摘要
以尿素为沉淀剂,通过均相沉积-沉淀法合成了CuO/CNTs(CNTs即碳纳米管)复合材料,对CuO/CNTs在不同气氛和温度下进行预处理;并采用X射线衍射(XRD)和透射电子显微镜(TEM)对预处理后的CuO_(x)/CNTs催化剂的物相结构、微观形貌和粒径大小进行了表征,发现不同预处理方式可以控制Cu物种的价态分布;然后详细研究了Cu物种的价态对CuO/CNTs催化丙烯氧气环氧化反应性能的影响。结果表明:随着N_(2)预处理温度升高,Cu^(2+)物种逐渐被CNTs还原为Cu^(+)物种,Cu^(+)物种进一步被还原为Cu^(0)物种,但是由于CNTs的限域效应,Cu物种的形貌和粒径大小几乎没有发生变化;CuO_(x)/CNTs的丙烯环氧化反应活性随着N_(2)预处理温度的升高先增加后降低,当N_(2)预处理温度为350℃时,Cu^(+)物种含量最高,此时环氧丙烷的形成速率最大;CuO_(x)/CNTs催化剂上丙烯环氧化反应活性的变化趋势与Cu^(+)物种含量的变化趋势完全一致,Cu^(+)物种最有利于环氧丙烷的生成,有可能是CuO_(x)/CNTs催化剂上丙烯氧气环氧化反应的活性中心。
CuO_(x)/CNTs samples were synthesized by a homogeneous deposition-precipitation method using urea as precipitation reagent.The crystalline phase,morphology and size of CuO_(x)/CNTs catalysts with different pretreatment atmospheres and temperatures were characterized by XRD and TEM,respectively.The valence state of Cu species is adjusted by different pretreatment methods,and the catalytic activities of CuO_(x)/CNTs catalysts with different valence states of Cu species in propylene epoxidation were also detailedly investigated.With elevating the N_(2)pretreatment temperatures,Cu^(2+)species are gradually reduced to Cu^(+)species and then Cu^(+)species was further reduced to metallic Cu^(0)by CNTs.However,the morphology and size of Cu species remains almost unchanged due to the confinement effect of CNTs.Catalytic performance of CuO_(x)/CNTs catalysts in propylene epoxidation is increasing at first and then decreasing with enhancement of N_(2)pretreatment temperatures.The propylene oxide formation rate and the content of Cu^(+)species both reach the highest value when CuO_(x)/CNTs is pretreated in N_(2)at 350℃.The propylene epoxidation activity is in good agreement with the content of Cu^(+)species,hence Cu^(+)species are beneficial to produce propylene oxide and Cu^(+)species are the main active site for propylene epoxidation reaction over CuO_(x)/CNTs catalyst by oxygen.
作者
苏暐光
孔磊
张策
宋旭东
王焦飞
于广锁
姚敏
SU Weiguang;KONG Lei;ZHANG Ce;SONG Xudong;WANG Jiaofei;YU Guangsuo;YAO Min(College of Chemistry and Chemical Engineering,State Key Laboratory of High-Efficiency Utilization of Coal and Green Chemical Engineering,Ningxia University,Yinchuan 750021,China;Chinese Energy Ningxia Coal Industry Co.Ltd.,Yinchuan 750001,China)
出处
《石油学报（石油加工）》
EI
CAS
CSCD
北大核心
2021年第4期858-865,共8页
Acta Petrolei Sinica(Petroleum Processing Section)
基金
国家自然科学基金项目(21463018)
2017年宁夏重点研发(西部之光)项目
宁夏重大研发计划项目(2019BCH01001)
宁夏重点研发计划项目(2019BDE03003)基金资助。
