Bio-oil light fraction-based bread-shaped porous activated carbon as well as preparation method and application thereof

Abstract

The invention provides bio-oil light fraction-based bread-shaped porous activated carbon as well as a preparation method and application thereof. The preparation method comprises the following steps of selecting a light fraction prepared by coupling biomass rapid pyrolysis with molecular distillation as a precursor; directly mixing an activating agent with the light fraction, and stirring to obtain a homogeneous liquid; then carrying out second-order temperature one-step carbonization and activation on the homogeneous liquid in an inert atmosphere; and after the activation is finished, washing and carrying out suction filtration on the obtained solid, removing an activator reaction product and impurities, and drying to obtain the activated carbon for the supercapacitor electrode carbon material. The method makes full use of the fact that the obtained light fraction is rich in water, acids, ketones, aldehydes, monophenol and other small molecular compounds, the small molecular compounds and water can interact with the activator, and the usage amount of the activator is effectively reduced; the prepared activated carbon has a porous bread-shaped structure macroscopically and is small in density, large in specific surface area and uniform in pore, and specific capacitance, power density and energy density of the supercapacitor can be effectively improved.

Description

technical field [0001] The invention relates to the field of high-value utilization of biomass pyrolysis bio-oil molecular distillation light distillate, in particular to a bread-shaped porous activated carbon based on bio-oil light distillate and its preparation method and application. Background technique [0002] Activated carbon (AC) is often used as the most commonly used electrode material for electric double-layer supercapacitors (EDLCs) due to its large specific surface area and porosity that closely matches the ion size. Activated carbon prepared from biomass as a carbon source is one of the current preferred carbon materials due to its high electrical conductivity, chemical stability in water and organic electrolytes, low cost, and abundant sources. It is used in supercapacitors and other fields It has very good application value. [0003] In the conventional process of preparing activated carbon, the activator and the precursor are usually mixed in the state of "...

AI Technical Summary

Problems solved by technology

[0003] In the conventional process of preparing activated carbon, the activator and the precursor are usually mixed in the state of "solid", "solid-liquid", and "solid-gas", where "solid-solid" mixing refers to directly mixing the solid precursor or unactivated The crude carbon and the solid activator are mixed by mechanical force. For example, in the patent CN202010095842.5, the pomelo seed powder is carbonized to obtain the coarse carbon material. The coarse carbon material and the alkali activator (mass ratio is 1~2:1~2) Grinding, mixing, and reactivation are used to prepare carbon materials for supercapacitor electrodes. Under the action of mechanical stirring, the solid precursor and solid activator can only show a uniform mixing state at the macroscopic level, but cannot achieve uniformity at the microscopic molecular level. Therefore, it is necessary to significantly increase the amount of activator, and the distribution of microscopic pores in the final product activated carbon is not uniform, and most of them exist in the form of mesopores (2~50 nm) and macropores (>50 nm), which is not suitable for supercapacitors. Electrode active material

[0004] "Solid-liquid" mixing refers to mixing solid precursors or unactivated coarse carbon with an activator solution, such as the solid biomass materials such as starch, lignin, corncobs, rice husks, and wheat ears in patent CN201610300981.0 After mixing with KOH (concentration: 0.01~5 mol / L) solution, the modified precursor is obtained by ultrasonic vibration and stirring, and then the mixture of activator and precursor is obtained by heat drying or freeze drying, and then activated and prepared for application For supercapacitor electrode carbon materials, during the drying process of the precursor and activator mixed in this way, the activator will be saturated and precipitated from the aqueous solution, and appear on the surface of the precursor in the form of a solid, and cannot Uniform mixing is achieved at the level and the amount of activator will be increased

[0005] "Solid-gas" mixing refers to putting solid precursors or unactivated coarse carbon into the activation furnace, and then introducing active gases, such as water vapor, carbon dioxide, air, ammonia, etc., such as patent CN201810885112. Biomass such as wood and broad-leaved wood is used as the primary material, and after the first and second gas activation, the carbon material used in the electrode of the supercapacitor is prepared. In the process, a large amount of active gas needs to be fed continuously for a long time in a high temperature environment above 800 °C, resulting in a large amount of energy consumption and waste of activated gas, and the obtained activated carbon has uneven pore distribution, and the specific surface area is generally lower than 1000 m 2 / g, not suitable as an electrode active material for supercapacitors

[0006] The activation of the precursor and the activator after mixing in the form of "solid-solid", "solid-liquid", and "solid-gas" has the following disadvantages: (1) The activator cannot fully contact with the precursor, resulting in uneven mixing; (2) due to The activator and the precursor cannot form a uniform mixture, resulting in uneven distribution of pores in the activated carbon product, and the distribution of pore size is not uniform, and is widely distributed in the range of mesopores and macropores; (3) the use of a large amount of activator, the quality of the activator Usually several times higher than the quality of the precursor, such as patent CN201910824987.1 The mass ratio of the carbonized material based on bamboo shoot shells to the activator is 1:3~5 or a higher ratio of activator

For example, patent CN109467085A uses biomass with higher ash content as raw material, and reduces the ash in the raw material by adopting hydrothermal carbonization process, but cannot completely remove the ash in activated carbon; Ash content in activated carbon, but its content is about 1% ~ 5%

Images