摘要
研究了Mn/Ce摩尔比、反应温度、氧气和水对MnO_(x)-CeO_(2)催化剂催化氯苯氧化性能(活性、选择性和稳定性)的影响,并分析了其理化性能、作用过程和反应机理.结果表明,在含H_(2)Ogas和O_(2)(体积分数均为5%)条件下,Mn_(2)Ce_(1)O_(x)在100,200和300℃下分别取得了80.6%,86.8%和97.5%的氯苯转化率;反应温度和氧气含量的增加及水的存在均有利于提高催化活性和反应稳定性;MnO_(x)和CeO_(2)复合提高了比表面积(128.61 m^(2)/g)、降低了孔径(6.17 nm)且增强了表面酸性(中酸和强酸位点)和氧化还原能力,价态电子交互循环过程(Ce^(4+)/Ce^(3+)←→—Mn^(4+)/Mn^(3+)/Mn_(2)+)和氧循环作用(吸附氧←→—晶格氧)是催化反应的关键驱动过程.氯苯分子吸附在Mn_(2)Ce_(1)O_(x)催化剂表面发生脱氯反应形成苯酚,进一步开环氧化为关键的乙酸盐中间物种,最终转化为CO_(2),HCl或Cl_(2),H_(2)O.水和氧气可以活化为羟基和[O*]等活性氧物种,促进了氯苯的吸附活化和中间产物的深度氧化,降低了中间副产物(氯代乙氧基、苯酚和醛类等)的形成与表面Cl物种的沉积,进而提升了催化活性和反应稳定性.
The influence factors(Mn/Ce molar ratio,reaction temperature,oxygen,water),physicochemical properties,interaction process and reaction mechanism are analyzed and proposed on MnO_(x)-CeO_(2) catalysts for chlorobenzene oxidation performances(activity,selectivity and stability).With 5%(volume fraction)H_(2)O gas and 5%(volume fraction)O_(2),the optimum Mn_(2)Ce_(1)O_(x) catalyst obtains the chlorobenzene conversion rate of 80.6%,86.8%and 97.5%at 100,200 and 300℃,respectively.High reaction temperature,high oxygen content and also the presence of water are beneficial to the improvement of catalytic conversion and reaction stability.The doping proce⁃dure of MnO_(x) and CeO_(2) multi-oxides increases specific surface area to 128.61 m^(2)/g,decreases pore size to 6.17 nm,and strengthens surface acidity(especially at middle&strong acid sites)and also redox performance.The electron interaction(Ce^(4+)/Ce^(3+)←→Mn^(4+)/Mn^(3+)/Mn_(2)+)and oxygen cycle(surface adsorbed oxygen←→lattice oxygen)are the essential driving processes to promote the catalytic oxidation.Chlorobenzene molecules are adsorbed on the surface of Mn_(2)Ce_(1)O_(x) catalyst to de-chlorinate and form phenol,in turn,the ring-opening of aromatic ring is occurred and then oxidated into the formation of most critical acetate intermediates that result in as finial as possible CO_(2),HCl or Cl_(2),H_(2)O.Under the activation actions of water and oxygen molecules to hydroxyl groups and active-oxygen species,the adsorption-activation of chlorobenzene and deep oxidation of intermediates are enhanced and more beneficial to reduce the generation of by-products(chloroethoxyl,phenol and aldehydes,etc.)and also Cl-containing species,thus improving the catalytic activity and reaction stability.
作者
高凤雨
陈都
罗宁
姚小龙
段二红
易红宏
赵顺征
唐晓龙
GAO Fengyu;CHEN Du;LUO Ning;YAO Xiaolong;DUAN Erhong;YI Honghong;ZHAO Shunzheng;TANG Xiaolong(Beijing Key Laboratory of Resource-oriented Treatment of Industrial Pollutants,School of Energy and Environmental Engineering,University of Science and Technology Beijing,Beijing 100083,China;Key Laboratory of Cleaner Production and Integrated Resource Utilization of China National Light Industry,Beijing Technology and Business University,Beijing 100048,China;School of Environmental Science and Engineering,Hebei University of Science and Technology,Shijiazhuang 050018,China)
出处
《高等学校化学学报》
SCIE
EI
CAS
CSCD
北大核心
2023年第4期109-120,共12页
Chemical Journal of Chinese Universities
基金
中国轻工业清洁生产和资源综合利用重点实验室开放课题基金资助课题(批准号:CP2021YB02)
国家自然科学基金(批准号:U20A20130)
中央高校基本科研业务费(批准号:06500152)资助。
