A method for producing mixed gas for synthetic ammonia

Abstract

The present invention provides a method for producing a mixed gas for synthetic ammonia, which uses carbon dioxide and natural gas as raw materials for reforming and preparing the mixed gas, and uses the mixed gas as raw material to produce synthetic ammonia; wherein, the active components of the catalyst used during reforming are Ni, Mo and Fe, the active auxiliary agent is La2O3 and MgO in a mass ratio of 1: (1~3), and the carrier is formed by ZSM‑5 molecular sieve and 4A molecular sieve in a mass ratio of 1: (4~8); based on the mass of the catalyst as 100%, the content of the active component is 4% to 16%, the content of the auxiliary agent is 8% to 12%, and the remainder is the carrier. The catalyst of the present invention is a new material with simple composition, a wide range of raw material sources for preparation, can significantly reduce the cost of the catalyst, and also has excellent catalytic performance, providing more choices for the market.

Description

Technical Field

[0001] The present invention relates to the field of industrial production of synthetic ammonia, and more specifically, to a method for producing a mixed gas for synthetic ammonia. Background Art

[0002] Synthetic ammonia is ammonia directly synthesized from nitrogen and hydrogen under high temperature, high pressure and catalyst conditions. Synthetic ammonia is an important raw material for the fertilizer industry and basic organic chemical industry. It has a significant impact on agricultural production and chemical manufacturing, and is closely related to the lives of the general public.

[0003] In the industrial production process of synthetic ammonia, how to obtain low-cost raw materials (i.e. nitrogen and hydrogen, especially hydrogen) through the integration of various production chains and improve the utilization efficiency of materials is one of the key factors to improve the economic benefits of enterprises. At present, the widely used low-cost sources of raw gas required for synthetic ammonia include coke oven gas, blast furnace gas, synthesis gas, etc. In addition, as people's understanding of the greenhouse effect deepens, how to reduce the emission of CO2, one of the strongest greenhouse gases, and realize its green conversion and application has attracted the attention of academia and enterprises. Since Ashcroft et al. (Nat. Chem., 1991, 352: 225-226) reported the research on carbon dioxide reforming methane in 1991, the technical direction of carbon dioxide reforming methane has attracted widespread attention in the industry. Carbon dioxide reforming methane can simultaneously utilize CO2 and CH4, two major greenhouse gases, which is of great significance to greenhouse gas emission reduction. The mixed gas formed contains hydrogen and carbon monoxide, etc., which can be used as raw gas for industrial synthetic ammonia, methanol or their combined production.

[0004] The catalyst used in the process of obtaining raw gas from carbon dioxide reforming methane will significantly affect the conversion efficiency of carbon dioxide and methane, the yield and selectivity of hydrogen and carbon monoxide, etc., and thus change the way of using the obtained mixed gas. Therefore, industry insiders have conducted a lot of research on catalysts and disclosed some research results. German patent DE9400513 discloses that after the Pd / ZrO2 catalyst is used continuously for 500 hours, the reaction activity remains basically unchanged. However, the disadvantage of precious metal catalysts is that they are expensive and do not have economic advantages when industrialized. Patent CN108636418B discloses a rare earth modified nickel-based catalyst for pressurized carbon dioxide reforming methane to produce synthesis gas, the carrier is at least one of SiO2, Al2O3, TiO2, the active ingredient is Ni, Ni-Fe or Ni-Co, and the additive is La2O3, Sm2O3, Pr6O 11, Nd2O3, Y2O3; therefore, the additives used are relatively scarce and difficult to obtain, which is not conducive to industrial promotion and use. In particular, the catalyst requires a special combustion preparation method involving the use of combustion additives, etc. The preparation method is immature and the process is relatively complicated, which is not suitable for widespread use in industrial production.

[0005] Therefore, it is of great significance to continuously develop new catalysts to obtain catalysts that can minimize production costs while ensuring better catalytic effects. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a method for producing a mixed gas for synthetic ammonia. The catalyst is a new type of material with simple ingredients, easy to obtain, and a wide range of raw materials for preparation, which can significantly reduce the cost of the catalyst and also has excellent catalytic performance, providing more choices for the market.

[0007] An embodiment of the present invention provides a method for producing a mixed gas for synthetic ammonia, wherein carbon dioxide and natural gas are reformed as raw materials to prepare the mixed gas, and synthetic ammonia is produced using the mixed gas as raw material; wherein the active ingredients of the catalyst used in the reforming are Ni, Mo and Fe, the active auxiliary agent is La2O3 and MgO in a mass ratio of 1:(1-3), and the carrier is formed by ZSM-5 molecular sieve and 4A molecular sieve in a mass ratio of 1:(4-8); based on the mass of the catalyst as 100%, the content of the active ingredient is 4%-16%, the content of the auxiliary agent is 8%-12%, and the balance is the carrier.

[0008] As an embodiment, the mass ratio of the active ingredients Ni, Mo and Fe is 1:(1-1.2):(2-5).

[0009] As an implementation mode, based on 100% mass of the catalyst, the content of the active ingredient is 7.2% to 12%, the content of the auxiliary agent is 10% to 12%, and the remainder is the carrier.

[0010] As an embodiment, the preparation method of the catalyst is: according to the composition formula of the catalyst, the carrier is first impregnated with a salt solution containing an active ingredient, and then dried and calcined once; the product after the first calcination is then impregnated in a salt solution containing La and Mg, and then dried, calcined twice, and then cooled and granulated to obtain the catalyst; wherein the first calcination and the second calcination are both carried out in an air atmosphere.

[0011] As an embodiment, the temperature of the first calcination is 600-720° C., and the calcination time is 3-10 hours; the temperature of the second calcination is 680-850° C., and the calcination time is 4-8 hours.

[0012] As an embodiment, the catalyst is spherical particles of 60-80 mesh.

[0013] As an embodiment, the carrier is pre-treated with a mixed acid solution obtained by mixing 25wt% hydrochloric acid solution and 5wt% hydrofluoric acid in a volume ratio of 2:1, heated and stirred for 4 to 6 hours at a heating temperature of 30 to 40°C; then washed with pure water and dried for use.

[0014] As an embodiment, the catalyst is reduced and activated with a reducing gas before being used for reforming carbon dioxide and natural gas; the reducing gas is hydrogen, or a mixture of hydrogen and an inert gas.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1. Through the synergistic cooperation between the active ingredients, the active additives and the carrier, the composition formula of the catalyst is simplified, and the expensive and heavy components or components that are difficult to obtain in the existing catalyst are replaced by cheap and readily available materials, thereby reducing the production cost of the catalyst.

[0017] 2. Since the catalyst cost of the present invention is significantly reduced, and the use of the catalyst for the integration of carbon dioxide and natural gas can increase the yield of hydrogen, the cost of obtaining hydrogen raw materials for the synthetic ammonia production line is reduced, thereby improving the comprehensive economic benefits of the synthetic ammonia enterprise.

[0018] 3. The preparation method of the catalyst of the present invention is classic and mature, and the probability of introducing external substances as auxiliary conditions is low, which is conducive to obtaining catalysts with stable quality in each batch and ensuring the quality of the catalyst. In addition, the preparation process does not require the use of organic additives for combustion and other process links, which is also green and environmentally friendly. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention is clearly and completely described below. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] Unless otherwise specified, the substances and materials used in the present invention can be obtained through common market procurement methods.

[0021] Example 1

[0022] The composition of the catalyst and the information on the raw materials for preparation are as follows:

[0023]

[0024] The preparation method of the catalyst is:

[0025] (1) According to the composition formula, raw materials and dosage of the catalyst shown in the above table, the ZSM-5 molecular sieve and the 4A molecular sieve were first impregnated with an aqueous solution containing nickel nitrate hexahydrate, ammonium heptamolybdate and ferric nitrate nonahydrate as active ingredients, the solid was filtered out, and then dried and calcined once in an air atmosphere; the temperature of the first calcination was 600° C. and the calcination time was 10 hours;

[0026] (2) immersing the product after the primary calcination in an aqueous solution prepared by lanthanum nitrate hexahydrate and magnesium nitrate, and then drying and performing a secondary calcination in an air atmosphere; the secondary calcination temperature is 680° C. and the calcination time is 8 hours;

[0027] (3) After the secondary calcination, the product is naturally cooled, molded and granulated to obtain spherical particles of 60-80 mesh, that is, the catalyst is obtained.

[0028] Example 2

[0029] The composition of the catalyst and the information on the raw materials for preparation are as follows:

[0030]

[0031] The preparation method of the catalyst is:

[0032] (1) According to the composition formula, raw materials and dosage of the catalyst shown in the above table, the ZSM-5 molecular sieve and the 4A molecular sieve were first impregnated with an aqueous solution containing nickel nitrate hexahydrate, ammonium heptamolybdate and ferric nitrate nonahydrate as active ingredients, the solid was filtered out, and then dried and calcined once in an air atmosphere; the temperature of the first calcination was 640° C. and the calcination time was 7 hours;

[0033] (2) immersing the product after the primary calcination in an aqueous solution prepared by lanthanum nitrate hexahydrate and magnesium nitrate, and then drying and performing a secondary calcination in an air atmosphere; the secondary calcination temperature is 720° C. and the calcination time is 6 hours;

[0034] (3) After the secondary calcination, the product is naturally cooled, molded and granulated to obtain spherical particles of 60-80 mesh, that is, the catalyst is obtained.

[0035] Example 3

[0036] The composition of the catalyst and the information on the raw materials for preparation are as follows:

[0037]

[0038] The preparation method of the catalyst is:

[0039] (1) According to the composition formula, raw materials and dosage of the catalyst shown in the above table, the ZSM-5 molecular sieve and the 4A molecular sieve were first impregnated with an aqueous solution containing nickel nitrate hexahydrate, ammonium heptamolybdate and ferric nitrate nonahydrate as active ingredients, the solid was filtered out, and then dried and calcined once in an air atmosphere; the temperature of the first calcination was 680° C. and the calcination time was 6 hours;

[0040] (2) immersing the product after the primary calcination in an aqueous solution prepared by lanthanum nitrate hexahydrate and magnesium nitrate, and then drying and performing a secondary calcination in an air atmosphere; the secondary calcination temperature is 760° C. and the calcination time is 5 hours;

[0041] (3) After the secondary calcination, the product is naturally cooled, molded and granulated to obtain spherical particles of 60-80 mesh, that is, the catalyst is obtained.

[0042] Example 4

[0043] The composition of the catalyst and the information on the raw materials for preparation are as follows:

[0044]

[0045] The preparation method of the catalyst is:

[0046] (1) According to the composition formula, raw materials and dosage of the catalyst shown in the above table, the ZSM-5 molecular sieve and the 4A molecular sieve were first impregnated with an aqueous solution containing nickel nitrate hexahydrate, ammonium heptamolybdate and ferric nitrate nonahydrate as active ingredients, the solid was filtered out, and then dried and calcined once in an air atmosphere; the temperature of the first calcination was 720° C. and the calcination time was 3 hours;

[0047] (2) immersing the product after the primary calcination in an aqueous solution prepared by lanthanum nitrate hexahydrate and magnesium nitrate, and then drying and performing a secondary calcination in an air atmosphere; the secondary calcination temperature is 850° C. and the calcination time is 4 hours;

[0048] (3) After the secondary calcination, the product is naturally cooled, molded and granulated to obtain spherical particles of 60-80 mesh, that is, the catalyst is obtained.

[0049] Example 5

[0050] The only difference from Example 1 is that the ZSM-5 molecular sieve and the 4A molecular sieve are treated as follows:

[0051] Before use, a mixed acid solution obtained by mixing 25 wt % hydrochloric acid solution and 5 wt % hydrofluoric acid in a volume ratio of 2:1 was heated and stirred for 6 hours at a heating temperature of 30° C. The mixture was then washed with pure water and dried before use.

[0052] Example 6

[0053] The only difference from Example 1 is that the ZSM-5 molecular sieve and the 4A molecular sieve are treated as follows:

[0054] Before use, a mixed acid solution obtained by mixing 25 wt % hydrochloric acid solution and 5 wt % hydrofluoric acid in a volume ratio of 2:1 was heated and stirred for 4 hours at a heating temperature of 40° C. The solution was then washed with pure water and dried before use.

[0055] Comparative Example 1

[0056] The difference from Example 1 is that the ZSM-5 molecular sieve is replaced by the HX molecular sieve, and the rest is the same as Example 1.

[0057] Comparative Example 2

[0058] The difference from Example 1 is that the 4A molecular sieve is removed, and the rest is the same as Example 1.

[0059] Comparative Example 3

[0060] The difference from Example 1 is that the mass ratio of ZSM-5 molecular sieve to 4A molecular sieve is 1:9, the amount of ZSM-5 molecular sieve used is 8.8 g, the amount of 4A molecular sieve used is 79.2 g, and the rest is consistent with Example 1.

[0061] Test example

[0062] The catalysts prepared in Examples 1 to 6 and Comparative Examples 1 to 3 are used to catalyze the carbon dioxide reforming methane reaction, and the specific method is as follows:

[0063] 0.15 g of the catalysts prepared in Examples 1 to 6 and Comparative Examples 1 to 3 were placed in a fixed bed reactor, and a mixture of H2 and N2 with a volume ratio of 1:4 was introduced at a flow rate of 50 mL min -1 , at 4℃·min -1 The heating rate was increased from room temperature to 700 °C and the reduction was carried out for 2.5 hours.

[0064] Then, H2 was turned off and N2 was continued to flow at 2℃·min -1 The temperature was raised to 750 °C at a rate of 1.5 °C. After the temperature stabilized, the reaction gas was switched to a mixture of CO2 and CH4 with a volume ratio of 1:1. The total amount of the reaction gas was 130 mL min -1 , at a pressure of 1.0 MPa, a temperature of 750°C, CO2 / CH4 = 1.0, and a space velocity of 53200 mL·g -1 ·h -1 The reaction was carried out under the following conditions, and the gas after the reaction was detected and analyzed by a chromatograph (chromatographic columns were 5A and PQ columns) with a Shanghai Huaai GC9560 thermal conductivity cell detector. The final experimental results are shown in Table 1.

[0065] Table 1

[0066]

[0067] Although the embodiments disclosed in the present invention are as above, the contents described are only embodiments adopted to facilitate understanding of the present invention and are not intended to limit the present invention. Any technician in the field to which the present invention belongs can make any modifications and changes in the form and details of implementation without departing from the spirit and scope disclosed in the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A method for producing a mixed gas for synthetic ammonia, characterized in that: Carbon dioxide and natural gas are used as raw materials for reforming to prepare the mixed gas, and the mixed gas is used as raw material to produce synthetic ammonia; wherein the active components of the catalyst used in the reforming are Ni, Mo and Fe, the active auxiliary agent is La2O3 and MgO in a mass ratio of 1: (1-3), and the carrier is formed by ZSM-5 molecular sieve and 4A molecular sieve in a mass ratio of 1: (4-8); based on the mass of the catalyst as 100%, the content of the active component is 4% to 16%, the content of the auxiliary agent is 8% to 12%, and the balance is the carrier; The mass ratio of active ingredients Ni, Mo and Fe is 1:(1~1.2):(2~5).

2. The method for producing a mixed gas for synthetic ammonia according to claim 1, characterized in that: Taking the mass of the catalyst as 100%, the content of the active ingredient is 7.2% to 12%, the content of the auxiliary agent is 10% to 12%, and the remainder is the carrier.

3. The method for producing a mixed gas for synthetic ammonia according to claim 1, characterized in that: The preparation method of the catalyst is as follows: according to the composition formula of the catalyst, the carrier is first impregnated with a salt solution containing active ingredients, then dried and calcined once; the product after the primary calcination is then impregnated in a salt solution containing La and Mg, then dried, calcined twice, and then cooled and granulated to obtain the catalyst; wherein the primary calcination and the secondary calcination are both carried out in an air atmosphere.

4. The method for producing a mixed gas for synthetic ammonia according to claim 3, characterized in that: The temperature of the first calcination is 600-720°C, and the calcination time is 3-10 hours; the temperature of the second calcination is 680-850°C, and the calcination time is 4-8 hours.

5. The method for producing a mixed gas for synthetic ammonia according to claim 3, characterized in that: The catalyst is in the form of spherical particles of 60-80 mesh.

6. The method for producing a mixed gas for synthetic ammonia according to claim 3, characterized in that: Before use, the carrier is treated with a mixed acid solution obtained by mixing 25wt% hydrochloric acid solution and 5wt% hydrofluoric acid in a volume ratio of 2:1, heated and stirred for 4-6 hours at a heating temperature of 30-40°C; then washed with pure water and dried for use.

7. The method for producing a mixed gas for synthetic ammonia according to any one of claims 1 to 6, characterized in that: The catalyst is reduced and activated by using a reducing gas before being used for reforming carbon dioxide and natural gas; the reducing gas is hydrogen, or a mixed gas consisting of hydrogen and an inert gas.

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