Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C17/00—Preparation of halogenated hydrocarbons
  • C07C17/35—Preparation of halogenated hydrocarbons by reactions not affecting the number of carbon or of halogen atoms in the reaction
  • C07C17/357—Preparation of halogenated hydrocarbons by reactions not affecting the number of carbon or of halogen atoms in the reaction by dehydrogenation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/22—Halogenating
  • B01J37/26—Fluorinating
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
  • B01J35/61—Surface area
  • B01J35/613—10-100 m2/g
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C17/00—Preparation of halogenated hydrocarbons
  • C07C17/25—Preparation of halogenated hydrocarbons by splitting-off hydrogen halides from halogenated hydrocarbons
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C21/00—Acyclic unsaturated compounds containing halogen atoms
  • C07C21/02—Acyclic unsaturated compounds containing halogen atoms containing carbon-to-carbon double bonds
  • C07C21/18—Acyclic unsaturated compounds containing halogen atoms containing carbon-to-carbon double bonds containing fluorine
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
  • B01J21/02—Boron or aluminium; Oxides or hydroxides thereof
  • B01J21/04—Alumina
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07B—GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR
  • C07B61/00—Other general methods

Definitions

• This disclosure relates to a method for producing fluoroolefins.
• Patent Document 1 describes a method for producing fluoroolefins that includes a dehydrofluorination step in which fluorocarbon is contacted with a metal catalyst to dehydrofluorinate it, and that is carried out in the gas phase in the presence of water, with the water concentration being 500 ppm relative to the fluorocarbon, and ⁇ -alumina is used as the catalyst. Furthermore, Non-Patent Document 1 describes a method for obtaining trifluoroethylene using ⁇ -alumina, ⁇ -alumina, ⁇ -alumina, etc. in the dehydrofluorination reaction of 1,1,1,2-tetrafluoroethane.
• Patent Document 1 when ⁇ -alumina was used as a catalyst, the conversion rate tended to decrease over long periods of production. Also, as described in Non-Patent Document 1, when ⁇ -alumina, ⁇ -alumina, or a combination of these was used as a catalyst, the initial conversion rate was high, but the conversion rate decreased over long periods of production. Also, when ⁇ -alumina was used as a catalyst, the conversion rate was very low at 1.2%.
• the objective of one embodiment of the present invention is to provide a method for producing fluoroolefins that has a higher conversion rate than conventional methods and that suppresses the decrease in conversion rate over long production periods.
• the present disclosure includes the following aspects. ⁇ 1>
• the method includes a step of contacting a fluorocarbon represented by the following formula (1) with a catalyst to produce a fluoroolefin represented by the following formula (2):
• the catalyst contains 65% by mass or more of ⁇ -alumina and has an amount of Lewis acid sites of 0.005 to 0.10 mmol/g as measured by ammonia temperature programmed desorption method.
• CX1X2 CX3X4 ...
• X 1 , X 2 , X 3 and X 4 each independently represent a hydrogen atom or a fluorine atom, provided that at least one of X 1 , X 2 , X 3 and X 4 is a fluorine atom.
• ⁇ 2> The method for producing a fluoroolefin according to ⁇ 1>, wherein the amount of the Lewis acid sites is 0.005 to 0.05 mmol/g.
• ⁇ 3> The method for producing a fluoroolefin according to ⁇ 1> or ⁇ 2>, wherein the amount of the Lewis acid sites is 0.008 to 0.05 mmol/g.
• ⁇ 4> The method for producing a fluoroolefin according to any one of ⁇ 1> to ⁇ 3>, wherein the amount of the fluorocarbon supplied to the catalyst is 350 kg/hr/m3 or more .
• ⁇ 5> The method for producing a fluoroolefin according to any one of ⁇ 1> to ⁇ 4>, wherein the fluorocarbon is at least one selected from the group consisting of 1,1,1-trifluoroethane, 1,1,2-trifluoroethane, 1,1,2,2-tetrafluoroethane, and 1,1,1,2-tetrafluoroethane.
• ⁇ 6> The method for producing a fluoroolefin according to any one of ⁇ 1> to ⁇ 5>, wherein the fluoroolefin is at least one selected from the group consisting of 1,2-difluoroethylene, 1,1-difluoroethylene, and trifluoroethylene.
• ⁇ 7> The method for producing a fluoroolefin according to any one of ⁇ 1> to ⁇ 6>, wherein the fluorocarbon is 1,1,1,2-tetrafluoroethane and the fluoroolefin is trifluoroethylene.
• ⁇ 8> The method for producing a fluoroolefin according to any one of ⁇ 1> to ⁇ 7>, wherein the fluorocarbon is contacted with the catalyst at a temperature of 300 to 800° C. ⁇ 9> The fluorocarbon is contacted with the catalyst in the presence of an inert gas, The method for producing a fluoroolefin according to any one of ⁇ 1> to ⁇ 8>, wherein the inert gas is at least one selected from the group consisting of nitrogen, helium, argon, octafluorocyclobutane, and carbon dioxide.
• ⁇ 10> The method for producing a fluoroolefin according to any one of ⁇ 1> to ⁇ 9>, further comprising a step of drying the catalyst before contacting the fluorocarbon with the catalyst.
• the fluorocarbon is contacted with the catalyst in the presence of water in a gas phase,
• X 1 , X 2 , X 3 and X 4 each independently represent a hydrogen atom or a fluorine atom, provided that at least one of X 1 , X 2 , X 3 and X 4 is a fluorine atom.
• the present disclosure provides a method for producing fluoroolefins that has a higher conversion rate than conventional methods and suppresses a decrease in conversion rate over long production periods.
• a numerical range indicated using “to” means a range that includes the numerical values before and after “to” as the minimum and maximum values, respectively.
• the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in the present disclosure.
• the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples.
• combinations of two or more preferred aspects are more preferred aspects.
• the amount of each component means the total amount of the multiple substances, unless otherwise specified.
• long-term production refers to production for 50 hours by contacting the fluorocarbon with the catalyst, and may be production for 50 hours or more.
• a method for producing a fluoroolefin in a first embodiment of the present disclosure includes a step of producing a fluoroolefin represented by the following formula (2) by contacting a fluorocarbon represented by the following formula (1) with a catalyst, the catalyst containing 65 mass % or more of ⁇ -alumina and having an amount of Lewis acid sites of 0.005 to 0.10 mmol/g as measured by ammonia temperature programmed desorption spectrometry.
• a method for producing a fluoroolefin in a second embodiment of the present disclosure includes a step of contacting a fluorocarbon represented by the following formula (1) with a catalyst to produce a fluoroolefin represented by the following formula (2), wherein the conversion rate 10 hours after contacting the fluorocarbon with the catalyst is 7.0 to 13.0%, and the conversion maintenance rate, which is the ratio of the conversion rate after 50 hours to the conversion rate after 10 hours, is 69% or more.
• CX1X2 CX3X4 ...
• X 1 , X 2 , X 3 and X 4 each independently represent a hydrogen atom or a fluorine atom, provided that at least one of X 1 , X 2 , X 3 and X 4 is a fluorine atom.
• the fluoroolefin production method of the first embodiment and the fluoroolefin production method of the second embodiment are collectively referred to as the fluoroolefin production method of the present disclosure.
• the disclosed method for producing fluoroolefins achieves a higher conversion rate than conventional methods, and prevents a decrease in conversion rate over long production periods. The reason for this is unclear, but is believed to be as follows.
• the catalyst has an effective amount of active sites that activate C—F bonds, which results in the expression of dehydrofluorination reaction activity. It was also found that the use of a catalyst containing 65% by mass or more of ⁇ -alumina and having an amount of Lewis acid sites of 0.10 mmol/g or less as measured by ammonia temperature programmed desorption method suppresses the decrease in catalytic activity during long-term production. This is believed to be because the catalyst is appropriately prevented from being fluorinated by hydrogen fluoride generated by the reaction. It is also believed to be because the phenomenon of coking, in which carbon generated by decomposition of the raw materials accumulates on the catalyst, is appropriately suppressed.
• Patent Document 1 describes a method for producing fluoroolefins using ⁇ -alumina.
• the crystal structure of ⁇ -alumina changes significantly in a high-temperature environment, when ⁇ -alumina is used as a catalyst, the conversion rate tends to decrease over a long period of production.
• Non-Patent Document 1 describes a method for producing trifluoroethylene using Al 2 O 3 -1200 containing 100% by mass of ⁇ -alumina. It is described that Al 2 O 3 -1200 does not have any Bronsted acid sites but has an amount of Lewis acid sites of 0.004 mmol/g, as analyzed by ammonia temperature programmed desorption (NH 3 -TPD) or IR spectrum (Py-IR) of adsorbed pyridine. It is described that the conversion rate is about 1.2% when this Al 2 O 3 -1200 is used. It is presumed that the conversion rate is low because the amount of Lewis acid sites in Al 2 O 3 -1200 is less than 0.005 mmol/g, and therefore the catalyst has few active sites.
• NH 3 -TPD ammonia temperature programmed desorption
• Py-IR IR spectrum
• Non-Patent Document 1 describes a method for producing trifluoroethylene using Al 2 O 3 -1150, which contains 64.3 mass% of ⁇ -alumina and has an acid site amount of 0.006 mmol/g. It also describes that the conversion rate is about 1.2% when this Al 2 O 3 -1150 is used.
• Non-Patent Document 1 the amount of fluorocarbons fed to the catalyst is calculated to be 307 kg/h/ m3 , and the feed rate is set low, which is a condition for achieving a high conversion rate.
• the feed rate is low, industrial productivity decreases, so it is necessary to increase the feed rate.
• the conversion rate becomes lower than the above value.
• Non-Patent Document 1 describes a method for producing trifluoroethylene using an alumina catalyst with an acid site amount of 0.065 to 0.362 mmol/g.
• alumina catalysts are composed of ⁇ -alumina, ⁇ -alumina, etc., and do not contain ⁇ -alumina.
• the initial conversion rate is high, but the conversion rate drops significantly after 15 hours. This is presumably because, as mentioned above, ⁇ -alumina, ⁇ -alumina, etc., whose crystal structures are easily changed in high-temperature environments, are used.
• Non-Patent Document 1 the production is performed under high conversion conditions, with an initial conversion rate of about 28% or more and a conversion rate of 20% or more after 10 hours. In this case, the conversion rate after 15 hours is significantly reduced. This is considered to be because if the initial conversion rate is too high, the amount of hydrogen fluoride generated increases, and fluorination, which is one of the causes of catalyst deactivation, progresses. If the fluorination of the catalyst progresses, catalyst coking tends to progress, and as a result, the catalyst tends to be deactivated. If the production time is further extended to 50 hours in Non-Patent Document 1, it is expected that the deactivation of the catalyst will progress and the conversion rate will further decrease.
• the conversion rate maintenance rate after 50 hours is maintained at 69% or more.
• a preferred method for effectively suppressing the conversion rate after 10 hours to 7-13% is to use the catalyst according to the first embodiment.
• a fluorocarbon represented by formula (1) In the method for producing a fluoroolefin according to the present disclosure, a fluorocarbon represented by the following formula (1) is used as a raw material.
• X 1 , X 2 , X 3 and X 4 each independently represent a hydrogen atom or a fluorine atom, provided that at least one of X 1 , X 2 , X 3 and X 4 is a fluorine atom.
• Examples of the fluorocarbon represented by formula (1) include the following compounds.
• CHF2CH3 1,1-difluoroethane (HFC - 152a)
• CF3CH3 1,1,1-trifluoroethane (HFC - 143a)
• CHF2CH2F 1,1,2- trifluoroethane (HFC-143)
• CF3CH2F 1,1,1,2- tetrafluoroethane (HFC-134a)
• CHF2CHF2 1,1,2,2-tetrafluoroethane (HFC - 134)
• CF3CHF2 1,1,1,2,2-pentafluoroethane (HFC - 125)
• the fluorocarbon represented by formula (1) is preferably at least one selected from the group consisting of HFC-143a, HFC-143, HFC-134a, and HFC-134, from the viewpoint of minimizing side reactions and suppressing the production of by-products.
• the fluorocarbon represented by formula (1) is preferably HFC-134a, since one type of fluoroolefin can be obtained with high selectivity.
• a fluoroolefin represented by formula (2) In the method for producing a fluoroolefin according to the present disclosure, a fluoroolefin represented by the following formula (2) is obtained as a reaction product.
• CX1X2 CX3X4 ... ( 2 )
• X 1 , X 2 , X 3 and X 4 each independently represent a hydrogen atom or a fluorine atom, provided that at least one of X 1 , X 2 , X 3 and X 4 is a fluorine atom.
• fluoroolefin represented by formula (2) examples include the following compounds.
• CHF CH 2 : Fluoroethylene CF 2 ⁇ CH 2 : 1,1-difluoroethylene (HFO-1132a)
• CHF CHF: 1,2-difluoroethylene (HFO-1132(E), HFO-1132(Z))
• CHF CF2 : Trifluoroethylene (HFO-1123)
• CF2 CF2 : tetrafluoroethylene
• the fluoroolefin represented by formula (2) is preferably at least one selected from the group consisting of HFO-1132, HFO-1132a, and HFO-1123.
• the fluorocarbon is HFC-134a and the fluoroolefin is HFO-1123.
• olefins other than the fluoroolefin represented by formula (2) may be produced, and the olefins other than the fluoroolefin represented by formula (2) may include ethylene.
• a fluorocarbon represented by formula (1) is contacted with a catalyst.
• the catalyst to be contacted with the fluorocarbon contains ⁇ -alumina in an amount of at least 65 mass %, and has an amount of Lewis acid sites measured by ammonia temperature programmed desorption spectrometry (NH 3 -TPD) of 0.005 to 0.10 mmol/g.
• Alumina is a dehydrated product of aluminum hydroxide, and its properties differ depending on the degree of dehydration and the degree of crystallinity.
• alumina such as ⁇ -alumina, ⁇ -alumina, and ⁇ -alumina, depending on the crystal structure.
• ⁇ -alumina and ⁇ -alumina are called activated alumina, and have a higher free energy of formation than ⁇ -alumina, and are thermodynamically unstable.
• the high-temperature stable phase with a high degree of crystallinity is ⁇ -alumina, which has a small specific surface area but is thermally stable and has a high thermal conductivity.
• the catalyst used in the method for producing fluoroolefins of the present disclosure includes ⁇ -alumina.
• ⁇ -alumina Compared with other alumina structures, ⁇ -alumina has a high barrier for conversion from Al-O to Al-F in the presence of hydrogen fluoride, and the use of a catalyst containing ⁇ -alumina makes it possible to suppress the generation of AlF 3. It is believed that the generation of AlF 3 leads to the deactivation of the catalyst, a decrease in selectivity, and the like.
• ⁇ -alumina in the catalyst can be confirmed by the diffraction pattern obtained by X-ray diffraction, in other words, XRD (X-Ray Diffractometer).
• XRD X-Ray Diffractometer
• the catalyst when the catalyst contains 65% by mass or more of ⁇ -alumina, the durability of the catalyst is high, and a decrease in conversion rate is suppressed even during long-term production.
• the catalyst can be confirmed to contain 65% by mass or more of ⁇ -alumina by performing Rietveld analysis on the crystal structure of XRD. Specifically, the peaks obtained by XRD measurement of the catalyst are compared with known peak models derived from each alumina structure, and the mass proportion of each crystal structure is calculated by performing Rietveld analysis.
• the catalyst contains ⁇ -alumina at 65% by mass or more, preferably at 70% by mass or more, more preferably at 75% by mass or more, even more preferably at 80% by mass or more, and particularly preferably at 85% by mass or more, and may contain 100% by mass.
• the catalyst may contain compounds other than ⁇ -alumina.
• compounds other than ⁇ -alumina include alumina with a different crystal structure from ⁇ -alumina and oxides other than alumina.
• oxides other than alumina include ⁇ -alumina, ⁇ -alumina, ⁇ -alumina, ⁇ -alumina, boehmite, and gibbsite.
• oxides other than alumina include chromium oxide, copper oxide, iron oxide, nickel oxide, magnesium oxide, zinc oxide, and zirconium oxide.
• the catalyst may also contain compounds other than ⁇ -alumina, such as aluminum oxide fluoride, which is ⁇ -alumina fluorinated.
• the ⁇ -alumina may function not only as a catalyst but also as a support while functioning as a catalyst, and the ⁇ -alumina may be supported on a support other than ⁇ -alumina.
• Supports include, for example, carbon, ⁇ -alumina, ⁇ -alumina, zirconia, silica, and titania.
• the catalyst has an amount of Lewis acid sites, as measured by an ammonia temperature programmed desorption method, of 0.005 to 0.10 mmol/g, preferably 0.005 to 0.05 mmol/g, and more preferably 0.008 to 0.05 mmol/g from the viewpoint of further suppressing the decrease in conversion rate after 100 hours.
• the catalyst may be one that has been dried, one that has been activated, one that has been both, or one that has neither.
• the state of the catalyst in this disclosure is assumed to be the state of the catalyst at the start of the reaction (immediately before the start of the reaction), and if various treatments are performed, the catalyst after the treatment is the subject of measurement of the Lewis acid point. Note that if the amount of acid points does not change substantially even after various treatments are performed, the Lewis acid point may be measured on the catalyst before the treatment.
• the ammonia temperature programmed desorption method is a method in which ammonia ( NH3 ) is adsorbed on a measurement sample, and then the temperature is continuously raised at a constant heating rate to measure the amount of ammonia desorbed and the desorption temperature.
• the amount of acid in the measurement sample can be measured from the amount of desorbed NH3 .
• the acid strength of the measurement target can also be measured. Therefore, in the present disclosure, the peak intensity of the amount of ammonia desorbed at temperatures below 200° C.
• the Lewis acid site is an acid site that accepts an electron pair from a partner molecule
• the Bronsted acid site is an acid site that donates a proton to the partner molecule.
• Ammonia temperature programmed desorption (NH 3 -TPD) measurements are performed using a catalyst analyzer (for example, "BELCAT II” manufactured by MicrotracBEL). In the measurements, the temperature is raised to 810°C at a heating rate of 10°C/min and held for 10 minutes. Helium is used as the carrier gas at a flow rate of 50 mL/min (sccm).
• the form of the catalyst is not particularly limited, and may be in the form of a powder, pellets, or spheres.
• the ⁇ -alumina is preferably in the form of a molded body such as a sphere or pellet.
• a molded body is different from a powder and can be obtained, for example, by putting a powder into a mold and compressing it.
• the raw material gas may contain a fluorocarbon represented by formula (1), and may contain components other than the fluorocarbon represented by formula (1).
• the raw material gas may consist of only the fluorocarbon represented by formula (1), or may contain isomers, disproportionation products, impurities, etc. obtained during the production of the fluorocarbon represented by formula (1).
• the raw material gas preferably contains an inert gas such as nitrogen, argon, helium, carbon dioxide, and octafluorocyclobutane in addition to the fluorocarbon represented by formula (1).
• the inert gas can dilute the target product and the by-product hydrogen fluoride.
• the content of the fluorocarbon represented by formula (1) is preferably 60 mol% or more, more preferably 70 mol% or more, even more preferably 75 mol% or more, and particularly preferably 80 mol% or more, based on the total amount of the raw material gas.
• the method for producing fluoroolefins disclosed herein may be carried out in either the gas phase or the liquid phase. Since the fluorocarbon represented by formula (1) is a gas at room temperature, it is preferable to contact the fluorocarbon with the catalyst in the gas phase.
• the reactor in which the fluorocarbon is brought into contact with the catalyst may be one that can withstand the temperature and pressure described below, and there are no particular limitations on its shape or structure.
• An example of the reactor is a cylindrical vertical reactor.
• materials for the reactor include glass, stainless steel, iron, nickel, and alloys mainly composed of iron or nickel.
• the reactor may be equipped with a heating means such as an electric heater for heating the inside of the reactor.
• the catalyst may be housed in any of the following formats: fixed bed, fluidized bed, or moving bed. If it is a fixed bed, it may be either a horizontal fixed bed or a vertical fixed bed.
• the reaction system may be either a flow system or a batch system.
• a moving bed reactor In a fixed bed reactor, various molded bodies of catalyst-supporting carriers are filled to reduce pressure loss of the reaction fluid.
• the catalyst layer In a fluidized bed reactor, the catalyst layer is operated so that it exhibits fluid-like properties due to the reaction fluid, so the catalyst particles are suspended in the reaction fluid and move inside the reactor.
• Fixed bed reactors are preferred because they offer a wide range of catalyst shape options and can suppress catalyst wear. Fixed bed reactors include tubular reactors and tank reactors, and tubular reactors are preferred because of the ease of controlling the reaction temperature.
• a multi-tube heat exchange reaction in which a large number of reaction tubes with small diameters are arranged in parallel and a heat medium is circulated on the outside can be used.
• multiple catalyst layers are installed. There should be at least one catalyst layer, but there may be two or more.
• the fluoroolefin production method of the present disclosure is preferably carried out in a flow-through manner using a fixed-bed reactor (particularly a vertical fixed-bed type reactor).
• the amount of fluorocarbon supplied to the catalyst is preferably 350 kg/hr/m3 or more , more preferably 375 kg/hr/m3 or more , and even more preferably 400 kg/hr/m3 or more .
• the raw material supply amount is preferably 3000 kg/hr/m3 or less , more preferably 2500 kg/hr/m3 or less , and even more preferably 2000 kg/hr/m3 or less .
• the raw material supply amount is the amount of fluorocarbon (raw material) supplied per 1 m3 of catalyst per unit time (kg/hr), and it is preferable that the amount of fluorocarbon that comes into contact with the catalyst by being supplied thereto is within the above range.
• the fluorocarbon and the catalyst are preferably contacted at a temperature of 300 to 800°C, more preferably at a temperature of 400 to 700°C, and even more preferably at a temperature of 400 to 600°C. If the contact temperature is 300°C or higher, the conversion rate of the fluoroolefin is improved. On the other hand, if the contact temperature is 800°C or lower, decomposition of the fluoroolefin can be suppressed.
• the contact temperature is 300°C or higher, the reaction will proceed properly. On the other hand, if the contact temperature is 800°C or lower, the selectivity will decrease due to the cleavage of the carbon-carbon bonds in the raw material, and the disproportionation reaction of the product (unsaturated compound) will be suppressed.
• the dehydrofluorination reaction is generally an endothermic reaction
• the decrease in the conversion rate can be suppressed by appropriately maintaining the reaction temperature.
• the reaction temperature in the catalyst layer increases, the conversion rate of the raw material increases. Therefore, it is preferable to maintain the reaction temperature in the catalyst layer at a desired temperature so that a high conversion rate can be maintained.
• a method of heating the catalyst layer from the outside with a heat medium or the like can be mentioned. Catalysts usually deteriorate over time as the reaction progresses.
• the decrease in the conversion rate can be suppressed by heating the catalyst layer with a heat medium or the like and appropriately maintaining or increasing the reaction temperature.
• the reaction zone begins at the introduction point for the raw material gas.
• the catalyst at the introduction point for the raw material gas deteriorates over time as the reaction progresses, the reaction zone moves downstream in the direction of gas flow. Since the low-temperature product gas generated in the reaction zone flows into the vicinity of the downstream side of the reaction zone, the vicinity of the downstream side is usually the coldest in the catalyst layer.
• the temperature of this region of the catalyst layer that is at the coldest temperature is referred to as the "minimum temperature of the catalyst layer.”
• the temperature from the vicinity of the downstream side further downstream usually increases from the minimum temperature of the catalyst layer as it moves away from the reaction zone.
• the raw material gas containing fluorocarbons may be supplied to the reactor at room temperature. However, it is preferable to properly heat (preheat) the raw material gas before supplying it to the reactor. When preheating is performed, it is preferable to heat the raw material gas to a temperature of 80 to 600°C before supplying it to the reactor. Preheating to 80°C or higher makes it difficult for the internal temperature of the reactor to decrease, making it easier to achieve the set conversion rate. Preheating to 600°C or lower also makes it difficult for the internal temperature of the reactor to increase, suppressing undesirable reactions and improving the selectivity.
• the dehydrofluorination reaction in the present disclosure is a reaction in which the number of molecules increases, so increasing the pressure makes the forward reaction unfavorable.
• the pressure when the fluorocarbon is contacted with the catalyst is not particularly limited, but from the viewpoint of improving the conversion rate, it is preferably from ⁇ 0.05 to 2 MPa, more preferably from ⁇ 0.01 to 1 MPa, and even more preferably from normal pressure to 0.5 MPa. In this disclosure, pressure means gauge pressure.
• the contact time (seconds) between the fluorocarbon and the catalyst is preferably 0.5 to 100.0 seconds, more preferably 1.0 to 50.0 seconds, and even more preferably 2.0 to 20.0 seconds.
• the contact time (g ⁇ sec/mL) between the fluorocarbon and the catalyst is preferably 1 to 200 g ⁇ sec/mL, more preferably 5 to 175 g ⁇ sec/mL, even more preferably 7 to 150 g ⁇ sec/mL, and particularly preferably 10 to 125 g ⁇ sec/mL. If the contact time (g ⁇ sec/mL) is 1 g ⁇ sec/mL or more, the conversion rate is improved. If the contact time (g ⁇ sec/mL) is 200 g ⁇ sec/mL or less, equipment costs can be reduced.
• an inert gas is preferably at least one selected from the group consisting of nitrogen, helium, argon, octafluorocyclobutane, and carbon dioxide. Of these, the inert gas is preferably nitrogen.
• an inert gas refers to a gas that is inert to reaction with the raw material.
• the molar ratio of fluorocarbon to inert gas in the gas phase is preferably 0.1 to 30, more preferably 0.5 to 25.
• the fluorocarbon and the catalyst are contacted in the gas phase in the presence of water, and the concentration of water is less than 500 ppm by mass based on the total amount of the raw material gas containing the fluorocarbon.
• the concentration of water is less than 500 ppm by mass based on the total amount of the raw material gas containing the fluorocarbon.
• the above water concentration is preferably 300 mass ppm or less, more preferably 100 mass ppm or less, even more preferably 50 mass ppm or less, and particularly preferably 10 mass ppm or less, from the viewpoint of further improving the conversion rate and obtaining the target compound with a higher selectivity.
• the lower the water concentration the more preferable it is, but from the viewpoint of the cost of the dehydration treatment of fluorocarbon and inert gas and the difficulty of process management, it is preferably 0.5 mass ppm or more, more preferably 1 mass ppm or more.
• a common method for measuring water concentration is to use a commercially available Karl Fischer water content meter.
• the above water concentration is the water content contained in the raw gas when the fluorocarbon is brought into contact with the catalyst. Note that the water concentration may be replaced with the water content contained in the raw gas before it is flowed into the reactor.
• a step of drying the catalyst water contained in the catalyst is removed, increasing its reactivity with fluorocarbons and improving the conversion rate.
• the method for drying the catalyst is not particularly limited, and the catalyst may be dried before being filled into the reactor, or may be dried after being filled into the reactor. In the case of drying the catalyst after being filled into the reactor, it is preferable because the reactor can be preheated while drying the catalyst. Specifically, it is preferable to dry the catalyst by filling the reactor with the catalyst and heating the reactor while passing an inert gas through it.
• hydrogen fluoride is produced as a by-product.
• Hydrogen fluoride has the function of fluorinating oxides contained in the catalyst and strengthening the acidity. Therefore, it is preferable to reduce the concentration of hydrogen fluoride.
• concentration of hydrogen fluoride By reducing the concentration of hydrogen fluoride, the selectivity is maintained, the deactivation of the catalyst is suppressed, and the decrease in reaction activity due to the decrease in the specific surface area of the catalyst is suppressed.
• One method for reducing the concentration of hydrogen fluoride is to dilute it with an inert gas. Since the use of an inert gas increases the energy load in the purification step after the reaction, it is preferable to appropriately control the use of the inert gas.
• the hydrogen fluoride concentration during the reaction is preferably 15 mol% or less. From the viewpoint of extending the catalyst life, the hydrogen fluoride concentration is more preferably 13 mol% or less, even more preferably 10 mol% or less, particularly preferably 8 mol% or less, and most preferably 7 mol% or less. Also, from the viewpoint of productivity and energy load in the purification process, the hydrogen fluoride concentration is preferably 0.5 mol% or more, more preferably 0.8 mol% or more, even more preferably 1.0 mol% or more, particularly preferably 1.3 mol% or more, and most preferably 1.5 mol% or more.
• the fluoroolefin production method of the present disclosure is preferably carried out in the presence of an oxidizing agent.
• the oxidizing agent is preferably oxygen, chlorine, bromine or iodine, since it has a high conversion rate and can obtain the target compound with high selectivity. Among them, oxygen is more preferable as the oxidizing agent.
• the concentration of the oxidizing agent is preferably 0.01 to 21 mol% relative to the raw material gas.
• the concentration of the oxidizing agent is more preferably 1 to 20 mol% relative to the raw material compound, even more preferably 5 to 18 mol%, and particularly preferably 7.5 to 16 mol%, since it can further improve the conversion rate and obtain the target compound with higher selectivity.
• the conversion rate means the ratio (mol %) of the total molar amount of compounds other than the raw material compounds contained in the effluent gas from the reactor outlet to the molar amount of the raw material compounds supplied to the reactor. In general, a higher conversion rate is preferable from the viewpoint of productivity. However, in the dehydrofluorination reaction of the present disclosure, it is preferable that the conversion rate is appropriately controlled. When the conversion rate is controlled, the concentration of hydrogen fluoride produced in the gas phase is reduced, and it is considered that deactivation of the catalyst by hydrogen fluoride is suppressed.
• the use of an inert gas increases the energy load of the purification process after the reaction, so that the use of an excessive inert gas is not preferable. From the viewpoint of extending the catalyst life, it is preferable to suppress the hydrogen fluoride concentration during the reaction to 15 mol% or less.
• the conversion rate maintenance rate which is the ratio of the conversion rate after 50 hours to the conversion rate after 10 hours, is preferably 69% or more. And, the conversion rate maintenance rate after 100 hours from contacting the fluorocarbon with the catalyst is preferably 30% or more, more preferably 40% or more, and even more preferably 50% or more.
• the conversion rate after 10 hours does not become too high, and deactivation of the catalyst is suppressed.
• a catalyst containing 65 mass % or more of ⁇ -alumina and having an amount of Lewis acid sites of 0.005 to 0.10 mmol/g as measured by an ammonia temperature programmed desorption method the conversion rate after 10 hours does not become too high, and deactivation of the catalyst is suppressed.
• the selectivity means the ratio (mol %) of the molar amount of the target product contained in the reactor outlet gas to the total molar amount of compounds other than the raw material compounds contained in the reactor outlet gas.
• a selectivity of 100% is preferred since it eliminates the need for post-reaction purification steps, but side reactions may occur in the reaction temperature range required to achieve the desired conversion.
• a high selectivity is preferred because it reduces the amount of waste, reduces the energy load of post-reaction purification steps, and extends the catalyst life.
• the selectivity 50 hours after contacting the fluorocarbon with the catalyst is preferably 90% or more, more preferably 93% or more, and even more preferably 95% or more.
• HFO-1123 is obtained with high selectivity by using HFC-134a as the fluorocarbon.
• Other compounds contained in the reactor outlet gas other than the raw material compounds and the target product include, for example, hydrogen fluoride, carbon monoxide, carbon dioxide, water, etc.
• HFC-134a is used as the raw material compound fluorocarbon
• other compounds further include HFC-134, 1,1-difluoroethylene (VdF), E/Z-1,2-difluoroethylene (HFO-1132(E)/(Z)), etc.
• Examples 1 to 6 are working examples
• Examples 7 and 8 are comparative examples.
• Example 1 1 mL of ⁇ -alumina (product name " ⁇ -alumina, average particle size 0.5 ⁇ m", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was weighed out and used as a catalyst.
• a stainless steel (SUS304) reaction tube having an inner diameter of 1.02 cm and a length of 30 cm was filled with the catalyst and placed in a tubular electric furnace, and the catalyst-filled part was heated to 475° C. in the tubular furnace while flowing nitrogen to dehydrate the catalyst. Thereafter, a 0.1/1 (mol/mol) mixed gas of nitrogen/HFC-134a was passed through for a contact time of 4.7 seconds to carry out a dehydrofluorination reaction to HFO-1123.
• the water concentration in the 0.1/1 (mole/mole) mixed gas of nitrogen/HFC-134a was measured with a Karl Fischer water content analyzer and was found to be 5 ppm by mass.
• Example 2 to 8 In Examples 2 to 8, the HF deprotection reaction was carried out in the same manner as in Example 1, except that the catalyst was changed and the various conditions were changed to the values shown in Table 2. The catalysts used in Examples 2 to 8 will be described below.
• Example 2 ⁇ -alumina (product name "SA52124", manufactured by Saint-Gobain) was used as a catalyst.
• Example 3 ⁇ -alumina (product name "SA52238", manufactured by Saint-Gobain) was used as a catalyst.
• Example 4 ⁇ -alumina (product name "FGL-40", manufactured by Iwatani Chemical Industries, Ltd.) was used as a catalyst.
• Example 5 ⁇ -alumina (product name "LT303D", manufactured by Nippon Light Metal Co., Ltd.) was used as a catalyst.
• Example 6 ⁇ -alumina (product name "C500”, manufactured by Nippon Light Metals Co., Ltd.) was used as a catalyst.
• Example 7 ⁇ -alumina (product name "N612N", manufactured by JGC Catalysts and Chemicals) was used as the catalyst.
• Example 8 A catalyst containing ⁇ -alumina as the main component and ⁇ -alumina as a part (product name "SA3177", manufactured by Saint-Gobain) was used.
• the Lewis acid point of each catalyst was determined by NH 3 -TPD using "BELCAT II" manufactured by MicrotracBEL Co., Ltd. The measurement conditions were as described above. The Lewis acid point was measured before the catalyst was packed into the reaction tube.
• the product gas (hereinafter also referred to as "reactor outlet gas”) extracted from the reactor outlet 10 hours and 50 hours after the start of the reaction was analyzed by gas chromatography. Specifically, a column (product name "DB-1301”, Agilent, length 60 m, inner diameter 0.25 mm, film thickness 1 ⁇ m) was attached to a gas chromatograph (product name "GC6850”, Agilent) and analyzed. The conversion rate of HFC-134a and the selectivity of HFO-1123 were calculated using the molar amount calculated from the area ratio (GCArea%) of the reactor outlet gas.
• Examples 1 to 6 include a step of producing a fluoroolefin represented by formula (2) by contacting a fluorocarbon represented by formula (1) with a catalyst, and the catalyst contains 65 mass % or more of ⁇ -alumina and has an amount of Lewis acid sites measured by ammonia temperature programmed desorption spectrometry of 0.005 to 0.10 mmol/g. Therefore, it was found that the conversion rate was higher than that of the conventional method and that a decrease in the conversion rate was suppressed during long-term production. On the other hand, in Example 7 which did not contain ⁇ -alumina and had a Lewis acid site amount of more than 0.10 mmol/g, the conversion rate was very low as compared with Examples 1 to 6.
• Example 8 which contained ⁇ -alumina but had a Lewis acid site amount of more than 0.10 mmol/g, the conversion rate after 10 hours was equivalent to those in Examples 1 to 6, but the decrease in conversion rate was significant in the long-term production of 50 hours.
• the process includes a step of contacting a fluorocarbon represented by formula (1) with a catalyst to produce a fluoroolefin represented by formula (2), and since the conversion rate 10 hours after contacting the fluorocarbon with the catalyst is 7 to 13%, it was found that a decrease in conversion rate is suppressed during long-term production.
• Example 9 and 10 Furthermore, for the catalysts used in Examples 4 and 5, HF decomposition reactions were carried out in the same manner as in Example 1 except that the various conditions were changed to the values shown in Table 3, resulting in Examples 9 and 10. Then, the conversion rate of HFC-134a and the selectivity of HFO-1123 were calculated 10 hours and 100 hours after the start of the reaction.
• Example 9 where the amount of Lewis acid sites is within the range of 0.008 to 0.05 mmol/g, it was found that the decrease in conversion rate was more effectively suppressed during the production for a longer period of time, such as 100 hours, compared to Example 10, where the amount of Lewis acid sites is outside this range.
• the raw material supply amount in this example is 1257 kg/hr/ m3 , which is about four times larger than the raw material supply amount of 307 kg/h/ m3 in Non-Patent Document 1, and is a condition that results in a low conversion rate.
• the process includes a step of contacting a fluorocarbon represented by formula (1) with a catalyst to produce a fluoroolefin represented by formula (2), the catalyst contains 65 mass% or more of ⁇ -alumina, and the amount of Lewis acid sites measured by ammonia temperature programmed desorption method is 0.005 to 0.10 mmol/g, the conversion rate is excellent and a decrease in the conversion rate during long-term production is suppressed.
• the catalyst contains 65 mass% or more of ⁇ -alumina, and the amount of Lewis acid sites measured by ammonia temperature programmed desorption method is 0.005 to 0.10 mmol/g, the conversion rate is excellent and a decrease in the conversion rate during long-term production is suppressed.

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