Process for producing fluorine-containing olefin

Abstract

The present invention provides a process for producing a fluoroolefin by reacting, in a gas phase, a fluorinating agent and a chlorine-containing alkene or a chlorine-containing alkane in the presence of at least one catalyst selected from the group consisting of chromium oxide, at least part of which is crystallized, and fluorinated chromium oxide obtained by fluorinating the chromium oxide. According to the present process, a target fluoroolefin can be obtained at a high conversion rate of the starting material and with high selectivity.

Claims

1. A process for producing a fluoroolefin comprising: reacting a fluorinating agent and a chlorine-containing compound in a gas phase in the presence of at least one catalyst selected from the group consisting of chromium oxide, at least part of which is crystallized, and fluorinated chromium oxide obtained by fluorinating the chromium oxide, wherein the chlorine-containing compound is a chlorine-containing alkene of formula (3): CX.sub.3(CX.sub.2).sub.nCClCH.sub.2, wherein each X is independently F or Cl, and n is an integer of 0 to 2, and the fluoroolefin is a compound of formula (6): CF.sub.3(CF.sub.2).sub.nCA=CHB, wherein one of A and B is F and the other is H, and n is an integer of 0 to 2.

2. The process for producing a fluoroolefin according to claim 1, wherein the chromium oxide, at least part of which is crystallized, has a crystallinity of 30% or more.

3. The process for producing a fluoroolefin according to claim 1, wherein the chromium oxide, at least part of which is crystallized, has a crystallinity of 60% or more.

4. The process for producing a fluoroolefin according to claim 1, wherein the chromium oxide, at least part of which is crystallized, has a crystallinity of 70% or more.

5. The process for producing a fluoroolefin according to claim 1, wherein the crystallized chromium oxide has an average crystallite diameter of 50 nm or less.

6. The process for producing a fluoroolefin according to claim 1, wherein the chromium oxide has a specific surface area of 10 m.sup.2/g or more.

7. The process for producing a fluoroolefin according to claim 1, wherein the at least one catalyst is supported on a carrier.

8. The process for producing a fluoroolefin according to claim 7, wherein the carrier is at least one member selected from the group consisting of SiO.sub.2, Al.sub.2O.sub.3, zeolite, activated carbon, and zirconium oxide.

9. The process for producing a fluoroolefin according to claim 1, wherein the catalyst comprising the chromium oxide, at least part of which is crystallized, is fluorinated, and then the chlorine-containing compound is reacted with the fluorinating agent.

10. The process for producing a fluoroolefin according to claim 1, wherein the fluorinating agent is anhydrous hydrogen fluoride.

11. The process for producing a fluoroolefin according to claim 1, wherein the fluoroolefin is a compound of formula (6-1): CF.sub.3(CF.sub.2).sub.nCFCH.sub.2, wherein n is an integer of 0 to 2.

12. The process for producing a fluoroolefin according to claim 11, wherein the chlorine-containing compound used as a starting material is at least one member selected from the group consisting of CCl.sub.3CClCH.sub.2 (HCO-1230xf) and CF.sub.3CClCH.sub.2 (HCFO-1233xf), and the fluoroolefin is CF.sub.3CFCH.sub.2 (HFO-1234yf).

13. The process for producing a fluoroolefin according to claim 12, wherein the chlorine-containing compound used as a starting material is CF.sub.3CClCH.sub.2 (HCFO-1233xf), and the fluoroolefin is CF.sub.3CFCH.sub.2 (HFO-1234yf).

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows an XRD pattern of the amorphous chromium oxide obtained in Production Example 2, and a XRD pattern index of Cr.sub.2O.sub.3 crystal.

(2) FIG. 2 shows XRD patterns of the chromium oxide, at least part of which is crystallized, obtained in Production Examples 3 to 7, and a XRD pattern index of Cr.sub.2O.sub.3 crystal.

DESCRIPTION OF EMBODIMENTS

(3) The present invention is described in more detail below with reference to Production Examples of catalysts used in the present invention and Examples of the present invention.

Production Example 1 (Preparation of Chromium Oxide Catalyst Precursor)

(4) 10% aqueous ammonia (118 g) was added to 900 g of an aqueous solution in which 77 g of chromium nitrate nonahydrate was dissolved to precipitate chromium hydroxide by neutralization. The chromium hydroxide precipitate was collected by filtration with a Buchner funnel, washed with water (3 L), and filtered, thereby obtaining chromium hydroxide.

Production Example 2 (Preparation of Amorphous Chromium Oxide Catalyst)

(5) The solid obtained in Production Example 1 was dried at 120 C. for 12 hours. After making the solid into a powder, graphite was added in an amount of 3% based on the total weight, and the resulting mixture was molded into pellets (2-mm dia.2 mm) and calcined at 400 C. in a nitrogen flow for 2 hours, thereby obtaining chromium oxide.

(6) According to the XRD pattern of the oxide powder, the diffraction pattern derived from crystal was not observed, and the oxide was amorphous. In FIG. 1, the diffraction peak around 2=26.5 indicated added graphite.

Production Example 3 (Preparation of Partially Crystallized Chromium Oxide Catalyst: Crystallinity: 38%, Average Crystallite Diameter: 32.3 nm)

(7) The solid obtained in Production Example 1 was dried at 120 C. for 12 hours. After making the solid into a powder, the powder was calcined at 350 C. in an air flow for 3 hours, thereby obtaining chromium oxide.

(8) According to the XRD pattern of the oxide powder, the diffraction pattern derived from -Cr.sub.2O.sub.3 was observed, the crystallinity obtained from the pattern area was 38%, and the oxide was chromium oxide containing a crystal portion and an amorphous portion. Based on the full width at half maximum, the crystallized chromium oxide had an average crystallite diameter of 32.3 nm.

Production Example 4 (Preparation of Partially Crystallized Chromium Oxide Catalyst: Crystallinity: 62%, Average Crystallite Diameter: 25.3 nm)

(9) The solid obtained in Production Example 1 was dried at 120 C. for 12 hours. After making the solid into a powder, the powder was calcined at 400 C. in an air flow for 3 hours, thereby obtaining chromium oxide.

(10) According to the XRD pattern of the oxide powder, the diffraction pattern derived from -Cr.sub.2O.sub.3 was observed, the crystallinity obtained from the pattern area was 62%, and the oxide was chromium oxide containing a crystal portion and an amorphous portion. Based on the full width at half maximum, the crystallized chromium oxide had an average crystallite diameter of 25.3 nm.

Production Example 5 (Preparation of Partially Crystallized Chromium Oxide Catalyst: Crystallinity: 73%, Average Crystallite Diameter: 24.0 nm)

(11) The solid obtained in Production Example 1 was dried at 120 C. for 12 hours. After making the solid into a powder, the powder was calcined at 550 C. in an air flow for 3 hours, thereby obtaining chromium oxide.

(12) According to the XRD pattern of the oxide powder, the diffraction pattern derived from -Cr.sub.2O.sub.3 was observed, the crystallinity obtained from the pattern area was 73%, and the oxide was chromium oxide containing a crystal portion and an amorphous portion. Based on the full width at half maximum, the crystallized chromium oxide had an average crystallite diameter of 24.0 nm.

Production Example 6 (Preparation of Crystallized Chromium Oxide Catalyst: Crystallinity: 100%, Average Crystallite Diameter: 34.3 nm)

(13) The solid obtained in Production Example 1 was dried at 120 C. for 12 hours. After making the solid into a powder, the powder was calcined at 700 C. in an air flow for 3 hours, thereby obtaining chromium oxide.

(14) According to the XRD pattern of the oxide powder, the diffraction pattern derived from -Cr.sub.2O.sub.3 was observed, the crystallinity obtained from the pattern area was 100%, and the oxide was crystalline chromium oxide. Based on the full width at half maximum, the crystallized chromium oxide had an average crystallite diameter of 34.3 nm. In FIG. 2, the diffraction peak around 2=26.5 indicated graphite added for molding.

Examples 1 to 4

(15) Each of the chromium oxide catalysts (7.0 g) prepared in Production Examples 3 to 6 was placed in a 1 m-long tubular Hastelloy reactor.

(16) The reactor was heated, and the catalyst was first fluorinated by introducing nitrogen gas and hydrogen fluoride gas. To avoid the deterioration of the catalyst due to the rapid reaction of the catalyst and hydrogen fluoride, the reaction was gradually performed in two steps using heating temperatures and introduction rates shown below.

(17) Step 1: Nitrogen gas at 450 Nml/min (flow rate at 0 C. and 0.1 Mpa, the same as below) and hydrogen fluoride gas at 50 Nml/min for 1 hour at 200 C.

(18) Step 2: Nitrogen gas at 100 Nml/min, hydrogen fluoride gas at 400 Nml/min for 1 hour at 330 C.

(19) Between Steps 1 and 2, it took 1.5 hours to change the temperature and the flow rate of the nitrogen gas and the hydrogen fluoride gas.

(20) The temperature of the reactor was raised to 350 C., and anhydrous hydrogen fluoride gas and oxygen gas were supplied to the reactor at flow rates of 42 NmL/min and 0.42 NmL/min, respectively, and maintained for 0.5 hours. Thereafter, CF.sub.3CClCH.sub.2 (HCFC-1233xf) gas was supplied at a flow rate of 4.2 NmL/min. About 30 hours later, the effluent gas from the reactor was analyzed by gas chromatography.

(21) Table 1 shows the results. Since HFC-245cb in the product is a useful compound that can be converted into HFO-1234yf by a hydrogen fluoride elimination reaction, Table 1 also shows the total selectivity of HFO-1234yf and HFC-245cb. In addition, Table 1 shows the conversion rate of the starting material, and the total yield of HFO-1234yf and HFC-245cb based on the starting material, calculated on the total selectivity of HFO-1234yf and HFC-245cb.

(22) The symbols shown in the table indicate the following compounds:

(23) TABLE-US-00001 1233xf CF.sub.3CClCH.sub.2 1234yf CF.sub.3CFCH.sub.2 245cb CF.sub.3CF.sub.2CH.sub.3 1234ze CF.sub.3CHCHF 1233zd CF.sub.3CHCHCl

Comparative Example 1

(24) Fluorination treatment of a catalyst and fluorination reaction were performed as in Example 1, except that the amorphous chromium oxide obtained in Production Example 2 was used as a catalyst. Table 1 shows the results.

(25) TABLE-US-00002 TABLE 1 Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 1 Catalyst Prod. Prod. Prod. Prod. Prod. preparation Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 2 example Crystallinity 38 62 73 100 0 (%) Specific 20 24 11 10 203 surface area (m.sup.2/g) Average 32.3 25.3 24.0 34.3 crystallite diameter (nm) 1233xf 11 20 20 20 17 conversion (GC %) 1234yf 68 68 67 68 66 selectivity (GC %) 245cb 23 22 23 23 23 selectivity (GC %) 1234ze 0.6 3.4 3.9 4.3 2.8 selectivity (GC %) 1233zd 0.5 1.4 1.6 1.3 0.9 selectivity (GC %) CO.sub.2 2.6 1.8 1.7 0.9 4.2 selectivity (GC %) Other by- 5.3 3.4 2.8 2.5 3.1 product selectivity (GC %) 1234yf + 245cb 91 90 90 91 89 selectivity (GC %) 1234yf + 245cb 10 18 18 18 15 total yield (%)

(26) As is clear from Table 1, Examples 2 to 4, in which partially or wholly crystallized chromium oxide satisfying the conditions that the crystallity degree was 60% or more, the average crystallite diameter was 24 to 35 nm, and the specific surface area was 10 m.sup.2/g or more was used as a catalyst, showed high levels in the selectivity and the total yield of HFO-1234yf and HFC-245cb, which are useful compounds, as well as a high HCFC-1233xf conversion rate compared to those of Comparative Example 1, in which amorphous chromium oxide was used as a catalyst. In particular, Example 4, in which chromium oxide having a crystallinity of 100% was used as a catalyst, showed the highest 1234yf+245cb selectivity, i.e., 91%; thus, an excellent effect was attained.

(27) In the aforementioned Examples and in Comparative Example 1, the highest HCFC-1233xf conversion rate was 20%, and thus an unreacted starting material will be recycled and reused in the actual process. Accordingly, the greater the 1234yf+245cb selectivity, the greater the yield of the target product in the actual process. When compared under the same conditions, the greater the 1233xf conversion rate, the lower the equipment costs. This is because the recycled amount of an unreacted starting material is reduced.

(28) Consequently, the processes of Examples 2 to 4 in which chromium oxide with a crystallinity of 60% or more, an average crystallite diameter of 24 to 35 nm, and a surface area of 10 m.sup.2/g or more was used as a catalyst, are industrially advantageous because they have a high 1233xf conversion rate and high 1234yf+245cb selectivity.

(29) Example 1, in which chromium oxide having a crystallinity of 38% was used as a catalyst, showed a low HCFC-1233xf conversion rate and a low total yield of HFO-1234yf and HFC-245cb compared to Comparative Example 1, but had high HFO-1234yf and HFC-245cb selectivity. Therefore, in the actual process, in which the starting material is reused, the total yield of HFO-1234yf and HFC-245cb is higher than in a process in which an amorphous chromium oxide is used as a catalyst; thus, the process of Example 1 is industrially advantageous