The chemoselective hydrodeoxygenation of natural lignocellulosic materials plays a crucial role in converting biomass into value-added chemicals.Yet their complex molecular structures often require multiple active sit...The chemoselective hydrodeoxygenation of natural lignocellulosic materials plays a crucial role in converting biomass into value-added chemicals.Yet their complex molecular structures often require multiple active sites synergy for effective activation and achieving high chemoselectivity.Herein,it is reported that a high-entropy alloy(HEA)on high-entropy oxide(HEO)hetero-structured catalyst for highly active,chemoselective,and robust vanillin hydrodeoxygenation.The heterogenous HEA/HEO catalysts were prepared by thermal reduction of senary HEOs(NiZnCuFeAlZrO_(x)),where exsolvable metals(e.g.,Ni,Zn,Cu)in situ emerged and formed randomly dispersed HEA nanoparticles anchoring on the HEO matrix.This catalyst exhibits excellent catalytic performance:100%conversion of vanillin and 95%selectivity toward high-value 2-methyl-4 methoxy phenol at low temperature of 120℃,which were attributed to the synergistic effect among HEO matrix(with abundant oxygen vacancies),anchored HEA nanoparticles(having excellent hydrogenolysis capability),and their intimate hetero-interfaces(showing strong electron transferring effect).Therefore,our work reported the successful construction of HEA/HEO heterogeneous catalysts and their superior multifunctionality in biomass conversion,which could shed light on catalyst design for many important reactions that are complex and require multifunctional active sites.展开更多
Traffic-related pollutants adversely affect air quality, especially in regions near major roadways. The vehicleinduced turbulence(VIT) is a significant factor that controls the initial dilution, dispersion, and ultima...Traffic-related pollutants adversely affect air quality, especially in regions near major roadways. The vehicleinduced turbulence(VIT) is a significant factor that controls the initial dilution, dispersion, and ultimately the chemical and physical fate of pollutants by altering the conditions in the microenvironment. This study used a computational fluid dynamics(CFD) software FLUENT to model the vehicle-induced turbulence(VIT) generated on roadways, with a focus on impact of vehicle-vehicle interactions, traffic density and vehicle composition on turbulent kinetic energy(TKE). We show, for the first time, that the overall TKE from multiple vehicles traveling in series can be estimated by superimposing the TKE of each vehicle, without considering the distance between them while the distance is greater than one vehicle length. This finding is particularly significant since it enables a new approach to VIT simulations where the overall TKE is calculated as a function of number of vehicles. We found that the interactions between vehicles traveling next to each other in adjacent lanes are insignificant,regardless the directions of the traffic flow. Consequently, simulations of different traffic scenarios can be substantially simplified by treating two-way traffic as one-way traffic, with less than 5% difference in the overall volume-averaged TKE. We also developed equations that allow the estimation of the overall volume-averaged TKE as a function of the number and the type of vehicles.展开更多
Biochar is traditionally used as solid fuel and for soil amendment where its electrical conductivity is largely irrelevant and unexplored.However,electrical conductivity is critical to biochar’s performance in new ap...Biochar is traditionally used as solid fuel and for soil amendment where its electrical conductivity is largely irrelevant and unexplored.However,electrical conductivity is critical to biochar’s performance in new applications such as supercapacitor energy storage and capacitive deionization of water.In this study,sugar maple and white pine were carbonized via a slow pyrolysis process at 600,800 and 1000°C and conductivities of monolithic biochar samples along the radial direction were measured using the 4-probe method.Biochars were characterized using an elemental analyzer,scanning electron microscopy,X-ray diffraction and Raman spectroscopy.The solid carbon in biochar samples was found to consist primarily of disordered carbon atoms with small graphitic nanocrystallites that grow with increasing temperature.The bulk conductivity of biochar was found to increase with pyrolysis temperature-1 to~1000 S/m for maple and 1 to~350 S/m for pine,which was accompanied by an increase in carbon content-91 to 97 wt%and 90 to 96 wt%for maple and pine,respectively.The skeletal conductivity of biochar samples carbonized at 1000°C is about 3300 S/m and 2300 S/m for maple and pine,respectively(assuming solid carbon is amorphous);both values are above that of amorphous carbon(1250-2000 S/m).This work demonstrated the importance of carbonization and graphitization to electrical conductivity and suggested electron hopping as a likely mechanism for electric conduction in biochar-an amorphous carbon matrix embedded with graphitic nanocrystallites.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52006074,52101255)Natural Science Foundation of Guangdong Province,China(Grant No.2021A1515010886)+2 种基金Youth science and technology innovation talent of Guangdong TeZhi planChina(Grant No.2019TQ05N068)the Fundamental Research Funds for the Central Universities,HUST:2021GCRC046
文摘The chemoselective hydrodeoxygenation of natural lignocellulosic materials plays a crucial role in converting biomass into value-added chemicals.Yet their complex molecular structures often require multiple active sites synergy for effective activation and achieving high chemoselectivity.Herein,it is reported that a high-entropy alloy(HEA)on high-entropy oxide(HEO)hetero-structured catalyst for highly active,chemoselective,and robust vanillin hydrodeoxygenation.The heterogenous HEA/HEO catalysts were prepared by thermal reduction of senary HEOs(NiZnCuFeAlZrO_(x)),where exsolvable metals(e.g.,Ni,Zn,Cu)in situ emerged and formed randomly dispersed HEA nanoparticles anchoring on the HEO matrix.This catalyst exhibits excellent catalytic performance:100%conversion of vanillin and 95%selectivity toward high-value 2-methyl-4 methoxy phenol at low temperature of 120℃,which were attributed to the synergistic effect among HEO matrix(with abundant oxygen vacancies),anchored HEA nanoparticles(having excellent hydrogenolysis capability),and their intimate hetero-interfaces(showing strong electron transferring effect).Therefore,our work reported the successful construction of HEA/HEO heterogeneous catalysts and their superior multifunctionality in biomass conversion,which could shed light on catalyst design for many important reactions that are complex and require multifunctional active sites.
基金financial support from Environment Canada and the Government of Ontario (72021622) for a scholarship to YK
文摘Traffic-related pollutants adversely affect air quality, especially in regions near major roadways. The vehicleinduced turbulence(VIT) is a significant factor that controls the initial dilution, dispersion, and ultimately the chemical and physical fate of pollutants by altering the conditions in the microenvironment. This study used a computational fluid dynamics(CFD) software FLUENT to model the vehicle-induced turbulence(VIT) generated on roadways, with a focus on impact of vehicle-vehicle interactions, traffic density and vehicle composition on turbulent kinetic energy(TKE). We show, for the first time, that the overall TKE from multiple vehicles traveling in series can be estimated by superimposing the TKE of each vehicle, without considering the distance between them while the distance is greater than one vehicle length. This finding is particularly significant since it enables a new approach to VIT simulations where the overall TKE is calculated as a function of number of vehicles. We found that the interactions between vehicles traveling next to each other in adjacent lanes are insignificant,regardless the directions of the traffic flow. Consequently, simulations of different traffic scenarios can be substantially simplified by treating two-way traffic as one-way traffic, with less than 5% difference in the overall volume-averaged TKE. We also developed equations that allow the estimation of the overall volume-averaged TKE as a function of the number and the type of vehicles.
文摘Biochar is traditionally used as solid fuel and for soil amendment where its electrical conductivity is largely irrelevant and unexplored.However,electrical conductivity is critical to biochar’s performance in new applications such as supercapacitor energy storage and capacitive deionization of water.In this study,sugar maple and white pine were carbonized via a slow pyrolysis process at 600,800 and 1000°C and conductivities of monolithic biochar samples along the radial direction were measured using the 4-probe method.Biochars were characterized using an elemental analyzer,scanning electron microscopy,X-ray diffraction and Raman spectroscopy.The solid carbon in biochar samples was found to consist primarily of disordered carbon atoms with small graphitic nanocrystallites that grow with increasing temperature.The bulk conductivity of biochar was found to increase with pyrolysis temperature-1 to~1000 S/m for maple and 1 to~350 S/m for pine,which was accompanied by an increase in carbon content-91 to 97 wt%and 90 to 96 wt%for maple and pine,respectively.The skeletal conductivity of biochar samples carbonized at 1000°C is about 3300 S/m and 2300 S/m for maple and pine,respectively(assuming solid carbon is amorphous);both values are above that of amorphous carbon(1250-2000 S/m).This work demonstrated the importance of carbonization and graphitization to electrical conductivity and suggested electron hopping as a likely mechanism for electric conduction in biochar-an amorphous carbon matrix embedded with graphitic nanocrystallites.
