An eggshell type catalyst, its preparation method and application

Abstract

The application provides an eggshell type catalyst and a preparation method and application thereof. The eggshell type catalyst comprises an active component, an auxiliary active component and a carrier, the active component comprises PdCl2, the PdCl2 is loaded on the surface layer of the carrier, and the auxiliary active component comprises CuCl2, the CuCl2 is loaded on the surface and the inside of the carrier. Based on the structural characteristics of the eggshell type catalyst, the utilization efficiency of the noble metal Pd is high, the economic benefit is good, the auxiliary active component CuCl2 has good valence stability on the Pd, and the eggshell type catalyst has good selectivity and space-time yield in the reaction of low-pressure gas-phase synthesis of dimethyl carbonate from CO and methyl nitrite.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalysts, and particularly relates to a shell-type catalyst and a preparation method and application thereof. BACKGROUND

[0002] In recent years, the development of new energy vehicles has rapidly increased the demand for high-end carbonate products, thereby driving the market demand for dimethyl carbonate (DMC).

[0003] The explosion of DMC demand has led to attention and development of DMC synthesis technology. Existing DMC synthesis processes mainly include ester exchange method, urea method, oxalate decarboxylation method, and methanol gas-phase oxidative carbonylation method. At present, the ester exchange method is mainly used as the production process in China. Due to the fact that the raw material ethylene / propylene oxide in the ester exchange method is restricted by the petrochemical industry, the unit volume equipment capacity is low, and it is difficult to meet the increasing demand for DMC. The CO carbonylation gas-phase method uses CO and methyl nitrite to synthesize dimethyl carbonate at low pressure in the gas phase. The raw material synthesis gas used in this process ultimately comes from coal, and China is rich in coal resources, with a clear energy advantage. In addition, this technology has a significant advantage in large-scale production due to its low raw material cost and fewer product impurities.

[0004] Japan Ubos early developed the methanol gas-phase oxidative carbonylation method for synthesizing dimethyl carbonate and was successful. In 1992, the first 3,000-ton dimethyl carbonate production device was built, and in 1996, the capacity was expanded to 6,000 tons. Domestic institutions such as the Fujian Institute of Research on Structure of Matter of the Chinese Academy of Sciences and Tianjin University have carried out in-depth research on the methanol gas-phase oxidative carbonylation method for synthesizing dimethyl carbonate. Guo Guodong et al. of the Fujian Institute of Research on Structure of Matter proposed a Cu 2+ and Cl -The reaction intermediate C1-Pd(II)-COOCH3 is a key to the generation of DMC in the reaction, the Pd element in the catalyst needs to maintain a +2 valence state in the reaction; in addition, it is also proposed that the Pd / NaY molecular sieve catalyst with a new structure has excellent activity. Ma Xinbin of Tianjin University designed various new carbonylation catalysts, such as a new catalyst PdCl2-CuCl2-KCl / AC added with an additive KCl, a PdCl2-CuCl2 / Li-Al-O catalyst using a new carrier, and the like, which perform excellently in the catalytic reaction. CN99100460.4 proposes a process for synthesizing dimethyl carbonate at low pressure of carbon monoxide, uses Pd / NaY molecular sieve as a catalyst, and proposes a synthesis, regeneration reaction and coupling matching, alcohol and water separation, and product dimethyl carbonate separation and refining process; CN202111653375.4 further proposes a dimethyl carbonate synthesis catalyst prepared by using a microporous structure carrier, and high activity and selectivity are obtained. In addition, CN201710652161.2 proposes a wacker type catalyst for gas phase synthesis of dimethyl carbonate from CO and methyl nitrite at low temperature and low pressure, and CN201911387258.0 proposes a dimethyl carbonate and synthesis catalyst using spinel as a carrier to improve the activity of the catalyst. At present, there are many research results for improving the activity of the catalyst, but there are few researches on improving the utilization rate of the noble metal Pd. SUMMARY

[0005] To solve all or part of the above technical problems, the present application provides the following technical solutions:

[0006] One of the purposes of the present application is to provide an eggshell type catalyst, which comprises an active component, an auxiliary active component and a carrier, the active component comprises PdCl2, the PdCl2 is loaded on the surface layer of the carrier, and the auxiliary active component comprises CuCl2, the CuCl2 is loaded on the surface and the inside of the carrier.

[0007] The eggshell type catalyst has the advantages that the structure of the eggshell type catalyst is beneficial to reducing the diffusion distance of the reactants in the pores of the catalyst, improving the adsorption and desorption efficiency, and improving the catalytic activity; the PdCl2 is loaded on the surface layer of the carrier, which can improve the utilization rate of the noble metal Pd and effectively reduce the amount of the noble metal Pd; the presence of the CuCl2 can transfer the C1 in the CuCl2 to the PdCl2 when the PdCl2 is reduced and loses C1, thereby stabilizing the valence state of the Pd element and improving the selectivity and stability of the catalyst; the CuCl2 is loaded on the surface and the inside of the carrier, that is, the CuCl2 is distributed in the whole catalyst, and this distribution mode can improve the loading amount and the migration amount of the CuCl2 and improve the valence state stabilization effect of the Pd.

[0008] In some embodiments, the eggshell catalyst has a Pd content of 0.15wt% to 1.55wt%. Within this range, the eggshell catalyst has good catalytic effect. If the Pd content is too low, the conversion rate will be low and the activity will decrease. If the Pd content is too high, the catalyst will be too expensive and the economic benefit will be poor. Preferably, the Pd content is 0.5wt% to 1wt%, which is beneficial to further improve the catalytic activity.

[0009] In some embodiments, the eggshell catalyst has a Cu content of 0.5wt% to 5.0wt%. Within this range, CuCl2 has a better effect on the valence state stability of Pd. If the Cu content is too low, the catalyst will be rapidly deactivated. If the Cu content is too high, the conversion rate of the catalyst will be low. Preferably, the Cu content is 1.5wt% to 3wt%, which is beneficial to further improve the catalytic activity.

[0010] In some embodiments, the ratio of the contents of Cu and Pd in the eggshell catalyst is 1 to 5. Within this range, the eggshell catalyst has better catalytic activity. Preferably, the ratio of the contents of Cu and Pd is 1.5 to 3.

[0011] In some embodiments, the carrier includes Al2O3.

[0012] Further, the carrier includes at least one of γ-Al2O3 and η-Al2O3.

[0013] In some embodiments, the carrier includes at least one of spherical particles, columnar particles, clover-shaped particles, and Raschig ring-shaped particles.

[0014] In some embodiments, the eggshell catalyst has a half particle size of D, and the PdCl2 is distributed on the surface of the eggshell catalyst to a surface layer with a depth of 0.1D to 0.25D.

[0015] In some embodiments, the eggshell catalyst further includes an auxiliary agent, which is loaded on the surface and inside of the carrier. The auxiliary agent is beneficial to improve the activity and selectivity of the catalyst.

[0016] Further, the auxiliary agent includes MCl2, where M is at least one of Mg, Ca, and Sr.

[0017] Still further, the M content is 0.2wt% to 5wt%.

[0018] The second object of the present application is to provide a preparation method of an eggshell catalyst, which includes:

[0019] immersing the initial carrier in a first solution containing CuCl2, making CuCl2 uniformly loaded on the surface and inside of the initial carrier, evaporating and drying the solvent of the first solution to obtain a first intermediate;

[0020] immersing the first intermediate in a filling solvent, making the filling solvent fill part or all of the internal pores of the first intermediate, filtering and evaporating part of the filling solvent to obtain a second intermediate;

[0021] immersing the second intermediate in a second solution containing PdCl2, making the PdCl2 loaded on the surface layer of the second intermediate, evaporating the solvent of the second solution, and drying and calcining to obtain an eggshell type catalyst.

[0022] In some embodiments, the concentration of CuCl2 in the first solution is 0.14-1.6 mol / L. Preferably, it is 0.5-1 mol / L.

[0023] In some embodiments, the first solution further comprises MCl2, wherein M is at least one of Mg, Ca, and Sr. Further, the concentration of MCl2 is 0.15-1.1 mol / L.

[0024] In some embodiments, the temperature of immersing the initial carrier in the first solution is 25-60°C.

[0025] In some embodiments, the time of immersing the initial carrier in the first solution is 2 hours or more. Preferably, the time of immersing is 2-12 hours.

[0026] In some embodiments, the filling solvent is immiscible with water, and the boiling point of the filling solvent is below 160°C. Preferably, the boiling point of the filling solvent is 100-150°C. More preferably, the filling solvent comprises n-butanol, but is not limited thereto. The filling solvent is used to fully occupy the internal pores of the carrier, avoiding PdCl2 entering the inside of the carrier.

[0027] In some embodiments, the evaporating part of the filling solvent specifically comprises: weighing the mass of the first intermediate before and after immersing in the filling solvent, obtaining the increment of the mass of the first intermediate as m, evaporating the filling solvent with a mass of 0.25m-0.35m, and obtaining the second intermediate. The beneficial effect of this technical solution is that the filling solvent in the surface layer pores of the carrier is preferentially evaporated.

[0028] In some embodiments, the concentration of PdCl2 in the second solution is 0.08-0.9 mol / L.

[0029] In some embodiments, the temperature of immersing the second intermediate in the second solution is room temperature.

[0030] In some embodiments, the second intermediate is immersed in the second solution for 2 hours or more. Preferably, the immersion time is 2-12 hours.

[0031] In some embodiments, after the second intermediate is immersed in the second solution, drying and calcination are performed to obtain the eggshell catalyst.

[0032] Further, the drying temperature is 100-120°C. The drying time is 2 hours or more. Preferably, the drying time is 2-12 hours.

[0033] Further, the calcination temperature is 150-200°C. The calcination time is 6 hours or more. Preferably, the calcination time is 6-24 hours.

[0034] In some embodiments, the solvent of the second solution comprises ammonia. That is, the active component comprising PdCl2 is uniformly dispersed in ammonia to obtain the second solution.

[0035] The third object of the present application is to provide the use of the eggshell catalyst in any of the above technical solutions in the preparation of dimethyl carbonate from CO and methyl nitrite.

[0036] The fourth object of the present application is to provide a method for preparing dimethyl carbonate, comprising: catalyzing the mixed reaction gas containing CO and methyl nitrite in the presence of the eggshell catalyst in any of the above technical solutions to obtain dimethyl carbonate.

[0037] In some embodiments, the CO content in the mixed reaction gas is 10-25%.

[0038] In some embodiments, the methyl nitrite content in the mixed reaction gas is 10-25%.

[0039] In some embodiments, the mixed reaction gas further comprises HCl gas. Further, the HCl gas content is 50-500 ppm.

[0040] In some embodiments, the mixed reaction gas is diluted with nitrogen.

[0041] In some embodiments, the reaction temperature of the catalytic reaction is 110-140°C.

[0042] In some embodiments, the pressure of the catalytic reaction is 0.1-1 MPa.

[0043] In some embodiments, the space velocity of the catalytic reaction is 1000-5000 h -1 .

[0044] Compared with the prior art, the present application has at least the following beneficial effects:

[0045] (1) The eggshell type catalyst provided by the present application can reduce the diffusion distance of reactants in the catalyst channel, improve the adsorption and desorption efficiency, improve the catalytic activity, and at the same time improve the utilization rate of the noble metal palladium and effectively reduce the amount of the noble metal palladium;

[0046] (2) The active ingredient PdCl2 in the eggshell type catalyst provided by the present application is distributed on the surface layer of the catalyst, and the auxiliary active ingredient CuCl2 is loaded on the surface and the inside of the carrier, i.e. the whole distribution, which is conducive to stabilizing the Pd valence state and improving the stability of the catalyst; at the same time, compared with the structure in which the auxiliary active ingredient CuCl2 is also concentrated on the surface layer, the catalyst structure in the present application can ensure a large amount of CuCl2 loading while avoiding the concentration of CuCl2 on the surface layer to cover PdCl2, which leads to a decrease in the activity of the catalyst;

[0047] (3) The eggshell type catalyst provided by the present application is suitable for the reaction system of CO and methyl nitrite to prepare dimethyl carbonate, and exhibits high selectivity and space-time yield, which is conducive to promoting the industrialization process of the gas-phase synthesis of dimethyl carbonate by CO carbonylation. BRIEF DESCRIPTION OF DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0049] Figure 1 is a physical picture of the eggshell type catalyst prepared in an embodiment of the present application;

[0050] Figure 2 is a cross-sectional morphology diagram of the eggshell type catalyst prepared in an embodiment of the present application after reduction. DETAILED DESCRIPTION

[0051] The technical solutions of the present application will be described in detail below with specific embodiments, so that those skilled in the art can better understand and implement the technical solutions of the present application. The specific functional details disclosed in this paper should not be interpreted as being limited, but only as a basis for the claims and for teaching those skilled in the art to adopt the representative basis of the present application in different ways in any appropriate detailed embodiment.

[0052] Example 1

[0053] CuCl2, CaCl2 were uniformly dispersed in water to prepare a first solution, wherein the concentration of CuCl2 was 0.56 mol / L and the concentration of CaCl2 was 0.63 mol / L; PdCl2 was dispersed in ammonia water to prepare a second solution, wherein the concentration of PdCl2 was 0.53 mol / L;

[0054] 100 g of γ-Al2O3 spherical particles were mixed with 60 ml of the first solution, impregnated at room temperature for 3 h, and then the solvent water was evaporated and dried at a temperature of 120°C to obtain a first intermediate;

[0055] The mass of the first intermediate was weighed as m1; the first intermediate with a mass of m1 was added to n-butanol, impregnated uniformly, filtered, and then weighed, with a mass of m2, and the mass increment (m2-m1) was the mass of n-butanol in the intermediate after impregnation; 30% of the n-butanol with a mass of (m2-m1) was volatilized to obtain a second intermediate;

[0056] The second intermediate was mixed with 18 ml of the second solution, impregnated at room temperature for 3 h, and then dried at 100°C for 2 h and calcined at 160°C for 12 h to obtain an eggshell type catalyst. Figure 1 is a physical map of the eggshell type catalyst in this embodiment, which is light yellow in color; Figure 2 is a cross-sectional view of the eggshell type catalyst after reduction at 160°C in a hydrogen atmosphere for 3 h, from which Figure 1 and Figure 2 It can be seen that the eggshell type catalyst prepared exhibits good apparent morphology and uniform particle size, and from Figure 2 it can be clearly seen that the Pd part is on the surface layer of the catalyst.

[0057] The loading rate of Pd in the eggshell type catalyst was 0.96 wt%, the loading rate of Cu was 2 wt%, and the loading rate of Ca was 1.5 wt%.

[0058] The eggshell type catalyst was used for the gas-phase synthesis of dimethyl carbonate by CO carbonylation, which specifically included: the eggshell type catalyst was placed in a fixed reactor with an inner diameter of 18 mm, the loading amount of the catalyst was 50 ml, 50 ml of inert quartz sand was loaded above and below the bed layer of the catalyst, and a three-section temperature control type was used for temperature control of the reaction tube; the raw gas was a mixed reaction gas of CO, methyl nitrite, and nitrogen (balance gas), and a trace amount of HCl gas was introduced, wherein the content of CO in the mixed reaction gas was 15%, the content of methyl nitrite was 15%, and the content of HCl was 200 ppm; the space velocity of the catalytic reaction was 3000 h -1The reaction temperature is controlled at 120-130℃, and the reaction pressure is controlled at 0.18-0.22 MPa; after the catalyst is stable for 1 hour, the product in the collection tank is removed, the synthesis reaction is continued for 8 hours, and then the product is collected; the raw material gas, tail gas and product are detected and analyzed by weighing and gas chromatography, and the conversion rate of methyl nitrite and the selectivity rate of dimethyl carbonate are calculated. The reaction method is the activity test method of the catalyst.

[0059] The conversion rate of methyl nitrite is calculated by the following formula:

[0060]

[0061] The selectivity of dimethyl carbonate is calculated by analyzing the product by gas chromatography, and the content of dimethyl carbonate in the product is the selectivity. The performance evaluation of the catalyst in this embodiment is shown in Table 1.

[0062] Example 2

[0063] CuCl2 and SrCl2 are uniformly dispersed in water to prepare a first solution, wherein the concentration of CuCl2 is 0.42 mol / L and the concentration of SrCl2 is 0.4 mol / L; PdCl2 is dispersed in ammonia water to prepare a second solution, wherein the concentration of PdCl2 is 0.53 mol / L;

[0064] 100 g of η-Al2O3 spherical particles are mixed with 60 ml of the first solution, and impregnated at room temperature for 3 h, then the solvent water is evaporated, and dried at a temperature of 120℃ to obtain a first intermediate;

[0065] The mass of the first intermediate is weighed as m1; the first intermediate with a mass of m1 is added to n-butanol, impregnated uniformly, filtered and weighed, and the mass is m2, then the mass increment (m2-m1) is the mass of n-butanol in the intermediate after impregnation; 30% of the n-butanol with a mass of (m2-m1) is volatilized to obtain a second intermediate;

[0066] The second intermediate is mixed with 18 ml of the second solution, impregnated at room temperature for 3 h, then dried at 100℃ for 2 h, and then calcined at 150℃ for 12 h to obtain an eggshell type catalyst.

[0067] The loading rate of Pd in the eggshell type catalyst is 0.96 wt%, the loading rate of Cu is 1.5 wt%, and the loading rate of Sr is 2 wt%.

[0068] The eggshell type catalyst is used for the reaction of gas phase synthesis of dimethyl carbonate by CO carbonylation, and the difference from Example 1 is only that the eggshell type catalyst in Example 1 is replaced by the catalyst in this embodiment. The performance evaluation of the catalyst in this embodiment is shown in Table 1.

[0069] Example 3

[0070] CuCl2 and MgCl2 were uniformly dispersed in water to prepare a first solution, wherein the concentration of CuCl2 was 0.14 mol / L and the concentration of MgCl2 was 0.15 mol / L; PdCl2 was dispersed in ammonia water to prepare a second solution, wherein the concentration of PdCl2 was 0.08 mol / L;

[0071] 100 g of γ-Al2O3 columnar particles were mixed with 60 ml of the first solution, impregnated at 60°C for 2 h, and then the solvent water was evaporated and dried at a temperature of 120°C to obtain a first intermediate;

[0072] The mass of the first intermediate was weighed as m1; the first intermediate with a mass of m1 was added to n-butanol, impregnated, filtered, and then weighed, with a mass of m2, and the mass increment (m2-m1) was the mass of n-butanol in the intermediate after impregnation; 30% of the n-butanol with a mass of (m2-m1) was volatilized to obtain a second intermediate;

[0073] The second intermediate was mixed with 18 ml of the second solution, impregnated at room temperature for 2 h, and then dried at 120°C for 2 h and calcined at 200°C for 6 h to obtain an eggshell type catalyst.

[0074] The loading rate of Pd in the eggshell type catalyst was 0.15 wt%, the loading rate of Cu was 0.5 wt%, and the loading rate of Mg was 0.2 wt%.

[0075] The eggshell type catalyst was used for the gas phase synthesis of dimethyl carbonate by CO carbonylation, and the difference from Example 1 was that the eggshell type catalyst in Example 1 was replaced by the catalyst in the present example. The performance evaluation of the catalyst in the present example is shown in Table 1.

[0076] Example 4

[0077] CuCl2 and SrCl2 were uniformly dispersed in water to prepare a first solution, wherein the concentration of CuCl2 was 1.6 mol / L and the concentration of SrCl2 was 1.1 mol / L; PdCl2 was dispersed in ammonia water to prepare a second solution, wherein the concentration of PdCl2 was 0.9 mol / L;

[0078] 100 g of γ-Al2O3 Raschig ring particles were mixed with 60 ml of the first solution, impregnated at 60°C for 6 h, and then the solvent water was evaporated and dried at a temperature of 120°C to obtain a first intermediate;

[0079] The first intermediate is weighed as m1; the first intermediate with a mass of m1 is added to n-butanol, impregnated uniformly, filtered, and weighed as m2, and the mass increment (m2-m1) is the mass of n-butanol in the impregnated intermediate; 30% of the n-butanol with a mass of (m2-m1) is volatilized to obtain a second intermediate;

[0080] The second intermediate is mixed with 18 ml of the second solution, impregnated at room temperature for 12 h, and then dried at 100°C for 5 h and calcined at 150°C for 24 h to obtain an eggshell catalyst.

[0081] The loading rate of Pd in the eggshell catalyst is 1.5 wt%, the loading rate of Cu is 5 wt%, and the loading rate of Sr is 5 wt%.

[0082] The eggshell catalyst is used for the gas-phase synthesis of dimethyl carbonate by CO carbonylation, and the difference from Example 1 is that the eggshell catalyst in Example 1 is replaced by the catalyst in the present example. The performance evaluation of the catalyst in the present example is shown in Table 1.

[0083] Example 5

[0084] CuCl2 and CaCl2 are uniformly dispersed in water to prepare a first solution, wherein the concentration of CuCl2 is 0.28 mol / L and the concentration of CaCl2 is 0.32 mol / L; PdCl2 is dispersed in ammonia water to prepare a second solution, wherein the concentration of PdCl2 is 0.28 mol / L;

[0085] 100 g of γ-Al2O3 spherical particles are mixed with 60 ml of the first solution, impregnated at room temperature for 3 h, and then the solvent water is evaporated and dried at a temperature of 120°C to obtain a first intermediate;

[0086] The first intermediate is weighed as m1; the first intermediate with a mass of m1 is added to n-butanol, impregnated uniformly, filtered, and weighed as m2, and the mass increment (m2-m1) is the mass of n-butanol in the impregnated intermediate; 30% of the n-butanol with a mass of (m2-m1) is volatilized to obtain a second intermediate;

[0087] The second intermediate is mixed with 18 ml of the second solution, impregnated at room temperature for 3 h, and then dried at 100°C for 2 h and calcined at 160°C for 12 h to obtain an eggshell catalyst.

[0088] The loading rate of Pd in the eggshell catalyst is 0.48 wt%, the loading rate of Cu is 1 wt%, and the loading rate of Ca is 0.8 wt%.

[0089] The eggshell type catalyst was used in the reaction of gaseous phase synthesis of dimethyl carbonate by CO carbonylation. The difference between this example and Example 1 is that the eggshell type catalyst in Example 1 is replaced by the catalyst in this example. The performance evaluation of the catalyst in this example is shown in Table 1.

[0090] Example 6

[0091] CuCl2 and CaCl2 were uniformly dispersed in water to prepare a first solution, wherein the concentration of CuCl2 was 0.28 mol / L and the concentration of CaCl2 was 0.63 mol / L; PdCl2 was dispersed in ammonia water to prepare a second solution, wherein the concentration of PdCl2 was 0.53 mol / L;

[0092] 100 g of γ-Al2O3 clover-shaped particles were mixed with 60 ml of the first solution, and impregnated at room temperature for 3 h. Then the solvent water was evaporated, and the first intermediate was dried at a temperature of 120°C to obtain a first intermediate;

[0093] The mass of the first intermediate was weighed as m1; the first intermediate with a mass of m1 was added to n-butanol, and after impregnation and filtration, the mass was weighed as m2. The mass increment (m2-m1) was the mass of n-butanol in the intermediate after impregnation; 30% of the n-butanol with a mass of (m2-m1) was volatilized to obtain a second intermediate;

[0094] The second intermediate was mixed with 18 ml of the second solution, and impregnated at room temperature for 3 h, and then dried at 100°C for 2 h, and then calcined at 160°C for 12 h to obtain an eggshell type catalyst.

[0095] The loading rate of Pd in the eggshell type catalyst was 0.48 wt%, the loading rate of Cu was 2 wt%, and the loading rate of Ca was 1.5 wt%.

[0096] The eggshell type catalyst was used in the reaction of gaseous phase synthesis of dimethyl carbonate by CO carbonylation. The difference between this example and Example 1 is that the eggshell type catalyst in Example 1 is replaced by the catalyst in this example. The performance evaluation of the catalyst in this example is shown in Table 1.

[0097] Comparative Example 1

[0098] CuCl2 and CaCl2 were uniformly dispersed in water to prepare a first solution, wherein the concentration of CuCl2 was 0.28 mol / L and the concentration of CaCl2 was 0.32 mol / L; PdCl2 was dispersed in ammonia water to prepare a second solution, wherein the concentration of PdCl2 was 0.28 mol / L;

[0099] 100 g of γ-Al2O3 clover-shaped particles were mixed with 60 ml of the first solution, impregnated at room temperature for 3 h, and then dried at a temperature of 120°C to obtain a first intermediate;

[0100] The first intermediate was mixed with 18 ml of the second solution, impregnated at room temperature for 3 h, and then dried at 100°C for 2 h and calcined at 160°C for 12 h to obtain the catalyst.

[0101] The catalyst was not treated by filling the internal pores with n-butanol, and thus PdCl2 was loaded on the whole of the catalyst, with a Pd loading rate of 0.48 wt%, a Cu loading rate of 1 wt%, and a Ca loading rate of 0.8 wt%.

[0102] The catalyst was used for the gas-phase synthesis of dimethyl carbonate by CO carbonylation, and the difference from Example 1 was that the eggshell-shaped catalyst in Example 1 was replaced by the catalyst in the present comparative example. The performance evaluation of the catalyst in the present comparative example is shown in Table 1.

[0103] Comparative Example 2

[0104] CuCl2 and CaCl2 were uniformly dispersed in water to prepare a first solution, with a CuCl2 concentration of 0.28 mol / L and a CaCl2 concentration of 0.32 mol / L; and PdCl2 was dispersed in ammonia water to prepare a second solution, with a PdCl2 concentration of 0.28 mol / L;

[0105] 100 g of γ-Al2O3 spherical particles were added to n-butanol, impregnated uniformly, filtered, and weighed, with a mass of m2. The mass increment of the carrier after impregnation was (m2-100 g). 30% of the n-butanol with a mass of (m2-100 g) was volatilized to obtain a first intermediate;

[0106] The first intermediate was mixed with 18 ml of the first solution, impregnated at room temperature for 3 h, and then dried at a temperature of 120°C to obtain a second intermediate;

[0107] The second intermediate was mixed with 18 ml of the second solution, impregnated at room temperature for 3 h, and then dried at 100°C for 2 h and calcined at 160°C for 12 h to obtain an eggshell-shaped catalyst.

[0108] The Pd loading rate of the eggshell-shaped catalyst was 0.48 wt%, the Cu loading rate was 1 wt%, and the Ca loading rate was 0.8 wt%.

[0109] The eggshell type catalyst was used in the reaction of gaseous phase synthesis of dimethyl carbonate by CO carbonylation. The difference between this example and Example 1 was that the eggshell type catalyst in Example 1 was replaced by the catalyst in this example. The performance evaluation of the catalyst in this example is shown in Table 1.

[0110] Comparative Example 3

[0111] CaCl2 was uniformly dispersed in water to prepare a first solution, wherein the concentration of CaCl2 was 0.32 mol / L; PdCl2 was dispersed in ammonia water to prepare a second solution, wherein the concentration of PdCl2 was 0.28 mol / L;

[0112] 100 g of γ-Al2O3 spherical particles were mixed with 60 ml of the first solution, and impregnated at room temperature for 3 h. Then the solvent water was evaporated, and the first intermediate was dried at a temperature of 120°C to obtain a second intermediate;

[0113] The mass of the first intermediate was m1; the first intermediate with a mass of m1 was added to n-butanol, and after impregnation and filtration, the mass was m2. The mass increment (m2-m1) was the mass of n-butanol in the intermediate after impregnation; 30% of the n-butanol with a mass of (m2-m1) was volatilized to obtain the second intermediate;

[0114] The second intermediate was mixed with 18 ml of the second solution, and impregnated at room temperature for 3 h, and then dried at 100°C for 2 h, and then calcined at 160°C for 12 h to obtain an eggshell type catalyst.

[0115] The loading rate of Pd in the eggshell type catalyst was 0.48 wt%, the loading rate of Cu was 1 wt%, and the loading rate of Ca was 0.8 wt%.

[0116] The eggshell type catalyst was used in the reaction of gaseous phase synthesis of dimethyl carbonate by CO carbonylation. The difference between this example and Example 1 was that the eggshell type catalyst in Example 1 was replaced by the catalyst in this example. The performance evaluation of the catalyst in this example is shown in Table 1.

[0117] Table 1 Performance of the catalysts in Examples 1-6 and Comparative Examples 1-5

[0118]

[0119] According to Table 1, the eggshell type catalyst prepared by the preparation method provided in the present application exhibited good catalytic performance in the reaction system of preparing dimethyl carbonate by the reaction of CO and methyl nitrite.

[0120] From Comparative Example 5 and Comparative Example 1, it can be seen that, under the condition of the same Pd, Cu, M loadings, the eggshell catalyst with PdCl2 loaded on the surface layer exhibits higher conversion of methyl nitrite, selectivity of dimethyl carbonate and higher catalyst space-time yield.

[0121] From Comparative Example 5 and Comparative Example 2, it can be seen that, compared with the structure in which PdCl2 and CuCl2 are both concentrated on the surface layer, the eggshell catalyst structure provided by the application in which PdCl2 is loaded on the surface layer and CuCl2 is distributed throughout the whole structure can better reflect good catalytic performance, so that the eggshell catalyst structure in the application can ensure a large CuCl2 loading while avoiding the CuCl2 being concentrated on the surface layer to cover the PdCl2, thereby reducing the activity of the catalyst.

[0122] From Comparative Example 5 and Comparative Example 3, it can be seen that the catalyst containing the co-activating component CuCl2 exhibits higher catalytic activity than the pure PdCl2 catalyst.

[0123] Aspects, embodiments, features, and examples of the application are to be considered in all respects as illustrative only and not restrictive, the scope of the application being indicated only by the appended claims. Other embodiments, modifications, and uses thereof will occur to those skilled in the art upon consideration of the specification and may be made without departing from the spirit and scope of the application.

[0124] In addition, the present inventors have also carried out tests with other raw materials, process operations and process conditions described in the specification with reference to the foregoing examples, and all ideal results have been obtained.

[0125] While the application has been described with reference to illustrative embodiments, those skilled in the art will appreciate that various other changes, omissions, and / or additions can be made thereto without departing from the spirit and scope of the application. Additionally, many modifications can be made to adapt a particular situation or material to the teachings of the application without departing from the scope thereof. Accordingly, it is intended that the application not be limited to the disclosed embodiments, but that it include all embodiments falling within the scope of the appended claims. Furthermore, to the extent that the term "includes" is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term "comprising" as "comprising" is interpreted when employed as a transitional word in the introductory clauses of the claims.

Claims

1. An eggshell-shaped catalyst, characterized in that: The eggshell-shaped catalyst comprises an active component, a co-active component, an additive, and a support. The active component includes PdCl2, and half the particle size of the eggshell-shaped catalyst is D. The PdCl2 is distributed on the surface of the eggshell-shaped catalyst to a surface layer with a depth of 0.1D to 0.25D. The co-active component includes CuCl2, and the additive includes MCl2, wherein M = at least one of Mg, Ca, and Sr. The CuCl2 and the additive are supported on the surface and inside the support. The eggshell-shaped catalyst contains 0.48wt% to 1.55wt% Pd, 1wt% to 5.0wt% Cu, and 0.8wt% to 5wt% M.

2. The eggshell-type catalyst according to claim 1, characterized in that: In the eggshell-shaped catalyst, the ratio of Cu to Pd content is 1 to 5.

3. The eggshell-type catalyst according to claim 2, characterized in that: The ratio of Cu to Pd content is 1.5 to 3.

4. The eggshell-type catalyst according to claim 1, characterized in that: The carrier includes Al2O3.

5. The eggshell-type catalyst according to claim 4, characterized in that: The support is at least one of γ-Al2O3 and η-Al2O3.

6. The eggshell-type catalyst according to claim 1, characterized in that: The carrier includes at least one of spherical particles, columnar particles, clover-shaped particles, and Raschig ring-shaped particles.

7. The method for preparing the eggshell-type catalyst according to any one of claims 1-6, characterized in that, include: The support is immersed in a first solution containing CuCl2 and MCl2, so that CuCl2 is loaded on the surface and inside of the support, and the solvent of the first solution is evaporated and dried to obtain a first intermediate. The first intermediate is immersed in a filling solvent, which fills part or all of the internal pores of the first intermediate. The mass of the first intermediate before and after immersion in the filling solvent is weighed separately to obtain the mass increment of the first intermediate as m. The filling solvent with a mass of 0.25m to 0.35m is evaporated to obtain the second intermediate. The second intermediate is impregnated in a second solution containing PdCl2, so that the PdCl2 is loaded on the surface of the second intermediate. The solvent of the second solution is evaporated, and the intermediate is dried and calcined to obtain an eggshell-shaped catalyst.

8. The preparation method according to claim 7, characterized in that: The concentration of CuCl2 in the first solution is 0.14–1.6 mol / L.

9. The preparation method according to claim 8, characterized in that: The concentration of CuCl2 in the first solution is 0.5~1 mol / L.

10. The preparation method according to claim 7, characterized in that: The concentration of MCl2 in the first solution is 0.15–1.1 mol / L.

11. The preparation method according to claim 7, characterized in that: The carrier is immersed in the first solution at a temperature of 25–60°C and / or for a time of 2 hours or more.

12. The preparation method according to claim 7, characterized in that: The filling solvent is immiscible with water and has a boiling point below 160°C.

13. The preparation method according to claim 12, characterized in that: The filling solvent includes n-butanol.

14. The preparation method according to claim 7, characterized in that: The concentration of PdCl2 in the second solution is 0.08–0.9 mol / L.

15. The preparation method according to claim 7, characterized in that: The second intermediate is impregnated in the second solution at room temperature and / or for 2 hours or more.

16. The preparation method according to claim 7, characterized in that: The drying process is carried out at a temperature of 100–120°C and / or for a drying time of 2 hours or more.

17. The preparation method according to claim 7, characterized in that: The calcination treatment is carried out at a temperature of 150–200°C and / or for a calcination time of 6 hours or more.

18. The preparation method according to claim 7, characterized in that: The solvent for the second solution includes ammonia.

19. The use of the eggshell-type catalyst according to any one of claims 1 to 6 in the reaction of CO with methyl nitrite to prepare dimethyl carbonate.

20. A method for preparing dimethyl carbonate, characterized in that, include: In the presence of any one of the eggshell-type catalysts according to claims 1 to 6, a mixed reaction gas containing CO and methyl nitrite is subjected to a catalytic reaction to obtain dimethyl carbonate.

21. The preparation method according to claim 20, characterized in that: The mixed reaction gas contains 10-25% CO and / or 10-25% methyl nitrite.

22. The preparation method according to claim 20, characterized in that: The mixed reaction gas also includes HCl gas.

23. The preparation method according to claim 22, characterized in that: The content of the HCl gas is 50~500ppm.

24. The preparation method according to claim 20, characterized in that: The mixed reaction gas is diluted with nitrogen.

25. The preparation method according to claim 20, characterized in that: The reaction temperature of the catalytic reaction is 110~140℃; and / or, the pressure of the catalytic reaction is 0.1~1MPa; and / or, the space velocity of the catalytic reaction is 1000~5000h⁻¹. -1 .

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