Preparation method of PtRu bimetallic catalyst and application of PtRu bimetallic catalyst in catalytic oxidation of multi-component volatile organic compounds

Abstract

The invention discloses a preparation method of a PtRu bimetallic catalyst and application of the PtRu bimetallic catalyst in catalytic oxidation of multi-component volatile organic compounds, and belongs to the field of catalysis. The preparation method comprises the following steps: firstly, preparing a P-CeO2 nanorod by using an in-situ doping hydrothermal method; ptRu nanoparticles are prepared by adopting a polyvinyl alcohol protected sodium borohydride reduction method, the PtRu nanoparticles are loaded on P-CeO2 nanorods, a loaded sample is sequentially subjected to suction filtration, washing and drying treatment, an obtained solid is ground and then transferred into a muffle furnace, the temperature is increased to 400 DEG C from the room temperature at the speed of 5 DEG C / min, and the PtRu / P-CeO2 catalyst is obtained after calcination is conducted for 6 h. The preparation process route is simple, the operation steps are easy to control, excellent thermal stability and good catalytic selectivity are achieved, no by-product is generated in the reaction process, the preparation and application links follow the green chemistry concept, and the catalyst is especially suitable for catalytic elimination of common methylbenzene and DCM mixtures in industrial tail gas.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial preparation, and relates to a PtRu bimetallic catalyst, its preparation method, and its application in the catalytic oxidation of multi-component volatile organic compounds. Background Technology

[0002] The pharmaceutical industry, as a major emitter of volatile organic compounds (VOCs), produces waste gases characterized by large emissions, complex composition, and high toxicity. Toluene and dichloromethane (DCM), commonly used solvents in the pharmaceutical industry, are widely present in various stages of pharmaceutical production. Toluene is highly volatile at room temperature and has irritant and anesthetic properties; inhalation of high concentrations of toluene vapor can cause headaches and nausea, and long-term exposure may damage liver and kidney function. DCM also possesses carcinogenic, teratogenic, and mutagenic properties, primarily entering the human body through the respiratory tract or skin contact; short-term exposure may cause dizziness, nausea, and mucosal irritation. Catalytic oxidation is considered an ideal method for VOCs control due to its high catalytic efficiency, low energy consumption, and lack of secondary pollution. The key to this method is the development of catalysts with good low-temperature oxidation activity, high-temperature stability, and low cost.

[0003] Currently, catalysts used for the catalytic oxidation of VOCs are mainly divided into two categories: transition metal oxide catalysts and supported noble metal catalysts. It is worth noting that chlorinated volatile organic compounds (CVOCs) are significantly more difficult to oxidize completely than traditional VOCs due to their molecular structure. Furthermore, single-component catalysts often fail to simultaneously meet the three core requirements of low-temperature activity, reaction selectivity, and long-term stability. Therefore, the functional synergy and rational coordination of multiple components has become a key approach to developing catalytic systems with high activity, high selectivity, and high stability. Rare earth metal oxide CeO2 possesses high oxygen storage capacity and abundant oxygen vacancies; however, it is prone to deactivation due to the accumulation of chlorine species. In view of this, this invention first uses in-situ hydrothermal doping to prepare a phosphorus (P)-doped cerium oxide support (P-CeO2), and then loads PtRu bimetallic compounds onto the P-CeO2 support via impregnation. By precisely controlling the P content and the loading of the PtRu bimetallic compounds, a PtRu / P-CeO2 catalyst was successfully prepared. Experimental results show that this catalyst can efficiently catalyze the elimination of toluene and DCM mixtures, while exhibiting excellent durability and good selectivity: during a continuous reaction process lasting up to 24 hours, the catalyst showed no significant deactivation and no harmful chlorine-containing byproducts were generated. To our knowledge, there are currently no reports on the use of PtRu / P-CeO2 catalysts for the catalytic oxidation of toluene and DCM mixtures. In summary, this invention is significantly innovative, and its preparation and application follow green chemistry principles throughout, promising to provide an efficient, stable, and environmentally friendly technical solution for industrial organic waste gas purification and VOCs treatment. Summary of the Invention

[0004] The purpose of this invention is to prepare a PtRu bimetallic catalyst for the catalytic oxidation of toluene and DCM mixtures. The PtRu / P-CeO2 catalyst prepared by in-situ doping hydrothermal method and sodium borohydride (NaBH4) reduction method exhibits excellent activity and durability in the catalytic oxidation of toluene and DCM mixtures.

[0005] A PtRu bimetallic catalyst for the catalytic oxidation of a mixture of toluene and DCM, and a method for its preparation thereof, comprising the following steps:

[0006] (1) Preparation of P-CeO2 catalyst:

[0007] Cerium nitrate hexahydrate, trimethyl phosphate, and NaOH were added sequentially to deionized water and stirred at room temperature for 30 min. The mixture was then transferred to a polytetrafluoroethylene-lined reactor and hydrothermally reacted at 100 °C for 24 h. After cooling to room temperature, the mixture was washed by centrifugation with deionized water and ethanol, and dried overnight in an oven at 80 °C. The resulting solid was ground and transferred to a muffle furnace, where it was heated from room temperature to 400 °C at a rate of 5 °C / min and calcined for 6 h to obtain the P-CeO2 catalyst support.

[0008] (2) Preparation of PtRu / P-CeO2 catalyst:

[0009] The preparation process is as follows: Under ice-water bath and stirring conditions, a certain amount of H2PtCl6∙6H2O solution was first added to the PVA solution. After vigorous stirring for 30 min, NaBH4 solution was quickly added to the above Pt-containing solution. This mixed solution is designated as solution A. Similarly, under ice-water bath and stirring conditions, a certain amount of RuCl3 solution was mixed with the PVA solution and stirred vigorously for 30 min. Then, NaBH4 solution was quickly added to the above Ru-containing solution. This mixed solution is designated as solution B. Solution A and solution B were then mixed and stirred vigorously for 10 min to obtain a PtRu-containing mixed solution. The P-CeO2 catalyst support was impregnated in the PtRu-containing mixed solution and stirred for 6 h. The mixed solution was then filtered and washed with deionized water and ethanol, and dried in an oven at 80 ℃ for 12 h. Finally, the obtained solid was ground and transferred to a muffle furnace, and heated from room temperature to 400 ℃ at a heating rate of 5 ℃ / min, and calcined for 6 h. After h, the PtRu / P-CeO2 catalyst was obtained.

[0010] The P loading in the P-CeO2 catalyst is 0.3-4 wt%, for example 0.36 wt%, and the theoretical PtRu loading in the PtRu / P-CeO2 catalyst is 0.8 wt%-1.5%, with a Pt to Ru mass ratio of 0.8:1-1:1.

[0011] The catalyst obtained in this invention is used for the catalytic oxidation of a mixture of toluene and DCM to produce CO2, H2O, and HCl. The mixed gas containing toluene and DCM undergoes a catalytic reaction under oxygen-containing conditions using the PtRu / P-CeO2 catalyst obtained in this invention. The catalytic oxidation of the toluene and DCM mixture was successfully achieved at a relatively low temperature of 310 °C, and no significant deactivation was observed during the reaction process, which lasted up to 24 hours.

[0012] Catalyst evaluation:

[0013] The obtained catalyst was tested for activity at different temperatures in a gaseous environment of 500 ppm DCM + 500 ppm toluene + 20 vol% O2 + N2 equilibrium and a space velocity (GHSV) of 24,000 mL / (gh).

[0014] The preparation process of this invention is simple, the operation steps are easy to control, and it exhibits excellent thermal stability and good catalytic selectivity. No polychlorinated byproducts are produced during the reaction, and both the preparation and application stages adhere to green chemistry principles. It is particularly suitable for the catalytic elimination of toluene and DCM mixtures commonly found in industrial exhaust gases. It has significant practical application value and broad application prospects in the fields of air pollution control and ecological environment governance.

[0015] The crystal structure and morphology of the prepared catalyst were characterized using a D8 ADVANCE X-ray diffractometer (XRD) and a JEOL-2010 transmission electron microscope (TEM). The catalytic oxidation performance and durability of the catalyst for toluene and dichloromethane were evaluated using a Shimadzu GC-2014 gas chromatograph (GC). The results showed that the catalyst exhibited a well-defined nanorod morphology. TEM scans revealed a uniform distribution of elements on the catalyst surface, with Pt and Ru exhibiting a particulate state. The PtRu / P-CeO2 catalyst not only possesses excellent activity and stability but also exhibits good catalytic selectivity. No polychlorinated byproducts were detected, and the entire process from preparation to application adhered to green chemistry principles, demonstrating excellent environmental compatibility. Attached Figure Description

[0016] Figure 1 The images show the XRD patterns of the prepared catalysts. From top to bottom, they represent the XRD patterns of PtRu / P-CeO2, Pt / PP-CeO2, Ru / P-CeO2, P-CeO2, and CeO2.

[0017] Figure 2 The images show TEM, HRTEM, and HAADF-STEM images of the PtRu / P-CeO2 catalyst. (A) is the TEM image of PtRu / P-CeO2, (B, C) are the HRTEM images of the PtRu / P-CeO2 catalyst, and (D) is the HAADF-STEM image of the PtRu / P-CeO2 catalyst, along with elemental surface scans of Ce, O, P, Pt, and Ru.

[0018] Figure 3 The graphs show the catalytic activity of the prepared catalyst and its comparative sample against (A) toluene and (B) DCM.

[0019] Figure 4 This is a graph showing the durability and thermal stability of the PtRu / P-CeO2 catalyst. Detailed Implementation

[0020] To further illustrate the present invention, the following embodiments are provided in detail, but the present invention is not limited to the following embodiments.

[0021] Example 1

[0022] (1) Preparation of CeO2 catalyst:

[0023] CeO2 catalyst was prepared using a traditional hydrothermal method, with the following typical preparation process: 1.52 g of cerium nitrate hexahydrate was dissolved in 70 mL of deionized water, and 16.98 g of NaOH was added. The mixture was stirred at room temperature for 30 min. The solution was then transferred to a polytetrafluoroethylene-lined reactor and hydrothermally reacted at 100 °C for 24 h. After cooling to room temperature, the precipitate was washed with deionized water by centrifugation until the supernatant was neutral. The precipitate was washed twice with ethanol and dried overnight in an oven at 80 °C. The resulting solid was ground and transferred to a muffle furnace, where it was calcined from room temperature to 400 °C at a rate of 5 °C / min for 6 h to obtain the CeO2 catalyst.

[0024] (2) Preparation of P-CeO2 catalyst:

[0025] The P-CeO2 catalyst was prepared using a traditional hydrothermal method, with the following typical preparation process: 1.52 g of cerium nitrate hexahydrate and 0.084 mL of trimethyl phosphate were dissolved together in 70 mL of deionized water, and 16.98 g of NaOH was added. The mixture was stirred at room temperature for 30 min. Then, it was transferred to a polytetrafluoroethylene-lined reactor and hydrothermally reacted at 100 °C for 24 h. After cooling to room temperature, the precipitate was washed with deionized water by centrifugation until the supernatant was neutral. The precipitate was washed twice with ethanol and dried overnight in an oven at 80 °C. The resulting solid was ground and transferred to a muffle furnace, where the temperature was increased from room temperature to 400 °C at a rate of 5 °C / min, and calcined for 6 h to obtain the P-CeO2 catalyst.

[0026] (3) Preparation of Pt / P-CeO2 and Ru / P-CeO2 catalysts:

[0027] A Pt / P-CeO2 catalyst was prepared using a polyvinyl alcohol (PVA)-protected NaBH4 reduction method. The typical preparation process is as follows: Under ice-water bath and stirring conditions, 1.98 mL of a 10 g / L H2PtCl6∙6H2O solution was first added to a 2 g / L PVA solution (Pt / PVA mass ratio of 1:1.2). After vigorous stirring for 10 min, 1.0 g of P-CeO2 support was impregnated in the Pt-containing solution, and stirring continued for 30 min. Then, freshly prepared 0.1 mol / L NaBH4 solution was rapidly added to the above Pt-containing solution, with a Pt / NaBH4 molar ratio of 1:5. After stirring for 6 h, the catalyst was filtered and washed with deionized water and ethanol, and then dried in an oven at 80 °C for 12 h. Finally, the obtained solid was ground and transferred to a muffle furnace, and heated from room temperature to 400 °C at a heating rate of 5 °C / min. After calcination for 6 h, a Pt / P-CeO2 catalyst was obtained.

[0028] Similar to the preparation process of Pt / P-CeO2 catalyst, Ru / P-CeO2 with a theoretical loading of 1.0 wt% was prepared by NaBH4 reduction method, and RuCl3 solution was used as the precursor.

[0029] (4) Preparation of PtRu / P-CeO2 catalyst:

[0030] Under ice-water bath and stirring conditions, 0.99 mL of a 10 g / L H₂PtCl₆∙6H₂O solution was first added to a 2 g / L PVA solution. After vigorous stirring for 30 min, a freshly prepared 0.1 mol / L NaBH₄ solution was rapidly added to the Pt-containing solution. This mixture was designated as solution A. Similarly, under ice-water bath and stirring conditions, 0.77 mL of a 10 g / L RuCl₃ solution was added to a 2 g / L PVA solution. After vigorous stirring for 30 min, a NaBH₄ solution was rapidly added to the Ru-containing solution. This mixture was designated as solution B. Then, solutions A and B were mixed and vigorously stirred for 10 min. 1.0 g of P-CeO₂ support was then impregnated in the PtRu-containing mixture. After stirring for 6 h, the mixture was filtered and washed with deionized water and ethanol, and then dried in an oven at 80 ℃ for 12 h. Finally, the obtained solid was ground and transferred to a muffle furnace, heated from room temperature to 400 °C at a heating rate of 5 °C / min, and calcined for 6 h to obtain the PtRu / P-CeO2 catalyst.

[0031] The theoretical P loading in the P-CeO2 catalyst is 3.6 wt% (the actual loading is 0.36 wt% due to some loss), while the theoretical PtRu loading in the PtRu / P-CeO2 catalyst is 1.0 wt% (the actual loading is 0.94 wt%, of which Pt accounts for 0.39 wt% and Ru accounts for 0.45 wt%). In comparison, the actual P loading in the catalyst is 0.36 wt%, the actual Pt loading is 0.94 wt%, and the actual Ru loading is 0.82 wt%.

[0032] (5) The prepared catalyst was used for the catalytic oxidation of a mixture of toluene and DCM. All catalysts were tested for activity under a gaseous environment of 500 ppm toluene + 500 ppm DCM, 20 vol% O2, N2 (equilibrium gas), and GHSV = 24,000 mL / (gh). The catalyst's To of toluene during the catalytic oxidation of toluene and DCM was determined. 50% and T 90% The T values ​​for DCM are 120℃ and 137℃ respectively. 50% and T 90% The temperatures were 238 ℃ and 312 ℃, respectively.

Claims

1. A method for preparing a PtRu bimetallic catalyst, characterized in that, Includes the following steps: (1) Preparation of P-CeO2 catalyst: Cerium nitrate hexahydrate, trimethyl phosphate, and NaOH were added sequentially to deionized water and stirred at room temperature for 30 min. The mixture was then transferred to a polytetrafluoroethylene-lined reactor and hydrothermally reacted at 100 °C for 24 h. After cooling to room temperature, the mixture was washed by centrifugation with deionized water and ethanol, and dried in an oven at 80 °C overnight. The resulting solid was ground and transferred to a muffle furnace, where the temperature was increased from room temperature to 400 °C at a rate of 5 °C / min. After calcination for 6 h, the P-CeO2 catalyst support was obtained. (2) Preparation of PtRu / P-CeO2 catalyst: The preparation process is as follows: Under ice-water bath and stirring conditions, a certain amount of H2PtCl6 solution was first added to the PVA solution. After vigorous stirring, NaBH4 solution was quickly added to the above Pt-containing solution. This mixed solution is designated as solution A. Under the same ice-water bath and stirring conditions, a certain amount of RuCl3 solution was mixed and stirred with the PVA solution. After vigorous stirring, NaBH4 solution was quickly added to the above Ru-containing solution. This mixed solution is designated as solution B. Then, solution A and solution B were mixed and stirred vigorously for 10 min to obtain a mixed solution containing PtRu. The P-CeO2 catalyst support was impregnated in the mixed solution containing PtRu. After stirring for 6 h, the mixed solution was filtered, washed, and dried with deionized water and ethanol. Finally, the obtained solid was ground and transferred to a muffle furnace. The temperature was increased from room temperature to 400 °C at a heating rate of 5 °C / min. After calcination for 6 h, the PtRu / P-CeO2 catalyst was obtained.

2. The method according to claim 1, characterized in that, The P loading in the P-CeO2 catalyst support is 0.3-4 wt%.

3. The method according to claim 1, characterized in that, The theoretical PtRu loading in the PtRu / P-CeO2 catalyst is 0.8 wt%-1.5%, and the mass ratio of Pt to Ru is 0.8:1-1:

1.

4. The PtRu bimetallic catalyst prepared according to any one of claims 1-3.

5. The application of the PtRu bimetallic catalyst prepared according to any one of claims 1-3 for the catalytic oxidation of a mixture of toluene and DCM to produce CO2, H2O and HCl.

6. According to the application described in claim 5, toluene and DCM mixture were successfully catalytically oxidized at a relatively low temperature of 310°C, and no significant deactivation was observed during the reaction process, which lasted up to 24 hours.

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