CN110511149A - A kind of method for directly preparing dimethylamine from synthesis gas - Google Patents

Abstract

The present invention relates to a kind of methods that dimethylamine is directly produced by synthesis gas, it is characterized by: this method includes synthesising gas systeming carbinol reaction and two tandem reactions of methanol aminating reaction, wherein catalysts are made of catalyst for methanol and methylamine catalyst, this method carries out in continuous fixed bed hair reactor, reaction temperature is 200-400 DEG C, pressure is 0.1-5MPa, and feed gas volume ratio is H₂/CO/NH₃=1-3:1:1-3, catalyst for methanol and methylamine catalyst mass ratio are 1:0.5-5, and the present invention realizes that one-step method from syngas directly produces dimethylamine reaction by coupling catalyst for methanol and methylamine catalyst.Series-connected catalyst is formed by CuZnAl and core-shell structure compound molecular sieve by designing, has the advantages that synthesis is simple, catalyst is at low cost, equipment investment is low etc., realization significantly improves dimethylamine selectivity in product.

Description

A kind of method for directly preparing dimethylamine from synthesis gas

technical field

The invention belongs to the field of chemical synthesis, and relates to a tandem catalytic synthesis reaction technology, in particular to a multifunctional composite catalyst, in particular to a method for directly preparing dimethylamine from synthesis gas.

Background technique

Methylamine is an important organic chemical raw material, widely used in pharmaceuticals, pesticides, solvents, templates and other industries, and has a wide range of uses. At present, methanol and ammonia gas-phase catalytic method is used to synthesize methylamine in industry. However, due to the control of thermodynamic equilibrium, the equilibrium composition of monomethylamine/dimethylamine/trimethylamine is 23/27/50 (mass ratio), of which dimethylamine It has the largest market demand, accounting for more than 80%, and it is an important raw material for generating dimethylformamide solvent.

my country is rich in coal resources, and the production of methanol from coal-derived syngas is an important energy development approach. Early US patent US2821537 reported that mixed synthesis gas and ammonia can directly produce methylamine (CO+H ₂ +NH ₃ → CH ₃ NH ₂ +CH ₃ -NH-CH ₃ +(CH ₃ ) ₃ N), this route The direct synthesis of methylamine by one-stage method has great economic and environmental significance. This route includes the following two steps: (1) synthesis of methanol from synthesis gas, CO+H ₂ →CH ₃ OH, the industrial methanol synthesis catalyst CuZnAl is very mature; (2) methanol gas phase ammoniation to synthesize methylamine, CH ₃ OH+NH ₃ →(CH ₃ ) _1-3 NH _0-2 +H ₂ O, this step is a dehydration reaction, and currently it is mainly a molecular sieve catalyst.

Baiker et al. used Cu/Al ₂ O ₃ catalyst to directly synthesize methylamine under the reaction conditions of 0.6 MPa, 200-300 ℃, CO/H ₂ /NH ₃ =1/1/3, in which Cu was synthesized from synthesis gas hydrogenation. Methanol catalyst, acidic Al ₂ O ₃ is used as catalytic methanol ammoniation catalyst (Journal of the Chemical Society, Chemical Communications, 1995, 1, 73-74), but due to the disordered nature of Al ₂ O ₃ pores, it is not shape-selective to the product Catalysis, resulting in a significantly higher proportion of trimethylamine in the product and a lower selectivity of dimethylamine. In 1978, Mobil Company developed ZSM series of molecular sieves by using the shape-selective catalysis of molecular sieves, which greatly improved the selectivity of dimethylamine.

In 1984, Nitto Chemical Company of Japan used the modified MOR molecular sieve catalyst to synthesize dimethylamine with high selectivity, and the work of synthesizing dimethylamine with high selectivity has been industrialized, and the selectivity of dimethylamine is as high as 60%. However, MOR is a 12-membered ring and an 8-membered ring channel structure. The kinetic diameter of trimethylamine is 0.39 nm, and it can diffuse freely in the 12-membered ring molecular sieve channel. Therefore, reducing the molecular sieve pore size can inhibit trimethylamine in the molecular sieve channel. In and out, and then achieve shape-selective catalysis. When the pore size of the molecular sieve is less than or equal to the molecular diameter of trimethylamine, trimethylamine is not easily generated. Literature (Chinese Journal of Catalysis, 2017, 38, 574–582; Chemical Reviews, 2018, 118, 5265-5329) reported that small-pore 8-membered ring molecular sieves effectively inhibit the formation of trimethylamine, of which RHO molecular sieves have the highest dimethylamine selectivity and Minimum trimethylamine selectivity.

To sum up, whether it is the synthesis gas to methanol reaction or the methanol ammoniation to methylamine reaction, these two reactions have been industrialized. But as mentioned above, if using synthesis gas and ammonia gas as raw materials, coupling methanol synthesis and methanol ammoniation reaction, and directly producing dimethylamine, it can effectively reduce energy consumption, simplify the reaction process, and is very advantageous in industrial economy. craft. Therefore, although there are many catalysts for this reaction, it is still necessary to find a high-efficiency catalyst that simultaneously satisfies:

(1) The matching of two reaction process conditions of methanol synthesis and methanol ammoniation, such as conditions such as temperature and pressure;

(2) The compounding method of the catalyst, such as physical mixing, two-stage method or core-shell structure catalyst;

(3) The shape-selective catalytic effect of molecular sieves controls the pore structure of molecular sieves and maximizes the selectivity of dimethylamine.

SUMMARY OF THE INVENTION

The object of the present invention is to overcome the deficiencies of the prior art, and to provide a method for directly producing dimethylamine from synthesis gas. Simplify the process flow, reduce equipment investment, save energy and reduce costs. In addition, the present invention provides a method for directly preparing a catalyst for dimethylamine from synthesis gas. The composite molecular sieve synthesized by the solid phase synthesis method is a molecular sieve catalyst with a core-shell structure, and its catalytic efficiency is high, and the catalyst is prepared at the same time. Simple and easy to operate, low energy consumption, further reducing catalyst cost.

The present invention solves its technical problem by adopting the following technical solutions to realize:

A method for directly producing dimethylamine from synthesis gas, the method comprises two series reactions of synthesis gas to methanol reaction and methanol ammoniation reaction, wherein the reaction catalyst is composed of methanol catalyst and methylamine catalyst, and the method is carried out in a continuous fixed bed. The reaction temperature is 200-400 ℃, the pressure is 0.1-5MPa, the volume ratio of raw material gas is H ₂ /CO/NH ₃ =1-3:1:1-3, the quality of methanol catalyst and methylamine catalyst The ratio is 1:0.5-5, wherein the synthesis gas to methanol reaction is CO+2H ₂ →CH ₃ OH, and the methanol ammoniation reaction is CH ₃ OH+NH ₃ →(CH ₃ ) _1-3 NH _0-2 +H ₂ O.

Moreover, the methanol catalyst is a CuZnAl catalyst, and its weight percentage components are CuO: 30-60%, ZnO: 30-60%, Al ₂ O ₃ : 5-10%, and the catalyst is prepared by a co-precipitation method.

Moreover, the catalyst is shaped by slicing and sieving to a particle size of 20-80 meshes.

And, the preparation method of described methanol catalyst, comprises the following steps:

(1) The copper salt, the zinc salt and the aluminum salt are prepared into a mixed salt solution according to the metal molar ratio of CuO: 30-60%, ZnO: 30-60%, Al ₂ O ₃ : 5-10%, copper salt solution and zinc The salt solution is one or more of hydrochloride solution, nitrate solution and acetate solution;

(2) The mixed salt solution and the precipitating agent are reacted, the pH value of the solution is 8-10, the precipitation temperature is 40-80 ° C, and the precipitating agent is one of Na ₂ CO ₃ , NaHCO ₃ , NaOH, and urea or several;

(3) After the precipitate is separated from the mother liquor, the precipitate is repeatedly washed with deionized water, the temperature of the deionized water is 40-60 ° C, and then dried and roasted in the air, the drying temperature is 90-120 ° C, and the drying time is 12- 24h, the calcination temperature is 300-500°C, and the calcination time is 5-10h to obtain a methanol catalyst.

Moreover, the methylamine catalyst is a composite molecular sieve material with a core-shell structure, wherein the core is one or two of ZSM-5 and ZSM-35, and the shell is one of SAPO-34, AlPO ₄ -25 or Two, the existing form of the composite molecular sieve material includes at least one of physical mixing and co-crystal structure.

Moreover, the methylamine catalyst is a molecular sieve catalyst, prepared by a solid-phase synthesis method, and its structure is a core-shell structure of a molecular sieve coated molecular sieve, wherein the shell is a molecular sieve with an 8-membered ring topology structure, and SAPO-34, AlPO ₄ can be selected. One or two of -25, the core is a molecular sieve with a 10-membered ring topology, and one or two of ZSM-5 and ZSM-35 can be selected.

And, the preparation method of described methylamine catalyst, comprises the following steps:

(1) Add the solid silicon source, aluminum source, phosphorus source, and template agent into an agate mortar and grind for 5-60 minutes, put it into a hydrothermal kettle, and crystallize at 100-250 ° C for 16-240 hours, and the product is washed and dried. get molecular sieve core;

(2) In step (1), the molecular sieve core is a crystal core, and a secondary crystallization method is used to grow a molecular sieve shell on the crystal core, and the molecular sieve core, silicon source, and template are mixed in an agate mortar and ground for 5-60 min at room temperature, Then hydrothermally crystallized at 100-250°C for 24-72h, the product was washed, dried, and calcined at 300-600°C for 5-10h to obtain methylamine catalyst.

Moreover, the drying temperature in step (2) is 80-120° C., and the drying time is 6-24 h.

Moreover, the selected silicon source is one or more of silica, SiO ₂ gel, silicic acid, and sodium silicate, and the selected aluminum source is pseudoboehmite, aluminum nitrate, sodium aluminate, aluminum sulfate and one or more in kaolin, selected phosphorus source is one or two in phosphoric acid, ammonium dihydrogen phosphate, and the mol ratio of described silicon source, aluminum source, phosphorus source, template agent is 1-50: 0.1-1:0-1:0.1-1.

Moreover, the molar ratio of the silicon source and the template agent is 1-50:0.1-1, and the mass ratio of the molecular sieve shell to the silicon source is 10-100:1.

The advantages and positive effects of the present invention are:

1. In the present invention, by coupling CO hydrogenation to methanol reaction and methanol ammoniation to methylamine reaction, a fixed bed reactor is filled with methanol catalyst and methylamine catalyst to realize the matching of two reaction conditions of methanol synthesis and methanol ammoniation It can react with synthesis gas to directly produce dimethylamine.

2. The present invention adopts the solid-phase synthesis method to prepare the composite molecular sieve catalyst with core-shell structure. By controlling the pore structure of the molecular sieve and utilizing the shape-selective catalytic effect of the molecular sieve, methanol ammoniation can be used to synthesize dimethylamine with high selectivity.

3. The present invention realizes the reaction of directly preparing dimethylamine from synthesis gas by one-step method by coupling methanol catalyst and methylamine catalyst. By designing a series catalyst composed of CuZnAl and core-shell structure composite molecular sieve, it has the advantages of simple synthesis, low catalyst cost, low equipment investment, etc., and the selectivity of dimethylamine in the product can be significantly improved.

Description of drawings

Fig. 1 syngas one-step method prepares dimethylamine technical drawing;

Fig. 2 is the XRD spectrum of CuZnAl methanol catalyst;

Fig. 3 is the XRD spectrum of ZSM-5 molecular sieve;

Fig. 4 is the XRD spectrum of ZSM-35 molecular sieve;

Fig. 5 is the XRD spectrum of AlPO4-25 molecular sieve;

Fig. 6 is the XRD spectrum of SAPO-34 molecular sieve;

Fig. 7 is the XRD spectrum of HZSM-35@SAPO-34 molecular sieve;

Fig. 8 is the XRD pattern of HZSM-5@SAPO-34 molecular sieve;

Figure 9 is the XRD pattern of HZSM-5@AlPO4-25 molecular sieve.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are only descriptive, not restrictive, and cannot limit the protection scope of the present invention.

A method for directly preparing dimethylamine from synthesis gas, as shown in Figure 1, the method includes two series reactions of synthesis gas-to-methanol reaction and methanol ammoniation reaction, wherein the reaction catalyst is composed of a methanol catalyst and a methylamine catalyst, The method is carried out in a continuous fixed-bed reactor, the reaction temperature is 200-400° C., the pressure is 0.1-5MPa, the volume ratio of raw gas is H ₂ /CO/NH ₃ =1-3:1:1-3, methanol is The mass ratio of the catalyst and the methylamine catalyst is 1:0.5-5, wherein, the synthesis gas to methanol reaction is CO+2H ₂ →CH ₃ OH, and the methanol ammoniation reaction is CH ₃ OH+NH ₃ →(CH ₃ ) _1-3 NH _0-2 +H ₂ O.

Moreover, the methanol catalyst is a CuZnAl catalyst, and its weight percentage components are CuO: 30-60%, ZnO: 30-60%, Al ₂ O ₃ : 5-10%, and the catalyst is prepared by a co-precipitation method.

Moreover, the catalyst is shaped by slicing and sieving to a particle size of 20-80 meshes.

And, the preparation method of described methanol catalyst, comprises the following steps:

(1) The copper salt, the zinc salt and the aluminum salt are prepared into a mixed salt solution according to the metal molar ratio of CuO: 30-60%, ZnO: 30-60%, Al ₂ O ₃ : 5-10%, copper salt solution and zinc The salt solution is one or more of hydrochloride solution, nitrate solution and acetate solution;

(2) The mixed salt solution and the precipitating agent are reacted, the pH value of the solution is 8-10, the precipitation temperature is 40-80 ° C, and the precipitating agent is one of Na ₂ CO ₃ , NaHCO ₃ , NaOH, and urea or several;

(3) After the precipitate is separated from the mother liquor, the precipitate is repeatedly washed with deionized water, the temperature of the deionized water is 40-60 ° C, and then dried and roasted in the air, the drying temperature is 90-120 ° C, and the drying time is 12- 24h, the calcination temperature is 300-500°C, and the calcination time is 5-10h to obtain a methanol catalyst.

Moreover, the methylamine catalyst is a composite molecular sieve material with a core-shell structure, wherein the core is one or two of ZSM-5 and ZSM-35, and the shell is one of SAPO-34, AlPO ₄ -25 or Two, the existing form of the composite molecular sieve material includes at least one of physical mixing and co-crystal structure.

Moreover, the methylamine catalyst is a molecular sieve catalyst, prepared by a solid-phase synthesis method, and its structure is a core-shell structure of a molecular sieve coated molecular sieve, wherein the shell is a molecular sieve with an 8-membered ring topology structure, and SAPO-34, AlPO ₄ can be selected. One or two of -25, the core is a molecular sieve with a 10-membered ring topology, and one or two of ZSM-5 and ZSM-35 can be selected.

And, the preparation method of described methylamine catalyst, comprises the following steps:

(1) Add the solid silicon source, aluminum source, phosphorus source, and template agent into an agate mortar and grind for 5-60 minutes, put it into a hydrothermal kettle, and crystallize at 100-250 ° C for 16-240 hours, and the product is washed and dried. get molecular sieve core;

(2) In step (1), the molecular sieve core is a crystal core, and a secondary crystallization method is used to grow a molecular sieve shell on the crystal core, and the molecular sieve core, silicon source, and template are mixed in an agate mortar and ground for 5-60 min at room temperature, Then hydrothermally crystallized at 100-250°C for 24-72h, the product was washed, dried, and calcined at 300-600°C for 5-10h to obtain methylamine catalyst.

Moreover, the drying temperature in step (2) is 80-120° C., and the drying time is 6-24 h.

Moreover, the selected silicon source is one or more of silica, SiO ₂ gel, silicic acid, and sodium silicate, and the selected aluminum source is pseudoboehmite, aluminum nitrate, sodium aluminate, aluminum sulfate and one or more in kaolin, selected phosphorus source is one or two in phosphoric acid, ammonium dihydrogen phosphate, and the mol ratio of described silicon source, aluminum source, phosphorus source, template agent is 1-50: 0.1-1:0-1:0.1-1.

Moreover, the molar ratio of the silicon source and the template agent is 1-50:0.1-1, and the mass ratio of the molecular sieve shell to the silicon source is 10-100:1.

The molecular sieve crystal form prepared in the embodiment of the present invention is measured by Japanese Rigaku Ultima IV X-ray diffractometer (XRD), and the experimental conditions are: CuKa radiation, tube voltage 40kV, tube current 40mA.

Example 1

Methanol catalyst CuZnAl synthesis: Weigh 10.87g of copper nitrate trihydrate, 13.38g of zinc nitrate hexahydrate and 3.75g of aluminum nitrate nonahydrate, put them into a beaker containing 200mL, keep at 60°C, and take this solution as solution A. Dissolve 9.54 g of sodium carbonate solution in 100 mL of deionized water, and use this solution as solution B. The solution B was slowly added dropwise to the solution A, while vigorously stirring, the temperature was maintained at 60°C, and the pH in the system was controlled at about 8.6 by the rate of addition of the sodium carbonate solution. After the precipitation was completed, it was aged at room temperature overnight, filtered, washed with deionized water at 60 °C for 5 times until the filtrate was neutral, and finally dried at 120 °C for 6 hours, and calcined at 350 °C for 5 hours in a muffle furnace to obtain CuZnAl methanol catalyst, CuZnAl The molar ratio is 45:45:10, and the XRD pattern of the CuZnAl sample is shown in Figure 2.

Example 2

Synthesis of HZSM-5 catalyst: Weigh 4.87g of silica, 0.48g of boehmite, 0.28g of sodium hydroxide, and 0.25g of tetrapropylammonium bromide, add them to an agate mortar, grind for 5-10min, and then add them to In a hydrothermal kettle, crystallize at 200°C for 16h. After crystallization, cool to room temperature in an ice-water bath, repeatedly wash with deionized water until neutral, and dry at 120°C overnight to obtain NaZSM-5 molecular sieve. The NaZSM-5 powder was added to a 1M ammonium nitrate aqueous solution with a solid-liquid mass ratio of 1:10, vigorously stirred, and ion exchanged at 80 °C. This process was repeated three times. After filtration, the powder was dried at 120 °C for 6 hours. Finally, it was calcined in air at 500 °C for 5 h to obtain HZSM-5 molecular sieve. The XRD pattern of the ZSM-5 sample is shown in Figure 3.

Example 3

Synthesis of HZSM-35 molecular sieve: Weigh 4.4g of white carbon black, 2.08g of aluminum nitrate, 1.6g of sodium hydroxide, and 2.8g of ethylenediamine, add them to an agate mortar, grind for 5-10min, and then add them to a hydrothermal kettle , crystallized at 200°C for 24h, after crystallization, cooled to room temperature in an ice-water bath, washed repeatedly with deionized water until neutral, and dried at 120°C overnight to obtain NaZSM-35 molecular sieve. The NaZSM-35 powder was added to 1M ammonium nitrate aqueous solution, the solid-liquid mass ratio was 1:10, vigorously stirred, and ion exchange was carried out at 80 °C. This process was repeated 3 times. After filtration, the powder was dried at 120 °C for 6 hours. Finally, it was calcined in air at 500℃ for 5h to obtain HZSM-35 molecular sieve. The XRD spectrum of ZSM-35 sample is shown in Tuyu 4.

Example 4

Synthesis of AlPO 4-25 molecular sieve: Weigh _0.40g of silica, 4.18g of aluminum isopropoxide, 2.36g of phosphoric acid, and 1.35g of dimethylamine (40wt%), add them to an agate mortar, grind for 15-25min, and then Add it to a hydrothermal kettle, crystallize at 200 °C for 24 hours, after crystallization, cool it to room temperature in an ice-water bath, repeatedly wash it with deionized water until it becomes neutral, dry at 120 °C overnight, and finally roast it in air at 500 °C for 5 hours to obtain AlPO ₄ -25 molecular sieve, XRD patterns of AlPO ₄ -25 samples are shown in Figure 5.

Example 5

Synthesis of SAPO-34 molecular sieve: Weigh 0.15g of silica, 0.58g of boehmite, 0.52g of ammonium dihydrogen phosphate, and 1.30g of morpholine, add them to an agate mortar, grind for 5-10min, and then add them to a hydrothermal kettle In the middle, crystallize at 200 °C for 24 hours. After the crystallization is completed, the ice water bath is quenched to room temperature, repeatedly washed with deionized water until neutral, dried at 120 °C overnight, and finally calcined at 500 °C in air for 5 hours to obtain SAPO-34 molecular sieve, SAPO The XRD pattern of the -34 sample is shown in Figure 6.

Example 6

Synthesis of HZSM-35@SAPO-34 composite molecular sieve: Weigh 1.0 g of HZSM-35 molecular sieve prepared in Example 3 and put it into agate, then weigh 0.15 g of silica, 0.58 g of boehmite, ammonium dihydrogen phosphate 0.52g, 1.30g morpholine, add it into an agate mortar equipped with HZSM-35 molecular sieve, grind for 5-10min, then add it to a hydrothermal kettle, crystallize at 200 ℃ for 24h, after the crystallization is completed, the ice water bath is quenched to room temperature , repeatedly washed with deionized water until neutral, dried at 120 °C overnight, and finally calcined in air at 500 °C for 5 h to obtain HZSM-35@SAPO-34 methylamine catalyst. The XRD pattern of HZSM-35@SAPO-34 molecular sieve is as follows shown in Figure 7.

Example 7

Synthesis of HZSM-5@SAPO-34 composite molecular sieve: Weigh 1.0 g of the HZSM-5 molecular sieve prepared in Example 2 and put it into agate, then weigh 0.15 g of silica, 0.58 g of boehmite, ammonium dihydrogen phosphate 0.52g, 1.30g morpholine, add it into an agate mortar equipped with HZSM-5 molecular sieve, grind for 5-10min, then add it to a hydrothermal kettle, crystallize at 200°C for 24h, after crystallization, cool it to room temperature in an ice-water bath , repeatedly washed with deionized water until neutral, dried at 120 °C overnight, and finally calcined in air at 500 °C for 5 h to obtain HZSM-5@SAPO-34 methylamine catalyst. The XRD pattern of HZSM-5@SAPO-34 molecular sieve is as follows shown in Figure 8.

Example 8

Synthesis of HZSM-5@AlPO ₄ -25 composite molecular sieve: Weigh 2.0g of HZSM-5 molecular sieve prepared in Example 2 and put it into agate, weigh 0.40g of white carbon black, 4.18g of aluminum isopropoxide, and 2.36g of phosphoric acid , 1.35g of dimethylamine (40wt%), added to the agate mortar, ground for 15-25min, then added to the hydrothermal kettle, crystallized at 200°C for 24h, after the crystallization was completed, the ice-water bath was quenched to room temperature, repeated use Deionized water was washed to neutrality, dried at 120 °C overnight, and finally calcined in air at 500 °C for 5 h to obtain HZSM-5@AlPO ₄ -25 molecular sieve. The XRD pattern of HZSM-5@AlPO ₄ -25 molecular sieve is shown in Figure 9. Show.

Example 9

Load 0.5 g of CuZnAl methanol catalyst, the catalyst particle size is 20-40 mesh, into a micro-reverse single tube, and the upper and lower ends of the catalyst are fixed with quartz wool. The reaction conditions of the catalyst are: 250° C., 0.5 MPa, H ₂ /CO/NH ₃ molar ratio 2/1/1, and mixed gas flow rate 20 mL/min. The reaction results are shown in Table 1, the CO conversion rate is 8.1%, and the methanol selectivity reaches 99%, indicating that the CuZnAl methanol catalyst has a very high selectivity.

Example 10

Load 0.5g of CuZnAl methanol catalyst, 0.5g of HZSM-5@SAPO-34 methylamine catalyst, methanol and methanol catalyst are granulated 20-40 mesh, and then loaded into micro-reverse single tube in turn, each catalyst is at the upper and lower ends Secure with quartz wool. The reaction conditions of the catalyst are: 250° C., 0.5 MPa, H ₂ /CO/NH ₃ molar ratio 2/1/1, and mixed gas flow rate 20 mL/min. The reaction results are shown in Table 1, the CO conversion rate was 9.5%, and the dimethylamine selectivity was 38%. It is shown that the molecular sieve catalyst has strong dehydration ability. In Comparative Example 1, the type selection of dimethylamine is obviously improved, and a small amount of dimethyl ether is a by-product.

Example 11

Load 0.5g of CuZnAl methanol catalyst, 0.5g of HZSM-35@SAPO-34 methylamine catalyst, methanol and methanol catalyst are granulated 20-40 mesh, and then loaded into micro-reverse single tube in turn, the upper and lower ends of each catalyst are Secure with quartz wool. The reaction conditions of the catalyst are: 250° C., 0.5 MPa, H ₂ /CO/NH ₃ molar ratio 2/1/1, and mixed gas flow rate 20 mL/min. The reaction results are shown in Table 1. Comparative Example 10 shows a slight decrease in CO conversion. Since the pores of HZSM-35 are smaller than that of ZSM-5, the selectivity of monomethylamine is obviously improved, and the selectivity of trimethylamine is also inhibited.

Example 12

Load 0.5g of CuZnAl methanol catalyst, 0.5g of HZSM-5@AlPO ₄ -25 methylamine catalyst, methanol and methanol catalyst are both granulated 20-40 mesh, and then loaded into micro-reverse single tube in turn, each catalyst is two The ends are fixed with quartz wool. The reaction conditions of the catalyst were as follows: 250° C., 0.5 MPa, H ₂ /CO/NH 3 molar ratio 2/1/1, and mixed gas flow rate 20 mL/min. The reaction results are shown in Table 1, the CO conversion rate is 10.2%, and compared with Example 10, the dimethylamine is significantly improved, indicating that AlPO ₄ -25 has strong shape-selective catalytic performance.

Example 13

Load 0.5g of CuZnAl methanol catalyst, 0.5g of HZSM-5@AlPO ₄ -25 methylamine catalyst, methanol and methanol catalyst are both granulated 20-40 mesh, mixed and put into a micro-reverse single tube, the upper and lower ends of the catalyst Secure with quartz wool. The reaction conditions of the catalyst are: 250° C., 0.5 MPa, H ₂ /CO/NH ₃ molar ratio 2/1/1, and mixed gas flow rate 20 mL/min. The reaction results are shown in Table 1. In Comparative Example 12, the CO conversion rate was further increased to 13.6%, the dimethylamine selectivity reached 53%, and the trimethylamine selectivity was significantly reduced.

Table 1 Each catalytic reaction activity and product selectivity

Although the embodiments and drawings of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the invention and the appended claims Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims (10)

1. a kind of method for directly producing dimethylamine by synthesis gas, it is characterised in that: this method includes synthesising gas systeming carbinol reaction With two tandem reactions of methanol aminating reaction, wherein catalysts are made of catalyst for methanol and methylamine catalyst, this method It is carried out in continuous fixed bed hair reactor, reaction temperature is 200-400 DEG C, pressure 0.1-5MPa, and feed gas volume ratio is H₂/CO/NH₃=1-3:1:1-3, catalyst for methanol and methylamine catalyst mass ratio are 1:0.5-5, wherein synthesising gas systeming carbinol is anti- It should be CO+2H₂→CH₃OH, methanol aminating reaction are CH₃OH+NH₃→(CH₃)_1-3NH_0-2+H₂O。

2. a kind of method for directly producing dimethylamine by synthesis gas according to claim 1, it is characterised in that: the methanol Catalyst is CuZnAl catalyst, weight percent composition CuO:30-60%, ZnO:30-60%, Al₂O₃: 5-10%, it should Catalyst is prepared using coprecipitation.

3. a kind of method for directly producing dimethylamine by synthesis gas according to claim 1 or claim 2, it is characterised in that: described Being shaped to beat piece, being sized to granularity for catalyst is 20-80 mesh.

4. a kind of method for directly producing dimethylamine by synthesis gas according to claim 1, it is characterised in that: the methanol The preparation method of catalyst, comprising the following steps:

(1) by mantoquita, zinc salt and aluminium salt according to CuO:30-60%, ZnO:30-60%, Al₂O₃: 5-10% metal molar is than configuration At mixing salt solution, copper salt solution and zinc solution be one of HCI solution, nitrate solution and acetate solution or It is several；

(2) mixing salt solution and precipitating reagent are reacted, and the pH value of solution is in 8-10, and precipitation temperature is 40-80 DEG C, the precipitating Agent is Na₂CO₃、NaHCO₃, NaOH, one or more of urea；

(3) after sediment is separated with mother liquor, sediment is cleaned using deionized water repeatedly, deionized water temperature is 40-60 DEG C, so Afterwards in dry in air and roasting, drying temperature is 90-120 DEG C, drying time 12-24h, and maturing temperature is 300-500 DEG C, Calcining time 5-10h, obtains catalyst for methanol.

5. a kind of method for directly producing dimethylamine by synthesis gas according to claim 1, it is characterised in that: the methylamine is urged Agent is the composite molecular screen material with core-shell structure, one of center ZSM-5, ZSM-35 or two kinds, and shell is SAPO-34、AlPO₄One of -25 or two kind, form existing for the composite molecular screen material includes physical mixed, cocrystallization At least one of structure.

6. according to claim 1 or a kind of 5 methods for directly producing dimethylamine by synthesis gas, it is characterised in that: described Methylamine catalyst is molecular sieve catalyst, is prepared using solid-phase synthesis, and structure is the nucleocapsid knot that molecular sieve coats molecular sieve Structure, wherein shell is that can choose SAPO-34, AlPO with 8 member ring topological structure molecular sieves₄One of -25 or two kind, core is With 10 member ring topological structure molecular sieves, one of ZSM-5, ZSM-35 or two kinds can be chosen.

7. a kind of method for directly producing dimethylamine by synthesis gas according to claim 6, it is characterised in that: the methylamine The preparation method of catalyst, comprising the following steps:

(1) solid silicon source, silicon source, phosphorus source, template are added in agate mortar and grind 5-60min, be packed into water heating kettle, In 100-250 DEG C of crystallization 16-240h, product is washed, dry, obtains molecular sieve core；

(2) molecular sieve core is nucleus in step (1), using second-crystallized method, molecule screen shell is grown on nucleus, in agate mortar Middle mixed molecular sieve core, template, grinds 5-60min at silicon source at room temperature, then the hydrothermal crystallizing 24-72h at 100-250 DEG C, Product is washed, dry, and 300-600 DEG C of roasting 5-10h obtains methylamine catalyst.

8. a kind of method for directly producing dimethylamine by synthesis gas according to claim 7, it is characterised in that: in step (2) Dry temperature is 80-120 DEG C, drying time 6-24h.

9. a kind of method for directly producing dimethylamine by synthesis gas according to claim 7, it is characterised in that: selected silicon source is White carbon black, SiO₂One of gel, silicic acid, sodium metasilicate are a variety of, selected silicon source be boehmite, aluminum nitrate, sodium aluminate, One of aluminum sulfate and kaolin are a variety of, and selected phosphorus source is one of phosphoric acid, ammonium dihydrogen phosphate or two kinds, the silicon Source, silicon source, phosphorus source, the molar ratio of template are 1-50:0.1-1:0-1:0.1-1.

10. a kind of method for directly producing dimethylamine by synthesis gas according to claim 7, it is characterised in that: the silicon source, The molar ratio of template is 1-50:0.1-1, and the molecule screen shell and silicon source mass ratio are 10-100:1.