CeOx-TiO2 catalyst for efficient catalytic degradation of chlorine-containing VOCs as well as preparation method and application of CeOx-TiO2 catalyst

Abstract

The invention provides a CeOx-TiO2 catalyst for efficiently catalyzing and degrading chlorine-containing VOCs (Volatile Organic Compounds) as well as a preparation method and application of the CeOx-TiO2 catalyst, and belongs to the field of catalysts. The method comprises the following steps: dispersing a titanium source and a cerium source in deionized water, then adding ammonia water, stirring, filtering and washing until the pH value of filtrate is close to neutral, and drying and roasting to obtain the cerium nano island catalyst CeOx-TiO2 with uniformly dispersed titanium dioxide surface. According to the invention, the zeta negative potential of titanium dioxide and the positive potential of [Ce (OH) x] y < + > interact under an alkaline condition to prepare cerium active sites which are isolated and dispersed on the surface of titanium dioxide, and finally, precursor powder is calcined to prepare the Cl-VOCs catalyst with cerium nano islands dispersed on the surface of titanium dioxide. The Cl-VOCs catalyst prepared by the method has low-temperature purification performance on chlorobenzene and chlorine poisoning resistance, and meanwhile, the sintering resistance of the Ce active component is also effectively relieved.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and in particular to a CeO x -TiO2 highly efficient catalytic degradation of chlorine-containing VOCs catalyst and its preparation method and application. Background Art

[0002] PM2.5, PM10, O3, NO2 and SO2 are the primary pollutants of air pollution. Among them, the days with PM2.5, PM10 and O3 exceeding the standard account for more than 99% of the total number of days exceeding the standard. Volatile organic compounds (VOCs) are the main precursors of fine particulate matter PM2.5, PM10 and O3, and are important inducing factors of complex air pollution such as photochemical smog. Chlorinated volatile organic compounds (CVOCs) are one type of VOCs, and common ones include dichloromethane (DCM), dichloroethane (DCE), trichloroethylene (TCE), carbon tetrachloride (CT) and chlorobenzene (PhCl). As a commonly used organic solvent and semi-finished product in the chemical production process, they are widely used in medicine, leather making, electronics and pesticides. However, CVOCs contain Cl elements and have strong chemical stability, and their hazards and toxicity are more serious than general VOCs.

[0003] Therefore, it is urgent to study the treatment technology of CVOCs. Compared with treatment technologies such as absorption, adsorption, and condensation, the catalytic combustion method can convert CVOCs into harmless products such as CO2 and H2O. It has the characteristics of low conversion temperature and not easy to produce secondary pollution, and has gradually become a hot topic of current research. Among them, the activity of the catalyst directly affects the purification efficiency of CVOCs. Catalysts prepared by loading active components of cerium on carriers such as titanium dioxide and alumina can be used for catalytic oxidation of CVOCs. For example, the paper Catalytic Oxidation of Chlorobenzene over MnxCe1-xO2 / HZSM-5 Catalysts: A Study with Practical Implications published by Weng et al. in the journal Environmental Science & Technology focused on the effect of the catalyst prepared by wet impregnation method on the oxidation performance of chlorobenzene loaded with active components Mn and Ce on the HZSM-5 carrier, in which the active components were significantly poisoned by chlorine. The paper Catalytic oxidation of chlorobenzene over noble metals (Pd, Pt, Ru, Rh) and the distributions of polychlorinated by-products published by Liu et al. in Journal of Hazardous Materials studied the performance of catalysts impregnated with titanium dioxide and loaded with noble metals in degrading chlorobenzene, indicating that high-temperature aggregation of noble metals and chlorine poisoning are the main factors affecting the catalytic activity.Comparing the existing Ce-based loading technology and catalyst performance, for example, Yan et al. published a study on Three-dimensional porous CuO-modified CeO2-Al2O3 catalysts with chlorine resistance for simultaneous catalytic oxidation of chlorobenzene and mercury: Cu-Ce interaction and structure in the Journal of Hazardous Materials. The CuCeAl catalyst prepared by the template impregnation method was used for chlorobenzene oxidation, but the active components were easily poisoned, resulting in insufficient activity. Wang et al. published a study on TiO2-coated CeCoOx-PVP catalysts derived from Prussian blue analogue for synergistic elimination of NOx and o-DCB: The coupling of redox and acidity in the Chemical Engineering Journal. It was found that the Ce-based active components loaded on the titanium dioxide surface were prone to agglomeration, resulting in deactivation and other problems.

[0004] At present, the catalysts used for catalytic oxidation of CVOCs have problems such as high-temperature sintering, chlorine poisoning, and unstable catalyst activity. A large number of studies have shown that by introducing protection sites and sacrificial sites, the cerium active component can be dispersed and fixed to improve the activity of the catalyst. However, due to the poor high-temperature stability of the carrier and the active component cerium, the existing technology still cannot effectively alleviate the high-temperature sintering and chlorine resistance of the catalyst. Therefore, the key to catalytic oxidation technology to eliminate CVOCs lies in finding a catalyst that is resistant to high-temperature sintering, chlorine poisoning, simple in process, and low in cost. Summary of the invention

[0005] The purpose of the present invention is to provide a chlorine-containing VOCs catalyst with a simple preparation process and low cost, which can stably bind cerium nano-islands on the surface of a titanium dioxide carrier based on positive and negative potentials. The catalyst prepared by the present invention has a low-temperature purification performance of chlorobenzene (T 90 =357℃) and anti-chlorine poisoning performance, and can also alleviate the high temperature sintering of Ce active components.

[0006] The present invention provides a CeO x -The preparation method of a TiO2 catalyst for efficiently catalyzing the degradation of chlorine-containing VOCs comprises the following steps:

[0007] (1) dispersing a titanium source and a cerium source in deionized water to obtain a suspension;

[0008] (2) quickly adding ammonia water to the suspension until the pH value reaches 8.5-9.5, stirring for a period of time, filtering and washing until the pH value of the filtrate reaches 7-8, drying and calcining to obtain a cerium nano-island catalyst CeO with uniform dispersion on the surface of titanium dioxide. x -TiO2;

[0009] The molar ratio of the titanium source to the cerium source in step (1) is 20-294:1.

[0010] Furthermore, the titanium source in step (1) is selected from at least one of nano titanium dioxide, rutile titanium dioxide and anatase titanium dioxide.

[0011] Furthermore, the particle size of the nano titanium dioxide is 10nm-25nm.

[0012] Furthermore, the cerium source in step (1) is selected from at least one of cerium nitrate, cerium chloride and cerium sulfate.

[0013] Furthermore, step (1) adopts ultrasonic dispersion, and the ultrasonic time is 0.1-2h.

[0014] Furthermore, the concentration of the ammonia water in step (2) is 1-4 mol / L.

[0015] Furthermore, in step (2), the filtration and washing are performed until the pH value of the filtrate reaches 8.7.

[0016] Furthermore, the drying condition in step (2) is room temperature, and the calcination condition is heating to 300-600°C at a rate of 5-10°C / min and calcining for 4-12h.

[0017] The present invention also provides CeO prepared according to the method x -TiO2 highly efficient catalytic degradation of chlorine-containing VOCs catalyst, and the application of the catalyst in the field of purifying chlorine-containing VOCs.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention improves the loading process of the existing loaded Ce-based catalyst, utilizes positive and negative potentials to stably combine titanium dioxide and Ce species, and simultaneously forms independent nano-island active sites, thereby ensuring full utilization of the active sites and effectively improving the resistance to chlorine poisoning through separate action sites.

[0020] The present invention has the characteristics of simple preparation method, easy operation and implementation, and the prepared titanium dioxide loaded cerium nano-island catalyst has more stable oxidation activity and sintering resistance. Compared with precious metal catalysts, the titanium dioxide loaded cerium nano-island catalyst has lower production cost and is more suitable for actual waste gas treatment applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the X-ray diffraction pattern of the catalyst prepared in Examples 1-3 of the present invention.

[0022] Figure 2 The chlorobenzene oxidation performance of the catalysts prepared in Examples 1-3 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0023] The present invention provides a CeO x -The preparation method of a TiO2 catalyst for efficiently catalyzing the degradation of chlorine-containing VOCs comprises the following steps:

[0024] (1) dispersing a titanium source and a cerium source in deionized water to obtain a suspension;

[0025] (2) quickly adding ammonia water to the suspension until the pH value reaches 8.5-9.5, stirring for a period of time, filtering and washing until the pH value of the filtrate reaches 7-8, drying and calcining to obtain a cerium nano-island catalyst CeO with uniform dispersion on the surface of titanium dioxide. x -TiO2;

[0026] The molar ratio of the titanium source to the cerium source in step (1) is 20-294:1. Preferably, the molar ratio of the titanium source to the cerium source is 98:1.

[0027] Furthermore, the titanium source in step (1) is selected from at least one of nano titanium dioxide, rutile titanium dioxide and anatase titanium dioxide. Preferably, the titanium source is nano titanium dioxide.

[0028] Furthermore, the particle size of the nano titanium dioxide is 10nm-25nm.

[0029] Furthermore, the cerium source in step (1) is selected from at least one of cerium nitrate, cerium chloride and cerium sulfate. Preferably, the cerium source is cerous nitrate.

[0030] Furthermore, step (1) is carried out by ultrasonic dispersion, and the ultrasonic time is 0.1-2h, preferably, the ultrasonic time is 0.5h.

[0031] Furthermore, the concentration of the ammonia water in step (2) is 1-4 mol / L. Preferably, the concentration of the ammonia water is 2 mol / L.

[0032] Furthermore, it is necessary to quickly add ammonia water into the suspension during the stirring process.

[0033] Furthermore, in step (2), the filtration and washing are performed until the pH value of the filtrate reaches 8.7.

[0034] Furthermore, the drying condition in step (2) is room temperature, and the calcination condition is to increase the temperature to 300-600°C at a rate of 5-10°C / min and calcine for 4-12h. Preferably, the calcination condition is to increase the temperature to 500°C at a rate of 5°C / min and calcine for 12h.

[0035] The present invention also provides CeO prepared according to the method x -TiO2 highly efficient catalytic degradation of chlorine-containing VOCs catalyst, and the application of the catalyst in the field of purifying chlorine-containing VOCs.

[0036] The present invention utilizes the negative zeta potential of titanium dioxide under alkaline conditions and [Ce(OH) x ] y+ The interaction between the positive zeta potential of Ce and nano-titanium dioxide is used to stably combine the Ce sites with the nano-titanium dioxide. At the same time, the alkalinity of the titanium dioxide surface is controlled by filtration and washing, and the Ce species are isolated and dispersed on the titanium dioxide surface to obtain isolated and dispersed cerium active sites on the titanium dioxide surface. Finally, the precursor powder is calcined to prepare a chlorine-containing VOCs catalyst with dispersed cerium nanoislands on the titanium dioxide surface.

[0037] The present invention uses a simple, easy-to-operate and convenient process to prepare a catalyst with isolated and dispersed cerium active sites on the surface of titanium dioxide for catalytic oxidation treatment of chlorobenzene pollutants. At a reaction temperature of 300°C, the catalyst still has high catalytic activity and resistance to chlorine poisoning for chlorobenzene. At the same time, it can effectively overcome the catalyst deactivation problem of traditional catalysts that are easy to sinter and agglomerate at higher temperatures and the shortcomings of incomplete oxidation of chlorobenzene to release toxic products, and has the characteristics of being economical and environmentally friendly.

[0038] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0039] The experimental methods or test methods described in the following examples are conventional methods unless otherwise specified; the raw materials and auxiliary agents are obtained from conventional commercial channels or prepared by conventional methods unless otherwise specified.

[0040] Example 1

[0041] A CeO x -The preparation method of TiO2 highly efficient catalytic degradation of chlorine-containing VOCs catalyst, the specific steps are as follows:

[0042] (1) 1 g of nano-titanium dioxide (10 nm) was ultrasonically dispersed in 100 ml of deionized water for 0.5 h at an ultrasonic power of 120 W and a frequency of 40 kHz to obtain a heterogeneous solution; the heterogeneous solution was then transferred to a stirring table for stirring, 0.093 g of Ce(NO3)3·6H2O was weighed and added to the heterogeneous solution, and stirred for 3 min to obtain a suspension;

[0043] (2) then quickly adding 0.8 ml of 2 mol / L NH3·H2O to the suspension until the pH value reaches 7.8, stirring for 3 min, then filtering and washing until the pH value of the filtrate is about 8.7, and drying at room temperature overnight to obtain a dried yellow powder;

[0044] (3) The dried yellow powder was heated to 500°C at a rate of 5°C / min and calcined in a muffle furnace for 12 h. The resulting solid powder was a cerium nano-island catalyst with 3% CeO dispersed evenly on the surface of titanium dioxide. x -TiO2.

[0045] Example 2

[0046] A CeO x -The preparation method of TiO2 highly efficient catalytic degradation of chlorine-containing VOCs catalyst, the specific steps are as follows:

[0047] (1) 1 g of nano-titanium dioxide (10 nm) was ultrasonically dispersed in 100 ml of deionized water for 0.5 h at an ultrasonic power of 120 W and a frequency of 40 kHz to obtain a heterogeneous solution; the heterogeneous solution was then transferred to a stirring table for stirring, 0.156 g of Ce(NO3)3·6H2O was weighed and added to the heterogeneous solution, and stirred for 3 min to obtain a suspension;

[0048] (2) then quickly adding 0.8 ml of 2 mol / L NH3·H2O to the suspension until the pH value reaches 7.8, stirring for 3 min, then filtering and washing until the pH value of the filtrate is about 8.7, and drying at room temperature overnight to obtain a dried yellow powder;

[0049] (3) The dried yellow powder was heated to 500°C at a rate of 5°C / min and calcined in a muffle furnace for 12 h. The resulting solid powder was a cerium nano-island catalyst with 5% CeO dispersed evenly on the surface of titanium dioxide. x -TiO2.

[0050] Example 3

[0051] A CeO x -The preparation method of TiO2 highly efficient catalytic degradation of chlorine-containing VOCs catalyst, the specific steps are as follows:

[0052] (1) 1 g of nano-titanium dioxide (10 nm) was ultrasonically dispersed in 100 ml of deionized water for 0.5 h at an ultrasonic power of 120 W and a frequency of 40 kHz to obtain a heterogeneous solution; the heterogeneous solution was then transferred to a stirring table for stirring, 0.477 g of Ce(NO3)3·6H2O was weighed and added to the heterogeneous solution, and stirred for 3 min to obtain a suspension;

[0053] (2) then quickly adding 0.8 ml of 2 mol / L NH3·H2O to the suspension until the pH value reaches 7.8, stirring for 3 min, then filtering and washing until the pH value of the filtrate is about 8.7, and drying at room temperature overnight to obtain a dried yellow powder;

[0054] (3) The dried yellow powder was heated to 500°C at a rate of 5°C / min and calcined in a muffle furnace for 12 h. The resulting solid powder was a cerium nano-island catalyst with 15% CeO dispersed evenly on the surface of titanium dioxide. x -TiO2.

[0055] Comparative Example 1

[0056] A CeO x -The preparation method of TiO2 catalytic degradation of chlorine-containing VOCs catalyst, the specific steps are as follows:

[0057] (1) 1 g of nano-titanium dioxide (10 nm) was ultrasonically dispersed in 100 ml of deionized water for 0.5 h at an ultrasonic power of 120 W and a frequency of 40 kHz to obtain a heterogeneous solution; the heterogeneous solution was then transferred to a stirring table for stirring, 0.093 g of Ce(NO3)3·6H2O was weighed and added to the heterogeneous solution, and stirred for 3 min to obtain a suspension;

[0058] (2) then drying the suspension at room temperature overnight to obtain a dried yellow powder;

[0059] (3) The dried yellow powder was heated to 500°C at a rate of 5°C / min and calcined in a muffle furnace for 12 h. The resulting solid powder was a catalyst with cerium nano-islands dispersed on the surface of titanium dioxide (3% CeO). x -TiO2.

[0060] Performance Testing

[0061] 1. X-ray diffraction analysis was performed on the catalysts prepared in Examples 1-3. The results are as follows: Figure 1 As shown by Figure 1 It can be seen that with the increase in the number of Ce nano-islands on the titanium dioxide surface, the peak of cerium oxide species begins to appear, which indicates that low-content Ce can be highly dispersed on the carrier surface in the form of nano-islands, confirming that the combination of positive and negative potentials is beneficial to promote the dispersion and formation of Ce nano-islands, thereby promoting the improvement of the catalytic oxidation performance of chlorobenzene.

[0062] 2. The catalysts prepared in Examples 1-3 and Comparative Example 1 were tested for chlorobenzene catalytic oxidation activity. The test method was as follows: 0.1 g of catalyst (40-60 mesh) was placed in a fixed bed reactor, and the simulated gas was used to bubble liquid chlorobenzene into the reaction system through compressed air, wherein the chlorobenzene concentration was controlled at 500±10 ppm by air, the total gas flow rate was 50 ml / min, and the mass space velocity was 30000 ml / (g*h). The concentrations of chlorobenzene and CO2 were monitored in real time by online chromatography. The T values ​​of different catalysts for chlorobenzene oxidation were 90 and T 50 The results are shown in Table 1:

[0063] T used in activity test 90 (℃) and T 50 (℃) represent the reaction temperatures when the CVOCs conversion rate is 50% and 90%, respectively.

[0064] Table 1

[0065] Group catalyst <![CDATA[Degradation of chlorobenzene T 90 (°C)]]> <![CDATA[Degradation of chlorobenzene T 50 (℃)]]> Example 1 <![CDATA[3%CeOx-TiO2]]> 357 284 Example 2 <![CDATA[5%CeOx-TiO2]]> 387 327 Example 3 <![CDATA[15%CeOx-TiO2]]> 395 328 Comparative Example 1 <![CDATA[3%CeO x / TiO2]]> >400 327

[0066] As shown in Table 1, the 3% CeOx-TiO2 catalyst prepared in Example 1 has the best low-temperature catalytic activity for chlorobenzene, while the 3% CeOx-TiO2 catalyst prepared in Comparative Example 1 without alkaline solution treatment has poor low-temperature catalytic activity, indicating that the alkaline environment is conducive to the stable combination of titanium dioxide and Ce species, and the formation of independent nano-island active sites, so that the Cl-VOCs catalyst prepared by the present invention has low-temperature purification performance for chlorobenzene (CB). It also shows that by controlling the number of cerium nano-islands on the surface of titanium dioxide, the overall activity of the catalyst can be regulated, thereby achieving complete oxidation of chlorobenzene.

[0067] Figure 2 The chlorobenzene oxidation performance of the catalysts prepared in Examples 1-3 of the present invention and Comparative Example 1. Figure 2 It can be seen that the catalysts prepared in Examples 1-3 can exhibit excellent catalytic activity at high temperatures and have a certain anti-sintering ability, which further improves the practical application potential of the catalysts of the present invention.

[0068] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A CeO x - A method for preparing a TiO2 catalyst for high-efficiency catalytic degradation of chlorine-containing VOCs, characterized in that: The following steps are involved: (1) dispersing a titanium source and a cerium source in deionized water to obtain a suspension; (2) quickly adding ammonia water to the suspension until the pH value reaches 8.5-9.5, stirring for a period of time, filtering and washing until the pH value of the filtrate reaches 7-8, drying and calcining to obtain a cerium nano-island catalyst CeO with uniform dispersion on the surface of titanium dioxide. x -TiO2; The molar ratio of the titanium source to the cerium source in step (1) is 20-294:

1.

2. CeO according to claim 1 x - A method for preparing a TiO2 catalyst for high-efficiency catalytic degradation of chlorine-containing VOCs, characterized in that: The titanium source in step (1) is selected from at least one of nano titanium dioxide, rutile titanium dioxide and anatase titanium dioxide.

3. CeO according to claim 2 x - A method for preparing a TiO2 catalyst for high-efficiency catalytic degradation of chlorine-containing VOCs, characterized in that: The particle size of the nano titanium dioxide is 10nm-25nm.

4. CeO according to claim 1 x - A method for preparing a TiO2 catalyst for high-efficiency catalytic degradation of chlorine-containing VOCs, characterized in that: The cerium source in step (1) is selected from at least one of cerium nitrate, cerium chloride and cerium sulfate.

5. CeO according to claim 1 x - A method for preparing a TiO2 catalyst for high-efficiency catalytic degradation of chlorine-containing VOCs, characterized in that: The step (1) is carried out by ultrasonic dispersion, and the ultrasonic time is 0.1-2h.

6. CeO according to claim 1 x - A method for preparing a TiO2 catalyst for high-efficiency catalytic degradation of chlorine-containing VOCs, characterized in that: The concentration of the ammonia water in step (2) is 1.5-4 mol / L.

7. CeO according to claim 1 x - A method for preparing a TiO2 catalyst for high-efficiency catalytic degradation of chlorine-containing VOCs, characterized in that: The filtering and washing in step (2) is carried out until the pH value of the filtrate reaches 8.

7.

8. CeO according to claim 1 x - A method for preparing a TiO2 catalyst for high-efficiency catalytic degradation of chlorine-containing VOCs, characterized in that: The drying condition in step (2) is room temperature, and the calcination condition is to increase the temperature to 300-600°C at a rate of 5-10°C / min and calcine for 4-12h.

9. CeO prepared according to the method according to any one of claims 1 to 8 x -TiO2 is a highly efficient catalyst for the degradation of chlorine-containing VOCs.

10. CeO prepared according to the method according to any one of claims 1 to 8 x -TiO2 highly efficient catalytic degradation of chlorine-containing VOCs catalyst, or the use of the catalyst according to claim 9 in the field of purifying chlorine-containing VOCs.

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