Method for producing hydrogen by cascade reforming of biomass hydrothermal liquefaction water-phase by-product

Abstract

The invention provides a method for producing hydrogen by utilizing cascade reforming of a biomass hydrothermal liquefaction water-phase byproduct, and belongs to the technical field of reutilization of a hydrothermal liquefaction water-phase product. The method comprises the following steps: mixing a biomass hydrothermal liquefaction water-phase byproduct with a catalyst 1, and carrying out primary reforming hydrogen production reaction under argon protection to obtain hydrogen and a water-phase product 1; mixing the water-phase product 1 and a catalyst 2, and carrying out secondary reforming hydrogen production reaction under the protection of argon to obtain hydrogen and a water-phase product 2; mixing the water-phase product 2 and a catalyst 3, and carrying out three-stage reforming hydrogen production reaction under the protection of argon to obtain hydrogen and a water-phase product 3; the catalyst 1, the catalyst 2 and the catalyst 3 are Ni / CeO2 catalysts. According to the method, resource utilization of the water-phase by-product is achieved, meanwhile, the environmental risk can be effectively reduced, meanwhile, the content of organic matter in the water-phase by-product is effectively reduced by adopting three-stage water-phase reforming hydrogen production, and the hydrogen yield is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of reuse of hydrothermal liquefaction aqueous phase products, and in particular to a method for producing hydrogen by utilizing cascade reforming of biomass hydrothermal liquefaction aqueous phase byproducts. Background Art

[0002] Concerns about mitigating climate change and replacing petroleum-based energy are rapidly growing, increasing research interest in alternative and renewable energy strategies. Hydrogen production is one of the most important alternative energy technologies for meeting future energy needs. Compared to traditional petroleum-based fuels, it is clean and efficient.

[0003] Hydrothermal liquefaction is a promising liquefaction method that has attracted considerable attention in recent years. Hydrothermal liquefaction of biomass involves the decomposition of solid biopolymer structures into primarily liquid components in a high-temperature, high-pressure aqueous environment over a sufficient period of time, followed by thermochemical conversion into liquid fuel. Typical hydrothermal treatment conditions are temperatures of 523-647 K and operating pressures of 4-22 MPa. Compared to pyrolysis, low operating temperature, high energy efficiency, and low tar yield are key parameters attracting researchers' attention to the liquefaction process. During the hydrothermal liquefaction process, biomass is decomposed into liquid fuel (bio-oil), aqueous byproducts, and solid residues in a high-temperature, high-pressure aqueous environment. The aqueous byproducts typically contain large amounts of organic matter and are difficult to process. Therefore, the efficient utilization of these aqueous byproducts for hydrogen production and their resource utilization remains a key research priority. Summary of the Invention

[0004] Based on the above, the present invention aims to provide a method for producing hydrogen through cascade reforming of the aqueous byproducts of biomass hydrothermal liquefaction. This method can achieve high-value utilization of the aqueous byproducts of biomass hydrothermal liquefaction, while reducing the organic matter content in the aqueous byproducts and increasing hydrogen production.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A method for producing hydrogen by utilizing cascade reforming of aqueous byproducts from biomass hydrothermal liquefaction, comprising the following steps:

[0007] After mixing the aqueous byproduct of biomass hydrothermal liquefaction with catalyst 1, a primary reforming hydrogen production reaction is carried out under argon protection to obtain hydrogen and aqueous product 1;

[0008] After mixing the aqueous phase product 1 and the catalyst 2, a secondary reforming hydrogen production reaction is carried out under argon protection to obtain hydrogen and an aqueous phase product 2;

[0009] After mixing the aqueous phase product 2 and the catalyst 3, a three-stage reforming hydrogen production reaction is carried out under argon protection to obtain hydrogen and the aqueous phase product 3;

[0010] The catalyst 1, catalyst 2 and catalyst 3 are all Ni / CeO2 catalysts.

[0011] In a preferred embodiment of the present invention, the method for preparing the aqueous by-product of biomass hydrothermal liquefaction is: mixing biomass and water and performing a hydrothermal liquefaction reaction, and the aqueous phase obtained after the reaction is the aqueous by-product of biomass hydrothermal liquefaction.

[0012] In a preferred embodiment of the present invention, the preparation method of the Ni / CeO2 catalyst comprises the following steps:

[0013] Step 1. Ni is loaded on CeO2 by an impregnation method to obtain a catalyst precursor;

[0014] Step 2. calcining the catalyst precursor under air atmosphere to obtain NiO / CeO2;

[0015] Step 3. Reducing the NiO / CeO2 in a H2 atmosphere to obtain the Ni / CeO2 catalyst.

[0016] In a preferred embodiment of the present invention, in the Ni / CeO2 catalyst, Ni accounts for 5%-15% of the mass of the Ni / CeO2 catalyst (ie, the Ni loading in the Ni / CeO2 catalyst is 5wt%-15wt%).

[0017] In a preferred embodiment of the present invention, in the Ni / CeO2 catalyst, Ni accounts for 5%, 10% or 15% of the mass of the Ni / CeO2 catalyst.

[0018] In the present invention, nickel is loaded onto CeO2 by an impregnation method to obtain a catalyst precursor. The specific steps are: dissolving a nickel salt in water, adding CeO2, stirring, allowing the mixture to stand for aging, and then drying to obtain the catalyst precursor. The nickel salt is preferably Ni(NO3)2·6H2O.

[0019] In a preferred embodiment of the present invention, the calcination temperature is 500° C., the time is 4 hours, and the heating rate is 10° C. / min; the reduction temperature is 500° C., and the time is 2 hours.

[0020] In a preferred embodiment of the present invention, in the primary reforming hydrogen production reaction, the volume mass ratio of the biomass hydrothermal liquefaction aqueous byproduct and the catalyst 1 is 60 mL: 0.5-2 g; the temperature of the primary reforming hydrogen production reaction is 260-320 ° C, and the time is 1-4 h;

[0021] In the secondary reforming hydrogen production reaction, the volume mass ratio of the aqueous phase product 1 and the catalyst 2 is 60 mL:0.5-2 g; the temperature of the secondary reforming hydrogen production reaction is 260-320° C., and the time is 1-4 h;

[0022] In the three-stage reforming hydrogen production reaction, the volume mass ratio of the aqueous phase product 2 and the catalyst 3 is 60 mL:0.5-2 g; the temperature of the two-stage reforming hydrogen production reaction is 260-320° C., and the time is 1-4 h.

[0023] In a preferred embodiment of the present invention, in the primary reforming hydrogen production reaction, the volume mass ratio of the biomass hydrothermal liquefaction aqueous byproduct and catalyst 1 is 60 mL:1.5 g; the temperature of the primary reforming hydrogen production reaction is 300 ° C, and the time is 2 h;

[0024] In the secondary reforming hydrogen production reaction, the volume mass ratio of the aqueous phase product 1 and the catalyst 2 is 60 mL:1.5 g; the temperature of the secondary reforming hydrogen production reaction is 300° C. and the time is 2 h;

[0025] In the three-stage reforming hydrogen production reaction, the volume mass ratio of the aqueous phase product 2 and the catalyst 3 is 60 mL:1.5 g; the temperature of the two-stage reforming hydrogen production reaction is 300° C. and the time is 2 h.

[0026] The present invention provides a method for producing hydrogen by cascade reforming of aqueous byproducts from biomass hydrothermal liquefaction. The aqueous byproducts obtained from the biomass hydrothermal liquefaction process are used as a hydrogen production feedstock, and this feedstock is applied to cascade aqueous phase reforming to produce hydrogen. Compared with the prior art, the present invention has the following advantages:

[0027] (1) The aqueous by-products produced by biomass hydrothermal liquefaction are difficult to handle. This process not only realizes the resource utilization of aqueous by-products, but also effectively reduces their environmental risks.

[0028] (2) The reaction conditions for hydrogen production by aqueous phase reforming are relatively mild, which helps to reduce energy consumption and improve economic efficiency;

[0029] (3) The Ni / CeO2 catalyst used in the present invention has the advantages of low price, high dispersion and high activity. It can obtain higher hydrogen production under the condition of less metal loading, providing a new idea for biomass hydrogen production.

[0030] (4) The use of three-stage aqueous phase reforming to produce hydrogen effectively reduced the organic matter content in the aqueous phase bio-oil and significantly increased hydrogen production. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 The present invention shows a flow chart of the hydrogen production by cascade reforming of aqueous byproducts from biomass hydrothermal liquefaction.

[0033] Figure 2 These are SEM spectra of Ni / CeO2 catalysts prepared in Examples 1, 2, and 3 of the present invention, where (a) is Example 1, (b) is Example 2, and (c) is Example 3.

[0034] Figure 3 The XRD spectra of Ni / CeO2 catalysts prepared in Examples 1, 2 and 3 of the present invention are shown.

[0035] Figure 4 The COD variation trend of the aqueous phase products obtained in Examples 4, 5, and 6 of the present invention is shown.

[0036] Figure 5 The TOD variation trend of the aqueous phase products obtained in Examples 4, 5, and 6 of the present invention is shown. DETAILED DESCRIPTION

[0037] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0038] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0039] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0040] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0041] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0042] The present invention uses the aqueous phase by-products generated by the hydrothermal liquefaction of biomass in the aqueous phase reforming hydrogen production reaction process, thereby achieving waste recycling while producing hydrogen.

[0043] The method comprises: using the aqueous phase by-product obtained in the biomass hydrothermal liquefaction process as raw material and Ni / CeO2 as catalyst to carry out a cascade aqueous phase reforming hydrogen production reaction.

[0044] The preparation method of the aqueous by-product of biomass hydrothermal liquefaction is as follows:

[0045] The biomass raw material and water were placed in a reactor at a ratio of 10 g:100 mL; the reaction temperature was set to 320°C, the reaction time was 40 min, and the stirrer speed was 150 rpm; after the reaction, the reactor was cooled to room temperature and the liquid product was taken out, and the aqueous phase was obtained by vacuum filtration and stored, which was the aqueous phase by-product of biomass hydrothermal liquefaction.

[0046] The biomass raw material is preferably corn straw.

[0047] The preparation method of Ni / CeO2 catalyst is as follows:

[0048] Step 1. Ni is loaded on CeO2 by an impregnation method to obtain a catalyst precursor;

[0049] Step 2. calcining the catalyst precursor under air atmosphere to obtain NiO / CeO2;

[0050] Step 3. Reducing the NiO / CeO2 in a H2 atmosphere to obtain the Ni / CeO2 catalyst.

[0051] Among them, the cascade aqueous phase reforming hydrogen production reaction is as follows:

[0052] After mixing the aqueous byproduct of biomass hydrothermal liquefaction with catalyst 1, a primary reforming hydrogen production reaction is carried out under argon protection to obtain hydrogen and aqueous product 1;

[0053] After mixing the aqueous phase product 1 and the catalyst 2, a secondary reforming hydrogen production reaction is carried out under argon protection to obtain hydrogen and an aqueous phase product 2;

[0054] After the aqueous phase product 2 and the catalyst 3 are mixed, a three-stage reforming hydrogen production reaction is carried out under argon protection to obtain hydrogen and the aqueous phase product 3.

[0055] Unless otherwise specified, the technical solutions described in the present invention are all conventional solutions in the field, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0056] In the embodiment, the preparation of the aqueous by-product of biomass hydrothermal liquefaction is as follows:

[0057] (1) Weigh 10 g of dry corn stalks and 100 mL of deionized water, place them in a reactor, and then introduce N2 and purge to remove all air from the reactor;

[0058] (2) After exhausting the air, the reaction temperature was set to 320°C, the reaction time was 40 min, and the stirrer speed was 150 rpm;

[0059] (3) After the reaction is completed, the reactor is cooled to room temperature and the liquid phase product is taken out. The aqueous phase is obtained by vacuum filtration and stored, which is the aqueous phase by-product of biomass hydrothermal liquefaction.

[0060] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

[0061] Example 1

[0062] Preparation of Ni / CeO2 catalyst:

[0063] (1) Weigh 0.5220 g of Ni(NO3)2·6H2O and 2 g of CeO2 and mix them evenly. Add 20 mL of deionized water and stir at room temperature for 30 min. Then age at room temperature for 12 h and dry in a 120°C forced air drying oven for 24 h to obtain a catalyst precursor.

[0064] (4) The obtained catalyst precursor was ground into powder and placed in a muffle furnace, and calcined at 500°C (heating rate of 10°C / min) for 4 h in an air atmosphere to obtain NiO / CeO2;

[0065] (5) NiO / CeO2 was placed in a horizontal tube furnace and reduced at 500°C in a H2 atmosphere for 2 h to obtain a Ni / CeO2 catalyst which was stored in a vacuum drying dish (the Ni loading in the Ni / CeO2 catalyst was 5 wt%).

[0066] Example 2

[0067] The only difference from Example 1 is that the amount of Ni(NO3)2·6H2O is adjusted so that the Ni loading in the Ni / CeO2 catalyst is 10 wt%. The other steps and parameters are the same as those in Example 1.

[0068] Example 3

[0069] The only difference from Example 1 is that the amount of Ni(NO3)2·6H2O is adjusted so that the Ni loading in the Ni / CeO2 catalyst is 15wt%. The other steps and parameters are the same as those in Example 1.

[0070] Figure 2 The following are SEM images of the catalysts prepared in Examples 1, 2, and 3. As can be seen from the images, the Ni particles are evenly dispersed, with no apparent agglomeration. Therefore, well-dispersed Ni particles facilitate the exposure of more active sites on the Ni / CeO2 surface.

[0071] Figure 3 The XRD spectra of the catalysts prepared in Examples 1, 2 and 3 of the present invention are shown in FIG. Figure 3 As shown in the figure (in the figure, 5% represents Example 1, 10% represents Example 2, and 15% represents Example 3), XRD characterization shows that the characteristic diffraction peaks of CeO2 in the reduced Ni / CeO2 catalyst appear at 28.560°, 33.096°, 47.506°, 56.370°, 59.118°, and 69.450°, which are attributed to the (111), (200), (220), (311), (222), and (400) crystal planes of CeO2, respectively (PDF No.34-0394), and the characteristic diffraction peaks at 44.497° and 51.850° are attributed to Ni (PDF No.04-0850), indicating that reduced metallic Ni is produced and exists in a face-centered cubic structure.

[0072] Example 4

[0073] Study on the optimal reaction conditions for hydrogen production by primary aqueous phase reforming:

[0074] 60 mL of the aqueous byproduct of biomass hydrothermal liquefaction was added to the reactor. The initial reaction temperature was set to 280°C, the reaction time was 3 h, the amount of Ni / CeO2 catalyst used was 0.5 g to 2 g, wherein the Ni loading in the Ni / CeO2 catalyst was 5 wt%, 10 wt%, and 15 wt%, the stirrer speed was 300 rpm, and the pressure was 1 MPa.

[0075] (1) The reaction time was controlled, the Ni loading amount in the catalyst and the catalyst dosage remained unchanged (reaction time was 3 h, catalyst dosage was 0.5 g, and Ni loading amount in the catalyst was 5 wt%), and the reaction temperatures were set to 260°C, 280°C, 300°C, and 320°C, respectively; after the reaction was completed, the reactor was cooled to room temperature and the gas phase product was collected, and the liquid phase product was taken out, and the aqueous phase product was obtained by vacuum filtration and stored.

[0076] By analyzing the gas phase products using a gas chromatograph, it was found that the temperature condition with the highest proportion of hydrogen was 300°C, and the proportion of hydrogen was 43.31%.

[0077] (2) The reaction temperature, the Ni loading in the catalyst, and the amount of catalyst used were kept constant (the reaction temperature was 300°C, the catalyst amount was 1.5 g, and the Ni loading in the catalyst was 10 wt%), and the reaction times were set to 1 h, 2 h, 3 h, and 4 h, respectively; after the reaction was completed, the reactor was cooled to room temperature and the gas phase product was collected, and the liquid phase product was taken out, and the aqueous phase product was obtained by vacuum filtration and stored.

[0078] The gas phase products were analyzed by gas chromatography, and it was found that the time condition with the highest proportion of hydrogen was 2h, and the proportion of hydrogen was 43.82%.

[0079] (3) The reaction temperature, reaction time, and catalyst dosage were kept constant (reaction temperature was 300°C, reaction time was 2 h, and catalyst dosage was 1.5 g), and the Ni loading in the catalyst was set to 5 wt%, 10 wt%, and 15 wt%, respectively. After the reaction, the reactor was cooled to room temperature and the gas phase product was collected. The liquid phase product was taken out and the aqueous phase product was obtained by vacuum filtration and stored.

[0080] The gas phase products were analyzed by gas chromatography, and it was found that the catalyst Ni loading condition with the highest proportion of hydrogen was 10%, and the proportion of hydrogen was 37.39%.

[0081] (4) The reaction temperature, reaction time, and Ni loading in the catalyst were kept constant (reaction temperature was 300°C, reaction time was 2 h, and Ni loading in the catalyst was 10 wt%), and the catalyst dosage was set to 0.5 g, 1 g, 1.5 g, and 2 g, respectively; after the reaction was completed, the reactor was cooled to room temperature and the gas phase product was collected, and the liquid phase product was taken out, and the aqueous phase product was obtained by vacuum filtration and stored.

[0082] The gas phase products were analyzed by gas chromatography, and it was found that the catalyst dosage with the largest proportion of hydrogen was 1.5g, and the proportion of hydrogen was 39.70%.

[0083] In summary, the optimal reaction parameters for the primary reforming hydrogen production reaction are reaction temperature 300°C, reaction time 2h, Ni loading in the catalyst 10wt%, and catalyst dosage 1.5g.

[0084] Example 5

[0085] Research on the optimal reaction conditions for hydrogen production by secondary reforming:

[0086] The aqueous product obtained under the optimal reaction parameters of the primary reforming hydrogen production reaction in Example 1 (reaction temperature 300°C, reaction time 2h, Ni loading in the catalyst 10wt%, and catalyst dosage 1.5g) was used as a raw material, and the same single-factor experiment as the primary reforming hydrogen production reaction in Example 1 was carried out, and the optimal reaction parameters for the secondary reforming hydrogen production reaction were obtained as reaction temperature 300°C, reaction time 2h, Ni loading in the catalyst 10wt%, and catalyst dosage 1.5g.

[0087] Example 6

[0088] Study on the optimal reaction conditions for three-stage reforming hydrogen production:

[0089] The aqueous product obtained under the optimal reaction parameters of the secondary reforming hydrogen production reaction in Example 5 (reaction temperature 300°C, reaction time 2h, Ni loading in the catalyst 10wt%, and catalyst dosage 1.5g) was used as a raw material, and the same single factor experiment as the primary reforming hydrogen production reaction in Example 1 was carried out, and the optimal reaction parameters for the tertiary reforming hydrogen production reaction were obtained as reaction temperature 300°C, reaction time 2h, Ni loading in the catalyst 10wt%, and catalyst dosage 1.5g.

[0090] Figure 4 and Figure 5 ( Figure 4 and Figure 5 In the figure, the first level represents the aqueous phase product obtained under the optimal parameters of the first-level reforming hydrogen production reaction, the second level represents the aqueous phase product obtained under the optimal parameters of the second-level reforming hydrogen production reaction, and the third level represents the aqueous phase product obtained under the optimal parameters of the third-level reforming hydrogen production reaction) are the COD change trends and TOD change trends of the aqueous phase products obtained in Examples 4, 5, and 6 of the present invention, respectively. Figure 4 and Figure 5 It can be seen that with the increase of the number of reforming hydrogen production reaction stages, the organic matter in the aqueous phase products obtained after each stage of reaction gradually decreases, and the TOC and COD values ​​also decrease step by step.

[0091] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for producing hydrogen by utilizing cascade reforming of aqueous byproducts from biomass hydrothermal liquefaction, characterized in that: The following steps are involved: After mixing the aqueous byproduct of biomass hydrothermal liquefaction with catalyst 1, a primary reforming hydrogen production reaction is carried out under argon protection to obtain hydrogen and aqueous product 1; After mixing the aqueous phase product 1 and the catalyst 2, a secondary reforming hydrogen production reaction is carried out under argon protection to obtain hydrogen and an aqueous phase product 2; After mixing the aqueous phase product 2 and the catalyst 3, a three-stage reforming hydrogen production reaction is carried out under argon protection to obtain hydrogen and the aqueous phase product 3; The catalyst 1, catalyst 2 and catalyst 3 are all Ni / CeO2 catalysts.

2. The method according to claim 1, characterized in that The method for preparing the water-phase by-product of biomass hydrothermal liquefaction comprises: mixing biomass and water and performing a hydrothermal liquefaction reaction; the water phase obtained after the reaction is completed is the water-phase by-product of biomass hydrothermal liquefaction.

3. The method according to claim 1, characterized in that The preparation method of the Ni / CeO2 catalyst comprises the following steps: Step 1. Ni is loaded on CeO2 by an impregnation method to obtain a catalyst precursor; Step 2. calcining the catalyst precursor under air atmosphere to obtain NiO / CeO2; Step 3. Reducing the NiO / CeO2 in a H2 atmosphere to obtain the Ni / CeO2 catalyst.

4. The method according to claim 3, characterized in that In the Ni / CeO2 catalyst, Ni accounts for 5%-15% of the mass of the Ni / CeO2 catalyst.

5. The method according to claim 3, characterized in that The calcination temperature is 500° C., the time is 4 hours, and the heating rate is 10° C. / min; the reduction temperature is 500° C., and the time is 2 hours.

6. The method according to claim 1, characterized in that In the primary reforming hydrogen production reaction, the volume mass ratio of the biomass hydrothermal liquefaction water phase byproduct and the catalyst 1 is 60mL:0.5-2g; the temperature of the primary reforming hydrogen production reaction is 260-320°C, and the time is 1-4h.

7. The method according to claim 1, characterized in that In the secondary reforming hydrogen production reaction, the volume mass ratio of the aqueous phase product 1 and the catalyst 2 is 60 mL:0.5-2 g; the temperature of the secondary reforming hydrogen production reaction is 260-320° C., and the time is 1-4 h.

8. The method according to claim 1, characterized in that In the three-stage reforming hydrogen production reaction, the volume mass ratio of the aqueous phase product 2 and the catalyst 3 is 60 mL:0.5-2 g; the temperature of the two-stage reforming hydrogen production reaction is 260-320° C., and the time is 1-4 h.

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