Pt-CoMnO3 catalyst and preparation and application thereof

Abstract

The invention discloses a Pt-CoMnO3 catalyst as well as preparation and application thereof. The preparation method comprises the following steps: fully dissolving cobalt acetate, manganese acetate and ammonium bicarbonate in ethylene glycol to form a hydrothermal reaction solution; after the hydrothermal reaction, centrifugally separating out a precipitate; carrying out calcination treatment in an air atmosphere to obtain a CoMnO3 oxide; and fully dissolving the obtained CoMnO3 oxide in water, then adding H2PtCl6. 6H2O, NaBH4 and NaOH, fully mixing, and then drying to obtain the catalyst. The catalyst is simple in preparation process, mild in condition, rapid in deposition, low in cost, good in controllability of product morphology and size, low in Pt loading capacity and good in dispersity, Pt and the CoMnO3 carrier can generate strong interaction, and the catalyst is especially suitable for catalytic oxidation of toluene.

Description

Technical Field

[0001] The present invention generally relates to a catalyst, and more particularly to a Pt-supported catalyst for toluene degradation. Background Art

[0002] Volatile organic compounds (VOCs) are key intermediates of secondary organic aerosols and photochemical smog, posing a serious threat to both the atmospheric environment and human health. Catalytic combustion with noble metal-supported catalysts is considered a promising method for removing VOCs from industrial waste gas due to its high oxidation activity, low operating temperature, and strong regeneration ability. However, due to the high cost and scarcity of noble metals, it is urgent to improve the catalytic performance of noble metal-supported catalysts while further reducing the loading in order to achieve cost-effectiveness and wider applicability. Summary of the invention

[0003] The present invention aims to provide a Pt-CoMnO2 composite material which can be used to effectively degrade toluene and has a low Pt loading. 3 catalyst.

[0004] According to a first aspect of the present invention, there is provided a Pt-CoMnO 3 A method for preparing a catalyst comprises:

[0005] Co(CH 3 COO 2 ·4H 2 O and Mn(CH 3 COO 2 ·4H 2 O is fully dissolved in ethylene glycol to form a mixed salt solution, in which Co(CH 3 COO 2 ·4H 2 O and Mn(CH 3 COO 2 ·4H 2 The molar ratio of O is about 1:1;

[0006] Then NH 4 HCO 3 Add to the mixed salt solution to form a reaction solution, in which NH 4 HCO 3 With Co(CH 3 COO 2 ·4H 2 The molar ratio of O is about 10:1;

[0007] The reaction solution is subjected to a hydrothermal reaction at a temperature of 180 to 210° C. and a reaction time of 20 to 32 hours;

[0008] The precipitate was then separated from the reaction solution by centrifugation and calcined in an air atmosphere to obtain CoMnO 3 Oxide, wherein the calcination temperature is 480°C to 520°C and the calcination time is 4 to 8 hours;

[0009] The obtained CoMnO 3 The oxide is fully dissolved in water, and then H 2 PtCl 6 6H 2 O、NaBH 4 and NaOH, mixed thoroughly and dried to obtain a catalyst, wherein H 2 PtCl 6 6H 2 O and CoMnO 3 The molar ratio of NaBH is about 0.00012:1. 4 With H 2 PtCl 6 6H 2 The molar ratio of O is about 3:1, H 2 PtCl 6 6H 2 The molar ratio of O to NaOH is about 1:5.

[0010] The preparation method according to the present invention further comprises: washing and drying the obtained catalyst.

[0011] According to the preparation method of the present invention, the hydrothermal reaction temperature is preferably about 200° C., and the reaction time is preferably about 24 h.

[0012] According to the preparation method of the present invention, the calcination temperature is preferably about 500° C., and the calcination time is preferably about 6 hours. In addition, the heating rate can be about 2° C. / min.

[0013] According to another aspect of the present invention, there is also provided a Pt-CoMnO 3 The catalyst is prepared by the above method.

[0014] According to another aspect of the present invention, there is also provided use of the above catalyst in catalytic oxidation of toluene.

[0015] The present invention prepares Pt-CoMnO with ultra-low Pt loading by hydrothermal synthesis 3 Catalyst. The loading of Pt can induce the formation of more oxygen vacancies and more Co 3+ For the activation of toluene, CoMnO 3 The oxygen vacancies on the surface can induce the generation of many reactive oxygen species, which can effectively migrate to the active sites (Pt-CoMnO 3interface), replacing the oxygen consumed on the surface, thereby improving the stability of the catalyst.

[0016] The present invention loads platinum atoms on a special bimetallic oxide so that Pt and CoMnO 3 Strong metal-support interaction (SMSI) between supports is enhanced, which can induce more Pt 0 For oxygen adsorption and activation, more Co 3 + for the activation of toluene. In addition, CoMnO 3 The oxygen vacancies on the surface can induce the generation of many reactive oxygen species, which can effectively migrate to the active sites (Pt-CoMnO 3 interface), replacing the oxygen consumed on the surface, thereby improving the stability of the catalyst.

[0017] The platinum-based catalyst prepared according to the present invention is evenly distributed, has a low Pt loading (ICP measurement results show that it is 0.03wt%), is simple to operate, and is easy to prepare. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The Pt-CoMnO prepared according to a specific embodiment of the present invention 3 XRD patterns of catalyst samples.

[0019] Figure 2(a) is a transmission electron microscope (TEM) image of the above catalyst; Figure 2(b) is an EDS spectrum image of cobalt therein; Figure 2(c) is an EDS spectrum image of manganese therein; and Figure 2(d) is an EDS spectrum image of platinum therein.

[0020] Figure 3(a) is an X-ray photoelectron spectroscopy (XPS) image of cobalt in the above catalyst; Figure 3(b) is an XPS image of manganese therein; Figure 3(c) is an XPS image of oxygen therein; and Figure 3(d) is an XPS image of platinum therein.

[0021] Figure 4 This is a graph showing the toluene conversion rate of the above catalyst. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with the embodiments and drawings. Those skilled in the art should understand that the embodiments and drawings are only for a better understanding of the present invention and are not intended to be limiting in any way.

[0023] Preparation of Pt-CoMnO 3 catalyst

[0024] Add 50 mL of ethylene glycol and 4 mmol of Co(CH 3 COO 2 ·4H 2 O and 4 mmol Mn(CH 3COO 2 ·4H 2 O, and then add 40 mmol NH 4 HCO 3 The mixture was stirred for 3 h to obtain a reaction solution.

[0025] The reaction solution was added into a reactor equipped with a polytetrafluoroethylene liner, and hydrothermally reacted at 200° C. for 24 h. A precipitate was obtained after centrifugal separation.

[0026] The obtained precipitate was washed with water 3 times and with alcohol 3 times, and dried in a vacuum drying oven at 60°C overnight to obtain a powder solid.

[0027] The powder solid was placed in a muffle furnace, heated at a rate of 2 °C / min, and calcined at 500 °C for 6 h to obtain CoMnO 3 Oxide.

[0028] CoMnO 3 The oxide was dissolved in ultrapure water and H 2 PtCl 6 6H 2 O、NaBH 4 and NaOH, mix thoroughly (so that Pt 4+ NaBH 4 Reduction), and dried to obtain a black solid powder, wherein H 2 PtCl 6 6H 2 O and CoMnO 3 The molar ratio of NaBH is 0.0001185:1. 4 With H 2 PtCl 6 6H 2 The molar ratio of O is 3:1, H 2 PtCl 6 6H 2 The molar ratio of O to NaOH was 1:5, and NaBH4 and NaOH were added in the form of solutions (0.1 mol / L).

[0029] The obtained black solid powder was washed once with water and once with alcohol, and then placed in a vacuum drying oven at 60°C to dry overnight to obtain the final Pt-CoMnO 3 The final Pt loading of the catalyst sample was determined to be 0.03 wt% (ICP measurement result).

[0030] XRD pattern analysis

[0031] Figure 1 is the XRD pattern of the above catalyst sample. Figure 1It can be seen that the sample has obvious diffraction peaks at 24.5°, 33.5°, 36.4°, 41.6°, 50.3°, 54.7°, 63.7° and 65.5°, which is consistent with the CoMnO 3 The diffraction peaks corresponding to Pt or Pt0x were not observed in XRD, which usually means that Pt is in the CoMnO 3 Highly dispersed and / or low loading on the support.

[0032] TEM image analysis

[0033] Figure 2(a) is a transmission electron microscope (TEM) image of the above catalyst; Figure 2(b) is an EDS spectrum image of cobalt; Figure 2(c) is an EDS spectrum image of manganese; Figure 2(d) is an EDS spectrum image of platinum. It can be clearly observed that a large amount of Pt is uniformly dispersed in the CoMnO 3 Support surface, indicating the successful loading of Pt.

[0034] XPS characterization analysis

[0035] Figure 3(a) is an X-ray photoelectron spectroscopy (XPS) image of cobalt in the above catalyst; Figure 3(b) is an XPS image of manganese; Figure 3(c) is an XPS image of oxygen; Figure 3(d) is an XPS image of platinum. The valence distribution of various elements can be clearly observed. Cobalt is mainly in the form of Co 3+ and Co 2+ Manganese exists mainly in the form of Mn 3+ and Mn 4+ Oxygen exists mainly in the form of lattice oxygen (O L ), oxygen vacancies (O v ) and adsorbed oxygen (O c ) forms; platinum exists mainly in the form of Pt 0 and Pt 2+ Form exists.

[0036] Toluene catalytic combustion performance test

[0037] 0.1 g of the above catalyst sample was mixed with 0.3 g of quartz sand and a toluene catalytic combustion test was carried out in a continuous flow fixed bed quartz microreactor (ie, = 6 mm). Figure 4 is the toluene conversion rate diagram of the above catalyst. Figure 4 As shown in Figure 2, under the test conditions of 1000 ppm and 20,000 mL / g·h, the temperature at which the catalyst reaches 90% conversion is around 207°C (T 90), which is superior to many commonly used catalysts. The reason may be: Pt and CoMnO 3 Strong metal-support interaction (SMSI) between supports is enhanced, which can induce more Pt 0 For oxygen adsorption and activation, more Co 3 + for the activation of toluene. In addition, CoMnO 3 The oxygen vacancies on the surface can induce the generation of many reactive oxygen species, which can effectively migrate to the active sites (Pt-CoMnO 3 interface), replacing the oxygen consumed on the surface, thereby improving the stability of the catalyst.

[0038] As described above, the catalyst product of the present invention is prepared by hydrothermal synthesis, which has simple process, mild conditions, rapid deposition, good controllability of product morphology and size, good Pt dispersion, and good Pt and CoMnO 3 The carriers can interact strongly with each other, have good repeatability and low price, and are particularly suitable for catalytic oxidation of toluene.

Claims

1. A method for preparing a Pt-CoMnO3 catalyst, comprising: Fully dissolving Co(CH3COO)2·4H2O and Mn(CH3COO)2·4H2O in ethylene glycol to form a mixed salt solution, wherein the molar ratio of Co(CH3COO)2·4H2O to Mn(CH3COO)2·4H2O is about 1:1; Then, NH4HCO3 is added to the mixed salt solution to form a reaction solution, wherein the molar ratio of NH4HCO3 to Co(CH3COO)2·4H2O is about 10:1; The reaction solution is subjected to a hydrothermal reaction at a temperature of 180 to 210° C. and a reaction time of 20 to 32 hours; Then, the precipitate is separated from the reaction solution by centrifugation, and calcined in an air atmosphere to obtain CoMnO3 oxide, wherein the calcination temperature is 480°C to 520°C, and the calcination time is 4 to 8 hours; The obtained CoMnO3 oxide is fully dissolved in water, and then H2PtCl6·6H2O, NaBH4 and NaOH are added, fully mixed and dried to obtain a catalyst, wherein the molar ratio of H2PtCl6·6H2O to CoMnO3 is about 0.00012:1, the molar ratio of NaBH4 to H2PtCl6·6H2O is about 3:1, and the molar ratio of H2PtCl6·6H2O to NaOH is about 1:

5.

2. The preparation method according to claim 1, further comprising: The resulting catalyst was washed and dried.

3. A Pt-CoMnO3 catalyst prepared according to the method of claim 1 or 2.

4. Use of the catalyst according to claim 3 in catalytic oxidation of toluene.

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