KR20110101862A - Heteropolyacid catalyst immobilized on carbon aerogel support, preparation method thereof and production method of acetone by oxidation of isopropanol using said catalyst - Google Patents

Abstract

The present invention relates to a heteropolyacid-supported catalyst immobilized on a carbon aerogel, a method for preparing the same, and a method for preparing acetone by oxidation of isopropanol using the catalyst, and more particularly, to an amine group (-NR ₁ R ₂ R ₃ ⁺ , R ₁ , R _2, and R ₃ are each independently hydrogen or C 1 to C 20 alkyl group) carbon aerogels, characterized in that the anionic heteropoly acid reacted in a weight ratio of 1: 0.01 to 2 by weight and ion-bonded The present invention relates to a heteropolyacid-supported catalyst chemically immobilized on an airgel carrier, a method for preparing the same, and a method for preparing acetone by oxidation of isopropanol using the catalyst. Introducing a cationic functional group to the surface and reacting the heteropoly acid having an anion characteristic thereto to provide a chemically immobilized heteropoly acid-supported catalyst, the acid catalyst properties when the acetone production by oxidation of isopropanol is performed using the catalyst Suppressed and the oxidation catalyst properties are activated At every reaction it exhibited a high conversion ratio of isopropanol and acetone, high selectivity.

Description

Heteropoly acid-supported catalyst immobilized on a carbon aerogel, a method for preparing the same and a method for producing acetone by oxidation of isopropanol using the catalyst }

The present invention relates to a heteropolyacid-supported catalyst immobilized on a carbon aerogel, a method for preparing the same, and a method for preparing acetone by oxidation of isopropanol using the catalyst, and more particularly, to an amine group (-NR ₁ R ₂ R ₃ ⁺ , R ₁ , R _2, and R ₃ are each independently hydrogen or C 1 to C 20 alkyl group) carbon aerogels, characterized in that the anionic heteropoly acid reacted in a weight ratio of 1: 0.01 to 2 by weight and ion-bonded The present invention relates to a heteropolyacid supported catalyst chemically immobilized on an airgel carrier, a method for preparing the same, and a method for producing acetone by oxidation of isopropanol using the catalyst.

Heteropolyacid catalysts are bifunctional catalysts having both acid and oxidation characteristics, and are well soluble in polar solvents containing oxygen such as water, alcohols and ethers. Heteropoly acids act as Br ㆆ nsted acid when acting as an acid catalyst, and the strong acid properties of heteropolyacids are distinguished from those of nitric acid or sulfuric acid and have a stronger acid point than ordinary silica and alumina. . In general, heteropolyacids can be prepared with various combinations of compounds by mutually displacing the various compositions constituting the catalyst, and through this, there is an advantage of controlling the intrinsic catalyst properties of the catalyst. Heteropolyacid catalysts having both acid and oxidation properties are used not only for heterogeneous reactions in gas and liquid phases, but also for fine chemical reactions through homogeneous reactions in liquid phases.

Since the bulk heteropolyacid catalyst has a very small specific surface area (less than 10 m ² / g), in order to overcome the small specific surface area and maximize the activity of the catalyst, various inorganic materials (alumina, silica, titania), the skeleton of the conductive polymer ( It is supported on polyaniline, polypyrrole, poly 4-vinyl-pyridine) and carbon, and is used for gas phase reaction and liquid phase reaction. Attempts to prepare such heteropolyacid-supported catalysts have been made as part of a method for lowering the cost of using a heteropolyacid catalyst in actual reactions by increasing the active area of the heteropolyacid catalyst, and reducing catalyst deactivation due to a long catalyst reaction time.

Examples of preparing a heteropolyacid-supported catalyst and using it for catalytic reactions have been reported variously through papers and patents. Examples of Heteropoly Acids Supported on Catalytic Reactions Supported by Silica Materials [B. Qiu, X. Yi, L. Lin, W. Fang, H. Wan, Catal. Today, Vol. 131, p. 464 (2008) / C.S. Caetano, I.M. Fonseca, A.M. Ramos, J. Vital, J.E. Castanheiro, Catal. Commun., Vol. 9, p. 1996 (2008) / A. Lapkin, A. Bozkaya, T. Mays, L. Borello, K. Edler, B. Crittenden, Catal. Today, Vol. 81, p. 611 (2003) / P.M. Rao, A. Wolfson, S. Kabaya, S. Vega, M.V. Landau, J. Catal., Vol. 232, pp. 210 (2005)] impregnated heteropolyacids on the surface of silica by impregnation using various silica materials, or by adding heteropolyacids together when preparing a catalyst carrier. The method of supporting heteropoly acid on the silica skeleton by copolymerization was used. In addition, a method of chemically immobilizing a heteropoly acid by introducing a cationic functional group to a conductive polymer carrier [Song In-gyu, Kim Hee-su, Jung Cheol, Korean Patent No. 801,443 (2008) / H. Kim, J.C. Jung, D. R. Park, S.-H. Baeck, I.K. Song, Appl. Catal. A., vol. 320, p. 159 (2007) / H. Kim, J.C. Jung, D. R. Park, H. Lee, J. Lee, S.H. Lee, S.-H. Baeck, K.-Y. Lee, J. Yi, I.K. Song, Catal. Today, Vol. 132, 58 (2008)]. In addition, a method of using a polymer film as a carrier of a heteropolyacid catalyst for supporting heteropoly acid [Lee Hwa Young, Song In Kyu, Jong Kuk Lee, Korean Patent No. 186,707 (1998)] has been attempted, and a method of supporting heteropoly acid on a carbon-gel type carrier [ SR Mukai, T. Sugiyama, H. Tamon, Appl. Catal. A., 256, 99 (2003)].

Carbon airgel is a super porous material having nano-porous structure properties, and has been used in various fields due to its excellent electrochemical properties and high specific surface area. As used herein, 'carbon aerogel' refers to a carbon structure having a continuous monolithic three-dimensional network structure, a medium pore between 2-100 nm and a specific surface area in the range of 400-1200 m ² / g. Carbon aerogels are characterized by having a lower density of physical properties than ordinary carbon materials because the air layer is contained inside the pores of 100 nm or less, where spherical particles of 2-5 nm size form a three-dimensional network. Unlike ordinary medium-sized pore carbons, these unique structural properties make it possible to prepare them in various forms such as beads, powders or thin films as well as continuous monoliths. A wide range of applications is possible, including applications as. In addition, it has high electrical conductivity found in general carbon, and it is known that not only the structure is stable in acid-alkali reaction but also thermally stable at high temperature. By utilizing such high electrical conductivity and surface area, carbon aerogels can be used as an electrode material in electrochemical reactions or as a catalyst carrier for fuel cells, and because they are very chemically stable, they are less structurally modified and contain heavy metals or highly toxic organic substances. It can also be used as an adsorbent to remove waste dyes from dyeing processes.

On the other hand, the method for preparing acetone from isopropanol is carried out through an oxidation catalytic reaction of isopropanol. The conventional heteropolyacid catalyst has a very small specific surface area, which does not maximize the activity of the catalyst, and has both an acid and a redox characteristic, thus catalyzing catalytic reaction characteristics. In the catalytic reaction, both an acid catalyzed reaction and an oxidation catalyzed reaction occur, resulting in a decrease in yield and selectivity due to unwanted side reactions. Therefore, in order for the heteropolyacid catalyst to work efficiently in the acetone production reaction by the oxidation of isopropanol, it is necessary to prepare a supported catalyst capable of dispersing the heteropolyacid widely and suppressing the acid property of the catalyst and at the same time improving the oxidation reaction property. It is essential.

However, the preparation of supported catalysts of heteropolyacids reported in the related art, including those disclosed in the above-mentioned documents, does not control the strong acid properties of heteropolyacids in the supporting process, thereby maintaining amphoteric catalyst properties having both acid and redox characteristics. Therefore, when used in the oxidation catalytic reaction, an unwanted acid catalyzed reaction is generated as a side reaction, and there is a problem in that the yield of the desired product is lowered and the selectivity is deteriorated due to the generation of by-products.

Therefore, the technical problem of the present invention is excellent dispersion degree to solve the low surface area of the bulk heteropolyacid catalyst, the combination of the heteropoly acid and the carrier is composed of chemical bonds, high stability and selectivity for the oxidation catalyst activity while suppressing the acid catalyst properties The present invention provides a heteropolyacid supported catalyst immobilized on a high carbon airgel and a method of preparing the same.

Another technical problem of the present invention is to increase the conversion rate of isopropanol and at the same time improve the production of acetone by inhibiting the acid catalytic reaction characteristics of the heteropolyacid catalyst and promoting the oxidation catalytic reaction characteristic in the oxidation reaction of the isopropanol using the heteropolyacid supported catalyst. will be.

In order to achieve the above technical problem, the present invention provides an amine group (-NR ₁ R ₂ R ₃ ⁺ , R ₁ , R _2, and R ₃ are each independently hydrogen or C 1 to C 20 alkyl group) carbon aerogels, characterized in that the anionic heteropoly acid reacted in a weight ratio of 1: 0.01 to 2 by weight and ion-bonded Provided is a heteropolyacid supported catalyst chemically immobilized on an airgel carrier.

In addition, the present invention, the heteropoly acid is a heteropoly acid of the Keggin form or Wells-Dawsons form 12-molybdate phosphoric acid (H ₃ PMo ₁₂ O ₄₀ ), 12- tungstoic acid (H ₃ PW ₁₂ O ₄₀ ), 12- tungstosilonic acid (H ₄ SiW ₁₂ O ₄₀ ), 12-molybdo tungstophosphoric acid (H ₃ PMo _{12 - x} W _x O ₄₀ , x = 0-12), 12- Molybdobanadophosphoric acid (H _{3 + x} PMo _{12 - x} V _x O ₄₀ , x = 0-12), _{12 -} tungstobanadophosphoric acid (H _{3 + x} PW _{12 - x} V _x O ₄₀ , x = 0-12), 18-molybdate phosphoric acid (H ₆ P ₂ Mo ₁₈ O ₆₂ ), 18- tungstophosphoric acid (H ₆ P ₂ W ₁₈ O ₆₂ ), 18-molybdo tungstophosphoric acid (H ₆ P ₂ Mo _{18 - x} W _x O ₆₂ , x = 0-18), 18-molybdobanadophosphate (H _{6 + x} P ₂ Mo _{18 -x} V _x O ₆₂ , x = 0-18), 18- Tungsutobanadophosphate (H _{6 + x} P ₂ W _{18 - x} V _x O ₆₂ , x = 0-18), 18-tungstoniobium phosphate (H _{6 + x} P ₂ W _{18 - x} Nb _x O ₆₂ , x = 0-18), and the like. The heteropolyacid-supported catalyst immobilized on the carbon airgel carrier, characterized in that at least one member selected from the group consisting of Provided.

In addition, the present invention comprises the steps of iii) activating carbon by hydrogenating the surface of the carbon airgel; Ii) reacting the surface activated carbon airgel with sulfuric acid and nitric acid solution in the presence of acetic anhydride to attach nitro groups to the surface of the carbon airgel; Iii) reducing the nitro group attached to the surface of the carbon airgel to amine it, and iii) reacting the amine and heteropolyacid formed on the surface of the carbon airgel in a weight ratio of 1: 0.01 to 2 for ion bonding. Provided is a method for preparing a heteropolyacid supported catalyst immobilized on a carbon airgel.

The present invention also provides a method for producing acetone by oxidation of isopropanol in the presence of a heteropolyacid supported catalyst chemically immobilized on the carbon airgel carrier.

The heteropolyacid catalyst immobilized on the carbon airgel of the present invention treats the porous carbon airgel having a large surface area by chemical method to introduce a cationic functional group on the surface of the carbon, and then reacts the heteropolyacid having an anionic property thereto to react the chemically immobilized heteropolyacid. When the acetone production by oxidation of isopropanol was performed using the catalyst, the supported catalyst was suppressed from the acid catalyst property and the oxidation catalyst property was activated, indicating high isopropanol conversion and high acetone selectivity during the catalytic reaction.

1 is a diagram illustrating the preparation of a heteropoly acid-supported catalyst immobilized on a carbon airgel of the present invention.
Figure 2 is a result of nitrogen adsorption-desorption experiment for analyzing the pore structure and pore characteristics of the heteropoly acid (12- molybdo phosphoric acid) supported catalyst immobilized on the carbon airgel.
FIG. 3 is a field emission scanning electron microscope image of a carbon airgel carrier particle and a heteropolyacid (12-molybdate phosphoric acid) supported catalyst immobilized on a carbon airgel. FIG.
4 is an X-ray diffraction spectrum of a heteropolyacid (12-molybdate phosphoric acid) supported catalyst immobilized on a carbon aerogel of the present invention and a carbon aerogel and an unsupported heteropolyacid (12-molybdate phosphoric acid) catalyst which are carriers.

Hereinafter, the present invention will be described in detail.

The present invention provides an amine group (-NR ₁ R ₂ R ₃ ⁺ , R ₁ , R _2, and R ₃ are each independently hydrogen or C 1 to C 20 alkyl group) carbon aerogels, characterized in that the anionic heteropoly acid reacted in a weight ratio of 1: 0.01 to 2 by weight and ion-bonded Provided is a heteropolyacid supported catalyst chemically immobilized on an airgel carrier.

As described above, known heteropolyacid catalysts are generally used in the form of bulk or supported catalysts. However, in the case of general heteropoly acid-supported catalyst, since it is fixed by a method such as impregnation with general metal oxide, its surface area is not large, and even when supported on a carrier having a large surface area, the bond between the carrier and the catalyst is only a physical bond. There is a problem of deactivation, in which a heteropoly acid as a component is dissolved (leaching) and thus the catalytic activity drops sharply. In addition, in the case of the physically immobilized heteropolyacid-supported catalyst, since the acid properties of the catalyst cannot be controlled, the strong acid properties of the heteropolyacid catalyst are maintained, so that the acid catalysis and the oxidation catalysis proceed simultaneously, so that the selectivity of the oxidation reaction in the oxidation catalyst reaction There is a problem that falls and the yield is not high. On the other hand, the heteropolyacid-carrying catalyst chemically immobilized on the carbon aerogel of the present invention introduces a cationic functional group on the surface of the carbon airgel having a large surface area and a large pore size, and chemically immobilizes the anionic heteropolyacid to induce high dispersion of the heteropolyacid. By suppressing the dissolution of the heteropolyacid catalyst from the carrier after the reaction, it is possible to reduce the deterioration of the catalytic activity, and also to suppress the acid catalyst activity in the characteristics of the catalyst and at the same time to activate the oxidation catalyst reaction to increase the selectivity for the oxidation catalyst reaction. .

The heteropolyacid supported catalyst immobilized on the carbon airgel of the present invention includes the steps of introducing a cationic functional group on the surface of the carbon airgel; The cationic functional group is introduced through a manufacturing step including the step of immobilizing the carbon aerogel and heteropoly acid introduced into the weight ratio in the range of 1: 0.01 to 2 by ionic bond form. Carbon aerogels applied as a carrier to the heteropolyacid supported catalyst of the present invention can be prepared by condensation reaction using resorcinol and formaldehyde as reactants. The carbon particles thus produced are preferably medium pore carbons having a mean pore size in the range of 2 to 100 nm, more preferably 10 to 30 nm. In one embodiment of the present invention, the airgel was prepared using resorcinol and formaldehyde and pyrolyzed to prepare a carbon airgel. The carbon aerogel prepared by the above method may be structurally changed by a catalyst added during the production reaction. In the present invention, the ratio of resorcinol: catalyst is 900 to 1100: 1 and is in the range of 10 to 30 nm. A medium porosity carbon airgel having an average pore size was prepared.

As described above, the carbon aerogels prepared by the method described above have a hydrophobic surface property, and in the case of supporting a heteropoly acid in a general manner, the catalyst is separated from the carrier after the catalytic reaction or the activity of the catalyst is sharply reduced. have. Therefore, in the present invention, a cationic functional group was introduced to the surface of the carbon airgel, which is difficult to introduce functional groups, through various chemical treatment methods, and a heteropolyacid catalyst having anion characteristics was immobilized (supported). Preferred examples of the cationic functional group include an amine group (-NR ₁ R ₂ R ₃ ⁺ ), pyridinium or phosphonium, and among them, an amine group is most preferred. Wherein the amine group ^{_{(-NR 1 R 2 R 3 +}} ) of the R _1, R ₂ and R ₃ may be each independently represents a hydrogen or a C1 to C20. The alkyl group is preferably in the range of C1 to C20 because the alkyl group exceeds C20 may cause steric hindrance to the catalytic reaction at the surface due to the longer chain length. More preferably, R ₁ , R ₂ and R ₃ are each independently hydrogen or lower alkyl of C1 to C6.

The reaction of introducing an amine group to the surface of the carbon airgel, iii) activating carbon by hydrogenating the surface of the carbon airgel; Ii) reacting the surface activated carbon airgel with sulfuric acid and nitric acid solution in the presence of acetic anhydride to attach nitro groups to the surface of the carbon airgel; And iii) reducing the nitro group attached to the surface of the carbon airgel to amine it. The above-described carbon activation step or nitro group attachment reaction is known to all those skilled in the art to which the present invention pertains, and no further detailed description will be given herein. In a preferred embodiment of the present invention, carbon is activated by reacting hydrogen gas at a predetermined temperature, and nitro group is attached to the surface activated carbon aerogel in a mixed solution of nitric acid and sulfuric acid, which is a nitration reaction of a general hydrocarbon. The reaction was carried out in the presence of acetic anhydride. In addition, the reaction for reducing the nitro group attached to the surface of the carbon airgel is a known reduction method, for example, after reacting with ammonia in the presence of sodium bisulfite or hydrogenating in the presence of a reducing catalyst to amination (-NH ₂ ), According to the alkylation step after the further may be added to the acid in the form of an ammonium salt can be reacted with the heteropoly acid. In a preferred embodiment of the present invention, the amination is carried out by reacting with ammonia in the presence of sodium bisulfite after attaching the nitro group to the surface activated carbon airgel.

The present invention is characterized in that after preparing a carbon aerogel having an amine group on its surface through various chemical treatment methods, the heteropolyacid catalyst is immobilized therein in a molecular state. In the heteropolyacid supported catalyst immobilized on the carbon aerogel of the present invention, no particular limitation is imposed on the type of the heteropolyacid supported, and molybdenum (Mo), tungsten (W), vanadium (V), niobium (Nb), etc. 12-mol Keggin-type heteropolyacid containing phosphorus (P), silicon (Si), germanium (Ge), arsenic (As), boron (B), cobalt (Co), etc. Libdophosphoric acid (H ₃ PMo ₁₂ O ₄₀ ), 12- tungstophosphoric acid (H ₃ PW ₁₂ O ₄₀ ), 12- tungstosilonic acid (H ₄ SiW ₁₂ O ₄₀ ), 12-molybdo tungstophosphoric acid ( H ₃ PMo _{12 - x} W _x O ₄₀ , x = 0-12), 12-molybdobanadophosphoric acid (H _{3 + x} PMo _{12 - x} V _x O ₄₀ , x = 0-12), 12-tongue In addition to stobanadophosphate (H _{3 + x} PW _{12 - x} V _x O ₄₀ , x = 0-12), 18-molybdoic acid (H ₆ P ₂ Mo ₁₈ ) in the form of Wells-Dawsons O ₆₂ ), 18- tungstophosphoric acid (H ₆ P ₂ W ₁₈ O ₆₂ ), 18-molybdo tungstophosphoric acid (H ₆ P ₂ Mo _{18 -x} W _x O ₆₂ , x = 0-18), 18 -Molybdenum Banado Phosphate ( H _{6 + x} P ₂ Mo _{18 - x} V _x O ₆₂ , x = 0-18), 18- tungsutobanadophosphate (H _{6 + x} P ₂ W _{18 - x} V _x O ₆₂ , x = 0-18 ), And one or two or more kinds selected from 18-tungstenium phosphate (H _{6 + x} P ₂ W _{18 - x} Nb _x O ₆₂ , x = 0-18) and the like. In a preferred embodiment of the present invention, the heteropolyacid is immobilized on a carbon aerogel substituted with an amine group using acetonitrile as a medium, and the amount of heteropoly acid used is 0.02-2.0 g, preferably 0.05, per 1 g of carbon aerogel. Preference is given to using -1.0 g. If the weight ratio of the carbon airgel carrier and heteropolyacid into which the cationic functional group is introduced is less than 1: 0.01, the effect of the heteropolyacid catalyst is difficult to be expressed. If the ratio exceeds 1: 2.0, the loss of the heteropolyacid catalyst is reduced since the catalyst is no longer supported on the carrier. Because it can cause.

The present invention also provides a method for producing acetone by oxidizing isopropanol to produce acetone, wherein isopropanol is oxidized in the presence of a heteropoly acid-supported catalyst immobilized on the carbon airgel. The heteropoly acid-supported catalyst immobilized on the carbon aerogel of the present invention utilizes the advantages of high surface area and thermal stability of carbon and compensates for the disadvantages of the carbon material, thereby preparing a heteropolyacid-supported catalyst chemically immobilized on the carbon airgel. The supported catalyst was applied to the oxidation reaction of isopropanol to induce higher catalytic activity than the unsupported heteropolyacid catalyst. In addition, unlike general heteropolyacid catalysts having an acid and redox amphoteric catalysis, the heteropolyacid catalyst supported on the carbon aerogel of the present invention suppresses the acid catalyst property and instead improves the activity of the oxidation reaction, thereby selecting the oxidation reaction of the catalyst. This has a rising feature. The immobilized heteropoly acid supported catalyst shows different catalytic properties from the unsupported catalyst. In the present invention, a supported catalyst immobilized on carbon airgel is used for isopropanol oxidation reaction to provide a method of improving the oxidation characteristics of the heteropolyacid catalyst.

Hereinafter, the present invention will be described in more detail with reference to Preparation Examples and Examples.

Manufacturing example  1: carbon airgel Carrier  Produce

Method for producing a carbon aerogel as a carrier of the present invention comprises the steps of (a) preparing a sol by putting resorcinol in distilled water and then injecting formaldehyde after stirring the Na ₂ CO ₃ catalyst; (b) gelling the sol prepared in step (a) at 60 to 90 ^° C. to prepare a wet gel; (c) replacing distilled water contained in the wet gel prepared in step (b) with acetone; (d) preparing the airgel by drying the wet gel substituted with acetone in the step (c) at normal pressure and room temperature for 10 to 30 hours and then drying at 40 to 80 ^o C for 10 to 30 hours; (e) thermally decomposing the airgel prepared in step (d) at 600 to 800 ^° C. under a nitrogen atmosphere to produce a carbon airgel; (f) crushing the carbon airgel prepared in step (e) to form a powder.

Hereinafter, the carbon airgel carrier of the present invention will be described in detail. The catalyst used in the step (a) is not limited to the catalyst as Na ₂ CO ₃ It can be used for other basic catalyst according to any purpose. More specifically, the ratio of resorcinol, formaldehyde, and catalyst included in step (a) is as follows. When the sample is prepared such that the molar ratio of resorcinol: formaldehyde is 1: 2 and the molar ratio of resorcinol: catalyst is 900 to 1100: 1, 33.82 g of resorcinol and 0.02 to 0.04 g of resorcinol are prepared. Put it and stir for about 10 minutes. Thereafter, 40.28 g of formaldehyde was added and stirred for about 1 hour to prepare a sol. In order to manufacture the wet gel in step (b), the sol prepared in step (a) is sealed and gelated for 48 hours to 80 hours at 80 ^° C. to 90 ^° C. In step (c), the wet gel is placed in 40-50 ^° C. acetone for 24 hours. Every 3 hours, acetone-substituted wet gel is prepared by replacing with fresh acetone so that distilled water in the wet gel is completely replaced. The wet gel substituted with acetone in the step (d) is dried at room temperature and atmospheric pressure for 20 to 30 hours to prepare an airgel. After that, dry for 20 to 30 hours at 40 to 50 ^o C to completely remove the acetone in the pores of the airgel produced. The airgel dried in the step (e) is pyrolyzed at 600-800 ^° C. for 2-20 hours in a kiln under a nitrogen atmosphere to produce a carbon airgel. At this time, the flow rate of nitrogen is fixed at 100 ml / min, and the temperature rise temperature is raised to 5 ^o C / min. The resultant was crushed to prepare a carbon aerogel in powder form.

Manufacturing example  2: carbon aerogels on the surface An amine group  Attach

Powdered carbon airgel prepared in Preparation Example 1 is converted to a carbon airgel having an amine group on the surface through the following chemical treatment. 1 is a diagram illustrating the preparation of a heteropolyacid supported catalyst immobilized on a carbon airgel of the present invention. The carbon airgel prepared as in Preparation Example 1 was activated under a hydrogen atmosphere of 100 ^° C. for 2 hours. Activated carbon airgel is added to aqueous nitric acid solution (30% by weight) and sulfuric acid solution (30% by weight) together with acetic anhydride and stirred for at least 5 days.The surface is replaced with nitro group (-NO ₂ ). Aerogels are prepared. The carbon aerogel containing nitro group (-NO ₂ ) prepared as described above was placed in a 35% by weight aqueous ammonia solution, and then stirred for 12 hours by addition of sodium hydrosulfite, followed by thorough washing with distilled water. Carbon airgels are prepared in which groups have been changed to amine groups.

Example  1: 12- immobilized on carbon airgel Molybdate phosphoric acid ( H ₃ PMo ₁₂ O ₄₀ Supported Catalyst Preparation

As shown in FIG. 1, 0.85 g of _12- molybdolic acid (H ₃ PMo ₁₂ O ₄₀ ) was dissolved in 50 ml of acetonitrile solution, and then the solution was prepared in Preparation Example 2 above. The prepared carbon aerogels were added and stirred for 24 hours. Thereafter, the solid sample is separated through filtration, and then washed again with distilled water sufficiently to remove the physically bound heteropoly acid, and finally, the solid material is dried at 80 ^° C. to be immobilized on the carbon airgel targeted in the present invention. A supported catalyst was prepared with _12- molybdophosphoric acid (H ₃ PMo ₁₂ O ₄₀ ).

The physical and chemical properties of the carbon airgel carrier and the heteropolyacid supported catalyst prepared in Preparation Examples 1 and 2 to Example 1 were analyzed, and the results are summarized in Table 1 below. In addition, Table 1 also describes the physical properties of the unsupported bulk heteropolyacid catalyst (H ₃ PMo ₁₂ O ₄₀ ) and the like in order to contrast with the heteropolyacid supported catalyst immobilized on the carbon airgel of the present invention.

Nitrogen content (% by weight) 12-molybdate phosphoric acid content (% by weight) Specific surface area (m ² / g) Pore Volume (cm ³ / g) 12-molybdate phosphoric acid
(H ₃ PMo ₁₂ O ₄₀ ) - - 10 - Carbon aerogels - - 689 1.58 The surface is substituted with an amine group
Carbon airgel carrier 1.1 - 597 1.51 12-molybdate phosphoric acid catalyst immobilized on carbon airgel 0.9 3.0 549 1.49

As can be seen in Table 1, the surface area of unsupported ₁₂ -molybdate phosphoric acid (H ₃ PMo ₁₂ O ₄₀ ) is very low at about 10 m ² / g, but for carbon aerogels having a surface area of 689 m ² / g Even if the surface was substituted with an amine group, the surface area was maintained at a very large level of 597 m ² / g, and even after the heteropoly acid was supported, the surface area as high as 549 m ² / g was maintained. The pore volume of the carbon aerogels also decreased sequentially as the surface modification and heteropoly acid supported progressed, but the pore volume of the 12-molybdophosphate supported catalyst immobilized on the carbon aerogel was still relatively high. The supported amount of 12-molybdate phosphoric acid in the catalyst supported on 12-molybdate phosphoric acid immobilized on the carbon aerogel was 3.0 wt%. As described in Example 1, the physically adsorbed 12-molybdate phosphoric acid was stirred. Since it is sufficiently washed with distilled water after removal, the loading amount of 3.0% by weight means the amount of 12-molybdo phosphoric acid chemically immobilized.

In addition, nitrogen adsorption-desorption experiments were performed to analyze the pore structure and characteristics of the prepared carbon airgel carrier and the heteropolyacid supported catalyst, and the results are shown in FIG. 2. As shown in FIG. 2, the carbon airgel carrier and the heteropolyacid-supported catalyst samples showed typical Type IV isotherms as a result of nitrogen adsorption-desorption experiments, and showed a hysteresis of Type H2. In the case of carbon aerogels, the surface is substituted with an amine group and 12-molybdate phosphoric acid supported, respectively, showed similar isotherms and hysteresis. This means that it remains unchanged. This means that the pores of the carrier are well maintained even after the ₁₂ -molybdate phosphoric acid (H ₃ PMo ₁₂ O ₄₀ ) catalyst is supported.

Figure 3 shows a field emission scanning electron microscope image of each of the heteropolyacid catalyst supported on the carbon airgel prepared by the method of the present invention. As shown in FIG. 3, the field emission scanning electron microscope image of the carbon aerogel carrier and the field emission scanning electron microscope image of the 12-molybdate phosphoric acid (H ₃ PMo ₁₂ O ₄₀ ) supported catalyst immobilized on the carbon airgel were compared. You can see that there is no big difference in particle shape. This means that the carbon airgel used as the carrier is chemically stable in the process of introducing an amine group onto the surface of the carbon airgel carrier and in the process of chemically bonding the heteropolyacid catalyst. Therefore, the method of chemically immobilizing the heteropolyacid catalyst on the carbon airgel introduced in the method of the present invention is considered to be a suitable method for preparing the heteropolyacid supported catalyst without modifying the structure of the carbon airgel carrier. In addition, the 12-molybdate phosphoric acid catalyst is not visually distinguished between the carbon aerogel carrier and the 12-molybdate phosphoric acid supported catalyst immobilized on the carbon aerogel. This means that it is very highly dispersed.

4 is an X-ray diffraction spectrum of a heteropolyacid (H ₃ PMo ₁₂ O ₄₀ ) supported catalyst, a carbon aerogel carrier, and an unsupported heteropolyacid catalyst (H ₃ PMo ₁₂ O ₄₀ ), which is immobilized on a carbon airgel of the present invention. As can be seen in FIG. 4, the unsupported catalyst 12-molybdate phosphoric acid (H ₃ PMo ₁₂ O ₄₀ ) exhibits a characteristic peak of heteropolyacid near 2θ = 25 °, whereas 2θ = 23.5 ° in a carbon aerogel carrier. At and near 43.8 °, two large peaks due to pseudo graphite structures were identified. In addition, even when 12-molybdate phosphoric acid is supported on the carbon aerogel, characteristic peaks inherent in the 12-molybdate phosphoric acid disappear and amorphous peaks appearing only on the carbon airgel carrier are observed. In the phosphoric acid catalyst, the 12-molybdophosphate catalyst does not exist as a phase having a crystal structure but as an amorphous substance. As a result, the 12-molybdophosphate catalyst is dispersed very evenly on a molecular basis on the carbon airgel carrier. It means.

Example  2: Unsupported Heteropolyacid (12- Molybdate phosphoric acid Heteropoly acid (12-) immobilized on catalyst and carbon airgel Molybdate phosphoric acid Preparation of Acetone by Isopropanol Oxidation over Supported Catalysts

Oxidation reaction of the unsupported heteropolyacid and the isopropanol of the heteropolyacid (H ₃ PMo ₁₂ O ₄₀ ) supported catalyst immobilized on the carbon airgel prepared in Example 1 was carried out in a gaseous state. The catalyst activity was analyzed by mounting a catalyst in a continuous flow Pyrex reactor under atmospheric pressure, and the reaction was introduced while flowing nitrogen (20 ml / min) and oxygen (5 ml / min), respectively, after sufficient vaporization of isopropanol for the reaction. It was. Isopropanol was adjusted to enter the reactor at a constant rate of 3.9 x 10 ^-3 moles per hour. Before the reaction, the catalyst was activated for 1 hour while flowing nitrogen (20 ml / min) and oxygen (5 ml / min) at a temperature of 240 ^° C., and the catalytic reaction was performed at a temperature of 220 ^° C. for 5 hours. The amount of the catalyst was based on 20 mg of the unsupported catalyst 12-molybdate phosphoric acid in consideration of the amount of 12-molybdate phosphoric acid in the supported catalyst 12-molybdate phosphoric acid immobilized on the carbon airgel. Isopropanol is converted to acetone by oxidation catalysis of heteropolyacids and to propylene by acid catalysis. As mentioned above, heteropolyacid catalysts are binary catalysts having both acidic and oxidation catalytic properties. As a result of performing the oxidation reaction of isopropanol, the selectivity of acetone, which is represented by the oxidizing property, was superior to that of the 12-molybdate phosphoric acid catalyst which was not supported with the 12-molybdate phosphoric acid supported catalyst immobilized on the carbon airgel. On the other hand, the selectivity of propylene, which is represented by the acid catalysis, is greater than that of unsupported 12-molybdophosphate catalysts compared to the 12-molybdophosphate supported catalysts immobilized on carbon aerogels. Showed the opposite trend. The above results indicate that in the case of the 12-molybdic acid-supported catalyst immobilized on the carbon aerogel, the acid catalyst property is decreased and the oxidation catalyst property is relatively improved compared to the unsupported heteropolyacid mother catalyst. This is because the three hydrogen cations (H ⁺ ) present in the bulk of the heteropolyacid catalyst are dropped during the preparation of the 12-molybdolic acid-supported catalyst immobilized on the carbon airgel, and the heteropolyanion is chemically immobilized on the cationic functional group of the carbon airgel. This is because the amount of hydrogen cations present in the catalyst is reduced. The conversion of isopropanol was also better than that of the 12-molybdophosphate supported catalyst, which was not supported on the carbon aerogel. This is because the 12-molybdate phosphoric acid catalyst is highly dispersed in the molecular state on the supported catalyst, thereby increasing the active area of the catalyst and increasing the activity of the catalyst. The catalytic activity of the unsupported heteropoly acid and the heteropoly acid supported catalyst immobilized on the carbon airgel prepared in Example 1 was measured, and the results are summarized in Table 2 below.

Isopropanol conversion (%) Acetone selectivity (%) Acetone yield (%) Propylene Selectivity (%) Propylene Yield (%) 12-molybdate phosphoric acid
(H ₃ PMo ₁₂ O ₄₀ ) 20.7 12.2 2.5 87.7 18.2 12-molybdate phosphoric acid catalyst immobilized on carbon airgel 29.9 41.4 12.4 58.6 17.6

As described above, the heteropolyacid catalyst having both acid and oxidation characteristics by the method of the present invention is chemically immobilized on the carbon airgel by supporting it on a carbon airgel having a large pore volume and a large surface area and having a surface substituted with a cationic functional group. In the preparation of the supported heteropolyacid supported catalyst, it is not simply physically bonded but is strongly immobilized by chemical bonding, and also the acid catalyst property is suppressed and the oxidation reaction property is activated, so that the reaction selectivity is very high in the oxidation catalyst reaction, resulting in isopropanol oxidation reaction. It is advantageous in that it can be utilized as a selective oxidation catalyst by suppressing the acid catalytic reaction characteristics and improving the catalytic activity for the oxidation catalytic reaction.

The embodiments of the present invention described above should not be construed as limiting the technical idea of the present invention. The protection scope of the present invention is limited only by the matters described in the claims, and those skilled in the art can change and change the technical idea of the present invention in various forms. Therefore, such improvements and modifications will fall within the protection scope of the present invention, as will be apparent to those skilled in the art.

Claims (4)

An amine group on the surface (-NR ₁ R ₂ R ₃ ⁺ , R ₁ , R _2, and R ₃ are each independently hydrogen or C 1 to C 20 alkyl group) carbon aerogels, characterized in that the anionic heteropoly acid reacted in a weight ratio of 1: 0.01 to 2 by weight and ion-bonded Heteropoly acid supported catalyst chemically immobilized on an airgel carrier. The method of claim 1,
The heteropolyacid catalyst is a 12-molybdate phosphoric acid (H ₃ PMo ₁₂ O ₄₀ ), a 12- tungstoic acid (H ₃ PW ₁₂ O ₄₀ ), 12- tungstosilonic acid (H ₄₎ SiW ₁₂ O ₄₀ ), 12-molybdoungstophosphoric acid (H ₃ PMo _{12 - x} W _x O ₄₀ , x = 0-12), 12-molybdobanadophosphoric acid (H _{3 + x} PMo _{12 - x} V _x O ₄₀ , x = 0-12) and 12-tungstovavanophosphate (H _{3 + x} PW _12-x V _x O ₄₀ , x = 0-12) and Wells-Dawsons forms Heteropolyacids of 18-molybdophosphoric acid (H ₆ P ₂ Mo ₁₈ O ₆₂ ), 18- tungstophosphoric acid (H ₆ P ₂ W ₁₈ O ₆₂ ), 18-molybdo tungstophosphoric acid (H ₆ P ₂ Mo _{18 - x} W _x O ₆₂ , x = 0-18), 18-molybdobanadophosphoric acid (H _{6 + x} P ₂ Mo _{18 - x} V _x O ₆₂ , x = 0-18), 18-tungsto Banadophosphoric acid (H _{6 + x} P ₂ W _{18 - x} V _x O ₆₂ , x = 0-18) and 18-tungsteniobium phosphate (H _{6 + x} P ₂ W _18-x Nb _x O ₆₂ , x Heteropoly acid-supported catalyst immobilized on a carbon airgel, characterized in that at least one selected from the group consisting of = 0-18). Iii) hydrogenating the surface of the carbon airgel to activate carbon;
Ii) reacting the surface activated carbon airgel with sulfuric acid and nitric acid solution in the presence of acetic anhydride to attach nitro groups to the surface of the carbon airgel;
Iii) amination by reducing the nitro group attached to the surface of the carbon airgel, and
And iii) reacting the amine formed on the surface of the carbon airgel with the heteropolyacid in a weight ratio of 1: 0.01 to 2 to ion-bond the heteropolyacid-supported catalyst immobilized on the carbon airgel. A method for producing acetone by oxidation of isopropanol, wherein the isopropanol is oxidized in the presence of a heteropolyacid-supported catalyst chemically immobilized on the carbon airgel carrier of claim 1.

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