A highly efficient strategy for the synthesis of polylactide with the UV absorption ability was established by employing a Salan-yttrium complex（acting as a fast runing catalyst） combined with large excess hydroxyl ...A highly efficient strategy for the synthesis of polylactide with the UV absorption ability was established by employing a Salan-yttrium complex（acting as a fast runing catalyst） combined with large excess hydroxyl functionalized benzophenone, BP′-OH. During polymerization, BP′-OH, acting as the chain transfer agent, attached to the active rare-earth metal catalyst via a rapid-reversible exchange reaction to initiate the polymerization. Thus, more polyester chains appeared to grow from one active metal species, and the UV absorption fragments were incorporated into the polymer chains at specific sites, in situ. A high productivity up to 1000 mol LA/mol（Salan-Y） was successfully achieved and 100 BP′-labeled PLA chains grew from each active metal center.展开更多
The highly dispersed supported ruthenium-yttrium (Ru-Y) bimetallic catalysts were prepared by impregnation method and their catalytic performance for hydrogenation of ester was fully investigated. The catalyst was cha...The highly dispersed supported ruthenium-yttrium (Ru-Y) bimetallic catalysts were prepared by impregnation method and their catalytic performance for hydrogenation of ester was fully investigated. The catalyst was characterized by X-ray diffraction and field emission scanning electron microscopy. The results show that the average particle diameter of the bimetallic crystallites was less than 10 nm. The effects of the reaction temperature, the hydrogen pressure, the amount of catalyst and the proportion of yttrium in catalyst on the hydrogenation of ester were studied. The experimental results show that the introduction of yttrium not only changed the chemical and textural properties of ruthenium-based catalyst but also controlled the formation of Ru-Y alloy. The Ru-Y catalyst (Ru-2%Y/TiO2) exhibited high catalytic activity and good selectivity towards the higher alcohols. Under optimal reaction conditions of 240°C and 5 MPa hydrogen pressure, the conversion of palm oil esters was above 93.4% while the selectivity towards alcohol was above 99.0%.展开更多
The addition of yttrium chloride(YCl) to an activated carbon-supported Au catalyst(Au/AC) can markedly promote the catalytic performance of acetylene hydrochlorination to the vinyl chloride monomer(VCM), The structure...The addition of yttrium chloride(YCl) to an activated carbon-supported Au catalyst(Au/AC) can markedly promote the catalytic performance of acetylene hydrochlorination to the vinyl chloride monomer(VCM), The structure and physicochemical features of the YCl-modified catalysts(Y-Au/AC)were measured by X-ray diffraction, X-ray photoelectron spectroscopy, temperature-programmed reduction, CH-temperature programmed desorption, and scanning transmission electron microscopy.The presence of YClwas found suppressing the reduction of highly oxidized Au(δ=1,3) to metallic Au~0 dependently and thus retard the agglomeration of Au nanoparticles during the reaction. In addition,the additive of YClto the Au/AC catalyst greatly inhibits the coke deposition on the catalyst surface. The optimized catalyst with an atomic ratio of Y/Au = 5(1 wt% Au loading weight) yields an 87.8% acetylene conversion and almost 100% selectivity for VCM under the reaction of GHSV(CH) = 800 hat 180 ℃.The durability test indicates that the 5 Y-1 Au/AC catalyst maintains high catalytic activity for more than2300 h at 30 hGHSV(CH) and 180 ℃, indicating great promise as a non-mercury catalyst for PVC manufacture.展开更多
This paper presented a study on the role of yttrium addition to CuO/CeO2 catalyst for water-gas shift reaction. A single-step co-precipitation method was used for preparation of a series of yttrium doped CuO/CeO2 cata...This paper presented a study on the role of yttrium addition to CuO/CeO2 catalyst for water-gas shift reaction. A single-step co-precipitation method was used for preparation of a series of yttrium doped CuO/CeO2 catalysts with yttrium content in the range of 0-5wt.%. Properties of the obtained samples were characterized and analyzed by X-ray diffraction （XRD）, Raman spectroscopy, H2-TPR, cyclic voltammetry （CV） and the BET method. The results revealed that catalytic activity was increased with the yttrium content at first, but then decreased with the further increase of yttrium content. Herein, CuO/CeO2 catalyst doped with 2wt.% of yttrium showed the highest catalytic activity （CO conversion reaches 93.4% at 250 ℃） and thermal stability for WGS reaction. The catalytic activity was correlated with the surface area, the area of peak γ of H2-TPR profile （i.e., the reduction of surface copper oxide （crystalline forms） interacted with surface oxygen vacancies on ceria）, and the area of peak C2 and A1 （Cu^0→←Cu^2＋ in cyclic voltammetry process）, respectively. Besides, Raman spectra provided evidences for a synergistic Cu-Ovacancy interaction, and it was indicated that doping yttrium may facilitate the formation of oxygen vacancies on ceria.展开更多
The utilization of pure hydrogen as an energy source in fuel cells gave rise to renewed interest in developing active and stable water-gas shift catalysts. Gold catalysts have proven to be very efficient for water-gas...The utilization of pure hydrogen as an energy source in fuel cells gave rise to renewed interest in developing active and stable water-gas shift catalysts. Gold catalysts have proven to be very efficient for water-gas shift reaction at low temperature. The aim of the present study was to investigate the effect of:(i) different preparation methods(impregnation and coprecipitation) to obtain a modified ceria support,and(ii) the amount of Y_2 O_3(1.0 wt%, 2.5 wt%, 5.0 wt% and 7.5 wt%) as dopant on the water-gas shift activity of Au/CeO_2 catalysts. An extended characterization by means of S_(BET), XRD, HRTEM/HAADF, FTIR,H_2-TPR and CO-TPR measurements in combination with careful evaluation of the catalyst behavior allowed to shed light on the parameters governing the water-gas shift activity. The catalysts show very high activity(>90% CO conversion) in the temperature range 180-220 ℃,with a slightly better performance of the gold catalysts on supports prepared by impregnation. The decreased activity with increasing Y_2 O_3 concentration is related to the hindering of oxygen mobility due to ordering of surface oxygen vacancies in vicinity of segregated Y^(3+). The effect of catalyst pre-treatments and the stability of the best performing samples were examined as well.展开更多
Catalytic combustion of methane was conducted by using a Cu-based catalyst prepared by the plasma-assisted impregnation method. The properties of the catalysts were surveyed by X-ray diffraction （XRD）, X-ray photoel...Catalytic combustion of methane was conducted by using a Cu-based catalyst prepared by the plasma-assisted impregnation method. The properties of the catalysts were surveyed by X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS） and temperature-programmed reduction （H2-TPR）. The results showed that the activity of CuO/ZrO2 with the CeO2 and Y2O3 was obviously increased compared with the CuO/ZrO2 catalyst, which was examined in relation to the structure and surface characteristics and might be correlated with their surface oxygen species and redox properties. Among the investigated catalysts, the Ce-CuO/ZrO2 sample exhibited the highest activity for methane combustion.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.21361140371,51021003,21774119 and 21774071)
文摘A highly efficient strategy for the synthesis of polylactide with the UV absorption ability was established by employing a Salan-yttrium complex（acting as a fast runing catalyst） combined with large excess hydroxyl functionalized benzophenone, BP′-OH. During polymerization, BP′-OH, acting as the chain transfer agent, attached to the active rare-earth metal catalyst via a rapid-reversible exchange reaction to initiate the polymerization. Thus, more polyester chains appeared to grow from one active metal species, and the UV absorption fragments were incorporated into the polymer chains at specific sites, in situ. A high productivity up to 1000 mol LA/mol（Salan-Y） was successfully achieved and 100 BP′-labeled PLA chains grew from each active metal center.
文摘The highly dispersed supported ruthenium-yttrium (Ru-Y) bimetallic catalysts were prepared by impregnation method and their catalytic performance for hydrogenation of ester was fully investigated. The catalyst was characterized by X-ray diffraction and field emission scanning electron microscopy. The results show that the average particle diameter of the bimetallic crystallites was less than 10 nm. The effects of the reaction temperature, the hydrogen pressure, the amount of catalyst and the proportion of yttrium in catalyst on the hydrogenation of ester were studied. The experimental results show that the introduction of yttrium not only changed the chemical and textural properties of ruthenium-based catalyst but also controlled the formation of Ru-Y alloy. The Ru-Y catalyst (Ru-2%Y/TiO2) exhibited high catalytic activity and good selectivity towards the higher alcohols. Under optimal reaction conditions of 240°C and 5 MPa hydrogen pressure, the conversion of palm oil esters was above 93.4% while the selectivity towards alcohol was above 99.0%.
基金Project supported by the Natural Science Foundation of China(91545115,21403178,and 21503278)the Program for Innovative Research Team in Chinese Universities(IRT_14R31)+1 种基金the Scientific Program of Fujian Province for Young College Teachers(JA15002)Fundamental Research Funds for the Central Universities(20720170024)
文摘The addition of yttrium chloride(YCl) to an activated carbon-supported Au catalyst(Au/AC) can markedly promote the catalytic performance of acetylene hydrochlorination to the vinyl chloride monomer(VCM), The structure and physicochemical features of the YCl-modified catalysts(Y-Au/AC)were measured by X-ray diffraction, X-ray photoelectron spectroscopy, temperature-programmed reduction, CH-temperature programmed desorption, and scanning transmission electron microscopy.The presence of YClwas found suppressing the reduction of highly oxidized Au(δ=1,3) to metallic Au~0 dependently and thus retard the agglomeration of Au nanoparticles during the reaction. In addition,the additive of YClto the Au/AC catalyst greatly inhibits the coke deposition on the catalyst surface. The optimized catalyst with an atomic ratio of Y/Au = 5(1 wt% Au loading weight) yields an 87.8% acetylene conversion and almost 100% selectivity for VCM under the reaction of GHSV(CH) = 800 hat 180 ℃.The durability test indicates that the 5 Y-1 Au/AC catalyst maintains high catalytic activity for more than2300 h at 30 hGHSV(CH) and 180 ℃, indicating great promise as a non-mercury catalyst for PVC manufacture.
基金supported by the National Natural Science Foundation of China (20771025)A-type Science and Technology Projects of Fujian Provincial Department of Education (JA08021)
文摘This paper presented a study on the role of yttrium addition to CuO/CeO2 catalyst for water-gas shift reaction. A single-step co-precipitation method was used for preparation of a series of yttrium doped CuO/CeO2 catalysts with yttrium content in the range of 0-5wt.%. Properties of the obtained samples were characterized and analyzed by X-ray diffraction （XRD）, Raman spectroscopy, H2-TPR, cyclic voltammetry （CV） and the BET method. The results revealed that catalytic activity was increased with the yttrium content at first, but then decreased with the further increase of yttrium content. Herein, CuO/CeO2 catalyst doped with 2wt.% of yttrium showed the highest catalytic activity （CO conversion reaches 93.4% at 250 ℃） and thermal stability for WGS reaction. The catalytic activity was correlated with the surface area, the area of peak γ of H2-TPR profile （i.e., the reduction of surface copper oxide （crystalline forms） interacted with surface oxygen vacancies on ceria）, and the area of peak C2 and A1 （Cu^0→←Cu^2＋ in cyclic voltammetry process）, respectively. Besides, Raman spectra provided evidences for a synergistic Cu-Ovacancy interaction, and it was indicated that doping yttrium may facilitate the formation of oxygen vacancies on ceria.
基金supported by the Bulgarian National Science Fund(ContractдH09/5/2016)the CONACYT PDCPN 1216 and the University of Turin(Ricerca Locale 2016-2017)
文摘The utilization of pure hydrogen as an energy source in fuel cells gave rise to renewed interest in developing active and stable water-gas shift catalysts. Gold catalysts have proven to be very efficient for water-gas shift reaction at low temperature. The aim of the present study was to investigate the effect of:(i) different preparation methods(impregnation and coprecipitation) to obtain a modified ceria support,and(ii) the amount of Y_2 O_3(1.0 wt%, 2.5 wt%, 5.0 wt% and 7.5 wt%) as dopant on the water-gas shift activity of Au/CeO_2 catalysts. An extended characterization by means of S_(BET), XRD, HRTEM/HAADF, FTIR,H_2-TPR and CO-TPR measurements in combination with careful evaluation of the catalyst behavior allowed to shed light on the parameters governing the water-gas shift activity. The catalysts show very high activity(>90% CO conversion) in the temperature range 180-220 ℃,with a slightly better performance of the gold catalysts on supports prepared by impregnation. The decreased activity with increasing Y_2 O_3 concentration is related to the hindering of oxygen mobility due to ordering of surface oxygen vacancies in vicinity of segregated Y^(3+). The effect of catalyst pre-treatments and the stability of the best performing samples were examined as well.
基金Project supported by National Natural Science Foundation of China (90610005, 20836008 and U0633003)the Project of Science and Technology Department of Zhejiang Province of China (2007C1306)
文摘Catalytic combustion of methane was conducted by using a Cu-based catalyst prepared by the plasma-assisted impregnation method. The properties of the catalysts were surveyed by X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS） and temperature-programmed reduction （H2-TPR）. The results showed that the activity of CuO/ZrO2 with the CeO2 and Y2O3 was obviously increased compared with the CuO/ZrO2 catalyst, which was examined in relation to the structure and surface characteristics and might be correlated with their surface oxygen species and redox properties. Among the investigated catalysts, the Ce-CuO/ZrO2 sample exhibited the highest activity for methane combustion.
