KR100810739B1 - Catalyst for methanol and dimethyl ether synthesis from syngas and preparation method thereof - Google Patents

Abstract

The present invention relates to a catalyst for synthesizing methanol and dimethyl ether from a synthesis gas and a method for preparing the same, and more particularly, to a porous catalyst of a Cu-Zn-Al-based oxide containing CuO, ZnO and Al ₂ O ₃ in a fixed ratio, The catalyst has a dual pore structure having a specific specific surface area and relatively different pore sizes, and also eliminates the use of other types of binder components in additional catalyst pretreatment and catalyst forming to improve stability of the conventional catalyst. A catalyst capable of simultaneously producing methanol and dimethyl ether from syngas (CO / CO ₂ / H ₂ ) in which carbon dioxide is present in excess, and suppressing the production of by-product carbon dioxide, and having excellent methanol and dimethyl ether selectivity and a method of preparing the same It is about.

Cu-Zn-Al oxide, methanol, dimethyl ether, double pore, catalyst

Description

Catalyst for preparing methanol and dimethyl ether simultaneously from synthesis gas and preparation method thereof {Catalyst for methanol and dimethyl ether synthesis from syngas and preparation method

1 is a carbon monoxide synthesis and dehydration reaction was carried out under the catalyst having a double pore porous structure prepared in Examples 1 to 7 and the simple mixed single pore structure prepared in Comparative Examples 1 to 6 according to the present invention. The conversion and selectivity of carbon dioxide in the product are shown.

FIG. 2 shows individual pore distribution diagrams of catalysts in which activity experiments were performed by simply mixing the catalysts for methanol synthesis and dehydration reactions prepared in Comparative Example 3. FIG.

Figure 3 shows the BET surface area and pore distribution of the catalyst having a double pore structure of Examples 1 and 5 and the catalyst of Comparative Example 1 according to the present invention.

The present invention relates to a catalyst for synthesizing methanol and dimethyl ether from a synthesis gas and a method for preparing the same, and more particularly, to a porous catalyst of a Cu-Zn-Al-based oxide containing CuO, ZnO and Al ₂ O ₃ in a fixed ratio, The catalyst has a dual pore structure having a specific specific surface area and relatively different pore sizes, and also eliminates the use of other types of binder components in additional catalyst pretreatment and catalyst forming to improve stability of the conventional catalyst. A catalyst capable of simultaneously producing methanol and dimethyl ether from syngas (CO / CO ₂ / H ₂ ) in which carbon dioxide is present in excess, and suppressing the production of by-product carbon dioxide, and having excellent methanol and dimethyl ether selectivity and a method of preparing the same It is about.

Under the current situation in which alternative fuels are being actively developed due to the high oil prices due to the continuous rise in oil prices, the importance of dimethyl ether is gradually increasing, and the development of technology for economic production is being conducted in various fields. It is true.

In particular, dimethyl ether has very similar chemical and physical properties to LPG, and thus has been in the spotlight as an alternative fuel. It can also be used as a fuel for synthetic gasoline production technology and diesel engines, and its demand is expected to increase continuously in the future. .

The industrial process for preparing commercialized dimethyl ether is a one-step process for synthesizing methanol from syngas over heterogeneous solid catalysts based on Cu and Zn in fixed bed and slurry reactors, and dehydration of methanol using solid acid catalysts. It consists of a two-step process for producing dimethyl ether. The two-stage process has increased initial investment costs and the competitiveness in production cost has decreased due to the complicated process configuration. Currently, the technology development for the one-stage process for simultaneously producing methanol and dimethyl ether using a hybrid catalyst is active. Is going on.

In addition, the advantage of the one-stage reaction process is that the methanol synthesis process is thermodynamically equilibrium reaction, so that the reaction must proceed at high temperature and high pressure in order to improve the conversion rate of the synthesis gas. The conversion reaction of dimethyl ether to the equilibrium reaction can be overcome and at the same time a high synthesis gas conversion can be obtained, so the necessity and competitiveness of technology development for the one-stage process are increasing. The reaction consists of three parts.

(1) Methanol synthesis reaction: CO + 2H ₂ = CH ₃ OH

(2) Dehydration reaction: 2CH ₃ OH = CH ₃ OCH ₃ + H ₂ O

(3) Water gas shift reaction: CO + H ₂ O = H ₂ + CO ₂

Methanol synthesis reaction (1) is an equilibrium reaction is advantageous in low temperature and high pressure reaction, but the initial investment costs increase because the reaction must proceed at high temperature (> ~ 200 ℃) and high pressure in order to increase the reaction rate. However, in the case of using a hybrid catalyst, while the dehydration reaction in which the generated methanol is converted to dimethyl ether proceeds, hydrogen is further generated by the water gas reaction in the generated water, thereby increasing the conversion rate of the synthesis gas. There is a problem that must be overcome the problem of minimizing the emission of greenhouse gases such as CO ₂ generated with this.

In order to produce dimethyl ether, which has been spotlighted as a diesel fuel substitute at low cost, manufacturing cost reduction is an important success factor due to the increase in yield due to the development of an efficient hybrid catalyst, and in particular, the production of by-products containing CO ₂ on the hybrid catalyst is suppressed to the maximum. There is a need for an approach that reduces the cost of separation and minimizes the loss of reactants.

In the case of using a hybrid catalyst, many cases have been reported in which the methanol synthesis catalyst is physically mixed with the dehydration catalyst or the methanol synthesis catalyst is impregnated on the surface of the dehydration catalyst. Patent 7,033,972 B2; US Patent No. 5,753,716; Japanese Patent Laid-Open No. 9-309852; Korean Patent No. 10-0573055; Korean Patent Laid-Open No. 10-2005-0094267]. Some of these have prepared methanol synthesis catalysts of commonly used Cu-Zn-Al or Cu-Zn-Cr composition, which are prepared physically or by impregnation with alumina [US Patent No. 7,033,972 B2; Japanese Patent Application Laid-Open No. 9-309852 discloses a method for effectively preparing dimethyl ether from syngas. In addition, a method of using a variety of zeolite-based solid acid catalyst to improve the conversion of methanol dehydration reaction [Korea Patent No. 10-0573055; Korean Patent Application Publication No. 2005-0094267] and a method of using aluminum phosphate for methanol dehydration reaction (US Patent No. 5,753,716) and the like have been reported in various ways.

In general, the methanol dehydration catalyst is reported to have a disadvantage in that the production of by-products is suppressed in the solid acid catalyst having a weak acid point such as alumina, but the yield of dimethyl ether is reduced due to the small distribution of the entire active point.

Accordingly, many attempts have been made to use a solid acid catalyst in which an excessive acidic point such as zeolite is present in order to increase the yield to dimethyl ether. However, in the zeolite solid acid catalyst, (1) carbon dioxide by oxidation of carbon monoxide Increasing the conversion rate of methanol caused a decrease in methanol yield, and (2) the increase of the conversion rate from the strong acid to hydrocarbon and the aqueous reaction of carbon dioxide predominantly resulted in a decrease in yield and byproduct formation [Applied catalysis A, 149 (1997) 289; Catalysis Today, 101 (2005) 39] has the disadvantage of increasing the separation cost in the overall process.

Therefore, in order to solve this process problem and improve the stability of the catalyst, efforts to control the amount of strong acid point by pre-treating the zeolite solid acid catalyst with various metals have been attempted at present.

In order to present a method for solving the problems of the prior art economically and efficiently, the present inventors have a double pore that is more reactive than a zeolite catalyst having a strong acid point as an oxide-based porous catalyst in which copper, zinc and alumina are mixed at a constant ratio. Focused on the development of porous catalysts. As a result, a Cu-Zn-Al-based oxide catalyst containing CuO, ZnO and Al ₂ O ₃ forms a double pore in which both small and large pores having a specific specific surface area and relatively different pore sizes exist simultaneously. It was found to be economical and excellent in activity by omitting the pretreatment of the catalyst for the adjustment of the strong acid point. In addition, the catalyst not only improves the conversion rate of the methanol to dimethyl ether while suppressing the formation of by-products such as carbon dioxide when the methanol dehydration reaction is performed, and the alumina component is a commercially available material because the same composition can be used as the binder at the same time as the catalyst. The present invention has been accomplished by knowing that it does not reduce the activity of the catalyst in the shaping of the catalyst.

Therefore, the present invention is composed of Cu-Zn-Al-based oxide, and the specific specific surface area and small pores and large pores are present at the same time for the simultaneous production of methanol and dimethyl ether which can minimize the by-product generation with high conversion of the synthesis gas It is an object of the present invention to provide a porous catalyst of a double pore and a method for producing the same.

The present invention is a porous catalyst of the contained Cu-Zn-Al oxide containing 30 to 45% by weight of CuO, 25 to 35% by weight of ZnO and 20 to 45% by weight of Al ₂ O ₃ , the catalyst having a relatively pore size Double pores are formed in which small pores (PS ₁ ) and large pores (PS ₂ ) are present at the same time. The pore sizes of the small pores (PS ₁ ) and large pores (PS ₂ ) range from methanol and dimethyl ether as shown below. Its characteristics are the catalysts for simultaneous production.

2 ≤ PS ₁ ≤ 20 nm

20 <PS ₂ ≤ 100 nm

Hereinafter, the present invention will be described in detail.

The present invention is a catalyst capable of simultaneously producing methanol and dimethyl ether from syngas (CO / CO ₂ / H ₂ ) in which carbon dioxide is present in excess, and specifically Cu-Zn-Al consisting of CuO, ZnO and Al ₂ O ₃ A catalyst comprising a double oxide having a small oxide and a large pore at the same time having a specific specific surface area and size, wherein the catalyst is a pretreatment process for controlling a strong acid point of a solid acid catalyst such as alumina. The present invention relates to a porous catalyst which can be omitted and simultaneously produces methanol and dimethyl ether from syngas with excellent yield while suppressing the formation of by-products such as carbon dioxide.

In particular, in the case of preparing dimethyl ether using syngas, it is effective when the amount of carbon dioxide in the syngas is present at an appropriate ratio, and it is reported that the reactivity of the catalyst decreases as the amount of carbon dioxide increases. The catalyst forms a double pore, which is excellent in mass transfer and heat transfer due to the characteristics of the structure, and by-product generation into carbon dioxide is suppressed by the water gas conversion reaction in the fine pores, thereby minimizing the reduction of catalytic reaction activity due to the excessive generation of carbon dioxide. Not only can it be suppressed, there is an advantage that can be used even when using a synthesis gas containing excess carbon dioxide. Furthermore, alumina, a component of the catalyst, contains alumina of high specific surface area, which is a catalyst component. Since alumina has the same composition as a material that can be used as a binder at the same time as the catalyst, it is used separately to improve the catalyst strength of the prior art. The use of an excess of binder of inert material is ruled out and the degradation of catalytic activity due to its use is improved.

The catalyst used in the present invention is a Cu-Zn-Al-based oxide porous catalyst consisting of CuO, ZnO and Al ₂ O ₃ , the total specific surface area of the prepared catalyst is 70 ~ 180 m 2 / g, relatively different in size Heterogeneous pores, specifically 2 ≤ small pores (PS ₁ ) It is a catalyst having double pores in which ≦ 20 nm and 20 <large pores (PS ₂ ) ≦ 100 nm exist simultaneously. In general, using a catalyst composed of copper, zinc and alumina, a methanol synthesis catalyst and a solid acid catalyst such as alumina are known as methanol dehydration catalysts, ie catalysts for the production of dimethyl ether. However, the catalyst of the present invention has a dual pore structure, and has a new concept of a method of improving the yield to methanol and dimethyl ether by applying the catalyst as a catalyst having specific properties such as specific surface area and pore distribution. It is a catalyst.

The heterogeneous pore structure generally means that a catalyst prepared by calcining a metal such as copper, zinc, and alumina has a single pore distribution as a compound, but the catalyst of the present invention forms two main pores different from each other. it means. In other words, the catalyst of the present invention is a relatively large pores in the dehydration catalyst (boehmite or alumina) using the catalyst particles for the synthesis of micron size methanol synthesized by coprecipitation using copper, zinc and alumina precursors. By supporting or dehydrating the catalyst surface for dehydration using micron-sized catalyst particles for synthesis of methanol with nano-sized pores, each catalyst is maintained in the intergranular structure on the mixed catalyst while maintaining nano-sized small pores. The resulting large pores are further formed, resulting in a structure having two different pore sizes. This has the advantage of superior heat transfer and mass transfer compared to a single pore size, suppressing the production of carbon dioxide by the water gas shift reaction and increasing the selectivity to methanol and dimethyl ether. If the small pore size is smaller than 2 nm, it may be disadvantageous in heat and mass transfer and may cause an increase in generation of by-products such as carbon dioxide. If the large pore size exceeds 100 nm, the pores are present in excess. In this case, the specific surface area of the catalyst may be reduced, and thus the conversion may be reduced, which is not effective. In the catalyst of the present invention, the small pores in the range of 2 to 20 nm have a porosity of 20 to 65%, and the large pores of the 20 to 100 nm range have a porosity of 35 to 80%.
At this time, the small pores in the range of 2 to 20 nm is the pore size expressed in the micropores of the alumina itself or the methanol catalyst itself composed of Cu-Zn-Al, and in the case of the large pores in the range of 20 to 100 nm The pore size expressed in particles between methanol synthesis catalysts (Cu-Zn-Al) contained or co-precipitated on the surface of alumina with high specific surface area. As shown in the pore distribution diagram of FIG. 3, the catalyst prepared according to the present invention exhibits a double pore structure in which relatively small pores and large pores exist. As shown in the above pore distribution diagram, 200 Å (20 nm), which represents the lowest point between two peaks, is divided by the boundary values of large and small pores.
In other words, the size of the pores of the present invention is to distinguish the size of the relatively small pores and large pores on the basis of the pore distribution pattern of the prepared catalyst, each of these pore porosity is also obtained based on this.
If the porosity of the large pores is less than 35%, the specific surface area is large, but it does not provide enough active sites for methanol synthesis, thereby reducing the reaction activity and increasing the production of CO ₂ by the water gas shift reaction on the surface of alumina. In the case of more than 80%, it is desirable to maintain the above porosity, since a decrease in the total specific surface area and a decrease in activity for the production of dimethyl ether due to the acid point reduction of the solid acid catalyst occur. .

In addition, according to the known technology, a method for producing alumina having a specific surface area of 300 m 2 / g or less is already known, and alumina used as a methanol dehydration solid acid catalyst has 150 m 2 having a commercially available single porous pore structure. It is common to have a specific surface area in the range of / g-200 m <2> / g. However, in the case of using the dual pore structure catalyst prepared by the method proposed in the present invention, since the catalytic reaction selectivity is better than that by using simple mixing with the existing alumina catalyst, methanol and dimethyl ether are simultaneously produced from syngas. It is suitable as a catalyst for doing so.

The catalyst prepared according to the present invention maintains a specific surface area in the range of 70 to 180 m 2 / g. When the specific surface area is less than 70 m 2 / g, the activity point of the dehydration reaction is small, so that the conversion rate to dimethyl ether is reduced and 180 m 2 / g. If it exceeds g, the conversion of carbon monoxide decreases due to a decrease in hydrothermal stability of alumina and a decrease in the active site for methanol synthesis.

On the other hand, a known method of preparing a hybrid catalyst, specifically a method of simply physically mixing two kinds of catalysts, does not provide a suitable method for inhibiting the stability of the catalyst and the conversion to carbon dioxide by a water gas reaction. . Therefore, the present invention proposes a method for maximizing selectivity to the final desired product using a novel catalyst having a double pore structure to improve the selectivity of methanol and dimethyl ether and to suppress the water gas reaction as much as possible. Give a way.

In addition, as a method for minimizing the by-products generated at the strong acid point of the general commercial solid acid catalyst, a method having excellent heat and mass transfer performance, specifically, a double pore catalyst to convert methanol to dimethyl ether on a solid acid catalyst A method was proposed to increase the selectivity while suppressing the water gas shift reaction.

In addition, it was possible to solve the reduction of the yield due to the conversion of carbon monoxide to carbon dioxide by the increase in water gas conversion reaction with the increase in by-product generation at the strong acid point, which is a problem that occurs when applying the conventional commercial alumina. This is because the high specific surface area alumina contained in the alumina component according to the present invention is uniformly dispersed in Cu-Zn-Al-based oxides prepared by mixing respective Cu, Zn and Al precursors, thereby increasing the conversion reaction of methanol and the appropriate acid point of alumina. By increasing the selectivity to dimethyl ether by the conversion of methanol in the following it was confirmed that the production of by-products was suppressed to increase the overall reaction yield.

If the above-mentioned methanol synthesis catalyst and methanol dehydration catalyst are simply mixed as in the conventionally known method, the by-products generated at the strong acid point along with the reduction in the yield of methanol and dimethyl ether by the water gas shift reaction Inactivation and rapid progress of the catalyst caused a phenomenon that the reaction efficiency is lowered. Therefore, when the catalyst of the present invention is prepared by appropriately treating the methanol synthesis catalyst and the dehydration reaction catalyst by an organic combination according to the method described below, the desired yield of the present invention can be ensured.

The catalyst is composed of Cu-Zn-Al-based oxides containing 30 to 45% by weight of CuO, 25 to 35% by weight of ZnO and 20 to 45% by weight of Al ₂ O ₃ . The amount of metal oxide present is measured. If the content of CuO is less than 30% by weight, a decrease in yield occurs due to the reduction of the active site for methanol synthesis. If the content of the CuO is more than 45% by weight, it is difficult to form an appropriate catalyst structure with other metals. Occurs. In addition, if the content of ZnO is less than 25% by weight, there is a problem in forming a suitable porous material with Cu and Al. If the content of ZnO is more than 35% by weight, the methanol synthesis reaction rate decreases due to the reduction of active ingredient CuO. do. When the Al ₂ O ₃ content is less than 20% by weight, the conversion reaction of the produced methanol to dimethyl ether decreases, and the yield decreases. When the Al ₂ O ₃ content exceeds 45% by weight, the methanol synthesis reaction rate is reduced by the reduction of the active ingredient for methanol synthesis. It is preferable to maintain the above range because a problem of deterioration occurs. The alumina contains high specific surface area alumina in the specific surface area of 300-800 m 2 / g. That is, the present invention produces a Cu-Zn-Al-based oxide catalyst by mixing alumina having a high specific surface area and Cu, Zn, and Al precursors, and thus high specific surface area alumina and other alumina are present at the same time. At this time, the Al precursor component is a structural promoter for forming the structure of the catalyst, and the high specific surface area alumina is dispersed in the catalyst to increase the conversion reaction of methanol and methanol to the conversion of methanol at the proper acid point of alumina. By increasing the selectivity of the by-products is suppressed to play a role in increasing the overall reaction yield.
When the specific surface area is less than 300 m 2 / g, the activity point of the dehydration reaction is small, so that the conversion to dimethyl ether decreases. When the specific surface area exceeds 800 m 2 / g, the hydrothermal stability of the alumina decreases during the synthesis of the hybrid catalyst, resulting in alumina structure. The collapse causes a problem that makes it difficult to produce a hybrid catalyst of a desired specific surface area.

The content of alumina having such a high surface area is in the range of 0.1 to 1.0 weight ratio based on 1 weight of the Cu-Zn-Al-based oxide based on the alumina content. When the content is less than 0.1 weight ratio, there is a disadvantage in that conversion to dimethyl ether is low. In addition, if it exceeds 1.0 weight ratio, it is preferable to maintain the above range because the conversion rate of the synthesis gas is decreased, so that the yield to dimethyl ether is reduced, and the amount of carbon dioxide produced by the aqueous reaction is increased.

When the catalyst is prepared by the method and composition of the present invention using commercial alumina having a specific surface area of 300 m 2 / g or less, which is a conventional methanol dehydration catalyst, a substantial portion of the pores of the alumina catalyst are clogged to reduce the dehydration reaction of methanol. As a result, there is a problem of decreasing yield, which is not effective.

The present invention is further characterized by a method for preparing a double pore structure catalyst for methanol and dimethyl ether production. The method includes a mixed metal of Cu, Zn, and Al in a slurry in which alumina having a high surface area is dispersed in a solution. It can be prepared by coprecipitation or by mixing the mixed metal of Cu, Zn and Al and high surface area alumina prepared by independently coprecipitation method in the slurry solution.

Both methods are generally used in the art, but there are differences in the preparation of the double-porous porous structure catalyst according to the components used and the reaction conditions thereof, thereby causing a difference in the reactivity of the catalyst.

First, a method of manufacturing by coprecipitation of Cu, Zn, Al metal in a slurry state in which boehmite or alumina of high surface area is dispersed in a solution is specifically as follows.

An aluminum alkoxide solution dissolved in an alcoholic organic solvent, an organic carboxylic acid having a pKa value of 3.5 to 5 and water are mixed, and then heated to 80 to 130 ° C. to prepare a boehmite sol, and the solvent is removed to prepare a powdery boehmite. do. At this time, the prepared boehmite powder may be converted to alumina by firing at a temperature of 400 to 700 ° C. The powdery boehmite and alumina preferably maintain a specific surface area in the range of 300 to 800 m 2 / g.

The alcohol-based organic solvent is preferably a lower alcohol having 1 to 4 carbon atoms in consideration of solubility in the aluminum alkoxide and ease of removal. In this case, aluminum alkoxide is generally used in the art, and is not particularly limited, but it is preferable to use an alkoxide having 1 to 4 carbon atoms.
The pKa value of the organic carboxylic acid is used as an important parameter for synthesizing boehmite and alumina having a high specific surface area by suppressing particle size increase due to particle agglomeration at the time of boehmite particle formation by initial nucleation. If the pKa value is less than 3, the initial nucleation rate increases and the boehmite particle generation increases, resulting in a decrease in crystallinity, which results in the formation of acid strength on the surface of alumina suitable for methanol dehydration. In the case of weak acid with a pKa value greater than 3.5, the initial nucleation rate decreases and the particle size is increased due to the cohesion of boehmite particles, resulting in a decrease in specific surface area. The problem of not being able to manufacture alumina of bar may occur, and if the above range is maintained, the high specific surface area of boehmite and alumina can be manufactured. Such organic carboxylic acids are carboxylic acids having 1 to 4 carbon atoms having a pKa value of 3.5 to 5, and specifically, may be selected from acetic acid, formic acid and propionic acid.

delete

The organic carboxylic acid is used in an amount of 0.01 to 1 mole per 1 mole of aluminum alkoxide solution. If the amount is less than 0.01 mole ratio, the amount is insignificant and less effective. It is preferable to maintain the above range because a problem that can form the aluminum carboxylate occurs.

The water is used to carry out the hydrolysis reaction, and the water is used in a ratio of 2 to 12 moles per mole of aluminum alkoxide solution. If the amount is less than 2 molar ratio, the hydrolysis reaction is difficult, and if it exceeds 12 molar ratio, it is preferable to maintain the above range because the problem of economical deterioration occurs in the separation process.

The boehmite sol is obtained through a heating process of 80 ~ 130 ℃, if the temperature is less than 80 ℃ slow the crystal growth reaction of boehmite, if the temperature exceeds 130 ℃ boehmite crystals by the rapid reaction will be large There may be a problem. In addition, when the calcination temperature is less than 400 ℃, the crystal growth of alumina is lowered, and if it exceeds 700 ℃ it is preferable to maintain the above range because there is a problem of a sharp decrease in the specific surface area due to the phase change of alumina.

Thereafter, in the suspension solution containing the boehmite in powder form, the Cu-Zn-Al-based precursor mixture containing the copper precursor, the zinc precursor, and the aluminum precursor was co-precipitated under an aqueous solution of pH 7-8, and then aged to filter the precipitate. Wash. In this case, the boehmite is used in the range of 0.1 to 1.0 weight ratio based on the alumina with respect to 1 weight of the Cu-Zn-Al-based precursor mixture based on the alumina.

In order to maintain pH 7 to 8 during the coprecipitation, a basic precipitant is used. Specifically, the basic precipitant may preferably use sodium carbonate, calcium carbonate, sodium bicarbonate and the like. This is carried out in the neutral range of pH 7 ~ 8 in order to effectively perform the acid-base reaction of the acidic Cu-Zn-Al-based precursor mixture and the basic precipitant.

Alternatively, in order to prepare the hybrid catalyst, the coprecipitation reaction may be performed in a slurry state in which high surface area alumina is dispersed in the solution before the coprecipitation reaction is performed. The aging of the catalyst is preferably carried out at 50-90 ° C., which favors the formation of a catalyst structure with good activity in the range of aging time presented, thus improving the syngas and methanol conversion reaction.

The aging is preferably performed for 2 to 20 hours, preferably 2 to 15 hours. If the aging time is short, the catalyst structure for methanol synthesis is not well developed, which is disadvantageous in terms of reaction. It is not suitable because the particle size of the methanol synthesis catalyst increases, the active point decreases, and the synthesis time increases, which is not economical.

The washed precipitate is dried in an oven at 100 ° C. or more for one day, and then the prepared precipitate is calcined in the range of 200 to 700 ° C., preferably in the range of 200 to 500 ° C. If the firing temperature is less than 200 ℃ there is a problem that the metal precursor is not converted to the oxide form, the appropriate catalyst structure is not formed, the activity is reduced, if the temperature exceeds 700 ℃, activity by the sublimation of copper and growth of particle size Problems such as a decrease in the reaction rate due to the reduction of the point occurs.

As another method, Cu-Zn-Al hydroxide prepared by performing coprecipitation independently and high surface area of boehmite or alumina are prepared by mixing in a slurry solution as follows.

An aluminum alkoxide solution dissolved in an alcoholic organic solvent, an organic carboxylic acid having a pKa value of 3.5 to 5 and water are mixed, and then heated to 80 to 130 ° C. to prepare a boehmite sol, and the solvent is removed to remove powdery boehmite or calcining. Alumina is prepared by reprocessing with.

A Cu-Zn-Al precursor mixture consisting of a copper precursor, a zinc precursor and an alumina precursor is co-precipitated under an aqueous solution of pH 7-8 and then aged to prepare a Cu-Zn-Al hydroxide by filtration and washing of the precipitate.

Powdered boehmite or alumina prepared in step 1 was mixed in an amount of 0.1 to 1.0 weight ratio based on 1 weight of Cu-Zn-Al hydroxide based on the alumina prepared in step 2 to prepare a slurry aqueous solution, and precipitated to obtain a precipitate. Filtrate and wash. The prepared precipitate is calcined in the range of 200 ~ 700 ℃.

The amount of the Cu-Zn-Al precursor mixture used is mixed with the powdered boehmite, and the composition of the porous catalyst for the final purpose is 30 to 45% by weight of CuO, 25 to 35% by weight of ZnO and 20 to 45% by weight of Al ₂ O _3. An appropriate amount is used to satisfy%, specifically, 45 to 55% by weight of the copper precursor, 35 to 45% by weight of the zinc precursor, and 1 to 20% by weight of the aluminum precursor may be used.

The method of simultaneously producing methanol and dimethyl ether from syngas using the hybrid catalyst prepared above is as follows.

The prepared double-porous porous structure catalyst is used in the catalytic reaction after reduction in a hydrogen atmosphere in the region of 200 ~ 500 ℃ in a fixed bed reactor. The reduced hybrid catalyst is a bar, in particular the reaction temperature is carried out in a reaction condition similar to the general methanol synthesis reaction on a fixed-bed reactor is 200 ~ 400 ℃, the reaction pressure is 30 ~ 60 kg / ㎠ and a space velocity of 1000 ~ 10000 h ^- It is preferable to perform at ¹ , but is not limited thereto.

The double pore catalyst prepared by the above method has the advantage of high yield from syngas to methanol and dimethyl ether and less than 1% of the by-products are generated in the total product. The superior transfer characteristics result in a significant decrease in the conversion of reactant carbon monoxide to carbon dioxide, compared to the previously reported catalyst system, resulting in increased process efficiency due to the reduced process cost of reprocessing carbon dioxide, a greenhouse gas. .

Hereinafter, the present invention will be described in detail with reference to the following examples, but the present invention is not limited by the following examples.

Example 1

A biporous catalyst for synthesizing methanol and dimethyl ether from syngas was prepared using the following coprecipitation method.

First, in order to prepare alumina having a high surface area, aluminum isopropoxide was mixed with a 2-propanol solution to prepare a slurry, and acetic acid and water were added to the solution to produce amorphous aluminum hydroxide by a hydrolysis reaction. Synthesis molar ratio of aluminum isopropoxide: 2-propanol: acetic acid: water as a reactant was fixed to 1: 25: 0.5: 6 to prepare a slurry solution. The prepared slurry solution was vacuum dried to obtain boehmite powder. The boehmite powder was calcined at 600 ° C. for 6 hours to obtain high surface area alumina (specific surface area = 350 m 2 / g). An alumina aqueous solution was prepared by adding 1.61 g of alumina prepared by the above method to 200 mL of tertiary distilled water at 70 ° C.

Next, copper acetate monohydrate _{(Cu (C 2 H 3 O} 2) 2 and H ₂ O) 5.05 g, zinc acetate hydrate _{(Zn (C 2 H 3 O} 2) 2 and 2H ₂ O) 4.31 g and aluminum nitrate hydrate (Al (NO ₃ ) ₃ .9H ₂ O) A solution of 2.94 g of a mixed metal dissolved in 600 mL of tertiary distilled water was prepared at the same time, and the solution had a pH of 5.5. As a precipitant, 8.34 g of sodium carbonate was dissolved in 600 mL of tertiary distilled water, and the pH of the solution was 10.5.

The mixed metal solution prepared above was slowly injected into a 2000 mL flask in which an alumina aqueous solution was stirred to maintain a final pH of 7.5 to 8.0 to form a slurry solution.

The slurry solution was stirred for about 3 hours at a temperature of 70 ℃ for aging, and the prepared double pore porous catalyst was washed three times or more with 2000 mL of distilled water, filtered and dried.

The catalyst size was prepared from 1.2 mm to 2.0 mm pellets for the activity test of the catalyst and calcined at 350 ° C. for 5 hours in an air atmosphere before being introduced into the reactor. The composition of the double pore porous structure catalyst after firing was 35% by weight of CuO, 28% by weight of ZnO and 37% by weight of Al ₂ O ₃ based on the metal oxide. After the reduction treatment was performed for 5 hours under a hydrogen atmosphere of 250 ° C. before the reaction was started, the molar ratio of carbon monoxide: hydrogen: carbon dioxide, which is a reactant, at a reaction temperature of 250 ° C. at a reaction pressure of 40 kg / cm 2 and a space velocity of 5500 h ⁻¹ was 41%. : 38%: fixed at a ratio of 21% by injection into the reactor was carried out the reaction is shown in the following Table 1.

Example 2

The catalyst was prepared in the same manner as in Example 1, but the catalyst was prepared by extending the aging time to 6 hours, filtered, washed, calcined, and then introduced into the reactor to reduce the reaction. .

Example 3

The catalyst was prepared in the same manner as in Example 1, but the catalyst was prepared by extending the aging time to 9 hours, filtered, washed, calcined, and then introduced into the reactor to reduce the reaction. .

Example 4

The catalyst was prepared in the same manner as in Example 1, but the catalyst was prepared by extending the aging time to 15 hours, filtered, washed, calcined, and then introduced into the reactor to reduce the reaction. .

Example 5

A catalyst was prepared in the same manner as in Example 1, but a catalyst was prepared using 0.90 g of alumina having a specific surface area of 350 m 2 / g. In this case, the final composition of the porous porous catalyst of the double pore prepared above was 42% by weight of CuO, 33% by weight of ZnO and 25% by weight of Al ₂ O ₃ based on the metal oxide. After filtering, washing, and calcining, the result of performing the reduction reaction by introducing this into the reactor is shown in Table 1 below.

Example 6

To prepare a catalyst in the same manner as in Example 1, to synthesize a high surface area alumina boehmite by changing the molar ratio of the reactant aluminum isopropoxide: 2-propanol: acetic acid: water to 1: 25: 0.035: 3 After the preparation, the alumina having a high surface area having a specific surface area of 455 m 2 / g was fired.

1.61 g of the alumina prepared above was co-precipitated with a mixed metal solution while stirring in tertiary distilled water at 70 ° C., and then aged and calcined for 5 hours to prepare a porous catalyst having a double pore. At this time, the composition of the prepared catalyst was 35% by weight of CuO, 28% by weight of ZnO and 37% by weight of Al ₂ O ₃ based on the metal oxide. Reduction was performed using the catalyst prepared above, and the results are shown in Table 1 below.

Example 7

To prepare a catalyst in the same manner as in Example 1, in order to synthesize a high surface area of boehmite by fixing the molar ratio of aluminum isopropoxide: 2-propanol: acetic acid: water as 1: 25: 0.035: 3 Bohe Mite was prepared to obtain high surface area boehmite having a specific surface area of 750 m 2 / g.

After mixing 2.30 g of boehmite in a third distilled water at 70 ° C., the mixed metal solution was aged for 5 hours to prepare a hybrid catalyst, and then calcined at 400 ° C. for 5 hours. 35% by weight of CuO, 28% by weight of ZnO and 37% by weight of Al ₂ O ₃ on an oxide basis. Reduction was performed using the catalyst prepared above, and the results are shown in Table 1 below.

Comparative Example 1

A catalyst was prepared in the same manner as in Example 1, but was prepared by aging the catalyst using 5.70 g of alumina having a specific surface area of 350 m 2 / g, and the composition of the prepared catalyst was 25% by weight of CuO and ZnO based on the metal oxide. 20 wt% and 55 wt% Al ₂ O ₃ .

After filtering, washing, and calcining, the result of performing the reduction reaction by introducing this into the reactor is shown in Table 1 below.

Comparative Example 2

A catalyst was prepared in the same manner as in Example 1, except that 1.61 g of alumina was mixed in a third distilled water at 70 ° C., and a mixed metal solution of Cu-Zn-Al was mixed to prepare a catalyst. The amount of the material used as the metal precursor was 3.79 g of copper acetate hydrate (Cu (C ₂ H ₃ O ₂ ) ₂ ㆍ H ₂ O), zinc acetate hydrate (Zn (C ₂ H ₃ O ₂ ) ₂ ㆍ 2H ₂ O) 3.06 g and 4.17 g of aluminum nitrate hydrate (Al (NO ₃ ) ₃ .9H ₂ O) were dissolved and prepared in 600 mL of tertiary distilled water at the same time, and the pH of the solution was 5.5. As a precipitant, a solution in which 8.12 g of sodium carbonate was dissolved in 600 mL of tertiary distilled water was used, and the pH was 10.5. The composition of the catalyst prepared above was 28 wt% CuO, 21 wt% ZnO and 51 wt% Al ₂ O ₃ based on the metal oxide. After filtering, washing, and calcining, the result of performing the reduction reaction by introducing this into the reactor is shown in Table 1 below.

Comparative Example 3

A catalyst was prepared in the same manner as in Example 1, but a metal mixed catalyst made of alumina and Cu-Zn-Al was independently prepared and then mixed at a predetermined ratio to be used as a catalyst.

First, in order to prepare alumina having a high surface area, aluminum isopropoxide was mixed with a 2-propanol solution to prepare a slurry, and acetic acid and water were added to the solution to produce amorphous aluminum hydroxide by a hydrolysis reaction. Synthesis molar ratio of aluminum isopropoxide: 2-propanol: acetic acid: water as a reactant was fixed to 1: 25: 0.5: 6 to prepare a slurry solution. The prepared slurry solution was vacuum dried to obtain boehmite powder. The boehmite powder was calcined at 600 ° C. for 6 hours to obtain high surface area alumina (specific surface area = 350 m 2 / g).

Next, a catalyst made of Cu-Zn-Al was prepared by coprecipitation while stirring tertiary distilled water at 70 ° C. The amount of copper acetate monohydrate _{(Cu (C 2 H 3 O} 2) 2 and H ₂ O) 5.05 g, zinc acetate hydrate _{(Zn (C 2 H 3 O} 2) 2 and 2H ₂ O) of the material used as the metal precursor 4.31 g and 2.94 g of aluminum nitrate hydrate (Al (NO ₃ ) ₃ .9H ₂ O) were dissolved and prepared in 600 mL of tertiary distilled water at the same time, and the solution had a pH of 5.5. As a precipitant, a solution in which 8.34 g of sodium carbonate was dissolved in 600 mL of tertiary distilled water was used, and the pH was 10.5. The solution prepared above was slowly injected at the same time into a 2000 mL flask in which 200 mL of distilled water was stirred at 70 ° C. to maintain a final pH of 7.5 to 8.0. The slurry solution was stirred for about 3 hours at a temperature of 70 ℃, the methanol catalyst prepared was washed three times or more with 2000 mL of distilled water, filtered and dried.

The catalyst and alumina made of Cu-Zn-Al prepared above were each independently calcined at 350 ° C., and then the catalyst size was prepared in pellets of 1.2 mm to 2.0 mm and physically mixed for the activity test of the catalyst. The two physically mixed catalysts were mixed so as to be 35% by weight of CuO, 28% by weight of ZnO and 37% by weight of Al ₂ O ₃ based on the metal oxide, and then introduced into the reactor and reduced to hydrogen using a catalyst having a space velocity of 2750 L / The reaction was performed at kgcat / hr and the results are shown in Table 1 below.

Comparative Example 4

Using the physically mixed catalyst prepared in the same manner as in Comparative Example 3, the space velocity was carried out at 5500 L / kgcat / hr, the results are shown in Table 1 below.

Comparative Example 5

Using a physically mixed catalyst prepared in the same manner as in Comparative Example 3, the space velocity was carried out at 11000 L / kgcat / hr, and the results are shown in Table 1 below.

Comparative Example 6

A catalyst was prepared in the same manner as in Example 1, except that 1.61 g of commercial alumina having a specific surface area of 200 m 2 / g was co-precipitated with a metal mixture solution of Cu-Zn-Al while stirring in tertiary distilled water at 70 ° C. to obtain a double pore. A hybrid catalyst having a porous structure of was prepared. Thereafter, the reaction was performed using a catalyst reduced at 250 ° C. after calcining under an oxygen atmosphere of 350 ° C., and the results are shown in Table 1 below.

Comparative Example 7

The catalyst was prepared in the same manner as in Example 1, but the catalyst was prepared by reducing the aging time to 1 hour, filtered, washed, calcined, and then introduced into the reactor to reduce the reaction. .

Comparative Example 8

A catalyst was prepared in the same manner as in Example 1, except that 1.61 g of zeolite (HZSM-5) having a specific surface area of 400 m 2 / g and a ratio of SiO ₂ / Al ₂ O ₃ was dissolved in Cu- A catalyst was prepared by coprecipitation with a metal mixture solution of Zn-Al. Thereafter, the reaction was performed using the catalyst, and the results are shown in Table 1 below.

Table 1 shows the distribution of specific surface area and pore size of the catalysts prepared in Examples 1 to 7 and Comparative Examples 1 to 8, CO conversion rate, carbon selectivity, and product distribution ratio using the catalyst.

division CO conversion rate (%) Carbon selectivity ¹⁾ (%) MeOH / DME / CO ₂ Product Distribution Ratio ²⁾ (MeOH + DME) / CO ₂ Catalyst specific surface area (㎡ / g) Porosity ³⁾ 2-20 nm 20 to 100 nm Example 1 24.4 42.5 / 20.2 / 36.7 1.7 92 45 55 Example 2 25.3 61.1 / 11.2 / 27.0 2.7 136 50 50 Example 3 29.4 38.4 / 20.1 / 39.9 1.5 110 39 61 Example 4 22.3 47.8 / 17.7 / 33.9 1.9 98 51 49 Example 5 27.6 58.8 / 7.0 / 33.3 2.0 87 29 71 Example 6 22.8 46.0 / 25.5 / 27.4 2.6 - - - Example 7 20.2 65.5 / 8.3 / 25.7 2.9 - - - Comparative Example 1 16.9 22.2 / 38.3 / 39.2 1.5 141 68 32 Comparative Example 2 3.7 33.2 / 25.5 / 40.7 1.4 - - - Comparative Example 3 40.4 1.4 / 13.0 / 85.5 0.2 178 (average) - - Comparative Example 4 32.2 6.5 / 29.9 / 63.4 0.6 178 (average) - - Comparative Example 5 20.8 13.8 / 36.4 / 49.7 1.0 178 (average) - - Comparative Example 6 23.5 10.9 / 41.5 / 47.1 1.1 - - - Comparative Example 7 19.6 29.6 / 20.2 / 49.6 1.0 - - - Comparative Example 8 16.0 54.2 / 14.4 / 30.0 2.3 - - - 1) Selectivity: The remaining amount contains by-products whose main component is methane. 2) Ratio of production of methanol / dimethyl ether as a main product and carbon dioxide as a by-product 3) Relative volume ratio of each region in the total pore volume of the double porous catalyst

As shown in Table 1 above, when synthesizing methanol and dimethyl ether from synthesis gas using a catalyst having a double pore porous structure prepared according to the present invention, the catalyst of the single porous structure of Comparative Examples 3 to 5 was physically It can be seen that the conversion to carbon dioxide by the aqueous reaction is significantly suppressed compared with the case of mixing and using, and the selectivity to methanol and dimethyl ether, which is a desired product, can be improved. This was carried out by methanol synthesis and dehydration under the catalyst having a double pore porous structure prepared in Examples 1 to 7 and the simple mixed single pore structure prepared in Comparative Examples 1 to 6, respectively, It can also be seen in FIG. 1 showing the selectivity, and in FIG. 3 showing the BET surface area and pore distribution of the catalyst having the double pore structure of Examples 1 and 5 and the catalyst of Comparative Example 1. FIG.
As shown in FIG. 3, the catalyst of the present invention exhibits a porous structure of double pores, and the present invention is represented by numerical values of relatively small pores and large pores. At this time, the numerical value was divided into a boundary between the lowest point (20 nm) between the two highest points.
In addition, even when using a catalyst having a porous structure of a double pore, as shown in Comparative Examples 1 to 2, the metal oxide composition is out of the range shown in the present invention, or can be found in Comparative Example 6 using commercial alumina instead of alumina having a high surface area. As can be seen that the desired production rate (yield) of MeOH and DME can not be obtained.

delete

Therefore, when each of the known catalysts are independently prepared and calcined, the catalysts are physically mixed and used, and as shown in Comparative Examples 3 to 5, the water gas shift reaction proceeds easily on the surface of the solid acid catalyst. Since the conversion reaction from carbon monoxide to carbon dioxide is significantly increased, in order to suppress this, it is necessary to calcinate and use a catalyst having a porous structure having a double pore structure by coprecipitation or slurry using a high surface area alumina and a metal mixed solution. It is believed that there are many advantageous aspects due to the improvement of the yield of methanol and dimethyl ether and the suppression of the production of carbon dioxide during the reaction. Next, Figure 2 shows the individual pore distribution of the catalyst for the activity experiments by simply mixing the respective catalysts for methanol synthesis and dehydration reaction prepared in Comparative Example 3 can be confirmed that there is a difference from the embodiment of the present invention have.

In addition, among the synthesis methods presented in the present invention, as shown in Comparative Examples 1 and 2, the reaction from syngas to methanol and dimethyl ether only when the catalyst was prepared in the composition of Cu-Zn-Al active ingredient in a constant region. It can be seen that it is possible to prepare a catalyst with excellent activity, which is thought to be a decrease in the production rate (yield) of MeOH and DME due to the increase of the alumina component and the decrease of the active point of the methanol synthesis catalyst.

The bi-porous porous catalyst prepared according to the present invention is not limited to the above examples but may be utilized for the conversion of syngas to methanol and dimethyl ether in a fixed bed, fluidized bed reactor, and slurry reactor.

As discussed above, under the situation that high oil prices continue to rise due to rising oil prices, the utilization of dimethyl ether as an alternative fuel and reactant for fuel cells is expected to increase rapidly. Under these circumstances, the development of an efficient one-stage hybrid catalyst that can make dimethyl ether from syngas more inexpensive becomes important. In the present invention, in order to control the strong acid point of the previously reported zeolite and solid acid catalyst, A method of economically preparing methanol and dimethyl ether from syngas by using a high pore area alumina proposed in the present invention without using a catalyst reprocessing process is proposed.

In addition, from the viewpoint of the production of a commercial catalyst, in general, in order to improve the strength of the commercial heterogeneous catalyst, there is a problem in that the activity of the final catalyst is reduced or the by-products are changed by using an excess amount of binder during the molding process. Since the binder and the catalytic action can be performed at the same time, it is determined that the problems occurring during the scale-up process of the catalyst production can be minimized.

The dual-porous porous catalyst proposed in the present invention has the advantage of economically obtaining high-purity dimethyl ether with separation cost reduction by minimizing the production of by-products by inhibiting the water gas conversion reaction of carbon monoxide to carbon dioxide. .

Claims (15)

It is a porous catalyst of Cu-Zn-Al oxide containing 30 to 45% by weight of CuO, 25 to 35% by weight of ZnO and 20 to 45% by weight of Al ₂ O ₃ , and the catalyst has a relatively small pore size (PS). ₁ ) and double pores are formed at the same time with the large pores (PS ₂ ), Catalyst for simultaneous production of methanol and dimethyl ether, characterized in that the pore size range of the small pores (PS ₁ ) and large pores (PS ₂ ) is as follows: 2 ≤ PS ₁ ≤ 20 nm 20 <PS ₂ ≤ 100 nm The catalyst according to claim 1, wherein the total specific surface area of the catalyst is maintained in the range of 70 to 180 m 2 / g. The catalyst of claim 1, wherein the small pore in the range of 2 to 20 nm has a porosity of 20 to 65%, and the large pore in the range of 20 to 100 nm has a porosity of 35 to 80%. An aluminum alkoxide solution dissolved in an alcoholic organic solvent, an organic carboxylic acid having a pKa of 3.5 to 5 and water were mixed, and then heated at 80 to 130 ° C. to prepare a boehmite sol, and the solvent was removed to obtain a powdery boehmite. 1 step of manufacturing; Coprecipitation and aging in an aqueous solution of pH 7-8 by adding a basic precipitant and a Cu-Zn-Al precursor mixture containing a copper precursor, a zinc precursor and an aluminum precursor to the suspension aqueous solution containing the powdered boehmite prepared in step 1 Filtering and washing the formed precipitate by two; And Three steps of firing the prepared precipitate in the range of 200 ~ 700 ℃ Method of producing a catalyst for the simultaneous production of methanol and dimethyl ether from a synthesis gas comprising a. An aluminum alkoxide solution dissolved in an alcoholic organic solvent, an organic carboxylic acid having a pKa of 3.5 to 5 and water were mixed, and then heated at 80 to 130 ° C. to prepare a boehmite sol, and the solvent was removed to obtain a powdery boehmite. 1 step of manufacturing; Cu-Zn-Al hydroxide by filtering and washing the precipitate formed by coprecipitation and ripening at pH 7-8 by adding an aqueous solution containing a Cu-Zn-Al precursor mixture containing a copper precursor, a zinc precursor and an aluminum precursor and a basic precipitant. Preparing two steps; Mixing the boehmite powder prepared in step 1 with the Cu-Zn-Al hydroxide prepared in step 2 to prepare an aqueous slurry solution, and then precipitate and filter and wash the precipitate by precipitation; And Four steps of firing the prepared precipitate in the range of 200 ~ 700 ℃ Method of producing a catalyst for the simultaneous production of methanol and dimethyl ether from a synthesis gas comprising a. The production method according to claim 4 or 5, wherein the powdery boehmite has a specific surface area in the range of 300 to 800 m 2 / g. The method according to claim 4 or 5, further comprising the step of calcining the powdered boehmite at a temperature of 400 to 700 ℃ to convert to alumina having a specific surface area of 300 to 800 m 2 / g. Way. 6. The method according to claim 4 or 5, wherein the organic carboxylic acid is selected from acetic acid, formic acid and propionic acid. The method according to claim 4 or 5, wherein the organic carboxylic acid is used in an amount of 0.01 to 1 mole per 1 mole of the aluminum alkoxide solution. The method according to claim 4 or 5, wherein the water is used in a ratio of 2 to 12 moles per 1 mole of the aluminum alkoxide solution. The production method according to claim 4 or 5, wherein the precursor of copper, zinc or aluminum is one or a mixture of two or more selected from acetates and nitrates of these metals. 6. The process according to claim 4 or 5, wherein the basic precipitant is selected from sodium carbonate, potassium carbonate and sodium hydrogen carbonate. The method according to claim 6, wherein the powdered boehmite is used in an amount of 0.1 to 1.0 weight ratio based on alumina, based on 1 weight of the Cu-Zn-Al precursor mixture. The method according to claim 4 or 5, wherein the aging is carried out at 50 to 90 ° C for 2 to 20 hours. The process according to claim 4 or 5, wherein the composition of the calcined catalyst is 30 to 45 wt% of CuO, 25 to 35 wt% of ZnO and 20 to 45 wt% of Al ₂ O ₃ .

Images