Method for preparing boron-doped carbon nanospheres from lignin, and product

Abstract

The invention belongs to the field of lignin utilization, and discloses a method for preparing boron-doped carbon nanospheres from lignin, and a product. The method comprises the following steps: S1,dissolving lignin and a boron-based additive in water according to a preset mass ratio to prepare a mixed solution; S2, carrying out ultrasonic treatment on the mixed solution to hydrolyze the boron additive to generate tetrahydroxy borate ions, and carrying out a cross-linking reaction on the tetrahydroxy borate ions and hydroxyl functional groups to obtain a lignin solution; S3, drying and grinding the lignin solution to obtain lignin powder; and S4, pyrolyzing and cooling the lignin powder to obtain the boron-doped carbon nanospheres. The boron additive reacts with lignin macromolecular functional groups to prevent the lignin macromolecules from being agglomerated and caked in a pyrolytic reaction, meanwhile, the additive has the functions of a plasticizer and a doping agent, obtained lignin coke is in a nanoscale spherical shape microcosmically, boron elements are uniformly embedded into a coke skeleton, and the lignin coke is a boron-doped carbon material with high additional value and good adsorption and catalysis carriers and energy storage materials.

Description

technical field [0001] The invention belongs to the field of lignin utilization, and more specifically relates to a method and product for preparing boron-doped carbon nanospheres from lignin. Background technique [0002] Lignin is the only natural aromatic polymer in nature, and its content in biomass is second only to cellulose. The paper industry produces a large amount of waste lignin resources every year, most of which are used for combustion. Pyrolysis is a biomass utilization technology with great development prospects and potential, which is easy to realize, high in economy and less in pollutants. Lignin pyrolysis can produce a variety of high-value-added products, such as phenol-rich bio-oil, high-calorific-value biogas, and high-value-added carbon materials. [0003] Existing lignin pyrolysis technologies are all developed on the basis of conventional biomass pyrolysis technologies. However, due to the particularity of the physical and chemical structure of ligni...

AI Technical Summary

Problems solved by technology

One of the bottlenecks that limits the large-scale application of lignin pyrolysis technology is that lignin is easy to agglomerate in the initial stage of pyrolysis, which leads to problems such as reactors, pipeline blockage and coke collection difficulties.

Lignin will undergo glass transition at low temperature (150°C). As the temperature rises, the degree of freedom of lignin molecules increases. Microscopically, lignin macromolecules are cross-linked, reorganized and aggregated. Macroscopically, lignin coke volume Expansion and agglomeration, which lead to easy blockage of the lignin feeding device, difficulty in collecting coke inside the reactor, and inability to carry out the pyrolysis reaction stably and continuously, and the coke obtained has low utilization value

[0004] Aiming at the problems that lignin is easy to agglomerate, continuous operation is difficult, and coke utilization rate is low, the following solutions currently exist: For example, patent CN105038833A discloses a method for preparing light aromatic hydrocarbons by catalytic pyrolysis of lignin in a fluidized bed, wherein Lignin coke agglomerates to form a hard shell covering the USY molecular sieve catalyst, which uses oxygen-enriched conditions to ablate it to achieve the purpose of regeneration. However, oxygen-enriched conditions require the use of air separation equipment, which has high energy consumption and is economical. The problem of poor performance is not suitable for large-scale application; another example is CN109796994A, which proposes an internal rotary biomass pyrolysis furnace, which uses the rotating blades in the pyrolysis furnace to mechanically break the agglomerated biomass coke to achieve continuous operation. The problem is that it needs to consume additional electric energy, and mechanical crushing will not change the microscopic appearance of lignin coke; another example is patent CN110256690A which discloses a method of using calcium hydroxide and magnesium hydroxide as additives to inhibit lignin The method of pyrolysis and agglomeration, the coke obtained has nano-spherical characteristics, but due to the low solubility of calcium hydroxide and magnesium hydroxide in water, the water consumption in the pretreatment process is large, the drying energy consumption is high, and the coke particle size is uneven. The morphology is difficult to control and is not suitable for large-scale applications

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