Preparation of a hydrogenolysis dehalogenation catalyst and its application in the generation of ethylene from 1,2-dichloroethane

Abstract

The application discloses a preparation of a hydrogenolysis dehalogenation catalyst and application of the hydrogenolysis dehalogenation catalyst in generation of ethylene from 1,2-dichloroethane. The preparation method of the catalyst is as follows: a soluble salt of metal A and a soluble salt of metal B are used as precursors, are uniformly dissolved in deionized water to prepare a metal precursor solution, then a solvent and a surfactant are added, and after being uniformly mixed, an impregnation solution is obtained, then the impregnation solution is mixed with a carrier, the soluble salt of metal A and the soluble salt of metal B are loaded on the carrier through impregnation, the impregnated carrier is dried and then is placed in a microwave drying box for treatment to obtain the hydrogenolysis dehalogenation catalyst. The application provides application of the prepared hydrogenolysis dehalogenation catalyst in generation of ethylene from 1,2-dichloroethane. The alloying rate of the catalyst is significantly improved, and through the unique electronic structure of the catalyst, the conversion rate of the 1,2-dichloroethane to ethylene reaction and the selectivity of the product ethylene are improved.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation technology, and in particular to the preparation of a hydrogen dehalogenation catalyst and its application in the production of ethylene from 1,2-dichloroethane. Background Technology

[0002] Chlorofluorocarbons (CFCs) are a class of compounds widely used in refrigeration, solvents, foaming agents, and aerosols. They are particularly crucial components in the refrigeration and air conditioning industry. However, with increasing global concern about environmental issues, CFCs have become a focal point of environmental problems due to their strong greenhouse effect, and have been subject to strict regulation and restrictions. Among them, 1,2-dichloroethane (1,2-DCE) plays an important role in synthetic chemistry; however, due to its toxicity and environmental risks, its hydrogenation and dechlorination to convert it into more valuable and environmentally friendly products has become a research focus. The core objective of this reaction is to remove the chlorine atom from 1,2-dichloroethane through the action of a catalyst, generating more valuable products such as ethylene.

[0003] However, the traditional hydrodechlorination reaction of 1,2-dichloroethane is subject to several limitations, such as restrictions on reaction conditions, catalyst performance, and product selectivity. To overcome these limitations, researchers have begun exploring new preparation methods to improve reaction efficiency and product selectivity. For example, Chinese invention patent CN116493041A provides a method for preparing a composite catalyst for the production of vinyl chloride from 1,2-dichloroethane. This method uses SAPO-34 molecular sieve as a support, impregnates it in a solution of lanthanum chloride or lanthanum nitrate, then mixes it uniformly with other inorganic oxide matrices such as pseudohydrophobic water, tianqing powder, and deionized water, extrudes it into strips, and calcines it at 550°C for 8 hours to obtain composite catalyst particles. This catalyst is used for the hydrodechlorination reaction of 1,2-dichloroethane under conditions of 380°C and a 1,2-dichloroethane weight hourly space velocity of 0.5 h⁻¹. -1 At this temperature, the selectivity for vinyl chloride is 97%, and the conversion rate is 57%. However, the rare earth element content of this catalyst, calculated as La₂O₃, is between 3 and 8 wt%. Furthermore, to achieve its desired effect, the catalyst needs to be calcined at a relatively high temperature (550°C) for up to 8 hours. It is worth noting that setting the reaction temperature at 380°C may cause coking, thus affecting the catalyst's lifespan and increasing energy consumption.

[0004] In recent years, an increasing number of researchers have begun to explore more efficient catalysts. Chinese invention patent CN116251610A proposes a single-atom catalyst for the production of vinyl chloride from 1,2-dichloroethane. Ni(CH3COO)2·4H2O and o-phenanthroline monohydrate are dissolved in anhydrous ethanol, and nano-magnesium oxide (50 nm) is added. The mixture is stirred in a water bath and dried for 12 hours. The dried powder is heated to 500℃ and held for 2 hours in a nitrogen or argon atmosphere, then acid-washed with nitric acid solution for 24 hours. Finally, the dried material is heated to 300℃ and held for 2 hours in N2 to obtain a single-atom Ni-NC catalyst with a nickel content of 6.3% and a nitrogen content of 8.3%. 1,2-dichloroethane is introduced into a fixed-bed reactor using a bubbling method with N2 at a reaction temperature of 250℃, an N2 flow rate of 5 mL / min, a 1,2-dichloroethane temperature of 5℃, and a catalyst mass of 0.1 g. At this point, the conversion rate of 1,2-dichloroethane was 36%, the selectivity for vinyl chloride was greater than 99%, and the catalyst remained deactivated for 40 hours. However, this method has a limited throughput of 1,2-dichloroethane and a relatively low conversion rate. Furthermore, the catalyst preparation process is cumbersome and time-consuming.

[0005] Understanding the mechanism of 1,2-dichloroethane hydrodechlorination and designing and constructing catalyst active sites plays a crucial role in the efficient hydrodechlorination of 1,2-dichloroethane. For example, Lang Xu and Eric E. Stangland et al., in their paper "Hydrodechlorination of 1,2-Dichloroethane on Platinum Catalysts: Insights from Reaction Kinetics Experiments, Density Functional Theory, and Microkinetic Modeling" (ACS Catal. 2021, 11, 13, 7890–7905), utilized density functional theory calculations, reaction kinetics experiments, and the construction of microkinetic models to explore the reaction kinetics and reveal the mechanism of 1,2-dichloroethane hydrodechlorination.

[0006] First, hydrogen gas is adsorbed and dissociated at the active sites, forming active hydrogen atoms. Simultaneously, 1,2-dichloroethane also adsorbs at the active sites. These active hydrogen atoms react with adjacent 1,2-dichloroethane atoms, losing halogen atoms to form ethylene. Some ethylene may not desorb in time and further react with active hydrogen atoms at the active sites to form ethane.

[0007] The construction of catalyst active sites must first ensure sufficient activation capacity for hydrogen, while also possessing different adsorption strengths for feedstocks and products to improve catalyst selectivity. Simultaneously, the metal in the catalyst is a core component of the active sites. The metal dispersion and nanoparticle size affect the number of available active sites on the catalyst surface, thus influencing the reaction rate. By controlling the preparation conditions, uniform dispersion of metal nanoparticles can be achieved, increasing the density of active sites and thereby enhancing the catalytic effect of the reaction. Bimetallic catalysts have attracted considerable attention in various chemical reactions due to their unique catalytic properties. Since the bimetallic structure can regulate the electron cloud density and adsorption capacity of reactants in the reaction, it is of great significance for the selective formation of the target product in the hydrodechlorination reaction of 1,2-dichloroethane.

[0008] In summary, existing methods for preparing bimetallic catalysts suffer from problems such as long preparation cycles and energy waste. However, the use of microwave irradiation technology to prepare bimetallic catalysts offers advantages such as speed, efficiency, and environmental friendliness. Therefore, inventing a novel preparation method that utilizes microwave irradiation technology to improve the alloying rate of bimetallic catalysts and reduce environmental and resource waste has significant research and application value. The development of this technology is expected to bring new breakthroughs to the field of catalyst preparation, promote the development and application of more high-performance catalysts, and advance the greening and sustainable development of chemical synthesis processes. Summary of the Invention

[0009] To address the problems of high energy consumption and low catalyst activity in traditional preparation methods, this invention provides a method for preparing a hydrogen dehalogenation catalyst and its application in the production of ethylene from 1,2-dichloroethane. This method significantly improves the catalyst's alloying rate and, through the catalyst's unique electronic structure, enhances both the conversion rate of the hydrogen dechlorination reaction of 1,2-dichloroethane and the selectivity of the ethylene product.

[0010] The technical solution adopted in this invention is as follows:

[0011] In a first aspect, the present invention provides a method for preparing a hydrogen dehalogenation catalyst, wherein the hydrogen dehalogenation catalyst is a bimetallic catalyst, the bimetal being metal A and metal B, wherein metal A and metal B are different, wherein metal A is selected from any one of Pd, Pt, Ru, Ni, Co, Cu, Fe, and Zn, and metal B is selected from any one of Pd, Pt, Ru, Ni, Co, Cu, Fe, and Zn, the total loading of metal A and metal B in the bimetallic catalyst is 0.3-3 wt%, and the loading ratio of metal A to metal B is 1:2-1:8; the preparation method is as follows: using metal A... Soluble salts of metal A and metal B are used as precursors. They are uniformly dissolved in deionized water to prepare a metal precursor solution. Then, solvent and surfactant are added and mixed evenly to obtain an impregnation solution. The impregnation solution is then mixed with a support. Soluble salts of metal A and metal B are loaded onto the support through impregnation. After the impregnated support is dried, it is placed in a microwave drying oven with a microwave power of 100-1000W, a frequency of 1-4GHz, a wavelength of 7.5cm-30cm, and a heating time of 0.5min-20min. Nitrogen is used as a protective gas with a flow rate of 30-50ml / min. Finally, a hydrogen dehalogenation catalyst is obtained.

[0012] The solvent is deionized water, methanol, concentrated hydrochloric acid, 0.05 g / ml - 0.1 g / ml of EDTA-disodium aqueous solution, 0.3 g / ml - 0.6 g / ml of citric acid aqueous solution, 0.5 g / ml - 1.0 g / ml of urea aqueous solution, or 0.1 g / ml - 0.2 g / ml of glycine aqueous solution;

[0013] The surfactant is hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, or sodium dodecylbenzenesulfonate.

[0014] The metal loading capacity of this invention is calculated based on the condition that the fed metal is fully loaded onto the carrier. The total loading capacity of metal A and metal B = m (金属A+金属B) / m 载体 ×100%, where m (金属A+金属B) The sum of the masses of metal A and metal B contained in the soluble salts of metal A and metal B fed into the feed.

[0015] Preferably, the carrier is activated carbon, alumina, or silicon dioxide, with activated carbon carrier being more preferred.

[0016] Preferably, the concentration of metal A ions in the impregnation solution is 0.1-2 wt%, and the concentration of surfactant is 0.001-0.005 M.

[0017] Preferably, the total loading of metal A and metal B in the hydrogen dehalogenation catalyst is 0.3-1 wt%.

[0018] Preferably, the ratio of the carrier mass to the impregnation liquid volume is 1g:(1-5)mL, and more preferably 1g:(2-4)mL.

[0019] Preferably, the process of "mixing the impregnation solution with the carrier and loading the soluble salts of metal A and metal B onto the carrier through impregnation" is specifically carried out as follows: the carrier is first dehydrated by vacuum drying at 60-90℃ for 1-3 hours, and then rapidly added to the impregnation solution while maintaining the temperature. The carrier is then gradually cooled to room temperature during the impregnation process, with an impregnation time of 0.5-3 hours, preferably 2 hours. As a further preferred embodiment, the dehydration temperature is 80℃, and the dehydration time is 2 hours.

[0020] Preferably, the drying process is shade drying.

[0021] Preferably, the soluble salts of metal A and metal B are soluble salts such as hydrochloride, nitrate, acetate, etc., such as palladium chloride, palladium nitrate, platinum chloride, platinum nitrate, nickel chloride, nickel nitrate, zinc chloride, etc., and more preferably nitrates.

[0022] In a second aspect, the present invention provides the application of the hydrogen dehalogenation catalyst prepared according to the preparation method described in the first aspect in the production of ethylene from 1,2-dichloroethane.

[0023] The specific application is as follows: The dehalogenation catalyst is loaded into a fixed-bed reactor. Inert gas is introduced to fully replace the air in the fixed-bed reactor. After maintaining this for a certain time (e.g., 30 min), hydrogen is introduced at a flow rate of 3-20 mL / min, maintaining an H2 / N2 flow ratio of 1:1-1:10. After a certain time (e.g., 15 min), catalyst pre-activation is performed: keeping the previous gas flow rate constant, the fixed-bed reactor is heated from room temperature to 250-400℃ at a rate of 3-10℃ / min, and held at this temperature for 1-3 hours to complete pre-activation. Then, the gas is switched to a balance gas (helium, nitrogen, or argon). Once the reactor temperature is adjusted to the reaction temperature (200-350℃), the feed is introduced via bubbling. The raw material 1,2-dichloroethane, hydrogen, and balance gas are mixed evenly and then passed through the catalyst bed. Under the action of the catalyst, 1,2-dichloroethane undergoes a dehalogenation reaction to produce ethane. After the reaction, HCl is removed through an alkali tube equipped with a heat preservation device. A portion of the product is extracted and injected into a gas chromatograph for product analysis (maintained at 120℃ throughout the process). The remaining product is treated as tail gas.

[0024] As a preferred option, the pre-activation treatment conditions are: hydrogen gas flow rate of 5-10 mL / min, H2 / N2 flow ratio of 1:2-1:5, heating rate of 5℃ / min, reduction temperature of 300-400℃, and constant temperature for 2 hours.

[0025] As a preferred option, the raw material ratio is controlled as n(H2):n(1,2-DCE)=2-15:1.

[0026] Preferably, the reaction temperature is 250-350℃, more preferably 280-350℃.

[0027] Preferably, the airspeed is controlled at 1500-10000 h. -1 More preferably 5000-10000 h -1 .

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] (1) The catalyst preparation method of the present invention prepares a bimetallic catalyst with high alloying degree through a simple impregnation and drying process. It has the advantages of short preparation time, low energy consumption and high alloying degree, and avoids the energy consumption problem and excessive metal agglomeration problem caused by high temperature treatment. The prepared catalyst has significant advantages of high activity, long life and high selectivity when applied to the hydrogenation dechlorination reaction of 1,2-dichloroethane.

[0030] (2) In the preparation of bimetallic catalysts, the use of microwave radiation can significantly improve the alloying rate. Microwave radiation can accelerate the dissolution and diffusion of metal precursors, promote interatomic interactions, and make alloy formation more rapid and uniform. Compared with traditional heat treatment, bimetallic catalysts prepared by microwave radiation have higher metal dispersion, more uniform particle size distribution and higher alloying rate, thereby improving catalytic activity and selectivity. Attached Figure Description

[0031] Figure 1 This is a TEM image of the bimetallic catalyst prepared in Example 1. The alloy shown in the line scan image is a PtCo alloy.

[0032] Figure 2 This is a TEM image of the catalyst prepared in Comparative Example 1.

[0033] Figure 3 This is the XRD pattern of the catalyst. Detailed Implementation

[0034] The following examples are only used to further illustrate the present invention, but the scope of protection of the present invention is not limited thereto.

[0035] Example 1:

[0036] Preparation process:

[0037] Dissolve platinum chloride (soluble metal salt A) and cobalt chloride hexahydrate (soluble metal salt B) separately in concentrated hydrochloric acid (37%) and deionized water to prepare a 0.5% chloroplatinic acid solution and a 4% cobalt chloride hexahydrate aqueous solution by mass fraction (Note: the mass fraction of all metal salt aqueous solutions mentioned in the examples and comparative examples refers to the mass fraction of the metal element). Take 5 ml of the 0.5% chloroplatinic acid solution and 2.5 ml of the 4% cobalt chloride hexahydrate aqueous solution and place them in a 50 ml beaker. Add 7.5 ml of deionized water and then add 0.003 M hexadecyltrimethylammonium bromide (surfactant C). Stir magnetically to mix evenly and let stand for 30 minutes.

[0038] 5 g of activated carbon carrier (Cabot Norritar activated carbon DARCO 1220, crushed to 20-30 mesh) was immersed in the above solution, soaked overnight at room temperature for 12 hours, and then air-dried.

[0039] The catalyst was placed in a microwave drying oven with a microwave power of 200 W, a frequency of 2.45 GHz, a microwave irradiation time of 5 min, and a nitrogen flow rate of 30 mL / min. Under microwave irradiation, the significant difference in electrical conductivity between the metal and carbon materials enabled rapid heating of the metal, promoting more efficient diffusion and interaction. Furthermore, the metal particles were affected by electron oscillations during microwave irradiation. These electrons oscillated in the electric field and interacted with atoms within the grains, causing atoms around the grain boundaries to move, leading to grain boundary migration and thus increasing the alloying rate of the bimetallic catalyst.

[0040] Catalyst evaluation conditions:

[0041] 0.5 g of catalyst was loaded into a quartz tube reactor, with a bed height of approximately 3.5 cm.

[0042] The reaction system was purged with nitrogen at a flow rate of 30 mL / min for 30 minutes.

[0043] Aerate at a hydrogen flow rate of 10 mL / min, maintaining an H2 / N2 flow rate ratio of 1:3, for 15 minutes.

[0044] The catalyst was pre-activated by heating at a rate of 5 °C / min from room temperature to 300 °C and held at that temperature for 2 hours.

[0045] Catalyst activity evaluation results:

[0046] At 280 °C, the nitrogen flow rate of the equilibrium gas was adjusted to achieve a feed content of 25000 ppm, n(H2):n(1,2-DCE) = 6:1, and a space velocity of 1550 h⁻¹.-1 After a 30-minute reaction, the product was analyzed by gas chromatography. The results showed that the catalyst exhibited a 90.7% conversion of 1,2-dichloroethane and an ethane selectivity of 85.3%.

[0047] This example demonstrates that the high-alloy bimetallic catalyst prepared by microwave irradiation exhibits excellent catalytic performance in the hydrodechlorination reaction of 1,2-dichloroethane, showcasing the high efficiency and environmental friendliness of the preparation method. TEM characterization further confirms this. Figure 1 It can be seen that the catalyst prepared by the microwave method has good size distribution and alloying degree, as can be seen from the XRD diffraction data ( Figure 3 Calculations showed that the catalyst prepared by this method had an alloying rate of 60.4%. The high alloying rate catalyst not only exhibits high conversion rate but also high selectivity.

[0048] Example 2:

[0049] In this embodiment, 5 ml of a 0.5% platinum nitrate aqueous solution and 2.5 ml of a 4% cobalt nitrate hexahydrate aqueous solution were used, and the other preparation procedures were the same as in Example 1. The catalyst activity evaluation method was the same as in Example 1.

[0050] Evaluation results show that soluble metal salts have a certain impact on the catalytic performance of the prepared catalyst. Due to the strong complexing ability of chloride ions on metals, the metal precursor may be poorly dispersed, resulting in larger metal particles. Conversely, the weaker complexing ability of nitrate ions on metals makes the metal salts more soluble in water and promotes metal dispersion. The catalyst exhibits a 94.2% conversion rate of 1,2-dichloroethane and an 89.4% selectivity for ethylene.

[0051] Examples 3 and 4:

[0052] Examples 3 and 4 differ from Example 2 in that the metal ratios are varied. In Example 3, 5 ml of a 0.5% platinum nitrate aqueous solution and 4 ml of a 2% cobalt nitrate hexahydrate aqueous solution were used. In Example 4, 5 ml of a 0.5% platinum nitrate aqueous solution and 5 ml of a 2% cobalt nitrate hexahydrate aqueous solution were used. The other preparation processes were the same as in Example 2. The catalyst activity evaluation method was the same as in Example 1.

[0053] Evaluation results showed that adjusting the metal ratio altered the distribution and interactions of the metals in the reaction, leading to changes in the electronic structure of the catalyst and affecting the reaction activity and selectivity. Higher Co content improved ethylene selectivity but resulted in a decrease in conversion. The catalyst in Example 3 exhibited a 1,2-dichloroethane conversion of 92.5% and an ethane selectivity of 92.3%, while the catalyst in Example 4 exhibited a 1,2-dichloroethane conversion of 90.1% and an ethane selectivity of over 95.2%.

[0054] Examples 5 and 6:

[0055] Example 5 differs from Example 2 in that the ratio of carbon support to impregnation solution was changed. 5 ml of a 0.5% platinum nitrate aqueous solution and 2.5 ml of a 4% cobalt nitrate hexahydrate aqueous solution were used, along with 12.5 ml of deionized water. The ratio of carbon support to impregnation solution was 1 g:4 mL. In Example 6, 17.5 ml of deionized water was added, and the ratio of carbon support to impregnation solution was 1:5. Other preparation procedures were the same as in Example 2. The catalyst activity evaluation method was the same as in Example 1.

[0056] The alloying rate of the metal is affected by the ratio of carbon support to impregnation solution. A higher impregnation solution volume may promote a more uniform distribution of the metal on the support, resulting in a more uniform and efficient alloying process, which helps to improve the activity of the catalyst. However, an excessively high impregnation solution volume may cause the metal to not bond firmly with the support or be difficult to adsorb during impregnation, leading to a decrease in conversion rate. However, the effect on selectivity is minimal, and the selectivity may even be slightly improved due to the decrease in conversion rate. The catalyst of Example 5 exhibited a 1,2-dichloroethane conversion rate of 95.7% and an ethylene selectivity of 91.3%, while the catalyst of Example 6 exhibited a 1,2-dichloroethane conversion rate of 92.3% and an ethylene selectivity of 92.6%, respectively.

[0057] Example 7:

[0058] In this example, an aqueous solution of disodium ethylenediaminetetraacetate (0.1 g / ml) was used as the solvent, and sodium dodecyl sulfate (0.002 M) was used as the surfactant. 5 ml of a 0.5% (w / w) aqueous solution of platinum nitrate EDTA-disodium salt and 2.5 ml of a 4% (w / w) aqueous solution of copper nitrate in EDTA were also used. Other preparation procedures were the same as in Example 1. The catalyst activity evaluation method was the same as in Example 1. The catalyst exhibited a 92.3% conversion rate of 1,2-dichloroethane and an 87.9% selectivity for ethylene. Calculations and analysis of the XRD diffraction data showed that the alloying rate of the catalyst was 58.1%.

[0059] Example 8:

[0060] In this example, 5 ml of a 0.5% (w / w) platinum nitrate EDTA aqueous solution and 5 ml of a 2% (w / w) copper nitrate EDTA-disodium aqueous solution were used. Other preparation procedures were the same as in Example 7. The catalyst activity evaluation method was the same as in Example 1. The catalyst exhibited a 1,2-dichloroethane conversion of 88.8% and an ethylene selectivity of 94.0%, respectively.

[0061] Example 9:

[0062] In this embodiment, citric acid aqueous solution (0.8 g / ml) was used as the solvent, along with 5 ml of 0.5% platinum nitrate aqueous solution and 5 ml of 2% copper nitrate aqueous solution. Sodium dodecylbenzenesulfonate (0.003 M) was used as the surfactant. Other preparation procedures were the same as in Example 1. The catalyst activity evaluation method was the same as in Example 1. The catalyst exhibited a 1,2-dichloroethane conversion of 87.4% and an ethylene selectivity of 89.6%. Calculations and analysis of the XRD diffraction data showed that the alloying rate of the catalyst was 56.5%.

[0063] Example 10:

[0064] In this example, an aqueous solution of disodium ethylenediaminetetraacetate (0.1 g / ml) was used as the solvent, along with 5 ml of a 0.5% platinum nitrate EDTA solution, 2.5 ml of a 4% copper nitrate EDTA solution, and 7.5 ml of deionized water. The rest of the preparation process was the same as in Example 1. The catalyst activity evaluation method was the same as in Example 9. The catalyst exhibited a 1,2-dichloroethane conversion of 93.3% and an ethylene selectivity of 90.1%.

[0065] Comparative Example 1:

[0066] Comparative Example 1 is a catalyst prepared using a forced-air drying oven, unlike Example 1 which did not undergo microwave treatment. The specific preparation process is as follows:

[0067] Dissolve platinum chloride (soluble metal salt A) and cobalt chloride hexahydrate (soluble metal salt B) separately in concentrated hydrochloric acid (37%) and deionized water to obtain a 0.5% chloroplatinic acid solution and a 4% cobalt chloride hexahydrate aqueous solution. Take 5 ml of the 0.5% chloroplatinic acid solution and 2.5 ml of the 4% cobalt chloride hexahydrate aqueous solution and place them in a 50 ml beaker. Add 7.5 ml of deionized water and then add 0.003 M hexadecyltrimethylammonium bromide (surfactant C). Stir magnetically to mix evenly and let stand for 30 minutes.

[0068] Immerse 5 g (20-30 mesh) of activated carbon carrier in the above solution, soak overnight at room temperature, and then air dry.

[0069] The catalyst was placed in a forced-air drying oven, with a heating rate of 10℃ / min, a drying temperature of 200℃, and a drying time of 3 h. The catalyst preparation was completed, and the evaluation conditions remained consistent.

[0070] 0.5 g of catalyst was loaded into a quartz tube reactor, with a bed height of approximately 3.5 cm.

[0071] The reaction system was purged with nitrogen at a flow rate of 30 mL / min for 30 minutes.

[0072] Aerate at a hydrogen flow rate of 10 mL / min, maintaining an H2 / N2 flow rate ratio of 1:3, for 15 minutes.

[0073] The catalyst was pre-activated by heating at a rate of 5 °C / min from room temperature to 300 °C and held at that temperature for 2 hours.

[0074] Catalyst activity evaluation results:

[0075] At 280 °C, the nitrogen flow rate of the equilibrium gas was adjusted to achieve a feed content of 25000 ppm, n(H2):n(1,2-DCE) = 6:1, and a space velocity of 1550 h⁻¹. -1 After a 30-minute reaction, the product was analyzed by gas chromatography. The results showed that the catalyst exhibited a 64.5% conversion of 1,2-dichloroethane and an ethane selectivity of 80.3%.

[0076] Characterization analysis revealed that the alloying rate of the microwave-treated catalyst was significantly higher than that of the catalyst in Comparative Example 1 (see attached figure). Figure 1 , 2 After calculating and analyzing the XRD diffraction data (TEM line scan), the alloying rate of the catalyst in Comparative Example 1 was only 32.1%, which was significantly lower than that of the microwave-treated catalyst. This is the fundamental reason why the catalyst in this comparative example had poor conversion rate and selectivity.

[0077] Comparative Example 2:

[0078] Comparative Example 2, compared to Example 1, only loaded with metallic Pt. The specific preparation process is as follows:

[0079] Take 5 ml of 0.5% chloroplatinic acid solution and 10 ml of deionized water, then add 0.003 M hexadecyltrimethylammonium bromide (surfactant C), stir magnetically to mix evenly, and let stand for 30 minutes.

[0080] Immerse 5 g (20-30 mesh) of activated carbon carrier in the above solution, soak overnight at room temperature, and then air dry.

[0081] The catalyst was placed in a microwave drying oven with a microwave power of 200 W, a frequency of 2.45 GHz, a microwave irradiation time of 5 min, and a nitrogen flow rate of 30 mL / min. The catalyst preparation was completed, and the evaluation conditions remained consistent.

[0082] 0.5 g of catalyst was loaded into a quartz tube reactor, with a bed height of approximately 3.5 cm.

[0083] The reaction system was purged with nitrogen at a flow rate of 30 mL / min for 30 minutes.

[0084] Aerate at a hydrogen flow rate of 10 mL / min, maintaining an H2 / N2 flow rate ratio of 1:3, for 15 minutes.

[0085] The catalyst was pre-activated by heating at a rate of 5 °C / min from room temperature to 300 °C and held at that temperature for 2 hours.

[0086] Catalyst activity evaluation results:

[0087] At 280 °C, the nitrogen flow rate of the equilibrium gas was adjusted to achieve a feed content of 25000 ppm, n(H2):n(1,2-DCE) = 6:1, and a space velocity of 1550 h⁻¹. -1 After a 30-minute reaction, the product was analyzed by gas chromatography. The results showed that the catalyst exhibited a 1,2-dichloroethane conversion of over 64.7% and an ethane selectivity of over 14.6%.

[0088] The comparative results show that the formation of the bimetallic catalyst alloy is of great significance for improving catalyst selectivity. Furthermore, the alloy formation leads to changes in the electron cloud structure of the metal, which also plays an important role in improving the catalyst's activity and stability. The catalyst structure characterization of this comparative example is shown in the attached figure. Figure 3 As shown in curve 2.

[0089] Comparative Example 3:

[0090] Comparative Example 3, compared to Example 1, only loaded with metallic Co. The specific preparation process is as follows:

[0091] Take 2.5 ml of 4% cobalt chloride hexahydrate aqueous solution, 12.5 ml of deionized water, and add 0.003 M hexadecyltrimethylammonium bromide (surfactant C). Stir magnetically to mix evenly and let stand for 30 minutes.

[0092] Immerse 5 g (20-30 mesh) of activated carbon carrier in the above solution, soak overnight at room temperature, and then air dry.

[0093] The catalyst was placed in a microwave drying oven with a microwave power of 200 W, a frequency of 2.45 GHz, a microwave irradiation time of 5 min, and a nitrogen flow rate of 30 mL / min. The catalyst preparation was completed, and the evaluation conditions remained consistent.

[0094] 0.5 g of catalyst was loaded into a quartz tube reactor, with a bed height of approximately 3.5 cm.

[0095] The reaction system was purged with nitrogen at a flow rate of 30 mL / min for 30 minutes.

[0096] Aerate at a hydrogen flow rate of 10 mL / min, maintaining an H2 / N2 flow rate ratio of 1:3, for 15 minutes.

[0097] The catalyst was pre-activated by heating at a rate of 5 °C / min from room temperature to 300 °C and held at that temperature for 2 hours.

[0098] Catalyst activity evaluation results:

[0099] At 280 °C, the nitrogen flow rate of the equilibrium gas was adjusted to achieve a feed content of 25000 ppm, n(H2):n(1,2-DCE) = 6:1, and a space velocity of 1550 h⁻¹. -1 After a 30-minute reaction, the product was analyzed by gas chromatography. The results showed that the catalyst exhibited a 1,2-dichloroethane conversion of 8.3% and an ethane selectivity of 77.4%.

[0100] The comparative results show that, due to the mechanism of hydrodechlorination, noble metals, which have a stronger ability to activate hydrogen atoms, achieve higher conversion rates in this reaction. However, there is also an over-hydrogenation that leads to the formation of alkanes. For transition metal Co, its ability to activate hydrogen is known to be inferior to that of noble metals, resulting in a lower conversion rate in this reaction pathway, but it exhibits higher olefin selectivity. This is of great importance for the construction of bimetallic catalysts and the regulation of electron clouds.

[0101] Example 11:

[0102] To further verify the universality of the microwave method in improving the alloying rate, Example 11 used 5 ml of 0.5% ruthenium chloride solution and 2.5 ml of 4% zinc acetate dihydrate aqueous solution in a 50 ml beaker, added 7.5 ml of deionized water, and then added 0.003 M hexadecyltrimethylammonium bromide (surfactant C). The mixture was magnetically stirred until homogeneous and allowed to stand for 30 minutes.

[0103] Immerse 5 g (20-30 mesh) of activated carbon carrier in the above solution, soak overnight at room temperature, and then air dry.

[0104] The catalyst was placed in a microwave drying oven with a microwave power of 300W, a frequency of 3 GHz, a microwave irradiation time of 5 min, and a nitrogen flow rate of 30 mL / min.

[0105] Catalyst evaluation conditions:

[0106] 0.5 g of catalyst was loaded into a quartz tube reactor, with a bed height of approximately 3.5 cm.

[0107] The reaction system was purged with nitrogen at a flow rate of 30 mL / min for 30 minutes.

[0108] Aerate at a hydrogen flow rate of 10 mL / min, maintaining an H2 / N2 flow rate ratio of 1:3, for 15 minutes.

[0109] The catalyst was pre-activated by heating at a rate of 5 °C / min from room temperature to 300 °C and held at that temperature for 2 hours.

[0110] Catalyst activity evaluation results:

[0111] At 280 °C, the nitrogen flow rate of the equilibrium gas was adjusted to achieve a feed content of 25000 ppm, n(H2):n(1,2-DCE) = 6:1, and a space velocity of 1550 h⁻¹. -1 After a 30-minute reaction, the product was analyzed by gas chromatography. The results showed that the catalyst exhibited a 1,2-dichloroethane conversion of 90.3% and an ethane selectivity of 85.6%. Calculation analysis based on XRD diffraction data indicated that the alloying rate of the catalyst was 57.3%.

[0112] Examples 12 and 13:

[0113] Example 12 differed from Example 11 in that the microwave processing conditions were modified. In Example 12, the microwave tube furnace was set to a power of 600 W and the magnetron microwave emission frequency was set to 3.5 GHz. In Example 13, the microwave tube furnace was set to a power of 200 W and the magnetron microwave emission frequency was set to 1.5 GHz. The microwave duration remained at 5 min, and the nitrogen flow rate remained at 30 ml / min. Other methods for the catalyst were consistent with those in Example 11. The evaluation results showed that the catalyst in Example 12 exhibited a 1,2-dichloroethane conversion rate of 92.4% and an ethylene selectivity of 88.0%, while the catalyst in Example 13 exhibited a 1,2-dichloroethane conversion rate of 93.3% and an ethylene selectivity of 93.1%.

[0114] Examples 14 and 15:

[0115] Compared to Example 11, Examples 14 and 15 differed in that the microwave processing time was changed. In these examples, the microwave time was set to 10 min and 15 min, respectively. The flow rate of the protective nitrogen gas remained at 30 ml / min. The power of the microwave tube furnace was set to 300 W, and the microwave emission frequency of the magnetron was kept unchanged at 3 GHz. Other methods for the catalyst remained consistent with those in Example 11. The evaluation results showed that the catalyst of Example 14 exhibited a 1,2-dichloroethane conversion rate of 87.5% and an ethylene selectivity of 84.6%, while the catalyst of Example 15 exhibited a 1,2-dichloroethane conversion rate of 94.2% and an ethylene selectivity of 95.9%.

[0116] Examples 16, 17, and 18:

[0117] Example 16 differed from Example 1 in that the impregnation solvent was changed. In Example 16, 5 ml of 0.5% platinum nitrate aqueous solution and 2.5 ml of 4% ferric nitrate nonahydrate aqueous solution were used, along with 7.5 ml of urea aqueous solution (1 g / ml). The ratio of reducing gas H2 / N2 was adjusted to 1:2, while other conditions remained unchanged. Example 17 differed from Example 16 in that the ratio of reducing gas H2 / N2 was changed to 1:4, while other conditions remained unchanged. Example 18 differed from Example 17 in that the ratio of reducing gas H2 / N2 was changed to 1:5, while other conditions remained unchanged. The evaluation results showed that the catalyst in Example 16 had a 1,2-dichloroethane conversion rate of 92.5% and an ethylene selectivity of 90.0%; the catalyst in Example 17 had a 1,2-dichloroethane conversion rate of 93.3% and an ethylene selectivity of 89.2%; and the catalyst in Example 18 had a 1,2-dichloroethane conversion rate of 90.5% and an ethylene selectivity of 92.0%.

[0118] Examples 19, 20, 21, and 22:

[0119] Example 19 differs from Example 16 in that the impregnation solvent was changed. In Example 19, 5 ml of a 0.5% platinum nitrate aqueous solution and 2.5 ml of a 4% nickel nitrate hexahydrate aqueous solution were used, along with 7.5 ml of a glycine aqueous solution (0.2 g / ml). The hydrogen to raw material ratio n(H2):n(N2) was adjusted to 3:1, while all other conditions remained unchanged. Example 20 differs from Example 19 in that the hydrogen to raw material ratio n(H2):n(N2) was changed to 5:1, while all other conditions remained unchanged. Example 21 differs from Example 20 in that the hydrogen to raw material ratio n(H2):n(N2) was changed to 10:1, while all other conditions remained unchanged. Example 21 also differs from Example 20 in that the hydrogen to raw material ratio n(H2):n(N2) was changed. =15:1, with all other conditions remaining unchanged; the evaluation results showed that the catalysts of Examples 19, 20, 21 and 22 had 1,2-dichloroethane conversion rates of 91.6%, 93.4%, 95.3% and 96.2% or higher, respectively, and ethylene selectivity of 89.7%, 86.1%, 87.5% and 82.9%, respectively.

[0120] Examples 23, 24, and 25:

[0121] Example 23 differs from Example 19 in that the impregnation solvent is changed. In Example 23, 5 ml of a 0.5% platinum nitrate aqueous solution and 2.5 ml of a 4% nickel nitrate hexahydrate aqueous solution are used, along with 7.5 ml of deionized water. The space velocity is adjusted to 5000 h⁻¹. -1 The reaction temperature was adjusted to 250°C, while all other conditions remained unchanged; in Example 24, the space velocity was adjusted to 8000 h⁻¹ compared to Example 23. -1 The reaction temperature was adjusted to 330°C, while all other conditions remained unchanged; in Example 24, the space velocity was adjusted to 10,000 h⁻¹ compared to Example 23. -1 The reaction temperature was adjusted to 350℃, while other conditions remained unchanged. Evaluation results showed that the catalysts in Examples 23, 24, and 25 achieved 1,2-dichloroethane conversion rates of 83.4%, 93.4%, and 96.6%, respectively, and ethylene selectivity of 85.6%, 93.0%, and 96.9%, respectively. Calculation and analysis of XRD diffraction data showed that the alloying rates of the catalysts were 53.8%, 56.2%, and 56.8%, respectively.

[0122] After calculating and analyzing the XRD data, the metal alloying rate of the corresponding catalyst can be obtained, as shown in Table 1 below.

[0123] Table 1. Particle size and alloying degree of calcined catalysts

[0124] Catalysis Plane D(nm) Da(%) <![CDATA[Pt1Co4 - Comparative Example 1]]> 111 25.20 32.11 <![CDATA[Pt1Co4 - Example 2]]> 111 13.32 51.30 <![CDATA[Pt1Co4 - Example 1]]> 111 17.91 60.42 Pt 111 — — Co 111 — —

[0125] Example of alloying rate calculation:

[0126] Based on the information in the XRD pattern, the interplanar spacing (d) of the AB alloy can be calculated using the Bragg equation:

[0127] (1)

[0128] Where θ is the angle between the incident X-ray and the reflecting crystal plane, n is the diffraction order, and λ is the wavelength of the X-ray, which is taken as λ = 0.15041.

[0129] For the (111) plane of a face-centered cubic crystal, the interplanar spacing d and the lattice parameter a satisfy the following relationship: [1] :

[0130] (2)

[0131] Where h, k, and l are diffraction indices.

[0132] Therefore, the lattice parameter a of the catalyst can be obtained through calculation.

[0133] Since both metal A and metal B have a face-centered cubic crystal structure, according to Vigarde's law, the lattice parameters of the AB alloy decrease with increasing B doping concentration. Furthermore, based on XRD data, the lattice parameters of the AB alloy can be calculated as follows:

[0134] a T = a A (1-X) +a B X (3)

[0135] Among them, a T a A a B , respectively, are the lattice parameters of alloy, metal A, and metal B, and X is the molar ratio of metal B in alloy AB.

[0136] The degree of alloying (Da) of the sample can be calculated using the obtained AB alloy lattice parameters:

[0137] Da = (a - a0) / (a T - a0) (4)

[0138] Where 'a' represents the specific lattice parameter of the alloy sample, 'a0' represents the lattice parameter of pure A nanoparticles, and 'a' represents the lattice parameter of the a nanoparticles. T It refers to the lattice parameters of the alloy obtained after assuming that all B atoms are alloyed.

[0139] After processing the XRD pattern using plotting software, relevant information about the (111) plane diffraction peaks can be obtained. The particle size (D) of the catalyst can then be calculated using the Scherrer formula.

[0140] (5)

[0141] Where K is the Scherrer constant, taken as K=0.89; β is the half-width at half maximum (FWHM) of the diffraction peak of the measured sample.

[0142] By calculating and comparing the diffraction peak positions, particle size, interplanar spacing, lattice parameters, and alloying degree of the catalysts, it was found that the catalyst prepared by the conventional impregnation method (Comparative Example 1) had the lowest alloying degree, at only 32.11%, while the catalyst prepared by the method of the present invention had an alloying degree of 51.30% and 60.42%, as shown in Table 1 above.

[0143] References

[0144] [1] Shi Z , Yang P , Tao F ,et al.New insight into the structure ofCeO2–TiO2 mixed oxides and their excellent catalytic performances for 1,2-dichloroethane oxidation[J].Chemical Engineering Journal, 2016, 295:99-108.

Claims

1. The application of a hydrogen dehalogenation catalyst in the hydrogen dechlorination reaction of 1,2-dichloroethane, characterized in that: The hydrogen dehalogenation catalyst is a bimetallic catalyst, where the bimetal is represented by metal A and metal B, and metal A and metal B are different. Metal A is selected from Pd, Pt, or Ru, and metal B is selected from any one of Ni, Co, Cu, Fe, and Zn. The total loading of metal A and metal B in the hydrogen dehalogenation catalyst is 0.3-3 wt%, and the loading ratio of metal A to metal B is 1:2-1:

8. The preparation method of the hydrogen dehalogenation catalyst is as follows: using soluble salts of metal A and metal B as precursors, uniformly dissolving them in a... A metal precursor solution was prepared in deionized water, and then a solvent and surfactant were added and mixed evenly to obtain an impregnation solution. The impregnation solution was then mixed with a support, and soluble salts of metal A and metal B were loaded onto the support through impregnation. After the impregnated support was dried, it was placed in a microwave drying oven with a microwave power of 100-1000W, a frequency of 1-4GHz, a wavelength of 7.5cm-30cm, and a heating time of 0.5min-20min. Nitrogen gas was used as a protective gas with a flow rate of 30-50ml / min to finally obtain the hydrogen dehalogenation catalyst. The solvent is deionized water, methanol, concentrated hydrochloric acid, 0.05 g / ml - 0.1 g / ml of ethylenediaminetetraacetic acid disodium aqueous solution, 0.3 g / ml - 0.6 g / ml of citric acid aqueous solution, 0.5 g / ml - 1.0 g / ml of urea aqueous solution, or 0.1 g / ml - 0.2 g / ml of glycine aqueous solution; The surfactant is hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, or sodium dodecylbenzenesulfonate.

2. The application as described in claim 1, characterized in that: The carrier is activated carbon, alumina, or silicon dioxide.

3. The application as described in claim 1, characterized in that: The impregnation solution contains 0.1-2 wt% metal A ions and 0.001-0.005 M surfactant.

4. The application as described in claim 1, characterized in that: The total loading of metal A and metal B in the hydrogen dehalogenation catalyst is 0.3-1 wt%.

5. The application as described in claim 1, characterized in that: The process of "mixing the impregnation solution with the carrier and loading the soluble salts of metal A and metal B onto the carrier through impregnation" is specifically carried out as follows: the carrier is first dehydrated by vacuum drying at 60-90℃ for 1-3 hours, and the carrier is quickly added to the impregnation solution while maintaining the temperature. The carrier is then gradually cooled to room temperature during the impregnation process, and the impregnation time is 0.5-3 hours.

6. The application as described in any one of claims 1-5, characterized in that: The specific application is as follows: The hydrodehalogenation catalyst is loaded into a fixed-bed reactor. Inert gas is introduced to fully replace the air in the fixed-bed reactor. After maintaining this for a certain time, hydrogen is introduced at a flow rate of 3-20 mL / min, maintaining an H2 / N2 flow ratio of 1:1-1:

10. After a certain period of gas introduction, catalyst pre-activation is performed: keeping the previous gas flow rate constant, the fixed-bed reactor is heated from room temperature to 250-400℃ at a rate of 3-10℃ / min, and held at this temperature for 1-3 hours to complete pre-activation. Then, the gas is switched to equilibrium gas. Once the reactor temperature is adjusted to the reaction temperature (200-350℃), the feed is introduced via bubbling. The raw material 1,2-dichloroethane, hydrogen, and equilibrium gas are mixed evenly and then passed through the catalyst bed. Under the action of the catalyst, 1,2-dichloroethane undergoes a hydrodehalogenation reaction to produce ethane.

7. The application as described in claim 6, characterized in that: The pre-activation conditions were as follows: hydrogen gas flow rate of 5-10 mL / min, H2 / N2 flow ratio of 1:2-1:5, heating rate of 5℃ / min, reduction temperature of 300-400℃, and constant temperature for 2 hours.

8. The application as described in claim 6, characterized in that: The molar ratio of the raw material hydrogen to 1,2-dichloroethane is controlled to be 2-15:

1.

9. The application as described in claim 6, characterized in that: The reaction temperature is 250-350℃; the space velocity is controlled at 1500-10000 h⁻¹. -1 .

10. The application as described in claim 9, characterized in that: The reaction temperature was 280-350℃; the space velocity was controlled at 5000-10000 h⁻¹. -1 .

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