Preparation and application of polypropylene thermochemical chain gasification hydrogen production oxygen carrier taking activated alumina ball as carrier

Abstract

The invention belongs to the technical field of waste plastic resource utilization, and discloses preparation and application of a polypropylene thermochemical chain gasification hydrogen production oxygen carrier taking an activated alumina ball as a carrier. The oxygen carrier comprises an active component and a carrier skeleton, the active component is selected from one or two metal oxides of iron, cobalt, nickel and copper, and the carrier framework is selected from an active alumina ball with the diameter of 3-5mm. The polypropylene thermochemical chain gasification hydrogen production oxygen carrier with the activated alumina balls as the carrier has high selectivity and good stability on polypropylene steam gasification hydrogen production reaction at high temperature, the oxygen carrier preparation method is simple, the cost is low, and large-scale industrial production can be carried out.

Description

Technical Field

[0001] The invention belongs to the technical field of waste plastic resource utilization, and relates to the preparation and application of a polypropylene thermochemical chain gasification hydrogen production oxygen carrier using activated alumina balls as carriers. Background Art

[0002] Since its invention, plastics have been widely used in packaging, construction, automobiles, electronics and other fields due to their lightweight, durability and plasticity. As the global annual consumption of plastics increases year by year, the rate of waste plastic generation far exceeds the processing capacity of traditional landfill and incineration technologies. The microplastic pollution and carbon emissions caused by it have become a global challenge restricting sustainable development. In this context, thermochemical conversion is regarded as a key path to achieve closed-loop resource utilization by converting waste plastics into high-value-added products such as synthesis gas and liquid fuels. However, existing technologies such as pyrolysis, catalytic pyrolysis and gasification still have many problems.

[0003] Although the traditional thermal cracking process can directly decompose plastics to generate hydrocarbon products through high temperature, its disordered cracking results in heavy tar accounting for more than 40% of the products, and the selectivity of hydrogen and low-carbon gases is less than 25%, which makes it difficult to meet the needs of chemical raw material purification. Catalytic pyrolysis technology improves product selectivity by introducing molecular sieves or metal oxide catalysts, but the free carbon and aromatic condensates produced during the cracking of plastics will cover the active sites of the catalyst, causing an activity loss of more than 60%. Gasification technology can alleviate the problem of catalyst deactivation by introducing water vapor or carbon dioxide as the gasification medium, but the existing iron-based and nickel-based oxygen carrier materials have a specific surface area of ​​less than 50m 2 / g, poor dispersion of active components and high-temperature sintering, etc., have caused the syngas selectivity to hover between 55% and 65% for a long time.

[0004] In view of the above technical defects, activated alumina balls provide a breakthrough solution for building efficient gasification oxygen carriers with their unique structure-performance synergy. Its porous structure can provide ≥80m 2 / g high specific surface area, effectively increasing the active site density, and its pore gradient design (2-50nm) can simultaneously improve the gas-solid mass transfer efficiency and carbon deposition inhibition ability; the Lewis acid sites on the surface selectively adsorb long-chain hydrocarbon radicals in the plastic pyrolysis gas phase through the electron transfer effect, inducing CH bond cleavage, and reducing the amount of carbon deposition to less than 1 / 3 of the traditional oxygen carrier. More importantly, by loading transition metals (such as Fe, Co, Ni, Cu) on its skeleton to form a composite active center, multiple redox cycle pathways can be constructed to increase the syngas yield of waste plastic gasification to 67%-95%, providing a technical path that is both efficient and economical for large-scale waste plastic resource utilization. Summary of the invention

[0005] The purpose of the present invention is to provide a preparation method and application of a polypropylene thermochemical chain gasification hydrogen production oxygen carrier with activated alumina balls as carriers. The oxygen carrier comprises an active component and a carrier skeleton; the active component is selected from one or two metal oxides of iron, cobalt, nickel and copper, and the carrier skeleton is selected from activated alumina balls with a diameter of 3-5 mm. The contents of the active component and the carrier are both calculated as oxides.

[0006] Technical solution of the present invention:

[0007] A method for preparing a polypropylene thermochemical chain gasification hydrogen-producing oxygen carrier with activated alumina balls as carriers comprises the following steps:

[0008] (1) using one or two metal nitrate hydrates of iron, cobalt, nickel, and copper as precursors and deionized water or ethanol as solvent to prepare a precursor solution;

[0009] (2) Immerse the activated alumina ball carrier with a diameter of 3-5 mm after high-temperature drying and dehydration in the precursor solution, stir and heat for 4 hours, filter out the excess precursor solution, dry it overnight with natural ventilation, and dry it at 65° C. for 8 hours;

[0010] (3) After drying, the mixture is placed in a muffle furnace and calcined at 900° C. for 4 hours to obtain an oxygen carrier, namely, a polypropylene thermochemical chain gasification hydrogen production oxygen carrier with activated alumina balls as carriers.

[0011] The active component loading is 1-15 wt%.

[0012] The relative mass ratio of the two active components of the dual-active component composite oxygen carrier is 1:1-5:1.

[0013] The polypropylene thermochemical chain gasification hydrogen production oxygen carrier with activated alumina balls as carriers is applied to the gasification hydrogen production or synthesis gas process of various plastics and plastic products such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, etc.

[0014] The beneficial effects of the present invention are as follows: when the reaction temperature of the polypropylene thermochemical chain gasification hydrogen production oxygen carrier provided by the present invention is 900°C and the water-carbon ratio is 2.34, the composite oxygen carrier synthesized by using iron oxide-nickel oxide bimetallic oxide as the active component can produce hydrogen in the gasified tail gas. 2 The volume content is above 65.26%, and the hydrogen yield is 124.65mmol / g pp , hydrogen volume 3.05L / g pp. In the laboratory stability test of 10 cycles, the composite oxygen carrier maintained good stability without obvious deactivation. The composite oxygen carrier synthesized with iron oxide-nickel oxide bimetallic oxide as the active component has improved the interaction between metal oxides, making the oxygen carrier have higher selectivity, gasification activity, stability and anti-carbon deposition performance in the thermochemical chain gasification hydrogen production reaction of polypropylene. The preparation method of the oxygen carrier is simple, low-cost, and can be mass-produced industrially. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a flow chart of the preparation of oxygen carrier of the present invention;

[0016] Figure 2 A schematic diagram of oxygen supply and regeneration of the oxygen carrier prepared by the present invention in the process of chemical chain cycle hydrogen production;

[0017] Figure 3 It is a flow chart of a reaction device for an embodiment of applying the oxygen carrier of the present invention to the thermochemical chain gasification of polypropylene to produce hydrogen.

[0018] Figure 4 This is the EDS image of the active components of the fresh 3-5 mm activated alumina balls loaded with bimetallic iron oxide-nickel oxide composite oxygen carrier prepared in Example 5 of the present invention, wherein (a) is a SEM image, (b) is an EDS image of the Fe element distribution, and (c) is an EDS image of the Ni element distribution.

[0019] Figure 5 These are SEM images of the morphology of the 3-5 mm activated alumina balls loaded with bimetallic iron oxide-nickel oxide composite oxygen carriers before and after the reaction in Example 5 of the present invention, wherein (a) is the SEM image of the composite oxygen carrier before the gasification reaction, and (b) is the SEM image of the composite oxygen carrier after the gasification reaction.

[0020] In the figure: 1 nitrogen bottle; 2 controller; 3 cold trap; 4 circulating refrigerator; 5 wet flow meter; 6 gas collecting bag; 7 reactor heating zone; 8 insulation furnace body; 9 quartz hanging basket; 10 oxygen carrier bed; 11 quartz sieve plate; 12 steam preheating furnace; 13 micro liquid phase pump; 14 steam preheating furnace temperature controller; 15 quartz tube reactor. DETAILED DESCRIPTION

[0021] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0022] The activity evaluation of the oxygen carrier of the present invention is carried out in a self-made quartz tube reactor, the reaction atmosphere is nitrogen, the mass of the raw material polypropylene is 0.5g, the mass of the oxygen carrier is 10g, the reaction gas flow is controlled by a solenoid valve, the water feed amount is controlled by a micro liquid phase pump, and the gas enters a quartz reaction container after being preheated at 300°C in a preheating furnace; the product gas after thermochemical chain gasification is condensed by a cold trap and collected by an air bag, and after the reaction is completed, the product gas is dried in a dryer and then enters an Agilent-7900D gas chromatograph for analysis, the chromatographic column is a filling column, the detector is a thermal conductivity (TCD) detector, the injection temperature is 100°C, the detector temperature is 120°C, and the column temperature is 60°C.

[0023] A preparation method and application method of an oxygen carrier used for hydrogen production by thermochemical chain gasification of polypropylene.

[0024] The gas yield rate is calculated as follows:

[0025] The hydrogen yield (mmol / g pp ) as an example

[0026]

[0027] The hydrogen selectivity is defined as H 2 The ratio of the amount of synthesis gas to the total amount of synthesis gas is:

[0028]

[0029] The calculation method of relative volume content of gas components is:

[0030]

[0031] Among them, γ i is the relative content of gas components, V i is the volume of gas phase products of each component.

[0032] Example 1: Oxygen carrier A

[0033] (1) Place a 3-5 mm diameter activated alumina ball in a crucible and place it in a muffle furnace. Set the temperature program to rise from room temperature to 900°C at 5°C / min, keep it for 4 hours, and then cool it naturally to room temperature to obtain a dried activated alumina ball oxygen carrier skeleton.

[0034] (2) Weigh 150 g of Fe(NO 3 ) 3 9H 2O in a beaker, add 400 ml of anhydrous ethanol, put in a magnet, transfer the beaker to a magnetic stirrer, set the heating temperature to 65 ° C, stir at 200 r / min until the precursor is completely dissolved, add 100 g of dried activated alumina ball carrier, and stir at 100 r / min intermittently for 5 minutes every 1 hour. After 4 hours, the activated alumina balls are basically evenly loaded with the precursor solution.

[0035] (3) Filter out the remaining solution in the beaker, dry it under natural ventilation overnight, and dry it in an oven at 95°C for 4 hours.

[0036] (4) After drying, the mixture is placed in a muffle furnace, and the temperature is slowly raised from room temperature to 900° C. at a temperature rising program of 3° C. / min, and calcined for 4 hours to obtain an oxidized oxygen carrier, namely, an activated alumina ball-loaded monometallic iron oxide oxygen carrier, wherein the active component is iron oxide.

[0037] (5) This example is to prepare an oxygen carrier with a loading of 12 wt% of active component iron oxide, that is, the mass fraction of iron oxide accounts for 12% of the total mass of the oxygen carrier. The maximum loading of the oxygen carrier that can be prepared by the over-impregnation method with 3-5 mm diameter activated alumina balls as the carrier is 12 wt%.

[0038] (6) Place polypropylene in a quartz reaction tube basket and place it on the top of the reaction vessel; the oxygen carrier is placed on the middle sieve plate of the quartz reaction tube. The reaction atmosphere is nitrogen, and water vapor is injected into the preheating furnace by a micro-liquid phase pump and merged with the carrier gas into the quartz reaction tube. The infrared furnace temperature is raised to the reaction temperature at a rate of 5°C / s and maintained for 2 minutes. The quartz basket containing polypropylene is lowered from the top to the heating area. The reaction time is 30 minutes. Hydrogen-rich gas is prepared and recording begins. The reaction conditions are: reaction pressure is normal pressure, reaction temperature T = 900°C, water-carbon molar ratio S / C = 2.34, and carrier gas velocity is 100 ml / min. The evaluation results are shown in Tables 1 and 2.

[0039] Example 2: Oxygen Carrier B

[0040] The difference from Example 1 is that the precursor is Co(NO 3 ) 2 6H 2 O, the active component of the oxygen carrier is cobalt oxide, that is, the activated alumina ball supports a single metal cobalt oxide oxygen carrier. The conditions for its application in the thermochemical chain gasification of polypropylene to produce hydrogen remain unchanged, and the evaluation results are shown in Tables 1 and 2.

[0041] Example 3: Oxygen Carrier C

[0042] The difference from Example 1 is that the precursor is Ni(NO 3 ) 2 6H 2O, the active component of the oxygen carrier is nickel oxide, that is, the activated alumina ball supports a single metal nickel oxide oxygen carrier. The conditions for its application in the thermochemical chain gasification of polypropylene to produce hydrogen remain unchanged, and the evaluation results are shown in Tables 1 and 2.

[0043] Example 4: Oxygen Carrier D

[0044] The difference from Example 1 is that the precursor is Cu(NO 3 ) 2 ·3H 2 O, the active component of the oxygen carrier is copper oxide, that is, the activated alumina ball supports a single metal copper oxide oxygen carrier. The conditions for its application in the thermochemical chain hydrogen production of polypropylene remain unchanged, and the evaluation results are shown in Tables 1 and 2.

[0045] Example 5: Oxygen Carrier E

[0046] (1) Place a 3-5 mm diameter activated alumina ball in a crucible and place it in a muffle furnace. Set the temperature program to rise from room temperature to 900°C at 5°C / min, keep the temperature for 4 hours, and then cool naturally to room temperature to obtain a dried activated alumina ball carrier.

[0047] (2) Weigh 75 g of Fe(NO 3 ) 3 9H 2 O and Ni (NO 3 ) 2 6H 2 O in a beaker, add 400 ml of anhydrous ethanol, put in a magnet, transfer the beaker to a magnetic stirrer, set the heating temperature to 65 ° C, stir at 200 r / min until the precursor is completely dissolved, add 100 g of dried 3-5 mm diameter activated alumina ball carrier, stir at 100 r / min intermittently for 5 minutes every 1 hour, and after 4 hours, the activated alumina balls are basically evenly loaded with the precursor.

[0048] (3) Filter out the remaining solution in the beaker, dry it under natural ventilation overnight, and dry it in an oven at 95°C for 4 hours.

[0049] (4) After drying, the mixture is placed in a muffle furnace, and the temperature is slowly increased from room temperature to 900°C at a temperature rising program of 3°C / min, and the mixture is calcined for 4 hours to obtain a composite oxygen carrier, namely, an activated alumina ball-loaded bimetallic iron oxide-nickel oxide composite oxygen carrier, wherein the active components are iron oxide-nickel oxide, and the relative mass ratio thereof is 1:1.

[0050] (5) This example is to prepare a composite oxygen carrier with a loading of 12 wt% active components of iron oxide-nickel oxide, that is, the mass fraction of iron oxide and nickel oxide accounts for 12% of the total mass of the oxygen carrier. The maximum loading of the oxygen carrier that can be prepared by the over-impregnation method with 3-5 mm diameter activated alumina balls as the carrier is 12 wt%.

[0051] (6) Place polypropylene in a quartz hanging basket of a quartz reaction tube and place it on the top of the reaction vessel; the oxygen carrier is placed on the quartz sieve plate in the middle of the quartz reaction tube. The reaction atmosphere is nitrogen, and water vapor is injected into the preheating furnace by a micro-liquid phase pump and merged with the carrier gas into the quartz reaction tube. The infrared furnace heats up the reactor to the reaction temperature at a rate of 5°C / s and maintains it for 2 minutes. The quartz hanging basket containing polypropylene is lowered from the top to the heating area. The reaction time is 30 minutes. Hydrogen-rich gas is prepared and recording begins. The reaction conditions are: reaction pressure is normal pressure, reaction temperature T = 900°C, water-carbon molar ratio S / C = 2.34, and carrier gas velocity is 100 ml / min. The evaluation results are shown in Tables 1 and 2.

[0052] Example 6: Oxygen Carrier F

[0053] The difference from Example 5 is that the precursor is Co(NO 3 ) 2 6H 2 O and Ni (NO 3 ) 2 6H 2 O, the active component of the oxygen carrier prepared is cobalt oxide-nickel oxide, that is, activated alumina balls loaded with bimetallic cobalt oxide-nickel oxide composite oxygen carrier. It is applied to the thermochemical chain gasification of polypropylene for hydrogen production under the same conditions, and the evaluation results are shown in Tables 1 and 2.

[0054] Example 7: Oxygen Carrier G

[0055] The difference from Example 5 is that the precursor is Cu(NO 3 ) 2 ·3H 2 O and Ni (NO 3 ) 2 6H 2 O, the active component of the oxygen carrier prepared is copper oxide-nickel oxide, that is, activated alumina balls loaded with bimetallic copper oxide-nickel oxide composite oxygen carrier. It is applied to the thermochemical chain gasification of polypropylene for hydrogen production under the same conditions, and the evaluation results are shown in Tables 1 and 2.

[0056] Comparative Example 1

[0057] (1) Place SiO2 of a certain particle size in the crucible 2 , put it in a muffle furnace. Set the temperature program to rise from room temperature to 900℃ at 5℃ / min, keep it for 4 hours and then cool it naturally to room temperature to obtain dry silicon dioxide solid. Silicon dioxide is a blank control bed layer and has no effect on water vapor gasification hydrogen production.

[0058] (2) Place polypropylene in a quartz hanging basket of a quartz reaction tube and place it on the top of the reaction vessel; SiO 2Place it on the quartz sieve plate in the middle of the quartz reaction tube. The reaction atmosphere is nitrogen, and water vapor is injected into the preheating furnace by a micro-liquid phase pump and merged into the quartz reaction tube with the carrier gas. The infrared furnace heats up at a rate of 5°C / s to raise the reactor to the reaction temperature and maintains it for 2 minutes. The quartz hanging basket filled with polypropylene is lowered from the top to the heating area. The reaction time is 30 minutes, hydrogen-rich gas is prepared, and recording begins. The reaction conditions are: reaction pressure is normal pressure, reaction temperature T=900°C, water-carbon molar ratio S / C=2.34, and carrier gas velocity is 100ml / min. The evaluation results are shown in Tables 1 and 2. The hydrogen yield after gasification of the oxygen carrier E in Example 5, i.e., the composite Ni-Fe oxygen carrier, is 10.38 times higher than that of the blank control group in Comparative Example 1, proving that its gasification performance is excellent. The gasification performance of the oxygen carriers described in the remaining groups of embodiments is 2-7 times higher than that of Comparative Example 1.

[0059] Comparative Example 2

[0060] (1) Place activated alumina balls with a diameter of 3-5 mm in a crucible and place it in a muffle furnace. Set the temperature program to rise from room temperature to 900°C at 5°C / min, keep it for 4 hours, and then cool it naturally to room temperature to obtain a dried activated alumina ball carrier, that is, an oxygen carrier skeleton without active components.

[0061] (2) Place polypropylene in a quartz hanging basket of a quartz reaction tube and place it on the top of the reaction vessel; place the alumina carrier on the quartz sieve plate in the middle of the quartz reaction tube. The reaction atmosphere is nitrogen, and water vapor is injected into the preheating furnace by a micro-liquid phase pump and merged into the quartz reaction tube with the carrier gas. The infrared furnace heats up the reactor to the reaction temperature at a rate of 5°C / s and maintains it for 2 minutes. The quartz hanging basket containing polypropylene is lowered from the top to the heating area. The reaction time is 30 minutes. Hydrogen-rich gas is prepared and recording begins. The reaction conditions are: reaction pressure is normal pressure, reaction temperature T=900°C, water-carbon molar ratio S / C=2.34, and carrier gas velocity is 100ml / min. The evaluation results are shown in Tables 1 and 2. Use 3-5mm activated alumina balls as the intermediate control bed to compare the SiO 2 The hydrogen yield of the blank bed after gasification is increased by 1.44 times, and the corresponding hydrogen selectivity and synthesis gas selectivity are greatly improved compared with comparative example 1, which proves that the activated alumina balls can not only provide a good oxygen carrier skeleton, but also have a certain catalytic effect on the gasification process of polypropylene.

[0062] The gas phase products of the above-mentioned embodiments and comparative examples were uniformly subjected to gas chromatography analysis, and the evaluation results of each synthesized oxygen carrier, i.e., hydrogen yield, relative content in the gas, hydrogen selectivity and synthesis gas selectivity, are summarized in Table 1, and the volume yield of each component in the product gas is summarized in Table 2.

[0063] Table 1

[0064]

[0065]

[0066] Table 2

[0067]

[0068] As shown in Tables 1 and 2, the composite oxygen carrier with active components of iron oxide-nickel oxide loaded on activated alumina balls, i.e., oxygen carrier E used in Example 5, has extremely high selectivity for hydrogen in the thermochemical chain gasification of polypropylene, with a hydrogen yield of 124.65 mmol / g. pp , the total hydrogen volume yield is 3.05L / g pp ; The corresponding hydrogen accounts for 69% of the syngas selectivity, and the total syngas selectivity reaches 94.57%; the use of bimetallic oxides as active components is significantly higher than that of single metal oxide active components as oxygen carriers; the hydrogen-rich combustible gas produced by the reaction mainly contains hydrogen, methane, and carbon monoxide; through comparative examples 1 and 2, it can be found that the use of alumina balls as oxygen carrier skeletons makes the hydrogen yield higher than that of SiO 2 The blank bed layer increased by 1.44 times, and the selectivity of hydrogen and synthesis gas increased by more than double. 2 O 3 Due to the catalytic activity of the weakly acidic sites (Lewis acid) on its surface, the spheres promote CC bond breaking and lightweight reactions, and improve gas yield and anti-carbon deposition capabilities by inhibiting the polycondensation pathway and catalyzing the gasification of residual carbon, verifying their excellent performance as an oxygen carrier skeleton.

[0069] From the EDS image of the fresh oxygen carrier E, it is found that the active component of the oxygen carrier prepared by the method is uniformly loaded and has a good dispersion effect; from the SEM image, the oxygen carrier E still maintains a good morphology and pore structure before and after the reaction, and there is no sintering and agglomeration of the active component. The specific surface area of ​​the composite oxygen carrier of Example 5 whose active component is iron oxide-nickel oxide is measured, and its specific surface area is 94.76 (m 2 / g), which is 106.68 (m 2 / g), the specific surface area slightly decreased after loading, the active components were fully immersed in the pores, and the internal pores of the carrier skeleton were not blocked. This is one of the reasons why the composite oxygen carrier in Example 5 has high gasification performance.

[0070] The specific embodiments described above provide a detailed description of the objectives, technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention, and the scope of the attached claims should be given the broadest interpretation. Any equivalent replacement or change of the technical solution and inventive concept created by the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a polypropylene thermochemical chain gasification hydrogen oxygen carrier with activated alumina balls as carriers, characterized in that: The following steps are involved: (1) using one or two metal nitrate hydrates of iron, cobalt, nickel, and copper as precursors and deionized water or ethanol as solvent to prepare a precursor solution; (2) Immerse the activated alumina ball carrier with a diameter of 3-5 mm after high-temperature drying and dehydration in the precursor solution, stir and heat for 4 hours, filter out the excess precursor solution, dry it overnight with natural ventilation, and dry it at 65° C. for 8 hours; (3) After drying, the mixture is placed in a muffle furnace and calcined at 900° C. for 4 hours to obtain an oxygen carrier, namely, a polypropylene thermochemical chain gasification hydrogen production oxygen carrier with activated alumina balls as carriers.

2. The preparation method according to claim 1, characterized in that: The loading amount of the precursor is 1-15 wt%.

3. The preparation method according to claim 1, characterized in that: When two metals are selected as precursors, the mass ratio of the two metals is 1:1-5:

1.

4. The activated alumina balls obtained by the preparation method according to any one of claims 1 to 3 are used as the polypropylene thermochemical chain gasification hydrogen production oxygen carrier for the process of gasification of plastics and plastic products to produce hydrogen or synthesis gas.

5. The use according to claim 4, characterized in that: The plastics and plastic products are polyethylene, polypropylene, polystyrene and polyvinyl chloride.

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