Application of CuO-CeO2 / ZrO2 supported catalyst in transesterification preparation of organic carbonate

Abstract

The invention discloses an application of a CuO-CeO2 / ZrO2 supported catalyst in preparation of organic carbonate through ester exchange. The organic carbonate is one of dimethyl carbonate, diethyl carbonate, diisopropyl carbonate and di-n-amyl carbonate. The specific application process is as follows: alcohol and ethylene carbonate are used as raw materials, and under the action of the CuO-CeO2 / ZrO2 supported catalyst, ester exchange reaction is performed at 90-180 DEG C to prepare organic carbonate; the alcohol is one of methanol, ethanol, isopropanol and n-amyl alcohol; the molar ratio of the alcohols to the ethylene carbonate is (6-11): 1. When the CuO-CeO2 / ZrO2 supported catalyst is applied to preparation of organic carbonic ester through ester exchange, excellent catalytic activity and stability can be shown, and higher DMC selectivity and DMC yield can be achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal catalysts, and in particular relates to the application of a CuO-CeO2 / ZrO2 supported catalyst in preparing organic carbonates by ester exchange. Background Art

[0002] As an important class of chemicals, organic carbonates play a vital role in the fields of chemical industry and pharmaceutical industry. As an important green, environmentally friendly and non-toxic chemical intermediate, organic carbonates are widely used in organic chemicals, medicines, cleaning agents, coatings and paints. In addition, organic carbonates have the characteristics of high octane number, good oil-water partition coefficient and excellent electrical conductivity, and are widely used in fuel additives and battery electrolytes. Dimethyl carbonate, diethyl carbonate, diisopropyl carbonate and di-n-pentyl carbonate are relatively common organic carbonates.

[0003] At present, the methods for synthesizing organic carbonates from carbon dioxide mainly include transesterification, urea alcoholysis, alcohol oxidation carbonylation, and direct synthesis from methanol and CO2. The transesterification method has a wide range of industrial applications, with an atomic utilization rate of up to 100%, extremely high economic efficiency, and is in line with the requirements of green chemical industry. The method first uses ethylene oxide (EO) and CO2 to react to synthesize ethylene carbonate (EC) intermediates, and then EC is transesterified with alcohols to generate organic carbonates, while co-producing ethylene glycol (EG). In the first step, CO2 can react with high-energy compounds EO to prepare EC. This process has been successfully implemented in industrial production and has high reactivity and selectivity. Many researchers have also conducted extensive research on the second step reaction. The selection of catalysts for this reaction is a key technology. At present, traditional catalysts use sodium methoxide, which has a high catalytic activity, but it has a fatal disadvantage. After the catalyst sodium methoxide is deactivated, solid waste residue is generated, making the subsequent separation process very complicated and not conducive to industrial production.

[0004] Common heterogeneous catalysts for the production of organic carbonates by transesterification include metal oxides, hydrotalcite, ion exchange resins, supported catalysts, etc. In the CeCu composite metal oxide catalyst prepared by Kumar P et al., a 71.9% yield of dimethyl carbonate (DMC) was obtained under the conditions of a raw material alcohol-ester molar ratio of 10:1, a reaction time of 4h, and a reaction temperature of 160°C. The reaction conditions are relatively harsh. (Kumar P, Srivastava VC, Mishra I M. Dimethyl carbonate synthesis by transesterification of propylene carbonate with methanol: Comparative assessment of Ce-M (M=Co, Fe, Cu and Zn) catalysts [J]. Renewable Energy, 2016, 88: 457-464.). Patent CN202210539015.X discloses a B-doped g-C3N4 catalyst for the synthesis of dimethyl carbonate, with a raw material alcohol-ester molar ratio of 8:1, a reaction time of 5h, a reaction temperature of 150°C, and a reaction pressure of 0.7MPa to obtain a DMC yield of 66.4%. The preparation process of the catalyst is relatively complicated. Therefore, the development of cheap, efficient, environmentally friendly, and recyclable heterogeneous catalysts is of great significance for the preparation of organic carbonates by transesterification. Summary of the invention

[0005] The purpose of the present invention is to provide an application of a CuO-CeO2 / ZrO2 supported catalyst in the preparation of organic carbonates by ester exchange. The application of the CuO-CeO2 / ZrO2 supported catalyst in the preparation of organic carbonates by ester exchange can show excellent catalytic activity and stability, higher DMC selectivity and DMC yield.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] The invention discloses an application of a CuO-CeO2 / ZrO2 supported catalyst in preparing an organic carbonate by ester exchange. The organic carbonate is one of dimethyl carbonate, diethyl carbonate, diisopropyl carbonate and di-n-pentyl carbonate.

[0008] Furthermore, the specific application process is: using alcohols and ethylene carbonate as raw materials, an ester exchange reaction is carried out at 90-180°C under the action of a CuO-CeO2 / ZrO2 supported catalyst to obtain an organic carbonate; the alcohol is one of methanol, ethanol, isopropanol, and n-pentanol; the molar ratio between the alcohol and ethylene carbonate is (6-11):1, the amount of the CuO-CeO2 / ZrO2 supported catalyst is 11.4% of the mass of ethylene carbonate, and the reaction time is 1-3h.

[0009] Preferably, the organic carbonate is prepared by transesterification reaction at 90° C.; the molar ratio between the alcohol and ethylene carbonate is 10:1, and the reaction time is 1 hour.

[0010] Furthermore, the preparation method of the CuO-CeO2 / ZrO2 supported catalyst comprises the following steps:

[0011] (1) dissolving cerium nitrate and zirconium nitrate in deionized water to form a mixed solution, then adding a precipitant to carry out a hydrothermal reaction, and after the reaction is completed, filtering, washing, drying, grinding, and then heating to 400° C. to calcine to obtain a CeO2 / ZrO2 carrier;

[0012] (2) The CeO2 / ZrO2 carrier prepared in step (1) was impregnated with an aqueous solution of copper acetate, dried, ground, and then heated to 600°C for calcination to obtain a CuO-CeO2 / ZrO2 supported catalyst, with a CuO loading of 4%wt.

[0013] Preferably, in step (1), the molar ratio of cerium nitrate to zirconium nitrate is 6:1; the concentrations of cerium nitrate and zirconium nitrate in the mixed solution are 0.2 mol / L and 0.034 mol / L, respectively; the hydrothermal reaction temperature is 50° C., and the hydrothermal reaction time is 3 h.

[0014] Preferably, in step (1), the precipitant is a sodium carbonate aqueous solution with a mass concentration of 42.4%, and the volume ratio of the precipitant to the mixed solution is 1:2.

[0015] Preferably, in step (2), the concentration of the copper acetate aqueous solution is 0.5 mmol / ml, and 1 ml of the copper acetate aqueous solution is added to each gram of CeO2 / ZrO2 carrier for impregnation.

[0016] Preferably, the drying temperature in step (1) and step (2) is 80° C. and the drying time is 12 h.

[0017] Preferably, the heating rate in step (1) and step (2) is 5°C / min.

[0018] Preferably, the calcination time in step (1) and step (2) is 5 hours.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] (1) The raw material ethylene carbonate used in the present invention is obtained by the addition reaction of carbon dioxide and ethylene oxide. The CuO-CeO2 / ZrO2 catalyst provided by the present invention is used in the ester exchange reaction to prepare organic carbonates and exhibits excellent catalytic activity, higher DMC selectivity and DMC yield;

[0021] (2) The CuO-CeO2 / ZrO2 catalyst provided by the present invention does not need to be activated during the reaction process and can maintain a high activity after repeated reactions, thereby showing excellent stability.

[0022] (3) The preparation method of the CuO-CeO2 / ZrO2 catalyst provided by the present invention is simple, the preparation cost is low, and the industrial application prospect is good; the prepared CuO-CeO2 / ZrO2 catalyst has a larger pore size and more pores, which is more conducive to contact with the raw materials and improves its catalytic performance; on the other hand, it also has abundant active sites, which promotes the adsorption and activation of methanol and is beneficial to improving the activity of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flow chart of the preparation method of CuO-CeO2 / ZrO2 supported catalyst;

[0024] Figure 2 Scanning electron micrographs of the CeO2 / ZrO2 carrier (a) and the CuO-CeO2 / ZrO2 supported catalyst (b) prepared in the examples of the present invention;

[0025] Figure 3 XRD patterns (a) of the CeO2 / ZrO2 carrier, the CuO-CeO2 / ZrO2 supported catalyst and the CuO-CeO2 / ZrO2 catalyst after 4 cycles of reaction prepared in the examples of the present invention, and (b) is a partial enlarged view of (a);

[0026] Figure 4 N2 adsorption / desorption curves (a) and pore size distribution diagram (b) of CeO2 / ZrO2 carrier and CuO-CeO2 / ZrO2 supported catalyst prepared in the examples of the present invention;

[0027] Figure 5 XPS spectra of CeO2 / ZrO2 carrier and CuO-CeO2 / ZrO2 supported catalyst prepared in the examples of the present invention: Cu 2p (a), Zr 3d (b), Ce 3p (c) and O1s (d). DETAILED DESCRIPTION

[0028] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products with a purity of analytical grade or above.

[0030] like Figure 1 As shown, the preparation process of the CuO-CeO2 / ZrO2 supported catalyst used in the following examples is:

[0031] (1) 0.02 mol of cerium nitrate and 0.0034 mol of zirconium nitrate were dissolved in deionized water to form a mixed solution, and then 50 mL of an aqueous solution containing 0.0368 g of sodium carbonate was added dropwise, and the mixture was subjected to a hydrothermal reaction at 50° C. (stirring for 2 h, aging for 1 h). After the reaction was completed, the mixture was filtered, washed, dried (drying temperature was 80° C., drying time was 12 h), ground, and then heated to 400° C. at a heating rate of 5° C. / min and calcined for 5 h to obtain a CeO2 / ZrO2 carrier;

[0032] (2) Take 4 g of CeO2 / ZrO2 carrier, dissolve 2 mmol of copper acetate in 4 ml of deionized water and then impregnate the CeO2 / ZrO2 carrier, dry (drying temperature is 80°C, drying time is 12 h), grind, and then heat to 600°C at a heating rate of 5°C / min and calcine for 5 h to obtain a CuO-CeO2 / ZrO2 supported catalyst. Figure 2 It can be seen from (a) and (b) that the catalyst has a porous sheet structure after high-temperature calcination, which is more conducive to contact with the raw materials and improves its catalytic performance. Figure 3 As can be seen in (a), after loading CuO, the peak width of the catalyst becomes narrower and the peak intensity increases. Figure 3 (b) Figure 3 The local enlarged image of (a) shows that the peak of CuO-CeO2 / ZrO2 is shifted compared to CeO2 / ZrO2. The unit cell parameters of CuO-CeO2 / ZrO2 are Smaller than the unit cell parameters of pure CeO2 Description 4+ (radius 0.097nmn) is surrounded by Zr with a smaller radius 4+ (radius 0.086nm) or Cu 2 + (radius 0.072nm) to form Ce-Zr solid solution or Cu-Ce-Zr solid solution. In addition, the unit cell parameters of CuO-CeO2 / ZrO2 Smaller cell parameters than CeO2 / ZrO2 Therefore, it can be inferred that Cu 2+Entering into the Ce-Zr lattice, a Cu-Ce-Zr solid solution was formed. The catalyst was tested using a N2 physical adsorption and desorption instrument, and the adsorption and desorption isotherms obtained were as follows: Figure 4 As shown in (a), based on the IUPAC classification, the prepared catalyst has a typical type IV adsorption isotherm curve. Figure 4 (b) After loading CuO, the average pore size of the catalyst increases, which is conducive to contact with the raw materials and promotes the reaction. The physical structure characteristics of the catalyst are shown in Table 1. The XPS spectrum of Cu 2p of CuO-CeO2 / ZrO2 is shown in Figure 5 As shown in (a), the high binding energy Cu2p 3 / 2 The peak (932.8 eV) and satellite peaks are due to Cu 2+ The presence of species, such as Figure 5 As shown in (b), the catalyst contains Zr3d 5 / 2 and Zr 3d 3 / 2 There are two peaks. Since zirconium replaces the lattice position of cerium, the binding energy of the former is higher than that of metal Zr and lower than that of ZrO2, such as Figure 5 As shown in (c), the catalyst is Ce 4+ Species mainly and a small amount of Ce 3+ Species, Ce 3+ The speciation may be due to the Zr 4+ or Cu 2+ Replace Ce 4+ Species, among which 882.4, 888.4, and 897.9 eV are attributed to Ce 4+ 3D 5 / 2 , 900.85, 907.4, 916.3 eV are attributed to Ce 4+ 3D 3 / 2 , the peak represented by 884.5 eV belongs to Ce 3+ In Figure 5 As shown in (d), the α peak is the lattice oxygen of the metal oxide, the β peak is the defect oxygen, and the γ peak is the surface hydroxyl group, which can usually promote catalytic activity.

[0033] Table 1 Physical structure characteristics of catalysts

[0034] sample <![CDATA[Specific surface area (m 2 / g)]]> <![CDATA[Pore volume (cm 2 / g)]]> Average pore size (nm) <![CDATA[CeO2 / ZrO2]]> 28.695 0.091 1.267 <![CDATA[CuO-CeO2 / ZrO2]]> 14.026 0.149 4.252

[0035] Example 1

[0036] A CuO-CeO2 / ZrO2 supported catalyst is used in preparing dimethyl carbonate by transesterification, and the specific application process is as follows:

[0037] The performance test for the synthesis of dimethyl carbonate from methanol and ethylene carbonate was carried out in a microreactor. After the reactor was thoroughly dried, 4.49g methanol (0.14mol) and 1.76g ethylene carbonate (0.02mol) were placed in a reactor with a rotor, and 0.2g CuO-CeO2 / ZrO2 supported catalyst was added. The transesterification reaction was carried out at 90°C for 1h. After the reaction, the catalyst was separated by a centrifuge after the reactor was cooled, and the product mixture was quantitatively analyzed by a gas chromatograph with an FID detector. The content of each product was determined by the internal standard method. The conversion rate of ethylene carbonate (EC), the selectivity of organic carbonates and the yield were calculated according to the following formula:

[0038]

[0039] The activity data of the catalyst in the ester exchange process for producing dimethyl carbonate is shown in Appendix 2.

[0040] Example 2

[0041] A CuO-CeO2 / ZrO2 supported catalyst is used in preparing diethyl carbonate by transesterification, and the specific application process is as follows:

[0042] The performance test for the synthesis of diethyl carbonate from ethanol and ethylene carbonate was carried out in a microreactor, where 4.49 g of methanol in Example 1 was replaced with 6.45 g of ethanol (0.14 mol), 90° C. in Example 1 was replaced with 110° C., and the remaining steps were the same as in Example 1. The activity data of the catalyst in the production of diethyl carbonate by transesterification are shown in Appendix 2.

[0043] Example 3

[0044] A CuO-CeO2 / ZrO2 supported catalyst is used in preparing diisopropyl carbonate by transesterification, and the specific application process is as follows:

[0045] The performance test for synthesizing diisopropyl carbonate from isopropyl alcohol and ethylene carbonate was carried out in a microreactor, where 4.49 g of methanol in Example 1 was replaced with 8.40 g of isopropyl alcohol (0.14 mol), 90° C. in Example 1 was replaced with 150° C., and the remaining steps were the same as in Example 1. The activity data of the catalyst in the production of diisopropyl carbonate by transesterification are shown in Appendix 2.

[0046] Example 4

[0047] A CuO-CeO2 / ZrO2 supported catalyst is used in preparing di-n-pentyl carbonate by transesterification, and the specific application process is as follows:

[0048] The performance test for the synthesis of di-n-pentyl carbonate from n-pentanol and ethylene carbonate was carried out in a microreactor, where 4.49 g of methanol in Example 1 was replaced with 12.34 g of n-pentanol (0.14 mol), 90° C. in Example 1 was replaced with 160° C., and the remaining steps were the same as in Example 1. The activity data of the catalyst in the production of di-n-pentyl carbonate by transesterification are shown in Appendix 2.

[0049] Example 5

[0050] The 1h in Example 1 was replaced by 2h, and the remaining steps were the same as in Example 1. The activity data of the catalyst are shown in Appendix 2.

[0051] Example 6

[0052] The 1h in Example 1 was replaced by 3h, and the remaining steps were the same as in Example 1. The activity data of the catalyst are shown in Appendix 2.

[0053] Example 7

[0054] The 4.49 g of methanol in Example 1 was replaced by 3.84 g of methanol, and the remaining steps were the same as in Example 1. The activity data of the catalyst are shown in Table 2.

[0055] Example 8

[0056] The 4.49 g of methanol in Example 1 was replaced with 5.13 g of methanol, and the remaining steps were the same as in Example 1. The activity data of the catalyst are shown in Table 2.

[0057] Example 9

[0058] The 4.49 g of methanol in Example 1 was replaced with 5.77 g of methanol, and the remaining steps were the same as in Example 1. The activity data of the catalyst are shown in Appendix 2.

[0059] Example 10

[0060] The 4.49 g of methanol in Example 1 was replaced by 6.41 g of methanol, and the remaining steps were the same as in Example 1. The activity data of the catalyst are shown in Appendix 2.

[0061] Embodiment 11

[0062] The 4.49 g of methanol in Example 1 was replaced by 7.05 g of methanol, and the remaining steps were the same as in Example 1. The activity data of the catalyst are shown in Appendix 2.

[0063] Table 2 Catalytic activity data of each example

[0064]

[0065]

[0066] The activity of the reaction of methanol, ethanol, isopropanol, n-butanol, n-pentanol and ethylene carbonate in the transesterification of methanol, ethanol, isopropanol, n-butanol, n-pentanol and ethylene carbonate to synthesize the corresponding organic carbonate was studied in an intermittent microreactor using a supported catalyst CuO-CeO2 / ZrO2, and its performance is shown in Table 2. In the 4 cycles of Example 6, the yield of organic carbonate was slightly reduced, which was mainly due to the loss of part of the catalyst after each use, resulting in a decrease in the yield of organic carbonate. However, after the catalyst was circulated 4 times, the EC conversion rate only decreased by about 2%, and the selectivity of organic carbonate did not decrease, still 100%, and the results showed that the catalyst has excellent stability. Comparing Example 1 and Examples 7-11, it can be seen that when the ratio of methanol to ethylene carbonate is optimized to 10:1, the catalyst exhibits the best reaction activity, and the highest yield of organic carbonate is 79.95%.

[0067] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. An application of a CuO-CeO2 / ZrO2 supported catalyst in the preparation of an organic carbonate by ester exchange, wherein the organic carbonate is one of dimethyl carbonate, diethyl carbonate, diisopropyl carbonate, and di-n-pentyl carbonate.

2. The use of a CuO-CeO2 / ZrO2 supported catalyst in preparing organic carbonates by transesterification according to claim 1, characterized in that: The specific application process is: using alcohols and ethylene carbonate as raw materials, an ester exchange reaction is carried out at 90-180°C under the action of a CuO-CeO2 / ZrO2 supported catalyst to obtain an organic carbonate; the alcohol is one of methanol, ethanol, isopropanol, and n-pentanol; the molar ratio between the alcohol and ethylene carbonate is (6-11):1, the amount of the CuO-CeO2 / ZrO2 supported catalyst is 11.4% of the mass of ethylene carbonate, and the reaction time is 1-3h.

3. The use of a CuO-CeO2 / ZrO2 supported catalyst in preparing organic carbonates by transesterification according to claim 2, characterized in that: The organic carbonate is prepared by ester exchange reaction at 90° C. The molar ratio between the alcohol and ethylene carbonate is 10:1, and the reaction time is 1 hour.

4. Use of a CuO-CeO2 / ZrO2 supported catalyst according to claim 1 or 2 in preparing organic carbonates through transesterification, characterized in that: The preparation method of the CuO-CeO2 / ZrO2 supported catalyst comprises the following steps: (1) dissolving cerium nitrate and zirconium nitrate in deionized water to form a mixed solution, then adding a precipitant to carry out a hydrothermal reaction, and after the reaction is completed, filtering, washing, drying, grinding, and then heating to 400° C. to calcine to obtain a CeO2 / ZrO2 carrier; (2) The CeO2 / ZrO2 carrier prepared in step (1) was impregnated with an aqueous solution of copper acetate, dried, ground, and then heated to 600°C for calcination to obtain a CuO-CeO2 / ZrO2 supported catalyst, with a CuO loading of 4%wt.

5. The use of a CuO-CeO2 / ZrO2 supported catalyst in preparing organic carbonates by transesterification according to claim 4, characterized in that: In step (1), the molar ratio of cerium nitrate to zirconium nitrate is 6:1; the concentrations of cerium nitrate and zirconium nitrate in the mixed solution are 0.2 mol / L and 0.034 mol / L, respectively; the hydrothermal reaction temperature is 50° C., and the hydrothermal reaction time is 3 h.

6. The use of a CuO-CeO2 / ZrO2 supported catalyst in preparing organic carbonates by transesterification according to claim 4, characterized in that: In step (1), the precipitant is a sodium carbonate aqueous solution with a mass concentration of 42.4%, and the volume ratio of the precipitant to the mixed solution is 1:

2.

7. The use of a CuO-CeO2 / ZrO2 supported catalyst in preparing organic carbonates by transesterification according to claim 4, characterized in that: In step (2), the concentration of the copper acetate aqueous solution is 0.5 mmol / ml, and 1 ml of the copper acetate aqueous solution is added to each gram of CeO2 / ZrO2 carrier for impregnation.

8. The use of a CuO-CeO2 / ZrO2 supported catalyst in preparing organic carbonates by transesterification according to claim 4, characterized in that: The drying temperature in step (1) and step (2) is 80° C. and the drying time is 12 h.

9. The use of a CuO-CeO2 / ZrO2 supported catalyst in preparing organic carbonates by transesterification according to claim 4, characterized in that: The heating rate in step (1) and step (2) is 5°C / min.

10. Use of a CuO-CeO2 / ZrO2 supported catalyst in preparing organic carbonates by transesterification according to claim 4, characterized in that: The calcination time in step (1) and step (2) is 5 hours.

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