La（0.6）Sr（0.4）Co（0.2）Fe（0.8）O（3-δ）（LSCF） anodes were infiltrated by Gd（0.2）Ce（0.8）O（1.9）GDC） nanoparticles to improve the oxygen evolution reaction（OER） performance of solid oxide electrolysis ce...La（0.6）Sr（0.4）Co（0.2）Fe（0.8）O（3-δ）（LSCF） anodes were infiltrated by Gd（0.2）Ce（0.8）O（1.9）GDC） nanoparticles to improve the oxygen evolution reaction（OER） performance of solid oxide electrolysis cells（SOECs） in CO2 electroreduction. The effect of GDC loading was investigated, and 10 wt% GDC nanoparticle infiltration of the LSCF（10 GDC/LSCF） anode results in the highest OER performance. Electrochemical impedance spectra measurements indicate that the infiltration by GDC nanoparticles greatly decreases the polarization resistance of the SOECs with the 10 GDC/LSCF anodes. The following distribution of relaxation time analysis suggests that four individual electrode processes are involved in the OER and that all of them are accelerated on the 10 GDC/LSCF anode. Three phase boundaries, surface oxygen vacancies, and bulk oxygen mobility increased, based on scanning electron microscopy and temperature-programmed desorption of O2 characterizations, and contributed to the enhancement of the four electrode processes of the OER and electrochemical performance of SOECs.展开更多
The simultaneous removal of up to 92% of the surfactant template and chemical implantation of transition metal complexes into mesopores has been successfully achieved by treating as-synthesized pure siliceous MCM-41 w...The simultaneous removal of up to 92% of the surfactant template and chemical implantation of transition metal complexes into mesopores has been successfully achieved by treating as-synthesized pure siliceous MCM-41 with supercritical CO2 modified with CH2Cl2/MeOH mixture, resulting in the formation of functionalized material with uniform pore structure.展开更多
The optimum Mo/[H^+] ratio per unit cell of the active precursors in Mo/HZSM-5 catalysts for methane dehydro-aromatization, measured by1H MAS NMR, was found to be about 1 when adjusting the acid sites by altering eith...The optimum Mo/[H^+] ratio per unit cell of the active precursors in Mo/HZSM-5 catalysts for methane dehydro-aromatization, measured by1H MAS NMR, was found to be about 1 when adjusting the acid sites by altering either the SiO2/Al2O3 ratios or the Mo loading. This implies that a concerted interaction between the Mo species and the Bronsted acid sites probably features the bifunctionality of the Mo/HZSM-5 catalyst. On the other hand, it was found that the driving force for Mo species to move into the HSZM-5 zeolite channels and the interaction between the Mo species and the Bronsted acid sites are closely and proportionably related with the amount of Bronsted acid sites per unit cell.展开更多
The elegant 2D multiquantum (MQ) MAS NMR has been applied to investigate the coordination of Al atoms in SAPO-34. The results show that the effects of the template and/or water on the coordination of Al atoms are sig...The elegant 2D multiquantum (MQ) MAS NMR has been applied to investigate the coordination of Al atoms in SAPO-34. The results show that the effects of the template and/or water on the coordination of Al atoms are significant, which lead to the formation of various Al species. Up to four kinds of Al species are distinctly resolved.展开更多
The electrocatalysts of Pt/C, PtRu/C and Ru/C were prepared by the impregnation method. The facet characterization, the dispersion and the particle size for the catalysts were determined by means of X ray diffractio...The electrocatalysts of Pt/C, PtRu/C and Ru/C were prepared by the impregnation method. The facet characterization, the dispersion and the particle size for the catalysts were determined by means of X ray diffraction and transmission electron microscopy. X ray photoelectron spectroscopy was also used to analyze the state and the valency of the noble metals. The results show that the particle size was in nanometer range and the binary metals have come into being an alloy. The platinum in the catalysts existed in zero valency. The valency of the ruthenium on the surface is different from that in the body, while the ruthenium on the surface existed in oxide form. PtRu/C and Pt/C are of good activity to the electrooxidation of hydrogen except Ru/C. PtRu/C is more tolerant of CO than Pt/C, and CO is only adsorbed on Pt.展开更多
The interactions of oxygen with pre-reduced silver catalysts as well as theircatalytic properties for CO selective oxidation in H_2 after oxygen pre-treatment are studied inthis paper. It is found that the pretreatmen...The interactions of oxygen with pre-reduced silver catalysts as well as theircatalytic properties for CO selective oxidation in H_2 after oxygen pre-treatment are studied inthis paper. It is found that the pretreatment exerts a strong influence on the activity andselectivity of the silver catalyst. A drop in activity and selectivity is observed after treating apre-reduced catalyst with oxygen at low temperatures, whereas a converse result is obtained after anoxidizing treatment at high temperatures (T ≥ 350℃). O_2-TPD results show that surface oxygenspecies adsorbs on silver surface after the oxygen treatment at low temperatures. However,penetration of oxygen into the silver is enhanced by a high temperature treatment, meanwhile thesurface oxygen species disappear. No other silver species except metallic silver are observed on allthe catalysts by XRD, and the size of silver particle is not changed after the treatment withoxygen at low temperatures. The surface oxygen species formed by oxygen treatment can also beremoved by hydrogen reduction. The strongly-adsorbed surface oxygen species prohibit the adsorptionand diffusion of oxygen species in reaction gas on the surface of silver catalyst, causing thedecrease in CO oxidation activity, in other words, it is important to obtain a clean silver surfacefor increasing the catalyst activity in CO removal from H_2-rich feed gas. The differences inactivity and selectivity due to the oxygen pretreatment at different temperatures are discussed interms of the changes in the surface/subsurface oxygen species of the silver particles.展开更多
Various VO_x/SiO_2 catalysts were prepared by the methods of physical mixing,conventional wetness impregnation and ultrasonication-assistant impregnation. The catalysts werecharacterized by XRD, UV-Vis DRS, Raman, TPR...Various VO_x/SiO_2 catalysts were prepared by the methods of physical mixing,conventional wetness impregnation and ultrasonication-assistant impregnation. The catalysts werecharacterized by XRD, UV-Vis DRS, Raman, TPR, ESR and TPSR techniques and the nature of the vanadiumspecies were correlated to their catalytic performance in the reaction of direct conversion ofmethane to formaldehyde. It is concluded that highly dispersed monomeric and low oligomeric vanadiaspecies are formed on the sample prepared with both traditional wetness impregnation method andultrasonication-assistant impregnation, whereas in the latter case, the amount of oligomeric vanadiaspecies is much smaller. The V_2O_5 microcrystallines are the dominant species on the materialprepared by physical mixing method. During the selective oxidation of methane, V^V species arereduced to V^(IV) paramagnetic species and both microcrystalline V_2O_5 species and oligomericvanadia species are found to further disperse and transform into tetrahedral vanadia species. Basedon the results of UV Raman spectroscopy and TPSR, CO_2 is suggested to be formed via two differentroutes, in which one is from the sequence reaction of CH_4 → HCHO → CO → CO_2 over monomericvanadia species, and the other is from the direct oxidation of methane to CO_2 over oligomericvanadia species. Oligomeric vanadia species is more active than monomeric vanadia species formethane activation.展开更多
A NaA zeolite membrane was synthesized on the surface of the stainless steel slab. The membrane was characterized by XRD and SEM. The membrane was continuous and highly intergrown. The size of NaA zeolite crystals ...A NaA zeolite membrane was synthesized on the surface of the stainless steel slab. The membrane was characterized by XRD and SEM. The membrane was continuous and highly intergrown. The size of NaA zeolite crystals was about 5 ~ 6 mm.展开更多
The effects of CO2 on the partial oxidation of heptane for hydrogen generation have been studied. Based on the experimental results and thermodynamic equilibrium calculations, the validity of CO2 addition to weaken t...The effects of CO2 on the partial oxidation of heptane for hydrogen generation have been studied. Based on the experimental results and thermodynamic equilibrium calculations, the validity of CO2 addition to weaken the hot spots, and the feasibility of the autothermal operation are discussed.展开更多
The effect of dimethyl ether (DME) co-feed on the catalytic performance of methane dehy-droaromatization (MDA) over 6Mo/HZSM-5 catalyst was investigated as a function of DME concentration under reaction conditions of ...The effect of dimethyl ether (DME) co-feed on the catalytic performance of methane dehy-droaromatization (MDA) over 6Mo/HZSM-5 catalyst was investigated as a function of DME concentration under reaction conditions of T=1023 K, p=101 kPa and SV=1500 ml/(g·h). A high benzene yield was obtained and the stability of the catalyst was improved by adding 1.5%DME to the CH4 feed. The C6H6 yield was as high as ca. 10% even after reaction for 6 h. The stability of the catalyst was further improved when DME concentration in the co-feed gas was increased to an appropriate value. TGA and TPO results of the used 6Mo/HZSM-5 catalyst showed that the amount of coke on the used catalyst was reduced and the chemical nature of the coke was changed. When 1.5%DME was added to the CH4 feed, the coke formed on the catalyst could be burned off more easily than that when only CH4 was used as reactant. It is supposed that the oxygen in DME may play a role in preventing the coke burnt off at lower temperature from transforming into the coke burnt off at higher temperature, which results in the improvement of the stability of the catalyst.展开更多
High quality A-type zeolite membranes, with enlarged area over 70 cm2, were successfully synthesized on a tubular a-Al2O3 support by applying the vacuum seeding method.
Conventional oven drying (COD) and supercritical drying (SCD) methods wereapplied to the preparation of Mn-substituted hexaaluminate (BaMnAl_(11)O_(19-α)) catalysts. Theeffect of drying methods on phase composition, ...Conventional oven drying (COD) and supercritical drying (SCD) methods wereapplied to the preparation of Mn-substituted hexaaluminate (BaMnAl_(11)O_(19-α)) catalysts. Theeffect of drying methods on phase composition, specific surface area, pore structure, reductionbehavior of Mn^(3+) ions, and combustion activity of the samples was investigated. The homogenousmixing of the components in the sol-gel process could be maintained by SCD, and the hexaaluminatephase was almost the only phase of the resulting materials after calcination. H_2-TPR revealed thatthe Mn^(3+) ions in the sample obtained by SCD were easier to be reduced than that by COD. Moreover,the samples obtained by SCD have higher surface area, narrower pore size distribution, and highercombustion activity than those obtained by COD.展开更多
基金This work was supported by the National Key R&D Program of China(2017YFA0700102)the National Natural Science Foundation of China(21703237,21573222,91545202)+1 种基金Dalian Institute of Chemical Physics(DICP DMTO201702)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB17020200)and CAS Youth Innovation Promotion(2015145)~~
文摘La（0.6）Sr（0.4）Co（0.2）Fe（0.8）O（3-δ）（LSCF） anodes were infiltrated by Gd（0.2）Ce（0.8）O（1.9）GDC） nanoparticles to improve the oxygen evolution reaction（OER） performance of solid oxide electrolysis cells（SOECs） in CO2 electroreduction. The effect of GDC loading was investigated, and 10 wt% GDC nanoparticle infiltration of the LSCF（10 GDC/LSCF） anode results in the highest OER performance. Electrochemical impedance spectra measurements indicate that the infiltration by GDC nanoparticles greatly decreases the polarization resistance of the SOECs with the 10 GDC/LSCF anodes. The following distribution of relaxation time analysis suggests that four individual electrode processes are involved in the OER and that all of them are accelerated on the 10 GDC/LSCF anode. Three phase boundaries, surface oxygen vacancies, and bulk oxygen mobility increased, based on scanning electron microscopy and temperature-programmed desorption of O2 characterizations, and contributed to the enhancement of the four electrode processes of the OER and electrochemical performance of SOECs.
文摘The simultaneous removal of up to 92% of the surfactant template and chemical implantation of transition metal complexes into mesopores has been successfully achieved by treating as-synthesized pure siliceous MCM-41 with supercritical CO2 modified with CH2Cl2/MeOH mixture, resulting in the formation of functionalized material with uniform pore structure.
文摘The optimum Mo/[H^+] ratio per unit cell of the active precursors in Mo/HZSM-5 catalysts for methane dehydro-aromatization, measured by1H MAS NMR, was found to be about 1 when adjusting the acid sites by altering either the SiO2/Al2O3 ratios or the Mo loading. This implies that a concerted interaction between the Mo species and the Bronsted acid sites probably features the bifunctionality of the Mo/HZSM-5 catalyst. On the other hand, it was found that the driving force for Mo species to move into the HSZM-5 zeolite channels and the interaction between the Mo species and the Bronsted acid sites are closely and proportionably related with the amount of Bronsted acid sites per unit cell.
基金We are grateful to the support of the National Natural Science Foundation of China and the Ministry of Science and Technology of China. We appreciate Dr. R. Fu (NHMFL Tallahassee) for his kind help regarding the MQ MAS NMR experiments.
文摘The elegant 2D multiquantum (MQ) MAS NMR has been applied to investigate the coordination of Al atoms in SAPO-34. The results show that the effects of the template and/or water on the coordination of Al atoms are significant, which lead to the formation of various Al species. Up to four kinds of Al species are distinctly resolved.
基金Supported by the National 973project(No.G2 0 0 0 0 2 6 4 10 ) and Inovation Funds of Dalian Insitute of Chem icalPhysics
文摘The electrocatalysts of Pt/C, PtRu/C and Ru/C were prepared by the impregnation method. The facet characterization, the dispersion and the particle size for the catalysts were determined by means of X ray diffraction and transmission electron microscopy. X ray photoelectron spectroscopy was also used to analyze the state and the valency of the noble metals. The results show that the particle size was in nanometer range and the binary metals have come into being an alloy. The platinum in the catalysts existed in zero valency. The valency of the ruthenium on the surface is different from that in the body, while the ruthenium on the surface existed in oxide form. PtRu/C and Pt/C are of good activity to the electrooxidation of hydrogen except Ru/C. PtRu/C is more tolerant of CO than Pt/C, and CO is only adsorbed on Pt.
文摘The interactions of oxygen with pre-reduced silver catalysts as well as theircatalytic properties for CO selective oxidation in H_2 after oxygen pre-treatment are studied inthis paper. It is found that the pretreatment exerts a strong influence on the activity andselectivity of the silver catalyst. A drop in activity and selectivity is observed after treating apre-reduced catalyst with oxygen at low temperatures, whereas a converse result is obtained after anoxidizing treatment at high temperatures (T ≥ 350℃). O_2-TPD results show that surface oxygenspecies adsorbs on silver surface after the oxygen treatment at low temperatures. However,penetration of oxygen into the silver is enhanced by a high temperature treatment, meanwhile thesurface oxygen species disappear. No other silver species except metallic silver are observed on allthe catalysts by XRD, and the size of silver particle is not changed after the treatment withoxygen at low temperatures. The surface oxygen species formed by oxygen treatment can also beremoved by hydrogen reduction. The strongly-adsorbed surface oxygen species prohibit the adsorptionand diffusion of oxygen species in reaction gas on the surface of silver catalyst, causing thedecrease in CO oxidation activity, in other words, it is important to obtain a clean silver surfacefor increasing the catalyst activity in CO removal from H_2-rich feed gas. The differences inactivity and selectivity due to the oxygen pretreatment at different temperatures are discussed interms of the changes in the surface/subsurface oxygen species of the silver particles.
基金Financial support from the Ministry of Science and Technology of China(National Key Project of Fundamental Research:Grant G1999022406)is gratefully acknowledged.
文摘Various VO_x/SiO_2 catalysts were prepared by the methods of physical mixing,conventional wetness impregnation and ultrasonication-assistant impregnation. The catalysts werecharacterized by XRD, UV-Vis DRS, Raman, TPR, ESR and TPSR techniques and the nature of the vanadiumspecies were correlated to their catalytic performance in the reaction of direct conversion ofmethane to formaldehyde. It is concluded that highly dispersed monomeric and low oligomeric vanadiaspecies are formed on the sample prepared with both traditional wetness impregnation method andultrasonication-assistant impregnation, whereas in the latter case, the amount of oligomeric vanadiaspecies is much smaller. The V_2O_5 microcrystallines are the dominant species on the materialprepared by physical mixing method. During the selective oxidation of methane, V^V species arereduced to V^(IV) paramagnetic species and both microcrystalline V_2O_5 species and oligomericvanadia species are found to further disperse and transform into tetrahedral vanadia species. Basedon the results of UV Raman spectroscopy and TPSR, CO_2 is suggested to be formed via two differentroutes, in which one is from the sequence reaction of CH_4 → HCHO → CO → CO_2 over monomericvanadia species, and the other is from the direct oxidation of methane to CO_2 over oligomericvanadia species. Oligomeric vanadia species is more active than monomeric vanadia species formethane activation.
基金We are grateful to the financial support from the National Natural Science Foundation of China (59789201) and the National Advanced Materials Committee of China (715-006-0122).
文摘A NaA zeolite membrane was synthesized on the surface of the stainless steel slab. The membrane was characterized by XRD and SEM. The membrane was continuous and highly intergrown. The size of NaA zeolite crystals was about 5 ~ 6 mm.
文摘The effects of CO2 on the partial oxidation of heptane for hydrogen generation have been studied. Based on the experimental results and thermodynamic equilibrium calculations, the validity of CO2 addition to weaken the hot spots, and the feasibility of the autothermal operation are discussed.
基金Financial supports from the Ministry of Science and Technology of Chinathe Natural Science Foundation of China+1 种基金the Chinese Academy of Sciencethe BP-China Joint Research Center are gratefully acknowledged.
文摘The effect of dimethyl ether (DME) co-feed on the catalytic performance of methane dehy-droaromatization (MDA) over 6Mo/HZSM-5 catalyst was investigated as a function of DME concentration under reaction conditions of T=1023 K, p=101 kPa and SV=1500 ml/(g·h). A high benzene yield was obtained and the stability of the catalyst was improved by adding 1.5%DME to the CH4 feed. The C6H6 yield was as high as ca. 10% even after reaction for 6 h. The stability of the catalyst was further improved when DME concentration in the co-feed gas was increased to an appropriate value. TGA and TPO results of the used 6Mo/HZSM-5 catalyst showed that the amount of coke on the used catalyst was reduced and the chemical nature of the coke was changed. When 1.5%DME was added to the CH4 feed, the coke formed on the catalyst could be burned off more easily than that when only CH4 was used as reactant. It is supposed that the oxygen in DME may play a role in preventing the coke burnt off at lower temperature from transforming into the coke burnt off at higher temperature, which results in the improvement of the stability of the catalyst.
文摘High quality A-type zeolite membranes, with enlarged area over 70 cm2, were successfully synthesized on a tubular a-Al2O3 support by applying the vacuum seeding method.
文摘Conventional oven drying (COD) and supercritical drying (SCD) methods wereapplied to the preparation of Mn-substituted hexaaluminate (BaMnAl_(11)O_(19-α)) catalysts. Theeffect of drying methods on phase composition, specific surface area, pore structure, reductionbehavior of Mn^(3+) ions, and combustion activity of the samples was investigated. The homogenousmixing of the components in the sol-gel process could be maintained by SCD, and the hexaaluminatephase was almost the only phase of the resulting materials after calcination. H_2-TPR revealed thatthe Mn^(3+) ions in the sample obtained by SCD were easier to be reduced than that by COD. Moreover,the samples obtained by SCD have higher surface area, narrower pore size distribution, and highercombustion activity than those obtained by COD.
