KR20030003243A - A process for the preparation of 1,1,1,2-tetrafluoroethane - Google Patents

Abstract

The present invention comprises the steps of coprecipitation of chromium metal hydroxide and aluminum metal hydroxide from a corresponding trivalent metal salt solution using NH ₄ OH, NaOH or KOH as base; And calcining to obtain a composite oxide procatalyst in amorphous form impregnated with an amount of zinc compound promoted by the activity of zinc. The present invention relates to a method for preparing a co-precipitated Cr ₂ O ₃ / Al ₂ O ₃ catalyst with zinc. This catalyst is used to fluorinate trichloroethylene to produce HFC-134a, and to fluorinate the intermediate of the previous stage reaction (HCFC-133a).

Description

A process for the preparation of 1,1,1,2-tetrafluoroethane

Methods of catalytic gas phase fluorination of haloalkanes with hydrogen fluoride to form fluorine-rich haloalkanes are known in the art. Aluminum fluoride is one of the catalysts for halogen exchange known in the art. However, suitable catalysts are required to fluorinate the haloalkenes to yield fluorine-rich haloalkanes.

As US Pat. No. 2,885,427 (1959) discloses that CrF ₃ 3H ₂ O is suitable as a catalyst for fluorinating haloalkanes and haloalkenes, CrF ₃ , 3H ₂ O is oxidized at 600 ° C. so that the formula is CrOF ₃ , F ₂ . It is the only procatalyst to obtain an active catalyst. Trichloroethylene (hereinafter referred to as TCE) at 350 ° C using the above catalyst was reacted with HF in the gas phase to produce 2-chloro-1,1,1-trifluoroethane as a main component (hereinafter referred to as HCFC-133a). And a small amount of HFC-134a were obtained.

The method of forming HFC-134a from TCE involves several steps. The first step is the addition of HF in accordance with Markovnikov's law to obtain 1-fluoro-1,1,2-trichloroethane (HCFC-131a). Subsequently, when chlorine in HCFC-131a is replaced with fluorine, the intermediate product 1,2-dichloro-1,1-difluoroethane (HCFC-132b) and HCFC-133a are replaced with fluorine. 134a will be obtained. In order to easily replace chlorine bonded to carbon with fluorine, the present invention is in the order of trihalide (-CX3)> dihalide (-CHX2)> primary halide (-CH ₂ X) (where X = Cl). Known in the field of In the specific case of catalytically fluorinating TCE, HCFC-133a is obtained in very high yield. However, to achieve good conversion and high selectivity, which are important in commercial manufacturing processes, efficient catalysts and relatively high temperatures are required to replace the primary halides present in HCFC-133a. Fluorination of TCE was essentially divided into two stages. The first step involves the fluorination of TCE to give HCFC-133a. The second step involves the fluorination of HCFC-133a to yield HFC-134a. UK patent GB 2,030,981 A (1979) reported a method of fluorinating HCFC-133a at 400 ° C. using CrF ₃ , 3H ₂ O as procatalyst. The catalyst was first activated by treatment with air and then with a mixture of HF and air. After activation and at the beginning of the fluorination, HCFC-133a and HF with a molar ratio of 1: 6 were passed through the catalyst to obtain 31% conversion and 98% selectivity for HFC-134a. Subsequently, when both conversion and selectivity began to slowly fall, additional air was injected to sustain the reaction.

The discovery of oxygenated CrF ₃ , 3H ₂ O as a procatalyst led to the development of several new catalysts based on oxides such as chromium, nickel, cobalt and aluminum. U.S. Pat.Nos. 3722850 (1973) and 3859424 (1975) disclose the use of Cr (OH) ₃ or Cr ₂ O ₃ XH ₂ O as a procatalyst activated by calcination and fluorination with HF. Is disclosed. The method of fluorinating TCE to obtain HCFC-133a was carried out at atmospheric pressure using HF: TCE having a molar ratio of 6: 1. The best conversions and selectivities were obtained at temperatures ranging from 300 ° C to 340 ° C. The yield of HCFC-133a was 93%. U.S. Patent Nos. 3,755,477 (1973), 4,129,603 (1978) and 4,158,675 (1979) disclose the steps of precipitating Cr (OH) ₃ from Cr ³⁺ salts using a base, steaming at 95 ° C., dehydration step. Fluorination catalysts prepared by a series of steps according to the calcination step and the HF treatment step have been reported. In US Pat. No. 3,755,477, the yield of HCFC-133a was reported to be 85% when using HF: TCE with a molar ratio of 6: 1 at a temperature of 300 ° C. and atmospheric pressure. US Pat. Nos. 4,129,603 and 4,158,675 claim the highest conversion rates of 18.2% in fluorination with HF: HCFC-133a having a molar ratio of 3: 1 under reaction temperatures and atmospheric pressures ranging from 335 ° C to 355 ° C. The selectivity for HFC-134a was 91%.

In addition, there are other modifications to the preparation of procatalysts based on chromium hydroxide. EP 0514932 (1992) discloses a process for producing Cr (OH) ₃ from Cr (NO ₃ ) _{3 with} different surface areas in the range from 48 to 180 m 2 / g and using graphite as an additive. This catalyst provided a maximum conversion of 20.3% and a selectivity of 95.7% for HFC-134a when using HF: HCFC-133a with a molar ratio of 4.6: 1 at a reaction temperature of 330 ° C. and a space velocity of 2250 / h.

EP 0546883 (1992) reports the preparation of chromia with or without the Ni compound using the solgel technique. The addition of nickel compound improves the life of the catalyst.

EP0486333 A1 (1991) and EP0554165 A1 (1993) reported catalysts comprising partially fluorinated alumina or chromia / nickel salts impregnated on AlF ₃ . Fluorination of HCFC-133a was carried out in the presence of oxygen under pressure to yield HFC-134a with a maximum conversion of 21% and 99%, respectively.

EP0641598 A2 (1994) discloses a process for the preparation of a fluorinated catalyst which combusts chromium (III) hydroxide in a hydrogen atmosphere. The catalyst obtained was crystalline Cr ₂ O ₃ . The catalyst prepared in this patent included two steps using HF: TCE with a molar ratio of 15: 1, yielding a TCE conversion of 91.2% and a selectivity of 95.3% for HCFC-133a. In the second step using HF: 133a (8: 1), a conversion of 19.8% HCFC-133a and a selectivity of 99.3% for HFC-134a were obtained. The catalyst obtained in the process of this invention has only two components. This catalyst is crystalline and coprecipitation takes place at lower dilution. On the other hand, the catalyst of this invention comprises three components (Cr / Al / Zn) impregnated with ZnCl ₂ on the chromia / alumina catalyst, which is amorphous and coprecipitation takes place only at higher dilution. .

U.S. Patent No. 4792643 (1988) discloses a process for preparing HFC-134a using a catalyst prepared by coextrusion of aluminum oxyhydroxide and chromium oxide and starting with HCFC-133a. The method for producing HCFC-133a from TCE uses a catalyst prepared by a coextrusion catalyst impregnated with cobalt chloride. This patent reports a method for preparing other catalysts by impregnating CrO ₃ , TiCl ₄ , CrCl ₃ , CoCl ₂ and NiCl ₂ on porous activated alumina. These catalysts were used to directly fluorinate TCE to obtain HFC-134a. TCE conversion and integrated selectivity for HFC-134a and HCFC-133a are low in large scale formulations. In summary, this patent discloses a process for the simultaneous or sequential co-deposition of compounds of chromia and transition metals (Ti, Zr, Mo, Mg, Co, Ni) on alumina. In addition, this invention is distinguished from the present invention in particular in advantage.

U.S. Pat.No. 5,515,508 (1992) discloses a process for preparing chromia and transition metals (Ti, Zr, Mo, Mg, Co, Ni) simultaneously or sequentially by co-depositing on alumina. This patent discloses a catalyst prepared by mixing Al (OH) ₃ and chromium oxide in the presence of a solvent. The catalyst, which has undergone the calcination and fluorination steps, was used for the reaction of HF and TCE under pressure and for the reaction of HF and HCFC-133a. In the case of TCE, a high selectivity for HCFC-133a was reported but no specific value was given. Fluorination of HCFC-133a has been reported to provide 18% conversion and 94% selectivity for HFC-134a. In summary, the patent discloses a process for preparing HFC-134a from HCFC-133a using a catalyst prepared by coextrusion of aluminum oxyhydroxide and chromium oxide. The process for producing HCFC-133a from TCE utilizes a catalyst prepared by coextrusion of aluminum oxyhydroxide / chromium oxide or by coextrusion catalyst impregnated with cobalt chloride. This invention is completely different from the invention in particular in that it is a catalyst by coextrusion or coevaporation.

EP 0328127 A1 (1989) reports a method for fluorinating HCFC-133a using a catalyst obtained by impregnating a compound of Co, Mn, Ni, Pd, Ag and Ru on alumina or AlOF as a procatalyst. The catalyst obtained from CoCl ₂ / Al ₂ O ₃ provides 33.5% conversion and 93.7% selectivity to HFC-134a in the fluorination reaction of HCFC-133a with HF containing ppm levels of oxygen. The catalyst was further modified with additives selected from compounds of metals with atomic numbers 58-71 (Indian patent 172054 (1989)). The conversion of 30-40% was obtained using HF: HCFC-133a having a molar ratio of 10: 1 to 20: 1 at a temperature of 350 ° C. or higher. At higher temperatures, the conversion increased but the selectivity dropped to 82.9%.

WO 92/16480 (1992) and WO 92/16481 (1992) are prepared by impregnating zinc compounds on Al ₂ O ₃ and optionally comprising one or more other metals selected from the group consisting of atomic numbers 57 to 71. The catalyst is disclosed. This catalyst was used for the fluorination of TCE and HCFC-133a to provide very high selectivity for HCFC-133a and HFC-134a, respectively. However, the fluorination of TCE requires very long contact times.

A method using a compound of zinc and / or magnesium as a promoter on a chromium-based catalyst impregnated on alumina or AlF ₃ is reported in EP 0502605 A1 (1992). In fluorination using HF: TCE with a molar ratio of 10: 1, the conversion was only 40.9% at a temperature of 310 ° C. and a contact time of 1 s. The same catalyst gave 20.5% conversion and> 99% selectivity for fluorination with HF: HCFC-133a with a molar ratio of 3.5: 1 at a reaction temperature of 33 ° C. and a contact time of 2s.

The present invention relates to a process for preparing a coprecipitation chromia-alumina catalyst impregnated with zinc salt, and a process for preparing 1,1,1,2-tetrafluoroethane (named HFC-134a) using the catalyst.

It is an object of the present invention to provide a process for preparing a coprecipitation chromium-aluminum catalyst impregnated with zinc chloride. Another object is to provide a method for preparing HFC-134a by fluorination of trichloroethylene.

Another object of the present invention is to reduce the relative percentage of the strong acid position of the catalyst to achieve high selectivity.

Another object is to provide the catalyst with sufficient breaking strength for use under pressure.

The present invention relates to a process for preparing a co-precipitated Cr ₂ O ₃ / Al ₂ O ₃ catalyst promoted with zinc, which process comprises chromium metal hydroxide and aluminum metal from a corresponding trivalent metal salt solution using NHOH, NaOH or KOH as base. Coprecipitation of the hydroxide; And calcining to obtain an amorphous composite oxide procatalyst impregnated with an amount of zinc compound of the activity promoting amount, wherein the chromium metal hydroxide used is bulk chromia.

Another embodiment of the invention,

(a) fluorinated trichloroethylene (TCE) with anhydrous hydrogen fluoride (AHF) in contact with a coprecipitation Cr ₂ O ₃ / Al ₂ O ₃ catalyst promoted by zinc salt and produced by the process described above Obtaining 2-chloro-1,1,1-trifluoroethane (HCFC-133a); And

(b) fluorinating HCFC-133a with AHF under contact with a coprecipitation Cr ₂ O ₃ / Al ₂ O ₃ catalyst promoted with a zinc salt as described above to obtain HFC-134a. It relates to a method for producing 1,2-tetrafluoroethane (HFC-134a).

In one embodiment, the present invention provides a 2-chloro-1,1, by contacting a gaseous feed consisting of trichloroethylene and THF with a chromia alumina ZnCl ₂ catalyst at a temperature ranging from 275 to 400 ° C. and optionally under pressure. It provides a method for producing 1,1,1,2-tetrafluoroethane comprising the step of recovering 1-trifluoroethane (HCFC-133a).

In another embodiment, the present invention provides coprecipitation chromia impregnated with zinc chloride in a gaseous feed consisting of 2-chloro-1,1,1-trifluoroethylene and HF at temperatures and pressures in the range of 275 to 400 ° C. Contacting on an alumina catalyst to recover 1,1,1,2-tetrafluoroethane from the product stream according to conventional methods.

In another embodiment, the coprecipitation chromia alumina catalyst will comprise chromium-aluminum having an atomic ratio of 1: 1 to 1:14, and the amount of zinc compound used for impregnation of the coprecipitation chromia / alumina catalyst is from 2 to 12 wt%. %to be.

Preferably, the molar ratio of anhydrous hydrogen fluoride and trichloroethylene is 6: 1 to 12: 1, and the molar ratio of anhydrous hydrogen fluoride and 2-chloro-1,1,1-trifluoroethylene is 4: 1 to 15: 1.

In another embodiment, the molar ratio (W / F) of catalyst to feed is 65 to 150 g / mole and contacting the gas feed with the catalyst will be carried out at a pressure in the range of 15 to 210 psig.

In commercial HFC-134a process, trichloroethylene (TCE) and anhydrous hydrogen fluoride are used as raw materials. The reaction of adding HF to TCE and exchanging chlorine for fluorine is carried out in the presence of a catalyst suitable to provide maximum atomic efficiency. This method is convenient to divide into two steps:

Step-I: Fluorinating TCE to afford HCFC-133a.

Step-II: Fluorinating HCFC-133a to Obtain HFC-134a.

This method can be carried out under atmospheric pressure and even under pressure. The reaction under pressure has the advantage of feeding the product stream directly to the distillation column operating under pressure to separate the desired product and by-products and to recover and recycle unreacted starting materials and intermediates.

Factors affecting conversion and selectivity are listed below:

1. the degree of activation of the procatalyst and its HF.

2. The molar ratio of HF: TCE and HF: HCFC-133a.

3. Reaction temperature.

4. Weight ratio of catalyst to moles of feed per hour expressed in w / F g.h / mole.

5. Pressure.

The catalytic activity in halogen exchange is due to the Lewis acid center. In the case of chromia-based catalysts, the activity was due to several reversible oxidative positions in the catalyst. In alumina based catalysts, formation of B-AlF ₃ upon activation is critical to catalytic activity. Catalysts based on chromia only have been found to be very effective for fluorination at atmospheric pressure. Under pressure, this catalyst showed a decrease in conversion and selectivity. In addition, when volatile compounds are generated and condensed at the reactor outlet to block the reactor outlet, there is a serious loss in industrial applications. The use of graphite to increase the strength of the catalyst leads to a loss of activity.

The present invention takes advantage of the catalytic activity of both chromia and alumina and discloses a process for the preparation of co-precipitation catalysts starting with salts of Cr ³⁺ and Al (NO ₃ ) ₃ . The relative atomic ratio of Cr: Al is 1: 1 to 1:14, preferably 1: 3 to 1:10, most preferably 1: 3 to 1: 5.

Coprecipitation is carried out with a base selected from NaOH, KOH and NH ₄ OH, preferably NH ₄ OH. Precipitation is carried out in diluents of various concentrations with a base of 1-6 molar concentrations, preferably 4-6 molar concentrations. The amount of water used to dissolve the total amount of chromium (III) salt and aluminum nitrate is 38: 1 to 4: 1 by weight, preferably 19: 1 to 4: 1, and most preferably 10: 1 to 4: 1. . The total acidity of the procatalyst is known to vary depending on the pH at which the hydroxide is formed. Precipitation is completed by adjusting the final pH to 7-8. The hydroxide is filtered off, washed with water and dried to a constant weight at a temperature in the range from 70 to 150 ° C, preferably 70 to 120 ° C. The dried catalyst is powdered and molded or extruded into a tablet and calcined under nitrogen atmosphere for 24 to 48 hours at a temperature in the range from 350 to 400 ° C., preferably 380 to 400 ° C. The form of the catalyst has no effect on its activity.

The calcined catalyst is treated with N ₂ at 400 ° C. for 24 hours and then activated by fluorination at a temperature in the range from 150 to 400 ° C. until the HF exhaust stream contains less than 1% moisture. This method reduces the use of Cr compounds, which are raw materials for the production of catalysts, thereby minimizing the problems associated with unit cost and the waste associated with the spent catalyst waste.

It has been found that the performance of the coprecipitation Cr ₂ O ₃ / Al ₂ O ₃ catalyst can be further improved by impregnating or depositing with zinc compounds to reduce the total acid value. Addition of a zinc compound results in 2-chloro-1,1,1,2-tetrafluoroethane (HCFC-124), pentafluoroethane (HFC-125) and 1,1, in the formation of TCE and HCFC-133a. Formation of 1-trifluoroethane (HFC-143a) is inhibited. The addition of zinc compounds onto Cr ₂ O ₃ / Al ₂ O ₃ reduced the percentage of strong acid centers relative to weak and intermediate acids, as indicated by TPD of ammonia. The amount of zinc compound is such that the zinc content is from 2 to 12% by weight, preferably from 3 to 7% by weight relative to the weight of the coprecipitation Cr ₂ O ₃ / Al ₂ O ₃ catalyst.

The stoichiometric ratio of HF: TCE required to obtain HCFC-133a is 3: 1. It was found that excess HF was required to obtain maximum conversion and selectivity. The ratio of HF: TCE is in the range of 6: 1 to 12: 1, preferably 7: 1 to 10: 1. Likewise the ratio of HF: HCFC-133a in the fluorination of HCFC-133a to HFC-134a is 4: 1 to 15: 1, preferably 6: 1 to 10: 1.

The reaction for fluorination of TCE to give HCFC-133a is a multistage reaction. The conversion and selectivity depend on the residence time that determines the W / F value. Preferred W / F values are found to be between 65 and 150, most preferably between 70 and 100. Likewise, the preferred W / F values for fluorinating HCFC-133a to obtain HFC-134a are 80 to 150, most preferably 100 ± 5.

The pressure was found to be effective to fluorinate HCFC-133a to yield HFC-134a. Under the same conditions of temperature, number of moles and W / F, the conversion was higher at atmospheric pressure compared to the reaction under pressure. It has been found useful to carry out all of the fluorination steps under pressure separating the different components in the resulting mixture. The required pressure was found to be in the range of 70 to 210 psig.

Fluorination of TCE and HCFC-133a can be carried out in the range from 275 to 400 ° C., preferably from 300 to 375 ° C. to obtain good conversion and selectivity for the desired product.

A key feature of the present invention is that as a catalyst it is possible to obtain high selectivity and optimum conversion at all stages of the reaction. The preparation of the procatalyst, its activation and its use when fluorinating TCE to give HFC-134a are described in the Examples below.

Example: Preparation of Catalyst

All chemicals used are commercial grade materials. Demineralized water was used.

Catalyst A: Cr ₂ O ₃ / Al ₂ O ₃ Catalyst

341 g of Cr (NO ₃ ) ₃ .9H ₂ O and 1440 g of Al (NO ₃ ) ₂ .9H ₂ O were dissolved in 8600 g of water at room temperature. The solution is stirred and a 10% ammonia solution is added at a constant rate of 1300 g / h to a pH of 7.5. The resulting slurry was charged to an autoclave and heated at 90 ° C. for 2 hours and then cooled to 50 ° C. The resulting slurry was filtered and washed with water. The obtained coke was divided into two parts so that the weight ratio was 3: 1. The large portion was dried at 70 ° C. and then at 120 ° C. for 2 hours to obtain a constant weight. The dried cake was powdered to a particle size> 125 mesh. A small portion was partially dried at 70 ° C. and mixed with the powder of the main portion to extrude into a 2.5 mm die pellet according to standard processes. The extrudate was calcined at 400 ° C. for 24 hours under N ₂ atmosphere to yield 262 g of a coprecipitation catalyst designated Catalyst-A. The catalyst is amorphous by X-ray analysis.

Catalyst B: ZnCl ₂ / Cr ₂ O ₃ / Al ₂ O ₃

100 g of the extrudate of catalyst A was suspended in a solution prepared by dissolving 15.4 g of ZnCl ₂ in 89.0 g of water for 1 hour. The mixture was filtered by gravity and the solid was dried at 120 ° C. to a constant weight to yield 110 g of impregnated catalyst ZnCl ₂ / Cr ₂ O ₃ / Al ₂ O ₃ . X-ray analysis showed the amorphous properties of the catalyst. The zinc content of the catalyst was found to be 4.3% by weight.

Catalyst C: ZnCl ₂ / Cr ₂ O ₃ / Al ₂ O ₃

157.35 g of Cr (NO ₃ ) ₃ .9H ₂ O and 532.7 g of Al (NO ₃ ) ₃ .9H ₂ O were dissolved in 25.75 kg of water. While stirring the solution, 1.7% of ammonia solution was added to the solution at a constant rate over 18.25 hours to complete the precipitation and bring the final pH to 7.5. The slurry is filtered, washed with water and dried at 120 ° C. to constant weight to give 116.7 g of catalyst.

50 g of the catalyst was powdered and mixed with a solution prepared by dissolving 4.17 g of ZnCl ₂ in 55 g of water. The mixture is placed on a rotavapor and slowly evaporated to remove water. The solid obtained is molded into a tablet of 3 mm and calcined at 400 ° C. for 24 hours under N ₂ atmosphere to obtain 40.5 g of catalyst C. X-ray analysis showed the amorphous properties of the catalyst.

Catalyst D: ZnCl ₂ / Cr ₂ O ₃ / Al ₂ O ₃

157.35 g of Cr (NO ₃ ) ₃ .9H ₂ O and 532.7 g of Al (NO ₃ ) ₃ .9H ₂ O were dissolved in 12.89 kg of water. While stirring the solution, ammonia solution (5%) was added to this solution at a constant rate over 18.25 hours to complete the precipitation and bring the final pH to 7.5. The slurry is filtered, washed with water and dried at 120 ° C. to constant weight to give 128.7 g of base catalyst.

50 g of the catalyst was powdered and mixed with a solution prepared by dissolving 4.5 g of ZnCl ₂ in 45 g of water. The following process was carried out in the same manner as in the case of catalyst C, to obtain 39.5 g of catalyst D. X-ray results showed the amorphous properties of the catalyst.

Catalyst E: ZnCl ₂ / Cr ₂ O ₃ / Al ₂ O ₃

A mixture of 157.35 g of Cr (NO ₃ ) ₃ .9H ₂ O and 532.7 g of Al (NO ₃ ) ₃ .9H ₂ O was dissolved in 6.45 kg of water. While stirring the solution constantly, 1.7% of ammonia solution was added to the solution at a constant rate over 19.25 hours to allow precipitation. The slurry is filtered, washed with water and dried at 120 ° C. to constant weight to give 116.7 g of catalyst.

50 g of the catalyst was powdered and mixed with a solution prepared by dissolving 4.5 g of ZnCl ₂ in 45 g of water. The water was removed as described for Catalyst C. The dried catalyst was calcined at 400 ° C. for 24 hours and then molded into a tablet of 3 mm size to give 38.6 g of catalyst E, which showed amorphous properties as a result of X-ray analysis.

Catalyst F: ZnCl ₂ / Cr ₂ O ₃ / Al ₂ O ₃

157.35 g of Cr (NO ₃ ) ₃ .9H ₂ O and 532.7 g of Al (NO ₃ ) ₃ .9H ₂ O were dissolved in 6.4 kg of water. While stirring the solution constantly, 1.7% ammonia solution was added to this solution over 12 minutes to allow precipitation to complete and a final pH of 7.5 was obtained. The slurry is filtered, washed with water and dried at 120 ° C. to constant weight to give 136.5 g of base catalyst.

50 g of the catalyst was powdered and mixed with a solution prepared by dissolving 4.16 g of ZnCl ₂ in 45 g of water. The water was removed as described for Catalyst C. The dried catalyst was calcined at 400 ° C. for 24 hours and then molded into a 3 mm size tablet to give 40.5 g of catalyst F. X-ray analysis showed amorphous properties.

Catalyst G: ZnCl ₂ / Cr ₂ O ₃ / Al ₂ O ₃

Cr (NO ₃ ) ₃ .9H ₂ O (157.35 g) and Al (NO ₃ ) ₃ .9H ₂ O (532.7 g) were dissolved in 19.32 kg of water to prepare a solution, and the solution was stirred with constant stirring. 1.7% ammonia solution was added over 18 hours to obtain a pH of 7.5. The slurry was filtered, washed with water and then dried at 120 ° C. until constant weight was obtained to yield 149.4 g of catalyst.

The catalyst 50 was powdered and mixed with a solution prepared by dissolving 4.5 g of ZnCl ₂ in 45 g of water. The water was removed on a rotary evaporator as described for Catalyst C and then the solids were calcined at 400 ° C. for 24 hours and molded into 3 mm tablets to give 36 g of Catalyst G. X-ray analysis showed amorphous properties.

Catalyst H: ZnCl ₂ / Cr ₂ O ₃ / Al ₂ O ₃

To 58.41g of Cr (NO _{3) 3} 9H ₂ O and and 197.9g of Al (NO _{3) 3} 9H ₂ O and dissolved in H ₂ O of 1600㎖. 3.75% ammonia solution was added at a constant rate over 7 hours to reach a pH of 7.5. The slurry was filtered, washed with water, and the obtained wet cake was placed in an autoclave and mixed with 500 g of water. This mixture was placed in a closed system and stirred at 90 ° C. for 6 hours. After the heat treatment, the slurry was cooled to 35 ° C., filtered, washed with water, and dried at 120 ° C. to obtain a constant weight to give 59.5 g of Cr ₂ O ₃ / Al ₂ O ₃ catalyst.

25 g of the catalyst was powdered and mixed with a solution prepared by dissolving 1 g of zinc chloride in 17 g of water. Place on rotary evaporator, remove water and dry to yield 27 g of catalyst. The catalyst was molded into a tablet of 3 mm size and then calcined at 400 ° C. for 24 hours to yield 18.67 g of catalyst H.

Catalyst I: Cr ₂ O ₃ / Al ₂ O ₃

According to the method described for Catalyst A, 95 g of Cr (NO ₃ ) ₃ .9H ₂ O and 603 g of Al (NO ₃ ) ₃ .9H ₂ O, and 10% ammonia solution dissolved in 3.4 kg of water were started. The coprecipitation catalyst was prepared as a material to obtain 103 g of calcined catalyst I.

Catalyst J: ZnCl ₂ / Cr ₂ O ₃ / Al ₂ O ₃

92 g of catalyst A was suspended in a solution prepared by dissolving 16.35 g of zinc chloride in 100 g of water, and the mixture was slowly evaporated to dryness in vacuo on a rotary evaporator. The resulting product was dried at 120 ° C. to a constant weight to yield 110 g of catalyst J.

Catalyst K: ZnCl ₂ / Cr ₂ O ₃ / Al ₂ O ₃

92 g of catalyst A was suspended in a solution prepared by dissolving 24.65 g of zinc chloride in 100 g of water, and the mixture was slowly evaporated to dryness in vacuo on a rotary evaporator. The resulting product was dried at 120 ° C. to a constant weight to yield 119 g of catalyst K.

Bulk Chromia Catalyst Cr ₂ O ₃

CrO ₃ is reduced to ethanol to obtain CrOOH according to the method disclosed in Inorganic Synthesis (1946), Vol. II, pp 190-191, which is filtered, washed with water and then until a constant weight is obtained. Dried at 120 ° C. The product was powdered and molded into 3 mm tablets and calcined at 400 ° C. for 24 hours under a nitrogen atmosphere.

Common Fluorination Methods

The experimental apparatus was cooled in each feed line, evaporator, 90 cm long, 1 "inner diameter, 1" inner diameter reactor, pressure release trap, alkali scrubber, dryer, condenser, and dry ice acetone mixture for HF and TCE or HCFC-133a. Samples of the product stream are withdrawn periodically from the sampling valve between the dryer and the condenser Maintain temperature in different zones using electrically heated block furnaces and a PID controller.

The catalyst is loaded into a tubular reactor and pretreated with nitrogen at 400 ° C. for 24 hours. The temperature is then lowered to 150 ° C. and a slow HF stream is introduced with nitrogen. After the initial exotherm, nitrogen is slowly withdrawn while raising the temperature of the catalyst layer to 375 ° C. Continue fluorination until the water content of the released HF is below 1%. The temperature of the catalyst bed is then raised to the reaction temperature and TCE or HCFC-133a is introduced into the system along with HF. Adjust the amount of TCE or HCFC-133a to provide the desired molar ratio and W / F. The product stream is scrubbed with aqueous KOH solution and then condensed in a trap cooled in anhydrous ice acetone. The composition of the product stream is measured by GC analysis after reaching a steady state and determined as the peak area. Fluorination experiments were performed both under atmospheric pressure and under pressure, as shown in the following examples:

Example 1

TCE Fluorination Method at Atmospheric Pressure

catalyst Catalyst A Catalyst B Bulk chromia Reaction temperature (℃) 300 300 300 Molar ratio, HF / TCE 7 6 6 W / F, g.h / mole 55 100 98 TCE conversion rate (%) 97 96.5 96 Selectivity to HCFC-133a (%) 96.5 97.5 97.5 % Selectivity for HFC-134a 2.0 1.0 1.0

Example 2

How to Fluoride HCFC-133a to HFC-134a at Atmospheric Pressure

catalyst Catalyst A Catalyst B Bulk chromia Reaction temperature (℃) 350 360 350 Molar ratio, HF / TCE 9 8 12 W / F, g.h / mole 100 100 113 HCFC-133a Conversion Rate (%) 27 22 32 % Selectivity for HFC-134a 85 96 95

Example 3

Fluorination of TCE Under Pressurization

catalyst Catalyst B Reaction temperature (℃) 300 300 300 Molar ratio, HF / TCE 6 6 6 Pressure (psig) 70 70 70 W / F, g.h / mole 100 70 50 TCE conversion rate (%) 99.0 97.5 96.5 Selectivity to HCFC-133a (%) 95.5 97.0 95.3 % Selectivity for HFC-134a 2.0 0.5 0.2

Example 4

How to Fluoride HCFC-133a to HFC-134a Under Pressurization

catalyst Catalyst A Reaction temperature (℃) 355 330 330 Molar ratio, HF / HCFC-133a 6 6 4 Pressure (psig) 70 70 70 W / F, g.h / mole 50 50 50 HCFC-133a Conversion Rate (%) 35 19 15 % Selectivity for HFC-134a 73 80 82

Example 5

How to Fluoride HCFC-133a to HFC-134a Under Pressurization

catalyst Catalyst B Reaction temperature (℃) 360 360 360 Molar ratio, HF / HCFC-133a 8 6 6 Pressure (psig) 70 70 70 W / F, g.h / mole 100 70 50 HCFC-133a Conversion Rate (%) 24.0 22.0 14.4 % Selectivity for HFC-134a 96.0 88.2 84.5

Example 6

Fluorination of TCE under atmospheric pressure using a catalyst prepared by diluting to different concentrations

catalyst Catalyst C Catalyst D Catalyst E Catalyst F Reaction temperature (℃) 300 300 300 300 Molar ratio, HF / TCE 6 6 6 6 W / F, g.h / mole 100 100 100 100 TCE conversion rate (%) 96.8 96.5 97.5 87.6 % Selectivity for HCFC-133a and HFC-134a 98.0 98.3 97.5 96.7

A key feature of the present invention is that one catalyst is usefully used in both stages of the reaction to provide high selectivity and optimal conversion. The preparation of the procatalyst, its activation and its use in fluorinating TCE to give HFC-134a will be described in the following examples:

Example: Preparation of Catalyst

All chemicals used are commercial grade materials. Demineralized water was used.

Catalyst A: Cr ₂ O ₃ / Al ₂ O ₃ Catalyst

341 g of Cr (NO ₃ ) ₃ .9H ₂ O and 1440 g of Al (NO ₃ ) ₂ .9H ₂ O were dissolved in 8600 g of water at room temperature. The solution is stirred and a 10% alumina solution is added at a constant rate of 1300 g / h to a pH of 7.5. The resulting slurry was charged to an autoclave and heated at 90 ° C. for 2 hours and then cooled to 50 ° C. The resulting slurry was filtered and washed with water. The obtained coke was divided into two parts so that the weight ratio was 3: 1. The large portion was dried at 70 ° C. and then at 120 ° C. for 2 hours to obtain a constant weight. The dried cake was powdered to a particle size> 125 mesh. A small portion was partially dried at 70 ° C. and mixed with a large portion of the powder and extruded into a 2.5 mm die pellet according to standard processes. The extrudate was calcined at 400 ° C. for 24 hours under N ₂ atmosphere to yield 262 g of a coprecipitation catalyst designated Catalyst-A. The catalyst is amorphous by X-ray analysis.

Claims (16)

Coprecipitation of chromium metal hydroxide and aluminum metal hydroxide from a corresponding trivalent metal salt solution using NH ₄ OH, NaOH or KOH as the base; And calcining to obtain a composite oxide procatalyst in amorphous form, impregnated with an amount of zinc compound promoted by the activity, in a co-precipitated Cr ₂ O ₃ / Al ₂ O ₃ catalyst promoted with zinc. The method of claim 1 wherein the chromium metal hydroxide is bulk chromia. The method according to claim 1, wherein the coprecipitation Cr ₂ O ₃ / Al ₂ O ₃ is impregnated with a zinc compound of an activity promoting amount. The method according to claim 1, wherein the atomic ratio of Cr: Al is 1: 1 to 1:14. The method according to claim 1, wherein the atomic ratio of water and trivalent metal salt is 4: 1 to 38: 1. The process according to claim 1, wherein the hydroxide is precipitated at a pH in the range of 7-8 by adding 1-6 moles of base solution over 0.2-20 hours. (a) fluorinating trichloroethylene (TCE) with anhydrous hydrogen fluoride (AHF) in contact with a zinc salt-promoted coprecipitation Cr ₂ O ₃ / Al ₂ O ₃ catalyst as described in claim 1 Obtaining 2-chloro-1,1,1-trifluoroethane (HCFC-133a); And (b) 1,1,1,2-tetrafluoroethane by fluorination of HCFC-133a with AHF in contact with a coprecipitation Cr ₂ O ₃ / Al ₂ O ₃ catalyst promoted with a zinc salt as described in claim 1; A method for producing HFC-134a comprising the step of obtaining (HFC-134a). The method of claim 7, wherein the coprecipitation chromia-alumina catalyst comprises chromium-aluminum having an atomic ratio of Cr: Al of 1: 1 to 1:14. 8. A process according to claim 7, wherein the zinc content in the catalyst ranges from 2 to 12% by weight. The method of claim 7, wherein the molar ratio of AHF and TCE is 6: 1 to 12: 1, and the W / F value is 65 to 150. The method of claim 7, wherein the molar ratio of AHF and HCFC-133a is 4: 1 to 15: 1 and the W / F value is 80 to 150. 8. A process according to claim 7, wherein the fluorination step is carried out in a temperature range of 275-400 ° C. 8. A process according to claim 7, wherein said fluorination is carried out in a pressure range of 15 to 210 psig. 8. A process according to claim 7, wherein the stoichiometric ratio of HF: TCE required to obtain HCFC-133a is 3: 1 and excess HF is required to obtain maximum conversion and selectivity. 8. A process according to claim 7, wherein the ratio of HF: TCE is in the range of 6: 1 to 12: 1, preferably 7: 1 to 10: 1. 8. A process according to claim 7, wherein the ratio of HF: HCFC-133a is 4: 1 to 15: 1, preferably 6: 1 to 10: 1 when the HCFC-133a is fluorinated with HFC-134a.