碱性位和缺陷对MgAl-LDHs催化芴与CO_(2)直接羧基化反应的影响  

Effects of basic sites and defects of MgAl-LDHs on direct carboxylation of fluorene with CO_(2)

作　　者：郝洪波 高卿 叶翠平[1] 穆建丽 李文英[2] HAO Hongbo;GAO Qing;YE Cuiping;MU Jianli;LI Wenying(College of Environment and Ecology,Taiyuan University of Technology,Jinzhong 030600,China;State Key Laboratory of Clean and Efficient Coal Utilization,Taiyuan University of Technology,Taiyuan 030024,China)

机构地区：[1]太原理工大学环境与生态学院,山西晋中030600 [2]太原理工大学省部共建煤基能源清洁高效利用国家重点实验室,山西太原030024

出　　处：《燃料化学学报(中英文)》2025年第4期472-480,共9页Journal of Fuel Chemistry and Technology

基　　金：国家自然科学基金(22038008);山西浙大新材料与化工研究院项目(2021SX-FR003)资助。

摘　　要：将CO_(2)转化为高附加值的化学品,对于缓解CO_(2)造成的环境污染和减少对化石能源的依赖至关重要。而以CO_(2)为羧基源直接合成羧酸是其资源化利用的重要途径。为了实现CO_(2)在温和条件下的高效转化,实验考察了无水K_(2)CO_(3)、K_(2)CO_(3)/LDHs、K_(2)CO_(3)+LDHs/LDO等固体碱对CO_(2)直接羧基化合成9-芴甲酸(9-FCA)的影响,结合XPS、XRD、CO_(2)-TPD及FT-IR等探讨了其催化活性存在差异的原因。结果表明,仅使用K_(2)CO_(3)时,9-芴甲酸的产率为64.61%。再生过程中K_(2)CO_(3)从γ-K_(2)CO_(3)相转变为低活性的β-K_(2)CO_(3)相,碱性位点减少,碱量降低,导致催化活性下降。负载K_(2)CO_(3)会影响LDHs碱性中心的数量和碱强度,Mg_(2)Al-LDH-C-40%和Mg_(3)Al-LDH-H-40%对应的9-芴甲酸产率分别为66.15%和44.45%。焙烧后Mg_(2)Al-LDO-500尖晶石相(MgAl_(2)O_(4))增加,羟基(-OH)减少、结晶度降低、中等强度碱性位点和氧空位(Ov)增加,添加量为K_(2)CO_(3)的7%时,9-芴甲酸的产率提升至78.36%。Converting CO_(2)into high value-added chemicals is essential for mitigating environmental pollution caused by CO_(2)and reducing dependence on fossil fuels.One significant approach to resource utilization is the direct synthesis of carboxylic acids using CO_(2)as a carboxyl source.Utilizing fluorene as the raw material along with CO_(2)for the synthesis of 9-fluorenecarboxylic acid(9-FCA)provides a readily available feedstock while eliminating the need for toxic phosgene or carbon monoxide.Due to the thermodynamic stability and kinetic inertness of CO_(2),an appropriate catalytic system is crucial for ensuring that the reaction proceeds efficiently.Layered double hydroxides(LDHs)represent an important class of solid bases that facilitate the control of alkalinity by adjusting the composition and ratio of M^(2+)and M^(3+)elements within the LDH layers.Their catalytic performance is influenced by both the basic strength and the quantity of the active phase.Layered double oxides(LDOs),which are derived from LDHs after calcination,exhibit developed pore structures and abundant tunable surface basic sites,which are beneficial for the adsorption and activation of CO_(2).Exploring and understanding the effects of basic sites and defects on the direct carboxylation of fluorene with CO_(2)catalyzed by MgAl-LDHs is beneficial to the non-dissociation activation of CO_(2)and has certain reference significance for improving the yield of 9-FCA under mild conditions.To achieve efficient CO_(2)conversion under mild conditions,this study investigates the effects of solid bases such as anhydrous K_(2)CO_(3),K_(2)CO_(3)/LDHs and K_(2)CO_(3)+LDHs/LDO on the direct carboxylation of CO_(2)to synthesize 9-FCA.The variations in catalytic activity were analyzed using X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD),CO_(2)temperature-programmed desorption(CO_(2)-TPD),and Fourier-transform infrared spectroscopy(FT-IR).Results indicate that during the recycling of K_(2)CO_(3),weak alkaline sites gradually transform into medium-

关 键 词：碱性位 缺陷 MgAl-LDHs/LDO CO_(2) 羧基化反应 

分 类 号：O621.3[理学—有机化学]