System and method for low-temperature preparation of propylene by infrared laser cracking of n-butane

Abstract

The present application relates to a kind of system and method for preparing propylene by infrared laser low temperature, belong to propylene preparation technical field, specifically related to a kind of no catalyst using infrared laser directly induced model molecule n-butane cracking reaction system for preparing propylene.For the problems such as high reaction temperature, product selectivity is difficult to control in traditional thermal cracking, the present application is under the condition of no catalyst, by the infrared laser of wavelength 9-11 microns irradiation reaction system, can selectively and the carbon-carbon bond of the two ends in n-butane molecular structure resonance, to direct production propylene, realize accurate molecular tailoring, while reducing the required reaction temperature.

Description

Technical Field

[0001] This invention relates to a system and method for preparing propylene at low temperature by cracking n-butane with infrared laser, belonging to the field of propylene preparation technology, specifically to a reaction system for preparing propylene by directly inducing the cracking of the model molecule n-butane with infrared laser without a catalyst. Background Technology

[0002] The main industrial production routes for propylene include the following:

[0003] Propylene production via steam cracking of naphtha is the most important propylene production route in my country. It involves steam cracking ethylene feedstocks such as naphtha, ethane, and propane to obtain propylene. Specifically, the naphtha-based ethylene cracking route yields approximately 31% ethylene and 16% propylene, while the ethane-based route yields approximately 80% ethylene and 3% propylene. The production process mainly includes cracking, compression, and separation. Propylene steam cracking typically involves multiple parallel cracking furnaces, with high outlet temperatures approaching 850°C. Thousands of chemical reactions occur within these furnaces. Traditionally, refineries and propylene plants are often separate, with propylene plants using purchased naphtha as feedstock. Therefore, optimizing and balancing many intermediate products between refining and propylene production is difficult.

[0004] Refinery propylene mainly comes from three types of units: catalytic cracking (FCC), viscous / thermal cracking, and coking. FCC propylene accounts for approximately 97% of refinery propylene, making it the second largest source. Propane dehydrogenation (PDH) is an on-purpose process, typically requiring 1.2 tons of propane to produce one ton of propylene. It has rapidly developed in recent years and has become an effective supplement to propylene supply. Olefin disproportionation is the process of reacting ethylene and 2-butene as feedstock to produce propylene. Relatively mature technologies include Lummus' OCT process and IFP's Meta-4 process. Methanol-to-olefins (MTO) and coal-to-olefins (CTO) use methanol as feedstock, or coal processed through methanol; the ethylene / propylene yield ratio can be adjusted between 0.77 and 1.33. There are also dedicated propylene production processes, such as MTP, exemplified by Lurgi.

[0005] All of the above propylene production routes require high temperatures (>400℃), and the product selectivity of propylene is difficult to control. Summary of the Invention

[0006] The technical problem solved by this invention is to overcome the shortcomings of existing technologies in the preparation of propylene from n-butane, such as low selectivity. This invention proposes a system and method for the low-temperature preparation of propylene from n-butane via infrared laser pyrolysis. It is a catalyst-free reaction system utilizing an infrared laser coupled to a quartz laser reactor and its application in inducing the pyrolysis of n-butane to produce propylene. Addressing the problems of high reaction temperature and difficulty in controlling product selectivity in traditional thermal pyrolysis, this invention employs an infrared laser with a wavelength of 9-11 micrometers to irradiate the reaction system under catalyst-free conditions. This laser selectively resonates with the carbon-carbon bonds at both ends of the n-butane molecule, thereby directionally producing propylene, achieving precise molecular tailoring, and simultaneously reducing the required reaction temperature.

[0007] The technical solution of this invention is:

[0008] A system for the low-temperature preparation of propylene using infrared laser, the system comprising a laser system and a reactor system;

[0009] The laser system includes an infrared laser and a coupling device. The infrared laser is used to provide infrared laser of a set wavelength in the infrared spectral region. The cross-section of the infrared laser source is circular with a diameter of 3 mm.

[0010] The coupling device includes a transformer, a cooling water device, and a heating jacket;

[0011] The reactor system includes a quartz laser reactor, rubber ring a, rubber ring b, zinc selenide lens a, and zinc selenide lens b;

[0012] Among them, a transformer is used to maintain the normal operation of the infrared laser, a cooling water device is used to cool the infrared laser, and a heating jacket is used to heat the quartz laser reactor in the reactor system to the set temperature.

[0013] The quartz laser reactor is a quartz tube with an inlet and an outlet pipe on its side. The zinc selenide lens is used as a light transmission window, which has high transmittance, low absorption coefficient, high thermal stability, and a melting point of up to thousands of degrees Celsius, significantly enhancing the thermal stability and durability of the reactor system.

[0014] A method for preparing propylene at low temperature using infrared laser, the method comprising the following steps:

[0015] The first step is to build the reactor system. Place rubber ring a on the right side of the quartz laser reactor, then place zinc selenide lens a on the right side of rubber ring a, place rubber ring b on the left side of the quartz laser reactor, then place zinc selenide lens b on the left side of rubber ring b, and use clamps to fix and connect the quartz laser reactor, rubber ring a, rubber ring b, zinc selenide lens a and zinc selenide lens b to ensure airtightness.

[0016] The second step is to build the laser system. Place the infrared laser horizontally on the table and couple a cooling water device to it. The cooling water device is used to cool the infrared laser, and the direction of the cooling water flow is consistent with the direction of the infrared laser beam. Wrap a heating jacket around the quartz tube of the quartz laser reactor to heat the gas inside. Couple a transformer to the infrared laser, with the positive and negative terminals of the infrared laser connected to the positive and negative terminals of the transformer. The transformer provides the required high voltage to the infrared laser. When installing the infrared laser, ensure that the emitted infrared laser beam passes through the center of the reactor system.

[0017] The third step involves closing the outlet pipe of the quartz tube, opening the inlet pipe of the quartz tube to introduce the reaction raw materials, and closing the inlet pipe after the set time has elapsed. The reaction raw materials are then heated to the set temperature using a heating mantle. The infrared laser is then turned on to emit infrared laser light, which is used to irradiate the reaction raw materials for the set time. After irradiation, the infrared laser is turned off, and the outlet pipe of the quartz tube is opened to collect propylene. The collected propylene is then introduced into a gas chromatograph to detect the product.

[0018] The inner diameter of the quartz tube in the quartz laser reactor is 16 mm.

[0019] The reaction feedstock is n-butane;

[0020] Before the infrared laser irradiates the prepared reactant n-butane, the positive and negative terminals of the infrared laser need to be connected to the positive and negative terminals of the transformer, and the cooling water device needs to be turned on, wherein the direction of the cooling water flow is consistent with the direction of the infrared laser beam.

[0021] The infrared laser generated by the infrared laser has a power of 10-150W. Specifically, the power of the infrared laser can be 10, 20, 40, 60, 80, 100, 120, 150W or any value between two of the above ranges; preferably, the power of the infrared laser is 40W.

[0022] The wavelength of the infrared laser is 9-11 micrometers. Specifically, the wavelength of the infrared laser can be 9, 9.5, 10, 10.5, 11 micrometers or any value between two of the above ranges; preferably, the wavelength of the infrared laser is 10.3 micrometers.

[0023] The illumination time of the infrared laser is 1-10 minutes. Specifically, the illumination time of the infrared laser can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 minutes or any value between two of the above ranges; preferably, the illumination time of the infrared laser is 5 minutes.

[0024] The heating jacket heats the reaction raw materials to a set temperature of 200-400℃. Specifically, the heating temperature can be 200, 220, 240, 260, 280, 300, 320, 340, 360, 380, 400℃ or any two of the above values; preferably, the temperature is 340-350℃.

[0025] Beneficial effects

[0026] (1) The laser system described in this invention uses infrared laser to induce the cracking of n-butane gas without using a beam expander and catalyst, and the n-butane conversion rate is optimal.

[0027] (2) The laser system described in this invention uses infrared laser to induce the cracking of n-butane gas under the condition of using a coupling device heating jacket and no catalyst, and the n-butane conversion rate is optimal.

[0028] (3) The reactor system described in this invention uses an infrared laser to induce the cracking of n-butane gas when using zinc selenide lenses, resulting in the most stable reaction system and a significantly improved service life.

[0029] (4) The reaction system described in this invention provides a method for preparing propylene by inducing the cracking of n-butane using the above-described reaction system without a catalyst. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the reactor system.

[0031] Figure 2 This is a schematic diagram of the system composition for the low-temperature preparation of propylene using infrared lasers according to the present invention. Detailed Implementation

[0032] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0033] According to the present invention, the laser system described above preferably does not use a beam expander in the entire optical path. A beam expander is designed to enlarge the diameter of the parallel input beam to a larger parallel output beam, but this would reduce the conversion rate of the reactant gas.

[0034] According to the present invention, the infrared laser described above requires thousands or even tens of thousands of volts of high voltage, and a coupling device transformer is required to maintain the normal operation of the infrared laser.

[0035] Zinc selenide lenses have excellent transmittance in the 0.5-22 micrometer range, especially in the 9-11 micrometer range. They also have excellent low absorption coefficient and high thermal shock resistance, and have a melting point of over 1,000 degrees Celsius, which enhances the stability of the reactor system.

[0036] According to the present invention, a rubber ring is required to connect the zinc selenide lens and the quartz laser reactor to ensure the airtightness of the entire reactor system.

[0037] like Figure 1 As shown, when using the quartz laser reactor, it is necessary to connect the quartz laser reactor in the following order: "zinc selenide lens b → rubber ring b → quartz laser reactor → rubber ring a → zinc selenide lens a", and it must be placed horizontally at the same height as the light source.

[0038] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0039] Example 1

[0040] A method for preparing propylene at low temperature using infrared laser, such as Figure 1 and Figure 2 As shown, the steps of this method include:

[0041] The first step is to build the reactor system. Place rubber ring a on the right side of the quartz laser reactor, then place zinc selenide lens a on the right side of rubber ring a, place rubber ring b on the left side of the quartz laser reactor, then place zinc selenide lens b on the left side of rubber ring b, and use clamps to fix and connect the quartz laser reactor, rubber ring a, rubber ring b, zinc selenide lens a and zinc selenide lens b to ensure airtightness.

[0042] The second step is to build the laser system. Place the infrared laser horizontally on the table and couple a cooling water device to it. The cooling water device is used to cool the infrared laser, and the direction of the cooling water flow is consistent with the direction of the infrared laser beam. Wrap a heating jacket around the quartz tube of the quartz laser reactor to heat the gas inside. Couple a transformer to the infrared laser, with the positive and negative terminals of the infrared laser connected to the positive and negative terminals of the transformer. The transformer provides the required high voltage to the infrared laser, which operates at a power of 40W. During installation, ensure that the infrared laser beam emitted by the laser passes through the center of the reactor system.

[0043] Third, close the outlet pipe of the quartz tube and open the inlet pipe of the quartz tube to introduce n-butane gas at a rate of 5 g / h. After 5 minutes, close the inlet pipe of the quartz tube and heat the n-butane gas to 350°C using a heating mantle. Then, turn on the infrared laser to emit infrared laser light with a wavelength of 10.3 micrometers and irradiate the reaction raw materials for 5 minutes. After irradiation, turn off the infrared laser, open the outlet pipe of the quartz tube to collect propylene, and introduce the collected propylene into a gas chromatograph for product detection.

[0044] Test results: The conversion rate of n-butane gas was 98.19%, the yield of ethylene was 12.11%, and the yield of propylene was 29.98%. The selectivity of ethylene was 12.33%, and the selectivity of propylene was 30.53%.

[0045] Example 2

[0046] Similar to Example 1, except that the infrared laser operates at a power of 100W in the third step.

[0047] Test results: The conversion rate of n-butane gas was 98.72%, the yield of ethylene was 13.32%, and the yield of propylene was 29.85%. The selectivity of ethylene was 13.49%, and the selectivity of propylene was 30.23%.

[0048] Example 3

[0049] Similar to Example 1, except that the reaction temperature in the third step is 340°C.

[0050] Test results: The conversion rate of n-butane gas was 97.94%, the yield of ethylene was 11.82%, and the yield of propylene was 28.21%. The selectivity of ethylene was 12.07%, and the selectivity of propylene was 28.80%.

[0051] Example 4

[0052] Similar to Example 1, except that the irradiation time in the third step is 10 minutes.

[0053] Test results: The conversion rate of n-butane gas was 99.37%, the yield of ethylene was 14.19%, and the yield of propylene was 27.28%. The selectivity of ethylene was 14.28%, and the selectivity of propylene was 27.45%.

[0054] Example 5

[0055] Similar to Example 1, except that the wavelength of the infrared laser in the third step is 11 micrometers.

[0056] Detection results: The conversion rate of n-butane gas was 26.19%, the yield of ethylene was 4.52%, and the yield of propylene was 6.81%. The selectivity of ethylene was 17.26%, and the selectivity of propylene was 26.00%.

[0057] Comparative Example

[0058] Similar to Example 1, except that in the third step, only the heating jacket is used to heat to 350°C, and the infrared laser is not turned on.

[0059] Test results: The conversion rate of n-butane was 0.050%, the yields of propylene and ethylene were extremely low, and the selectivity was negligible.

[0060] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing propylene at low temperature using infrared laser, characterized in that... The reaction feedstock for this method is n-butane, and the steps include: The first step is to build the reactor system. Place rubber ring a on the right side of the quartz laser reactor, then place zinc selenide lens a on the right side of rubber ring a, place rubber ring b on the left side of the quartz laser reactor, then place zinc selenide lens b on the left side of rubber ring b, and use clamps to fix and connect the quartz laser reactor, rubber ring a, rubber ring b, zinc selenide lens a and zinc selenide lens b to ensure airtightness. The second step is to build the laser system. Place the infrared laser horizontally on the table. Connect the positive and negative terminals of the infrared laser to the positive and negative terminals of the transformer. Couple the cooling water device to the infrared laser. The cooling water device is used to cool the infrared laser. The direction of the cooling water flow in the cooling water device is consistent with the direction of the infrared laser beam generated by the infrared laser. Wrap the heating jacket around the quartz tube of the quartz laser reactor. The heating jacket is used to heat the gas inside the quartz laser reactor. When installing the infrared laser, ensure that the infrared laser beam emitted by the infrared laser can pass through the center of the reactor system. The third step is to close the outlet pipe of the quartz tube, open the inlet pipe of the quartz tube to introduce the reaction raw materials, and close the inlet pipe of the quartz tube after the introduced time reaches the set value. The reaction raw materials are heated to the set temperature through the heating jacket, and then the infrared laser is turned on to emit infrared laser light to irradiate the reaction raw materials for the set time. After the irradiation is completed, the infrared laser is turned off, and the outlet pipe of the quartz tube is opened to collect propylene.

2. The method for preparing propylene at low temperature using infrared laser according to claim 1, characterized in that: The inner diameter of the quartz tube in the quartz laser reactor is 16 mm. The reaction feedstock is n-butane; The infrared laser irradiates the reaction raw materials for 1-10 minutes; The heating jacket heats the reaction raw materials to a set temperature of 200-400 ℃.

3. The method for preparing propylene at low temperature using infrared laser according to claim 2, characterized in that: The infrared laser irradiates the reaction raw materials for 5 minutes; The heating jacket heats the reaction raw materials to a set temperature of 340-350 ℃.

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