KR101477203B1 - Mixed metal oxide supported alkali or alkaline-earth metal catalyst, syntheric method thereof and production method of dimethyl carbonate from methanol and ethylene carbonate using said catalyst - Google Patents

Abstract

The present invention relates to a composite metal oxide catalyst, a method for preparing the same, and a method for synthesizing dimethyl carbonate by using the catalyst. More particularly, the present invention relates to a composite metal oxide-supported catalyst, a method for preparing the same, and a method for preparing dimethyl carbonate from methanol and ethylene carbonate by using the catalyst, wherein the catalyst used to prepare dimethyl carbonate from methanol and ethylene carbonate is characterized by supporting 1-20 wt% of an oxide of one or more kinds of alkalis selected from the group consisting of lithium, potassium, cesium, barium, and strontium or an alkaline earth metal based on a total weight of the catalyst to a composite metal oxide, which is prepared by mixing a cerium oxide (CeO_2) precursor and a magnesium oxide precursor at a molar ratio of 0.01 to 100 and oxidizing the resultant through a coprecipitation method using an acid as a precipitating agent. When dimethyl carbonate is prepared from methanol and ethylene carbonate by using the catalyst of the present invention, dimethyl carbonate can be prepared at high yield.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for producing dimethyl carbonate from methanol and ethylene carbonate using the catalyst, AND ETHYLENE CARBONATE USING SAID CATALYST}

The present invention relates to a composite metal oxide supported catalyst, a process for producing the catalyst, and a process for producing dimethyl carbonate from methanol and ethylene carbonate using the catalyst, and more particularly, to a catalyst for the production of dimethyl carbonate from methanol and ethylene carbonate (CeO ₂ ) precursor and a magnesium oxide precursor in a molar ratio ranging from 0.01 to 100, and oxidizing the mixture by coprecipitation using an acid as a precipitant, wherein the composite metal oxide comprises lithium, potassium, cesium, barium and strontium By weight of an alkali metal or an alkaline earth metal oxide selected from the group consisting of alkali metals and alkaline earth metals in an amount of 1 to 20% by weight based on the total weight of the catalyst, a process for producing the same, From ethylene carbonate, dimethyl carbonate is added And the like.

Dimethyl carbonate is an environmentally friendly material and has recently attracted attention as an important material in the chemical industry. Dimethyl carbonate is used as a methylation reaction instead of dimethyl sulfate or dimethyl halide, which is very toxic, or as a carbonylation reaction instead of phosgene. Polycarbonate, an engineering plastic used for information and communication materials such as mobile phones and notebooks, Polycarbonate (PC) is used as the main raw material. Generally, polycarbonate is synthesized by reacting bisphenol A (BPA) with phosgene. However, phosgene used in this reaction is seriously toxic and poses a problem in terms of environmental safety. Therefore, a process for replacing phosgene is proposed in which polycarbonate is produced from carbon dioxide and epoxide via dimethyl carbonate and diphenyl carbonate. Demand for dimethyl carbonate is expected to increase gradually as demand for polycarbonate increases. Also, since dimethyl carbonate contains a lot of oxygen, it is widely used as a fuel additive to replace methyl tertiary butyl ether (MTBE). Recently, it has been used as an electrolyte of a secondary battery, As well.

Various processes are currently known as processes for producing dimethyl carbonate. Typically, there is a phosgene process for producing dimethyl carbonate using phosgene known as methanol and toxic substances (Non-Patent Document 1 and Patent Documents 1 and 2). However, this method is avoiding the use of poisonous phosgene and high concentration of caustic soda solution due to high risk in industry. The methanol oxidation method (EniChem process, Italy) was developed to replace the phosgene process. It is a method of oxidizing carbon monoxide and methanol in the air using a copper chloride catalyst, using toxic carbon monoxide as a raw material. (Non-Patent Document 2 and Patent Documents 3 to 4). The methyl nitrite method (Ube process, Japan) has also been developed as a phosgene replacement process and consists of a total of two steps (Non-Patent Documents 3 to 5 and Patent Document 5). In the first step of this process, methanol is oxidized with nitrogen dioxide to produce methyl nitrite. In the second step, dimethyl carbonate produced by the reaction of methyl nitrite and carbon monoxide generated in the first step using a palladium catalyst . In this process, the nitrogen monoxide produced as a by-product is reoxidized to the reactant nitrogen dioxide and reused in the first process step. However, this process also requires a reaction device for preventing corrosion, a safety device for preventing explosion and a precise concentration adjusting device by using carbon monoxide and nitrogen oxide, which are toxic and corrosive, and there is a risk of leakage of reactant. The above processes have problems such as the use of toxic reactants such as phosgene, nitrogen monoxide, carbon monoxide, corrosion problems of reactors, high process cost due to multi-stage process, and difficulty of separation and purification due to the production of byproducts.

In order to overcome such problems, recently, a method for producing dimethyl carbonate by the ester exchange method has been studied (Non-patent Documents 6 to 7 and Patent Documents 6 to 8). The process comprises a step of synthesizing ethylene carbonate by the reaction of carbon dioxide and ethylene oxide, and a multi-step process of reacting the produced ethylene carbonate with methanol to produce dimethyl carbonate. This process is advantageous in that it uses low cost and less toxic raw materials, less corrosion problem of the reactor, and ethylene glycol which is produced as a byproduct of the reaction, can be recycled to ethylene oxide as reactant through appropriate chemical reaction. Various excellent catalysts and catalyst processes suitable for the production of dimethyl carbonate by the ester exchange method have been disclosed, but up to now, homogeneous catalyst processes have conventionally been applied (Non-patent Documents 8 to 9). However, in the case of homogeneous catalytic process, there are various disadvantages that can be caused by the continuous inclusion of homogeneous catalysts in the actual reaction process in addition to the problem of catalyst separation, and gradually the heterogeneous reaction process is recognized as a more realistic reaction system . For the heterogeneous reaction process, the development of heterogeneous catalysts is important, and the reaction rate and the yield of dimethyl carbonate synthesis should be shown to be practically useful. In addition, it is necessary to develop a durable catalyst having durability and chemical resistance that can maintain its shape in various chemical agents that last for a long time.

It has been reported that acid catalysts and base catalysts can be utilized as catalyst candidate groups that can be used in the process of producing dimethyl carbonate from methanol and ethylene carbonate (Non-Patent Document 10 and Patent Documents 9 to 11). However, it is known that the reaction using a base catalyst is more effective for the synthesis of dimethyl carbonate (Non-Patent Document 7 and Patent Document 12). A variety of base catalysts have been studied for use in the production of dimethyl carbonate from methanol and ethylene carbonate. However, a suitable catalyst system and an efficient production method have not yet been proposed.

On the other hand, it is known that the composite metal oxide catalyst, which is an oxide composed of two or more metals, has different base characteristics depending on its molar ratio and exhibits better base properties than a single metal oxide (Non-Patent Document 11). Generally, a sol-gel method or coprecipitation method is used as a method for preparing a metal composite oxide catalyst. The sol-gel method has the advantage that the specific surface area of the catalyst is large and relatively uniform, but the process is complicated and takes a long time. In the coprecipitation method, the metal precursor is dissolved in a solvent and the pH of the solution is adjusted to precipitate the solution, which is not uniform compared to the sol-gel method. However, the preparation method is relatively simple and the solvent and temperature are changed during the precipitation, Particle size, and crystal phase size (Non-Patent Documents 12 to 13).

On the other hand, it is known that when the third metal oxide is supported on the metal oxide support, the physical and chemical properties, acid and base properties, and thermal properties of the catalyst are changed (Non-Patent Document 14). It has been reported that another metal oxide is supported on a metal oxide carrier by using this characteristic change to form a catalyst and applied to the reaction. In particular, there is a report that when the alkali metal or alkaline earth metal is supported on the metal oxide carrier, the base properties of the catalyst are improved (Non-Patent Documents 15 to 16).

H. Zimmermann, K. Brenner, H-J. Scheiper, W. Sauer, H. Hartmann, U.S. Patent 5,319,111 (1994). J-A. T. Schwartz, U.S. Patent 5,478,952 (1995). U. Romano, R. Tesel, G. Cipriani, L. Micucci, U.S. Patent 4,218,391 (1980). G. Paret, G. Donati, M. Ghirardini, EP 460, 735 (1991). K. Nishimura, K. Fujii, K. Nishihira, S. Uchiumi, US Patent 4,229,589 (1980). CD. Chang, L.E. Hoglen, Z. Jiang, R.B. LaPierre, US Patent 6,162, 940 (2000). Z. Jiang, R.B. LaPierre, J.G. Santiesteban, H.K.C. Timken, W.A. Weber, US Pantent 6,207,850 (2001). Y. Urano, M. Kirishiki, Y. Onda, H. Tsuneki, US Patent 5,430,170 (1995). T. Kondoh, Y. Okada, F. Tanaka, S. Asaoka, S. Yamanoto, US Patent 5,436,362 (1995). R.G. Duranlean, E.C.Y. Nieh, J.F. Knifton US Patent 4,611,609 (1987). CD. Chang, L.E. Hoglen, Z. Jiang, R.B. LaPierre, US Patent 6,166, 240 (2000). S.S. Shih, M.M. Wu, T.Y. Yan, US Pantent 5,430,170 (1996).

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Accordingly, an object of the present invention is to provide a catalyst for the production of dimethyl carbonate having improved physical and chemical properties of the catalyst by further comprising an alkali and an alkaline earth metal oxide supported on the catalyst by changing the molar ratio of the complex metal oxide for the purpose of controlling the base property of the catalyst, And a method for producing the same.

Another object of the present invention is to provide a process for producing dimethyl carbonate which maximizes efficiency in the production of dimethyl carbonate from methanol and ethylene carbonate using the developed composite metal oxide catalyst supported with alkali and alkaline earth metal oxide.

In order to achieve the above object, the present invention provides a catalyst for use in the production of dimethyl carbonate from methanol and ethylene carbonate, wherein a cerium oxide (CeO ₂ ) precursor and a magnesium oxide precursor are mixed in a molar ratio ranging from 0.01 to 100, And at least one alkali or alkaline earth metal oxide selected from the group consisting of lithium, potassium, cesium, barium and strontium is added to the composite metal oxide prepared by the coprecipitation method in an amount of 1 to 20% by weight based on the total weight of the catalyst And a supported catalyst supported on the support.

The present invention also provides a composite metal oxide supported catalyst characterized in that the acid is oxalic acid.

The present invention also provides a method for preparing a precipitate comprising the steps of: i) adding an acid to a cerium oxide precursor and a magnesium oxide precursor solution to form a precipitate; Ii) aging the precipitate for crystal growth for 5 to 24 hours; Iii) filtering, washing and drying the precipitate, and calcining the precipitate at a temperature of 300 to 800 ° C. for 3 to 12 hours to produce a composite metal oxide; Iv) impregnating the composite metal oxide with an alkali or alkaline earth metal precursor solution in which one or more alkali or alkaline earth metal precursors selected from the group consisting of lithium, potassium, cesium, barium and strontium are dissolved in distilled water; And v) calcining the composite metal oxide catalyst having alkali or alkaline earth metal supported thereon by drying at 70 to 120 ° C and then at a temperature of 300 to 700 ° C for 3 to 12 hours.

The metal oxide precursor or the alkali or alkaline earth metal oxide precursor is at least one selected from the group consisting of nitrate, chloride, bromide, acetate, and acetylacetonate. A method for producing a catalyst is provided.

The present invention also relates to a process for the production of a catalyst, which comprises reacting methanol and ethylene carbonate in the presence of the catalyst under the conditions of a temperature of 80 to 150 ° C, a pressure of 3 to 25 bar, a stirring speed of 300 to 1000 rpm and a reaction time of 1 to 24 hours Dimethyl carbonate. ≪ / RTI >

The dimethyl carbonate produced from methanol and ethylene carbonate showed a high yield of dimethyl carbonate when the composite metal oxide supported catalyst prepared according to the present invention was produced.

1 shows the X-ray diffraction analysis results of CeO ₂ (X) -MgO (1-X) (X = 0, 0.25, 0.5, 0.75 and 1.0) composite metal oxides prepared according to Production Example 2 of the present invention .
FIG. 2 is a graph showing a carbon dioxide temperature desorption experiment (CO ₂ ) of the CeO ₂ (X) -MgO (1-X) (X = 0, 0.25, 0.5, 0.75 and 1.0) composite metal oxide produced by Production Example 2 according to the present invention -TPD).
FIG. 3 is a graph showing the results of experiments for preparing dimethyl carbonate from methanol and ethylene carbonate using MO-MgO (MO = Y ₂ O ₃ , CeO ₂ , ZrO ₂ and ZnO) catalysts prepared in Production Example 1 according to the present invention .
4 is a _{CeO 2 (X) -MgO (1} -X) having a different mole ratio prepared by the Preparation Example 2 in accordance with the present invention (X = 0, 0.25, 0.5, 0.75, and 1.0) composite metal oxide was used as a catalyst for the production of dimethyl carbonate from methanol and ethylene carbonate.
FIG. 5 is a graph showing the results of measurement of CeO ₂ (X) -MgO (1-X) having various molar ratios prepared according to Production Example 2 of the present invention. (X = 0, 0.25, 0.5, 0.75 and 1.0) composite metal oxide and the reaction activity.
6 is _{M / CeO 2 (0.25) -MgO} (0.75) a variety of alkali and alkaline earth metal oxides prepared by the preparation 3 of the present invention, the supported _{(M = Li 2 O, K} 2 O, Cs 2 O, BaO And SrO) catalysts were used to perform dimethyl carbonate production reaction experiments from methanol and ethylene carbonate.
FIG. 7 is a graph showing the results of a comparison between Li ₂ O (X) / CeO ₂ (0.25) -MgO (0.75) (X = 0, 3, 5, 7 and 9 Wt.%) Catalyst prepared in the same manner as in Example 1, except that the reaction was carried out in the presence of methanol and ethylene carbonate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the drawings attached hereto.

The composite metal oxide supporting catalyst of the present invention is a catalyst used for producing dimethyl carbonate from methanol and ethylene carbonate. The cerium oxide (CeO ₂ ) precursor and the magnesium oxide precursor are mixed in the molar ratio of 0.01 to 100, An oxide of one or more alkali or alkaline earth metals selected from the group consisting of lithium, potassium, cesium, barium and strontium is added to the composite metal oxide prepared by the coprecipitation method in an amount of 1 to 20 wt% based on the total weight of the catalyst .

The composite metal oxide supporting catalyst of the present invention is produced by simultaneously oxidizing and precipitating the respective precursors of magnesium oxide and cerium oxide, which is another metal oxide, by a coprecipitation method to produce a complex type composite metal oxide having an alkali or alkaline earth metal Oxide. In the case of the composite metal oxide, it is preferably a composite of magnesium oxide and cerium oxide. As shown in the examples, when a metal oxide other than cerium oxide (Y ₂ O ₃ , ZrO _2, and ZnO) was formed with magnesium oxide, the catalytic activity was lower than that when magnesium oxide alone was used. In the case of using cerium oxide It shows that the catalyst exhibits better catalytic activity than magnesium oxide. Also, in the composite metal oxide supported catalyst of the present invention, the magnesium oxide and cerium oxide are controlled in a molar ratio ranging from 0.01 to 100, whereby the basicity of the catalyst is controlled and a composite metal oxide catalyst having a composition most suitable for the production of dimethyl carbonate Can be selected. In the composite metal oxide supported catalyst of the present invention, the molar ratio of the magnesium oxide to the cerium oxide is preferably in the range of 0.01 to 100, and more preferably the molar ratio is in the range of 0.1 to 10. When the molar ratio of magnesium oxide to cerium oxide is less than 0.01, there is a problem that crystal formation of magnesium oxide is inhibited in the catalyst preparation process and the production of the composite metal oxide is difficult. On the other hand, when the molar ratio of magnesium oxide and cerium oxide exceeds 100 Since the amount of the precursor for synthesis of cerium oxide is very small, a catalyst having the same shape as the magnesium oxide single metal oxide is produced.

In the composite metal oxide supported catalyst of the present invention, the alkali or alkaline earth metal supported on the composite metal oxide may be lithium oxide (Li ₂ O), potassium oxide (K ₂ O), cesium oxide (Cs ₂ O), barium oxide (BaO) and strontium oxide (SrO), and the supported amount is preferably in the range of 1 to 20% by weight based on the weight of the total catalyst. When the amount is less than 1% by weight, the supported amount is insufficient to improve the catalytic activity. On the other hand, when the supported amount is more than 20% by weight, the supported alkali and alkaline earth metal oxides do not adequately bond with the composite metal oxide It is difficult for the metal to act as an active point since it forms a large mass between the metals. The thus-prepared supported catalyst can produce dimethyl carbonate in a simple and high yield compared to the catalyst which was conventionally used in the reaction of methanol and ethylene carbonate to produce dimethyl carbonate.

The composite metal supported catalyst according to the present invention specifically comprises: i) adding an acid to a cerium oxide precursor and a magnesium oxide precursor solution to form a precipitate; Ii) aging the precipitate for crystal growth for 5 to 24 hours; Iii) filtering, washing and drying the precipitate, and calcining the precipitate at a temperature of 300 to 800 ° C. for 3 to 12 hours to produce a composite metal oxide; Iv) impregnating the composite metal oxide with an alkali or alkaline earth metal precursor solution in which one or more alkali or alkaline earth metal precursors selected from the group consisting of lithium, potassium, cesium, barium and strontium are dissolved in distilled water; And v) drying the composite metal oxide catalyst carrying the alkali or alkaline earth metal at 70 to 120 ° C and then calcining at a temperature of 300 to 700 ° C for 3 to 12 hours.

In the present invention, the metal precursor and the alkali metal or alkaline earth metal precursor for preparing the composite metal oxide are preferably at least one selected from the group consisting of nitrate, chloride, bromide, acetate, and acetylacetonate .

In addition, the acid used as the precipitant of the present invention is preferably oxalic acid, and the concentration is preferably 50 to 100% based on the aqueous solution. The aging time for crystal growth is preferably 5 to 24 hours.

Also, the present invention provides a process for preparing a catalyst for the production of dimethyl carbonate, characterized in that the precipitate is filtered, dried at a temperature of 70 to 120 ° C and then calcined at a temperature of 300 to 800 ° C for 3 to 12 hours.

Further, the catalyst for preparing dimethyl carbonate, which is characterized in that the composite metal oxide catalyst carrying the alkali and alkyllithium oxide of the present invention is dried at 70 to 120 ° C and then calcined at a temperature of 300 to 700 ° C for 3 to 12 hours ≪ / RTI >

Dimethyl carbonate is produced by reacting methanol and ethylene carbonate using the composite metal oxide supported catalyst of the present invention. The reaction is carried out in the presence of a composite metal oxide and a composite metal oxide catalyst supported with an alkali and alkaline earth metal using a batch reactor at a temperature in the range of 80 to 150 캜, a pressure of 3 to 25 bar, a pressure of 300 to 1000 rpm A stirring speed and a reaction time of 1 to 24 hours.

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

Preparation Example 1: Preparation of metal oxide-magnesium oxide (MO-MgO (MO = Y ₂ O ₃ , CeO ₂ , ZrO ₂  And ZnO)) composite metal oxide catalysts

A metal oxide-magnesium oxide composite metal oxide catalyst containing two or more metal oxides based on magnesium oxide was prepared by coprecipitation. The preparation method is as follows. Precursor is cerium nitrate hydrate _{(Ce (NO 3) 3 ·} 6H 2 O), zinc nitrate hydrate _{(Zn (NO 3) 2 ·} 6H 2 O), yttrium nitrate hydrate _{(Y (NO 3) 3 ·} 6H ₂ O), zirconium nitrate hydrate (ZrO (NO ₃ ) ₂ .XH ₂ O), and magnesium nitrate hydrate (Mg (NO ₃ ) ₃ .6H ₂ O) were used. The catalyst is prepared by quantitatively determining the metal precursor to be bound to Mg (NO ₃ ) ₃ .6H ₂ O in a molar ratio of 1: 1, and then dissolving the metal precursor in a predetermined amount of ethanol in a single beaker. When the precursor is completely dissolved, the oxalic acid solution (99%) prepared in advance is injected at a rate of 100 ml / h. Oxalic acid aqueous solution is injected, and the mixture is further stirred at room temperature for about 2 hours. After 12 hours of aging for further crystal growth, the resulting precipitate is first washed with distilled water under reduced pressure to remove any remaining impurities and to form a metal oxide upon drying, and then washed again with ethanol to prevent shrinkage. The washed precipitate is dried in an oven at 80 DEG C for 24 hours. The product after drying is made into a powder form, heated to 5 ° C per minute up to 550 ° C in an air atmosphere, and then baked for 3 hours. The prepared catalysts were named MO-MgO (MO = Y ₂ O ₃ , CeO ₂ , ZrO ₂ and ZnO), where MO (Metal Oxide) was designated as a second metal oxide binding to MgO.

Preparation Example 2: Cerium oxide-magnesium oxide (CeO ₂ (X) -MgO (1-X) (X = 0, 0.25, 0.5, 0.75 and 1.0)

A process for producing a cerium oxide-magnesium oxide (CeO ₂ -MgO) composite metal oxide catalyst having a different molar ratio of cerium oxide to magnesium oxide is as follows. The precursor was cerium nitrate hydrate (Ce (NO ₃ ) ₃ .6H ₂ O) and magnesium nitrate hydrate (Mg (NO ₃ ) ₂ .6H ₂ O). The metal precursor was quantified so that the molar ratios of CeO ₂ and MgO were 1.0: 0, 0.75: 0.25, 0.5: 0.5, 0.25: 0.75 and 0: 1.0, respectively, and then dissolved in a predetermined amount of ethanol in a single beaker. When the precursor is completely dissolved, the oxalic acid solution (99%) prepared in advance is injected at a rate of 100 ml / h. Oxalic acid aqueous solution is injected, and the mixture is further stirred at room temperature for about 2 hours. After 12 hours of aging for further crystal growth, the resulting precipitate is first washed with distilled water under reduced pressure to remove any remaining impurities and to form a metal oxide upon drying, and then washed again with ethanol to prevent shrinkage. The washed precipitate is dried in an oven at 80 DEG C for 24 hours. The product after drying is made into a powder form, heated to 5 ° C per minute up to 550 ° C in an air atmosphere, and then baked for 3 hours. The prepared catalyst was named CeO ₂ (X) -MgO (1-X) catalyst, where X represents the mole fraction of CeO _{2 in} the two components.

Analytical Example 1: Preparation of CeO 2 ₂ (X) -MgO (1-X) (X = 0, 0.25, 0.5, 0.75 and 1.0)

Table 1 shows the composition of the CeO ₂ (X) -MgO (1-X) (X = 0, 0.25, 0.5, 0.75 and 1.0) composite metal oxide catalyst prepared in Production Example 2 and the specific surface area The results of ICP-AES analysis and BET analysis are shown in Fig. From the results of ICP-AES analysis, it was found that the theoretical composition and the actual analytical result of the prepared catalyst were almost the same, and it was found that the catalyst was successfully produced with the desired composition. BET experiments were conducted to determine the specific surface area of the prepared catalyst. The CeO ₂ (X) -MgO (1-X) catalyst showed a larger specific surface area than that of pure CeO ₂ , but showed a smaller specific surface area than the pure MgO catalyst. However, no significant correlation was found between the amount of dimethyl carbonate and the specific surface area.

catalyst CeO ₂ : MgO mole ratio Specific surface area
(m ² / g) Theoretical value Actual value CeO ₂ 1: 0 1: 0 20.6 _{CeO 2 (0.75) -MgO (0.25} ) 0.75: 0.25 0.76: 0.24 33.0 _{CeO 2 (0.5) -MgO (0.5} ) 0.5: 0.5 0.51: 0.49 38.2 _{CeO 2 (0.25) -MgO (0.75} ) 0.25: 0.75 0.26: 0.74 54.2 MgO 0: 1 0: 1 54.3

1 shows X-ray diffraction analysis results of CeO ₂ (X) -MgO (1-X) (X = 0, 0.25, 0.5, 0.75 and 1.0) composite metal oxide catalysts prepared according to Production Example 2 of the present invention . K- _a radiation operating at 50 kV and 100 mA using an X-ray diffractometer (Rigaku, D-MAX2500-PC). As a result of X-ray diffraction analysis, crystal phases of CeO ₂ and MgO were observed irrespective of each composition, and no peak shift or formation of a new crystal phase was observed. As a result, it was confirmed that CeO ₂ and MgO were mixed with each other to form a catalyst in which phases of CeO ₂ and MgO were uniformly dispersed without forming a new solid solution, and each phase was uniformly dispersed. In particular, the CeO ₂ (0.5) -MgO (0.5) catalyst, which was prepared at a molar ratio of CeO ₂ to MgO of 1: 1, showed that the characteristic peak of CeO ₂ had a much higher peak intensity than the characteristic peak of MgO have. This is because the crystal growth rate of CeO ₂ is much faster than the crystallization rate of MgO in a solution containing CeO ₂ and MgO. Therefore, it can be concluded that MgO was formed in amorphous form or very small crystal size.

2 is a graph showing the results of a carbon dioxide elevation desorption experiment to determine the base characteristics of CeO ₂ (X) -MgO (1-X) (X = 0, 0.25, 0.5, 0.75 and 1.0) (CO ₂ -TPD) results. _{CeO 2 (X) -MgO (1} -X) was in the form of CO ₂ -TPD desorption curve differs depending on the molar ratio of the catalyst, pure CeO ₂ catalyst with _{CeO 2 (0.75) -MgO (0.25} ) the catalyst is well-desorption curve But not developed. Table 2 shows the basicity of the catalyst calculated from the peak area in FIG. Similar to the results of the CO ₂ -TPD desorption curve, the calculated amounts of base were larger than those of pure CeO ₂ and MgO catalysts for CeO ₂ (0.5) -MgO (0.5) and CeO ₂ (0.25) -MgO (0.75) It can be seen that it has an amount.

catalyst Basicity
(μmol-CO ₂ / g-catalyst) CeO ₂ 14.2 _{CeO 2 (0.75) -MgO (0.25} ) 15.1 _{CeO 2 (0.5) -MgO (0.5} ) 33.5 _{CeO 2 (0.25) -MgO (0.75} ) 42.5 MgO 27.9

Preparation Example 3 Preparation of Cerium Oxide-Magnesium Oxide Supported with Alkali or Alkaline Earth Metal Oxide (M / CeO ₂ (0.25) -MgO (0.75) (M = Li ₂ O, K ₂ O, Cs ₂ O, BaO and SrO) catalysts

Preparation Example 2 with a molar ratio of cerium oxide and magnesium oxide, 1 prepared by: 3 or _{CeO 2 (0.25) -MgO (0.75} ) different alkali or alkaline earth metal oxide to the composite metal oxide as a support _{(Li 2 O, K 2 O} , Cs ₂ O, BaO, and SrO) is carried as follows.

As the alkali or alkaline earth metal oxide precursors include lithium nitrate (LiNO _3), potassium nitrate (KNO _3), strontium nitrate _{(Sr (NO 3) 2)} , cesium nitrate (CsNO _3), and barium nitrate ( Ba (NO ₃ ) ₂ ) was used. The preparation of the catalyst is carried out by dissolving the supported alkali or alkaline earth metal oxide in the distilled water in an amount corresponding to 3 wt% (wt%) so that the supported CeO ₂ (0.25) -MgO (0.75) composite metal oxide is supported on the carrier . When the precursor was completely dissolved, a predetermined amount of CeO ₂ (0.25) -MgO (0.75) composite metal oxide prepared in advance was placed in the beaker and impregnated by a simple impregnation method. Thereafter, after drying at 100 ° C for 12 hours, the temperature is raised to 5 ° C per minute to 500 ° C, and the mixture is maintained for 3 hours. The catalyst thus prepared was named M / CeO ₂ (0.25) -MgO (0.75), where M is an alkali or alkaline earth metal oxide (Li ₂ O) supported on a CeO ₂ (0.25) -MgO (0.75) K ₂ O, Cs ₂ O, BaO and SrO).

PREPARATION EXAMPLE 4 Preparation of Lithium Oxide-loaded Cerium Oxide-Magnesium Oxide (Li ₂ O (X) / CeO ₂ (0.25) -MgO (0.75) (X = 0, 3, 5, 7 and 9 wt%

A method for preparing a catalyst in which various oxides of lithium oxide are supported on the cerium oxide-magnesium oxide catalyst prepared in Preparation Example 2 is as follows.

Lithium nitrate (LiNO ₃ ), a lithium precursor, is mixed with lithium oxide (Li ₂ O): cerium oxide-magnesium oxide (CeO ₂ (0.25) -MgO (0.75)) composite metal oxide carrier at weight ratios of 0, 7 and 9% by weight, and dissolved in distilled water. When the precursor was completely dissolved, a CeO ₂ (0.25) -MgO (0.75) composite metal oxide carrier prepared in advance was impregnated into the precursor solution. Thereafter, after drying at 100 ° C for 12 hours, the temperature is raised to 5 ° C per minute to 500 ° C, and the mixture is maintained for 3 hours. The catalyst thus prepared was named Li ₂ O (X) / CeO ₂ (0.25) -MgO (0.75) where X is lithium oxide (Li ₂ O) supported on a CeO ₂ (0.25) O).

Example 1: Preparation of MO-MgO (MO = Y ₂ O ₃ , CeO ₂ , ZrO ₂  And ZnO) catalyst

Dimethyl carbonate production reaction was carried out from methanol and ethylene carbonate using various composite metal oxides prepared in Preparation Example 1.

The reactor was a batch reactor, and the reaction was carried out at 110 ° C and 10 bar for 3 hours with stirring at 400 rpm. The catalyst in the reaction vessel was charged with 1 g of the composite metal oxide catalyst prepared in Preparation Example 1, and methanol was added in an excess amount of methanol and ethylene carbonate at a molar ratio of 6: 1 as a reactant. In order to detect the product by internal standard method using gas chromatography, 1 ml of ethylbenzene as an internal standard was injected. The reaction pressure was controlled by carbon dioxide gas, and the gas inside the reactor was purged several times through the carbon dioxide before the reaction. After the reaction, the product was filtered and the catalyst was removed and analyzed by gas chromatography equipment (HP 5890 II, FID). The conversion of the reaction product and the yield of dimethyl carbonate after the reaction were calculated by the following formula.

[Equation 1]

&Quot; (2) "

FIG. 3 is a graph showing the results of experiments for the production of dimethyl carbonate from methanol and ethylene carbonate using MO-MgO (MO = Y ₂ O ₃ , CeO ₂ , ZrO ₂ and ZnO) catalysts prepared in Production Example 1 of the present invention The results are shown. For comparison, a single metal oxide, magnesium oxide (MgO), was also prepared and a reaction experiment was conducted. The results are shown in FIG. In the case of ZnO-MgO, ZrO ₂ -MgO and Y ₂ O ₃ -MgO composite metal oxides, the catalyst performance was not improved as compared with MgO, which is a single metal oxide, whereas the yield of dimethyl carbonate was 9.87% for CeO ₂ -MgO catalyst And showed excellent activity compared to the reaction experiment using MgO.

Example 2: Preparation of CeO ₂ (X) -MgO (1-X) (X = 0, 0.25, 0.5, 0.75 and 1.0)

CeO ₂ (X) -MgO (1-X) having various molar ratios prepared according to Preparation Example 2, (X = 0, 0.25, 0.5, 0.75 and 1.0) composite metal oxide catalyst was used to carry out a dimethyl carbonate production reaction from methanol and ethylene carbonate. The experimental method and reaction conditions were the same as in Example 1, and the reaction results are shown in FIG.

The CeO ₂ (0.25) -MgO (0.75) catalyst among the prepared composite metal oxide catalysts exhibited the most excellent activity with a yield of dimethyl carbonate of 10.15%, indicating that the molar ratio of cerium oxide and magnesium oxide prepared in Example 1 was 1: 1 CeO ₂ (0.5) showed -MgO excellent reaction activity than the (0.5) catalyst. From the above results, it was possible to select the most suitable cerium oxide and magnesium oxide molar ratio in CeO ₂ (X) -MgO (1-X) catalysts with various molar ratios.

FIG. 5 shows the relationship between the catalytic base characteristics obtained through CO ₂ -TPD and the reaction activity in order to examine the effect of the base characteristics of the catalyst on the reaction activity. As can be seen from the figure, the reaction activity tends to increase with the increase of the basicity of the catalyst. In the mechanism of the production of dimethyl carbonate from ethylene carbonate and methanol, the methanol forms methoxide ions by the Lewis base point of the catalyst, and then dimethyl carbonate and ethylene glycol are produced by the chain reaction. Thus, as the amount of base in the catalyst is increased, more methoxide ions are formed, thereby improving the yield of dimethyl carbonate. Therefore, it can be seen that the base properties of the catalyst have a very important effect on the reaction activity. The prepared CeO ₂ (X) -MgO (1-X) (X = 0, 0.25, 0.5 , 0.75 and 1.0), complex metal oxide catalysts of the base amount is the largest _{CeO 2 (0.25) -MgO (0.75} ) the catalyst was found to exhibit the most excellent catalytic activity.

Example 3: M / CeO ₂ (0.25) -MgO (0.75) (M = Li ₂ O, K ₂ O, Cs ₂ O, BaO and SrO) catalysts

The various alkali and alkaline earth metal oxide prepared by the Preparation Example 3 carrying the _{M / CeO 2 (0.25) -MgO} (0.75) (M = Li 2 O, K 2 O, Cs 2 O, BaO , and SrO) catalyst Dimethylcarbonate production reaction was carried out from methanol and ethylene carbonate. The experimental method and reaction conditions were the same as in Example 1, and the reaction results are shown in FIG.

Among the prepared catalysts, Li ₂ O / CeO ₂ (0.25) -MgO (0.75) and K ₂ O / CeO ₂ (0.25) -MgO (0.75) catalysts exhibited superior activity compared to CeO ₂ (0.25) -MgO It looked. In particular, the Li ₂ O / CeO ₂ (0.25) -MgO (0.75) catalyst showed the most excellent reaction activity with a yield of dimethyl carbonate of 10.68%. Based on the above results, lithium oxide (Li ₂ O) was selected as an alkali and alkaline earth metal to be supported on CeO ₂ (0.25) -MgO (0.75) composite metal oxide.

Example 4: Preparation of Li ₂ O (X) / CeO ₂ (0.25) -MgO (0.75) (X = 0, 3, 5, 7 and 9 wt%

(X = 0, 3, 5, 7 and 9% by weight) catalysts prepared by the preparation example 4 and having various contents of lithium oxide supported thereon Li ₂ O (X) / CeO ₂ (0.25) Dimethylcarbonate production reaction was carried out from methanol and ethylene carbonate. The experimental method and reaction conditions were the same as in Example 1, and the results of the reaction are shown in FIG.

As the content of lithium oxide increases to 7 wt% in the prepared catalyst, the reaction activity tends to gradually increase. On the other hand, when 9 wt% of lithium oxide is supported, the reaction activity decreases. When an adequate amount of lithium oxide is introduced, lithium oxide acts as an active site to improve the reaction activity of the catalyst. However, when excess lithium oxide is introduced, it is no longer active due to sintering between the lithium metal oxides But rather is located at the active site of the carrier and inhibits its activity. Therefore, Li ₂ O (7) / CeO ₂ (0.25) -MgO (0.75) catalyst with the optimum amount of lithium oxide supported catalyst showed the best reaction activity.

The embodiments of the present invention described above should not be construed as limiting the technical idea of the present invention. The scope of protection of the present invention is limited only by the matters described in the claims, and those skilled in the art will be able to modify the technical idea of the present invention in various forms. Accordingly, such improvements and modifications will fall within the scope of the present invention as long as they are obvious to those skilled in the art.

Claims (5)

delete delete I) adding oxalic acid to a cerium oxide precursor and a magnesium oxide precursor solution to form a precipitate;
Ii) aging the precipitate for crystal growth for 5 to 24 hours;
Iii) filtering, washing and drying the precipitate, and calcining the precipitate at a temperature of 300 to 800 ° C. for 3 to 12 hours to produce a composite metal oxide;
Iv) impregnating the composite metal oxide with an alkali or alkaline earth metal precursor solution in which one or more alkali or alkaline earth metal precursors selected from the group consisting of lithium, potassium, cesium, barium and strontium are dissolved in distilled water;
And (v) drying the composite metal oxide catalyst having an alkali or alkaline earth metal supported thereon at 70 to 120 ° C. and then calcining the catalyst at a temperature of 300 to 700 ° C. for 3 to 12 hours. The method of claim 3,
Wherein the metal oxide precursor or the alkaline or alkaline earth metal oxide precursor is at least one selected from the group consisting of nitrate, chloride, bromide, acetate, and acetylacetonate. delete

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