非甲烷总烃分析仪专用Co_(3)O_(4)/Al_(2)O_(3)催化剂的制备及性能研究

Preparation and catalytical performance study of Co_(3)O_(4)/Al_(2)O_(3) for the analysis of non-methane total hydrocarbon

挥发性有机化合物(volatile organic compounds,VOCs)是引发霾和光化学烟雾等环境问题的重要原因,达到一定浓度会对人类健康造成威胁。非甲烷总烃(non-methane hydrocarbon,NMHC)作为VOCs总量统计的重要指标,在一定程度上可以简单、直观地反映VOCs污染状况,因此,监控NMHC对保护环境与人类健康具有重要意义。本文中制备了层状结构、球形结构和立方体结构3种不同形貌的Co_(3)O_(4)纳米材料,将纳米材料均匀负载于活性Al_(2)O_(3)颗粒表面作为NMHC分析专用催化剂。通过XRD、FESEM、BET和XPS技术对制备的Co_(3)O_(4)催化剂进行表征;并将催化剂用于NMHC的检测,对不同形貌催化剂的催化性能进行评价。结果表明,当煅烧温度为400℃、煅烧时间为3 h,催化剂具有较高的催化活性,其中立方体结构催化剂具有最高的催化活性,能在236℃将NMHC完全降解,层状结构与球形结构催化剂分别在261℃与257℃将NMHC完全降解。升高煅烧温度有助于催化活性的提高,因为煅烧温度的升高增大了催化剂中Co_(3)O_(4)的相对结晶度与O_(ads)/O_(latt)摩尔比,使得气体转移速度加快,因而使催化剂具有更高的催化活性。催化剂经过耐水性、热失重测试与催化循环测试后仍能保持较高的催化活性。

Volatile organic compounds(VOCs) not only contribute seriously to environmental issues such as smog and photochemical smog but can also pose a threat to human health at certain concentrations.Non-methane hydrocarbon(NMHC) is an important indicator for estimating the total quantity of VOCs and can provide a simple and intuitive representation of VOC pollution levels to a certain extent.Therefore,monitoring NMHC is of great significance to protect the environment and human health.This study prepared Co_(3)O_(4) nanomaterials with three different morphologies:layered,spherical,and cubic structures.The nanomaterials were evenly loaded onto the surface of active Al_(2)O_(3) particles for using as catalysts specifically for NMHC analyzers.The Co_(3)O_(4) catalysts were characterized using XRD,FESEM,BET,and XPS techniques and then used in an NMHC assay to evaluate the performance of different morphology catalysts.When the calcination temperature was 400 ℃ and the time was 3 hours,the catalysts demonstrated the highest catalytic activity.The cubic structure catalyst had the highest catalytic activity and could completely degrade NMHC at 236 ℃.The layered structure and spherical structure catalysts completely degraded NMHC at 261 ℃ and 257 ℃ respectively.Increasing the calcination temperature improved catalytic activity by increasing the crystallinity and O_(ads)/O_(latt) molar ratio of the catalysts,resulting in higher catalytic activity due to faster gas transfer.The catalysts tested for water resistance,heat weight loss and catalytic cycling,and still maintained a high catalytic activity.