Anti-carbon-deposition montmorillonite catalyst modified with organic and supported with molybdenum vanadium oxide, its preparation method and application

Abstract

The application discloses an anti-carbon-deposition montmorillonite catalyst loaded with organic modified molybdenum vanadium oxide and a preparation method and application thereof. The application uses hydroquinone to organically modify the montmorillonite catalyst loaded with molybdenum and vanadium after acidification, and the obtained catalyst is used in a gas-phase glycerol catalytic dehydration oxidation reaction, has good anti-carbon-deposition performance, improves the selectivity of a product and the utilization rate of raw materials, and prolongs the service life of the catalyst.

Description

Technical Field

[0001] This invention relates to a montmorillonite catalyst with organically modified molybdenum vanadium oxide for resisting carbon deposition, its preparation method, and its application in the catalytic dehydration oxidation of glycerol. Background Technology

[0002] Glycerol is one of the main byproducts of biodiesel production in industry, and how to convert it into more valuable chemical products is an urgent problem to be solved. Among them, the reaction of glycerol to high-value organic compounds such as acrolein / acrylic acid through catalytic dehydration oxidation is a popular research direction; for this reaction, there have been many studies on catalysts. Common glycerol dehydration oxidation catalysts include: metal phosphates, metal sulfates, metal oxides, heteropoly acids, zeolites, clay minerals and solid acid catalysts loaded with redox substances (Zhou Chunhui, Yu Weihua, Tong Dongshen. A montmorillonite-based solid acid catalyst and its application in the selective dehydration of glycerol to acrolein: CN104826657B, 2017.). In addition, existing studies have shown that Mo and V are typical active substances for the one-step dehydration oxidation of glycerol to prepare acrylic acid (Lu Zixuan, Li Shuangming, Yu Sansan. Research progress of composite metal oxide catalysts for the oxidation of glycerol to acrylic acid [J]. Molecular Catalysis, 2020, 34(05):484-494.). The combination of molybdenum and vanadium can modulate the oxidizing properties of vanadium and the acid sites of the support, showing good results in the catalytic dehydration oxidation of glycerol. However, during the reaction, the catalyst is prone to carbon deposition, leading to rapid deactivation.

[0003] Current research has focused on the causes of coking and its impact on catalyst activity. The acidity, physical structure, and reaction conditions (such as reaction temperature, water and oxygen content) of the catalyst all affect the intensity of coking. Some studies have attempted to suppress coking by adjusting the catalyst's acid strength and pore size, but the effects have been limited. (Chun-Jiang Jia, Yong Liu, Wolfgang Schmidt, An-Hui Lu, Ferdi Schüth. Small-sized HZSM-5zeolite as highly active catalyst for gas phase dehydration of glycerol toacrolein[J]. Journal of Catalysis, 2010, 269:71-79.)

[0004] Clay minerals are organically modifiable, and organic modification is often used to enhance the loading capacity of clay minerals when loading other metals (Bao Yongsheng. A method for preparing organically modified kaolin supported palladium nanocatalysts: CN106513052A, 2017.). Organic modification allows other substances to be loaded onto the catalyst, participating in and altering the reaction process, which may have a positive effect on preventing carbon deposition. Currently, many reported anti-carbon deposition methods are based on changing reaction conditions and catalyst composition; there is a lack of research applying organic modification to anti-carbon deposition. Summary of the Invention

[0005] This invention provides a montmorillonite catalyst with organically modified molybdenum-vanadium oxide for resisting carbon deposition, its preparation method, and its application. The catalyst of this invention can prevent carbon deposition and extend catalyst lifetime in the catalytic oxidation of glycerol.

[0006] Technical principle: The formation of carbon deposits is due to the generation of free radicals in the reaction of glycerol. These free radicals initiate a condensation reaction, leading to the formation of large molecular carbon deposits. Therefore, organic modification can enable the catalyst to acquire a certain ability to eliminate free radicals, thereby preventing the formation of carbon deposit precursors.

[0007] The technical solution of the present invention is as follows:

[0008] A method for preparing a montmorillonite catalyst with organically modified molybdenum vanadium oxide for resisting carbon deposition includes the following steps:

[0009] Step 1: Natural sodium-based montmorillonite is crushed, ground, sieved, and dried to obtain montmorillonite powder;

[0010] Step 2: Add the montmorillonite powder obtained in Step 1 to the phosphoric acid aqueous solution, heat to 50-80℃ and stir for 1-6 hours, cool to room temperature, centrifuge, wash (with deionized water), and dry to obtain acidified montmorillonite;

[0011] The preferred molar ratio of phosphoric acid to montmorillonite is 1:1 to 3:1;

[0012] The preferred liquid-to-solid ratio of phosphoric acid aqueous solution to montmorillonite is 10:1 to 30:1, mL / g;

[0013] Step 3: Dissolve ammonium molybdate tetrahydrate and ammonium metavanadate in water to obtain a metal-supported solution. Add the acidified montmorillonite obtained in Step 2 to the metal-supported solution and stir at 60-80°C for 5-8 hours. Then, soak for 16-32 hours, centrifuge, dry, and calcine in a muffle furnace at 400-600°C for 4-8 hours to obtain acidified montmorillonite supported on molybdenum-vanadium bimetallic oxide.

[0014] The preferred molar ratio of ammonium molybdate tetrahydrate to ammonium metavanadate is 1:1 to 5:1;

[0015] The preferred liquid-to-solid ratio of the metal-supported liquid to the acidified montmorillonite is 10:1 to 30:1, mL / g;

[0016] Step 4: Dissolve hydroquinone in deionized water to obtain a hydroquinone solution. Grind the acidified montmorillonite loaded with molybdenum-vanadium bimetallic oxide obtained in Step 3 and add it to deionized water. Disperse it evenly by ultrasonication. Then add the hydroquinone solution and stir at 60-80℃ for 8-12 hours. Centrifuge, wash (with deionized water), and dry to obtain the carbon-resistant organic modified montmorillonite catalyst loaded with molybdenum-vanadium oxide.

[0017] The preferred mass ratio of hydroquinone to acidified montmorillonite supported on molybdenum-vanadium bimetallic oxide is 1:100 to 1:25.

[0018] This invention relates to a montmorillonite catalyst with organically modified molybdenum vanadium oxide that resists carbon deposition, prepared by the above-described method.

[0019] The montmorillonite catalyst with anti-carbon-deposition organic modification and supported molybdenum vanadium oxide described in this invention can be applied to the gas-phase catalytic dehydration oxidation reaction of glycerol.

[0020] The beneficial effects of this invention are as follows:

[0021] This invention utilizes an organic modification method to enhance the montmorillonite catalyst, thereby increasing its resistance to carbon buildup during the catalytic dehydration and oxidation of glycerol. This effectively improves the catalyst's lifespan and reaction selectivity, making it suitable for industrial applications. Attached Figure Description

[0022] Figure 1 Thermogravimetric analysis of the spent catalyst of HQ-Mo-V MMT prepared in Example 1.

[0023] Figure 2 Thermogravimetric analysis of the spent catalyst of HQ-Mo-V MMT prepared in Example 2.

[0024] Figure 3 Thermogravimetric analysis of the spent catalyst of HQ-Mo-V MMT prepared in Example 3.

[0025] Figure 4 Comparison of thermogravimetric analysis (TGA) curves of spent catalysts from Mo-V MMT. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer with the description. However, these embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solutions of the present invention without departing from the spirit and scope of the present invention described above, but all such modifications and substitutions fall within the protection scope of the present invention.

[0027] In the following embodiments,

[0028] Sodium montmorillonite was sourced from Qingyang County, Anhui Province; phosphoric acid was sourced from Sinopharm Chemical Reagent Co., Ltd.; hydroquinone was sourced from Sinopharm Chemical Reagent Co., Ltd.; and ammonium molybdate tetrahydrate and ammonium metavanadate were sourced from Sinopharm Chemical Reagent Co., Ltd.

[0029] Example 1

[0030] Sodium-based montmorillonite was ground into powder using a mortar and pestle. After thorough grinding, the powder was passed through a 100-mesh sieve to obtain montmorillonite powder. A 1 mol / L H3PO4 solution was prepared, and the sodium-based montmorillonite was then mixed with the 1 mol / L H3PO4 solution to form a 5 wt.% montmorillonite suspension. The suspension was stirred in an 80°C water bath for 4 hours, and then cooled to room temperature. The suspension was centrifuged at 3000 rpm and washed with deionized water. If the washed liquid was acidic, centrifugation and washing were continued until the washed liquid was neutral. The obtained white precipitate was placed in an evaporating dish and dried overnight in an oven at 80°C to obtain acidified montmorillonite. 0.0904 g of ammonium molybdate and 0.0146 g of ammonium metavanadate were accurately weighed and placed in a 50 mL beaker. 20 mL of deionized water was added and stirred at 60°C until completely dissolved. 2 g of acidified montmorillonite was weighed and added to the above solution. After stirring for 5 hours, the mixture was soaked for 24 hours. Then, the sample was placed in an oven at 80℃ and dried for 12 hours. Finally, the dried sample was calcined in a muffle furnace at 500℃ for 4 hours to obtain a catalyst supported on molybdenum-vanadium bimetallic oxide. 0.02 g of hydroquinone was dissolved in 100 ml of deionized water at 70℃ to obtain an organic modifier. 2 g of the catalyst was ground and crushed, then added to 100 ml of deionized water. After ultrasonic treatment for 1 hour, the organic modifier was added. The mixture was then stirred at 70℃ for 8 hours, washed with deionized water, centrifuged, and dried in an oven at 60℃ for 12 hours to obtain the organically modified montmorillonite catalyst HQ-Mo-V MMT.

[0031] Example 2

[0032] Sodium-based montmorillonite was ground into powder using a mortar and pestle. After thorough grinding, the powder was passed through a 100-mesh sieve to obtain montmorillonite powder. A 1 mol / L H3PO4 solution was prepared, and the sodium-based montmorillonite was then mixed with the 1 mol / L H3PO4 solution to form a 5 wt.% montmorillonite suspension. The suspension was stirred in an 80°C water bath for 4 hours, and then cooled to room temperature. The suspension was centrifuged at 3000 rpm and washed with deionized water. If the washed liquid was acidic, centrifugation and washing were continued until the washed liquid was neutral. The obtained white precipitate was placed in an evaporating dish and dried overnight in an oven at 80°C to obtain acidified montmorillonite. 0.0904 g of ammonium molybdate and 0.0146 g of ammonium metavanadate were accurately weighed and placed in a 50 mL beaker. 20 mL of deionized water was added and stirred at 60°C until completely dissolved. 2 g of acidified montmorillonite was weighed and added to the above solution. After stirring for 5 hours, the mixture was soaked for 24 hours. Then, the sample was placed in an oven at 80℃ and dried for 12 hours. Finally, the dried sample was calcined in a muffle furnace at 500℃ for 4 hours to obtain a catalyst supported on molybdenum-vanadium bimetallic oxide. 0.04 g of hydroquinone was dissolved in 100 ml of deionized water at 70℃ to obtain an organic modifier. 2 g of the catalyst was ground and crushed, then added to 100 ml of deionized water. After ultrasonic treatment for 1 hour, the organic modifier was added. The mixture was then stirred at 70℃ for 8 hours, washed with deionized water, centrifuged, and dried in an oven at 60℃ for 12 hours to obtain the organically modified montmorillonite catalyst HQ-Mo-V MMT.

[0033] Example 3

[0034] Sodium-based montmorillonite was ground into powder using a mortar and pestle. After thorough grinding, the powder was passed through a 100-mesh sieve to obtain montmorillonite powder. A 1 mol / L H3PO4 solution was prepared, and the sodium-based montmorillonite was then mixed with the 1 mol / L H3PO4 solution to form a 5 wt.% montmorillonite suspension. The suspension was stirred in an 80°C water bath for 4 hours, and then cooled to room temperature. The suspension was centrifuged at 3000 rpm and washed with deionized water. If the washed liquid was acidic, centrifugation and washing were continued until the washed liquid was neutral. The obtained white precipitate was placed in an evaporating dish and dried overnight in an oven at 80°C to obtain acidified montmorillonite. 0.0904 g of ammonium molybdate and 0.0146 g of ammonium metavanadate were accurately weighed and placed in a 50 mL beaker. 20 mL of deionized water was added and stirred at 60°C until completely dissolved. 2 g of acidified montmorillonite was weighed and added to the above solution. After stirring for 5 hours, the mixture was soaked for 24 hours. Then, the sample was placed in an oven at 80℃ and dried for 12 hours. Finally, the dried sample was calcined in a muffle furnace at 500℃ for 4 hours to obtain a catalyst supported on molybdenum-vanadium bimetallic oxide. 0.02 g of hydroquinone was dissolved in 100 ml of deionized water at 70℃ to obtain an organic modifier. 2 g of the catalyst was ground and crushed, then added to 100 ml of deionized water. After ultrasonic treatment for 1 hour, the organic modifier was added. The mixture was then stirred at 80℃ for 12 hours, washed with deionized water, centrifuged, and dried in an oven at 60℃ for 12 hours to obtain the organically modified montmorillonite catalyst HQ-Mo-V MMT.

[0035] Comparative Example 1

[0036] The preparation of the montmorillonite catalyst Mo-V MMT in this embodiment differs from that in Example 1 only in that no subsequent operations are performed after obtaining the catalyst supported on molybdenum-vanadium bimetallic oxide. Everything else is the same as in Example 1 and will not be repeated here.

[0037] Performance testing

[0038] The catalysts prepared in the examples and comparative examples were used in the gas-phase catalytic dehydration oxidation reaction of glycerol, as follows:

[0039] A fixed-bed reactor was used. 0.3 g of the prepared catalyst was uniformly mixed with 1.0 g of quartz sand and packed into a column. The catalyst was fixed in the reaction position using silica wool. A 20 wt.% glycerol aqueous solution was used as the reactant, with a feed rate of 0.1 mL / min. Air was used as the carrier gas at a flow rate of 20 mL / min. The feed vaporization chamber temperature was 180℃, the pipeline insulation temperature was 160℃, the valve box temperature was 160℃, the reaction temperature was 320℃, the condenser temperature was 5℃, and the bed pressure was one atmosphere. The feed pump was started after the reactor temperature reached 320℃, and the reaction was stopped after 5 hours. The reacted catalyst was removed and pulverized and sieved to obtain a catalyst with carbon deposits. The carbon deposition of the catalyst with carbon deposits was then analyzed using a thermogravimetric analyzer: the temperature was programmed to rise from room temperature to 1000℃ under a N2 atmosphere, and the thermogravimetric analysis results were obtained. Two thermogravimetric analyses were performed on the same sample to ensure data accuracy.

[0040] The thermogravimetric analysis (TGA) plots of the examples and comparative examples show that the catalysts without hydroquinone modification exhibit significantly higher carbon deposition after undergoing the same glycerol catalytic reaction conditions compared to those with hydroquinone modification: the total mass percentage of carbon deposits in the unmodified catalyst was approximately 12.37%; in Example 1, it was approximately 6.03%; in Example 2, it was approximately 8.55%; and in Example 3, it was approximately 6.83%. This demonstrates that the catalysts modified with hydroquinone exhibit stronger anti-carbon deposition effects, extending their service life and promoting the development of green and efficient glycerol catalytic reaction catalysts.

Claims

1. A method for preparing an anti-carbon-deposited organic-modified supported molybdenum vanadium oxide montmorillonite catalyst, characterized by, The method comprises the following steps: Step 1: natural sodium-based montmorillonite is crushed, ground, sieved and dried to obtain montmorillonite powder; Step 2: the montmorillonite powder obtained in step 1 is added to a phosphoric acid aqueous solution, heated to 50-80℃ and stirred for 1-6h, cooled to room temperature, centrifuged, washed and dried to obtain acidified montmorillonite; Step 3: ammonium molybdate and ammonium metavanadate are dissolved in water to obtain a metal loading solution, the acidified montmorillonite obtained in step 2 is added to the metal loading solution, stirred at 60-80℃ for 5-8h, then immersed for 16-32h, then centrifuged, dried and calcined in a muffle furnace at 400-600℃ for 4-8h to obtain acidified montmorillonite loaded with molybdenum-vanadium bimetallic oxide; Step 4: hydroquinone is dissolved in deionized water to obtain a hydroquinone solution, the acidified montmorillonite loaded with molybdenum-vanadium bimetallic oxide obtained in step 3 is ground and added to deionized water, ultrasonically dispersed uniformly, then the hydroquinone solution is added, stirred at 60-80℃ for 8-12h, centrifuged, washed and dried to obtain the anti-coking organic modified montmorillonite catalyst loaded with molybdenum-vanadium oxide; The mass ratio of hydroquinone to acidified montmorillonite loaded with molybdenum-vanadium bimetallic oxide is 1:100-1:

25.

2. The method for preparing the montmorillonite catalyst with anti-carbon deposition organic modification and supported molybdenum vanadium oxide as described in claim 1, characterized in that, In step 2, the molar ratio of phosphoric acid to montmorillonite is 1:1-3:

1.

3. The method for preparing the montmorillonite catalyst with anti-carbon deposition organic modification and supported molybdenum vanadium oxide as described in claim 1, characterized in that, In step 2, the liquid-solid ratio of the phosphoric acid aqueous solution to montmorillonite is 10:1-30:1, mL / g.

4. The method for preparing the montmorillonite catalyst with anti-carbon deposition organic modification and supported molybdenum vanadium oxide as described in claim 1, characterized in that, In step 3, the molar ratio of ammonium molybdate to ammonium metavanadate is 1:1-5:

1.

5. The method for preparing the montmorillonite catalyst with anti-carbon deposition organic modification and supported molybdenum vanadium oxide as described in claim 1, characterized in that, In step 3, the liquid-solid ratio of the metal loading solution to acidified montmorillonite is 10:1-30:1, mL / g.

6. The anti-coking organic modified montmorillonite catalyst loaded with molybdenum-vanadium oxide prepared by the preparation method of any one of claims 1-5.

7. The use of the anti-coking organic modified montmorillonite catalyst loaded with molybdenum-vanadium oxide in the catalytic dehydration oxidation reaction of gas-phase glycerol.

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