烘焙脱氧毛竹与高密度聚乙烯共催化热解制备轻质芳烃

Production of light bio-aromatics from co-catalytic fast pyrolysis of torrefied bamboo and high-density polyethylene

轻质芳烃是化工领域重要的基础有机原料,可通过生物质和废塑料共催化热解技术路线制取。首先,采用烘焙预处理对毛竹进行脱氧改性提质;其次,通过Na_(2)CO_(3)溶液对微孔HZSM-5进行碱扩孔预处理,制备多级孔分子筛催化剂,最后通过烘焙毛竹和高密度聚乙烯(HDPE)共催化热解制取轻质芳烃,研究烘焙温度、Na_(2)CO_(3)浓度、原料共混比例、热解温度等因素对轻质芳烃产率的影响。结果表明,毛竹经烘焙脱氧预处理后,碳元素显著增加,氧元素显著下降,氧脱除率达到40.3%,高位热值从17.47 MJ/kg增加至25.64 MJ/kg;微孔HZSM-5经Na_(2)CO_(3)溶液碱扩孔预处理后,介孔容积、总孔容和平均孔径均增加,表明经过碱扩孔后HZSM-5形成了一定程度的介孔结构,使其转变为具有微-介孔结构的多级孔分子筛;烘焙毛竹热解产生的呋喃类含氧中间产物和HDPE热解产生的轻烯烃中间产物会发生“双烯合成”反应,成为轻质芳烃生成的关键协同催化反应,当烘焙温度为250℃、Na_(2)CO_(3)浓度为0.6 mol/L、烘焙毛竹和HDPE质量比为1∶2和热解温度为800℃时,BTX(苯、甲苯和二甲苯)等轻质芳烃产率达到最大值,为3.05×10^(8) p.a./mg。

Light aromatics are extremely important building blocks in the chemical industry which can be produced from the co-catalytic fast pyrolysis(Co-CFP)of biomass and waste plastics.In this work,torrefaction pretreatment was first employed to remove the oxygen element from bamboo for improving the the quality of bamboo.Then,the hierarchical HZSM-5 was prepared by alkali pretreatment of HZSM-5 using Na_(2)CO_(3) solution.At last,the optimal operation condition was investigated during Co-CFP of bamboo and high-density polyethylene(HDPE).Results showed that during torrefaction pretreatment process,the carbon content of bamboo gradually increased with the increase of torrefaction temperature,while the oxygen content decreased.The oxygen removal rate and HHV reached their maximum value of 40.3%and 25.64 MJ/kg at 300℃,respectively.The specific surface area,pore volume of mesopore,and average pore size of HZSM-5 increased after alkali pretreatment,indicating the development of the micro-mesoporous hierarchical structure in HZSM-5.The Diels-Alder reaction between the furans from pyrolysis of bamboo and the light olefins from pyrolysis of HDPE was the most important synergistic catalytic reaction which could highly promote the formation of light aromatics.The maximum yield of BTX(benzene,toluene,and xylene)was 3.05×10^(8) p.a./mg when the torrefaction temperature,the concentration of Na_(2)CO_(3),the mass ratio of torrefied bamboo and HDPE,and the pyrolysis temperature were 250℃,0.6 mol/L,1∶2,and 800℃,respectively.