Currently,the solid adsorbents with porous structure have been widely applied in CO_(2)capture.However,the unmodified MgO-ZrO_(2)adsorbents appeared to be low adsorption capacity of CO_(2).The solid adsorbent material...Currently,the solid adsorbents with porous structure have been widely applied in CO_(2)capture.However,the unmodified MgO-ZrO_(2)adsorbents appeared to be low adsorption capacity of CO_(2).The solid adsorbent materials were successfully synthesized by loading TEPA onto the pore MgO/ZrO_(2)carriers in the paper.The pore structure and surface characteristic of the samples were analyzed by using XRD,BET,FT-IR and SEM.The adsorbent materials exhibited microcrystalline state,and the crystallinity of all samples gradually decreased as the increase of TEPA content.The pore structure analysis indicated that the modification of MgO-ZrO_(2)adsorbents with TEPA led to the decrease of the specific surface areas,but the narrow micro-mesopore size distributions ranging from 1.8-12 nm in the adsorbents still were maintained.FT-IR spectrum results further verified the successful loading of TEPA.The adsorption capacity of the adsorbents for CO_(2)were tested by using an adsorption apparatus equipped with gas chromatography.The results indicated that when the TEPA loading reached 50%,the sample exhibited the maximum adsorption value for CO_(2),reaching 4.07 mmol/g under the operation condition of 75℃and atmospheric pressure.This result could be assigned to not only the base active sites but also the coexistence of both micropore and mesopore in the adsorbent.After three cycles tests for CO_(2)capture,the adsorption value of the sample for CO_(2)can also reached 95%of its original adsorption capacity,which verified the excellent cyclic operation stability.展开更多
The novel magnetic sepiolite/Fe_(3)O_(4)/zero-valent iron(nZVI)nanocomposite(nZVI@SepH-Mag)was prepared and used to achieve the removal of Cr(VI)in this work.The nZVI@SepH-Mag composites were characterized by XRD,FTIR...The novel magnetic sepiolite/Fe_(3)O_(4)/zero-valent iron(nZVI)nanocomposite(nZVI@SepH-Mag)was prepared and used to achieve the removal of Cr(VI)in this work.The nZVI@SepH-Mag composites were characterized by XRD,FTIR,BET,SEM and TEM.The characterization results indicated that the structure of the composite consisted of small nanoscale nZVI and magnetite(Mag)particles uniformly anchoring on the surface of acid-activated sepiolite(SepH).Batch experiments were used to analyze the effects of main factors on Cr(VI)removal.A 100%removal efficiency in 60 min and enhanced reaction ratio were reached by the composite comparing other existing materials.The kinetic of the adsorption and possible Cr(VI)removal mechanism of the hybrids were also evaluated and proposed.Based on the removal products identified by Raman,XRD and XPS,a reduction mechanism was proposed.The results indicated that the SepH and Mag can inhibit the agglomeration and enhance the dispersibility of nZVI,and Mag and nZVI displayed good synergetic effects.展开更多
In this paper,the content and density of adsorbed water in fine-grained soil are determined.According to the test results,the calculation method of compaction degree of the solid-phase and void ration of soil is impro...In this paper,the content and density of adsorbed water in fine-grained soil are determined.According to the test results,the calculation method of compaction degree of the solid-phase and void ration of soil is improved.Four kinds of fine-grained soils from different regions in China were selected,and the adsorbed water content and density of four kinds of fine-grained soils were determined by thermogravimetry and volumetric flask method.Furthermore,SEM and XRD experiments were used to analyze the differences in the ability of each soil sample to absorb water.In order to study the compression characteristics of adsorbed water,four saturated soil samples were tested by consolidation method.The results show that the desorption temperature range of the adsorbed water and its density were equal to 100−115℃and 1.30 g/cm^(3),respectively.Adsorbed water plays a positive role in keeping the compressibility of fine-grained soil at a low rate when it has high water content.Besides,adsorbed water can be a stable parameter and is difficult to discharge during the operation period of subgrade.The settlement of fine-grained soil embankment is predicted by engineering example,and compared with the result of conventional calculation method.The results show that it is more close to the field monitoring results by using the improved void ratio of soil as the parameter.展开更多
The sewage sludge was used to produce adsorbent by controlling the pyrolytic and chemical conditions. Using the adsorbent derived from sewage sludge to adsorb the low concentration SO2 in fixed bed system, the effects...The sewage sludge was used to produce adsorbent by controlling the pyrolytic and chemical conditions. Using the adsorbent derived from sewage sludge to adsorb the low concentration SO2 in fixed bed system, the effects of the metallic derivatives on characteristics of the adsorbent were investigated at different compositions of the gaseous mixtures. The results show that when the mass fraction of vanadium reaches 0.5% and the mass fraction of （iron,） calcium, copper, nickel reach approximately 0.9%, under the condition that the adsorption mixture contains （0.12%SO2,） 3%O2 and 10% water vapor, the maximum adsorption capacity of SO2 can be obtained to be 128, 109, 90, 82, 78 mg·g-1, respectively. So the metallic derivatives fixed onto adsorbent derived from sewage sludge especially vanadium have great effects on of the sorption characteristics of the adsorbent with respect to SO2.展开更多
Thirty-six typical REE deposits extracted from literatures,mineral resource database or reports,which are served as a basis for classifying deposit type.And then the five principal deposit types were identified:(1)alk...Thirty-six typical REE deposits extracted from literatures,mineral resource database or reports,which are served as a basis for classifying deposit type.And then the five principal deposit types were identified:(1)alkali-related type;(2)Ion-adsorbed type;(3)metamorphosed sedimentary type;(4)placer type;(5)sedimentary phosphate type.Data gathered for each deposit includes the deposit scale,geologic settings,main metallogenic ages,main and accessory minerals,and ore-bearing intrusions.展开更多
A series of transition metal Mn,Cu,Ce and Fe were loaded on TiO_(2) by sol-gel method with noble metal Pd as promotor for the application of passive NO_(x) absorber.Experiments on adsorption and desorption of NO_(x) w...A series of transition metal Mn,Cu,Ce and Fe were loaded on TiO_(2) by sol-gel method with noble metal Pd as promotor for the application of passive NO_(x) absorber.Experiments on adsorption and desorption of NO_(x) were conducted and characterization methods such as X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),transmission electron microscopy(TEM)and in situ Fourier transform infrared spectroscopy(in situ DRIFTS)were involved.The experimental results show that Mn-contained catalysts,Mn-Ti and Pd-Mn-Ti,performed excellent NO_(x) adsorbing ability and appropriate desorption temperature window.On the other hand,Ce-and Cu-contained samples were not suitable for the purpose of PNA.In addition to the low adsorption capacity,these two series of catalysts released massive amount of NO below 150℃.Characterization results indicated that Pd was highly dispersed on all catalysts.The loading of Pd lowered not only the valence states of transition metals but surface oxygen percentage as well.From in situ DRIFTS tests,the Pd had little influence on the types of adsorbed substances for Mn,Ce and Cu series.However,the storage forms of NO_(x) were obviously different on Pd-Fe-Ti and Fe-Ti.展开更多
The binding energies of ethylene oxide (Et-O) adsorbed on Cu(110) surface for different adsorption sites and orientations are calculated with an atom superposition and electron delocalization molecular orbital (ASED-M...The binding energies of ethylene oxide (Et-O) adsorbed on Cu(110) surface for different adsorption sites and orientations are calculated with an atom superposition and electron delocalization molecular orbital (ASED-MO) using cluster models. It shows that the top site of Cu(110) surface is preferable for Et-O adsorption and the orientation of C-C bond of Et-O is parallel to the [110] direction of the substratc. The distance of an oxygen of Et-O to the Cu atom is approximately 1.5817(?). It is different from the supposition of C. Benndorf et al., in which the oxygen was proposed on the short bridge site with C-C bond orientating to [110] direction of Cu(110)展开更多
The control synthesis of nanoparticles was the implementation process of material ideal design. Nano-hydroxyapatite(HAP) was prepared by a hydrothermal method with calcium nitrate and diammonium hydrogen phosphate as ...The control synthesis of nanoparticles was the implementation process of material ideal design. Nano-hydroxyapatite(HAP) was prepared by a hydrothermal method with calcium nitrate and diammonium hydrogen phosphate as raw material, to study its characteristics for morphology modification by arginine-functionalization and doping with rare earth such as Tb^(3+). The crystallization, grain size and dispersibility of the sample HAP were analyzed and discussed. The results show that the surface Zeta potential of arginine-functionalized HAP is changed, and the growth rate of HAP is inhibited to a certain extent during the synthesis. The structure of HAP/Arg is not affected during the synthesis by a small amount of rare earth ions doped such as Tb^(3+), and has a single phase of HAP with good dispersibility. The synthesized HAP is also of nano-sized level. Nano-hydroxyapatite argininefunctionalized and doped with rare earth such as Tb^(3+), is suitable for the application of gene delivery as a gene carrier.展开更多
We report the first observation of hydrogen induced displacement of chemisorbed CO from the Ni（100） surface. This displacement is unexpected since the heat of adsorption for CO is 126 kJ/mole, about 30 kJ/mole large...We report the first observation of hydrogen induced displacement of chemisorbed CO from the Ni（100） surface. This displacement is unexpected since the heat of adsorption for CO is 126 kJ/mole, about 30 kJ/mole larger than the 96 kJ/mole heat of adsorption for hydrogen, Rates of displacement were measured by Fluorescence Yield Near Edge Spectroscopy （FYNES） and Temperature Programmed Desorption （TPD）. Excellent agreement is observed between both methods. Hydrogen pressures in the 10<sup>-4</sup> to 10<sup>-1</sup> Torr range cause displacement of chemisorbed CO in the 270 to 330 K temperature range in a matter of minutes. The displacement reaction is clearly positive order in CO coverage. The CO coverage data suggested two first order reaction regions with a decrease in rate with decreasing coverage. Displacement is about half order in hydrogen pressure. The activation energy for the high coverage displacement rate is approximately 29±4 kJ/mole while the activation energy for the low coverage displacement rate about展开更多
The impregnations of different kinds of titania support with aqueous solution or ferricions at various pH values and with the solution of these ions in a polar aprotic solvent,dimethylformamide(DMF),were invcstigated....The impregnations of different kinds of titania support with aqueous solution or ferricions at various pH values and with the solution of these ions in a polar aprotic solvent,dimethylformamide(DMF),were invcstigated.The results suggest that the surface ofhydrated titania is amphoteric,and has the function of a cationic exchanger,its ion ex-change properties arc dependent on the pH of the impregnating solutions.The higher theconcentration of metal ions in the impregnating solution and the more polar thc solvent,thehigher the loading on the support material having thc higher degree of crystallinity and alarger surface area without any pretreatments such as dehydration and calcination.展开更多
The adsorption and desorption of CO on the Ag-rich and Pd-rich surface of Ag-Pd al-loy have been investigated with work function measurement, Auger spectroscopy （AES）,and thermal desorption spectroscopy （TDS） in a...The adsorption and desorption of CO on the Ag-rich and Pd-rich surface of Ag-Pd al-loy have been investigated with work function measurement, Auger spectroscopy （AES）,and thermal desorption spectroscopy （TDS） in an ultrahigh vacuum system, respectively.AES showed that the surface of the alloy (X<sub>Pd.bulk</sub>=40% at.) was rich in Ag after an-ncaling as would normally be expected and was rich in Pd after Ar<sup>+</sup> bombardment possiblycaused by different sputtering rate on account of their different surface binding energy.Afteradmission of CO the work functions of both surfaces （Pd-rich and Ag-rich） are raised. Theresults of AES and work function measurement confirmed that the Ag-rich alloy becamecnriched with Pd upon prolonged contact with CO at 293 K. With TDS, one singledesorption peak of adsorbed CO was observed throughout the whole range of exposure forthe Ag-Pd system. This result implied that Pd atom in the surface were acting as individualchemisorption centers and that the Ag atoms were merely acting as a展开更多
XPS has been applied to study the interactions of formic and acetic acids with preoxidised iron surfaces. Exposure of the surface to acetic acid at 300 K would result in two Cls peaks of similar intensities at 285.2 e...XPS has been applied to study the interactions of formic and acetic acids with preoxidised iron surfaces. Exposure of the surface to acetic acid at 300 K would result in two Cls peaks of similar intensities at 285.2 eV and 289.0 eV B.E. （Binding Energy）. An Ols component with FWHM about 2.2 eV was also observed at 532.0 eV B.E. It was suggested that CH<sub>3</sub>COOH adsorbed as CH<sub>3</sub>COO（a） and OH（a） on the surface according to surface acid-base interaction: CH<sub>3</sub>COOH（g）+O<sup>2-</sup>（a）（?） CH<sub>3</sub>COO（a）+OH（a） （1） The above mechanism was strongly supported stoichiometrically, using the Roberts—Carley equation for surface concentration calculations. When a preoxidised iron surface was exposed to formic acid at 300 K, two Cls peaks at 285.6 eV and 289.1 eV B.E. were clearly observed. The Cls peak at 289.1 eV B.E. was attributed to HCOO（a）. Its formation mechanism also belongs to the kind of surface acid-base interaction: HCOOH（g）+O<sup>2-</sup>（a）（?）HCOO（a）+OH（a） （2） The other Cls peak at 285.6 eV was proposed to be CH<sub>x</sub>O（a）. It展开更多
The various adsorption states of oxygen on different sites of silver surfaces have been studied using CNDO method. The result shows that a fairly strong, adsorption bond is formed when oxygen molecule is adsorbed, in ...The various adsorption states of oxygen on different sites of silver surfaces have been studied using CNDO method. The result shows that a fairly strong, adsorption bond is formed when oxygen molecule is adsorbed, in lying down position with its axis parallel to the surface, at the surface bridge site having larger silver-silver distance. In this case, the adsorbed oxygen molecule has fairly strong tendency to dissociate. The most favorite sites on Ag（110） and Ag（111） surfaces for oxygen molecules or atoms to be adsorbed have been suggested after calculation and analysis. The differences of oxygen adsorption on these two surfaces mentioned above have been compared. The most stable adsorption states of oxygen are O<sub>2</sub><sup>2-</sup>, O<sup>2-</sup> on Ag（110） and O<sub>2</sub><sup>-</sup>, O<sup>-</sup>on Ag（111）. On silver film or polycrystalline silver, O<sub>2</sub><sup>2-</sup>, O<sub>2</sub><sup>-</sup>, O<sup>2-</sup>, O<sup>-</sup> may coexist. The results are in agreement with experiments.展开更多
The mechanism of methanol adsorption induced by oxygen and the effect of water on the methanol oxidation on electrolytic silver have been studied by ultra-high vacuum temperature programmed reaction spectroscopy(TPRS)...The mechanism of methanol adsorption induced by oxygen and the effect of water on the methanol oxidation on electrolytic silver have been studied by ultra-high vacuum temperature programmed reaction spectroscopy(TPRS), transient response method and isotopic exchange experiment. It has been found that oxygen adsorbed on silver can greatly promote methanol adsorption and can also react with methanol to produce water. Experimental results show that oxygen in the water comes from the adsorbed oxygen and hydrogen from the methyl and the hydroxyl in methanol. It has also been found that there exists competitive adsorption between water and oxygen on silver and water can increase the selectivity of methanol oxidation to formaldehyde. This result is consistent with the catalytic activities.展开更多
基金supported by Shanxi Provincial Key Research and Development Project(202102090301026)Graduate Education Innovation Project of Taiyuan University of Science and Technology(SY2023024)。
文摘Currently,the solid adsorbents with porous structure have been widely applied in CO_(2)capture.However,the unmodified MgO-ZrO_(2)adsorbents appeared to be low adsorption capacity of CO_(2).The solid adsorbent materials were successfully synthesized by loading TEPA onto the pore MgO/ZrO_(2)carriers in the paper.The pore structure and surface characteristic of the samples were analyzed by using XRD,BET,FT-IR and SEM.The adsorbent materials exhibited microcrystalline state,and the crystallinity of all samples gradually decreased as the increase of TEPA content.The pore structure analysis indicated that the modification of MgO-ZrO_(2)adsorbents with TEPA led to the decrease of the specific surface areas,but the narrow micro-mesopore size distributions ranging from 1.8-12 nm in the adsorbents still were maintained.FT-IR spectrum results further verified the successful loading of TEPA.The adsorption capacity of the adsorbents for CO_(2)were tested by using an adsorption apparatus equipped with gas chromatography.The results indicated that when the TEPA loading reached 50%,the sample exhibited the maximum adsorption value for CO_(2),reaching 4.07 mmol/g under the operation condition of 75℃and atmospheric pressure.This result could be assigned to not only the base active sites but also the coexistence of both micropore and mesopore in the adsorbent.After three cycles tests for CO_(2)capture,the adsorption value of the sample for CO_(2)can also reached 95%of its original adsorption capacity,which verified the excellent cyclic operation stability.
基金Projects(52474138,52104261,52525401)supported by the National Natural Science Foundation of ChinaProject supported by the New Cornerstone Science Foundation through the XPLORER PRIZE,ChinaProject supported by the Shanxi Key Laboratory Funds of Mine Rock Strata Control and Disaster Prevention,China。
文摘The novel magnetic sepiolite/Fe_(3)O_(4)/zero-valent iron(nZVI)nanocomposite(nZVI@SepH-Mag)was prepared and used to achieve the removal of Cr(VI)in this work.The nZVI@SepH-Mag composites were characterized by XRD,FTIR,BET,SEM and TEM.The characterization results indicated that the structure of the composite consisted of small nanoscale nZVI and magnetite(Mag)particles uniformly anchoring on the surface of acid-activated sepiolite(SepH).Batch experiments were used to analyze the effects of main factors on Cr(VI)removal.A 100%removal efficiency in 60 min and enhanced reaction ratio were reached by the composite comparing other existing materials.The kinetic of the adsorption and possible Cr(VI)removal mechanism of the hybrids were also evaluated and proposed.Based on the removal products identified by Raman,XRD and XPS,a reduction mechanism was proposed.The results indicated that the SepH and Mag can inhibit the agglomeration and enhance the dispersibility of nZVI,and Mag and nZVI displayed good synergetic effects.
基金Project(51978085)supported by the National Natural Science Foundation of ChinaProject(K2019G045)supported by the Science and Technology Research and Development Plan of China National Railway Group Co.,Ltd.Project(201808430102)supported by the China Scholarship Council。
文摘In this paper,the content and density of adsorbed water in fine-grained soil are determined.According to the test results,the calculation method of compaction degree of the solid-phase and void ration of soil is improved.Four kinds of fine-grained soils from different regions in China were selected,and the adsorbed water content and density of four kinds of fine-grained soils were determined by thermogravimetry and volumetric flask method.Furthermore,SEM and XRD experiments were used to analyze the differences in the ability of each soil sample to absorb water.In order to study the compression characteristics of adsorbed water,four saturated soil samples were tested by consolidation method.The results show that the desorption temperature range of the adsorbed water and its density were equal to 100−115℃and 1.30 g/cm^(3),respectively.Adsorbed water plays a positive role in keeping the compressibility of fine-grained soil at a low rate when it has high water content.Besides,adsorbed water can be a stable parameter and is difficult to discharge during the operation period of subgrade.The settlement of fine-grained soil embankment is predicted by engineering example,and compared with the result of conventional calculation method.The results show that it is more close to the field monitoring results by using the improved void ratio of soil as the parameter.
文摘The sewage sludge was used to produce adsorbent by controlling the pyrolytic and chemical conditions. Using the adsorbent derived from sewage sludge to adsorb the low concentration SO2 in fixed bed system, the effects of the metallic derivatives on characteristics of the adsorbent were investigated at different compositions of the gaseous mixtures. The results show that when the mass fraction of vanadium reaches 0.5% and the mass fraction of （iron,） calcium, copper, nickel reach approximately 0.9%, under the condition that the adsorption mixture contains （0.12%SO2,） 3%O2 and 10% water vapor, the maximum adsorption capacity of SO2 can be obtained to be 128, 109, 90, 82, 78 mg·g-1, respectively. So the metallic derivatives fixed onto adsorbent derived from sewage sludge especially vanadium have great effects on of the sorption characteristics of the adsorbent with respect to SO2.
基金supported by the China Geological Survey(Grant Nos.12120111210451212011121040)
文摘Thirty-six typical REE deposits extracted from literatures,mineral resource database or reports,which are served as a basis for classifying deposit type.And then the five principal deposit types were identified:(1)alkali-related type;(2)Ion-adsorbed type;(3)metamorphosed sedimentary type;(4)placer type;(5)sedimentary phosphate type.Data gathered for each deposit includes the deposit scale,geologic settings,main metallogenic ages,main and accessory minerals,and ore-bearing intrusions.
基金Project(52106173)supported by the National Natural Science Foundation of ChinaProject(2020TQ0187)supported by the Postdoctoral Research Foundation of China。
文摘A series of transition metal Mn,Cu,Ce and Fe were loaded on TiO_(2) by sol-gel method with noble metal Pd as promotor for the application of passive NO_(x) absorber.Experiments on adsorption and desorption of NO_(x) were conducted and characterization methods such as X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),transmission electron microscopy(TEM)and in situ Fourier transform infrared spectroscopy(in situ DRIFTS)were involved.The experimental results show that Mn-contained catalysts,Mn-Ti and Pd-Mn-Ti,performed excellent NO_(x) adsorbing ability and appropriate desorption temperature window.On the other hand,Ce-and Cu-contained samples were not suitable for the purpose of PNA.In addition to the low adsorption capacity,these two series of catalysts released massive amount of NO below 150℃.Characterization results indicated that Pd was highly dispersed on all catalysts.The loading of Pd lowered not only the valence states of transition metals but surface oxygen percentage as well.From in situ DRIFTS tests,the Pd had little influence on the types of adsorbed substances for Mn,Ce and Cu series.However,the storage forms of NO_(x) were obviously different on Pd-Fe-Ti and Fe-Ti.
文摘The binding energies of ethylene oxide (Et-O) adsorbed on Cu(110) surface for different adsorption sites and orientations are calculated with an atom superposition and electron delocalization molecular orbital (ASED-MO) using cluster models. It shows that the top site of Cu(110) surface is preferable for Et-O adsorption and the orientation of C-C bond of Et-O is parallel to the [110] direction of the substratc. The distance of an oxygen of Et-O to the Cu atom is approximately 1.5817(?). It is different from the supposition of C. Benndorf et al., in which the oxygen was proposed on the short bridge site with C-C bond orientating to [110] direction of Cu(110)
基金Project(2013SK2024)supported by the Key Projects in Social Development Pillar Program of Hunan Province,ChinaProject(20130162120094)supported by Specialized Research Fund for the Doctoral Program of Higher Education(SRFDP),Ministry of Education,ChinaProject supported by State Key Laboratory of Powder Metallurgy,Central South University,China
文摘The control synthesis of nanoparticles was the implementation process of material ideal design. Nano-hydroxyapatite(HAP) was prepared by a hydrothermal method with calcium nitrate and diammonium hydrogen phosphate as raw material, to study its characteristics for morphology modification by arginine-functionalization and doping with rare earth such as Tb^(3+). The crystallization, grain size and dispersibility of the sample HAP were analyzed and discussed. The results show that the surface Zeta potential of arginine-functionalized HAP is changed, and the growth rate of HAP is inhibited to a certain extent during the synthesis. The structure of HAP/Arg is not affected during the synthesis by a small amount of rare earth ions doped such as Tb^(3+), and has a single phase of HAP with good dispersibility. The synthesized HAP is also of nano-sized level. Nano-hydroxyapatite argininefunctionalized and doped with rare earth such as Tb^(3+), is suitable for the application of gene delivery as a gene carrier.
文摘We report the first observation of hydrogen induced displacement of chemisorbed CO from the Ni（100） surface. This displacement is unexpected since the heat of adsorption for CO is 126 kJ/mole, about 30 kJ/mole larger than the 96 kJ/mole heat of adsorption for hydrogen, Rates of displacement were measured by Fluorescence Yield Near Edge Spectroscopy （FYNES） and Temperature Programmed Desorption （TPD）. Excellent agreement is observed between both methods. Hydrogen pressures in the 10<sup>-4</sup> to 10<sup>-1</sup> Torr range cause displacement of chemisorbed CO in the 270 to 330 K temperature range in a matter of minutes. The displacement reaction is clearly positive order in CO coverage. The CO coverage data suggested two first order reaction regions with a decrease in rate with decreasing coverage. Displacement is about half order in hydrogen pressure. The activation energy for the high coverage displacement rate is approximately 29±4 kJ/mole while the activation energy for the low coverage displacement rate about
文摘The impregnations of different kinds of titania support with aqueous solution or ferricions at various pH values and with the solution of these ions in a polar aprotic solvent,dimethylformamide(DMF),were invcstigated.The results suggest that the surface ofhydrated titania is amphoteric,and has the function of a cationic exchanger,its ion ex-change properties arc dependent on the pH of the impregnating solutions.The higher theconcentration of metal ions in the impregnating solution and the more polar thc solvent,thehigher the loading on the support material having thc higher degree of crystallinity and alarger surface area without any pretreatments such as dehydration and calcination.
基金Research supported by Chinese Universities Science and Technology Foundation Grant.
文摘The adsorption and desorption of CO on the Ag-rich and Pd-rich surface of Ag-Pd al-loy have been investigated with work function measurement, Auger spectroscopy （AES）,and thermal desorption spectroscopy （TDS） in an ultrahigh vacuum system, respectively.AES showed that the surface of the alloy (X<sub>Pd.bulk</sub>=40% at.) was rich in Ag after an-ncaling as would normally be expected and was rich in Pd after Ar<sup>+</sup> bombardment possiblycaused by different sputtering rate on account of their different surface binding energy.Afteradmission of CO the work functions of both surfaces （Pd-rich and Ag-rich） are raised. Theresults of AES and work function measurement confirmed that the Ag-rich alloy becamecnriched with Pd upon prolonged contact with CO at 293 K. With TDS, one singledesorption peak of adsorbed CO was observed throughout the whole range of exposure forthe Ag-Pd system. This result implied that Pd atom in the surface were acting as individualchemisorption centers and that the Ag atoms were merely acting as a
基金This work was financially supported by Academia Sinica,(Young Scientists Research Award,1986).
文摘XPS has been applied to study the interactions of formic and acetic acids with preoxidised iron surfaces. Exposure of the surface to acetic acid at 300 K would result in two Cls peaks of similar intensities at 285.2 eV and 289.0 eV B.E. （Binding Energy）. An Ols component with FWHM about 2.2 eV was also observed at 532.0 eV B.E. It was suggested that CH<sub>3</sub>COOH adsorbed as CH<sub>3</sub>COO（a） and OH（a） on the surface according to surface acid-base interaction: CH<sub>3</sub>COOH（g）+O<sup>2-</sup>（a）（?） CH<sub>3</sub>COO（a）+OH（a） （1） The above mechanism was strongly supported stoichiometrically, using the Roberts—Carley equation for surface concentration calculations. When a preoxidised iron surface was exposed to formic acid at 300 K, two Cls peaks at 285.6 eV and 289.1 eV B.E. were clearly observed. The Cls peak at 289.1 eV B.E. was attributed to HCOO（a）. Its formation mechanism also belongs to the kind of surface acid-base interaction: HCOOH（g）+O<sup>2-</sup>（a）（?）HCOO（a）+OH（a） （2） The other Cls peak at 285.6 eV was proposed to be CH<sub>x</sub>O（a）. It
基金Present address:Chemistry Department,South China University of Technology,Gusng Zhou,China
文摘The various adsorption states of oxygen on different sites of silver surfaces have been studied using CNDO method. The result shows that a fairly strong, adsorption bond is formed when oxygen molecule is adsorbed, in lying down position with its axis parallel to the surface, at the surface bridge site having larger silver-silver distance. In this case, the adsorbed oxygen molecule has fairly strong tendency to dissociate. The most favorite sites on Ag（110） and Ag（111） surfaces for oxygen molecules or atoms to be adsorbed have been suggested after calculation and analysis. The differences of oxygen adsorption on these two surfaces mentioned above have been compared. The most stable adsorption states of oxygen are O<sub>2</sub><sup>2-</sup>, O<sup>2-</sup> on Ag（110） and O<sub>2</sub><sup>-</sup>, O<sup>-</sup>on Ag（111）. On silver film or polycrystalline silver, O<sub>2</sub><sup>2-</sup>, O<sub>2</sub><sup>-</sup>, O<sup>2-</sup>, O<sup>-</sup> may coexist. The results are in agreement with experiments.
文摘The mechanism of methanol adsorption induced by oxygen and the effect of water on the methanol oxidation on electrolytic silver have been studied by ultra-high vacuum temperature programmed reaction spectroscopy(TPRS), transient response method and isotopic exchange experiment. It has been found that oxygen adsorbed on silver can greatly promote methanol adsorption and can also react with methanol to produce water. Experimental results show that oxygen in the water comes from the adsorbed oxygen and hydrogen from the methyl and the hydroxyl in methanol. It has also been found that there exists competitive adsorption between water and oxygen on silver and water can increase the selectivity of methanol oxidation to formaldehyde. This result is consistent with the catalytic activities.
