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CO x ‐Resistant Oxidative Dehydrogenation of Cyclohexane Catalyzed by sp 3 @sp 2 Nanodiamonds towards Highly Selective Cyclohexene Production
Author(s) -
Du Pengfei,
Zhang XinXing,
Zhang Shaoqian,
Zhao Yang,
Zhang Liyun,
Zhang Bingsen,
Yang Bing
Publication year - 2021
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.202001380
Subject(s) - dehydrogenation , cyclohexene , cyclohexane , catalysis , chemistry , selectivity , bond cleavage , oxide , photochemistry , reactivity (psychology) , benzene , metal , inorganic chemistry , organic chemistry , medicine , alternative medicine , pathology
Deep oxidation/dehydrogenation are longstanding problems for decades in catalytic oxidative dehydrogenation (ODH) of cyclohexane and other alkanes. Here we show a metal‐free catalyst of nanodiamonds (NDs) with unique sp 3 @sp 2 hybrid structure that catalyzes CO x ‐resistant cyclohexane ODH with remarkable reactivity towards cyclohexene production. The selectivity of cyclohexene can reach as high as 67 % with significantly suppressed CO x emission (<5 %), which is on top of the highest reported values among other metal(oxide)/metal‐free catalysts. Structural evolution of sp 3 @sp 2 NDs under annealing treatments and their specific surface functional groups are systematically studied using TEM, XPS, Raman and TPD. By comparing with carbon nanotubes (CNTs), we found that the carbonyl groups stabilized on strained sp 3 @sp 2 core‐shell NDs enhanced the cyclohexene selectivity via preferential cleavage of C−H over C−C bond. Kinetic studies further revealed the underlying reaction pathways that cyclohexane is rapidly dehydrogenated to cyclohexene which subsequently transforms into benzene (fast) and CO x (slow). Deep oxidation of both cyclic hydrocarbons is largely suppressed due to the low density of electrophilic functional groups on strongly curved graphitic surface of sp 3 @sp 2 NDs.