JP7611764B2 - Catalyst for producing acetone and method for producing acetone - Google Patents

Description

The present invention relates to a catalyst for producing acetone and a method for producing acetone.

There have been several reports on the synthesis of acetone from ethanol and water. Non-Patent Document 1 studies the use of a catalyst in which calcium oxide is added to zinc oxide. Non-Patent Document 2 studies the use of an oxide catalyst made of iron and various metal components. It is disclosed that in a continuous reaction using a catalyst that combines iron and zinc, the acetone yield after 24 hours changes from 86% to 57%. Patent Document 1 studies the use of a catalyst that contains iron, zinc, and an alkali metal and/or an alkaline earth metal, with a molar ratio of the alkali metal and/or alkaline earth metal to zinc of 0.2 to 2.

Journal of the Chemical Society, Chemical Communications, pp. 394-395 (1987) Journal of Materials Chemistry, Vol. 4, pp. 853-858 (1994)

Patent Publication 2012-240913

As mentioned above, there are several known methods for producing acetone from ethanol and water, but they do not have sufficient catalytic performance, and there is room for improvement in order to produce acetone stably.

The present invention has been made in consideration of these circumstances, and aims to provide a catalyst for acetone production that can stably produce acetone for a long period of time in the production of acetone from ethanol and water, and a method for producing acetone.

The present inventors conducted various studies to achieve the above object and came up with the present invention. That is, the present disclosure relates to a catalyst for producing acetone and a method for producing acetone, which contain one or more metals (Me) selected from the group consisting of magnesium, calcium, manganese, and zinc, iron, and aluminum.

The present disclosure aims to provide a catalyst for producing acetone that produces acetone in high yields and stably over a long period of time, and a method for producing acetone.

The present disclosure will be described in detail below. Note that a combination of two or more of the individual preferred embodiments of the present disclosure described below is also a preferred embodiment of the present disclosure.

[Catalyst for producing acetone according to the present disclosure]
<Catalyst>
The catalyst of the present disclosure comprises the elements of one or more metals selected from the group consisting of magnesium, calcium, manganese and zinc (Me), iron, and aluminum.

The catalyst of the present disclosure is not particularly limited and may contain other metal elements.

The state of the metal element contained in the catalyst of the present disclosure is not particularly limited, and examples thereof include a metal oxide containing the metal element, a carrier containing the metal element, and a carrier supporting the metal element. The metal oxide may be supported on a carrier.

The metal oxide may be a composite metal oxide.

Examples of composite metal oxides include spinel type, perovskite type, magnetoplumbite type, and garnet type, with the spinel type being preferred.

As the composite metal oxide, an iron composite _oxide (sometimes called ferrite) represented by the general formula _MeO.nFe2O3 (Me represents one or more metals selected from the group consisting of magnesium, _calcium , manganese and zinc, and n represents an integer of 1 to _{6 )} is preferable. Specific examples include MgO.Fe2O3 and _ZnO.Fe2O3 .

Carriers include activated carbon, silica, alumina, silica-alumina, zeolite, silica-calcia, zirconia, ceria, magnesia, diatomaceous earth, etc.

The shape of the carrier is not particularly limited, but examples include spheres, pellets, and honeycombs.

The BET specific surface area of the carrier is preferably 20 to 200 m2/g, and more preferably 40 to 200 m2/g. Using a carrier with a high specific surface area is preferable because it makes it easier for the catalyst components to be supported in a dispersed state, thereby increasing the catalytic activity.

The state of the aluminum element contained in the catalyst of the present disclosure is not particularly limited. It may be contained as a compound containing only aluminum as a metal, as an element of a composite metal oxide containing other metal elements, or as a carrier.

An example of a compound containing only aluminum as a metal is aluminum oxide. An example of a composite metal oxide containing other metal elements is a composite metal oxide of aluminum and Sn, Pb, Zn, Fe, In, or the like. Examples of a support include alumina (Al ₂ O ₃ ), silica-alumina, and the like. From the viewpoint of catalyst performance, Al ₂ O ₃ is more preferable.

In the catalyst of the present disclosure, the one or more metals (Me) selected from the group consisting of magnesium, calcium, manganese and zinc are preferably 0.4 to 0.7 moles per mole of iron, more preferably 0.4 to 0.6 moles, and even more preferably 0.45 to 0.55 moles. By setting the one or more metals (Me) selected from the group consisting of magnesium, calcium, manganese and zinc in the above molar range per mole of iron, good catalytic activity can be obtained.

In the catalyst of the present disclosure, the amount of aluminum per mole of iron is preferably 0.01 to 0.5 moles, more preferably 0.05 to 0.5 moles, and even more preferably 0.1 to 0.4 moles. By setting the amount of aluminum per mole of iron within the above molar range, good durability can be achieved.

The total amount of one or more metals (Me) selected from the group consisting of magnesium, calcium, manganese, and zinc, iron, and aluminum contained in the catalyst of the present disclosure is preferably 50 to 100 mass%, and more preferably 80 to 100 mass%, relative to 100 mass% of the catalyst.

<Catalyst manufacturing method>
The catalyst of the present disclosure may be produced by any method, including impregnation, precipitation, and coprecipitation. More preferably, the coprecipitation method is used. A coprecipitate (sometimes called a catalyst precursor) in which the metal elements constituting the catalyst are uniformly and highly dispersed can be obtained, which is preferable because it allows the production of a catalyst with excellent performance. The dispersion state of each catalyst component in the produced catalyst can be evaluated, for example, using an electron microprobe analyzer (EPMA). When using EPMA, the dispersibility of the metal component, for example aluminum, contained in the catalyst is measured by measuring the amount of X-rays in a plane of 900 μm in each of the X-axis and Y-axis directions on the catalyst surface, and the average value (S) and its standard deviation (σ) are obtained from any measured point. The dispersibility of aluminum contained in the catalyst can be evaluated by the ratio (σ/S) of the standard deviation (σ) to the average value (S). The value of the ratio (σ/S) is preferably less than 0.25, more preferably less than 0.2, and even more preferably less than 0.15.

The coprecipitation method may include the steps of adding a basic aqueous solution to a solution containing a metal (Me), iron, and aluminum to obtain a coprecipitate, filtering the coprecipitate, drying the obtained coprecipitate, and calcining the coprecipitate.

The amount of metal element in the solution can be changed as appropriate.

[Method of producing acetone according to the present disclosure]
In the production method of the present disclosure, acetone-containing gas is obtained by reacting ethanol with water in the presence of a catalyst.

<Reaction of ethanol with water>
The method for producing acetone disclosed herein can obtain a reaction product containing acetone, hydrogen, and carbon dioxide by contacting raw materials, ethanol and water, with a catalyst.

The acetone production method disclosed herein is not particularly limited and may be either a batch method or a continuous method, but a continuous method is preferred from the viewpoint of productivity.

The acetone production method of the present disclosure is preferably a gas phase reaction. Reaction formats for gas phase reactions include fixed bed, moving bed, and fluidized bed, but the more convenient fixed bed format is preferred.

When the acetone production method disclosed herein is a fixed bed type, the feed gas may be mixed with gaseous ethanol and gaseous water (sometimes called steam) and then supplied to the reactor to be brought into contact with the catalyst, or the gaseous ethanol and steam may be supplied separately to the reactor to be brought into contact with the catalyst.

Gaseous ethanol can be obtained, for example, by heating liquid ethanol in a vaporizer. Gaseous water can be obtained, for example, by heating water in a vaporizer.

The raw material gas may contain an inert gas such as nitrogen or helium. Here, raw material gas includes all gases supplied to the reactor.

The concentration of ethanol contained in the raw material gas is preferably 3 to 66 mol %, and more preferably 5 to 50 mol %.
The molar ratio of water to ethanol contained in the raw material gas is preferably 0.5 to 10, and more preferably 1 to 5.

The ethanol used for the raw material gas is not particularly limited. Examples include ethanol obtained by the hydration reaction of ethylene, and bioethanol made from biomass raw materials, such as carbohydrates such as sugar cane, starches such as grains, and cellulose such as plants.

It is preferable that the ethanol used in the raw gas contains bioethanol. The content of bioethanol contained in 100% by mass of ethanol is more preferably 50% by mass or more, even more preferably 75% by mass or more, and even more preferably 90% by mass or more.

The reaction pressure in the acetone production method disclosed herein can be reduced pressure, normal pressure, or increased pressure, but is preferably 0.07 MPa to 0.2 MPa, and more preferably 0.1 MPa to 0.15 MPa.

The reaction temperature in the acetone production method disclosed herein is preferably 250 to 600°C, more preferably 300 to 550°C, and even more preferably 330 to 500°C.

In the acetone production method disclosed herein, the space velocity is preferably 300 to 10,000 (1/h), more preferably 400 to 8,000 (1/h), and even more preferably 500 to 6,000 (1/h).

<Other processes>
(Refining process)
The reaction products after contacting ethanol and water with the catalyst may contain not only acetone, hydrogen, and carbon dioxide, but also the raw materials ethanol and water.

The amount of acetone contained in the reaction product is preferably 2 mol% or more, more preferably 4 mol% or more, and even more preferably 8 mol% or more, based on 100 mol% of the reaction product.

The acetone production method disclosed herein may include a step of obtaining purified acetone (sometimes called purified acetone) from the reaction product by a known method. For example, gas-liquid separation or distillation may be included.

Gas-liquid separation can be performed by known methods, for example, to separate the reaction product into gases such as hydrogen and carbon dioxide, and a liquid mixture mainly consisting of acetone. Distillation can be performed by known methods to obtain purified acetone from a liquid mixture containing acetone.

The content of acetone in the purified acetone is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 98% by mass or more, based on 100% by mass of purified acetone.

(Catalyst regeneration process)
In the acetone production method of the present disclosure, if a change in the activity of the catalyst is observed, a step of regenerating the catalyst may be included. The method of regeneration is not particularly limited, but the catalyst can be regenerated by contacting it with an oxidizing gas such as oxygen at high temperature. For example, when the raw material gas is supplied to a fixed-bed type reactor, the raw material gas may be changed to an oxidizing gas, or the catalyst may be extracted from the reactor.

[Acetone production apparatus according to the present disclosure]
The production apparatus is preferably a fixed-bed reactor, which may be connected to a vaporizer for obtaining a raw material gas.

The material of the manufacturing equipment is not particularly limited, but is preferably stainless steel. Representative examples of stainless steel include autenitic stainless steel, such as SUS304, SUS304L, SUS316, and SUS316L of the Japanese Industrial Standards (hereinafter referred to as JIS); ferritic stainless steel, such as SUS405, SUS401L, and SUS430 of the JIS; and martensitic stainless steel, such as SUS403, SUS410, SUS416, and SUS431 of the JIS.

[Uses of acetone according to the present disclosure]
The use of the acetone of the present disclosure is not particularly limited, but it can be suitably used as a raw material for the production of isopropyl alcohol. The acetone of the present disclosure can be hydrogenated by a known method to produce isopropyl alcohol.

The present invention will be explained in more detail below with reference to examples. However, the present invention is not limited to the following examples, and it is of course possible to carry out the invention with appropriate modifications within the scope of the above and below-mentioned aims, and all such modifications are included in the technical scope of the present invention.

Example 1
12.3 g of zinc nitrate hexahydrate (manufactured by Wako Pure Chemical Industries, Ltd., purity 99.0% or more), 4.7 g of aluminum nitrate hexahydrate (manufactured by Wako Pure Chemical Industries, Ltd., purity 97.0% or more), and 33.4 g of iron nitrate nonahydrate (manufactured by Nacalai Tesque, purity 98.0% or more) were dissolved in 400 mL of pure water to prepare a mixed aqueous solution of zinc nitrate, iron nitrate, and aluminum nitrate. While stirring the mixed aqueous solution with a magnetic stirrer, ammonia water (manufactured by Wako Pure Chemical Industries, Ltd., purity 28.0%) was added dropwise at room temperature to adjust the pH to 8.
The resulting precipitate was collected by filtration, dried at 120°C for 10 hours, and then calcined at 450°C for 2 hours to obtain catalyst 1. Elemental analysis of the obtained catalyst 1 was performed using an X-ray fluorescence analyzer. The measurement sample was prepared by filling the powder of catalyst 1, which had been uniformly ground in an agate mortar, into a polyvinyl chloride disk, and compressing it at 30 MPaG using a compression molding machine to form a disk. As a result, the molar ratios of zinc and aluminum to iron in catalyst 1 were 0.44 and 0.12, respectively.
The crystal structure of the obtained catalyst 1 was analyzed by powder X-ray diffraction. The obtained diffraction pattern was almost identical to the pattern of ZnFe ₂ O ₄ (JCPDF 00-022-1012), and no diffraction peaks derived from ZnO or Al ₂ O ₃ were detected.
Acetone production using catalyst 1 was carried out using a SUS316 tubular reactor (outer diameter 10 mm, inner diameter 8 mm). The powder of catalyst 1, which was uniformly ground in an agate mortar, was packed into a vinyl chloride disk, compressed into a disk shape at 30 MPaG using a compression molding machine, crushed and classified to 0.71 to 1.18 mm, and 1.4 g of the granular catalyst was packed into a SUS tubular reaction tube. The reaction tube packed with catalyst 1 was placed in a circular electric furnace, nitrogen was supplied at 26.25 mL/min. (0°C, 1 atm equivalent), and the temperature was raised to 400°C by heating the electric furnace and maintained at that temperature for 30 min. Thereafter, nitrogen, ethanol, and water were supplied at 26.25 mL/min. (0°C, 1 atm equivalent), 5.22 mL/min. (0°C, 1 atm equivalent), and 20.89 mL/min., respectively. (0° C., 1 atm equivalent) and the reaction was carried out. The reaction was carried out continuously for 142 hours, and the ethanol conversion rate and acetone yield were measured with the passage of reaction time. The results are shown in Table 1.

Here, the ethanol conversion rate and the acetone yield were calculated according to the formulas (1) and (2).
(Equation 1)

(Equation 2)

The synthesis reaction of acetone from ethanol and water is represented by the following reaction formula (3).
(Equation 3)

The acetone yield in formula (2) is evaluated based on the amount of carbon in the acetone produced relative to the total carbon contained in the ethanol supplied to the reactor inlet. Therefore, the maximum acetone yield is 75%.

The reactor outlet gas was introduced into an absorption bottle containing pure water placed in an ice-water bath, and the components captured by the water were quantified using a gas chromatograph. Components that were not captured by the absorption bottle containing pure water were quantified by introducing the absorption bottle outlet gas into a gas chromatograph. The flow rates of each component contained in the reactor outlet gas were calculated from these analytical values, and the ethanol conversion rate and acetone yield were calculated using the above formulas (1) and (2).

(Comparative Example 1)
9.2 g of zinc nitrate hexahydrate (manufactured by Wako Pure Chemical Industries, Ltd., purity 99.0% or more) and 25.1 g of iron nitrate nonahydrate (manufactured by Nacalai Tesque, purity 98.0% or more) were dissolved in 400 mL of pure water to prepare a mixed aqueous solution of zinc nitrate and iron nitrate. While stirring the mixed aqueous solution of zinc nitrate and iron nitrate with a magnetic stirrer, ammonia water (manufactured by Wako Pure Chemical Industries, Ltd., purity 28.0%) was added dropwise at room temperature to adjust the pH to 8. The obtained precipitate was collected by filtration, dried at 120 ° C. for 10 hours, and then calcined at 450 ° C. for 2 hours to obtain catalyst 2.

Elemental analysis of the obtained catalyst 2 was performed by fluorescent X-ray analysis in the same manner as in Example 1, and the molar ratio of zinc to iron was found to be 0.44.

The crystal structure of catalyst 2 was examined by powder X-ray diffraction in the same manner as in Example 1. The obtained diffraction pattern was almost identical to the pattern of ZnFe ₂ O ₄ (JCPDF 00-022-1012), and no diffraction peaks of ZnO were detected.

Acetone production using catalyst 2 was carried out in the same manner as described in Example 1. The reaction was carried out continuously for 137.5 hours, and the ethanol conversion rate and acetone yield were measured over the reaction time. The results are shown in Table 2.

(Comparative Example 2)
3.74 g of zinc nitrate hexahydrate (manufactured by Wako Pure Chemical Industries, purity 99.0% or more) and 1.09 g of strontium nitrate (manufactured by Wako Pure Chemical Industries, purity 98.0% or more) were dissolved in 4.0 g of pure water to prepare an aqueous solution containing zinc and strontium. The aqueous solution containing zinc and strontium was added to 10.03 g of iron hydroxide oxide (manufactured by Kanto Chemical, purity 95.0% or more) that had been thoroughly dried at 120°C, and the mixture was kneaded with a glass rod for 5 minutes to form a slurry-like substance. This slurry-like substance was dried at 120°C for 10 hours and then calcined at 600°C for 3 hours to obtain catalyst 3.

Elemental analysis of the obtained catalyst 3 was performed by fluorescent X-ray analysis in the same manner as in Example 1, and the molar ratios of zinc and strontium to iron were found to be 0.12 and 0.05, respectively.

The crystal structure of Catalyst 3 was analyzed by powder X-ray diffraction in the same manner as in Example 1, and the diffraction peaks of Fe ₂ O ₃ (JCPDF 00-001-1053) and ZnO (JCPDF 00-005-0593) were detected in the obtained diffraction pattern.

Acetone production using catalyst 3 was carried out in the same manner as described in Example 1. The reaction was carried out continuously for 137 hours, and the ethanol conversion rate and acetone yield were measured over the reaction time. The results are shown in Table 3.

(Comparative Example 3)
3.00g of zinc nitrate hexahydrate (manufactured by Wako Pure Chemical Industries, purity 99.0% or more), 0.87g of strontium nitrate (manufactured by Wako Pure Chemical Industries, purity 98.0% or more), and 6.50g of aluminum nitrate hexahydrate (manufactured by Wako Pure Chemical Industries, purity 97.0% or more) were dissolved in 6.0g of pure water to prepare an aqueous solution containing zinc and strontium. The aqueous solution containing zinc, strontium, and aluminum was added to 8.02g of iron oxide hydroxide (manufactured by Kanto Chemical, purity 95.0% or more) that had been thoroughly dried at 120°C, and the mixture was kneaded with a glass rod for 5 minutes to form a slurry-like substance. This slurry-like substance was dried at 120°C for 10 hours and then calcined at 600°C for 3 hours to obtain catalyst 4.

Elemental analysis of the obtained catalyst 4 was performed by X-ray fluorescence analysis in the same manner as in Example 1, and the molar ratios of zinc, strontium, and aluminum to iron were 0.12, 0.05, and 0.2, respectively.

The crystal structure of Catalyst 4 was analyzed by powder X-ray diffraction in the same manner as in Example 1, and the diffraction peaks of Fe ₂ O ₃ (JCPDF 00-001-1053) and ZnO (JCPDF 00-005-0593) were detected in the obtained diffraction pattern.

Acetone production using catalyst 4 was carried out in the same manner as described in Example 1. The reaction was carried out continuously for 112 hours, and the ethanol conversion rate and acetone yield were measured over the reaction time. The results are shown in Table 4.

Example 2
The catalyst 1 prepared in Example 1 was compressed, crushed, and classified into 0.71 to 1.18 mm, and 0.7 g of the granular catalyst was packed into a SUS tubular reaction tube. The reaction tube packed with catalyst 1 was placed in a circular electric furnace, nitrogen was supplied at 70 mL/min. (0°C, 1 atm equivalent), and the temperature was raised to 400°C by electric furnace heating and maintained for 30 min. Thereafter, the reaction temperature was changed to a predetermined temperature, and nitrogen, ethanol, and water were supplied at 70 mL/min. (0°C, 1 atm equivalent), 13.9 mL/min. (0°C, 1 atm equivalent), and 55.7 mL/min. (0°C, 1 atm equivalent), respectively, to carry out the reaction. The ethanol conversion rate and acetone yield at 400, 425, and 450°C were measured. The results are shown in Table 5.

(Comparative Example 5)
30.12 g of zinc nitrate hexahydrate (manufactured by Wako Pure Chemical Industries, purity 99.0% or more) was dissolved in 400 mL of pure water to prepare an aqueous zinc nitrate solution. While stirring the aqueous zinc nitrate solution with a magnetic stirrer, ammonia water (manufactured by Wako Pure Chemical Industries, purity 28.0%) was added dropwise at room temperature to adjust the pH to 7. The resulting precipitate was collected by filtration and dried at 120 ° C for 10 hours to prepare zinc hydroxide. 0.335 g of calcium hydroxide (manufactured by Wako Pure Chemical Industries, purity 99.0% or more) was added to 4.0 g of the obtained zinc hydroxide, and a small amount of water was added and thoroughly kneaded in a mortar. The obtained kneaded product was dried at 120 ° C for 10 hours and then calcined at 500 ° C for 2 hours to obtain catalyst 5.

An acetone production test was carried out in the same manner as in Example 2, except that catalyst 1 was replaced with catalyst 5, and the ethanol conversion rate and acetone yield were measured at 450 and 475°C. The results are shown in Table 6.

Claims (7)

Metals (Me) consisting of zinc , iron, and aluminum,
_A catalyst for producing acetone , comprising spinel ferrite ( _{MeFe2O4 ) and} Al2O3 . The catalyst for producing acetone according to claim 1, in which the number of moles of aluminum per mole of iron is 0.01 to 0.5. The catalyst for producing acetone according to claim 1 or 2, in which the number of moles of the metal (Me) per mole of iron is 0.4 to 0.7. A method for producing acetone from ethanol and water in the presence of a catalyst, the catalyst comprising a metal (Me) consisting of zinc, iron, and aluminum,
A method for producing acetone _, comprising spinel ferrite ( _{MeFe2O4 ) and} Al2O3 . 5. The method for producing acetone according to claim 4 , wherein the number of moles of aluminum per mole of iron contained in the catalyst is 0.01 to 0.5. 6. The method for producing acetone according to claim 4 or 5 , wherein the number of moles of the metal (Me) per mole of iron contained in the catalyst is 0.4 to 0.7. The method for producing acetone according to any one of claims 4 to 6 , wherein the ethanol is derived from biomass.