稻杆的热溶剂提质及多级分离

Upgrading and multistage separation of rice straw by degradative solvent extraction

采用1-甲基萘(1-MN)为溶剂,在不同温度下(250、300、350℃)对稻秆进行热溶剂提质及多级分离,获得3种主要固体产物:低分子量萃取物(soluble)、高分子量萃取物(deposit)和萃取残渣(residue),以及少量气体产物和液体产物。对各组分的元素组成、化学结构、物理化学特性等进行了详细分析,并采用ICP-MS测定了其碱金属和碱土金属(AAEM)含量。结果发现,低分子量萃取物收率随着温度的升高而增大,350℃时碳基收率达到33.48%。3种固体产物的碳含量和氧含量随着温度的升高而分别升高和降低,350℃时soluble、deposit的碳含量分别高达82.36%、80.59%,氧含量分别低至9.50%、12.03%,稻杆原样中高达86.99%的氧以H2O或CO2的形式释放。soluble几乎无灰,deposit的灰含量也低于1.50%。3种固体产物的高位发热量显著高于稻杆原样。FT-IR结果表明,稻杆热溶剂处理过程中除发生了脱水反应、脱羧基反应外,还有明显的芳香化反应。soluble和deposit的Na、Mg和K含量极低,而且随温度的升高其含量逐渐降低。总之,热溶剂提质及多级分离法实现了温和条件下的生物质脱水脱氧提质,并获得低灰低氧含量、高碳含量和发热量的多种产物,此方法有较好的应用前景。

Upgrading and multi-s tage separation （UMSS）o f rice straw was conducted at different temperatures using 1-methylnaphthalene （1-MN） as solvent.Three main solid products were obtained： low molecular weight extract （soluble）, high molecular weight extract （deposit） and extraction residue （ residu e）.The elemen tal composition, chemical struc ture andp hysicochemicalc haracteristic of each component were analyzed in detail. Alkali and alkaline earth metal （AAEM） contents of solid products and rice straw were also measured by ICP-MS.The results showed th e yield of soluble increased with tempera ture, and th e carbon-b ased yield of soluble reached 33.48% at 350 ℃.The carbon conten t and oxygen content of th rees olid products （soluble, deposit, and residue） increa sed and decrease d wit h tempe rature, respectively.The carbon content of soluble and deposit reached up to 82.36% and 80.59% respectively.Meanwhile the oxygen contents of them were as low as 9.50%and 12.03% respectively.More than 86.99% oxygen of rice straw was removed as H2 O and CO2 .Soluble was almost free from ash, and the ash content of deposit was also less than 1.50%.The higher heating values （HHV） of three solid products were significantly higher than that of rice straw.The FT-IR results indicated that not only dehydration reaction and decarboxylation reaction occurred, but also including obvious aromatization reaction.The contents of Na, Mg and K of soluble and deposit were extremely low, and they decreased with temperature gradually. In conclusion, the degradative solvent extraction method realized dehydration, deoxygenation and multistage separation of biomass under mild condition, and obtained a variety of products of low ash and oxygen content as well as high carbon content and HHV.