A solid acid catalyst for amide dehydration, its preparation method and application

Abstract

The present invention relates to a solid acid catalyst for amide dehydration, a preparation method thereof and an application. The catalyst comprises: a carbon base and heteroatoms supported on the carbon base; based on the total weight of the catalyst, the content of the heteroatoms in the form of the simple substance is 0.2 wt% to 30 wt%, and the content of the carbon base is 70 wt% to 99.8 wt%; the Raman spectrum of the catalyst has a D peak and a G peak, and I D / I G is 0.88 to 1.20. The catalyst has high reaction activity and good stability, and is suitable for the reaction of preparing nitrile compounds by amide dehydration.

Description

Technical Field

[0001] The present invention belongs to the field of catalysts, and particularly relates to a solid acid catalyst for amide dehydration, a preparation method thereof, and an application thereof. Background Art

[0002] Cyano-substituted nitrile compounds have wide applications in the fields of medicine, pesticides, fine chemicals, polymers, etc., and are important chemical raw materials. Nitrile compounds can be synthesized through two routes: ammoxidation and chemical methods. The ammoxidation method obtains nitriles in one step under the action of a catalyst in the presence of oxygen and ammonia. The steps are simple and the yield is high. However, the R & D cost of the catalyst is high. Moreover, due to the molecular structure, some nitrile compounds still have disadvantages such as harsh reaction conditions, low yield, and many by-products. Therefore, the chemical synthesis of nitrile compounds still has certain value.

[0003] There are many chemical synthesis routes for nitrile compounds, which usually include cyanide substitution method, aldoxime dehydration method, amide dehydration method, etc. Among them, the amide dehydration method has lower toxicity, is environmentally friendly, has low raw material cost, and is more feasible. Therefore, the research on the preparation of nitrile compounds by the amide dehydration method has important significance. Commonly used amide dehydrating agents include phosphorus pentoxide, phosphorus pentachloride, phosphorus oxychloride, thionyl chloride, phosgene, p-toluenesulfonyl chloride, etc. Other dehydration systems also include titanium tetrachloride-tertiary amine, triphenylphosphine-carbon tetrachloride-triethylamine, trichloroacetyl chloride-triethylamine, trifluoromethanesulfonic anhydride-triethylamine, dibutyltin oxide, etc. In addition, there are also a few catalytic methods reported, such as under strong heating conditions, using catalytic species such as alumina, silica, and aluminum phosphate, and using molecular sieves and other auxiliary agents to absorb water.

[0004] CN104774160A discloses a preparation method of a cyclopropylmethyl cyanide derivative. This method uses cyclopropylformamide as a raw material and synthesizes cyclopropylmethyl cyanide under the action of a dehydrating agent. The dehydrating agent is selected from one of thionyl chloride, liquid phosgene, phosphorus pentoxide, and p-toluenesulfonyl chloride.

[0005] In the above methods, the dehydrating agents used have problems such as being toxic, having relatively large corrosion to equipment, or complex product separation, and the heterogeneous reaction system also has problems such as poor stability or low reaction activity. Summary of the Invention

[0006] Aiming at the problems existing in the prior art, the purpose of the present invention is to provide a solid acid catalyst for amide dehydration, a preparation method thereof, and an application thereof. This catalyst has high reaction activity, good stability, is simple to prepare, has low cost, and has a wide range of raw material sources, realizes the continuous reaction dehydration process of amide compounds, and is suitable for large-scale chemical production of nitrile compounds.

[0007] The present invention provides a solid acid catalyst for amide dehydration, and the catalyst comprises: a carbon-based material and heteroatoms supported on the carbon-based material; based on the total weight of the catalyst, the content of the heteroatoms in elemental form is 0.2 wt% to 30 wt%, preferably 0.8 wt% to 20 wt%; the content of the carbon-based material is 70 wt% to 99.8 wt%, preferably 80 wt% to 99.2 wt%; in the Raman spectrum of the catalyst, there are D peak and G peak, and I D / I G is 0.88 to 1.20.

[0008] According to the present invention, further, the heteroatoms are one or more of Group IIIA, Group VA and Group VIA, preferably at least one of P and S.

[0009] According to the present invention, further, the catalyst further contains a metal promoter; the metal promoter includes at least one of metals in Group IA, Group IIA, and Zn, Zr, Mo, W, Ti, Mn, Co, and Ni. Preferably, based on the total weight of the solid acid catalyst, the content of the metal promoter in elemental form is 0.2% to 5%, preferably 0.3% to 2%.

[0010] According to the present invention, based on the total weight of the solid acid catalyst, within the range of the content of the carbon-based material, the non-limiting specific point values of the carbon-based material can be: 61%, 63%, 65%, 67%, 69%, 71%, 73%, 75%, 77%, 79%, 81%, 83%, 85%, 87%, 90%, 92%, 94%, 96%, 98%, 99%, 99.5%.

[0011] The second aspect of the present invention provides a preparation method of the above solid acid catalyst; the method comprises the following steps:

[0012] (1) Using starch as a carbon source, mixing the starch and water evenly;

[0013] (2) Mixing the heteroatom source solution and optionally the metal promoter source solution with the product of step (1), carrying out hydrothermal carbonization, and separating to obtain a solid product;

[0014] (3) Performing heat treatment on the solid product obtained in step (2) to obtain the solid acid catalyst.

[0015] According to the present invention, further, in step (1), the mass ratio of starch to water is 1:8 to 15. Preferably, the mixing can be carried out under heating conditions. Among them, the heating temperature is 80 to 100 °C, and the time is 0.5 to 2 h.

[0016] According to the present invention, further, in step (2), the raw materials are mixed by dropwise adding the heteroatom source solution to the product of step (1). The device for hydrothermal carbonization is a hydrothermal autoclave; the conditions for hydrothermal carbonization are: temperature 180 - 220 °C, time 8 - 48 h. The pressure for hydrothermal carbonization is not particularly limited and is the self-generated pressure of the reaction. The solid-liquid separation method is at least one of filtration and suction filtration. Preferably, after filtering the solid product, it can be washed and dried. The washing is preferably carried out first with water and then with ethanol. The drying conditions are: temperature 80 - 120 °C, time 2 - 24 h.

[0017] According to the present invention, further, in step (2), the heteroatom source is a heteroatom-containing compound; preferably one or more of oxides, acids, ammonium salts, halides, and organic compounds of the heteroatom, more preferably one or more of heteroatom acids, and even more preferably one or more of H2SO4 and H3PO4. If the heteroatom is S, the sulfur source does not include oxides.

[0018] According to the present invention, further, in step (2), the mass concentration of the heteroatom source solution is 30 wt% - 98 wt%. The mass of the heteroatom source solution is 9% - 100% of the mass of the product of step (1). If there are two or more heteroatoms, the mass of the heteroatom source solution in step (2) is the sum of the masses of all heteroatom solutions.

[0019] According to the present invention, further, in step (2), the metal promoter source is at least one of an acid and a salt of the metal promoter.

[0020] According to the present invention, further, in step (2), the mass concentration of the metal promoter source solution in terms of metal atoms is 0.2 wt% - 13 wt%. The mass of the metal promoter source solution is 1% - 100% of the mass of the product of step (1). If there are two or more metal promoters, the mass of the metal promoter source solution in step (2) is the sum of the masses of all metal promoter solutions.

[0021] According to the present invention, further, in step (3), the conditions for the heat treatment are: temperature 500 - 1200 °C, time 4 - 16 h. The treatment atmosphere is a non-oxygen atmosphere; preferably at least one of He, N2, and Ar.

[0022] The third aspect of the present invention provides the use of the above solid acid catalyst or the solid acid catalyst prepared by the above method in the preparation of nitrile compounds.

[0023] According to the present invention, further, the use is to cause the amide compound dissolved in an organic solvent to undergo an amide dehydration reaction under the action of the solid acid catalyst to generate the corresponding nitrile compound.

[0024] According to the present invention, further, dissolving the amide compound in an organic solvent enables the amide compound to be continuously fed in a liquid state.

[0025] According to the present invention, further, the molar ratio of the amide compound to the organic solvent is 1:(1 - 5), preferably 1:(1.5 - 2.5).

[0026] According to the present invention, further, the amide compound includes at least one of benzamide, isophthalamide, phthalamide, terephthalamide, adipamide, acetamide, and acrylamide.

[0027] According to the present invention, further, the organic solvent includes one or more selected from N,N - dimethylformamide, N,N - dimethylacetamide, and N - methylpyrrolidone.

[0028] According to the present invention, further, the conditions for the amide dehydration reaction include: the reaction temperature is 150 - 450 °C, the mass space velocity of the amide compound is 0.05 - 4 h -1 , and the reaction pressure (absolute pressure) is atmospheric pressure to 0.2 MPa.

[0029] Further, a protective gas can be introduced during the reaction process; the gas includes at least one of NH3, N2, He, and Ar.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) In the present invention, the solid acid catalyst for the amide dehydration reaction includes: a carbon base and a heteroatom supported on the carbon base; based on the total weight of the catalyst, the content of the heteroatom in elemental form is 0.2 wt% - 30 wt%, preferably 0.8 wt% - 20 wt%; the content of the carbon base is 70 wt% - 99.8 wt%, preferably 80 wt% - 99.2 wt%; the Raman spectrum of the catalyst has a D peak and a G peak, and I D / I G is 0.88 - 1.2. The catalyst of the present invention has high reaction activity and good stability, and is suitable for the reaction of amide dehydration to prepare nitrile compounds.

[0032] (2) In the present invention, in the preparation method of the catalyst, starch is used as the carbon source, and through hydrothermal carbonization and heat treatment with a heteroatom source solution and optionally a metal promoter source solution, a solid acid catalyst is obtained. In this method, the specific carbon source starch is selected, with a wide range of raw material sources. Moreover, both carbonization and loading are completed in one step by hydrothermal treatment, the product is easy to separate, the cost is low, the preparation method is simple and practical, and it is convenient for large-scale production. The obtained catalyst has high reaction activity and good stability, and is suitable for the reaction of dehydrating amides to prepare nitrile compounds. In addition, in the reaction of preparing nitriles, compared with the existing liquid-phase dehydrating agents or other solid acid catalysts, the present invention adopts a continuous reaction mode, with simple operation and high production efficiency.

[0033] (3) In the reaction of using the catalyst of the present invention for dehydrating amides to prepare nitrile compounds, the catalyst has high reaction activity and good stability. In the reaction of the present invention for dehydrating amides to prepare nitriles, a continuous reaction mode is adopted, with simple operation and high production efficiency. Description of the Drawings

[0034] Figure 1 It is the Raman spectra of the catalysts obtained in Examples 1 to 3 and Comparative Examples 1 and 2. Detailed Embodiments

[0035] The following further describes the present invention in detail with specific embodiments. The implementation manners of the present invention are not limited thereto, and at the same time, the embodiments do not limit the protection scope of the present invention.

[0036] In the implementation manner of the present invention, the pore structure characterization of the catalyst by low-temperature nitrogen adsorption analysis is measured by a Micromeritics TriStar 3000 multi-channel physical adsorption instrument, and the operating temperature is -196 °C. The catalyst is vacuum degassed at 180 °C for 4 hours before measurement, and the specific surface area of the molecular sieve is calculated according to the Brunauer-Emmett-Teller (BET) model.

[0037] In the implementation manner of the present invention, the Raman spectrum of the catalyst is analyzed using a Jobin Yvon LabRam-1B. The light source is a He-Ne laser (632.8 nm), the power is 64 mW, and a CCD detector is used. In the Raman spectrum, I D is the peak intensity of the highest peak of the D peak (defect peak) in the range of 1200 - 1400 cm -1 , and I G is the peak intensity of the highest peak of the G peak (sp -1 hybridized carbon atom vibration peak) in the range of 1500 - 1700 cm 2 . Then, the intensity ratio of the D peak and the G peak is calculated to obtain I D / I G .

[0038] In the embodiment of the present invention, the composition of the catalyst is analyzed by inductively coupled plasma optical emission spectrometer (ICP). After the catalyst is crushed and ground into powder, it is mixed and soaked with 2 mol / L HF solution and the powdered catalyst after sufficient grinding in a volume ratio of 2:1 for 4 hours. The liquid is filtered, diluted 20 times, and then the heteroatom content is analyzed.

[0039] In the embodiment of the present invention, the conversion rate % of the amide compound and the nitrile yield % are defined as follows:

[0040]

[0041]

[0042] In the above formula, the molar number of amide feed is the molar number of the amide compound in the raw material; the amide compound includes at least one of benzamide, isophthalamide, phthalic amide, terephthalamide, adipamide, acetamide, and acrylamide; the molar number of amide in the product in the above formula does not include N,N-dimethylformamide and N,N-dimethylacetamide in the organic solvent.

[0043]

Example 1

[0044] (1) Starch and water are mixed at a mass ratio of 1:8 and stirred at 80 °C for 1 h until evenly mixed.

[0045] (2) 10% of the mass of the mixture in step (1) is weighed as a 98% H2SO4 solution, which is added dropwise to the mixed solution obtained in step (1). Then, the obtained raw material liquid is transferred to a hydrothermal autoclave and carbonized at 200 °C for 12 h. The obtained solid is filtered by suction, washed with water and ethanol respectively, and then dried at 80 °C for 12 h.

[0046] (3) The solid product obtained in step (2) is transferred into a quartz boat, placed in an Ar atmosphere, and heat-treated at 750 °C for 4 hours to obtain a carbon-based solid acid catalyst.

[0047] The composition of the obtained catalyst is as follows: the carbon content is 98.9 wt%, and the S content is 1.1%.

[0048] The Raman spectrum of the obtained catalyst is shown in Figure 1 .I D / I G is 0.95.

[0049] Charge 1 g of the carbon-based solid acid catalyst of this example into a fixed-bed reactor. Dissolve benzamide in the organic solvent N,N-dimethylformamide, with the molar ratio of benzamide:DMF being 1:2, and continuously feed it in a liquid state. Carry out the reaction under N2 protection. The reaction temperature is 300 °C, the reaction pressure is 0.125 MPa, and the mass space velocity of benzamide is 1.5 h -1 . React for 8 hours, and the conversion rate of benzamide is measured to be 95.6%, and the selectivity for benzonitrile is 93.5%. Operate continuously for 120 hours, and the conversion rate of benzamide is measured to be 94.3%, and the selectivity for benzonitrile is 92.7%.

[0050]

Example 2

[0051] (1) Starch and water are mixed in a mass ratio of 1:8 and stirred at 80 °C for 1 h to be uniformly mixed.

[0052] (2) Weigh 98% H2SO4 solution according to 10% of the mass of the mixture in step (1), and add it dropwise to the mixed solution obtained in step (1). Subsequently, weigh 3% KNO3 solution according to 20% of the mass of the mixture in step (1), and add it dropwise to the above mixed solution. Then, transfer the obtained raw material liquid to a hydrothermal autoclave and carbonize it at 200 °C for 12 h. The obtained solid is filtered by suction, washed with water and ethanol respectively, and then dried at 80 °C for 12 h.

[0053] (3) Transfer the solid product obtained in step (2) into a quartz boat, place it in an Ar atmosphere, and heat-treat it at 750 °C for 4 hours to obtain a carbon-based solid acid catalyst.

[0054] The composition of the obtained catalyst is as follows: the carbon content is 98.4 wt%, the S content is 1.1%, and the K content is 0.5%.

[0055] The Raman spectrum of the obtained catalyst is shown in Figure 1 .

[0056] The Raman spectrum I D / I G is 0.98.

[0057] Charge 1 g of the carbon-based solid acid catalyst of this example into a fixed-bed reactor. Dissolve m-methylbenzamide in the organic solvent N,N-dimethylformamide, with the molar ratio of m-methylbenzamide:DMF being 1:2, and continuously feed it in a liquid state. Carry out the reaction under N2 protection. The reaction temperature is 350 °C, the reaction pressure is 0.125 MPa, and the mass space velocity of m-methylbenzamide is 1.5 h -1The reaction was carried out for 8 hours, and the conversion rate of m-methylbenzamide was 96.7%, and the selectivity of m-methylbenzonitrile was 95.3%. After long-term operation for 120 hours, the conversion rate of m-methylbenzamide was measured to be 93.8%, and the selectivity of m-methylbenzonitrile was 90.5%.

[0058]

Example 3

[0059] (1) Starch and water were mixed evenly at a mass ratio of 1:8 and stirred at 80 °C for 1 h.

[0060] (2) A sulfuric acid solution with a mass fraction of 98% was weighed according to 10% of the mass of the mixture in step (1), and a phosphoric acid solution with a mass fraction of 85% was weighed according to 10% of the mass of the mixture in step (1). After mixing them, they were added dropwise to the mixed solution obtained in step (1). Subsequently, a potassium nitrate solution with a mass fraction of 4% was weighed according to 20% of the mass of the mixture in step (1) and added dropwise to the above mixed solution. Then, the obtained raw material liquid was transferred to a hydrothermal autoclave and carbonized at 200 °C for 12 h. The obtained solid was filtered by suction and washed with water and ethanol respectively, and then dried at 80 °C for 12 h.

[0061] (3) The solid product obtained in step (2) was transferred into a quartz boat and placed in an Ar atmosphere, and heat-treated at 750 °C for 4 hours to obtain a carbon-based solid acid catalyst.

[0062] The composition of the obtained catalyst is as follows: the carbon content is 96.5 wt%, the S content is 1.7%, the P content is 1.2%, and the K content is 0.6%.

[0063] The Raman spectrum I D / I G is 1.03.

[0064] 1 g of the carbon-based solid acid catalyst was loaded into a fixed-bed reactor. Phthalic amide was dissolved in an organic solvent of N,N-dimethylformamide, and the molar ratio of phthalic amide to DMF was 1:2. It was fed continuously in a liquid state and reacted under N2 protection. The reaction temperature was 350 °C, the reaction pressure was 0.125 MPa, and the mass space velocity of m-methylbenzamide was 1.5 h -1 . The reaction was carried out for 8 hours, and the conversion rate of phthalic amide was 97.0%, and the selectivity of phthalonitrile was 80.1%. After long-term operation for 120 hours, the conversion rate of phthalic amide was measured to be 92.3%, and the selectivity of phthaloyl nitrile was 74.5%.

[0065]

Example 4

[0066] (1) Starch and water were mixed evenly at a mass ratio of 1:10 and stirred at 80 °C for 1 h.

[0067] (2) Weigh 98% H₂SO₄ solution according to 10% of the mass of the mixture in step (1) and add it dropwise to the mixture obtained in step (1). Subsequently, weigh 85% phosphoric acid according to 5% of the mass of the mixture in step (1), dissolve it, and add it dropwise to the above mixture. Then, transfer the obtained raw material liquid to a hydrothermal autoclave and carbonize it at 220 °C for 16 h. The obtained solid is filtered by suction, washed with water and ethanol respectively, and then dried at 80 °C for 12 h.

[0068] (3) Transfer the solid product obtained in step (2) into a quartz boat, place it in an Ar atmosphere, and heat-treat it at 750 °C for 4 hours to obtain a carbon-based solid acid catalyst.

[0069] The composition of the obtained catalyst is as follows: the carbon content is 97.9 wt%, the S content is 1.6%, and the P content is 0.5%.

[0070] The Raman spectrum I D / I G is 1.00.

[0071] Load 1 g of the carbon-based solid acid catalyst into a fixed-bed reactor. Dissolve acetophenone amide in an organic solvent of N,N-dimethylformamide. The molar ratio of acetophenone amide to DMF is 1:2, and it is fed continuously in a liquid state. The reaction is carried out under N₂ protection. The reaction temperature is 330 °C, the reaction pressure is 0.125 MPa, and the mass space velocity of acetophenone amide is 1.5 h -1 . After reacting for 8 hours, the conversion rate of acetophenone amide is 97.4%, and the selectivity for benzonitrile is 92.1%. After running for 120 hours continuously, the measured conversion rate of acetophenone amide is 91.6%, and the selectivity for benzonitrile is 85.7%.

[0072]

Example 5

[0073] (1) Starch and water are mixed evenly at a mass ratio of 1:10 by stirring at 80 °C for 1 h.

[0074] (2) Weigh 98% H₂SO₄ solution according to 5% of the mass of the mixture in step (1) and add it dropwise to the mixture obtained in step (1). Subsequently, weigh 85% H₃PO₄ according to 4% of the mass of the mixture in step (1) and weigh 3% RbNO₃ solution according to 2% of the mass of the mixture in step (1). After mixing H₃PO₄ and RbNO₃ solutions, add them dropwise to the above solution. Then, transfer the obtained raw material liquid to a hydrothermal autoclave and carbonize it at 190 °C for 12 h. The obtained solid is filtered by suction, washed with water and ethanol respectively, and then dried at 80 °C for 12 h.

[0075] (3) Transfer the solid product obtained in step (2) into a quartz boat, place it in an Ar atmosphere, and heat-treat it at 750 °C for 4 hours to obtain a carbon-based solid acid catalyst.

[0076] The composition of the obtained catalyst is as follows: the carbon content is 98.2 wt%, the S content is 0.7%, the P content is 0.8%, and the Rb content is 0.3%.

[0077] The Raman spectrum I of the obtained catalyst D / I G is 1.00.

[0078] Charge 1 g of the carbon-based solid acid catalyst in a fixed-bed reactor. Dissolve 2-pyridinecarboxamide in the organic solvent N,N-dimethylformamide. The molar ratio of 2-pyridinecarboxamide to DMF is 1:2, and it is fed continuously in a liquid state. The reaction is carried out under N2 protection. The reaction temperature is 280 °C, the reaction pressure is 0.125 MPa, and the mass space velocity of 2-pyridinecarboxamide is 3 h -1 . After reacting for 8 h, the conversion rate of 2-pyridinecarboxamide is 99.0%, and the selectivity for 2-cyanopyridine is 98.5%. After operating for 120 h continuously, the conversion rate of 2-pyridinecarboxamide is measured to be 96.8%, and the selectivity for 2-cyanopyridine is 96.0%.

[0079]

Example 6

[0080] (1) Starch and water are mixed at a mass ratio of 1:8 and stirred at 80 °C for 1 h to be uniformly mixed.

[0081] (2) Weigh a 98% H2SO4 solution according to 5% of the mass of the mixture in step (1) and add it dropwise to the mixed solution obtained in step (1). Subsequently, weigh 85% H3PO4 according to 8% of the mass of the mixture in step (1), and weigh a 12.5% Ba(NO3)2 solution according to 1% of the mass of the mixture in step (1). After mixing, add it dropwise to the above solution. Then, transfer the obtained raw material liquid to a hydrothermal autoclave and carbonize it at 210 °C for 12 h. The obtained solid is filtered by suction, washed with water and ethanol respectively, and then dried at 80 °C for 12 h.

[0082] (3) Transfer the solid product obtained in step (2) into a quartz boat, place it in an Ar atmosphere, and heat-treat it at 750 °C for 4 hours to obtain a carbon-based solid acid catalyst.

[0083] The composition of the obtained catalyst is as follows: the carbon content is 97.7 wt%, the S content is 0.8%, the P content is 0.9%, and the Ba content is 0.6%.

[0084] The Raman spectrum I of the obtained catalyst D / I GIt is 1.01.

[0085] Charge 1 g of carbon-based solid acid catalyst in a fixed-bed reactor. Dissolve 2-pyrazinecarboxamide in the organic solvent N,N-dimethylformamide. The ratio of 2-pyrazinecarboxamide to DMF is 1:2, and it is continuously fed in liquid form. The reaction is carried out under N2 protection. The reaction temperature is 280 °C, the reaction pressure is 0.125 MPa, and the mass space velocity of 2-pyrazinecarboxamide is 3 h -1 . After reacting for 8 h, the conversion rate of 2-pyrazinecarboxamide is 97.7%, and the selectivity of 2-cyanopyrazine is 98.1%. After running for 120 h continuously, the conversion rate of 2-pyrazinecarboxamide is measured to be 93.4%, and the selectivity of 2-cyanopyrazine is 89.9%.

[0086]

Example 7

[0087] (1) Starch and water are mixed in a mass ratio of 1:8 and stirred at 80 °C for 1 h to be evenly mixed.

[0088] (2) Weigh 98% H2SO4 solution according to 12% of the mass of the mixture in step (1) and add it dropwise to the mixed solution obtained in step (1). Subsequently, weigh 85% H3PO4 according to 15% of the mass of the mixture in step (1), and weigh 7.5% Ba(NO3)2 solution according to 2% of the mass of the mixture in step (1). Mix them and add them dropwise to the above mixed solution. Then, transfer the obtained raw material liquid to a hydrothermal autoclave and carbonize it at 190 °C for 16 h. The obtained solid is filtered by suction, washed with water and ethanol respectively, and then dried at 80 °C for 12 h.

[0089] (3) Transfer the solid product obtained in step (2) into a quartz boat, place it in an Ar atmosphere, and heat-treat it at 800 °C for 6 hours to obtain a carbon-based solid acid catalyst.

[0090] The composition of the obtained catalyst is as follows: the carbon content is 97.7 wt%, the S content is 0.8%, the P content is 0.9%, and the Ba content is 0.6%.

[0091] The Raman spectrum I D / I G is 0.97.

[0092] Charge 1 g of carbon-based solid acid catalyst in a fixed-bed reactor. Dissolve adipamide in the organic solvent N,N-dimethylformamide. The ratio of adipamide to DMF is 1:2, and it is continuously fed in liquid form. The reaction is carried out under N2 protection. The reaction temperature is 350 °C, the reaction pressure is 0.15 MPa, and the mass space velocity of adipamide is 3 h -1After reacting for 8 h, the conversion rate of adipamide was 98.6%, and the selectivity for adiponitrile was 98.1%. After long-term operation for 120 h, the conversion rate of adipamide was measured to be 92.2%, and the selectivity for adiponitrile was 90.1%.

[0093]

Example 8

[0094] (1) Starch and water were mixed at a mass ratio of 1:15 and stirred at 80 °C for 1 h to be uniformly mixed.

[0095] (2) A 98% H2SO4 solution was weighed at 10% of the mass of the mixture in step (1) and added dropwise to the mixed solution obtained in step (1). Subsequently, 85% H3PO4 was weighed at 15% of the mass of the mixture in step (1), and a 10% Zn(NO3)2 solution was weighed at 2% of the mass of the mixture in step (1). After mixing them, they were added dropwise to the above solution. Then, the obtained raw material liquid was transferred to a hydrothermal autoclave and carbonized at 190 °C for 24 h. The obtained solid was filtered by suction, washed with water and ethanol respectively, and then dried at 80 °C for 12 h.

[0096] (3) The solid product obtained in step (2) was transferred into a quartz boat, placed in an Ar atmosphere, and heat-treated at 750 °C for 12 h to obtain a carbon-based solid acid catalyst.

[0097] The composition of the obtained catalyst was as follows: the carbon content was 96.1 wt%, the S content was 1.9%, the P content was 1.0%, and the Zn content was 1.0%.

[0098] The Raman spectrum I D / I G was 0.96.

[0099] 1 g of the carbon-based solid acid catalyst was loaded in a fixed-bed reactor. Acetamide was dissolved in an organic solvent of N,N-dimethylformamide, and the ratio of acetamide:DMF was 1:2. It was continuously fed in a liquid state and reacted under N2 protection. The reaction temperature was 370 °C, the reaction pressure was 0.14 MPa, and the mass space velocity of acetamide was 4 h -1 After reacting for 8 h, the conversion rate of acetamide was 100.0%, and the selectivity for acetonitrile was 97.6%. After long-term operation for 120 h, the conversion rate of acetamide was measured to be 92.1%, and the selectivity for acetonitrile was 93.5%.

[0100]

Comparative Example 1

[0101] (1) Activated carbon was selected as the carbon source. According to the stoichiometric ratio in the catalyst composition of Example 1, H2SO4 solution was added dropwise to the above carbon source for equal-volume impregnation. It was left at room temperature of 25 °C for 120 hours, then dried at 80 °C for 12 h, and finally transferred into a quartz boat and placed in an Ar atmosphere for heat treatment at 750 °C for 4 hours to obtain a carbon-based solid acid catalyst.

[0102] The composition of the obtained catalyst was as follows: the carbon content was 98.9 wt%, and the S content was 1.1%.

[0103] The Raman spectrum of the obtained catalyst is shown in Figure 1 . I D / I G was 0.82.

[0104] 1 g of the carbon-based solid acid catalyst of this comparative example was loaded into a fixed-bed reactor. Benzamide was dissolved in the organic solvent N,N-dimethylformamide, and the molar ratio of benzamide:DMF was 1:2. It was fed continuously in liquid form and reacted under N2 protection. The reaction temperature was 300 °C, and the reaction pressure was 0.125 MPa. The mass space velocity of benzamide was 1.5 h -1 . After reacting for 8 hours, the conversion rate of benzamide was measured to be 94.3%, and the selectivity for benzonitrile was 91.7%. After running for 120 hours continuously, the conversion rate of benzamide was measured to be 85.3%, and the selectivity for benzonitrile was 79.6%.

[0105]

Comparative Example 2

[0106] Starch was used as the carbon source. A certain amount of starch was taken. According to the stoichiometric ratio in the catalyst composition of Example 1, H2SO4 solution was added dropwise to the above carbon source for equal-volume impregnation. It was left at room temperature of 25 °C for 120 hours, then dried at 80 °C for 12 h, and finally transferred into a quartz boat and placed in an Ar atmosphere for heat treatment at 750 °C for 4 hours to obtain a carbon-based solid acid catalyst.

[0107] The composition of the obtained catalyst was as follows: the carbon content was 98.9 wt%, and the S content was 1.1%.

[0108] The Raman spectrum of the catalyst is shown in Figure 1 . I D / I G was 0.78.

[0109] 1 g of the carbon-based solid acid catalyst of this comparative example was loaded into a fixed-bed reactor. Benzamide was dissolved in the organic solvent N,N-dimethylformamide, and the ratio of benzamide:DMF was 1:2. It was fed continuously in liquid form and reacted under N2 protection. The reaction temperature was 300 °C, and the reaction pressure was 0.125 MPa. The mass space velocity of benzamide was 1.5 h -1。The reaction was carried out for 8 hours, and the conversion rate of benzamide was measured to be 53.2%, and the selectivity for benzonitrile was 49.1%. After long-term operation for 120 hours, the conversion rate of benzamide was measured to be 39.6%, and the selectivity for benzonitrile was 35.3%.

Claims

1. A solid acid catalyst for amide dehydration, the catalyst comprising: A carbon-based material and a heteroatom supported on the carbon-based material; based on the total weight of the catalyst, the content of the heteroatom in elemental form is 0.2 wt% to 30 wt%; the content of the carbon-based material is 70 wt% to 99.8 wt%; the Raman spectrum of the catalyst has a D peak and a G peak, and I D / I G is 0.88 to 1.20; The heteroatom is at least one of P and S; The preparation method of the solid acid catalyst comprises the following steps: (1) Using starch as a carbon source, mixing starch and water evenly; (2) Mixing the heteroatom source solution and optionally the metal promoter source solution with the product of step (1), performing hydrothermal carbonization, and separating to obtain a solid product; (3) Performing heat treatment on the solid product obtained in step (2) to obtain the solid acid catalyst.

2. The solid acid catalyst according to claim 1, wherein Based on the total weight of the catalyst, the content of the heteroatom in elemental form is 0.8 wt% to 20 wt%; the content of the carbon-based is 80 wt% to 99.2 wt%.

3. The solid acid catalyst according to claim 1, wherein The catalyst contains a metal promoter.

4. The solid acid catalyst according to claim 3, wherein Based on the total weight of the solid acid catalyst, the content of the metal promoter in elemental form of the metal is 0.2% to 5%.

5. The solid acid catalyst according to claim 4, wherein The content of the metal promoter in elemental form of the metal is 0.3% to 2%.

6. The solid acid catalyst according to claim 3, characterized in that, The metal promoter includes at least one of metals of Group IA and Group IIA and Zn, Zr, Mo, W, Ti, Mn, Co, and Ni.

7. A preparation method of the solid acid catalyst according to any one of claims 1 to 6, the method comprising the following steps: (1) Using starch as a carbon source, mixing starch and water evenly; (2) Mixing the heteroatom source solution and optionally the metal promoter source solution with the product of step (1), performing hydrothermal carbonization, and separating to obtain a solid product; (3) Performing heat treatment on the solid product obtained in step (2) to obtain the solid acid catalyst.

8. The preparation method according to claim 7, characterized in that, In step (1), the mass ratio of starch to water is 1:8 to 15; and / or, the mixing in step (1) is carried out under heating conditions, the heating temperature is 80 to 100 °C, and the time is 0.5 to 2 h.

9. The preparation method according to claim 7, characterized in that, The mixing method of the raw materials in step (2) is to dropwise add the heteroatom source solution into the product of step (1); and / or, the conditions of the hydrothermal carbonization in step (2) are: temperature 180 to 220 °C, time 8 to 48 h.

10. The preparation method according to claim 7, characterized in that, In step (2), the heteroatom source is a heteroatom-containing compound; and / or, the mass concentration of the heteroatom source solution in elemental form of the heteroatom is 30 wt% to 98 wt%; the mass of the heteroatom source solution is 9% to 100% of the mass of the product of step (1); and / or, the metal promoter source in step (2) is at least one of an acid and a salt of the metal promoter; and / or, the mass concentration of the metal promoter source solution in elemental form of the metal atom is 0.2 wt% to 13 wt%; the mass of the metal promoter source solution is 1% to 100% of the mass of the product of step (1).

11. According to the preparation method described in claim 10, characterized in that, In step (2), the heteroatom source is one or more of oxides, acids, ammonium salts, halides, and organic compounds of the heteroatom.

12. According to the preparation method described in claim 11, characterized in that, In step (2), the heteroatom source is one or more of heteroatom acids.

13. According to the preparation method described in claim 12, wherein, In step (2), the heteroatom source is one or more of H2SO4 and H3PO4.

14. The preparation method according to claim 7, characterized in that, In step (3), the conditions of the heat treatment are: temperature 500 to 1200 °C, time 4 to 16 h; and / or, the treatment atmosphere of the heat treatment in step (3) is a non-oxygen atmosphere.

15. The preparation method according to claim 14, characterized in that, The treatment atmosphere of the heat treatment in step (3) is at least one of He, N2, and Ar.

16. Use of the solid acid catalyst according to any one of claims 1 to 6 or the solid acid catalyst prepared by the preparation method according to any one of claims 7 to 15 in the dehydration of amides to prepare nitrile compounds.

17. The application according to claim 16, wherein The use is that an amide compound dissolved in an organic solvent undergoes an amide dehydration reaction under the action of the solid acid catalyst to generate a corresponding nitrile compound; and / or, the organic solvent includes one or more selected from N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

18. The application according to claim 17, wherein The amide compounds include at least one of benzamide, isophthalamide, phthalamide, terephthalamide, adipamide, acetamide, and acrylamide.

19. The application according to claim 16 or 17, characterized in that, The molar ratio of the amide compound to the organic solvent is 1:(1-5); and / or, the conditions for the amide dehydration reaction include: the reaction temperature is 150-450 °C, and the mass space velocity of the amide compound is 0.05-4 h -1 , and the reaction pressure is atmospheric pressure - 0.2 MPa.

20. The application according to claim 19, wherein The molar ratio of the amide compound to the organic solvent is 1:(1.5 - 2.5).

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