A hydrothermal carbon supported nanometer titanium dioxide catalyst, a preparation method and application thereof

Abstract

The application provides a hydrothermal carbon loaded nanometer titanium dioxide catalyst and a preparation method and application thereof, and relates to the technical field of catalysts.The preparation method of the hydrothermal carbon loaded nanometer titanium dioxide catalyst provided by the application comprises the following steps: mixing agricultural waste powder and a tetrabutyl titanate solution, and performing hydrothermal carbonization treatment to obtain the hydrothermal carbon loaded nanometer titanium dioxide catalyst; the temperature of the hydrothermal carbonization treatment is 160-280 DEG C.The hydrothermal carbon loaded nanometer titanium dioxide catalyst prepared by the application has high catalytic activity and stability, can be applied to adsorption-degradation of ammonia, and can effectively utilize crop resources, which is beneficial to sustainable development of agriculture.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a hydrothermal carbon-supported nano-titanium dioxide catalyst, its preparation method, and its application. Background Technology

[0002] As is widely known, severe air pollution has caused numerous negative impacts, even posing a significant threat to human life and development, especially in developing countries. Ammonia, an inorganic gaseous pollutant with the molecular formula NH3, is typically present in low concentrations indoors, and the environmental effects of livestock manure emissions have been identified as a critical issue. Ammonia is extremely irritating to the human body, damaging the skin, eyes, and mucous membranes, and causing harm to various tissues. Inhaling excessive amounts of ammonia can lead to lung swelling, impaired oxygen transport, and even death. Therefore, developing effective methods to purify ammonia is of paramount importance.

[0003] Titanium dioxide is an ideal photocatalyst for degrading toxic gases, attracting widespread attention due to its excellent chemical and thermal stability and environmentally friendly properties. Despite its impressive advantages, titanium dioxide-based materials suffer from relatively low efficiency due to their large band gap, rapid recombination of photogenerated electrons, and poor adsorption of reactants.

[0004] Biochar is a porous carbon material produced by the pyrolysis of biomass raw materials under limited or anaerobic conditions. It possesses good stability, is not easily degraded, has a large specific surface area, abundant porous structure, and strong adsorption capacity. In recent years, it has been widely used in agriculture, ecological restoration, and environmental protection, showing promising applications in soil improvement, carbon sequestration, and pollutant adsorption and degradation. In recent years, low-cost biochar prepared from agricultural waste (such as straw) has become an emerging adsorbent. Statistics show that my country's annual straw production is approximately 1 billion tons, growing at a rate of 2.38% annually. However, its utilization rate is very low, especially since direct burning of straw in farmland causes serious environmental pollution and health risks. Summary of the Invention

[0005] The purpose of this invention is to provide a hydrothermal carbon-supported nano-titanium dioxide catalyst, its preparation method, and its application. The hydrothermal carbon-supported nano-titanium dioxide catalyst prepared by this invention has high catalytic activity and stability, and can be applied to the adsorption and degradation of ammonia; at the same time, it can effectively utilize agricultural resources, which is conducive to the sustainable development of agriculture.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing a hydrothermal carbon-supported nano-titanium dioxide catalyst, comprising the following steps:

[0008] Agricultural waste powder and tetrabutyl titanate solution were mixed and subjected to hydrothermal carbonization to obtain hydrothermally carbonized nano-titanium dioxide catalyst; the temperature of the hydrothermal carbonization was 160-280℃.

[0009] Preferably, the agricultural waste powder includes one or more of corn stalk powder, rice husks, and sawdust.

[0010] Preferably, the tetrabutyl titanate solution is an ethanol solution of tetrabutyl titanate.

[0011] Preferably, the mass-to-volume ratio of the agricultural waste powder to the tetrabutyl titanate solution is 1g:10-20mL; and the concentration of the tetrabutyl titanate solution is 0.1-0.5mol / L.

[0012] Preferably, the holding time for the hydrothermal carbonization treatment is 1 to 7 hours.

[0013] Preferably, the hydrothermal carbonization treatment is carried out under stirring conditions; the stirring speed is 60-220 r / min.

[0014] Preferably, the hydrothermal carbonization process further includes solid-liquid separation; the solid material obtained from the solid-liquid separation is washed, dried and ground in sequence to obtain a hydrothermal carbon-supported nano-titanium dioxide catalyst.

[0015] The present invention provides a hydrothermal carbon-supported nano-titanium dioxide catalyst prepared by the preparation method described above, comprising hydrothermal carbon and nano-titanium dioxide supported on the hydrothermal carbon.

[0016] Preferably, the titanium content of the hydrothermal carbon-supported nano-titanium dioxide catalyst is 10-20 wt%.

[0017] This invention provides the application of the hydrothermal carbon-supported nano-titanium dioxide catalyst described above in the adsorption and / or degradation of ammonia.

[0018] This invention provides a method for preparing a hydrothermal carbon-supported nano-titanium dioxide catalyst, comprising the following steps: mixing agricultural waste powder and tetrabutyl titanate solution, and performing hydrothermal carbonization treatment to obtain the hydrothermal carbon-supported nano-titanium dioxide catalyst; the hydrothermal carbonization treatment temperature is 160-280℃. This invention uses agricultural waste powder as raw material and prepares a catalyst by loading nano-titanium dioxide onto hydrothermal carbon in a one-pot process. The resulting catalyst exhibits high catalytic activity and stability and can be applied to the adsorption and degradation of ammonia. Furthermore, it effectively utilizes agricultural resources, which is beneficial to the sustainable development of agriculture. In addition, the preparation method provided by this invention is simple and inexpensive. Attached Figure Description

[0019] Figure 1XRD patterns of the hydrothermal carbon-supported nano-titanium dioxide catalysts prepared in Examples 1-7;

[0020] Figure 2 SEM images of the hydrothermal carbon-supported nano-titanium dioxide catalysts prepared in Examples 1-3;

[0021] Figure 3 The EDS spectrum of 3Ti-160-7 prepared in Example 5;

[0022] Figure 4 Comparison of the effects of hydrothermal carbon-supported nano-titanium dioxide catalysts prepared in Examples 1-3 on ammonia adsorption-degradation;

[0023] Figure 5 Comparison of the effects of hydrothermal carbon-supported nano-titanium dioxide catalysts prepared in Examples 1 and 4-5 on ammonia adsorption-degradation;

[0024] Figure 6 The graphs show a comparison of the effects of hydrothermal carbon-supported nano-titanium dioxide catalysts prepared in Examples 5-7 on ammonia adsorption-degradation. Detailed Implementation

[0025] This invention provides a method for preparing a hydrothermal carbon-supported nano-titanium dioxide catalyst, comprising the following steps:

[0026] Agricultural waste powder and tetrabutyl titanate solution were mixed and subjected to hydrothermal carbonization to obtain hydrothermally carbonized nano-titanium dioxide catalyst; the temperature of the hydrothermal carbonization was 160-280℃.

[0027] In this invention, the agricultural waste powder is preferably agricultural waste straw, more preferably including one or more of corn stalk powder, rice husks, and sawdust. In this invention, the particle size of the corn stalk powder is preferably ≤0.425mm. In this invention, the corn stalk powder is preferably obtained by air-drying and pulverizing corn stalks and passing them through a 40-mesh sieve.

[0028] In this invention, the tetrabutyl titanate solution is preferably an ethanol solution of tetrabutyl titanate; the preparation method of the tetrabutyl titanate solution preferably includes: dissolving tetrabutyl titanate in ethanol, adding water, to obtain the tetrabutyl titanate solution. In this invention, the volume ratio of tetrabutyl titanate to ethanol is preferably 1:1 to 5, more preferably 1:3. In this invention, the concentration of the tetrabutyl titanate solution is preferably 0.1 to 0.5 mol / L, more preferably 0.3 mol / L.

[0029] In this invention, the preferred mass-to-volume ratio of the agricultural waste powder and the tetrabutyl titanate solution is 1g:10-20mL, more preferably 1g:10mL.

[0030] In this invention, the temperature of the hydrothermal carbonization treatment is 160–280℃, preferably 160–220℃; the holding time is preferably 1–7 h, more preferably 4–7 h. In this invention, the hydrothermal carbonization treatment is preferably carried out under stirring conditions; the stirring speed is preferably 60–220 r / min, more preferably 200 r / min. In this invention, hydrothermal carbon is a heterogeneous reaction carried out under high temperature and high pressure conditions using water as the reaction medium, which has advantages such as low synthesis temperature, mild conditions, stable system, and low impurity contamination. Compared with pyrolytic carbon, hydrothermal carbon has the following advantages: 1) In the hydrothermal process of biomass, uniformly sized carbon microspheres can be formed through regulation, and their surfaces are rich in oxygen-containing functional groups, resulting in good physicochemical stability; 2) Its stability in strong acid and strong alkali systems is superior to industrial-based Al2O3, SiO2, and other carriers; 3) The morphology of hydrothermal carbon microspheres helps in the timely removal of degradation products, thus becoming its unique advantage as a carrier.

[0031] In this invention, the hydrothermal carbonization treatment preferably further includes solid-liquid separation; the solid material obtained from the solid-liquid separation is sequentially washed, dried, and ground to obtain a hydrothermally carbonized supported nano-titanium dioxide catalyst. In this invention, the solid-liquid separation is preferably filtration, more preferably vacuum filtration. In this invention, the washing liquid is preferably deionized water. In this invention, the drying temperature is preferably 105°C; the drying time is preferably 8 hours.

[0032] In this invention, the hydrothermal carbon-supported nano-titanium dioxide catalyst is in powder form.

[0033] This invention provides a hydrothermal carbon-supported nano-titanium dioxide catalyst prepared by the method described above, comprising hydrothermal carbon and nano-titanium dioxide supported on the hydrothermal carbon. In this invention, the hydrothermal carbon is carbon microspheres; the pore size of the hydrothermal carbon is preferably 5–15 nm; the pore volume is preferably 0.025–0.05 cm³. 3 / g.

[0034] In this invention, the titanium content of the hydrothermal carbon-supported nano-titanium dioxide catalyst is preferably 10-20 wt%, more preferably 14 wt%.

[0035] This invention also provides the application of the hydrothermal carbon-supported nano-titanium dioxide catalyst described above in the adsorption and / or degradation of ammonia. In this invention, the preferred conditions for the application include: using nitrogen as the carrier gas; an ammonia concentration of 5–25 ppm and a flow rate of 1–5 L / min; using 0.1–1 g of the hydrothermal carbon-supported nano-titanium dioxide catalyst; and a reaction time of 1–5 h. In this invention, the application is preferably carried out under darkness, sunlight, or ultraviolet light, more preferably under ultraviolet light.

[0036] This invention utilizes agricultural waste powder (such as corn stalks, which are abundant in agriculture) as raw material and constructs a highly efficient catalyst loaded with nano-sized titanium through a green and simple hydrothermal carbonization process. The catalyst prepared by this invention through hydrothermal carbonization exhibits a well-developed spherical structure, achieving uniform loading of nano-sized titanium dioxide onto the catalyst and enabling its application in air pollution control.

[0037] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0038] Example 1

[0039] After air-drying and crushing the corn stalks, they are passed through a 40-mesh sieve to obtain corn stalk powder.

[0040] Tetrabutyl titanate and ethanol were mixed at a volume ratio of 1:3, purified water was added, and the mixture was sonicated for 10 min to ensure uniform mixing, resulting in a tetrabutyl titanate solution with a concentration of 0.3 mol / L.

[0041] 5g of the corn stalk powder and 50mL of the tetrabutyl titanate solution were added to a glass-lined flanged magnetic reactor (NSI, Tianjin Mafur Technology Co., Ltd., China), with a solid-liquid ratio of 1:10 (g / mL). The stirring speed was 200r / min, and the mixture was kept at 160℃ for 4h for hydrothermal carbonization. After the reaction system cooled to room temperature, the product of the hydrothermal carbonization was vacuum filtered, the hydrothermal solid was washed with deionized water, dried in a 105℃ forced-air drying oven for 8h, and ground to obtain a hydrothermal carbonized supported nano-titanium dioxide catalyst, denoted as 3Ti-160-4.

[0042] Example 2

[0043] The preparation method is basically the same as that in Example 1, except that the temperature of the hydrothermal carbonization treatment is adjusted from "160℃" to "220℃", which is denoted as 3Ti-220-4.

[0044] Example 3

[0045] The preparation method is basically the same as that in Example 1, except that the temperature of the hydrothermal carbonization treatment is adjusted from "160℃" to "280℃", which is denoted as 3Ti-280-4.

[0046] Example 4

[0047] The preparation method is basically the same as that in Example 1, except that the holding time of hydrothermal carbonization is adjusted from "4h" to "1h", which is denoted as 3Ti-160-1.

[0048] Example 5

[0049] The preparation method is basically the same as that in Example 1, except that the holding time of hydrothermal carbonization is adjusted from "4h" to "7h", which is denoted as 3Ti-160-7.

[0050] Example 6

[0051] The preparation method is basically the same as that in Example 1, except that the concentration of tetrabutyl titanate solution is adjusted from "0.3mol / L" to "0.1mol / L" and the holding time of hydrothermal carbonization treatment is adjusted from "4h" to "7h", which is denoted as 1Ti-160-7.

[0052] Example 7

[0053] The preparation method is basically the same as that in Example 1, except that the concentration of tetrabutyl titanate solution is adjusted from "0.3mol / L" to "0.5mol / L" and the holding time of hydrothermal carbonization treatment is adjusted from "4h" to "7h", denoted as 5Ti-160-7.

[0054] Application examples

[0055] The hydrothermal carbon-supported nano-titanium dioxide catalysts prepared in Examples 1-7 were used for ammonia adsorption-degradation. The concentration of ammonia was 10 ppm, the flow rate was 1 L / min, and the amount of hydrothermal carbon-supported nano-titanium dioxide catalyst used was 0.1 g.

[0056] The ammonia concentration and flow rate were controlled using a portable gas calibrator (146i-GO, Thermo Fisher Scientific, USA). The hydrothermal carbon-supported nano-titanium dioxide catalyst prepared in the example was placed in a quartz tube, and the gas concentration after the reaction was detected using an air quality instrument (17i, Thermo Fisher Scientific, USA).

[0057] First, without a catalyst, nitrogen gas was introduced for 1 hour to eliminate interference from other gases. Then, ammonia gas at a concentration of 10 ppm was continuously introduced at a rate of 1 L / min for 90 minutes to obtain the background value of the device, which was recorded as CO.

[0058] The hydrothermal carbon-supported nano-titanium dioxide catalyst prepared in the examples was placed in a quartz tube and subjected to adsorption-degradation reactions under different light sources. The light sources were set to no light, ultraviolet light, and fluorescent light. Ammonia gas with a concentration of 10 ppm at a rate of 1 L / min was continuously introduced for 90 min. The ammonia adsorption-degradation effect of the hydrothermal carbon-supported nano-titanium dioxide catalyst under different light sources was tested. The change in ammonia concentration under different materials and different light sources was recorded as C1.

[0059] The effectiveness of the photocatalyst was evaluated by the adsorption-degradation rate (RE), which was calculated using the following formula:

[0060] RE = (C0-C1) / C0, where C0 is the real-time concentration of ammonia without catalyst and C1 is the real-time concentration of ammonia under catalyst testing.

[0061] Test Results

[0062] Figure 1 The images show the XRD patterns of the hydrothermal carbon-supported nano-titanium dioxide catalysts prepared in Examples 1-7. Figure 1 It can be seen that as the hydrothermal temperature increases, the diffraction peaks at 2θ = 25.3°, 37.7°, 48.1°, 55.1°, 62.7°, 70.2°, and 75.0° become increasingly sharp, corresponding to the (101), (004), (200), (211), (204), (220), and (215) crystal planes of the anatase phase (standard card PDF#04-0477), respectively. When the hydrothermal temperature is 160°C, the diffraction peaks are weaker, indicating that the titanium dioxide formed at low temperature is smaller.

[0063] Figure 2 The images show SEM images of the hydrothermal carbon-supported nano-titanium dioxide catalysts prepared in Examples 1-3. Figure 2 (a) is a scanning electron microscope (SEM) image of 3Ti-160-4 at 30 KX, (b) is a scanning electron microscope (SEM) image of 3Ti-220-4 at 30 KX, and (c) is a scanning electron microscope (SEM) image of 3Ti-280-4 at 30 KX. (From...) Figure 2 It can be seen that the original structure of the corn stalks was destroyed after hydrothermal carbonization, and a large number of irregular, cross-linked nanoscale spherical carbon particles of different sizes appeared on the surface. This is because hemicellulose, cellulose, and lignin in the corn stalks were partially converted into small organic molecules after hydrolysis, and these substances formed spherical carbon particles through condensation polymerization. Moreover, titanium dioxide nanoparticles can be seen loaded on the surface of the carbon microspheres.

[0064] Figure 3 The image shows the EDS spectrum of 3Ti-160-7 prepared in Example 5. Figure 3 It can be seen that Ti accounts for 14% of the surface weight and C accounts for 59.5%.

[0065] The effects of the hydrothermal carbon-supported nano-titanium dioxide catalysts prepared in Examples 1-3 on ammonia adsorption-degradation are as follows: Figure 4 As shown in Table 1.

[0066] Table 1. Adsorption-degradation rate of ammonia by hydrothermal carbon-supported nano-titanium dioxide catalysts prepared in Examples 1-3

[0067]

[0068] Depend on Figure 4 As shown in Table 1, the effect under no light decreases to some extent with the increase of preparation temperature, but not significantly. Under the preparation condition of 220℃, the effect is basically the same under the three light sources, indicating that the adsorption-degradation effect of hydrothermal carbon-supported nano-titanium dioxide catalyst is not significantly improved under light irradiation. Under the preparation condition of 280℃, although the effect is better in the early stage, the effect is unstable and the failure is very fast with the increase of reaction time. The material prepared at 160℃ has a better and more stable effect.

[0069] The effects of the hydrothermal carbon-supported nano-titanium dioxide catalysts prepared in Examples 1 and 4-5 on ammonia adsorption-degradation are as follows: Figure 5 As shown in Table 2.

[0070] Table 2. Ammonia adsorption-degradation rate of the hydrothermal carbon-supported nano-titanium dioxide catalysts prepared in Examples 1 and 4-5

[0071]

[0072] Depend on Figure 5 As can be seen from Table 2, the adsorption-degradation effect on ammonia increases with the extension of hydrothermal carbonization time.

[0073] The effects of the hydrothermal carbon-supported nano-titanium dioxide catalysts prepared in Examples 5-7 on ammonia adsorption-degradation are as follows: Figure 6 As shown in Table 3.

[0074] Table 3 shows the adsorption-degradation rate of ammonia by the hydrothermal carbon-supported nano-titanium dioxide catalysts prepared in Examples 5-7.

[0075]

[0076] Depend on Figure 6 As shown in Table 3, the adsorption-degradation effect of ammonia gas first increases and then decreases with the increase of titanium ion concentration in the solution.

[0077] The results showed that the effect under ultraviolet light was improved compared to the absence of light, indicating that not only adsorption reaction occurred under ultraviolet light, but also catalytic degradation reaction occurred, thus improving the removal effect.

[0078] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a hydrothermal carbon-supported nano-titanium dioxide catalyst, comprising the following steps: Agricultural waste powder and tetrabutyl titanate solution were mixed and subjected to hydrothermal carbonization to obtain hydrothermally carbonized nano-titanium dioxide catalyst; the temperature of the hydrothermal carbonization was 160-280℃.

2. The preparation method according to claim 1, characterized in that, The agricultural waste powder includes one or more of corn stalk powder, rice husks, and sawdust.

3. The preparation method according to claim 1, characterized in that, The tetrabutyl titanate solution is an ethanol solution of tetrabutyl titanate.

4. The preparation method according to claim 1 or 3, characterized in that, The mass-to-volume ratio of the agricultural waste powder to the tetrabutyl titanate solution is 1g:10-20mL; the concentration of the tetrabutyl titanate solution is 0.1-0.5mol / L.

5. The preparation method according to claim 1, characterized in that, The holding time for the hydrothermal carbonization treatment is 1 to 7 hours.

6. The preparation method according to claim 1, characterized in that, The hydrothermal carbonization process is carried out under stirring conditions; the stirring speed is 60-220 r / min.

7. The preparation method according to claim 1, characterized in that, The hydrothermal carbonization process also includes solid-liquid separation; the solid material obtained from the solid-liquid separation is washed, dried and ground in sequence to obtain a hydrothermal carbon-supported nano-titanium dioxide catalyst.

8. The hydrothermal carbon-supported nano-titanium dioxide catalyst prepared by the preparation method according to any one of claims 1 to 7 comprises hydrothermal carbon and nano-titanium dioxide supported on the hydrothermal carbon.

9. The hydrothermal carbon-supported nano-titanium dioxide catalyst according to claim 8, characterized in that, The titanium content of the hydrothermal carbon-supported nano-titanium dioxide catalyst is 10-20 wt%.

10. The application of the hydrothermal carbon-supported nano-titanium dioxide catalyst according to any one of claims 8 to 9 in the adsorption and / or degradation of ammonia.

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