Preparation of Oxygen-Deficient Vanadium Niobium Composite Oxide Catalysts by Sol-Gel Method and Their Application in Desulfurization
The oxygen-rich vanadium-niobium composite oxide catalyst is prepared by the sol-gel method, which solves the problem of high-temperature and high-pressure desulfurization in the prior art, and achieves the effect of efficient removal of aromatic sulfides in fuel oil under mild conditions. The catalyst structure is stable and can be reused multiple times.
Patent Information
- Application Number
- CN202211694663.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-12-28
- Publication Date
- 2025-07-29
- Estimated Expiration
- 2042-12-28
AI Technical Summary
The prior art requires harsh conditions at high temperature and high pressure when removing aromatic sulfides such as dibenzothiophene (DBT) and their derivatives in fuel oil, and metal oxide catalysts are prone to agglomeration, resulting in a decrease in active sites and affecting catalytic performance.
The oxygen-rich vanadium-niobium composite oxide catalyst was prepared by sol-gel method, and the crystal phase was regulated by calcining in air, and then calcining under a nitrogen atmosphere increased the oxygen vacancy concentration to form a stable catalyst structure.
Under mild reaction conditions, oxidation and removal of sulfides such as DBT, 4-MDBT and 4,6-DMDBT in fuel oil have stable catalyst structure and good recycling ability.
Smart Images
Figure CN115920878B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of material preparation and catalytic reaction, relates to a desulfurization catalyst, and particularly relates to a sol-gel method for preparing a vanadium niobium composite oxide catalyst with rich oxygen defect sites and its desulfurization application. Technical Background
[0002] In recent years, with the increasing attention of countries around the world and the formulation of environmental laws and regulations, the sulfur content in fuel oils has been restricted to be lower and lower. The production of low-sulfur or even sulfur-free fuel oils is an important research topic. Hydrodesulfurization (HDS) is a widely used desulfurization technology in industry at present. However, in order to remove aromatic sulfides such as dibenzothiophene (DBT) and its derivatives, the hydrodesulfurization technology requires harsh reaction conditions such as high temperature and high pressure. Therefore, non-hydrodesulfurization technologies with mild conditions have been widely studied, mainly including extraction desulfurization, adsorption desulfurization, and oxidative desulfurization (ODS), etc. Among them, oxidative desulfurization technology is considered to be one of the most promising high-efficiency desulfurization methods.
[0003] In the oxidative desulfurization system, DBT is oxidized by an oxidant to the corresponding sulfone (DBTO2), which increases its polarity and is easy to separate from the system. In the reaction process, an efficient catalyst is usually selected to improve the desulfurization efficiency. Among them, transition metal oxides are a relatively suitable type of catalyst. Transition metal oxide materials have the advantages of high catalytic efficiency, easy separation and recovery after the reaction, etc. Many metal oxides show certain catalytic oxidative desulfurization performance, but most metal oxides have the problem of easy agglomeration during the reaction process, resulting in a reduction in the exposure of active sites, a decrease in catalytic performance, and affecting their further application. If a second metal is introduced into a single metal oxide, not only can its surface acidity be adjusted, but also oxygen defect sites can be generated by using the lattice misalignment between the two metals, improving the catalytic oxidation performance. Moreover, the two metal oxides can also produce a synergistic effect. When applied to the catalytic oxidative desulfurization system, it has the advantages of mild reaction operating conditions and high desulfurization efficiency. Summary of the Invention
[0004] Aiming at the deficiencies existing in the above-mentioned prior art, the purpose of the present invention is to provide a sol-gel method for preparing a vanadium niobium composite oxide catalyst with rich oxygen defect sites. This composite oxide catalyst can efficiently utilize oxygen as an oxidant to deeply oxidize and remove various sulfur-containing compounds such as DBT, 4-methyldibenzothiophene (4-MDBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT) in fuel oils under relatively mild reaction conditions, and has good industrial application prospects.
[0005] Technical Solution
[0006] A method for preparing a vanadium niobium composite oxide catalyst with oxygen-rich defect sites by sol-gel method, comprising: separately dissolving niobium pentachloride and vanadium trichloride in ethanol, dropping a citric acid aqueous solution during stirring, fully stirring for hydrolysis, drying, then calcining at 600-800 °C for 3-8 h in an air atmosphere, and then calcining at 400-600 °C for 3-8 h in a nitrogen atmosphere, naturally cooling to room temperature and then grinding to obtain a vanadium niobium composite oxide catalyst with oxygen-rich defect sites (VNbO x ).
[0007] In a preferred disclosure example of the present invention, the solid-liquid ratio of niobium pentachloride, vanadium trichloride to ethanol is 1.014-1.690 g:0.590-0.983 g:5-15 mL, preferably 1.352 g:0.787 g:10 mL.
[0008] In a preferred disclosure example of the present invention, the concentration of the citric acid aqueous solution is 0.5-1.5 mol / L, preferably 1 mol / L; the dropping amount is the same as the volume of ethanol.
[0009] In a preferred disclosure example of the present invention, the stirring time is 0.5-5 h, preferably 4 h.
[0010] In a preferred disclosure example of the present invention, the drying temperature is 80-140 °C and the time is 5-15 h, preferably drying at 140 °C for 10 h.
[0011] In a preferred disclosure example of the present invention, calcine at 800 °C for 5 h in the air atmosphere.
[0012] In a preferred disclosure example of the present invention, calcine at 500 °C for 5 h in the nitrogen atmosphere.
[0013] In a preferred disclosure example of the present invention, the nitrogen flow rate during calcination in the nitrogen atmosphere is 50-300 mL / min, preferably 200 mL / min.
[0014] In a preferred disclosure example of the present invention, the programmed heating rate is 2-10 °C / min, preferably 5 °C / min.
[0015] Another object of the present invention is to apply the vanadium niobium composite oxide catalyst with oxygen-rich defect sites prepared by the above method to the field of oxidative desulfurization technology, and it can be applied to remove sulfur-containing compounds such as DBT, 4-MDBT and 4,6-DMDBT in fuel oil using oxygen as an oxidant.
[0016] It has been reported that there is a positive correlation between the active center sites of metal oxide catalysts and the oxygen vacancy concentration, and the oxygen vacancy concentration has become an important factor affecting the catalyst performance. In the present invention, the crystal phase of vanadium niobium composite oxide is adjusted by controlling the reaction parameters, and the oxygen vacancy concentration of vanadium niobium bimetallic oxide is increased by using the difference in the oxygen vacancy formation energy of different crystal phases, thereby improving the oxidative desulfurization activity. Compared with the conventional method, the present invention uses the simple sol-gel method to prepare the vanadium niobium composite oxide catalyst, regulates the crystal phase by calcination in air, and then calcines in nitrogen atmosphere to increase the oxygen vacancy concentration, providing a new method and way to adjust the oxygen vacancy concentration. The catalyst has mild oxidative desulfurization reaction conditions, stable structural properties, good recycling ability, and good catalytic oxidation ability for sulfides such as DBT, 4-MDBT, and 4,6-DMDBT in diesel. In practical applications, it can be combined with other desulfurization technologies to produce clean diesel under green and mild conditions.
[0017] The morphology and structure of the product were analyzed by wide-angle X-ray powder diffraction (XRD), Raman spectroscopy (Raman), and X-ray photoelectron spectroscopy (XPS). A diesel model oil was prepared with dibenzothiophene as a typical sulfur-containing compound, and the above-synthesized vanadium niobium composite oxide catalyst was applied to the oxidative desulfurization reaction using oxygen as the oxidant. The catalytic performance of the catalyst was evaluated by detecting the remaining amount of DBT in the oil phase after the reaction by gas chromatography (GC).
[0018] Beneficial effects
[0019] The present invention has simple operation. Different crystal phases of vanadium niobium composite oxide are obtained through a simple synthesis process, the oxygen vacancy concentration of the composite oxide is increased, thereby enhancing the oxidative desulfurization activity. The reaction conditions of the present invention are mild, oxygen is used as the oxidant, the desulfurization efficiency of the catalyst is high and it shows excellent stability. It has good catalytic oxidation ability for sulfides such as DBT, 4-MDBT, and 4,6-DMDBT in diesel, and the vanadium niobium composite oxide catalyst can be reused multiple times, having excellent industrial application prospects. Description of the drawings
[0020] Figure 1 . Wide-angle XRD pattern of vanadium niobium composite oxide;
[0021] Figure 2 . Raman spectrum of vanadium niobium composite oxide;
[0022] Figure 3 . XPS spectrum of vanadium niobium composite oxide;
[0023] Figure 4 . EPR spectrum of vanadium niobium composite oxide;
[0024] Figure 5SEM and TEM images of vanadium-niobium composite oxides;
[0025] Figure 6 Catalytic oxidation desulfurization rates of different vanadium-niobium composite oxides for DBT. Detailed implementation manners
[0026] The present invention will be described in detail below in conjunction with embodiments, so that those skilled in the art can better understand the present invention, but the present invention is not limited to the following embodiments.
[0027] Example 1
[0028] A method for preparing a vanadium-niobium composite oxide catalyst with oxygen-rich defect sites by sol-gel method, including: adding 15 mL of ethanol to a beaker, and then weighing 1.690 g (0.00625 mol) of NbCl5(V) and 0.984 g (0.00625 mol) of VCl3(Ⅲ) into the glass beaker. Then, 15 mL of citric acid aqueous solution (1 mol / L) is added. Then the mixture solution is stirred evenly for 5 h to carry out a preliminary hydrolysis process. The precursor is obtained after stirring. The precursor is placed in the beaker and dried overnight at 140 °C. Then it is calcined in an air atmosphere, the temperature is programmed to 600 °C (5 °C / min), and held for 5 h. Finally, it is calcined in a nitrogen atmosphere, the temperature is programmed to 500 °C (5 °C / min), and held for 5 h to obtain vanadium-niobium composite oxide 600-VNbO x .
[0029] Example 2
[0030] A method for preparing a vanadium-niobium composite oxide catalyst with oxygen-rich defect sites by sol-gel method, including: adding 10 mL of ethanol to a beaker, and then weighing 1.352 g (0.005 mol) of NbCl5(V) and 0.787 g (0.005 mol) of VCl3(Ⅲ) into the glass beaker. Then, 10 mL of citric acid aqueous solution (1 mol / L) is added. Then the mixture solution is stirred evenly for 5 h to carry out a preliminary hydrolysis process. The precursor is obtained after stirring. The precursor is placed in the beaker and dried overnight at 140 °C. Then it is calcined in an air atmosphere, the temperature is programmed to 700 °C (5 °C / min), and held for 5 h. Finally, it is calcined in a nitrogen atmosphere, the temperature is programmed to 500 °C (5 °C / min), and held for 5 h. Vanadium-niobium composite oxide 700-VNbO is obtained x .
[0031] Example 3
[0032] A method for preparing an oxygen-rich defective vanadium-niobium composite oxide catalyst by sol-gel method, comprising: adding 10 mL of ethanol to a beaker, and then weighing 1.352 g (0.005 mol) of NbCl5(V) and 0.787 g (0.005 mol) of VCl3(Ⅲ) into the glass beaker. Then, 10 mL of citric acid aqueous solution (1 mol / L) is added. Then the mixture solution is stirred evenly for 5 h to carry out the preliminary hydrolysis process. The precursor is obtained after stirring. The precursor is placed in the beaker and dried overnight at 140 °C. Then it is calcined in air, the temperature is programmed to 800 °C (5 °C / min), and kept for 5 h. Finally, the calcination procedure is carried out under a nitrogen atmosphere, the temperature is programmed to 500 °C (5 °C / min), and kept for 5 h. The vanadium-niobium composite oxide 800-VNbO is obtained. x 。
[0033] From Figure 1 the characteristic peaks of the vanadium-niobium composite oxide can be seen, indicating that the vanadium-niobium composite oxide material is successfully prepared by the sol-gel method.
[0034] From Figure 2 the characteristic peaks of the vanadium-niobium composite oxide can be seen, further indicating the successful preparation of the vanadium-niobium composite oxide.
[0035] From Figure 3 it can be seen that the prepared material contains vanadium, niobium and oxygen elements, and there are low-valence vanadium and niobium in the vanadium-niobium composite oxide, indicating the existence of oxygen vacancies.
[0036] From Figure 4 it can be seen that the oxygen vacancy concentration in the prepared vanadium-niobium composite oxide increases with the increase of temperature, and the oxygen vacancy concentration of 800-VNbO x is the highest.
[0037] From Figure 5 it can be seen that the prepared vanadium-niobium composite oxide gradually agglomerates from a granular structure with the increase of the calcination temperature, and finally forms a rod-like structure.
[0038] Example 4
[0039] The application of vanadium-niobium composite oxide in catalytic oxidation desulfurization, comprising:
[0040] The vanadium-niobium composite oxides (600-VNbO x , 700-VNbO x and 800-VNbO x obtained in the above Examples 1-3 are used.)Applied to the catalytic oxidation for removing DBT (initial content is 200 ppm) in model oil, the specific reaction conditions are as follows: m(catalyst) = 0.05 g, reaction temperature T = 120 °C, the flow rate of oxidant oxygen is V(O2) = 100 mL / min, V(model oil) = 20 mL. After the reaction starts, the upper oil phase is sampled every 1 h and detected by a gas chromatograph, and the desulfurization rate is calculated through the residual sulfur content.
[0041] It can be seen from Figure 6 that under these reaction conditions, different vanadium-niobium composite oxides all have a certain oxidation and removal effect on DBT, and 800-VNbO x has the best catalytic performance, and the removal rate of DBT reaches 100% under this condition. The removal rates of DBT by 600-VNbO x and 700-VNbO x are 95.6% and 88.9% respectively.
[0042] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. All equivalent structural or equivalent process transformations made using the description of the present invention, or directly or indirectly applied in other related technical fields, are similarly included in the patent protection scope of the present invention.
Claims
1. A method for preparing an oxygen-rich defective vanadium niobium composite oxide catalyst by a sol-gel method, characterized in that, Comprising: Take niobium pentachloride and vanadium trichloride respectively and dissolve them in ethanol. While stirring, drip citric acid aqueous solution. After fully stirring and hydrolysis, dry it, then calcine it at 600 - 800 °C for 3 - 8 h in an air atmosphere, and then calcine it at 400 - 600 °C for 3 - 8 h in a nitrogen atmosphere. After natural cooling to room temperature, grind it to obtain; wherein, the solid-liquid ratio of niobium pentachloride, vanadium trichloride to ethanol is 1.014 - 1.690 g : 0.590 - 0.983 g : 5 - 15 mL; the concentration of the citric acid aqueous solution is 0.5 - 1.5 mol / L, and the dripping amount is the same as the volume of ethanol.
2. The method for preparing an oxygen-rich defective site vanadium niobium composite oxide catalyst by the sol-gel method according to claim 1, characterized in that: The solid-liquid ratio of niobium pentachloride, vanadium trichloride to ethanol is 1.352 g : 0.787 g : 10 mL.
3. The method for preparing an oxygen-rich defect site vanadium niobium composite oxide catalyst by the sol-gel method according to claim 1, characterized in that: The concentration of the citric acid aqueous solution is 1 mol / L.
4. The method for preparing an oxygen-rich defect site vanadium niobium composite oxide catalyst by the sol-gel method according to claim 1, characterized in that: The stirring time is 0.5 - 5 h.
5. The method for preparing an oxygen-rich defective site vanadium niobium composite oxide catalyst by the sol-gel method according to claim 4, wherein: The stirring time is 4 h.
6. The method for preparing an oxygen-rich defective vanadium niobium composite oxide catalyst by the sol-gel method according to claim 1, wherein: The drying temperature is 80 - 140 °C, and the time is 5 - 15 h.
7. The method for preparing an oxygen-rich defective site vanadium niobium composite oxide catalyst by the sol-gel method according to claim 6, characterized in that: The drying temperature is 140 °C, and the time is 10 h.
8. The method for preparing an oxygen-rich defective site vanadium niobium composite oxide catalyst by the sol-gel method according to claim 1, characterized in that: Calcine it at 800 °C for 5 h in an air atmosphere.
9. The method for preparing an oxygen-rich defective site vanadium niobium composite oxide catalyst by the sol-gel method according to claim 1, characterized in that: Calcine it at 500 °C for 5 h in a nitrogen atmosphere.
10. The method for preparing an oxygen-rich defective site vanadium niobium composite oxide catalyst by the sol-gel method according to claim 1, characterized in that: When calcining in a nitrogen atmosphere, the nitrogen flow rate is 50 - 300 mL / min.
11. The method for preparing an oxygen-rich defect site vanadium niobium composite oxide catalyst by the sol-gel method according to claim 10, characterized in that: When calcining in a nitrogen atmosphere, the nitrogen flow rate is 200 mL / min.
12. The oxygen-rich defect-site vanadium niobium composite oxide catalyst prepared by the method according to any one of claims 1 - 11.
13. Use of the oxygen-rich defective vanadium niobium composite oxide catalyst as described in claim 12, characterized in that: Apply it to the field of oxidative desulfurization technology.
14. Use of the oxygen-rich defective site vanadium niobium composite oxide catalyst according to claim 13, characterized in that: Apply it to remove sulfur-containing compounds such as DBT, 4-MDBT, and 4,6-DMDBT in fuel with oxygen as the oxidant.