碱/碱土金属对纤维素热解特性的影响

Effects of alkali/alkaline earth metals on pyrolysis characteristics of cellulose

为了解碱/碱土金属(AAEM)及存在形态对生物质热解特性的影响,用4种金属的不同盐溶液浸渍微晶纤维素,进行热重分析和管式炉热解试验。结果表明,AAEM能够促进纤维素在低温下热解,降低热解速率并提高固体焦产率;能降低纤维素热解的表观活化能,活化能随AAEM含量的增加而降低;使热解气体中的CO及C2体积分数降低、CO2和CH4体积分数提高。4种金属元素对纤维素热解催化能力的顺序为:K>Na>Mg,Ca。碱金属的存在形态对其催化能力有影响,乙酸盐金属对热解反应温度、产物的影响显著大于氯化物金属,并使纤维素热解过程分为两段,增加热解气体中H2的含量,而氯化物金属会降低气体中H2的含量,其催化能力易受到添加量的影响。生物质中以有机结合态存在的碱金属对热解过程的影响大于以无机态存在的同种金属。生物质催化热解气化过程及产物分布受金属种类及其存在形态的影响。

In order to understand the effects of alkali and alkaline earth metals（AAEM） on the pyrolysis characteristics of biomass, microcrystalline cellulose（Mcc） loaded K,Na,Mg,Ca with different concentrations were investigated by thermogravimetric analysis and tubular furnace. The results indicated that AAEM could catalyze pyrolysis process, increase the char yields markedly, shift the pyrolysis process to lower temperature, reduce the activation energy for pyrolysis, decrease CO and C2 content and increase CO2 and CH4 in produced gas. The catalysis of the metal added on the cellulose was KNaMg, Ca. The catalysis of metal Chloride （MCl） was relatively weak compared to CH3COOM, and the catalysis was limited when the added concentration of MCl was low. CH3COOM addition affected pyrolysis temperature and production of cellulose remarkably, separated the pyrolysis into two process, and increased H2 content in produced gas. The organically bound alkali metals may catalyze pyrolysis of biomass more than the inorganically alkalis in biomass. The characteristic and production distribution of biomass pyrolysis is affected by AAEM species and forms.