A method for producing high-purity hydrogen by two-phase reforming of methanol

Abstract

The present invention discloses a method for efficiently producing hydrogen from methanol, belonging to the technical field of hydrogen production. This method controls the phase of a methanol-water solution in the reaction system, allowing both a gas phase and a liquid phase to coexist. By controlling the ratio of the gas-liquid phases, this method achieves efficient hydrogen production from methanol with extremely low CO content in the product. Compared with traditional gas-phase hydrogen production, this method can effectively reduce the CO content in the product. Compared with aqueous phase reforming, this technology can significantly improve methanol conversion.

Description

Technical Field

[0001] The invention relates to a novel method for producing hydrogen by reforming methanol, and belongs to the technical field of hydrogen preparation. Background Art

[0002] The development and utilization of new energy sources has become a top priority for the development of human society. Hydrogen energy is the cleanest and most efficient of the secondary energy sources. Given its numerous advantages and its crucial role in the future, many countries are accelerating the deployment and implementation of hydrogen energy strategies. However, like electricity, hydrogen energy has no direct Earth resources and must be converted from other primary energy sources. Therefore, hydrogen energy is classified as a secondary energy source.

[0003] Hydrogen is a promising renewable energy source, and the use of fuel cell vehicles, in particular, has further expanded its applications. However, because hydrogen is a very light gas, it contains much less energy per unit volume than traditional liquid fuels at the same pressure. Therefore, using storage materials to release the required hydrogen in situ is a very promising route. Currently, the world's main hydrogen production technologies include fossil fuel hydrogen production, hydrolysis hydrogen production, and biomass hydrogen production. Among them, fossil fuel hydrogen production and biomass hydrogen production can both be achieved through the methanol platform. Fossil fuels and biomass can be converted into synthesis gas, which can then be used to synthesize methanol. Methanol hydrogen production has important applications in some small-scale refinery hydrogenation units and mobile source hydrogenation units, especially in the in-situ hydrogen production of automotive hydrogen fuel cells, which has very important potential value.

[0004] In-situ hydrogen production through methanol and water reforming, which is inexpensive, easy to store and transport, and has a high hydrogen content, is becoming a key component of future fuel cell vehicles. Current research on methanol and water reforming for hydrogen production includes steam reforming and aqueous phase reforming. Methanol steam reforming has a high CO selectivity, which is insufficient for fuel cell use. Currently, methanol reforming for hydrogen production mostly uses methanol steam reforming, also known as gas-phase reforming, where methanol and water react after vaporization. This commercialization utilizes a copper-zinc-aluminum catalyst. However, the Cu catalyst is easily oxidized by water at reaction temperatures between 250°C and 300°C. Besides Cu-based catalysts, precious metal catalysts are generally supported on oxides. However, methanol decomposes more readily on oxide-supported precious metal catalysts, resulting in very high CO concentrations that far exceed the tolerance of fuel cells.

[0005] In addition to methanol steam reforming, the existing technology also includes methanol aqueous phase reforming, that is, pressurizing the reaction system so that methanol and water remain in the liquid phase in the system. The CO selectivity of methanol aqueous phase reforming is very low. This may be due to the different activities of the water-gas shift reaction under the two conditions. However, in aqueous phase reforming technology, the methanol conversion rate needs to be improved under higher space velocity conditions. For example, we reported that under continuous flow aqueous phase reforming conditions, at a space velocity of 1.47h-1 When the methanol conversion rate can reach 100%, the space velocity is increased to 5.88h -1 When the conversion rate is 20%, it drops to about 40% (ACS Catalysis, 2019, 9, 9671-9682).

[0006] In summary, it can be seen that the CO content in hydrogen produced by methanol steam reforming in the existing technology is high, and although aqueous phase reforming can effectively reduce the CO content, the methanol conversion rate drops severely at high space velocity. Summary of the Invention

[0007] The purpose of the present invention is to overcome the defects of the prior art in that the CO content of methanol steam reforming is high and the conversion rate of aqueous phase reforming decreases when the space velocity increases, and to provide a new method for producing hydrogen by methanol reforming, which takes into account both low CO content and relatively high conversion rate at high space velocity.

[0008] In order to achieve the above objectives, the present invention adopts the following technical solutions:

[0009] A method for producing hydrogen by gas-liquid phase catalytic reforming of methanol, comprising the steps of: reforming methanol and water at a certain gas-liquid phase ratio in the presence of a catalyst; and characterized in that methanol and water must exist in both the gas phase and the liquid phase, and the gas-liquid phase ratio must conform to a strict numerical range at a specific temperature.

[0010] Furthermore, the gas-liquid phase ratio of the methanol and water is 0.25-9, preferably 0.43-4, of the total raw material.

[0011] Furthermore, to achieve the above-mentioned reforming process, the catalyst is one or more of a noble metal Pt-based catalyst, a non-noble metal Ni-based catalyst, an Fe-based catalyst and a Cu-based catalyst.

[0012] Optionally, the Pt-based catalyst is a supported catalyst, and the support is a metal oxide alumina, spinel such as magnesium aluminum spinel, nickel aluminum spinel, perovskite such as lanthanum nickel perovskite, carbon, etc. Preferably, it is nickel aluminum spinel.

[0013] Optionally, the Pt loading amount is 0.1%-5%, preferably 0.2%-1.2%, and the loading method is impregnation or co-precipitation.

[0014] Optionally, the Ni-based catalyst is a supported or skeletal type. The supported carrier is the same as that described in claim 5, with a Ni loading of 1-50%, preferably 3-20%. The skeletal Ni catalyst can be one or more of Raney nickel, NiB, and NiP amorphous alloys.

[0015] Optionally, the Fe-based catalyst is a composite oxide catalyst, including but not limited to FeCrOx, FeAlOx, etc.

[0016] Optionally, the Cu-based catalyst is one or more of CuO-ZnO-Al2O3 and CuO-ZnO-SiO2.

[0017] Furthermore, the molar ratio of methanol to water is 0.01-1.0, preferably 0.05-0.8.

[0018] Furthermore, the raw materials include methanol and water with a space velocity of 0.1-15 h -1 , preferably 1-5 h -1 .

[0019] The beneficial effects of the present invention are as follows:

[0020] (1) At the same reaction temperature, the methanol conversion rate of gas-liquid two-phase reforming is high; (2) The CO concentration in the produced hydrogen is low, generally below 100 ppm, and can reach a minimum of 10 ppm. DETAILED DESCRIPTION

[0021] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments. Those skilled in the art should understand that the following specific description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0022] Embodiment 1:

[0023] Methanol gas-liquid two-phase reforming was carried out in a fixed-bed reactor with an inner diameter of 6 mm. The catalyst was a nickel-aluminum spinel catalyst loaded with 1 wt% Pt, with a loading of 1 mL and a space velocity of 5.88 h-1. -1 By adjusting the reaction system pressure and temperature, the 10 wt% methanol-water solution existed in the reaction system as a gas-liquid two-phase system with a gas-liquid ratio of 0.67. After the reaction was allowed to proceed for 20 hours, the system reached equilibrium and samples were collected for analysis of the concentrations of products such as hydrogen and CO.

[0024] Example 2:

[0025] The conditions were the same as in Example 1, except that the gas-liquid phase ratio was adjusted to 1.5.

[0026] Example 3:

[0027] The conditions were the same as in Example 1, except that the gas-liquid two-phase ratio was adjusted to 4.

[0028] Comparative Example 1:

[0029] The conditions are the same as those in Example 1, except that the methanol aqueous solution is entirely present in the gas phase in the reaction system.

[0030] Comparative Example 2:

[0031] The conditions are the same as those in Example 1, except that the methanol aqueous solution is entirely present in the liquid phase in the reaction system.

[0032] Embodiment 4:

[0033] The conditions were the same as in Example 1, except that the catalyst was replaced with Pt / Al2O3.

[0034] Comparative Example 3:

[0035] The conditions are the same as those in Example 4, except that the methanol aqueous solution is entirely present in the gas phase in the reaction system.

[0036] Comparative Example 4:

[0037] The conditions are the same as those in Example 4, except that the methanol aqueous solution is entirely present in the liquid phase in the reaction system.

[0038] Example 5:

[0039] The conditions were the same as in Example 1, except that the catalyst was replaced with Pt / SiO2.

[0040] Comparative Example 5:

[0041] The conditions are the same as those in Example 5, except that the methanol aqueous solution is entirely present in the gas phase in the reaction system.

[0042] Comparative Example 6:

[0043] The conditions are the same as those in Example 5, except that the methanol aqueous solution is entirely present in the liquid phase in the reaction system.

[0044] The results of each embodiment and comparative example are shown in Table 1.

[0045] Table 1 Comparison of methanol reforming reaction activity for hydrogen production.

[0046]

[0047] As can be seen from Table 1, the gas-liquid two-phase reforming technology of the present invention, when used on the same catalyst, performs very well in improving the methanol conversion rate and reducing the CO concentration in the product.

[0048] Note: The gas-liquid two-phase ratio in the embodiment of the present invention is obtained by thermodynamic calculation (the calculation software used in the present invention is AspenPlus), and the reaction temperature is 210 o C. Control the gas-liquid two-phase ratio by controlling the system reaction pressure.

Claims

1. A method for producing hydrogen by gas-liquid phase catalytic reforming of methanol, comprising: a reforming reaction of methanol and water at a certain gas-liquid phase ratio in the presence of a catalyst, characterized in that: Methanol and water must exist in both the gas and liquid phases, and the reaction temperature must be 210°C; The gas-liquid phase ratio of the methanol and water is 0.25-9 of the total raw material; and the catalyst is a Pt-loaded nickel-aluminum spinel catalyst.

2. The method for producing hydrogen by gas-liquid phase catalytic reforming of methanol according to claim 1, characterized in that: The gas-liquid phase ratio of the total raw materials is 0.43-4.

3. The method for producing hydrogen by gas-liquid phase catalytic reforming of methanol according to claim 1, characterized in that: The Pt loading amount is 0.1%-5%; the loading method is impregnation or co-precipitation.

4. The method for producing hydrogen by gas-liquid phase catalytic reforming of methanol according to claim 3, characterized in that: The Pt loading amount is 0.3%-1.2%.

5. The method for producing hydrogen by gas-liquid phase catalytic reforming of methanol according to any one of claims 1 to 4, characterized in that: The molar ratio of methanol to water is 0.01-1.

0.

6. The method for producing hydrogen by gas-liquid phase catalytic reforming of methanol according to claim 5, characterized in that: The molar ratio of the methanol to the water is 0.05-0.

8.

7. The method for producing hydrogen by gas-liquid phase catalytic reforming of methanol according to any one of claims 1 to 4, characterized in that: The raw materials include methanol and water with a space velocity of 0.1-15h- 1 .

8. The method for producing hydrogen by gas-liquid phase catalytic reforming of methanol according to claim 7, characterized in that: The raw materials include methanol and water with a space velocity of 1-5h- 1 .

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