JP7589148B2 - Method for producing ethylene and method for producing polymer - Google Patents

Description

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 the ethylene obtained by the production method as a raw material.

Traditionally, ethylene is produced using 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 high-pressure methods, ethylene with a purity of 99.9% or more is used. For this reason, a technique has been known in the past in which raw olefins such as ethylene are purified and then polymerized.

For example, Patent Document 1 describes an invention relating to an olefin polymerization method, which is characterized in that a raw material olefin containing carbon dioxide as an impurity is brought into contact with a hybrid adsorbent made of a mixture of activated alumina and zeolite to purify the raw material olefin, and then the purified olefin is brought into contact with a transition metal complex catalyst to polymerize it.
According to Patent Document 1, a metallocene catalyst has been developed that has few of the drawbacks of the Ziegler-Natta catalysts that have been used conventionally, that the metallocene catalyst is extremely sensitive to impurities in the raw olefin, that industrial ethylene obtained from naphtha, crude oil, natural gas, etc. contains carbon dioxide at about several ppm (volume) to several hundred ppm (volume), and that carbon dioxide has an adverse effect as a catalyst poison in polymerization with a metallocene catalyst. The invention described in Patent Document 1 also describes that by using the hybrid adsorbent to economically, simply, and efficiently remove carbon dioxide, it is possible to sufficiently suppress the decrease in catalytic activity caused by impurities in olefin polymerization with a transition metal complex catalyst such as a metallocene catalyst, and it is possible to industrially and stably produce polymers with high productivity.

In recent years, the importance of carbon neutrality and carbon circulation has been debated, and bioethanol produced from sources such as sugarcane and ethanol derived from waste is being researched. Of these, bioethanol is problematic in terms of competition with food and biodiversity, so ethanol derived from waste is gaining attention.

JP 2017-137464 A

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

Therefore, the objective of the present invention is to provide a method for producing ethylene in which the ethylene polymerization reaction proceeds properly and the obtained polymer is of good quality, even when ethylene is produced using waste-derived ethanol as a raw material.

The present invention relates to the following items [1] to [8].
[1] an ethylene production step of obtaining an ethylene-containing product containing ethylene from raw material ethanol containing ethanol derived from waste;
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 the above [1], wherein the first purification step includes 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 the above [1] or [2], 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.

According to the present invention, even when ethylene is produced using waste-derived ethanol as a raw material, the ethylene polymerization reaction proceeds smoothly and the quality of the obtained polymer is good.

Hereinafter, the present invention will be described 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 a waste material, 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, even when waste-derived ethanol is used as the raw material, the ethylene polymerization reaction proceeds appropriately and the molecular weight of the polymer obtained becomes sufficiently high, resulting in a good quality polymer.

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 may be 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.

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 carrying out a raw material gas production process in which raw material gas is produced by gasifying waste, and then carrying out 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.

(Raw material gas generation process)
In the raw gas generation process, the waste may be gasified using, for example, a gasification furnace. The gasification furnace is a furnace that burns (incompletely combusts) a carbon source, and examples of such a furnace 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 gas is not particularly limited, but is usually 100 to 2500°C, and preferably 200 to 2100°C.

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

The raw material gas is produced by subjecting the waste to a heat treatment (commonly known as gasification) in which the waste is combusted (incomplete combustion), i.e., by partially oxidizing the waste, and the gas contains carbon monoxide in an amount of, although there is no particular restriction, 0.1% by volume or more, preferably 10% by volume or more, and more preferably 20% by volume or more.

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

In the synthetic gas purification process, the raw gas may be purified by processing using one or more of the following: a moisture separator consisting of a gas chiller, a low-temperature separation method (cryogenic method) 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 device (sulfide separator), a membrane separation method separator, a deoxygenation device, a pressure swing adsorption method separator (PSA), a temperature swing adsorption method separator (TSA), a pressure temperature swing adsorption method separator (PTSA), a separator using activated carbon, and a deoxygenation catalyst, specifically a separator using a copper catalyst or a palladium catalyst, to obtain a synthetic gas.

When ethanol is obtained by microbial fermentation, it is preferable to reduce the carbon dioxide gas concentration in the raw gas. For example, it is preferable to use 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.

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 vol. % or more and 80 vol. % or less, preferably 30 vol. % or more and 55 vol. % or less, and more preferably 30 vol. % or more and 50 vol. % or less, based on the total concentration of carbon monoxide, carbon dioxide, hydrogen, and nitrogen in the synthesis gas.

The carbon dioxide concentration in the synthesis gas is not particularly limited, but is usually 0.1 to 40% by volume, 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 viewpoint, the carbon dioxide concentration is more preferably 0.5 to 25% by volume.
The nitrogen concentration in the synthesis gas is usually 40 vol. % or less, preferably 1 vol. % or more and 20 vol. % or less, and more preferably 5 vol. % or more and 15 vol. % or less, based on the total concentration of carbon monoxide, carbon dioxide, hydrogen, and nitrogen in the synthesis gas.

The concentrations of carbon monoxide, carbon dioxide, hydrogen and nitrogen in the synthesis gas can be adjusted to within a predetermined range by appropriately changing combustion conditions such as the type of waste, the gasification temperature in the raw material gas production 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, and if you want to reduce the nitrogen concentration, you can supply gas with a higher oxygen concentration in the raw gas production process.
Furthermore, at least one of the raw material gas and the synthesis gas may be appropriately adjusted in concentration for each of the components carbon monoxide, carbon dioxide, hydrogen, and nitrogen. The concentration adjustment may be performed 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.

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

Generally, the microbial fermenter may be of any shape, including stirring, airlift, bubble column, loop, open bond, and photobio types. In the present invention, however, the microbial fermenter may preferably be a known loop reactor having a main tank section and a reflux section.
The synthesis gas to be 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 specified gas, such as at least one selected from the group consisting of sulfur compounds such as sulfur dioxide, phosphorus compounds, and nitrogen compounds.

The microbial fermenter may be continuously supplied with synthetic gas and microbial culture liquid, but it is not necessary to supply synthetic gas and microbial culture liquid simultaneously. Synthetic gas may be supplied to a microbial fermenter to which microbial culture liquid has been previously supplied. It is known that certain anaerobic microorganisms produce ethanol and the like from substrate gases such as synthetic gas by fermentation, and this type of gas-utilizing microorganism is cultured in a liquid medium. For example, a liquid medium and gas-utilizing bacteria may be supplied and accommodated, and synthetic gas may be supplied into the microbial fermenter while stirring the liquid medium in this state. This allows gas-utilizing bacteria to be cultured in a liquid medium, and ethanol to be produced from synthetic gas by the fermentation action of the bacteria.

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 at least 1 hour in continuous culture, more preferably at least 7 days, particularly preferably at least 30 days, and most preferably at least 60 days. There is no upper limit, but from the viewpoint of regular maintenance of the equipment, it is preferably 720 days or less, and more preferably 365 days or less. The culture time means the time from adding the seed bacteria to the culture tank to discharging the entire amount of the culture liquid in the culture tank.

The microorganisms (species) contained in the microbial culture solution are not particularly limited as long as they can produce ethanol by microbial fermentation of synthetic gas using carbon monoxide as the main raw material. For example, the microorganisms (species) are preferably those that produce ethanol from synthetic gas by the fermentation action of gas-utilizing bacteria, and in particular, those that have a metabolic pathway for acetyl-COA. Among gas-utilizing bacteria, the genus Clostridium is more preferable, and examples of such bacteria include Clostridium autoethanogenum, Clostridium ljungdahlii, Clostridium aceticum, Clostridium carboxidivorans, Moorella thermoacetica, and Acetobacterium woodii. Among these, Clostridium autoethanogenum is particularly preferable.

The medium used to culture the above-mentioned microorganisms (species) is not particularly limited as long as it has an appropriate composition according to the bacteria, 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-utilizing bacteria can grow well. For example, when using the genus Clostridium as the microorganism, the medium can be found in U.S. Patent Application Publication No. 2017/260552, paragraphs "0097" to "0099", etc.

By the microbial fermentation, a culture solution containing ethanol (ethanol-containing culture solution) is obtained. The culture solution containing ethanol is then subjected to a separation step.
In the separation step, for example, the ethanol-containing culture liquid may be heated to 23 to 500° C. under conditions of 0.01 to 1000 kPa (absolute pressure) to separate the liquid or solid component containing the microorganism and the 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, which will be described later, so that 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, which will be described later.

In the above 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 under normal pressure, at a temperature of preferably 50 to 200°C, more preferably at a temperature of 80°C to 180°C, and even more preferably at a temperature of 100 to 150°C.
The gaseous component containing ethanol obtained in the above separation step may be liquefied by condensation to obtain 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 the condenser include a water-cooled type, an air-cooled type, and an evaporative type, and among them, a water-cooled type is preferable. The condenser may be a single-stage condenser or a multi-stage condenser.

In addition, in the separation process, 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.

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. In addition, when 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 above-mentioned separation step.
The first stage purification step is a step of separating the ethanol-containing liquid into a distillate having an increased ethanol concentration and a bottoms liquid having a decreased ethanol concentration. Examples of the apparatus 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 having a boiling point lower than that of ethanol, a treatment apparatus for removing high-boiling substances having 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. As the unit operation, a distillation apparatus or membrane separation can be suitably used, and a distillation apparatus is more preferred. In addition, as the membrane separation, a zeolite membrane can be suitably used.

When a distillation apparatus is used, heated distillation is performed. In heated distillation, the desired ethanol can be obtained as the 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.

In the case of heat 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 of the bottom of the distillation column is raised to 90°C or higher within 30 minutes, and then the ethanol-containing liquid is introduced from the middle of the distillation column. In addition, in the case of heat distillation using a distillation apparatus, it is preferable to perform the distillation process with the temperature difference between the bottom, middle, and top of the column being within ±15°C. When the temperature difference is within ±15°C, it is easy to obtain high-purity ethanol. The distillation temperature difference is preferably ±13°C, and more preferably ±11°C. With these distillation temperature differences, separation from other components, i.e., purification by distillation of ethanol can be more reliably performed.

The pressure inside the distillation apparatus during the distillation of ethanol may be normal pressure, but is preferably less than atmospheric pressure, and more preferably about 60 to 95 kPa (absolute pressure). By setting the pressure inside the distillation apparatus within the above range, it is possible to improve the efficiency of ethanol separation, and thus the yield of ethanol.

The ethanol obtained through the above-mentioned first-stage purification process is used as a raw material for obtaining an ethylene-containing product in the ethylene production process 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: CH ₃ CH ₂ OH), but is a composition containing impurities, and is also called "raw material ethanol." The impurities are contained in the raw material ethanol produced through each of the above-mentioned processes, and most of them are compounds derived from waste.

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

Examples of the promoter active metal include titanium, magnesium, vanadium, etc. By supporting the promoter active metal in addition to the hydrogenation active metal, it is possible to further increase the CO conversion rate, the ethanol selectivity, and the like.
The metal catalyst is preferably a rhodium catalyst. The rhodium catalyst may be used in combination with a metal catalyst other than the rhodium 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, so the product should be subjected to a preliminary purification step such as distillation to obtain raw material ethanol.

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

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 more than the above lower limit, the polymerization reaction using ethylene as a raw material proceeds favorably through 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. 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 materials.

[Ethylene production process]
The raw material ethanol is converted to 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 to ethylene. The raw material ethanol is converted to ethylene by a dehydration reaction.

The catalyst to be used is not limited as long as it can convert ethanol to ethylene, but examples include zeolites, modified zeolites such as P-modified zeolites, 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.

Zeolites that contain at least one type of 10-membered ring in their structure are advantageous and have 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.

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

The zeolite is also preferably a dealuminated zeolite, from which about 10% by weight of aluminum is advantageously removed, the dealumination being advantageously carried out by steam treatment, optionally followed by leaching.
The zeolite and the dealuminated zeolite are advantageously essentially in the H type and may contain, as a secondary component (component amounting to 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.

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 withstand the temperatures and other conditions used in the dehydration process of the present invention. The binder is at least one inorganic material selected from clays, silica, metal silicates, metal oxides (e.g., _ZrO2 ), or gels containing mixtures of silica and metal oxides.

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

In addition, 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 weight, preferably between 0.3 and 7% by weight.
It is also advantageous if, for the starting zeolite, at least 10% by weight of aluminum has been extracted and removed from the zeolite by leaching.

The catalyst using the P-modified zeolite may be the P-modified zeolite itself, or may be a blended type P-modified zeolite that combines the P-modified zeolite with other materials. By using the blended type, the hardness or catalytic activity of the catalyst can be improved.
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 ingredients 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.
Suitable examples of P-modified zeolites are silicoaluminophosphates, more preferably silicoaluminophosphates of 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. Silicon is inserted into the ALPO framework by adding a silicon precursor during the synthesis, creating acid sites on the surface of the micropores of the 10-ring zeolite. The silicon content is 0.1-10 atomic % (Al+P+Si is 100).

It is also preferred to use alumina (particularly gamma-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 having a wide range of acid strength distribution and Lewis-type and Bronsted-type acid sites. Activated alumina is preferably used as the alumina.

It is also preferable to deposit silicon, zirconium, titanium, fluorite, etc. on the surface of the alumina to improve the selectivity of the catalyst. That is, the catalyst may be silicated, zirconated, or titanated to improve the selectivity of the catalyst. For the preparation of such a catalyst, a suitable commercially available alumina, preferably eta or gamma alumina having a surface area of 10 to 500 m ² /g and an alkali content of 0.5% or less, may be used. The catalyst may be prepared by adding silicon, zirconium, titanium, etc. in a total amount of 0.05 to 10% by mass. The addition of these metals may be carried out during the preparation of the alumina, or may be added to the alumina after preparation, or these metals may be added in the form of a precursor. Fluorinated alumina itself is known and may be prepared according to conventional techniques.

In the ethylene production step, a heteropolyacid supported catalyst is also preferred 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 in the form of 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 a polyvalent metal atom with 12 to 18 oxygen atoms attached thereto, known as peripheral atoms, which surround one or more central atoms in a symmetrical manner. 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 comprise 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.

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.
Examples of suitable heteropolytungstic acids include 18-phosphotungstic acid (H ₆ [P ₂ W ₁₈ O ₆₂ ].xH ₂ O), 12-phosphotungstic acid (H ₃ [PW ₁₂ O ₄₀ ].xH ₂ O), 12-silicon tungstic acid (H ₄ [SiW ₁₂ O ₄₀ ].xH ₂ O), cesium hydrogen silicon tungstate (Cs ₃ H[SiW ₁₂ O ₄₀ ].xH ₂ O), monopotassium phosphotungstate (KH ₅ [P ₂ W ₁₈ O ₆₂ ].xH ₂ O), 12-monosodium silicon tungstate (NaK ₃ [SiW ₁₂ O ₄₀ ].xH ₂ O), and potassium phosphotungstate (K ₆ [P ₂ W ₁₈ O ₆₂ ].xH ₂ O). Mixtures of two or more different heteropolytungstic acids and salts can also be used.

More preferably, the heteropolyacid component of the supported heteropolyacid catalyst is selected from silicotungstic acid, _{phosphotungstic} acid, and mixtures thereof, such as 12 _- silicotungstic acid ( _H4 [ _SiW12O40 ].xH2O), 12-phosphotungstic acid ( _H3 [ _PW12O40 ] _.xH2O ), and mixtures thereof. Even more preferably _, the heteropolyacid is silicotungstic acid, and most preferably, the heteropolyacid is 12-silicotungstic acid.

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

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 cogels, silica-zirconia cogels, carbon-coated alumina, zeolites, zinc oxide, and flame pyrolysis oxides. Silica-based catalyst supports, such as silica gel supports and supports prepared by flame hydrolysis of SiCl4, 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.

Although not particularly limited, the raw material ethanol is preferably converted to ethylene in a gas phase by contacting with the catalyst. The raw material ethanol may be further mixed with water, and may be mixed with optional components other than the raw material ethanol and water, and one or both of the water and the optional components may be contacted with the catalyst as a gas together with the raw material ethanol.
The catalyst may be filled, for example, in a reaction vessel, and the raw material ethanol or the 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, and a gas-phase dehydration reaction may be carried out to discharge an ethylene-containing product in the gas phase from the reaction vessel. When 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.

In the case of a zeolite or alumina-based catalyst, the temperature of 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) of 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.

In the case of a heteropolyacid supported catalyst, the temperature of 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 supported heteropolyacid catalyst, the supported heteropolyacid 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 supported heteropolyacid catalyst.

[First and second purification steps]
In the ethylene production method of the present invention, as described above, at least one of a first purification step of purifying the raw material ethanol is carried out before the ethylene production step, or a second purification step of purifying the ethylene-containing product is carried out after the ethylene production step. 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.

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 deteriorate the quality of the polymer obtained from ethylene. Therefore, by removing hydrocarbons, alcohols, and ethers with specific carbon numbers in the first purification process, the polymerization reaction of ethylene can be favorably progressed, and the quality of the obtained polymer can also be easily improved.

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 a mode in which the target substance is completely removed from the raw material ethanol or the ethylene-containing product, but also a mode in which the content of the target substance is reduced.

As described in the description of the first purification step, in the second purification step, by removing hydrocarbons, alcohols, and ethers having specific carbon numbers, the polymerization reaction of ethylene can be favorably advanced and the quality of the obtained polymer can be easily improved.
Carbon monoxide and oxygen have high electronegativity and may inhibit the polymerization reaction of ethylene. For example, when a specific catalyst such as a Ziegler-Natta catalyst is used, the polymerization reaction may be inhibited. In addition, oxygen can be a polymerization initiator in radical polymerization such as high pressure polymerization, so that the polymerization may run out of control if a large amount of oxygen is contained. Therefore, by removing carbon monoxide and oxygen from the ethylene-containing composition in the second purification step, it is possible to prevent the inhibition of the polymerization reaction of ethylene by them.

It is preferable that the ethylene produced by the present invention has a carbon monoxide content of 1 vol% or less by removing carbon monoxide. By making the carbon monoxide content 1 vol% or less, it is possible to prevent the polymerization reaction using ethylene from being inhibited by carbon monoxide. From this viewpoint, the carbon monoxide content is more preferably 0.5 vol% or less, and even more preferably 0.1 vol% 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 vol%.

It is preferable that the ethylene produced by the present invention has an oxygen content of 1% by volume or less by removing oxygen. By making the oxygen content 1% by volume or less, it is possible to prevent the polymerization reaction using ethylene from being inhibited by oxygen. From this viewpoint, the oxygen content is more preferably 0.5% by volume or less, and even more preferably 0.1% by volume or less. In addition, 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.

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 it is preferable that the aliphatic unsaturated hydrocarbons having 3 to 14 carbon atoms removed in either step include propylene. If propylene is contained in ethylene, when the ethylene is used in a polymerization reaction, propylene becomes 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.

It is preferable that the ethylene produced by the present invention has a propylene content of 1 vol% or less by removing propylene. By making the propylene content 1 vol% or less, the effect of reducing branched chains can be achieved. From this viewpoint, the propylene content is more preferably 0.5 vol% or less, and even more preferably 0.1 vol% or less. In addition, 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 vol%.

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 it is preferable that the aliphatic saturated hydrocarbons having 3 to 14 carbon atoms removed in either step 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 are preferably linear. A specific example of the aliphatic saturated hydrocarbons having 6 to 14 carbon atoms is preferably 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 raw material ethanol derived from waste. On the other hand, these aliphatic saturated hydrocarbons are highly compatible with fat and oil components contained in food, and if the polymer produced from the ethylene produced in the present invention is used as a packaging material for food products, 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.
Moreover, the aliphatic saturated hydrocarbons having 3 to 14 carbon atoms removed in any of the above-mentioned steps preferably contain aliphatic saturated hydrocarbons having 10 to 14 carbon atoms, from the viewpoint that they are contained in large amounts in the raw material ethanol derived from waste.

In the ethylene produced by the present invention, the aliphatic saturated hydrocarbons having 6 to 14 carbon atoms are removed, so that the content of the aliphatic saturated hydrocarbons having 6 to 14 carbon atoms is preferably 0.3 vol% or less, more preferably 0.2 vol% or less, and even more preferably 0.1 vol% or less. 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 the aliphatic saturated hydrocarbons having 6 to 14 carbon atoms is 0 vol%.

In addition, it is preferable that the alcohol having 3 to 10 carbon atoms is removed in the first purification step, the second purification step, or both, and the alcohol having 3 to 10 carbon atoms removed in either step includes, for example, 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 by removing these alcohols in the first purification step, the second purification step, or both, the polymerization reaction using ethylene described below can be favorably carried out, and the quality of the obtained polymer can also be easily improved.

In addition, it is preferable that the alcohol having 3 to 10 carbon atoms that is removed in any of the above-mentioned steps 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 of the polymer, so by removing 2-propanol, it is possible to reduce the number of branched chains in the polymer. Therefore, it is particularly preferable to remove 2-propanol 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.

It is preferable that the ethylene produced by the present invention has a 2-propanol content of 0.3 vol% or less by removing 2-propanol. By making the content 0.3 vol% or less, it becomes easier to exert the effect of reducing branched chains. From this viewpoint, the 2-propanol content is more preferably 0.1 vol% or less, and even more preferably 0.05 vol% 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 vol%.

The ethers having 3 to 10 carbon atoms may be removed in the first purification step, the second purification step, or both, and the ethers having 3 to 10 carbon atoms removed in either step include, for example, at least one selected from diethyl ether and dibutyl ether. These ethers are contained in relatively large amounts in the raw material ethanol derived from waste, and removing these ethers in the first purification step, the second purification step, or both, 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.

The ethers having 3 to 10 carbon atoms removed in any of the above steps preferably include dibutyl ether. Since dibutyl ether is a volatile organic compound (VOC), removing dibutyl ether is beneficial in that it reduces the risk of adverse effects, such as health risks, that may be caused by VOCs.

It is preferable that the ethylene produced by the present invention has a dibutyl ether content of 0.3 vol% or less by removing dibutyl ether. By making the dibutyl ether content 0.3 vol% or less, it becomes easier to exert the effect of reducing the risk of adverse effects such as health risks. From this viewpoint, the dibutyl ether content is more preferably 0.1 vol% or less, and even more preferably 0.05 vol% or less. In addition, the ethylene produced by the present invention may not contain dibutyl ether at all, and therefore the lower limit of the dibutyl ether content is 0 vol%.

In addition, since water is produced by a dehydration reaction in the ethylene production step, it is preferable to remove at least the water in the second purification step. Furthermore, since unreacted ethanol generally remains in the ethylene-containing product produced in the ethylene production step, it is preferable to remove the unreacted ethanol as well. By removing water and ethanol, the polymerization reaction using ethylene, which will be described later, can be favorably carried out, and the quality of the obtained polymer can be easily improved.

The ethylene produced by the present invention preferably has a water content of 0.3% by volume or less, as the water is removed in the second purification step. By making the water content 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. In addition, 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.

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 making the ethanol content 0.3% by volume or less, it becomes easier to proceed favorably with the polymerization reaction using ethylene, and it also becomes easier to improve the quality of the obtained polymer. From this viewpoint, the ethanol content is more preferably 0.1% by volume or less, and even more preferably 0.05% by volume or less. In addition, 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.

In addition, the ethylene produced in the present invention is generally a gas, and the volume percentage of each of the above components can be measured by analyzing the gaseous ethylene using GC-TCD and GC-FID to analyze each inorganic gas (oxygen, carbon monoxide, etc.) and organic gas.

Purification methods for each of the first and second purification steps include moisture separation devices consisting of gas chillers or the like, separation devices using adsorbents such as activated carbon, pressure swing adsorption type separation devices (PSA), temperature swing adsorption type separation devices (TSA), pressure temperature swing adsorption type separation devices (PTSA), low temperature separation type (cryogenic type) separation devices, water-soluble impurity separation devices such as scrubbers, desulfurization devices (sulfide separation devices), membrane separation type separation devices, distillation devices, separation devices with chromatography, solution absorption devices, etc.

Various forms of low-temperature separation can be used, for example, a method 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, and an alkaline solution such as an amine solution can be used as the absorbing solution. For example, if an alkaline solution is used in the first purification step, carbon dioxide and the like in the gasified raw material ethanol can be absorbed.

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, and among these, it is more preferable to remove those with a relatively large carbon number, and it is particularly preferable to remove aliphatic unsaturated hydrocarbons having 6 to 14 carbon atoms. Organic compounds with a large carbon number 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.
In the first purification step, the method for removing the aliphatic unsaturated hydrocarbons having 6 to 14 carbon atoms is not particularly limited, but it is preferable to remove them using a separation device having a chromatography. As the chromatography, it is preferable to use reverse phase chromatography or the like. Furthermore, they may be removed using a distillation device, activated carbon adsorption, or the like.

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. As described above, in the second purification step, it is preferable to remove at least one selected from a specific organic compound, carbon monoxide, and oxygen, and it is more preferable that the specific organic compound removed is a low-molecular-weight organic compound having a relatively low molecular weight (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 in the second purification step, in addition to water and unreacted ethanol, at least a specific low-molecular-weight organic compound having a relatively low molecular weight is removed, and it is also preferable that in the second purification step, carbon monoxide and oxygen are removed in addition to these.
More preferably, the specific organic compounds removed in the second purification step specifically include at least one selected from low molecular weight alcohols such as 2-propanol and low molecular weight ethers such as diethyl ether. Furthermore, it is even more preferable that the specific organic compounds removed in the second purification step 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 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.
In addition, 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. 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.

In the second purification step, although there is no particular limitation, purification is preferably performed using a separation device of a low-temperature separation type. Specifically, there is a method in which ethylene is solidified and separated by a condenser using a refrigerant (chiller) cooled to a temperature below the melting point of ethylene (−170° C. or lower at normal pressure).
In this case, substances such as water, carbon dioxide, ethanol, and other organic compounds having a melting point higher than that of ethylene may be removed by using one or more upstream condensers having a refrigerant temperature higher than that of the condenser. As the upstream condensers, for example, a first condenser having a relatively high refrigerant temperature (e.g., 0 to 25°C at normal pressure) and a second condenser having a lower refrigerant temperature 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 shape, and the ethylene-containing product in a gas phase may be brought into contact with a metal tube or the like through which a refrigerant passes, or the ethylene-containing product may be brought into direct contact with the refrigerant.

[Method of producing polymer]
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 structural units derived from ethylene. In the polymerization step, a monomer containing ethylene is polymerized to obtain a polymer. 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.

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).
In addition, other than these may be used as long as the polymer contains a structural unit derived from ethylene, and for example, the polymer may be a copolymer with a monomer other than ethylene. The monomer other than ethylene is not particularly limited, and examples thereof include 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 the copolymer 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).

Low-density polyethylene has short-chain branches and long-chain branches in its molecular structure, and has a density of 0.910 g/ ^cm3 or more and less than 0.942 g/ ^cm3 , typically a density of 0.930 g/cm3 ^or less. High-density polyethylene has a molecular structure with few branches and a density of 0.942 g/cm3 or ^more . Polyethylene with a density of 0.930 g/ ^cm3 or more and less than 0.942 g/ ^cm3 is sometimes called medium-density polyethylene.
Linear low density polyethylene is generally a copolymer of ethylene and a small amount of α-olefin other than ethylene, and the α-olefin other than ethylene includes α-olefins having 3 to 10 carbon atoms, specifically, propylene, butene-1, pentene-1, 4-methyl-pentene-1, hexene-1, octene-1, decene-1, etc. The density of linear low density polyethylene is less than 0.942 g/cm ³ , typically the density is 0.930 g/cm ³ or less, and is, for example, 0.880 g/cm ³ or more, typically 0.910 g/cm ³ or more.

Ultra-high molecular weight polyethylene (UHMWPE) is a polyethylene having a larger molecular weight than general polyethylene, for example, a polyethylene resin having a weight average molecular weight of 400,000 or more, preferably a weight average molecular weight of 1,000,000 or more. With an increased weight average molecular weight, the ultra-high molecular weight polyethylene has good mechanical strength in various respects. In addition, 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, from the viewpoint of ease of polymerization. The weight average molecular weight is the weight average molecular weight in terms of standard polystyrene measured by gel permeation chromatography (GPC).
The ultra-high molecular weight polyethylene (UHMWPE) may be an ethylene homopolymer, or may be a copolymer of ethylene and an α-olefin other than ethylene. The α-olefin other than ethylene is as described above for LLDPE.

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 of these.

Ethylene can also be polymerized in the presence of a catalyst such as a redox catalyst to produce polyethylene resin. Examples of redox catalysts include Ziegler-Natta catalysts, metallocene catalysts, Phillips catalysts, and standard catalysts.

As the Ziegler-Natta catalyst, for example, a triethylaluminum-titanium tetrachloride solid composite is used. The Ziegler-Natta catalyst may be, for example, a combination of a titanium trichloride composition obtained by reducing titanium tetrachloride with an organoaluminum compound and further treating it with various electron donors and electron acceptors, an organoaluminum compound, and an aromatic carboxylic acid ester, or a supported catalyst may be prepared by contacting magnesium halide with titanium tetrachloride and various electron donors.
Examples of metallocene catalysts include compounds such as bis(cyclopentadienyl) metal complexes having a structure in which a transition metal is sandwiched between π-electron unsaturated compounds, etc. More specifically, 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 can be mentioned.
The Ziegler-Natta catalyst and the metallocene catalyst may each be used in combination with a specific cocatalyst (promoter), such as methylaluminoxane (MAO) or a boron-based compound.

The Phillips catalyst is, for example, a catalyst system containing a chromium compound such as chromium oxide. Specific examples of the catalyst 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.

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

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

The present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples in any way.

<Production of raw material ethanol>
(Raw material gas generation process)
The gas discharged after incineration of general waste in a waste incineration facility was used. The raw gas contained approximately 30% by volume of carbon monoxide, approximately 30% by volume of carbon dioxide, approximately 30% by volume of hydrogen, and approximately 10% by volume of nitrogen.

(Synthetic gas refining process)
The raw material gas produced as described above was heated to a gas temperature of 80° C. using a pressure swing adsorption type separation apparatus (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 using a double-pipe heat exchanger using cooling water at 25° C. to precipitate impurities, which were then removed using a filter to produce a synthesis gas.

(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, a synthesis gas supply hole, and a discharge hole, and filled with a seed culture of Clostridium autoethanogenum (a microorganism) and a liquid medium for bacterial culture (containing appropriate amounts of phosphorus compounds, nitrogen compounds, various minerals, etc.), and culture (microbial fermentation) was performed continuously for 300 hours at 37° C. After that, about 8000 L of the culture liquid containing ethanol was extracted from the discharge hole.

(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.

(Preliminary purification process)
The ethanol-containing liquid was then introduced into a distillation apparatus equipped with a heater using steam at 170°C. After the temperature of the bottom of the distillation column was raised to 101°C within 8 to 15 minutes, the ethanol-containing liquid was introduced from the middle of the distillation column, and during continuous operation, the column bottom was kept at 101°C, the middle at 99°C, and the top at 91°C, and the operation was continued under the conditions of 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.

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

(Ethylene production process)
A product containing ethylene is produced from the raw material ethanol refined in the first refinement 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. 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 containing ethylene.

(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.

(Production of polyethylene resin)
After replacing the atmosphere in the reaction tube with nitrogen, modified methylaluminoxane (MMAO) as a co-catalyst, Ziegler-Natta catalyst, and toluene are added. After stirring at room temperature under normal pressure, the temperature is raised to 50°C and ethylene is supplied to polymerize, producing polyethylene resin (HDPE).
The polyethylene produced in this example is subjected to the first and second purification steps, so that the polymerization activity in the ethylene polymerization reaction proceeds favorably and the quality of the obtained polymer can be improved. For comparison, polyethylene polymerized using commercially available high purity ethylene has a similar molecular weight.

Claims (11)

an ethanol conversion step of producing an ethanol-containing culture solution from a waste-derived synthesis gas by microbial fermentation using a gas-utilizing microorganism;
A separation step of separating components containing microorganisms from the obtained ethanol-containing culture liquid to obtain an ethanol-containing liquid;
A preliminary purification step of purifying the ethanol-containing liquid using a distillation apparatus to obtain raw material ethanol containing ethanol derived from waste;
a first purification step of further purifying the raw ethanol by any one of chromatography, distillation, and activated carbon adsorption to remove aliphatic unsaturated hydrocarbons having 6 to 14 carbon atoms ;
an ethylene production step of obtaining an ethylene-containing product containing ethylene from the raw material ethanol that has been subjected to the first purification step;
A method for producing ethylene comprising the steps of: 2. The method for producing ethylene according to claim 1, wherein the content of aliphatic saturated hydrocarbons having 6 to 14 carbon atoms in the produced ethylene is 0.3 vol % or less. 3. The method for producing ethylene according to claim 1 or 2, further comprising, after the ethylene production step, a second purification step of 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 . The method for producing ethylene according to claim 3, wherein carbon monoxide and oxygen are removed in the second purification step. an ethanol conversion step of producing an ethanol-containing culture solution from a waste-derived synthesis gas by microbial fermentation using a gas-utilizing microorganism;
A separation step of separating components containing microorganisms from the obtained ethanol-containing culture liquid to obtain an ethanol-containing liquid;
A preliminary purification step of purifying the ethanol-containing liquid using a distillation apparatus to obtain raw material ethanol containing ethanol derived from waste;
an ethylene production step of obtaining an ethylene-containing product containing ethylene from the raw material ethanol;
a second purification step of purifying the ethylene-containing product after the ethylene production step to remove carbon monoxide and oxygen;
A method for producing ethylene comprising the steps of: 6. The method for producing ethylene according to claim 5, comprising a first purification step of 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 prior to the ethylene production step. 7. The method for producing ethylene according to any one of claims 4 to 6, wherein the produced ethylene has a carbon monoxide content of 1 vol% or less and an oxygen content of 1 vol% or less. The method for producing ethylene according to claim 3 or 6 , wherein the aliphatic unsaturated hydrocarbon having 3 to 14 carbon atoms includes propylene. The method for producing ethylene according to any one of claims 3, 6 and 8 , wherein the alcohol having 3 to 10 carbon atoms includes 2-propanol. The method for producing ethylene according to any one of claims 3, 6, 8 and 9 , wherein the ether having 3 to 10 carbon atoms comprises dibutyl ether. 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 claims 1 to 10 to obtain a polymer.