TWI400122B - Preparation of Ammonia Pyrolysis Catalysts - Google Patents

Description

Method for producing ammonia cracking catalyst

The present invention relates to a method for producing a catalyst, and more particularly to a method for producing an ammonia cracking catalyst.

The manufacture and application of catalysts can be seen everywhere in life, such as hydrogenation of liquid vegetable oils to obtain vegetable margarine which is solid at room temperature, as well as, for example, gasoline refining and the synthesis of numerous organic substances, and plastics. The manufacture of materials and ammonia, etc.

The coke oven gas produced by the coking plant of the existing steelmaking plant is generally used as the main fuel for the downstream process. However, in addition to the coal tar (Tar), the coke oven gas also contains clogging and corrosion of the coke oven gas transmission line. Gas impurities such as hydrogen sulfide (H ₂ S), cyanic acid (HCN), and ammonia (NH ₃ ).

Therefore, the existing consistent steelmaking plant first removes ammonia, cyanate and hydrocarbons from the coke oven gas, and then desulfurizes the coke oven gas through the Claus process of the sulfur plant to avoid vulcanization. Ammonium crystals cause blockage and process equipment failure.

The existing method is to pass the coke oven gas through an ammonia cracking catalyst to remove ammonia in the coke oven gas. Generally, the strength of the catalyst is the basis of the catalyst performance. If the catalyst is easily broken, the reaction gas is passed. The pressure drop during the catalyst bed is greatly increased, the operating cycle is shortened, and the economic benefits of the device are affected. Therefore, mechanical strength is a very important control indicator in the development of catalysts.

To this end, in recent years, many scholars have actively engaged in research on the strength of catalysts. For example, Song Lei pointed out in the article "Preparation conditions for mechanical strength of ethylbenzene dehydrogenation catalysts" (Petrochemicals, Vol. 33, 2004). Factors affecting the mechanical strength of the catalyst include the water-powder ratio during molding, the binder, the dry powder particle size, and the kneading time. Among them, the water powder ratio is too high or too low, which will affect the strength of the catalyst, although the catalyst strength will increase with the cement content. However, it will also reduce the activity of the catalyst, and the catalyst strength of the catalyst obtained is 2.1~2.5MPa; in addition, Jiang Yanyu "experimental study on improving the mechanical strength of vanadium catalyst" (Journal of Sichuan University, Vol.36) , 2004) pointed out that in the preparation process of granular vanadium catalyst in sulfuric acid industry, molding pressure, water content and binder content are factors affecting mechanical strength, which is 10-20 Mpa, 25-30% water content and The catalyst strength of the catalyst obtained by 3 to 5% of the binder is 3 MPa.

Accordingly, it is an object of the present invention to provide a method for producing an ammonia cracking catalyst which can increase the strength of a catalyst.

Thus, the method for producing an ammonia cracking catalyst of the present invention comprises a preparation step, a granulation step, a sieving step, a molding step, a sintering step, and an activation step.

The preparation step is to prepare a raw material containing a nickel metal compound and magnesium oxide; the granulation step is to mechanically stir the raw materials, water and additives uniformly to aggregate into a granular raw material, wherein the water accounts for 3 wt% of the whole raw material. ~15wt%, and the additive accounts for 3wt%~12wt% of the whole raw material, and the rest is a balanced amount of raw materials.

The sieving step is to screen the raw material having a particle size between 50 and 325 mesh; the molding step is to press-form the raw material through the sieving step into a blank, and dry the blank; the sintering The step is to sinter the dried rough embryo at a temperature of 900 ° C to 1500 ° C; the activation step is to activate the nickel metal in the blank of the sintering step with a reducing gas containing nitrogen and hydrogen between 650 ° C and 1250 ° C. Compound.

The effect of the invention is to control the particle size ratio of the raw material and the content of the water and the additive in the mixing step and the granulation step, respectively, and then control the raw material before the molding through the sieving step to make the particle size of the raw material relatively average, and then The sintering temperature of the sintering step is controlled, and finally the nickel metal compound in the blank of the sintering step is activated to produce an ammonia cracking catalyst having high cracking efficiency and high strength.

The above and other technical contents, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments.

Referring to Figure 1, a preferred embodiment of the method for producing an ammonia cracking catalyst of the present invention comprises a preparation step 11, a granulation step 12, a sieving step 13, a molding step 14, a sintering step 15, and an activation step. 16.

The preparation step 11 is to prepare a raw material containing a nickel metal compound and magnesium oxide, wherein the particle size ratio of the raw material is between 10% and 60%, and the preferred particle size ratio is between 20% and 40%. between. Wherein, the nickel metal compound in the raw material may be nickel nitrate, nickel sulfate, nickel carbonate, nickel oxide, nickel monoxide, or nickel hydroxide, or a mixture of at least two of them; and the magnesium oxide in the raw material may be It is magnesium hydroxide, magnesium oxide, or magnesium peroxide, and may be a mixture of at least two of them.

The granulation step 12 is a raw material in which the raw materials, water and additives are uniformly stirred and aggregated into a granular material, wherein the water accounts for 3 wt% to 15 wt% of the whole raw material, and the additive accounts for 3 wt% of the whole raw material. 12wt%, the balance is a balanced amount of raw materials, and preferably water accounts for 5% by weight to 10% by weight of the whole raw material, and the additive accounts for 7wt% to 10% by weight of the whole raw material, and the balance is a balanced amount of raw materials.

Wherein the additive is selected from the group consisting of ammonium polyacrylate, methyl cellulose, silicate, or clay, and may also be a mixture of at least two of them.

The sieving step 13 is to screen the raw material having a particle size between 50 and 325 mesh, and preferably to screen the raw material having a particle size between 100 and 250 mesh; the molding step 14 is to pass the screening step. The raw meal of 13 is press-formed into a blank 17 as shown in Fig. 2, and the blank 17 is dried. The blank 17 in the preferred embodiment has a cylindrical portion 171 and protrusions 172 formed at opposite ends of the cylindrical portion 171 and having an arc shape. Since the particle size of the raw material passing through the sieving step 13 is relatively uniform, the strength of the blank can be effectively improved at the time of press molding.

The sintering step 15 sinters the dried blank 17 at a temperature of from 900 ° C to 1500 ° C, and preferably the dried blank 17 is sintered at a temperature of from 950 ° C to 1300 ° C.

The activation step 16 is to activate the nickel metal compound in the blank 17 of the sintering step 15 between 650 ° C and 1250 ° C with a reducing gas containing nitrogen and hydrogen, and preferably between 800 ° C and 1100 ° C. The reducing gas activates the nickel metal compound in the blank 17 of the sintering step 15.

The reducing gas in the activation step 16 contains 10 to 40 vol% of hydrogen and 60 to 90 vol% of nitrogen. The preferred reducing gas contains 15 to 35 vol% of hydrogen and 65 to 85 vol% of nitrogen.

In order to verify the efficacy of the ammonia cracking catalyst produced by the manufacturing method of the present invention, the inventors used three different sets of process parameters to produce a majority of ammonia cracking catalysts, and conducted ammonia cracking reaction tests and strengths using the ammonia cracking catalyst. test.

Referring to Fig. 3, the ammonia cracking ability is tested by placing an ammonia cracking catalyst (shown as an imaginary line in the figure) in a tubular quartz glass reaction tube 21 having a length of 50 cm and a diameter of 3 cm, and then the quartz glass. The reaction tube 21 is placed in a cylindrical reaction furnace 22 for ammonia gas cracking capability test, and a vacuum tube 23 is connected to the tail end of the quartz glass reaction tube 21 and an absorption bottle 24, and finally the ammonia gas source 25 is The quartz glass reaction tube 21 is connected, and the absorption bottle 24 is filled with 100 ml of 0.2 N sulfuric acid to absorb the residual ammonia gas which is not cracked, and then the ammonia in the sulfuric acid is measured by an ion chromatography analyzer (not shown). The ammonia cracking efficiency of each ammonia cracking catalyst can be known by ion (NH ₄ ⁺ ) concentration and converted to ammonia gas concentration, wherein the ammonia cracking reaction temperature is 800 °C.

The strength test of the ammonia cracking catalyst is to carry out the strong test of the ammonia cracking catalyst by using a universal testing machine. Since the strength test of the material by the universal testing machine is a well-known technique known to those skilled in the art, it is here. Do not repeat them.

The ammonia cracking efficiency and average strength of the ammonia cracking catalyst prepared by each process parameter are shown in Table 1.

Among them, Experimental Examples 2, 3 and Experimental Example 1 are different from the process parameters in Table 1, and are activated at a temperature of 650 ° C to 1250 ° C at a temperature of 650 ° C to 1250 ° C by a reducing gas containing 10 to 40 vol % of hydrogen. Nickel metal compound in the blank 17 of the embryo.

As can be seen from Table 1, the ammonia cracking efficiency of the ammonia cracking catalyst produced by the production method of the present invention is similar to that of the existing commercial catalyst, and the strength of Experimental Example 2 is higher than that of the existing catalyst, so that it can be effective. Avoid the disruption of the catalyst and affect the effect and economic benefits of the catalyst.

In summary, the method for producing an ammonia cracking catalyst of the present invention controls the particle size ratio of the raw materials in the mixing step, and then controls the content of water and additives in the granulation step 12, and then controls the molding before the molding through the screening step 13. The raw material enables the particle size of the raw material to be relatively average, and then the sintering temperature of the sintering step 15 is controlled, and finally the nickel metal compound in the blank 17 of the sintering step 15 is activated via the activation step 16, and the high cracking can be produced. The ammonia cracking catalyst which is efficient and has high strength can indeed achieve the object of the present invention.

The above is only the preferred embodiment of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent changes and modifications made by the scope of the invention and the description of the invention are All remain within the scope of the invention patent.

11. . . Preparation step

12. . . Granulation step

13. . . Screening step

14. . . Molding step

15. . . Sintering step

16. . . Activation step

17. . . Hair embryo

171. . . Cylindrical part

172. . . Protrusion

twenty one. . . Reaction tube

twenty two. . . Reaction furnace

twenty three. . . Vacuum tube

twenty four. . . Absorption bottle

25. . . Ammonia source

Figure 1 is a flow chart showing a preferred embodiment of the method for producing an ammonia cracking catalyst of the present invention;

Figure 2 is a side elevational view showing the aspect of the ammonia cracking catalyst produced by the preferred embodiment;

Figure 3 is a schematic diagram showing a test apparatus for ammonia gas cracking ability.

11. . . Preparation step

12. . . Granulation step

13. . . Screening step

14. . . Molding step

15. . . Sintering step

16. . . Activation step

Claims (12)

A method for producing an ammonia cracking catalyst, comprising: a preparation step of preparing a raw material containing a nickel metal compound and magnesium oxide; and a granulation step of uniformly stirring the raw materials, water and additives into a granular raw material by mechanical means Wherein, the water accounts for 3 wt% to 15 wt% of the whole raw material, and the additive accounts for 3 wt% to 12 wt% of the whole raw material, and the balance is a balanced amount of raw materials; a screening step, the screening particle size is between 50 and 325 mesh a raw material; a molding step, press-forming the raw material subjected to the sieving step into a blank, and drying the blank; and in a sintering step, drying the blank at 900 ° C to 1500 ° C The temperature is sintered; and an activation step activates the nickel metal compound in the blank of the sintering step between 650 ° C and 1250 ° C with a reducing gas containing nitrogen and hydrogen. The method for producing an ammonia cracking catalyst according to the first aspect of the invention, wherein the particle size ratio of the raw material in the preparation step is between 10% and 60%. The method for producing an ammonia cracking catalyst according to the second aspect of the invention, wherein the particle size ratio of the raw material in the preparation step is between 20% and 40%. The method for producing an ammonia cracking catalyst according to claim 1, wherein the water in the granulation step accounts for 5 wt% to 10 wt% of the whole raw material, and the additive accounts for 7 wt% to 10 wt% of the whole raw material, and the rest To balance the amount of raw materials. The method for producing an ammonia cracking catalyst according to the first aspect of the invention, wherein the screening step is to screen a raw material having a particle diameter of between 100 and 250 mesh. The method for producing an ammonia cracking catalyst according to the first aspect of the invention, wherein the sintering step is to sinter the dried blank at a temperature of 950 ° C to 1300 ° C. The method for producing an ammonia cracking catalyst according to the first aspect of the invention, wherein the activating step is to activate the nickel metal compound in the blank of the sintering step with a reducing gas between 800 ° C and 1100 ° C. The method for producing an ammonia cracking catalyst according to the first aspect of the invention, wherein the reducing gas in the activating step contains 10 to 40 vol% of hydrogen and 60 to 90 vol% of nitrogen. The method for producing an ammonia cracking catalyst according to the eighth aspect of the invention, wherein the reducing gas in the activating step contains 15 to 35 vol% of hydrogen and 65 to 85 vol% of nitrogen. The method for producing an ammonia cracking catalyst according to the first aspect of the invention, wherein the nickel metal compound in the preparation step is selected from the group consisting of nickel nitrate, nickel sulfate, nickel carbonate, nickel oxide, and the like. Nickel oxide, nickel hydroxide or a combination of these. The method for producing an ammonia cracking catalyst according to the fourth aspect of the invention, wherein the magnesium oxide in the preparation step is selected from the group consisting of magnesium hydroxide, magnesium oxide, magnesium peroxide or the like. A combination. The method for producing an ammonia cracking catalyst according to the first aspect of the invention, wherein the additive in the granulation step is selected from the group consisting of ammonium polyacrylate, methyl cellulose, silicate, clay Or a combination of these.