Method for producing hydrogen from methanol and co-producing high-purity CO2

Abstract

The invention provides a method for producing hydrogen from methanol and co-producing high-purity CO2, and relates to the field of hydrogen production from methanol. Comprising the following steps: S1, gasifying a raw material: heating a mixture of methanol and desalted water to 80-90 DEG C, carrying out ultrasonic oscillation treatment for 20-30 minutes, and then continuously heating and gasifying to obtain a gasified raw material; s2, catalytic reforming: mixing the gasification raw material with a catalyst, and performing catalytic reaction to obtain reformed gas; s3, condensing: condensing the reformed gas, and carrying out gas-liquid separation to obtain purified gas; s4, first-stage PSA: the purified gas enters a first-stage PSA separation process to be treated, and hydrogen-rich gas and CO2-rich gas are separated out; the hydrogen-rich gas enters a second-stage PSA separation process, and CO2-rich gas is subjected to low-temperature cooling adsorption to obtain liquid CO2; and S5, second-stage PSA: after the hydrogen-rich gas is treated by a second-stage PSA separation process, H2 gas and mixed gas are separated out, and the mixed gas is returned to the catalytic reforming process. According to the method, high-purity hydrogen and high-purity carbon dioxide can be obtained, and under the action of the catalyst, the conversion efficiency of methanol is high.

Description

Technical Field

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

[0002] As a clean energy, hydrogen has significant advantages such as high calorific value, zero emissions, and a wide range of sources, and is considered an important component of the future energy system. Methanol, as a renewable resource, is widely found in biomass such as crop straw and wood fiber. Its sustainable supply makes it an ideal raw material for hydrogen production. Therefore, methanol-to-hydrogen is also an important source of hydrogen.

[0003] The main methods of producing hydrogen from methanol include: hydrogen production from methanol steam reforming, hydrogen production from methanol cracking and hydrogen production from methanol partial oxidation. Hydrogen production from methanol steam reforming is a process in which a mixture of methanol and water vapor undergoes a chemical reaction under the action of a catalyst at 250-300°C and 1-5MPa to generate hydrogen and carbon dioxide. The reforming product undergoes a purification process such as pressure swing adsorption to obtain high-purity hydrogen. This technology is relatively mature and has the advantages of easy operation, mild reaction conditions and easy separation of by-products. It is currently the most widely used method in industry.

[0004] However, the carbon dioxide produced in the process of methanol to hydrogen production has a certain impact on the environment, and the carbon dioxide needs to be captured and recycled. Secondly, the catalysts used in methanol steam reforming to produce hydrogen are mostly copper-based, copper-zinc-based and precious metal catalysts, but the relatively cheap copper-based and copper-zinc-based catalysts have problems such as catalyst deactivation and difficulty in catalyst 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] The embodiment of the present invention provides a method for producing high-purity CO2 by producing hydrogen from methanol, comprising the following steps:

[0008] S1 Raw material gasification: The mixture of methanol and desalted water is heated to 80-90°C, and ultrasonically shaken for 20-30 minutes, and then continued to heat and gasify to obtain a gasified raw material;

[0009] S2 catalytic reforming: the gasified raw material is mixed with the catalyst and subjected to catalytic reaction to obtain reformed gas;

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

[0011] S4 One-stage PSA: 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 cooled and adsorbed at low temperature to obtain liquid CO2;

[0012] S5 two-stage PSA: After the hydrogen-rich gas is treated in the two-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] At 70-90° C., adding sodium hydroxide solution to the cerium nitrate aqueous solution, stirring, cooling to room temperature, filtering, drying, roasting at 400-500° C., and crushing to obtain first active particles;

[0017] At room temperature, adding zinc nitrate solution to 2-methylimidazole solution, stirring evenly, then adding first active particles, stirring evenly, standing, solid-liquid separation, collecting solids, drying and crushing to obtain 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, 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 comprises:

[0023] The CO2-rich gas is washed, pre-cooled and buffered, then enters a CO2 air compressor for treatment, is 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 gasification 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 does not generate pollutants; secondly, before the catalytic reforming of methanol, the mixture of methanol and desalted water is firstly subjected to ultrasonic oscillation treatment, and under the action of high-frequency ultrasonic waves, some molecular bonds between methanol molecules and water molecules are broken, so as to prepare for subsequent catalytic reforming and 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, so as to improve the subsequent reaction rate. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

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

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

[0029] 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, and then continue to heat it 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 material is mixed with the catalyst and subjected to 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 One-stage PSA: 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 cooled and adsorbed at low temperature to obtain liquid CO2;

[0033] S5 two-stage PSA: After the hydrogen-rich gas is treated in the two-stage PSA separation process, H2 gas and mixed gas (the main components are 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 comprises the following steps:

[0036] At 70-90° C., adding sodium hydroxide solution to the cerium nitrate aqueous solution, stirring, cooling to room temperature, filtering, drying, roasting at 400-500° C., and crushing to obtain first active particles;

[0037] At room temperature, adding zinc nitrate solution to 2-methylimidazole solution, stirring evenly, then adding first active particles, stirring evenly, standing, solid-liquid separation, collecting solids, drying and crushing to obtain 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, 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 organic-metal framework materials (ZIF-8) to obtain cerium oxide active particles loaded on organic-metal framework materials. The second active particles, copper nitrate and zinc nitrate are loaded with zeolite as a carrier. 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 of organic-metal framework materials and zeolite particles. The specific surface of the catalyst is large, the better the adsorption of gas, the higher the reaction efficiency, the lower the probability of carbon deposition on the catalyst, and the service life of the catalyst can be extended; 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-size zeolite particles make the second active particles loaded relatively independent and dispersed, which improves the dispersion of the second active particles (cerium oxide), copper oxide and zinc oxide, and further reduces the probability of carbon deposition.

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

[0042] The CO2-rich gas is washed, pre-cooled and buffered, then enters a CO2 air compressor for treatment, is 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 in conjunction with 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, a sodium hydroxide solution was added dropwise to a 0.15 mol / L cerium nitrate aqueous solution 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, add 10 mL of 0.5 mol / L zinc nitrate solution to 100 mL of 2 mol / L 2-methylimidazole solution, stir quickly and evenly, then add the first active particles, stir evenly, let stand, separate the solid and liquid, collect the solid, dry and crush, and pass 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. for 10 hours under stirring, and then calcined at 450° C. for 2 hours, cooled to room temperature, and crushed to obtain the catalyst.

[0049] In the 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 at a mass ratio of 0.9 and heat to 80

[0058] ±1°C, use ultrasonic waves with a frequency of 40kHz to perform ultrasonic oscillation treatment for 30 minutes, and then continue to heat to 250°C for gasification to obtain a gasified raw material;

[0059] S2 catalytic reforming: the gasified raw material is fed into a reactor containing a catalyst (catalysts AG correspond to Examples 1-7 in sequence), 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 and liquid are separated and the gas is washed to obtain purified gas;

[0061] S4 One-stage PSA: 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, and 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 two-stage PSA: After the hydrogen-rich gas is treated in the two-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 processing 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 catalysts, 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. for 10 hours under stirring, and 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 prepared in step S4 and the H2 gas prepared 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 rate is: The term "M" before the reaction refers to the mass of methanol before the reaction, and the term "M" after the reaction refers to the mass of methanol in the reactants after the reforming reaction.

[0080] Table 1

[0081]

[0082]

[0083] It can be concluded from Table 1 that the catalysts of Examples 1-10 have a high methanol conversion efficiency of more than 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 effect, long service life, and are not prone 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 gasification raw materials are molecularly reformed under the action of a catalyst to obtain hydrogen and carbon dioxide, and 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 oscillation treatment, and 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 degree of mixing of methanol molecules and water molecules is higher, which can improve the subsequent reaction rate.

[0086] The embodiments described above are part of the embodiments of the present invention, rather than all of the embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments 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.

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: The mixture of methanol and desalted water is heated to 80-90°C, and ultrasonically shaken for 20-30 minutes, and then continued to heat and gasify to obtain a gasified raw material; S2 catalytic reforming: the gasified raw material is mixed with the catalyst and subjected to catalytic reaction to obtain reformed gas; S3 condensation: condensation of reformed gas, gas-liquid separation, and purification of gas; S4 One-stage PSA: 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 cooled and adsorbed at low temperature to obtain liquid CO2; S5 two-stage PSA: After the hydrogen-rich gas is treated in the two-stage PSA separation process, H2 gas and mixed gas are separated, and the mixed gas returns to the catalytic reforming process.

2. The method for producing high-purity CO2 by methanol-to-hydrogen 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 to hydrogen 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 by methanol-to-hydrogen according to claim 1, characterized in that: The preparation method of the catalyst comprises the following steps: At 70-90° C., adding sodium hydroxide solution to the cerium nitrate aqueous solution, stirring, cooling to room temperature, filtering, drying, roasting at 400-500° C., and crushing to obtain first active particles; At room temperature, adding zinc nitrate solution to 2-methylimidazole solution, stirring evenly, then adding first active particles, stirring evenly, standing, solid-liquid separation, collecting solids, drying and crushing to obtain 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, 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.

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

6. The method for producing high-purity CO2 from methanol according to claim 4, characterized in that: The mass ratio of the second active particles, copper nitrate and zeolite particles is 1:(1-2):(0.5-1).

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

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

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