CN103301850A - Three-dimensional sequential macroporous Co3O4 loaded nanometer Au catalyst as well as preparation method and application thereof - Google Patents

Abstract

The invention relates to a three-dimensional sequential macroporous Co3O4 loaded nanometer Au catalyst as well as a preparation method and an application thereof, and belongs to a transition metal oxide loaded nanometer noble metal catalyst. The pore wall of Co3O4 with a 3DOM structure is supported with cubic phase Au nanometer particles. According to the preparation method, 3DOM Co3O4 is prepared by a polyethyleneglycol 400 assisted PMMA (polymethyl methacrylate) colloidal crystal template method, and then a gold nanometer adhesive is loaded on 3DOM Co3O4 by using a polyvinyl alcohol protection bubble reduction method, so that Au/3DOM Co3O4 is obtained. The raw materials of the three-dimensional sequential macroporous Co3O4 loaded nanometer Au catalyst is cheap in price and can be easily obtained, the preparation process is simple, and the product obtained by the preparation method is controllable in shape, size and pore diameter.

Description

Three-dimensional ordered macroporous Co 3O 4Loaded with nano Au catalyst, preparation method and application

Technical field

The present invention relates to the Co that a kind of bubbling reducing process that adopts glue crystal template method and polyvinyl alcohol to protect prepares respectively three-dimensional ordered macroporous (3DOM) structure ₃O ₄And gold-supported (Au/3DOM Co ₃O ₄) preparation method of catalyst, and to the catalytic performance of CO and volatile organic matter oxidation, relate in particular to the Co that the bubbling reducing process that adopts polymethyl methacrylate (PMMA) glue crystal template method and polyvinyl alcohol protection prepares respectively the 3DOM structure ₃O ₄With Au/3DOM Co ₃O ₄The preparation method of catalyst, and to the catalytic performance of CO and toluene oxidation, belong to transition metal oxide nano-noble-metal-loaded catalyst.

Background technology

Industrial waste gas [such as volatile organic matter (VOCs) etc.] pollutant atmosphere, the harm health of human body.Production by Catalytic Combustion Process is one of technology of at present the most frequently used removal VOCs, and by catalytic action, VOCs can be in the lower oxidation of lower temperature (＜500 ℃), and its clearance is usually above 95%.The selection of catalyst is crucial.The catalyst that is applied at present the VOCs catalytic combustion comprises carried noble metal, single transition metal oxide and composite metal oxide.In the catalyst of having studied, supported precious metal catalyst is best to the catalytic activity of CO and VOCs oxidation reaction, and wherein the Au nanocatalyst shows good catalytic activity to CO and VOCs oxidation.Au is carried on the transition metal oxide (MO of high-specific surface area _y) on the carrier, also can further improve it to the catalytic performance of CO and VOCs oxidation.Such as: Yu etc. (X.H.Yu, et al., The Journal of Physical Chemistry C, 2012,116:851-860) observe Pt/MnO ₂Catalyst oxidation of formaldehyde reaction and display is catalytic activity preferably.Jin etc. (M.S.Jin, et al., Catalysis Today, 2012,185:183-190) prepared meso-pore Ce O ₂And Mn ₂O ₃The palladium catalyst of load is found Pd/ meso-pore Ce O ₂The CO oxidation reaction is demonstrated the highest catalytic activity.Sinha etc. (A.K.Sinha, et al., Angewandte Chemie International Edition, 2007,46:2891-2894) studied toluene, acetaldehyde and n-hexane at Au/ γ-MnO ₂Oxidation reaction on the catalyst finds that it shows good catalytic performance.Xue etc. (W.J.Xue, et al., Catalysis Communication, 2011,12:1265 – 1268) are at different-shape Co ₃O ₄Upper load Au finds that the carrier of different-shape is very large to the activity influence of catalyst, and this is because different-shape Co ₃O ₄The active crystal face that exposes is different and cause different from the degree of strength of Au nano particle effect.Solsona etc. (B.Solsona, et al., Journal of Hazardous Materials, 2011,187:544 – 552) have studied at Co ₃O ₄Upper load Au nano particle finds that to toluene, propane and CO oxidation reaction it shows excellent catalytic performance, and this is because can improve significantly Co behind the load Au particle ₃O ₄Reducing power, have strong interaction between Au and the carrier, significantly improve Au ¹⁺Concentration.

Three-dimensional ordered macroporous (3DOM) structure catalyst makes it that very large application prospect be arranged in a lot of fields because having higher specific area, larger pore volume and flourishing pore structure.Macroporous structure is conducive to reduce resistance to mass tranfer and impels guest molecule to arrive active sites, thereby is conducive to the absorption and diffusion of reactant molecule.In in the past 10 years, Chinese scholars has carried out inquiring into widely to the 3DOM material preparation.People utilize recently set up can obtain the aperture at tens of extremely 3DOM materials of hundreds of nanometers take colloid brilliant [such as polymethyl methacrylate (PMMA) and polystyrene (PS) etc.)] micron ball as the brilliant synthetic technology of the glue of hard template.For example: Stein and partner thereof (A.Stein, et al., Chemistry of Materials, 2000,12:1134-1141) take the PS microballoon as template, take metal acetate salt or oxalates as predecessor, synthesized the Fe of 3DOM structure ₂O ₃, Cr ₂O ₃, Mn ₂O ₃And Co ₃O ₄, the aperture is that 380-550nm and specific area are 20-39m ²/ g.Ueda and partner thereof (W.Ueda, et al., Chemistry of Materials, 2007,19:5779-5785) utilize the PMMA microballoon of different-diameter to make template and metal nitrate is predecessor, synthesized the Fe of 3DOM structure ₂O ₃, Cr ₂O ₃, Mn ₂O ₃, Mn ₃O ₄And Co ₃O ₄, the aperture is that 170-180nm and specific area are 13-57m ²/ g.

Co ₃O ₄The catalysis material with excellent activity, if it is made 3DOM Co ₃O ₄, then can greatly improve its specific area, improve mutually character and be conducive to diffusion and the activation absorption of reactant molecule of surface and body, thereby improve significantly its catalytic activity; If more an amount of Au nano particle is supported 3DOM Co ₃O ₄On the carrier, then can further improve catalytic performance.3DOM Co ₃O ₄In the Co ion contain multiple oxidation state, have stronger oxidation-reduction (Redox) ability, Co ₃O ₄And may have strong interaction and synergy between the Au, be conducive to promote the Redox process of catalyst, thereby be conducive to the raising of catalytic activity.Up to now, there is no document and patent report and cross the transition metal oxide supported precious metal catalyst Au/3DOM Co that uses glue crystal template method to have the 3DOM structure in conjunction with the bubbling reducing process preparation of polyvinyl alcohol protection ₃O ₄Therefore, research and development prepare the Co with 3DOM structure ₃O ₄Carried noble metal nanometer Au catalysis material is significant.

Summary of the invention

The object of the present invention is to provide 3DOM Co ₃O ₄PMMA glue crystal template method and Au/3DOM Co ₃O ₄The bubbling reducing process of polyvinyl alcohol protection.

Three-dimensional ordered macroporous Co ₃O ₄Loaded with nano Au catalyst, i.e. Au/3DOM Co ₃O ₄Catalyst is characterized in that, has the Co of 3DOM structure ₃O ₄Hole wall on load Emission in Cubic Au nano particle is arranged.

3DOM Co ₃O ₄With Au/3DOM Co ₃O ₄The preparation method, it is characterized in that, adopt the bubbling reducing process of the auxiliary PMMA glue crystal template method of PEG400 and polyvinyl alcohol protection to prepare respectively 3DOM Co ₃O ₄With Au/3DOM Co ₃O ₄, specifically may further comprise the steps:

(1) preparation 3DOM Co ₃O ₄: get cobalt nitrate hexahydrate and join and stir 10min in the absolute methanol, obtain precursor liquid, add PEG400 in the precursor liquid to mixing, cobalt nitrate hexahydrate wherein: absolute methanol: PEG400 is 20mmol:9ml:1ml, behind the stirring at room 30min, add again the PMMA hard template, in room temperature dipping 3h, filtration, drying at room temperature 24h namely obtain 3DOM Co through after the roasting ₃O ₄Carrier, calcination steps and condition are: (a) at N ₂Be warming up to 300 ℃ with 1 ℃/min speed by room temperature under the atmosphere, and keep 3h, naturally be down to subsequently room temperature; (b) under air atmosphere, be warming up to 300 ℃ with 1 ℃/min speed by room temperature, keep 2h, rise to 450 ℃ with 1 ℃/min speed subsequently, keep naturally being down to room temperature behind the 3h;

(2) preparation Au/3DOM Co ₃O ₄: ice-water bath lucifuge environment: aqueous solution of chloraurate is joined in the aqueous solution of PVA, Au/PVA mass ratio=1.5:1, uniform stirring 10min adds rapidly NaBH subsequently ₄Water solution A u/NaBH ₄Mol ratio=1:5 behind the stirring 30min, namely makes the Au nanometre glue;

Adopt bubbling reducing process and the infusion process of PVA protection to prepare xAu/3DOM Co ₃O ₄Catalyst: according to Au/3DOM Co ₃O ₄The Au load capacity of estimating in the catalyst adds the 3DOM Co for preparing in the step (1) in the Au nanometre glue ₃O ₄Carrier adsorbs gas sparging is auxiliary lower, after glue clarification (i.e. absorption fully), filter, washing and under 110 ℃ dry 12h, namely make Au/3DOM Co ₃O ₄Catalyst.

Au/3DOM Co ₃O ₄Middle Au load factor be x (such as x=2,4,6,8%), as adding 200mg 3DOM Co in the colloidal sol of Au nano particle of preparation different quality ₃O ₄Carrier obtains actual Au load capacity and is followed successively by 1.1,2.7,5.2 and 6.5% xAu/3DOM Co ₃O ₄Catalyst.

The present invention has the features such as raw material is cheap and easy to get, and preparation process is simple, and products therefrom pattern, particle diameter and aperture are controlled.

The Au/3DOM Co of the present invention's preparation ₃O ₄(x=1-8%) have the characteristics of 3DOM structure and the catalytic activity of excellence, have a good application prospect at CO and VOCs catalytic oxidation field.

Utilize crystal structure, particle morphology and the pore structure of the instrumental characterizing gained target products such as D8 ADVANCE type X-ray diffractometer (XRD), ZEISS SUPRA55 type SEM (SEM), JEOL-2010 type transmission electron microscope (TEM), utilize inductively coupled plasma atomic emission spectrum (ICP-AES) to measure Au actual negative carrying capacity.The result shows, according to the prepared xAu/3DOM Co of the inventive method ₃O ₄(x=1-8%) catalyst present the 3DOM structure and on large hole wall uniform load Emission in Cubic Au nano particle is arranged, and the Au nanometer particle size is between 2.4-3.7nm.

Description of drawings

Fig. 1 is obtained xAu/3DOM Co ₃O ₄The XRD spectra of (x=1.1,2.7,5.2,6.5%) catalyst, wherein curve (a), (b), (c), (d) are respectively the XRD spectra of embodiment 1, embodiment 2, embodiment 3, embodiment 4 catalyst.

Fig. 2 is prepared xAu/3DOM Co ₃O ₄(x=1.1,2.7,5.2,6.5%) the SEM photo of catalyst, wherein figure (a) with (b), (c) with (d), (e) with (f), (g) and the SEM photo that (h) is respectively embodiment 1, embodiment 2, embodiment 3, embodiment 4 catalyst.

Fig. 3 is prepared xAu/3DOM Co ₃O ₄The HRTEM photo of (x=1.1,2.7,5.2,6.5%) catalyst, wherein figure (a), (b), (c) and (d) be respectively TEM photo under the different amplification of embodiment 1, embodiment 2, embodiment 3, embodiment 4 catalyst.

Fig. 4 is prepared xAu/3DOM Co ₃O ₄(x=1.1,2.7,5.2,6.5%) and catalyst is through the Au nanometer particle size distribution map of HRTEM figure statistics, wherein figure (a), (b), (c) and (d) be respectively the Au nanometer particle size distribution map of embodiment 1, embodiment 2, embodiment 3, embodiment 4 catalyst.

Fig. 5 is prepared xAu/3DOM Co ₃O ₄(x=1.1,2.7,5.2,6.5%) catalytic activity of catalyst, wherein figure (a), (b), (c) and (d) be respectively embodiment 1, embodiment 2, embodiment 3, embodiment 4 catalyst CO concentration be 100ppm, CO and oxygen mol ratio be 1/20 and air speed be CO oxidation activity curve under 10000mL/ (gh) condition.

Fig. 6 is prepared xAu/3DOM Co ₃O ₄(x=1.1,2.7,5.2,6.5%) catalytic activity of catalyst, wherein figure (a), (b), (c) and (d) be respectively embodiment 1, embodiment 2, embodiment 3, embodiment 4 catalyst toluene concentration be 1000ppm, toluene and oxygen mol ratio be 1/400 and air speed be toluene oxidation activity curve under 40000mL/ (g h) condition.

The specific embodiment

Embodiment 1:

(1) getting the 20mmol cobalt nitrate hexahydrate joins in the 9mL absolute methanol and stirs 10min, add the 1mL PEG400 in the precursor liquid to mixing, behind the stirring at room 30min, add again an amount of PMMA hard template, in room temperature dipping 3h, filtration, drying at room temperature 24h namely obtain 3DOM Co through after the roasting ₃O ₄Carrier.Roasting condition is: (1) is at N ₂Be warming up to 300 ℃ with 1 ℃/min speed by room temperature under the atmosphere, and keep 3h, naturally be down to subsequently room temperature; (2) under air atmosphere, be warming up to 300 ℃ with 1 ℃/min speed by room temperature, keep 2h, rise to 450 ℃ with 1 ℃/min speed subsequently, keep naturally being down to room temperature behind the 3h.

(2) ice-water bath lucifuge environment: get that (the Au/PVA mass ratio=1.5:1), uniform stirring 10min adds 1.92mL NaBH subsequently fast in the aqueous solution (2.0mg/mL) that 13.54mL aqueous solution of chloraurate (1.5mmol/L) joins 1.33mL PVA ₄The aqueous solution (2.0mg/mL) (Au/NaBH ₄Mol ratio=1:5), when solution becomes brownish black, form the Au nanometre glue, stand-by behind the rapid stirring 30min.

(3) add 200mg3DOM Co in the Au nanometre glue that makes to (2) ₃O ₄Carrier is at N ₂Gas sparging is auxiliary lower to be adsorbed, after glue clarification (i.e. absorption fully), filter, washing and under 110 ℃ dry 12h, namely make 1.1Au/3DOM Co ₃O ₄Catalyst, the aperture is about 290nm, and Au nano particle average grain diameter is 2.4nm.

Embodiment 2:

(1) getting the 20mmol cobalt nitrate hexahydrate joins in the 9mL absolute methanol and stirs 10min, add the 1mL PEG400 in the precursor liquid to mixing, behind the stirring at room 30min, add again an amount of PMMA hard template, in room temperature dipping 3h, filtration, drying at room temperature 24h namely obtain 3DOM Co through after the roasting ₃O ₄Carrier.Roasting condition is: (1) is at N ₂Be warming up to 300 ℃ with 1 ℃/min speed by room temperature under the atmosphere, and keep 3h, naturally be down to subsequently room temperature; (2) under air atmosphere, be warming up to 300 ℃ with 1 ℃/min speed by room temperature, keep 2h, rise to 450 ℃ with 1 ℃/min speed subsequently, keep naturally being down to room temperature behind the 3h.

(2) ice-water bath lucifuge environment: get that (the Au/PVA mass ratio=1.5:1), uniform stirring 10min adds 3.84mL NaBH subsequently fast in the aqueous solution (2.0mg/mL) that 27.08mL aqueous solution of chloraurate (1.5mmol/L) joins 2.67mL PVA ₄The aqueous solution (2.0mg/mL) (Au/NaBH ₄Mol ratio=1:5), when solution becomes brownish black, form the Au nanometre glue, stand-by behind the rapid stirring 30min.

(3) add 200mg 3DOM Co in the Au nanometre glue that makes to (2) ₃O ₄Carrier is at N ₂Gas sparging is auxiliary lower to be adsorbed, after glue clarification (i.e. absorption fully), filter, washing and under 110 ℃ dry 12h, namely make 2.7Au/3DOM Co ₃O ₄Catalyst, the aperture is about 260nm, and Au nano particle average grain diameter is 2.6nm.

Embodiment 3:

(1) getting the 20mmol cobalt nitrate hexahydrate joins in the 9mL absolute methanol and stirs 10min, add the 1mL PEG400 in the precursor liquid to mixing, behind the stirring at room 30min, add again an amount of PMMA hard template, in room temperature dipping 3h, filtration, drying at room temperature 24h namely obtain 3DOM Co through after the roasting ₃O ₄Carrier.Roasting condition is: (1) is at N ₂Be warming up to 300 ℃ with 1 ℃/min speed by room temperature under the atmosphere, and keep 3h, naturally be down to subsequently room temperature; (2) under air atmosphere, be warming up to 300 ℃ with 1 ℃/min speed by room temperature, keep 2h, rise to 450 ℃ with 1 ℃/min speed subsequently, keep naturally being down to room temperature behind the 3h.

(2) ice-water bath lucifuge environment: get that (the Au/PVA mass ratio=1.5:1), uniform stirring 10min adds 5.76mL NaBH subsequently fast in the aqueous solution (2.0mg/mL) that 40.62mL aqueous solution of chloraurate (1.5mmol/L) joins 4.00mL PVA ₄The aqueous solution (2.0mg/mL) (Au/NaBH ₄Mol ratio=1:5), when solution becomes brownish black, form the Au nanometre glue, stand-by behind the rapid stirring 30min.

(3) add 200mg 3DOM Co in the Au nanometre glue that makes to (2) ₃O ₄Carrier is at N ₂Gas sparging is auxiliary lower to be adsorbed, after glue clarification (i.e. absorption fully), filter, washing and under 110 ℃ dry 12h, namely make 5.2Au/3DOM Co ₃O ₄Catalyst, the aperture is about 280nm, and Au nano particle average grain diameter is 2.9nm.

Embodiment 4:

(1) getting the 20mmol cobalt nitrate hexahydrate joins in the 9mL absolute methanol and stirs 10min, add the 1mL PEG400 in the precursor liquid to mixing, behind the stirring at room 30min, add again an amount of PMMA hard template, in room temperature dipping 3h, filtration, drying at room temperature 24h namely obtain 3DOM Co through after the roasting ₃O ₄Carrier.Roasting condition is: (1) is at N ₂Be warming up to 300 ℃ with 1 ℃/min speed by room temperature under the atmosphere, and keep 3h, naturally be down to subsequently room temperature; (2) under air atmosphere, be warming up to 300 ℃ with 1 ℃/min speed by room temperature, keep 2h, rise to 450 ℃ with 1 ℃/min speed subsequently, keep naturally being down to room temperature behind the 3h.

(2) ice-water bath lucifuge environment: get that (the Au/PVA mass ratio=1.5:1), uniform stirring 10min adds 7.68mL NaBH subsequently fast in the aqueous solution (2.0mg/mL) that 54.16mL aqueous solution of chloraurate (1.5mmol/L) joins 5.33mL PVA ₄The aqueous solution (2.0mg/mL) (Au/NaBH ₄Mol ratio=1:5), when solution becomes brownish black, form the Au nanometre glue, stand-by behind the rapid stirring 30min.

(3) add 200mg 3DOM Co in the Au nanometre glue that makes to (2) ₃O ₄Carrier is at N ₂Gas sparging is auxiliary lower to be adsorbed, after glue clarification (i.e. absorption fully), filter, washing and under 110 ℃ dry 12h, namely make 6.5Au/3DOM Co ₃O ₄Catalyst, the aperture is about 270nm, and Au nano particle average grain diameter is 3.7nm.

Product material of the present invention is novel, and particle morphology and hole dimension are controlled, have good catalytic activity.CO concentration be 100ppm, CO and oxygen mol ratio be 1/20 and air speed be under 10000mL/ (g h) condition, 6.5Au/3DOM Co ₃O ₄Temperature when toluene conversion reaches 10%, 50% and 100% on the catalyst is respectively-68 ℃ ,-42 ℃ and-30 ℃.Toluene concentration be 1000ppm, toluene and oxygen mol ratio be 1/400 and air speed be under 40000mL/ (g h) condition, 7.5Au/3DOM Mn ₂O ₃Temperature when toluene conversion reaches 10%, 50% and 90% on the catalyst is respectively 215 ℃, 244 ℃ and 256 ℃.

Claims (4)

1. three-dimensional ordered macroporous Co ₃O ₄Loaded with nano Au catalyst is characterized in that, has the Co of 3DOM structure ₃O ₄Hole wall on load Emission in Cubic Au nano particle is arranged.

2. prepare three-dimensional ordered macroporous Co claimed in claim 1 ₃O ₄The method of loaded with nano Au catalyst is characterized in that, adopts the bubbling reducing process of the auxiliary PMMA glue crystal template method of PEG400 and polyvinyl alcohol protection to prepare respectively 3DOM Co ₃O ₄With Au/3DOM Co ₃O ₄, specifically may further comprise the steps:

(1) preparation 3DOM Co ₃O ₄: get cobalt nitrate hexahydrate and join and stir 10min in the absolute methanol, obtain precursor liquid, add PEG400 in the precursor liquid to mixing, cobalt nitrate hexahydrate wherein: absolute methanol: PEG400 is 20mmol:9ml:1ml, behind the stirring at room 30min, add again the PMMA hard template, in room temperature dipping 3h, filtration, drying at room temperature 24h namely obtain 3DOM Co through after the roasting ₃O ₄Carrier, calcination steps and condition are: (a) at N ₂Be warming up to 300 ℃ with 1 ℃/min speed by room temperature under the atmosphere, and keep 3h, naturally be down to subsequently room temperature; (b) under air atmosphere, be warming up to 300 ℃ with 1 ℃/min speed by room temperature, keep 2h, rise to 450 ℃ with 1 ℃/min speed subsequently, keep naturally being down to room temperature behind the 3h;

(2) preparation Au/3DOM Co ₃O ₄: ice-water bath lucifuge environment: aqueous solution of chloraurate is joined in the aqueous solution of PVA, Au/PVA mass ratio=1.5:1, uniform stirring 10min adds rapidly NaBH subsequently ₄Water solution A u/NaBH ₄Mol ratio=1:5 behind the stirring 30min, namely makes the Au nanometre glue;

Adopt bubbling reducing process and the infusion process of PVA protection to prepare xAu/3DOM Co ₃O ₄Catalyst: according to Au/3DOM Co ₃O ₄The Au load capacity of estimating in the catalyst adds the 3DOM Co for preparing in the step (1) in the Au nanometre glue ₃O ₄Carrier adsorbs gas sparging is auxiliary lower, after glue clarification (i.e. absorption fully), filter, washing and under 110 ℃ dry 12h, namely make Au/3DOM Co ₃O ₄Catalyst.

3. according to the method for claim 2, it is characterized in that, the Au load factor is 1-8%.

4. three-dimensional ordered macroporous Co claimed in claim 1 ₃O ₄Loaded with nano Au catalyst is used for CO and VOCs catalytic oxidation.

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