Methanol oxidative dehydrogenation and dehydration on carbon nanotubes: active sites and basic reaction kinetics
Methanol oxidative dehydrogenation and dehydration on carbon nanotubes: active sites and basic reaction kinetics
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碳纳米管上甲醇氧化脱氢和脱水：活性中心和基本反应动力学
DOI：
10.1039/d0cy00619j
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发表时间：
2020-08
影响因子：
5
通讯作者：
Pengqiang Yan;Xuefei Zhang;Felix Herold;Fan Li;Xueyan Dai;Tianlong Cao;B. Etzold;W. Qi
中科院分区：
文献类型：
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作者：
Pengqiang Yan;Xuefei Zhang;Felix Herold;Fan Li;Xueyan Dai;Tianlong Cao;B. Etzold;W. Qi
甲醇脱氢制甲醛或脱水制二甲醚都是高附加值的工业工艺。在这里，我们将氧化多壁碳纳米管(OCNTs)应用于氧气存在下的甲醇转化反应。在温和的反应条件下，oCNT催化剂的甲醇转化率为60%，主要产物为二甲醚(65%)和甲酸(30%)，并可长期稳定在150 h以上。碳纳米管的催化性能甚至可以与工业金属催化剂相媲美。现场滴定实验表明，羧基是生成二甲醚的活性中心。作为模型催化剂的有机小分子可能是甲醇脱氢反应生成甲醛的喹诺基，而藜芦酸和酮基共同作用于二氧化碳的总氧化。系统研究了甲醇氧化脱氢脱水的基本反应动力学和反应级数、表观活化能、速率决定步骤等反应机理。碳纳米管催化剂具有独特的温和的氧化还原催化活性，可以减少过氧化损失。
Methanol dehydrogenation to formaldehyde or dehydration to dimethyl ether are high-value-added industrial processes. Here, we applied oxidized multi-walled carbon nanotubes (oCNTs) in a methanol conversion reaction in the presence of oxygen. oCNT catalysts exhibit a methanol conversion of 60% under gentle reaction conditions, yielding DME (65%) and FA (30%) as the main products, and long term stability for over 150 h is achieved. The catalytic performance of oCNTs is even comparable to industrial metal catalysts. An in situ site titration experiment revealed that carboxyl groups were the active sites for the formation of dimethyl ether. Small organic molecules as model catalysts suggested that quinoidic carbonyl groups may be responsible for methanol ODH producing formaldehyde, while both quinoidic and ketonic carbonyl groups are responsible for total oxidation to carbon dioxide. Basic reaction kinetics and mechanisms such as reaction orders, apparent activation energy, rate determining step, etc. for the oxidative dehydrogenation and dehydration of methanol were studied systematically. A unique gentle redox catalytic activity of oCNT catalysts could be realized to reduce the overoxidation losses.