Amorphous Ni-B/ZrO2 catalysts were prepared by coprecipitation-chemical reduction with KBH4 aqueous solution,and various crystalline phase ZrO2(amorphous-ZrO2,tetragonal-ZrO2 and monoclinic-ZrO2) supported Ni-B cataly...Amorphous Ni-B/ZrO2 catalysts were prepared by coprecipitation-chemical reduction with KBH4 aqueous solution,and various crystalline phase ZrO2(amorphous-ZrO2,tetragonal-ZrO2 and monoclinic-ZrO2) supported Ni-B catalysts were obtained by thermal treatment in 5%H2-N2 stream at different temperature.The effect of ZrO2 polymorphs and the treatment temperature on the catalytic performance for the CO selective methanation were investigated,and the catalysts were characterized by N2 physisorption,Powder X-ray diffraction(XRD), Temperature-Programmed Desorption(CO-TPD and H2-TPD),and Differential Scanning Calorimeter(DSC).The treatment temperature affected strongly the crystalline structure of ZrO2,and the CO methanation activity and selectivity of the Ni-B/ZrO2 catalysts were significantly influenced by the crystalline phase of ZrO2.Of the three forms of ZrO2 polymorphs(amorphou-ZrO2,tetragonal-ZrO2 and monoclinic-ZrO2),the amorphous-ZrO2 supported nickle catalyst showed highest CO methanation activity,attributing in large part to the largest specific surface area and the optimum CO/H2 absorption intensity of the Ni-B/amorphous-ZrO2 catalyst.展开更多
Series of carbon nanotube supported Ru-based catalysts were prepared by impregnation method and applied successfully for complete removal of CO by CO selective methanation from H2-rich gas stream conducted in a fixed-...Series of carbon nanotube supported Ru-based catalysts were prepared by impregnation method and applied successfully for complete removal of CO by CO selective methanation from H2-rich gas stream conducted in a fixed-bed quartz tubular reactor at ambient pressure. It was found that the metal promoter, reduction temperature and metal loading affected the catalytic properties significantly. The most excellent performance was presented by 30 wt% Ru-Zr/CNTs catalyst reduced at 350 ℃. Since it decreased CO concentration to below 10 ppm from 12000 ppm by CO selective methanation at the temperature range of 180-240 ℃, and kept CO selectivity higher than 85% at the temperature below 200 ℃. Characterization using XRD, TEM, H2-TPR and XPS suggests that Zr modification of Ru/CNTs results in the weakening of the interaction between Ru and CNTs, a higher Ru dispersion and the oxidization of surface Ru. Amorphous and high dispersed Ru particles with small size were obtained for 30 wt% Ru-Zr/CNTs catalyst reduced at 350 ℃, leading to excellent catalytic performance in CO selective methanation.展开更多
The Ni-B-Oδ and Ni-B-Zr-Oδ catalysts were prepared by the method of chemical reduction, and the deep removal of CO by selective methanation from the reformed fuels was performed over the as-prepared catalysts. The r...The Ni-B-Oδ and Ni-B-Zr-Oδ catalysts were prepared by the method of chemical reduction, and the deep removal of CO by selective methanation from the reformed fuels was performed over the as-prepared catalysts. The results showed that zirconium strongly influenced the activity and selectivity of the Ni-B-Zr-Oδ catalysts. Over the Ni-B-Oδ catalyst, the highest CO conversion obtained was only 24.32% under the experi-mental conditions studied. However, over the Ni-B-Zr-Oδ catalysts, the CO methanation conversion was higher than 90% when the temperature was increased to 220℃. Additionally, it was found that the Ni/B mole ratio also affected the performance of the Ni-B-Zr-Oδ catalysts. With the increase of the Ni/B mole ratio from 1.8 to 2.2, the CO methanation activity of the catalyst was improved. But when the Ni/B mole ratio was higher than 2.2, the performance of the catalyst for CO selective methanation decreased instead. Among all the catalysts, the Ni29B13Zr58Oδ catalyst investigated here exhibited the highest catalytic performance for the CO selective methanation, which was capable of reducing the CO outlet concentration to less than 40 ppm from the feed gases stream in the temperature range of 230-250℃, while the CO2 conversion was kept below 8% all along. Characterization of the Ni-B-Oδ and Ni-B-Zr-Oδ catalysts was provided by XRD, SEM, DSC, and XPS.展开更多
Ni/ZrO2 catalysts were prepared by the incipient-wetness impregnation method and were investigated in activity and selectivity for the selective catalytic methanation of CO in hydrogen-rich gases with more than 20 vol...Ni/ZrO2 catalysts were prepared by the incipient-wetness impregnation method and were investigated in activity and selectivity for the selective catalytic methanation of CO in hydrogen-rich gases with more than 20 vol% CO2. The result showed that Ni loadings significantly influenced the performance of Ni/ZrO2 catalyst. The 1.6 wt% Ni loading catalyst exhibited the highest catalytic activity among all the catalysts in the selective methanation of CO in hydrogen-rich gas. The outlet concentration of CO was less than 20 ppm with the hydrogen consumption below 7%, at a gas-hourly-space velocity as high as 10000 h-1 and a temperature range of 260 °C to 280 °C. The X-ray diffraction （XRD） and temperature programmed reduction （TPR） measurements showed that NiO was dispersed thoroughly on the surface of ZrO2 support if Ni loading was under 1.6 wt%. When Ni loading was increased to 3 wt% or above, the free bulk NiO species began to assemble, which was not favorable to increase the selectivity of the catalyst.展开更多
Amorphous Ni-Ru-B/ZrO2 catalyst was prepared by the means of chemical reduction, and selective CO methanation as a strategy for CO removal in fuel processing applications was investigated over the amorphous Ni-Ru-B/Zr...Amorphous Ni-Ru-B/ZrO2 catalyst was prepared by the means of chemical reduction, and selective CO methanation as a strategy for CO removal in fuel processing applications was investigated over the amorphous Ni-Ru-B/ZrO2 catalyst. The result showed that, at the temperature of 210-230 ℃, the catalyst was shown to be capable of reducing CO in a hydrogen-rich reformate to less than 10 ppm, while keeping the CO2 conversion below 1.55% and the hydrogen consumption below 6.50%. ？2009 Xin Fa Dong. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.展开更多
Amorphous Ni-Ru-B/ZrO2 catalysts were prepared by chemical reduction method. The effects of Ni-Ru-B loading and Ru/Ni mole ratio on the catalytic performance for selective CO methanation from reformed fuel were studie...Amorphous Ni-Ru-B/ZrO2 catalysts were prepared by chemical reduction method. The effects of Ni-Ru-B loading and Ru/Ni mole ratio on the catalytic performance for selective CO methanation from reformed fuel were studied, and the catalysts were characterized by BET, ICP, XRD and TPD. The results showed that Ru strongly affected the catalytic activity and selectivity by increasing the thermal stability of amorphous structure, promoting the dispersion of the catalyst particle, and intensifying the CO adsorption. For the catalysts with Ru/Ni mole ratio under 0.15, the CO methanation conversion and selectivity increased significantly with the increasing Ru/Ni mole ratio. Among all the catalysts investigated, the 30 wt% Ni-Ru-B loading amorphous Ni61Ru9B30/ZrO2 catalyst with 0.15 Ru/Ni mole ratio presented the best catalytic performance, over which higher than 99.9% of CO conversion was obtained in the temperature range of 230℃-250℃, and the CO2 conversion was kept under the level of 0.9%.展开更多
Nanostructured titanium dioxides were synthesized via various post-treatments of titanate nanofibers obtained from titanium precursors by hydrothermal reactions. The microstructures of TiO2 and supported Ru/TiO2 catal...Nanostructured titanium dioxides were synthesized via various post-treatments of titanate nanofibers obtained from titanium precursors by hydrothermal reactions. The microstructures of TiO2 and supported Ru/TiO2 catalysts were characterized with X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray analysis, and nitrogen adsorption isotherms. The phase structure, particle size, morphology, and specific surface area were determined. The supported Ru catalysts were applied for the selective methanation of CO in a hydrogen-rich stream. The results indicated that the Ru catalyst supported on rutile and TiO2-B exhibited higher catalytic performance than the counterpart supported on anatase, which suggested the distinct interaction between Ru nanoparticles and TiO2 resulting from different crystalline phases and morphology.展开更多
Selective photocatalytic aerobic oxidation of methane to value-added chemicals offers a promising pathway for sustainable chemical industry,yet remains a huge challenge owing to the consecutive overoxidation of primar...Selective photocatalytic aerobic oxidation of methane to value-added chemicals offers a promising pathway for sustainable chemical industry,yet remains a huge challenge owing to the consecutive overoxidation of primary products.Here,a type II heterojunction were constructed in Ag-AgBr/ZnO to reduce the oxidation potential of stimulated holes and prevent the undesirable CH_(4) overoxidation side reactions.For photocatalytic oxidation of methane under ambient temperature,the products yield of 1499.6μmol gcat^(-1) h^(-1) with a primary products selectivity of 77.9%was achieved over Ag-AgBr/ZnO,which demonstrate remarkable improvement compared to Ag/ZnO(1089.9μmol gcat^(-1) h^(-1) ,40.1%).The superior activity and selectivity result from the promoted charge separation and the redox potential matching with methane activation after introducing AgBr species.Mechanism investigation elucidated that the photo-generated holes transferred from the valence band of ZnO to that of AgBr,which prevent H_(2)O oxidation and enhance the selective generation of•OOH radical.展开更多
The oxide sample NiO/CeO_2 with feed atomic ratio of Ni/Ce at 40%, prepared by co-precipitation method and calcination at 500 oC for 2 h, was impregnated by aqueous solution of NH_4Cl to dope chlorine ions. After the ...The oxide sample NiO/CeO_2 with feed atomic ratio of Ni/Ce at 40%, prepared by co-precipitation method and calcination at 500 oC for 2 h, was impregnated by aqueous solution of NH_4Cl to dope chlorine ions. After the impregnated samples were dried and calcined at 400 oC for 2 h, the calcined samples NiO（Cl_x）/CeO_2（x=0.1–0.5） were characterized by means of X-ray diffraction（XRD） and temperature programmed reduction（TPR） techniques. It was comfirmed that the doped chlorine ions hindered reduction of Ni^（2＋） ions in the calcined samples, and suppressed adsorption of CO_2 and CO on the reduced sample Ni（Cl_（0.3））/CeO_2. The reduced samples Ni（Cl_x）/CeO_2（x=0.0–0.5） were used as catalysts for selective methanation of CO in H_2-rich gas. When chlorine ions were doped at the feed atomic ratio of Cl/Ce（x） equal to 0.3–0.5, CO in the H_2-rich gas could be removed to below 10 ppm with a high selectivity more than 50% in a wide reaction temperature range of 220–280 oC. However, the selectivity of CO methanation decreased with reaction time in the durability tests over the catalyst Ni（Cl_（0.3））/CeO_2 at the reaction temperature of 260 oC and even at 220 oC. The lowering of the selectivity was found to be related with the surface composition change of the catalyst in the catalytic reaction.展开更多
A series of Ce1-xFexO2 （x=0, 0.2, 0.4, 0.6, 0.8, 1） complex oxide catalysts were prepared using the coprecipitation method. The catalysts were characterized by means of XRD and H2-TPR. The reactions between methane ...A series of Ce1-xFexO2 （x=0, 0.2, 0.4, 0.6, 0.8, 1） complex oxide catalysts were prepared using the coprecipitation method. The catalysts were characterized by means of XRD and H2-TPR. The reactions between methane and lattice oxygen from the complex oxides were investigated. The characteristic results revealed that the combination of Ce and Fe oxide in the catalysts could lower the temperature necessary to reduce the cerium oxide. The catalytic activity for selective CH4 oxidation was strongly influenced by dropped Fe species. Adding the appropriate amount of Fe2O3 to CeO2 could promote the action between CH4 and CeO2. Dispersed Fe2O3 first returned to the original state and would then virtually form the Fe species on the catalyst, which could be considered as the active site for selective CH4 oxidation. The appearance of carbon formation was significant and the oxidation of carbon appeared to be the rate-determining step; the amounts of surface reducible oxygen species in CeO2 were also relevant to the activity. Among all the catalysts, Ce0.6Fe0.402 exhibited the best activity, which converted 94.52% of CH4 at 900 ℃.展开更多
Large surface areas nano-scale zirconia was prepared by the self-assembly route and was employed as support in nickel catalysts for the CO selective methanation. The effects of Ni loading and the catalyst calcination ...Large surface areas nano-scale zirconia was prepared by the self-assembly route and was employed as support in nickel catalysts for the CO selective methanation. The effects of Ni loading and the catalyst calcination temperature on the performance of the catalyst for CO selective methanation reaction were investigated. The cata- lysts were characterized by Brunauer-Emmett-Teller （BET）, transmission electron microscope （TEM）, X-ray dif- fraction （XRD） and temperature-programmed reduction （TPR）. The results showed that the as-synthesized Ni/nano-ZrO2 catalysts presented high activity for CO methanation due to the interaction between Ni active particle and nano zir- conia support. The selectivity for the CO methanation influenced significantly by the particle size of the active Ni species. The exorbitant calcination resulted in the conglomeration of dispersive Ni particles and led to the decrease of CO methanation selectivity. Among the catalysts studied, the 7.5% （by mass） Ni/ZrO2 catalyst calcinated at 500℃ was the most effective for the CO selective methanation. It can preferentially catalyze the CO methanation with a higher 99% conversion in the CO/CO2 competitive methanation system over the temperature range of 260-280℃, while keeping the CO2 conversion relatively low.展开更多
A citric acid complex method was employed to prepare Ce/Ni mixed oxides with various Ce/Ni ratios useful for selective oxidation methane to syngas in the absence of gaseous oxygen,and the catalytic activity measuremen...A citric acid complex method was employed to prepare Ce/Ni mixed oxides with various Ce/Ni ratios useful for selective oxidation methane to syngas in the absence of gaseous oxygen,and the catalytic activity measurement was investigated in a fixed bed reactor at 800 oC.The prepared oxygen carriers were characterized by various characterization techniques such as TG-DSC,XRD and TPR.The results of TG-DSC indicated that the Ce1-xNixO2 precursor generated a stable phase after the heat-treatment at temperatures above 800 oC.The XRD characterization suggested that some Ce-Ni solid solution was formed when Ni2+ ions was incorporated into the lattice of CeO2,and it led to the generation of O-vacancy which could improve the oxygen mobility in the lattice of oxygen carriers.It was found that Ce0.8Ni0.2O2 gave the highest activity in the selective oxidation methane to syngas reaction,and the average methane conversion,CO and H2 selectivity reached to 82.31%,82.41% and 87.64%,respectively.The reason could be not only attributed to the fitting amount of NiO dispersed on the CeO2 surface and bulk but also to actual lattice oxygen amount increased in oxygen carrier.展开更多
Chemical interaction of Ce-Fe mixed oxides was investigated in methane selective oxidation via methane temperature programmed reduction and methane isothermal reaction tests over Ce-Fe oxygen carriers. In methane temp...Chemical interaction of Ce-Fe mixed oxides was investigated in methane selective oxidation via methane temperature programmed reduction and methane isothermal reaction tests over Ce-Fe oxygen carriers. In methane temperature programmed reduction test, Ce-Fe oxide behaved complete oxidation at the lower temperature and selective oxidation at higher temperatures. Ce-Fe mixed oxides with the Fe content in the range of 0.1~）.5 was able to produce syngas with high selectivity in high-temperature range （800-900 ~C）, and a higher Fe amount over 0.5 seemed to depress the CO formation. In isothermal reaction, complete oxidation oc- curred at beginning following with selective oxidation later. Ce~_xFexO2~ oxygen carriers （x5_0.5） were proved to be suitable for the selective oxidation of methane. Ce-Fe mixed oxides had the well-pleasing reducibility with high oxygen releasing rate and CO selec- tivity due to the interaction between Ce and Fe species. Strong chemical interaction of Ce-Fe mixed oxides originated from both Fe＊ activated CeO2 and Ce3＋ activated iron oxides （FeOm）, and those chemical interaction greatly enhanced the oxygen mobility and selectivity.展开更多
A series of Fe2O3/Al2O3, Fe2O3/CeO2, Ce0.7Zr0.3O2, and Fe2O3/Ce1-xZrxO2（x = 0.1–0.4） oxides was prepared and their physicochemical features were investigated by X-ray diffraction（XRD）, transmission electron micro...A series of Fe2O3/Al2O3, Fe2O3/CeO2, Ce0.7Zr0.3O2, and Fe2O3/Ce1-xZrxO2（x = 0.1–0.4） oxides was prepared and their physicochemical features were investigated by X-ray diffraction（XRD）, transmission electron microscope（TEM）, and H2-temperature-programmed reduction（H2-TPR） techniques. The gas–solid reactions between these oxides and methane for syngas generation as well as the catalytic performance for selective oxidation of carbon deposition in O2-enriched atmosphere were investigated in detail. The results show that the samples with the presence of Fe2O3show much higher activity for methane oxidation compared with the Ce0.7Zr0.3O2solid solution,while the CeO2-contained samples represent higher CO selectively in methane oxidation than the Fe2O3/Al2O3sample. This suggests that the iron species should be the active sites for methane activation, and the cerium oxides provide the oxygen source for the selective oxidation of the activated methane to syngas during the reaction between methane and Fe2O3/Ce0.7Zr0.3O2. For the oxidation process of the carbon deposition, the CeO2-containing samples show much higher CO selectivity than the Fe2O3/Al2O3sample, which indicates that the cerium species should play a very important role in catalyzing the carbon selective oxidation to CO. The presence of the Ce–Zr–O solid solution could induce the growth direction of the carbonfilament, resulting in a loose contact between the carbon filament and the catalyst. This results in abundant exposed active sites for catalyzing carbon oxidation, strongly improving the oxidation rate of the carbon deposition over this sample. In addition, the Fe2O3/Ce0.7Zr0.3O2also represents much higher selectivity（ca. 97 %） for the conversion of carbon to CO than the Fe2O3/CeO2sample, which can be attributed to the higher concentration of reduced cerium sites on this sample. The increase of the Zr content in the Fe2O3/Ce1-xZrxO2samples could improve the reactivity of the materials for methane oxidation, but it also reduces the selectivity for CO formation.展开更多
The concentration of the major greenhouse gas CO_(2)is rapidly increasing in the atmosphere,leading to global warming and a range of environmental issues.An efficient circulation and utilization of CO_(2)is critical i...The concentration of the major greenhouse gas CO_(2)is rapidly increasing in the atmosphere,leading to global warming and a range of environmental issues.An efficient circulation and utilization of CO_(2)is critical in the current environmental context.Methanation,an exothermic process,emerges as a critical strategy for effective CO_(2)utilization.On this front,there is a significant demand for rational design of catalysts that maintain high activity and methane selectivity over a wide temperature range(250-550℃).The catalyst that can promise a consistent reaction even at 500℃under an atmospheric pressure is thus obliged.The present study investigated bimetallic catalysts with SiC,which is known for its exceptional thermal conductivity,and CeO_(2),which is characterized by its CO_(2)affinity,as base materials.We incorporated Ni-M and Ru-M(M=Co and Mn)as the active metals,each loaded at 2%.Impressively,with merely 20 mg,the Ni-Co/SiC catalyst achieved a CO_(2)conversion rate of 77%and CH_(4)selectivity of 88%at 500℃,in a fixed-bed tubular reactor system with conditions of H_(2)/CO_(2)=4,a total flow rate of 70 ml min^(-1),and a steady GHSV of 12,000 h^(-1).Moreover,2Ni-2Co/CeO_(2)catalyst demonstrated exceptional performance with a 76%conversion of CO_(2)and a 83%selectivity for CH_(4),all under identical conditions.The catalyst’s durability was confirmed by a subsequent 40-hour stability test,which showed only a 3-5%degradation.The developed catalysts were comprehensively characterized by BET/BJH,CO pulse chemisorption,H_(2)-TPR,HAADF-STEM-EDS,SEM-EDS and XRD etc.to unveil their physicochemical and surface traits.It was found that Co and Mn,when integrated,effectively restrained the agglomeration of Ni and Ru particles,ensuring optimal metal dispersion on the support.In conclusion,our synthesized bimetallic catalysts shown a sustained catalytic capability,even in the high-temperature environment.展开更多
CO in H2-rich gas must be removed to meet various requirements in industrial applications. Four methods, i.e., the precipitation method using aqueous ammonia, the complexing method using urea, the complexing method us...CO in H2-rich gas must be removed to meet various requirements in industrial applications. Four methods, i.e., the precipitation method using aqueous ammonia, the complexing method using urea, the complexing method using citric acid and the precipitation method using ammonium carbonate, were adopted to prepare samples NiO/CeO2 as catalyst precursors for removal of CO from H2-rich gas via selective methanation reaction. The sample NiO/CeO2 prepared by the precipitation method using aqueous ammonia as precipitant exhibited the highest catalytic activity both for CO methanation and for CO2 methanation after reduction prior to the catalytic reaction. Chlorine ion was then doped to suppress CO2 conversion. Effect of chlorine doping was investigated. Over the optimal catalyst 40%Ni（Cl（0.2））/CeO2, CO in the H2-rich gas was removed to below 10 ppm with selectivity of 60% or higher at reaction temperatures 230–250 ℃ in the test period of 75 h.展开更多
The methane selective oxidation was a"holy grail"reaction.However,peroxidation and low selectivity limited the application.Herein,we combined three Au contents with TiO_(2)in both encapsulation(xAu@TiO_(2))a...The methane selective oxidation was a"holy grail"reaction.However,peroxidation and low selectivity limited the application.Herein,we combined three Au contents with TiO_(2)in both encapsulation(xAu@TiO_(2))and surface-loaded(xAu/TiO_(2))ways by MOF derivation strategy,reported a catalyst 0.5Au@TiO_(2)exhibited a CH_(3)OH yield of 32.5μmol·g^(-1)·h^(-1)and a CH_(3)OH selectivity of 80.6%under catalytic conditions of only CH_(4),O_(2),and H_(2)O.Mechanically speaking,the catalytic activity was controlled by both electron-hole separation efficiency and core-shell structure.The interfacial contact between Au nanoparticles and TiO_(2)in xAu@TiO_(2)and xAu/TiO_(2)induced the formation of oxygen vacancies,with 0.5 Au content showing the highest oxygen vacancy concentration.At the same Au content,xAu@TiO_(2)generated more oxygen vacancies than xAu/TiO_(2).The oxygen vacancy acted as an effective electron cold trap,which enhanced the photogenerated carrier separation efficiency and thereby improved the catalytic activity.In-situ DRIFTs revealed that the isolated OH(non-hydrogen bond adsorption)were key species for the methane selective oxidation,playing a role in the activation of CH_(4)to^(*)CH_(3).However,an overabundance of isolated OH led to severe overoxidation.Fortunately,the core-shell structure over xAu@TiO_(2)provided a slow-release environment for isolated OH through the intermediate state of^(*)OH(hydrogen bond adsorption)to balance the formation rate and consumption rate of isolated OH,doubling the methanol yield and increasing the>29%selectivity.These results showed a new strategy for the control of the overoxidation rate via a strategy of MOF encapsulation followed by pyrolytic derivation for methane selective oxidation.展开更多
The adsorption behavior of CO_2, CH_4 and their mixtures in bituminous coal was investigated in this study. First, a bituminous coal model was built through molecular dynamic(MD) simulations, and it was confirmed to b...The adsorption behavior of CO_2, CH_4 and their mixtures in bituminous coal was investigated in this study. First, a bituminous coal model was built through molecular dynamic(MD) simulations, and it was confirmed to be reasonable by comparing the simulated results with the experimental data. Grand Canonical Monte Carlo(GCMC)simulations were then carried out to investigate the single and binary component adsorption of CO_2 and CH_4with the built bituminous coal model. For the single component adsorption, the isosteric heat of CO_2 adsorption is greater than that of CH_4 adsorption. CO_2 also exhibits stronger electrostatic interactions with the heteroatom groups in the bituminous coal model compared with CH_4, which can account for the larger adsorption capacity of CO_2 in the bituminous coal model. In the case of binary adsorption of CO_2 and CH_4mixtures, CO_2 exhibits the preferential adsorption compared with CH_4 under the studied conditions. The adsorption selectivity of CO_2 exhibited obvious change with increasing pressure. At lower pressure, the adsorption selectivity of CO_2 shows a rapid decrease with increasing the temperature, whereas it becomes insensitive to temperature at higher pressure. Additionally, the adsorption selectivity of CO_2 decreases gradually with the increase of the bulk CO_2 mole fraction and the depth of CO_2 injection site.展开更多
The results of studying the interaction of H2 and O2 with Pt-, Ru- and Pt-Ru catalysts supported on 2% Ce/（θ＋α）-AlEO3, at varying the ratios and concentrations of supported elements by using the temperature-progr...The results of studying the interaction of H2 and O2 with Pt-, Ru- and Pt-Ru catalysts supported on 2% Ce/（θ＋α）-AlEO3, at varying the ratios and concentrations of supported elements by using the temperature-programmed desorption method are presented. It has been shown that HE is adsorbed as four forms, differing in the structure, temperature, order and activation energy of desorption： HEads, HE＋ads, Hads, Hat （Tdes 〉 873 K）. The relationship of activity and selectivity of Pt-Ru catalysts with the presence of active centers able to adsorb atomic hydrogen with desorption energy （Edes） = 60-70 kJ/mol in the catalytic oxidation of methane was determined. It was found that the O2 adsorbed as two forms differing in the structure, temperature and activation energy of desorption. It has been determined that changing the atomic ratio of elements in the catalysts significantly affect on the adsorption Of OE. The introduction of ruthenium into the platinum catalyst increases the oxygen adsorption; and the surface is stabilized in a homogeneous state. Quantum chemical calculations of the activation of C-H bonds in a molecule of methane on Ru,,Pt, （m ＋ n = 4） clusters have been carried out.展开更多
Photocatalytic CH_(4) coupling into high-valued C_(2)H_(6) is highly attractive,whereas the photosynthetic rate,especially under oxygen-free system,is still unsatisfying.Here,we designed the negatively charged metal s...Photocatalytic CH_(4) coupling into high-valued C_(2)H_(6) is highly attractive,whereas the photosynthetic rate,especially under oxygen-free system,is still unsatisfying.Here,we designed the negatively charged metal supported on metal oxide nanosheets to activate the inert C-H bond in CH_(4)and hence accelerate CH_(4) coupling performance.As an example,the synthetic Au/ZnO porous nanosheets exhibit the C_(2)H_(6) photosynthetic rate of 1,121.6μmol g^(-1)_(cat)h^(-1)and the CH_(4) conversion rate of 2,374.6μmol g^(-1)_(cat)h^(-1) under oxygen-free system,2 orders of magnitude higher than those of previously reported photocatalysts.By virtue of several in situ spectroscopic techniques,it is established that the generated Au^(δ-)and O^-species together polarized the C-H bond,while the Au^(δ-)and O^-species jointly stabilized the CH_(3) intermediates,which favored the coupling of CH_(3) intermediate to photosynthesize C_(2)H_(6) instead of overoxidation into CO_(x).Thus,the design of dual active species is beneficial for achieving high-efficient CH_(4)-to-C_(2)H_(6) photoconversion.展开更多
基金Supported by the National Natural Science Foundation of China(21076047)the Natural Science Foundation of Zhongkai University of Agriculture and Engineering(G3100026)
文摘Amorphous Ni-B/ZrO2 catalysts were prepared by coprecipitation-chemical reduction with KBH4 aqueous solution,and various crystalline phase ZrO2(amorphous-ZrO2,tetragonal-ZrO2 and monoclinic-ZrO2) supported Ni-B catalysts were obtained by thermal treatment in 5%H2-N2 stream at different temperature.The effect of ZrO2 polymorphs and the treatment temperature on the catalytic performance for the CO selective methanation were investigated,and the catalysts were characterized by N2 physisorption,Powder X-ray diffraction(XRD), Temperature-Programmed Desorption(CO-TPD and H2-TPD),and Differential Scanning Calorimeter(DSC).The treatment temperature affected strongly the crystalline structure of ZrO2,and the CO methanation activity and selectivity of the Ni-B/ZrO2 catalysts were significantly influenced by the crystalline phase of ZrO2.Of the three forms of ZrO2 polymorphs(amorphou-ZrO2,tetragonal-ZrO2 and monoclinic-ZrO2),the amorphous-ZrO2 supported nickle catalyst showed highest CO methanation activity,attributing in large part to the largest specific surface area and the optimum CO/H2 absorption intensity of the Ni-B/amorphous-ZrO2 catalyst.
文摘Series of carbon nanotube supported Ru-based catalysts were prepared by impregnation method and applied successfully for complete removal of CO by CO selective methanation from H2-rich gas stream conducted in a fixed-bed quartz tubular reactor at ambient pressure. It was found that the metal promoter, reduction temperature and metal loading affected the catalytic properties significantly. The most excellent performance was presented by 30 wt% Ru-Zr/CNTs catalyst reduced at 350 ℃. Since it decreased CO concentration to below 10 ppm from 12000 ppm by CO selective methanation at the temperature range of 180-240 ℃, and kept CO selectivity higher than 85% at the temperature below 200 ℃. Characterization using XRD, TEM, H2-TPR and XPS suggests that Zr modification of Ru/CNTs results in the weakening of the interaction between Ru and CNTs, a higher Ru dispersion and the oxidization of surface Ru. Amorphous and high dispersed Ru particles with small size were obtained for 30 wt% Ru-Zr/CNTs catalyst reduced at 350 ℃, leading to excellent catalytic performance in CO selective methanation.
基金the National Natural Science Foundation of China (20576023)the Guangdong Province Natural Science Foundation (06025660)
文摘The Ni-B-Oδ and Ni-B-Zr-Oδ catalysts were prepared by the method of chemical reduction, and the deep removal of CO by selective methanation from the reformed fuels was performed over the as-prepared catalysts. The results showed that zirconium strongly influenced the activity and selectivity of the Ni-B-Zr-Oδ catalysts. Over the Ni-B-Oδ catalyst, the highest CO conversion obtained was only 24.32% under the experi-mental conditions studied. However, over the Ni-B-Zr-Oδ catalysts, the CO methanation conversion was higher than 90% when the temperature was increased to 220℃. Additionally, it was found that the Ni/B mole ratio also affected the performance of the Ni-B-Zr-Oδ catalysts. With the increase of the Ni/B mole ratio from 1.8 to 2.2, the CO methanation activity of the catalyst was improved. But when the Ni/B mole ratio was higher than 2.2, the performance of the catalyst for CO selective methanation decreased instead. Among all the catalysts, the Ni29B13Zr58Oδ catalyst investigated here exhibited the highest catalytic performance for the CO selective methanation, which was capable of reducing the CO outlet concentration to less than 40 ppm from the feed gases stream in the temperature range of 230-250℃, while the CO2 conversion was kept below 8% all along. Characterization of the Ni-B-Oδ and Ni-B-Zr-Oδ catalysts was provided by XRD, SEM, DSC, and XPS.
基金the National Natural Science Foundation of China (20576023)the Guangdong Province Natural Science Foundation (06025660)
文摘Ni/ZrO2 catalysts were prepared by the incipient-wetness impregnation method and were investigated in activity and selectivity for the selective catalytic methanation of CO in hydrogen-rich gases with more than 20 vol% CO2. The result showed that Ni loadings significantly influenced the performance of Ni/ZrO2 catalyst. The 1.6 wt% Ni loading catalyst exhibited the highest catalytic activity among all the catalysts in the selective methanation of CO in hydrogen-rich gas. The outlet concentration of CO was less than 20 ppm with the hydrogen consumption below 7%, at a gas-hourly-space velocity as high as 10000 h-1 and a temperature range of 260 °C to 280 °C. The X-ray diffraction （XRD） and temperature programmed reduction （TPR） measurements showed that NiO was dispersed thoroughly on the surface of ZrO2 support if Ni loading was under 1.6 wt%. When Ni loading was increased to 3 wt% or above, the free bulk NiO species began to assemble, which was not favorable to increase the selectivity of the catalyst.
基金supported by the National Natural Science Foundation of China(No.20576023)the Guangdong Province Natural Science Foundation(No.06025660).
文摘Amorphous Ni-Ru-B/ZrO2 catalyst was prepared by the means of chemical reduction, and selective CO methanation as a strategy for CO removal in fuel processing applications was investigated over the amorphous Ni-Ru-B/ZrO2 catalyst. The result showed that, at the temperature of 210-230 ℃, the catalyst was shown to be capable of reducing CO in a hydrogen-rich reformate to less than 10 ppm, while keeping the CO2 conversion below 1.55% and the hydrogen consumption below 6.50%. ？2009 Xin Fa Dong. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
基金supported by the National Natural Science Foundation of China (No: 20576023)the Guangdong Province Natural Science Foundation(No: 06025660)the Natural Science Foundation of Zhongkai University of Agriculture and Engineering (G3100026)
文摘Amorphous Ni-Ru-B/ZrO2 catalysts were prepared by chemical reduction method. The effects of Ni-Ru-B loading and Ru/Ni mole ratio on the catalytic performance for selective CO methanation from reformed fuel were studied, and the catalysts were characterized by BET, ICP, XRD and TPD. The results showed that Ru strongly affected the catalytic activity and selectivity by increasing the thermal stability of amorphous structure, promoting the dispersion of the catalyst particle, and intensifying the CO adsorption. For the catalysts with Ru/Ni mole ratio under 0.15, the CO methanation conversion and selectivity increased significantly with the increasing Ru/Ni mole ratio. Among all the catalysts investigated, the 30 wt% Ni-Ru-B loading amorphous Ni61Ru9B30/ZrO2 catalyst with 0.15 Ru/Ni mole ratio presented the best catalytic performance, over which higher than 99.9% of CO conversion was obtained in the temperature range of 230℃-250℃, and the CO2 conversion was kept under the level of 0.9%.
基金V. ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.20703042）, the National Basic Research Program of China （No.2010 CB923300）, USTC-NSRL Association Funding （No.KY 2060030009）, and Fundamental Research Funds for the Central Universities （No.WK2060030010）.
文摘Nanostructured titanium dioxides were synthesized via various post-treatments of titanate nanofibers obtained from titanium precursors by hydrothermal reactions. The microstructures of TiO2 and supported Ru/TiO2 catalysts were characterized with X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray analysis, and nitrogen adsorption isotherms. The phase structure, particle size, morphology, and specific surface area were determined. The supported Ru catalysts were applied for the selective methanation of CO in a hydrogen-rich stream. The results indicated that the Ru catalyst supported on rutile and TiO2-B exhibited higher catalytic performance than the counterpart supported on anatase, which suggested the distinct interaction between Ru nanoparticles and TiO2 resulting from different crystalline phases and morphology.
基金supported by the National Natural Science Foundation of China(22208290,22288102,22078288,22225802)the key R&D Program Projects in Zhejiang Province(2021C03005).
文摘Selective photocatalytic aerobic oxidation of methane to value-added chemicals offers a promising pathway for sustainable chemical industry,yet remains a huge challenge owing to the consecutive overoxidation of primary products.Here,a type II heterojunction were constructed in Ag-AgBr/ZnO to reduce the oxidation potential of stimulated holes and prevent the undesirable CH_(4) overoxidation side reactions.For photocatalytic oxidation of methane under ambient temperature,the products yield of 1499.6μmol gcat^(-1) h^(-1) with a primary products selectivity of 77.9%was achieved over Ag-AgBr/ZnO,which demonstrate remarkable improvement compared to Ag/ZnO(1089.9μmol gcat^(-1) h^(-1) ,40.1%).The superior activity and selectivity result from the promoted charge separation and the redox potential matching with methane activation after introducing AgBr species.Mechanism investigation elucidated that the photo-generated holes transferred from the valence band of ZnO to that of AgBr,which prevent H_(2)O oxidation and enhance the selective generation of•OOH radical.
基金Project supported by the National Natural Science Foundation of China(21643008)
文摘The oxide sample NiO/CeO_2 with feed atomic ratio of Ni/Ce at 40%, prepared by co-precipitation method and calcination at 500 oC for 2 h, was impregnated by aqueous solution of NH_4Cl to dope chlorine ions. After the impregnated samples were dried and calcined at 400 oC for 2 h, the calcined samples NiO（Cl_x）/CeO_2（x=0.1–0.5） were characterized by means of X-ray diffraction（XRD） and temperature programmed reduction（TPR） techniques. It was comfirmed that the doped chlorine ions hindered reduction of Ni^（2＋） ions in the calcined samples, and suppressed adsorption of CO_2 and CO on the reduced sample Ni（Cl_（0.3））/CeO_2. The reduced samples Ni（Cl_x）/CeO_2（x=0.0–0.5） were used as catalysts for selective methanation of CO in H_2-rich gas. When chlorine ions were doped at the feed atomic ratio of Cl/Ce（x） equal to 0.3–0.5, CO in the H_2-rich gas could be removed to below 10 ppm with a high selectivity more than 50% in a wide reaction temperature range of 220–280 oC. However, the selectivity of CO methanation decreased with reaction time in the durability tests over the catalyst Ni（Cl_（0.3））/CeO_2 at the reaction temperature of 260 oC and even at 220 oC. The lowering of the selectivity was found to be related with the surface composition change of the catalyst in the catalytic reaction.
基金the National Natural Science Foundation of China (50574046)National Natural Science Foundation of Major Research Projects (90610035)+1 种基金Natural Science Foundation of Yunnan Province (2004E0058Q)High School Doctoral Subject Special Science and Re- search Foundation of Ministry of Education (20040674005)
文摘A series of Ce1-xFexO2 （x=0, 0.2, 0.4, 0.6, 0.8, 1） complex oxide catalysts were prepared using the coprecipitation method. The catalysts were characterized by means of XRD and H2-TPR. The reactions between methane and lattice oxygen from the complex oxides were investigated. The characteristic results revealed that the combination of Ce and Fe oxide in the catalysts could lower the temperature necessary to reduce the cerium oxide. The catalytic activity for selective CH4 oxidation was strongly influenced by dropped Fe species. Adding the appropriate amount of Fe2O3 to CeO2 could promote the action between CH4 and CeO2. Dispersed Fe2O3 first returned to the original state and would then virtually form the Fe species on the catalyst, which could be considered as the active site for selective CH4 oxidation. The appearance of carbon formation was significant and the oxidation of carbon appeared to be the rate-determining step; the amounts of surface reducible oxygen species in CeO2 were also relevant to the activity. Among all the catalysts, Ce0.6Fe0.402 exhibited the best activity, which converted 94.52% of CH4 at 900 ℃.
基金Supported by the National Natural Science Foundation of China(21276054,21376280)
文摘Large surface areas nano-scale zirconia was prepared by the self-assembly route and was employed as support in nickel catalysts for the CO selective methanation. The effects of Ni loading and the catalyst calcination temperature on the performance of the catalyst for CO selective methanation reaction were investigated. The cata- lysts were characterized by Brunauer-Emmett-Teller （BET）, transmission electron microscope （TEM）, X-ray dif- fraction （XRD） and temperature-programmed reduction （TPR）. The results showed that the as-synthesized Ni/nano-ZrO2 catalysts presented high activity for CO methanation due to the interaction between Ni active particle and nano zir- conia support. The selectivity for the CO methanation influenced significantly by the particle size of the active Ni species. The exorbitant calcination resulted in the conglomeration of dispersive Ni particles and led to the decrease of CO methanation selectivity. Among the catalysts studied, the 7.5% （by mass） Ni/ZrO2 catalyst calcinated at 500℃ was the most effective for the CO selective methanation. It can preferentially catalyze the CO methanation with a higher 99% conversion in the CO/CO2 competitive methanation system over the temperature range of 260-280℃, while keeping the CO2 conversion relatively low.
基金Project supported by the Natural Science Foundation of Chinese (50774038)the Natural Science Foundation of Yunnan Province (2008E030M)+1 种基金the Research Fund for the Doctoral Program of Higher Education of China (20095314120005)the Foundation of Kunming University of Science and Technology (KKZ3200927010)
文摘A citric acid complex method was employed to prepare Ce/Ni mixed oxides with various Ce/Ni ratios useful for selective oxidation methane to syngas in the absence of gaseous oxygen,and the catalytic activity measurement was investigated in a fixed bed reactor at 800 oC.The prepared oxygen carriers were characterized by various characterization techniques such as TG-DSC,XRD and TPR.The results of TG-DSC indicated that the Ce1-xNixO2 precursor generated a stable phase after the heat-treatment at temperatures above 800 oC.The XRD characterization suggested that some Ce-Ni solid solution was formed when Ni2+ ions was incorporated into the lattice of CeO2,and it led to the generation of O-vacancy which could improve the oxygen mobility in the lattice of oxygen carriers.It was found that Ce0.8Ni0.2O2 gave the highest activity in the selective oxidation methane to syngas reaction,and the average methane conversion,CO and H2 selectivity reached to 82.31%,82.41% and 87.64%,respectively.The reason could be not only attributed to the fitting amount of NiO dispersed on the CeO2 surface and bulk but also to actual lattice oxygen amount increased in oxygen carrier.
基金Project supported by National Natural Science Foundation of China(51204083,51374004,51104074,51174105,51306084)the Applied Basic Research Program of Yunnan Province(2012FD016)the Candidate Talents Training Fund of Yunnan Province(2012HB009)
文摘Chemical interaction of Ce-Fe mixed oxides was investigated in methane selective oxidation via methane temperature programmed reduction and methane isothermal reaction tests over Ce-Fe oxygen carriers. In methane temperature programmed reduction test, Ce-Fe oxide behaved complete oxidation at the lower temperature and selective oxidation at higher temperatures. Ce-Fe mixed oxides with the Fe content in the range of 0.1~）.5 was able to produce syngas with high selectivity in high-temperature range （800-900 ~C）, and a higher Fe amount over 0.5 seemed to depress the CO formation. In isothermal reaction, complete oxidation oc- curred at beginning following with selective oxidation later. Ce~_xFexO2~ oxygen carriers （x5_0.5） were proved to be suitable for the selective oxidation of methane. Ce-Fe mixed oxides had the well-pleasing reducibility with high oxygen releasing rate and CO selec- tivity due to the interaction between Ce and Fe species. Strong chemical interaction of Ce-Fe mixed oxides originated from both Fe＊ activated CeO2 and Ce3＋ activated iron oxides （FeOm）, and those chemical interaction greatly enhanced the oxygen mobility and selectivity.
基金financially supported by the National Natural Science Foundation of China (Nos. 51004060, 51104074, and 51174105)the Natural Science Foundation of Yunnan Province (No. 2010ZC018)
文摘A series of Fe2O3/Al2O3, Fe2O3/CeO2, Ce0.7Zr0.3O2, and Fe2O3/Ce1-xZrxO2（x = 0.1–0.4） oxides was prepared and their physicochemical features were investigated by X-ray diffraction（XRD）, transmission electron microscope（TEM）, and H2-temperature-programmed reduction（H2-TPR） techniques. The gas–solid reactions between these oxides and methane for syngas generation as well as the catalytic performance for selective oxidation of carbon deposition in O2-enriched atmosphere were investigated in detail. The results show that the samples with the presence of Fe2O3show much higher activity for methane oxidation compared with the Ce0.7Zr0.3O2solid solution,while the CeO2-contained samples represent higher CO selectively in methane oxidation than the Fe2O3/Al2O3sample. This suggests that the iron species should be the active sites for methane activation, and the cerium oxides provide the oxygen source for the selective oxidation of the activated methane to syngas during the reaction between methane and Fe2O3/Ce0.7Zr0.3O2. For the oxidation process of the carbon deposition, the CeO2-containing samples show much higher CO selectivity than the Fe2O3/Al2O3sample, which indicates that the cerium species should play a very important role in catalyzing the carbon selective oxidation to CO. The presence of the Ce–Zr–O solid solution could induce the growth direction of the carbonfilament, resulting in a loose contact between the carbon filament and the catalyst. This results in abundant exposed active sites for catalyzing carbon oxidation, strongly improving the oxidation rate of the carbon deposition over this sample. In addition, the Fe2O3/Ce0.7Zr0.3O2also represents much higher selectivity（ca. 97 %） for the conversion of carbon to CO than the Fe2O3/CeO2sample, which can be attributed to the higher concentration of reduced cerium sites on this sample. The increase of the Zr content in the Fe2O3/Ce1-xZrxO2samples could improve the reactivity of the materials for methane oxidation, but it also reduces the selectivity for CO formation.
基金support made this research possible.Additionally,Chopendra G.Wasnik(D2001369)support provided by JICA(Japan International Cooperation Agency,Japan)through the IITH-JICA FRIENDSHIP scholarship during the study。
文摘The concentration of the major greenhouse gas CO_(2)is rapidly increasing in the atmosphere,leading to global warming and a range of environmental issues.An efficient circulation and utilization of CO_(2)is critical in the current environmental context.Methanation,an exothermic process,emerges as a critical strategy for effective CO_(2)utilization.On this front,there is a significant demand for rational design of catalysts that maintain high activity and methane selectivity over a wide temperature range(250-550℃).The catalyst that can promise a consistent reaction even at 500℃under an atmospheric pressure is thus obliged.The present study investigated bimetallic catalysts with SiC,which is known for its exceptional thermal conductivity,and CeO_(2),which is characterized by its CO_(2)affinity,as base materials.We incorporated Ni-M and Ru-M(M=Co and Mn)as the active metals,each loaded at 2%.Impressively,with merely 20 mg,the Ni-Co/SiC catalyst achieved a CO_(2)conversion rate of 77%and CH_(4)selectivity of 88%at 500℃,in a fixed-bed tubular reactor system with conditions of H_(2)/CO_(2)=4,a total flow rate of 70 ml min^(-1),and a steady GHSV of 12,000 h^(-1).Moreover,2Ni-2Co/CeO_(2)catalyst demonstrated exceptional performance with a 76%conversion of CO_(2)and a 83%selectivity for CH_(4),all under identical conditions.The catalyst’s durability was confirmed by a subsequent 40-hour stability test,which showed only a 3-5%degradation.The developed catalysts were comprehensively characterized by BET/BJH,CO pulse chemisorption,H_(2)-TPR,HAADF-STEM-EDS,SEM-EDS and XRD etc.to unveil their physicochemical and surface traits.It was found that Co and Mn,when integrated,effectively restrained the agglomeration of Ni and Ru particles,ensuring optimal metal dispersion on the support.In conclusion,our synthesized bimetallic catalysts shown a sustained catalytic capability,even in the high-temperature environment.
基金Project supported partially by the National Natural Science Foundation of China(21171020)
文摘CO in H2-rich gas must be removed to meet various requirements in industrial applications. Four methods, i.e., the precipitation method using aqueous ammonia, the complexing method using urea, the complexing method using citric acid and the precipitation method using ammonium carbonate, were adopted to prepare samples NiO/CeO2 as catalyst precursors for removal of CO from H2-rich gas via selective methanation reaction. The sample NiO/CeO2 prepared by the precipitation method using aqueous ammonia as precipitant exhibited the highest catalytic activity both for CO methanation and for CO2 methanation after reduction prior to the catalytic reaction. Chlorine ion was then doped to suppress CO2 conversion. Effect of chlorine doping was investigated. Over the optimal catalyst 40%Ni（Cl（0.2））/CeO2, CO in the H2-rich gas was removed to below 10 ppm with selectivity of 60% or higher at reaction temperatures 230–250 ℃ in the test period of 75 h.
文摘The methane selective oxidation was a"holy grail"reaction.However,peroxidation and low selectivity limited the application.Herein,we combined three Au contents with TiO_(2)in both encapsulation(xAu@TiO_(2))and surface-loaded(xAu/TiO_(2))ways by MOF derivation strategy,reported a catalyst 0.5Au@TiO_(2)exhibited a CH_(3)OH yield of 32.5μmol·g^(-1)·h^(-1)and a CH_(3)OH selectivity of 80.6%under catalytic conditions of only CH_(4),O_(2),and H_(2)O.Mechanically speaking,the catalytic activity was controlled by both electron-hole separation efficiency and core-shell structure.The interfacial contact between Au nanoparticles and TiO_(2)in xAu@TiO_(2)and xAu/TiO_(2)induced the formation of oxygen vacancies,with 0.5 Au content showing the highest oxygen vacancy concentration.At the same Au content,xAu@TiO_(2)generated more oxygen vacancies than xAu/TiO_(2).The oxygen vacancy acted as an effective electron cold trap,which enhanced the photogenerated carrier separation efficiency and thereby improved the catalytic activity.In-situ DRIFTs revealed that the isolated OH(non-hydrogen bond adsorption)were key species for the methane selective oxidation,playing a role in the activation of CH_(4)to^(*)CH_(3).However,an overabundance of isolated OH led to severe overoxidation.Fortunately,the core-shell structure over xAu@TiO_(2)provided a slow-release environment for isolated OH through the intermediate state of^(*)OH(hydrogen bond adsorption)to balance the formation rate and consumption rate of isolated OH,doubling the methanol yield and increasing the>29%selectivity.These results showed a new strategy for the control of the overoxidation rate via a strategy of MOF encapsulation followed by pyrolytic derivation for methane selective oxidation.
基金Supported by the CNPC Huabei Oilfield Science and Technology Development Project(HBYT-CYY-2014-JS-378,HBYT-CYY-2015-JS-47)
文摘The adsorption behavior of CO_2, CH_4 and their mixtures in bituminous coal was investigated in this study. First, a bituminous coal model was built through molecular dynamic(MD) simulations, and it was confirmed to be reasonable by comparing the simulated results with the experimental data. Grand Canonical Monte Carlo(GCMC)simulations were then carried out to investigate the single and binary component adsorption of CO_2 and CH_4with the built bituminous coal model. For the single component adsorption, the isosteric heat of CO_2 adsorption is greater than that of CH_4 adsorption. CO_2 also exhibits stronger electrostatic interactions with the heteroatom groups in the bituminous coal model compared with CH_4, which can account for the larger adsorption capacity of CO_2 in the bituminous coal model. In the case of binary adsorption of CO_2 and CH_4mixtures, CO_2 exhibits the preferential adsorption compared with CH_4 under the studied conditions. The adsorption selectivity of CO_2 exhibited obvious change with increasing pressure. At lower pressure, the adsorption selectivity of CO_2 shows a rapid decrease with increasing the temperature, whereas it becomes insensitive to temperature at higher pressure. Additionally, the adsorption selectivity of CO_2 decreases gradually with the increase of the bulk CO_2 mole fraction and the depth of CO_2 injection site.
文摘The results of studying the interaction of H2 and O2 with Pt-, Ru- and Pt-Ru catalysts supported on 2% Ce/（θ＋α）-AlEO3, at varying the ratios and concentrations of supported elements by using the temperature-programmed desorption method are presented. It has been shown that HE is adsorbed as four forms, differing in the structure, temperature, order and activation energy of desorption： HEads, HE＋ads, Hads, Hat （Tdes 〉 873 K）. The relationship of activity and selectivity of Pt-Ru catalysts with the presence of active centers able to adsorb atomic hydrogen with desorption energy （Edes） = 60-70 kJ/mol in the catalytic oxidation of methane was determined. It was found that the O2 adsorbed as two forms differing in the structure, temperature and activation energy of desorption. It has been determined that changing the atomic ratio of elements in the catalysts significantly affect on the adsorption Of OE. The introduction of ruthenium into the platinum catalyst increases the oxygen adsorption; and the surface is stabilized in a homogeneous state. Quantum chemical calculations of the activation of C-H bonds in a molecule of methane on Ru,,Pt, （m ＋ n = 4） clusters have been carried out.
基金supported by the National Key R&D Program of China(2019YFA0210004,2022YFA1502904,2021YFA1501502)the National Natural Science Foundation of China(22125503,21975242,U2032212,21890754,22002148)+1 种基金2023 Synchrotron Radiation Joint Fund of USTCthe Youth Innovation Promotion Association of CAS(CX2340007003)。
文摘Photocatalytic CH_(4) coupling into high-valued C_(2)H_(6) is highly attractive,whereas the photosynthetic rate,especially under oxygen-free system,is still unsatisfying.Here,we designed the negatively charged metal supported on metal oxide nanosheets to activate the inert C-H bond in CH_(4)and hence accelerate CH_(4) coupling performance.As an example,the synthetic Au/ZnO porous nanosheets exhibit the C_(2)H_(6) photosynthetic rate of 1,121.6μmol g^(-1)_(cat)h^(-1)and the CH_(4) conversion rate of 2,374.6μmol g^(-1)_(cat)h^(-1) under oxygen-free system,2 orders of magnitude higher than those of previously reported photocatalysts.By virtue of several in situ spectroscopic techniques,it is established that the generated Au^(δ-)and O^-species together polarized the C-H bond,while the Au^(δ-)and O^-species jointly stabilized the CH_(3) intermediates,which favored the coupling of CH_(3) intermediate to photosynthesize C_(2)H_(6) instead of overoxidation into CO_(x).Thus,the design of dual active species is beneficial for achieving high-efficient CH_(4)-to-C_(2)H_(6) photoconversion.
