A method for producing high-purity CO2 from methanol and hydrogen

Abstract

The present invention proposes a method for producing high-purity CO2 from methanol and hydrogen, which relates to the field of methanol hydrogen production. The method comprises the following steps: S1: raw material gasification: heating a mixture of methanol and desalted water to 80-90°C and ultrasonically shaking it for 20-30 minutes, followed by further heating and gasification to obtain a gasified raw material; S2: catalytic reforming: mixing the gasified raw material with a catalyst and subjecting it to a catalytic reaction to obtain a reformed gas; S3: condensing the reformed gas and subjecting it to gas-liquid separation to obtain a purified gas; S4: first-stage PSA: the purified gas enters a first-stage PSA separation process to separate hydrogen-rich gas and CO2-rich gas; the hydrogen-rich gas enters a second-stage PSA separation process, where the CO2-rich gas undergoes low-temperature cooling and adsorption to obtain liquid CO2; S5: second-stage PSA: after the hydrogen-rich gas is treated in the second-stage PSA separation process, H2 gas and a mixed gas are separated, and the mixed gas returns to the catalytic reforming process. This method can produce high-purity hydrogen and high-purity carbon dioxide, and under the action of the catalyst, the methanol conversion efficiency is high.

Description

Technical Field

[0001] The present invention relates to the field of methanol hydrogen production, and in particular to a method for producing methanol hydrogen and co-producing high-purity CO2. Background Art

[0002] As a clean energy source, hydrogen boasts significant advantages such as high calorific value, zero emissions, and widespread availability, and is considered a crucial component of the future energy system. Methanol, a renewable resource, is widely found in biomass such as crop straw and wood fiber. Its sustainable supply makes it an ideal feedstock for hydrogen production, making methanol-to-hydrogen a key source of hydrogen.

[0003] Methanol hydrogen production mainly includes methanol steam reforming, methanol cracking, and methanol partial oxidation. Methanol steam reforming involves a chemical reaction between a mixture of methanol and water vapor over a catalyst at 250-300°C and 1-5 MPa, producing hydrogen and carbon dioxide. The reformed product undergoes purification processes such as pressure swing adsorption to produce high-purity hydrogen. This mature technology offers advantages such as ease of operation, mild reaction conditions, and easy separation of by-products, making it the most widely used method in industry.

[0004] However, the carbon dioxide produced during the methanol-to-hydrogen process has a certain impact on the environment and needs to be captured and recycled. Secondly, the catalysts required for methanol steam reforming to produce hydrogen are mostly copper-based, copper-zinc-based, and precious metal catalysts. However, the relatively cheap copper-based and copper-zinc-based catalysts have problems such as catalyst deactivation and difficulty in regeneration, resulting in high costs for methanol steam reforming to produce hydrogen. Summary of the Invention

[0005] The object of the present invention is to provide a method for producing hydrogen from methanol and co-producing high-purity CO2, which can obtain high-purity hydrogen and high-purity carbon dioxide, and under the action of a catalyst, the conversion efficiency of methanol is high.

[0006] The present invention solves the technical problem by adopting the following technical solutions.

[0007] An embodiment of the present invention provides a method for producing hydrogen from methanol and co-producing high-purity CO2, comprising the following steps:

[0008] S1 Raw material gasification: Heat the mixture of methanol and desalted water to 80-90°C and treat it with ultrasonic vibration for 20-30 minutes, then continue heating and gasification to obtain gasification raw material;

[0009] S2 catalytic reforming: The gasified raw materials are mixed with the catalyst and undergo catalytic reaction to obtain reformed gas;

[0010] S3 condensation: condensation of reformed gas, gas-liquid separation, and purification of gas;

[0011] S4: The purified gas enters the first-stage PSA separation process to separate hydrogen-rich gas and CO2-rich gas; the hydrogen-rich gas enters the second-stage PSA separation process, and the CO2-rich gas is cooled and adsorbed at low temperatures to obtain liquid CO2;

[0012] S5 Second-stage PSA: After the hydrogen-rich gas is treated in the second-stage PSA separation process, H2 gas and mixed gas are separated, and the mixed gas returns to the catalytic reforming process.

[0013] In some embodiments of the present invention, in step S1, the temperature of heating and gasification is 250-300°C.

[0014] In some embodiments of the present invention, in step S1, the mass ratio of methanol to desalted water is 0.9-1.1.

[0015] In some embodiments of the present invention, the method for preparing the catalyst comprises the following steps:

[0016] Adding sodium hydroxide solution dropwise to the cerium nitrate aqueous solution at 70-90°C, stirring, cooling to room temperature, filtering, drying, calcining at 400-500°C, and pulverizing to obtain first active particles;

[0017] At room temperature, zinc nitrate solution is added to the 2-methylimidazole solution, stirred evenly, and then the first active particles are added. After stirring evenly, the mixture is allowed to stand for solid-liquid separation, and the solid is collected, dried, and crushed to obtain the second active particles.

[0018] The second active particles are added to a mixed solution of copper nitrate and zinc nitrate, stirred evenly, and then zeolite particles are added. The mixture is dried at 100-110° C. with stirring for 10-12 hours, then calcined at 400-450° C. for 2-3 hours, cooled to room temperature, and crushed to obtain the catalyst.

[0019] In some embodiments of the present invention, the molar ratio of cerium nitrate to total zinc nitrate is 1:1-2.

[0020] In some embodiments of the present invention, the mass ratio of the second active particles, copper nitrate, and zeolite particles is 1:(1-2):(0.5-1).

[0021] In some embodiments of the present invention, the average particle size of the zeolite particles is 2-4 mm.

[0022] In some embodiments of the present invention, in step S4, the low-temperature cooling adsorption includes:

[0023] The CO2-rich gas is washed, pre-cooled and buffered, then enters a CO2 air compressor for treatment, cooled, and then enters an adsorption tower for adsorption, cooling, liquefaction, distillation, and supercooling to obtain the liquid CO2.

[0024] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects:

[0025] The method for preparing hydrogen from methanol provided by the present invention comprises the following steps: methanol and desalted water vaporized raw materials are molecularly reformed under the action of a catalyst to obtain hydrogen and carbon dioxide; and hydrogen and carbon dioxide are separated in a two-stage PSA pressure swing adsorption treatment process to obtain high-purity hydrogen and carbon dioxide, which is energy-saving and environmentally friendly and produces no pollutants. Secondly, before the catalytic reforming of methanol, the mixture of methanol and desalted water is first subjected to ultrasonic vibration treatment. Under the action of high-frequency ultrasonic waves, some molecular bonds between methanol molecules and water molecules are broken, preparing for subsequent catalytic reforming and improving the conversion rate of methanol. On the other hand, under the action of high-frequency ultrasonic waves, the mixing degree of methanol molecules and water molecules is higher, which can improve the subsequent reaction rate. DETAILED DESCRIPTION

[0026] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0027] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to specific embodiments.

[0028] An embodiment of the present invention provides a method for producing hydrogen from methanol and co-producing high-purity CO2, comprising the following steps:

[0029] S1 raw material gasification: a mixture of methanol and desalted water is heated to 80-90°C and subjected to ultrasonic vibration for 20-30 minutes, and then further heated to 250-300°C for gasification to obtain a gasification raw material; wherein the mass ratio of methanol to desalted water is 0.9-1.1.

[0030] S2 catalytic reforming: The gasified raw materials are mixed with the catalyst and undergo catalytic reaction to obtain reformed gas;

[0031] S3 Condensation: The reformed gas is condensed and separated into gas and liquid through a heat exchanger to obtain purified gas, and the liquid phase can be further returned to the methanol and desalted water mixing process to reduce the loss of methanol and water;

[0032] S4: The purified gas enters the first-stage PSA separation process to separate hydrogen-rich gas and CO2-rich gas; the hydrogen-rich gas enters the second-stage PSA separation process, and the CO2-rich gas is cooled and adsorbed at low temperatures to obtain liquid CO2;

[0033] S5 Second-stage PSA: After the hydrogen-rich gas is treated in the second-stage PSA separation process, H2 gas and mixed gas (mainly CO, CO2 and a trace amount of methane) are separated, and the mixed gas returns to the catalytic reforming process.

[0034] It should be noted that in the embodiments provided by the present invention, the operating parameters of the one-stage PSA and two-stage PSA pressure swing adsorption technologies used are the same as those in the prior art.

[0035] In the catalytic reforming process, the preparation method of the catalyst used includes the following steps:

[0036] Adding sodium hydroxide solution dropwise to the cerium nitrate aqueous solution at 70-90°C, stirring, cooling to room temperature, filtering, drying, calcining at 400-500°C, and pulverizing to obtain first active particles;

[0037] At room temperature, zinc nitrate solution is added to the 2-methylimidazole solution, stirred evenly, and then the first active particles are added. After stirring evenly, the mixture is allowed to stand for solid-liquid separation, and the solid is collected, dried, and crushed to obtain the second active particles.

[0038] The second active particles are added to a mixed solution of copper nitrate and zinc nitrate, stirred evenly, and then zeolite particles are added. The mixture is dried at 100-110° C. with stirring for 10-12 hours, then calcined at 400-450° C. for 2-3 hours, cooled to room temperature, and crushed to obtain the catalyst.

[0039] The molar ratio of cerium nitrate to total zinc nitrate is 1:1-2. The mass ratio of the second active particles, copper nitrate, and zeolite particles is 1:(1-2):(0.5-1). The average particle size of the zeolite particles is 2-4 mm.

[0040] The catalyst used in the embodiment of the present invention combines cerium oxide particles with an organic-metal framework material (ZIF-8) to obtain a second active particle on which cerium oxide active particles are loaded on the organic-metal framework material, and then zeolite is used as a carrier to load the second active particles, copper nitrate and zinc nitrate. After high-temperature roasting, the second active particles, copper oxide, zinc oxide and copper-zinc compounds are loaded on the surface and internal pores of the zeolite. Active ingredients. On the one hand, in the catalyst, there are two carriers, organic-metal framework material and zeolite particles. The larger the specific surface area of the catalyst, the better the adsorption of gas, the higher the reaction efficiency, the lower the probability of carbon deposition on the catalyst, and the longer the service life of the catalyst. On the other hand, the particle size of the zeolite particles is large, and it is not easy to aggregate between the zeolite particles. Zeolite is the main skeleton material of the catalyst and is loaded with the second active particles. The large-particle zeolite particles make the second active particles loaded relatively independent and dispersed, thereby improving the dispersion of the second active particles (cerium oxide), copper oxide and zinc oxide, and further reducing the probability of carbon deposition.

[0041] In step S4, the low-temperature cooling adsorption includes:

[0042] The CO2-rich gas is washed, pre-cooled and buffered, then enters a CO2 air compressor for treatment, cooled, and then enters an adsorption tower for adsorption, cooling, liquefaction, distillation, and supercooling to obtain the liquid CO2.

[0043] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0044] Examples 1-7

[0045] Catalysts AE with different ratios were prepared as follows.

[0046] Under the condition of heating at 80°C in a water bath, sodium hydroxide solution was added dropwise to a 0.15 mol / L aqueous solution of cerium nitrate until the pH value was 9, the mixture was stirred evenly, cooled to room temperature, filtered, dried, calcined at 450°C, crushed, and passed through a 50-mesh sieve to obtain first active particles (cerium oxide);

[0047] At room temperature, 10 mL of 0.5 mol / L zinc nitrate solution was added to 100 mL of 2 mol / L 2-methylimidazole solution, and the mixture was rapidly stirred. The first active particles were then added and stirred. The mixture was allowed to stand for solid-liquid separation, and the solid was collected, dried, crushed, and passed through a 100-mesh sieve to obtain the second active particles.

[0048] The second active particles are added to a mixed solution of 10% copper nitrate and 10% zinc nitrate by mass, stirred evenly, and then zeolite particles are added. The mixture is dried at 100° C. with stirring for 10 hours, then calcined at 450° C. for 2 hours, cooled to room temperature, and crushed to obtain the catalyst.

[0049] In catalyst A, the molar ratio of cerium nitrate to total zinc nitrate is 1:1, and the mass ratio of the second active particles, copper nitrate, and zeolite particles is 1:1:1. The average particle size of the zeolite particles is 3 mm.

[0050] In catalyst B, the molar ratio of cerium nitrate to total zinc nitrate is 1:2, and the mass ratio of the second active particles, copper nitrate, and zeolite particles is 1:1:1. The average particle size of the zeolite particles is 3 mm.

[0051] In catalyst C, the molar ratio of cerium nitrate to total zinc nitrate is 1:1, and the mass ratio of the second active particles, copper nitrate, and zeolite particles is 1:1:0.5. The average particle size of the zeolite particles is 3 mm.

[0052] In catalyst D, the molar ratio of cerium nitrate to total zinc nitrate is 1:1, and the mass ratio of the second active particles, copper nitrate, and zeolite particles is 1:2:1. The average particle size of the zeolite particles is 3 mm.

[0053] In catalyst E, the molar ratio of cerium nitrate to total zinc nitrate is 1:1, and the mass ratio of the second active particles, copper nitrate, and zeolite particles is 1:1:1. The average particle size of the zeolite particles is 2 mm.

[0054] In Catalyst F, the molar ratio of cerium nitrate to total zinc nitrate is 1:1, and the mass ratio of the second active particles, copper nitrate, and zeolite particles is 1:1:1. The average particle size of the zeolite particles is 4 mm.

[0055] In catalyst G, the molar ratio of cerium nitrate to total zinc nitrate is 1:1.5, and the mass ratio of the second active particles, copper nitrate, and zeolite particles is 1:1.5:0.8. The average particle size of the zeolite particles is 3 mm.

[0056] Hydrogen and carbon dioxide were prepared as follows:

[0057] S1 Raw material gasification: Mix methanol and desalted water in a mass ratio of 0.9 and heat to 80

[0058] ±1°C, ultrasonically vibrate for 30 minutes using an ultrasonic wave at a frequency of 40 kHz, and then continue to heat to 250°C for vaporization to obtain a gasified raw material;

[0059] S2 catalytic reforming: The gasified raw material is fed into a reactor containing a catalyst (catalysts A to G correspond to Examples 1 to 7, respectively), mixed with the catalyst, and subjected to a catalytic reaction to obtain a reformed gas;

[0060] S3 condensation: After the reformed gas is condensed in the heat exchanger, the gas is separated into liquid and the gas is washed to obtain purified gas;

[0061] S4: The purified gas enters the first-stage PSA separation process for treatment, and hydrogen-rich gas and CO2-rich gas are separated; the hydrogen-rich gas enters the second-stage PSA separation process, and the CO2-rich gas is washed, pre-cooled and buffered, then enters the CO2 air compressor for treatment, cooling, and then enters the adsorption tower for adsorption, cooling, liquefaction, distillation, and supercooling to obtain liquid CO2;

[0062] S5 Second-stage PSA: After the hydrogen-rich gas is treated in the second-stage PSA separation process, H2 gas and mixed gas are separated, and the mixed gas returns to the catalytic reforming process.

[0063] Example 8

[0064] The difference from Example 1 is that, in this example, the mass ratio of methanol to desalted water is 1, and the remaining raw materials and steps are the same as those in Example 1.

[0065] Example 9

[0066] The difference from Example 1 is that, in this example, the mass ratio of methanol to desalted water is 1.1, and the remaining raw materials and steps are the same as those in Example 1.

[0067] Example 10

[0068] The difference from Example 1 is that, in this example, the frequency of ultrasonic oscillation is 60 kHz, the treatment time is 20 min, and the remaining raw materials and steps are the same as those in Example 1.

[0069] Comparative Example 1

[0070] The difference between this comparative example and Example 1 is that the mixture of methanol and desalted water is not subjected to ultrasonic oscillation treatment, and the remaining steps and raw materials are the same as those in Example 1.

[0071] Comparative Example 2

[0072] The difference between this comparative example and Example 1 is that the second active particles are used as the catalyst, and the remaining steps and raw materials are the same as those of Example 1.

[0073] Comparative Example 3

[0074] The difference between this comparative example and Example 1 is that no zeolite particles are added during the preparation of the catalyst used, and the remaining steps and raw materials are the same as those of Catalyst A. The preparation method and raw materials for producing hydrogen from methanol are also the same as those of Example 1.

[0075] Comparative Example 4

[0076] The difference between this comparative example and Example 1 is that, when preparing the catalyst used, no metal-organic framework material is prepared. That is, the first active particles are directly added to a mixed solution of 10% copper nitrate and 10% zinc nitrate by mass, stirred evenly, and then zeolite particles are added. The mixture is dried at 100°C with stirring for 10 hours, then calcined at 450°C for 2 hours, cooled to room temperature, and crushed to obtain the catalyst. The remaining steps and raw materials are the same as those of Catalyst A, and the preparation method and raw materials for hydrogen production from methanol are also the same as those of Example 1.

[0077] Experimental example

[0078] The reactants and products of the catalytic reforming reactions of Examples 1-10 and Comparative Examples 1-4 were subjected to chromatographic analysis, and the methanol conversion efficiency was calculated according to the following formula; the liquid CO2 produced in step S4 and the H2 gas produced in step S5 were subjected to chromatographic analysis, and the purity was measured and calculated. The results are shown in Table 1.

[0079] The calculation formula for methanol conversion is: The M before refers to the mass of methanol before the reaction, and the M after refers to the mass of methanol in the reactants after the reforming reaction.

[0080] Table 1

[0081]

[0082]

[0083] As can be seen from Table 1 above, the catalysts of Examples 1-10 have a high methanol conversion efficiency of over 95%. After the catalysts are used continuously for 100 hours, the methanol conversion efficiency is still higher than 90%, indicating that the catalysts prepared by the present invention have good catalytic effects, long service life, and are not susceptible to catalyst poisoning.

[0084] The difference between Comparative Example 1 and Example 1 is that ultrasonic oscillation treatment is not performed. It can be seen from Table 1 that the methanol conversion rate of Comparative Example 1 is significantly lower than that of Example 1, indicating that the reaction efficiency of methanol reforming to produce hydrogen can be improved by ultrasonic oscillation treatment.

[0085] In summary, in the method for preparing hydrogen from methanol provided by an embodiment of the present invention, methanol and desalted water vaporization raw materials are molecularly reformed under the action of a catalyst to obtain hydrogen and carbon dioxide, and the hydrogen and carbon dioxide gases are separated in a two-stage PSA pressure swing adsorption treatment process to obtain high-purity hydrogen and carbon dioxide, which is energy-saving and environmentally friendly and does not produce pollutants; secondly, before the catalytic reforming of methanol, the mixture of methanol and desalted water is first subjected to ultrasonic vibration treatment. Under the action of high-frequency ultrasonic waves, some molecular bonds between methanol molecules and water molecules are broken, preparing for subsequent catalytic reforming, which can improve the conversion rate of methanol; on the other hand, under the action of high-frequency ultrasonic waves, the mixing degree of methanol molecules and water molecules is higher, which can improve the subsequent reaction rate.

[0086] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

Claims

1. A method for producing high-purity CO2 by producing hydrogen from methanol, characterized in that: The following steps are involved: S1 Raw material gasification: Heat the mixture of methanol and desalted water to 80-90°C and treat it with ultrasonic vibration for 20-30 minutes, then continue heating and gasification to obtain gasification raw material; S2 catalytic reforming: The gasified raw materials are mixed with the catalyst and undergo catalytic reaction to obtain reformed gas; S3 condensation: condensation of reformed gas, gas-liquid separation, and purification of gas; S4: The purified gas enters the first-stage PSA separation process to separate hydrogen-rich gas and CO2-rich gas; the hydrogen-rich gas enters the second-stage PSA separation process, and the CO2-rich gas is cooled and adsorbed at low temperatures to obtain liquid CO2; S5 Second-stage PSA: After the hydrogen-rich gas is treated in the second-stage PSA separation process, H2 gas and mixed gas are separated, and the mixed gas returns to the catalytic reforming process; The preparation method of the catalyst comprises the following steps: Adding sodium hydroxide solution dropwise to the cerium nitrate aqueous solution at 70-90°C, stirring, cooling to room temperature, filtering, drying, calcining at 400-500°C, and pulverizing to obtain first active particles; At room temperature, zinc nitrate solution is added to the 2-methylimidazole solution, stirred evenly, and then the first active particles are added. After stirring evenly, the mixture is allowed to stand for solid-liquid separation, and the solid is collected, dried, and crushed to obtain the second active particles. The second active particles are added to a mixed solution of copper nitrate and zinc nitrate, stirred evenly, and then zeolite particles are added. The mixture is dried at 100-110° C. with stirring for 10-12 hours, then calcined at 400-450° C. for 2-3 hours, cooled to room temperature, and crushed to obtain the catalyst.

2. The method for producing high-purity CO2 by methanol-hydrogen production according to claim 1, characterized in that: In the step S1, the temperature of heating and gasification is 250-300°C.

3. The method for producing high-purity CO2 from methanol according to claim 1, characterized in that: In step S1, the mass ratio of methanol to desalted water is 0.9-1.

1.

4. The method for producing high-purity CO2 from methanol according to claim 1, characterized in that: The molar ratio of cerium nitrate to total zinc nitrate is 1:1-2.

5. The method for producing high-purity CO2 from methanol according to claim 1, characterized in that: The mass ratio of the second active particles, copper nitrate and zeolite particles is 1:(1-2):(0.5-1).

6. The method for producing high-purity CO2 from methanol according to claim 1, characterized in that: The average particle size of the zeolite particles is 2-4 mm.

7. The method for producing high-purity CO2 from methanol according to claim 1, characterized in that: In step S4, the low-temperature cooling adsorption includes: The CO2-rich gas is washed, pre-cooled and buffered, then enters a CO2 air compressor for treatment, cooled, and then enters an adsorption tower for adsorption, cooling, liquefaction, distillation, and supercooling to obtain the liquid CO2.

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