Nanodiamond(ND)has long been recognized as an effective carbocatalyst for synthesizing styrene via direct dehydrogenation(DDH).However,the induced drastic pressure drop of its powder form limits its industrial applica...Nanodiamond(ND)has long been recognized as an effective carbocatalyst for synthesizing styrene via direct dehydrogenation(DDH).However,the induced drastic pressure drop of its powder form limits its industrial application in heterogeneous catalytic process.In this work,we report a facile hexamethylenetetramine nitrate(HN)-assisted thermal impregnation(HNTI)strategy for fabricating a novel nanodiamondbased monolithic foam(ND/CNT-SiC-ms-HN)catalyst through a two-step approach:One is to soak the carbon nanotube-modified Si C foam(CNT-SiC)with the slurry composed of HN,KCl,Li Cl,and dispersed ND,and the other is to heat the slurry-soaked CNT-SiC(ND-HN-KCl-Li Cl/CNT-SiC)in N_(2) atmosphere at750℃.The as-synthesized ND/CNT-SiC-ms-HN monolithic foam features the enriched surface kenotic C=O by promoted ND dispersion and O-doping,abundant stuctural defects,and improved nucleophilicity by N-doping,originating from the promoted ND dispersion by thermal impregnation(TI)in KCl-LiCl molten salt(MS)and the presence of HN in the annealing process.As a result,the ND/CNT-Si C-ms-HN monolithic foam catalyst by HNTI strategy exhibits 1.5 folds higher steady-state styrene rate(5.49 mmol g^(-1)h^(-1))associated with 98.4%of styrene selectivity compared to the ND-based monolithic foam catalyst(ND/CNT-SiC).Moreover,the ND/CNT-Si C-ms-HN monolithic foam shows excellent long-term stability for the direct dehydrogenation of ethylbenzene to styrene.This work also comes up with a novel way of preparing other highly-dispersed nanocarbons-based monolithic foam catalysts with promising catalytic performance for diverse transformations.展开更多
Synthesis of hybrid carbon materials with core-shell structure and robust catalytic performance is of great research interest,and remains a great challenge in catalytic dehydrogenation of hydrocarbons reaction.In this...Synthesis of hybrid carbon materials with core-shell structure and robust catalytic performance is of great research interest,and remains a great challenge in catalytic dehydrogenation of hydrocarbons reaction.In this paper,few-layer sp^(2) carbon decorated SiC nanocrystals with core-shell structure(SiC@C)were fabricated through a dual-confined magnesiothermic method by employing glucose and SiO_(2) as precursors.The SiC@C nanocrystals were further crosslinked to be a three dimensional(3D)mesoporous hybrid by the in situ generated carbon as binders and exhibiting a 410.30 m^(2) g^(−1) large surface area.The as-prepared SiC@C hybrid materials as metal-free catalysts were evaluated in the steam-free direct dehydrogenation of ethylbenzene to styrene.Benefiting from the abundant surface carbonyl groups on the graphite carbon layers,the optimized yield rate of styrene normalized by carbon mass was as high as 11.58 mmol g^(−1) carbon h^(−1),nearly 4 times that of nanodiamonds.Considering the low cost and excellent catalytic activity,the hybrid 3D SiC@C material may be a promising candidate for direct dehydrogenation of hydrocarbons.展开更多
基金financially supported by the National Natural Science Foundation of China(No.21676046)the Chinese Ministry of Education via the Program for New Century Excellent Talents in Universities(No.NCET-12-0079)。
文摘Nanodiamond(ND)has long been recognized as an effective carbocatalyst for synthesizing styrene via direct dehydrogenation(DDH).However,the induced drastic pressure drop of its powder form limits its industrial application in heterogeneous catalytic process.In this work,we report a facile hexamethylenetetramine nitrate(HN)-assisted thermal impregnation(HNTI)strategy for fabricating a novel nanodiamondbased monolithic foam(ND/CNT-SiC-ms-HN)catalyst through a two-step approach:One is to soak the carbon nanotube-modified Si C foam(CNT-SiC)with the slurry composed of HN,KCl,Li Cl,and dispersed ND,and the other is to heat the slurry-soaked CNT-SiC(ND-HN-KCl-Li Cl/CNT-SiC)in N_(2) atmosphere at750℃.The as-synthesized ND/CNT-SiC-ms-HN monolithic foam features the enriched surface kenotic C=O by promoted ND dispersion and O-doping,abundant stuctural defects,and improved nucleophilicity by N-doping,originating from the promoted ND dispersion by thermal impregnation(TI)in KCl-LiCl molten salt(MS)and the presence of HN in the annealing process.As a result,the ND/CNT-Si C-ms-HN monolithic foam catalyst by HNTI strategy exhibits 1.5 folds higher steady-state styrene rate(5.49 mmol g^(-1)h^(-1))associated with 98.4%of styrene selectivity compared to the ND-based monolithic foam catalyst(ND/CNT-SiC).Moreover,the ND/CNT-Si C-ms-HN monolithic foam shows excellent long-term stability for the direct dehydrogenation of ethylbenzene to styrene.This work also comes up with a novel way of preparing other highly-dispersed nanocarbons-based monolithic foam catalysts with promising catalytic performance for diverse transformations.
基金supported by the Ministry of Science and Technology(No.2016YFA0204100)the National Natural Science Foundation of China(Nos.21703261,91845201,21961160722 and 22072162)+1 种基金the Institute of Metal Research,the Liaoning Revitalization Talents Program(No.XLYC1907055)the Sinopec China and the Joint fund between Shenyang National Laboratory for Materials Science and State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals(No.18LHPY010)。
文摘Synthesis of hybrid carbon materials with core-shell structure and robust catalytic performance is of great research interest,and remains a great challenge in catalytic dehydrogenation of hydrocarbons reaction.In this paper,few-layer sp^(2) carbon decorated SiC nanocrystals with core-shell structure(SiC@C)were fabricated through a dual-confined magnesiothermic method by employing glucose and SiO_(2) as precursors.The SiC@C nanocrystals were further crosslinked to be a three dimensional(3D)mesoporous hybrid by the in situ generated carbon as binders and exhibiting a 410.30 m^(2) g^(−1) large surface area.The as-prepared SiC@C hybrid materials as metal-free catalysts were evaluated in the steam-free direct dehydrogenation of ethylbenzene to styrene.Benefiting from the abundant surface carbonyl groups on the graphite carbon layers,the optimized yield rate of styrene normalized by carbon mass was as high as 11.58 mmol g^(−1) carbon h^(−1),nearly 4 times that of nanodiamonds.Considering the low cost and excellent catalytic activity,the hybrid 3D SiC@C material may be a promising candidate for direct dehydrogenation of hydrocarbons.