Utilizing single atom sites doping into metal oxides to modulate their intrinsic active sites,achieving precise selectivity control in complex organic reactions,is a highly desirable yet challenging endeavor.Meanwhile...Utilizing single atom sites doping into metal oxides to modulate their intrinsic active sites,achieving precise selectivity control in complex organic reactions,is a highly desirable yet challenging endeavor.Meanwhile,identifying the active site also represents a significant obstacle,primarily due to the intricate electronic environment of single atom site doped metal oxide.Herein,a single atom Cu doped TiO_(2)catalyst(Cu_(1)-TiO_(2)) is prepared via a simple“colloid-acid treatment”strategy,which switches aniline oxidation selectivity of TiO_(2) from azoxybenzene to nitrosobenzene,without using additives or changing solvent,while other metal or nonmetal doped TiO_(2) did not possess.Comprehensive mechanistic investigations and DFT calculations unveil that Ti-O active site is responsible for triggering the aniline to form a new PhNOH intermediate,two PhNOH condense to azoxybenzene over TiO_(2) catalyst.As for Cu_(1)-TiO_(2),the charge-specific distribution between the isolated Cu and TiO_(2) generates unique Cu_(1)-O-Ti hybridization structure with nine catalytic active sites,eight of them make PhNOH take place spontaneous dissociation to produce nitrosobenzene.This work not only unveils a new mechanistic pathway featuring the PhNOH intermediate in aniline oxidation for the first time but also presents a novel approach for constructing single-atom doped metal oxides and exploring their intricate active sites.展开更多
A series of CuSO4/TiO2 catalysts were prepared using a wet impregnation method.The activity of each sample in the selective catalytic reduction of NO by NH3（NH3-SCR） was determined.The effects of SO2 and H2O,and the...A series of CuSO4/TiO2 catalysts were prepared using a wet impregnation method.The activity of each sample in the selective catalytic reduction of NO by NH3（NH3-SCR） was determined.The effects of SO2 and H2O,and their combined effect,on the activity were examined at 340 ℃ for 24 h.The catalysts were characterized using N2 adsorption-desorption,X-ray diffraction,X-ray photoelectron spectroscopy,temperature-programmed reduction of H2（H2-TPR）,temperature-programmed desorption of NH3（NH3-TPD）,and in situ diffuse-reflectance infrared Fourier-transform spectroscopy（DRIFTS）.The CuSO4/TiO2 catalysts had good activities,with low production of N2O above 340 ℃.SO2 or a combination of SO2 and H2O had little effect on the activity,and H2O caused only a slight decrease in activity during the experimental period.The NH3-TPD and H2-TPR results showed that CuSO4 increased the amounts of acid sites and adsorbed oxygen on the catalyst.In situ DRIFTS showed that the NH3-SCR reaction on the CuSO4/TiO2 catalysts followed an Eley-Rideal mechanism.The reaction of gaseous NO with NH3 adsorbed on Lewis acid sites to form N2 and H2O could be the main reaction pathway,and oxygen adsorption might favor this process.展开更多
The selective oxidation of alcohol using molecular oxygen as an oxidant and water as a green sol‐vent is of great interest in green chemistry. In this work, we present a systematic study of a Pt/ZnO catalyst for the ...The selective oxidation of alcohol using molecular oxygen as an oxidant and water as a green sol‐vent is of great interest in green chemistry. In this work, we present a systematic study of a Pt/ZnO catalyst for the selective oxidation of benzyl alcohol at room temperature under base‐free aqueous conditions. Experimental observations and density functional theory calculations suggest that ZnO as a support can facilitate the adsorption of benzyl alcohol, which subsequently reacts with the activated oxygen species on the Pt catalyst, producing benzaldehyde. The resulting solid achieves a high conversion（94.1 ± 5.1% in 10 h） of benzyl alcohol and nearly 100% selectivity to benzalde‐hyde with ambient air as the oxidant. In addition, by introducing a small amount of Bi（1.78 wt%） into Pt/ZnO, we can further enhance the activity by 350%.展开更多
Objective: To explore the characteristics of NF-闎 activation in the progress of pancreatitis, the relationship with expression of TNF- in the inflammatory reaction, and prevent the exacerbation of pancreatitis by usi...Objective: To explore the characteristics of NF-闎 activation in the progress of pancreatitis, the relationship with expression of TNF- in the inflammatory reaction, and prevent the exacerbation of pancreatitis by using NAC. Method: Forty-eight rats were divided into three groups: therapy (group C), pancreatitis (group B) and control (group A). NAC served as the inhibitor of NF-闎 activation. In the time intervals of 1.5, 3.0, 6.0, 12.0 hour, NF-闎 activation was detected with flow cytometry (FCM) and the expression of TNF- mRNA and protein with in situ hybridization (ISH) and enzyme-linked immuno-sorbent assay (ELISA) respectively. Meanwhile, the level of lipase and amylase in the serum was assayed and the pathological change was evaluated. Result: NF-闎 activation in the pancreatitis group was higher than that in the control group (P<0.01), peaked at 3 hours, and was depressed by the inhibitor of NF-闎, NAC. The expression of TNF- as well as the level of lipase and amylase in the serum also rose synchronously with activation of NF-闎. In contrast to group A, it was significantly different (P<0.01) in group B. After using NAC in group C, all of these values were decreased and the in-flammatory reaction in the pancreas abated evidently. The pathology changes of the pancreas were shown to be alleviated in group C. Conclusion: First, NF-闎 activity is intensively initiated in the course of pancreatitis and shown to have closely relationship with the release of cytokines. Second, use of NAC markedly depressed NF-闎 activation. TNF- expression is down regulated by cytokines. It is suggested that NAC probably acts as a useful agent for treatment of pancreatitis by indirectly inhibiting activation of NF-闎.展开更多
文摘Utilizing single atom sites doping into metal oxides to modulate their intrinsic active sites,achieving precise selectivity control in complex organic reactions,is a highly desirable yet challenging endeavor.Meanwhile,identifying the active site also represents a significant obstacle,primarily due to the intricate electronic environment of single atom site doped metal oxide.Herein,a single atom Cu doped TiO_(2)catalyst(Cu_(1)-TiO_(2)) is prepared via a simple“colloid-acid treatment”strategy,which switches aniline oxidation selectivity of TiO_(2) from azoxybenzene to nitrosobenzene,without using additives or changing solvent,while other metal or nonmetal doped TiO_(2) did not possess.Comprehensive mechanistic investigations and DFT calculations unveil that Ti-O active site is responsible for triggering the aniline to form a new PhNOH intermediate,two PhNOH condense to azoxybenzene over TiO_(2) catalyst.As for Cu_(1)-TiO_(2),the charge-specific distribution between the isolated Cu and TiO_(2) generates unique Cu_(1)-O-Ti hybridization structure with nine catalytic active sites,eight of them make PhNOH take place spontaneous dissociation to produce nitrosobenzene.This work not only unveils a new mechanistic pathway featuring the PhNOH intermediate in aniline oxidation for the first time but also presents a novel approach for constructing single-atom doped metal oxides and exploring their intricate active sites.
基金supported by the Bureau of Science and Technology,Fujian Province,China(2015H0043)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB05050500)the National Natural Science Foundation of China(21403210)~~
文摘A series of CuSO4/TiO2 catalysts were prepared using a wet impregnation method.The activity of each sample in the selective catalytic reduction of NO by NH3（NH3-SCR） was determined.The effects of SO2 and H2O,and their combined effect,on the activity were examined at 340 ℃ for 24 h.The catalysts were characterized using N2 adsorption-desorption,X-ray diffraction,X-ray photoelectron spectroscopy,temperature-programmed reduction of H2（H2-TPR）,temperature-programmed desorption of NH3（NH3-TPD）,and in situ diffuse-reflectance infrared Fourier-transform spectroscopy（DRIFTS）.The CuSO4/TiO2 catalysts had good activities,with low production of N2O above 340 ℃.SO2 or a combination of SO2 and H2O had little effect on the activity,and H2O caused only a slight decrease in activity during the experimental period.The NH3-TPD and H2-TPR results showed that CuSO4 increased the amounts of acid sites and adsorbed oxygen on the catalyst.In situ DRIFTS showed that the NH3-SCR reaction on the CuSO4/TiO2 catalysts followed an Eley-Rideal mechanism.The reaction of gaseous NO with NH3 adsorbed on Lewis acid sites to form N2 and H2O could be the main reaction pathway,and oxygen adsorption might favor this process.
基金supported by the National Natural Science Foundation of China (21703050, 21271153, 21373181)China Postdoctoral Science Foun‐dation (512200‐X91701)Special Research Foundation of Young Teachers in Hangzhou Dianzi University (ZX150204307002/032)~~
文摘The selective oxidation of alcohol using molecular oxygen as an oxidant and water as a green sol‐vent is of great interest in green chemistry. In this work, we present a systematic study of a Pt/ZnO catalyst for the selective oxidation of benzyl alcohol at room temperature under base‐free aqueous conditions. Experimental observations and density functional theory calculations suggest that ZnO as a support can facilitate the adsorption of benzyl alcohol, which subsequently reacts with the activated oxygen species on the Pt catalyst, producing benzaldehyde. The resulting solid achieves a high conversion（94.1 ± 5.1% in 10 h） of benzyl alcohol and nearly 100% selectivity to benzalde‐hyde with ambient air as the oxidant. In addition, by introducing a small amount of Bi（1.78 wt%） into Pt/ZnO, we can further enhance the activity by 350%.
文摘Objective: To explore the characteristics of NF-闎 activation in the progress of pancreatitis, the relationship with expression of TNF- in the inflammatory reaction, and prevent the exacerbation of pancreatitis by using NAC. Method: Forty-eight rats were divided into three groups: therapy (group C), pancreatitis (group B) and control (group A). NAC served as the inhibitor of NF-闎 activation. In the time intervals of 1.5, 3.0, 6.0, 12.0 hour, NF-闎 activation was detected with flow cytometry (FCM) and the expression of TNF- mRNA and protein with in situ hybridization (ISH) and enzyme-linked immuno-sorbent assay (ELISA) respectively. Meanwhile, the level of lipase and amylase in the serum was assayed and the pathological change was evaluated. Result: NF-闎 activation in the pancreatitis group was higher than that in the control group (P<0.01), peaked at 3 hours, and was depressed by the inhibitor of NF-闎, NAC. The expression of TNF- as well as the level of lipase and amylase in the serum also rose synchronously with activation of NF-闎. In contrast to group A, it was significantly different (P<0.01) in group B. After using NAC in group C, all of these values were decreased and the in-flammatory reaction in the pancreas abated evidently. The pathology changes of the pancreas were shown to be alleviated in group C. Conclusion: First, NF-闎 activity is intensively initiated in the course of pancreatitis and shown to have closely relationship with the release of cytokines. Second, use of NAC markedly depressed NF-闎 activation. TNF- expression is down regulated by cytokines. It is suggested that NAC probably acts as a useful agent for treatment of pancreatitis by indirectly inhibiting activation of NF-闎.
