金属离子催化生物质热裂解规律及其对产物的影响

THE BEHAVIOR OF BIOMASS PYROLYSIS CATALYZED BY METALLIC IONS AND THEIR EFFECTS ON THE PRODUCTS

在红外辐射热裂解实验装置上研究了K+和Ca2+催化纤维素热裂解规律及其对热裂解产物分布的影响。结果表明,中温条件下两种金属离子的催化作用主要都发生在固相中,仅有极少量进入液态或者气态产物空间,该特性为制取环保液体燃料提供了保证条件。从总体上讲,两种金属离子对热裂解过程的催化作用比较相似,在促进焦炭和气体产物生成的同时阻碍了生物油的产生。但是,经由催化脱水过程,生物油有机成分氧含量降低,品质得到了部分提高。分析其催化机理,K+有利于裂变和歧化反应,促进乙醇醛、乙醛以及低相对分子质量醇基、醛基、酮基化合物的生成;Ca2+则强烈地影响单糖碎片的重整和异构化过程,促进呋喃类和杂环衍生物的生成。这一催化选择性为热裂解采用合适的条件和工艺,有目的地选取特定金属盐来优化产物的生成提供了基础。

Catalytic behavior and effects of K + and Ca 2+ in the process of cellulose pyrolysis were studied in an infrared radiation pyrolysis system. In the case of medium pyrolysis temperature, catalysis of potassium salt and calcium salt mainly occurred in solid phase, only few ions were released out of solid particles and entered into the liquid or gaseous products, which is beneficial for clean liquid fuel production from biomass. Both ions present the same catalysis behavior on biomass pyrolysis, as restrained formation of aqueous oil and enhanced production of char and gas. Besides , the quality of liquid product was improved by de-oxygen reaction catalyzed by K + and Ca 2+ . In addition, K + enhanced the cracking and disproportionating process of molecules to improve the production of hydroxyacetaldehyde, acetaldehyde and small-molecule components including groups of alcohols, ketones or aldehydes , while Ca 2+ mainly influenced the rearrangement and isomerization of the monomeric sugar fragments to yield more furan and heterocyclic compounds. The selective catalysis behavior makes it possible to optimize biomass pyrolysis by selecting appropriate operation condition and metallic salts.