Ethylene production method and polymer production method

Abstract

To provide a method for producing ethylene that enables a polymerization reaction of ethylene to proceed suitably even when ethylene is produced with waste-derived ethanol as a raw material and that improves the quality of a polymer obtained.SOLUTION: The method of the present invention for producing ethylene comprises: an ethylene formation step of obtaining ethylene-containing product from raw material ethanol containing ethanol derived from waste; and at least one of a first purification step of purifying the raw material ethanol before the ethylene formation step and a second purification step of purifying the ethylene-containing product after the ethylene formation step.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing ethylene from raw material ethanol, including ethanol derived from waste, and a method for producing a polymer using ethylene obtained by the production method as a raw material. [Background technology]

[0002] Conventionally, ethylene is produced from naphtha, crude oil, natural gas, etc. as raw materials. High purity ethylene is required due to requirements for the polymerization reaction and the quality of the polymer. For example, in ethylene polymerization using a high-pressure method, ethylene with a purity of 99.9% or more is used. Therefore, conventionally, a technique has been known in which raw olefins such as ethylene are purified and then polymerized.

[0003] For example, Patent Document 1 describes an invention relating to an olefin polymerization method, which is characterized by bringing a raw material olefin containing carbon dioxide as an impurity into contact with a hybrid adsorbent made of a mixture of activated alumina and zeolite to purify the raw material olefin, and then bringing the purified olefin into contact with a transition metal complex catalyst to polymerize it. Patent Document 1 describes the development of a metallocene catalyst that has few of the drawbacks of conventionally used Ziegler-Natta catalysts, that metallocene catalysts are extremely sensitive to impurities in the raw olefin, that industrial ethylene obtained from naphtha, crude oil, natural gas, etc. contains carbon dioxide at levels ranging from several ppm (volume) to several hundred ppm (volume), and that carbon dioxide has a detrimental effect as a catalyst poison in metallocene-catalyzed polymerization. Patent Document 1 also describes the invention that uses the hybrid adsorbent to economically, simply, and efficiently remove carbon dioxide, thereby sufficiently suppressing the decline in catalytic activity caused by impurities in olefin polymerization using transition metal complex catalysts such as metallocene catalysts, enabling stable industrial production of polymers with high productivity.

[0004] In recent years, the importance of carbon neutrality and carbon circulation has been debated, and bioethanol produced from sugarcane and other sources, as well as ethanol derived from waste, are being researched. Of these, bioethanol has been problematic from the perspectives of food competition and biodiversity, and waste-derived ethanol is gaining attention. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-137464 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when conventional technology is applied to waste-derived ethanol as a raw material to produce ethylene and then a polymer using that ethylene, it has been found that the polymerization reaction does not proceed properly and the quality of the polymer may be insufficient because the origin is different from that of conventional industrial ethylene.

[0007] Therefore, an object of the present invention is to provide a method for producing ethylene in which the ethylene polymerization reaction proceeds appropriately and the quality of the obtained polymer is good, even when ethylene is produced using ethanol derived from waste as a raw material. [Means for solving the problem]

[0008] The present invention is summarized as follows [1] to [8]. [1] an ethylene production step of obtaining an ethylene-containing product containing ethylene from raw material ethanol including waste-derived ethanol; The method includes at least one of a first purification step of purifying the raw material ethanol before the ethylene production step, and a second purification step of purifying the ethylene-containing product after the ethylene production step. A method for producing ethylene. [2] The method for producing ethylene according to [1] above, wherein the first purification step comprises removing at least one selected from the group consisting of aliphatic unsaturated hydrocarbons having 3 to 14 carbon atoms, aliphatic saturated hydrocarbons having 3 to 14 carbon atoms, alcohols having 3 to 10 carbon atoms, and ethers having 3 to 10 carbon atoms from the raw material ethanol. [3] The method for producing ethylene according to [1] or [2] above, wherein the second purification step comprises removing at least one selected from the group consisting of aliphatic unsaturated hydrocarbons having 3 to 14 carbon atoms, aliphatic saturated hydrocarbons having 3 to 14 carbon atoms, alcohols having 3 to 10 carbon atoms, ethers having 3 to 10 carbon atoms, carbon monoxide, and oxygen from the ethylene-containing product. [4] The method for producing ethylene according to the above [2] or [3], wherein the aliphatic unsaturated hydrocarbon having 3 to 14 carbon atoms includes propylene. [5] The method for producing ethylene according to any one of the above [2] to [4], wherein the aliphatic saturated hydrocarbons having 3 to 14 carbon atoms include aliphatic saturated hydrocarbons having 6 to 14 carbon atoms. [6] The method for producing ethylene according to any one of the above [2] to [5], wherein the alcohol having 3 to 10 carbon atoms includes 2-propanol. [7] The method for producing ethylene according to any one of the above [2] to [6], wherein the ether having 3 to 10 carbon atoms includes dibutyl ether. [8] A method for producing a polymer, comprising a polymerization step of polymerizing an ethylene-containing monomer produced by the method according to any one of the above [1] to [7] to obtain a polymer. [Effects of the Invention]

[0009] According to the present invention, even when ethylene is produced using ethanol derived from waste as a raw material, the polymerization reaction of ethylene proceeds favorably and the quality of the obtained polymer is good. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described below with reference to embodiments. The present invention includes an ethylene production step of obtaining an ethylene-containing product containing ethylene from raw material ethanol including ethanol derived from waste, and at least one of a first purification step of purifying the raw material ethanol before the ethylene production step and a second purification step of purifying the ethylene-containing product after the ethylene production step. In the present invention, by carrying out a purification step before or after the ethylene production step, or both, the ethylene polymerization reaction proceeds appropriately even when waste-derived ethanol is used as the raw material, and the molecular weight of the polymer obtained is sufficiently high, thereby resulting in a good quality polymer.

[0011] The present invention will be described in detail below. [Raw material ethanol] The raw material ethanol used as a raw material in the present invention includes ethanol derived from waste materials. Waste-derived ethanol is produced from waste-derived gas obtained by burning or pyrolyzing waste materials. The waste may be industrial waste such as industrial solid waste, or general waste such as municipal solid waste (MSW), including combustible materials such as plastic waste, food waste, discarded tires, biomass waste, food waste, building materials, wood, wood chips, fibers, paper, etc. Of these, municipal solid waste (MSW) is preferred. The waste-derived gas is preferably converted to ethanol by either gas-utilizing microorganisms or metal catalysts.

[0012] The waste-derived gas is preferably a synthesis gas containing carbon monoxide and hydrogen. An example in which the waste-derived gas is synthesis gas will be described in detail below. Synthesis gas can be obtained by performing a raw material gas production process in which raw material gas is produced by gasifying waste, and then performing a synthesis gas purification process in which specific substances such as various pollutants, soot particles, impurities, and undesirable amounts of compounds are removed or reduced from the produced raw material gas.

[0013] (raw material gas generation process) In the raw material gas generation step, the waste may be gasified using, for example, a gasification furnace. A gasification furnace is a furnace that burns (incompletely combusts) a carbon source, and examples thereof include a shaft furnace, a kiln furnace, a fluidized bed furnace, a gasification reforming furnace, and a plasma gasification furnace. The temperature at which the waste is gasified into the raw material gas is not particularly limited, but is usually 100 to 2500°C, and preferably 200 to 2100°C.

[0014] The raw material gas obtained by gasifying waste preferably contains carbon monoxide and hydrogen, but may also contain carbon dioxide, oxygen, and nitrogen. The raw material gas may also contain components such as soot, tar, nitrogen compounds, sulfur compounds, phosphorus compounds, and organic compounds. The raw material gas typically contains 0.1% to 80% by volume of carbon monoxide and 0.1% to 80% by volume of hydrogen. The raw material gas may also preferably contain 0.1% to 70% by volume of carbon dioxide.

[0015] The raw material gas is produced by subjecting waste to a heat treatment (commonly known as gasification) in which the waste is combusted (incompletely combusted), i.e., by partially oxidizing the waste, and contains carbon monoxide in an amount of, although not particularly limited to, 0.1% by volume or more, preferably 10% by volume or more, and more preferably 20% by volume or more.

[0016] (Synthetic gas refining process) As described above, the feed gas can be converted into a synthesis gas by removing or reducing specific substances such as various pollutants, dust particles, impurities, and undesirable amounts of compounds. When ethanol is obtained from synthesis gas by microbial fermentation, it is preferable to reduce or remove substances and undesirable amounts of compounds that are undesirable for stable cultivation of microorganisms from the feed gas so that the content of each component in the feed gas is within a range suitable for stable cultivation of microorganisms. Furthermore, when ethanol is obtained from synthesis gas using a metal catalyst, it is also preferable to reduce or remove substances that deactivate the metal catalyst.

[0017] In the synthesis gas purification process, the raw material gas may be purified by processing using one or more of the following: a moisture separator such as a gas chiller; a low-temperature separation (cryogenic) separator; a particulate separator for separating particulates such as soot, represented by various filters such as a cyclone or a bag filter; a water-soluble impurity separator such as a scrubber; a desulfurization apparatus (sulfide separator); a membrane separation separator; a deoxygenation apparatus; a pressure swing adsorption (PSA) separator; a temperature swing adsorption (TSA) separator; a pressure temperature swing adsorption (PTSA) separator; a separator using activated carbon; and a separator using a deoxygenation catalyst, specifically a copper catalyst or a palladium catalyst, to obtain a synthesis gas.

[0018] Furthermore, when ethanol is obtained by microbial fermentation, it is preferable to reduce the carbon dioxide gas concentration in the feed gas, for example, by using a pressure swing adsorption type separation device filled with a regenerated adsorbent containing zeolite to adsorb the carbon dioxide gas in the synthesis gas onto the regenerated adsorbent, thereby reducing the carbon dioxide gas concentration in the synthesis gas.

[0019] The resulting synthesis gas contains at least carbon monoxide and hydrogen as essential components as described above, and may further contain carbon dioxide and nitrogen. The carbon monoxide concentration in the synthesis gas is usually 20% by volume or more and 80% by volume or less, preferably 25% by volume or more and 50% by volume or less, and more preferably 30% by volume or more and 45% by volume or less, based on the total concentration of carbon monoxide, carbon dioxide, hydrogen, and nitrogen in the synthesis gas. The hydrogen concentration in the synthesis gas is usually 10% by volume or more and 80% by volume or less, preferably 30% by volume or more and 55% by volume or less, and more preferably 30% by volume or more and 50% by volume or less, based on the total concentration of carbon monoxide, carbon dioxide, hydrogen, and nitrogen in the synthesis gas.

[0020] The carbon dioxide concentration in the synthesis gas is not particularly limited, but is usually 0.1 to 40% by volume, and preferably 0.3 to 30% by volume, based on the total concentration of carbon monoxide, carbon dioxide, hydrogen, and nitrogen in the synthesis gas. It is particularly preferable to lower the carbon dioxide concentration when ethanol is produced by microbial fermentation, and from this perspective, the carbon dioxide concentration is more preferably 0.5 to 25% by volume. The nitrogen concentration in the synthesis gas is usually 40% by volume or less, preferably 1% by volume or more and 20% by volume or less, and more preferably 5% by volume or more and 15% by volume or less, based on the total concentration of carbon monoxide, carbon dioxide, hydrogen, and nitrogen in the synthesis gas.

[0021] The concentrations of carbon monoxide, carbon dioxide, hydrogen, and nitrogen in the synthesis gas can be adjusted to a predetermined range by appropriately changing combustion conditions such as the type of waste, the gasification temperature in the raw material gas generation process, and the oxygen concentration of the supply gas during gasification. For example, if you want to change the carbon monoxide or hydrogen concentration, you can change to waste with a higher ratio of hydrocarbons (carbon and hydrogen), such as waste plastic, or if you want to lower the nitrogen concentration, you can supply gas with a higher oxygen concentration in the raw gas generation process. Furthermore, the concentrations of carbon monoxide, carbon dioxide, hydrogen, and nitrogen in at least one of the raw material gas and the synthesis gas may be adjusted as appropriate. The concentration adjustment can be achieved by adding at least one of these components to the raw material gas or the synthesis gas. The amount of addition is, for example, less than 50% by volume, preferably less than 30% by volume, and more preferably less than 10% by volume, based on the total amount of the raw material gas or the synthesis gas.

[0022] (Ethanol conversion process) The synthesis gas is converted into ethanol in the ethanol conversion step. As described above, the synthesis gas may be converted into ethanol using either a gas-assimilating microorganism or a metal catalyst in the ethanol conversion step, but conversion using a gas-assimilating microorganism is preferred. When conversion into ethanol is performed using a gas-assimilating microorganism, the synthesis gas is supplied to a microbial fermenter, and the synthesis gas is fermented by microorganisms in the microbial fermenter to produce ethanol. The microbial fermenter is preferably a continuous fermentation device.

[0023] Generally, any shape of microbial fermenter can be used, including agitation type, airlift type, bubble column type, loop type, open bond type, and photobio type. In the present invention, however, a known loop reactor having a main tank section and a reflux section can be suitably used as the microbial fermenter. The synthesis gas supplied to the microbial fermenter may be the synthesis gas obtained through the synthesis gas purification step described above, or may be supplied after adding another predetermined gas, such as at least one selected from the group consisting of sulfur compounds such as sulfur dioxide, phosphorus compounds, and nitrogen compounds.

[0024] The microbial fermenter may be continuously supplied with synthesis gas and a microbial culture solution, but it is not necessary to supply the synthesis gas and the microbial culture solution simultaneously; synthesis gas may be supplied to a microbial fermenter to which a microbial culture solution has already been supplied. It is known that certain anaerobic microorganisms produce ethanol and the like from substrate gases such as synthesis gas through fermentation, and these types of gas-assimilating microorganisms are cultured in a liquid medium. For example, a liquid medium and gas-assimilating bacteria may be supplied and housed in advance, and synthesis gas may be supplied into the microbial fermenter while stirring the liquid medium in this state. This allows the gas-assimilating bacteria to be cultured in the liquid medium, and ethanol to be produced from synthesis gas through the fermentation process.

[0025] In the microbial fermenter, the temperature of the medium (culture temperature) may be any temperature, but is preferably about 30 to 45°C, more preferably about 33 to 42°C, and even more preferably about 36.5 to 37.5°C. The culture time is preferably 1 hour or more in continuous culture, more preferably 7 days or more, particularly preferably 30 days or more, and most preferably 60 days or more. There is no particular upper limit, but from the perspective of regular equipment maintenance, it is preferably 720 days or less, more preferably 365 days or less. The culture time means the time from when the seed bacteria is added to the culture tank until the entire culture medium in the culture tank is discharged.

[0026] The microorganisms (species) contained in the microbial culture solution are not particularly limited as long as they can produce ethanol by microbial fermentation of syngas using carbon monoxide as the primary feedstock. For example, the microorganisms (species) are preferably those that produce ethanol from syngas through the fermentation action of gas-utilizing bacteria, particularly those that have a metabolic pathway for acetyl-COA. Among gas-utilizing bacteria, the genus Clostridium is more preferred, including Clostridium autoethanogenum, Clostridium ljungdahlii, Clostridium aceticum, Clostridium carboxidivorans, Moorella thermoacetica, and Acetobacterium woodii. Of these, Clostridium autoethanogenum is particularly preferred.

[0027] The medium used to culture the above-mentioned microorganisms (species) is not particularly limited as long as it has an appropriate composition depending on the bacterium, but is a liquid containing water as the main component and nutrients (e.g., vitamins, phosphoric acid, etc.) dissolved or dispersed in the water. The composition of such a medium is prepared so that gas-assimilating bacteria can grow well. For example, when using the genus Clostridium as the microorganism, reference can be made to paragraphs "0097" to "0099" of U.S. Patent Application Publication No. 2017 / 260552.

[0028] A culture broth containing ethanol (ethanol-containing culture broth) is obtained by microbial fermentation. The ethanol-containing culture broth is then subjected to a separation step. In the separation step, for example, the ethanol-containing culture solution may be heated to 23 to 500°C under conditions of 0.01 to 1000 kPa (absolute pressure) to separate it into a liquid or solid component containing the microorganism and a gas component containing ethanol. By carrying out such a separation step, foaming does not occur in the distillation apparatus during the distillation operation for separating and purifying ethanol, as described below, and the distillation operation can be carried out continuously. Furthermore, the separation and purification of ethanol can be carried out efficiently during the separation and purification operation, as described below.

[0029] In the separation step, from the viewpoint of efficiently separating the liquid or solid component containing microorganisms, their carcasses, proteins derived from microorganisms, etc., from the gas component containing ethanol, the ethanol-containing culture solution is heated preferably under conditions of 10 to 200 kPa, more preferably under conditions of 50 to 150 kPa, and even more preferably at normal pressure, at a temperature of preferably 50 to 200°C, more preferably at a temperature of 80 to 180°C, and even more preferably at a temperature of 100 to 150°C. The gaseous component containing ethanol obtained in the separation step may be liquefied by condensation to produce an ethanol-containing liquid. The device used in the liquefaction step is not particularly limited, but it is preferable to use a heat exchanger, particularly a condenser. Examples of condensers include water-cooled, air-cooled, and evaporative types, with water-cooled types being preferred. The condenser may be a single-stage or multi-stage type.

[0030] Furthermore, in the separation step, instead of separating into a liquid or solid component containing microorganisms and a gaseous component containing ethanol as described above, the solid component containing microorganisms and the liquid component containing ethanol (ethanol-containing liquid) may be separated using a solid-liquid separation device such as a solid-liquid separation filter device.

[0031] After the separation step, a first purification step may be carried out to further purify the ethanol-containing liquid. The first purification step refers to a purification step carried out before the first purification step described below. Furthermore, if the ethanol-containing liquid obtained by microbial fermentation has already had components such as microorganisms removed, the first purification step may be carried out without going through the separation step described above. The first purification step is a step of separating an ethanol-containing liquid into a distillate with an increased ethanol concentration and a bottoms liquid with a decreased ethanol concentration. Examples of equipment used in the purification step include a distillation apparatus, a treatment apparatus including a pervaporation membrane, a treatment apparatus including a zeolite membrane, a treatment apparatus for removing low-boiling substances with a boiling point lower than that of ethanol, a treatment apparatus for removing high-boiling substances with a boiling point higher than that of ethanol, and a treatment apparatus including an ion exchange membrane. These apparatuses may be used alone or in combination of two or more. A distillation apparatus or membrane separation can be suitably used as a unit operation, with a distillation apparatus being more preferred. Furthermore, a zeolite membrane can be suitably used for membrane separation.

[0032] When a distillation apparatus is used, heated distillation is performed. In heated distillation, the desired ethanol can be obtained as a distillate with high purity. The temperature inside the distillation apparatus during the distillation of ethanol is not particularly limited, but is preferably 110°C or lower, and more preferably about 70 to 105°C. By setting the temperature inside the distillation apparatus within the above range, separation of ethanol from other components, i.e., distillation of ethanol, can be performed more reliably.

[0033] In thermal distillation, the ethanol-containing liquid is introduced into a distillation apparatus equipped with a heater using steam at 100°C or higher, and the temperature at the bottom of the distillation column is raised to 90°C or higher within 30 minutes. The ethanol-containing liquid is then introduced into the middle of the distillation column. Furthermore, in thermal distillation using a distillation apparatus, the distillation step is preferably carried out with a temperature difference between the bottom, middle, and top of the column of within ±15°C. A temperature difference of ±15°C or less makes it easier to obtain high-purity ethanol. The distillation temperature difference is preferably ±13°C, more preferably ±11°C. These distillation temperature differences allow for more reliable separation from other components, i.e., purification of ethanol by distillation.

[0034] The pressure inside the distillation apparatus during ethanol distillation may be normal pressure, but is preferably less than atmospheric pressure, more preferably about 60 to 95 kPa (absolute pressure). By setting the pressure inside the distillation apparatus within this range, the ethanol separation efficiency can be improved, and therefore the ethanol yield can be improved.

[0035] The ethanol obtained through the above-mentioned first-stage purification step is used as a raw material for obtaining an ethylene-containing product in the ethylene production step described below. In the present invention, the "ethanol" used as a raw material does not mean pure ethanol as a compound (ethanol represented by the chemical formula: CH3CH2OH), but is a composition containing impurities, and is also referred to as "raw material ethanol." The impurities are contained in the raw material ethanol produced through each of the above-mentioned steps, and most of these are compounds derived from waste.

[0036] Furthermore, as described above, raw material ethanol may be produced from synthesis gas using a metal catalyst. Examples of the metal catalyst include hydrogenation active metals and combinations of hydrogenation active metals and co-active metals. Examples of hydrogenation active metals include metals that are conventionally known as metals capable of synthesizing ethanol from mixed gases, such as alkali metals (lithium, sodium, etc.), elements belonging to Group 7 of the periodic table (manganese, rhenium, etc.), elements belonging to Group 8 of the periodic table (ruthenium, etc.), elements belonging to Group 9 of the periodic table (cobalt, rhodium, etc.), and elements belonging to Group 10 of the periodic table (nickel, palladium, etc.). These hydrogenation active metals may be used alone or in combination of two or more. As the hydrogenation active metal, a combination of rhodium or ruthenium with an alkali metal and another hydrogenation active metal, such as a combination of rhodium, manganese and lithium, or a combination of ruthenium, rhenium and sodium, is preferred, in terms of further improving the CO conversion rate and the ethanol selectivity.

[0037] Examples of the promoter active metal include titanium, magnesium, vanadium, etc. By supporting a promoter active metal in addition to a hydrogenation active metal, it is possible to further increase the CO conversion rate, ethanol selectivity, etc. The metal catalyst is preferably a rhodium-based catalyst. The rhodium-based catalyst may be used in combination with a metal catalyst other than the rhodium-based catalyst. Examples of the other metal catalyst include a catalyst in which copper alone or copper and a transition metal other than copper are supported on a carrier. When a metal catalyst is used, a product containing acetaldehyde and acetic acid in addition to ethanol is usually obtained, and the product is preferably subjected to a preliminary purification step such as distillation to obtain raw material ethanol.

[0038] The first purification step may be omitted. That is, after ethanol production, it is not necessary to perform both the first purification step and the first purification step described below as a purification step, and only the first purification step may be performed. In this case, the ethanol-containing liquid described above serves as raw material ethanol, and the first purification step is preferably performed using a distillation apparatus or membrane separation, and thermal distillation using a distillation apparatus is particularly preferred, with details of the thermal distillation being as described above. Of course, when the second purification step is performed, both the first purification step and the first purification step may be omitted. However, it is preferable to perform the first purification step, and it is even more preferable to perform the first purification step in addition.

[0039] The raw material ethanol has an ethanol purity (i.e., ethanol content) of, for example, 85% by volume or more. When the ethanol purity is equal to or higher than the above lower limit, the polymerization reaction using ethylene as a raw material proceeds smoothly by undergoing at least one of the first and second purification steps, and the quality of the polymer obtained from ethylene is good. The ethanol purity of the raw material ethanol is preferably 90% by volume or more, more preferably 95% by volume or more, and even more preferably 99.5% by volume or more. Furthermore, the raw material ethanol may have an ethanol purity of less than 100% by volume. Furthermore, the raw material ethanol may be a commercially available product as long as it contains ethanol derived from waste.

[0040] [Ethylene production process] The raw material ethanol is converted into ethylene in an ethylene production step, thereby obtaining an ethylene-containing product. Specifically, the raw material ethanol is brought into contact with a catalyst to convert it into ethylene. The raw material ethanol is converted into ethylene by a dehydration reaction.

[0041] The catalyst to be used is not limited as long as it can convert ethanol to ethylene, but examples include zeolite, modified zeolite such as P-modified zeolite, silica-alumina, alumina, silicated, titanated, zirconated or fluorinated alumina, and acid catalysts such as silicoaluminophosphate (hereinafter, these may be collectively referred to as "zeolite or alumina-based catalysts"). Other examples include heteropolyacid-supported catalysts.

[0042] The zeolite is advantageously one containing at least one 10-membered ring in its structure, and is a microporous material consisting of silicon, aluminum, oxygen, and optionally boron. Specific examples include MFI (ZSM-5, silicalite-1, boralite C, TS-1), MEL (ZSM-11, silicalite-2, boralite D, TS-2, SSZ-46), FER (ferrierite, FU-9, ZSM-35), MTT (ZSM-23), MWW (MCM-22, PSH-3, ITQ-1, MCM-49), TON (ZSM-22, Theta-1, NU-10), EUO (ZSM-50, EU-1), MFS (ZSM-57), ZSM-48, etc.

[0043] The zeolite is preferably a zeolite having a Si / Al ratio of at least 10. The zeolite having a Si / Al ratio of at least 10 preferably has a Si / Al ratio of at least 100, and preferably contains at least one selected from MFI and MEL.

[0044] The zeolite is also preferably a dealuminated zeolite, advantageously having about 10% by weight of aluminum removed from the dealuminated zeolite, advantageously by steam treatment followed by optional leaching. The zeolite and the dealuminated zeolite are advantageously essentially in the H-type and may contain, as a secondary component (component of about 50% or less), at least one metal compensating ion selected from the group consisting of Na, Mg, Ca, La, Ni, Ce, Zn, and Co.

[0045] The zeolite is mixed with a binder, preferably an inorganic binder, and formed into a desired shape, such as pellets. The binder is selected to be durable at the temperatures and other conditions used in the dehydration process of the present invention. The binder is at least one inorganic material selected from clay, silica, metal silicates, metal oxides (e.g., ZrO), or gels containing mixtures of silica and metal oxides.

[0046] The P-modified zeolite is a phosphorus-modified zeolite. In the ethylene production process, a preferred embodiment uses the P-modified zeolite. The phosphorus-modified zeolite can be produced, for example, based on a microporous zeolite having an initial Si / Al atomic ratio of 4 to 500, specifically, MFI, MOR, MEL, clinoptilolite, FER, MWW, TON, EUO, MFS, ZSM-48, or the like. The initial Si / Al atomic ratio is preferably 100 or less, more preferably 4 to 30. The P-modified zeolite produced by this method can also be obtained based on an inexpensive zeolite having a low Si / Al ratio (30 or less).

[0047] Furthermore, the P-modified zeolite can also be further modified with at least one metal selected from Mg, Ca, La, Ni, Ce, Zn, Co, Ag, Fe, and Cu. Advantageously, the phosphorus atom content in the P-modified zeolite is at least 0.05% by mass, preferably 0.3 to 7% by mass. Advantageously, at least 10% by weight of aluminum has been extracted and removed from the zeolite by leaching, relative to the starting zeolite.

[0048] The catalyst using P-modified zeolite may be the P-modified zeolite itself, or may be a blended P-modified zeolite that combines P-modified zeolite with other materials. The blended P-modified zeolite can improve the hardness or catalytic activity of the catalyst. Materials that can be mixed with the P-modified zeolite include various inert or catalytically active materials, or various binder materials. These include kaolin, other clay-like compositions, various forms of rare earth metals, phosphates, alumina or alumina sol, titania, zirconia, quartz, silica or silica sol, and mixtures thereof. These components are effective in increasing the compressive strength of the catalyst and catalyst formulations. The catalyst can be formed into pellets, spheres, extruded into other shapes, or spray-dried particles. The amount of P-modified zeolite in the final catalyst product is 10-90% by weight of the total catalyst, preferably 20-70% by weight of the total catalyst. A suitable example of a P-modified zeolite is a silicoaluminophosphate, more preferably a silicoaluminophosphate from the AEL group, a representative example of which is SAPO-11. SAPO-11 is based on ALPO-11, with an Al / P ratio of essentially 1 atom / atom. Adding a silicon precursor during synthesis inserts silicon into the ALPO framework, creating acid sites on the surface of the micropores of the 10-membered ring zeolite. The silicon content is 0.1-10 atomic % (Al + P + Si = 100).

[0049] A preferred embodiment is to use alumina (particularly γ-alumina) as a catalyst in the ethylene production process. It is also preferred to use alumina that has been silicated, zirconated, titanated, or fluorinated. Alumina is generally characterized by a wide range of acid strength distribution and Lewis-type and Bronsted-type acid sites. Activated alumina is preferably used as the alumina.

[0050] It is also preferable to improve the selectivity of the catalyst by depositing silicon, zirconium, titanium, fluorite, etc. on the surface of alumina. That is, the selectivity of the catalyst may be improved by silicating, zirconating, or titanating. To produce such a catalyst, a suitable commercially available alumina, preferably one having a surface area of ​​10 to 500 m, is used. 2It is recommended to use eta- or gamma-alumina with an alkali content of 0.5% or less per 10000 kJ / g. It is also recommended to prepare the alumina by adding silicon, zirconium, titanium, etc. in a total amount of 0.05 to 10% by mass. These metals can be added during the production of the alumina or can be added to the alumina after production. These metals can also be added in the form of a precursor. Fluorinated alumina itself is known and can be produced according to conventional techniques.

[0051] In the ethylene production step, a preferred embodiment is one in which a heteropolyacid-supported catalyst is used as the catalyst. The heteropolyacid-supported catalyst comprises a heteropolyacid supported on a suitable catalyst carrier. The term "heteropolyacid" refers to a heteropolyacid compound in the form of a free acid or a heteropolyacid salt such as an alkali metal salt, an alkaline earth metal salt, an ammonium salt, a salt of a bulky cation, and / or a metal salt (in these cases, the salt may be either a complete salt or a partial salt). The anion of a heteropolyacid typically comprises 12 to 18 oxygen-bonded polyvalent metal atoms, known as peripheral atoms, symmetrically surrounding one or more central atoms. The peripheral atoms are suitably selected from molybdenum, tungsten, vanadium, niobium, tantalum, and combinations thereof. The central atom is preferably silicon or phosphorus. The central atom may also include any one selected from the atoms of Groups I to VIII of the Periodic Table of the Elements, such as copper, beryllium, zinc, cobalt, nickel, boron, aluminum, gallium, iron, cerium, arsenic, antimony, bismuth, chromium, rhodium, silicon, germanium, tin, titanium, zirconium, vanadium, sulfur, tellurium, manganese nickel, platinum, thorium, hafnium, tellurium, and iodine. Suitable heteropolyacids include Keggin, Wells-Dawson, and Anderson-Evans-Perloff heteropolyacids.

[0052] The heteropolyacid component of the heteropolyacid supported catalyst is preferably a heteropolytungstic acid, which is a heteropolyacid in which the peripheral atoms are tungsten atoms. Preferred heteropolytungstic acids are any based on the Keggin or Wells-Dawson structure. An example of a suitable heteropolytungstic acid is 18-phosphotungstic acid (H6[P2W 18 O 62 ]·xH2O), 12-phosphotungstic acid (H3[PW 12 O 40 ]·xH2O), 12-silicotungstic acid (H4[SiW 12 O 40 ]·xH2O), cesium hydrogen silicotungstate (Cs3H[SiW 12 O 40 ]·xH2O), monopotassium phosphotungstate (KH5[P2W 18 O 62 ]·xH2O), 12-monosodium silicotungstate (NaK3[SiW 12 O 40 ]·xH2O), and potassium phosphotungstate (K6[P2W 18 O 62 ]·xH2O). Mixtures of two or more different heteropolytungstic acids and salts can also be used.

[0053] More preferably, the heteropolyacid component of the heteropolyacid supported catalyst is silicotungstic acid, phosphotungstic acid, and mixtures thereof, such as 12-silicotungstic acid (H4[SiW 12 O 40 ]·xH2O), 12-phosphotungstic acid (H3[PW 12 O 40 ]·xH2O), and mixtures thereof. More preferably, the heteropolyacid is tungstosilicic acid, and most preferably, the heteropolyacid is 12-tungstosilicic acid.

[0054] The molecular weight of the heteropolyacid is preferably more than 700 and less than 8500, more preferably more than 2800 and less than 6000. Such heteropolyacids also include dimerized complexes thereof.

[0055] The catalyst support used in the heteropolyacid-supported catalyst may be any suitable catalyst support known in the art. Suitable sources of catalyst supports include mordenite (e.g., montmorillonite), clay, bentonite, diatomaceous earth, titania, activated carbon, alumina, silica, silica-alumina, silica-titania cogel, silica-zirconia cogel, carbon-coated alumina, zeolite, zinc oxide, and flame-pyrolyzed oxides. Silica-based catalyst supports, such as silica gel supports and supports prepared by flame hydrolysis of SiCl, are preferred. The shape of the catalyst support is not particularly limited, and may be, for example, in powder form, granular form, pelletized form, spherical form, or extruded form.

[0056] Although not particularly limited, the raw material ethanol is preferably converted to ethylene in a gas phase by contacting the catalyst. The raw material ethanol may be further mixed with water, or may be mixed with an optional component other than the raw material ethanol and water, and one or both of the water and the optional component may be contacted with the catalyst in the form of a gas together with the raw material ethanol. The catalyst may be filled, for example, in a reaction vessel, and raw material ethanol, or raw material ethanol and at least one selected from water and other optional components, may be supplied as a gas to the reaction vessel filled with the catalyst to carry out a gas-phase dehydration reaction, thereby discharging an ethylene-containing product in the gas phase from the reaction vessel. If ethanol remains in the gas discharged from the reaction vessel, the ethanol-containing component may be separated from the ethylene-containing product, and the ethanol-containing component may be supplied again to the reaction vessel.

[0057] In the case of a zeolite or alumina catalyst, the temperature in the reaction vessel is, for example, 280 to 600° C., preferably 300 to 550° C., and more preferably 330 to 530° C. The pressure (absolute pressure) in the reaction vessel is, for example, 50 kPa to 3 MPa, preferably 50 kPa to 1 MPa, and more preferably 0.12 MPa to 0.65 MPa.

[0058] In the case of a heteropolyacid-supported catalyst, the temperature in the reaction vessel is, for example, 170° C. or higher, preferably in the range of 180 to 270° C., more preferably in the range of 190 to 260° C., and even more preferably in the range of 200 to 250° C. The pressure is preferably in the range of 0.1 to 4.5 MPa, more preferably in the range of 1.0 to 3.5 MPa, and even more preferably in the range of 1.0 to 2.8 MPa. In the case of a heteropolyacid-supported catalyst, the heteropolyacid-supported catalyst may be heated to a temperature of 220°C or higher before contacting with the raw material ethanol and maintained at that temperature for a sufficient period of time to remove bound water from the heteropolyacid component of the heteropolyacid-supported catalyst.

[0059] [First and second purification steps] As described above, in the ethylene production method of the present invention, at least one of a first purification step of purifying raw material ethanol before the ethylene production step and a second purification step of purifying an ethylene-containing product after the ethylene production step is carried out. Preferably, both the first and second purification steps are carried out. In this specification, when the second purification step is performed, the ethylene-containing product purified by the second purification step is referred to as "ethylene" produced by the production method of the present invention, and when the second purification step is omitted, the ethylene-containing product obtained in the ethylene production step is referred to as "ethylene" produced by the production method of the present invention. The "ethylene" produced by the production method of the present invention may consist of ethylene alone, or may be a composition containing impurities that are inevitably mixed in even after synthesis or purification.

[0060] In the first purification step, it is preferable to remove at least one organic compound selected from the group consisting of aliphatic unsaturated hydrocarbons having 3 to 14 carbon atoms, aliphatic saturated hydrocarbons having 3 to 14 carbon atoms, alcohols having 3 to 10 carbon atoms, and ethers having 3 to 10 carbon atoms from the raw material ethanol. Waste contains various components, and therefore, raw material ethanol produced from waste contains various organic compounds. Furthermore, among organic compounds, organic compounds with the above carbon numbers often remain in the raw material ethanol obtained through various processes. If such organic compounds remain in the raw material ethanol, they may inhibit the dehydration reaction in the ethylene production process and the subsequent polymerization reaction using ethylene, or may reduce the quality of the polymer obtained from ethylene. Therefore, removing hydrocarbons, alcohols, and ethers with specific carbon numbers in the first purification process allows the ethylene polymerization reaction to proceed smoothly and also tends to improve the quality of the resulting polymer.

[0061] On the other hand, in the second purification step, it is preferable to remove at least one selected from specific organic compounds consisting of aliphatic unsaturated hydrocarbons having 3 to 14 carbon atoms, aliphatic saturated hydrocarbons having 3 to 14 carbon atoms, alcohols having 3 to 10 carbon atoms, and ethers having 3 to 10 carbon atoms, carbon monoxide, and oxygen from the produced ethylene-containing product. The term "removal" in the first and second purification steps includes not only the complete removal of the target substance from the raw material ethanol or the ethylene-containing product, but also the reduction of the content of the target substance.

[0062] In the second purification step, as described in the first purification step above, the removal of hydrocarbons, alcohols, and ethers having specific carbon numbers allows the ethylene polymerization reaction to proceed favorably and also makes it easier to improve the quality of the obtained polymer. Carbon monoxide and oxygen have high electronegativity and can inhibit the polymerization reaction of ethylene. For example, they can inhibit the polymerization reaction when certain catalysts, such as Ziegler-Natta catalysts, are used. Furthermore, oxygen can act as a polymerization initiator in radical polymerizations such as high-pressure polymerization, and excessive oxygen content can lead to runaway polymerization. Therefore, removing carbon monoxide and oxygen from the ethylene-containing composition in the second purification step can prevent them from inhibiting the ethylene polymerization reaction.

[0063] The ethylene produced by the present invention preferably has a carbon monoxide content of 1% by volume or less by removing carbon monoxide. By keeping the carbon monoxide content at 1% by volume or less, it is possible to prevent the polymerization reaction using ethylene from being inhibited by carbon monoxide. From this perspective, the carbon monoxide content is more preferably 0.5% by volume or less, and even more preferably 0.1% by volume or less. Furthermore, the ethylene produced by the present invention may not contain any carbon monoxide at all, and therefore the lower limit of the carbon monoxide content is 0% by volume.

[0064] The ethylene produced by the present invention preferably has an oxygen content of 1% by volume or less by removing oxygen. By keeping the oxygen content at 1% by volume or less, it is possible to prevent the polymerization reaction using ethylene from being inhibited by oxygen. From this perspective, the oxygen content is more preferably 0.5% by volume or less, and even more preferably 0.1% by volume or less. Furthermore, the ethylene produced by the present invention may not contain any oxygen at all, and therefore the lower limit of the oxygen content is 0% by volume.

[0065] The aliphatic unsaturated hydrocarbons having 3 to 14 carbon atoms may be removed in the first purification step, the second purification step, or both, but the aliphatic unsaturated hydrocarbons having 3 to 14 carbon atoms removed in either step preferably contain propylene. If propylene is contained in ethylene, when a polymerization reaction is carried out using that ethylene, the propylene will become a branched chain of the polymer, so removing propylene can reduce the number of branched chains. Therefore, removal of propylene is particularly suitable when it is desired to reduce the number of branched chains of the polymer, such as when producing high-density polyethylene (HDPE) from ethylene, as described below.

[0066] The ethylene produced by the present invention preferably has a propylene content of 1% by volume or less by removing propylene. By setting the propylene content to 1% by volume or less, the effect of reducing branched chains can be achieved. From this perspective, the propylene content is more preferably 0.5% by volume or less, and even more preferably 0.1% by volume or less. Furthermore, the ethylene produced by the present invention may not contain any propylene at all, and therefore the lower limit of the propylene content is 0% by volume.

[0067] Additionally, the aliphatic saturated hydrocarbons having 3 to 14 carbon atoms may be removed in the first purification step, the second purification step, or both, and the aliphatic saturated hydrocarbons having 3 to 14 carbon atoms removed in either step preferably include aliphatic saturated hydrocarbons having 6 to 14 carbon atoms. The aliphatic saturated hydrocarbons having 6 to 14 carbon atoms may be linear or may have at least one of a branched structure and a cyclic structure, but linear structure is preferred. Specific examples of the aliphatic saturated hydrocarbons having 6 to 14 carbon atoms include at least one selected from n-hexane, n-heptane, n-octane, n-decane, n-dodecane, and n-tetradecane. These aliphatic saturated hydrocarbons with a relatively large carbon number (6 to 14 carbon atoms) are contained in relatively large amounts in waste-derived raw material ethanol. However, these aliphatic saturated hydrocarbons are highly compatible with the fat and oil components contained in food, and if the polymer produced from ethylene produced by the present invention is used in food packaging, there is a concern that they may leak into the food. Therefore, removing the aliphatic saturated hydrocarbons with a relatively large carbon number is preferable in terms of food safety. Furthermore, the aliphatic saturated hydrocarbons having 3 to 14 carbon atoms removed in any of the above steps preferably contain aliphatic saturated hydrocarbons having 10 to 14 carbon atoms, since these are contained in large amounts in raw material ethanol derived from waste.

[0068] The ethylene produced by the present invention has a content of aliphatic saturated hydrocarbons having 6 to 14 carbon atoms of preferably 0.3% by volume or less, more preferably 0.2% by volume or less, and even more preferably 0.1% by volume or less, due to the removal of the aliphatic saturated hydrocarbons having 6 to 14 carbon atoms. Furthermore, the ethylene produced by the present invention may not contain any aliphatic saturated hydrocarbons having 6 to 14 carbon atoms at all, and therefore the lower limit of the content of aliphatic saturated hydrocarbons having 6 to 14 carbon atoms is 0% by volume.

[0069] The alcohol having 3 to 10 carbon atoms may be removed in either the first purification step, the second purification step, or both, and examples of the alcohol having 3 to 10 carbon atoms removed in either step include at least one selected from 1-propanol, 2-propanol, 1-butanol, 2-butanol, and tert-butanol. These alcohols are contained in relatively large amounts in the raw material ethanol derived from waste, and removing these alcohols in either the first purification step, the second purification step, or both facilitates the favorable progress of the polymerization reaction using ethylene, which will be described later, and also facilitates the improvement of the quality of the obtained polymer.

[0070] Furthermore, the alcohol having 3 to 10 carbon atoms removed in any of the above steps preferably contains 2-propanol. If 2-propanol is contained in ethylene, when a polymerization reaction is carried out using that ethylene, the 2-propanol will become a branched chain in the polymer, and therefore, by removing 2-propanol, the number of branched chains in the polymer can be reduced. Therefore, removing 2-propanol is particularly suitable when it is desired to reduce the number of branched chains in the polymer, such as when producing high-density polyethylene (HDPE) from ethylene, as described below.

[0071] The ethylene produced by the present invention preferably has a 2-propanol content of 0.3% by volume or less by removing 2-propanol. By adjusting the content to 0.3% by volume or less, the effect of reducing branched chains is more easily achieved. From this perspective, the 2-propanol content is more preferably 0.1% by volume or less, and even more preferably 0.05% by volume or less. Furthermore, the ethylene produced by the present invention may not contain any 2-propanol at all, and therefore the lower limit of the 2-propanol content is 0% by volume.

[0072] The ethers having 3 to 10 carbon atoms may be removed in the first purification step, the second purification step, or both, and examples of the ethers having 3 to 10 carbon atoms removed in either step include at least one selected from diethyl ether and dibutyl ether. These ethers are contained in relatively large amounts in raw material ethanol derived from waste, and removing these ethers in the first purification step, the second purification step, or both facilitates the favorable progress of the polymerization reaction using ethylene, which will be described later, and also facilitates the improvement of the quality of the obtained polymer.

[0073] The ether having 3 to 10 carbon atoms removed in any of the above steps preferably includes dibutyl ether. Because dibutyl ether is a volatile organic compound (VOC), removing dibutyl ether is beneficial in that it can reduce the risk of adverse effects, such as health risks, that may be caused by VOCs.

[0074] The ethylene produced by the present invention preferably has a dibutyl ether content of 0.3% by volume or less by removing dibutyl ether. By keeping the dibutyl ether content at 0.3% by volume or less, the effect of reducing the risk of adverse effects such as health risks is more likely to be achieved. From this perspective, the dibutyl ether content is more preferably 0.1% by volume or less, and even more preferably 0.05% by volume or less. Furthermore, the ethylene produced by the present invention may not contain any dibutyl ether at all, and therefore the lower limit of the dibutyl ether content is 0% by volume.

[0075] In the ethylene production step, water is produced by a dehydration reaction, so it is preferable to remove at least water in the second purification step. In addition, unreacted ethanol generally remains in the ethylene-containing product produced in the ethylene production step, so it is preferable to remove the unreacted ethanol as well. Removal of water and ethanol allows the polymerization reaction using ethylene, which will be described later, to proceed favorably, and also makes it easier to improve the quality of the obtained polymer.

[0076] The ethylene produced by the present invention preferably has a water content of 0.3% by volume or less due to the removal of water in the second purification step. By adjusting the water content to 0.3% by volume or less, the polymerization reaction using ethylene can be easily carried out favorably, and the quality of the obtained polymer can be easily improved. From this viewpoint, the water content is more preferably 0.1% by volume or less, and even more preferably 0.05% by volume or less. Furthermore, the ethylene produced by the present invention may not contain any water at all, and therefore the lower limit of the water content is 0% by volume.

[0077] The ethylene produced by the present invention preferably has an ethanol content of 0.3% by volume or less by removing ethanol in the second purification step. By adjusting the ethanol content to 0.3% by volume or less, the polymerization reaction using ethylene can be easily carried out favorably, and the quality of the obtained polymer can be easily improved. From this perspective, the ethanol content is more preferably 0.1% by volume or less, and even more preferably 0.05% by volume or less. Furthermore, the ethylene produced by the present invention may not contain any ethanol at all, and therefore the lower limit of the ethanol content is 0% by volume.

[0078] The ethylene produced in the present invention is generally in the form of a gas, and the volume percentage of each of the above components can be measured by analyzing the gaseous ethylene for each inorganic gas (oxygen, carbon monoxide, etc.) and organic gas using GC-TCD and GC-FID.

[0079] Purification methods for each of the first and second purification steps include a water separation device such as a gas chiller, a separation device using an adsorbent such as activated carbon, a pressure swing adsorption separation device (PSA), a temperature swing adsorption separation device (TSA), a pressure temperature swing adsorption separation device (PTSA), a low-temperature separation (cryogenic) separation device, a water-soluble impurity separation device such as a scrubber, a desulfurization device (sulfide separation device), a membrane separation device, a distillation device, a separation device with chromatography, and a solution absorption device.

[0080] Various types of low-temperature separation methods can be used, including, for example, those using a condenser. A solution absorption device is a device equipped with an absorbing solution that selectively absorbs specific gas components by contacting the gas. An alkaline solution such as an amine solution can be used as the absorbing solution. For example, using an alkaline solution in the first purification step can absorb carbon dioxide and other components in the gasified raw ethanol.

[0081] As described above, in the first purification step, it is preferable to remove any of aliphatic unsaturated hydrocarbons having 3 to 14 carbon atoms, aliphatic saturated hydrocarbons having 3 to 14 carbon atoms, alcohols having 3 to 10 carbon atoms, and ethers having 3 to 10 carbon atoms, but it is more preferable to remove those with a relatively large number of carbon atoms, and it is particularly preferable to remove aliphatic unsaturated hydrocarbons having 6 to 14 carbon atoms. Organic compounds with a large number of carbon atoms can be easily removed in the first purification step due to the difference in molecular weight from ethanol, and removing them also makes it easier to proceed with the reaction in the ethylene production step more appropriately. In the first purification step, the method for removing the aliphatic unsaturated hydrocarbons having 6 to 14 carbon atoms is not particularly limited, but they may be removed using a separation device equipped with chromatography. As the chromatography, reverse phase chromatography or the like may be used. Furthermore, they may also be removed using a distillation device, activated carbon adsorption, or the like.

[0082] In the second purification step, it is preferable to remove either the water produced in the ethylene production step or the unreacted ethanol, and it is preferable to remove both of them. Furthermore, as described above, it is preferable to remove at least one selected from specific organic compounds, carbon monoxide, and oxygen in the second purification step, and it is more preferable that the specific organic compounds removed are low-molecular-weight organic compounds (e.g., having 3 to 5 carbon atoms). That is, it is more preferable that aliphatic saturated hydrocarbons having 6 to 14 carbon atoms are removed in the first purification step, and that at least specific low-molecular-weight organic compounds having relatively low molecular weights are removed in the second purification step in addition to water and unreacted ethanol, and it is also preferable that carbon monoxide and oxygen are removed in the second purification step in addition to these. Specifically, the specific organic compounds removed in the second purification step preferably include at least one selected from low molecular weight alcohols such as 2-propanol and low molecular weight ethers such as diethyl ether. Furthermore, the specific organic compounds removed in the second purification step preferably further include, in addition to these, low molecular weight aliphatic unsaturated hydrocarbons such as propylene. That is, in the second purification step, it is even more preferable that propanol and diethyl ether are removed as low molecular weight organic compounds, and it is particularly preferable that propylene is also removed in addition to these. Low molecular weight organic compounds can be efficiently removed from ethylene along with unreacted ethanol, carbon monoxide, oxygen, etc. using specific separation equipment. Furthermore, diethyl ether can be a raw material for producing ethylene together with ethanol in the ethylene production step. Therefore, it is preferable to remove a larger proportion of diethyl ether in the second purification step than in the first purification step. Note that the "proportion" refers to the proportion relative to the raw material ethanol in the first purification step and the proportion relative to the ethylene-containing product in the second purification step.

[0083] In the second purification step, although not particularly limited, purification is preferably performed using a low-temperature separation system. Specifically, a method of solidifying and separating ethylene using a condenser using a refrigerant (chiller) cooled to below the melting point of ethylene (below −170° C. at normal pressure) can be mentioned. In this case, substances with a melting point higher than that of ethylene, such as water, carbon dioxide, ethanol, and other organic compounds, may be removed using one or more upstream condensers in which the refrigerant temperature is higher than that of the condenser. As the upstream condensers, for example, a first condenser in which the refrigerant temperature is relatively high (e.g., 0 to 25°C at normal pressure) and a second condenser in which the refrigerant temperature is lower than that of the first condenser (e.g., -50 to -90°C at normal pressure) may be used in combination. The condenser may be of any type, and the ethylene-containing product in a gaseous phase may be brought into contact with a metal tube or the like through which a refrigerant passes, or the refrigerant may be brought into direct contact with the ethylene-containing product.

[0084] [Polymer manufacturing method] The ethylene produced by the present invention can be used for various applications, but is preferably subjected to a polymerization step for producing a polymer containing ethylene-derived structural units. In the polymerization step, a polymer is obtained by polymerizing a monomer containing ethylene. The polymer may be a homopolyethylene obtained by polymerizing ethylene alone, or a copolymer obtained by polymerizing ethylene and a monomer component other than ethylene.

[0085] The polymer is preferably a polyethylene resin such as low density polyethylene (LDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE), or ultra-high molecular weight polyethylene (UHMWPE). Furthermore, other polymers containing ethylene-derived structural units may also be used, such as copolymers with monomers other than ethylene. Examples of such monomers other than ethylene include, but are not limited to, propylene, 1-butene, 2-butene, isobutene, 1-pentene, 1-hexene, 1-heptene, 1-octene, vinyl acetate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, acrylonitrile, vinyl fluoride, vinyl chloride, vinyl bromide, tetrafluoroethylene, diethyl maleate, diethyl fumarate, and carbon monoxide. Specific examples of copolymers include ethylene-vinyl acetate copolymer (EVA), ethylene-methyl acrylate copolymer, ethylene-ethyl (meth)acrylate copolymer, ethylene-(meth)acrylic acid copolymer, ethylene-propylene rubber (EPM), and ethylene-propylene diene rubber (EPDM).

[0086] Low-density polyethylene has a molecular structure that includes short-chain branches and long-chain branches, and has a density of 0.910 g / cm 3 More than 0.942g / cm3 less than 0.930 g / cm 3 High density polyethylene has a molecular structure with few branches and a density of 0.942 g / cm 3 The density of the polyethylene is 0.930 g / cm 3 More than 0.942g / cm 3 Polyethylenes with a density of less than this are sometimes called medium-density polyethylenes. Linear low-density polyethylene is generally a copolymer of ethylene and a small amount of an α-olefin other than ethylene. Examples of the α-olefin other than ethylene include α-olefins having 3 to 10 carbon atoms, specifically propylene, butene-1, pentene-1, 4-methyl-pentene-1, hexene-1, octene-1, and decene-1. The density of linear low-density polyethylene is 0.942 g / cm. 3 typically has a density of 0.930 g / cm 3 or less, and for example, 0.880 g / cm 3 or more, typically 0.910 g / cm 3 That's all.

[0087] Ultra-high molecular weight polyethylene (UHMWPE) is a polyethylene with a larger molecular weight than ordinary polyethylene, for example, a polyethylene resin with a weight-average molecular weight of 400,000 or more, preferably 1,000,000 or more. With a high weight-average molecular weight, the ultra-high molecular weight polyethylene exhibits good mechanical strength in various respects. From the viewpoint of ease of polymerization, the weight-average molecular weight of the ultra-high molecular weight polyethylene is preferably 7,000,000 or less, more preferably 4,000,000 or less. The weight-average molecular weight is the weight-average molecular weight measured by gel permeation chromatography (GPC) in terms of standard polystyrene. Ultra-high molecular weight polyethylene (UHMWPE) may be an ethylene homopolymer, or a copolymer of ethylene and an α-olefin other than ethylene, as described above for LLDPE.

[0088] Ethylene can be polymerized, for example, in the presence of a radical initiator to form a polyethylene resin. Radical initiators include, but are not limited to, oxygen-based initiators such as organic peroxides, peroxyesters, dialkyl peroxides, or combinations thereof. Specific examples of radical initiators include, but are not limited to, t-butyl peroxypivalate, di-t-butyl peroxide (DTBP), t-butyl peroxyacetate (TBPO), t-butyl peroxy-2-ethylhexanoate, t-butyl peroxyneodecanoate (PND), t-butyl peroxyoctoate, and combinations of any two or more thereof.

[0089] Ethylene can also be polymerized to produce polyethylene resins in the presence of a redox catalyst, such as a Ziegler-Natta catalyst, a metallocene catalyst, a Phillips catalyst, or a standard catalyst.

[0090] The Ziegler-Natta catalyst may be, for example, a triethylaluminum-titanium tetrachloride solid composite. The Ziegler-Natta catalyst may be, for example, a titanium trichloride composition obtained by reducing titanium tetrachloride with an organoaluminum compound and then treating it with various electron donors and electron acceptors, combined with an organoaluminum compound and an aromatic carboxylic acid ester, or may be a supported catalyst prepared by contacting magnesium halide with titanium tetrachloride and various electron donors. Examples of metallocene catalysts include compounds such as bis(cyclopentadienyl) metal complexes, which have a structure in which a transition metal is sandwiched between π-electron unsaturated compounds. More specifically, examples include compounds in which one or more cyclopentadienyl rings or analogs thereof exist as ligands on a tetravalent transition metal such as titanium, zirconium, nickel, palladium, hafnium, or platinum. Ziegler-Natta catalysts and metallocene catalysts may each be used in combination with a specific cocatalyst (promoter), such as methylaluminoxane (MAO) or a boron compound.

[0091] The Phillips catalyst is a catalyst system containing a chromium compound such as chromium oxide, and specific examples thereof include catalysts in which a chromium compound such as chromium trioxide or a chromate ester is supported on a solid oxide such as silica, alumina, silica-alumina, or silica-titania. The standard catalyst is a known catalyst using molybdenum oxide, such as gamma-alumina-molybdenum oxide.

[0092] When a radical initiator is used, a high-pressure method can be used to polymerize ethylene. In the high-pressure method, ethylene is polymerized using, for example, a multi-stage gas compressor under an environment of 1000 to 4000 atmospheres and 100 to 350°C. The residual monomer is then separated and cooled to obtain the polymer. Low-density polyethylene (LDPE) can be produced from ethylene produced by the high-pressure method.

[0093] When using catalysts such as Ziegler-Natta catalysts, metallocene catalysts, Phillips catalysts, and standard catalysts, ethylene can be polymerized using low- or medium-pressure processes. When using these catalysts, it is preferable to use liquid-phase, gas-phase, or suspension polymerization methods. HDPE can be produced by polymerizing ethylene using these catalysts using low- or medium-pressure processes. LLDPE can also be produced by copolymerizing ethylene with a small amount of α-olefins other than ethylene using these catalysts. Furthermore, ultra-high molecular weight polyethylene can be obtained by long-term polymerization, for example, using low-pressure suspension polymerization. [Example]

[0094] The present invention will be explained in more detail by way of examples, but the present invention is not limited to these examples in any way.

[0095] <Production of raw material ethanol> (raw material gas generation process) The gas used was the gas emitted after incineration of municipal waste in a waste incineration facility. The raw gas consisted of approximately 30% by volume of carbon monoxide, 30% by volume of carbon dioxide, 30% by volume of hydrogen, and 10% by volume of nitrogen.

[0096] (Synthetic gas refining process) The feed gas produced as described above was heated to a gas temperature of 80°C using a pressure swing adsorption separation unit (PSA) to remove 60 to 80% by volume of carbon dioxide contained in the synthesis gas. The gas was then heated in a double-pipe heat exchanger using steam at 150°C and re-cooled in another double-pipe heat exchanger using cooling water at 25°C to precipitate impurities, which were then removed using a filter to produce synthesis gas.

[0097] (Ethanol conversion process) The synthesis gas obtained as described above was continuously supplied to a continuous fermentation apparatus (microbial fermentation tank) equipped with a main reactor, synthesis gas inlet, and outlet, and filled with a Clostridium autoethanogenum (microorganism) seed culture and a liquid culture medium for bacterial culture (containing appropriate amounts of phosphorus compounds, nitrogen compounds, and various minerals). Cultivation (microbial fermentation) was carried out continuously for 300 hours at 37°C. Approximately 8,000 L of the ethanol-containing culture medium was then withdrawn from the outlet.

[0098] (separation process) The ethanol-containing culture solution obtained in the ethanol conversion step was subjected to solid-liquid separation using a solid-liquid separation filter device under conditions of a culture solution introduction pressure of 200 kPa or more and a temperature of 37°C to obtain an ethanol-containing solution.

[0099] (first stage purification process) The ethanol-containing liquid was then introduced into a distillation apparatus equipped with a heater using 170°C steam. After raising the temperature of the bottom of the distillation column to 101°C within 8 to 15 minutes, the ethanol-containing liquid was introduced into the middle of the distillation column. During continuous operation, the column bottom was kept at 101°C, the middle at 99°C, and the top at 91°C, and the distillation rate was 15 sec / L to obtain purified ethanol. The pressure inside the distillation column was 60 to 95 kPa (absolute pressure). The purified ethanol (raw material ethanol) had an ethanol purity of 90% by volume or more.

[0100] (First purification step) The resulting ethanol is purified by reverse phase chromatography to remove aliphatic saturated hydrocarbons, mainly those having 6 to 14 carbon atoms.

[0101] (Ethylene production process) A product containing ethylene is produced from the raw material ethanol purified in the first purification step. Specifically, an activated alumina catalyst is packed into a reaction tube, and the temperature and pressure are adjusted to 525°C and 0.5 MPaG, respectively. Ethanol obtained in the first purification step is supplied to the reaction tube, and a gas-phase dehydration reaction is carried out to produce an ethylene-containing product.

[0102] (Second purification step) A first condenser cooled to 5°C, a second condenser cooled to -70°C, and a third condenser cooled to -170°C are arranged in this order, and the ethylene-containing product produced above is sequentially bubbled through these condensers to produce purified ethylene. Water is mainly removed in the first condenser, unreacted ethanol, 2-propanol, and diethyl ether are mainly removed in the second condenser, and propylene, carbon monoxide, and oxygen are mainly removed in the third condenser.

[0103] (Production of polyethylene resin) After replacing the atmosphere in the reactor with nitrogen, the co-catalyst modified methylaluminoxane (MMAO), Ziegler-Natta catalyst, and toluene are added. After stirring at room temperature under atmospheric pressure, the temperature is raised to 50°C and ethylene is supplied to polymerize the mixture, producing polyethylene resin (HDPE). The polyethylene produced in this example undergoes the first and second purification steps, which allows the polymerization activity in the ethylene polymerization reaction to proceed favorably and improves the quality of the resulting polymer. For comparison, polyethylene polymerized using commercially available high-purity ethylene also has a similar molecular weight.

Claims

1. an ethylene production step in which raw material ethanol containing waste-derived ethanol is contacted with a catalyst in a gas phase to obtain an ethylene-containing product containing ethylene; and a purification step of purifying the ethylene-containing product after the ethylene production step, the purification step includes a step of removing mainly water, a step of removing mainly unreacted ethanol, 2-propanol, and diethyl ether, and a step of removing mainly propylene, carbon monoxide, and oxygen.

2. The method further comprises a first purification step of purifying the raw material ethanol before the ethylene production step, 2. The method for producing ethylene for polymerization according to claim 1, wherein the first purification step comprises removing at least one selected from the group consisting of aliphatic unsaturated hydrocarbons having 3 to 14 carbon atoms, aliphatic saturated hydrocarbons having 3 to 14 carbon atoms, alcohols having 3 to 10 carbon atoms, and ethers having 3 to 10 carbon atoms from the raw material ethanol.

3. 3. The method for producing ethylene for polymerization according to claim 2, wherein the aliphatic unsaturated hydrocarbon having 3 to 14 carbon atoms comprises propylene.

4. 4. The process for producing ethylene for polymerization according to claim 2 or 3, wherein the aliphatic saturated hydrocarbons having 3 to 14 carbon atoms include aliphatic saturated hydrocarbons having 6 to 14 carbon atoms.

5. A method for producing a polymer, comprising a polymerization step of polymerizing a monomer containing ethylene produced by the method according to any one of claims 1 to 4 to obtain a polymer.