HK1170473A - Catalysts and process to manufacture 2,3,3,3-tetrafluoropropene - Google Patents

Description

Catalyst and process for preparing 2,3,3, 3-tetrafluoropropene

Cross Reference to Related Applications

This patent application claims priority from us provisional application 61/183,674 filed on 6/3/2009 and us provisional application 61/256,341 filed on 10/30/2009.

Background information

FIELD OF THE DISCLOSURE

This disclosure relates generally to methods for the synthesis of fluorinated olefins.

Description of related Art

Since the montreal protocol mandates the gradual cessation of the use of ozone depleting chlorofluorocarbons (CFCs) and Hydrochlorofluorocarbons (HCFCs), the fluorocarbon industry has been working for the past several decades to find alternative refrigerants. A solution for many applications is the commercialization of Hydrofluorocarbon (HFC) compounds for use as refrigerants, solvents, fire extinguishing agents, blowing agents and propellants. These novel compounds, such as HFC refrigerants, HFC-134a and HFC-125, which are currently most widely used, have zero ozone depletion potential and therefore are not affected by the current regulatory phase out due to the montreal protocol.

In addition to the ozone depletion problem, global warming is another environmental problem associated with many of these applications. Thus, there is a need for compositions that meet both low ozone depletion standards and have low global warming potentials. It is believed that certain hydrofluoroolefins meet both goals. Accordingly, there is a need for a process that can provide for the production of halogenated hydrocarbons and fluoroolefins that do not contain chlorine while having low global warming potential.

There is also considerable interest in developing new refrigerants with the potential to mitigate the global warming phenomenon for the automotive air conditioning market.

HFC-1234yf (CF) both having zero ozone depletion and low global warming potential₃CF＝CH₂) And HFC-1234ze (CF)₃CH ═ CHF) has been considered as a potential refrigerant. U.S. patent publication 2006/0106263A1 discloses a liquid crystal display made from CF₃CF₂CH₃Or CF₃CHFCH₂Preparation of HFC-1234yf by F-catalyzed vapor phase dehydrofluorination, and from CF₃CH₂CHF₂Catalytic vapor phase dehydrofluorination to produce HFC-1234ze (a mixture of E-and Z-isomers).

There is a continuing need for more selective and efficient production processes for the production of HFC-1234 yf.

Summary of The Invention

In one aspect, the present invention discloses a process for the preparation of 2,3,3, 3-tetrafluoropropene comprising: dehydrofluorinating 1, 1, 1, 2, 3-pentafluoropropane in the presence of a dehydrofluorination catalyst comprising chromium (III) oxide and an alkali metal to produce a product mixture comprising 2,3,3, 3-tetrafluoropropene; and recovering the 2,3,3, 3-tetrafluoropropene from the product mixture produced by dehydrofluorination.

The foregoing summary, as well as the following detailed description, is intended to be exemplary and illustrative only, and is not intended to be limiting, as defined by the appended claims.

Detailed Description

In one aspect, the present invention discloses a process for the preparation of 2,3,3, 3-tetrafluoropropene comprising: dehydrofluorinating 1, 1, 1, 2, 3-pentafluoropropane in the presence of a dehydrofluorination catalyst comprising chromium (III) oxide and an alkali metal to produce a product mixture comprising 2,3,3, 3-tetrafluoropropene; and recovering the 2,3,3, 3-tetrafluoropropene from the product mixture produced by dehydrofluorination. In one embodiment, the product mixture comprising 2,3,3, 3-tetrafluoropropene further comprises less than 20 parts per hundred on a molar basis of 1, 1, 1, 2, 2-pentafluoropropane. In another embodiment, the product mixture comprising 2,3,3, 3-tetrafluoropropene further comprises less than 10 parts per hundred on a molar basis of 1, 1, 1, 2, 2-pentafluoropropane. In one embodiment, the dehydrofluorination catalyst comprises chromium (III) oxide and at least 1000ppm of an alkali metal. In another embodiment, the dehydrofluorination catalyst comprises chromium (III) oxide and at least 3000ppm of an alkali metal. In another embodiment, the dehydrofluorination catalyst comprises chromium oxide and at least 5000ppm of an alkali metal. In another embodiment, the dehydrofluorination catalyst comprises chromium oxide and at least 1000ppm of potassium. In another embodiment, the dehydrofluorination catalyst comprises from 0.1% to 3% boron and at least 3000ppm of an alkali metal. In another embodiment, the dehydrofluorination catalyst comprises from 0.5% to 2% boron and at least 3000ppm of alkali metal. In another embodiment, the dehydrofluorination catalyst comprises from 0.5% to 2% boron and at least 3000ppm sodium. In another embodiment, the dehydrofluorination catalyst comprises from 0.5% to 2% boron and at least 2000ppm potassium.

Many aspects and embodiments have been described above and are merely exemplary and not limiting. After reading this description, the skilled person will realize that other aspects and embodiments are possible without departing from the scope of the invention.

Other features and advantages of any one or more embodiments will become apparent from a reading of the following detailed description and the claims.

Before addressing details of the embodiments described below, certain terms are defined or clarified.

Catalytic dehydrofluorination of hydrofluorocarbons to produce hydrofluoroolefins is typically carried out in the vapor phase using a dehydrofluorination catalyst. Vapor phase dehydrofluorination catalysts are well known in the art. These catalysts include, but are not limited to, alumina, aluminum fluoride, fluorided alumina, metal compounds supported on aluminum fluoride, metal compounds supported on fluorided alumina; chromium oxide, fluorinated chromium oxide, and cubic chromium trifluoride; oxides, fluorides and oxyfluorides of magnesium, zinc and mixtures of magnesium and zinc and/or aluminum; lanthanum oxide and fluorinated lanthanum oxide; carbon, acid-washed carbon, activated carbon, three-dimensional matrix carbonaceous material; and a metal compound supported on carbon. The metal compound is an oxide, fluoride, and oxyfluoride of at least one metal selected from the group consisting of sodium, potassium, rubidium, cesium, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, chromium, iron, cobalt, rhodium, nickel, copper, zinc, and mixtures thereof.

In passing CF₃CHFCH₂In the dehydrofluorination of F to HFC-1234yf, either HFC-1234yf or HFC-1234ze may be obtained, depending on which pair of adjacent fluorine and hydrogen atoms are eliminated. Generally, HFC-1234yf is the major product, however, depending on the reaction conditions, HFC-1234ze can be produced in amounts of up to 10pph or more compared to HFC-1234 yf. It was also found that CF₃CHFCH₂Another by-product of F (HFC-245eb) catalyzed dehydrofluorination is CF₃CF₂CH₃(HFC-245cb), which is very difficult to separate from HFC-1234 yf. It is believed that this product is produced via the re-addition of hydrogen fluoride to HFC-1234yf in the opposite direction to its elimination. Although HFC-245cb can be catalytically dehydrofluorinated to HFC-1234yf, in practice, the dehydrofluorination of HFC-245cb requires higher temperatures and different catalysts. Depending on the catalyst and reaction conditions, the amount of HFC-245cb produced via isomerization can be as much as 30 to 60 parts per hundred parts HFC-1234yf, resulting in significant yield loss. The selectivity to HFC-1234yf may be expressed as parts per hundred of by-product relative to the amount of HFC-1234 yf. For example, a product mixture comprising 60% HFC-1234yf, 20% HFC-245cb and 3% HFC-1234ze produced from the dehydrofluorination of HFC-245eb would have 33pph of HFC-245cb and 5pph of HFC-1234 ze.

Using a catalyst comprising chromium (III) oxide and an alkali metal, it is possible to convert CF with high selectivity₃CHFCH₂Dehydrofluorination of F (HFC-245eb) to HFC-1234yf and very little HFC-245cb is formed. In one embodiment, the alkali metal is at least one of sodium, potassium and cesium, or mixtures thereof.

In one embodiment, the catalyst comprises chromium (III) oxide and an effective amount of an alkali metal to produce 2,3,3, 3-tetrafluoro-1-propene while producing less than 20pph of 1, 1, 1, 2, 2-pentafluoropropane. The effective amount of alkali metal required will depend on the manner in which it is distributed in the catalyst composition. The effective amount of alkali metal required will also depend on the alkali metal selected. The effective amount of cesium is less than the effective amount of potassium, which is less than the effective amount of sodium.

In one embodiment, the dehydrofluorination catalyst comprises chromium (III) oxide and at least 1000ppm of an alkali metal. In another embodiment, the dehydrofluorination catalyst comprises chromium (III) oxide and at least 3000ppm of an alkali metal. In another embodiment, the dehydrofluorination catalyst comprises chromium oxide and at least 5000ppm of an alkali metal. In another embodiment, the dehydrofluorination catalyst comprises chromium oxide and at least 1000ppm of potassium. In another embodiment, the dehydrofluorination catalyst comprises from 0.1% to 3% boron and at least 3000ppm of an alkali metal. In another embodiment, the dehydrofluorination catalyst comprises from 0.5% to 2% boron and at least 3000ppm of alkali metal. In another embodiment, the dehydrofluorination catalyst comprises from 0.5% to 2% boron and at least 3000ppm sodium. In another embodiment, the catalyst comprises chromium (III) oxide, 0.5% to 2% boron, and at least 2000ppm potassium. In one embodiment, the catalyst is a chromium composition known as a Guignet green pigment.

In one embodiment, the dehydrofluorination catalyst can be prepared by slurrying preformed pellets or particles of the chromium (III) oxide catalyst in an aqueous solution of an alkali metal salt, such as sodium carbonate, potassium carbonate or cesium carbonate. The slurry is then dried.

In another embodiment, the dehydrofluorination catalyst can be prepared by slurrying chromium (III) oxide powder with an aqueous solution of an alkali metal salt such as sodium carbonate, potassium carbonate or cesium carbonate. The slurry is then dried. In one embodiment, the dehydrofluorination catalyst is then extruded, ground into particles, and sieved to 12/20 mesh particles.

In another embodiment, the catalyst may be prepared by fusing a mixture of 3 to 16 parts boric acid and 1 part potassium dichromate at 800 ℃, cooling the mixture in air, crushing the solids to produce a powder, hydrolyzing, filtering, drying, grinding and sieving. Various examples of the preparation of Guignet green can be found in the art, including U.S. patent 3,413,363, the disclosure of which is incorporated herein by reference.

The physical shape of the catalyst is not critical and may include, for example, pellets, powder or granules.

In one embodiment, the catalytic dehydrofluorination is suitably carried out at a reactor temperature set point in the range of from about 250 ℃ to about 350 ℃. In another embodiment, the catalytic dehydrofluorination is carried out at a reactor temperature set point in the range of from about 250 ℃ to about 300 ℃. In one embodiment, the contact time is generally from about 1 to about 450 seconds. In another embodiment, the contact time is from about 10 to about 120 seconds.

The reaction pressure may be subatmospheric, atmospheric or superatmospheric. Generally, near atmospheric pressure is preferred. However, it is beneficial to conduct the dehydrofluorination reaction at reduced pressure (i.e., a pressure less than one atmosphere).

In one embodiment, the catalytic dehydrofluorination is carried out in the presence of an inert gas such as nitrogen, helium or argon. The addition of an inert gas can increase the degree of dehydrofluorination. Of note are processes wherein the molar ratio of inert gas to hydrofluorocarbon undergoing the dehydrofluorination reaction is from about 5: 1 to about 0.5: 1. In one embodiment, the inert gas is nitrogen.

The reaction products HFC-1234yf and any unconverted HFC-245eb are recovered from the effluent leaving the reactor. Unconverted HFC-245eb can be recycled back to the reactor to produce additional HFC-1234 yf. In one embodiment of the invention, unconverted HFC-245eb is recycled back to the reactor as its azeotrope with HF. Published PCT patent application WO 2008/002501, filed on 27.2006, month 6, and disclosing the HF/HFC-245eb azeotrope, is incorporated herein in its entirety. U.S. patent 7,423,188 discloses azeotropes of the E-isomer of HFC-1234ze with HF and processes for separating HFC-1234ze from the azeotrope, and U.S. patent 7,476,771 discloses azeotropes of HFC-1234yf with HF and processes for separating HFC-1234yf from the azeotrope. HFC-1234ze may be recovered as an HF/HFC-1234ze azeotrope. Similarly, HFC-1234yf may be recovered as an HF/HFC-1234yf azeotrope. Pure HFC-1234ze and pure HFC-1234yf may be further recovered from their HF azeotropes by employing processes similar to those described in U.S. patent 7,423,188 and U.S. patent 7,476,771, and both are incorporated herein by reference.

The reactor, or reactor bed, distillation column, and feed lines, discharge lines and accessories attached thereto, used in applying the process of the present invention should be constructed of a material resistant to hydrogen fluoride. Typical materials of construction well known in the fluorination art include stainless steels (especially austenitic stainless steels), well known high nickel alloys (e.g., Monel)^TMNickel-copper alloy, Hastelloy^TMNickel-based alloy and Inconel^TMNichrome), and copper clad steel.

As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Furthermore, unless expressly stated to the contrary, "or" refers to an inclusive "or" and not to an exclusive "or". For example, the condition a or B is satisfied in any of the following cases: a is true (or present) and B is spurious (or absent), a is spurious (or absent) and B is true (or present), and both a and B are true (or present).

Also, the use of "a" or "an" is used to describe elements and components described herein. This is done merely for convenience and to provide a general sense of the scope of the invention. Such description should be understood to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.

The use of group numbers corresponding to columns in the periodic Table of elements is described in the "New nomenclature" convention described in "CRC Handbook of chemistry and Physics", 81 th edition (2000-2001).

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can also be used in the practice or testing of embodiments of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety, unless a specific paragraph is cited. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

Examples

The concepts described herein will be further described in the following examples, which do not limit the scope of the invention described in the claims.

In the examples, the following abbreviations or codes may be used:

CT-contact time

1234yf＝CF₃CF＝CH₂

245eb＝CF₃CHFCH₂F

1234ze＝CF₃CH＝CHF

245cb＝CF₃CF₂CH₂

Example 1

Example 1 illustrates the dehydrofluorination of 1, 1, 1, 2, 3-pentafluoropropane over a chromia catalyst, which catalyst further comprises boron, potassium and sodium.

A inconel tube (5/8 inch OD) was filled with 6cc (4.9g) of hydrated chromium oxide (also known as Guignet green) in the form of an extrudate that had been crushed and sieved to 12/20 mesh. A typical analysis of the catalyst showed the following composition: 54.5% Cr, 1.43% B, 3400ppm Na, 120ppm K. The temperature of the catalyst bed was raised to 325 ℃ and nitrogen (38sccm, 6.3X 10)^-7m³/s) purge for 120 minutes, then at 300 ℃ for 80 minutes. The nitrogen flow was then reduced to 27sccm (4.5X 10)^-7m³S) and HF at 9sccm (1.5X 10)^-7m³Flow rate/s) for 500 minutes. The nitrogen flow was then reduced to 19sccm (3.2X 10)^-7m³S) and the HF flow was increased to 15sccm (2.5X 10)^-7m³S), 25 minutes. The nitrogen flow was then reduced to 11sccm (1.8X 10)^-7m³S) and the HF flow was raised to 21sccm (3.5X 10)^-7m³S), feeding for 30 minutes. The nitrogen flow was then reduced to 4sccm (6.7X 10)^-8m³S) and the HF flow was raised to 27sccm (4.5X 10)^-7m³S), feeding for 30 minutes. The nitrogen flow was then stopped and the HF flow was increased to 30sccm (5.0X 10)^-7m³S), 160 minutes. After this activation phase, the catalyst bed temperature is changed to the reaction conditions.

The reactor temperature was stabilized at a temperature of 250 ℃ to 302 ℃ and at 6.4sccm (1.1X 10)^-7m³Flow rate of/s) adding CF₃CHFCH₂F. Make CF₃CHFCH₂F is in 4Evaporated at 1 ℃ while letting nitrogen gas at 6.4sccm (1.1X 10)^-7m³Flow/s) through the vaporizer. Part of the reactor effluent was passed through a series of valves and analyzed by GCMS. The results in table 1 are the average of at least two GC injections per set of conditions. The amounts of 245cb and 1234ze are expressed as molar parts per hundred parts of 2,3,3, 3-tetrafluoropropene produced.

TABLE 1

1234yf mol%	245cb(pph)	1234ze(pph)	245eb(％)	Temperature of	CT (second)
						71.7	8.9	5.2	17.5	302	28
47.9	6.1	4.0	46.6	275	28
						28.9	4.5	2.8	68.4	250	28

Example 2

Example 2 illustrates the dehydrofluorination of 1, 1, 1, 2, 3-pentafluoropropane over a chromia catalyst that also contains varying amounts of boron, potassium, and sodium.

A inconel tube (1/2 inch OD) was filled with 6cc (4.9g) of hydrated chromium oxide in the form of an extrudate that had been crushed and sieved to 12/20 mesh. The catalyst composition relating to B, Na and K is shown in Table 2. The temperature of the catalyst bed was raised to 300 ℃ and purged with nitrogen (30cc/min) for 200 minutes. The nitrogen flow was then reduced to 60cc/min and HF was fed at a flow rate of 20cc/min for 60 minutes. The temperature was raised to 325 ℃ for 300 minutes. The nitrogen flow was then reduced to 30cc/min and the HF flow was increased to 30cc/min, feeding for 30 minutes. The nitrogen flow was then reduced to 12cc/min and the HF flow was increased to 48cc/min, feeding for 60 minutes. The nitrogen flow was then stopped and the HF flow was increased to 48cc/min, feeding for 30 minutes. The reactor temperature was then reduced to 250 ℃ and held for 30 minutes. Thereafter, the HF was turned off and the reactor was purged with 30cc/min of nitrogen. The reactor temperature was then stabilized at 300 deg.C, the nitrogen flow was turned off, and CF was added at a rate of 3.2mL/hr (12cc/min)₃CHFCH₂F. CF is prepared by₃CHFCH₂F was evaporated at 175 ℃. Part of the reactor effluent was passed through a series of valves and analyzed by GCMS. 245cb and 1234zeThe amounts are expressed as molar parts per hundred parts of 2,3,3, 3-tetrafluoropropene produced.

TABLE 2

Example 3

Example 3 illustrates the dehydrofluorination of 1, 1, 1, 2, 3-pentafluoropropane over a chromia catalyst that also contains varying amounts of potassium added.

Chromium oxide catalysts having a starting composition of 55.8% Cr, 175ppm Na, 60ppm K, 53ppm Cu and 20ppm Zn were doped with varying levels of potassium. The composition of the catalyst with respect to the amount of K added is shown in Table 3.

A inconel tube (1/2 inch OD) was packed with 6cc (4.9g) of the catalyst prepared as follows. Hydrated chromium oxide in the form of extrudates crushed and sieved to 12/20 mesh was doped with varying levels of potassium by slurrying the catalyst with aqueous potassium carbonate containing sufficient potassium to provide the indicated potassium levels. The solution was then evaporated to dryness and the resulting catalyst was dried at 200 ℃ for 3 hours. After feeding to the reaction tube, the temperature of the catalyst bed was raised to 300 ℃ and purged with nitrogen (30cc/min) for 200 minutes. The nitrogen flow was then reduced to 60cc/min and HF was fed at a flow rate of 20cc/min for 60 minutes. The temperature was raised to 325 ℃ for 300 minutes. The nitrogen flow was then reduced to 30cc/min and the HF flow was increased to 30cc/min, feeding for 30 minutes. The nitrogen flow was then reduced to 12cc/min and the HF flow was increased to 48cc/min, feeding for 60 minutes. The nitrogen flow was then stopped and the HF flow was increased to 48cc/min, feeding for 30 minutes. The reactor temperature was then reduced to 250 ℃ and held for 30 minutes. Thereafter, the HF was turned off and the reactor was purged with 30cc/min of nitrogen. The reactor temperature was then stabilized at 300 deg.C, the nitrogen flow was turned off, and the flow at 3.2mL/hr (12cc/min)Adding CF in an amount₃CHFCH₂F. CF is prepared by₃CHFCH₂F was evaporated at 175 ℃. Part of the reactor effluent was passed through a series of valves and analyzed by GCMS. The amounts of 245cb and 1234ze are expressed as molar parts per hundred parts of 2,3,3, 3-tetrafluoropropene produced.

TABLE 3

Added K-ppm	1234ze(pph)	245eb(％)	1234yf(％)	245cb(pph)
					100	12.97	9.73	31.01	45.60
5000	5.30	11.83	73.4	9.47
					6500	3.87	34.7	58.55	2.88
10000	0.73	82.41	16.52	0

Example 4

Example 3 illustrates the dehydrofluorination reaction of 1, 1, 1, 2, 3-pentafluoropropane over a gamma-alumina dehydrofluorination catalyst.

A batch of gamma-alumina (BASF) (6cc, 3.19g) was activated as was the catalyst in example 1 above. As shown in the following table, the reactor temperature was controlled at a temperature of 249 ℃ to 299 ℃ and at 6.4sccm (11X 10)^-7m³Flow rate of/s) adding CF₃CHFCH₂F. Make CF₃CHFCH₂F was evaporated at 41 ℃ while letting nitrogen gas at 6.4sccm (1.1X 10)^-7m³Flow/s) through the vaporizer. Part of the reactor effluent was passed through a series of valves and analyzed by GCMS. The results in table 4 are the average of at least two GC injections per set of conditions. The amounts of 245cb and 1234ze are expressed as molar parts per hundred parts of 2,3,3, 3-tetrafluoropropene produced.

TABLE 4

1234yf mol%	245cb(pph)	1234ze(pph)	245eb(％)	Temperature of	CT (second)
						68.7	32.5	8.0	2.9	299	28
64.4	43.3	6.1	3.3	276	28
						57.3	46.9	3.3	13.5	249	28

Example 5

Example 5 illustrates the dehydrofluorination of 1, 1, 1, 2, 3-pentafluoropropane over an alpha-chromium oxide catalyst.

A batch of alpha-chromium oxide (6cc, 8.51g) as described in US 5,036,036 was activated as the catalyst in example 1 above. Analysis of the catalyst showed the following composition: 55.8% Cr, 0% B, 175ppm Na, 60ppm K. As shown in the following table, the reactor temperature was controlled at a temperature of 249 ℃ to 298 ℃ and at 6.4sccm (1.1X 10)^-7m³Flow rate of/s) adding CF₃CHFCH₂F. Make CF₃CHClCH₂CCl₂CF₃Evaporated at 41 ℃ while letting nitrogen gas at 5.4sccm (9.5X 10)^{- 8}m³Flow/s) through the vaporizer. Part of the reactor effluent was passed through a series of valves and analyzed by GCMS. The results in table 5 are the average of at least two GC injections per set of conditions. The amounts of 245cb and 1234ze are expressed as molar parts per hundred parts of 2,3,3, 3-tetrafluoropropene produced.

Analysis of the alpha-chromium oxide catalyst showed that it contained 55.8% chromium, 53ppm copper, 120ppm iron, 175ppm sodium, 60ppm potassium, 23ppm manganese and 20ppm zinc.

TABLE 5

1234yf mol%	245cb(pph)	1234ze(pph)	245eb(％)	Temperature of	CT (second)
						65.5	34.5	11	4.1	298	31
61.8	46.3	8.1	4.1	277	31
						57.7	59.4	5.2	4.6	249	31

Example 6

Example 6 illustrates the dehydrofluorination of 1, 1, 1, 2, 3-pentafluoropropane over a chromia gel catalyst.

A batch of chromium oxide gel (6cc, 7.47g) from BASF was activated as the catalyst in example 1 above. As shown in the following table, the reactor temperature was controlled at a temperature of 249 ℃ to 298 ℃ and at 6.4sccm (1.1X 10)^-7m³Flow rate of/s) adding CF₃CHFCH₂F. Make CF₃CHClCH₂CCl₂CF₃Evaporating at 41 deg.CWhile nitrogen gas is made to flow at 5.4sccm (9.5X 10)^{- 8}m³Flow/s) through the vaporizer. Part of the reactor effluent was passed through a series of valves and analyzed by GCMS. The results in table 6 are the average of at least two GC injections per set of conditions. The amounts of 245cb and 1234ze are expressed as molar parts per hundred parts of 2,3,3, 3-tetrafluoropropene produced.

TABLE 6

1234yf mol%	245cb(pph)	1234ze(pph)	245eb(％)	Temperature of	CT (second)
						69.0	33.9	6.4	1.8	299	31
64.4	47.0	4.0	1.5	277	31
						59.5	63.4	1.5	0.9	248	31

Example 7

Example 7 illustrates the dehydrofluorination of 1, 1, 1, 2, 3-pentafluoropropane over a chromia gel catalyst.

A batch of chromium oxide gel (6cc, 5.9g) from Synetix (CPA200A) was activated as the catalyst in example 1 above. As shown in the following table, the reactor temperature was controlled at a temperature of 251 ℃ to 301 ℃ and at 6.4sccm (1.1X 10)^-7m³Flow rate of/s) adding CF₃CHFCH₂F. Make CF₃CHClCH₂CCl₂CF₃Evaporated at 41 ℃ while letting nitrogen gas at 5.4sccm (9.5X 10)^{- 8}m³Flow/s) through the vaporizer. Part of the reactor effluent was passed through a series of valves and analyzed by GCMS. The results in table 7 are the average of at least two GC injections per set of conditions. The amounts of 245cb and 1234ze are expressed as molar parts per hundred parts of 2,3,3, 3-tetrafluoropropene produced.

Analysis of the chromia gel catalyst showed it to contain 62.9% chromium, 350ppm copper, 198ppm sodium, 145ppm iron and 50ppm potassium.

TABLE 7

1234yf mol%	245cb(pph)	1234ze(pph)	245eb(％)	Temperature of	CT (second)
						70.8	30.5	6.2	1.8	301	31
65.9	43.6	3.9	1.5	276	31
						67.3	42.6	1.9	1.3	251	31

It should be noted that not all of the activities described above in the general description or the examples are required, that a portion of a specific activity is not required, and that one or more other activities may be performed in addition to those described. Further, the order in which the acts are listed are not necessarily the order in which they are performed.

In the foregoing specification, various concepts have been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present invention.

Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any feature(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or element of any or all the claims.

It is appreciated that certain features are, for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any subcombination. Further, recitation of ranges of values herein are inclusive of each value within the range.

Claims (11)

1. A process for preparing 2,3,3, 3-tetrafluoropropene, the process comprising: (a) dehydrofluorinating 1, 1, 1, 2, 3-pentafluoropropane in the presence of a dehydrofluorination catalyst comprising chromium (III) oxide and an effective amount of an alkali metal to produce a product mixture comprising 2,3,3, 3-tetrafluoropropene and less than 20 parts per hundred of 1, 1, 1, 2, 2-pentafluoropropane; and (b) recovering said 2,3,3, 3-tetrafluoropropene from said product mixture produced in (a).

2. The process of claim 1 wherein said product mixture comprises 2,3,3, 3-tetrafluoropropene, said 2,3,3, 3-tetrafluoropropene comprising less than 10 parts per hundred on a molar basis of 1, 1, 1, 2, 2-pentafluoropropane.

3. The process of claim 1 wherein said dehydrofluorination catalyst comprises from 0.1% to 2% of an alkali metal disposed on the surface of said catalyst.

4. The process of claim 1 wherein said dehydrofluorination catalyst comprises from 0.1% to 1% alkali metal disposed on the surface of said catalyst.

5. The process of claim 1, wherein said dehydrofluorination catalyst comprises from 0.1% to 1% potassium disposed on the surface of said catalyst.

6. The process of claim 1 wherein said dehydrofluorination catalyst comprises from 0.5% to 2% alkali metal dispersed throughout said catalyst particles.

7. The process of claim 1 wherein said dehydrofluorination catalyst comprises from 0.1% to 3% boron and at least 3000ppm of an alkali metal.

8. The process of claim 1 wherein said dehydrofluorination catalyst comprises from 0.5% to 2% boron and at least 3000ppm sodium.

9. The process of claim 1 wherein said dehydrofluorination catalyst comprises from 0.55 to 2% boron and at least 1000ppm potassium.

10. The process of claim 1, wherein the temperature of the catalyst is maintained at a set point of 250 ℃ to 350 ℃.

11. The process of claim 8, wherein the temperature of the catalyst is maintained at a set point of 250 ℃ to 300 ℃.