A catalyst for synthesizing melamine, a preparation method and use thereof

Abstract

The application belongs to the field of melamine synthesis, and particularly relates to a preparation method of a catalyst for synthesizing melamine, which comprises the following steps: aging and hole expanding of silica gel particles, acid foaming, water washing and slurry, filtration, and obtaining of wet glue; mixing of phosphorus powder into the wet glue, and obtaining of modified wet glue; mixing of HZSM-5 molecular sieve powder, carbon black and colloidal pseudo-boehmite, and then adding of the modified wet glue, and stirring to obtain a mixed slurry; spray drying and molding of the mixed slurry, and then calcination and cooling in an inert atmosphere, and screening, to obtain the catalyst for synthesizing melamine. The method obtains a new catalyst, which has the advantages of good durability, long service life, good catalytic activity and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of melamine synthesis, more particularly, to a catalyst for synthesizing melamine and a preparation method and use thereof. BACKGROUND

[0002] Melamine (also known as trimethylguanidine) is an important organic chemical intermediate product, mainly used for producing melamine-formaldehyde resin, and widely used in the fields of wood processing, paint, papermaking, textile, leather processing, etc. With the continuous improvement of people's living standards, the application field and range of melamine are more and more extensive, and the market demand also increases significantly, so many enterprises or research units further increase the research investment on the synthesis process of melamine, and the catalyst is widely concerned because it has a greater impact on the process.

[0003] At present, the silica-alumina catalyst is mostly used in the domestic gas phase melamine production device, and the research on the silica-alumina catalyst is also continuously deepened. However, the strength, durability and catalyst activity of the silica-alumina microspheres catalyst that can be actually sold on the market still have room for improvement. In addition, a variety of catalyst products can provide more selection space for users, and the coexistence of various products is conducive to stabilizing the catalyst market.

[0004] Therefore, the present application is proposed. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a preparation method of a catalyst for synthesizing melamine, which has the advantages of simple process, good durability, long service life, good catalytic activity, etc.

[0006] The basic idea of the technical scheme of the present application is as follows:

[0007] A preparation method of a catalyst for synthesizing melamine, comprising the following steps:

[0008] S1, aging and hole expansion of silica gel particles, then acid soaking, water washing and slurry, filtration, to obtain wet gel;

[0009] S2, mixing phosphorus powder into the wet gel to obtain modified wet gel;

[0010] S3, mixing HZSM-5 molecular sieve powder, carbon black and pseudoboehmite in a colloidal state uniformly, and then adding the modified wet gel, stirring to obtain a mixed slurry;

[0011] S4, spray drying the mixed slurry to form, then calcining and cooling under inert atmosphere, and screening to obtain the catalyst for synthesizing melamine.

[0012] The embodiment of the present application provides an example, in step S2, the amount of phosphorus powder is 0.5-2 parts by weight, based on 100 parts by weight of the silica gel particles.

[0013] The embodiment of the present application provides an example, in step S3, the amount of HZSM-5 molecular sieve powder is 5-10 parts by weight, based on 100 parts by weight of the silica gel particles, the amount of carbon black is 0.2-1 parts by weight, and the amount of pseudoboehmite in a colloidal state is 1-3 parts by weight.

[0014] The embodiment of the present application provides an example, in step S4, in an inert atmosphere, first constant temperature calcination is carried out at 350-450 DEG C for 3-7 h, and then constant temperature calcination is carried out at 450-600 DEG C for 2-4 h.

[0015] The embodiment of the present application provides an example, in step S4, the temperature is raised to 350-450 DEG C at a speed of 10-20 DEG C / min, and then raised to 450-600 DEG C at a speed of 5-10 DEG C / min.

[0016] The present application also provides a catalyst for synthesizing melamine, which is obtained by the preparation method of the catalyst for synthesizing melamine according to any one of the above.

[0017] The embodiment of the present application provides an example, the catalyst for synthesizing melamine is a spherical particle with a D50 of 80-100 mu m.

[0018] The present application also provides the use of the catalyst for synthesizing melamine as described above, that is, melamine is synthesized in a gas phase under the action of the catalyst for synthesizing melamine, with urea as a raw material.

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

[0020] 1. The present application obtains a new catalyst for synthesizing melamine, which has good wear resistance while ensuring catalytic activity, long service life, can reduce the catalyst consumption rate of enterprises, and improve the economic benefits of the production line.

[0021] 2. The present application achieves the effect of considering wear resistance and catalytic activity by the mutual cooperation of HZSM-5 molecular sieve powder, phosphorus powder and carbon black in a silica gel system.

[0022] 3. The process flow of the preparation method of the present application is convenient to operate, suitable for industrial production, and can be practically pushed to the market. DETAILED DESCRIPTION

[0023] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application are described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the described embodiments of the present application, all other embodiments obtained by those skilled in the art without any inventive effort fall within the scope of protection of the present application.

[0024] The reagents used in the case of the present application are all ordinary products purchased from the market unless otherwise specified.

[0025] Embodiment 1

[0026] S1, 100 parts by weight of silica gel particles with a particle size of 1.5-2.5 mm (which can be purchased from the market or prepared by referring to the prior art, and is purchased in the present application) are aged for 1.5 h at 55℃ for reaming; the reamed silica gel particles are subjected to acid bubbling and water washing until the conductivity is less than 1000 μs / cm, and then are subjected to pulping in a pulper, and the pulp is filtered to obtain wet glue, which is ready for use;

[0027] S2, 0.5 parts by weight of phosphorus powder is added to the wet glue and mixed uniformly to obtain modified wet glue;

[0028] S3, 5 parts by weight of HZSM-5 molecular sieve powder, 0.2 parts by weight of carbon black and 1 part by weight of colloidal pseudo-boehmite are mixed uniformly, and then the modified wet glue is added and stirred to obtain a mixed slurry;

[0029] S4, the mixed slurry is subjected to spray drying and molding, and then is heated at a programmed temperature in an inert atmosphere, with the temperature being raised to 350℃ at a speed of 10℃ / min, and then being kept constant for 7 h, and then being raised to 450℃ at a speed of 5℃ / min, and then being kept constant for 4 h; then the temperature is lowered, and the spherical particle material with a D50 of 80-100 μm is collected by sieving, to obtain the catalyst for synthesizing melamine.

[0030] Embodiment 2

[0031] S1, 100 parts by weight of silica gel particles with a particle size of 1.5-2.5 mm (which can be purchased from the market or prepared by referring to the prior art) are aged for 2 h at 45℃ for reaming; the reamed silica gel particles are subjected to acid bubbling and water washing until the conductivity is less than 1000 μs / cm, and then are subjected to pulping in a pulper, and the pulp is filtered to obtain wet glue, which is ready for use;

[0032] S2, 2 parts by weight of phosphorus powder is added to the wet glue and mixed uniformly to obtain modified wet glue;

[0033] S3, 10 parts by weight of HZSM-5 molecular sieve powder, 1 part by weight of carbon black and 3 parts by weight of pseudoboehmite in a colloidal state are uniformly mixed, and then the modified wet glue is added and stirred to obtain a mixed slurry;

[0034] S4, the mixed slurry is spray dried and formed, then in an inert atmosphere, using a programmed temperature rising method, the temperature is raised to 450℃ at a speed of 15℃ / min, and then the temperature is kept constant for 3h, and then the temperature is raised to 600℃ at a speed of 10℃ / min, and then the temperature is kept constant for 2h; then the temperature is lowered, and the spherical particle material with D50 of 80-100μm is collected by sieving, to obtain the synthetic melamine catalyst.

[0035] Example 3

[0036] S1, 100 parts by weight of silica gel particles with a particle size of 1.5-2.5mm (which can be purchased on the market or prepared by referring to the prior art) are aged at 50℃ for 2h to expand the pores; the expanded silica gel particles are subjected to acid bubbling and water washing until the conductivity is less than 1000μs / cm, and then are subjected to pulping in a beater, and the slurry is filtered to obtain a wet glue, which is ready for use;

[0037] S2, 0.8 parts by weight of phosphorus powder is added to the wet glue and uniformly mixed to obtain a modified wet glue;

[0038] S3, 7 parts by weight of HZSM-5 molecular sieve powder, 0.4 parts by weight of carbon black and 1.2 parts by weight of pseudoboehmite in a colloidal state are uniformly mixed, and then the modified wet glue is added and stirred to obtain a mixed slurry;

[0039] S4, the mixed slurry is spray dried and formed, then in an inert atmosphere, using a programmed temperature rising method, the temperature is raised to 400℃ at a speed of 20℃ / min, and then the temperature is kept constant for 5h, and then the temperature is raised to 550℃ at a speed of 10℃ / min, and then the temperature is kept constant for 2.5h; then the temperature is lowered, and the spherical particle material with D50 of 80-100μm is collected by sieving, to obtain the synthetic melamine catalyst.

[0040] Example 4

[0041] S1, 100 parts by weight of silica gel particles with a particle size of 1.5-2.5mm (which can be purchased on the market or prepared by referring to the prior art) are aged at 55℃ for 1.5h to expand the pores; the expanded silica gel particles are subjected to acid bubbling and water washing until the conductivity is less than 1000μs / cm, and then are subjected to pulping in a beater, and the slurry is filtered to obtain a wet glue, which is ready for use;

[0042] S2, 1.1 parts by weight of phosphorus powder is added to the wet glue and uniformly mixed to obtain a modified wet glue;

[0043] S3, 9 parts by weight of HZSM-5 molecular sieve powder, 0.6 parts by weight of carbon black and 2 parts by weight of pseudoboehmite in a colloidal state were uniformly mixed, and then the modified wet glue was added and stirred to obtain a mixed slurry;

[0044] S4, the mixed slurry was spray dried and formed, then in an inert atmosphere, the temperature was raised to 400℃ at a rate of 10℃ / min, and then the temperature was kept constant for 5h, then the temperature was raised to 500℃ at a rate of 5℃ / min, and then the temperature was kept constant for 3h; then the temperature was lowered, and the spherical particle material with D50 of 80-100μm was collected by sieving, thereby obtaining the synthetic melamine catalyst.

[0045] Comparative Example 1

[0046] Compared with Example 1, the process lacks the addition of phosphorus powder in step S2. Other aspects are consistent with Example 1.

[0047] Comparative Example 2

[0048] Compared with Example 2, HZSM-5 molecular sieve powder is not added in step S3, and other aspects are consistent with Example 2.

[0049] Comparative Example 3

[0050] Compared with Example 3, carbon black powder is not added in step S3, and other aspects are consistent with Example 3.

[0051] Comparative Example 4

[0052] Compared with Example 4, ZSM-5 molecular sieve powder is added in step S3, and other aspects are consistent with Example 4.

[0053] Test Example

[0054] Under the same test conditions, the durability and catalytic performance of the catalysts obtained in Examples 1-4 and Comparative Examples 1-4 were determined.

[0055] The durability performance was investigated according to the method for measuring the wear index in HG / T 4861-2015.

[0056] The catalytic performance was determined by the following simulation process: the carrier gas was a mixture of ammonia and carbon dioxide at a weight ratio of 1:1, the carrier gas flow rate was 25-40kg / h, the reaction temperature was 390-420℃, the loading amount of the catalyst was 50-60kg, the urea feeding amount was 6-10kg / h, and the melamine yield was the ratio of the theoretical urea amount required for the melamine produced by the device in 72h of stable operation to the feeding urea amount.

[0057] Table 1

[0058]

[0059] Although the present application has been described with reference to specific embodiments thereof, it will be apparent to one of ordinary skill in the art that a person can make modifications and variations to the described embodiments without departing from the spirit and scope of the application. Accordingly, the patent protection scope of the present application shall be defined only by the appended claims.

Claims

1. A process for the preparation of a catalyst for the synthesis of melamine, characterized in that, Comprising the following steps: S1, aging, reaming of silica gel particles, then acid foaming, water washing, slurry, filtration, to obtain wet glue; S2, incorporating phosphorus powder in the wet glue, mixing uniformly, to obtain modified wet glue; S3, mixing HZSM-5 molecular sieve powder, carbon black and pseudoboehmite in colloidal state uniformly, then adding the modified wet glue, stirring to obtain mixed slurry; S4, spray drying the mixed slurry into shape, then calcining under inert atmosphere, cooling, screening, to obtain the synthetic melamine catalyst.

2. The method for preparing a catalyst for synthesizing melamine according to claim 1, characterized by, In step S2, the amount of phosphorus powder is 0.5-2 parts by weight based on 100 parts by weight of silica gel particles.

3. The method for preparing a catalyst for synthesizing melamine according to claim 1, characterized by, In step S3, the amount of HZSM-5 molecular sieve powder is 5-10 parts by weight, the amount of carbon black is 0.2-1 parts by weight, and the amount of pseudoboehmite in colloidal state is 1-3 parts by weight based on 100 parts by weight of silica gel particles.

4. The method for preparing a catalyst for synthesizing melamine according to claim 1, characterized by, In step S4, first constant temperature calcination at 350-450℃ for 3-7h, then constant temperature calcination at 450-600℃ for 2-4h under inert atmosphere.

5. The method for preparing the catalyst for synthesizing melamine according to claim 4, characterized in that, In step S4, the temperature is raised to 350-450℃ at a rate of 10-20℃ / min, and then raised to 450-600℃ at a rate of 5-10℃ / min.

6. A catalyst for the synthesis of melamine, characterized in that, The synthetic melamine catalyst is prepared by the method according to any one of claims 1-5.

7. The catalyst for synthesis of melamine according to claim 6, characterized by that The synthetic melamine catalyst is spherical particle with D50 of 80-100μm.

8. Use of the catalyst according to claim 6 or 7 for the synthesis of melamine, characterized in that, Urea is used as raw material to synthesize melamine in gas phase under the action of the synthetic melamine catalyst.

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