Pd / black talc catalyst for synthesizing oxalate through CO gas-phase oxidative coupling and application of Pd / black talc catalyst

Abstract

The invention discloses a Pd / black talc catalyst for synthesizing oxalate through CO gas-phase oxidative coupling and application of the Pd / black talc catalyst, and belongs to the technical field of oxalate preparation. A carrier of the catalyst is black talc, and an active component of the catalyst is Pd nanoparticles; according to the mass of the catalyst carrier, the content of the active component Pd is 0.05-2%, and the active component Pd nano-particles are high in dispersity, large in specific surface area, small in size and uniform in particle size distribution. The novelty of the catalyst is that black talc is adopted as a carrier, while most of the existing catalysts adopt alpha-aluminum oxide as a carrier. Experiments show that compared with a catalyst which takes alpha-aluminum oxide as a carrier and is prepared under the same condition, the catalyst disclosed by the invention shows better catalytic activity in the reaction of synthesizing oxalate through CO gas-phase oxidative coupling. The conversion per pass of CO is as high as 62%, the selectivity of oxalate is 95%, and the space time yield of oxalate is higher than 1250 g.L <-1 >. H <-1 > (the space velocity is 3000 h <-1 >).

Description

Technical Field

[0001] The invention belongs to the technical field of oxalate preparation, and relates to a Pd / black talc catalyst for synthesizing oxalate by gas-phase oxidation coupling of CO in coal-to-ethylene glycol production, and application thereof. Background Art

[0002] As an important organic chemical raw material, oxalate is not only used as a reaction solvent and extractant, but also widely used in the preparation of fine chemical products. In particular, oxalate hydrogenation can produce ethylene glycol, an extremely important basic chemical raw material. The traditional oil-to-ethylene glycol route faces the problem of resource shortage, and my country is a country rich in coal, less oil, and lacking in gas. Therefore, the development of coal-to-ethylene glycol can not only make up for the shortage of my country's oil resources, but also improve the efficient and clean conversion and utilization of coal resources.

[0003] Coal-to-ethylene glycol technology mainly includes three catalytic reactions: 1) catalytic removal of a small amount of hydrogen in CO after separation of coal-based synthesis gas by pressure swing adsorption; 2) CO gas-phase oxidative coupling to produce dimethyl oxalate; 3) dimethyl oxalate hydrogenation to produce ethylene glycol. Among them, CO gas-phase oxidative coupling to produce dimethyl oxalate: 2CH3ONO+2CO→(COOCH3)2+2NO, which is the key step in converting inorganic C1 into organic carbon C2. Pd / α-Al2O3 catalyst has been proven to be an active catalyst for this process. Although many research institutions at home and abroad have carried out a lot of research on CO gas-phase oxidative coupling to produce oxalate, there are still several problems that need to be solved urgently. 1. The Pd loading in the current industrial catalyst is relatively high (2%), and the high loading of precious metals will affect its industrial use, resulting in increased product costs. 2. Most of the catalysts reported so far use α-Al2O3 as a carrier, while there are few reports on high-efficiency Pd-based catalysts prepared with other carriers. Therefore, the development of Pd-based nanocatalysts with low precious metal loading and high performance prepared by other carriers is of great significance for improving the space-time yield of oxalate, solving the problem of excessive consumption of precious metal resources, and reducing catalyst costs.

[0004] The black talc in Guangfeng, Shangrao, Jiangxi Province has three characteristics: large reserves, good quality, and easy mining. At present, the proven reserves are 190 million tons, accounting for about a quarter of the total proven talc in the world. The prospective reserves are 1 billion tons, ranking first in the world. As a natural clay mineral, black talc has a TOT-type layered structure, consisting of two silicon-oxygen tetrahedral sheets and one magnesium-oxygen octahedron. As a layered silicate mineral without interlayer charge, it has excellent chemical stability. At the same time, the surface of black talc contains active functional groups, such as Mg-O, Si-O, OH, Si-OH, etc. After crushing, the surface functional groups are exposed, and surface active sites and alkaline sites appear. It can be used as an adsorbent and catalyst carrier, and has huge development potential and broad application prospects. Summary of the invention

[0005] In view of the shortcomings of the existing catalysts in the process of synthesizing oxalate by CO gas phase oxidative coupling, most of them use α-alumina as a carrier, the precious metal Pd loading is relatively high, and the oxalate space-time yield is relatively low. The present invention provides a Pd / black talc catalyst for synthesizing oxalate by CO gas phase oxidative coupling and its application. Black talc is used as a carrier, the precious metal Pd loading is relatively low, the CO single-pass conversion rate is as high as 62%, the oxalate selectivity is 95%, and the oxalate space-time yield is higher than 1250g·L -1 ·h -1 (Airspeed is 3000h -1 ).

[0006] In order to achieve the above-mentioned object of the invention, the present invention is implemented by the following technical solutions:

[0007] A catalyst for synthesizing oxalate by CO gas phase oxidative coupling, wherein the catalyst carrier is black talc and the active component is noble metal palladium; the composition of the catalyst is calculated based on the mass of the carrier, and the content of palladium in the active component is 0.05-2%.

[0008] The specific surface area of ​​the black talc carrier is 10-50m 2 / g, pore size is 2-50nm.

[0009] The preparation method of the catalyst of the present invention is prepared by adopting an improved impregnation method, comprising the following steps:

[0010] (1) adding a soluble palladium salt to a solvent to prepare a solution, wherein the palladium ion concentration in the solution is 0.001-0.1 M;

[0011] (2) adding the black talc carrier to the solution of step (1) and stirring evenly to obtain a suspension, so that the carrier is evenly dispersed in the palladium solution;

[0012] (3) placing the suspension of step (2) in a 20-150° C. water bath or oil bath and magnetically stirring until the solvent evaporates to dryness to obtain a solid, so that the soluble palladium salt is uniformly adsorbed onto the surface of the black talc carrier;

[0013] (4) drying the solid material of step (3) in a drying oven at 50-150° C. for 2-15 hours, and then calcining in an air atmosphere at 300-500° C. for 2-8 hours;

[0014] (5) reducing the solid obtained in step (4) for 2-10 hours under a reducing atmosphere, wherein the reducing gas is pure hydrogen or a hydrogen-nitrogen mixed gas, the reducing temperature is 200-500° C., and the reducing gas space velocity is 500-4000 h -1 , and then cooled to room temperature in a reducing atmosphere to obtain the catalyst.

[0015] In step (1) of the preparation method, the soluble palladium salt is selected from any one of palladium acetate, potassium chloropalladate, palladium chloride, palladium nitrate, potassium chloropalladate, ammonium chloropalladate or palladium acetylacetonate.

[0016] The solvent in step (1) of the preparation method is selected from any one of water, methanol, ethanol, acetone, chloroform, cyclohexane, ether, pyridine, benzene or toluene.

[0017] The catalyst of the invention is applied to the CO gas phase oxidative coupling reaction to synthesize oxalate, wherein the oxalate is dimethyl oxalate or diethyl oxalate.

[0018] The application method of the CO gas phase oxidative coupling synthesis oxalate catalyst provided by the present invention comprises the following steps: using a fixed bed reactor, the catalyst dosage is 0.2-2 mL, the flow ratio of the raw gas CO and methyl nitrite is controlled between 1.2-1.6, and the gas phase space velocity is 2000-5000h -1 The raw gas is contacted with the catalyst under normal pressure and 90-150° C. to obtain dimethyl oxalate product. The raw gas and the product are monitored and analyzed online by gas chromatography.

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

[0020] 1. Most existing catalysts use α-alumina as a carrier, while the catalyst of the present invention uses black talc as a carrier. The surface of black talc contains active functional groups, such as Mg-O, Si-O, OH, Si-OH, etc. After being crushed, the surface functional groups are exposed, and strong surface active sites and alkaline sites appear. It shows excellent catalytic activity in the CO gas-phase oxidative coupling reaction to synthesize oxalate, with a CO single-pass conversion rate of up to 62%, an oxalate selectivity of 95%, and an oxalate space-time yield of more than 1250 g·L -1 ·h -1 (Airspeed is 3000h -1 ). By comparison, compared with the catalyst prepared under the same conditions and using α-alumina as a carrier, the Pd / black talc catalyst of the present invention exhibits better catalytic activity in the CO gas phase oxidative coupling reaction to synthesize oxalate.

[0021] 2. The active component Pd nanoparticles in the catalyst disclosed in the present invention have high dispersion, large specific surface area, small size, and uniform particle size distribution, thereby enhancing the CO oxidative coupling catalytic activity.

[0022] 3. The precious metal palladium loading in the catalyst of the present invention is relatively low, accounting for only 0.5% of the carrier mass, which can greatly reduce the catalyst cost and solve the problem of excessive consumption of precious metal resources.

[0023] 4. The catalyst of the present invention adopts an improved impregnation method, the preparation process is simple and easy to operate, the energy consumption is low, and it is conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a scanning electron microscope photograph of the black talc support used in Examples 1, 2, and 3.

[0025] Figure 2 This is the CO2-TPD chart of the black talc support used in Examples 1, 2, and 3.

[0026] Figure 3 This is a transmission electron microscope photograph of the Pd / black talc catalyst prepared in Example 1. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0028] Embodiment 1:

[0029] Pd(OAc)2 was dissolved in acetone to prepare a solution with a Pd ion concentration of 0.005M. Then 1.06g of black talc was added to the above 10mL solution and stirred for 0.5 hours. Then, the solution was magnetically stirred in a 50℃ water bath until the solvent evaporated to dryness to obtain a solid. The solid was dried at 100℃ for 8 hours, then calcined in an air atmosphere at 400℃ for 4 hours, and then reduced with pure hydrogen at a temperature of 300℃ for 3 hours, with a reducing gas space velocity of 3000h -1 Then, the catalyst was prepared by cooling to room temperature in a reducing atmosphere, wherein the Pd loading amount was 0.5% of the carrier mass.

[0030] Catalyst evaluation: The catalyst in the embodiment of the present invention was applied to the synthesis of oxalate by CO gas phase oxidative coupling. The catalyst dosage was 1 mL, the flow ratio of raw gas CO and methyl nitrite was 1.4, and the gas phase space velocity was 3000 h -1 The reaction temperature is 90-150°C, the reaction pressure is 0.1Mpa, the raw gas and the product are monitored and analyzed by gas chromatography online, and the reaction results are shown in Table 1.

[0031] Table 1: Catalytic performance of the catalyst of Example 1 in the CO gas phase oxidative coupling reaction to produce dimethyl oxalate

[0032]

[0033]

[0034] Comparative Example 1:

[0035] Pd(OAc)2 was dissolved in acetone to prepare a solution with a Pd ion concentration of 0.005M. Then 1.06g of α-alumina was added to the above 10mL solution and stirred for 0.5 hours. Then, the solution was magnetically stirred in a 50℃ water bath until the solvent evaporated to dryness to obtain a solid. The solid was dried at 100℃ for 8 hours, then calcined in an air atmosphere at 400℃ for 4 hours, and then reduced with pure hydrogen at a temperature of 300℃ for 3 hours, with a reducing gas space velocity of 3000h -1 Then, the catalyst was prepared by cooling to room temperature in a reducing atmosphere, wherein the Pd loading amount was 0.5% of the carrier mass.

[0036] Embodiment 2:

[0037] K2PdCl4 was dissolved in deionized water to prepare a solution with a Pd ion concentration of 0.005M. Then 1.06g of black talc was added to the above 10mL solution and stirred for 0.5 hours. Then, the solution was magnetically stirred in a 120℃ oil bath until the solvent evaporated to dryness to obtain a solid. The solid was dried at 100℃ for 8 hours, then calcined in an air atmosphere at 400℃ for 4 hours, and then reduced with pure hydrogen at a temperature of 300℃ for 3 hours, with a reducing gas space velocity of 3000h -1 Then, the catalyst was prepared by cooling to room temperature in a reducing atmosphere, wherein the Pd loading amount was 0.5% of the carrier mass.

[0038] Embodiment 3:

[0039] Pd(acac)2 was dissolved in acetone to prepare a solution with a Pd ion concentration of 0.005M. Then 1.06g of black talc was added to the above 10mL solution and stirred for 0.5 hours. Then, the solution was magnetically stirred in a 50℃ water bath until the solvent evaporated to dryness to obtain a solid. The solid was dried at 100℃ for 8 hours, then calcined in an air atmosphere at 400℃ for 4 hours, and then reduced with pure hydrogen at a temperature of 300℃ for 3 hours, with a reducing gas space velocity of 3000h -1 Then, the catalyst was prepared by cooling to room temperature in a reducing atmosphere, wherein the Pd loading amount was 0.5% of the carrier mass.

[0040] The catalysts of Comparative Example 1, Example 2 and Example 3 were evaluated in the same manner as Example 1, wherein the reaction temperature was 130° C. The reaction results are shown in Table 2.

[0041] Table 2: Catalytic performance of the catalysts prepared in the examples and comparative examples in the CO gas phase oxidative coupling reaction to produce dimethyl oxalate

[0042]

[0043] It can be seen from the data in Table 2 that the Pd / black talc catalyst of the present invention can efficiently catalyze the synthesis of oxalate by gas-phase oxidative coupling of CO at a relatively low noble metal loading, and the CO conversion rate, oxalate selectivity and space-time yield are relatively high. Compared with the catalyst prepared under the same conditions and using α-alumina as a carrier, the Pd / black talc catalyst of the present invention exhibits better catalytic activity in the synthesis of oxalate by gas-phase oxidative coupling of CO.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A Pd / black talc catalyst for CO gas phase oxidative coupling synthesis of oxalate, characterized in that: The catalyst carrier is black talc, and the active component is Pd nanoparticles; the composition of the catalyst is calculated based on the mass of the carrier, and the content of palladium in the active component is 0.05-2%.

2. The Pd / black talc catalyst according to claim 1, characterized in that The specific surface area of ​​the black talc carrier is 10-50m 2 / g, pore size is 2-50nm.

3. The use of the Pd / black talc catalyst according to claim 1 in the process of synthesizing oxalate by CO gas phase oxidative coupling, the application method comprising the following steps: raw gas CO and nitrite are heated at a flow volume ratio of 1.2-1.6 and a gas phase space velocity of 2000-5000h -1 Under the conditions of normal pressure and 90-150° C., a fixed bed reactor loaded with the catalyst is used to generate oxalate by gas phase catalytic reaction; the raw gas and the product are monitored and analyzed by online gas chromatography.

4. The use of the Pd / black talc catalyst according to claim 3 in the process of synthesizing oxalate by CO gas phase oxidative coupling, characterized in that: The catalyst is applied to the CO gas phase oxidative coupling reaction to synthesize oxalate, wherein the oxalate is dimethyl oxalate or diethyl oxalate.

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