Method for producing hydrogen-rich synthesis gas by one-pot liquefaction and reforming of whole components of lignocellulose

Abstract

The application discloses a method for preparing hydrogen-rich synthesis gas through one-pot liquefaction and reforming of lignocellulose full components, and the method is characterized in that: lignocellulose is used as raw material, glycerol and water are used as solvents, and the hydrogen-rich synthesis gas is directly and efficiently prepared through liquefaction and aqueous-phase reforming under the joint action of organic acid and a solid-phase catalyst, so that the problem of complicated steps and low efficiency caused by separation in traditional polyol preparation and hydrogen preparation through aqueous-phase reforming of polyol is avoided, and the catalyst is easy to recover and stable in performance.

Description

Technical field:

[0001] The present invention relates to the field of energy technology, and in particular to a method for producing hydrogen-rich synthesis gas by one-pot liquefaction and reforming of all components of lignocellulose. Background technology:

[0002] Hydrogen, hailed as the ultimate energy source of the 21st century, boasts high calorific value and is pollution-free, occupying a crucial position in future energy infrastructure. Currently, hydrogen is primarily produced industrially from fossil resources such as coal and natural gas. While the technology is relatively mature, it cannot meet the demands of sustainable development. While water electrolysis offers simple equipment and high hydrogen purity, its high cost predominates in small-scale hydrogen production. Lignocellulosic biomass, the most abundant renewable resource on Earth, can be converted into syngas through gasification, which can then be purified through pressure swing adsorption to produce high-purity hydrogen. However, the high gasification temperature results in significant energy consumption. In contrast, aqueous phase reforming (APR) offers a simple reaction process and can be applied to aqueous or water-soluble feedstocks to produce hydrogen in a single step using a low-temperature, low-pressure process. In recent years, using biomass-derived polyols such as glycerol, butanediol, propylene glycol, ethylene glycol, and erythritol as feedstocks, by manipulating the reaction pressure and temperature of APR, products with low CO content and high hydrogen yields have been achieved. Chinese patent CN103586029B discloses a NiFeCo-based catalyst for aqueous-phase reforming of ethylene glycol, a biomass depolymerization product, to produce hydrogen, and its preparation method. Chinese patent CN102946995B discloses a MgAl metal oxide-supported PtCu-based catalyst for aqueous-phase reforming of glycerol to produce hydrogen, and its preparation method. This suggests that existing biomass aqueous-phase reforming hydrogen production technologies all utilize biomass-derived polyols as feedstock, while research on converting all biomass components into hydrogen through aqueous-phase reforming has been lacking. Summary of the invention:

[0003] The purpose of the present invention is to provide a method for preparing hydrogen-rich synthesis gas by one-pot liquefaction and reforming of all components of lignocellulose. With lignocellulose as raw material and glycerol and water as solvent, hydrogen-rich synthesis gas is directly and efficiently converted into syngas through two steps of liquefaction and aqueous phase reforming under the joint action of an organic acid and a solid-phase catalyst, thereby avoiding the problems of cumbersome steps and low efficiency caused by the separation of traditional polyol preparation and polyol aqueous phase reforming hydrogen production processes.

[0004] The present invention is achieved through the following technical solutions:

[0005] A method for preparing hydrogen-rich synthesis gas by one-pot liquefaction and reforming of all components of lignocellulose, comprising the following steps: using lignocellulose as raw material, glycerol and water as solvents, directly converting the lignocellulose into hydrogen-rich synthesis gas through a two-step reaction of liquefaction and aqueous phase reforming under the action of an organic acid and a solid-phase catalyst, the reaction temperature being 180-230°C, the reaction pressure being 0-3 MPa, the reaction time being 1-6 hours, and cooling and collecting the gas after the reaction; the solid-phase catalyst using an ultra-high cross-linked adsorption resin (HCLR) as a carrier, one of the noble metals Pt, Ru, Rh, Pd, and Ir as a main active metal M1, and one of the transition metals Cu, Ni, Co, and Mo as a doping metal M2, the expression being xM1-yM2 / HCLR, wherein x and y are the loading amounts of M1 and M2, respectively, with x being 0.2-2% and y being 2-10%.

[0006] The specific preparation method of the solid-phase catalyst is as follows: first, a mixed ethanol-water solution composed of precursor salts of metal M1 and metal M2 is prepared and an ultra-high cross-linked adsorption resin is added thereto; then, the solution is impregnated under vacuum and negative pressure at room temperature for 10 to 30 hours; the catalyst particles are dried in an oven at 80°C; and finally, the target catalyst is obtained by simultaneous calcination and reduction using 10% H2 / Ar at 250 to 350°C for 3 to 5 hours.

[0007] The metal precursor salt is a metal nitrate, acetate, chloride, oxalate, or citrate; the volume ratio of ethanol to water in the mixed ethanol-water solution is 0.5:1; the vacuum degree during vacuum impregnation is between -50 and -95 kPa. The ultrahighly cross-linked adsorption resin was prepared with reference to CN115418022A.

[0008] Preferably, the method for preparing hydrogen-rich synthesis gas by one-pot liquefaction and reforming of all components of lignocellulose specifically comprises the following steps: 5 to 10 parts by weight of lignocellulose powder, 20 to 50 parts by weight of glycerol, 20 to 50 parts by weight of water, 0.5 to 2 parts by weight of organic acid and 0.5 to 5 parts by weight of solid-phase catalyst are charged into a reactor, nitrogen is introduced to exhaust the air in the reactor and the reactor is re-pressurized to 0 to 3 MPa, the temperature is slowly raised to 180 to 230° C. and the reaction is carried out for 1 to 6 hours, and the tail gas after the reaction is passed into an ice-water bath to collect the synthesis gas through gas-liquid separation.

[0009] Preferably, the liquid after the reaction is filtered to recover the catalyst and then recycled for lignocellulose liquefaction and aqueous phase reforming reactions.

[0010] The wood cellulose is selected from one of wheat straw, bagasse, rice straw, rice husk, corn cob, corn straw, eucalyptus, pine, fir, camphor, birch, beech and poplar.

[0011] The organic acid is one of formic acid and acetic acid.

[0012] The beneficial effects of the present invention are as follows:

[0013] (1) Organic acid is used as a catalyst. On the one hand, it can catalyze the rapid liquefaction and degradation of cellulose into polyols and convert them into biomass-based polyols rich in active hydroxyl groups. On the other hand, organic acid can also serve as a hydrogen source. Under the action of solid-phase catalysts, it decomposes and produces hydrogen and induces biomass-based polyols to undergo aqueous phase reforming to produce hydrogen-rich synthesis gas, effectively avoiding the problem of equipment corrosion caused by liquid inorganic acid catalysts.

[0014] (2) An ultra-high cross-linked adsorption resin with a microporous-mesoporous-macroporous multi-level pore structure and good hydrothermal stability is used as a carrier to load precious metals and transition metals, effectively improving the metal dispersion of the catalyst. The synergistic effect between the two metals is utilized to promote the efficient reforming of all biomass components through biomass-based polyol intermediates to produce hydrogen-rich synthesis gas. The selectivity for alkanes is low, the catalyst is easy to recover, and the performance is stable.

[0015] In summary, the present invention uses lignocellulose as raw material and glycerol and water as solvents, and directly and efficiently converts hydrogen-rich synthesis gas through two-step reactions of liquefaction and aqueous phase reforming under the joint action of organic acid and solid-phase catalyst, thereby avoiding the problems of cumbersome steps and low efficiency caused by the separation of traditional polyol preparation and polyol aqueous phase reforming hydrogen production processes. The catalyst is easy to recover and has stable performance. Specific implementation method:

[0016] The following is a further description of the present invention, but not a limitation of the present invention.

[0017] Example 1:

[0018] (1) Catalyst preparation: According to the catalyst composition of 0.2% Pt-5% Cu / HCLR, appropriate amounts of chloroplatinic acid and copper nitrate were weighed and fully dissolved in an ethanol-water mixed solution with a volume ratio of 0.5:1. HCLR with a particle size of 20-60 mesh (HCLR prepared by referring to Example 3 of CN115418022A) was added to the above mixed solution, and the mixture was placed in a vacuum oven at a vacuum degree of -95 kPa and impregnated at negative pressure for 15 hours. The solid phase catalyst was then dried at 80°C overnight and simultaneously calcined and reduced at 250°C in a 10% H2 / Ar atmosphere for 5 hours to prepare the solid phase catalyst.

[0019] (2) Catalytic reaction: 5 g of wheat straw powder (>100 mesh), 20 g of glycerol, 20 g of water, 0.5 g of formic acid and 1 g of solid-phase catalyst 0.2% Pt-5% Cu / HCLR were added to a reactor, and stirring was started. The air in the reactor was replaced with N2 three times and refilled with N2 to 1 MPa. The temperature was slowly raised to 180°C and reacted for 4 h. The temperature was then lowered to room temperature and the tail gas after the reaction was passed into an ice-water bath for gas-liquid separation to collect the synthesis gas. The composition of the synthesis gas was analyzed by gas chromatograph. The results are shown in Table 1.

[0020] Comparative Example 1:

[0021] 1 g of the solid-phase catalyst 0.2% Pt-5% Cu / HCLR prepared in Example 1 was added to a mixture of 5 g of wheat straw powder without formic acid, 20 g of glycerol, and 20 g of water. The other conditions remained unchanged and the wheat straw liquefaction-reforming reaction to produce synthesis gas was carried out. The composition analysis results of the obtained synthesis gas are shown in Table 1.

[0022] It can be seen that compared with Example 1, when the reaction system does not contain formic acid, the degradation rate of lignocellulose is significantly reduced, and the hydrogen selectivity is also reduced. This is because: on the one hand, formic acid, as an acidic catalyst, can promote the rapid liquefaction and degradation of lignocellulose, thereby improving the lignocellulose conversion rate; on the other hand, formic acid also acts as a hydrogen donor to decompose and produce hydrogen, providing an activator for the subsequent biomass-based polyol aqueous phase reforming reaction, inducing highly selective conversion to produce hydrogen.

[0023] Comparative Example 2:

[0024] The same method as in Example 1 was used to prepare a HCLR-loaded Pt-based catalyst (0.2% Pt / HCLR) and a HCLR-loaded Cu-based catalyst (5% Cu / HCLR). Wheat straw liquefaction-reforming to produce synthesis gas was carried out under the same conditions as in Example 1. The composition analysis results of the resulting synthesis gas are shown in Table 1.

[0025] It can be seen that compared with 0.2%Pt / HCLR and 5%Cu / HCLR, the bimetallic catalyst 0.2%Pt-5%Cu / HCLR has higher hydrogen production activity and hydrogen selectivity and lower alkane selectivity, reflecting the synergistic effect between the noble metal Pt and the transition metal Cu.

[0026] Comparative Example 3:

[0027] A MgAl metal oxide-supported PtCu-based catalyst, 0.2% Pt-5% Cu / Mg(O)Al, was prepared according to patent CN102946995B and subjected to wheat straw liquefaction-reforming to syngas production under the same conditions as in Example 1. The composition analysis results of the resulting syngas are shown in Table 1. As can be seen, compared with the 0.2% Pt-5% Cu / HCLR catalyst of the present invention, its lignocellulose degradation rate and hydrogen selectivity were significantly reduced, indicating that this catalyst is not suitable for the one-pot liquefaction and reforming of lignocellulose to produce syngas. This is because the Mg(O)Al support has a small specific surface area and pore volume, which is not conducive to the loading and dispersion of the metal active components. In addition, when compounded with an organic acid for lignocellulose liquefaction and reforming reactions, the organic acid affects the structure of the Mg(O)Al support, resulting in poor catalyst stability. In comparison, the ultra-high cross-linked adsorption resin HCLR has significant advantages in terms of specific surface area, pore volume, acid resistance, and heat resistance.

[0028] Example 2:

[0029] (1) Catalyst preparation: According to the catalyst composition of 1% Ru-10% Mo / HCLR, appropriate amounts of ruthenium chloride and ammonium molybdate were weighed and fully dissolved in an ethanol-water mixed solution with a volume ratio of 0.5:1. HCLR with a particle size of 40-100 mesh (HCLR prepared with reference to Example 3 of CN115418022A) was added to the above mixed solution, and the mixture was placed in a vacuum oven at a vacuum degree of -50 kPa and impregnated at a negative pressure for 30 hours. The solid phase catalyst was then dried at 80°C overnight and simultaneously calcined and reduced at 350°C in a 10% H2 / Ar atmosphere for 3 hours to prepare the solid phase catalyst.

[0030] (2) Catalytic reaction: 8 g of bagasse powder (>100 mesh), 50 g of glycerol, 40 g of water, 1 g of acetic acid and 3 g of solid-phase catalyst 1% Ru-10% Mo / HCLR were added to a reactor, and stirring was started. The air in the reactor was replaced with N2 three times and refilled with N2 to 3 MPa. The temperature was slowly raised to 200°C and reacted for 2 h. The temperature was then lowered to room temperature and the tail gas after the reaction was passed into an ice-water bath for gas-liquid separation to collect the synthesis gas. The composition of the synthesis gas was analyzed by gas chromatograph. The results are shown in Table 1.

[0031] Example 3:

[0032] HCLR-loaded catalysts with varying Ru contents (0.2% Ru-10% Mo / HCLR, 0.5% Ru-10% Mo / HCLR, 1.5% Ru-10% Mo / HCLR, and 2% Ru-10% Mo / HCLR) were prepared using the same method as in Example 2. Bagasse liquefaction-reforming to produce syngas was performed under the same conditions as in Example 1. The composition analysis of the resulting syngas is shown in Table 1. As can be seen, increasing the Ru loading increases both the lignocellulose degradation rate and hydrogen selectivity. This is because the large specific surface area of ​​the HCLR support promotes high dispersion of the active metal, providing strong C-C bond cleavage activity for lignocellulose liquefaction and degradation and aqueous reforming of biomass-based polyols.

[0033] Example 4:

[0034] (1) Catalyst preparation: According to the catalyst composition of 0.5% Ir-2% Ni / HCLR, appropriate amounts of iridium chloride and nickel nitrate were weighed and fully dissolved in an ethanol-water mixed solution with a volume ratio of 0.5:1. HCLR with a particle size of 20-60 mesh (HCLR prepared by referring to Example 3 of CN115418022A) was added to the above mixed solution, and the mixture was placed in a vacuum oven at a vacuum degree of -80 kPa and impregnated at negative pressure for 10 hours. The solid phase catalyst was then dried at 80°C overnight and simultaneously calcined and reduced at 300°C in a 10% H2 / Ar atmosphere for 3 hours to prepare the solid phase catalyst.

[0035] (2) Catalytic reaction: 10 g of pine wood powder, 50 g of glycerol, 50 g of water, 2 g of formic acid and 5 g of solid-phase catalyst 0.5% Ir-2% Ni / HCLR were added to a reactor, and stirring was started. The air in the reactor was replaced with N2 three times without pressurization. The temperature was slowly raised to 230°C and reacted for 6 h. The temperature was then lowered to room temperature and the tail gas after the reaction was passed through an ice-water bath for gas-liquid separation to collect the synthesis gas. The composition of the synthesis gas was analyzed by gas chromatograph. The results are shown in Table 1.

[0036] Example 5:

[0037] (1) Catalyst preparation: According to the catalyst composition of 1% Pd-5% Co / HCLR, appropriate amounts of palladium nitrate and cobalt nitrate were weighed and fully dissolved in an ethanol-water mixed solution with a volume ratio of 0.5:1. HCLR with a particle size of 40-60 mesh (HCLR was prepared with reference to Example 3 of CN115418022A) was added to the above mixed solution, and the mixture was placed in a vacuum oven at a vacuum degree of -90 kPa and impregnated at negative pressure for 24 hours. The solid phase catalyst was then dried at 80°C overnight and simultaneously calcined and reduced at 280°C in a 10% H2 / Ar atmosphere for 4 hours to prepare the solid phase catalyst.

[0038] (2) Catalytic reaction: 6 g of poplar wood powder, 30 g of glycerol, 20 g of water, 1 g of formic acid and 2 g of solid-phase catalyst 1% Pd-5% Co / HCLR were added to a reactor, and stirring was started. The air in the reactor was replaced with N2 three times and refilled with N2 to 2 MPa. The temperature was slowly raised to 180°C and reacted for 4 h. The temperature was then lowered to room temperature and the exhaust gas after the reaction was passed into an ice-water bath for gas-liquid separation and the synthesis gas was collected. The composition of the synthesis gas was analyzed by gas chromatograph. The results are shown in Table 1.

[0039] Table 1

[0040]

[0041]

Claims

1. A method for producing hydrogen-rich synthesis gas by one-pot liquefaction and reforming of all components of lignocellulose, characterized in that: The method comprises the following steps: using lignocellulose as raw material, glycerol and water as solvents, directly converting and producing hydrogen-rich synthesis gas through two-step reactions of liquefaction and aqueous phase reforming under the action of organic acid and solid-phase catalyst, the reaction temperature is 180-230°C, the reaction pressure is 0-3MPa, the reaction time is 1-6h, and the gas is cooled and collected after the reaction; the solid-phase catalyst uses an ultra-high cross-linked adsorption resin with a microporous-mesoporous-macroporous multi-level pore structure and good hydrothermal stability as a carrier, one of the noble metals Pt, Ru, Rh, Pd, and Ir as the main active metal M1, and transition metals Cu, Ni, Co, and Mo as the main active metal M2. One of them is doped metal M2, and its expression is xM1-yM2 / HCLR, wherein x and y are the loading amounts of M1 and M2 respectively, x is 0.2-2%, and y is 2-10%; the specific preparation method of the solid-phase catalyst is: first, a mixed ethanol-water solution composed of precursor salts of metal M1 and metal M2 is prepared and an ultra-high cross-linked adsorption resin is added thereto, followed by vacuum negative pressure impregnation at room temperature for 10-30 hours, and then the catalyst particles are dried in an 80°C oven, and finally, 10% H2 / Ar is used for simultaneous calcination and reduction at 250-350°C for 3-5 hours to obtain the target catalyst.

2. The method according to claim 1, characterized in that The metal precursor salt is one of metal nitrate, acetate, chloride, oxalate or citrate; the volume ratio of ethanol to water in the mixed ethanol-water solution is 0.5:1; and the vacuum degree of the vacuum negative pressure impregnation is -50 to -95 kPa.

3. The method according to claim 1, characterized in that The method for preparing hydrogen-rich synthesis gas by one-pot liquefaction and reforming of all components of lignocellulose specifically comprises the following steps: 5 to 10 parts by weight of lignocellulose powder, 20 to 50 parts by weight of glycerol, 20 to 50 parts by weight of water, 0.5 to 2 parts by weight of organic acid and 0.5 to 5 parts by weight of solid-phase catalyst are charged into a reactor, nitrogen is introduced to exhaust the air in the reactor and the reactor is re-pressurized to 0 to 3 MPa, the temperature is slowly raised to 180 to 230° C. and the reaction is carried out for 1 to 6 hours, and the tail gas after the reaction is passed into an ice-water bath for gas-liquid separation to collect the synthesis gas.

4. The method according to claim 1 or 3, characterized in that The liquid after the reaction is filtered to recover the catalyst and then recycled for lignocellulose liquefaction and aqueous phase reforming reaction.

5. The method according to claim 1, wherein The wood cellulose is selected from one of wheat straw, bagasse, rice straw, rice husk, corn cob, corn straw, eucalyptus, pine, fir, camphor, birch, beech and poplar.

6. The method according to claim 1, characterized in that The organic acid is one of formic acid and acetic acid.

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