Cu-Al尖晶石的合成及非等温生成动力学分析  

Synthesis of Cu-Al spinels and its non-isothermal formation kinetics analysis

作　　者：刘雅杰 庆绍军[2] 侯晓宁[2] 张磊[3] 高志贤 相宏伟[2] LIU Ya-jie;QING Shao-jun;HOU Xiao-ning;ZHANG Lei;GAO Zhi-xian;XIANG Hong-wei(College of Chemistry and Chemical Engineering,Jinzhong University,Jinzhong 030600,China;Institute of Coal Chemistry,Chinese Academy of Sciences,Taiyuan 030001,China;Liaoning Shihua University,Fushun 113001,China)

机构地区：[1]晋中学院化学化工学院,山西晋中030600 [2]中国科学院山西煤炭化学研究所,山西太原030001 [3]辽宁石油化工大学,辽宁抚顺113001

出　　处：《燃料化学学报》2020年第3期338-348,I0006,共12页Journal of Fuel Chemistry and Technology

基　　金：国家自然科学基金(21673270);山西省高等学校科技创新项目(2019L0880);晋中学院博士科研经费(2019)资助。

摘　　要：以程序升温碳化法合成β-Mo2C载体,采用原位沉淀法制备负载量不同的Au/β-Mo2C催化剂,利用XRD、STEM和氮气吸附-脱附等手段对Au在载体表面的分散性、微观形貌及孔结构等进行表征,并在逆水煤气变换(RWGS)反应中对其高温热稳定性进行了研究。XRD表征结果表明,在34.44°、38.02°、39.44°、52.12°、61.53°、69.62°和74.65°处出现了β-Mo2C对应的(100)、(002)、(101)、(102)、(110)、(103)和(200)晶面的X射线特征衍射峰;同时,未出现Au物种的特征吸收峰,说明Au负载量较低的0.1%和0.5%的催化剂上Au纳米粒子的分散性较好。STEM表征结果也显示,当负载量较低(0.5%、1.0%和2.0%)时,金纳米粒子以2 nm左右的原子簇形式均匀分散并锚定在β-Mo2C载体上。氮气吸附-脱附表征结果表明,催化剂具有良好的介孔结构。反应评价结果表明,0.2%Au/β-Mo2C催化剂在RWGS反应中具有较好的催化活性和较高的CO选择性,且反应后孔结构良好,Au纳米粒子仍然均匀分散,说明Au/β-Mo2C催化剂在此反应中具有较高的催化性能和高温热稳定性。Cu-Al spinels were synthesized by a solid phase method using Cu(OH)2 and pseudo-boehmite as the raw materials.The effects of synthesis temperature,synthesis time and Cu/Al molar ratio on the formation and properties of Cu-Al spinels were fully investigated by the thermogravimetry(TG/DTG),X-ray diffraction(XRD),H2 temperature programmed reduction(H2-TPR).The non-isothermal kinetics of Cu-Al spinel formation process were analyzed using Coats-Redfern method and two diffusion-controlled kinetic models.Characterization results showed that the Cu-Al surface spinels with unsaturated coordination formed easily at the temperature as low as 400℃,and the content of these surface spinel decreased sharply with the synthesis temperature rising.The hardly-reducible spinel Cu^2+species and easily-reducible spinel Cu^2+species were identified at the synthesis temperature of 700 and 800℃,respectively.The spinel content increased gradually with the synthesis temperature increasing,leading to the formation of Al-rich spinel solid solutions with different Cu/Al molar ratios.At a higher temperature of 1200℃,however,the formation of stoichiometric CuAl2O4 spinel was observed.Hence,the spinel reducibility varied dramatically with the synthesis temperature as illustrated by the drastic change of the molar ratio of hardly-reducible spinel Cu^2+species and easily-reducible spinel Cu^2+species.An appropriate excess of Al3+(Cu/Al=1∶3)could result in the formation of spinel solid solution with more hardly-reducible spinel Cu^2+species,while an excess of Cu^2+would lead to the formation of delafossite-type CuAlO2.Both samples owned low reducibility as compared to the stochiometric CuAl2O4 spinel.Besides,a longer synthesis time would favor the spinel formation as well but to a limited extent.Non-isothermal kinetics analysis showed that the formation process of Cu-Al spinel owned three kinetic regions in terms of synthesis temperature,namely 700-850,850-950 and 950-1200℃,and the apparent activation energies were determined to be 85.2,3

关 键 词：原位沉淀 晶格取向 RWGS反应 热稳定性 催化剂 

分 类 号：O643[理学—物理化学]