杨木湿法烘焙预处理耦合金属改性多级孔分子筛催化热解制取轻质芳烃

Enhancement of the production of light aromatics from poplar wood by combined approach of wet torrefaction pretreatment and catalytic fast pyrolysis using metal modified hierarchical zeolite

轻质芳烃是化工领域重要的基础有机原料,生物质催化热解的技术路线可制取生物基的轻质芳烃化学品。首先,采用湿法烘焙预处理,对杨木进行协同脱氧和脱灰改性提质;其次,采用NaOH脱硅预处理和负载活性金属(Zn、Ga和Fe),对微孔HZSM-5进行修饰改性,构建金属改性多级孔HZSM-5催化剂,并将其用于湿法烘焙杨木催化热解,研究烘焙温度、催化剂改性、催化剂与原料质量比和热解温度等参数对轻质芳烃产率的影响。结果表明,随着湿法烘焙温度的升高,杨木的脱氧率和碱/碱土金属脱除率逐渐增加,其中,O、K、Mg、Ca和Na的最大脱除率分别为47.96%、90.99%、86.65%、66.09%和36.29%。与HZSM-5相比,采用NaOH脱硅后的多级孔HZSM-5(Hie-H)及金属改性的多级孔HZSM-5(Ga/Hie-H、Zn/Hie-H和Fe/Hie-H),均促进了轻质芳烃的形成,其中,Zn/Hie-H对杨木湿法烘焙后固体产物催化热解制取轻质芳烃产率最高;在湿法烘焙温度为220℃,Zn/Hie-H与烘焙杨木质量比为3∶1,热解温度为850℃时,轻质芳烃的产率达到最大值,为7.83×107p.a./mg。

Light aromatics are extremely important building blocks in the chemical industry which can be produced from the catalytic fast pyrolysis(CFP)of biomass.In this work,wet torrefaction pretreatment(WTP)was employed to improve the quality of poplar wood(PW)in terms of the synergetic deoxygenation and demineralization.Then,metal-modified hierarchical HZSM-5 was prepared by the combined approach of NaOH desilication pretreatment and metal(Zn,Ga,and Fe)modification.At last,the CFP of torrefied PW was carried out by using the metal-modified hierarchical HZSM-5 as catalyst to produce light aromatics.Results showed that the deoxygenation and demineralization rates gradually increased with the increase of WTP temperature from 180 to 260℃,the maximum removal rates of oxygen,K,Mg,Ca,and Na were 47.96%,90.99%,86.65%,66.09%,and 36.29%,respectively.NaOH desilication pretreatment and metal modification on HZSM-5 promoted the formation of light aromatics.The Zn-modified hierarchical HZSM-5 presented the highest yield of light aromatics.The yield of aromatics increased first with the raise of catalyst-to-torrefied PW ratio from 1:1 to 1∶3,then decreased slightly at the highest catalyst-to-torrefied PW ratio of 1∶5.At last,the operation parameter of WTP and CFP was optimized which the maximum yield of light aromatics was 7.83×107 p.a./mg at WTP temperature of 220℃,catalyst-to-biomass ratio of 3∶1,and CFP temperature of 850℃.