Title of Invention: PROCESS FOR PRODUCTION OF 2,3,3,3-TETRAFLUOROPROPENE

Technical Field

The present invention relates to a process for producing 2,3,3,3-tetrafluoropropene.

Background Art 2,3,3,3-Tetrafluoropropene (CF ₃ CF=CH ₂ , HFO- 1234yf) is a compound with low toxicity and low global warming potential, and thus is a promising candidate for use as an alternative refrigerant for chlorofluorocarbon. Accordingly, there is a need for a process for producing HFO- 1234yf under industrially advantageous conditions with high selectivity, using inexpensive starting materials. Patent Literature (PTL) 1 listed below discloses a process for producing

HFO- 1234yf wherein CF ₂ =CF ₂ (TFE) and CH ₃ Cl are reacted in a gas phase at 850 ⁰ C. However, the HFO- 1234yf yield of this process is only about 5%, which is not satisfactory.

Patent Literature 2 listed below discloses the production Of CF ₃ CF ₂ CH ₃ and HFO- 1234yf by reacting TFE and CH ₃ F in the presence of SbF ₅ supported on activated carbon. This reaction is costly because the CH ₃ F used as a starting material is expensive. Further, this reaction uses SbFs, which is corrosive, and thus poses many problems for industrial purposes.

As another production process, Non-Patent Literature (NPL) 1 listed below discloses a single-step process for producing HFO"1234yf, wherein CF ₃ CF ₂ CH ₂ X (X = Cl or I) is reacted with zinc in ethanol. This process, however, is not suitable for industrial purposes, because zinc is expensive, and large amounts of waste are produced.

Moreover, Patent Literature 3 listed below discloses producing CF ₃ CF=CCl ₂ by the dehydrofluorination reaction of CF ₃ CF ₂ CHCl ₂ , and subsequently reducing CF ₃ CF=CCl ₂ with hydrogen in a gas phase, using a palladium catalyst supported on a carrier such as alumina, fluorided alumina, or the like, thereby obtaining a mixture containing 50% of HFO"1234yf. This process, however, has a low yield and requires further improvement. Further, the starting material CF ₃ CF ₂ CHCl ₂ is synthesized by the addition reaction of TFE and CFCl ₃ , followed by reduction of the reaction product. Since CFCl ₃ is a material derived from CCU, this process is rather costly.

Other processes for producing HFO- 1234yf that have been reported include a process wherein chloromethyl tetrafluoropropanoate is reacted with an amine (Patent Literature 4); a process that involves thermal decomposition of l-trifluoromethyM,2,2-trifluorocyclobutane (Patent Literature 5); etc.

These processes, however, are not considered to be effective for industrial purposes, because the starting materials are difficult to produce and are not easily obtained, the reaction conditions are severe, the reaction reagents are expensive, the yield is low, etc. Thus, there is a need for an economically suitable process for easily producing HFO- 1234yf.

TFE is a material produced in large quantities on an industrial scale. Various processes for increasing the carbon number by reacting TFE with Ci compounds have been reported. Examples of such processes include a process wherein TFE is reacted with (CH2θ) _n (Non-Patent Literature 2), a process wherein TFE is reacted with CHCI3, CCU, or the like (Patent Literature 6), and a process wherein TFE is reacted with CH2CIF. Particularly the process wherein CCU, CHCI3, or the like used as a Ci compound is reacted with TFE to produce CF2CICF2CCI3 (CFC-214cb), CF2CICF2CHCI2 (HCFC'224ca), or the like, can be advantageous in that the yield is good, and low-cost starting materials are used. Regarding the compounds obtained by this process, however, no method has been reported to reduce the polychloromethyl group adjacent to the difluoromethylene group with good selectivity. For example, Patent Literatures 8 and 9 listed below disclose reduction of the polychloromethyl group adjacent to the difluoromethylene group. These methods, however, are difficult to use for the production of HFO-1234yf on an industrial scale, because the selectivity to

CF2CICF2CH3 in the reduction reaction of CFC-214cb or HCFC"224ca is less than 60%.

Citation List

Patent Literature PTL l: U.S. Pat. No. 2,931,840

PTL T- U.S. Pat. Publication No. 2006/0258891

PTL 3: WO 2008/060614

PTL 4: Japanese Unexamined Patent Publication No. 63-211245

PTL 5: U.S. Pat. No. 3,996,299 PTL 6: U.S. Pat. No. 2,462,402

PTL 7: WO 2008/054778 PTL 8: Japanese Unexamined Patent Publication No. 2-204445 PTL 9: Japanese Unexamined Patent Publication No. 2-131437 Non Patent Literature NPL l: J. Chem. Soc. 1957, 2193 NPL 2: J. Org. Chem.1963, 28, 492

Summary of Invention Technical Problem

The present invention was made in view of the above-described prior art problems. A principal object of the invention is to provide a novel process for producing 2,3,3,3-tetrafluoropropene (HFO- 1234yf) that is capable of producing HFO1234yf in a high yield, using inexpensive starting materials.

Solution to Problem The present inventors conducted extensive research in order to achieve this object. Consequently, the inventors found that the desired

2,3,3,3-tetrafluoropropene (HFO1234yf) can be produced with high selectivity and high yield by using as a starting material a specific halogenated fluoropropane that can be obtained from tetrafluoroethylene and a relatively inexpensive halogenated methane, such as chloroform, carbon tetrachloride, or the like! and by treating this starting material according to a specific reaction process. The present invention was accomplished based on this finding.

The present invention provides a process for producing 2,3,3,3-tetrafluoropropene as summarized below. 1. A process for producing 2,3,3,3-tetrafluoropropene comprising the following steps:

(0 reducing a halogenated fluoropropane represented by formula (l): ACF2CF2CHxF _y Az, wherein A is Cl, Br, or L' x is an integer from 0 to % y and z are each an integer from 0 to 3! and the total number of x, y, and z is 3, to produce a 1 -halogenated- 1, 1,2,2-tetrafluoropropane represented by formula (2): ACF2CF2CH3; and

(ii) contacting the 1-halogenated-l, 1,2,2-tetrafluoropropane obtained in step (i) with a catalyst in a gas phase to produce 2,3,3,3-tetrafluoropropene.

2. The process according to item 1, wherein the halogenated fluoropropane represented by formula (l): ACF2CF2CHxF _y A _z is a chlorofluoropropane represented by formula (l') ^: ClCF2CF2CH _n Cl3n, wherein n is an integer from 0 to 2.

3. The process according to item 1 or 2, wherein step (0 is performed by a method comprising reducing the halogenated fluoropropane represented by formula (l): ACF2CF2CHxF _y Az with hydrogen in the presence of a catalyst.

4. The process according to item 3, wherein step (i) is performed by a method comprising reducing the halogenated fluoropropane represented by formula (l): ACF2CF2CHχF _y Az with hydrogen at 80 to 200 ⁰ C in the presence of at least one catalyst selected from the group consisting of platinum, palladium, rhodium, ruthenium, nickel, rhenium, molybdenum, and zirconium.

5. The process according to any one of items 1 to 4, wherein step (ii) is performed by a method comprising contacting the l-halogenated-l,l,2,2-tetrafluoropropane with at least one catalyst selected from the group consisting of chromium oxides, fluorinated chromium oxides, and iron fluorides in a gas phase.

6. The process according to any one of items 1 to 5, wherein step (ϋ) is performed by a method comprising contacting the l-halogenated-l,l,2,2-tetrafluoropropane with the catalyst in the presence of hydrogen fluoride and oxygen; the amount of the hydrogen fluoride being from 0.1 to 2 mol per 1 mol of the l-halogenated-l,l,2,2"tetrafluoropropane; and the amount of the oxygen being from 0.1 to 21 mol% based on the total amount of the l-halogenated-l,l,2,2-tetrafluoropropane, hydrogen fluoride, and oxygen. 7. The process according to any one of items 1 to 6, wherein the halogenated fluoropropane represented by formula (l)- ACF2CF2CH _x F _y Az is obtained by an addition reaction of tetrafluoroethylene and a halogenated methane represented by formula (3): CH _x F _y Az+i, wherein A is Cl, Br, or L x is an integer from 0 to 2', y and z are each an integer from 0 to 35 and the total number of x, y, and z is 3. 8. The process according to item 7, wherein the addition reaction is performed by a method comprising contacting tetrafluoroethylene with the halogenated methane represented by formula (3) in a solvent that is inert to the addition reaction or without a solvent in the presence of a Lewis acid catalyst.

9. The process according to item 8, wherein the halogenated methane represented by formula (3) is a chloromethane represented by the formula CH _n CU n, wherein n is an integer from 0 to 2.

10. The process according to item 9, wherein the chloromethane represented by the formula CH _n CUn, wherein n is an integer from 0 to 2, is at least one compound selected from the group consisting of carbon tetrachloride and chloroform. 11. A process for producing a l-halogenated-l,l,2,2-tetrafluoropropane comprising reducing a halogenated fluoropropane represented by formula (l)- ACF2CF2CHxF _y Az, wherein A is Cl, Br, or L' x is an integer from 0 to 2; y and z are each an integer from 0 to 3! and the total number of x, y, and z is 3, with hydrogen at 80 to 200 ⁰ C in the presence of at least one catalyst selected from the group consisting of platinum, palladium, rhodium, ruthenium, nickel, rhenium, molybdenum, and zirconium.

The process of the invention is a process wherein a halogenated fluoropropane represented by formula (l) ACF2CF2CHxF _y A _z , wherein A is Cl, Br, or I; x is an integer from 0 to 2; y and z are each an integer from 0 to 3) and the total number of x, y, and z is 3, is used as a starting material, and 2,3,3,3-tetrafluoropropene

(HFO- 1234yf) is produced according to a reaction procedure including the following two steps.

(i) Reduction Step

A step of reducing a halogenated fluoropropane represented by formula (l): ACF2CF2CHχF _y Az, wherein A, x, y, and z are as defined above, to produce a l"halogenated-l,l,2,2-tetrafluoropropane represented by formula (2) ACF2CF2CH3, wherein A is as defined above.

(ii) Dehydrofluorination and Fluorination Step

A step of dehydrofluorinating and fluorinating the l-halogenated-l,l,2,2-tetrafluoropropane obtained in step (i) to produce 2,3,3,3-tetrafluoropropene.

According to the process including the above-described two steps, the desired product can be obtained with high selectivity in each step, and the ultimately desired 2,3,3,3-tetrafluoropropene can be produced with high selectivity and high yield. The process of the invention is described in detail below,

(l) Starting Compound

In the invention, a halogenated fluoropropane represented by formula (l): ACF2CF2CHxF _y Az, wherein A is Cl, Br, or I; x is an integer from 0 to 2; y and z are each an integer from 0 to 31 and the total number of x, y, and z is 3, is used as a starting compound.

The halogenated fluoropropane is obtainable by, for example, a method that includes the addition reaction of tetrafluoroethylene and a halogenated methane represented by formula (3): CH _x FyA _z +i, wherein A, x, y, and z are as defined above. In this case, among the halogenated methanes represented by formula (3), a chloromethane represented by the formula CH _n CUn, wherein n is an integer from 0 to 2, is a starting material that is particularly advantageous because of its low cost. Specific examples of these halogenated methanes include carbon tetrachloride (CCI4), chloroform (CHCI3), and the like. Accordingly, the halogenated fluoropropane obtained by the addition reaction of the chloromethane represented by the formula CHnCU _n , wherein n is an integer from 0 to 2, to tetrafluoroethylene, i.e., a compound represented by formula (l') ^: ClCF2CF2CH _n Cl3n, wherein n is an integer from 0 to 2, is very advantageous for industrial purposes as an inexpensive starting material.

The addition reaction of the halogenated methane to tetrafluoroethylene may be performed by, for example, contacting tetrafluoroethylene with the halogenated methane represented by formula (3) in a solvent that is inert to the reaction or without a solvent in the presence of a Lewis acid catalyst.

This causes the addition reaction of the halogenated methane represented by formula (3) to tetrafluoroethylene, thereby producing a halogenated fluoropropane represented by formula (l) ACF2CF2CH _x F _y Az, wherein A, x, y, and z are as defined above. For example, when carbon tetrachloride or chloroform is used as a halogenated methane represented by formula (l), l,l,l,3-tetrachloro-2,2,3,3-tetrafluoropropane (CFC"214cb) or l,l,3-trichloro-2,2,3,3-tetrafluoropropane (HCFC-224ca) is obtained in a high yield, as shown in the following schemes:

CF2=CF ₂ + CCl ₄ (a Lewis acid catalyst) → CF2CICF2CCI3 CF ₂ =CF ₂ + CHCl ₃ (a Lewis acid catalyst) → CF2CICF2CHCI2

The Lewis acid catalyst used in this reaction step is not limited, but may, for example, be a halide containing at least one element selected from the group consisting of B, Al, Ga, In, Fe, Ni, Co, Sb, Nb, Sn, Ti, Zr, W, and Ta. Examples of usable halides include BF ₃ , BCl ₃ , BBr ₃ , AlF ₃ , AlCl ₃ , AlBr ₃ , GaCl ₃ , InCl ₃ , FeCl ₃ , NiCl ₂ , C0CI2, SbF ₅ , SbCl ₅ , NbCl ₅ , SnCl ₂ , TiCk, ZrCl ₄ , WCl ₆ , TaCl ₅ , etc.

Among these Lewis acid catalysts, particularly preferable is an aluminum halide represented by AIZ3, wherein the three Z are the same or different, each being F, Cl, or Br, provided that not all of the Z are F. Particularly preferable is a fluorinated aluminum chloride with the average composition AlCl _x Fy, wherein x is from about 0.05 to about 2.95; y is from about 0.05 to about 2.95; and the sum of x and y is 3. The fluorinated aluminum chloride is typically a mixture of compounds with different compositions. A particularly preferable catalyst is a mixture wherein y is from about 1.00 to about 2.95. The production of the fluorinated aluminum chloride is detailed in U.S. Pat. No. 5, 162,594. When the catalyst represented by AlZ ₃ , wherein the three Z are the same or different, each being F, Cl, or Br, provided that not all of the Z are F, is used for the addition reaction in the reaction system, it changes to the above-mentioned particularly preferable catalyst. In order to promote the activation, the reaction of tetrafluoroethylene and the halogenated methane may be performed in the presence of aluminum chloride and a fluorine compound. Examples of fluorine compounds used for activation are not limited as long as they are alkanes or alkenes with fluorine atom(s). Specific examples include CFO214cb, fluorotrichloromethane, dichlorodifluoromethane, chlorotrifluoromethane, chlorodifluoromethane, l,l,2-trichloro-l,2,2-trifluoroethane, chlorotrifluoroethylene, hexafluoropropene, etc. The amount of the fluorine compound added is not limited, but the addition of a large amount of fluorine compound reduces the yield per batch and thus is not efficient.

Therefore, the amount of the fluorine compound is preferably up to about 50 parts by weight based on 100 parts by weight of the halogenated methane represented by formula (3). Particularly for effective addition of the fluorine compound, the amount of fluorine compound is more preferably from about 1 to about 30 parts by weight based on 100 parts by weight of the halogenated methane represented by formula (3).

The addition reaction of tetrafluoroethylene and the halogenated methane represented by formula (3) can be performed in a solvent such as perfluorooctane, perfluorobutyl tetrahydrofuran, or the like, which is inert to the addition reaction; however, the reaction is preferably performed without a solvent, in order to facilitate the purification.

Typically, the amount of the Lewis acid catalyst used is preferably from about 0.1 to about 50 parts by weight, and more preferably from about 0.5 to about 10 parts by weight, based on 100 parts by weight of the total amount of the tetrafluoroethylene and the halogenated methane represented by formula (3). The reaction temperature may typically be from about -40 to about 200 ⁰ C, and preferably from about 10 to about 150°C. The reaction pressure may be from an ordinary pressure to about 2 MPa, and particularly preferably from an ordinary pressure to about 1 MPa.

The reaction time may be typically from about 0.5 to about 12 hours. According to the above-described process, the desired halogenated fluoropropane represented by formula (l): ACF2CF2CHxF _y Az can be obtained with high conversion and good selectivity.

(2) Process for Producing 2.3.3.3-Tetrafluoropropene (i) Reduction Step In the process of the invention, firstly, a halogenated fluoropropane represented by formula (l): ACF2CF2CHxF _y A _z is reduced to produce a l-halogenated-l,l,2,2-tetrafluoropropane represented by formula (2): ACF2CF2CH3.

For example, the halogenated fluoropropane represented by formula (l): ACF2CF2CHχF _y Az obtained by the addition reaction of tetrafluoroethylene and a halogenated methane may be separated and purified, as required, according to a usual method, before being used as a starting material in the reduction step.

In the reduction step, the l-halogenated-l,l,2,2-tetrafluoropropane represented by formula (2) can be obtained by reducing the halogenated fluoropropane represented by formula (l)- ACF2CF2CH _x F _y Az with hydrogen in the presence of a catalyst. For example, when l,l,l,3-tetrachloro-2,2,3,3-tetrafluoropropane

(CFC-214cb) or l,l,3-trichloro-2,2,3,3-tetrafluoropropane (HCFO224ca) is used as a starting material, l-chloro-l,l,2,2-tetrafluoropropane can be obtained according to the following reaction scheme-

CF2CICF2CCI3 + H ₂ (hydrogenation catalyst) → CF2CICF2CH3 CF2CICF2CHCI2 + H2 (hydrogenation catalyst) → CF2CICF2CH3

Usable as the catalyst used in the reduction reaction are noble metal catalysts such as platinum, palladium, rhodium, and ruthenium; and metal catalysts such as nickel, rhenium, molybdenum, and zirconium; with a noble metal catalyst being particularly preferable. Although the form of the catalyst used is not limited, the catalyst is preferably supported on a carrier. Examples of suitable carrier include alumina, activated carbon, zeolite, etc. A conventional method for preparing a noble metal catalyst can be applied to prepare such a supported catalyst. Preferably, the catalyst undergoes a hydrogen reduction treatment prior to use, in order to exhibit stable properties. The reduction reaction in Reduction Step (0 can be performed in a liquid phase or gas phase.

In the case of a gas-phase reaction, the reaction may be performed, for example, by supplying hydrogen and the halogenated fluoropropane represented by formula (l): ACF2CF2CH _x F _y A _z into a reactor charged with the above-mentioned catalyst in a gas phase.

The proportions of the hydrogen and the starting material can be substantially varied; however, in order to completely react hydrogen with the starting material and intermediate products such as l,3-dichloro-l,l,2,2-tetrafluoropropane (HCFC"234cb), it is preferred that hydrogen be used in an amount considerably larger than the stoichiometric quantity, such as, for example, in an amount of 2 mol or more based on 1 mol of the halogenated fluoropropane represented by formula (l). It is particularly preferred that hydrogen be used in an amount of about 2 to about 10 mol based on 1 mol of the halogenated fluoropropane represented by formula (l).

The reaction temperature in a gas-phase reaction may be from about 70 to about 350 ⁰ C, and particularly preferably from about 80 to about 200 ⁰ C, to prevent the production of Cβ byproduct compounds wherein starting materials are bound to each other.

In the reduction step, particularly when the amount of the hydrogen supplied is from about 2 to about 10 mol based on 1 mol of the halogenated fluoropropane represented by formula (l), and the reaction temperature is from 80 to 200 ⁰ C, the l-halogenated-l,l,2,2-tetrafluoropropane represented by formula (2) can be obtained with high conversion and high selectivity by suppressing the side reaction.

In the gas-phase reaction, generally, the contact time represented by the ratio of the catalyst weight W (g) relative to the total flow rate Fo (flow rate at O ⁰ C and 1 atm^ cc/sec) of the starting gases (i.e., the halogenated fluoropropane and hydrogen) passed in the reaction system, i.e., W/Fo, is preferably from about 0.1 to about 30 g -sec/cc. The contact time is more preferably from about 1 to about 20 g -sec/cc, because if the contact time is too short, sufficient conversion of the starting material will not be obtained! whereas if the contact time is too long, the production of the Ce by-product compounds or the decomposition reaction to produce Ci or C2 compounds will take place. In the case of a liquid-phase reaction, the reaction can be performed using a solvent, e.g., ethanol, isopropyl alcohol, or a like alcohol, acetic acid, ethyl acetate, or pyridine, or can be performed without a solvent. The reaction temperature in the liquid-phase reaction is preferably from about room temperature to about 150 ⁰ C, and the reaction pressure is preferably from ordinary pressure to about 5 MPa. The reaction time may be suitably selected according to the reactivity of the halogenated fluoropropane represented by formula (l) used, but may be typically from about 4 to about 72 hours.

(ii) Dehvdrofluorination and Fluorination Step

Next, the desired 2,3,3, 3-tetrafluoropropene can be obtained by contacting the l-halogenated-l,l,2,2-tetrafluoropropane represented by formula (2) obtained in the reduction step above with a catalyst in a gas phase.

Typically, the product obtained in the reduction step may be separated and purified, as required, according to a usual method, before being used as a starting material in this step. It is assumed that in this step, the HF is eliminated once, and the desired

2,3,3,3-tetrafluoropropene (HFO- 1234yf) represented by the formula CF2CF=CH2 is formed utilizing the eliminated HF, according to the following reaction schemes: CF2ACF2CH3 → CF ₂ ACF=CH ₂ + HF CF ₂ ACF=CH ₂ + HF → CF ₃ CF=CH ₂ + HA

Examples of catalysts usable in this reaction include halides, oxides, and the like containing at least one element selected from the group consisting of Al, Cr, Mg, Ca, Sr, Ba, Fe, Ni, Co, Mn, Sb, Nb, and Ta.

Such a catalyst can be prepared by any method that is capable of homogeneously dispersing a halide or an oxide containing at least one element selected from the above-mentioned elements. Examples of such methods include coprecipitation, kneading, ion exchange, vapor deposition, etc. Preferable methods include a method wherein a hydroxide is precipitated from an aqueous solution of a salt of the above-mentioned metal element; a method wherein a hydroxide cake is kneaded and ground using a ball mill, a homogenizer, or the like! etc. The above-described catalyst may undergo a fluorination treatment for activation. The fluorination treatment can be performed by contacting the catalyst with hydrogen fluoride, e.g., according to the method described in Japanese Unexamined Patent Publication No. 5-146680. The reaction temperature in the fluorination treatment may be a temperature at which the water produced is not condensed (e.g., about 150 °C at 1 atm). The fluorination temperature may be from about 100 to about 460°C. The pressure during fluorination is not limited, but is preferably the pressure at which the catalytic reaction is performed.

It is particularly preferred that at least one catalyst selected from the group consisting of chromium oxides, fluorinated chromium oxides, and iron fluorides be used. The desired HFO- 1234yf can be obtained with good selectivity and high yield by using the above-mentioned catalyst, and employing the reaction conditions described below.

Among the above-mentioned catalysts used in the invention, usable as chromium oxides are, for example, those of the formula CrOm, wherein m is 1.5 < m <3, preferably 2 < m < 2.75, and more preferably 2 < m < 2.3. One example of a method for preparing such a chromium oxide is as follows.

First, an aqueous solution of a chromium salt (chromium nitrate, chromium chloride, chromium alum, chromium sulfate, or the like) is mixed with aqueous ammonia to produce a precipitate of chromium hydroxide. The precipitate is then filtered, washed, and dried. Drying may be performed, for example, in air, at about 70 to about 200 ⁰ C, and particularly at about 120 ⁰ C, for about 1 to about 100 hours, and particularly for about 12 hours. The product obtained at this stage is referred to as being in the state of chromium hydroxide.

This product is subsequently disintegrated into a powder. The disintegrated chromium hydroxide powder is blended with graphite in an amount of about 3 wt% or less, as needed, and formed into pellets using a tableting machine. The pellets may, for example, be about 3.0 mm in diameter and about 3.0 mm in height.

Lastly, the molded pellets are calcined in an inert atmosphere, e.g., in a nitrogen stream, to produce an amorphous chromium oxide.

The calcined chromium oxide has a specific surface area of about 170 m ² /g or more, preferably about 180 m ² /g or more, and more preferably about 200 m ² /g or more. The upper limit of the specific surface area is about 240 m ² /g, and preferably about 220 m ² /g. A specific surface area of 240 m ² /g or more increases the activity, but also increases the degradation rate, whereas a specific surface area of less than 170 m ² /g reduces the catalytic activity! thus, these ranges are undesired. Note that the specific surface area is herein measured according to the BET method.

A fluorinated chromium oxide can be prepared according to the method described in Japanese Unexamined Patent Publication No. 5- 146680. A fluorinated chromium oxide can be obtained by, for example, fluorinating the chromium oxide obtained by the above-described method with hydrogen fluoride (HF treatment). The pressure during fluorination is not limited, but is preferably a pressure at which the catalytic reaction is performed. The fluorination temperature is, for example, from about 100 to about 460 ⁰ C.

The fluorination treatment reduces the surface area of a catalyst; in general, however, the higher the specific surface area is, the higher the activity is. Thus, the specific surface area of the fluorinated chromium oxide is preferably from about 25 to about 130 m ² /g, and more preferably from about 40 to about 100 m ² /g, but is not limited to this range.

The fluorination reaction of a chromium oxide may be performed, prior to carrying out the process of the invention described below, by supplying hydrogen fluoride to a reactor charged with the chromium oxide.

Although the degree of fluorination is not limited, a fluorinated chromium oxide having a fluorine content of about 10 to about 30 wt% can be suitably used.

Further, the chromium-based catalyst disclosed in Japanese Unexamined Patent Publication No. 11-171806 is usable as a chromium oxide catalyst or a fluorinated chromium oxide catalyst in the invention. This chromium-based catalyst principally comprises a chromium compound containing at least one metal element selected from the group consisting of indium, gallium, cobalt, nickel, zinc, and aluminum, wherein the average valence of the chromium in the chromium compound is +3.5 or more and +5.0 or less, and the chromium-based catalyst is amorphous. The iron fluoride used as a catalyst is not limited, but is preferably an iron fluoride represented by the formula FeF _x , wherein x is from 2 to 3. Examples of such iron fluorides that can be used include commercially available products in the form of pellets, pellets produced from commercially available powdery products using a compacting machine or the like, etc. The at least one catalyst selected from the group consisting of chromium oxides, fluorinated chromium oxides, and iron fluorides can be supported on a carrier such as alumina, activated carbon, or the like.

In the dehydrofluorination and fluorination step, the reaction may be typically performed by a method wherein the 1-halogenated- 1, 1,2,2-tetrafluoropropane represented by formula (2) is supplied into a reactor charged with the above-mentioned catalyst in a gas phase. It is assumed that according to this method, the hydrogen fluoride is eliminated from the l-halogenated-l,l,2,2-tetrafluoropropane to produce 3-halogenated-2,3,3-trifluoropropene represented by the formula CF2ACF=CH2, and the desired HFO1234yf is subsequently formed utilizing the eliminated hydrogen fluoride. Accordingly, the reaction can proceed without the addition of hydrogen fluoride (HF), resulting in an excellent HF utilization efficiency.

Thus, in this step, the l-halogenated-l,l,2,2-tetrafluoropropane can be used alone as a starting material! however, hydrogen fluoride may be additionally supplied. When hydrogen fluoride is supplied, the conversion of the 1-halogenated- 1, 1,2,2-tetrafluoropropane may decrease to some extent, but the selectivity to HFO- 1234yf can be improved.

When hydrogen fluoride is used, in general, it may be supplied into a reactor together with the 1-halogenated- 1, 1,2,2-tetrafluoropropane in a gas phase. Typically, the amount of hydrogen fluoride is preferably from about 2 mol or less, and more preferably from about 1.5 mol or less, based on 1 mol of the

1-halogenated- 1, 1,2,2-tetrafluoropropane represented by formula (2). An amount of hydrogen fluoride exceeding 2 mol based on 1 mol of the

1-halogenated- 1, 1,2,2-tetrafluoropropane is undesirable because the selectivity to HFO- 1234yf will not be significantly improved, and the conversion of the 1-halogenated- 1, 1,2,2-tetrafluoropropane may decrease.

If the amount of hydrogen fluoride is small, the amount of 2-halogenated-3,3,3-trifluoropropene produced may increase, or the catalyst may degrade. It is thus preferred that 0.1 mol or more of hydrogen fluoride be used based on 1 mol of the l"halogenated-l,l,2,2-tetrafluoropropane represented by formula (2). Therefore, when the amount of hydrogen fluoride is from 0.1 to 2 mol based on 1 mol of the l-halogenated-l,l,2,2-tetrafluoropropane represented by formula (2), both of the conversion of the l-halogenated-l,l,2,2-tetrafluoropropane and the selectivity to HFO- 1234yf can be maintained within a satisfactory range.

The starting material may be supplied as is into the reactor, or may be diluted with an inert gas such as nitrogen, helium, or argon. The starting material may also be supplied to the reactor together with oxygen, in order to maintain the catalytic activity for an extended period of time. In this case, the amount of oxygen is preferably from about 0.1 mol% or more, and more preferably from about 0.1 to about 21 mol%, based on the total amount of the l-halogenated-l,l,2,2-tetrafluoropropane represented by formula (2), hydrogen fluoride, and oxygen. If the amount of oxygen is too small, the effect obtained by the addition of oxygen will be low, whereas if the amount of oxygen is too large, the oxygen will be wastefully used, and the production rate of HFO1234yf per unit amount of catalyst will decrease, which is undesirable.

In this step, particularly when hydrogen fluoride is supplied in an amount of about 0.1 mol or more, and preferably about 0.1 to about 2 mol, based on 1 mol of the l-halogenated-l,l,2,2-tetrafluoropropane, and oxygen is supplied in an amount of about 0.1 to about 21 mol%, and preferably about 5 to about 21 mol%, based on the total number of moles of the l-halogenated-l,l,2,2-tetrafluoropropane, hydrogen fluoride, and oxygen supplied, the conversion of the l-halogenated-l,l,2,2-tetrafluoropropane can be significantly improved, and excellent catalytic activity can be maintained for an extended period of time by suppressing the degradation of the catalyst.

The type of the reactor used in this step is not limited; examples of usable reactors include an adiabatic reactor charged with the catalyst, a multitube reactor heated with a heating medium, etc. The reactor used is preferably made of a material resistant to the corrosive action of hydrogen fluoride, such as Hastelloy, Inconel, Monel, or the like.

In this step, the reaction temperature in the reactor is preferably from about 200 to about 45O ⁰ C, and more preferably from about 250 to about 400 ⁰ C. If the temperature is higher than this range, the catalytic activity will decrease, whereas if the temperature is lower, the conversion of the starting material will become low, which is undesirable.

The reaction can be performed at any pressure, e.g., at ordinary pressure or under increased pressure. More specifically, the reaction of the invention can be performed at atmospheric pressure (0.1 MPa), but may be performed at an increased pressure of up to about 1.0 MPa.

Although the reaction time is not limited, the contact time represented by the ratio of the catalyst weight W (g) relative to the total flow rate Fo (flow rate at O ⁰ C and 1 atm: cc/sec) of the starting gases (l-halogenated-l,l,2,2-tetrafluoropropane, hydrogen fluoride, and oxygen) passed in the reaction system, i.e., W/Fo, is from 5 to 100 g -sec/cc, and preferably from about 10 to about 40 g -sec/cc.

A reaction product containing HFO- 1234yf can be obtained at the outlet of the reactor.

The reaction product can be purified by distillation or the like and collected. Unreacted starting materials can be separated and purified, and then returned into the reactor and recycled. Because unreacted starting materials can be thus recycled, high productivity can be maintained even if the conversion of the starting material is low.

Advantageous Effects of Invention According to the above-described process for producing

2,3,3,3-tetrafluoropropene, 2,3,3, 3-tetrafluoropropene can be produced with good selectivity and high yield.

Particularly when a halogenated fluoropropane, which is obtained by using an inexpensive starting material, i.e., a chloromethane represented by the formula CH _n CUn and tetrafluoromethylene, is used as a starting material,

2,3,3,3-tetrafluoropropene can be obtained with good selectivity and high yield using the inexpensive starting material.

Accordingly, the process of the invention is very advantageous as a process for producing 2,3,3,3-tetrafluoropropene on an industrial scale. Description of Embodiments

The invention is described in greater detail below with reference to the Examples.

Example 1 (1) Production of Starting Compound (CFC"214cb) l,l,l,3-Tetrachloro-2,2,3,3-tetrafluoropropane (CFC"214cb) was produced according to the following reaction scheme '• CCl ₄ + TFE → CFC-214cb A l L stainless steel autoclave was charged with anhydrous aluminum chloride (50 g, 0.37 mol), CCl ₄ (1.0 kg, 6.50 mol), and CFC-214cb (200 g, 0.79 mol) and degassed under reduced pressure with stirring, after which tetrafluoroethylene (TFE) was supplied up to 0.05 MPa, and the autoclave was heated to 6O ⁰ C.

Tetrafluoroethylene (total- 0.33 kg, 3.30 mol) was subsequently supplied, with the pressure maintained at 0.4 MPa. After further stirring for 1 hour, the autoclave was cooled to room temperature, and the reaction solution was analyzed using gas chromatography. As a result, the conversion of CCl ₄ was 50%, and the selectivity to

CFC-214cb was 91%. After filtering the reaction solution, the crude product was purified by distillation to obtain CFC-214cb (0.96 kg, 3.78 mol).

(2) Production of HFO1234vf

(i) Reduction Step Using the thus-obtained CFC"214cb as a starting material, l-chloro-l,l,2,2-tetrafluoropropane (HCFC-244cc) was obtained by the method described below.

A gas-phase reactor including a cylindrical reaction tube (Hastelloy; diameter^ 13 mm, length- 30 cm) equipped with an electric furnace was charged with activated carbon pellets (10 g) having palladium supported thereon in a proportion of

0.5 wt%. The reaction tube was heated to 15O ⁰ C while supplying hydrogen (83 mL/min, flow rate at O ⁰ C and 1 atm; this also applies to the Examples and Reference Examples shown below), and CFC-214cb (0.19 g/min, 17 mL/min in terms of gas volume) was subsequently supplied thereto. The outlet gas from the reaction tube was washed with water through a washing column and dried through a calcium chloride column to remove the acid content and water content, and subsequently collected with a cold trap. The collected liquid was analyzed using gas chromatography. As a result, the conversion of

CFC-214cb was 100%, and the product selectivities were as follows: HCFC-244cc: 82%; l,3-dichloro-l,l,2,2-tetrafluoropropane (HCFC"234cb): 4%, and

1, l,3-trichloro-2,2,3,3-tetrafluoropropane (HCFC"224ca): 5%. A total of 500 g of

CFC-214cb (1.97 mol) was used for the reaction to yield 278 g of a crude product.

The resulting crude product was subjected to rectification distillation at atmospheric pressure to yield HCFC'244cc (233 g, 1.55 mol). HCFC"234cb and HCFC-224ca separated by the distillation can be reduced with hydrogen again for conversion to HCFC-244cc. (ii) Dehvdrofluorination and Fluorination Step

Using the HCFC-244cc obtained in step (i) above, 2,3,3,3-tetrafluoropropene (HFO- 1234yf) was obtained by the method described below.

A gas-phase reactor including a cylindrical reaction tube (Hastelloyl diameter: 13 mm, length: 30 cm) equipped with an electric furnace was charged with 8.2 g of a catalyst obtained by fluorinating a chromium oxide represented by the formula Crθ2 (cylindrical shape; diameter: 3 mm; height: 3 mm,' fluorine content: about 15 wt%). This reaction tube was maintained at 300 ⁰ C, and 60 mL/min of anhydrous hydrogen fluoride was supplied thereto and maintained for 1 hour. The reaction tube was heated to 400 ⁰ C while supplying nitrogen (100 mL/min), and maintained at 400 ⁰ C for 1 hour. The supply of the nitrogen gas was ceased, and HCFC"244cc (100 mL/min), anhydrous hydrogen fluoride (15 mL/min), and oxygen (3.9 mL/min, 8 vol% of the total gas flow) were subsequently supplied. The outlet gas from the reaction tube was washed with water and dried with calcium chloride, and subsequently collected with a cold trap. After the elapse of 10 hours from the beginning of the introduction of

HCFC-244cc, the gas flowing from the reactor outlet was analyzed using gas chromatography. As a result, the GC composition was as follows: HCFC-244cc: 55 %, HFO1234yf: 40 %, 3-chloro-2,3,3-trifluoropropene (HCFO- 1233yf): 2 %, 1,1,1,2,2-pentafluoropropane (HFC-245cb): 1 %, and others: 2 %; the HCFC-244cc conversion was 45%; and HFO- 1234yf was obtained at 92% selectivity. A total of 255 g of HCFC"244cc (1.70 mol) was used for the reaction to yield 235 g of a crude product.

The crude product was rectified under increased pressure using a 20-plate rectification column of stainless steel, thereby yielding HFO"1234yf (68 g, 0.60 mol). HCFC-244cc (i.e., starting material), HCFO- 1233yf, and HFC-245cb, which were separated by rectification, can be reacted again under the conditions of this step for conversion to HFO"1234yf.

Example 2

(1) Production of Starting Compound (CFC-224ca) 1, l,3-Trichloro-2,2,3,3-tetrafluoropropane (HCFC"224ca) was produced according to the following reaction scheme: CHCl ₃ + TFE → HCFC-224ca

A l L stainless steel autoclave was charged with anhydrous aluminum chloride (50 g, 0.37 mol), CHCl ₃ (l.O kg, 8.38 mol), and HCFC-224ca (200 g, 0.91 mol) and degassed under reduced pressure with stirring, after which TFE was supplied up to 0.05 MPa, and the autoclave was heated to 8O ⁰ C. TFE (total: 0.33 kg, 3.30 mol) was subsequently supplied, with the pressure maintained at 0.8 MPa. After further stirring for 1 hour, the autoclave was cooled to room temperature, and the reaction solution was analyzed using gas chromatography. As a result, the conversion of CHCb was 36%, and the selectivity to HCFO224ca was 88%. After filtering the reaction solution, the crude product was purified by distillation to obtain HCFO224ca (0.79 kg,

3.60 mol).

(2) Production of HFO1234vf

(i) Reduction Step

Using the thus-obtained HCFO224ca as a starting material, l"chloro-l,l,2,2-tetrafluoropropane (HCFO244cc) was obtained by the method described below.

A gas phase reactor including a cylindrical reaction tube (HastelloyJ diameter: 25 mm, length: 30 cm) equipped with an electric furnace was charged with activated carbon pellets (15 g) having palladium supported thereon in a proportion of 3.0 wt%. The reaction tube was heated to 200 ⁰ C while supplying hydrogen (180 mL/min), and then HCFO224ca (0.44 g/min, 45 mL/min in terms of gas volume) was supplied thereto.

The outlet gas from the reaction tube was washed with water through a washing column and dried through a calcium chloride column to remove the acid content and water content, and subsequently collected with a cold trap. The collected liquid was analyzed using gas chromatography. As a result, the conversion of

HCFC-224ca was 100%, and HCFO244cc and HCFO234cb were obtained at selectivities of 79% and 15%, respectively. A total of 500 g of HCFO224ca (2.27 mol) was used for the reaction to yield 303 g of a crude product. The resulting crude product was subjected to rectification distillation at atmospheric pressure using a 20-plate rectification column to yield HCFO244cc (255 g,

1.70 mol). HCFO234cb separated by distillation can be reduced with hydrogen again for conversion to to HCFO244cc.

(ii) Dehydrofluorination and Fluorination Step Using the HCFO244cc obtained in step (i) above,

2,3,3,3-tetrafluoropropene (HFO- 1234yf) was obtained by the method described below. A gas phase reactor including a cylindrical reaction tube (Hastelloyl diameter: 13 mm, length: 30 cm) equipped with an electric furnace was charged with 8.2 g of a catalyst obtained by fluorinating a chromium oxide represented by the formula Crθ2 (cylindrical shape! diameter: 3 mm; height: 3 mm! fluorine content: about 15 wt%).

This reaction tube was maintained at 300 ⁰ C, and 60 mL/min of anhydrous hydrogen fluoride was supplied thereto and maintained for 1 hour. The reaction tube was heated to 400 ⁰ C while supplying nitrogen (100 mL/min), and maintained at 400 ⁰ C for 1 hour. The supply of the nitrogen gas was ceased, and HCFC-244cc (100 mL/min), anhydrous hydrogen fluoride (15 mL/min), and oxygen (3.9 mL/min, 8 vol% of the total gas flow) were subsequently supplied. The outlet gas from the reaction tube was washed with water and dried with calcium chloride, and subsequently collected with a cold trap. After the elapse of 10 hours from the beginning of the introduction of HCFC-244cc, the gas flowing from the reactor outlet was analyzed using gas chromatography. As a result, the GC composition was as follows- HCFC-244cc: 55 %, HFO-1234yf: 40 %, HCFO- 1233yf: 2 %, HFC-245cb: 1 % and others: 2 %; the

HCFC-244cc conversion was 45%; and HFO- 1234yf was obtained at 92% selectivity. A total of 255 g of HCFC-244cc (1.70 mol) was used for the reaction to yield 235 g of a crude product.

The resulting crude product was rectified under increased pressure using a 20-plate rectification column of stainless steel, thereby yielding HFO- 1234yf (68 g, 0.60 mol). The CFC"244cc as a starting material, HCFO- 1233yf, and HFC-245cb, which were separated by rectification, can be reacted again under the conditions of this step for conversion to HFO-1234yf.

Examples with respect to the reduction reaction in the first step of the present invention are shown below.

Example 3

A gas-phase reactor including a cylindrical reaction tube (Hastelloy! diameter: 13 mm, length: 30 cm) equipped with an electric furnace was charged with activated carbon pellets (10 g) having palladium supported thereon in a proportion of 0.5 wt%, to prepare a reaction tube. The reaction tube was heated to 150 ⁰ C while supplying H2 gas (85 mL/min), and l,l,l,3-tetrachloro-2,2,3,3-tetrafluoropropane (CFC-214cb) (17 mL/min in terms of gas volume) was subsequently supplied thereto. The molar ratio of H2 to CFC-214cb was 5, and the contact time (W/Fo) was 6.0 g-sec/cc. The outlet gas from the reaction tube was washed with water through a heated washing column and dried through a calcium chloride column to remove the acid content and water content, and subsequently collected with a cold trap. The resulting product was analyzed using gas chromatography. As a result, the conversion of CFC-214cb was 99%, and the following products were obtained: HCFC"244cc at 84% selectivity! HCFC"234cb at 3.4% selectivity! HCFC-224ca at 4.0% selectivity! and other byproducts at 8.3% selectivity.

Example 4

The reaction was performed in the same manner as Example 3, except that the H2 gas was supplied at 88 mL/min, and CFO214cb was supplied at 12 mL/min (in terms of gas volume). The molar ratio of H2 to CFO214cb was 7, and W/Fo was 6.0 g -sec/cc.

The resulting product was analyzed using gas chromatography. As a result, the conversion of CFO214cb was 100%, and the following products were obtained: HCFO244cc at 84% selectivity! HCFO234cb at 2.6% selectivity! HCFO224ca at 2.4% selectivity,' and other by-products at 11% selectivity.

Example 5

The reaction was performed in the same manner as Example 3, except that the reaction tube was heated to 100 ⁰ C.

The resulting product was analyzed using gas chromatography. As a result, the conversion of CFO214cb was 99%, and the following products were obtained:

HCFC-244cc at 83% selectivity! HCFO234cb at 1.6% selectivity! HCFO224ca at 8.4% selectivity; and the other byproducts at 6.9% selectivity.

Example 6

The reaction was performed in the same manner as Example 4, except that the reaction tube was heated to 100 ⁰ C. The molar ratio of H2 to CFC-214cb was 7, and W/Fo was 6.0 g -sec/cc. The resulting product was analyzed using gas chromatography. As a result, the conversion of CFC"214cb was 99%, and the following products were obtained:

HCFC-244cc at 84% selectivity! HCFC-234cb at 0.9% selectivity! HCFC-224ca at 5.1% selectivity! and other by-products at 9.6% selectivity.

Comparative Example 1

The reaction was performed in the same manner as Example 4, except that the reaction tube was heated to 250 ⁰ C. The molar ratio of H2 to CFC-214cb was 7, and W/FQ was 6.0 g -sec/cc.

The resulting product was analyzed using gas chromatography. As a result, the conversion of CFC-214cb was 100%, and the following products were obtained: HCFC-244cc at 71% selectivity! HCFC"234cb at 4.0% selectivity! and other byproducts at 25% selectivity.

Reference Examples with respect to the dehydrofluorination and fluorination reaction in the second step of the present invention are shown below.

Reference Example 1

A tubular Hastelloy reactor with an inner diameter of 15 mm and a length of 1 m was charged with 30 g of a catalyst obtained by fluorinating a chromium oxide represented by the formula Crθ2 (fluorine content: about 15 wt%). The reactor was maintained at atmospheric pressure (l atm) and 300 ⁰ C, and anhydrous hydrogen fluoride (HF) gas was supplied to the reactor at 60 cc/min for 1 hour. CF2CICF2CH3 (HCFO244cc) gas was subsequently supplied at a rate of 30 cc/min, and the temperature of the reactor was changed to 320°C. The molar ratio of HF to HCFO244cc was 2, and the contact time (WfFo) was 20 g -sec/cc. One hour after the desired reaction temperature was reached, the outlet gas from the reactor was analyzed using gas chromatography. The results are shown in Table 1. The structure of each product was as follows^

CF ₃ CF=CH ₂ (HFO- 1234y£) CF ₂ ClCF=CH ₂ (HCFO- 1233yf)

CF ₃ CCl=CH ₂ (HCFO- 1233x£»

Reference Example 2

The experiment was conducted under the same conditions as Reference Example 1, except that the amount of the catalyst was changed to 25 g, and the flow rate of the anhydrous hydrogen fluoride (HF) gas was changed to 45 cc/min. The molar ratio of HF to HCFC-244cc was 1.5, and the contact time (WfFo) was 20 g -sec/cc. The analytical results are shown in Table 1.

Reference Example 3

The experiment was conducted under the same conditions as Reference Example 1, except that the amount of the catalyst was changed to 20 g, and the flow rate of the anhydrous hydrogen fluoride (HF) gas was changed to 30 cc/min. The molar ratio of HF to HCFC"244cc was 1, and the contact time (WfFo) was 20 g -sec/cc. The analytical results are shown in Table 1. Reference Example 4

The experiment was conducted under the same conditions as Reference Example 3, except that the reaction temperature was changed to 280 ⁰ C. The molar ratio of HF to HCFO244cc was 1, and the contact time (WfFo) was 20 g -sec/cc. The analytical results are shown in Table 1.

Reference Example 5

The experiment was conducted under the same conditions as Reference Example 1, except that the amount of the catalyst was changed to 15 g, and the flow rate of the anhydrous hydrogen fluoride (HF) gas was changed to 15 cc/min. The molar ratio of HF to HCFO244cc was 0.5, and the contact time (W/Fo) was 20 g -sec/cc. The analytical results are shown in Table 1.

Reference Example 6 A tubular Hastelloy reactor with an inner diameter of 15 mm and a length of 1 m was charged with 20 g of the same catalyst as that used in Reference Example 1 (fluorine content: about 15 wt%). The reactor was maintained at atmospheric pressure (l atm) and 300 ⁰ C, and anhydrous hydrogen fluoride (HF) gas was supplied to the reactor at 60 cc/min for 1 hour. The supply of HF was subsequently ceased, and then each of nitrogen (N ₂ ) gas and CF2CICF2CH3 (HCFO244cc) gas was supplied at 30 cc/min, and the temperature of the reactor was changed to 350°C. The molar ratio of HF to HCFC-244cc was 0, and the contact time (W/Fo) was 20 g ^• sec/cc. One hour after the desired reaction temperature was reached, the outlet gas from the reactor was analyzed using gas chromatography. The results are shown in Table 2.

Reference Example 7

A tubular Hastelloy reactor with an inner diameter of 15 mm and a length of 1 m was charged with 16 g of the same catalyst as that used in Reference Example 1 (fluorine content: about 15 wt%). The reactor was maintained at atmospheric pressure (l atm) and 300 ⁰ C, and anhydrous hydrogen fluoride (HF) gas was supplied to the reactor at 60 cc/min for 1 hour. The supply of HF was subsequently ceased, and nitrogen (N2) gas was supplied at a rate of 60 cc/min, and further maintained for another 1 hour. The supply of the nitrogen (N2) gas was subsequently ceased, and CF2CICF2CH3 (HCFC-244cc) gas was supplied at a rate of 48 cc/min, and the temperature of the reactor was changed to 35O ⁰ C. The molar ratio of HF to

HCFC-244cc was 0, and the contact time (W/Fo) was 20 g -sec/cc. One hour after the desired reaction temperature was reached, the outlet gas from the reactor was analyzed using gas chromatography. The results are shown in Table 2.

Reference Example 8 A Tubular Hastelloy straight reactor (diameter: 2.54 cm) equipped with an electric furnace was charged with 82 g of the same fluorinated chromium oxide catalyst as that of Reference Example 1. The reactor was heated to 400 ⁰ C while passing nitrogen (N2) gas to dry the catalyst, and the temperature was held at 400 ⁰ C for 1 hour. The supply of the nitrogen gas was ceased, and oxygen (O2) gas was introduced at a flow rate of 2.2 cc/min (8 vol% of the total gas flow) and CF2CICF2CH3

(HCFC"244cc) gas was introduced at a flow rate of 25 cc/min via the reactor inlet. After the elapse of 1 hour from the beginning of the introduction of HCFC"244cc, the gas flowing from the reactor outlet was analyzed by gas chromatography. The results are shown in Table 2.

Reference Example 9

A Tubular Hastelloy straight reactor (diameter: 2.54 cm) equipped with an electric furnace was charged with 8.2 g of the same fluorinated chromium oxide catalyst as that of Reference Example 1. The reactor was heated to 400 ⁰ C while passing nitrogen (N2) gas to dry the catalyst, and the temperature was held at 400 ⁰ C for 1 hour. The supply of the nitrogen gas was ceased, and then anhydrous hydrogen fluoride (HF) gas was introduced at a flow rate of 15 cc/min (0.5 mol per mol of 244 cc), oxygen (O2) gas was introduced at 3.9 cc/min (8 vol% of the total gas flow), and CF2CICF2CH3 (HCFC-244cc) gas was introduced at 30 cc/min via the reactor inlet. After the elapse of 4 hours from the beginning of the introduction of

HCFC"244cc, the gas flowing from the reactor outlet was analyzed by gas chromatography. The results are shown in the column "Ref. Ex. 9-1" of Table 2. Additionally, after the elapse of 10 hours from the beginning of the introduction of HCFC-244cc, the outlet gas from the reactor was analyzed in the same manner as above. As a result, the gas composition was as shown in the column "Ref. Ex. 9"2" of Table 2; no decrease in conversion due to the degradation of the catalyst was observed.

Reference Example 10

A commercially available iron fluoride powder represented by the formula FeF∑ was formed into cylindrical pellets with a diameter of about 2 mm and a height of about 5 mm, using a compacting machine. A Tubular Hastelloy straight reactor with a diameter of 2.54 cm was charged with 10 g of the iron fluoride catalyst pellets to prepare a reactor. The reactor was heated to 400 ⁰ C while passing nitrogen (N2) gas to dry the catalyst, and the temperature was held at 400 ⁰ C. The supply of the nitrogen gas was subsequently ceased, and a mixed gas of 18 cc/min CF2CICF2CH3 (HCFC"244cc) gas and 1.6 cc/min oxygen was introduced via the reactor inlet.

After 1 hour from the beginning of the introduction, the gas flowing from the reactor outlet was analyzed by gas chromatography. The analysis revealed that the reaction proceeded at a 244cc conversion of 1.8%, and HFO- 1234yf was obtained in the resulting product at 93% selectivity.

Table 1

Ref. Ex. 1 Ref. Ex. 2 Ref. Ex. 3 Ref. Ex. 4 Ref. Ex. 5

Reaction Temperature ( ⁰ C) 320 320 320 280 320

HF/HCFC-244cc (Molar Ratio) 2.0 1.5 1.0 1.0 0.5

O2/Total Gas (Molar Ratio) 0 0 0 0 0

HCFC-244cc Conversion (%) 10.8 14.7 16.8 14.1 17.8

Product Selectivity (%)

HFO-1234yf 94.6 92.9 84.9 88.7 82.3

HFC-245cb 0.5 0.2 0.3 0.1 0.3

HCFO- 1233yf 4.6 6.5 14.2 10.8 16.6

HCFO- 1233xf 0.1

Others 0.3 0.4 0.6 0.4 0.7

Table 2

Ref. Ex.6 Ref. Ex.7 Ref. Ex.8 Ref. Ex.9-1 Ref. Ex.9-2

Reaction Temperature ( ⁰ C) 350 350 400 400 400

HF/HCFC-244cc (Molar Ratio) 0 0 0 0.5 0.5

02/Total Gas (Molar Ratio) 0 0 0.08 0.08 0.08

HCFC-244cc Conversion (%) 19.3 24.4 50.9 40.0 45.4

Product Selectivity (%)

HFO-1234yf 72.5 63.7 85.5 91.2 92.0

HFC-245cb 0.0 0.0 1.8 2.3 2.1

HCFO-1233yf 25.5 31.4 7.1 5.6 5.7

HCFO- 1233xf 0.2 1.8

Others 1.8 3.1 5.6 0.9 0.2