Pd / TiO2 material with sulfur resistance, preparation method of Pd / TiO2 material and application of Pd / TiO2 material in catalytic oxidation of toluene

Abstract

The invention discloses a Pd / TiO2 composite nano-material with sulfur resistance, a preparation method of the Pd / TiO2 composite nano-material and application of the Pd / TiO2 composite nano-material in catalytic oxidation of volatile organic pollutants, and belongs to the technical field of preparation of catalytic materials. The preparation method comprises the following steps: 1) weighing a certain amount of TiO2 and calcining at 500 DEG C for 4 hours; (2) weighing the carrier obtained in the step (1), putting the carrier into a beaker, adding deionized water to disperse the carrier, adding a certain amount of Pd (NO3) 2 solution in the stirring process, and magnetically stirring at normal temperature; and (3) carrying out water bath evaporation drying on the solution obtained in the step (2), carrying out vacuum drying after evaporation drying, cooling to room temperature, grinding, and calcining to obtain the Pd / TiO2 composite nano material. According to the preparation method of Pd / TiO2 for promoting relatively strong interaction of metal carriers by adopting a wet impregnation method, the sulfur-resistant practicability of Pd / TiO2 is strong, and the preparation method has a potential application prospect in the aspect of removal and treatment of VOCs (Volatile Organic Compounds).

Description

Technical Field

[0001] The invention belongs to the technical field of material preparation and thermal catalytic toluene oxidation, and particularly relates to a Pd / TiO 2 The invention relates to a preparation method of the material and its application in catalytic toluene oxidation. Background Art

[0002] Volatile organic compounds (VOCs) as a source of ozone and PM 2.5 Toluene is an important precursor of VOCs and has attracted extensive attention. As an important component of industrial solvents and fuels, toluene is often used as a model pollutant for research. Catalytic combustion technology stands out among many technologies for removing volatile organic compounds due to its high economic feasibility, low production of secondary pollutants, and ability to completely degrade VOCs components under low temperature conditions. It has become the control technology with the most development potential and prospects.

[0003] Palladium (Pd)-based catalysts are more likely to adsorb VOCs due to their unsaturated d-orbital electronic characteristics. At the same time, their excellent CH bond activation ability makes Pd-based catalysts widely used in the field of VOCs catalytic oxidation. However, catalyst deactivation is a common problem in the field of catalytic combustion. Among them, the phenomenon of sulfur poisoning of catalysts caused by sulfides has attracted widespread attention. Catalyst sulfur poisoning comes from SO 2 It is easily adsorbed on the catalyst surface and then oxidized to sulfite or sulfate, thereby inhibiting further catalytic reactions. 2 , but it is widely used to construct sulfur-resistant catalysts because the sulfates it generates are not stable, which makes it difficult for sulfates to deposit on the catalyst surface.

[0004] By Pd / TiO 2 Conduct SO 2 Pretreatment can accurately quantify the degree of sulfur poisoning and analyze the changes in its structure and chemical properties. This method is relatively simple, easy to implement, and closer to actual working conditions. However, so far, no wet impregnation method has been used to load palladium nanoclusters on TiO 2 Report on its application in thermal catalytic toluene oxidation and sulfur-resistant system. Summary of the invention

[0005] In view of the shortcomings and deficiencies of the prior art, the present invention aims to provide a Pd / TiO 2 The preparation method of the composite nanomaterial has a simple preparation process and is green and pollution-free. Another object of the present invention is to provide a Pd / TiO 2 The application of composite nanomaterials has potential application prospects in the thermal catalytic toluene oxidation and sulfur-resistant system.

[0006] In order to solve the above problems, the technical solution adopted by the present invention is as follows: a Pd / TiO 2 Composite nanomaterials, based on TiO 2 Pd / TiO was prepared by wet impregnation method. 2 Composite nanomaterials, the Pd nanoclusters in TiO 2 The loading amount is 0.1-1.0wt%.

[0007] Preferably, the Pd nanoclusters are in the TiO 2 The loading on was 0.5 wt%.

[0008] The present invention provides the Pd / TiO 2 The preparation method of the composite nanomaterial comprises the following steps: 1) TiO 2 Pre-treating and calcining the mixture, and dispersing the mixture with deionized water to obtain a dispersed solution; 2) Change Pd(NO 3 ) 2 Slowly add dropwise to each dispersed solution and stir magnetically; 3) The stirred solution is evaporated to dryness, dried, cooled to room temperature, ground, and calcined to obtain Pd / TiO 2 Composite nanomaterials.

[0009] Preferably, in step 1), TiO 2 The pretreatment calcination temperature was 500 °C, the heating rate was 5 °C / min, and the calcination time was 4 h.

[0010] Preferably, in step 2), Pd(NO 3 ) 2 The concentration was 0.03 M and the volume was 3 mL.

[0011] Preferably, in step 2), the magnetic stirring time is 3 h.

[0012] Preferably, in step 3), evaporation to dryness is performed in an oil bath, and drying is performed in a vacuum.

[0013] Preferably, in step 3), the oil bath evaporation temperature is 110°C, the vacuum drying temperature is 80°C, and the drying time is 12 h.

[0014] Preferably, in step 3), the calcination temperature is 400°C, the heating rate is 5°C / min, and the calcination time is 6h.

[0015] The Pd / TiO 2 The composite nanomaterial can be used in the thermal catalytic toluene oxidation anti-sulfur system.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) Pd / TiO prepared by the present invention 2 The catalyst has a green and environmentally friendly preparation process and is simple to operate. The material has good environmental stability and has potential application prospects in solving the sulfur resistance of thermal catalytic toluene oxidation. (2) The present invention uses a simple wet impregnation method to 2 The defects on the surface anchor the active species Pd clusters, forming a strong interface interaction; (3) Pd / TiO prepared by the present invention 2 It can be used as a catalyst with excellent sulfur resistance. 2 Afterwards, due to Pd / TiO 2 Unstable sulfate is formed on the surface. When SO 2 The sulfate generated by the reaction with the catalyst is transferred to the carrier TiO 2 When overflow occurs, the sulfate on the support decomposes; therefore, this Pd / TiO 2 Composite materials have broad prospects in the field of thermal catalytic toluene oxidation and sulfur-resistant systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Sample SO prepared in Example 1-5 2 XRD spectra before and after pretreatment.

[0018] Figure 2 Sample SO prepared in Example 1-5 2 FT-IR spectra before and after pretreatment.

[0019] Figure 3 Sample SO prepared in Example 1-5 2 TG spectra before and after pretreatment.

[0020] Figure 4 Sample SO prepared in Example 1-5 2 S 2p XPS spectra before and after pretreatment.

[0021] Figure 5 The sample SO prepared in Example 1-2 2 Activity diagram of thermal catalytic toluene oxidation before and after pretreatment. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described below in conjunction with specific embodiments. In the following embodiments, unless otherwise specified, the technical means used are conventional means well known to those skilled in the art. Example 1

[0023] Preparation of Pd / TiO 2 The composite nanomaterial comprises the following steps: (1) TiO 2 The pretreatment was carried out by calcining at 500 °C for 4 h, and then dispersed with deionized water to obtain a dispersed solution; (2) Pd(NO) with a volume of 3 mL and a concentration of 0.03 M was added. 3 ) 2 Slowly add dropwise to each dispersed solution and stir magnetically for 3 h; (3) The stirred solution was evaporated to dryness in an oil bath at 110 °C, dried in a vacuum oven at 80 °C for 12 h, cooled to room temperature, ground, and calcined at 400 °C for 6 h to obtain Pd / TiO 2 Composite nanomaterials, the resulting Pd nanoclusters on TiO 2 The loading on was 0.5 wt %. Example 2

[0024] Preparation of Pd / CeO 2 The composite nanomaterial comprises the following steps: (1) CeO 2 The pretreatment was carried out by calcining at 500 °C for 4 h, and then dispersed with deionized water to obtain a dispersed solution; (2) Pd(NO) with a volume of 3 mL and a concentration of 0.03 M was added. 3 ) 2 Slowly add dropwise to each dispersed solution and stir magnetically for 3 h; (3) The stirred solution was evaporated to dryness in an oil bath at 110 °C, vacuum dried at 80 °C for 12 h, cooled to room temperature, ground, and calcined at 400 °C for 6 h to obtain Pd / CeO 2 Composite nanomaterials, the resulting Pd nanoclusters in CeO 2 The loading on was 0.5 wt %. Example 3

[0025] Preparation of Pd / SiO 2 The composite nanomaterial comprises the following steps: (1) SiO 2 The pretreatment was carried out by calcining at 500 °C for 4 h, and then dispersed with deionized water to obtain a dispersed solution; (2) Pd(NO) with a volume of 3 mL and a concentration of 0.03 M was added. 3 ) 2 Slowly add dropwise to each dispersed solution and stir magnetically for 3 h; (3) The stirred solution was evaporated to dryness in an oil bath at 110 °C, dried in a vacuum oven at 80 °C for 12 h, cooled to room temperature, ground, and calcined at 400 °C for 6 h to obtain Pd / TiO 2 Composite nanomaterials, the resulting Pd nanoclusters on SiO 2 The loading on was 0.5 wt %. Example 4

[0026] Preparation of Pd / Al 2 O 3 The composite nanomaterial comprises the following steps: (1) Al 2 O 3 The pretreatment was carried out by calcining at 500 °C for 4 h, and then dispersed with deionized water to obtain a dispersed solution; (2) Pd(NO) with a volume of 3 mL and a concentration of 0.03 M was added. 3 ) 2 Slowly add dropwise to each dispersed solution and stir magnetically for 3 h; (3) The stirred solution was evaporated to dryness in an oil bath at 110 °C, vacuum dried at 80 °C for 12 h, cooled to room temperature, ground, and calcined at 400 °C for 6 h to obtain Pd / Al 2 O 3 Composite nanomaterials, the resulting Pd nanoclusters in Al 2 O 3 The loading on was 0.5 wt %. Example 5

[0027] The palladium nanoparticle composites prepared in Examples 1-4 were subjected to SO 2 Preprocessing includes the following steps: (1) 0.6 g of the palladium nanoparticle composite material was poured into a porcelain boat and placed in a tube furnace. The temperature was then programmed to rise from room temperature at a rate of 5 °C min in an air atmosphere. -1 The heating rate was increased to 300 °C with an air flow rate of 180 mL min -1 ; (2) When the temperature rises to 300 °C, another 1% SO 2 / N 2 Gas and constant temperature for 2 h, 1% SO 2 / N 2 The gas flow rate was 20 mL min -1 ; (3) Stop the program and stop accessing SO 2 / N 2 The gas is then cooled down naturally in the tube furnace to obtain Pd / TiO 2 -S, Pd / CeO2 -S, Pd / SiO 2 -S, Pd / Al 2 O 3 -S composite nanomaterials.

[0028] Figure 1 The XRD spectra of the samples prepared in Examples 1-5 show that no diffraction signals of Pd species were detected in the XRD spectra, indicating that the Pd species on the sample surface has a high dispersion. 2 There is no obvious change in the XRD spectrum after pretreatment, which indicates that 2 During the pretreatment process, no 2 The crystal structure is destroyed and no crystal diffraction peaks of sulfate are detected.

[0029] Figure 2 FT-IR spectra of samples prepared in Examples 1-5, Figure 2 It can be seen that the samples are all at 3390 and 1630 cm -1 The stretching vibration peak and deformation vibration peak attributed to the surface hydroxyl (OH) appeared at Pd / TiO 2 -S at 1120 cm -1 A weak broad peak of bidentate sulfate anion (S=O symmetric stretching vibration) appears at 1040 cm -1 A weak corresponding shoulder peak (SO antisymmetric stretching vibration) appears. This indicates that Pd / TiO 2 Composite nanomaterials in SO 2 Less sulfate is formed after pretreatment.

[0030] Figure 3 The TG spectra of the samples prepared in Example 1-5 are as follows: Figure 3 It can be seen that Pd / TiO 2 The weight loss of the -S sample in the temperature range of 300-700 °C is attributed to SO 2 TiSO after pretreatment 4 and PdSO 4 decomposition.

[0031] Figure 4 The S 2p XPS spectra of the samples prepared in Examples 1-5 are shown in FIG. Figure 4 It can be seen that the binding energy of 169.1 eV is attributed to S 6+ The characteristic peaks of the species indicate that the sample is in SO 2 After pretreatment, sulfate species were generated. 2 The characteristic peak of the -S sample shifts toward lower binding energy compared to the binding energy of other samples, which indicates that the interaction between the sulfate on its surface and the sample is weaker and it is easier to decompose. Example 6

[0032] The catalyst prepared in Examples 1-5 was applied to the thermal catalytic toluene oxidation reaction, and the specific steps were as follows: The catalytic activity of toluene was tested on a fixed bed microreactor built in the laboratory. Under a constant temperature water bath at 25 °C, 1000 ppm toluene was introduced into the mixing buffer bottle in a steady airflow state by bubbling. The mixed gas was fully mixed in the mixing buffer bottle and then entered the reactor. The air flow rate was 50 ml min -1 The tail gas after the reaction was then detected in real time online by gas chromatography to detect and analyze the concentration of gas components after the reaction. Weigh 100 mg of the catalyst after sieving through a 40-60 mesh sieve and put it into a quartz tube, then set the temperature program and start the program temperature reaction from 100 °C. Keep each test point for 30 minutes, collect 3 parallel samples at each point, and take the average value as the activity result. Toluene conversion rate (X toluene ,%) is calculated as follows: X toluene (%) = (C in - C out ) / C in × 100 % Among them, C in and C out are the toluene concentrations at the inlet and outlet of the sample gas, respectively. Figure 5 The thermal catalytic toluene oxidation performance diagram of the samples prepared in Examples 1 and 2 is shown in FIG. Figure 5 It can be seen that Pd / TiO 2 With SO 2 Pd / TiO after pretreatment 2 -S has a comparable toluene oxidation activity, which is due to the Pd / TiO 2 By SO 2 The sulfate generated after pretreatment is 2 is not stable, so when SO 2 The sulfate generated by the reaction with the catalyst is transferred to the carrier TiO 2 When “overflow” occurs, the sulfate on the support will decompose, thereby reducing the deposition of sulfate on the surface and protecting the activity of the catalyst. Therefore, compared with other samples, Pd / TiO 2 The composite nanomaterial has excellent anti-sulfur properties.

[0033] 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 Pd / TiO2 composite nanomaterial, characterized in that: The Pd / TiO2 composite nanomaterial is prepared by using TiO2 and Pd nanoclusters as raw materials through a wet impregnation method, wherein the loading amount of the Pd nanoclusters on TiO2 is 0.1-1.0wt%.

2. The Pd / TiO2 composite nanomaterial according to claim 1, characterized in that: The loading amount of the Pd nanoclusters on TiO2 is 0.5 wt%.

3. The method for preparing the Pd / TiO2 composite nanomaterial according to claim 1, characterized in that: The following steps are involved: 1) Pre-treating and calcining TiO2, and dispersing it with deionized water to obtain a dispersed solution; 2) Slowly add Pd(NO3)2 dropwise to each dispersed solution and stir magnetically; 3) The stirred solution is evaporated to dryness, dried, cooled to room temperature, ground, and then calcined to obtain Pd / TiO2 composite nanomaterials.

4. The method for preparing the Pd / TiO2 composite nanomaterial according to claim 3, characterized in that: In the step 1), the TiO2 pretreatment calcination temperature is 400-600 o C, heating rate is 2-10 o C / min, and the calcination time was 4 h.

5. The method for preparing the Pd / TiO2 composite nanomaterial according to claim 3, characterized in that: In the step 2), the concentration of Pd(NO3)2 is 0.01-0.09M and the volume is 1-9 mL.

6. The method for preparing the Pd / TiO2 composite nanomaterial according to claim 3, characterized in that: In the step 2), the magnetic stirring time is 3 h.

7. The method for preparing the Pd / TiO2 composite nanomaterial according to claim 3, characterized in that: In the step 3), the evaporation to dryness is performed in an oil bath, and the drying is performed in a vacuum drying.

8. The method for preparing the Pd / TiO2 composite nanomaterial according to claim 7, characterized in that: In step 3), the oil bath evaporation temperature is 110 o C, vacuum drying temperature is 80 o C, drying time is 12 h.

9. The method for preparing the Pd / TiO2 composite nanomaterial according to claim 3, characterized in that: In the step 3), the calcination temperature is 300-500 o C, heating rate is 2-10 o C / min, and the calcination time was 6 h.

10. The Pd / TiO2 composite nanomaterial according to claim 1 is used in a thermal catalytic toluene oxidation anti-sulfur system.

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