KR100346017B1 - Paladium on Activated Carbon Catalysts and Preparation Methods thereof, and Method for Preparing Fluorohydrocarbon from Chlorofluorocarbon by Using the Same - Google Patents

Abstract

The present invention relates to a palladium (Pd) catalyst (Pd / C) supported on activated carbon (C), which is used as a catalyst in the catalytic hydrogenation reaction for the production of hydrofluorocarbons from chlorofluorocarbons, and to a process for preparing the same, and to fluorocarbons using the same. A method for the selective production of fluorohydrocarbons. The Pd / C catalyst of the present invention is prepared by pretreating activated carbon with alkali (NaOH) and strong acid (fluoric acid or hydrochloric acid and hydrofluoric acid) before supporting palladium on activated carbon, and then supporting palladium on activated carbon by adsorption precipitation or impregnation. do. In the Pd / C catalyst of the present invention, metal components contained in trace amounts in the activated carbon are removed by alkali and acid treatment, so that the surface properties of the carrier are changed to improve the catalytic activity. The catalyst of the present invention increases the selectivity of the dehydrogenation reaction during the dehalogenation reaction when hydrogenating chlorofluorocarbons (CFCs), and deactivates the catalyst due to sintering of the Pd as well as the dehydrogenation reaction. Since it inhibits deactivation, it is a particularly suitable catalyst for preparing hydrofluorocarbons (HFCs) from chlorofluorocarbons.

Description

Palladium on Activated Carbon Catalysts and Preparation Methods etc, and Method for Preparing Fluorohydrocarbon from Chlorofluorocarbon by Using the Same}

The present invention relates to a palladium (Pd) catalyst (hereinafter referred to as "Pd / C catalyst") supported on activated carbon (C) used as a catalyst in the catalytic hydrogenation reaction for producing fluorohydrocarbons from chlorofluorocarbons, and a method for producing the same; And a method for the selective production of fluorohydrocarbons from chlorofluorocarbons using the same.

Chlorinated fluorocarbon (CFC) compounds have high thermal and chemical stability and have been widely used as refrigerants, blowing agents, and propellants. However, as CFCs have been found to be a major cause of ozone depletion and global warming, the production and use of CFCs has been regulated by international regulations, and the development of CFC substitutes has emerged as an important research task.

Hydrogenation and dechlorination of CFCs produces difluoromethane (CH ₂ F ₂ , hereinafter referred to as "HFC-32") from dichlorodifluoromethane (CCl ₂ F ₂ , referred to as "CFC-12"). or chloro pentafluoroethyl pentafluoroethane from (CClF ₂ CF _3, hereinafter "CFC-115" denoted by) ethane producing the (CHF ₂ CF _3, hereinafter "HFC-125" expressed as) such as replacement key of materials developed to Recognized as a pathway, several researchers have been working on the development of catalysts for dehydrochlorination of CFCs.

Hydrogenation of CFCs results in dechlorination reactions in which chlorine and hydrogen are substituted, and dehydrofluorination reactions in which fluorine and hydrogen are replaced. As a result, in addition to the desired product HFC (partially hydrogenated product by dechlorination reaction), by-products such as methane and ethane (complete hydrogenation products by dechlorination and defluorination reaction) are generated, so that demineralization to minimize the formation of these by-products is achieved. Hydrogenation reaction studies are needed. In addition, since the HF produced in the defluorination reaction changes the carrier and affects the activity of the catalyst, the research on the same has also been conducted.

B. Coq et al. Catal., 141, (1993) 21] studied the reaction activity and the characteristics of the catalyst for the hydrogenation of CFC-12 on a catalyst in which various precious metals were supported on a carrier such as Al ₂ O ₃ , AlF ₃ , graphite or activated carbon, Started. Pd / AlF ₃ catalyst was impregnated with Pd in AlF ₃ has activity was relatively low, but as the reaction time, the change in the catalytic activity almost no, Pd / graphite, Pd / Al ₂ O ₃ and Pd / carbon black catalyst, the initial reaction Showed a sharp change in activity and selectivity. In particular, Pd / Al ₂ O ₃ catalysts were described as having a change in selectivity because of the change in the form of the carrier and the composition and properties of the catalyst during the hydrogenation reaction. The selectivity for CH ₂ F ₂ was reported to be lowest with Pd / graphite catalyst and highest with Pd / AlF ₃ .

Moon et al., Appl. Catal. A: General, 168 (1998) 154] hydrofluoric acid or hydrochloric acid produced during the dehydrochlorination of CFC-115 reacts with an oxide such as Al ₂ O ₃ to destroy the structure of the carrier and reduce the specific surface area of the catalyst. It has been found that the catalyst promotes sintering of the catalyst, and thus, the oxide is not preferred as a carrier of the catalyst for the hydrogenation reaction of CFC.

Juszczyk et al., Appl. Catal. A: General, 155, (1997) 55] investigated the improvement of selectivity by varying the pretreatment temperature of Pd / Al ₂ O ₃ catalyst, and the reaction conversion rate was low but only chlorine (Cl) was removed. The route of partial dechlorination reaction was estimated.

On the other hand, Pd / C catalysts loaded with palladium (Pd) on activated carbon have been reported to have relatively little effect from hydrochloric acid or hydrofluoric acid produced as by-products of the reaction. It is becoming.

Wiersma et al., Catal. Today, 27 (1996) 257, 35 (1997) 163] disclosed a study to improve the selectivity of catalysts by treating activated carbon with sodium hydroxide and hydrochloric acid.

The results of studies on the properties of activated carbon used as a carrier have been published in many literatures, for example, in H. P. Boehm, Adv. Catal., 16, (1966) 179 and JB Dornet [Carbon, 6, (1968) 161] disclose the characteristics of oxide groups on the surface of activated carbon, and K. Morigawa et al. See Adv. Catal., 20, (1969) 97] reported that pretreatment with nitric acid to form surface hydroxyl groups on the surface of activated carbon, followed by the preparation of Pd / C catalysts by ion exchange, can improve the dispersion of Pd. .

In addition, impurities such as Fe and Mg contained in activated carbon are known to act as a Friedel-Crafts reaction catalyst to cause a full hydrogenation reaction to hydrocarbons (British Patent, 2, 171, 925 ( And other impurities such as Ca also appear to influence the selectivity in the hydrogenation of CFCs.

Pd catalyst, which is mainly used in hydrogenation reaction, has a very high hydrogenation ability, and when hydrogenated CFC, it causes a complete dehalogenation reaction that promotes dechlorination as well as defluorination reaction, and impurities contained in activated carbon carrier Promotes dehalogenation. That is, when CFC-12 is hydrogenated on a commercial Pd catalyst, the conversion reaction to methane (complete dehalogenation hydrogenation) is promoted more than the conversion reaction to HFC-32 (dehydrochlorination reaction), and thus the desired reaction (dehydrogenation). It is difficult to increase the selectivity of the reaction). In addition, the deactivation of the catalyst is promoted by the generation of HF due to the complete dehalogenation, so that the conversion to HFC-32 may gradually decrease when the catalyst is used for a long time.

Therefore, the present inventors expect that the selectivity of HFCs in the hydrogenation of CFCs can be increased by pretreatment and removal of impurities contained in activated carbon carriers, and the activated carbons can be maintained for a longer time. Intensive research has been made regarding the pretreatment of the present invention.

It is an object of the present invention to provide an improved Pd / C catalyst for CFC hydrogenation which promotes the conversion to HFC and increases the catalytic activity for a long time by increasing the selectivity of the dehydrogenation reaction in the hydrogenation of CFCs.

Another object of the present invention is to provide a method for producing a Pd / C catalyst for the hydrogenation of the CFC.

Another object of the present invention is to provide a method for selectively producing HFC from CFC using the improved Pd / C catalyst for CFC hydrogenation reaction.

According to the present invention, catalytic hydrogenation of chlorofluorocarbons (CFCs) comprising palladium (Pd) supported on activated carbon (C) from which alkali treatment with sodium hydroxide and acid treatment with hydrofluoric acid has removed impurities present A Pd / C catalyst for reaction is provided. .

In addition, according to the present invention,

(a) alkali treating activated carbon (C) with an aqueous sodium hydroxide solution;

(b) acid treating the alkali treated activated carbon (C) with a hydrofluoric acid (HF) solution; And

(c) supporting palladium (Pd) on the acid treated activated carbon;

Provided is a method for producing a Pd / C catalyst for catalytic hydrogenation of chlorofluorocarbon (CFC).

As activated carbon used as a carrier in the preparation of the Pd / C catalyst according to the present invention, activated carbon used as a carrier in the production of a conventional Pd / C catalyst, for example, activated carbon (Darco G-60) from Aldrich Co. Commercially available activated carbon, such as activated carbon (32-60 mesh) for catalyst carriers from Kuraray Chemical, can be used.

According to the invention, Activated carbon is first alkali treated. Alkali treatment is repeated 2 to 5 times for 1 to 5 hours at a temperature of 60 to 80 ℃ using an aqueous NaOH solution of 0.2 to 1 molar concentration.

Alkali treated activated carbon is then acid treated. The acid treatment is repeated 2 to 5 times for 1 to 15 hours at a temperature of 50 to 80 ° C using a hydrofluoric acid solution at a concentration of 5 to 50%.

In the method for producing a Pd / C catalyst according to the present invention, activated carbon treated with an aqueous NaOH solution may be further treated with hydrochloric acid before acid treatment with a hydrofluoric acid solution. The activated carbon acid treated with hydrofluoric acid may be further treated with hydrochloric acid before supporting palladium.

The hydrochloric acid treatment performed before and after the acid treatment may be repeated 2 to 5 times for 1 to 15 hours at a temperature of 50 to 80 ° C. using a hydrochloric acid solution at a concentration of 5 to 37%.

In the method for producing a Pd / C catalyst according to the present invention, activated carbon may be subjected to alkali treatment with NaOH aqueous solution, followed by acid treatment with HF solution and further treatment with HCl aqueous solution before and after HF treatment.

Physical properties data for the alkali treated and acid treated activated carbons according to the present invention are shown in the respective comparative examples and examples.

The activated carbon treated with alkali and acid treatment in this way is supported with Pd by a conventional adsorption precipitation method or impregnation method.

The Pd / C catalyst prepared according to the present invention increases the selectivity of dehydrochlorination rather than dehydrofluorination in the hydrogenation reaction of chlorofluorocarbons with dehalogen, thereby selectively preparing hydrofluorocarbons. Is a preferred catalyst. Thus, using the Pd / C catalyst prepared according to the present invention, HFC-32 can be prepared with high selectivity from CFC-12.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are intended to compare and illustrate the invention, but not to limit the invention. In the following examples, the catalyst and the comparative catalyst of the present invention were prepared according to the pretreatment method and the catalyst supporting method of the activated carbon carrier, and the properties of the catalyst were investigated by measuring the BET surface area, impurity analysis, XRD, etc. . In addition, changes in the carrier structure and / or change in the impurity content were measured to investigate the effect of impurities on the catalytic activity.

Comparative Example 1

Pd / DC Catalyst Manufacturing

Pd / C catalysts were prepared by adsorption precipitation using Aldrich's activated carbon (denoted by Darco G-60, hereinafter DC) as a carrier, which was not treated with alkali and acid.

20 g of unpretreated activated carbon was added to 260 ml of 0.087N HCl aqueous solution in which 0.6803 g of PdCl ₂ was dissolved at about 40 ° C. Precipitated and adsorbed by neutralizing with 0.1 mol ammonium bicarbonate (NH ₄ HCO ₃ ) solution until pH 7. While strongly stirring the aqueous solution of the precipitated Pd / C catalyst, the water was evaporated under reduced pressure at about 70 to 80 ° C., and dried at 110 ° C. for 12 hours to prepare a Pd / DC catalyst having 2% by weight of Pd. .

The results of Mg, Ca and Fe analysis of activated carbon before catalyst preparation were 37, 29 and 15 ppm, respectively, and there was no change to 35, 26 and 15 ppm after catalyst preparation. The specific surface area was also 1100 ㎡ / g and 1050 ㎡ / g did not change significantly.

Comparative Example 2

Pd / DC (-NHO ₃ ) Manufacturing-HNO ₃ DC preprocessed with

After treating DC (activated carbon from Aldrich, Darco G-60) with nitric acid, a catalyst was prepared as in Comparative Example 1.

50 g of DC was placed in 500 ml of 50% HNO ₃ aqueous solution in a 1 L container, and maintained at 65 to 75 ° C., and stirred for 12 hours. After filtering the aqueous HNO ₃ solution, washing and filtration were repeated several times using 5 L of distilled water. The pretreated activated carbon was dried at 110 ° C. for 24 hours to prepare a DC (-NHO ₃ ) carrier.

The Mg, Ca, Fe, Al, K and Si contents were 37, 29, 15, 43, 2.9 ppm and 1.4% before HNO ₃ treatment and 17, 9.8, 9, 30, 2.5 ppm and 1.21% after treatment. Lowered. Activated charcoal was pulverized upon HNO ₃ treatment, and after drying, the surface area was measured to be significantly reduced to 65 to 95 m 2 / g.

Pd was precipitated and adsorbed and supported in the same manner as in Comparative Example 1 to prepare a Pd / DC (-HNO ₃ ) catalyst. There was no difference in the content of metal components before and after Pd loading.

Comparative Example 3

Pd / KC Catalyst Preparation

A catalyst was prepared in the same manner as in Comparative Example 1 except that Kuraray Chemical's activated carbon (32 to 60 mesh, hereinafter referred to as KC) which was not treated with alkali and acid was used as a carrier.

Before preparation of the catalyst, the specific surface area of KC activated carbon was 990 m 2 / g, and the Mg, Ca, Fe, Al, K, Si analysis results of activated carbon were 3, 12, 2, 2.6, 14, 73 ppm, respectively. More relatively, the impurity metal component content was low. In addition, there was no change in the metal component content before and after Pd loading.

Comparative Example 4

Pd / KC (-HNO ₃ ) Manufacture -HNO ₃ Use pretreated KC

KC (32 to 60 mesh of activated carbon from Kuraray Chemical) was treated with nitric acid as in Comparative Example 2, and then a Pd / C catalyst was prepared.

After HNO ₃ pretreatment, the amounts of Mg, Ca and Fe contained in activated carbon were 3, 8, and 2 ppm, respectively, which were not significantly different after pretreatment. As in the preparation of DC (-HNO ₃ ) of Comparative Example 2, activated carbon was pulverized and the specific surface area was greatly reduced to 100 m 2 / g or less.

Pd was precipitated and adsorbed and supported in the same manner as in Comparative Example 1 to prepare a Pd / KC (-HNO ₃ ) catalyst.

Comparative Example 5

Manufacture of Pd / KC (-HF)-using HF pretreated KC

After KC was treated with HF, Pd / C catalysts were prepared.

50 g of KC activated carbon was added to 500 ml of 50% HF aqueous solution, and maintained at 30 to 40 ° C. for 12 hours. The aqueous HF solution was discarded, washed and filtered with 5 L of distilled water, and dried at 110 ° C. for 24 hours to prepare a KC (-HF) carrier.

Before and after treatment with HF, the contents of impurity metals Mg and Ca decreased from 2.7 ppm to 1.2 ppm and 12 ppm to 8.0 ppm, respectively, Fe was unchanged to 2 ppm, and the Si content was almost zero. Activated charcoal was partially crushed during HF treatment, but the specific surface area decreased slightly before and after treatment to 990 m 2 / g and 930 m 2 / g, and SEM showed no difference in surface structure.

As in Comparative Example 1, Pd was precipitated and adsorbed to prepare a Pd / KC (-HF) catalyst.

Comparative Example 6

Manufacture of Pd / KC (-NaOH)-using NaOH pretreated KC

150 g of KC activated carbon was added to 2 L of a 0.5 molar NaOH aqueous solution in a 3 L container and stirred for 2 hours while maintaining 65 to 75 ° C. The remaining NaOH aqueous solution was discarded and the above procedure was repeated three times. Alkaline treated activated carbon was washed several times with 5 L of distilled water, filtered and then dried at 110 ° C. for 24 hours to prepare a KC (-NaOH) carrier.

Changes in the contents of impurity metals with NaOH treatment decreased from 3 ppm to 2.7 ppm in Mg, from 73 ppm to 11 ppm in Si, and from 14 ppm to 5.6 ppm in K and 12 ppm in Ca and Fe. And no change to 2 ppm. The specific surface area slightly increased from 990 m 2 / g to 1090 m 2 / g, but there was no surface change.

In the catalyst supporting method, Pd / KC (-NaOH) catalyst was prepared using Pd precipitation adsorption supporting method as in Comparative Example 1.

Comparative Example 7

Preparation of Pd / KC (-NaOH-HCl)-using KOH pretreated with NaOH and HCl

In Comparative Example 6, KC (-NaOH) treated with NaOH was treated again with HCl, and Pd was supported to prepare a Pd / C catalyst.

50 g of alkali-treated activated carbon was added to 500 ml of 37% HCl aqueous solution, and the mixture was stirred for 12 hours while maintaining 65 to 75 ° C. Aqueous solution of HCl was discarded and washed with 5 L of distilled water and filtered, and then dried at 110 ° C. for 24 hours to prepare KC (-NaOH-HCl) carrier.

After NaOH and HCl treatment, the contents of impurity metals Mg and Ca were reduced from 2.7 ppm to 2 ppm and from 12 ppm to 7.8 ppm, respectively. Some of the activated carbon was crushed but the specific surface area decreased slightly to 1090 m 2 / g and 950 m 2 / g before and after HCl reprocessing.

As in Comparative Example 1, Pd was precipitated and adsorbed to prepare a Pd / KC (-NaOH-HCl) catalyst.

Example 1

Manufacture of Pd / KC (-NaOH-HF)-using NaOH and HF pretreated KC

In Comparative Example 6, KC (-NaOH) treated with NaOH was treated again with HF, and then Pd was supported to prepare a Pd / C catalyst.

50 g of alkali-treated activated carbon was placed in 500 ml of 50% HF aqueous solution, and stirred for 12 hours while maintaining at 30 to 40 ° C. The aqueous HF solution was discarded, washed and filtered with 5 L of distilled water, and dried at 110 ° C. for 24 hours to prepare a KC (-NaOH-HF) carrier.

After NaOH and HF treatment, the contents of impurity metals Mg and Ca were reduced from 2.7 ppm to 0.62 ppm and 12 ppm to 2.9 ppm, respectively. During pretreatment, some of the activated carbon was crushed and the specific surface area was slightly reduced to 1090 m 2 / g and 900 m 2 / g before and after HF retreatment.

As in Comparative Example 1, Pd was precipitated and adsorbed to prepare a Pd / KC (-NaOH-HF) catalyst.

Example 2

Preparation of Pd / KC (-NaOH-HF-HCl)-Using NaOH / HF / HCl pretreated KC

In Example 1, KC (-NaOH-HF) treated with NaOH and HF was retreated with HCl, and Pd was supported to prepare a Pd / C catalyst.

Alkali and strong acid (HF) treated activated carbon was treated with aqueous HCl solution as in Comparative Example 7 to prepare KC (-NaOH-HF-HCl). Pd was precipitated and supported on the pretreated carrier as in Comparative Example 1 to prepare a Pd / KC (-NaOH-HF-HCl) catalyst. There was little change in the content of impurity metals and specific surface area before and after HCl retreatment.

Example 3

Preparation of Pd / KC (-NaOH-HCl-HF)-Using NaOH-HCl-HF pretreated KC

In Comparative Example 7, KC (-NaOH-HCl) treated with NaOH and HCl was retreated with HF, and Pd was supported to prepare a Pd / C catalyst.

Activated carbon treated with alkali and strong acid (HCl) was treated with aqueous HF solution as in Example 1 to prepare KC (-NaOH-HCl-HF). Pd was precipitated and supported on the pretreated carrier as in Comparative Example 1 to prepare a Pd / KC (-NaOH-HCl-HF) catalyst. After HF retreatment, the contents of impurity metals Mg and Ca were slightly decreased below 1 ppm and 2 ppm and there was little change in specific surface area.

Example 4

Preparation of Pd / KC (-NaOH-HCl-HF) -I-Using NaOH-HCl-HF pretreated KC

After preparing the carrier in the same manner as in Example 3, a conventional impregnation method (a method of adding an aqueous solution of PdCl ₂ to the carrier, followed by evaporation under reduced pressure and drying) was used without using the precipitation adsorption method as a Pd supporting method. . After impregnating and supporting Pd, it was dried at 110 ° C for 12 hours to prepare a Pd / KC (-NaOH-HCl-HF) -I catalyst having 2% by weight of Pd.

The specific surface area of the carrier and catalyst was measured using a surface measuring instrument (Germini 2375, Version 4.01). The pretreatment of activated carbon with strong nitric acid (50% or more) was found to cause pulverization of activated carbon and a sharp decrease in surface area. However, the use of 35% HCl or 50% aqueous HF solution resulted in very little pulverization of activated carbon. Although the surface area of activated carbon was very large (1000 m 2 / g) and the measurement error was relatively ± 50 m 2 / g, it was difficult to accurately determine the change of specific surface area, but the surface area reduction was small in HCl and HF treatment. In addition, the pore structure change of activated carbon during NaOH treatment and HCl and HF pretreatment is not significant. Metal content in activated carbon was not significantly changed during alkali treatment, but it was confirmed that Mg, Ca, Fe, etc. were significantly reduced when treated with strong acid (HNO ₃ , HF). In particular, it was confirmed that the use of HF can remove the impurity metal components including Si more efficiently than when using HCl or HNO ₃ .

Reaction Experiment 1

Basic Experiment of Hydrogenation of CFC-12

The hydrogenation reaction was carried out using catalysts prepared by various catalyst preparation methods. The reaction experiments used a typical fixed bed catalytic reactor made of Inconel-600 tubes of 1/2 inch (internal diameter 0.99 mm) and 30 cm in length. 0.5 g of catalyst was placed in a reactor, nitrogen gas containing 20% hydrogen was introduced at a flow rate of 40 cc / min, and the Pd / C catalyst was reduced for 300 hours at 300 ° C. to be suitable for hydrogenation. The flow rates of CFC-12, hydrogen, and nitrogen as diluent are supplied at 10, 4, and 6 cc / min using mass flow controller, respectively. Hydrogenation reaction was carried out. HF and HCl produced as by-products in the reaction product were neutralized by passing NaOH aqueous solution trap, and the reaction product was analyzed after removing trace amount of water through a dryer filled with silica gel. On-line analysis was carried out using gas chromatography (HP-5890 series II Plus) with capillary (Poraplot Q from Chrompack) and GC / MS (GC: HP-5890, with the same column attached). The component was confirmed using MS searcher: 5971A).

After 40 hours of reaction, the activity of the catalyst was compared by comparing the conversion of CFC-12 with the selectivity of the main components. The reaction conversion and distribution of products (except CFC-12) for different catalysts are shown in Table 1.

As shown in Table 1, it can be seen that the trace impurity metal affects the reaction, but even when the metal content is similar, the selectivity of HFC-32, which is a dehydrogenated substance, in the product is different. That is, it was determined that the properties of the catalyst surface were changed according to the pretreatment method and the order as well as the content of the minor component, which influenced the reaction activity.

Comparative Example % Conversion Product distribution (%) except CFC-12 HFC-32 CH ₄ C ₂ H ₆ Etc Comparative Example 1 3.2 38.9 21.6 12.2 27.3 Comparative Example 2 4.2 55.5 28.7 8.0 7.8 Comparative Example 3 7.4 42.2 22.3 13.4 22.1 Comparative Example 4 8.6 56.3 26.5 11.2 6.0 Comparative Example 5 16.6 59.0 18.4 9.6 13.0 Comparative Example 6 7.7 20.5 43.3 17.6 18.6 Comparative Example 7 15. 19.4 47.1 20.5 13.0 Example 1 18.7 68.5 15.2 3.0 13.3 Example 2 17.8 66.8 14.7 7.4 11.1 Example 3 20.4 72.2 12.4 6.8 8.6 Example 4 19.8 71.8 12.7 6.9 8.6

Reaction experiment 2

Active comparison experiment

Pd / KC (-HF), Pd / KC (-NaOH-HF), Pd / KC (-NaOH-HF-HCl), Pd / KC (-NaOH-HCl) -HF), Pd / KC (-NaOH-HCl-HF) -I catalyst inactivation was compared. The reaction conversion and the distribution of products (except CFC-12) after 200 hours under the experimental conditions of Reaction Experiment 1 are shown in Table 2. When Pd / KC (-NaOH-HF-HCl) catalyst was used, the reaction conversion was reduced by about 35% and Pd / KC (-HF) catalyst was decreased by 13%, but Pd / KC (-NaOH-HF), Pd For / KC (-NaOH-HCl-HF) and Pd / KC (-NaOH-HCl-HF) -I catalysts, there was little change in activity, with the decrease in reaction activity within about 5%.

When activated carbon, which is a carrier, is treated with alkali (NaOH) and acid (HCl, HF), the final treatment with HF effectively promotes deactivation of the catalyst by generating HF by complete dehalogenation, which is one of the problems in dehalogenation hydrogenation. It was found that it can be suppressed.

Catalyst preparation method After 40 hours reaction After 200 hours reaction Reaction Conversion Rate (%) HFC-32 Composition (%) Reaction Conversion Rate (%) HFC-32 Composition (%) Comparative Example 5 16.6 59.0 14.5 61.2 Example 1 18.7 68.5 17.6 69.8 Example 2 7.8 66.8 11.7 67.0 Example 3 20.4 72.2 19.6 73.5 Example 4 19.8 71.8 19.4 69.8

The higher selectivity of HFC-32, the main product in the hydrogenation of CFC-12, suppresses the production of hydrocarbons such as methane and ethane, and reduces the production of hydrofluoric acid (HF) produced as a byproduct of the reaction. Accordingly, the sintering of the Pd catalyst by hydrofluoric acid and the deactivation of the catalyst may be reduced. The carrier can also be pretreated with hydrofluoric acid to inhibit inactivation.

Therefore, according to the present invention, pretreatment of activated carbon by the treatment method of alkali (NaOH aqueous solution) and strong acid (fluoric acid or hydrochloric acid and hydrofluoric acid) and using this to prepare a 'palladium supported activated carbon catalyst' (Pd / C catalyst) to produce CFC-12 When used in the hydrogenation of chlorofluorocarbons (CFC) such as can significantly increase the selectivity of dehydrochlorination products such as HFC-32, it is possible to suppress the deactivation of the catalyst due to the sintering of the Pd catalyst.

Claims (7)

Alkaline treatment of activated carbon (C) with an aqueous solution of sodium hydroxide and acid treatment of the alkali-treated activated carbon (C) with a hydrofluoric acid (HF) solution include palladium (Pd) supported on activated carbon (C) from which impurities are removed. Pd / C catalyst for catalytic hydrogenation reaction of chlorofluorocarbon (CFC). The Pd / C catalyst according to claim 1, wherein the activated carbon is further treated with a hydrochloric acid solution before or after the acid treatment. (a) alkali treating activated carbon (C) with an aqueous sodium hydroxide solution; (b) acid treating the alkali treated activated carbon (C) with a hydrofluoric acid (HF) solution; And (c) supporting palladium (Pd) on the acid treated activated carbon; A method for producing a Pd / C catalyst for catalytic hydrogenation of chlorofluorocarbon (CFC) comprising a. 4. The method of claim 3, further comprising treating the alkali treated activated carbon with a hydrochloric acid solution before treating with hydrofluoric acid solution. The method of claim 3, further comprising treating the activated carbon treated with the hydrofluoric acid solution with a hydrochloric acid solution before supporting palladium. The method according to any one of claims 3 to 5, wherein the palladium is supported on the treated activated carbon by precipitation adsorption or impregnation. A method for producing hydrogen fluoride hydrocarbon (HFC) by catalytic hydrogenation of chlorofluorocarbon (CFC), comprising using the catalyst according to claim 1.