CN110665521A

CN110665521A - Catalyst for synthesizing melamine and preparation method thereof

Info

Publication number: CN110665521A
Application number: CN201911041889.7A
Authority: CN
Inventors: 王婷; 谭映临; 杨海龙; 石铁磐; 张新功; 叶红; 李世鹏; 张晓佳
Original assignee: Qingdao Hui Cheng Environmental Technology Co Ltd
Current assignee: Qingdao Hui Cheng Environmental Technology Co Ltd
Priority date: 2019-10-29
Filing date: 2019-10-29
Publication date: 2020-01-10

Abstract

A catalyst for producing melamine, which contains 30 to 55 weight percent of Al₂O₃45 to 70 weight percent of SiO₂And 0 to 10 wt% of P₂O₅。Al₂O₃Comprises two parts, one part is used as an active component, and the other part is used as a binder. SiO 2₂Comprises two parts, one part is taken as an active component Al₂O₃A part of the carrier of (3) is used as a binder. P₂O₅Used as a binder. The preparation method comprises the following steps: mixing SiO₂Adding water into the carrier, pulping, and adding an active component Al₂O₃Adding acid solution to regulate pH value, finally adding binder, adopting spray granulation, roasting, washing and drying treatment so as to obtain the invented melamine catalyst. The aluminum silicate type III prepared by the inventionThe polycyanamine catalyst has good physicochemical properties, such as high strength (namely low abrasion), large water hole, large specific surface area adjustment range and the like, and has the advantages of simple preparation method, low investment, no pollution discharge, low production cost, low energy consumption and obvious economic and social benefits.

Description

Catalyst for synthesizing melamine and preparation method thereof

Technical Field

The invention relates to a catalyst for synthesizing melamine and a preparation method thereof.

Background

Melamine is an important nitrogen heterocyclic ring organic chemical intermediate product, and is mainly used for producing triamine formaldehyde resin. As a thermosetting resin, the thermosetting resin has the characteristics of heat resistance, aging resistance, acid and alkali resistance, flame retardance and the like. The flame-retardant polyurethane resin is widely applied to industries such as wood processing, coating, papermaking, textile, leather, decorative board, laminated board, composite floor, flame-retardant material, water reducing agent, adhesive, melamine molding powder and the like. In recent years, with the deep research on melamine and the continuous improvement of living standard of people, the application field and the range of the melamine are continuously expanded, and after the melamine enters twenty-first century, the annual growth rate of the melamine exceeds 15 percent due to market demands.

At present, the production of melamine mostly depends on a urea method, urea is added into a reactor and is in fluidized contact reaction with a catalyst (a silica gel catalyst or an alumina catalyst or a silica alumina catalyst), the reaction is endothermic, a molten salt carrier is used for circular heating, the urea is gasified and decomposed in the reactor to generate melamine, carbon dioxide and ammonia, and the equation is as follows:

6(NH₂)₂CO→C₃H₆N₆+6NH₃+3CO₂

(Urea) (Melamine) (Ammonia) (carbon dioxide)

The normal and low pressure melamine production process with urea as material has strict requirement on catalyst, high strength, high activity, great load, low cost and other advantages. It can be said that the selection of the catalyst and the exertion of its use properties are directly related to the various indexes of the whole melamine production plant, such as production capacity, output quality, raw material consumption and operation cycle. Foreign BASF (BASF) melamine technologyThe catalyst adopts gamma-Al₂O₃The vast majority of the melamine catalysts in China adopt coarse-pore silica gel, and part of the melamine device catalysts in China begin to use aluminum silicate type catalysts in the middle and later stages of the nineties of the twentieth century.

CN1846848A discloses a method for producing an alumina catalyst for melamine production, which is prepared by mixing alumina and aluminum hydroxide, spraying water and rolling into pellets, drying, sieving and roasting. However, the catalyst only contains one component of alumina, so that the catalyst has the advantages of low strength, serious abrasion, low specific surface area, poor carbon precipitation resistance and quick inactivation.

CN101024171A discloses a catalyst for synthesizing melamine and a preparation method thereof, wherein commercially available aluminum-silicon oxide and commercially available aluminum oxide are put into a kneader, water or acid solution is added, and after granulation, drying, sieving and activation treatment, the melamine catalyst is obtained. Because the preparation process belongs to mechanical mixing, the two raw materials cannot be fully combined, and the problems of more fine powder, quick activity reduction and the like can occur in the using process.

USP5514797 describes a high temperature, high pressure process for the production of melamine which yields melamine having a purity of up to 99% or more and which is substantially free of melamine, melem and other impurities. Although the method can obtain high-purity melamine, the energy consumption is high and the cost is high.

CN1493565A discloses a co-production method for producing melamine by a one-step method, which adopts silica gel/silica alumina gel as a catalyst, overcomes the defects of the co-production process by a one-step method, a two-step method and a two-step method in the existing normal pressure method, and provides a co-production process with low investment and low cost.

CN1723203A discloses a melamine two-step reactor, which is a method for preparing melamine by decomposing urea on a solid catalyst using a main reactor and a post reactor. The main reactor is a fluidized bed, a catalyst with low Lewis acidity is adopted, the post reactor is a fixed bed, the catalyst with high Lewis acidity is adopted, the two-step reactor can avoid the premature inactivation of the catalyst caused by the excessive deposition of a condensation product on the surface of the catalyst in the reaction, and the post reactor has the catalyst with high Lewis acidity, so that the high conversion rate can be realized. However, the method also brings the problems of high investment cost, overlong reaction flow and harsh reaction conditions.

Disclosure of Invention

In order to overcome the defects of the prior catalyst technology, the invention provides a novel synthetic melamine catalyst and a preparation method thereof. The catalyst has the advantages of high strength, low abrasion rate, low reaction temperature, large carrying capacity of the catalyst on raw material urea, high selectivity, few byproducts, short induction period and the like. The preparation method is simple and has low cost, thereby having higher cost performance.

The invention provides a catalyst for synthesizing melamine, which contains 30-55 wt% of Al₂O₃45 to 70 weight percent of SiO₂And 0 to 10 wt% of P₂O₅. The Al is₂O₃Comprises two parts, one part of Al₂O₃As an active component, a part of Al₂O₃Used as a binder. The SiO₂Comprises two parts, one part of SiO₂Is used as active component Al₂O₃A part of SiO₂Used as a binder. The P is₂O₅Used as a binder. The preparation method comprises the following steps: mixing SiO₂Adding water into the carrier, pulping, and adding an active component Al₂O₃Adding acid solution to regulate pH value, finally adding binder, adopting spray granulation, roasting, washing and drying treatment so as to obtain the invented melamine catalyst.

In the melamine catalyst provided by the invention, the Al used as an active component₂O₃Is pseudo-boehmite.

In the melamine catalyst provided by the invention, the Al used as a binder₂O₃Is selected from one or more of aluminum sol, phosphor aluminum glue or silicon aluminum gel.

In the melamine catalyst provided by the invention, the SiO used as the carrier₂Silicon powder, SiO, from treatment of spent catalytic cracking catalyst₂The content is not less than 98 wt%, and the specific surface area is not less than 120m²/g。

In the melamine catalyst provided by the invention, the SiO used as the binder₂One or more selected from silica sol or silica-alumina gel.

In the melamine catalyst provided by the invention, the acid solution is hydrochloric acid or nitric acid.

Compared with the prior catalyst technology, the melamine catalyst and the preparation method thereof have the following advantages:

1. the silicon powder is derived from the waste catalytic cracking catalyst, so that the problem of treatment of the waste catalytic cracking catalyst is solved, and a high-quality catalyst carrier is provided;

2. the catalyst has high strength and low wear rate;

3. the reasonable proportion of the carrier and the active component ensures that the catalyst has higher activity at low temperature, thus reducing the occurrence probability of side reaction, reducing the deposition of by-products on the surface of the catalyst, slowing down the inactivation rate of the catalyst, simultaneously improving the carrying capacity and the selectivity of the catalyst, finally improving the conversion rate of the reaction and improving the yield of melamine.

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

Example 1

(1) Weighing 555g of silicon powder, adding 1000g of water, and uniformly stirring;

(2) weighing 462g of pseudoboehmite, adding into the slurry obtained in the step (1), and adding a hydrochloric acid solution to adjust the pH value to about 3.2;

(3) weighing 200g of silica sol and 682g of phosphor-aluminum sol, adding into the slurry obtained in the step (2), adding 434g of water, and fully and uniformly stirring;

(4) spray-forming with LX-15 centrifugal spray tower, calcining, washing, drying to obtain melamine catalyst, and recording as M-A.

Example 2

(1) 611g of silicon powder is weighed, 1050g of water is added, and the mixture is stirred uniformly;

(2) 385g of pseudo-boehmite is weighed and added into the slurry obtained in the step (1), and a nitric acid solution is added to adjust the pH value to about 3.2;

(3) 909g of alumina sol is weighed and added into the slurry obtained in the step (2), 378g of water is added, and the mixture is fully and uniformly stirred;

(4) spray-forming with LX-15 centrifugal spray tower, calcining, washing, drying to obtain melamine catalyst, and recording as M-B.

Example 3

(1) Weighing 667g of silicon powder, adding 1100g of water, and stirring;

(2) weighing 308g of pseudoboehmite, adding into the slurry obtained in the step (1), and adding a hydrochloric acid solution to adjust the pH value to about 3.2;

(3) weighing 200g of silica sol and 682g of alumina sol, adding into the slurry obtained in the step (2), adding 376g of water, and fully and uniformly stirring;

(4) spray-forming with LX-15 centrifugal spray tower, calcining, washing, drying to obtain melamine catalyst, and making it be recorded as M-C.

Comparative example 1

Prepared according to example 2 described in CN 101024171A.

Using commercially available aluminium silicon oxide [ Hz ]][Al_2-XH_X][Si_4-yAl_y]O₁₂(wherein x is 0.15, y is 0.07, z is 0.22)700g, adding 300g of commercial pseudo-thin hydrated alumina, mixing uniformly, adding 3% dilute phosphoric acid, and kneading, wherein the dosage of the dilute phosphoric acid is 700 ml; kneading is carried out for about 40 minutes, and then the strands are extruded in an extruder at a pressure of 5MPa and a strand diameter of 3 mm. The strip is dried at 105 ℃, crushed by a crusher, sieved by a vibrating screen of 60-120 meshes and activated for 3 hours at 480 ℃ to obtain the melamine catalyst which is recorded as DB-1.

The physicochemical analysis data of the catalysts prepared in the examples and comparative examples are shown in Table 1.

TABLE 1 catalyst physicochemical analysis data

Sample numbering	Wear/percent	Bulk ratio/g.mL^-1	Water pore/mL. g^-1	Specific surface area/m²·g^-1	Pore volume/mL. g^-1
						M-A	0.1	0.84	0.27	162	0.18
M-B	0.4	0.80	0.29	185	0.19
						M-C	1.0	0.74	0.40	194	0.24
DB-1	1.7	0.72	0.30	151	0.14

Claims

1. A catalyst for synthesizing melamine contains 30-55 wt% of Al₂O₃45 to 70 weight percent of SiO₂And 0 to 10 wt% of P₂O₅. The Al is₂O₃Comprises two parts, one part of Al₂O₃As an active component, a part of Al₂O₃Used as a binder. The SiO₂Comprises two parts, one part of SiO₂Is used as active component Al₂O₃A part of SiO₂Used as a binder. The P is₂O₅Used as a binder. The preparation method comprises the following steps: mixing SiO₂Adding water into the carrier, pulping, and adding an active component Al₂O₃Adding acid solution to regulate pH value, finally adding binder, adopting spray granulation, roasting, washing and drying treatment so as to obtain the invented melamine catalyst.

2. Melamine catalyst according to claim 1, characterized in that Al as active component₂O₃Is pseudo-boehmite.

3. Melamine catalyst according to claim 1, characterized in that Al as binder₂O₃Is selected from one or more of aluminum sol, aluminum phosphate glue and silicon-aluminum gel.

4. Melamine catalyst according to claim 1, characterized in that the SiO as support₂Silica fume from waste catalytic cracking catalyst treatment，SiO₂The content is not less than 98 wt%, and the specific surface area is not less than 120m²/g。

5. Melamine catalyst according to claim 1, characterized in that the SiO as binder₂Is selected from one or more of silica sol or silica-alumina gel.

6. Melamine catalyst according to claim 1, characterised in that the acid solution is an acid solution of hydrochloric acid or nitric acid.