Preparation Of Morphology Controlled Porous Carbons From Larch Sawdust

Porous carbon materials with specific morphology and pore size have the vital significance on the perspective of synthetic materials science and the perspective of material application. Biomass raw materials mainly include cellulose, hemicellulose and lignin, contain more oxygen on structure. It is typical of solid-phase carbonization without going through liquid phase during pyro lysis in this step; microcrystalline preferred orientation is difficult, obtained highly ordered pore structure is difficult also. Using biomass as matrix, carbonization and activation by the conventional style under inert atmosphere, its biological ceramic-wood structure will be largely preserved. As a result, preparation of specified shape and aperture structure of biomass carbon by the traditional method has a big obstacle.This paper aimed to preparing spherical carbons with hierarchical micro-mesoporous structures from the resinification, self-assembly activation and carbonization from phenolic resin as source. Based on the preliminary exploration, spherical mesoporous carbon was prepared using larch sawdustas the starting material, which is cheap and renewable, F127as soft-templed by liquefaction, resinification, self-assembly polymerization, activation, carbonization technology. After chemical activation, micro-mesoporous carbon spheres were obtained. In view of the carbon materials with good pore structure, the molecular sieve carbon memebrane was preparated without supporting through controlling the reaction condition adjustment reactant viscosity. The obtained porous carbon materials were characterized by X-ray diffraction (XRD), scanning electron spectroscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption-desorption isotherms, and thermogravimetric analysis (TGA).In this paper, bionass energy, wood liquefaction, mesoporous carbon, micro-mesoporous carbon and molecular sieve carbon membranes were reviewed. Furthermore, the topic research background, methods, contents and innovation points and the main research methods were introduced.A facile soft-template method was developed for the synthesis of spherical micro-mesoporous hierarchical carbon material (HCSp) by using phenol and formaldehyde as carbon and Pluronic F127as templat. Results showed that morphology of caron can be regulated by the dosage of soft-template, pH and activation temperature. The optimum condition was determined as mass fraction of F12720%, pH0.5and activation temperature700℃. The prepared porous carbon exhibited spherical morphology with uniformly diameter of100-200nm. Vermicular pore structure, together with bimodal pore size distribution peak2.9nm and1.3nm was observed. Maximum of surface area and pore volume can reach503.20m2/g and 0.42cm3/g, respectively. Results revealed that surface area, pore total volume of carbon spheres increased with the increasing of activation temperature. However, pore size showed reverse trendency.Mesoporous carbon spheres (CS1) with tunable morphology and pore structure were prepared from liquefied larch sawdust via coupling soft-templated and the hydrothermal method. The morphology and size of carbon spheres can by controlled by the concentration of F127; the pore structure can be tunable by carbonization temperature. The results showed that perfect carbon sphere can be achieved when the concentration of F127was6%. The morphology of carbons was from spherical-shaped to raspberry-like, and particle size decreased with increasing F127concentration. Pore structure transformed from spiral-like, vermicular-like to wave-like with the increasing of the carbonization temperature, meanwhile, the surface area, pores volume and microporous content were increased to410m2/g,0.291cm3/g and48.5%respectively when carbonization increased to700℃. However, pore size showed reverse trendency.Spherical carbons with hierarchical micro-mesoporous structures (HCS1) were prepared from the liquefaction, resinification and activation of larch sawdust. Block copolymer F127reacts with liquefied larch to form carbon spheres. Carbon spheres with diameters20-30μm, together with vermicular porous structures consisting of2.0-4.3nm mesopores and1.2-2.0nm micropores were formed. The maximum surface area and pore volume were1064m2/g and0.503cm3/g, respectively, at an activation temperature of700℃. The carbon pore size was controlled by KOH at different activation temperatures. At high temperatures, the mesopores and micropores in the material increased. When the activation temperature increased to700℃, the maximum surface area and pore volume reached1064m2/g and0.503cm3/g, respectively. In addition, the surface area and the SHC pore total volume increased with increasing activation temperature. The mesophase of SHC decomposed rapidly in four stages, at250,375,450and650℃, corresponding to the decomposition of F127, primary carbonized products, secondary carbonized products and K2CO3, respectively.Based on the result of the preparation of mesoporous carbon spheres from larch-sawdust, molecule sieves carbon membrane (MSCM) with thickness of400μm and pore size centrated at1-3nm was preparated by adjusting reaction time and temperature to control viscosity of liquefied larch. The surface area increased from367m2/g to469m2/g, pores volume increased from0.198cm3/g to0.250cm3/g, because of microporous content increased from80%to87%. It indicated that molecule sieves carbon membrane had more microporous, resulted average pore size decreased from2.15nm to2.13nm.