摘要
在固定床反应器中进行了HZSM 5分子筛催化剂催化苯氧化生成苯酚时的积炭和失活实验 ,催化剂经高温水蒸气处理 ,反应条件为 :9 7%N2 O 90 3%N2 混合气流速 115ml/min ,苯流速 6 g/h ,反应温度 4 0 0℃ .采用TG ,吸附吡啶的IR谱 ,13 CNMR和低温N2 吸附法对催化剂进行了表征 ,并用连续流动吸附法测定催化剂上正己烷和环己烷的吸附量 .结果表明 ,苯氧化生成苯酚的反应过程中 ,催化剂表面积炭导致分子筛微孔孔口堵塞是造成催化剂失活的主要原因 .与其他有机物在ZSM 5上的积炭相似 ,B酸中心是积炭的活性中心 .积炭物种主要为带有烷基的芳烃和多环芳烃 ,同时含有少量带有羟基的多环芳烃 ,这可能是由在L酸中心上生成的苯酚进一步氧化、脱氢和聚合形成的 .
Coking and deactivation experiments of HZSM-5 zeolite catalyst during benzene oxidation to phenol were carried out in a fixed-bed reactor, and the zeolite was pretreated with steam at high temperature. The reaction conditions were catalyst loading of 1 g, 9.7% N2O-90.3 % N-2 (flow rate 115 ml/min), benzene flow rate of 6 g/h, reaction temperature of 400 degreesC and reaction time of 0similar to6 h. The catalyst was characterized by TG, IR after pyridine adsorption, C-13 NMR and N-2 adsorption techniques. The adsorption amount of hexane and cyclohexane was measured by continuous flow method. The results showed that the deactivation of HZSM-5 was due to the coke formed on the catalyst surface which blocked the pore mouth of zeolite channels. Similar to most coking processes of other organic compounds on ZSM-5 zeolite, Bronsted acid sites were the active sites which promoted coke formation. The coke consisted mainly of aromatic compounds with alkyl and polycyclic aromatic hydrocarbons, and it also comprised some aromatic compounds with hydroxy group produced by further oxidation, dehydrogenation and polymerization of phenol on Lewis acid sites.
出处
《催化学报》
SCIE
CAS
CSCD
北大核心
2005年第1期10-14,共5页
