Direct conversion of methane to formaldehyde and CO on B2O3 catalysts

甲烷作为天然气的主要成分，是非常重要的碳基资源。不过，甲烷分子的化学惰性使得其转化通常需要在高温条件下进行，反应选择性难于控制。如何实现甲烷的高选择性定向转化一直是化学研究中的重要挑战，甚至被誉为化学领域的“圣杯”。化学化工学院王帅教授与华盛顿州立大学王勇教授合作在甲烷选择氧化反应非金属硼基催化剂的研究中取得重要进展，本研究中发现负载型氧化硼催化剂在甲烷直接氧化反应中表现出优异的抗深度氧化能力。本研究工作是在王帅教授和王勇教授的共同指导下完成。2015级博士生田金树（已毕业）、硕士生谈江乔（已毕业）以及醇醚酯清洁生产国家工程实验室张朝霞工程师为共同第一作者，林敬东副教授和万绍隆副教授等参与了部分研究和讨论。【Abstract】Direct oxidation of methane to value-added C1 chemicals (e.g. HCHO and CO) provides a promising way to utilize natural gas sources under relatively mild conditions. Such conversions remain, however, a key selectivity challenge, resulting from the facile formation of undesired fully-oxidized CO2. Here we show that B2O3-based catalysts are selective in the direct conversion of methane to HCHO and CO (~94% selectivity with a HCHO/CO ratio of ~1 at 6% conversion) and highly stable (over 100 hour time-on-stream operation) conducted in a fixed-bed reactor (550 °C, 100 kPa, space velocity 4650 mL gcat−1 h−1 ). Combined catalyst characterization, kinetic studies, and isotopic labeling experiments unveil that molecular O2 bonded to tri-coordinated BO3 centers on B2O3 surfaces acts as a judicious oxidant for methane activation with mitigated CO2 formation, even at high O2/CH4 ratios of the feed. These findings shed light on the great potential of designing innovative catalytic processes for the direct conversion of alkanes to fuels/chemicals.This work was supported by the National Natural Science Foundation of China (No. 21922201, 21872113, 91945301, 21673189, and 91545114) and the Fundamental Research Funds for the Central Universities (No. 20720190036 and 20720160032).研究工作得到了国家自然科学基金（21922201、21872113、91945301、21673189、91545114）和中央高校基本科研业务费专项资金（20720190036、20720160032）的资助与支持