摘要
木质素富含芳香基团,对其催化热解可制取高值单酚,然而木质素热解气组分复杂,易导致单酚收率低及催化剂快速积碳失活,不利于提高经济效益。该研究利用酸溶-碱沉淀耦合焙烧处理方法制备低成本活化赤泥催化材料,研究活化赤泥催化热解玉米芯木质素制取高值单酚化学品的影响规律,同时对玉米芯木质素及活化赤泥催化剂进行结构表征,并对活化赤泥的催化性能及应用潜能进行分析。结果表明:赤泥活化处理过程可显著改善其自身的表面形貌、孔结构和催化性能;相比于木质素常规热解,活化赤泥提升了生物油中苯酚、烷基酚等高值单酚的含量(60.38%);与商业分子筛催化剂相比,低成本活化赤泥可高效制取单酚,且具备较好的循环使用性能,能作为商业介孔分子筛的有效补充;同时赤泥和木质素2种废弃物耦合共处理,具备潜在的经济与生态环境效益。研究成果为赤泥和木质素等固废的资源化利用提供基础参考。
Lignin is a kind of natural aromatic polymer with complex three-dimensional amorphous structure.It has also gradually become an ideal raw material for value-added fine chemical production.The pyrolysis liquefaction technology can be used to achieve the depolymerization of lignin into phenolic compounds.However,the thermal depolymerization process is normally associated with many highly reactive benzene ring radicals.These radicals are not sensitive to the formation of high-value mono-phenol,due to they can further be condensed to coke.A feasible pathway,including catalytic pyrolysis of lignin,can be selected to produce value-added mono-phenol.Herein,the selection of catalyst become critical to the directional catalytic pyrolysis with monophenols as the target product.The physical-chemical characteristics of catalysts can directly determine the composition and enrichment of mono-phenol in bio-oil.At present,many low-cost catalytic materials have been synthesized to further broaden the source of the catalysts for save-costing technology of catalytic pyrolysis.In this paper,the acid digestion-alkali precipitation coupled calcination treatment was employed to activate the red mud waste derived from alumina industry.The synthetic low-cost catalyst was introduced into the catalytic pyrolysis of maize cob lignin process,to produce the value-added mono-phenol in bio-oil.Proximate analysis,ultimate analysis,and ultraviolet-visible spectroscopy(UV-Vis)were used to characterize the maize cob lignin.The synthesized low-cost catalytic materials(denoted as ACRM)were characterized by X-ray fluorescence(XRF),X-ray diffraction(XRD),scanning electron microscopy coupling with energy-dispersive X-ray spectroscopy(SEM-EDS),transmission electron microscopy(TEM),thermogravimetry-differential thermal gravimetry(TG-DTG)and the N2 isothermal absorption-desorption analysis.The distributions of bio-oil groups and main phenolic compounds were investigated at the function of ACRM samples.The comparative analysis of ACRM with commercial catalysts was performed to evaluate the application potential of red mud as a low-cost catalyst for the catalytic pyrolysis lignin.Results showed that the maize cob lignin can serve as a renewable raw material to produce high-value aromatic chemicals,indicating abundant para-aromatic ring structure,with unique ferulic acid(FA)and para-coumaric acid(PCA).The activated process can significantly improve the surface morphology,pore structure and catalytic properties of red mud.The activated red mud can produce pore structure and abundant active metal oxides(Fe2O3,Al2O3 and TiO2),indicating a high specific surface area(72.36 m2/g).Most Na and Ca elements were efficiently removed from the red mud structure,indicating the reduction of strong alkalinity.The relative peak area of phenol and alkylphenols can reach up to 60.38%at the function of ACRM catalysts,mainly due to the enhanced dehydroxylation,demethylation,demethoxy reaction,and alkylation reaction.Compared with commercial molecular sieves,the modified red mud was a supplement to mesoporous molecular sieves with a better recycling performance.A possible reaction pathway of lignin pyrolysis vapors was proposed under the function of ACRM catalyst.Therefore,the activated red mud catalyst was used as a low-cost catalyst material for lignin catalyzed pyrolysis to produce value-added mono-phenol,indicating the energy utilization of typical waste resources with potential economic and ecological benefits.The application of ACRM can be expected to guide the utilization of solid waste.The findings can provide a sound reference for the reasonable disposal of waste resources from biorefining,pulp engineering and alumina industry.
作者
王绍庆
李志合
易维明
高亮
李玉峰
柏雪源
Wang Shaoqing;Li Zhihe;Yi Weiming;Gao Liang;Li Yufeng;Bai Xueyuan(School of Agricultural Engineering and Food Science,Shandong University of Technology,Shandong Research Center of Engineering and Technology for Clean Energy,Zibo 255000,China)
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2020年第13期203-211,共9页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家重点研发计划项目(2019YFD1100600)
山东省自然科学基金项目(ZR2017MEE004,ZR2016YL012)
国家自然科学基金项目(51536009,51976112)
泰山学者工程专项经费
山东省优势学科资助项目。
关键词
木质素
催化热解
活化赤泥
单酚
lignin
catalytic pyrolysis
activated red mud
mono-phenol
