Pd / PNaY catalyst, preparation method thereof and application of Pd / PNaY catalyst in preparation of dimethyl carbonate through CO esterification

Abstract

The invention discloses a Pd / PNaY catalyst, a preparation method of the Pd / PNaY catalyst and application of the Pd / PNaY catalyst to preparation of dimethyl carbonate through CO esterification, and belongs to the field of catalysts. The Pd / PNaY catalyst comprises a PNaY carrier and a Pd active component; the PNaY carrier is a phosphate modified NaY molecular sieve. A phosphate modified NaY molecular sieve carrier is adopted to form PNaY, then an active component Pd is loaded through an ammonia distillation method, the catalyst is applied to a reaction for preparing dimethyl carbonate through CO esterification, very high dimethyl carbonate all-component selectivity (up to 83%) is shown, and the selectivity of by-products methyl formate and dimethoxymethane is remarkably reduced compared with that of an unmodified catalyst.

Description

Technical Field

[0001] The present application relates to a Pd / PNaY catalyst, a preparation method thereof, and an application thereof in the esterification of CO to dimethyl carbonate, belonging to the field of catalysts. Background Art

[0002] Dimethyl carbonate has various chemical reaction activities and very low toxicity. It is an ideal substitute for highly toxic reagents such as phosgene and dimethyl sulfate, and is known as a green chemical. It is mainly applied in three aspects: 1) Dimethyl carbonate has characteristics such as a high dielectric constant, relatively high electrochemical stability, and low viscosity, and is the main solvent for lithium-ion battery electrolytes; 2) Dimethyl carbonate is one of the main raw materials for producing polycarbonate; 3) Dimethyl carbonate can be used as a gasoline and diesel additive. Since its oxygen content is as high as 53%, adding 40% of the amount of methyl tert-butyl ether can obtain a similar blending effect, and at the same time, the emission of harmful exhaust gases is reduced by more than 50%.

[0003] The esterification of CO and methyl nitrite to dimethyl carbonate (CO + 2CH 3 ONO → (CH 3 O) 2 CO + 2NO, 4NO + O 2 + 4CH 3 OH → 4CH 3 ONO + 2H 2 O) has received widespread attention due to its advanced technology. Since the acidity of NaY zeolite will cause partial decomposition of the raw material methyl nitrite into by-products methyl formate and dimethoxymethane, thereby reducing the selectivity of the main product dimethyl carbonate (Acta Chim. Sinica 2022, 80, 438 - 443).

[0004] Therefore, it is necessary to develop a catalyst with high selectivity for all components of dimethyl carbonate. Summary of the Invention

[0005] Aiming at the problem that the NaY zeolite catalyst carrier for the esterification reaction of CO to dimethyl carbonate has decomposition of the raw material methyl nitrite, the present invention uses phosphate to modify the NaY zeolite carrier to form PNaY, and then loads the active component Pd by the ammonia evaporation method and applies it to the esterification reaction of CO to dimethyl carbonate, which can significantly inhibit the decomposition of the raw material and effectively improve the selectivity of all components of the main product dimethyl carbonate.

[0006] According to the first aspect of the present application, a Pd / PNaY catalyst is provided. This catalyst uses phosphate-modified PNaY as the carrier and Pd as the active component, and the acid amount of the modified Pd / PNaY catalyst is greatly reduced.

[0007] A Pd / PNaY catalyst, wherein the Pd / PNaY catalyst comprises a PNaY support and a Pd active component;

[0008] The PNaY support is a phosphate-modified NaY molecular sieve.

[0009] Optionally, the phosphate is selected from at least one of disodium hydrogen phosphate and dipotassium hydrogen phosphate.

[0010] Optionally, the Pd active component covers the surface of the PNaY support in the form of single sites.

[0011] Optionally, in the PNaY support, the loading amount of the phosphate is 1-30%, preferably 10-15%;

[0012] Wherein, the loading amount of the phosphate is the mass percentage of the phosphate in the NaY molecular sieve.

[0013] Optionally, the loading amount of the Pd active component is 0.2-2%, preferably 0.6-1.2%;

[0014] Wherein, the loading amount of the Pd active component is the mass percentage of Pd in the PNaY support.

[0015] According to the second aspect of the present application, a preparation method of a Pd / PNaY catalyst is provided. Compared with the traditional impregnation method, this method uses the ammonia evaporation method to introduce Pd into PNaY, covering it on the surface of PNaY in the form of single sites, and the interaction between the metal and the support is very strong.

[0016] The preparation method of the above-mentioned Pd / PNaY catalyst comprises the following steps:

[0017] S1 A mixture containing phosphate, NaY molecular sieve and water is heated, stirred, dried and calcined to obtain a PNaY support;

[0018] S2 The PNaY support is added to a palladium ammonia complex solution, ammonia evaporation is carried out, separation, drying and calcination are carried out to obtain the Pd / PNaY catalyst.

[0019] The phosphate and the NaY molecular sieve are mixed, heated, stirred and air-calcined to obtain PNaY. The phosphate successfully enters the interior of the molecular sieve and is connected to the framework without destroying the pore structure of the NaY molecular sieve; the PNaY is added to the palladium ammonia complex solution and stirred for a period of time, and then ammonia evaporation is carried out. During the ammonia evaporation process, the active metal Pd is loaded on the pore surface of the support in the form of single sites and is connected to the molecular sieve framework to form a strong metal-support interaction; centrifugally washed three times, the Pd / PNaY is vacuum dried and then calcined in an air atmosphere.

[0020] Optionally, in the step S1, the conditions for heating and stirring are: the temperature is 30 to 70 °C, and the time is 1 to 6 h.

[0021] Specifically, in the step S1, the conditions for heating and stirring are: the temperature is 50 °C, and the time is 4 h.

[0022] Optionally, in the step S1, the conditions for roasting are: roasting in an air atmosphere, the temperature is 200 to 600 °C, and the time is 1 to 6 h.

[0023] Specifically, in the step S1, the conditions for roasting are: roasting in an air atmosphere, the temperature is 550 °C, and the time is 4 h.

[0024] Optionally, in the step S2, the palladium ammonia complex solution is obtained by the following method:

[0025] Dissolve a palladium precursor and ammonia water in a solvent to obtain a palladium ammonia complex solution;

[0026] The palladium precursor is selected from at least one of palladium acetylacetonate, palladium nitrate, and palladium acetate;

[0027] Select a suitable solvent according to solubility.

[0028] The palladium ammonia complex solution can use water, ammonia water, ethanol, acetone, etc. as solvents according to solubility, and ammonia water and water are preferred.

[0029] Optionally, in the step S2, the conditions for ammonia evaporation are: the temperature is 50 to 100 °C, and the time is 4 to 12 h.

[0030] Preferably, in the step S2, the conditions for ammonia evaporation are: the temperature is 60 to 80 °C, and the time is 5 to 7 h.

[0031] Optionally, in the step S2, the conditions for roasting are: roasting in an air atmosphere, the temperature is 100 to 400 °C, and the time is 1 to 6 h.

[0032] Preferably, in the step S2, the conditions for roasting are: roasting in an air atmosphere, the temperature is 150 to 200 °C, and the time is 1 to 3 h.

[0033] Optionally, in steps S1 and S2, the drying method is selected from vacuum drying, the temperature is 60 to 120 °C, and the vacuum drying time is 8 to 12 h.

[0034] According to the third aspect of the present application, there is provided an application of a Pd / PNaY catalyst. A phosphate-modified NaY zeolite support is used to form PNaY, and then the active component Pd is loaded by the ammonia evaporation method and applied to the reaction of CO esterification to dimethyl carbonate, showing a very high selectivity for all components of dimethyl carbonate (up to 83% at most), and the selectivities of by-products methyl formate and dimethoxymethane are significantly decreased compared with the unmodified catalyst.

[0035] A method for preparing dimethyl carbonate by CO esterification, in which a raw material gas containing CO and methyl nitrite is introduced into a reactor filled with a Pd / PNaY catalyst for reaction to obtain dimethyl carbonate;

[0036] The Pd / PNaY catalyst is selected from the Pd / PNaY catalysts described above.

[0037] Optionally, the reaction conditions are: the volume ratio of CO to methyl nitrite is 1:2 - 6, the space velocity is 500 - 5000 L·kg cat. -1 ·h -1 , the temperature is 80 - 160 °C, and the pressure is 0.01 - 2 MPa.

[0038] Preferably, the space velocity is 1000 - 3000 L·kg cat. -1 ·h -1 , the temperature is 100 - 140 °C, and the pressure is 0.05 - 0.3 MPa.

[0039] The beneficial effects that can be produced by the present application include:

[0040] For the Pd / PNaY catalyst provided by the present application, the NaY zeolite is used as the support, which is modified by phosphate to form PNaY, reducing the acidity of NaY, inhibiting the decomposition of the raw material methyl nitrite, and improving the selectivity of all components of the target product dimethyl carbonate.

[0041] For the preparation method of the Pd / PNaY catalyst provided by the present application, the ammonia evaporation method is used. Compared with the traditional impregnation method, the ion exchange process helps the active metal to firmly adhere to the surface of the support and form a strong metal-support interaction with the zeolite framework.

[0042] The Pd / PNaY catalyst provided by the present application shows a very high selectivity for all components of dimethyl carbonate (up to 83% at most) in the reaction of CO esterification to dimethyl carbonate, and the selectivities of by-products methyl formate and dimethoxymethane are significantly decreased compared with the unmodified catalyst. Description of the Drawings

[0043] Figure 1Powder diffraction (XRD) patterns of the Pd / PNaY-3, Pd / PNaY-6, Pd / PNaY-9, Pd / PNaY-12, Pd / PNaY-15 catalysts prepared in Example 2 and the Pd / NaY catalyst of Comparative Example 1;

[0044] Figure 2 Transmission electron microscope images and elemental analysis diagrams of the Pd / PNaY-6 and Pd / PNaY-12 catalysts prepared in Example 2 and the Pd / NaY catalyst of Comparative Example 1. The upper (a-c) diagrams correspond to the Pd / NaY catalyst, the middle (d-f) diagrams correspond to the Pd / PNaY-6 catalyst; the lower (g-i) diagrams correspond to the Pd / PNaY-12 catalyst;

[0045] Figure 3 Pyridine infrared spectra of the Pd / PNaY-6, Pd / PNaY-12, Pd / PNaY-15 catalysts prepared in Example 2 and the Pd / NaY catalyst of Comparative Example 1;

[0046] Figure 4 Temperature-programmed desorption of ammonia diagrams of the Pd / PNaY-6, Pd / PNaY-12, Pd / PNaY-15 catalysts prepared in Example 2 and the Pd / NaY catalyst of Comparative Example 1. Detailed implementation manners

[0047] The present application will be described in detail below with reference to the examples, but the present application is not limited to these examples.

[0048] Unless otherwise specified, the raw materials in the examples of the present application are all purchased through commercial channels.

[0049] Unless otherwise specified, the test methods are all conventional methods, and the instrument settings are all the settings recommended by the manufacturers.

[0050] The instrument for X-ray diffraction analysis (XRD) is Miniflex600, and the analysis conditions are Cu-Kα rays (hν = 8047.8 eV, ), working voltage 40 KV and working current 30 mA. The scanning range of the measured samples is 5° - 60° (scanning speed is 5° / min).

[0051] The instrument for transmission electron microscopy and elemental analysis is Thermoscientific Talos F200X. The main components and parameters of the instrument include a high-angle annular dark-field detector (HAADF), an annular dark-field detector (ADF), a bright-field detector (BF), an integrated differential phase contrast detector (iDPC), a Super-X energy spectrometer, a GATAN Oneview camera, a point resolution ≤ 0.25 nm, a line resolution ≤ 0.14 nm, a STEM resolution ≤ 0.16 nm, and an information resolution ≤ 0.12 nm.

[0052] The instrument for pyridine infrared spectrum analysis is a TENSOR II Fourier transform infrared spectrometer. The analysis conditions are 64 scans and a resolution of 4 cm -1 , and the measurement range is 600 - 4000 cm -1 . A small amount of powder sample is pressed together with KBr into a 1.5 cm sample tablet and placed in an in-situ cell for sealing. It is evacuated to 10-3 Pa at room temperature, then heated to 400 °C and held for 2 h to remove moisture and gas molecules on the sample surface. After cooling to room temperature, the background is collected. Pyridine gas is introduced into the in-situ cell. After 1 h of adsorption saturation, the pyridine infrared spectrum of pyridine adsorption is recorded; after heating to 200 °C and holding for 30 min, the pyridine infrared desorption spectrum is recorded; after continuing to heat to 350 °C and holding for 30 min, the desorption spectrum is recorded. The obtained pyridine infrared spectra can be used to identify the acid types on the surface of the sample.

[0053] The instrument for ammonia temperature-programmed desorption analysis is an ALTAMIRA AMI-300. The analysis conditions are that 100 mg of the catalyst is treated under He atmosphere at 150 °C for 1 h to remove adsorbed impurities. After cooling to 50 °C, a 5% NH 3 -He mixed gas is introduced into the catalyst at a flow rate of 30 mL / min for 1 h, then purged with He gas for 30 min, and then heated to 600 °C at a rate of 10 °C / min under He atmosphere. The desorbed NH 3 is recorded through a TCD detector.

[0054] The analytical instrument for on-line gas chromatography is an Agilent GC8890. The conditions are an inlet temperature of 100 °C; a detector temperature of 250 °C; a chromatographic column FFAP (30 m × 0.25 mm × 0.25 μm); a thermal conductivity detector and a flame ionization detector; an air flow rate of 400 mL / min; a hydrogen flow rate of 30 mL / min; and a make-up gas N 2 flow rate of 25 mL / min.

[0055] The calculation methods for CO conversion rate, dimethyl carbonate total component selectivity, dimethoxymethane total component selectivity, methyl formate total component selectivity, and dimethyl oxalate total component selectivity are as follows:

[0056] CO conversion rate = [(CO) in / (Ar) in -(CO) out / (Ar) out / [(CO) in / (Ar) in ×100%

[0057] Among them, [Ar] in and [Ar] out respectively represent the peak area of argon before reaction and the peak area of argon after reaction; [CO] in and [CO] out respectively represent the peak area of CO before reaction and the peak area of CO after reaction;

[0058] Dimethyl carbonate total component selectivity = (2×S DMC ×R - F DMC / M DMC ) / (2×S DMC ×R - F DMC / M DMC +2×S DMO ×R - F DMO / M DMO +2×S MF ×R - F MF / M MF +3×S DMM ×R - F DMM / M DMM )×100%

[0059] Dimethoxymethane total component selectivity = (3×S DMM ×R - F DMM / M DMM ) / (2×S DMC ×R - F D MC / M DMC +2×S DMO ×R - F DMO / M DMO +2×S MF ×R - F MF / M MF +3×S DMM ×R - F DMM / M DM M )×100%

[0060] Methyl formate total component selectivity = (2×S MF ×R - F MF / M MF ) / (2×S DMC ×R - FDMC / M DMC + 2×S DMO ×R - F DMO / M DMO + 2×S MF ×R - F MF / M MF + 3×S DMM ×R - F DMM / M DMM ) × 100%

[0061] Dimethyl oxalate total component selectivity = (2×S DMO ×R - F DMO / M DMO ) / (2×S DMC ×R - F DMC / M DMC + 2×S DMO ×R - F DMO / M DMO + 2×S MF ×R - F MF / M MF + 3×S DMM ×R - F DMM / M DMM ) × 100%

[0062] Among them, S DMC , S DMO , S DMM and S MF respectively refer to the peak areas of dimethyl carbonate (DMC), dimethyl oxalate (DMO), dimethoxymethane (DMM), and methyl formate (MF) after the reaction. R - F DMC , R - F DMO , R - F DMM , R - F MF respectively refer to the relative correction factors of DMC, DMO, DMM, and MF. M DMC , M DMO , M DMM and M MF respectively represent the relative molecular masses of DMC, DMO, DMM, and MF.

[0063] In Example 1, modified PNaY was prepared by heating, stirring, and air calcination.

[0064] A certain amount of disodium hydrogen phosphate was dissolved in 20 mL of water to form a solution, and 1 g of NaY zeolite was added. After heating and stirring at a certain temperature for a period of time, the loaded PNaY was vacuum - dried at 80 °C for 8 h and then calcined in an air atmosphere to obtain the PNaY support.

[0065] Table 1 Experimental parameters of the modified PNaY support

[0066]

[0067]

[0068] Among them, the mass percentage dosage of disodium hydrogen phosphate is the mass percentage of disodium hydrogen phosphate in NaY zeolite.

[0069] * Potassium hydrogen phosphate is used in the preparation process of the PNaY support numbered J.

[0070] In Example 2, the Pd / PNaY catalyst was prepared by the ammonia evaporation method.

[0071] A certain amount of palladium acetylacetonate and ammonia water were dissolved in 20 mL of water to form a solution. 1 g of the modified molecular sieve support in Example 1 was added. After ammonia evaporation and stirring at a certain temperature for a period of time, the powder loaded with Pd was centrifuged multiple times, vacuum dried at 80 °C for 8 h, and calcined in an air atmosphere to obtain Pd / PNaY.

[0072] Table 2 Experimental parameters for preparing the Pd / PNaY catalyst

[0073]

[0074]

[0075] Among them, the Pd loading is the mass percentage of Pd in the modified molecular sieve support.

[0076] Among them, the Pd / PNaY catalysts numbered 2, 3, 4, 5, 6 (corresponding to the modified PNaY support numbers A, B, C, D, E) are denoted as Pd / PNaY-3, Pd / PNaY-6, Pd / PNaY-9, Pd / PNaY-12, Pd / PNaY-15 respectively.

[0077] Comparative Example 1

[0078] The operation was the same as the preparation method of the Pd / PNaY-3 catalyst numbered 2, except that disodium hydrogen phosphate was not used, and the unmodified Pd / NaY catalyst, numbered D1, was obtained.

[0079] Characterization and testing

[0080] The Pd / PNaY catalyst prepared in Example 2 above was subjected to characterization and testing.

[0081] Taking the Pd / PNaY-3, Pd / PNaY-6, Pd / PNaY-9, Pd / PNaY-12, Pd / PNaY-15 catalysts as examples, their XRD patterns are as Figure 1As shown, it can be seen that all the catalysts prepared by phosphate modification still maintain the same molecular sieve structure.

[0082] Taking Pd / PNaY-6 and Pd / PNaY-12 catalysts as examples, their transmission electron microscope images and elemental analysis images are as Figure 2 shown. Figures (a-c) above correspond to the Pd / NaY catalyst, figures (d-f) in the middle correspond to the Pd / PNaY-6 catalyst; figures (g-i) below correspond to the Pd / PNaY-12 catalyst; it can be seen that the Pd active substance is evenly distributed on the surface of the molecular sieve.

[0083] Taking Pd / PNaY-6, Pd / PNaY-12, and Pd / PNaY-15 catalysts as examples, their pyridine infrared spectra are as Figure 3 shown. It can be seen that the catalyst mainly contains Lewis acid sites.

[0084] Taking Pd / PNaY-6, Pd / PNaY-12, and Pd / PNaY-15 catalysts as examples, their ammonia temperature-programmed desorption spectra are as Figure 4 shown. It can be seen that the peak area in the range of 100 - 200 °C is significantly weakened, indicating a decrease in the acid amount.

[0085] Example 3 Performance Evaluation of Pd / PNaY Catalyst

[0086] Charge 200 mg of Pd / PNaY catalyst and introduce the reaction raw material gas: 19% CO, 45% methyl nitrite, 3% Ar (as an internal standard gas), and 33% N 2 (as a balance gas). The total mass space velocity is 2500 L·kg cat. -1 ·h -1 , the reaction pressure is 0.1 MPa, and the reaction temperature is 120 °C. The reaction raw materials and products are analyzed in real time by on-line gas chromatography. Table 3 shows the performance evaluation results of the catalyst after 5 h of reaction.

[0087] Table 3 Performance Evaluation Results of Pd / PNaY Catalyst

[0088]

[0089] The above are only several embodiments of the present application and do not impose any form of limitation on the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any person skilled in the art, without departing from the scope of the technical solution of the present application, making some changes or modifications using the disclosed technical content is equivalent to equivalent implementation cases and all belong to the scope of the technical solution.

Claims

1. A Pd / PNaY catalyst, characterized in that: The Pd / PNaY catalyst comprises a PNaY carrier and a Pd active component; The PNaY carrier is a phosphate-modified NaY molecular sieve.

2. The Pd / PNaY catalyst according to claim 1, characterized in that The phosphate is selected from at least one of disodium hydrogen phosphate and dipotassium hydrogen phosphate.

3. The Pd / PNaY catalyst according to claim 1, characterized in that The Pd active component is covered on the surface of the PNaY carrier in the form of a single point.

4. The Pd / PNaY catalyst according to claim 1, characterized in that In the PNaY carrier, the loading amount of phosphate is 1 to 30%, preferably 10 to 15%; The loading amount of phosphate is the mass percentage of phosphate to the NaY molecular sieve.

5. The Pd / PNaY catalyst according to claim 1, characterized in that The loading amount of the Pd active component is 0.2-2%, preferably 0.6-1.2%; The loading amount of the Pd active component is the mass percentage of Pd in ​​the PNaY carrier.

6. The method for preparing the Pd / PNaY catalyst according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: heating, stirring, drying, and calcining a mixture containing phosphate, NaY molecular sieve, and water to obtain a PNaY carrier; S2: adding the PNaY carrier into the palladium-ammine complex solution, performing ammonia evaporation, separation, drying, and calcination to obtain the Pd / PNaY catalyst.

7. The preparation method according to claim 6, characterized in that: In step S1, the heating and stirring conditions are: temperature of 30 to 70° C., time of 1 to 6 hours; Preferably, in step S1, the calcination conditions are: calcination in an air atmosphere at a temperature of 200 to 600° C. for a time of 1 to 6 hours.

8. The preparation method according to claim 6, characterized in that: In the step S2, the palladium ammonia complex solution is obtained by the following method: dissolving a palladium precursor and ammonia water in a solvent to obtain a palladium-ammonia complex solution; The palladium precursor is selected from at least one of palladium acetylacetonate, palladium nitrate, and palladium acetate; Choose the appropriate solvent based on solubility; Preferably, in step S2, the conditions for evaporating ammonia are: temperature of 50-100° C., time of 4-12 h; Preferably, in step S2, the calcination conditions are: calcination in an air atmosphere at a temperature of 100 to 400° C. for a time of 1 to 6 hours.

9. A method for preparing dimethyl carbonate by CO esterification, characterized in that: The raw gas containing CO and methyl nitrite is passed into a reactor equipped with a Pd / PNaY catalyst to react and obtain dimethyl carbonate; The Pd / PNaY catalyst is selected from the Pd / PNaY catalyst according to any one of claims 1 to 5.

10. The preparation method according to claim 9, characterized in that: The reaction conditions are: the volume ratio of CO to methyl nitrite is 1:2-6, and the air velocity is 500-5000 L·kg cat. -1 ·h -1 , temperature is 80~160℃, and pressure is 0.01~2MPa.

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