Chlorine-doped nickel / activated carbon catalyst, its preparation method and application

Abstract

The application provides a chlorine-doped nickel / activated carbon catalyst and a preparation method and application thereof, and particularly relates to the field of catalysis technology. The chlorine-doped nickel / activated carbon catalyst prepared by the application comprises nickel / activated carbon and chlorine elements doped in the nickel / activated carbon, the nickel / activated carbon comprises activated carbon and nickel particles loaded on the surface of the activated carbon; and the mass ratio of chlorine to nickel in the chlorine-doped nickel / activated carbon catalyst is 0.5-1.3:100. The electronic interaction between nickel and activated carbon is effectively improved by chlorine doping, and the stability of the nickel / activated carbon is strengthened. Experimental results show that the chlorine-doped nickel / activated carbon catalyst provided by the application has good catalytic stability and catalytic activity, the nickel content in the catalyst is only reduced by 13.7% after 30 hours of reaction, the carbon deposition amount is 24.9%, and the conversion rate of ethanol is still above 70%.

Description

Technical Field

[0001] This invention belongs to the field of catalysis technology, specifically relating to a chlorine-doped nickel / activated carbon catalyst, its preparation method, and its application. Background Technology

[0002] Propionic acid and its derivatives are important chemical products and organic synthesis intermediates, used in the preservation of food and feed, as well as in the synthesis of plastics, pharmaceuticals, pesticides, and fragrances. With the rapid development of China's food, feed, pesticide, and fragrance industries, the demand for propionic acid is expected to continue to grow.

[0003] Under normal pressure conditions, propionic acid and ethyl propionate are synthesized via heterogeneous carbonylation using ethanol, iodoethane, and CO as raw materials. This method overcomes the drawbacks of homogeneous carbonylation catalysts, such as high cost, harsh conditions, and difficult separation, and offers advantages such as low reaction temperature, low operating pressure, and low equipment requirements. Currently, heterogeneous carbonylation catalyst systems mainly consist of noble metal and non-noble metal-based catalysts. Catalysts with noble metals such as Rh, Ir, Re, and Au as active components exhibit good performance in the gas-phase carbonylation of alcohols, but suffer from high costs. Activated carbon-supported nickel-based non-noble metal catalysts offer the advantage of low cost, and electron transfer exists between activated carbon and Ni species. During the reaction, elemental nickel interacts with iodoethane, undergoing oxidative addition to form C2H5-Ni. 2+ -I intermediate substance, then CO migrates and inserts to form C2H5CO-Ni 2+ The -I intermediate eventually undergoes reductive elimination under the action of H2O or C2H5OH to generate propionic acid (C2H5COOH) or ethyl propionate (C2H5COOC2H5). The presence of activated carbon accelerates the redox cycle in the reaction. Therefore, activated carbon-supported nickel catalysts have good activity for the carbonylation of alcohols and have broad application prospects.

[0004] However, nickel / activated carbon catalysts suffer from problems such as loss, aggregation, and carbon deposition of nickel active components, resulting in poor catalyst stability and greatly limiting their industrial application. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a chlorine-doped nickel / activated carbon catalyst, its preparation method, and its application. The chlorine-doped nickel / activated carbon catalyst provided by this invention exhibits good stability and can be applied to the carbonylation of gas-phase ethanol to synthesize propionic acid and its derivatives.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] The present invention provides a chlorine-doped nickel / activated carbon catalyst, comprising nickel / activated carbon and chlorine element doped in the nickel / activated carbon, wherein the nickel / activated carbon comprises activated carbon and nickel particles supported on the surface of the activated carbon;

[0008] The mass ratio of chlorine to nickel in the chlorine-doped nickel / activated carbon catalyst is 0.5–1.3:100.

[0009] Preferably, the nickel content in the chlorine-doped nickel / activated carbon catalyst is 5-15% by mass.

[0010] This invention also provides a method for preparing the chlorine-doped nickel / activated carbon catalyst described in the above technical solution, comprising the following steps:

[0011] A nickel source and a chlorine source are dissolved in water to obtain a mixed solution, wherein the molar ratio of chlorine to nickel in the mixed solution is 2 to 8:1;

[0012] Activated carbon is impregnated into the mixed solution, dried, and calcined to obtain a catalyst precursor;

[0013] The catalyst precursor was reduced in a hydrogen-nitrogen mixed atmosphere to obtain the chlorine-doped nickel / activated carbon catalyst.

[0014] Preferably, the molar ratio of nickel to activated carbon in the nickel source is 0.005–0.013 mol: 5 g.

[0015] Preferably, the nickel source includes nickel acetate, nickel nitrate, or nickel sulfate;

[0016] The chlorine source includes ammonium chloride, sodium chloride, potassium chloride, or hydrochloric acid.

[0017] Preferably, the calcination temperature is 400–550°C and the time is 3–6 hours.

[0018] Preferably, the reduction temperature is 400–500°C and the time is 3–6 hours.

[0019] Preferably, the volume percentage of hydrogen in the hydrogen-nitrogen mixed atmosphere is 5-25%.

[0020] Preferably, the flow rate of the hydrogen-nitrogen mixed atmosphere is 20-60 mL / min.

[0021] The present invention also provides the application of the chlorine-doped nickel / activated carbon catalyst prepared by the above technical solution in the gas-phase ethanol carbonylation reaction to synthesize propionic acid and ethyl propionate.

[0022] This invention provides a chlorine-doped nickel / activated carbon catalyst, comprising nickel / activated carbon and chlorine doped in the nickel / activated carbon. The nickel / activated carbon includes activated carbon and nickel particles supported on the surface of the activated carbon. The mass ratio of chlorine to nickel in the chlorine-doped nickel / activated carbon catalyst is 0.5–1.3:100. This invention effectively enhances the electronic interaction between nickel and activated carbon through chlorine doping, enabling the prepared catalyst to effectively suppress the loss, aggregation, and carbon deposition of the nickel active component during the carbonylation of gas-phase ethanol, thereby improving the catalyst's stability and achieving long-term stable catalysis. Experimental results show that the chlorine-doped nickel / activated carbon catalyst provided by this invention has good catalytic stability and activity. After 30 hours of reaction, the nickel content in the catalyst decreases by only 13.7%, the carbon deposition is 24.9%, the ethanol conversion rate remains above 70%, and the combined selectivity for propionic acid and ethyl propionate is 40–50%. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 The above are H2-TPR diagrams of the catalysts prepared in Example 3 and Comparative Examples 1-2.

[0025] Figure 2 This is a transmission electron microscope (TEM) image of the catalyst prepared in Example 3 after 30 hours of reaction.

[0026] Figure 3 The image is a transmission electron microscope (TEM) image of the catalyst prepared in Comparative Example 1 after 30 hours of reaction.

[0027] Figure 4 This is a transmission electron microscope (TEM) image of the catalyst prepared in Comparative Example 2 after 30 hours of reaction. Detailed Implementation

[0028] The present invention provides a chlorine-doped nickel / activated carbon catalyst, comprising nickel / activated carbon and chlorine element doped in the nickel / activated carbon, wherein the nickel / activated carbon comprises activated carbon and nickel particles supported on the surface of the activated carbon;

[0029] The mass ratio of chlorine to nickel in the chlorine-doped nickel / activated carbon catalyst is 0.5–1.3:100.

[0030] In this invention, unless otherwise specified, all raw materials and equipment used are commercially available products well known in the art.

[0031] In this invention, the mass ratio of chlorine to nickel in the chlorine-doped nickel / activated carbon catalyst is 0.5–1.3:100, preferably 0.8–1.2:100, and more preferably 1.0–1.1:100. In specific embodiments of this invention, the mass ratios of chlorine to nickel in the chlorine-doped nickel / activated carbon catalyst are 0.85:100, 1.00:100, 1.15:100, and 1.16:100, respectively.

[0032] In this invention, the nickel content in the chlorine-doped nickel / activated carbon catalyst is preferably 5-15%, more preferably 8-12%, and even more preferably 10-11%.

[0033] In this invention, the mesh size of the activated carbon is preferably 20 to 40 mesh.

[0034] In the chlorine-doped nickel / activated carbon catalyst obtained by this invention, the doping of chlorine effectively improves the electronic interaction between nickel and activated carbon, enhances the stability of nickel / activated carbon, and enables the prepared catalyst to effectively suppress the loss, aggregation and carbon deposition of nickel active components during the carbonylation of gas-phase ethanol, thereby achieving long-term stable catalysis.

[0035] This invention also provides a method for preparing the chlorine-doped nickel / activated carbon catalyst described in the above technical solution, comprising the following steps:

[0036] A nickel source and a chlorine source are dissolved in water to obtain a mixed solution, wherein the molar ratio of chlorine to nickel in the mixed solution is 2 to 8:1;

[0037] Activated carbon is impregnated into the mixed solution, dried, and calcined to obtain a catalyst precursor;

[0038] The catalyst precursor was reduced in a hydrogen-nitrogen mixed atmosphere to obtain the chlorine-doped nickel / activated carbon catalyst.

[0039] The present invention dissolves a nickel source and a chlorine source in water to obtain a mixed solution, wherein the molar ratio of chlorine to nickel in the mixed solution is 2 to 8:1.

[0040] In this invention, the nickel source preferably includes nickel acetate, nickel nitrate, nickel sulfate, or nickel chloride, more preferably nickel acetate and nickel chloride, and even more preferably nickel acetate. The chlorine source preferably includes ammonium chloride, sodium chloride, potassium chloride, or hydrochloric acid, more preferably hydrochloric acid. The molar ratio of chlorine to nickel in the mixed solution is preferably 4-6:1. This invention does not have special requirements for the mixing; any method well-known in the art that can mix the components uniformly is acceptable, such as stirring or ultrasonication. This invention does not have special requirements for the amount of water used, as long as it is sufficient to completely dissolve the nickel and chlorine sources and ensure that the resulting mixed solution completely submerges the activated carbon.

[0041] After obtaining the mixed solution, the present invention impregnates activated carbon into the mixed solution, dries it, and calcines it to obtain a catalyst precursor.

[0042] In this invention, the molar ratio of nickel in the nickel source to the mass ratio of activated carbon is preferably 0.005–0.013 mol:5 g, more preferably 0.008–0.010 mol:5 g. This invention does not have special requirements for the impregnation method of activated carbon; any impregnation method well-known to those skilled in the art can be used. In a specific embodiment of this invention, impregnation is performed under ultrasonic conditions.

[0043] In this invention, the drying process is preferably performed by first drying under an infrared lamp, followed by a second drying in an oven. Preferably, the infrared lamp has a wattage of 500W, and the first drying time is preferably 30–60 minutes, more preferably 35–45 minutes. The first drying is preferably performed under stirring conditions. This invention utilizes an infrared lamp for drying first, resulting in a faster drying speed. Simultaneously, stirring during the drying process ensures a more uniform distribution of the nickel and chlorine sources loaded onto the activated carbon.

[0044] In this invention, the temperature of the second drying is preferably 80-150°C, more preferably 90-120°C, and the time is preferably 6-12 hours, more preferably 8-10 hours.

[0045] In this invention, the calcination temperature is preferably 400–550°C, more preferably 450–500°C, the calcination time is preferably 3–6 h, more preferably 4–5 h, and the heating rate is preferably 2–10°C / min, more preferably 5–6°C / min. The calcination in this invention is preferably carried out in a nitrogen atmosphere. This invention converts a nickel source into nickel oxide and nickel chloride through calcination.

[0046] After obtaining the catalyst precursor, the present invention reduces the catalyst precursor in a hydrogen-nitrogen mixed atmosphere to obtain the chlorine-doped nickel / activated carbon catalyst.

[0047] In this invention, the volume percentage of hydrogen in the hydrogen-nitrogen mixed atmosphere is preferably 5-25%, more preferably 15-20%. In a specific embodiment of this invention, the volume ratio of hydrogen to nitrogen in the hydrogen-nitrogen mixed atmosphere is 1:4. In this invention, the flow rate of the hydrogen-nitrogen mixed atmosphere is preferably 20-60 mL / min, more preferably 30-50 mL / min. This invention utilizes hydrogen to reduce nickel oxide supported on activated carbon to elemental nickel.

[0048] In this invention, the reduction temperature is preferably 400–500°C, more preferably 440–480°C, and the reduction time is preferably 3–6 hours, more preferably 4–5 hours. This invention does not have special requirements for the reduction method; any reduction method well-known to those skilled in the art can be used. In a specific embodiment of this invention, the reduction is carried out in a tube furnace. Through reduction, nickel oxide and nickel chloride in the catalyst are reduced to nickel nanoparticles, while chloride is adsorbed onto activated carbon in ionic form. Under the action of chloride ions, the electronic interaction between nickel and activated carbon is enhanced, thereby increasing the stability of the catalyst.

[0049] The present invention also provides the application of the chlorine-doped nickel / activated carbon catalyst described above in the gas-phase ethanol carbonylation reaction to synthesize propionic acid and ethyl propionate.

[0050] In this invention, the reaction raw materials for the gas-phase ethanol carbonylation synthesis of propionic acid and ethyl propionate include ethanol, iodoethane, and carbon monoxide.

[0051] In this invention, the preferred temperature for the gas-phase ethanol carbonylation reaction to synthesize propionic acid and ethyl propionate is 220°C, and the preferred time is 4 hours; the preferred molar ratio of ethanol to iodoethane is 10:1, and the preferred total space velocity of ethanol and iodoethane is 0.5 L / (kg·L· ... cat ·h) -1 The preferred space velocity of CO is 1200 L / (kg·K). cat ·h) -1 .

[0052] The present invention does not have any special requirements for the specific implementation method of the gas-phase ethanol carbonylation reaction to synthesize propionic acid and ethyl propionate. Any implementation method well known in the art can be used. In the embodiments of the present invention, a chlorine-doped nickel / activated carbon catalyst is placed in the isothermal section of the reaction tube, and the bed is filled with quartz sand as support. Ethanol and iodoethane are made into a mixed solution, heated to 120°C, and introduced into the reactor. Then CO is introduced into the reactor, and the reaction is carried out at 220°C for 4 hours. The gaseous products are detected online, and the liquid products are detected offline after condensation.

[0053] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. The described embodiments are only some embodiments of the present invention, and not all embodiments. Any modifications, equivalent substitutions, improvements, etc., made to the embodiments of the present invention based on the technical essence and general principles of the present invention without creative effort should be within the protection scope of the present invention.

[0054] Example 1

[0055] 2.35 g of nickel acetate Ni(CH3COO)2·4H2O and 1.86 g of hydrochloric acid (mass fraction 37%) were mixed with 6 mL of deionized water to obtain a mixed solution in which the molar ratio of chlorine to nickel was 2:1.

[0056] The obtained mixed solution was mixed with 5.00 g of 20-40 mesh activated carbon and sonicated for 30 min. The mixture was then dried under a 500 W infrared lamp with stirring for 30 min, and finally dried at 120 °C for 12 h. The dried sample was placed in a tube furnace, and N2 gas was introduced to raise the temperature from room temperature to 450 °C at a rate of 5 °C / min. The mixture was calcined for 3 h to obtain a chlorine-doped nickel / activated carbon catalyst precursor.

[0057] The chlorine-doped nickel / activated carbon catalyst precursor was reduced at 400℃ for 3 hours in a mixed atmosphere of hydrogen / nitrogen with a volume ratio of 1:4 to obtain the chlorine-doped nickel / activated carbon catalyst. The mass content of nickel in the catalyst was determined to be 10.51% by inductively coupled plasma optical emission spectrometer (ICP-OES).

[0058] Example 2

[0059] 2.35 g of nickel acetate Ni(CH3COO)2·4H2O and 3.72 g of hydrochloric acid (mass fraction 37%) were mixed with 6 mL of deionized water to obtain a mixed solution in which the molar ratio of chlorine to nickel was 4:1.

[0060] The obtained mixed solution was mixed with 5.00 g of 20-40 mesh activated carbon and sonicated for 30 min. The mixture was then dried under a 500 W infrared lamp with stirring for 60 min, and finally dried at 80 °C for 12 h. The dried sample was placed in a tube furnace and calcined at 2 °C / min from room temperature to 400 °C for 6 h to obtain a chlorine-doped nickel / activated carbon catalyst precursor.

[0061] The chlorine-doped nickel / activated carbon catalyst precursor was reduced at 400℃ for 3 hours in a mixed atmosphere of hydrogen / nitrogen with a volume ratio of 1:4 to obtain the chlorine-doped nickel / activated carbon catalyst with a nickel loading of 10.60%.

[0062] Example 3

[0063] 2.35 g of nickel acetate Ni(CH3COO)2·4H2O and 5.58 g of hydrochloric acid (mass fraction 37%) were mixed with 6 mL of deionized water to obtain a mixed solution in which the molar ratio of chlorine to nickel was 6:1.

[0064] The obtained mixed solution was mixed with 5.00 g of 20-40 mesh activated carbon and sonicated for 30 min. The mixture was then stirred and dried under a 500 W infrared lamp for 40 min, and finally dried at 150 °C for 6 h. The dried sample was placed in a tube furnace and calcined at 450 °C from room temperature for 4 h with N2 gas at a heating rate of 10 °C / min to obtain a chlorine-doped nickel / activated carbon catalyst precursor.

[0065] The chlorine-doped nickel / activated carbon catalyst precursor was reduced at 400℃ for 3 hours in a mixed atmosphere of hydrogen / nitrogen with a volume ratio of 1:4 to obtain the chlorine-doped nickel / activated carbon catalyst with a nickel loading of 10.73%.

[0066] Example 4

[0067] 2.35 g of nickel acetate Ni(CH3COO)2·4H2O and 3.03 g of ammonium chloride were mixed with 6 mL of deionized water to obtain a mixed solution in which the molar ratio of chlorine to nickel was 6:1.

[0068] The obtained mixed solution was mixed with 5.00 g of 20-40 mesh activated carbon and sonicated for 30 min. The mixture was then stirred and dried under a 500 W infrared lamp for 30 min, and finally dried at 120 °C for 8 h. The dried sample was placed in a tube furnace, and N2 gas was introduced to raise the temperature from room temperature to 500 °C at a rate of 5 °C / min. The mixture was calcined for 3 h to obtain a chlorine-doped nickel / activated carbon catalyst precursor.

[0069] The chlorine-doped nickel / activated carbon catalyst precursor was reduced at 400℃ for 3 hours in a mixed atmosphere of hydrogen / nitrogen with a volume ratio of 1:4 to obtain the chlorine-doped nickel / activated carbon catalyst with a nickel loading of 10.66%.

[0070] Comparative Example 1

[0071] 2.35g of nickel acetate Ni(CH3COO)2·4H2O was mixed with 6mL of deionized water to obtain a mixed solution.

[0072] The obtained mixed solution was mixed with 5.00 g of 20-40 mesh activated carbon and sonicated for 30 min. The mixture was then stirred and dried under a 500 W infrared lamp for 30 min, and finally dried at 120 °C for 12 h. The dried sample was placed in a tube furnace, and N2 gas was introduced to raise the temperature from room temperature to 450 °C at a rate of 5 °C / min. The mixture was calcined for 3 h to obtain the nickel / activated carbon catalyst precursor.

[0073] The chlorine / activated carbon catalyst precursor was reduced at 400°C for 3 hours in a mixed atmosphere of hydrogen / nitrogen with a volume ratio of 1:4 to obtain a nickel / activated carbon catalyst.

[0074] Comparative Example 2

[0075] 2.35 g of nickel acetate Ni(CH3COO)2·4H2O and 1.75 g of nitric acid (mass fraction 68%) were mixed with 6 mL of deionized water to obtain a mixed solution.

[0076] The obtained mixed solution was mixed with 5.00 g of 20-40 mesh activated carbon and sonicated for 30 min. The mixture was then stirred and dried under a 500 W infrared lamp for 30 min, and finally dried at 120 °C for 12 h. The dried sample was placed in a tube furnace, and N2 gas was introduced to raise the temperature from room temperature to 450 °C at a rate of 5 °C / min. The mixture was calcined for 3 h to obtain the nickel / activated carbon catalyst precursor.

[0077] The nickel / activated carbon catalyst precursor was reduced at 400°C for 3 hours in a mixed atmosphere of hydrogen / nitrogen with a volume ratio of 1:4 to obtain the nickel / activated carbon catalyst.

[0078] Comparative Example 3

[0079] Mix 2.25g of nickel chloride (NiCl2·6H2O) with 6mL of deionized water to obtain a mixed solution.

[0080] The obtained mixed solution was mixed with 5.00 g of 20-40 mesh activated carbon and sonicated for 30 min. The mixture was then dried under a 500 W infrared lamp with stirring for 30 min, and finally dried at 120 °C for 12 h. The dried sample was placed in a tube furnace, and N2 gas was introduced to raise the temperature from room temperature to 450 °C at a rate of 5 °C / min. The mixture was calcined for 3 h to obtain a chlorine-doped nickel / activated carbon catalyst precursor.

[0081] The chlorine-doped nickel / activated carbon catalyst precursor was reduced at 400℃ for 3 hours in a mixed atmosphere of hydrogen / nitrogen with a volume ratio of 1:4 to obtain the chlorine-doped nickel / activated carbon catalyst.

[0082] The catalysts prepared in Examples 1-4 and Comparative Examples 1-3 were used for the gas-phase carbonylation of ethanol to synthesize propionic acid and ethyl propionate. The specific operating conditions were as follows: 2.0 g of catalyst was weighed and placed in the isothermal section of the reaction tube, with quartz sand filling the bed for support. A mixed solution of ethanol and iodoethane at a molar ratio of 10:1 was prepared and heated to 120°C. The mixture was then flowed at a space velocity of 0.5 L / (kg·K⁻¹). cat ·h) -1 CO is introduced into the reactor at a space velocity of 1200 L / (kg·K). cat ·h) -1 The catalyst was introduced into the reactor and reacted at 220℃ for 4 hours. The gaseous products were then analyzed online and separated from γ-Al₂O₃ (30m × 0.53mm × 10.0μm) using FID (Fluorescent Identification). The liquid products were condensed and analyzed offline using a Porapak Q packed column and TCD (Transient Catalyst Diode) for separation. The catalyst performance test results are the average values ​​over 4 hours.

[0083] Table 1. Results of the gas-phase ethanol carbonylation reaction of the catalysts prepared in Examples 1-4 and Comparative Examples 1-3.

[0084]

[0085] Table 1 shows that the chlorine-doped nickel / activated carbon catalyst prepared by the method of the present invention exhibits good stability. In Comparative Example 1, the yields of propionic acid and ethyl propionate decreased by 31.7% and 57.6% after 20 and 30 hours of reaction, respectively. The chlorine-doped nickel / activated carbon catalysts (i.e., the catalysts of Examples 1-4) showed significantly smaller decreases in the yields of propionic acid and ethyl propionate compared to Comparative Example 1. Hydrochloric acid impregnation lowers the pH of the impregnation solution. To eliminate the influence of the impregnation solution's pH on the catalyst activity, Comparative Example 2 catalyst, impregnated with nitric acid at the same pH as in Example 1, was prepared. Table 1 shows that in Comparative Example 2, the yields of propionic acid and ethyl propionate decreased by 29.3% and 55.0% after 20 and 30 hours of reaction, respectively. In contrast, the yields of propionic acid and ethyl propionate in Example 1 decreased by 20.1% and 42.0% after 20 and 30 hours of reaction, respectively, indicating that chlorine doping effectively improves the catalyst's stability. Furthermore, the stability of the catalyst increased with increasing chlorine doping concentration. In Example 2, the yields of propionic acid and ethyl propionate decreased by 18.2% and 31.6% after 20 and 30 hours of reaction, respectively. In Example 3, the yields of propionic acid and ethyl propionate decreased by 9.3% and 26.2% after 20 and 30 hours of reaction, respectively. However, when the chlorine source was changed from hydrochloric acid to ammonium chloride (Example 4), the yields of propionic acid and ethyl propionate decreased by 14.7% and 26.9% after 20 and 30 hours of reaction, respectively, with a slightly higher deactivation rate than the catalyst using hydrochloric acid as the chlorine source. After direct impregnation with nickel chloride, the yields of propionic acid and ethyl propionate decreased by 28.9% and 55.0% after 20 and 30 hours of reaction, respectively, with a significantly higher deactivation rate than the catalyst using hydrochloric acid and ammonium chloride as the chlorine source. This may be because chlorine and nickel exist in a stoichiometric ratio in the catalyst, and the chlorine is removed during the calcination and reduction processes, thus the catalyst stability is not improved.

[0086] The nickel content in the catalysts prepared in Example 3 and Comparative Examples 1-2 was tested using inductively coupled plasma optical emission spectrometer (ICP-OES), and the results are shown in Table 2.

[0087] Table 2 Comparison of nickel content in the catalysts prepared in Example 3 and Comparative Examples 1-2

[0088]

[0089] Table 2 shows that the nickel content of the catalyst in Comparative Example 1 decreased from 10.49% to 7.14% after 30 hours of reaction, a reduction of 31.9%; the nickel content of the catalyst in Comparative Example 2 decreased from 11.14% to 7.52% after 30 hours of reaction, a reduction of 31.4%; while the nickel / activated carbon catalyst doped with chlorine in Example 3 decreased from 10.73% to 9.26% after 30 hours of reaction, a reduction of only 13.7%, which is far lower than the rate of nickel loss in the chlorine-free catalysts in Comparative Examples 1 and 2.

[0090] The mass of chlorine and nickel in the reduced catalyst was determined by scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and the results are shown in Table 3.

[0091] Table 3 shows the mass ratio of chlorine to nickel in the catalysts prepared in Examples 1-4.

[0092]

[0093] Table 2 shows that the mass ratio of chlorine to nickel in the catalysts prepared in Examples 1 to 4 is between 0.85 and 1.16:100.

[0094] Figure 1 The images show the H2-TPR diagrams of the catalysts prepared in Example 3 and Comparative Examples 1-2. Figure 1 As can be seen, the reduction peak temperature of the catalyst prepared in Example 3 is significantly higher than that of the catalysts prepared in Comparative Examples 1 and 2, indicating that the interaction between nickel and the support in the catalyst prepared in Example 3 is stronger than that in the catalysts prepared in Comparative Examples 1 and 2. The chlorine-doped nickel / activated carbon catalyst prepared in this invention exhibits strong interaction between nickel and the support due to the effect of chlorine, thus possessing excellent ability to suppress nickel loss and improving the stability of the catalyst during the reaction process.

[0095] The amount of carbon deposited after reaction of the catalysts prepared in Example 3 and Comparative Examples 1-2 was determined by a synchronous thermal analyzer, and the results are shown in Table 4.

[0096] Table 4 Comparison of carbon deposition after reaction of catalysts prepared in Example 3 and Comparative Examples 1-2

[0097]

[0098] As can be seen from Table 4, the carbon deposition of the chlorine-doped nickel / activated carbon catalyst prepared in Example 3 was 24.9% after 30 hours of reaction, which was significantly lower than the carbon deposition of 28.2% in Comparative Example 1 and 30.6% in Comparative Example 2.

[0099] Figure 2 This is a transmission electron microscope (TEM) image of the catalyst prepared in Example 3 after reacting for 30 hours. Figure 3The image is a transmission electron microscope (TEM) image of the catalyst prepared in Comparative Example 1 after 30 hours of reaction. Figure 4 This is a transmission electron microscope (TEM) image of the catalyst prepared in Comparative Example 2 after 30 hours of reaction. Figures 2-4 It can be seen that, compared with the catalyst without chlorine doping, the degree of nickel aggregation of the chlorine-doped nickel / activated carbon catalyst prepared in Example 3 after 30 hours of reaction is significantly lower than that of the catalysts prepared in Comparative Examples 1 and 2 without chlorine doping. This indicates that there is a strong interaction between nickel and the support in the catalyst, which can effectively inhibit the migration and aggregation of nickel during the reaction.

[0100] As can be seen from the above examples and comparative examples, the chlorine-doped nickel / activated carbon catalyst prepared by the present invention has good activity in the synthesis of propionic acid and ethyl propionate in the carbonylation of gas-phase ethanol. Under the action of chlorine, nickel and support in the catalyst have strong interaction, which can inhibit the loss and aggregation of nickel active components and has a certain anti-carbon deposition ability, thus greatly improving the stability of the catalyst.

[0101] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. The application of a chlorine-doped nickel / activated carbon catalyst in the gas-phase carbonylation of ethanol to synthesize propionic acid and ethyl propionate, wherein the chlorine-doped nickel / activated carbon catalyst comprises nickel / activated carbon and chlorine element doped in the nickel / activated carbon, wherein the nickel / activated carbon comprises activated carbon and nickel particles supported on the surface of the activated carbon; The mass ratio of chlorine to nickel in the chlorine-doped nickel / activated carbon catalyst is 1~1.3:100; The preparation method of the chlorine-doped nickel / activated carbon catalyst includes the following steps: A nickel source and a chlorine source are dissolved in water to obtain a mixed solution, wherein the molar ratio of chlorine to nickel in the mixed solution is 4~8:1; Activated carbon is impregnated into the mixed solution, dried, and calcined to obtain a catalyst precursor; The catalyst precursor was reduced in a hydrogen-nitrogen mixed atmosphere to obtain the chlorine-doped nickel / activated carbon catalyst.

2. The application according to claim 1, characterized in that, The nickel content in the chlorine-doped nickel / activated carbon catalyst is 5-15% by mass.

3. The application according to claim 1, characterized in that, The molar ratio of nickel to activated carbon in the nickel source is 0.005~0.013 mol: 5g.

4. The application according to claim 1, characterized in that, The nickel source includes nickel acetate, nickel nitrate, or nickel sulfate; The chlorine source includes ammonium chloride, sodium chloride, potassium chloride, or hydrochloric acid.

5. The application according to claim 1, characterized in that, The calcination temperature is 400~550℃, and the time is 3~6h.

6. The application according to claim 1, characterized in that, The reduction temperature is 400~500℃, and the time is 3~6h.

7. The application according to claim 1, characterized in that, The hydrogen-nitrogen mixed atmosphere has a hydrogen volume percentage of 5-25%.

8. The application according to claim 1 or 7, characterized in that, The flow rate of the hydrogen-nitrogen mixed atmosphere is 20~60 mL / min.

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