微波辅助铁催化低阶煤热解特性

Characteristics of catalytic pyrolysis of low-rank coal via microwave-assisted Fe

微波加热技术具有快速均匀、选择性加热和安全环保的优势,为煤炭高效分级转化利用提供了新途径。为研究微波辅助兼具介电响应和催化性能的金属组分Fe对低阶煤热解产品分布、气相组成及半焦碳微晶结构和介电性能的影响,在微波管式炉上对酸洗后负载不同量Fe的华夏低阶煤进行了催化热解实验。借助向量网络分析仪、XRD、FT-IR、Raman和SEM表征了不同Fe负载量煤样微波热解半焦的物化性质。结果表明:Fe催化剂有效强化了煤样对微波的介电损耗,能够显著提高升温速率使得煤样在短时间内即可达到热解终温。微波优先与Fe催化剂作用可高效诱发煤大分子有机质催化裂解反应的发生,使得合成气(CO+H2)产量由酸洗煤样的221 mL/g明显提高至负载1%,3%和5%Fe煤样的273,394和457 mL/g。金属组分Fe的引入明显增大了热解半焦的介电损耗因子ε″r和损耗角正切值tanδ,进而充分增强了半焦以热能形式耗散微波能的能力。微波辅助Fe催化剂抑制了半焦基本结构单元横向的内部生长和纵向的结合缩聚,增大了芳香碳网的不规整度,促进了碳骨架结构中小芳香环体系和无定形碳含量的提升,将有利于增强半焦的气化反应活性。此外,微波辐照下Fe催化剂的引入有助于半焦孔隙结构的构筑,促进了半焦表面形态由平滑致密层状向疏松多孔状的发展。

Microwave heating technology offers a new way for an efficient coal-staged conversion due to its advantages of rapid and uniform heating,selective heating and high efficiency and safety.This study was undertaken to investigate the effect of metal species Fe with both catalytic action and dielectric response on the product distribution,gas composition,and the char carbon crystallite structure of microwave-assisted pyrolysis of low-rank coal,and the catalytic pyrolysis experiments of demineralized Huaxia low-rank coal loaded with different amounts of Fe has been conducted in a microwave tube furnace.Physicochemical properties of chars produced from the microwave-assisted pyrolysis of coal samples loaded with different amounts of Fe were characterized by a vector network analyzer,XRD,FT-IR,Raman and SEM.Results show that the introduction of Fe can effectively strengthen the dielectric loss of coal samples and can promote coal samples achieve the final pyrolysis temperature within a short time by improving heating rate.Microwave interacted preferentially with Fe catalyst can efficiently induce the occurrence of catalytic cracking reaction of coal macromolecular organic matter,resulting the syngas yield is significantly increased from 221 mL/g of demineralized coal to 273,394 and 457 mL/g of coal samples load with 1%,3%and 5%Fe.Furthermore,the addition of Fe considerably improves the ability of coal chars of dissipate microwave energy with the form of heat by increasing the value of dielectric loss factorε″r and loss tangent tanδ.Microwave assisted Fe inhibits the internal growth of char basic structural unit while remarkably increasing the irregular value of the aromatic carbon network.In the meantime,the amount of small aromatic rings and amorphous carbon in carbon skeleton structure are dramatically improved which is favorable for enhancing the char gasification reactivity.Additionally,the introduction of Fe catalyst is conducive to the construction of pore structure of coal chars and can promote the development of surface morphology of coal chars from smooth and dense to porous under microwave radiation.