A kind of bio-oil light distillate-based bread-shaped porous activated carbon and its preparation method and application

Abstract

The present invention proposes a bio-oil light distillate-based bread-shaped porous activated carbon and its preparation method and application. The light distillate produced by biomass fast pyrolysis coupling molecular distillation is selected as a precursor; the activator is directly mixed with the light distillate Mixing and stirring to obtain a homogeneous liquid; then the homogeneous liquid is subjected to one-step carbonization and activation at the second-order temperature under an inert atmosphere; after the activation is completed, the obtained solid is washed and filtered to remove the activator reaction product and impurities, and then After drying, the activated carbon used for supercapacitor electrode carbon materials can be obtained. This method makes full use of the obtained light distillate rich in water, acids, ketones, aldehydes, monophenols and other small molecular compounds, small molecular compounds and water can interact with the activator, and effectively reduce the use of activators Quantity; The prepared activated carbon has a porous bread-like structure macroscopically with low density, large specific surface area and uniform pores, which can effectively improve the specific capacitance, power density and energy density of supercapacitors.

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 (EDLC) 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 o...

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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 coarse 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. Mixing requires a significant increase in the amount of activator, and the final product activated carbon has uneven distribution of microscopic pores, mostly in the form of mesopores (2-50nm) and macropores (>50nm), which are not suitable for electrode activity of supercapacitors. 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: 0.01-5mol / 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 prepared by activation. Supercapacitor electrode carbon materials, the precursor and activator mixed in this way will be saturated and precipitated from the aqueous solution during the drying process, and appear on the surface of the precursor in the form of a solid, and cannot be detected at the microscopic molecular level. to achieve uniform mixing, and will increase the amount of activator

[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. During 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 pores are unevenly distributed, and the specific surface area is generally lower than 1000m 2 / g, not suitable as an electrode active material for supercapacitors

[0006] The reactivation of the precursor and the activator after mixing in the form of "solid", "solid liquid", and "solid gas" has the following disadvantages: (1) The activator cannot fully contact with the precursor, resulting in uneven mixing; (2) The activator and the precursor cannot form a uniform mixture, resulting in uneven pore distribution in the activated carbon product, and the pore size distribution is not uniform, and is widely distributed in the range of mesopores and macropores; (3) using 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% to 5%.

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