JP2541256B2 - Method for producing tetrafluoroethane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to 1,1,1,2-tetrafluoroethane (R-134
It relates to the manufacturing method of a).

[Prior Art and Problems] As one of the methods for producing R-134a, 1,1-dichloro-
There is a production method in which 1,2,2,2-tetrafluoroethane (R-114a) is reacted with hydrogen in the presence of a hydrogenation catalyst. Application of known hydrogenation catalysts for this purpose, i.e. nickel or metals of Group VIIIa of the Periodic Table, their alloys or their oxides and salts, especially those which are hydrochloric acid resistant. Therefore, a method using palladium, which is relatively low in cost, has already been reported (see Japanese Patent Publication No. 56-38131). However, in this reduction reaction, for example, hydrogen chloride is by-produced as shown in the following formula, so that the catalyst is required to have acid resistance.

CF ₃ CCl ₂ F + H ₂ → CF ₃ CHClF + HCl CF ₃ CHClF + H ₂ → CF ₃ CH ₂ F + HCl Palladium is inexpensive in the platinum group and has excellent hydrogenation ability. However, it has a high hydrogen storage capacity and stores up to 1: 1 atomic ratio of hydrogen. When the amount of hydrogen stored increases, the strain of the lattice also increases, and it becomes more susceptible to mechanical deterioration. Further, unlike other elements in the same family, palladium has a drawback that it is easily dissolved in concentrated nitric acid or boiling sulfuric acid, and also dissolved in concentrated hydrochloric acid in the presence of oxygen.

[Means for Solving Problems] Causes of deterioration of catalyst characteristics are generally classified into adsorption inhibition by raw materials, reaction intermediates or products, catalyst poisoning, carbon deposition, sintering, chemical change of catalyst, etc. To be done. According to the research conducted by the present inventor, it has been found that the palladium catalyst causes remarkable particle growth of the catalyst particles in use in the present reduction reaction, which is one of the causes of the short life of the palladium catalyst.
Therefore, it is judged that the suppression of sintering is effective in improving the life of the palladium catalyst.

Atom transfer in a metal is usually active when the temperature expressed in degrees Celsius is at least one third of the melting point of the metal. Therefore, it can be said that the higher the melting point of the metal, the less likely the grain growth will occur at the same temperature. Palladium has a melting point of 1552 ° C and is the lowest of the precious metals. Therefore, it can be said that the element is likely to move atoms and easily cause sintering. Therefore, alloying with a refractory metal is effective in suppressing sintering. Among the high melting point metals, those having hydrogenation ability and hydrochloric acid resistance are particularly preferable, but when the addition amount is small, those characteristics are not so important. That is, iridium (2454 ℃), ruthenium (2500 ℃), rhodium (1966
℃), molybdenum (2610 ℃), tungsten (3410
It was found that alloying palladium with one or more elements selected from osmium (3000 ° C.) and osmium (3000 ° C.) is effective in suppressing sintering. (Melting point in parentheses).

Thus, the present invention has been completed based on the above findings, and R-114a contains palladium as a component and at least one refractory metal selected from the group consisting of iridium, ruthenium, rhodium, molybdenum, osmium and tungsten. A method for producing R-134g, which comprises reacting with hydrogen in the presence of a hydrogenation catalyst.

The hydrogenation catalyst in the present invention is a hydrogenation catalyst containing palladium and at least one refractory metal selected from the group consisting of iridium, ruthenium, rhodium, molybdenum, osmium and tungsten, preferably palladium and the high melting point. It is a hydrogenation catalyst composed of an alloy composed of a metal or an oxide thereof. The proportion of the refractory metal is preferably 0.01 to 90% by weight, more preferably 0.
It is 1 to 30% by weight.

As a preparation method, a conventional hydrogenation catalyst preparation method can be applied. For example, there is a method of impregnating a carrier with an aqueous solution of a salt containing a catalyst component and then reducing the carrier with hydrogen or the like. Further, reduction with borohydride (borane, sodium borohydride, etc.), hypophosphite, etc. is also possible.

In the present invention, as the carrier of the hydrogenation catalyst, for example, alumina, activated carbon and the like are suitable. As a supporting method, a conventional method for preparing a noble metal catalyst can be applied. In use, at least a part of the metal compound is reduced.

The ratio of hydrogen to R-114a can vary widely. However, usually a stoichiometric amount of hydrogen is used to replace the chlorine atoms with hydrogen. It is also possible to use considerably more than stoichiometric amounts of hydrogen, for example 4 mol or more, based on the total number of moles of R-114a.

Regarding the reaction pressure, normal pressure or a pressure higher than normal pressure can be used.

The reaction temperature is preferably 120 ° C or higher, but it is suitable to carry out in the gas phase at a temperature not exceeding 450 ° C.

The contact time is usually 0.1 to 3 when the reaction is carried out in the gas phase.
00 seconds, especially 5 to 30 seconds.

[Examples] Examples of the present invention will be shown below.

Preparation Example 1 Activated carbon was immersed in pure water, and water was impregnated inside the pores. Palladium chloride and iridium chloride were added at a ratio of 90:10 by weight of the respective metal components, and an aqueous solution of 0.5% of the total weight of the metal components was added dropwise to the activated carbon to gradually add the ionic components to the activated carbon. Adsorbed. After washing with pure water, it was dried at 150 ° C. for 5 hours. Next, after drying in nitrogen at 550 ° C for 4 hours, introducing hydrogen,
The temperature was reduced to 5 ° C. for 5 hours.

Preparation Example 2 Activated carbon was immersed in pure water, and water was impregnated inside the pores. To this, palladium chloride and osmium chloride were added at a ratio of 90:10 by weight of each metal component, and an aqueous solution of 0.5% of the total weight of the metal components relative to the weight of the activated carbon was dropped little by little to add the ionic components to the activated carbon. Adsorbed. After washing with pure water, it was dried at 150 ° C. for 5 hours. Next, after drying in nitrogen at 550 ° C for 4 hours, introducing hydrogen,
The temperature was reduced to 5 ° C. for 5 hours.

Preparation Example 3 Activated carbon was immersed in pure water, and water was impregnated inside the pores. To this, palladium chloride and ruthenium chloride were respectively added at a ratio of 90:10 by weight of the metal component, and an aqueous solution prepared by dissolving 0.5% of the total weight of the metal component with respect to the weight of the activated carbon was dropped little by little, and the ionic component was added to the activated carbon. Adsorbed. After washing with pure water, it was dried at 150 ° C. for 5 hours. Next, after drying in nitrogen at 550 ° C for 4 hours, introducing hydrogen,
The temperature was reduced to 5 ° C. for 5 hours.

Preparation Example 4 Activated carbon was immersed in pure water, and water was impregnated inside the pores. Palladium chloride and potassium tungstate are added to this in a weight ratio of palladium metal component and tungsten metal component.
At a ratio of 99: 1, an aqueous solution in which 0.5% of the total weight of both metal components was dissolved with respect to the weight of activated carbon was dropped little by little to adsorb the ionic component to the activated carbon. After washing with pure water, it was dried at 150 ° C. for 5 hours. Then, after drying in nitrogen at 550 ° C. for 4 hours, hydrogen was introduced, and the mixture was held at 300 ° C. for 5 hours to reduce the amount.

Preparation Example 5 Activated carbon was immersed in pure water, and water was impregnated inside the pores. Palladium chloride and potassium molybdate were added to this in a weight ratio of the palladium metal component and the molybdenum metal component of 99: 1.
The total weight of both metal components is 0.
An aqueous solution in which only 5% was dissolved was dropped little by little to adsorb the ionic component on the activated carbon. After cleaning with pure water,
It was dried at 150 ° C. for 5 hours. Then, after drying in nitrogen at 550 ° C. for 4 hours, hydrogen was introduced, and the mixture was held at 300 ° C. for 5 hours to reduce the amount.

Preparation Example 6 Activated carbon was immersed in pure water, and water was impregnated inside the pores. Palladium chloride and rhodium chloride were added at a ratio of 90:10 in terms of the weight ratio of the respective metal components, and an aqueous solution prepared by dissolving 0.5% of the total weight of the metal components with respect to the weight of the activated carbon was dropped little by little to make the ionic components active carbon Adsorbed. After washing with pure water, it was dried at 150 ° C. for 5 hours. Next, after drying in nitrogen at 550 ° C for 4 hours, introducing hydrogen, 300 ° C
It was kept for 5 hours and reduced.

Comparative Preparation Example Activated carbon was immersed in pure water, and water was impregnated inside the pores. An aqueous solution in which 0.5% of the total weight of the metal components was dissolved in palladium chloride based on the weight of the activated carbon was gradually added dropwise to adsorb the ionic components to the activated carbon. After washing with pure water, it was dried at 150 ° C. for 5 hours. Then in nitrogen 550
After drying at ℃ for 4 hours, hydrogen was introduced and the temperature was kept at 300 ℃ for 5 hours for reduction.

Example 1 An Inconel 600 reaction tube having an inner diameter of 2.54 cm and a length of 100 cm, which was filled with 300 cc of the catalyst prepared as in Preparation Example, was immersed in a salt bath furnace.

Hydrogen and starting materials (R-114a and 1,2-dichloro-1,1,2,2
-Consisting of tetrafluoroethane. Molar ratio 40:60)
It was introduced into the reaction tube in a molar ratio of 2: 1. The flow rates of hydrogen and starting material were 100 cc / min and 50 cc / min, respectively. Reaction temperature 250
The reaction was carried out at ℃ for 4.2 seconds. The gas composition at the outlet of the reaction tube was analyzed using a gas chromatograph. Further, the average particle size of contact was measured by observation using a scanning electron microscope. The results are shown in Table 1.

[Effects of the Invention] As shown in the examples, the present invention can produce R-134a in a good yield and also has an excellent effect in improving the durability of the catalyst.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location B01J 23/46 311 B01J 23/46 311X 23/652 C07B 61/00 300 C07B 61/00 300 B01J 23/64 103X

Claims (7)

(57) [Claims] 1. 1,1-Dichloro-1,2,2,2-tetrafluoroethane is added to at least one refractory metal selected from the group consisting of iridium, ruthenium, rhodium, molybdenum, osmium and tungsten and palladium. A method for producing 1,1,1,2-tetrafluoroethane, which comprises reacting with hydrogen in the presence of a hydrogenation catalyst as a component. 2. The process according to claim 1, wherein at least a stoichiometric amount of hydrogen is used with respect to 1,1-dichloro-1,2,2,2-tetrafluoroethane. 3. The production method according to claim 1, wherein the hydrogenation catalyst is an alloy of palladium and the refractory metal or an oxide thereof. 4. The hydrogenation catalyst has a ratio of the refractory metal of 0.
4. The method according to claim 3, wherein the alloy is an alloy of 01 to 90% by weight of palladium and the refractory metal, or an oxide thereof. 5. The hydrogenation catalyst has a ratio of the refractory metal of 0.
The manufacturing method according to claim 3, which is an alloy of 1 to 30% by weight of palladium and the refractory metal or an oxide thereof. 6. The production method according to any one of claims 1 to 5, wherein the hydrogenation catalyst is supported on an activated carbon carrier or an alumina carrier. 7. The method according to any one of claims 1 to 6, wherein the reaction is carried out in the gas phase in the temperature range of 120 ° C to 450 ° C.