Method for producing propylene

Abstract

To provide a method for producing propylene that allows enhancement of a carbon-based yield of propylene.SOLUTION: A method for producing propylene according to one embodiment of the present invention includes a reaction step of supplying a fresh feedstock and a recycle feedstock to a reactor to obtain a crude product, a gas-liquid separation step of separating the crude product into a gas phase and a liquid phase, a propylene recovery step of recovering propylene from the gas phase, and a recycle step of recovering the recycle feedstock from the liquid phase.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing propylene. [Background technology]

[0002] Non-Patent Document 1 describes a method for producing propylene using ethanol as a raw material. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Iwamoto, M. et al., Pulse and IR study on the reaction pathways for the conversion of ethanol to propene over scandium-loaded indium oxide catalysts, ACS Catal., 4(10), 3463-3469, 2014 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above-mentioned conventional techniques have a problem in that the yield of propylene on a carbon basis is low.

[0005] An object of one aspect of the present invention is to provide a method for producing propylene that can increase the carbon-based yield of propylene. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, a method for producing propylene according to one embodiment of the present invention includes a reaction step of supplying a fresh raw material containing ethanol and acetone and a recycled raw material containing acetone to a reactor and reacting them to obtain a crude product; a gas-liquid separation step of separating the crude product into a gas phase containing propylene and a liquid phase containing acetone; a propylene recovery step of recovering propylene from the gas phase; and a recycling step of recovering the recycled raw material from the liquid phase. [Effects of the Invention]

[0007] According to one aspect of the present invention, the carbon-based yield of propylene can be increased. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing a process for producing propylene according to one embodiment of the present invention. [Figure 2] FIG. 1 is a process flow diagram used in the process simulation of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0009] A propylene production method according to one embodiment of the present invention will be described in detail below with reference to FIG. 1. FIG. 1 is a schematic diagram showing an example of an apparatus used in the propylene production method according to one embodiment of the present invention. The propylene production method according to one embodiment of the present invention includes a reaction step in which a fresh feedstock containing ethanol and acetone and a recycled feedstock containing acetone are supplied to a reactor and reacted to obtain a crude product, a gas-liquid separation step in which the crude product is separated into a gas phase containing propylene and a liquid phase containing acetone, a propylene recovery step in which propylene is recovered from the gas phase, and a recycling step in which the recycled feedstock is recovered from the liquid phase. The recycled feedstock recovered in the recycling step is supplied to the reaction step.

[0010] (Reaction step) The reaction step is a step in which a fresh raw material containing ethanol and acetone and a recycled raw material containing acetone are supplied to a reactor and reacted to obtain a crude product. The reaction step is carried out, for example, in the reactor shown in Figure 1, and the fresh raw material and the recycled raw material are supplied to the reactor.

[0011] In this specification, the term "fresh raw material" refers to a raw material newly supplied to the reactor from outside the reaction system. The fresh raw material may be purchased or recovered from a reaction system other than the present reaction system. The fresh raw material may be a biomass raw material. The term "recycled raw material" described below refers to a raw material containing at least acetone that is recovered from the liquid phase separated in the gas-liquid separation process. The term "raw material" refers to a mixture of the fresh raw material and other components (including recycled raw materials) supplied to the reactor. The ethanol is not particularly limited, but examples that can be used include biomass-derived ethanol, ethanol produced from carbon dioxide and hydrogen as raw materials, and ethanol produced from waste gas containing hydrogen and carbon dioxide separated in the propylene recovery process described below. These ethanols can be used alone or in combination of two or more.

[0012] Examples of carbon oxides that can be used as raw materials for ethanol include carbon oxides produced by decomposing biomass, carbon oxides produced from fossil fuels, carbon oxides generated during the process of using fossil resources as energy, carbon oxides generated during the production of steel or chemical products, carbon oxides produced using plastics as raw materials, and carbon dioxide recovered from the air. These carbon oxides can be used alone or in combination of two or more. Examples of hydrogen that can be used as raw materials for ethanol include hydrogen derived from fossil fuels and / or hydrogen produced by electrolysis of water. Acetone is not particularly limited, but examples include acetone obtained by fermentation and / or acetone produced using aromatic peroxides as raw materials. In addition to ethanol and acetone, the fresh raw materials and recycled raw materials may contain at least one selected from the group consisting of oxygenated hydrocarbons such as isopropanol and acetaldehyde, and water. When the fresh raw material contains oxygenated hydrocarbons such as isopropanol and acetaldehyde, oxygenated hydrocarbons such as isopropanol and acetaldehyde obtained by fermentation or oxygenated hydrocarbons such as isopropanol and acetaldehyde derived from fossil raw materials can be used, although there are no particular limitations on these.

[0013] In the reaction step, the molar ratio of acetone contained in the fresh feedstock to ethanol contained in the fresh feedstock supplied to the reactor is preferably 0.010 or more, more preferably 0.25 or more, and even more preferably 0.30 or more. Furthermore, this molar ratio is preferably 1.70 or less, more preferably 1.60 or less, and even more preferably 1.50 or less. Having this molar ratio within this range can further increase the carbon-based propylene yield. Here, the carbon-based propylene yield is the ratio of the number of moles of carbon contained in the propylene recovered in the propylene recovery step to the total number of moles of carbon contained in ethanol, acetone, isopropanol, and oxygenated hydrocarbons such as acetaldehyde contained in the fresh feedstock supplied to the reactor.

[0014] The molar ratio of the total acetone to the total ethanol contained in the fresh and recycled feedstocks supplied to the reactor is preferably 0.010 or more, more preferably 0.25 or more, and even more preferably 0.30 or more, and is preferably 1.7 or less, more preferably 1.60 or less, and even more preferably 1.50 or less.

[0015] The crude product obtained in the reaction step contains at least propylene and acetone, and may further contain ethanol and / or isopropanol. The crude product obtained in the reaction step may also contain light-boiling components (e.g., acetaldehyde) having a boiling point lower than that of acetone.

[0016] From the viewpoint of increasing the carbon-based yield of propylene, the carbon-based propylene concentration in the crude product at the reactor outlet is preferably 5% or more, more preferably 10% or more, and even more preferably 15% or more. Here, the carbon-based propylene concentration is the ratio of the number of moles of carbon contained in propylene at the reactor outlet to the total number of moles of carbon contained in the product gas at the reactor outlet, excluding inert components, which is supplied from the crude product to the reactor.

[0017] From the viewpoint of increasing the carbon-based yield of propylene, the carbon-based acetone concentration in the crude product at the reactor outlet is preferably 1% or more, more preferably 5% or more, and even more preferably 10% or more. Here, the carbon-based acetone concentration is the ratio of the number of moles of carbon contained in acetone at the reactor outlet to the total number of moles of carbon contained in the product gas, excluding inert components, supplied to the reactor from the crude product at the reactor outlet.

[0018] In the reaction step, it is preferable to also supply water to the reactor. In the reaction step, when ethanol undergoes a dehydration reaction, ethylene as a by-product may be produced. However, by supplying water to the reactor, the production of ethylene as a by-product can be reduced. As a result, the carbon-based yield of propylene can be increased. The amount of water supplied to the reactor is preferably 10 mol % or more, more preferably 20 mol % or more, and even more preferably 30 mol % or more, relative to 100 mol % of the total amount of ethanol and acetone.

[0019] In the reaction step, ethanol and acetone are preferably gasified, supplied to a reactor, and contacted with a catalyst. The catalyst may be any catalyst for producing propylene from ethanol and acetone. For example, a catalyst containing 50% by mass or more but less than 100% by mass of component (A), which is zirconium oxide, and more than 0% by mass but less than 50% by mass of component (B), which is at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, calcium, strontium, barium, scandium, yttrium, cerium, titanium, vanadium, chromium, copper, silver, gold, gallium, germanium, and tin (where the total mass of component (A) and component (B) is taken as 100% by mass) can be used.

[0020] The element (B) may be in the form of a simple substance or an oxide of the element. When the element is in the form of an oxide, the mass of the element (B) is the mass of the element contained in the oxide, excluding the mass of oxygen. The element (B) may be at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, calcium, strontium, barium, scandium, yttrium, titanium, vanadium, chromium, copper, silver, gold, gallium, germanium, and tin.

[0021] The raw material and the catalyst may be brought into contact in a reactor, or the raw material and the catalyst may be brought into contact with each other and then supplied to the reactor. The raw material may be a liquid or a gas. An example of a method for bringing the raw material into contact with the catalyst is a method in which the raw material is heated to gasify it and the gasified raw material is supplied to a reactor pre-filled with a catalyst.

[0022] The reactor may be any reactor capable of bringing the raw material into contact with the catalyst. Examples of the reactor include a fixed-bed reactor, a fluidized-bed reactor, and a batch reactor. From the viewpoint of reaction heat, the reactor may be an adiabatic reactor, an isothermal reactor, or a heat exchange reactor.

[0023] The reaction temperature is preferably 270 to 700°C, more preferably 300 to 650°C, and even more preferably 350 to 550°C.

[0024] The reaction pressure is preferably 10 kPa to 100,000 kPa, and more preferably 100 kPa to 1,000 kPa.

[0025] From the viewpoint of stabilizing the composition of the gas supplied to the reaction step and stabilizing the operating conditions of the reactor, the propylene production method according to one embodiment of the present invention preferably further includes a dehydration step of separating water from the crude product obtained in the reaction step. In the dehydration step, the amount of water removed is preferably 10% or more, more preferably 30% or more, based on the number of moles of acetone contained in the fresh raw material.

[0026] (Gas-liquid separation process) The gas-liquid separation step is a step of separating the crude product obtained in the reaction step into a gas phase containing propylene and a liquid phase containing acetone. The gas-liquid separation step is performed, for example, in the gas-liquid separator shown in Figure 1, and the crude product obtained in the reactor is supplied to the gas-liquid separator.

[0027] The gas-liquid separation step may be performed by any method capable of separating the majority of propylene contained in the crude product into a gas phase and the majority of acetone into a liquid phase. Therefore, a small amount of acetone may be contained in the gas phase. The liquid phase may contain not only acetone but also ethanol, and may further contain light-boiling components having a boiling point lower than that of acetone (for example, dissolved gas components such as propylene, and acetaldehyde).

[0028] The method for separating the crude product into a gas phase containing propylene and a liquid phase containing acetone is not particularly limited, and examples thereof include a method of separation by pressurization or cooling. When separation is performed by cooling, the cooling temperature can be adjusted depending on the pressure in the system, for example, to a temperature at which 50% or more of the acetone is present in the liquid phase and 50% or more of the propylene is present in the gas phase.

[0029] (Propylene recovery process) The propylene recovery step is a step of recovering propylene (referred to as product propylene) from the gas phase separated in the gas-liquid separation step. In the propylene recovery step, it is sufficient if propylene can be recovered by any of the following (i) to (iii).

[0030] (i) The gas phase is recovered as product propylene.

[0031] (ii) The gas phase is pressurized and condensed components containing propylene are recovered as product propylene.

[0032] (iii) The condensed components obtained in (ii) are distilled to recover the product propylene.

[0033] (ii) is carried out, for example, in the booster in Fig. 1, and the gas phase separated in the gas-liquid separator is supplied to the booster. (iii) is carried out, for example, in the propylene distillation column in Fig. 1, and the condensed components obtained in (ii) are supplied to the propylene distillation column, where they are distilled and separated into product propylene and waste oil. From the viewpoint of increasing the degree of purification of the recovered propylene, it is preferable to purify and recover propylene by at least one of methods (ii) and (iii), and it is more preferable to purify and recover propylene by method (iii).

[0034] The pressure in (ii) is not particularly limited, but may be any pressure at which propylene can be condensed. A lower pressure reduces the amount of power required for compression, while a higher pressure increases the amount of condensed propylene. Therefore, it is preferable to select an appropriate pressure for each device.

[0035] The distillation in (iii) is not particularly limited, but existing propylene distillation techniques in naphtha crackers, propane dehydrogenation, catalytic cracking processes, and the like can be used.

[0036] The condensed component may contain oxygenated hydrocarbons such as acetaldehyde and acetone. In the propylene recovery step, it is preferable to further recover a condensed component containing oxygenated hydrocarbons such as acetaldehyde and acetone. The recovered liquid phase is preferably supplied to at least one step selected from the group consisting of a reaction step, a gas-liquid separation step, and a recycle step. In this way, by recycling not only the oxygenated hydrocarbons such as acetaldehyde and acetone contained in the recycled raw material but also the oxygenated hydrocarbons such as acetaldehyde and acetone contained in the condensed component, the carbon-based yield of propylene can be increased. Furthermore, in the propylene recovery step, a liquid phase containing oxygenated hydrocarbons such as acetaldehyde and acetone, which is the residue remaining after distillation of the condensed component obtained in (iii), is further recovered. The liquid phase may be supplied to at least one step selected from the group consisting of a reaction step, a gas-liquid separation step, and a recycle step.

[0037] The carbon-based yield of propylene obtained in the propylene recovery step is preferably 30 mol%, more preferably 45 mol% or more, even more preferably 50 mol% or more, and even more preferably 55 mol% or more. The upper limit of the carbon-based yield of propylene obtained in the propylene recovery step is the higher the better, and may be, for example, 92 mol% or less, 85 mol% or less, 80 mol% or less, or 75 mol% or less.

[0038] Alternatively, hydrogen (H2) and carbon dioxide (CO2) may be recovered from the gas phase, which is the residue remaining after the pressure increase in (ii). For example, a pressure swing adsorption (PSA) device may be used to separate the waste gas containing hydrogen (H2) and carbon dioxide (CO2), and the hydrogen may be recovered as a product.

[0039] The recovered propylene can be used as a raw material for polypropylene, propylene oxide, aromatic hydrocarbons, aromatic alcohols, etc., and methods for producing these are also included within the scope of the present invention.

[0040] (Recycling process) The recycling step is a step of recovering a recycled material containing acetone from the liquid phase separated in the gas-liquid separation step. The recycled material recovered in the recycling step is supplied to the reaction step. A method for recovering the recycled material from the liquid phase includes, for example, distilling the liquid phase to recover the recycled material. The recycled material may further contain oxygenated hydrocarbons such as ethanol, acetaldehyde, and isopropanol, and preferably contains ethanol and / or isopropanol. The recycling step is carried out, for example, in the recycled material distillation column shown in FIG. 1. The liquid phase separated in the gas-liquid separator is supplied to the recycled material distillation column, the recycled material recovered in the recycled material distillation column is supplied to the reactor, and water is discharged from the recycled material distillation column. In this way, by supplying the recycled material containing acetone to the reaction step and recycling it, the carbon-based yield of propylene can be increased.

[0041] The distillation conditions in the recycled material distillation column are not particularly limited, and the distillation in the recycled material distillation column can be carried out under any conditions.

[0042] The method for supplying the recycled raw materials to the reaction step is not particularly limited, and the recycled raw materials may be mixed with the fresh raw materials in advance and then supplied to the reactor, or the fresh raw materials and the recycled raw materials may be supplied separately to the reactor.

[0043] Preferably, the propylene production method according to one embodiment of the present invention further includes a step of recovering low-boiling components having a boiling point lower than that of acetone from the liquid phase and supplying the low-boiling components to at least one step selected from the group consisting of a reaction step, a gas-liquid separation step, and the recycling step. Examples of the low-boiling components include acetaldehyde. By recycling not only the acetone-containing recycled raw material but also the low-boiling components, the carbon-based yield of propylene can be increased.

[0044] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Example]

[0045] [Simulation example 1] A propylene production process including the following steps (1) to (4) was simulated, and the theoretical yield was calculated.

[0046] (1) Reaction process Liquid ethanol and liquid acetone are used as fresh feedstocks, with 0.5 moles of liquid acetone per mole of liquid ethanol, and 0.7 moles of acetone per mole of the liquid ethanol are gasified and supplied to a reactor. The reactor is filled with a catalyst containing 1 part by mass of component (A), which is zirconium oxide, and 0.009 parts by mass of component (B), which is calcium. The ethanol and acetone supplied to the reactor are brought into contact with the catalyst.

[0047] (2) Gas-liquid separation process The crude product recovered from the reactor outlet is cooled to condense high boiling point components and separate into a liquid phase containing acetone and a gas phase containing propylene.

[0048] (3) Propylene recovery process The gas phase separated in the gas-liquid separation step is extracted and propylene is recovered.

[0049] (4) Recycling process A portion of the water is separated from the liquid phase separated in the gas-liquid separation step, and a recycled feedstock containing 0.7 moles of acetone per mole of ethanol in the fresh feedstock is fed to the reactor.

[0050] (Calculation of theoretical yield) The carbon-based propylene concentration in the crude product at the reactor outlet at steady state was assumed to be 35%.

[0051] The theoretical yield was calculated using the following formula (I) based on the molar ratio of ethanol to acetone in the fresh feedstock, the molar ratio of acetone in the recycled feedstock to ethanol in the fresh feedstock, and the propylene concentration in the crude product, assumed as described above.

[0052] Y=X / 100×(Fe+Fa+Ra) / (Fe+Fa)×100…Formula (I) Y: Propylene yield X: Carbon-based propylene concentration in the crude product at the reactor outlet Fe: Number of moles of carbon in ethanol contained in fresh raw material Fa: Number of moles of carbon in acetone contained in the fresh raw material Ra: The number of moles of carbon in acetone as oxygenated hydrocarbons contained in recycled materials Formula (I) is a theoretical yield assuming no loss of fresh or recycled raw materials. In other words, the yield was calculated when the total number of moles of carbon (Fe + Fa + Ra) fed to the reactor matches the total number of moles of carbon at the reactor outlet.

[0053] The theoretical yield was calculated and was estimated to be 56%, as shown in the following formula (II).

[0054] 56=0.35×{1×2+(0.7+0.5)×3} / (1×2+0.5×3)×100 …Formula (II) [Comparative Simulation Example 1] In the case of the simulation example 1, which includes step (1) but does not include steps (2) to (4), and in which 1.2 moles of liquid acetone are supplied as fresh raw material per mole of liquid ethanol in step (1), the carbon-based propylene concentration in the crude product at the reactor outlet is 35%. In other words, the theoretical yield was assumed to be 35%.

[0055] [Preparation Example 1] Zirconium oxide (Daiichi Kigenso, RC-100) was sized to 0.3 to 0.6 mm. 1.20 g of a solution consisting of 0.0889 g of calcium acetate monohydrate and 1.11 g of Millipore water was added little by little to 5.00 g of the sized zirconium oxide while allowing it to penetrate, yielding a pore-filled material. This pore-filled material was kept in air at 120°C for 3 hours, and then in air at 500°C for 2 hours, yielding catalyst A.

[0056] Example 1 (One-pass experiment) A quartz reactor was filled with 1.25 g of catalyst A. A mixed gas with an ethanol / acetone / water / nitrogen molar ratio of 8 / 4 / 74 / 14 was fed into the reactor at a rate of 96 ml / min, and the reaction was carried out at 0.2 MPa-G and 450 °C. 1.5 hours after the start of the reaction, the gas and liquid discharged from the reactor's gas outlet were sampled and analyzed by gas chromatography to determine the product composition. The product composition, expressed as (number of carbon moles in the product) / (number of carbon moles in the raw material compounds used in the reaction) × 100 (%), was 26.1% propylene, 11.5% ethylene, 9.3% CO2, 29.0% acetone, and 1.8% IPA. When the components that appeared as peaks other than the above compounds on gas chromatography were considered to be 1-pentene, the product composition accounted for 1.5% of the other components.

[0057] Example 1 (Simulation) After setting the following, the material balance with and without recycling was obtained by process simulation. The process flow is as shown in Figure 2, and includes a reaction process, a gas-liquid separation process, an acetone (ACT) recovery process, a compression process, a CO2 separation process, a water separation process, a decarbonization process, and a decarbonization process. The acetone recovery process (recycled raw material recovery process) involved flash distillation of the aqueous phase containing acetone. The material balance at the outlet of the reaction process was determined by reference to the material balance calculated from the results of gas chromatography in Example 1. The balance of carbon components was adjusted on the assumption that hexane was produced. For the hydrogen balance and oxygen balance, it was assumed that water and hydrogen were produced.

[0058] The simulation results are shown in Table 1. The results at the reactor inlet G1 and reactor outlet G2 were adjusted to match the feedstock and reactor outlet material balance in the one-pass experiment results. The results at G3 after the decarbonization step and G4 after acetone recovery (after recovery of recycled raw materials) are simulation results.

[0059] The simulation results showed that in steady state, the amount of fresh acetone can be reduced by recycling the acetone aqueous solution recovered through gas-liquid separation and returning it to the reaction process. With acetone recycling, the propylene yield is 35.9%.

[0060] Comparative Example 1 The simulation results showed that if the acetone aqueous solution recovered after gas-liquid separation is not recycled, it is not possible to reduce the amount of acetone in the fresh feedstock. Without acetone recycling, the propylene yield is 25.7%. [Table 1] [Industrial Applicability]

[0061] The present invention can be used in a method for producing propylene.

Claims

1. a reaction step of supplying a fresh raw material containing ethanol and acetone and a recycled raw material containing acetone to a reactor and reacting them to obtain a crude product; a gas-liquid separation step of separating the crude product into a gas phase containing propylene and a liquid phase containing acetone; a propylene recovery step of recovering propylene from the gas phase; a recycling step of recovering the recycled raw material from the liquid phase; A method for producing propylene, comprising:

2. 2. The method for producing propylene according to claim 1, wherein in the reaction step, a molar ratio of acetone contained in the fresh raw material to ethanol contained in the fresh raw material supplied to the reactor is 0.010 to 1.

7.

3. 3. The method for producing propylene according to claim 1, further comprising a step of recovering low-boiling components having a boiling point lower than that of acetone from the liquid phase and supplying the low-boiling components to at least one step selected from the group consisting of the reaction step, the gas-liquid separation step, and the recycling step.

4. 3. The method for producing propylene according to claim 1, further comprising a step of recovering a condensed component containing acetone in the propylene recovery step, and supplying the condensed component to at least one step selected from the group consisting of the reaction step, the gas-liquid separation step, and the recycling step.

5. The method for producing propylene according to claim 1 , wherein the recycled raw material contains ethanol and / or isopropanol.

6. The method for producing propylene according to any one of claims 1 to 5, further comprising a dehydration step of separating water from the crude product obtained in the reaction step.

7. The method for producing propylene according to any one of claims 1 to 6, wherein water is also supplied to the reactor in the reaction step.

8. 8. The method for producing propylene according to claim 7, wherein in the reaction step, the amount of water supplied to the reactor is 10 mol % or more relative to 100 mol % in total amount of ethanol and acetone supplied to the reactor.

Images