KOH活化法制备高比表面积活性炭通常需要消耗大量KOH。为提高KOH利用效率,开发了一种基于K插层-脱插循环(以下简称“K循环”)的KOH活化石油焦制备高比表面积活性炭并联产H_(2)的方法:在升温活化过程,KOH与碳质原料反应转化为单质K、K_(...KOH活化法制备高比表面积活性炭通常需要消耗大量KOH。为提高KOH利用效率,开发了一种基于K插层-脱插循环(以下简称“K循环”)的KOH活化石油焦制备高比表面积活性炭并联产H_(2)的方法:在升温活化过程,KOH与碳质原料反应转化为单质K、K_(2)O和K_(2)CO_(3)并析出H_(2),而K_(2)CO_(3)可继续反应生成单质K和K_(2)O;在降温脱插过程,脱插试剂水蒸气与插层K、游离单质K和K2O反应生成KOH和H_(2);生成的KOH在二次升温活化时再次与碳质原料反应,如此构成K循环。在水平舟式反应器中考察了碳质原料种类(石油焦和石墨)、活化剂KOH和其活化中间产物K_(2)CO_(3)对活化过程气体产物析出规律和产品活性炭孔隙结构性质的影响,并在此基础上分析了K循环机理。结果表明,K循环效率和H_(2)产量因所用碳质原料与活化剂不同而不同:石油焦的反应活性远高于石墨,KOH活化性能优于K_(2)CO_(3)。在KOH活化石油焦的K循环过程中,KOH转化率达80%,而K_(2)CO_(3)转化率为18.5%,经由K_(2)CO_(3)的转化环节决定了K循环效率。以石油焦为碳质原料、KOH为活化剂,在活化温度为800℃及脱插温度为250℃的条件下,4.5 g干燥后的石油焦与13.5 g KOH经二次活化-脱插,所得活性炭比表面积达2808 m^(2)/g,并联产1403 mL/g H_(2)(1 g石油焦产生1403 mL H_(2))。展开更多
Lignin-derived porous carbons have emerged as promising electrode materials for supercapacitors.However,the challenge remains in designing and controlling their structure to achieve ideal electrochemical performance d...Lignin-derived porous carbons have emerged as promising electrode materials for supercapacitors.However,the challenge remains in designing and controlling their structure to achieve ideal electrochemical performance due to the complex molecular structure of lignin and its intricate chemical reactions during the activation process.In this study,three porous carbons were synthesized from lignin by spray drying and chemical activation with vary-ing KOH ratios.The specific surface area and structural order of the prepared porous carbon continued to increase with the increase of the KOH ratio.Thermogravimetric-mass spectrometry(TG-MS)was employed to track the molecular fragments generated during the pyrolysis of KOH-activated lignin,and the mechanism of the thermochemical conversion was investigated.During the thermochemical conversion of lignin,KOH facili-tated the removal of H2 and CO,leading to the formation of not only more micropores and mesopores,but also more ordered carbon structures.The pore structure exhibited a greater impact than the carbon structure on the electrochemical performance of porous carbon.The optimized porous carbon exhibited a capacitance of 256 F g-1 at a current density of 0.2 A g-1,making it an ideal electrode material for high-performance supercapacitors.展开更多
文摘KOH活化法制备高比表面积活性炭通常需要消耗大量KOH。为提高KOH利用效率,开发了一种基于K插层-脱插循环(以下简称“K循环”)的KOH活化石油焦制备高比表面积活性炭并联产H_(2)的方法:在升温活化过程,KOH与碳质原料反应转化为单质K、K_(2)O和K_(2)CO_(3)并析出H_(2),而K_(2)CO_(3)可继续反应生成单质K和K_(2)O;在降温脱插过程,脱插试剂水蒸气与插层K、游离单质K和K2O反应生成KOH和H_(2);生成的KOH在二次升温活化时再次与碳质原料反应,如此构成K循环。在水平舟式反应器中考察了碳质原料种类(石油焦和石墨)、活化剂KOH和其活化中间产物K_(2)CO_(3)对活化过程气体产物析出规律和产品活性炭孔隙结构性质的影响,并在此基础上分析了K循环机理。结果表明,K循环效率和H_(2)产量因所用碳质原料与活化剂不同而不同:石油焦的反应活性远高于石墨,KOH活化性能优于K_(2)CO_(3)。在KOH活化石油焦的K循环过程中,KOH转化率达80%,而K_(2)CO_(3)转化率为18.5%,经由K_(2)CO_(3)的转化环节决定了K循环效率。以石油焦为碳质原料、KOH为活化剂,在活化温度为800℃及脱插温度为250℃的条件下,4.5 g干燥后的石油焦与13.5 g KOH经二次活化-脱插,所得活性炭比表面积达2808 m^(2)/g,并联产1403 mL/g H_(2)(1 g石油焦产生1403 mL H_(2))。
基金funding from the Key Research and Development Projects of Zhejiang Province(2022C01236)and the Ningbo Top Talent Project.
文摘Lignin-derived porous carbons have emerged as promising electrode materials for supercapacitors.However,the challenge remains in designing and controlling their structure to achieve ideal electrochemical performance due to the complex molecular structure of lignin and its intricate chemical reactions during the activation process.In this study,three porous carbons were synthesized from lignin by spray drying and chemical activation with vary-ing KOH ratios.The specific surface area and structural order of the prepared porous carbon continued to increase with the increase of the KOH ratio.Thermogravimetric-mass spectrometry(TG-MS)was employed to track the molecular fragments generated during the pyrolysis of KOH-activated lignin,and the mechanism of the thermochemical conversion was investigated.During the thermochemical conversion of lignin,KOH facili-tated the removal of H2 and CO,leading to the formation of not only more micropores and mesopores,but also more ordered carbon structures.The pore structure exhibited a greater impact than the carbon structure on the electrochemical performance of porous carbon.The optimized porous carbon exhibited a capacitance of 256 F g-1 at a current density of 0.2 A g-1,making it an ideal electrode material for high-performance supercapacitors.
