ACF-loaded CeO2 / TiO2 photocatalyst, and preparation method and application thereof

Abstract

The invention provides an ACF (activated carbon fiber)-loaded CeO2 / TiO2 photocatalyst as well as a preparation method and application of the ACF-loaded CeO2 / TiO2 photocatalyst. According to the photocatalyst, CeO2 is uniformly dispersed among TiO2 particles by utilizing a sol-gel method preparation process, and bonding of Ti-O-Ce elements occurs in a catalyst synthesis process, so that not only is the photo-generated charge separation efficiency of the catalyst improved, but also CeO2 / TiO2 is uniformly loaded on the surface of ACF in the form of a smooth film, and the photocatalytic activity of the ACF is improved. The defect that the adsorption capacity is reduced due to the fact that adsorption pore channels in activated carbon fibers in an existing catalyst are blocked is overcome.

Description

Technical Field

[0001] The present invention relates to the technical field of removing hydrocarbon VOCs in the petroleum and petrochemical industries, and in particular to an ACF-loaded CeO2 / TiO2 photocatalyst, a preparation method and use thereof. Background Art

[0002] As a pillar industry of the national economy, the petroleum and petrochemical industry provides the necessary petroleum energy and chemical products for social development, but at the same time, the environmental pollution problems it brings are becoming increasingly prominent. The exhaust gas emitted by the petroleum and petrochemical industry is complex in composition, with volatile organic compounds (VOCs) as the main component, including a variety of toxic and harmful gases, such as non-methane hydrocarbon pollutants, benzene series, halogenated hydrocarbons, alcohols... Among them, VOCs have carcinogenic and mutagenic hazards that seriously threaten the atmospheric environment and human health. For VOCs, the main treatment technologies are adsorption, condensation, incineration, catalytic combustion, photocatalysis, etc. However, the current single treatment technology can no longer achieve efficient removal of pollutants. Some scholars have combined adsorption with photocatalysis technology, using composite materials of activated carbon fibers and active metals such as titanium dioxide and manganese dioxide as photocatalysts for removing VOCs.

[0003] However, the activated carbon fiber (ACF) and titanium dioxide composite materials prepared by the current method, although they achieve the combination of adsorption and photocatalysis, cannot achieve the effect of one plus one being greater than two. The main reason is that the titanium dioxide is loaded on the activated carbon fiber, which blocks the adsorption pores on the activated carbon fiber, reduces the specific surface area, and thus reduces the adsorption performance. Moreover, in the composite materials prepared by most researchers, the titanium dioxide is only loaded on the surface of the activated carbon fiber, with a low loading amount and low photocatalytic ability, and cannot achieve efficient treatment.

[0004] CN103331158B discloses a catalyst for ethanol hydrogenation from acetic acid and its preparation method. The catalyst is a multi-component supported catalyst, comprising components a, b, and c, and a carrier. Component a is selected from one or more of calcium, potassium, sodium, barium, strontium, or their oxides; component b is selected from one or more of tin, cobalt, molybdenum, nickel, iron, or their oxides; component c is selected from one or more of platinum, palladium, ruthenium, rhodium, or their oxides; and the carrier is selected from silica, cerium dioxide, titanium dioxide, graphite, aluminum oxide, or activated carbon. The mass ratio of components a, b, and c to the carrier is 1-20:0.5-2:0.5-1:100. This technology uses a multi-step impregnation process to prepare the multi-component supported catalyst. This patent uses cerium dioxide, titanium dioxide, graphite, aluminum oxide, or activated carbon as a carrier and loads other metals for use as a catalyst in other fields. However, the catalyst's inherent structural defects prevent it from meeting the high adsorption capacity requirements for VOC removal in the petroleum and petrochemical industries.

[0005] Looking at the current catalytic landscape, rare earth elements, as the most common elements in the natural environment, have a proven track record of practical application in environmental catalysis. Therefore, the urgent need to address the challenge is to combine suitable rare earth elements with titanium dioxide and load them onto activated carbon to create composite catalysts with enhanced oxygen storage and release capacity, higher photocatalytic activity, and excellent cyclic stability, thereby achieving a synergistic effect of adsorption-coupled photocatalytic activity. Summary of the Invention

[0006] In response to the shortcomings of the existing technology, the present invention provides an ACF-loaded CeO2 / TiO2 photocatalyst. The photocatalyst utilizes a sol-gel preparation process to uniformly disperse CeO2 between TiO2 particles, and bonding of Ti-O-Ce elements occurs during the catalyst synthesis process, which not only improves the photogenerated charge separation efficiency of the catalyst, but also uniformly loads CeO2 / TiO2 on the ACF surface in the form of a smooth film, solving the defect of reduced adsorption capacity caused by clogging of adsorption channels on the activated carbon fiber in existing catalysts.

[0007] The technical solutions of the present invention are as follows:

[0008] The present invention provides an ACF-loaded CeO2 / TiO2 photocatalyst, wherein the photocatalyst comprises CeO2 and TiO2 loaded on the ACF. Based on the mass of the photocatalyst, the loading amount of TiO2 is 40wt%-80wt%, the loading amount of CeO2 is 0.5wt%-2.5wt%, and the particle size of the photocatalyst is 18nm-21nm.

[0009] Furthermore, in the photocatalyst, characteristic diffraction peaks of TiO2 anatase phase appear at 2θ=25.3°(101), 37.9°(004), 48.05°(200), 55.02°(211), and 62.9°(204); and characteristic diffraction peaks of CeO2 cerium ore appear at 2θ=28.55°(111) and 33.08°(200).

[0010] Furthermore, in the photocatalyst, the lattice fringe spacing of the (111) lattice plane of CeO2 is 0.32 nm.

[0011] Furthermore, in the photocatalyst, the lattice fringe spacing of the (101) lattice plane of TiO2 is 0.35 nm.

[0012] Furthermore, in the photocatalyst, CeO2 is uniformly dispersed between TiO2 particles using a sol-gel method, thereby enhancing the interaction between the two phases and forming a Ti-O-Ce bond.

[0013] Furthermore, in the photocatalyst, the Ti element in TiO2 exists mainly in the form of +4 valence, and the Ce element in CeO2 exists in a mixed valence state of +3 and +4 valence.

[0014] Furthermore, the specific surface area of ​​the photocatalyst is 530m 2 / g-620m 2 / g.

[0015] The present invention also provides a method for preparing the aforementioned photocatalyst, the preparation method comprising the following steps:

[0016] Step 1: Preparation of CeO2:

[0017] Prepare a Ce salt solution and record it as solution A, and prepare an alkali solution of the same volume and record it as solution B;

[0018] Add solution B dropwise into solution A, continue stirring until the mixture is uniform, pour into a high-pressure reactor, react at 120-200°C for 4-12 hours, centrifuge the reaction solution after completion of the reaction, wash, and vacuum dry to obtain a CeO2 precursor;

[0019] Step 2: Preparation of ACF-loaded CeO2 / TiO2 photocatalyst:

[0020] Tetrabutyl titanate, acetic acid and anhydrous ethanol are mixed together until uniformly stirred, which is recorded as solution C. The CeO2 precursor obtained in step 1, anhydrous ethanol, deionized water and acetic acid are mixed together until uniformly stirred, which is recorded as solution D. Under stirring conditions, solution D is slowly dripped into solution C, and stirring is continued. The mixture is allowed to stand for 12-36 hours to obtain an aged sol.

[0021] ACF was added to the aged sol, and then the sol was subjected to ultrasonication, impregnation and drying. This process was recorded as composite material impregnation once;

[0022] Optionally repeat the above steps, repeat the impregnation 1-3 times, place the impregnated composite material in a tube furnace, and calcine it at 400°C-650°C for 1-6h in a nitrogen environment to obtain an ACF-loaded CeO2 / TiO2 photocatalyst.

[0023] Furthermore, in step 1, the mass concentration of the Ce salt solution is 0.01-0.1 mol.

[0024] Furthermore, in step 1, the Ce salt solution is selected from any one of Ce(NO3)3, Ce(SO4)2, and CeCl3.

[0025] Furthermore, in step 1, the mass concentration of the alkaline solution is 0.01-0.1 mol.

[0026] Furthermore, in step 1, the alkaline solution is selected from any one of NaOH, KOH, and ammonia water.

[0027] Furthermore, in step 1, the reaction pressure of the high-pressure reactor is 0.1-1 MPa.

[0028] Furthermore, in step 1, the reaction temperature in the high-pressure reactor is controlled to be 120-200° C., and the reaction time is 4 h to 12 h.

[0029] Furthermore, in step 1, the washing is washing with deionized water.

[0030] Furthermore, in step 1, the drying is carried out in a vacuum drying oven at 30-150° C. for 4-16 hours.

[0031] Furthermore, in step 2, in the solution C, the volume ratio of tetrabutyl titanate, acetic acid, and ethanol is (1-15): (5-25): (15-50).

[0032] Furthermore, in step 2, tetrabutyl titanate, acetic acid and anhydrous ethanol are poured into a beaker and stirred for 0.5-6 hours.

[0033] Furthermore, in step 2, the amount of the CeO2 precursor added is 0.5 wt%-2.5 wt%, based on the mass of the ACF-loaded CeO2 / TiO2 photocatalyst.

[0034] Furthermore, in step 2, in the solution D, the volume ratio of anhydrous ethanol, deionized water and acetic acid is (1-15): (10-50): (1-10).

[0035] Furthermore, in step 2, after the solution D is added dropwise to the solution A, stirring is continued for 1-6 hours, and then allowed to stand for 12-36 hours.

[0036] Furthermore, in step 2, the ACF is activated in advance.

[0037] Furthermore, the ACF pre-activation process is as follows: the block ACF is placed in a 5-30% concentration ethanol solution and ultrasonically stirred for 0.5-3 hours, then transferred to 100°C boiling water and boiled for 0.5-3 hours to remove surface impurities, and finally dried in a 50-150°C oven for 4-8 hours.

[0038] Furthermore, in step 2, the activated ACF was cut into small cubes and added into the aged sol, and then the sol was ultrasonicated for 5 minutes and then immersed for 30 minutes.

[0039] Furthermore, in step 2, ACF is added to the aged sol and immersed twice, so that CeO2 / TiO2 is uniformly loaded on the surface of the ACF in the form of a smooth film.

[0040] Furthermore, in step 2, the aging is to let the sol stand for a period of time to allow the colloid particles therein to grow.

[0041] The present invention also provides a use of the aforementioned photocatalyst for removing hydrocarbon volatile organic compounds. The photocatalyst is built into a photocatalytic reactor, an 8-24W ultraviolet light is turned on, and then hydrocarbon volatile organic compounds are introduced to cause an adsorption-coupled photocatalytic reaction. The initial concentration of the hydrocarbon volatile organic compounds is controlled at 300-1100 mg / m 3 , airspeed controlled at 1500-8000h -1 The volume of the photocatalyst is (10-15 cm)×(10-15 cm) block.

[0042] Furthermore, the photocatalytic reaction device primarily comprises multiple small reaction units connected in series or parallel. Each of the small reaction units consists of three components: an 8-24W UV lamp, a quartz tube housing, and a photocatalyst. The photocatalyst is supported on a stainless steel mesh. The spacing between the small reaction units and the distance between the outer wall and the inner wall of the photocatalytic reaction device are 18-30 mm.

[0043] Furthermore, the temperature of the adsorption-coupled photocatalytic reaction is controlled at 25°C.

[0044] Furthermore, the hydrocarbon volatile organic compounds include toluene, ethylbenzene, formaldehyde, acetaldehyde and other organic compounds.

[0045] Furthermore, the photocatalyst has a toluene removal yield of 60-80%.

[0046] Furthermore, when the loading amount of CeO2 in the photocatalyst is 1.5 wt%, the removal efficiency of the photocatalyst for toluene is 75%.

[0047] Furthermore, the photocatalyst is used for removing hydrocarbon volatile organic compounds in the field of petroleum and petrochemicals.

[0048] The photocatalytic principle of the photocatalyst of the present invention (such as Figure 1 shown) is:

[0049] The removal of hydrocarbon volatile organic compounds such as toluene is mainly determined by the synergistic effect of ACF adsorption and CeO2 / TiO2 photocatalysis. The specific steps are as follows:

[0050] First, toluene molecules are adsorbed on the surface of the photocatalyst, especially the active sites of ACF; second, under the action of photocatalysis, toluene molecules are converted into carbon dioxide, water molecules and certain intermediates; finally, the remaining active sites can continue to adsorb toluene molecules, promoting the in situ regeneration of ACF.

[0051] There are many channels between the fibers of ACF, which can promote mass transfer, accelerate the flow of gas, and facilitate the reaction; and there are a large number of grooves on the surface of ACF, which is conducive to increasing the specific surface area and improving the adsorption capacity. In addition, CeO2 / TiO2 is evenly loaded on the surface of ACF in the form of a smooth film, which can inhibit the decomposition of toluene molecules. Under light conditions, TiO2 and CeO2 absorb different wavelengths and undergo inter-band transitions, generating photogenerated electrons and hole pairs at the valence band and conduction band positions of the catalyst, respectively, thereby promoting the separation efficiency of electrons and holes and facilitating the progress of photocatalytic reactions. In addition, CeO2 has Ce 4+ / Ce 3+ Redox electron pair, Ce 4+ Ions can easily capture photogenerated electrons to generate Ce 3+ ions, while Ce 4+ The captured electrons are difficult to recombine with holes, further inhibiting the recombination of electrons and holes. At the same time, ACF not only has a large specific surface area, which increases the adsorption capacity of the photocatalyst, but also can be used as a carbon material with good electron transfer performance, which can promote electron conduction and inhibit the recombination of electrons and holes. Therefore, the high removal efficiency of the photocatalyst of the present invention for toluene is mainly caused by the synergistic effect of adsorption coupled photocatalysis. Under ultraviolet light irradiation, oxygen reacts with electrons to generate O2 - ;H2O or -OH and h + A reaction occurs to generate hydroxyl radicals (·OH), which eventually degrade the toluene molecules.

[0052] The present invention has the beneficial effects:

[0053] 1. The present invention provides an ACF (activated carbon fiber)-loaded CeO2 / TiO2 (cerium dioxide and titanium dioxide) photocatalyst. Compared with existing ACF-loaded CeO2 catalytic materials, the present invention reduces the catalyst grain size (from 27.3nm to 19.54nm) after combining TiO2 and CeO2. The reduction in particle size indicates that the introduction of CeO2 inhibits the grain growth of the ACF-loaded CeO2 / TiO2 photocatalyst. The smaller the grain size, the higher the efficiency of photogenerated charge separation, which enhances the activity of the photocatalyst. Therefore, ACF-loaded CeO2 / TiO2 has higher photocatalytic activity than ACF-loaded TiO2.

[0054] 2. The present invention uses a sol-gel method to evenly disperse CeO2 crystals within the TiO2 matrix, effectively enhancing the interaction between the two phases and enabling Ti-O-Ce bonding during the material synthesis process. Compared to the photocatalyst before the photocatalytic reaction, the TiO2 crystal form after the adsorption-coupled photocatalytic reaction remains virtually unchanged, demonstrating the composite catalyst's excellent photocatalytic stability.

[0055] 3. CeO2 exists in an interstitial state on the TiO2 surface, causing the TiO2 lattice to distort. Moderate TiO2 lattice distortion or expansion will cause defect dislocation, effectively separating electron holes, contributing to the generation of photogenerated electrons, and improving the photocatalytic activity of TiO2. The addition of CeO2 can achieve the purpose of modifying TiO2 and is an effective means to improve the performance of TiO2. With the increase of CeO2 loading, the toluene removal efficiency first increases and then decreases. This is because with the increase of CeO2 doping, the number of reactive sites generated increases, resulting in an increase in the number of photogenerated electrons. However, excessive CeO2 has a partial inhibitory effect on the photocatalytic performance. When the CeO2 loading is 1.5% by weight, the photocatalyst reaches a maximum removal efficiency of toluene (75%).

[0056] 4. In the preparation method of the present invention, the pretreated ACF surface is smooth and free of impurities, resulting in grooves on the ACF surface that increase the contact area with the photocatalyst, which plays a key role in adsorption and photocatalytic mass transfer, thereby accelerating the flow of toluene within the ACF. Furthermore, CeO2 / TiO2 is uniformly loaded onto the grooves and surface of the ACF via an impregnation method. Experimental results show that even after two coatings, the ACF surface remains smooth despite being covered with CeO2 / TiO2, indicating that the CeO2 / TiO2 is uniformly loaded onto the ACF surface in the form of a smooth film.

[0057] 5. In the adsorption-coupled photocatalytic reaction of the present invention, as the calcination temperature increases, TiO2 gradually transforms from anatase phase to rutile phase, and TiO2 grains gradually grow and even sinter, causing the catalyst pores to collapse or block, reducing the specific surface area of ​​the catalyst, and thus reducing its catalytic activity. When the calcination temperature is 450°C, the anatase content of TiO2 is the highest.

[0058] 6. The photocatalyst of the present invention has both excellent adsorption and photocatalytic properties, has a highly efficient removal effect on VOCs, good cycle stability, and a simple preparation method with low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 This is the mechanism analysis diagram of CeO2 / TiO2 / ACF photocatalyst for removing toluene.

[0060] Figure 2 middle, Figure 2 (Left) X-ray diffraction patterns of TiO2 / ACF and CeO2 / TiO2 / ACF with different loading amounts; Figure 2 (Right) X-ray diffraction pattern of 1.5%-CeO2 / TiO2 / ACF photocatalyst before and after photocatalytic reaction.

[0061] Figure 3 middle, Figure 3 (a, b) are SEM images of ACF; Figure 3 (c, d), (e, f), (g, h) are SEM images of photocatalysts coated once, twice, and three times, respectively.

[0062] Figure 4 (a) TEM image and (b) HRTEM image of the photocatalyst of the present invention.

[0063] Figure 5 This is a diagram showing the effect of toluene removal by CeO2 / TiO2 / ACF with different loading amounts.

[0064] Figure 6 This is a diagram showing the effect of different calcination temperatures on the removal of toluene by CeO2 / TiO2 / ACF.

[0065] Figure 7 This is a graph showing the number of recycling times for 1.5%-CeO2 / TiO2 / ACF photocatalyst in removing toluene. DETAILED DESCRIPTION

[0066] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. Instead, these embodiments are provided to make the present invention more thorough and complete and to fully convey the scope of the present invention to those skilled in the art.

[0067] Example 1

[0068] Example 1 provides an ACF-loaded CeO2 / TiO2 photocatalyst, comprising CeO2 and TiO2 loaded on ACF, wherein based on the mass of the photocatalyst, the loading amount of TiO2 is 40 wt % and the loading amount of CeO2 is 1 wt %.

[0069] Step 1: Preparation of CeO2:

[0070] Prepare 15 mL of 0.01 mol Ce(NO3)3 solution and record it as solution A. Also prepare the same volume of 0.04 mol NaOH and record it as solution B.

[0071] Solution B was added dropwise to solution A, and stirring was continued for 4 hours to mix evenly. The mixture was then poured into a high-pressure reactor and reacted at a constant temperature of 160°C for 8 hours under a pressure of 0.5 MPa. The resulting solution was centrifuged, washed with deionized water, and dried in a vacuum drying oven at 50°C for 12 hours to obtain a CeO2 precursor.

[0072] Step 2: Preparation of ACF-loaded CeO2 / TiO2 photocatalyst:

[0073] 10 mL of tetrabutyl titanate, 17 mL of acetic acid, and 34 mL of anhydrous ethanol were poured into a 200 mL beaker and stirred for 30 min, which was recorded as solution C. A CeO2 precursor with a loading of 1 wt%, 10 mL of anhydrous ethanol, 30 mL of deionized water, and 2 mL of acetic acid were added and mixed, and stirred for 30 min to obtain solution D. Under stirring conditions, solution D was slowly dripped into solution C, and stirring was continued for 2 h. The mixture was allowed to stand for 24 h to obtain an aged sol.

[0074] The activated ACF was cut into small cubes, placed in the aged sol, ultrasonicated for 5 min, immersed for 30 min, and then placed in an oven for drying;

[0075] Repeat the above steps and impregnate twice. Place the impregnated composite material in a tube furnace and calcine it at 450°C for 4 hours in a nitrogen environment to obtain a CeO2 / TiO2 / ACF photocatalyst.

[0076] Example 2

[0077] Example 2 provides an ACF-loaded CeO2 / TiO2 photocatalyst, comprising CeO2 and TiO2 loaded on ACF. Based on the mass of the photocatalyst, the loading amount of TiO2 is 60 wt % and the loading amount of CeO2 is 1.5 wt %.

[0078] Step 1: Preparation of CeO2:

[0079] Prepare 15 mL of 0.01 mol Ce(NO3)3 solution and record it as solution A. Also prepare the same volume of 0.04 mol NaOH and record it as solution B.

[0080] Solution B was added dropwise to solution A, and stirring was continued for 4 hours to mix evenly. Then, the mixture was poured into a high-pressure reactor and reacted at a constant temperature of 180°C for 6 hours under a pressure of 1 MPa. The obtained solution was centrifuged, washed with deionized water, and dried in a vacuum drying oven at 75°C for 8 hours to obtain a CeO2 precursor.

[0081] Step 2: Preparation of ACF-loaded CeO2 / TiO2 photocatalyst:

[0082] 10 mL of tetrabutyl titanate, 17 mL of acetic acid, and 34 mL of anhydrous ethanol were poured into a 200 mL beaker and stirred for 30 min, which was recorded as solution C. A CeO2 precursor with a loading of 1.5 wt%, 10 mL of anhydrous ethanol, 30 mL of deionized water, and 2 mL of acetic acid were added and mixed, and stirred for 30 min to obtain solution D. Under stirring conditions, solution D was slowly dripped into solution C, and stirring was continued for 6 h. The mixture was allowed to stand for 36 h to obtain an aged sol.

[0083] The activated ACF was cut into small cubes, placed in the aged sol, ultrasonicated for 5 min, immersed for 30 min, and then placed in an oven for drying;

[0084] Repeat the above steps and impregnate for 3 times. Place the impregnated composite material in a tube furnace and calcine it at 550°C for 3 hours in a nitrogen environment to obtain a CeO2 / TiO2 / ACF photocatalyst.

[0085] Example 3

[0086] Example 3 provides an ACF-loaded CeO2 / TiO2 photocatalyst, comprising CeO2 and TiO2 loaded on ACF. Based on the mass of the photocatalyst, the loading amount of TiO2 is 80 wt %, and the loading amount of CeO2 is 2 wt %.

[0087] Step 1: Preparation of CeO2:

[0088] Prepare 15 mL of 0.01 mol Ce(NO3)3 solution and record it as solution A. Also prepare the same volume of 0.04 mol NaOH and record it as solution B.

[0089] Solution B was added dropwise to solution A, and stirring was continued for 4 hours to mix evenly. The mixture was then poured into a high-pressure reactor and reacted at a constant temperature of 200°C for 8 hours under a pressure of 0.75 MPa. The resulting solution was centrifuged, washed with deionized water, and dried in a vacuum drying oven at 50°C for 8 hours to obtain a CeO2 precursor.

[0090] Step 2: Preparation of ACF-loaded CeO2 / TiO2 photocatalyst:

[0091] 10 mL of tetrabutyl titanate, 17 mL of acetic acid, and 34 mL of anhydrous ethanol were poured into a 200 mL beaker and stirred for 30 min, which was recorded as solution C. 2 wt% CeO2, 10 mL of anhydrous ethanol, 30 mL of deionized water, and 2 mL of acetic acid were added and mixed, and stirred for 30 min to obtain solution D. Under stirring conditions, solution D was slowly dripped into solution C, and stirring was continued for 4 h. The mixture was allowed to stand for 16 h to obtain an aged sol.

[0092] The activated ACF was cut into small cubes, placed in the aged sol, ultrasonicated for 5 min, immersed for 30 min, and then placed in an oven for drying;

[0093] Repeat the above steps and impregnate once more. Place the impregnated composite material in a tube furnace and calcine it at 650° C. for 2 h in a nitrogen environment to obtain a CeO 2 / TiO 2 / ACF photocatalyst.

[0094] like Figure 2 As shown, Figure 2 (Left) XRD crystal characterization of TiO2 / ACF and different loading amounts of CeO2 / TiO2 / ACF photocatalysts. As can be seen from the figure, the characteristic peaks of anatase phase TiO2 (JCPDS no. 21-1272) appear at 2θ = 25.3° (101), 37.9° (004), 48.05° (200), 55.02° (211), and 62.9° (204), indicating that TiO2 in the photocatalyst calcined at 450°C mainly exists in the form of anatase; the broad peaks appearing at 2θ = 28.55° and 33.08° correspond to the (111) and (200) crystal plane diffraction peaks of CeO2 ceresite, respectively, and the peak intensity increases with the increase of CeO2 doping amount.

[0095] Figure 2 (Right) The peak intensity of CeO2 / TiO2 / ACF photocatalyst is slightly lower than that of CeO2 / TiO2, and the diffraction peak gradually broadens, indicating that the introduction of CeO2 reduces the grain size of the composite catalyst and weakens the crystallinity of TiO2. The Scherrer equation was used to calculate the catalyst grain size. The calculation results show that the particle size of TiO2 particles in CeO2 / TiO2 is 27.3nm, while the particle size of TiO2 particles after composite with CeO2 is reduced to 19.54nm, which indicates that CeO2 has a significant inhibitory effect on the grain growth of CeO2 / TiO2 / ACF photocatalyst. The smaller the grain size, the higher the separation efficiency of photogenerated charges, resulting in the continuous enhancement of the photocatalytic activity of CeO2 / TiO2 / ACF, which also shows that CeO2 / TiO2 / ACF is better than TiO 2 / ACF has higher photocatalytic activity. In addition, TiO 2 / The diffraction peak positions of ACF and CeO2 / TiO2 / ACF are almost the same, indicating that Ce 4+ It does not enter the lattice to replace Ti 4+ This is mainly due to Ce 4+ The radius (0.102nm) is much larger than that of Ti 4+radius (0.064nm). Due to the small size of CeO2 crystals and their uniform dispersion between TiO2 particles through the sol-gel method, bonding of Ti-O-Ce elements may occur during the material synthesis process. These factors have inhibited the transformation of TiO2 anatase phase to rutile phase to a certain extent. Defect dislocations in the anatase lattice can produce oxygen vacancies that capture photogenerated holes and promote the separation of electrons and holes. Compared with the photocatalyst before the photocatalytic reaction, the crystal form (anatase) of titanium dioxide in the catalyst after the adsorption-coupled photocatalytic reaction has hardly changed, while the cerium oxide with cubic fluorite structure has lattice microstrain after the reaction, and the peak intensity decreases and becomes broadened. This phenomenon may be due to Ce 4+ Partially reduced to Ce 3+ This indicates that the lattice distortion and lattice defects of cerium oxide crystals increase, which also shows that there is a strong interaction between cerium oxide and titanium dioxide.

[0096] Figure 3 The SEM images of ACF and CeO2 / TiO2 / ACF photocatalysts with different impregnation times are shown. Figure 3 As shown in (a, b), the surface of the ACF after pretreatment is smooth and free of impurities, indicating that the impurities on the surface of the ACF have been basically removed. The grooves on the surface of the ACF increase the contact area of ​​the photocatalyst, which plays a key role in adsorption and photocatalytic mass transfer. There are a large number of irregularly arranged fiber strips in the ACF, each of which has linear grooves and ridges arranged in the longitudinal direction. The large number of large pores between the fibers not only allow oxygen and toluene in the air to accumulate on the surface of CeO2 / TiO2 / ACF, but also help to reduce pressure drop and support mass transfer, thereby accelerating the flow of toluene in the porous composite material. The CeO2 / TiO2 catalyst is evenly loaded onto the grooves and surface of the ACF by impregnation. Figure 3 (c, d), (e, f), and (g, h) are SEM images of the photocatalysts coated once, twice, and three times, respectively. The images show that the catalyst loading was too low after the first coating, while the CeO2 / TiO2 catalyst coated three times aggregated on the ACF surface as small particles or clusters, blocking the adsorption channels. This also indicates that the CeO2 / TiO2 photocatalyst successfully entered the pores of the activated carbon fiber. The surface of the ACF coated twice was covered with CeO2 / TiO2 but still maintained a smooth surface, indicating that the CeO2 / TiO2 was uniformly loaded on the ACF surface in the form of a smooth film.

[0097] Figure 4 (a) TEM image and (b) HRTEM image of the photocatalyst of the present invention. Figure 4As can be seen in (a), TiO2 is in the form of a transparent gauze with many wrinkles. The presence of these wrinkles increases the surface area of ​​the catalyst and also reduces its surface energy. CeO2 particles are relatively evenly dispersed on the surface of TiO2, with some agglomeration. This also proves that the ACF-loaded CeO2 / TiO2 catalyst was successfully prepared, which is consistent with the SEM results. Figure 4 As can be seen in (b), two types of lattice fringes are present, with lattice fringe spacing of 0.32nm and 0.35nm, respectively, corresponding to the (111) lattice plane of CeO2 and the (101) lattice plane of anatase TiO2, indicating that both crystals are highly crystalline and tightly bound. Furthermore, the material is found to consist almost entirely of CeO2 and TiO2 phases, with no other new phases appearing, indicating that Ce ions cannot truly replace Ti atoms in the TiO2 lattice.

[0098] Figure 5 The figure shows the effect of different loading amounts of CeO2 / TiO2 / ACF on the removal of toluene. The removal efficiency of TiO2 / ACF and different loading amounts of CeO2 / TiO2 / ACF photocatalysts on toluene under ultraviolet light is shown in Figure 2. Figure 5 As shown in the figure, the toluene removal efficiency of CeO2 / TiO2 / ACF is superior to that of TiO2 / ACF. After 3 hours of illumination, the toluene removal efficiency of 1.5% CeO2 / TiO2 / ACF was approximately 75%, significantly higher than the 54% achieved by TiO2 / ACF. Cerium oxide exists interstitially on the TiO2 surface, causing lattice distortion. Moderate lattice distortion or expansion can lead to defect dislocations, effectively separating electron holes, facilitating the generation of photogenerated electrons, and enhancing the photocatalytic activity of TiO2. The addition of CeO2 can achieve the purpose of TiO2 modification and is an effective means of improving TiO2 performance. With increasing CeO2 content, the removal efficiency initially increases and then decreases. This is because increasing CeO2 doping creates more reactive sites, leading to an increase in the number of photogenerated electrons. However, the presence of excessive CeO2 partially inhibits the photocatalytic performance of the photocatalyst, which is speculated to be related to the presence of unpaired electrons in the 4f orbitals of the Ce ions. These unpaired electrons can effectively capture the photogenerated electrons and holes, preventing them from diffusing to the TiO2 surface, thereby significantly reducing the photocatalytic activity. When the CeO2 loading is 1.5%, the toluene removal efficiency of CeO2 / TiO2 / ACF reaches the maximum.

[0099] Figure 6Figure 3. Effect of different calcination temperatures on toluene removal by CeO2 / TiO2 / ACF. The effects of different calcination temperatures (400°C, 450°C, 550°C, and 650°C) on the toluene gas removal performance of CeO2 / TiO2 / ACF photocatalysts were investigated. As can be seen from the figure, the catalytic removal efficiency of CeO2 / TiO2 / ACF for toluene first increases and then decreases with increasing calcination temperature, reaching its maximum at 450°C. With increasing calcination temperature, TiO2 gradually transforms from anatase to rutile phase, with the highest anatase content formed at 450°C, consistent with XRD analysis. Defect dislocations in the anatase lattice can generate oxygen vacancies that capture photogenerated holes, promoting the separation of electrons and holes. The toluene removal efficiencies at calcination temperatures of 400°C, 450°C, 550°C, and 650°C were 68.45%, 76.42%, 67.9%, and 60%, respectively, all higher than the toluene degradation rate of pure TiO2 (54%). As the temperature rises, the TiO2 grains gradually grow and even sinter, causing pore collapse or blockage, reducing the specific surface area of ​​the catalyst, and thus reducing its catalytic activity. 4+ The radius and Ti 4+ The radius of TiO2 is quite different, CeO2 can be dispersed or covered on the surface of TiO2 to form a second phase. 4+ The ions easily enter the CeO2 lattice and even replace the Ce ions, forming Ti-O-Ce bonds. The second phase can inhibit the crystal growth of the rutile phase, and the phase transition from anatase to rutile in the CeO2-doped TiO2 composite material is suppressed.

[0100] Figure 7 The number of times the 1.5%-CeO2 / TiO2 / ACF photocatalyst is recycled to remove toluene. In order to explore the number of times the photocatalyst can be recycled in the process of gaseous toluene removal, the same material was used repeatedly to remove gaseous toluene, and the trends in its removal efficiency were compared. During the gas-solid phase catalytic reaction, intermediate products occupy active sites, resulting in catalyst deactivation. Therefore, after each reaction, the photocatalyst was regenerated by high-temperature calcination (450°C). After three cycles, there was no significant decrease in the removal efficiency of 1.5%-CeO2 / TiO2 / ACF for toluene, indicating that the photocatalyst has good cyclic stability.

[0101] The above description is merely a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification or equivalent variation based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. An ACF-loaded CeO2 / TiO2 photocatalyst, characterized in that: The photocatalyst includes CeO2 and TiO2 loaded on ACF. Based on the mass of the photocatalyst, the loading amount of TiO2 is 40wt%-80wt%, the loading amount of CeO2 is 0.5wt%-2.5wt%, and the particle size of the photocatalyst is 18nm-21nm.

2. The photocatalyst according to claim 1, characterized in that The photocatalyst exhibits characteristic diffraction peaks of TiO2 anatase phase at 2θ=25.3°(101), 37.9°(004), 48.05°(200), 55.02°(211), and 62.9°(204); and characteristic diffraction peaks of CeO2 cerium ore at 2θ=28.55°(111) and 33.08°(200).

3. The photocatalyst according to claim 2, characterized in that In the photocatalyst, the lattice fringe spacing of the (111) lattice plane of CeO2 is 0.32 nm.

4. The photocatalyst according to claim 3, characterized in that In the photocatalyst, the lattice fringe spacing of the (101) lattice plane of TiO2 is 0.35 nm.

5. The photocatalyst according to claim 4, characterized in that The sol-gel method is used to evenly disperse CeO2 between TiO2 particles, enhance the interaction between the two phases, and form a Ti-O-Ce bond.

6. The photocatalyst according to claim 5, characterized in that The specific surface area of ​​the photocatalyst is 530 m 2 / g-620m 2 / g.

7. A method for preparing the photocatalyst according to claims 1-6, characterized in that: The preparation method comprises the following steps: Step 1: Preparation of CeO2: Prepare a Ce salt solution and record it as solution A, and prepare an alkali solution of the same volume and record it as solution B; Add solution B dropwise into solution A, continue stirring until the mixture is uniform, pour into a high-pressure reactor, react at 120-200°C for 4-12 hours, centrifuge the reaction solution after completion of the reaction, wash, and vacuum dry to obtain a CeO2 precursor; Step 2: Preparation of ACF-loaded CeO2 / TiO2 photocatalyst: Tetrabutyl titanate, acetic acid and anhydrous ethanol are mixed together until uniformly stirred, which is recorded as solution C. The CeO2 precursor obtained in step 1, anhydrous ethanol, deionized water and acetic acid are mixed together until uniformly stirred, which is recorded as solution D. Under stirring conditions, solution D is slowly dripped into solution C, and stirring is continued. The mixture is allowed to stand for 12-36 hours to obtain an aged sol. ACF was added to the aged sol, and then the sol was subjected to ultrasonication, impregnation and drying. This process was recorded as composite material impregnation once; Optionally repeat the above steps, repeat the impregnation 1-3 times, place the impregnated composite material in a tube furnace, and calcine it at 400°C-650°C for 1-6h in a nitrogen environment to obtain an ACF-loaded CeO2 / TiO2 photocatalyst.

8. The preparation method according to claim 7, characterized in that In step 1, the mass concentration of the Ce salt solution is 0.01-0.1 mol.

9. The preparation method according to claim 7, characterized in that In step 1, the mass concentration of the alkaline solution is 0.01-0.1 mol.

10. Use of the photocatalyst according to claim 1-6, characterized in that: The photocatalyst is used to remove hydrocarbon volatile organic compounds. The photocatalyst is built into a photocatalytic reactor, 8-24W ultraviolet light is turned on, and then hydrocarbon volatile organic compounds are introduced to cause adsorption coupling photocatalytic reaction. The initial concentration of the hydrocarbon volatile organic compounds is controlled at 300-1100mg / m 3 , airspeed controlled at 1500-8000h -1 The volume of the photocatalyst is (10-15 cm)×(10-15 cm) block.

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