交联预处理对生物质石墨制备的影响

Effect of cross-linking pretreatment on the preparation of biomass graphite

为了研究不同交联预处理对竹粉化学结构、热解特性及高温炭化石墨化的影响,以废弃竹粉为碳源,经甲醛(FA)、1,2,3,4-丁烷四羧酸(BTCA)交联预处理,高温炭化等工艺制备生物质石墨,探索一种新型生物质石墨的制备方法。用傅里叶变换红外光谱(FTIR)和热重分析(TG/DTG)对交联预处理前后的竹粉进行表征,用X射线衍射谱图(XRD)、X射线光电子能谱图(XPS)和拉曼光谱(Raman)对竹基生物质石墨进行表征。结果表明:具有双官能度的甲醛,可与竹粉中的纤维素、木质素发生交联反应;BTCA的官能度为4,可与竹粉中的纤维素酯化交联,从而提高竹粉热解固体残余量。与FA相比,BTCA交联预处理对生物质石墨的制备具有促进作用,BTCA改性后生物质石墨样品(002)衍射峰强提高,(002)晶面衍射角度增大,对应晶面层间距减小,石墨化度达77.91%;样品中C含量和石墨化碳(sp^(2) C)占比提高,缺陷密度(I_(D)/I_(G))下降,降幅为10.6%。

This study aimed to investigate the effects of various cross-linking pretreatments on the chemical structure,pyrolysis characteristics and carbonization graphitization of bamboo powder,as well as to explore a novel way to fabricate biomass graphite(BG).Waste bamboo powder was used as the carbon source to prepare BG.Two cross-linking agents,formaldehyde(FA)and 1,2,3,4-butanetetracarboxylic acid(BTCA),were then used to pretreat bamboo powder that was carbonized at a high temperature to prepare BG.Fourier transform infrared spectroscopy and thermogravimetric analysis were used to characterize bamboo powder before and after pretreatment.X-ray diffraction spectroscopy,X-ray photoelectron spectroscopy,and Raman spectroscopy were used to characterize bamboo-based BG.The results show that:the functionality of FA is 2,which can cross-link with cellulose and lignin in bamboo powder;the functionality of BTCA is 4,which can be esterified and cross-linked with cellulose in bamboo powder,thereby increasing the residual solid content of bamboo powder pyrolysis.Compared with FA,BTCA cross-linking pretreatment can promote the preparation of BG.Following BTCA modification,the(002)diffraction peak intensity of the BG sample increased,the diffraction angle of(002)crystal plane increased,the layer spacing decreased,the graphitization degree reached 77.91%,the C content and the proportion of sp^(2) C increased,and the defect density(I_(D)/I_(G))decreased by 10.6%.