four hydrocarbon includes 85-98wt% n-butane, 2-15wt% iso-butane.
[0014] The method as described above, the mass ratio of carbon four hydrocarbon and methanol in the catalytic cracking reaction is 1:1-5.
[0015] The method as described above, the reaction pressure of the catalytic cracking reaction is 0.2-0.6MPa, the mass space velocity is 1-5h -1 .
[0016] The method for preparing low carbon olefin from carbon four hydrocarbon provided by the application takes carbon four hydrocarbon and methanol as raw materials, can reduce the temperature of catalytic cracking reaction, has lower energy consumption, and has higher yield of low carbon olefin. DETAILED DESCRIPTION
[0017] To make the objectives, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.
[0018] The present application provides a method for preparing low carbon olefin from carbon four hydrocarbon, comprising the following steps:
[0019] The raw material system comprising carbon four hydrocarbon and methanol is subjected to catalytic cracking reaction at 240-430℃ to obtain low carbon olefin.
[0020] The present application takes carbon four hydrocarbon and methanol as raw materials, and prepares high value-added low carbon olefin comprising ethylene, propylene and butylene through fixed bed catalytic cracking reaction at a temperature of 240-430℃.
[0021] The catalytic cracking reaction in the present application is carried out at 240-430℃, the reaction temperature is lower, the energy consumption is lower, and the yield of the prepared low carbon olefin is higher. It is speculated that this may be because the hydrocarbon cracking reaction is a strong endothermic reaction, the activation of hydrocarbon molecules requires very high activation energy, and a very high energy barrier must be overcome to start conversion; at the same time, the reaction of methanol conversion is a strong exothermic reaction, and the heat released by methanol conversion can be provided to the hydrocarbon cracking reaction to achieve heat transfer. It can avoid the generation of a large amount of dry gas and coke due to too high reaction temperature, thereby affecting the product yield. From the perspective of energy balance, co-reaction of methanol and carbon four hydrocarbon can achieve effective utilization of energy.
[0022] In addition, when the carbon tetramer and the methanol are co-reacted, coupling exists between the two. When the methanol is added to the system, the cracking of the residual carbon tetramer can greatly promote the amount of olefins in the system. The increase in the amount of olefins has the following two effects: 1) an induction period exists in the methanol conversion process, thereby promoting the activation of the methanol; and 2) the aromatic ring cycle in the methanol conversion process is inhibited, the amount of aromatic ring products in the system is reduced, thereby effectively inhibiting the deactivation of the catalyst, and the product selectivity of the low-carbon olefins is improved. The carbon tetramer and the methanol are coupled and promoted, and the raw material conversion rate and the low-carbon olefin selectivity are simultaneously improved. Therefore, the yield of the low-carbon olefins is greatly improved.
[0023] The present application is not limited to the specific composition of the carbon tetramer. For example, the carbon tetramer can include n-butane, isobutane, isobutene, 1-butene, 2-butene and butadiene.
[0024] The present application provides a method for preparing low-carbon olefins from carbon tetramer. The carbon tetramer and the methanol are used as raw materials. The endothermic reaction of the carbon tetramer cracking and the exothermic reaction of the methanol dehydration are coupled, which is beneficial to achieve the heat effect balance of the reaction, reduce the reaction temperature, save energy and reduce consumption. In addition, the yield of the low-carbon olefins can also be improved. At the same time, the raw materials of the reaction are widely available and low in price. The products are in short supply and high in price, and the economic benefits are significant. The fixed bed reaction mode is adopted, and the process is simple and easy to operate.
[0025] In some embodiments of the present application, the catalyst for the catalytic cracking reaction includes at least one twelve-membered ring molecular sieve and at least one eight-membered ring molecular sieve.
[0026] In the present application, the twelve-membered ring molecular sieve and the eight-membered ring molecular sieve included in the catalyst for the catalytic cracking reaction are both hydrogen-type molecular sieves.
[0027] The mechanism of the catalytic cracking reaction of the carbon tetramer and the methanol in the present application is a negative hydrogen transfer reaction mechanism. Negative hydrogen transfer exists universally in the molecular sieve catalyzed hydrocarbon conversion process. Through negative hydrogen transfer, the adsorbed active carbon cation can be reacted with alkane to realize the activation of the alkane and the generation of new carbon cations. In the process of preparing low-carbon olefins by catalytic cracking reaction of the carbon tetramer and the methanol, the catalyst needs to have a large pore structure that can accommodate a bimolecular negative hydrogen transfer transition state. The hydrogen-type twelve-membered ring molecular sieve can simultaneously satisfy the initiation of the hydrogen reactant and the larger pore volume. The hydrogen-type eight-membered ring molecular sieve has suitable acidity and pore structure, which is beneficial to the generation of low-carbon olefins. The two cooperate with each other to efficiently complete the reaction of the coupling catalytic cracking of the carbon tetramer and the methanol to prepare low-carbon olefins.
[0028] The combination of the twelve-membered ring molecular sieve and the eight-membered ring molecular sieve in the application can improve the activity and selectivity of the catalyst, the synergistic effect of the two can make the catalytic cracking reaction more efficient, the yield of low-carbon olefins is higher, and the carbon deposition resistance and deactivation resistance of the catalyst can be improved, the service life of the catalyst is prolonged, the replacement frequency of the catalyst is reduced, and the production cost is reduced.
[0029] In some embodiments of the application, the proportion of the twelve-membered ring molecular sieve in the catalyst is 10-45%, and the proportion of the eight-membered ring molecular sieve is 55-90%.
[0030] The proportion of the twelve-membered ring molecular sieve in the catalyst of the application is 10-45%, and further can be 25-40%; the proportion of the eight-membered ring molecular sieve is 55-90%, and further can be 60-75%.
[0031] The proportion of the two kinds of molecular sieves in the application can further improve the activity and selectivity of the catalyst, thereby improving the yield of low-carbon olefins, improving the carbon deposition resistance and deactivation resistance of the catalyst, prolonging the service life of the catalyst, reducing the replacement frequency of the catalyst, and reducing the production cost.
[0032] In some embodiments of the application, the molecular sieve comprises at least one of FAU, MOR, BEA and at least one of CHA, AEI and AFX.
[0033] The FAU, MOR and BEA in the application are twelve-membered ring molecular sieves, and the CHA, AEI and AFX are eight-membered ring molecular sieves.
[0034] The molecular sieve in the application comprises at least one of FAU, MOR and BEA and at least one of CHA, AEI and AFX, the FAU, MOR and BEA molecular sieves have large pore structure, high activity, are suitable for catalyzing macromolecular reactions, and can effectively improve the reaction rate and the selectivity of the product; the CHA, AEI and AFX molecular sieves have unique pore channel topological structure and catalytic characteristics, can be finely controlled for catalytic cracking reaction, and realize higher catalytic efficiency. The combination of the two not only can improve the yield of low-carbon olefins, but also is beneficial to reducing the carbon deposition phenomenon on the surface of the catalyst, improving the deactivation resistance of the catalyst, thereby prolonging the service life of the catalyst.
[0035] In some embodiments of the application, the average particle size of the catalyst is 0.5-3mm.
[0036] The average particle size of the catalyst in the application is 0.5-3mm, and further can be 1-2mm.
[0037] It can be understood that the particle size of the catalyst directly affects the contact area with the reactants, when the average particle size of the catalyst is 0.5-3 mm, in a suitable range, the reactants are beneficial to fully contact with the active sites of the catalyst, promote the diffusion and mass transfer of the reactants and products inside the catalyst, reduce the mass transfer resistance, so as to improve the reaction rate and improve the yield of the product.
[0038] In some embodiments of the present application, the reaction temperature of the catalytic cracking reaction is 300-400℃.
[0039] In the present application, the reaction temperature of the catalytic cracking reaction is further limited to 300-400℃, which can further improve the yield of low-carbon olefins and reduce energy consumption.
[0040] In some embodiments of the present application, the carbon four hydrocarbon includes residual carbon four hydrocarbon after etherification and / or alkylation.
[0041] It can be understood that in the residual carbon four hydrocarbon after etherification and / or alkylation, isobutene, butene and other components have been utilized, and the remaining carbon four hydrocarbon is mainly composed of n-butane, and a small amount of isobutane.
[0042] Using residual carbon four hydrocarbon after etherification and / or alkylation and methanol as raw materials to prepare low-carbon olefins through catalytic cracking reaction can recycle the residual carbon four hydrocarbon, improve the utilization rate of resources, reduce the waste of resources, and use low-value residual carbon four hydrocarbon to produce low-carbon olefins with higher added value, which can improve the overall economic benefit.
[0043] In some embodiments of the present application, the carbon four hydrocarbon includes 85-98wt% n-butane and 2-15wt% isobutane.
[0044] In the present application, the carbon four hydrocarbon includes 85-98wt% n-butane and 2-15wt% isobutane, that is, the main component of the carbon four hydrocarbon participating in the catalytic cracking reaction is n-butane, and a small amount of isobutane is contained. By controlling the composition of the carbon four hydrocarbon, the catalytic cracking reaction has higher reaction efficiency and selectivity, reduces the generation of by-products, improves the yield of the target product low-carbon olefins, and overcomes the problem that alkanes cannot be fully utilized.
[0045] In some embodiments of the present application, the mass ratio of carbon four hydrocarbon to methanol in the catalytic cracking reaction is 1:1-5.
[0046] In the present application, the mass ratio of carbon four hydrocarbon to methanol in the catalytic cracking reaction is limited to 1:1-5, and further can be 1:2-3.5.
[0047] By adjusting the mass ratio of carbon four hydrocarbon and methanol, the exothermic energy of methanol conversion and the endothermic energy of hydrocarbon cracking are balanced, the temperature of the whole reaction system is maintained at a relatively low temperature, the co-conversion of hydrocarbon and methanol is realized, the energy consumption is saved, and the yield of dry gas and coke in the product is greatly reduced, and the yield of target product low carbon olefin is increased. At the same time, the carbon deposition can be reduced, the catalyst life is prolonged, and the fixed bed reaction mode with simple process and convenient operation is possible.
[0048] In some embodiments of the present application, the reaction pressure of the catalytic cracking reaction is 0.2-0.6MPa, and the mass space velocity is 1-5h -1 .
[0049] In the present application, the reaction pressure of the catalytic cracking reaction is 0.2-0.6MPa, and further can be 0.2-0.4MPa; the mass space velocity is 1-5h -1 , and further can be 2-3.5h -1 .
[0050] In the present application, the reaction pressure of the catalytic cracking reaction is limited to 0.2-0.6MPa, and the mass space velocity is 1-5h -1 , in a suitable range, so that the catalytic cracking reaction can be carried out under relatively mild conditions, which helps to reduce the occurrence of side reactions, improve the selectivity of target product low carbon olefin, and also helps to maintain the activity of catalyst, so that the reaction is more efficient, and the stability of operation is improved. Suitable mass space velocity can ensure sufficient contact space between catalyst and reactants, so as to realize higher conversion rate and yield. At the same time, it can also reduce the carbon deposition and deactivation of catalyst, prolong the service life of catalyst, reduce the regeneration frequency of catalyst, and reduce the cost.
[0051] In the present application, the target product of the catalytic cracking reaction is three kinds of low carbon olefins, namely ethylene, propylene and butene, wherein the yield of ethylene is 30-35wt%, the yield of propylene is 20-30wt%, the yield of butene is 25-30wt%, and the yield of dry gas+coke+cracking oil byproduct is 5-25wt%.
[0052] The method for preparing low-carbon olefins from C4 hydrocarbons provided by this invention uses C4 hydrocarbons and methanol as raw materials. Compared with conventional methods for producing low-carbon olefins by catalytic cracking of C4 hydrocarbons, this method is based on the principle of the balance between the endothermic reaction of hydrocarbons and the exothermic conversion of methanol. It features lower reaction temperature, better product selectivity, and significant economic benefits. Refineries produce a large amount of C4 hydrocarbons as a byproduct annually. With the successful implementation of the West-East Gas Pipeline project, the value of these C4 hydrocarbons has further decreased. However, by coupling them with the more abundant and cheaper methanol as raw materials for catalytic cracking to produce the scarce low-carbon olefins, the added value of C4 hydrocarbons can be significantly increased, the product structure optimized, and the economic benefits of refining enterprises improved.
[0053] The technical solution of the present invention will be further described below with reference to specific embodiments.
[0054] Main raw material sources and main analytical methods in the examples and comparative examples
[0055] 1. Main sources of raw materials:
[0056] C4 hydrocarbons: industrial grade, supplied by Lanzhou Petrochemical Company.
[0057] Methanol: Industrial grade, purchased from Sinopharm Chemical Reagent Co., Ltd.
[0058] H-FAU, H-MOR, H-BEA, H-CHA, H-AEI, H-AFX: Industrial grade, commercially available.
[0059] 2. Main analytical methods:
[0060] The analytical methods involved in this invention are mainly analytical methods for the elemental content of various samples. The analytical method for solid samples is XRF, which uses a ZSX Primus X-ray fluorescence spectrometer manufactured by Rigaku Corporation of Japan for elemental analysis of the samples. The X-ray tube is an Rh target with good excitation efficiency for heavy and light elements. The current of the X-ray tube is 50mA, the voltage is 50kV, the diameter of the field of view aperture is 20mm, and the attenuation is 1.
[0061] The fixed-bed catalytic cracking reaction evaluation method involved in this invention uses a fixed-bed evaluation device produced by Beijing Huier Sanji Green Chemical Technology Co., Ltd. Before catalyst evaluation, hydrothermal aging treatment is required. The aging conditions are: 800℃, 100% water vapor, and aging time of 10 hours. The gas and liquid compositions generated in the reaction are analyzed using an Agilent 7890B gas chromatograph, and the coke yield is determined using a CO2 analyzer.
[0062] Example 1
[0063] The method for preparing low-carbon olefins from C4 hydrocarbons in this embodiment includes the following steps:
[0064] A mixture of 1 kg of alkylated residual C4 hydrocarbon (containing 90% n-butane and 10% iso-butane) and 3 kg of methanol was mixed well as the raw material for the reaction, and a catalytic cracking reaction was carried out in a fixed bed reactor at a cracking reaction temperature of 370°C, a reaction pressure of 0.3 MPa, a weight hourly space velocity of 3 h -1 The catalyst was loaded in a dose of 200 g, a special small ball catalyst was used, the particle size was 1 mm, the composition was 40% H-FAU + 60% H-CHA, and gas chromatography was used to analyze the products after the reaction. The specific results are shown in Table 1.
[0065] Example 2-20
[0066] Example 2-20 and the method for preparing low-carbon olefins in Example 1 are basically the same, except that one or more of the preparation conditions are changed. The specific results are shown in Table 1.
[0067] Example 21
[0068] Example 21 and the method for preparing low-carbon olefins in Example 1 are basically the same, except that etherized residual C4 hydrocarbon and methanol are used as raw materials. The specific results are shown in Table 1.
[0069] Comparative Example 1
[0070] The comparative example and the method for preparing low-carbon olefins in Example 1 are basically the same, except that only 4 kg of alkylated C4 hydrocarbon is used as the reaction raw material. The specific results are shown in Table 1.
[0071] Comparative Example 2
[0072] The comparative example and the method for preparing low-carbon olefins in Example 1 are basically the same, except that only 4 kg of methanol is used as the reaction raw material. The specific results are shown in Table 1.
[0073] Comparative Examples 3-4
[0074] Comparative Examples 3-4 and the method for preparing low-carbon olefins in Example 1 are basically the same, except that the reaction temperatures are different. The specific results are shown in Table 1.
[0075] Table 1
[0076]
[0077] As can be seen from Table 1, compared with the comparative examples, the method for preparing low-carbon olefins from C4 hydrocarbon provided by the present application uses C4 hydrocarbon and methanol as raw materials, can reduce the temperature of the catalytic cracking reaction, has lower energy consumption, and has higher yield of low-carbon olefins.
[0078] From the comparison of the example 1 and the comparative examples 1-4, it can be seen that the method for preparing low carbon olefins from carbon four hydrocarbon provided by the present application can reduce the temperature of catalytic cracking reaction, has lower energy consumption, and has higher yield of low carbon olefins.
[0079] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.
Claims
1. A process for the production of lower olefins from carbon four hydrocarbons, characterized by, The method comprises the following steps: carrying out catalytic cracking reaction of a raw material system comprising carbon four hydrocarbon and methanol at 240-430 DEG C to obtain low carbon olefin.
2. The method of claim 1, wherein, The catalyst for the catalytic cracking reaction comprises at least one twelve-membered ring molecular sieve and at least one eight-membered ring molecular sieve.
3. The method of claim 2, wherein, The proportion of the twelve-membered ring molecular sieve in the catalyst is 10-45%, and the proportion of the eight-membered ring molecular sieve is 55-90%.
4. The method of claim 3, wherein, The molecular sieve comprises at least one of FAU, MOR, BEA and at least one of CHA, AEI, AFX.
5. The method of claim 2, wherein, The average particle size of the catalyst is 0.5-3 mm.
6. The method of claim 1, wherein, The reaction temperature of the catalytic cracking reaction is 300-400 DEG C.
7. The method of claim 1, wherein, The carbon four hydrocarbon comprises residual carbon four hydrocarbon after etherification and / or alkylation.
8. The method of claim 7, wherein, The carbon four hydrocarbon comprises 85-98 wt% of n-butane and 2-15 wt% of isobutane.
9. The method of claim 1, wherein, The mass ratio of carbon four hydrocarbon to methanol in the catalytic cracking reaction is 1:1-5.
10. The method according to any one of claims 1 to 9, characterized in that, The catalytic cracking reaction has a reaction pressure of 0.2-0.6 MPa, a mass space velocity of 1-5 h -1 .