KR20180090001A - Method for heterogeneous catalyst and method for the synthesis of compounds using the same - Google Patents

Abstract

The present invention relates to a heterogeneous catalyst containing carbon nitride having a rhodium-supported mesoporous structure, and a production method thereof. It is possible to improve performance of the catalyst by suppressing inactivation of the catalyst due to self-aggregation of rhodium and leaching of rhodium and reaction products. Since the heterogeneous catalyst is easily recovered by simple separation processes, it is possible to secure improved efficiency in a process of synthesizing acetic acid and methyl acetate via a carbonylation reaction.

Description

TECHNICAL FIELD The present invention relates to a method for producing a heterogeneous catalyst and a method for producing a compound using the same,

More particularly, the present invention relates to a method for producing acetic acid using the same.

Commercially available processes for producing acetic acid can be divided into methanol carbonylation reaction, ethylene oxidation reaction and ethane oxidation reaction. Among them, the methanol carbonylation reaction is the most typical process during the synthesis of acetic acid (CH ₃ COOH), and more than 60% of the amount of acetic acid supplied to the world is produced through the corresponding process [J. Am. Chem. Soc., 126 (2004) 2847-2861]. The carbonylation reaction of methanol uses carbon monoxide (CO) and methanol as reactants, and the active metal and the reaction phase can be classified according to the kind thereof. The Monsanto process, which was invented in the early 1960s, uses rhodium (Rh) as an active metal and has a carbonyl group (-CO) and an iodide group (Iodide, -I) Catalyst precursor [US Patent 3769329 (1973)]. The Cativa process, which was invented in the 1990s, is a homogeneous catalytic reaction similar to that of the Monsanto process. However, iridium (Ir) is used as a reaction active material and methyl acetic acid above a certain amount is used as a reactant And has a much higher productivity than conventional processes [EP Patent 752406 (1995)].

Both of these processes have high conversion of methanol and high selectivity to acetic acid due to the homogeneous catalytic reaction, but the adsorption of rhodium and iridium on the product resulted in leaching (melting) , And a separate process for separating the resultant and the catalyst is required, resulting in a large economic cost.

Heterogenized - homogeneous catalysis has emerged as an effort to solve this problem, and the representative example is the Acetica process ( ^TM ). This process utilizes rhodium ion as the active material of the catalytic reaction and causes the carbonylation reaction of methanol using P4VP (Poly 4-vinyl pyridine) as a support as a support for producing a heterogeneous catalyst [US Pat. No. 5,364,963 1994), U.S. Pat. No. 5,576,458 (1996)]. In the case of the acetacid process, the reusability of the catalyst and the recovery of the catalyst from the result are easy, but the conversion of methanol and the selectivity of acetic acid are relatively low because the content of rhodium of the reactive active component per catalyst is low. In addition, in the case of a polymer used as a support, the catalyst is inactivated under high pressure and high temperature process conditions.

It is an object of the present invention to provide a catalyst and a method for producing a catalyst in which carbon nitride having a wide specific surface area and mesoporous structure is used as a support and rhodium is immobilized on a support.

Another object of the present invention is to provide a process for producing acetic acid and methyl acetate by carbonylation reaction of methanol.

A heterogeneous catalyst for one purpose of the present invention comprises rhodium immobilized on carbon nitride having a mesoporous structure.

In one embodiment, the mesopore structure may be a regular pore structure and have a specific surface area of 300 m ² / g to 1500 m ² / g.

In one embodiment, with respect to 100 parts by weight of carbon nitride, the rhodium immobilized on the carbon nitride may be 0.5 to 6 parts by weight.

A method for producing a heterogeneous catalyst for another purpose of the present invention includes a first step of heat treating an aqueous solution containing a carbon source and a mesoporous template mixed with distilled water; A second step of removing the template from the heat-treated aqueous solution to produce a carbon nitride support having a mesoporous structure; And a third step of mixing the carbon nitride support and the rhodium precursor to prepare a rhodium-immobilized heterogeneous catalyst on the support.

In one embodiment, the first step may be performed by charging distilled water mixed with the carbon source and the template into a reactor, and flowing nitrogen gas at a flow rate of 70 ml / min and heating.

In one embodiment, the third step may include reducing the metal salt by adding a solution containing an excess of sodium borohydride.

In one embodiment, the carbon source may be hexamethylenetetramine.

In one embodiment, the template may have a specific surface area of 200 m ² / g or more and a mesopore size of 4.0 nm or more.

Another method for producing acetic acid according to the present invention is a method for producing acetic acid from methanol and cabon monoxide in the presence of a heterogeneous catalyst according to claim 1 and a method for producing acetic acid from acetic acid and methyl acetate. And a carbonylation reaction.

According to the heterogeneous catalyst in which rhodium is immobilized on the carbon nitride support according to an embodiment of the present invention, rhodium is uniformly dispersed on the carbon nitride support having mesopores, so that the active sites exposed to the bulk material A large amount of mesoporous material can be easily dispersed in the reactant. In addition, rhodium is leached to the reaction product due to the strong interaction between the support carbonitride and rhodium, which is the active material, and the inactivation of the catalyst due to the self-agglomeration of the rhodium element is suppressed to secure the stability of the catalyst and the long- It is possible to increase the possibility of Since it is a heterogeneous catalyst, the product of the carbonylation reaction can be easily separated and recovered through a simple separation process, thereby improving the efficiency of the process. The Rh (5) / mpg-C ₃ N ₄ catalyst according to the present invention has a high selectivity for acetic acid and methyl acetate, as well as a high conversion of methanol in the carbonylation reaction using methanol and carbon dioxide.

1 is a graph showing the results of experiments on the samples of Examples 1 to 4;
Fig. 2 is a view showing pore analysis results for the samples of Examples 1 to 4. Fig.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It is to be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the term "comprises" or "having ", etc. is intended to specify that there is a feature, step, operation, element, part or combination thereof described in the specification, , &Quot; an ", " an ", " an "

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

Carbonylation reaction is a reaction that generally produces carbonyl compounds by the action of carbon monoxide (CO). The process of synthesizing an acrylic acid (C ₃ H ₄ O ₂ ) derivative by the reaction of acetylene (C ₂ H ₂ ) with carbon monoxide is the most important. This is a kind of reppe reaction, It is also called anger. The reaction of acetylene with carbon monoxide in the presence of pentacarbonyliron (C ₅ FeO ₅ ) to form hydroquinone (C ₆ H ₄ (OH) ₂ ) is also a kind of carbonylation reaction of acetylene.

Methyl acetate is an organic chemical source and solvent that can be used to synthesize acetic acid, acetic acid anhydride, and acetic acid derivatives such as vinyl acetate. Methyl acetate can also be used to synthesize ethanol through hydrogen reduction, which is now considered as an alternative to the process of producing ethanol. Methyl acetate is also used as an environment-friendly solvent for adhesives, paints, and ink resins.

Heterogeneous catalysts are called heterogeneous catalysts when the reaction rate is changed by a substance that differs from the reactant and phase such as gas-solid system and liquid-solid system. In the heterogeneous catalytic reaction, the reactant first diffuses to the catalyst surface to cause chemisorption, and the adsorbed molecules are involved in the reaction, and the product is released from the catalyst surface and diffuses into the gas phase or the liquid phase to come out of the system. Most of the heterogeneous catalysts are solid, and the reaction is carried out on the surface of the catalyst.

Carbon nitride is a carbon material containing nitrogen which is expressed by the chemical formula of C ₃ N ₄ and is also referred to as carbon nitride. The carbon nitride may be collectively referred to as a binary compound alpha (alpha), beta (beta), cubic system, pseudocubic system and Graphitic carbon nitride in which carbon and nitrogen form a covalent bond. The graphitic carbon nitride has a meso-sized spherical pores regularly arranged, and has a three-dimensionally interconnected shape, and has an advantage of facilitating internal electron movement because of its abundant nitrogen content. The graphitic carbon nitride containing rhodium metal has an increased internal Lewis acidic retention capacity and can play a role in catalyzing the interaction between the catalyst and the reaction from electron transport and is advantageously provided in that the metal material is immobilized on the carbon nitride support.

A heterogeneous catalyst for one purpose of the present invention comprises rhodium immobilized on carbon nitride having a mesoporous structure.

The present invention provides a novel catalyst for increasing the dispersibility of rhodium by using carbon nitride having pores having a large specific surface area and meso size as a support and immobilizing rhodium as an active metal on a support.

In one embodiment, the mesopore structure may be a regular pore structure and have a specific surface area of 300 m ² / g to 1500 m ² / g.

The carbon nitride used for improving the dispersibility of the rhodium metal and ensuring the carbonylation reactivity has a specific surface area of 300 m ² / g to 1500 m ² / g, preferably a specific surface area of 500 m ² / g to 1100 m ² / g and mesoporous graphitic carbon nitride (mpg-C ₃ N ₄ ) having mesopores having an average pore size of 2 nm to 10 nm.

In one embodiment, with respect to 100 parts by weight of carbon nitride, the rhodium immobilized on the carbon nitride may be 0.5 to 6 parts by weight.

In addition, the present invention is a heterogeneous catalyst capable of controlling the conversion of methanol and carbon monoxide and the selectivity of acetic acid and / or methyl acetate through the content of rhodium by immobilizing rhodium metal as an active material on a carbon nitride support.

The total content of rhodium may be 1 wt% to 7 wt% based on the weight of the carbon nitride support. If the content of rhodium exceeds 7 wt%, economical efficiency may be deteriorated due to the use of expensive rhodium.

A method for producing a heterogeneous catalyst for another purpose of the present invention includes a first step of heat treating an aqueous solution containing a carbon source and a mesoporous template mixed with distilled water; A second step of removing the template from the heat-treated aqueous solution to produce a carbon nitride support having a mesoporous structure; And a third step of mixing the carbon nitride support and the rhodium precursor to prepare a rhodium-immobilized heterogeneous catalyst on the support.

In one embodiment, the first step may be performed by charging distilled water mixed with the carbon source and the template into a reactor, and flowing nitrogen gas at a flow rate of 70 ml / min and heating.

In one embodiment, the third step may include reducing the metal salt by adding a solution containing an excess of sodium borohydride.

In one embodiment, the carbon source may be hexamethylenetetramine.

In the present invention, a silica template is used as a template for synthesizing a catalyst having a wide pore and a high surface area. The silica template is located inside the carbon nitride by carburization and removes the silica template through the subsequent extraction process to secure pores.

In one embodiment, the template may have a specific surface area of 200 m ² / g or more and a mesopore size of 4.0 nm or more. Specifically, SBA-15, KiT-6, MCM-41, FSM-16 and the like can be used.

The extraction of the silica template material uses a strongly basic or strongly acidic solution, but is not limited thereto. Preferably, the solution used for the extraction of the template is a sodium hydroxide-distilled water solution, and a solution prepared by dissolving sodium hydroxide in distilled water at a concentration of 4 M can be used.

Specifically, the first step is a step of mixing rhodium nitrate with hexamethylenetetramine used as a carbon source and SBA-15, a silica template material, and rhodium nitrate as a rhodium precursor, to prepare Rh (x), hexamethylenetetramine, / mpg-C ₃ N ₄ precursor.

In the process of mixing the prepared mpg-C ₃ N ₄ and the rhodium precursor, a step of dropping a solution containing an excess of sodium borohydride into the precursor solution while reducing the metal salt.

The metal salt may be an ammonium salt, an acetate salt, a hydroxide, a nitrate, a halide, a phosphate, a perchlorate, a sulfate, and the like, but is not limited thereto.

The reducing agent used in the reduction reaction may not be limited to NaBH ₄ , Na (BH ₃ CN), LiBH ₄ , N ₂ H ₄ , AlBH ₄ , LiAlH _4, and the like.

The second process is maintained at 600 ° C to 900 ° C for 5 hours under a nitrogen atmosphere. This leads to self-polymerization of hexamethylenetetramine, which leads to carbon and nitrogen rearrangement, resulting in powdered Rh (x) / mpg-C ₃ N ₄ precursors.

In the third step, the precursor prepared in the first step is mixed with 4M NaOH solution and stirred at 80 ° C for 30 minutes. After filtration and washing with 1 L of distilled water, the resultant is dried in a circulating drier maintained at 80 ° C. to prepare a powdered Rh (x) / mpg-C ₃ N ₄ catalyst.

Another method for producing acetic acid according to the present invention is a method for producing acetic acid from methanol and cabon monoxide in the presence of a heterogeneous catalyst according to claim 1 and a method for producing acetic acid from acetic acid and methyl acetate. And a carbonylation reaction.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are intended to illustrate the present invention, and the scope of application of the present invention is not limited to these examples.

Production Example 1. Preparation of SBA-15 catalyst

16.0 g of pluronic p123 copolymer was placed in 150 ml of distilled water and stirred vigorously until completely dissolved. Then, 25 ml of a 37% hydrochloric acid aqueous solution was added to 428 ml of distilled water, and the mixture was stirred at 35 ° C. After confirming that the prepared pluronic p123 copolymer solution was completely dissolved in distilled water, the solution was added to a hydrochloric acid solution under stirring and further stirred for 1 hour while maintaining the temperature at 35 ° C. Then, 34.4 g of TEOS (tetraethoxysilane) was added to the reaction solution Lt; RTI ID = 0.0 > 35 C < / RTI > for 24 hours. After confirming that a white precipitate was formed in the reaction solution in which the stirring was completed for 24 hours, the reaction solution was transferred to an autoclave equipped with a Teflon container and subjected to hydrothermal synthesis at about 100 ° C. for one day. After completion of the hydrothermal synthesis, the reaction solution was filtered without washing before washing. After thoroughly removing the solvent through filtration, the reaction solution was dried in an oven at 110 ° C for about 1 hour. The dried white powder was heated to 500 ° C at a heating rate of 1 ° C / min and maintained for 6 hours. SBA-15 mesoporous silica in fine white powder form was finally prepared. SBA- -15 has a specific surface area of 727 m ² / g and an average pore size of 5.9 nm.

Preparation Example 2 mpg-C ₃ N ₄  Preparation of support

3 g of SBA-15 and 10.2 g of hexamethylenetetramine ((CH ₂ ) ₆ N ₄ , Hexamethylenetetramine) prepared above were mixed with 160 ml of distilled water solution, and hexamethylenetetramine was completely dissolved in the solution. Dried under reduced pressure while stirring at a constant rate of 180 rpm under a constant temperature condition where the temperature was kept at 60 ° C. The precursor dried under reduced pressure was placed in a circulating dryer at 80 캜 for drying for 12 hours or more. The dried precursor was added to a quartz reactor and the heating reaction was carried out while flowing nitrogen gas at a flow rate of 70 ml / min. For the heating reaction, the temperature was raised from room temperature to 750 ° C at a heating rate of 3 ° C / minute, and then maintained at 750 ° C for 300 minutes to perform an autopolymerization reaction. Thereafter, the silica template material was removed using a 4 M NaOH solution, followed by filtration and washing with 1 L of distilled water, followed by drying in an oven at 80 ° C. for 12 hours. Finally, a carbon nitride support having mesopores in powder form can be obtained. The catalyst prepared above was designated mpg-C ₃ N _4. The specific surface area of the prepared catalyst was 656 m ² / g, the pore volume was 0.56 cm ³ / g, and the average pore size was 3.8 nm.

Example 1. Rh (3) / mpg-C ₃ N ₄  Preparation of heterogeneous catalyst

A mpg-C ₃ N ₄ substrate and 0.309 g of rhodium nitrate of 0.5 g prepared from the Rh (NO ₃₎ after the ₃ mixed with 50 ml of distilled water, the precursor to 10 ml solution into the NaBH ₄ in excess solution Dropwise, and the mixture is stirred at room temperature for 30 minutes at a stirring speed of 180 rpm. Thereafter, the powdery catalyst was prepared by filtration and drying in a circulating dryer at 80 DEG C for 12 hours or more. The finally prepared catalyst was a heterogeneous catalyst on which rhodium was immobilized on a carbon nitride support, and the content of rhodium relative to the weight of the support was 3 wt%. The prepared catalyst was denoted by Rh (3) / mpg-C 3 N 4. The specific surface area is 926 m ² / g, the pore volume is 0.74 cm ³ / g, and the average pore size is 3.5 nm.

Examples 2 and 5. Rh (5) / mpg-C ₃ N ₄  Preparation of heterogeneous catalyst

A heterogeneous catalyst was prepared in the same manner as in Example 1 except that 0.5 g of an mpg-C ₃ N ₄ support and 0.526 g of rhodium were added in order to prepare a catalyst having a rhodium content of 5 wt% Nitrate (Rh (NO ₃ ) ₃ ) was used. The prepared catalyst is represented by Rh (5) / mpg-C ₃ N ₄ , having a specific surface area of 1280 m ² / g, a pore volume of 1.01 cm ³ / g, and an average pore size of 3.4 nm.

Example 3. Rh (1) -mpg-C ₃ N ₄  Preparation of heterogeneous catalyst

The heterogeneous rhodium-nitrided carbon catalyst having mesopores was prepared through the nano-replication method using the prepared SBA-15. 0.5 g of SBA-15 was mixed with 20 ml of distilled water, 1.7 g of hexamethylenetetramine and 0.0686 g of rhodium nitrate (Rh (NO ₃ ) ₃ ) were added to the solution, and the amount of rhodium nitrate And the weight of the rhodium was calculated. Stirring was carried out at a constant rate of 180 rpm under a constant temperature condition at 60 캜. After confirming that hexamethylenetetramine and rhodium nitrate were completely dissolved in distilled water, they were dried under reduced pressure at 70 ° C. Thereafter, it was put into a circulating dryer at 80 캜 and dried for 12 hours or more. The dried precursor was introduced into a quilting reactor and heated under a flow of nitrogen gas at a flow rate of 70 ml / min. For the heating reaction, the silica template material was removed using a NaOH solution heated from room temperature to 750 ° C at a heating rate of 3 ° C / min, followed by filtration and washing with distilled water, followed by drying in an oven at 80 ° C for 12 hours , And finally a rhodium-carbon nitride catalyst in the form of a black powder was obtained. The catalyst thus prepared was designated Rh (1) -mpg-C ₃ N _4. The catalyst had a specific surface area of 422 m ² / g, a pore volume of 0.40 cm ³ / g and an average pore size of 3.8 nm.

Example 4. Rh (4) -mpg-C ₃ N ₄  Preparation of heterogeneous catalyst

A heterogeneous catalyst was prepared in the same manner as in Example 3, except that 0.283 g of rhodium nitrate (Rh (NO ₃ ) ₃ ) was added to prepare a catalyst having a rhodium content of 4 wt% Respectively. The prepared catalyst is represented by Rh (4) -mpg-C ₃ N ₄ , and has a specific surface area of 1028 m ² / g, a pore volume of 0.77 cm ³ / g, and an average pore size of 3.2 nm.

Comparative Example 1 Rh (7) / mpg-C ₃ N ₄  Preparation of heterogeneous catalyst

A heterogeneous catalyst was prepared in the same manner as in Example 1 except that 0.5 g of an mpg-C ₃ N ₄ support and 0.752 g of rhodium were added to prepare a catalyst having a rhodium content of 7 wt% Nitrate Rh (NO ₃ ) ₃ was used. The prepared catalysts are Rh (7) / mpg-C 3 N ₄ as indicated, and the specific surface area is 1156 m ² / g, pore volume is 0.91 cm ³ / g, an average pore size of 3.5 nm.

Comparative Example 2 Rh (3) / g-C ₃ N ₄  Preparation of heterogeneous catalyst

(1) Production of carbon nitride support

10 g of melamine powder was charged into a tube reactor, and a heating reaction was carried out while flowing nitrogen gas at a flow rate of 50 mL / min. When the temperature is raised from room temperature to 250 ° C at a heating rate of 1.9 ° C / min for the heating reaction, the temperature is maintained at 250 ° C for 30 minutes. Thereafter, it was heated from 250 캜 to 350 캜 at a heating rate of 1.7 캜 / min, and then maintained at 350 캜 for 30 minutes. Subsequently, the substrate was heated from 350 ° C to 550 ° C at a heating rate of 3.3 ° C / min, and then maintained at 550 ° C for 240 minutes. The specific surface area of the carbon nitride support produced by slow carburization is 12.8 m ² / g.

(2) Preparation of rhodium complex

After 0.652 g of dichlorotetracarbonyldiiron (C ₄ O ₄ Cl ₄ Rh ₂ ) was dissolved in 30 mL of dichloromethane, 0.6271 g of 3-benzoylpyridine (C ₆ H ₅ COC ₅ H ₄ N) was added as a ligand . After aging at room temperature (about 25 ° C) for about 1 hour, the solvent-removed water was washed with 30 mL of hexane through vacuum drying. After completion of the hexane washing process, the rhodium complex was dried at room temperature for 24 hours or more.

(3) Production of heterogeneous catalyst

0.012 g of a rhodium complex and 0.388 g of a carbon nitride support were used to prepare a catalyst having a rhodium complex content of 3 wt% based on the weight of the support. The catalyst thus prepared is represented by Rh (3) / gC ₃ N ₄ .

Comparative Example 3. Rh (7) / W _x C heterogeneous catalyst

0.028 g of the prepared rhodium complex and 0.372 g of tungsten carbide as a support were dissolved in 50 ml of dichloromethane and stirred at a stirring speed of 180 rpm at room temperature for 2 hours. Dichloromethane as a solvent was removed through reduced pressure drying and dried at room temperature for 12 hours or more to prepare a powdery catalyst. The catalyst finally prepared was a catalyst having a rhodium complex content of 7 wt% based on the weight of the tungsten carbide support, and the prepared catalyst was designated as Rh (7) / W _x C. The specific surface area of the used tungsten carbide support was 10.4 m ² / g and the average pore size was 5.4 nm. Analysis by Xray diffraction showed that WC and W ₂ C were composed with a molar ratio of [W ₂ C] / [WC] = 9.2 Respectively.

Comparative Example 4 Preparation of Rh (10) / PVP heterogeneous catalyst

0.040 g of the prepared rhodium complex and 0.360 g of poly (4-vinylpyridine) as a polymer support were used to prepare a catalyst having a rhodium complex content of 10 wt% based on the weight of the support. The catalyst thus prepared was designated Rh (10) / PVP.

Experimental Example 1 N ₂  Adsorption, desorption and BET / BJH pore analysis

N ₂ adsorption, desorption, pore volume and pore size analysis were performed using all the samples according to the Examples and Comparative Examples. Specifically, nitrogen adsorption and desorption isotherm curves were obtained at 77 K using a Micromeritics TriStar 3000, from which the surface area and pore volume were measured by BET (Brunaure-Emmett-Teller) and BJH (Barrett-Joyner-Halenda) The pore size was calculated. Particularly, the specific surface area was calculated by using a section where the accuracy of the correlation coefficient is at least 99.99% by defining a linearly increasing portion from P / P ₀ to a point of from 0.3 to 0.05. The contents thereof are shown in Fig. 1 and Fig.

Experimental Example 2 Preparation of Acetic Acid and Methyl Acetate by Carbonylation of Methanol

The carbonylation reaction of methanol and carbon monoxide to acetic acid using the heterogeneous catalysts prepared in Examples 1 and 2 and Comparative Examples 1 to 4 was carried out in a 125 ml batch type high pressure reactor equipped with a Pyrex vessel Autoclave. As the reactants used in the carbonylation reaction, 8 ml of methanol, 10 ml of reaction catalyst (Iodomethane, CH ₃ I), 2 ml of distilled water and 0.1 g of the prepared heterogeneous catalyst were used Respectively. In order to prepare the atmosphere of reaction proceeding at high pressure, carbon monoxide as a reactant was injected up to 40 bar in the form of a mixed gas of 90: 10 at a molar ratio with nitrogen as an internal standard substance to prepare a reaction. Thereafter, the reactants and the cocatalyst were stirred at a rate of 100 rpm. After the internal temperature of the reactor was raised to 140 ° C, when the internal temperature of the reactor reached 140 ° C, the temperature was increased to 300 rpm Carbonylation reaction was carried out for a period of time.

Experimental Example 3. Preparation of Acetic Acid and Methyl Acetate by Carbonylation of Methanol Containing Acetic Acid and Methyl Acetate

Carbonylation reactions of methanol and carbon monoxide to acetic acid using the heterogeneous catalysts prepared in Examples 3 to 5 were carried out in a 125 ml batch type high pressure reactor equipped with a Pyrex vessel. 4.495 g of methanol, 2 ml of reaction catalyst iodomethane, 1.081 g of distilled water and 1.489 g of methyl acetate produced in the carbonylation reaction and 8 ml of acetic acid were added to the carbonylation reaction. The prepared heterogeneous catalyst was used. In order to prepare the atmosphere of reaction proceeding at high pressure, carbon monoxide as a reactant was injected up to 40 bar in the form of a mixed gas of 90: 10 at a molar ratio with nitrogen as an internal standard substance to prepare a reaction. Thereafter, the reactants and the cocatalyst were stirred at a rate of 100 rpm. After the internal temperature of the reactor was raised to 190 ° C, when the internal temperature of the reactor reached 190 ° C, the temperature was elevated to 300 rpm Carbonylation reaction was carried out for a period of time. The above reaction was carried out for 3 hours after the start of the reaction, in which the conversion of methanol as a reactant was stabilized at a certain level, and methanol conversion and product selectivity were calculated.

division catalyst Methanol conversion rate
(Carbon mole%) Selectivity (mol%) Yield ^{2 )}
(mole%) Acetic acid methyl
acetate Others ^{1 )} Example 1 Rh (3) / mpg-C 3 N 4 69.0 50.9 45 4.1 66.1 Example 2 Rh (5) / mpg-C 3 N 4 90.1 44.3 52.1 4.6 85.9 Example 3 _{Rh (1) -mpg-C 3} N 4 92.3 -9.2 109.2 - 92.3 Example 4 _{Rh (4) -mpg-C 3} N 4 99.9 37.3 62.7 - 99.9 Example 5 Rh (5) / mpg-C 3 N 4 100.0 56.4 43.6 - 100 Comparative Example 1 Rh (7) / mpg-C 3 N 4 40.9 34.7 61.8 3.5 39.4 Comparative Example 2 _{Rh (3) / gC 3 N} 4 56.8 72.0 18.7 9.3 51.5 Comparative Example 3 Rh (7) / W _x C 69.9 53.9 28.7 17.4 57.7 Comparative Example 4 Rh (10) / PVP 72.5 51.3 35.0 13.6 62.5

1) Other: analyzed as acetaldehyde and acetone

2) Yield = (methanol conversion) * (selectivity for acetic acid + selectivity for methyl acetate)

As shown in the above Table 1, the catalysts of Examples 1 to 5 are heterogeneous catalysts having a wide specific surface area and a mesopore as disclosed in the present invention, in which the amounts of rhodium atoms in the support, (5) / mpg-C ₃ N ₄ catalyst was adjusted to be 1 wt% to 5 wt% based on the weight of the catalyst, the catalytic conversion of methanol as the reactant was 90% It was confirmed that the activity was excellent.

On the other hand, in the case of Comparative Example 1 tested under the conditions of Experimental Example 1, it was confirmed that the improvement effect of the catalytic activity by an amount exceeding 7 wt% based on the weight of the support could not be expected. Comparing Example 1 and Comparative Example 2 having the same rhodium content, in Comparative Example 2, the conversion of methanol was 56.8 mol%, the yield of acetic acid and methyl acetate was 51.5 mol%, and the yield of acetone and acetaldehyde The selectivity was increased to 9.3 mol%.

In Comparative Examples 3 and 4, a rhodium complex was supported in an excess amount of 7 wt% to 10 wt% on bulk tungsten carbide and a polymer support, and the results of the activity test with Example 2 were compared. As a result, It can be confirmed that the conversion rate and the yields of the products acetic acid and methyl acetate are not high. On the other hand, the selectivities of acetone and acetaldehyde as by-products tended to increase to 13.6 mol% or more.

Unlike Experimental Example 1, in Experimental Example 2, in Experimental Conditions in which acetone and methyl acetate contained in the reactant were contained in the actual process, Examples 1 to 5, which were tested under these conditions, showed a methanol conversion of at least 92.3 Mol%, the selectivity of acetic acid was 56.4 mol%, and the content of methyl acetate was 43.6 mol%.

In addition, in the case of Example 3, methyl acetate is predominantly produced, and as compared with Examples 4 and 5, the production rate of acetic acid tends to increase as the amount of rhodium increases. In the case of the catalyst of the present invention, when a carbon nitride support having a large specific surface area is used, rhodium as an active material is uniformly dispersed, exhibits high catalytic activity even with a small rhodium content, and has low selectivity for acetone and acetaldehyde as by-products Since a high purity product is obtained, there is an advantage that an additional process for treating by-products may not be necessary, and a separation process may not be necessary as a heterogeneous catalyst.

1 is a graph showing the results of experiments on the samples of Examples 1 to 4;

Fig. 2 is a view showing pore analysis results for the samples of Examples 1 to 4. Fig.

Referring to FIGS. 1 and 2, FIG. 1 is a graph of N ₂ adsorption and desorption for the samples of Examples 1 to 4, and FIG. 2 is a graph of BET / BJH pore analysis results for the samples of Examples 1 to 4. Since the sample of Example 5 is the same catalyst sample as that of Example 2, it is excluded from Fig. 1 and Fig. The nitrogen adsorption and desorption isotherms of all the samples shown in FIG. 1 and the distributions of the BET / BJH pore analysis show that the isotherms of the mesoporous type-IV including the hysteresis curve appear.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims. It can be understood that it is possible.

Claims (9)

Characterized in that rhodium is fixed to carbon nitride having a mesoporous structure.
Heterogeneous catalyst.
The method according to claim 1,
Wherein the mesopore structure is a regular pore structure and has a specific surface area of 300 m ² / g to 1500 m ² / g.
Heterogeneous catalyst.
The method according to claim 1,
Characterized in that the rhodium fixed to the carbon nitride is 0.5 to 6 parts by weight based on 100 parts by weight of carbon nitride.
Heterogeneous catalyst.
A first step of heat treating an aqueous solution containing a carbon source and a mesoporous template mixed with distilled water;
A second step of removing the template from the heat-treated aqueous solution to produce a carbon nitride support having a mesoporous structure; And
And a third step of mixing the nitride carbon support and the rhodium precursor to produce a rhodium-immobilized heterogeneous catalyst on the support.
A method for producing a heterogeneous catalyst.
5. The method of claim 4,
The first step
Characterized in that distilled water mixed with the carbon source and the template is introduced into a reactor and nitrogen gas is flowed at a flow rate of 70 ml / min and heated.
A method for producing a heterogeneous catalyst.
5. The method of claim 4,
In the third step,
Comprising the step of reducing the metal salt by adding a solution of sodium borohydride in excess,
A method for producing a heterogeneous catalyst.
5. The method of claim 4,
Wherein the carbon source is hexamethylenetetramine,
A method for producing a heterogeneous catalyst.
5. The method of claim 4,
Wherein the template has a specific surface area of 200 m ² / g or more and a mesopore size of 4.0 nm or more.
A method for producing a heterogeneous catalyst.
Characterized in that it comprises a carbonylation reaction for producing acetic acid and methyl acetate from methanol and cabon monoxide in the presence of a heterogeneous catalyst according to claim 1,
Acetic acid.

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