Preparation method and application of 3D printing porous monolithic catalyst of polyacid type
By using porous alumina and boron nitride in synergy with phosphotungstic acid in 3D printing catalysts, the problems of catalyst ink compatibility and active site dispersion were solved, achieving deep desulfurization of fuel oil with high catalytic efficiency and easy recovery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGSU UNIV
- Filing Date
- 2026-04-02
- Publication Date
- 2026-06-19
AI Technical Summary
Existing 3D-printed multi-acid catalyst inks have poor compatibility and uneven dispersion of active sites, resulting in low catalytic efficiency. Traditional powder catalysts are prone to agglomeration, equipment blockage, and are difficult to recycle, making it difficult to achieve deep desulfurization of fuel.
Using porous alumina as a support and boron nitride as a bifunctional additive in synergy with phosphotungstic acid, a porous monolithic catalyst was prepared by 3D printing technology, which improved the dispersion of active sites and the rheological properties of ink, thus forming a highly efficient catalyst.
Under mild conditions, the sulfur content in fuel can be reduced from hundreds of ppm to below 10 ppm. The catalyst active sites are evenly dispersed, the desulfurization rate is as high as 98% or more, the structure is stable and easy to recycle, and the cost and pollution risk are reduced.
Smart Images
Figure CN122230754A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of materials catalysis and fuel purification technology, specifically relating to a method for preparing a 3D-printed multi-acid porous monolithic catalyst and its application, which is particularly suitable for catalytic oxidation to remove organic sulfur compounds from fuel, thereby achieving deep desulfurization of fuel. Background Technology
[0002] SO produced by fuel combustion x This can lead to serious environmental pollution problems such as acid rain and smog, harming the ecological environment and human health. Currently, countries around the world have introduced strict regulations to limit the sulfur content of fuel oil, and most countries and regions have limited the sulfur content of gasoline and diesel to below 10 ppm. Achieving deep desulfurization of fuel oil has become an urgent technical challenge to be solved.
[0003] Among existing desulfurization technologies, hydrodesulfurization is the mainstream. However, this technology suffers from drawbacks when removing sterically hindered organic sulfides such as dibenzothiophene (DBT), 4-methyldibenzothiophene (4-MDBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT), including demanding operating conditions (high temperature and high pressure), difficulty in removing low-concentration sulfides, and high equipment investment. Oxidative desulfurization technology, due to its high selectivity for thiophene sulfides and mild reaction conditions, can serve as a supplement to hydrodesulfurization to achieve ultra-low sulfur fuel production. Its core lies in developing high-performance catalysts.
[0004] Polyoxometalates (such as phosphotungstic acid) possess both strong acidity and redox dual functions, exhibiting excellent catalytic performance in oxidative desulfurization. They can effectively activate sulfides and promote their oxidation to more polar sulfones, facilitating subsequent removal. However, traditional phosphotungstic acid catalysts are mostly in powder form, which has significant drawbacks: the powder is prone to agglomeration and diffusion, leading to equipment blockage, reduced specific surface area, and decreased catalytic activity; low mass and heat transfer efficiency, with diffusion barriers formed by agglomeration hindering contact between reactants and active sites; and difficult recovery, with spent catalysts easily causing secondary pollution.
[0005] 3D printing technology (especially ink-to-write (DIW) technology) offers a new approach to catalyst molding due to its advantages of flexible molding, high precision, and ability to construct complex three-dimensional structures, effectively addressing the aforementioned shortcomings of powdered catalysts. However, the current use of 3D printing to prepare polyacid catalysts faces two major challenges: first, the rheological properties (viscoelasticity) of the catalyst ink are difficult to adapt to the requirements of 3D printing, easily leading to printing collapse and poor molding results; second, after printing, the polyacid active components tend to agglomerate, resulting in uneven dispersion of active sites and a decrease in catalytic efficiency.
[0006] While existing technologies have attempted to disperse active components using porous supports and add additives to adjust ink rheological properties, there are no reports of using boron nitride as a dual-functional additive for "active site dispersion + ink rheology adjustment" in combination with porous alumina to construct a multi-acid monolithic catalyst. Therefore, developing a 3D-printed multi-acid porous monolithic catalyst that can balance ink printing compatibility and catalytic activity to achieve deep desulfurization of fuel oil has significant practical value and innovative implications. Summary of the Invention
[0007] To address the shortcomings of existing 3D-printed multi-acid catalysts, such as poor ink compatibility, uneven dispersion of active sites, insufficient desulfurization efficiency, and inherent defects of traditional powder catalysts, this invention provides a 3D-printed multi-acid porous monolithic catalyst and its preparation method. Through material synergistic design, the invention achieves dual optimization of ink rheology and catalytic activity, thereby achieving deep desulfurization of fuel oil.
[0008] The core innovation of this invention lies in the adoption of a synergistic system of "porous alumina + boron nitride + phosphotungstic acid": porous alumina serves as a carrier, providing abundant pore structure, significantly increasing the specific surface area of the catalyst, and achieving initial dispersion of active sites; boron nitride, as a bifunctional additive, further disperses the active components of phosphotungstic acid and prevents agglomeration, while also adjusting the viscoelasticity of the 3D printing ink, improving printability; phosphotungstic acid, as the active center, exerts both strong acidity and redox dual functions, efficiently catalyzing the oxidation of sulfides. The synergistic combination of these three components with 3D printing technology solves the problem in existing technologies where ink printability and catalytic activity are difficult to balance, achieving deep desulfurization of fuel oil.
[0009] A method for preparing a 3D-printed multi-acid porous monolithic catalyst includes the following steps: (1) Preparation of porous alumina: P123, polyvinyl alcohol (PVA), polyethylene glycol (PEG), and aluminum isopropoxide were mixed in proportion and ground for 30-40 minutes until a uniform paste was formed. The temperature was then increased from room temperature to 350-450°C and held for 3.5-4.5 hours. After cooling to room temperature, the mixture was pulverized and sieved to obtain porous alumina (meso-Al2O3). (2) Preparation of 3D printing ink: The porous alumina, boron nitride, and phosphotungstic acid prepared in step (1) are mixed in proportion, an appropriate amount of binder is added, and the mixture is placed in a planetary ball mill and ball-milled until it is evenly mixed to obtain a milky white 3D printing ink. (3) 3D printing: Using an ink direct writing (DIW) 3D printer, the 3D printing ink prepared in step (2) is loaded into the printing syringe; a three-dimensional model is designed using CAD software, and the printing parameters are set as follows: mesh density is set to 75%~85%; printing speed is 35~45mm / s, layer thickness is 0.6~1.0mm, and printing temperature is 25~30℃; after printing, the blank is placed in a ventilated and dry place to air dry naturally for 20~28h to obtain a solid blank, which is the 3D printed multi-acid porous monolithic catalyst.
[0010] In step (1), the mass ratio of P123, polyvinyl alcohol (PVA), polyethylene glycol (PEG) to aluminum isopropoxide is 1:1.8~2.2:0.8~1.2:4~6; wherein, the molecular weight of P123 is ≥5800, the molecular weight of PVA is 1750, and the molecular weight of PEG is 800.
[0011] In step (1), the heating rate is 1.2~1.8℃ / min; the sieve size is 100~120 mesh; and the specific surface area of the obtained porous alumina (meso-Al2O3) is 320~420m². 2 / g, with an average pore size of 2~8nm.
[0012] In step (2), the mass ratio of porous alumina to boron nitride is 1:0.6~1.4; The boron nitride is hexagonal boron nitride (h-BN) with a purity ≥99.2%, a particle diameter ≤8μm, and a specific surface area of 15~45m². 2 / g, pore size 2~8nm; The phosphotungstic acid is of analytical grade with a purity of ≥99.5%, and its mass accounts for 1~8% of the mass of the 3D printing ink. The adhesive is a PVA solution with a concentration of 5~7g / L. The mass ratio of the adhesive to the porous alumina, boron nitride and phosphotungstic acid mixed solid is 4:3~4. This ratio can ensure that the ink has good viscoelasticity and at the same time ensure that the active components are uniformly dispersed.
[0013] In step (2), the ball milling speed is 200~300 r / min and the time is 60~90 min.
[0014] In step (2), the 3D printing ink is a milky white fluid with no special odor, a water content of 35~55wt%, and a viscosity of 800~1800Pa·s, which is suitable for ink direct writing 3D printing requirements.
[0015] In step (3), the printing syringe is made of a printing needle with a diameter of 0.4~0.6mm.
[0016] In step (3), the solid blank after natural air drying can also be subjected to low-temperature drying treatment according to actual needs, with a drying temperature of 60~80℃ and a drying time of 4~6h, to further remove residual moisture and improve the mechanical strength and stability of the catalyst.
[0017] The 3D-printed multi-acid porous monolithic catalyst prepared in this invention is used for catalytic oxidation to remove organic sulfur compounds from fuel oil. Under mild conditions, the sulfur content in fuel oil can be reduced from hundreds of ppm to below 10 ppm, achieving deep desulfurization. It is suitable for the purification of fuel oils such as gasoline and diesel.
[0018] The organic sulfide includes one or more of dibenzothiophene, 4-methyldibenzothiophene, and 4,6-dimethyldibenzothiophene; in the catalytic oxidation reaction, the reaction temperature is 45~75℃ and the oxygen-sulfur ratio is 5.7~11.4:1.
[0019] Compared with the prior art, the present invention has the following significant advantages: (1) Synergistic effect of dual-function additives: Boron nitride has both "active site dispersion" and "ink rheology regulation" functions, which not only solves the problem of agglomeration of phosphotungstic acid active components, but also optimizes ink viscoelasticity, avoids problems such as printing collapse and poor forming, and achieves dual improvement of printing adaptability and catalytic activity.
[0020] (2) Significant advantages of porous structure: Porous alumina provides a rich multi-level pore structure, which greatly increases the specific surface area of the catalyst, further disperses the active sites, promotes the contact between reactants and active sites, accelerates the mass transfer rate, and improves desulfurization efficiency.
[0021] (3) The preparation process is simple and controllable: the catalyst is printed using ink direct writing 3D printing technology. The molding process is simple and has high precision. The three-dimensional structure of the catalyst can be designed according to actual needs and adapted to different reaction equipment. The raw materials are readily available, the preparation cost is low, and it is easy to carry out large-scale production.
[0022] (4) Excellent and stable desulfurization effect: The catalyst active sites are evenly dispersed and the catalytic oxidation efficiency is high. Deep desulfurization of fuel can be achieved under mild conditions (temperature 45~75℃, oxygen-sulfur ratio 5.7~11.4:1), and the desulfurization rate can reach more than 98%. The integral structure is easy to recycle and reuse. After being reused 5 times, the desulfurization rate is still maintained at more than 83%, reducing the cost of use and the risk of environmental pollution. Attached Figure Description
[0023] Figure 1 To prepare customized catalysts using an ink-to-write 3D printer and the 3D printing ink of this invention.
[0024] Figure 2 The images show the BET diagrams of the materials prepared in Example 1 of this invention. Detailed Implementation
[0025] The present invention will be further described in detail below through specific embodiments and comparative examples. However, the present invention is not limited to the following embodiments. All improvements and optimizations made based on the technical solutions of the present invention shall fall within the protection scope of the present invention.
[0026] It should be noted that: in the following examples, the method for preparing porous alumina is the method of step (1) in the present invention; in the desulfurization experiment, the model oil is made by dissolving DBT, 4-MDBT, and 4,6-DMDBT in dodecane, and adding n-tetradecane as an internal standard, with an initial sulfur content of 500 ppm; the desulfurization rate is calculated as follows: desulfurization rate % = (initial sulfur content − remaining sulfur content after reaction) / initial sulfur content × 100%; unless otherwise specified, the reaction conditions are: temperature 65℃, oxygen-sulfur ratio 11.4:1, and reaction time 2h; the amount of catalyst used is 0.5% of the mass of the model oil to ensure the consistency and comparability of the experimental conditions.
[0027] Example 1
[0028] (1) Preparation of porous alumina: P123, PVA, PEG and aluminum isopropoxide were mixed in a mass ratio of 1:2.0:1.0:5 and ground for 35 min. The temperature was increased to 400℃ at 1.5℃ / min and held for 4 h. After cooling and pulverizing, the mixture was passed through a 110-mesh sieve to obtain porous alumina (specific surface area 380 m² / g, average pore size 5 nm).
[0029] (2) Ink preparation: Take 10g of porous alumina, 10g of boron nitride (purity 99.5%, particle diameter 6μm, specific surface area 30m² / g), and 1.2g of phosphotungstic acid (accounting for 2.4% of the ink mass), mix them evenly, add 28g of PVA solution with a concentration of 6g / L (binder to mixed solid mass ratio 4:3.5), and ball mill for 75min to obtain milky white ink (water content 45wt%, viscosity 1200Pa·s).
[0030] (3) 3D printing: A DIW 3D printer was used, with a printing needle diameter of 0.5 mm. The model was a cylinder with a diameter of 24 mm and a height of 8 mm, and a mesh density of 80%. The printing speed was 40 mm / s, the layer thickness was 0.8 mm, and the printing temperature was 28℃. After printing, the model was naturally air-dried for 24 hours to obtain the solid catalyst 3D-HPW / BN-Al2O3.
[0031] Figure 1 Solid catalyst 3D-HPW / BN-Al2O3 was prepared using an ink direct-write 3D printer and the 3D printing ink of the present invention.
[0032] Figure 2 The BET diagrams are shown for the materials prepared in Example 1 of this invention. The specific surface area of the obtained porous alumina is 320~420 m². 2 / g, with an average pore size of 2~8nm. The specific surface area of the obtained solid catalyst 3D-HPW / BN-Al2O3 is 200.6349 m² / g. 2 / g, with an average pore size of 5.8229 nm.
[0033] Desulfurization test results: DBT model oil desulfurization rate was 98.5%, 4-MDBT model oil desulfurization rate was 89.2%, and 4,6-DMDBT model oil desulfurization rate was 78.6%; the catalyst was recovered and reused 5 times, and the desulfurization rate remained above 90%.
[0034] Example 2
[0035] The difference from Example 1 is that the mass ratio of porous alumina to boron nitride is 1:0.8 (10g porous alumina and 8g boron nitride), 2.24g phosphotungstic acid (accounting for 5.5% of the ink mass), 20.5g of PVA solution with a concentration of 6g / L is added, the ink water content is 50wt%, the viscosity is 1500Pa·s, the printing speed is 38mm / s, and the layer thickness is 0.9mm.
[0036] Desulfurization test results: DBT model oil desulfurization rate was 92.3%, 4-MDBT model oil desulfurization rate was 81.5%, and 4,6-DMDBT model oil desulfurization rate was 70.3%; after being reused 5 times, the desulfurization rate remained above 85%.
[0037] Example 3
[0038] The difference from Example 1 is that the mass ratio of porous alumina to boron nitride is 1:1.4 (10g of porous alumina and 14g of boron nitride), 0.54g of phosphotungstic acid (accounting for 1.1% of the ink mass), 24.84g of PVA solution with a concentration of 6g / L is added, the ink water content is 50wt%, the viscosity is 900Pa·s, the printing speed is 42mm / s, and the layer thickness is 0.7mm.
[0039] Desulfurization test results: DBT model oil desulfurization rate was 90.1%, 4-MDBT model oil desulfurization rate was 78.8%, and 4,6-DMDBT model oil desulfurization rate was 67.9%; after being reused 5 times, the desulfurization rate remained above 83%.
[0040] Example 4
[0041] The difference from Example 1 is that the reaction temperature is 55°C and the oxygen-to-sulfur ratio is 7.6:1.
[0042] Desulfurization test results: DBT model oil desulfurization rate was 97.8%, 4-MDBT model oil desulfurization rate was 87.5%, and 4,6-DMDBT model oil desulfurization rate was 76.2%.
[0043] Comparative Example 1 (without boron nitride)
[0044] The difference from Example 1 is that boron nitride is not added, while the other preparation and reaction conditions are the same.
[0045] Experimental results: The ink viscosity was only 400 Pa·s, and it collapsed during the printing process, making it impossible to form. When the mixture was directly pressed into tablets to make a catalyst, the desulfurization rate of the DBT model oil was only 32.7%, the active sites were severely agglomerated, and the specific surface area dropped to 120 m² / g.
[0046] Comparative Example 2 (non-porous alumina)
[0047] The difference from Example 1 is that: no porous alumina is added, and ordinary alumina (specific surface area 80m²) is used. 2 / g (without porous structure) was substituted, and all other preparation and reaction conditions were the same.
[0048] Experimental results: The ink forming effect was acceptable, but the catalyst specific surface area dropped to 150 m² / g and the active sites were unevenly dispersed; the desulfurization rate of DBT model oil was only 65.3%, and the desulfurization rate of 4,6-DMDBT model oil was only 42.8%, which could not achieve deep desulfurization.
[0049] Comparative Example 3 (Traditional Powder Catalyst)
[0050] The porous alumina, boron nitride, and phosphotungstic acid from Example 1 were mixed in the same proportions, and the powder catalyst was obtained by ball milling without 3D printing. The remaining reaction conditions were the same as in Example 1.
[0051] Experimental results: The desulfurization rate of DBT model oil was 78.5%. During the reaction, powder agglomeration and blockage of the reaction device occurred. Recovery was difficult, and after being reused twice, the desulfurization rate dropped to below 50%.
[0052] Comparative Example 4 (Existing 3D Printing Catalyst)
[0053] Using existing technology, a 3D printing catalyst was prepared with porous alumina as the carrier, phosphotungstic acid as the active component, and sodium carboxymethyl cellulose as a rheology modifier. The remaining reaction conditions were the same as in Example 1.
[0054] Experimental results: The ink viscosity was unstable and it was prone to cracking after printing; the desulfurization rate of DBT model oil was 82.1%, the dispersion effect of active sites was average, and the desulfurization rate dropped to below 70% after repeated use 3 times.
[0055] Based on the above embodiments and comparative examples, a detailed analysis is conducted on the core components, preparation process, and performance influencing factors to further demonstrate the innovativeness and practicality of the present invention: (1) The role of the bifunctional additive boron nitride: Compared with Comparative Example 1, without boron nitride, the ink viscosity is much lower than the requirements of this invention, the printing collapses and cannot be formed, and the active sites are severely aggregated and the desulfurization rate is extremely low; after adding boron nitride, the ink viscosity is suitable for 3D printing, and at the same time, the active components of phosphotungstic acid are effectively dispersed, and the desulfurization rate is increased to 98.5%, which fully proves the necessity of boron nitride as a bifunctional additive, and is also the core innovation of this invention.
[0056] (2) The role of porous alumina: Compared with Comparative Example 1 and Comparative Example 2, ordinary alumina has no multi-level channels, resulting in low specific surface area of the catalyst and uneven dispersion of active sites, which makes it impossible to achieve deep desulfurization; porous alumina, with its rich channel structure, significantly improves specific surface area and mass transfer efficiency, providing core support for the high performance of the catalyst.
[0057] (3) Advantages of 3D printing: Compared with Example 1 and Comparative Example 3, traditional powder catalysts are prone to agglomeration, clogging of equipment and difficult to recycle; 3D printed integral catalysts have a stable structure, high desulfurization rate and are easy to recycle and reuse, effectively solving the inherent defects of powder catalysts.
[0058] (4) Advantages of existing 3D printing catalysts: Compared with Example 1 and Comparative Example 4, the existing technology uses sodium carboxymethyl cellulose as a rheology modifier, which has problems such as unstable ink viscosity, poor molding and poor dispersion of active sites; the present invention uses boron nitride as a bifunctional additive, and its comprehensive performance is significantly better than that of the existing technology, reflecting the innovation and superiority of the technology.
[0059] (5) Parameter influence analysis: Combined with Examples 1 to 4, the mass ratio of porous alumina to boron nitride, the content of phosphotungstic acid, printing and reaction parameters all affect the catalyst performance; the parameter combination of Example 1 (mass ratio 1:1, phosphotungstic acid content 4%, printing speed 40mm / s, etc.) makes the catalyst have the best comprehensive performance; if the phosphotungstic acid content is too high, it will easily agglomerate, and if it is too low, the activity will be insufficient. It can still maintain a high desulfurization rate under mild reaction temperature, which proves that the catalyst of the present invention has good practical application prospects.
Claims
1. A method for preparing a 3D-printed multi-acid porous monolithic catalyst, characterized in that, Includes the following steps: (1) Preparation of porous alumina: P123, polyvinyl alcohol (PVA), polyethylene glycol (PEG), and aluminum isopropoxide are mixed in proportion and ground for 30-40 minutes until a uniform paste is formed. The temperature is then increased from room temperature to 350-450°C and held for 3.5-4.5 hours. After cooling to room temperature, the mixture is pulverized and sieved to obtain porous alumina. (2) Preparation of 3D printing ink: The porous alumina, boron nitride, and phosphotungstic acid prepared in step (1) are mixed in proportion, an appropriate amount of binder is added, and the mixture is placed in a planetary ball mill and ball-milled until it is evenly mixed to obtain a milky white 3D printing ink. (3) 3D printing: Using an ink-to-write 3D printer, the 3D printing ink prepared in step (2) is loaded into the printing syringe; a three-dimensional model is designed using CAD software, and the printing parameters are set as follows: mesh density is set to 75%~85%; printing speed is 35~45mm / s, layer thickness is 0.6~1.0mm, and printing temperature is 25~30℃; after printing, the blank is placed in a ventilated and dry place to air dry naturally for 20~28h to obtain a solid blank, which is the 3D printed multi-acid porous monolithic catalyst.
2. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of P123, polyvinyl alcohol (PVA), polyethylene glycol (PEG) to aluminum isopropoxide is 1:1.8~2.2:0.8~1.2:4~6; wherein, the molecular weight of P123 is ≥5800, the molecular weight of PVA is 1750, and the molecular weight of PEG is 800.
3. The preparation method according to claim 1, characterized in that, In step (1), the heating rate is 1.2~1.8℃ / min; the sieve size is 100~120 mesh; and the specific surface area of the obtained porous alumina is 320~420m². 2 / g, with an average pore size of 2~8nm.
4. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of porous alumina to boron nitride is 1:0.6~1.4; wherein the boron nitride is hexagonal boron nitride (h-BN), with a purity ≥99.2%, a particle diameter ≤8μm, and a specific surface area of 15~45m². 2 / g, pore size 2~8nm; the phosphotungstic acid is analytical grade, with a purity ≥99.5%, and its mass accounts for 1~8% of the 3D printing ink mass; The adhesive is a PVA solution with a concentration of 5~7g / L, and the mass ratio of the adhesive to the porous alumina, boron nitride and phosphotungstic acid mixed solid is 4:3~4.
5. The preparation method according to claim 1, characterized in that, In step (2), the ball milling speed is 200~300 r / min and the time is 60~90 min.
6. The preparation method according to claim 1, characterized in that, In step (2), the 3D printing ink is a milky white fluid with no special odor, a water content of 35~55wt%, and a viscosity of 800~1800Pa·s, which is suitable for ink direct writing 3D printing requirements.
7. The preparation method according to claim 1, characterized in that, In step (3), the printing syringe is made of a printing needle with a diameter of 0.4~0.6mm.
8. The preparation method according to claim 1, characterized in that, In step (3), the solid blank after natural air drying can also be subjected to low-temperature drying treatment according to actual needs, with a drying temperature of 60~80℃ and a drying time of 4~6h.
9. A 3D-printed multi-acid porous monolithic catalyst, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.
10. The use of the 3D-printed multi-acid porous monolithic catalyst of claim 9 for the catalytic oxidation removal of organic sulfur compounds from fuel oil.