CN106560234B - A method for preparing carbon aerogel using plant remains - Google Patents

Abstract

The invention relates to a method for preparing carbon aerogel based on plant relics as a template. Specifically, the plant remains are treated by physical or chemical methods to improve the connectivity of the three-dimensional network inside the fiber, and then combined with an organosol to prepare a sol, which is then aged and dried to obtain a xerogel, and finally a carbothermic reduction method is used to obtain a graded porous carbon gas gel. It is used in the field of carbon aerogel preparation.

Description

A method for preparing carbon aerogel using plant remains

technical field

The invention relates to a method for preparing graded porous carbon aerogel by using plant remains as a template and combining organic solvents, and belongs to the technical field of carbon material preparation.

Background technique

The preparation of traditional carbon aerogel generally includes several steps such as preparation of organosol, polycondensation and aging of organosol, drying of organogel, and carbonization of organic aerogel. The technology is dry, the production cycle is long, the production cost is high, and the synthetic raw materials are generally toxic, which limits the development and application of carbon aerogels to a certain extent.

It is the long-term effort of materials researchers to seek economical, suitable and abundant precursor materials and use environmentally friendly methods to prepare carbon aerogels. At present, the preparation of carbon aerogel materials from biomass materials and their derivatives has become a research hotspot. By selecting different biological templates (such as polysaccharides, bagasse, rice husks) and processing methods, different structures and Uses of carbon aerogels. Plant remains, as natural porous materials abundant in nature, can be prepared into composite porous materials by a combination of chemical and mechanical methods. At present, most of them use plant cellulose to self-assemble into aerogel materials with a network structure, and then carbonize to obtain nanocellulose carbon aerogels, or use special physical and chemical methods to treat plant remains and preserve their porous structure, and then carbonized to obtain carbon aerogels.

The carbon aerogel prepared by the existing method has problems such as low strength, high brittleness, and difficult control of the porous structure. Moreover, the preparation method of the carbon aerogel by the traditional method has a long period, high cost and high toxicity. Using plant remains as a template to compound organic solvent, the prepared carbon aerogel can solve the above problems, and the prepared carbon aerogel has a hierarchical porous structure.

Hierarchical porous carbon aerogel refers to a carbon material with a combination of hierarchical pore size structures. The macropores in the structure are conducive to the transport of substances, the passage of large particles, the mesopores can provide a large electrode-electrolyte contact area, and the micropores greatly increase the specific surface area. , provide reactive sites, slow down the liquid flow rate, and the macropore-mesoporous-microporous structure of hierarchical porous materials makes them widely used in functional fields such as selective adsorption, filtration, catalyst carriers, and supercapacitors.

SUMMARY OF THE INVENTION

The invention solves the problems of long preparation period, high cost and high toxicity of traditional carbon aerogels, and provides a method for preparing graded porous carbon aerogels by utilizing plant remains.

Specifically through the following technical methods:

(1) Plant relics treatment: Pretreatment of natural plant relics by physical/chemical methods to remove structures that block pores such as pit membrane and infiltrating tissue in plant conduits, increase the three-dimensional network connectivity of pores, and then Wash, dry and crush.

(2) Preparation of organic solvent: Calculate the raw materials according to the proportion, stir and mix evenly for use.

(3) Preparation of plant remains/organic solvent composite aerogel: add organic solvent to the plant fragments until just submerged, remove air bubbles to ensure that the organic solvent completely fills the gaps between the plant fragments. The composite aerogel was obtained by standing and aging for 1 day. After the two were cured, they were dried at 50° C. for 4 hours, and finally dried at 100° C. for 5 hours.

(4) Preparation of carbon aerogel: The composite aerogel was heated in a tube furnace under nitrogen protection, and an appropriate heating process curve was set according to the different characteristics of the selected plants.

Detailed ways

Example 1

(1) Wash bagasse with hot water, remove impurities, dry under vacuum at 100°C, and then use a pulverizer to cut to 60 mesh to fine.

(2) Preparation of RF sol: Mix resorcinol (R), formaldehyde (F), and deionized water (H ₂ O) evenly, and then add catalyst hexamethylenetetramine (HMTA), whose molar ratio is: R : F : H ₂ O : HMTA=1 : 2 : 14 : 1/500, stirred for 1 hour.

(3) Preparation of composite aerogel: take 0.4 g bagasse, add 3.2 g RF solution, composite according to the mass ratio m _bagasse : m _RF = 1:8, let stand for 1 day, and after the two are cured, bake at 50 °C. Dry for 4 hours, and finally dry at 100°C for 5 hours to obtain a composite aerogel.

(4) Preparation of carbon aerogel: The composite aerogel was heated in a tube furnace under the protection of nitrogen, heated to 150 °C at 5 °C/min, and then kept for 30 min to remove free water and unreacted liquid. 3°C/min increased to 390°C for 30min to reduce the shrinkage of the composite aerogel, then heated to 800°C at 5°C/min, and kept for 2 hours to make the carbon skeleton structure more stable, and finally at 5°C/min rate of cooling.

Example 2

(1) Wash bagasse with hot water, remove impurities, dry under vacuum at 100°C, and then use a pulverizer to cut to 60 mesh to fine.

(2) Preparation of RF sol: Mix resorcinol (R), formaldehyde (F), deionized water (H ₂ O) evenly, and then add catalyst sodium carbonate (Na ₂ CO ₃ ), and its molar ratio is: R : F : H ₂ O : Na ₂ CO ₃ =1 : 2 : 14 : 1/500, stirred for 1 hour.

(3) Preparation of composite aerogel: take 0.4 g bagasse, add 3.2 g RF solution, composite according to the mass ratio m _bagasse : m _RF = 1:8, let stand for 1 day, and after the two are cured, bake at 50 °C. Dry for 4 hours, and finally dry at 100°C for 5 hours to obtain a composite aerogel.

(4) Preparation of carbon aerogel: The composite aerogel was heated in a tube furnace under the protection of nitrogen, heated to 150 °C at 5 °C/min, and then kept for 30 min to remove free water and unreacted liquid. 3°C/min increased to 390°C for 30min to reduce the shrinkage of the composite aerogel, then heated to 800°C at 5°C/min, and kept for 2 hours to make the carbon skeleton structure more stable, and finally at 5°C/min rate of cooling.

Example 3

(1) The paulownia wood chips are extracted and treated with 5% dilute ammonia water, then washed with deionized water, dried in vacuum at 100°C, and pulverized to 80 mesh by a pulverizer.

(2) Preparation of RF sol: Mix resorcinol (R), formaldehyde (F), deionized water (H ₂ O) evenly, then add catalyst urotropine (HMTA), and its molar ratio is: R : F : H ₂ O : HMTA=1 : 2 : 22 : 1/500, stirred for 1 hour.

(3) Preparation of composite aerogel: take 0.5 g of paulownia wood chips and add 1.5 g of RF solution, that is, according to the mass ratio m _{paulownia wood chips} : m _RF = 1: 4, the composite aerogel is left for 1 day. After the two are cured, they are dried at 50 °C. Dry for 4 hours, and finally dry at 100°C for 5 hours to obtain a composite aerogel.

(4) Preparation of carbon aerogel: The composite aerogel was heated in a tube furnace under nitrogen protection, heated to 150 °C at 5 °C/min, and then kept for 30 min to remove free water and unreacted liquid, and then continue Rising to 300°C at 5°C/min, then raising to 400°C for 30min at 4°C/min to reduce the shrinkage rate of the composite aerogel, then heating to 800°C at 5°C/min and holding for 2 hours to make the composite aerogels shrink. The carbon skeleton structure is more stable, and finally the temperature is lowered at a rate of 5 °C/min.

Claims (1)

1. a kind of lose the method that state prepares charcoal-aero gel for template based on plant, it is characterised in that the following steps are included:

(1) bagasse is cleaned using hot water, it is dry under 100 DEG C of vacuum conditions after removing impurity, then cut using pulverizer To 60 mesh；

(2) prepared by RF colloidal sol: resorcinol (R), formaldehyde (F), deionized water being uniformly mixed, six first of catalyst are added Urotropine (HMTA), molar ratio are as follows: R: F: H₂O: HMTA=1: 2: 14: 1/500, it stirs 1 hour；

(3) prepared by composite aerogel: taking 0.4 g bagasse, 3.2g RF colloidal sol is added, according to mass ratio m_Bagasse: m_RF=1: 8 Compound, standing 1 day is carried out, after the two solidification, 50 DEG C are dried 4 hours, and last 100 DEG C dry 5 hours, obtain compound airsetting Glue；

(4) preparation of charcoal-aero gel: using diamond heating for composite aerogel under nitrogen protection, is warming up to 5 DEG C/min 30min is kept the temperature after to 150 DEG C, excludes Free water and unreacted liquid, 390 DEG C of heat preservations are then risen to 3 DEG C/min 30min reduces the shrinking percentage of composite aerogel, then 800 DEG C is heated to 5 DEG C/min, and keep the temperature 2 hours, so that charcoal skeleton Structure is more stable, is finally cooled down with the rate of 5 DEG C/min.