A 3D printing catalyst for preparing low-carbon olefins from carbon dioxide and a preparation method and application thereof

Abstract

The application discloses a 3D printing catalyst for preparing low-carbon olefins from carbon dioxide and a preparation method and application thereof, relates to the field of catalysis, and comprises the following steps: 1) using metal iron-based alloy powder as raw material, an iron-based catalyst precursor is obtained by using a selective laser melting technology, and then the catalyst precursor is cleaned, dried and calcined; 2) the catalyst obtained in the step 1) is soaked in a potassium hydroxide solution; and 3) the catalyst after soaking in the step 2) is dried and calcined. The application aims at enhancing the disturbance of reaction gas, enhancing the effective contact area of the catalyst and raw material gas and the mass and heat transfer efficiency, and improving the catalytic reaction efficiency by designing a porous columnar catalyst with a unique pore channel and horizontal plate structure. The catalyst exhibits good catalytic performance in the reaction of preparing low-carbon olefins from carbon dioxide and hydrogen, and provides a new way for CO2 conversion and utilization.

Description

Technical Field

[0001] The present invention relates to the field of catalysis, and in particular to a 3D printing catalyst for preparing light olefins from carbon dioxide, and a preparation method and application thereof. Background Art

[0002] Against the backdrop of global climate change and increasingly scarce resources, the efficient conversion and utilization of carbon dioxide (CO2) has become a key area of ​​scientific research and technological innovation. As a major greenhouse gas, CO2 emissions reduction and resource utilization are crucial for mitigating a range of environmental issues, including global warming and ocean acidification. Furthermore, low-carbon olefins (such as ethylene and propylene), as important chemical raw materials, are widely used in industries such as plastics, rubber, and synthetic fibers, generating significant market demand.

[0003] Traditional methods for producing light olefins rely primarily on petroleum cracking, a process that not only consumes significant fossil resources but also generates additional CO2 emissions. Therefore, developing new technologies for producing light olefins using CO2 as a feedstock not only helps reduce greenhouse gas emissions but also enables resource recycling, possessing significant economic and environmental value.

[0004] The traditional catalysts for producing light olefins using CO2 as raw material have the following shortcomings:

[0005] 1. Complex preparation process: Traditional catalyst preparation process usually involves multiple steps and processes, and requires strict condition control, which makes the preparation process cumbersome and time-consuming.

[0006] 2. Human error in the preparation process: In traditional catalyst preparation, material processing (such as grinding, mixing, and molding) usually relies on manual operations or simple mechanical equipment. These operations may cause errors due to the operator's skill level and the accuracy limitations of the equipment.

[0007] 3. Low mass and heat transfer efficiency: Traditional catalysts have a single particle size distribution, limited thermal conductivity and poor thermal stability in terms of mass and heat transfer efficiency. Summary of the Invention

[0008] The purpose of the present invention is to solve the above-mentioned problems in the prior art, and to provide a 3D printing catalyst for the preparation of light olefins from carbon dioxide, and its preparation method and application. By designing a porous columnar catalyst with a unique pore and transverse plate structure, it is intended to enhance the disturbance of the reaction gas, enhance the effective contact area and mass transfer and heat transfer efficiency between the catalyst and the feed gas (CO2 and H2), so as to improve the efficiency of the catalytic reaction. After the catalyst is printed and formed using the 3D printing technology of selective laser melting (SLM), the catalyst precursor is treated with a KOH solution of a certain molar concentration. The catalyst exhibits good catalytic performance in the reaction of CO2 hydrogenation to produce light olefins, providing a new way for the conversion and utilization of CO2. In short, the present invention overcomes the limitations of traditional catalysts in the CO2 conversion process and achieves a more direct and environmentally friendly production of light olefins.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A method for preparing a 3D printing catalyst for producing light olefins from carbon dioxide comprises the following steps:

[0011] 1) Using an alloy powder mainly composed of metallic iron as raw material, an iron-based catalyst precursor is printed using selective laser melting technology, which is then cleaned, dried, and then calcined;

[0012] 2) soaking the catalyst obtained in step 1) in a potassium hydroxide solution;

[0013] 3) drying and calcining the catalyst soaked in step 2).

[0014] The iron-based catalyst precursor has a porous columnar structure as a whole, consisting of two layers of inner and outer circular columnar structures, and both the inner and outer circular columnar structures are provided with multiple channels; multiple vertical plates are provided radiating from the center of the circle to the outer circular columnar structure, and multiple horizontal plates are provided between the inner and outer circular columnar structures, and multiple channels are arranged at equal intervals on each vertical plate and each horizontal plate.

[0015] In step 1), the calcination temperature is 500-900°C.

[0016] In step 2), the concentration of the potassium hydroxide solution is 0.1 to 1.5 mol / L.

[0017] In step 3), the calcination temperature is 500-900°C.

[0018] A 3D printing catalyst for producing light olefins from carbon dioxide is prepared using the above preparation method.

[0019] The application of the 3D printed catalyst for producing light olefins from carbon dioxide is used for producing light olefins by hydrogenation of carbon dioxide, and specifically a high-pressure fixed-bed reactor is used to evaluate the performance of the CO2 hydrogenation reaction.

[0020] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0021] 1. The present invention uses 3D printing technology to prepare a CO2 to light olefins catalyst. Compared with the preparation of traditional catalysts, the present invention simplifies the catalyst preparation process.

[0022] 2. This invention allows precise control of the printed catalyst structure during catalyst preparation, reducing human error in traditional catalyst preparation processes. 3D printing technology enables program-controlled, precise preparation of catalysts with unique pore structures suitable for CO2 to light olefins, as well as control of the turbulence of the reactant gas flow and the catalyst bed surface area. The printed catalysts exhibit high fidelity, excellent mechanical properties, high mass and heat transfer efficiencies, and good chemical stability.

[0023] 3. The preparation of the CO2-to-low-carbon olefin printing catalyst of the present invention uses iron-based alloy powder as raw material. Compared with traditional CO2-to-low-carbon olefin catalysts, the preparation cost is low, which can greatly reduce the waste of raw materials. The raw material powder can be reused, which can reduce energy consumption. These advantages are in line with the concepts of green chemistry and sustainable development, and have great application potential and prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic structural diagram of the catalyst model of Example 1; wherein, Figure 1 A is a schematic diagram of the overall structure of the catalyst. Figure 1 B is a schematic diagram of the top view of the catalyst. Figure 1 C in the figure is a schematic diagram of the internal structure of the catalyst. Figure 1 D is a schematic diagram of the top view of C;

[0025] Figure 2 The product diagrams of the uncalcined and calcined catalyst of Example 1 are shown; wherein, Figure 2 A and C are the overall structure and top view of the uncalcined catalyst; Figure 2 B and D are the overall structure and top view of the catalyst after calcination;

[0026] Figure 3 is the X-ray powder diffraction pattern of the catalyst of Example 1;

[0027] Figure 4 The performance diagram of the catalyst soaked in potassium hydroxide with different concentrations;

[0028] Figure 5 is a graph showing the catalyst performance at different calcination temperatures in step 7);

[0029] Figure 6 Performance diagram of catalysts soaked with different potassium compounds. DETAILED DESCRIPTION

[0030] In order to make the contents of the present invention easier to understand, the technical solutions of the present invention are further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0031] Example 1

[0032] 1) Use solidworks software for auxiliary design and build digital models and tasks. Digital tasks include laser power, scanning rate, scanning path, slice thickness, etc. Digital model see Figure 1 , is a porous columnar catalyst (PCC), which consists of two layers of inner and outer circular columnar structures, and both inner and outer circular columnar structures are provided with multiple channels; multiple vertical plates are provided between the outer circular columnar structure radiating from the center of the circle. Specifically, the inner and outer circular columnar structures are connected by 16 equally divided vertical plates (the inner circular ring is provided with 8 vertical plates, and there are 8 vertical plates between the outer and inner circular rings). Each vertical plate has 6 circular holes arranged equidistantly from top to bottom, and there are 6 holes between the outer and inner circular rings from top to bottom. Five horizontal plates are evenly spaced and arranged in a staggered pattern. The first, third, and fifth horizontal plates are located on the inner side of the outer ring, while the second and fourth horizontal plates are located on the outer side of the inner ring. Two circular holes are evenly spaced on the first, third, and fifth horizontal plates at a 45° angle, while one circular hole is evenly spaced on the second and fourth horizontal plates at a 45° angle. Twelve circular holes are evenly spaced from top to bottom on the outer ring between the two vertical plates, while six circular holes are evenly spaced from top to bottom on the inner ring between the two vertical plates. The catalyst structure has a total height of 20 mm; the outer ring has a diameter of 10.8 mm; the inner ring has a diameter of 5.4 mm; all plates are 0.6 mm thick, and the circular holes have a diameter of 1 mm.

[0033] 2) 3D printing catalyst preparation using 316L stainless steel alloy powder as raw material. The 3D printer selectively laser melts the metal powder using pre-set parameters such as laser power, scan rate, scan path, and slice thickness.

[0034] 3) Using a wire-cut CNC machine tool, the sample printed in step 2) was cut and separated from the substrate. The cut sample was washed with kerosene 2 to 3 times and naturally dried. The porous columnar catalyst precursor was ultrasonically cleaned with ethanol and ultrapure water for 3 to 4 times, and then dried in a sample oven for 12 hours at a drying temperature of 60°C to obtain a sample as shown in FIG. Figure 2 As shown in A and C;

[0035] 4) placing the sample obtained in step 3) into a porcelain boat and calcining it in a high-temperature muffle furnace at a temperature of 700° C., a heating rate of 5° C. / min, and a calcination time of 12 h;

[0036] 5) Soaking the samples obtained in step 4) in 50 mL of 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, 1.5 mol / L, and 7.0 mol / L KOH solutions for 2 h, respectively;

[0037] 6) drying the sample obtained in step 5) in a sample oven at 100° C. for 12 h;

[0038] 7) The sample obtained in step 6) was placed in a porcelain boat and calcined in a high-temperature muffle furnace at a temperature of 700°C, a heating rate of 5°C / min, and a calcination time of 12h. Figure 2 The porous columnar catalyst shown in B and D is named PCC-M KOH-700, where M represents the molar concentration of KOH, and the values ​​of M are 0, 0.05, 0.1, 0.5, 1.5, 7.0, and 700 represents the calcination temperature of 700°C. PCC-700 is a porous columnar catalyst obtained by calcining at 700°C without soaking.

[0039] Figure 3 The XRD pattern of the catalyst prepared in Example 1 is as follows. Figure 3 It can be seen that the iron oxide peak on the surface of the PCC-700 catalyst that has not been soaked is not obvious after calcination; however, after being soaked in KOH solution, iron oxide is more easily generated through calcination, indicating that soaking in KOH solution can promote the formation of iron oxide, form active sites on the catalyst surface, and affect the catalytic activity of CO2 to light olefins.

[0040] Example 2

[0041] The difference between Example 2 and Example 1 is that the concentration of KOH in step 5) is fixed and the high-temperature calcination temperature in step 7) is different. The calcination temperature in step 7) of Example 2 ranges from 500 to 900°C, the heating rate is 5°C / min, and the calcination time is 12 h. The other preparation steps are the same as those in Example 1. Finally, a porous columnar catalyst sample is obtained, and the catalyst is named PCC-0.5KOH-X (X represents the numerical value of the calcination temperature, and the value of X is 500, 600, 700, 800, 900).

[0042] Comparative Example 1

[0043] The difference between Comparative Example 1 and Example 1 is that in step 5), the soaking solution is 50 mL of 0.5 mol / L KCl, KOH and KNO3, respectively. The other preparation steps are the same as those in Example 1. Finally, porous columnar catalyst samples are obtained, and the catalysts are named PCC-0.5KCl-700, PCC-0.5KOH-700, and PCC-0.5KNO3-700, respectively.

[0044] Application Examples

[0045] A 3D printed porous columnar catalyst sample with a total height of 20 mm and a diameter of 10.8 mm was loaded into a transparent quartz tube with an inner diameter of 12 mm. An appropriate amount of quartz wool was placed at both ends of the catalyst to fix the catalyst. The quartz tube was placed inside the reactor and fixed in a heating furnace for CO2 hydrogenation reaction performance test. After ensuring the airtightness of the device, H2 was introduced for reduction pretreatment, and the H2 reduction flow rate was accurately controlled to 30 mL / min by a mass flow meter. The temperature was then programmed to 400°C at a heating rate of 2°C / min, and in-situ reduction was carried out at 400°C for 8 h. After H2 reduction was completed, the temperature was lowered to room temperature, and a CO2 / H2 / Ar mixed gas was introduced through the valve. The reaction flow rate was accurately controlled to 20 mL / min by a mass flow meter, and the reaction pressure was controlled to 3.0 MPa by a back pressure valve. The catalyst performance was evaluated by programming the temperature to 300°C at 2°C / min. The product after 8 h of reaction was used for detection and analysis.

[0046] Figure 4 This is a performance diagram of the catalyst obtained in Example 1 in the CO2 hydrogenation to light olefins reaction. From the performance diagram, it can be seen that the catalytic performance of the porous columnar catalyst in KOH solutions with different molar concentrations is significantly different. When the porous columnar catalyst is not treated with KOH solution, the product distribution is mainly methane, and almost no light olefins are generated. At the same time, the CO2 conversion rate and the by-product CO selectivity are low; as the molar concentration of KOH increases to 0.05 mol / L, the CO2 conversion rate increases, and the light olefins increase slightly to 3.5%; when the molar concentration of KOH gradually increases When the molar concentration of KOH solution reaches 0.1mol / L, the CO2 conversion rate increases to a certain extent, and the selectivity of light olefins increases significantly to 18.3%. When the molar concentration of KOH solution is further increased to 0.5mol / L, the CO2 conversion rate increases to 26.3%, and the selectivity of light olefins reaches 34.5%, and the selectivity of by-product CO also remains at a low level; as the molar concentration of KOH continues to increase to 1.5mol / L and 7.0mol / L, the CO2 selectivity and light olefin selectivity gradually decrease, and the by-product CO selectivity further increases. At 7.0mol / L When the porous columnar catalyst was immersed in KOH solution, the by-product CO selectivity reached 55.4%. Combined with the product distribution diagram, it can be observed that the CO2 conversion rate showed a trend of first increasing and then decreasing with the increase of the molar concentration of KOH. The CO2 conversion rate gradually increased from 16.3% to 26.3% and then gradually decreased to 16.7%. The by-product CO selectivity increased from 15.8% to 55.4%, and the light olefin selectivity increased from 0.2% to 34.5% and then decreased to 26.9%. The porous columnar catalyst (PCC-0.5KOH-700) showed the best catalytic performance in a moderate KOH concentration of 0.5 mol / L.

[0047] Figure 5 The performance diagram of the catalyst obtained in Example 2 in the CO2 hydrogenation reaction to produce light olefins is shown. As can be seen from the performance diagram, the CO2 conversion rate of the porous columnar catalyst (PCC-0.5KOH-500) is 11.4%, the by-product light olefin selectivity is 73.3%, and the light olefin selectivity is only 21.3%; as the calcination temperature is gradually increased to 600°C, the CO2 conversion rate increases to 21.6%, and the light olefin selectivity increases to 29.3%; when the calcination temperature is gradually increased to 700°C, the CO2 conversion rate reaches 26.3%, and the light olefin selectivity reaches 34.5%; as the calcination temperature continues to increase, the CO2 conversion rate gradually decreases. When the calcination temperature reaches 900°C, the CO2 conversion rate decreases to 15.2%, and the light olefin selectivity decreases to 10.3%. From the overall performance point of view, the CO2 conversion rate and light olefin selectivity show a trend of first increasing and then decreasing with the increase of calcination temperature, while the by-product CO selectivity first decreases and then increases, and the best performance is shown when the catalyst calcination temperature is 700°C.

[0048] Figure 6 This is the performance diagram of the catalyst obtained in Comparative Example 1 in the CO2 hydrogenation to light olefins reaction. It can be seen from the performance diagram that the 3D printed porous columnar catalyst (PCC-0.5KCl-700) obtained by treatment with 0.5mol / L KCl solution has a CO2 conversion rate of 21.4%, a light olefin selectivity of only 18%, and a high selectivity for by-product CH4; the PCC-0.5HNO3-700 catalyst obtained by treatment with 0.5mol / L KNO3 solution has a CO2 conversion rate of 20.1%, a light olefin selectivity of 27.1%, and a by-product CO selectivity of 46.1%. Comprehensively comparing the three different types of potassium compounds, PCC-0.5KOH-700 exhibits the best catalytic performance.

[0049] The 3D-printed catalyst for converting carbon dioxide to light olefins provided by the present invention is based on computer-aided modeling software and combines metal 3D printing technology with 316L stainless steel alloy powder as the printing base raw material. The catalyst precursor is printed using selective laser melting (SLM) 3D printing technology. The printed catalyst precursor is calcined and soaked in potassium hydroxide. After post-processing operations such as drying and calcination, a catalyst sample is obtained, which has good carbon dioxide to light olefin activity.

Claims

1. A method for preparing a 3D printing catalyst for preparing light olefins from carbon dioxide, characterized in that: The following steps are involved: 1) Using an alloy powder mainly composed of metallic iron as raw material, an iron-based catalyst precursor is printed using selective laser melting technology, which is then cleaned, dried, and then calcined; 2) soaking the catalyst obtained in step 1) in a potassium hydroxide solution; 3) drying and calcining the catalyst soaked in step 2); The iron-based catalyst precursor is composed of two layers of inner and outer circular cylindrical structures, and both the inner and outer circular cylindrical structures are provided with multiple channels; multiple vertical plates are provided radiating from the center of the circle to the outer circular cylindrical structure, and multiple horizontal plates are provided between the inner and outer circular cylindrical structures, and multiple channels are arranged at equal intervals on each vertical plate and each horizontal plate.

2. The method for preparing a 3D printing catalyst for converting carbon dioxide to light olefins according to claim 1, wherein: In step 1), the calcination temperature is 500-900°C.

3. The method for preparing a 3D printing catalyst for converting carbon dioxide to light olefins according to claim 1, wherein: In step 2), the concentration of the potassium hydroxide solution is 0.1 to 1.5 mol / L.

4. The method for preparing a 3D printing catalyst for converting carbon dioxide to light olefins according to claim 1, wherein: In step 3), the calcination temperature is 500-900°C.

5. A 3D printing catalyst for producing light olefins from carbon dioxide, characterized by: Prepared by the preparation method according to any one of claims 1 to 4.

6. The use of a 3D printing catalyst for preparing light olefins from carbon dioxide according to claim 5, characterized in that: Used for carbon dioxide hydrogenation to produce light olefins.

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