In a recent contribution[1]to this journal,Guo and co‐workers reported on the design of a dual beam FT‐IR spectrometer system aiming,among others,at totally removing the contribution of gas‐phase species during ope...In a recent contribution[1]to this journal,Guo and co‐workers reported on the design of a dual beam FT‐IR spectrometer system aiming,among others,at totally removing the contribution of gas‐phase species during operando studies of heterogeneous catalytic reactions.The system consists of two identical cells located in two separate FT‐IR spectrometers,one being loaded with a catalyst wafer and the other one being empty and used as a reference signal.The exhaust gas of the sample cell is sent to the reference cell,both being heated up at the same temperature.Any indication on cell volume or the nature of the flow regime(e.g.,plug flow or continuously stirred tank reactor(CSTR))is not mentioned.展开更多
Magnesium and rare earth mixed oxides（Mg3 REOx（RE=La, Y. Ce）） were prepared and characterized by Xray diffraction（XRD）, N_2 adsorption-desorption, infrared spectra and microcalorimetry of CO_2. The results revea...Magnesium and rare earth mixed oxides（Mg3 REOx（RE=La, Y. Ce）） were prepared and characterized by Xray diffraction（XRD）, N_2 adsorption-desorption, infrared spectra and microcalorimetry of CO_2. The results reveal that the Mg_3 CeO_x catalyst is present in the form of Mg-Ce-O solid solution,while the Mg3 LaOx and Mg_3 YO_x catalysts are probably rare earth oxides dispersed on MgO surface. As a result, among the calcined Mg_3 REO_x catalysts, the Mg_3 CeO_x catalyst presents the highest rate constant for acetone aldolization, which is well correlated to its more homogeneous distribution of basic sites. In contrary, the Mg_3 YO_x catalyst exhibit the lowest catalytic activity for acetone aldolization. Upon hydration pre-treatment, the basic properties on the surface of the Mg_3 REO_x catalysts were changed markedly. The Mg_3 YO_x catalyst after hydration treatment shows the highest amount of basic sites on catalyst surface, and then exhibits the highest activity among the hydrated Mg_3 REO_x catalysts. These results make it possible to fine-tune basic sites for acetone aldolization.展开更多
Heterogeneous reactions of NO2 on different surfaces play an important role in atmospheric NOxremoval and HONO formation,having profound impacts on photochemistry in polluted urban areas.Previous studies have suggeste...Heterogeneous reactions of NO2 on different surfaces play an important role in atmospheric NOxremoval and HONO formation,having profound impacts on photochemistry in polluted urban areas.Previous studies have suggested that the NO2 uptake on the ground or aerosol surfaces could be a dominant source for elevated HONO during the daytime.However,the uptake behavior of NO2 varies with different surfaces,and different uptake coefficients were used or derived in different studies.To obtain a more holistic picture of heterogeneous NO2 uptake on different surfaces,a series of laboratory experiments using different flow tube reactors was conducted,and the NO2 uptake coefficients(γ)were determined on inorganic particles,sea water and urban grime.The results showed that heterogeneous reactions on those surfaces were generally weak in dark conditions,with the measuredγvaried from<10-8 to 3.2×10-7 under different humidity.A photo-enhanced uptake of NO2 on urban grime was observed,with the obvious formation of HONO and NO from the heterogeneous reaction.The photo-enhancedγwas measured to be 1.9×10-6 at 5%relative humidity(RH)and 5.8×10-6 at 70%RH on urban grime,showing a positive RH dependence for both NO2 uptake and HONO formation.The results demonstrate an important role of urban grime in the daytime NO2-to-HONO conversion,and could be helpful to explain the unknown daytime HONO source in the polluted urban area.展开更多
Fully palladium/copper catalytic oxidative cross-coupling of acrylates with α-methylstyrene was performed in a DMSO/AcOH(1:1) mixture at 60℃ in the air.This improves previous procedures which employed stoichiometric...Fully palladium/copper catalytic oxidative cross-coupling of acrylates with α-methylstyrene was performed in a DMSO/AcOH(1:1) mixture at 60℃ in the air.This improves previous procedures which employed stoichiometric amounts of copper and oxygen.Thus various acrylates were effectively coupled to α-methylstyrene giving the expected compounds in moderate to good yields(44%-65%) as a mixture of E and Z isomers.展开更多
Photocatalysis is based on the double aptitude of the photocatalyst(essentially titania) to simultaneously adsorb reactants and absorb efficient photons.Heterogeneous photocatalysis is able to be efficient in Fine,&qu...Photocatalysis is based on the double aptitude of the photocatalyst(essentially titania) to simultaneously adsorb reactants and absorb efficient photons.Heterogeneous photocatalysis is able to be efficient in Fine,"Green" and Environmental Chemistry.Photocatalysis induces mild oxidations in the absence of water by generating active neutral atomic O* species.For instance,the oxidation of 4-tert-butyl-toluene is 100% selective in 4-tert-butyl-benzaldehyde.In water treatment,many toxic inorganic ions are oxidized in their harmless upper oxidized state.The elimination of organic pollutants is the main field of water photocatalytic decontamination.Most of aliphatic and aromatic pollutants are totally mineralized into CO2 and innocuous inorganic anions.More complex molecules,such as pesticides(herbicides,insecticides,fungicides,etc.) or dyes,are totally destroyed.Another example of green chemistry is the total degradation of dyes in water,in particular for the azo-dyes,with 100% selective degradation of -N=N-azo-groups into di-nitrogen.Photocatalysis is also active in the "bio-world" by killing bacteria(E.Coli,streptococcus,etc.) in water without re-growth.Air pollutants can also be destroyed,especially all the VOC's(volatile organic compounds),providing certain air humidity enabling titania to produce cracking OH* radicals.For chemical engineering reasons,the photocatalyst has to be fixed on a photo-inert support.In these conditions,UV-irradiated titania-based photocatalysis could be applied to the elimination of air pollutants,VOC's,solvents,odors,chemicals,etc.Air treatment has to be associated with water and solid waste treatment because of odors.This is conducted by covering water treatment ponds or lagunas by rafts on which large sheets of Ahlstrom paper are deposited,supporting titania associated with activated carbon.Eventually,virus AH5N2,a model virus close to H5N1,responsible for the avian flu could be totally inactivated.Photocatalysis is directly connected with all 12 principles of Green Chemistry defined by Anastas(1998) and possesses open perspectives for China.展开更多
Wet air oxidation （WAO） and catalytic wet air oxidation （CWAO） are efficient processes to degrade organic pollutants in water. In this paper, we especially reviewed the WAO and CWAO processes for phenolic compound...Wet air oxidation （WAO） and catalytic wet air oxidation （CWAO） are efficient processes to degrade organic pollutants in water. In this paper, we especially reviewed the WAO and CWAO processes for phenolic compounds degradation. It provides a comprehensive introduction to the CWAO processes that could be beneficial to the scientists entering this field of research. The influence of different reaction parameters, such as temperature, oxygen pressure, pH, stirring speed are analyzed in detail; Homogenous catalysts and heterogeneous catalysts including carbon materials, transitional metal oxides and noble metals are extensively discussed, among which Cu based catalysts and Ru catalysts were shown to be the most active. Three different kinds of the reactor implemented for the CWAO （autoclave, packed bed and membrane reactors） are illustrated and compared. To enhance the degradation efficiency and reduce the cost of the CWAO process, biological degradation can be combined to develop an integrated technology.展开更多
In the recent years, photocatalytic self-cleaning and ＂depolluting＂ materials have been suggested as a remediation technology mainly for NOx and aromatic VOCs in urban areas. A number of products incorporating the a...In the recent years, photocatalytic self-cleaning and ＂depolluting＂ materials have been suggested as a remediation technology mainly for NOx and aromatic VOCs in urban areas. A number of products incorporating the aforementioned technology have been made commercially available with the aim to improve urban air quality. These commercial products are based on the photocatalytic properties of a thin layer of TiO2 at the surface of the material （such as glass, pavement, etc.） or embedded in paints or concrete. The use of TiO2 photocatalysts as an emerging air pollution control technology has been reported in many locations worldwide. However, up to now, the effectiveness measured in situ and theexpected positive impact on air quality of this relatively new technology has only been demonstrated in a limited manner. Assessing and demonstrating the effectiveness of these depolluting techniques in real scale applications aims to create a real added value, in terms of policy making （i.e., implementing air quality strategies） and economics （by providing a demonstration of the actual performance of a new technique）.展开更多
文摘In a recent contribution[1]to this journal,Guo and co‐workers reported on the design of a dual beam FT‐IR spectrometer system aiming,among others,at totally removing the contribution of gas‐phase species during operando studies of heterogeneous catalytic reactions.The system consists of two identical cells located in two separate FT‐IR spectrometers,one being loaded with a catalyst wafer and the other one being empty and used as a reference signal.The exhaust gas of the sample cell is sent to the reference cell,both being heated up at the same temperature.Any indication on cell volume or the nature of the flow regime(e.g.,plug flow or continuously stirred tank reactor(CSTR))is not mentioned.
基金Project supported by National Basic Research Program of China(2010CB732300)111 Project(B08021)China Scholarship Council for the Joint-Training Scholarship Program with Institut de Recherches sur la Catalyse et l'Environnement de Lyon(IRCELYON)and Universite Claude Bernard Lyon 1(UCBL1)
文摘Magnesium and rare earth mixed oxides（Mg3 REOx（RE=La, Y. Ce）） were prepared and characterized by Xray diffraction（XRD）, N_2 adsorption-desorption, infrared spectra and microcalorimetry of CO_2. The results reveal that the Mg_3 CeO_x catalyst is present in the form of Mg-Ce-O solid solution,while the Mg3 LaOx and Mg_3 YO_x catalysts are probably rare earth oxides dispersed on MgO surface. As a result, among the calcined Mg_3 REO_x catalysts, the Mg_3 CeO_x catalyst presents the highest rate constant for acetone aldolization, which is well correlated to its more homogeneous distribution of basic sites. In contrary, the Mg_3 YO_x catalyst exhibit the lowest catalytic activity for acetone aldolization. Upon hydration pre-treatment, the basic properties on the surface of the Mg_3 REO_x catalysts were changed markedly. The Mg_3 YO_x catalyst after hydration treatment shows the highest amount of basic sites on catalyst surface, and then exhibits the highest activity among the hydrated Mg_3 REO_x catalysts. These results make it possible to fine-tune basic sites for acetone aldolization.
基金supported by the French National Research Agency/Research Grants Council of Hong Kong Special Administrative Region,China(ANR/RGC)Joint Research Scheme(project A-PolyU502/16-SEAM)National Natural Science Foundation of China(Nos.91744204,91844301)+1 种基金the Research Grants Council of Hong Kong Special Administrative Region,China(Nos.T24/504/17,15265516,C5022-14G)。
文摘Heterogeneous reactions of NO2 on different surfaces play an important role in atmospheric NOxremoval and HONO formation,having profound impacts on photochemistry in polluted urban areas.Previous studies have suggested that the NO2 uptake on the ground or aerosol surfaces could be a dominant source for elevated HONO during the daytime.However,the uptake behavior of NO2 varies with different surfaces,and different uptake coefficients were used or derived in different studies.To obtain a more holistic picture of heterogeneous NO2 uptake on different surfaces,a series of laboratory experiments using different flow tube reactors was conducted,and the NO2 uptake coefficients(γ)were determined on inorganic particles,sea water and urban grime.The results showed that heterogeneous reactions on those surfaces were generally weak in dark conditions,with the measuredγvaried from<10-8 to 3.2×10-7 under different humidity.A photo-enhanced uptake of NO2 on urban grime was observed,with the obvious formation of HONO and NO from the heterogeneous reaction.The photo-enhancedγwas measured to be 1.9×10-6 at 5%relative humidity(RH)and 5.8×10-6 at 70%RH on urban grime,showing a positive RH dependence for both NO2 uptake and HONO formation.The results demonstrate an important role of urban grime in the daytime NO2-to-HONO conversion,and could be helpful to explain the unknown daytime HONO source in the polluted urban area.
基金the National Agency of Research (CATAQ N° ANR-07-CP2D-0167-01/02) for funding
文摘Fully palladium/copper catalytic oxidative cross-coupling of acrylates with α-methylstyrene was performed in a DMSO/AcOH(1:1) mixture at 60℃ in the air.This improves previous procedures which employed stoichiometric amounts of copper and oxygen.Thus various acrylates were effectively coupled to α-methylstyrene giving the expected compounds in moderate to good yields(44%-65%) as a mixture of E and Z isomers.
文摘Photocatalysis is based on the double aptitude of the photocatalyst(essentially titania) to simultaneously adsorb reactants and absorb efficient photons.Heterogeneous photocatalysis is able to be efficient in Fine,"Green" and Environmental Chemistry.Photocatalysis induces mild oxidations in the absence of water by generating active neutral atomic O* species.For instance,the oxidation of 4-tert-butyl-toluene is 100% selective in 4-tert-butyl-benzaldehyde.In water treatment,many toxic inorganic ions are oxidized in their harmless upper oxidized state.The elimination of organic pollutants is the main field of water photocatalytic decontamination.Most of aliphatic and aromatic pollutants are totally mineralized into CO2 and innocuous inorganic anions.More complex molecules,such as pesticides(herbicides,insecticides,fungicides,etc.) or dyes,are totally destroyed.Another example of green chemistry is the total degradation of dyes in water,in particular for the azo-dyes,with 100% selective degradation of -N=N-azo-groups into di-nitrogen.Photocatalysis is also active in the "bio-world" by killing bacteria(E.Coli,streptococcus,etc.) in water without re-growth.Air pollutants can also be destroyed,especially all the VOC's(volatile organic compounds),providing certain air humidity enabling titania to produce cracking OH* radicals.For chemical engineering reasons,the photocatalyst has to be fixed on a photo-inert support.In these conditions,UV-irradiated titania-based photocatalysis could be applied to the elimination of air pollutants,VOC's,solvents,odors,chemicals,etc.Air treatment has to be associated with water and solid waste treatment because of odors.This is conducted by covering water treatment ponds or lagunas by rafts on which large sheets of Ahlstrom paper are deposited,supporting titania associated with activated carbon.Eventually,virus AH5N2,a model virus close to H5N1,responsible for the avian flu could be totally inactivated.Photocatalysis is directly connected with all 12 principles of Green Chemistry defined by Anastas(1998) and possesses open perspectives for China.
文摘Wet air oxidation （WAO） and catalytic wet air oxidation （CWAO） are efficient processes to degrade organic pollutants in water. In this paper, we especially reviewed the WAO and CWAO processes for phenolic compounds degradation. It provides a comprehensive introduction to the CWAO processes that could be beneficial to the scientists entering this field of research. The influence of different reaction parameters, such as temperature, oxygen pressure, pH, stirring speed are analyzed in detail; Homogenous catalysts and heterogeneous catalysts including carbon materials, transitional metal oxides and noble metals are extensively discussed, among which Cu based catalysts and Ru catalysts were shown to be the most active. Three different kinds of the reactor implemented for the CWAO （autoclave, packed bed and membrane reactors） are illustrated and compared. To enhance the degradation efficiency and reduce the cost of the CWAO process, biological degradation can be combined to develop an integrated technology.
文摘In the recent years, photocatalytic self-cleaning and ＂depolluting＂ materials have been suggested as a remediation technology mainly for NOx and aromatic VOCs in urban areas. A number of products incorporating the aforementioned technology have been made commercially available with the aim to improve urban air quality. These commercial products are based on the photocatalytic properties of a thin layer of TiO2 at the surface of the material （such as glass, pavement, etc.） or embedded in paints or concrete. The use of TiO2 photocatalysts as an emerging air pollution control technology has been reported in many locations worldwide. However, up to now, the effectiveness measured in situ and theexpected positive impact on air quality of this relatively new technology has only been demonstrated in a limited manner. Assessing and demonstrating the effectiveness of these depolluting techniques in real scale applications aims to create a real added value, in terms of policy making （i.e., implementing air quality strategies） and economics （by providing a demonstration of the actual performance of a new technique）.
