Palladium-supported catalyst for propane catalytic combustion and preparation method and application thereof

Abstract

The invention discloses a palladium-supported catalyst for propane catalytic combustion and a preparation method and application thereof. According to the method, a coprecipitation method is utilized under stirring, polyvinylpyrrolidone is used as a guiding agent, cerium dioxide is used as a metal precursor, palladium nitrate is used as a doping agent, and sodium hydroxide and sodium carbonate are used as chemical environment regulating agents to prepare a metal-doped catalyst; the metal-doped catalyst is used in a propane catalytic combustion reaction, efficient degradation of propane is achieved, the catalytic conversion temperature of precious metal is remarkably reduced, and the metal-doped catalyst has the advantages that the one-way propane conversion rate is high, and the reaction is mild; relates to the field of petrochemical engineering.

Description

[0001] The invention relates to the field of petrochemical industry, in particular to a palladium-loaded catalyst for propane catalytic combustion. The invention also relates to a preparation method and application of the catalyst. Background Art

[0002] Volatile organic compounds (VOCs) refer to volatile organic compounds with a melting point below room temperature and a boiling point between 50 and 260 °C. Generally speaking, most of the VOCs emitted are composed of alkanes, alkenes, halogenated hydrocarbons, aldehydes, ketones, aromatic hydrocarbons, alcohols, and sulfur / nitrogen compounds. VOCs contain short-chain alkanes represented by propane (C3H8), which mainly come from natural and anthropogenic sources, such as waste gas from the petrochemical industry, liquefied petroleum gas carriers in transportation and building materials. Due to the size and insolubility of short-chain alkanes, catalytic oxidation technology is a widely used technology for the removal of short-chain alkanes that is more effective than adsorption and absorption methods. However, due to its simple and stable CC and CH chain structure, C3H8 is one of the most difficult VOCs to degrade. Therefore, in order to improve ambient air quality and protect human health, effective technologies for removing propane from polluted air streams are needed. So far, catalytic oxidation technology is considered to be the best degradation method for completely converting VOCs into CO2 and H2O. Due to the structural stability of propane, it is necessary to develop and design more efficient and durable catalysts.

[0003] Precious metal-based materials are generally considered to be highly efficient catalysts for deep oxidation of VOCs due to their excellent activity and stability. In the selection of catalysts, precious metals such as Pt, Pd, Au, Rh, etc. are often used for the catalytic combustion of alkanes because these precious metals not only have stable chemical properties but also have high catalytic activity. Studies by Lu et al. showed that the different structural characteristics of CeO2 (octahedral, strip-shaped and cubic CeO2) significantly affected the chemical state of Pd species. The T90 of the Pd-loaded octahedral CeO2 propane oxidation catalyst was lower than that of the other two-sided CeO2 loaded by Pd, so it had higher activity. The anti-sintering performance of precious metals still needs to be improved, and highly stable supports with strong metal-support interaction (SMSI) such as stable γ-Al2O3 are one of the feasible strategies. In general, bulk doping or surface modification such as SiO2, TiO2, CeO2, La2O3, are considered to be effective strategies to improve high temperature stability to obtain stable Pd-loaded catalysts. The introduction of La into the support reduces the electron cloud density of Pd particles and weakens the adsorption of CH, thus affecting the water resistance and stability of Pd-based catalysts. Phosphorus-modified γ-Al2O3 nanosheets have enhanced γ-Al2O3 thermal stability and anti-PdOx sintering performance; PdOx-supported P-modified Al2O3 calcined at 1000°C still exhibits superior propane combustion catalytic activity due to the redispersion of PdOx particles and SMSI at high temperatures.

[0004] Although the catalyst for propane catalytic combustion prepared by the above researchers has good performance in catalytic combustion of propane, it still faces some problems, such as high content of precious metals, complex synthesis method, and undetermined active sites of precious metals, which make the manufacturing cost of the catalyst high and will be limited in practical applications. Therefore, we need a catalyst with a simple preparation method to catalyze propane combustion. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a manganese-based metal-doped catalyst based on the problems currently faced by palladium-supported catalysts, which are transition metal catalysts, and has high catalytic activity for propane.

[0006] To this end, the first technical solution provided by the present invention is as follows.

[0007] A method for preparing a palladium-supported catalyst for propane catalytic combustion comprises the following steps in sequence: (1) Prepare Pd(NO3)2 and CeO2 mixed solution A; (2) preparing a mixed alkaline solution B of NaOH and Na2CO3; (3) PVP is prepared into solution C; (4) Solution A in step (1) and solution B in step (2) were simultaneously added dropwise to solution C to obtain a uniform solution. During the addition, NaOH solution was added dropwise to maintain the solution pH = 10. (5) stirring the homogeneous solution at room temperature for 6 h to obtain a PdCeO solution; (6) After the reaction is completed, the PdCeO solution is centrifuged, washed with deionized water, and finally dried with air to obtain a solid product PdCeO; (7) The above solid product was further calcined in a muffle furnace, and the obtained sample was denoted as PdCeOx.

[0008] Furthermore, in the above-mentioned method for preparing the palladium-supported catalyst, the molar ratio of palladium nitrate to cerium dioxide in step (1) is 0-0.5%:1.

[0009] Furthermore, in the above-mentioned method for preparing the palladium-supported catalyst, the molar ratio of NaOH to Na2CO3 in step (2) is 0.5-1.0:1.

[0010] Furthermore, in the above-mentioned method for preparing the palladium-supported catalyst, the concentration of NaOH in step (4) is 1 mol / L.

[0011] Furthermore, in the above-mentioned method for preparing the palladium-supported catalyst, the stirring speed in step (5) is 200-2000 r / min.

[0012] Furthermore, in the above-mentioned preparation method of palladium-supported catalyst, the centrifugal parameters in step (6) are: 8000 r / min, time 3 min; the washing conditions are: washing with deionized water 3 to 5 times; the drying temperature is 60°C, and the time is 6 to 10 h.

[0013] Furthermore, in the above-mentioned method for preparing the palladium-supported catalyst, the calcination temperature in step (7) is 600° C. and the calcination time is 6 h.

[0014] The second technical solution provided by the present invention is catalysis by the palladium-supported catalyst prepared by the above method.

[0015] The catalyst is used for catalytic combustion of propane. The catalytic conditions are as follows: propane concentration is 5000 ppm, oxygen concentration is 8%, the remainder is nitrogen, the space velocity is 15000 mL / (g·h), and the reaction temperature is 100-300°C.

[0016] The palladium-supported catalyst provided by the present invention is applied to the field of high-temperature thermal catalysis. The catalyst has a certain catalytic efficiency for light alkanes and can be used to degrade common organic pollutants in chemical plants.

[0017] Compared with the prior art, the technical solution provided by the present invention has the following technical advantages: (1) Pd loading modifies CeO2, greatly reducing the catalytic activity; (2) Cerium improves its ability to absorb oxygen by increasing oxygen mobility and high oxygen storage rate, thereby improving its ability to activate oxygen in the propane catalytic reaction; (3) The preparation conditions are simple, the operation is convenient, and it is easy to scale up production in industry. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 This is the propane catalytic combustion activity diagram of PdCeOx catalyst; Figure 2 This is the SEM image of PdCeOx catalyst. DETAILED DESCRIPTION

[0019] The present invention is further described below in conjunction with embodiments, but the protection scope of the present invention is not limited to the scope represented by the embodiments.

[0020] Example 1: This example provides a method for preparing a palladium-supported catalyst for thermal catalytic propane combustion, the specific steps of which are: (1) 0.0013 g Pd(NO3)2 and 2.65 g CeO2 were added to 30 mL deionized water, which was called solution A. (2) 0.8 g NaOH (1 mol / L) and 1.056 g Na2CO3 were added to 30 mL deionized water, which was called mixed alkaline solution B. (3) 0 .5g PVP is mixed to prepare solution C; (4) solution A in step (1) and solution B in step (2) are added dropwise to solution C at the same time to obtain a uniform solution, and NaOH solution is added dropwise during the addition process to maintain the solution pH = 10; (5) the above uniform solution is stirred uniformly at 2000 r / min for 6 hours at room temperature to obtain a 0.5Pd-CeO2 solution; (6) after the reaction is completed, the 0.5Pd-CeO2 solution is centrifuged at 8000 rpm for 3 minutes, washed with deionized water for 3 times, and finally dried at 60°C for 6 hours to obtain a solid product 0.5Pd-CeO2; (7) the above solid product is calcined at 600°C for 6 hours in an air atmosphere, and the obtained sample is denoted as 0.5Pd-CeO2.

[0021] Example 2: This example provides a method for preparing a palladium-supported catalyst for thermal catalytic propane combustion, the specific steps of which are: (1) Add 0.0106 g Pd(NO3)2 and 2.65 g CeO2 to 30 mL deionized water, referred to as solution A; (2) Add 0.8 g NaOH (1 mol / L) and 1.056 g Na2CO3 to 30 mL deionized water, referred to as mixed alkaline solution B; (3) .5g PVP is mixed to prepare solution C; (4) solution A in step (1) and solution B in step (2) are added dropwise to solution C at the same time to obtain a uniform solution, and NaOH solution is added dropwise during the addition process to maintain the solution pH = 10; (5) the above uniform solution is stirred uniformly at 2000 r / min for 6 hours at room temperature to obtain a 0.4Pd-CeO2 solution; (6) after the reaction is completed, the 0.4Pd-CeO2 solution is centrifuged at 8000 rpm for 3 minutes, washed with deionized water for 3 times, and finally dried at 60°C for 6 hours to obtain a solid product 0.4Pd-CeO2; (7) the above solid product is calcined at 600°C for 6 hours in an air atmosphere, and the obtained sample is denoted as 0.4Pd-CeO2.

[0022] Example 3: This example provides a method for preparing a palladium-supported catalyst for thermal catalytic propane combustion, the specific steps of which are: (1) Take 0.00795g Pd(NO3)2 and 2.65g CeO2 and add them to 30mL deionized water, which is called solution A; (2) Take 0.8g NaOH (1mol / L) and 1.056g Na2CO3 and add them to 30mL deionized water, which is called mixed alkaline solution B; (3) Take 0.5g PVP is mixed to prepare solution C; (4) solution A in step (1) and solution B in step (2) are added dropwise to solution C simultaneously to obtain a uniform solution, and NaOH solution is added dropwise during the addition process to maintain the solution pH = 10; (5) the above uniform solution is stirred uniformly at 2000 r / min for 6 hours at room temperature to obtain a 0.3Pd-CeO2 solution; (6) after the reaction is completed, the 0.3Pd-CeO2 solution is centrifuged, and the centrifugation parameters are: 8000 rpm, time 3 minutes, and deionized water is washed 3 times, and finally dried at 60°C for 6 hours to obtain a solid product 0.3Pd-CeO2; (7) the above solid product is calcined at 600°C for 6 hours in an air atmosphere, and the obtained sample is denoted as 0.3Pd-CeO2.

[0023] Example 4: This example provides a method for preparing a palladium-supported catalyst for thermal catalytic propane combustion, the specific steps of which are: (1) Add 0.0053 g Pd(NO3)2 and 2.65 g CeO2 to 30 mL deionized water, referred to as solution A; (2) Add 0.8 g NaOH (1 mol / L) and 1.056 g Na2CO3 to 30 mL deionized water, referred to as mixed alkaline solution B; (3) .5g PVP was mixed to prepare solution C; (4) solution A in step (1) and solution B in step (2) were added dropwise to solution C to obtain a uniform solution, and NaOH solution was added dropwise during the addition to maintain the pH value of the solution at 10; (5) the above uniform solution was stirred uniformly at 2000 r / min for 6 h at room temperature to obtain a 0.2Pd-CeO2 solution; (6) after the reaction was completed, the 0.2Pd-CeO2 solution was centrifuged at 8000 rpm for 3 min, washed with deionized water for 3 times, and finally dried at 60°C for 6 h to obtain a solid product 0.2Pd-CeO2; (7) the above solid product was calcined at 600°C for 6 h in an air atmosphere, and the obtained sample was denoted as 0.2Pd-CeO2

[0024] Example 5: This example provides a method for preparing a palladium-supported catalyst for thermal catalytic propane combustion, the specific steps of which are: (1) Take 0.00265g Pd(NO3)2 and 2.65g CeO2 and add them to 30mL deionized water, which is called solution A; (2) Take 0.8g NaOH (1mol / L) and 1.056g Na2CO3 and add them to 30mL deionized water, which is called mixed alkaline solution B; (3) Take 0.5g PVP is mixed to prepare solution C; (4) solution A in step (1) and solution B in step (2) are added dropwise to solution C simultaneously to obtain a uniform solution, and NaOH solution is added dropwise during the addition process to maintain the solution pH = 10; (5) the above uniform solution is stirred uniformly at 2000 r / min for 6 hours at room temperature to obtain a 0.1Pd-CeO2 solution; (6) after the reaction is completed, the 0.1Pd-CeO2 solution is centrifuged, and the centrifugation parameters are: 8000 rpm, time 3 minutes, washed with deionized water 3 times, and finally dried at 60°C for 6 hours to obtain a solid product 0.1Pd-CeO2; (7) the above solid product is calcined at 600°C for 6 hours in an air atmosphere, and the obtained sample is denoted as 0.1Pd-CeO2.

[0025] The catalyst activity is expressed as propane conversion, which is calculated using the following formula: [C3H8] inlet is the gas chromatography inlet concentration [C3H 8】outlet is the gas chromatograph outlet concentration

[0026]

[0027] The prepared cerium-doped manganese-based catalyst was applied to the catalytic combustion reaction of propane. 200 mg PdCeOx was weighed and mixed with 800 mg quartz sand and placed in a quartz tube supporting the fixed bed. The mixture was heated at 100°C-300°C, normal pressure and a space velocity of 15000 h-1. -1 The reaction was carried out under the conditions of , and the gas after the reaction was monitored in real time by gas chromatography to analyze the propane conversion rate. Figure 1 This is the performance diagram of propane catalytic combustion, which has relatively excellent performance.

[0028] The above are only preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the structure of the present invention, which will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A preparation method for a palladium-supported catalyst for catalytic combustion of propane, characterized in that: The steps are as follows: (1) Prepare Pd(NO3)2 and CeO2 mixed solution A; (2) preparing a mixed alkaline solution B of NaOH and NaCO3; (3) PVP is prepared into solution C; (4) Solution A in step (1) and solution B in step (2) were simultaneously added dropwise to solution C to obtain a uniform solution. During the addition, NaOH solution was added dropwise to maintain the solution pH = 10. (5) stirring the homogeneous solution at room temperature for 6 h to obtain a PdCeO solution; (6) After the reaction is completed, the PdCeO solution is centrifuged, washed with deionized water, and finally dried with air to obtain a solid product PdCe; (7) The above solid product was further calcined in a muffle furnace, and the obtained sample was denoted as PdCeOx.

2. The preparation method of a palladium supported catalyst according to claim 1, wherein The molar ratio of palladium nitrate to cerium dioxide in step (1) is 0-0.5%:

1.

3. The preparation method of palladium supported catalyst according to claim 1, wherein The molar ratio of NaOH to Na2CO3 in step (2) is 0.5-1.0:

1.

4. The preparation method of a palladium supported catalyst according to claim 1, wherein The NaOH concentration described in step (4) is 1 mol / L.

5. The preparation method of palladium supported catalyst according to claim 1, wherein In step (5), the stirring speed is 200-2000 r / min.

6. The preparation method of palladium supported catalyst according to claim 1, wherein The centrifugal parameters in step (6) are: 8000 r / min, time 3 min; the washing conditions are: washing with deionized water 3 to 5 times; the drying temperature is 60°C, and the time is 6 to 10 h.

7. The preparation method of a palladium supported catalyst according to claim 1, wherein In step (7), the calcination temperature is 600°C and the calcination time is 6 h.

Images