阅读说明：本技术 金属氧化物催化剂的制备方法及金属氧化物催化剂 (Method for producing metal oxide catalyst and metal oxide catalyst ) 是由 金钟植 河宪弼 于 2021-06-25 设计创作，主要内容包括：本发明涉及金属氧化物催化剂的制备方法及金属氧化物催化剂。本发明的金属氧化物催化剂,通过包括超临界二氧化碳萃取法的合成法制备而成,包含：包括一种以上的金属氧化物的活性位点以及用于负载所述活性位点的载体,其中,所述金属氧化物为选自元素周期表中的过渡金属(transition metal；原子序数为21～29、39～47、72～79或104～108)、镧系元素(lanthanide；原子序数为57～71)、后过渡金属(post-transition metal；原子序数为13、30～31、48～50、80～84、112)、准金属(metalloid；原子序数为14、32～33、51～52、85)以及它们的组合中的金属的氧化物。(The present invention relates to a method for producing a metal oxide catalyst and a metal oxide catalyst. The metal oxide catalyst of the present invention is prepared by a synthesis method including a supercritical carbon dioxide extraction method, and comprises: the metal oxide is an oxide of a metal selected from transition metals (atomic numbers 21-29, 39-47, 72-79 or 104-108), lanthanides (atomic numbers 57-71), post-transition metals (atomic numbers 13, 30-31, 48-50, 80-84, 112), metalloids (atomic numbers 14, 32-33, 51-52, 85) and combinations thereof in the periodic table of elements.)

1. A method of preparing a metal oxide catalyst, the metal oxide catalyst comprising: comprising active sites of one or more metal oxides and a carrier for supporting the active sites,

it is characterized in that the preparation method is characterized in that,

the preparation method uses a supercritical carbon dioxide extraction method.

2. The method for preparing a metal oxide catalyst according to claim 1, comprising the steps of:

dissolving a metal oxide catalyst grain precursor in a synthesis solvent and then precipitating the metal oxide catalyst grain precursor on the surface of a carrier;

drying the catalyst grain precursor-carrier intermediate product by using a supercritical carbon dioxide extraction method; and

the dried catalyst grain precursor-support intermediate is subjected to a calcination treatment to prepare a metal oxide catalyst.

3. The method for producing a metal oxide catalyst according to claim 1,

the supercritical carbon dioxide extraction method is carried out at the temperature of 50-150 ℃ for 0.1-24 hours and 10 hours^-5～10⁵CO at a flow rate of mL/min of 75-150 atm₂Under pressure.

4. The method for producing a metal oxide catalyst according to claim 2,

the supercritical carbon dioxide fluid extracted by the supercritical carbon dioxide extraction method reduces the interaction between the carrier and the synthesis solvent.

5. A metal oxide catalyst, comprising:

active sites comprising more than one metal oxide; and

a vector for supporting the active site(s),

wherein the metal oxide is a transition metal selected from the group consisting of transition metals having an atomic number of 21 to 29, 39 to 47, 72 to 79, or 104 to 108 in the periodic Table of elements; a lanthanide having an atomic number of 57-71; late transition metals with atomic numbers of 13, 30-31, 48-50, 80-84, 112; metalloids with atomic numbers of 14, 32-33, 51-52, 85; and oxides of the metals in combinations thereof.

6. The metal oxide catalyst of claim 5,

the active sites are porous and have a diameter ranging from 0.1nm to 500 μm.

7. The metal oxide catalyst of claim 5,

the composition range of the active site is 10 with respect to 100 parts by weight of the carrier^-4About 50 parts by weight.

8. The metal oxide catalyst of claim 5,

the carrier comprises an alkaline earth metal selected from the group consisting of atomic numbers 4, 12, 20, 38, 56, 88 of the periodic table of the elements; a transition metal having an atomic number of 21 to 29, 39 to 47, 72 to 79, or 104 to 108; a lanthanide having an atomic number of 57-71; late transition metals with atomic numbers of 13, 30-31, 48-50, 80-84, 112; metalloids with atomic numbers of 14, 32-33, 51-52, 85; and more than one element of carbon.

9. The metal oxide catalyst of claim 5,

the support is microporous, mesoporous, macroporous or multi-stage porous.

10. The metal oxide catalyst of claim 8,

the support comprises oxides of more than one of the elements.

Technical Field

The invention relates to a supercritical CO extraction process₂extraction) and control/enhancement of speed (rate) and performance (performance) in heterogeneous catalytic reactions (heterocatalysis) utilizing the same. Specifically, the regulation of the catalyst surface properties (surface properties) and the speed/performance improvement of the catalyst based on the preferred realization of the crystal structure (crystal structure)/porosity (porosity) of the support (support), the dispersion (dispersion) of the metal oxide active sites (active sites) dispersed within the support/crystal phase (crystal phase) are based.

Background

Heterogeneous catalysts (heterocatalysts) are generally composed of active sites and a carrier to make them highly dispersed. However, when a porous solid having weak chemical/physical (thermal) stability is used as a support of a catalyst, existing methods (e.g., filtration, washing, or thermal drying) of removing a synthesis solvent for dispersing active site precursors to the support frequently cause a phenomenon (aggregation) of destruction/collapse or aggregation of active sites of the support/active sites originally preferred after firing (or calcination). This is attributed to chemical bonds (e.g., dative bonds or hydrogen bonds) between the solvent and the carrier/active site and surface tension (surface tension) of the synthetic solvent, and in particular, a phenomenon (caliper effect) in which the synthetic solvent strongly attracts the carrier/active site during its removal from the pores of the carrier. Supercritical carbon dioxide fluids (fluids) can provide properties of 1) low viscosity (viscosity), 2) high diffusivity (dispersion) into solvent molecules based on miscibility (miscibility) with various polar solvents (solvents), 3) weak interaction (interaction) with the carrier/active sites of the solid phase, etc. Therefore, the supercritical carbon dioxide fluid (fluid) can stably remove/extract the synthetic solvent contained in the pores (pores) of the carrier having a porosity weak in chemical/physical (thermal) stability or having a significant interaction with the carrier/active sites, and thus can provide an advantage of minimizing the deterioration and deformation of the surface physical properties of the solid catalyst.

By supercritical CO extraction₂extract) has the advantage of providing high activity (activity), high conversion (conversion) or high selectivity (selectivity) in a variety of heterogeneously catalyzed reactions, in particular, the activation of the N-O/N-H/C-O/O-H bonds comprised by the reactants (activation) or in the cleavage reaction (fragmentation). More specifically, it is possible to preferably realize/control bronsted acid sites which may exist on the surface of a metal oxide catalyst formed by firing (or calcining) after supercritical treatment ((r))acid sites), Lewis acid sites (Lewis acid sites), distribution/number/strength of surface active oxygen species (labilexogen), oxygen vacancies (oxygen vacancies), etc., and redox characteristics, etc., such that the rate, conversion, or selectivity (selectivity) of the heterogeneously catalyzed reaction accompanied by one or more of the acid sites, oxygen species, or oxygen vacancies (oxygen vacancies) is improved or maximized.

For example, in the use of ammonia (NH)₃) For Nitrogen Oxide (NO) as precursor of fine particulate matter_XX ═ 1 or 2) is reduced to form nitrogen (N) selectively₂) And water (H)₂O) selective reduction of nitrogen oxides (selecivie catalytic NO)_Xreduction: SCR, in the reactions of the formulae (1) and (2)), it is possible to selectively activate the N-O bond of the nitrogen oxide in order to modify the nitrogenGas/water productivity.

4NO+4NH₃+O₂→4N₂+6H₂O…(1)

2NO₂+4NH₃+O₂→3N₂+6H₂O…(2)

In addition, for example, ammonia (NH) as a precursor of fine particulate matter can be selectively activated₃) Containing N-H bonds and using oxygen (O)₂) Carrying out oxidation (selective catalytic NH)₃oxidation: SCO) and improves the selectivity of nitrogen as a preferred product (selectivity, equation (3)) and minimizes Nitrogen Oxides (NO) as a non-preferred product_XReaction formulae (4) and (5)) and N₂Selectivity of O (reaction formula (6)).

4NH₃+3O₂→2N₂+6H₂O…(3)

4NH₃+5O₂→4NO+6H₂O…(4)

4NH₃+7O₂→4NO₂+6H₂O…(5)

4NH₃+2O₂→N₂O+3H₂O…(6)

However, even though the preparation of the metal oxide catalyst by the supercritical carbon dioxide extraction and the proposed catalytic reaction example have significant advantages and expected effects, there has been no example thereof so far.

Prior art documents

Patent document

(1) Granted patent publication No. 10-0878459

Disclosure of Invention

Technical problem

It is an object of the present invention to provide a novel synthesis method of a heterogeneous catalyst using supercritical carbon dioxide extraction, which is used to solve various problems derived from the above-mentioned metal oxide heterogeneous catalyst preparation method, and which is capable of providing an improved rate, conversion or selectivity (selectivity) for the selective activation reaction of N-O/N-H/C-O/O-H bonds contained in reactants, as compared to the existing catalyst preparation method.

In addition, it is an object of the present invention to provide a methodology which enables control of the preferred Bronsted acid sites for the selective activation of the N-O/N-H/C-O/O-H bonds ((S))acid site), Lewis acid site (Lewis acid site), distribution/number/intensity of surface active oxygen species (labyrin), oxygen vacancy (oxyden vacancy), etc., and redox characteristics. These issues are exemplary and the scope of the present invention is not limited in this respect.

Technical scheme

According to an aspect of the present invention for solving the above-described technical problems, there is provided a method for preparing a metal oxide catalyst comprising: the preparation method comprises the steps of preparing a carrier for loading active sites, wherein the carrier comprises the active sites of more than one metal oxide, and the preparation method uses a supercritical carbon dioxide extraction method.

According to an aspect of the present invention, the preparation method may include the steps of: precipitating (precipitation) the metal oxide catalyst crystallite precursor to the surface of the support after dissolving it in the synthesis solvent; drying the catalyst grain precursor-carrier intermediate product by using a supercritical carbon dioxide extraction method; the dried catalyst grain precursor-support intermediate is subjected to a calcination treatment to prepare a metal oxide catalyst.

According to one aspect of the present invention, the supercritical carbon dioxide extraction can be performed at a temperature of 50-150 ℃ for 0.1-24 hours and 10 hours^-5～10⁵CO at a flow rate of mL/min of 75-150 atm₂Under pressure.

According to an aspect of the present invention, the supercritical carbon dioxide fluid extracted by the supercritical carbon dioxide extraction method can reduce interaction between the carrier and the synthesis solvent.

According to another aspect of the present invention for solving the above technical problems, there is provided a heterogeneous catalyst comprising: active sites comprising more than one metal oxide; and a carrier capable of dispersing the active sites.

According to an aspect of the present invention, the metal of the metal oxide may be one or more selected from transition metals (atomic numbers 21 to 29, 39 to 47, 72 to 79, or 104 to 108), lanthanides (atomic numbers 57 to 71), post-transition metals (post-transition metals; atomic numbers 13, 30 to 31, 48 to 50, 80 to 84, 112), metalloids (atomic numbers 14, 32 to 33, 51 to 52, 85), and combinations thereof.

According to one aspect of the present invention, the carrier may be one or more elements selected from alkaline earth metals (atomic numbers: 4, 12, 20, 38, 56, 88), transition metals (atomic numbers: 21 to 29, 39 to 47, 72 to 79, or 104 to 108), lanthanides (atomic numbers: 57 to 71), post-transition metals (post-transition metals; atomic numbers: 13, 30 to 31, 48 to 50, 80 to 84, 112), metalloids (atomic numbers: 14, 32 to 33, 51 to 52, 85), or carbon (C), or may include one or more oxides of the elements.

According to one aspect of the invention, the active site or carrier may be a porous structure.

According to an aspect of the present invention, the diameter of the active site may be 0.1nm to 500 μm.

According to an aspect of the present invention, the carrier may comprise 10 parts by weight per 100 parts by weight of the carrier^-4About 50 parts by weight of said active sites.

Advantageous effects

According to the aspect of the present invention, the bronsted acid sites (i) present on the surface of the catalyst can be preferably controlled by preparing the catalyst in which the oxide of one or more metals selected from the periodic table of elements is dispersed on the carrier by the supercritical carbon dioxide extraction methodacid site), Lewis acid site (L)ewis acid site), distribution/number/intensity of surface active oxygen species (labile oxygen), oxygen vacancies (oxygen vacancy), etc., and redox characteristics.

In addition, the metal oxide catalyst prepared by the supercritical carbon dioxide extraction method can achieve selective activation of bonds contained in the reactant, for example, N-O bonds, N-H bonds, C-O bonds, O-H bonds, thereby enabling higher rate, more improved conversion (conversion), or selectivity (selectivity) than the metal oxide catalyst prepared by the conventional method (filtration, washing, or thermal drying). The catalyst prepared based on the advantages provided by the above supercritical carbon dioxide extraction method has the effect of remarkably improving the reaction performance and the durable life, compared with the catalyst prepared by the existing conventional method.

These issues are exemplary and the scope of the present invention is not limited in this respect.

Drawings

Fig. 1A to 1B are results of observing the catalysts prepared in examples 1 to 2 of the present invention using a Scanning Electron Microscope (SEM), and fig. 1C to 1D are results of observing the catalysts prepared in examples 1 to 2 of the present invention using a High Resolution Transmission Electron Microscope (HRTEM).

Fig. 2 is a diagram showing an X-ray diffraction pattern (XRD pattern) of the catalysts prepared in examples 1 to 2 of the present invention.

Fig. 3A and 3B are diagrams showing electron diffraction analysis patterns (SAED patterns) of the catalysts prepared in examples 1 to 2 of the present invention.

FIGS. 4A and 4B are hydrogen temperature programmed reduction spectra (H) of the catalysts prepared in examples 1 to 2 of the present invention₂-temperature programmed reduction(H₂-TPR) profile).

Fig. 5A and 5B are graphs showing X-ray photoelectron spectra (X-ray photoelectron (XP) spectra) in the O1s region of the catalysts prepared in examples 1 to 2 of the present invention.

FIGS. 6A and 6B are graphs showing the nitrogen oxide conversion rate (X) in the SCR reaction of the catalysts prepared in examples 1 to 2_NOX) And nitrogen selectivity (S)_N2) The figure (a).

FIG. 7 is a graph showing that catalysts prepared in examples 1 to 2 react in an SCR reaction according to the presence or absence of oxygen (O)₂) To undergo a change in performance (X)_NOX/X_NOX，0) The figure (a).

FIGS. 8A and 8B are graphs showing the ammonia conversion rate (X) in SCO reaction of the catalysts prepared in examples 1 to 2_NH3) And N₂/NO_X/N₂O selectivity (S)_N2/S_NOX/S_N2O) The figure (a).

FIGS. 9A and 9B are views showing that the catalysts prepared in examples 1 to 2 react in SCO according to the presence or absence of oxygen (O)₂) To undergo a change in performance (X)_NH3/X_NH3，0And S_N2) The figure (a).

FIG. 10 shows that the catalysts prepared in examples 1 to 2 have SO of 50ppm at a low temperature (180 ℃ C.) in the SCR reaction₂Long-term performance stability (long-term stability) under the conditions of (1).

FIG. 11 shows that the catalysts prepared in examples 1 to 2 have 500ppm of SO at low temperatures (180 ℃ C. and 200 ℃ C.) in the SCR reaction₂Long-term performance stability (long-term stability) under the conditions of (1).

Detailed Description

The following detailed description of the invention refers to the accompanying drawings, which illustrate specific embodiments by way of example, in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It is to be understood that the various embodiments of the invention are distinct from each other and are not necessarily mutually exclusive. For example, the features, structures, and characteristics described herein are associated with one embodiment and may be implemented in other embodiments without departing from the spirit and scope of the present invention. In addition, it is to be understood that the location or arrangement of individual elements within each disclosed embodiment may be modified without departing from the spirit and scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims and equivalents thereof, as appropriate. Like reference numerals in the drawings refer to the same or similar functionality in many respects, and may be exaggerated for convenience.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily practice the invention.

The metal oxide catalyst according to an embodiment of the present invention includes active sites (active sites) that are regions where a reactant is adsorbed and a product is desorbed after a reaction occurs, and a carrier (support) supporting the active sites.

The method for synthesizing the catalyst composed of the active sites/carriers by using the supercritical carbon dioxide extraction method comprises the following steps: step 1), precipitating a metal oxide catalyst crystal grain precursor (precipitation) on the surface of a carrier; step 2), drying the catalyst grain precursor-carrier intermediate product by using a supercritical carbon dioxide extraction method (step of removing the synthetic solvent); and 3) carrying out calcination (calcination) treatment on the dried catalyst grain precursor-carrier intermediate product, thereby preparing the metal oxide catalyst.

The catalyst grain precursor-support intermediate described above can be prepared by a variety of methods. For example, it can be prepared by one or more of hydrothermal synthesis (hydrothermal synthesis), solvothermal synthesis (solvothermal synthesis), non-template synthesis or template synthesis (non-templated or patterned synthesis), wet or dry impregnation with pH adjustment (wet or dry impregnation method), and thermal decomposition (thermal decomposition using metallic complex), but it is preferable to prepare an intermediate product in which the catalyst grain precursors are precipitated on a carrier (precipitation) in order to maximize the advantages provided by the above/later-described supercritical carbon dioxide extraction method.

For the above catalyst grain precursorSupercritical carbon dioxide extraction, in which the support intermediate is dried to remove the synthesis solvent, can be carried out by charging the precursor-support intermediate into a batch/continuous reactor and then subjecting the carbon dioxide (CO)₂) The treatment gas is exposed to the surface of the intermediate product at a predetermined flow rate/temperature/pressure, preferably at a temperature of 31 ℃ or higher and a pressure of 72.8atm or higher at which the supercritical carbon dioxide fluid is generated. The ranges of conditions for the generation of the supercritical carbon dioxide fluid are shown in table 1 below.

TABLE 1

When the supercritical carbon dioxide extraction condition is less than 50 deg.C, less than 0.1 hr, and less than 10 ℃^-5Flow rate of mL/min or CO of less than 75atm₂At pressure, the supercritical carbon dioxide extraction effect on the catalyst surface may be weak. In contrast, when the supercritical carbon dioxide extraction conditions are greater than 150 ℃ for greater than 24 hours for greater than 10⁵Flow rate of mL/min or CO of more than 150atm₂Under stress, it may cause structural destruction/deformation of the active site/carrier, or annihilation of surface active oxygen species/oxygen vacancies (oxygen vacancies), or severe reduction of redox properties. Thus, supercritical carbon dioxide extraction for removing the synthesis solvent contained in the precursor-support intermediate can be performed within the above-described ranges of conditions.

The metal oxide catalyst of one embodiment of the present invention comprises at least one selected from transition metals (atomic numbers 21 to 29, 39 to 47, 72 to 79, or 104 to 108), lanthanides (atomic numbers 57 to 71), post-transition metals (post-transition metals; atomic numbers 13, 30 to 31, 48 to 50, 80 to 84, 112), metalloids (atomic numbers 14, 32 to 33, 51 to 52, 85), or combinations thereof as an active site.

The method for preparing a metal oxide catalyst according to an embodiment of the present invention uses a supercritical carbon dioxideThe carbon oxide extraction method removes a synthesis solvent for dissolving the active site precursor, and firing (or calcining) conditions are adjusted to control the stoichiometry of metal and oxygen (stoichimetry). In addition, realizing a plurality of metal oxide structures, controlling metal-oxygen coordination bonds and the like, thereby enabling to control preferentially the bronsted acid sites present on the surface of the metal oxide regardless of the kind of the metal used for preparing the active sites (b) ((r))acid site), lewis acid site (lewis acid site), distribution/number/strength of surface active oxygen species (labyrin), oxygen vacancy (oxyden vacancy), etc., and redox characteristics.

For example, oxides of manganese can be subjected to supercritical carbon dioxide extraction, 1) removal of a synthesis solvent for dissolving a precursor of oxides of manganese and adjustment of firing (or calcination) conditions, 2) varied to α -MnO₂、γ-MnO₂、Mn₂O₃、Mn₃O₄Etc., 3) adjusting the distribution and manganese oxidation number on the support surface of each structure, 4) adjusting the coordination number, vacancy (vacancy) or defect (defect) number/intensity and redox characteristics of Mn — O bonds contained in the above structure, 5) controlling selective activation of N — O bonds, N — H bonds and related properties.

The metal oxide active sites of one embodiment of the present invention may have porosity and may be dispersed in a porous carrier as described below.

The diameter (maximum diameter) of the metal oxide active site of an embodiment of the present invention may be 0.1nm to 500 μm, and the composition range of the metal oxide active site may be 10 with respect to 100 parts by weight of the support^-4About 50 parts by weight.

The metal oxide catalyst of one embodiment of the present invention comprises at least one selected from the group consisting of alkaline earth metals (atomic numbers: 4, 12, 20, 38, 56, 88), transition metals (atomic numbers: 21 to 29, 39 to 47, 72 to 79, or 104 to 108), lanthanides (atomic numbers: 57 to 71), post-transition metals (post-transition metals; atomic numbers: 13, 30 to 31, 48 to 50, 80 to 84, 112), metalloids (atomic numbers: 14, 32 to 33, 51 to 52, 85), and carbon (C), or a combination thereof as a carrier.

The carrier is capable of utilizing a supercritical carbon dioxide extraction method, 1) minimizing destruction and structural collapse of porosity, 2) improving pores of active sites or dispersion (dispersity) on the surface of the carrier, 3) preferably controlling distribution/quantity/intensity of surface active oxygen species (labile oxygen) and oxygen vacancies (oxygen vacancy) and the like and redox characteristics regardless of the kind of metal used for preparing the carrier.

In particular, when the supercritical carbon dioxide extraction method proposed in the present invention is used for a support containing microporosity, its effect is great because the supercritical carbon dioxide fluid (fluid) can significantly reduce the interaction between the microporosity and the synthesis solvent for dissolving the active site precursor. That is, since the surface tension (surface tension) and the capillary effect (capillary effect) of the synthesis solvent, which are problematic in the removal process of the synthesis solvent, can be significantly reduced, it is possible to contribute to minimizing the collapse of micropores when removing the synthesis solvent and to maintain the microporosity of the support after the calcination treatment. Therefore, the supercritical carbon dioxide extraction method can finally realize the surface physical properties of the active sites more preferable for the selective activation of the bonds contained in the reactant, for example, the N — O bond, the N — H bond, the C — O bond, or the O — H bond, within the micropores within a range that does not hinder the dispersion degree of the active sites dispersed in the micropores.

Specifically, when the supercritical carbon dioxide extraction method proposed in the present invention is applied to a reducing support (for example, CeO) which may contain active oxygen species (reactive oxygen species) or oxygen vacancies (oxygen vacancy) on the surface thereof₂Or TiO₂) And the effect thereof is great because 1) the synthesis solvent or organic matter/foreign matter contained in the active site precursor can be efficiently removed before the calcination treatment, thereby maximizing the number/distribution of active oxygen species or oxygen vacancies (oxygen vacancies) exposed to the surface after the calcination treatment and the redox characteristics,2) the supercritical carbon dioxide extraction method or the calcination treatment conditions can be controlled, so that the interaction (bonding strength) between active oxygen species or oxygen vacancies (oxygen vacancies) and catalytic reactants, the redox characteristics and the like can be adjusted.

Hereinafter, various embodiments for assisting understanding of the present invention will be described. However, the following embodiments are only for assisting understanding of the present invention, and the embodiments of the present invention are not limited to the following embodiments.

₂Examples 1 to 2: preparation of Mn and Mn (Sc CO) catalysts

37.5mL of a solution of 6.9g of sulfuric acid (98% H)₂SO₄) Is heated to 50 ℃ and 11.25g of TiOSO, a titanium salt, is added₄After that, the solution was dissolved for 30 minutes. Thereafter, 75g of urea (urea, CO (NH)) was added₂)₂) And 500mL of distilled water, and then warmed to 100 ℃ and stirred for 18 hours. Cooling the formed intermediate product to 25 ℃, filtering/washing the intermediate product by using distilled water, and realizing supercritical CO of the obtained solid under the conditions of temperature of 60-70 ℃ and pressure of 90-100 atm₂(99.99%) fluid (Sc CO)₂) After the lower exposure for about 30 minutes, a calcination treatment was performed at 400 ℃ for 3 hours, thereby obtaining titanium oxide (TiO) having a mixed mesoporous (mesoporous) and microporous (microporous) porosity and having a hierarchical porosity₂). Catalysts of examples 1 to 2 utilizing the above TiO₂Synthesized as a carrier. To synthesize the catalyst of example 1, 1.95g of manganese salt Mn (NO) was added to 250mL of distilled water₃)₂·XH₂O and 3.4g of TiO₂And after stirring for 30 minutes at 25 ℃ NH is used₄OH adjusts the pH of the liquid phase mixture to 10. Thereafter, dehydration was performed after stirring at 25 ℃ for 18 hours, and a calcination treatment was performed at 400 ℃ for 3 hours, thereby obtaining a catalyst of example 1, which was named Mn. To synthesize the catalyst of example 2, 1.95g of manganese salt Mn (NO) was added to 250mL of distilled water₃)₂·XH₂O and 3.4g of TiO₂And after stirring for 30 minutes at 25 ℃ NH is used₄OH solutionThe pH of the phase mixture was adjusted to 10. After that, after stirring at 25 ℃ for 18 hours, filtration/washing was performed with distilled water. Supercritical CO realized by the obtained solid under the conditions of the temperature of 60-70 ℃ and the pressure of 90-100 atm₂(99.99%) fluid (Sc CO)₂) After about 30 minutes of the exposure, a calcination treatment was carried out at 400 ℃ for 3 hours, thereby obtaining the catalyst of example 2, which was named Mn (Sc CO)₂)。

Experimental example 1: analysis of catalyst Properties

The surface morphology (morphology) of the catalysts prepared in examples 1 to 2 was analyzed using a Scanning Electron Microscope (SEM) and a High Resolution Transmission Electron Microscope (HRTEM), and the results thereof are shown in fig. 1A to 1D. Referring to fig. 1A to 1D, it can be confirmed that TiO having particle diameters (maximum diameters) of several hundred nanometers to several hundred micrometers, respectively, among the prepared catalysts₂The agglomerates (agglomerates) constitute a porous carrier.

In order to confirm the degree of porosity of the catalyst according to examples 1 to 2, nitrogen adsorption (N) was performed₂physisorption) experiment, and measuring the micropore surface area (S) of the catalyst by using a non-localized density function (non-localized functional) technical method_MICRO) And mesoporous surface area (S)_MESO). In addition, the components of the catalysts prepared in examples 1 to 2 were analyzed using X-ray fluorescence spectrum analysis. The measurement results are shown in table 2.

TABLE 2

Capable of removing the surface area (S) of the micropores_MICRO) And mesoporous surface area (S)_MESO) As a result, it was confirmed that the catalysts of examples 1 to 2 had hierarchical porosity (hierarchical porosity) in which micropores and mesopores were mixed. In addition, the inclusion of the catalyst active site can be confirmedThe theoretical value of the quantity is similar to the observed value. Specifically, examples 1 and 2 were found to have about 15 wt% of Mn (about 2.73 mmol)_Mn,/g), which means that the content of active sites is similar between the catalyst prepared in association with the supercritical carbon dioxide extraction process and the catalyst not prepared in the state associated with the supercritical carbon dioxide extraction process.

The crystal structures of examples 1 to 2 were analyzed using an X-ray diffractometer (X-ray diffractor), and an X-ray diffraction pattern (XRD pattern) derived as a result thereof is shown in fig. 2. Referring to FIG. 2, it was confirmed that the catalysts of examples 1 to 2 all contained TiO atoms₂Crystal face of anatase phase of tetragonal (tetragonal) crystal structure of the carrier. On the other hand, α -MnO having a tetragonal (tetragonal) crystal structure was observed from the X-ray diffraction pattern of example 1₂Phase, gamma-MnO with orthogonal (orthohomombic) crystal structure₂Phase, alpha-MN having cubic (cubic) crystal structure₂O₃Phase and Mn having tetragonal (tetragonal) crystal structure₃O₄Crystal planes of the phases, but crystal planes of the above-mentioned various manganese oxides were not observed from the X-ray diffraction pattern of example 2. This is explained as the bulk (bulk) crystal structure of the manganese oxide of example 2 prepared with the supercritical carbon dioxide extraction process is so small that it cannot be detected by X-ray diffraction analysis.

Therefore, the catalysts of examples 1 to 2 were analyzed using a selected area electron diffraction pattern (SAED pattern), and the results thereof are shown in fig. 3A and 3B. Referring to fig. 3A and 3B, as the X-ray diffraction analysis results, the (101) and (004) planes (red concentric circles) of an anatase phase having a tetragonal (tetragonal) crystal structure were observed. In addition, α -MnO having a tetragonal (tetragonal) crystal structure was also simultaneously observed₂Phase (yellow concentric circles 1 and 3), gamma-MnO with orthogonal (orthohorombic) crystal structure₂Phase (yellow concentric circle 2), alpha-Mn with cubic (cubic) crystal structure₂O₃Phase (yellow concentric circles 6) and having four directions (tetra)gonal) crystal structure of Mn₃O₄Crystal faces of the phases (yellow concentric circles 1-6). From this, it was confirmed that the manganese oxide as the catalyst active site in examples 1 to 2 was successfully dispersed in the TiO having hierarchical porosity₂And (3) a carrier.

Reduction with hydrogen temperature programmed (H)₂-temperature programmed reduction，H₂TPR) technical method for the active sites (manganese oxide) and the support (TiO) of the catalysts of examples 1 to 2₂) The bonding strength (interaction) between them was analyzed, and the result (H) was obtained₂TPR spectra) are shown in FIGS. 4A and 4B. Referring to fig. 4A and 4B, the hydrogen temperature-programmed reduction spectra (H) of examples 1 to 2 were obtained₂TPR spectra) five bands were observed, which represent manganese oxide and TiO, respectively₂Degree of interaction (red band), Mn contained in manganese oxide⁴⁺Is reduced to Mn³⁺Mn contained in (turquoise) manganese oxide³⁺Is reduced to Mn²⁺/Mn³⁺(blue color band), Mn contained in manganese oxide²⁺/Mn³⁺Is reduced to Mn²⁺(sky blue color band), TiO₂Containing Ti⁴⁺Is reduced to Ti³⁺(purple band). Example 2 was observed to exhibit more manganese oxide and TiO than example 1₂The interaction of (red band; 7.4% for example 1; 20.6% for example 2). This means that example 2 can reduce catalyst poisons contained in the exhaust gas during the reaction (for example, SO in the SCR reaction) as compared with example 1₂) The opportunity of interaction with the manganese oxide as an active site, thereby minimizing the poisoning phenomenon of the catalyst by the poison and increasing the resistance (resistance) of the catalyst to the poison.

The redox characteristics of the catalysts of examples 1 to 2 were analyzed by X-ray photoelectron spectroscopy in the O1s region, and the results are shown in fig. 5A and 5B. Referring to fig. 5A and 5B, H present on the surface of the catalyst chemisorbed was observed in the catalysts of examples 1 to 2₂Oxygen species in O (O)_α'), active oxygen species (O)_α) And oxygen species (O) present in the catalyst lattice_β). It was observed that example 2 contained more active oxygen species (O) at the surface than example 1_α) This means that the catalyst of example 2 is able to provide more active oxygen species during the catalytic reaction than the catalyst of example 1, and thus is able to increase the rate and performance (conversion, selectivity) of the catalytic reaction.

Hereinafter, the results of performance analysis of the catalysts of examples 1 to 2 of the present invention in the SCR and SCO reactions will be described with reference to fig. 6 to 11.

Experimental example 2: performance analysis of the SCR reaction (1)

The performance of the SCR process was measured using the catalysts of examples 1-2. Conversion of Nitrogen Oxides (NO) in the temperature range of 150 ℃ to 400 ℃_X conversion，X_NOX) And nitrogen selectivity (N)₂selectivity，S_N2) Shown in fig. 6A and 6B. As a condition of the SCR process, the reaction fluid contains 200ppm of NO_X200ppm NH₃3% by volume of O₂6% by volume of H₂O, 500ppm SO₂And inert gas (inert gas) N₂Total flow rate (total flow rate) of 500mL/min, space velocity (space velocity) of 30,000hr^-1. Referring to fig. 6A and 6B, it can be seen that the catalyst of example 2 shows improved performance in a temperature range of 150 to 400 ℃ compared to example 1, which means that the catalyst of example 2 prepared by the supercritical carbon dioxide extraction method shows improved N based on the SCR reaction in a low temperature region (200 ℃ or less) compared to the catalyst of example 1 prepared by the conventional method₂Productivity, lower side reactant (N) by SCR reaction in medium temperature region (200-280 deg.C)₂O) productivity, shows more improved N based on SCR and SCO reactions in the high temperature region (more than 280 ℃ C.)₂And (4) the productivity. In addition, this means that the catalyst of example 2 is more selective in activation of the surface containing a bond for N-O or N-H than the catalyst of example 1Preferred are bronsted acids, lewis acids and redox properties.

Experimental example 3: performance analysis of the SCR reaction (2)

The performance of the SCR process was measured using the catalysts of examples 1-2. With or without O at 180 DEG C₂Under the condition (1-4 hours), the conversion rate (NO) of nitrogen oxide_X conversion，X_NOX) Divided by the initial nitrogen oxide conversion (X)_NOX，0) And is shown in FIG. 7 (X)_NOX/X_NOX，0). As a condition of the SCR process, the reaction fluid contains 200ppm of NO_X200ppm NH₃3% by volume of O₂6% by volume of H₂O and inert gas N₂The total flow rate is 500mL/min, and the space velocity is 30,000hr^-1. Referring to FIG. 7, it can be seen that the catalyst of example 2 exhibits more preferable redox (redox) characteristics in terms of selective activation of N-O bond or N-H bond in a low temperature region (180 ℃) than that of example 1, since the catalyst of example 2 prepared by the supercritical carbon dioxide extraction method is free of O in comparison with the catalyst of example 1 prepared by the conventional method₂Under the condition of (1), X_NOX/X_NOX，0Greater value of (A), X_NOX/X_NOX，0The rate of decrease in value is less.

Experimental example 4: performance analysis of the SCO reaction (1)

The performance of the SCO process was measured using the catalysts of examples 1-2. Conversion of ammonia (NH) at a temperature in the range of 150 ℃ to 400 ℃₃ conversion，X_NH3) And the product (N)₂、NO_X、N₂O) selectivity (N)₂/NO_X/N₂O selectivity，S_N2/S_NOX/S_N2O) Shown in fig. 8A and 8B. As a condition for the SCO process, the reaction fluid contained 200ppm of NH₃3% by volume of O₂6% by volume of H₂O and inert gas N₂The total flow rate is 500mL/min, and the space velocity is 30,000hr^-1. Referring to fig. 8A and 8B, mayIt is known that the catalyst of example 2 shows improved performance in a temperature range of 150 to 400 ℃ compared to example 1, which is resulted from more improved X based on SCO reaction at the same reaction temperature of the catalyst of example 2 prepared by the supercritical carbon dioxide extraction method compared to the catalyst of example 1 prepared by the conventional method_NOXValue, greater selectivity (S) for preferred products_N2) Value, less selectivity (S) to non-preferred products_NOXAnd S_N2O) The value proves. This means that the catalyst of example 2 contains more preferable bronsted acid, lewis acid and redox characteristics in terms of selective activation of N — H bond on the surface than the catalyst of example 1.

Experimental example 5: performance analysis of the SCO reaction (2)

The performance of the SCO process was measured using the catalysts of examples 1-2. At 350 ℃ in the presence or absence of O₂Under the condition (1 to 4 hours), the conversion rate (NH) of ammonia₃ conversion，X_NH3) Divided by the initial ammonia conversion (X)_NH3，0) And is shown in FIG. 9A (X)_NH3/X_NH3，₀) And selectivity of nitrogen (N) as a preferred product₂selectivity，S_N2) Shown in fig. 9B. As a condition for the SCO process, the reaction fluid contained 200ppm of NH₃3% by volume of O₂6% by volume of H₂O and inert gas N₂The total flow rate is 500mL/min, and the space velocity is 30,000hr^-1. Referring to fig. 9A and 9B, it can be seen that the catalyst of example 2 exhibits more preferable redox characteristics in terms of selective activation of N — H bonds in a high temperature region (350 ℃) than the catalyst of example 1, since the catalyst of example 2 prepared by the supercritical carbon dioxide extraction method does not have O in comparison with the catalyst of example 1 prepared by the conventional method₂Under the condition of (1), X_NH3/X_NH3，0Greater value of (A), X_NH3/X_NH3，₀The rate of decrease of the value is smaller, S_N2Greater values of (c).

Experimental example 6: performance analysis of the SCR reaction (3)

At 30,000hr^-1And contains 200ppm of NO_X200ppm NH₃50ppm SO₂3% by volume of O₂6% by volume of H₂O and inert gas N₂The SCR process performance of the catalysts of examples 1 to 2 was measured at 180 ℃, and the results are shown in fig. 10. In particular, it is observed that₂O/SO₂Poisoning of the catalyst surface by/AS (ammonium sulfate)/ABS (ammonium bisulfate), etc., and conversion rate of nitrogen oxide (X) of the catalyst_NOX) A reduced tendency. Referring to FIG. 10, the catalyst of example 2 is in a low temperature (180 ℃) region, with or without SO, compared to example 1₂Under the conditions of (A), a greater conversion of nitrogen oxides (X) is exhibited_NOX). This means that the catalyst of example 2 is more resistant to poisons supplied/generated during the reaction than example 1. This means that the catalyst of example 2 prepared by the supercritical carbon dioxide extraction method was imparted with poison (H) in comparison with the catalyst of example 1 prepared by the conventional method₂O/SO₂AS/ABS) and means that extended catalyst life is provided.

Experimental example 7: performance analysis of the SCR reaction (4)

At 30,000hr^-1And contains 200ppm of NO_X200ppm NH₃500ppm SO₂3% by volume of O₂6% by volume of H₂O and inert gas (inert gas) N₂The performance of the SCR process of the catalysts of examples 1 to 2 was measured at 180 ℃ and 200 ℃, and the results are shown in fig. 11. Specifically, the conversion rate (X) of nitrogen oxides of the catalyst_NOX) Divided by the initial period of the reaction (no SO present)₂Under the conditions of (b) conversion of nitrogen oxides (X)_NOX，0). In addition, measure and is based on H₂O/SO₂/AS (ammonium sulfate, amo)Poisoning of the catalyst surface by nium sulfate/ABS (ammonium bisulfate) and the like, the catalyst exhibited a performance (X) of 65% of the initial performance_NOX/X_NOX，00.65) time required. Referring to fig. 11, it can be observed that the catalyst of example 2 (10 hours at 180 ℃; 18 hours at 200 ℃) shows more improved resistance to poisons in the low temperature region than that of example 1 (6 hours at 180 ℃; 15 hours at 200 ℃). This means that the catalyst of example 2 prepared by the supercritical carbon dioxide extraction method was imparted with poison (H) in comparison with the catalyst of example 1 prepared by the conventional method₂O/SO₂AS/ABS) and means that extended catalyst life is provided.

The present invention has been described in terms of the preferred embodiments described above, but the present invention is not limited to the embodiments, and those skilled in the art can make various modifications and alterations without departing from the spirit of the present invention. But variations and modifications should be considered to be within the scope of the invention and the appended claims.