Desulfurization catalyst of macroporous ZSM-5 molecular sieve loaded heteropolyacid as well as preparation and application of desulfurization catalyst

Abstract

The invention discloses a macroporous ZSM-5 molecular sieve loaded heteropolyacid desulfurization catalyst as well as preparation and application thereof, and belongs to the technical field of light fuel oil desulfurization. The method comprises the following steps: adding sodium metavanadate dihydrate, sodium dihydrogen phosphate hydrate and sodium molybdate dihydrate as raw materials into an aqueous solution, adjusting the pH value to about 4, refluxing for 8 hours, cooling, extracting with diethyl ether to obtain vanadium-substituted Dawson type heteropolyacid, and adjusting the material ratio to obtain different amounts of vanadium-substituted heteropolyacid. Then, the supported catalyst POM-CNTs (at) MOF-199-ZSM-5 is prepared through a one-pot method, and the obtained catalyst is applied to oxidative desulfurization of a light fuel simulation system. Oxygen in air is used as an oxidizing agent, and the thiophene removal rate can reach 98.90% after 2.5 h at 70 DEG C.

Description

Technical Field

[0001] This invention belongs to the field of light fuel oil desulfurization technology, specifically relating to a method for preparing a novel macroporous ZSM-5 supported heteropolyacid catalyst and its application in oxidative desulfurization. Background Technology

[0002] In recent years, with the increasing prominence of environmental pollution, countries and regions around the world have successively formulated and promulgated environmental protection regulations. As these regulations become increasingly stringent, developed countries and regions, represented by the European Union and the United States, have imposed stricter requirements on exhaust emissions from transportation vehicles. To meet these increasingly stringent regulations, various countries have introduced relevant policies and established strict fuel oil quality standards, especially regarding the sulfur content of fuel oil. Therefore, to improve the environment and meet these requirements, the production of low-sulfur fuel oil and even ultra-clean sulfur-free fuel oil has become a primary task.

[0003] In 1993, the EU required diesel fuel to have a sulfur content of <2000 ppm. Within just six years, this requirement was lowered to 350 ppm in 1997, below 50 ppm in 2005, and has remained at 10 ppm since 2009. Meanwhile, my country is also committed to environmental protection and is continuously striving to control the concentration of sulfur compounds in fuel oil. However, the quality of diesel fuel in my country still lags behind that of developed countries. Since 2000, my country has required diesel fuel to have a sulfur concentration of less than 2000 ppm, and since 2013, it has implemented the National V standard, requiring a sulfur content of less than 10 ppm. Looking at the history of oil quality upgrading in my country, since the beginning of the new century, my country has covered in about 10 years what European and American countries took 20-30 years to achieve. Compared with the EU at the same stage, my country is still relatively lagging behind. Therefore, reducing the sulfur content in fuel oil and improving its quality remains a major task for China today.

[0004] Currently, the most widely studied desulfurization technologies mainly include hydrodesulfurization and non-hydrodesulfurization. Hydrodesulfurization is a traditional and mature desulfurization method. It involves converting sulfur-containing compounds in fuel oil into H2S under high temperature, high pressure, and hydrogen conditions, and then decomposing hydrogen sulfide into elemental sulfur and hydrogen, thereby achieving fuel desulfurization. Hydrodesulfurization can effectively remove some simple sulfides from fuel oil, but with increasingly stringent requirements for sulfur content, it cannot fully meet the requirements of industrial production. Therefore, non-hydrodesulfurization has attracted widespread attention. Among non-hydrodesulfurization technologies, oxidative desulfurization technology has attracted widespread attention and research from researchers at home and abroad due to its advantages such as mild reaction conditions and low equipment investment. Furthermore, this technology does not consume hydrogen and has high desulfurization efficiency for dibenzothiophene compounds that are difficult to remove by hydrodesulfurization, enabling ultra-deep desulfurization of fuel oil. Moreover, the sulfones or sulfoxides obtained after oxidative desulfurization can be used as industrial raw materials, optimizing resource allocation. Therefore, oxidative desulfurization technology is considered an innovative and green refining technology for the 21st century.

[0005] Heteropolyacids (HPAs) are powerful solid acid catalysts with unique acidity, multifunctionality, and "pseudo-liquid" behavior. They can be controllably designed by adjusting different elements, are environmentally friendly, and do not cause pollution. Supported catalysts based on heteropolyacids can be widely used in various fields. Summary of the Invention

[0006] To address the problems of complex desulfurization processes and low desulfurization efficiency in current methods, this invention provides a method for preparing a supported catalyst, POM-CNTs@MOF-199-ZSM-5, by encapsulating heteropolyacids in carbon nanotube-modified MOF-199 and then further loading them, for deep desulfurization under molecular oxygen conditions.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A method for preparing a desulfurization catalyst supported on macroporous ZSM-5 molecular sieve and heteropolyacids involves encapsulating heteropolyacid compounds in a hybrid material CNTs@MOF-199, which is then further supported on a macroporous ZSM-5 support to obtain the catalyst POM-CNTs@MOF-199-ZSM-5. CNTs are excellent conductors, accelerating the cycling of heteropolyacids (POMs) between their oxidized and reduced states, thus maintaining the sustained high catalytic activity of the POM active centers.

[0009] Furthermore, the heteropolyacid compound is prepared by solvent-extraction method to synthesize Dawson-type heteropolyacids with different numbers of vanadium substitutions.

[0010] Furthermore, the heteropolyacid compound is H7[P2Mo] 17 V1O 62 ], H8[P2Mo 16 V2O 62 ], H9[P2Mo 15 V3O 62 ], H 10 [P2Mo 14 V4O 62 ] or H 11 [P2Mo 13 V5O 62 Any one of them.

[0011] Furthermore, the specific preparation method of the heteropolyacid compound is as follows: sodium metavanadate dihydrate, sodium dihydrogen phosphate dihydrate, and sodium molybdate dihydrate are added to an aqueous solution, the pH is adjusted to about 4, refluxed for 8 hours and then cooled, and extracted with diethyl ether to obtain vanadium-substituted Dawson type heteropolyacid.

[0012] Furthermore, H 6+n [P2Mo 18-n V n O 62 The synthesis of mH2O (n=1-5)

[0013] Weigh out n mmol of NaVO3·2H2O and 0.2760 g (2.00 mmol) of NaH2PO4·H2O, dissolve them in 10 mL of distilled water to obtain a yellow mixed solution, which is labeled as solution A. Weigh out 18-n mmol of Na2MoO4·2H2O. Dissolve in 7.5 mL of distilled water; this solution is labeled as solution B. Pour solution A into a 100 mL three-necked flask equipped with a reflux condenser. Add concentrated H₂SO₄ dropwise with constant stirring until the pH of the solution reaches 4. Then, add solution B in small amounts several times to the above mixed solution. The solution gradually changes from yellow to brick red. Adjust the pH of the mixed solution again to 3.4 with concentrated H₂SO₄. Adjust the oil bath temperature to reach 120 °C and reflux at 120 °C for 8 h.

[0014] After the reaction was complete, the solution was allowed to cool to room temperature. Then, the solution was transferred to a separatory funnel, and an equal volume of diethyl ether was added. After thorough shaking and standing, the solution separated into three layers; the lower layer was a brick-red heteropolyacid ether compound. The lower ether compound was collected and dried to obtain a brick-red powder compound, labeled Mo. 18-n V n (n=1-5).

[0015] The second aspect of the present invention provides a desulfurization catalyst for macroporous ZSM-5 molecular sieve supported on heteropoly acids prepared by the above preparation method.

[0016] Furthermore, the desulfurization catalyst has a multi-level pore structure consisting of "micropores of MOF-confined POM, mesopores of CNTs lumen and gaps, and macropores of ZSM-5 carrier".

[0017] The second aspect of this invention provides an application of a desulfurization catalyst supported on macroporous ZSM-5 molecular sieve and heteropoly acid in the oxidative desulfurization of light fuel oil systems.

[0018] Furthermore, using oxygen from the air as an oxidant, the thiophene removal rate reached 98.90% after 2.5 hours at 70°C.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] This invention provides a preparation method for a POM-CNTs@MOF-199-ZSM-5 catalyst, which has high desulfurization efficiency and is simple to prepare.

[0021] This application creates a hierarchical pore system to enhance mass transfer and diffusion: the hollow lumen of the CNTs themselves, combined with MOF-199, introduces abundant mesoporous channels. This forms a multi-level pore structure of "micropores (MOF-confined POM) - mesopores (CNT lumen and gaps) - macropores (ZSM-5 support)," which greatly optimizes the diffusion paths of reactant and product molecules, ensuring efficient utilization of active sites, and is particularly suitable for deep desulfurization of large-molecule sulfur compounds in fuel oil.

[0022] The introduction of CNTs in this invention is like implanting a "steel skeleton" during MOF growth. Their high-strength one-dimensional nanotube structure provides heterogeneous nucleation sites and physical support for MOF crystals, effectively inhibiting the excessive growth and aggregation of MOF particles, forming a more robust composite framework, thereby significantly improving the overall mechanical stability and recyclability of the catalyst.

[0023] The Dawson-type heteropolyacids prepared in this invention are further loaded after being encapsulated in a one-pot process to obtain a supported heteropolyacid oxidative desulfurization catalyst, which is applied to the oxidative desulfurization of a light fuel oil simulation system. Using oxygen in the air as the oxidant, the thiophene removal rate can reach 98.90% after 2.5 hours at 70°C. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the catalyst preparation process in this application.

[0026] Figure 2 Desulfurization curve of catalyst POM-CNTs@MOF-199-ZSM-5.

[0027] Figure 3 This is the infrared spectrum of the catalyst POM-CNTs@MOF-199-ZSM-5.

[0028] Figure 4 This is a transmission electron microscope (TEM) image of the large-aperture ZSM-5.

[0029] Figure 5 It's Mo 16 Transmission electron microscopy image of V2-CNTs@MOF-199-ZSM-5 catalyst. Detailed Implementation

[0030] To gain a deeper understanding of this invention, we will provide a comprehensive and detailed description. However, this invention has various implementations and is not limited to the specific examples listed herein. These examples are presented to enhance a full understanding of the disclosure of this invention.

[0031] The five heteropoly acids are shown below:

[0032] Molecular formula: H7[P2Mo] 17 V1O 62 ], abbreviation: Mo 17 V1;

[0033] Molecular formula: H8[P2Mo] 16 V2O 62 ], abbreviation: Mo 16 V2;

[0034] Molecular formula: H9[P2Mo] 15 V3O 62 ], abbreviation: Mo 15 V3;

[0035] Molecular formula: H 10 [P2Mo 14 V4O 62 ], abbreviation: Mo 14 V4;

[0036] Molecular formula: H 11 [P2Mo 13 V5O 62 ], abbreviation: Mo 13 V5.

[0037] Example 1: Preparation of catalyst POM-CNTs@MOF-199-ZSM-5

[0038] Mix 0.1815 g (0.5 mmol) Cu(NO3)2·3H2O with 0.1000 g Mo 17 The V1 heteropolyacid mixture was added to 10 mL of distilled water and stirred thoroughly until completely dissolved. Then, 0.01 g of CNTs and 0.1000 g of macroporous ZSM-5 were added, and the mixture was stirred until homogeneous. Next, 0.0946 g (0.5 mmol) of trimesic acid and 0.2718 g (1.0 mmol) of (CH3)4NOH·5H2O were added separately. The mixture was stirred at room temperature for 24 h, then filtered, washed, and dried to obtain a blue powder, Mo. 17 V1-CNTs@MOF-199-ZSM-5.

[0039] catalyst Mo 16 V2-CNTs@MOF-199-ZSM-5, Mo 15 V3-CNTs@MOF-199-ZSM-5, Mo 14 V4-CNTs@MOF-199-ZSM-5 and Mo 13 The preparation method of V5-CNTs@MOF-199-ZSM-5 is the same as the above method, except that different heteropoly acids are changed.

[0040] Example 2: Desulfurization property test

[0041] 663 μL of thiophene (BT) was pipetted into a solution dissolved in a certain amount of n-octane. The solution was then transferred to a 250 mL volumetric flask and diluted to volume with n-octane to obtain simulated diesel oil with a sulfur content of 1000 ppm. 50 mL of the simulated oil and 0.10 g of catalyst were added to a three-necked flask. Samples were taken at irregular intervals for analysis under continuous air blowing and stirring. The test results showed that the desulfurization rate reached equilibrium after 150 min of reaction. The optimal catalyst was Mo. 16 The desulfurization rate of V2-CNTs@MOF-199-ZSM-5 can reach 98.90%.

[0042] Example 3:

[0043] Mo 16IR of V2-CNTs@MOF-199-ZSM-5 catalyst

[0044] As can be seen from the infrared spectrum, the synthesized catalyst POM-CNTs@MOF-199-ZSM-5 exhibits the characteristic peaks of each individual component material, indicating that the catalyst has been synthesized.

[0045] Large-pore ZSM-5 and Mo 16 V2-MOF-199-ZSM-5 catalyst TEM

[0046] For pure ZSM-5 and Mo 16 TEM analysis was performed on the V2-MOF-199-ZSM-5 catalyst. The results showed that pure ZSM-5 has a hollow, ultra-large porous structure (TEM results showed that the size of ZSM-5 is about 300 nm), and the hollow structure was clearly filled after loading.

[0047] Contents not described in detail in this specification are prior art known to those skilled in the art. Although illustrative specific embodiments of the invention have been described above to facilitate understanding by those skilled in the art, it should be understood that the invention is not limited to the scope of the specific embodiments. Various modifications are readily apparent to those skilled in the art as long as they fall within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of this invention are protected.

Claims

1. A method for preparing a desulfurization catalyst supported on macroporous ZSM-5 molecular sieve and containing heteropolyacids, characterized in that: The catalyst POM-CNTs@MOF-199-ZSM-5 was prepared by encapsulating heteropolyacid compounds in the hybrid material CNTs@MOF-199 and then further loading them onto the macroporous ZSM-5 support.

2. The method for preparing a desulfurization catalyst supported on macroporous ZSM-5 molecular sieve and heteropolyacid according to claim 2, characterized in that: The heteropolyacid compounds are prepared by solvent-extraction method to synthesize Dawson-type heteropolyacids with different numbers of vanadium substitutions.

3. The method for preparing a desulfurization catalyst supported on macroporous ZSM-5 molecular sieve and heteropolyacid according to claim 2, characterized in that: The heteropolyacid compound is H7[P2Mo]. 17 V1O 62 ], H8[P2Mo 16 V2O 62 ], H9[P2Mo 15 V3O 62 ], H 10 [P2Mo 14 V4O 62 ] or H 11 [P2Mo 13 V5O 62 Any one of them.

4. The method for preparing a desulfurization catalyst supported on macroporous ZSM-5 molecular sieve and heteropolyacid according to claim 2, characterized in that: The preparation method of the heteropolyacid compound is as follows: sodium metavanadate dihydrate, sodium dihydrogen phosphate dihydrate and sodium molybdate dihydrate are added to an aqueous solution, the pH is adjusted to 4, refluxed for 8 hours and then cooled, and extracted with diethyl ether to obtain vanadium-substituted Dawson type heteropolyacid.

5. The method for preparing a desulfurization catalyst supported on macroporous ZSM-5 molecular sieve and heteropolyacid according to claim 2, characterized in that: Specifically, the following steps are included: H 6+n [P2Mo 18-n V n O 62 The synthesis of mH2O, where n = 1~5; Weigh out n mmol of NaVO3·2H2O and NaH2PO4·H2O and dissolve them in distilled water to obtain a yellow mixed solution. This mixed solution is labeled as solution A. Weigh out 18-n mmol of Na2MoO4·2H2O and dissolve it in distilled water. This solution is labeled as solution B. Pour solution A into a three-necked flask equipped with a reflux condenser, and add concentrated H2SO4 dropwise while stirring continuously until the solution pH = 4; Then, solution B was added in small amounts multiple times to the above mixed solution with pH = 4. The solution gradually changed from yellow to brick red. The pH of the mixed solution was adjusted to 3.4 again with concentrated H2SO4. The solution was then refluxed at 120℃ oil bath temperature for 8 h. After the reaction was completed, the solution was allowed to stand and cool to room temperature. The solution was then transferred to a separatory funnel, and an equal volume of diethyl ether was added. After thorough shaking and standing, the solution separated into three layers. The lower layer was a brick-red heteropolyacid ether compound. The lower ether compound was collected and dried to obtain a brick-red powder compound, labeled Mo. 18-n V n n = 1~5.

6. A desulfurization catalyst for macroporous ZSM-5 molecular sieve supported on heteropolyacids prepared by the preparation method according to any one of claims 1 to 5.

7. The desulfurization catalyst of macroporous ZSM-5 molecular sieve supported on heteropolyacid according to claim 6, characterized in that: The desulfurization catalyst has a multi-level pore structure consisting of "micropores of MOF-confined POM, mesopores of CNTs lumen and gaps, and macropores of ZSM-5 carrier".

8. The application of the macroporous ZSM-5 molecular sieve supported heteropoly acid desulfurization catalyst prepared by any one of claims 1 to 5 in the oxidative desulfurization of light fuel oil systems.

9. The application of the desulfurization catalyst according to claim 8 in the oxidative desulfurization of light fuel oil systems, characterized in that: Using oxygen from the air as an oxidant, the thiophene removal rate reached 98.90% after 2.5 hours at 70°C.

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