Nanoscale graphene oxide(NGO)sheets were synthesized and used as carbocatalysts for effectiveoxidation of benzylic alcohols and aromatic aldehydes.For oxidation of alcohols in the presence ofH2O2at80°C,the NGOs(2...Nanoscale graphene oxide(NGO)sheets were synthesized and used as carbocatalysts for effectiveoxidation of benzylic alcohols and aromatic aldehydes.For oxidation of alcohols in the presence ofH2O2at80°C,the NGOs(20%mass fraction)as carbocatalysts showed selectivity toward aldehyde.The rate and yield of this reaction strongly depended on the nature of substituents on the alcohol.For4‐nitrobenzyl alcohol,<10%of it was converted into the corresponding carboxylic acid after24h.By contrast,4‐methoxybenzyl alcohol and diphenylmethanol were completely converted into thecorresponding carboxylic acid and ketone after only9and3h,respectively.The conversion ratesfor oxidation of aromatic aldehydes by NGO carbocatalysts were higher than those for alcohol oxidation.For all the aldehydes,complete conversion to the corresponding carboxylic acids wasachieved using7%(mass fraction)of NGO at70°C within2–3h.Possible mechanisms for NGOcarbocatalyst structure‐dependent oxidation of benzyl alcohols and structure‐independent oxidationof aromatic aldehydes are discussed.展开更多
Gold catalysts supported on Mg-Al mixed oxides for oxidative esterification of methacrolein are prepared by impregnation.Effects of the support particle size,concentration of HAuCl4 solution and Mg/Al ratio on gold lo...Gold catalysts supported on Mg-Al mixed oxides for oxidative esterification of methacrolein are prepared by impregnation.Effects of the support particle size,concentration of HAuCl4 solution and Mg/Al ratio on gold loading and catalytic properties are investigated.The catalysts are characterized by CO_(2)-TPD,EDS,XPS,STEM and XRD techniques.Catalysts with smaller support particle size show more uniform gold distribution and higher gold dispersion,resulting in a higher catalytic performance,and the uniformity of gold and the activity of the catalysts with larger support particle size can be improved by decreasing the concentration of HAuCl4 solution.The Mg/Al molar ratio has significant effect on the uniformity of gold and the activity of the catalyst,and the optimum Mg/Al molar ratio is 0.1–0.2.This study underlines the importance of engineering support particle size,concentration of HAuCl4 solution and density of adsorption sites for efficient gold loading on support by impregnation.展开更多
Waterborne nanoscale carbon black dispersion （NCBD） was widely used in inkjet printing, spun.dyeing fibers and coloration fabrics. In this paper, NCBD was prepared using sodium carboxymethyl cellulose （CMC） as dis...Waterborne nanoscale carbon black dispersion （NCBD） was widely used in inkjet printing, spun.dyeing fibers and coloration fabrics. In this paper, NCBD was prepared using sodium carboxymethyl cellulose （CMC） as dispersant. Effects of CMC viscosity, ultrasonic time and oxidation with hydrogen peroxide on carbon black （CB） particle size were discussed. The results showed that CB particle size decreased by mechanical agitation while it Increased by ultrasonic with the increase of CMC viscosity. Uitrasonk is a more effective method to disperse CB particles than that of mechanical agitation. CB particle size lbviously decreased with itcreasing ultrasonic time and arrived at about 160 nm for 60min.In addition,oxidation with 2 mol/L of H2O2 and 0.2wt% of CMC300 reduced CB particle size to 160nm at 90℃ for 2.5h.展开更多
In this paper,a series of cobalt catalysts supported on reduced graphene oxide(rGO)nanosheets with the loading of 5,15 and 30 wt-%were provided by the impregnation method.The activity of the prepared catalysts is eval...In this paper,a series of cobalt catalysts supported on reduced graphene oxide(rGO)nanosheets with the loading of 5,15 and 30 wt-%were provided by the impregnation method.The activity of the prepared catalysts is evaluated in the Fischer-Tropsch synthesis(FTS).The prepared catalysts were carefully characterized by nitrogen adsorption-desorption,hydrogen chemisorption,X-ray diffraction,Fourier transform infrared spectroscopy,Raman spectroscopy,temperature programmed reduction,transmission electron microscopy,and field emission scanning electron microscopy techniques to confirm that cobalt particles were greatly dispersed on the rGO nanosheets.The results showed that with increasing the cobalt loading on the rGO support,the carbon defects are increased and as a consequence,the reduction of cobalt is decreased.The FTS activity results showed that the cobalt-time yield and turnover frequency passed from a maximum for catalyst with the Co0 average particle size of 15 nm due to the synergetic effect of cobalt reducibility and particle size.The products selectivity results indicated that the methane selectivity decreases,whereas the C5+selectivity raises with the increasing of the cobalt particle size,which can be explained by chain propagation in the primary chain growth reactions.展开更多
Two continuously regenerating diesel particulate filter （CRDPF） with different configurations and one particles oxidation catalyst （POC） were employed to perform experiments in a controlled laboratory setting to e...Two continuously regenerating diesel particulate filter （CRDPF） with different configurations and one particles oxidation catalyst （POC） were employed to perform experiments in a controlled laboratory setting to evaluate their effects on NO2, smoke and particle number emissions. The results showed that the application of the after-treatments increased the emission ratios of NO2/NOx significantly. The results of smoke emissions and particle number （PN） emissions indicated that both CRDPFs had sufficient capacity to remove more than 90% of total particulate matter （PM） and more than 97% of solid particles. However, the POC was able to remove the organic components of total PM, and only partially to remove the carbonaceous particles with size less than 30 nm. The negligible effects of POC on larger particles were observed due to its honeycomb structure leads to an inadequate residence time to oxidize the solid particles or trap them. The particles removal efficiencies of CRDPFs had high degree of correlations with the emission ratio of NO2/NOx. The PN emission results from two CRDPFs indicated that more NO2 generating in diesel oxidation catalyst section could obtain the higher removal efficiency of solid particles. However this also increased the risk of NO2 exposure in atmosphere.展开更多
Decomposition mass loss and pyrolysis products analyses of particles sampled at various locations along the tailpipe of a Euro-IV diesel engine were performed using a thermo gravimetry in conjunction with Fourier tran...Decomposition mass loss and pyrolysis products analyses of particles sampled at various locations along the tailpipe of a Euro-IV diesel engine were performed using a thermo gravimetry in conjunction with Fourier transformation infrared spectrometrymass spectrum.Diesel particles were collected at the same location with and without diesel oxidation catalyst(DOC)mounted on the test engine separately.The three poles in thermal gravity-differential thermal gravity images suggested that the decomposition process of diesel particles could be divided into three stages which correspond to the decompositions of lower boiling substances,higher boiling substances and soot respectively.It is noticed that no matter whether DOC was mounted or not,the further the particles were sampled away from the engine block,the lower the peak temperatures and the heavier the mass losses within the first two stages,which indicated that the soluble organic fraction in the particle samples increased and therefore lowering the activation energy of thermal decomposition.Hydroxyl,ammonia,C_xH_y fragments,benzene,toluene,and phenol were found to be the primary products of particle decomposition,which didn’t change with the location of particle sample point.The employment of DOC increased the activation energy for particle oxidation and resulted in a higher peak temperature and lower mass loss within the first-stage.Moreover,the C=O stretching bands of aldehyde and ketone at 1771 cm-1 was only detected without a DOC,while the N02 peak at 1634 cm-1 was solely noticed with the presence of DOC.Compared to the first-stage pyrolysis products,more polycyclic aromatic hydrocarbons and less C_xH_y fragments were seen in the second-stage.展开更多
The interfacial reactions of oxidized SiC particles reinforced Al-Mg matrix composites were investigated by the field emission-scanning electron microscopy (FE-SEM), TEM and X-ray diffraction. It was found that the na...The interfacial reactions of oxidized SiC particles reinforced Al-Mg matrix composites were investigated by the field emission-scanning electron microscopy (FE-SEM), TEM and X-ray diffraction. It was found that the nanoscale MgO forms initially due to the interfacial reaction, then whether it reacts with molten Al continuously or not depends on the content of Mg in the matrix and its covering densification at the surface of particles. When there is not enough Mg in the matrix for the formation of dense MgO layer, MgO will transform into MgAl2O4 crystal owing to the continuous reaction with SiO2 and molten Al. When dense MgO layer forms at the surface of the particles due to the affluence of Mg for the initial reaction, it will protect the inner SiC from the attack of molten Al. However, the reaction products of both MgO and MgAl2O4 are thermo-stable phases at the surface of the particles under high temperature. The results clarify the interfacial reaction route and they are of great value to the展开更多
The ultrafine V 2O 5 TiO 2 composite oxide particles have been prepared by the high energy ball milling method and characterized by X ray diffraction, transmission electron microscopy, laser Raman spectroscopy, temper...The ultrafine V 2O 5 TiO 2 composite oxide particles have been prepared by the high energy ball milling method and characterized by X ray diffraction, transmission electron microscopy, laser Raman spectroscopy, temperature programmed reduction, and microreactor testing. It has been shown that the milling process induces the formation of ultrafine V 2O 5 TiO 2 composite oxide particles with dispersed vanadium oxide on the surface of anatase TiO 2, accompanied by a decrease in particle size of V 2O 5 and TiO 2. The TPR results indicate that the strong interaction between dispersed V O species and TiO 2 increases the reducibility of the vanadium oxide. The catalytic properties of the catalysts for the selective oxidation of o xylene were evaluated. Under the similar o xylene conversion (58%), the ultrafine V 2O 5 TiO 2 composite oxide catalyst exhibits a higher selectivity for phthalic anhydride (44%) than the catalyst prepared by the conventional impregnation method (23%), and the catalyst composition has a great influence on the catalytic properties.展开更多
文摘Nanoscale graphene oxide(NGO)sheets were synthesized and used as carbocatalysts for effectiveoxidation of benzylic alcohols and aromatic aldehydes.For oxidation of alcohols in the presence ofH2O2at80°C,the NGOs(20%mass fraction)as carbocatalysts showed selectivity toward aldehyde.The rate and yield of this reaction strongly depended on the nature of substituents on the alcohol.For4‐nitrobenzyl alcohol,<10%of it was converted into the corresponding carboxylic acid after24h.By contrast,4‐methoxybenzyl alcohol and diphenylmethanol were completely converted into thecorresponding carboxylic acid and ketone after only9and3h,respectively.The conversion ratesfor oxidation of aromatic aldehydes by NGO carbocatalysts were higher than those for alcohol oxidation.For all the aldehydes,complete conversion to the corresponding carboxylic acids wasachieved using7%(mass fraction)of NGO at70°C within2–3h.Possible mechanisms for NGOcarbocatalyst structure‐dependent oxidation of benzyl alcohols and structure‐independent oxidationof aromatic aldehydes are discussed.
基金Open Project of Yunnan Precious Metals Laboratory Co.,Ltd(YPML-2023050269)the Fundamental Research Funds for the Central Universities(226-2023-00085,226-2023-00057).
文摘Gold catalysts supported on Mg-Al mixed oxides for oxidative esterification of methacrolein are prepared by impregnation.Effects of the support particle size,concentration of HAuCl4 solution and Mg/Al ratio on gold loading and catalytic properties are investigated.The catalysts are characterized by CO_(2)-TPD,EDS,XPS,STEM and XRD techniques.Catalysts with smaller support particle size show more uniform gold distribution and higher gold dispersion,resulting in a higher catalytic performance,and the uniformity of gold and the activity of the catalysts with larger support particle size can be improved by decreasing the concentration of HAuCl4 solution.The Mg/Al molar ratio has significant effect on the uniformity of gold and the activity of the catalyst,and the optimum Mg/Al molar ratio is 0.1–0.2.This study underlines the importance of engineering support particle size,concentration of HAuCl4 solution and density of adsorption sites for efficient gold loading on support by impregnation.
基金Supported by National Natural Science Foundation of China( No.50173012) and863Hi-tech Research and Development Program ofChina (2002AA327120)
文摘Waterborne nanoscale carbon black dispersion （NCBD） was widely used in inkjet printing, spun.dyeing fibers and coloration fabrics. In this paper, NCBD was prepared using sodium carboxymethyl cellulose （CMC） as dispersant. Effects of CMC viscosity, ultrasonic time and oxidation with hydrogen peroxide on carbon black （CB） particle size were discussed. The results showed that CB particle size decreased by mechanical agitation while it Increased by ultrasonic with the increase of CMC viscosity. Uitrasonk is a more effective method to disperse CB particles than that of mechanical agitation. CB particle size lbviously decreased with itcreasing ultrasonic time and arrived at about 160 nm for 60min.In addition,oxidation with 2 mol/L of H2O2 and 0.2wt% of CMC300 reduced CB particle size to 160nm at 90℃ for 2.5h.
基金The authors of this work appreciate the financial support of the Ferdowsi University of Mashhad,Iran(Grant No.3/45803-29/9/96).
文摘In this paper,a series of cobalt catalysts supported on reduced graphene oxide(rGO)nanosheets with the loading of 5,15 and 30 wt-%were provided by the impregnation method.The activity of the prepared catalysts is evaluated in the Fischer-Tropsch synthesis(FTS).The prepared catalysts were carefully characterized by nitrogen adsorption-desorption,hydrogen chemisorption,X-ray diffraction,Fourier transform infrared spectroscopy,Raman spectroscopy,temperature programmed reduction,transmission electron microscopy,and field emission scanning electron microscopy techniques to confirm that cobalt particles were greatly dispersed on the rGO nanosheets.The results showed that with increasing the cobalt loading on the rGO support,the carbon defects are increased and as a consequence,the reduction of cobalt is decreased.The FTS activity results showed that the cobalt-time yield and turnover frequency passed from a maximum for catalyst with the Co0 average particle size of 15 nm due to the synergetic effect of cobalt reducibility and particle size.The products selectivity results indicated that the methane selectivity decreases,whereas the C5+selectivity raises with the increasing of the cobalt particle size,which can be explained by chain propagation in the primary chain growth reactions.
基金supported by the National Natural Science Foundation of China (No. 50876013)
文摘Two continuously regenerating diesel particulate filter （CRDPF） with different configurations and one particles oxidation catalyst （POC） were employed to perform experiments in a controlled laboratory setting to evaluate their effects on NO2, smoke and particle number emissions. The results showed that the application of the after-treatments increased the emission ratios of NO2/NOx significantly. The results of smoke emissions and particle number （PN） emissions indicated that both CRDPFs had sufficient capacity to remove more than 90% of total particulate matter （PM） and more than 97% of solid particles. However, the POC was able to remove the organic components of total PM, and only partially to remove the carbonaceous particles with size less than 30 nm. The negligible effects of POC on larger particles were observed due to its honeycomb structure leads to an inadequate residence time to oxidize the solid particles or trap them. The particles removal efficiencies of CRDPFs had high degree of correlations with the emission ratio of NO2/NOx. The PN emission results from two CRDPFs indicated that more NO2 generating in diesel oxidation catalyst section could obtain the higher removal efficiency of solid particles. However this also increased the risk of NO2 exposure in atmosphere.
基金supported by the Open Research Program of State Key Laboratory of Engine Combustion(No.K2018-11)the National Nature Science Foundation of China(No.51806015)the National Engineering Laboratory for Mobile Source Emission Control Technology(No.NELMS2018A17)
文摘Decomposition mass loss and pyrolysis products analyses of particles sampled at various locations along the tailpipe of a Euro-IV diesel engine were performed using a thermo gravimetry in conjunction with Fourier transformation infrared spectrometrymass spectrum.Diesel particles were collected at the same location with and without diesel oxidation catalyst(DOC)mounted on the test engine separately.The three poles in thermal gravity-differential thermal gravity images suggested that the decomposition process of diesel particles could be divided into three stages which correspond to the decompositions of lower boiling substances,higher boiling substances and soot respectively.It is noticed that no matter whether DOC was mounted or not,the further the particles were sampled away from the engine block,the lower the peak temperatures and the heavier the mass losses within the first two stages,which indicated that the soluble organic fraction in the particle samples increased and therefore lowering the activation energy of thermal decomposition.Hydroxyl,ammonia,C_xH_y fragments,benzene,toluene,and phenol were found to be the primary products of particle decomposition,which didn’t change with the location of particle sample point.The employment of DOC increased the activation energy for particle oxidation and resulted in a higher peak temperature and lower mass loss within the first-stage.Moreover,the C=O stretching bands of aldehyde and ketone at 1771 cm-1 was only detected without a DOC,while the N02 peak at 1634 cm-1 was solely noticed with the presence of DOC.Compared to the first-stage pyrolysis products,more polycyclic aromatic hydrocarbons and less C_xH_y fragments were seen in the second-stage.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 59631080).
文摘The interfacial reactions of oxidized SiC particles reinforced Al-Mg matrix composites were investigated by the field emission-scanning electron microscopy (FE-SEM), TEM and X-ray diffraction. It was found that the nanoscale MgO forms initially due to the interfacial reaction, then whether it reacts with molten Al continuously or not depends on the content of Mg in the matrix and its covering densification at the surface of particles. When there is not enough Mg in the matrix for the formation of dense MgO layer, MgO will transform into MgAl2O4 crystal owing to the continuous reaction with SiO2 and molten Al. When dense MgO layer forms at the surface of the particles due to the affluence of Mg for the initial reaction, it will protect the inner SiC from the attack of molten Al. However, the reaction products of both MgO and MgAl2O4 are thermo-stable phases at the surface of the particles under high temperature. The results clarify the interfacial reaction route and they are of great value to the
文摘The ultrafine V 2O 5 TiO 2 composite oxide particles have been prepared by the high energy ball milling method and characterized by X ray diffraction, transmission electron microscopy, laser Raman spectroscopy, temperature programmed reduction, and microreactor testing. It has been shown that the milling process induces the formation of ultrafine V 2O 5 TiO 2 composite oxide particles with dispersed vanadium oxide on the surface of anatase TiO 2, accompanied by a decrease in particle size of V 2O 5 and TiO 2. The TPR results indicate that the strong interaction between dispersed V O species and TiO 2 increases the reducibility of the vanadium oxide. The catalytic properties of the catalysts for the selective oxidation of o xylene were evaluated. Under the similar o xylene conversion (58%), the ultrafine V 2O 5 TiO 2 composite oxide catalyst exhibits a higher selectivity for phthalic anhydride (44%) than the catalyst prepared by the conventional impregnation method (23%), and the catalyst composition has a great influence on the catalytic properties.
