WO2018088736A1 - Catalyst for preparing dimethyl ether from synthetic gas and method for producing same - Google Patents

Abstract

The present disclosure provides: a Cu/ZnO/Al₂O₃-based catalyst, which is produced without making a large change in a conventional catalyst production method while a seed material, such as zeolite or γ-alumina, and/or other materials are not added; a method for producing the same; and a method for efficiently preparing dimethyl ether from synthetic gas in the presence of the catalyst.

Description

Catalyst for preparing dimethyl ether from synthesis gas and process for preparing same

The present disclosure relates to a catalyst for producing dimethyl ether from synthesis gas and a process for producing the same. More specifically, the present disclosure relates to a catalyst capable of effectively converting synthesis gas produced by gasification of various raw materials into dimethyl ether, a method for preparing the same, and a method for preparing dimethyl ether using the catalyst.

Due to the depletion of petroleum resources, there is a demand for the production of high value-added chemical products using coal, especially low-grade coal, and the gasification process is in the limelight.

Gasification process generally refers to a series of processes in which a carbonaceous raw material is reacted under the supply of a gasifying agent (e.g., oxygen, steam, carbon dioxide or a mixture thereof) to convert the main component into a synthesis gas consisting of hydrogen and carbon monoxide. do. Herein, "carbonaceous raw material" broadly includes solid, liquid, and gaseous carbonaceous materials that can be used to generate synthesis gas. Such carbonaceous materials are not necessarily limited to a specific kind, but biomass (botanical and animal materials such as herbaceous and woody materials), coal (anthracite, bituminous coal (reverse coal, lignite, peat, etc.), lower activated carbon, etc.) , Organic waste, sail oil, coke, tar and the like can be exemplified.

Examples of typical reaction mechanisms for such gasification reactions can be shown in Schemes 1 to 3 below.

Scheme 1

C + 1 / 2O ₂ → CO (partial oxidation)

Scheme 2

C + H ₂ O → CO + H ₂ (steam reforming)

Scheme 3

C + CO ₂ → 2CO (carbon dioxide reforming)

Coal, a representative raw material for the gasification process, is distributed in large quantities in a wide range of regions around the world, and is re-emerged as a fuel source to replace petroleum depletion that is widely used to date. In addition, biomass, which has recently been in the spotlight, can also provide basic oils of various fuels and platform compounds through various treatment processes, and this technology is also known to be applied as a raw material for gasification reaction.

In recent years, the gasification process technology is not only a technology for producing raw materials and fuels of various compounds, but also its application range is extended to areas such as power generation. For example, it can be applied to hydrogen power generation, ammonia production, refinery process using hydrogen in synthesis gas, which is the main product of gasification process, and diesel using synthesis gas as raw material of Fischer-Tropsch reaction. Oil, jet oil, lube base oil, naphtha, etc. can be manufactured.

As another application, techniques are known for converting synthesis gas into methanol and converting it to high value chemicals such as dimethyl ether.

In this regard, dimethyl ether (CH ₃ OCH ₃ ) is not only similar to propane and butane, which are main components of LPG, in physical and chemical properties, but also excellent in many respects. In particular, it can be used as an aerosol propellant, a substitute for diesel fuel, an intermediate of chemical reactions, and the like, and is an oxygen-containing compound that has recently attracted attention. In addition, it is of great utility as a clean fuel that is easy to transport and store.

In the process of preparing dimethyl ether from the synthesis gas, the synthesis gas is converted into methanol through a hydrogenation reaction as shown in Scheme 4 below (methanol synthesis reaction), and the methanol synthesized as in Scheme 5 is converted into dimethyl ether through a dehydration reaction. It involves a reaction to convert (methanol dehydration).

Scheme 4

CO + 2H ₂ → CH ₃ OH ΔH =-43.2 kcal / mol

Scheme 5

2CH ₃ OH → CH ₃ OCH ₃ + H ₂ O ΔH =-5.6 kcal / mol

In this connection, (i) a process for synthesizing dimethyl ether by direct dehydration from the converted methanol to methanol, and (ii) a catalyst for synthesizing methanol from the syngas and the resulting methanol dewatered A method of using a hybrid catalyst in combination with a solid acid catalyst for reacting is known.

For process (i), methanol is produced from the synthesis gas in the presence of a typical methanol synthesis catalyst such as a Cu / ZnO / Al ₂ O ₃ catalyst. At this time, the alumina (Al ₂ O ₃ ) component is contained in a small amount as a promoter. Then, the hydrophilic solid acid catalyst (eg, zeolite (J. Am. Chem. Soc., 132 (2010) 8129-8136)), gamma-alumina (eg, US patent) No. 4,605,788; Energy Fuels, 24 (2010) 804-810), silica-alumina (eg, US Pat. No. 4,885,405), and the like.

For process (ii), a plurality of reactions (ie methanol synthesis, water gas shift and dehydration) are run together in a single reactor on the hybrid catalyst. For this purpose, the ingredients such as zeolite, γ- alumina after the pre-prepared ^{Cu 2 +, Zn 2 +,} Al 3 + is a method of synthesizing by injecting the co-precipitation of the metal precursor, such as is also known (Fuel Proc. Tech., 121 (2014) 38-46).

In addition, the sol in order to introduce an acid function-gel method (.. Catal Commun, 8 ( 2007) 598-606) to that used in a technique for introducing the Al ^{3 +,} using a precipitating agent known to NaAlO ₂ bar, wherein the oxalic acid ( oxalate acid) and ethanol need to be used additionally.

As such, the dehydration catalyst in which the acid function is introduced needs to be introduced through zeolite or gamma-alumina as a seed, or may be purchased from another manufacturer. However, when introducing the acid functions without using a seed material injected into the Al ^{3 +} has lead to the complexity of the process, and has a problem in that the catalyst efficiency goes down.

Due to this problem, it can be said that a process of preparing dimethyl ether from a synthesis gas is generally performed in a multistage process of a hydrogenation reaction-dehydration reaction.

Nevertheless, if it is possible to use a catalyst which can effectively convert synthesis gas to dimethyl ether using a single reactor or by a single reaction rather than in a multistage reaction, it is economical to produce dimethyl ether because it does not involve multiple process steps. The process can be implemented. In order to realize these advantages, a catalyst having good activity for both reactions (hydrogenation and dehydration) is required, but there is a limit to increasing the two activities to a significant level by the prior art. Thus, there is a need for a high activity catalyst technology that can produce dimethyl ether in high yield from synthesis gas in a single reactor.

Accordingly, in one embodiment of the present disclosure, without adding seed materials and / or other materials such as zeolites, γ-aluminas, etc., without making any significant changes in the conventional method for preparing Cu / ZnO / Al ₂ O ₃ based catalysts An object of the present invention is to provide a Cu / ZnO / Al ₂ O ₃ based catalyst having excellent methanol conversion of syngas through hydrogenation and dimethyl ether conversion of methanol by dehydration.

In addition, another embodiment of the present disclosure is to provide a process for producing dimethyl ether with high yield and high selectivity from synthesis gas in the presence of the catalyst described above.

According to the first aspect of the present disclosure,

a) providing a metal precursor solution containing Cu ^{+ 2} and Zn ^{2 +} precursor precursor;

b) forming the metal precursor solution in Cu ^{+ 2} and Zn ^{2 +} precursor The first catalyst precursor by crystallization of the precursor represented by _{Cu x Zn 1-x (OH} ) 2 CO 3;

c) forming a second catalyst precursor by carrying out the precipitation by addition of Al ^{3 +} precursor to the first metal precursor; And

d) calcining and reducing the second catalyst precursor;

Provided is a method for preparing a Cu / ZnO / Al ₂ O ₃ based catalyst comprising a.

According to an exemplary embodiment, the second catalyst precursor is substantially free of hydrotalcite crystal structure.

According to an exemplary embodiment, the first catalyst precursor may exhibit an XRD pattern that does not contain peaks with 2θ ranging from 10 to 14 °.

According to an exemplary embodiment, the second catalyst precursor does not release CO ₂ upon pyrolysis treatment at a temperature of at least 500 ° C.

According to an exemplary embodiment, step b) is

b1) precipitating by combining the metal precursor solution with a basic precipitant solution; And

b2) may first comprise aging the precipitate produced in step b1) to form a first catalyst precursor.

According to an exemplary embodiment, said step c) may be carried out after the pH decrease takes place in step b2).

According to an exemplary embodiment, the step c) is

c1) the step of precipitation by addition of Al ^{3 +} precursor solution to said first catalyst precursor; And

c2) secondary aging of the precipitate produced in step c1) to form a second catalyst precursor comprising Cu _x Zn _{1 - x} (OH) ₂ CO ₃ and Al (OH) ₃ ;

It may include.

According to a second aspect of the present disclosure,

Cu / ZnO / Al ₂ O ₃ based catalyst comprising crystalline Cu / ZnO and amorphous Al ₂ O ₃ as active ingredients,

The catalyst comprises 30 to 60% Cu, 10 to 30% Zn and 13 to 40% Al on an atomic basis,

Amorphous Al ₂ O ₃ is dispersed in the surface of crystalline Cu / ZnO and / or is present in a form that at least partially covers, and

A catalyst is provided having a specific surface area of Cu in the range of 10 to 35 m 2 / g.

According to an exemplary embodiment, the atomic ratio of Cu / Zn in the catalyst may range from 50/50 to 80/20.

According to an exemplary embodiment, the Cu / ZnO / Al ₂ O ₃ based catalyst may be present in the form of an amorphous Al ₂ O ₃ shell on the crystalline Cu / ZnO core.

According to a third aspect of the present disclosure,

Providing a synthesis gas comprising CO and H ₂ as reactant;

Reacting the synthesis gas under the presence of the above-described Cu / ZnO / Al ₂ O ₃ based catalyst, a temperature of 200 to 400 ° C. and a pressure of 1 to 100 atm using a single reactor to form a product containing dimethyl ether. step; And

Separating and recovering dimethyl ether from the product;

There is provided a method of producing dimethyl ether from a synthesis gas comprising a.

According to an exemplary embodiment, the product contains methanol and dimethyl ether, wherein the molar ratio of dimethyl ether to methanol may range from 0.05 to 4.

According to an exemplary embodiment, the step of separating dimethyl ether from the product may be carried out by liquefaction or distillation.

According to an exemplary embodiment, the method may further include combining the reactant with components other than the separated dimethyl ether in the product.

According to an exemplary embodiment, the single reactor is a continuous reactor and the reaction of the synthesis gas may be carried out under a space velocity (GHSV) condition of 1,000 to 100,000 cm 3 g _cat · h ⁻¹ .

Conventional Cu / ZnO / Al ₂ O ₃ based catalysts have been used primarily for synthesizing methanol from synthesis gas by hydrogenation reaction, but the catalysts according to the present disclosure have the same or approximate amount of activity as in the prior art. Even if it contains the component, it exhibits a high CO conversion rate and high selectivity to dimethyl ether in the synthesis gas. As a result, the yield of the dimethyl ether can be achieved by replacing the conventional multistage reaction form consisting of the hydrogenation reaction-dehydration reaction only by a process composed of a one-pot reaction method. In particular, the catalysts according to the present disclosure can be prepared without the presence of seeds used in the preparation of conventional catalysts, and furthermore, can be prepared in a relatively simple manner without undue change to conventional catalyst preparation methods. Therefore, broad commercialization is expected in the future.

1 is a diagram conceptually showing the morphological characteristics of a Cu / ZnO / Al ₂ O ₃ based catalyst according to one embodiment of the present disclosure;

FIG. 2 is a diagram illustrating composition and morphological changes when treating a second catalyst precursor containing Cu, Zn and Al in the order of a calcination step and a reduction step, according to one embodiment of the disclosure;

3 is a schematic illustration of an example of a process for preparing dimethyl ether from synthesis gas in a single reaction mode using a catalyst according to one embodiment of the present disclosure;

4 is a graph showing the CO conversion and the selectivity of dimethyl ether and the yield of dimethyl ether in a process for preparing dimethyl ether from synthesis gas in the presence of a catalyst according to each of Examples (SP) and Comparative Examples (CP);

5 is a graph showing a change in pH over time during the preparation of a catalyst according to Example SP and a catalyst according to Comparative Examples CZ and CP, respectively;

6 is a graph showing the results of XRD analysis on the catalyst precursor formed during the preparation of the catalyst according to Example (SP) and the catalyst according to Comparative Examples (CZ and CP), respectively;

7 is a graph showing the results of TGA analysis for the thermal stability evaluation of the catalyst precursor formed during the preparation of the catalyst according to Example (SP) and the catalyst according to Comparative Examples (CZ and CP), respectively;

8 is a graph showing the results of XRD analysis for the catalyst in the form of oxide according to the catalyst according to Example (SP) and Comparative Examples (CZ and CP) respectively;

9 is a graph showing the results of performing IPA-TPSR analysis while varying the Al content to evaluate the amount of acid point in the catalyst in the oxide form according to the catalyst according to Example (SP) and Comparative Example (CP), respectively. ;

10 is a graph showing methanol yield in the reaction for converting synthesis gas to methanol in the presence of a catalyst according to each of Examples (SP) and Comparative Examples (CZ and CP);

11 is an HR-TEM photograph of a CP-30 catalyst in a catalyst according to Comparative Example (CP); And

12 shows the HR-TEM photograph of the SP-30 catalyst, the EDS mapping result of Cu, Zn, and Al, the enlarged HR-TEM photograph, and the composition profile of Cu, Zn, and Al in the catalyst according to Example (SP) It is a graph.

The present invention can all be achieved by the following description. The following description is to be understood as describing preferred embodiments of the invention, but the invention is not necessarily limited thereto. In addition, it is to be understood that the accompanying drawings are provided for ease of understanding and the present invention is not limited thereto.

Terms used in the present specification may be defined as follows.

The term "synthetic gas" means a mixed gas that is typically produced by a gasification reaction and contains CO and H ₂ principal components, and may further include CH ₄ and / or CO ₂ .

The term "crystalline" or "crystalline" can mean any solid material typically arranged to have a valence lattice structure (eg, three-dimensional order), generally X It can be specified by -ray diffraction analysis (XRD), nuclear magnetic resonance analysis (NMR), differential scanning calorimetry (DSC) or a combination thereof.

The term "amorphous" or "amorphous" can mean any solid material that lacks a lattice structure (eg, three-dimensional regularity), as opposed to "crystalline" or "crystalline". to be.

Dimethyl ether synthesis catalyst

1 conceptually illustrates the morphological characteristics of a Cu / ZnO / Al ₂ O ₃ based catalyst according to one embodiment of the disclosure.

As shown, the catalyst is typically a three component catalyst containing three metal components as the active component. In some cases, however, the composition may further include other components (eg, binder or matrix components) that do not substantially affect the basic catalytic activity.

In the illustrated Cu / ZnO / Al ₂ O ₃ -based catalyst, Cu and Zn are evenly distributed while intimately contacting each other at the core portion of the catalyst in a state of showing crystallinity. At this time, Cu is present in a reduced form as a whole by a reduction treatment after oxidation, while Zn is present in an oxide form, and thus Cu may be expressed as Cu / ZnO.

In addition, alumina (Al ₂ O ₃ ) has an amorphous property and is dispersed in the surface of crystalline Cu / ZnO and / or exists in the form of at least partially covering. At this time, the term "dispersed on the surface" is to be understood in a comprehensive sense, and in some cases may include a depth from the surface, for example up to about 75 nm (specifically up to about 50 nm). (E.g., when Al is present in a rich state from the Cu / ZnO surface to a certain depth).

As described above, when amorphous alumina (Al ₂ O ₃ ) is coated on Cu / ZnO, the thickness of the coating layer (or shell) is, for example, about 25 to 100 nm, specifically about 27 to 75 nm. And more specifically in the range of about 30-50 nm.

In addition, according to an exemplary embodiment, the particle size of the Cu crystal in the catalyst may range from, for example, about 4 to 8 nm, specifically about 4.5 to 7 nm, more specifically about 4.8 to 6.5 nm.

In the Cu / ZnO / Al ₂ O ₃ based catalyst according to the present embodiment, when the alumina (Al ₂ O ₃ ) is partially coated on the Cu / ZnO core, the alumina (Al ₂ O ₃ ) is aggregated into a band (or band) form or small in size. It can exist as is. Alternatively, the Cu / ZnO / Al ₂ O ₃ based catalyst may be present in the form of an amorphous Al ₂ O ₃ shell formed on the crystalline Cu / ZnO core.

As such, as the crystalline Cu / ZnO cores are positioned adjacent to amorphous Al ₂ O ₃ , methanol synthesis activity and amorphous (Al ₂ O ₃₎ by crystalline Cu / ZnO have little effect on their respective structures. It is possible to sufficiently provide the acid point required for the dehydration reaction by).

In one embodiment, the Cu / ZnO / Al ₂ O ₃ based catalyst contains about 30 to 60%, specifically about 35 to 55%, more specifically about 40 to 50% Cu on an atomic basis. In addition, Zn is contained in about 10 to 30%, specifically about 13 to 28%, more specifically about 15 to 25%. In this regard, the ratio of Cu / Zn (atomic basis) is for example in the range of about 50/50 to 80/20, specifically about 60/40 to 75/25 and more specifically about 65/35 to 70/30. This is because it is suitable for forming Cu _x Zn _1-x (OH) ₂ CO ₃ as a catalyst precursor as described below in the ratio range of Cu / Zn.

In addition, the content of Al in the catalyst may be in the range of about 13 to 40%, specifically about 15 to 35%, more specifically about 20 to 30% on an atomic basis, so that the dehydration reaction of methanol should be at an appropriate level. The acid point required for the synthesis of dimethyl ether can be ensured. In particular, it should be noted that the Cu / ZnO: Al catalyst for conventional methanol synthesis contains only a small amount of Al (for example, about 3%) to act as a promoter, but significantly in this embodiment. Contains high levels.

Furthermore, the Cu / ZnO / Al ₂ O ₃ based catalyst according to this embodiment has a morphological characteristic in which amorphous Al ₂ O ₃ surrounds the surface (or surroundings) of crystalline Cu / ZnO as described above. As the Al content increases, Cu specific surface area, which is an indicator of hydrogenation activity, is not significantly affected. Therefore, the synthesis gas undergoes a cascade or tandem transformation process (hydrogenation-dehydration reaction). Can be easily converted to dimethyl ether. However, when an excessively large amount of Al is introduced, it may be advantageous to appropriately control within the above-described content range as Cu specific surface area may be reduced.

According to one embodiment, the specific surface area of Cu in the catalyst may range from about 10 to 35 m 2 / g, specifically about 15 to 32 m 2 / g, more specifically about 20 to 30 m 2 / g, as described above. Likewise, even if the Al content is increased, the Cu specific surface area remains almost the same, or even if it is decreased, the degree is relatively small. Therefore, the synthesis gas as a feedstock can easily access a catalytic site having a hydrogenation function. In this regard, the specific surface area of the catalyst (or precursor catalyst) can be measured by N ₂ O-RFC (reactive frontal chromatography). Such specific surface area measurement techniques are described in detail in Angew. Chem. Int. Ed., 53 (2014) 7043-7047, which is incorporated herein by reference.

Method for preparing dimethyl ether synthesis catalyst

According to one embodiment, a method for preparing a Cu / ZnO / Al ₂ O ₃ based catalyst for converting synthesis gas into dimethyl ether is provided, which will be described in more detail below.

First, prepare the Cu ^{+ 2} and Zn ^{2 +} precursor metal precursor solution containing a precursor, particularly the metal precursor solution to form a hydrogenation component. In this case, the use of available Cu ^{2 +} precursor may include a water-soluble copper salt such as copper nitrate, copper sulfate, copper acetate, formate, copper chloride (II), copper, copper iodide, used alone, or two It can use combining a species or more. In addition, the as Zn ^{2 +} precursor, for example, zinc nitrate, zinc sulfate, zinc acetate, formate, zinc chloride (II), zinc may be used a water-soluble zinc salt such as zinc iodide, alone or in combination of two or more It can be used in combination. At this time, the input amount between the Cu ^{2 +} precursor and the Zn ^{2 +} precursor may be adjusted to meet the content range of Cu and Zn in the final catalyst (element-based), and further, in the ratio range of Cu / Zn as described above. In addition, the concentration of the total metal precursors (Cu precursor and Zn precursor) in the solution is, for example, adjustable in the range of about 0.1 to 1.5 M, specifically about 0.5 to 1.4 M, more specifically about 1 to 1.2 M.

Thereafter, a step of crystallizing the Cu precursor and the Zn precursor in the precursor solution together is performed (formation of the first catalyst precursor).

According to one embodiment, a precipitant, in particular a basic precursor, may be used to form the solid Cu / Zn precursor. At this time, examples of the precipitant which may be used may include carbonates or bicarbonates of alkali metals (lithium, sodium, potassium, etc.) or ammonium, and these may be used alone or in combination. In an exemplary embodiment, a precipitant solution, specifically an aqueous precipitant solution, is prepared separately from the preparation of the metal (Cu and Zn) precursor solutions described above. By way of example, the concentration of precipitant in the precipitant solution may be, for example, in the range of about 0.01 to 1.2 M, specifically about 0.05 to 1 M, more specifically about 0.1 to 0.5 M.

Then, a process of inducing precipitation of Cu and Zn is performed by combining (adding) the metal precursor solution to the precipitant solution. This precipitation process involves heating the precipitant solution, for example, to a temperature range of about 20 to 90 ° C., specifically about 50 to 80 ° C., more specifically about 60 to 70 ° C., followed by addition of the metal precursor solution (specifically, It can be done in such a way). In this case, the amount (based on weight) of the metal (Cu and Zn) precursor / precipitant may be adjusted within a range of, for example, about 0.5 to 2, specifically about 1 to 1.8, and more specifically about 1.1 to 1.5.

As such, amorphous initial particles are formed by adding the metal precursor (or metal precursor solution) to the precipitant solution.

Thereafter, a first aging step of the precipitate in the solution (combination solution) in which the metal precursor solution and the precipitant solution are combined is performed. During the aging process, amorphous initial particles are converted into a crystalline form, and the process is performed. At the pH of the combined solution (or Cu and Zn-containing precipitates) is reduced. In this specification, it refers to a crystallization product of Cu ^{+ 2} and Zn ^{2 +} precursor precursor as "first catalyst precursor." In other words, a decrease in pH in the combined solution or precipitate indicates that the initial particles consisting of the Cu precursor and the Zn precursor were converted from amorphous to crystalline.

In one embodiment, it is possible to form the catalyst precursor (the first catalyst precursor) having a desired crystal properties by the addition of Al ^{3 +} precursor after the point at which the pH is reduced in the aging process. In the exemplary embodiment, the pH can be added to the Al ^{3 +} precursor after, for example, down to the extent of at least about 0.1, at least about 0.07, more specifically at least about 0.05, specifically.

As an example, the aging step (primary aging step) can be performed, for example for at least about 15 minutes, specifically about 20 to 180 minutes, more specifically about 30 to 90 minutes. In addition, the aging temperature can be adjusted, for example, in the range of about 20 to 90 ° C, specifically about 40 to 80 ° C, more specifically about 60 to 70 ° C.

In the present embodiment, the first catalyst precursor has a crystalline structure represented by Cu _x Zn _{1 - x} (OH) ₂ CO _3. According to XRD analysis, for example, 2θ is about 10 to 14 °, Specifically, it is preferable not to contain a peak having 2θ of about 11 to 13 °, more specifically 2θ of 11.5 to 12 °.

This phenomenon occurs, reducing the pH of the metal precursor precipitate during fermentation process, as described above, the process of adding the Al ^{3 +} precursor as a next step is performed. According to the embodiment, Al ^{3 +} precursor can be mentioned aluminum nitrate, aluminum sulfate, aluminum acetate, aluminum formate, aluminum iodide such as, can be used alone or in combination. In addition, Al ^{3 +} precursor solution (specifically, an aqueous solution) bars which can be added in the form, its concentration is, for example, about 0.1 to 1.5 M, particularly about 0.5 to 1.2 M, more specifically about 0.8 to 1 M Adjustable within the range.

In this way, the addition of Al ^{3 +} precursor to form a precipitate, and further performing a secondary aging step to form a second catalyst precursor. At this time, the addition amount of the Al ^{3 +} precursor may be selected in consideration of the Al content range in the final catalyst as described above.

On the other hand, the temperature conditions of the precipitation and the secondary aging step according to the addition of Al ^{3 +} precursor may be set the same or similar to the first catalyst precursor forming step. In addition, the further aging step (secondary aging step) can be carried out, for example, for at least about 15 minutes, specifically about 20 to 180 minutes, more specifically about 30 to 90 minutes.

Prepared according to the above procedure a second catalyst precursor precursor Cu ^{2 +,} Zn ^{2 +} and Al precursors in the ³⁺ precursor catalyst precursor is typically formed by precipitation with (Cu, Zn, Al) hydrotalcite crystal structure, that is, Cu ₃ Zn ₃ Al ₂ (OH) ₁₆ CO ₃ OH H ₂ O and has a different characteristic from that shown. As can be seen through XRD and TG analysis, the second catalyst precursor is present in a mixture of crystalline form (Cu _x Zn _{1- x} ) (OH) ₂ (CO ₃ ) and amorphous Al (OH) _3. It seems to be. In other words, two types of precursors having different properties and functions (hydrogenation and dehydration) are synthesized, and the two types of catalyst components are combined through a subsequent calcination and reduction treatment step ( Crystalline Cu / ZnO hydrogenation catalyst component and amorphous alumina acid catalyst (dehydration reaction) component).

In addition, the second catalyst precursor is distinguished from a precursor having a hydrotalcite structure in terms of thermal stability, for example, when pyrolyzed at a temperature of at least about 500 ° C., specifically at least about 550 ° C., more specifically at least about 570 ° C. It does not emit CO ₂ . On the other hand, in the case of the (Cu, Zn, Al) hydrotalcite crystal structure, CO ₂ is generated by the decarboxylation reaction at a thermal decomposition temperature (typically about 600 to 700 ° C.) or more.

The second catalyst precursor prepared as described above, optionally undergoes a drying step, with typical drying temperatures ranging from about 80 to 120 ° C. (specifically about 95 to 110 ° C., more specifically about 100 to 105 ° C.). Can be. Thereafter, the dried second catalyst precursor (containing Cu, Zn and Al) is treated in the order of the calcination step and the reduction (activation) step as shown in FIG. 2 to change the composition and morphological characteristics, thereby changing Cu / ZnO / Al ₂ O ₃ -based catalyst will be formed.

In this regard, the calcination step is carried out under the conditions of an oxygen-containing atmosphere (eg air) to convert the metal components contained in the second catalyst precursor into the oxide form (ie CuO / ZnO / Al _2). Mixed oxides of O ₃ ). According to an exemplary embodiment, the calcination temperature can be adjusted, for example, in the range of about 300 to 700 ° C. (specifically about 350 to 500 ° C., more specifically about 400 to 450 ° C.) under the supply of oxygen (air). In addition, exemplary calcination times may range from, for example, about 2 to 7 hours, specifically about 3 to 6 hours. In addition, the heating rate during the calcination process may be, for example, about 0.1 to 20 ℃ / min, specifically about 2 to 10 ℃ / min range.

The catalyst converted to the oxide by the calcination step forms a Cu / ZnO / Al ₂ O ₃ -based catalyst by a reduction (activation) treatment, wherein the reduction treatment converts the oxide catalyst to a reducing gas (eg hydrogen and / or carbon monoxide). May be carried out in contact with Specifically, the reducing gas may be introduced and treated in the form of a mixed gas combined with an inert gas (nitrogen, argon, etc.). By way of example, the reduction treatment may be performed for about 1 to 24 hours under a temperature of about 250 to 350 ° C. (specifically about 270 to 320 ° C.) and a pressure of about 1 to 200 atmospheres (specifically about 10 to 100 atmospheres). Can be.

Conversion process of dimethyl ether from synthesis gas

According to one embodiment, the Cu / ZnO / Al ₂ O ₃ -based catalyst can be effectively applied to a process using a single reactor because of the high activity of converting the synthesis gas into dimethyl ether. In this case, the reaction conditions may be determined in consideration of the conversion of methanol in the reactor (specifically, a single reactor) and the conversion into dimethyl ether from a thermodynamic point of view, and typically, about 200 to 400 ° C., more typically about It may range from 230 to 350 ° C. In addition, in the case of the reaction pressure, it can be appropriately adjusted in consideration of reaction operability, for example, may be about 1 to 100 atm, specifically about 5 to 50 atm.

In this regard, FIG. 3 shows a process for preparing dimethyl ether from synthesis gas in a single reaction mode using a catalyst according to one embodiment of the present disclosure.

The feedstock synthesis gas mainly contains hydrogen and carbon monoxide and may further comprise CH ₄ and / or CO ₂ . In this regard, the molar ratio of H ₂ / CO in the synthesis gas may, for example, range from about 1 to 10, specifically about 1.5 to 5, more specifically about 1.8 to 3. If the amount of hydrogen does not reach the desired level, it is possible to increase the proportion of hydrogen in the feedstock by adding a water gas shift reaction (WGS) step in front of the reactor.

According to one embodiment, dimethyl ether may be prepared by batch and continuous modes, but in consideration of economical efficiency, such as continuous mode is preferred.

In the continuous mode, the reactor is not particularly limited, but, for example, a gaseous fixed bed reactor, a fluidized bed reactor, or the like may be used, and a fixed bed reactor may be advantageous. In this case, the gas hourly space velocity (GHSV) is determined by comprehensively considering the productivity and the conversion rate through catalytic contact. If too low, the productivity will be decreased, whereas if too high, the contact of the catalyst will be insufficient. will be. In view of this, the space velocity is, for example, about 1,000 to 100,000 cm 3 g _cat · h ⁻¹ , specifically about 1,500 to 20,000 cm 3 g _cat · h ⁻¹ , more specifically 2,000 to 10,000 cm 3 g _cat · h May range from ^-1 . However, it may be advantageous to selectively place a mixer in front of the reactor (eg fixed bed reactor) to pass the catalyst bed along with an inert gas (eg helium, nitrogen, etc.).

According to the illustrated embodiment, the unreacted feedstock may be introduced into the reactor in combination with the new feedstock by separating and recycling the dimethyl ether conversion process. However, it may be advantageous to recycle after separating and removing the water generated by the dehydration reaction.

The product may also contain methanol which is not converted to dimethylether during the reaction. In this regard, the CO conversion can be, for example, in the range of about 10 to 80%, specifically about 20 to 70%, more specifically about 40 to 65%, and the selectivity of dimethyl ether is about 5 to 85%, Specifically about 20 to 80%, more specifically about 40 to 70%.

In particular, the molar ratio of dimethylether / methanol in the reaction product may, for example, range from about 0.05 to 4, specifically from about 0.25 to 3, more specifically from about 0.25 to 2.5. Can be recovered separately. Thus, distillation (for example, distillation using a separation-wall column), gas-liquid separation (dimethyl ether separation through methanol liquefaction), etc. are mentioned as a method of separating dimethyl ether from methanol etc. In addition, as an optional step, dimethyl ether can be separated off and recovered and the remaining product can be recycled and introduced into the reactor with the fresh feedstock.

In the case of using a conventional Cu / ZnO / Al ₂ O ₃ -based catalyst, at least two reactors are used because they mainly show a conversion activity to methanol. In the first reactor, the synthesis gas is converted into methanol, while in the first reactor, The two-stage reactor which feeds | generates the produced | generated methanol into a 2nd reactor and dehydrates in presence of acid catalysts, such as a zeolite, and converts into dimethyl ether is used. But. In this embodiment, by using a Cu / ZnO / Al ₂ O ₃ -based catalyst which simultaneously provides good hydrogenation and dehydration reaction activity, it is possible to effectively prepare dimethyl ether from synthesis gas even when using a single reactor.

The present invention can be more clearly understood by the following examples, which are only intended to illustrate the present invention and are not intended to limit the scope of the invention.

Comparative Example 1

Preparation of Cu / ZnO / Al ₂ O ₃ Catalysts (CP-13, 30, 40) Using Conventional Coprecipitation

A catalyst having Al content of 13%, 30%, and 40% was synthesized by maintaining a ratio of Cu / Zn = 70/30 on an atomic basis using a conventional catalyst preparation method (co-precipitation, CP). As Cu ^{2 +} precursor in accordance with each of the Al content of _{Cu (NO 3) 2 · 3H} 2 O, Zn 2 + as a precursor _{Zn (NO 3) 2 · 6H} 2 O, and Al ^{3 +} as Al (NO ₃₎ precursor ₃ 9H ₂ O was separately prepared, then dissolved in 175.0 mL H ₂ O and injected at once. 4,200 mL H ₂ O was prepared in a 5 L glass vessel, 42.77 g of NaHCO ₃ was dissolved as precipitant and the temperature was set to 70 ° C. When reaching the set temperature, the Cu ^{+ 2} and Zn ^{2 +} precursor the precursor is a metal-containing precursor solution was injected into 14 mL / min using a master flex (masterflex).

The metal precursor solution was aged for 90 minutes, after which the precipitated material was recovered. In order to remove Na ⁺ and NO ₃ ⁻ in the precipitate, a total of four washing and filtering processes were repeated and dried in an oven set at 105 ° C. for 12 hours.

Subsequently, calcination was performed for 3 hours under a temperature condition of 400 ° C. (5 K / min) in a Muffle furnace, and 5% H ₂ / for 5 hours at 300 ° C. (5 K / min) prior to the reaction. It was used as a catalyst after a reduction process under N ₂ atmosphere.

Comparative Example 2

Reaction experiment for preparing dimethyl ether from synthesis gas using Cu / ZnO / Al ₂ O ₃ catalyst prepared by conventional coprecipitation

The reaction gas (H ₂ / CO / N ₂ = 63 / 31.5 / balance) was injected into the catalyst activated by the reduction treatment, pressurized to 50 bar, and the reaction was performed by heating up to 250 ° C. at a temperature increase rate of 5 K / min. (H ₂ / CO = 2). At this time, the space velocity (GHSV) is 2,000 ㎤ kg _cat ^-1 h ^- said been ^{1, the} product was analyzed by FID (flame ionized detector) of the on-line GC (gas chromatography) . The results are shown in Table 1 below.

Comparative Example 3

Preparation of Cu / ZnO-Based Catalysts (CZ)

Al ^{3 +} was precipitated with the exception that it does not inject the precursor and maintains the ratio of Cu / Zn = 70/30 according to the same manner as in Comparative Example 1, aging-calcination-treated in the order of the reduction catalyst (CZ) Prepared.

Comparative Example 4

Reaction experiment for preparing dimethyl ether from synthesis gas using Cu / ZnO-based catalyst (CZ)

A reaction for converting dimethyl ether from the synthesis gas was performed under the same reaction conditions except that the Cu / ZnO-based catalyst (CZ) prepared in Comparative Example 3 was used as the catalyst. The results are shown in Table 1 below.

Example 1

Preparation of Multifunctional Containing Cu / ZnO / Al ₂ O ₃ Catalysts (SP-13, 30, 40)

SP-13 with an Al content of 13% was prepared using sequential precipitation (SP) as follows:

As Cu ^{2 +} precursor in _{152.3 mL H 2 O Cu (NO} 3) 2 · 3H 2 O 31.21 g, Zn 2 + prepare a metal precursor solution and sufficiently dissolving _{Zn (NO 3) 2 · 6H} 2 O 16.64 g as precursor It was. When a precipitation agent, the temperature of the glass container with a NaHCO ₃ is dissolved has reached to 70 ℃, it was injected in the same way a metal precursor solution containing a precursor Cu ^{2 +} and Zn ^{2 +} precursors and in Comparative Example 1. Fig.

Thereafter, the change in pH was monitored while undergoing aging for 60 minutes. After the pH decreased determine, by dissolving _{Al (NO 3) 3 · 9H} 2 O 10.45 g as Al ^{3 +} precursor in 22.8 mL H ₂ O In order to introduce a function of the acid catalyst was injected into it. Thereafter, the precipitate was recovered by aging for an additional 30 minutes. Then, calcination and reduction treatments were performed in the same manner as in Comparative Example 1.

In addition, in the case of a catalyst having a different Al content ratio, a catalyst was prepared by preparing a metal precursor solution in accordance with the molar ratio of the metal.

Example 2

Reaction experiment for preparing dimethyl ether from synthesis gas using Cu / ZnO / Al ₂ O ₃ based catalyst according to the present disclosure

A reaction was performed in which dimethyl ether was converted from the synthesis gas under the same reaction conditions except that the Cu / ZnO / Al ₂ O ₃ based catalyst prepared in Example 1 was used as the catalyst. The results are shown in Table 1 and FIG. 4 (CO conversion: green bar, DME selectivity (red bar), DME yield of SP catalyst: blue filled circle, and CP catalyst). DME yield: shown in blue blank circle.

Metal content (%) Dimethyl ether synthesis results Cu Zn Al CO conversion rate (%) Dimethyl ether selectivity (%) Dimethyl ether production rate (g kg _cat ^-1 h ^-1 ) CZ 70.6 29.4 23.2 ± 1.5 0.7 ± 0.1 2.1 ± 0.2 SP-13 60.6 26.5 13.0 41.7 ± 0.8 21.3 ± 0.5 115.4 ± 4.9 SP-30 48.4 21.0 30.5 61.6 ± 1.4 54.3 ± 0.9 433.0 ± 15.4 SP-40 46.4 19.1 34.4 57.9 ± 0.3 51.9 ± 0.7 389.8 ± 4.4 CP-13 60.4 25.5 14.1 35.1 ± 0.7 7.0 ± 0.3 31.8 ± 0.9 CP-30 49.7 17.8 32.5 42.5 ± 0.9 26.6 ± 0.9 146.6 ± 5.4 CP-40 42.6 14.3 43.1 37.5 ± 0.3 37.6 ± 0.3 182.7 ± 2.5

In the tables and figures, the contents of Cu, Zn and Al were analyzed using ICP-AES, wherein the Cu / Zn ratio was fixed at about 70:30. However, the Al content ratio was up to about 5.6% from 13%, 30% and 40% of the set content, but was prepared to approximate the set content as a whole.

As a result of the reaction, in the case of the Cu / ZnO-based catalyst (CZ) in which the Al component was not mixed as in Comparative Example 3, the selectivity to dimethyl ether and its production rate were insignificant because it did not have an acid catalyst function for the dehydration reaction. .

In addition, in the case of the catalysts according to Example 1 (SP-13, SP-30 and SP-40), dimethyl ether compared to the catalysts according to Comparative Example 1 of the same composition (CP-13, CP-30 and CP-40) It was confirmed that the production rate of was increased by about 2 to 3 times. Specifically, when using the catalyst of Example 1 (SP-13) having an Al content of 13% dimethyl ether production rate is 115.4 g kg _cat ^-1 h ^-1 when using the catalyst of Comparative Example 1 (CP-13) The production rate of dimethyl ether increased more than three times compared to 31.8 g kg _cat ^-1 h ^-1 .

In addition, in the reaction using the catalyst of Example 1 (SP-30 and SP-40) having an Al content of 30% and 40%, respectively, the production rate of dimethyl ether was 433.0 g kg _cat ^-1 h ^-1 and 389.8, respectively. g kg _cat ^-1 h ^{- 1} . This is the production rate of dimethyl ether (146.6 g kg _cat ^-1 h ^-1 and 182.7 g kg _cat ^-1 ) measured in the reaction using the catalysts of Comparative Example 1 (CP-30 and CP-40) having substantially the same Al content h ^{- 1} ) about 2 to 3 times increase. That is, when the catalyst according to Example 1 is used, both the CO conversion rate and the dimethyl ether selectivity are increased to increase the production rate of dimethyl ether as a target product.

However, in the case of the reaction using the catalyst according to Comparative Example 1, in the conversion reaction of the synthesis gas composed of the multi-stage reaction mechanism to dimethyl ether, if the acid function is added and the dehydration reaction proceeds continuously, the thermodynamic equilibrium is advantageous and Al content is achieved. As this increase, the CO conversion rate increased to 35.1%, 42.5%, and 37.5%, while the hydrogenation reaction decreased, which is believed to limit the speed of dimethyl ether production.

In analyzing such differences in dimethyl ether yield, it is determined that the hydrogenation reaction, which is the first reaction in the multistage reaction, exhibits different activities depending on the crystal structure of the catalyst precursor. That is, in the catalyst preparation method according to Example 1, the catalyst precursor does not form a (Cu, Zn, Al) hydrotalcite structure ((Cu ₃ Zn ₃ Al ₂ (OH) ₁₆ CO ₃ )), so as to favor the activity As a result of the presence of the crystalline form (Cu _x Zn _{1- x} ) (OH) ₂ (CO ₃ ) and amorphous Al (OH) ₃ in a mixed form, it is determined that the CO conversion is increased.

Further, in Example 1 in a more improved acid function by adding a metal precursor ^{3 +} Al after formation of the crystalline form _{(Cu x Zn 1 -x) (} OH) 2 (CO 3) , and thus there is a precipitate containing additionally Al- It can be seen to increase the selectivity of dimethyl ether because it can be expressed.

However, in the case of the catalyst (SP-13) having an Al content of 13% in Example 1, compared to the catalysts (SP-30 and SP-40) of the other embodiment, the addition amount of the Al precursor during the manufacturing process was insufficient and partially Cu / Since Zn / Al hydrotalcite structure is produced, it is considered that there is a limit in increasing the hydrogenation reaction activity.

Catalyst Analysis According to Examples and Comparative Examples

-PH change with time when preparing catalyst precursor

The pH change of the catalyst precursor solution with time during the catalyst preparation process of Example 1 and Comparative Examples 1 and 3 was monitored and shown in FIG. 5.

Referring to FIG. 5, when a metal precursor solution is added dropwise to a precipitant solution having a pH of about 8, a precipitate is formed and a time point of decreasing pH during the aging process is shown. Also in the case of the catalyst (CZ) of Comparative Example 3, which does not contain Al, after the addition of the metal precursor to the precipitant solution, the pH decreases instantaneously during the aging process. This is a phenomenon observed when the Cu / Zn ratio is 70:30 because the amorphous initial particles are converted into crystalline particles of a specific composition.

In this regard, in the case of Comparative Example 1 in which the Al precursor is simultaneously added with the Cu precursor and the Zn precursor, the above-described form was not observed. On the other hand, in Example 1, since the initial particles composed of Cu and Zn are converted to a crystalline form, the Al precursor solution is added to prepare a catalyst, and thus a phenomenon of decreasing pH can be observed. These results suggest that the Al precursor should be added after the pH decrease occurs during the aging process after precipitation.

XRD and TG analysis of the catalyst precursor

Crystal structures of the catalyst (CP) according to Comparative Example 1 and the catalyst precursor according to Example 1 were evaluated through XRD (X-ray diffraction) analysis, and the results are shown in FIG. 6.

In the figure, the catalyst precursor SP of Example 1 is black, and the catalyst precursor CP of Comparative Example 1 is shown in gray. Also shown together is an enlarged graph at 2θ = 30-36 °, wherein the red and blue vertical bars are (Cu _x Zn _{1- x} ) (OH) ₂ (CO ₃ ) and Cu ₃ Zn, respectively. ₃ Al ₂ (OH) ₁₆ CO ₃ H ₂ O.

When the (Cu, Zn, Al) catalyst having a high Al content is prepared in the same manner as in Comparative Example 1, the (Cu, Zn, Al) hydrotalcite (Cu ₃ Zn ₃ Al) having the property of (003) surface appears ₂ (OH) ₁₆ CO ₃ H ₂ O) Crystal structure is synthesized. On the other hand, in Example 1, (Cu _x Zn _{1- x} ) (OH) ₂ (CO ₃ ), which is a crystal structure in which Cu is partially substituted with Zn, is formed. This can be confirmed through the phenomenon that the (20-1) plane moves to the right. That is, since no crystalline peak associated with Al was found in the crystal structure of the catalyst according to Example 1, it is expected that the Al metal precursor added thereto is amorphous.

Specifically, in Example 1, the reflection of the catalyst precursor at 14.66 °, 17.49 °, 24.11 ° and 32.32 ° was similar to that of the precursor (combination catalyst precursor) in Comparative Example 3 (CZ). In particular, (20-1) -d-spacing (2.768 kPa) at 32.32 ° for Comparative Example 3 (CZ) precursor was in the range of 32.06 to 32.31 ° despite the addition of significant amounts of Al. The corresponding d (20-1) value of 2.768-2.808 kV means that the precursor of the SP catalyst consists of a Cu / Zn atomic ratio of 70/30 to 80/20. Therefore, the addition of the Al precursor has little effect on the crystalline structure, which can be seen as the particles grew considerably during the aging process.

This crystal characteristic was not observed in the catalyst precursor (CP) of Comparative Example 1. In the catalyst precursor (CP) according to Comparative Example 1, the main structure shows the (003) -reflective property of the strong hydrotalcite at 11.84 ° as hydrotalcite, as such, as the Al content increases (e.g., More than 6.5 mol%), (Cu, Zn, Al) catalyst precursors having a crystal structure similar to hydrotalcite can be seen to form.

In contrast, in the case of the catalyst precursor (SP) according to Example 1, (Cu _x Zn _{1- x} ) (OH) ₂ (CO ₃ ) is formed in which the peak of 2θ = 11.84 ° is not observed in the XRD analysis result. It seems to be.

In addition, TG (thermogravimetric) analysis was performed by sedimenting only Al precursors separately to understand the Al-related morphology. Considering that m / z = 18, Al is determined to exist in the form of Al (OH) ₃ . Thus, the catalyst precursor prepared according to Example 1 can be seen that the crystalline form (Cu _x Zn _{1- x} ) (OH) ₂ (CO ₃ ) and amorphous Al (OH) ₃ is mixed.

Thermal stability analysis of catalyst precursors (TGA)

TG analysis was performed to evaluate the thermal stability of the catalyst precursors in Example 1 (SP) and Comparative Examples 1 and 3 (CP and CZ), respectively, and the results are shown in FIG. 7. At this time, the TG test was performed in combination with the product gas analysis.

According to the figure, the thermal stability of the catalyst precursor (CZ) of Comparative Example 3 showed a form similar to that of the catalyst precursor (SP) of Example 1. Specifically, two DTG peaks were observed, the first m / z = 18 and 44, the second only m / z = 44 was observed. In this regard, in the first decomposition reaction, it can be seen that the dehydroxylation reaction (dehydroxylation) in which OH is decomposed and the decarboxylation reaction (decarbonlyation) in which CO ₃ is decomposed simultaneously occur.

Meanwhile, CO ₃ decomposed at 400 ° C. or higher is HT-CO ₃ (high-temperature carbonate), which is known to play a role of connecting Cu and ZnO. The catalyst precursor (CP) prepared by the conventional coprecipitation method, the DTG peak was observed in the 100 to 200 ℃ and 600 to 700 ℃ section. This may be due to the (Cu, Zn, Al) hydrotalcite crystal structure as described in the previous XRD analysis.

It should be noted that the catalyst precursor SP according to Example 1 is substantially free of CO ₂ , especially in the thermal decomposition temperature zone of at least 500 ° C. Specifically, the thermal decomposition at 200 to 250 ° C. for the precursor of the catalyst (SP-40) of Example 1 releases H ₂ O from Al (OH) ₃ as supported by the thermal decomposition of pure Al precipitates. Corresponds to However, in the case of the SP-13 catalyst, since the hydrotalcite crystal was partially contained, a small amount of CO ₂ was released even in the pyrolysis temperature range exceeding 500 ° C.

-XRD analysis of oxide catalyst

 When the catalyst precursor is subjected to a heat treatment (firing) step, it is converted into a metal oxide form. The XRD analysis is performed while changing the Al content of the catalyst (SP) of Example 1 and the catalysts (CZ and CP) of Comparative Examples 1 and 3. Was performed. The results are shown in FIG.

As a result, CuO (tenorite) form appears in the catalyst having a Cu / Zn ratio of 70:30, but the CuO crystal structure was mainly observed in the catalysts prepared in Examples 1 and 3. Peak intensity of the catalyst (CZ) according to Comparative Example 3 was the highest, and both the catalysts according to Example 1 and Comparative Example 1 showed a tendency to decrease the peak intensity as the Al content increases.

However, in the case of the catalyst (CP) according to Comparative Example 1, compared with the catalyst (SP) according to Example 1, the width of the peak decrease was significantly increased, which is high thermal of the (Cu, Zn, Al) hydrotalcite crystal structure. It may be due to the stability. As such, when calcining the catalyst prepared according to Example 1, it was confirmed that a metal oxide catalyst having sufficient crystallinity in the form of CuO could be prepared. That is, the oxide catalyst prepared according to Example 1 has higher crystallinity than the catalyst according to the conventional production method (Comparative Example 1).

-Acid point evaluation of oxide catalyst

The acid point of the catalyst (SP) of Example 1 and the catalyst (CP) of Comparative Example 1 was evaluated. The acid point of the catalyst can be evaluated relatively by the temperature-programmed surface reaction of isopropanol, ie iso-propanaol temperature-programmed surface reaction (IPA-TPSR). IPA-TPSR is a technique for analyzing acid sites by identifying propylene fragments that are desorbed at elevated temperatures after adsorption of iso-propanol. 121-137), which is incorporated herein by reference.

In this evaluation, a series of reactions taking place on the acid site, i.e., iso-C ₃ H ₇ OH → C ₃ H ₆ + H ₂ O, C ₃ H ₆ → CH = CHCH ₃ + 0.5 H ₂ m / z = 41 CH = CHCH ₃ was monitored by quadruple mass spectroscopy (QMS), while isopropanol was adsorbed onto the sample at room temperature and then heated. In this evaluation, the relative ratio of the amount of acid points of the catalyst SP of Example 1 to the amount of acid points of the catalyst CP of Comparative Example 1 was measured.

The relative amount of acid point is the ratio of the acid point (A _SP ) of the catalyst of Example 1 to the acid point (A _CP ) of the catalyst of Comparative Example 1, and the total acid point, strong acid point and weak acid point (Ra _T , Ra _S and Ra _W). ) Was evaluated. The results are shown in Table 2 and FIG.

IPA-TPSR Results (A _SP / A _CP ) Ra _T Ra _S Ra _W 13% Al 1.03 1.10 0.94 30% Al 1.81 2.38 1.11 40% Al 2.15 2.81 1.14

According to the table, in 13% Al, almost no difference was observed between the catalyst of Comparative Example 1 (CP) and the catalyst of Example 1 (SP), but in the case of Al 30% and Al 40%, there was a significant difference in the ratio of strong acid points. There was. In particular, it has been observed that the catalysts (SP-30 and SP-40) according to Example 1 emit almost twice as much propylene fragment as 1.81 and 2.15 times the total area ratio, respectively.

9, the ion current spectra of the oxide catalyst (SP) of Example 1 and the oxide catalyst (CP) of Comparative Example 1 for the propylene fragment (m / z = 41) produced by the dehydration reaction of adsorbed isopropanol are Shown in black and gray, respectively, each spectrum was deconvolved into two peaks (orange and blue regions for SP and CP, respectively).

According to the figure, the two peaks at 96-114 ° C. and 182-204 ° C. were slightly shifted, meaning that the acid strengths of all the catalysts tested were similar. However, on the basis of the calculation of the relative total area (Ra _T ), it can be confirmed that the amount of the total acid point for the catalyst (SP) of Example 1 is very high. In addition, the relative areas of the strong acid point (Ra _S ) which induce the release of CH = CHCH ₃ at low temperature were 1.10 (SP-13), 2.38 (SP-30), and 2.81 (SP-40). These results can be explained by the catalyst according to Example 1 to increase the dehydration reaction rate for the conversion of methanol to dimethyl ether.

Specifically, the ratio of the strong acid point Ra _S at low temperature increased by approximately 3 times as the Al content increased. In addition, in the case of the weak acid point ratio (Ra _W ), the Al content showed a tendency to increase slightly.

From the above results, the acid point of the catalyst (SP) prepared according to Example 1 was more than two times higher than that of the catalyst (CP) prepared according to Comparative Example 1, thereby increasing the production rate of dimethyl ether by methanol dehydration reaction. It can be expected to be done.

-Measurement of copper specific surface area and evaluation of the effect on methanol synthesis

In order to prepare dimethyl ether from the synthesis gas, hydrogenation and dehydration reactions must be accompanied, and the copper specific surface area is used as an index of this hydrogenation reaction. Therefore, the catalyst (SP) according to Example 1 and the catalysts (CP and CZ) according to Comparative Examples 1 and 3, respectively, were analyzed through N ₂ O reactive frontal chromatography (N ₂ O-RFC) analysis in order to measure the copper specific surface area. The specific surface area of copper was measured while varying the Al content. The results are shown in Table 3 below.

Copper Specific Surface Area (m ² g ^-1 ) Example 1 Comparative Example 1 CZ 27.9 ± 2.3 13% Al 28.5 ± 2.0 32.2 ± 3.2 30% Al 28.8 ± 2.3 14.8 ± 2.2 40% Al 24.4 ± 2.0 14.5 ± 2.7

According to the table, in the catalyst of Comparative Example 1, the specific surface area of copper was 32.2 m ² with increasing Al content. g ^-1 to 14.5 m ² significantly reduced to g ⁻¹ . However, the copper specific surface area of the catalyst of Example 1 is 28.5 m ² g ^-1 , 28.8 m ² g ^-1 , and 24.4 m ² There was no significant decrease as g ⁻¹ . As such, the catalyst prepared according to Example 1 was able to maintain a high copper specific surface area in spite of an increase in Al content, and thus exhibited a copper specific surface area more than two times higher than that of the catalyst prepared according to Comparative Example 1.

In addition, the reaction of converting the synthesis gas to methanol while changing the Al content for the catalyst (SP) according to Example 1 and the catalysts (CP and CZ) according to Comparative Examples 1 and 3 respectively (reaction temperature: 230 ° C., reaction Pressure: 30 bar, reaction mixture: H ₂ / CO / CO ₂ / N ₂ , balance in reaction mixture: He, space velocity (GHSV): 60,000 cm 3 g _cat · h ^{− 1} , the yield of methanol was measured. The results are shown in FIG.

According to this figure, the catalyst (SP) of Example 1 showed a significantly higher methanol yield, especially at Al 30% and Al 40%, compared to the catalyst (CP) of Comparative Example 1.

Considering the results of the above-described evaluation of the syngas-to-DME (STD) activity of the synthesis gas, the catalyst (SP) of Example 1 was prepared in Comparative Example 1 in both methanol synthesis and dehydration reaction. It can be seen that it has higher activity than the catalyst (CP). That is, the catalyst of Example 1 can exhibit more improved STD conversion activity because it contains higher copper specific surface area and more acid point.

However, when the Al content is 13%, the catalyst of Example 1 (SP-13) was lower than that of Comparative Example 1 (CP-13) in terms of methanol synthesis yield.

HR-TEM analysis and EDS mapping analysis

HR-TEM analysis was performed to confirm the form in which the catalyst of Comparative Example 1 (CP-30) and Example 1 catalyst (SP-30) exist as an oxide. In addition, for the catalyst (SP-30) of Example 1, EDS mapping analysis (Cu: red, Zn: blue, Al: yellow) and composition profile analysis were performed separately. The results are shown in FIGS. 11 and 12.

According to FIG. 11, it can be seen that the catalyst (CP-30) of Comparative Example 1 is in a form in which Cu, Zn, and Al are evenly dispersed. On the other hand, according to Figure 12, although Cu and Zn are evenly dispersed in the particles, it can be seen that Al is agglomerated in a band form or a small size in the outer portion of the particles (arrows s and a are respectively of the amorphous alumina) Shell and small aggregates).

In addition, according to the TEM photographs in which the A and B regions were enlarged in the HR-TEM photograph of the catalyst (SP-30) of Example 1, amorphous and crystalline particles were present. In this case, as a result of calculating the electron diffraction pattern of the crystalline portion, it can be seen that the CuO is deformed to 2.52 Å. In addition, it was confirmed that the amorphous portion is an Al portion through mapping.

In addition, in the enlarged image of the C region of the HR-TEM image, a composition profile of Cu, Zn, and Al was obtained along the yellow line, and the amorphous Al covered the crystalline Cu / Zn with a thickness of about 75 nm. (Al ₂ O ₃ shell: 25 nm and Al-rich outer surface: 50 nm).

As such, the catalyst prepared according to Example 1 is present in a form in which Al is dispersed in the periphery of Cu / Zn particles or aggregated into small particles, rather than a form in which Cu, Zn and Al are evenly dispersed.

Simple modifications and variations of the present invention can be readily used by those skilled in the art, and all such variations or modifications can be considered to be included within the scope of the present invention.

Claims (20)

a) providing a metal precursor solution containing Cu ^{+ 2} and Zn ^{2 +} precursor precursor; b) forming the metal precursor solution in Cu ^{+ 2} and Zn ^{2 +} precursor The first catalyst precursor by crystallization of the precursor represented by _{Cu x Zn 1-x (OH} ) 2 CO 3; c) forming a second catalyst precursor by carrying out the precipitation by addition of Al ^{3 +} precursor to the first metal precursor; And d) calcining and reducing the second catalyst precursor; Method for producing a Cu / ZnO / Al ₂ O ₃ -based catalyst comprising a. The method of claim 1, wherein step b) b1) precipitating by combining the metal precursor solution with a basic precipitant solution; And b2) first aging the precipitate produced in step b1) to form a first catalyst precursor; Method for producing a Cu / ZnO / Al ₂ O ₃ -based catalyst comprising a. The method of claim 2, wherein step c) c1) the step of precipitation by addition of Al ^{3 +} precursor solution to said first catalyst precursor; And c2) secondary aging of the precipitate produced in step c1) to form a second catalyst precursor comprising Cu _x Zn _{1 - x} (OH) ₂ CO ₃ and Al (OH) ₃ ; Method for producing a Cu / ZnO / Al ₂ O ₃ -based catalyst comprising a. 3. The method of claim 2, wherein step c) is a step b2) of the process for producing Cu / ZnO / Al ₂ O ₃ catalyst, characterized in that is carried out after the pH decrease took place in. The method of claim 1 wherein the production of the second catalyst precursor is Cu / ZnO / Al ₂ O ₃ catalyst, characterized in that does not contain the hydrotalcite crystal structure. The Cu / ZnO / Al ₂ O ₃ system of claim 3, wherein the second catalyst precursor comprises crystalline Cu _x Zn _{1 - x} (OH) ₂ CO ₃ and amorphous Al (OH) ₃ . Method for preparing a catalyst. The method of claim 1 wherein the production of said first catalyst precursor is from 10 to 14 2θ ° range of the Cu / ZnO / Al ₂ O, characterized in that represents the XRD pattern does not contain a peak ₃ based catalyst. The method of claim 1 wherein the production of the second catalyst precursor is Cu / ZnO / Al ₂ O ₃ catalyst, it characterized in that the pyrolysis process does not release when CO ₂ at a temperature of at least 500 ℃. 2. The method of claim 1, wherein Cu ^{2 +} precursor is selected from copper nitrate, copper sulfate, copper acetate, formate, copper chloride (II), copper, copper iodide, and the group consisting of a combination thereof; The Zn ^{2 +} precursor is selected from zinc nitrate, zinc sulfate, zinc acetate, zinc formate, chloride (II) zinc, zinc iodide, and the group consisting of a combination thereof; And The method of the Al ^{3 +} precursor aluminum nitrate, aluminum sulfate, aluminum acetate, aluminum formate, aluminum iodide and the combination of Cu / ZnO / Al ₂ O wherein is selected from the group consisting of its _three-based catalyst as. In the method of producing a precipitation agent is an alkali metal or ammonium carbonate or bicarbonate of Cu / ZnO / Al ₂ O ₃ catalyst, characterized in that at least one is selected according to claim 2. 4. The method of claim 3, wherein the first aging step and the secondary maturing step process for producing a Cu / ZnO / Al ₂ O ₃ catalyst, characterized in that is carried out for at least 15 minutes each. The method of claim 1, wherein the calcination step is carried out under the supply of oxygen and temperature conditions of 300 to 700 ℃, The reduction step is a method for producing a Cu / ZnO / Al ₂ O ₃ catalyst, characterized in that carried out under a supply of reducing gas and temperature conditions of 250 to 350 ℃. Cu / ZnO / Al ₂ O ₃ based catalyst comprising crystalline Cu / ZnO and amorphous Al ₂ O ₃ as active ingredients, The catalyst comprises 30 to 60% Cu, 10 to 30% Zn and 13 to 40% Al on an atomic basis, Amorphous Al ₂ O ₃ is dispersed in the surface of crystalline Cu / ZnO and / or is present in a form that at least partially covers, and The specific surface area of Cu ranges from 10 to 35 m 2 / g. The catalyst of claim 13 wherein the atomic ratio of Cu / Zn in the catalyst is in the range of 50/50 to 80/20. The catalyst of claim 13, wherein the Cu / ZnO / Al ₂ O ₃ based catalyst has a form in which an amorphous Al ₂ O ₃ shell is formed on a crystalline Cu / ZnO core. The catalyst of claim 13 wherein the thickness of the amorphous alumina (Al ₂ O ₃ ) coating layer ranges from 25 to 100 nm. Providing a synthesis gas comprising CO and H ₂ as reactant; A product containing dimethyl ether is reacted by reacting the synthesis gas under the presence of a catalyst according to any one of claims 13 to 16, a temperature of 200 to 400 ° C. and a pressure of 1 to 100 atm using a single reactor. Forming; And Separating and recovering dimethyl ether from the product; Method for producing a dimethyl ether from a synthesis gas comprising a. 18. The process of claim 17, wherein the product contains methanol and dimethyl ether and the molar ratio of dimethyl ether to methanol in the product is in the range of 0.05-4. 18. The method of claim 17, further comprising the step of recycling components other than the separated dimethyl ether in the product to combine with the reactants. 18. The method of claim 17, wherein the single reactor is a continuous reactor, wherein the reaction of the synthesis gas is performed under a space velocity (GHSV) condition of 1,000 to 100,000 cm 3 g _cat · h ⁻¹ .

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