A system and method for separating and preparing high-purity propane and high-purity propylene

Abstract

This invention belongs to the field of petrochemical technology and discloses a system and method for separating and preparing high-purity propane and high-purity propylene. The system mainly utilizes a pre-reactor, storage tank, catalytic distillation column, catalytic cracking distillation column, and heat exchanger. Propylene first undergoes an etherification reaction in the pre-reactor, and then the remaining propylene undergoes an etherification reaction in the catalytic distillation column, with high-purity propane obtained from the top of the column. The bottom material enters the catalytic cracking distillation column for catalytic cracking, with high-purity propylene obtained from the top of the column. This invention can obtain propane products with a content ≥99.9% and propylene products with a content ≥99.9%, and can also co-produce the fine chemical methyl isopropyl ether. This invention combines reactive distillation and catalytic cracking distillation processes, resulting in high propylene and propane yields, strong adaptability to raw materials, and the ability to handle mixtures with a wide range of propane and propylene contents. This method requires fewer distillation column trays, has low equipment investment, and is simple to operate.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical technology, specifically, it relates to a system and method for separating propylene and propane and co-producing the fine chemical methyl isopropyl ether. Background Technology

[0002] Propylene is a fundamental raw material among the three major synthetic materials and plays a vital role in chemical production. It is widely used in the production of petrochemical products such as polypropylene, propylene oxide, isopropanol, acrylonitrile, butanol, and octanol. Since 2000, the demand growth rate for propylene has exceeded that of ethylene. Propylene is one of the most important indicators of a country's chemical production level.

[0003] Propylene is mainly obtained through three methods: first, as a byproduct of steam cracking in ethylene plants; second, as a byproduct of catalytic cracking; and third, through methods such as olefin conversion, propane dehydrogenation, and methanol-to-olefins. Regardless of the method used, propylene is always a mixture of propylene and propane. Currently, the main methods for separating propane and propylene include absorption separation, adsorption separation, distillation separation, and membrane separation.

[0004] Absorption separation is a method that selectively separates propane and propylene by utilizing the difference in solubility of the absorbent. Associate Professor Ding Xue of the State Key Laboratory of Heavy Oil Processing at China University of Petroleum (East China) reported a method for separating propane and propylene using ionic liquids. This method leverages the difference in electron clouds between propane and propylene through adsorption separation by ionic liquids. While this research has yielded excellent results, the stability, time, and cost of the ionic liquid make it difficult to apply stably in industrial applications.

[0005] Adsorption separation is a method that separates propane and propylene by utilizing the difference in adsorption capacity of adsorbents. Yang Jianwen reported the preparation of multi-defect organometallic framework compounds, which, by adjusting the oxidation state and coordination unsaturation of their copper metal sites, generated Cu(I) unsaturated sites for selective adsorption separation of propane and propylene. However, this method has limited adsorption separation capacity, requires multi-stage adsorption separation, and has a limited lifespan for the metal framework materials used in adsorption separation, making it difficult to widely apply industrially. Patent CN111747818 reported the selective adsorption separation of propane and propylene using imidazole-modified molecular sieves. While it can separate propane and propylene, the adsorbent cost is high, the selectivity is low, and the adsorption capacity is small, still making industrial application unlikely.

[0006] Distillation separation utilizes the differences in boiling points and relative volatility of materials for separation. Yan Guanliang reported that propane and propylene have relative volatility close to 1, and distillation was used to separate them. Under standard conditions, propane has a boiling point of -42.1℃, and propylene has a boiling point of -47.7℃. Because the boiling points of propylene and propane are very close, the optimal number of trays in the distillation column was 200–240. Using Aspen Plus software, the number of trays in the propylene distillation column was optimized based on reflux ratio and energy consumption analysis. The optimal number of trays for propane-propylene separation was determined to be 215, with a distillation reflux ratio of approximately 20. Although this method can separate propane and propylene, the equipment investment and energy consumption are relatively high.

[0007] Membrane separation is a method of separating a mixture by utilizing the difference in permeation rates of its components through a membrane under pressure differential. HKYasuda et al. reported using porous zirconia and ceramic membranes as base membranes and silver nitrate aqueous solution as the absorbent, utilizing the complexation principle of silver ions with olefins to separate propane and propylene. The highest propylene recovery rate reached 80%, and the propylene permeation reached 3.4 cm³. 3 / cm 2 While this method can separate propane and propylene, the use of silver ions is costly and the separation effect is not ideal. CN102795956 reports a combination of membrane separation and cryogenic separation to separate the reaction products of propane dehydrogenation to propylene, but the membrane separation recovery rate is low and the total energy consumption is not reduced.

[0008] Therefore, considering the shortcomings of existing technologies, a simple and high-yield method for separating propane and propylene is needed. Currently, no new process technology has been found to produce high-purity propane and high-purity propylene in parallel, yielding the fine chemical methyl isopropyl ether. Summary of the Invention

[0009] This invention aims to solve the high energy consumption problem of separating propylene and propane through traditional distillation, and provides a system and method for separating and preparing high-purity propane and high-purity propylene. The system is simple to operate and separates the two materials through a low-energy chemical reaction, and can obtain high-purity propane and high-purity propylene, and co-produce the fine chemical product methyl isopropyl ether.

[0010] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0011] According to one aspect of the present invention, a system for separating and preparing high-purity propane and high-purity propylene is provided, comprising a pre-reactor, a catalytic distillation column, a catalytic cracking distillation column, a first storage tank, a second storage tank, a first heat exchanger, a second heat exchanger, a third heat exchanger, a first condenser, a second condenser, a first reboiler, and a second reboiler;

[0012] The inlet of the pre-reactor is used to introduce the heat-exchanged propane-propylene mixture and methanol, respectively. The outlet of the pre-reactor is connected to the inlet of the first storage tank. The outlet of the first storage tank is connected to the inlet of the first heat exchanger. The outlet of the first heat exchanger is connected to the feed inlet of the catalytic distillation column.

[0013] The top outlet of the catalytic distillation column is connected to the inlet of the first condenser. The outlet of the first condenser is divided into two branches: one branch is connected to the top material reflux inlet of the catalytic distillation column, and the other branch is used for propane separation.

[0014] The bottom outlet of the catalytic distillation column is divided into two branches: one branch is connected to the inlet of the first reboiler, and the outlet of the first reboiler is connected to the bottom material reflux inlet of the catalytic distillation column; the other branch is connected to the inlet of the second heat exchanger, and the outlet of the second heat exchanger is connected to the inlet of the catalytic cracking distillation column.

[0015] The top outlet of the catalytic cracking distillation column is connected to the inlet of the second condenser. The outlet of the second condenser is divided into two branches: one branch is connected to the top material reflux inlet of the catalytic cracking distillation column, and the other branch is used for propylene separation.

[0016] The bottom outlet of the catalytic cracking distillation column is divided into two branches: one branch is connected to the inlet of the second reboiler, and the outlet of the second reboiler is connected to the bottom material reflux inlet of the catalytic cracking distillation column; the other branch is connected to the inlet of the second storage tank.

[0017] The outlet of the second storage tank is connected to the inlet of the third heat exchanger, and the outlet of the third heat exchanger is connected to the methanol inlet of the pre-reactor.

[0018] Preferably, the catalytic cracking distillation column has 2 to 10 trays.

[0019] According to another aspect of the present invention, a method for separating and preparing high-purity propane and high-purity propylene is provided, based on the above-described system for separating and preparing high-purity propane and high-purity propylene, and comprising the following reaction process:

[0020] Step 1: Propylene undergoes an etherification reaction in the pre-reactor:

[0021] First, the propane-propylene mixture and methanol are heated separately and then fed into the pre-reactor, where propylene reacts with methanol to produce methyl isopropyl ether.

[0022] Step 2: The remaining propylene undergoes an etherification reaction in the catalytic distillation column, separating high-purity propane.

[0023] The reaction product from the pre-reactor passes through the first storage tank and the first heat exchanger before entering the catalytic distillation column for further etherification. The catalytic distillation column has both reaction and separation functions. By carrying out reaction and separation simultaneously, the chemical equilibrium is broken, the conversion rate and selectivity of propylene are improved, and the reaction is promoted towards the formation of methyl isopropyl ether.

[0024] The top sample of the catalytic distillation column is analyzed. If the propane content in the sample is ≥99.9%, the top component is collected. If the propane content in the sample is <99.9%, the top component is refluxed to collect propane with a content ≥99.9%. The bottom of the column collects a mixture of heavy components methyl isopropyl ether and methanol.

[0025] Step 3: Catalytic cracking reaction, and separation of high-purity propylene:

[0026] The mixture of methyl isopropyl ether and methanol is passed through the second heat exchanger and then fed into the catalytic cracking distillation column. In the catalytic cracking distillation column, methyl isopropyl ether is cracked to produce propylene and methanol. Propylene with a content of ≥99.9% is collected at the top of the column, and methanol with a content of 99.9% is obtained at the bottom of the column.

[0027] Furthermore, the propane content of the propane-propylene mixture is between 5% and 80%.

[0028] Preferably, the temperature in the pre-reactor is a reaction temperature of 60℃~70℃, and the reaction pressure is 0.6~1.0MPa.

[0029] Preferably, the feed temperature of the catalytic distillation column is 70℃~80℃ and the pressure is 0.5~0.9Mpa.

[0030] Preferably, the feed temperature of the catalytic cracking distillation column is 150℃~170℃, and the pressure is 0.2~0.4Mpa.

[0031] Preferably, the reaction sections of the pre-reactor and the catalytic distillation column both employ etherified acidic catalysts, while the reaction section of the catalytic cracking distillation column employs a catalytic cracking catalyst.

[0032] Preferably, both the pre-reactor and the reaction section of the catalytic distillation column employ a modified strong acid cation exchange resin catalyst. The catalyst is prepared as follows: Commercially available Amberlyst-15 or Dowex-50 strong acid cation exchange resin is impregnated with a 0.1 mol / L to 5 mol / L sulfuric acid aqueous solution to induce ion exchange and modification. The amount of sulfuric acid aqueous solution used is 5 to 20 times the weight of the resin, the impregnation time is 1 to 48 hours, the impregnation temperature is 20°C to 50°C, and slight stirring is maintained during impregnation. After impregnation, the strong acid cation exchange resin is dried at 80°C for 24 to 48 hours to obtain the modified strong acid cation exchange resin catalyst.

[0033] Preferably, the reaction section of the catalytic cracking distillation column uses a supported catalytic cracking catalyst for methyl isopropyl ether. The catalyst is prepared as follows: 99.999% pure γ-alumina is impregnated with a 0.1 mol / L to 5 mol / L ammonium sulfate solution, wherein the amount of ammonium sulfate solution is 5 to 20 times the weight of the γ-alumina. The impregnation time is 2 to 48 hours, and the impregnation temperature is 20°C to 40°C, with continuous stirring during the impregnation process. After impregnation, the mixture is filtered, and then microwave dried and calcined. The drying and calcination are carried out uniformly with a temperature gradient of 0.1°C / min, with the highest drying and calcination temperature being 180°C, and maintained at this temperature for 10 hours to obtain the supported catalytic cracking catalyst for methyl isopropyl ether.

[0034] The beneficial effects of this invention are:

[0035] (i) This invention uses low-temperature operation, has a small number of distillation column plates, and the number of plates in the reaction distillation column for separating and preparing high-purity propane is between 2 and 10; the number of plates in the catalytic cracking distillation column for reacting and preparing high-purity propylene is between 2 and 10; the process is simple and the equipment investment and maintenance costs are low.

[0036] (ii) The propylene content obtained by this invention is ≥99.9%, which meets the needs of downstream products. The process parameters can be adjusted according to the market demand for propylene content to meet the needs of downstream customers.

[0037] (III) This invention can prepare the fine chemical product methyl isopropyl ether. Methyl isopropyl ether can be used as a pharmaceutical intermediate raw material and also as an anesthetic. On the one hand, according to market demand, methyl isopropyl ether and methanol can be separated from the heavy components in the catalytic distillation process of this invention to recover the required amount of methyl isopropyl ether. On the other hand, by controlling the ratio of methanol to propylene in this invention, i.e., with an appropriate excess of propylene and a reduction in the amount of methanol, all methanol can be reacted. The light components in the reactive distillation process are propane and unreacted propylene, while the heavy components are all methyl isopropyl ether. Methyl isopropyl ether can also act as an antiknock agent for gasoline, replacing methyl tert-butyl ether.

[0038] (iv) The present invention is highly adaptable to raw materials and can process and separate a wide range of propane and propylene contents, with propane content ranging from 5% to 80%. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the system for separating and preparing high-purity propane and high-purity propylene provided by the present invention.

[0040] In the above diagram: 1. Pre-reactor; 2. First storage tank; 3. Catalytic distillation column; 4. Catalytic cracking distillation column; 5. Second storage tank; 6. First condenser; 7. Second condenser; 8. First reboiler; 9. Second heat exchanger; 10. Second reboiler; 11. Third heat exchanger; 12. First heat exchanger. Detailed Implementation

[0041] like Figure 1 As shown, this embodiment provides a system for separating and preparing high-purity propane and high-purity propylene, including a pre-reactor 1, a catalytic distillation column 3, a catalytic cracking distillation column 4, a first storage tank 2, a second storage tank 5, a first heat exchanger 12, a second heat exchanger 9, a third heat exchanger 11, a first condenser 6, a second condenser 7, a first reboiler 8, and a second reboiler 10.

[0042] The inlet of the pre-reactor 1 is used to introduce the heat-exchanged propane-propylene mixture and methanol, respectively. The first storage tank 2 is used to store the mixture of methyl isopropyl ether (the product of the reaction between propylene, propane, and methanol), unreacted residual propylene, and unreacted propane. The outlet of the pre-reactor 1 is connected to the inlet of the first storage tank 2, the outlet of the first storage tank 2 is connected to the inlet of the first heat exchanger 12, and the outlet of the first heat exchanger 12 is connected to the feed inlet of the catalytic distillation column 3.

[0043] The top outlet of the catalytic distillation column 3 is connected to the inlet of the first condenser 6. The outlet of the first condenser 6 is divided into two branches: one branch is connected to the top material reflux inlet of the catalytic distillation column 3, and the other branch is used for propane separation.

[0044] The bottom outlet of the catalytic distillation column 3 is divided into two branches: one branch is connected to the inlet of the first reboiler 8, and the outlet of the first reboiler 8 is connected to the bottom material reflux inlet of the catalytic distillation column 3; the other branch is connected to the inlet of the second heat exchanger 9, and the outlet of the second heat exchanger 9 is connected to the inlet of the catalytic cracking distillation column 4.

[0045] The top outlet of the catalytic cracking distillation column 4 is connected to the inlet of the second condenser 7. The outlet of the second condenser 7 is divided into two branches: one branch is connected to the top material reflux feed inlet of the catalytic cracking distillation column 4, and the other branch is used for propylene separation.

[0046] The bottom outlet of the catalytic cracking distillation column 4 is divided into two branches: one branch is connected to the inlet of the second reboiler 10, and the outlet of the second reboiler 10 is connected to the bottom reflux feed inlet of the catalytic cracking distillation column 4; the other branch is connected to the inlet of the second storage tank 5. The outlet of the second storage tank 5 is connected to the inlet of the third heat exchanger 11, and the outlet of the third heat exchanger 11 is connected to the methanol feed inlet of the pre-reactor 1.

[0047] The method for separating and preparing high-purity propane and high-purity propylene based on the above system includes the following reaction process:

[0048] Step 1: Propylene undergoes an etherification reaction in pre-reactor 1.

[0049] First, the propane-propylene mixture and methanol are heated separately before entering pre-reactor 1. Within pre-reactor 1, a corresponding chemical reaction occurs: propylene reacts with methanol to produce methyl isopropyl ether. The reaction equation is as follows:

[0050]

[0051] In pre-reactor 1:

[0052] The optimal temperature for the reaction of propylene and methanol under the catalysis of an etherified acidic catalyst is 60℃~70℃. When the temperature exceeds 90℃, the sulfonic acid group decomposes to produce sulfonic acid, which causes significant damage to both the equipment and the catalyst. When the reaction temperature exceeds 120℃, the catalyst undergoes irreversible deactivation.

[0053] If the reaction is carried out in a liquid phase environment, the reaction pressure has a relatively small impact on the selectivity and conversion rate of the reaction.

[0054] If the reaction is carried out in a gas phase environment, 1 molecule of gaseous propylene reacts with 1 molecule of gaseous methanol to produce 1 molecule of gaseous methyl isopropyl ether. Appropriately increasing the pressure is beneficial to improving the conversion rate and selectivity of the reaction. The preferred reaction pressure is 0.6 to 1.0 MPa.

[0055] Regarding the material ratio, when the alcohol-to-propylene ratio (molar ratio of methanol to propylene) is less than 1, propylene cannot be completely converted; when the alcohol-to-propylene ratio is too large, it will increase the production load and operating cost of the equipment. The present invention controls the alcohol-to-propylene ratio (molar ratio of methanol to propylene) within the range of 1.01 to 1.04 through experiments.

[0056] In pre-reactor 1, propylene with a boiling point of -47.7°C under standard conditions is etherified with methanol to produce methyl isopropyl ether with a boiling point of 32.5°C under standard conditions.

[0057] Step 2: The remaining propylene undergoes an etherification reaction in a catalytic distillation column, separating high-purity propane.

[0058] The first-step reaction product from the pre-reactor 1 enters the catalytic distillation column 3 after passing through the first storage tank 2 and the first heat exchanger 12 to continue the etherification reaction. The catalytic distillation column 3 has both reaction and separation functions, and has 2 to 10 trays. The catalytic distillation column 3 couples the catalytic reactor and the separator together, allowing the catalytic reaction and separation to occur simultaneously. It also disrupts the chemical equilibrium, improves the conversion rate and selectivity of propylene, and promotes the reaction towards the formation of methyl isopropyl ether.

[0059] The process flow of the catalytic distillation column 3 is as follows: the reaction product of the pre-reactor 1 enters the catalytic distillation column 3 after heat exchange in the first storage tank 2 and the first heat exchanger 12. The feed position is selected in the middle of the rectification section and the reaction section of the catalytic distillation column 3. The feed temperature is 70℃~80℃ and the pressure is 0.5~0.9Mpa.

[0060] The remaining propylene from the reaction in pre-reactor 1 enters catalytic distillation column 3, where it reacts with methanol under the catalysis of an etherifying acidic catalyst to produce methyl isopropyl ether. The reaction equation is as follows:

[0061]

[0062] Analysis of the top sample: If the propane content in the sample is ≥99.9%, the top component propane is collected; if the propane content is <99.9%, the top component is refluxed. The reflux ratio is adjusted according to the top component content. After the reaction stabilizes, reflux is generally not required. Propylene reacts with methanol to produce methyl isopropyl ether. The bottom sample is a mixture of the heavy component methyl isopropyl ether and methanol. The top sample is the light component propane, yielding propane with a content ≥99.9%, and a propane recovery rate of 99.9%.

[0063] Under standard conditions, methyl isopropyl ether has a boiling point of 32.5℃, and methanol has a boiling point of 64.7℃. The separation process can be selected based on the market demand for methyl isopropyl ether. When there is a high market demand for methyl isopropyl ether, the mixture containing a small amount of methanol can be separated by distillation. When the market demand for methyl isopropyl ether is low, the methanol-containing mixture can be left unseparated and directly fed into a catalytic cracking distillation column to prepare propylene.

[0064] As a preferred embodiment, the present invention provides a modified strong acid cation exchange resin catalyst for the reaction section of the pre-reactor 1 and the catalytic distillation column 3. The preparation method of the catalyst is as follows: commercially available Amberlyst-15 strong acid cation exchange resin or Dowex-50 strong acid cation exchange resin is impregnated with a 0.1 mol / L to 5 mol / L sulfuric acid aqueous solution to induce ion exchange and modification. The amount of sulfuric acid aqueous solution used is 5 to 20 times the weight of the resin, the impregnation time is 1 h to 48 h, the impregnation temperature is 20 °C to 50 °C, and slight stirring is maintained during the impregnation process. After impregnation, the strong acid cation exchange resin is dried at 80 °C for 24 h to 48 h to obtain the above-mentioned modified strong acid cation exchange resin catalyst.

[0065] The modified strong acid cation exchange resin catalyst developed and used in this process has good catalytic effect and high selectivity for the catalytic reaction of propylene and methanol. All propylene is converted into methyl isopropyl ether, and the separated propane has high content and high recovery rate.

[0066] Step 3: Catalytic cracking reaction, and separation of high-purity propylene.

[0067] The mixture of heavy component methyl isopropyl ether and methanol obtained from the propylene etherification reaction is passed through the second heat exchanger 9 to reach a temperature of 160°C, and then fed into the catalytic cracking distillation column 4. A chemical reaction occurs in the catalytic cracking distillation column 4, namely the cracking reaction of methyl isopropyl ether to produce propylene and methanol. The reaction equation is as follows:

[0068]

[0069] Catalytic cracking distillation column 4 couples the catalytic cracking reactor and the separator together, so that the catalytic cracking reaction and separation occur simultaneously, and the chemical equilibrium is broken, thereby improving the conversion rate and selectivity of methyl isopropyl ether cracking to propylene and promoting the reaction to proceed in the direction of propylene production.

[0070] The reaction of methyl isopropyl ether (MISO) to propylene and methanol is carried out using reactive distillation to promptly remove the reaction products, thus overcoming the equilibrium conversion limit. The optimization of this process design lies in the rapid removal of the reaction products, which not only promotes the forward reaction but also reduces the residence time of the products in the reaction bed, preventing side reactions and saving on post-processing steps. The product collected at the top of the column is the light component propylene (99.9% purity), and the product collected at the bottom is the heavy component methanol (99.9% purity). The methanol obtained from the bottom can be reused in the propylene etherification reaction process. By adjusting the operating parameters of the catalytic distillation column, the complete conversion of MISO to methanol and propylene is achieved.

[0071] The process flow of catalytic cracking distillation column 4 is as follows: the reaction products of catalytic distillation column 3 are heated by the second heat exchanger 9 and then enter catalytic cracking distillation column 4. The feed location is selected between the rectification section and the reaction section of catalytic cracking distillation column 4. The feed temperature is 150℃~170℃, and the pressure is 0.2~0.4Mpa. The number of trays in catalytic cracking distillation column 4 is 2~10, which can be used for different feed concentration ranges. According to this process, the light component propylene is collected from the top of the column, and the heavy component methanol is collected from the bottom of the column. The recovery rates of propylene and methanol both reach over 99%.

[0072] The cleavage reaction of methyl isopropyl ether is a strongly endothermic reaction, so it is more reasonable to carry it out at an appropriate high temperature. Of course, the reaction temperature cannot be too high, as this will produce byproducts. Although the aforementioned modified strong acid cation exchange resin and other catalysts can also cleave and decompose methyl isopropyl ether, these catalysts have poor temperature tolerance. When the reaction temperature is higher than 80°C, the catalyst is deactivated, making it unsuitable for use under higher reaction temperature conditions.

[0073] The reaction section of catalytic cracking distillation column 4 is filled with a catalytic cracking catalyst.

[0074] As a preferred embodiment, the present invention provides a supported catalytic cracking catalyst for the reaction section of a catalytic cracking distillation column 4. The catalyst is prepared as follows: 99.999% pure γ-alumina is impregnated with a 0.1 mol / L to 5 mol / L ammonium sulfate solution, wherein the amount of ammonium sulfate aqueous solution is 5 to 20 times the weight of γ-alumina, the impregnation time is 2 h to 48 h, the impregnation temperature is 20 °C to 40 °C, and the mixture is stirred continuously during the impregnation process. After impregnation, the mixture is filtered and then microwave dried and calcined. The drying and calcination are carried out uniformly with a temperature gradient of 0.1 °C / min, and the highest drying and calcination temperature is 180 °C, which is maintained at this temperature for 10 h to obtain the supported catalytic cracking catalyst for methyl isopropyl ether.

[0075] In this embodiment, in the first step—the etherification reaction of propylene in pre-reactor 1—and the second step—the etherification reaction of the remaining propylene in a catalytic distillation column—the modified strong acid cation exchange resin catalyst used is a pollution-free modified sulfonic acid-based divinyl polystyrene-type macroporous cation exchange resin. This catalyst is environmentally friendly, stable over long-term use, and has high catalytic efficiency. Compared to conventional catalysts (concentrated sulfuric acid, phosphoric acid, trifluoroacetic acid, p-toluenesulfonic acid) used in the etherification reaction of alcohols and olefins, this avoids problems such as non-recoverable catalysts, easy pollution, severe corrosion of equipment, and significant environmental pollution. Furthermore, the system and method of this invention are not limited to the aforementioned modified strong acid cation exchange resin catalyst; commercially available etherification acid catalysts can also achieve the etherification reaction of propylene and methanol.

[0076] The third step in this invention, the catalytic cracking reaction and separation of high-purity propylene, utilizes a self-developed cracking catalyst. This catalyst is a highly efficient supported catalytic cracking catalyst for methyl isopropyl ether, and the cracking reaction is carried out at a suitable high temperature. Combining the high conversion rate and high selectivity of the modified catalytic cracking catalyst for methyl isopropyl ether, and immediately separating the propylene and methanol generated in the catalytic cracking distillation column 4 before side reactions occur, the cracking reaction and separation are coupled through kinetic control, avoiding the formation of by-products. This achieves high selectivity and high conversion rate in the cracking of methyl isopropyl ether to propylene. Furthermore, the system and method of this invention are not limited to the aforementioned supported catalytic cracking catalyst for methyl isopropyl ether; commercially available catalytic cracking catalysts can also achieve the cracking of methyl isopropyl ether to propylene and methanol.

[0077] To further understand the invention's content, features, and effects, the following embodiments are provided in detail:

[0078] Example 1

[0079] 1. Preparation of modified strong acid cation exchange resin catalyst

[0080] Specifically, commercially available Amberlyst-15 strong acid cation exchange resin was impregnated with a 0.1 mol / L sulfuric acid aqueous solution to induce ion exchange and modification. The sulfuric acid aqueous solution was used in quantities five times the weight of the resin, the impregnation time was 1 hour, the impregnation temperature was 50°C, and slight stirring was maintained during the impregnation process. After impregnation, the strong acid cation exchange resin was dried at 80°C for 24 hours to obtain the modified strong acid cation exchange resin. The prepared modified strong acid cation exchange resin was then loaded into the reaction section of pre-reactor 1 and catalytic distillation column 3.

[0081] 2. Etherification reaction and separation yield high-purity propane, a low-boiling-point material.

[0082] 2000g of the propane-propylene mixture to be separated (propylene mass fraction of 50%, propane mass fraction of 50%) and 791.9g of methanol (methanol content of 99.9%) were introduced into pre-reactor 1 with a methanol to propylene molar ratio of 1.04. The process parameters were: reaction temperature of 60℃ and reaction pressure of 0.7MPa.

[0083] The reaction products from the pre-reactor 1 are fed into the catalytic distillation column 3 after passing through the storage tank 2 and being temperature-controlled by a heat exchanger. The feed location is chosen between the rectification section and the reaction section of the catalytic distillation column 3, with a feed temperature of 70℃ and a pressure of 0.5 MPa. The catalytic distillation column 3 has two trays. The catalytic distillation column 3 couples the catalytic reactor and the separator, allowing the catalytic reaction and separation to occur simultaneously. A sample is taken from the top of the column for analysis. If the propane content in the sample is ≥99.9%, the top component, propane, is collected; if the propane content is <99.9%, the top component is refluxed, with the reflux ratio adjusted based on the top component content. The bottom product is a mixture of heavy components, methyl isopropyl ether and methanol, while the top product is light component propane, yielding 999.0 g of propane with a content ≥99.9%, achieving a propane recovery rate of 99.9%.

[0084] 3. Preparation of catalysts for catalytic cracking of methyl isopropyl ether

[0085] γ-alumina with a purity of 99.999% was impregnated with a 0.1 mol / L ammonium sulfate solution, wherein the amount of ammonium sulfate solution was 20 times the weight of γ-alumina, the impregnation time was 48 h, the impregnation temperature was 20 °C, and the mixture was stirred continuously during the impregnation process. After impregnation, the mixture was filtered, and then microwave dried and calcined. The drying and calcination were carried out uniformly with a temperature gradient of 0.1 °C / min, and the highest drying and calcination temperature was 180 °C, which was maintained at this temperature for 10 h to obtain a supported catalytic cracking catalyst for methyl isopropyl ether. This catalyst was loaded and used in the reaction section of catalytic cracking distillation column 4.

[0086] 4. Catalytic cracking reaction, and separation of high-purity propylene.

[0087] A mixture of methyl isopropyl ether and methanol, obtained from the propylene etherification reaction, is passed through heat exchanger 9 to reach a temperature of 160°C before being introduced into catalytic cracking distillation column 4 at a reaction pressure of 0.4 MPa. Catalytic cracking distillation column 4 has 10 trays. The catalytic cracking distillation column couples the catalytic cracking reactor and the separator, allowing the catalytic cracking reaction and separation to occur simultaneously. A sample is taken from the top of the column for analysis. If the propylene content in the sample reaches 99.9%, the top component propylene is collected; if the propylene content is <99.9%, the top component is refluxed, with the reflux ratio adjusted based on the top component content. Propylene is collected from the top of the column, and methanol is collected from the bottom. The methanol collected from the bottom is reused in the propylene etherification reaction process. By adjusting the operating parameters of the catalytic distillation column, all methyl isopropyl ether is converted into methanol and propylene. 999.0 g of propylene with a content ≥99.9% is collected from the top of the column, achieving a propylene recovery rate of 99.9%. The bottom of the column yielded 791.1g of methanol with a purity of 99.9%, achieving a methanol recovery rate of 99.9%.

[0088] Example 2

[0089] 1. Preparation of modified strong acid cation exchange resin catalyst

[0090] Specifically, commercially available Dowex-50 strong acid cation exchange resin was impregnated with a 5 mol / L sulfuric acid aqueous solution to induce ion exchange and modification. The sulfuric acid aqueous solution was used in an amount 20 times the weight of the resin, the impregnation time was 48 hours, the impregnation temperature was 20°C, and slight stirring was maintained during the impregnation process. After impregnation, the strong acid cation exchange resin was dried at 80°C for 48 hours to obtain the modified strong acid cation exchange resin. The prepared modified strong acid cation exchange resin was then loaded into the reaction section of pre-reactor 1 and catalytic distillation column 3.

[0091] 2. Etherification reaction and separation yield high-purity propane, a low-boiling-point material.

[0092] 3000g of the propane-propylene mixture to be separated (propylene mass fraction of 40% and propane mass fraction of 60%) and 922.9g of methanol (methanol content of 99.9%) were introduced into pre-reactor 1 with a methanol to propylene molar ratio of 1.01. The process parameters were: reaction temperature of 70℃ and reaction pressure of 1.0MPa.

[0093] The reaction products from the pre-reactor 1 are fed into the catalytic distillation column 3 after passing through the first storage tank 2 and being temperature-controlled by a heat exchanger. The feed location is chosen between the rectification section and the reaction section of the catalytic distillation column 3, with a feed temperature of 80℃ and a pressure of 0.9 MPa. The catalytic distillation column 3 has 10 trays. The catalytic distillation column 3 couples the catalytic reactor and the separator together, allowing the catalytic reaction and separation to occur simultaneously. A sample is taken from the top of the column for analysis. If the propane content in the sample is ≥99.9%, the top component, propane, is collected; if the propane content is <99.9%, the top component is refluxed, with the reflux ratio adjusted based on the top component content. The bottom product is a mixture of heavy components, methyl isopropyl ether and methanol, while the top product is light component propane, yielding 1798.2 g of propane with a content ≥99.9%, resulting in a propane recovery rate of 99.9%.

[0094] 3. Preparation of catalysts for catalytic cracking of methyl isopropyl ether

[0095] γ-alumina with a purity of 99.999% was impregnated with a 5 mol / L ammonium sulfate solution, wherein the amount of ammonium sulfate solution was 5 times the weight of γ-alumina, the impregnation time was 2 h, the impregnation temperature was 40℃, and the mixture was stirred continuously during the impregnation process. After impregnation, the mixture was filtered and then microwave dried and calcined. The drying and calcination were carried out uniformly with a temperature gradient of 0.1℃ / min, and the highest drying and calcination temperature was 180℃, which was maintained at this temperature for 10 h to obtain a supported catalytic cracking catalyst for methyl isopropyl ether. This catalyst was loaded and used in the reaction section of catalytic cracking distillation column 4.

[0096] 4. Catalytic cracking reaction, and separation of high-purity propylene.

[0097] A mixture of methyl isopropyl ether and methanol, obtained from the propylene etherification reaction, is passed through a second heat exchanger (9) to reach a temperature of 150°C before being introduced into a catalytic cracking distillation column (4) at a reaction pressure of 0.2 MPa. The catalytic cracking distillation column (4) has two trays. A sample is taken from the top of the column for analysis. If the propylene content in the sample reaches 99.9%, the top component propylene is collected; if the propylene content is <99.9%, the top component is refluxed, with the reflux ratio adjusted based on the top component content. Propylene is collected from the top of the column, and methanol is collected from the bottom. The methanol collected from the bottom is reused in the propylene etherification reaction process. By adjusting the operating parameters of the catalytic distillation column, the complete conversion of methyl isopropyl ether into methanol and propylene is achieved. 1198.8 g of propylene with a content ≥99.9% is collected from the top of the column, with a propylene recovery rate of 99.9%. 921.9 g of methanol with a content of 99.9% is obtained from the bottom of the column, with a methanol recovery rate of 99.9%.

[0098] Example 3

[0099] 1. Preparation of modified strong acid cation exchange resin catalyst

[0100] Specifically, commercially available Amberlyst-15 strong acid cation exchange resin was impregnated with a 4 mol / L sulfuric acid aqueous solution to induce ion exchange and modification. The sulfuric acid aqueous solution was used in quantities 10 times the weight of the resin, the impregnation time was 24 hours, the impregnation temperature was 30°C, and slight stirring was maintained during the impregnation process. After impregnation, the strong acid cation exchange resin was dried at 80°C for 24-48 hours to obtain the modified strong acid cation exchange resin. The prepared modified strong acid cation exchange resin was then loaded into the reaction section of pre-reactor 1 and catalytic distillation column 3.

[0101] 2. Etherification reaction and separation yield high-purity propane, a low-boiling-point material.

[0102] 4000g of the propane-propylene mixture to be separated (propylene mass fraction of 30% and propane mass fraction of 70%) and 932.0g of methanol (methanol content of 99.9%) were introduced into pre-reactor 1 with a methanol to propylene molar ratio of 1.02. The process parameters were: reaction temperature of 65℃ and reaction pressure of 0.9MPa.

[0103] The reaction products from the pre-reactor 1, after passing through the first storage tank 2 and being temperature-controlled by a heat exchanger, enter the catalytic distillation column 3. The feed location is chosen between the rectification section and the reaction section of the catalytic distillation column 3, with a feed temperature of 75℃ and a pressure of 0.8 MPa. The catalytic distillation column 3 has 5 trays. The catalytic distillation column couples the catalytic reactor and the separator together, allowing the catalytic reaction and separation to occur simultaneously.

[0104] Analysis was performed on samples taken from the top of the column. If the propane content in the sample was ≥99.9%, the top component, propane, was collected; if the propane content was <99.9%, the top component was refluxed, and the reflux ratio was adjusted according to the content of the top component. The bottom sample was a mixture of heavy components methyl isopropyl ether and methanol, while the top sample was the light component, propane. A total of 2797.2 g of propane with a content ≥99.9% was obtained, with a propane recovery rate of 99.9%.

[0105] 3. Preparation of catalysts for catalytic cracking of methyl isopropyl ether

[0106] γ-alumina with a purity of 99.999% was impregnated with a 3 mol / L ammonium sulfate solution, wherein the amount of ammonium sulfate solution was 10 times the weight of γ-alumina, the impregnation time was 24 h, the impregnation temperature was 25 °C, and the mixture was stirred continuously during the impregnation process. After impregnation, the mixture was filtered and then microwave dried and calcined. The drying and calcination were carried out uniformly with a temperature gradient of 0.1 °C / min, and the highest drying and calcination temperature was 180 °C, which was maintained at this temperature for 10 h to obtain a supported catalytic cracking catalyst for methyl isopropyl ether. This catalyst was loaded and used in the reaction section of catalytic cracking distillation column 4.

[0107] 4. Catalytic cracking reaction, and separation of high-purity propylene.

[0108] A mixture of methyl isopropyl ether and methanol, obtained from the propylene etherification reaction, is passed through a second heat exchanger (9) to reach a temperature of 170°C before being introduced into a catalytic cracking distillation column (4) at a reaction pressure of 0.3 MPa. The catalytic cracking distillation column (4) has 8 trays. A sample is taken from the top of the column for analysis. If the propylene content in the sample reaches 99.9%, the top component propylene is collected; if the propylene content is <99.9%, the top component is refluxed, with the reflux ratio adjusted based on the top component content. Propylene is collected from the top of the column, and methanol is collected from the bottom. By adjusting the operating parameters of the catalytic distillation column, the complete conversion of methyl isopropyl ether into methanol and propylene is achieved. 1198.8 g of propylene with a content ≥99.9% is collected from the top of the column, achieving a propylene recovery rate of 99.9%. 931.0 g of methanol with a content of 99.9% is obtained from the bottom of the column, achieving a methanol recovery rate of 99.9%.

[0109] As can be seen, the system and method for separating and preparing high-purity propane and high-purity propylene of the present invention can obtain propane products with a content ≥99.9% and propylene products with a content ≥99.9%, and can also co-produce the fine chemical methyl isopropyl ether. Employing a green, environmentally friendly, and highly efficient catalyst, combined with reactive distillation and catalytic cracking distillation processes, it achieves high propylene and propane yields, and is highly adaptable to raw materials, capable of handling mixtures with a wide range of propane and propylene contents. Furthermore, the system and method of the present invention require fewer distillation column trays, have lower equipment investment, and are simpler to operate.

[0110] Although the preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many specific modifications under the guidance of the present invention without departing from the spirit and scope of the claims, and these modifications all fall within the scope of protection of the present invention.

Claims

1. A system for separating and preparing high-purity propane and high-purity propylene, characterized in that, It includes a pre-reactor, a catalytic distillation column, a catalytic cracking distillation column, a first storage tank, a second storage tank, a first heat exchanger, a second heat exchanger, a third heat exchanger, a first condenser, a second condenser, a first reboiler, and a second reboiler; The inlet of the pre-reactor is used to introduce the heat-exchanged propane-propylene mixture and methanol, respectively. The outlet of the pre-reactor is connected to the inlet of the first storage tank. The outlet of the first storage tank is connected to the inlet of the first heat exchanger. The outlet of the first heat exchanger is connected to the feed inlet of the catalytic distillation column. The top outlet of the catalytic distillation column is connected to the inlet of the first condenser. The outlet of the first condenser is divided into two branches: one branch is connected to the top material reflux inlet of the catalytic distillation column, and the other branch is used for propane separation. The bottom outlet of the catalytic distillation column is divided into two branches: one branch is connected to the inlet of the first reboiler, and the outlet of the first reboiler is connected to the bottom material reflux inlet of the catalytic distillation column; the other branch is connected to the inlet of the second heat exchanger, and the outlet of the second heat exchanger is connected to the inlet of the catalytic cracking distillation column. The top outlet of the catalytic cracking distillation column is connected to the inlet of the second condenser. The outlet of the second condenser is divided into two branches: one branch is connected to the top material reflux inlet of the catalytic cracking distillation column, and the other branch is used for propylene separation. The bottom outlet of the catalytic cracking distillation column is divided into two branches: one branch is connected to the inlet of the second reboiler, and the outlet of the second reboiler is connected to the bottom material reflux inlet of the catalytic cracking distillation column; the other branch is connected to the inlet of the second storage tank. The outlet of the second storage tank is connected to the inlet of the third heat exchanger, and the outlet of the third heat exchanger is connected to the methanol inlet of the pre-reactor.

2. The system for separating and preparing high-purity propane and high-purity propylene according to claim 1, characterized in that, The catalytic cracking distillation column has 2 to 10 trays.

3. A method for separating and preparing high-purity propane and high-purity propylene, characterized in that, The system for separating and preparing high-purity propane and high-purity propylene according to any one of claims 1-2, and comprising the following reaction process: Step 1: Propylene undergoes an etherification reaction in the pre-reactor: First, the propane-propylene mixture and methanol are heated separately and then fed into the pre-reactor, where propylene reacts with methanol to produce methyl isopropyl ether. Step 2: The remaining propylene undergoes an etherification reaction in the catalytic distillation column, separating high-purity propane. The reaction product from the pre-reactor passes through the first storage tank and the first heat exchanger before entering the catalytic distillation column for further etherification. The catalytic distillation column has both reaction and separation functions. By carrying out reaction and separation simultaneously, the chemical equilibrium is broken, the conversion rate and selectivity of propylene are improved, and the reaction is promoted towards the formation of methyl isopropyl ether. The top sample of the catalytic distillation column is analyzed. If the propane content in the sample is ≥99.9%, the top component is collected. If the propane content in the sample is <99.9%, the top component is refluxed to collect propane with a content ≥99.9%. A mixture of heavy components methyl isopropyl ether and methanol is collected in the bottom of the column. Step 3: Catalytic cracking reaction, and separation of high-purity propylene: The mixture of methyl isopropyl ether and methanol is passed through the second heat exchanger and then fed into the catalytic cracking distillation column. In the catalytic cracking distillation column, methyl isopropyl ether is cracked to produce propylene and methanol. Propylene with a purity of ≥99.9% is collected at the top of the column, and methanol with a purity of 99.9% is obtained at the bottom of the column.

4. The method for separating and preparing high-purity propane and high-purity propylene according to claim 3, characterized in that, The propane content of the propane-propylene mixture is between 5% and 80%.

5. The method for separating and preparing high-purity propane and high-purity propylene according to claim 3, characterized in that, The temperature in the pre-reactor is 60℃~70℃, and the reaction pressure is 0.6~1.0MPa.

6. The method for separating and preparing high-purity propane and high-purity propylene according to claim 3, characterized in that, The feed temperature of the catalytic distillation column is 70℃~80℃, and the pressure is 0.5~0.9MPa.

7. The method for separating and preparing high-purity propane and high-purity propylene according to claim 3, characterized in that, The feed temperature of the catalytic cracking distillation column is 150℃~170℃, and the pressure is 0.2~0.4MPa.

8. The method for separating and preparing high-purity propane and high-purity propylene according to claim 3, characterized in that, The reaction sections of the pre-reactor and the catalytic distillation column both use etherified acidic catalysts, while the reaction section of the catalytic cracking distillation column uses a catalytic cracking catalyst.

9. The method for separating and preparing high-purity propane and high-purity propylene according to claim 8, characterized in that, Both the pre-reactor and the reaction section of the catalytic distillation column employ modified strong acid cation exchange resin catalysts. The preparation method of the modified strong acid cation exchange resin catalyst is as follows: commercially available Amberlyst-15 strong acid cation exchange resin or Dowex-50 strong acid cation exchange resin is impregnated with a 0.1 mol / L to 5 mol / L sulfuric acid aqueous solution to induce ion exchange and modification. The amount of sulfuric acid aqueous solution used is 5 to 20 times the weight of the resin, the impregnation time is 1 to 48 hours, the impregnation temperature is 20°C to 50°C, and slight stirring is maintained during the impregnation process. After impregnation, the strong acid cation exchange resin is dried at 80°C for 24 to 48 hours to obtain the modified strong acid cation exchange resin catalyst.

10. The method for separating and preparing high-purity propane and high-purity propylene according to claim 8, characterized in that, The reaction section of the catalytic cracking distillation column uses a supported catalytic cracking catalyst for methyl isopropyl ether. The preparation method of the supported catalytic cracking catalyst for methyl isopropyl ether is as follows: γ-alumina with a purity of 99.999% is impregnated with a 0.1 mol / L to 5 mol / L ammonium sulfate solution, wherein the amount of ammonium sulfate aqueous solution is 5 to 20 times the weight of γ-alumina, the impregnation time is 2 h to 48 h, the impregnation temperature is 20 °C to 40 °C, and the mixture is stirred continuously during the impregnation process. After impregnation, the mixture is filtered and then microwave dried and calcined. The drying and calcination are carried out uniformly with a temperature gradient of 0.1 °C / min, and the highest drying and calcination temperature is 180 °C, which is maintained at this temperature for 10 h to obtain the supported catalytic cracking catalyst for methyl isopropyl ether.

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