Catalyst for dimethyl ether, method of producing catalyst and method of producing dimethyl ether

Abstract: A catalyst suitable for producing dimethyl ether comprises alumina particles having an average size of 200 µm or less and a methanol synthesis catalyst layer formed around each of the alumina particles. The methanol synthesis catalyst has a weight ratio of 0.05 to 5 to a weight of the alumina particles. The catalyst is produced by forming a layer comprising a methanol synthesis catalyst around each of alumina particles. The dimethyl ether is produced by the method of foming a slurry by introducing the catalyst into a solvent and introducing a mixed gas comprising carbon monoxide and hydrogen into the slurry.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst for producing dimethyl ether, and a method for producing dimethyl ether by using the catalyst. 2. Description of the Related Arts Synthesis of dimethyl ether proceeds following the three equilibrium reactions shown below. CO + 2H 2  CH 3 OH 2CH 3 OH  CH 3 OCH 3 + H 2 O H 2 O + CO  H 2 + CO 2 Fig. 1 shows reaction equilibria of H 2 , CO, methanol, CO 2 , and water, on the basis of reactions (1), (2), and (3). There are several known methods for manufacturing dimethyl ether starting from a mixed gas of carbon monoxide, carbon dioxide, and hydrogen under the presence of a catalyst suspended in a solvent. For example, JP-A-2-9833 (the term "JP-A-" referred to herein signifies "Unexamined Japanese patent publication"), JP-A-3-181435, JP-A-3-52835, JP-A-4 264 046 (corresponding to EP-A-0 483 609), WO 93/10069 (corresponding to EP-A-0 591 538) disclose methods for manufacturing dimethyl ether or a mixture of dimethyl ether and methanol through the contact of a synthesis gas with a mixture of a methanol synthesis catalyst and a methanol dehydration catalyst suspended in an inert liquid. The method disclosed in JP-A-2-9833 is a method of direct synthesis of dimethyl ether from a synthesis gas, which method comprises the step of contacting a synthesis gas consisting of hydrogen, carbon monoxide and carbon dioxide with a solid catalyst, or reacting the synthesis gas react under the presence of the solid catalyst to conduct catalytic synthesis of dimethyl ether from the synthesis gas, wherein the synthesis gas undergoes catalytic action under the presence of the solid catalyst system, and wherein the solid catalyst is a single catalyst or a mixture of plurality of catalysts which are suspended in a liquid medium in a three-phase (slurry phase) reactor system, and wherein the three-phase reactor system comprises at least a single three-phase reactor. The method disclosed in JP-A-3-181435 is a method for manufacturing dimethyl ether from a mixed gas of carbon monoxide and hydrogen, or a mixed gas of carbon monoxide and hydrogen and further containing carbon dioxide and/or water vapor, wherein a catalyst is used in a slurry form by suspending thereof in a solvent. The method disclosed in JP-A-3-52835 is a method of dimethyl ether synthesis characterized in that a synthesis gas is reacted under the presence of a solid methanol synthesis catalyst to produce methanol, and that the produced methanol is reacted under the presence of a solid dehydration catalyst to produce dimethyl ether. According to the method, dimethyl ether is synthesized from a synthesis gas consisting of hydrogen, carbon monoxide, and carbon dioxide. That is, the synthesis gas is contacted with a solid catalyst system comprising a methanol-synthesizing ingredient and a dehydrating (ether-forming) ingredient, wherein the solid catalyst system is a single catalyst or a mixture of plurality of catalysts in a three-phase (liquid phase) reactor system, and wherein the reactor system is controlled to keep the minimum effective methanol rate to at least a level of 1.0 g-mole of methanol per 1 kg of catalyst per hour. The method disclosed in WO 93/10069 (EP-A-0 591 538) is a method for manufacturing dimethyl ether from a mixed gas containing carbon monoxide and either or both of water and water vapor, or from a mixed gas containing carbon monoxide and either or both of water and water vapor and further containing carbon dioxide, wherein a catalyst is used in a form of solvent slurry, which catalyst is prepared by pulverizing a mixed catalyst containing at least zinc oxide and, copper oxide or chromium oxide, and aluminum oxide, by adhering these ingredients together under pressure, and by pulverizing them again to suspend in the solvent. On the other hand, dimethyl ether is synthesized generally in a fixed bed system. There is a known catalyst for fixed bed system, which catalyst is prepared by depositing a methanol synthesis catalyst onto a support of metallic oxide such as alumina, then by calcining them together. (JP-A-2-280386) The methods for manufacturing dimethyl ether disclosed in JP-A-2-9833, JP-A- 3-52835, JP-A-4-264046 (EP-A- 0 483 609), and JP-A-3-181435, however, raise problems such that the two kinds of or three kinds of catalysts suspended in a solvent separate from each other in the reactor owing to the difference in specific gravity among the methanol synthesis catalyst, the methanol dehydration catalyst, and the water gas shift catalyst, which induces a distribution in catalyst concentration or deposition of one of these catalysts, thus significantly degrading the use efficiency of the catalysts. The catalyst disclosed in WO 93/10069 (EP-A-0 591 538) is prepared by integrating the above-described three kinds of catalysts by means of a mechanical method. That type of catalysts also raises a problem that, during a period of use in a slurry state, the catalyst particles separate from each other to induce a distribution in catalyst concentration and catalyst deposition. SUMMARY OF THE INVENTION It is an object of the present invention to provide a catalyst suitable for producing dimethyl ether at a high yield and a method for producing dimethyl ether at a high space time yield. To attain the object, the present invention provides a catalyst suitable for producing dimethyl ether obtainable by a method comprising the steps of: (a) preparing a methanol synthesis catalyst, a methanol dehydration catalyst, a water gas shift catalyst and a solvent; (b) calculating an A value regarding the methanol synthesis catalyst, the methanol dehydration catalyst and the water gas shift catalyst using an average particle size of the catalyst, a particle density of the catalyst and a density of the solvent, the A value being defined by the following equation: A = D 2 (P-S), where D denotes the average particle size of the catalyst, (cm), P denotes the particle density of the catalyst, (g/cm 3 ), and S denotes the density of the solvent, (g/cm 3 ), (c) controlling at least one of the group consisting of the average particle size of the catalyst, the particle density of the catalyst and the density of the solvent to maintain differences in the A values within ± 1 x 10 -6 g/cm among the methanol synthesis catalyst, the methanol dehydration catalyst, and the water gas shift catalyst; (d) after the step(c), suspending the methanol synthesis catalyst, the methanol dehydration catalyst, and the water gas shift catalyst in the solvent. Furthermore, dimethyl ether can be produced by the method comprising the introduction of a mixed gas containing carbon monoxide and hydrogen into the above catalyst. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing reaction equilibria of H 2 , CO, methanol, CO 2 and H 2 O. DETAILED DESCRIPTION OF THE INVENTION The inventors developed a method for manufacturing a catalyst to produce dimethyl ether, which method comprises: suspending a methanol synthesis catalyst, a methanol-dehydration catalyst, and a water gas shift catalyst in a solvent while maintaining the difference in an A value within ± 1 x 10 -6 g/cm among the methanol synthesis catalyst, the methanol-dehydration catalyst, and the water gas shift catalyst, wherein the A is defined by an equation of A = D 2 (P - S), where D denotes average particle size of catalyst concerned, (cm), P denotes particle density of catalyst concerned, (g/cm 3 ), and S denotes solvent density, (g/cm 3 ). The inventors found that the use of thus prepared catalyst in a slurry state achieved the production of dimethyl ether at a high yield and a high space time yield from a mixed gas of carbon monoxide and hydrogen, or further containing carbon dioxide and/or water vapor. Thus the inventors completed the present invention. According to the present invention, each of the methanol synthesis catalyst, the methanol-dehydration catalyst, and the water gas shift catalyst is prepared under a control of the particle density and the particle size, then they are mixed together by a physical means. As a result, the method according to the present invention ensures prompt progress of the reaction described below to improve the yield of dimethyether by making the distance among these catalysts close by each other while preventing separation thereeach during the reaction period. That is, the reaction proceeds in sequent order of: yielding methanol on the methanol synthesis catalyst from carbon monoxide and hydrogen; moving the methanol onto the methanol-dehydration catalyst to yield dimethyl ether and water by dehydration-condensation; moving the water onto the water gas shift catalyst and/or the methanol synthesis catalyst to yield hydrogen by the reaction of the water with carbon monoxide. The reaction is expressed by the formulae given below. CO + 2H 2 → CH 3 OH 2CH 3 OH → CH 3 OCH 3 + H 2 O CO + H 2 O → CO 3 + H 2 The catalyst according to the present invention basically comprises a methanol synthesis catalyst, a methanol-dehydration catalyst, and a water gas shift catalyst. Since, however, the methanol synthesis catalyst is inherently an excellent water gas shift catalyst, the methanol synthesis catalyst may function also the water gas shift catalyst. Methanol synthesis catalyst may be copper oxide - zinc oxide - alumina system and zinc oxide - chromium oxide - alumina system. A preferable mixing ratio of individual ingredients of copper oxide, zinc oxide, and alumina is: in an approximate range of from 0.05 to 20 wt.parts of zinc oxide to 1 wt.parts of copper oxide, more preferably in an approximate range of from 0.1 to 5 wt.parts; in an approximate range of from 0 to 2 wt.parts of alumina, more preferably in an approximate range of from 0 to 1 wt.parts. A preferable mixing ratio of individual ingredients of zinc oxide, chromium oxide, and alumina is: in an approximate range of from 0.1 to 10 of chromium oxide to 1 wt.parts of zinc oxide, more preferably in an approximate range of from 0.5 to 5; and in an approximate range of from 0 to 2 wt.parts of alumina, more preferably in an approximate range of from 0 to 1 wt.parts. Applicable methanol-dehydration catalyst includes γ-alumina, silica-alumina, and zeolite. Examples of metallic oxide ingredient in zeolite are oxide of alkali metal such as sodium and potassium, and oxide of alkali earth metal such as calcium and magnesium. Examples of water gas shift catalyst are copper oxide - zinc oxide system and iron oxide - chromium oxide system. A preferable ratio of copper oxide to zinc oxide is in an approximate range of from 0.1 to 20 wt.parts of copper oxide to 1 wt.parts of iron oxide, more preferably in an approximate range of from 0.5 to 10. A preferable ratio of iron oxide to chromium oxide is in an approximate range of from 0.1 to 20 wt.parts of chromium oxide to 1 wt.parts of iron oxide, more preferably in an approximate range of from 0.5 to 10. A copper (including copper oxide) - alumina system is a catalyst which functions both as methanol-dehydration catalyst and as water gas shift catalyst. Each of these methanol synthesis catalyst, methanol-dehydration catalyst, and water gas shift catalyst may be manufactured by known methods. For example, water soluble salt of each metallic ingredient is used to prepare an aqueous solution containing these salts. The kind of salt is either inorganic salt or organic salt. Nevertheless, a salt that likely generates hydroxide in water is not suitable one. Nitrate, carbonate, organic acid salt, and halide are applicable as the salt. A preferable concentration of each ingredient is in an approximate range of from 0.1 to 3 mole/l. A base is added to the aqueous solution to neutralize thereof and to precipitate hydroxide. Then the solid is separated from liquid, which is then rinsed and dried, followed by calcining to obtain the target catalyst. Alternatively, a commercial catalyst may be used. The mixing ratio of above-described methanol synthesis catalyst, methanol-dehydration catalyst, and water gas shift catalyst is not specifically limited, and is selected at an adequate ratio responding to the kind of each ingredient and the reaction condition. A preferable mixing ratio is often in an approximate range of from 0.5 to 10 wt.parts of methanol-dehydration catalyst per 1 wt.parts of methanol synthesis catalyst, and in an approximate range of from 0 to 5 wt.parts of water gas shift catalyst per 1 wt.parts of methanol synthesis catalyst. The difference in value of A that is derived from the above-described equation among individual catalyst types is within ± 1 x 10 -6 g/cm which was given before, and preferably within ± 5 x 10 -7 g/cm. If the difference in A value exceeds ± 1 x 10 -6 , then the conversion of carbon monoxide decreases. The method for controlling the value A is not specifically limited. Generally, however, the control is carried out based mainly on the average particle size and the particle density of catalyst concerned because the density of solvent shows no significant change. If only the average particle size is kept constant, the particle density does not show significant change. Accordingly, the control of average particle size is a simple control method. Pulverization by ball mill is a method for controlling the average particle size. The determination of average particle size is done by sieve method (JIS Z8801-1982), sedimentation method, or other methods. The determination of particle density is carried out by picnometer method (JIS R-5201) and buoyancy method (JIS R6125). The catalyst is used as a slurry with a solvent. The amount of catalyst in the solvent depends on the kind of the solvent, the reaction conditions, and other variables. Normally, the amount of catalyst is in a range of from 1 to 50 wt.% to the amount of the solvent. The kind of solvent used for synthesizing dimethyl ether according to the present invention is arbitrarily selected if only the solvent is in liquid phase under the reaction condition. Examples of the solvent are hydrocarbons of aliphatic, aromatic, and alicyclic groups, alcohol, ether, ester, ketone, halide, or their mixture. Alternatively, gas oil after removing sulfur ingredients, vacuum gas oil, high boiling point distillates of coal tar after treated by hydrogenation are also applicable as the solvent. By passing a mixed gas of carbon monoxide and hydrogen through thus prepared slurry of catalyst with solvent, dimethyl ether is obtained at a high yield. Applicable range of molar mixing ratio of hydrogen to carbon monoxide (H 2 /CO) is wide, for instance, in a range of from 20 to 0.1 as (H 2 /CO), and more preferably from 10 to 0.2. According to the reaction system, the mixed gas does not directly contact with the catalyst, which direct contact occurs in a gas-solid catalytic reaction system, but the carbon monoxide and hydrogen contact with catalyst only after dissolved into a solvent. Consequently, selection of an adequate kind of solvent taking into account of the solubility of carbon monoxide and hydrogen to the solvent establishes a constant composition of carbon monoxide and hydrogen in the solvent independent of the gas composition, and sustains the supply of the mixed gas at an established composition to the catalyst surface. In the case of a mixed gas with significantly low ratio of (H 2 /CO), for example, 0.1 or less, or in the case of sole carbon monoxide without containing hydrogen, it is necessary to separately supply steam to convert a part of the carbon monoxide into hydrogen and carbon dioxide within the reactor. Since solvent exists between the raw material gases and the catalyst, the gas composition does not necessarily agree with the composition on the catalyst surface. Therefore, it is acceptable that the mixed gas of carbon monoxide and hydrogen, or sole carbon monoxide gas includes relatively high concentration of carbon dioxide (in a range of from 20 to 50%). The manufacturing method according to the present invention significantly reduces the effect of ingredients that may act as catalyst-poison on the catalyst compared with the gas-solid contact catalyst system. Examples of the catalyst-poisoning ingredients which may exist in the raw material gas are sulfur compounds such as hydrogen sulfide, cyan compounds such as hydrogen cyanide, and chlorine compounds such as hydrogen chloride. Even when the catalyst decreased its activity resulted from poisoning, the productivity of total reactor system is maintained at a constant level by withdrawing the slurry from the reactor and by charging fresh slurry containing catalyst of high activity to the reactor. The reaction heat is recovered in a form of medium pressure steam using a cooling coil installed inside of the reactor while passing hot water through the cooling coil. The cooling system controls the reaction temperature at arbitrary level. A preferable reaction temperature is in a range of from 150 to 400°C, and particularly preferable in a range of from 200 to 350 °C. The reaction temperature below 150 °C and above 400 °C degrades the conversion of carbon monoxide. A preferable reaction pressure is in a range of from 10 to 300 kg/cm 2 , and particularly preferable in a range of from 15 to 150 kg/cm 2 . The reaction pressure below 10 kg/cm 2 results in a low conversion of carbon monoxide, and that above 300 kg/cm 2 requires special design of reactor and is uneconomical because of the need of large amount of energy for pressurizing the system. A preferable space velocity (charge rate of mixed gas per 1 g of catalyst under standard condition) is in a range of from 100 to 50000 ml/g.h, and particularly preferable from 500 to 30000 ml/g·h. The space velocity above 50000 ml/g·h degrades the conversion of carbon monoxide, and that below 100 ml/g·h is uneconomical because of the need of an excessively large reactor. Example I. Preparation of catalyst 1) Preparation of catalyst [1] Each of 185 g of copper nitrate (Cu(NO 3 ) 2 3H 2 O), 117 g of zinc nitrate (Zn(NO 3 ) 2 6H 2 O), and 52 g of aluminum nitrate (Al(NO 3 ) 3 9H 2 O) were dissolved into about 1 liter of ion-exchanged water. Separately, about 200 g of sodium carbonate (Na 2 CO 3 ) was dissolved into about 1 liter of ion-exchanged water. Both of the solutions were added dropwise to about 3 liters of ion-exchanged water in a stainless steel vessel which was controlled at about 60 °C within about 2 hours. while maintaining the contents to pH 7.0 ± 0.5. Then, the contents were allowed to stand for about 1 hour for aging. When, during the treatment, the pH value went out from a range of pH 7.0 ± 0.5, either of an aqueous solution of about 1 mole/liter nitric acid or an aqueous solution of about 1 mole/liter sodium carbonate was added dropwise to keep the range of pH 7.0 ± 0.5. The resulted precipitate was filtered, and the cake was rinsed by ion-exchanged water until nitric acid ion was not detected anymore. After the rinse, the cake was dried at 120 °C for 24 hours. followed by calcining thereof in air at 350 °C for 3 hours, to obtain the catalyst [1]. Analysis of thus obtained catalyst [1] gave the composition as CuO:ZnO:Al 2 O 3 = 61:37:7 (by weight). 2) Preparation of catalyst [2] Each of 91 g of copper nitrate (Cu(NO 3 ) 2 3H 2 O) and 256 g of zinc nitrate (Zn(NO 3 ) 2 6H 2 O) were dissolved into about 1 liter of ion-exchanged water. Separately, about 130 g of sodium carbonate (Na 2 CO 3 ) was dissolved into about 1 liter of ion-exchanged water. Both of the solutions were added dropwise to about 3 liters of ion-exchanged water in a stainless steel vessel which was controlled at about 60 °C within about 2 hours, while maintaining the contents to pH 8.5 ± 0.5. Then, the contents were allowed to stand for about 1 hr for aging. When, during the treatment, the pH value went out from a range of pH 8.5 ± 0.5, either of an aqueous solution of about 1 mole/l nitric acid or an aqueous solution of about 1 mole/liter sodium carbonate was added dropwise to keep the range of pH 8.5 ± 0.5. The resulted precipitate was filtered, and the cake was rinsed by ion-exchanged water until nitric acid ion was not detected anymore. After the rinse, the cake was dried at 120 °C for 24 hours. followed by calcining thereof in air at 350 °C for 3 hours. to obtain the catalyst [2]. Analysis of thus obtained catalyst [2] gave the composition as CuO:ZnO = 3:7 (by weight). 3) Preparation of catalyst [3] An 100 g of alumina (N612, Nikki Kagaku Co.) was dried in air at 120 °C for 24 hours. followed by calcining in air at 450 °C for 3 hours to obtain the target alumina catalyst [3]. 4) Preparation of catalyst [4] A 15.7 g of copper acetate (Cu(CH 3 COO) 2 H 2 O) was dissolved into about 200 ml of ion-exchanged water. A 95 g aliquot of alumina catalyst prepared in the step 3) was further added to the mixture. The mixture was then vaporized to dry. The dried material was further dried in air at 120 °C for 24 hours. followed by calcining in air at 450 °C for 3 hours. The calcined material was treated in hydrogen gas stream at 400 °C for 3 hours to obtain the catalyst [4]. Analysis of the catalyst gave the composition as Cu:Al 2 O 3 = 5:95 (by weight). 5) Preparation of catalyst [5] A 736 g of aluminum nitrate (Al(NO 3 ) 3 9H 2 O) was dissolved into about 2 liters of ion-exchanged water. Separately, about 350 g of sodium carbonate (Na 2 CO 3 ) was dissolved into about 2 liters of ion-exchanged water. Both of the solutions were added dropwise to about 3 liters of ion-exchanged water in a stainless steel vessel at room temperature within about 2 hours while maintaining the contents to pH 7.5 ± 0.5. Then, the contents were allowed to stand for about 1 hour for aging. When, during the treatment, the pH value went out from a range of pH 7.5 ± 0.5, either of an aqueous solution of about 1 mole/liter nitric acid or an aqueous solution of about 1 mole/liter sodium carbonate was added dropwise to keep the range of pH 7.5 ± 0.5. The resulted precipitate was filtered, and the cake was rinsed by ion-exchanged water until nitric acid ion was not detected anymore. After the rinse, the cake was dried at 120 °C for 24 hours. followed by calcining thereof in air at 350 °C for 3 hours to obtain alumina. Then, 15.7 g of copper acetate (Cu(CH 3 COO) 2 H 2 O) was dissolved into about 200 ml of ion-exchanged water. A 95 g aliquot of the prepared alumina was added to the mixture, which mixture was then evaporated to dry. The dried material was further dried in air at 120 °C for 24 hours followed by calcining in air at 450 °C for 4 hours. The calcined material was treated in hydrogen gas stream at 400 °C for 3 hours. to obtain the catalyst [5]. Analysis of thus obtained catalyst [5] gave the composition as CuO:Al 2 O 3 = 5:95 (by weight). Example 1 The catalyst [1] was pulverized in a ball mill to fine powder having an average particle size of 16.9 µm. The catalyst [2] was pulverized in a ball mill to fine powder having an average particle size of 15.6 µm. The catalyst [3] was pulverized in a ball mill to fine powder having an average particle size of 15.5 µm. A 2.4 g aliquot of the fine powder of catalyst [1], an 1.2 g aliquot of the fine powder of catalyst [2], and an 1.2 g aliquot of the fine powder of catalyst [3] were physically mixed together. Example 2 The catalyst [1] was pulverized in a ball mill to fine powder having an average particle size of 16.9 µm. The catalyst [4] was pulverized in a ball mill to fine powder having an average particle size of 15.2 µm. A 2.4 g aliquot of the fine powder of catalyst [1] and an 1.2 g aliquot of the fine powder of catalyst [4] were physically mixed together. Example 3 A 2.4 g aliquot of the fine powder of catalyst [1] having an average particle size of 14.4 µm and an 1.2 g aliquot of the fine powder of catalyst [4] having an average particle size of 12.9 µm were physically mixed together. Example 4 A 2.4 g aliquot of the fine powder of catalyst [1] having an average particle size of 16.9 µm and an 1.2 g aliquot of the fine powder of catalyst [5] having an average particle size of 18.4 µm were physically mixed together. Comparative Example 1 Catalysts were mixed conforming to the procedure of. Example 1 except that the average particle size of the catalyst [2] was 20.1 µm and that the average particle size of the catalyst [3] was 18.5 µm. Comparative Example 2 Catalysts were mixed conforming to the procedure of Example 2 except that the average particle size of the catalyst [4] was 12.9 µm. II. Method for activating catalyst and reaction method A 24 g of n-hexadecane (31.1 ml) was charged to a bubble-tower reactor having 2 cm of inside diameter and 2 m of height, and 3.6 g of each of the above-described catalyst powders was added to make the contents of the reactor in a suspended state. A mixed gas of hydrogen, carbon monoxide, and nitrogen (at a molar ratio H 2 :CO:N 2 of 1:1:9) was introduced to pass through the bubble-tower at a flow rate of about 300 ml/min. While flowing the mixed gas through the bubble-tower, the temperature in the bubble-tower was gradually raised from room temperature to 220 °C within a period of several hours. At the same time, the concentration of nitrogen in the mixed gas was gradually reduced to a final level of zero. Then, the reaction system was held at 220 °C for about 3 hours to activate the catalyst. The reaction was conducted at a specified temperature and pressure while introducing the mixed gas of hydrogen, carbon monoxide, and carbon dioxide at a molar ratio of H 2 /CO/CO 2 = 47.5/47.5/5.0 and at a flow rate of 336 ml/min. (converted at a condition of normal temperature and pressure). The obtained reaction products and non-reacted substances were analyzed by gas chromatography. III. Reaction conditions and experimental results The reaction conditions and experimental results are shown in Tables 1 and 2. Conversion of dimethylether(%) = Charge rate of dimethylether - Discharge rate of non - reacted dimethyleter Charger rate of dimethyleter × 100 Yield of methanol(%) = 1 2 × Yielding rate methanol Charge rate of dimethyleter × 100 Yield of hydrocarbons(%) = Σ[n/2 × yielding rate of hidrocabons (number of carbons : n) Charge rate of dimethylether = × 100 Yield of CO 2 (%) = 1 4 × Yielding rate of CO 2 Charge rate of dimethylether × 100 Example 1 Example 2 Example 3 Catalyst Catalyst No. 1 ○ 2 ○ 3 ○ 1 ○ 4 ○ 1 ○ 4 ○ Particle Density(g/cm 2 ) 28.2 3.17 3.20 2.82 3.31 2.82 3.31 Particle size(cm) × 10 4 16.9 15.6 15.5 16.9 15.2 14.4 12.9 Weight(g) 2.4 1.2 1.2 2.4 1.2 2.4 1.2 Value of A(g/cm) × 10 5 5.85 5.83 5.83 5.85 5.86 4.25 4.22 Condition Temperature (°C) 280 280 280 Pressure (kg/cm 2 -G) 30 30 30 Reaction Result CO conversion (%) 40.1 53.9 52.1 Yield (C-mol%) Dimethyl ether 31.2 36.2 34.0 Methanol 2.5 2.5 2.6 Hydrocarbons 1.2 0.8 0.5 CO 2 5.5 14.4 15.0 Dimethyl ether space time yield (g/kg-cat·h) 853 990 930 Example 1 Comparative example 1 Comparative example 2 Catalyst Catalyst No. 1 ○ 5 ○ 1 ○ 2 ○ 3 ○ 1 ○ 4 ○ Particle Density(g/cm 2 ) 2.82 2.50 2.82 3.17 3.20 2.82 3.31 Particle size(cm) × 10 4 16.9 18.4 16.9 20.1 18.5 16.9 12.9 Weight (g) 2.4 1.2 2.4 2.4 1.2 2.4 1.2 Value of A (g/cm) × 10 5 5.85 5.85 5.85 9.68 8.31 5.85 4.22 Condition Temparature (°C) 280 280 280 Pressure (kg/cm 2 -G) 30 30 30 Reaction Result CO conversion (%) 52.7 33.4 41.6 Yield (C-mol%) Dimethylether 35.1 23.3 26.9 Methanol 2.1 1.2 2.0 Hydrocarbons 0.9 0.8 0.5 CO 2 14.6 8.1 12.2 Dimethyl ether space time yield (g/kg-cat·h) 960 637 736 The catalyst for manufacturing dimethyl ether according to the present invention provides effects of preventing separation of individual catalyst ingredients from each other during reaction, of assuring smooth progress of reaction cycle, and of achieving high dimethyl ether yield owing to the controlled particle density and particle size for each of the methanol synthesis catalyst, the methanol-dehydration catalyst, and the water gas shift catalyst conforming to a derived equation. The method for manufacturing dimethyl ether according to the present invention uses a slurry of solvent with a catalyst comprising a methanol synthesis catalyst, a methanol-dehydration catalyst, and a water gas shift catalyst being integrated together, so the method provides effects of achieving high space time yield of dimethyl ether, of being free from problems of plugging of catalyst and of mechanical strength of catalyst, of easiness for removing reaction heat and for controlling reaction heat, of assuring wide application range of the ratio of carbon monoxide to hydrogen, of progress of reaction under the presence of high concentration of carbon dioxide, and of less influence of impurities and catalyst poisons.

Claims: A catalyst suitable for producing dimethyl ether obtainable by the method comprising the steps of: (a) preparing a methanol synthesis catalyst, a methanol dehydration catalyst, a water gas shift catalyst and a solvent; (b) calculating an A value regarding the methanol synthesis catalyst, the methanol dehydration catalyst and the water gas shift catalyst using an average particle size of the catalyst, a particle density of the catalyst and a density of the solvent, the A value being defined by the following equation: A = D 2 (P - S), where D denotes the average particle size of the catalyst, (cm), P denotes the particle density of the catalyst, (g/cm 3 ), and S denotes the density of the solvent, (g/cm 3 ), (c) controlling at least one of the average particle size of the catalyst, the particle density of the catalyst and the density of the solvent to maintain differences in the A values within ± 1 x 10 -6 g/cm among the methanol synthesis catalyst, the methanol dehydration catalyst, and the water gas shift catalyst; (d) after the step (c), suspending the methanol synthesis catalyst, the methanol dehydration catalyst, and the water gas shift catalyst in the solvent. The catalyst of claim 1, wherein the methanol synthesis catalyst comprises copper oxide, zinc oxide and alumina. The catalyst of claim 1 or 2, wherein the methanol synthesis catalyst has a weight ratio of the copper oxide: the zinc oxide: the alumina being 1 : (0.05 to 20) : (0 to 2). The catalyst of claim 1, wherein the methanol synthesis catalyst comprises zinc oxide, chromium oxide and alumina. The catalyst of claim 4, wherein the methanol synthesis catalyst has a weight ratio of the zinc oxide: the chromium oxide: the alumina being 1 : (0.1 to 10) : (0 to 2). The catalyst of any one of claims 1-5, wherein the methanol dehydration catalyst is at least one selected from the group consisting of γ-alumina, silica-alumina and zeolite. The catalyst of any one of claims 1 to 6, wherein the water gas shift catalyst comprises iron oxide and chromium oxide or copper oxide and zinc oxide. A method for producing dimethyl ether, wherein the method comprises introducing a mixed gas comprising carbon monoxide and hydrogen into the catalyst of any of claims 1 to 7. The method of claim 8, wherein the mixed gas further comprises carbon dioxide. The method of claim 8 or 9, wherein the mixed gas further comprises water vapour.

Inventors: FUJIMOTO KAORU, MIZUGUCHI MASATSUGU, OGAWA TAKASHI, OHNO YOTARO, ONO MASAMI, SHIKADA TSUTOMU, FUJIMOTO, KAORU, MIZUGUCHI, MASATSUGU, OGAWA, TAKASHI, OHNO, YOTARO, ONO, MASAMI, SHIKADA, TSUTOMU, Mizuguchi, Masatsugu, Int. Prop. Dept., NKK Corp., Ogawa, Takashi, Int. Prop. Dept., NKK Corp., Ohno, Yotaro, Int. Prop. Dept., NKK Corp., Ono, Masami, Int. Prop. Dept., NKK Corp., Shikada, Tsutomu, Int. Prop. Dept., NKK Corp.
Applicants: JFE HOLDINGS INC, JFE HOLDINGS, INC.
Application year: 1997
Main classification: B01J23
IPC codes: G06Q20, B01J23, C07C41, B01J37