A one-dimensional nitrogen-phosphorus-oxygen catalyst, its preparation, and its application in dehydrogenation for preparing olefin-containing compounds

Abstract

The present invention relates to the field of catalysis, and specifically discloses a preparation method of a one-dimensional nitrogen-phosphorus-oxygen catalyst. The raw materials of formula 1 are subjected to two-stage heat treatment in a mixed atmosphere containing ammonia-oxygen to obtain the one-dimensional nitrogen-phosphorus-oxygen catalyst; in the mixed atmosphere, the volume content of ammonia is 85-98%; the two-stage heat treatment process includes a T1 heat preservation section and a T2 heat preservation section, wherein the temperature of T1 is 100-130 °C; the temperature of T2 is 750-950 °C. The present invention also includes the catalyst prepared by the above preparation method and its application in dehydrogenation to produce olefins. The present invention has prepared a brand-new catalyst, and it can obtain better catalytic selectivity and stability based on a brand-new action mode.

Description

Technical Field

[0001] The present invention relates to the field of industrial catalysis, specifically to a field of dehydrogenation catalysts for alkyl compounds. Background Art

[0002] Currently, styrene, as an industrial raw material, has a broad application market in multiple industries. Relevant data shows that since 2014, the import volume of styrene in China has remained above 1.5 million tons per year, while the export volume is only less than 0.25 million tons, indicating that the domestic production of styrene has been unable to meet the demand and relies on imports. Therefore, the research on new catalysts for improving the styrene yield is crucial.

[0003] Currently, the preparation of styrene is mainly obtained by catalytic dehydrogenation of ethylbenzene under high-temperature conditions. Using potassium-containing iron oxide as a catalyst and water vapor as a high-temperature dehydrogenation medium for ethylbenzene dehydrogenation is the most widely used technology in the industry at present. The main problems of this technology are twofold: First, the catalyst is prone to carbon deposition, so a large amount of water vapor must be introduced simultaneously to remove carbon deposition, resulting in high energy consumption; Second, the introduction of water vapor is also likely to cause the loss of potassium elements in the catalyst, leading to a decrease in the stability of the catalyst. The catalysts reported in patents CN200910057803, CN101829576A, CN102040466A, CN103028419A, CN101279263, CN10142273, and European patent 0177832 are based on the above potassium-containing iron oxide catalyst and added heavy metal elements such as cerium, molybdenum, lead, and copper to reduce the water-hydrocarbon ratio. However, the addition of heavy metals not only increases the cost of the catalyst but also causes more pollution to the environment. In addition, the addition of multiple metal elements also makes the preparation process of these catalysts more cumbersome and the corresponding cost increases.

[0004] Recently, researchers have extended their research direction to non-metal catalysts. For example, boron carbide reported in CN109126843A, nanodiamond reported in CN112717972A, and phosphorus-doped boron nitride reported in CN201910739798.4 and CN202110541901.1 all showed good alkane dehydrogenation ability under the condition of no water vapor introduction. The invention of the above catalysts has greatly promoted the research on the application of non-metal catalysts in ethylbenzene dehydrogenation. However, due to the relatively cumbersome preparation process of carbon materials and boron nitride materials, with many steps, it is not conducive to the scale-up of industrial catalysts. Therefore, on the basis of ensuring certain performance, simplifying the preparation process of the catalyst is of great significance for the popularization of this type of catalyst. Summary of the Invention

[0005] Aiming at the problems of complex preparation and unsatisfactory performance of existing non-metal dehydrogenation catalysts, the first object of the present invention is to provide a preparation method of a one-dimensional nitrogen-phosphorus-oxygen catalyst, aiming to obtain a brand-new dehydrogenation catalyst with excellent dehydrogenation ability.

[0006] The second object of the present invention is to provide a one-dimensional nitrogen-phosphorus-oxygen catalyst prepared by the above-mentioned preparation method.

[0007] The third object of the present invention is to provide the application of the one-dimensional nitrogen-phosphorus-oxygen catalyst in the dehydrogenation of ethyl group (C-C) to prepare vinyl group (C=C).

[0008] A preparation method of a one-dimensional nitrogen-phosphorus-oxygen catalyst, wherein the raw materials of formula 1 are subjected to two-stage heat treatment in a mixed atmosphere containing ammonia-oxygen to obtain the one-dimensional nitrogen-phosphorus-oxygen catalyst;

[0009]

[0010] In the above-mentioned mixed atmosphere, the volume content of ammonia is 85-98%.

[0011] The two-stage heat treatment process includes a T1 holding section and a T2 holding section. Among them, the temperature of T1 is 90-150°C; the temperature of T2 is 750-950°C.

[0012] Research in the present invention shows that innovatively subjecting the compound of formula 1 to two-stage calcination treatment (two-stage heat treatment) in a mixed atmosphere of ammonia-oxygen, and further cooperating with the combined control of the structure of formula 1, the atmosphere ratio of the mixed gas, and the temperature parameters of the two-stage calcination, can achieve synergy, and unexpectedly obtain a metal-free nitrogen-phosphorus-oxygen catalyst with a one-dimensional structure. Research in the present invention also shows that the prepared catalyst has excellent application performance in dehydrogenation to produce olefins, especially can show excellent product selectivity and operation stability.

[0013] In the present invention, the raw materials of formula 1 can be placed in a conventional tubular furnace with heating equipment, and heated from the starting temperature (usually room temperature) to the temperature of T1 in one stage. After heat preservation treatment at this temperature, it is then heated to the T2 section and kept warm to obtain the catalyst.

[0014] In the present invention, the combined control of the structure of formula 1, the ammonia-oxygen mixed atmosphere and its content ratio, the two-stage calcination mechanism, and the temperature is the key to overall synergistically improving the performance of the prepared material in dehydrogenation to produce olefins.

[0015] In the present invention, in the above-mentioned mixed atmosphere, the volume content of ammonia is preferably 90-95%. Research in the present invention shows that by performing two-stage heat treatment in the mixed atmosphere with this preferred ratio, the conversion rate and product selectivity of the prepared material in dehydrogenation to produce olefins can be further improved.

[0016] There is no special requirement for the heating rate in the heat treatment stage. For example, it can be 1 to 10 °C / min;

[0017] In the present invention, the temperature of T1 is 100 to 130 °C, and further preferably 100 to 120 °C;

[0018] The holding time of the T1 holding section can be adjusted as needed. Considering the processing efficiency, the holding time of the T1 holding section is 20 to 200 min, further can be 40 to 90 min, and still further can be 50 to 70 min.

[0019] Preferably, the temperature of T2 is 800 to 900 °C;

[0020] The holding time of the T2 holding section can be adjusted as needed. Considering the processing efficiency, the holding time of the T2 holding section is 20 to 300 min, further can be 50 to 130 min, and still further preferably 80 to 100 min.

[0021] The present invention also provides a one-dimensional nitrogen-phosphorus-oxygen catalyst prepared by the described preparation method.

[0022] The present invention researches and discovers that the described preparation method can endow the product with special physical and chemical characteristics and morphology, so as to be conducive to endowing it with excellent dehydrogenation to olefin selectivity and stability.

[0023] The one-dimensional nitrogen-phosphorus-oxygen catalyst of the present invention has a nanotubular structure;

[0024] Preferably, in the one-dimensional nitrogen-phosphorus-oxygen catalyst, the element molar ratio of phosphorus, nitrogen, and oxygen is 1:x:y, where preferably x is 1.4 - 2.6, preferably 1.5 to 2.1, and y is 0.25 - 5, preferably 0.3 to 0.5.

[0025] The present invention also provides an application of the one-dimensional nitrogen-phosphorus-oxygen catalyst prepared by the described preparation method. Contact a raw material containing an ethyl group with the one-dimensional nitrogen-phosphorus-oxygen catalyst prepared by the preparation method of the present invention to carry out a dehydrogenation reaction, dehydrogenate the ethyl group (C-C) in the raw material, and prepare the corresponding olefin product (C=C).

[0026] For example, in the present invention, the raw material containing an ethyl group is a compound having the structural formula 2;

[0027]

[0028] Formula 2

[0029] Among them, R1 to R4 are independently H, an alkyl group of C1 to C 10 an alkyl group, a cycloalkyl group or an aryl group of C3 to C 10 ; or, R1 and R4 are cyclized with each other to form a ring group;

[0030] The alkyl group, cycloalkyl group, cyclo group or aryl group mentioned above may be substituted with substituents, and the substituents are at least one of C1-C6 alkyl groups, C1-C6 alkoxy groups, halogens, phenyl groups, nitro groups, and trifluoromethyl groups;

[0031] Preferably, the aryl group is a benzene ring, a five-membered heteroaryl group, a six-membered heteroaryl group, or a fused ring formed by the fusion of two or more aromatic rings among a benzene ring, a five-membered heteroaryl group, and a six-membered heteroaryl group.

[0032] In a more specific embodiment of the present invention, the raw material containing ethyl group is a compound having the structure of Formula 2-A;

[0033]

[0034] In Formula 2-A, R1 is H, a C1-C2 alkyl group, an isopropyl group, a phenyl group or a substituted phenyl group; the benzene ring of the substituted phenyl group contains at least one of a C1-C2 alkyl group, an isopropyl group, a C1-C3 alkoxy group, a halogen, a phenyl group, a nitro group, and a trifluoromethyl group;

[0035] The R3 mentioned above is H or a C1-C2 alkyl group.

[0036] In the application of the present invention, a one-dimensional nitrogen phosphorus oxygen catalyst and a carrier are compounded, and then the dehydrogenation reaction is carried out.

[0037] In the present invention, the temperature of the dehydrogenation reaction is 500-700 °C; preferably 550-650 °C;

[0038] Preferably, the dehydrogenation reaction is carried out under anhydrous conditions;

[0039] Preferably, the dehydrogenation reaction is carried out under anaerobic conditions.

[0040] Beneficial effects:

[0041] In the present invention, the compound of Formula 1 is innovatively subjected to two-stage calcination treatment in a mixed atmosphere of ammonia and oxygen. Further, in combination with the joint control of the structure of Formula 1, the atmosphere ratio in the mixed atmosphere, and the temperature parameters of the two-stage calcination, synergy can be achieved, and a metal-free nitrogen phosphorus oxygen catalyst with a one-dimensional structure can be unexpectedly obtained. And through research, it is found that the prepared catalyst has excellent application performance in dehydrogenation to produce olefins, especially can show better selectivity and stability than existing similar catalysts.

[0042] It is found through research that under the test conditions of the present invention, the conversion rate of ethylbenzene can reach more than 54%, and, valuably, the selectivity of styrene reaches 94-98%, and the stability exceeds 50 hours, taking into account excellent selectivity and stability.

[0043] Compared with the current carbon-based and boron nitride-based catalysts, the nitrogen-phosphorus-oxygen catalyst described in the present invention has the significant advantage of simple preparation. Description of the Drawings

[0044] Appendix Figure 1 Scanning electron microscope (SEM) image of the catalyst in Example 1;

[0045] Appendix Figure 2 X-ray photoelectron spectroscopy (XPS) survey spectrum of the catalyst in Example 1. Detailed Description of the Invention

[0046] In the following cases, the heat treatment process is carried out in a tubular furnace.

[0047] The ratios of the mixed gas atmospheres in the heat treatment stage all refer to volume ratios.

[0048] The so-called room temperature is 5 to 45 °C.

[0049] In the following cases, the so-called stable operation refers to the operation time under the maintained conversion rate and selectivity.

[0050] Example 1

[0051] Weigh 10.90 g of the commercially available formula, load it into a corundum boat, and then place it in a tubular furnace. Introduce a mixed gas (90% ammonia - 10% oxygen) at a flow rate of 60 mL / min for high-temperature calcination. The high-temperature calcination is divided into two stages. The first stage is to rise from room temperature to 120 °C (marked as T1) at a rate of 5 °C / min and hold for 60 min. The second stage is to rise from 120 °C to 800 °C (marked as T2) at a rate of 5 °C / min, hold for 90 min, and then cool naturally to room temperature. The obtained catalyst is named PN--60-800-90. After testing, the molar ratio of elements in the obtained catalyst is P:N:O = 1:2.1:0.48.

[0052] The test method for the catalyst performance is as follows: Weigh 50 mg of the PN--60-800-90 catalyst, add 2 ml of quartz sand with a particle size of 40 - 60 mesh for dilution, and load it into a Φ8 mm fixed-bed quartz reaction tube. Introduce nitrogen at a flow rate of 20 ml / min, heat the catalytic bed from room temperature to 600 °C at a rate of 4 °C / min, and then introduce a mixed feed gas with an ethylbenzene volume fraction of 2.8% at a flow rate of 20 mL / min. The carrier gas is nitrogen for reaction. The reaction products are collected with ethanol at 5 °C, and their composition is analyzed by a gas chromatograph. The ethylbenzene conversion rate is 54%, the styrene selectivity is 95%, and it can operate stably for more than 50 hours.

[0053] Example 2

[0054] Compared with Example 1, the only difference is that the mixed gas is changed to a 95% ammonia - 5% oxygen mixed gas, and other preparation steps are the same as those in Example 1. The obtained catalyst is still loaded, reacted, and performance - tested by the method of Example 1. The performance of the catalyst is measured as follows: the conversion rate of ethylbenzene is 50%, the selectivity of styrene is 96%, and it can operate stably for more than 50 hours.

[0055] Example 3

[0056] Compared with Example 1, the only difference is that the mixed gas is changed to an 85% ammonia - 15% oxygen mixed gas, and other preparation steps are the same as those in Example 1. The obtained catalyst is still loaded, reacted, and performance - tested by the method of Example 1. The performance of the catalyst is measured as follows: the conversion rate of ethylbenzene is 45%, the selectivity of styrene is 98%, and it can operate stably for more than 50 hours.

[0057] Example 4

[0058] Compared with Example 1, the only difference is that the temperature of T2 is changed to 900 °C, and other preparation steps are the same as those in Example 1.

[0059] After testing, the molar ratio of elements in the obtained catalyst is P:N:O = 1:1.5:0.3. The obtained catalyst is still loaded, reacted, and performance - tested by the method of Example 1. The performance of the catalyst is measured as follows: the conversion rate of ethylbenzene is 45%, the selectivity of styrene is 94%, and it can operate stably for more than 50 hours.

[0060] Example 5

[0061] Compared with Example 1, the only difference is that the temperature of T1 is changed to 100 °C, and other preparation steps are the same as those in Example 1.

[0062] The obtained catalyst is still loaded, reacted, and performance - tested by the method of Example 1. The performance of the catalyst is measured as follows: the conversion rate of ethylbenzene is 53%, the selectivity of styrene is 95%, and it can operate stably for more than 50 hours.

[0063] Comparative Example 1

[0064] Replace the formula 1 in Example 1 with hydroxyethylidene diphosphonic acid (HEDP), and other preparation steps are the same as those in Example 1. The obtained catalyst is still loaded, reacted, and performance - tested by the method of Example 1. The performance of the catalyst is measured as follows: the conversion rate of ethylbenzene is 11%, the selectivity of styrene is 93%.

[0065] Comparative Example 2

[0066] In Example 1, change Formula 1 to ammonium dihydrogen phosphate (MAP), and keep the other preparation steps the same as in Example 1. The obtained catalyst is still loaded, reacted, and performance-tested in the same way as in Example 1. The performance of the catalyst is measured as follows: the conversion rate of ethylbenzene is 9.7%, and the selectivity of styrene is 84%.

[0067] Comparative Example 3

[0068] Compared with Example 1, the only difference is that the mixed gas is changed to pure nitrogen (99.9% nitrogen), and the other preparation steps are the same as in Example 1. Almost no catalyst product can be obtained, and the preparation fails.

[0069] Comparative Example 4

[0070] Compared with Example 1, the only difference is that the mixed gas is changed to air, and the other preparation steps are the same as in Example 1. Almost no catalyst product can be obtained, and the preparation fails.

[0071] Comparative Example 5

[0072] Compared with Example 1, the only difference is that the mixed gas is changed to 99.9% ammonia, and the other preparation steps are the same as in Example 1. The obtained catalyst is still loaded, reacted, and performance-tested in the same way as in Example 1. The performance of the catalyst is measured as follows: the conversion rate of ethylbenzene is 39%, the selectivity of styrene is 94%, and the dehydrogenation performance significantly decays after running for 20 hours.

[0073] Comparative Example 6

[0074] Compared with Example 1, the only difference is that the temperature of T2 is changed to 700 °C, and the other preparation steps are the same as in Example 1. After testing, the molar ratio of elements in the obtained catalyst is P:N:O = 1:2.9:0.36. The obtained catalyst is still loaded, reacted, and performance-tested in the same way as in Example 1. The performance of the catalyst is measured as follows: the conversion rate of ethylbenzene is 33%, the selectivity of styrene is 94%, and the dehydrogenation performance significantly decays after running for 20 hours.

[0075] Comparative Example 7

[0076] Compared with Example 1, the only difference is that the temperature of T2 is changed to 1000 °C, and the other preparation steps are the same as in Example 1. After testing, the molar ratio of elements in the obtained catalyst is P:N:O = 1:1.3:0.2. The obtained catalyst is still loaded, reacted, and performance-tested in the same way as in Example 1. The performance of the catalyst is measured as follows: the conversion rate of ethylbenzene is 23%, and the selectivity of styrene is 94%.

[0077] Comparative Example 8

[0078] In Example 1, the heat preservation in the first stage of high-temperature calcination was cancelled, and the temperature was directly raised to 800 °C. Other preparation steps were the same as those in Example 1. The amount of the obtained catalyst was extremely small, and the preparation failed.

[0079] Comparative Example 9

[0080] Compared with Example 1, the difference was only that the temperature of T1 was changed to 80 °C, and other preparation steps were the same as those in Example 1. The obtained catalyst was still loaded, reacted, and performance-tested by the method of Example 1. The performance of the catalyst was measured as follows: the conversion rate of ethylbenzene was 26%, the selectivity of styrene was 92%, and the dehydrogenation performance significantly decayed after running for 20 hours.

[0081] Comparative Example 10

[0082] Using commercial phosphorus nitride as the catalyst, the catalyst was still loaded, reacted, and performance-tested by the method of Example 1. The performance of the catalyst was measured as follows: the conversion rate of ethylbenzene was 25%, the selectivity of styrene was 96%, and the dehydrogenation performance significantly decayed after running for 20 hours.

[0083] Table 1 Comparison of the main preparation conditions and performance of the catalysts in the examples

[0084]

[0085] Table 2 Comparison of the main preparation conditions and performance of the catalysts in the comparative examples

[0086]

[0087] It can be seen from Example 1 and Comparative Examples 1-2 that the use of Formula 1 is crucial for the performance of the prepared material, and its ethylbenzene conversion rate on the obtained catalyst is much higher than that of HEDP and MAP.

[0088] It can be seen from Example 1, Example 2, Example 3, and Comparative Examples 3-5 that the calcination atmosphere has a great influence on the performance of the catalyst. When calcined in a nitrogen or air atmosphere, almost no catalyst product can be obtained, and the preparation fails. In a mixed atmosphere of ammonia and oxygen, better catalyst performance can be obtained. Among them, when the concentration of ammonia is 85-95%, the conversion rate of the catalyst can be maintained at a relatively high level of 45-54%. An atmosphere completely free of oxygen or with too high an oxygen content is not conducive to the performance of the catalyst.

[0089] It can be seen from Example 1, Example 4, and Comparative Examples 6-7 that the calcination temperature in the second stage also has a great influence on the performance of the catalyst. Calcination at 800-900 °C can obtain better catalyst performance. Too low or too high a temperature is not conducive to the performance of the catalyst.

[0090] It can be seen from Example 1, Example 5, and Comparative Examples 8-9 that the calcination temperature in the first stage has a great influence on the performance of the catalyst. By staying at 100-120 °C for a period of time, better catalyst performance can be obtained. If there is no stay at this stage or the temperature is too low (such as 80 °C), a catalyst product of sufficient quality cannot be obtained, the preparation fails, and its performance test cannot be carried out.

[0091] It can be seen from the examples and Comparative Example 10 that the commercial phosphorus nitride powder, which does not contain oxygen, has significantly lower performance.

Claims

1. A preparation method of a one-dimensional nitrogen-phosphorus-oxygen catalyst, characterized in that, The raw material of formula 1 is subjected to two-stage heat treatment in a mixed atmosphere containing ammonia and oxygen to obtain the one-dimensional nitrogen-phosphorus-oxygen catalyst described above; Formula 1 In the described mixed atmosphere, the volume content of ammonia is 85-98%; The two-stage heat treatment process includes a T1 heat preservation section and a T2 heat preservation section. Among them, the temperature of T1 is 90-150 °C; the temperature of T2 is 750-950 °C.

2. The preparation method of the one-dimensional nitrogen-phosphorus-oxygen catalyst according to claim 1, characterized in that, In the described mixed atmosphere, the volume content of ammonia is 90-95%.

3. The preparation method of the one-dimensional nitrogen-phosphorus-oxygen catalyst according to claim 1, wherein, The temperature of the described T1 is 100-130 °C.

4. The preparation method of the one-dimensional nitrogen-phosphorus-oxygen catalyst according to claim 1, characterized in that, The heat preservation time of the T1 heat preservation section is 20-200 min.

5. The preparation method of the one-dimensional nitrogen-phosphorus-oxygen catalyst according to claim 4, characterized in that, The heat preservation time of the T1 heat preservation section is 40-90 min.

6. The preparation method of the one-dimensional nitrogen-phosphorus-oxygen catalyst according to claim 1, wherein, The temperature of the described T2 is 800-900 °C.

7. The preparation method of the one-dimensional nitrogen-phosphorus-oxygen catalyst according to claim 1, characterized in that, The heat preservation time of the T2 heat preservation section is 20-300 min.

8. The preparation method of the one-dimensional nitrogen-phosphorus-oxygen catalyst according to claim 7, characterized in that, The heat preservation time of the T2 heat preservation section is 50-130 min.

9. A one-dimensional nitrogen-phosphorus-oxygen catalyst prepared by the preparation method according to any one of claims 1-8.

10. The one-dimensional nitrogen-phosphorus-oxygen catalyst according to claim 9, wherein, The described one-dimensional nitrogen-phosphorus-oxygen catalyst has a nanotubular structure.

11. The one-dimensional nitrogen-phosphorus-oxygen catalyst according to claim 9, characterized in that, In the described one-dimensional nitrogen-phosphorus-oxygen catalyst, the elemental molar ratio of phosphorus, nitrogen, and oxygen is 1: x : y , where x is 1.4 - 2.6, y is 0.25 - 5.

12. Use of a one-dimensional nitrogen-phosphorus-oxygen catalyst prepared by the preparation method according to any one of claims 1 to 8, characterized in that, Contact the raw material containing ethyl group with the described one-dimensional nitrogen-phosphorus-oxygen catalyst to carry out a dehydrogenation reaction to dehydrogenate the ethyl group in the raw material to obtain the corresponding olefin product.

13. The application according to claim 12, characterized in that The described raw material containing ethyl group is a compound with the structural formula of formula 2; Formula 2 wherein, R1 to R4 are each independently H, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, or an aryl group; or, R1 and R4 are cyclized with each other to form a ring group; Substituents are allowed on the described alkyl group, cycloalkyl group, cyclo group or aryl group, and the substituents are at least one of C1-C6 alkyl group, C1-C6 alkoxy group, halogen, phenyl group, nitro group, trifluoromethyl group.

14. The application according to claim 13, characterized in that, The described aryl group is a benzene ring, a five-membered heteroaryl group, a six-membered heteroaryl group, or a fused ring formed by the fusion of two or more aromatic rings among a benzene ring, a five-membered heteroaryl group, and a six-membered heteroaryl group.

15. The application according to claim 13, characterized in that The described raw material containing ethyl group is a compound with the structure of formula 2-A; Formula 2-A In formula 2-A, R1 is H, C1-C2 alkyl group, isopropyl group, phenyl group or substituted phenyl group; the benzene ring of the substituted phenyl group contains at least one of C1-C2 alkyl group, isopropyl group, C1-C3 alkoxy group, halogen, phenyl group, nitro group, trifluoromethyl group; The described R3 is H or C1-C2 alkyl group.

16. The application according to claim 12, characterized in that, Use the one-dimensional nitrogen-phosphorus-oxygen catalyst alone or in combination with a carrier, and then carry out the dehydrogenation reaction.

17. The application according to any one of claims 12 to 16, characterized in that, The temperature of the dehydrogenation reaction is 500-700 °C.

18. The application according to claim 17, wherein The temperature of the dehydrogenation reaction is 550-650 °C.

19. The application according to claim 16, characterized in that, The dehydrogenation reaction is carried out under anhydrous conditions.

20. The application according to claim 16, wherein The dehydrogenation reaction is carried out under anaerobic conditions.

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