KR20180068590A - Method for Disposing HFCs by Decomposition - Google Patents

Abstract

Provided is a method for decomposing and treating hydrofluorocarbons (HFCs), which catalytically pyrolyzes HFCs using a decomposition catalyst including Al_2O_3 with specific surface area of 200-300 m^2/g, average pore size of 3-10 nm, and pore volume of 0.8-1.5 cm^3/g.

Description

Method for Disposing HFCs by Decomposition

The present invention relates to a method for decomposing and treating HFCs which are non-CO ₂ greenhouse gases.

Chlorofluorocarbons (CFCs) and Hydro-Chlorofluorocarbons (HCFCs) are harmless and stable substances in the human body. They are widely used in various fields such as refrigerants, injecting agents and foaming agents. , The production and use of which was regulated by the Montreal Protocol, which was signed in May 1992.

Hydrofluorocarbons (HFCs) and perfluorinated compounds (PFCs) have been developed as substitutes for the CFCs and HCFCs. However, these substances are known to have a greater impact on climate change because the Global Warming Potential (GWP) is as high as 1,430 and 7,390 times that of CO ₂ , respectively. In order to regulate the greenhouse gases for the refrigerant, the Korean government has adopted the "Law on the Circulation of Resources of Electricity, Electronics, and Automobiles", Article 25 of the Law, "" The waste gas processor is the gas that contains the substances that cause changes in the climate ecosystem. Recycled, or disposed of safely ".

At present, consumption of domestic HFCs is steadily increasing every year. Among the HFCs, the refrigerants used in electric appliances and automobiles are present in a small amount of less than 1 kg, and HFC-134a (1,1,1,2-Tetrafluoroethane, CH2FCF3, hereinafter referred to as HFC-134a) is used most frequently. HFCs are emitted in the form of a small amount of point sources after use of the product. In the case of waste household appliances and scrap cars, where waste HFCs are the most discharged, HFCs are finally disposed of through recovery, storage, and transportation processes, so transportation costs for treatment are high.

In addition, high energy (temperature) is required for the decomposition of HFCs that are physically and chemically stable, and at the same time, there is a problem in operating the HFCs treatment process due to the corrosion of the device due to HF generated in the process.

Therefore, it is urgent to develop HFCs processing technology with high application efficiency and high processing efficiency.

Korean Patent Publication No. 10-2002-0000152

Disclosure of Invention Technical Problem [8] The present invention has been made to overcome the above-mentioned disadvantages of the prior art, and it is an object of the present invention to provide a decomposition treatment method of HFCs which is a non-CO ₂ greenhouse gas excellent in treatment efficiency and field application.

The present invention, in order to achieve the above object,

Catalytic cracking of HFCs is carried out using a cracking catalyst comprising Al ₂ O ₃ having a specific surface area of 200 to 300 m ² / g, an average pore size of 3 to 10 nm and a pore volume of 0.8 to 1.5 cm ³ / g Wherein the HFC decomposition treatment method comprises the steps of:

In addition,

Using a decomposition catalyst comprising Al ₂ O ₃ having a specific surface area of 200 to 300 m ² / g, an average pore size of 3 to 10 nm and a pore volume of 0.8 to 1.5 cm ³ / g, And catalytic cracking the HFCs while supplying water vapor.

In addition,

Using a decomposition catalyst comprising Al ₂ O ₃ having a specific surface area of 200 to 300 m ² / g, an average pore size of 3 to 10 nm and a pore volume of 0.8 to 1.5 cm ³ / g, And catalytic cracking the HFCs at 550 to 650 ° C. while supplying water vapor.

The method for decomposing HFCs according to the present invention provides excellent decomposition efficiency of HFCs by employing effective decomposition catalysts and effective reaction conditions for the decomposition catalysts.

In addition, since the method for decomposing HFCs according to the present invention can be applied to a small-scale decomposition apparatus that can be applied in the field, it is possible to effectively treat HFCs that are non-CO ₂ greenhouse gases.

FIG. 1 and FIG. 2 are diagrams schematically showing an example of a HFCs thermal catalytic cracking apparatus used in the HFCs decomposition treatment method of the present invention.
FIG. 3 is a graph showing decomposition rates of HFC-134a according to pyrolysis or catalytic pyrolysis of HFC-134a at 300 to 600 ° C.
FIG. 4 is a graph showing XRD measurement results of catalysts obtained after HFC-134a decomposition at various temperatures. FIG.
FIG. 5 is a graph showing the peak areas of CO ₂ and trifluoroethylene (C ₂ HF ₃ ) for each catalyst and reaction temperature, which are released into gas byproducts by decomposition of HFC-134a.
FIG. 6 is a graph showing the reaction efficiency of pyrolysis of HFC-134a continuous catalyst according to reaction temperature measured using a g-Al ₂ O ₃ -B catalyst.
FIG. 7 is a graph showing changes in the trifluoroethylene and CO ₂ formed as the reaction time elapses in the pyrolysis reaction of HFC-134a nitrate according to the reaction temperature. FIG.
8 is a graph showing the results of XRD analysis of the catalyst after reacting HFC-134a with g-Al ₂ O ₃ -B catalyst for 24 hours.
9 is a graph showing the decomposition rate according to the HFC-134a injection concentration.
10 is a photograph showing the corrosion state of the reactor according to the composition of the injection gas.
11 is a graph showing the decomposition rate of HFC-134a according to hydrolysis reaction time by steam supply.
12 is a graph showing the XRD analysis results of the catalyst recovered after 24 hours hydrolysis reaction by steam supply.
13 is a graph showing the change of HFC-134a decomposition rate by the space velocity per unit mass of catalyst (WHSV) on g-Al ₂ O ₃ .
FIG. 14 is a SEM image of the specific surface and structural changes before and after catalytic pyrolysis and hydrolysis reaction by steam supply.

The present invention relates to the use of a cracking catalyst comprising Al ₂ O ₃ having a specific surface area of 200 to 300 m ² / g, an average pore size of 3 to 10 nm and a pore volume of 0.8 to 1.5 cm ³ / g, Catalytic cracking of the HFCs.

The decomposition catalyst has a larger specific surface area and a larger pore volume and a smaller average pore size, thereby providing a superior decomposition effect. Therefore, it provides a decomposition effect of excellent HFCs within the range described above. The Al ₂ O ₃ may be? -Al ₂ O ₃ .

The HFCs are alkanes (CnH ₂ n ₊₂₎ means a haloalkane (Haloalkanes) compound substituted with a part of the hydrogen fluoride, specifically, HFCs is HFC-23, HFC-32, HFC-125, and HFC-134a, HFC -152a, HFC-143a, HFC-227ea, HFC-236fa, HFC-245ca, or a mixed refrigerant containing one or more of the above components.

HFCs have the following physical and chemical properties

ingredient The Molecular Weight
(g / mol) Melting point
() Boiling point
() Vapor pressure
(Bar at 20) nature
Decay time
(Years) Warming Index
(Based on 100 years) HFC-23 CHF ₃ 70 -155 -82.2 41.6 270 11,700 HFC-32 CH ₂ F ₂ 52 -136 -52 13.8 5.6 650 HFC-125 C ₂ HF ₅ 120 -103 -48.5 12.1 32.6 2,800 HFC-134a CH ₂ FCF ₃ 102 -101 -26 5.7 14.6 1,300 HFC-152a C ₂ H ₄ F ₂ 67 -117 -25 5.1 1.5 140 HFC-143a C ₂ H ₃ F ₃ 84 -111 -47.6 11.1 48.3 3,800 HFC-227ea C ₃ HF ₇ 170 -131 -16.4 4 36.5 2,900 HFC-236fa C ₃ H ₂ F ₆ 151 -94.2 -1.1 2.5 (25) 209 6,300 HFC-245ca C ₃ H ₃ F ₅ 134 -73.4 25 6.6 560

Examples of the HFCs mixed refrigerant include those listed in Table 4 below.

In the present invention, catalytic pyrolysis of HFCs is preferably carried out at 300 to 650 ° C, more preferably at 550 to 650 ° C. When the decomposition is carried out at the temperature of 550 to 650 ° C., the effect that the 100% decomposition duration of HFCs is remarkably lengthened can be obtained.

In the present invention, the catalytic cracking of HFCs is preferably carried out by filling the column with a catalyst so that the space velocity (WHSV) per mass of the catalyst unit is 500 to 700 mL / g _cat · h. This is because the more the use of the catalyst, the higher the decomposition efficiency of HFCs.

The present invention also uses a decomposition catalyst comprising Al ₂ O ₃ having a specific surface area of 200 to 300 m ² / g, an average pore size of 3 to 10 nm and a pore volume of 0.8 to 1.5 cm ³ / g And catalytic cracking the HFCs while supplying water vapor in an inert gas atmosphere.

The decomposition catalyst has a larger specific surface area and a larger pore volume and a smaller average pore size, thereby providing a superior decomposition effect. Therefore, it provides a decomposition effect of excellent HFCs within the range described above. The Al ₂ O ₃ may be? -Al ₂ O ₃ .

The HFCs are alkanes (CnH ₂ n ₊₂₎ means a haloalkane (Haloalkanes) compound substituted with a part of the hydrogen fluoride, specifically, HFCs is HFC-23, HFC-32, HFC-125, and HFC-134a, HFC -152a, HFC-143a, HFC-227ea, HFC-236fa, HFC-245ca, or a mixed refrigerant containing one or more of the above components.

The physical and chemical properties of the HFCs and examples of the HFCs mixed refrigerant can be found in Table 1 and Table 2.

In the present invention, the catalytic pyrolysis of HFCs is preferably performed in a state in which oxygen is not supplied. When the oxygen is supplied, the flow rate of the reaction gas is not kept constant during the addition of oxygen, and the amount of gas collected in the sampling bag for 20 minutes after the reaction is significantly decreased as compared with the catalytic pyrolysis condition. In particular, A problem arises in that a considerable amount of solid by-product is formed, which is not preferable.

It is preferable that the HFCs and the water vapor are supplied at a volume ratio of 2: 3 to 2: 4 in view of decomposition efficiency of HFCs.

In the present invention, catalytic pyrolysis of HFCs is preferably carried out at 300 to 650 ° C, more preferably at 550 to 650 ° C. When the decomposition is carried out at the temperature of 550 to 650 ° C., the effect that the 100% decomposition duration of HFCs is remarkably lengthened can be obtained.

The present invention also uses a decomposition catalyst comprising Al ₂ O ₃ having a specific surface area of 200 to 300 m ² / g, an average pore size of 3 to 10 nm and a pore volume of 0.8 to 1.5 cm ³ / g And catalytically cracking the HFCs at 550 to 650 ° C while supplying water vapor in an inert gas atmosphere.

The contents of the decomposition catalyst and steam in the above are the same as those described above.

In this case, it is preferable that the catalyst is pyrolyzed in the catalyst so that the space velocity (WHSV) per unit mass of the catalyst is 500 to 700 mL / g _cat · h. This is because the more the use of the catalyst, the higher the decomposition efficiency of HFCs.

The method for decomposing HFCs according to the present invention is suitable for downsizing a processing apparatus which can implement the method because the processing method is simple. In addition, it is possible to provide excellent decomposition efficiency even in an apparatus that is excellent in decomposition efficiency and is miniaturized.

Therefore, the method of decomposing HFCs of the present invention makes it possible to provide a small-scale catalytic cracking apparatus that can be applied in the field, thereby contributing to the effective reduction of HFCs which are non-CO ₂ greenhouse gases.

The method for decomposing HFCs of the present invention can be specifically carried out by a decomposition apparatus as shown in Fig.

That is, the apparatus 100 for decomposing HFCs used in the present invention includes a reaction gas supply unit 10, a reaction unit 20, and a decomposition gas discharge unit 30,

The reaction gas supply unit 10 includes an HFCs supply unit 11; An inert gas supply unit (12); And a reaction gas injection tube 13 connecting the reaction gas supply unit 10 and the reaction unit 20 and injecting the reaction gas into the reaction unit,

The reaction part 20 comprises a catalyst filling column 21 and a heater 22 surrounding the catalyst filling column,

The decomposition gas discharge unit 30 includes a decomposition gas discharge pipe 31,

The reaction gas injection tube 13 is connected to one end of the catalyst filling column 21 and the decomposition gas discharge pipe 31 is connected to the other end,

The catalyst loading column 21 is provided with a decomposition catalyst containing Al ₂ O ₃ having a specific surface area of 200 to 300 m ² / g, a pore size of 3 to 10 nm and a pore volume of 0.8 to 1.5 cm ³ / g Can be filled.

The reaction gas supply unit 10 may further include a flow rate regulator 15 for regulating the flow rate of each reaction gas.

The decomposition gas discharge unit 30 may further include an decomposed gas collection unit 32 and a decomposed gas neutralization unit 33 connected to the decomposed gas discharge pipe 31.

The decomposed gas collector 32 is collected by using, for example, a gas sampling bag so as to collect and analyze the decomposed gas, and is collected by a gas chromatography / mass spectrometer (GC / MS, 7890A / 5975C inert, Agilent Technologies) to analyze the cracked gas.

The neutralization unit 33 neutralizes the acidic substance (HF) using an acidic neutralization trap and discharges the exhaust gas through the fume hood. The neutralization trap may comprise, for example, a NaOH solution.

The heater 22 in the reaction part 20 is not particularly limited and any known in the art may be used without limitation. For example, an electric furnace type circular heater can be used.

The catalyst filling column 21 may be configured such that glass wool 24 is filled at both ends of a metal tubular column and the decomposition catalyst 23 is filled between the glass wool columns.

As the metal tubular column used as the catalyst filling column, for example, a SUS tube having a diameter of 1/2 inch and a length of 75 cm may be used, and SUS-316L may be used in consideration of corrosion resistance and high temperature application possibility .

The catalyst charging column 21 may have a structure in which a reaction gas injection tube 13 is connected to the lower end portion and an exhaust gas discharge pipe 31 is connected to the upper end portion.

The reaction gas supply unit 10 may further include a water vapor supply unit 14 as shown in FIG. In this case, HFCs can be decomposed while feeding nitrogen gas and steam together with HFCs to the catalyst-charged column.

The water vapor supply unit 14 can supply water vapor to the reactor using, for example, a syringe pump (kd Scientific Co.).

 The apparatus for decomposing HFCs used in the present invention is not limited to the apparatus exemplified above, and the apparatus for decomposing HFCs known in the art can be used without limitation. Therefore, components not known in the structure of the HFCs decompositionally treating apparatus exemplified above can be employed without limitation in known components of the field.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples.

Example  1: Evaluation of physical properties of catalyst

Na ₂ CO ₃ , CaO, CaCO ₃ , g-Al ₂ O ₃ -A, and g-Al ₂ O ₃ -B were selected as catalysts to compare the decomposition rates of HFC-134a (Pure Mann). A BET measuring device (3Flex, Micromeritics Instrument Co.) was used to measure the specific surface area, pore size and pore volume of the selected catalyst, and the results are shown in Table 3 below. All of the catalysts used for ensuring consistency and stability in the actual reaction experiments were separated and sorted using catalysts having a particle size of 1.7 mm or less through sieving. The catalysts were calcined at 750 ° C. for 3 hours and dried at 105 ° C. for 4 hours And then stored in a desiccator.

catalyst Specific  표면 area (m ² / g) Pore  size (nm) Pore  volume (cm ³ / g) Na ₂ CO ₃ N.D. . N.D. . N.D. . CaO 5.4 20 0.035 CaCO ₃ 2.6 37 0.021 g- Al ₂ O ₃ -A 154.5 13 0.554 g- Al ₂ O ₃ -B 255.0 5 1.14 N.D. . : Note Detectable

X-ray diffraction (XRD, Ultima IV) was used to confirm the crystallization state of the catalyst before and after the HFC-134a decomposition reaction. At this time, the current and voltage required for operating the X-ray diffractometer were set at 40 mA and 40 kV, and the XRD measurement rate was measured in the range of 5 to 80 ^° (2-Theta) at 4 degree ^o / min. In order to observe the changes in specific surface area and surface state before and after the reaction, additional BET and scanning electron microscope (SEM) analyzes were performed on the catalyst recovered after the reaction.

Example  2: Structure of HFC-134a decomposition reaction system

A self-made tubular flow reactor was used for HFC-134a decomposition and a schematic diagram of the system is shown in FIG. The reaction system includes a reaction gas supply unit 10, a reaction unit 20, and a decomposition gas discharge unit 30, and the reaction gas supply unit 10 includes an HFCs supply unit 11; An inert gas supply unit (12); And a reaction gas inlet pipe 13 connecting the water vapor supply unit 14 and the reaction gas supply unit 10 to the reaction unit 20 and injecting the reaction gas into the reaction unit, And a heater 22 surrounding the charging column 21. The decomposed gas discharging unit 30 includes a decomposition gas discharge pipe 31 and the catalyst charging column 21 The reaction gas inlet tube 13 is connected to one end of the reaction gas supply pipe 10 and the decomposition gas discharge pipe 31 is connected to the other end of the reaction gas supply pipe 10, The decomposition gas discharge unit 30 is provided with the decomposition gas collection unit 32 connected to the decomposition gas discharge pipe 31 and the decomposition gas neutralization unit 33.

The decomposition gas neutralization part was composed of a neutralization trap (NaOH solution, 0.2N, 200 ml). The supply pressure of the reaction gas was fixed to 345 kPa through a regulator connected to the gas container. The flow rate of the supplied reaction gas to the reactor was controlled by a mass control device (mass controller, fow controller, MFC) . The water vapor was supplied to the reactor using a syringe pump (kdScientific Co.) and the total gas supply flow rate to the reactor was fixed at 50 mL / min for all reactions.

The SUS-316L material was used for the reactor, in order to fill the catalyst, a SUS tube having a diameter of 1/2 inch and a length of 75 cm was used and the corrosion resistance and high temperature application possibility were considered. The heat applied to the reactor was an electric furnace type circular heater which surrounds the outside, and a K-type thermometer was used to measure the reactor temperature. Also, for smooth contact between the reaction gas and the catalyst, the reactor was arranged vertically and the reaction gas flowed from bottom to top.

In order to prevent the catalyst inside the reactor from escaping to the outside during the reaction, the position of the catalyst was fixed by using a glass wool on / under the catalyst. After the reaction, the exhaust gas (HFC-134a or product gas) was collected using a gas sampling bag for 20 minutes and analyzed by a gas chromatography / mass spectrometer (GC / MS, 7890A / 5975C inert, Agilent Technologies) Respectively. Except for the collection time, the exhaust gas generated from the process operation was neutralized with acid neutralization trap (HF) and discharged through the fume hood.

The GC / MS apparatus and analysis conditions used in this experiment are shown in Table 4 below. The MS peaks on the chromatogram obtained by the GC / MS analysis were compared with the mass spectra of NIST 8th library (National Institute of Standards and Technology, USA) and qualitative analysis was carried out. By comparing the areas obtained by integrating the MS peaks, The amount of gas by-products and the decomposition ratio of HFC-134a were calculated according to the reaction conditions.

GC  ( Agilent  7890A) Inlet 250 Column GS-GASPRO (60 m x 0.32 mm i.d.) Total flow Helium 2 mL / min Oven 50 20 / min 260 (5 min) Injection amount 100 MS transfer line 280 MS  ( Agilent  5975C inert ) Ion source 230 Quadrupole 150 Ionization current 70 eV Scan range 10 to 800 amu Scan speed 3.64 scans / sec

Example  3: Evaluation of catalyst performance through reaction

In order to find an excellent catalyst, 10 g ± 0.02 g of the target catalyst was loaded in the reactor, and the reactor was purged with N ₂ (40 mL / min) for 10 minutes to remove oxygen and impurities remaining in the system before the reaction, Lt; / RTI > When the temperature of the reactor rose to the set temperature (300, 400, 500, 600 ° C) and stabilized, the HFC-134a gas injection valve was opened and fed to the reactor at a constant volume flow rate (10 mL / min). At the same time as the reaction was started, a gas collection bag was attached to the final gas discharge portion to collect the generated gas for 20 minutes and perform GC / MS analysis. The amount of gas byproduct and the decomposition rate of HFC-134a were calculated according to each reaction condition.

FIG. 3 shows decomposition rates of HFC-134a according to pyrolysis or catalytic cracking reaction of HFC-134a at 300 to 600 ° C. The decomposition ratio of HFC-134a was calculated by the following equation (1).

[Equation 1]

AreaIN = peak area of HFC-134a MS before reaction

Area OUT = HFC-134a MS peak area after reaction

From the results of the non-catalytic pyrolysis from FIG. 3, it can be seen that HFC-134a is almost completely discharged without being decomposed in the temperature range of 300 to 600 ° C. applied in the present invention. This can be explained by the high thermal stability of HFC-134a.

When HFC-134a is decomposed on five catalysts (Na ₂ CO ₃ , CaO, CaCO ₃ , g-Al ₂ O ₃ -A and g-Al ₂ O ₃ -B) It can be seen that there are differences. In the case of Na ₂ CO ₃ , which had no pores of the catalyst and no specific surface area, HFC-134a was decomposed and its decomposition efficiency began to increase with increasing temperature. However, at 600 ° C, the decomposition rate of HFC-134a was only about 40.4% .

On the other hand, other catalysts except Na ₂ CO ₃ exhibited higher decomposition efficiency and g-Al ₂ O ₃ catalysts (BET: 154.5 ~ 255.0 m 2 / g) having a large specific surface area were CaO : 5.4 m 2 / g) and CaCO ₃ (BET: 2.6 m 2 / g). In particular, in the case of g-Al ₂ O ₃ -B catalyst having the largest specific surface area, 110% of HFC-134a was decomposed even at 400 ° C.

The results of the catalytic pyrolysis at 300 ° C of the present invention show that the specific surface area and the pore volume of the catalyst are large and the pore size is small, the efficiency of decomposition of HFC-134a is high (Table 3). However, at 400 and 500 ° C, CaO with a high specific surface area shows lower HFC-134a decomposition efficiency than CaCO ₃ . It is considered that the phase structure of CaO is changed at the reaction temperature and the activity of the catalyst is decreased.

FIG. 4 shows XRD measurement results of catalysts obtained after HFC-134a decomposition at various temperatures. The XRD pattern of CaO shows that the phase change from CaO to CaF2 is apparent at 400 ° C. However, in the case of CaCO ₃ , no phase change is observed. It is believed that the phase change of the CaO catalyst is due to the reaction between the HF formed by the dehydrofluorination of HFC-134a and the catalyst. On the other hand, the XRD results of CaO obtained after the decomposition reaction of HFC-134a at high reaction temperatures (500, 600 ° C) show that CaO is present together with CaF 2 unlike 400 ° C. Although the decomposition efficiency of HFC-134a is higher at high temperature, the formation of CaF2 is less than that of the catalyst obtained after 400 ° C reaction, which means that the decomposition reaction mechanism of HFC-134a on CaO catalyst is different according to the temperature.

Although the change in catalytic structure from CaO to CaF2 is mainly observed at 400 ° C, the overall XRD peak sensitivity of CaO decreases with increasing temperature, indicating that decomposition reaction of HFC-134a proceeds, This means that the structural change of the CaO catalyst gradually appears as the efficiency increases.

In the case of g-Al ₂ O ₃ (FIG. 4), as the reaction temperature increases, the reaction efficiency increases and the XRD pattern gradually changes from Al ₂ O ₃ to AlF ₃ . This change was confirmed to be a phase change from 500 ° C for g-Al ₂ O ₃ -A to 400 ° C for AlF ₃ in case of g-Al ₂ O ₃ -B. The temperature at which the phase change to AlF ₃ was observed agrees with the 100% decomposition temperature range of HFC-134a (FIG. 3). This phase change to AlF ₃ is believed to be due to the gas-solid direct reaction between HFC-134a and the catalyst (g-Al ₂ O ₃ ).

The degradation performance and the XRD pattern of the two g-Al ₂ O ₃ catalysts applied in this experiment show that g-Al ₂ O ₃ B has a wider specific surface area than g-Al ₂ O ₃ -A HFC-134a decomposition performance showing g-Al ₂ O ₃ structure a conformational change of the AlF ₃ is a specific surface area of the higher g-Al ₂ O ₃ -B are viewed as being less progress-Al ₂ O ₃ catalyst performance g and The relationship between the specific surface area and the specific surface area depends on the specific surface area of g-Al ₂ O _{3 that} can accept fluorine atoms in the gas-solid reaction.

In the present invention, CO ₂ and trifluoroethylene (C ₂ HF 3) were detected as a byproduct of the decomposition of HFC-134a, and the peak area of the compound for each catalyst and the reaction temperature was shown in FIG.

In the case of CaO and CaCO ₃ , the highest amount of trifluoroethylene was formed at 400 ° C.

On the other hand, in the case of g-Al ₂ O ₃ -B, the amount of trifluoroethylene was highest at 400 ° C in g-Al ₂ O ₃ -A at 300 ° C, but the amount of trifluoroethylene was relatively small and was not detected at 500 ° C or more . The amount of CO ₂ emission per catalyst (FIG. 5) increased in proportion to the reaction temperature. In this experiment, since oxygen was not injected into the reaction gas as an auxiliary gas, it can be concluded that CO ₂ obtained from the result is formed in the process of converting g-Al ₂ O ₃ into AlF ₃ .

Example  4: Evaluation of decomposition performance by continuous decomposition reaction of HFC-134a

The g-Al2O3-B catalyst was used for the decomposition reaction continuously for 24 hours, and the optimal conditions for decomposition of HFC-134a were derived. For this, the decomposition reaction and the effect of HFC-134a on the reaction temperature, the reactant (HFC-134a) concentration, the space velocity (catalytic amount) change and the addition of oxygen and water vapor were compared and analyzed. Table 5 shows the experimental conditions applied and the optimum condition was derived by applying the optimum conditions obtained in each step to the next step. The exhaust gas generated during the continuous reaction under each condition was collected using a gas collection bag for 20 minutes at intervals of 2 hours and the decomposition performance of HFC-134a was analyzed by GC / MS analysis.

step Step-by-step evaluation factors Evaluation condition One Evaluation of catalytic efficiency by temperature - Performance evaluation of HFC-134a according to 400, 500, 600 2 Performance evaluation according to reactant concentration - HFC-134a concentration: 5, 10, 20%
(Flow rate: 2.5, 5, 10 mL / min) 3 Performance evaluation by additional oxygen injection - Flow rate of HFC-134a fixed at 10 mL / min
- HFC-134a: nitrogen: oxygen volume ratio = 20: 50: 30 4 Due to additional water vapor injection
Performance evaluation - Flow rate of HFC-134a fixed at 10 mL / min
- 0.2 ml / h injection using a syringe pump
- HFC-134a: nitrogen: water vapor volume ratio = 20:50:30 5 Depending on the change of space velocity (catalyst amount)
Performance evaluation - Flow rate of HFC-134a fixed at 10 mL / min
- Change in catalytic quantity 5, 10, 15 g

Example  5: Derivation of optimum conditions for HFC-134a decomposition

5-1: HFC-134a by reaction temperature Continuous catalytic cracking  Comparison of reaction efficiency

FIG. 6 shows the results of measuring the pyrolysis efficiency of HFC-134a continuous catalyst according to the reaction temperature using the g-Al ₂ O ₃ -B catalyst selected through the previous experiment. As a result of catalytic cracking, the initial decomposition rate was 100% at all reaction temperatures, but the decomposition rate of HFC-134a gradually decreased with the reaction time.

Particularly, the lower the reaction temperature, the faster the degradation rate of HFC-134a is, and the higher the reaction temperature, the longer the decomposition rate of HFC-134a is maintained. The decomposition rate of HFC-134a was maintained at 100% until 6 hours in the case of 600 ° C catalytic cracking, unlike the case of 400 ° C at which the decomposition rate of HFC-134a rapidly decreased and gradually decreased at 500 ° C. .

The reduction of the decomposition rate according to the reaction time is due to the conversion of g-Al ₂ O ₃ into AlF ₃ by the gas-solid reaction between the reactant HFC-134a and the catalyst and the deactivation of the catalyst.

Although the decomposition rate of HFC-134a is continuously decreased at all temperatures, the decrease rate of HFC-134a gradually decreases after a certain period of time, and a constant decomposition rate (about 30% at 600 ° C and about 5% at 400 ° C) Respectively. This can be interpreted as the fact that the reaction progresses gradually and the degree of deactivation of the catalyst progresses to a certain extent, which can decompose a certain amount of HFC-134a.

FIG. 7 shows changes in the trifluoroethylene and CO ₂ formed as the reaction time elapses in the thermal decomposition reaction of HFC-134a nitrate according to the reaction temperature. In the case of Trifluoroethylene, it gradually increased with the lapse of reaction time, and it was confirmed that the production amount decreased with 6 hours. Trifluoroethylene was detected at 400 ℃, which is the lowest reaction temperature, at 500 and 600 ℃, and the highest amount of trifluoroethylene was formed at all reaction times. CO ₂ , which was not detected over the entire reaction time at 400 ° C, was detected at the beginning of the reaction at 500 ° C and 600 ° C. As the reaction progressed, the amount of CO ₂ gradually decreased. And no CO ₂ was detected from the time point of time. It can be interpreted that the catalytic pyrolysis reaction mechanism of HFC-134a gradually changes with reaction temperature and reaction time.

According to the experimental results of the present invention, the catalytic pyrolysis of HFC-134a catalyst is considered to have two different routes depending on the reaction temperature condition and the reaction time. The first reaction path is decomposition of HFC-134a by the gas-solid direct reaction of HFC-134a and g-Al ₂ O ₃ , which can be expressed by the following equation 1, and the second path is represented by dehydrofluorination of HFC-134a The reaction between the formed HF and g-Al ₂ O ₃ can be expressed as shown in the following reaction formula 2.

It is shown that the gas-solid direct reaction forms CO ₂ and AlF ₃ , while the dehydrofluorination reaction forms trifluoroethylene and AlF ₃ . Therefore, it is considered that the product change pattern according to each decomposition temperature is due to different decomposition pathways.

[Reaction Scheme 1]

[Reaction Scheme 2]

In the case of 400 ° C catalytic pyrolysis, there was no CO ₂ emission during the entire reaction time. The catalytic pyrolysis reaction of HFC-134a at 400 ° C was mainly due to the decomposition reaction of HFC-134a It means that it will proceed. As the reaction progresses, the decomposition efficiency of HFC-134a decreases due to the change of the structure of the catalyst and the formation of coke on the surface. As the deactivation of the catalyst progresses gradually, the reaction rate between HFC-134a and g-Al ₂ O ₃ Which is also a result of a decrease in the production of trifluoroethylene in the product. On the other hand, as the reaction temperature increases, it can be interpreted that the dehydrofluorination reaction by the direct reaction of the catalyst-reactive gas in which HF is continuously decomposed from HFC-134a (Scheme 1) acts as the main reaction path, The higher the CO ₂ emissions and the lower the production rate of trifluoroethylene, the higher the reaction temperature.

FIG. 8 shows the results of XRD analysis of the catalyst after 24 hours of reaction. As a result, it was confirmed that AlF ₃ was converted to AlF ₃ by reaction with HFC-134a at all temperatures and the intensity of AlF ₃ was increased with increasing reaction temperature. This means that as the decomposition of HFC-134a proceeds, the change from Al ₂ O ₃ to AlF ₃ is a major factor in the reduction of catalyst performance.

The formation of trifluoroethylene at each reaction time gradually decreases (400, 500 ° C), but it is formed throughout the entire reaction period and maintains a constant level at the final reaction time. The fact that the structure of the catalyst changes from Al ₂ O ₃ to AlF ₃ phase This means that the decomposition of HFC-134a is proceeding, which is weaker than Al ₂ O _3, but it can be interpreted that AlF ₃ has decomposition effect of HFC-134a.

5-2: Evaluation of decomposition performance according to HFC-134a concentration

The decomposition reaction characteristics of HFC-134a in the continuous catalytic cracking reaction were investigated according to the concentration of HFC-134a. For this, the experiment was carried out at the highest reaction temperature (600 ℃) in the previous experiment. HFC-134a 5 ~ 20% (v / v) and N2 base gas 95-80% (v / v) And the other conditions except for the concentration of HFC-134a were set to be the same. The space velocity (WHSV) was operated at 300 mL / g _cat · h for 24 hours with 10 g of catalyst loaded at a total flow rate of 50 mL / min.

The decomposition rate according to the HFC-134a injection concentration is as shown in FIG. As the concentration of HFC-134a was increased, the duration of 100% decomposition was decreased. When the concentration of HFC-134a was changed from 5% to 16 hours, 10% to 8 hours and 20% to 6 hours, respectively, when the concentration of 100% Which means that the decomposition efficiency is reduced in a short time.

However, the concentration of HFC-134a was equal to 40 mL for 5, 10%, and 60 mL for 20% of HFC-134a. This means that the concentration of HFC-134a in the injection concentration range (5 ~ 20%) applied does not have a large effect on the injection efficiency. Therefore, 20% of the HFC-134a, which has the largest treatment capacity per hour, was used as the injection concentration in the subsequent process conditions.

5-3: Evaluation of degradation performance by additional oxygen injection

In order to evaluate the decomposition performance of HFC-134a in accordance with the oxygen added to the injection, the inlet gas 50 mL / min of gas by a composition of 20% HFC-134a (v / v), O 2 50% (v / v), based on gas N ₂ was fixed at 30% (v / v). The reaction temperature and space velocity were 600 ° C and 300 mL / g _cat · h, respectively, for 24 hours.

As a result, the flow rate of the reaction gas during the addition of oxygen was not kept constant, and the amount of gas collected in the sampling bag for 20 minutes after the reaction was significantly decreased as compared with the catalytic pyrolysis condition. In particular, , A considerable amount of solid by-products were formed, making it difficult to carry out continuous experiments.

FIG. 10 shows the corrosion state of the reactor according to the composition of the injection gas. Of course, even when nitrogen is injected in combination with HFC-134a, the color change, which is presumed to be caused by internal corrosion, is found. However, the phenomenon that the inner surface of the reactor is corroded and the thickness of the reactor is reduced can not be confirmed in the experiment over several months . However, in the case of mixed oxygen injection, it was confirmed that the inside surface of the reactor was corroded due to the interaction with the reactant as in the bottom part of FIG. 10, and the thickness of the reactor after the reaction was reduced to such an extent that the stability of the apparatus operation could not be guaranteed .

Therefore, in the present invention, the improvement of the decomposition ratio of HFC-134a due to the injection of oxygen into the reactor has not been progressed in consideration of the stability of the experiment and possibility of introduction into the commercialization process.

5-4: Performance evaluation by additional water vapor injection

In order to compare the decomposition characteristics of HFC-134a catalytic pyrolysis with the addition of water vapor (hydrolysis), the reactants were mixed at a volume ratio of HFC-134a: H ₂ O = 20: 30 / v)).

Fig. 11 shows the decomposition rate of HFC-134a according to the hydrolysis reaction time. Unlike the catalytic cracking, which shows a decrease in decomposition rate over the reaction time, HFC-134a is stable and highly efficient . This shows that the injected H ₂ O is a phenomenon that is caused by removing fluorine remaining on the surface of the catalyst, and it is preferable to inject H ₂ O to lower the degree of inactivity of the catalyst.

In the case of hydrolysis, propane was produced in addition to trifluoroethylene and CO ₂ . This appears to be due to the recombination reaction between decomposition gases.

12 is as in XRD analysis of the recovered catalyst after the reaction 24 hours hydrolysis, in the same manner as catalyst pyrolysis result, all g-Al ₂ the structure of the O ₃ will be seen to byeonhwadoem as AlF _3, the reaction temperature increased The intensity of AlF ₃ was increased. Also, the catalyst obtained after hydrolysis had a higher intensity at all temperatures than the AlF ₃ intensity (FIG. 8) of catalytic pyrolysis. This is because hydrolysis of HFC-134a on g-Al ₂ O ₃ shows higher decomposition rate and fluorine fixation rate of HFC-134a compared with catalytic cracking.

5-5: Hydrolysis performance evaluation according to spatial velocity change

13 shows the change in HFC-134a decomposition rate by the space velocity per unit mass of catalyst (WHSV) on g-Al ₂ O ₃ . In order to change the WHSV in the present invention, the amount of catalyst in the reactor was varied to 5, 10 and 15 g, and the hydrolysis efficiency of HFC-134a according to WHSV at 600 ° C. was compared. In this case, the injected gas in the reactor consisted of 20% (v / v) of HFC-134a, 30% (v / v) of H2O and 50% (v / v) of N2, min. The space velocity was estimated to be 200 ~ 600 mL / g _cat · h according to the change of catalyst amount under the reaction conditions. Actual reaction was continuously performed for 24 hours as before. FIG. 13 shows the decomposition rate of HFC-134a according to the change of space velocity. It is shown that the decomposition efficiency of HFC-134a is improved as the space velocity is smaller. This means that the 100% degradation rate duration proportionally increases as the amount of the catalyst charged increases. This means that, in the future scale-up of the equipment for HFC-134a decomposition, if the amount of the catalyst is increased in proportion to the increase of the reactor size, the decomposition ratio of HFC-134a will be maintained at about the same level, This is a suggestion that there is.

5-6: HFC catalyst For pyrolysis  Effect of water use on catalyst and decomposition reaction of HFC-134a

SEM and BET measurements were performed to observe the changes in specific surface and structure before and after catalytic pyrolysis and hydrolysis. SEM images (FIG. 14) also show some different patterns depending on the use of water as shown in the XRD analysis results (FIGS. 8 and 12). This means that when the reaction efficiency is increased by using water, the change of the catalyst structure to AlF ₃ proceeds more and more. In the SEM image, the structure of g-Al ₂ O ₃ decreased and the hexagonal structure AlF ₃ was more clearly observed as the reaction temperature increased in both catalytic pyrolysis and hydrolysis. XRD analysis also showed no water When used, it can be seen that the pattern of AlF ₃ clearly appears. As shown in Table 14, when the specific surface area of the catalyst was changed by each reaction temperature, it can be confirmed that the reaction was carried out by injecting water to have a smaller specific surface area. It is considered that the conversion of AlF ₃ to AlF ₃ is higher when water is used, and that the converted AlF ₃ has a hexagonal structure with a larger specific surface area than that of g-Al ₂ O ₃ .

Preliminary studies showing that fluorine-based greenhouse gases are injected together with water to increase the fluorine removal rate show that most of the AlF ₃ formed by the dehydrofluorination reaction is converted into Al ₂ O ₃ by the additionally added water, . ≪ / RTI > However, looking at the results of the present invention determined that more even when using water amounts formation of AlF ₃ doemeuro conversion of Al ₂ O ₃ on AlF ₃ will have throughout the reaction because the development in a short time in the form of a reversible reaction AlF ₃ , but the formation of Al ₂ O ₃ is also accompanied by the injection of water in the continuous reaction, which can be interpreted as an improvement in the persistence of the entire HFC-134a decomposition reaction.

10: Reaction gas supply unit 11: HFCs supply unit
12: Inert gas supply part 13: Reaction gas injection tube
14: Water vapor supply unit 15: Flow rate regulator
20: Reactor 21: Catalyst filling column
22: heater 23: decomposition catalyst
24: glass wool 30: decomposition gas discharge part
31: decomposition gas discharge pipe 32: decomposed gas collection part
33: decomposition gas neutralization part 100: HFCs decomposition processing device

Claims (16)

Catalytic cracking of HFCs is carried out using a cracking catalyst comprising Al ₂ O ₃ having a specific surface area of 200 to 300 m ² / g, an average pore size of 3 to 10 nm and a pore volume of 0.8 to 1.5 cm ³ / g ≪ / RTI > The method according to claim 1,
Wherein the Al ₂ O ₃ is γ-Al ₂ O ₃ . The method according to claim 1,
The HFCs are alkanes (CnH ₂ n ₊₂₎ HFCs decomposition treatment method, it characterized in that a haloalkane (Haloalkanes) compound substituted with a part of the hydrogen fluoride. The method of claim 3,
Wherein the HFCs are selected from the group consisting of HFC-23, HFC-32, HFC-125, HFC-134a, HFC-152a, HFC-143a, HFC- 227ea, HFC- And decomposing the HFCs. The method according to claim 1,
Wherein the catalytic pyrolysis of HFCs is carried out at 300 to 650 占 폚. The method according to claim 1,
Wherein the catalytic pyrolysis of HFCs is carried out at 550 to 650 占 폚. The method according to claim 1,
The _{500 ~ 700 mL / g cat ·} h to HFCs decomposition processing method characterized by using the catalyst in a column filled with a space velocity (WHSV) per unit mass of catalyst. Using a decomposition catalyst comprising Al ₂ O ₃ having a specific surface area of 200 to 300 m ² / g, an average pore size of 3 to 10 nm and a pore volume of 0.8 to 1.5 cm ³ / g, Characterized in that the HFCs are catalytically cracked by supplying water vapor. The method of claim 8,
Wherein the HFCs are not supplied with oxygen in catalytic pyrolysis. The method of claim 8,
Wherein the Al ₂ O ₃ is γ-Al ₂ O ₃ . The method of claim 8,
The HFCs are alkanes (CnH ₂ n ₊₂₎ HFCs decomposition treatment method, it characterized in that a haloalkane (Haloalkanes) compound substituted with a part of the hydrogen fluoride. The method of claim 11,
Wherein the HFCs are selected from the group consisting of HFC-23, HFC-32, HFC-125, HFC-134a, HFC-152a, HFC-143a, HFC- 227ea, HFC- And decomposing the HFCs. The method of claim 8,
Wherein the HFCs and steam are supplied at a volume ratio of 2: 3 to 2: 4. The method of claim 8,
The _{500 ~ 700 mL / g cat ·} h to HFCs decomposition processing method characterized by using the catalyst in a column filled with a space velocity (WHSV) per unit mass of catalyst. Using a decomposition catalyst comprising Al ₂ O ₃ having a specific surface area of 200 to 300 m ² / g, an average pore size of 3 to 10 nm and a pore volume of 0.8 to 1.5 cm ³ / g, And catalytic cracking the HFCs at 550 to 650 ° C while supplying water vapor. 16. The method of claim 15,
The _{500 ~ 700 mL / g cat ·} h to HFCs decomposition processing method characterized by using the catalyst in a column filled with a space velocity (WHSV) per unit mass of catalyst.

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