Method for preparing synthesis gas by modified red mud catalytic pyrolysis of plastic-containing kitchen waste
Patent Information
- Application Number
- CN202610868994.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-16
- Publication Date
- 2026-10-09
AI Technical Summary
[0004]本发明针对现有含塑料餐厨垃圾厌氧发酵渣处置困难、传统热解催化剂成本高昂、原始赤泥直接催化活性低且易积碳失活的技术难题，提供一种改性赤泥催化热解含塑料餐厨垃圾厌氧发酵渣制备合成气的方法，旨在实现赤泥、餐厨垃圾、废塑料多源固废协同资源化与高值能源化转化
[0015]（1）实现了餐厨垃圾、废塑料与工业固废赤泥的协同资源化。通过厌氧发酵-催化热解耦合工艺，利用厌氧发酵使塑料与有机质形成均质复合体，强化了后续热解过程中的氢转移与脱氧反应，显著提高了合成气产率。实验表明，在优化条件下，含HDPE发酵渣的H2产率达690.96 mL/g，CO产率达554.33 mL/g。
Smart Images
Figure CN122878992A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of solid waste resource utilization technology, specifically relating to a method for preparing syngas rich in H2 and CO by catalytic pyrolysis of plastic-containing kitchen waste using a modified red mud catalyst. Background Technology
[0002] In recent years, with the rapid development of the food delivery industry, the amount of food waste generated has continued to rise, with a large amount of disposable plastic packaging mixed in, resulting in a high degree of mixing between waste plastic and food waste. Anaerobic fermentation is one of the important technologies for the resource utilization of food waste, capable of converting easily degradable organic matter into biogas. However, most waste plastics are difficult to biodegrade and ultimately accumulate in the fermentation residue, producing a large amount of anaerobic fermentation residue containing plastic. If this fermentation residue is directly landfilled or incinerated, it not only wastes land resources and emits greenhouse gases, but also makes it difficult to recover the residual energy, posing significant environmental risks and resource waste problems. Therefore, developing an economical and efficient post-treatment technology to realize the energy conversion of anaerobic fermentation residue containing plastic has become a pressing practical problem to be solved in the field of solid waste treatment.
[0003] However, while catalytic pyrolysis technology can convert plastic-containing kitchen waste into syngas, the high cost of traditional catalysts limits its large-scale application. Red mud, a major alkaline solid waste generated by the alumina industry, has a stockpile exceeding 1.1 billion tons in my country. Rich in metal oxides such as Fe2O3, Al2O3, and CaO, it possesses the potential to serve as a low-cost pyrolysis catalyst. However, raw red mud has a small specific surface area, few active sites, and limited catalytic activity. Existing technologies lack a systematic understanding of the catalyst deactivation mechanism and fermentation-pyrolysis coupling effect in the complex system of anaerobic fermentation residue containing plastic-containing kitchen waste. Therefore, this invention proposes a method for producing syngas from plastic-containing kitchen waste through catalytic pyrolysis of modified red mud. This method involves preparing a highly active catalyst through acid modification and metal loading, and utilizing anaerobic fermentation pretreatment to enhance the pyrolysis reaction, achieving synergistic resource utilization of multiple solid waste sources. Summary of the Invention
[0004] This invention addresses the technical challenges of difficult disposal of anaerobic fermentation residue from plastic-containing kitchen waste, high cost of traditional pyrolysis catalysts, and low direct catalytic activity and easy carbon deposition and deactivation of raw red mud. It provides a method for preparing syngas by catalytic pyrolysis of modified red mud from anaerobic fermentation residue of plastic-containing kitchen waste, aiming to achieve the synergistic resource utilization and high-value energy conversion of multi-source solid waste such as red mud, kitchen waste, and waste plastics.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for preparing syngas from modified red mud through catalytic pyrolysis of plastic-containing kitchen waste, comprising the following steps:
[0006] (1) Anaerobic fermentation of kitchen waste containing plastic to obtain anaerobic fermentation residue containing plastic;
[0007] (2) Acid modification and metal loading were performed on red mud to obtain modified red mud catalysts;
[0008] (3) The plastic-containing anaerobic fermentation residue obtained in step (1) is mixed with the modified red mud catalyst obtained in step (2) and catalytically pyrolyzed under an inert atmosphere to obtain syngas.
[0009] As a preferred embodiment of the present invention, the mass fraction of plastic in the plastic-containing kitchen waste in step (1) is 10%-50%; the plastic is one or two of high-density polyethylene (HDPE) and polyethylene terephthalate (PET); the anaerobic fermentation time is 15 days; the plastic-containing anaerobic fermentation residue is dried and crushed before use, and the particle size is 0.15-0.18 mm.
[0010] As a preferred embodiment of the present invention, the acid modification in step (2) is as follows: red mud is stirred with 4 mol / L citric acid solution at 85°C for 5 hours, and then washed and dried to obtain acid-modified red mud; the metal loading is as follows: acid-modified red mud is impregnated in nickel salt solution, dried and then calcined at 600°C for 4 hours to obtain modified red mud catalyst; the nickel loading in the modified red mud catalyst is 10 wt%.
[0011] As a preferred embodiment of the present invention, the temperature of catalytic pyrolysis in step (3) is 700℃-800℃, and when the plastic is HDPE, the temperature of catalytic pyrolysis is 800℃; the mass ratio of the plastic-containing anaerobic fermentation residue to the modified red mud catalyst is 1:1; and the time of catalytic pyrolysis is 30 minutes.
[0012] Furthermore, the modified red mud catalyst is regenerated by calcining in air at 600°C for 4 hours after use, and then recycled.
[0013] In this invention, during the direct pyrolysis of plastic-containing kitchen waste, the pyrolysis temperatures of the plastic and organic matter are asynchronous, resulting in low synergistic efficiency. Anaerobic fermentation converts easily degradable organic matter into biogas, allowing residual plastic, organic matter, and microbial cells to form a tightly packed homogeneous complex, achieving simultaneous thermal decomposition. During catalytic pyrolysis, hydrogen-rich free radicals generated from plastic pyrolysis undergo hydrogen transfer reactions with oxygen-containing free radicals generated from organic matter pyrolysis, promoting deoxygenation and inhibiting tar formation. Simultaneously, water vapor and CO2 generated from organic matter pyrolysis serve as gasification media, reacting with hydrocarbons from plastic pyrolysis to undergo reforming reactions, further generating H2 and CO. Through these physical and chemical synergistic effects, the syngas yield is significantly improved.
[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0015] (1) The co-resource utilization of kitchen waste, waste plastics and industrial solid waste red mud was realized. Through the anaerobic fermentation-catalytic pyrolysis coupled process, the anaerobic fermentation was used to form a homogeneous complex between plastics and organic matter, which enhanced the hydrogen transfer and deoxygenation reaction in the subsequent pyrolysis process and significantly improved the syngas yield. The experiment showed that under optimized conditions, the H2 yield of fermentation residue containing HDPE reached 690.96 mL / g and the CO yield reached 554.33 mL / g.
[0016] (2) A low-cost, high-activity modified red mud catalyst is provided. Using industrial solid waste red mud as raw material, the catalyst prepared by citric acid modification and nickel metal loading has a specific surface area as high as 168.65 m². 2 / g, with abundant oxygen vacancies and highly dispersed NiO active sites, has significantly better catalytic performance than the original red mud, and its cost is much lower than that of traditional precious metal or molecular sieve catalysts.
[0017] (3) The catalyst has good stability and regenerability. The catalyst containing HDPE system still maintains high activity after multiple cycles. After the deactivated catalyst is regenerated by calcining in air at 600℃ for 4 hours, the H2 yield can be restored to about 380 mL / g, which has good prospects for industrial application. Attached Figure Description
[0018] Figure 1 Process flow diagram for preparing syngas from modified red mud through catalytic pyrolysis of plastic-containing kitchen waste;
[0019] Figure 2 The graph shows a comparison of the syngas yield and lower heating value prepared in Examples 1-5 and Comparative Examples 1-5. Detailed Implementation
[0020] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.
[0021] The red mud used in the embodiments and comparative examples of this invention is derived from industrial solid waste discharged from the Bayer process of bauxite leaching.
[0022] Example 1
[0023] like Figure 1 As shown, a method for preparing syngas from anaerobic fermentation residue of plastic-containing kitchen waste via catalytic pyrolysis of modified red mud includes the following steps:
[0024] (1) After removing impurities from the kitchen waste, add 10%-50% HDPE by mass, crush and pulp it, and place it in an anaerobic fermentation tank. Ferment at room temperature in the dark for 15 days to obtain mixed HDPE anaerobic fermentation residue. Crush and sieve the fermentation residue to 0.15-0.18 mm, and dry it at 105℃ for 12 h for later use.
[0025] (2) Take 25 g of raw red mud and mix it with 150 mL of 4 mol / L citric acid solution. Stir at a constant speed for 5 h in a constant temperature water bath at 85℃. Adjust the pH to 8 with ammonia water, wash with deionized water until neutral, and dry at 105℃ to constant weight to obtain citric acid modified red mud.
[0026] (3) Take 20 g of citric acid modified red mud, add nickel nitrate solution containing 2.0 g of nickel, make up the volume of the solution to 120 mL, stir in a constant temperature water bath at 80℃ until viscous, dry at 105℃, place in a muffle furnace and heat to 600℃ at a heating rate of 2℃ per minute for 4 h, and cool naturally to obtain modified red mud catalyst;
[0027] (4) A vertical tube furnace is used. 1 g of the modified red mud catalyst prepared in step 3 is placed in the middle of the quartz tube, and 1 g of the mixed HDPE anaerobic fermentation residue prepared in step 1 is placed in the raw material silo. After purging with nitrogen gas at 100 mL per minute for 20 min, the temperature is raised to 800℃ at a heating rate of 10℃ per minute. After the temperature stabilizes, the ball valve is opened to allow the raw material to fall into the reaction zone. The pyrolysis reaction is carried out for 30 min, and the gaseous products are collected to obtain syngas.
[0028] Example 2
[0029] A method for preparing syngas from anaerobic fermentation residue of plastic-containing kitchen waste via catalytic pyrolysis of modified red mud includes the following steps:
[0030] (1) After removing impurities from the kitchen waste, add 10%-50% high-density polyethylene by mass, crush and pulp it, and place it in an anaerobic fermentation tank. Ferment at room temperature in the dark for 15 days to obtain mixed HDPE anaerobic fermentation residue. Crush and sieve the fermentation residue to 0.15-0.18 mm, and dry it at 105℃ for 12 h for later use.
[0031] (2) Take 25 g of raw red mud and mix it with 150 mL of citric acid solution with a concentration of 4 mol / L. Stir at a constant speed for 5 h in a constant temperature water bath at 85℃. Adjust the pH to 8 with ammonia water, wash with deionized water until neutral, and dry at 105℃ to constant weight to obtain citric acid modified red mud.
[0032] (3) Take 20 g of citric acid modified red mud, add nickel nitrate solution containing 2.0 g of nickel, make up the volume of the solution to 120 mL, stir in a constant temperature water bath at 80℃ until viscous, dry at 105℃, place in a muffle furnace and heat to 600℃ at a heating rate of 2℃ per minute for 4 h, and cool naturally to obtain modified red mud catalyst;
[0033] (4) A vertical tube furnace is used. 1 g of the modified red mud catalyst prepared in step 3 is placed in the middle of the quartz tube, and 1 g of the mixed HDPE anaerobic fermentation residue prepared in step 1 is placed in the raw material silo. After purging with nitrogen gas at 100 mL per minute for 20 min, the temperature is raised to 750°C at a heating rate of 10°C per minute. After the temperature stabilizes, the ball valve is opened to allow the raw material to fall into the reaction zone. The pyrolysis reaction is carried out for 30 min, and the gaseous products are collected to obtain syngas.
[0034] Example 3
[0035] A method for preparing syngas from anaerobic fermentation residue of plastic-containing kitchen waste via catalytic pyrolysis of modified red mud includes the following steps:
[0036] (1) After removing impurities from the kitchen waste, add 10%-50% HDPE by mass, crush and pulp it, and place it in an anaerobic fermentation tank. Ferment at room temperature in the dark for 15 days to obtain mixed HDPE anaerobic fermentation residue. Crush and sieve the fermentation residue to 0.15-0.18 mm, and dry it at 105℃ for 12 h for later use.
[0037] (2) Take 25 g of raw red mud and mix it with 150 mL of citric acid solution with a concentration of 4 mol / L. Stir at a constant speed for 5 h in a constant temperature water bath at 85℃. Adjust the pH to 8 with ammonia water, wash with deionized water until neutral, and dry at 105℃ to constant weight to obtain citric acid modified red mud.
[0038] (3) Take 20 g of citric acid modified red mud, add nickel nitrate solution containing 2.0 g of nickel, make up the volume of the solution to 120 mL, stir in a constant temperature water bath at 80℃ until viscous, dry at 105℃, place in a muffle furnace and heat to 600℃ at a heating rate of 2℃ per minute for 4 h, and cool naturally to obtain modified red mud catalyst;
[0039] (4) A vertical tube furnace is used. 1 g of the modified red mud catalyst prepared in step 3 is placed in the middle of the quartz tube, and 1 g of the mixed HDPE anaerobic fermentation residue prepared in step 1 is placed in the raw material silo. After purging with nitrogen gas at 100 mL per minute for 20 min, the temperature is raised to 700°C at a heating rate of 10°C per minute. After the temperature stabilizes, the ball valve is opened to allow the raw material to fall into the reaction zone. The pyrolysis reaction is carried out for 30 min, and the gaseous products are collected to obtain syngas.
[0040] Example 4
[0041] A method for preparing syngas from anaerobic fermentation residue of plastic-containing kitchen waste via catalytic pyrolysis of modified red mud includes the following steps:
[0042] (1) After removing impurities from the kitchen waste, add 10%-50% PET by mass, crush and pulp it, and place it in an anaerobic fermentation tank. Ferment at room temperature in the dark for 15 days to obtain mixed PET anaerobic fermentation residue. Crush and sieve the fermentation residue to 0.15-0.18 mm, and dry it at 105℃ for 12 h for later use.
[0043] (2) Take 25 g of raw red mud and mix it with 150 mL of citric acid solution with a concentration of 4 mol / L. Stir at a constant speed for 5 h in a constant temperature water bath at 85℃. Adjust the pH to 8 with ammonia water, wash with deionized water until neutral, and dry at 105℃ to constant weight to obtain citric acid modified red mud.
[0044] (3) Take 20 g of citric acid modified red mud, add nickel nitrate solution containing 2.0 g of nickel, make up the volume of the solution to 120 mL, stir in a constant temperature water bath at 80℃ until viscous, dry at 105℃, place in a muffle furnace and heat to 600℃ at a heating rate of 2℃ per minute for 4 h, and cool naturally to obtain modified red mud catalyst;
[0045] (4) A vertical tube furnace is used. 1 g of the modified red mud catalyst prepared in step 3 is placed in the middle of the quartz tube, and 1 g of the mixed PET anaerobic fermentation residue prepared in step 1 is placed in the raw material silo. After purging with nitrogen gas at 100 mL per minute for 20 min, the temperature is raised to 800°C at a heating rate of 10°C per minute. After the temperature stabilizes, the ball valve is opened to allow the raw material to fall into the reaction zone. The pyrolysis reaction is carried out for 30 min, and the gaseous products are collected to obtain syngas.
[0046] Example 5
[0047] A method for preparing syngas from anaerobic fermentation residue of plastic-containing kitchen waste via catalytic pyrolysis of modified red mud includes the following steps:
[0048] (1) After removing impurities from the kitchen waste, add 10%-50% by mass of HDPE and PET mixture at a mass ratio of 1:1. After crushing and pulping, place it in an anaerobic fermentation tank and ferment at room temperature in the dark for 15 days to obtain mixed HDPE + PET anaerobic fermentation residue. Crush and sieve the fermentation residue to 0.15-0.18 mm and dry it at 105℃ for 12 h for later use.
[0049] (2) Take 25 g of raw red mud and mix it with 150 mL of citric acid solution with a concentration of 4 mol / L. Stir at a constant speed for 5 h in a constant temperature water bath at 85℃. Adjust the pH to 8 with ammonia water, wash with deionized water until neutral, and dry at 105℃ to constant weight to obtain citric acid modified red mud.
[0050] (3) Take 20 g of citric acid modified red mud, add nickel nitrate solution containing 2.0 g of nickel, make up the volume of the solution to 120 mL, stir in a constant temperature water bath at 80℃ until viscous, dry at 105℃, place in a muffle furnace and heat to 600℃ at a heating rate of 2℃ per minute for 4 h, and cool naturally to obtain modified red mud catalyst;
[0051] (4) A vertical tube furnace is used. 1 g of the modified red mud catalyst prepared in step 3 is placed in the middle of the quartz tube. 1 g of the mixed HDPE + PET anaerobic fermentation residue prepared in step 1 is placed in the raw material silo. After purging with nitrogen gas at 100 mL per minute for 20 min, the temperature is raised to 800℃ at a heating rate of 10℃ per minute. After the temperature stabilizes, the ball valve is opened to allow the raw material to fall into the reaction zone. The pyrolysis reaction is carried out for 30 min, and the gaseous products are collected to obtain syngas.
[0052] Comparative Example 1
[0053] The raw materials and conditions used in the preparation process of this comparative example are the same as those in Example 1, except that the pyrolysis reaction temperature is 600℃. The specific steps are as follows:
[0054] (1) After removing impurities from the kitchen waste, add 10%-50% HDPE by mass, crush and pulp it, and place it in an anaerobic fermentation tank. Ferment at room temperature in the dark for 15 days to obtain mixed HDPE anaerobic fermentation residue. Crush and sieve the fermentation residue to 0.15-0.18 mm, and dry it at 105℃ for 12 h for later use.
[0055] (2) Take 25 g of raw red mud and mix it with 150 mL of 4 mol / L citric acid solution. Stir at a constant speed for 5 h in a constant temperature water bath at 85℃. Adjust the pH to 8 with ammonia water, wash with deionized water until neutral, and dry at 105℃ to constant weight to obtain citric acid modified red mud.
[0056] (3) Take 20 g of citric acid modified red mud, add nickel nitrate solution containing 2.0 g of nickel, make up the volume of the solution to 120 mL, stir in a constant temperature water bath at 80℃ until viscous, dry at 105℃, place in a muffle furnace and heat to 600℃ at a heating rate of 2℃ per minute for 4 h, and cool naturally to obtain modified red mud catalyst;
[0057] (4) A vertical tube furnace is used. 1 g of the modified red mud catalyst prepared in step 3 is placed in the middle of the quartz tube, and 1 g of the mixed HDPE anaerobic fermentation residue prepared in step 1 is placed in the raw material silo. After purging with nitrogen gas at 100 mL per minute for 20 min, the temperature is raised to 600°C at a heating rate of 10°C per minute. After the temperature stabilizes, the ball valve is opened to allow the raw material to fall into the reaction zone. The pyrolysis reaction is carried out for 30 min, and the gaseous products are collected to obtain syngas.
[0058] Comparative Example 2
[0059] The raw materials and conditions used in the preparation process of this comparative example are the same as those in Example 1, except that the mass ratio of catalyst to raw materials is 0.2:1. The specific steps are as follows:
[0060] (1) After removing impurities from the kitchen waste, add 10%-50% HDPE by mass, crush and pulp it, and place it in an anaerobic fermentation tank. Ferment at room temperature in the dark for 15 days to obtain mixed HDPE anaerobic fermentation residue. Crush and sieve the fermentation residue to 0.15-0.18 mm, and dry it at 105℃ for 12 h for later use.
[0061] (2) Take 25 g of raw red mud and mix it with 150 mL of 4 mol / L citric acid solution. Stir at a constant speed for 5 h in a constant temperature water bath at 85℃. Adjust the pH to 8 with ammonia water, wash with deionized water until neutral, and dry at 105℃ to constant weight to obtain citric acid modified red mud.
[0062] (3) Take 20 g of citric acid modified red mud, add nickel nitrate solution containing 2.0 g of nickel, make up the volume of the solution to 120 mL, stir in a constant temperature water bath at 80℃ until viscous, dry at 105℃, place in a muffle furnace and heat to 600℃ at a heating rate of 2℃ per minute for 4 h, and cool naturally to obtain modified red mud catalyst;
[0063] (4) A vertical tube furnace was used. 0.2 g of the modified red mud catalyst prepared in step 3 was placed in the middle of the quartz tube, and 1 g of the mixed HDPE anaerobic fermentation residue prepared in step 1 was placed in the raw material silo. After purging with nitrogen gas at 100 mL per minute for 20 min, the temperature was increased to 800°C at a heating rate of 10°C per minute. After the temperature stabilized, the ball valve was opened to allow the raw material to fall into the reaction zone. The pyrolysis reaction was carried out for 30 min, and the gaseous products were collected to obtain syngas.
[0064] Comparative Example 3
[0065] The raw materials and conditions used in the preparation process of this comparative example are the same as those in Example 1, except that the raw material is pure HDPE, and the process does not involve mixing with kitchen waste and anaerobic fermentation. The specific steps are as follows:
[0066] (1) Take HDPE raw material, crush and screen it to 0.15-0.18 mm, and dry it at 105℃ for 12 h for later use;
[0067] (2) Take 25 g of raw red mud and mix it with 150 mL of 4 mol / L citric acid solution. Stir at a constant speed for 5 h in a constant temperature water bath at 85℃. Adjust the pH to 8 with ammonia water, wash with deionized water until neutral, and dry at 105℃ to constant weight to obtain citric acid modified red mud.
[0068] (3) Take 20 g of citric acid modified red mud, add nickel nitrate solution containing 2.0 g of nickel, make up the volume of the solution to 120 mL, stir in a constant temperature water bath at 80℃ until viscous, dry at 105℃, place in a muffle furnace and heat to 600℃ at a heating rate of 2℃ per minute for 4 h, and cool naturally to obtain modified red mud catalyst;
[0069] (4) A vertical tube furnace is used. 1 g of the modified red mud catalyst prepared in step 3 is placed in the middle of the quartz tube, and 1 g of the HDPE raw material prepared in step 1 is placed in the raw material silo. After purging with nitrogen gas at 100 mL per minute for 20 min, the temperature is raised to 800°C at a heating rate of 10°C per minute. After the temperature stabilizes, the ball valve is opened to allow the raw material to fall into the reaction zone. The pyrolysis reaction is carried out for 30 min, and the gaseous products are collected to obtain synthesis gas.
[0070] Comparative Example 4
[0071] The raw materials and conditions used in the preparation process of this comparative example are the same as those in Example 1, except that the raw material is pure PET, and the process does not involve mixing with kitchen waste and anaerobic fermentation. The specific steps are as follows:
[0072] (1) Take PET raw material, crush and screen it to 0.15-0.18 mm, and dry it at 105℃ for 12 h for later use;
[0073] (2) Take 25 g of raw red mud and mix it with 150 mL of 4 mol / L citric acid solution. Stir at a constant speed for 5 h in a constant temperature water bath at 85℃. Adjust the pH to 8 with ammonia water, wash with deionized water until neutral, and dry at 105℃ to constant weight to obtain citric acid modified red mud.
[0074] (3) Take 20 g of citric acid modified red mud, add nickel nitrate solution containing 2.0 g of nickel, make up the volume of the solution to 120 mL, stir in a constant temperature water bath at 80℃ until viscous, dry at 105℃, place in a muffle furnace and heat to 600℃ at a heating rate of 2℃ per minute for 4 h, and cool naturally to obtain modified red mud catalyst;
[0075] (4) A vertical tube furnace is used. 1 g of the modified red mud catalyst prepared in step 3 is placed in the middle of the quartz tube, and 1 g of the PET raw material prepared in step 1 is placed in the raw material silo. After purging with nitrogen gas at 100 mL per minute for 20 min, the temperature is raised to 800°C at a heating rate of 10°C per minute. After the temperature stabilizes, the ball valve is opened to allow the raw material to fall into the reaction zone. The pyrolysis reaction is carried out for 30 min, and the gaseous products are collected to obtain syngas.
[0076] Comparative Example 5
[0077] The raw materials and conditions used in the preparation process of this comparative example are the same as those in Example 1, except that the raw material is anaerobic fermentation residue of kitchen waste without added plastic. The specific steps are as follows:
[0078] (1) After removing impurities from the kitchen waste, crush and pulp it and place it in an anaerobic fermentation tank. Ferment it at room temperature in the dark for 15 days to obtain the anaerobic fermentation residue of the kitchen waste. Crush the fermentation residue and sieve it to 0.15-0.18 mm. Dry it at 105℃ for 12 h for later use.
[0079] (2) Take 25 g of raw red mud and mix it with 150 mL of 4 mol / L citric acid solution. Stir at a constant speed for 5 h in a constant temperature water bath at 85℃. Adjust the pH to 8 with ammonia water, wash with deionized water until neutral, and dry at 105℃ to constant weight to obtain citric acid modified red mud.
[0080] (3) Take 20 g of citric acid modified red mud, add nickel nitrate solution containing 2.0 g of nickel, make up the volume of the solution to 120 mL, stir in a constant temperature water bath at 80℃ until viscous, dry at 105℃, place in a muffle furnace and heat to 600℃ at a heating rate of 2℃ per minute for 4 h, and cool naturally to obtain modified red mud catalyst;
[0081] (4) A vertical tube furnace is used. 1 g of the modified red mud catalyst prepared in step 3 is placed in the middle of the quartz tube, and 1 g of the anaerobic fermentation residue of kitchen waste prepared in step 1 is placed in the raw material silo. After purging with nitrogen gas at 100 mL per minute for 20 min, the temperature is raised to 800°C at a heating rate of 10°C per minute. After the temperature stabilizes, the ball valve is opened to allow the raw material to fall into the reaction zone. The pyrolysis reaction is carried out for 30 min, and the gaseous products are collected to obtain syngas.
[0082] The synthesis gases prepared in Examples 1-5 and Comparative Examples 1-5 were analyzed by gas chromatography. The yields of each gas component and the lower heating value of the synthesis gas were measured, and the results are shown in Table 1.
[0083] Table 1
[0084]
[0085] As shown in Table 1, the method provided by this invention can efficiently convert anaerobic fermentation residue containing plastics into syngas rich in H2 and CO. Under optimal conditions (Example 1: mixed HDPE sludge, 800℃, catalyst / raw material ratio 1:1), the H2 yield can reach 690.959 mL / g, the CO yield can reach 554.331 mL / g, and the lower heating value of the syngas is as high as 151.5 kJ / g. Examples 2 and 3 show that as the pyrolysis temperature decreases from 800℃ to 700℃, the syngas yield decreases, but still remains at a high level. Examples 4 and 5, using mixed PET sludge and mixed HDPE+PET sludge as raw materials respectively, also obtained considerable syngas yields, verifying the wide applicability of this invention to different plastic components. Comparative Examples 1-5 further confirm that the anaerobic fermentation pretreatment, modified red mud catalyst, and optimized pyrolysis conditions (temperature, catalyst ratio, etc.) used in this invention have a significant synergistic effect on improving syngas yield and selectivity.
[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.
Claims
1. A method for preparing syngas from plastic-containing kitchen waste via catalytic pyrolysis of modified red mud, characterized in that, Includes the following steps: (1) Anaerobic fermentation of kitchen waste containing plastic to obtain anaerobic fermentation residue containing plastic; (2) Acid modification and metal loading were performed on red mud to obtain modified red mud catalysts; (3) The plastic-containing anaerobic fermentation residue is mixed with the modified red mud catalyst and catalytically pyrolyzed under an inert atmosphere to obtain syngas, which contains H2 and CO.
2. The method according to claim 1, characterized in that, The plastic content in the food waste containing plastic is 10%-50% by mass.
3. The method according to claim 1 or 2, characterized in that, The plastic is one or both of high-density polyethylene and polyethylene terephthalate.
4. The method according to claim 1, characterized in that, The anaerobic fermentation time is 15 days; the anaerobic fermentation residue containing plastic is dried and crushed before use, with a particle size of 0.15-0.18 mm.
5. The method according to claim 1, characterized in that, The acid modification is carried out by stirring red mud with 4 mol / L citric acid solution at 85°C for 5 hours, followed by washing and drying to obtain acid-modified red mud.
6. The method according to claim 1, characterized in that, The metal loading is as follows: acid-modified red mud is impregnated in a nickel salt solution, dried, and then calcined at 600°C for 4 hours to obtain a modified red mud catalyst; the nickel loading in the modified red mud catalyst is 10 wt%.
7. The method according to claim 1, characterized in that, The catalytic pyrolysis temperature is 700℃-800℃, and when the plastic is high-density polyethylene, the catalytic pyrolysis temperature is 800℃.
8. The method according to claim 1, characterized in that, The mass ratio of the plastic-containing anaerobic fermentation residue to the modified red mud catalyst is 1:
1.
9. The method according to claim 1, characterized in that, The catalytic pyrolysis time is 30 minutes.
10. The method according to claim 1, characterized in that, The modified red mud catalyst is regenerated by calcining in air at 600°C for 4 hours after use.