A method for preparing hydrogen-rich pyrolysis gas by catalytic co-pyrolysis of biomass and plastics

Abstract

The present invention belongs to the technical field of pyrolysis gas preparation, and specifically relates to a method for preparing hydrogen-rich pyrolysis gas by catalytic co-pyrolysis of biomass and plastic. The method comprises: pyrolyzing plastic to obtain plastic pyrolysis volatile products; polymerizing condensable pyrolysis tar and ferrocene in the pyrolysis volatile products of plastic to obtain ferrocene-biochar; pyrolyzing biomass with light hydrocarbons (non-condensable gases) in the pyrolysis volatile products of plastic as atmosphere, and catalyzing with ferrocene-biochar to obtain hydrogen-rich pyrolysis gas. The present invention prepares ferrocene-biochar from the pyrolysis tar and ferrocene produced by high-temperature pyrolysis of plastic, and ferrocene is used as the carbon skeleton for polymerization of plastic pyrolysis tar. When pyrolysis of wood fiber biomass in the atmosphere of light hydrocarbons produced by catalytic pyrolysis of plastic is performed, the iron element in ferrocene-biochar can provide empty orbits or electrons for chemical reactions, reduce the activation energy of the reaction, and catalyze the generation of more combustible gas (hydrogen) and porous biochar.

Description

Technical Field

[0001] The invention belongs to the technical field of pyrolysis gas preparation, and specifically relates to a method for preparing hydrogen-rich pyrolysis gas by catalytic co-pyrolysis of biomass and plastic. Background Art

[0002] Biomass energy is a very important renewable energy source with abundant reserves, convenient access, green, environmentally friendly and low CO2 emissions. Biomass is the only renewable energy source in the form of carbon-containing substances. Various biomass-based precursors have become attractive precursors for the production of some high value-added products and have the potential to replace fossil energy to obtain chemicals and fuels. Effective use of biomass resources will help solve a series of problems caused by the current overuse and gradual depletion of fossil energy.

[0003] Strategic use of biomass for pyrolysis will provide new resource value-added potential, however, biomass has the characteristics of low hydrogen content and high carbon content, and pyrolysis easily produces amorphous biochar with low porosity. In addition, the yield of hydrogen-rich gas from a single pyrolysis process is low and the gas composition is complex, which makes the pyrolysis gas yield directly obtained by pyrolysis of biomass low and the combustible components in the gas less, which cannot meet the requirements.

[0004] Plastics are rich in carbon and hydrogen. Through pyrolysis technology, they can be converted into high-value chemicals such as liquid fuels and carbon nanotubes, which has great environmental benefits. Plastics are pyrolyzed into single-molecule and double-molecule hydrocarbons at higher temperatures, while releasing hydrogen free radicals and acting as hydrogen donors and high-purity carbon sources in the process of co-pyrolysis with biomass. However, the hydrogen content in the pyrolysis gas obtained by co-pyrolysis of biomass and plastics is currently low. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a method for preparing hydrogen-rich pyrolysis gas by catalytic co-pyrolysis of biomass and plastics. In the present invention, tar produced by pyrolysis of plastics is polymerized with ferrocene to prepare ferrocene-biochar, which is used as a catalyst to catalyze the co-pyrolysis of light hydrocarbon pyrolysis gas produced by pyrolysis of plastics and biomass, and the obtained pyrolysis gas has a high hydrogen content.

[0006] The present invention provides a method for preparing hydrogen-rich pyrolysis gas by catalytic co-pyrolysis of biomass and plastics, comprising the following steps:

[0007] Using ferrocene-biochar as a catalyst, biomass and non-condensable gases in the volatile products of plastic pyrolysis are co-pyrolyzed to obtain hydrogen-rich pyrolysis gas;

[0008] The plastic pyrolysis volatile product is obtained by pyrolysis of the plastic, and the plastic pyrolysis volatile product includes non-condensable gas and condensable pyrolysis tar;

[0009] The ferrocene-biochar is obtained by polymerizing condensable pyrolysis tar and ferrocene in volatile products of plastic pyrolysis.

[0010] Preferably, the plastic is polyethylene ground film.

[0011] Preferably, the pyrolysis temperature is 500-600°C, and the heating rate from room temperature to the pyrolysis temperature is 10°C / min.

[0012] Preferably, the mass ratio of the plastic to ferrocene is 2:1 to 1:2.

[0013] Preferably, the polymerization temperature is 300-400° C., and the insulation time is 1-12 hours.

[0014] Preferably, the biomass is lignocellulosic biomass.

[0015] Preferably, the lignocellulosic biomass comprises corn stover.

[0016] Preferably, the mass ratio of the biomass to the plastic is 2:1 to 1:2.

[0017] Preferably, the co-pyrolysis temperature is 800-1000° C., and the insulation time is 5-15 min.

[0018] The present invention also provides a ferrocene-biochar, comprising a carbon skeleton provided by ferrocene and pyrolysis tar polymerized on the carbon skeleton, wherein the pyrolysis tar is condensable pyrolysis tar in volatile products of plastic pyrolysis.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention provides a method for preparing hydrogen-rich pyrolysis gas by catalytic co-pyrolysis of biomass and plastics, comprising the following steps: using ferrocene-biochar as a catalyst to co-pyrolyze non-condensable gases in volatile products of pyrolysis of biomass and plastics to obtain hydrogen-rich pyrolysis gas; the volatile products of pyrolysis of plastics are obtained by pyrolysis of plastics, and the volatile products of pyrolysis of plastics include non-condensable gases and condensable pyrolysis tar; the ferrocene-biochar is obtained by polymerizing condensable pyrolysis tar and ferrocene in the volatile products of pyrolysis of plastics.

[0021] The present invention polymerizes tar produced by plastic pyrolysis with ferrocene to obtain ferrocene-biochar. Ferrocene serves as the carbon skeleton for the polymerization of plastic pyrolysis tar. When ferrocene is used as a catalyst to catalyze the co-pyrolysis of light hydrocarbons and biomass produced by plastic pyrolysis, the iron element in the ferrocene-biochar can provide empty orbitals or electrons for chemical reactions, thereby reducing the activation energy of the reaction and catalytically generating more combustible gas (hydrogen) and porous biochar.

[0022] The present invention uses the macromolecular condensable substances in the high-temperature pyrolysis gas of plastics for low-temperature tar polymerization, and uses ferrocene with a specific structure as the carbon skeleton to produce ferrocene-biochar, which can reduce the emission of macromolecular volatile products in the high-temperature pyrolysis gas of plastics. Subsequently, the tar biochar is used as a catalyst in the high-temperature biopyrolysis process, and is used in the biomass pyrolysis process with small molecular volatile products (light hydrocarbons) in the high-temperature pyrolysis gas of plastics as the atmosphere. Ferrocene-biochar is used to reduce the tar products in the newly generated pyrolysis gas, and at the same time, the iron element in ferrocene-biochar catalyzes the generation of more combustible gases and porous biochar. In addition, the light hydrocarbons generated by the pyrolysis of plastics are co-pyrolyzed with lignin biomass to produce a secondary reaction to generate more hydrogen.

[0023] In the process of co-pyrolysis of biomass and plastic, a large amount of tar will inevitably be produced, which will not only reduce the heat and mass transfer rate of biomass pyrolysis and reduce the generation of volatile gases, but also block the pores of biochar, which is not conducive to the generation of stereotyped porous biochar. The present invention polymerizes tar with ferrocene, fully utilizes tar, and reduces tar in the reaction system at the same time. Biomass and light hydrocarbons are co-pyrolyzed, which is conducive to obtaining porous biochar and hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. 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 creative work.

[0025] Figure 1 This is a flow chart of the method for preparing hydrogen-rich pyrolysis gas by catalytic co-pyrolysis of biomass and plastics in the embodiment;

[0026] Figure 2 This is the SEM image of the biochar prepared in Comparative Example 1;

[0027] Figure 3 This is the SEM image of the biochar prepared in Comparative Example 2;

[0028] Figure 4 This is the SEM image of the biochar prepared in Comparative Example 3;

[0029] Figure 5 This is the SEM image of the biochar prepared in Example 1. DETAILED DESCRIPTION

[0030] The present invention provides a method for preparing hydrogen-rich pyrolysis gas by catalytic co-pyrolysis of biomass and plastics, comprising the following steps:

[0031] Using ferrocene-biochar as a catalyst, biomass and non-condensable gases in the volatile products of plastic pyrolysis are co-pyrolyzed to obtain hydrogen-rich pyrolysis gas;

[0032] The plastic pyrolysis volatile product is obtained by pyrolysis of the plastic, and the plastic pyrolysis volatile product includes non-condensable gas and condensable pyrolysis tar;

[0033] The ferrocene-biochar is obtained by polymerizing condensable pyrolysis tar and ferrocene in volatile products of plastic pyrolysis.

[0034] In the present invention, unless otherwise specified, the materials and equipment used are commercially available products in the art.

[0035] The present invention pyrolyzes plastic to obtain plastic pyrolysis volatile products (plastic high-temperature pyrolysis gas).

[0036] In the present invention, the plastic is preferably polyethylene ground film; the polyethylene ground film is preferably ground film waste. The plastic is preferably used in the form of powder; the powder is preferably obtained by drying, crushing and sieving the plastic in sequence, the drying temperature is preferably 105°C, the time is preferably 3 hours, and the function of the drying is to remove moisture; the crushing is preferably carried out using a micro-crusher, and the particle size of the powder is preferably 60-100 μm.

[0037] In the present invention, the pyrolysis temperature is preferably 500-600°C; the heating rate from room temperature to the pyrolysis temperature is preferably 10°C / min, and the plastic is pyrolyzed during the heating process to obtain plastic high-temperature pyrolysis gas; the reaction atmosphere of the pyrolysis is preferably nitrogen, and nitrogen is preferably introduced into the pyrolysis reactor before the pyrolysis, and the flow rate of the nitrogen is preferably 50-100 mL / min, and the time is preferably 30 min.

[0038] In the present invention, the high-temperature pyrolysis gas of the plastic obtained by pyrolysis includes heavy hydrocarbons, light hydrocarbons, and hydrogen. The heavy hydrocarbons are condensed to form pyrolysis tar, and the light hydrocarbons are non-condensable gases, which are subsequently used as biomass pyrolysis atmosphere and co-pyrolyzed with the biomass. The yield of pyrolysis tar obtained after pyrolysis of the plastic is about 50wt.%.

[0039] After obtaining the high-temperature pyrolysis gas of the plastic, the present invention polymerizes the condensable pyrolysis tar and ferrocene in the high-temperature pyrolysis gas of the plastic to obtain ferrocene-biochar.

[0040] In the present invention, the purity of ferrocene is preferably 99.8%. Ferrocene is a cost-effective raw material with high relative iron content, large molecular weight and high volatility; ferrocene has a symmetrical hydrocarbon ring structure, which can provide a carbon skeleton for the regular growth of tar vector ends, and tar is polymerized on ferrocene.

[0041] In the present invention, the mass ratio of the plastic to ferrocene is preferably 2:1 to 1:2, more preferably 1:1.

[0042] In the present invention, the polymerization temperature is preferably 300-400°C, more preferably 300-350°C, and the holding time is preferably 1-12h; the heating rate from room temperature to the polymerization temperature is preferably 5°C / min. The polymerization pressure is preferably 0.8-1.0MPa, and the polymerization pressure is preferably autogenous pressure. At the polymerization temperature of the present invention, the ferrocene structure is stable and can provide a tar charcoal growth skeleton.

[0043] The present invention preferably directly introduces the high-temperature pyrolysis gas of plastic obtained by pyrolysis of plastic into a reactor containing ferrocene, wherein the pyrolysis tar and ferrocene are polymerized to obtain ferrocene-biochar; the light hydrocarbons therein do not participate in the polymerization reaction.

[0044] After obtaining ferrocene-biochar, the present invention uses ferrocene-biochar as a catalyst to co-pyrolyze biomass and non-condensable gases in volatile products of plastic pyrolysis to obtain hydrogen-rich pyrolysis gas.

[0045] In the present invention, the biomass is preferably lignocellulosic biomass, the lignocellulosic biomass is preferably agricultural waste, and the agricultural waste preferably includes corn stalks; the lignocellulosic biomass is preferably used in the form of powder, and the powder is preferably obtained by drying, crushing and sieving the lignocellulosic biomass in sequence, the drying temperature is preferably 105°C, the time is preferably 3h, and the function of the drying is to remove moisture; the crushing is preferably carried out using a micro-crusher; the particle size of the powder is preferably 60~100μm, and the lignocellulosic biomass sample described in the present invention is uniform in size and has good thermal conductivity.

[0046] In the present invention, the mass ratio of the biomass to the plastic is preferably 2:1 to 1:2, more preferably 1:1.

[0047] In the present invention, the co-pyrolysis is preferably carried out in a nitrogen atmosphere, and the flow rate of the nitrogen is preferably 50 mL / min.

[0048] In the present invention, the co-pyrolysis temperature is preferably 800-1000°C, and the holding time is preferably 5-15 minutes. During the co-pyrolysis process, ferrocene-biochar decomposes as a catalyst structure, and the iron element promotes the generation of porous shaped carbon and hydrogen-rich pyrolysis gas.

[0049] The present invention preferably prepares hydrogen-rich pyrolysis gas in a three-stage pyrolysis reactor, the plastic is pyrolyzed in the second-stage pyrolysis furnace, the generated plastic high-temperature pyrolysis gas passes through ferrocene in the third-stage pyrolysis furnace, pyrolysis tar and ferrocene are polymerized to form biochar with ferrocene as the carbon skeleton, wood fiber biomass is introduced into the first-stage pyrolysis furnace, and co-pyrolysis is carried out with light hydrocarbons in the plastic high-temperature pyrolysis gas, and a pyrolysis catalytic reaction is carried out using ferrocene-biochar as a catalyst to obtain hydrogen-rich pyrolysis gas.

[0050] The present invention provides a method for preparing hydrogen-rich pyrolysis gas by catalytic co-pyrolysis of biomass and plastics. Figure 1 This is a flow chart for preparing hydrogen-rich pyrolysis gas in an embodiment, wherein plastics with high carbon and hydrogen content are pyrolyzed to generate condensable and non-condensable high-temperature pyrolysis gases, wherein the condensable gas (heavy hydrocarbons) is polymerized into carbon with ferrocene as the carbon skeleton in a reactor, and the non-condensable gas participates in the high-temperature pyrolysis reaction of wood fiber biomass, and a mixture of light hydrocarbon gas and sublimated ferrocene is used as the atmosphere of the straw pyrolysis reaction gas to produce hydrogen-rich gas and shaped porous biochar.

[0051] The present invention also provides a ferrocene-biochar, comprising a carbon skeleton provided by ferrocene and pyrolysis tar polymerized on the carbon skeleton, wherein the pyrolysis tar is condensable pyrolysis tar in volatile products of plastic pyrolysis.

[0052] To further illustrate the present invention, the method for preparing hydrogen-rich pyrolysis gas by catalytic co-pyrolysis of biomass and plastics provided by the present invention is described in detail below with reference to the accompanying drawings and examples, but they should not be construed as limiting the scope of protection of the present invention.

[0053] In the following examples or comparative examples, corn stalks were used as wood fiber biomass. The dust on the surface of the corn stalks was washed with deionized water and then dried in the sun for 3 days. The corn stalks were then cut into 1 cm 3 The dried corn stalks were crushed and sieved to obtain a 100 μm dry powder for subsequent tests. The ground film was used as a plastic sample, and its main component was polyethylene. Similarly, the ground film was crushed and sieved to obtain a 100 μm dry powder for subsequent tests.

[0054] In the following examples or comparative examples, pyrolysis product analysis was performed (the collected biochar and pyrolysis tar were weighed to calculate the pyrolysis gas yield), pyrolysis tar yield ( Y tar , wt.%), biochar yield ( Y char , wt.%) and pyrolysis gas yield ( Y gas , wt.%) are calculated as follows:

[0055] (1)

[0056] (2)

[0057] (3)

[0058] Where, the initial mass of the reactants (including corn stalks and / or mulch film) is M (g), the weights of tar and biochar obtained by pyrolysis are M tar (g) and M char (g).

[0059] Comparative Example 1

[0060] Corn straw pyrolysis:

[0061] The pyrolysis furnace was heated from 30°C to 800°C, and N2 was introduced with a carrier gas flow rate of 100 mL / min for 30 min. The N2 carrier gas flow rate was adjusted to 50 mL / min. 20 g of corn straw sample was introduced into the first stage pyrolysis furnace and pyrolyzed for 5 min. The pyrolysis gas was recovered using a gas collection bag, and the H2 content in the produced gas was analyzed by GC. The surface morphology and pore distribution of the pyrolytic carbon were analyzed by SEM and BET. The SEM results are shown in Figure 2. Figure 2 shown.

[0062] Comparative Example 2

[0063] Pyrolysis of ground film:

[0064] 20g of mulch sample was placed in the first stage pyrolysis furnace, and the temperature was raised from 30℃ to 500℃ at a heating rate of 10℃ / min. N2 was introduced with a carrier gas flow rate of 50 mL / min. The mulch sample was pyrolyzed during the heating process, and the pyrolysis gas was recovered by a gas collection bag. The H2 content in the produced gas was analyzed by GC, and the surface morphology and pore distribution of the pyrolytic carbon were analyzed by SEM and BET. The SEM results are shown in Figure 2. Figure 3 shown.

[0065] Comparative Example 3

[0066] Co-pyrolysis of mulch film and corn straw:

[0067] 10g of mulch was placed in the second stage pyrolysis furnace, N2 was introduced into the pyrolysis furnace, the carrier gas flow rate was 100 mL / min, and the purging was carried out for 30 min. The pyrolysis furnace was heated from 30℃ to 500℃, and the heating rate was 10℃ / min. The first stage pyrolysis reactor was heated to 800℃, 10g of corn stalks were introduced, the carrier gas flow rate was adjusted to 50 mL / min, and the reaction was carried out for 5min. The pyrolysis gas was recovered by a gas collection bag, and the H2 content in the gas was analyzed by GC. The surface morphology and pore distribution of the pyrolysis carbon were analyzed by SEM and BET. The SEM results are shown in Figure 2. Figure 4 shown.

[0068] Example 1

[0069] The mulch film with ferrocene added was co-pyrolyzed with corn straw using a three-stage pyrolysis reactor:

[0070] 10g of mulch was placed in the second pyrolysis furnace, N2 was introduced into the pyrolysis furnace, the carrier gas flow rate was 100mL / min, the purging was 30min, the carrier gas flow rate was adjusted to 50mL / min, the pyrolysis furnace was heated from 30℃ to 500℃, and the heating rate was 10℃ / min. After the mulch pyrolysis section reached the reaction temperature, the nitrogen was turned off. In the closed pyrolysis reactor, the mulch pyrolysis gas passed through 10g of ferrocene (placed in the third pyrolysis furnace), the reactor temperature was 300℃, the heating rate was 5℃ / min, the residence time was 1h, and the closed container pressure reached 0.8MPa, and the macromolecular volatile pyrolysis oil was polymerized to generate biochar. Then the pyrolysis reactor was heated to 800℃, 10 g corn stalks were introduced from the first stage pyrolysis reactor, the carrier gas (nitrogen) flow rate was adjusted to 50 mL / min, the reaction was continued for 5 min, the pyrolysis gas was recovered by a gas collecting bag, and the H2 content in the pyrolysis gas was analyzed by GC. The surface morphology and pore distribution of the pyrolysis carbon were analyzed by SEM and BET. The SEM results are shown in Figure 2. Figure 5 shown.

[0071] The hydrogen contents in the pyrolysis gases obtained in Comparative Examples 1, 2, 3 and Example 1 were 9.83 vol%, 16.97 vol%, 22.56 vol% and 47.21 vol%, respectively.

[0072] The pyrolysis gas yields obtained in Comparative Examples 1, 2, 3 and Example 1 were 35.77wt.%, 42.62wt.%, 48.53wt.% and 62.21wt.%, respectively, the pyrolysis tar yields were 41.65wt.%, 47.33wt.%, 32.76wt.% and 7.26wt.%, respectively, and the biochar yields were 22.58wt.%, 10.05wt.%, 18.71wt.% and 30.53wt.%, respectively. The pyrolysis tar yield of Example 1 was only 15.3% of that of Comparative Example 2. The tar yield was significantly reduced when the mulch film with ferrocene added was co-pyrolyzed with corn straw.

[0073] The BET specific surface areas of the pyrolytic carbons obtained in Comparative Examples 1, 2, 3 and Example 1 are 60.29 m 2 / g, 96.78m 2 / g, 138.11m 2 / g and 245.11m 2 / g; By comparing the SEM results of the pyrolytic carbons of Examples 1 to 3 with those of Example 1, it can be seen that the pore structure of the biochar obtained in Example 1 is increased and the specific surface area is increased.

[0074] Although the above-mentioned embodiments have made a detailed description of the present invention, they are only some embodiments of the present invention, rather than all embodiments. People can also obtain other embodiments based on the embodiments of the present invention without creative work, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for preparing hydrogen-rich pyrolysis gas by catalytic co-pyrolysis of biomass and plastics, characterized in that: The following steps are involved: Ferrocene-biochar is used as a catalyst to co-pyrolyze biomass and non-condensable gases in volatile products of plastic pyrolysis to obtain hydrogen-rich pyrolysis gas; the co-pyrolysis is carried out in a nitrogen atmosphere; during the co-pyrolysis, ferrocene-biochar is decomposed as a catalyst structure, and the iron element promotes the generation of porous shaped carbon and hydrogen-rich pyrolysis gas; The plastic pyrolysis volatile product is obtained by pyrolysis of plastic, and the plastic pyrolysis volatile product includes non-condensable gas and condensable pyrolysis tar; the plastic is polyethylene mulch; the polyethylene mulch is mulch waste; the pyrolysis temperature is 500-600°C, and the heating rate from room temperature to the pyrolysis temperature is 10°C / min; the reaction atmosphere of the pyrolysis is nitrogen; The ferrocene-biochar is obtained by polymerizing condensable pyrolysis tar and ferrocene in the volatile products of plastic pyrolysis; the polymerization temperature is 300-400°C, and the insulation time is 1-12 hours; the ferrocene has a symmetrical hydrocarbon ring structure, providing a carbon skeleton with regular growth at the vector end of the condensable pyrolysis tar, and the polymerization is a polymerization to form charcoal reaction using ferrocene as the carbon skeleton.

2. The method for preparing hydrogen-rich pyrolysis gas by catalytic co-pyrolysis of biomass and plastics according to claim 1, characterized in that: The mass ratio of the plastic to ferrocene is 2:1 to 1:

2.

3. The method for preparing hydrogen-rich pyrolysis gas by catalytic co-pyrolysis of biomass and plastics according to claim 1, characterized in that: The biomass is wood fiber biomass.

4. The method for preparing hydrogen-rich pyrolysis gas by catalytic co-pyrolysis of biomass and plastics according to claim 3, characterized in that: The lignocellulosic biomass includes corn stover.

5. The method for preparing hydrogen-rich pyrolysis gas by catalytic co-pyrolysis of biomass and plastics according to claim 1, characterized in that: The mass ratio of the biomass to the plastic is 2:1 to 1:

2.

6. The method for preparing hydrogen-rich pyrolysis gas by catalytic co-pyrolysis of biomass and plastics according to claim 1 or 5, characterized in that: The co-pyrolysis temperature is 800-1000° C., and the insulation time is 5-15 minutes.

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