KR101337301B1 - Aluminosilicate Nano-spheres having 3-Dimensional Open Pores, Method for Preparing the Same and Method for Producing Acrylic Acid from Glycerol Using the Same - Google Patents

Abstract

The present invention is an alumino which can be used in various acid catalysis reactions because it has open pores and a wide specific surface area of a three-dimensional shape that increases in size in the direction of increasing the particle radius from the center of the particle, and at the same time has excellent acid properties. A silicate spherical nanoparticle and a method for producing the same are provided. The present invention also provides a method for directly producing acrylic acid from glycerol using the aluminosilicate spherical nanoparticles in excellent yield.

Description

Aluminosilicate Nano-spheres having 3-Dimensional Open Pores, Method for Preparing the Same and Aluminosilicate Spherical Nanoparticles with Three-dimensional Open Pore Structure Method for Producing Acrylic Acid from Glycerol Using the Same}

The present invention relates to aluminosilicate spherical nanoparticles having an open pore structure in a three-dimensional form, a method for preparing the same, and a method for producing acrylic acid from glycerol using the nanoparticles. More specifically, the present invention can be used for various acid catalysis because it has open pores and wide specific surface area of the three-dimensional shape which increases in size from the center of the particle to the direction of increasing the particle diameter, and at the same time has excellent acid properties. A novel aluminosilicate spherical nanoparticle which can be made and a method for producing the same. The present invention also relates to a method for effectively producing acrylic acid from glycerol using the nanoparticles.

Solid acids in chemical processes are widely used as catalysts and adsorbents of various chemical reactions such as dehydration, isomerization, cracking, etherification, esterification, etc. It is used. In recent years, efforts to use renewable and clean biomass resources instead of fossil resources such as petroleum and coal have increased, and the importance of solid acid materials has been highlighted. This is because solid acid materials can promote the conversion of high-value fuels and compounds by lowering the high O / C ratio of biomass such as hydrolysis, dehydration, and hydrogenolysis. For example, glycerol obtained as a maximum byproduct of about 10% or more in the production of biodiesel may be converted into acrolein, which is used as a raw material for polymers, through a dehydration reaction using a solid acid catalyst. In addition, cellulose, which accounts for about 40% of the total biomass composition, can be converted into sugars such as glucose through a hydrolysis reaction using a solid acid catalyst.

Examples of materials used as solid acid catalysts in conventional chemical processes include crystalline zeolites, amorphous aluminosilicates, heteropolyacids, acid treated metal oxides, metal phosphates, and the like. On the other hand, since all catalysis, including acid catalysis, takes place on the surface of the catalyst, a large specific surface area is an important factor in determining the performance of the catalyst. Therefore, in order to prepare an acid catalyst having excellent performance, a lot of researches have been made to form pores that can widen the specific surface area inside the solid acid material and use such pores. In particular, since crystalline zeolites have micropores of the same size as the molecules themselves, they are frequently used for controlling reaction selectivity using pore sizes.

Specifically, the conventional pore forming technique mainly utilizes self-assembly between the surfactant and the precursor to remove regular and ordered micropores (<2 nm) or mesopores (mesopore, 2-50 nm). It has developed in the direction of formation. However, unlike most petroleum-based compounds, most biomass resources are in the form of high molecular weight polymers and have low solubility in common solvents. As pointed out in Sci., 2009, 2, 610, etc., it is difficult to transfer into the pores by mass transfer resistance. And in many publications (Green Chem. 2008, 10, 1033; Green Chem. 2010, 12, 2079; Chem Sus Chem, 2009, 2, 719; Chem. Soc. Rev., 2011, 40, 5588, etc.). Although the catalysts have the acid properties needed to convert biomass resources, they do not report high performance in actual biomass conversion reactions. Therefore, in order to effectively convert biomass resources into high value-added compounds and fuels, an acid catalyst material having a novel form of pore structure with good acid properties and easily accessible to the reactants is required.

On the other hand, acid catalyzed reactions such as hydrolysis and dehydration reactions are effective in reducing the content of oxygen functional groups in biomass resources, but additional processes and reactions, including separation / purification, are required to produce a final product with excellent economic and industrial performance. I need more. For example, acrolein obtained through dehydration of glycerol is mainly used to produce acrylic acid. Therefore, if the acrolein obtained from glycerol can be directly converted to acrylic acid, the separation / purification process can be omitted, thereby improving process efficiency and economics. In addition, since acrolein is not easy to handle because of its low reactivity and strong toxicity at room temperature, it is necessary to develop a process that can directly convert glycerol to acrylic acid without separating / purifying intermediate acrolein.

In order to solve these problems, the inventors have invented new aluminosilicate spherical nanoparticles having an open pore structure in three dimensions. The spherical nanoparticles according to the present invention have pores in the form of retaining the acidic properties of aluminosilicates and at the same time increasing in size in the direction of increasing the radius of the particles from the center of the particles. Therefore, unlike the existing micropore or medium pore acid catalyst, the inlet of the pores is very wide has the advantage that the reactants can easily move into the pores. In addition, by controlling the ratio of silicon (Si) and aluminum (Al) atoms constituting the nanoparticles has the advantage that can control the acid properties. In addition, the present inventors have developed a new process that can directly convert glycerol to acrylic acid through a double catalyst layer reaction using the nanoparticles.

It is an object of the present invention to provide aluminosilicate spherical nanoparticles having new pore structure and acid properties simultaneously.

It is another object of the present invention to provide aluminosilicate spherical nanoparticles having a three-dimensional open pore structure and a large specific surface area that can minimize mass transfer resistance when reactants move into the pores.

It is still another object of the present invention to provide aluminosilicate spherical nanoparticles that can be effectively used for acid catalyzed reaction of compounds derived from fossil fuels and biomass resources.

Still another object of the present invention is to provide a method for easily and effectively preparing the aluminosilicate spherical nanoparticles.

Still another object of the present invention is to provide a method for directly converting glycerol to acrylic acid through a bilayer reaction using the aluminosilicate spherical nanoparticles.

The above and other objects of the present invention can be achieved by the present invention described in detail below.

In order to achieve the above object, the aluminosilicate spherical nanoparticles according to the embodiment of the present invention has open pores in the form of increasing in size in the direction of increasing the radius of the particle from the center of the particle.

The nanoparticles may have a silicon (Si): aluminum (Al) atomic ratio of 1: 1 to 300: 1.

The nanoparticles may have an average diameter of 50 ~ 3,000 nm.

The nanoparticles may have a specific surface area of 100 m ² / g or more, more specifically 200-800 m ² / g.

Method for producing aluminosilicate spherical nanoparticles according to another embodiment of the present invention comprises the steps of first hydrothermal treatment in a pressure vessel a solution comprising a silica precursor, a polar solvent, a nonpolar solvent, an ionic surfactant and a basic compound; Adjusting the pH of the first hydrothermally treated solution to 2 to 7 using an acidic aqueous solution; Injecting an aluminum precursor into the pH controlled solution; And a second hydrothermal treatment of the solution into which the aluminum precursor is added, in a pressure vessel.

The silica precursor and the aluminum precursor are preferably used so that the atomic ratio of silicon: aluminum is 1: 1 to 300: 1.

The silica precursor may be selected from the group consisting of tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, and mixtures thereof.

The polar solvent may be selected from the group consisting of water, alcohols and mixtures thereof.

The nonpolar solvent may be selected from the group consisting of hexane, cyclohexane, methylcyclohexane, toluene, heptane, octane, and mixtures thereof.

The alcohol may be selected from the group consisting of propanol, butanol, pentanol, hexanol and mixtures thereof.

The ionic surfactant is selected from the group consisting of cetylpyridinium chloride, cetylpyridinium bromide, cetyltrimetylammonium chloride, cetyltrimetylammonium bromide and mixtures thereof Can be.

The basic compound may be selected from the group consisting of aqueous ammonia solution, urea, and mixtures thereof.

The acidic aqueous solution may be selected from the group consisting of aqueous hydrochloric acid, aqueous nitric acid, aqueous sulfuric acid, aqueous phosphoric acid and mixtures thereof.

The aluminum precursor may be selected from the group consisting of aluminum chloride, aluminum bromide, aluminum sulfate, aluminum nitrate, aluminum acetate, and mixtures thereof. .

Method for producing acrylic acid from glycerol according to another embodiment of the present invention is a glycerol vaporized in a flow gas phase reactor filled with aluminosilicate spherical nanoparticles and a mixed oxide catalyst comprising molybdenum (Mo) and vanadium (V) And reacting with oxygen gas.

The nanoparticles and the mixed oxide catalyst are filled in the reactor to form different layers, and the layer of the nanoparticles is preferably disposed closer to the inlet side of the reactor than the layer of the mixed oxide catalyst.

The mixed oxide catalyst preferably has a molybdenum: vanadium atom ratio of 1: 1 to 10: 1.

The reaction is preferably carried out at a temperature of 250 ~ 400 ^° C and atmospheric pressure.

Since the aluminosilicate spherical nanoparticles according to the embodiment of the present invention have open pores of a three-dimensional shape that increases in size in the direction of increasing the radius of the particles from the center of the particles, the reactant can be easily transferred into the pores. The transfer resistance can be minimized. In addition, since the nanoparticles retain the acid properties of the aluminosilicate and have a large specific surface area, the nanoparticles may exhibit excellent catalytic performance in acid catalysis of fossil resources as well as biomass resources. In addition, the nanoparticles can easily control the acid properties required for various catalytic reactions by adjusting the ratio of silicon and aluminum atoms constituting the particles.

In addition, the double catalyst layer reaction using the aluminosilicate spherical nanoparticles can directly convert glycerol, which is the largest byproduct of biodiesel, into acrylic acid, which is a high value compound.

In addition, the manufacturing method of the aluminosilicate spherical nanoparticles according to another embodiment of the present invention is to prepare a new aluminosilicate nanoparticles having a three-dimensional open pore structure, a wide specific surface area and excellent acid properties through simple pH adjustment. It's simple and very effective.

1 is a schematic view showing aluminosilicate spherical nanoparticles according to the present invention.
2 is a field emission scanning electron microscope (FE-SEM) photograph of the aluminosilicate spherical nanoparticles prepared in Examples 1 to 5 and the commercial aluminosilicate catalyst of Comparative Example 1. FIG.
3 is a transmission electron microscope (TEM) photograph of the aluminosilicate spherical nanoparticles prepared in Examples 1 to 5 and the commercial aluminosilicate catalyst of Comparative Example 1. FIG.
4 (a) and (b) are graphs showing the results of nitrogen adsorption and desorption analysis of the aluminosilicate spherical nanoparticles prepared in Examples 1 to 5 and the commercial aluminosilicate catalysts of Comparative Examples 1 and 2, respectively.
5 is a graph showing the X-ray diffraction pattern of the aluminosilicate spherical nanoparticles prepared in Examples 1 to 5 and the commercial aluminosilicate catalyst of Comparative Example 1.
6 is a graph showing the ammonia TPD pattern of the aluminosilicate spherical nanoparticles prepared in Examples 1 to 5 and the commercial aluminosilicate catalyst of Comparative Example 1.
7 (a) and (b) are graphs comparing glycerol conversion and acrylic acid selectivity, which appear after 3 hours in the reaction experiments of Examples 6 to 10 and Comparative Examples 3 to 4, respectively.

Hereinafter, with reference to the accompanying drawings, the aluminosilicate spherical nanoparticles having a three-dimensional open pore structure according to embodiments and embodiments of the present invention, a method for producing the same and a method for producing acrylic acid from glycerol using the same Explain. However, the present invention is not limited to the following embodiments and examples, and those skilled in the art may realize the present invention in various other forms without departing from the spirit of the present invention. It should be understood that there may be variations and examples.

In addition, the terms or words used in the specification and claims should not be construed as being limited to the common or dictionary meanings, and the inventors should appropriately define the concept of terms in order to explain their invention in the best way. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that it can.

Aluminosilicate  Spherical nanoparticles

The aluminosilicate spherical nanoparticles according to the present invention have open pores in the form of increasing in size in the direction of increasing the particle radius from the center of the particles. Specifically, referring to the schematic diagram shown in FIG. 1, the spherical nanoparticles have a three-dimensional open pore structure in which a wide inlet is formed while the pore size increases from the center of the particle toward the particle surface. Therefore, the nanoparticles according to the present invention, unlike conventional micro and medium pore materials, large molecules such as biomass can be easily transferred into the pores of the particles, it is possible to minimize the mass transfer resistance.

Meanwhile, general porous materials such as SBA-15 have a regular pore structure in which cylindrical pores having a diameter of about 2 to 10 nm and a length of several μm are arranged in a hexagonal array. However, since the nanoparticles according to the present invention have pores in the shape of irregular cones as shown in FIGS. 1 and 2, and the total length of the pores is in nanometers, the surface area exposed inside the pores is wide, and It has the advantage of short delivery length. On the other hand, since the pore inlet of the nanoparticles has an irregular shape, it is not easy to accurately measure the diameter, but the length thereof is approximately 10 to 100 nm, and is not limited thereto and may have a larger pore inlet. .

Aluminosilicate is composed of a combination of silicon (Si), aluminum (Al), and oxygen (O) atoms, similar to crystalline zeolites, and the bridge oxygen sites linking silicon with aluminum serve as the main scattering point. . Specifically, when hydrogen ions are bonded to the cross-linked oxygen, hydrogen ions can be easily supplied to the outside to act as Bronsted acid. On the other hand, if no other cation is bonded to the cross-linked oxygen site, the oxygen atom may attract electrons from the outside to act as Lewis acid. Therefore, the acid property of the aluminosilicate is mainly determined by the atomic ratio of silicon and aluminum, and it is known that the acid property increases as the ratio of aluminum to silicon increases.

The nanoparticles according to the present invention may have a silicon: aluminum atom ratio of 1: 1 to 300: 1, and preferably have a silicon: aluminum atom ratio of 3: 1 to 100: 1. If the atomic ratio of silicon to aluminum is less than 1: 1 or greater than 300: 1, the possibility of bonding the same elements in the form of silicon and silicon or aluminum and aluminum increases, so that the acidic point of the crosslinked oxygen connecting silicon and aluminum is sufficient. Hard to make.

In addition, since the nanoparticles according to the present invention can control the atomic ratio of silicon: aluminum by changing the ratio of silica and aluminum precursor used in the manufacture, it is easy to adjust the required acid properties (acid strength and amount) according to the reaction type. Can be controlled.

The nanoparticles are not particularly limited but preferably have an average diameter of 50 to 3,000 nm. If the average diameter of the nanoparticles is less than 50 nm, it is difficult to take advantage of the advantages of open pores because the size of the pores is smaller, and if the average diameter of more than 3,000 nm, the length of the pores increases, there is a fear that the mass transfer resistance inside the pores increases.

The nanoparticles have a large specific surface area. Since the catalysis takes place on the surface of the particles, the larger the specific surface area, the more favorable the catalytic reaction. Therefore, the upper limit of the specific surface area is not particularly limited. In an embodiment of the invention, the nanoparticles have a specific surface area of 100 m ² / g or more, specifically 150-1,500 m ² / g, more specifically 200-800 m ² / g.

Aluminosilicate  Method for producing spherical nanoparticles

Method for producing aluminosilicate spherical nanoparticles according to the present invention comprises the steps of first hydrothermal treatment in a pressure vessel of a solution containing a silica precursor, a polar solvent, a nonpolar solvent, an ionic surfactant and a basic compound, using an acidic aqueous solution Adjusting the pH of the first hydrothermally treated solution to 2 to 7, adding an aluminum precursor to the pH-adjusted solution, and performing a second hydrothermal treatment of the aluminum precursor-treated solution in a pressure vessel; Is done.

Specifically, a solution is first prepared by mixing a silica precursor, a polar solvent, a nonpolar solvent, an ionic surfactant and a basic compound. The mixed solution is placed in a pressure vessel and subjected to a first hydrothermal treatment. At this time, the order of mixing the respective components is not particularly limited. In an embodiment of the present invention, after preparing a first mixture of a polar solvent, an ionic surfactant and a basic compound, and a second mixture of a silica precursor and a nonpolar solvent, respectively, the first and second mixtures are mixed again. It is desirable to.

Conventional porous materials mainly dissolve surfactants in critical solvents above a critical micelle concentration to form micelles, which induce metal bonds around these micelles. Then, when the micelles are removed while hardening the metal precursor by heat treatment, the micelles are empty and the pores are made.

However, the manufacturing method according to the present invention uses an emulsion of a polar solvent and a non-polar solvent that do not mix with each other to form a three-dimensional open pore structure inside the nanoparticles to bond the metal precursors outward from the center of the particles. Induce them to grow. Specifically, the addition of an ionic surfactant to a mixture of polar and nonpolar solvents that do not mix with each other stabilizes the interface of the two solutions by the micelle of the surfactant, forming an emulsion of very small size. The emulsion may have a form in which the non-polar solvent particles are dispersed in the polar solvent or the polar solvent particles are dispersed in the non-polar solvent according to the relative amounts of the polar solvent and the non-polar solvent. In the embodiment of the present invention, it is preferable that the polar solvent particles stabilized by the hydrophilic head of the ionic surfactant are dispersed in the nonpolar solvent.

As described above, when the mixed solution in which the emulsion micelle is formed is first hydrothermally treated in a pressure vessel, the silica precursor grows by forming a silica bond outward from the center of the micelle while being hydrolyzed and condensed under the catalytic action of the basic compound. In this case, the silica bond does not grow in the portion blocked by the surfactant, and the silica bond grows only through the portion in which the micelle is opened. Therefore, the portion where the silica bond cannot be made by the surfactant forms pore sites in the particles. In addition, since the silica grows radially outward from the center of the particle, the pores are also made in the form of increasing in size in the direction of increasing the radius of the particle from the center of the particle.

The first hydrothermal treatment may be performed using a closed pressure vessel such as an autoclave, without adjusting the pressure generated by itself. The temperature of the first hydrothermal treatment is not particularly limited as long as it can be a hydrolysis and condensation reaction of the silica precursor. In the specific example of this invention, the said 1st hydrothermal process is advanced in 50-250 degree | times, Preferably it is 80-200 degree | times, More preferably, it is 100-150 degree | times.

It is preferable to use an alkoxy silane compound as the silica precursor. Specific examples of the silica precursor may include tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), tetrapropyl orthosilicate (TPOS), and mixtures thereof. It is not limited. Since the amount of the silica precursor used may be adjusted in consideration of the atomic ratio of silicon: aluminum included in the final nanoparticles and the amount of the solvent used, the silica precursor is not particularly limited and has a general knowledge in the art to which the present invention pertains. You can choose your own.

As the polar solvent, water, alcohol or a mixture thereof may be used. Specific examples of the alcohol include propanol, butanol, pentanol, hexanol, and mixtures thereof, but are not necessarily limited thereto. The nonpolar solvent is not particularly limited as long as it can form an emulsion by working with the polar solvent, and any one can be used. For example, hexane, cyclohexane, methylcyclohexane, toluene, heptane, octane, or a mixture thereof may be used as the nonpolar solvent. The amount of the polar solvent and the nonpolar solvent is not particularly limited as long as it is sufficient to constitute the emulsion, and in the embodiment of the present invention, the polar solvent and the nonpolar solvent are 0.5: 1-5: 1, preferably 0.6: 1-3. Can be used in a volume ratio of 1: 1.

As described above, the ionic surfactant stabilizes the interface between the polar solvent and the nonpolar solvent to form an emulsion, and serves to create pore pores by spatially inhibiting the growth of silica bonds. On the other hand, the surfactant forms micelles of various structures depending on the effective area of the polar head and the length and volume of the non-polar tail. In order to create a three-dimensional open pore structure, these elements of the surfactant are considered. It is preferable to select. Specific examples of the surfactant include cetylpyridinium chloride, cetylpyridinium bromide, cetyltrimetylammonium chloride, cetyltrimethylammonium bromide, and mixtures thereof. . The surfactant is preferably used in an amount sufficient to form micelles, and in embodiments of the present invention, it is used in a ratio of about 0.1 to 1 mole with respect to 1 mole of silica precursor.

The basic compound is not particularly limited as long as it can act as a catalyst for promoting hydrolysis and condensation reaction of the silica precursor, and any one can be used. For example, an aqueous ammonia solution, urea, or a mixture thereof may be used as the basic compound. It is preferable to use the said basic compound in the ratio of 0.1-2 mol per mol of silica precursors, The ratio of 0.3-1.5 mol is more preferable, The ratio of 0.5-1 mol is further more preferable. If the basic compound is used in less than 0.1 mole per 1 mole of silica, it is difficult to form silica bonds, and when used in excess of 2 moles, the size of the particles may be uneven.

Thus, the solution which completed the 1st hydrothermal treatment adjusts the pH of a solution to 2-7 using an acidic aqueous solution. Subsequently, an aluminum precursor is added to the pH adjusted solution. The first hydrothermally treated solution has a basicity of pH 8 or higher under the influence of a basic compound. However, the aluminum precursor has a property of easily precipitated in the form of insoluble aluminum hydroxide (Al ₂ OH ₃ ) under such basic conditions. Since precipitation of the aluminum precursor is difficult to form a bond between silica and aluminum, it is necessary to lower the pH of the solution to below neutral before adding the aluminum precursor. On the other hand, when the pH of the solution is lowered to a strong acid condition of less than 2, the weakly bonded silica is dissolved again or the rate of bonding of the silica and aluminum is excessively increased in the subsequent second hydrothermal treatment to form a uniform aluminosilicate. It can be difficult.

The kind and concentration of the acidic aqueous solution are not particularly limited. For example, an aqueous hydrochloric acid solution, an aqueous nitric acid solution, an aqueous sulfuric acid solution, an aqueous phosphoric acid solution, or a mixture thereof may be used as the acidic aqueous solution.

Specific examples of the aluminum precursors include aluminum chloride, aluminum bromide, aluminum sulfate, aluminum nitrate, aluminum acetate, and mixtures thereof. It is not necessarily limited thereto. The aluminum precursor is preferably used so that the atomic ratio of silicon: aluminum is 1: 1 to 300: 1.

The solution in which the aluminum precursor is added is subjected to a second hydrothermal treatment in a pressure vessel again. Silica bonds made during the first hydrothermal treatment are structurally unstable because they have not undergone heat treatment, and other ions can easily penetrate between the bonds. Therefore, the aluminum ions added after the pH adjustment are formed by incorporation into the surface and the inside of the silica binder during the second hydrothermal treatment process, thereby forming aluminosilicate bonds linked with crosslinked oxygen.

The second hydrothermal treatment is preferably performed at the same temperature as the first hydrothermal treatment. In addition, when the silica bond is formed too strong in the first hydrothermal treatment process, since the aluminosilicate bond is difficult to form in the second hydrothermal treatment process, the first hydrothermal treatment time is preferably shorter than the second hydrothermal treatment time. In an embodiment of the present invention, the first hydrothermal treatment is preferably performed for 2 to 4 hours, and the second hydrothermal treatment is preferably performed for 3 to 6 hours.

As such, when the second hydrothermal treatment is completed, the aluminosilicate spherical nanoparticles are made, and the nanoparticles prepared by a method such as centrifugation or filtration can be recovered from the solution. The invention for recovering the nanoparticles can be easily carried out by those of ordinary skill in the art. In addition, the recovered nanoparticles may be further subjected to drying and heat treatment (firing) to harden the bonds between the components and to remove surfactants and impurities. In the embodiment of the present invention, the drying process is preferably carried out in a range of room temperature to 60 degrees. In addition, the heat treatment may be performed in the range of 300 ~ 1,000 degrees.

How to prepare acrylic acid from glycerol

The aluminum silicate spherical nanoparticles of the present invention prepared by the method described above have a three-dimensional open pore structure. In addition, since it contains abundantly crosslinked oxygen sites that connect silicon and aluminum and serve as acid sites, it can exhibit excellent catalytic performance in acid catalysis. Specifically, the nanoparticles according to the present invention may promote the dehydration reaction of glycerol to effectively produce acrolein. In addition, using a catalyst capable of oxidizing with the nanoparticles can be directly converted to glycerol acrylic acid.

In an embodiment of the present invention, a method for preparing acrylic acid from glycerol includes glycerol and oxygen gas vaporized in a flow gas phase reactor filled with aluminosilicate spherical nanoparticles and a mixed oxide catalyst including molybdenum (Mo) and vanadium (V). It comprises the reaction by passing through.

Specifically, when the glycerol and oxygen gas vaporized in the flow gas phase reactor filled with the nanoparticles and the mixed oxide catalyst according to the present invention, the nanoparticles can promote the dehydration reaction of glycerol to make acrolein. The acrolein thus produced may be partially oxidized by the mixed oxide catalyst and oxygen gas and converted into acrylic acid.

At this time, in order to increase the yield of acrylic acid while suppressing the production of by-products, it is preferable that a reaction in which glycerol is converted to acrolein and a reaction in which acrolein is converted to acrylic acid are performed sequentially. In one embodiment of the present invention, a dual catalyst layer may be used to control the reaction sequence as described above. Specifically, the nanoparticles and the mixed oxide catalyst are filled inside the reactor to form different layers, and the layer made of the nanoparticles is disposed closer to the reactor inlet side than the layer of the mixed oxide catalyst. As such, when the double catalyst layer is used, the glycerol reactant is first reacted with the nanoparticles to be converted into acrolein, and the resulting acrolein may meet the mixed oxide catalyst layer located at the rear to sequentially produce acrylic acid.

The mixed oxide catalyst includes molybdenum and vanadium, and specifically, molybdenum and vanadium are preferably contained in an atomic ratio of 1: 1 to 10: 1. When the atomic ratio of molybdenum: vanadium is less than 1: 1, the selectivity of acrylic acid may be lowered, and when it exceeds 10: 1, the conversion of acrolein may be lowered. In addition, the mixed oxide catalyst is optionally tungsten (W), iron (Fe), bismuth (Bi), copper (Cu), manganese (Mn), antimony (Sb), chromium (Cr), strontium (Sr) or their It may further comprise a mixture of two or more.

The mixed oxide catalyst may be prepared by combining the above components in an aqueous solution using hydrothermal synthesis or by supporting the above components on a carrier such as silica, alumina, titania, or the like. The method for producing the mixed oxide catalyst using the hydrothermal synthesis method or the supporting method can be easily carried out by those skilled in the art.

In the embodiment of the present invention, the reaction for converting glycerol to acrylic acid is preferably performed at a temperature of 250 to 400 degrees and atmospheric pressure. If the reaction temperature is less than 250 degrees, it is difficult to maintain the gas phase reaction conditions, the reaction activity is low, and if it exceeds 400 degrees, there is a possibility that the side reactions increase and the yield of acrylic acid decreases.

Hereinafter, it will be described in more detail through Examples and Comparative Examples of the present invention.

Aluminosilicate  Preparation of Spherical Nanoparticles

Example  One

About 0.6 g (0.01 mole) of urea and about 1 g (0.0026 mole) of cetylpydinium bromide were dissolved in 30 mL of distilled water to prepare a first solution. Then, about 2.5 g (0.012 mol) of tetraethyl orthosilicate (TEOS) and 1.5 mL of 1-pentanol were dissolved in 30 mL of cyclohexane to prepare a second solution. Then, the prepared first solution and the second solution were mixed and stirred for about 30 minutes. The stirred solution was placed in an autoclave and subjected to primary hydrothermal treatment at about 120 degrees for about 2 hours and 30 minutes. The pH of the first hydrothermally treated solution was about 9.5. The pH of the solution was adjusted to about 5 using 2 M aqueous hydrochloric acid. Then, a solution in which about 0.1632 g of aluminum sulfate octadecahydrate was dissolved in about 2 mL of distilled water was added to the pH-controlled solution so that the atomic ratio of Si: Al was 50: 1. Subsequently, the solution into which the aluminum sulfate was added was put back into the autoclave and subjected to secondary hydrothermal treatment at about 120 ° for about 4 hours. The prepared nanoparticles were recovered by centrifugation and washing, dried at room temperature, and calcined (heat treated) at about 550 ° C. for about 6 hours. The finished aluminosilicate spherical nanoparticles were denoted by DAS (Si / Al = 50).

Example  2

A solution of about 0.2040 g of aluminum sulfate 18 hydrate in about 2 mL of distilled water was prepared in the same manner as in Example 1 except that an atomic ratio of Si: Al was dissolved in about 2 mL of distilled water. The finished aluminosilicate spherical nanoparticles were denoted by DAS (Si / Al = 40).

Example  3

A solution of about 0.3264 g of aluminum sulfate 18 hydrate in about 2 mL of distilled water was prepared in the same manner as in Example 1 except that an atomic ratio of Si: Al was dissolved in about 2 mL of distilled water. The finished aluminosilicate spherical nanoparticles were denoted by DAS (Si / Al = 25).

Example  4

A solution of about 0.5440 g of aluminum sulfate 18 hydrate in about 2 mL of distilled water was prepared in the same manner as in Example 1 except that an atomic ratio of Si: Al was dissolved in about 2 mL of distilled water. The finished aluminosilicate spherical nanoparticles were denoted by DAS (Si / Al = 15).

Example  5

A solution in which about 0.8160 g of aluminum sulfate 18 hydrate was dissolved in about 2 mL of distilled water so that the atomic ratio of Si: Al was 8: 1 was prepared in the same manner as in Example 1 except that the solution was added to a pH-controlled solution. The finished aluminosilicate spherical nanoparticles were denoted by DAS (Si / Al = 8).

Comparative Example  One

A commercially available mesoporous aluminosilicate catalyst, MCM-41 (Catalog No. 643653-5), was purchased from Aldrich. Commercial aluminosilicates of Comparative Example 1 are designated MCM-41.

Comparative Example  2

A commercial bulk aluminosilicate catalyst (Catalog No. 34335-8) was purchased from Aldrich and used. Commercial aluminosilicates of Comparative Example 2 are designated as bulk AS.

Experimental Example

One. Field emission  Scanning electron microscope and energy dispersive x-ray spectroscopy FE - SEM  & EDS ) analysis

Field emission scanning electron microscope (FE-SEM) to determine the surface morphology and Si: Al atomic ratio exposed on the surface of the aluminosilicate spherical nanoparticles prepared in Examples 1 to 5 and the MCM-41 catalyst of Comparative Example 1 And energy dispersive X-ray spectroscopy (EDS) analysis. Referring to Figure 2, it can be seen that the nanoparticles prepared in Examples 1 to 5 all have a three-dimensional open pore structure. In addition, the average diameter of the nanoparticles prepared in Examples 1 to 5 is about 500 to 600 nm, very uniform, and the major axis length of the pore inlet is about 20 to 70 nm. On the other hand, in Comparative Example 1 using a commercial aluminosilicate catalyst MCM-41, it can be seen that the shape and size of the particles are irregular and the pore inlet is very small and difficult to observe by SEM.

Table 1 below shows the results of comparing the Si: Al atomic ratio of the precursors used in the preparation of Examples 1 to 5 with the Si: Al atomic ratio of the nanoparticles measured using EDS. Referring to Table 1, it can be seen that as the Si: Al ratio of the precursor used to prepare the nanoparticles increases, the Si: Al atomic ratio of the prepared nanoparticles also increases. Therefore, it can be seen that the manufacturing method according to the present invention can control the Si: Al atomic ratio of the nanoparticles simply by controlling the amount of the precursor used. On the other hand, the Si: Al atomic ratio measured by EDS lower than the Si: Al atomic ratio of the precursor means that the aluminum precursor is more bonded to the silica on the nanoparticle surface.

Si: Al atomic ratio of precursor
Si: Al atomic ratio measured by EDS
Example 1
50
38.0
Example 2
40
33.2
Example 3
25
18.9
Example 4
15
13.9
Example 5
8
6.4

2. Transmission electron microscope ( TEM ) analysis

3 is a transmission electron microscope (TEM) photograph of the aluminosilicate spherical nanoparticles prepared in Examples 1 to 5 and the MCM-41 catalyst of Comparative Example 1. FIG. Referring to FIG. 3, it can be seen that all of the nanoparticles prepared in Examples 1 to 5 have pores of a size that increases in size from the center of the particle toward the surface direction in which the radius of the particle increases. In the TEM image, the deep center of the particles is a phenomenon in which there are many inner walls of the pores near the center of the particles, and the electron transmittance decreases because the pore size decreases toward the center. On the other hand, in Comparative Example 1 using a commercial MCM-41 catalyst, small pores of about 2 to 3 nm are regularly arranged in a hexagonal shape, and it can be seen that the length of the pores is very long. Therefore, the catalyst of Comparative Example 1 can be easily seen that the reactants are less likely to enter the pores and have a stronger mass transfer resistance inside the pores than the nanoparticles according to the present invention.

3. Specific surface area  And pore volume analysis

Nitrogen adsorption and desorption experiments were performed on the aluminosilicate spherical nanoparticles prepared in Examples 1 to 5 and commercial aluminosilicate catalysts of Comparative Examples 1 to 2 to measure specific surface area and pore volume. Table 2 shows the results of arranging the specific surface area and the pore volume of Examples 1 to 5 and Comparative Examples 1 to 2, and shows the results of the nitrogen adsorption and desorption curves in FIG. 4.

Specific surface area (m ² / g)
Total pore volume (cm ³ / g)

Example 1 (DAS (Si / Al = 50))
479.5
1.0
Example 2 (DAS (Si / Al = 40))
494.0
1.1
Example 3 (DAS (Si / Al = 25))
429.0
1.1
Example 4 (DAS (Si / Al = 15))
457.7
1.1
Example 5 (DAS (Si / Al = 8))
481.5
1.3
Comparative Example 1 (MCM-41)
1087.5
1.0
Comparative Example 2 (Bulk AS)
421.2
0.6

Referring to Table 2 and Figure 4 (a), the aluminosilicate spherical nanoparticles prepared in Examples 1 to 5 have a large specific surface area of about 420 to 500 m ² / g and pores of about 1.0 to 1.3 cm ³ / g It can be seen that it has a volume. On the other hand, MCM-41 of Comparative Example 1 has a large specific surface area and pore volume, but shows hysteresis in a low relative pressure range as shown in FIG. 4 (b), indicating that the pore size is small. And this result is in good agreement with the TEM analysis result. In addition, the bulk AS catalyst of Comparative Example 2 was found to have a smaller surface area and pore volume than the nanoparticles of Examples 1 to 5.

4. X-ray diffraction ( XRD ) analysis

5 is a graph showing X-ray diffraction patterns of the aluminosilicate spherical nanoparticles prepared in Examples 1 to 5 and the MCM-41 catalyst of Comparative Example 1. FIG. Referring to Figure 5 it can be seen that the nanoparticles of Examples 1 to 5 have an amorphous bonding structure similar to the MCM-41 catalyst of Comparative Example 1.

5. Ammonia Heating  Desorption( TPD ) Experiment

In order to analyze the acid characteristics of the aluminosilicate spherical nanoparticles prepared in Examples 1 to 5 and the commercial MCM-41 catalyst of Comparative Example 1, an ammonia ₃ temperature programmed desorption experiment was performed. 6 is shown.

In general, the area of the ammonia TPR graph is proportional to the amount of acid point possessed by the catalyst, and the peak temperature is related to the intensity of the acid point. Referring to FIG. 6, it can be seen that the nanoparticles of Examples 1 to 5 have more acid points, although the specific surface area is smaller than that of the commercial MCM-41 catalyst of Comparative Example 1. In addition, the nanoparticles of Examples 1 to 5 and the commercial MCM-41 of Comparative Example 1 showed a TPR peak in a similar temperature range of about 250 degrees, confirming that the intensity of the acid spots was similar.

Preparation of Acrylic Acid from Glycerol

Example  6

Acrylic acid was prepared from glycerol by using the aluminosilicate spherical nanoparticles prepared in Example 1 (DAS (Si / Al = 50)) and a MoVO _x / SiO ₂ catalyst. Specifically, first, about 0.2 g of MoVO _x / SiO ₂ catalyst was charged into a quartz reactor, and then about 0.2 g of DAS (Si / Al = 50) catalyst of Example 1 was charged on the MoVO _x / SiO ₂ catalyst layer to form a double catalyst layer. It was. The MoVO _x / SiO ₂ catalyst is commercially prepared by dissolving ammonium molybdate and ammonium vanadate in distilled water so that the atomic ratio of molybdenum and vanadium is 4: 1 using an initial impregnation method. It was prepared by sintering at about 300 degrees for about 4 hours after being supported on a silica (degusa product) carrier. At this time, the MoVO _x / SiO ₂ catalyst was prepared such that the combined mass of MoO ₃ and V ₂ O ₄ is about 30% by weight of the total catalyst weight.

An aqueous solution of about 10% by weight of glycerol was then vaporized at about 270 degrees and then fed from the top to the bottom of the quartz reactor maintained at about 300 degrees with oxygen and nitrogen gas to react through the double catalyst bed. Specific reaction conditions are shown in Table 3 below. The product obtained at the bottom of the reactor was liquefied using a condenser running with cooling water, which was then collected and analyzed by gas chromatography (GC). Conversion of glycerol and selectivity of acrylic acid were calculated using the following equations (1) and (2).

Reaction temperature 300 ° C Feed rate of 10 wt% aqueous solution of glycerol 2.1 mL / min Nitrogen Gas Feed Rate 15 mL / min Oxygen gas feed rate 1.9 mL / min

[Equation 1]

Glycerol Conversion Rate (%) = (Moles of Glycerol Produced / Moles of Glycerol Supplied) × 100

&Quot; (2) &quot;

Acrylic acid selectivity (%) = (moles of acrylic acid produced / moles of glycerol supplied) x 100

Example  7 to 10

The same procedure as in Example 6 was carried out except that the aluminosilicate spherical nanoparticles prepared in Examples 2 to 5 were used.

Example  3 to 4

The same process as in Example 6 was conducted except that the commercial aluminosilicate catalysts of Comparative Examples 1 and 2 were used.

7 (a) and (b) are graphs comparing glycerol conversion and acrylic acid selectivity, which appear after 3 hours in the reaction experiments of Examples 6 to 10 and Comparative Examples 3 to 4, respectively. Referring to FIG. 7, all the catalysts tested showed about 100% glycerol conversion, but there were many differences in acrylic acid selectivity. Specifically, it can be seen that all of the aluminosilicate spherical nanoparticles according to the present invention can produce acrylic acid with higher selectivity than the commercial bulk AS catalyst of Comparative Example 4. In addition, the DAS (Si / Al = 8) particles of Example 6 and the DAS (Si / Al = 40) particles of Example 9 were more effective in producing acrylic acid than the commercial MCM-41 catalyst of Comparative Example 3 having a very large specific surface area. Able to know.

Claims (15)

An aluminosilicate spherical nanoparticle having open pores whose size increases from the center of the particle in the direction of increasing the radius of the particle. The nanoparticle of claim 1, wherein the nanoparticles have a silicon: aluminum ratio of 1: 1 to 300: 1. According to claim 1, wherein the nanoparticles are nanoparticles, characterized in that having an average diameter of 50 ~ 3,000 nm. The nanoparticle of claim 1, wherein the nanoparticles have a specific surface area of 100 m ² / g or more. The nanoparticles of claim 4, wherein the specific surface area is 200 to 800 m ² / g. First hydrothermally treating in a pressure vessel a solution comprising a silica precursor, a polar solvent, a nonpolar solvent, an ionic surfactant and a basic compound;
Adjusting the pH of the first hydrothermally treated solution to 2 to 7 using an acidic aqueous solution;
Injecting an aluminum precursor into the pH controlled solution; And
Method for producing aluminosilicate spherical nanoparticles comprising the step of hydrothermally treating the solution in which the aluminum precursor is injected in a pressure vessel. The method of claim 6, wherein the silica precursor and the aluminum precursor are used such that an atomic ratio of silicon: aluminum is 1: 1 to 300: 1. The method of claim 6, wherein the silica precursor is selected from the group consisting of tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate and mixtures thereof, and the polar solvent Is selected from the group consisting of water, alcohols and mixtures thereof, and the nonpolar solvent is hexane, cyclohexane, methylcyclohexane, toluene, heptane, octane ) And mixtures thereof. The method of claim 8, wherein the alcohol is selected from the group consisting of propanol, butanol, butanol, pentanol, hexanol and mixtures thereof. The method of claim 6, wherein the ionic surfactant is cetylpyridinium chloride (cetylpyridinium chloride), cetylpyridinium bromide (cetylpyridinium bromide), cetyltrimetylammonium chloride (cetyltrimetylammonium bromide) and their Process for producing nanoparticles, characterized in that selected from the group consisting of a mixture. The method of claim 6, wherein the basic compound is selected from the group consisting of aqueous ammonia solution, urea, and mixtures thereof, and the acidic aqueous solution is a group consisting of aqueous hydrochloric acid, aqueous nitric acid, sulfuric acid, aqueous phosphoric acid, and mixtures thereof. The aluminum precursor is selected from the group consisting of aluminum chloride, aluminum bromide, aluminum sulfate, aluminum nitrate, aluminum acetate, and mixtures thereof. Method for producing a nanoparticles, characterized in that selected. A gaseous glycerol and oxygen gas are passed through a flow-type gas phase reactor filled with aluminosilicate spherical nanoparticles according to any one of claims 1 to 4 and a mixed oxide catalyst comprising molybdenum (Mo) and vanadium (V). Process for producing acrylic acid comprising reacting by making. The method of claim 12, wherein the nanoparticles and the mixed oxide catalyst are filled in the reactor to form different layers, and the layer of the nanoparticles is disposed closer to the inlet side of the reactor than the layer of the mixed oxide catalyst. The manufacturing method of acrylic acid characterized by the above-mentioned. The method of claim 12, wherein the mixed oxide catalyst has a molybdenum: vanadium atom ratio of 1: 1 to 10: 1. The method of claim 12, wherein the reaction is performed at a temperature of 250 ^° C. to 400 ^° C. and atmospheric pressure.

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